Abstract: A propeller shaft comprises two torque transmission members, a viscous fluid damper and a torsion bar which are arranged in parallel between the torque transmission members, and a stopper for restricting the maximum torsion angle of the torsion bar. Thus, torsional vibration characteristic is adjusted in a wide range. Accordingly, a vibration a and noise in a power transmission system can be prevented, and also, a starting acceleration performance of a vehicle can be improved.

Abstract: A planetary gear device as a central differential distributes an output torque of a transmission to the front wheels and the rear wheels of a four-wheel drive motor vehicle. A fluid operated clutch is provided between a sun gear and a ring gear of the planetary gear device. A desired speed ratio between front-wheel speed and rear-wheel speed at cornering is calculated based on vehicle speed and steering angle of the vehicle. A torque distribution ratio is determined in accordance with a difference between the desired speed ratio and an actual speed ratio between the front-wheel speed and the rear-wheel speed. The clutch pressure is controlled in response to the torque distribution ratio for engaging the clutch so that the average speed ratio coverages to the desired speed ratio.

Abstract: A system for a four-wheel drive vehicle for automatically changing the transmission of the engine of the vehicle from two-wheel drive to four-wheel drive when braking. The transmission transmits power from the engine to two main driving wheels, and an electromagnetic clutch having a magnetizing coil is provided for transmitting the power of the engine to the two-wheels. A brake switch is provided for producing a signal when the brake pedal is depressed a predetermined stroke, and a control circuit is provided for allowing the clutch current to pass through the coil of the electromagnetic clutch when the signal from the brake switch is applied.

Abstract: A system is for a four-wheel drive vehicle for automatically changing the transmission of the engine of the vehicle from two-wheel drive to four-wheel drive or vice versa in accordance with the driving condition. The transmission transmits power from the engine to two main wheels, and an electromagnetic clutch having a magnetizing coil transmits the power of the engine to drive two auxiliary wheels. A steering angle sensor produces an output signal when the steering angle exceeds a predetermined value, and a control circuit controls the clutch current applied to the coil of the electromagnetic clutch. The control circuit operates such that when the output signal of the steering angle sensor is applied thereto, the clutch current is cut off so as to disengage the electromagnetic clutch so as to provide two-wheel driving.