Control valve for variable displacement compressor

Abstract

 A compact control valve for a variable displacement compressor comprises a first valve 11 having a check valve function opening and closing by the differential pressure (Pdh-Pdl), a second valve 12 that opens and closes by sensing the differential pressure (Pdh-Pc), and a solenoid 14 for setting the value of the differential pressure across the first valve 11. The motion of a valve element 20 of the first valve 11 is transmitted via a shaft (29) to a valve element 27 of the second valve 12. The second valve 12 controls the pressure Pc in the crankcase such that the differential pressure across the first valve 11 becomes equal to a fixed value set by the solenoid 14, whereby the flow rate discharged from a compressor outlet port can be controlled to be constant.

Description

[0001] The invention relates to a control valve according to the preamble of claim 1, particularly for a variable displacement compressor in a refrigeration cycle of an automotive air conditioner.

[0002] Variable displacement compressors capable of varying the compression capacity of refrigerant are employed to obtain an adequate cooling capacity without being constrained by the speed of the vehicle engine driving the compressor. In a known variable displacement compressor, a wobble plate on a shaft driven by the engine is coupled to compression pistons. By varying the inclination angle of the wobble plate by introducing part of compressed refrigerant into a crankcase and changing the balance of pressures on the opposite sides of each piston by a control valve, the stroke of the pistons is varied to vary the discharge amount.

[0003] The control valve is disposed either between the discharge chamber and the crankcase or between the crankcase and the suction chamber and maintains the differential pressure across a valve such that the flow rate between the discharge chamber and the crankcase at a predetermined value. The differential pressure can be set to the predetermined value by externally changing a value of control current supplied to a solenoid of the control valve. When the engine speed rises to increase the discharge pressure, the pressure in the crankcase is increased to reduce the compression capacity. When the engine speed drops, the crankcase pressure decreases to increase the compression capacity. The compression capacity of the compressor is maintained constant irrespective of the engine speed.

[0004] A control valve known from JP 2001-107854 A controls the discharge flow rate to become constant. Two spaced apart pressure sensors in a refrigerant passage toward the suction chamber detect a differential pressure to indirectly measure the drawn in flow rate. The control valve then controls a constant flow rate between the discharge chamber and the crankcase to thereby control the control discharge flow rate. The known system requires expensive pressure sensors and a control device for detecting the differential pressure across the refrigerant circulation passage and for controlling the control valve. This leads to increased costs of the automotive air conditioner.

[0005] It is an object of the invention to provide a control valve for a variable displacement compressor for controlling a constant discharge flow rate which can be constructed compact and without pressure sensors.

[0006] This object is achieved by the features of claim 1.

[0007] The control valve is configured such that the first valve indirectly measures the discharge flow rate of refrigerant, and such that the second valve is controlled based on a value of the discharge flow rate to thereby control the pressure in the crankcase. This is advantageous in that it is possible to dispense with expensive pressure sensors for detecting the discharge flow rate, and to reduce the cost of the automotive air conditioner.

[0008] The first valve has a structure that opens depending on the flow rate between the discharge chamber and the outlet port, and hence closes when the compressor shifts to the minimum capacity operation to minimize the flow rate, discharge chamber and the outlet port of the compressor has changed e.g. immediately after a transition to the minimum capacity operation, to hold the pressure at the outlet port at the pressure value assume before the transition to the minimum capacity operation has taken place. This allows to abolish a check vale at the outlet port of the compressor for this purpose, and thereby reduces the cost of the compressor.

[0009] The first valve is also configured to have a larger pressure-receiving area for receiving the discharge pressure on the discharge chamber side than the second valve. This allows to construct a highly responsive variable displacement compressor that is operable when the rotational compressor speed has rapidly changed, to promptly react in a direction of suppressing a change of the displacement.

[0010] Embodiments of the invention will be explained with the help of the drawings:

Fig. 1

is a longitudinal section of a first embodiment of a control valve for a variable displacement compressor,

Fig. 2

is an enlarged section of essential parts of the control valve of Fig. 1 immediately after energization,

Fig. 3

is an enlarged section in a transitional state after energization,

Fig. 4

is an enlarged section in a balanced state,

Fig. 5

is an enlarged section in a transitional state at the time of a rapid increase in discharge pressure,

Fig. 6

is a longitudinal section of a second embodiment of a control valve,

Fig. 7

is a longitudinal section of a third embodiment of a control valve,

Fig. 8

is an enlarged sectional view taken on line A-A of FIG. 7,

Fig. 9

is an enlarged section of essential parts of the control valve of Fig. 7, in a non-energized state,

Fig. 10

is an enlarged section in a state immediately after energization,

Fig. 11

is an enlarged section in a controlled state,

Fig. 12

is a longitudinal section of a fourth embodiment of a control valve,

Fig. 13

is a longitudinal section of a fifth embodiment of a control valve,

Fig. 14

is a longitudinal section of a sixth embodiment of a control valve,

Fig. 15

is a longitudinal section of a seventh embodiment of a control valve, and

Fig. 16

by way of an example, an application of the control valve of Fig. 15 to a variable displacement compressor of a carbon dioxide refrigeration cycle.

