Expansion device

Description

CROSS-REFERENCES TO RELATED APPLICATIONS, IF ANY

This application claims priority of Japanese Application No. 2003-315493 filed on Sep. 8, 2003 and entitled “EXPANSION DEVICE” and No. 2004-070947 filed on Mar. 12, 2004, entitled “EXPANSION DEVICE”.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to an expansion device that is disposed in a flow passage of refrigerant circulating through a refrigeration cycle, and comprises a differential pressure valve for controlling differential pressure thereacross.

(2) Description of the Related Art

Conventionally, a refrigeration cycle for an automotive air-conditioner is known which uses an accumulator that performs gas/liquid separation by storing excess refrigerant on an outlet side of an evaporator, and an expansion device of a supercooling degree control type that comprises an orifice (restriction flow passage) that controls the flow rate of refrigerant in response to changes in the supercooling degree and dryness of high-pressure refrigerant flowing out from a condenser, and a differential pressure valve that provides control such that a predetermined degree of supercooling of the refrigerant is obtained (e.g. Japanese Unexamined Patent Publication (Kokai) No. H11-257802).

The expansion device of this type comprises a cylinder fixed within piping of the refrigeration cycle, and a valve element disposed within the cylinder. The valve element slides within the cylinder while being supported by a compression spring or the like. Refrigerant passages, including a predetermined orifice, are formed at a boundary between the inside of the valve element and the cylinder such that movement of the valve element within the cylinder in response to a change in the differential pressure across the expansion device causes a change in the flow passage of refrigerant. That is, so long as the differential pressure across the expansion device is small, the flow passage of refrigerant is set to the predetermined orifice, and when the differential pressure has become equal to or higher than a predetermined value, a flow passage of refrigerant is added to thereby prevent an abnormal rise in the pressure of refrigerant.

Further, from the viewpoint of preventing an abnormal rise in the pressure within the expansion device to protect the internal components thereof, a safety rapture plate formed by a thin plate is provided in part of the cylinder in advance, and when the differential pressure has become equal to or higher than a predetermined value, rupture of the plate is caused to relieve the pressure.

However, in the above-described configuration of the expansion device, to enable the valve element to normally operate under high-pressure conditions, it is necessary to secure the elastic force of the compression spring or the like, and hence a large-sized compression spring need be used. This increases the size of the entire expansion device, resulting in increased manufacturing costs thereof.

SUMMARY OF THE INVENTION

The present invention has been made in view of these points, and an object thereof is to provide an expansion device that is configured compact in size and capable of effectively preventing an abnormal rise in pressure within the expansion device caused by the differential pressure across the expansion device.

To solve the above problems, the present invention provides an expansion device that is disposed in a flow passage of refrigerant circulating through a refrigeration cycle, for passing the refrigerant introduced from an upstream side thereof through an internal refrigerant passage thereof to thereby cause decompression of the refrigerant and allow the decompressed refrigerant to flow downstream, and is equipped with a relief mechanism that is operable when a differential pressure across the expansion device has become equal to or higher than a predetermined value, to open a flow passage other than the refrigerant passage which is closed by a valve element urged by an elastic member disposed within the expansion device, to thereby allow at least part of the refrigerant flowing in from the upstream side to escape via the flow passage to flow downstream, the expansion device comprising a pressure-cancelling structure that cancels part of pressure of the refrigerant acting on the valve element in a valve-opening direction.

Further, the present invention provides an expansion device that is disposed in a flow passage of refrigerant circulating through a refrigeration cycle, comprising a cylinder in the form of a hollow cylinder, the cylinder having a first valve seat formed by a stepped portion provided inside the hollow cylinder, a first valve element that has a body in the form of a hollow cylinder inserted in the cylinder, and includes a valve portion that forms part of the body and can be removably seated on the first valve seat, a guided portion that is guided along an inner peripheral surface of the cylinder when the body is moved to and away from the first valve seat, and a first refrigerant passage that extends through an inside of the body and has a stepped portion formed therein at which the first refrigerant passage is expanded in an upstream-to-downstream direction, the first refrigerant passage allowing passage of the refrigerant, a first elastic member that is disposed within the cylinder, for urging the first valve element in a valve-closing direction, a pressure-cancelling structure that cancels at least part of pressure of the refrigerant acting on the first valve element in a valve-opening direction, the pressure-cancelling structure comprising a valve-closing pressure-receiving surface that receives pressure of the refrigerant acting on the first valve element in the valve-closing direction and has a pressure-receiving area smaller than a pressure-receiving area of a valve-opening pressure-receiving surface that receives pressure of the refrigerant acting on the first valve element in the valve-opening direction, a first relief mechanism that is operable when a differential pressure across the expansion device has become equal to or higher than a first predetermined value to cause the valve portion to be moved away from the first valve seat, to allow at least part of the refrigerant flowing in from an upstream side to escape into a flow passage other than the first refrigerant passage within the cylinder to thereby allow the refrigerant to flow downstream, an inner shaft member in the form of a hollow cylinder that is formed therein with a flow-restricting portion having a cross-section smaller than a cross-section of the first refrigerant passage, and is partially inserted into an expanded side of the stepped portion of the first valve element, the inner shaft member protruding downstream from the first valve element, an inner cylinder in the form of a hollow cylinder that is fixed to an inside of the cylinder, and has at least one slit formed through a side wall of an upstream end thereof, the upstream end being capable of having a downstream end of the inner shaft member engaged thereat, the inner cylinder being formed with a communication hole extending therethrough for communication with the flow-restricting portion, a second valve element that has a body in the form of a hollow cylinder inserted in the inner cylinder, the second valve element including a valve portion that forms part of the body of the second valve element and can be removably seated on a second valve seat formed on a downstream end face of the inner shaft member, a guided portion that is guided along the communication hole when the body of the second valve element is moved to and away from the second valve seat, and a second refrigerant passage that extends through an inside of the body of the second valve element and has a cross-section smaller than the cross-section of the flow-restricting portion, a second elastic member that is disposed within the inner cylinder, for urging the second valve element in a valve-closing direction, and a second relief mechanism that is operable when the differential pressure across the expansion device has become equal to or higher than a second predetermined value smaller than the first predetermined value to cause the valve portion of the second valve element to be moved away from the second valve seat, to allow at least part of the refrigerant flowing in from the upstream side to escape into a flow passage other than the second refrigerant passage within the inner cylinder to thereby allow the refrigerant to flow downstream.

The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view showing an expansion device according to a first embodiment, in a state disposed in piping of a refrigeration cycle.

FIGS. 2A and 2B are longitudinal cross-sectional views of the expansion device.

FIGS. 3A and 3B are transverse cross-sectional views of the expansion device.

FIG. 4 is an explanatory view showing the relationship between the differential pressure across the expansion device and the opening area of the refrigerant passage therethrough.

FIGS. 5A, 5B and 5C are cross-sectional views of an expansion device according to a second embodiment.

FIGS. 6A, 6B and 6C are cross-sectional views of an expansion device according to a third embodiment.

FIGS. 7A, 7B and 7C are longitudinal cross-sectional views of an expansion device according to a fourth embodiment.

FIG. 8 is a cross-sectional view taken on line E-E of FIG. 7A.

FIG. 9 is an explanatory view showing the relationship between the differential pressure across the expansion device and the opening area of the refrigerant passage therethrough.

FIGS. 10A, 10B and 10C are longitudinal cross-sectional views of an expansion device according to a fifth embodiment.

FIGS. 11A, 11B and 11C are longitudinal cross-sectional views of an expansion device according to a sixth embodiment.

FIG. 12A to 12E are cross-sectional views of the configuration of an inner cylinder as a component element of the expansion device.

FIGS. 13A, 13B and 13C are longitudinal cross-sectional views of an expansion device according to a seventh embodiment.

FIG. 14 is a cross-sectional view taken on line G-G of FIG. 13A.

FIGS. 15A, 15B and 15C are longitudinal cross-sectional views of an expansion device according to an eighth embodiment.

FIG. 16 is an explanatory view showing the relationship between the differential pressure across the expansion device and the opening area of the refrigerant passage therethrough.

FIGS. 17A, 17B and 17C are longitudinal cross-sectional views of an expansion device according to a ninth embodiment.

FIG. 18 is a cross-sectional view taken on line H-H of FIG. 17A.

FIG. 19 is an explanatory view showing the relationship between the differential pressure across the expansion device and the opening area of the refrigerant passage therethrough.

FIGS. 20A, 20B and 20C are longitudinal cross-sectional views of an expansion device according to a tenth embodiment.

FIG. 21 is a cross-sectional view taken on line I-I of FIG. 20A.

FIGS. 22A, 22B and 22C are longitudinal cross-sectional views of an expansion device according to an eleventh embodiment.

FIG. 23 is a cross-sectional view taken on line J-J of FIG. 22A.

FIG. 24 is an explanatory view showing the relationship between the differential pressure across the expansion device and the opening area of the refrigerant passage therethrough.

FIGS. 25A and 25B are longitudinal cross-sectional views of an expansion device according to a twelfth embodiment.

FIGS. 26A and 26B are transverse cross-sectional views of an expansion device according to the twelfth embodiment.

FIGS. 27A, 27B and 27C are cross-sectional views of an expansion device according to a thirteenth embodiment.

FIGS. 28A, 28B and 28C are longitudinal cross-sectional views of an expansion device according to a fourteenth embodiment.

FIG. 29 is a cross-sectional view taken on line N-N of FIG. 28A.

FIGS. 30A, 30B and 30C are longitudinal cross-sectional views of an expansion device according to a fifteenth embodiment.

FIGS. 31A and 31B are longitudinal cross-sectional views of an expansion device according to a sixteenth embodiment.

FIGS. 32A and 32B are longitudinal cross-sectional views of an expansion device according to a seventeenth embodiment.

FIGS. 33A and 33B are transverse cross-sectional views of an expansion device according to the seventeenth embodiment.

FIGS. 34A, 34B and 34C are explanatory views showing the configuration of a restriction mechanism.

FIG. 35 is an explanatory view showing the relationship between the differential pressure across the expansion device and the opening area of the refrigerant passage therethrough.

FIGS. 36A and 36B are longitudinal cross-sectional views of an expansion device according to an eighteenth embodiment.

FIGS. 37A and 37B are transverse cross-sectional views of an expansion device according to the eighteenth embodiment.

FIGS. 38A and 38B are longitudinal cross-sectional views of an expansion device according to a nineteenth embodiment.

FIGS. 39A and 39B are transverse cross-sectional views of an expansion device according to the nineteenth embodiment.

FIG. 40 is an explanatory view showing the relationship between the differential pressure across the expansion device and the opening area of the refrigerant passage therethrough.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First Embodiment

First, a first embodiment of the present invention will be described. FIG. 1 is an explanatory view showing an expansion device according to the present embodiment disposed in piping of a refrigeration cycle. FIGS. 2A and 2B are longitudinal cross-sectional views of the expansion device. FIG. 3A and 3B are transverse cross-sectional views of the expansion device, in which FIG. 3A is a cross-sectional view of the expansion device taken on line A-A of FIG. 2A, and FIG. 3B is a cross-sectional view of the expansion device taken on line B-B of FIG. 2A.

Referring first to FIG. 1, the expansion device 1 is disposed in the piping 50 forming a flow passage of refrigerant circulating through a refrigeration cycle for an automotive air conditioner, and formed by a differential pressure valve that controls a differential pressure thereacross such that a predetermined supercooling degree of the refrigerant is obtained. It should be noted that flows of refrigerant are indicated by arrows in FIG. 1 (the same applies in the following). In the following description of the configuration shown in FIG. 1, the right side and the left side, as viewed in the figure, are sometimes referred to as the “upstream side” and the “downstream side”, respectively, with reference to the direction of flow of refrigerant.

As shown in FIG. 2A, the expansion device 1 comprises a cylinder 10 in the form of a hollow cylinder, and a valve element 20 in the form of a hollow cylinder inserted in the cylinder 10.

The cylinder 10 has a hollow cylindrical body 11, and includes a valve seat 12 formed by a stepped portion formed at an upstream location inside the body 11. In other words, a refrigerant passage that allows passage of refrigerant is formed through the cylinder 10, by a small pipe portion 13 that is formed toward the upstream end, and a large pipe portion 14 that is formed on the downstream side of the small pipe portion 13 in a manner communicating therewith such that the large pipe portion 14 has a larger passage cross-section than that of the small pipe portion 13.

At an upstream end of the cylinder 10, a strainer 15 is fitted on an inlet of the small pipe portion 13 through which high-pressure refrigerant is introduced, and a flange 16 is formed which extends radially outward for securing the expansion device 1 to the piping 50. Further, the cylinder 10 has a fitting groove 10a circumferentially formed in an outer periphery of the small pipe portion 13 for having an O ring fitted therein for preservation of hermeticity when the expansion device 1 is fixed to the piping 50. Furthermore, a stopper 17 in the form of a bottomed hollow cylinder is fixed in the cylinder 10 at a location in the vicinity of a downstream end of the large pipe portion 14, with a spring 18 interposed between the stopper 17 and the valve element 20.

On the other hand, the valve element 20 has a stepped hollow cylindrical body 21 inserted into the cylinder 10. The body 21 has a valve portion 22 formed at an upstream end thereof such that the valve portion 22 can be moved to and away from the valve seat 12, a guided portion 23 formed at a location downstream of the valve portion 22, for being guided along an inner peripheral surface of the cylinder 10, and further a refrigerant passage 24 formed in a manner axially extending through the body 21 for passage of refrigerant therethrough.

The valve portion 22 is formed to have a tapered shape such that an outer diameter thereof is progressively reduced toward the upstream end of the body 21. When the valve portion 22 is seated on the valve seat 12, the foremost end of the valve portion 22 is inserted into the small pipe portion 13 by a predetermined amount.

The guided portion 23 is formed by three protrusions 23a extending from the body 21 toward the inner surface of the cylinder 10 at equal intervals (of 120 degrees), and other refrigerant passages than the refrigerant passage 24 are formed between the protrusions 23a, to allow passage of refrigerant. The foremost ends of the protrusions 23a slide along the inner surface of the cylinder 10, whereby the valve element 20 can be moved to and away from the valve seat 12.

The refrigerant passage 24 has a stepped portion 25 where the refrigerant passage 24 expanded from the upstream side toward the downstream side, and from the expanded side of the stepped portion 25, an inner shaft member 30 in the form of a hollow cylinder is inserted which functions as a restriction mechanism. That is, the flow passage through the inner shaft member 30 provides a restriction that has a cross-section smaller than the cross-section of the refrigerant passage 24, and decompresses refrigerant flowing through the refrigerant passage 24, such that the refrigerant pressure is reduced across the restriction. Although the inner shaft member 30 is supported by the valve element 20, it is not fixed to any part of an internal structure within the cylinder 10, and part of the inner shaft member 30 protrudes downward from the valve element 20, with the downstream end face thereof being in abutment with the bottom of the stopper 17 and held thereat, whereby the downstream movement of the inner shaft member 30 is limited. That is, although the inner shaft member 30 has the radial movement and the axial movement thereof limited by the valve element 20 and the stopper 17, respectively, it is not fixed to any part of the internal structure, and therefore it brings about no inconveniences such as limiting of the movement of the valve element 20.

At a location where the stopper 17 is in contact with the inner shaft member 30, there is formed a through hole 17a having a larger passage cross-section than that of the passage or restriction through the inner shaft member 30, thereby preventing the flow of refrigerant from being blocked even when the inner shaft member 30 is slightly radially displaced. Further, as shown in FIG. 3B, around the through hole 17a, there are provided four slots 17b (second through holes) that are connected to the aforementioned other refrigerant passages than the refrigerant passage 24. The sum of flow passage areas of these four slots 17b is sufficiently larger than the flow passage area of a gap formed between the valve portion 22 and the valve seat 12 when the valve element 20 is opened, which suppresses pressure loss of the refrigerant which can occur in the slots 17b.

