US 5,862,505 A · Misfire discriminating method and apparatus for an engine

Abstract

A rotational difference between the speed corresponding to a cylinder at a combustion stroke and the speed corresponding to the cylinder at a previous combustion is calculated. Then, a corrected value is derived from averaging all the rotational differences up to the present combustion stroke. A corrected rotational difference is calculated by subtracting the corrected value from the rotational difference. The misfire judgment level is calculated and set with an interpolated calculation by referring to the map that has the parameters of engine speed and fuel injection pulse width. The level is then compared with the corrected rotational difference. If the corrected rotational difference is larger than the misfire judgement level, and if the corrected rotational difference at the previous combustion stroke is smaller than the level that has a minus value, it can be accurately judged that the cylinder at the previous combustion stroke is in a condition of misfire.

Claims34

Dependent claims

Misfire discriminating method for an engine, comprising:

detecting a first engine speed during a combustion stroke of a first cylinder;
detecting a second engine speed during a combustion stroke of a second cylinder previous to the combustion stroke of the first cylinder;
calculating a rotational difference corresponding to the first cylinder by subtracting the second engine speed from the first engine speed;
computing a corrected rotational difference corresponding to the first cylinder by subtracting a present rotational difference correction value corresponding to the first cylinder from the rotational difference corresponding to the first cylinder;
determining a rotational difference change corresponding to the first cylinder by subtracting a corrected rotational difference corresponding to the second cylinder from the corrected rotational difference corresponding to the first cylinder;
and
judging a misfire condition for the combustion stroke of the second cylinder when
the rotational difference change corresponding to the first cylinder is equal to or larger than a first predetermined misfire level and
a rotational difference change corresponding to the second cylinder is equal to or smaller than a second predetermined misfire level.

6 more elements

Misfire discriminating method for an engine, comprising:

detecting a first engine speed during a combustion stroke of a first cylinder;
detecting a second engine speed during a combustion stroke of a second cylinder previous to the combustion stroke of the first cylinder;
calculating a rotational difference corresponding to the first cylinder by subtracting the second engine speed from the first engine speed;
computing a corrected rotational difference corresponding to the first cylinder by subtracting a present rotational difference weighed average value corresponding to the first cylinder from the rotational difference corresponding to the first cylinder;
and
judging a misfire condition for the combustion stroke of the first cylinder when the corrected rotational difference is smaller than a negative value of a predetermined misfire level.

3 more elements

Misfire discriminating method for an engine, comprising:

detecting a first engine speed during a combustion stroke of a first cylinder;
detecting a second engine speed during a combustion stroke of a second cylinder previous to the combustion stroke of the first cylinder;
calculating a rotational difference corresponding to the first cylinder by subtracting the second engine speed from the first engine speed;
computing a corrected rotational difference corresponding to the first cylinder by subtracting a present rotational difference correction value corresponding to the first cylinder from the rotational difference corresponding to the first cylinder;
determining a rotational difference change corresponding to the first cylinder by subtracting a corrected rotational difference corresponding to the second cylinder from the corrected rotational difference corresponding to the first cylinder;
deciding a continuation of a misfire condition when the rotational difference change corresponding to the first cylinder is larger than a first predetermined misfire level and a rotational difference change corresponding to the second cylinder is equal to or smaller than a second predetermined misfire level;
and
deciding a finish of said misfire condition when the rotational difference change corresponding to the second cylinder is larger than the first predetermined misfire level.

5 more elements

A misfire discriminating apparatus for an engine having cylinders, comprising:

first sensing means for sensing a first engine speed during a combustion stroke of a first cylinder;
second sensing means for sensing a second engine speed during a combustion stroke of a second cylinder previous to the combustion stroke of the first cylinder;
calculating means for calculating a rotational difference corresponding to the first cylinder by subtracting the second engine speed from the first engine speed;
correcting means for correcting the rotational difference corresponding to the first cylinder by subtracting a present rotational difference correction value corresponding to the first cylinder from the rotational difference corresponding to the first cylinder to obtain a corrected rotational difference corresponding to the first cylinder;
determining means for determining a rotational difference change corresponding to the first cylinder by subtracting a corrected rotational difference corresponding to the second cylinder from the corrected rotational difference corresponding to the first cylinder;
and
misfire judging means for judging a misfire condition for the combustion stroke of the second cylinder when
the rotational difference change corresponding to the first cylinder is larger than a first predetermined misfire level and
a rotational difference corresponding to the second cylinder change is smaller than a second predetermined misfire level.

6 more elements

A misfire discriminating apparatus for an engine having cylinders, comprising:

first sensing means for sensing a first engine speed during a combustion stroke of a first cylinder;
second sensing means for sensing a second engine speed during a combustion stroke of a second cylinder previous to the combustion stroke of the first cylinder;
calculating means for calculating a rotational difference corresponding to the first cylinder by subtracting the second engine speed from the first engine speed;
correcting means for correcting the rotational difference corresponding to the first cylinder by subtracting a present rotational difference weighed average value corresponding to the first cylinder from the rotational difference corresponding to the first cylinder;
and
misfire judging means for judging a misfire condition for the combustion stroke of the first cylinder when the corrected rotational difference corresponding to the first cylinder is smaller than a negative value of a predetermined misfire level.

3 more elements

A misfire discriminating apparatus for an engine having cylinders, comprising:

first sensing means for sensing a first engine speed during a combustion stroke of a first cylinder;
second sensing means for sensing a second engine speed during a combustion stroke of a second cylinder previous to the combustion stroke of the first cylinder;
calculating means for calculating a rotational difference corresponding to the first cylinder by subtracting the second engine speed from the first engine speed;
correcting means for correcting the rotational difference corresponding to the first cylinder by subtracting a present rotational difference correction value corresponding to the first cylinder from the rotational difference corresponding to the first cylinder to obtain a corrected rotational difference corresponding to the first cylinder;
determining means for determining a rotational difference change corresponding to the first cylinder by subtracting a corrected rotational difference corresponding to the second cylinder from the corrected rotational difference corresponding to the first cylinder;
and
misfire judging means for judging
a continuation of a misfire condition when the rotational difference change corresponding to the first cylinder is larger than a first predetermined misfire level and a rotational difference change corresponding to the second cylinder is equal to or smaller than a second predetermined misfire level, and
a finish of the misfire condition when the rotational difference change corresponding to the second cylinder is larger than the first predetermined misfire level.

6 more elements

Dependencies are inferred from the claim text.

Misfire discriminating method and apparatus for an engine

Life of this patent

Misfire discriminating method and apparatus for an engine

Life of this patent

Abstract

Claims34