| 摘要 |
PROBLEM TO BE SOLVED: To prevent steep turn of a vehicle turning in a high speed gain transmission state by providing automatic changeover means in a transmission changeover mechanism, for automatically switching from a high speed running state to a low speed running state if a steering device is operated to a preset state. SOLUTION: A high and low speed changeover valve 30 is stored in a right and left running motor 4 to be switched according to supply of pilot pressure oil. A charge pump 3a is provided in an HST pump 3 such that the oil discharged from the pump 3a is supplied to a solenoid valve 31. The solenoid valve 31 is switched according to operation of steering detection sensors 29L, 29R or a high and low speed range changeover switch 32. Based on the switching operation, the oil discharged from the charge pump 3a is supplied to the high and low speed changeover valve 30 via an oil passage 31a as the pilot pressure oil so as to switch the valve 30 to the high speed side. In contrast, if the oil ejected from the pump 3a is discharged to a hydraulic tank 33, the high and low speed changeover valve 30 is switched to the low speed side.
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