DOUBLE- HEADED PISTON TYPE SWASH PLATE COMPRESSOR

Abstract

A double-headed piston type swash plate compressor includes a rotation shaft, a housing, a swash plate, two cylinder bores, a double-headed piston, and two shoes. The double-headed piston includes two shoe holders, a neck, two heads, and two coupling portions. At least one of the two coupling portions includes a load receiving portion. The load receiving portion is configured to receive bending load that is applied from the swash plate to the double-headed piston and acts toward an inner side in the radial direction. The load receiving portion is separated from the wall surface of the cylinder bore when load applied to the double-headed piston is less than a specific threshold value. The load receiving portion abuts against the inner wall of the cylinder bore and receives the bending load when the load applied to the double-headed piston is greater than the specific threshold value.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a double-headed piston type swash plate compressor.

One example of a compressor is a double-headed piston type swash plate compressor including a swash plate that rotates when a rotation shaft rotates and a double-headed piston that reciprocates in a pair of cylinder bores when the swash plate rotates. The double-headed piston compresses fluid in compression chambers that are defined in the two cylinder bores when the double-headed piston reciprocates (refer to Japanese Laid-Open Patent Publication No. 2015-161173). The double-headed piston type swash plate compressor compresses fluid that is subject to compression when the double-headed piston reciprocates.

In the structure of the double-headed piston type swash plate compressor, the fluid, which is subject to compression, and the swash plate apply load to the double-headed piston. Load includes bending load that acts toward the inner side in the radial direction of the rotation shaft. Thus, the double-headed piston requires strength that counters the bending load. Abutment of the double-headed piston against an inner wall of the cylinder bore may be increased to increase the strength of the piston. However, this will increase power loss and is not desirable.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a double-headed piston type swash plate compressor that receives bending load applied to a double-headed piston.

To achieve the above object, a double-headed piston type swash plate compressor according to one aspect of the present invention includes a rotation shaft, a housing, a swash plate, two cylinder bores, a double-headed piston, and two shoes. The rotation shaft extends in an axial direction and a radial direction. The housing accommodates the rotation shaft. The swash plate rotates when the rotation shaft rotates. The two cylinder bores are located in the housing at an outer side of the rotation shaft in the radial direction. The double-headed piston reciprocates in the two cylinder bores. The two shoes couple the double-headed piston to the swash plate. The two cylinder bores and the double-headed piston define two compression chambers. Rotation of the swash plate reciprocates the double-headed piston in the two cylinder bores and compresses fluid in each of the compression chambers. The double-headed piston includes two shoe holders, a neck, two heads, and two coupling portions. The two shoe holders hold the two shoes. The two shoe holders are opposed to each other in an axial direction of the double-headed piston. The neck couples the two shoe holders. The neck is located at an outer circumferential side of the swash plate and deformable in the radial direction. The two heads are respectively located at two ends of the double-headed piston in the axial direction of the double-headed piston. Each of the two heads includes a side surface opposing a wall surface of the cylinder bore. Two coupling portions couple the two shoe holders and the two heads, respectively. At least one of the two coupling portions includes a load receiving portion located between the corresponding head and the corresponding shoe holder as viewed in the radial direction. The load receiving portion is configured to receive bending load that is applied from the swash plate to the double-headed piston and acts toward an inner side in the radial direction. The load receiving portion is separated from the wall surface of the cylinder bore when load applied to the double-headed piston is less than a specific threshold value. The load receiving portion abuts against the inner wall of the cylinder bore and receives the bending load when the load applied to the double-headed piston is greater than the specific threshold value.

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

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 1 is a cross-sectional view schematically showing a double-headed piston type swash plate compressor;

FIG. 2 is a perspective view of a double-headed piston shown in FIG. 1;

FIG. 3 is a perspective view of the double-headed piston shown in FIG. 1;

FIG. 4 is a plan view of the double-headed piston shown in FIG. 1 as viewed from a radially inner side;

FIG. 5 is an enlarged view schematically showing the double-headed piston shown in FIG. 1 and the surrounding of the double-headed piston during a low-load period;

FIG. 6 is an enlarged view schematically showing the double-headed piston shown in FIG. 1 and the surrounding of the double-headed piston during a high-load period; and

FIG. 7 is an enlarged view schematically showing the double-headed piston shown in FIG. 1 and the surrounding of the double-headed piston during the high-load period.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One embodiment of the present invention will now be described with reference to FIGS. 1 to 7. The double-headed piston type swash plate compressor of the present embodiment is installed in a vehicle for use with a vehicle air conditioner. That is, fluid that is subject to compression by the double-headed piston type swash plate compressor of the present embodiment is refrigerant containing oil (lubricant). In FIGS. 1 and 5 to 7, the double-headed piston 100 is shown in a side view. In FIG. 5, the double-headed piston 100 is shown in a side view and a partially enlarged view.

As shown in FIG. 1, a double-headed piston type swash plate compressor 10 (hereinafter referred to as compressor 10) includes a housing 11 that forms the shell of the compressor 10. The entire housing 11 is tubular.

The housing 11 rotationally accommodates a rotation shaft 20. The rotation shaft 20 is located near the center in the housing 11. The axial direction Z of the rotation shaft 20 corresponds to the axial direction of the housing 11. In the following description, the axial direction Z of the rotation shaft 20 is referred to as the axial direction Z.

The housing 11 includes a tubular front housing 12, which forms one end of the housing 11 in the axial direction Z, a tubular rear housing 13, which has a bottom and forms the other end of the housing 11 in the axial direction Z, and two cylinder blocks 14 and 15 (first cylinder block 14 and second cylinder block 15), which are arranged between the front housing 12 and the rear housing 13. The cylinder blocks 14 and 15 are cylindrical and respectively include first and second shaft holes 21 and 22 through which the rotation shaft 20 can be inserted.

The first cylinder block 14 includes the first shaft hole 21 that extends through the first cylinder block 14 in the axial direction Z. The first shaft hole 21 includes a first small diameter hole 21a, which has a slightly larger diameter than the rotation shaft 20, and a first large diameter hole 21b, which is larger than the first small diameter hole 21a. The first small diameter hole 21a is located closer to the front housing 12 than the first large diameter hole 21b.

The second cylinder block 15 includes the second shaft hole 22 that extends through the second cylinder block 15 in the axial direction Z. The second shaft hole 22 includes a second small diameter hole 22a, which has a slightly larger diameter than the rotation shaft 20, and a second large diameter hole 22b, which is larger than the second small diameter hole 22a. The second small diameter hole 22a is located closer to the rear housing 13 than the second large diameter hole 22b. The two cylinder blocks 14 and 15 are coupled to each other with the two shaft holes 21 and 22 (more specifically, two large diameter holes 21b and 22b) opposing each other in the axial direction Z.

A first valve/port body 23 is arranged between the front housing 12 and the first cylinder block 14. A second valve/port body 24 is arranged between the rear housing 13 and the second cylinder block 15. The valve/port bodies 23 and 24 each have the form of a flat ring. The valve/port bodies 23 and 24 have a larger inner diameter than the rotation shaft 20.

The rotation shaft 20 is inserted through the two shaft holes 21 and 22 and the two valve/port bodies 23 and 24 and extended from the front housing 12 to the rear housing 13. In this case, one end of the rotation shaft 20 in the axial direction Z is located in the front housing 12, and the other end of the rotation shaft 20 in the axial direction Z is located in a regulation chamber A1, which is defined by the rear housing 13 and the second cylinder block 15. That is, the rotation shaft 20 extends through the two cylinder blocks 14 and 15. The regulation chamber A1 will be described later.

As shown in FIG. 1, a first radial bearing 31 that rotationally supports the rotation shaft 20 is arranged between the rotation shaft 20 and a wall surface of the first small diameter hole 21a. In the same manner, a second radial bearing 41 that rotationally supports the rotation shaft 20 is arranged between the rotation shaft 20 and a wall surface of the second small diameter hole 22a. The rotation shaft 20 is supported by the two radial bearings 31 and 41 in the housing 11 in a rotatable manner.

The rotation shaft 20 includes a first shaft projection 20a and a second shaft projection 20b. The first shaft projection 20a is located in the first large diameter hole 21b and projected in the radial direction R of the rotation shaft 20 (hereinafter referred to as the radial direction R), and the second shaft projection 20b is located in the second large diameter hole 22b and projected in the radial direction R. The first shaft projection 20a is opposed to a ring-shaped step surface in the axial direction X. The step surface connects the first small diameter hole 21a to the first large diameter hole 21b. A first thrust bearing 32 is arranged between the first shaft projection 20a and the step surface. The second shaft projection 20b is opposed to a ring-shaped step surface in the axial direction X. The step surface connects the second small diameter hole 22a to the second large diameter hole 22b. A second thrust bearing 42 is arranged between the second shaft projection 20b and the step surface.

