Patent ID: 6874321

Claim:
A Stirling-cycle engine comprising a piston that reciprocates inside a cylinder and a displacer that reciprocates inside the cylinder as a result of a working medium being compressed or expanded by the reciprocating movement of the piston, the piston and the displacer being arranged so that center axes thereof coincide with a center axis of the cylinder, the Stirling-cycle engine having a first space formed between the displacer and the piston, a second space formed so as to extend from a side of the piston facing away from the displacer and include a portion adjacent to at least part of a side wall of the cylinder, a third space formed on a side of the displacer facing away from the piston, a first groove formed so as to run from an end surface of the piston facing the first space in a direction of the reciprocating movement, and a second groove formed around a periphery of the piston so as to cross the first groove, and a hole formed through the side wall of the cylinder, the Stirling-cycle engine being so structured that, when the piston is in a center position of the reciprocating movement thereof, the second grove and the hole connect to each other so that the first and second spaces communicate with each other, wherein an opening of the hole has a shape of an elongate circle or a rectangle having a minor axis or shorter sides thereof aligned with the direction of the reciprocating movement of the piston.