WOBBLE PLATE COMPRESSOR

Abstract: A wobble plate compressor with a variable displacement mechanism includes a compressor housing (3) 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 housing. A rotor (9) is fixed on the drive shaft (7) and variably connected to an inclined plate (11) through a hinge mechanism which includes a first arm portion (93) which is formed on either one of the rotor or inclined plate, a second arm portion (114) which is provided with an elongate hole (115) formed on the other thereof and a guide pin (12) which is fixedly disposed in a hole which is formed through the first arm portion. A wobble plate (13) is adjacent (8) the inclined plate and converts rotary motion of the inclined plate into nutating motion thereof. A plurality of pistons (19) are coupled with the wobble plate through a plurality of connecting rods (18) each of which is reciprocably fitted within a respective one of the cylinders and of which the stroke volume is changed in accordance with variation of the angle of the inclined plate. The elongate hole is shaped so that a top clearance of the piston provides the least volume at the time that the angle of the inclined plate is largest, and the top clearance of the piston provides the largest volume at the time that the angle of the inclined plate is smallest. Therefore, even though the range of inclination of the angle of the inclined plate is narrow, a wide range of control of the displacement volume of the compressor can be accomplished.

Description: The present invention relates to a wobble plate compressor with a variable displacement mechanism. A wobble plate compressor which reciprocates pistons by converting the rotational movement of a cam rotor into nutational movement of a wobble plate is well known as shown in Japanese Patent Application Publication No. 58-158,382. Changing the inclined angle of the wobble plate changes the stroke of the pistons and therefore changes the displacement volume of the cylinders. Figs. 1 and 2 of the accompanying drawings show the construction of a conventional wobble plate compressor 1 which includes a front end plate 2, a generally cylindrical compressor housing 3 having a cylinder block 31, a valve plate 4, and a cylinder head 5. The front end plate 2 is fixed on one end of the housing 3 by securing bolts (not shown). An axial hole 21, which is formed through the centre of the front end plate 2, receives a drive shaft 7. A radial bearing 8 is disposed in the axial hole 21 to rotatably support the drive shaft 7. An annular sleeve portion (not shown) projects from the front end plate 2 and surrounds the drive shaft 7, defining a seal cavity. The housing casing 3 is provided with a crank chamber 32. The cylinder block 31 has a plurality of equiangularly spaced cylinders 33 formed therein. A cam rotor 9 is fixed on the drive shaft 7 by a guide pin 12. A thrust needle bearing 10 is disposed between the inner wall surface of the front end plate 2 and the adjacent axial end surface of the cam rotor 9. An arm portion 91 of the cam rotor 9 extends in the direction of the cylinder block 31. An elongate hole 92 is formed on the arm portion 91. An inclined plate 11, which is provided with a flange portion 111, an arm portion 112 and a cylindrical portion 113, is disposed around the drive shaft 7. The arm portion 112 is formed on the outer surface of the flange portion 111 of the inclined plate 11 and overlaps the arm portion 91 of the cam rotor 9. A hole formed in the arm portion 112 is aligned with the elongate hole 92. A guide pin 12, which is fixedly disposed through the hole, is slidably movable within the elongate hole 92. A ring-shaped wobble plate 13 is mounted on the outer surface of the cylindrical portion 113 of the inclined plate 11 through a radial bearing 14 and is prevented from axial movement by the flange portion 111 and a snap ring 15 which is disposed on the cylindrical portion 113. The wobble plate 13 is also prevented from rotating by a guide plate 25 which extends within the crank chamber 32. A thrust needle bearing 16 is disposed in a gap between the flange portion 111 and the wobble plate 13. The other end of the drive shaft 7 is rotatably supported through a radial bearing 17 in a central bore 34 of the cylinder block 31. One end of a piston rod 18 is rotatably connected to a seat 131 of the wobble plate 13. The other end of the piston rod 18 is rotatably connected to a piston 19 which is slidably fitted within a respective one of the cylinders 33. Suction ports 41 and discharge ports 42 are formed through the valve plate 4. A suction reed valve (not shown) is disposed on the valve plate 4. A discharge reed valve is disposed on the side of the valve plate 4 opposite the suction reed valve. The cylinder head 5 is connected to the cylinder casing 3 through gaskets (not shown) and the valve plate 4. A partition wall 51 extends axially from the inner surface of the cylinder head 5 and divides the interior of the cylinder head 5 into a suction chamber 52 and a discharge chamber 53. The suction chamber 52 is connected to the external fluid circuit through a fluid inlet port 54 formed in the cylinder head 5. A discharge chamber 53 is connected to the external fluid circuit through a fluid outlet port 55 formed in the cylinder head 5. The crank chamber 32 of the housing 3 and the suction chamber 52 of the cylinder head 5 are interconnected with one another via a conduit 311 to control the angle of the inclined plate 11 and wobble plate 13. The conduit 311, which is formed within the cylinder block 31, and which includes a hollow portion 312, connects the crank chamber 32 with the suction chamber 52 to introduce the gas in the crank chamber 