JP2009040214A - Control method of refrigerating cycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method capable of reducing cost in a refrigerating cycle capable of respectively air-conditioning the front side and the rear side, and having an internal heat exchanger. <P>SOLUTION: A front side expansion valve 4 is formed of a temperature type expansion valve for so controlling a refrigerant of an outlet of a front side evaporator 5 as to become a predetermined overheating degree. A rear side expansion valve 6 is formed of a constitutionally simple, inexpensive and solenoid operation solenoid expansion valve for controlling a flow rate of the refrigerant supplied to a rear side evaporator 7 in response to differential pressure between inlet pressure and outlet pressure of the rear side evaporator 7, closing the valve when an electric current is not carrier and setting preset differential pressure in response to a current value flowed to a solenoid when opening the valve when the electric current is carried. Though the current value flowed to the solenoid is set by driving voltage of an air blower 10, this rough control is absorbed by accurate control on the front side and the presence of the internal heat exchanger 8. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control method for a refrigeration cycle, and more particularly to a refrigeration cycle for an automotive air conditioner capable of independently air-conditioning a front side and a rear side in a vehicle interior, from a receiver to a front side expansion valve and a rear side expansion. Equipped with a double-tube internal heat exchanger that exchanges heat between the high-temperature and high-pressure refrigerant going to the valve and the low-temperature and low-pressure refrigerant going from the front and rear evaporators to the variable capacity compressor. The present invention relates to a control method of a refrigeration cycle.

  A vehicle having a large cabin capacity may be equipped with an automotive air conditioner that can independently air-condition the front and rear sides of the cabin. In such an automotive air conditioner, a front side expansion valve and front evaporator circuit that performs front side air conditioning control and a rear side expansion valve and rear side evaporator circuit that perform rear side air conditioning control are arranged in parallel. A refrigeration cycle arranged and configured is used. Here, as expansion valves used in the front side circuit and the rear side circuit, the temperature and pressure of the refrigerant at the outlet of each evaporator are sensed and evaporated so that the refrigerant at the outlet of the evaporator has a predetermined superheat degree. In many cases, a temperature-type expansion valve that controls the flow rate of the refrigerant supplied to the vessel is used.

  The refrigeration cycle generally includes an internal heat exchanger that exchanges heat between the condensed high-temperature / high-pressure refrigerant directed to the expansion valve and the low-temperature / low-pressure refrigerant directed from the evaporator to the variable capacity compressor. It is also known that the efficiency of the system can be improved (see, for example, Patent Document 1). This is because the condensed refrigerant is further cooled by the internal heat exchanger to lower the enthalpy of the refrigerant at the inlet of the expansion valve and the evaporator, and the refrigerant that has left the evaporator is further superheated by the internal heat exchanger. This is because the coefficient of performance is improved by increasing the enthalpy of the refrigerant at the inlet of the variable capacity compressor.

If such an internal heat exchanger is applied to a refrigeration cycle having an expansion valve and an evaporator for the front and rear, respectively, the efficiency of the system can be improved in the same manner. As the internal heat exchanger, a double tube structure in which an inner tube and an outer tube are concentrically arranged is used because of the simplicity of the structure.
JP 2001-108308 A

  However, even in the refrigeration cycle in which air conditioning is possible on the front side and the rear side, a temperature type expansion valve is used for the front side expansion valve, and the refrigerant circuit can be closed to the rear side expansion valve when air conditioning is stopped. There is a problem that the cost of the air conditioner for automobiles is increased because the structure uses a complicated and expensive temperature expansion valve with a solenoid valve.

  The present invention has been made in view of the above points, and provides a control method of a refrigeration cycle that can be air-conditioned on the front side and the rear side, respectively, and that can reduce the cost of the refrigeration cycle having an internal heat exchanger. The purpose is to do.

  In the present invention, in order to solve the above problem, a high-temperature / high-pressure refrigerant from the receiver to the front-side expansion valve and the rear-side expansion valve and a low-temperature / low-pressure refrigerant from the front-side evaporator and the rear-side evaporator to the variable capacity compressor. In the control method of a refrigeration cycle including an internal heat exchanger having a double-pipe structure for exchanging heat with a refrigerant, the rear side expansion valve is a differential pressure between an inlet pressure and an outlet pressure of the rear side evaporator. The flow rate of the refrigerant supplied to the rear-side evaporator is controlled in accordance with the value, and the set differential pressure when the valve is closed when not energized and opened when energized is set according to the value of the current flowing through the solenoid. A solenoid-operated electromagnetic expansion valve that estimates the amount of air in the passenger compartment that is blown to the rear-side evaporator, and sets the flow rate of refrigerant to be supplied to the rear-side evaporator according to the estimated amount of air. Corresponding set differential pressure The method of the refrigeration cycle, characterized in that so as to set is provided.

  According to such a control method of the refrigeration cycle, as the rear side expansion valve, a solenoid-operated valve in which a set differential pressure when closing the valve when not energized and opening when energized is set according to the value of the current flowing through the solenoid. The electromagnetic expansion valve eliminates the need for an electromagnetic valve for closing the refrigerant circuit when air conditioning is stopped, and the electromagnetic expansion valve is arranged in accordance with the differential pressure between the inlet pressure and the outlet pressure of the rear evaporator. Since the flow rate of the refrigerant supplied to the side evaporator is controlled, the power element required for the temperature type expansion valve is unnecessary, so the cost of the rear side expansion valve can be greatly reduced. The control of the electromagnetic expansion valve is based on the amount of air in the passenger compartment that is blown to the rear-side evaporator that represents the rear-side air load. Although the accuracy of control of the electromagnetic expansion valve is lower than that of the temperature expansion valve, even if the flow rate is such that it cannot be completely evaporated by the rear side evaporator, the internal heat exchanger is not connected to the rear side evaporator. Since the refrigerant with much moisture is completely evaporated, the introduction of liquid refrigerant, which is a serious failure factor of the variable capacity compressor, can be prevented.