[0011] The control valve 10 of Fig. 1 (first embodiment)comprises a first valve 11 operating in dependence on the flow rate discharged from the compressor, a second valve 12 for controlling pressure Pc in the crankcase, a third valve 13 for controlling the amount of leakage of refrigerant, and a solenoid 14 for externally setting the flow rate discharged from the compressor.

[0012] The first valve 11 is formed in a first body 15 disposed at an upper end location. The first body 15 has a port 16 communicating with the discharge chamber (discharge pressure Pdh). A port 17 communicates with an outlet port of the compressor (discharge pressure Pdl). A refrigerant passage 18 connects these ports 16 and 17. A valve seat 19 is formed in the refrigerant passage 18. A valve element 20 is movably disposed on the side of the valve seat 19 toward the port 17. The valve element 20 is urged by a weak spring 21 in the direction of closing the refrigerant passage 18. The first valve 11 is constructed as a check valve that opens when the discharge pressure Pdh at the port 16 is higher than the discharge pressure Pdl at the port 17 by more than the urging force of the spring 21, and that otherwise closes.

[0013] The second valve 12 is formed in a second body 22 to which the first body 15 is secured by press-fitting. The second body 22 defines a refrigerant introducing space 22a into which the discharge pressure Pdh is introduced via a refrigerant passage 23 in the first body 15. A strainer 24 covers an inlet port side of the refrigerant passage 23. The second body 22 has a port 25 communicating with the crankcase to discharge refrigerant at a controlled pressure Pc to the crankcase. In the centre of the upper part of the second body 22, there is formed a valve hole between the refrigerant introducing space 22a and an internal space 25a communicating with the port 25. A valve element 27 is movably guided by the second body 22 in relation to a valve seat 26 formed at a lower end of the valve hole. The valve element 27 is urged by a spring 28 in a direction away from the valve seat 26. The second valve 12 controls the flow rate at the discharge pressure Pdh to supply pressure Pc to the crankcase, i.e. is a Pd-Pc valve.

[0014] In the first body 15 a shaft 29 movably extends through an axial through hole 15a. The shaft 29 also extends through the valve hole of the second valve 12. An upper end of the shaft 29 is loosely fitted into the valve element 20. A lower end of the shaft 29 is loosely fitted into the valve element 27 of the second valve 12. An upper part of the shaft 29 has an outer diameter larger than an inner diameter of the through hole 15a of the first body 15, such that a tapered stepped portion 29a is formed at a boundary between the upper part and a lower part. When the shaft 29 moves downward the portion 29a will abut at the upper end face of the through hole 15a to thereby close a radial clearance between the lower part of the shaft 29 and the through hole 15a. This valve mechanism forms the third valve 13.

[0015] The second body 22 has a hole in the centre of a lower part. The open rim of a bottomed sleeve 30 is tightly connected to the hole. The bottomed sleeve 30 contains a fixed core 31 and a plunger 32 of the solenoid. The core 31 as well is fixed to the hole of the first body 15 and to the bottomed sleeve 30 by press-fitting. The plunger 32 is axially slidable in the bottomed sleeve 30, and is fixed to one end of a shaft 33 which axially extends with clearance through the core 31. The plunger 32 is urged toward the core 31 by a spring 34 to bring the other shaft end into contact with a lower end face of the valve element 27. A coil 35 surrounds the bottomed sleeve 30. A harness 36 leads from the coil 35to the outside of the solenoid 14. The inside of the bottomed sleeve 30 communicates with an internal space communicating with the port 25 via a pressure equalizing hole 37 in the second body 22.

[0016] When the solenoid 14 is de-energized, the second valve 12 is fully open by the spring 28 acting against the spring 34. The first valve 11 is fully closed by the spring 21.

[0017] Fig. 1 shows a state of the control valve 10 immediately after stoppage of the operation of the automotive air conditioner. This corresponds to the case where after the automotive air conditioner has been in operation, the solenoid 14 is de-energized. The solenoid 14 ceases to create a force attracting the plunger 32 toward the core 31, and hence the second valve 12 is fully opened by the spring 28 acting against the spring 34 in valve-opening direction. Refrigerant at the discharge pressure Pdh is supplied from the port 25 to the crankcase via the strainer 24, the refrigerant passage 23, and the second valve 12. The compressor is shifted to the minimum capacity operation. This causes the compressor to do almost no work, so that the discharge pressure Pdh introduced into the compressor 10 becomes lower than the discharge pressure Pdl at the outlet port of the compressor, and the differential pressure between the discharge pressure Pdh and the discharge pressure Pdl closes the first valve 11.

