Slant plate type compressor with variable capacity control mechanism

Abstract: A slant plate type compressor having a capacity adjusting mechanism includes a housing enclosing a crank chamber (22), a suction chamber (241) and a discharge chamber (251) therein. A piston is slidably fitted within each of the cylinders. An inlet port (650) of the compressor is continually linked to a crank chamber in fluid communication through an pressure equalizing path. A pressure applying path (640) conducts the discharge pressure to the regulating mechanism, which regulates a flow amount from the inlet port (620) to the suction chamber, from the discharge chamber so as to apply the discharge pressure force to the regulating mechanism. The pressure force applied to the regulating mechanism varies in response to change in pressure in the inlet port, so that the flow amount from the inlet port to the suction chamber is adjusted thereby adjusting the pressure differential between the crank and suction chambers. A oil flow back path is overlapped with the pressure applying path in part, so that the lubricating oil can effectively flow back to the crank chamber from the discharge chamber during the capacity control stage of the compressor.

Description: BACKGROUND OF THE INVENTION Technical Field of the Invention The present invention relates to a refrigerant compressor, and more particular, to a slant plate type compressor, such as a wobble plate type compressor, having a variable displacement mechanism which is suitable for use in an automobile air conditioning system. Description of the Prior Art Slant plate type piston compressors including variable displacement or capacity adjusting mechanism for controlling the compression ratio of a compressor in response to demand are generally known in the art. For example, JP-A-64-56972 (=JP-A-1-56972) discloses a wobble plate type compressor including a cam rotor driving device and a wobble plate linked to a plurality of pistons. Rotation of the cam rotor driving device causes the wobble plate to nutate and thereby successively reciprocate the pistons in the corresponding cylinders. The stroke length of the pistons and thus the capacity of the compressor may be easily changed by adjusting the slant angle of the wobble plate. The slant angle is changed in response to the pressure differential between the suction chamber and the crank chamber. In the above '972 Japanese Patent Application Publication, an inlet port is provided at a compressor housing of the compressor so as to conduct the refrigerant gas therethrough into the suction chamber from an evaporator, which forms a part of a refrigerant circuit of the automotive air conditioning system. The inlet port of the compressor is continually linked to a crank chamber in fluid communication through a first path or a passageway (so-called pressure equalizing passageway), so that pressure in the inlet port of the compressor is maintained to be equal to pressure in a crank chamber. A fluid communication between the suction chamber and the inlet port of the compressor is controlled by a first valve mechanism so as to adjust the pressure differential therebetween. As the pressure differential between the suction chamber and the inlet port of the compressor is adjusted, the pressure differential between the suction chamber and the crank chamber is adjusted as well, because of the existence of the first passageway. The first valve mechanism includes an operating chamber into which the refrigerant having pressure higher than that in the inlet port of the compressor is conducted, and a valve element which is slidably disposed in the operating chamber. A flow amount of the refrigerant conducted into the operating chamber is controlled by a second valve mechanism so as to adjust the pressure differential between the operating chamber and the inlet port of the compressor. In response to the pressure differential between the operating chamber and the inlet port of the compressor, a position of the valve element in the operating chamber changes so that the fluid communication between the suction chamber and the inlet port of the compressor is controlled. As the fluid communication between the suction chamber and the inlet port of the compressor is controlled, the pressure differential between the suction chamber and the inlet port of the compressor is adjusted, and therefore, the pressure differential between the suction chamber and the crank chamber is adjusted. In response to the pressure differential between the suction chamber and the crank chamber, the slant angle of the wobble plate changes, so that the stroke length of the pistons and thus the capacity of the compressor is changed. Furthermore, during operation of the automotive air conditioning system, the lubricating oil circulates through the refrigerant circuit of the automotive air conditioning system together with the refrigerant, and temporarily stays in the crank chamber of the compressor so as to lubricate the internal component parts which are operatively disposed in the crank chamber of the compressor. However, when the automotive air conditioning system operates in the severe operational condition, such that a heat load on the evaporator is high and/or that a rotational speed of the drive shaft of the compressor is high, an amount of the lubricating oil temporarily staying in the crank chamber may decrease to the value at which the internal component parts of the compressor can not be effectively lubricated. This may cause the deficiency to the compressor in durability. From DE 195 17 333 A1 a slant plate type refrigerant compressor according to the preamble of claim 1 is known. SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a variable capacity type slant plate compressor of which internal component parts are effectively lubricated even when an automotive air conditioning system operates in the severe operational condition. This object is solved by a slant plate type refrigerant compressor as set forth in claim 1. Preferred developments of the invention are given in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall vertical longitudinal sectional view of a slant plate type compressor in accordance with a first embodiment of the present invention. FIG. 2 is an enlarged partial cross sectional view of FIG. 1. FIG. 3 is a graph illustrating an operational characteristic of a valve control mechanism shown in FIG. 1. FIG. 4 is an overall vertical