WOBBLE PLATE TYPE COMPRESSOR WITH VARIABLE CAPACITY MECHANISM

Abstract: This invention is directed to a wobble plate type com­ pressor which is provided with a variable displacement me­ chanism. The variable displacement mechanism is controlled by the slant angle of the wobble plate (40) due to change of pressure in the crank chamber, and comprises a passageway (335) communicated between suction chamber (341) and crank chamber (32), and a valve me­ chanism (45) to control the opening and closing of the passageway. The valve mechanism includes a first valve control means for directly controlling the opening and closing of passageway and second valve control means (46) which is complied with the first valve means and forcedly opens the passageway while opening itself.

Description: This invention relates to a wobble plate type compressor for an automotive air conditioner, and more particularly, to a wobble plate type compressor with a variable capacity mechanism which has an effective characteristic for cooling down. One construction of a wobble plate type compressor with a variable capacity mechanism which is suitable in use for an automotive air conditioner is disclosed in U.S. Pat. No. 3,861,829. The change of inclined angle of a wobble plate of the above compressor is accomplished by adjusting the pres­ sure in a crank chamber, i.e., adjusting gas pressure added to the rear side of the pistons. Referring to Fig. 1, the construction of a conventional wobble plate type compressor is shown. The compressor in­ cludes a compressor housing 1 having a cylinder block 2 which is provided with a plurality of cylinders 22 and a crank chamber 3, and a cylinder head 4 which is mounted on one end portion of cylinder block 2 through a valve plate 5. A drive shaft 6 is rotatably supported on a tubular extension 11 which is formed on the other end of the compressor housing 1 through a bearing 7 and, the inner terminal end of the drive shaft 6 is extended within the crank chamber 3 to rotatably support on a central hole 21 of cylinder block 2 through a bearing 8. A rotor 9 is fixed on the drive shaft 6 and the end of the rotor 9 is connected to an inclined plate 10 through a hinge mechanism 91, therefore, the inclined plate 10 is driven together with the rotor 9 and hinge mechanism 91 while vary­ ing the inclination angle of plate 10. The slant surface of the inclined plate 10 is in close proximity to the surface of a wobble plate 12 which is rotatably supported thereon. A thrust bearing 13 is disposed between the slant surface of the inclined plate 10 and the wobble plate 12. A guide bar 14 is axially extended within the crank chamber 3 so as to con­ nect one end of the compressor housing 1 and cylinder block 2. The lower end portion of wobble plate 12 engages a guide bar 14 to enable wobble plate 12 to reciprocate along guide bar 14 while preventing any rotational motion. A plurality of pistons 15 are slidably fitted within a respective cylinder 22 and are connected to wobble plate 12 through connecting rods 16. Cylinder head 4 is divided into a suction chamber 41 and a discharge chamber 42. Control valve mechanism 17 with a precise structure as shown in Fig. 2 is disposed in a suction chamber 41 and is controlling the opening and closing of the first channel 18 which is connecting the crank chamber 3 with the suction chamber 41. Control valve mechanism 17 includes a first casing 171, a second casing 172 which is fixed on one end surface of the first casing 171, and bellows 173 which is disposed with­ in the interior space of the first casing 171 and holding its position by a coil spring 174. Bellows 173 is provided with a valve porltion 173a at the outer end surface thereof and a coil spring (not shown) is disposed within bellows 173, to control the expansion and contraction of bellows 173. The first casing 171 is provided with an aperture 171a at its outer peripheral portion to communicate the interior of first casing 171 with suction chamber 41. The second casing 172 is provided with a second channel 172a communicated with suction chamber 41 through first channel 18 and a third channel 172b which communicates the interior of the first casing 171 with the crank chamber 3 through the first channel 18 and the second channel 172b. Thus, crank chamber 3 and suction cham­ ber 41 can be connected with one another through the control valve mechanism 17. Operation of the control valve mechanism 17 will be de­ scribed below. If the pressure in suction chamber 41 exceeds a predetermined value, the bellows 173 in the first casing 171 shrinks and moves valve portion 173a toward left in the drawing. Accordingly, the opening of the third channel 172b is opened, and crank chamber 3 is communicating with suction chamber 41 through first channel 18, second channel 172a