Mounting structure of expansion valve

Abstract

To reduce the number of refrigerant external leak-prone spots, in a portion where an expansion valve is mounted. A casing is joined to a refrigerant outlet of an evaporator, and a low-pressure pipe extending to a compressor is connected to the casing by a pipe clamp. An expansion valve is disposed within the casing. Within the casing, an inlet port of the expansion valve and a high-pressure pipe are connected to each other, and an outlet port of the expansion valve and an inlet pipe of an evaporator are connected to each other. This limits the portions of the expansion valve which can cause refrigerant external leakage to portions connected by the pipe clamp.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a mounting structure of an expansion valve according to a first embodiment.

FIG. 2 is a cross-sectional view taken on line A-A of FIG. 1.

FIG. 3 is a cross-sectional view useful in explaining the operation of the expansion valve according to the first embodiment.

FIG. 4 is a cross-sectional view showing a mounting structure of an expansion valve according to a second embodiment.

FIG. 5 is a cross-sectional view taken on line B-B of FIG. 4.

FIG. 6 is a cross-sectional view showing a mounting structure of an expansion valve according to a third embodiment.

FIG. 7 is a cross-sectional view showing a mounting structure of an expansion valve according to a fourth embodiment.

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

FIG. 9 is a cross-sectional view showing a mounting structure of an expansion valve according to a fifth embodiment.

FIG. 10 is a cross-sectional view taken on line D-D of FIG. 9.

FIG. 11 is a cross-sectional view showing a mounting structure of an expansion valve according to a sixth embodiment.

FIG. 12 is a cross-sectional view taken on line E-E of FIG. 11.

FIG. 13 is a cross-sectional view showing a mounting structure of an expansion valve according to a seventh embodiment.

FIG. 14 is a cross-sectional view showing a mounting structure of an expansion valve according to a eighth embodiment.

FIG. 15A is a cross-sectional view showing a mounting structure of an expansion valve according to a ninth embodiment.

FIG. 15B is a cross-sectional view taken on line F-F of FIG. 15A.

FIG. 16A is a cross-sectional view taken in a plane containing the center line of the high-pressure pipe and that of the low-pressure pipe, regarding a mounting structure of an expansion valve according to a tenth embodiment.

FIG. 16B is a cross-sectional view taken on line G-G of FIG. 16A.

FIG. 17A is a cross-sectional view showing a mounting structure of an expansion valve according to an eleventh embodiment.

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

FIG. 18 is a cross-sectional view showing a mounting structure of an expansion valve according to a twelfth embodiment.

FIG. 19 is a cross-sectional view showing a mounting structure of an expansion valve according to a thirteenth embodiment.

FIG. 20 is an exploded perspective view showing a mounting structure of an expansion valve according to a fourteenth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

FIG. 1 is a cross-sectional view showing a mounting structure of an expansion valve according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view taken on line A-A of FIG. 1. FIG. 3 is a cross-sectional view useful in explaining the operation of the expansion valve according to the first embodiment.

The evaporator 1 is formed by laminating a plurality of aluminum plates, and has a header portion thereof formed with a refrigerant inlet 2 for introducing refrigerant and a refrigerant outlet 3 for delivering refrigerant. An inlet pipe 5 is integrally formed with the refrigerant inlet 2 by pressing an end plate 4 as a component of the evaporator 1. A hollow cylindrical casing 6 forming a low-pressure return pipe extending from the evaporator 1 is joined to the end plate 4 in a manner enclosing the opening of the inlet pipe 5 and that of the refrigerant outlet 3. The evaporator 1 is formed by simultaneously welding the laminated plates and the end plate 4 by an NB (Noncorrosive Flux Brazing) method in which brazing is performed using fluoride-based flux within a nitrogen atmosphere in a furnace, and at this time the casing 6 is also welded together, whereby the evaporator 1 and the casing 6 are formed integral with each other.

The casing 6 has an expansion valve 7 mounted therein. The expansion valve 7 has a body 10 integrally formed with an inlet port 8 for introducing high-pressure refrigerant and an outlet port 9 for delivering low-pressure refrigerant. The body 10 has a valve hole formed therethrough for communication between the inlet port 8 and the outlet port 9, and a valve element 11 is disposed in the body 10 for opening and closing the valve hole, in a state urged in the valve-closing direction by a spring 12 from a low pressure side. The spring 12 is received in an adjustment member 13 press-fitted into a lower end opening, as viewed in FIG. 1, of the body 10. The load of the spring 12 is adjusted by the press-fitted amount of the adjustment member 13 press-fitted into the body 10, whereby the set value of the expansion valve 7 is adjusted. The valve element 11 is integrally formed with a shaft 14 supported by the body 10 in a manner movable in the valve opening/closing direction, and a V ring 15 is fitted on the shaft 14 so as to prevent the high-pressure refrigerant introduced into the inlet port 8 from leaking into the casing 6 through a clearance between the body 10 and the shaft 14.

The body 10 has a power element 16 screwed into an upper end thereof, as viewed in FIG. 1. The power element 16 comprises an upper housing 17 and a lower housing 18, each made of thick metal, a diaphragm 19 made of a flexible thin metal plate and disposed in a manner partitioning a space enclosed by the upper and lower housings 17 and 18, and a center disk 20. The space enclosed by the upper housing 17 and the diaphragm 19 forms a temperature-sensing chamber, which is filled with refrigerant gas. The center disk 20 has an upper surface thereof held in contact with the lower surface of the diaphragm 19, and a lower surface thereof held in contact with an end surface of the shaft 14 protruding from the body 10, so as to transmit the displacement of the diaphragm 19 to the valve element 11. The lower housing 18 has a gas-passing hole 21 formed so as to introduce refrigerant passing through the casing 6 into space below the diaphragm 19. The amount of refrigerant to be introduced is adjusted by changing the size or number of the gas-passing hole 21. Further, a heat-insulating cover 22 made of resin or rubber is attached to the power element 16 in a manner covering the same.

The outlet port 9 of the expansion valve 7 is fitted on the inlet pipe 5 of the evaporator 1 and is sealed by an O ring 23. The inlet port 8 of the expansion valve 7 is fitted in a high-pressure pipe 24 extending from a receiver, and is sealed by an O ring 25. The casing 6 is connected to a low-pressure pipe 26 extending to a compressor. In the illustrated example 1, the low-pressure pipe 26 has a joint part 27 welded to an end portion thereof (as indicated by black triangles), and the joint part 27 is connected to the casing 6 by a pipe clamp 28 and is sealed by two O rings 29 so as to minimize refrigerant external leakage. The low-pressure pipe 26 and the high-pressure pipe 24 are formed by a concentric double pipe such that the high-pressure pipe 24 is disposed within the low-pressure pipe 26.

The expansion valve 7 housed in the casing 6 is positioned in the center of the casing 6, and therefore, as shown in FIG. 2, the body 10 and the heat-insulating cover 22 have respective outer contours formed along the inner shape of the casing 6.