The spring 18 is formed by a compression coil spring having a predetermined elastic coefficient, and has an upstream portion thereof inserted around the body 21 of the valve element 20. The spring 18 has one end thereof in abutment with the bottom of the stopper 17 at a location in the vicinity of the peripheral edge thereof, and the other end thereof in abutment with a downstream end face of the guided portion 23 of the valve element 20, thereby urging the valve element 20 toward the valve seat 12 (in the valve-closing direction) with a predetermined elastic force thereof.

Further, the stopper 17 is equipped with an adjusting mechanism, that is, the stopper 17 has an outer periphery formed with an external thread, and a downstream end of the cylinder 10 is formed with an internal thread mating with the external thread. By adjusting the amount of screwing of the stopper 17 into the cylinder 10, the position of the stopper 17 is adjusted, whereby the elastic force of the spring 18 can be adjusted.

The expansion device 1 configured as described above is fixed to the piping 50 as shown in FIG. 1. More specifically, the piping 50 has a joint structure which connects between a downstream-side pipe 51 and an upstream-side pipe 52, at an location where the expansion device 1 is installed therein. The downstream-side pipe 51 has a stepped portion 53 formed by expanding an upstream end thereof, and the downstream end of the upstream-side pipe 52 is inserted into the expanded portion of the downstream-side pipe 51 whereby the two pipes are joined. The hermeticity between these downstream-side and upstream-side pipes 51 and 52 is preserved by an O ring 54 fitted in a groove formed in the downstream end of the upstream-side pipe 52.

The expansion device 1 has its flange 16 sandwiched between the stepped portion 53 of the downstream-side pipe 51 and the downstream end face of the upstream-side pipe 52, whereby it is fixed within the piping 50. The hermeticity between the expansion device 1 and the piping 50 is preserved by the O ring 10b provided within the fitting groove 10a in the cylinder 10. The expansion device 1 is not equipped with a casing or the like for accommodating the cylinder 10, but has its cylinder 10 directly fixed to the piping 50.

Next, the pressure-cancelling structure of the expansion device 1 will be described.

As shown in FIG. 2A, in the expansion device 1, the valve portion 22 of the valve element 20 is formed with a valve-opening pressure-receiving surface 26 facing upstream for receiving refrigerant pressure which acts on the valve element in the valve-opening direction, as is conventional with the valve element. In addition, the stepped portion 25 of the valve element 20 is formed with a valve-closing pressure-receiving surface 27 for receiving refrigerant pressure which acts on the valve element 20 in the valve-closing direction. That is, refrigerant introduced into the inner space between the stepped portion 25 of the valve element 20 and the inner shaft member 30 applies pressure to the valve element 20 in the valve-closing direction (rightward as viewed in FIG. 2A), to thereby cancel part of the refrigerant pressure acting on the valve element 20 in the valve-opening direction. In the present embodiment, the passage cross-section of the small pipe portion 13 is formed to be larger than the cross-section of the expanded pipe side of the stepped portion 25, so that when the valve element 20 is seated on the valve seat 12, the valve-closing pressure-receiving surface 27 has a smaller pressure-receiving area than that of the valve-opening pressure-receiving surface 26. Therefore, the resultant of the pressure received at the valve-closing pressure-receiving surface 27 and the elastic force of the spring 18 acts against the refrigerant pressure received at the valve-opening pressure-receiving surface 26.

Next, the relief mechanism of the expansion device 1 will be described.

As shown in FIGS. 2A and 2B, in the expansion device 1, when the differential pressure across the expansion device 1 has become equal to or higher than a predetermined value to cause the valve portion 22 to be moved away the valve seat 12, most of refrigerant flowing in from the upstream side is allowed to escape through the gap between the valve portion 22 and the valve seat 12, and flow downstream through the aforementioned other refrigerant passages formed between the valve element 20 and the cylinder 10 and the slots 17b of the stopper 17. This prevents an abnormal rise in the refrigerant pressure inside the expansion device 1.

FIG. 4 is an explanatory view showing the relationship between the differential pressure across the expansion device 1 and the opening area of the refrigerant passage(s) thereof.

As shown in FIG. 4, so long as the valve element 20 is seated on the valve seat 12 (state shown in FIG. 2A), even if the differential pressure rises, the opening area is held at the cross-sectional area of the refrigerant passage 24. Then, when the differential pressure becomes higher than the predetermined value, the valve element 20 is moved away from the valve seat 12 to allow the refrigerant to escape into the other refrigerant passages outside the valve element 20 to relieve the refrigerant pressure. Thus, the opening area is instantly increased (state shown in FIG. 2B).

As described above, in the expansion device 1 according to the present embodiment, the pressure-cancelling structure cancels part of the refrigerant pressure. That is, the elastic force required of the spring 18 can be reduced by the amount of pressure received at the valve-closing pressure-receiving surface 27. As a result, a small-sized spring can be employed for the spring 18, which enables the entire expansion device 1 to be made compact in size.

Further, when the differential pressure across the expansion device 1 has become equal to or higher than the predetermined value, the refrigerant flowing in from the upstream side can be caused to escape into the other refrigerant passages than the refrigerant passage 24 of the valve element 20, which makes it possible to prevent an abnormal rise in the refrigerant pressure inside the expansion device 1, to thereby prevent breakage or the like of the internal components.

Second Embodiment

Next, a second embodiment of the present invention will be described. FIGS. 5A to 5C are cross-sectional views of an expansion device according to the present embodiment, in which FIGS. 5A and 5B are longitudinal cross-sectional views of the expansion device, while FIG. 5C is a cross-sectional view taken on line C-C of FIG. 5A. It should be noted that components similar to those of the first embodiment will be designated by identical reference numerals, and description thereof is omitted.

As shown in FIG. 5A, the expansion device 201 comprises a cylinder in the form of a hollow cylinder 210, and a valve element in the form of a hollow cylinder 220 inserted into the cylinder 210.

The cylinder 210 comprises a valve seat portion 213 as a separate member in the form of a hollow cylinder fixed to the inside of the cylinder 210, a large pipe portion 214 having a larger passage cross-section than that of the valve seat portion 213 and communicating with the downstream side of the valve seat portion 213, and a guide pipe portion 215 having a smaller passage cross-section than that of the large pipe portion 214 and communicating with the downstream side of the large pipe portion 214.

The valve seat portion 213 has one end opening in the upstream direction, and is formed with a valve seat 212 at the other end thereof, for having the valve element 220 seated thereon.

When the expansion device 201 is disposed within the piping 50, the large pipe portion 214 and the guide pipe portion 215 define a refrigerant passage that allows passage of refrigerant, between these portions 214 and 215 and the piping 50.

As shown in FIG. 5C, the large pipe portion 214 has a valve portion 222, referred to hereinafter, of the valve element 220 inserted therein, and a pair of communication holes 214a formed through upper and lower portions of the side wall thereof, as viewed in the figure, for communication of the inside thereof with the above-mentioned refrigerant passage, and defines a space portion 241 communicating with the communication holes 214a, between itself and the valve element 220.

The guide pipe portion 215 has a guided portion 233, referred to hereinafter, of the valve element 220 inserted therein such that the guided portion 233 is slidably held thereby, and an orifice hole 215a (restriction mechanism), as a restriction, formed through a central portion of the downstream end thereof.

On the other hand, the valve element 220 has a body 221 in the form of a hollow cylinder inserted in the cylinder 201. The body 221 has the valve portion 222 formed at an upstream end thereof, for being removably seated on the valve seat 212, and the guided portion 223 formed on the downstream side of the valve portion 222, for being guided along the inner peripheral surface of the guide pipe portion 215. Further, a refrigerant passage 224 axially extends through the inside of the body 221 to allow passage of refrigerant.

The valve portion 222 is formed to have a tapered shape such that an outer diameter thereof is progressively reduced toward the upstream end of the body 221. When the valve portion 222 is seated on the valve seat 212, the foremost end of the valve portion 222 is inserted into the small pipe portion 213 by a predetermined amount.

The guided portion 223 is formed by a reduced-diameter portion of the body 221, and inserted into the guide pipe portion 215. The guided portion 223 is slid along the inner surface of the guide pipe portion 215, whereby the valve element 20 can be driven forward and backward with respect to the valve seat 12. A spring 218 is interposed between the downstream end face of the guided portion 223 and the downstream end face of the guide pipe portion 215, for urging the valve element 220 toward the valve seat 212 (in the valve-closing direction) with a predetermined elastic force thereof.

The refrigerant passage 224 extends with the same cross-section from the upstream side to the downstream side, and allows passage of high-pressure refrigerant flowing in via the strainer 15. The refrigerant having passed therethrough is decompressed by passing through the orifice hole 215a.

The valve seat portion 213 is equipped with an adjusting mechanism, that is, the valve seat portion 213 has an outer periphery formed with an external thread, and an upstream end of the cylinder 210 is formed with an internal thread mating with the external thread. By adjusting the amount of screwing of the valve seat portion 213 into the cylinder 210, the position of the valve seat portion 213 is adjusted, whereby the elastic force of the spring 218 can be adjusted via the valve element 220.

Next, the pressure-cancelling structure of the expansion device 201 will be described.

As shown in FIG. 5A, in the expansion device 201, the valve portion 222 of the valve element 220 is formed with a valve-opening pressure-receiving surface 226 facing upstream for receiving refrigerant pressure which acts on the valve element 220 in the valve-opening direction. In addition, a downstream end face of the guided portion 223 of the valve element 20 is formed with a valve-closing pressure-receiving surface 227 for receiving refrigerant pressure which acts on the valve element 20 in the valve-closing direction. That is, refrigerant introduced into the guide pipe portion 215 via the guided portion 223 of the valve element 220 applies pressure to the valve element 220 in the valve-closing direction (rightward as viewed in FIG. 5A), to thereby cancel part of the refrigerant pressure acting on the valve element 220 in the valve-opening direction. In the present embodiment, the passage cross-section of the valve seat portion 213 is formed to be larger than that of the guide pipe portion 215, so that when the valve element 220 is seated on the valve seat 212, the valve-closing pressure-receiving surface 227 has a smaller pressure-receiving area than that of the valve-opening pressure-receiving surface 226. Therefore, the resultant of the pressure received at the valve-closing pressure-receiving surface 227 and the elastic force of the spring 218 acts against the refrigerant pressure received at the valve-opening pressure-receiving surface 226.

Next, the relief mechanism of the expansion device 201 will be described.

As shown in FIGS. 5A and 5B, in the expansion device 201, when the differential pressure across the expansion device 201 has become equal to or higher than a predetermined value to cause the valve portion 222 to be moved away the valve seat 212, most of refrigerant flowing in from the upstream side is allowed to escape through a gap between the valve portion 222 and the valve seat 212, and introduced into the refrigerant passage formed between the piping 50 and the cylinder 210 via the space portion 241 and the communication holes 214a, to flow downstream. This prevents an abnormal rise in the refrigerant pressure inside the expansion device 201 is prevented.

As described above, in the expansion device 201 according to the present embodiment, since the pressure-cancelling structure cancels part of the refrigerant pressure, a small-sized spring can be employed for the spring 218. As a result, it is possible to make the entire expansion device 201 compact in size.

Further, when the differential pressure across the expansion device 201 has become equal to or higher than the predetermined value, the refrigerant flowing in from the upstream side can be caused to escape into a flow passage other than the refrigerant passage 224 of the valve element 220, which makes it possible to prevent an abnormal rise in the refrigerant pressure inside the expansion device 201, to thereby prevent breakage or the like of the internal components.

Third Embodiment

Next, a third embodiment of the present invention will be described. FIGS. 6A to 6C are cross-sectional views of an expansion device according to the present embodiment, in which FIGS. 6A and 6B are longitudinal cross-sectional views of the expansion device, while FIG. 6C is a cross-sectional view taken on line D-D of FIG. 6A. It should be noted that components similar to those of the first embodiment will be designated by identical reference numerals, and description thereof is omitted.

As shown in FIG. 6A, the expansion device 301 comprises a cylinder in the form of a hollow cylinder 310, and a valve element 320 in the form of a hollow cylinder inserted in the cylinder 310.

The cylinder 310 includes a small pipe portion 313 slidably supporting a guided portion, referred to hereinafter, of the valve element 320, and a large pipe portion 314 that has a larger passage cross-section than that of the small pipe portion 313, and has a valve portion, referred to hereinafter, of the valve element 320 inserted therein. A valve seat 312 is formed by a stepped portion formed on a communicating portion between the small pipe portion 313 and the large pipe portion 314.

The small pipe portion 313 is, as shown in FIG. 6C, has a pair of introducing holes 313a formed through upper and lower portions of the side wall, as viewed in the figure, for having refrigerant introduced therein, with a closed upstream end of the small pipe portion 313 and a downstream end of the same communicating with the large pipe portion 314. The small pipe portion 313 is expanded by a predetermined amount toward the large pipe portion 314 to form an expanded pipe portion 313b in the vicinity of the valve seat 312. A strainer 315 is fitted on the small pipe portion 313 such that it covers the small pipe portion 313 from outside.

A stopper 317 in the form of a hollow cylinder is fixed to the large pipe portion 314 at a location in the vicinity of the downstream end thereof, and a spring 318 is inserted between the stopper 317 and the valve element 320, for urging the valve element 320 in the direction of the valve seat 312.

On the other hand, the valve element 320 has a body 321 in the form of a hollow cylinder. The body 321 has the guided portion 322 formed at an upstream end thereof, for sliding along the inner surface of the small pipe portion 313, and a valve portion 323 formed at a downstream end thereof, for being removably seated on the valve seat 312. Further, a refrigerant passage 324 axially extends through the inside of the body 321 to allow passage of refrigerant. Further, a space portion 341 communicating with the introducing holes 313a is defined between the valve element 320 and the small pipe portion 313, at the location of a pipe portion 325 between the guided portion 322 of the valve portion 323 of the valve element 320.

The pipe portion 325 has a side wall formed with an orifice hole 331 that communicates between the space portion 341 and the refrigerant passage 324, and functions a restriction mechanism, and when the valve element 320 is seated, the refrigerant flowing in from the piping 50 is introduced via the introducing holes 313a and the orifice hole 331 into the refrigerant passage 324. At the downstream end of the refrigerant passage 324, there is formed an expanded pipe portion 332 which is expanded by a predetermined amount for suppressing pressure loss of the refrigerant flowing through the refrigerant passage 324.

The stopper 317 is equipped with an adjusting mechanism, that is, the stopper 317 has an outer periphery formed with an external thread, and a downstream end of the cylinder 310 is formed with an internal thread mating with the external thread. By adjusting the amount of screwing of the stopper 317 into the cylinder 310, the position of the stopper 317 is adjusted, whereby the elastic force of the spring 318 can be adjusted.

Next, the pressure-cancelling structure of the expansion device 301 will be described.

As shown in FIG. 6A, in the expansion device 301, the valve portion 323 of the valve element 320 is formed with a valve-opening pressure-receiving surface 326 facing upstream for receiving refrigerant pressure which acts on the valve element 320 in a valve-opening direction. In addition, the downstream end of the guided portion 322 of the valve element 320 is formed with a valve-closing pressure-receiving surface 327 for receiving refrigerant pressure which acts on the valve element 320 in the valve-closing direction. That is, refrigerant introduced into the space portion 341 through the introducing hole 313a applies pressure to the valve-opening pressure-receiving surface 327 of the valve element 320 in the valve-closing direction (rightward as viewed in FIG. 6A), and to the valve-opening pressure-receiving surface 326 of the same in the valve-opening direction (leftward as viewed in FIG. 6A) to thereby cancel part of the refrigerant pressure acting on the valve element 320 in the valve-opening direction. In the present embodiment, since the expanded pipe portion 313b is provided, so that when the valve element 320 is seated on the valve seat 312, the valve-closing pressure-receiving surface 327 has a smaller pressure-receiving area than that of the valve-opening pressure-receiving surface 326. Therefore, the resultant of the pressure received at the valve-closing pressure-receiving surface 327 and the elastic force of the spring 318 acts against the refrigerant pressure received at the valve-opening pressure-receiving surface 326.

