Abstract: During turning of a vehicle, a vehicle body deceleration due to a cornering drag is obtained. An electronically controlled coupling is controlled to give, to rear wheels, a pre-torque set to be larger as the vehicle body deceleration is larger. Also, the pre-torque is restricted by an upper limit of the pre-torque that is set to be lower as a differential rotational speed of the front and rear wheels is smaller. By giving the pre-torque to the rear wheels, if a shift condition for a four-wheel drive state is established subsequently, a driving force can be generated in the rear wheels substantially at the same time that a fastening force of the electronically controlled coupling is increased, thereby the shift to the four-wheel drive state is immediately completed. Consequently, delay in response is not generated in the shift.

Abstract: During turning of a vehicle, a vehicle body deceleration due to a cornering drag is obtained. An electronically controlled coupling is controlled to give, to rear wheels, a pre-torque set to be larger as the vehicle body deceleration is larger. Also, the pre-torque is restricted by an upper limit of the pre-torque that is set to be lower as a differential rotational speed of the front and rear wheels is smaller. By giving the pre-torque to the rear wheels, if a shift condition for a four-wheel drive state is established subsequently, a driving force can be generated in the rear wheels substantially at the same time that a fastening force of the electronically controlled coupling is increased, thereby the shift to the four-wheel drive state is immediately completed. Consequently, delay in response is not generated in the shift.

Abstract: A vehicle coupling includes a wet type multiple disc clutch that selectively connects or disconnects a driving member to or from a driven member; a piston that engages the wet type multiple disc clutch by pushing against the wet type multiple disc clutch in an axial direction; a pushing mechanism that generates force with which the piston pushes against the wet type multiple disc clutch, based on the relative torque between the driving member and the driven member; and a hydraulic mechanism that generates hydraulic pressure for generating thrust to move the piston away from the wet type multiple disc clutch, according to differential rotation between the driving member and the driven member when the wet type multiple disc clutch is released.