Abstract: A microcomputer is provided for controlling an automatic transmission for a motor vehicle. The microcomputer operates to control line pressure in a hydraulic circuit for the automatic transmission. A control circuit is provided to respond to an output signal of the microcomputer for energizing a solenoid to control the line pressure. A driving circuit is provided to respond to closing operation of a starting motor switch of an engine to energize the solenoid to reduce the line pressure.

Abstract: A system for controlling a drag torque of an electromagnetic clutch at releasing of an accelerator pedal of a motor vehicle. A detector is provided for detecting whether vehicle speed is lower than a predetermined low speed. At the low vehicle speed, drag current is corrected in dependency on engine speed so as to provide a constant drag torque.

Abstract: A control system for an automatic transmission having a first gear hold range, and a second gear hold range. A detector is provided for detecting a selected gear hold range and for producing a gear hold signal, and a sensing device is provided for producing an engine speed signal dependent on engine speed. When the engine speed signal exceeds a predetermined speed under the selection of one of gear hold ranges, the gear hold range is released and transmission is upshifted.

Abstract: A system for controlling clutch current of an electromagnetic clutch at release of an accelerator pedal of a vehicle in a low vehicle speed range. The clutch is disengaged when the accelerator pedal is released in the low vehicle speed range. The disengagement of the clutch and reduction of an engine are delayed so s to prevent oscillaiton of the speed of a power transmission system.

Abstract: A system has a start mode in which clutch torque of the clutch increases with increase of speed of an engine of the motor vehicle, a lock-up engagement mode in which the clutch torque is increased, and a drag mode in which the clutch torque is reduced to produce a drag torque, one of the modes being selected in accordance with depression of the accelerator pedal and speed of the vehicle. When a vehicle speed detector does not produce a vehicle speed signal for a predetermined period in the start mode at engine speed higher than a predetermined speed, a fail-safe signal is produced. In response to the fail-safe signal, the system operates to keep clutch torque.

Abstract: A four-wheel drive vehicle has a transmission, main drive wheels operatively connected to an output shaft of the transmission, auxiliary drive wheels, and a transfer clutch for transmitting output of the transmission to the auxiliary drive wheels. A control system is provided with a detector for detecting speed ratio of front-wheel speed and rear-wheel speed and for producing a speed ratio signal, which represents steering operation of the vehicle and for producing a steering angle signal. A control unit is responsive to the steering angle signal for controlling torque of the transfer clutch so as to cause the transfer clutch to slip in dependency on the steering angle signal.

Abstract: A system for controlling an electromagnetic clutch of an engine for a motor vehicle having a transmission. The system has various sensors such as an engine speed sensor, a vehicle speed sensor for detecting low vehicle speed, an accelerator pedal position sensor for detecting the acceleration of the engine, and a selector lever position sensor. The system has computing means for determining the clutch current at the beginning of the engagement of the electromagnetic clutch. The clutch current is determined such that a large clutch current is supplied at lower engine speed, and a small clutch current is supplied at higher engine speed at the beginning of the engagement of the clutch.

Abstract: A system for controlling an electromagnetic clutch of an engine for a motor vehicle having a transmission. The system has various sensors such as an engine speed sensor, a vehicle speed sensor for detecting low vehicle speed, an accelerator pedal position sensor for detecting the acceleration of the engine, and a selector lever position sensor. The system has a computing unit for determining the clutch current at the beginning of engagement of the electromagnetic clutch. The rate of change of clutch current with respect to engine speed increases as the acceleration of engine speed increases.

Abstract: A four-wheel drive vehicle has an engine clutch for transmitting the output of an engine to a transmission, main drive wheels operatively connected to an output shaft of the transmission, auxiliary drive wheels, and a transfer clutch for transmitting the output of the transmission to the auxiliary drive wheels. A control system is provided with a steering angle sensor producing a steering signal dependent on steering angle of the vehicle, a throttle position sensor producing a signal dependent on throttle position, and a vehicle speed sensor producing a vehicle speed signal. A control unit is provided to respond to the steering signal, the throttle position signal and the vehicle speed signal for controlling the torque capacity of the transfer clutch so as to reduce the torque capacity with increase of the steering angle and with decrease of the vehicle speed and degree of throttle position opening.

Abstract: A system for controlling clutch torque for a vehicle having a transmission and an electromagnetic clutch provided between an engine and the transmission. The system comprises an engine speed sensor, a computing unit for determining the speed of a driven member of the electromagnetic clutch, an accelerator pedal switch for detecting the acceleration of the vehicle and for producing an acceleration signal, and a comparator for comparing the engine speed with the speed of said driven member and for producing an output when both speeds substantially coincide with each other. The system has an AND gate responsive to the acceleration signal and the output for producing a clutch engaging signal, thereby engaging the electromagnetic clutch.

