Suction structure in piston type compressor

Abstract

A suction structure allows refrigerant from a suction pressure region in a piston type compressor. The suction structure includes a shifting device, a bleed passage, and a check valve. The shifting device has a valve body, a return spring, a backpressure chamber, and a backpressure passage. The valve body is movable between a connecting position and a disconnecting position. The return spring urges the valve body from the connecting position toward the disconnecting position. The backpressure chamber is defined by the valve body. The backpressure passage communicates with the suction pressure region and the backpressure chamber. The bleed passage communicates with the suction pressure region and the backpressure chamber. The check valve allows a fluid to flow from the backpressure chamber into the bleed passage.

1 . A suction structure for allowing refrigerant from a suction pressure region in a piston type compressor, wherein cylinder bores for accommodating a respective piston are arranged around a rotary shaft, wherein the piston is coupled to the rotary shaft through a cam body so that the rotation of the rotary shaft is transmitted to the piston, wherein a compression chamber is defined by the piston in the respective cylinder bore, wherein a rotary valve has a supply passage for introducing the refrigerant from the suction pressure region to the compression chamber, wherein the rotary valve is rotated integrally with the rotary shaft, wherein the supply passage has an outlet and an inlet, the suction structure comprising:
 a shifting device for shifting between a connecting state and a disconnecting state, wherein in the connecting state the suction pressure region is connected to the outlet of the supply passage, and in the disconnecting state the suction pressure region is disconnected from the outlet of the supply passage, the shifting device including;
 a valve body movable between a connecting position and a disconnecting position, wherein the connecting position corresponds to the connecting state and the disconnecting position corresponds to the disconnecting state; 
 a return spring urging the valve body from the connecting position toward the disconnecting position; 
 a backpressure chamber defined by the valve body; and 
 a backpressure passage communicating with the suction pressure region and the backpressure chamber; 
   a bleed passage communicating with the suction pressure region and the backpressure chamber; and   a check valve allowing a fluid to flow from the backpressure chamber into the bleed passage.   
   
   
       2 . The suction structure according to  claim 1 , wherein the valve body includes a piston portion defining the backpressure chamber, the backpressure chamber has a bottom surface, and the piston portion has a pressure-receiving surface receiving a pressure in the backpressure chamber and coming into surface contact with the bottom surface of the backpressure chamber. 
   
   
       3 . The suction structure according to  claim 2 , wherein the pressure-receiving surface and the bottom surface are flat and parallel to each other. 
   
   
       4 . The suction structure according to  claim 2 , wherein the bleed passage has an inlet that is open at the bottom surface of the backpressure chamber. 
   
   
       5 . The suction structure according to  claim 4 , wherein the valve body is moved in axial direction of the rotary shaft between the connecting position and the disconnecting position. 
   
   
       6 . The suction structure according to  claim 1 , wherein the compressor includes a rear housing defining the suction pressure region and having a rear housing wall, and the bleed passage is formed inside the rear housing wall so as to communicate with the suction pressure region. 
   
   
       7 . The suction structure according to  claim 1 , wherein the backpressure passage has an inlet disposed above the backpressure chamber. 
   
   
       8 . The suction structure according to  claim 1 , wherein the backpressure passage has an inlet surrounded circumferentially by a stepped portion in the suction pressure region. 
   
   
       9 . The suction structure according to  claim 1 , wherein the valve body is placed so that the inlet of the supply passage is disconnected from the suction pressure region when the shifting device is in the disconnecting state. 
   
   
       10 . The suction structure according to  claim 1 , wherein the compressor includes a cylinder block and a rear housing, the cylinder block is formed with the cylinder bores, the rear housing is connected to the cylinder block and formed with a suction chamber as the suction pressure region, and the valve body is provided in the rear housing. 
   
   
       11 . The suction structure according to  claim 1 , wherein the supply passage has an in-shaft passage formed inside the rotary shaft and extending in axial direction of the rotary shaft, the inlet of the supply passage is open at an end surface of the rotary valve and communicating with the in-shaft passage, the outlet of the supply passage is open at an outer periphery of the rotary valve and communicating with the in-shaft passage, the valve body is disposed in the in-shaft passage, the valve body is movable in the axial direction of the rotary shaft between the connecting position and the disconnecting position in the in-shaft passage, and the valve body at the disconnecting position disconnects the outlet of supply passage from the in-shaft passage. 
   
   
       12 . The suction structure according to  claim 1 , wherein the rotary shaft is coupled to an external drive source through a clutch. 
   
   
       13 . A suction structure for allowing refrigerant to flow from a suction pressure region in a piston type compressor, wherein cylinder bores for accommodating a respective piston are arranged around a rotary shaft, wherein the piston is coupled to the rotary shaft through a cam body so that the rotation of the rotary shaft is transmitted to the piston, wherein a compression chamber is defined by the piston in the respective cylinder bore, wherein a valve mechanism is disposed adjacent to the compression chamber, the suction structure comprising:
 a shifting device for shifting between a connecting state and a disconnecting state, wherein in the connecting state the compression chamber is connected to the suction pressure region upstream the shifting device through the valve mechanism and in the disconnecting state the compression chamber is disconnected from the suction pressure region upstream the shifting device through the valve mechanism, the shifting device including;
 a valve body movable between a connecting position and a disconnecting position, wherein the connecting position corresponds to the connecting state and the disconnecting position corresponds to the disconnecting state; 
 a return spring urging the valve body from the connecting position toward the disconnecting position; 
 a backpressure chamber defined by the valve body; and 
 a backpressure passage communicating with the suction pressure region and the backpressure chamber; 
   a bleed passage communicating with the suction pressure region and the backpressure chamber; and   a check valve allowing a fluid to flow from the backpressure chamber into the bleed passage.   
   
   
       14 . A piston type compressor, comprising:
 a housing;   a plurality of cylinder bores formed in the housing;   a rotary shaft around which the cylinder bores are arranged;   a plurality of pistons accommodated in the respective cylinder bore;   a cam body coupling to the piston and the rotary shaft so that the rotation of the rotary shaft is transmitted to the piston;   a plurality of compression chambers defined by the piston in the respective cylinder bore;   a rotary valve rotated integrally with the rotary shaft, the rotary valve including a supply passage having an inlet and an outlet for introducing refrigerant from a suction pressure region in the compressor to the compression chamber;   a shifting device for shifting between a connecting state and a disconnecting state, wherein in the connecting state the suction pressure region is connected to the outlet of the supply passage, and in the disconnecting state the suction pressure region is disconnected from the outlet of the supply passage, the shifting device including;
 a valve body movable between a connecting position and a disconnecting position, wherein the connecting position corresponds to the connecting state and the disconnecting position corresponds to the disconnecting state; 
 a return spring urging the valve body from the connecting position toward the disconnecting position; 
 a backpressure chamber defined by the valve body; and 
 a backpressure passage communicating with the suction pressure region and the backpressure chamber; 
   a bleed passage communicating with the suction pressure region and the backpressure chamber; and   a check valve allowing a fluid to flow from the backpressure chamber into the bleed passage.