Expansion device

CROSS-REFERENCE TO RELATED APPLICATIONS, IF ANY

This application claims priorities of Japanese Application No. 2004-335225 filed on Nov. 19, 2004, entitled “EXPANSION DEVICE”, No. 2004-375158 filed on Dec. 27, 2004, entitled “EXPANSION DEVICE”, No. 2005-045214 filed on Feb. 22, 2005, entitled “EXPANSION DEVICE” and No. 2005-178718 filed on Jun. 20, 2005, entitled “EXPANSION DEVICE”.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to an expansion device used in a refrigeration cycle for an automotive air-conditioner, and more particularly to an expansion device which is applicable to a refrigeration cycle using carbon dioxide. (CO₂) and is capable of efficiently operating the same.

(2) Description of the Related Art

As a refrigeration cycle for an automotive air-conditioner, there is known not only a refrigeration cycle that employs a receiver for separating refrigerant condensed by a condenser into a gas and a liquid and a thermostatic expansion valve for expanding liquid refrigerant obtained by the gas/liquid separation but also a refrigeration cycle that employs an orifice tube for throttling and expanding refrigerant condensed by a condenser and an accumulator for separating refrigerant evaporated by an evaporator into a gas and a liquid. The orifice tube is formed by a small-diameter tube, and hence it is simple in construction, low in manufacturing costs, and high in the degree of freedom for layout. However, as is distinct from the refrigeration cycle using the thermostatic expansion valve, the refrigeration cycle using the orifice tube causes the refrigerant to be throttled and expanded only by the small-diameter tube, and hence is not provided with the function of controlling the flow rate of refrigerant and is incapable of efficiently operating the refrigeration cycle in every situation.

In view of this, an expansion device has been proposed which is applied particularly to a refrigeration cycle using CO₂as refrigerant, and configured to be capable of changing a restriction passage cross-sectional area of an orifice for throttling refrigerant according to the pressure and temperature of refrigerant on a gas cooler outlet side, thereby making it possible to efficiently operate the refrigeration cycle (see e.g. Japanese Unexamined Patent Publication (Kokai) No. H09-264622 (FIG. 4)).

This expansion device proposed in Japanese Unexamined Patent Publication (Kokai) No. H09-264622 has a valve structure in which a hermetically sealed space which is partitioned by a displacement member (diaphragm) is provided on an upstream side of a valve hole, for detecting the pressure and temperature of refrigerant introduced from the gas cooler, and the valve hole is opened and closed by displacement of the displacement member from an upstream side. The hermetically sealed space is filled with refrigerant at a density within a range ranging from a saturated liquid density at a refrigerant temperature of 0° C. to a saturated liquid density at a critical point of the refrigerant. Thus, when the pressure of the introduced refrigerant is lower than pressure in the hermetically sealed space corresponding to the temperature of the refrigerant, the valve hole is closed, whereas when the pressure of the introduced refrigerant becomes higher than the pressure in the hermetically sealed space by predetermined pressure, the valve hole starts to open, and when the differential pressure between the pressure of the introduced refrigerant and the pressure in the hermetically sealed space becomes larger than the predetermined pressure, the valve hole opens at a valve lift dependent on the differential pressure. As a result, the pressure and temperature of refrigerant on the gas cooler outlet side can be controlled along an optimum control line determined by the temperature of the refrigerant on the gas cooler outlet side and pressure maximizing a coefficient of performance, this makes it possible to efficiently operate the refrigeration cycle using CO₂.

Further, in the case where the refrigerant is CO₂, it is filled in the hermetically sealed space at a liquid density within the above-described range, so that when the expansion device is left standing in the atmosphere at normal temperature, the pressure of the refrigerant in the hermetically sealed space becomes very high, causing the differential pressure between the pressure of the refrigerant in the hermetically sealed space and the atmospheric pressure to become so large a value of e.g. 7 to 8 MPa. Therefore, when the expansion device is in the state of a part not mounted, the displacement member forming the hermetically sealed space can be deformed or broken due to the large differential pressure. To cope with this inconvenience, another expansion device has been proposed which has a displacement member configured to be hard to be deformed or broken (see e.g. Japanese Unexamined Patent Publication (Kokai) No. H11-63740 (FIG. 2)).

In this expansion device proposed in Japanese Unexamined Patent Publication (Kokai) No. H11-63740, a bellows is used as the displacement member, and while making use of a characteristic of the bellows that it has durability against external pressure due to its structure, the hermetically sealed space is formed by the bellows and a housing arranged to enclose the bellows from outside, and is filled with refrigerant. A shaft portion for transmitting the displacement of the bellows to a valve element is inserted into the bellows, and hence even if high-pressure refrigerant is filled in the hermetically sealed space under an atmospheric pressure environment, the shaft prevents a corrugated portion of the bellows from being deformed inward by the differential pressure between the pressure of the refrigerant and the atmospheric pressure.

However, the conventional expansion devices are configured such that they include a hermetically sealed space sealed by a displacement member so as to sense the pressure and temperature of introduced refrigerant to vary the valve lift, and the hermetically sealed space is filled with refrigerant at very high pressure, and therefore if the expansion devices are left standing under normal temperature and normal pressure environments, there is a danger of rupture of the hermetically sealed space. This requires a high-level quality control, which increases the costs of the expansion devices.

SUMMARY OF THE INVENTION

The present invention has been made in view of these problems, and an object thereof is to provide a low-cost expansion device which dispenses with a high-pressure hermetically sealed space, and includes a restriction passage which is capable of changing a passage cross-sectional area thereof according to the pressure and temperature of introduced refrigerant.