Next, the relief mechanism of the expansion device 301 will be described.

As shown in FIGS. 6A and 6B, in the expansion device 301, when the differential pressure across the expansion device 301 has become equal to or higher than a predetermined value to cause the valve portion 323 to be moved away the valve seat 312, most of refrigerant flowing in from the upstream side is allowed to escape through a refrigerant passage formed by a gap between the valve portion 323 and the valve seat 312, to flow downstream by being guided through the large pipe portion 314. This prevents an abnormal rise in the refrigerant pressure inside the expansion device 301.

As described above, in the expansion device 301 according to the present embodiment, since the pressure-cancelling structure cancels part of the refrigerant pressure, a small-sized spring can be employed for the spring 318. As a result, it is possible to make the entire expansion device 301 compact in size.

Further, when the differential pressure across the expansion device 301 has become equal to or higher than the predetermined value, the refrigerant flowing in from the upstream side can be caused to escape into a flow passage other than the refrigerant passage 324 of the valve element 320, which makes it possible to prevent an abnormal rise in the refrigerant pressure inside the expansion device 301, to thereby prevent breakage or the like of the internal components.

Fourth Embodiment

Next, a fourth embodiment of the present invention will be described. FIG. 7A to 7C are longitudinal cross-sectional views of an expansion device according to the present embodiment, and FIG. 8 is a cross-sectional view taken on line E-E of FIG. 7A. It should be noted that since most of the components of the expansion device according to the present embodiment are similar to those of the first embodiment, components similar to those of the first embodiment will be designated by identical reference numerals, and description thereof is omitted.

As shown in FIG. 7A, the expansion device 401 comprises a cylinder 10 in the form of a hollow cylinder, and a valve element 420 in the form of a hollow cylinder inserted in the cylinder 10.

The valve element 420 has a body 421 in the form of a stepped hollow cylinder inserted in the cylinder 10, and a valve portion 422 is formed at an upstream end of the body 421, for being removably seated on the valve seat 12, with a refrigerant passage 424 axially extending through the inside of the body 421 to allow passage of refrigerant.

The valve portion 422 has a tapered end the outer diameter of which decreases toward the upstream end of the body 421, and an extended portion that is extended from the tapered end by a predetermined amount, and is configured to be fitted in the small pipe portion 13 by the predetermined amount when the valve element 420 is seated. Further, as shown in FIG. 8, a slit 431 is formed through a side wall of an upstream end of the valve portion 422, which opens toward the small pipe portion 13.

Next, the pressure-cancelling structure of the expansion device 401 is distinguished from that of the first embodiment in that a valve-opening pressure-receiving surface 426 formed on the valve portion 422 of the valve element 420 in a manner facing upstream, for receiving refrigerant pressure acting on the valve element 420 in the valve-opening direction has a shape slightly different from that of the valve-opening pressure-receiving surface 26 of the first embodiment, but is the same in that the resultant of the pressure received at the valve-closing pressure-receiving surface 27 and the elastic force of the spring 18 acts against the refrigerant pressure received at the valve-opening pressure receiving surface 426.

Next, the relief mechanism of the expansion device 401 will be described.

As shown in FIGS. 7A to 7C, in the expansion device 401, when the differential pressure across the expansion device 401 has become equal to or higher than a predetermined value to cause the valve portion 422 to start to be moved away the valve seat 12, part of refrigerant flowing in from the upstream side is allowed to flow downstream through a refrigerant passage formed between the valve element 420 and the cylinder 10 via the slit 431.

Then, as the differential pressure further rises, the opening communicating between the small pipe portion 13 and the large pipe portion 14 is progressively increased due to the slit 431, and when the upstream end of the valve portion 420 is removed from the small pipe portion 13, the opening is sharply increased, whereby most of the refrigerant flowing in from the upstream side is allowed to escape into a flow passage other than the refrigerant passage 424 in the valve element 420, to allow the same to flow to the downstream side.

FIG. 9 is an explanatory view showing the relationship between the differential pressure across the expansion device 401 and the opening area of the refrigerant passage(s) thereof.

As shown in FIG. 9, so long as the valve element 420 is seated on the valve seat 12 (state shown in FIG. 7A), even if the differential pressure rises, the opening area is held at the cross-sectional area of the restriction of the inner shaft member 30. Then, when the differential pressure becomes higher than a predetermined value, the refrigerant is allowed to escape through the slit 431, which allows the opening area to be gently increased in response to changes in the differential pressure across the expansion device (state shown in FIG. 7B). Then, when the differential pressure further rises, the upstream end of the valve element 420 is removed from the small pipe portion 13, which instantly increases the opening area in response to a change in the differential pressure (state shown in FIG. 7C).

As described above, in the expansion device 401 according to the present embodiment, the refrigerant flowing in from the upstream side is allowed to escape in a stepwise manner. As a result, it is possible to prevent an abnormal rise in the refrigerant pressure inside the expansion device 401, to thereby prevent breakage or the like of the internal components. Further, by the stepwise relief, of the refrigerant pressure, the flow characteristics representative of the relationship between the differential pressure across the expansion device 401 and the opening area of the refrigerant passage thereof can be set differently from those of the first embodiment.

Fifth Embodiment

Next, a fifth embodiment of the present invention will be described. The present embodiment is an application of the configuration of the fourth embodiment to the configuration of the second embodiment. FIGS. 10A to 10C are longitudinal cross-sectional views of an expansion device according to the present embodiment. It should be noted that most of the configuration of the expansion device according to the present embodiment is similar to that of the second embodiment, and therefore description thereof is omitted by designating the similar components with identical reference numerals.

As shown in FIG. 10A, the expansion device 501 comprises a cylinder in the form of a hollow cylinder 210, and a valve element 520 in the form of a hollow cylinder inserted in the cylinder 210.

A valve portion 522 of the valve element 520 has a tapered end extended upstream by a predetermined amount such that the outer diameter thereof decreases toward the upstream end of a body 521, and is configured to be fitted in the valve seat portion 213 by the predetermined amount when the valve element 520 is seated. Further, a slit 531 is formed through a side wall of an upstream end of the valve portion 522, which opens toward the valve seat portion 213. It should be noted that the slit 531 shown in FIGS. 10A to 10C operate similarly to the slit 431 of the fourth embodiment, and therefore description thereof is omitted.

Thus, in the expansion device 501 according to the present embodiment as well, with the provision of the slit 531, the refrigerant flowing in from the upstream side is allowed to escape in a stepwise manner. As a result, the flow characteristics representative of relationship between the differential pressure across the expansion device 501 and the opening area of the refrigerant passage can be configured differently from those of the first embodiment.

Sixth Embodiment

Next, a sixth embodiment of the present invention will be described. In the present embodiment, the relief mechanism is provided in two stages. FIGS. 11A to 11C are longitudinal cross-sectional views of an expansion device according to the present embodiment. In FIGS. 12A to 12E, FIG. 12A is a longitudinal cross-sectional view of an inner cylinder, FIG. 12B a plan view of the same, FIG. 12C a cross-sectional view taken on line F-F of A, FIG. 12D a left side view, and further, FIG. 12E a right side view. It should be noted that components similar to those of the first embodiment will be designated by identical reference numerals, and description thereof is omitted.

As shown in FIG. 11A, the expansion device 601 comprises a cylinder 602 in the form of a hollow cylinder formed to be axially longer than the cylinder 10 of the first embodiment, a first relief mechanism 610 inserted in a upstream part of the cylinder 602, and a second relief mechanism 620 inserted in a downstream part of the same.

It should be noted that the first relief mechanism 610 is formed by a first valve element 20 which is removably seated on a first valve seat 12 formed by a stepped portion provided inside the cylinder 602, and hence is configured similarly to the relief mechanism of the first embodiment. Further, the first valve element 20 also has the pressure-cancelling structure as described in the first embodiment, and hence description of the relief mechanism and the pressure-cancelling structure will be omitted.

On the other hand, the second relief mechanism 620 comprises an inner cylinder 640 formed on the downstream side of the first relief mechanism 610 in a manner continuous therewith, and a second valve element 650 disposed within the inner cylinder 640.

The inner cylinder 640 has a body in the form of a hollow cylinder, as shown in FIGS. 12A to 12E, which has a stepped portion 641 with a reduced inner diameter formed at an upstream end thereof, and is configured such that the upstream end of the body can hold the downstream end of the inner shaft member 30. Further, a communication hole 644 is formed through the stepped portion 641, which communicates with the restriction of the inner shaft member 30.

Further, the upstream end of the inner cylinder 640 has a side wall formed with a pair of slits 642 which opens in the upstream direction, and the downstream end of the same with a slightly-increased outer diameter has an adjusting portion 643 constituting an adjusting mechanism, referred to hereinafter. The slits 642 communicate between a refrigerant passage formed between the inner cylinder 640 and the cylinder 602 and the inside of the inner cylinder 640, to allow passage of the refrigerant flowing through the refrigerant passage to thereby allow the refrigerant to flow downstream of the second valve element 650 of the inner cylinder 640.

Referring again to FIGS. 11A to 11C, the upstream end face of the inner cylinder 640 has a spring 18 in contact therewith which is interposed between the upstream end face of the inner cylinder 640 and the first valve element 20. That is, the adjusting portion 643 has an outer periphery formed with an external thread, and a downstream end of the cylinder 602 is formed with an internal thread mating with the external thread. By adjusting the amount of screwing of the inner cylinder 640 into the cylinder 602, the position of the inner cylinder 640 is adjusted, whereby the elastic force of the spring 18 can be adjusted. Further, the downstream end of the inner cylinder 640 has a stopper 617 in the form of a hollow cylinder fixed thereto, and a spring 618 (second elastic member) having a smaller elastic constant than that of the spring 18 is interposed between the stopper 617 and the second valve element 20.

On the other hand, the second valve element 650 has a body in the form of a hollow cylinder inserted in the inner cylinder 640, and includes a valve portion 651 and a guided portion 653 forming parts of the body. A second refrigerant passage 654 having a smaller cross-section than the passage cross-section of the restriction of the inner shaft member 30 extends trough the inside of the body.

The guided portion 653 has an outer diameter substantially equal to an inner diameter of the communication hole 644, and an upstream end of the guided portion 653 forms the valve portion 651. Further, on the downstream side of the guided portion 653, a flange 652 is formed which extends radially outward, and one end of the spring 618 is in abutment with the flange 652. A portion of the second valve element 650 on a further downstream side of the flange 652 has a tapered shape the outer diameter of which decreases downstream. The second valve element 650 moves to and away from the stepped portion 641 while being guided along the communication hole 644. The valve portion 651 is removably seated on the downstream end face of the inner shaft member 30 as a valve seat (second valve seat).

Further, the stopper 617 is equipped with an adjusting mechanism, that is, the stopper 617 has an outer periphery formed with an external thread, and a downstream end of the inner cylinder 640 is formed with an internal thread mating with the external thread. By adjusting the amount of screwing of the stopper 617 into the inner cylinder 640, the position of inner cylinder 640 is adjusted, whereby the elastic force of the spring 618 can be adjusted.

Next, the relief mechanism of the expansion device 601 will be described.

As shown in FIGS. 11A to 11C, in the expansion device 601, when the differential pressure across the expansion device 601 has become equal to or higher than a first predetermined value, the first relief mechanism 610 operates, and when the differential pressure has become equal to or higher than a second predetermined value, the second relief valve 620 operates. In the present embodiment, the first predetermined value is configured to be larger than the second predetermined value, and the amount of refrigerant allowed to escape by the first relief mechanism 610 is set to be larger than the amount of refrigerant allowed to escape by the second relief mechanism 620. Further, the second relief mechanism 620 on the downstream side is first operated to allow refrigerant to escape at a small flow rate, and thereafter, the first relief mechanism 610 on the upstream side is operated to allow the refrigerant to escape at a large flow rate.

That is, when the differential pressure across the expansion device 601 has become equal to or higher than the second predetermined value, as shown in FIGS. 11A and 11B, the upstream end face of the second valve element 650 of the second relief mechanism 620 is moved away from the downstream end face of the inner shaft member 30 to terminate the contact state therebetween, whereby part of refrigerant flowing through the restriction of the inner shaft member 30 into the communication hole 644 is allowed to escape through a gap between the downstream end face of the inner shaft member 30 and the upstream end face of the second valve element 650. The refrigerant flows via the slit 642 and the refrigerant passage between the inner cylinder 640 and the cylinder 602 (i.e. the other different passage than the second refrigerant passage 654) to the downstream side of the second valve element 650 of the inner cylinder 640.

Then, when the differential pressure across the expansion device 601 become equal to or higher than the first predetermined value to cause the valve portion 22 of the first relief mechanism 610 to be moved away from the valve seat 12, most of the refrigerant flowing in from the downstream side is allowed to escape via the gap between the valve portion 22 and the valve seat 12, and flow downstream via the refrigerant passage formed between the first valve element 20 and the cylinder 602, the refrigerant passage between the inner cylinder 640 and the cylinder 602, and the slit 642. This prevents an abnormal rise in the refrigerant pressure inside the expansion device 601.

As described above, in the expansion device 601 according to the present embodiment, the relief mechanism is provided in two stages, i.e. as the first relief mechanism 610 and the second relief mechanism 620, so that by shifting the timing of the relief of the refrigerant pressure, the refrigerant pressure inside the expansion device 601 can be reduced in two stages. Further, by differentiating the amount of relief between the two mechanisms, it is possible to carry out reduction control of the refrigerant pressure in various manners. Therefore, it is possible to realize delicate pressure reduction control such that the operations of the internal components of the expansion device 601 are not adversely affected, to thereby effectively prevent breakage or the like of the internal components.

Seventh Embodiment

Next, a seventh embodiment of the present invention will be described. In the present embodiment as well, the relief mechanism is provided in two stages. FIG. 13A to 13C are longitudinal cross-sectional views of an expansion device according to the present embodiment. FIG. 14 is a cross-sectional view taken on line G-G of FIG. 13A. It should be noted that components similar to those of the first embodiment will be designated by identical reference numerals, and description thereof is omitted.

As shown in FIG. 13A, the expansion device 701 comprises the hollow cylinder 702 formed to be axially longer than the cylinder 10 of the first embodiment, a first relief mechanism 710 inserted in a upstream part of the inside of the cylinder 702, and a second relief mechanism 720 inserted in a downstream part of the same.

It should be noted that the first relief mechanism 710 is formed by a first valve element 20 which is removably seated on a first valve seat 12 formed by a stepped portion provided inside the cylinder 702, and the second relief mechanism 720 is formed by a second valve element 20 which is removably seated on a second valve seat 752 formed by a downstream end of a stopper 750, referred to hereinafter, disposed within the cylinder 702. Both of the mechanisms are configured similarly to the relief mechanism of the first embodiment. However, the passage cross-section of the inner shaft member 730 of the second relief mechanism 720 is smaller than that of the inner shaft member 30 of the first relief mechanism 710 by a predetermined amount. It should be noted that in FIGS. 13A to 13C, the valve-opening pressure-receiving surface and the valve-closing pressure-receiving surface of the first valve element 20 on the upstream side form a first valve-opening pressure-receiving surface and a first valve-closing pressure-receiving surface, and the valve-opening pressure-receiving surface and the valve-closing pressure-receiving surface of the second valve element 20 on the downstream side form a second valve-opening pressure-receiving surface and a second valve-closing pressure-receiving surface.

Further, the first valve element 20 and the second valve element 20 each have the pressure-cancelling structure described in the first embodiment, and hence description of the mechanism and the structure will be omitted.