Now, the expansion valve 7 is mounted in the casing 6 functioning as a low-pressure return pipe from the evaporator 1, as follows: Since the evaporator 1 and the casing 6 are integrally welded such that the inlet pipe 5 of the evaporator 1 protrudes into the casing 6, first, the O ring 23 is fitted on the inlet pipe 5, and then the expansion valve 7 is pushed into the casing 6 until the outlet port 9 is fitted on the inlet pipe 5. The O ring 25 is fitted on the inlet port 8 of the expansion valve 7 in advance, or at this time. Next, the inlet port 8 is positioned such that it can be fitted in the high-pressure pipe 24, and the joint part 27 having the O rings 29 fitted beforehand in respective grooves formed by bending the end portion of the joint part 27 is pushed into the casing 6. Finally, a connecting portion of the casing 6 and that of the joint part 27 are connected by the pipe clamp 28.

Thus, the expansion valve 7 is mounted in the casing 6, with the inlet port 8 connected to the high-pressure pipe 24, and the outlet port 9 connected to the inlet pipe 5 of the evaporator 1. More specifically, the expansion valve 7 is accommodated in the low-pressure return pipe from the evaporator 1, together with the high-pressure pipe 24 and the connecting portion thereof, and hence connecting portions from which refrigerant can leak out are limited to only the connecting portions connected by the pipe clamp 28. Since the high-pressure pipe 24 and the connecting portion thereof are accommodated in the casing 6, even if a minute amount of high-pressure refrigerant leaks via the O ring 25, the refrigerant remains in the low-pressure return pipe without leaking out into the atmosphere.

Next, a description will be given of the operation of the expansion valve 7. When an automotive air conditioner is in stoppage, gas filling the temperature-sensing chamber of the power element 16 is condensed, so that the pressure of the gas is low. Therefore, as shown in FIG. 1, the diaphragm 19 is displaced inward (upward, as viewed in FIG. 1), and the displacement is transmitted to the valve element 11 via the shaft 14, whereby the expansion valve 7 is placed in the fully closed state.

When the automotive air conditioner is started in this state, refrigerant is drawn by the compressor, and hence pressure within the low-pressure return pipe drops. The power element 16 senses this, so that the diaphragm 19 is displaced outward to lift the valve element 11. On the other hand, refrigerant compressed by the compressor is condensed by a condenser, and liquid refrigerant obtained by gas/liquid separation in the receiver is supplied to the inlet port 8 of the expansion valve 7 through the high-pressure pipe 24. It should be noted that arrows appearing in the figures indicate respective directions of refrigerant flow. The high-temperature, high-pressure liquid refrigerant is expanded while passing through the expansion valve 7 and flows out as low-temperature, low-pressure gas-liquid mixture refrigerant from the outlet port 9. The refrigerant is supplied to the evaporator 1 through the inlet pipe 5 and the refrigerant inlet 2, and is evaporated in the evaporator 1 to flow out from the refrigerant outlet 3. The refrigerant having returned from the evaporator 1 returns to the compressor via the casing 6 and the low-pressure pipe 26.

The space enclosed by the diaphragm 19 of the power element 16 and the lower housing 18 of the same communicates with the inside of the casing 6 via the gas-passing hole 21, so that while refrigerant having returned from the evaporator 1 is passing through the casing 6, some of the refrigerant is introduced into the space within the power element 16, and the temperature of the introduced refrigerant is detected by the power element 16. In the early stage of the start of the automotive air conditioner, the temperature of the refrigerant returning from the evaporator 1 is high due to heat exchange with high-temperature air in the compartment, and the power element 16 senses the temperature of the refrigerant, so that the pressure within the temperature-sensing chamber becomes high. This causes, as shown in FIG. 3, the diaphragm 19 to be displaced in the valve-opening direction until the center disk 20 in contact therewith is brought into abutment with a shoulder of the lower housing 18, and this displacement is transmitted to the valve element 11 via the shaft 11, whereby the expansion valve 7 is fully opened.

As the temperature of refrigerant from the evaporator 1 becomes lower, the pressure within the temperature-sensing chamber also becomes lower. Accordingly, the diaphragm 19 is displaced upward, as viewed in FIG. 3, whereby the expansion valve 7 moves in the valve-closing direction to control the flow rate of refrigerant passing therethrough. At this time, the expansion valve 7 operates to detect the temperature of refrigerant at the outlet of the evaporator 1, and controls the flow rate of refrigerant supplied to the evaporator 1 such that the refrigerant maintains a predetermined degree of superheat. As a consequence, refrigerant in a superheated state is always returned to the compressor, which enables the compressor to perform an efficient operation.

It should be noted that since the power element 16 is disposed in the low-pressure return pipe from the evaporator 1 such that the temperature of refrigerant can be detected by the entire power element 16, the power element 16 would have a very short temperature-sensing time constant due to its structure. If the temperature-sensing time constant is short, the response to a change in the temperature of refrigerant becomes so sensitive as to perform an excessive feedback correction on the operation of the valve section, which can result in a periodic pressure variation (hunting). To eliminate this inconvenience, the heat-insulating cover 22 is provided to block the transfer of heat to the upper housing 17 to thereby increase the temperature-sensing time constant.

FIG. 4 is a cross-sectional view showing a mounting structure of an expansion valve according to a second embodiment of the present invention, and FIG. 5 is a cross-sectional view taken on line B-B of FIG. 5. Component elements appearing in FIGS. 4 and 5, 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 mounting structure of the expansion valve according to the second embodiment is distinguished from the mounting structure of the expansion valve according to the first embodiment, in that the double pipe extends in a direction substantially orthogonal to a direction in which the refrigerant inlet 2 and the refrigerant outlet 3 of the evaporator 1 extend.

In many cases, the evaporator 1 is installed in a vehicle compartment such that a header portion having the refrigerant inlet 2 and the refrigerant outlet 3 is directed transversely to the vehicle. For this reason, the high-pressure pipe 24 and the low-pressure pipe 26 extending from an engine room into the compartment are required to be bent at right angles at the expansion valve 7 and the refrigerant outlet 3. To bend pipes at right angles necessitates space therefor, and hence, in the present embodiment, the direction of inflow of refrigerant and that of outflow of the same are made at right angles at a location where the expansion valve 7 is mounted.

The evaporator 1 is integrally formed with the inlet pipe 5 and a connecting part 6a by furnace brazing. The casing 6 is connected to the connecting part 6a by the pipe clamp 28, and the joint part 27 is welded to an upper portion, as viewed in FIG. 4, of the pipe clamp 28. The joint part 27 is connected to the low-pressure pipe 26 by the pipe clamp 28. In the present embodiment, connecting portions of the joint part 27 and the low-pressure pipe 26 connected by the pipe clamp 28 are sealed by an O ring 29 and a backup ring 29a.

