Abstract: A belt drive continuously variable transmission of a four-wheel motor vehicle has a transmission ratio control valve which is operated in accordance with driven pulley speed. An analogous driven-pulley speed is calculated based on an analogous vehicle speed approximate to actual vehicle speed. In response to the analogous driven-pulley speed, the analogous driven pulley speed is used for operating the transmission ratio control valve instead of the driven pulley speed.

Abstract: A motor vehicle has a continuously variable belt-drive automatic transmission, an automatic clutch provided between the engine and the automatic transmission, a hydraulic control system and a hydraulic circuit including the oil pump for controlling the transmission. A wheel lock signal is produced when the deceleration of the wheel speed is so large that the wheels may be locked. In response to the wheel lock signal, a clutch release signal is produced when the engine speed is lower than a predetermined low speed. In response to the clutch release signal, the automatic clutch is released and the engine speed is increased, thereby maintaining sufficient output of the oil pump.

Abstract: A control system for a four-wheel drive vehicle with a continuously variable transmission having a drive pulley having a hydraulically shiftable disc and a hydraulic cylinder for operating the disc, a driven pulley having a hydraulically shiftable disc and a hydraulic cylinder, and a pressure regulator valve for regulating pressure of oil supplied to the hydraulic cylinders. A hydraulic actuator is provided for engaging a transfer clutch for establishing four-wheel driving. The pressure regulator valve has a pressure level changing port to increase the pressure of oil supplied to the cylinders. A solenoid operated valve is provided for supplying the oil regulated by the pressure regulator valve to the hydraulic actuator and to the pressure level changing port or for draining the actuator and the port. An orifice is provided in an inlet side of the solenoid operated valve.

Abstract: A continuously variable transmission for a motor vehicle has a drive pulley, a driven pulley, and a belt engaged with both the pulleys. A hydraulic circuit has a pump for supplying oil to hydraulic cylinders of both pulleys, and a transmission ratio control valve has a spool slidably mounted in a valve body for controlling the oil supplied to the cylinder of the drive pulley to change the transmission ratio. The locking of the wheels of the vehicle at braking of the vehicle is detected, and releasing of the locked wheels is detected. The transmission ratio is held at the detected locking of the wheels. And the held transmission ratio is released when releasing of the locked wheels is detected.

Abstract: A control system for a continuously variable transmission having a drive pulley with a hydraulically shiftable disc and a hydraulic cylinder for operating the disc, a driven pulley with a hydraulically shiftable disc and a hydraulic cylinder, and a pressure regulator valve for regulating pressure of oil supplied to the hydraulic cylinders. The pressure regulator valve has a pressure level changing port to increase the pressure of oil supplied to the cylinders. A solenoid operated valve is provided for supplying the oil to the pressure level changing port or for draining the port. When wheels of a vehicle spin, the solenoid operated valve is energized to supply the oil to the port, thereby increasing the pressure of the oil.

Abstract: A control system for a continuously variable transmission for a motor vehicle has a transmission ratio control valve having a spool for controlling oil supplied to a cylinder of a drive pulley to change the transmission ratio. The transmission ratio control valve has chambers at both ends of the spool. By controlling flow rate of oil supplied to the chambers in accordance with a desired transmission ratio, the spool is shifted, so that the transmission ratio changing rate is controlled. The transmission ratio changing rate is reduced at cold engine so as to prevent decrease of the vehicle speed at acceleration.

Abstract: A control system for a continuously variable transmission for a motor vehicle has a transmission ratio control valve having a spool for controlling oil supplied to a cylinder of a drive pulley to change the transmission ratio. The transmission ratio control valve has chambers at both ends of the spool. By controlling flow rate of oil supplied to the chambers in accordance with a desired transmission ratio, the spool is shifted, so that the transmission ratio changing speed is controlled. When an accelerator pedal of the vehicle is rapidly depressed while the transmission ratio is changing, the transmission ratio changing speed is reduced for a predetermined time.

Abstract: A control system for a continuously variable transmission for a motor vehicle has a transmission ratio control valve having a spool for controlling oil supplied to a cylinder of a drive pulley to change the transmission ratio. The transmission ratio control valve has chambers at both ends of the spool. By controlling flow rate of oil supplied a chamber in accordance with a desired transmission ratio, the spool is shifted, so that the rate of change of the transmission ratio is controlled. The transmission ratio changing rate is reduced as the difference between the actual transmission ratio and desired transmission ratio increases.

Abstract: A belt is formed by a plurality of metal elements which are assembled by a pair of endless carriers engaging with the elements at both lateral sides thereof. Each element has a plurality of protrusions at the front side thereof so as to engage with the rear side of an adjacent element. The protrusions are provided for appropriately deviating the belt at a tight side.

