Vapor-compression refrigerant cycle system with ejector

A vapor-compression refrigerant cycle system having an ejector includes a first evaporator for evaporating refrigerant from a pressure-increasing portion of the ejector, and a second evaporator for evaporating refrigerant to be drawn into a refrigerant suction port of the ejector. Furthermore, a valve member for opening and closing a refrigerant passage of the second evaporator is arranged in serious with the second evaporator in a refrigerant flow, and refrigerant flowing out of the second evaporator flows into the refrigerant suction port through a refrigerant suction pipe. The system is provided to restrict lubrication oil contained in refrigerant from being introduced from the ejector into and staying in the refrigerant suction pipe when the valve member is closed. For example, the refrigerant suction port is provided at an upper side of the ejector.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Applications No. 2004-284098 filed on Sep. 29, 2004 and No. 2005-28165 filed on Feb. 3, 2005, the contents of which are incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a vapor-compression refrigerant cycle system having an ejector used as a refrigerant decompression unit and a refrigerant circulating unit. The vapor-compression refrigerant cycle system is suitably used for a vehicle air conditioner, for example.

BACKGROUND OF THE INVENTION

A vapor-compression refrigerant cycle system (ejector cycle system) using an ejector as a refrigerant decompression unit and a refrigerant circulating unit is described in JP-B1-3322263 (corresponding to U.S. Pat. No. 6,574,987 and U.S. Pat. No. 6,477,857), for example. In this vapor-compression refrigerant cycle system, a first evaporator is arranged between the ejector and a gas-liquid separator located downstream from the ejector, and a second evaporator is arranged between a liquid refrigerant outlet side of the gas-liquid separator and a refrigerant suction port of the ejector, as an example.

The inventors of this application studied an example for switching a cooling function of the second evaporator. In this example, an electromagnetic valve is provided at an upstream portion of the second evaporator, and the electromagnetic valve is closed when the cooling function of the second evaporator stops. In this case, when the electromagnetic valve is closed, a refrigerant stream drawn from the second evaporator into the refrigerant suction port of the ejector is not generated. In this example, if the refrigerant suction port is opened at a lower portion of the ejector, lubrication oil (i.e., refrigerator oil) contained in a refrigerant flowing through the inside of the ejector falls into the refrigerant suction port by the weight of the lubrication oil. Accordingly, the lubrication oil stays in a refrigerant suction pipe connected to the refrigerant suction port of the ejector and the second evaporator, when the electromagnetic valve is closed. In this case, a returning amount of the lubrication oil returning to the compressor is reduced, and a lubrication oil shortage may be caused in the compressor.

SUMMARY OF THE INVENTION

In view of the above-described problems, it is an object of the present invention to provide a vapor-compression refrigerant cycle system having an ejector, which can prevent a returning amount of lubrication oil returning to a compressor from being reduced when a cooling function of an evaporator connected to a refrigerant suction port of the ejector stops.

According to an aspect of the present invention, a vapor-compression refrigerant cycle system includes a compressor which compresses refrigerant, a refrigerant radiator for cooling high-pressure refrigerant discharged from the compressor, and an ejector. The ejector includes a nozzle for decompressing and expanding refrigerant from the refrigerant radiator, a refrigerant suction port from which gas refrigerant is drawn by a refrigerant steam jetted from the nozzle, and a pressure-increasing portion in which the refrigerant jetted from the nozzle and the gas refrigerant drawn from the refrigerant suction port are mixed and pressure of the refrigerant is increased by converting the speed energy to pressure energy.

In the vapor-compression refrigerant cycle system, a first evaporator for evaporating refrigerant flowing out of the pressure-increasing portion of the ejector is located at a downstream side of the ejector, a second evaporator for evaporating refrigerant to be drawn into the refrigerant suction port of the ejector is provided, a valve member for opening and closing a refrigerant passage of the second evaporator is arranged in serious with the second evaporator in a refrigerant flow, and a refrigerant suction pipe is located to have a first end connected to a refrigerant outlet of the second evaporator and a second end connected to the refrigerant suction port of the ejector. Furthermore, the system is provided with means for restricting lubrication oil contained in refrigerant from being introduced into and staying in the refrigerant suction pipe through the refrigerant suction port when the valve member is closed. Thus, it can prevent the lubrication oil returning to the compressor from being insufficient when the valve member is closed, and lubrication property of the compressor can be improved.

For example, the refrigerant suction port is provided at an upper side of the ejector. In this case, it can prevent the lubrication oil from falling into the refrigerant suction port in the ejector with a simple structure.

Alternatively, the refrigerant suction pipe can be provided with a standing portion at a downstream position adjacent to the refrigerant suction port, and the standing portion extends upwardly to a position higher than the refrigerant suction port. In this case, the lubrication oil amount staying in the refrigerant suction pipe can be controlled to a small amount, even when the refrigerant suction port is provided at a lower portion of the ejector.

Alternatively, a check valve can be located at an inlet portion of the refrigerant suction port to only allow a refrigerant flow from the refrigerant suction pipe into the refrigerant suction port. Therefore, even when the refrigerant suction port is provided at a lower portion of the ejector, the check valve prevents the lubrication oil from flowing into the refrigerant suction pipe from the refrigerant suction port.

