Control valve for variable displacement compressor

Abstract

In order to reduce the amount of refrigerant circulating within a variable displacement compressor to thereby improve compression efficiency, a control valve is configured to comprise a ball valve for controlling the flow rate of refrigerant flowing from a discharge chamber to a crankcase, a spool valve for controlling the flow rate of refrigerant flowing from the crankcase to a suction chamber, a diaphragm for sensing suction pressure, and a solenoid for setting the suction pressure, wherein the spool valve starts flow rate control after the ball valve is fully closed or nearly fully closed, and the ball valve starts flow rate control after the valve lift of the spool valve is minimized or nearly minimized. As a result, a region is almost eliminated in which the ball valve and the spool valve are both open simultaneously during switching of flow rate control between the ball valve and the spool valve, which makes it possible to minimize the flow rate of the refrigerant circulating within the compressor without contributing to a refrigerating operation, to thereby improve the efficiency of the compressor.

1 . A control valve for a variable displacement compressor, which is capable of controlling pressure in a crankcase to thereby change a discharge amount of refrigerant, comprising: 
 a first valve that is disposed between a discharge chamber and the crankcase of the compressor, for controlling a flow rate of refrigerant flowing from the discharge chamber to the crankcase;    a second valve that is disposed between the crankcase and a suction chamber of the compressor, for controlling a flow rate of refrigerant flowing from the crankcase to the suction chamber to a predetermined minimum rate when the first valve is controlling the flow rate of the refrigerant flowing from the discharge chamber to the crankcase, and for controlling the flow rate of the refrigerant flowing from the crankcase to the suction chamber when the first valve is fully closed or nearly fully closed; and    a pressure-sensing section that senses suction pressure in the suction chamber, for changing a lift amount of the first valve and a lift amount of the second valve.    
   
   
       2 . The control valve according to  claim 1 , wherein the second valve has a clearance set between a diameter of a valve hole and a diameter of a valve element inserted into the valve hole when the first valve is controlling the flow rate of the refrigerant flowing from the discharge chamber to the crankcase, the clearance being provided with a fixed orifice function for controlling the flow rate of the refrigerant flowing from the crankcase to the suction chamber to the predetermined minimum rate.  
   
   
       3 . The control valve according to  claim 1 , comprising a shaft extending through the valve hole of the second valve coaxially with the valve hole, for transmitting an opening/closing operation of the second valve to the first valve.  
   
   
       4 . The control valve according to  claim 3 , wherein the shaft has a joining part joined to the valve element, formed such that the joining part has a frustconical shape.  
   
   
       5 . The control valve according to  claim 3 , wherein the shaft has an end thereof in contact with a valve element of the first valve, formed such that the end has a spool shape.  
   
   
       6 . The control valve according to  claim 3 , wherein the shaft can be brought into contact with and left the valve element of the first valve.  
   
   
       7 . The control valve according to  claim 3 , wherein a clearance set between a diameter of an end of the shaft in contact with the valve element of the first valve and a diameter of a valve hole of the first valve is provided with a fixed orifice function for controlling the flow rate of the refrigerant flowing from the discharge chamber to the crankcase to the predetermined minimum rate.  
   
   
       8 . The control valve according to  claim 1 , wherein the first valve is a spool valve.  
   
   
       9 . The control valve according to  claim 1 , comprising a fixed orifice that is formed in parallel with the second valve, for controlling the flow rate of the refrigerant flowing from the crankcase to the suction chamber to the predetermined minimum rate when the first valve is controlling the flow rate of the refrigerant flowing from the discharge chamber to the crankcase.  
   
   
       10 . The control valve according to  claim 1 , comprising a pressure-setting section that applies urging load to the pressure-sensing section to set a pressure control point of the control valve.  
   
   
       11 . The control valve according to  claim 10 , wherein the pressure-setting section is a solenoid that sets the pressure control point by applying the urging load in response to an external signal.  
   
   
       12 . The control valve according to  claim 10 , wherein the pressure-setting section is a spring that sets the pressure control point by a spring force.