longitudinal sectional view of a slant plate type compressor in accordance with a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1 and 4, for purposes of explanation only, the left side of the figures will be referenced as the forward end or front of the compressor, and the right side of the figures will be referenced as the rearward or rear of the compressor. With reference to FIG. 1, the construction of a slant plate type compressor, and more specifically, a wobble plate type refrigerant compressor 10, having a capacity control mechanism in accordance with a first embodiment of 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 enclosed within cylinder block 21 by front end plate 23, and rear end plate 24 attached to the other end of cylinder block 21. Front end plate 23 is mounted on cylinder block 21 forward of crank chamber 22 by a plurality of bolts (not shown) . Rear end plate 24 is also mounted on cylinder block 21 at the opposite end by a plurality of bolts (not shown). Valve plate 25 is located between rear end plate 24 and cylinder block 21. Opening 232 is centrally formed in front end plate 23 for supporting drive shaft 26 by bearing 30 disposed therein. The inner end portion of drive shaft 26 is rotatably supported by bearing 31 disposed within central bore 210 of cylinder block 21. Bore 210 extends to rear end surface of cylinder block 21. Adjusting screw 220 is screwingly disposed within bore 210, and is in contact with the inner end surface of drive shaft 26 through disc-shaped spacer 230. A construction and functional manner of the adjusting screw 220 and the spacer 230 are described in detail in U. S. Patent No. 4,948,343 to Shimizu. Cam rotor 40 is fixed on drive shaft 26 by pin member 261 and rotates with drive shaft 26. 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. Drive shaft 26 is disposed through opening 53. Slant plate 50 includes arm 51 having slot 52. 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 a plane perpendicular to the longitudinal axis of drive shaft 26. A balance weight ring 80 having a substantial mass is disposed on a nose of hub 54 of slant plate 50 in order to balance the slant plate 50 under dynamic operating conditions. Balance weight ring 80 is held in place by means of retaining ring 81. Wobble plate 60 is nutatably mounted on hub 54 of slant plate 50 through bearings 61 and 62 which allow slant plate 50 to rotate with respect to wobble plate 60. Fork-shaped slider 63 is attached to the radially outer peripheral end of wobble plate 60 and is slidable mounted about sliding rail 64 disposed between front end plate 23 and cylinder block 21. Fork-shaped slider 63 prevents the rotation of wobble plate 60 such that wobble plate 60 nutates along rail 64 when cam rotor 40, slant plate 50 and balance weight ring 80 rotate. Undesirable axial movement of wobble plate 60 on hub 54 of slant plate 50 is prevented by contact between a rear end surface of inner annular projection 65 of wobble plate 60 and a front end surface of balance weight ring 80. Cylinder block 21 includes a plurality of peripherally located cylinder chambers 70 in which pistons 71 are disposed. Each piston 71 is connected to wobble plate 60 by a corresponding connecting rod 72. Accordingly, nutation of wobble plate 60 thereby causes pistons 71 to reciprocate within their respective chambers 70. Rear end plate 24 includes peripherally located annular suction chamber 241 and centrally located discharge chamber 251. Valve plate 25 includes a plurality of suction openings 242 linking suction chamber 241 with respective cylinders 70. Valve plate 25 also includes a plurality of discharge openings 252 linking discharge chamber 251 with respective cylinders 70. Suction openings 242 and discharge openings 252 are provided with suitable reed valves as described in U. S. Patent No. 4,011,029 to Shimizu. Rear end plate 24 is provided with an inlet port 241a for linking suction chamber 241 to an outlet of evaporator (not shown) of the external cooling circuit in fluid communication. Rear end plate 24 is further provided with an outlet port (not shown) for linking discharge chamber 251 to an inlet of condenser (not shown) of the cooling circuit in fluid communication. A pair of gaskets (not shown) are located between cylinder block 21 and the inner surface of valve plate 25 and between 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. The gaskets and valve plate 25 thus form a valve plate assembly. A steel valve retainer 253 is fixed on a central region of the outer surface of valve plate 25 by bolt 254 and nut 255. Valve retainer 253 prevents excessive bend of the reed valve which is provided at discharge opening 252 during a compression stroke of piston 71. A first cylindrical cavity 400 is formed in rear end plate 24 separate from both the suction chamber 241 and the discharge chamber 251. First cylindrical cavity 400 extends in the radial direction from an outer periphery to a central portion of rear end plate 24 with lying across the inlet port 241a in generally right angle. An inner closed end surface 403 (to the bottom in FIG. 1) of cavity 400 is shaped to be a cone configuration. A piston member 500 is fittingly disposed in cavity 400 to be slidable therewithin. Piston member 500 includes a top end portion 501 (to the bottom in FIG. 1), a bottom end portion 502 (to the top in FIG. 1) and a narrowed connecting portion 503 connecting the top and bottom end portions 501 and 502. A first cylindrical depression 501b is formed at a top end surface 501a of top end portion 501 of piston member 500. A second cylindrical depression 502b is formed at a bottom end surface 502a of bottom end portion 502 of piston member 500. A plug member 510 is fixedly disposed at an opening end portion of cavity 400 by, for example, snap ring 520. O-ring seal element 530 of an elastic member is elastically disposed between an outer peripheral surface of plug member 510 and an inner peripheral wall of cavity 400 so as to seal therebetween. A coil spring 540 is resiliently disposed between the bottom end portion 502 of piston member 500 and plug member 510, so that piston member 500 is maintained to be urged upwardly (to the bottom in FIG. 1). The first cylindrical cavity 400 further includes a first chamber section 401 and second chamber section 402. The first chamber section 401 is defined between the plug member 510 and the bottom end surface 502a of bottom end portion 502 of piston member 