WOBBLE PLATE TYPE COMPRESSOR WITH VARIABLE DISPLACEMENT MECHANISM

Abstract: A wobble plate type compressor (1) with a variable displace­ ment mechanism includes a compressor housing which is pro­ vided with a crank chamber (32) and a cylinder block (31) in which a plurality of cylinders are formed. A drive shaft (7) is rotatably supported in the compressor housing. A rotor (9) is fixed on the drive shaft (7) and variably connected to an inclined plate (11) through a hinge mechanism. A wobble plate (13) is adjacent to the inclined plate (11) and converts rotary motion of the inclined plate (11) into nutating motion thereof. A plurality of pistons (19) are coupled with the wobble plate (13) each of which is reciprocably fitted within a respective one of the cylinders (33) and of which the stroke volume is changed in accordance with variation of the angle of the inclined plate. The hinge mechanism comprises a first arm portion (93) of the cam rotor (9) through which a hole is formed, a guide pin (12) which is fixedly disposed in the hole, and a second arm portion (114) of the inclined plate (11) through which an elongated hole (115) is formed, the guide pin (12) being inserted into the elongated hole (115). Therefore, the angle of the inclined plate (11) can be rapidly changed to a largest angle without using a return spring for returning the inclined plate (11) to the least angle.

Description: The present invention relates to a wobble plate type compressor with a variable displacement mechanism according to the precharacterizing portion of claim 1. A compressor of this type is disclosed in the US-A-2,964,234. In a compressor of this kind, pistons are reciprocated by converting the rotational movement of a cam rotor into nutational movement of a wobble plate. Changing the inclination angle of the wobble plate changes the stroke of the pistons and therefore changes the displacement volume of the cylinders. Referring to Fig. 1, the construction of a further conventional wobble plate type compressor is shown. A wobble plate type compressor 1 includes a front end plate 2, a cylinder casing 3 having a cylinder block 31, a valve plate 4, and a cylinder head 5. Front end plate 2 is fixed on one end of cylinder casing 3 by securing bolts 6. An axial hole 21, which is formed through the center of front end plate 2 receives a drive shaft 7. A radial bearing 8 is disposed in axial hole 21 to rotatably support drive shaft 7. An annular sleeve portion 22 projects from front end plate 2 and surrounds drive shaft 7, defining a seal cavity. Cylinder casing 3 is provided with cylinder block 31 and a crank chamber 32. Cylinder block 31 has a plurality of equiangularly spaced cylinders 33 formed therein. A cam rotor 9 is fixed on drive shaft 7 by a guide pin 12. A thrust needle bearing 10 is disposed between the inner wall surface of front end plate 2 and the adjacent axial end surface of cam rotor 9. A third arm portion 91 of cam rotor 9 extends in the direction of cylinder block 31. An elongated hole 92 is formed on an arm portion 91. An inclined plate 11, provided with a flange portion 111, a fourth arm portion 112 and a cylindrical portion 113, is disposed around drive shaft 7. Fourth arm portion 112 is formed on the outer surface of flange portion 111 of inclined plate 11 and faces third arm portion 91 of cam rotor 9. A hole (not shown) which is formed in fourth arm portion 112 is aligned with elongated hole 92. Guide pin 12, which is fixedly inserted through the hole, is slidably movable within elongated hole 92. Ring shaped wobble plate 13 is mounted on the outer surface of cylindrical portion 113 of inclined plate 11 through radial bearing 14 and is prevented from axial movement by flange portion 111 and a snap ring 15 which is disposed on cylindrical portion 113. Wobble plate 13 is also prevented from rotating by a guide plate 25 which extends within crank chamber 32. A thrust needle bearing 16 is disposed in a gap between flange portion 111 and wobble plate 13. The other end of drive shaft 7 is rotatably supported through radial bearing 17 in the central bore 34 of cylinder block 31. One end of a piston rod 18 is rotatably connected to receiving surface 131 of wobble plate 13. The other end of piston rod 18 is rotatably connected to a piston 19 which is slidably fitted within a cylinder 33. Suction ports 41 and discharge ports 42 are formed through a valve plate 4. A suction reed valve (not shown) and a discharge reed valve (not shown) opposite the suction reed valve are disposed on valve plate 4. Cylinder head 5 is connected to cylinder casing 3 through gaskets (not shown) and valve plate 4. A partition wall 51 extends axially from the inner surface of cylinder head 5 and divides the interior of cylinder head 5 into a suction chamber 52 and a discharge chamber 53. Suction chamber 52 is connected to the external fluid circuit through a fluid inlet port 54 formed in cylinder head 5. Discharge chamber 53 is connected to the external fluid circuit through a fluid outlet port 55 formed in cylinder head 5. Crank chamber 32 of cylinder casing 3 and suction chamber 52 of cylinder head 5 are connected to one another through a conduit 311 to control the angle of inclined plate 11 and wobble plate 13. Conduit 311, which is formed within cylinder block 31, communicates crank chamber 32 of cylinder casing 3 with suction chamber 52 of cylinder head 5 through a central bore 34 which is formed within cylinder block 31 