Misfire detection in internal combustion engines
AssigneeGeneral Motors Corporation
InventorsDaniel P. Grenn, Ronald J. Kubani
Life of this patent
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Abstract
Engine combustion malfunctions are detected and the responsible cylinder identified by an approach appropriate to the engine operating point by monitoring change in engine speed in a manner insensitive to engine output shaft tooth-to-tooth spacing variations, substantially linear changes in engine speed, and driveline ringing, such as from rough roads or a previously detected misfire. Multiple misfires may be detected in a single engine cycle.
Claims8
A method for diagnosing malfunctions in an internal combustion engine having n cylinders and having an output shaft with a predetermined set of reference points, comprising the steps of:
- measuring predetermined engine parameters indicative of an engine operating point;
- diagnosing malfunctions according to a first diagnostic method when the engine operating point is within a first predetermined region;
- diagnosing malfunctions according to a second diagnostic method when the engine operating point is within a second predetermined region, wherein the second diagnostic method comprises the steps of:
- calculating a first set of average speeds between a first predetermined set of adjacent reference points on the shaft;
- calculating a first set of average speed changes as the difference between the calculated first set of average speeds and a previous calculated set of average speeds between the first predetermined set of adjacent reference points on the shaft;
- comparing a predetermined function of the change in average speed to a predetermined average speed change threshold value;
- and
- indicating an engine malfunction when the predetermined function exceeds the average speed change threshold value.
A diagnostic system for an engine having n cylinders and an output shaft undergoing two complete revolutions for each engine cycle during which each of the cylinders undergoes a complete cylinder cycle, the system comprising:
- means for generating n/2 reference signals for each revolution of the output shaft, each reference signal being generated at a respective predetermined angular position of the output shaft so as to alternately represent a predetermined reference point in the cylinder cycle of each of two of the n cylinders;
- means for timing the duration between each of adjacent reference signals during rotation of the output shaft thereby providing a pair of timed durations between each consecutive predetermined angular positions of the output shaft during each engine cycle;
- means for determining a first difference between the timed duration in a first pair of timed durations;
- and
- means for indicating an engine malfunction when a predetermined function of the first difference exceeds a predetermined threshold.
An apparatus for indicating malfunctions in an internal combustion engine having n cylinders and having an output shaft with a predetermined set of reference points, comprising:
- means for calculating a first set of average speeds between a first predetermined set of adjacent reference points on the shaft;
- means for calculating a first set of average speed changes as the difference between the calculated first set of average speeds and a previous calculated set of average speeds between the first predetermined set of adjacent reference points on the shaft;
- means for comparing a predetermined function of the change in average speed to a predetermined average speed change threshold value;
- and
- means for indicating an engine malfunction when the predetermined function exceeds the average speed change threshold value.
Dependencies are inferred from the claim text.