COMPRESSOR

PURPOSE:To improve a compression efficiency by providing on the crank-shaft side of a piston holder which has a higher coefficient of thermal expansion than that of a piston constituent member to properly adjust and even a clearance between the piston and a cylinder in compressing operation. CONSTITUTION:At a specific insertion location 8a which is at the inner side of an open end of a piston 8 made of an Fe20 or the like in one body with a bottom on the side of a crankshaft, is fixed a disk keeper 17 of a piston wall keeper which is made of carbon steel for example having a higher coefficiency of thermal expansion than that of an FC and has a spherical bearing face 16 at the center. A deformation caused by a thermal expansion of the piston 8 in the radial direction of the crank- shaft therefore becomes similar to that caused by a thermal expansion of a top area of the piston 8 in the radial direction in order to properly adjust and even a clearance between the piston and the cylinder during compressing operation so that a compression efficiency and durability may be improved.