Control valve for variable displacement compressor

A control valve includes: a body having a main passage through which a discharge chamber and a control chamber communicate, and a sub-passage through which the control chamber and a suction chamber communicate; a main valve seat provided in the main passage; a main valve element configured to touch and leave the main valve seat to close and open a main valve; a sub-valve seat provided in the sub-passage; a sub-valve element configured to touch and leave the sub-valve seat to close and open a sub-valve; a solenoid configured to generate a drive force in a valve closing direction of the main valve; an actuating rod for transmitting the drive force of the solenoid to the main valve element and the sub-valve element; a spring for applying a biasing force to the main valve in a valve opening direction; a spring for applying a biasing force to the sub-valve in a valve closing direction; and a differential pressure valve opening mechanism configured to open the sub-valve when a pressure difference between a control pressure in the control chamber and a suction pressure in the suction chamber becomes a preset pressure difference or larger.