WOBBLE PLATE TYPE COMPRESSOR WITH VARIABLE DISPLACEMENT MECHANISM

Abstract: A variable displacement mechanism suitable for use with a wobble plate type compressor is disclosed. The variable displacement mechanism comprises a passageway to communicate between a suction chamber (151) and crank chamber (13), and control device for controlling the opening and closing of passageway. The control device includes a valve element (326′, 413) to actually control the communication between suction chamber (151) and discharge chamber (152), a first control device (32, 41) directly controlling the operation of the valve element in accordance with a change of the condition in an interior space (322) thereof, and a second control device (33, 42) to control the condition in the interior space (322) of the first control device. The operation of the valve element is thus substantially controlled in accordance with the actual operating condition of the compressor after a time delay.

Description: This invention relates to a wobble plate type compressor,and more particularly,to a wobble plate type compressor provided with a variable displacement mechanism. One construction of a wobble plate type compressor with a variable displacement mechanism suitable use for an automobile air conditioner is disclosed in U.S.Patent No.3,861,829. In this prior art,the change of inclined angle of wobble plate is accomplished by controlling the pressure of crank chamber,i.e., adjust the gas pressure added to the rear surface of the each pistons. Referring to Figure 1,the construction of a conventional wobble plate type compressor is shown. The compressor 1 includes a compressor housing 11 having a cylinder block 12 at its one end portion and a crank chamber 13,a front end plate 14 which is disposed on other end of housing 11 to cover its opening and formed integral with compressor housing 11, and cylinder head 15 which is disposed on one end portion of cylinder block 12 through valve plate 16. Drive shaft 2 is rotatably supported on front end plate 14 through radial bearing 3. The inner terminal end of drive shaft 2 is extended within central bore 121 formed on central portion of cylinder block 12 and rotatably supported thereon through radial bearing 4. Rotor 5 is placed in crank chamber 13 and fixed on drive shaft 2. Inclined plate 6 is hinged on rotor 5 through hinge mechanism 7 to rotated together therewith while varying the inclined angle of plate 6. The slant surface of inclined plate 6 is closed proximity to the surface of wobble plate 8. Thrust bearing 9 is disposed between slant surface of inclined plate 6 and wobble plate 8 to accomplish the smoothly rotational motion of plate 6. A guid bar 10 is extended within lower portion of crank chamber 13 of compressor housing 11. Lower portion of wobble plate 8 engages with guid bar 10 to accomplish the reciprocating motion of wobble plate 8 along the guid bar 10 while preventing any rotational motion of wobble plate 8. A plurality of pistons 20 are slidably fitted within respective cylinder 17 which are formed through cylinder block 12, and connected with wobble plate 8 through connecting rod 21. Cylinder head 15 is divided its interior space into two chambers,such as suction chamber 151 and discharge chamber 152. Variable displacement mechanism comprises a communication passageway 22 to communicat between crank chamber 13 and suction chamber 151 of cylinder head 15. The valve device 23 is disposed on suction chamber 151 to control the opening and closing of passageway 22. As shown in Figure 2,valve device 23 comprises first casing 231 and second casing 232 which is disposed on one end opening of first casing 231 to cover its opening and provided with communication holes 232a, 232b to communicat between passageway 22 and suction chamber 151. A bellows 233 is placed on the interior space of first casing 231 and held its position by coil spring 234. A valve element 235 is affixed on one end surface of bellows 233 and slidably supported on supporting plate 236 to control the opening and closing of communication hole 232b of second casing 232. The supporting plate 236 has a plurality of holes 236a to make a communication between communication hole 232b and the interior space of casing 231. The outer peripheral portion of first casing 231 has at least one of aperture 231a to accomplish the communication between the interior space of first casing 231 and suction chamber 151. Therefore, crank chamber 13 comunicats with suction chamber 151 through passageway 22, communication holes 232a, 232b of second casing 232 of valve device 23, and aperture 231a of first casing 231 while valve element 235 is open the communication hole 232a. In the above explained compressor, if pressure in suction chamber 151 exceed a predetermined value,bellows 233 in first casing 231 shrinks. Thus,valve element 235 moves toward left in the figure. As a result,valve element 235 opens the communication hole 232b and cause the communication between crank chamber 13 and suction chamber 151. Therefore, the pressure in crank chamber 13 is equalized with pressure in suction chamber 151 to thereby decreased the pressure added to rear surface of respective pistons 20. In this condition,the inclined angle of wobble plate 7 is increased, and thus the compressor is operated under maximum capacity. On the other hand, if pressure in suction chamber 151 belows the predetermined value,bellows 233 in first casing 231 of valve device 23 extends, and moves toward right in the figure. As a result, communication hole 232b is closed by valve element 235, to thereby interrupted the