| 摘要 |
<P>PROBLEM TO BE SOLVED: To restrain the occurrence of a shock when shifting a sub-transmission. Ž<P>SOLUTION: This tractor T performs multistage travel gear-shifting by serially joining a main transmission 5 and the sub-transmission 8 constituted by using hydraulic clutches C1-C4, CL and CH. A plurality of hydraulic clutches C1-C4 constituting the main transmission 5 respectively perform alternative operation control based on boosting control of electromagnetic proportional valves 16a-16d, and the hydraulic clutches CL and CH constituting the sub-transmission 8 perform operation control based on shifting control of an electromagnetic directional control valve 17. The sub-transmission 8 also has a neutral position, and in travel gear-shifting of requiring shifting of the sub-transmission 8, the sub-transmission 8 is put into neutral once, and after reducing a rotational difference between the transmission upstream side and the transmission downstream side of the sub-transmission 8, the hydraulic clutches CL and CH of the sub-transmission 8 are connected. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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