| 摘要 |
PURPOSE:To obtain a sufficient steering amount even for low delivery of hydraulic pump by limiting switch of a variable capacity hydraulic motor for driving drive wheels to high speed side when engine rotation is lower than a set value. CONSTITUTION:An excavator comprises a plurality of variable capacity hydraulic motors 2L, 2R for driving left and right drive wheels 1L, 1R and a plurality of operating valves 5L, 5R for controlling pressure oil supply from a plurality of hydraulic pumps 4L, 4R to the motors 2L, 2R. In such arrangement, a rotary sensor 9 for detecting actual rotation of an engine 3, an operating valve 10 for switching capacities of the motors 2L, 2R, a plurality of hydraulic cylinders 11L, 11R and a maneuvering lever 12 for setting engine rotation are provided. When actual rotation of the engine 3 exceeds over a set level, switching of the operating valve 10 to high speed side is allowed by a controller 7.
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