In the vapor-compression refrigerant cycle system, an auxiliary valve member can be arranged in a refrigerant passage through which refrigerant from the second evaporator is introduced to the refrigerant suction port of the compressor. In this case, the valve member is located at an inlet portion of the refrigerant suction port of the ejector, and the auxiliary valve member is opened when the valve member is closed, so that the refrigerant flowing out of the second evaporator flows into the suction side of the compressor. Accordingly, even when the refrigerant suction port is provided at a lower portion of the ejector, lubrication oil is prevented from staying in the refrigerant suction pipe by the valve member and the auxiliary valve member.

The second evaporator can be arranged to perform a cooling operation for cooling air, and a blower for blowing air to the second evaporator can be provided. In this case, the valve member is opened so that refrigerant always flows into the second evaporator when the compressor operates, and the blower is stopped when the cooling function of the second evaporator is stopped. Because the refrigerant always flows into the second evaporator, a refrigerant stream from the second evaporator to the refrigerant suction port of the ejector can be always formed, thereby preventing the lubrication oil from staying in the refrigerant suction pipe.

Alternatively, the valve member can be forcibly opened, when a predetermined time passes after the valve member is closed while the compressor operates. Therefore, it can prevent a shortage of the lubrication oil in the compressor.

Furthermore, when the cooling operation of the second evaporator is stopped when the compressor stats operating, the valve member is opened once for a predetermined time. Accordingly, even at a start time of the compressor, the lubrication oil staying in the second evaporator and the refrigerant suction pipe can be returned to the compressor, thereby preventing a shortage of the lubrication oil in the compressor.

In the vapor-compression refrigerant cycle system, a bypass passage, through which refrigerant from the refrigerant radiator flows into the refrigerant suction port while bypassing the second evaporator and the valve member, can be provided. In this case, an auxiliary valve member is located in the bypass passage for opening and closing the bypass passage, and the auxiliary valve member is opened when the valve member is closed while the compressor operates. Accordingly, when the refrigerant evaporating function (e.g., cooling function) of the second evaporator is stopped, it can prevent the lubrication oil from being insufficient in the compressor, and lubrication property of the compressor can be effectively improved.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

First Embodiment

In the first embodiment, a vapor-compression refrigerant cycle system having an ejector, shown inFIG. 1, is typically used for a vehicle air conditioner, as an example. The vapor-compression refrigerant cycle system includes a main refrigerant path15in which refrigerant flows in this order of a discharge side of a compressor10, a refrigerant radiator11, a flow adjustment valve12, an ejector13, a first evaporator14and a suction side of the compressor10.

In this embodiment, the compressor10for compressing refrigerant is driven and rotated by a vehicle engine through a belt and an electromagnetic clutch10a, etc. The operation of the compressor10is switched and controlled by the electromagnetic clutch10a. In this case, by controlling an on/off operation ratio of the compressor10, a refrigerant discharge capacity of the compressor10can be controlled.

The refrigerant radiator11cools high-pressure refrigerant discharged from the compressor10by performing a heat exchange between the high-pressure refrigerant and outside air (i.e., air outside a passenger compartment) blown by a cooling fan (now shown). In this embodiment, as an example, the refrigerant radiator11is a condenser integrated with a gas-liquid separator11a. The separator-integrated condenser (11) is constructed with a condensation portion for cooling and condensing the high-pressure refrigerant discharged from the compressor10, the gas-liquid separator11ain which the refrigerant from the condensation portion is separated into gas refrigerant and liquid refrigerant, and a super-cooling portion in which the liquid refrigerant separated in the gas-liquid separator11ais super-cooled.

The flow adjustment valve12is located at a downstream side of the refrigerant radiator11to adjust a refrigerant flow amount in the first evaporator14. As an example, a thermal expansion valve is used as the flow control valve12, in this embodiment. In this case, an open degree of the flow adjustment valve12(thermal expansion valve) is adjusted so that a superheating degree of refrigerant at a refrigerant outlet of the first evaporator14becomes a predetermined value.

The ejector13is a kinetic pump (refer to JIS Z 8126 No. 2.1.2.3) for performing a transporting of a fluid by entrainment of a jet flow of a drive fluid injected at a high speed.

Specifically, the ejector13includes a nozzle portion13aand a diffuser portion13b. The nozzle portion13adecompresses and expands refrigerant flowing from the flow adjustment valve12substantially in isentropic by reducing a refrigerant passage area. The refrigerant flow speed is increased in the nozzle portion13aby converting pressure energy of the refrigerant to speed energy of the refrigerant.

The ejector13has a refrigerant suction port13cfrom which gas refrigerant from the second evaporator21is drawn by the high speed refrigerant flow jetted from the nozzle portion13a.

In the diffuser portion13b, the speed energy of refrigerant (dynamic pressure) is converted to the pressure energy of refrigerant (stationary pressure) by gradually increasing a sectional passage area of the diffuser portion13b. Accordingly, the refrigerant pressure is increased in the diffuser portion13b.

The refrigerant flowing out of the diffuser portion13bflows into the first evaporator14. For example, the first evaporator14is arranged in an air passage of a front air conditioning unit to cool air to be blown into a front side in the passenger compartment.

