Piston type variable displacement compressor

Abstract

A piston type variable displacement compressor has a housing, a drive shaft, a first thrust regulating mechanism including a first thrust bearing and a second thrust regulating mechanism including a second thrust bearing. The drive shaft has a first end and a second end. The first end projects from the housing. The first thrust regulating mechanism regulates a drive shaft to move in the direction from the first end to the second end. The first thrust regulating mechanism allows the drive shaft to rotate. The first thrust bearing has a first radius. The second thrust regulating mechanism regulates the drive shaft to move in a direction from the second end to the first end. The second thrust regulating mechanism allows the drive shaft to rotate. The second thrust bearing has a second radius. The second radius is smaller than the first radius.

What is claimed is:  
     
         1 . A piston type variable displacement compressor comprising: 
 a housing including a cylinder block having a plurality of cylinder bores, the housing defining a crank chamber, a suction pressure region including a suction chamber and a discharge pressure region including a discharge chamber;    a drive shaft supported by the housing, the drive shaft having a first end and a second end, the first end of the drive shaft projecting from 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 slidably supported by the drive shaft, the cam plate being inclinable with respect to the drive shaft, the cam plate being rotated by the rotation of the drive shaft;    a plurality of pistons accommodated in the cylinder bores, each of the pistons being coupled to the cam plate, the rotation of the cam plate being converted into the reciprocating movement of the pistons, in accordance with the reciprocating movement of the pistons, refrigerant being introduced from the suction chamber into the cylinder bores, being compressed and being discharged from the cylinder bores to the discharge chamber, the discharge pressure region being connected to the crank chamber via a passage, the crank chamber being connected to the suction pressure region via another passage, the refrigerant flowing from the discharge pressure region to the crank chamber and flowing from the crank chamber to the suction pressure region, pressure in the crank chamber being varied by adjusting an opening degree of one of the passages, an inclination angle of the cam plate being varied by adjusting the pressure in the crank chamber;    a first thrust regulating mechanism including a first thrust bearing having a first radius, the first thrust regulating mechanism regulating the drive shaft to move in the direction from the first end to the second end, the first thrust regulating mechanism allowing the drive shaft to rotate; and    a second thrust regulating mechanism including a second thrust bearing having a second radius, the second thrust regulating mechanism regulating the drive shaft to move in the direction from the second end to the first end, the second thrust regulating mechanism allowing the drive shaft to rotate, the second radius being smaller than the first radius.    
     
     
         2 . The piston type variable displacement compressor according to  claim 1 , wherein the drive shaft has a central axis, the cylinder bores are radially arranged around the drive shaft, and the radius of the second thrust bearing is smaller than that of a hypothetical minimal circle which tangentially connects the cylinder bores and whose center is at the central axis of the drive shaft.  
     
     
         3 . The piston type variable displacement compressor according to  claim 1 , wherein the first thrust regulating mechanism further comprises: 
 a guide pin located on the cam plate; and    a lug plate fixedly placed on the drive shaft, the lug plate being connected to the guide pin.    
     
     
         4 . The piston type variable displacement compressor according to  claim 1 , wherein the second thrust regulating mechanism has a regulating member that is fixedly provided on a circumferential surface of the drive shaft and the second thrust bearing receives load transmitted from the drive shaft in the direction from the second end to the first end via the regulating member.  
     
     
         5 . The piston type variable displacement compressor according to  claim 4 , wherein the regulating member is a separate body with respect to the drive shaft.  
     
     
         6 . The piston type variable displacement compressor according to  claim 5 , wherein the regulating member is a regulating ring.  
     
     
         7 . The piston type variable displacement compressor according to  claim 6 , wherein the regulating ring contacts the second thrust bearing.  
     
     
         8 . The piston type variable displacement compressor according to  claim 1 , wherein the housing receives load transmitted from the drive shaft to the second thrust bearing in the direction from the second end to the first end of the drive shaft via the second thrust bearing.  
     
     
         9 . The piston type variable displacement compressor according to  claim 8 , wherein the cylinder block receives load transmitted from the drive shaft to the second thrust bearing in the direction from the second end to the first end of the drive shaft via the second thrust bearing.  
     
     
         10 . The piston type variable displacement compressor according to  claim 1 , wherein the first thrust regulating mechanism is placed in the crank chamber.  
     
     
         11 . The piston type variable displacement compressor according to  claim 1 , wherein the second thrust regulating mechanism is placed in the crank chamber.  
     
