ENGINE SPEED CONTROL DEVICE

An engine speed control device 30 performs: a first PID gain calculation step of calculating a target engine speed Nm to thereby calculate a first PID gain based on an engine speed deviation ΔN between the target engine speed Nm and an engine speed Nr detected by an engine speed detecting means 24; a target rack position calculation step of correcting the first PID gain based on a cooling water temperature Tw detected by a cooling water temperature detecting means 1a to thereby calculate a target rack position Rset of a fuel injection pump 2; a second PID gain calculation step of calculating a second PID gain based on a rack position deviation ΔR between the target rack position Rset and a rack position Rr detected by the rack position detecting means; and a rack control signal producing step of correcting the second PID gain based on a lubricating oil temperature (pump oil temperature Tp) detected by a lubricating oil temperature detecting means to thereby produce a rack control signal Rfset, and the engine speed control device 30 controls an engine speed by controlling a rack position based on the rack control signal Rfset.