500. The second chamber section 402 is defined between the inner closed end surface 403 of cavity 400 and the top end surface 501a of top end portion 501 of piston member 500. A first conduit 610 is formed in rear end plate 24 so as to link an inner hollow space 241b of inlet port 241a to the first chamber section 401 of the cavity 400 in fluid communication. The first conduit 610 has a small diameter to generate a throttling effect thereat. A second cylindrical cavity 700 is also formed in rear end plate 24 separate from both the suction chamber 241 and the discharge chamber 251. The second cylindrical cavity 700 extends in the radial direction from an outer periphery to a center of rear end plate 24, and is arranged to generally be a point symmetry with the first cavity 400. A valve control mechanism 800 is accommodated in second cavity 700. With reference to FIG. 2 in addition to FIG. 1, the construction of the valve control mechanism 800 is described in detail below. The second cavity 700 includes a large diameter portion 710 and a small diameter portion 720 radially inwardly extending from an inner end of the large diameter portion 710. Valve control mechanism 800 includes a first and second casings 810 and 820, which are disposed within the large and small diameter portions 710 and 720 of the second cavity 700, respectively. First casing 810 includes a top wall 810a which comprises an opening 810b formed at a central region thereof for receiving one end portion (to the top in FIG. 2) of a cylindrical column member 811. Cylindrical column member 811 includes a central hole 811a axially formed therethrough. The central hole 811a of cylindrical column member 811 slidably receives a cylindrical rod portion 812a of plunger 812 therein. Plunger 812 is made of magnetic material and includes basal portion 812b from which cylindrical rod portion 811a extends, and a shoulder portion 812c formed at a position which is a boundary between rod portion 812a and basal portion 812b. Cylindrical column member 811 and plunger 812 are covered by a cup-shaped member 813. One end portion (to the top in FIG. 2) of cylindrical column member 811 is forcibly inserted into opening 810b of the top wall 810a of first casing 810 together with an opening end (to the top in FIG. 2) of cup-shaped member 813, and the cylindrical column 811, the top wall 810a of first casing 810 and cup-shaped member 813 are fixedly connected to one another by, for example, welding. A closed bottom 813a of cup-shaped member 813 is received on a holder 814 functioning as a bottom wall of first casing 810. The holder 814 and first casing 810 are fixedly disposed within the large diameter portion 710 of the second cavity 700 by means of a retaining element, for example, snap ring 815. The basal portion 812b of plunger 812 is slidably disposed within the cup-shaped member 813 such that the basal portion 812b can move between a bottom end surface (to the bottom in FIG. 2) of the column member 811 and an inner surface of a closed bottom 813a of cup-shaped member 813. A cylindrical depression 812e is formed at a bottom end surface 812d (to the bottom in FIG. 2) of basal portion 812b of plunger 812. A coil spring 816 is resiliently disposed between an inner bottom surface of depression 812e of the basal portion 812b of plunger 812 and an inner surface of the closed bottom 813a of cup-shaped member 813, so that plunger 812 is maintained to be urged upwardly (to the top in FIG. 2). An electromagnetic coil assembly 817 is disposed within first casing 810 so as to surround the cup-shaped member 813. Thus, plunger 812 is surrounded by electromagnetic coil assembly 817 through cup-shaped member 813 and column member 811. Lead wire 818 is connected to an electromagnetic coil 817a of the electromagnetic coil assembly 817 to supply electric power thereto from an external electric power source, for example, a battery (not shown). The second casing 820 disposed within the small diameter portion 720 of the second cylindrical cavity 700 includes a top wall 820a and a thick bottom wall 820b. The bottom wall 820b of second casing 820 is snuggled with the top wall 810a of first casing 810. An axial hole 821 is axially formed through the bottom wall 820b of second casing 820. The axial hole 821 is arranged to be aligned with the central hole 811a of cylindrical column member 811. The axial hole 821 includes a first, second and third sections 821a, 821b and 821c. The first section 821a of axial hole 821 is arranged to be linked to the central hole 811a of cylindrical column member 811 in fluid communication. The third section 821c of axial hole 821 is arranged to be linked to an inner hollow space 822 of the second casing 820 in fluid communication. The second section 821b of axial hole 821 links the first section 821a to the third section 821c in fluid communication. The first section 821a is designed to be greater than the second section 821b in diameter. Further, the second section 821b is designed to be greater than the third section 821c in diameter. A plurality of first radial holes 823 are formed in the bottom wall 820b of second casing 820 so as to extend from axial hole 821 at a position which is a boundary between the second and third sections 821b and 821c of axial hole 821. A valve seat 824 having a shape of truncated cone is formed in axial hole 821 at a position which is a boundary between the first and second sections 821a and 821b of axial hole 821. A plurality of second radial holes 825 are also formed in the bottom wall 820b of second casing 820 so as to extend from the first section 821a of axial hole 821 at a position adjacent to the valve seat 824. The second casing 820 accommodates bellows 826 in its inner hollow space 822 to be responsive to pressure therein. Bellows 826 is manufactured to have resiliency in the axial direction thereof, and is evacuated. A axial bottom end (to the top in FIG. 2) of bellows 826 is fixedly secured to the top wall 820a of second casing 820. An axial top end (to the bottom in FIG. 2) of bellows 826 is fixedly attached to a bottom end (to the top in FIG. 2) of a rod member 827. Rod member 827 is disposed within the axial hole 821 to fitly slide through the third section 821c of the axial hole 821. A ball valve element 828 is resiliently held between the rod member 827 and the rod portion 812a of plunger 812 by means of bellows 826 and coil spring 816. O-ring seal element 831 of an elastic member is elastically