Engine speed control apparatus and method; engine system, vehicle and engine generator each having the engine speed control apparatus

An engine speed control apparatus (100, 100a) includes a throttle valve (170) for adjusting the amount of an intake air sucked into an engine (120), a drive unit (160) for driving the throttle valve (170), and a control unit (180) for generating a PWM signal for driving the drive unit (160). The control unit (180) includes a real speed detecting unit (210) for detecting a real engine speed (N) , a target speed setting unit (200a) for setting a target engine speed (N*), a target speed change amount calculating unit (220a) for calculating a target engine speed change amount (”N*) with the use of the real engine speed (N) and the target engine speed (N*), and a PWM pulse generating unit (200b) which calculates, according to the target engine speed change amount (”N*), a PWM control parameter for determining a PWM duty, and generates a PWM signal based on the PWM control parameter thus calculated, so as to supply the PWM signal thus generated to the drive unit (160). The PWM control parameter includes at least one of a PWM duty correction value (”duty) for correcting the duty ratio of a PWM signal, a PWM duty correction value maintaining time (t pwn ) during which the PWM duty correction value (”duty) is continuously applied, and a PWM duty correction frequency (n pwm ) at which the PWM duty correction value (”duty) is applied.