Pressure control valve

A pressure control valve has a temperature sensing portion. The temperature sensing portion includes a diaphragm and a cap member. A peripheral portion of the diaphragm is fixed to a peripheral portion of the cap member. One surface of the diaphragm and the cap member define a sealed space in which gas is airtightly filled. The other surface of the diaphragm is fixed to one end of the valve body, and subjected to fluid in a fluid chamber. A change of the temperature of the fluid changes a volume of the gas in the sealed space to displace the diaphragm and the valve body to open and close a valve port. A reinforcement member reinforces a fixture of the cap member to the diaphragm.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of Japanese Patent Application No. 2006-103485 filed on Apr. 4, 2006, the content of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a pressure control valve (expansion valve) that controls a fluid pressure in accordance with a fluid temperature. The present invention especially relates to the pressure control valve that controls a refrigerant pressure at an outlet side of a radiator (gas cooler) in a vapor-compression refrigeration cycle in accordance with a refrigerant temperature at the outlet side of the radiator. The pressure control valve is preferably applicable to a refrigeration cycle using a refrigerant, a working pressure of which reaches supercritical phase, such as carbon dioxide (CO2).

BACKGROUND OF THE INVENTION

JP-2002-13844-A, and JP-2000-81157-A having counterparts U.S. Pat. No. 6,189,326 and EP-0971184-B1 disclose pressure control valves that are preferably applicable to a vapor-compression refrigeration cycle for an air conditioning system for a vehicle.

As shown inFIG. 11, the pressure control valve according to JP-2002-13844-A is applied in a refrigeration cycle having a closed circuit that is composed of a compressor1, a condenser (gas cooler)2, a receiver (gas-liquid separator)9, an expansion valve (pressure control valve)103and an evaporator4, to circulate HFC-134a refrigerant therein. The pressure control valve103has a temperature sensing portion130that is formed by sandwiching a peripheral portion of a film-shaped diaphragm131between a first housing (cap member)132and a second housing (flange member)133so that the diaphragm131bulges in accordance with a variation of a pressure in a temperature sensing chamber S. Peripheral portions of these three members131,132,133are welded to each other, and the second housing132is fixed on a main body134of the pressure control valve103. Above-mentioned construction of the temperature sensing portion130endures well in a case in which a refrigerant having a relatively low working pressure (e.g. HFC-134a) circulates, and the diaphragm131is subjected to a relatively low refrigerant pressure at an outlet side of the evaporator4. In this regard, in a CO2refrigeration cycle in which CO2refrigerant circulates, it is necessary to keep the refrigerant pressure in a high pressure range in accordance with a refrigerant temperature at an outlet side of the gas cooler (radiator), in order to maximize a coefficient of performance (COP). If the pressure control valve103is applied in the CO2refrigeration cycle, the diaphragm131is subjected to the high pressure at the outlet side of the gas cooler2. The above-mentioned construction of the temperature sensing portion130does not endure this high refrigerant pressure, and the pressure control valve103is not suitable for a use in the CO2refrigeration cycle.

As shown inFIG. 12, the pressure control valve according to JP-2000-81157-A (U.S. Pat. No. 6,189,326, EP-0971184-B1) is applied in a refrigeration cycle having a closed circuit that is composed of a compressor1, a gas cooler (radiator)2, a pressure control valve203, an evaporator4, an accumulator5and an internal heat exchanger8, to circulate CO2refrigerant therein. The pressure control valve203has a temperature sensing portion230that is formed by bending a peripheral portion of the diaphragm231generally into a right angle to provide a bent portion231aas shown inFIG. 11, fitting the bent portion231aof the diaphragm231between a diaphragm cover (cap member)232and a diaphragm support (flange member)233, and welding these three members231,232,233at a rim portion of the bent portion231a.

However, a construction of the temperature sensing portion230of the pressure control valve203has the following disadvantages.

