Patent ID: 8229640

Claim:
A drive force transmission apparatus employed in a four-wheel-drive vehicle having main drive wheels, to which torque of a drive source is constantly transmitted, and auxiliary drive wheels, to which the torque of the drive source is transmitted when needed according to a state of the vehicle, the apparatus comprising: a torque coupling that is arranged between the drive source and the auxiliary drive wheels that is configured to change a capacity of torque transmission to the auxiliary drive wheels a steering sensor connected to a steering wheel that steers the vehicle, the steering sensor detecting the steering wheel turning angle; and a control device that controls operation of the torque coupling, wherein the control device calculates a turning radius of the vehicle based on speeds of the main drive wheels and the auxiliary drive wheels, wherein, if the calculated turning radius is smaller than or equal to a maximum value of a turning radius at which a tight corner braking phenomenon can occur, the control device performs tight corner control in which the torque transmission capacity is decreased compared to a case in which the calculated turning radius of the vehicle is greater than the maximum value of the turning radius, wherein, when determining that the vehicle is not skidding based on the speeds of the main drive wheels and the auxiliary drive wheels, the control device executes the tight corner control if a speed of the vehicle is less than an upper limit value of a vehicle speed range corresponding to a starting state of the vehicle, and the steering wheel turning angle of the steering wheel is greater than or equal to a minimum value of a steering wheel turning angle at which the tight corner braking phenomenon can occur, and wherein, when determining that the vehicle is skidding based on the speeds of the main drive wheels and the auxiliary drive wheels, the control device inhibits the tight corner control even if the vehicle speed is less than the upper limit value, and the steering wheel turning angle is greater than or equal to the minimum value of the steering wheel turning angle at which the tight corner braking phenomenon can occur; and wherein the upper limit value is set to different values depending on whether the vehicle is accelerating or decelerating.