communication between crank chamber 13 and suction chamber 151. The pressure in crank chamber 13 is thus gradually increased, i.e., the pressure added to rear surface of respective pistons 20 is increased, and inclined angle of wobble plate 7 is decreased. In this condition,the compressor is reduced its capacity. In an automobile air conditioning apparatus which is included with above mentioned compressor, if the compressor is initially start up under conditions that thermal load in the compartment of automobile is large and the engine is driven at high revolution, the pressure in suction chamber of the compressor is rapidly decreased and below the predetermined value,even if the refrigeration of compartment is not sufficient. That is variable displacement mechanism is operated,even if actual temperature in compartment is not sufficiently down. Thus, as shown in Figure 3, the characteristic for cooling down in above mentioned compressor is inferior that of conventional compressor which is not provided with variable displacement mechanism. Also,the pressure in crank chamber is drastically changed to change the inclined angle of wobble plate, it is feared that the lubricating oil contained in the crank chamber is flow out to the suction chamber. It is a primary object of this invention to provide a wobble plate type compressor with variable displacement mechanism which is more suitably controlled the temperature in compartement of automobile. It is another object of this invention to provide a wobble plate type compressor with variable displacement mechanism which can be improved the charactristic for cooling down of refrigerating apparatus. A wobble plate type compressor in accordance with this invention comprises a compressor housing having a cylinder block which is provided with a plurality of cylinders, and crank chamber adjacent the cylinder block. A rear end plate is disposed on one end surface of the cylinder block and formed with a suction chamber and discharge chamber. A piston is slidably fitted within respective cylinders and reciprocated by nutatable motion of wobble plate. The wobble plate couples with driving mechanism for enabling to change the inclined angle thereof. a variable displacement mechanism is disposed in the compressor housing and includes a passageway to communicated between the crank chamber and suction chamber, and valve device disposed on midway portion of the passageway to control the communication of passageway to adjacent the pressure in crank chamber. The valve device of variable displacement mechanism comprises a valve element controlled the opening and closing of the passageway, a first valve control device which is disposed on an isolated pressure sensitive chamber and provided with pressure sensitive portion to operat the valve element, and a second valve control device which is controlled the communication between the suction chamber and the isolated pressure chamber. Further objects, features and other apsects of this invention will be understood from the following detailed description of a preferred embodiments of this invention, while referring to the annexed drawings. Figure 1 is a cross sectional view of wobble plate type compressor which is provided with conventional variable displacement mechaism. Figure 2 is a cross sectional view of valve device of displacement mechanism in Figure 1. Figure 3 is a graph illustrating the characteristic for cooling down in two conventional type of compressors. Figure 4 is a cross sectional view of a wobble plate type compressor in accordance with one embodiment of this invention. Figure 5 is a cross sectional view of a first valve device of variable displacement mechanism utilized in compressor of Figure 4. Figure 6 is a cross sectional view of a second valve device of variable displacement mechanism utilized in the compressor of Figure 4. Figure 7 is a cross sectional view of valve device of variable displacement mechanism utilized in the compressor of Figure 4. Figure 8 is a diagrammatic graph illustrating the characteristic of coil spring of second valve device. Figure 9 is a graph illustrating characteristic for cooling down on this invention and conventional compressor. Figure 10 is a graph illustrating the changing of suction pressure in on the compressor of this invention and conventional compressor. Figure 11 is a cross sectional view of second valve device modified of Figure 6. Figure 12 is a cross sectional view of wobble plate type compressor in accordance with another embodiment of this invention. Figure 13 is a cross sectional view of first control device utilized in compressor of Figure 12. Figure 14 is a cross sectional view of second control device utilized in compressor of Figure 12. Figure 15 is a cross sectional view of control device assembled on first and second control device. Figure 16 is a diagrammatic view of refrigerating circuit included with compressor of Figure 12. Figure 17 is a diagrammatic view illustrating the connection between pressure switch and electromagnetic device. With reference to Figure 4, a wobble plate type compressor with variable displacement mechanism in accordance with one embodiment of this invention is shown. The basic construction of the wobble plate type compressor is the same as that of the conventional compressor which is explained with reference to Figure 1 except that the variable displacement mechanism. Therefore, for similar parts of the compressor in Figure 4 the same reference numerals as in Figure 1 are used to simplify the explanation, and mainly explain the construction of the variable displacement