STEUERUNG FUER EIN STUFENLOSES GETRIEBE.

摘要

A system for an infinitely variable belt-drive transmission for an engine comprises a primary pulley having a hydraulically shiftable disc, a secondary pulley having a hydraulically shiftable disc, a belt engaged with both pulleys, and a hydraulic circuit. A transmission ratio control valve having a spool is provided to be responsive to engine speed for controlling the oil and for shifting the disc of the primary pulley to change the transmission ratio. Pitot pressure dependent of the engine speed is applied to the spool to shift it against a spring, the force of which is determined by the depression of an accelerator pedal. The load on the spring is increased to provide a downshifting operation of the transmission, when the large transmission ratio range is selected.