Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
2001-07-17
2003-12-02
Vo, Hieu T. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C073S117020, C123S406240, C123S406140
Reexamination Certificate
active
06658346
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
The present invention is related to Japanese patent application No. 2000-235903, Aug. 3, 2000; the contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to a misfire detection apparatus for an internal combustion engine, and more particularly, for a misfire detection apparatus that detects a misfire which occurs in an engine.
DESCRIPTION OF RELATED ART
Conventionally, as a known technique of detecting an engine misfire, Japanese Patent No. 2982381 discloses performing misfire determination in a four-cylinder internal combustion engine based on a rotational speed deviation (first variation amount) between two cylinders where expansion strokes are successively made and a rotational speed deviation (second variation amount) between two cylinders 360° CA (crank angle) ahead where expansion strokes are successively made (hereinbelow referred to as a 360° CA difference calculation).
Further, another known technique of detecting a misfire similarly from two variation amounts is performing misfire determination based on a rotational speed deviation (first variation amount) between two cylinders where expansion strokes are successively made and a rotational speed deviation (second variation amount) between two cylinders 720° CA ahead where successive expansion strokes are successively made (hereinbelow referred to as a 720° CA difference calculation).
However, in the 360° CA difference calculation, where a misfire occurs in a misfire determination subject cylinder and in a cylinder 360° CA ahead of the subject cylinder, the rotational variation which appears in the first variation amount due to the misfire is cancelled by the second variation amount. Therefore, the misfire cannot be detected. Similarly, in the 720° CA difference calculation, when a misfire continuously occurs in a particular same cylinder, the rotational variation due to the misfire is cancelled, and the misfire cannot be detected.
As a technique to detect such specific pattern misfire, the present inventors have proposed a technique disclosed in JP-A No. Hei 10-54295. The technique is, in an eight-cylinder internal combustion engine, calculating a rotational variation amount by cylinder for two cylinders where expansion strokes are successively made as a first variation amount, calculating a deviation between a current rotational speed and a previous rotational speed of the same cylinder as a rotational variation amount, calculating a second variation amount by dividing the rotational variation amount by the number of cylinders, and performing misfire determination based on a deviation between the first and second variation amounts.
However, in any of the above conventional techniques, as a so-called difference calculation is used for performing misfire determination based on the first variation amount and the second variation amount, where the rate of increase in the rotational speed is high at the beginning and then becomes lower upon engine start, such as during abrupt acceleration or the like, there is a possibility of erroneous determination of misfire.
For example, for misfire detection by the 360° CA difference calculation in a six-cylinder internal combustion engine, the first variation amount is “&ohgr;
n-1
−&ohgr;
n
”, and the second variation amount by the 360° CA difference calculation is “&ohgr;
n-4
−&ohgr;
n-3
”, as shown in FIG.
4
. Note that &ohgr;
n
represents a current rotational speed of misfire determination subject cylinder n, and &ohgr;
n-i
, the i-times previous rotational speed of the misfire determination subject cylinder n.
As in the engine start time, in a running state where the rate of increase in the engine rotational speed is high at the beginning and then becomes lower, as the second variation amount “&ohgr;
n-4
−&ohgr;
n-3
” becomes greater than the first variation amount “&ohgr;
n-1
−&ohgr;
n
”, the difference between the first variation amount and the second variation amount (hereinbelow referred to as a final variation amount &Dgr;&ohgr;) is large.
The problem also occurs in the second variation amount in the 720° CA difference calculation and the second variation amount in other difference calculations.
Accordingly, in a running state where the change rate of rotational speed is high at the beginning and then becomes lower as shown in
FIG. 5
, the final variation amount &Dgr;&ohgr; becomes large by the influence of the second variation amount. For this reason, in the above conventional techniques, there is a possibility that the final variation amount &Dgr;&ohgr; exceeds a misfire determination level (A in FIG.
5
), and erroneous determination of misfire may be made even though a misfire has not actually occurred.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and provides a misfire detection apparatus for an internal combustion engine which does not erroneously detect misfire even in a running state where the rate of increase in the engine rotational speed is high at the beginning and then becomes lower upon engine start, abrupt acceleration or the like.
In a first aspect, a misfire detection apparatus for an internal combustion engine is provided that comprises a rotational angle signal output means for outputting a rotational angle signal at a predetermined rotational angle in accordance with rotation of an output shaft of a multiple cylinder internal combustion engine; rotational speed calculation means for calculating a rotational speed of the output shaft of the internal combustion engine in each cylinder, based on the rotational angle signal output from the rotational angle signal output means; first variation amount calculation means for calculating the rotational speed between two cylinders where expansion strokes are successively made, by using the rotational speed calculation means, and calculating a first variation amount based on the rotational speed between the two cylinders; second variation amount calculation means for calculating the rotational speed between two cylinders of the internal combustion engine by using the rotational speed calculation means, and calculating a second variation amount based on the rotational speed between the two cylinders; first misfire determination means for performing misfire determination based on the first variation amount and the second variation amount; and second misfire determination means for performing misfire determination based on the first variation amount, wherein in a running state with a possibility of erroneous misfire detection due to the second variation amount, the second misfire determination means performs misfire determination.
In this arrangement, in the running state with a possibility of erroneous misfire detection due to the second variation amount, as the second misfire determination means performs misfire determination based on the first variation amount, even in a running state where the rate of increase in rotational speed of the internal combustion engine is high at the beginning and then becomes lower, misfire determination can be performed without influence of the second variation amount, thereby erroneous misfire detection can be prevented.
Note that in the present invention, the first variation amount includes a deviation of rotational speed between successive cylinders, a ratio of rotational speed between the successive cylinder, a deviation of time required for predetermined rotation between the successive cylinders, and a ratio of time required for predetermined rotation between the successive cylinders.
Further, in the present invention, the second variation amount includes a deviation of rotational speed between two cylinders, a ratio of rotational speed between the two cylinders, a deviation of time required for predetermined rotation between the two cylinders, and a ratio of time required for predetermined rotation between the two cylinders.
In another aspect, the second variation amount calculation means calculates the
Denso Corporation
Nixon & Vanderhye P.C.
Vo Hieu T.
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