[0018] When the compressor is operating with a predetermined capacity, the valve element 20 of the first valve 11 has been moved away from the valve seat 19. The shaft 29 is pushed downward to close the third valve 13. When the solenoid 14 is de-energized to allow the valve element 20 of the first valve 11 to move upward and the valve element 27 of the second valve 12 to move downward (Fig. 1). The shaft 29 receives the high discharge pressure Pdl on the top end and the discharge pressure Pdh lower than the discharge pressure Pdl on the bottom end, which holds the third valve 13 closed. This prevents that the high discharge pressure Pdl may leak via the radial clearance to the upstream side of the second valve 12 the pressure at which has become lower than the discharge pressure Pdl.

[0019] As a result, the pressure at the compressor outlet port can maintain the discharge pressure Pdl assumed before the stoppage of the operation of the automotive air conditioner. This is advantageous for the efficiency of the compressor since it is not necessary to compress refrigerant to the discharge pressure Pdl when the automotive air conditioner later resumes operation. Further, normally, a separate check valve would have to be provided at the outlet port of the compressor for this purpose, but in the present embodiment, the first valve 11 already fulfils the check valve function, such that a separate check valve is not needed, to reduce the cost of the compressor.

[0020] First, after the solenoid 14 was de-energized as in Fig. 1, if a predetermined electric current is supplied, then, immediately thereafter, the second valve 12 instantaneously fully closes by the urging force of the solenoid 14. This causes the compressor to start the maximum capacity operation, but immediately after the energization, the discharge pressure Pdh is still lower than the discharge pressure Pdl at the compressor outlet port, and hence the first valve 11 is fully-closed. At this time, the shaft 29 is pushed upward by the valve element 27, whereby the third valve 13 is opened. The discharge pressure Pdl leaks to the discharge pressure Pdh via the clearance between the shaft 29 and the through hole 15a. The leakage is small, and the discharge pressure Pdh is also about to rise immediately. Therefore, no particular problem is brought about.

[0021] The compressor starts operation with maximum capacity. When the discharge pressure Pdh becomes sufficiently higher than the discharge pressure Pdl (Fig. 3), the differential pressure therebetween causes the valve element 20 to move away from the valve seat 19. The first valve 11 opens and refrigerant at discharge pressure Pdh at port 16 changes into refrigerant at the discharge pressure Pdl, which flows from port 17 to the compressor outlet port. At this time, refrigerant flows through the first valve 11 at a flow rate corresponding to a value obtained by multiplying the passage area formed by opening the first valve 11 by the differential pressure across the first valve 11.

[0022] The valve element 20 of the first valve 11 is moved in valve-opening direction into abutment with the upper end of the shaft 29 which has been lifted upward, as viewed in FIG. 3, by the valve element 27 of the second valve 12. This causes the first valve 11 and the second valve 12 to operate interlocked with each other via the shaft 29. The second valve 12 operates by detecting the differential pressure between the discharge pressure Pdh and the discharge pressure Pdl acting on the first valve 11, and the differential pressure between the discharge pressure Pdh and the pressure Pc.

[0023] Then, when the differential pressure between the discharge pressure Pdh and the discharge pressure Pdl acting on the first valve 11 becomes still larger, since the pressure-receiving area of the valve element 20 of the first valve 11 is larger than that of the valve element 27 of the second valve 12, the valve element 20 of the first valve 11 urges the valve element 27 of the second valve 12 by the differential pressure thereacross, and when the differential pressure between the discharge pressure Pdh and the discharge pressure Pdl reaches a predetermined value, as shown in FIG. 4, the second valve 12 slightly opens to a position where the differential pressures across the first valve 11 and the second valve 12, the loads of the springs 21 and 28, the urging force of the solenoid 14 dependent on the current value are balanced, whereby the controlled pressure Pc is supplied to the crankcase to place the compressor in the state in which the capacity or displacement is controlled.

[0024] That is, the second valve 12 controls the pressure in the crankcase such that the differential pressure across the passage having the passage area produced by flow of refrigerant from the discharge chamber through the first valve 11 maintains a differential pressure set by the solenoid 14, to thereby control the compressor discharge flow rate to a constant flow rate. More specifically, e.g. when the engine speed increases to increase the discharge pressure Pdh, the valve element 20 of the first valve 11 urges the valve element 27 of the second valve 12 in opening direction, by the increased amount of the differential pressure. This increases the pressure Pc in the crankcase, and hence the compressor operates in the direction of reducing the displacement, whereby the discharge flow rate is controlled to a predetermined flow rate. Inversely, when the discharge pressure Pdh lowers to reduce the differential pressure across the first valve 11, the valve element 20 urges the valve element 27 of the second valve 12 in the direction of further closing the same. This reduces the pressure Pc in the crankcase and hence the compressor operates in the direction of increasing the displacement thereof, whereby the discharge flow rate is controlled to the predetermined flow rate.

