PURPOSE: To certainly control capacity by setting low the cycle of the driving current for the duty control of an electromagnetic control valve so that a swing inclination plate is held at the tilt angle for the duty ratio by varying the pressure in a crank chamber.
CONSTITUTION: A solenoid valve 6 for controlling the gas flow rate in an air supplying passage 8 which connects a crank chamber 2 and a discharge chamber 7 is controlled for the compression capacity of a compressor 1. The duty ratio of the solenoid valve 6 is calculated, and a control signal is outputted into a driving circuit 14 within a pressure range in which the variation of the pressure in the crank chamber 2 does not cause the change of the tilt angle of a swing inclination plate 5. Therefore, the tilt angle of the swing inclination plate 5 can be smoothly varied, and the stable capacity control is permitted.
NAKAMOTO AKIRA
HASEGAWA ATSUSHI
