JP5604626B2 - Expansion valve - Google Patents

Description

  The present invention relates to an expansion valve, and more particularly to an expansion valve that expands liquid refrigerant condensed in a vehicle air conditioner mounted on an electric vehicle or a hybrid electric vehicle to obtain a low-temperature refrigerant necessary for cooling operation and dehumidifying heating operation. .

  In a hybrid electric vehicle, the cooling water of the internal combustion engine does not reach a sufficiently high temperature necessary for heating operation, so the cooling water cannot be used as a heat source for heating. There is nothing that can be a heat source. For this reason, a heat pump type that can perform a cooling operation, a heating operation, and a dehumidifying heating operation has been proposed as an air conditioner for vehicles (see, for example, Patent Document 1).

  According to the device described in Patent Document 1, the ratio of the air passing through the evaporator, the internal condenser, and the internal condenser is adjusted in the duct that blows out the air whose temperature is adjusted by introducing the outside air or the inside air. And an air mix door. The refrigeration cycle consists of a closed circuit that returns from the compressor to the compressor again via the internal condenser, the first liquid tank, the first expansion valve, the external heat exchanger, the second liquid tank, the second expansion valve and the evaporator. It is configured.

  During complete cooling operation, the first expansion valve is fully opened, the external heat exchanger functions as a condenser, and the opening of the second expansion valve is adjusted to supply low-temperature refrigerant to the evaporator. The door is switched to the side that completely bypasses the internal capacitor. The adjustment of the air blowing temperature during the cooling operation is performed by adjusting the air mix door so as to increase the proportion of air passing through the internal condenser.

  During heating operation, the opening degree of the first expansion valve is adjusted so that the external heat exchanger functions as an evaporator, and the second expansion valve is fully opened to supply the refrigerant with heat absorbed by the external heat exchanger to the evaporator. The air mix door is switched to the side through which the internal condenser passes completely. At this time, in the evaporator, since some heat exchange is performed with the introduced air, dehumidification is performed to the extent that fogging of the window glass can be prevented.

  In this heating operation, in the case of full heat operation that does not require dehumidification by an evaporator, a bypass pipe that bypasses the second expansion valve and the evaporator is provided, and the refrigerant evaporated in the external heat exchanger can be directly directed to the compressor. Has been done. Here, whether to perform dehumidification during the heating operation is performed by providing a two-way valve in the bypass pipe and opening and closing the two-way valve. That is, by closing the two-way valve, the refrigerant from the external heat exchanger passes through the second expansion valve and the evaporator and goes to the compressor. At that time, the opening degree of the second expansion valve is increased. By adjusting, the air introduced by the evaporator can be dehumidified. On the other hand, since the refrigerant from the external heat exchanger goes to the compressor via the two-way valve by opening the two-way valve and closing the second expansion valve, heat exchange is not performed in the evaporator. It becomes full heat operation.

  In the system described in Patent Document 1, since the expansion valve in front of the refrigerant flow direction of the evaporator is an electric type, the expansion valve is closed and the two-way valve is opened. The operation mode can be set to full heat operation.

  However, there is a demand for the expansion valve installed in front of the evaporator in the refrigerant flow direction to be a temperature-type expansion valve capable of autonomous control instead of the expensive electronically-controlled electric expansion valve. In this case, the temperature type expansion valve is normally open except in a special case where the passenger compartment in which it is installed is extremely cold and its air temperature is detected. So that it does not close completely. Therefore, although it is very small, a part of the refrigerant to be bypassed may leak to the evaporator, and heat exchange may occur in the evaporator. Such heat exchange is a loss during full heat operation. Such a loss can be eliminated by installing a three-way valve at the connection portion between the pipe that goes to the expansion valve and the bypass pipe instead of the two-way valve of the bypass pipe.

Japanese Patent Laid-Open No. 9-240266

  However, since the three-way valve is complicated and expensive, it is desirable to use a temperature-type expansion valve that does not require electronic control for the expansion valve while leaving the two-way valve of the bypass pipe as it is. Then, there was a problem that a loss occurred during the full heat operation.

  The present invention has been made in view of these points, and an object thereof is to provide an expansion valve in which refrigerant does not leak to an evaporator when the vehicle air conditioner is in a full heat operation mode.

  In the present invention, in order to solve the above-mentioned problem, in the expansion valve that detects the degree of superheat of the refrigerant at the evaporator outlet and controls the flow rate of the refrigerant supplied to the evaporator, the first port in which the refrigerant to be expanded is introduced Low differential pressure that closes the passage between the first port and the second port when the differential pressure between the inlet pressure and the outlet pressure of the second port from which the expanded refrigerant is led out is lower than a set differential pressure An expansion valve is provided, characterized in that it comprises a sensing closing means.

  According to such an expansion valve, when the differential pressure between the inlet pressure and the outlet pressure is lower than the set differential pressure, such as when the vehicle air conditioner is operating in the evaporator in a full-heat operation, the differential pressure is low. Sensing closing means closes the passage between the first port and the second port. This ensures that the expansion valve closes the passage to the evaporator, which ensures that the refrigerant does not leak to the evaporator, and eliminates the loss during full heat operation by preventing unnecessary heat exchange in the evaporator. it can.

  The expansion valve having the above-described configuration reliably closes the passage between the first port and the second port when the low differential pressure sensing closing means has a low differential pressure. Therefore, the refrigeration cycle in which the circuit bypassing the evaporator is configured with a two-way valve. When used in the above, there is an advantage that the loss during the full heat operation can be surely eliminated.

  The low differential pressure sensing closing means is configured so that the movable valve seat moves in the valve closing direction when the differential pressure is low, so that the valve closes regardless of the degree of superheat. The passage between the two ports can be reliably closed.

  The low differential pressure sensing closing means is a differential pressure valve provided in the first port upstream of the expansion valve or the second port downstream, so as to ensure an appropriate amount of evaporation in the evaporator during dehumidifying heating operation. It can also be applied to a temperature expansion valve that uses a large-diameter control valve for superheat degree control that functions in the same manner.

