| 摘要 |
PROBLEM TO BE SOLVED: To easily perform a small turn revolution by turning a front wheel up to a large degree by constituting a vehicle so as to switch a drive mode switching device of a front and rear wheel constant speed four-wheel-drive, a front wheel accelerating four-wheel-drive and a rear wheel two-wheel-drive according to steering amount. SOLUTION: Control modes by a control mode switch 61 are decided after information on various kinds of sensors and switches is read. When the control mode is a road traveling mode A, energizing to solenoids 65a, 66a of a front and rear wheel constant speed four-wheel-drive valve and a front wheel accelerating four-wheel-drive is stopped and a rear wheel two-wheel-drive is adopted. When the control modes are work modes C, D, energizing to the solenoid 65a of the front and rear wheel constant speed four-wheel-drive valve is performed, a front and rear wheel constant speed four-wheel-drive is adopted and is held as it is. When the control mode is a work mode B, the drive is held to the front and rear wheel constant speed four-wheel- drive at the time of a direct advance. When steering amount becomes a fixed valueθ1 or more, energizing to the solenoid 66a of the front wheel accelerating four-wheel- drive valve is performed and a front wheel accelerating four-wheel-drive is adopted. Further, steering amount becomes a fixed valueθ2 (θ2 >θ1 ) or more, energizing to the solenoids 65a, 66a is stopped and the rear wheel two-wheel-drive is adopted.
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