CONTROL CYLINDER DEVICE IN VARIABLE DISPLACEMENT COMPRESSOR

Abstract: In control cylinder device in a variable displacement compressor (C), an annular cylinder (32₁) concentric with the driving rotary shaft (5) is provided in a housing (2) of a compressor body, and an annular control piston (33) is slidably fitted in the cylinder to define a control pressure chamber (34) within the cylinder (32₁). The annular control piston (32) is connected to the sleeve, so that the sliding movement of the sleeve (15) can be controlled by the operation of the control piston (33). Further, inner and outer seal rings (S₁, S₂) are interposed in an axially misaligned relation to each other between inner and outer slide surfaces of the cylinder (32₁) and control piston (33). This facilitates a accurate formation of the inner and outer surfaces of the cylinder (32₁) in the cylinder device on which the control piston (33) slides. Also, this easily insures sealing properties required between the slide surfaces of the cylinder (32₁) and the piston (33). In addition, it is possible to effectively prevent the inclination of the control piston (33) within the cylinder (32₁).

Description: The present invention relates to a variable displacement compressor used for an air-cooler of an automobile or the like, having a cylinder device for controlling the change of the angular position of a swingable swash plate to vary the displacement of the compressor. There is such a conventionally known variable displacement compressor in which the swinging movement of the swingable swash plate is controlled by a cylinder device for changing the sliding stroke of an operating piston to vary the displacement (see U.S.P. No. 4,037,993). In the above conventional cylinder device, a control piston for controlling the swinging movement of the swingable swash plate is arranged so that its inner peripheral surface is slidably guided by a driving rotary shaft and its outer peripheral surface is slidably guided by a guide member separate from the driving rotary shaft. Therefore, it is difficult to insure the high accuracy of the concentricity and the parallelism of inner and outer guide slide surfaces of the piston. Consequently, this will cause a variation in sealing performance, a deterioration of seals, and an uneven wearing of the slide surfaces, leading to problems of the performance and reliability of the compressor. Another problem of the above conventional cylinder device is as follows. It is required to insure sealing properties between slide surfaces of the cylinder and the control piston slidably fitted in the cylinder to ensure a smooth and nimble operation of the control piston, while preventing leakage of a pressurised fluid within a control pressure chamber defined by the above parts to the outside. In order to satisfy such requirements, it is necessary to increase the working accuracies of the cylinder, the control piston and peripheral parts related thereto, resulting in a substantial increase in cost. The present invention has been accomplished with the above circumstances in view. EP-0270613 discloses a variable displacement compressor comprising a compressor body including a housing, a cylinder block and a cylinder head; a driving rotary shaft rotatably carried on the compressor body; a sleeve axially slidably carried on the driving rotary shaft within the housing; a journal which is supported on the sleeve for swinging movement about an axis perpendicular to an axis of the driving rotary shaft and which is rotatable with the rotary shaft; a swingable swash plate carried on the journal so as to be swingable only about the axis of the journal; a plurality of operating pistons connected with the swingable swash plate by means of a plurality of connecting rods; a plurality of cylinders disposed around the driving rotary shaft in the cylinder block and each having the corresponding one of the operating pistons slidably received therein, wherein the angular positions of the journal and of the swingable swash plate are varied by controlling sliding movements of the sleeve in an axial direction of the driving rotary shaft, thereby varying operation strokes of said operating pistons; a control cylinder device comprising a cylinder and an annular control piston slidably fitted in the cylinder to define a control pressure chamber within the cylinder, said annular control piston being connected to the sleeve so that the sliding movements of the sleeve are controlled by the operation of the control piston. According to the present invention, the cylinder is annular and is provided in an end wall of the housing, the annular cylinder being concentric with and spaced apart from the driving shaft. A control plate may be provided and connected to the sleeve for rotation in