# Patent

## Title
Swash plate type variable displacement compressor

## Abstract

A compressor includes an actuator. The actuator is arranged in a swash plate chamber, while being rotational integrally with a drive shaft. With reference to the swash plate, the actuator is located in a region in which a first cylinder bore is located. The actuator includes a rotation body fixed to the drive shaft, a movable body, and a control pressure chamber. A link mechanism is located between the drive shaft and the swash plate. As the inclination angle of the swash plate is changed, the link mechanism moves the top dead center position of a first head by a greater amount than the top dead center position of a second head.

## Background
BACKGROUND OF THE INVENTION
The present invention relates to a swash plate type variable displacement compressor.
Japanese Laid-Open Patent Publications No. 2-19665 and No. 5-172052 disclose conventional swash plate type variable displacement type compressors (hereinafter, referred to as compressors). The compressors include a suction chamber, a discharge chamber, a swash plate chamber, and a plurality of cylinder bores, which are formed in a housing. A drive shaft is rotationally supported in the housing. The swash plate chamber accommodates a swash plate, which is rotatable through rotation of the drive shaft. A link mechanism, which allows change of the inclination angle of the swash plate, is arranged between the drive shaft and the swash plate. The inclination angle is defined with respect to a line perpendicular to the rotation axis of the drive shaft.
Each of the cylinder bores accommodates a piston in a reciprocal manner and thus forms a compression chamber. Each cylinder bore is formed by a front cylinder bore arranged in front of the swash plate and a rear cylinder bore arranged behind the swash plate. Each piston includes front head, which reciprocates in the front cylinder bore, and a rear head, which is integral with the front head and reciprocates in the rear cylinder bore.
A conversion mechanism reciprocates each of the pistons in the associated one of the cylinder bores by the stroke corresponding to the inclination angle of the swash plate through rotation of the swash plate. An actuator is capable of changing the inclination angle of the swash plate and controlled by a control mechanism.
In the compressor described in Japanese Laid-Open Patent Publication No. 2-19665, a pressure regulation chamber is formed in a rear housing member of the housing. A control pressure chamber is formed in a cylinder block, which is also a component of the housing, and communicates with the pressure regulation chamber. The actuator is arranged in the control pressure chamber, while being prevented from rotating integrally with the drive shaft.
Specifically, the actuator has a non-rotational movable body that overlaps with a rear end portion of the drive shaft. The inner peripheral surface of the non-rotational movable body rotationally supports the rear end portion of the drive shaft. The non-rotational movable body is movable in the direction of the rotation axis of the drive shaft. The non-rotational movable body is slidable in the control pressure chamber through the outer peripheral surface of the non-rotational movable body and slides in the direction of the rotation axis of the drive shaft. The non-rotational movable body is restricted from sliding about the rotation axis of the drive shaft. A pressing spring, which urges the non-rotational movable body forward, is arranged in the control pressure chamber or the pressure regulation chamber. The actuator has a movable body, which is joined to the swash plate and movable in the direction of the rotation axis of the drive shaft. A thrust bearing is arranged between the non-rotational movable body and the movable body. A pressure control valve, which changes the pressure in the control pressure chamber, is provided between the pressure regulation chamber and the discharge chamber. Through such change of the pressure in the control pressure chamber, the non-rotational movable body and the movable body are moved along the rotation axis.
The link mechanism is arranged in the swash plate chamber. The link mechanism has a movable body and a lug arm fixed to the drive shaft. A rear end portion of the lug arm has an elongated hole. The elongated hole extends in a direction that is perpendicular to the rotation axis of the drive shaft and transverse to rotation axis of the drive shaft. A pin is received in the elongated hole and supports the swash plate at a position forward to the swash plate such that the swash plate is allowed to pivot about a first pivot axis.
In the compressor described in Japanese Laid-Open Patent Publication No. 5-172052, a front end portion of the movable body also has an elongated hole, which extends in the direction perpendicular to and transverse to the rotation axis of the drive shaft. A pin is passed through the elongated hole and supports the swash plate at the rear end of the swash plate such that the swash plate is allowed to pivot about a second pivot axis, which is parallel to the first pivot axis.
In these compressors, when a pressure regulation valve is controlled to open, communication between the discharge chamber and the pressure regulation chamber is allowed, which raises the pressure in the control pressure chamber compared to the pressure in the swash plate chamber. This causes the non-rotational movable body and the movable body to proceed. The inclination angle of the swash plate is thus increased and the stroke of each piston is increased correspondingly. This increases the displacement of the compressor per rotation cycle. In contrast, by controlling the pressure regulation valve to close, the communication between the discharge chamber and the pressure regulation chamber is blocked. This lowers the pressure in the control pressure chamber to a level equal to the pressure level in the swash plate chamber. This causes the non-rotational movable body and the movable body to retreat. The inclination angle of the swash plate is thus decreased and the piston stroke is decreased correspondingly in this compressor. This reduces the displacement of the compressor per rotation cycle.
