TWO/FOUR-WHEEL DRIVE MODE SHIFT CONTROLLER FOR TRACTION-TRANSMITTING PART TIME FOUR-WHEEL DRIVE VEHICL AND METHOD FOR CONTROLLING THE SAME

摘要

Shifting with reduced shock can be performed of a drive from the two-wheel to the four-wheel drive in a traction-transmitting part-time four wheel drive vehicle provided with a gear clutch that cuts off a driven wheel in a secondary drive line. When shifting of a drive mode from two-wheel drive to four-wheel drive is requested (S11 and S12) during driving, an operation for changing driving condition of a traction-transmitting type transfer from non-driving to driving condition (step S18 and S22) is previously performed and as the shifting of the transfer advances, the gear clutch is engaged, if the difference (ΔVw) in the rotational speed of the primary driven wheel and the secondary driven wheel satisfies 0 ΔVw α, and shifting of the gear clutch from an unengaged state to engaged state without shock or noise (step 19) becomes possible, the gear clutch is engaged (step s21 and step s23). Thus a great shock or noise can be avoided.