Slant plate type compressor

Abstract: A slant plate type compressor (10) including a compressor housing (20) having a cylinder block (21) is disclosed. A plurality of peripherally located cylinders (70) are formed through the cylinder block. A piston (71) is slidably fitted in each of the cylinders (70) and is reciprocated by a drive mechanism which includes a slant plate (50). The slant plate (50) includes a boss (54) for mounting a balance weight ring (500) thereon. The balance weight ring (500) includes an annular depression formed at an inner peripheral portion thereof. The balance weight ring (500) is firmly attached to the boss (54) by means of an annular projection (549) extending axially from the boss (54) which is bent radially outwardly around the radially inner peripheral region of the balance weight.

Description: The present invention relates to a refrigerant compressor, and more particularly, to a slant plate type compressor, such as a wobble plate type compressor for use in an automotive air conditioning system. As disclosed in U.S.-A-4,073,603, and Japanese Patent Application Publication No. 64-29,678, a slant plate type compressor includes a balance weight ring of substantial mass disposed on the nose of the hub or "boss" of the slant plate, in order to balance the slant plate under dynamic operating conditions. The balance weight ring is held in place by means of a retaining ring. Figures 1 and 2 show a slant plate type compressor as disclosed in the Japanese application. Boss 54 of slant plate 50 includes smaller diameter portion 54a at an axially rearward end (to the right in Figure 1 and to the top in Figure 2) thereof, resulting in the formation of annular shoulder 541 forward of portion 54a. Annular balance weight ring 500 is mounted about smaller diameter portion 54a, in contact with shoulder 541. Balance weight ring 500 includes annular depression 501 formed at an inner periphery of the axially rearward surface, reducing the thickness of ring 500 at the inner periphery. Relatively thin plate portion 502 remains at the inner periphery of balance weight ring 500, forward of depression 501. With further reference to Figure 2 annular groove 55 is formed in the radially outer peripheral surface of smaller diameter portion 54a, and annular snap ring 56 is disposed therein. Snap ring 56 includes annular tapered surface 56a formed at a radially inner portion of the axially rearward surface. Rearward annular wall 55a of annular groove 55 slants inwardly (to the left in Figure 2) at an angle generally corresponding to the angle of annular tapered surface 56a of snap ring 56 such that snap ring 56 may be slidably fitted and retained within groove 55. The radially outer portion of snap ring 56 extends exteriorly of groove 55 and contacts thin-plate portion 502 of balance weight ring 500. Thin plate portion 502 of balance weight ring 500 is retained between snap ring 56 and annular shoulder 541. Therefore, balance weight ring 500 is retained on boss 54. However, when the compressor operates under unusual or extreme conditions, for example, when the rotational speed of the compressor is extremely high, when the rotational speed of the compressor is suddenly increased, or when refrigerant in the liquid state is present in the compressor, an extremely large force is produced which tends to cause snap ring 56 to expand in the radially outer direction. As a result, snap ring 56 may slip out of groove 55, and out of contact with balance weight ring 500. Without the retaining contact of snap ring 56, balance weight ring 500 will slip off of boss 54 and damage the internal elements of the compressor. A solution to this problem using a second annular member disposed around the snap ring to retain the snap ring in place is claimed in published parent application, EP-A-0366349. US-A-4073603 discloses a slant plate type refrigerant compressor comprising a compressor housing including a cylinder block, the cylinder block including a plurality of peripherally disposed cylinders, a crank chamber enclosed within the cylinder block at a location forward of the cylinders, the compressor housing including a suction chamber and a discharge chamber formed therein, a piston slidably fitted within each of the cylinders, a drive mechanism coupled to the pistons to reciprocate the pistons within the cylinders, the drive mechanism including a drive shaft rotatably supported in the housing, the drive mechanism further including coupling means for coupling the drive shaft to the pistons such that rotary motion of the drive shaft is converted into reciprocating motion of the pistons in the cylinders, the coupling means including a slant plate disposed in the drive shaft and having a surface disposed at an inclined angle relative to the drive shaft, the slant plate having a boss, an annular balance weight disposed on the boss, and a retaining means for retaining the balance weight on the slant plate; and according to the present invention, such a compressor is characterised by the retaining means including an annular projection extending axially from the boss, a shoulder being formed about the annular projection, and the balance weight being disposed on the shoulder about the annular projection such that the projection is bent radially outwardly around the radially inner peripheral region of the balance weight to secure the balance weight on the boss of the slant plate. In the accompanying drawings:- Figure 1 shows a vertical longitudinal sectional view of a slant plate type refrigerant compressor in accordance with the prior