VARIABLE DISPLACEMENT SWASH PLATE COMPRESSOR

BACKGROUND OF THE INVENTION

The present invention relates to a variable displacement swash plate compressor in which a piston engaged with a swash plate reciprocates with a stroke that is in accordance with the inclination angle of a swash plate.

Japanese Laid-Open Patent Publication No. 1-190972 discloses a variable displacement swash plate compressor including a movable body that is coupled to a swash plate and capable of changing the inclination angle of the swash plate. The movable body moves in the axial direction of a rotation shaft when control gas is drawn into a control pressure chamber of a housing thereby changing the pressure of the control pressure chamber. The movement of the movable body changes the inclination angle of the swash plate.

More specifically, when the pressure of the control pressure chamber increases and approaches the pressure of a discharge pressure region, the movable body moves in one direction along the axis of the rotation shaft. This increases the inclination angle of the swash plate. When the pressure of the control pressure chamber decreases and approaches the pressure of a suction pressure region, the movable body moves in the opposite direction along the axis of the rotation shaft. This decreases the inclination angle of the swash plate. The decrease in the inclination angle of the swash plate decreases the stroke of the piston. Accordingly, the displacement of the variable displacement swash plate compressor is decreased. In contrast, an increase in the inclination angle of the swash plate increases the stroke of the piston. Accordingly, the displacement of the variable displacement swash plate compressor is increased. The variable displacement swash plate compressor includes a displacement control valve that controls the pressure of the control pressure chamber.

In such a variable displacement swash plate compressor, when an air conditioning switch of the vehicle air conditioning device is turned off and an electromagnetic solenoid of the displacement control valve is deactivated, the inclination angle of the swash plate may remain greater than the minimum inclination angle due to a change in the pressure of the suction pressure region. In this case, when the air conditioning switch is turned on and the electromagnetic solenoid is activated again, a sudden increase in the displacement may increase the load on the variable displacement swash plate compressor. Thus, when the air conditioning switch is turned off and the electromagnetic solenoid is deactivated, it is desirable that the inclination angle of the swash plate be minimal.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a variable displacement swash plate compressor that is capable of minimizing the inclination angle of a swash plate and maintaining the minimum inclination angle when the electromagnetic solenoid is deactivated.

To achieve the above object, one aspect of the present invention is a variable displacement swash plate compressor that includes a housing including a discharge pressure region, of which pressure is a discharge pressure, and a suction pressure region, of which pressure is a suction pressure, a rotation shaft supported by the housing, and a swash plate accommodated in the housing. The swash plate rotates when receiving driving force from the rotation shaft and inclines relative to the rotation shaft at an inclination angle that is variable. A piston is engaged with the swash plate. A movable body is coupled to the swash plate and adapted to vary the inclination angle of the swash plate. A control pressure chamber is defined in the movable body and adapted to move the movable body in an axial direction of the rotation shaft when control gas drawn into the control pressure chamber changes pressure of the control pressure chamber. A discharge passage extends from the control pressure region to the suction pressure region. A displacement control valve is adapted to control the pressure of the control pressure chamber. When the pressure of the control pressure chamber approaches the discharge pressure, the movable body moves toward one axial end of the rotation shaft and increases the inclination angle of the swash plate. When the pressure of the control pressure chamber approaches the suction pressure, the movable body moves toward the other axial end of the rotation shaft and decreases the inclination angle of the swash plate. The piston reciprocates with a stroke that is in accordance with the inclination angle of the swash plate. The displacement control valve includes an electromagnetic solenoid, a driving force transmission member driven by the electromagnetic solenoid, and a valve body adapted to move in an open direction and a close direction, which is opposite to the open direction, to adjust an opening amount of the discharge passage. A pressure sensing mechanism is adapted to expand and contract in movement directions of the valve body in accordance with the suction pressure. The pressure sensing mechanism and the driving force transmission member are located at opposite sides of the valve body. A solenoid housing accommodates the electromagnetic solenoid. A valve housing accommodates the valve body and the pressure sensing mechanism. The valve housing includes an accommodation chamber, which accommodates the pressure sensing mechanism and is in communication with the control pressure chamber, and a valve chamber, which accommodates the valve body and is in communication with the suction pressure region. The valve body has a valve opening degree that is determined by an urging force applied to the valve body through the driving force transmission member when the electromagnetic solenoid is activated and by an urging force applied to the valve body by the expansion and contraction of the pressure sensing mechanism in accordance with the suction pressure. The valve body and the pressure sensing mechanism are formed integrally to form a valve unit. When the electromagnetic solenoid is deactivated, the pressure of the accommodation chamber acts on a back surface of the pressure sensing mechanism that is opposite to the driving force transmission member so that a force in the open direction is applied to the valve unit.

Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a cross-sectional view showing one embodiment a variable displacement swash plate compressor;

FIG. 2 is a cross-sectional view showing a displacement control valve of the variable displacement swash plate compressor of FIG. 1 when the inclination angle of the swash plate is minimum;

FIG. 3 is a cross-sectional view showing the displacement control valve of FIG. 2 when the inclination of the swash plate is maximum;

FIG. 4 is a cross-sectional view showing the variable displacement swash plate compressor when the inclination angle of the swash plate is maximum;

FIG. 5 is a cross-sectional view showing the displacement control valve when the pressure of the suction chamber exceeds a predetermined pressure when the electromagnetic solenoid is deactivated; and

FIG. 6 is a cross-sectional view showing the displacement control valve when the electromagnetic solenoid is activated when a bellows is contracted.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 to 6, one embodiment of a variable displacement swash plate compressor will now be described. The variable displacement swash plate compressor is used with a vehicle air conditioning device.

As shown in FIG. 1, a variable displacement swash plate compressor 10 includes a housing 11 that includes a first cylinder block 12, a second cylinder block 13, a front housing member 14, and a rear housing member 15. The first cylinder block 12, which is located at the front side (one side), and the second cylinder block 13, which is located at the rear side (the other side), are coupled to each other. The front housing member 14 is coupled to the first cylinder block 12. The rear housing member 15 is coupled to the second cylinder block 13.

A first valve/port formation body 16 is arranged between the front housing member 14 and the first cylinder block 12. A second valve/port formation body 17 is arranged between the rear housing member 15 and the second cylinder block 13.

A suction chamber 14a and a discharge chamber 14b are defined between the front housing member 14 and the first valve/port formation body 16. The discharge chamber 14b is located radially outward from the suction chamber 14a. A suction chamber 15a and a discharge chamber 15b are defined between the rear housing member 15 and the second valve/port formation body 17. The rear housing member 15 also defines a pressure adjustment chamber 15c that is located in the central section of the rear housing member 15. The suction chamber 15a is located radially outward from the pressure adjustment chamber 15c. The discharge chamber 15b is located radially outward from the suction chamber 15a. The discharge chambers 14b and 15b are connected to each other by a discharge passage (not shown), which is connected to an external refrigerant circuit (not shown). The discharge chambers 14b and 15b define a discharge pressure region. The pressure of the discharge pressure region is referred to as the discharge pressure.

The first valve/port formation body 16 includes suction ports 16a (only one shown in FIG. 1), which are in communication with the suction chamber 14a, and discharge ports 16b (only one shown in FIG. 1), which are in communication with the discharge chamber 14b. The second valve/port formation body 17 includes suction ports 17a (only one shown in FIG. 1), which are in communication with the suction chamber 15a, and discharge ports 17b (only one shown in FIG. 1), which are in communication with the discharge chamber 15b. The suction ports 16a and 17a each include a suction valve mechanism (not shown), and the discharge ports 16b and 17b each include a discharge valve mechanism (not shown).

A rotation shaft 21 is rotationally supported in the housing 11. The rotation shaft 21 extends along an axis L and includes a front axial end (one end) and a rear axial end (the other end) in the direction of an axis L (in the axial direction). The front end section of the rotation shaft 21 is located at the front side of the housing 11 and inserted through a shaft hole 12h that extends through the first cylinder block 12. The front end of the rotation shaft 21 is located in the front housing member 14. The rear end section of the rotation shaft 21 is located at the rear side of the housing 11 and inserted through a shaft hole 13h that extends through the second cylinder block 13. The rear end of the rotation shaft 21 is located in the pressure adjustment chamber 15c.

The front end section of the rotation shaft 21 is received in the shaft hole 12h and rotationally supported by the first cylinder block 12. The rear end section of the rotation shaft 21 is received in the shaft hole 13h and rotationally supported by the second cylinder block 13. A shaft sealing device 22 is arranged between the front housing member 14 and the rotation shaft 21. The shaft sealing device 22 is a lip seal. A vehicle engine E, which functions as an external driving source, is operatively coupled to the front end of the rotation shaft 21 through a power transmission mechanism PT. In the present embodiment, the power transmission mechanism PT is a clutchless mechanism that constantly transmits power and may be a combination of a belt and a pulley, for example.

The first cylinder block 12 and the second cylinder block 13 define a crank chamber 24 in the housing 11. The crank chamber 24 accommodates a swash plate 23 that is rotated by the driving force received from the rotation shaft 21. The swash plate 23 is inclinable in the axial direction relative to the rotation shaft 21. The swash plate 23 includes an insertion hole 23a that receives the rotation shaft 21. The insertion of the rotation shaft 21 into the insertion hole 23a couples the swash plate 23 to the rotation shaft 21.

Primary cylinder bores 12a (only one shown in FIG. 1) extend through the first cylinder block 12 around the rotation shaft 21 in the axial direction. Each primary cylinder bore 12a is in communication with the suction chamber 14a through the corresponding suction port 16a and in communication with the discharge chamber 14b through the corresponding discharge port 16b. Secondary cylinder bores 13a (only one shown in FIG. 1) extend through the second cylinder block 13 around the rotation shaft 21 in the axial direction. Each secondary cylinder bore 13a is in communication with the suction chamber 15a through the corresponding suction port 17a and in communication with the discharge chamber 15b through the corresponding discharge port 17b. Each of the primary cylinder bores 12a located at the front side is paired with a corresponding one of the secondary cylinder bores 13a located at the rear side. Each of the pairs of the primary cylinder bores 12a and the secondary cylinder bores 13a accommodates a double-headed piston 25 that can reciprocate in the front-rear direction. That is, the variable displacement swash plate compressor 10 of the present embodiment is a double-headed piston swash plate compressor.