The expansion valve 7 is mounted in the casing 6 and the joint part 27 having the openings facing in the respective directions orthogonal to each other, as described above. The body 10 of the expansion valve 7 has the inlet port 8 and the outlet port 9 formed in a manner facing in the respective directions orthogonal to each other. The body 10 has an outer shape extended in respective three directions up to the vicinity of the inner surface of the casing 6, as shown in FIG. 5, which makes it easy to position the expansion valve 7, when inserting the same into the casing 6 and connecting the outlet port 9 to the inlet pipe 5.

In the present embodiment, the low-pressure return pipe from the evaporator is required to be formed into an L shape, and hence junctures which can be responsible for external leakage of refrigerant are two connections, i.e. a juncture between the connecting part 6a and a juncture between the joint part 27 and the low-pressure pipe 26.

FIG. 6 is a cross-sectional view showing a mounting structure of an expansion valve according to a third embodiment of the present invention. Component elements appearing in FIG. 6, 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.

Similarly to the mounting structure of the expansion valve according to the second embodiment, the mounting structure of the expansion valve according to the third embodiment has an L-shaped structure in which the double pipe extends orthogonally to the direction in which the refrigerant inlet 2 and the refrigerant outlet 3 of the evaporator 1 extend. However, the mounting structure of the expansion valve according to the third embodiment is distinguished from the mounting structure of the expansion valve according to the second embodiment in that it has only one connection from which refrigerant can leak out.

More specifically, in the present embodiment, the evaporator 1, the inlet pipe 5, and the casing 6 are integrally formed by furnace brazing. At this time, the casing 6 and the inlet pipe 5 as well has through parts thereof hermetically joined. Further, the inlet pipe 5 and the casing 6 are independently joined to the refrigerant inlet 2 and the refrigerant outlet 3, respectively, such that the free end of the inlet pipe 5 bent at right angles extends into the casing 6. The casing 6 is connected to the low-pressure pipe 26 by fixing a backup ring 29b to an end face of the casing 6 by the pipe clamp 28 with the low-pressure pipe 26 inserted into the casing 6, and the O ring 29 prevents refrigerant from leaking out from the low-pressure return pipe. This reduces the number of junctures of the low-pressure return pipe from the evaporator 1 to one.

It should be noted that the expansion valve 7 employed in the present embodiment is different in the structure of the power element 16 from the expansion valve 7 described by way of example in the first and second embodiments. More specifically, the power element 16 comprises a temperature-sensing chamber formed by sandwiching the outer peripheral edge of the diaphragm 19 between the upper housing 17 and the lower housing 18 and welding them, and a belleville spring 30 provided within the temperature-sensing chamber. The belleville spring 30 is configured to assist the force of gas filled in the temperature-sensing chamber, for pushing the diaphragm 19 outward according to a sensed temperature. The belleville spring 30 acts to cause a pseudo-increase in the pressure of the gas. In the valve section, a ball-shaped valve element 11 is used, and the valve element 11 is joined to one end of the shaft 14 by spot welding. The shaft 14 has a pipe 31 fitted on the other end thereof, which is supported by the body 10 in a manner slidable along the axis of the shaft 14. The shaft 14 and the pipe 31 have respective end faces thereof held in contact with the diaphragm 19 of the power element 16. The V ring 15 is fitted on a reduced-diameter portion formed by fitting the pipe 31 on the shaft 14, for preventing high-pressure refrigerant from leaking into the low-pressure return pipe.

FIG. 7 is a cross-sectional view showing a mounting structure of an expansion valve according to a fourth embodiment of the present invention, and FIG. 8 is a cross-sectional view taken on line C-C of FIG. 7. Component elements appearing in FIGS. 7 and 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 mounting structure of the expansion valve according to the fourth embodiment is distinguished from the mounting structure of the expansion valve according to the first embodiment, in that the high-pressure pipe 24 and the low-pressure pipe 26 extending toward a compressor from the expansion valve 7 are not formed by a double pipe.

More specifically, in this mounting structure, the high-pressure pipe 24 and the low-pressure pipe 26 have respective end portions thereof connected to the joint part 27 through an end treatment by welding. The joint part 27 has two hollow cylindrical parts 27a and 27b integrally formed by pressing. The end face of the hollow cylindrical part 27a and a peripheral surface of the high-pressure pipe 24 are welded in a state where the high-pressure pipe 24 is inserted through the hollow cylindrical part 27a, and the end face of the hollow cylindrical part 27b and that of the low-pressure pipe 26 are welded in a state where the low-pressure pipe 26 is inserted into the hollow cylindrical part 27b, whereby joining portions of the joint part 27 to the high-pressure pipe 24 and the low-pressure pipe 26 are sealed. Further, the joint part 27 is connected to the casing 6 by the pipe clamp 28, and a juncture therebetween is sealed by the O ring 29. As shown in FIG. 8, the casing 6 is formed to have an oval cross section so as to facilitate guiding insertion of the expansion valve 7 and positioning performed for connection between the outlet port 9 of the expansion valve 7 and the inlet pipe 5 of the evaporator 5. In the structure described above, the number of junctures of the low-pressure return pipe extending from the evaporator 1 is reduced to one.

It should be noted that the expansion valve 7 employed in the present embodiment is of a different type from the expansion valve 7 described by way of example in the first and second embodiments. More specifically, the expansion valve 7 employed in the present embodiment has a retainer 32 disposed in the temperature-sensing chamber formed by the upper housing 17 and the diaphragm 19 of the power element 16, and an activated carbon 33 is filled in a space between the retainer 32 and the upper housing 17. The activated carbon 33 is provided to convert temperature into pressure utilizing its adsorption characteristic. The activated carbon 33 determines pressure within the temperature-sensing chamber in accordance with a change in the detected temperature. Further, the activated carbon 33 has a characteristic that due to its low thermal conductivity, it takes much time before the pressure changes in response to a change in temperature. This makes it possible to dispense with the heat-insulating cover 22 for blocking the transfer of heat to the upper housing 17 of the power element 16.

FIG. 9 is a cross-sectional view showing a mounting structure of an expansion valve according to a fifth embodiment of the present invention, and FIG. 10 is a cross-sectional view taken on line D-D of FIG. 9. Component elements appearing in FIGS. 9 and 10, which have functions identical to or equivalent to those of the component elements appearing in FIGS. 1 and 6, are designated by identical reference numerals, and detailed description thereof is omitted.

The mounting structure of the expansion valve according to the fifth embodiment is distinguished from the mounting structure of the expansion valve according to each of the first to fourth embodiments, in which the expansion valve 7 is mounted in the casing 6 connected, as the low-pressure return pipe, to the evaporator 1, in that the expansion valve 7 is mounted in a low-pressure pipe extending between the vehicle compartment in which the evaporator 1 is installed and the engine room in which the compressor and the receiver are installed. In particular, in the present embodiment, the expansion valve 7 is mounted in the low-pressure pipe of the structure in which not only the high-pressure pipe 24 and the low-pressure pipe 26 but also the inlet pipe 5 and the low-pressure pipe 26 are formed by a double pipe.

