JP2007333290A - Mounting structure of expansion valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smoothly return oil to a compressor in a mounting structure of an expansion valve with a reduced number of positions of leakage of a refrigerant. <P>SOLUTION: A case 11 for storing the expansion valve 1 is disposed between an evaporator outlet pipe 10 from an evaporator and a low-pressure pipe 13 to the compressor. A high-pressure pipe 15 from a receiver and an inlet port 21 of the expansion valve 1 are connected to each other and an evaporator entrance pipe 12 and an exit port 22 of the expansion valve 1 are connected to each other inside the case 11, so that the place where the refrigerant may leak to atmospheric air is only a place sealed with an O-ring 17 in the mounting position of the expansion valve 1. Inside the case 11, the evaporator outlet pipe 10 and the low-pressure pipe 13 are disposed lower than the high-pressure pipe 15 and the evaporator entrance pipe 12, so that there will be no oil puddle in the case 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an expansion valve mounting structure, and in particular, an expansion valve that expands a high-temperature / high-pressure refrigerant supplied from a condenser in a refrigeration cycle of a vehicle air conditioner and sends out the low-temperature / low-pressure refrigerant to an evaporator. Relates to the mounting structure.

  A refrigeration cycle of a vehicle air conditioner generally includes a compressor that compresses a circulating refrigerant, a condenser that condenses the compressed refrigerant, a receiver that stores the refrigerant in the refrigeration cycle and separates the condensed refrigerant into gas and liquid. An expansion valve that squeezes and expands the separated liquid refrigerant, and an evaporator that evaporates the refrigerant expanded by the expansion valve. As the expansion valve, for example, a temperature type expansion valve that senses the temperature and pressure of the refrigerant at the outlet of the evaporator and controls the flow rate of the refrigerant sent to the evaporator is used.

  This temperature type expansion valve includes a block having a built-in valve portion and a power element that senses the temperature and pressure of the refrigerant returned from the evaporator and controls the valve portion. The block has a connection hole connecting a high-pressure pipe to which high-temperature and high-pressure refrigerant is supplied from the receiver and a low-pressure pipe that sends low-temperature and low-pressure refrigerant expanded by this expansion valve to the evaporator. It has a connection hole, a connection hole that connects the return pipe from the evaporator outlet, and a connection hole that connects the pipe for returning the refrigerant that has passed through the expansion valve to the compressor. is doing. The block also has a screw hole for connecting the power element to one end face in the longitudinal direction and a screw hole into which an adjustment screw for adjusting the set value from the outside is screwed into the other end face. Have. Each hole is provided with a seal member such as an O-ring in order to keep the inside airtight in a state where each pipe is inserted and the power element and the adjustment screw are screwed.

  By the way, in a vehicle air conditioner, currently, chlorofluorocarbon (HFC-134a) is generally used as a refrigerant. Since chlorofluorocarbon has a large global warming potential, it has an influence on global warming when leaked into the atmosphere. It is said to be big. As a countermeasure against global warming, there are considered a method of switching chlorofluorocarbon to a refrigerant having a small global warming potential and a method of collecting chlorofluorocarbon when it becomes unnecessary so as not to leak into the atmosphere.

  In the refrigeration cycle, the part where the chlorofluorocarbon leaks to the outside is a pipe connection part or the like, and the seal member arranged there is a factor of external leakage. In particular, in an expansion valve having a block with a built-in valve portion and a power element coupled thereto, the body also serves as a joint, so there are four places where a seal member is required only at the connecting portion of the pipe. In addition, the connecting portion of the power element and the portion provided with the adjusting screw are added, and there are a total of six external leakage portions.

  Therefore, the applicant of the present invention has installed the expansion valve in such a manner that the expansion valve is completely accommodated in the return low pressure pipe from the evaporator to the compressor, and the expansion valve is connected to the high pressure pipe and the evaporator inlet pipe in the low pressure pipe. A structure has been proposed (Japanese Patent Application No. 2006-139007). According to this proposal, in particular, the joint portion of the high-pressure pipe at the inlet port of the expansion valve is a portion where the possibility that chlorofluorocarbon permeates the seal member and leaks outside is higher than the joint portion of the low-pressure pipe at the outlet port. Even if the chlorofluorocarbon leaks to the outside at the connecting portion of the high-pressure pipe, the chlorofluorocarbon does not leak into the atmosphere because it is in the low-pressure pipe.

