Nippondenso Co., Ltd.

Tokyo Gas Company Limited

Kazumi Ishida

Hiroshi Haraguchi

Toshio Kondo

Masakazu Hishinuma

Akio Fujiwara

An air fuel ratio controlling apparatus for an internal combustion engine, comprises: a catalytic converter, provided in an exhaust system for purifying an exhaust gas of the engine; a first oxygen density sensor, provided upstream from the catalytic converter in the exhaust system, responsive to a first oxygen density of a first exhaust gas of the engine for detecting whether an air fuel ratio of the engine is in a rich condition or a lean condition with respect to a theoretical air fuel ratio of the engine; a second oxygen density sensor, provided downstream from the catalytic converter in the exhaust system, responsive to a second oxygen density of a second exhaust gas passed through the catalytic converter for detecting whether the air fuel ratio of the engine is in a rich or a lean condition with respect to a theoretical air fuel ratio of the engine; and an air fuel ratio control portion for controlling the air fuel ratio in accordance with the detection results of the first and second oxygen sensors, wherein; the first oxygen sensor has a function for oxidizing and reducing a specific component more powerful than that of the second oxygen density sensor.

Air fuel ratio control apparatus for an internal combustion engine

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.

Air-fuel ratio control apparatus for engine

An air-fuel ratio control apparatus in which an air-fuel ratio of a mixture gas supplied to an engine, especially, a gas engine, is controlled in accordance with an output signal of each of oxygen concentration sensors disposed in upper and lower streams of an exhaust gas catalyzer of the engine. The output signal of the oxygen concentration sensor disposed on the upper stream side of the catalyzer is provided as one input signal of an air-fuel ratio control unit and the output signal of the oxygen concentration sensor disposed on the lower stream side of the catalyzer is provided as an input signal of an output signal correction amount determination unit, respectively. A mixing member for mixing an exhaust gas is disposed in an upper stream of each oxygen concentration sensor to detect the concentration of oxygen in the exhaust gas which is well mixed. The air-fuel ratio control unit controls an air-fuel ratio of a mixture gas in accordance with the output signal of the oxygen concentration sensor disposed on the upper stream side of the catalyzer and an output signal correction amount which is an output signal of the output signal correction amount determination unit. Since the exhaust gas is sufficiently mixed by the mixing member, variations of a measured value caused by the attachment position of each oxygen concentration sensor ar eliminated, thereby making it possible to control the air-fuel ratio of the mixture gas to a value close to a theoretical air-fuel ratio with a satisfactory precision.

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Aichi, Japan

Kazumi Ishida