[0025] The discharge pressure Pdh varies sensitively in response to a change in the compressor speed. Therefore, when the engine speed rapidly increases to rapidly increase the compressor speed as well, the discharge pressure Pdh also rapidly increases. In such a case, in the control valve 10, since the pressure receiving area of the valve element 20 of the first valve 11 is set to be larger than that of the valve element 27 of the second valve 12, the force of the valve element 20 of the first valve 11 urging the valve element 27 of the second valve 12 in the direction of further opening the same by a change in the differential pressure across the valve element 20 is instantaneously increased, and as shown in Fig. 5, the second valve 12 operates instantaneously more intensely than during normal opening operation, whereby the compressor is promptly controlled in the direction of reducing the displacement. Inversely, when the engine speed rapidly drops to rapidly decrease the discharge pressure Pdh, the valve element 20 of the first valve 11 also operates instantaneously more intensely in valve-closing direction, and hence the second valve 12 also operates instantaneously more intensely in valve-closing direction, whereby the compressor is promptly controlled in the direction of increasing the displacement. Thus, after reacting to a rapid change in the discharge pressure Pdh with high responsiveness, the control valve 10 is capable of promptly restoring the compressor to a predetermined displacement.

[0026] In the control valve 10a of Fig. 6 (second embodiment), the pressure which the second valve 12 senses and to which it responds is changed. That is, while the second valve 12 of the first embodiment senses the differential pressure between the discharge pressure Pdh on the discharge side and the pressure Pc in the crankcase, the second valve 12 of the control valve 10a senses the differential pressure between the discharge pressure Pdh on the discharge side and the suction pressure Ps in the suction chamber.

[0027] In the control valve 10a, the second body 22 has a port 38 communicating with the suction chamber (suction pressure Ps). The second body 22 movably guides a shaft 39 which is integral with the valve element 27 of the second valve 12. The outer diameter of the shaft 39 is approximately equal to an effective discharge pressure Pdh receiving diameter of the second valve 12. The valve element 27 receives the discharge pressure Pdh on the discharge side. The lower end of the shaft 39 receives the suction pressure Ps to sense the differential pressure (Pdh-Ps). In order to accurately sense the differential pressure (Pdh-Ps) the outer diameter of the shaft 39 is only required to be equal to the inner diameter of the valve hole of the second valve 12. In order to simplify guiding the shaft 39, the outer diameter of the shaft 39 is made larger than the inner diameter of the valve hole of the second valve 12 to such an extent that there is no substantial influence on the operation of the second valve 12. A spring 28 at the lower end of the shaft 39 urges the valve element 27 of the second valve 12 in valve-opening direction. The bottomed sleeve 30 communicates with the port 38 to receive the suction pressure Ps.

[0028] The control valve 10a operates similar to the control valve 10 of Fig. 1..

[0029] The control valve 10b of Figs 7-11 (third embodiment) differs from the first and second embodiments in the construction of the first valve 11. While in the control valves 10 and 10a the first valve 11 provides a passage area dependent on the flow rate of refrigerant, the first valve 11 of the control valve 10b of Figs 7-11 does not vary the passage area according to the flow rate within a normal control region and after the first valve 11 once is open.

[0030] The first valve 11 valve element 20 is movable in the refrigerant passage 18 of the first body 15, and has (Fig 8) a plurality of guides 40 integrally formed at the outer periphery for guiding the valve element 20 in axial direction in the refrigerant passage 18, and has refrigerant passages 41 between the valve element 20 and the inner wall of the refrigerant passage 18, the passage area of which does not vary even when the flow rate is varied and when the valve lift varies.

[0031] In the first valve 11, a hollow cylindrical valve seat-forming member 42 is disposed upstream of and opposed to the valve element 20. The valve seat-forming member 42 is press-fitted in the port 16 (discharge pressure Pdh).

[0032] The shaft 29 forming the valve element of the third valve 13 is axially movable in the valve element 20 of the first valve 11. A spring 21 between the valve element 20 and the shaft 29 urges the valve element 20 and the shaft 29 in respective directions of moving apart to thereby maintain the closed states of the first valve 11 and the third valve 13 when the solenoid 14 is de-energized.

[0033] The second valve element 27 is integral with the shaft 33 of the solenoid 14. The spring 28 urging the valve element 27 in valve-opening direction is interposed between the core 31 and the plunger 32. The shaft 33 terminates by a transmission shaft 43 extending through the valve hole of the second valve 12. The transmission shaft 43 is movable in a hole formed between the refrigerant passage 23 and the port 17 connected to the compressor outlet port.

[0034] When the solenoid 14 is de-energized (Fig. 9), the first valve 11 and the third valve 13 have the valve element 20 and the shaft 29 urged by the spring 21 in respective directions of moving away from each other. The valve element 20 is seated on the end face of the valve seat-forming member 42 and the shaft 29 is seated on the opening end of the hole holding the transmission shaft 43, both being fully closed. The spring 28 urges the plunger 32 against the spring 34 away from the core 31. The valve element 27 is moved downward. The second valve 12 is fully open.

[0035] Refrigerant (pressure Pdh) from the discharge chamber is completely supplied from the port 25 to the crankcase via the refrigerant passage 23, and the second valve 12, so that the compressor is operated with the minimum capacity. If this de-energized state of the solenoid 14 corresponds to a state of the compressor which has stopped operation after firstly having operated with a predetermined capacity, the discharge pressure Pdh at port 16 becomes lower than the discharge pressure Pdl at the port 17 connected to the compressor outlet port so that the differential pressure (Pdh-Pdl) holds the first valve 11 (check valve functions) fully closed.