In this case, a first blower16(e.g., electrical blower) is disposed in the front air conditioning unit so that air to be blown into the front side of the passenger compartment is sent to the first evaporator14. Therefore, low-pressure refrigerant decompressed in the ejector13is evaporated in the first evaporator14by absorbing heat from air passing through the first evaporator14, thereby the air to be blown into the front side of the passenger compartment is dehumidified and cooled. The gas refrigerant evaporated in the first evaporator14is drawn into the compressor10, and is circulated in the main refrigerant circulating path15.

First and second branch passages17,18branched from the main refrigerant circulating path15are provided at a refrigerant outlet portion of the refrigerant radiator11. The first branch passage17is a refrigerant passage from the refrigerant outlet portion of the refrigerant radiator11to the refrigerant suction port13cof the ejector13. In the first branch passage17, there is provided with an electromagnetic valve19, a throttle mechanism20and a second evaporator21in serious, in this order from a refrigerant upstream side to a refrigerant downstream side.

The electromagnetic valve19is a switching valve for switching a refrigerant flow in the first branch passage17. The throttle mechanism20decompresses high-pressure refrigerant from the refrigerant outlet portion of the refrigerant radiator11into gas-liquid two-phase refrigerant having a low temperature and low pressure, and also adjusts a flow amount of refrigerant flowing into the second evaporator21.

For example, the second evaporator21is located in a refrigerator mounted on a vehicle, and cools air blown by a second blower22(e.g., electrical blower) located in the refrigerator. Generally, a variation in a thermal load of the refrigerator is small, a fixed throttle can be used as the throttle mechanism20. However, a suitable variable throttle can be used as the throttle mechanism20, and the electromagnetic valve19and the throttle mechanism20can be constructed with a single member.

The second branch passage18is a refrigerant passage from the refrigerant outlet portion of the refrigerant radiator11to the suction side of the compressor10. In the second branch passage18, a throttle mechanism23and a third evaporator24are arranged in serious in this order. For example, the third evaporator24is arranged in an air passage of a rear air conditioning unit (not shown) to cool air to be blown to a rear seat side in the passenger compartment.

For example, air is sent to the third evaporator24by a third blower (e.g., electrical blower)24a, which is located in the rear air conditioning unit, and the cooled air from the third evaporator24is blown toward the rear seat side in the passenger compartment. Low-pressure refrigerant after decompressed in the throttle mechanism23is evaporated in the third evaporator24by absorbing heat from air to be blown to the rear seal side of the passenger compartment, so that air to be blown toward the rear seat side of the passenger compartment is cooled and cooling function can be obtained. In this example shown inFIG. 1, a thermal expansion valve is used as the throttle mechanism23, and a flow amount of refrigerant flowing into the third evaporator24is adjusted by the throttle mechanism23. In this case, a valve opening degree of the throttle mechanism23can be adjusted so that a super-heating degree of the refrigerant at the outlet of the evaporator24becomes a predetermined value.

FIG. 2is a cross-sectional view of the ejector13taken along line II—II inFIG. 1. The top-bottom direction inFIG. 2corresponds to the top-bottom direction when the ejector13is mounted to a vehicle. As shown inFIG. 2, the ejector13has a cylindrical housing13d, and the refrigerant suction port13cis opened in the housing13dat a top portion.

A refrigerant suction pipe25has a vertically extending portion that is connected to the refrigerant suction port13cand has a height H1. The refrigerant suction pipe25is a refrigerant pipe from the outlet portion of the second evaporator21to the refrigerant suction port13cof the ejector13, as shown inFIG. 1. InFIG. 2, a cylindrical portion13epositioned inside the housing13dby a predetermined clearance constructs an inlet passage of the nozzle portion13.

The electromagnetic clutch10aof the compressor10, the first to third blowers16,22,24aand the electromagnetic valve19, etc. are electrically controlled by control signals from a control device26. The control device26is constructed with a microcomputer and circuits around the microcomputer. Detection signals of a sensor group (not shown) and operation signals of an operation member of an air-conditioning operation panel are input to the control device26.

Next, operation of the vapor-compression refrigerant cycle system according to this embodiment will be described. When a cooling operation (cooling function) is necessary for the refrigerator mounted to the vehicle, a refrigerator switch (not shown) of the air-conditioning operation panel is turned on by a passenger. In the cooling operation of the refrigerator, the operation of the electromagnetic valve19is controlled by the control device26so that the electromagnetic valve19is opened. In this state, when the compressor10is operated by the vehicle engine, the compressor10compresses refrigerant to be in a high-pressure and high-temperature state. The high-pressure and high-temperature refrigerant discharged from the compressor10flows into the refrigerant radiator11, and is cooled and condensed by outside air.

The cooled refrigerant flowing out of the refrigerant radiator11is branched into a refrigerant stream flowing through the main refrigerant circulating path15, a refrigerant stream flowing through the first branch passage17and a refrigerant stream flowing through the second branch passage18.