32 into the suction chamber 52 in response to operation of a control valve 20. The control valve 20 controls opening and closing of the conduit 311 in response to gas pressure in the crank chamber 32. The angle of the inclined plate 11 and wobble plate 13 is thus varied in accordance with opening and closing operation of the control valve 20. If the communication between the crank chamber 32 and suction chamber 52 is prevented by closing operation of control valve 20, the gas pressure in the crank chamber 32 gradually increases, and high gas pressure acts on the rear surface of the pistons 19 thereby reducing the angle of the inclined plate 11. Thus, the capacity of the compressor is reduced. Contrarily, if the crank chamber 32 and suction chamber 52 are interconnected with one another by opening operation of control valve 20, gas pressure in crank chamber 32 is reduced thereby increasing the angle of the inclined plate 11 and wobble plate 13. Thus, the capacity of the compressor is increased. A conventional hinge mechanism includes the arm portion 91 of the cam rotor 9 having an arc-shaped elongate hole 92 of which the centre of the arc is adjacent to the seat on the wobble plate 13 for the piston rod 18. Since the centre of the circle which forms the arc of the elongate hole 92 is located at the above mentioned position, the axial location of the guide pin 12 at the time that the angle of the inclined plate 11 is largest or smallest are almost equal although they are indeed different from each other in the radial direction. Accordingly, even though the angle of the inclined plate 11 varies from the largest angle to the smallest angle, a clearance, which is a re-expansion volume, between the top of a piston 19 and the inner end surface of the valve plate 4 is varied only a little. Therefore, it is necessary to reduce greatly the angle of the inclined plate 11 to decrease the refrigerating capacity of the compressor appreciably. Furthermore, when the angle of the inclined plate 11 becomes its smallest, the piston 19 does not provide significant compression thereby a significant reaction force against the compression force also does not act on the end surface of piston 19. Therefore, it is necessary to use a part such as a return spring for returning the inclined plate 11 towards the cam rotor 9. It is an object of this invention to provide a wobble plate compressor with a variable displacement mechanism which can control refrigerating capacity in a wide range even though the angle of the inclined plate is varied in an only narrow range. It is another object to provide a wobble plate compressor with a variable displacement mechanism which has a hinge mechanism to rapidly return the inclined plate to the position of the largest angle thereof in response to reduction of the gas pressure in the crank chamber. According to the invention, a wobble plate compressor with a variable displacement mechanism includes a compressor housing provided with a crank chamber and a cylinder block in which a plurality of cylinders are formed; a drive shaft rotatably supported in the housing; a rotor fixed on the drive shaft and variably connected to an inclined plate through a hinge mechanism including a first arm portion formed on one of the rotor and inclined plate, a second arm portion provided with an elongate hole formed on the other thereof, and a guide pin fixedly disposed in a hole formed through the first arm portion; a wobble plate adjacent to the inclined plate and arranged to convert rotary motion of the inclined plate into nutating motion thereof; and a plurality of pistons coupled with the wobble plate through a plurality of connecting rods each of which is reciprocably fitted within a respective one of the cylinders and of which the stroke volume is changable in accordance with variation of the angle of the inclined plate; the elongate hole being formed in the shape of an arc and so arranged that a top clearance of the pistons provides the least volume at the time that the angle of the inclined plate is largest, and the top clearance of the piston provides the largest volume at the time that the angle of the inclined plate is smallest (as disclosed in EP-A-0190013) and according to the invention such a compressor is characterised in that the centre of the arc of the elongate hole is located adjacent to the side of the drive shaft when the angle of the inclined plate is largest. In the accompanying drawings: Fig. 1 is a cross-sectional view of a conventional wobble plate compressor with a variable displacement mechanism, of which the inclined plate is shown at its largest angle of inclination; Fig. 2 is a view similar to Fig. 1 but with the inclined plate shown at its smallest angle of inclination; Fig. 3 is a cross-sectional view of a wobble plate type compressor with a variable displacement mechanism in accordance with the invention, with the inclined plate shown at its largest angle of inclination; Fig. 4 is a view similar to Fig. 3, but with the inclined plate shown at its smallest angle of inclination; Fig. 5 is a perspective view of a drive mechanism to illustrate the shape of an elongate hole used in a hinge mechanism of a compressor in accordance with the invention; Fig. 6 is a graph illustrating the relationship between the refrigerating capacity of a compressor and the angle of an inclined plate. Referring to Figs. 3 and 4, the same reference numerals are used for parts corresponding to those in Figs. 1 and 2, and the description of these parts is not repeated. A hinge mechanism, which is used in a drive mechanism, includes a first arm portion 93 of the cam rotor 9, which portion is provided with a hole, a second arm portion 114 of