Gerotor motor and case drain flow arrangement therefor

Abstract

A rotary fluid pressure device is disclosed of the type including a gerotor displacement mechanism (17), a rotary valve member (55), and a valve seating mechanism (75). The valve seating mechanism includes a balancing ring member (77) seated in an annular groove (81) defined by the valve housing (21). Leakage fluid from the gerotor displacement mechanism passes from the central case drain region (83) through the bearings (33 and 35) to an annular chamber (87). The leakage fluid is communicated from the annular chamber (87) to whichever of the ports (75 or 61) is connected to the system reservoir, through a series of fluid passages (131, 133, 135, 137, and 139). The fluid passage (139) communicates with the annular groove (81), and the leakage fluid flows past whichever of the balancing ring seals (143 or 145) is subjected to low pressure fluid, the balancing ring seal thus acting as a check valve. The invention eliminates the complicated and expensive prior art check valve assemblies (103, 105).