Stirling refrigerator

A Stirling refrigerator, comprising:

• a housing formed by casting, wherein a motor and a crank are disposed inside the housing, and a working gas is sealed inside the housing, a part of the housing has a thin portion, and a fitting is installed on the thin portion, and the fitting is fixed on the thin portion by a tapping screw;
• a cylinder fixed on a top of the housing;
• a piston, reciprocating inside the cylinder;
• a piston rod moving with the crank, wherein one end of the piston rod links the piston and passes through the housing;
• and
• an oil seal bellows sealing a space between the housing and the cylinder,
• wherein a tip end of the oil seal bellows is sealed and fixed on the piston or the piston rod inside the cylinder, and a base end of the oil seal bellows is installed on the housing, and
• the oil seal bellows reciprocating with a stroke, wherein the tip end of the oil seal bellows is compressed to a compression side from a position of free length then returns to the position of free length.