It is a system figure showing an example of composition of a refrigerating cycle of an air-conditioner for vehicles to which an expansion valve of the present invention is applied. It is a center longitudinal cross-sectional view which shows the expansion valve which concerns on 1st Embodiment. It is a figure explaining operation | movement of a refrigerating cycle, (A) is a Mollier diagram which shows the refrigerating cycle at the time of air_conditionaing | cooling operation, (B) is a Mollier diagram which shows the refrigerating cycle at the time of dehumidification heating operation. It is a center longitudinal cross-sectional view which shows the expansion valve which concerns on 2nd Embodiment. It is a center longitudinal cross-sectional view which shows the expansion valve which concerns on 3rd Embodiment. It is a center longitudinal cross-sectional view which shows the expansion valve which concerns on 4th Embodiment. It is the center longitudinal cross-sectional view cut | disconnected in the orthogonal | vertical direction along the axis line of the shaft of FIG.

  Hereinafter, in the embodiment of the present invention, the superheat degree for controlling the flow rate of the refrigerant supplied to the evaporator inlet so that the superheat degree of the refrigerant at the outlet of the evaporator maintains a predetermined value in the refrigeration cycle of the vehicle air conditioner. A case where the present invention is applied to a sensing temperature expansion valve will be described in detail with reference to the drawings.

FIG. 1 is a system diagram showing a configuration example of a refrigeration cycle of a vehicle air conditioner to which an expansion valve of the present invention is applied.
The refrigeration cycle of the vehicle air conditioner includes a compressor 1, an internal condenser 2, a control valve 3 and an orifice 4, an external heat exchanger 5, a two-way valve 6, an expansion valve 7, an evaporator 8, and an accumulator. 9 and.

  The compressor 1 is an electric compressor with a built-in motor, and can change the discharge capacity of the refrigerant according to the number of rotations of the motor. The discharge port of the compressor 1 is connected to the internal capacitor 2.

  The internal condenser 2 is installed on the downstream side of a duct arranged in the vehicle interior so as to adjust the air temperature, and condenses by introducing a high-temperature refrigerant discharged from the compressor 1. Since the internal capacitor 2 radiates the refrigerant in the duct, it functions as a heater that heats the air that has passed through the evaporator 8. The outlet of the internal capacitor 2 is connected to the control valve 3 and the orifice 4.

  The control valve 3 and the orifice 4 are connected in parallel to each other. The control valve 3 includes a valve portion that opens and closes the main passage and a solenoid that opens and closes the valve portion, and the opening area when the control valve 3 is opened is set to be sufficiently larger than that of the orifice 4. Yes. For this reason, when the control valve 3 is closed, the refrigerant supplied from the internal condenser 2 passes through the orifice 4 as an expansion device, is adiabatically expanded here, and is supplied to the external heat exchanger 5. When the control valve 3 is opened, the refrigerant from the internal condenser 2 passes through the control valve 3 as it is and is supplied to the external heat exchanger 5.

  The external heat exchanger 5 is installed outside the passenger compartment, and performs heat exchange between the refrigerant passing through the inside and the outside air. The external heat exchanger 5 functions as a condenser that condenses the refrigerant when the operation mode of the refrigeration cycle is the cooling operation, and functions as an evaporator that evaporates the refrigerant during the heating operation. The outlet of the external heat exchanger 5 is connected to the inlets of the two-way valve 6 and the expansion valve 7.

  The two-way valve 6 is provided in a bypass pipe that is piped so as to bypass the expansion valve 7 and the evaporator 8, and includes a valve section that opens and closes the bypass pipe and a solenoid that switches and drives the valve section. The two-way valve 6 is closed during the cooling operation and the dehumidifying heating operation, supplies the refrigerant introduced from the external heat exchanger 5 to the expansion valve 7, and is opened during the full heat heating operation. Then, the refrigerant introduced from the external heat exchanger 5 is switched to supply to the accumulator 9.

  The expansion valve 7 includes a port T1 for introducing the refrigerant supplied from the external heat exchanger 5, a port T2 for leading the atomized refrigerant that has been adiabatically expanded to a low temperature / low pressure to the evaporator 8, and a return from the evaporator 8. Ports T3 and T4 through which the incoming refrigerant passes are provided. The expansion valve 7 detects the degree of superheat when the refrigerant at the outlet of the evaporator 8 passes through the ports T3 and T4, and the flow rate of refrigerant supplied to the inlet of the evaporator 8 so that the degree of superheat maintains a predetermined value. It is a temperature type expansion valve that controls.

  The evaporator 8 is installed on the upstream side in the duct for adjusting the air temperature, and evaporates the low-temperature refrigerant discharged from the expansion valve 7 by heat exchange with the outside air or the inside air introduced into the duct. The air cooled and dehumidified by the latent heat of vaporization at that time is divided into one that passes through the internal capacitor 2 and one that bypasses the internal capacitor 2 according to the opening of the air mix door. The air that has passed through the internal condenser 2 is heated there. The heated air is mixed with the air bypassing the internal condenser 2 on the downstream side of the internal condenser 2, adjusted to a predetermined temperature, and blown out into the vehicle interior.

  The accumulator 9 stores a part of the refrigerant circulating in the refrigeration cycle, and has a function of deriving the gas-liquid separated gas-phase refrigerant and the lubricating oil accumulated below the liquid-phase refrigerant to the compressor 1. ing.

  2 is a central longitudinal sectional view showing the expansion valve according to the first embodiment, FIG. 3 is a diagram for explaining the operation of the refrigeration cycle, and (A) is a Mollier diagram showing the refrigeration cycle during the cooling operation. (B) is a Mollier diagram showing a refrigeration cycle during a dehumidifying heating operation.