To solve the above problem, the present invention provides an expansion device for throttling and expanding refrigerant circulating through a refrigeration cycle, comprising a differential pressure valve that operates in a valve opening direction as a differential pressure between a pressure on an upstream side to which the refrigerant is introduced and a pressure on a downstream side from which the refrigerant is delivered becomes larger, and a temperature-sensing section having a hermetically sealed container that can expand and contract in opening and closing directions of the differential pressure valve, the hermetically sealed container being filled with a solid or liquid material having a large coefficient of volumetric expansion, the temperature-sensing section causing the differential pressure valve to operate in a valve closing direction as a temperature of the refrigerant on the upstream side becomes higher.

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 a central longitudinal cross-sectional view of the construction of an expansion device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the temperature characteristics of a temperature-sensing section.

FIG. 3 is a central longitudinal cross-sectional view showing the expansion device according to the first embodiment, in an operating condition in which the pressure of refrigerant has become high.

FIG. 4 is a central longitudinal cross-sectional view showing the expansion device according to the first embodiment, in an operating condition in which the temperature of refrigerant has become low.

FIG. 5 is a diagram showing the relationship among the differential pressure across the expansion device according to the first embodiment, the temperature of refrigerant, and the passage cross-sectional area of a restriction passage.

FIG. 6 is a central longitudinal cross-sectional view of the construction of an expansion device according to a second embodiment of the present invention.

FIG. 7 is a central longitudinal cross-sectional view of the construction of an expansion device according to a third embodiment of the present invention.

FIG. 8 is a central longitudinal cross-sectional view of the construction of an expansion device according to a fourth embodiment of the present invention.

FIG. 9 is a central longitudinal cross-sectional view of the construction of an expansion device according to a fifth embodiment of the present invention.

FIG. 10 is a central longitudinal cross-sectional view of the construction of an expansion device according to a sixth embodiment of the present invention.

FIG. 11 is a central longitudinal cross-sectional view of the construction of an expansion device according to a seventh embodiment of the present invention.

FIG. 12 is a central longitudinal cross-sectional view of the construction of an expansion device according to an eighth embodiment of the present invention.

FIG. 13 is a central longitudinal cross-sectional view of the construction of an expansion device according to a ninth embodiment of the present invention.

FIG. 14 is a central longitudinal cross-sectional view of the construction of an expansion device according to a tenth embodiment of the present invention.

FIG. 15 is a central longitudinal cross-sectional view of the construction of an expansion device according to an eleventh embodiment of the present invention.

FIG. 16 is a system diagram showing a refrigeration cycle to which is applied the expansion device according to the present invention.

FIG. 17 is a cross-sectional view of essential elements of an expansion device according to the present invention which is mounted in an internal heat exchanger, by way of a first example.

FIG. 18 is a cross-sectional view of essential elements of the expansion device according to the present invention which is mounted in an internal heat exchanger, by way of a second example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described in detail based on an example in which it is applied to a refrigeration cycle using CO₂.

FIG. 1 is a central longitudinal cross-sectional view of the construction of an expansion device according to a first embodiment of the present invention, and FIG. 2 is a diagram showing the temperature characteristics of a temperature-sensing section.

The expansion device according to the first embodiment is disposed within a pipe 1 which is laid between a gas cooler and an evaporator of the refrigeration cycle, for circulating refrigerant. The expansion device includes a differential pressure valve 2 that has a valve lift thereof controlled according to the differential pressure across the expansion device, and a temperature-sensing section 3 that further controls the valve lift of the differential pressure valve 2 according to the inlet temperature of refrigerant. It should be noted that an upper portion of the pipe 1, as viewed in FIG. 1, corresponds to an upstream side into which refrigerant flows from the gas cooler, and a lower portion of the pipe 1, as viewed in FIG. 1, corresponds to a downstream side from which refrigerant flows out to the evaporator.

The differential pressure valve 2 has a body 4. A valve hole 5 is axially formed in an upper central portion of the body 4, and a valve element 6 in the form of a spool is disposed in the valve hole 5 in a manner movable axially back and forth. When a portion of the valve element 6, at which the outer diameter of the valve element 6 starts to be smaller, is located within the valve hole 5, a restriction passage through which refrigerant passes has a minimum restriction passage cross-sectional area. The downstream side of the valve hole 5 communicates with an outlet port 7 formed in the body 4. The valve element 6 is integrally formed with a piston 8 extending coaxially therewith. The piston 8 has a larger outer diameter than that of the valve element 6, and is axially slidably disposed within a cylinder 9 formed in the body 4. The cylinder 9 has a lower end, as viewed in FIG. 1, closed by a lid 10, to thereby form a pressure-adjusting chamber 11. The valve element 6 and the piston 8 are formed with a pressure passage 12 axially extending therethrough such that the pressure-adjusting chamber 11 communicates with the upstream side of the differential pressure valve 2 via the pressure passage 12 so as to introduce the inlet pressure of refrigerant into the pressure-adjusting chamber 11. Further, the pressure-adjusting chamber 11 has a spring 13 disposed therein for urging the piston 8 toward the upstream side.

The temperature-sensing section 3 is disposed on an upper end of the valve element 6. The temperature-sensing section 3 comprises a bellows 14 that can axially expand and contract, a sealing member 15 that seals an opening of the bellows 14, and a wax 16 filled in a container hermetically formed by the bellows 14 and the sealing member 15. As shown in FIG. 2, the wax 16 has a property that its volume expands with a rise in the temperature. More specifically, the wax 16 has the characteristics that when it is in a solid state at a low temperature, or when it is in a liquid state at a high temperature, it has a small coefficient of volumetric expansion with respect to the temperature, whereas when it is in a state of solid solution in which it is changed from a solid to a liquid, at an intermediate temperature, it has a large coefficient of volumetric expansion with respect to the temperature. Therefore, the temperature-sensing section 3 forms an actuator which controls the differential pressure valve 2 by sensing temperature within a range in which the wax 16 is in the state of solid solution where the wax 16 has a large coefficient of volumetric expansion. It should be noted that the range of temperatures which the temperature-sensing section 3 senses is determined by the composition of the wax 16.