unison with the driving shaft, the control piston being relatively rotatably supported on the control plate through a bearing. This control plate may have a cylindrical portion which extends axially and is fitted over and supported on an outer peripheral surface of the driving rotary shaft with an end face of the cylindrical portion being engaged with an end face of the sleeve. A spring may be compressed in the control pressure chamber to urge the control plate, via the control piston, into abutment against the sleeve. There may be provided seals at inner side and outer side sliding surfaces respectively of the control piston with respect to the cylinder such that these seals are misaligned in the axial direction of the driving rotary shaft. With the above constructions, the cylinder of the cylinder device for changing the displacement is integrally formed on the housing composing the compressor body, and it is possible to concurrently or continuously finish-machine the inner and outer peripheral surfaces of the cylinder on which the piston slides, by machining, thereby achieving a high accuracy of a concentricity and a parallelism. This ensures that the control piston slidably fitted in the cylinder is smoothly and nimbly operated, and the sealing properties between the piston and the cylinder are improved. In addition, the interposition of the seal rings in the axially misaligned relation between the inner and outer slide surfaces of the cylinder and the piston makes it possible to insure the sealing properties between the control piston and the cylinder without requiring a high machining accuracy of the control piston and the related peripheral parts. Particularly, even if a force acts to tilt the control piston for any reason, the seal rings oppose such force to inhibit the tilting of the control piston, thereby insuring the smooth and nimble sliding movement of the control piston. Further, if in addition to the above construction, the control piston is relatively rotatably supported, via bearings, on a control plate which is connected to the sleeve for rotation in unison with the driving rotary shaft, the control piston is not forced to rotated within the cylinder. Thus, more smooth and nimble operation of the control piston is insured, and the sealing properties between the piston and the cylinder are further improved. For a better understanding of the present invention and to show how it may be carried into effect reference will now be made by way of example to the accompanying drawings, in which: The drawings illustrate one embodiment of the present invention, wherein Figure 1 is a side view in a longitudinal section of an essential portion of a variable displacement compressor according to the present invention; and Fig.2 is a sectional view taken along a line II-II in Fig.1. DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will now be described by way of one embodiment with reference to the accomapnying drawings. Referring to Fig.1, there is shown, in longitudinal section, an essential portion of a variable displacement compressor C in this embodiment. In Fig.1, a compressor body 1 of the compressor C is generally formed of a bottomed hollow cylindrical housing 2, a cylinder block 3 secured to an opened end face of the housing 2, and a cylinder head 4 overlaid on an end face of the cylinder block 3, these components being integrally connected. A driving rotary shaft 5 longitudinally passes through the housing 2 and is rotatably carried in the cylinder block 3 and an end wall 2₁ of the housing 2 through radial needle bearings 6 and 7. The driving rotary shaft 5 lies on an axis L1 of the compressor body 1 and a driving pulley 8 containing a clutch therein is integrally connected to a right-hand end of the shaft 5 projecting from the compressor body 1. The driving pulley 8 is operatively connected to a drive source such as an engine which is not shown, so as to be rotatively driven therefrom. A plurality of cylinders 9 are formed in the cylinder block 3 parallel with the driving rotary shaft 5 at uniform distances therebetween on a concentric circle having a center on the axis L1, and an operating piston 10 is slidably received in each of these cylinders 9. Each piston 10 divides the interior of the corresponding cylinder 9 into a compression chamber 12 and a back pressure chamber 13. A connecting rod 11 is rotatably connected at one spherical end thereof to a back of each operating piston 10 on the back pressure chamber side. Each of the connecting rods 11 extends axially within the cylinder 9 and its other spherical end extends into the housing 2 and is rotatably connected to a swingable swash plate 19 of a swash plate type driving mechanism D which will be described hereinafter. The structure of the swash plate