  In the expansion valve 10 according to the first embodiment, a port T1 connected to the refrigerant outlet of the external heat exchanger 5 is provided on the lower side portion of the body 11, and the opposite side portion of the body 11 is provided on the opposite side portion. A port T2 connected to the evaporator 8 is provided. Above the body 11, ports T3 and T4 to which the evaporator 8 and the accumulator 9 are connected are provided.

  Below the body 11, a large-diameter cylinder connected to the port T1 and a small-diameter cylinder connected to the port T2 are coaxially arranged in the longitudinal direction of the body 11 (vertical direction in the figure). A movable valve seat 12 is disposed in the large-diameter cylinder so as to be movable back and forth in the axial direction, and an O-ring 13 for sealing is provided on the outer periphery of the movable valve seat 12. The step portion formed at the boundary between the large diameter cylinder and the small diameter cylinder functions as a stopper of the movable valve seat 12 and defines the upper limit of the movable range of the movable valve seat 12. The movable valve seat 12 is also urged downward in the figure by a compression coil spring 14 as an urging member installed in a small diameter cylinder. When the pressure difference ΔP between the inlet pressure P1 of the port T1 and the outlet pressure P2 of the port T2 is lower than a set differential pressure of 0.1 MPa, for example, the load of the compression coil spring 14 causes the movable valve seat 12 to It is set to a value that can be pushed down.

  In the large-diameter cylinder, a ball-shaped valve body 15 is arranged so as to be able to contact and separate from the movable valve seat 12. The valve body 15 is biased in a direction to be seated on the movable valve seat 12 by a compression coil spring 16 disposed in the large diameter cylinder. The compression coil spring 16 is received by an adjustment screw 17 screwed to the lower end surface of the body 11. The adjustment screw 17 adjusts the load of the compression coil spring 16 and thus sets the value of the degree of superheat to be controlled by the expansion valve 10.

  The body 11 also supports a shaft 18 that can move forward and backward in the vertical direction in the figure, and one end portion of the body 11 extends through the small diameter cylinder and the valve hole of the movable valve seat 12. The lower end surface of the shaft 18 is in contact with the valve body 15. The other end of the shaft 18 is in contact with a power element 19 screwed to the upper end of the body 11 in the figure. The power element 19 includes an upper housing, a lower housing, a diaphragm that partitions a space surrounded by these, and a disk disposed on the lower surface of the diaphragm. The lower surface of the disk has an upper end surface of the shaft 18. It is in contact. A closed space surrounded by the upper housing and the diaphragm is filled with a substance having characteristics similar to those of a refrigerant circulating in the refrigeration cycle. A space surrounded by the lower housing and the diaphragm communicates with a return refrigerant passage communicating between the ports T3 and T4, and the refrigerant flowing through the return refrigerant passage can be introduced. The power element 19 detects the degree of superheat of the refrigerant flowing through the return refrigerant passage between the ports T3 and T4, and feeds back the axial position of the valve body 15, that is, the valve opening degree, via the shaft 18 according to the degree of superheat. Control. Here, the power element 19, the movable valve seat 12, and the valve body 15 constitute an on-off valve that opens and closes according to the degree of superheat.

  Next, the operation of the expansion valve 10 having the above configuration will be described with reference to FIGS. In FIG. 1, the arrows indicate the flow of the refrigerant. Moreover, the code | symbol af in FIG. 1 respond | corresponds to the code | symbol of the point attached | subjected to the refrigerating cycle on the Mollier diagram of FIG. 1 will be described as the expansion valve 10 according to the first embodiment shown in FIG.

  First, when the operation mode of the vehicle air conditioner is the cooling operation, the control valve 3 is opened and the two-way valve 6 is closed in the system of FIG. Thereby, the internal capacitor | condenser 2 and the external heat exchanger 5 function as a capacitor | condenser of a refrigerating cycle. In the duct, the air mix door is controlled to be fully closed or close to it and switched to the side that completely or almost bypasses the internal capacitor 2. At this time, since the differential pressure ΔP between the inlet pressure P1 and the outlet pressure P2 is sufficiently large, the movable valve seat 12 is moved to the upper limit position shown in FIG. doing. In addition, the refrigeration cycle during the cooling operation behaves as shown in FIG.

  During the cooling operation, the compressor 1 draws in refrigerant from the accumulator 9 (point a), adiabatically compresses and discharges high-temperature and high-pressure refrigerant (point b). The refrigerant discharged from the compressor 1 is dissipated and condensed when passing through the internal condenser 2, the control valve 3, and the external heat exchanger 5, and is introduced into the expansion valve 10 (point e). When the refrigerant reaches the expansion valve 10, it is in a supercooled liquid phase state. In the expansion valve 10, the liquid refrigerant introduced into the port T1 flows to the port T2 through a gap between the movable valve seat 12 and the valve body 15, but is adiabatically expanded when passing through the gap. It becomes a low-temperature and low-pressure vapor refrigerant (point f). This vapor refrigerant is supplied to the evaporator 8, where it is evaporated by heat exchange with the air in the passenger compartment. At this time, heat is taken away by the latent heat of vaporization and cooled, and the cooled air is blown out into the passenger compartment. The evaporated refrigerant is introduced into the port T3 of the expansion valve 10, and is led out from the port T4 as it is. The refrigerant derived from the expansion valve 10 returns to the compressor 1 through the accumulator 9. At this time, the refrigerant returned to the compressor 1 is overheated to a predetermined superheat degree SH by the evaporator 8.