Further, the temperature-sensing section 3 is fitted on the upper portion of the valve element 6 by the sealing member 15, and urged by a spring 17 in the direction of closing of the differential pressure valve 2. The spring 17 is brought into abutment with a cup-shaped member 18 that is mounted on an upper end of the body 4 in a manner such that an upper end of the cup-shaped member 18 covers the temperature-sensing section 3. The set load of the spring 17 is adjusted by the press-fitted amount of the body 4 press-fitted into an open end of the cup-shaped member 18. The cup-shaped member 18 has an opening formed in a part thereof, and the opening has a filter 19 provided thereon. It should be noted that the sealing member 15 has a cutout formed in a portion thereof where it is fitted on the valve element 6 such that a space accommodating the temperature-sensing section 3 and the pressure passage 12 formed through the valve element 6 and the piston 8 communicate with each other.

In the expansion device constructed as above, high-temperature, high-pressure refrigerant having flowed out from the gas cooler flows into the expansion device from above, as viewed in FIG. 1, through the pipe 1. Then, the refrigerant flows through the expansion device such that it flows into the cup-shaped member 18 through the filter 19, and flows out from the outlet port 7 through the restriction passage between the valve hole 5 and the valve element 6 of the differential pressure valve 2. When passing through the restriction passage, the refrigerant is adiabatically expanded to be changed into low-pressure, low-temperature refrigerant in a gas-liquid two-phase state, and supplied to the evaporator. In the evaporator, the refrigerant in the gas-liquid two-phase state is evaporated by absorbing heat from air within a vehicle compartment, and when evaporated, it cools air in the vehicle compartment by depriving the air of latent heat of vaporization.

Next, a description will be given of the operation of the expansion device performed when the pressure and temperature of refrigerant introduced therein change.

FIG. 3 is a central longitudinal cross-sectional view showing the expansion device according to the first embodiment, in an operating condition in which the pressure of refrigerant has become high. FIG. 4 is a central longitudinal cross-sectional view showing the expansion device according to the first embodiment, in an operating condition in which the temperature of refrigerant has become low. FIG. 5 is a diagram showing the relationship among the differential pressure across the expansion device according to the first embodiment, the temperature of refrigerant, and the passage cross-sectional area of the restriction passage.

First, as shown in FIG. 5, the expansion device has the characteristics that in a region where the differential pressure across the expansion device is small, the restriction passage has a constant cross-sectional area determined by a clearance between the valve hole 5 and the valve element 6, and that when the differential pressure exceeds a predetermined value, the differential pressure valve 2 starts to open, thereby proportionally increasing the passage cross-sectional area of the restriction passage, and at the same time the predetermined value at which the differential pressure valve 2 starts to open becomes higher as the temperature of refrigerant becomes higher. Further, as shown in FIG. 2, the wax 16 has a small coefficient of volumetric expansion with respect to the rise in the temperature when it is in the solid or liquid state, and it has a very large coefficient of volumetric expansion when it is in the state of solid solution, so that in FIG. 5, the distance between temperature gradients is shown to be small when the wax 16 is in the solid or liquid state, and larger when the wax 16 is in the state of solid solution. In view of the above characteristics, the closed state of the expansion device, shown in FIG. 1, shows a case in which when the temperature of refrigerant introduced into the expansion device is e.g. 60° C., the differential pressure across the restriction valve is not higher than 8 MPa, by way of example. At this time, although the valve element 6 receives the inlet pressure of refrigerant in a valve closing direction, and the piston 8 receives the inlet pressure introduced into the pressure-adjusting chamber 11 via the pressure passage 12 in a valve opening direction, a force in the valve opening direction always acts on the valve element 6 due to the difference in pressure-receiving area between the valve element 6 and the piston 8, since the outer diameter of the piston 8 is set to be larger than that of the valve element 6. Therefore, the valve element 6 is stopped at a location where a force generated by the inlet pressure and acting in the valve opening direction, the load of the spring 17 acting in the valve closing direction, and the load of the spring 13 interposed in the pressure-adjusting chamber 11 and acting in the valve opening direction are balanced.

After that, from the state shown in FIG. 1, when the inlet pressure of refrigerant at the inlet of the expansion device becomes higher with no change in the inlet temperature of refrigerant, the force in the valve opening direction acting on the valve element 6 due to the difference in pressure-receiving area between the valve element 6 and the piston 8 is increased, so that the valve element 6 is moved in the valve opening direction against the urging force of the spring 17 urging the valve element 6 in the valve closing direction via the temperature-sensing section 3. When the inlet pressure of refrigerant increases until the differential pressure across the restriction passage reaches 8 MPa, the differential pressure valve 2 starts to open, and when the differential pressure exceeds 8 MPa, the passage cross-sectional area of the restriction passage is increased in proportion to the differential pressure, whereby the expansion device is placed in a state shown in FIG. 3. At this time, since the inlet temperature of refrigerant does not change, the wax 16 does not change in volume, and hence the temperature-sensing section 3 does not expand or contract in the axial direction.

Further, from the state shown in FIG. 1, when the inlet temperature of refrigerant becomes lower with no change in the inlet pressure of refrigerant introduced into the expansion device, the volume of the wax contracts, whereby the temperature-sensing section 3 is axially shortened. At this time, since the inlet pressure of refrigerant does not change, neither the force acting on the valve element 6 in the valve opening direction due to the difference in pressure-receiving area between the valve element 6 and the piston 8, nor the urging force of the spring 17 in the valve closing direction changes, so that the valve element 6 is moved in the valve opening direction by a distance corresponding to the axial contraction of the temperature-sensing section 3. As a result, the passage cross-sectional area of the restriction passage becomes larger, whereby the expansion device is placed in a state shown in FIG. 4.

