Cryogenic refrigerator

Abstract

In a cryogenic refrigerator, a displacer includes a cover portion at a low temperature end of the displacer. A cylinder accommodates the displacer to be reciprocated in a longitudinal direction and forms an expansion space of a refrigerant gas between the cover portion and the cylinder. A refrigerant gas channel through which the displacer and the expansion space communicate with each other is formed in the cover portion. In the refrigerant gas channel, a flowing-out direction of the refrigerant gas flowing into the expansion space is inclined with respect to the longitudinal direction of the displacer.

What is claimed is: 
     
         1 . A cryogenic refrigerator comprising:
 a displacer;   a cover portion which is provided on a low temperature end of the displacer; and   a cylinder which accommodates the displacer to be reciprocated in a longitudinal direction and to form an expansion space of a refrigerant gas between the cover portion and the cylinder,   wherein a refrigerant gas channel, through which the displacer and the expansion space communicate with each other, is formed in the cover portion, and   wherein a flowing-out direction of the refrigerant gas flowing into the expansion space is inclined with respect to the longitudinal direction of the displacer in the refrigerant gas channel.   
     
     
         2 . The cryogenic refrigerator according to  claim 1 ,
 wherein the refrigerant gas channel is provided so that the refrigerant gas flowing into the expansion space is directed to a side surface of the cylinder.   
     
     
         3 . The cryogenic refrigerator according to  claim 1 ,
 wherein the cover portion includes a plurality of the refrigerant gas channels.   
     
     
         4 . The cryogenic refrigerator according to  claim 3 ,
 wherein among the plurality of refrigerant gas channels, a direction in which the refrigerant gas passing through one channel flows into the expansion space is different from a direction in which the refrigerant gas passing through other channels flows into the expansion space.   
     
     
         5 . The cryogenic refrigerator according to  claim 3 ,
 wherein the plurality of refrigerant gas channels are provided to be rotationally symmetrical with respect to a central axis in the longitudinal direction of the displacer.