The refrigerant flowing through the main refrigerant circulating path15passes through the flow adjustment valve12, and flows into the ejector13. The refrigerant flowing into the ejector13from the flow adjustment valve12is decompressed and expanded in the nozzle portion13a. That is, the pressure energy of the refrigerant is converted to the speed energy of the refrigerant in the nozzle portion13a, and high-speed refrigerant is jetted from a jet port of the nozzle portion13a. At this time, a refrigerant pressure is reduced around the outlet of the nozzle portion13adue to the high-speed jet flow of refrigerant, so that gas refrigerant evaporated in the second evaporator21is drawn from the refrigerant suction port13c.

The refrigerant jetted from the nozzle portion13and the refrigerant drawn from the refrigerant suction port13care mixed at a downstream side of the nozzle portion13a, and flows into the diffuser portion13b. Because the passage sectional area is enlarged in the diffuser portion13b, the speed energy of the refrigerant is converted to the pressure energy in the diffuser portion13b, so that the pressure of refrigerant is increased in the diffuser portion13b. The refrigerant flowing out of an outlet port of the diffuser portion13bflows into the first evaporator14.

In the first evaporator14, the refrigerant is evaporated by absorbing heat from air passing through the first evaporator14so that air to be blown to the front seat side in the passenger compartment is cooled. The gas refrigerant from the first evaporator14is drawn into the compressor10and is compressed in the compressor10to be circulated in the main refrigerant circulating path15. The cool air cooled in the evaporator14is blown by the first blower16toward the front seat side in the passenger compartment. Accordingly, a cooling operation for cooling the front seat area of the passenger compartment can be performed.

When the flow adjustment valve12is a thermal expansion valve, a valve opening degree of the flow adjustment valve12can be adjusted so that the super-heating degree of refrigerant at the outlet portion of the first evaporator14becomes a predetermined value, and a refrigerant amount flowing in the first evaporator14can be adjusted.

The refrigerant branched from the main refrigerant circulating path15into the second branch passage18is decompressed in the throttle mechanism23. Low-pressure refrigerant decompressed in the throttle mechanism23flows into the third evaporator24, and is evaporated by absorbing heat from air to be blown toward the rear seat side of the passenger compartment. The evaporated gas refrigerant from the third evaporator24is drawn into the suction side of the compressor10and is compressed in the compressor10. The cool air cooled by the third evaporator24is blown toward the rear seat area in the passenger compartment by the third blower24aso as to cool the rear seat area in the passenger compartment.

The refrigerant from the first evaporator14and the refrigerant from the third evaporator24are joined at a downstream refrigerant side of the first evaporator14and the third evaporator24before the refrigerant flows into the compressor10. Therefore, a refrigerant evaporation pressure of the first evaporator14is the same as a refrigerant evaporation pressure of the third evaporator24. As a result, a refrigerant evaporation temperature is the same at both the first and third evaporators10and24, and cooling capacity having the same temperature level can be obtained in both the first and third evaporators14and24.

The refrigerant flowing from the main refrigerant circulating path15into the first branch passage17passes the opened electromagnetic valve19, and then is decompressed in the throttle mechanism20. Low pressure refrigerant after being decompressed in the throttle mechanism20flows into the second evaporator21, and is evaporated in the second evaporator21by absorbing heat from air blown into the refrigerator by the second blower22. Therefore, cooling function of the refrigerator can be obtained by the second evaporator21. Gas refrigerant evaporated in the second evaporator21is drawn into the refrigerant suction port13cof the ejector13.

The refrigerant evaporation pressure of the first evaporator14corresponds to the pressure after pressure-increased in the diffuser portion13b. In contrast, because the refrigerant outlet side of the second evaporator21is coupled to the refrigerant suction port13cof the ejector13, a reduced pressure immediately after decompressed at the nozzle portion13ais applied to the second evaporator21.

Accordingly, the refrigerant evaporation pressure of the second evaporator21can be made lower than the refrigerant evaporation pressure of the first evaporator14and the third evaporator24. Therefore, the refrigerant evaporation temperature of the second evaporator21can be made lower than the refrigerant evaporation temperature of the first evaporator14and the third evaporator24. Thus, a cooling function in a relatively low temperature range suitable to the cooling operation in the refrigerator can be obtained, while a cooling function in a relatively high temperature range suitable to the cooling operation of the passenger compartment can be obtained by the first evaporator14and the third evaporator24.

When the cooling operation for cooling the refrigerator is unnecessary, the refrigerator switch of the air conditioning operation panel is turned off by the passenger. In this case, electrical power supplied to the electromagnetic valve19is stopped by the control device26, and the electromagnetic valve19is closed. With this operation, the operation of the second blower22is stopped by the control device26.

The refrigerant flowing into the first branch passage17is shut because the electromagnetic valve19is closed. In this case, refrigerant flows through the main refrigerant circulating path15and the second branch passage18, and cooling function for cooling the passenger compartment can be obtained by the first evaporator14and the second evaporator24.

When the refrigerant flow of the first branch passage17is shut, refrigerant is not drawn into the refrigerant suction port13cof the ejector13. In this case, because the density of the lubrication oil contained in the refrigerant becomes larger in a downstream space of the nozzle portion13awithin the ejector13, the lubrication oil tends to collect at a lower portion within the ejector13at the downstream side of the nozzle portion13a.