type driving mechanism D will be described below. A sleeve 15 is axially slidably fitted over the driving rotary shaft 5 within a working chamber 14 in the housing 2. A pair of left and right pivots 16 are integrally projected on laterally opposite sides of the sleeve 15 and have a center on an axis L2 that extends normally to the sheet surface of Fig. 1 and perpendicular to the axis L1 of the driving rotary shaft 5. A board-like journal 17 is carried on each of the left and right pivots 16 for backward and forward swinging movement in the axial direction of the driving rotary shaft 5. The swingable swash plate 19 is rotatably carried through a radial bearing 18 on that cylindrical portion 17₁ of the journal 17 which extends so as to surround the sleeve 15, and a thrust needle bearing 20 is interposed between opposed faces of the swingable swash plate 19 and the journal 17. A detent member 21 is connected to an outer end of the swingable swash plate 19 through a connecting pin 22 and slidably engaged in a guide groove 23 which is formed within the working chamber 14 in parallel with the driving rotary shaft 5 to extend over one end face of the cylinder block 3 and the end face 2₁ of the housing 2. The guide groove 23 and the detent member 21 compose a detent mechanism 24 for the swingable swash plate 19. A drive pin 25 is integrally provided on the driving rotary shaft 5 to diametrically project therefrom within the working chamber 14. The drive pin 25 is integrally formed at its tip end with a pair of connecting arms 26 each of which has an arcuate engaging hole 27 made therein. An engaging pin 28 is integrally projected from a mounting piece 17₂ of the journal 17 and is slidably engaged in the engaging holes 27. The arcuate engaging holes 27 permit a swinging movement of the swingable swash plate 19 about the pivot 16 in an extent of the length of the engaging hole 27. The journal 17 rotates as the driving rotary shaft 5 rotates. As described above, the connecting rods 11 connected to the corresponding pistons 10 are at their other spherical ends rotatively connected to one face of the swingable swash plate 19. Accordingly, the operation stroke of each operating piston 10, i.e., the displacement depends upon the angular position of the swingable swash plate 19 about the axis L2 defined by the pivots 16. The driving rotary shaft 5 has a smaller diameter shank portion 5₂ formed at its end closer to the cylinder block 3 through a stepped locking portion 5₁. A first spring SP1 formed of a compression coiled spring is wound around the smaller diameter shank portion 5₂ and engaged at one end thereof on a spring seat 30 fitted over and lockated to smaller diameter shank portion 5₂ and at the other end thereof on an annular stopper 31 locked to the stepped locking portion 5₁. When the sleeve 15 slides leftward as viewed in Fig.1, the stopper 31 engages with one end face of the sleeve 15 while compressing the first spring SP1. The housing 2 is integrally provided at a central portion of its end wall 2₁ with an outward projecting bottomed cylinder portion 32 concentric with the driving rotary shaft 5, and an annular control piston 33 is slidably received in an annular cylinder 32₁ formed in the cylinder portion 32. Seal rings S1 and S2 are fitted respectively around inner and outer peripheral surfaces of the control piston 33 in an axially misaligned arrangement to provide a fluid-tight sealing between the respective inner and outer slide surfaces of the cylinder 32₁ and control piston 33. Even if a force acts on the control piston 33 in a direction to tilt the latter, these seal rings S1 and S2 act to suppress any tilting of the control piston 33 against such force due to their arrangement misaligned axially of the control piston 33. A control pressure chamber 34 is defined between the control piston 33 and an end wall of the cylinder portion 32. A second spring SP2 formed of a compression coiled spring is contained in the control pressure chamber 34 and has opposite ends retained on the control piston 33 and the end wall of the cylinder portion 32 to bias the control piston 33 leftward as viewed in Fig.1, i.e., toward the working chamber 14. The control piston 33 is rotatably carried at its end closer to the working chamber 14 on a control plate 36 through an angular ball bearing 35. The control plate 36 is integrally formed with an axially extending cylindrical portion 36₁ which is rotatably fitted over and carried on an outer peripheral surface of the driving rotary shaft 5, with its end face engaged with an end face of the sleeve 15 by a repulsive force of the second spring SP2. In addition, the cylindrical portion 36₁ is provided with an axial slit 37 through which the drive pin 25 extends, so that the driving rotary shaft 5 and