and thrid channel 172b. Therefore, the pressure in crank chamber 3, i.e., rear pressure added to pistons 15 is decreased, thus the inclination angle of wobble plate 12 is increased. As a result, the stroke volume of pistons 15 is increased, and the capacity of the compressor is also increased. Reversely, if the pressure in suction chamber 41 is below the predetermined value, the bellows 173 in the first casing 171 expands and moves valve portion 173a toward right in the drawing. Accordingly, the opening of the third channel 172b is closed, and the communication between crank chamber 3 and suction chamber 41 is interrupted. The pressure in crank chamber 3 is thus gradually increased by gas leakage from cylinders 22. Therefore, the rear pressure to pistons 15 is increased, and the inclination angle of wobble plate 12 is decreased. As a result, the stroke volume of pistons 15 is decreased, and the capacity of the compressor is decreased. In an automotive air conditioning system in which the above-mentioned compressor is included, if the compressor is initially started under the condition that thermal load in a compartment of a car is large and the engine is driven at high revolution, such as during high speed of a car, the pressure in the suction chamber of the compressor is rapidly decreased until a predetermined value of the control mechanism. Therefore, the capacity control mechanism of the compressor is operated in spite of the insufficient decrease of temperature in the compartment of the car. Thus, the characteristic of cooling down in the above compressor is not good as compared with a conventional wobble plate type compressor within a variable capacity mechanism. It is a primary object of this invention to provide a wobble plate type compressor with a capacity mechanism which can more effectively control the temperature in a compartment of a car. Further, a wobble plate type compressor with a capacity mechanism shall be provided which has an improved character­ istic for cooling down. A wobble plate type compressor according to this inven­ tion includes a compressor housing having a cylinder block provided with a plurality of cylinders and a crank chamber adjacent the cylinder block. A piston is slidably fitted within each of the cylinders and reciprocated by a swash plate driven by a drive mechanism. The stroke of the piston is varied by changes of pressure in the crank chamber. A front end plate is mounted on the compressor housing, rotat­ ably supporting the drive mechanism. A rear end plate is mounted on the opposite end of the compressor housing and is dividing its interior space into a suction chamber and a dis­ charge chamber. A passageway is formed through the housing to connect the crank chamber and the suction chamber. A variable capacity control means is disposed on the rear end plate for controlling the opening and closing of the passageway. The variable capacity control means includes a first valve con­ trol means for controlling movement of a valve element to open and close the passageway in response to changes of re­ frigerant pressure in the compressor, and second valve con­ trol means coupled to the first valve control means and forcedly open the passageway in spite of the movement of the first valve control means. Further objects, features and other aspects of this in­ vention will be understood from the following detailed de­ scription of preferred embodiments of this invention, while referring to the annexed drawings, in which Fig. 1 is a cross-sectional view of a conventional wobble plate type compressor with a variable capacity mechan­ ism; Fig. 2 is a cross-sectional view of a variable capacity mechanism shown in Fig. 1; Fig. 3 is a cross-sectional view of a wobble plate type compressor with a variable capacity mechanism in accordance with one embodiment of this invention; Fig. 4 is a cross-sectional view of a control valve mechanism shown in Fig. 3; Fig. 5 is a cross-sectional view of an electromagnetic actuator shown in Fig. 3; Fig. 6 is a cross-sectional view of a variable capacity mechanism which includes a control valve mechanism and an electromagnetic actuator shown in Fig. 3; Fig. 7 is a graph which shows the relationship between time and temperature for cooling down in a wobble plate type compressor with a conventional variable capacity mechanism or a present variable capacity mechanism; Fig. 8 is a cross-sectional view of a wobble plate type compressor which is shown in Fig. 8; Fig. 9 is a cross-sectional view of a variable capacity mechanism which is modified as compared with that shown in Fig. 6; Fig. 10 is a part of a cross-sectional view of a wobble plate type compressor in accordance with another embodiment of this invention; and Fig. 11 is a cross-sectional view of a vacuum actuator shown in Fig. 