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US 7,841,442 B2Granted
Hydrostatic transmission
AssigneeZF Friedrichshafen AG
InventorsTorsten Berg, Jürgen Legner, Jörg Geis
Life of this patent
Estimating the term…
Abstract
A hydrostatic transmission that is operated in an open loop by way of an adjustable hydraulic motor (5), which is adjusted for the purpose of acceleration or deceleration with the aid of an electronic control unit (8) such that a desired vehicle speed corresponds to a measured vehicle speed.
Claims8
A hydrostatic transmission for a vehicle comprising:
- at least one hydraulic pump (2) and at least one hydraulic motor (5) having an adjustable intake volume;
- a reducing gear (7) having a selectable gear ratio arranged downstream of the hydraulic motor (5),
- two working lines (6) being connected to the hydraulic motor (5);
- the hydraulic pump (2) being connected to the hydraulic motor (5) by at least one of the two working lines (6) for removing hydraulic fluid from a hydraulic fluid reservoir (3) and supplying the hydraulic fluid to the hydraulic motor (5);
- a main control valve (4) located between the hydraulic pump (2) and the hydraulic motor (5);
- a brake valve for controllably restricting a flow of the hydraulic fluid leaving the hydraulic motor (5);
- a sensor (11) determining at least one of a vehicle speed and an output rotational speed corresponding to the vehicle speed;
- an electronic control unit (8) responsive to at least one of the vehicle speed and the output rotational speed for:
- determining a desired vehicle speed from at least one of a hydraulic motor output rotational speed for an engaged gear ratio, an accelerator pedal signal and a main control valve signal,
- measuring an actual vehicle speed from at least one of a measured transmission output rotational speed and a measured hydraulic motor output rotational speed for the engaged gear ratio,
- determining a deviation between an actual vehicle deceleration level determined from a change in one of the hydraulic motor output rotational speed at the engaged gear ratio and the actual vehicle speed and a previously defined deceleration level, and
- adjusting the intake volume of the hydraulic motor (5) such that:
- one of the actual vehicle speed and actual output rotational speed, determined by the sensor (11), substantially corresponds to one of the desired vehicle speed and the desired output rotational speed, and
- the previously defined deceleration level is maintained, during a braking operation, regardless of the engaged gear ratio of the reducing gear (7).
11 more elements
Dependencies are inferred from the claim text.