the control plate 36 rotate in unison. A thrust needle bearing 38 is interposed between a back of the control plate 36 and the end wall 2₁ of the housing 2. If the control piston 33 slides laterally as viewed in Fig. 1, the sleeve 15 moves axially to follow the control piston 33 and with such movement, the angular positions of the journal 17 and the swingable swash plate 19 about the pivots 16 are varied. Specifically, when the control piston 33 moves leftward as viewed in Fig. 1, the sleeve 15 also moves leftward. With such movement, the journal 17 and the swingable swash plate 19 turn clockwise, leading to a reduced slide stroke of each operating piston 10. On the other hand, when the control piston 33 moves rightward, the sleeve 15 also moves rightward due to an operational pressure acting on the operating pistons 10. With such movement, the journal 17 and the swingable swash plate 19 turn counter-clockwise as viewed in Fig. 1, leading to an increased slide stroke of each operating piston 10. The short cylindrical cylinder head 4 is secured to the end face of the cylinder block 3 through a partition plate 40 with a packing 41 interposed therebetween. The cylinder head 4 includes a discharge chamber 42 centrally defined therein, with a boundary of the discharge chamber 42 with the cylinder block 3 being provided by the partition plate 40. A discharge line 44 formed in the cylinder head 4 communicates with the discharge chamber 42. The cylinder head 4 includes a suction chamber 45 also defined therein so as to surround the discharge chamber 42, with a boundary of the suction chamber 45 with the cylinder block 3 being also provided by the partition plate 40. The suction chamber 45 communicates with the working chamber 14 in the housing 2 through a communication passage 46 made in the cylinder block 3. Further, a suction line 47 is made in a wall the housing 2 and communicates with the working chamber 14. The partition plate 40 is provided with a discharge port 48 which permits the communication between the discharge chamber 42 and the compression chamber 12 in the cylinder 9, and a discharge valve 49 is mounted at the discharge port 48 and adapted to open the discharge port 48 when the operating piston 10 is in compressied or advancing operation. The partition plate 40 is further provided with a suction port 50 which permits the communication between the suction chamber 45 and the compression chamber 12 in the cylinder 9, and a suction valve 51 is mounted at the suction port 50 and adpated to open the suction port 50 when the operating piston 10 is in drawing or retreating operation. When the plurality of operating pistons 10 of the compressor C are reciprocally moved in sequence in the suction stroke, a refrigerant is supplied through the suction line 47, the working chamber 14 and the communication passage 46 into the suction chamber 45 from which it is drawn into the compression chamber 12 by opening of the suction valve 51. As a result of a compression stroke of the compressor C, the compressed refrigerant in the compression chamber 12 opens the discharge valve 49 and is pumped through the discharge chamber 42 into the discharge line 44. The displacement of the variable displacement compressor C constructed in the above-described manner is controlled by a control valve V. The construction of this control valve V will be described below. The control valve V is interposed among a discharge passage 52 connected to the discharge chamber 42, a suction passage 53 connected to the suction chamber 45 via the working chamber 14 and the communication chamber 46 and a control passage 54 connected to the control pressure chamber 34. A valve body 56 is mounted in a valve housing 55 formed on the end wall 2₁ of the housing 2. The valve body 56 defines, within the valve housing 55, a discharge pressure valve chest 57 with which the discharge passage 52 communicates, and the valve body 56 also includes a suction pressure valve chest 58 with which the suction passage 53 communicates, and a passage 59 with which the control passage 54 communicates. The passage 59 permits the communication between the discharge pressure valve chest 57 and the suction pressure valve chest 58. The valve body 56 is provided with a first valve mechanism 60 capable of putting the discharge pressure valve chest 57 and the passage 59 into and out of communication with each other, and a second valve mechanism 61 capable of putting the passage 59 and the suction pressure valve chest 58 into and out of communication with each other. The first valve mechanism 60 comprises a valve sphere 63 seatable on a valve seat 62 formed on the valve body 56, a valve spring 64 for biasing the valve sphere 63 in a valve-closing direction, and a push rod 65 for operating the valve