  The control method for the refrigeration cycle according to the present invention is based on the rear side evaporator according to the differential pressure between the inlet pressure and the outlet pressure of the rear side evaporator instead of the expensive temperature type expansion valve with solenoid valve. By using an electromagnetic expansion valve that controls the flow rate of the refrigerant supplied to the vehicle, the cost of the air conditioner for automobiles can be reduced, and the electromagnetic expansion valve is blown to the rear-side evaporator that represents the air load on the rear side. By controlling based on the amount of air in the vehicle interior, there is an advantage that the control itself can be simplified. For this reason, the accuracy of the flow rate control is lower than that of the temperature type expansion valve, but the malfunction caused by it is not a problem because the internal heat exchanger absorbs it.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a system diagram showing a refrigeration cycle of an automotive air conditioner according to a first control method.

  This refrigeration cycle is arranged in an engine room of a vehicle, and a variable capacity compressor 1 that compresses the refrigerant, a condenser 2 that cools and condenses the compressed refrigerant, and separates the condensed refrigerant into gas and liquid. And a receiver 3 for sending out the liquid refrigerant. A front side expansion valve 4 for adiabatically expanding the liquid refrigerant and a front side evaporator 5 for evaporating the expanded refrigerant are disposed on the front side of the vehicle interior, and the liquid refrigerant is insulated on the rear side of the vehicle interior. A rear side expansion valve 6 for expansion and a rear side evaporator 7 for evaporating the expanded refrigerant are arranged. The receiver 3 and the front side expansion valve 4 and the rear side expansion valve 6 are connected by an internal heat exchanger 8 having a double pipe structure. Further, in the vicinity of the front-side evaporator 5 and the rear-side evaporator 7, blowers 9 and 10 are provided for allowing the air in the vehicle compartment to pass therethrough.

  The front side expansion valve 4 senses the temperature and pressure of the refrigerant at the outlet of the front side evaporator 5 and supplies the refrigerant to the outlet of the front side evaporator 5 to the front side evaporator 5 so as to have a predetermined superheat degree. It is a temperature type expansion valve which controlled the flow volume of the refrigerant | coolant to perform.

  The rear side expansion valve 6 controls the flow rate of the refrigerant supplied to the rear side evaporator 7 according to the differential pressure between the inlet pressure and the outlet pressure of the rear side evaporator 7, and is closed when not energized. The solenoid-operated electromagnetic expansion valve is set in accordance with the value of the current that flows through the solenoid. The value of the current flowing through the solenoid is controlled by the control unit 11. The controller 11 is connected to a temperature sensor 12 installed near the air inlet of the rear evaporator 7, a temperature sensor 13 installed near the air outlet of the rear evaporator 7, and the blower 10. The temperature sensor 12 detects the inlet air temperature of the rear side evaporator 7, and the temperature sensor 13 detects the outlet air temperature of the rear side evaporator 7. In the blower 10, since the drive voltage applied to this corresponds to the amount of air blown to the rear evaporator 7, the amount of air blown is estimated by detecting the drive voltage of the blower 9. This represents the air load on the rear side. Therefore, the control unit 11 controls the flow rate of the rear side expansion valve 6 based on the drive voltage of the blower 10.

  Here, for example, when air conditioning is performed only on the front side, the rear side expansion valve 6 is in a non-energized state and is closed, so that no refrigerant flows into the refrigerant flow path of the rear side circuit. When the variable capacity compressor 1 and the front blower 9 are started in this state, the high-temperature and high-pressure refrigerant compressed by the variable capacity compressor 1 is condensed in the condenser 2 and stored in the receiver 3. . The liquid refrigerant in the receiver 3 is supplied to the front side expansion valve 4 through the internal heat exchanger 8, where it is adiabatically expanded to become a low-temperature / low-pressure refrigerant. The refrigerant that has become a low-temperature and low-pressure refrigerant is sent to the front-side evaporator 5, where it is evaporated by heat exchange with the air in the vehicle compartment sent by the blower 9. The evaporated refrigerant is sent to the inlet of the variable capacity compressor 1 through the front side expansion valve 4 and the internal heat exchanger 8.

  When the evaporated refrigerant passes through the front side expansion valve 4, the power element senses the temperature and pressure of the refrigerant that has left the front side evaporator 5, and the refrigerant at the outlet of the front side evaporator 5 has a predetermined overheat. The flow rate of the refrigerant sent to the front-side evaporator 5 is controlled so as to be at the same level. The internal heat exchanger 8 exchanges heat between the high-temperature refrigerant flowing from the receiver 3 toward the front side expansion valve 4 and the low-temperature refrigerant flowing from the front side expansion valve 4 toward the variable capacity compressor 1. Thereby, the refrigerant sent to the front side expansion valve 4 is further cooled, and the refrigerant sent to the variable capacity compressor 1 is further heated, so that the inlet of the front side expansion valve 4 and the inlet of the variable capacity compressor 1 are The enthalpy difference increases. As a result, since the coefficient of performance of the refrigeration cycle is improved, the load on the traveling engine that drives the variable capacity compressor 1 can be reduced, and the efficiency of the air conditioner for automobiles can be improved.

  When rear-side air conditioning is performed, the rear-side expansion valve 6 is energized and the blower 10 is activated. As a result, the high-temperature and high-pressure liquid refrigerant branched by the internal heat exchanger 8 is supplied to the rear side expansion valve 6, where it is adiabatically expanded to become a low-temperature and low-pressure refrigerant. The refrigerant that has become a low-temperature and low-pressure refrigerant is sent to the rear-side evaporator 7, where it is evaporated by heat exchange with the air in the vehicle compartment sent by the blower 10. The evaporated refrigerant is sent to the inlet of the variable capacity compressor 1 via the rear side expansion valve 6 and the internal heat exchanger 8. When the evaporated refrigerant passes through the rear side expansion valve 6, the rear side expansion valve 6 senses the differential pressure across the rear evaporator 7, and the differential pressure corresponds to a predetermined differential pressure corresponding to the supplied current. The flow rate of the refrigerant sent to the rear evaporator 7 is controlled so as to maintain the above. At this time, the control unit 11 estimates the amount of air that the blower 9 blows to the rear evaporator 7 from the drive voltage of the blower 9 and controls the flow rate of the rear side expansion valve 6 based on this. That is, the larger the amount of air to be blown, the larger the current value (set differential pressure) that flows through the solenoid of the rear side expansion valve 6 is controlled to increase the flow rate of the refrigerant sent to the rear side evaporator 7. To do. Further, the temperature sensor 12 and the temperature sensor 13 detect the inlet air temperature and the outlet air temperature of the rear side evaporator 7, and know the degree of cooling of the vehicle interior air by the rear side evaporator 7 by obtaining the temperature difference between them. Therefore, the control unit 11 adjusts the value of the current flowing through the solenoid of the rear side expansion valve 6 to increase as the temperature difference increases, and corrects the set differential pressure value.