In these compressors, the link mechanism is arranged such that, as the inclination angle of the swash plate is changed, the top dead center position of the piston front head is moved by a greater extent than the top dead center position of the piston rear head. Specifically, when the inclination angle of the swash plate is changed, the top dead center position of the piston rear head is scarcely moved, while the top dead center position of the piston front head is largely moved. As the inclination angle of the swash plate approaches zero degrees, the piston performs a little compression work only with the rear head, while performing no compression work with the front head.
In the above describe conventional compressors, however, the actuator is located behind the swash plate, or closer to the rear cylinder bores with respect to the swash plate. Therefore, in the housing of the compressor, it is difficult to create a space behind the swash plate for allowing the non-rotational movable body and the movable body to proceed and retreat. The size of the actuator in the radial direction thus needs to be reduced. However, it is difficult for a small actuator to perform the displacement control. If the radial size of the housing is increased to allow the inclination angle of the swash plate to be easily changed, the mountability of the compressor on a vehicle will be degraded.
SUMMARY OF THE INVENTION
Accordingly, it is an objective of the present invention to provide a compressor that is compact in size and ensures improved displacement control.
In accordance with one aspect of the present invention, a swash plate type variable displacement compressor includes a housing in which a suction chamber, a discharge chamber, a swash plate chamber, and a cylinder bore are formed, a drive shaft rotationally supported by the housing, a swash plate rotatable in the swash plate chamber by rotation of the drive shaft, a link mechanism, a piston, a conversion mechanism, an actuator, and a control mechanism. The link mechanism is arranged between the drive shaft and the swash plate and allows change of an inclination angle of the swash plate with respect to a line perpendicular to the rotation axis of the drive shaft. The piston is reciprocally received in the cylinder bore. The conversion mechanism causes the piston to reciprocate in the cylinder bore by a stroke corresponding to the inclination angle of the swash plate through rotation of the swash plate. The actuator is capable of changing the inclination angle of the swash plate. The control mechanism controls the actuator. The cylinder bore is formed by a first cylinder bore, which is located in a first region facing a first surface of the swash plate, and a second cylinder bore, which is located in a second region facing a second surface of the swash plate. The piston includes a first head, which reciprocates in the first cylinder bore, and a second head, which is integrated with the first head and reciprocates in the second cylinder bore. The link mechanism is configured such that, as the inclination angle is changed, a top dead center position of the first head is moved by a greater amount than a top dead center position of the second head. The actuator is arranged in the swash plate chamber and on a side of the swash plate where the first cylinder bore is located, and is integrally rotational with the drive shaft. The actuator includes a rotation body fixed to the drive shaft, a movable body, which is coupled to the swash plate and moves along the rotation axis of the drive shaft to be movable relative to the rotation body, and a control pressure chamber, which is defined by the rotation body and the movable body. An internal pressure of the control pressure chamber is changed such that the movable body is moved.
When the inclination angle of the swash plate of the compressor according to the present invention is changed, the top dead center position of the second head of the piston is scarcely moved, while the top dead center position of the first head of the piston is largely moved. This allows a relatively large space to be created in a region of the swash plate chamber where the first cylinder bore is located. With reference to the swash plate, the actuator is located in the region in which the first cylinder bore is located. Thus, in the compressor, the actuator can be easily increased in size in the radial direction without increasing the size of the housing in the radial direction.
Therefore, since the compressor according to the present invention is compact, it is possible to achieve an improved mountability and ensure improved displacement control.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view showing a compressor according to a first embodiment of the present invention in a state corresponding to the maximum displacement;
FIG. 2 is a schematic diagram showing a control mechanism of compressors according to the first embodiment;
FIG. 3 is a cross-sectional view showing the compressor according to the first embodiment in a state corresponding to the minimum displacement; and
FIG. 4 is a schematic diagram showing a control mechanism of compressors according to a second embodiment.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First and second embodiments of the present invention will now be described with reference to the attached drawings. A compressor of each of the first and second embodiments forms a part of a refrigeration circuit in a vehicle air conditioner and is mounted in a vehicle.
First Embodiment
As shown in FIGS. 1 and 3, a compressor according to a first embodiment of the invention includes a housing 1, a drive shaft 3, a swash plate 5, a link mechanism 7, a plurality of pistons 9, pairs of front and rear shoes 11a, 11b, an actuator 13, and a control mechanism 15, which is illustrated in FIG. 2.
With reference to FIG. 1, the housing 1 has a front housing member 17 at a front position in the compressor, a rear housing member 19 at a rear position in the compressor, and a first cylinder block 21 and a second cylinder block 23, which are arranged between the front housing member 17 and the rear housing member 19.
The front housing member 17 has a boss 17a, which projects forward. A shaft sealing device 25 is arranged in the boss 17a and arranged between the inner periphery of the boss 17a and the drive shaft 3. A suction chamber 27a and a first discharge chamber 29a are formed in the front housing member 17. The first suction chamber 27a is arranged at a radially inner position and the first discharge chamber 29a is located at a radially outer position in the front housing member 17.