In the refrigeration cycle, the refrigerant contains lubricating oil for the compressor and circulates together with the refrigerant. In the expansion valve, liquid-phase refrigerant and lubricating oil are supplied, where they are squeezed and expanded to form a mist, and are sent to the evaporator. In the evaporator, the refrigerant evaporates and returns to the compressor, but the lubricating oil does not evaporate at the evaporating temperature of the refrigerant, so that the lubricating oil is returned to the compressor in the form of being blown away by the flow rate of the evaporated refrigerant in the liquid phase. However, when the opening of the expansion valve is small, such as when the refrigeration load is small, the flow rate of the refrigerant becomes extremely slow, so that the lubricating oil cannot be pushed to the compressor side, and the liquid-phase lubricating oil is not contained in the evaporator. In other words, a stagnation phenomenon is likely to occur in the low pressure piping returning from the evaporator to the compressor. When such a stagnation of lubricating oil occurs, the amount of oil returned to the compressor is insufficient, and the compressor is poorly lubricated and is subject to serious adverse effects such as seizure of sliding parts and abnormal decrease in durability. End up. As a means to eliminate such shortage of oil return amount, the lubricating oil that remains is reduced to the compressor by reducing the cross-sectional area of the return low-pressure piping from the evaporator to the compressor, thereby increasing the flow rate of the refrigerant. It is known to flush away (see, for example, Patent Document 1).
JP-A-8-121886 (paragraph [0004])

  However, in the expansion valve mounting structure in which the expansion valve is accommodated in the return low-pressure pipe from the evaporator to the compressor, the portion of the case that accommodates the expansion valve in the return low-pressure pipe is a flow path rather than the pipe immediately after the evaporator outlet. Since the cross-sectional area is large, the flow rate of the refrigerant flowing into the case is slow, and there is a problem that the lubricating oil tends to accumulate in the case.

  This invention is made in view of such a point, and it aims at providing the mounting structure of the expansion valve which makes oil return favorable, reducing the external leak location of a refrigerant | coolant.

  In the present invention, in order to solve the above problem, an expansion valve is accommodated in a return low-pressure pipe between the evaporator outlet and the compressor inlet, the connection between the inlet port of the expansion valve and the high-pressure pipe, and the expansion valve In the expansion valve mounting structure in the refrigeration cycle in which the connection between the outlet port and the evaporator inlet pipe is performed in the return low-pressure pipe, at the position in the return low-pressure pipe housing the expansion valve, to the compressor An expansion valve mounting structure is provided, wherein the low pressure pipe is located below the high pressure pipe connected to the expansion valve and the evaporator inlet pipe.

  According to such an expansion valve mounting structure, the low-pressure pipe is positioned below the high-pressure pipe and the evaporator inlet pipe, so that the low-pressure pipe is positioned near the bottom of the portion housing the expansion valve. As a result, even if the lubricating oil accumulates in the portion accommodating the expansion valve, it immediately overflows and flows out to the low pressure pipe.

  In the present invention, the expansion valve is housed in a return low-pressure pipe between the outlet of the evaporator and the inlet of the compressor, the connection between the inlet port of the expansion valve and the high-pressure pipe, the outlet port of the expansion valve and the evaporator inlet In the expansion valve mounting structure in the refrigeration cycle in which the connection to the piping is performed in the return low pressure piping, the opening end of the case accommodating the expansion valve and connected to the low pressure piping to the compressor is below gravity. An expansion valve mounting structure is provided that is directed.

  According to such an expansion valve mounting structure, the low-pressure pipe is connected from the bottom to the case that is open at the bottom, so that the lubricating oil that flows into the case together with the refrigerant falls and remains in the low-pressure pipe. Come in. For this reason, lubricating oil does not accumulate in the case, and the compressor does not run out of oil.