More specifically, in the present mounting structure, the casing 6 is connected between an evaporator-side low-pressure pipe 26a and a compressor-side low-pressure pipe 26b, and the expansion valve 7 is disposed in the casing 6. Further, the high-pressure pipe 24 is connected to the inlet port 8 of the expansion valve 7, and the inlet pipe 5 of the evaporator is connected to the outlet port 9 of the expansion valve 7. For this reason, each of the low-pressure pipes 26a and 26b has an end thereof to which the joint part 27 is welded in advance so that the low-pressure pipes 26a and 26b can be easily connected to the casing 6. As a consequence, the number of junctures of the low-pressure return pipe extending from the evaporator 1 and having the expansion valve 7 mounted therein is reduced to two.

Further, as shown in FIG. 10, the casing 6 is partially deformed such that insertion of the expansion valve 7 can be guided, and such that the expansion valve 7 disposed in the casing 6 can maintain a predetermined position. In the illustrated example, an upper central portion, as viewed in the figure, of the casing 6 is formed into a recessed shape in a manner adapted to the shape of the top of the power element 16, and a portion of the casing 6 corresponding to the legs of the body 10 are curved along the outer shape of the leg of the body 10 so that the motion of the leg can be restricted.

It should be noted that the expansion valve 7 employed in the present embodiment is similar to the type employed in the third embodiment (FIG. 6) in that the belleville spring 30 is provided in the temperature-sensing chamber of the power element 16. Further, the upper housing 17 of the power element 16 is formed with a hole for introducing gas into the temperature-sensing chamber. After the temperature-sensing chamber is filled with gas, the hole is sealed by resistance welding of a metal ball, and in the present expansion valve 7, a portion surrounding the hole is recessed to prevent the metal ball from protruding from the top surface of the upper housing 17.

FIG. 11 is a cross-sectional view showing a mounting structure of an expansion valve according to a sixth embodiment of the present invention, and FIG. 12 is a cross-sectional view taken on line E-E of FIG. 11. Component elements appearing in FIGS. 11 and 12, which have functions identical to or equivalent to those of the component elements appearing in FIGS. 9 and 10, are designated by identical reference numerals, and detailed description thereof is omitted.

The mounting structure of the expansion valve according to the sixth embodiment is distinguished from the mounting structure of the expansion valve according to the fifth embodiment, in which the number of junctures of the low-pressure return pipe extending from the evaporator 1 at a location where the expansion valve 7 is mounted is two, in that the number of junctures of the same is reduced to one.

More specifically, in the present mounting structure, the evaporator-side low-pressure pipe 26a and the casing 6 are welded in advance, whereby the number of junctures of the low-pressure return pipe extending from the evaporator 1 is reduced to one.

It should be noted that in the expansion valve 7 employed in the present embodiment, the power element 16 is fixed to the body 10 by swaging. Further, this expansion valve 7 has a structure in which the valve element 11 formed by pressing is joined to an end face of the shaft 14 by spot welding. Further, the adjustment member 13 is provided with a differential pressure control valve 34 operated by a differential pressure between inlet t pressure and outlet pressure of the evaporator 1. The differential pressure control valve 34 comprises a valve element 35 disposed on the low-pressure return pipe side of a valve hole formed through the adjustment member 13, and a spring 36 urging the valve element 35 in the valve closing direction. The differential pressure control valve 34 is configured to open when refrigeration load is so high as to make the differential pressure across the evaporator 1 higher than a predetermined value, to supply a refrigerant having high moisture into the low-pressure return pipe, thereby lowering the temperature of refrigerant returned to the compressor. This operation of the differential pressure control valve 34 is necessitated for the following reason: The expansion valve 7 controls the flow rate of refrigerant supplied to the evaporator 1, such that refrigerant at the outlet of the evaporator 1 maintains a predetermined degree of superheat, to thereby cause refrigerant having a predetermine degree of superheat to be returned to the compressor, but since the high-pressure pipe 24 and the low-pressure pipe 26b form a double-pipe structure, the refrigerant having the predetermined degree of superheat is further heated, while flowing through the low-pressure pipe 26b, by refrigerant flowing through the high-pressure pipe 24. The differential pressure control valve 34 is provided to prevent the temperature of refrigerant compressed by the compressor from becoming excessively high due to the double-pipe structure.

FIG. 13 is a cross-sectional view showing a mounting structure of an expansion valve according to a seventh embodiment of the present invention. Component elements appearing in FIG. 13, which have functions identical to or equivalent to those of the component elements appearing in FIGS. 1 and 9, are designated by identical reference numerals, and detailed description thereof is omitted.

The mounting structure of the expansion valve according to the seventh embodiment is distinguished from the mounting structure of the expansion valve according to each of the fifth and sixth embodiments, in which not only the high-pressure pipe 24 and the low-pressure pipe 26b but also the inlet pipe 5 and the low-pressure pipe 26a are formed by a double pipe, and the expansion valve 7 is mounted in an intermediate portion of the double pipe, in that the high-pressure pipe 24 and the inlet pipe 5 of the evaporator 1 are formed separately from the respective low-pressure pipes 26a and 26b.

In the present embodiment, the inlet pipe 5 of the evaporator 1 and the low-pressure pipe 26a have respective ends thereof integrally joined to the casing 6 e.g. by welding, and the end of the high-pressure pipe 24 opposed to that of the inlet pipe 5 and the end of the low-pressure pipe 26b opposed to that of the low-pressure pipe 26a are rigidly joined to a disk-shaped joint part 27 by welding. The casing 6 and the joint part 27 are connected by the pipe clamp 28. As a consequence, the number of junctures of the low-pressure return pipe extending from the evaporator 1 is reduced to one.

It should be noted that the expansion valve 7 described by way of example in each of the first to six embodiments acts in the valve opening direction when it receives high-pressure refrigerant, whereas the expansion valve 7 employed in the present embodiment is configured to act in the valve closing direction when it receives high-pressure refrigerant. Further, the heat-insulating cover 22 covering the power element 16 is integrally formed with fixing legs 22a by resin-molding. Although not shown, each fixing leg 22a has a hook formed at an end thereof, and the hook is engaged with a stepped portion formed in the body 10, whereby the heat-insulating cover 22 is fixed.

FIG. 14 is a cross-sectional view showing a mounting structure of an expansion valve according to a eighth embodiment of the present invention. Component elements appearing in FIG. 14, which have functions identical to or equivalent to those of the component elements appearing in FIGS. 1 and 9, are designated by identical reference numerals, and detailed description thereof is omitted.