[0036] When the solenoid 14 first was de-energized as in Fig. 9, if then a predetermined electric current is supplied, immediately thereafter (Fig. 10) the second valve 12 instantaneously fully closes by the urging force of the solenoid 14. The compressor shifts to the maximum capacity operation, but immediately after the energization, the discharge pressure Pdh is still lower than the discharge pressure Pdl, so that the first valve 11 is fully-closed. At this time, the shaft 29 of the third valve 13 is pushed upward by the transmission shaft 43 and the valve element 27 of the second valve 12.

[0037] When the compressor continues to operate with maximum capacity to make the discharge pressure Pdh higher than the discharge pressure Pdl by a predetermined value or more (Fig. 11), the differential pressure (Pdh-Pdl) pushes open the valve element 20. Refrigerant at discharge pressure Pdh passes from the port 16 through the refrigerant passages 41 between the valve element 20 and the inner wall of the refrigerant passage 18 to be changed into refrigerant at the discharge pressure Pdl, which flows from the port 17 to the compressor outlet port.

[0038] When the first valve 11 is opened, the valve element 20 is moved over the upper end face of the shaft 29 and the lower end of the shaft 29 abuts at the upper end face of the transmission shaft 43. As a consequence, after the first valve 11 is opened, the valve element 20 of the first valve 11, the valve element 27 of the second valve 12, and the shaft 29 of the third valve 13 come to operate in unison with each other. This causes the first valve 11 and the second valve 12 to operate interlocked via the shaft 29, whereby the second valve 12 operates by detecting the differential pressure (Pdh-Pdl) acting on the first valve 11 and the differential pressure (Pdh-Pc).

[0039] Here, let it be assumed that a predetermined energization current is supplied to control the compressor to a predetermined capacity, and that the control valve 10b is in a balanced state (Fig. 11). If the engine speed increases to increase the discharge pressure Pdh, the valve element 20 is lifted by an amount corresponding to the increase in the differential pressure across the first valve 11, thereby urging the valve element 27 of the second valve 12 via the shaft 29 in valve-opening direction. This increases the pressure Pc in the crankcase so that the compressor operates in the direction of reducing the capacity, whereby it is controlled to a predetermined discharge flow rate. Inversely, when the discharge pressure Pdh lowers to reduce the differential pressure across the first valve 11, the valve element 20 moves the valve element 27 of the second valve 12 in the direction to further close the valve. This reduces the pressure Pc in the crankcase, so that the compressor operates in the direction of increasing the capacity, whereby it is again controlled to the predetermined discharge flow rate.

[0040] The control valve 10c in Fig. 12 (fourth embodiment) is distinguished from the third embodiment, in that a port 44 for introducing refrigerant into the second valve 12 is provided independently of the port 16 for introducing refrigerant into the first valve 11. This port 44 is formed in a side of the second body 22. O-rings are provided on axially opposite sides of the valve element 27, with the port 44 located therebetween.

[0041] It is possible to introduce part of refrigerant at the discharge pressure Pdh from the discharge chamber into the port 16 of the first valve 11, and also into the port 44 of the second valve 12. However, preferably, the control valve 10c in Fig. 12 is applied to a variable displacement compressor equipped with an oil separator downstream of the discharge chamber whereby refrigerant at another discharge pressure Pdh2 is supplied from the oil separator to the port 44 instead.

[0042] The control valve 10d of Fig. 13 (fifth embodiment) is distinguished from the fourth embodiment in that the port 44 for introducing refrigerant into the second valve 12 and the port 25 for delivering refrigerant have reversed locations.

[0043] Due to this arrangement of the ports 44, 25, refrigerant at the controlled pressure Pc is delivered between the valve element 27 integral with the shaft 33 and the transmission shaft 43, via the port 25. The pressure Pc is applied to the valve element 27 and the transmission shaft 43 from opposite directions such that its pressure influence is cancelled. This eliminates influences of the pressure Pc on the control operation of the control valve 10d. Therefore, the control valve 10d controls a flow rate determined by the passage area of the refrigerant passages 41 between the valve element 20 and the inner wall of the refrigerant passage 18 and by the differential pressure (Pdh-Pdl) on opposite sides of the refrigerant passage 41. The value of the differential pressure (Pdh-Pdl) is set by the solenoid 14, and will be held at the predetermined value by the first valve 11 and the second valve 12 operating in an interlocked manner to control the pressure Pc in the crankcase. As a result, the flow rate through the first valve 11 to the compressor outlet port is held constant.

[0044] The control valve 10e in Fig. 14 (sixth embodiment) is distinguished from the fifth embodiment by an improvement of avoiding influences of internal refrigerant leakage on the variable displacement control.

