Hydraulisches Steuergerät für ein stufenloses Getriebe mit einem von der Fahrgeschwindigkeit abhängig arbeitenden Schaltventil.

摘要

A hydraulic control apparatus for controlling a continuously variable transmission (14) for a motor vehicle, including a shift control valve spool (350, 472) adapted to receive a first thrust corresponding to the currently required engine output and a second thrust corresponding to the input shaft speed of the transmission such that the spool is biased by the first and second thrusts in a shift-down and a shift-up direction for shifting down and shifting up the transmission, respectively, so that the speed ratio of the transmission is changed according to a distance of movement of the spool from a neutral position thereof in one of the shift-down and shift-up directions. The apparatus includes a device (308, 86, 386, 388) for producing a control pressure which varies with the vehicle speed, a gain changing spring (360, 482) for changing the distance of movement of the valve spool by the thrusts, and a device (358, 362, 464, 466) for permitting a biasing force of the spring to act on the spool, based on the control pressure, such that the distance of movement of the spool by the thrusts decreases with an increase in the vehicle speed.