Abstract: A control system for a transmission comprising 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 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 responsive to the transmission ratio for increasing line pressure in the hydraulic circuit with increase of the transmission ratio. A throttle position sensor produces a signal in dependency on the opening degree of a throttle valve of the engine. A solenoid operated valve is responsive to the signal for operating the pressure regulator valve so as to increase the line pressure with an increase of the opening degree of the throttle valve.

Abstract: A control system for an infinitely variable belt-drive transmission which has a drive pulley having a hydraulically shiftable disc and a servo chamber for shifting the disc, a driven pulley having a hydraulically shiftable disc and a servo chamber for shifting the disc, and a belt engaged with both the pulleys. A hydraulic control circuit is provided for supplying oil to the servo chambers and for draining the servo chambers. A lubricating oil circuit is provided in the hydraulic control circuit for supplying lubricating oil to the drive pulley, and a passage is provided for supplying a part of the lubricating oil to the servo chamber of the drive pulley, thereby filling the servo chamber with the oil before the starting of transmission operation.

Abstract: A 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 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 responsive to the transmission ratio for increasing line pressure in the hydraulic circuit with an increase of the transmission ratio. A sensor is engaged with the disc of the primary pulley to be moved together with the disc so as to move a spool of the pressure regulator valve to increase the line pressure with an increase of engine speed.

Abstract: A system for a four-wheel drive vehicle for automatically changing transmission torque to rear wheels. The system is provided with a fluid pressure controlled friction clutch which is in a partial engagement state in an ordinary driving condition for transmitting the power of the engine to rear wheels. Therefore, when the vehicle turns a corner, the friction clutch slips to allow the rear wheels to rotate slower than front wheels. A load sensor and slip detecting device are provided for producing signals. A control system is provided to respond to the signals for increasing the engagement part of the friction clutch to provide a sufficient four-wheel driving.