Double-headed piston type swash plate compressor

Abstract

A double-headed piston type swash plate compressor includes first and second cylinder blocks, a rotation shaft, a double-headed piston, a crank chamber, a drive force transmission member, a swash plate, a movable body, a control pressure chamber, and a support. The control pressure chamber is defined by the movable body in the housing. The control pressure chamber moves the movable body in the axial direction of the rotation shaft. The support is located on the swash plate and supported by the rotation shaft. The drive force transmission member and the movable body are located at a first side of the swash plate in the axial direction of the rotation shaft, and the support is located at a second side of the swash plate. The drive force transmission member, the movable body, and the support set the inclination angle of the swash plate relative to the rotation shaft.

Claims

1. A double-headed piston type swash plate compressor comprising: a first cylinder block and a second cylinder block that form a housing, wherein the first cylinder block includes a first cylinder bore, and the second cylinder block includes a second cylinder bore; a rotation shaft; a double-headed piston accommodated in the first cylinder bore and the second cylinder bore, wherein the double-headed piston is movable back and forth in the first cylinder bore and the second cylinder bore; a crank chamber; a drive force transmission member accommodated in the crank chamber and fixed to the rotation shaft, wherein the drive force transmission member is rotatable integrally with the rotation shaft; a swash plate accommodated in the crank chamber, wherein the swash plate is rotated when receiving drive force from the rotation shaft through the drive force transmission member, the swash plate is inclined at an angle relative to the rotation shaft that is changeable, the swash plate is coupled to the double-headed piston, and the double headed piston moves back and forth with a stroke that is in accordance with the inclination angle of the swash plate; a movable body coupled to the swash plate, wherein the movable body is capable of changing the inclination angle of the swash plate; a control pressure chamber defined by the movable body in the housing, wherein the control pressure chamber draws in control gas that changes the pressure in the control pressure chamber to move the movable body in an axial direction of the rotation shaft; and a support located on the swash plate and supported by the rotation shaft, wherein the drive force transmission member and the movable body are located at a first side of the swash plate in the axial direction of the rotation shaft, the support is located at a second side of the swash plate that is opposite from the first side in the axial direction of the rotation shaft, the swash plate is supported by the rotation shaft through the drive force transmission member, the movable body, and the support, the inclination angle of the swash plate relative to the rotation shaft is set by the drive force transmission member, the movable body, and the support, the drive force transmission member includes a main body, and two arms which project from an end face of the main body toward the swash plate, a bottom portion defining a first guide surface extends between the two arms, the swash plate includes a projection that projects from the swash plate toward the drive force transmission member, the projection is located between the two arms and slides along the first guide surface, and when the swash plate is inclined at a minimum inclination angle, at least a part of the first guide surface is arranged inside the movable body.

2. The double-headed piston type swash plate compressor according to claim 1, wherein the rotation shaft includes a second guide surface that guides the support as the inclination angle of the swash plate changes, the second guide surface guides the support so that the center of the swash plate and an axis of the rotation shaft coincide with each other when the swash plate is inclined at a maximum inclination angle, and the second guide surface guides the support so that the center of the swash plate is located toward the support from the axis of the rotation shaft when the swash plate is inclined at the minimum inclination angle.

3. The double-headed piston type swash plate compressor according to claim 2, wherein the second guide surface includes a slope that guides the support away from the axis of the rotation shaft as the movable body moves in a direction in which the inclination angle of the swash plate increases from the minimum inclination angle, the slope is configured so that a sloped angle of the slope gradually decreases in a portion where the support and the slope come into contact as the movable body moves in a direction that increases the inclination angle of the swash plate; and the sloped angle of the slope is the angle of the slope relative to the axis of the rotation shaft.

4. The double-headed piston type swash plate compressor according to claim 1, wherein the first guide surface is configured to have a sloped angle that varies in a portion where the projection and the first guide surface come into contact as the inclination angle of the swash plate changes, and the sloped angle of the first guide surface is the angle of the first guide surface relative to an axis of the rotation shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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:

(2) FIG. 1 is a cross-sectional side view showing a double-headed piston type swash plate compressor according to a first embodiment of the present invention;

(3) FIG. 2 is a schematic diagram showing the relationship of a control pressure chamber, a pressure regulation chamber, a suction chamber, and a discharge chamber in FIG. 1;

(4) FIG. 3 is a cross-sectional side view showing the compressor of FIG. 1 when a swash plate is located at a minimum inclination angle position;

(5) FIG. 4 is a partial, cross-sectional side view showing the compressor of FIG. 1 when the swash plate is located at a maximum inclination angle position;

(6) FIG. 5 is a partial, cross-sectional side view showing the compressor of FIG. 1 when the swash plate is located at the minimum inclination angle position;

(7) FIG. 6 is a graph showing movement of the center of the swash plate in FIG. 1;

(8) FIG. 7 is a graph showing movement of a first end and movement of a second end of the swash plate in FIG. 1;

(9) FIG. 8 is a partial, cross-sectional side view showing a double-headed piston type swash plate compressor according to a second embodiment of the present invention when the swash plate is located at the minimum inclination position;

(10) FIG. 9 is a partial, cross-sectional side view showing the compressor of FIG. 8 when the swash plate is located at the maximum inclination position;

(11) FIG. 10 is a graph showing the relationship of the pressure of the control pressure chamber and the inclination angle of the swash plate in FIG. 8;

(12) FIG. 11 is a partial, cross-sectional side view showing a double-headed piston type swash plate compressor according to a third embodiment of the present invention;

(13) FIG. 12 is a graph showing the relationship of the pressure of the control pressure chamber and the inclination angle of the swash plate in FIG. 11;

(14) FIG. 13 is a cross-sectional side view showing a prior art example variable displacement type swash plate compressor; and

(15) FIG. 14 is a cross-sectional side view showing the variable displacement type swash plate compressor of FIG. 13 when a swash plate is located at a maximum inclination angle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

(16) A first embodiment of the present invention will now be described with reference to FIGS. 1 to 7. A double-headed piston type swash plate compressor (hereinafter simply referred to as the compressor) is installed in a vehicle.