Each double-headed piston 25 is engaged with the outer portion of the swash plate 23 by a pair of shoes 26. The rotation of the swash plate 23 caused by the rotation of the rotation shaft 21 is converted to reciprocal linear movement of the double-headed piston 25 through the shoes 26. The double-headed piston 25 and the first valve/port formation body 16 define a primary compression chamber 20a in each primary cylinder bore 12a. The double-headed piston 25 and the second valve/port formation body 17 define a secondary compression chamber 20b in each secondary cylinder bore 13a.

The first cylinder block 12 includes a first large diameter hole 12b, which is continuous with the shaft hole 12h and has a larger diameter than the shaft hole 12h. The first large diameter hole 12b is in communication with the crank chamber 24. A suction passage 12c, which extends through the first cylinder block 12 and the first valve/port formation body 16, communicates the crank chamber 24 and the suction chamber 14a.

The second cylinder block 13 includes a second large diameter hole 13b, which is continuous with the shaft hole 13h and has a larger diameter than the shaft hole 13h. The second large diameter hole 13b is in communication with the crank chamber 24. A suction passage 13c, which extends through the second cylinder block 13 and the second valve/port formation body 17, communicates the crank chamber 24 and the suction chamber 15a.

The circumferential wall of the second cylinder block 13 includes a suction inlet 13s, which is connected to the external refrigerant circuit. The refrigerant gas that is drawn into the crank chamber 24 from the external refrigerant circuit through the suction inlet 13s is then drawn into the suction chambers 14a and 15a through the suction passages 12c and 13c, respectively. Thus, the suction chambers 14a and 15a and the crank chamber 24 define a suction pressure region. The pressure of the suction pressure region is referred to as the suction pressure. The suction chambers 14a and 15a and the crank chamber 24 have substantially the same pressure.

An annular flange 21f projects from the rotation shaft 21 in the first large diameter hole 12b. A first thrust bearing 27a is arranged between the flange 21f and the first cylinder block 12 in the axial direction of the rotation shaft 21. The rear end portion of the rotation shaft 21 is fitted into a cylindrical support 39. An annular flange 39f extends from the outer circumferential surface of the support 39 in the second large diameter hole 13b. A second thrust bearing 27b is arranged between the flange 39f and the second cylinder block 13 in the axial direction of the rotation shaft 21.

An annular fixed body 31 is fixed to the rotation shaft 21 at a location between the flange 21f and the swash plate 23. The fixed body 31 is rotatable integrally with the rotation shaft 21. A movable body 32 is arranged between the flange 21f and the fixed body 31. The movable body 32 is movable relative to the fixed body 31 in the axial direction of the rotation shaft 21.

The movable body 32 includes an annular end portion 32a and a cylindrical portion 32b extending from the rim of the end portion 32a in the axial direction of the rotation shaft 21. The end portion 32a includes an insertion hole 32e that receives the rotation shaft 21. The inner surface of the cylindrical portion 32b can slide on the outer circumference of the fixed body 31. The movable body 32 can rotate integrally with the rotation shaft 21. A sealing member 33 seals the gap between the inner surface of the cylindrical portion 32b and the outer circumference of the fixed body 31. A sealing member 34 seals the gap between the end portion 32a and the rotation shaft 21. In addition, a control pressure chamber 35 is defined between the fixed body 31 and the movable body 32.

The rotation shaft 21 includes a first inner passage 21a extending in the axial direction of the rotation shaft 21. The rear end of the first inner passage 21a opens in the pressure adjustment chamber 15c. The rotation shaft 21 also includes a second inner passage 21b extending in the radial direction of the rotation shaft 21. One end of the second inner passage 21b is connected to the front end of the first inner passage 21a, and the other end of the second inner passage 21b opens in the control pressure chamber 35. Thus, the first inner passage 21a and the second inner passage 21b communicate the control pressure chamber 35 and the pressure adjustment chamber 15c.

A lug arm 40 is arranged between the swash plate 23 and the flange 39f in the crank chamber 24. The lug arm 40 is substantially L-shaped. A first end of the lug arm 40 includes a weight 40a. The lug arm 40 extends through a slot 23b in the swash plate 23 so that the weight 40a is located at the front side of the swash plate 23.

A first pin 41, which traverses the slot 23b, couples the first end of the lug arm 40 to the upper side of the swash plate 23, as viewed in FIG. 1. The axis of the first pin 41 functions as a first pivot axis M1. The first end of the lug arm 40 is supported to be pivotable about the first pivot axis M1 relative to the swash plate 23. A second pin 42 couples a second end of the lug arm 40 to the support 39. The axis of the second pin 42 functions as a second pivot axis M2. The second end of the lug arm 40 is supported to be pivotable about the second pivot axis M2 relative to the support 39.