Abstract: A system for slipping an electromagnetic clutch when a motor vehicle is driven at a low speed in a closed choke valve condition. The system is provided with a choke switch for producing a choke signal, accelerator pedal position switch for producing a release signal and a vehicle speed signal detector in order to reduce current passing in the clutch to cause the clutch to slip at the release of an accelerator pedal in a low vehicle speed range. The slipping is controlled to keep the vehicle speed constant.

Abstract: A control system for a motor vehicle provided with a continuously variable transmission and a clutch for transmitting power of an engine to the transmission. The transmission has a transmission ratio control valve having ports and a spool for controlling the transmission ratio. A throttle position sensor is provided for detecting the load on an engine and for deciding a desired transmission ratio in accordance with the load. The clutch is automatically disengaged at low vehicle speed. When an accelerator pedal is depressed in order to re-accelerate the vehicle, the desired transmission ratio is increased to increase the speed of a drive pulley of the transmission so that the drive pulley speed equals the speed of the engine.

Abstract: A control system for a motor vehicle provided with a clutch and a continuously variable transmission. The transmission has a line pressure control valve having ports and a spool for controlling the line pressure of oil supplied to a cylinder of a pulley device to change the transmission ratio. The transmitting torque in an engine power transmission system is detected and a clutch torque dependent on the transmitting torque is obtained. The line pressure is set to a minimum value sufficient for holding a belt of the pulley device for transmitting the clutch torque.

Abstract: A control system for a motor vehicle provided with a continuously variable transmission which has a transmission ratio control valve having a spool for controlling the transmission ratio. During the deceleration of the vehicle by closing a throttle valve of the engine, the transmission ratio is upshifted when engine speed does not greatly fluctuate, so that engine speed is reduced further.

Abstract: A control system for a motor vehicle provided with a continuously variable transmission which has a transmission ratio control valve having a spool for controlling the transmission ratio. During the acceleration of the vehicle, the transmission ratio is quickly reduced in a low vehicle speed range, whereby speed of an engine is kept low compared with a high vehicle speed range.

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. A transmission ratio control valve having a spool 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. Pitot pressure dependent on the engine speed is applied to the spool to shift it against a spring, the force of which is determined by the depression of an accelerator pedal. An actuator is proviced to increase the load on the spring to downshift the transmission. A manual select device is provided to opeate the actuator for downshifting.

Abstract: A system for controlling an infinitely variable transmission is provided with a vehicle speed sensor for sensing vehicle speed and for producing a signal when the vehicle speed exceeds a predetermined value, a neutral range sensor of the transmission, a drive range sensor, and an accelerator pedal release sensor. The system further has an actuator for cutting off fuel. When the vehicle coasts under conditions of the drive range, accelerator pedal release, and at a higher vehicle speed than the predetermined value, fuel is cut off. When the neutral range is selected under the fuel cut off state, the clutch is engaged with a delay.

Abstract: A system for controlling an electromagnetic clutch has a vehicle speed sensor and an accelerator pedal switch. The clutch current is cut off at a low speed of a vehicle in response to a signal of the accelerator pedal switch at the release of an accelerator pedal. The system is arranged to supply a small drag current to the coil of the clutch in a very low vehicle speed range including stopping of the vehicle.

Abstract: A control system for a continuously variable transmission has a line pressure control valve having ports and a spool for controlling the line pressure of oil supplied to a cylinder of a pulley device to change the transmission ratio. The line pressure control valve has chambers. When the transmission ratio reaches a maximum value after disengagement of a clutch, a line pressure reducing signal generates. The signal is applied to the line pressure control valve to shift the spool thereof, so that the line pressure is reduced to a minimum value. By controlling the pressure of oil supplied to the chambers in accordance with a desired line pressure, the spool is shifted, so that the line pressure is controlled.

Abstract: A system for controlling an electromagnetic clutch has a reference valve generator which produces clutch-engaging and clutch-disengaging engine speed signals in a low vehicle speed range. Engine speed is compared with the engine speed signals by a comparator. The clutch is engaged at a higher engine speed than a clutch disengaging speed and disengaged at a lower engine speed than a clutch engaging speed in accordance with the result of the comparison.

Abstract: A system for an infinitely variable transmission having a primary pulley having a hydraulically shiftable disc and a hydraulic cylinder for shifting the disc, a secondary pulley having a hydraulically shiftable disc and a hydraulic cylinder for operating the disc, a belt engaged with both pulleys. A hydraulic circuit has a transmission ratio control valve comprising a spool for selectively shifting the disc of the primary pulley in the downshift direction and upshift direction, and a pressure regulator valve for regulating the oil pressure is operatively connected to the hydraulically shiftable disc to detect transmission ratio during operation. A shifting device is provided for shifting the spool of the transmission ratio control valve in the upshift and downshift direction in dependency on throttle position.