(17) The left side, right side, upper side, and lower side as viewed in FIG. 1 respectively correspond to a first side (front side), second side (rear side), third side (upper side), and fourth side (lower side). A compressor 10 includes a housing 11 formed by a first cylinder block 12 located at the first side, a second cylinder block 13 located at the second side, a front housing 14 coupled to the first cylinder block 12, and a rear housing 15 coupled to the second cylinder block 13. The first cylinder block 12 and the second cylinder block 13 are coupled to each other.

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

(19) A suction chamber 14a and a discharge chamber 14b are defined between the front housing 14 and the first valve-port formation body 16. The discharge chamber 14b is located at the radially outer side of the suction chamber 14a. A suction chamber 15a and a discharge chamber 15b are defined between the rear housing 15 and the second valve-port formation body 17. The rear housing 15 includes a pressure regulation chamber 15c. The pressure regulation chamber 15c is located at a central portion of the rear housing 15. The suction chamber 15a is located at the radially outer side of the pressure regulation chamber 15c. The discharge chamber 15b is located at the radially outer side of the suction chamber 15a. A discharge passage (not shown) connects the discharge chambers 14b and 15b. The discharge passage is connected to an external refrigerant circuit (not shown).

(20) The first valve-port formation body 16 includes a suction port 16a, which is in communication with the suction chamber 14a, and a discharge port 16b, which is in communication with the discharge chamber 14b. The second valve-port formation body 17 includes a suction port 17a, which is in communication with the suction chamber 15a, and a discharge port 17b, which is in communication with the discharge chamber 15b. Each of the suction ports 16a and 17a includes a suction valve mechanism (not shown), and each of the discharge ports 16b and 17b includes a discharge valve mechanism (not shown).

(21) A rotation shaft 21 is held to be rotatable in the housing 11. The rotation shaft 21 includes a front end portion inserted into a shaft hole 12h extending through the first cylinder block 12. The front end portion of the rotation shaft 21 is located at the front side of the housing 11 and is defined by the portion of the rotation shaft 21 near the front end in the direction of the axis L (axial direction of rotation shaft 21). The front end of the rotation shaft 21 is located in the front housing 14. Further, the rotation shaft 21 includes a rear end portion inserted into a shaft hole 13h extending through the second cylinder block 13. The rear end portion of the rotation shaft 21 is located at the rear side of the housing 11 and is defined by the portion of the rotation shaft 21 near the rear end in the axial direction of rotation shaft 21. The rear end of the rotation shaft 21 is located in the pressure regulation chamber 15c.

(22) The front end portion of the rotation shaft 21 is supported to be rotatable by the first cylinder block 12 in the shaft hole 12h. The rear end portion of the rotation shaft 21 is supported to be rotatable by the second cylinder block 13 in the shaft hole 13h. A shaft seal 22, which is of a lip seal type, is arranged between the front housing 14 and the rotation shaft 21.

(23) 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, which is rotated by drive force from the rotation shaft 21. The swash plate 23 is inclinable relative to the axial direction of the rotation shaft 21. The swash plate 23 includes an insertion hole 23a through which the rotation shaft 21 can be inserted. The swash plate 23 includes an upper half located at the upper side of the center O and a lower half located at the lower side of the center O.

(24) The first cylinder block 12 includes first cylinder bores 12a formed around the rotation shaft 21. FIG. 1 shows only one first cylinder bore 12a. Each first cylinder bore 12a extends through the first cylinder bore 12a in the axial direction. Further, each cylinder bore 12a is in communication with the suction chamber 14a through the suction port 16a and in communication with the discharge chamber 14b through the discharge port 16b. The second cylinder block 13 includes second cylinder bores 13a formed around the rotation shaft 21. FIG. 1 shows only one second cylinder bore 13a. Each second cylinder bore 13a extends through the second cylinder bore 13a in the axial direction. Further, each second cylinder bore 13a is in communication with the suction chamber 15a through the suction port 17a and in communication with the discharge chamber 15b through the discharge port 17b. Corresponding ones of the first and second cylinder bores 12a and 13a are paired at the front and rear of the compressor 10. A double-headed piston 25 is accommodated in each of the paired first and second cylinder bores 12a and 13a to be movable back and forth in the axial direction of the compressor 10.

(25) Two shoes 26 couple each double-headed piston 25 to the peripheral portion of the swash plate 23. The shoes 26 convert rotation of the swash plate 23, which is rotated by the rotation shaft 21, to linear reciprocation of the double-headed piston 25. The double-headed piston 25 and the first valve-port formation body 16 define a first compression chamber 20a in each first cylinder bore 12a. The double-headed piston 25 and the second valve-port formation body 17 define a second compression chamber 20b in each second cylinder bore 13a.

(26) The first cylinder block 12 includes a first large diameter hole 12b, which is in communication 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. The crank chamber 24 and the suction chamber 14a are in communication through a suction passage 12c, which extends through the first cylinder block 12 and the first valve-port formation body 16.

(27) The second cylinder block 13 includes a second large diameter hole 13b, which is in communication 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. The crank chamber 24 and the suction chamber 15a are in communication through a suction passage 13c, which extends through the second cylinder block 13 and the second valve-port formation body 17.

(28) The circumferential wall of the second cylinder block 13 includes an inlet 13s, which is connected to an external refrigerant circuit. Refrigerant gas is drawn into the crank chamber 24 through the inlet 13s. Then, the refrigerant gas is drawn through the suction passages 12c and 13c into the suction chambers 14a and 15a. In this manner, the suction chambers 14a and 15a and the crank chamber 24 form a suction pressure region. The pressure is substantially equal throughout the suction pressure region.

(29) An annular flange 21f projects from the rotation shaft 21 in the first large diameter hole 12b. A thrust bearing 27a is arranged between the flange 21f and the first cylinder block 12 in the axial direction of the rotation shaft 21.

(30) An annular drive force transmission member 31 is fixed to the rotation shaft 21 between the flange 21f and the swash plate 23. The drive force transmission member 31 is rotatable integrally with the rotation shaft 21. The drive force transmission member 31 includes an annular main body 31a and two arms 31b, which project from an end face of the main body 31a toward the swash plate 23. A bottom portion defining a guide surface 31c extends between the two arms 31b.