A coupling portion 32c extends from the distal end of the cylindrical portion 32b of the movable body 32 toward the swash plate 23. The coupling portion 32c includes a movable body hole 32h that receives a third pin 43. The lower section of the swash plate 23 as viewed in FIG. 1 includes a swash plate hole 23h that receives the third pin 43. The third pin 43 couples the coupling portion 32c to the lower section of the swash plate 23.

A restriction 36a extends through the second valve/port formation body 17. The restriction 36a is in communication with the discharge chamber 15b. In addition, the end surface of the second cylinder block 13 that faces toward the second valve/port formation body 17 includes a communication portion 36b. The communication portion 36b is a recess that communicates the pressure adjustment chamber 15c and the restriction 36a. The discharge chamber 15b is in communication with the control pressure chamber 35 through the restriction 36a, the communication portion 36b, the pressure adjustment chamber 15c, the first inner passage 21a, and the second inner passage 21b. Thus, the restriction 36a, the communication portion 36b, the pressure adjustment chamber 15c, the first inner passage 21a, and the second inner passage 21b form a supply passage extending from the discharge chamber 15b to the control pressure chamber 35. The supply passage narrows in the restriction 36a. That is, the restriction 36a reduces the cross-sectional area of the supply passage.

The pressure of the control pressure chamber 35 is adjusted by drawing refrigerant gas into the control pressure chamber 35 from the discharge chamber 15b and by discharging the refrigerant gas from the control pressure chamber 35 to the suction chamber 15a. Thus, the refrigerant gas drawn into the control pressure chamber 35 functions as a control gas that controls the pressure of the control pressure chamber 35. The difference in the pressure of the control pressure chamber 35 and the pressure of the crank chamber 24 moves the movable body 32 relative to the fixed body 31 in the axial direction of the rotation shaft 21. An electromagnetic displacement control valve 50, which adjusts the pressure of the control pressure chamber 35, is coupled to the rear housing member 15. The displacement control valve 50 is electrically connected to a control computer 50c. The control computer 50c is connected to an air conditioning switch 50s, which sends signals to the control computer 50c.

As shown in FIG. 2, the displacement control valve 50 includes a valve housing 50h. The valve housing 50h includes a cylindrical solenoid housing member 51, a cylindrical valve housing member 52, and a lid 52f. The solenoid housing member 51 accommodates an electromagnetic solenoid 53. The valve housing member 52 is coupled to the solenoid housing member 51. The valve housing member 52 includes an end wall 52e and an opening, which is located at the opposite side of the solenoid housing member 51. The lid 52f is fitted into and closes the opening of the valve housing member 52.

The electromagnetic solenoid 53 includes a coil 53c, a fixed core 54, and a movable core 55. When electric current is supplied to the coil 53c to energize the electromagnetic solenoid 53, the movable core 55 is attracted to the fixed core 54. The fixed core 54 is arranged between the movable core 55 and the valve housing member 52. The electromagnetic force of the electromagnetic solenoid 53 moves the movable core 55 toward the fixed core 54. The control computer 50c controls the activation (duty ratio) of the electromagnetic solenoid 53. A spring 56 is arranged between the fixed core 54 and the movable core 55. The spring 56 urges the movable core 55 away from the fixed core 54.

A post-shaped driving force transmission member 57 is coupled to the movable core 55. The driving force transmission member 57 moves integrally with the movable core 55. A back pressure chamber 58 is defined between the end wall 52e of the valve housing member 52 and the fixed core 54. The driving force transmission member 57 extends to the back pressure chamber 58 through the fixed core 54. The back pressure chamber 58 is defined by the end wall 52e of the valve housing member 52 and a recess 54e. The recess 54e is formed in the end surface of the fixed core 54 that faces toward the end wall 52e and surrounds the driving force transmission member 57.

The valve housing member 52 includes an accommodation chamber 59 that accommodates a pressure sensing mechanism 60. The pressure sensing mechanism 60 includes a bellows 61, a pressure receiving body 62, which is coupled to one end of the bellows 61, a support body 63, which is coupled to the other end of the bellows 61, and a spring 64, which is located in the bellows 61 and urges the pressure receiving body 62 and the support body 63 away from each other.

A stopper 62a is formed integrally with the pressure receiving body 62 and located in the bellows 61. In addition, the support body 63 includes a stopper 63a extending toward the stopper 62a of the pressure receiving body 62. The stopper 62a and the stopper 63a when in contact with each other set the minimum length of the bellows 61.

The end wall 52e of the valve housing member 52 includes a recess 52a that is continuous with the accommodation chamber 59. Further, an annular valve seat member 65 is arranged in the accommodation chamber 59 near the end wall 52e. The valve seat member 65 includes a valve hole 65h and is separate from the valve housing member 52. The valve seat member 65 includes a flat surface that faces the recess 52a and is in contact with a step 52b of the valve housing member 52 that connects the inner surface defining the accommodation chamber 59 and the inner surface defining the recess 52a. An annular protrusion 65a protrudes from the inner section of the end surface of the valve seat member 65 that faces toward the pressure sensing mechanism 60. The protrusion 65a protrudes toward the pressure sensing mechanism 60.