(1) The diaphragm231must be made of a material having a relatively high strength such as precipitation hardening stainless steel, in order to secure enough endurance for working. As mentioned above, CO2refrigerant has a relatively high working pressure with respect to the working pressure of the conventional HFC-134a refrigerant. Thus, the pressure control valve203according to JP-2000-81157-A (U.S. Pat. No. 6,189,326, EP-0971184-B1) secures sufficiently large burst pressure, by using the diaphragm231having relatively large thickness and by bending the peripheral portion of the diaphragm231into an L-shape.

In this construction, however, the diaphragm231, which has a relatively large strength, is bent, so that an elastic restoration of the diaphragm231distorts in a proximity of the bent portion231a, to deteriorate flatness of the diaphragm231. Thus, when the diaphragm231is fitted to the diaphragm cover232and to a diaphragm support233, a gap is generated between the diaphragm cover232or the diaphragm support233and the diaphragm231, to decrease a dimensional accuracy and/or an endurance of the diaphragm231.

(2) CO2refrigerant has a relatively high working pressure, to increase thickness of the diaphragm cover232and the diaphragm support233. Further, the diaphragm cover232and the diaphragm support233are made of the same kind of stainless material as the diaphragm231is, to be welded to the diaphragm231. Thus, the diaphragm cover232and the diaphragm support233are not easily machined, and the diaphragm cover232and the diaphragm support233having large thicknesses cannot be processed by stamping, to raise manufacturing cost thereof.
(3) CO2refrigerant is ordinarily used in supercritical fluid phase, so that a refrigerant pressure increases as a refrigerant temperature increases. When the compressor1is stopped, the CO2refrigerant cooled in the gas cooler2does not flow especially in the temperature sensing portion230that is filled with the CO2refrigerant, and the CO2refrigerant in the temperature sensing portion230is heated up to a temperature in the engine room. Thus, the refrigerant pressure in the temperature sensing portion230exceeds a maximum working pressure of the refrigeration cycle. It is necessary to prevent parts of the pressure control valve203from scattering even if the refrigerant pressure increases beyond a strength of the temperature sensing portion230. However, rim portions of the members231,232,233have relatively small thicknesses to secure enough melt depth, so that the strength of the temperature sensing portion230is small in the rim portions of the members231,232,233with respect to the strength in the other portion. Thus, a breakage of the temperature sensing portion230can start in the rim portions to scatter the diaphragm cover232.

SUMMARY OF THE INVENTION

The present invention is achieved in view of the above-described issues, and has an object to provide a pressure control valve of which elements that form a temperature sensing portion (e.g. a diaphragm cover (cap member), a diaphragm, a support member (flange member)) can be easily processed, to improve accuracies of parts and to decrease manufacturing cost thereof.

Another object of the present invention is to provide a pressure control valve that is applicable to a refrigeration cycle using a refrigerant (e.g. CO2refrigerant) of which a working pressure is relatively high, and having parts compatible with uses in another kind of pressure control valve that is applicable to a refrigeration cycle using a refrigerant (e.g. HFC-134a refrigerant) of which a working pressure is relatively low, to make manufacturing equipments of the pressure control valves shareable to improve productivity of the parts.

Still another object of the present invention is to provide a pressure control valve of which a breakage of a temperature sensing portion starts in a predetermined portion, to restrict the breakage to a partial breakage to prevent the parts from scattering.

The pressure control valve for controlling a pressure of a fluid in accordance with a temperature of the fluid includes a main body, a valve body, a temperature sensing portion and a reinforcement member. The main body has a valve port and a fluid chamber in which the fluid passes. The valve body is movably installed in the main body to open and close the valve port. The temperature sensing portion is installed on the main body, and provided with a generally film-shaped diaphragm and a cap member. A peripheral portion of the diaphragm is fixed to a peripheral portion of the cap member so that one surface of the diaphragm and the cap member defines a sealed space in which a gas is airtightly filled. The other surface of the diaphragm is fixed to one end of the valve body. The other surface of the diaphragm is subjected to the fluid in the fluid chamber so that a change of the temperature of the fluid changes a volume of the gas in the sealed space to displace the diaphragm and the valve body to open and close the valve port. The reinforcement member is located on the cap member and fastened to the main body to prevent the change of the volume of the gas in the sealed space from breaking a fixture of the peripheral portion of the cap member to the peripheral portion of the diaphragm.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Pressure control valves according to first to ninth embodiments are described in the following, referring to the drawings.

