Structure of channel in variable displacement piston type compressor

Abstract

A variable displacement piston type compressor has a housing, a drive shaft, a cam plate and a piston. The drive shaft is rotatably supported by the housing. The drive shaft has a first end and a second end. The first end of the drive shaft extends through the housing. The cylinder block is placed between the first end and the second end. The suction chamber and the discharge chamber are defined near the first end relative to the cylinder block. The crank chamber is defined near the second end relative to the cylinder block. The refrigerant in the crank chamber is bled into the suction pressure region through a bleed passage. Thereby, the inclination angle of the cam plate is controlled. The crank chamber and the suction chamber are connected with each other through the bleed passage. The bleed passage is formed outside of the drive shaft.

What is claimed is:  
     
         1 . A variable displacement piston type compressor comprising: 
 a housing having a cylinder block including a plurality of cylinder bores, the housing defining a crank chamber, a suction pressure region and a discharge pressure region, the suction pressure region including a suction chamber, the discharge pressure region including a discharge chamber;    a drive shaft rotatably supported by the housing, the drive shaft having a first end and a second end, the first end of the drive shaft extending through the housing, the cylinder block being placed between the first end and the second end, the suction chamber and the discharge chamber being defined near the first end relative to the cylinder block, the crank chamber being defined near the second end relative to the cylinder block;    a cam plate inclinably supported by the drive shaft in the crank chamber, the cam plate being integrally rotated with the drive shaft;    a piston accommodated in each cylinder bore, the rotation of the cam plate being converted into the reciprocating movement of the piston in accordance with the inclination angle of the cam plate, refrigerant in the suction chamber being drawn into the cylinder bores due to the suction work of the piston, the refrigerant in the cylinder bores being discharged into the discharge chamber due to the discharge work of the piston, refrigerant in the discharge pressure region being supplied into the crank chamber and the refrigerant in the crank chamber being bled into the suction pressure region through a bleed passage for controlling pressure in the crank chamber, thereby the inclination angle of the cam plate being controlled, the crank chamber and the suction chamber being connected with each other through the bleed passage, the bleed passage being formed outside of the drive shaft.    
     
     
         2 . The variable displacement piston type compressor according to  claim 1 , wherein at least a part of the bleed passage is formed in a shaft hole of the cylinder block through which the drive shaft extends.  
     
     
         3 . The variable displacement piston type compressor according to  claim 2 , wherein the drive shaft is rotatably supported by a radial bearing in the cylinder block, the radial bearing being placed in the bleed passage.  
     
     
         4 . The variable displacement piston type compressor according to  claim 1 , wherein the discharge chamber and the suction chamber are separated from the cylinder bores by a valve plate assembly, a part of the bleed passage extends through the cylinder block and the valve plate assembly, and a part of the bleed passage in the valve plate assembly is a throttled passage.  
     
     
         5 . The variable displacement piston type compressor according to  claim 1 , wherein the upstream end of the bleed passage is opened to the bottom of the crank chamber.  
     
     
         6 . The variable displacement piston type compressor according to  claim 5 , wherein the bleed passage passes through the cylinder block and then reaches the circumferential surface of the drive shaft, and the circumferential surface of the drive shaft and the bleed passage in the cylinder block meet more upward in a vertical direction than the central axis of the drive shaft.  
     
     
         7 . The variable displacement piston type compressor according to  claim 1 , further comprising a throttling means having a blocking member in the bleed passage and a throttled passage formed on the blocking member, the blocking member being made of resin or rubber.  
     
     
         8 . The variable displacement piston type compressor according to  claim 7 , wherein the blocking member is made of polytetrafluoroethylene.  
     
     
         9 . The variable displacement piston type compressor according to  claim 7 , wherein the blocking member is made of nitrile-butadiene rubber.  
     
     
         10 . The variable displacement piston type compressor according to  claim 1 , wherein the cam plate is inclinable swash plate for varying displacement of the compressor.  
     
     
         11 . The variable displacement piston type compressor according to  claim 1 , further comprising lubricant oil that fluids with the refrigerant therein.  
     
     
         12 . A variable displacement piston type compressor comprising: 
 a cylinder block including a plurality of cylinder bores;    a piston for compressing refrigerant in each cylinder bore;    a cam plate movably connected to the piston for reciprocating the piston;    a crank chamber defined near one end of the cylinder block;    a drive shaft having a rotational axis for rotating to drive the cam plate, wherein the drive shaft is urged in a direction of the rotational axis while the piston reciprocates;    a suction chamber defined near the opposite end to the crank chamber relative to the cylinder block, the refrigerant in the suction chamber being drawn into the cylinder bores due to the suction work of the piston;    a discharge chamber defined near the opposite end to the crank chamber relative to the cylinder block, the refrigerant in the cylinder bores being discharged to the discharge chamber due to the discharge work of the piston; and    wherein the refrigerant in the discharge chamber is supplied into the crank chamber and the refrigerant in the crank chamber is bled into the suction chamber through a bleed passage for controlling pressure in the crank chamber, the bleed passage being formed outside of the drive shaft.    
     
     
         13 . The variable displacement piston type compressor according to  claim 12 , wherein at least a part of the bleed passage is formed in a shaft hole of the cylinder block through which the drive shaft extends.  
     
     
         14 . The variable displacement piston type compressor according to  claim 13 , wherein the drive shaft is rotatably supported by a radial bearing in the cylinder block, the radial bearing being placed in the bleed passage.  
     
     
         15 . The variable displacement piston type compressor according to  claim 12 , wherein the discharge chamber and the suction chamber are separated from the cylinder bores by a valve plate assembly, a part of the bleed passage extends through the cylinder block and the valve plate assembly, and a part of the bleed passage in the valve plate assembly is a throttled passage.  
     
     
         16 . The variable displacement piston type compressor according to  claim 12 , wherein the upstream end of the bleed passage is opened to the bottom of the crank chamber.  
     
     
         17 . The variable displacement piston type compressor according to  claim 16 , wherein the bleed passage passes through the cylinder block and then reaches the circumferential surface of the drive shaft, and the circumferential surface of the drive shaft and the bleed passage in the cylinder block meet more upward in a vertical direction than the central axis of the drive shaft.  
     
     
         18 . The variable displacement piston type compressor according to  claim 12 , further comprising a throttling means having a blocking member in the bleed passage and a throttled passage formed on the blocking member, the blocking member being made of resin or rubber.