Patent ID: 7715968

Claim:
A control method for a four-wheel drive vehicle, comprising: inhibiting (i) switching auxiliary drive wheels from a same speed condition to an increasing speed condition with respect to main drive wheels, and (ii) switching an outer wheel of said auxiliary drive wheels from said same speed condition to said increasing speed condition with respect to an inner wheel of said auxiliary drive wheels, when (1) said vehicle is at a first predetermined vehicle speed or less, (2) said vehicle is between said first predetermined vehicle speed and a second predetermined speed, said second predetermined speed being higher than said first predetermined speed, or (3) said vehicle is in a turning condition at said second predetermined vehicle speed or more, and was not previously in a straight driving condition at said second predetermined speed or more, permitting the (i) switching said auxiliary drive wheels from said same speed condition to said increasing speed condition with respect to said main drive wheels, and the (ii) switching said an outer wheel of said auxiliary drive wheels from said same speed condition to said increasing speed condition with respect to an inner wheel of said auxiliary drive wheels, when said vehicle is in the turning condition at said second predetermined speed or more and was previously in the straight driving condition at said second predetermined speed or more, and wherein said vehicle includes said main drive wheels connected to a driving source, said auxiliary drive wheels whose drive torque is adjustable, and a speed increasing mechanism capable of switching between said same speed condition and said increasing speed condition for said auxiliary drive wheels with respect to said main drive wheels and capable of switching between said same speed condition and said increasing speed condition for said outer wheel of said auxiliary drive wheels with respect to said inner wheel of said auxiliary drive wheels.