(31) A projection 23c projects from the upper half of the swash plate 23 toward the drive force transmission member 31. The projection 23c is located between the two arms 31b. The projection 23c is movable along the guide surface 31c between the two arms 31b. The projection 23c includes a distal end portion that is capable of sliding on the guide surface 31c. The projection 23c and the guide surface 31c cooperate to allow the swash plate 23 to incline in the axial direction of the rotation shaft 21. The two arms 31b transmit drive force from the rotation shaft 21 to the projection 23c. This rotates the swash plate 23. When inclining the swash plate 23 in the axial direction of the rotation shaft 21, the distal end portion of the projection 23c slides on the guide surface 31c.

(32) A movable body 32 is arranged between the flange 21f and the drive force transmission member 31. The movable body 32 is tubular and has a closed end. Further, the movable body 32 is movable in the axial direction of the rotation shaft 21 relative to the drive force transmission member 31. The drive force transmission member 31 and the movable body 32 are accommodated in the first cylinder block 12 and the second cylinder block 13 in a region located at the inner side of where the double-headed pistons 25 reciprocate in the radial direction of the rotation shaft 21. The drive force transmission member 31 and the movable body 32 are arranged at the front side of the swash plate 23 in the axial direction of the rotation shaft 21.

(33) The movable body 32 includes an annular end portion 32a and a tubular portion 32b. The end portion 32a includes an insertion hole 32e through which the rotation shaft 21 is inserted. The tubular portion 32b extends from the outer circumference of the end portion 32a in the axial direction of the rotation shaft 21 and covers the rotation shaft 21. The movable body 32 moves in the axial direction of the rotation shaft 21 as an inner circumferential surface 321b of the tubular portion 32b slides along an outer circumferential surface 311a of the main body 31a of the drive force transmission member 31. The movable body 32 is rotatable integrally with the rotation shaft 21. A seal 33 seals the gap between the inner circumferential surface 321b of the tubular portion 32b and the main body 31a of the drive force transmission member 31.

(34) A protrusion 32f projects from the end portion 32a where the rotation shaft 21 is inserted toward the drive force transmission member 31 in the axial direction of the rotation shaft 21. An inner circumferential surface of the protrusion 32f includes an annular holding groove 32d. The holding groove 32d receives a seal 34 that seals the gap between the wall of the insertion hole 32e and the rotation shaft 21. The drive force transmission member 31 and the movable body 32 define a control pressure chamber 35.

(35) The rotation shaft 21 includes a first in-shaft passage 21a, which extends in the axial direction of the rotation shaft 21. The first in-shaft passage 21a includes a rear end that opens to the pressure regulation chamber 15c. Further, the rotation shaft 21 includes a second in-shaft passage 21b, which extends in the radial direction of the rotation shaft 21. The second in-shaft passage 21b includes a rear end that is in communication with a distal end of the first in-shaft passage 21a. The control pressure chamber 35 and the pressure regulation chamber 15c are in communication through the first in-shaft passage 21a and the second in-shaft passage 21b.

(36) As shown in FIG. 2, the pressure regulation chamber 15c and the suction chamber 15a are in communication through a bleeding passage 36. The bleeding passage 36 includes an orifice 36a that throttles the flow rate of the refrigerant gas flowing through the bleeding passage 36. The pressure regulation chamber 15c and the discharge chamber 15b are in communication through a gas supplying passage 37. An electromagnetic control valve 37s is arranged in the gas supplying passage 37. The control valve 37s is capable of regulating the open amount of the gas supplying passage 37 based on the pressure of the suction chamber 15a. The control valve 37s regulates the flow rate of the refrigerant gas flowing through the gas supplying passage 37.

(37) The pressure in the control pressure chamber 35 is adjusted by drawing refrigerant gas from the discharge chamber 15b into the control pressure chamber 35 through the gas supplying passage 37, the pressure regulation chamber 15c, the first in-shaft passage 21a, and the second in-shaft passage 21b and discharging refrigerant gas from the control pressure chamber 35 into the suction chamber 15a through the second in-shaft passage 21b, the first in-shaft passage 21a, the pressure regulation chamber 15c, and the bleeding passage 36. The pressure difference of the control pressure chamber 35 and the crank chamber 24 moves the movable body 32 relative to the drive force transmission member 31 in the axial direction of the rotation shaft 21. Thus, the refrigerant gas drawn into the control pressure chamber 35 moves the movable body 32 in the axial direction of the rotation shaft 21.

(38) As shown in FIG. 1, a coupling portion 32c projects from the distal end of the tubular portion 32b of the movable body 32 toward the swash plate 23. The coupling portion 32c includes an elongated insertion hole 32h into which a cylindrical pin 41 is insertable. Further, the lower half of the swash plate 23 includes a circular insertion hole 23h into which the pin 41 is insertable. The pin 41 is fitted to the insertion hole 23h and restrained by the swash plate 23. The pin 41 couples the coupling portion 32c to the lower half of the swash plate 23. The pin 41 is fitted into the insertion hole 23h and held on the swash plate 23. The pin 41 is held to be movable in the insertion hole 32h.

(39) A tubular member 42 is arranged integrally on the rear surface of the swash plate 23, that is, the end face of the swash plate 23 opposite to the drive force transmission member 31. The tubular member 42 includes a through hole 42h that is in communication with the insertion hole 23a of the swash plate 23. The tubular member 42 includes two insertion holes 42a that open in the through hole 42h. A cylindrical abutment pin 43 is inserted through the two insertion holes 42h. The abutment pin 43 bridges different wall portions of the through hole 42h so as to extend across the interior of the through hole 42h. The abutment pin 43 is located at the rear side of the swash plate 23 in the axial direction of the rotation shaft 21.

(40) The rotation shaft 21 includes a guide surface 44 that guides the abutment pin 43 as the inclination angle of the swash plate 23 changes. The abutment pin 43 slides and moves on the guide surface 44. The guide surface 44 is linearly sloped to approach the axis L of the rotation shaft 21 at locations farther from the swash plate 23.