  Further, in the present invention, an expansion valve is accommodated in a return low-pressure pipe between the outlet of the evaporator and the inlet of the compressor, the connection between the inlet port of the expansion valve and the high-pressure pipe, the outlet port of the expansion valve and the evaporator inlet In the refrigeration cycle mounting structure in which the connection to the piping is performed in the return low-pressure piping, the expansion valve is installed in a horizontal direction so as to accommodate the expansion valve and forms a part of the return low-pressure piping. And a low-pressure pipe leading to the inlet of the compressor is connected to the case via a joint part joined to the lowermost end, and one end of the connection part between the case and the joint part is a bottom surface of the case An expansion valve mounting structure is provided in which a capillary tube is straddled so that the other end extends into the low-pressure pipe. It is.

  According to such an expansion valve mounting structure, even if lubricating oil accumulates at the bottom of the case, most of it overflows and flows out into the low-pressure pipe, but the capillary tube is caused by the difference in flow velocity generated at its downstream end. Since the lubricating oil remaining at the bottom of the case is sucked out by the venturi effect, the lubricating oil does not collect in the case.

  In the expansion valve mounting structure according to the present invention, the low-pressure pipe to the compressor is disposed in the gravity downward direction with respect to the portion accommodating the expansion valve, so the flow rate of the refrigerant in the portion accommodating the expansion valve Since the lubricating oil that accumulates at the bottom due to the decrease of the overflow overflows and flows out to the low-pressure pipe, there is an advantage that a large amount of oil does not accumulate inside.

  In addition, by adopting a structure in which the open end on the compressor side of the case containing the expansion valve faces downward, the lubricating oil that enters the case falls and flows directly to the low-pressure pipe, so that the oil pool inside Does not exist.

  Furthermore, since the lubricating oil remaining at the bottom of the case is sucked out by providing the capillary tube, it is possible to prevent the lubricating oil from accumulating in the case.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view showing an expansion valve mounting structure according to the first embodiment.
In this figure, the part in which the expansion valve 1 is mounted in the refrigeration cycle is shown. An evaporator outlet pipe 10 extending from the outlet of the evaporator is joined by welding to a cylindrical case 11 having one end closed at its tip, and the evaporator 11 is connected to the case 11 at a position above the gravity of the evaporator outlet pipe 10. An evaporator inlet pipe 12 extending from the inlet is joined by welding with its tip inserted inside. The low pressure pipe 13 leading to the suction chamber of the compressor has a disk-shaped joint portion 14 joined to the tip thereof by welding, and the high pressure pipe 15 extending from the receiver to a position above the gravity of the low pressure pipe 13. Are joined by welding with the tip inserted inside. The case 11 and the joint portion 14 are connected by a pipe clamp 16, and the connection portion is sealed from the atmosphere by an O-ring 17. Note that the evaporator outlet pipe 10 and the low-pressure pipe 13 are respectively cylindrical tubes, but the joint portion between the case 11 and the joint portion 14 is deformed into an ellipse so that the flow passage cross-sectional area is not changed as much as possible. In addition, the case 11 is prevented from becoming larger than necessary.

  In the case 11, the expansion valve 1 is connected to the high-pressure pipe 15 and the evaporator inlet pipe 12, and is mounted so as to sense the temperature of the refrigerant returning from the evaporator to the compressor. The expansion valve 1 includes a body 23 that is integrally formed with an inlet port 21 that is connected to a high-pressure pipe 15 and introduces a high-pressure refrigerant, and an outlet port 22 that is connected to the evaporator inlet pipe 12 and leads out a low-pressure refrigerant. Have. The body 23 has a valve hole in which the inlet port 21 and the outlet port 22 communicate with each other, and a valve body 24 that opens and closes the valve hole is biased in the valve closing direction by a spring 25 on the low pressure side. It is arranged in the state. The spring 25 is received by an adjustment screw 26 screwed into the upper end opening of the body 23 in the drawing, and the load is adjusted by the amount of screwing the adjustment screw 26 into the body 23, and the expansion valve 1. The set value has been adjusted. The valve body 24 is formed integrally with a shaft 27 supported by the body 23 so as to be movable back and forth in the opening and closing direction.