Of course, in the expansion device, when the inlet pressure of refrigerant changes in a decreasing direction, or the inlet temperature of refrigerant changes in an increasing direction, the restriction passage is changed in a direction of decreasing the cross-sectional area.

FIG. 6 is a central longitudinal cross-sectional view of the construction of an expansion device according to a second embodiment of the present invention. It should be noted that component elements in FIG. 6 identical to those shown in FIG. 1 are designated by identical reference numerals, and detailed description thereof is omitted.

The expansion device according to the second embodiment is distinguished from the expansion device according to the first embodiment in that it has a shorter axial length. More specifically, in the expansion device according to the first embodiment, the valve element 6, the temperature-sensing section 3, and the spring 17 are arranged in series, which inevitably increases the axial length of the expansion device. In contrast, the expansion device according to the second embodiment is configured such that the urging force of the spring 17 is transmitted to the temperature-sensing section 3 via a cup-shaped spring-receiving portion 20. The cup-shaped spring-receiving portion 20 has a flange portion radially outwardly extending from the open end thereof such that the flange portion receives one end of the spring 17, whereby the temperature-sensing section 3 and the spring 17 are arranged in parallel with each other while being caused to operate in series, to thereby reduce the axial length of the expansion device, making the expansion device compact in size. With this construction, a position where the spring 17 applies the urging force to the temperature-sensing section 3 is closer to the valve element 6, and hence the temperature-sensing section 3 becomes insusceptible to an external force acting in a direction perpendicular to the axis of the expansion device. This prevents an upper end of the temperature-sensing section 3, as viewed in FIG. 6, from being swung, whereby the temperature-sensing section 3 can be stably disposed.

FIG. 7 is a central longitudinal cross-sectional view of the construction of an expansion device according to a third embodiment of the present invention. It should be noted that component elements appearing in FIG. 7, which have functions identical to or equivalent to those of the component elements appearing in FIG. 1, are designated by identical reference numerals, and detailed description thereof is omitted.

The expansion device according to the third embodiment is distinguished from the expansion devices according to the first and second embodiments in that the construction of the temperature-sensing section 3 is modified, and the degree of freedom of adjustment of the spring 17 is enhanced. More specifically, in the expansion device, the bellows 14 is disposed within a cup-shaped member 21, and open ends of the bellows 14 and the cup-shaped member 21 are sealed to each other. The wax 16 is filled between the bellows 14 and the cup-shaped member 21. In the expansion device, a bottom portion of the cup-shaped member 21 is fitted in a holder 23 rigidly fixed to an upstream-side opening of a hollow cylindrical housing 22 outside the cup-shaped member 21, and the spring 17 is interposed between the temperature-sensing section 3 and the valve element 6. The spring 17 is disposed between a disk 24 disposed on a bottom portion of the bellows 14 in contact therewith, and a spring-receiving member 25 having a lower end face, as viewed in FIG. 7, with which the valve element 6 is in abutment. The holder 23 is provided with an inlet port 26 for introducing refrigerant. The spring-receiving member 25 has a cutout formed in a portion thereof where the spring-receiving member 25 is brought into abutment with the valve element 6 such that the space accommodating the temperature-sensing section 3 communicates with the pressure-adjusting chamber 11 via the pressure passage 12 formed through the valve element 6 and the piston 8.

Further, the expansion device has a bias spring 27 interposed between a stepped portion formed on the hollow cylindrical housing 22 and the spring-receiving member 25. The bias spring 27 is configured to be disposed in parallel with the temperature-sensing section 3 and the spring 17 arranged in series with each other. As described above, the bias spring 27 which does not undergo a change by the temperature is disposed in parallel with the spring 17 which undergoes a change by the temperature. This makes it possible to set a combination of the spring constants of the springs 27 and 17, to thereby adjust changes in pressure caused by temperature. It should be noted that the set load of the spring 17 and the bias spring 27 is adjusted by the press-fitted amount of the body 4 press-fitted into a lower open end of the hollow cylindrical housing 22, as viewed in FIG. 7.

FIG. 8 is a central longitudinal cross-sectional view of the construction of an expansion device according to a fourth embodiment of the present invention. It should be noted that component elements appearing in FIG. 8, which have functions identical to or equivalent to those of the component elements appearing in FIG. 1, are designated by identical reference numerals, and detailed description thereof is omitted.

The expansion device according to the fourth embodiment is distinguished from the expansion devices according to the first to third embodiments in that the construction of the temperature-sensing section 3 is modified. More specifically, the temperature-sensing section 3 of the expansion device comprises a cup-shaped member 28, a diaphragm 29 rigidly fixed to an open flange portion of the cup-shaped member 28, and the wax 16 filled in a container hermetically sealed by the cup-shaped member 28 and the diaphragm 29. An upper surface of a displacement-transmitting member 30 fitted on the valve element 6 is in abutment with a central portion of the diaphragm 29. The spring 17 for urging the temperature-sensing section 3 in the valve closing direction is disposed between the open flange portion of the cup-shaped member 28 and the cup-shaped member 18 disposed in a manner covering the temperature-sensing section 3.

In the expansion device constructed as above, the operation of the differential pressure valve 2 responsive to changes in the inlet pressure of refrigerant is the same as those of the differential pressure valves 2 of the expansion devices according to the first to third embodiments. The wax 16 of the temperature-sensing section 3 expands or contracts according to changes in the inlet temperature of refrigerant, whereby the central portion of the diaphragm 29 is axially displaced. This displacement is transmitted to the valve element 6 via the displacement-transmitting member 30 to thereby control the valve lift of the differential pressure valve 2. For example, if the temperature of refrigerant becomes high, the wax 16 of the cup-shaped member 28 expands to swell toward the diaphragm 29 displaceable in the axial direction, which displaces the diaphragm 29 in the valve closing direction. Inversely, if the temperature of refrigerant lowers, the diaphragm 29 is displaced in the valve opening direction.