The housing 11 includes two suction chambers 33 and 43 (first suction chamber 33 and second suction chamber 43) and two discharge chambers 34 and 44 (first discharge chamber 34 and second discharge chamber 44). Each of the first suction chamber 33 and the first discharge chamber 34 is defined by the front housing 12 and the first valve/port body 23. Each of the second suction chamber 43 and the second discharge chamber 44 is defined by the rear housing 13 and the second valve/port body 24. The two suction chambers 33 and 43 oppose each other in the axial direction Z, and the two discharge chambers 34 and 44 oppose each other in the axial direction Z. The suction chambers 33 and 43 and the discharge chambers 34 and 44 are formed to be annular as viewed in the axial direction Z, and the discharge chambers 34 and 44 are located at the outer sides of the suction chambers 33 and 43.

As shown in FIG. 1, the compressor 10 includes a swash plate 50 that rotates when the rotation shaft 20 rotates. The swash plate 50 is inclined with respect to a direction that is orthogonal to the axial direction Z of the rotation shaft 20.

The swash plate 50 includes a swash plate body 52, which has the form of a flat ring. The swash plate body 52 includes a swash plate insertion hole 51 through which the rotation shaft 20 is inserted. The swash plate body 52 includes a first inclined surface 52a, which is directed toward the first cylinder block 14, and a second inclined surface 52b, which is directed toward the side opposite to the first inclined surface 52a.

The swash plate 50 of the present embodiment is configured so that the inclination angle can be changed with respect to the direction orthogonal to the axial direction Z of the rotation shaft 20.

The housing 11 includes a swash plate chamber A2 that accommodates the swash plate 50. The swash plate chamber A2 is defined by the two cylinder blocks 14 and 15. The swash plate chamber A2 is located between the two shaft holes 21 and 22 and is in communication with the two shaft holes 21 and 22.

As shown in FIG. 1, a side wall of the second cylinder block 15 defining the swash plate chamber A2 includes a suction port 53. Thus, the suction port 53 is in communication with the swash plate chamber A2. Further, the housing 11 includes a suction passage 54 through which the swash plate chamber A2 is in communication with the suction chambers 33 and 43. The suction passage 54 includes a first suction passage 54a and a second suction passage 54b. The first suction passage 54a extends through the first cylinder block 14 and the first valve/port body 23 in the axial direction Z and allows communication between the swash plate chamber A2 and the first suction chamber 33. The second suction passage 54b extends through the second cylinder block 15 and the second valve/port body 24 in the axial direction Z and allows communication between the swash plate chamber A2 and the second suction chamber 43. A plurality of the suction passages 54a and 54b extend in the circumferential direction around the shaft holes 21 and 22 in the cylinder blocks 14 and 15.

In such a structure, fluid that is drawn from the suction port 53 flows through the swash plate chamber A2 and the suction passage 54 into the suction chambers 33 and 43. In this case, the swash plate chamber A2 and the two large diameter holes 21b and 22b that are in communication with the swash plate chamber A2 have the same pressure as the fluid drawn from the suction port 53.

The housing 11 includes a discharge passage 55 that is in communication with the two discharge chambers 34 and 44. The discharge passage 55 is located at the outer side of the swash plate chamber A2 and cylinder bores 91 and 92 (first and second cylinder bores 91 and 92, described below) in the radial direction R. The discharge passage 55 is in communication with a discharge port 56, which is located in the housing 11 (more specifically, side wall of second cylinder block 15). Fluid in the two discharge chambers 34 and 44 is discharged out of the discharge port 56 through the discharge passage 55.

As shown in FIG. 1, the compressor 10 includes a link mechanism 60 that allows the inclination angle of the swash plate 50 to change and links the swash plate 50 to the rotation shaft 20 so that the swash plate 50 and the rotation shaft 20 integrally rotate. The link mechanism 60 is located closer to the front housing 12 than the swash plate 50 except for part of the link mechanism 60.

The link mechanism 60 includes a lug arm 61, a first link pin 62, and a second link pin 63. The lug arm 61 extends from the first large diameter hole 21b to the swash plate chamber A2. The first link pin 62 pivotally couples the lug arm 61 to the swash plate 50. The second link pin 63 pivotally couples the lug arm 61 to the rotation shaft 20.

The lug arm 61 is L-shaped and includes a basal portion opposing the front housing 12 and a distal portion opposing the swash plate 50. The distal portion of the lug arm 61 projects out of the swash plate 50 toward the rear housing 13 through an arm through hole 52c in the swash plate body 52 of the swash plate 50. The projecting portion includes a weight.

The arm through hole 52c, for example, does not have an annular shape extending over the entire circumference of the swash plate 50 and is rectangular as viewed in the axial direction Z. The arm through hole 52c includes an inner surface including two opposing inner surfaces that are opposed to each other in the direction orthogonal to both of the thickness-wise direction of the swash plate 50 and the direction parallel to the axes of the swash plate insertion hole 51 and the arm through hole 52c.

The first link pin 62 is, for example, cylindrical. The first link pin 62 is located in the arm through hole 52c so that the axial direction of the first link pin 62 corresponds to the opposing direction of the two opposing inner surfaces. The first link pin 62 is extended through a portion of the lug arm 61 extending in the axial direction Z and attached to the swash plate 50. The portion of the lug arm 61 extending in the axial direction Z is supported by the swash plate 50 pivotally about the axis of the first link pin 62, which serves as the first pivot center M1.

The second link pin 63 is, for example, cylindrical. The second link pin 63 is arranged so that the axial direction of the second link pin 63 is parallel to the axial direction of the first link pin 62. The second link pin 63 is located in the basal portion of the lug arm 61 separated from where the lug arm 61 extends in the axial direction Z. The second link pin 63 is extended through the basal portion of the lug arm 61 and fixed to the rotation shaft 20. The basal portion of the lug arm 61 is pivotally supported by the rotation shaft 20 about the axis of the second link pin 63, which serves as the second pivot center M2.

As shown in FIG. 1, the compressor 10 includes an actuator 70 that changes the inclination angle of the swash plate 50. The actuator 70 is located closer to the rear housing 13 than the swash plate 50.

The actuator 70 includes a movable body 71 that is movable in the axial direction Z, and a partition 72 that defines a control chamber A3 in cooperation with the movable body 71, and two coupling pieces 73 that couple the movable body 71 to the swash plate 50. The compression chamber A3 is used to control the inclination angle of the swash plate 50.

The movable body 71 has the form of a tube (more specifically, cylindrical tube) and includes a bottom and a tubular portion. The movable body opens toward one side. The bottom of the movable body 71 includes an insertion hole through which the rotation shaft 20 can be inserted. The movable body 71 rotates integrally with the rotation shaft 20 with the rotation shaft 20 inserted through the insertion hole and the open end of the movable body 71 directed toward the swash plate chamber A2.

The partition 72 has the form of a flat ring and has an outer diameter that is set to be substantially the same as an inner diameter of the movable body 71. The partition 72, which is fitted onto the rotation shaft 20 and into the movable body 71, is fixed to the rotation shaft 20 so that the partition 72 rotates integrally with the rotation shaft 20. The partition 72 closes the open end of the movable body 71 that is close to the swash plate chamber A2. The control chamber A3 is defined by an inner circumferential surface of the movable body 71 and a surface of the partition 72 located at the side opposite to the swash plate chamber A2.

A portion between the inner circumferential surface of the movable body 71 and an outer circumferential surface of the partition 72 is sealed to restrict movement of fluid between the control chamber A3 and the swash plate chamber A2. This allows the control chamber A3, the swash plate chamber A2, and the second large diameter hole 22b to have different pressures. The position of the movable body 71 changes in accordance with the pressure difference of the control chamber A3 and the swash plate chamber A2.

The rotation shaft 20 includes a shaft passage 74 that allows communication between the regulation chamber A1 and the control chamber A3. The shaft passage 74 includes an axial portion, which opens in the regulation chamber A1 and extends in the axial direction Z, and a radial portion, which is in communication with the axial portion. The radial portion opens in the control chamber A3 and extends in the radial direction R. The shaft passage 74 allows fluid to move between the control chamber A3 and the regulation chamber A1. Thus, the control chamber A3 and the regulation chamber A1 have the same pressure.

The compressor 10 includes a pressure controller 75 that controls the pressure of the regulation chamber A1. The pressure controller 75 includes a low-pressure passage that allows communication between the second suction chamber 43 and the regulation chamber A1, a high-pressure passage that allows communication between the second discharge chamber 44 and the regulation chamber A1, a valve that is located on the low-pressure passage and regulates the amount of fluid discharged from the regulation chamber A1 into the second suction chamber 43, and an orifice that is located in the high-pressure passage and regulates the flow rate of the discharged fluid flowing in the high-pressure passage. The pressure controller 75 controls the pressure of the regulation chamber A1 by controlling the valve. This allows the position of the movable body 71 to be adjusted.