8. With reference to Fig. 3, the construction of a wobble plate type compressor with a variable capacity mechanism in accordance with one embodiment of this invention is shown. The compressor includes a front end plate 30, a compressor housing 31 which is provided with a crank chamber 32 and a cylinder block 33, and a cylinder head 34 which is attached on one end surface of the cylinder block 33 through a valve plate 35 by securing belts (not shown). A drive shaft 36 is rotatably supported within the front end plate 30 through a bearing 301 at one end thereof and ex­ tends into a central aperture 331 of the cylinder block 33. The other end of drive shaft 36 is rotatably supported within the cylinder block 33 through a bearing 332 in a central hole 331. A rotor 37 is fixedly disposed on the outer terminal end of drive shaft 36 and is connected to an inclined plate 38 through a hinge mechanism 39. Inclined plate 38 is axially and movably disposed on the outer surface of drive shaft 36 and rotates together with rotor 37. Hinge mechanism 39 in­ cludes a pin 391 which is fixed within a hole 371 of rotor 37 and a longitudinal hole 381 of inclined plate 38. The other end of pin 391 is movably fitted within a longitudinal hole 381 to operate inclined plate 38 axially. A wobble plate 40 is placed in close proximity to the surface of the inclined plate 38 and radially supported on the outer surface of a tubular portion 382 of the inclined plate 38 through bearing 383. A thrust needle bearing 40 is disposed between the sloping surface of inclined plate 38 and wobble plate 40. The lower end portion of wobble plate 40 engages a guide bar 42 to enable the wobble plate 40 to re­ ciprocate along guide bar 42 while preventing any rotating motion. A plurality of pistons 43 are reciprocatably fitted within respective cylinders 333 and each of pistons 42 is connected to the other end of wobble plate 40 through respective con­ necting rods 44. Cylinder block 34 is divided into a suction chamber 341 and a discharge chamber 342 and each of chambers 341, 342 is communicating with a refrigerant circuit through an inlet or outlet port (not shown). A control valve mechanism 45 is disposed in a cavity 334 of cylinder block 33 and is controlling the opening and clos­ ing of the opening of channel 335 which connects crank cham­ ber 32 with cavity 334. An electromagnetic actuator 46 pro­ jects into suction chamber 341, which is connected to one end of control valve mechanism 45 through a bracket 47. Referring to Fig. 4, the construction of the control valve mechanism 45 is shown. Control valve mechanism 45 in­ cludes a cup shaped casing 451 which is provided with an aperture 451a at its peripheral portion to communicate the interior of casing 451 with crank chamber 32 through a channel 335 and operature 451a, and a bellows 452 which is disposed within the interior of casing 451. An O-ring 453 is disposed on the outer surface of casing 451 for sealing between the inner surface of cavity 334 and the outer peripheral surface of valve mechanism 45. Bellows 452 is provided with an ad­ justing screw 452a for adjusting an operating point of bellows 452, which is attached on the upper end surface thereof, and a valve portion 452b which is fixed on the lower end surface thereof. In the above construction, communication between crank chamber 32 and suction chamber 341 is controlled in accordance with operation of control valve mechanism 45. With reference to Fig. 5, the construction of an electro­ magnetic actuator 46 is shown. The actuator 46 includes a casing 461 within which an electromagnetic coil 463 is dis­ posed, connecting a frame 462 attached on one end surface of casing 461 and actuator pin 464 which is axially slidably ex­ tended within a central aperture of casing 461 and frame 462. Connecting casing 462 is provided with a cavity 462a and a screw thread 462b which is formed on the outer surface there­ of. A pin 464 is provided with a radial flange portion 464a which is disposed within cavity 462a of connecting frame 462 for receiving recoil strength of a coil spring 465, and an armature portion 464b which is attracted to an electromagnetic coil 463 as electromagnetic coil 463 is supplied with electric current. Referring to Fig. 6, the construction of an improved variable capacity mechanism is shown which includes the con­ trol valve mechanism 45 and the electromagnetic actuator 46. Control valve mechanism 45 and electromagnetic actuator 46 are connected through the bracket 47. Bracket 47 includes a cup-shaped casing 471 which is provided with an aperture 471a for communicating the suction chamber 341 with the interior of the casing 471, and an aperture 471b which is formed so as to receive screw thread 462b of the connecting casing 462. An opening 472 of cup-shaped casing 