[0045] In the control valve 10e, a port 45 communicating with the suction chamber is formed between the port 17 receiving the discharge pressure Pdl and the port 25 (controlled crankcase pressure Pc). This lengthens the distance between the port 17 (discharge pressure Pdl) and the port 25 (controlled pressure Pc). The transmission shaft 43 of the shaft 33 as well is lengthened, so that as an additional component a shaft 46 is interposed between the transmission shaft 43 and the third valve 13. One end of the movable part of the solenoid 14 is supported by the transmission shaft 43 alone.

[0046] When the control valve 10e is performing variable displacement control of the compressor, the third valve 13 is open, and hence even if the refrigerant at the discharge pressure Pdl leaks via the clearance between the shaft 46 and the first body 15 guiding the shaft 46, the leaked refrigerant flows via the port 45 into the suction chamber, but does not flow to the port 25 connected to the crankcase. Therefore, refrigerant leakage into the crankcase which could directly determine the displacement of the compressor does not occur, and hence the pressure Pc in the crankcase does not vary due to such leakage. This results in an accurate displacement control. It should be noted that refrigerant leakage also may occur between the port 25 (controlled pressure Pc) and the port 45 (suction pressure Ps) through the clearance between the transmission shaft 43 and the guiding bore of the first body 15. However, this clearance defines a smaller passage area than an orifice provided within the compressor at a location between the crankcase and the chamber pressure, for allowing refrigerant to flow from the crankcase into the suction pressure, and hence it does not adversely affect the displacement control of the compressor. If the passage area of the orifice is pre-set by taking the mentioned clearance into account, influences of refrigerant leakages through the clearance can be substantially eliminated.

[0047] In the embodiments described above, it is assumed that the respective systems use Hydrochlorofluorocarbon "HFC-134a" as the refrigerant in the refrigeration cycle. On the other hand, when the present invention is applied to a system using refrigerant with very high operating pressure, such as carbon dioxide, it is required to control higher pressures, and hence, particularly, in the second valve 12, the valve diameter and the like are required to be made smaller so as to reduce the pressure-receiving area. Also the way of sealing the control valve and the compressor needs to be changed, i.e. as in Fig. 15.

[0048] The control valve 10f in Fig. 15 (seventh embodiment) is distinguished from the fifth embodiment in that the valve element 27 of the second valve 12 and the transmission shaft 43 are formed separately from the shaft 33. Both are urged by the spring 28 in opening direction of the second valve 12. This makes it possible to form the valve element 27 relatively thin from a robust material bust, and to enhance the freedom of design. In the control valve 10f, the second body 22 and the core 31 of the solenoid 14 are integral, and the core 31 is press-fitted into the bottomed sleeve 30 which has an open end and a flange. The outer periphery of the flange carries a packing 47 made of a material which is impervious to refrigerant penetration. A screw thread 49 for mounting the control valve 10f in the compressor is formed on an outer peripheral portion, close to the flange, of a casing 48 serving as a yoke of the solenoid.

[0049] The variable displacement compressor in Fig. 16 includes a hermetically sealed crankcase 51 containing a driven rotating shaft 52. One end of the shaft 52 extends through a sealed bearing device to the outside of the crankcase 51. A pulley 53 transmits the drive force from the engine of the automotive vehicle to the shaft 52. A wobble plate 54 is fitted on the shaft 52, such that the inclination angle of the wobble plate 54 can be varied. Cylinders 55 (one of which is shown in Fig. 16) are arranged around the axis of the shaft 52. Each cylinder 55 contains a piston 56 converting the wobbling motion of the wobble plate 54 into reciprocation. The cylinder 55 is connected via a suction relief valve 57 to a suction chamber 59 and via a discharge relief valve 58 to a discharge chamber 60. The control valve 10f is disposed between the discharge chamber 60 and an outlet port 61 and between the discharge chamber 60 and the crankcase 51. An orifice 62 is provided between the crankcase 51 and the suction chamber 59. The compressor comprises a passage, (broken line in Fig. 16) extending from the discharge chamber 60 to the control valve 10f. The control valve 10f is screwed into a mounting hole of the compressor.

[0050] The outlet port 61 is connected via a gas cooler 63 and an internal heat exchanger 64 by a high-pressure refrigerant conduit line to an expansion valve 65. The expansion valve 65 is connected by a low-pressure refrigerant conduit line via an evaporator 66, an accumulator 67, and again the internal heat exchanger 64, to an inlet port communicating with the suction chamber 59. The refrigeration cycle is a closed circuit.

[0051] Each piston 56 connected to the outer peripheral part of the wobbling wobble plate 54 reciprocates parallel to the axis of the shaft 52. Refrigerant at suction pressure Ps in the suction chamber 59 is drawn into the cylinder 55 and is compressed, and is discharged at discharge pressure Pdh into the discharge chamber 60. High-pressure refrigerant in the discharge chamber 60 is decompressed to discharge pressure Pdl when passing through the control valve 10f, and is delivered from the outlet port 61 to the gas cooler 64. Part of the high-pressure refrigerant at the discharge pressure Pdh2 is introduced via the control valve 10f into the crankcase 51. The pressure Pc rises whereby the inclination angle of the wobble plate 54 is set such that the bottom dead centre of the piston 56 is brought to a position where the pressure in the cylinder 55 and the pressure Pc in the crankcase 51 are balanced. Thereafter, refrigerant is returned from the crankcase 51 via the orifice 62 to the suction chamber 59.