art. Figure 2 shows an enlarged partial sectional view of the compressor shown in Figure 1 including the balance weight ring and retaining mechanism. Figure 3 shows a vertical longitudinal sectional view of a slant plate type refrigerant compressor in accordance with the present invention. Figures 4(a) and 4(b), respectively, show an enlarged partial sectional view before and after formation of the retaining mechanism as shown in Figure 3. In Figures 3-4, identical reference numerals are used to denote elements which are identical to the similarly numbered elements shown in prior art Figures 1 and 2. Additionally, although compressor 10 is shown and is described with respect to Figures 3-4 as a wobble plate type compressor, the invention is not limited thereto and is applicable to any type of slant plate type compressor, including both fixed and variable capacity compressors of the wobble or swash plate type. Furthermore, in the following description, the left side of Figure 3, will be referred to as the front or forward side and the right side will be referred to as the rear side. The remaining Figures show views shifted by approximately 90°. The term "axial" refers to a direction parallel to the longitudinal axis of the drive shaft, and the term "radial" refers to the perpendicular direction. Of course all of the reference directions are made for the sake of convenience of description and are not intended to limit the invention in any way. With reference to Figure 3, the construction of slant plate type compressor 10 in accordance with the present invention is shown. 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 front end plate 23, and rear end plate 24 disposed at the opposite end of cylinder block 21. Front end plate 23 is mounted on the open forward end of cylinder block 21 by a plurality of bolts 101 to enclose crank chamber 22 therein. Rear end plate 24 is mounted on cylinder block 21 at its opposite end by a plurality of bolts 102. Valve plate 25 is located between rear end plate 24 and cylinder block 21. Opening 231 is centrally formed in front end plate 23. Drive shaft 26 is supported by bearing 30 disposed in opening 231. Central bore 210 extends through cylinder block 21 to a rearward end surface. The inner (rear) end portion of drive shaft 26 is rotatably supported by bearing 31 disposed within central bore 210 of cylinder block 21. Valve control mechanism 19 is disposed in bore 210 to the rear of drive shaft 26. Cam rotor 40 is fixed on drive shaft 26 by pin member 261, and rotates with shaft 26. Thrust needle bearing 32 is disposed between the axial inner (rear) end surface of front end plate 23 and the adjacent forward axial end surface of cam rotor 40. Cam rotor 40 includes arm 41 having pin member 42 extending therefrom. Slant plate 50 is disposed about drive shaft 26 and includes opening 53 through which drive shaft 26 passes. Slant plate 50 is disposed adjacent cam rotor 40. Slant plate 50 includes arm 51 having slot 52, and boss 54. Cam rotor 40 and slant plate 50 are connected by pin member 42, which is inserted in slot 52 to create a hinged joint. Pin member 42 is slidable 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 mounted about boss 54 of slant plate 50 through bearings 61 and 62 so that slant plate 50 is rotatable with respect thereto. Rotational motion of slant plate 50 causes nutational motion of wobble plate 60. Fork shaped slider 63 is attached to the outer peripheral end of wobble plate 60 and is slidably mounted on sliding rail 64 held between front end plate 23 and cylinder block 21. Fork shaped slider 63 prevents rotation of wobble plate 60 and wobble plate 60 reciprocates along rail 64 when cam rotor 40 and slant plate 50 rotate. Cylinder block 21 includes a plurality of peripherally located cylinder chambers 70 in which pistons 71 reciprocate. Each piston 71 is connected to wobble plate 60 at a peripheral location by a corresponding connecting rod 72. Nutational motion of wobble plate 60 causes pistons 71 to reciprocate in cylinders 70 to compress refrigerant therein. Rear end plate 24 includes peripherally located annular suction chamber 241 and centrally located 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.-A-4,011,029. Suction chamber 241 includes inlet portion 241a which is connected to an evaporator of the 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 located 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, to seal the mating surfaces of cylinder block 21, valve plate 25 and rear end plate 24. Communication path 600 links crank chamber 22 and suction chamber 241 and includes central bore 210 and passageway 150. Valve control mechanism 19 controls the opening and closing of communication path 600 in order to vary the capacity of the compressor, as disclosed in Japanese Patent Application Publication No. 01- 142,276. During operation of compressor 10, drive shaft 26 is rotated by the engine of the vehicle through electromagnetic clutch 300. Cam rotor 40 is rotated with drive shaft 26, rotating slant plate 50 as well, causing wobble plate 60 to nutate. Nutational motion of wobble plate 60 reciprocates pistons 71 in their respective cylinders 70. As pistons 71 are reciprocated, refrigerant gas which is introduced into suction chamber 241 through inlet portion 241a, flows into each cylinder 70 through suction ports 242 and is compressed therein. The compressed refrigerant gas is discharged into discharge chamber 251 from each cylinder 70 through discharge ports 252, and therefrom into the cooling circuit through outlet portion 251a. The