The pressure control valves in the following embodiments are used in a refrigeration cycle (supercritical refrigeration cycle) in which carbon dioxide (CO2) is used as a refrigerant. However, the pressure control valve according to the present embodiment is not limited to these usages.FIG. 1depicts a refrigeration cycle having an internal heat exchanger, in which the refrigerant (CO2) circulates.FIGS. 2-10depict pressure control valves3(3A-3I) according to the embodiments of the present invention, which are applied in the refrigeration cycle shown inFIG. 1.

In the refrigeration cycle shown inFIG. 1, a compressor1sucks and compresses CO2refrigerant, which is used in a relatively high pressure condition with respect to a pressure condition in which other kind of refrigerant such as HFC refrigerant is used. A gas cooler (radiator)2cools the CO2refrigerant compressed by the compressor1. The CO2refrigerant is cooled further in an internal heat exchanger8, and flows into the pressure control valve (expansion valve)3. The pressure control valve3controls a refrigerant pressure at an outlet side of the internal heat exchanger8in accordance with a refrigerant temperature at an outlet side of the gas cooler2, and also serves as a pressure-reducing regulator that decreases the refrigerant pressure. A temperature sensing portion30of the pressure control valve3is located in an outlet side piping of the gas cooler2. The pressure control valve3has a movable portion in which a valve body (35) is displaced in accordance with the refrigerant temperature detected by the temperature sensing portion30to regulate a valve opening degree. InFIG. 1, the temperature sensing portion (30) of the pressure control valve3is illustrated as a temperature sensing tube7and a capillary tube6. In this configuration, a gas filled in the temperature sensing tube7and the capillary tube6changes its volume in accordance with a temperature of the temperature sensing tube7. In the movable portion, a movable member such as a diaphragm (31), a bellows, etc., is displaced to move the valve body (35) to regulate the valve opening degree. That is, the valve opening degree of the refrigerant temperature is regulated by a pressure change of the gas filled in the temperature sensing tube7. In the following embodiments, the gas filled in the temperature sensing tube7is CO2as same as the refrigerant circulated in refrigeration cycle shown inFIG. 1. As shown inFIG. 2, the temperature sensing portion30of the pressure control valve3is configured without the capillary tube6.

In the refrigeration cycle shown inFIG. 1, an evaporator4vaporizes the CO2refrigerant, the pressure of which is reduced in the pressure control valve3. An accumulator5separates gas phase CO2refrigerant from liquid phase CO2refrigerant, and temporarily reserves an excessive CO2refrigerant in the refrigeration cycle. The gas phase CO2refrigerant flows out of the accumulator5into the internal heat exchanger8. Then, the gas phase CO2refrigerant is heated in the internal heat exchanger8and sucked into the compressor1. The internal heat exchanger8is arranged in the refrigeration cycle to perform a heat exchange between the CO2refrigerant flowing from the gas cooler2to the pressure control valve3and the CO2refrigerant flowing from the accumulator5to the compressor1. As such, the pressure control valve3is located in a refrigerant passage between the internal heat exchanger8and the evaporator4. The above-mentioned components of the refrigeration cycle are connected by piping to form a closed circuit to circulate the CO2refrigerant in a sequence the compressor1, the gas cooler2, the internal heat exchanger8, the pressure control valve (expansion valve)3, the evaporator4, the accumulator5, the internal heat exchanger8, and the compressor1.

