Measuring and testing – Vehicle drive train – Rear end
Patent
1995-08-11
1997-07-15
Chilcot, Richard
Measuring and testing
Vehicle drive train
Rear end
G01M 1500
Patent
active
056486022
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a misfire detection apparatus for an internal combustion engine.
BACKGROUND ART
Heretofore known internal combustion engine misfire detection apparatus, detect cylinder pressure with a cylinder pressure sensor and integrate the detected value over a predetermined interval to obtain the indicated mean effective pressure. This is then compared with a predetermined misfire level, and when equal to or below the predetermined misfire level, misfire is judged and a warning generated.
With such misfire detection apparatus however, since the misfire level is fixed, changes with time (due for example to sensor deterioration or a drop in compression ratio due to cylinder leakage and the like) cannot be allowed for, so that the occurrence of erroneous output becomes a problem, particularly in ranges such as at low load where the noise/signal ratio level is high.
In view of the above problem with the conventional technology, it is an object of the present invention to improve detection accuracy by allowing for changes with time.
DISCLOSURE OF THE INVENTION
Accordingly with the present invention, there is provided a misfire detection apparatus for an internal combustion engine comprising: a cylinder pressure detection device for detecting engine cylinder pressures, an indicated mean effective pressure computing device for computing indicated mean effective pressures by integrating the detected cylinder pressures, and a misfire judgment device for judging misfire by comparing the computed indicated mean effective pressures with a misfire level, is constructed as follows so as to appropriately set misfire levels used for judgment in the misfire judgment means.
That is to say there is provided: a rewritable misfire level storage device in which is stored misfire levels of indicated mean effective pressure for different engine operating conditions, an engine operating conditions detection device for detecting engine operating conditions, a fuel cut-off detection device for detecting whether or not fuel to the engine is being cut-off, a misfire level learning device for updating, during fuel cut-off, misfire levels corresponding to an actual engine operating condition, based on the indicated mean effective pressures computed by the indicated mean effective pressure computing device, and rewriting the stored values in the storage device, and a misfire level retrieval device for retrieving a misfire level corresponding to an actual engine operating condition from the storage device and supplying this to the misfire judgment device.
With such a construction, the indicated mean effective pressures are computed by the indicated mean effective pressure computing device when the fuel to the engine is being cut off, to thus make these to be the misfire indicated mean effective pressures, and the misfire levels corresponding to the actual engine operating condition then updated based on these indicated mean effective pressures. The misfire levels which provide the reference for misfire judgment can thus be kept appropriate, enabling an improvement in detection accuracy.
Here the engine rotational speed can be used as an engine operating conditions parameter, and misfire levels of indicated mean effective pressure for different engine rotational speeds stored in the misfire level storage means.
Moreover, a misfire judgment inhibit device may be provided for inhibiting misfire judgment by the misfire judgment device during fuel cut-off. In this case, erroneous judgment during fuel cut-off can be prevented.
A warning device may also be provided for generating a warning based on the judgment results of the misfire judgment device.
Other characteristic constructions, and functions and effects resulting from these, will become more apparent from the following description of the embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS.
FIG. 1 is a functional block diagram showing a construction of the present invention;
FIG. 2 is a system diagram showing an embodiment of the present invention
REFERENCES:
patent: 5105657 (1992-04-01), Nakaniwa
patent: 5127262 (1992-07-01), Demizu et al.
patent: 5263453 (1993-11-01), Wakahara et al.
patent: 5307671 (1994-05-01), Akase
patent: 5442954 (1995-08-01), Fukui et al.
patent: 5469735 (1995-11-01), Watanabe
patent: 5505077 (1996-04-01), Fukui et al.
Hoshina Atsumi
Watanabe Satoru
Chilcot Richard
McCall Eric S.
Unisia Jecs Corporation
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