Cryogenic refrigerator

Abstract

A cryogenic refrigerator includes : a axially extending cylinder; an axially reciprocating displacer provided inside the cylinder, at a gap between an inner circumferential surface of the cylinder and an outer circumferential surface of the displacer, the displacer shifting to create an expansion space between the displacer and a first axial end portion of the cylinder; a regenerator built in the displacer; and a sleeve disposed along the inner circumferential surface of the first axial end portion of the cylinder, encompassing the expansion space. A first passage for guiding the refrigerant gas from the regenerator to the gap is provided in the displacer, and a second passage for guiding the refrigerant gas from the gap to the expansion space is provided between the first axial end of the cylinder and the sleeve, and/or is provided between the outer surface and the inner surface of the sleeve.

Dependencies are inferred from the claim text.