mechanism. The variable displacement mechanism for the wobble plate type compressor comprises a passageway 30 formed through cylinder block 12 and valve plate 16 to communicate between crank chamber 13 and suction chamber 151, and a valve device 31 partly disposed on passageway 30 and suction chamber 151 to control the communication of passageway 30. The valve device 31 comprises a first valve device 32 which is substantially disposed on large bore portion 301 of passageway 30 and extends into suction chamber 151 at its one end portion, and a second valve device 33 which is affixed on one end portion of first valve device 32 through locknut 34 and disposed on suction chamber 151. Referring to Figure 5, first valve device 32 includes a casing 321 in which a pressure sensitive chamber 322 is defined by two plates 323, 324. The pressure sensitive chamber 322 communicates with the inner space of second valve device 33 through connecting hole 324a in plate 324. Casing 321 of first valve device 32 is provided with a communication chamber 325 at one end portion thereof and a threaded portion 326 at the other end portion thereof to be connected with the second valve device 33. A bellows 35 the interior of which is maintained under vacuum condition and placed a coil spring (not shown) is disposed in pressure chamber 322 and fixed on valve element 326 at its one end surface. An adjusting screw 36 is placed on the other end portion of bellows 35 and supported on one of plate 324 to adjust the operating point thereof. A valve element 326′ extends into interior space of communication chamber 325 and is slidably supported on the other plate 323. A plurality of communicating holes 325a, 325b are formed through communication chamber 325 to communicate with suction chamber 151 to crank chamber 13, and the opening and closing of communication hole 325a which communicates with suction chamber 13 is controlled by valve element 326. Further referring to Figure 6, the second valve device 33 includes a cup shaped casing 331 and divides its interior space into two chambers 331a, 331b by plate 332. A bottom plate portion of casing 331 is formed with a through hole 333 to communicate between suction chamber 151 and chamber 331a in casing 331. A spring supporting plate 334 is disposed on an opening portion of casing 331 and provided with a central hole 334a for communicating between the other chamber 331b in casing 331 and pressure sensitive chamber 322 of the first valve device 32. A pair of coil springs 335, 336 are disposed in chamber 331b in casing 331 to hold the position of a spring retainer plate 337 on which a valve element 338 is fixed. The valve element 338 is slidably supported on plate 332 and extends into chamber 331a to control the opening and closing of hole 333 due to sliding motion of valve element 338. Coil spring 335 is disposed between retainer plate 337 and spring supporting plate 334 to control the sliding motion of valve element 338 and formed by shaped memory alloy. The other spring 336 is disposed between plate 332 and retainer plate 337 to maintain the posture of retainer plate 337. This second valve element 33 is fastened on first control device 32 by lock-nut 34 which is screwed on the threaded portion 326 of casing 32 as shown in Figure 6. Therefore, pressure sensitive chamber 322 is connected with suction chamber 151 through the interior space of the second valve control device 33 and hole 333. The shape memory alloy of coil spring 335 has a characteristic that the alloy will memory its outer shape under high temperature condition and lower temperature condition. That is, if spring 335 is placed on higher temperature than predetermined temperature, the spring 335 extends and, reversely if the spring 338 is placed on lower temperature than the predetermined temperature, the spring 335 shrinks. Also, the spring 335 has hysteresis, as shown in Figure 8, i.e., the predetermined temperature t2 for changing the configuration of spring 335 from the extended position to the shrink position and the predetermined temperature t1 for changing the configuration of spring 335 from shrunk position to the extended position is different. As to operation of above explained valve device 31, if heat load in the compartment is high, the refrigerating circuit is thermally and pressurely held the balance. In that condition, the temperature in space disposed on spring 335 exceeds the predetermined temperature to change the outer configuration of spring 335, i.e., spring 335 extends. Therefore, valve elements 338 closes hole 333 of casing 331 of the second valve device 32, thereby interrupting the communication between suction chamber 151 and the interior space of valve device 31. Also, bellows 35 disposed in pressure sensitive chamber 322 of valve device 31 is shrank, the valve element 326′ opens the communication hole 325a to hold the communication between suction chamber 151 and crank chamber 13. In this condition, if the compressor is driven, the compressor is operated under maximum capacity and the pressure in crank chamber 13 is reduced following with reduction of pressure in suction chamber 151. At that time, since the pressure sensitive chamber 332 and interior space of second valve device 33 are sealed off from suction chamber 151, the valve device 31 does not directly respond to reduction of pressure in suction chamber 151. However, the temperature in suction chamber 151 is reduced following the reduction of pressure in suction chamber 151. Thus, the temperature in the interior space of valve device 31 is reduced. As a result, pressure in the interior space of