Abstract: A control system for an infinitely variable belt-drive transmission comprises a primary pulley having a hydraulically shiftable disc, a secondary pulley having a hydraulically shiftable disc, a belt engaged with both pulleys, and a hydraulic circuit having a pump for supplying oil. A transmission ratio control valve is provided to be responsive to engine speed for controlling the oil and for shifting the disc of the primary pulley to change the transmission ratio, and a pressure regulator valve is provided to respond to the transmission ratio for increasing the pressure of the oil with an increase of the transmission ratio. A pickup is provided to produce pulses dependent on engine speed, and a electric circuit is responsive to the pulses for producing pulses. An electromagnetic valve is provided to respond to the pulses for draining the oil applied to the transmission ratio control valve thereby controlling the valve so as to provide at least two transmission ratio characteristics.

Abstract: A control system for an infinitely variable belt-drive transmission for an engine comprises a primary pulley having a hydraulically shiftable disc, a secondary pulley having a hydraulically shiftable disc, a belt engaged with both pulleys, and a hydraulic circuit having a pump for supplying oil. A transmission ratio control valve is provided to be responsive to engine speed for controlling the oil and for shifting the disc of the primary pulley to change the transmission ratio, and a pressure regulator valve is provided to respond to the transmission ratio for controlling the line pressure in the hydraulic circuit. A piston is slidably mounted in the hydraulic cylinder of the primary pulley and a hydraulic circuit operated valve having a solenoid is provided to apply the line pressure to the hydraulic cylinder by the operation of the solenoid operated valve to shift the piston so as to restrict shifting of the disc of the primary pulley to the maximum transmission ratio position.

Abstract: A kickdown system for an infinitely variable belt-drive transmission comprises a primary pulley having a hydraulically shiftable disc, a secondary pulley having a hydraulically shiftable disc, a belt engaged with both pulleys, and a hydraulic circuit having a pump for supplying oil. A transmission ratio control valve is provided to be responsive to engine speed for controlling the oil and for shifting the disc of the primary pulley to change the transmission ratio, and a pressure regulator valve is provided to respond to the transmission ratio for increasing the pressure of the oil with an increase of the transmission ratio. A kickdown switch is provided to produce a signal upon the full depression of an accelerator pedal of a vehicle. A solenoid device is responsive to the signal for operating the pressure regulator valve so as to increase the pressure of the oil, whereby the downshifting of transmission is enhanced.