Air-fuel ratio control apparatus for engine

摘要

An air-fuel ratio feedback control apparatus for a gas engine. A mixer mixes intake air and a fuel gas. A subsidiary supply path supplies at least one of the intake air and the fuel gas downstream of the mixer. Oxygen concentration sensors detect a concentration of oxygen in an exhaust gas; and operation condition detectors detect operating conditions of the gas engine. A basic amount setting unit sets a basic amount of at least one of the intake air and the fuel gas supplied through the subsidiary supply path. A correction amount setting unit sets a correction amount proportional to a total fuel gas supply rate, and a control amount setting unit for setting a control amount of at least one of the intake air and the fuel gas supplied through the subsidiary supply path by adding the basic amount and the correction amount together, whereby the air-fuel ratio of the gas engine can be controlled at a desired value even when a bypass supply ratio of the fuel gas varies.