  Thus, in the front side expansion valve 4 on the front side, the flow rate of the refrigerant sent to the front side evaporator 5 is always accurately controlled so that the refrigerant discharged from the front side evaporator 5 has a predetermined superheat degree, While the liquid refrigerant causing the failure of the variable capacity compressor 1 is never returned to the variable capacity compressor 1, the rear side expansion valve 6 is more accurate than the front side expansion valve 4. A precise flow rate control is not required. This is because the refrigeration cycle includes the internal heat exchanger 8. That is, even if the rear side expansion valve 6 performs rough flow control and the rear side evaporator 7 does not completely evaporate and a refrigerant with a high level of moisture is discharged, Before reaching the inlet of the variable capacity compressor 1, it is completely evaporated by the internal heat exchanger 8 and further heated. Therefore, an inexpensive rear expansion valve that has a simple configuration and can be closed when not energized without using an expensive temperature expansion valve or an expansion valve integrated with a solenoid valve. 6 can be used. Next, a specific example of such a rear side expansion valve 6 will be described.

FIG. 2 is a cross-sectional view showing a configuration example of the rear side expansion valve in a non-energized state.
The rear side expansion valve 6 is configured to be directly connected to the refrigerant inlet and the refrigerant outlet of the rear side evaporator 7. The rear-side evaporator 7 is configured by laminating a plurality of aluminum plates, and has a refrigerant inlet pipe 22 for introducing a refrigerant and a refrigerant outlet pipe 23 for leading out the refrigerant in a header portion thereof. The refrigerant outlet pipe 23 is disposed substantially coaxially with the refrigerant inlet pipe 22 so as to surround the refrigerant inlet pipe 22 and has a double pipe structure. The rear evaporator 7 is formed by simultaneously welding the stacked plates by brazing in the furnace. At this time, the refrigerant inlet pipe 22 and the refrigerant outlet pipe 23 are also welded together. Are integrally formed.

  The rear side expansion valve 6 is provided with a body 26 having an outer shape in which a main cylindrical portion 24 extending in the left-right direction in FIG. 2 and a sub cylindrical portion 25 extending in the downward direction in FIG. The sub-cylindrical part 25 constitutes a pipe connection part connected to the pipe of the internal heat exchanger 8 having a double pipe structure. The main cylindrical portion 24 and the sub-cylindrical portion 25 have a double pipe structure in their end surfaces. The main cylindrical portion 24 has a central hole in the center thereof in which the movable portion of the expansion valve is accommodated in the axial direction, and a plurality of low-pressure refrigerant introduced from the rear-side evaporator 7 flows around the central hole. A passage is formed penetrating in the axial direction. Therefore, preferably, the body 26 is made of an extruded hollow material in which a central hole and / or a plurality of passages are formed in advance by hollow extrusion, and processed into a double tube structure on three sides. Yes.

  In the middle of the central hole of the main cylindrical portion 24, a valve shaft guide 27 and a ring-shaped valve seat 28 are fixed to the body 26 by caulking. A valve element 29 is disposed so as to be able to contact and separate from the valve seat 28. The valve body 29 is urged in the valve closing direction by a spring 30, and the spring 30 is press-fitted into an inner pipe of a double pipe formed on the rear side evaporator 7 side of the main cylindrical portion 24. Received by 31. The load of the spring 30 is adjusted by the press-fitting amount of the spring receiving member 31 that is press-fitted into the inner pipe of the double pipe.

  The valve body 29 is formed integrally with a valve shaft 32 extending in the axial direction via the valve seat 28 and the valve shaft guide 27. A cylindrical pressure receiving member 33 is fitted on the end of the valve shaft 32 opposite to the side on which the valve body 29 is formed, and the valve shaft 32 closer to the valve body 29 than the cylindrical pressure receiving member 33 is sealed. An O-ring 34 is provided around. The inner diameter of the inner tube of the double pipe, which is the central hole of the main cylindrical portion 24 that accommodates the cylindrical pressure receiving member 33, is approximately equal to the inner diameter of the valve hole of the valve seat 28. Since the effective pressure receiving area in which the high pressure receives the high pressure in the valve opening direction and the effective pressure receiving area in which the O-ring 34 receives the high pressure in the valve closing direction are approximately equal, the high pressure received by the valve body 29 in the valve opening direction is The O-ring 34 is canceled by the same pressure received in the valve closing direction.

  The inner tube of the double cylindrical structure formed on the side where the spring receiving member 31 of the main cylindrical portion 24 is press-fitted constitutes a low-pressure refrigerant outlet 35 of the rear side expansion valve 6 and is formed on the outer periphery thereof. The annular groove constitutes a return low-pressure refrigerant inlet 36 that receives the refrigerant returned from the rear-side evaporator 7. Here, the low-pressure refrigerant outlet 35 of the rear side expansion valve 6 is fitted into the refrigerant inlet pipe 22 of the rear side evaporator 7, and the fitting portion is sealed by an O-ring. Further, the return low-pressure refrigerant inlet 36 of the rear side expansion valve 6 is fitted into the refrigerant outlet pipe 23 of the rear side evaporator 7 and mechanically coupled to the rear side evaporator 7 by caulking the entire tip. The fitting portion with the refrigerant outlet pipe 23 is sealed with an O-ring.

