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Variable displacement compressorRelated Patent Categories: Pumps, Condition Responsive Control Of Drive Transmission Or Pump Displacement, Adjustable Cam Or Linkage, Axial Cam, With Sump Pressure ActuationVariable displacement compressor description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070014674, Variable displacement compressor. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The present invention relates to a variable displacement compressor whose displacement is variable by changing angle of inclination of a swash plate of the compressor. [0002] In this type of variable displacement compressor (hereinafter referred to merely as a compressor), refrigerant gas in a discharge chamber is supplied into a crank chamber through a supply passage while the refrigerant gas in the crank chamber is drawn out to a suction chamber through a bleed passage for controlling pressure in the crank chamber, whereby the angle of inclination of the swash plate is adjusted. A control valve is provided in the supply passage. As an opening degree of the control valve is adjusted, flow rate of the refrigerant gas supplied into the crank chamber is adjusted, so that the angle of inclination of the swash plate is adjusted thereby to adjust stroke of a piston and hence the displacement of the compressor. [0003] A shaft seal chamber is provided in an outer side of a drive shaft in a housing of the compressor. A shaft seal member is accommodated in the shaft seal chamber for preventing the refrigerant gas from leaking out of the compressor along the circumferential surface of the drive shaft. Since the shaft seal member is constantly in slide contact with the circumferential surface of the drive shaft, the shaft seal member generates heat during operation of the compressor. To prevent degradation caused by excessive generation of heat of the shaft seal member, the compressor has a structure for cooling the shaft seal member. [0004] Japanese Unexamined Patent Application Publication (KOKAI) No. 4-179874 discloses one example of the structure. Specifically, the shaft seal chamber is provided in the supply passage, through which the refrigerant gas is supplied from the discharge chamber to the crank chamber. The refrigerant gas is decompressed by the control valve to lower its temperature, and then is supplied into the crank chamber through the shaft seal chamber. Therefore, the refrigerant gas is blown to the shaft seal member in the shaft seal chamber thereby to cool the shaft seal member. This prevents the degradation caused by excessive generation of heat of the shaft seal member. [0005] In the above-referenced compressor, however, since the refrigerant gas discharged into the discharge chamber is high temperature, even if the refrigerant gas is decompressed by the control valve to lower its temperature, the refrigerant gas blown to the shaft seal member in the shaft seal chamber is still high temperature. Therefore, cooling effect of the shaft seal member caused by the refrigerant gas is not sufficiently performed. [0006] The present invention is directed to a variable displacement compressor for sufficiently cooling the shack seal member. SUMMARY OF THE INVENTION [0007] The present invention provides a variable displacement compressor for forming a refrigerant circuit with an external refrigerant circuit. The variable displacement compressor includes a housing, a drive shaft, a swash plate, a shaft seal member, a supply passage, a control valve and a gas passage. The housing has a suction chamber, a crank chamber, a discharge chamber and a shaft seal chamber formed therein. The drive shaft is rotatably supported by the housing. The swash plate is connected to the drive shaft so that angle of inclination of the swash plate relative to the drive shaft is variable. The swash plate is accommodated in the crank chamber. The shaft seal member is accommodated in the shaft seal chamber. The discharge chamber is in communication with the crank chamber through the supply passage. The supply passage includes the shaft seal chamber. The control valve is disposed in the supply passage. Flow rate of refrigerant gas supplied from the discharge chamber to the crank chamber through the supply passage is adjusted by adjusting an opening degree of the control valve. The discharge chamber is in communication with the external refrigerant circuit through the gas passage. The supply passage is formed differently from the gas passage. A part of the supply passage is located adjacent to the suction chamber and nearer to the suction chamber than the discharge chamber. [0008] Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0009] The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: [0010] FIG. 1 is a longitudinal sectional view showing a variable displacement compressor according to a first embodiment of the present invention; [0011] FIG. 2 is a cross sectional view taken in the direction of the arrows substantially along the line 2-2 of FIG. 1; [0012] FIG. 3 is a longitudinal sectional view showing a variable displacement compressor according to a second embodiment of the present invention; [0013] FIG. 4 is a longitudinal sectional view showing a variable displacement compressor according to a third embodiment of the present invention; [0014] FIG. 5 is a cross sectional view taken in the direction of the arrows substantially along the line 5-5 of FIG. 4; [0015] FIG. 6 is a cross sectional view of a variable displacement compressor showing another example of a position at which a part of a supply passage is arranged; [0016] FIG. 7 is a cross sectional view of a variable displacement compressor showing another example of a position at which a part of a supply passage is arranged; [0017] FIG. 8 is a cross sectional view of a variable displacement compressor showing another example of a position at which a part of a supply passage is arranged; and [0018] FIG. 9 is a cross sectional view of a variable displacement compressor showing another example of a position at which a part of a supply passage is arranged. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0019] The following will describe a variable displacement compressor (hereinafter referred to merely as a compressor) according to a first preferred embodiment of the present invention with reference to FIGS. 1 and 2. [0020] FIG. 1 shows a longitudinal sectional view of a compressor 10 of the first embodiment. In FIG. 1, the left side and the right side of the drawing correspond to the front side and the right side of the compressor 10, respectively. As shown in FIG. 1, the compressor 10 includes a cylinder block 11, a front housing 12 which is fixedly joined to the front end of the cylinder block 11, and a rear housing 14 which is fixedly joined to the rear end of the cylinder block 11 through a valve plate assembly 13. The cylinder block 11, the front housing 12 and the rear housing 14 form a housing of the compressor 10. Continue reading about Variable displacement compressor... 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