FIG. 9 is a central longitudinal cross-sectional view of the construction of an expansion device according to a fifth embodiment of the present invention. It should be noted that component elements appearing in FIG. 9, which have functions identical to or equivalent to those of the component elements appearing in FIG. 8, are designated by identical reference numerals, and detailed description thereof is omitted.

The expansion device according to the fifth embodiment is distinguished from the expansion device according to the fourth embodiment in that the construction of the temperature-sensing section 3 is modified. That is, the temperature-sensing section 3 of the expansion device employs a cup-shaped member 28 having a hole formed in a bottom thereof, and the cup-shaped member 28 is finally sealed by a ball 31. More specifically, the diaphragm 29 is rigidly fixed to the open flange portion of the cup-shaped member 28 e.g. by laser welding in the atmosphere, and the cup-shaped member 28 is placed in a large container with the bottom formed with the hole positioned upward, and is evacuated. Then, the wax 16 liquefied by heating is caused to flow into the cup-shaped member 28 through the hole. Further, the ball 31 is placed on the hole of the bottom in a manner closing the hole, and rigidly fixed to the cup-shaped member 28 e.g. by resistance welding, to thereby hermetically seal the cup-shaped member 28. The wax 16 is thus filled in the cup-shaped member 28 of the hermetically sealed container.

FIG. 10 is a central longitudinal cross-sectional view of the construction of an expansion device according to a sixth embodiment of the present invention. It should be noted that component elements appearing in FIG. 10, which have functions identical to or equivalent to those of the component elements appearing in FIG. 9, are designated by identical reference numerals, and detailed description thereof is omitted.

The expansion device according to the sixth embodiment is distinguished from the FIG. 9 expansion device according to the fifth embodiment in that the temperature-sensing section 3 and the spring 17 are reversely arranged. More specifically, in the expansion device, the cup-shaped member 28 of the temperature-sensing section 3 is fitted in a hole formed in a bottom of the cup-shaped member 18 having the body 4 press-fitted in an open lower end thereof, as viewed in FIG. 9, and the spring 17 is disposed between the diaphragm 29 and the valve element 6. As a result, the expansion device is configured similarly to the FIG. 7 expansion device according to the third embodiment such that the valve element 6 is urged in the valve closing direction with respect to the temperature-sensing section 3 in a fixed positional relationship with the body 4.

In the expansion device constructed as above, the differential pressure valve 2 operates in the valve opening direction when the differential pressure between the inlet pressure and the outlet pressure of refrigerant becomes high, and operates in the valve closing direction when the inlet temperature of refrigerant introduced into the expansion device becomes high, and hence the differential pressure valve 2 operates similarly to the differential pressure valves 2 of the expansion devices according to the first to fifth embodiments.

FIG. 11 is a central longitudinal cross-sectional view of the construction of an expansion device according to a seventh embodiment of the present invention. It should be noted that component elements appearing in FIG. 11, which have functions identical to or equivalent to those of the component elements appearing in FIG. 10, are designated by identical reference numerals, and detailed description thereof is omitted.

The expansion device according to the seventh embodiment is distinguished from the FIG. 10 expansion device according to the sixth embodiment in that the construction of the differential pressure valve 2 is modified. More specifically, the differential pressure valve 2 comprises a movable valve seat 32 of which the axial position is changed according to the inlet temperature of refrigerant, and a hollow cylindrical valve element 33 of which the valve lift with respect to the movable valve seat 32 is changed by the differential pressure between the inlet pressure and the outlet pressure of refrigerant.

In the temperature-sensing section 3, flange portions fixedly securing the cup-shaped member 28 and the diaphragm 29 to each other are fixed to an open upper end of the body 4 by swaging, and the movable valve seat 32 is pressed against a lower surface of the diaphragm 29 by a spring 34 having a large spring force. Thus, the movable valve seat 32 forms a valve seat axially displaced in a manner interlocked with the diaphragm 29 axially displaced according to the inlet temperature of the introduced refrigerant. The hollow cylindrical valve element 33 is held by the body 4 in a manner movable axially back and forth, and is urged by a spring 35 in a direction of being seated on the movable valve seat 32. The hollow cylindrical valve element 33 is configured such that high inlet pressure acts on an end face opposed to the movable valve seat 32 in a direction away from the movable valve seat 32, that is, in the valve opening direction, and low outlet pressure acts on an end face on an opposite side to the movable valve seat 32 in the valve closing direction. Therefore, the differential pressure valve 2 is opened and closed by the differential pressure between the inlet pressure and the outlet pressure acting on the opposite end faces of the hollow cylindrical valve element 33 and the urging force of the spring 35.

In the expansion device constructed as above, when the differential pressure between the inlet pressure and the outlet pressure of refrigerant is low, and the hollow cylindrical valve element 33 is seated on the movable valve seat 32, thereby closing the differential pressure valve 2, the minimum flow rate of refrigerant is determined by a clearance between the hollow cylindrical valve element 33 and the body 4 holding the valve element 33. Refrigerant introduced from above, as viewed in FIG. 11, is throttled by the clearance, and undergoes adiabatic expansion when flowing out into an downstream-side space where the spring 35 is disposed, to be delivered downward, as viewed in FIG. 11. At this time, the temperature-sensing section 3 axially expands or contracts according to the inlet temperature of refrigerant, whereby the movable valve seat 32 is axially displaced, with the differential pressure valve 2 being closed.