Between the first relief mechanism 710 and the second relief mechanism 720, the stopper 750 in the form of a bottomed hollow cylinder is interposed. At a location where the stopper 750 is in contact with the inner shaft member 30, there is formed a through hole 751 having a larger passage cross-section than that of the inner shaft member 30, thereby preventing the flow of refrigerant from being blocked even when the inner shaft member 30 is slightly radially displaced. Further, as shown in FIG. 14, part of the outer periphery of the stopper 750 is formed as a cutout portion 753 which is cut out parallel to the axis, thereby forming a refrigerant passage between the cutout 753 and the cylinder 702, which communicates between the upstream side and the downstream side of the stopper 750.

Further, the stopper 750 is equipped with an adjusting mechanism, that is, the stopper 750 has an outer periphery formed with an external thread, and an inner wall of the cylinder 702 is formed with an internal thread mating with the external thread. By adjusting the amount of screwing of the stopper 750 into the cylinder 702, the position of the stopper 750 is adjusted, whereby the elastic force of the spring 18 can be adjusted.

Next, the relief mechanism of the expansion device 701 will be described.

As shown in FIGS. 13A to 13C, in the expansion device 701, the spring constant of the spring 18 as a component of the first relief mechanism 710 and the spring constant of the spring 718 as a component of the second relief mechanism 720 are made different from each other, such that when the differential pressure across the expansion device 701 has become equal to or higher than a first predetermined value, the first relief mechanism 710 operates, and when the differential pressure has become equal to or higher than a second predetermined value, the second relief valve 720 operates. In the present embodiment, the first predetermined value is configured to be larger than the second predetermined value. Further, the second relief mechanism 720 on the downstream side is first operated to allow refrigerant to escape at a small flow rate, and thereafter, the first relief mechanism 710 on the upstream side is operated to allow the refrigerant to escape at a large flow rate.

That is, when the differential pressure across the expansion device 701 has become equal to or higher than the second predetermined value, as shown in FIGS. 13A and 13B, the valve portion 22 of the second relief mechanism 720 is moved away from the second valve seat 752, whereby part of the refrigerant flowing in from the upstream side via the inner shaft member 30 and the stopper 750 is allowed to escape through a gap between the valve portion 22 and the valve seat 752, and flow downstream via the refrigerant passage formed between the second valve element 20 and the cylinder 702.

Then, further when the differential pressure across the expansion device 701 become equal to or higher than the first predetermined value to cause the valve portion 22 of the first relief mechanism 710 to be moved away from the valve seat 12, most of the refrigerant flowing in from the upstream side is allowed to escape via the gap between the valve portion 22 and the valve seat 12, and flow downstream via the refrigerant passage formed between the first valve element 20 and the cylinder 702, the refrigerant passage between the cutout portion 753 and cylinder 702, and the refrigerant passage between the second valve element 20 and the cylinder 702. This prevents an abnormal rise in the refrigerant pressure inside the expansion device 701.

As described above, in the expansion device 701 according to the present embodiment, the relief mechanism is provided in two stages. Therefore, similarly to the sixth embodiment, it is possible to realize delicate pressure reduction control such that the operations of the internal components of the expansion device 701 are not adversely affected, to thereby effectively prevent breakage or the like of the internal components.

Eighth Embodiment

Next, an eighth embodiment of the present invention will be described. FIGS. 15A to 15C are longitudinal cross-sectional views of an expansion device according to the present embodiment. It should be noted that since most of the components of the expansion device according to the present embodiment are similar to those of the first embodiment, components similar to those of the first embodiment will be designated by identical reference numerals, and description thereof is omitted.

As shown in FIG. 15A, the expansion device 801 comprises a cylinder 10 in the form of a hollow cylinder, and a valve element 820 in the form of a hollow cylinder inserted in the cylinder 10.

The valve element 820 has a body 821 in the form of a stepped hollow cylinder inserted in the cylinder 10, and a valve portion 822 is formed at an upstream end of the body 821, for being removably seated on the valve seat 12, further with a refrigerant passage 824 axially extending through the body 821 to allow passage of refrigerant.

The valve element 822 is configured to have a tapered shape the outer diameter of which decreases toward the upstream end of the body 821, and when the valve element 820 is seated, the upstream end thereof is inserted into the small pipe portion 13 such that a predetermined gap is formed between the upstream end and the inner wall of the small pipe portion 13.

Next, the pressure-cancelling structure of the expansion device 801 is distinguished from that of the first embodiment in that a valve-opening pressure-receiving surface 826 formed on the valve portion 822 of the valve element 820 in a manner facing upstream, for receiving refrigerant pressure acting on the valve element 820 in the valve-opening direction has a shape slightly different from that of the valve-opening pressure-receiving surface 26 of the first embodiment, but is the same in that the resultant of the pressure received at the valve-closing pressure-receiving surface 27 and the elastic force of the spring 18 acts against the refrigerant pressure received at the valve-opening pressure receiving surface 826.

Next, the relief mechanism of the expansion device 801 will be described.

As shown in FIGS. 15A and 15C, in the expansion device 801, when the differential pressure across the expansion device 801 has become equal to or higher than a predetermined value to cause the valve portion 822 to start to be moved away the valve seat 12, part of refrigerant flowing in from the upstream side is leaked through the gap between the valve element 820 and the small pipe portion 13. Further, when the upstream end of the valve element 820 is moved away from the small pipe portion 13, the refrigerant is allowed to escape at a larger flow rate, whereby the refrigerant is allowed to escape into the other flow passage than the refrigerant passage 824 through the valve element 820 in a stepwise increasing manner, to thereby allow the refrigerant to flow downstream.

FIG. 16 is an explanatory view showing the relationship between the differential pressure across the expansion device 801 and the opening area of the refrigerant passage(s) thereof.

As shown in FIG. 16, so long as the valve element 820 is seated on the valve seat 12 (state shown in FIG. 15A), even if the differential pressure rises, the opening area is held at the cross-sectional area of the refrigerant passage 824. Then, when the differential pressure becomes higher than a predetermined value, the aforementioned gap provides an opening, which once increases the opening area (state shown in FIG. 15B). Thereafter, as the gap continues to provide a fixed opening area, the differential pressure across the expansion device 801 further rises, which causes the upstream end of the valve element 820 to be moved away from the small pipe portion 13, which instantly increases the opening area in response to a change in the differential pressure across the expansion device 801 (state shown in FIG. 15C).

As described above, in the expansion device 801 according to the present embodiment, the refrigerant flowing in from the upstream side is allowed to escape in a stepwise manner. As a result, it is possible to prevent an abnormal rise in the refrigerant pressure inside the expansion device 801, to thereby prevent breakage or the like of the internal components. Further, by the stepwise relief of the refrigerant pressure, the flow characteristics representative of the differential pressure and the opening area of the refrigerant passage by the expansion device 801 can be set differently from those of the first embodiment.

It should be noted that such flow characteristics can be also realized in the sixth and seventh embodiments described above.

Ninth Embodiment

Next, a ninth embodiment of the present invention will be described. FIGS. 17A to 17C are longitudinal cross-sectional views of an expansion device according to the present embodiment, and FIG. 18 is a cross-sectional view taken on line H-H of FIG. 17A. It should be noted that since most of the components of the expansion device according to the present embodiment are similar to those of the first embodiment, components similar to those of the first embodiment will be designated by identical reference numerals, and description thereof is omitted.

As shown in FIG. 17A, the expansion device 901 comprises a cylinder 10 in the form of a hollow cylinder, and a valve element 920 in the form of a hollow cylinder inserted in the cylinder 10.

The valve element 920 includes a body 921 in the form of a stepped hollow cylinder inserted in the cylinder 10, and a valve portion 922 is formed at an upstream end of the body 921, for being removably seated on the valve seat 12, with a refrigerant passage 924 axially extending through the body 921 to allow passage of refrigerant.

The refrigerant passage 924 has a stepped portion 925 which is expanded from the upstream side to the downstream side, and into the expanded side of the stepped portion 925 there is inserted an inner shaft member 930 which functions as a restriction mechanism. In the present embodiment, the stepped portion 925 is disposed at a location downstream of the guided portion 23, and the inner shaft member 930 is formed to be axially shorter than the inner shaft member 30 of the first embodiment.

Further, as shown in FIG. 18, a portion of a side wall slightly downstream of the stepped portion 925 of the valve element 920 is formed with a communication hole 941 communication between the inside and outside of the restriction passage 924.

Next, the pressure-cancelling structure of the expansion device 901 is the same as that of the first embodiment in that the resultant of the pressure received at the valve-closing pressure-receiving surface 927 of the stepped portion 925 and the elastic force of the spring 18 acts against the refrigerant pressure received at the valve-opening pressure receiving surface 26.

Next, the relief mechanism of the expansion device 901 will be described.

As shown in FIGS. 17A and 17C, in the expansion device 901, when the valve element 920 is seated, the communication hole 941 is opened, which allows part of the refrigerant flowing through the refrigerant passage 924 to escape into another flow passage, and when the differential pressure across the expansion device 901 has become equal to or higher than a predetermined value to cause the valve portion 922 to start to be moved away the valve seat 12, the upstream end of the inner shaft member 930 closes the communication hole 941. Then, as soon as the upstream end of the valve element 920 is removed from the small pipe portion 13, most of the refrigerant flowing in from the upstream side is allowed to escape through a gap between the valve portion 922 and the valve seat 12, and flow downstream via the refrigerant passage formed between the valve element 920 and the cylinder 10 and the plurality of slots 17b of the stopper 17. This prevents an abnormal rise in the refrigerant pressure inside the expansion device 901.

FIG. 19 is an explanatory view explanatory view showing the relationship between the differential pressure across the expansion device 901 and the opening area of the refrigerant passage(s) thereof.

As shown in FIG. 19, so long as the valve element 920 is seated on the valve seat 12 (state shown in FIG. 17A), even if the differential pressure rises, the opening area is held at the sum of the cross-sectional area of the refrigerant passage 924 and that of the communication hole 942. Then, when the differential pressure becomes higher than a predetermined value, the communication hole 941 starts to be closed, and therefore the cross-sectional area is once decreased (state shown in FIG. 17B). When the differential pressure further rises thereafter, the upstream end of the valve element 920 is removed from the small pipe portion 13, which instantly increases the opening area in response to a change in the differential pressure (state shown in FIG. 17C).

As described above, in the expansion device 901 according to the present embodiment, e.g. by once stopping the escape of the refrigerant flowing in from the upstream side to once decrease the opening area, the flow characteristics representative of relationship between the differential pressure of the expansion device 901 and the opening area of the refrigerant passage(s) thereof can be set differently from those of the first embodiment.

Further, the cooling performance of the expansion device 901 can be also enhanced e.g. by increasing the degree of supercooling (subcooling) by once decreasing the opening area to thereby temporarily decrease the flow rate of the refrigerant.

Tenth Embodiment

Next, a tenth embodiment of the present invention will be described. The present embodiment is an application of the configuration of the ninth embodiment to that of the second embodiment. FIGS. 20A to 20C are cross-sectional views of an expansion device according to the present embodiment, and FIG. 21 is a cross-sectional view taken on line I-I of FIG. 20A. It should be noted that since most of the components of the expansion device according to the present embodiment are similar to those of the second embodiment, components similar to those of the second embodiment will be designated by identical reference numerals, and description thereof is omitted.

As shown in FIG. 20A, the expansion device 1001 comprises a cylinder in the form of a hollow cylinder 210, and a valve element 1020 in the form of a hollow cylinder inserted in the cylinder 210.

As shown in FIG. 21 as well, a portion of the side wall of the valve element 1020 at a location opposed to the space portion 241 on the downstream side of the valve portion 222 is formed with a communication hole 1041 which communicates between the inside and the outside of the refrigerant passage 224.

Next, the relief mechanism of the expansion device 1001 will be described.

As shown in FIGS. 20A to 20C, in the expansion device 1001, when the valve element 1020 is seated, the communication hole 1041 is opened, which allows part of the refrigerant flowing through the refrigerant passage 224 to be introduced into the refrigerant passage formed between the piping 50 and the cylinder 210 via the space portion 241 and the communication holes 214a, to flow downstream. Then, when the differential pressure across the expansion device 1001 has become equal to or higher than a predetermined value to cause the valve portion 222 to start to be moved away the valve seat 212, the valve element 1020 is moved downstream, whereby the communication hole 1041 is closed by the guide pipe portion 215. Then, when the upstream end of the valve element 1020 is removed from the valve seat portion 213, most of the refrigerant flowing in from the upstream side is allowed to escape via a gap created between the valve portion 222 and the valve seat 212, to flow downstream. This prevents an abnormal rise in the refrigerant pressure inside the expansion device 1001.

As described above, in the expansion device 1001 according to the present embodiment, with the provision of the communication hole 1041, the refrigerant flowing in from the upstream side is allowed to escape in a stepwise manner. As a result, the flow characteristics representative of the relationship between the differential pressure across the expansion device 1001 and the opening area of the refrigerant passage(s) of the same can be set differently from those of the second embodiment.

Further, the cooling performance of the expansion device 1001 can be also enhanced e.g. by increasing the degree of supercooling (subcooling) by once decreasing the opening area to thereby temporarily decrease the flow rate of the refrigerant.

Eleventh Embodiment

Next, an eleventh embodiment of the present invention will be described. The present embodiment is an application of the configuration of the ninth embodiment to a part of the configuration similar to the corresponding part of the seventh embodiment. FIGS. 22A to 22C are cross-sectional views of an expansion device according to the present embodiment, and FIG. 23 is a cross-sectional view taken on line J-J of FIG. 22A. It should be noted that components similar to those of the seventh embodiment will be designated by identical reference numerals, and description thereof is omitted.

As shown in FIG. 22A, the expansion device 1101 comprises a first relief mechanism 710 inserted in a upstream part of the cylinder 702, and a second relief mechanism 1220 inserted in a downstream part of the same.

The second relief mechanism 1220 comprises a second valve element 1120, and a stopper 750.

The second valve element 1120 has a body in the form of a stepped hollow cylinder. An upstream end of the body is reduced in a tapered manner, and from the forward end of the reduced portion axially extends a guided portion 1122, and a downstream end of the same is formed with a flange 1123 which extends radially outward. The guided portion 1122 is inserted in the stopper 750 in the form of a hollow cylinder such that it is slidably held therein, and a stepped portion 1125 formed inside the tapered portion. The cross-section of the downstream side of the stepped portion 1125 is larger than that of the passage cross-section of the stopper 750. Further, the outer surface of the tapered portion forms a valve portion 1121 which can be seated on the valve seat 752 on the downstream end of the stopper 750.

Further, as also shown in FIG. 23, a portion of the side wall of the guided portion 1122 in the vicinity of the tapered portion is formed with a communication hole 1141 that communicates between the inside and the outside of the refrigerant passage 1124. On the other hand, the downstream end of the valve element 1120 has a tapered shape the outer diameter of which decreases downstream, and is in abutment with the end face of the stopper 17. The refrigerant passage formed between the valve element 1120 and the cylinder 702 communicates with the slots 17b. A spring 1118 is interposed between the flange 1123 and the downstream end face of the stopper 750, for urging the second valve element 1120 in the downstream direction.

Next, the relief mechanism of the expansion device 1101 will be described.

As shown in FIGS. 22A to 22C, in the expansion device 1101, when the differential pressure across the expansion device 1101 is lower than the second predetermined value, the valve element 1120 is not seated, so that the communication hole 1141 is made open, to allow part of the refrigerant flowing through the refrigerant passage 1124 to be introduced into the refrigerant passage formed between the valve element 1120 and the cylinder 702 via the communication hole 1141, and flow downstream via the outside of the flange 1123 and the slots 17b. Then, when the differential pressure has become equal to or higher than the second predetermined value to cause the valve element 1121 to start to be moved toward the valve seat 752, the second valve element 1120 is moved upstream, so that the stopper 750 starts to close the communication hole 1141. When the valve element 1121 is seated on the valve seat 752, the communication hole 1141 is completely closed.