471 is threaded on a thread portion 451c of the casing 451. Control valve mechanism 45 and electromagnetic actuator 46 are connected with each other through the bracket 47 by securing each of screw threads 451c, 462b. As to the operation of control valve mechanism 45 and electromagnetic actuator 46 control valve mechanism 45 operates to equalize suction pressure while detect the pres­ sure in crank chamber 32. That is, if the pressure in suction chamber 341 exceeds the predetermined value, bellows 452 shrinks. Aperture 451b of the casing 451 is thus opened. Ac­ cordingly, suction chamber 341 communicates with crank chamber 32 through channel 335 formed within the cylinder block 33. The pressure added to the rear side of the piston 43 gradually decreases, and the inclination angle of the wobble plate 40 to drive shaft 36 is decreased. Therefore, the stroke of piston 43 in cylinder 333 increases, and the capacity of the compressor becomes large. On the other hand, if the pressure in suction chamber 341 is below the predetermined value, bellows 452 extends. Aper­ ture 451b of casing 451 is thus closed. Accordingly, the com­ munication between suction chamber 341 and crank chamber 32 is interrupted, and the pressure added to the rear side of piston 43 gradually increases. The inclination angle of wobble plate 40 to drive shaft 36 is gradually increased in accord­ ance with an increase of the pressure in crank chamber 32. Therefore, the stroke of piston 43 also gradually decreases, and the capacity of the compressor becomes small. As mentioned above, control valve mechanism 45 is operated in accordance with the pressure in suction chamber 341 to adjust the inclination angle of the wobble plate 40. That is, the stroke of piston 43 is controlled so as to make the pressure in suction chamber 341 a predetermined value. Furthermore, when the electromagnetic coil 463 is ener­ gized, electromagnetic coil 463 generates electromagnetic force arround itself, and attracts armature portion 464b of pin 464 toward casing 461. Accordingly, pin 464 moves upward­ ly against the recoil strength of coil spring 465. Therefore, on condition that the pressure in suction chamber 341 becomes less than a predetermined value and bellows 452 is extended downwardly, as a result the pin 464 pushes the valve portion 452b of bellows 452 upwardly to open the aperture 451b. Thus, aperture 451b is forcedly opened in spite of operation of con­ trol valve mechanism 45 while the electromagnetic coil 463 is energized. On the other hand, when the electromagnetic coil 48 is not energized, operating pin 464 moves downwardly. Therefore, bellows 452 recovers in general operation. Referring to Fig. 7, the relationship between the charac­ teristic for cooling down in a wobble plate type compressor with a conventional variable capacity mechanism or a variable capacity mechanism in accordance with one embodiment of this invention is shown. The comparison with the above mechanism refers to the temperature in the compartment of a car and of the air blown from a louver. Dotted lines show the tempera­ ture in relation to a conventional variable capacity mechanism and solid lines show the temperature in relation to a variable capacity mechanism in accordance with one embodiment of this invention. This graph indicates that the mechanism in accord­ ance with this invention has a better characteristic for cooling down in each of the possible conditions than the con­ ventional mechanism. As explained with reference to Figures 3 to 6, the ope­ ration of bellows 452 is disposed on the space in which the pressure of crank chamber 32 is introduced, and pressure of suction chamber is applied to one end portion of bellow 452. Alternatively, the bellow may be disposed on the space in which the pressure of suction chamber 341 is introduced, and the pressure in the crank chamber 32 is applied to one end portion of bellows 452, as shown in Figure 8. The construc­ tion of the control mechanism utilized in this embodiment is the same as that o control mechanism 17 which is explained with reference to Figure 2. In this embodiment, as shown in Figure 9, control mechanism 17 is provided with an electro­ magnetic actuator 46, the construction of which is clearly explained with reference to Figure 5. Therefore, the angle of inclination of wobble plate 40 is varied in accordance with operation of control mechanism 17, as previously explained. Furthermore, under the energization of electromagnetic actua­ tor 46, the compressor is operated at high capacity. As shown in Figure 10, vacuum actuator 50 will be re­ placed for electromagnetic actuator 46 of the first embodi­ ment. Vacuum actuator 50 includes a casing 502 which is di­ vided into an air chamber 502a and a negative pressure chamber 502b with a diaphragm 501, and