When the differential pressure between the inlet pressure and the outlet pressure of refrigerant becomes larger than the urging force of the spring 35, the differential pressure valve 2 is opened. At this time, the valve opening position of the differential pressure valve 2 changes according to the inlet temperature of refrigerant detected by the temperature-sensing section 3. More specifically, when the inlet temperature is low, the movable valve seat 32 is positioned at an upper position, as viewed in FIG. 11, and when the inlet temperature is high, the movable valve seat 32 is positioned at a lower position, as viewed in FIG. 11. Therefore, as the temperature rises, the movable valve seat 32 moves downward, as viewed in FIG. 11, to thereby act in a direction of contracting the spring 35 via the hollow cylindrical valve element 33, so that the spring 35 acts to strengthen a spring force thereof. As a result, the valve opening position of the differential pressure valve 2 is shifted toward a higher differential pressure side, and hence the differential pressure valve 2 is changed toward a side where it is more difficult to open the valve 2.

FIG. 12 is a central longitudinal cross-sectional view of the construction of an expansion device according to an eighth embodiment of the present invention. It should be noted that component elements appearing in FIG. 12, which have functions identical to or equivalent to those of the component elements appearing in FIG. 11, are designated by identical reference numerals, and detailed description thereof is omitted.

The expansion device according to the eighth embodiment is distinguished from the FIG. 11 expansion device according to the seventh embodiment in that the hollow cylindrical valve element 33 of the differential pressure valve 2 is provided with a damper mechanism so as to prevent the differential pressure valve 2 from sensitively reacting to a abrupt change in the pressure of introduced refrigerant, to thereby prevent hunting of the refrigeration cycle.

The movable valve seat 32 is provided with an orifice 36 for adjusting the minimum flow rate of refrigerant such that introduced refrigerant can be caused to flow directly into the inside of the hollow cylindrical valve element 33 as a space on the downstream side of the hollow cylindrical valve element 33. The hollow cylindrical valve element 33 has a groove 37 circumferentially formed in an outer periphery thereof inside a portion of the body 4 that holds the valve element 33. The groove 37 communicates with the inside space of the valve element 33 via a communication hole 38. Therefore, the orifice 36 of the movable valve seat 32, together with the clearance between the valve element 33 and the body 4 holding the same, determines the minimum flow rate of refrigerant capable of being caused to flow in the closed state of the differential pressure valve 2.

An annular piston 40, which is axially slidably disposed within a cylinder 39 formed in the body 4 on the downstream side of the differential pressure valve 2, is fixed to the hollow cylindrical valve element 33, and the valve element 33 is urged via the piston 40 by the spring 35 in the valve closing direction. The piston 40 defines a damper chamber 41 within the cylinder 39, and the damper chamber 41 communicates with the space on the downstream side of the valve element 33 via a clearance between the piston 40 and the body 4, and the clearance between the valve element 33 and the body 4 and the communication hole 38. Refrigerant flows into and out of the damper chamber 41 through the restricted passages of the clearances, which serves as a resistance against the axial motion of the piston 40, and forms the damper mechanism of the valve element 33. It should be noted that the groove 37 and the communication hole 38 formed in the valve element 33 are for causing high-pressure refrigerant to flow into the low-pressure downstream side via an intermediate portion of the clearance between the valve element 33 and the body 4 so as to prevent high-pressure refrigerant from flowing into the damper chamber 41 via the clearance.

In the expansion device constructed as above, the normal operation thereof is the same as that of the expansion device according to the seventh embodiment shown in FIG. 11. Now, when the inlet pressure of introduced refrigerant undergoes a rapid change, although the differential pressure valve 2 is about to perform a rapid opening or closing operation in response thereto, the damper mechanism prevents the hollow cylindrical valve element 33 from performing a rapid opening or closing operation in a manner following up the rapid opening or closing operation about to be performed by the differential pressure valve 2. As a result, when the refrigeration cycle undergoes a rapid change in the pressure of refrigerant, the refrigeration cycle is prevented from sensitively reacting to the rapid change in the pressure of refrigerant to cause hunting thereof.

FIG. 13 is a central longitudinal cross-sectional view of the construction of an expansion device according to a ninth embodiment of the present invention. It should be noted that component elements appearing in FIG. 13, which have functions identical to or equivalent to those of the component elements appearing in FIG. 12, are designated by identical reference numerals, and detailed description thereof is omitted.

The expansion device according to the ninth embodiment is distinguished from the FIG. 12 expansion device according to the eighth embodiment in that the construction of the damper mechanism provided for the hollow cylindrical valve element 33 of the differential pressure valve 2 is modified. More specifically, in the expansion device according to the ninth embodiment, the damper chamber 41 is formed by the piston 40 fixed to the valve element 33 and a closing portion 46 fixed to the cylinder 39. The closing portion 46 is formed with an orifice 47. Within the damper chamber 41, the spring 35 is disposed for urging the valve element 33 in the valve closing direction via the piston 40, and the load of the spring 35 is adjusted by the press-fitted amount of the closing portion 46 press-fitted into the cylinder 39. A space above the piston 40, as viewed in FIG. 13, communicates with the space on the downstream side of the valve element 33 via the communication hole 38 formed in the valve element 33, and is always maintained at low pressure.

In the expansion device constructed as above, the normal operation thereof is the same as that of the expansion device according to the eighth embodiment shown in FIG. 12. Further, when the inlet pressure of introduced refrigerant undergoes a rapid change, since the damper mechanism suppresses the rapid opening or closing operation of the hollow cylindrical valve element 33, the differential pressure valve 2 is insensitive to the rapid change in the pressure of refrigerant. This makes it possible to prevent the differential pressure valve 2 from sensitively reacting to the rapid change in the pressure of refrigerant to cause hunting of the refrigeration cycle.

FIG. 14 is a central longitudinal cross-sectional view of the construction of an expansion device according to a tenth embodiment of the present invention. It should be noted that component elements appearing in FIG. 14, which have functions identical to or equivalent to those of the component elements appearing in FIG. 11, are designated by identical reference numerals, and detailed description thereof is omitted.