The two coupling pieces 73 project toward the swash plate 50 from part of the annular open end of the movable body 71 as viewed in the axial direction Z. More specifically, the two coupling pieces 73 project toward the swash plate 50 from a portion of the movable body 71 located toward the side opposite to the distal portion of the lug arm 61 from the rotation shaft 20 as viewed in the axial direction Z. The two coupling pieces 73 oppose each other in the pivot axes of the two pivot centers M1 and M2 (direction in which pivot centers M1 and M2 extend).

The swash plate 50 includes a plate-shaped coupling receiving portion 76 that projects from the second inclined surface 52b and overlaps the two coupling pieces 73 as viewed in the pivot axis. The coupling receiving portion 76 and the arm through hole 52c are located in the second inclined surface 52b at opposite sides of the swash plate insertion hole 51. The coupling receiving portion 76 includes a coupling hole through which a coupling pin 77 extending in the pivot axis can be inserted. The coupling pin 77 is located between the two coupling pieces 73. The coupling pin 77 is inserted through the coupling hole and fixed to the two coupling pieces 73. Thus, the swash plate 50 is coupled to the movable body 71. In this case, the movement of the movable body 71 changes the inclination angle of the swash plate 50. That is, adjustment of the position of the movable body 71 adjusts the inclination angle of the swash plate 50.

To simplify the drawings, the coupling pin 77 and the coupling hole have the same shape. However, the coupling hole actually has an oval shape elongated in the vertical direction and has a larger diameter than the coupling pin 77 so as to correspond to changes in the inclination angle of the swash plate 50.

As shown in FIG. 1, the swash plate 50 includes a first projection 81 that projects from the first inclined surface 52a and a second projection 82 that projects from the second inclined surface 52b. The second projection 82 is separate from the coupling receiving portion 76.

The first projection 81 does not extend over the entire circumference of the first inclined surface 52a. Rather, the first projection 81 extends over a portion of the first inclined surface 52a located at the opposite side of the arm through hole 52c with respect to the swash plate insertion hole 51. The second projection 82 extends in the circumferential direction around the swash plate insertion hole 51 in the second inclined surface 52b. The two projections 81 and 82 are located in the radial direction R at the inner side of a portion of the inclined surfaces 52a and 52b that is held by two shoes 121 and 122 (described later). Thus, the swash plate 50 includes a circumferential portion that is thinner than the portion where the two projections 81 and 82 and the coupling receiving portion 76 are arranged.

A recovery spring 83 is fixed to the first shaft projection 20a of the rotation shaft 20. The recovery spring 83 extends in the axial direction Z from the first shaft projection 20a toward the swash plate chamber A2. Further, an inclination reduction spring 84 is arranged between the partition 72 and the swash plate 50. The inclination reduction spring 84 includes one end fixed to the partition 72 and the other end fixed to the swash plate 50. The inclination reduction spring 84 biases the swash plate 50 in a direction that decreases the inclination angle of the swash plate 50.

The compressor 10 includes pairs of cylinder bores 91 and 92. The cylinder bores 91 and 92 of each pair are opposed to each other in the axial direction Z and located at the outer side of the rotation shaft 20 in the radial direction R in the housing 11. The cylinder bores 91 and 92 are located at the outer side of the shaft holes 21 and 22 in the radial direction R. The pairs of the cylinder bores 91 and 92 extend in the circumferential direction around the shaft holes 21 and 22 of the cylinder blocks 14 and 15. The cylinder bores 91 are opposed to the cylinder bores 92 at opposite sides of the swash plate chamber A2. The cylinder bores 91 and 92 are coaxial.

To facilitate understanding, FIG. 1 shows only one of the cylinder bores 91 and one of the cylinder bores 92. Further, the cylinder bores 91 and 92 are separated from the suction passages 54a and 54b in the circumferential direction so that the cylinder bores 91 and 92 do not interfere with the suction passages 54a and 54b around the shaft holes 21 and 22.

The cylinder bores 91 and 92 have the form of a tube (more specifically, cylindrical tube) and extend through the corresponding cylinder blocks 14 and 15 in the axial direction Z. One opening of each of the cylinder bores 91 and 92 is in communication with the swash plate chamber A2, and the other opening of each of the cylinder bores 91 and 92 is closed by the valve/port body 23 or 24. The first valve/port body 23 partitions each first cylinder bore 91 from the first suction chamber 33 and the first discharge chamber 34, and the second valve/port body 24 partitions each second cylinder bore 92 from the second suction chamber 43 and the second discharge chamber 44.

As shown in FIG. 1, the valve/port bodies 23 and 24 close the openings of the cylinder bores 91 and 92 and include suction ports 23a and 24a that are respectively in communication with the suction chambers 33 and 43 and discharge ports 23b and 24b, which are respectively in communication with the discharge chambers 34 and 44 through the valve. The suction ports 23a and 24a and the discharge ports 23b and 24b extend in the circumferential direction in correspondence with the cylinder bores 91 and 92 that extend in the circumferential direction.

As described above, refrigerant contains oil. Thus, oil exists in a space where refrigerant exists, more specifically, in the swash plate A2 and the cylinder bores 91 and 92 that are in communication with the swash plate A2.

The compressor 10 includes the double-headed piston 100 that reciprocates in each pair of the cylinder bores 91 and 92 and the two shoes 121 and 122 that couple the double-headed piston 100 to the swash plate 50.

The double-headed piston 100 is accommodated in each pair of the cylinder bores 91 and 92 so that the axial direction of the double-headed piston 100 corresponds to the axial direction Z of the rotation shaft 20 (in other words, opposing direction of two cylinder bores 91 and 92). More specifically, the double-headed piston 100 is arranged in each pair of the cylinder bores 91 and 92 so that the double-headed piston 100 is coaxial with the two cylinder bores 91 and 92.

The double-headed pistons 100 extend in the circumferential direction in correspondence with the cylinder bores 91 and 92 extend in the circumferential direction. That is, each pair of the cylinder bores 91 and 92 includes one of the double-headed pistons 100.

The structures of the double-headed piston 100 and the like will now be described in detail.

As shown in FIGS. 2 to 5, the double-headed piston 100 includes a neck 101, shoe holders 102 and 112 that hold the two shoes 121 and 122, two heads 103 and 113 located at the two ends in the axial direction of the double-headed piston 100, and two coupling portions 104 and 114 that respectively couple the shoe holders 102 and 112 to the heads 103 and 113. The two shoe holders 102 and 112 oppose each other in the axial direction of the double-headed piston 100. The neck 101 couples the two shoe holders 102 and 112.

The coupling portions 104 and 114 include inner portions 105 and 115 and outer portions 106 and 116 extending in the axial direction of the double-headed piston 100. The inner portions 105 and 115 are respectively opposed to the outer portions 106 and 116 in the radial direction R. Further, the coupling portions 104 and 114 include plates 107 and 117 that couple the inner portions 105 and 115 to the outer portions 106 and 116, respectively. The inner portions 105 and 115 are located at the inner side of the outer portions 106 and 116 in the radial direction R (i.e., in portion of double-headed piston 100 that is close to rotation shaft 20).

The axial direction of the double-headed piston 100 is the direction in which the head 103 is opposed to the head 113, and the radial direction R is the direction in which the inner portions 105 and 115 are opposed to the outer portions 106 and 116. To facilitate understanding, a direction orthogonal to both of the axial direction of the double-headed piston 100 and the opposing direction of the inner portions 105 and 115 and the outer portions 106 and 116 is hereinafter referred to as the widthwise direction W.

The coupling portions 104 and 114 of the present embodiment are deformed more easily in the widthwise direction W than in the radial direction R. More specifically, the coupling portions 104 and 114 are configured to have a smaller section modulus in the widthwise direction W than in the radial direction R. Each of the coupling portions 104 and 114 has a width that is less than or equal to that of the neck 101.

As shown in FIG. 5, the two shoe holders 102 and 112 include semi-spherical surfaces 102a and 112a. The semi-spherical surfaces 102a and 112a are recessed away from each other. The circumferential portion of the swash plate 50 is arranged between the shoe holders 102 and 112.

