Hydrodynamic spiral-grooved journal bearing for electromagnetically rotated and reciprocated compressor piston

An apparatus comprising a smooth walled circular cylinder and a piston having a pair of end faces that is reciprocable and rotatable in said cylinder and in which a working fluid is provided in said cylinder for being worked on by said piston during piston reciprocation or for working on said piston to reciprocate said piston in said cylinder, a fluid pressure difference existing across said piston during piston reciprocation which acts on said end faces,

• the improvement comprising:
• means for rotating said piston in said cylinder while said piston is reciprocating;
• and
• said piston comprising a bearing part having a pattern of grooves which cooperate with said cylinder wall and said fluid to dynamically support and center said piston in said cylinder for rotating and reciprocating piston movement, and a sealing part for reducing the pressure difference across said bearing part comprising a smooth circular cylindrical surface defining a gap between said sealing surface and said cylinder wall, the length of said surface and the size of said gap being chosen so that the pressure difference across said bearing surface is reduced to a level such that said piston is free of radial dynamic instability and remains stable in said cylinder during piston reciprocation and rotation.