sphere 63 in a valve-opening direction. The valve sphere 63 and the valve spring 64 are mounted in the discharge pressure valve chest 57, and the push rod 65 is movably passed longitudinally through the passage 59. The second valve mechanism 61 comprises a valve spool 68 integral with the push rod 65 and seatable on a valve seat 67 formed on the valve body 56, and a valve spring 69 for biasing the valve spool 68 in a valve-closing direction. The valve spool 68 and the valve spring 69 are contained in the suction pressure valve chest 58 defined in the valve body 56. A bellows 70 is contained in the suction pressure valve chest 58 to surround the valve spring 69 and is fluid-tightly connected at its opposite ends to the valve spool 68 and an end plate 58₁ of the suction pressure valve chest 58. The inside of the bellows 70 communicates with the atmosphere via a through hole 71 made in the end plate 58₁. Thus, if the sucked pressure Ps in the suction pressure valve chest 58 is increased, the bellows 70 is shrunk to open the second valve mechanism 61. If the sucked pressure Ps in the suction pressure valve chest 58 is reduced, the bellows 70 is expanded to open the first valve mechanism 60. The variable control of the discharge displacement will be described below. An air-cooler has a characteristic that If the cooling load is larger, the sucked pressure Ps is increased, whereas if the cooling load is smaller, the sucked pressure Ps is reduced. Therefore, If the cooling load is now decreased resulting in a reduced sucked-pressure Ps, the valve sphere 63 of the first valve mechanism 60 moves away from the seat 62 to open the valve, thereby to permit the discharge passage 52 and the control passage 54 into communication with each other, so that the control pressure Pc in the control chamber 34 is increased due to the discharged pressure Pd. With such increase, the control piston 33 is moved leftward as viewed in Fig.1 by the aid of the repulsive force of the second spring SP₂ to move the sleeve 15 leftward. This causes the journal 17 to be swung clockwise about the pivots 16, i.e., in a direction to stand the swingable swash plate 19 upright. Consequently, the operation strokes of the plurality of operating pistons 10 are reduced, and the displacement of the compressor is decreased. When the displacement of the compressor becomes a minimum, the sleeve 15 has reached the left limit while compressing the first spring SP₁ through the stopper 31. If the load of the air-cooler is increased resulting In an increased sucked-pressure Ps, then the bellows 70 are shrunk, so that the valve spool 68 of the second valve mechanism 61 moves away from the seat 67 to open the valve while the first valve mechanism 60 becomes closed. This brings the passage 59 and the suction pressure passage 53 into communication with each other to reduce the pressure Pc in the control chamber 34. With such reduction, the control piston 33 is moved rightward as viewed in Fig.1. This causes the sleeve 15 to be moved rightward due to of a working pressure exerted on the plurality of operating pistons 10. Thus, the journal 17 is moved counter-clockwise about the pivots 16 to tilt down the swingable swash plate 19 in the same direction, resulting in an increased operation stroke of each operating piston 10 and threby an increased displacement of the compressor C. The displacement of the variable displacement compressor C is controlled in the above manner. It should be noted that since the cylinder 32₁ in which the control piston 33 is slidably fitted is Integrally formed on the end wall 2₁ of the housing 2 composing the compressor body 1 as described above, it is possible to concurrently or continuously finish-machine the inner and outer slide surfaces of the cylinder 32₁ by machining, thereby insuring the high accuracy of the concentricity and the parallelism of the inner and outer slide surfaces. This ensures that the control piston 33 is smoothly and nimbly operated and moreover, the sealing properties between the cylinder 32₁ and the control piston 33 are improved. In addition, since the seal rings S1 and S2 are interposed, in the axially misaligned relation, i.e. at an axial distance from each other, between the inner and outer peripheral surfaces of the cylinder 32₁ and the control piston 33, these seal rings enable high sealing properties to be insured between the control piston 33 and the cylinder 32₁ without need for finish-machining of the control piston 33 and the related peripheral parts with a high accuracy. Particularly, even if a force acts to tilt the control piston 33, the seal rings S1 and S2 oppose such force to prevent the control piston 33 from being tilted, thereby ensuring the smooth and nimble operation, while insuring the high sealing properties.