The mounting structure of the expansion valve according to the eighth embodiment is distinguished from the mounting structure of the expansion valve according to each of the second and third embodiments, in which the high-pressure pipe 24 and the low-pressure pipe 26 are formed by a double pipe, and are connected to the inlet port 8 of the expansion valve 7 and the casing 6, respectively, in that the high-pressure pipe 24 and the low-pressure pipe 26 formed as separate members are used, and respective ends thereof are welded to a hollow cylindrical casing 6 having one end thereof closed. It should be noted that although not shown, the low-pressure pipe 26 is welded to the casing 6 at a surface of the casing 6 facing in a direction at right angles to the sheet of FIG. 14.

Further, the present embodiment is distinguished from the above-described embodiments in connection between the inlet port 8 of the expansion valve 7 and the high-pressure pipe 24 and connection between the outlet port 9 of the expansion valve 7 and the inlet pipe 5 of the evaporator 1, within the casing 6. This concerns the structure of the expansion valve 7, and hence, first, a description will be given of the expansion valve 7 employed in the present embodiment.

In the present expansion valve 7, a hollow cylindrical valve body 37 axially movably holding the shaft 14 integrally formed with the valve element 11 is integrally formed with the lower housing 18 of the power element 16, and the end face of the valve body 37 is utilized as a valve seat. Further, the hollow cylindrical adjustment member 13 is press-fitted on the valve body 37. The adjustment member 13 has an end bent into a groove in which the O ring 23 is disposed, and a stepped portion formed by the bending in a manner protruding inward plays the role of a receiver for the spring 12 for adjusting the set value of the expansion valve 7.

The valve body 37 is held by a resin body 38. The resin body 38 houses a collar 39 and the O ring 25 and an O ring 25a at respective locations on a refrigerant inlet side thereof. The collar 39 connects between the inlet port 8 formed on the curved surface of the expansion valve 7 and an opening formed in the curved casing 6 and connected with the high-pressure pipe 24, with the connecting portions sealed by the respective O rings 25 and 25a. Further, the resin body 38 has a recessed part 40 formed in the outer peripheral surface on a diametrically opposite side from the side where the collar 39 is housed. After the expansion valve 7 is inserted into the casing 6, the casing 6 is deformed inwardly by swaging toward the recessed part 40 of the resin body 38 on the diametrically opposite side of the casing 6 from the opening connected with the high-pressure pipe 24 to thereby press the resin body 38 toward the opening connected with the high-pressure pipe 24. This not only facilitates insertion of the expansion valve 7 with the O ring 25a mounted thereon into the casing 6, before the swaging, but also makes it possible to further ensure sealing of the connection between the inlet port 8 of the expansion valve 7 and the high-pressure pipe 24 by the O ring 25a, after the swaging.

Further, the inlet pipe 5 of the evaporator 1 is integrally formed with the connecting part 6a and joined to the evaporator 1, and connection between the inlet pipe 5 and the outlet port 9 of the expansion valve 7 is made by inserting the adjustment member 13 forming the outlet port 9 into the inlet pipe 5 and provides sealing by the O ring 23.

In the present embodiment, since the high-pressure pipe 24 and the low-pressure pipe 26 are welded to the casing 6, and the casing 6 is connected by the pipe clamp 28 to the connecting part 6a integrally formed with the evaporator 1, the number of junctures of the low-pressure return pipe extending from the evaporator 1 is reduced to one.

FIG. 15A is a cross-sectional view showing a mounting structure of an expansion valve according to a ninth embodiment of the present invention. FIG. 15B is a cross-sectional view taken on line F-F of FIG. 15A. Component elements appearing in FIGS. 15A and 15B, which have functions identical to or equivalent to those of the component elements appearing in FIG. 14, are designated by identical reference numerals, and detailed description thereof is omitted.

The mounting structure of the expansion valve according to the ninth embodiment is similar to the second and third embodiments in that the high-pressure pipe 24 and the low-pressure pipe 26 are formed by a double pipe, and the low-pressure pipe 26 and the casing 6 are joined to each other by the O ring 29 and by swaging. More specifically, the casing 6 is formed by pressing integrally with a hollow cylindrical joint part 27 extending outward from the peripheral surface of the hollow cylindrical portion thereof. The resin body 38 housing the expansion valve 7 is integrally formed with an inlet hollow cylindrical part 41 located at the inlet port 8 of the expansion valve 7 and connected to the high-pressure pipe 24, and an outlet hollow cylindrical part 42 connected to the inlet pipe 5 of the evaporator 1. An O ring restriction member 43 is fitted in the outlet hollow cylindrical part 42.

The resin body 38 is formed into a hollow cylindrical outer shape so as to be inserted into the hollow cylindrical casing 6 from the open end thereof, while the foremost end of the low-pressure pipe 26 has a flat end face. A washer 44 having a non-uniform circumferential thickness is interposed between the resin body 38 and the low-pressure pipe 26 so as to accommodate the difference in shape between the connecting portions of the two.

In the process of inserting the expansion valve 7 into the casing 6, first, the resin body 38 having the expansion valve 7 mounted therein is inserted from the open end of the casing 6 on the side for connection to the connecting part 6a joined to the evaporator 1, and then the double pipe of the high-pressure pipe 24 and the low-pressure pipe 26 is inserted into the joint part 27 of the casing 6. At this time, the high-pressure pipe 24 is fitted on the inlet hollow cylindrical part 41 of the resin body 38, and sealed by the O ring 25. Next, the open end of the joint part 27 is swaged, and the surface of the casing 6 on the opposite side from the joint part 27 is swaged toward the joint part 27. Thereafter, the casing 6 having the expansion valve 7 inserted therein is fitted on the connecting part 6a of the evaporator 6. At this time, the outlet hollow cylindrical part 42 of the resin body 38 is connected to the inlet pipe 5 of the evaporator 1 in a state sealed by the O ring 23. Then, the open end portion of the casing 6 and the connecting part 6a of the evaporator 1 are connected by the pipe clamp 28. As a consequence, the number of junctures, from which refrigerant can leak out, of the low-pressure return pipe extending from the evaporator 1 at a location where the expansion valve 7 is mounted is reduced to two.

FIG. 16A is a cross-sectional view taken in a plane containing the center line of the high-pressure pipe and that of the low-pressure pipe, in a mounting structure of an expansion valve according to a tenth embodiment of the present invention. FIG. 16B is a cross-sectional view taken on line G-G of FIG. 16A. Component elements appearing in FIGS. 16A and 16B, which have functions identical to or equivalent to those of the component elements appearing in FIGS. 15A and 15B, are designated by identical reference numerals, and detailed description thereof is omitted.

