Hydraulisches Steuersystem für ein stufenloses Getriebe

摘要

Hydraulic pressure generated by an oil pump (47) driven by an engine is regulated to a secondary pressure by means of a secondary pressure control valve (51). The secondary pressure is employed for controlling a secondary pulley (21) and a primary pulley (18). On the other hand, the secondary pressure is reduced to a clutch pressure by means of a clutch pressure control valve (57). The communication between an apply chamber (9a) and a release chamber (9b) of a torque converter, oil chambers of actuators for a forward clutch (32a) and a reverse brake (45a) of a forward and reverse changeover apparatus and a clutch pressure line and a lubrication pressure line are controlled by means a switching valve (65). The clutch pressure is regulated to a high clutch pressure and to a low clutch pressure, respectively by controlling reverse signal pressures supplied to these outer pilot chambers. Thus, respective hydraulic controls for the pulleys, the lockup clutch and the forward and reverse changeover apparatus can be performed independently by use of a single hydraulic pressure source.