(41) In the compressor 10, a decrease in the open amount of the control valve 37s reduces the amount of refrigerant gas drawn into the control pressure chamber 35 from the discharge chamber 15b through the gas supplying passage 37, the pressure regulation chamber 15c, the first in-shaft passage 21a, and the second in-shaft passage 21b. The discharge of refrigerant gas from the control pressure chamber 35 to the suction chamber 15a through the second in-shaft passage 21b, the first in-shaft passage 21a, the pressure regulation chamber 15c, and the bleeding passage 36 results in the pressure of the control pressure chamber 35 approaching the pressure of the suction chamber 15a. A decrease in the pressure difference between the control pressure chamber 35 and the crank chamber 24 moves the movable body 32 in the axial direction of the rotation shaft 21 so that the end portion 32a approaches the drive force transmission member 31.

(42) Referring to FIG. 3, the pin 41 moves inside the insertion hole 32h so that the projection 23c approaches the rotation shaft 21 on the guide surface 31c. Further, the abutment pin 43 moves along the guide surface 44 to approach the axis L of the rotation shaft 21. As a result, the lower half of the swash plate 23 is moved away from the drive force transmission member 31. This decreases the inclination angle of the swash plate 23. Thus, the stroke of the double-headed pistons 25 decreases and the displacement of the compressor 10 decreases.

(43) An increase in the open amount of the control valve 37s increases the amount of refrigerant gas drawn into the control pressure chamber 35 from the discharge chamber 15b through the gas supplying passage 37, the pressure regulation chamber 15c, the first in-shaft passage 21a, and the second in-shaft passage 21b. Thus, the pressure of the control pressure chamber 35 approaches the pressure of the discharge chamber 15b. The increase in the pressure difference between the control pressure chamber 35 and the crank chamber 24 moves the movable body 32 in the axial direction of the rotation shaft 21 so that the end portion 32a moves away from the drive force transmission member 31.

(44) Referring to FIG. 1, the pin 41 is moved in the insertion hole 32h, and the projection 23c is moved on the guide surface 31c away from the rotation shaft 21. Further, the abutment pin 43 is moved along the guide surface 44 away from the axis L of the rotation shaft 21. As a result, the lower half of the swash plate 23 is moved toward the drive force transmission member 31. This increases the inclination angle of the swash plate 23. Thus, the stroke of the double-headed pistons 25 increases and the displacement of the compressor 10 increases. In this manner, by permitting movement of the movable body 32 in the axial direction of the rotation shaft 21, the inclination angle of the swash plate 23 is changed in accordance with changes in the internal pressure of the control pressure chamber 35.

(45) Referring to FIG. 4, when the swash plate 23 is located at position corresponding to the maximum inclination max, the abutment pin 43 is guided by the guide surface 44 so that the center O of the swash plate 23 and the axis of the rotation shaft 21 coincide with each other. Referring to FIG. 5, when the swash plate 23 is located at a position corresponding to the minimum inclination min, the abutment pin 43 is guided by the guide surface 44 so that the center O of the swash plate 23 is located toward the abutment pin 43 from the axis L of the rotation shaft 21, that is, at the lower side of the axis L of the rotation shaft 21 in the present embodiment. In this manner, the sloped angle of the guide surface 44 is set so that the center O of the swash plate 23 and the axis of the rotation shaft 21 coincide with each other when the swash plate 23 is located at the position corresponding to the maximum inclination max, and the center O of the swash plate 23 is located toward the abutment pin 43 from the axis L of the rotation shaft 21 when the swash plate 23 is located at the position corresponding to the minimum inclination min.

(46) The operation of the first embodiment will now be described.

(47) Referring to FIG. 4, each double-headed piston 25 produces compression reaction forces P1 and P2 that act on the swash plate 23 in the compressor 10. The compression reaction forces P1 and P2 act on the swash plate 23 to change the inclination angle of the swash plate 23. When the inclination angle of the swash plate 23 is between the maximum inclination max and the minimum inclination min, the compression reaction force P1 is greater than the compression reaction force P2. The swash plate 23 tends to move in the radial direction of the rotation shaft 21 (upper direction as viewed in FIG. 4) when receiving the compression reaction forces P1 and P2. Here, force F1 from the swash plate 23 acts on the guide surface 44 of the rotation shaft 21 via the abutment pin 43. In this manner, the abutment pin 43 serves as a support that is supported by the rotation shaft 21.

(48) On the outer surface of the rotation shaft 21, the guide surface 44 contacts the swash plate 23. However, surfaces of the rotation shaft 21 other than the guide surface 44 do not contact the swash plate 23. The wall surface of the insertion hole 23a includes a portion 231a located toward the guide surface 44. The insertion hole 23a is formed so that the portion 231a does not contact the rotation shaft 21. As shown in FIGS. 4 and 5, the portion 231a does not contact the rotation shaft 21 when the swash plate 23 has any inclination angle between the maximum inclination angle max and the minimum inclination angle min. The swash plate 23 is supported by the rotation shaft 21 through the drive force transmission member 31, the movable body 32, and the abutment pin 43. The inclination angle of the swash plate 23 relative to the rotation shaft 21 is set by the drive force transmission member 31, the movable body 32, and the abutment pin 43.

(49) Due to the balance of forces, the reaction force F2 of the force F1, which acts on the guide surface 44 of the rotation shaft 21, acts on the swash plate 23 from the guide surface 44 through the abutment pin 43. The moment acting about the portion where the drive force transmission member 31 and the swash plate 23 are coupled, that is, the portion where the projection 23c and the guide surface 31c are in contact, will now be discussed. The reaction force F2 increases as the portion where the reaction force F2 acts on becomes closer to the portion where the drive force transmission member 31 and the swash plate 23 are coupled.

