Method of diagnosing a mechanism for improving combustion in an internal combustion engine and apparatus therefor

An apparatus for diagnosing a mixture leaning mechanism for improving combustion in an internal combustion engine, said mixture leaning mechanism including an operation unit operated by an actuator and controlling the supply of a combustion component into the internal combustion engine by means of said operation unit, said apparatus comprising:

• stability detecting means for detecting stability of an engine;
• air-to-fuel ratio increasing means for gradually increasing an air-to-fuel ratio of the combustion mixture gas under a condition where combustibility is to be improved by said mixture leaning mechanism, until the stability of the engine detected by said stability detecting means reaches a previously set allowable limit;
• and
• malfunction diagnosing means for outputting a fault diagnosis signal indicating the occurrence of malfunction in said mixture leaning mechanism when the air-to-fuel ratio is equal to or smaller than a reference air-to-fuel ratio at a moment when the stability of the engine has reached the allowable limit as a result of increasing the air-to-fuel ratio by said air-to-fuel ratio increasing means.

An apparatus for diagnosing a mixture leaning mechanism in an internal combustion engine, comprising:

• an assist air feeding mechanism incorporating a valve for opening and closing a supply passage for an assist air, for bringing fuel injected from a fuel injection valve into collision with a portion of intake air as the assist air to atomize the fuel;
• stability detecting means for detecting stability of an engine;
• air-to-fuel ratio increasing means for gradually increasing an air-to-fuel ratio of the combustion mixture gas under a condition where said valve is controlled to open and the assist air is supplied, until the stability of the engine detected by said stability detecting means reaches a previously set allowable limit;
• and
• malfunction diagnosing means for outputting a fault diagnosis signal indicating occurrence of a malfunction in said assist air feeding mechanism when, at a moment when the stability of the engine has reached the allowable limit, the air-to-fuel ratio obtained by said air-to-fuel increasing means is equal to or smaller than a reference air-to-fuel ratio expected under a condition where the assist air is normally supplied.

An apparatus for diagnosing a mixture leaning mechanism in an internal combustion engine, comprising:

• an intake air control mechanism including an intake air control valve which opens and closes an intake system so as to swirl a mixture gas and to homogenize the mixture gas;
• stability detecting means for detecting stability of an engine;
• air-to-fuel ratio increasing means for gradually increasing an air-to-fuel ratio of the combustion mixture gas under a condition where the intake air control valve is controlled to close so as to swirl the mixture gas until the stability of the engine detected by said stability detecting means reaches a previously set allowable limit;
• and
• malfunction diagnosing means for outputting a fault diagnosis signal indicating occurrence of a malfunction in said intake air control mechanism when, at a moment when the stability of the engine has reached the allowable limit, the air-to-fuel ratio is equal to or smaller than a reference air-to-fuel ratio expected under a condition where the mixture gas is normally swirled by said intake air control valve.

An method for diagnosing a mixture leaning mechanism in an internal combustion engine, the mixture leaning mechanism including an assist air feeding mechanism incorporating a valve for opening and closing a supply passage for an assist air, for bringing fuel injected from a fuel injection valve into collision with a portion of intake air as the assist air to atomize the fuel, comprising the steps of:

• detecting stability of an engine;
• gradually increasing an air-to-fuel ratio of the combustion mixture gas under a condition where said valve of said assist air feeding mechanism is controlled to open and the assist air is supplied,
• continuing said step of gradually increasing until the detected stability of the engine reaches a previously set allowable limit;
• and
• outputting a fault diagnosis signal indicating occurrence of a malfunction in said assist air feeding mechanism when, at a moment when the detected stability of the engine has reached the allowable limit, the air-to-fuel ratio obtained by said air-to-fuel increasing means is equal to or smaller than a reference air-to-fuel ratio expected under a condition where the assist air is normally supplied.

A method for diagnosing a mixture leaning mechanism in an internal combustion engine, the mixture leaning mechanism including an intake air control mechanism having an intake air control valve which opens and closes an intake system so as to swirl a mixture gas and to homogenize the mixture gas, comprising the steps of:

• detecting stability of an engine;
• gradually increasing an air-to-fuel ratio of the combustion mixture gas under a condition where the intake air control valve is controlled to close so as to swirl the mixture gas,
• continuing said step of gradually increasing until the detected stability of the engine reaches a previously set allowable limit;
• and
• outputting a fault diagnosis signal indicating occurrence of a malfunction in said intake air control mechanism when, at a moment when the detected stability of the engine has reached the allowable limit, the air-to-fuel ratio is equal to or smaller than a reference air-to-fuel ratio expected under a condition where the mixture gas is normally swirled by said intake air control valve.