The first shoe 121 of the two shoes 121 and 122 is located between the first inclined surface 52a of the swash plate 50 and the first semi-spherical surface 102a of the first shoe holder 102, and the second shoe 122 is located between the second inclined surface 52b of the swash plate 50 and the second semi-spherical surface 112a of the second shoe holder 112. The two shoes 121 and 122 are semi-spherical. The two shoes 121 and 122 include bottom surfaces that abut against the circumferential portions of the corresponding inclined surfaces 52a and 52b and spherical surfaces that abut against the corresponding semi-spherical surfaces 102a and 112a. The shoe holders 102 and 112 hold the two shoes 121 and 122 with the two shoes 121 and 122 holding the circumferential portions of the swash plate 50. Thus, the two shoes 121 and 122 couple the double-headed piston 100 to the swash plate 50.

In such a structure, rotation of the swash plate 50 applies load, including a component in the axial direction Z, to the double-headed piston 100 through the two shoes 121 and 122. This converts the rotation of the swash plate 50 into reciprocation of the double-headed piston 100. In this case, the stroke of the double-headed piston 100 changes in accordance with the inclination angle of the swash plate 50.

The neck 101 is located at an outer circumferential side of the swash plate 50, more specifically, at the outer side of the swash plate 50 in the radial direction R. The neck 101 is larger in the widthwise direction W than in the radial direction R so that the neck 101 is deformable in the radial direction R. More specifically, the neck 101 is plate-shaped, and the radial direction R of the neck 101 refers to a thickness-wise direction. The section modulus of the neck 101 is smaller in the radial direction R than in the widthwise direction W. The two shoe holders 102 and 112 are located at the two ends of the inner surface of the neck 101 in the axial direction of the double-headed piston 100.

In the present embodiment, the neck 101 has a width that is equal to that of each of the shoe holders 102 and 112. However, the neck 101 may have a width that is greater than that of each of the shoe holders 102 and 112.

As shown in FIG. 3, the outer surface of the neck 101 is curved in conformance with a wall surface 91a that is the wall surface of the first cylinder bore 91. The outer surface of the neck 101 includes neck recesses 101a that are recessed from the outer surface of the neck 101 toward the inner side in the radial direction R. The two neck recesses 101a are separated from each other in the widthwise direction W. Thus, the two ends of the neck 101 in the widthwise direction are thinner than the central portion of the neck 101 in the widthwise direction W and easily deformed in the radial direction R.

As shown in FIGS. 2 to 5, each of the heads 103 and 113 is tubular and has a bottom. The heads 103 and 113 include bottom surfaces 103a and 113a, which have a slightly smaller diameter than the first wall surfaces 91a of the first cylinder bore 91 and a second wall surface 92a of the second cylinder bore 92 and side surfaces 103b and 113b (i.e., outer circumferential surfaces 103b and 113b), respectively. Further, the heads 103 and 113 open toward the shoe holders 102 and 112.

As shown in FIG. 5, the first wall surface 91a of the first cylinder bore 91 is opposed to the side surface 103b of the first head 103, and a first gap 108 is formed between the first wall surface 91a and the side surface 103b. The first head 103 is at least partially accommodated in the first cylinder bore 91 regardless of where the double-headed piston 100 is located.

The first cylinder bore 91 includes a first compression chambers A4 that is defined by the bottom surface 103a of the first head 103, the first wall surfaces 91a, and the first valve/port body 23. The first compression chamber A4 is in communication with the first suction chamber 33 with the first suction ports 23a located in between and is in communication with the first discharge chamber 34 with the first discharge port 23b located in between.

In the same manner, the second wall surface 92a of the second cylinder bore 92 is opposed to the side surface 113b of the second head 113, and a second gap 118 is formed between the second wall surface 92a and the side surface 113b. The second head 113 is at least partially accommodated in the second cylinder bore 92 regardless of where the double-headed piston 100 is located.

The second cylinder bore 92 includes a second compression chambers A5 that is defined by the bottom surface 113a of the second head 113, the second wall surfaces 92a, and the second valve/port body 24. The second compression chamber A5 is in communication with the second suction chamber 43 with the second suction ports 24a located in between and is in communication with the second discharge chamber 44 with the second discharge port 24b located in between.

In such a structure, reciprocation of the double-headed piston 100 draws fluid from the suction chambers 33 and 43 into the compression chambers A4 and A5, where the fluid is compressed. Then, the fluid is discharged into the discharge chambers 34 and 44. The stroke of the double-headed piston 100 changes in accordance with the inclination angle of the swash plate 50 and varies the displacement of the compressed fluid. That is, the compressor 10 of the present embodiment is of a variable displacement type.

As shown in FIG. 6, the position of the double-headed piston 100 where the inclination angle is the maximum and the first compression chamber A4 is most compressed (i.e., position where double-headed piston 100 is most proximate to first valve/port body 23) is referred to as the first position (top dead center of first head 103 of double-headed piston 100). Further, as shown in FIG. 7, the position of the double-headed piston 100 where the inclination angle is the maximum and the second compression chamber A5 is most compressed (i.e., position where double-headed piston 100 is most proximate to second valve/port body 24) is referred to as the second position (top dead center of second head 113 of double-headed piston 100). The double-headed piston 100 reciprocates between the first position and the second position. That is, the double-headed piston 100 can reciprocate from the first position to the second position.

As shown in FIG. 5, the head 103 has a larger diameter than the second head 113. The first cylinder bore 91 is larger than the second cylinder bore 92 in correspondence with the difference in diameter of the two heads 103 and 113. More specifically, the first wall surface 91a has a larger diameter than the second wall surface 92a. Thus, the two gaps 108 and 118 have substantially the same size (more specifically, same length in radial direction R).

The wall surfaces 91a and 92a of the two cylinder bores 91 and 92, which are coaxially opposed to each other have different diameters. Thus, the outer portion of the first wall surface 91a in the radial direction R is located outward in the radial direction R from the outer side of the second wall surface 92a in the radial direction R. As shown in FIG. 6, the outer portion of the first wall surface 91a in the radial direction R is flush with a side wall inner surface 15a that is an inner surface of the side wall of the second cylinder block 15 that defines the swash plate chamber A2. The side wall inner surface 15a and the second wall surface 92a form a step.

As shown in FIGS. 3 and 5, the first outer portion 106 extends in the axial direction of the double-headed piston 100 from the outer portion of the first head 103 in the radial direction R and couples the first head 103 to the first shoe holder 102 with the neck 101. More specifically, the first outer portion 106 connects the end of the neck 101 where the first shoe holder 102 is arranged to the outer portion of the first head 103 in the radial direction R. The first outer portion 106 is a plate having a width in the widthwise direction W and a thickness in the radial direction R. The first outer portion 106 includes an outer surface curved in conformance with the first wall surface 91a.

The first outer portion 106 has a width that is less than or equal to that of the neck 101. Further, the first outer portion 106 is at least partially narrower than the two shoe holders 102 and 112. In the present embodiment, the portion of the first outer portion 106 excluding the longitudinal ends of the first outer portion 106 is narrower than the two shoe holders 102 and 112.

The first inner portion 105 extends in the axial direction of the double-headed piston 100 from the inner portion of the first head 103 in the radial direction R. The first inner portion 105 includes a first basal portion 105a located near the first head 103 and a first distal portion 105b located near the first shoe holder 102. The first distal portion 105b of the first inner portion 105 is located between the first head 103 and the first shoe holder 102 as viewed in the radial direction R, more specifically, located at the portion of the first coupling portion 104 closer to the first shoe holder 102 than the first head 103. The first distal portion 105b corresponds to “an end of the inner portion near the shoe holder.”

As shown in FIG. 4, the first inner portion 105 is a plate having a width in the widthwise direction W and a thickness in the radial direction R. The first inner portion 105 includes a first fixed-width portion 105c having a fixed width. The first fixed-width portion 105c is located between the two ends 105a and 105b. In the present embodiment, the first fixed-width portion 105c has a width that is less than that of each of the two shoe holders 102 and 112. The first distal portion 105b of the first inner portion 105 is wider than the first fixed-width portion 105c.

As shown in FIG. 5, the first inner portion 105 is located further inward from the side surface 103b of the first head 103. Thus, the first distal portion 105b of the first inner portion 105 is located further inward from the side surface 103b of the first head 103.

The first inner portion 105 includes a first inner surface 105d opposing the first wall surface 91a in the radial direction R. The first inner surface 105d is curved in conformance with the first wall surface 91a. The first inner surface 105d is farther from the portion of the first wall surface 91a opposing the first inner surface 105d than the side surface 103b of the first head 103. That is, the side surface 103b of the first head 103 and the first inner surface 105d form a step so that the first inner surface 105d is farther from the first wall surface 91a than the side surface 103b of the first head 103.

The step may include, for example, a surface orthogonal to the axial direction of the double-headed piston 100 as shown in FIG. 5. Instead, the step may be, for example, tapered so that the outer diameter gradually decreases from the first head 103 toward the first shoe holder 102.