disposed between an outer surface of a side wall 820c of second casing 820 and an inner peripheral surface of the small diameter portion 720 of the second cavity 700 at a position adjacent to the top wall 820a of second casing 820 so as to seal therebetween. O-ring seal element 832 of an elastic member is elastically disposed between an outer side surface of the bottom wall 820b of second casing 820 and the inner peripheral surface of the small diameter portion 720 of the second cavity 700 at a position between the first radial holes 823 and the second radial holes 825 so as to seal therebetween. O-ring seal element 833 of an elastic member is elastically disposed between an outer side surface of the top wall 810a of first casing 810 and an inner peripheral surface of the large diameter portion 710 of the second cavity 700 so as to seal therebetween. The second cavity 700 includes a first, second and third chamber sections 701, 702 and 703. The first chamber section 701 is defined between a top end surface (to the top in FIG. 2) of the top wall 820a of the second casing 820 and an inner closed end surface 721 (to the top in FIG. 2) of the small diameter portion 720 of the second cavity 700. The second chamber section 702 is defined between the outer surface of the side wall 820c of second casing 820 and the inner peripheral surface of the small diameter portion 720 of the second cavity 700 at a position between the O-ring seal elements 831 and 832. The third chamber section 703 is an annular cavity radially outwardly extending from the second cavity 700 at a position which is a boundary between the large and small diameter portions 710 and 720 of the second cavity 700. The third chamber section 703 is located at a position between the O-ring seal elements 832 and 833. The first chamber section 701 of the second cavity 700 is linked to the inner hollow space 822 of the second casing 820 in fluid communication through a plurality of holes 829 formed through the top wall 820a of second casing 820. The second chamber section 702 of the second cavity 700 is linked to the axial hole 821 at the position boundary between the second and third sections 821b and 821c of the axial hole 821 in fluid communication through the first radial holes 823. The third chamber section 703 of the second cavity 700 is linked to the first section 821a of the axial hole 821 in fluid communication through the second radial holes 825. A second conduit 620 is formed in rear end plate 24 so as to link the inner hollow space 241b of inlet port 241a to the first chamber section 701 of the cavity 700 in fluid communication. A third conduit 630 is also formed in rear end plate 24 so as to link the second chamber section 402 of cavity 400 to the third chamber section 703 of the cavity 700 in fluid communication. A fourth conduit 640 is formed in rear end plate 24 so as to link the third chamber section 703 of the cavity 700 to the discharge chamber 251 in fluid communication. The fourth conduit 640 has a small diameter to generate a throttling effect thereat. A diameter of the fourth conduit 640 is designed to be smaller than that of the second section 821b of the axial hole 821 formed through the bottom wall 820b of second casing 820. A fifth conduit 650 is formed through rear end plate 24, the valve plate 25 and cylinder block 21 so as to link the second conduit 620 to the crank chamber 22 in fluid communication. A sixth conduit 660 is also formed in rear end plate 24, the valve plate 25 and cylinder block 21 so as to link the second chamber section 702 of the cavity 700 to bore 210 in fluid communication. A seventh conduit 670 is formed in cylinder block 21 and the valve plate 25 so as to link the suction chamber 241 to the crank chamber 22 in fluid communication. The seventh conduit 670 includes a small diameter portion 671 to generate a throttling effect thereat. A diameter of the small diameter portion 671 of the seventh conduit 670 is designed to be smaller than that of the second section 821b of the axial hole 821 formed through the bottom wall 820b of second casing 820. During operation of the compressor 10, drive shaft 26 is rotated by the engine of the automobile through electromagnetic clutch 300. Cam rotor 40 is rotated with drive shaft 26, thereby rotating slant plate 50 as well, which in turn causes wobble plate 60 to nutate. The nutational motion of wobble plate 60 then reciprocates pistons 71 in their respective cylinders 70. As pistons 71 are reciprocated, refrigerant gas introduced into suction chamber 241 through inlet port 241a flows into each cylinder 70 through suction openings 242, and is then compressed. The compressed refrigerant gas is then discharged to discharge chamber 251 from each cylinder 70 through discharge openings 252, and continues therefrom into the cooling circuit through the outlet port (not shown). The capacity of compressor 10 is adjusted by changing the angle of the slant plate 50, which is dependent upon pressure in the crank chamber 22, or more precisely, which is dependent upon the pressure differential between the crank chamber 22 and the suction chamber 241. The pressure differential between the crank chamber 22 and the suction chamber 241 is adjusted by controlling a motion of the piston member 500, which is responsive to an operation of the valve control mechanism 800. A capacity control operation of compressor 10 in accordance with the first embodiment of the present invention is carried out in the following manner. With reference to FIGS. 1 and 2, in a condition where an operation of the compressor 10 is stopped, the first and second chamber sections 401 and 402 of the first cylindrical cavity 400 are balanced with each other in pressure at about, for example, 6 Kgf/cm 2 ·G. Therefore, piston member 500 substantially receives the restoring force of the coil spring 540 only, and is urged to be located at the uppermost position (to the bottom in FIG. 1) as illustrated in FIG. 1. As a result, a fluid communication between the suction chamber 241 and the inlet port 241a is maintained to be fully blocked by the bottom portion 502 of the piston member 500. When the compressor 10 starts to operate, the slant plate 50 begins to rotate so that the pistons 71 begin to reciprocate in their respective cylinders 70 through the wobble plate 60. As a result, pressure in the suction chamber 241 gradually decreases. As the suction chamber pressure gradually decreases relative to