A control mechanism 15 is received in the rear housing member 19. A second suction chamber 27b, a second discharge chamber 29b, and a pressure regulation chamber 31 are formed in the rear housing member 19. The second suction chamber 27b is arranged at a radially inner position and the second discharge chamber 29b is located at a radially outer position in the rear housing member 19. The pressure regulation chamber 31 is formed in the middle of the rear housing member 19. The first discharge chamber 29a and the second discharge chamber 29b are connected to each other through a non-illustrated discharge passage. The discharge passage has an outlet communicating with the exterior of the compressor.
A swash plate chamber 33 is formed by the first cylinder block 21 and the second cylinder block 23. The swash plate chamber 33 is arranged substantially in the middle of the housing 1.
A plurality of first cylinder bores 21a are formed in the first cylinder block 21 to be spaced apart concentrically at equal angular intervals, and extend parallel to one another.
The first cylinder block 21 has a first shaft hole 21b, through which the drive shaft 3 is passed. A first recess 21c is formed in the first cylinder block 21 at a position rearward to the first shaft hole 21b. The first recess 21c communicates with the first shaft hole 21b and is coaxial with the first shaft hole 21b. The first recess 21c communicates with the swash plate chamber 33. A step is formed in an inner peripheral surface of the first recess 21c. A first thrust bearing 35a is arranged at a front position in the first recess 21c. The first cylinder block 21 also includes a first suction passage 37a, through which the swash plate chamber 33 and the first suction chamber 27a communicate with each other.
As in the first cylinder block 21, a plurality of second cylinder bores 23a are formed in the second cylinder block 23.
A second shaft hole 23b, through which the drive shaft 3 is inserted, is formed in the second cylinder block 23. The second shaft hole 23b communicates with the pressure regulation chamber 31. The second cylinder block 23 has a second recess 23c, which is located forward to the second shaft hole 23b and communicates with the second shaft hole 23b. The second recess 23c and the second shaft hole 23b are coaxial with each other. The second recess 23c communicates with the swash plate chamber 33. A step is formed in an inner peripheral surface of the second recess 23c. A second thrust bearing 35b is arranged at a rear position in the second recess 23c. The second cylinder block 23 also has a second suction passage 37b, through which the swash plate chamber 33 communicates with the second suction chamber 27b. 
The swash plate chamber 33 is connected to a non-illustrated evaporator through an inlet 330, which is formed in the second cylinder block 23.
A first valve plate 39 is arranged between the front housing member 17 and the first cylinder block 21. The first valve plate 39 has suction ports 39b and discharge ports 39a. The number of the suction ports 39b and the number of the discharge ports 39a are equal to the number of the first cylinder bores 21a. A non-illustrated suction valve mechanism is arranged in each of the suction ports 39b. Each one of the first cylinder bores 21a communicates with the first suction chamber 27a via the corresponding one of the suction ports 39b. A non-illustrated discharge valve mechanism is arranged in each of the discharge ports 39a. Each one of the first cylinder bores 21a communicates with the first discharge chamber 29a via the corresponding one of the discharge ports 39a. A communication hole 39c is formed in the first valve plate 39. The communication hole 39c allows communication between the first suction chamber 27a and the swash plate chamber 33 through the first suction passage 37a. 
A second valve plate 41 is arranged between the rear housing member 19 and the second cylinder block 23. Like the first valve plate 39, the second valve plate 41 has suction ports 41b and discharge ports 41a. The number of the suction ports 41b and the number of the discharge ports 41a are equal to the number of the second cylinder bores 23a. A non-illustrated suction valve mechanism is arranged in each of the suction ports 41b. Each one of the second cylinder bores 23a communicates with the second suction chamber 27b via the corresponding one of the suction ports 41b. A non-illustrated discharge valve mechanism is arranged in each of the discharge ports 41a. Each one of the second cylinder bores 23a communicates with the second discharge chamber 29b via the corresponding one of the discharge ports 41a. A communication hole 41c is formed in the second valve plate 41. The communication hole 41c allows communication between the second suction chamber 27b and the swash plate chamber 33 through the second suction passage 37b. 
The first suction chamber 27a and the second suction chamber 27b communicate with the swash plate chamber 33 via the first suction passage 37a and the second suction passage 37b, respectively. This substantially equalizes the pressure in the first and second suction chambers 27a, 27b and the pressure in the swash plate chamber 33. More specifically, the pressure in the swash plate chamber 33 is influenced by blow-by gas and thus slightly higher than the pressure in each of the first and second suction chambers 27a, 27b. The refrigerant gas sent from the evaporator flows into the swash plate chamber 33 via the inlet 330. As a result, the pressure in the swash plate chamber 33 and the pressure in the first and second suction chambers 27a, 27b are lower than the pressure in the first and second discharge chambers 29a, 29b. The swash plate chamber 33 is thus a low pressure chamber.