FIG. 3is a comparison example in which the refrigerant suction port13cconnected to the second evaporator21is positioned at a bottom side of the ejector13and the refrigerant suction pipe25is connected to the refrigerant suction port13cunder the ejector13. In this case, the lubrication oil falls into the refrigerant suction port13cby its weight, and stays in the refrigerant suction pipe25.

In contrast, in the first embodiment, the refrigerant suction port13cof the ejector13is located at the upper portion (e.g., the top portion inFIG. 2) of the housing13dof the ejector13, and the extending portion vertically extended by the predetermined height H is provided in the refrigerant suction pipe25. Therefore, it can prevent the lubrication oil contained in the refrigerant from falling into the refrigerant suction port13c, at a downstream area of the nozzle portion13awithin the ejector13.

Accordingly, the lubrication oil is prevented from staying in the refrigerant suction pipe25when the electromagnetic valve19is closed. As a result, a shortage of the lubrication oil in the compressor10can be prevented.

In the above-described embodiment, the refrigerant suction port13cis arranged at the top portion of the housing13dof the ejector13. However, the refrigerant suction port13cof the ejector13can be arranged at the positions “a” and “b” shown by the chain line inFIG. 2, lower than the top portion and higher than the center portion. In this case, the refrigerant suction pipe25can be connected to the refrigerant suction port13cin a slant state as shown inFIG. 2. Even in this case, it can prevent the lubrication oil from falling into the refrigerant suction port13c, and thereby preventing the lubrication oil from staying in the refrigerant suction pipe25.

Furthermore, the refrigerant suction port13ccan be arranged at an upper portion of the housing13dof the ejector13in the range “c” (the upper side range of 180°) shown inFIG. 2.

Second Embodiment

In the above-described first embodiment, the refrigerant suction port13cof the ejector13is provided at an upper portion of the housing13d. However, in the second embodiment, the refrigerant suction port13cis provided at a lower portion of the housing13d, and a standing portion25aextending in a vertical direction is formed at a downstream portion in the refrigerant suction pipe25, as shown inFIG. 4. The standing portion25acan be vertically extended upwardly from a lowest portion of the ejector13by a predetermined height. InFIG. 4, H2indicates the height of the standing portion25avertically extended.

In this embodiment, a downstream pipe portion downstream from the standing portion25ain the refrigerant suction pipe25can be made shorter. Accordingly, even when the refrigerant suction portion13cis arranged at the lower portion (e.g., bottom portion) of the housing13d, the lubrication amount staying in the refrigerant suction pipe25can be controlled at a little amount.

InFIG. 4, the standing portion25aand the upstream portion upstream from the standing portion25aare vertically bent, however, may be bent in a circular arc shape. Further, the height of the standing portion25acan be changed only when the top portion of the standing portion25ais higher than the refrigerant suction port13c. Furthermore, when the top portion of the standing portion25ais set higher than a center portion of the ejector13, the lubrication amount staying in the refrigerant suction pipe25can be effectively reduced.

In the second embodiment, the other parts may be made similar to those of the above-described first embodiment.

Third Embodiment

FIG. 5shows a vapor-compression refrigerant cycle system of the third embodiment. In the third embodiment, the electromagnetic valve19is not provided in the first branch passage17, and refrigerant flowing from the main refrigerant circulating path15flows into the second evaporator21in the first branch portion17after passing through the throttle mechanism20. Therefore, when the compressor10is operated, refrigerant always flows into the second evaporator21in the first branch passage17.

Thus, in this embodiment, when the refrigerator function (refrigerator cooling operation) is stopped, the operation of the second blower22is stopped. When the second blower22is stopped, a heat absorbing amount of the refrigerant in the second evaporator2is very small, and a large amount of the liquid refrigerant having passed through the throttle mechanism20is drawn into the refrigerant suction port of the ejector13without being evaporated in the second evaporator21.

In the third embodiment, a refrigerant suction stream from the refrigerant suction pipe25to the refrigerant suction port13cis always formed when the compressor10operates. Accordingly, even when the refrigerant suction port13cis arranged at a lower portion (e.g., bottom portion), the lubrication oil does not fall into the refrigerant suction port13cby its weight.

In the third embodiment, the other parts may be set similar to those of the above-described first embodiment. Further, even in the third embodiment, the refrigerant suction port13ccan be arranged at an upper portion of the housing13dof the ejector13.

Fourth Embodiment

FIG. 6shows a vapor-compression refrigerant cycle system of the fourth embodiment. In the vapor-compression refrigerant cycle system, the refrigerant suction port13cis provided at a lower portion (e.g., bottom portion) of the ejector13, and a check valve27is provided at an inlet portion of the refrigerant suction port13c. That is, the check valve27, which only allows one direction refrigerant flow from refrigerant suction pipe25to the refrigerant suction port13c, is located at a downstream end portion of the refrigerant suction pipe25. Therefore, the check valve27prevents a reverse flow of the refrigerant and the lubrication oil from the refrigerant suction port13cto the refrigerant suction pipe25.

Accordingly, the check valve27prevents the lubrication oil from staying in the refrigerant suction pipe25when the electromagnetic valve19closes. That is, when the refrigerator function (refrigerator cooling operation) is stopped, the check valve27prevents the lubrication oil from flowing into the refrigerant suction pipe25from the refrigerant suction port13ceven when the refrigerant suction port13cis provided at the bottom portion of the housing13d.