valve device 31 is reduced. The response to reduction of temperature in the interior space of valve device 31 against the reduction of temperature in suction chamber 151 is delayed, therefore, the response to reduction of pressure in the interior space of valve device 31 against that of suction chamber 151 is delayed. As a result, if the temperature in the interior space of valve device 31 is exceeding the predetermined temperature, the communication between suction chamber 151 and the interior space of valve device 31 is still interrupted, although the pressure in suction chamber 151 is below the predetermined pressure which is determined by the operation of first valve device 32. Thus, the compressor is driven while maintaining the maximum stroke of piston, i.e., driven under maximum capacity condition. On the other hand, if the temperature in the interior space of valve device 31 is below the predetermined temperature t2, the spring 335 is shrank and moved the valve element 338 toward right in figure. Thus, valve element 338 opens the hole 333 to accomplish the communication between the interior space of valve device 31, particularly pressure sensitive chamber 332, and suction chamber 151, i.e., the operation of bellows 35 depends upon the changing of pressure in suction chamber 151. Under the above mentioned condition, if the pressure in suction chamber 151 is below the predetermined pressure, the pressure in pressure sensitive chamber 322 is equal to the pressure in suction chamber 151. Therefore, bellows 35 disposed in pressure sensitive chamber 322 is extended, and closes finally the communication hole 325a by valve element 326′. The communication between crank chamber 13 and suction chamber 151 is thus interrupted thereby increasing the pressure in crank chamber 13 due to blow-by gas. Following the increasing of pressure in crank chamber 13, the pressure acted on rear surface of respective pistons 20 is increased to vary the inclined angle of incline plate 6. The stroke of piston 20 within cylinder 17 is thus shortened to reduce the capacity of compressor. The operation of controlling the capacity of the compressor due to operation of the first valve device is progressed in response to the change of the pressure condition in suction chamber 151 and, this operation of first valve device is continued until the temperature in the interior space of valve device 31 exceeds the predetermined temperature t1. In this embodiment, second valve device 33 includes coil spring 335 to control the valve element 338 in accordance with change of temperature in the interior space thereof. Alternatively, as shown in Figure 11, second valve device 33 includes bellows 339 which controls opening and closing of hole 333 due to sliding motion of valve element 338. The sliding motion of valve element 338 corresponds to the pressure in the interior space of second valve device 33. As mentioned above, the variable displacement mechanism for the wobble plate type compressor comprises two control devices. One of the control devices is directly controlling the change of displacement of the compressor in accordance with change of suction pressure, and the other control device is controlling the operation of first control device in accordance with the environmental situation to cause the delay of operation of first control device, i.e., the changing of capacity by condition of suction pressure is delayed against the actual change of suction pressure. For example, in the initial stage, although the compressor is driven by high speed and suction pressure is suddenly reduced to a pressure lower than the predetermined pressure (this situation is shown in Figure 9), the valve device for variable displacement mechanism is not operated. Thus, as shown in Figure 9, the characteristic for cooling down is improved. That is the temperature in the compartment is rapidly cooled down compared with a conventional apparatus. Referring to Figures 11 to 14, another embodiment of this invention is shown. In this embodiment, operation of first valve device which is directly controlled the operation of capacity control mechanism is operated by external environmental condition of the compressor. A variable displacement mechanism 40 of this embodiment comprises a first control device 41 disposed in cylinder head 15, and second control device 42 which is connected with first control device 41 and mainly placed on the outer space of the compressor. As clearly shown in Figure 13, first control device 41 comprises a cylindrical casing 41 which is provided with communication holes 411a, 411b to communicate with suction chamber 151 or crank chamber 13, and bellows 412 disposed in the interior space of casing 411. A valve element 413 is attached on one end side of bellows 412 and slidably supported on supporting plate 44. One end portion of valve element 413 extends into communication hole 411a and controls the opening and closing of hole 411c which is formed through the casing 411 to connect the two communication holes 411a, 411b. Therefore, communication between suction chamber 151 and crank chamber 13 is controlled by sliding motion of valve element 413. An adjusting screw 415 is fitted to the other end surface of bellows 412 to determine the operating point of bellows 412 and to hold the position of bellows 412. Adjusting screw 415 is supported on plate 416 which comprises a plurality of holes 416a to hold the communication between the opening portion of casing 411 and the interior space of casing 411. A threaded portion 417 is formed on the inner surface of the other end portion of casing 