SLANT PLATE TYPE COMPRESSOR WITH VARIABLE DISPLACEMENT MECHANISM

Abstract: A slant plate type compressor is disclosed having a plurality of cylinders (70) formed around the periphery of a cylinder block (21) and a piston (71) slidably fitted within each of the cylinders for reciprocation by a drive mechanism (26). The drive mechanism includes a drive shaft (26) rotatably supported in the compressor housing, a rotor (40) coupled to the drive shaft and rotatable therewith, and a coupling mechanism (50,60) for drivingly coupling the drive to the pistons such that the rotary motion of the rotor is converted into reciprocating motion of the pistons. The coupling mechanism includes a plate (50) having a surface disposed at a slant angle relative to the drive shaft. The slant angle changes in response to a change in pressure in the crank chamber to change the capacity of the compressor. A bias spring (34) is mounted on the drive shaft located between the slant plate and the cylinder block to urge the slant plate toward the maximum slant angle. An inner diameter of the cylinder block end of the bias spring is smaller than a diameter of the drive shaft in order to firmly secure the cylinder block side end portion of the bias spring to the drive shaft.

Description: The present invention generally relates to a refrigerant compressor and, more particularly, to a slant plate type compressor, such as a wobble plate type compressor, with a variable displacement mechanism suitable for use in an automotive air conditioning system. A wobble plate compressor with a variable displacement mechanism suitable for use in an automotive air conditioning system is disclosed in U.S. Patent No. 3,861,829 issued to Roberts et al. As disclosed therein, the compression ratio of the compressor may be controlled by changing the slant angle of the sloping surface of the wobble plate. The slant angle of the wobble plate is adjusted in response to change is crank chamber pressure. Change in crank chamber pressure is generated by a valve control mechanism which controls communication between the suction chamber and crank chamber. U.S. Patent No. 4,480,964 issued to Skinner further discloses a bias spring in the form of a split ring return spring of which one end is firmly secured to a drive shaft. The other end of the spring is engaged by a sleeve connected to a drive plate, which corresponds with a slant plate of this invention, during movement to the zero wobble angle position and is thereby conditioned to initiate return movement. Were a bias spring to be mounted on a drive shaft without firmly securing one end thereof to the drive shaft, the bias spring may move along the drive shaft. This action of the bias spring causes the bias spring to stick in an undesirable position of the drive shaft thereby a part of slanting motion of the slant plate is affected by the bias spring. Accordingly, the compressor may operate with an ineffective variable displacement. It is a primary object of this invention to provide a variable capacity slant plate type compressor in which a slant plate can be initiated its return movement by a bias spring without affecting the slanting motion of the slant plate. The 964 patent discloses the features of the preamble of claim 1 of this application, over which the present invention is characterised by the inner diameter of at least one helical portion of the bias spring, other than at the end of the spring adjacent the slant plate, being smaller than a diameter of the drive shaft in order to firmly secure the bias spring to the drive shaft. In the drawings: Figure 1 illustrates a longitudinal sectional view of a wobble plate type refrigerant compressor in accordance with a first embodiment of this invention. Particularly, this drawing illustrates minimum displacement stage of the compressor. Figure 2 illustrates a maximum displacement stage of the compressor shown in Figure 1. Figure 3 illustrates an enlarged perspective view of an essential portion of the first embodiment shown in Figure 1. Figure 4 illustrates an exploded perspective view of the essential portion of the first embodiment shown in Figure 3. Figure 5 illustrates an essential portion of a second embodiment of this invention similarly shown Figure 3. Figure 6 illustrates an essential portion of a third embodiment of this invention similarly shown Figure 3. Although the present invention is described below in terms of a wobble plate type compressor, is not limited in this respect. The present invention is broadly applicable to slant plate type compressor. A wobble plate type refrigerant compressor in accordance with a first embodiment of the present invention is shown in Figure 1. Compressor 10 includes cylindrical housing assembly 20 including