In the fourth embodiment, the other parts can be made similar to those of the above-described first embodiment.

Fifth Embodiment

FIG. 7shows a vapor-compression refrigerant cycle system of the fifth embodiment. In the above-described first embodiment, the electromagnetic valve19is provided at an upstream side of the throttle mechanism20in the first branch passage17. In this fifth embodiment, the refrigerant suction port13cis provided at a lower portion (e.g., bottom portion) of the housing13d, and the electromagnetic valve19is located at an inlet portion of the refrigerant suction port13c. That is, the electromagnetic valve19is located at a downstream end portion of the refrigerant suction pipe25. Furthermore, a bypass passage28connected to the suction side of the compressor10is connected to the first branch passage17at a downstream side of the second evaporator21. An auxiliary electromagnetic valve29operatively linked with the electromagnetic valve19is located in the bypass passage28.

In the fifth embodiment, when the switch of the refrigerator is turned off and a refrigerator stopping state is set, the electromagnetic valve19is closed by the control output of the control device26, and the auxiliary electromagnetic valve29is opened. Furthermore, the operation of the second blower22is stopped by the control output of the control device26.

Because the electromagnet valve19located at the inlet portion of the refrigerant suction port13cis closed, it can prevent the lubrication oil from staying in the refrigerant suction pipe25even when the refrigerant suction port13cis provided at the lower portion of the ejector13. Furthermore, because the refrigerant introduced into the first branch passage17flows toward the suction side of the compressor10through the bypass passage28, it can prevent the lubrication oil from staying in the second evaporator21when the electromagnetic valve19is closed.

In the fifth embodiment, when the switch of the refrigerator is turned on and the refrigerator is operated, the electromagnetic valve19is opened, the auxiliary electromagnetic valve29is closed, and the second blower22is operated by control output of the control device26.

Sixth Embodiment

FIG. 8shows a vapor-compression refrigerant cycle system of the sixth embodiment. In the sixth embodiment, the refrigerant suction port13cis provided at the lower portion of the ejector13, and the refrigerant suction pipe25is connected to the refrigerant suction portion13at the bottom side of the ejector13, similarly to the comparison example ofFIG. 3.

In the sixth embodiment, the turning on and off operation of the electromagnetic valve19is controlled in the refrigerator stop state. Specifically, a timer26ais provided in the control device26. The function of the timer26ais started, when the refrigerator switch of the air conditioning panel is turned off and the refrigerator stop state is set while the compressor10operates.

The function of the timer26awill be described with reference toFIG. 9. The abscissa ofFIG. 9indicates an elapsed time after the refrigerator stop state is set. When a predetermined time t1passes after the refrigerator stop state is set, that is, after a closing state of the electromagnetic valve19is continued for the predetermined time, the electromagnetic valve19is forcibly switched (opened and closed) by a predetermined number based on a signal from the timer26aof the control device26.

That is, the operation of the electromagnetic valve19is controlled by the timer26aof the control device26, such that the open state of the electromagnetic valve19performed for a first predetermined time “ton” and the close state of the electromagnetic valve19performed for a second predetermined time “off” are repeated alternately by predetermined times. In this case, refrigerant can flows into the first branch passage17intermittently, and lubrication oil staying in the refrigerant suction pipe25can be sent to the refrigerant suction port13cof the ejector13.

FIG. 10shows a case where the electromagnetic valve19is closed during the refrigerator stop state. The abscissa ofFIG. 10indicates an elapsed time after the refrigerator stop state is set. When the electromagnetic valve19is closed, the lubrication amount staying in the refrigerant suction pipe25is increased as the elapsed time becomes longer. Therefore, a circulating rate R1(oil circulating rate) of the lubrication oil drawn into the compressor10becomes decreased. The oil circulating rate R1can be calculated by the following formula.
R1=A1/(A1+A2)×100 (%)

Wherein A1shows a lubrication oil amount returning to the compressor10, and A2shows a refrigerant amount returning to the compressor10.

As shown inFIG. 10, after the time t1elapses after the electromagnetic valve19is closed, the oil shortage of the compressor10is caused. Therefore, the temperature of the compressor10is increased to a limit temperature, and the compressor10becomes a maximum hot state (heat limit).

Accordingly, in the sixth embodiment, after the predetermined time t1passes after the electromagnetic valve19is closed, the opening and closing of the electromagnetic valve19are alternately repeated by the predetermined time, as shown inFIG. 9. In this case, the oil circulating ratio can be increased to a necessary level, and a shortage of the lubrication oil in the compressor10can be prevented.

InFIG. 9, the repeat of the forcibly opening of the electromagnetic valve19is set at three times. However, the repeat can be set at plural times more than one time.

Seventh Embodiment

The seventh embodiment of the present invention will be now described with reference toFIG. 11.FIG. 11shows a control operation of the control device26according to a modification of the sixth embodiment. In the seventh embodiment, the operation of step S12is added in the control operation of the sixth embodiment. That is, the other steps except for step S12can be performed similar to the control operation of the above-described sixth embodiment.

The control operation of the seventh embodiment will be now described. First, at step S1, it is determined whether a cooling operation of the second evaporator21is performed. When the cooling operation of the second evaporator21is not performed, the operation at step S12is performed.

