Patent ID: 9022158
Filing Date: 2015-05-05
Classification: B60K

Abstract:
1. A four-wheel-drive vehicle that is able to travel in any one of a two-wheel-drive mode and a four-wheel-drive mode, comprising: a drive source that generates torque for causing the four-wheel-drive vehicle to travel; a pair of right and left main drive wheels to which the torque is constantly transmitted from the drive source regardless of whether the four-wheel-drive vehicle is traveling in the two-wheel-drive mode or in the four-wheel-drive mode; a pair of right and left auxiliary drive wheels to which the torque is transmitted from the drive source, depending upon a travelling state; a propeller shaft that transmits the torque output from the drive source toward the auxiliary drive wheels; a first engagement-disengagement device that is provided between the propeller shaft and the drive source; a second engagement-disengagement device that is provided between the propeller shaft and the auxiliary drive wheels; and a control unit that controls the first engagement-disengagement device and the second engagement-disengagement device, wherein one of the first engagement-disengagement device and the second engagement-disengagement device is a dog clutch that includes two rotary members and that transmits the torque when the rotary members are engaged with each other, the other one of the first engagement-disengagement device and the second engagement-disengagement device is a torque coupling that is able to adjust a torque transmission amount, and when a drive mode is switched from the two-wheel-drive mode in which transmission of torque by the first engagement-disengagement device and transmission of torque by the second engagement-disengagement device are both interrupted, to the four-wheel-drive mode in which the torque is transmitted from the drive source toward the auxiliary drive wheels via the propeller shaft, the control unit sets the amount of torque that is transmitted by the torque coupling to a first torque value to increase a speed of rotation of the propeller shaft, and then sets the amount of torque that is transmitted by the torque coupling to a second torque value that is lower than the first torque value, and engages the rotary members of the dog clutch with each other when a difference in rotational speed between the rotary members becomes equal to or smaller than a predetermined value, wherein the control unit sets the amount of torque that is transmitted by the torque coupling to the second torque value to increase the speed of rotation of the propeller shaft, and then sets the amount of torque that is transmitted by the torque coupling to a third torque value that is lower than the second torque value, and engages the rotary members of the dog clutch with each other when the difference in rotational speed between the rotary members of the dog clutch becomes equal to or smaller than a predetermined value while the torque transmission amount is the third torque value.