The expansion device according to the tenth embodiment is distinguished from the FIG. 11 expansion device according to the seventh embodiment in that the construction of a part of the differential pressure valve 2, where the temperature-sensing section 3 varies the position of the valve seat according to a change in the inlet temperature of refrigerant, is modified. More specifically, in the expansion device according to the seventh embodiment, the movable valve seat 32 receives low pressure to an area corresponding to the inner diameter of the hollow cylindrical valve element 33, and hence a large force acts on the movable valve seat 32 in a direction of closing the differential pressure valve 2, by the differential pressure between the received low pressure and the inlet pressure of refrigerant, and this large force is received by the spring 34 having a large spring force. In contrast, in the expansion device according to the tenth embodiment, the valve seat movable by the temperature-sensing section 3 is configured to be hardly influenced by the high inlet pressure, whereby the spring 34 is implemented by one having a small spring force.

The differential pressure valve 2 comprises a hollow cylindrical movable valve seat 42 held by the body 4 in a manner movable axially back and forth, and a valve element 43 disposed on the downstream side of the movable valve seat 42. The hollow cylindrical movable valve seat 42 has an upper end, as viewed in FIG. 14, fitted on the displacement-transmitting member 30. Further, the movable valve seat 42 has a communication hole 44 formed through a portion thereof toward the displacement-transmitting member 30, and is urged by the spring 34 toward the temperature-sensing section 3. The valve element 43 is centered within the cylinder 39 formed in the body 4 on the downstream side by a plurality of guides 45 extending radially outward from the valve element 43, and is at the same time axially slidably disposed within the cylinder 39, in a state urged by the spring 35 in a direction of being seated on the movable valve seat 42.

The valve element 43 has an end face opposed to the movable valve seat 42, which is inwardly recessed in the form of a dish such that the sloped portion of the recessed end face is seated on an outer periphery of the opposed end face of the movable valve seat 42. This makes it possible for high-pressure refrigerant to flow into the movable valve seat 42 through the communication hole 44. When the high-pressure refrigerant flows into the movable valve seat 42, a force acting on the movable valve seat 42 in the downward direction, as viewed in FIG. 14, is cancelled by a force acting on the movable valve seat 42 in the upward direction, as viewed in the figure, since an area having an annular shape corresponding to the radial thickness in cross section of the movable valve seat 42 forms a pressure-receiving area on which the high pressure acts in the downward direction, and almost all the lower end face, as viewed in FIG. 14, except for the outer periphery on which the valve element 43 is seated, forms a pressure-receiving area on which the high pressure acts in the upward direction. Accordingly, the hollow cylindrical movable valve seat 42 forms a movable valve seat which is free from influence of the high inlet pressure.

In the expansion device constructed as above, the construction in which the differential pressure valve 2 performs the opening and closing operations in response to the differential pressure between the inlet pressure and the outlet pressure of refrigerant, and the temperature-sensing section 3 varies the position of the valve seat of the differential pressure valve 2 according to the inlet temperature of refrigerant is the same as those of the expansion devices according to the seventh and eighth embodiments. However, the movable valve seat 42 is configured to have a structure for canceling the high pressure, and hence it is possible to reduce the force of the spring 34 urging the movable valve seat 42 toward the diaphragm 29 of the temperature-sensing section 3.

FIG. 15 is a central longitudinal cross-sectional view of the construction of an expansion device according to an eleventh embodiment of the present invention. It should be noted that component elements appearing in FIG. 15, which have functions identical to or equivalent to those of the component elements appearing in FIGS. 14 and 13, are designated by identical reference numerals, and detailed description thereof is omitted.

The expansion device according to the eleventh embodiment is distinguished from the FIG. 14 expansion device according to the tenth embodiment in that it has the damper mechanism included in the FIG. 13 expansion device according to the ninth embodiment. More specifically, the expansion device includes the piston 40 axially slidably disposed in the cylinder 39 formed within the body 4 on the downstream side, and the closing portion 46 for closing the lower end of the cylinder 39, as viewed in FIG. 15, to thereby form the damper chamber 41 therebetween. The piston 40 is integrally formed with the valve element 43, and urged upward, as viewed in FIG. 15, by the spring 35 disposed between the same and the closing portion 46. The closing portion 46 is formed with the orifice 47 for adjusting the potency of the damper mechanism in cooperation in the clearance between the piston 40 and the cylinder 39.

The expansion device constructed as above has the movable valve seat 42 configured to cancel the high pressure, and the valve element 43 includes the damper mechanism that reacts insensitively to a rapid change in the pressure of refrigerant. This makes it possible to reduce the force of the spring 34 urging the hollow cylindrical movable valve seat 42 toward the diaphragm 29 of the temperature-sensing section 3, and prevent hunting of the refrigeration cycle.

By the way, although in the above-described embodiments, the expansion devices are disposed within the pipe laid between the gas cooler and the evaporator of the refrigeration cycle, for circulating refrigerant, by way of example, this is not limitative, but a refrigeration cycle using CO₂as refrigerant, employs an internal heat exchanger to enhance efficiency thereof, and therefore, actually, each expansion device is disposed within a pipe laid between the internal heat exchanger and an evaporator, for circulating refrigerant. This causes the expansion device to sense the temperature of refrigerant at an outlet of the internal heat exchanger, for control of high pressure.

Further, it is known that the expansion device as described above senses the temperature of refrigerant at an inlet of the internal heat exchanger, and controls high pressure, whereby it is possible to further enhance the efficiency of the refrigeration cycle. In the following, a description will be given of a case where the expansion device according to the present invention is applied to the refrigeration cycle constructed as above.

FIG. 16 is a system diagram showing a refrigeration cycle to which is applied the expansion device according to the present invention.

