Device for changing the speeds of the front and rear wheels in a four-wheel-drive vehicle

摘要

A device for changing the speeds of the front and rear wheels in a four-wheel-drive vehicle, which is equipped with a continuously variable speed-changing mechanism for the front wheels which changes the input rotational speed and outputs it to the front wheel drive shafts and a continuously variable speed-changing mechanism for the rear wheels which changes the input rotational speed and outputs it to the rear wheel drive shafts. The device for changing the speeds of the front and rear wheels comprises a detector means for detecting the operation conditions of the vehicle and a controller for variably controlling the speeds of said continuously variable speed-changing mechanism for the front wheels and of said continuously variable speed-changing mechanism for the rear wheels based on the operation conditions of the vehicle detected by said detector means. The controller calculates a tire diameter ratio of the front wheels to the rear wheels when the vehicle travels straight, sets a target speed-changing ratio obtained based on the vehicle operation conditions detected by the detector means to be a target speed-changing ratio for the rear wheels in the continuously variable speed-changing mechanism for the rear wheels or to be a target speed-changing ratio for the front wheels in the continuously variable speed-changing mechanism for the front wheels, and sets a speed-changing ratio obtained by correcting the target speed-changing ratio based on the tire diameter ratio to be a target speed-changing ratio for the front wheels or to be a target speed-changing ratio for the rear wheels.