The accommodation chamber 59 accommodates a spring 66, which is located between the valve seat member 65 and the lid 52f. One end of the spring 66 is connected to the lid 52f, and the other end is connected to a section of the valve seat member 65 that is located radially outward from the protrusion 65a. The protrusion 65a is located in the spring 66. Thus, the protrusion 65a restricts radial movement of the spring 66. The spring 66 presses the valve seat member 65 against the step 52b and positions the valve seat member 65.

A valve chamber 67 is formed between the valve seat member 65 and the end wall 52e in the valve housing member 52. In addition, the valve housing member 52 accommodates a valve 68 extending through the end wall 52e of the valve housing member 52. The valve 68 extends from the back pressure chamber 58 to the accommodation chamber 59 through the valve chamber 67 and the valve hole 65h. The valve 68 includes a valve body 68v accommodated in the valve chamber 67. The end of the valve 68 that faces toward the accommodation chamber 59 includes a post-shaped projection 68a, which is coupled to the support body 63. Thus, the valve 68 is formed integrally with the pressure sensing mechanism 60. The pressure sensing mechanism 60 and the driving force transmission member 57 are located at opposite sides of the valve body 68v. The valve 68 (valve body 68v) and the pressure sensing mechanism 60 are formed integrally with each other as a valve unit 70.

The end surface of the valve seat member 65 that faces the recess 52a includes a valve seat 65e extending around the valve hole 65h. The valve seat 65e receives the valve body 68v. The valve body 68v opens and closes the valve hole 65h by moving toward and away from the valve seat 65e. A cylindrical guide wall 69, which is formed in the end wall 52e of the valve housing member 52, guides the valve 68 in the movement direction of the driving force transmission member 57. The back pressure chamber 58 is located between the electromagnetic solenoid 53 and the valve chamber 67. A gap 69s formed between the guide wall 69 and the valve 68 communicates the valve chamber 67 and the back pressure chamber 58. The end wall 52e of the valve housing member 52 includes a communication passage 73 that communicates the valve chamber 67 and the back pressure chamber 58. A gap between the driving force transmission member 57 and the fixed core 54 communicates the back pressure chamber 58 and the accommodation chamber 55a, which accommodates the movable core 55.

The accommodation chamber 59 is in communication with the pressure adjustment chamber 15c through the passage 71. The valve chamber 67 is in communication with the suction chamber 15a through the passage 72. Thus, the second inner passage 21b, the first inner passage 21a, the pressure adjustment chamber 15c, the passage 71, the accommodation chamber 59, the valve hole 65h, the valve chamber 67, and the passage 72 form a discharge passage extending from the control pressure chamber 35 to the suction chamber 15a.

The cross-sectional area of the valve hole 65h, which is opened and closed by the valve body 68v, is the same as the effective pressure receiving area of the bellows 61. Thus, when the valve hole 65h is closed by the valve body 68v, the pressure of the accommodation chamber 59 does not affect the pressure sensing mechanism 60. The bellows 61 expands and contracts in the movement directions of the valve body 68v in accordance with the pressure applied to the valve 68 in the back pressure chamber 58 and the pressure applied to the valve body 68v in the valve chamber 67. The expansion and contraction of the bellows 61 moves the valve body 68v and adjusts the valve opening degree of the valve body 68v. The valve opening degree of the valve body 68v is determined by the balance of the urging force applied to the valve body 68v by the activated electromagnetic solenoid 53 through the driving force transmission member 57, the urging force of the spring 56, and the urging force applied to the valve body 68v by the expansion or contraction of the pressure sensing mechanism 60.

The valve body 68v adjusts the open amount (cross-sectional area) of the discharge passage, that is, the valve hole 65h. When the valve body 68v is seated on the valve seat 65e, the valve body 68v is in a closed state and closes the discharge passage. When the valve body 68v is separated from the valve seat 65e, the valve body 68v is in an open state and opens the discharge passage.

The inner surface of the lid 52f includes a stepped recess 75, which includes a small diameter portion 75a and a large diameter portion 75b. The small diameter portion 75a receives a valve open spring 76. The valve open spring 76 urges the valve unit 70 in the open direction of the valve body 68v. The urging force of the valve open spring 76 is set to be smaller than the urging force of the spring 64 that urges the pressure receiving body 62 and the support body 63 away from each other. The pressure receiving body 62 is inserted in the large diameter portion 75b of the stepped recess 75. A communication passage 77 is formed between the large diameter portion 75b and the pressure receiving body 62. The communication passage 77 communicates the accommodation chamber 59 and the small diameter portion 75a.

When the urging force of the valve open spring 76 urges the valve unit 70 in the open direction of the valve body 68v, the large diameter portion 75b guides the pressure receiving body 62 in a movement direction of the valve body 68v. Thus, the large diameter portion 75b functions as a guide portion that guides the valve unit 70 in the movement direction of the valve body 68v.

The operation of the present embodiment will now be described.