[0052] The first valve 11 detects the flow rate between the discharge chamber 60 and the gas cooler 63. The second valve 12 introduces a flow rate into the crankcase 51 dependent on the detected flow rate, thereby providing control such that the flow rate of the refrigerant sent from the discharge chamber 60 to the gas cooler 63 becomes constant. For example, when the engine speed increases, the discharge pressure Pdh rises. This increases the flow rate from the discharge chamber 60 to the gas cooler 63 via the control valve 10f, to increase the differential pressure across the first valve 11. According to an increase in the differential pressure, the second valve 12 opens, and the flow rate at discharge pressure Pdh2 introduced into the crankcase 51 also increases, whereby the pressure Pc in the crankcase 51 increases. Accordingly, the wobble plate 54 inclination is varied until the wobble plate 54 forms a right angle with the shaft 52 to decrease the stroke of the pistons 56 to reduce the discharge flow rate. Thus, even when the discharged flow rate is about to increase due to an increase in the engine speed, the control valve 10f increases the flow rate into the crankcase 51 according to the increase in the flow rate of refrigerant, whereby the pressure Pc in the crankcase 51 is increased to reduce the displacement of the compressor. Therefore, the discharged flow rate of the compressor is controlled to be constant. Similarly, when the engine speed drops, the flow rate at discharge pressure Pdl from the discharge chamber 60 to the gas cooler 63 is decreased via the control valve 10f, whereby the flow rate at discharge pressure Pd2 introduced into the crankcase 51 is also decreased to lower the pressure Pc in the crankcase 51.

[0053] As a result, the compressor has the discharge flow rate controlled such that it is increased, whereby the discharge flow rate is controlled to be constant.

Claims

1. A control valve (10, 10a, 10b, 10c, 10d, 10e, 10f) for a variable displacement compressor, for controlling a discharged flow to a constant flow rate, characterised by:

a first valve (11) defining a passage area the size of which is set according to a flow rate between a compressor discharge chamber (60) and a compressor outlet port (61);

a second valve (12) for controlling pressure (Pc) in a compressor crankcase (5) in a manner interlocked with the operation of the first valve (11) such that a differential pressure across the first valve (11) is maintained at a predetermined value; and

a solenoid (14) for setting a differential pressure across the passage having the passage area set by the first valve (11) to the predetermined differential pressure dependent on a flow rate to which the flow of refrigerant is to be controlled.

2. The control valve according to claim 1, characterised in that the first valve (11) comprises a first valve seat (19) in a first refrigerant passage (18) between the discharge chamber (60) and the outlet port (61), and a first valve element (20) opposed to the first valve seat (19), in a state urged from a downstream side in valve-closing direction, and
that the second valve (12) comprises a second valve seat (26) in a second refrigerant passage between the discharge chamber (60) and the crankcase (51), and a second valve element (27) downstream of the second valve seat (26), the second valve element (27) having a smaller pressure-receiving area than the first valve element (20), and a spring (28) urging the second valve element (27) against an urging force of the solenoid (14), in valve-opening direction, and
that a shaft (29) is disposed between the first and second valve elements (20, 27) for transmitting the urging force of the solenoid (14) to the first valve element (20) and for transmitting a change in the differential pressure across the first passage (18) received by the first valve element (20) to the second valve element (27).

3. The control valve according to claim 2, characterised in that the shaft (29) is axially movably guided in a through hole (15a) of a body (15) of the first valve (11), that the shaft (29) has a larger outer diameter on an end facing the first valve element (20) than an inner diameter of the through hole (15a), thereby forming a third valve (13) for opening and closing a passage area formed by a clearance between another end of shaft (29) and the through hole (15a) when the second valve (12) is fully opened by the spring (28) during a de-energized state of the solenoid (14).

4. The control valve according to claim 2, characterised in that the second valve (12) is configured to operate by sensing a differential pressure (Pdh-Pc) between the discharge chamber (60) and the crankcase (51).

5. The control valve according to claim 2, characterised in that the second valve (12) is configured to operate by sensing a differential pressure (Pdh-Pc) between the discharge chamber (60) and the suction chamber (59) of the compressor.

6. The control valve according to claim 5, characterised in that in the second valve (12) the second valve element (27) and another shaft (39) are integral with each other, the another shaft (39) having an outer diameter approximately equal to an effective diameter of the second valve element (27) on which discharge pressure (Pd) from the discharge chamber (60) is received, and that the another shaft (39) receives the suction pressure (Ps) on an end face remote from the second valve element (27).