and a hollow portion 312 to introduce the fluid gas in crank chamber 32 to suction chamber 52 responsive to operation of a control valve 20. Control valve 20 controls opening and closing of conduit 311 in response to the difference between the gas pressure in crank member 32 and that in suction chamber 52. The angle of inclined plate 11 and wobble plate 13 is varied by the volume of the pressure difference. If the communication between crank chamber 32 and suction chamber 52 is prevented by closing operation of control valve 20, gas pressure in crank chamber 32 gradually increases and high gas pressure acts on the rear surface of pistons 19, thereby reducing the angle of inclined plate 11. Thus, the capacity of the compressor is changed into a small capacity. On the other hand, if crank chamber 32 and suction chamber 52 communicate with each other by opening operation of control valve 20, gas pressure in crank chamber 32 is reduced, thereby increasing the angle of inclined plate 11 and wobble plate 13. Thus, the capacity of the compressor is changed into a large capacity. A conventional hinge mechanism includes third arm portion 91 of cam rotor 9 having elongated hole 92, fourth arm portion 112 of inclined plate 11 and guide pin 12. With reference to Figs. 2 and 3, the construction of a drive mechanism including a conventional hinge mechanism is shown. As shown in Figs. 2 and 3, since guide pin 12 is fixedly disposed in a hole which is formed on fourth arm portion 112 of inclined plate 11, guide pin 12 gradually approaches drive shaft 7 as the angle of inclined plate 11 is reduced; the distance L between the central axis of drive shaft 7 and the center of guide pin 12 is reduced. Resultant force ΣFpi, which is the resulant force of the reaction force against the compression force of piston 19, is not so much influenced relative to the magnitude and operating point thereof, even though the angle of inclined plate 11 is changed. However, moment M for changing the angle of inclined plate 11 from the least angle to the largest one is influenced. Moment M is determined from the following equation: M = ΣFpi.Le wherein distance Le is the difference between L and Lf, Lf being the distance between the central axis of drive shaft 7 and the operating point of resultant force ΣFpi. As guide pin 12 is fixed at the side of inclined plate 11, as mentioned above, Le is reduced when the angle of inclined plate 11 is reduced, distance and thereby moment M is reduced. Thus, inclined plate 11 can not be rapidly returned to the position at which the angle of inclined plate 11 is largest. As one solution to the above problem, a return spring is used for increasing the angle of inclined plate 11 as shown in disclosed Japanese Patent Application Publication No. 61-261,681. It is an object of this invention to provide a wobble plate type compressor with a variable displacement mechanism which has a hinge mechanism allowing the inclined plate to rapidly return to the position having the largest angle in response to the gas pressure in the crank chamber. This object is acchieved by means of the features of claim 1. A wobble plate type compressor with a variable displacement mechanism according to the present invention includes a compressor housing which is provided with a crank chamber 32 and a cylinder block 31 in which a plurality of cylinders 33 are formed. A drive shaft 7 is rotatably supported in the compressor housing. A rotor 9 is fixed on the drive shaft 7 and variably connected to an inclined plate 11 through a hinge mechanism. A wobble plate 13 is adjacent the inclined plate 11 and converts rotary motion of the inclined plate 11 into nutating motion thereof. A plurality of pistons 19 are coupled with the wobble plate 13 each of which is reciprocably fitted within a respective one of the cylinders 33 and of which the stroke volume is changed in accordance with variation of the angle of the inclined plate 11. The hinge mechanism comprises a first arm portion 93 of the cam rotor 9 through which a hole is formed, a guide pin 12 which is fixedly disposed in the hole, and a second arm portion 114 of the inclined plate 11 through which an elongated hole 115 is formed. The guide pin 12 is slidably movable within the elongated hole 115. Further objects, features and other aspects of the invention will be understood from the following description of the preferred embodiments of the invention referring to the attached drawings. Fig. 1 is a cross-sectional view of a conventional wobble plate type compressor with a variable displacement mechanism. Fig. 2 is a perspective view of a drive mechanism which includes a conventional hinge mechanism, the angle of an inclined plate thereof being the largest angle. Fig. 3 is a perspective view of a drive mechanism which includes a conventional hinge mechanism, the angle of an inclined plate thereof being the least angle. Fig. 4 is a cross-sectional view of a wobble plate type compressor with a variable displacement mechanism in accordance with one embodiment of this invention. Fig. 5 is a perspective view of a drive mechanism which includes a hinge mechanism in accordance with one embodiment of this invention, the angle of an inclined plate thereof being the largest angle. Fig. 6 is a perspective view of a drive mechanism which includes a hinge mechanism in accordance with one embodiment of this invention, the angle of an inclined plate thereof being the least angle. Referring to