Abstract: An active torque-split control system for a four-wheel-drive vehicle comprises a transfer clutch, and sensors for detecting a wheel-speed difference between a primary drive wheel and a secondary drive wheel, a throttle opening, a vehicle speed, depressed or undepressed states of a brake pedal. The system is capable of executing both a feedback control based on the wheel-speed difference and a feedforward control based on the throttle opening. The system is responsive to at least a feedback control signal from the feedback control system and an anticipating correction signal from the feedforward control system for determining a distribution ratio of driving torque of the secondary drive wheel to the primary drive wheel depending on the highest one of the feedback control signal value and the anticipating correction signal value.

Abstract: In a driving force transfer apparatus for a part-time four-wheel drive vehicle with a fail safe structure, a high-speed gear range shift position and a low-speed gear range shift position in a high-speed and low-speed gear range position switching mechanism in a sub transmission are determined without special position sensors. In a case where the special position sensors are installed in the transfer apparatus, a shift position sensor diagnosis operation is effected so that a failure in either of a high-speed gear range position or low-speed gear range position sensor can easily be detected. If the failure in either of the position sensor occurs, a hydraulic (oil) pressure supply for providing a clutch pressure for a frictional clutch is made effective. Furthermore, a failure of either of revolution speed sensor detecting a first output axle revolution speed or detecting a second output axle revolution speed can also be detected. The first output axle is connected to mainly driven road wheels.

Abstract: In a control system for distributing a driving force from an engine between the front and rear wheels of a vehicle, a controller is designed to decrease the driving force transmitted to the secondary drive wheels which may be the front wheels by modifying a driving force distribution control characteristic when the vehicle is in a predetermined constant speed steady state, in order to improve the fuel economy in the steady state operation while maintaining a vivid vehicle response to a driver's accelerator input. Preferably, the controller determines an offset quantity L which has at least a cubic term proportional to the third power of a vehicle speed when the predetermined steady state exists, and increases the driving force to the secondary wheels as an excess of the wheel speed difference over the offset quantity increases from zero.

Abstract: A system for determining a residual life of a friction clutch is constructed so that the loaded condition of the clutch is determined in accordance with detected differential revolution, control oil pressure, oil temperature, and loading time, with which the residual life of the friction clutch is calculated.

Abstract: In a driving force transfer apparatus for a part-time four-wheel driving vechicle, a dog clutch structure is provided at both sides of first and second output axles, the first output axle being connected toward driven road wheels such as rear road wheels and the second output axle being connected toward non-driven road wheels such as front wheels. The dog clutch structure serves to connect the first output axle to the second output axle so that the four road wheels are forced into a four-wheel drive state during a low-speed gear range position switched through a sub transmission mechanism lever. In a first embodiment, a play in each tooth space structure constituting the dog clutch structure is provided so as to make a smooth mesh of the clutch structure, thus an operating force applied to a lever of the sub transmission mechanism can be lowered.

Abstract: A multi-plate type frictional clutch for a four-wheel drive vehicle is provided in a transfer unit for effecting variable driving force distribution in a 4WD vehicle. An inner wall of a transfer casing includes rotation restriction members so as to restrict rotational movement according to axial movement of a clutch piston disposed within the transfer casing. A cylinder chamber is defined between the rotation restriction members and the clutch piston. Also, the clutch piston is engageable with a rotational portion of a multi-plate type friction clutch via a thrust shaft receiving member disposed between the piston and the rotational portion of the multi-plate clutch. Further, the rotation restriction arrangement includes a casing boss and a piston boss engageable with an input shaft of the transfer unit according to rotational movement thereof. The engagement strength of the casing boss and the piston boss are set to be substantially low.

Abstract: An automobile driving-torque distribution control system for controlling a torque distribution between front and rear road wheels, comprises a torque-distribution adjustment mechanism responsive to a control signal for adjusting a distribution of driving torque between the front and rear wheels, sensors for detecting front and rear wheel speeds, and a controller for producing the control signal based on the difference between the front and rear wheel speeds. The controller includes a correction circuit for correcting the control signal value, to keep the control signal value at a designated torque-distribution limiting value when satisfying both a first condition in which the wheel-speed difference decreases to a value below a predetermined threshold, and a second condition in which an elapsed time calculated from the time when the first condition has been satisfied, is less than a predetermined time period.

Abstract: An anti-skid brake control system for a four-wheel drive vehicle employs a transfer which distributes a driving torque to front and rear differentials, a front-wheel mean revolution-speed sensor, a rear-wheel mean revolution-speed sensor, and a four-wheel-drive control section. The four-wheel-drive control section controls a driving-torque distribution ratio of the transfer based on the two mean revolution-speeds detected by the sensors. The system comprises an anti-skid brake control section intercommunicated with the four-wheel-drive control section. The anti-skid brake control section controls a wheel-brake cylinder pressure of each road wheel based on at least a revolution-speed of one of the front road wheels, a revolution-speed of the other wheel of the front road wheels, and the mean revolution-speed detected by the rear-wheel mean revolution-speed sensor. An additional sensor is provided at the one front wheel.