| 摘要 |
A hydraulic control device for a motor vehicle automatic transmission has a main pressure control valve for generating a main pressure varying as a function of the load condition of the engine, the control piston of which can be acted upon by an engine load-dependent, upwardly limited control pressure. In order to achieve improved adjustment of the main pressure to, for example, a parabolic torque curve of the engine, in which relatively high torques are achieved even at low throttle valve angles, it is proposed to provide a piston arrangement loaded by the control pressure with at least two active surfaces, of which, up to a predetermined mean level of the control pressure, both operate in order to transmit pressure to the control piston, and thereafter only one. For this the piston arrangement may have a first piston, designed for direct actuation of the control piston and a second piston, held concentrically and axially displaceable on the first piston, the said second piston acting on the control piston by way of a spring and coming to bear on a stop fixed to the housing when the predetermined mean control pressure level is reached. <IMAGE>
|
