| 摘要 |
PURPOSE:To eliminate necessity for providing a detector in each operating means so as to simplify a structure by controlling a rotational speed of a prime mover to a low value of the preset speed or less, when a differential pressure between a delivery pressure of an oil hydraulic pump and its maximum load pressure is increased to a predetermined value or more. CONSTITUTION:Pipe lines 4A, 4B are branched from a delivery pipe line 4 of a variable displacement oil hydraulic pump 2 driven by a prime mover 1, and a work cylinder device 7 is connected to the pipe line 4A through pipe lines 8A, 8B. The pipe line 4 is connected to a running oil hydraulic motor 5 through a pair of pipe lines 6A, 6B, and control valves 9, 10 for work and running are provided on the way of the pipe line 4 or the like. The prime mover 1 is provided with a governor 27 for controlling its rotational speed, and this governor 27 is driven by an electric motor 28 controlled by a controller 30 connected to a fuel lever 26, differential pressure sensor 25 and a turn angle sensor 29 or the like. When a differential pressure between a delivery pressure and a maximum load pressure is increased to a predetermined value or more higher than a target differential pressure, a rotational speed of the prime mover is controlled to a low value of preset rotational speed or less. |
