| 摘要 |
A first target engine speed Nh and a high-speed control field F1 are set in accordance with a command value by command means. A second target engine speed N2 on the low rotation side and a high-speed control field F2 are set based on the first target engine speed Nh. When a matching point between an engine load and an engine output torque exceeds a first set position A which is a first predetermined pump displacement during control of an engine in the high-speed control field F2, the high-speed control field F2 is shifted toward the high-speed control field F1. Using, as a new high-speed control field, a high-speed control field 3 in which a differential pressure between a pump discharge pressure and a load pressure of an actuator satisfies a load sensing differential pressure in a pump control device 8, the engine is controlled in the high-speed control field 3, and when the differential pressure does not satisfies the load sensing differential pressure, the speed control field is shifted to the high-speed control field F1. With this, it is possible to provide an engine control device and a control method thereof in which the fuel economy of the engine is enhanced, and when the maximum speed of an operating machine is required, the required maximum speed of the operating machine is not lowered.
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