  A power element 28 constituting the temperature sensing part of the expansion valve 1 is attached to the lower end of the body 23 in the figure. The power element 28 is fixed by a locking portion 29, and a heat insulating cover 30 is fixed by a locking portion 31 so as to cover the exposed surface of the power element 28. The locking portions 29 and the locking portions 31 are formed integrally with the resin body 23, for example, and are provided in plural in the circumferential direction at the outer peripheral edge of the lower end surface. The heat insulating cover 30 is for adjusting the time required for the power element 28 to sense the temperature of the refrigerant at the evaporator outlet. Periodic pressure fluctuation (hunting) due to sensitive reaction to the temperature change of the refrigerant. It is for preventing.

  The expansion valve 1 is disposed in a case 11 inserted in the middle of a straight portion extending in the horizontal direction in the return low-pressure pipe from the evaporator to the compressor. The port 21 is connected to the high pressure pipe 15, and the outlet port 22 is connected to the evaporator inlet pipe 12. The lower position of the case 11 is a passage where the refrigerant evaporated from the evaporator returns to the compressor, and the power element 28 is disposed there.

  In the above configuration, there is only one joint portion where the refrigerant may leak outside to the atmosphere. Since the high-pressure pipe 15 and the evaporator inlet pipe 12 connected to the expansion valve 1 are connected to the inlet port 21 and the outlet port 22 in the case 11, even if the refrigerant leaks slightly at the connecting portion, the leakage Since it comes out in the return low-pressure piping, it does not leak into the atmosphere.

  Next, the operation of the expansion valve 1 will be described. First, when the vehicle air conditioner is stopped, the gas enclosed in the temperature-sensitive room of the power element 28 is condensed and the pressure is low, so the diaphragm is displaced inward (downward in the figure) The displacement is transmitted to the valve body 24 through the shaft 27, and the expansion valve 1 is in a fully closed state.

  Here, when the vehicle air conditioner is activated, the refrigerant is sucked by the compressor, so that the pressure of the return low-pressure pipe is lowered, and this is detected by the power element 28 so that the diaphragm is displaced outwardly to lift the valve body 24. become. On the other hand, the refrigerant compressed by the compressor is condensed by the condenser, and the liquid refrigerant gas-liquid separated by the receiver is supplied to the inlet port 21 of the expansion valve 1 through the high-pressure pipe 15. In addition, the arrow in a figure has shown the flow direction of the refrigerant | coolant. The high-temperature and high-pressure liquid refrigerant is expanded when passing through the expansion valve 1 and exits the outlet port 22 as a low-temperature and low-pressure gas-liquid mixed refrigerant. The refrigerant is supplied to the evaporator via the evaporator inlet pipe 12, is evaporated inside, and comes out of the evaporator. The refrigerant that has exited the evaporator returns to the compressor via the evaporator outlet pipe 10, the case 11, and the low-pressure pipe 13. At this time, the power element 28 senses the temperature of the refrigerant passing through the case 11. In the initial stage of startup of the vehicle air conditioner, the temperature of the refrigerant evaporated and returned by the evaporator is high due to heat exchange with hot air in the passenger compartment. For this reason, the power element 28 senses its temperature and the pressure in the temperature sensing chamber increases, so that the diaphragm is displaced in the valve opening direction, and the displacement is transmitted to the valve body 24 through the shaft 27, and the expansion valve 1 is fully opened. It becomes a state.

  Eventually, when the temperature of the refrigerant returning from the evaporator decreases, the pressure in the temperature-sensitive greenhouse decreases, and accordingly, the diaphragm is displaced downward in the figure, and the expansion valve 1 operates in the valve closing direction. Thus, the flow rate of the refrigerant passing through this is controlled. At this time, the expansion valve 1 senses the refrigerant temperature at the evaporator outlet, and controls the flow rate of the refrigerant supplied to the evaporator so that the refrigerant maintains a predetermined degree of superheat. As a result, the overheated refrigerant always returns to the compressor, so that the compressor can be operated efficiently.