The mounting structure of the expansion valve according to the tenth embodiment is distinguished from the ninth embodiment in which the double pipe is used, in that the high-pressure pipe 24 and the low-pressure pipe 26 are joined to the casing 6 by the respective O rings 25 and 29 and swaging. More specifically, the casing 6 has a hollow cylindrical portion having sides thereof integrally formed with the joint part 27 and a joint part 45 both extending outward in respective directions orthogonal to each other. The high-pressure pipe 24 has a foremost end provided with the two O rings 25 and 25a for sealing between the inlet hollow cylindrical part 41 of the resin body 38 and the casing 6, and is joined to the casing 6 by the O ring 25a and by swaging of the joint part 45. On the other hand, the low-pressure pipe 26 is joined to the casing 6 by the O ring 29 and by swaging of the joint part 27. Therefore, the number of junctures, from which refrigerant can leak out, of the low-pressure return pipe at a location where the expansion valve 7 is mounted is reduced to two.

It should be noted that the expansion valve 7 employed in the present embodiment has the resin body 38 having a valve seat formed by insert, and the resin body 38 holds the shaft 14 integrally formed with the valve element 11, such that the shaft 14 is movable in the valve opening or closing direction, with the adjustment member 13 screwed into the resin body 38, for adjusting the set value, and the power element 16 rigidly secured to the resin body 38 by engagement of the heat-insulating cover 22 therewith.

FIG. 17A is a cross-sectional view showing a mounting structure of an expansion valve according to an eleventh embodiment of the present invention. FIG. 17B is a cross-sectional view taken on line H-H of FIG. 17A. Component elements appearing in FIGS. 17A and 17B, which have functions identical to or equivalent to those of the component elements appearing in FIG. 14, are designated by identical reference numerals, and detailed description thereof is omitted.

The mounting structure of the expansion valve according to the eleventh embodiment is different from the eighth embodiment in which the high-pressure pipe 24 and the low-pressure pipe 26 are welded to the casing 6, in that the method of sealing between the inlet port 8 of the expansion valve 7 and the outlet port 9 of the same is changed. More specifically, the expansion valve 7 according to the present embodiment is connected to the high-pressure pipe 24 and the inlet pipe 5 of the evaporator 1 via the resin body 38, but sealing between the inlet port 8 and the outlet port 9 after mounting of the expansion valve 7 in the resin body 38 is made by a lip 46. The lip 46 is integrally formed with the resin body 38 as a thin hollow cylindrical portion at the peripheral edge of an opening between the inlet port 8 and the outlet port 9 of the expansion valve 7 in which the valve section is press-fitted. This makes it possible to dispense with one of the O rings required in mounting the expansion valve 7 in the resin body 38.

It should be noted that the expansion valve 7 employed in the present embodiment is configured such that the hollow cylindrical valve body 37 which axially movably holds the shaft 14 integrally formed with the valve element 11, and has a stepped portion formed in the central portion thereof as a valve seat is press-fitted in the lower housing 18 of the power element 16, and further the adjustment member 13 is press-fitted in the valve body 37, for adjusting the set value. A portion of the valve body 37 sealed by the lip 46 is tapered to form a wedge in the press-fitting direction.

In the mounting structure of the expansion valve according to the eleventh embodiment, the pipe clamp 28 connecting between the connecting part 6a welded to the evaporator 1 and the casing 6 is formed by two engaging plates engaging in the opening edge of the connecting part 6a and the opening edge of the casing 6, respectively, and a bolt, as shown in FIG. 17 by way of example.

Further, in the mounting structure of the expansion valve according to the eleventh embodiment, as shown in FIG. 17B, in a juncture between the high-pressure pipe 24 and the inlet hollow cylindrical part 41 of the resin body 38 for introducing high-pressure refrigerant into the expansion valve 7, a portion of the casing 6 where the high-pressure pipe 24 is welded and its vicinity are formed to have a flat surface. This prevents the shape of the O ring 25 for sealing between the inner surface of the casing 6 and the inlet hollow cylindrical part 41 from being changed between when the expansion valve 7 is inserted into the casing 6 and when sealing is effected by deforming the casing 6 from a side diametrically opposite to a side where the high-pressure pipe 24 is welded, so as to press the inlet hollow cylindrical part 41 of the resin body 38 toward the high-pressure pipe 24. This makes it possible to improve assemblability.

Furthermore, in the mounting structure of the expansion valve according to the eleventh embodiment, the refrigerant inlet 2 and the refrigerant outlet 3 of the evaporator 1 are arranged in parallel, and the expansion valve 7 mounted in the resin body 38 is connected to the refrigerant inlet 2 and the refrigerant outlet 3 arranged in parallel, by way of example, as shown in FIG. 17. When the refrigerant inlet 2 and the refrigerant outlet 3 of the evaporator 1 are thus arranged in parallel, the outlet hollow cylindrical part 42 of the resin body 38 for connecting the outlet port 9 of the expansion valve 7 to the inlet pipe 5 of the evaporator 1 is formed in a manner eccentric toward the inlet pipe 5 with respect to the center of the expansion valve 7.

According to the above-described mounting structure, at a location where the expansion valve 7 is mounted, the low-pressure return pipe has only one juncture from which refrigerant can leak out at a location where the connecting part 6a and the casing 6 are connected by the pipe clamp 28.

FIG. 18 is a cross-sectional view showing a mounting structure of an expansion valve according to a twelfth embodiment of the present invention. Component elements appearing in FIG. 18, which have functions identical to or equivalent to those of the component elements appearing in FIG. 17, are designated by identical reference numerals, and detailed description thereof is omitted.

The mounting structure of the expansion valve according to the twelfth embodiment is distinguished from the eleventh embodiment in which the invention is applied to the evaporator 1 having the refrigerant inlet 2 and the refrigerant outlet 3 formed in parallel in a plurality of plates and end plates laminated one upon another, in that the invention is applied to an evaporator 1a having the refrigerant inlet 2 and the refrigerant outlet 3 concentrically arranged. The expansion valve 7 is disposed within the casing 6 such that the outlet port 9 is coaxial with the inlet pipe 5 of the evaporator 1a.

The evaporator 1a comprises two header portions and a core portion connecting between the header portions by a plurality of pipes. The juncture of one of the header portions with the casing 6 and the expansion valve 7 has a double-pipe structure. The inlet pipe 5 disposed as the inner one of the double pipe extends into the header portion up to an intermediate portion thereof and the foremost end portion of the inlet pipe 5 partitions the header portion in a manner dividing the same into two in the longitudinal direction. With this construction, one half of the header portion on the connection side forms a return collective space, and the other half forms a forward collective space.

It should be noted that although the expansion valve 7 employed in the present embodiment is similar in construction to the expansion valve 7 described by way of example in the eleventh embodiment illustrated in FIG. 17, the present expansion valve 7 is configured such that the valve body 37 is press-fitted into the resin body 38 instead of providing the lip 46 to thereby dispense with an O ring, and the valve body 37 is connected to the inlet pipe 5 of the evaporator 1a. Further, although not shown, the low-pressure pipe 26 is welded to the casing 6 in a direction at right angles to the sheet of FIG. 18.

