Electrohydraulic control for an automatic transmission
AssigneeDr. Ing. h.c.F. Porsche Aktiengesellschaft
InventorJoseph Petersmann
Life of this patent
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Abstract
The invention relates to an electrohydraulic control for an automatic transmission of a motor vehicle. In order to be able to utilize, in the coasting operation of the motor vehicle in the driving position D of the automatic transmission, also the first gear, a one-way clutch, which transmits only driving torques but is required for the shifting operation, when the first gear is engaged, is bridged by a brake so that the transmission can transmit not only driving but also coasting torques and can therefore transmit the engine braking torque.
Claims10
An arrangement for the electrohydraulic control of an automatic transmission of a motor vehicle having a selector lever, with gear positions P, N, D, 3, 2 and 1 being selected via the selector lever, the arrangement comprising:
- solenoid valves which shift individual transmission gears together with one-way clutches as well as clutches and brakes which can be acted upon by pressure;
- an electric control unit coupled to receive the selected gear positions from the selector lever, the control unit controlling said solenoid valves;
- a hydraulic shift slide mechanically connected to the selector lever and with which a plurality of shift valves are connected, said plurality of shift valves hydraulically controlling the automatic transmission;
- wherein a first one of said one-way clutches is assigned to the first gear, and a first one of said brakes is parallel to said first one-way clutch, and wherein for the shifted gear position D and a shifted first gear, the first one-way clutch is bridged by admission of pressure to the first brake.
Dependencies are inferred from the claim text.