  At this time, the refrigerant evaporated by the evaporator pushes away the lubricating oil of the compressor accumulated in the evaporator. When the refrigerant from the evaporator enters the case 11, the cross-sectional area of the flow path suddenly becomes larger than that of the evaporator outlet pipe 10, so that the flow rate of the refrigerant that has pushed the lubricating oil becomes slow and lubricates the case 11. Oil starts to accumulate. However, in the case 11, since the evaporator outlet pipe 10 and the low pressure pipe 13 are located below the gravity and open near the bottom surface, the volume in which the lubricating oil can be stored is reduced. For this reason, the lubricating oil that has been pushed down to the case 11 by the evaporated refrigerant is somewhat accumulated at the bottom of the case 11, but immediately overflows and is pushed to the low-pressure pipe 13.

  FIG. 2 is a cross-sectional view showing an expansion valve mounting structure according to the second embodiment. 2, elements having the same or equivalent functions as those shown in FIG. 1 are given the same reference numerals, and detailed descriptions thereof are omitted.

  The expansion valve mounting structure according to the second embodiment is configured to eliminate the place where the lubricating oil is accumulated in the case 11 in which the expansion valve is accommodated. That is, in this embodiment, the evaporator 40 is installed in the vehicle in such a posture that the refrigerant inlet 41 and the refrigerant outlet 42 are opened horizontally on the same side, and the refrigerant inlet 41 is higher than the refrigerant outlet 42. Installed. The low-pressure pipe 13 and the high-pressure pipe 15 are configured by a double pipe in which the high-pressure pipe 15 is concentrically arranged in the low-pressure pipe 13.

  The case 11 is joined to the refrigerant outlet 42 of the evaporator 40. The case 11 has a cylindrical shape with the upper end closed, and the lower end is open downward in gravity. In addition, one end of an evaporator inlet pipe 12 bent at a substantially right angle is joined to the refrigerant inlet 41, and the other end of the evaporator inlet pipe 12 extends through the closed portion of the case 11 into the case 11. And joined to the case 11. The case 11 and the evaporator inlet pipe 12 are integrally formed with the evaporator 40 by brazing in a furnace.

  The expansion valve 1 a has an outlet port 22 connected to the evaporator inlet pipe 12 in the case 11. In the case 11, a low-pressure pipe 13 extending from below is connected by an O-ring 17, a backup ring 43 and a pipe clamp 16. At that time, the high-pressure pipe 15 disposed in the low-pressure pipe 13 is simultaneously connected to the inlet port 21 of the expansion valve 1.

  The expansion valve 1 a is configured such that the function of the pressurizing gas charged together with the condensed gas in the temperature sensitive chamber of the power element 28 is performed by the disc spring 44. In the valve portion, a ball-shaped valve body 24 is used and joined to one end of the shaft 27 by spot welding. A pipe 45 is fitted to the other end of the shaft 27 and is supported by the body 23 so as to be slidable in the axial direction of the shaft 27. In this expansion valve 1a, the adjustment member 26a receiving the spring 25 is press-fitted into the body 23. The spring load is adjusted by the amount of the press-fitting to adjust the set value of the expansion valve 1a. .

  According to this configuration, the refrigerant that has flowed out of the evaporator 40 enters the wide case 11 that accommodates the expansion valve, so that the flow velocity decreases there. However, the lubricating oil pushed away from the evaporator 40 by the refrigerant is not contained in the case 11. And the oil is sucked into the low-pressure pipe 13 together with the refrigerant, so that the lubricating oil does not accumulate in the case 11.

