Patent ID: 8177672
Filing Date: 2012-05-15
Classification: B60K,Y02T

Abstract:
1. A driving-force transmitting apparatus for a four-wheel-drive vehicle capable of switching between a four-wheel drive mode of transmitting a driving force to front wheels and rear wheels and a two-wheel drive mode of transmitting the driving force only to the front wheels, the apparatus comprising: a front-wheel differential device that distributes and outputs a driving force input from an engine to left-front and right-front wheels; a driving-force transmitting unit that transmits the driving force from the engine via the front-wheel differential device to the rear wheels; a rear-wheel differential device that distributes and outputs the driving force input from the driving-force transmitting unit to left-rear and right-rear wheels; a first disengaging mechanism that cuts off and connects a joint between the front-wheel differential device and the driving-force transmitting unit; a second disengaging mechanism that cuts off and connects a joint between the rear-wheel differential device and at least one of the left-rear and right-rear wheels and has a synchronizing mechanism that synchronizes a rotation of a driving-force transmitting unit side and a rotation of an opposing side at the time of connection; and a control unit that connects the first disengaging mechanism and the second disengaging mechanism to transmit the driving force from the engine to the left-rear and right-rear wheels in the four-wheel drive mode, and cuts off the first disengaging mechanism and the second disengaging mechanism to stop a rotation of the driving-force transmitting unit in the two-wheel drive mode, wherein the driving-force transmitting unit configures a change gear ratio between the front and rear wheels so that the driving-force transmitting unit side of the first disengaging mechanism rotates at a speed higher than that of the opposing side with the first disengaging mechanism being cut off at the time of completion of synchronization of the second disengaging mechanism, and in switching from the two-wheel drive mode to the four-wheel drive mode, the control unit first starts synchronization of the second disengaging mechanism to increase a rotation speed of the driving-force transmitting unit, and next connects the first disengaging mechanism when a difference in rotation speed between the driving-force transmitting unit side of the first disengaging mechanism and the opposing side is decreased to a predetermined range.