a tubular extension 503 which is connected with casing 502. An operating pin 504 is reci­ procably disposed within the tubular extension 503 and fixed on diaphragm 501. Tubular extension 503 is provided with a stopper portion 505 for limiting the axial moving range of operating pin 504 at the inner end portion thereof. Coil spring 506 is disposed between stopper portion 505 and dia­ phragm 501 for supporting diaphragm 501 at the stationary position. O-rings 507 and packing 508 are disposed on the outer surface of the operating pin 504 for sealing between pin 504 and tubular extension 503. A screw 503a is formed on the outer surface of tubular extension 503 in order to fix vacuum actuator 50 within cylinder head 34 and a nut 51. When the vacuum actuator 50 is placed on a predetermined position, the outer terminal end of the operating pin 504 is opposed to the valve portion 452b of bellows 452. In opera­ tion, if negative pressure is introduced into the interior of negative pressure chamber 502b through introduction tube 509, diaphragm 501 is attracted toward negative pressure chamber 502b and moves until one end surface of diaphragm 501 is in contact with stopper portion 505. Accordingly, operating pin 504 moves upwardly together with diaphragm 501 and, upper end of the operating pin 504 pushes the valve portion 452b of bellows 452 to move upwardly. Thus, aperture 451b is forced to open without regard for operation of control valve me­ chanism 45. Therefore, crank chamber 32 communicates with suction chamber 341, and the stroke of the piston 43 can be maintained in the largest. On the other hand, when air is introduced into the in­ terior of the negative pressure chamber 502b through the in­ troduction tube 509, diaphragm 501 is formed to return with recoil strength of coil spring 506. Accordingly, operating pin 504 moves downwardly together with diaphragm 501. There­ fore, control valve mechanism 45 can control opening and closing of aperture 451b. The operation of actuator 46, for example, depends upon the temperature of the compartment of the automobile. If the temperature of the compartment is exceeding a predetermined temperature of which situation is indicated that the high re­ frigerant capacity is required, the electromagnetic coil 463 of actuator 46 is energized. Therefore, the compressor is operated under maximum capacity, even if the suction pressure is below the predetermined level. On the other hand, if the temperature of the compartment is below the predetermined temperature of which situation is indicated that very small refrigerant capacity is sufficient to compensate the change of temperature, the electromagnetic coil 463 is not energized. This invention has been described in detail in connec­ tion with preferred embodiments, but these are examples only and this invention is not restricted thereto. It will be easily understood by those skilled in the art that other variations and modifications can be easily made within the scope of this invention.

Claims: 1. In a wobble plate type compressor including a com­ pressor housing (31) having a cylinder block (33) provided with a plurality of cylinders (333) and a crank chamber (32) adjacent said cylinder block (33), a piston (43) slidably fitted within each of said cylinders (333) and reciprocated by a swash plate driven by a drive mechanism, (of which a stroke is varied by changes of pressure in said crank cham­ ber,) a front end plate (30) disposed on said compressor housing (31) for rotatably supporting said drive mechanism, a rear end plate disposed on the opposite end of said com­ pressor housing (31) and having a suction chamber (341) and a discharge chamber (342), a passageway (335) connecting said crank chamber (32) with said suction chamber (341), and vari­ able capacity control means (45) for controlling the closing and opening of said passageway (335), the improvement com­ prising said variable capacity control means (45) including first valve control means for controlling movement of said valve element to open and close said passageway in response to changes of refrigerant pressure in the compressor, and second valve control means (46, 50) coupled to said first valve control means (45) for forcedly opening said passageway (335) in spite of said movement of said first valve control means (45). 2. The wobble plate type compressor of claim 1, wherein said first valve control means (45) is a bellows (452). 3. The wobble plate type compressor of claims 1, 2, wherein said second valve control means (46) is an electro­ magnetic actuator. 4. The wobble plate type compressor of claims 1, 2, wherein said second valve control means is a vacuum actuator.

Inventors: TAGUCHI,YUKIHIKO
Applicants: SANDEN CORPORATION
Application year: 1987
Main classification: F04B1
IPC codes: F04B27