To improve a device for switching a steering mode of a tractor.
In switching plural steering modes, when a steering mode select switch is turned on, it is determined whether it is in the course of switching the steering mode or not, and if yes, the steering angles of right and left front wheels 2, 2 and right and left rear wheels 3, 3 are detected by angle sensors 26, 26. Subsequently, it is determined whether the detected angle changes from the reference angle 0 in the rectilinear advancing state to an angle of a designated range or not. In the case of a designated angle range, according to a command signal of a control device 24, the flows of flow control valves 23 are throttled to the decrease side by a designated amount to slowly steer the wheels, and when the steering reference angle 0 of the right and left front wheels 2, 2 and the right and left rear wheels 3, 3 are detected by the angle sensors 25, 25, the steering turning of the wheels is stopped to be switched to a selected steering mode. Thus, when the steering angles of the right and left front wheels 2, 2 and the right and left rear wheels 3, 3 become close to the rectilinear advance state, the steering speed of the wheels becomes slow, and the wheels are stopped near the rectilinear advance state to complete switching the steering mode. Accordingly, steering in the switched steering mode can be accurately performed.
WAKINO TAKASHI
NAGAI MASATO
MIYAUCHI YASUHIRO
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