  The installation space of the valve shaft guide 27 in the central hole of the main cylindrical part 24 communicates with the inner pipe of the double pipe structure formed in the sub-cylindrical part 25, and the central hole and the central hole around the central hole of the main cylindrical part 24. The passages formed in parallel communicate with a space between the inner tube and the outer tube formed in the sub-cylindrical portion 25. Here, the inner tube of the sub-cylindrical portion 25 constitutes a high-pressure refrigerant inlet 37, and the space between the inner tube and the outer tube of the sub-cylindrical portion 25 has a variable capacity for the refrigerant that has passed through the rear side expansion valve 6. A return low-pressure refrigerant outlet 38 that is returned to the inlet of the compressor 1 is configured. Therefore, the high-pressure refrigerant inlet 37 of the rear side expansion valve 6 is fitted with a high-pressure pipe 39 to which high-temperature and high-pressure liquid refrigerant from the receiver 3 is supplied and is sealed by an O-ring. Further, the return low-pressure refrigerant outlet 38 of the rear side expansion valve 6 is fitted into the return low-pressure pipe 40, and the return low-pressure pipe is formed by caulking the entire circumference so as to fix the backup ring 41 fitted in the tip portion. 40 and mechanically coupled to the return low-pressure pipe 40 is sealed by an O-ring. The high-pressure pipe 39 and the return low-pressure pipe 40 connected to the sub-cylindrical portion 25 have a substantially coaxial double pipe structure in which a plurality of heat transfer fins (not shown) are spirally arranged between them. 1 constitutes the internal heat exchanger 8 of FIG.

  The opposite side of the main cylindrical portion 24 to the side connected to the rear evaporator 7 also has a double tube structure, and its open end is closed by a solenoid 42. The solenoid 42 has a core 43, and its flange portion is airtightly coupled to the main cylindrical portion 24 by caulking the outer tube of a double tube structure all around. The core 43 is fitted with an open end of a bottomed sleeve 44 extending in the same direction as the valve shaft 32, and a plunger 45 is disposed in the bottomed sleeve 44. The plunger 45 is fixed to a shaft 46 that penetrates the core 43 and extends in the same direction as the valve shaft 32. The shaft 46 is fixed to the bottom of the bearing portion 47 and the bottomed sleeve 44 that are press-fitted and fixed to the core 43. The formed bearing portion 48 is held so as to be movable back and forth in the axial direction. In the solenoid 42, a coil 49 is provided around the bottomed sleeve 44 and surrounded by a yoke 50. Therefore, in the rear side expansion valve 6, when the coil 49 is not energized, the valve body 29 is seated on the valve seat 28 by the biasing force of the spring 30 and is closed. When the coil 49 is energized, the plunger 45 is attracted by the core 43 and the shaft 46 fixed to the plunger 45 against the biasing force of the spring 30 causes the valve shaft 32 integrated with the valve body 29 to open in the valve opening direction. Push to open. The lift of the valve body 29 is set according to the magnitude of the current supplied to the coil 49.

  In the rear side expansion valve 6 configured as described above, front side air conditioning is performed, but when the rear side air conditioning is stopped, power is not supplied to the coil 49 of the solenoid 42, as shown in FIG. The rear side expansion valve 6 is closed. That is, since the air conditioner for automobiles performs air conditioning on the front side, high-temperature and high-pressure liquid refrigerant is supplied from the receiver 3 through the high-pressure pipe 39 of the internal heat exchanger 8 to the high-pressure refrigerant inlet 37. Since the high pressure is canceled by making the inner diameter of the inner pipe of the double pipe of the main cylindrical portion 24 accommodating the cylindrical pressure receiving member 33 substantially equal to the inner diameter of the valve hole, the valve element 29 is It is seated on the valve seat 28 by the urging force of the spring 30 and is closed.

  Here, when the coil 49 of the solenoid 42 is energized to perform air conditioning on the rear side, the valve element 29 is lifted according to the magnitude of the energized current, and the rear side expansion valve 6 is opened. When high-temperature and high-pressure liquid refrigerant is supplied from the receiver 3 to the high-pressure refrigerant inlet 37 through the high-pressure pipe 39 of the internal heat exchanger 8, the liquid refrigerant passes through the gap between the valve seat 28 and the valve element 29. It flows out to the low-pressure refrigerant outlet 35. At this time, the refrigerant is adiabatically expanded to become a low-temperature / low-pressure gas-liquid mixed refrigerant, and is introduced into the rear evaporator 7 through the refrigerant inlet pipe 22. In addition, the arrow in a figure has shown the flow direction of the refrigerant | coolant. In the rear side evaporator 7, the introduced refrigerant is evaporated by heat exchange with the air in the passenger compartment and flows out from the refrigerant outlet pipe 23. The refrigerant is introduced from the return low-pressure refrigerant inlet 36, flows out to the return low-pressure refrigerant outlet 38 through a plurality of low-pressure refrigerant passages, and is returned to the inlet of the variable capacity compressor 1 through the return low-pressure pipe 40.

  Here, the expansion valve inlet pressure of the refrigerant supplied by the high-pressure pipe 39 is Po, the expansion valve outlet pressure (evaporator inlet pressure) of the refrigerant adiabatically expanded is Px, and the evaporator outlet returned from the rear-side evaporator 7. When the pressure is Pe, the evaporator inlet pressure Px is applied to the valve body 29 in the valve closing direction, and the end face of the valve shaft 32 and the tubular pressure receiving member 33 integral with the valve body 29 is exposed to the evaporator in the valve opening direction. The outlet pressure Pe is applied. Therefore, since the differential assembly (Px-Pe) between the inlet pressure and the outlet pressure of the rear evaporator 7 is applied to the integral assembly of the valve body 29, the valve shaft 32, and the cylindrical pressure receiving member 33, The assembly constitutes a differential pressure sensing unit that senses the differential pressure (Px−Pe) with the rear side expansion valve 6.

  When the rear side expansion valve 6 is supplying the refrigerant to the rear side evaporator 7 with a predetermined valve lift set by the solenoid 42, the flow rate of the refrigerant passing through the rear side evaporator 7 is increased and the rear side evaporation is performed. When the pressure loss in the vessel 7 increases, the differential pressure across the evaporator (Px−Pe) increases, so that the valve element 29 moves in the valve closing direction and acts to throttle the flow rate. On the contrary, when the flow rate of the refrigerant passing through the rear evaporator 7 decreases and the evaporator front-rear differential pressure (Px−Pe) decreases, the valve body 29 moves in the valve opening direction and acts to increase the flow rate. . Therefore, the rear side expansion valve 6 controls the flow rate of the refrigerant sent to the rear side evaporator 7 to be substantially constant by controlling the pressure difference between the inlet and the outlet of the rear side evaporator 7 to be constant. Works. Further, since the differential pressure to be controlled to be constant is set by the solenoid 42, the rear side expansion valve 6 has the flow rate of the refrigerant passing through the rear side evaporator 7 substantially constant to the flow rate set by the solenoid 42. It is also what controls. Moreover, the differential pressure across the evaporator (Px−Pe) is not affected at all by the magnitude of the expansion valve inlet pressure Po because the expansion valve inlet pressure Po is canceled by the back pressure.