At step S12, an oil returning control is performed by only one time after the vapor-compression refrigerant cycle system (compressor10) is operated. During the oil returning control, the electromagnetic valve19used as a switching valve is opened for a predetermined time. After the oil returning control is performed, the electromagnetic valve19is closed, and at the same time, the control program moves to step S13. For example, in the vapor-compression refrigerant cycle system shown inFIG. 8, even when the cooling function of the second evaporator21is stopped at a time where the vapor-compression refrigerant cycle system starts, the lubrication oil staying in the second evaporator21and the refrigerant pipes at the side of the second evaporator21can be drawn into the refrigerant suction port13c, and can be returned to the suction side of the compressor10.

Next, at step S13, the timer26aof the control device26, described in the sixth embodiment, is operated. Then, at step S14, it is determined whether a predetermined time elapses after the timer26ais set.

After the predetermined time elapses at step S14, the oil returning control is performed for a predetermined time period at step S15. That is, the electromagnetic valve19is opened for the predetermined time period during the oil retuning control. After the electromagnetic valve19is opened for the predetermined time period, the electromagnetic valve19is closed and the control program processes to step S15.

At step S16, the timer26ais reset so that the control program shown inFIG. 11can be repeated.

According to the seventh embodiment, when the cooling function of the second evaporator21is stopped when the vapor-compression refrigerant cycle system starts, the electromagnetic valve19is opened for a predetermined time period. Therefore, even when the cooling function of the second evaporator21is not performed at a time where the vapor-compression refrigerant cycle system starts, the lubrication oil staying in the second evaporator21and the refrigerant pipes at the side of the second evaporator21can be drawn into the refrigerant suction port13conce, and can be returned to the suction side of the compressor10.

Accordingly, a shortage of the oil amount returning to the compressor10can be prevented when the cooling function of the second evaporator21stops, and the compressor10can be stably and effectively operated. After the oil retuning operation is performed by one time, the electromagnetic valve19is forcibly opened after the closing state of the electromagnetic valve19is continued for a time period, similarly to the sixth embodiment.

Eighth Embodiment

FIG. 12shows a vapor-compression refrigerant cycle system of the eighth embodiment. In the vapor-compression refrigerant cycle system shown inFIG. 12, a bypass passage31and an auxiliary electromagnetic valve32for opening and closing the bypass passage31are provided additionally, as compared with the structure of the comparison example ofFIG. 3. Through the bypass passage31, refrigerant from the main refrigerant circulating path15flows into the refrigerant suction port13cwhile bypassing the electromagnetic valve19and the second evaporator21.

In the eighth embodiment, when the cooling operation of the second evaporator21is not performed, the auxiliary electromagnetic valve32is opened so that refrigerant flows through the bypass passage31by a predetermined amount. The electromagnetic valve19and the auxiliary electromagnetic valve32are controlled by the control device26. The flow amount of the refrigerant in the bypass passage31is set to only prevent the lubrication oil from falling into the refrigerant suction port13cdue to the weight of the lubrication oil. Therefore, the flow amount of the refrigerant in the bypass passage31can be set small, and a capillary tube can be used as the bypass passage31.

According to the eighth embodiment, when the cooling operation of the second evaporator21is stopped by closing the electromagnetic valve19, refrigerant flows through the bypass passage31by a predetermined flow amount. Therefore, refrigerant always flows into the refrigerant suction port13cof the ejector13from the bypass passage31, thereby preventing the lubrication oil from falling into the refrigerant suction port13cby its weight.

As a result, it can prevent the returning amount of the lubrication oil to the compressor10from being insufficient when the cooling operation of the second evaporator21is stopped. Therefore, the lubricating property of the compressor10can be effectively maintained.

Ninth Embodiment

In the above-described first to eighth embodiments, the first branch passage17, through which the downstream side of the refrigerant radiator11is connected to the refrigerant suction port13cof the ejector13, is provided. Furthermore, the electromagnetic valve19, the throttle mechanism20and the second evaporator21are arranged in the first branch passage17in serious. In the ninth embodiment, the arrangement structure of the first branch passage17is changed as shown inFIG. 13.

In the ninth embodiment, a gas-liquid separator30is arranged at a downstream side of the first evaporator14, and the refrigerant flowing out of the first evaporator14is separated in a gas-liquid separator30. The liquid refrigerant separated in the gas-liquid separator30is stored in the gas-liquid separator30, and the gas refrigerant in the gas-liquid separator30is supplied to the suction side of the compressor10.

Furthermore, a liquid refrigerant outlet30ais provided at a lower portion of the gas-liquid separator30, and the liquid refrigerant outlet30ais connected to the refrigerant suction port13cof the ejector13by using a first branch passage17. In the first branch passage17, the electromagnetic valve19, the throttle mechanism20and the second evaporator21are arranged in serious in this order in a refrigerant flow direction of the first branch passage17.

The refrigerant suction port13cis provided at an upper portion of the ejector13, similar to the above-described first embodiment. Further, the refrigerant suction port25has a standing portion vertically extending from the refrigerant suction port13cupwardly. Therefore, it can effectively prevent the lubrication oil from falling into the refrigerant suction port13cby its weight.

