Method of controlling air fuel ratio of engine

Abstract

Abstract PURPOSE:To avoid the thermal damage of a supercharger provided for an engine, by supplying the engine with a mixture whose air fuel ratio is lower than the theoretical one, when the engine is being run under heavy load higher than a prescribed level and the temperature of exhaust gas threatens to reach a critical level. CONSTITUTION:In the operation of an engine, a controller 50 calculates a fuel injection time on the basis of the output signals of an air flow meter 19, a rotation angle sensor 45, an intake air temperature sensor 41, a water temperature sensor 42 and an oxygen sensor 44 and then judges whether or not the ratio of the quantity Q of intake air to the rotational frequency N of the engine is larger than a prescribed value A. When the ratio Q/N is larger than the prescribed value A, namely, the temperature of exhaust gas threatens to reach a critical level, the controller 50 proceeds to a step to judge whether or not a throttle valve 16 is fully open. When the throttle valve 16 is judged to be fully open, the quantity of fuel is increased after the lapse of a prescribed time. When the throttle valve 16 is not judged to be fully open, the quantity of fuel is increased after the lapse of another longer prescribed time. As a result, the engine is supplied with a mixture whose air fuel ratio is smaller than the theoretical one.

Inventors

• 👤 Yoshiyasu Ito
• 👤 嘉康 伊藤
• 👤 Yuji Takeda
• 👤 武田　勇二
• 👤 Toshio Suematsu
• 👤 末松　敏男

Bibliographic Details