Passive and active misfire diagnosis for internal combustion engines
First Claim
1. A system for detecting a misfire condition in a cylinder of an internal combustion engine, comprising:
- a sensor operable to transmit a plurality of timing signals corresponding to the position of the engine driveshaft at the firing of each cylinder in a firing sequence for each engine cycle; and
an engine control module (ECM) receiving said timing signals and including;
a time processing unit operable to determine a firing time for each cylinder based on said plurality of timing signals;
means for determining a differential firing time parameter for each cylinder based upon the difference in firing time between each cylinder and the next prior cylinder in the firing sequence; and
means for comparing said differential firing time parameter for each cylinder to a passive test threshold value and identifying cylinders falling outside said passive test threshold value as misfiring cylinders.
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Accused Products
Abstract
A system and method for detecting a misfire condition for a cylinder of an internal combustion engine is based upon the firing times for each cylinder and a comparison of firing times between successive cylinders in the engine firing sequence. A differential firing time parameter represents the result of this comparison and is used a passive test to determine whether a particular cylinder is misfiring. Cylinders identified in the passive test are subjected to an active test in which the cylinder is overfueled by increasing amounts for each engine cycle after commencement of the active misfire test. The change in differential firing parameter for the identified resulting from the overfueling is compared to an active test threshold value indicative of an expected change for a healthy cylinder. A cylinder falling outside this active threshold value is determined to be a bad cylinder.
34 Citations
26 Claims
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1. A system for detecting a misfire condition in a cylinder of an internal combustion engine, comprising:
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a sensor operable to transmit a plurality of timing signals corresponding to the position of the engine driveshaft at the firing of each cylinder in a firing sequence for each engine cycle; and an engine control module (ECM) receiving said timing signals and including; a time processing unit operable to determine a firing time for each cylinder based on said plurality of timing signals; means for determining a differential firing time parameter for each cylinder based upon the difference in firing time between each cylinder and the next prior cylinder in the firing sequence; and means for comparing said differential firing time parameter for each cylinder to a passive test threshold value and identifying cylinders falling outside said passive test threshold value as misfiring cylinders. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A system for active detection of a misfire condition in a cylinder of an internal combustion engine, comprising:
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a fuel control module operable to control the amount of fuel supplied to each cylinder of the engine in response to a fuel control signal; a sensor operable to transmit a plurality of timing signals corresponding to the position of the engine driveshaft at the firing of each cylinder in a firing sequence for each engine cycle; and an engine control module (ECM) receiving said timing signals and including; means for providing said fuel control signal according to a predetermined engine control routine to provide a predetermined amount of fuel to each cylinder; a time processing unit operable to determine a firing time for each cylinder based on said plurality of timing signals; means for determining a differential firing time parameter for each cylinder based upon the difference in firing time between each cylinder and the next prior cylinder in the firing sequence over each engine cycle; means for modifying said fuel control signal to increase the fueling to an identified cylinder above said predetermined amount of fuel dictated by the engine control routine upon commencement of an active misfire test; means for determining a change in differential firing time parameter for said identified cylinder relative to a baseline differential firing time parameter obtained prior to commencement of the active misfire test, for each engine cycle after commencement of the active misfire test; and means within said ECM for comparing said change in differential firing time parameter to an active test threshold value and identifying cylinders falling outside said active test threshold value as bad cylinders. - View Dependent Claims (14, 15, 16, 17)
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18. A method for detecting a misfire condition in a cylinder of an internal combustion engine comprising the steps of:
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determining the firing time of each cylinder of the engine; comparing the firing time of each cylinder with the firing time of the next prior cylinder in the firing sequence to obtain a differential firing time parameter for each cylinder;
comparing the differential firing time parameter for each cylinder to a passive test threshold value; andidentifying cylinders falling outside the passive test threshold value as misfiring cylinders. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26)
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Specification