Piston type variable displacement compressor

A compressor having a swash plate mounted on a drive shaft for an integral rotation in a crank chamber and a piston coupled to the swash plate and disposed in a cylinder bore, the rotation of the drive shaft being converted to a reciprocating movement of the piston to vary a capacity of the cylinder bore to compress gas which is supplied to the cylinder bore from an external circuit by way of a suction chamber and discharged to a discharge chamber, said swash plate being tiltable between a maximum inclining angle and a minimum inclining angle with respect to an axis of the drive shaft according to a difference between pressures in the crank chamber and the suction chamber, wherein said swash plate controls a displacement of the compressor to be maximum and minimum when the swash plate is at the maximum inclining angle and at the minimum inclining angle, respectively, and wherein a pressure passage for adjusting the pressure in the crank chamber is selectively open and closed in accordance with instruction of an external computer, said instruction being based on an operation status of the compressor, said compressor comprising:

• said pressure passage connecting the crank chamber and the suction chamber;
• an electromagnetic valve for selectively opening and closing the pressure passage in accordance with the instruction of the external computer, wherein said swash plate is inclined toward the maximum inclining angle when the pressure passage is open to release the pressure in the crank chamber to the suction chamber, and said swash plate is inclined toward the minimum inclining angle when the pressure passage is closed to increase the pressure in the crank chamber;
• and
• a spool movable in association with the inclining motion of the swash plate, whereby said spool disconnects the external circuit with the suction chamber when the swash plate is at the minimum inclining angle.