JPH05248406

PURPOSE:To operate running levers at the same angular amount regardless of the speed of the preset speed and to enable running at a required setting speed by inputting a displacement detection signal of the running lever and a signal of a running speed setting operation unit to a controller. CONSTITUTION:A working mode change-over switch 20 and a running speed setting operation unit 27 are operated, a signal from the change-over switch 20 is input to a controller 19' to decide the target rotating speed of an engine 17, and displacement detecting signals of potentiometers 25, 26 are input to the controller 19' by running levers 1L, 1R. According to the above signals, a preset speed signal of the running speed setting operation unit 27, and a pump characteristic relative to the current preset speed of a memory 23, a pump tilting amount command signal is output to an electromagnetic proportional pressure reducing valve 24. The pilot pressure corresponding to the signal works on regulators 14, 15, the pump tilting amount of the variable pumps 12', 13' is regulated in so as to discharge the preset amount. Accordingly, regardless of the speed of the required preset speed, the running levers are operated at the same angle to run at the required preset speed.