(50) In the present embodiment, the abutment pin 43 is located at the rear side of the swash plate 23 in the axial direction of the rotation shaft 21. That is, the abutment pin 43 and the drive force transmission member 31 are located on opposite sides of the swash plate 23 in the axial direction of the rotation shaft 21. This separates the portion where the reaction force F2 acts on as far as possible from the coupling portion of the drive force transmission member 31 and the swash plate 23. Further, the reaction force F2 is minimized in the moment of the force acting on the swash plate 23 about the coupling portion of the drive force transmission member 31 and the swash plate 23. Thus, the inclination angle of the swash plate 23 is smoothly changed.

(51) Further, in the axial direction of the rotation shaft 21, the abutment pin 43 is located on one side of the swash plate 23, and the drive force transmission member 31 and the movable body 32 are located on the opposite side of the swash plate 23. Thus, in comparison with when the abutment pin 43 is located at the front side of the swash plate 23 in the axial direction of the rotation shaft 21, components may be laid out in a scattered manner. This allows for reduction in the area occupied by the drive force transmission member 31 and the movable body 32 at the radially inner side of the region where the double-headed pistons 25 reciprocate.

(52) Further, the abutment pin 43 is located in a portion separated from the drive force transmission member 31 and the movable body 32. This ensures an area in the axial direction of the rotation shaft 21 where the abutment pin 43 may be arranged. Thus, the abutment pin 43 is greatly separated from the coupling portion of the drive force transmission member 31 and the swash plate 23.

(53) In the present embodiment, the upper end of the swash plate 23 is located farthest from the axis in the upper half of the swash plate 23. More specifically, the upper end of the swash plate 23 is the portion of the swash plate 23 where the outer diameter is largest and is located on the opposite side of the abutment pin 43 with respect to the rotation shaft 21. Distance H1 is the distance between the upper end of the swash plate 23 and the axis L of the rotation shaft 21. The lower end of the swash plate 23 is located farthest from the axis in the lower half of the swash plate 23. More specifically, the lower end of the swash plate 23 is the portion where the outer diameter is largest and located on the lower half of the swash plate 23 at the same side as the abutment pin 43 with respect to the rotation shaft 21. Distance H2 is the distance between the lower end of the swash plate 23 and the axis L of the rotation shaft 21. A change in the distance H1 and the distance H2 changes the inclination angle of the swash plate 23.

(54) In FIG. 6, solid line L10 shows movement of the center O of the swash plate 23 relative to the axis L of the rotation shaft 21 when the inclination angle of the swash plate 23 changes.

(55) An example in which the abutment pin 43 guides the guide surface 44 under a situation in which the center O of the swash plate 23 is located above the axis L of the rotation shaft 21, that is, at the opposite side of the abutment pin 43 when the swash plate 23 is located at a position corresponding to the maximum inclination position max, and the center O of the swash plate 23 and the axis of the rotation shaft 21 coincide with each other when the swash plate 23 is located at a position corresponding to the minimum inclination position min will now be discussed. In this case, when the inclination angle of the swash plate 23 is changing, the center O of the swash plate 23 is greatly separated toward the upper side from the axis L of the rotation shaft 21.

(56) This results in the maximum distance between the upper end of the swash plate 23 and the axis L being greater than the maximum distance between the lower end of the swash plate 23 and the axis L. Consequently, when the upper end of the swash plate 23 is most separated from the axis L, the swash plate 23 may interfere with the double-headed pistons 25. Thus, to avoid interference between the swash plate 23 and each double-headed piston 25, a cutout portion (recess) needs to be formed in the double-headed piston 25 near the swash plate 23.

(57) In the present embodiment, the abutment pin 43 is guided by the guide surface 44 so that the center O of the swash plate 23 and the axis of the rotation shaft 21 coincide with each other when the swash plate 23 is located at the position corresponding to the maximum inclination angle max and the center O of the swash plate 23 is located at the lower side of the axis L, that is, toward the abutment pin 43, when the swash plate 23 is located at the position corresponding to the minimum inclination angle min. Thus, as shown by the sold line L10 in FIG. 6, when the inclination angle of the swash plate 23 changes, the center O of the swash plate 23 is not greatly separated to the upper side from the axis L of the rotation shaft 21.

(58) In FIG. 7, solid line L11 indicates changes in the distance H1 when the inclination angle of the swash plate 23 changes, and broken line L12 shows changes in the distance H2 when the inclination angle of the swash plate 23 changes.

(59) As shown in FIG. 7, the maximum value of the distance H1 (maximum distance between the upper end of the swash plate 23 and the axis L of the rotation shaft 21) and the maximum value of the distance H2 (maximum distance between the lower end of the swash plate 23 and the axis L of the rotation shaft 21) are both Hx and the same. This eliminates the need to form a cutout portion in each double-headed piston 25 near the swash plate 23.

(60) The first embodiment has the advantages described below.

(61) (1) The abutment pin 43 receives reaction force F2 that acts on the swash plate 23 from the rotation shaft 21. The abutment pin 43 is located at the rear side of the swash plate 23 in the axial direction of the rotation shaft 21. That is, the abutment pin 43 and the drive force transmission member 31 are arranged on opposite sides of the swash plate 23 in the axial direction of the rotation shaft 21. Thus, when reaction force F2 from the rotation shaft 21 acts on the swash plate 23, the portion where the reaction force F2 acts on is separated as far as possible from the coupling portion of the drive force transmission member 31 and the swash plate 23. When taking into consideration moment balancing of the force applied to the swash plate 23 about the coupling portion of the drive force transmission member 31 and the swash plate 23, the reaction force F2 acting on the swash plate 23 may be minimized. Thus, the inclination angle of the swash plate 23 may be smoothly changed. Further, the abutment pin 43 is arranged on the opposite side of the drive force transmission member 31 and the movable body 32 from the swash plate 23 in the axial direction of the rotation shaft 21. Hence, the area occupied by the drive force transmission member 31 and the movable body 32 at the radially inner side of the region where the double-headed pistons 25 reciprocate may be reduced in size compared to when the abutment pin 43 is located at the front side of the swash plate 23 in the axial direction of the rotation shaft 21. As a result, the inclination angle of the swash plate 23 may be smoothly changed while limiting enlargement in the size of the compressor 10.