Referring to FIG. 3, when the air conditioning switch 50s is turned on and the electromagnetic solenoid 53 of the variable displacement swash plate compressor 10 is activated, the electromagnetic force of the electromagnetic solenoid 53 prevails over the urging force of the spring 56 and attracts the movable core 55 toward the fixed core 54. As a result, the driving force transmission member 57 presses the valve 68 and decreases the valve opening degree of the valve body 68v. This reduces the flow rate of the refrigerant gas that flows from the control pressure chamber 35 to the suction chamber 15a through the second inner passage 21b, the first inner passage 21a, the pressure adjustment chamber 15c, the passage 71, the accommodation chamber 59, the valve hole 65h, the valve chamber 67, and the passage 72. Thus, the pressure of the control pressure chamber 35 approaches the pressure of the discharge chamber 15b due to the refrigerant gas in the control pressure chamber 35 flowing from the discharge chamber 15b through the restriction 36a, the communication portion 36b, the pressure adjustment chamber 15c, the first inner passage 21a, and the second inner passage 21b.

Referring to FIG. 4, an increase in the difference between the pressure of the control pressure chamber 35 and the pressure of the crank chamber 24 moves the end portion 32a of the movable body 32 away from the fixed body 31. Consequently, the swash plate 23 pivots about the first pivot M1. The pivoting of the swash plate 23 about the first pivot M1 pivots the two ends of the lug arm 40 about the first pivot M1 and the second pivot M2, respectively, and moves the lug arm 40 away from the flange 39f of the support 39. This increases the inclination angle of the swash plate 23 and the stroke of the double-headed pistons 25. Accordingly, the displacement of the variable displacement swash plate compressor 10 increases. The movable body 32 contacts the flange 21f when the inclination angle of the swash plate 23 becomes maximal. The contact between the movable body 32 and the flange 21f maintains the swash plate 23 at the maximum inclination angle.

Referring to FIG. 2, an increase in the valve opening degree of the valve body 68v increases the flow rate of the refrigerant gas that flows from the control pressure chamber 35 to the suction chamber 15a through the second inner passage 21b, the first inner passage 21a, the pressure adjustment chamber 15c, the passage 71, the accommodation chamber 59, the valve hole 65h, the valve chamber 67, and the passage 72. Accordingly, the pressure of the control pressure chamber 35 approaches the pressure of the suction chamber 15a.

Referring to FIG. 1, a decrease in the difference between the pressure of the control pressure chamber 35 and the pressure of the crank chamber 24 moves the end portion 32a of the movable body 32 toward the fixed body 31. Consequently, the swash plate 23 pivots about the first pivot M1 in the direction opposite to the direction that increases the inclination angle of the swash plate 23. The pivoting of the swash plate 23 about the first pivot M1 pivots the two ends of the lug arm 40 about the first pivot M1 and the second pivot M2, respectively, in the direction opposite to the direction that increases the inclination angle of the swash plate 23. Accordingly, the lug arm 40 approaches the flange 39f of the support 39. This decreases the inclination angle of the swash plate 23 and the stroke of the double-headed pistons 25. Thus, the displacement of the variable displacement swash plate compressor 10 decreases. The lug arm 40 contacts the flange 39f of the support 39 when the inclination angle of the swash plate 23 becomes minimal. The contact between the lug arm 40 and the flange 39f maintains the swash plate 23 at the minimum inclination angle.

If the pressure of the suction chamber 15a is greater than a predetermined pressure (e.g., 0.35 MPaG) when the air conditioning switch 50s is turned off and the electromagnetic solenoid 53 is deactivated, the pressure of the back pressure chamber 58, which is part of the suction pressure region, would also be greater than the predetermined pressure. Thus, the pressure of the back pressure chamber 58 and the pressure of the valve chamber 67 would urge the valve unit 70 in the close direction of the valve body 68v. In this case, the discharge passage communicates the suction chamber 15a and the control pressure chamber 35. Thus, the pressure of the control pressure chamber 35 would be greater than the predetermined pressure.

Referring to FIG. 5, when the pressure of the control pressure chamber 35 is greater than the predetermined pressure, the refrigerant gas flows into the small diameter portion 75a from the accommodation chamber 59 through the communication passage 77. Accordingly, the pressure of the accommodation chamber 59 acts on the back surface of the pressure sensing mechanism 60 that is opposite to the driving force transmission member 57. Thus, the valve unit 70 receives a force in the open direction of the valve body 68v. In addition, the valve open spring 76 urges the valve unit 70 in the open direction of the valve body 68v. Thus, the urging force of the valve open spring 76 moves the valve unit 70 in the open direction of the valve body 68v while the large diameter portion 75b guides the pressure receiving body 62 in the movement direction of the driving force transmission member 57. This ensures that the valve 68 is maintained in the open state.

As a result, the refrigerant gas in the control pressure chamber 35 is discharged to the suction chamber 15a through the second inner passage 21b, the first inner passage 21a, the pressure adjustment chamber 15c, the passage 71, the accommodation chamber 59, the valve hole 65h, the valve chamber 67, and the passage 72. This allows the pressure of the control pressure chamber 35 to be substantially the same as the pressure of the suction chamber 15a. Thus, when the electromagnetic solenoid 53 is deactivated, the inclination angle of the swash plate 23 becomes minimal, and the swash plate 23 is maintained at the minimum inclination angle.