the crank chamber pressure, the slant angle of the slant plate 50 as well as the slant angle of wobble plate 60 with respect to the plane perpendicular to the axis of the drive shaft 26 gradually decreases, thereby gradually decreasing the capacity of the compressor. In a little while after the start of operation of the compressor 10, the displacement of compressor 10 reaches to the minimum value. Concurrently with the start of operation of the compressor 10, the electric power is continuously supplied to the electromagnetic coil 817a from the battery (not shown) through lead wire 818 to continuously excite the electromagnetic coil 817a, and thereby continuously generating force which acts on plunger 812 to move upwardly (to the top in FIGS. 1 and 2). Furthermore, as shown in FIG. 3, a value at which the pressure in the inner hollow space 241b of the inlet port 241a is controlled is adjusted by changing an ampere of the electric power which is supplied to the electromagnetic coil 817a. In this embodiment, the pressure in the inner hollow space 241b of the inlet port 241a is controlled to be at 2 Kgf/cm 2 ·G by supplying the electric power having 0.5 A to the electromagnetic coil 817a. As the operation of the compressor 10 with the minimum displacement continues, the pressure in the suction chamber 241 further gradually decreases. Since the first chamber section 401 of the first cylindrical cavity 400 is linked to the suction chamber 241 in fluid communication through the seventh conduit 670, the crank chamber 22, the fifth conduit 650, the second conduit 620, the inner hollow space 241b of the inlet port 241a and the first conduit 610, the pressure in the first chamber section 401 gradually decreases as well from the aforementioned value of 6 Kgf/cm 2 ·G. Accordingly, the pressure force acting on the bottom end surface 502a of bottom end portion 502 of the piston member 500 gradually decreases. At this situation, if the pressure in the inner hollow space 241b of the inlet port 241a is considerably greater than 2 Kgf/cm 2 ·G, for example, 4 Kgf/cm 2 ·G, the bellows 826 contracts in the direction of the longitudinal axis thereof due to pressure conducted into the inner hollow space 822 of the second casing 820 from the inner hollow space 241b of the inlet port 241a via the second conduit 620, first chamber section 701 of the second cavity 700 and holes 829. Accordingly, the rod member 827 moves downwardly (to the top in FIGS. 1 and 2). Therefore, the ball valve element 828 resiliently held between the rod member 827 and the rod portion 812a of plunger 812 is received on the valve seat 824 formed in the axial hole 821. Thus, the fluid communication between the third and second chamber sections 703 and 702 of the second cavity 700 via the second radial holes 825, the axial hole 821 and the first radial holes 823 is blocked. Accordingly, the refrigerant gas conducted into the third chamber section 703 of the second cavity 700 from the discharge chamber 251 through the fourth conduit 640 is entirely conducted to the second chamber section 402 of the first cylindrical cavity 400, so that the pressure in the second chamber section 402 is maintained at a value which is greater than the aforementioned value of 6 Kgf/cm 2 ·G. Accordingly, the top end surface 501a of top end portion 501 of piston member 500 receives the relatively large pressure force. When the operation of the compressor 10 in the minimum displacement continues while the pressure in the inner hollow space 241b of the inlet port 241a is considerably greater than 2 Kgf/cm 2 ·G, for example, 4 Kgf/cm 2 ·G, the sum of the restoring force of the coil spring 540 and the pressure force acting on the bottom end surface 502a of bottom end portion 502 of the piston member 500 is defeated by the pressure force acting on the top end surface 501a of top end portion 501 of piston member 500. Accordingly, the piston member 500 moves downwardly (to the top in FIG. 1) to be located at an upper most position thereof. Therefore, a blockade of the fluid communication between the inlet port 241a and the suction chamber 241 is fully canceled, so that the inlet port 241a is fully linked to the suction chamber 241 in fluid communication. As a result, the pressure differential between the suction chamber 241 and the inner hollow space 241b of the inlet port 241a becomes zero or the minimum value instantly, and hence, the pressure differential between the suction chamber 241 and the crank chamber 22 becomes zero or the minimum value instantly. As the pressure differential between the suction chamber 241 and the crank chamber 22 becomes zero or the minimum value, the slant angle of the slant plate 50 as well as the slant angle of wobble plate 60 with respect to the plane perpendicular to the axis of the drive shaft 26 becomes maximized so that the compressor 10 begins to operate in the maximum displacement. As the operation of the compressor 10 in the maximum displacement continues, pressure in the inner hollow space 241b of the inlet port 241a decreases. When the pressure in the inner hollow space 241b of the inlet port 241a decreases to the set value, i.e., 2 Kgf/cm 2 ·G, the bellows 826 expands in the direction of the longitudinal axis thereof due to the pressure conducted into the inner hollow space 822 of the second casing 820 from the inner hollow space 241b of the inlet port 241a via the second conduit 620, first chamber section 701 of the second cavity 700 and holes 829. Accordingly, the rod member 827 moves upwardly (to the bottom in FIGS. 1 and 2). Therefore, the ball valve element 828 resiliently held between the rod member 827 and the rod portion 812a of plunger 812 is moved to a position which is apart from the valve seat 824, so that the blockade of the fluid communication between the third and second chamber sections 703 and 702 of the second cavity 700 via the second radial holes 825, the axial hole 821 and the first radial holes 823 is canceled. Accordingly, the refrigerant gas conducted into the third chamber section 703 of the second cavity 700 from the discharge chamber 251 flows into the central bore 210 of the cylinder block 21 via the second radial holes 825, the axial hole 821, the first radial holes 823, the second chamber section 702 of the second cavity 700 and the sixth conduit 660. The refrigerant gas flowing into the central bore 210 further flows to the crank chamber 22 via a central hole 221 of the adjusting screw 220, a central