The step between the side surface 103b of the first head 103 and the first inner surface 105d may have any dimension, for example, less than or equal to 1 mm (excluding 0 mm). In each of the drawings, to facilitate understanding, the step is larger than the actual one. Further, the first distal portion 105b has an edge that is obliquely cut. Thus, the edge of the first inner surface 105d near the first distal portion 105b is inclined.

The first inner portion 105 is located at the inner side of the first shoe holder 102 in the radial direction R. Thus, the first distal portion 105b of the first inner portion 105 and the first shoe holder 102 form a step as viewed in the widthwise direction W.

The first coupling portion 104 includes a first rib 109 that connects the first shoe holder 102 and the first distal portion 105b of the first inner portion 105, which form a step. The first rib 109 connects the first distal portion 105b of the first inner portion 105 to the first shoe holder 102 so that a first space A11 is defined by the side of the first distal portion 105b of the first inner portion 105 as viewed in the widthwise direction W. More specifically, the first rib 109 is inclined as viewed in the widthwise direction W. As shown in FIG. 4, the length X11 of the first inner portion 105 in the axial direction of the double-headed piston 100 is greater than the length X12 of the first rib 109.

As shown in FIGS. 2 to 5, the thickness-wise direction of the first plate 107 in the first coupling portion 104 is the widthwise direction W. That is, the first plate 107 has a thickness in the widthwise direction W. The thickness of the first plate 107 is smaller than the widths of the first inner portion 105 and the first outer portion 106. The first plate 107 includes a first through hole 107a extending in the widthwise direction W. The first through hole 107a is, for example, defined by a wall recessed toward the first shoe holder 102 as viewed in the widthwise direction W and is in communication with the interior of the first head 103, which is tubular and has a bottom.

The second coupling portion 114 is basically the same as the first coupling portion 104 except that, for example, the second coupling portion 114 in the axial direction of the double-headed piston 100 is longer than the first coupling portion 104.

More specifically, as shown in FIGS. 3 and 5, the second outer portion 116 extends in the axial direction of the double-headed piston 100 from the outer portion of the second head 113 in the radial direction R and couples the second head 113 to the second shoe holder 112 with the neck 101. The second outer portion 116 includes an outer surface curved in conformance with the second wall surface 92a.

As shown in FIGS. 2 to 5, the second inner portion 115 extends in the axial direction of the double-headed piston 100 from the inner portion of the second head 113 in the radial direction R. The second inner portion 115 includes a second basal portion 115a located near the second head 113 and a second distal portion 115b located near the second shoe holder 112. The second distal portion 115b is located between the second head 113 and the second shoe holder 112 as viewed in the radial direction R, more specifically, located at the part of the second coupling portion 114 closer to the second shoe holder 112 than the second head 103. The second distal portion 115b corresponds to “an end of the inner portion near the shoe holder.”

As shown in FIG. 4, the second inner portion 115 is a plate having a width in the widthwise direction W and a thickness in the radial direction R. The second inner portion 115 includes a second fixed-width portion 115c having a fixed width. The second fixed-width portion 115c is located between the two ends 115a and 115b. In the present embodiment, the second fixed-width portion 115c has a width that is less than that of each of the two shoe holders 102 and 112. The second distal portion 115b of the second inner portion 115 is wider than the fixed-width portion 115c.

The second inner portion 115 is located further inward from the side surface 113b of the second head 113. The second inner portion 115 includes a second inner surface 115d opposing the second wall surface 92a in the radial direction R. The second inner surface 115d is curved in conformance with the second wall surface 92a. The second inner surface 115d is farther from the portion of the second wall surface 92a opposing the second inner surface 115d than the side surface 113b of the second head 113. That is, the side surface 113b of the second head 113 and the second inner surface 115d form a step so that the second inner surface 115d is farther from the second wall surface 92a than the side surface 113b of the second head 103. The step between the side surface 113b of the second head 113 and the second inner surface 115d may have any dimension, for example, less than or equal to 1 mm (excluding 0 mm). In each of the figures, to facilitate understanding, the dimension of the step is larger than the actual one. Further, the second distal portion 115b has an edge that is obliquely cut. Thus, the edge of the second inner surface 115d near the second distal portion 115b is inclined.

As shown in FIG. 5, the second inner portion 115 is located at the inner side of the second shoe holder 112 in the radial direction R. Thus, the second distal portion 115b of the second inner portion 115 and the second shoe holder 112 form a step. The second coupling portion 114 includes a second rib 119 that connects the second shoe holder 112 and the second distal portion 115b of the second inner portion 115, which form a step. The second rib 119 connects the second distal portion 115b of the second inner portion 115 to the second shoe holder 112 so that a second space A12 is defined by the side of the second distal portion 115b of the second inner portion 115 as viewed in the widthwise direction W. More specifically, the second rib 119 is inclined as viewed in the widthwise direction W. As shown in FIG. 4, the length X21 of the second inner portion 115 in the axial direction of the double-headed piston 100 is greater than the length X22 of the second rib 119.

As shown in FIGS. 2 to 5, the thickness of the second plate 117 of the second coupling portion 114 is smaller than the widths of the second inner portion 115 and the second outer portion 116. The second plate 117 includes a second through hole 117a extending in the widthwise direction W. The second through hole 117a is, for example, defined by a wall recessed toward the second shoe holder 112 as viewed in the widthwise direction W and is in communication with the interior of the second head 113, which is tubular and has a bottom.

As shown in FIGS. 3 to 5, the outer surface of the neck recesses 101a includes a rotation stopper 123 that restricts rotation of the double-headed piston 100 in the two cylinder bores 91 and 92. The rotation stopper 123 is located closer to the second shoe holder 112 than the neck recesses 101a, more specifically, on the end of the outer surface of the neck 101 that is closer to the second shoe holder 112. In other words, the rotation stopper 123 may be located on the outer surface of the neck 101 closer to the second head 113 than the first head 103 or on the outer surface of the neck 101 at a location that is closer to the second coupling portion 114 than the first coupling portion 104. The rotation stopper 123 extends in the widthwise direction W. As shown in FIG. 4, the two ends of the rotation stopper 123 in the widthwise direction W extend out of the neck 101 as viewed in the radial direction R. The rotation stopper 123 includes an outer surface curved in conformance with the side wall inner surface 15a. The outer surface of the rotation stopper 123 abuts against the side wall inner surface 15a to restrict rotation of the double-headed piston 100 in the cylinder bores 91 and 92.

In the present embodiment, the rotation stopper 123 is arranged near the second shoe holder 112 and not near the first shoe holder 102. Thus, the portion of the neck 101 near the first shoe holder 102 is deformed more easily than the portion near the second shoe holder 112, and the portion of the neck 101 near the second shoe holder 112 has a higher strength than the portion of the neck 101 near the first shoe holder 102.

Further, the double-headed piston 100 is movable to where the rotation stopper 123 abuts against the open end of the first cylinder bore 91 that is closer to the swash plate chamber A2. That is, the portion of the neck 101 near the first shoe holder 102 of the double-headed piston 100 can be partially inserted into the first cylinder bore 91.

Fluid in the compression chambers A4 and A5 and the swash plate applies load to the double-headed piston 100. Load includes force applied from the swash plate 50 through the two shoes 121 and 122 and compression reaction force that results from the compression of fluid in the compression chambers A4 and A5. The force includes a component in the axial direction Z and a component that acts toward the inner side in the radial direction R. That is, the double-headed piston 100 receives bending load that acts toward the inner side in the radial direction R.

Further, the degree of load applied to the double-headed piston 100 varies depending on, for example, the inclination angle of the swash plate 50, the position of the double-headed piston 100 during a single reciprocation, and the pressure of the compression chambers A4 and A5. That is, in accordance with the operation situation of the compressor 10, a low load may be applied to the double-headed piston 100 (hereinafter referred to as “low-load period”), and a high load that is higher than the low load may be applied to the double-headed piston 100 (hereinafter referred to as “high-load period”).

During the low-load period, the double-headed piston 100 receives load that is less than a specific threshold value. The low-load period may satisfy, for example, at least one of the following two conditions: (A) the inclination angle of the swash plate 50 is equal to the minimum inclination angle or closer to the minimum inclination angle than the maximum inclination angle; and (B) the compression reaction force that the double-headed piston receives from the compression chambers A4 and A5 is less than a threshold value.

During the high-load period, the double-headed piston 100 receives load that is greater than the specific threshold value. The high-load period may satisfy, for example, at least one of the following two conditions: (A) the inclination angle of the swash plate 50 is equal to the maximum inclination angle or closer to the maximum inclination angle than the minimum inclination angle; and (B) the compression reaction force that the double-headed piston receives from the compression chambers A4 and A5 is greater than or equal to a threshold value.

