Abstract: An engine speed control system for controlling the engine speed of an engine (30) for driving an industrial vehicle includes a control unit (50, 70, 85, 95) provided with an internal memory (72) and a first control system which reads a desired engine speed corresponding to an angular displacement of the accelerator pedal (44) detected by an accelerator pedal displacement detecting means (52) from the memory (72) when the running speed of the vehicle is not higher than a maximum running speed set by a maximum running speed setting means (56, 58, 76) connected to the control unit (50, 70, 85, 95) and controls an actuator (38) so as to regulate the opening of a throttle valve (36) of the carburetor (32) such that the engine speed coincides with the desired engine speed read from the memory (72), and a second control system that reads an upper limit desired engine speed for the engine (30) corresponding to the preset maximum running speed when the running speed reaches the preset maximum running speed and control

Abstract: A plurality of characteristic variables concerning the rotational speed are detected so as to be used for inference, and the plurality of characteristic variables are divided into a plurality of sets. Groups of rules each indicating the relationship between the characteristic variable corresponding to each set and an amount of gain adjustment, as well as the relationship between the magnitude of the characteristic variable corresponding to each set and the degree of adoption of the amount of gain adjustment, are stored. When it is determined that each of the characteristic variables cannot be controlled within a permissible range, the relationship between each of the characteristic variables of the groups of rules and the amount of gain adjustment is corrected in such a manner that the permissible range is broadened.