hole 231 of the spacer 230 and a small air gap created between the cylinder block 21 and the bearing 31. Accordingly, the refrigerant gas conducted into the second chamber section 402 of the first cavity 400 from the discharge chamber 251 flows to the crank chamber 22, so that the pressure in the second chamber section 402 of the first cavity 400 decreases. Therefore, the pressure force received by the top end surface 501a of top end portion 501 of piston member 500 decreases as well. As a result, the piston member 500 moves from the upper most position thereof to a first certain position, at which the sum of the restoring force of the coil spring 540 and the pressure force acting on the bottom end surface 502a of bottom end portion 502 of the piston member 500 is newly balanced with the pressure force acting on the top end surface 501a of top end portion 501 of piston member 500. When the piston member 500 is located at the first certain position, the fluid communicating passage between the inlet port 241a and the suction chamber 241 is narrowed to have a first opening area. Therefore, the flow of the refrigerant from the inlet port 241a to the suction chamber 241 is throttled. As a result, the pressure differential between the suction chamber 241 and the inner hollow space 241b of the inlet port 241a increases, and hence, the pressure differential between the suction chamber 241 and the crank chamber 22 increases. Accordingly, the slant angle of the slant plate 50 as well as the slant angle of wobble plate 60 with respect to the plane perpendicular to the axis of the drive shaft 26 decreases, so that the displacement of the compressor 10 is decreased to a first certain value from the maximum value . As the operation of the compressor 10 in the displacement having the first certain value continues, the pressure in the inner hollow space 241b of the inlet port 241a increases to a value which is slightly greater than 2 Kgf/cm 2 ·G. Accordingly, the bellows 826 again contracts in the direction of the longitudinal axis thereof. Therefore, the rod member 827 moves downwardly (to the top in FIGS. 1 and 2), so that the ball valve element 828 is again received on the valve seat 824. As a result, the fluid communication between the third and second chamber sections 703 and 702 of the second cavity 700 is again blocked. Accordingly, a flow of the refrigerant gas from the third chamber section 703 of the second cavity 700 to the crank chamber 22 is terminated. Therefore, the pressure in the second chamber section 402 of the first cavity 400 increases, so that the pressure force received by the top end surface 501a of top end portion 501 of piston member 500 increases as well. As a result, the piston member 500 moves downwardly (to the top in FIG.1) from the first certain position to a second certain position, at which the sum of the restoring force of the coil spring 540 and the pressure force acting on the bottom end surface 502a of bottom end portion 502 of the piston member 500 is newly balanced with the pressure force acting on the top end surface 501a of top end portion 501 of piston member 500. When the piston member 500 is located at the second certain position, the fluid communicating passage between the inlet port 241a and the suction chamber 241 is broadened to have a second opening area which is slightly greater than the first opening area. As a result, the pressure differential between the suction chamber 241 and the inner hollow space 241b of the inlet port 241a decreases, and hence, the pressure differential between the suction chamber 241 and the crank chamber 22 decreases. Accordingly, the slant angle of the slant plate 50 as well as the slant angle of wobble plate 60 with respect to the plane perpendicular to the axis of the drive shaft 26 increases, so that the compressor 10 operates in the displacement having a second certain value which is slightly greater than the first certain value. The above-described two manners of the operation of the valve control mechanism 800 are alternated so as to adjust the capacity or the displacement of compressor 10. As a result, the pressure in the inner hollow space 241b of the inlet port 241a is maintained at 2 Kgf/cm 2 ·G, irrespective of the changes in the heat load on the evaporator or the rotating speed of the drive shaft of the compressor. According to the first embodiment of the present invention, as described above, the lubricating oil in the discharge chamber 251 can effectively flow back to the crank chamber 22 together with the refrigerant while the capacity or the displacement of the compressor 10 is controlled. Accordingly, the inner component parts of the compressor 10 can be sufficiently lubricated even when the automotive air conditioning system operates in the severe operational condition. Furthermore, when temperature of the outside of an automobile is low, pressure in the inner hollow space 241b of the inlet port 241a becomes low. Accordingly, the bellows 826 expands in the direction of the longitudinal axis thereof, so that the ball valve element 828 is maintained to be located at a position which is apart from the valve seat 824. As a result, the fluid communication between the inlet port 241a and the suction chamber 241 is fully blocked by the piston member 500. Therefore, compressor 10 operates in the minimum displacement. In this situation, pressure in the inner hollow space 241b of inlet port 241a may decease to a value which is smaller than the set value of 2 Kgf/cm 2 ·G. Even though the fluid communication between the inlet port 241a and the suction chamber 241 is fully blocked by the piston member 500, the refrigerant gas flowing into the inlet port 241a from the evaporator (not shown) is allowed to further flow to the crank chamber 22 together with the lubricating oil via the second and fifth conduits 620 and 650, because that the refrigerant gas in the crank chamber 22 is allowed to flow into to the suction chamber 241 through the seventh conduit 670. In addition, a small part of the refrigerant gas in the discharge chamber 251 can also flow to the crank chamber 22 together with the lubricating oil via the fourth conduit 640, the third chamber section 703 of the second cavity 700, the second radial holes 825, the axial hole 821, the first radial holes 823, the second chamber section 702 of the second cavity 700, the sixth conduit 660, the central bore 210, the central hole 221 of the adjusting screw 220, the