Abstract: A two-speed gerotor motor of the type having a stationary valve member (19) defining a plurality of stationary valve passages, each including an upstream passage portion for commutating fluid communication with a moveable valve member (43), and a downstream passage portion in continuous fluid communication with a volume chamber (33) of the gerotor gear set. In some of the stationary valve passages (113), the upstream (115) and downstream (117) passage portions are blocked from direct fluid communication. A control valve spool (89) has a first position (FIG. 8) permitting unrestricted fluid communication between the upstream and downstream passage portions, for normal low-speed operation. The control valve spool has a second position (FIG.

Abstract: A two speed gerotor motor in which the rotary disk valve (47) and the balancing ring (67) cooperate with a control valve assembly (87) to define four different fluid zones arranged within a housing (21) in a generally concentric pattern to provide a relatively compact arrangement. Among the four fluid zones one (95) is always connected to an inlet (51) while another (101) is always connected to an outlet (53). The middle two zones (97, 99) communicate with each other in the high speed, low torque mode. Operatively associated with the control valve assembly (87) is a shuttle valve (103) such that high pressure is always communicated to the middle two zones, such that high pressure is always circulated within the gerotor gear set (17) in the high speed, low torque mode. The control valve (87) includes a spool valve (107) including dampening passages (123, 125, 127) which dampen or cushion the shifting of the spool valve between the high speed and low speed conditions.

Abstract: A gerotor motor of the valve-in-star type in which the star (27) is disposed adjacent a stationary valve plate (15). The stationary valve plate (15) defines a plurality N+1 of valve passages (69), extending through the valve plate. On the surface (73) of the valve plate (15) adjacent the endcap member (14), the valve plate defines a plurality of pressure relieving recesses (79), each one being disposed between a pair of adjacent valve passages (69). Each of the recesses (79) is in fluid communication with an O-ring groove (81), which is at low pressure. Thus, any leakage from a high pressure passage (69) to an adjacent low pressure passage (69) is received within the intervening relieving recess (79), substantially eliminating any separating forces between the endcap member (14) and the stationary valve plate (15) This results in substantially improved volumetric efficiency of the motor at higher pressure differentials.