(62) (2) The rotation shaft 21 includes the guide surface 44 that guides the abutment pin 43 when the inclination angle of the swash plate 23 changes. The guide surface 44 is formed to guide the abutment pin 43 so that the center O of the swash plate 23 and the axis of the rotation shaft 21 coincide with each other when the swash plate 23 is located at a position corresponding to the maximum inclination angle max and the center O of the swash plate 23 is located closer to the abutment pin 43 than the axis L of the rotation shaft 21 when the swash plate 23 is located at a position corresponding to the minimum inclination angle min. Thus, the center O of the swash plate 23 does not greatly move away from the axis L of the rotation shaft 21 toward the side opposite to the abutment pint 43 from the rotation shaft 21 when the inclination angle of the swash plate 23 is being changed. This eliminates the need for the formation of a cutout portion in each double-headed piston 25 to avoid interference of the swash plate 23 with the double-headed piston 25. Further, the strength of the double-headed piston 25 may be ensured.

Second Embodiment

(63) A second embodiment of the present invention will now be described with reference to FIGS. 8 to 10. In the description hereafter, like or same reference numerals are given to those components that are the same as the corresponding components of the first embodiment. Such components will not be described in detail.

(64) Referring to FIGS. 8 and 9, the guide surface 44 includes a slope 44a that guides the abutment pin 43 so that the abutment pin 43 moves away from the axis L of the rotation shaft 21 as the movable body 32 moves in the direction in which the inclination angle of the swash plate 23 increases from the minimum inclination angle min. The slope 44a includes a portion, which curves in an arcuate manner so that the sloped angle of the slope 44a relative to the axis L of the rotation shaft 21 gradually decreases. In the second embodiment, the sloped angle of the slope 44a gradually decreases from the rear side to the front side along the axis L of the rotation shaft 21.

(65) The operation of the second embodiment will now be described.

(66) In the contact portion of the abutment pin 43 and the slope 44a, force F3 from the swash plate 23 acts on the slope 44a in the normal direction of the slope 44a through the abutment pin 43. In the contact portion of the slope 44a and the abutment pin 43, due to the balance of forces, force F4, which is the reaction force of force F3, from the slope 44a acts on the swash plate 23 through the abutment pin 43. The force F4 is divided into force F4y, which exerts in a direction (vertical direction) perpendicular to the movement direction of the movable body 32, and force F4x, which exerts along the movement direction (horizontal direction) of the movable body 32.

(67) When controlling the inclination angle of the swash plate 23 under a situation in which the inclination angle of the swash plate 23 is close to the minimum inclination angle min, the pressure of the control pressure chamber 35 is close to the suction pressure. The pressure in the control pressure chamber 35 does not become lower than the suction pressure. Accordingly, if the necessary pressure of the control pressure chamber 35 that allows for the swash plate 23 to have the inclination angle close to the minimum inclination angle min is set to be lower than the suction pressure, the swash plate 23 cannot have the inclination angle close to the minimum inclination angle min.

(68) Referring to FIG. 8, the force F4x is transmitted from the slope 44a to the movable body 32 through the abutment pin 43 and the swash plate 23. The force transmitted to the movable body 32 may obstruct movement of the movable body 32 when the movable body 32 moves in a direction that increases the inclination angle of the swash plate 23 from the minimum inclination angle min. Thus, the movable body 32 may not be moved unless the pressure of the control pressure chamber 35 is increased to a relatively high value.

(69) In FIG. 10, solid line L13 shows the relationship of the pressure of the control pressure chamber 35 and the inclination angle of the swash plate 23 in the structure of the second embodiment illustrated in FIG. 8. Further, in FIG. 10, broken line L14 shows the relationship of the pressure of the control pressure chamber 35 and the inclination angle of the swash plate 23 in the structure of the first embodiment. In the first embodiment, as described above, the guide surface 44 is linearly sloped to approach the axis L of the rotation shaft 21 at locations farther from the swash plate 23.

(70) When the inclination angle of the swash plate 23 is close to the minimum inclination angle min, the force F4x of the second embodiment is greater than the similar force in the first embodiment, that is, the force exerting in the movement direction of the movable body 32 that acts on the contact portion of the guide surface 44 and the abutment pin 43. As a result, as shown in FIG. 10, the necessary pressure of the control pressure chamber 35 that allows for the swash plate 23 to have the inclination angle close to the minimum inclination angle min is set to be higher than the suction pressure. Accordingly, the swash plate 23 can have the inclination angle close to the minimum inclination angle min. That is, the configuration according to the second embodiment improves the controllability of the swash plate 23.

(71) When the swash plate 23 controls the inclination angle of the swash plate 23 under a situation in which the inclination angle of the swash plate 23 is close to the maximum inclination angle max, the pressure of the control pressure chamber 35 is close to the discharge pressure. The pressure in the control pressure chamber 35 does not become higher than the discharge pressure. Accordingly, if the necessary pressure of the control pressure chamber 35 that allows for the swash plate 23 to have the inclination angle close to the maximum inclination angle max is set to be higher than the discharge pressure, the swash plate 23 cannot have the inclination angle close to the maximum inclination angle max.

(72) As shown in FIGS. 8 and 9, the sloped angle of the slope 44a gradually decreases. Thus, as shown in FIG. 9, the force F4x decreases as the movable body 32 moves in the direction in which the sloped angle of the swash plate 23 increases. As a result, when the movable body 32 moves in the direction in which the inclination angle of the swash plate 23 increases, the force that obstructs the movement of the movable body 32 becomes small. This allows for movement of the movable body 32 even when the pressure of the control pressure chamber 35 used to move the movable body 32 is relatively small.

(73) When the inclination angle of the swash plate 23 is close to the maximum inclination angle max, the force F4x of the second embodiment is smaller than the similar force in the first embodiment, that is, the force exerting in the movement direction of the movable body 32 that acts on the contact portion of the guide surface 44 and the abutment pin 43. As a result, as shown in FIG. 10, the necessary pressure of the control pressure chamber 35 that allows for the swash plate 23 to have the inclination angle close to the maximum inclination angle max is set to be lower than the discharge pressure. Accordingly, the swash plate 23 can have the inclination angle close to the maximum inclination angle max. That is, the configuration according to the second embodiment improves the controllability of the swash plate 23.

