| 摘要 |
PURPOSE:To make it possible to automatically change a wheel tread, by utilizing rotation of a carrier of a planetary gear reduction mechanism installed on an upper transmission side of an axle axially moving a shaft portion on a lower transmission side of the axle. CONSTITUTION:In case of widening a wheel tread, a clutch member 5 is separated from a carrier 2a, and a shaft 1 on an upper transmission side is set to be rotated with a shaft 3 on a lower transmission side in an integral manner. When a drive pinion shaft 7 is forwardly rotated under this condition, the carrier 2a of a planetary gear reduction mechanism 2 is rotated at a reduced speed in the same manner as a normal forward running, while the shaft 3 on the lower transmission side is rotated integrally with the shaft 1 on the upper transmission side at high speed. That is, there is created difference in a rotational speed between the carrier 2a and the shaft 3, and accordingly the shaft 3 is separated from the shaft 1 by a thread portion 4 formed between both the members 2a and 3 thereby to widen a wheel tread. |