However, the low-load period and the high-load period do not have to be set in accordance with the above conditions. Instead, the low-load period and the high-load period may be set in accordance with, for example, the operation condition of the compressor 10. The high-load period may be, for example, when the compressor 10 is activated or when the vehicle is accelerated at a rate that is greater than or equal to a predetermined threshold acceleration rate. The low-load period may be when the compressor 10 is operated as the vehicle is traveling at a constant speed or as the vehicle is accelerated at a rate that is less than the predetermined threshold acceleration rate.

Alternatively, the low-load period and the high-load period may be set in accordance with the operation condition of a vehicle air-conditioner. For example, during the high-load period, the vehicle air-conditioner may be activated or a passenger compartment temperature may be maintained. As another option, during the high-load period, the vehicle air-conditioner may be operated to reach a set target temperature under the condition that the difference of the set target temperature and the passenger compartment temperature is greater than or equal to a threshold value, and during the low-load period, the vehicle air-conditioner may be operated to reach the set target temperature under the condition that the difference of the set target temperature and the passenger compartment temperature is less than a threshold value.

The low load may be referred to as a first load, and the high load may be referred to as a second load.

The double-headed piston 100 during the low-load period will now be described.

Referring to FIG. 5, the double-headed piston 100 receives a relatively small bending load during the low-load period. Thus, the neck 101 resists deforming. In this case, the side surfaces 103b and 113b of the heads 103 and 113 slide along (i.e., abut against) the wall surfaces 91a and 92a of the cylinder bores 91 and 92 and thus receive bending load. In this case, the distal portions 105b and 115b of the Inner portions 105 and 115 are farther from the wall surfaces 91a and 92a of the cylinder bores 91 and 92 than the side surfaces 103b and 113b of the heads 103 and 113. Thus, the double-headed piston 100 reciprocates with the distal portions 105b and 115b separated from the wall surfaces 91a and 92a of the cylinder bores 91 and 92. The low-load period may be when the neck 101 is not deformed or when the neck 101 is deformed but the distal portions 105b and 115b do not abut against the wall surfaces 91a and 92a of the cylinder bores 91 and 92.

The double-headed piston 100 during the high-load period will now be described. In the present embodiment, the double-headed piston 100 is located at the first position or the second position during the high-load period.

As shown in FIG. 6, when the double-headed piston 100 is located at the first position, the first distal portion 105b of the first inner portion 105 is opposed to the first wall surface 91a in the radial direction R. Further, when the double-headed piston 100 is located at the first position, the double-headed piston 100 receives a relatively large bending load. In this case, the neck 101 is deformed toward the inner side in the radial direction R so that the entire double-headed piston 100 is bent and bulged toward the inner side in the radial direction R.

When the double-headed piston 100 is bent, the side surfaces 103b and 113b of the heads 103 and 113 slide along (i.e., abut against) the wall surfaces 91a and 92a, and the first distal portion 105b (more specifically, portion of first inner surface 105d that corresponds to first distal portion 105b) slides along the first wall surface 91a. That is, the side surfaces 103b and 113b of the heads 103 and 113 and the first distal portion 105b receive bending load. In this case, since the distance from the first distal portion 105b to the first shoe holder 102 in the axial direction of the double-headed piston 100 is shorter than the distance from the first head 103 to the first shoe holder 102, bending moment that is produced at the double-headed piston 100 is reduced as compared to when bending load is received only by the heads 103 and 113. The first distal portion 105b corresponds to a “load receiving portion.”

The high-load period is when the neck 101 receives bending load and deforms such that the distal portions 105b and 115b abut against the wall surfaces 91a and 92a of the cylinder bores 91 and 92. That is, the specific threshold value refers to a lower limit value of load in which the distal portions 105b and 115b abut against the wall surfaces 91a and 92a of the cylinder bores 91 and 92 when the neck 101 is deformed.

When the first distal portion 105b abuts against the first wall surface 91a, further deformation of the double-headed piston 100 is restricted. In addition, when the double-headed piston 100 is bent, priority is given to the sliding of the edge of the first distal portion 105b, which is obliquely inclined, along the first wall surface 91a. When the first distal portion 105b slides along the first wall surface 91a, the first fixed-width portion 105c is separated from the first wall surface 91a.

Further, a first oil collection region A21 is defined between the side surface 103b of the first head 103 and the first distal portion 105b. The first oil collection region A21 is located between the first wall surface 91a and the first fixed-width portion 105c. Oil suspended in refrigerant flows into the first oil collection region A21. Then, the oil is supplied to where the side surface 103b of the first head 103 slides along (i.e., abuts against) the wall surface 91a and to where the first distal portion 105b slides along the first wall surface 91a.

When the double-headed piston 100 is located at the first position, the second projection 82 of the swash plate 50 is located in the second space A12. This avoids interference between the double-headed piston 100 and the second projection 82. The second space A12 does not interfere with the coupling receiving portion 76 and the second projection 82 regardless of the inclination angle of the swash plate 50 and the position of the double-headed piston 100 in the cylinder bores 91 and 92.

As shown in FIG. 7, when the double-headed piston 100 is located at the second position, the second distal portion 115b of the second inner portion 115 is opposed to the second wall surface 92a in the radial direction R. Further, since the double-headed piston 100 receives a relatively large bending load, the neck 101 is deformed toward the inner side in the radial direction R so that the entire double-headed piston 100 is bent and bulged toward the inner side in the radial direction R. The side surface 103b of the head 103 slides along the first wall surfaces 91a, and the side surface 113b of the second head 113 and the second distal portion 115b (more specifically, portion of second inner surface 115d that corresponds to second distal portion 115b) slide along the second wall surface 92a. That is, the side surfaces 103b and 113b of the heads 103 and 113 and the second distal portion 115b receive bending load. In this case, the distance from the second distal portion 115b to the second shoe holder 112 in the axial direction of the double-headed piston 100 is shorter than the distance from the second head 113 to the second shoe holder 112. This reduces the bending moment produced at the double-headed piston 100 as compared to when the bending load is received only by the heads 103 and 113. The second distal portion 115b corresponds to the “load receiving portion.”

When the second distal portion 115b abuts against the second wall surface 92a, further deformation of the double-headed piston 100 is restricted. In addition, when the double-headed piston 100 is bent, priority is given to the sliding of the edge of the second distal portion 115b, which is obliquely inclined, along the second wall surface 92a. The second fixed-width portion 115c is separated from the second wall surface 92a.

Further, a second oil collection region A22 is defined between the side surface 113b of the second head 113 and the second distal portion 115b. The second oil collection region A22 is located between the second wall surface 92a and the second fixed-width portion 115c. Oil suspended in refrigerant flows into the second oil collection region A22. Then, the oil is supplied to where the side surface 113b of the second head 113 slides along the second wall surface 92a and to where the second distal portion 115b slides along the second wall surface 92a.

When the double-headed piston 100 is located at the second position, the first projection 81 of the swash plate 50 is located in the first space A11. This avoids interference between the double-headed piston 100 and the first projection 81. The first space A11 does not interfere with the double-headed piston 100 and the first projection 81 regardless of the inclination angle of the swash plate 50 and the position of the double-headed piston 100 in the cylinder bores 91 and 92.

The above embodiment has the advantages described below.

(1) The compressor 10 is of a double-headed piston type swash plate type that compresses fluid in the compression chambers A4 and A5 of the cylinder bores 91 and 92 when rotation of the swash plate 50 rotates the double-headed piston 100 in the two cylinder bores 91 and 92.

The double-headed piston 100 includes the two shoe holders 102 and 112, which hold the two shoes 121 and 122 and are opposed to each other in the axial direction of the double-headed piston 100, and the neck 101, which couples the two shoe holders 102 and 112 and is located at a circumferential side of the swash plate 50. The neck 101 is deformable in the radial direction R. The double-headed piston 100 includes the two heads 103 and 113, which are respectively arranged at the two ends of the double-headed piston 100 in the axial direction, and the two coupling portions 104 and 114, which respectively couple the two heads 103 and 113 to the two shoe holders 102 and 112.

In such a structure, when the double-headed piston 100 receives load, the neck 101 is deformed toward the inner side in the radial direction R so that the double-headed piston 100 is bent and bulged toward the inner side in the radial direction R. The coupling portions 104 and 114 include the distal portions 105b and 115b, which serve as the load receiving portions receiving bending load that is applied from the swash plate 50 to the double-headed piston 100 and acts toward the inner side in the radial direction R. The distal portions 105b and 115b are located between the heads 103 and 113 and the shoe holders 102 and 112 as viewed in the radial direction R. During the low-load period, the load applied to the double-headed piston 100 is less than the specific threshold value. In this case, the distal portions 105b and 115b are separated from the wall surfaces 91a and 92a of the cylinder bores 91 and 92. During the high-load period, the load applied to the double-headed piston 100 is greater than the specific threshold value. In this case, when the neck 101 is deformed, each of the distal portions 105b and 115b abuts against the corresponding wall surface (first distal portion 105b abuts against first wall surface 91a and second distal portion 115b abuts against second wall surface 92a) and receives bending load.