(74) Accordingly, in addition to advantages (1) and (2) of the first embodiment, the second embodiment has the advantages described below.

(75) (3) The guide surface 44 includes the slope 44a that guides the abutment pin 43 away from the axis L of the rotation shaft 21 as the movable body 32 moves in the direction in which the inclination angle of the swash plate 23 increases from the minimum inclination angle min. As the movable body 32 moves in the direction in which the inclination angle of the swash plate 23 increases, the sloped angle of the slope 44a gradually decreases at the contact portion between the abutment pin 43 and the slope 44a. In the second embodiment, the sloped angle of the slope 44a at the contact portion between the abutment pin 43 and the slope 44a when the swash plate 23 has the minimum inclination angle min increases relative to that in the first embodiment. In this case, the force F4x in the second embodiment increases relative to that in the first embodiment. The force F4x is transmitted from the slope 44a to the movable body 32 through the abutment pin 43 and the swash plate 23. The force F4x transmitted to the movable body 32 may obstruct the movement of the movable body 32 when moving the movable body 32 in the direction that increases the inclination angle of the swash plate 23 from the minimum inclination angle min. Thus, in the second embodiment, the movable body 32 cannot be moved unless the pressure of the control pressure chamber 35 is increased relative to that in the first embodiment. As a result, as shown in FIG. 10, the necessary pressure of the control pressure chamber 35 that allows for the swash plate 23 to have the inclination angle close to the minimum inclination angle min is set to be higher than that in the first embodiment. That is, in the second embodiment, adjustment of the inclination angle of the inclined portion 44a enables to vary the necessary pressure of the control pressure chamber 35 that allows for the swash plate 23 to have the intended inclination angle.

(76) Accordingly, the second embodiment overcomes the effects due to the design conditions for the structural members of the compressor that would be taken into consideration when determining the necessary pressure of the control pressure chamber 35 that allows for the swash plate 23 to have the intended inclination angle. Second embodiment improves the flexibility in the design of the compressor.

(77) (4) As the movable body 32 moves in the direction in which the inclination angle of the swash plate 23 increases, the sloped angle of the slope 44a gradually decreases at the contact portion between the abutment pin 43 and the slope 44a. This decreases the force F4x acting on the contact portion between the slope 44a and the abutment pin 43 as the movable body 32 moves in the direction in which the inclination angle of the swash plate 23 increases. As a result, when the movable body 32 moves in the direction in which the inclination angle of the swash plate 23 increases, the force that obstructs movement of the movable body 32 may be decreased. This decreases the necessary pressure in the control pressure chamber 35 that allows for the movement of the movable body 32. In the second embodiment, the sloped angle of the slope 44a at the contact portion between the abutment pin 43 and the slope 44a when the swash plate 23 has the maximum inclination angle max decreases relative to that in the first embodiment. As a result, as shown in FIG. 10, the necessary pressure of the control pressure chamber 35 that allows for the swash plate 23 to have the inclination angle close to the maximum inclination angle max is set to be lower than that in the first embodiment. That is, in the second embodiment, adjustment of the inclination angle of the inclined portion 44a enables to vary the necessary pressure of the control pressure chamber 35 that allows for the swash plate 23 to have the intended inclination angle.

(78) (5) In a conventional structure in which the double-headed piston 25 is accommodated in the first cylinder bore 12a and the second cylinder bore 13a to be movable back and forth, when changing the inclination angle of the swash plate 23, although the dead volume of the second compression chamber 20b is not drastically increased, the dead volume is increased by a certain extent. The dead volume of the second compression chamber 20b refers to the clearance between the double-headed piston 25 and the second valve-port formation body 17. However, in the second embodiment, the shape of the slope 44a allows for the position of the swash plate 23 to be moved in the axial direction. Thus, even when the inclination angle of the swash plate 23 is changed, depending on the shape of the slope 44a, the dead volume of the second compression chamber 20b may be kept fixed. That is, the dead volume may be adjusted by setting a suitable shape for the slope 44a.

Third Embodiment

(79) A third embodiment of the present invention will now be described with reference to FIGS. 11 and 12. In the description hereafter, like or same reference numerals are given to those components that are the same as the corresponding components of the first embodiment. Such components will not be described in detail.

(80) Referring to FIG. 11, the guide surface 31c is curved in an arcuate manner to bulge outward and toward the swash plate 23. More specifically, the sloped angle of the guide surface 31c relative to the axis L of the rotation shaft 21 differs between a front position and a rear position on the guide surface 31c. Thus, the inclination angle of the swash plate 23 changes in accordance with the sloped angle of the guide surface 31c.

(81) The operation of the third embodiment will now be described.

(82) In a structure in which the double-headed piston 25 is accommodated in the first cylinder bore 12a and the second cylinder bore 13a to be movable back and forth, compression reaction forces P1 and P2 from the double-headed piston 25 act on the swash plate 23 to decrease the inclination angle of the swash plate 23.

(83) Further, in a structure in which the double-headed piston 25 is accommodated in the first cylinder bore 12a and the second cylinder bore 13a to be movable back and forth, as the inclination angle of the swash plate 23 decreases, the dead volume of the first compression chamber 20a increases. The dead volume of the first compression chamber 20a refers to the clearance between the double-headed piston 25 and the first valve-port formation body 16. In the second compression chamber 20b, the discharge stroke is performed without drastically increasing the dead volume. As the inclination angle of the swash plate 23 decreases from the maximum inclination angle max, the dead volume of the first compression chamber 20a increases. Thus, when the first compression chamber 20a is in the suction stroke, the re-expansion time is prolonged for decreasing the pressure of the first compression chamber 20a to the suction pressure. This increases the force from the double-headed piston 25 acting on the swash plate 23 to decrease the inclination angle of the swash plate 23.

