Hydraulic transmission control device

摘要

A control system for a power dividing type hydraulic transmission in which the motive power supplied from an engine is transmitted mechanically. Part of the motive power is converted to hydraulic power by hydraulic pump motors to obtain infinitely variable speed ratios. The transmission includes a hydraulic pressure control system that operates by the use of electrically controlled solenoid valves. The control system detects the rotational speeds of an input and an output shaft, and when the speed ratio between the shafts is smaller than the mode converting speed ratio, a first solenoid valve is operated to engage a first clutch. When the speed ratio is greater than the mode converting speed ratio, a second solenoid valve is operated to engage a second clutch. The engagement of the clutches is timed so that both clutches are not coincidentally disengaged.