| 摘要 |
PROBLEM TO BE SOLVED: To reduce exhaust emission by improving the control precision of an air/fuel ratio. SOLUTION: A response time constant varying means 31 continuously varies a response time constantτof a control model simulating control objects ranging from a fuel injection valve to an air/fuel ratio sensor corresponding to an inlet air amount, and a control gain varying means 32 continuously varies a control gainωcorresponding to the response time constantτ. A control parameter calculating means 33 calculates a control parameter (a coefficient of a calculation expression for an air/fuel ratio correcting coefficient) using the response time constantτ, the control gainω, an arithmetic intervalΔt, and an attenuation coefficientζand an air/fuel ratio correcting coefficient calculating means 34 calculates a present air/fuel ratio correcting coefficient from the calculation expression of the air/fuel ratio correcting coefficient, using the control parameter and a drift between a target excess fuel factor (a target air/fuel ratio) and a detected excess fuel factor (a detected air/fuel ratio). Then, a fuel injection amount calculating means 35 finds a fuel injection amount after correcting a basic injection amount found depending on an engine operating condition with a present air/fuel ratio correcting coefficient.
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