central hole 231 of the spacer 230 and the small air gap created between the cylinder block 21 and the bearing 31. Accordingly, the lubricating oil can effectively flow back to the crank chamber 22 from the external component of the cooling circuit (not shown) and the discharge chamber 251 while the compressor 10 operates in the minimum displacement. Therefore, the inner component parts of the compressor 10 can be sufficiently lubricated as well. With reference to FIG. 4, the construction of a wobble plate type refrigerant compressor including a capacity control mechanism in accordance with a second embodiment of the present invention is shown. As illustrated, like reference numerals are used to denote like elements corresponding to those shown in FIGS. 1 and 2. Except, where otherwise stated, the overall functioning of the compressor is the same as discussed above. In the second embodiment, the third conduit 630 formed in rear end plate 24 links the second chamber section 402 of cavity 400 to the second chamber section 702 of the cavity 700 in fluid communication. The sixth conduit 660 linking the second chamber section 702 of the cavity 700 to bore 210 in fluid communication includes a small diameter portion 661 to generate a throttling effect thereat. A diameter of the small diameter portion 661 of the sixth conduit 660 is designed to be smaller than that of the second section 821b of the axial hole 821 formed through the bottom wall 820b of second casing 820. A diameter of the fourth conduit 640 is designed to have a larger value than that of the first embodiment, so that no throttling effect is generate at the fourth conduit 640. A location of the inlet port 241a is arranged to be shifted toward the center of the rear end plate 24 in comparison with the first embodiment. According to the above construction, the capacity control operation of compressor 10 is carried out in the following manner. When the pressure in the inner space 241b of the inlet port 241a increases from the set value of 2 Kgf/cm 2 ·G to a third certain value which is greater than the set value of 2 Kgf/cm 2 ·G, the bellows 826 contracts in the direction of the longitudinal axis thereof. Accordingly, the rod member 827 moves downwardly (to the top in FIGS. 2 and 4), so that the ball valve element 828 is received on valve seat 824. As a result, the fluid communication between the discharge chamber 251 and the second chamber section 402 of the first cavity 400 is blocked. Therefore, the second chamber section 402 of the first cavity 400 is only linked to the crank chamber 22 in fluid communication via the third conduit 630, sixth conduit 660, central bore 210, central hole 221 of the adjusting screw 220, central hole 231 of the spacer 230 and the small air gap created between the cylinder block 21 and the bearing 31. Accordingly, the refrigerant gas conducted into the second chamber section 402 of the first cavity 400 flows to the crank chamber 22, so that the pressure in the second chamber section 402 of the first cavity 400 decreases. Therefore, the pressure force received by the top end surface 501a of top end portion 501 of piston member 500 decreases as well. As a result, the piston member 500 moves upwardly (to the bottom in FIG. 4) to a third certain position, at which the sum of the restoring force of the coil spring 540 and the pressure force acting on the bottom end surface 502a of bottom end portion 502 of the piston member 500 is newly balanced with the pressure force acting on the top end surface 501a of top end portion 501 of piston member 500. When the piston member 500 is located at the third certain position, the fluid communicating passage between the inlet port 241a and the suction chamber 241 is broadened to have a third opening area. Therefore, the throttling effect generated at a position between the inlet port 241a and the suction chamber 241 decreases. As a result, the pressure differential between the suction chamber 241 and the inner hollow space 241b of the inlet port 241a decreases, and hence, the pressure differential between the suction chamber 241 and the crank chamber 22 decreases. Accordingly, the slant angle of the slant plate 50 as well as the slant angle of wobble plate 60 with respect to the plane perpendicular to the axis of the drive shaft 26 increases, so that the displacement of the compressor 10 is increases to a third certain value. As the operation of the compressor 10 in the displacement having the third certain value continues, the pressure in the inner hollow space 241b of the inlet port 241a decreases to a value which is slightly smaller than the set value of 2 Kgf/cm 2 ·G. Accordingly, the bellows 826 expands in the direction of the longitudinal axis thereof, so that the rod member 827 moves upwardly (to the bottom in FIGS. 2 and 4). Therefore, the ball valve element 828 is moved to a position which is apart from the valve seat 824, so that the blockade of the fluid communication between the third and second chamber sections 703 and 702 of the second cavity 700 via the second radial holes 825, the axial hole 821 and the first radial holes 823 is canceled. Accordingly, the discharge chamber 251 is linked to the second chamber section 402 of the first cavity 400 in fluid communication. Since the sectional opening area of the small diameter portion 661 of the sixth conduit 660 is designed to be smaller than that of the second section 821b of the axial hole 821 formed through the bottom wall 820b of second casing 820, a small part of the refrigerant gas conducted into the second chamber section 402 of the first cavity 400 is allowed to further flows to the crank chamber 22. Accordingly, the pressure in the second chamber section 402 of the first cavity 400 increases. Therefore, the pressure force received by the top end surface 501a of top end portion 501 of piston member 500 increases as well. As a result, the piston member 500 moves downwardly (to the top in FIG. 4) from the third certain position to a fourth certain position, at which the sum of the restoring force of the coil spring 540 and the pressure force acting on the bottom end surface 502a of bottom end portion 502 of the piston member 500 is newly balanced with the pressure force acting on the top end surface 501a of top end portion 501 of piston member 500. When the piston member 500 is located at the fourth certain position, the fluid communicating passage between the inlet port 241a and the suction chamber 