HYDRAULIC CONTROL DEVICE FOR WINDING TRANSMISSION DEVICE

摘要

A hydraulic control system adapted to carry out a speed change in case of rotating a wrapping transmission under the situation where solenoid valves for controlling a pressure in a hydraulic chamber cannot be energized. A pair of pulleys 19 and 20 is individually provided with hydraulic chambers 19 and 20 to vary a width of a groove holding a belt 21. Those hydraulic chambers are connected with a hydraulic source through electrically controlled feeding control valves SP1 and SS1, and also connected with drain portions through electrically controlled relief control valve SP2 and SS2. The hydraulic control system comprises a communicating passage connecting the hydraulic chambers, and the hydraulic control system disconnects the hydraulic chambers from the hydraulic source and the drain portions in case none of the feeding control valves and the relief control valves can be energized.