Then, when the air conditioning switch 50s is turned on and the electromagnetic solenoid 53 is activated again, the variable displacement swash plate compressor 10 operates under a minimum displacement condition. Since a situation in which the compressor displacement suddenly increases is avoided, the load on the variable displacement swash plate compressor 10 is limited.

FIG. 6 shows a situation in which the air conditioning switch 50s is turned on and the electromagnetic solenoid 53 is activated when the pressure of the control pressure chamber 35 is greater than the predetermined pressure. Due to the pressure of the control pressure chamber 35, the stopper 62a of the pressure receiving body 62 is in contact with the stopper 63a of the support body 63 so that the bellows 61 is contracted to the minimum length. In this situation, the bellows 61 is contracted to the minimum length, and the pressure sensing mechanism 60 does not function to adjust the valve opening degree of the valve body 68v. Thus, the valve opening degree of the valve body 68v can be adjusted just by controlling the amount of current supplied to the electromagnetic solenoid 53. Since the valve opening degree of the valve body 68v is not affected by the urging force of the pressure sensing mechanism 60, the valve opening degree of the valve body 68v may be gradually decreased. Thus, when the air conditioning switch 50s is turned on, the pressure of the control pressure chamber 35 does not suddenly approach the pressure of the discharge chamber 15b. Since a situation in which the compressor displacement suddenly increases is avoided, the load on the variable displacement swash plate compressor 10 is limited.

In the present embodiment, the rotation shaft 21 receives rotational driving force from the engine E through the clutchless power transmission mechanism PT. Thus, even when the electromagnetic solenoid 53 is deactivated, the rotation shaft 21 receives the rotational driving force from the engine E through the power transmission mechanism PT. This consumes the power of the engine E although the consumed amount is small. Thus, when the electromagnetic solenoid 53 is deactivated, in order to minimize the power consumption of the engine E, it is desirable that the variable displacement swash plate compressor 10 operate under the minimum displacement condition, in which the swash plate 23 is maintained at the minimum inclination angle.

Thus, when the electromagnetic solenoid 53 is deactivated, the displacement control valve 50 operates to minimize the inclination angle of the swash plate 23. This is achieved by opening the valve body 68v to the maximum degree and discharging the refrigerant gas from the control pressure chamber 35 to the suction chamber 15a through the discharge passage so that the pressure of the control pressure chamber 35 becomes substantially the same as the pressure of the suction chamber 15a. However, if the pressure of the suction chamber 15a exceeds the predetermined pressure while the electromagnetic solenoid 53 is deactivated, the pressure of the back pressure chamber 58 also increases. This may result in the pressure of the back pressure chamber 58 causing the valve body 68v to close the discharge passage.

However, in the present embodiment, the pressure of the accommodation chamber 59 acts on the back surface of the pressure sensing mechanism 60 that is opposite to the driving force transmission member 57. This applies force to the valve unit 70 in the open direction of the valve body 68v. Thus, the valve body 68v is kept open, and the refrigerant gas flows from the control pressure chamber 35 to the suction chamber 15a through the second inner passage 21b, the first inner passage 21a, the pressure adjustment chamber 15c, the passage 71, the accommodation chamber 59, the valve hole 65h, the valve chamber 67, and the passage 72.

As a result, when the electromagnetic solenoid 53 is deactivated, the pressure of the control pressure chamber 35 becomes substantially the same as the pressure of the suction chamber 15a. This minimizes the inclination angle of the swash plate 23. Thus, in a structure in which the rotation shaft 21 receives rotational driving force from the engine E through the clutchless power transmission mechanism PT, even if the pressure of the suction chamber 15a changes while the electromagnetic solenoid 53 is deactivated, the inclination angle of the swash plate 23 is minimizes, and the swash plate 23 is maintained at the minimum inclination angle. This ensures that the variable displacement swash plate compressor 10 operates under the minimum displacement condition. Consequently, the power consumption of the engine E is minimized.

The advantages of the present embodiment will now be described.

(1) When the electromagnetic solenoid 53 is deactivated, the pressure of the accommodation chamber 59 acts on the back surface of the pressure sensing mechanism 60 that is opposite to the driving force transmission member 57. This applies force to the valve unit 70 in the open direction of the valve body 68v. If the pressure of the suction chamber 15a exceeds the predetermined pressure when the electromagnetic solenoid 53 is deactivated, the pressure of the suction chamber 15a urges the valve unit 70 in the close direction of the valve body 68v. Here, since the discharge passage communicates the suction chamber 15a and the control pressure chamber 35, the pressure of the control pressure chamber 35 is greater than the predetermined pressure. Further, the pressure of the accommodation chamber 59 acts on the back surface of the pressure sensing mechanism 60 that is opposite to the driving force transmission member 57 so that force is applied to the valve unit 70 in the open direction of the valve body 68v. This maintains the valve body 68v in the open state and allows the pressure of the control pressure chamber 35 to be substantially the same as the pressure of the suction chamber 15a. Thus, even when the pressure of the suction chamber 15a changes while the electromagnetic solenoid 53 is deactivated, the inclination angle of the swash plate 23 can be minimized, and the swash plate 23 can be maintained at the minimum inclination angle.