A swash plate 5, an actuator 13, and a flange 3a are attached to the drive shaft 3. The drive shaft 3 is passed rearward through the boss 17a and received in the first and second shaft holes 21b, 23b in the first and second cylinder blocks 21, 23. The front end of the drive shaft 3 is thus located inside the boss 17a and the rear end of the drive shaft 3 is arranged inside the pressure regulation chamber 31. The drive shaft 3 is supported by the walls of the first and second shaft holes 21b, 23b in the housing 1 in a manner rotatable about the rotation axis O. The swash plate 5, the actuator 13, and the flange 3a are accommodated in the swash plate chamber 33. A flange 3a is arranged between the first thrust bearing 35a and the actuator 13, or, more specifically, the first thrust bearing 35a and a movable body 13b, which will be described below. The flange 3a prevents contact between the first thrust bearing 35a and the movable body 13b. A radial bearing may be employed between the walls of the first and second shaft holes 21b, 23b and the drive shaft 3.
A support member 43 is mounted around a rear portion of the drive shaft 3 in a pressed manner. The support member 43 has a flange 43a, which contacts the second thrust bearing 35b, and an attachment portion 43b, through which a second pin 47b is passed as will be described below. An axial passage 3b is formed in the drive shaft 3 and extends from the rear end toward the front end of the drive shaft 3 in the direction of the rotation axis O. A radial passage 3c extends radially from the front end of the axial passage 3b and has an opening in the outer peripheral surface of the drive shaft 3. The axial passage 3b and the radial passage 3c are communication passages. The rear end of the axial passage 3b has an opening in the pressure regulation chamber 31, which is the low pressure chamber. The radial passage 3c has an opening in a control pressure chamber 13c, which will be described below.
The swash plate 5 is shaped as a flat annular plate and has a front surface 5a and a rear surface 5b. The front surface 5a of the swash plate 5 in the swash plate chamber 33 faces forward in the compressor. The rear surface 5b of the swash plate 5 in the swash plate chamber 33 faces rearward in the compressor. The front surface 5a and the rear surface 5b of the swash plate 5 correspond to a first surface and a second surface of the swash plate 5, respectively. In the compressor, the first cylinder bores 21a are located in a first region, which faces the front surface 5a of the swash plate 5, and the second cylinder bores 23a are located in a second region, which faces the rear surface 5b of the swash plate 5. The swash plate chamber 33 includes the first region and the second region, which are partitioned from each other by the swash plate 5, and the second region is smaller than the first region.
The swash plate 5 is fixed to a ring plate 45. The ring plate 45 is shaped as a flat annular plate and has a through hole 45a at the center. By passing the drive shaft 3 through the through hole 45a, the swash plate 5 is attached to the drive shaft 3 and thus arranged at a position in the vicinity of the second cylinder bores 23a in the swash plate chamber 33. In other words, the swash plate 5 is arranged at a position closer the rear end in the swash plate chamber 33.
The link mechanism 7 has a lug arm 49. The lug arm 49 is arranged rearward to the swash plate 5 in the swash plate chamber 33 and located between the swash plate 5 and the support member 43. The lug arm 49 substantially has an L shape. As illustrated in FIG. 3, the lug arm 49 comes into contact with the flange 43a of the support member 43 when the inclination angle of the swash plate 5 with respect to the rotation axis O is minimized. This allows the lug arm 49 to maintain the swash plate 5 at the minimum inclination angle in the compressor. A weight portion 49a is formed at the distal end of the lug arm 49. The weight portion 49a extends in the circumferential direction of the actuator 13 in correspondence with an approximately half the circumference. The weight portion 49a may be shaped in any suitable manner.
The distal end of the lug arm 49 is connected to the ring plate 45 through a first pin 47a. This configuration supports the distal end of the lug arm 49 to allow the distal end of the lug arm 49 to pivot about the axis of the first pin 47a, which is a first pivot axis M1, relative to the ring plate 45, or, in other words, relative to the swash plate 5. The first pivot axis M1 extends perpendicular to the rotation axis O of the drive shaft 3.
The basal end of the lug arm 49 is connected to the support member 43 through a second pin 47b. This configuration supports the basal end of the lug arm 49 to allow the basal end of the lug arm 49 to pivot about the axis of the second pin 47b, which is a second pivot axis M2, relative to the support member 43, or, in other words, relative to the drive shaft 3. The second pivot axis M2 extends parallel to the first pivot axis M1. The lug arm 49 and the first and second pins 47a, 47b correspond to the link mechanism 7 according to the present invention.
In the compressor, the swash plate 5 is allowed to rotate together with the drive shaft 3 by connection between the swash plate 5 and the drive shaft 3 through the link mechanism 7. Since the lug arm 49 is located between the swash plate 5 and the support member 43, the link mechanism 7 is located in the second region, which faces the rear surface 5b of the swash plate 5, in the swash plate chamber 33. In other words, the link mechanism 7 is located in the vicinity of the second cylinder bores 23a. That is, the link mechanism 7 is located behind the swash plate 5 in the swash plate chamber 33. The inclination angle of the swash plate 5 is changed through pivoting of the opposite ends of the lug arm 49 about the first pivot axis M1 and the second pivot axis M2 as illustrated in FIGS. 1 and 3.
