Hydrauliksteuersystem für stufenlose Getriebe

摘要

A CVT has primary and secondary pulleys, and a control unit for controlling the transmission ratio by controlling the line pressure applied to the first and secondary pulleys. The control unit calculates a standard step position of a step motor corresponding to the target transmission ratio and provides a command signal representative of the difference between the standard step position and the current position of the step motor. A shift control valve actuated by the step motor controls the pressure to be applied to the primary pulley. The control unit compares the actual transmission ratio with the target transmission ratio, and if the shift is not completed, the control unit commands an additional step number. Unless the shift to the HI side is accomplished when the additional step number reaches the threshold value, the line pressure is increased to achieve the shift.