capacity of compressor 10 may be adjusted to maintain a constant pressure in suction chamber 241 in response to a change in the heat load of the evaporator, or a change in the rotating speed of the compressor. The capacity of the compressor is adjusted by changing the angle of the slant plate with respect to a plane perpendicular to the axis of the drive shaft. This angle is dependent upon the crank chamber pressure. An increase in crank chamber pressure decreases the slant angle of the slant plate and the wobble plate, decreasing the capacity of the compressor. A decrease in the crank chamber pressure increases the angle of the slant plate and the wobble plate and thus increases the capacity of the compressor. In the compressor shown in Fig. 3, variable capacity mechanism 19 acts in response to the crank chamber pressure, such that the acting point is modified according to the discharge pressure, to control the link between the crank and suction chambers, to adjust the crank chamber pressure and thereby change the slant angle of slant plate 50 and vary the operating capacity of the compressor. Of course other types of variable displacement mechanisms, or none at all may be used in compressors according to the present invention. With reference to Figures 3 and 4a-4b, a slant plate type compressor including a retaining mechanism in accordance with the present invention is shown. Balance ring retaining mechanism 82 includes annular projection 549 integrally formed with and extending from boss 54 of slant plate 50. Shoulder 542 is formed on boss 54, around projection 549. Thin plate portion 502 of balance weight ring 500 is disposed on shoulder 542 of boss 54. Projection 549 is bent to extend around the radially inner periphery of annular thin plate portion 502 of balance weight ring 500, to secure balance weight ring 500 on boss 54. With reference to Figures 4(a)-4(b), the formation of retaining mechanism 81 is shown. Boss 54 is formed such that annular projection 549 extends substantially axially from the rear surface, forming annular shoulder 542 exteriorly thereof. Annular projection 549 is relatively thin and is made of a soft metal, for example, untempered iron, such that it may be bent by a press work (not shown). The outer diameter of annular projection 549 is selected to be slightly smaller than the inner diameter of balance weight ring 500 such that thin plate portion 502 may be disposed on shoulder 542. After thin plate portion 502 is disposed on shoulder 542, annular projection 549 is bent radially outwardly by mold 100 of the press work so as to clamp thin plate portion 502 against shoulder 542. Since the need for a snap ring is eliminated, balance weight ring 500 is securely retained on slant plate 50, even when the compressor operates under unusual conditions.

Claims: A slant plate type refrigerant compressor (10) comprising a compressor housing (20) including a cylinder block (21), the cylinder block including a plurality of peripherally disposed cylinders (70), a crank chamber (22) enclosed within the cylinder block (21) at a location forward of the cylinders, the compressor housing (20) including a suction chamber (241) and a discharge chamber (251) formed therein, a piston (71) slidably fitted within each of the cylinders (70), a drive mechanism coupled to the pistons (71) to reciprocate the pistons within the cylinders (70), the drive mechanism including a drive shaft (26) rotatably supported in the housing (20), the drive mechanism further including coupling means for coupling the drive shaft (26) to the pistons (71) such that rotary motion of the drive shaft (26) is converted into reciprocating motion of the pistons (71) in the cylinders (70), the coupling means including a slant plate (50) disposed in the drive shaft (26) and having a surface disposed at an inclined angle relative to the drive shaft, the slant plate (50) having a boss (54), an annular balance weight (500) disposed on the boss, and a retaining means for retaining the balance weight (500) on the slant plate, characterised by the retaining means including an annular projection (549) extending axially from the boss (54), a shoulder (542) being formed about the annular projection, and the balance weight (500) being disposed on the shoulder (542) about the annular projection such that the projection (549) is bent radially outwardly around the radially inner peripheral region of the balance weight (500) to secure the balance weight on the boss (500) of the slant plate (50). A compressor according to claim 1, wherein the annular projection (549) comprises a soft metal. A compressor according to claim 2, wherein the soft metal comprises untempered iron. A compressor according to any one of the preceding claims, wherein the coupling means further comprises a wobble plate (60) disposed about the boss (54), the pistons (71) are linked to the wobble plate (60) by connecting rods (72), and the slant plate (50) is rotatable with the drive shaft (26), whereby rotational motion of the drive shaft (26) and the slant plate (50) causes the wobble plate (60) to nutate and reciprocate the pistons (71) in the cylinders (70). A compressor according to any one of the preceding claims, wherein the balance weight (500) comprises a thin plate portion (502) at the radially inner periphery, and the annular projection (549) is disposed about the thin plate portion (502).

Inventors: SHIMIZU SHIGEMI, TAKAI KAZUHIKO, SHIMIZU, SHIGEMI, TAKAI, KAZUHIKO
Applicants: SANDEN CORP, SANDEN CORPORATION
Application year: 1992
Main classification: F04B27
IPC codes: F04B27