The weight portion 49a is provided at the opposite side to the second pivot axis M2 with respect to the distal end of the lug arm 49, or, in other words, with respect to the first pivot axis M1. As a result, when the lug arm 49 is supported by the ring plate 45 through the first pin 47a, the weight portion 49a passes through a groove 45b in the ring plate 45 and reaches a position corresponding to the front surface of the ring plate 45, that is, the front surface 5a of the swash plate 5. As a result, the centrifugal force produced by rotation of the drive shaft 3 about the rotation axis O is applied to the weight portion 49a at the side corresponding to the front surface 5a of the swash plate 5.
Pistons 9 each include a first piston head 9a at the front end and a second piston head 9b at the rear end. The first piston head 9a and second piston head 9b correspond to a first head and a second head, respectively.
The first piston head 9a is reciprocally received in the corresponding first cylinder bore 21a and forms a first compression chamber 21d. The second piston head 9b is reciprocally accommodated in the corresponding second cylinder bore 23a and forms a second compression chamber 23d. Each of the pistons 9 has a recess 9c. Each of the recesses 9c accommodates semispherical shoes 11a, 11b. The shoes 11a, 11b convert rotation of the swash plate 5 into reciprocation of the pistons 9. The shoes 11a, 11b correspond to a conversion mechanism according to the present invention. The first and second piston heads 9a, 9b thus reciprocate in the corresponding first and second cylinder bores 21a, 23a by the stroke corresponding to the inclination angle of the swash plate 5.
The actuator 13 is accommodated in the swash plate chamber 33 at a position forward to the swash plate 5 and allowed to proceed into the first recess 21c. The actuator 13 has a rotation body 13a and a movable body 13b. The rotation body 13a has a disk-like shape and is fixed to the drive shaft 3. This allows the rotation body 13a only to rotate with the drive shaft 3. An O ring is attached to the outer periphery of the movable body 13b. 
The movable body 13b is shaped as a cylinder and has a through hole 130a, a body portion 130b, and an attachment portion 130c. The drive shaft 3 is passed through the through hole 130a. The body portion 130b extends from the front side to the rear side of the movable body 13b. The attachment portion 130c is formed at the rear end of the body portion 130b. The drive shaft 3 extends into is the body portion 130b of the movable body 13b through the through hole 130a. The rotation body 13a is received in the body portion 130b in a manner that permits the body portion 130b to slide with respect to the rotation body 13a. This allows the movable body 13b to rotate together with the drive shaft 3 and move in the direction of the rotation axis O of the drive shaft 3 in the first region, which faces the front surface 5a of the swash plate 5, in the swash plate chamber 33. An O ring is mounted in the through hole 130a. The drive shaft 3 thus extends through the actuator 13 and allows the actuator 13 to rotate integrally with the drive shaft 3 about the rotation axis O.
By passing the drive shaft 3 through the actuator 13, the movable body 13b is arranged to face the link mechanism 7 with the swash plate 5 arranged in between in the swash plate chamber 33. More specifically, the actuator 13, which includes the movable body 13b, is located in the first region, which faces the front surface 5a of the swash plate 5, in the swash plate chamber 33, or in a region where the first cylinder bores 21a are located. That is, the actuator 13 is located in front of the swash plate 5 in the swash plate chamber 33. The actuator 13 is arranged in the first region, and the link mechanism 7 is arranged in the second region.
The ring plate 45 is connected to the attachment portion 130c of the movable body 13b through a third pin 47c. In this manner, the ring plate 45, or, in other words, the swash plate 5, is supported by the movable body 13b such that the ring plate 45, or the swash plate 5, is allowed to pivot about the third pin 47c, which is an operation axis M3. The operation axis M3 extend parallel to the first and second pivot axes M1, M2. The movable body 13b is thus held in a state connected to the swash plate 5. The movable body 13b comes into contact with the flange 3a when the inclination angle of the swash plate 5 is maximized. As a result, in the compressor, the movable body 13b is capable of maintaining the swash plate 5 at the maximum inclination angle.
The control pressure chamber 13c is defined between the rotation body 13a and the movable body 13b. The radial passage 3c has an opening in the control pressure chamber 13c. The control pressure chamber 13c communicates with the pressure regulation chamber 31 through the radial passage 3c and the axial passage 3b. 
With reference to FIG. 2, the control mechanism 15 includes a bleed passage 15a and a supply passage 15b each serving as a control passage, a control valve 15c, and an orifice 15d. 
The bleed passage 15a is connected to the pressure regulation chamber 31 and the second suction chamber 27b. The pressure regulation chamber 31 communicates with the control pressure chamber 13c through the axial passage 3b and the radial passage 3c. The bleed passage 15a thus allows communication between the control pressure chamber 13c and the second suction chamber 27b. The orifice 15d is formed in the bleed passage 15a to restrict the amount of the refrigerant gas flowing in the bleed passage 15a. 
