| 摘要 |
PURPOSE:To make improvements in traveling performance and controllability in a hydraulic shovel, by constituting it so as to be automatically selected from high speed travel to the low speed one at the time of high load such as direction changing, slope ascending or the like during high speed traveling of the shovel at a time when a switch is turned on. CONSTITUTION:A traveling hydraulic motor 4 of a hydraulic shovel makes discharge pressure of a pilot pump 16 act on a shift cylinder 6 of the hydraulic motor 4, and varies a tilt-rolling angle of a swash plate 5 whereby high-low speed transfer takes place. In this case, a shuttle valve 26 is installed between input-output ports of the hydraulic motor 4, while a pilot selector valve 27 is installed in the point midway in an oil passage with the shift cylinder 6. And, a pilot pressure receiving part 28 at the large area side of this selector valve 27 is connected to the discharge side of the pilot pump 16 via a solenoid valve 12, while a pilot pressure receiving part 29 at the small area side of the pilot selector valve 27 is connected to the shuttle valve 26, and an interval between both these pressure receiving parts 28 and 19 is connected via a check valve 30.
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