7. A control valve (10, 10a, 10b, 10c, 10d, 10e, 10f) for a variable displacement compressor for controlling a discharged refrigerant flow from the compressor to a constant flow rate, characterised by:

a first valve (11) in a first refrigerant passage (18) between a compressor discharge chamber (60) and a compressor outlet port (61), the first valve having the configuration and function of a check valve blocking flow between the outlet port (61) and the discharge chamber (60);

a second valve (12) in a second refrigerant passage between the discharge chamber (60) and a crankcase (51) of the compressor;

a shaft (29, 27) between the first and second valves (11, 12), for transmitting a change in a differential pressure across the first valve to the second valve (12), to cause the first and second valves (11, 12) to operate in an interlocked manner in the same valve-opening or valve-closing directions; and

a solenoid (14) for generating an urging force in valve-closing direction to the second valve (12) according to a value of an electric current, and for setting via the shaft (29, 27) a differential pressure across the first valve (11) to a predetermined value dependent on a flow rate to which the flow of refrigerant is to be controlled.

8. A control valve (10, 10a, 10b, 10c, 10d, 10e, 10f) for a variable displacement compressor, for controlling a discharged refrigerant flow to a constant flow rate, characterised by:

a first valve (11) that is lifted to open according to a flow rate between a compressor discharge chamber (60) and a compressor outlet port (61), the first valve (11) having a constant invariable passage area when lifted irrespective of the lift amount;

a second valve (12) for controlling the pressure (Pc) in a crankcase (51) in a manner interlocked with operation of the first valve (11) such that a differential pressure across the first valve (11) is maintained at a predetermined value; and

a solenoid (19) for setting a value of the differential pressure across the refrigerant passage (18) assumed when the first valve (11) is opened, to the predetermined value of the differential pressure dependent on a flow rate to which the flow of refrigerant is to be controlled.

9. The control valve according to claim 8, characterised in that the first valve (11) comprises a first valve seat (19) formed in a first refrigerant passage (18) between the discharge chamber (60) and the outlet port (61), a first valve element (20) which is movable downstream of the first valve seat (19) in a state in which an outer periphery of the first valve element (20) is spaced from an inner wall of the first refrigerant passage (18) by a predetermined distance, and a spring (21) urging the first valve element (20) in valve-closing direction towards the first valve seat (19),
that the second valve (12) comprises a second valve seat (26) in a second refrigerant passage between the discharge chamber (60) and the crankcase (51), a second valve element (27) movably disposed on a solenoid side opposed to the second valve seat (26), and being urged in valve-opening direction, the second valve element (27) having a smaller pressure-receiving area than the first valve element (20), that a transmission shaft (43) is movably guided in a through hole communicating with the first refrigerant passage (18) via a valve hole, for operating in unison with the second valve element (27), and
that a shaft (29) is provided for transmitting the urging force of the solenoid (14) generated for the second valve element (27) via the transmission shaft (43) to the first valve element (20) and for transmitting a change in the differential pressure across the refrigerant passage (18) as received by the first valve element (20) to the second valve element 27), respectively.

10. The control valve according to claim 9, characterised in that the shaft (29) is axially movably guided in the first valve element (20) and is urged with respect to the first valve element (20) by the spring (21) in a direction toward the second valve (12), and that the shaft (29) forms a third valve (13) such that the shaft (29) is abutted by the transmission shaft (43) urged to move out of the through hole into the first refrigerant passage (18), when the solenoid (19) is energized, to operate in unison with the first and second valve elements (20, 27), and when the solenoid (19) is de-energized to close the through hole containing the transmission shaft (43) which is retracted when the second valve element (27) is urged in valve-opening direction.

11. The control valve according to claim 9, characterised in that the second valve element (27), the transmission shaft (43) of the second valve (12) and a shaft (33) of the solenoid (19) are integral with each other.

12. The control valve according to claim 9, characterised in that a refrigerant inlet port of the first refrigerant passage (18) and a refrigerant inlet port of the second refrigerant passage communicate with a first port (16) and a second port (44) which are formed independently of each other, respectively.

13. The control valve according to claim 12, characterised in that the second port (44) as the refrigerant inlet port of the second refrigerant passage is situated closer to the first valve (11) with respect to the second valve seat (26), and that a third port (25) is disposed on a solenoid side of the second valve seat (26), which third port (25) communicates with a refrigerant outlet port of the second refrigerant passage.

14. The control valve according to claim 12, characterised in that the second port (44) as the refrigerant inlet port of the second refrigerant passage is disposed at the solenoid side of the second valve seat (26), and that a third port (25) is disposed on a side toward the first valve (11) with respect to the second valve seat (26), the third port (25) communicating with a refrigerant outlet port of the second refrigerant passage.

15. The control valve according to claim 14, characterised in that a fifth port (45) communicating with the compressor suction chamber (59) is disposed between the third port (25) and a fourth port (17) communicating with a refrigerant outlet of the first refrigerant passage (18), to lead refrigerant leakages occurring through a clearance between the through hole and the transmission shaft (43) into the fifth port (45).

Drawing