Combustion state determination method of internal combustion engine, as well as combustion state control method and combustion state control system for internal combustion engine

A method for a control of a state of combustion in an internal combustion engine, comprising:

• detecting a variance value in angular acceleration of a rotating shaft driven by said internal combustion engine;
• normalizing said variance value in accordance with a state of operation of said internal combustion engine to obtain a normalized variance value;
• comparing said normalized variance value with a first threshold to set a deteriorated combustion determining value;
• comparing said deteriorated combustion determining value with a predetermined reference value and controlling a combustion variance adjusting element of said internal combustion engine so that said deteriorated combustion determining value approaches toward said reference value;
• and
• comparing said normalized variance value with a second threshold to detect a misfire, said second threshold being set on a more combustion-deteriorated side than said first threshold.

A system for a control of a state of combustion in an internal combustion engine operable at an air/fuel ratio leaner than a stoichiometric air/fuel ratio, comprising:

• variance detecting means for detecting a variance value in an angular acceleration of a rotating shaft driven by said internal combustion engine;
• normalized variance value determining means for normalizing said variance value, which has been detected by said variance detecting means, in accordance with a state of operation of said internal combustion engine to determine a normalized variance value;
• deteriorated combustion determining value calculating means for comparing said normalized variance value with a first threshold to obtain a deteriorated combustion determining value;
• combustion state controlling means for referring to said deteriorated combustion determining value, comparing the same with a predetermined reference value and controlling a combustion variance adjusting element of said internal combustion engine so that said deteriorated combustion determining value approaches toward said reference value;
• and
• misfire determining means for comparing said normalized variance value with a second threshold to detect a misfire, said second threshold being set on a more combustion-deteriorated side than said first threshold.

A system for a control of a state of combustion in an internal combustion engine operable at an air/fuel ratio leaner than a stoichiometric air/fuel ratio, comprising:

• variance detecting means for detecting a variance value in an angular acceleration of a rotating shaft driven by said internal combustion engine;
• normalized variance value determining means for normalizing said variance value, which has been detected by said variance detecting means, in accordance with a state of operation of said internal combustion engine to determine a normalized variance value;
• combustion state controlling means for performing leaning control of said air/fuel ratio on the basis of said normalized variance value;
• rough road determining means for comparing said normalized variance value with a predetermined rough road determining threshold to determine rough road running;
• and
• leaning control limiting means for limiting said leaning control of said air/fuel ratio at said combustion state control means on the basis of the results of the determination by said rough road determining means.

A method for a control of combustion in a multicylinder internal combustion engine, said method including detecting, with respect to each cylinder, a revolution variance occurred upon operation of said internal combustion engine at an air/fuel ratio on a side leaner than a stoichiometric air/fuel ratio and permitting operation of said internal combustion engine in the vicinity of a lean-burn limit on the basis of the results of said detection, comprising:

• changing a fuel injection quantity so that a combustion variance determined from said revolution variance upon lean-burn operation can be held within a permissible range;
• detecting variations in intercylinder air/fuel ratio from the quantity of the change of said fuel injection quantity;
• and
• correcting, based on the results of said detection, an injector drive time upon operation at said stoichiometric air/fuel ratio.

A system for a control of a state of combustion in a multicylinder internal combustion engine, comprising:

• revolution variance detecting means for detecting, with respect to each cylinder, a revolution variance occurred when said internal combustion engine is operated at an air/fuel ratio on a side leaner than a stoichiometric air/fuel ratio;
• lean-burn limit operation means for operating said internal combustion engine in the vicinity of a lean-burn limit on the basis of the results of the detection by said revolution variance detecting means;
• fuel injection quantity change means for changing a fuel injection quantity so that a combustion variance determined from said revolution variance upon lean-burn operation by said lean-burn limit operation means can be held within a permissible range;
• intercylinder air/fuel ratio variation detecting means for detecting variations in intercylinder air/fuel ratio from the quantity of the change by said fuel injection quantity changing means;
• and
• injector drive correction means for correcting, based on the results of the detection by said intercylinder air/fuel ratio variation detecting means, an injector drive time upon operation at said stoichiometric air/fuel ratio.

A method for a determination of a state of combustion in an internal combustion engine, comprising:

• detecting a variance value in angular acceleration of a rotating shaft driven by said internal combustion engine;
• normalizing said variance value in accordance with a state of operation of said internal combustion engine to obtain a normalized variance value;
• comparing said normalized variance value with a predetermined threshold to set a deteriorated combustion determining value;
• and
• controlling a combustion variance adjusting element of said internal combustion engine so that said deteriorated combustion determining value falls between a predetermined upper limit reference value and a predetermined lower limit reference value.

A method for a determination of a state of combustion in an internal combustion engine, comprising:

• detecting a variance value in angular acceleration of a rotating shaft driven by said internal combustion engine;
• normalizing said variance value in accordance with a state of operation of said internal combustion engine to obtain a normalized variance value;
• comparing said normalized variance value with a predetermined threshold to set a deteriorated combustion determining value, said deteriorated combustion determining value being obtained by cumulating deterioration quantities of combustions in each of which said normalized variance value is smaller than said predetermined threshold;
• and
• comparing said deteriorated combustion determining value with a predetermined reference value and controlling a combustion variance adjusting element of said internal combustion engine so that said deteriorated combustion determining value approaches toward said reference value.

A method for a determination of a state of combustion in an internal combustion engine, comprising:

• detecting a variance value in angular acceleration of a rotating shaft driven by said internal combustion engine;
• normalizing said variance value in accordance with a state of operation of said internal combustion engine to obtain a normalized variance value;
• comparing said normalized variance value with a predetermined threshold to set a deteriorated combustion determining value, said deteriorated combustion determining value being updated every preset number of combustions;
• and
• comparing said deteriorated combustion determining value with a predetermined reference value and controlling a combustion variance adjusting element of said internal combustion engine so that said deteriorated combustion determining value approaches toward said reference value.