| 摘要 |
PROBLEM TO BE SOLVED: To solve following problems that sudden deceleration and an engine failure are caused by upwardly changing a speed change position during heavy loaded operation and the stability of work is damaged, while a speed change controller controlling the speed change position upward and downward by means of the stepping-in motion of an accelerator pedal is mounted on a working vehicle such as a tractor or the like. SOLUTION: The speed change controller comprises a step of detecting the pushing-down operation of acceleration and deceleration down switches 51 and 52 in the tractor, a step of driving speed change actuators 27p, 18a, and 18b by means of the controller 29, and a step of operating primary speed change units 27 and 30 upward and downward. The speed change actuators 27p, 18a, and 18b are driven by the controller 29 in response to the step-in motion of an acceleration pedal 22 so as to control the up-and-down operation of the primary speed change gears 27 and 30. When a switching system 39 for two-wheel-drive and four-wheel-drive of the tractor is set at a four-wheel-drive state, speed change operation by means of the acceleration pedal 22 is restrained on the assumption that high-load operation is performed. COPYRIGHT: (C)2005,JPO&NCIPI
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