The supply passage 15b is connected to the pressure regulation chamber 31 and the second discharge chamber 29b. As a result, as in the case of the bleed passage 15a, the control pressure chamber 13c and the second discharge chamber 29b communicate with each other through the supply passage 15b, the axial passage 3b, and the radial passage 3c. In other words, the axial passage 3b and the radial passage 3c each configure a section in the bleed passage 15a and a section in the supply passage 15b, each of which serves as the control passage.
The control valve 15c is arranged in the supply passage 15b. The control valve 15c is capable of adjusting the opening degree of the supply passage 15b in correspondence with the pressure in the second suction chamber 27b. The control valve 15c thus adjusts the amount of the refrigerant gas flowing in the supply passage 15b. A publicly available valve may be employed as the control valve 15c. 
A threaded portion 3d is formed at the distal end of the drive shaft 3. The drive shaft 3 is connected to a non-illustrated pulley or the pulley of a non-illustrated electromagnetic clutch through the threaded portion 3d. 
A pipe (not shown) extending to the evaporator is connected to the inlet 330. A pipe extending to a condenser (neither is shown) is connected to the outlet. The compressor, the evaporator, an expansion valve, and the condenser configure the refrigeration circuit in the air conditioner for a vehicle.
In the compressor having the above-described configuration, the drive shaft 3 rotates to rotate the swash plate 5, thus reciprocating the pistons 9 in the corresponding first and second cylinder bores 21a, 23a. This varies the volume of each first compression chamber 21d and the volume of each second compression chamber 23d in correspondence with the piston stroke. The refrigerant gas is thus drawn from the evaporator into the swash plate chamber 33 via the inlet 330 and sent into the first and second suction chambers 27a, 27b. The refrigerant gas is then compressed in the first and second compression chambers 21d, 23d before being sent into the first and second discharge chambers 29a, 29b. The refrigerant gas is then sent from the first and second discharge chambers 29a, 29b into the condenser through the outlet.
In the meantime, rotation members including the swash plate 5, the ring plate 45, the lug arm 49, and the first pin 47a receive the centrifugal force acting in such a direction as to decrease the inclination angle of the swash plate 5. Through such change of the inclination angle of the swash plate 5, displacement control is carried out by selectively increasing and decreasing the stroke of each piston 9.
Specifically, in the control mechanism 15, when the control valve 15c, which is shown in FIG. 2, reduces the amount of the refrigerant gas flowing in the supply passage 15b, the amount of the refrigerant gas flowing from the pressure regulation chamber 31 into the second suction chamber 27b through the bleed passage 15a is increased. This substantially equalizes the pressure in the control pressure chamber 13c to the pressure in the second suction chamber 27b. As a result, as the centrifugal force acting on the rotation members moves the movable body 13b rearward, the control pressure chamber 13c is reduced in size and thus the inclination angle of the swash plate 5 is decreased.
In other words, as illustrated in FIG. 3, the swash plate 5 pivots about the operation axis M3. The opposite ends of the lug arm 49 pivot about the corresponding first and second pivot axes M1, M2, and the lug arm 49 approaches the flange 43a of the support member 43. This decreases the stroke of each piston 9, thus reducing the suction amount and displacement of the compressor per rotation cycle. The inclination angle of the swash plate 5 shown in FIG. 3 corresponds to the minimum inclination angle in the compressor.
The swash plate 5 of the compressor receives the centrifugal force acting on the weight portion 49a. Thus, the swash plate 5 of the compressor easily moves in such a direction as to decrease the inclination angle. The movable body 13b moves rearward in the axial direction of the drive shaft 3 and the rear end of the movable body 13b is arranged inward to the weight portion 49a. As a result, when the inclination angle of the swash plate 5 of the compressor is decreased, the weight portion 49a overlaps with approximately a half the rear end of the movable body 13b. 
If the control valve 15c illustrated in FIG. 2 increases the amount of the refrigerant gas flowing in the supply passage 15b, the amount of the refrigerant gas flowing from the second discharge chamber 29b into the pressure regulation chamber 31 through the supply passage 15b is increased, in contrast to the case for decreasing the compressor displacement. The pressure in the control pressure chamber 13c is thus substantially equalized with the pressure in the second discharge chamber 29b. This moves the movable body 13b of the actuator 13 forward against the centrifugal force acting on the rotation members. This increases the volume of the control pressure chamber 13c and increases the inclination angle of the swash plate 5.
In other words, referring to FIG. 1, the swash plate 5 pivots about the operation axis M3 in the reverse direction. The opposite ends of the lug arm 49 pivot about the corresponding first and second pivot axes M1, M2 in the reverse directions, correspondingly. The lug arm 49 thus separates from the flange 43a of the support member 43. This increases the stroke of each piston 9, thus increasing the suction amount and displacement of the compressor per rotation cycle. The inclination angle of the swash plate 5 shown in FIG. 1 corresponds to the maximum inclination angle in the compressor.