cylinder block 21, front end plate 23 disposed at one end of cylinder block 21, crank chamber 22 formed between cylinder block 21 and rear end plate 24 attached to the other end of cylinder block 21. Front end plate 23 is secured to one end of cylinder block 21 by a plurality of bolts 101. Rear end plate 24 is secured to the opposite end of cylinder block 21 by a plurality of bolts 102. Valve plate 25 is disposed between rear end plate 24 and cylinder block 21. Opening 231 is formed centrally in front end plate 23 for supporting drive shaft 26 through bearing 30 disposed therein. Drive shaft 26 includes inner end portion 26a and intermediate portion 26b adjacent to inner end portion 26a. A diameter of inner end portion 26a is formed smaller than a diameter of intermediate portion 26b. Inner end portion 26a of drive shaft 26 is rotatable supported by bearing 31 disposed within central bore 210 of cylinder block 21. Bore 210 extends to a rear (to the right in Figure 1) end surface of cylinder block 21 and houses valve control mechanism 19 described in detail below. Cam rotor 40 is fixed on drive shaft 26 by pin member 261 and rotates therewith. Thrust needle bearing 32 is disposed between the inner end surface of front end plate 23 and the adjacent axial end surface of cam rotor 40. Cam rotor 40 includes arm 41 having pin member 42 extending therefrom. Slant plate 50 is disposed adjacent cam rotor 40 and includes opening 53 through which drive shaft 26 passes. Slant plate 50 includes arm 51 having slot 52. Cam rotor 40 and slant plate 50 are coupled by pin member 42 which inserted in slot 52 to form a hinged joint. Pin member 42 slides within slot 52 to allow adjustment of the angular position of slant plate 50 with respect to the longitudinal axis of drive shaft 26. Wobble plate 60 is rotatably mounted on slant plate 50 through bearing 61 and 62. For shaped slider 63 is attached to the outer peripheral end of wobble plate 60 by pin member 64 and is slidably mounted on sliding rail 65 disposed between front end plate 23 and cylinder block 21. Fork shaped slider 63 prevents rotation of wobble plate 60. Wobble plate 60 nutates along rail 65 when cam rotor 40 rotates. Cylinder block 21 includes a plurality of peripheral located cylinder chambers 70 in which pistons 71 reciprocate. Each piston 71 is coupled to wobble plate 60 by a corresponding connecting rod 72. Rear end plate 24 includes peripheral positioned annular suction chamber 241 and centrally positioned discharge chamber 251. Valve plate 25 is located between cylinder block 21 and rear end plate 24 and includes a plurality of valved suction ports 242 linking suction chamber 241 with respective cylinders 70. Valve plate 25 also includes a plurality of valved discharge ports 252 linking discharge chamber 251 with respective cylinders 70. Suction ports 242 and discharge ports 252 are provided with suitable reed valves as described in U.S Patent No. 4,011,029 to Shimizu. Suction chamber 241 includes inlet portion 241a which is connected to an evaporator of an external cooling circuit (not shown). Discharge chamber 251 is provided with outlet portion 251a connected to a condenser of the cooling circuit (not shown). Gaskets 27 and 28 are positioned between cylinder block 21 and the inner surface of valve plate 25 and the outer surface of valve plate 25 and rear end plate 24 respectively. Gasket 27 and 28 seal the mating surface of cylinder block 21, valve plate 25 and rear end plate 24. Valve control mechanism 19 including cup-shaped casing member 191 is disposed within central bore 210. Cup-shaped casing member 191 defines valve chamber 192 therein. O-ring 19a is disposed at an outer surface of casing member 191 to seal mating surface of casing member 191 and cylinder block 21. Circular plate 194 having central hole 19b is fixed to an open end (to the right in Figure 1) of cup-shaped casing member 191 to have axial gap 194b between valve plate 25 and thereof. Screw member 18 for adjusting an axial location of drive shaft 26 is disposed between inner end portion 26a of drive shaft 26 and a closed end (to the left in Figure 1) of cup-shaped casing 191. Screw member 18 includes a plurality of holes 18a formed at an outer peripheral portion thereof. A plurality of holes 193d are formed at an outer peripheral portion of the closed end of casing member 191. Valve control mechanism 19 further includes valve member 193 having bellows 193a, valve element 193b centrally attached to a top end (to the right in Figure 1) of bellows 193a to align hole 19b and male screw element 193c attached to a bottom end (to the left in Figure 1) of bellows 193a. Bellows 193a is charged with gas to maintain predetermined pressure. Male screw element 193c is screwed into the closed