| 摘要 |
A closed recirculating hydrostatic transmission system suitable for driving a traction vehicle. The system includes a pair of hydrostatic engine driven variable displacement pumps either of different displacements or engine driven at different speed ratios and each pump being operative to drive hydrostatic motors at the various wheels and in separate closed loop drive circuits such that accurate flow division as between the circuits is effected for driving the vehicle in four-wheel drive or, at the operator's selection, for driving the motors in the one closed loop circuit at a higher speed in two-wheel drive by means of the pump of larger discharge volume. An operator's control operates both pumps together with the limits of the smaller discharge pump in four-wheel drive, and operates the larger discharge pump within the limits thereof while rendering ineffective the smaller discharge pump in two-wheel drive. The operator's control includes a magnetizable linkage which, at the operator's election, may function as a rigid link to operate both pumps together or as a collapsible or expansible link which may operate the larger pump within its limits of displacement while returning the smaller pump to zero displacement. Valve means enables smooth transition and shifting between two and four-wheel drive at any time. Flow divider-combiner means in each closed loop circuit adjusts fluid flow to each motor as a function of steering angle to assure positive traction at each driven wheel in either forward or reverse drive under all surface conditions, and to differentiate, as required, wheel speeds during vehicle steering operations.
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