Pressure setting means for a multistage type piston compressor

摘要

A multistage piston compressor includes a case and a suction chamber and a discharge chamber provided in the case. A rotary shaft is supported in the case. A valve plate provided in the case includes suction ports and discharge ports. A plurality of bores are provided at predetermined intervals about the axis of the shaft. Pistons are housed in the bores and compress refrigerant by reciprocating in accordance with the rotation of the shaft. An intermediate chamber connects a discharge port with a suction port. The refrigerant is compressed in stages by passing through a plurality of bores via the intermediate chamber. Compression chambers are defined between the pistons and the valve plate. A communication passage is provided for setting the pressures acting on the rear faces of the pistons to an intermediate pressure between the suction pressure and the discharge pressure.