Motor lubrication with no external case drain

Abstract

An improved lubrication system is provided for a motor of the type including a gerotor displacement mechanism (17), an inlet port (57), an outlet port (61), and valve means (19,55) operable to control the flow of fluid from the inlet port through volume chambers (29) of the displacement mechanisms and back to the outlet port, thus defining a main fluid flow path. A shuttle valve (85) communicates a flow of lubrication fluid from the main fluid flow path to a lubrication flow path (79,81,82,83) which flows through the bearings and spline connections of the motor. In accordance with the invention, a restrictor member 113 is located in the outlet port (61) and defines a restricted orifice 115 which restricts outlet flow from the motor causing a back pressure which generates the flow of lubrication fluid. After fluid flows through the lubrication flow path, it flows to the outlet port, downstream of the restricted orifice 115, recombining with the low-pressure, exhaust flow from the motor. The lubrication system of the invention permits a greater flow of lubrication fluid, without loss of volumetric efficiency, and without the need for a separate case drain port.