Further, when the differential pressure has become equal to or higher than the first predetermined value larger than the second predetermined value, the first relief mechanism 710 operates as described hereinabove. More specifically, the valve portion 22 of the valve element 20 is moved away from the valve seat 12, to allow most of refrigerant flowing in from the upstream side to escape through a gap between the valve portion 22 and the valve seat 12, and flow downstream through a refrigerant passage formed between the first valve element 20 and the cylinder 702, and refrigerant passages formed between the cutout portion 753 and the cylinder 702 and between the valve element 1120 of the second relief mechanism 1220 and the cylinder 702. This prevents an abnormal rise in the refrigerant pressure inside the expansion device 1101.

FIG. 24 is an explanatory view showing the relationship between the differential pressure across the expansion device 1101 and the opening area of the refrigerant passage(s) thereof.

As shown in FIG. 24, before the second valve element 1120 is seated on the valve seat 752, even if the differential pressure rises, the opening area is held at the sum of the cross-sectional area of the refrigerant passage 1124 and that of the communication hole 1141 (state shown in FIG. 22A). Then, when the differential pressure becomes higher than a second predetermined value, the communication hole 1141 starts to be closed to once decrease the area of the opening, and when the communication hole 1141 is completely closed, the opening area is held constant again (state shown in FIG. 22B). Thereafter, when the differential pressure across the expansion device 1101 further rises, the valve portion 22 of the first relief mechanism 710 is removed from the valve seat 12, which instantly increases the opening area in response to a change in the differential pressure across the expansion device 1101(state shown in FIG. 22C).

As described above, in the expansion device 1101 according to the present embodiment, with the provision of the communication hole 1141, the refrigerant flowing in from the upstream side is allowed to escape in a stepwise manner. As a result, the flow characteristics representative of the relationship between the differential pressure across the expansion device 1101 and the opening area of the refrigerant passage(s) of the same can be set differently from those of the seventh embodiment.

Further, it is possible to enhance the cooling performance of the expansion device 1101 as well by once decreasing the opening area to temporarily decrease the flow rate of refrigerant, to thereby enhance the supercooling degree.

Twelfth Embodiment

Next, a twelfth embodiment of the present invention will be described. FIGS. 25A and 25B are longitudinal cross-sectional views of an expansion device according to the present embodiment. FIGS. 26A and 26B are transverse cross-sectional views of the expansion device, in which FIG. 26A is a cross-sectional view taken on line K-K of FIG. 25A, and FIG. 26B is a cross-sectional view taken on line L-L of FIG. 25A. It should be noted that most of the configuration of the expansion device according to the present embodiment is similar to that of the first embodiment, and therefore description thereof is omitted by designating similar components with identical reference numerals.

As shown in FIG. 25A, in the expansion device 1201, an inner shaft member 1230 is configured as a solid member having a cylindrical shape, which has a downstream end thereof fixed to a stopper 1217, referred to hereinafter. As shown in FIG. 26A as well, the outer diameter of the inner shaft member 1230 is smaller than the inner diameter of a stepped portion 25 of the valve element 20 by a predetermined amount, whereby a gap 1225 is formed between the inner shaft member 1230 and the inner wall of the valve element 20. This gap 1225 communicates with the refrigerant passage 24 and functions as the restriction mechanism.

Further, the stopper 1217 has a shape similar to that of the stopper 17 of the first embodiment, but a pair of slots 1217a are provided in upper and lower halves of the bottom thereof as viewed in FIG. 26B, and a fixing portion 1217b having a circular shape is formed between the slots 1217a, for fixing one end of the inner shaft member 1230 thereto.

Next, the relief mechanism of the expansion device 1201 will be described.

As shown in FIGS. 25A and 25B, in the expansion device 1201, the valve element 20 is seated on the valve seat 12 when the differential pressure thereacross is lower than a predetermined value. Therefore, when the refrigerant flowing in from the upstream side is introduced into the refrigerant passage 24, it is decompressed as it passes through the gap 1225, and flows downstream via the slots 1217a.

Then, when the differential pressure across the expansion device 1201 has become equal to or larger than the predetermined value to cause the valve portion 22 to be moved away from the valve seat 12, most of the refrigerant flowing in from the upstream side is allowed to escape through the refrigerant passage formed between the valve element 20 and the cylinder 10 and flow downstream.

In the expansion device 1201 described above, the inner shaft member 1230 is fixed to the stopper 1217, which makes it possible to hold the gap 1225 substantially constant, thereby securing the repeatability of the refrigerant flow.

When the repeatability of the refrigerant flow does not matter, the inner shaft member 1230 need not be fixed to the stopper 1217.

Thirteenth Embodiment

Next, a thirteenth embodiment of the present invention will be described. FIGS. 27A to 27C are cross-sectional views of an expansion device according to the present embodiment. FIG. 27C is a cross-sectional view taken on line M-M of FIG. 27A. It should be noted that most of the configuration of the expansion device according to the present embodiment is similar to that of the eleventh embodiment, and therefore description thereof is omitted by designating similar components with identical reference numerals.

As shown in FIG. 27A, in the expansion device 1301, the valve element 1320 has a structure corresponding to the second valve element 1120 of the eleventh embodiment, but in this structure, the communication hole 1141 is not formed, and a guided portion 1122 is inserted into the small pipe portion 13 such that it is axially slidably supported therein. Further, the downstream end of the valve element 1320 forms a valve portion 1321, and is configured such that it can be seated on the upstream end face (valve seat) of a stopper 17 disposed on the downstream side. Further, a spring 1118 is interposed between a flange 1123 of the valve element 1320 and a stepped portion of the cylinder 1310, for urging the valve element 1320 in the downstream direction.

Further, as shown in FIG. 27C as well, on the downstream side of the valve element 1320, an inner shaft member 1330 in the form of a cylinder is inserted which has a cutout portion 1330a formed by cutting off a side portion along the axis thereof while leaving a downstream end uncut, whereby a refrigerant passage 1331 is formed between the cutout portion 1330a and the inner surface of the valve element 1320.

Next, the relief mechanism of the expansion device 1301 will be described.

As shown in FIGS. 27A and 27B, in the expansion device 1301, the valve element 1320 is seated on the upstream end face of the stopper 17 when the differential pressure thereacross is lower than a predetermined value. Therefore, when the refrigerant flowing in from the upstream side is introduced into the refrigerant passage 1124, it is decompressed by passing through the restriction extending through the inner shaft member 1330, and flows downstream via the through hole 17a.

Then, when the differential pressure across the expansion device 1301 has become equal to or larger than the predetermined value to cause the valve portion 1321 to be moved away from the stopper 17, the refrigerant passage 1331 is made open to the cylinder 1310, to thereby allow most of the refrigerant flowing in from the upstream side to escape downstream through the refrigerant passage 1331, between the inner shaft member 1330 and the cylinder 1310, and the slots 17b.

Fourteenth Embodiment

Next, a fourteenth embodiment of the present invention will be described. FIGS. 28A to 28C are cross-sectional views of an expansion device according to the present embodiment. FIG. 29 is a cross-sectional view taken on line N-N of FIG. 28A. It should be noted that most of the configuration of the expansion device according to the present embodiment is similar to that of the thirteenth embodiment, and therefore description thereof is omitted by designating similar components with identical reference numerals.

As shown in FIGS. 28A and 29, the expansion device 1401 includes an inner shaft member 1430 which is a modification of the inner shaft member 1330 in the thirteenth embodiment in which a groove 1430a having a predetermined width is formed in the inner shaft member 1330 at a location circumferentially shifted from the cutout portion 1330a, in side view. The groove 1430a extends further downstream with respect to the cutout portion 1330a by a predetermined amount, thereby forming a refrigerant passage 1432 having a smaller passage cross-section than that of the refrigerant passage 1331, between the groove 1430a and the inner surface of the valve element 1320.

Next, the relief mechanism of the expansion device 1401 will be described.

As shown in FIGS. 28A to 28C, in the expansion device 1401, when the differential pressure across the expansion device 1401 has become equal to or higher than a predetermined value to cause the valve portion 1321 to start to be moved away the stopper 17, first, the refrigerant passage 1432 is made open to the cylinder 1310 to thereby allow part of refrigerant flowing in from the upstream side to escape downstream through the refrigerant passage 1432, a flow passage formed between the inner shaft member 1430 and the cylinder 1310, the slots 17b. Then, when the differential pressure becomes still higher, the valve element 1320 is moved further upstream to open the refrigerant passage 1331, to thereby allow most of the refrigerant flowing in from the upstream side to escape downstream via the refrigerant passage 1331, the flow passage between the inner shaft 1430 and the cylinder 1310, and the slots 17b.

Fifteenth Embodiment

Next, a fifteenth embodiment of the present invention will be described. FIGS. 30A to 30C are longitudinal cross-sectional views of an expansion device according to the present embodiment. It should be noted that most of the configuration of the expansion device according to the present embodiment is similar to that of the thirteenth embodiment, and therefore description thereof is omitted by designating similar components with identical reference numerals.

As shown in FIG. 30A, a valve element 1520 of the expansion device 1501 has a guided portion 1442 as a modification of the side wall of the guided portion 1122, through which is formed a communication hole 1521 communicating between the inside and outside of the refrigerant passage 1124, at a location in the vicinity of the tapered portion on the upstream side of the valve element 1320 in the thirteenth embodiment.

Next, the relief mechanism of the expansion device 1501 will be described.

As shown in FIGS. 30A and 30C, in the expansion device 1501, when the differential pressure across the expansion device 1501 is lower than the second predetermined value, the communication hole 1521 is made open, to allow part of the refrigerant flowing through the refrigerant passage 1124 to be introduced into the refrigerant passage formed between the valve element 1520 and the cylinder 1310 via the communication hole 1521, and flow downstream via the outside of the flange 1123 and the slots 17b. Then, when the differential pressure has become equal to or higher than the second predetermined value, to cause the valve element 1520 to be moved upstream, the small pipe portion 13 closes the communication hole 1521.

Further, when the differential pressure has become equal to or higher than the first predetermined value larger than the second predetermined value, the valve element 1520 is moved further upstream whereby the refrigerant passage 1331 is made open, to thereby allow most of refrigerant flowing in from the upstream side to escape through the refrigerant passage 1331, a flow passage between the inner shaft member 1330 and the cylinder 1310, and the slots 17b.

Sixteenth Embodiment

Next, a sixteenth embodiment of the present invention will be described. FIGS. 31A and 31B are cross-sectional views of an expansion device according to the present embodiment. It should be noted that the expansion device according to the present embodiment has such a configuration as a combination of the twelfth embodiment and the thirteenth embodiment, and therefore description of components of the present embodiment similar to those of these embodiments is omitted while designating the similar components with identical reference numerals.

As shown in FIG. 31A, in the expansion device 1601, an inner shaft member 1630 is configured as a solid member in the form of a cylinder, which has a downstream end thereof fixed to a stopper 1217. The diameter of the inner shaft member 1630 is smaller than the inner diameter of the stepped portion 1125 of the valve element 1320 by a predetermined amount, whereby a gap 1625 is formed between the inner shaft member 1630 and the inner wall of the valve element 1320. This gap 1625 communicates with the refrigerant passage 1124 and functions as the restriction mechanism. Further, the inner shaft member 1630 is formed with a cutout portion 1630a which is formed by cutting off a portion thereof along the axis, while leaving a downstream end thereof uncut, whereby a flow passage 1631 is formed between the cutout portion 1630a and the inner surface of the valve element 1320.

Next, the relief mechanism of the expansion device 1601 will be described.

As shown in FIGS. 31A and 31B, in the expansion device 1601, when the differential pressure thereacross is lower than a predetermined value, the refrigerant flowing in from the upstream side is decompressed by passing through the gap 1625, and flows downstream via slots 1217a.

Then, when the differential pressure across the expansion device 1601 has become equal to or larger than the predetermined value to cause the valve portion 1321 to be moved away from the stopper 1217, most of the refrigerant flowing in from the upstream side is allowed to escape downstream through the refrigerant passage 1631, a flow passage between the inner shaft member 1630 and the cylinder 1310, and the slots 17b.

Seventeenth Embodiment

Next, a seventeenth embodiment of the present invention will be described. FIGS. 32A and 32B are longitudinal cross-sectional views of an expansion device according to the present embodiment. Further, FIGS. 33A and 33B are transverse cross-sectional views of the expansion device, in which FIG. 33A is a cross-sectional view taken on line O-O of FIG. 32A, and FIG. 33B is a view taken from a direction of P of FIG. 32A. It should be noted that components similar to those of the first embodiment will be designated by identical reference numerals, and description thereof is omitted.

The present embodiment realizes a configuration that enhances the accuracy of the pressure cancellation. More specifically, similarly to the first embodiment as shown in FIG. 2, in a configuration where the pressure-receiving surface of the valve portion 22 has a tapered shape, the effective pressure-receiving area of the valve element 20 tends to become smaller as the valve element 20 is moved away from the valve seat 12. As a result, actually, as designated by dotted line in FIG. 35, with a rise in the differential pressure, the rate of increase in the opening area is lowered to cause the balance of the pressure cancellation to be lost, or degrade the relieving operation. The expansion device 1701 according to the present embodiment solves the problem.

As shown in FIG. 32A, the expansion device 1701 comprises a cylinder 10 in the form of a hollow cylinder, and a valve element 1270 in the form of a hollow cylinder inserted in the cylinder 10. A large pipe portion 14 of the cylinder 10 has a stopper 1717 in the form of a disk fixed thereto at a location in the vicinity of the downstream end thereof, and a spring 18 is interposed between the stopper 1717 and the valve element 1720, for urging the valve element 1720 toward a valve seat 12 (in the valve-closing direction).

The valve element 1720 comprises a body in the form of a stepped hollow cylinder inserted in the cylinder 10, a valve portion 1721 in the form of a hollow cylinder which can be removably seated on the valve seat 12, and a guided portion 1722 in the form of a stepped hollow cylinder disposed on the downstream side of the valve portion 1721.

The upstream end of the valve portion 1721 is provided with a tapered portion the outer diameter of which decreases upstream, and when the valve portion 1721 is seated, the foremost end of the tapered portion 1721 is inserted into the small pipe portion 13 by a predetermined amount.

As shown in FIG. 33A, the guided portion 1722 comprises a body 1723 having a generally hexagonal cross-section, and a reduced pipe portion 1724 in the form of a hollow cylinder formed continuous with the downstream side of the body 1723. Each vertex portion of the body 1723 is configured to have an arcuate shape extending along the inner peripheral surface of the large pipe portion 14, and refrigerant passages are formed between the vertex portions, which allow passage of refrigerant. The valve element 1720 is stably moved forward and backward within the cylinder 10, with the vertex portions sliding along the inner surface of the large pipe portion 14. Further, the reduced pipe portion 1724 has one end of the spring 18 fitted thereon.

The upstream end of the body 1723 is slightly expanded, and the downstream end of the valve portion 1721 is press-fitted therein. Therefore, a space portion S1 is formed between the valve portion 1721 and the reduced pipe 1724 of the guided portion 1722. In this space portion S1, a shaft-like member 1730 in the form of a stepped cylinder, referred to hereinafter, is partially inserted.