First Embodiment

The pressure control valve3A according to the first embodiment is described in the following, referring toFIG. 2. A main body34of the pressure control valve3A has: a first flow passage A, which forms a part of a refrigerant passage from the internal heat exchanger8via a valve port34ato the evaporator4; and a second flow passage B, which forms a refrigerant passage from the gas cooler2to the internal heat exchanger8, to be separated from each other. The main body34further has: a refrigerant inlet34bthat is communicated to the internal heat exchanger8; a refrigerant outlet34cthat is communicated to the evaporator4; a first bore34din which the temperature sensing portion30(which is described later) is installed; and a second bore34ein which an adjusting spring (coil spring)36is installed. A valve body35is installed in the main body34to open and close the valve port34a, to allow and interrupt a communication between the internal heat exchanger8and the evaporator4.

The temperature sensing portion30is installed the first bore34dof the main body34. The temperature sensing portion30includes a diaphragm31, a cap member32, a flange member33and a reinforcement member37, to form a sealed space S therein. Specifically, a peripheral portion of a film-shaped diaphragm31, which is formed by stamping process, is sandwiched between the cap member32and the flange member33, which are formed by stamping process. Rims of these three members31,32,33are airtightly fixed to each other by welding. The reinforcement member37is located on the cap member32to cover the peripheral portion and a radially inner side of the peripheral portion, to reinforce a joint structure of the diaphragm31, the cap member32and the flange member33. The temperature sensing portion30is formed in this manner. The peripheral portions of the diaphragm31, the cap member32and the flange member33are formed in flat shapes to provide peripheral flat portions31a,32a,33a. The peripheral flat portion31ais sandwiched between the peripheral flat portions32a,33a, and the peripheral flat portions31a,32a,33aare joined to each other, to form the joint structure not to leave a gap therebetween.

A top end surface of the valve body35is fixed to the diaphragm31by welding, etc. so that the valve body35regulates the valve opening degree of the valve port34ain accordance with a displacement of the diaphragm31. The valve body35has a chamber35atherein. The chamber35ais located in a radially central portion of the valve body35so that the chamber35ais opened to the diaphragm35. A small hole31bis formed in a radially central portion of the diaphragm31so as to communicate the chamber35ato the sealed space S that is defined by the diaphragm31and the cap member32. As such, a room in the sealed space S is extended to the chamber35a. CO2gas, which is the same chemical substance as the refrigerant in the refrigeration cycle, is filled in the sealed space S and the chamber35aat a predetermined pressure. Thus, the diaphragm31is displaced in accordance with a difference between the pressure in the sealed space S and the refrigerant pressure acting on the diaphragm31, so that the valve body35regulates the valve opening degree of the valve port34a.

The flange member33has a cylindrical portion33bin a radially inner portion thereof. A screw thread is formed on an outer circumference of the cylindrical portion33b, and the temperature sensing portion30is fixed to the main body34by screw-fastening the cylindrical portion33bto an inner circumference of the first bore34dof the main body34. Further, the temperature sensing portion30is fitted to a recess34fthat is provided in an upper portion of the main body34. A swaging portion34gis formed integrally with the upper portion of the main body34, and the swaging portion34gis swaged radially inward so that the swaging portion34gtightly fixes the temperature sensing portion30to the main body34to sandwich the reinforcement member37between the upper portion of the main body34and the swaging portion34g. An O-ring30ais installed between the flange member33of the temperature sensing portion30and the main body34to secure an airtightness of a chamber on a lower side of the diaphragm31, which is filled with CO2refrigerant.

The valve body35extends in an axial direction of the pressure control valve3A from the first bore34dto the second bore34e. One axial end portion (the top end surface) of the valve body35is fixed to the diaphragm31as mentioned above, and the inner circumference of the first bore34dand an outer circumference of the valve body35define an annular space d. The annular space d is communicated to the above-mentioned second flow passage B. As such, the refrigerant pressure at the outlet side of the gas cooler2acts via the annular space d on the diaphragm31. The CO2gas filled in the sealed space S of the temperature sensing portion30is subjected to the refrigerant temperature at the outlet side of the gas cooler2.

