PURPOSE: To reduce noise by contriving the engine control method in such a way that when the load of an engine decreases and the engine speed exceeds a prescribed value and the condition has continued for a prescribed time, if the neutral condition of a remote control valve continues for a prescribed time, the engine is operated at a low speed lower than an initially set speed.
CONSTITUTION: In a hydraulic machine such as a hydraulic shovel comprising an engine 1, a hydraulic pump 2 being driven thereby, a control valve 3 for controlling the output of the hydraulic pump 2, a hydraulic actuator 4 being controlled by the control valve 3, and a remote control valve 5 for controlling the control valve 3; a speed sensor 7 for detecting the engine speed, a neutral detecting switch 8 for detecting the neutral of the remote control valve 5, and a control calculator 10 to which the signal of a speed setting device 9 is input are provided. When the load of the engine decreases and the engine speed rises to exceed a prescribed speed, or the engine is in a noload condition, the engine speed is controlled to attain a speed lower than a predetermined value. When the neutral condition of the remote control valve 5 continues, the engine speed is controlled to attain a speed further lower than the deceleration speed.
HIROSE SHINYA
KONISHI HIDEO
MATSUBARA MORIHIKO
TANAKA MASAYUKI
MATOBA NOBUAKI