In the ninth embodiment, the refrigerant evaporation pressure (refrigerant evaporation temperature) of the second evaporator21is lower than the refrigerant evaporation pressure (refrigerant evaporation temperature) of the first evaporator14, as in the above-described first embodiment.

Further, in the ninth embodiment, the flow adjacent valve12and the gas-liquid separator11aof the refrigerant radiator11of the above-described first to eighth embodiments are omitted. In this ninth embodiment, the gas-liquid separator30is arranged at a downstream side of the first evaporator14, and the gas refrigerant separated in the gas-liquid separator30is sucked to the compressor10.

Further, when the cooling operation of the second evaporator21is performed, the electromagnetic valve19is opened so that liquid refrigerant in the gas-liquid separator30is introduced into the second branch passage17from the liquid refrigerant outlet30a. The liquid refrigerant from the liquid refrigerant outlet30aof the gas-liquid separator30is decompressed in the throttle mechanism20, and is evaporated in the second evaporator21. The refrigerant from the second evaporator21is drawn into the ejector13from the refrigerant suction port13c.

In the ninth embodiment, the changed structure of the first branch passage17and the gas-liquid separator30is used for and combined with the vapor-compression refrigerant cycle system of the first embodiment. However, this changed structure can be used for the vapor-compression refrigerant cycle system according to one of the second through eighth embodiments.

Other Embodiments

Although the present invention has been described in connection with some preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.

For example, in the above-described first to ninth embodiments, the first evaporator14is used for cooling the front seat area of the passenger compartment, the third evaporator24is used for cooling the rear seat area of the passenger compartment, and the second evaporator21is used for performing the cooling operation of a refrigerator. However, in the above-described embodiments, the third evaporator24and a refrigerant passage structure for the third evaporator24can be omitted. For example, the present invention can be applied to a vapor-compression refrigerant cycle system without the third evaporator24as shown inFIG. 14.

In this example shown inFIG. 14, the third evaporator24is omitted in the system structure of the ninth embodiment. However, the third evaporator24can be omitted in the vapor-compression cycle system according to one of the first to eighth embodiments.

In the above-described first to ninth embodiments, the second evaporator21is used for the cooling operation of a refrigerator mounted on a vehicle. However, the first and second evaporators14and21can be used for performing air conditioning operation for different areas in the passenger compartment of the vehicle. For example, in a case where the third evaporator24is not provided, the first evaporator14and the second evaporator21can be used for performing air conditioning in the front seat area and the rear seat area within the passenger compartment.

Alternatively, both the first evaporator14and the second evaporator21can be used for performing the cooling operation of a refrigerator. In this case, the first evaporator14, in which the refrigerant evaporation temperature is relatively high, can be used for a cooling chamber of the refrigerator, and the second evaporator21, in which the refrigerant evaporation temperature is relatively low, can be used for a freezing chamber of the refrigerator.

In the above-described embodiments, any refrigerant generally used in a vapor-compression refrigerant cycle system can be used. For example, a Freon group refrigerant, an organic compound refrigerant, HC group refrigerant and carbon dioxide can be used as the refrigerant. Furthermore, the vapor-compression refrigerant cycle system can be used as a super-critical refrigerant cycle system having a pressure of a high-pressure side refrigerant higher than the critical pressure of the refrigerant or can be used as a refrigerant cycle system having a pressure of a high-pressure side refrigerant lower than the critical pressure of the refrigerant. Here, the organic compound refrigerant is a normally used refrigerant composed of carbon, fluorine, chlorine and hydrogen. The Freon group refrigerant is for example, hydro chloro fluoro carbon (HCFC) group refrigerant or hydro fluoro carbon (HFC) group refrigerant. Furthermore, as the carbon hydride (HC) group refrigerant, isobutene (R600a), propane (R290), etc. can be used.

In the above-described embodiments, a fixed displacement compressor can be used as the compressor10. In this case, the compression operation of the compressor10is controlled by using the clutch10a, and a discharge amount of the refrigerant from the compressor10is controlled by controlling the on/off operation of the compressor10. Alternatively, a variable displacement compressor can be used as the compressor10. In this case, the displacement of the compressor10is controlled by the control device26, so that the refrigerant amount discharged from the compressor10can be controlled. Alternatively, an electrical compressor can be used as the compressor10. In this case, by controlling the rotation speed of the electrical compressor10, the refrigerant amount discharged from the compressor10can be controlled.

In the above-described embodiments, as the nozzle portion13a, a variable nozzle can be used. In this case, a refrigerant flow area (e.g., throttle open degree) of the nozzle portion13acan be changed.

In the above-described first to eighth embodiments, the flow adjustment valve12is arranged at the upstream portion of the ejector13. However, when the flow amount of the refrigerant flowing in the first evaporator14is adjusted by the throttling operation of the ejector13, the flow adjustment valve12can be omitted.

While the invention has been described with reference to preferred embodiments thereof, it is to be understood that the invention is not limited to the preferred embodiments and constructions. The invention is intended to cover various modification and equivalent arrangements. In addition, while the various elements of the preferred embodiments are shown in various combinations and configurations, which are preferred, other combinations and configuration, including more, less or only a single element, are also within the spirit and scope of the invention.