Claims: A variable displacement compressor (C) comprising a compressor body (1) including a housing (2), a cylinder block (3) and a cylinder head (4); a driving rotary shaft (5) rotatably carried on the compressor body (1); a sleeve (15) axially slidably carried on the driving rotary shaft (5) within the housing (2); a journal (17) which is supported on the sleeve (15) for swinging movement about an axis (L2) perpendicular to an axis (L1) of the driving rotary shaft (5) and which is rotatable with the rotary shaft (5); a swingable swash plate (19) carried on the journal (17) so as to be swingable only about the axis (L2) of the journal (17); a plurality of operating pistons (10) connected with the swingable swash plate (19) by means of a plurality of connecting rods (11); a plurality of cylinders (9) disposed around the driving rotary shaft (15) in the cylinder block (3) and each having the corresponding one of the operating pistons (10) slidably received therein, wherein the angular positions of the journal (17) and of the swingable swash plate (19) are varied by controlling sliding movements of the sleeve (15) in an axial direction of the driving rotary shaft (5), thereby varying operation strokes of said operating pistons (10); a control cylinder device comprising a cylinder (32₁) and an annular control piston (33) slidably fitted in the cylinder (32₁) to define a control pressure chamber (34) within the cylinder (32₁), said annular control piston (33) being connected to the sleeve (15) so that the sliding movements of the sleeve (15) are controlled by the operation of the control piston (33), characterized in that the cylinder (32₁) is annular and is provided in an end wall (2₁) of the housing (2), the annular cylinder (32₁) being concentric with and spaced apart from the driving shaft (5). A variable displacement compressor (C) as claimed in claim 1 in which a control plate (36) is provided and connected to said sleeve (15) for rotation in unison with the driving rotary shaft (5), said control piston (33) being relatively rotatably supported on the control plate (36) through a bearing (35). A variable displacement compressor as claimed in claim 2, in which the control plate (36) has a cylindrical portion (36₁) which extends axially and is fitted over and supported on an outer peripheral surface of the driving rotary shaft (5) with an end face of the cylindrical portion (36₁) being engaged with an end face of the sleeve (15). A variable displacement compressor as claimed in claim 2 or 3, in which a spring (S p2 ) is compressed in said control pressure chamber (34) to urge the control plate (36), via the control piston (33), into abutment against the sleeve (15). A variable displacement compressor as claimed in any one of the preceding claims, in which respective seals (S₁) (S₂) are provided at inner-side and outer-side sliding surfaces of the control piston (33) with respect to the cylinder (32₁) such that these seals are misaligned in the axial direction of the driving rotary shaft (5). A variable displacement compressor as claimed in any one of claims 2 to 5, in which a bearing (7) is interposed between said end wall (2₁) of the housing (2) defining the annularly cylinder (32₁) and said driving rotary shaft (5) and a thrust bearing (38) is interposed between the end wall (2₁) and the control plate (36).

Inventors: KATO, SEIJI K.K. HONDA GIJUTSU KENKYUSHO, MINAKAWA, YASUO K.K. HONDA GIJUTSU KENKYUSHO, NAKASONE, HIDETAKA K.K. HONDA GIJUTSU KENKYUSHO, OONO, HIROMITSU K.K. HONDA GIJUTSU KENKYUSHO
Applicants: HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1989
Main classification: F04B27
IPC codes: F04B27