SPEED CHANGE MECHANISM FOR WORKING VEHICLE

PURPOSE:To perform backward ridge crossing and the like desirably by providing a front wheel side and a rear wheel side speed increasing driving means on a front wheel axle in the state of being operated contrarily to each other, and operating each speed increasing driving means alternatively in linkage with the operation of a forward/backward switching means. CONSTITUTION:The running speed change gear 9 of a riding-type seedlings planting machine performs the multiple-stage speed change of engine rotation transmitted to an input shaft 14 by displacing a shift member 18 slidingly in the axial direction and transmits it to a front wheel axle 31. In this case, there is provided with a front wheel side speed increasing driving means 38 for driving in the state of the circumferential speed of front wheels 1 being increased compared to that of rear wheels 2 at the advancing time of a machine body when the claws 32a, 33a of gears 32, 33 are meshed with each other. There is also provided with a rear wheel side speed increasing driving means 39 for driving in the state of the circumferential speed of the rear wheels 2 being increased compared to that of the front wheels 1 at the backing time of the machine body. These driving means 38, 39 are provided on the front wheel axle 31 in such a way as to be operated contrarily to each other, and operated alternatively in linkage with the operation of a forward/backward switching means 37.