  In addition, in this 2nd Embodiment, although the evaporator 40 demonstrated the case where the refrigerant | coolant inlet 41 was formed in the position higher than the refrigerant | coolant outlet 42, the positional relationship may be reverse. When the refrigerant outlet 42 is formed at a position higher than the refrigerant inlet 41, the case 11 joined to the evaporator with the opening end facing downward in the direction of gravity is surrounded by the evaporator inlet 41 and the refrigerant outlet 42. And the evaporator inlet pipe 12 bent at a substantially right angle is joined to the refrigerant inlet 41 of the evaporator in the case 11. Further, in this case, the power element 28 of the expansion valve 1a is mounted not on the position facing the refrigerant outlet 42 but on the opposite side to FIG.

  In the first and second embodiments described above, the lubricating oil is structurally prevented from collecting in the case 11, but there may still be a case where the oil is stored due to the layout of the evaporator 40. Next, an example in which lubricating oil does not accumulate in the oil reservoir in such a case will be described.

  FIG. 3 is a cross-sectional view showing an expansion valve mounting structure according to the third embodiment. 3, elements having the same or equivalent functions as the components shown in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the expansion valve mounting structure according to the third embodiment, the lubricating oil accumulated at the bottom of the cylindrical case 11 placed in the horizontal direction is sucked out. That is, in this embodiment, the evaporator 40 is installed in a vehicle in such a posture that the refrigerant inlet 41 and the refrigerant outlet 42 are opened horizontally on the same side, and the refrigerant outlet 42 is higher than the refrigerant inlet 41. Is done. In the evaporator 40, the evaporator inlet pipe 12 is integrally formed, and the cylindrical case 11 is joined so as to surround the evaporator inlet pipe 12 and the refrigerant outlet 42. The case 11 is placed in the horizontal direction and constitutes a part of the return low-pressure pipe. A joint portion 14 is welded to the tip of the low-pressure pipe 13 having a double pipe configuration extending in the horizontal direction, and the joint portion 14 and the case 11 are connected by a pipe clamp 16. The welding of the low-pressure pipe 13 in the joint portion 14 is at a position shifted to the lowermost end of the joint portion 14 so as not to cause a level difference between the lower end of the low-pressure pipe 13 and the lower end of the case 11 as much as possible. In this embodiment, sealing is performed by two O-rings 17 in order to reduce external leakage of the refrigerant to the atmosphere as much as possible.

  The expansion valve 1 b has an outlet port 22 connected to the evaporator inlet pipe 12 extending into the case 11, and an inlet port 21 connected to the high-pressure pipe 15. A capillary tube 46 is provided below the high-pressure pipe 15. The capillary tube 46 extends over the connecting portion between the case 11 and the joint portion 14, one end thereof is bent and extends to the vicinity of the bottom surface of the case 11, and the other end is connected to the high pressure pipe 15 and the low pressure pipe. 13 to the space between the two.

  According to this configuration, the refrigerant that has flowed out of the evaporator 40 falls in the wide case 11 that accommodates the expansion valve, and the flow velocity is reduced. The lubricating oil that has been pushed away from the evaporator 40 by the refrigerant falls in the case 11. Then it will collect at the bottom. The refrigerant in the case 11 enters a narrow space between the high pressure pipe 15 and the low pressure pipe 13 and flows to the compressor. At this time, since the flow rate of the refrigerant is increased, a negative pressure is generated in the vicinity of the opening on the downstream side of the capillary tube 46. As a result, the capillary tube 46 sucks up the lubricating oil accumulated at the bottom of the case 11 by the venturi effect. become. The lubricating oil sucked up from the case 11 by the capillary tube 46 is pushed away toward the compressor by the refrigerant flowing in the low-pressure pipe 13. As described above, even if the oil reservoir is formed in the case 11, the lubricating oil can be sucked out from the oil reservoir due to the venturi effect of the capillary tube 46. Is avoided.

  Since the capillary tube 46 functions by being provided in a portion where the flow rate of the refrigerant is higher than that in the case 11, the capillary tube 46 has a section that is narrower than the section of the case 11 as in the case of the first embodiment. It may be arranged at the entrance of the low-pressure pipe 13.

