A silent room is composed of a rib(20a) surrounded by the sub- bearing(20) and a thick plate cover(22) attached to the rib. A reciprocating vane(8) moves the oil surface(5) vertically. A main bearing(5) and the sub-bearing(20) support the crank shaft(4). A closed space(24) is made in the rear portion of the vane by the bearing cross sections. A taper hole is formed between the closed space and the cylinder portion. The reciprocating of the vane pumps the oil of the closed space(24). The silent room decreases the nosse from the extrude port of the sub-bearing.
