Hydraulic coupling for vehicle drivetrain

Abstract

A control valve of a hydraulic coupling controls pumping through a casing inlet port by a hydraulic pump and/or through a casing outlet port to control coupling between two rotary members such as by operation of a clutch. The casing is connected to one of the rotary members while a pumping component embodied by an impeller is connected to the other rotary member and meshed with an internal ring gear having one more tooth than the number of impeller teeth to provide sufficient pumping capacity so that the pump can act as a brake while still having relatively constant pumping pressure. The control valve includes a valve system through which pressurized hydraulic fluid selectively flows to control the coupling of the pair of rotary members. The instant invention provides a thin-plate check valve and pressure port stack which creates a hydraulic flow path for a gerotor pump and maintains pressure equalization about the gerotor pump. The thin-plate check valve and pressure port stack comprises a series of relatively thin circular plates assembled in a stacked arrangement, including a spring plate and a seal plate which interface to create a check valve assembly, a port plate which provides a pocket to equalize pressure in different areas of the gerotor pump and a limiter plate which prevents the spring arm from being damages by a vacuum and which prevents the spring arm from over-travel and deformation. The number and/or thickness of the port plates determine how far the spring arm can travel under pressure. The plates forming the stack of this invention are relatively large when compared to prior known check valve arrangements and, therefore, are easy to handle and assemble. The plates also provide pressure equalization about the gerotor pump while eliminating relatively expensive machining in the differential case required for conventional valve arrangements.