Misfire detection in internal combustion engines
First Claim
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1. 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.
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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.
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Citations
8 Claims
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1. 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:
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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. - View Dependent Claims (2, 3)
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4. 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:
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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. - View Dependent Claims (5)
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6. 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:
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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. - View Dependent Claims (7, 8)
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Specification