Seal Device of Mini-Ecoboy

As seal devices of the Mini-Ecoboy, there were piston rings of the displacer and the power piston, a reciprocating rod seal at a displacer rod. The engine was designed to use various types of seal devices.

In the first manufacturing, a straight cut ring of 2 mm width was used as the piston ring of the displacer. An endless ring of 19 mm width was used as the piston ring of the power piston. Because, the endless ring has higher seal performance than that of a straight cut ring. It also works as a linear guide for a straight motion of the power piston. A linear bearing was used as the reciprocating rod seal at the displacer rod. All of the above seal devices were made of PTFE.

Also, in the first manufacturing, a lip seal was used as the rotating rod seal at the output shaft. However, as the result of an experiment to measure mechanical loss, its mechanical loss was too strong for a small Stirling engine. Thus, we tried to develop a hermetic generator set, because it can omit the rotating rod seal.