the inclined plate 11 which portion is provided with an arc-shaped elongate hole 115, and a guide pin 12 which is fixedly disposed in the hole. The guide pin 12 passes through the elongate hole 115 and controls the angle of the inclined plate 11 within the range of the elongate hole 115. The shape of the elongate hole 115, which is always arc-shaped, is formed so that the top clearance of the piston 19 provides the least volume when the angle of the inclined plate 11 is at its largest, and the top clearance of the piston 19 provides the largest volume when the angle of inclined plate is at its least. As the axial distance between the location of the guide pin 12 at the time that the angle of the inclined plate 11 is largest, and the location of the guide pin 12 at the time that the angle of the inclined plate 11 is smallest, becomes larger, the difference of the volumes provided by the top clearance at these times also becomes greater. Referring to Fig. 5, the construction of a driving mechanism which includes a hinge mechanism provided with an arc-shaped elongate hole in accordance with this invention is shown. Conventionally, centre O″ of the arc of an arc-shaped elongate hole, which is described by a dotted line, is located adjacent to centre O of the seat connection between one end of the piston rod 18 and the wobble plate 13 when the angle of the inclined plate 11 is largest. On the other hand, centre O′ of the arc of arc-shaped elongate hole 117 according to this invention, which is formed in an arm portion 116, is located adjacent to the outer surface of the drive shaft 7 when the angle of the inclined plate 11 is at its largest. Since the axially moving distance of the piston 19 is then longer than when a conventional elongate hole is used, the change in the top clearance of the piston 19 becomes larer as shown in Fig. 6. Although the increase of the top clearance of the piston 19 in accordance with increase of the angle of inclined plate 11 is little conventionally, that in accordance with increase of the angle of inclined plate 11 becomes relatively large in this invention. The re-expansion volume is proportional to the top clearance of the piston. In the above compressor, if the angle of the inclined plate 11 is reduced, the compression volume of the compressor is decreased. At this time, the top clearance is contrarily increased as shown in Fig. 6, thereby the re-expansion volume is also relatively increased. Referring to Fig. 7, the relationship between volumetric efficiency and angle of the inclined plate is shown. The characteristic shown in Fig. 7 is based on the following values; the pressure in the discharge chamber 53 is 8 kg/cm G, the pressure in the suction chamber 52 is 2 kg/cm G, and the rotational speed of the inclined plate 11 is 2000 rpm. Since the re-expansion volume is increased with decrease in the angle of the inclined plate 11, the volumetric efficiency of the compressor is rapidly reduced with decrease in the angle of the inclined plate 11. The refrigerating capacity of the compressor is also rapidly reduced with a small change in the angle of the inclined plate 11 as shown in Fig. 8. The characteristic shown in Fig. 8 is based on the same values as the above. Accordingly, a wide range of refrigerating capacity can be attained even though the variation range of the angle of inclined plate 11 is narrow. Furthermore, since the angle of the inclined plate 11 can be large relatively to that in the conventional arrangement at the time that the angle of the inclined plate is smallest, the inclined plate 11 is easily returned towards the location in which the angle of the inclined plate 11 is largest. The re-expansion volume at the time that the angle of the inclined plate 11 is smallest can be enlarged by moving centre O′ of the arc of the elongate hole 117 to the side of drive shaft 7. Furthermore, the same efficiency as the above can be accomplished by applying an elongate hole according to the invention to a conventional hinge mechanism as shown in Figs. 1 and 2, too.

Claims: 1. A wobble plate compressor with a variable displacement mechanism, the compressor including a compressor housing (3) 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 the housing; a rotor (9) fixed on the drive shaft and variably connected to an inclined plate (11) through a hinge mechanism including a first arm portion (93) formed on one of the rotor and inclined plate, a second arm portion (114) provided with an elongate hole (115) formed on the other thereof, and a guide pin (12) fixedly disposed in a hole formed through the first arm portion; a wobble plate (13) adjacent to the inclined plate and arranged to convert rotary motion of the inclined plate into nutating motion thereof; and a plurality of pistons (19) coupled with the wobble plate through a plurality of connecting rods (18) each of which is reciprocably fitted within a respective one of the cylinders and of which the stroke volume is changable in accordance with variation of the angle of the inclined plate; the elongate hole (115) being formed in the shape of an arc and so arranged that a top clearance of the pistons provides the least volume at the time that the angle of the inclined plate is largest, and the top clearance of the piston provides the largest volume at the time that the angle of the inclined plate is smallest characterised in that the centre (O′) of the arc of the elongate hole is located adjacent to the side of the drive shaft when the angle of the inclined plate is largest.

Inventors: HIGUCHI, TERUO, KIKUCHI, SEI, TAKAI, KAZUHIKO, TERAUCHI, KIYOSHI
Applicants: SANDEN CORPORATION
Application year: 1988
Main classification: F04B1
IPC codes: F04B27