In such a structure, during the low-load period, the side surfaces 103b and 113b of the heads 103 and 113 abut against the wall surfaces 91a and 92a of the cylinder bores 91 and 92, and the distal portions 105b and 115b do not abut against the wall surfaces 91a and 92a. This limits the power loss of the double-headed piston 100 that may occur when the distal portions 105b and 115b abut against the wall surfaces 91a and 92a.

During the high-load period, one of the two distal portions 105b and 115b receives bending load. Thus, three portions, namely, one of the two distal portions 105b and 115b and the side surfaces 103b and 113b of the heads 103 and 113, receive bending load. In this case, since the distance from the distal portions 105b and 115b to the shoe holders 102 and 112 to which bending load is applied is shorter in the axial direction of the double-headed piston 100 than the distance from the heads 103 and 113 to the shoe holders 102 and 112. This reduces the bending moment and thus reduces stress that is applied to the double-headed piston 100. Accordingly, the strength that counters bending load of the double-headed piston 100 is increased. Further, the double-headed piston 100 receives the bending load over more portions during the high-load period than during the low-load period. This disperses the bending load and thus limits local wear.

(2) The distal portions 105b and 115b of the inner portions 105 and 115 are located closer to the shoe holders 102 and 112 than the heads 103 and 113. This shortens the distance from each of the portions that receive bending load (i.e., distal portions 105b and 115b serving as load receiving portions) to each of the portions where bending load is applied (i.e., shoe holders 102 and 112). Thus, bending moment is reduced in a further preferred manner, and the strength that counters bending load is further increased.

(3) The coupling portions 104 and 114 respectively include the outer portions 106 and 116, which extend in the axial direction of the double-headed piston 100, and the inner portions 105 and 115, which are located at the inner sides of the outer portions 106 and 116 in the radial direction R and extended from the heads 103 and 113 in the axial direction of the double-headed piston 100. The inner portions 105 and 115 are opposed to the outer portions 106 and 116 in the radial direction R. The inner portions 105 and 115 respectively include the inner surfaces 105d and 115, which are opposed in the radial direction R to the wall surfaces 91a and 92a of the cylinder bores 91 and 92. The inner surfaces 105d and 115d and the side surfaces 103b and 113b of the heads 103 and 113 form a step so that the inner surfaces 105d and 115d are located further inward (i.e., farther from wall surfaces 91a and 92a of cylinder bores 91 and 92) than the side surfaces 103b and 113b. The distal portions 105b and 115b, which are the ends of the inner portions 105 and 115 located near the shoe holders 102 and 112, serve as the load receiving portions that receive bending load during the high-load period. In such a structure, since the inner surfaces 105d and 115d and the side surfaces 103b and 113b of the heads 103 and 113 form a step, the distal portions 105b and 115b are separated from the wall surfaces 91a and 92a of the cylinder bores 91 and 92 during the low-load period in which the neck 101 is not deformed. When the neck 101 is deformed such that the double-headed piston 100 is bent and bulged toward the inner side in the radial direction R, one of the distal portions 105b and 115b abuts against the wall surface of the corresponding cylinder bore and receives bending load. Thus, advantage (1) is obtained in a relatively simple structure.

In particular, the inner portions 105 and 115 extend from the heads 103 and 113 in the axial direction of the double-headed piston 100, and the distal portions 105b and 115b of the inner portions 105 and 115 are parts of the inner portions 105 and 115 located closest to the shoe holders 102 and 112. When the distal portions 105b and 115b receive bending load, the distance from each of the portions that receive bending load to each of the portions where bending load is applied is further shortened. This reduces bending moment.

(4) The inner portions 105 and 115 respectively include the fixed-width portions 105c and 115c, each having a fixed width. The distal portions 105b and 115b are wider than the fixed-width portions 105c and 115c. This increases the areas of the portions that receive bending load and thus reduces wear of the distal portions 105b and 115b (more specifically, portions of inner surfaces 105d and 115d that form distal portions 105b and 115b). Further, the fixed-width portions 105c and 115c that do not abut against the wall surfaces 91a and 92a of the cylinder bores 91 and 92 are narrow. This reduces the weight of the double-headed piston 100.

(5) The coupling portions 104 and 114 respectively include the ribs 109 and 119 that connect the distal portions 105b and 115b and the shoe holders 102 and 112 so that the spaces A1 and A12 are defined beside the distal portions 105b and 115b as viewed in the widthwise direction W. This allows the swash plate 50 to pass the spaces A11 and A12. Thus, interference between the swash plate 50 and the double-headed piston 100 is avoided.

(6) The lengths X11 and X21 of the inner portions 105 and 115 are larger than the lengths X12 and X22 of the ribs 109 and 119 in the axial direction of the double-headed piston 100. In such a structure, the distal portions 105b and 115b of the inner portions 105 and 115 become close to the shoe holders 102 and 112 to avoid interference with the swash plate 50. This avoids interference with the swash plate 50 and increases the strength that counters bending load of the double-headed piston 100 in the radial direction R.

(7) The cylinder bores 91 and 92 include oil. During the high-load period, the oil enters the oil collection regions A21 and A22 defined between the distal portions 105b and 115b, which abut against the wall surfaces 91a and 92a of the cylinder bores 91 and 92, and the heads 103 and 113. The oil that flow into the oil collection regions A21 and A22 is supplied to where the distal portions 105b and 115b abut against the wall surfaces 91a and 92a and to where the side surfaces 103b and 113b of the heads 103 and 113 abut against the wall surfaces 91a and 92a. Thus, the abut portions are supplied with a sufficient amount of oil, and wear is reduced.

(8) The double-headed piston 100 reciprocates from the first position to the second position when the inclination angle of the swash plate 50 is the maximum. The first distal portion 105b is opposed to the first wall surface 91a when the double-headed piston 100 is located at the first position. The second distal portion 115b is opposed to the second wall surface 92a when the double-headed piston 100 is located at the second position. In such a structure, when the double-headed piston 100 is located at least at the first location or the second location, the distal portions 105b and 115b receive bending load. This avoids situations in which the distal portions 105b and 115b are unable to receive bending load when receiving a relatively high load.

(9) The compressor 10 includes the actuator 70 that changes the inclination angle of the swash plate 50. The actuator 70 includes the movable body 71, which is movable in the axial direction Z of the rotation shaft 20, and the partition 72, which defines the control chamber A3 in cooperation with the movable body 71. The compressor 10 changes the inclination angle of the swash plate 50 when the movable body 71 moves in accordance with the pressure of the control chamber A3. Thus, adjustment of the pressure of the control chamber A3 allows for variable displacement.

When variable displacement is performed, the controllability of the variable displacement needs to be increased. In the present embodiment, the coupling portions 104 and 114 are relatively narrow (for example, less than or equal to width of neck 101) so that the coupling portions 104 and 114 are easily deformed in the widthwise direction W. Thus, as compared to the piston that is wide in the widthwise direction W to receive side force, the weight of the double-headed piston 100 is reduced. This increases the controllability of variable displacement.

(10) The second head 113 has a smaller diameter than the first head 103. In such a structure, the first head 103 and the second head 113 respectively include refrigerant pressure receiving areas that differ from each other. Accordingly, the first head 103 and the second head 113 have different compression reaction forces that result from the compression of fluid. This allows variable displacement to be performed relatively easily. Thus, the controllability of variable displacement is increased.

(11) The neck recesses 101 include the rotation stopper 123 that restricts rotation of the double-headed piston 100 in the two cylinder bores 91 and 92. The rotation stopper 123 is located at the portion of the neck 101 that is closer to the second head 113 than the first head 103. In such a structure, the rotation stopper 123 is located at the small diameter side where the strength has a tendency of being lower than the large diameter side. This limits decreases in the strength of the second head 113, which is an undesirable situation that may occur when the heads 103 and 113 have different diameters.

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

The coupling portions 104 and 114 are not limited to any specific shape. For example, each of the coupling portions may be smaller than the heads 103 and 113 and have a tubular or cylindrical shape.

The load receiving portions that receive bending load do not have to be the distal portions 105b and 115b. Instead, the load receiving portions may be, for example, projections that project from the inner surfaces 105d and 115d. In this case, the inner surfaces 105d and 115d may be located sufficiently outward from the side surfaces 103b and 113b of the heads 103 and 113 in the radial direction R so that the projections do not slide along the wall surfaces 91a and 92a of the cylinder bores 91 and 92 during the low load. Alternatively, the dimensions and the like of the projections may be adjusted.