The stopper 1717 is, as shown in FIG. 33B as well, formed with a screw hole 1717a extending through the center thereof. Around the screw hole 1717a, there are formed three elongated holes 1717b at equal intervals (of 120 degrees). The flow passage area as the sum of the these three elongated holes 1717b is sufficiently larger than that of the flow passage formed by a gap created between the valve portion 1721 and the valve seat 12, which prevents pressure loss of the refrigerant from occurring in the elongated holes 1717b. The stopper 1717 is equipped with an adjusting mechanism, that is, the stopper 1717 has an outer periphery formed with an external thread, and a downstream end of the cylinder 10 is formed with an internal thread mating with the external thread. By adjusting the amount of screwing of the stopper 1717 into the cylinder 10, the position of the stopper 1717 is adjusted, whereby the elastic force of the spring 18 can be adjusted. Further, through the screw hole 1717a of the stopper 1717, there is inserted a set screw 1740 (engaging member) with a slotted head or a hexagon socket by screwing, such that a foremost end thereof holds the downstream end face of the shaft-like member 1730. By adjusting the amount of screwing of the set screw 1740 with respect to the stopper 1717, the position of the set screw 1740 is adjusted, whereby the axial position of the shaft-like member 1730 within the cylinder 10 can be adjusted.

FIGS. 34A to 34C are explanatory views showing the configuration of the restriction mechanism according to the present embodiment, in which FIG. 34A is a partial expanded cross-sectional view showing the configuration of the vicinity of the valve element 1720, and FIGS. 34B and 34C show expanded views of Q portion in FIG. 34A.

As shown in 34A, the shaft-like member 1730 has an upstream end thereof formed with a tapered portion 1731 the cross-section of which increases upstream. A restriction passage is formed by a gap between the tapered surface of the tapered portion 1731 and an inner peripheral edge 1724a of the reduced pipe portion 1724. As shown in FIG. 34B, so long as the valve element 1720 is seated on the valve seat 12, the restriction passage holds the gap at a predetermined value c1 which realizes the passage cross-section of the normal restriction mechanism. Therefore, the refrigerant pressure is high on the upstream side of the gap, and low on the downstream side of the same. However, as shown FIG. 34C, when the valve element 1720 is moved away from the valve seat 12, the gap has become equal to a value c2 larger than the predetermined value c1, which makes it possible to allow the refrigerant to flow at a larger flow rate, but on the other hand, the function of the restriction mechanism is lowered. It should be noted that the size of the restriction passage in the closed state of the valve can be freely set by adjusting the position of the shaft-like member 1730 using the adjusting mechanism described above.

Further, the upstream end face of the shaft-like member 1730 is formed with a groove 1732 extending diametrically therethrough, as shown in FIG. 33A, and the remaining portion of the end face is capable of holding the valve portion 1721, and hence the valve element 1720 from the downstream side. Further, since the groove 1732 communicates with the refrigerant passage extending through the valve portion 1721, even when the valve portion 1721 is engaged with the shaft-like member 1730, the refrigerant can be allowed to flow through the communication passage formed by the groove 1732, the space portion S1, and the reduced pipe portion 1724.

Next, the pressure-cancelling structure of the expansion device 1701 will be described.

In the expansion device 1701, as shown in FIG. 34B, to receive the high-pressure refrigerant introduced from the upstream side into the refrigerant passage in the small pipe portion 13, a valve-opening pressure-receiving surface is formed by a portion 1751 of the upstream end face of the valve portion 1721, which is inserted into the small pipe portion 13, and an upstream end face 1752 of the reduced pipe portion 1724 of the guided portion 1722, and a valve-closing pressure-receiving surface is formed by the downstream end face 1753 of the valve portion 1721. Further, the inner diameter of the reduced pipe portion 1724 is made smaller than that of the small pipe portion 13 (see dotted lines in FIG. 34B) such that the pressure-receiving area of the entire valve-opening pressure-receiving surface becomes larger than the pressure-receiving area of the entire valve-closing pressure-receiving surface. That is, the refrigerant introduced into the space SI within the valve element 1720 acts to urge the valve element 1720 in the valve-closing direction (rightward as viewed in FIG. 34A) to thereby cancel part of the refrigerant pressure acting on the valve element 1720 in the valve-opening direction. Therefore, the resultant of the pressure received at the valve-closing pressure-receiving surface and the elastic force of the spring 18 acts against the refrigerant pressure received at the valve-opening pressure-receiving surface.

Next, the relief mechanism of the expansion device 1701 will be described.

As shown in FIGS. 32A and 32B, in the expansion device 1701, when the differential pressure across the expansion device 1701 has become equal to or higher than a predetermined value to cause the valve portion 1721 to be moved away the valve seat 12, most of refrigerant flowing in from the upstream side is allowed to escape through a gap between the valve portion 1721 and the valve seat 12, and flow downstream through a refrigerant passage formed between the valve element 1720 and the cylinder 10 and the elongated holes 1717b of the stopper 1717. This prevents an abnormal rise in the refrigerant pressure inside the expansion device 1701.

FIG. 35 is an explanatory view showing the relationship between the differential pressure across the expansion device 1701 and the opening area of the refrigerant passage(s) thereof.

As shown in FIG. 35, so long as the valve element 1720 is seated on the valve seat 12 (state shown in FIG. 32A), even if the differential pressure rises, the opening area is held constant by being limited by the restriction passage. Then, when the differential pressure becomes higher than a predetermined value, the valve element 1720 is moved away from the valve seat 12 to allow the refrigerant to escape into the outside refrigerant passage to relieve the pressure. Thus, the opening area is instantly increased (state shown in FIG. 32B). In this case, it is possible to prevent or suppress the lowering in the rate of increase in the opening area which might occur as the differential pressure across the expansion device 1701 rises as shown by a dotted line in FIG. 35, whereby it is possible to prevent the characteristics of the expansion device from being changed due to lowering in the received pressure, as shown by a solid line, thereby enabling the refrigerant to escape such that the refrigerant pressure is sufficiently relieved.

It is presumed that this is because a change (decrease) in the effective pressure-receiving area of the valve element 1720 and a change (increase) in the effective pressure-receiving area of the reduced pipe portion 1724 are cancelled each other, which makes it possible to cancel variation in the received pressure caused by the lift of the valve element 1720.

As described above, in the expansion device 1701 U according to the present embodiment, since the pressure-cancelling structure cancels part of the refrigerant pressure, a small-sized spring can be employed for the spring 18. As a result, it is possible to make the entire expansion device 1701 compact in size.

Further, when the differential pressure across the expansion device 1701 has become equal to or higher than the predetermined value, the refrigerant flowing in from the upstream side can be allowed to escape into the other flow passage than the normal refrigerant passage extending by way of the restriction passage, which makes it possible to prevent an abnormal rise in the refrigerant pressure inside the expansion device 1701, to thereby prevent breakage or the like of the internal components.

Further, as described above, the passage cross-section of the restriction passage on the downstream side is increased according to the valve opening condition of the valve element 1720. This prevents variation in the characteristics caused by the decrease in the received pressure, maintains the balance of the pressure cancellation, and improves the relieving operation.

Although in the present embodiment, the inner diameter of the reduced pipe portion 1724 is smaller than that of the small pipe portion 13, this is not limitative, but these inner diameters may be made equal to each other. Even with this configuration, due to the configuration in which the passage cross-section of the restriction passage on the downstream side is increased, it is possible to expect the effects of maintaining the balance of the pressure cancellation and the like.

Further, there may be provided a guide means for stably holding the shaft-like member 1730 within the cylinder 10. For example, the shaft-like member 1730 may be formed with a plurality of guide portions which extend radially outward from the outer peripheral surface of an upstream end thereof, so as to be guided by the inner peripheral surface of the guided portion 1722 of the valve element 1720.

Eighteenth Embodiment

Next, an eighteenth embodiment of the present invention will be described. FIGS. 36A and 36B are longitudinal cross-sectional views of an expansion device according to the present embodiment. Further, FIGS. 37A and 37B are transverse cross-sectional views of the expansion device, in which FIG. 37A is a cross-sectional view taken on line R-R of FIG. 36A, and FIG. 37B is a view taken from a direction of S of FIG. 36A. It should be noted that components similar to those of the first embodiment will be designated by identical reference numerals, and description thereof is omitted.

As shown in FIG. 36A, the expansion device 1801 comprises a cylinder 10 in the form of a hollow cylinder, a valve element 1820 in the form of a hollow cylinder inserted in the cylinder 10, and a ball valve seat 1830 in the form of a ball supported within the cylinder 10. In the vicinity of the downstream end of the large pipe portion 14 of the cylinder 10, a stopper 1817 in the form of a bottomed hollow cylinder is secured, with the ball valve seat 1830 being interposed between the stopper 1817 and the valve element 1820. Further, a spring 18 is interposed between the downstream end face of the small pipe portion 13 and the valve element 1820, for urging the valve element 1820 toward the ball valve seat 1830 (in the valve-closing direction).

The valve element 1820 has a body in the form of a stepped hollow cylinder which is expanded downstream in two stages. A hollow cylindrical portion as a central part of the body forms a body portion 1821, with a reduced pipe portion 1822 formed on the upstream side of the body portion 1821 by reducing the diameter of a corresponding portion of the body, and a guide portion 1823 formed on the downstream side of the body portion 1821 by increasing the diameter of a corresponding portion of the body. Further, a valve portion 1824 in the form of a hollow cylinder is formed by a downstream end of the body portion 1821.

The reduced pipe portion 1822 has an outer diameter slightly smaller than that of the small pipe portion 13, and movably inserted in the small pipe portion 13. The gap between the reduced pipe portion 1822 and the small pipe portion 13 forms a restriction passage (restriction mechanism). The junction of the reduced pipe portion 1822 and the body portion 1821 has a tapered shape in which the outer diameter thereof decreases toward the upstream end of the body.

As shown in FIG. 37A, the guide portion 1823 has an approximately hexagonal cross-section, and vertex portions each have an arcuate shape extending along the inner peripheral surface of the large pipe portion 14, defining refrigerant passages therebetween which allow passage of refrigerant. The vertex portions of the guide portion 1823 are slid along the inner surface of the large pipe portion 14, whereby the valve portion 1820 can be stably moved forward and backward within the cylinder. Further, the inside of the guide portion 1823 has a tapered shape in which the cross-section thereof is increased downstream, and a downstream end face of the tapered portion facing downstream can receive the ball valve seat 1830 in a manner covering an upstream portion of the ball valve seat 1830. As shown in FIG. 36A, when the valve portion 1824 of the valve element 1820 is seated on the ball valve seat 1830, a predetermine gap is formed between the tapered portion and the ball valve seat 1830. At this time, the ball valve seat 1830 is supported by the upstream end face of the stopper 1817 and the valve portion 1824 in a manner sandwiched therebetween. The aforementioned spring 18 is fitted on the body portion 1821, and interposed between an upstream end face of the guide portion 1823 and a downstream end face of the small pipe portion 13.

As shown in FIG. 37B as well, the stopper 1817 is formed with three slots 1817a around the center thereof at equal intervals (of 120 degrees), which form refrigerant passages. The cross-sectional area of a flow passage as the sum of the these three slots 1817a is sufficiently larger than that of a flow passage formed by a gap created between the valve portion 1824 and the ball valve seat 1830, which prevents pressure loss of the refrigerant from occurring in the slots 1817a. The stopper 1817 is equipped with an adjusting mechanism, that is, the stopper 1817 has an outer periphery formed with an external thread, and a downstream end of the cylinder 10 is formed with an internal thread mating with the external thread. By adjusting the amount of screwing of the stopper 1817 into the cylinder 10, the position of the ball valve seat 1830 supporting on the upstream side is adjusted.

Next, the pressure-cancelling structure of the expansion device 1801 will be described,.

In the expansion device 1801, an upstream end face of the reduced pipe portion 1822 forms a valve-closing pressure-receiving surface, and a downstream facing surface of the tapered portion at the boundary of the reduced pipe portion 1822 and the body portion 1821 within the valve element 1820 forms a valve-opening pressure-receiving surface larger in pressure-receiving area than the valve-closing pressure-receiving surface. That is, the refrigerant introduced from the upstream side acts on the valve element 1820 in the valve-closing direction (leftward as viewed in FIG. 36B) to thereby cancel part of the refrigerant pressure acting on the valve element 1820 in the valve-opening direction. Therefore, the resultant of the pressure received at the valve-closing pressure-receiving surface and the elastic force of the spring 18 acts against the refrigerant pressure received at the valve-opening pressure-receiving surface.

Next, the relief mechanism of the expansion device 1801 will be described.

As shown in FIGS. 36A and 36B, in the expansion device 1801, when the differential pressure across the expansion device 1801 has become equal to or higher than a predetermined value to cause the valve portion 1824 to be moved away the ball valve seat 1830, most of refrigerant flowing in from the upstream side is allowed to escape through a gap between the valve portion 1824 and the ball valve seat 1830, and flow downstream through the slots 1817a of the stopper 1817. This prevents an abnormal rise in the refrigerant pressure inside the expansion device 1801.

In the expansion device 1801 as well, the relationship between the differential pressure thereacross and the opening area of the refrigerant passage(s) is approximately the same as that shown in FIG. 35.

That is, so long as the valve element 1820 is seated on the ball valve seat 1830 (state shown in FIG. 36A), even if the differential pressure rises, the opening area is held constant by being limited by the restriction passage formed by the gap between the reduced pipe portion 1822 and the small pipe portion 13. Then, when the differential pressure becomes higher than a predetermined value, the valve element 1820 is moved away from the ball valve seat 1830 to allow the refrigerant to escape into an inner refrigerant passage to relieve the refrigerant pressure. Thus, the opening area is instantly increased (state shown in FIG. 36B).

As described above, in the expansion device 1801 according to the present embodiment as well, since the pressure-cancelling structure cancels part of the refrigerant pressure, it is possible to make the entire expansion device 1801 compact in size.

Further, when the differential pressure across the expansion device 1801 has become equal to or higher than a predetermined value, the relief mechanism prevents an abnormal rise in the differential pressure, thereby making it possible to prevent breakage or the like of the internal components.

Further, as described above, since the decrease in the effective pressure-receiving area is small when the valve element 1820 is opened, but on the contrary, the surface thereof urged in the valve-opening direction is increased, so that it is possible to increase the accuracy of the pressure cancellation, and cause the relieving function to operate more rapidly. As a result, the differential pressure across the expansion device before the required maximum valve lift is reached can be small, so that the pressure load on the entire expansion device can be reduced to protect the same.

Nineteenth Embodiment

Next, a nineteenth embodiment of the present invention will be described. FIGS. 38A and 38B are longitudinal cross-sectional views of an expansion device according to the present embodiment. Further, FIGS. 39A and 39B are transverse cross-sectional views of the expansion device, in which FIG. 39A is a cross-sectional view taken on line T-T of FIG. 38A, and FIG. 39B is a cross-sectional view taken on line U-U of FIG. 38A. It should be noted that components similar to those of the first embodiment will be designated by identical reference numerals, as required, and description thereof is omitted.

As shown in FIG. 38A, the expansion device 1901 comprises a cylinder 10 in the form of a hollow cylinder, and a valve element 1920 in the form of a hollow cylinder inserted in the cylinder 10. In the vicinity of the downstream end of the large pipe portion 14 of the cylinder 10, a stopper 1917 in the form of a hollow cylinder is secured. Further, a spring 18 is interposed between the stopper 1917 and the valve element 1920, for urging the valve element 1920 toward the small pipe portion 13 (in the valve-closing direction).

Further, the downstream end of the small pipe portion. 13 of the cylinder 10 is provided with a guide pipe 1930 in the form of a bottomed hollow cylinder extending downstream from the downstream-side opening of the small pipe portion 13. The guide pipe 1930 has its downstream end closed, and as also shown in FIG. 39A, a side wall thereof in the vicinity of the downstream end thereof is formed with communication holes 1931 which communicate between the inside and outside of the guide pipe 1930. Further, the guide pipe 1930 has the valve element 1920 fitted thereon in a manner slidable thereon, and the downstream end of the guide pipe 1930 is formed with a tapered portion 1932 the cross-section of which decreases downstream. The tapered portion 1932 forms a valve seat.