  The magnitude of the current supplied to the coil 49 of the solenoid 42 to control the rear side expansion valve 6 is set based on the estimated value of the rear side air load. The estimated value of the air load is obtained from the amount of air applied to the rear evaporator 7 by the blower 10, that is, the drive voltage of the blower 10. The driving voltage of the blower 10 is directly detected from the blower 10 or obtained by detecting an air volume designation signal from a device that controls the blower 10, and the control unit 11 calculates the air load based on these data. And a current having a value corresponding thereto is supplied to the coil 49 of the solenoid 42. The control unit 11 also calculates a temperature difference between the inlet air temperature and the outlet air temperature of the rear side evaporator 7, and generates a coil 49 of the solenoid 42 set based on the driving voltage of the blower 10 according to the temperature difference. The magnitude of the energized current is corrected.

FIG. 3 is a cross-sectional view showing a configuration example of the front side expansion valve.
The front side expansion valve 4 has a configuration of a temperature type expansion valve by replacing the solenoid 42 of the rear side expansion valve 6 with a power element 51. That is, the front side expansion valve 4 includes a body 54 having a main cylindrical portion 52 and a sub-cylindrical portion 53, and three end face shapes each have a double tube structure. One end of the main cylindrical portion 52 has an inner pipe serving as a low-pressure refrigerant outlet 55 and an outer pipe returning to a low-pressure refrigerant inlet 56, and is connected to a refrigerant inlet pipe 57 and a refrigerant outlet pipe 58 formed integrally with the front-side evaporator 5. Each is connected. The open end of the other end of the main cylindrical portion 52 is sealed by caulking all around so as to lock the outer peripheral edge of the power element 51. The power element 51 includes a thick metal upper housing 59 and a lower housing 60, a diaphragm 61 made of a flexible thin metal plate welded together in a state where an outer peripheral edge is sandwiched between them, and an inner portion of the lower housing 60. And a center disk 62 arranged in the center. A space surrounded by the upper housing 59 and the diaphragm 61 constitutes a greenhouse, and is filled with a gas having the same or similar characteristics as the refrigerant of the refrigeration cycle. The lower housing 60 has its open ends bent alternately inward and outward in the circumferential direction, the outer bent portion is used to prevent the sealing O-ring from falling off, and the inner bent portion is the center disc 62. It is a stopper to prevent falling off. The sub-cylindrical portion 53 has an inner pipe constituting the high-pressure refrigerant inlet 63, an outer pipe constituting the return low-pressure refrigerant outlet 64, and the high-pressure pipe 39a and the return low-pressure pipe 40a of the internal heat exchanger 8 are connected to each other. .

  The main cylindrical portion 52 of the body 54 has a central hole formed in the center thereof, and four low-pressure refrigerant passages are formed in parallel around the central hole, although not shown. In the center hole, a valve shaft guide 65 and a ring-shaped valve seat 66 are fitted and fixed to the body 54 by caulking. A valve body 67 is arranged so as to be able to contact and separate from the valve seat 66. The valve body 67 is formed integrally with a valve shaft 68 that extends in the axial direction via a valve seat 66 and a valve shaft guide 65. A cylindrical collar member 69 is fitted to the end of the valve shaft 68 opposite to the side on which the valve body 67 is formed, and on the valve body 67 side, a sealing O-ring is provided. 70 is arranged. The collar member 69 is in contact with the center disk 62 of the power element 51, and transmits the displacement of the diaphragm 61 to the valve body 67. The collar member 69 has an outer diameter substantially equal to the inner diameter of the valve hole of the valve seat 66, thereby canceling the pressure of the refrigerant introduced into the front side expansion valve 4.

  The valve body 67 is urged in the valve closing direction by a spring 71, and the spring 71 is press-fitted into an inner pipe of a double pipe formed on the front evaporator 5 side of the main cylindrical portion 52. The load of the spring 71 is adjusted by the amount of press-fitting of the spring receiving member 72 into the inner tube.

  In the front-side expansion valve 4 having the above configuration, when high-temperature and high-pressure liquid refrigerant is supplied from the receiver 3 to the high-pressure refrigerant inlet 63 through the high-pressure pipe 39 a, the liquid refrigerant is interposed between the valve seat 66 and the valve body 67. Flows out to the low-pressure refrigerant outlet 55. At this time, the refrigerant is adiabatically expanded to become a low-temperature / low-pressure gas-liquid mixed refrigerant, and is introduced into the front-side evaporator 5 through the refrigerant inlet pipe 57. In the front-side evaporator 5, the introduced refrigerant is evaporated by heat exchange with the air in the passenger compartment and flows out from the refrigerant outlet pipe 58. The refrigerant is introduced from the return low-pressure refrigerant inlet 56, flows out to the return low-pressure refrigerant outlet 64 through the low-pressure refrigerant passage, and is returned to the inlet of the variable capacity compressor 1 through the return low-pressure pipe 40 a of the internal heat exchanger 8. .

  Since the space surrounded by the diaphragm 61 and the lower housing 60 of the power element 51 communicates with the low-pressure refrigerant passage, when the refrigerant returned from the front evaporator 5 passes through the low-pressure refrigerant passage, The refrigerant is introduced and its temperature and pressure are detected by the power element 51. Since the pressure in the temperature sensitive room rises and falls according to the detected temperature and pressure of the refrigerant, the diaphragm 61 is displaced in the opening / closing direction of the valve body 67 according to the temperature and pressure. The displacement is transmitted to the collar member 69 via the center disk 62 and further transmitted to the valve body 67 via the valve shaft 68. As a result, the lift of the valve body 67 changes, and the flow rate of the refrigerant supplied to the front-side evaporator 5 is controlled. That is, the front side expansion valve 4 senses the temperature and pressure of the refrigerant that has exited the front side evaporator 5 and supplies the refrigerant to the front side evaporator 5 so that the refrigerant maintains a predetermined degree of superheat. The flow rate will be controlled.