  The expansion valve 10 detects the superheat degree SH of the refrigerant by the power element 19 when the refrigerant discharged from the evaporator 8 is allowed to pass through. This detected value is fed back to the valve body 15 via the shaft 18, and the valve body 15 controls the flow rate of the refrigerant supplied to the evaporator 8 so that the detected superheat degree SH becomes constant. That is, when the degree of superheat SH increases, the power element 19 is driven in a direction to open the valve body 15 via the shaft 18. Thereby, the flow rate of the refrigerant supplied to the evaporator 8 increases. In the evaporator 8, the amount of heat for evaporating the refrigerant is the same, so the degree of superheat SH decreases as the flow rate increases. On the contrary, when the degree of superheat SH decreases, the diaphragm of the power element 19 is displaced in a direction away from the valve body 15, so that the valve body 15 is driven in the valve closing direction by the urging force of the compression coil spring 16. As a result, the flow rate of the refrigerant supplied to the evaporator 8 decreases, and the superheat degree SH increases in the evaporator 8 as the flow rate decreases. In this way, the expansion valve 10 controls the superheat degree SH of the refrigerant derived from the evaporator 8 to be constant.

  Next, the case where the operation mode of the vehicle air conditioner is the dehumidifying operation will be described. In the dehumidifying and heating operation, the control valve 3 and the two-way valve 6 are closed in the system of FIG. Thereby, the orifice 4 functions as an expansion device, and the external heat exchanger 5 functions as an evaporator of the refrigeration cycle. In the duct, the air mix door is controlled to be fully open or close to the opening, and switched to the side where the internal capacitor 2 is completely or almost passed. Also at this time, since the expansion valve 10 is adiabatically expanded, the movable valve seat 12 is stationary at the upper limit position shown in FIG. 2 due to the differential pressure ΔP between the inlet pressure P1 and the outlet pressure P2.

  During the dehumidifying and heating operation, the compressor 1 sucks refrigerant from the accumulator 9 (point a), adiabatically compresses and discharges high-temperature and high-pressure refrigerant (point b). The refrigerant discharged from the compressor 1 is condensed by heat exchange with the air that has passed through the evaporator 8 in the internal condenser 2, and is introduced into the orifice 4 in a supercooled state (point c). At this time, the air that has passed through the internal condenser 2 is heated and blown into the vehicle interior. The condensed liquid refrigerant is adiabatically expanded when passing through the orifice 4 to become a low-temperature / low-pressure vapor refrigerant (point d) and introduced into the external heat exchanger 5. The refrigerant is evaporated by heat exchange with the outside air in the external heat exchanger 5 and introduced into the expansion valve 10 (point e). In the expansion valve 10, when the refrigerant introduced from the port T1 passes through the gap between the movable valve seat 12 and the valve body 15, it is adiabatically expanded to become a low-temperature / low-pressure vapor refrigerant (point f). . This vapor refrigerant is supplied to the evaporator 8, where it is further evaporated by heat exchange with the air in the passenger compartment. At this time, the air introduced into the duct is dehumidified by being cooled when passing through the evaporator 8 and heated when passing through the internal capacitor 2. The refrigerant derived from the evaporator 8 returns to the compressor 1 via the expansion valve 10 and the accumulator 9.

  At this time, the expansion valve 10 adjusts the flow rate of the refrigerant supplied to the evaporator 8 so that the refrigerant at the outlet of the evaporator 8 is maintained at a predetermined superheat degree SH. That is, when the degree of superheat SH increases, the power element 19 drives the valve body 15 in a direction that opens a gap with the movable valve seat 12 via the shaft 18. Thereby, the flow volume of the refrigerant | coolant supplied to the evaporator 8 increases, and superheat degree SH becomes small. Conversely, when the degree of superheat SH decreases, the diaphragm of the power element 19 is displaced upward in the figure, so that the valve body 15 is driven in the valve closing direction by the urging force of the compression coil spring 16. Thereby, the flow rate of the refrigerant supplied to the evaporator 8 is reduced, and the superheat degree SH is increased. In this way, the expansion valve 10 controls the refrigerant at the outlet of the evaporator 8 so as to maintain a predetermined superheat degree SH.

  Next, the case where the operation mode of the vehicle air conditioner is the full heat operation will be described. During the full heat operation, in the system of FIG. 1, the control valve 3 is closed and the two-way valve 6 is opened. Thereby, the orifice 4 functions as an expansion device, and the expansion valve 10 and the evaporator 8 are bypassed by the two-way valve 6.

  During the full heat operation, the orifice 4 functions as an expansion device, and the external heat exchanger 5 functions as an evaporator. Therefore, the operation of the refrigeration cycle is the same as that during the cooling operation. At this time, since the expansion valve 10 and the evaporator 8 are bypassed, the pressure inside the expansion valve 10 and the evaporator 8 is almost equalized, and the pressure difference ΔP between the inlet pressure P1 and the outlet pressure P2 of the expansion valve 10 is compressed. Lower than the set differential pressure by the coil spring 14. As a result, the movable valve seat 12 is pushed downward toward the valve body 15 by the compression coil spring 14, and the movable valve seat 12 is pressed against the valve body 15 and the expansion valve 10 is closed. Become. At this time, even if the power element 19 senses a change in the degree of superheat and changes the position of the valve body 15, the movable valve seat 12 moves following the position, so that the expansion valve 10 is closed. Will always be maintained. Here, the movable valve seat 12 and the compression coil spring 14 cooperate with the valve body 15 when the differential pressure ΔP between the inlet pressure P1 and the outlet pressure P2 of the expansion valve 10 is lower than the set differential pressure. Since the refrigerant passage between T1 and T2 is closed, a low differential pressure sensing closing means is provided. This low differential pressure sensing closing means reliably closes the expansion valve 10 during full heat operation, so that the refrigerant from the external heat exchanger 5 leaks to the evaporator 8 side, and the evaporator 8 performs heat exchange. The loss at the time of full-heat operation can be surely eliminated.

  FIG. 4 is a central longitudinal sectional view showing an expansion valve according to the second embodiment. In FIG. 4, the same or equivalent components as those shown in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted as appropriate.

