Eaton Corporation

Dennis E Szulczewski

Thomas Joseph Stoltz

Glenn Clark Fortune

David W Malaney

Mark S Jennen

James M Casey

Michel A Beyer

A hydraulic system includes a power source, a fluid displacement assembly, a plurality of actuators, a plurality of control valves and an electronic control unit. The fluid displacement assembly is coupled to the power source. The plurality of actuators is in selective fluid communication with the fluid displacement assembly. The plurality of control valves is adapted to provide selective fluid communication between the fluid displacement assembly and the plurality of actuators. The electronic control unit is adapted to actuate the plurality of control valves, the electronic control unit receives a rotational speed of the power source, determines a firing frequency of the power source based on the rotational speed, selects a frequency of the pulse width modulation signal for the plurality of control valves based on the firing frequency of the power source, and actuates the plurality of control valves in accordance with the frequency of the pulse width modulation signal.

Control valve actuation

A hydrostatic transaxle is disclosed of the type including a hydrostatic transmission (11;221), a differential gear means (19;243), and first (21;213) and second (23;215) axle shafts. The hydrostatic transmission includes a transmission case (34;229,231) having a second case portion (31;231) including an output hub portion (97;235). The transaxle includes axle housing casing halves 133,135:209,211) joined together on a plane containing the axis of rotation of the axle shafts, and including an output portion (163,165;209,211) in tight engagement about the output hub portion. Another portion (173;229,231,249) of the transmission case cooperates with one of the axle casing halves to define a secondary mounting means and a torque reaction means which, together with the output hub portion, comprise the only portions of the transmission case operatively associated with the axle housing (131;208). The disclosed mounting or coupling of the hydrostatic transmission and the axle housing makes it possible to integrate the hydrostatic transmission and gear axle assembly, while at the same time segregating the hydraulic fluid of the hydrostatic transmission from the lubricant of the gear axle assembly, but still simplifying the overall structure of the assembly.

Hydrostatic transaxle assembly and improved coupling arrangement therefor

A variable displacement, rotary fluid pressure pump (11) is disclosed of the type having a cam ring member (25) which is movable, in response to rotation of a control shaft (35), between a neutral position (FIG. 5) and a displaced position (FIG. 4). The pump housing (13, 15) includes a support member (25), and they cooperate to define a high-pressure fluid passage (51). In communication with the passage (51) is a recess (71), in which is disposed a dampening shoe (73). The dampening shoe is biased by high-pressure fluid in the passage (51) into engagement with an adjacent surface (77) of the cam ring (25). The surface (77) defines a neutral fluid passage (79), and the dampening shoe (73) defines a restricted opening (85). When the cam ring (25) is in the displaced position, the restricted opening (85) is blocked from communication with the neutral passage (79), but as the cam ring is returned to its neutral position, the opening (85) begins to communicate with the neutral passage (79), thus providing the pump with an increased neutral band overlap.

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Eden Prairie, MN, United States of America

Dennis E Szulczewski