In this compressor, the swash plate 5 and the drive shaft 3 are coupled to each other by the link mechanism 7, so that the swash plate 5 is located at a position in the swash plate chamber 33 that is closer to the second cylinder bores 23a. Accordingly, when the inclination angle of the swash plate 5 and the stroke of the pistons 9 are maximum in this compressor, the top dead center position of each first piston head 9a is closest to the first valve plate 39, and the top dead center position of the second piston head 9b is closest to the second valve plate 41. On the other hand, as the inclination angle of the swash plate 5 and the stroke of the pistons 9 decrease, the top dead center position of each first piston head 9a is gradually separated from the first valve plate 39. However, the top dead center position of each piston head 9b remains substantially unchanged from the state in which the stroke of each piston 9 is maximum and at the position close to the second valve plate 41.
As described above, when the inclination angle of the swash plate 5 of the compressor is changed, the top dead center position of the second piston head 9b of each piston 9 is scarcely moved, while the top dead center position of the first piston head 9a of the piston 9 is largely moved. Thus, with reference to the swash plate 5, a relatively large space is created in a region in the swash plate chamber 33 where the first cylinder bores 21a are located. Also, with reference to the swash plate 5, the actuator 13 is located in the region in the swash plate chamber 33 where the first cylinder bores 21a are located. Thus, in the compressor, the radial size of the actuator 13 can be increased without increasing the radial size of the housing 1, so that the size of the control pressure chamber 13c is ensured to be large. Accordingly, the movable body 13b is moved in a desirable manner based on fluctuation in the pressure of the refrigerant gas in the swash plate chamber 33 of the compressor.
Also, the link mechanism 7 of the compressor is located on the opposite side of the swash plate 5 from the movable body 13b and in a region where the second cylinder bores 23a are located. When the inclination angle of the swash plate 5 of the compressor is changed, the top dead center position of the second piston head 9b of each piston 9 is scarcely changed. Thus, only a relatively small space can be created in the region where the second cylinder bores 23a are located with reference to the swash plate 5 in the swash plate chamber 33. However, the link mechanism 7 of the compressor only functions to allow the inclination angle of the swash plate 5 to be changed. Also, since the lug arm 49 substantially has an L-shape, the lug arm 49 can be made compact and is ensured to have a sufficient range of pivoting. Accordingly, even though the link mechanism 7 is located in a narrow region in the swash plate chamber 33 where the second cylinder bores 23a are arranged, the link mechanism 7 is allowed to function sufficiently.
Further, since the link mechanism 7 of the compressor is located on the opposite side of the swash plate 5 from the movable body 13b and in a region where the second cylinder bores 23a are located, a large space can be created in the region in the swash plate chamber 33 where the first cylinder bores 21a are located.
Therefore, since the compressor according to the first embodiment is compact, it is possible to achieve an improved mountability to a vehicle and ensure improved displacement control.
Also, in the control mechanism 15 of the compressor, the bleed passage 15a allows communication between the control pressure chamber 13c and the second suction chamber 27b. The supply passage 15b allows communication between the control pressure chamber 13c and the second discharge chamber 29b. The control valve 15c adjusts the opening degree of the supply passage 15b. As a result, the compressor quickly raises the pressure in the control pressure chamber 13c using the high pressure in the second discharge chamber 29b, thus increasing the compressor displacement rapidly.
Further, the swash plate chamber 33 of the compressor is used as a path of the refrigerant gas to the first and second suction chambers 27a, 27b. This brings about a muffler effect. As a result, suction pulsation of the refrigerant gas is reduced to decrease the noise produced by the compressor.
Second Embodiment
A compressor according to a second embodiment of the invention includes a control mechanism 16 illustrated in FIG. 4, instead of the control mechanism 15 of the compressor of the first embodiment. The control mechanism 16 includes a bleed passage 16a and a supply passage 16b each serving as a control passage, a control valve 16c, and an orifice 16d. 
The bleed passage 16a is connected to the pressure regulation chamber 31 and the second suction chamber 27b. This configuration allows the bleed passage 16a to ensure communication between the control pressure chamber 13c and the second suction chamber 27b. The supply passage 16b is connected to the pressure regulation chamber 31 and the second discharge chamber 29b. The control pressure chamber 13c and the pressure regulation chamber 31 thus communicate with the second discharge chamber 29b through the supply passage 16b. The orifice 16d is formed in the supply passage 16b to restrict the amount of the refrigerant gas flowing in the supply passage 16b. 
The control valve 16c is arranged in the bleed passage 16a. The control valve 16c is capable of adjusting the opening degree of the bleed passage 16a in correspondence with the pressure in the second suction chamber 27b. The control valve 16c thus adjusts the amount of the refrigerant flowing in the bleed passage 16a. As in the case of the aforementioned control valve 15c, a publicly available product may be employed as the control valve 16c. The axial passage 3b and the radial passage 3c each configure a section of the bleed passage 16a and a section of the supply passage 16b. The other components of the compressor of the second embodiment are configured identically with the corresponding components of the compressor of the first embodiment. Accordingly, these components are referred to using common reference numerals and detailed description thereof is omitted herein.