  In this expansion valve 20, the low differential pressure sensing closing means is applied to a temperature type expansion valve having a function of ensuring an appropriate amount of evaporation in the evaporator 8 during the dehumidifying heating operation. That is, during the dehumidifying heating operation, in the Mollier diagram of FIG. 3B, the refrigerant is evaporated by the external heat exchanger 5 between the point d and the point e, and the point f and the point a During this period, the evaporator 8 evaporates the refrigerant. At this time, for example, when most of the refrigerant evaporates in the external heat exchanger 5 and the amount of evaporation in the evaporator 8 disappears (the difference in enthalpy between the point d and the point e becomes extremely small), dehumidification in the evaporator 8 Functions are lost. In addition, since the lubricating oil of the compressor 1 circulating in the refrigeration cycle cannot be transported by the completely evaporated refrigerant, the lubricating oil remains in the external heat exchanger 5 on the completely evaporated side and is not returned to the compressor 1 Occurs. The expansion valve 20 has a function of securing an appropriate evaporation amount in the evaporator 8 by controlling the point of transition (points e and f) from the evaporation state in the external heat exchanger 5 to the evaporation state in the evaporator 8. It has. Specifically, when the pressure difference ΔP between the inlet pressure P1 and the outlet pressure P2 of the expansion valve 20 is increased, the function is as follows. As shown by the dotted line in FIG. The principle that the difference in enthalpy between point f and point a) increases is used.

  Therefore, in this expansion valve 20, a large-diameter control valve having a valve hole having a larger diameter than the valve hole of the movable valve seat 12 is added to the expansion valve 10 according to the first embodiment. This large-diameter control valve is arranged in parallel with an on-off valve (hereinafter referred to as a small-diameter control valve) composed of a movable valve seat 12 and a valve body 15, and has a large-diameter main valve that opens and closes the passage between the port T1 and the port T2. 21 and a pilot valve 22 having a valve body formed integrally with the shaft 18.

  The main valve 21 of the large-diameter control valve has a large-diameter valve hole opened in a small-diameter cylinder communicating with the port T2, and a cylinder formed on the same axis as the valve hole has a large-diameter valve body. It is arranged so as to be able to advance and retract in the direction of opening and closing the valve hole. The cylinder is partitioned by a valve body. A pressure regulating chamber 23 is formed on the side opposite to the valve hole side, and a spring for biasing the valve body in the valve closing direction is formed in the pressure regulating chamber 23. Has been placed. A through hole having an opening area sufficiently smaller than that of the pilot valve 22 is formed in the valve body so that the high-pressure refrigerant introduced into the port T1 can leak into the pressure regulating chamber 23.

  Between the pressure regulating chamber 23 and the pilot valve 22, an on / off operation electromagnetic valve 24 for switching whether or not the large-diameter control valve is in a control state is disposed. The electromagnetic valve 24 is a normally closed control valve that closes when not energized and opens when energized to place the large-diameter control valve in a controlled state.

  The pilot valve 22 is formed integrally with the shaft 18 driven by the power element 19, and the valve hole is opened in a space communicating with the port T 2, that is, a downstream space of the small-diameter control valve.

  According to the expansion valve 20 having the above configuration, the electromagnetic valve 24 is deenergized and closed during cooling operation. At this time, the pressure regulating chamber 23 is a closed space and communicates with the port T1 through the through hole. For this reason, the pressure regulating chamber 23 has a pressure equal to the high inlet pressure P1 of the port T1, while the port T2 has a low pressure outlet pressure P2. The main valve 21 of the control valve is closed. At the same time, the movable valve seat 12 of the low differential pressure sensing closing means is also moved to the movable range upper limit position by the differential pressure ΔP between the inlet pressure P1 and the outlet pressure P2, and is stationary. Therefore, the expansion valve 20 functions as an ordinary temperature type expansion valve using only a small diameter control valve.

  When the dehumidifying and heating operation is performed, the expansion valve 20 is opened when the solenoid valve 24 is energized, and the pressure regulating chamber 23 and the pilot valve 22 are in communication with each other. In this case, the amount of refrigerant in the pressure regulating chamber 23 flows out to the port T2 via the pilot valve 22 more than the amount that flows in through the through hole. Near the outlet pressure P2. For this reason, the valve body of the main valve 21 is lifted by the high inlet pressure P1 of the port T1 against the biasing force of the spring, and the large-diameter control valve is opened. Since this large-diameter control valve has an extremely large opening area compared to the small-diameter control valve, the expansion valve 20 is substantially controlled only by the large-diameter control valve.

  In this state, when the degree of superheat SH increases, the power element 19 drives the shaft 18 to move the pilot valve 22 in the valve closing direction. As a result, the pressure in the pressure regulating chamber 23 increases, so that the main valve 21 moves in the valve closing direction, the inlet pressure P1 (point e) of the port T1 increases, and the evaporation pressure in the external heat exchanger 5 increases. As a result, the amount of evaporation of the refrigerant decreases, and instead, the amount of evaporation in the evaporator 8 increases. As the evaporation amount in the evaporator 8 increases, the superheat degree SH decreases. Conversely, when the superheat degree SH decreases, the superheat degree SH is consequently increased. In this manner, the expansion valve 20 controls the superheat degree SH of the refrigerant derived from the evaporator 8 to be constant, and ensures an appropriate amount of evaporation in the evaporator 8.

  The expansion valve 20 during the full heat operation is closed when the solenoid valve 24 is de-energized, the large-diameter control valve is removed from the control state, and the closed state is maintained. At this time, since the expansion valve 20 and the evaporator 8 are also removed from the refrigeration cycle, the differential pressure ΔP between the inlet pressure P1 and the outlet pressure P2 of the expansion valve 20 is lower than the set differential pressure by the compression coil spring 14. As a result, the movable valve seat 12 is urged by the compression coil spring 14 and pressed against the valve body 15, and the small-diameter control valve is closed. As a result, the expansion valve 10 closes both the small-diameter control valve and the large-diameter control valve, so that the refrigerant from the external heat exchanger 5 does not leak to the evaporator 8, and the loss during full-heat operation is reduced. It can be definitely eliminated.