According to this mounting structure as well, at a location where the expansion valve 7 is mounted, the low-pressure return pipe has only one juncture from which refrigerant can leak out at a location where the connecting part 6a and the casing 6 are connected by the pipe clamp 28.

FIG. 19 is a cross-sectional view showing a mounting structure of an expansion valve according to a thirteenth embodiment of the present invention. Component elements appearing in FIG. 19, which have functions identical to or equivalent to those of the component elements appearing in FIG. 18, are designated by identical reference numerals, and detailed description thereof is omitted.

The mounting structure of the expansion valve according to the thirteenth embodiment is distinguished from the mounting structure of the expansion valve according to the twelfth embodiment in that the expansion valve 7 and the casing 6 are configured to be sound-insulating and that the connecting part 6a and the casing 6 are connected to each other by swaging.

More specifically, in the present mounting structure, the expansion valve 7 disposed within the casing 6 is covered by a soundproofing member 47, and the casing 6 is covered by a soundproofing member 48. These soundproofing members 47 and 48 are made of a material which has large mass and a main content of rubber. The soundproofing member 47 also functions as a heat-insulating cover for adjusting the temperature-sensing time constant of the power element 16 of the expansion valve 7. The expansion valve 7 generates flow noise when throttling and expanding refrigerant, which makes a noise source. Since the expansion valve 7 is disposed in the vehicle compartment together with the evaporator 1a, noise is directly emitted into the vehicle compartment, which becomes a factor that largely impairs the quietness of the vehicle compartment. By covering the expansion valve 7 with the soundproofing member 47, flow noise emitted from the expansion valve 7 is absorbed and attenuated by the soundproofing member 47, so that the sound pressure of the noise source can be reduced. Moreover, since the casing 6 housing the expansion valve 7 provided with the soundproofing measure is covered by the soundproofing member 48, it is possible to further reduce noise.

Further, in this mounting structure, the casing 6 is not removably connected to the connecting part 6a of the evaporator 1a by the pipe clamp, but is connected to the evaporator 1a by swaging.

It should be noted that in the expansion valve 7 employed in the present embodiment, the valve body 37 is integrally formed with the lower housing 18 of the power element 16, with the end face of the valve body 37 being utilized as a valve seat, and a hollow cylindrical guide 49 axially movably holding the shaft 14 integrally formed with the valve element 11 is press-fitted into the valve body 37. The guide 49 axially movably holds a hollow cylindrical member 50 in which the shaft 14 is press-fitted. The hollow cylindrical member 50 has one end integrally formed with a flange portion, and the flange portion functions as a center disk for receiving the diaphragm 19 of the power element 16 and a spring receiver for the spring 12 urging the valve element 11 in the valve closing direction.

Although in the present embodiment, the soundproofing member 47 insulates noise from the expansion valve 7 by covering the expansion valve 7, the casing 6 may be lined with the soundproofing member 47 except for portions in contact with the resin body 38.

In the present embodiment, since the high-pressure pipe 24 and the low-pressure pipe 26 are welded to the casing 6, and the casing 6 is connected to the connecting part 6a integrally formed with the evaporator 1 by swaging, the low-pressure return pipe from the evaporator 1 has only one juncture.

FIG. 20 is an exploded perspective view showing a mounting structure of an expansion valve according to a fourteenth embodiment of the present invention. Component elements appearing in FIG. 20, which have functions identical to or equivalent to those of the component elements appearing in FIG. 17, are designated by identical reference numerals, and detailed description thereof is omitted.

The mounting structure of the expansion valve according to the fourteenth embodiment is distinguished from the mounting structure of the expansion valve according to the eleventh embodiment in that between the evaporator 1 having the refrigerant inlet 2 and the refrigerant outlet 3 formed in parallel and the connecting part 6a to which is connected the casing 6 housing the expansion valve 7, there is interposed a member for forming a flow passage through which refrigerant from the expansion valve 7 is guided to the refrigerant inlet 2. More specifically, between the evaporator 1 and the connecting part 6a, there is disposed a base plate 51. The base plate 51 has an elliptical cup-shaped member 52 which extends thereon from an approximately central portion thereof to a corner thereof associated with the refrigerant inlet 2 of the evaporator 1, and is open toward the evaporator 1, and the cup-shaped member 52 has an opening formed at a location corresponding to the approximately central portion of the base plate 51 and the inlet pipe 5 is formed in an manner surrounding the opening. Further, the base plate 51 has a hole 53 formed at a location corresponding to the refrigerant outlet 3 of the evaporator 1.

The connecting part 6a is shaped such that when overlaid on the base plate 51, the connecting part 6a covers the cup-shaped member 52, the inlet pipe 5, and the hole 53, and has a connecting end 54 formed in a central portion thereof for connection with the casing 6 in a manner concentric with the inlet pipe 5. The high-pressure pipe 24 and the low-pressure pipe 26 are welded to the peripheral surface of the casing 6.

The base plate 51 and the connecting part 6a are integrally formed with the evaporator 1 by furnace brazing. The expansion valve 7 is inserted in the casing 6, in advance, and the casing 6 is deformed inward from a diametrically opposite side of the casing 6 from a portion of the same to which is welded the high-pressure pipe 24, to thereby connect the inlet port to the high-pressure pipe 24. In assembling, the expansion valve 7 received within the casing 6 is inserted from the connecting end 54 of the connecting part 6a, whereby the portion of the expansion valve 7 formed with the outlet port is pushed into the inlet pipe 5. Thereafter, the connecting end 54 and the casing 6 are connected by a pipe clamp or by swaging the open end of the casing 6. As a consequence, high-pressure liquid refrigerant introduced from the high-pressure pipe 24 is throttled and expanded by the expansion valve 7 into atomized low-pressure refrigerant, and the atomized low-pressure refrigerant is introduced to the refrigerant inlet 2 of the evaporator 1 via the inlet pipe 5 and the cup-shaped member 52. Refrigerant evaporated by the evaporator 1 is introduced into a space within the connecting part 6a and a space within the casing 6 via the refrigerant outlet 3 and the hole 53 of the base plate 51, and then flows to the low-pressure pipe 26. At this time, the expansion valve 7 senses the temperature and pressure of the refrigerant flowing to the low-pressure pipe 26 and controls the flow rate of refrigerant delivered to the evaporator 1.

In the present embodiment as well, since the high-pressure pipe 24 and the low-pressure pipe 26 are welded to the casing 6, and the casing 6 is connected to the connecting part 6a integrally formed with the evaporator 1 by the pipe clamp or by swaging, the low-pressure return pipe from the evaporator 1 has only one juncture.

It should be noted that although in the first to thirteenth embodiments, the expansion valves 7 different in construction are employed, respectively, the expansion valves 7 are employed only by way of example, but they are not limitatively employed for the respective mounting structures.