end of casing member 191 to firmly secure the bottom end of bellows 193a to the closed end of casing member 191. Therefore, refrigerant gas in crank chamber 22 flows into valve chamber 192 via a gap between bearing 31 and the outer peripheral surface of inner end portion 26a of drive shaft 26 and the inner wall of bore 210, holes 18a and holes 193d thereby bellows 193a contracts and expands longitudinally to close and open hole 19b in response to pressure in crank chamber 22. Conduit 195 radially extending from gap 194b is formed at a rear end (to the right in Figure 1) of cylinder block 21 and is terminated at hole 196 formed at valve plate 25. Hole 196 links conduit 195 to suction chamber 241. Snap ring 33 is attached to inner end portion 26a of drive shaft 26 to be adjacent to intermediate portion 26b of drive shaft 26. Bias spring 34 is mounted on intermediate portion 26b of drive shaft 26 to have its location between slant plate 50 and snap ring 33. One end of bias spring is firmly secured to drive shaft 26 with contacting with snap ring 33. In relaxed stage, the other end of bias spring 34 is located so as not to contact with any portion of the rear end surface of slant plate 50 while slant plate 50 inclines in the range from the maximum slant angle as shown in Figure 2 to the lower mendium slant angle, that is, 30% of the maximum slant angle. Accordingly, slant plate 50 is urged toward the maximum slant angle by restoring force of bias spring 34 while slant plate 50 inclines under 30% of the maximum slant angle. Above-mentioned and mention later slant angle is an angle with respect to a perpendicular to an axis of drive shaft 26. Therefore, when slant plate 50 inclines the maximum slant angle, the compressor operates with maximum displacement. With reference to Figure 3, an essential portion of the first embodiment will be described in detail below. Inner end portion 26a of drive shaft 26 having a smaller diameter than a diameter of intermediate portion 26b of drive shaft 26 is integrated on tapered ridge portion 26c formed at a rear end (to the right in Figure 3) of intermediate portion 26b of drive shaft 26. Bias spring 34 is mounted on drive shaft 26. One end (to the right of Figure 3) of bias spring 34 is disposed at inner end portion 26a to be adjacent to tapered ridge portion 26c. The other end (to the left in Figure 3) of bias spring 34 extends toward slant plate 50 and is terminated to satisfy above-mentioned conditions. An inner diameter of one end of bias spring 34 is smaller than a diameter of intermediate portion 26b. Snap ring 33 is attached to inner end portion 26a to be sandwiched one end of bias spring 34 by tapered ridge portion 26c and snap ring 33. Accordingly, the axial movement of bias spring 34 along drive shaft 26 is prevented. With reference to Figure 4, an assembling process of the essential portion of the first embodiment will be described below. After facing an inner end of drive shaft 26 to the other end of bias spring 34, drive shaft 26 is inserted through bias spring 34 in order to contact one end of bias spring 34 with tapered ridge portion 26c of drive shaft 26. Then, snap ring 33 is mounted through drive shaft 26 from inner end of drive shaft 26. When snap ring 33 contacts with one end of bias spring 34, snap ring 33 is firmly fitted on inner end portion 26a drive shaft 26 to be sandwiched one end of bias spring 34 by tapered ridge portion 26c and snap ring 33. During operation of compressor 10, drive shaft 26 is rotated by the engine of the vehicle (not shown) through electromagnetic clutch 300. Cam rotor 40 is rotated with drive shaft 26 causing slant plate 50 to rotate. The rotation of slant plate 50 causes wobble plate 60 to nutate. The nutating motion of wobble plate 60 reciprocates pistons 71 in their respective cylinders 70. As pistons 71 are reciprocated, refrigerant gas introduced into suction chamber 241 through inlet portion 241a is drawn into cylinders 70 through suction ports 242 and subsequently compressed. The compressed refrigerant gas is discharged from cylinders 70 to discharge chamber 251 through respective discharge ports 252 and then into the cooling circuit through outlet portion 251a. Intermediately compressed refrigerant gas is blown into crank chamber 22 from cylinders 70 through the gap between respective pistons 71 and cylinders 70 during operation of compressor 10. The intermediately compressed refrigerant gas in crank chamber 22 then flows into valve chamber 192 via the gap between bearing 31 and the outer peripheral surface of inner end portion 26a of drive shaft 26 and the inner wall of bore 210, holes 18a and holes 193d. When pressure in crank chamber 22 that is, pressure in valve chamber 192 exceeds the predetermined pressure