Abstract: A system for controlling an electromagnetic clutch for an infinitely variable belt-drive transmission, which is provided with an accelerator pedal switch for producing an output signal at release of an accelerator pedal of a vehicle, and a vehicle speed detector for producing an output signal at a low vehicle speed. The system is arranged to produce a small drag current signal in dependency on the accelerator pedal release signal and the low vehicle speed signal, so that a small drag clutch current flows in a coil of the electromagnetic clutch.

Abstract: A system for controlling the clutch current of an electromagnetic clutch for a vehicle which has a transmission and a gear shift lever for changing change-speed gears in the transmission. A shift lever switch is operated when the shift lever is operated passing through a neutral position. A logic gate circuit is provided to respond to a signal of the shift lever switch for cutting off the clutch current. A timer is responsive to the disappearance of the signal upon engagement of the gears for producing an output with a delay, for opening the logic gate circuit, whereby the cluch remains disengaged for a predetermined period after engagement of the gears.

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 system for controlling an electromagnetic clutch for a vehicle having an infinitely variable transmission which has a high engine speed drive range (Ds range) for increasing the transmission ratio when selected. The system is provided with a control unit for producing a pulse train for controlling the clutch torque of the electromagnetic clutch. The duty ratio of the pulse train temporarily varies so as to decrease the clutch torque, when the Ds range is selected.

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 controlling clutch torque for a vehicle which has a transmission and an electromagnetic clutch provided between an engine and the transmission, the clutch current being increasing with increase of engine speed. The system comprises an engine speed sensor for sensing the speed of the engine and for producing an engine speed signal in proportion to the engine speed, and an acceleration detecting switch for producing an acceleration signal.A vehicle speed detecting unit is provided for sensing the vehicle speed and for producing an output when the vehicle speed reaches a predetermined value at a low engine speed.A clutch current control unit is provided to respond to the output of the vehicle speed detecting unit and to the acceleration signal for increasing the clutch current along at an inclination up to a rated current.

Abstract: A system for controlling the clutch torque of an electromagnetic clutch for a vehicle, having an accelerator pedal switch for producing an output signal when an accelerator pedal of the vehicle is released. A clutch current circuit including a transistor is provided for controlling the clutch current passing through a coil of the electromagnetic clutch. A logic gate circuit is provided to be responsive to the output signal of the accelerator pedal switch for controlling the transistor so as to decrease the clutch current to a low value approximating zero for a moment and thereafter to gradually increase the current to a predetermined value. The second circuit comprises a logic gate circuit and a pulse train generating circuit responsive to the output signal of the accelerator switch for producing a pulse train controlled by the logic gate circuit, and the duty ratio of the pulse train gradually varies so as to gradually increase the clutch current.

Abstract: A system for controlling the clutch torque of an electromagnetic clutch for a vehicle having an accelerator pedal switch for producing an output signal when an accelerator pedal of the vehicle is depressed. A clutch current circuit including a transistor is provided for controlling the clutch current passing through a coil of the electromagnetic clutch. A logic gate circuit is provided responsive to the output signal of the accelerator pedal switch for controlling the transistor so as to decrease the clutch current to a low value and thereafter to gradually increase the current to a rated value.

Abstract: A system for controlling the clutch current of an electromagnetic clutch for a vehicle which has an automatic transmission and a select lever for selecting driving ranges in the transmission. A driving range switch is provided to be operated when the select lever is operated to select a driving range. A logic gate circuit is provided to respond to a signal of the select lever switch for allowing the clutch current to flow. A delay circuit responds to the signal of the driving range switch for producing an output with a delay and for opening the logic gate circuit, whereby the clutch is engaged for a predetermined period after the operation of the select lever.

Abstract: A system for controlling the transmission ratio of an infinitely variable belt drive transmission having a primary pulley, a secondary pulley, a belt engaged with both pulleys, a pressure oil circuit having a pump for supplying pressure oil, and a transmission ratio control valve responsive engine speed for controlling the pressure oil and for changing the transmission ratio. The system has an electronic control circuit responsive to ignition pulses of the engine for producing output pulses dependent on the engine speed, and an electromagnetic valve responsive to the output pulses for controlling the amount of pressure oil applied to the transmission ratio control valve, thereby controlling the transmission ratio in dependency on the engine speed.