  FIG. 4 is a system diagram showing the refrigeration cycle of the automotive air conditioner according to the second control method. In FIG. 4, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  This refrigeration cycle controls the flow rate of the refrigerant supplied to the front side evaporator 5 according to the differential pressure between the inlet pressure and the outlet pressure of the front side evaporator 5 to the front side expansion valve 4. A solenoid-operated electromagnetic expansion valve is used, which is closed when energized and is set in accordance with the value of the current flowing through the solenoid. The rear-side evaporator 7 is connected to the rear-side evaporator 7. The flow rate of the refrigerant to be supplied to the rear evaporator 7 is controlled according to the pressure difference between the inlet pressure and the outlet pressure, and the set differential pressure when the valve is closed when not energized and when the valve is opened when energized is A solenoid-operated electromagnetic expansion valve that is set according to the value of the current flowing through the solenoid is used. The control of the rear side expansion valve 6 is the same as that described with respect to the first control method of FIG. 1, and a specific example of the configuration of the front side expansion valve 4 is the electromagnetic shown in FIG. Since this is the same as the expansion valve, the description thereof is omitted here.

  The front side expansion valve 4 is controlled by the front control unit 14. The front control unit 14 is connected to a pressure sensor 15 and a temperature sensor 16 installed at the low pressure side outlet of the internal heat exchanger 8, and further, on the high pressure side of the variable capacity compressor 1, for example, the receiver 3 if necessary. Is connected to a pressure sensor 17 or a temperature sensor 18 installed on the discharge side of the variable capacity compressor 1.

  According to the refrigeration cycle having the above configuration, in the front side expansion valve 4, the value of the current flowing through the solenoid of the electromagnetic expansion valve constituting the front side expansion valve 4 is set by the temperature and pressure at the low pressure side outlet of the internal heat exchanger 8. Thereby, the front side expansion valve 4 senses the temperature and pressure of the refrigerant at the low pressure side outlet of the internal heat exchanger 8 and supplies the refrigerant to the front side evaporator 5 so that the refrigerant maintains a predetermined degree of superheat. The flow rate of the refrigerant will be controlled. In this way, the front side expansion valve 4 controls the degree of superheat of the refrigerant at the low pressure side outlet that is the suction side of the variable capacity compressor 1 from the branching / merging point with the rear side circuit of the internal heat exchanger 8. Therefore, the entire air conditioning including the front side and the rear side is controlled.

  At this time, the coefficient of performance can be increased by controlling the degree of superheat of the refrigerant at the low pressure side outlet of the internal heat exchanger 8 as much as possible, thereby improving the efficiency of the automotive air conditioner. The extent to which the degree of superheat can be increased is determined by the fact that the refrigerant temperature on the discharge side of the variable capacity compressor 1 that sucks and compresses the refrigerant having such superheat does not exceed the continuous use heat resistance temperature of the lubricating oil. Is a condition.

  In order to satisfy this condition, it is necessary to know the refrigerant temperature on the discharge side of the variable capacity compressor 1, and the temperature can be detected by a temperature sensor 18 installed on the discharge side of the variable capacity compressor 1. Accordingly, the front control unit 14 monitors the temperature of the refrigerant on the discharge side of the variable capacity compressor 1 while controlling the degree of superheat of the front side expansion valve 4, and the temperature of the refrigerant on the discharge side is the heat resistance for continuous use of the lubricating oil. When the temperature becomes higher than a predetermined value corresponding to the temperature, the current value flowing through the solenoid set in the superheat degree control is adjusted to increase. As a result, the flow rate of the refrigerant supplied from the front side expansion valve 4 to the front side evaporator 5 is increased, and the degree of superheat of the refrigerant at the low pressure side outlet of the internal heat exchanger 8 is reduced. The refrigerant temperature on the discharge side can be lowered.

  Thus, in order to monitor the temperature of the refrigerant on the discharge side of the variable capacity compressor 1, it is necessary to newly install a temperature sensor 18 on the discharge side of the variable capacity compressor 1. However, since the pressure sensor 17 that is indispensable for safety in the existing air conditioner for automobiles is installed on the high pressure side of the variable capacity compressor 1, the temperature sensor 18 is changed using the pressure sensor 17. Without newly providing, the temperature of the refrigerant on the discharge side of the variable capacity compressor 1 can be estimated.

  The estimation of the refrigerant temperature on the discharge side of the variable capacity compressor 1 can be explained using a Mollier diagram representing the behavior of the refrigeration cycle. That is, in the ideal adiabatic compression of the variable capacity compressor 1, the entropy does not change, and the adiabatic compressed refrigerant increases the pressure and the enthalpy for the amount of work, so the variable capacity compressor on the Mollier diagram. A compression by 1 is represented by a right-up change along the isentropic line. The starting point of the change on the isentropic line can be specified from the pressure and temperature at the low-pressure side outlet of the internal heat exchanger 8 detected by the pressure sensor 15 and the temperature sensor 16, that is, the suction port of the variable capacity compressor 1. it can. On the other hand, the end point of the change on the isentropic line with the specified start point is detected by the isentropic line on the Mollier diagram because the pressure on the high pressure side of the variable capacity compressor 1 is detected by the pressure sensor 17. It is specified at a position that intersects with pressure. And the temperature of the refrigerant | coolant by the side of the discharge of the variable capacity compressor 1 can be estimated by calculating | requiring the isothermal line which passes the end point on a Mollier diagram.

  The temperature of the refrigerant on the discharge side of the variable capacity compressor 1 estimated in this way is a solenoid set from the pressure and temperature at the low-pressure side outlet of the internal heat exchanger 8 detected by the pressure sensor 15 and the temperature sensor 16. Used to correct the current value flowing through That is, the front control unit 14 controls the degree of superheat of the refrigerant at the low pressure side outlet of the internal heat exchanger 8 to be as large as possible, whereby the estimated temperature of the refrigerant on the discharge side of the variable capacity compressor 1 is variable. In order to exceed the continuous use heat resistance temperature of the lubricating oil of the compressor 1, the value of the current flowing through the solenoid is adjusted to increase so that the flow rate of the refrigerant flowing from the front side expansion valve 4 to the front side evaporator 5 is increased. Then, control is performed so as to reduce the temperature of the refrigerant on the discharge side of the variable capacity compressor 1 by reducing the degree of superheat of the refrigerant at the low pressure side outlet of the internal heat exchanger 8.

