SANDEN CORPORATION (named SANKYO ELECTRIC CO., LTD. prior to September 1982) developed a new automobile air conditioning compressor, the “TR” type, based upon the spiral machine principle.Two spiral components have 2.8 turn involute spiral walls projected from discs. Both spiral components are housed in a cylindrical casing, with one in a fixed position and the other interleaved with the former at an angular relationship of 180º. The free moving component is driven by a crankshaft in an orbiting motion. The orbiting motion of the free moving component provides a continuous compression process in two pairs of compression pockets.The “TR” compressor has several unique features in its physical and mechanical design: (1) Specifically disposed and shaped spiral components to maximize the displacement within a small diameter casing, (2) A compliant crank mechanism utilizing the swing motion of an eccentric bush, (3) A perfect dynamic balancing mechanism with minimized radial forces, and (4) An anti-rotation coupling mechanism with a function of the orbiting thrust bearing.These basic features result in a number of advantages in application which are of interest to today's automotive design engineers: (a) High refrigeration capacity from a compact, lightweight package achieved by combining the super high speed capability (up to 13,000 rpm) and a high volumetric efficiency (75% to 85%). (b) Extremely smooth operation with low torque requirement and inherently low torque variation. (c) Weight reduction of the compressor and its mounting means. (d) High performance, comfortability and drivability combined with low N.V.H. (Noise, Vibration, and Harshness) characteristics.