The mounting structure of the expansion valve according to the present invention is constructed such that the low-pressure return pipe extending from the evaporator to the compressor accommodates the expansion valve, and the expansion valve is connected to the high-pressure pipe and the evaporator inlet pipe, within the low-pressure return pipe. This makes it is possible to largely reduce the number of refrigerant external leak-prone spots in the mounting portions of the expansion valve.

By forming the casing for housing the expansion valve integrally with the evaporator, it is possible to further reduce the number of refrigerant external leak-prone spots at a juncture between the evaporator and the low-pressure return pipe.

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. A mounting structure of an expansion valve in a refrigeration cycle, wherein the expansion valve is accommodated in a low-pressure return pipe extending between an outlet of an evaporator and an inlet of a compressor, and connection between an inlet port of the expansion valve and a high-pressure pipe, and connection between an outlet port of the expansion valve and a low-pressure pipe to an inlet of the evaporator are made within the low-pressure return pipe.

2. The mounting structure of an expansion valve according to claim 1, wherein the evaporator is formed, by joining, integrally with a casing extending from the outlet of the evaporator and accommodating the expansion valve, and an inlet pipe disposed at the inlet of the evaporator and having a portion for connection with the outlet port of the expansion valve, the portion being open into the casing, and the low-pressure return pipe is connected to an open end of the casing.

3. The mounting structure of an expansion valve according to claim 2, wherein the casing is joined to the evaporator in a manner enclosing the inlet and the outlet of the evaporator.

4. The mounting structure of an expansion valve according to claim 2, wherein the casing is joined to the evaporator in a manner enclosing the outlet of the evaporator, and the inlet pipe having one end thereof joined to the inlet of the evaporator, and another end thereof positioned within the casing in a manner extending through the casing, and the inlet pipe and the casing are hermetically joined to each other.

5. The mounting structure of an expansion valve according to claim 2, wherein the low-pressure return pipe is connected to the open end of the casing via a joint part joined to a foremost end of the low-pressure return pipe, and the high-pressure pipe extends through the joint part, the high-pressure pipe and the joint part being hermetically joined to each other.

6. The mounting structure of an expansion valve according to claim 2, wherein the low-pressure return pipe and the high-pressure pipe are formed as a double pipe in which the high-pressure pipe is concentrically disposed within the low-pressure return pipe.

7. The mounting structure of an expansion valve according to claim 1, wherein a connecting part is connected to the evaporator in a manner enclosing the inlet and the outlet of the evaporator, and an inlet pipe is connected to the inlet of the evaporator, wherein a casing to which a joint part is joined in a manner extending in a direction orthogonal to the inlet pipe is connected to the connecting part, the low-pressure return pipe being connected to the joint part, and wherein the expansion valve having the inlet port and the outlet port thereof disposed in respective directions orthogonal to each other is disposed within the casing.

8. The mounting structure of an expansion valve according to claim 1, wherein a casing accommodating the expansion valve is disposed in an intermediate portion of the low-pressure return pipe, and the high-pressure pipe concentrically disposed in the low-pressure return pipe at a location closer to the compressor than to the casing is connected to the inlet port of the expansion valve.

9. The mounting structure of an expansion valve according to claim 1, wherein a casing accommodating the expansion valve is disposed in an intermediate portion of the low-pressure return pipe, and an evaporator inlet pipe concentrically disposed within the low-pressure return pipe at a location closer to the evaporator than to the casing is connected to the outlet port of the expansion valve.

10. The mounting structure of an expansion valve according to claim 9, wherein the portion of the low-pressure return pipe closer to the evaporator and the casing are joined to each other.

11. The mounting structure of an expansion valve according to claim 1, wherein a casing accommodating the expansion valve is disposed in an intermediate portion of the low-pressure return pipe, and the high-pressure pipe is connected to the inlet port of the expansion valve in a manner extending through the casing.

12. The mounting structure of an expansion valve according to claim 1, wherein a casing accommodating the expansion valve is disposed in an intermediate portion of the low-pressure return pipe, and an evaporator inlet pipe is connected to the outlet port of the expansion valve in a manner extending through the casing.

13. The mounting structure of an expansion valve according to claim 2, wherein the casing is formed such that a shape of the casing at a location where the expansion valve is mounted is adapted to an outer shape of the expansion valve.

14. The mounting structure of an expansion valve according to claim 1, wherein the evaporator is formed, by joining, integrally with a hollow cylindrical connecting part extending from the evaporator in a manner enclosing the inlet and the outlet of the evaporator and an evaporator inlet pipe, and a hollow cylindrical casing accommodating the expansion valve and having a peripheral surface thereof connected with the low-pressure return pipe and one end thereof closed is connected to the connecting part.

15. The mounting structure of an expansion valve according to claim 14, wherein the casing and the low-pressure return pipe are connected to each other by welding.

16. The mounting structure of an expansion valve according to claim 14, wherein the connection between the casing and the low-pressure return pipe is a connection effected by sealing using an O ring and swaging.

17. The mounting structure of an expansion valve according to claim 14, wherein the high-pressure pipe is concentrically disposed within the low-pressure return pipe, or is connected to the casing in a direction orthogonal to the low-pressure return pipe.

18. The mounting structure of an expansion valve according to claim 17, wherein a portion of the casing on a side opposite from a side where the high-pressure pipe is disposed is deformed inward to thereby press the expansion valve connected to the high-pressure pipe via a sealing portion, toward the high-pressure pipe.

19. The mounting structure of an expansion valve according to claim 17, wherein the connection between the high-pressure pipe and the casing in the direction orthogonal to the low-pressure return pipe is a connection effected by welding.

20. The mounting structure of an expansion valve according to claim 17, wherein the connection between the high-pressure pipe and the casing in the direction orthogonal to the low-pressure return pipe is a connection effected by sealing using an O ring and swaging.

21. The mounting structure of an expansion valve according to claim 18, wherein a portion of the casing where the high-pressure pipe is welded and its vicinity are formed to have a flat surface so as to make flat the sealing portion of an inner surface of the casing and the expansion valve.

22. The mounting structure of an expansion valve according to claim 14, wherein the evaporator has the inlet and the outlet thereof arranged in parallel, and the outlet port of the expansion valve is formed in a manner eccentric toward the inlet of the evaporator with respect to a center of the expansion valve.

23. The mounting structure of an expansion valve according to claim 14, wherein the evaporator has the inlet and the outlet thereof concentrically disposed, and the expansion valve is disposed in the casing such that the outlet port of the expansion valve and the inlet of the evaporator are on an identical axis.

24. The mounting structure of an expansion valve according to claim 14, wherein a soundproofing member is disposed on at least one of an inner inside and an outer outside of the casing, for insulating noise generated by the expansion valve.

25. The mounting structure of an expansion valve according to claim 24, wherein the soundproofing member is disposed on the inner side of the casing in a manner covering the expansion valve.

26. The mounting structure of an expansion valve according to claim 1, wherein the expansion valve is a thermostatic expansion valve.