The valve body35extends through the valve port34adownward beyond the valve portion35bto the other axial end portion35c. An adjusting nut38is screw-fastened on the other end portion35c. The adjusting spring (coil spring)36is interposed between an upper end of the second bore34eon a periphery of the valve port34aand the adjusting nut38to bias the valve body35in a direction to close the valve port34a. By turning the adjusting nut38, an initial load of the adjusting spring36, i.e., a spring force when the valve port34ais closed by the valve portion35b, as demanded. The adjusting spring36, the adjusting nut38and the other end portion35cof the valve body35is installed in the second bore34eof the main body34, which is communicated to an inlet side of the evaporator4. A lid39is fitted into the second body34eof the main body34, to close a lower end of the second bore34e.

In the pressure control valve3A having the above-described construction, a valve closing force of the valve body35is generated by the pressure of the CO2gas in the sealed space S in the temperature sensing portion30and the spring force of the adjusting spring36. A valve opening force of the valve body35is generated by the refrigerant pressure at the outlet side of the gas cooler2. The pressure control valve3A opens and closes the valve port34ain accordance with whether the above-mentioned valve opening force is larger than the valve-closing force or smaller. The pressure of the CO2gas in the sealed space S changes in accordance with the refrigerant temperature at the outlet side of the gas cooler2, and thereby the valve opening degree of the valve port34achanges, to regulate the refrigerant pressure at the outlet side of the internal heat exchanger8.

In the pressure control valve3A according to the first embodiment having the above-described construction, the temperature sensing portion30is formed by sandwiching the peripheral flat portion31aof the diaphragm31between the peripheral flat portions32a,33aof the cap member32and the flange member33. Further, the reinforcement member37tightly holds the joint structure of the diaphragm31, the cap member32and the flange member33, and the radially inner side of the joint structure, and the swaging portion34gof the main body34is swaged radially inward to tightly fix the diaphragm31, the cap member32, the flange member33and the reinforcement member37to the main body34. Accordingly, it is not necessary to bend the peripheral portion of the diaphragm31as in the conventional pressure control valve203shown inFIG. 12. Thus, the diaphragm31can be easily processed even if the diaphragm31is made of relatively hard stainless steel, and it is possible to easily secure an accuracy of flatness of the peripheral flat portion31a, which is fixed to the cap member32and to the flange member33.

Further, the pressure control valve3A is provided with the reinforcement member37. Thus, it is possible to form the cap member32and the flange member33in a thicknesses as small as the cap member132and the flange member133of the temperature sensing portion130in the conventional pressure control valve103shown inFIG. 11, which is applicable to a usage in a refrigeration cycle using HFC-134a refrigerant. Accordingly, it is easy to form the cap member32and the flange member33by stamping process, so that the cap member32and the flange member33can be processed by using a manufacturing equipment substantially as same as a manufacturing equipment for processing parts of the temperature sensing portion of conventional pressure control valve for the refrigeration cycle using HFC-134a refrigerant. This serves to improve productivity of the parts and to decrease manufacturing cost.

Furthermore, differences between thicknesses of the diaphragm31, the cap member32and the flange member33are small, to be easily welded to each other. The diaphragm31, the cap member32and the flange member33can be welded to each other at their rims as those in the conventional pressure control valve for HFC-134a refrigerant. Also this serves to improve productivity of the parts and to decrease manufacturing cost.

Still further, the reinforcement member37, which is for securing enough strength to endure the refrigerant pressure, is separated from the temperature sensing portion30. Thus, the reinforcement member37can be made of a material that is easily processed and has a low cost, such as steel.

Second Embodiment

FIG. 3depicts the pressure control valve3B according to the second embodiment. In the pressure control valve3B according to the second embodiment, the temperature sensing portion30does not include the flange member33, which is provided in the pressure control valve3A according to the first embodiment shown inFIG. 2. Specifically, in the pressure control valve3B, the peripheral flat portion31aof the diaphragm31and the peripheral flat portion32aof the cap member32are put on each other and the rims of the peripheral flat portions31a,32aare welded to each other. The reinforcement member37is arranged to cover the peripheral flat portions31a,32aand a radially inner side of the peripheral flat portions31a,32a, to form the temperature sensing portion30. As such, in the pressure control valve3B, a lower end surface of the recess34fof the main body34serves substantially as same as the peripheral flat portion33aof the flange member33in the pressure control valve3A according to the first embodiment. An O-ring30ais installed between the diaphragm31of the temperature sensing portion30and the main body34to secure the airtightness of the chamber on the lower side of the diaphragm31, which is filled with CO2refrigerant. The temperature sensing portion30having the above-described construction is fitted to the recess34fof the main body34in an analogous fashion to the first embodiment. The swaging portion34gis swaged radially inward to fix the temperature sensing portion30to the main body34so that the reinforcement member37applies a compressive force onto the rims of the peripheral flat portions31a,32a, which are welded to each other.