  FIG. 5 is a system diagram showing a refrigeration cycle of an automotive air conditioner according to a third control method. In FIG. 5, the same components as those shown in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this refrigeration cycle, the front side expansion valve 4 and the rear side expansion valve 6 are respectively connected to the front side evaporator 5 and the rear side according to the pressure difference between the inlet pressure and the outlet pressure of the front side evaporator 5 and the rear side evaporator 7. The flow rate of the refrigerant to be supplied to the evaporator 7 is controlled, and is closed when not energized and electromagnetically operated by a solenoid in which a set differential pressure when the valve is opened when energized is set according to a current value flowing through the solenoid. An expansion valve is used and is the same as in FIG. However, this refrigeration cycle control method differs from the case of FIG. 4 in that the pressure of the refrigerant at the low-pressure side outlet of the internal heat exchanger 8 is obtained without using an expensive pressure sensor 15.

  That is, in this refrigeration cycle, a temperature sensor 19 is installed in the vicinity of the refrigerant inlet of the front side evaporator 5 to detect the temperature of the inlet of the front side evaporator 5 supplied from the front side expansion valve 4. The front control unit 14 estimates the evaporation pressure in the front evaporator 5 by calculation from the temperature of the inlet of the front evaporator 5 detected by the temperature sensor 19. This estimation is based on the fact that the refrigerant supplied from the front side expansion valve 4 to the inlet of the front side evaporator 5 is a gas-liquid mixed refrigerant with much moisture, and in such a saturated state of gas-liquid mixing, the temperature and pressure are saturated. This is based on the fact that it is uniquely determined from the pressure-temperature characteristics.

  The front control unit 14 estimates the evaporation pressure at that time from the refrigerant temperature at the inlet of the front side evaporator 5, and the estimated evaporation pressure and the low pressure side outlet of the internal heat exchanger 8 detected by the temperature sensor 16. The value of the current flowing through the solenoid of the front side expansion valve 4 is set according to the temperature of the refrigerant in the front side and supplied to the front side evaporator 5 so that the refrigerant at the low pressure side outlet of the internal heat exchanger 8 maintains a predetermined degree of superheat. The flow rate of the refrigerant to be controlled is controlled.

  At this time, in order to safely control the degree of superheat of the refrigerant at the low pressure side outlet of the internal heat exchanger 8 as much as possible without causing deterioration of the lubricating oil, as in the case of FIG. The refrigerant temperature on the discharge side of the machine 1 is detected by the temperature sensor 18 or estimated from the pressure detected by the pressure sensor 17, and when the refrigerant temperature on the discharge side becomes higher than a predetermined value, the value of the current passed through the solenoid is increased. Adjust the direction.

  FIG. 6 is a system diagram showing a refrigeration cycle of an automotive air conditioner according to the fourth control method. In FIG. 6, the same components as those shown in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this refrigeration cycle, the use of solenoid-operated electromagnetic expansion valves for the front side expansion valve 4 and the rear side expansion valve 6 is the same as in the case of FIG. However, this refrigeration cycle control method differs from the case of FIG. 4 in that the pressure of the refrigerant at the low-pressure side outlet of the internal heat exchanger 8 is obtained without using an expensive pressure sensor 15.

  That is, in this refrigeration cycle, the suction pressure of the variable capacity compressor 1 is estimated from the external current of the capacity control valve 20 that controls the capacity of the variable capacity compressor 1. This capacity control valve 20 is of a type that senses the suction pressure of the suction chamber using a pressure sensitive member such as a bellows and controls the capacity so that the suction pressure maintains a predetermined value set by an external current. Is. Therefore, the external current is the control target value of the capacity control valve 20 and represents the suction pressure. Therefore, in the fourth control method, the front side expansion valve 4 uses the external current as the suction pressure. It is used for superheat degree control.

  The front control unit 14 estimates the suction pressure of the variable capacity compressor 1 from the external current of the capacity control valve 20, and the estimated suction pressure and the low-pressure side outlet of the internal heat exchanger 8 detected by the temperature sensor 16. The current value flowing through the solenoid of the front side expansion valve 4 is set according to the temperature of the refrigerant, and is supplied to the front side evaporator 5 so that the refrigerant at the low pressure side outlet of the internal heat exchanger 8 maintains a predetermined degree of superheat. Control the flow rate of refrigerant.

  At this time, in order to safely control the degree of superheat of the refrigerant at the low pressure side outlet of the internal heat exchanger 8 as much as possible without causing deterioration of the lubricating oil, as in the case of FIG. The refrigerant temperature on the discharge side of the machine 1 is detected by the temperature sensor 18 or estimated from the pressure detected by the pressure sensor 17, and when the refrigerant temperature on the discharge side becomes higher than a predetermined value, the value of the current passed through the solenoid is increased. Adjust the direction.

It is a system diagram which shows the refrigerating cycle of the motor vehicle air conditioner which concerns on a 1st control method. It is sectional drawing which shows the structural example of a rear side expansion valve in the state at the time of non-energization. It is sectional drawing which shows the structural example of a front side expansion valve. It is a system diagram which shows the refrigerating cycle of the motor vehicle air conditioner which concerns on a 2nd control method. It is a system diagram which shows the refrigerating cycle of the motor vehicle air conditioner which concerns on a 3rd control method. It is a system diagram which shows the refrigerating cycle of the motor vehicle air conditioner which concerns on a 4th control method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Variable capacity compressor 2 Condenser 3 Receiver 4 Front side expansion valve 5 Front side evaporator 6 Rear side expansion valve 7 Rear side evaporator 8 Internal heat exchanger 9,10 Blower 11 Control part 12,13 Temperature sensor 14 Front control Part 15 Pressure sensor 16 Temperature sensor 17 Pressure sensor 18, 19 Temperature sensor 20 Capacity control valve 22 Refrigerant inlet pipe 23 Refrigerant outlet pipe 24 Main cylinder part 25 Sub cylinder part 26 Body 27 Valve shaft guide 28 Valve seat 29 Valve body 30 Spring 31 Spring bearing member 32 Valve shaft 33 Cylindrical pressure receiving member 34 O-ring 35 Low pressure refrigerant outlet 36 Return low pressure refrigerant inlet 37 High pressure refrigerant inlet 38 Return low pressure refrigerant outlet 39 High pressure pipe 39a High pressure pipe 40 Return low pressure pipe 40a Return low pressure pipe 41 Backup ring 42 Solenoid 43 Core 44 Bottomed sleeve 45 Ranger 46 Shaft 47, 48 Bearing part 49 Coil 50 Yoke 51 Power element 52 Main cylinder part 53 Sub cylinder part 54 Body 55 Low pressure refrigerant outlet 56 Return low pressure refrigerant inlet 57 Refrigerant inlet pipe 58 Refrigerant outlet pipe 59 Upper housing 60 Lower housing 61 Diaphragm 62 Center disk 63 High-pressure refrigerant inlet 64 Return low-pressure refrigerant outlet 65 Valve shaft guide 66 Valve seat 67 Valve body 68 Valve shaft 69 Collar member 70 O-ring 71 Spring 72 Spring receiving member