411 to fasten first control device 41 on second control device 42. Second control device 42 comprises a cover plate 421 which is affixed to cylinder head 15, a central boss 422 radially and inwardly extending from the cover plate 421 provided with interior space to communicate with the interior space of first control device 41, and valve element 423. Cover plate 421 comprises a passageway 424 to communicate between the interior space of boss 422 and suction chamber 151. The operation of valve element 423 is controlled by electromagnetic device 425 disposed on the outer side of cover plate 421 and extends into the communicating portion between interior space of boss 422 and passageway 424 to control the communication therebetween. A threaded portion 426 is formed on the outer peripheral surface of boss 422 to screw on the threaded portion 417 of first control device to connect first control device 41 with second control device 41, as shown in Figure 15. The energization of electromagnetic device 425 is controlled by the actual operating condition of air conditioning apparatus, for example, pressure in accumulator A which is detected by pressure switch 43, That is, the compressor of this embodiment is disposed on the refrigerating circuit for air conditioning apparatus which includes a condenser "C", orifice tube "O", evaporator "E", and accumulator "A", as shown in Figure 15. Also, as shown in Figure 16, pressure switch 43 is normally closed the circuit, i.e., normally the electromagnetic device 425 is energized, and if the pressure in accumulator A is below the predetermined pressure, the pressure switch opens the circuit to cease the operation of electromagnetic device 423. As to operation of this embodiment, if the pressure in accumulator A is exceeding the predetermined pressure the valve element 423 is interrupting the communication between suction chamber 151 and interior space of valve device 40. Therefore, bellows 412 disposed in the interior space of valve device 40 is shrank, and secured the communication between suction chamber 151 and crank chamber 13. The compressor is thus operated under maximum capacity. On the other hand, if the pressure in accumulator "A" is below the predetermined pressure, electromagnetic device 425 is disenergized. Therefore, valve element 423 opens the communication between suction chamber 151 and the interior space of first control device 41 in which bellows 412 is disposed. The bellows 412 is operated to be extended or shrank in accordance with the change of pressure in suction chamber, i.e., capacity of compressor is changed due to change of pressure in suction chamber 151. This invention has been described in detail in connection 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 comprising a compressor housing (11) having a cylinder block (12) with a plurality of cylinders (17), and crank chamber (13) adjacent said cylinder block (12), a rear end plate disposed on one end surface of said cylinder block (12) and formed with suction chamber (151) and discharge chamber (152), a piston (20) slidably fitted within respective cylinders (17) and reciprocated by nutatable motion of a wobble plate (8), said wobble plate (8) being coupled with a driving mechanism for enabling the change of the inclined angle, a variable displacement mechanism disposed in the compressor housing (11) and including a passageway to communicate between said crank chamber (13) and said suction chamber (151) and a control device 32, 41) disposed on midway portion of said passageway to control the communication of said passageway to adjacent the pressure in crank chamber (13) to change the inclined angle of said wobble plate (8), characterized in that the control device (32, 41) includes a valve element (31, 32, 33, 326′; 41, 42, 413) for controlling the opening and closing of said passageway, a first control device (32, 41) is provided with an isolated pressure chamber (322) with a control element disposed therein for said valve element, and a second control device (33, 425) controlling the communication between said suction chamber (151) and said isolated pressure chamber (322) in accordance with the change of operating condition of the compressor. 2. The wobble plate type compressor of claim 1, characterized in that said second control device (32, 42) comprises a casing (331) the interior of which communicates with said isolated pressure chamber (322) and also with said suction chamber (151) through a passageway, a second valve element (338, 423) to control the opening and closing of said passageway, and a control element (335, 425) for said second valve element. 3. The wobble plate compressor of claim 2, wherein said control element (335) of second control device (33) is controlled by changing of temperature in said second control device. 4. The wobble plate compressor of claims 2 or 3, wherein said control element comprises a coil spring (335) formed of shaped-memory alloy and a retainer plate (337) fixed to said second valve element (338). 5. The wobble plate type compressor of claim 2, wherein said control element of the second control device (33′) is controlled by changing of pressure in said second control device. 6. The wobble plate type compressor of claim 5, wherein said control element comprises a bellows (389) affixed to said second valve element (338) at one end surface thereof. 7. The wobble plate type compressor of claim 2, wherein said control element is electromagnetic device (425).

Inventors: TAGUCHI, YUKIHIKO
Applicants: SANDEN CORPORATION
Application year: 1987
Main classification: F04B1
IPC codes: F04B25, F04B27