The valve element 1920 comprises a valve portion 1921 having a body in the form of a stepped hollow cylinder inserted in the cylinder 10, and a guided portion 1922 which is guided by the guide pipe 1930 while sliding thereon, and can be held by the downstream facing surface of a stepped portion provided at a boundary between the small pipe portion 13 and the large pipe portion 14 of the cylinder 10, i.e. a downstream end face 1912 of the small pipe portion 13.

The guided portion 1922 has an upstream portion which has an inner diameter approximately equal to the outer diameter of the guide pipe 1930 and is slidable thereon, whereby the valve element 1920 can be stably moved forward and backward within the cylinder 10. A downstream portion of the guide pipe 1922 is slightly increased in inner diameter to thereby form a space portion S2. Further, as shown in FIG. 39B, a portion of the upstream end of the guided portion 1922 is formed with a slit 1922a communicating between the inside and outside of the guided portion 1922, whereby the high-pressure refrigerant leaked through a gap between the guided portion 1922 and the guide pipe 1930 can be allowed to flow downstream.

On the other hand, the valve portion 1921 has a reduced pipe portion 1924 extending downstream with a reduced size, and one end of the spring 18 is fitted on the reduced pipe portion 1924. An upstream end of the valve portion 1921 is slightly increased in inner diameter, and the downstream end of the guided portion 1922 is press-fitted in the upstream end of the valve portion 1921. Therefore, within the valve element 1920, there is formed a space portion S2 defined by the valve portion 1921, the guided portion 1922, and the guide pipe 1930. The space portion S2 communicates with the upstream side via the communication holes 1931.

Further, the tapered surface of the tapered portion 1932 of the guide pipe 1930 and an inner peripheral edge 1924a of the reduced pipe portion 1924 form a restriction passage. When the valve element 1920 is held on the downstream end face 1912 of the small pipe portion 13, the restriction passage holds the gap at a preset value realizing the passage cross-section of the normal restriction mechanism. However, when the valve element 1920 is moved away from the downstream end face 1912 to be fully open, the function of the restriction mechanism is actually terminated, but a new refrigerant passage is formed which is increased in flow passage area. That is, the other refrigerant passage than the refrigerant passage that is open in the closed state of the valve is made open in an integrating manner.

It should be noted that an adjusting mechanism, described hereinabove, may be provided between the valve portion 1921 and the guided portion 1922, for adjusting the positional relationship between the valve portion 1921 and the guided portion 1922, thereby making it possible to set the size of the restriction passage as desired.

The stopper 1917 is equipped with an adjusting mechanism, that is, the stopper 1917 has an outer periphery formed with an external thread, and a downstream end of the cylinder 10 is formed with an internal thread mating with the external thread. By adjusting the amount of screwing of the stopper 1917 into the cylinder 10, the position of the stopper 1917 is adjusted, whereby the elastic force of the spring 18 can be adjusted.

Next, the pressure-cancelling structure of the expansion device 1901 will be described,.

In the expansion device 1901, within the space portion S2, the downstream facing surface of the guided portion 1922 forms a valve-closing pressure-receiving surface, and on the other hand, the upstream end of the reduced pipe portion 1924 forms a valve-opening pressure-receiving surface which is larger in pressure-receiving area than the valve-closing pressure receiving surface. Further, the inner diameter of the reduced pipe portion 1924 is made smaller than that of the guided portion 1922 such that the pressure-receiving area of the valve-opening pressure-receiving surface becomes larger than that of the valve-closing pressure-receiving surface. That is, the refrigerant introduced into the space S2 acts on the valve element 1920 in the valve-closing direction (rightward as viewed in FIG. 38A) to thereby cancel part of the refrigerant pressure acting on the valve element 1920 in the valve-opening direction. Therefore, the resultant of the pressure received at the valve-closing pressure-receiving surface and the elastic force of the spring 18 acts against the refrigerant pressure received at the valve-opening pressure-receiving surface.

Next, the relief mechanism of the expansion device 1901 will be described.

As shown in FIGS. 38A and 38B, in the expansion device 1901, when the differential pressure across the expansion device 1901 has become equal to or higher than a predetermined value to cause the guided portion 1922 to be moved away the downstream end face 1912, the opening area of the gap between the reduced pipe portion 1924 and the guide pipe 1930 is increased against the urging force of the spring 19, whereby refrigerant flowing in from the upstream side is allowed to escape at an increased flow rate. This prevents an abnormal rise in the refrigerant pressure inside the expansion device 1901.

FIG. 40 is an explanatory view showing the relationship between the differential pressure across the expansion device 1901 and the opening area of the refrigerant passage(s) thereof.

As shown in FIG. 40, so long as the valve element 1920 is held on the downstream end face 1912 of the small pipe portion 13 (state shown in FIG. 38A), even if the differential pressure rises, the opening area is held constant by being limited by the restriction passage. Then, when the differential pressure becomes higher than a predetermined value, the valve element 1920 is moved away from the downstream end face 1912 to allow refrigerant to flow downstream at the increased flow rate. Thus, the opening area is instantly increased (state shown in FIG. 38B). In this case, as shown in FIG. 38B, the rate of increase in the opening area is larger than that of the seventeenth embodiment (FIG. 35).

As described above, in the expansion device 1901 as well, the pressure-cancelling structure and the relief mechanism function effectively, and therefore the same advantageous effects as provided by the first embodiment can be obtained.

Further, in the expansion device 1901 as well, similarly to the eighteenth embodiment, when the valve element 1920 is opened, there occurs no decrease in the effective pressure-receiving area, which enables the balance of the pressure cancellation to be maintained, and improves the relieving operation. Further, in relieving the refrigerant pressure, the refrigerant passage can be expanded instantly, which decreases the differential pressure across the expansion device required for setting the maximum valve lift. Therefore, the pressure load on the entire expansion device can be reduced to thereby protect the same.

Although the preferred embodiments of the present invention have been described heretofore, the present invention is by no means limited to any specific one of the above-described embodiments, but various modifications and alterations can be made thereto without departing the spirit and scope of the present invention.

For example, although in the above-described embodiments, the cylinder of each expansion device is directly fixed to the piping 50, by way of example, this is not limitative, but the expansion device may be provided with a casing or the like which accommodates the cylinder, and the casing or the like may be fixed to the piping.

Further, although in the above embodiments, at least one of the outer peripheral surface of the inner shaft member and the inner peripheral surface of the valve element inserted therein may be formed with at least one labyrinth groove.

It should be noted that internal components forming expansion devices may be formed e.g. of resin.

The present invention can be applied to any expansion device so long as it is disposed in a flow passage of refrigerant circulating through a refrigeration cycle.

According to the expansion device of the present invention, in the valve element, part of the refrigerant pressure is cancelled by the pressure-cancelling structure, which makes it possible to reduce the elastic force required of the elastic member that holds the valve element in a manner acting against the refrigerant pressure. As a result, it is possible to employ a small-sized elastic member, and thereby make the configuration of the entire expansion device compact in size.

Further, with the compact configuration, the relief mechanism makes it possible to prevent an abnormal rise in the refrigerant pressure inside the expansion device, to thereby prevent breakage or the like of the internal components.

Further, by providing the relief mechanism in two stages, i.e. as the first relief mechanism and the second relief mechanism, refrigerant pressure reduction control can be carried out in a more delicate manner.

The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents.