  FIG. 5 is a central longitudinal sectional view showing an expansion valve according to the third embodiment. In FIG. 5, the same or equivalent components as those shown in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted as appropriate.

  This expansion valve 30 is obtained by applying a low differential pressure sensing closing means to a temperature type expansion valve having a function of ensuring an appropriate amount of evaporation in the evaporator 8 during a dehumidifying heating operation. A valve 24 is provided. Further, a differential pressure valve 31 is provided at the refrigerant outlet port T2 as a low differential pressure sensing closing means for the expansion valve 30.

  The solenoid valve 24 has a valve body that opens and closes a passage between the pressure regulating chamber 23 and the pilot valve 22 urged by a spring in a valve opening direction, and the movable iron core is attached by a spring in a direction away from the fixed iron core. The movable iron core urges the valve body to close the valve when energized. When the solenoid valve 24 is closed by energization when the refrigerant inlet port T1 is at high inlet pressure P1 during cooling or dehumidifying heating operation, the solenoid valve 24 is The valve closing state can be maintained by the differential pressure with the intermediate pressure P2 ′ on the upstream side of the differential pressure valve 31. When the electromagnetic valve 24 is closed, the two-way valve 6 of the refrigeration cycle is opened to switch the operation mode to full heat operation, and the differential pressure between the inlet pressure P1 and the intermediate pressure P2 ′ upstream of the differential pressure valve 31 is set. The electromagnetic valve 24 is released by lowering the urging force of the valve body in the valve opening direction and returned to the valve open state.

  The differential pressure valve 31 is formed by coaxially drilling a large-diameter cylinder connected to the evaporator 8 on the port T2 side, a small-diameter control valve, and a small-diameter cylinder communicating with the downstream side of the large-diameter control valve. The stepped part is a valve seat. The differential pressure valve 31 includes a valve body 32 that is disposed on a downstream large-diameter cylinder so as to be movable toward and away from the stepped portion, and a support portion 33 that supports the valve body 32 in a large-diameter cylinder so as to be movable back and forth in the axial direction. And a compression coil spring 34 that is disposed between the valve body 32 and the support portion 33 and biases the valve body 32 in the valve closing direction. If the pressure difference ΔP between the intermediate pressure P2 ′ on the upstream side of the differential pressure valve 31 and the outlet pressure P2 of the port T2 is lower than a set differential pressure of 0.01 MPa, for example, the load of the compression coil spring 34 is the valve body. The value is set to close the valve by energizing 32.

  According to the expansion valve 30 having the above configuration, when the cooling operation is started, the electromagnetic valve 24 is energized to be closed. Thereby, the pressure regulating chamber 23 of the large-diameter control valve that has been in a closed state before the start of the cooling operation becomes a closed space. When the inlet pressure P1 at the port T1 gradually increases, the pressure in the pressure regulating chamber 23 that communicates with the through-hole also increases and becomes equal to the inlet pressure P1 at the port T1. On the other hand, the differential pressure valve 31 immediately after the start of the cooling operation is closed with a small front-rear differential pressure, and the intermediate pressure P2 'is also equal to the outlet pressure P2 of the port T2. Therefore, the large-diameter control valve maintains its closed state and the solenoid valve 24 also maintains its closed state due to the differential pressure between the pressure (= P1) in the pressure regulating chamber 23 and the intermediate pressure P2 '. When the inlet pressure P1 of the port T1 is increased, the expansion valve 20 functions as a normal temperature expansion valve that includes only a small-diameter control valve. At this time, the differential pressure valve 31 is fully opened because the upstream intermediate pressure P2 ′ is sufficiently higher than the outlet pressure P2 of the port T2, and the refrigerant adiabatically expanded by the small-diameter control valve passes through the evaporator 8 from the port T2. Will be sent to. When the cooling operation only by the small-diameter control valve is stabilized, the electromagnetic valve 24 is brought into a non-energized state. Since the closed state of the solenoid valve 24 due to the differential pressure (P1-P2 ′) does not change even when the non-energized state is entered, the second embodiment is as much as the solenoid valve 24 is not energized during the subsequent cooling operation. The power consumption of the solenoid valve 24 can be reduced as compared with the expansion valve 20 according to the above.

  During the full heat operation, the two-way valve 6 of the refrigeration cycle is opened, and the expansion valve 30 and the evaporator 8 are removed from the refrigeration cycle. Thereby, when this full heat operation is immediately after the start of the vehicle air conditioner, there is no differential pressure in the refrigeration cycle, so the large-diameter control valve is closed, the solenoid valve 24 is opened, and the differential pressure valve 31 is closed. doing. On the other hand, when the full-heat operation is a transition from the cooling operation, the expansion valve 30 is removed from the refrigeration cycle by the two-way valve 6 so that the differential pressure ΔP between the inlet pressure P1 and the outlet pressure P2 of the expansion valve 30 is small. Become. At this time, the differential pressure valve 31 is closed when the front-rear differential pressure is lower than the set differential pressure by the compression coil spring 34. Thereby, since the refrigerant from the external heat exchanger 5 does not leak to the evaporator 8 side, the expansion valve 30 can reliably eliminate the loss during the full heat operation. Further, the solenoid valve 24 that has been closed during the cooling operation is opened by reducing the differential pressure across the valve body.

  The dehumidifying and heating operation is a transition from the full heat operation. At this time, the solenoid valve 24 is opened to bring the pressure regulating chamber 23 and the pilot valve 22 into communication, and the large-diameter control valve is in the control state. When the two-way valve 6 of the refrigeration cycle is closed and the refrigerant from the external heat exchanger 5 is introduced into the expansion valve 30, the valve body of the main valve 21 is the inlet of the refrigerant introduced into the port T1. The valve is lifted by the pressure P1, and the large-diameter control valve is opened. As a result, since the intermediate pressure P2 'on the downstream side of the large-diameter control valve becomes high, the differential pressure valve 31 is fully opened, and the expansion valve 30 is in a superheat degree control state by the large-diameter control valve.

