| 摘要 |
PURPOSE:To simply carry out the switchover between advancing and backing by stopping the feed of oil into a hydraulic clutch whereas feeding oil into a traveling brake in the middle stage of the switching operation of an advancing/backing switchover device, and feeding oil into the clutch while releasing braking at the time of finishing the switching operation. CONSTITUTION:Delivered oil out of a hydraulic pump 15 is partly used for a power steering 32 while the remaining delivered oil is fed into a traveling speed selecting control valve 14, speed change gear operating hydraulic cylinder- cum-selecting valves 11-13, an advancing/backing selector valve 16, the operation control part 22 of a hydraulic clutch 3, and a traveling brake 34 to carry out a defined speed change operation. In the middle stage of an advancing/ backing switchover operation, the selector valve 16 is set in a neutral position, the feed of oil into the clutch 3 by means of a valve 22a is stopped, and oil is fed into the traveling brake 34. Then, as the switching operation of the selector valve 16 is over, oil is fed into the clutch 3 and braking is released, thereby, carrying out automatic braking operation at the time of switching over between advancing and braking while enabling simple and smooth switchover. |