In the pressure control valve3B according to the second embodiment, a predetermined amount of CO2gas and a predetermined amount of inactive gas (e.g. N2, He) are filled in the sealed space S, to thereby leave out the adjusting spring36and other parts accompanied with the adjusting spring36(e.g. adjusting nut38), which are provided to bias the valve body35in a direction to close the valve port34a. Thus, one axial end of the valve body35, which is opposite from the temperature sensing portion30, is closed. The construction of the temperature sensing portion30of the pressure control valve3B according to the second embodiment can be applied to pressure control valves having the adjusting spring36, etc., such as the pressure control valve3A according to the first embodiment. It is possible to provide the pressure control valve according to the present invention with both of the inactive gas filled in the sealed space S and the adjusting spring36, to bias the valve body35to close the valve port34a.

The other portions of the pressure control valve3B according to the second embodiment have substantially the same construction as those of the pressure control valve3A according to the first embodiment, and not described hereby.

Third Embodiment

FIG. 4depicts the pressure control valve3C according to the third embodiment. The pressure control valve3C according to the third embodiment has a second reinforcement member37A, which is a part separately formed from the main body34, and corresponds to the recess34fand the swaging portion34gof the main body34of the pressure control valve3A according to the first embodiment. That is, peripheral portions of four members of the flange member33, the diaphragm31, the cap member32and the reinforcement member37of the temperature sensing portion30, in which a joint structure of the four members is formed, is fitted into a recess of the second reinforcement member37A. Then, a swaging portion of the second reinforcement member37A is swaged radially inward as shown inFIG. 4, to have a generally U-shaped cross-section, to reinforce the joint structure of the temperature sensing portion30. A screw thread is formed on the outer circumference of the cylindrical portion33b, and the temperature sensing portion30having the above-described construction is fixed to the main body34by screw-fastening the cylindrical portion33bto an inner circumference of the first bore34dof the main body34. A gasket (not shown), which is sandwiched between the main body34and the flange member33, and substantially as same as the O-ring30ain the first and second embodiments, secures the airtightness of the chamber on the lower side of the diaphragm31, which is filled with CO2refrigerant. The other portions of the pressure control valve3C according to the third embodiment have substantially the same construction as those of the pressure control valve3A according to the first embodiment, and not described hereby.

Fourth Embodiment

FIG. 5depicts the pressure control valve3D according to the fourth embodiment. The pressure control valve3C according to the fourth embodiment has a reinforcement member37having a single-piece construction that includes the reinforcement member37mainly for reinforcing the cap member32and the second reinforcing member37A mainly for reinforcing the peripheral portion of the temperature sensing portion30, which are separately provided in the third embodiment, so as to reduce the number of parts. As such, the reinforcement member37in the fourth embodiment covers an upper surface of the cap member32from the peripheral portion to the radially inner side of the peripheral portion, and the joint structure of the temperature sensing portion30from its lower surface to its upper surface in a U-shaped manner. The other portions of the pressure control valve3D according to the fourth embodiment have substantially the same construction as those of the pressure control valve3C according to the third embodiment, and not described hereby.