Claims (11)

Dual heat exchange between the high-temperature and high-pressure refrigerant from the receiver to the front and rear expansion valves and the low- and low-pressure refrigerant from the front and rear evaporators to the variable capacity compressor In a control method of a refrigeration cycle having an internal heat exchanger with a tube structure,
The rear side expansion valve controls the flow rate of the refrigerant supplied to the rear side evaporator according to the differential pressure between the inlet pressure and the outlet pressure of the rear side evaporator, and is closed when not energized. The solenoid-operated electromagnetic expansion valve is set in accordance with the value of the current flowing through the solenoid, and the set differential pressure when opening the valve when energized is estimated, and the amount of air in the vehicle compartment blown to the rear evaporator is estimated. A control method for a refrigeration cycle, wherein the set differential pressure corresponding to the flow rate of the refrigerant to be supplied to the rear evaporator is set according to the estimated amount of air.   The amount of air is estimated from the drive voltage of a blower that blows air to the rear-side evaporator, and the current value that flows through the solenoid is set to be larger as the drive voltage of the blower increases. The control method of the refrigerating cycle of Claim 1.   The inlet air temperature and the outlet air temperature of the rear evaporator are detected, and the current value flowing through the solenoid is adjusted to increase as the temperature difference between the inlet air temperature and the outlet air temperature increases. The refrigeration cycle control method according to claim 2.   The said front side expansion valve is a temperature type expansion valve which controls the flow volume of the refrigerant | coolant supplied to the said front side evaporator according to the temperature and pressure of the refrigerant | coolant which left the said front side evaporator. The control method of the refrigerating cycle of 1.   The front side expansion valve controls the flow rate of the refrigerant supplied to the front side evaporator according to the differential pressure between the inlet pressure and the outlet pressure of the front side evaporator, and is closed when not energized. A solenoid-operated electromagnetic expansion valve in which a set differential pressure when opening the valve when energized is set according to a current value flowing through the solenoid, and detects the temperature and pressure of the low-pressure side outlet of the internal heat exchanger, 2. The refrigeration cycle control method according to claim 1, wherein the current value flowing through the solenoid is set according to the temperature and pressure at the low-pressure side outlet of the internal heat exchanger.   The front side expansion valve controls the flow rate of the refrigerant supplied to the front side evaporator according to the differential pressure between the inlet pressure and the outlet pressure of the front side evaporator, and is closed when not energized. A solenoid-operated electromagnetic expansion valve in which the set differential pressure when opening the valve when energized is set according to the current value flowing through the solenoid, and the temperature of the low-pressure side outlet of the internal heat exchanger and the front-side evaporator The refrigerant temperature at the inlet is detected, and the value of the current flowing through the solenoid is detected, and the temperature at the low-pressure side outlet of the internal heat exchanger is detected and the evaporation pressure estimated from the detected refrigerant temperature at the inlet of the front-side evaporator 2. The refrigeration cycle control method according to claim 1, wherein the refrigeration cycle is set. In the variable capacity compressor, the capacity is controlled by a capacity control valve so that the suction pressure maintains a predetermined value set by an external current,
The front side expansion valve controls the flow rate of the refrigerant supplied to the front side evaporator according to the differential pressure between the inlet pressure and the outlet pressure of the front side evaporator, and is closed when not energized. A solenoid-operated electromagnetic expansion valve in which a set differential pressure when opening the valve when energized is set according to a current value flowing through the solenoid, and detects the temperature at the low-pressure side outlet of the internal heat exchanger, The value of the flowing current is set by the temperature of the low-pressure side outlet of the internal heat exchanger and the suction pressure estimated from the external current of the capacity control valve that controls the capacity of the variable capacity compressor. The control method of the refrigerating cycle of Claim 1 characterized by these.   The temperature of the refrigerant on the discharge side of the variable capacity compressor is detected, and when the temperature of the refrigerant on the discharge side becomes higher than a predetermined value, the set current value flowing through the solenoid is adjusted to increase. The control method of the refrigerating cycle of any one of Claim 5 thru | or 7.   The pressure of the refrigerant on the high pressure side of the variable capacity compressor is detected, and from the detected pressure of the refrigerant on the high pressure side and the temperature and pressure at the low pressure side outlet of the internal heat exchanger, the discharge side of the variable capacity compressor is detected. 6. The refrigeration according to claim 5, wherein the temperature of the refrigerant is estimated, and when the estimated temperature of the refrigerant on the discharge side becomes higher than a predetermined value, the set current value flowing through the solenoid is adjusted to increase. Cycle control method.   The pressure of the refrigerant on the high pressure side of the variable capacity compressor is detected, and the variable capacity compression is performed from the detected pressure of the refrigerant on the high pressure side, the temperature at the low pressure side outlet of the internal heat exchanger, and the estimated evaporation pressure. The temperature of the refrigerant on the discharge side of the machine is estimated, and when the estimated temperature of the refrigerant on the discharge side becomes higher than a predetermined value, the current value that flows through the set solenoid is adjusted to increase. Item 7. A refrigeration cycle control method according to Item 6.   The pressure of the refrigerant on the high pressure side of the variable capacity compressor is detected, and the discharge of the variable capacity compressor is detected from the detected pressure of the refrigerant on the high pressure side, the temperature of the low pressure side outlet of the internal heat exchanger, and the suction pressure. 8. The temperature of the refrigerant on the discharge side is estimated, and when the estimated temperature of the refrigerant on the discharge side becomes higher than a predetermined value, the set current value flowing through the solenoid is adjusted to increase. Refrigeration cycle control method.

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