  In this control state, when the degree of superheat SH increases, the power element 19 that senses this drives the shaft 18 to drive the pilot valve 22 in the valve closing direction. As a result, the pressure in the pressure regulating chamber 23 increases, so that the main valve 21 moves in the valve closing direction, the inlet pressure P1 (point e) of the port T1 increases, and the evaporation pressure in the external heat exchanger 5 increases. As a result, the amount of evaporation of the refrigerant decreases, and instead, the amount of evaporation in the evaporator 8 increases. As the evaporation amount in the evaporator 8 increases, the superheat degree SH decreases. Conversely, when the superheat degree SH decreases, the superheat degree SH is consequently increased. In this way, the expansion valve 30 is controlled so that the superheat degree SH of the refrigerant derived from the evaporator 8 becomes constant, and an appropriate amount of evaporation in the evaporator 8 is ensured.

  In this embodiment, the differential pressure valve 31 is installed in the port T2 on the downstream side of the small-diameter control valve and the large-diameter control valve. However, when there is no differential pressure between the ports T1 and T2, the small-diameter control valve And the large-diameter control valve need only be closed at the same time, and may be installed at the upstream port T1.

  FIG. 6 is a central longitudinal sectional view showing an expansion valve according to the fourth embodiment, and FIG. 7 is a central longitudinal sectional view cut in a direction perpendicular to the axis of the shaft of FIG. 6 and 7, the same or equivalent components as those shown in FIG. 5 are denoted by the same reference numerals, and detailed description thereof will be omitted as appropriate.

  In this expansion valve 40, the low differential pressure sensing closing means is applied to a temperature type expansion valve having a function of ensuring an appropriate amount of evaporation in the evaporator 8 during the dehumidifying heating operation. Power saving is achieved compared with the expansion valves 20 and 30 according to the third embodiment. Further, the differential pressure valve 31 as a low differential pressure sensing closing means of the expansion valve 40 is configured to move by a differential pressure between the inlet pressure P1 of the port T1 and the outlet pressure P2 of the port T2.

  The expansion valve 40 abolishes the electromagnetic valve 24 of the expansion valve 30 according to the third embodiment, and shows the function of the valve body that was operated by the differential pressure other than the electromagnetic force in the electromagnetic valve 24 in FIG. As shown, this is realized by a normally open differential pressure valve 41. The differential pressure valve 41 has a configuration in which a valve body that opens and closes a passage between the pressure regulating chamber 23 and the pilot valve 22 is urged in a valve opening direction by a spring. Therefore, the differential pressure valve 41 is closed when there is a large differential pressure between the inlet pressure P1 and the outlet pressure P2 of the expansion valve 40 as in the cooling operation, and the large-diameter control valve is closed. . The differential pressure valve 41 is also opened when the inlet pressure P1 of the refrigerant introduced into the port T1 is suddenly reduced by the orifice 4 as in the case of dehumidifying heating, and the large-diameter control valve is controlled by the pilot valve 22. To do. Of course, even during a full heat operation in which no differential pressure is generated in the expansion valve 40, the differential pressure valve 41 opens, but this does not mean that the large-diameter control valve performs a control operation.

  As shown in FIG. 6, the differential pressure valve 31 includes a piston 42 that is disposed in a small-diameter cylinder coaxial with the large-diameter cylinder of the port T2 and receives the inlet pressure P1 of the port T1. The piston 42 has a plurality of connecting rods arranged on the opposite side of the pressure receiving surface of the inlet pressure P1 with the shaft 18 interposed therebetween, so that the inlet pressure P1 can be transmitted to the valve body 32. For this reason, the piston 42 is preferably formed integrally with the connecting rod and the support body of the valve body 32.

  Here, when the vehicle air conditioner is stopped, or when the two-way valve 6 shown in FIG. 1 is opened and the vehicle air conditioner is in the full heat operation (or the evaporator pause operation), Or there is no big differential pressure in the expansion valve 40 of the above structure. For this reason, the main valve 21 of the large-diameter control valve is energized and closed by a spring in the pressure regulating chamber, and the differential pressure valve 41 is energized by the spring and opened.

  A case will be described in which the vehicle air conditioner is started in the cooling operation or the evaporator is switched from the evaporator resting operation state to the cooling operation. The cooling operation is started when the control valve 3 is opened, the two-way valve 6 is closed, and the compressor 1 is rotated in the system shown in FIG. When starting the cooling operation, since the temperature in the passenger compartment is usually high, the power element 19 senses the high temperature. Therefore, the small aperture control valve is driven to open the large aperture control. The pilot valve 22 of the valve is in a substantially closed state.

  When the compressor 1 starts rotating, the inlet pressure P1 at the port T1 of the expansion valve 40 increases and the outlet pressure P2 at the port T2 decreases, so that the differential pressure valve 31 as a low differential pressure sensing closing means senses the differential pressure. Then the valve is opened. At this time, since the pilot valve 22 is also generally closed, the large-diameter control valve remains closed, and the expansion valve 40 operates as a normal temperature-type expansion valve composed of the small-diameter control valve and the power element 19. Even when the pilot valve 22 is not closed, the differential pressure valve 41 is closed by the differential pressure before and after it, so that the main valve 21 of the large-diameter control valve similarly maintains its closed state. Even when the pilot valve 22 is closed, the small-diameter control valve and the power element 19 work as a normal temperature type expansion valve. Therefore, when the small-diameter control valve eventually starts the flow control, the pilot valve 22 is interlocked therewith. Will open and the differential pressure valve 41 will close.

