Piston-type variable displacement compressor

Abstract

In a piston-type variable displacement compressor according to the present invention, a rotary valve includes a guide passage having a main suction port for securing a flow rate corresponding to maximum displacement operation and a sub suction port for effecting throttling to a flow rate low enough to suppress pressure fluctuation during variable displacement operation, and during maximum displacement operation, the spool is moved by a suction gas flow to totally open both the main suction port and the sub suction port, and during variable displacement operation, the spool is moved by a pressure difference between the suction chamber pressure and the crank chamber pressure to close the main suction port while keeping the sub suction port open.

1 . A piston-type variable displacement compressor in which pistons are respectively accommodated in a plurality of cylinder bores arranged around a drive shaft and in which a rotary valve with a guide passage for introducing a suction gas into operation chambers in the cylinder bores defined by the pistons is arranged rotatably in synchronism with the drive shaft, variable control being effected on the stroke of the pistons in the cylinder bores by adjusting a crank chamber pressure, 
 the rotary valve comprising:    a guide passage having a main suction port for securing a flow rate corresponding to maximum displacement operation and a sub suction port for effecting throttling to a flow rate low enough to suppress pressure fluctuation during variable displacement operation, and    a spool axially movably arranged under a suction chamber pressure and the crank chamber pressure,    during maximum displacement operation, the spool being moved by a suction gas flow to totally open both the main suction port and the sub suction port, and    during variable displacement operation, the spool being moved by a pressure difference between the suction chamber pressure and the crank chamber pressure to close the main suction port while keeping the sub suction port open.    
   
   
       2 . A piston-type variable displacement compressor according to  claim 1 , wherein the rotary valve comprises a cylindrical member which rotates in synchronism with the drive shaft and which has the main suction port and the sub suction port, 
 the spool being axially movably arranged in the cylindrical member.    
   
   
       3 . A piston-type variable displacement compressor according to  claim 1 , wherein the spool comprises: 
 a first spool movably arranged in order to open and close the main suction port and adapted to receive the suction chamber pressure,    a second spool movably arranged on a back portion of the first spool and adapted to receive the crank chamber pressure, and    a spring arranged between the first spool and the second spool,    during maximum displacement operation, the second spool moving away from the first spool to totally open the main suction port without exerting any load due to the spring on the first spool, and    during variable displacement operation, the second spool moving toward the first spool to exert a load due to the spring on the first spool to thereby close the main suction port.    
   
   
       4 . A piston-type variable displacement compressor according to  claim 1 , wherein the main suction port comprises: 
 a first suction port for securing a flow rate corresponding to maximum displacement operation, and    a second suction port formed adjacent to the first suction port with respect to a rotating direction of the rotary valve.    
   
   
       5 . A piston-type variable displacement compressor according to  claim 1 , wherein the sub suction port is constantly open independently of the movement of the spool.  
   
   
       6 . A piston-type variable displacement compressor according to  claim 1 , further comprising: 
 a cylinder block defining the plurality of cylinder bores;    a front housing connected to a front end portion of the cylinder block and defining the crank chamber; and    a rear housing connected to a rear end portion of the cylinder block and defining the suction chamber,    the drive shaft being rotatably supported by the cylinder block and the front housing.    
   
   
       7 . A piston-type variable displacement compressor according to  claim 6 , wherein the rotary valve is arranged in the cylinder block.  
   
   
       8 . A piston-type variable displacement compressor according to  claim 1 , wherein a first communication passage providing communication between the crank chamber and the rotary valve is formed in the drive shaft.  
   
   
       9 . A piston-type variable displacement compressor according to  claim 6 , further comprising: 
 a discharge chamber formed in the rear housing;    a second communication passage establishing communication between the crank chamber and the discharge chamber;    a bleeding passage establishing communication between the crank chamber and the suction chamber; and    a displacement control valve arranged in the second communication passage and adapted to control the pressure in the crank chamber through adjustment of the opening of the second communication passage.