In the control mechanism 16 of the compressor, if the control valve 16c decreases the amount of the refrigerant gas flowing in the bleed passage 16a, the flow of refrigerant gas from the second discharge chamber 29b into the pressure regulation chamber 31 via the supply passage 16b and the orifice 16d is promoted. This substantially equalizes the pressure in the control pressure chamber 13c to the pressure in the second discharge chamber 29b. This moves the movable body 13b of the actuator 13 forward against the centrifugal force acting on the rotation members. This increases the volume of the control pressure chamber 13c and increases the inclination angle of the swash plate 5.
In the compressor of the second embodiment, the inclination angle of the swash plate 5 is increased to increase the stroke of each piston 9, thus raising the suction amount and displacement of the compressor per rotation cycle, as in the case of the compressor according to the first embodiment (see FIG. 1).
In contrast, if the control valve 16c illustrated in FIG. 4 increases the amount of the refrigerant gas flowing in the bleed passage 16a, refrigerant gas from the second discharge chamber 29b is less likely to flow into and be stored in the pressure regulation chamber 31 through the supply passage 16b and the orifice 16d. This substantially equalizes the pressure in the control pressure chamber 13c to the pressure in the second suction chamber 27b. The movable body 13b is thus moved rearward by the centrifugal force acting on the rotation body. This reduces the volume of the control pressure chamber 13c, thus decreasing the inclination angle of the swash plate 5.
As a result, by decreasing the inclination angle of the swash plate 5 and thus the stroke of each piston 9, the suction amount and displacement of the compressor per rotation cycle are lowered (see FIG. 3).
As has been described, the control mechanism 16 of the compressor of the second embodiment adjusts the opening degree of the bleed passage 16a by means of the control valve 16c. The compressor thus slowly lowers the pressure in the control pressure chamber 13c using the low pressure in the second suction chamber 27a to maintain desirable driving comfort of the vehicle. The other operations of the compressor of the second embodiment are the same as the corresponding operations of the compressor of the first embodiment.
Although the present invention has been described referring to the first and second embodiments, the invention is not limited to the illustrated embodiments, but may be modified as necessary without departing from the scope of the invention.
For example, in the compressors of the first and second embodiments, refrigerant gas is sent into the first and second suction chambers 27a, 27b via the swash plate chamber 33. However, the refrigerant gas may be drawn into the first and second suction chambers 27a, 27b directly from the corresponding pipe through the inlet. In this case, the compressor should be configured to allow communication between the first and second suction chambers 27a, 27b and the swash plate chamber 33 so that the swash plate chamber 33 corresponds to a low pressure chamber.
The compressors of the first and second embodiments may be configured without the pressure regulation chamber 31.

## Claims

1. A swash plate type variable displacement compressor comprising:
a housing in which a suction chamber, a discharge chamber, a swash plate chamber, and a cylinder bore are formed;
a drive shaft rotationally supported by the housing;
a swash plate rotatable in the swash plate chamber by rotation of the drive shaft;
a link mechanism arranged between the drive shaft and the swash plate, the link mechanism allowing change of an inclination angle of the swash plate with respect to a line perpendicular to the rotation axis of the drive shaft;
a piston reciprocally received in the cylinder bore;
a conversion mechanism that causes the piston to reciprocate in the cylinder bore by a stroke corresponding to the inclination angle of the swash plate through rotation of the swash plate;
an actuator capable of changing the inclination angle of the swash plate; and
a control mechanism that controls the actuator, wherein
the cylinder bore is formed by a first cylinder bore, which is located in a first region facing a first surface of the swash plate, and a second cylinder bore, which is located in a second region facing a second surface of the swash plate,
the piston includes a first head, which reciprocates in the first cylinder bore, and a second head, which is integrated with the first head and reciprocates in the second cylinder bore,
the link mechanism is configured such that, as the inclination angle is changed, a top dead center position of the first head is moved by a greater amount than a top dead center position of the second head,
the actuator is arranged in the swash plate chamber and on a side of the swash plate where the first cylinder bore is located, and is integrally rotational with the drive shaft, and
the actuator includes
a rotation body fixed to the drive shaft,
a movable body, which is coupled to the swash plate and moves along the rotation axis of the drive shaft to be movable relative to the rotation body, and
a control pressure chamber, which is defined by the rotation body and the movable body, wherein an internal pressure of the control pressure chamber is changed such that the movable body is moved.

2. The swash plate type variable displacement compressor according to claim 1, wherein the link mechanism is located in a region on the opposite side of the swash plate from the movable body and where the second cylinder bore is located.

3. The swash plate type variable displacement compressor according to claim 1, wherein
the swash plate chamber includes the first region and the second region, which are partitioned from each other by the swash plate, and the second region is smaller than the first region,
the actuator is arranged in the first region, and
the link mechanism is arranged in the second region.