The refrigeration cycle comprises a compressor 51 for compressing refrigerant, a gas cooler 52 for cooling the compressed refrigerant, an expansion device 53 for throttling and expanding the cooled refrigerant, an evaporator 54 for evaporating the expanded refrigerant, accumulator 55 for storing surplus refrigerant in the refrigeration cycle and separating refrigerant in gaseous phase from the evaporated refrigerant to send the separated refrigerant to the compressor 51. Further, the refrigeration cycle includes an internal heat exchanger 56 for performing heat exchange between refrigerant flowing from the gas cooler 52 to the expansion device 53 and refrigerant flowing from the accumulator 55 to the compressor 51.

The expansion device 53 is mounted in the internal heat exchanger 56. In doing this, a temperature-sensing section of the expansion device 53 is disposed such that it senses the temperature of refrigerant introduced from the gas cooler 52 into the internal heat exchanger 56, and a differential pressure valve is disposed such that high-pressure refrigerant having passed through the internal heat exchanger 56 is throttled and expanded to be delivered to the evaporator 54.

FIG. 17 is a cross-sectional view of essential elements of an expansion device according to the present invention which is mounted in an internal heat exchanger, by way of a first example. FIG. 18 is a cross-sectional view of essential elements of the expansion device according to the present invention which is mounted in an internal heat exchanger, by way of a second example. It should be noted that in these examples, the expansion device in use-has the construction of the expansion device according to the eighth embodiment shown in FIG. 12.

First, in the first example illustrated in FIG. 17, the internal heat exchanger 56 has a body 57 formed with a refrigerant inlet passage 58 into which high-pressure refrigerant is introduced from the gas cooler 52. The refrigerant inlet passage 58 communicates with a return passage 59 formed to extend through the internal heat exchanger 56 in parallel with the refrigerant inlet passage 58. The return passage 59 has a terminal end formed with a mounting hole 60 in which the expansion device 53 is mounted. The mounting hole 60 is formed to extend through the body 57 from the outside thereof to the refrigerant inlet passage 58 across the return passage 59, and the expansion device 53 is mounted in the mounting hole 60 such that the temperature-sensing section thereof is located in the refrigerant inlet passage 58. In the state where the expansion device 53 is mounted in the mounting hole 60, a pipe 61 leading to the evaporator 54 is mounted on the body 57 at an open end of the mounting hole 60 in a manner covering the outlet of the differential pressure valve of the expansion device 53.

When the expansion device 53 is mounted in the mounting hole 60, the upstream side of the differential pressure valve is configured to communicate with the return passage 59, and the outer periphery of the body of the differential pressure valve is sealed by an O ring between the high-pressure upstream side and the low-pressure downstream side of the differential pressure valve. An O ring for sealing is also provided on the outer periphery of the body of the differential pressure valve between the refrigerant inlet passage 58 and the return passage 59.

The expansion device 53 mounted in the internal heat exchanger as described above directly senses the temperature of refrigerant introduced from the gas cooler 52 since the temperature-sensing section thereof is located in the refrigerant inlet passage 58. Therefore, the expansion device 53 controls the movable valve seat of the differential pressure valve according to the inlet temperature of high-pressure refrigerant, while the differential pressure control valve performs differential pressure control of the high-pressure refrigerant. This enables the expansion device 53 to control high pressure such that the maximum efficiency is always attained with respect to the inlet temperature of the refrigerant.

Further, according to the second example illustrated in FIG. 18, the expansion device 53 is mounted such that it is caused to sense the temperature of refrigerant via a partition wall 62 by making use of the body 57 of the internal heat exchanger 56 made of a material having excellent thermal conductivity. More specifically, the partition wall 62 of a chamber accommodating the temperature-sensing section of the expansion device 53 is integrally formed with the body 57 in a manner protruding into the refrigerant inlet passage 58, and at the same time such that it has a size suitable for bringing the inserted temperature-sensing section into intimate contact with the partition wall 62. This makes it possible to transfer the temperature of refrigerant flowing through the refrigerant inlet passage 58 to the partition wall 62 and further transfer the temperature from the partition wall 62 to the temperature-sensing section of the expansion device 53. In this case, the expansion device 53 can be dispensed with the O ring for sealing between the refrigerant inlet passage 58 and the return passage 59.

Although in the preferred embodiments of the present invention described heretofore, the temperature-sensing section 3 controls the valve lift of the differential pressure valve 2 by making use of changes in the coefficient of volumetric expansion caused by the temperature of the wax 16, this is not limitative, but the temperature-sensing section 3 may be constructed using a liquid having a large coefficient of volumetric expansion, such as alcohol, in place of the wax 16. In this case, changes in the coefficient of volumetric expansion with respect to changes in the temperature of the liquid are linear in a wide range of changes in the temperature, so that the distances between temperature gradients appearing in FIG. 5 are shown to be uniform.

The expansion device according to the present invention is configured such that the differential pressure valve has its valve lift controlled in response to the pressure of introduced refrigerant, and the solid or liquid material contained in the temperature-sensing section and having a large coefficient of volumetric expansion further controls the valve lift of the differential pressure valve in response to the temperature of the introduced refrigerant, without provision of any hermetically sealed container filled with a high-pressure gas. This makes it possible to enhance safety in handling the expansion device when it is manufactured, stored, transported, and mounted in the refrigeration cycle.

Further, the expansion device according to the present invention is configured such that the differential pressure valve senses the pressure of refrigerant, and the temperature-sensing section senses the temperature of the refrigerant to thereby vary the cross-sectional area of a restriction passage, so that it is possible to perform a control operation similar to those of the conventional expansion devices which include a hermetically sealed space filled with a high-pressure gas to make them sensitive to the pressure and temperature of refrigerant simultaneously. This makes it possible to efficiently. operate the refrigeration cycle.

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.

Number	Date	Country	Kind
2004-335225	Nov 2004	JP	national
2004-375158	Dec 2004	JP	national
2005-045214	Feb 2005	JP	national
2005-178718	Jun 2005	JP	national

Expansion device

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CPC

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Priority Claims (4)