     
         12 . The piston type variable displacement compressor according to  claim 1 , wherein the second thrust regulating mechanism is placed in the suction chamber.  
     
     
         13 . The piston type variable displacement compressor according to  claim 1 , wherein the drive shaft has a large diameter portion and a small diameter portion, a step is formed between the large diameter portion and the small diameter portions, and the second thrust bearing receives load transmitted from the drive shaft in the direction from the second end to the first end via the step.  
     
     
         14 . The piston type variable displacement compressor according to  claim 1 , wherein the piston type variable displacement compressor is a clutchless type compressor.  
     
     
         15 . The piston type variable displacement compressor according to  claim 1 , wherein the refrigerant is carbon dioxide.  
     
     
         16 . The piston type variable displacement compressor according to  claim 1 , wherein compression reactive force is generated in compressing the refrigerant by the pistons, the sum of the compression reactive force and the force resulting from an atmospheric pressure is applied to the drive shaft in the direction from the first end of the drive shaft to the second end, the force resulting from the pressure in the crank chamber is applied to the drive shaft in the direction from the second end to the first end of the drive shaft.  
     
     
         17 . The piston type variable displacement compressor according to  claim 1 , wherein load is applied to the second thrust regulating mechanism when the inclination of the swash plate is relatively small.  
     
     
         18 . The piston type variable displacement compressor according to  claim 1 , wherein the cam plate is a swash plate.  
     
     
         19 . A compressor comprising: 
 a piston for compressing refrigerant in a cylinder bore;    a cam plate movably connected to the piston for reciprocating the piston;    a shaft having a rotational axis for rotating to drive the cam plate, the shaft experiencing a movement along the rotational axis while the piston reciprocates;    a first thrust regulating mechanism for regulating the movement of the shaft in a first direction along the rotational axis; and    a second thrust regulating mechanism for regulating the movement of the shaft in a second direction along the rotational axis, the second thrust regulating mechanism including a regulating ring fixedly placed on the shaft and having a second thrust bearing contact surface, the second thrust regulating mechanism further including a second thrust bearing fixedly placed near the shaft and in contact with the second thrust bearing contact surface to regulate the movement of the shaft in the second direction along the rotational axis.    
     
     
         20 . The compressor according to  claim 19 , wherein the first thrust regulating mechanism further comprises: 
 a guide pin located on the cam plate;    a lug plate fixedly placed on the shaft for receiving the guide pin, the lug plate having a first thrust bearing contact surface; and    a first thrust bearing fixedly placed near the shaft and in contact with the first thrust bearing contact surface to regulating the movement of the shaft in the first direction along the rotational axis.    
     
     
         21 . The compressor according to  claim 19 , wherein the cam plate is an inclinable swash plate for varying displacement of the compressor.  
     
     
         22 . The compressor according to  claim 19  further comprising a crank chamber and a suction chamber.  
     
     
         23 . The compressor according to  claim 22 , wherein the first thrust regulating mechanism and the second thrust regulating mechanism are located in the crank chamber.  
     
     
         24 . The compressor according to  claim 22 , wherein the first thrust regulating mechanism is located in the crank chamber while the second thrust regulating mechanism is located in the suction chamber.  
     
     
         25 . The compressor according to  claim 19 , wherein the first thrust regulating mechanism further comprises: 
 a guide pin located on the cam plate;    a lug plate fixedly placed on the shaft for receiving the guide pin, the lug plate having a first thrust bearing contact surface; and    a first thrust bearing fixedly placed around the shaft in a circular shape having a first radius, the first thrust bearing in contact with the first thrust bearing contact surface to regulate the movement of the shaft in the first direction along the rotational axis.    
     
     
         26 . The compressor according to  claim 25 , wherein the second thrust bearing is fixedly placed around the shaft in a circular shape having a second radius, the second radius is smaller than the first radius.  
     
     
         27 . The compressor according to  claim 26 , wherein a plurality of the pistons and a plurality of the cylinder bores are placed in concentric manner around the shaft, the second radius is smaller than that of a hypothetical minimal circle that tangentially touches every one of the cylinder bores.  
     
     
         28 . The compressor according to  claim 19 , wherein the shaft has a uniform radius.  
     
     
         29 . The compressor according to  claim 19 , wherein the shaft has at least two radii along the rotational axis.  
     
     
         30 . The compressor according to  claim 19 , wherein the refrigerant is carbon dioxide.