  Next, when the control valve 3 is closed and the operation mode is switched from the cooling operation to the dehumidifying heating operation, the main valve 21 is opened and the superheat control is performed by the large-diameter control valve. That is, in the dehumidifying heating operation, the orifice 4 functions as an expansion device, and the external heat exchanger 5 functions as an evaporator. At this time, since the orifice 4 depressurizes the high-pressure refrigerant, in the expansion valve 40, the inlet pressure P1 of the refrigerant introduced into the port T1 rapidly decreases. As a result, when the differential pressure across the differential pressure valve 41 becomes smaller, the differential pressure valve 41 is first opened, and the refrigerant in the pressure regulating chamber 23 passes through the differential pressure valve 41 and the pilot valve 22 to the downstream side space of the small-diameter valve. Shed. Therefore, when the main valve 21 is lifted by the inlet pressure P1, the large-diameter control valve is opened, and the refrigerant introduced into the port T1 flows to the port T2 via the main valve 21 and the differential pressure valve 31. Become. Thereafter, the expansion valve 40 performs throttle control of the large-diameter control valve according to the degree of superheat SH of the refrigerant at the outlet of the evaporator 8 detected by the power element 19.

  The expansion valve 40 can switch the operation mode from the cooling operation to the dehumidifying and heating operation, but does not include an actuator that closes the differential pressure valve 41. I can't. However, when the operation mode is switched from the dehumidifying and heating operation to the cooling operation, the operation mode is once switched to the full heat operation. That is, in the full heat operation without dehumidification, the two-way valve 6 is opened and the evaporator is brought into an operation stop state. As a result, the differential pressure across the main valve 21 disappears and the main valve 21 is closed. In this state, when the control valve 3 is opened and the cooling operation is started, the high pressure inlet pressure P1 introduced into the port T1 opens the differential pressure valve 31 as the low differential pressure sensing closing means. The differential pressure valve 41 is closed. As described above, the operation mode can be switched from the dehumidifying heating operation to the cooling operation by once switching the operation mode to the heating operation.

DESCRIPTION OF SYMBOLS 1 Compressor 2 Internal capacitor 3 Control valve 4 Orifice 5 External heat exchanger 6 Two-way valve 7 Expansion valve 8 Evaporator 9 Accumulator 10 Expansion valve 11 Body 12 Movable valve seat 13 O-ring 14 Compression coil spring 15 Valve body 16 Compression coil spring 17 Adjustment screw 18 Shaft 19 Power element 20 Expansion valve 21 Main valve 22 Pilot valve 23 Pressure regulating chamber 24 Solenoid valve 30 Expansion valve 31 Differential pressure valve 32 Valve element 33 Support part 34 Compression coil spring 40 Expansion valve 41 Differential pressure valve 42 Piston P1 Inlet pressure P2 outlet pressure P2 'Intermediate pressure

Claims (7)

In the expansion valve that detects the degree of superheat of the refrigerant at the evaporator outlet and controls the flow rate of the refrigerant supplied to the evaporator,
When the differential pressure between the inlet pressure of the first port to which the refrigerant to be expanded is introduced and the outlet pressure of the second port from which the expanded refrigerant is derived is lower than a set differential pressure, the first port and the first port An expansion valve comprising low differential pressure sensing closing means for closing a passage between two ports.   The low differential pressure sensing closing means constitutes a valve seat of an on-off valve that opens and closes according to the degree of superheat, and is arranged to be movable in the opening and closing direction of the on-off valve, and the difference between the inlet pressure and the outlet pressure. A movable valve seat that is stationary at the tip position in the valve opening direction of the movable range when the pressure is greater than or equal to the set differential pressure, and the movable valve seat when the differential pressure is lower than the set differential pressure. The expansion valve according to claim 1, further comprising: an urging member that closes the on-off valve by moving in a valve closing direction and press-contacting the valve body of the on-off valve. A large-diameter control valve that is installed in parallel with the on-off valve, and controls the valve hole with a larger diameter than the on-off valve as the degree of superheat increases;
The large-diameter control valve is a pilot-operated valve that opens and closes a main valve by operating a pilot valve in conjunction with the control of the on-off valve by the degree of superheat, the pressure regulating chamber of the main valve, the pilot valve, The expansion valve according to claim 2, wherein the expansion valve is disposed between the first and second switching valves to switch whether or not the large-diameter control valve is to be controlled.   2. The expansion valve according to claim 1, wherein the low differential pressure sensing closing means is a differential pressure valve installed in a refrigerant passage upstream or downstream of an on-off valve that opens and closes according to the degree of superheat. A large-diameter control valve that is installed in parallel with the on-off valve, and controls the valve hole with a larger diameter than the on-off valve as the degree of superheat increases;
The large-diameter control valve is a pilot-operated valve that opens and closes a main valve by operating a pilot valve in conjunction with the control of the on-off valve by the degree of superheat, the pressure regulating chamber of the main valve, the pilot valve, The expansion valve according to claim 4, wherein the expansion valve is disposed between the first and second valves and is switched by a normally open solenoid valve to switch whether or not the large-diameter control valve is in a control state.   The low differential pressure sensing closing means includes a differential pressure valve installed in a refrigerant passage on the downstream side of the on-off valve that opens and closes according to the degree of superheat, and is disposed coaxially with the differential pressure valve on the opposite side of the differential pressure valve. A piston that receives the inlet pressure of the first port, and the refrigerant when a differential pressure between the inlet pressure received by the piston and the outlet pressure received by the differential pressure valve is lower than the set differential pressure 2. The expansion valve according to claim 1, wherein the passage is closed. A large-diameter control valve that is installed in parallel with the on-off valve, and controls the valve hole with a larger diameter than the on-off valve as the degree of superheat increases;
The large-diameter control valve is a pilot-operated valve that opens and closes a main valve by operating a pilot valve in conjunction with the control of the on-off valve by the degree of superheat, the pressure regulating chamber of the main valve, the pilot valve, The expansion valve according to claim 6, wherein the expansion valve is arranged between the two and is configured to switch whether or not the large-diameter control valve is in a control state by a normally open differential pressure valve.

Images