Control device of an infinitely variable transmission

Claim 1

An automatic control system for a toric type infinitely variable transmission of a running vehicle, the speed of which is changed by varying a gear ratio corresponding to a running mode of the vehicle selected by a driver, said transmission comprising coaxially disposed input and output shafts with input and output disks having toroidal surfaces and respectively secured to the input and output shafts, a traction roller engaged with the toroidal surfaces of the disks, and a trunnion rotatably supporting the traction roller on a rotary shaft, said trunnion being linearly movable in the direction of a pivot axis which is perpendicular to the rotary shaft of the traction roller and being pivotable around the pivot axis so that the gear ratio between the input shaft and the output shaft may be changed, said control system comprising: a hydraulic cylinder receiving an axial end of the trunnion; a hydraulic circuit connecting the hydraulic cylinder with a hydraulic source, said hydraulic circuit including a solenoid valve, said valve having means for repeatedly opening and closing the valve at predetermined intervals and controlling hydraulic supply to said hydraulic cylinder and thereby controlling the linear movement of the trunnion in the direction of the pivot axis so as to vary the gear ratio; first detector means for detecting the amount of the linear movement of the trunnion in the direction of the pivot axis and producing a first signal; second detector means for detecting the amount of the pivotal movement of the trunnion and producing a second signal; and an electronic control circuit for receiving said first and second signals from said first and second detector means, determining a suitable gear ratio conforming to the running mode and said signals and feeding a pulse signal according to the suitable gear ratio back to the solenoid valve in order to open and close the solenoid valve at the predetermined intervals.