Fifth Embodiment

FIG. 6depicts the pressure control valve3E according to the fifth embodiment. In the fifth embodiment, the second reinforcement member37A, which is a part separately formed from the main body34, corresponds to the recess34fand the swaging portion of the main body34in the first embodiment. Thus, a construction of the second reinforcement member37A in the fifth embodiment is partially different from a construction of the second reinforcement member37A in the third embodiment. In the third embodiment, the temperature sensing portion30is fixed to the main body34by screw-fastening the cylindrical portion33bof the flange member33to the first bore34dof the main body34. In this regard, the second reinforcement member37A in the fifth embodiment is provided with a cylindrical portion37bin a radially inner portion thereof, and a screw thread is formed on an outer circumference of the cylindrical portion37a. Then, the temperature sensing portion30is fixed to the main body34by screw-fastening the cylindrical portion37bto the inner circumference of the first bore34dof the main body34. Thus, the flange member33in the fifth embodiment is not provided with the cylindrical portion33b. A gasket (not shown), which is sandwiched between the main body34and the second reinforcement member37A, secures the airtightness of the chamber on the lower side of the diaphragm31, which is filled with CO2refrigerant. The other portions of the pressure control valve3E according to the fifth embodiment have substantially the same construction as those of the pressure control valve3C according to the third embodiment, and not described hereby.

Sixth Embodiment

FIGS. 7A,7B depict the pressure control valve3F according to the sixth embodiment. A construction of the temperature sensing portion30in the sixth embodiment is substantially the same as the construction of the temperature sensing portion30in the third embodiment, except for the following point. In the third embodiment, thicknesses of the reinforcement member37and the second reinforcement member37A are respectively constant over an entire circumference of the temperature sensing portion30. In this regard, the reinforcement member37and the second reinforcement member37in the sixth embodiment respectively have a plurality of slit portions37c(three slit portions37cinFIGS. 7A,7B) that are arranged at intervals along the circumference of the temperature sensing portion30. The slit portions37cprovides portions in which strengths of the reinforcement member37and the second reinforcement member37A are smaller than strengths in the other portions of the reinforcement member37and the second reinforcement member37A. The other portions of the pressure control valve3F according to the sixth embodiment have substantially the same construction as those of the pressure control valve3C according to the third embodiment, and not described hereby.

When the temperature sensing portion30is subjected to an excessively large force to generate a crack in the welded joint structure of the temperature sensing portion30, a welded joint structure of the diaphragm31, the cap member32and the flange member33firstly breaks in the slit portions37c, by providing the reinforcement member37and the second reinforcement member37A with portions in which the reinforcement member37and the second reinforcement member37A have strengths smaller than in the other portions. Thus, the gas in the sealed space S starts leaking in the slit portions37c. As such, it is possible to prevent parts of the pressure control valve3F such as the cap member32, the reinforcement member37and the second reinforcement member37A from scattering.

Seventh Embodiment

FIGS. 8A,8B depict the pressure control valve3G according to the seventh embodiment. A construction of the temperature sensing portion30in the seventh embodiment is substantially the same as the construction of the temperature sensing portion30in the third embodiment, except for the following point. In the third embodiment, thickness of the second reinforcement member37A is constant over an entire circumference of the temperature sensing portion30. In this regard, the second reinforcement member37A in the seventh embodiment has a plurality of thin-walled portions37d(three thin-walled portions37cinFIGS. 8A,8B) that are arranged at intervals along the circumference of the temperature sensing portion30. The other portions of the pressure control valve3G according to the seventh embodiment have substantially the same construction as those of the pressure control valve3C according to the third embodiment, and not described hereby.

When the temperature sensing portion30is subjected to an excessively large force, the cap member32is deformed to open the swaging portion. By providing the second reinforcement member37A with the thin-walled portions37dthat are more easily deformed than in the other portions, it is possible to prevent the deformation of the swaging portion from extending to an entire circumference of the second reinforcement member37A. As such, parts of the pressure control valve3G from scattering.

