PURPOSE: To eliminate mixing of refrigerating machine oil effected by a vane and reduce the oil flowed out into a cycle remarkably by a method wherein the vane, defining a pump chamber, is slid in an enclosed space, formed by a cylinder constituting the pump chamber and bearings.

CONSTITUTION: An electric motor section 2 is inserted into the upper part of a case 1 forcibly and a pump section 3 is welded to the lower part of the case. The pump section 3 is operated by the rotation of the electric motor section 2, the refrigerating machine oil is reserved in the bottom of the case 1 and the vane 10 is enclosed by the cylinder 14, upper bearing, lower bearing 16 and a roller 7. According to this method, the refrigerating machine oil will never be mixed by the reciprocating motion of the vane 10, therefore, the run-off of the oil into the cycle may be prevented.