Misfire detecting apparatus for multicylinder internal combustion engines

A misfire detecting apparatus for a multi-cylinder internal combustion engine comprising:

• vehicle stop detecting means for detecting whether or not a vehicle is in a stopped state;
• rotary signal outputting means for outputting a rotary signal at every predetermined rotary angle in accordance with the rotation of a multicylinder internal combustion engine;
• tentative misfire deciding means for tentatively deciding, for each cylinder, whether or not misfire has occurred in said multicylinder internal combustion on the basis of the output signal form said rotary signal outputting means;
• counting means for counting, for each cylinder, the number of tentative misfires decided by said tentative misfire deciding means;
• counting result storage means for storing, for each cylinder, a counting result of said counting means;
• and
• real misfire deciding means for deciding, in a state where the vehicle is not in a stopped state and after a given number of tentative misfire decisions, that misfire has actually occurred only if the counting result, for a part of the cylinders, among the counting results for respective cylinders stored in said counting result storage means is larger than a first predetermined number, and for deciding, in a state where the vehicle is in a stopped state, that misfire has actually occurred if the counting result, for at least one cylinder, among the counting results for respective cylinders stored in said counting result storage means is larger than a second predetermined number.

A misfire detecting apparatus for an internal combustion engine comprising:

• rotary signal outputting means for outputting a rotary signal at every predetermined rotary angle in accordance with the rotation of an internal combustion engine;
• rotational speed change calculating means for detecting a rotational speed of said internal combustion engine on the basis of the rotary signal from said rotary signal outputting means and calculating changes of the rotational speed of said internal combustion engine;
• and
• misfire detecting means for deciding that misfire has occurred in said internal combustion engine, if a shape of the distribution of a plurality of calculation results obtained by said rotational speed change calculating means when said internal combustion engine rotates by a predetermined number of times of rotation is not a normal distribution shape.

A misfire, detecting apparatus for an internal combustion engine comprising:

• rotary signal outputting means for outputting a rotary signal at every predetermined rotary angle in accordance with the rotation of an internal combustion engine;
• rotational speed change calculating means for detecting a rotational speed of said internal combustion engine on the basis of the rotary signal from said rotary signal outputting means and calculating changes of the rotational speed of said internal combustion engine;
• index calculating means for calculating an index indicative of a degree of dispersion of a distribution shape of a plurality of calculation results obtained by said rotational speed change calculating means when said internal combustion engine rotates by a predetermined number of times of rotation;
• misfire decision reference value producing means for producing a misfire decision reference value on the basis of a calculation result of said index calculating means;
• and
• misfire deciding means for deciding whether or not misfire has occurred in said internal combustion engine by comparing the calculation results of said rotational speed change calculating means with the misfire decision reference value.