(2) The displacement control valve 50 includes the valve open spring 76 that urges the valve unit 70 in the open direction of the valve body 68v. Thus, even if the pressure of the suction chamber 15a increases and urges the valve unit 70 in the close direction of the valve body 68v, the valve open spring 76 urges the valve unit 70 in the open direction of the valve body 68v to ensure that the valve body 68v opens.

(3) The displacement control valve 50 includes the large diameter portion 75b that guides the valve unit 70 in the movement direction of the valve body 68v. Thus, the valve unit 70 does not tilt while moving in the movement direction of the valve body 68v. This allows for smooth movement of the valve unit 70.

(4) The double piston swash plate compressor that includes the double-headed pistons 25 cannot use the crank chamber 24 as a control pressure chamber to change the inclination angle of the swash plate 23 like a variable displacement swash plate compressor that includes single-headed pistons. Thus, the present embodiment changes the inclination angle of the swash plate 23 by changing the pressure of the control pressure chamber 35 defined by the movable body 32. The control pressure chamber 35 is smaller than the crank chamber 24. Thus, a smaller amount of refrigerant gas is drawn into the control pressure chamber 35. This allows for quick changes in the inclination angle of the swash plate 23.

(5) In the variable displacement swash plate compressor 10 of the present embodiment, the rotation shaft 21 receives rotational driving force from the engine E through the clutchless power transmission mechanism PT. Compared to a structure in which the rotation shaft 21 receives rotational driving force from the engine E through a power transmission mechanism that includes, for example, an electromagnetic clutch, the variable displacement swash plate compressor 10 is lighter and consumes less electric power.

(6) In the structure in which the rotation shaft 21 receives rotational driving force from the engine E through the clutchless power transmission mechanism PT, the present embodiment can minimize the inclination angle of the swash plate 23 and maintain the swash plate 23 at the minimum inclination angle even when the pressure of the suction chamber 15a is greater than the predetermined pressure when the electromagnetic solenoid 53 is deactivated. This ensures that the variable displacement swash plate compressor 10 is operated in the minimum displacement condition and thus minimizes the power consumption of the engine E.

(7) The present embodiment can minimize the inclination angle of the swash plate 23 when the electromagnetic solenoid 53 is deactivated. Thus, when the electromagnetic solenoid 53 is activated again, the variable displacement swash plate compressor 10 operates in the minimum displacement condition. Since a situation in which the compressor displacement suddenly increases is avoided, the load on the variable displacement swash plate compressor 10 is limited.

(8) The displacement control valve 50 includes the guide wall 69 that guides the valve 68 in the movement direction of the driving force transmission member 57. The gap 69s between the guide wall 69 and the valve 68 communicates the valve chamber 67 and the back pressure chamber 58. The guide wall 69 guides the valve 68 and limits tilting of the valve 68 relative to a movement direction of the valve 68. This ensures that the valve body 68v closes. Further, the gap 69s between the guide wall 69 and the valve 68 allows for smooth movement of the valve 68. This facilitates the operation of the displacement control valve 50.

(9) The communication passage 73 communicates the valve chamber 67 and the back pressure chamber 58. Thus, compared to a structure in which the communication passage 73 is not provided and only the gap 69s between the guide wall 69 and the valve 68 communicates the valve chamber 67 and the back pressure chamber 58, for example, the pressure of the back pressure chamber 58 can reach the pressure of the suction chamber 15a, which is equal to the pressure of the valve chamber 67, in less time.

It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the present invention may be embodied in the following forms.

The back pressure chamber 58 may be omitted, and the driving force transmission member 57 and the valve 68 may be formed integrally.

The valve open spring 76 may be omitted.

The pressure receiving body 62 does not have to be fitted into the large diameter portion 75b. That is, the pressure receiving body 62 may be in contact with the inner surface of the lid 52f.

The back pressure chamber 58 may be defined by the fixed core 54 and a recess that is formed at a position that surrounds the driving force transmission member 57 in the surface of the end wall 52e of the valve housing member 52 that faces toward the fixed core 54.

The valve chamber 67 may be in communication with the suction chamber 14a through the passage 72. Any structure may be employed as long as the discharge passage extends from the control pressure chamber 35 to the suction pressure region.

The discharge chamber 14b may be in communication with the control pressure chamber 35 through the restriction 36a, the communication portion 36b, the pressure adjustment chamber 15c, the first inner passage 21a, and the second inner passage 21b.

The cross-sectional area of the valve hole 65h does not have to be exactly the same as the effective pressure receiving area of the bellows 61. It is sufficient the areas be substantially the same.

The variable displacement swash plate compressor 10 may receive driving force from the external driving source using a clutch.

The variable displacement swash plate compressor 10 may be a single-headed piston swash plate compressor that uses single-headed pistons.

The present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.

VARIABLE DISPLACEMENT SWASH PLATE COMPRESSOR

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