in bellows 193a, bellows 193a contracts to be opened hole 19b by valve element 193b thereby crank chamber 22 is linked to suction chamber 241. Accordingly, pressure in crank chamber 22 is decreased to pressure in suction chamber 241. The other hand, when pressure in crank chamber 22 becomes below the predetermined pressure in bellows 193a, bellows 193a expands to be closed hole 19b by valve element 193b thereby the communication between crank chamber 22 and suction chamber 241 is blocked. Accordingly, pressure in crank chamber 22 is gradually increased due to the intermediately compressed refrigerant gas being blown into crank chamber 22 from cylinders 70. Thus, change in pressure in crank chamber 22 is controlled by valve control mechanism 19. Change in pressure in crank chamber 22 generates change in slant angle of slant plate 50, that is, wobble plate 60 so as to change a stroke of respective pistons 71 thereby the displacement of compressor 10 is changed. Furthermore, in a variable displacement stage, slant plate 50 is urged toward the maximum slant angle by restoring force of bias spring 34 while slant plate 50 inclines under 30 % of the maximum slant angle. With reference to Figure 5, an essential portion of a second embodiment of this invention is shwon. In the second embodiment, an inner diameter of one end of bias spring 34′ is smaller than a diameter of intermediate portion 26b of drive shaft 26. Bias spring 34′ forcibly mounted through drive shaft 26 from the inner end of drive shaft 26 to locate one end thereof adjacent to ridge 26d. Snap ring 33 is firmly fitted on inner end portion 26a of drive shaft 26 to contact with one end of bias spring 34′. With reference to Figure 6, an essential portion of a third embodiment of this invention is shown. In this embodiment, intermediate portion 26b of drive shaft 26 includes tapered portion 26e. Inner end portion 26 is integrated at a tapered end of tapered portion 26e (to the right in Figure 6) with same diameter of the tapered end of tapered portion 26e. An inner diameter of one end of bias spring 34″ is smaller than the diameter of the tapered end of tapered portion 26e. Bias spring 34″ is forcibly mounted through drive shaft 26 from the inner end of drive shaft 26 to locate one end thereof being adjacent to the tapered end of tapered portion 26e. Snap ring 33 is firmly fitted on inner end portion 26a of drive shaft 26 to contact with one end of bias spring 34″.

Claims: 1. A slant plate type compressor for use in a refrigeration circuit, the compressor including a compressor housing (20) having a cylinder block (21) provided with a plurality of cylinders (70); a front end plate (23) disposed on one end of the housing and enclosing a crank chamber (22); a piston (71) slidably fitted within each cylinder; a drive mechanism coupled to the pistons to cause them to reciprocate within the cylinders, the drive mechanism including a drive shaft (26) rotatably supported in the housing; a rotor (40) coupled to the drive shaft and rotatable therewith, and coupling means (50, 60) for drivingly coupling the pistons, such that the rotary motion of the rotor is converted into reciprocating motion of the pistons, the coupling means including a plate (50) having a surface disposed at a slant angle relative to the drive shaft, the slant angle changing in response to changes in pressure in the crank chamber to change the capacity of the compressor; a rear end plate (24) disposed on the opposite end of the cylinder block to the front end plate and defining a suction chamber (241) and a discharge chamber (251) therein; a communication path (210, 195, 196) linking the crank chamber with the suction chamber; a valve control means (19) for controlling the opening and closing of the communication path to cause a change in pressure in the crank chamber; and a bias spring (34) mounted on the drive shaft located between the plate (50) and the cylinder block (21) to urge the plate towards the maximum slant angle; characterised by: the inner diameter of at least one helical portion of the bias spring, other than at the end of the spring adjacent the slant plate (50), being smaller than a diameter of the drive shaft (26) in order to firmly secure the bias spring to the drive shaft. 2. A compressor according to claim 1, characterised in that when the bias spring is relaxed, the helical portion of the spring adjacent the slant plate is located so as not to contact any portion of the surface of the slant plate facing the cylinder block while the plate is inclined in a range from a maximum slant angle to a predetermined intermediate slant angle.

Inventors: HIGUCHI, TERUO
Applicants: SANDEN CORPORATION
Application year: 1989
Main classification: F04B1
IPC codes: F04B27, F04B49