To precisely make a small turn according to the condition of a paddy field in a four-wheel drive paddy field work vehicle with a front wheel transmission by providing a changing means for changing the acceleration ratio to the large side with the depth of the plow sole for grounding the front wheel and the rear wheel, and changing the acceleration ratio to the small side in the case that the plow sole is shallow.
In a riding rice transplanter traveling in the condition where front wheels 1 and rear wheels 2 sink in a paddy field surface G and grounded on plow sole at the bottom, a machine frame is provided with a potentiometer 43 for detecting the vertical angle of a link mechanism 4 for supporting a nursery planter 3 in such a manner as to freely elevate. When with a transmission lever operated to a low speed position, the machine frame reaches a levee edge and an operator largely lifts the nursery planter 3 and makes a turn, the depth KH of the plow sole K is detected from the detection value of the potentiometer just before the lifting operation. With the depth KH of the plow sole K, the acceleration ratio (the speed ratio of the front wheel to the speed of the rear wheel) is changed to the large side, and in the case that the plow sole is shallow, the acceleration ratio is changed to the small side to make a small sharp turn.
MUKAI TAKESHI
KITAI HIROAKI
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