Patent ID: 7841442

Claim:
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 ).