Idle speed control apparatus for internal combustion engine

Claim 1

Apparatus for controlling an internal combustion engine equipped with one or more fuel injection valves, comprising: (a) a throttle actuator for adjusting opening degree of a throttle valve disposed in an intake pipe of said engine; (b) engine speed detecting means for producing a first signal indicative of the rotational speed of said engine; (c) intake air quantity detecting means for producing a second signal indicative of the intake air quantity sucked by said engine; and (d) an electronic control means responsive to said first and second signals for producing and supplying fuel injection valve drive signals to said fuel injection valves and for producing and supplying throttle actuator drive signal to said throttle actuator, said electronic control means having a target idle speed setting unit, said electronic control means also having: (i) a target intake air quantity setting unit for determining a target intake air quantity corresponding to minimum fuel amount with which the rotational speed of said engine can be maintained at said target idle speed, on the basis of fuel injection amount-intake air quantity correlation pattern which is predetermined in accord with said target idle speed; and (ii) an integral-added optimal regulator for determining feedback amounts respectively in connection with the amount of fuel to be injected and the opening degree of said throttle valve in receipt of said target idle speed and said target intake air quantity on the basis of predetermined operating formulas used for estimating the internal state of said engine which formulas are determined in accordance with a dynamic model of the system relating to the operation of said engine, and an optimal feedback gain, and for outputting said fuel injection valve drive signals and said throttle actuator drive signals which are produced acccording to said feedback amounts thus determined.