Abstract: A control system for an electromagnetic clutch for a vehicle has an engine speed sensor, a clutch driven member speed sensor and a throttle position sensor. The system has a memory storing first torque capacities increasing with increase of engine speed and storing second torque capacities at clutch engagement rate 100% in accordance with engine speed and throttle position. The actual clutch engagement rate is calculated based on output signals of the engine speed sensor and the clutch driven member speed sensor. A first torque capacity and a second capacity are derived from the memory in accordance with output signals of the sensors. A torque capacity Tc for engaging the clutch is calculated as follows,Tc=Re.multidot.TcL+(1-Re).multidot.Tcswhere Re is the clutch engagement rate, Tcs is the first torque capacity and TcL is the second torque capacity.

Abstract: A system for detecting a slip for four wheels of a four-wheel drive motor vehicle has a speed difference detector for detecting the difference between the front-wheel speed and the rear-wheel speed and for producing a speed difference signal when the difference is larger than a predetermined value. A wheel acceleration calculator is provided for calculating wheel acceleration, and a vehicle body acceleration detector is provided for detecting vehicle body acceleration. When the difference of the wheel acceleration from the vehicle body acceleration is larger than a predetermined value, and when the speed difference signal is not generated, which means that there is no difference between the front and rear wheel speed, a four-wheel slip signal is generated.

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. When the clutch is disengaged, the line pressure is set to a minimum value sufficient for tensing a belt of the pulley device for preventing the belt from slipping when the clutch is re-engaged.

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 driven pulley. The pressure of the oil supplied to control the spool is controlled by an on-off control valve in accordance with engine operating conditions to control the line pressure. The duty ratio of pulses for operating the on-off control valve is obtained by positioning a desired line pressure between the lowest line pressure and the highest line pressure corresponding to duty ratios of 100% and 0%, respectively.

Abstract: A control system for a continuously variable transmission 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 control system operates to control the transmission ratio in accordance with a desired ratio including a desired overdrive ratio for providing an overdrive transmission ratio. In a low vehicle speed range, the overdrive transmission ratio is controlled to a value slightly larger than the overdrive transmission ratio.

Abstract: A control system for a motor vehicle provided with 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 of the transmission. When a throttle valve of an engine is rapidly opened, the line pressure is increased so as to prevent a belt of the pulley device from slipping.

Abstract: A control system for a motor vehicle provided with 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. When torque of an engine is rapidly increased, the line pressure is increased so as to prevent a belt of the pulley device from slipping.

Abstract: A control system for a motor vehicle provided with a continuously variable transmission and with an electromagnetic clutch for transmitting torque of an engine to the transmission. The transmission has a line pressure control valve having ports and a spool, a hydraulic circuit for supplying oil to the line pressure control valve so as to shift the spool to control the line pressure. When the clutch is slipping at the start of the vehicle, the line pressure control valve is controlled in accordance with a clutch transmitting torque. When the clutch is engaged, the control valve is controlled in accordance with an engine torque.

Abstract: An intake air control valve controls the amount of intake air of an engine. When a torque converter of an automatic transmission is locked for establishing the lock-up state, the control valve is closed to reduce the amount of air, so that engine speed is reduced without increasing the engine torque.

Abstract: A control system for a continuously variable transmission for a motor vehicle has a line pressure control valve having a spool for controlling oil supplied to a cylinder of a driven pulley to change the transmission ratio. The control system operates to increase the line pressure when the vehicle stops. The increased line pressure actuate the cylinder thereby increasing the transmission ratio.