(84) As the inclination angle of the swash plate 23 decreases to a predetermined inclination angle x, the dead volume of the first compression chamber 20a becomes a predetermined size. Here, the pressure of the first compression chamber 20a does not reach the discharge pressure. Thus, refrigerant gas is no longer discharged from the first compression chamber 20a. As the inclination angle of the swash plate 23 decreases from the predetermined inclination angle x to the minimum inclination angle min, refrigerant gas is neither discharged nor drawn in, and the compression and expansion of refrigerant gas is repeated. This decreases the force that presses the double-headed piston 25 with the pressure of the first compression chamber 20a which, in turn, decreases the force from the double-headed piston 25 that acts on the swash plate 23 to decrease the inclination angle of the swash plate 23.

(85) In FIG. 12, broken line L15 shows the relationship of the pressure of the control pressure chamber 35 and the inclination angle of the swash plate 23. In the first embodiment, the guide surface 31c is linearly sloped, and the sloped angle relative to the axis L of the rotation shaft 21 is fixed. As the inclination angle of the swash plate 23 changes from the minimum inclination angle min to a predetermined inclination angle x, due to the re-expansion of the refrigerant gas in the first compression chamber 20a, the force from the double-headed piston 25 that acts on the swash plate 23 to decrease the inclination angle of the swash plate 23 is relatively small. Thus, as shown in FIG. 12, to increase the inclination angle of the swash plate 23 from the minimum inclination angle min to the predetermined inclination angle x, the pressure of the control pressure chamber 35 only needs to be increased (condition from point O to point P in broken line L15).

(86) As the inclination angle of the swash plate 23 changes from the predetermined inclination angle x to the minimum inclination angle min, when the inclination angle of the swash plate 23 is the predetermined inclination angle x, due to the re-expansion of the refrigerant gas in the first compression chamber 20a, the force from the double-headed piston 25 that acts on the swash plate 23 to decrease the inclination angle of the swash plate 23 is the greatest.

(87) More specifically, when the inclination angle of the swash plate 23 is the predetermined inclination angle x, the resultant force of the compression reaction forces P1 and P2 from the double-headed piston 25 acting on the swash plate 23 and the force generated by re-expansion of the refrigerant gas in the first compression chamber 20a is the greatest.

(88) As the inclination angle of the swash plate 23 increases from the predetermined inclination angle x to the maximum inclination angle max, the dead volume of the first compression chamber 20a decreases. This decreases the force generated by the re-expansion of the refrigerant gas in the first compression chamber 20a.

(89) The pressure of the control pressure chamber 35 that maintains the inclination angle of the swash plate 23 is the greatest when the inclination angle of the swash plate 23 is the predetermined inclination angle x. As the inclination angle of the swash plate 23 increases from the predetermined inclination angle x to the maximum inclination angle max, the pressure of the control pressure chamber 35 decreases (condition of point P to point Q in broken line L1). As a result, in the prior art, the pressure of the control pressure chamber 35 required to increase the inclination angle of the swash plate 23 from the predetermined inclination angle x to the maximum inclination angle max and the pressure of the control pressure chamber 35 required to increase the inclination angle of the swash plate 23 from the minimum inclination angle min to the predetermined inclination angle x take the same value and exist in range Z1. Thus, it is difficult to accurately control the inclination angle of the swash plate 23.

(90) As shown in FIG. 11, in the present embodiment, the sloped angle of the swash plate 23 is adjusted to receive force from the double-headed piston 25 acting on the swash plate 23 to decrease the inclination angle of the swash plate 23 at the contact portion of the guide surface 31c and the projection 23c. This decreases the force from the double-headed piston 25 that acts on the swash plate 23 to decrease the inclination angle of the swash plate 23. Thus, as shown by solid line L16 in FIG. 12, the pressure of the control pressure chamber 35 only needs to be raised to increase the inclination angle of the swash plate 23 from the minimum inclination angle min to the maximum inclination angle max.

(91) Accordingly, in addition to advantages (1) and (2), the third embodiment has the advantages described below.

(92) (6) The sloped angle of the guide surface 31c relative to the axis L of the rotation shaft 21 differs between a front position and a rear position on the guide surface 31c. Thus, the inclination angle of the swash plate 23 changes in accordance with the sloped angle of the guide surface 31c. The sloped angle of the guide surface 31c relative to the axis of the rotation shaft 21 is varied to receive force from the double-headed piston 25 acting on the swash plate 23 to decrease the inclination angle of the swash plate 23. This decreases the force from the double-headed piston 25 that acts on the swash plate 23 to decrease the inclination angle of the swash plate 23. Thus, the pressure of the control pressure chamber 35 only needs to be raised to increase the inclination angle of the swash plate 23 from the minimum inclination angle min to the maximum inclination angle max.

(93) (7) In the third embodiment, the shape of the guide surface 31c allows the axial position of the swash plate 23 to be changed. Thus, even when the inclination angle of the swash plate 23 is changed, depending on the shape of the guide surface 31c, the dead volume of the second compression chamber 20b may be kept fixed. In other words, the dead volume may be adjusted by setting a suitable shape for the guide surface 31c.

(94) 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.

(95) The guide surface 44 in the first and third embodiments may be changed to the slope 44a of the second embodiment. The guide surface 31c of the first and second embodiments may be changed to the guide surface 31c of the third embodiment.

(96) In each of the above embodiments, the abutment pin 43 may be guided by the guide surface 44 so that the center O of the swash plate 23 and the axis of the rotation shaft 21 coincide with each other when the swash plate 23 is located at the position corresponding to the maximum inclination angle max and the swash plate 23 is located at the position corresponding to the minimum inclination angle min.

(97) In each of the above embodiments, the left side, right side, upper side, and lower side in the drawings may be changed when necessary.

(98) In each of the above embodiments, the upper end of the swash plate 23 is located at a position that is the farthest from the axis in the upper half of the swash plate 23. However, the position that is the farthest from the axis in the upper half of the swash plate 23 does not have to be the upper end of the swash plate 23. Further, the lower end of the swash plate 23 is located at a position that is the farthest from the axis in the lower half of the swash plate 23. However, the position that is the farthest from the axis in the lower half of the swash plate 23 does not have to be the lower end of the swash plate 23.

(99) 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.