Further, the load receiving portions may be the fixed-width portions 105c and 115c. In this case, the fixed-width portions 105c and 115c project further inward in the radial direction R (i.e., toward portions of wall surfaces 91a and 92a opposing fixed-width portions 105c and 115c) from the distal portions 105b and 115b. In the same manner, the load receiving portions may be the basal portions 105a and 115a of the inner portions 105 and 115. That is, the load receiving portions may be located at the portions of the coupling portions 104 and 114 closer to the heads 103 and 113 than the shoe holders 102 and 112 (between shoe holders 102 and 112 and heads 103 and 113). However, it is preferred that the load receiving portions be the distal portions 105b and 115b in order to further reduce bending moment.

The inner portions 105 and 115 may be omitted. In this case, for example, protrusions may protrude from the middle portions of the outer portions 106 and 116 toward the inner side in the radial direction R, and the protrusions may include distal portions that are separated from the wall surfaces 91a and 92a of the cylinder bores 91 and 92. In such a structure, when the neck 101 is deformed, the distal portions of the protrusions abut against the wall surfaces 91a and 92a. In other words, the load receiving portions may have any specific shape as long as the coupling portions 104 and 114 located between the heads 103 and 113 and the shoe holders 102 and 112 include the load receiving portions.

The two fixed-width portions 105c and 115c may be omitted. For example, the inner portions 105 and 115 may be gradually narrowed or widened from the basal portions 105a and 115a toward the distal portions 105b and 115b. In this case, the distal portions 105b and 115b may be wider than the portions of the inner portions 105 and 115 excluding the distal portions 105b and 115b. Alternatively, the distal portions 105b and 115b may be narrower than the shoe holders 102 and 112. As another option, one of the two fixed-width portions 105c and 115c may be omitted.

The fixed-width portions 105c and 115c may be wider than the shoe holders 102 and 112. In other words, the inner portions 105 and 115 may be at least partially narrower than the shoe holders 102 and 112, and the entire inner portions 105 and 115 may be wider than the shoe holders 102 and 112. Alternatively, the inner positions 105 and 115 may be wider than the neck 101.

Each of the coupling portions 104 and 114 may have a width that is less than or equal to that of the neck 101. Alternatively, each of the coupling portions 104 and 114 may have a width that is greater than that of the neck 101.

The outer portions 106 and 116 may be thicker or thinner than the inner portions 105 and 115. Further, at least one of the two outer portions 106 and 116 may be omitted.

In the embodiment, the first coupling portion 104 in the axial direction of the double-headed piston 100 is longer than the second coupling portion 114. Instead, the two coupling portions 104 and 114 may have the same length. Alternatively, the second coupling portion 114 may be longer than the first coupling portion 104.

The first head 103 and the second head 113 may have the same size. Alternatively, the second head 113 may be larger than the first head 103. In addition, the heads 103 and 113 may be cylindrical.

The ribs 109 and 119 may have any specific structure as long as the ribs 109 and 119 do not interfere with the swash plate 50. For example, the ribs 109 and 119 may be L-shaped or reverse L-shaped as viewed in the widthwise direction W.

The neck 101 and the coupling portions 104 and 114 are not limited to the forms illustrated in the embodiment.

The neck recess 101a may have any shape. Further, the neck recess 101a may be omitted.

The through holes 107a and 117a are not limited to any specific shape. Further, at least one of the through holes 107a and 117a may be omitted, and at least one of the plates 107 and 117 may be omitted.

The rotation stopper 123 may be located closer to the first shoe holder 102 than the neck recesses 101a. Alternatively, the rotation stopper 123 may be located closer to both of the first shoe holder 102 and the second shoe holder 112 than the neck recesses 101a. Further, the rotation stopper 123 may be omitted.

The actuator 70 may have any specific structure as long as the actuator 70 is capable of changing the inclination angle of the swash plate 50. In the same manner, the link mechanism 60 may have any specific structure as long as the link mechanism 60 is capable of transmitting power from the rotation shaft 20 to the swash plate 50.

At least one of the first projection 81 and the second projection 82 may be omitted.

The number of cylinder bores 91 and 92 and the number of double-headed pistons 100 are not limited to those of the embodiment and may each be, for example, one.

The lengths X11 and X21 of the inner portions 105 and 115 may be less than or equal to the lengths X12 and X22 of the ribs 109 and 119.

At least one of each of the inner portions 105 and 115 and each of the outer portions 106 and 116 may be slightly inclined with respect to the axial direction of the double-headed piston 100.

The compressor 10 of the embodiment is of a variable displacement type. Instead, the compressor 10 may be of a fixed displacement type in which the inclination angle of the swash plate 50 is fixed.

The fluid that is subject to compression by the compressor 10 is not limited to refrigerant and may be, for example, air.

The compressor 10 does not have to be installed in a vehicle.

The above embodiment may be combined with each of the modified examples.

Therefore, 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.

Claims

1. A double-headed piston type swash plate compressor comprising:

a rotation shaft extending in an axial direction and a radial direction;

a housing that accommodates the rotation shaft;

a swash plate that rotates when the rotation shaft rotates;

two cylinder bores located in the housing at an outer side of the rotation shaft in the radial direction;

a double-headed piston that reciprocates in the two cylinder bores; and

two shoes that couple the double-headed piston to the swash plate, wherein

the two cylinder bores and the double-headed piston define two compression chambers,

rotation of the swash plate reciprocates the double-headed piston in the two cylinder bores and compresses fluid in each of the compression chambers,

the double-headed piston includes: two shoe holders that hold the two shoes, wherein the two shoe holders are opposed to each other in an axial direction of the double-headed piston; a neck that couples the two shoe holders, wherein the neck is located at an outer circumferential side of the swash plate and deformable in the radial direction; two heads respectively located at two ends of the double-headed piston in the axial direction of the double-headed piston, wherein each of the two heads includes a side surface opposing a wall surface of the cylinder bore; and two coupling portions that couple the two shoe holders and the two heads, respectively,

at least one of the two coupling portions includes a load receiving portion located between the corresponding head and the corresponding shoe holder as viewed in the radial direction, wherein the load receiving portion is configured to receive bending load that is applied from the swash plate to the double-headed piston and acts toward an inner side in the radial direction,

the load receiving portion is separated from the wall surface of the cylinder bore when load applied to the double-headed piston is less than a specific threshold value, and

the load receiving portion abuts against the inner wall of the cylinder bore and receives the bending load when the load applied to the double-headed piston is greater than the specific threshold value.

2. The double-headed piston type swash plate compressor according to claim 1, wherein

each of the two coupling portions includes: an outer portion extending in the axial direction of the double-headed piston; and an inner portion located at the inner side of the outer portion in the radial direction and extended from the head in the axial direction of the double-headed piston,

the inner portion includes an inner surface opposing the wall surface of the cylinder bore in the radial direction,

the inner surface and the side surface of the head form a step so that the inner surface is farther from the wall surface of the cylinder bore than the side surface of the head, and

the load receiving portion is an end of the inner portion near the corresponding shoe holder.

3. The double-headed piston type swash plate compressor according to claim 2,

when referring to a direction orthogonal to both of the axial direction and an opposing direction of the inner portion and the outer portion as a widthwise direction,

the inner portion includes a fixed-width portion having a fixed width, and

the end of the inner portion near the corresponding shoe holder is wider than the fixed-width portion.

4. The double-headed piston type swash plate compressor according to claim 1, wherein

the cylinder bore includes oil and an oil collection region located between the load receiving portion and the corresponding head; and

the oil enters the oil collection region when load applied to the double-headed piston is greater than the threshold value.

5. The double-headed piston type swash plate compressor according to claim 1,

each of the two coupling portions includes the load receiving portion,

when the double-headed piston reciprocates from a first position to a second position,

a first one of the load receiving portions that is included in a first one of the two coupling portions opposes the wall surface of the cylinder bore when the double-headed piston is located at the first position, and

a second one of the load receiving portions that is included in a second one of the two coupling portions opposes the wall surface of the cylinder bore when the double-headed piston is located at the second position.

6. The double-headed piston type swash plate compressor according to claim 1, further comprising an actuator that changes an inclination angle of the swash plate, wherein

the actuator includes:

a movable body that is movable in the axial direction of the rotation shaft; and

a partition that defines a control chamber in cooperation with the movable body, and

the actuator is operable to change an inclination angle of the swash plate when the movable body is moved in accordance with pressure of the control chamber.

7. The double-headed piston type swash plate compressor according to claim 6, wherein

the two heads include a first head and a second head, and

the second head has a smaller diameter than a diameter of the first head.