Abstract: A valve plate accommodated in a reciprocatory piston type compressor and arranged between an axial end of a cylinder block provided with a plurality of cylinder bores in which a plurality of double-headed pistons are reciprocated to compress a refrigerant gas, and a housing member provided with a suction chamber and a discharge chamber. The valve plate is provided with a plurality of suction ports communicating between the suction chamber and the plurality of cylinder bores and openably closed by suction valves, and a plurality of discharge ports communicating between the discharge chamber and the plurality of cylinder bores of the cylinder block. The valve plate is provided with surface portions extended around each of the discharge ports to be cooperable with the spring steel discharge valves for opening and closing the discharge ports, and formed to have 10 through 20 Rz surface roughness and a Vicker's hardness of 120 through 450.

Abstract: A piston compressor having cylinder blocks, each defining cylinder bores in which a piston is axially reciprocally arranged. Front and rear housings are connected to the cylinder blocks via valve port plates, so that compression chambers are formed between the valve port plates and the cylinder blocks and inlet and outlet chambers are formed between the valve port plates. The valve port plates form inlet and outlet ports for each of the compression chambers and inlet valves and outlet valves formed as thin resilient web members are provided for the inlet and outlet ports, respectively, to control the feeding and discharge of the gas, respectively. The valve port plates having, on the surfaces thereof facing the outlet valve around the inlet ports, a roughened area having a surface roughness value R.sub.z of between 10 to 25 .mu.m and an average spacing value L of between to 50 to 100 .mu.m.