Eighth Embodiment

FIGS. 9A-9Ddepict the pressure control valve3H according to the eighth embodiment.FIGS. 9C,9D depict an action of the pressure control valve3H according to the eighth embodiment. A construction of the temperature sensing portion30in the eighth embodiment is substantially the same as the construction of the temperature sensing portion30in the third embodiment, except for the following point. In the third embodiment, thicknesses of the reinforcement member37and the second reinforcement member37A are respectively constant over an entire circumference of the temperature sensing portion30. In this regard, the reinforcement member37and the second reinforcement member37A in the eighth embodiment respectively have a plurality of thin-walled portions37d(five slit portions37dinFIGS. 9A-9D) that are arranged at intervals along the circumference of the temperature sensing portion30. The other portions of the pressure control valve3H according to the eighth embodiment have substantially the same construction as those of the pressure control valve3C according to the third embodiment, and not described hereby.

As shown inFIGS. 9C,9D, when the pressure in the sealed space S increases to apply an excessively large force to the temperature sensing portion30, the swaging portion of the second reinforcement member37A is deformed to open, the reinforcement member37, which reinforces the cap member32, is deformed in a portion between the thin-walled portions37dprior to the other portions, to prevent the deformation of the swaging portion from extending an entire circumference of the second reinforcement member37A. As such, parts of the pressure control valve3H from scattering.FIGS. 9C,9D illustrate a condition when the swaging portion of the second reinforcement member37A is deformed to open, to leak the gas in the sealed space S of the temperature sensing portion30. In the eighth embodiment, the reinforcement member37and the second reinforcement member37A are provided with the thin-walled portions37dhaving relatively small strengths, so that the gas leaks only in the portion between a couple of the thin-walled portions37das shown inFIGS. 9C,9D. As a result, the deformation of the swaging portion do not extend over the entire circumference of the second reinforcement member37A, to prevent the parts of the pressure control valve3H such as the cap member32and the reinforcement member37from scattering.

Each of the above-described pressure control valves3F-3H according to the sixth to eighth embodiments has the temperature sensing portion30that has basically the same construction as the construction of the temperature sensing portion30in the third embodiment, except for the reinforcement member37and/or the second reinforcement member37A. In this regard, the construction of the temperature sensing portion30, which is provided with slit portions37cand/or the thin-walled portions37dthat have smaller strengths than the strengths of the other portions, can be applied to the constructions of the temperature sensing portions30in the first, second, fourth and fifth embodiments. The temperature sensing portions30in the sixth to eighth embodiments has the slit portions37cand/or the thin-walled portions37dthat have strengths relatively smaller than the other portions. Alternatively, it is also possible to realize the temperature sensing portion30with portions having relatively small strengths, for example, by providing the reinforcement portion37and/or the second reinforcement portion37A with depressed portions, portions having relatively small cross-sectional area etc., or providing the swaging portions partially with a portion having a relatively small cross-sectional area.

Ninth Embodiment

FIG. 10depicts the pressure control valve3I according to the ninth embodiment. A construction of the pressure control valve3I in the ninth embodiment is substantially the same as the construction of the pressure control valve3A in the first embodiment, which is shown inFIG. 2, except for the following point. The pressure control valve3I in the ninth embodiment is provided with a cover40that covers the reinforcement member37, in addition to the construction of the pressure control valve3A according to the first embodiment shown inFIG. 2. The other portions of the pressure control valve3I according to the ninth embodiment have substantially the same construction as those of the pressure control valve3A according to the first embodiment, and not described hereby. The pressure control valve is installed in an engine room to regulate the refrigerant pressure at the outlet side of the gas cooler2. In this regard, an atmospheric temperature in the engine room is ordinarily larger than the refrigerant temperature. Thus, the refrigerant temperature cannot be detected with accuracy when the atmospheric temperature in the engine room heats the temperature sensing portion30. Further, the pressure control valve is installed normally to place the temperature sensing portion30vertically up. Thus, splashed water can remain in a dent portion radially inside the reinforcement member37, so that the temperature sensing portion30is cooled down to make it impossible to detect the refrigerant temperature with accuracy. Further, the water remaining in the dent portion inside the reinforcement member37can cause corrosion.

In this regard, the pressure control valve3I according to the ninth embodiment is provided with the cover40, which is made of rubber, resin and the like, to cover the dent portion to insulate the temperature sensing portion30and to prevent an entry of splashed water.