It is sectional drawing which shows the mounting structure of the expansion valve which concerns on 1st Embodiment. It is sectional drawing which shows the mounting structure of the expansion valve which concerns on 2nd Embodiment. It is sectional drawing which shows the mounting structure of the expansion valve which concerns on 3rd Embodiment.

Explanation of symbols

1, 1a, 1b Expansion valve 10 Evaporator outlet piping 11 Case 12 Evaporator inlet piping 13 Low pressure piping 14 Joint portion 15 High pressure piping 16 Pipe clamp 17 O-ring 21 Inlet port 22 Outlet port 23 Body 24 Valve body 25 Spring 26 Adjusting screw 26a Adjustment Member 27 Shaft 28 Power element 29 Locking portion 30 Heat insulation cover 31 Locking portion 40 Evaporator 41 Refrigerant inlet 42 Refrigerant outlet 43 Backup ring 44 Belleville spring 45 Pipe 46 Capillary tube

Claims (9)

An expansion valve is accommodated in the return low pressure pipe between the evaporator outlet and the compressor inlet, and the connection between the inlet port of the expansion valve and the high pressure pipe and the connection between the outlet port of the expansion valve and the evaporator inlet pipe are In the expansion valve mounting structure in the refrigeration cycle, which is performed in the return low-pressure pipe,
The low-pressure pipe to the compressor is located below the high-pressure pipe connected to the expansion valve and the evaporator inlet pipe at a position in the return low-pressure pipe that houses the expansion valve. A featured expansion valve mounting structure.   A case for accommodating the expansion valve is inserted in the middle of the part of the return low-pressure pipe extending in the horizontal direction, and the expansion valve is accommodated in the case so that the temperature sensing part is disposed at a position where the refrigerant passes. The expansion valve mounting structure according to claim 1, wherein the expansion valve mounting structure is provided. An expansion valve is accommodated in the return low pressure pipe between the evaporator outlet and the compressor inlet, and the connection between the inlet port of the expansion valve and the high pressure pipe and the connection between the outlet port of the expansion valve and the evaporator inlet pipe are In the expansion valve mounting structure in the refrigeration cycle, which is performed in the return low-pressure pipe,
An expansion valve mounting structure characterized in that an opening end of a case that accommodates the expansion valve and is connected to a low-pressure pipe to the compressor is directed downward in gravity.   4. The expansion valve mounting structure according to claim 3, wherein the case is joined to the evaporator on a side where both the refrigerant inlet and the refrigerant outlet are open in the horizontal direction.   The evaporator has the refrigerant inlet at a position higher than the refrigerant outlet, the case is joined to the evaporator so as to be connected to the refrigerant outlet, and the refrigerant inlet is bent at a substantially right angle. The expansion valve mounting structure according to claim 4, wherein one end of the expansion valve is joined, and the evaporator inlet pipe is joined to the case with the other end extending into the case.   The expansion valve mounting structure according to claim 3, wherein the low-pressure pipe connected to the case is a double pipe in which the high-pressure pipe is concentrically disposed. An expansion valve is accommodated in the return low pressure pipe between the evaporator outlet and the compressor inlet, and the connection between the inlet port of the expansion valve and the high pressure pipe and the connection between the outlet port of the expansion valve and the evaporator inlet pipe are In the expansion valve mounting structure in the refrigeration cycle, which is performed in the return low-pressure pipe,
A joint which is horizontally disposed to accommodate the expansion valve and forms a part of the return low-pressure pipe, and a low-pressure pipe leading to the inlet of the compressor is joined to the lower end of the case. A capillary tube is straddled so that one end of the connection portion between the case and the joint portion extends to the vicinity of the bottom surface of the case and the other end extends into the low-pressure pipe. An expansion valve mounting structure.   8. The expansion valve mounting structure according to claim 7, wherein the case is joined to the evaporator on a side where both the refrigerant inlet and the refrigerant outlet are open in the horizontal direction. 8. The expansion valve mounting structure according to claim 7, wherein the low-pressure pipe joined to the joint portion is a double pipe in which the high-pressure pipe is concentrically disposed.

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