Claims

1. An expansion device that is disposed in a flow passage of refrigerant circulating through a refrigeration cycle, for passing the refrigerant introduced from an upstream side thereof through an internal refrigerant passage thereof to thereby cause decompression of the refrigerant and allow the decompressed refrigerant to flow downstream, and is equipped with a relief mechanism that is operable when a differential pressure across the expansion device has become equal to or higher than a predetermined value, to open a flow passage other than the refrigerant passage which is closed by a valve element urged by an elastic member disposed within the expansion device, to thereby allow at least part of the refrigerant flowing in from the upstream side to escape via the flow passage to flow downstream, the expansion device comprising: a pressure-cancelling structure that cancels part of pressure of the refrigerant acting on the valve element in a valve-opening direction.
2. An expansion device that is disposed in a flow passage of refrigerant circulating through a refrigeration cycle, comprising: a cylinder in the form of a hollow cylinder, the cylinder having a valve seat formed by a stepped portion provided inside the hollow cylinder; a valve element that has a body in the form of a hollow cylinder, the valve element being movably inserted within the cylinder, and including a valve portion that forms part of the body and can be removably seated on the valve seat, and a refrigerant passage extending through an inside of the body to allow passage of the refrigerant; a restriction mechanism that decompresses the refrigerant passing through the refrigerant passage; an elastic member that is disposed within the cylinders for urging the valve element in a valve-closing direction; a pressure-cancelling structure that cancels at least part of pressure of the refrigerant acting on the valve element in a valve-opening direction, the pressure-cancelling structure comprising a valve-closing pressure-receiving surface that receives pressure of the refrigerant acting on the valve element in the valve-closing direction and has a pressure-receiving area which is smaller than a pressure-receiving area of a valve-opening pressure-receiving surface that receives pressure of the refrigerant acting on the valve element in the valve-opening direction; and a relief mechanism that is operable when a differential pressure across the expansion device has become equal to or higher than a predetermined value to cause the valve portion to be moved away from the valve seat, to allow at least part of the refrigerant flowing in from an upstream side to escape into a flow passage other than the refrigerant passage extending through the cylinder.
3. The expansion device according to claim 2, wherein, the valve element includes a guided portion that is guided along an inner peripheral surface of the cylinder when the valve element is moved to and away from the valve seat.
4. The expansion device according to claim 2, wherein the cylinder is directly fixed to an inside of the piping of the refrigeration cycle.
5. The expansion device according to claim 3, comprising: a stepped portion in the refrigerant passage of the valve element at which the refrigerant passage is expanded in an upstream-to-downstream direction; an inner shaft member in the form of a hollow cylinder that has a flow-restricting portion formed therein, the flow-restricting portion having a cross-section smaller than a cross-section of the refrigerant passage, and is partially inserted into an expanded side of the stepped portion of the valve element, the inner shaft member protruding downstream from the valve element, and functioning as the restriction mechanism; and a stopper that is fixed to the cylinder, and configured to be capable of having a downstream end of the inner shaft member engaged thereat, the stopper being formed with a through hole having a cross-section larger than a cross-section of the flow-restricting portion, and wherein an internal space is formed between the inner shaft member and the stepped portion, and the stepped portion forms the valve-closing pressure-receiving surface.
6. The expansion device according to claim 5, wherein the stopper is formed with at least one second through hole other than the through hole, the second through hole communicating with the flow passage other than the refrigerant passage, and wherein a flow passage area of an entirety of the second through hole is larger than a flow passage area of a gap formed between the valve portion and the valve seat when the valve element is opened.
7. The expansion device according to claim 5, wherein the inner shaft member is supported by the valve element, but not fixed to any part of an internal structure of the cylinder.
8. The expansion device according to claim 5, wherein the cylinder includes a small pipe portion that communicates with the refrigerant passage when the valve element is seated on the valve seat, and a large pipe portion that has a passage cross-section larger than a passage cross-section of the small pipe portion, and is configured such that the stepped portion is formed by the small pipe portion and the large pipe portion, and wherein the pressure-cancelling structure is formed by making the passage cross-section of the small pipe portion larger than a cross-section of the expanded side of the stepped portion of the valve element.
9. The expansion device according to claim 5, wherein the guided portion comprises a plurality of protruding portions extending from the body toward an inner surface of the cylinder, the protruding portions defining therebetween refrigerant flow passages that allow passage of the refrigerant, and on the other hand, the stopper has at least one second through hole formed around the through hole, the second through hole communicating with the refrigerant flow passages, and wherein when the valve portion is moved away from the valve seat, the relief mechanism allows at least part of the refrigerant flowing in from the upstream side to flow downstream via a gap between the valve portion and the valve seat, the refrigerant flow passages, and the second through hole.
10. The expansion device according to claim 5, wherein the elastic member is interposed between the stopper and the valve element, the expansion device comprising an adjusting mechanism that adjusts a position of the stopper within the cylinder, and wherein an elastic force of the elastic member can be adjusted by adjusting the position of the stopper using the adjusting mechanism.
11. The expansion device according to claim. 3, wherein the cylinder comprises: a valve seat portion in the form of a hollow cylinder that is fixed to an inside of the cylinder as a separate member, with one end thereof opening in an upstream direction, and an opposite end thereof being formed with the valve seat, the valve seat portion communicating with the refrigerant passage when the valve element is seated thereon; a large pipe portion that has a passage cross-section larger than a passage cross-section of the valve seat portion, and has the valve portion inserted therein; and a guide pipe portion that has the guided portion inserted therein such that the guided portion is slidably supported therein, and has a flow-restricting portion formed at a downstream end thereof, the flow-restricting portion functioning as the restriction mechanism, and wherein the pressure-cancelling structure is formed by making the passage cross-section of the valve seat portion larger than a passage cross-section of the guide pipe portion.
12. The expansion device according to claim 11, wherein the guide pipe portion and the large pipe portion are configured to define a refrigerant flow passage that allows passage of the refrigerant, between the guide pipe portion and the large pipe portion, and the piping of the refrigeration cycle, and wherein the large pipe portion has a side wall formed with at least one communication hole for causing an inside thereof to communicate with the refrigerant flow passage, and wherein the relief mechanism allows at least part of the refrigerant flowing in from the upstream side to flow downstream via a gap between the valve portion and the valve seat, the communication hole, and the refrigerant flow passage.
13. The expansion device according to claim 11, comprising an adjusting mechanism that adjusts a position of the valve seat portion within the cylinder, and wherein an elastic force of the elastic member can be adjusted via the valve element by adjusting the position of the valve seat portion using the adjusting mechanism.
14. The expansion device according to claim 3, wherein the cylinder has an introducing hole formed through a side wall thereof, for allowing the refrigerant to be introduced therein, and includes a small pipe portion that slidably supports the guided portion, and a large pipe portion that has a passage cross-section larger than a passage cross-section of the small pipe portion, and has the valve portion inserted therein, and wherein at a pipe portion of the valve element between the guided portion and the valve portion, a space portion is formed between the valve element and the small pipe portion, for communicating with the introducing hole, and wherein the pipe portion has an orifice hole formed through a side wall thereof, the orifice hole communicating between the space portion and the refrigerant passage, and functioning as the restriction mechanism, and wherein when the valve element is seated, the refrigerant flowing in via the piping of the refrigeration cycle is introduced into the refrigerant passage via the introducing hole and the orifice hole, and wherein the pressure-canceling structure is formed by forming an expanded pipe portion in the small pipe portion, at a location in the vicinity of the valve seat.
15. The expansion device according to claim 14, wherein the relief mechanism is operable when the valve portion is moved away from the valve seat, to allow at least part of the refrigerant flowing in from the upstream side to flow downstream via the space portion, and a gap between the valve portion and the valve seat.
16. The expansion device: according to claim 14, comprising: a stopper in the form of a hollow cylinder that is fixed to the cylinder, the elastic member being interposed between the stopper and the valve element; an adjusting mechanism that adjusts a position of the stopper within the cylinder, and wherein an elastic force of the elastic member can be adjusted by adjusting the position of the stopper using the adjusting mechanism.
17. The expansion device according to claim 2, wherein the cylinder comprises a small pipe portion that communicates with the refrigerant passage when the valve element is seated on the valve seat, and a large pipe portion that has a passage cross-section larger than a passage cross-section of the small pipe portion, and has the valve element inserted therein, the small pipe portion and the large pipe portion forming the stepped portion, and wherein, an upstream end of the valve element is configured such that the upstream end is fitted into the small pipe portion by a predetermined amount when the valve element is seated, and the upstream end has a side wall formed with at least one slit opening toward the small pipe portion, and wherein the relief mechanism is configured such that when the valve portion is moved away from the valve seat, the slit progressively increases an opening that communicates between the small pipe portion and the large pipe portion, and when the upstream end of the valve element is removed from the small pipe portion, the opening is rapidly increased, thereby allowing at least part of the refrigerant flowing in from the upstream side to stepwise escape into the flow passage other than the refrigerant passage extending through the cylinder to thereby allow the refrigerant to flow downstream.
18. The expansion device according to claim 17, comprising: a stopper in the form of a hollow cylinder that is fixed to the cylinders, the elastic member being interposed between the stopper and the valve element; an adjusting mechanism that adjusts a position of the stopper within the cylinder, and wherein an elastic force of the elastic member can be adjusted by adjusting the position of the stopper using the adjusting mechanism.
19. The expansion device according to claim 2, wherein the valve element having the pressure-cancelling structure, the elastic member urging the valve element, and the relief mechanism are provided in a plurality of stages, from the upstream side to a downstream side within the cylinder, and wherein the relief mechanisms are configured to stepwise operate by adjusting respective elastic forces of the elastic members urging the valve elements.
20. An expansion device that is disposed in a flow passage of refrigerant circulating through a refrigeration cycle, comprising: a cylinder in the form of a hollow cylinder, the cylinder having a first valve seat formed by a stepped portion provided inside the hollow cylinder; a first valve element that has a body in the form of a hollow cylinder inserted in the cylinder, and includes a valve portion that forms part of the body and can be removably seated on the first valve seat, a guided portion that is guided along an inner peripheral surface of the cylinder when the body is moved to and away from the first valve seat, and a first refrigerant passage that extends through an inside of the body and has a stepped portion formed therein at which the first refrigerant passage is expanded in an upstream-to-downstream direction, the first refrigerant passage allowing passage of the refrigerant; a first elastic member that is disposed within the, cylinder, for urging the first valve element in a valve-closing direction; a pressure-cancelling structure that cancels at least part of pressure of the refrigerant acting on the first valve element in a valve-opening direction, the pressure-cancelling structure, comprising a valve-closing pressure-receiving surface that receives pressure of the refrigerant acting on the first valve element in the valve-closing direction and has a pressure-receiving area smaller than a pressure-receiving area of a valve-opening pressure-receiving surface that receives pressure of the refrigerant acting on the first valve element in the valve-opening direction; a first relief mechanism that is operable when a differential, pressure across the expansion device has become equal to or higher than a first predetermined value to cause the valve portion to be moved away from the first valve seat, to allow at least part of the refrigerant flowing in from an upstream side to escape into a flow passage other than the first refrigerant passage within the cylinder to thereby allow the refrigerant to flow downstream; an inner shaft member in the form of a hollow cylinder that is formed therein with a flow-restricting portion having a cross-section smaller than a cross-section of the first refrigerant passage, and is partially inserted into an expanded side of the stepped portion of the first valve element, the inner shaft member protruding downstream from the first valve element; an inner cylinder in the form of a hollow cylinder that is fixed to an inside of the cylinder, and has at least one slit formed through a side wall of an upstream end thereof, the upstream end being capable of having a downstream end of the inner shaft member engaged thereat, the inner cylinder being formed with a communication hole extending therethrough for communication with the flow-restricting portion; a second valve element that has a body in the form of a hollow cylinder inserted in the inner cylinder, the second valve element including a valve portion that forms part of the body of the second valve element and can be removably seated on a second valve seat formed on a downstream end face of the inner shaft member, a guided portion that is guided along the communication hole when the body of the second valve element is moved to and away from the second valve seat, and a second refrigerant passage that extends through an inside of the body of the second valve element and has a cross-section smaller than the cross-section of the flow-restricting portion; a second elastic member that is disposed within the inner cylinder, for urging the second valve element in a valve-closing direction; and a second relief mechanism that is operable when the differential pressure across the expansion device has become equal to or higher than a second predetermined value smaller than the first predetermined value to cause the valve portion of the second valve element to be moved away from the second valve seat, to allow at least part of the refrigerant flowing in from the upstream side to escape into a flow passage other than the second refrigerant passage within the inner cylinder to thereby allow the refrigerant to flow downstream.
21. The expansion device according to claim 20, wherein an amount of refrigerant allowed to escape by the first relief mechanism is larger than an amount of refrigerant allowed to escape by the second relief mechanism.
22. The expansion device according to claim 20, wherein the first elastic member is interposed between the inner cylinder and the first valve element, the expansion device comprising an adjusting mechanism that adjusts a position of the inner cylinder within the cylinder, and wherein an elastic force of the first elastic member can be adjusted by adjusting the position of the inner cylinder using the adjusting mechanism.
23. The expansion device according to claim 20, comprising: a stopper in the form of a hollow cylinder that is fixed to the inner cylinder, the second elastic member being interposed between the stopper and the second valve element; and a second adjusting mechanism that adjusts a position of the stopper within the inner cylinder, and wherein an elastic force of the second elastic member can be adjusted by adjusting a position of the stopper using the second adjusting mechanism.
24. The expansion device according to claim 5, wherein the valve element having the pressure-cancelling structure, the elastic member urging the valve element, the relief mechanism, the inner shaft member, and the stopper are provided in two stages, from the upstream side to a downstream side within the cylinder, and wherein a valve seat is formed on a downstream end face of the stopper interposed between the two valve elements, for allowing a valve portion of the valve element on a downstream side to be seated thereon, wherein the elastic members are interposed between the stoppers and the valve elements, respectively, the expansion device comprising adjusting mechanisms that adjust respective positions of the stoppers within the cylinder, and wherein elastic forces of the elastic members can be adjusted by adjusting the positions of the stoppers using the adjusting mechanisms, respectively.
25. The expansion device according to claim 2, wherein, the cylinder includes a small pipe portion that communicates with the refrigerant passage when the valve element is seated on the valve seat, and a large pipe portion that has a passage cross-section larger than a passage cross-section of the small pipe portion, and has the valve element inserted therein, the stepped portion being formed by the small pipe portion and the large, pipe portion, and wherein when the valve element is seated, an upstream end of the valve element is inserted into the small pipe portion with a predetermined spacing from an inner wall of the small pipe potion, and wherein when the valve portion is moved away from the valve seat, until the upstream end of the valve element is removed from the small pipe portion, the relief mechanism allows part of the refrigerant flowing in from the upstream side to leak via the gap, and when the upstream end of the valve element has been removed from the small pipe portion, the relief mechanism allows the refrigerant to escape at a larger flow rate, whereby the refrigerant is allowed to stepwise escape into the flow passage other than the refrigerant passage through the cylinder to thereby allow the refrigerant to flow downstream.
26. The expansion device according to claim 25, comprising: a stopper in the form of a hollow cylinder that is fixed to the cylinder, the elastic member being interposed between the stopper and the valve element; an adjusting mechanism that adjusts a position of the stopper within the cylinder, and wherein an elastic force of the elastic member can be adjusted by adjusting the position of the stopper using the adjusting mechanism.
27. The expansion device according to claim 2, wherein the valve element has a side wall formed with at least one communication hole for communicating between an inside and an outside of the refrigerant passage, and wherein the relief mechanisms includes a flow passage-switching structure that switches between flow passages of the refrigerant by opening or closing the communication hole according to movement of the valve element.
28. The expansion device according to claim 27, wherein the cylinder includes a small pipe portion that communicates with the refrigerant passage when the valve element is seated on the valve seat, and a large pipe portion that has a passage cross-section larger than a passage cross-section of the small pipe portion, and has the valve element inserted therein, the stepped portion being formed by the small pipe portion and the large pipe portion, and wherein an upstream end of the valve element is inserted inside an inner wall of the small pipe portion by a predetermined amount when the valve element is seated, and wherein the relief mechanism opens the communication hole to allow the refrigerant to escape, when the valve element is seated, and the relief mechanism keeps the communication hole closed until the upstream end is removed from the small pipe portion, when the valve portion is moved away from the valve seat, and wherein when the upstream end of the valve element is moved away from the small pipe portion, at least part of the refrigerant flowing in from the upstream side is allowed to escape into the flow passage other than the refrigerant passage through the cylinder to flow downstream.
29. The expansion device according to claim 27, comprising: a stopper in the form of a hollow cylinder that is fixed to the cylinder, the elastic member being interposed between the stopper and the valve element; an adjusting mechanism that adjusts a position of the stopper within the cylinder, and wherein an elastic force of the elastic member can be adjusted by adjusting the position of the stopper using the adjusting mechanism.
30. The expansion device according to claim 5, wherein the valve element having the pressure-cancelling structure, the elastic member urging the valve element, and the relief mechanism, the inner shaft member, and the stopper are provided in a plurality of stages, from the upstream side to a downstream side within the cylinder, wherein on a downstream end face of one of the stoppers interposed between the valve elements, there is formed a valve seat for allowing the valve portion of one of the valve elements on a downstream side of the stopper to be seated thereon, wherein the elastic members are interposed between the stoppers and the valve elements, respectively, the expansion device comprising adjusting mechanisms that adjust positions of the stoppers within the cylinder, respectively, the relief mechanisms are configured to sequentially operates from the downstream side, in a stepwise manner, by adjusting elastic forces of the elastic members by adjusting the positions of the stoppers, using the adjusting mechanisms, respectively, and wherein the valve element on the downstream side has a side wall formed with at least one communication hole for communicating between an inside and an outside of the refrigerant passage, and wherein a flow passage-switching structure is provided which switches the flow passage of the refrigerant by opening or closing the communication hole according to the movement of the valve element formed with the communication hole.
31. The expansion device according to claim 30, wherein the flow passage-switching mechanism causes the communication hole to be once closed during a process of rise in the differential pressure across the expansion device.
32. An expansion device that is disposed in a flow passage of refrigerant circulating through a refrigeration cycle, comprising: a cylinder in the form of a hollow cylinder that has a valve seat formed therein; a valve element that has a body in the form of a hollow cylinder that is movably inserted in the cylinder and can define a refrigerant passage for allowing passage of refrigerant through the cylinder, the body having a portion forming a valve portion that can be moved to and away from the valve seat; a restriction mechanism that decompresses the refrigerant passing through the refrigerant passage; an elastic member that is disposed within the cylinder, for urging the valve element in a valve-closing direction; a pressure-cancelling structure that cancels part of pressure of the-refrigerant acting on the-valve element in a valve-opening direction, the pressure-cancelling structure comprising a valve-opening pressure-receiving surface that receives pressure of the refrigerant acting on the valve element in the valve-opening direction, and a valve-closing pressure-receiving surface that receives pressure of the refrigerant acting on the valve element in the valve-closing direction; and a relief mechanism that is operable when the differential pressure across the expansion device has become equal to or higher than a predetermined value to cause the valve portion to be moved away from the valve seat, to open a flow passage other than the refrigerant passage extending through the cylinder by way of the restriction mechanism, to thereby allow at least part of the refrigerant flowing in from the upstream side to escape into the flow passage other than the refrigerant passage to flow downstream.
33. The expansion device according to claim 32, wherein the valve seat is formed by a stepped portion formed inside the cylinder, and the valve-opening pressure-receiving surface and the valve-closing pressure-receiving surface of the valve element are both formed on an upstream side of the restriction mechanism, and wherein the restriction mechanism is formed by a gap between a reduced pipe portion provided downstream of the body of the valve element, and a shaft-like member partially inserted into the reduced pipe portion.
34. The expansion device according to claim 33, wherein the valve-opening pressure-receiving surface is formed also by an upstream end face of the reduced pipe portion, and a cross-sectional shape of the reduced pipe portion is configured such that a pressure-receiving area of an entirety of the valve-opening pressure-receiving surface becomes larger than a pressure-receiving area of an entirety of the valve-closing pressure-receiving surface.
35. The expansion device according to claim 33, wherein the restriction mechanism comprises a restriction flow passage formed by a gap between an inner peripheral end edge of the reduced pipe portion and an outer peripheral surface of the shaft-like member, and wherein a passage cross-section of the restriction flow passage is changed in an increasing direction, when the valve element operates in a valve-opening direction.
36. The expansion device: according to claim 35, wherein an upstream end of the shaft-like member is formed with a tapered portion a cross-section of which increases upstream, and the restriction flow passage is formed between a tapered surface of the tapered portion and an inner peripheral end edge of the reduced pipe portion.
37. The expansion device according to claim 36, comprising an engaging member that is supported within the cylinder, and has the shaft-like member engaged at a downstream end thereof; and an adjusting mechanism that adjusts a position of the engaging member within the cylinder, and wherein a passage cross-section of the restriction passage in a closed state of the valve element can be adjusted by adjusting a position of the shaft-like member by moving forward or backward the engaging member using the adjusting mechanism.
38. The expansion device according to claim 32, wherein the cylinder has a small pipe portion, and a large pipe portion, formed therein in an upstream-to-downstream order, by expanding an inside thereof toward the downstream side, and wherein the valve seat is supported within the large pipe portion, and wherein the valve element is formed with the valve portion in the form of a hollow cylinder at a location downstream of the body, and has a reduced pipe portion extended upstream of the body such that the reduced pipe portion is movably inserted into the small pipe portion, and wherein the restriction mechanism is formed by a gap between the reduced pipe portion of the valve element and the small pipe portion of the cylinder.
39. The expansion device according to claim 38, wherein the valve-closing pressure-receiving surface is formed by an upstream end face of the reduced pipe portion, and the valve-closing pressure-receiving surface having a pressure-receiving area larger than a pressure-receiving area of the valve-closing pressure-receiving surface is formed by a downstream facing surface of a stepped portion formed inside the body by the reduced pipe portion.
40. The expansion device according to claim 39, wherein a downstream facing surface having a cross-section larger than a cross-section of the valve portion is formed on a downstream side of the valve portion of the valve element, in a manner continuous therewith.
41. The expansion device according to claim 32, wherein the cylinder has a small pipe portion, and a large pipe portion, formed therein in an upstream-to-downstream order, by expanding an inside thereof in a upstream-to-downstream direction, and the expansion device including a guide pipe in the form of a bottomed hollow cylinder formed such that the guide pipe extends downstream from a downstream opening portion of the small pipe, with a downstream end thereof closed, and a communication hole formed through a side wall thereof in the vicinity of the downstream end, for communicating between an inside and an outside of the guide pipe, the guide pipe having the valve element slidably fitted thereon, and wherein the valve element has, on an upstream side thereof, a guided portion that is slidable along an outer peripheral surface of the guide pipe, and has a forward end face which can be engaged at a downstream facing surface of a stepped portion provided at a boundary between the small pipe portion and the large pipe portion, and the valve element is formed with a reduced pipe portion at a downstream end thereof, thereby defining a space portion for communicating with the communication hole, between the reduced pipe portion and the guided portion, and wherein in the space portion, the valve-closing pressure-receiving surface is formed by a downstream facing surface of the guided portion, and the valve-opening pressure-receiving surface larger in pressure-receiving area than the valve-closing pressure-receiving surface is formed by an upstream end face of the reduced pipe portion, and wherein when the valve element is close to the valve seat, a gap between the reduced pipe portion of the valve element and the guide pipe forms a restriction passage as the restriction mechanism, and wherein the relief mechanism expands an opening area of the gap between the reduced pipe portion and the guide pipe against an urging force of the elastic member, to thereby allow the refrigerant flowing in from the upstream side to escape downstream at a larger flow rate.
42. The expansion device according to claim 41, wherein a downstream end of the guide pipe is formed with a tapered portion a cross-section of which decreases downstream, and the restriction flow passage is formed between a tapered surface of the tapered portion and an inner peripheral end edge of the reduced pipe portion.

Priority Claims (2)

Number	Date	Country	Kind
2003-315493	Sep 2003	JP	national
2004-070947	Mar 2004	JP	national

Expansion device

Information

Publication Number

Date Filed

Date Published

Inventors

Original Assignees

CPC

US Classifications

International Classifications

Abstract

Description

Claims

Priority Claims (2)