Four-wheel drive vehicle operating system

摘要

An operating system used in a vehicle equipped with a part-time four-wheel drive comprises; a center-differential shiftable between at least a two-wheel drive mode and a four-wheel differential-locked drive mode; a free-wheeling device with a clutch mechanism incorporated in an output shaft of an axle differential associated with wheels which are rendered non-driven when the vehicle is traveling in the two-wheel drive mode and adapted to connect and disconnect the transmission of driving power between the axle differential and the non-driven wheel; a drive mode selecting member operated by a driver in the driver's compartment to select a desired driving mode of operation of the center-differential; and a shift control device which sequentially shifts the center-differential responding to an operation of the drive mode selecting member. The shift control device controls the center-differential to be intermediately shifted into a four-wheel differential-locked drive mode upon being shifted from one to the other between the two-wheel and four-wheel differential-locked drive modes. The shift control device shifts finally the center-differential into the other drive mode after locking the clutch mechanism to connect the transmission of driving power between the axle differential and the wheel which is rendered non-driven when the center-differential is traveling in two-wheel drive mode.