Electrohydraulic speed transmission control of continuously variable gear-box

摘要

An electrohydraulic control system for a continuously variable electronically controlled gearbox (10) for a car has a pump (23) with primary (25) and secondary (30) pressure valves, both being proportional valves with twin edge control, one acting as a gear ratio control valve and the other as a control valve for the contact pressure. There is a limiting valve (71) for the maximum pressure plus an additional pressure limiting valve (78) connected to the reservoir (27) and whose trip pressure is greater than that of the other valve. In the return pipeline from the secondary valve is a throttle (73) connected to a changeover valve (40) which controls the primary valve once a pressure threshold is exceeded.