Abstract: A four-wheel drive vehicle includes: a driving force transmission system which transmits torque of a drive source to front wheels and rear wheels via gear mechanisms; a clutch provided in the driving force transmission system and capable of controlling an amount of the torque transmitted to the rear wheels; and a pressing mechanism which presses the clutch by transforming a part of the torque transmitted to the rear wheels into axial thrust. In the driving force transmission system, gear ratios of the gear mechanisms are set such that a direction of a differential rotation between a drive shaft connected to an input side of the clutch and a drive shaft connected to an output side of the clutch is not reversed even when a steered angle of the front wheels changes to a maximum value while the four-wheel drive vehicle is traveling forwards.

Abstract: A four-wheel-drive vehicle includes: a drive source which generates torque forming a driving force of the vehicle; a driving force transmission system which transmits the torque of the drive source to main driven wheels and auxiliary driven wheels; and a dog clutch provided in the driving force transmission system and capable of transmitting the torque to an auxiliary driven wheel side by engagement of a recess portion and a protruding portion. The vehicle further includes: a determination unit which determines whether a friction coefficient of a road surface is lower than a predetermined value based on an index value relating to the friction coefficient of the road surface; and a control unit which generates a control signal which causes engagement of the dog clutch before the vehicle starts when the determination unit determines that the friction coefficient of the road surface is lower than the predetermined value.

Abstract: A four-wheel drive vehicle includes: a driving force transmission system which transmits torque of a drive source to front wheels and rear wheels via gear mechanisms; a clutch provided in the driving force transmission system and capable of controlling an amount of the torque transmitted to the rear wheels; and a pressing mechanism which presses the clutch by transforming a part of the torque transmitted to the rear wheels into axial thrust. In the driving force transmission system, gear ratios of the gear mechanisms are set such that a direction of a differential rotation between a drive shaft connected to an input side of the clutch and a drive shaft connected to an output side of the clutch is not reversed even when a steered angle of the front wheels changes to a maximum value while the four-wheel drive vehicle is traveling forwards.

Abstract: A four-wheel-drive vehicle includes: a drive source which generates torque forming a driving force of the vehicle; a driving force transmission system which transmits the torque of the drive source to main driven wheels and auxiliary driven wheels; and a dog clutch provided in the driving force transmission system and capable of transmitting the torque to an auxiliary driven wheel side by engagement of a recess portion and a protruding portion. The vehicle further includes: a determination unit which determines whether a friction coefficient of a road surface is lower than a predetermined value based on an index value relating to the friction coefficient of the road surface; and a control unit which generates a control signal which causes engagement of the dog clutch before the vehicle starts when the determination unit determines that the friction coefficient of the road surface is lower than the predetermined value.

Abstract: A driving force transmission apparatus includes: a driving force transmission shaft receiving driving force of a driving source from a rotating member and transmitting the driving force from a main driving wheel side to an auxiliary driving wheel side; a first driving force interruption unit connects/disconnects the driving force transmission shaft to/from the rotating member; a second driving force interruption unit connects/disconnects the driving force transmission shaft to/from at least one of two auxiliary driving wheels so that transmitted torque is variable; and a control unit controls connection and disconnection of the first and second driving force interruption units. The control unit causes the second driving force interruption unit to connect/disconnect the driving force transmission shaft to/from the at least one of the auxiliary driving wheels before causing the first driving force interruption unit to connect/disconnect the driving force transmission shaft to/from the rotating member.