Control valve for variable displacement compressor

Abstract

To provide a control valve for variable displacement compressor employing ON/OFF control, which is capable of taking measures for occurrence of an abnormally high pressure. When a solenoid is OFF, a spring causes a movable core to move a stopper in a direction away from a stationary core and to thereby separate a shaft fixed to the stopper from a valve seat, resulting in opening the control valve. When the solenoid is ON, the movable core is attracted by the stationary core by a stroke longer than that of the shaft, and a spring causes the shaft to seat on the valve seat, resulting in closing the control valve. If a discharge pressure Pd increases to an abnormally high pressure, a differential pressure between the discharge pressure Pd and a pressure Pc in a crankcase pushes the shaft while compressing the spring, so that the discharge pressure Pd flows out to the crankcase. Therefore, the pressure Pc in the crankcase increases and the variable displacement compressor shifts to operate at a minimum discharge capacity, resulting in decreasing the abnormally high pressure.

1 . A control valve for variable displacement compressor for changing a discharge capacity by controlling a flow rate of refrigerant to be introduced from a discharge chamber to a crankcase of the variable displacement compressor with ON/OFF control, the control valve comprising: 
 a valve section where a valve element is arranged on a downstream side of a valve hole for opening and closing the valve hole into which the refrigerant that is discharged from the discharge chamber is introduced; and    a solenoid for opening the valve section in a deenergized state and for closing the valve section in an energized state, wherein, in the solenoid, the valve element is held at a valve-opening position by a first spring imposing an urging force in a valve-opening direction in the deenergized state and a second spring imposing an urging force in a valve-closing direction, and is held at a valve-closing position by the second spring in the energized state, the valve element receiving a discharge pressure of the refrigerant introduced from the discharge chamber in the valve-opening direction.    
   
   
       2 . The control valve for variable displacement compressor according to  claim 1 , wherein, in the solenoid, a stroke of a movable core moving to be attracted by a stationary core in the energized state from a position where the valve element is positioned at the valve-opening position is set longer than a stroke of the valve element moving to the valve-closing position from the valve-opening position in the energized state.  
   
   
       3 . The control valve for variable displacement compressor according to  claim 2 , wherein, in the solenoid, the stationary core, the first spring, the movable core, a stopper, and the second spring are arranged from a side of the valve section in this order on a same axis as the valve hole, and a shaft that is loosely fitted in the stationary core and the movable core in a manner axially extending therethrough has one end serving as the valve element for opening and closing the valve hole and another end fixed to the stopper.