241 is narrowed to have a fourth opening area which is slightly greater than the third opening area. As a result, the pressure differential between the suction chamber 241 and the inner hollow space 241b of the inlet port 241a increases, and hence, the pressure differential between the suction chamber 241 and the crank chamber 22 increases. Accordingly, the slant angle of the slant plate 50 as well as the slant angle of wobble plate 60 with respect to the plane perpendicular to the axis of the drive shaft 26 decreases, so that the compressor 10 operates with the displacement having a fourth certain value which is slightly smaller than the third certain value. The above-described two manners of the operation of the valve control mechanism 800 are alternated so as to adjust the capacity or the displacement of compressor 10. As a result, as well as the first embodiment, the pressure in the inner hollow space 241b of the inlet port 241a is maintained at 2 Kgf/cm 2 ·G, irrespective of the changes in the heat load on the evaporator or the rotating speed of the drive shaft of the compressor. According to the second embodiment of the present invention, as described above, the lubricating oil in the discharge chamber 251 can effectively flow back to the crank chamber 22 together with the refrigerant while the capacity or the displacement of the compressor 10 is controlled. Accordingly, as well as the first embodiment, the inner component parts of the compressor 10 can be sufficiently lubricated even when the automotive air conditioning system operates in the severe operational condition. Furthermore, in the first and second embodiments, the first conduit 610 is formed in the rear end plate 24 so as to link the first chamber section 401 of the first cavity 400 to the inner hollow space 241b of the inlet port 241a in fluid communication. However, the first conduit 610 may be formed in the rear end plate 24 so as to link the first chamber section 401 of the first cavity 400 to the suction chamber 241 in fluid communication. Moreover, in the first and second embodiments, the present invention is applied to a variable capacity type wobble plate compressor. However, the present invention can be applied to a variable capacity type swash plate compressor.

Claims: A slant plate type refrigerant compressor (10) having a compressor housing (20) enclosing a crank chamber (22), a suction chamber (241) and a discharge chamber (251) therein, said compressor housing (20) comprising a cylinder block (21) having a plurality of cylinders (70) formed therethrough, a piston (71) slidably fitted within each of said cylinders (70), drive means (26, 40, 50, 60 , 72)coupled to said pistons (71) for reciprocating said pistons (71) within said cylinders (70), said drive means including a drive shaft (26) rotatably supported in said housing (20) and coupling means (50, 60, 72) for drivingly coupling said drive shaft (26) to said pistons (71) such that rotary motion of said drive shaft (26) is converted into reciprocating motion of said pistons (71), said coupling means including a slant plate (50) having a surface disposed at an adjustable inclined angle relative to a plane perpendicular to said drive shaft (26), the inclined angle of said slant plate (50) being adjustable in response to change in pressure differential between said crank chamber (22) and said suction chamber (241) to vary the stroke length of said pistons (71) in said cylinders (70) and to thereby vary the capacity of said compressor (10), a regulating means (500) for regulating a flow amount of the refrigerant flowing through a first passageway (241b) which links said suction chamber (241) to an outlet of an evaporator in fluid communication, a second passageway (620, 650) linking said crank chamber (22) to said first passageway (241b) at a position upstream to said regulating means (500) so as to equalize pressure therebetween, a third passageway (640, 703, 630, 402) linking said discharge chamber (251) to said regulating means (500) for conducting pressure in said discharge chamber (251) to said regulating means (500) so as to apply pressure force thereto, a valve control means (800) being associated with said third passageway (640, 630, 402) so as to control said pressure force applied to said regulating means (500) in response to change in pressure in said second passageway (620, 650) so that said flow amount of the refrigerant flowing through said first passageway (241b) is changed whereby the pressure differential between the crank chamber (22) and the suction chamber (241) is changed, characterized in that a fourth passageway (640, 703, 825, 821b, 823, 702, 660, 210, 221, 231), a part of which is overlapped with a part of said third passageway, links said discharge chamber (251) to said crank chamber (22) in fluid communication so that a fluid flow of the refrigerant from said discharge chamber (251) to said crank chamber (22) is maintained while said valve control means (800) is operating. The slant plate type compressor of claim 1 wherein said fourth passageway (640, 630, 703, 825, 821b, 823, 702, 660, 210, 221, 231) includes a throttled portion (640) which is located at a position (640) where a part thereof is overlapped with a part of said third passageway. The slant plate type compressor of claim 1 wherein said fourth passageway (640, 630, 703, 825, 821b, 823, 702, 660, 210, 221, 231) includes a throttled portion (661) which is located at a position (660) where a part thereof is not overlapped with a part of said third passageway. The slant plate type compressor of one of claims 2 and 3, said third passageway including a communicating path (821b) which is located at a position where a part of said fourth passageway is overlapped with a part of said third passageway and is controlled to be open and close, an opening cross sectional area of said throttled portion (640, 661) being designed to be smaller than that of said communicating path (821b). The slant plate type compressor of one of claims 1 to 4 comprising a fifth passageway (670) linking said crank chamber (22) to said suction chamber (241), said fifth passageway (670) including a throttled portion (671) of which an opening cross sectional area is designed to be smaller than that of said communicating path (821b).

Inventors: TAGUCHI YUKIHIKO, TAGUCHI, YUKIHIKO
Applicants: SANDEN CORP, SANDEN CORPORATION
Application year: 1997
Main classification: F04B1
IPC codes: F04B49, F04B39, F04B27