Fig. 4, the construction of a wobble plate type compressor with a variable displacement mechanism in accordance with one embodiment of this invention is shown. The same numerals designate alike elements of the construction shown in Fig. 1 and the description of that construction is omitted to simplify the specification of this application. The hinge mechanism in accordance with one embodiment of this invention includes a first arm portion 93 of cam rotor 9, guide pin 12 which is fixedly disposed in a hole formed in first arm portion 93, and a second arm portion 114 of inclined plate 11 which has an elongated hole 115 formed thereon. The holw formed in arm portion 93 is aligned with elongated hole 115. Referring to Figs. 5 and 6, the construction of a drive mechanism including the above hinge mechanism is shown. The angle of inclined plate 11 and wobble plate 13 is varied in accordance with changes of the gas pressure in crank chamber 32. In this motion, the angle of inclined plate 11 is varied within the range of elongated hole 115 in accordance with gas pressure in crank chamber 32 until guide pin 12 prevents the motion of inclined plate 11. Since guide pin 12 is fixed on first arm portion 93, the position of guide pin 12 is not moved. Thereby the distance L between the central axis of drive shaft 7 and the center of guide pin 12 is not changed. The volume and operating point of resultant force ΣFpi is not changed either, even though the angle of inclined plate 11 is changed, as mentioned above. Accordingly, Lf which is the distance between the central axis of drive shaft 7 and the operating point of resultant force ΣFpi is not changed so much, either. Thereby distance Le is maintained at a certain value in spite of variation of the angle of inclined plate 11. Therefore, moment M, which is determined from the above-mentioned equation, is also maintained at a certain value independent of variation of the angle of inclined plate 11. Thus, inclined plate 11 can be returned to the position at which the angle of inclined plate 11 is changed from the least angle to the largest one without using a part for returning inclined plate 11 such as a return spring. According to one experiment, if distance L between the central axis of drive shaft 7 and the center of guide pin 12 is determined within the range of 78 % ∼ 90 % of the distance PCR between the central axis of drive shaft 7 and the central axis of cylinder 33, the angle of inclined plate 11 is easily increased, even though the large changes of gas pressure in crank chamber 32 do not act on the rear surface of piston 19. If distance L is determined as mentioned above, pressure difference Pe between pressure Pc in crank chamber 32 and pressure Ps in suction chamber 52, which is needed to reduce and increase the angle of inclined plate 11, is determined from the following equation: Pe = 0.5∼1.0 kg/cm² ± ΔP kg/cm² wherein ΔP is additional pressure which is needed for moving inclined plate 11 in the axial direction of both sides. When ΔP is added to a certain value in the above equation, the angle of inclined plate 11 is the least angle. When ΔP is subtracted from the certain value, the angle of inclined plate 11 is the largest angle. Accordingly, as it is not necessary to have a high pressure difference Pe, and thus a wobble plate type compressor with a variable displacement mechanism which is high in durability can be provided. The present invention has been described in detail in connection with the preferred embodiment, but this is an example only, and the invention is not restricted thereto. It will be easily understood by those skilled in the art that other variations and modifications can be easily made within the scope of this invention.

Claims: In a wobble plate type compressor (1) with a variable displacement mechanism, said compressor (1) including a compressor housing provided with a crank chamber (32) and a cylinder block (31) in which a plurality of cylinders (33) are formed, a drive shaft (7) rotatably supported in said housing, a rotor (9) fixed on said drive shaft (7) and variably connected to an inclined plate (11) through a hinge mechanism, a wobble plate (13) adjacent to said inclined plate (11) and converting rotary motion of said inclined plate (11) into nutating motion thereof, and a plurality of pistons (19) coupled with said wobble plate (13) each of which is reciprocably fitted within a respective one of said cylinders (13) and of which the stroke volume is changed in accordance with variation of the angle of said inclined plate (11); said hinge mechanism comprises a first arm portion (93) of said cam rotor (9) and a guide pin (12) which is fixedly disposed on said portion (93), and a second arm portion (114) of said inclined plate (12) through which an elongated hole (115) is formed, said guide pin (12) being inserted into said elongated hole (115), characterized in that the distance between the centre of said guide pin (12) and the central axis of said drive shaft (7) is determined within the range of 78% to 90% of the distance between the central axis of said cylinder (33) und the central axis of said drive shaft (7). The wobble plate type compressor according to claim 1, characterized in that a hole is formed in said first arm portion (93) and said guide pin (12) is fixedly disposed in said hole.

Inventors: KAZUHIKO, TAKAI
Applicants: SANDEN CORPORATION
Application year: 1988
Main classification: F04B1
IPC codes: F04B27