Misfire detection in an internal combustion engine
First Claim
1. A method of detecting misfires of individual cylinder firings in a combustion engine, said method comprising the steps of:
- measuring engine acceleration corresponding to each of a plurality of cylinder firings during operation of said engine;
selecting one of said cylinder firings for detection;
determining an average acceleration over a series of said cylinder firings substantially centered on said selected cylinder firing;
determining deviation of acceleration of said selected cylinder firing from said average acceleration;
normalizing said deviation to a torque-related value coinciding with said selected cylinder firing;
comparing said normalized deviation with a predetermined threshold; and
detecting a misfire of said selected cylinder firing depending on the result of said comparing step.
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Accused Products
Abstract
A method and apparatus are provided for reliably detecting misfires in an internal combustion engine during actual driving conditions by monitoring fluctuations in engine speed between consecutive firing intervals. An average acceleration over a series of firing intervals is removed from an individual acceleration measurement corresponding to a particular firing interval to give an acceleration deviation which is then normalized to an expected torque to provide a power loss measurement. The power loss measurement indicates the occurrence of a misfire with a high signal-to-noise ratio. The information derived from misfire detection can be used to prevent destruction of a catalytic converter by unburned fuel mixtures and can be used to improve vehicle driveability by correcting for or indicating needed service for the vehicle. The misfire detection is implemented using existing sensors and processors and is adapted to be done on-board a vehicle in real time.
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Citations
26 Claims
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1. A method of detecting misfires of individual cylinder firings in a combustion engine, said method comprising the steps of:
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measuring engine acceleration corresponding to each of a plurality of cylinder firings during operation of said engine; selecting one of said cylinder firings for detection; determining an average acceleration over a series of said cylinder firings substantially centered on said selected cylinder firing; determining deviation of acceleration of said selected cylinder firing from said average acceleration; normalizing said deviation to a torque-related value coinciding with said selected cylinder firing; comparing said normalized deviation with a predetermined threshold; and detecting a misfire of said selected cylinder firing depending on the result of said comparing step. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. Apparatus for detecting misfires occurring during individual cylinder firings of a multi-cylinder combustion engine comprising:
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measuring means for measuring engine acceleration corresponding to each of a plurality of cylinder firings of each of said multiple cylinders during operation of said engine; averaging means coupled to said measuring means for determining an average acceleration over a series of said cylinder firings substantially centered on a selected one of said cylinder firings; deviation means coupled to said measuring means and said averaging means for determining deviation of acceleration of said selected cylinder firing from said average acceleration; torque means for determining an expected torque during each of said cylinder firings; normalizing means coupled to said torque means and to said deviation means for normalizing said deviation according to said expected torque during said selected cylinder firing; first comparing means coupled to said normalizing means for comparing said normalized deviation with a predetermined threshold, a misfire of said selected cylinder firing being detected depending on the result of said comparison. - View Dependent Claims (17, 18, 19)
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20. A method of detecting misfires of individual cylinder firings in a combustion engine, said method comprising the steps of:
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measuring engine acceleration corresponding to each of a plurality of cylinder firings during operation of said engine; selecting one of said cylinder firings for detection; determining an average acceleration over a series of said cylinder firings substantially centered on said selected cylinder firing; determining deviation of acceleration of said selected cylinder firing from said average acceleration; determining a torque-related value coinciding with said selected cylinder firing; and detecting a misfire of said selected cylinder firing in response to said deviation of acceleration and said torque-related value. - View Dependent Claims (21, 22)
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23. Apparatus for detecting misfires occurring during individual cylinder firings of a multi-cylinder combustion engine comprising:
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measuring means for measuring engine acceleration corresponding to each of a plurality of cylinder firings of each of said multiple cylinders during operation of said engine; averaging means coupled to said measuring means for determining an average acceleration over a series of said cylinder firings substantially centered on a selected one of said cylinder firings; deviation means coupled to said measuring means and said averaging means for determining deviation of acceleration of said selected cylinder firing from said average acceleration; torque means for determining an expected torque during each of said cylinder firings; and first comparing means coupled to said deviation means and said torque means for detecting a misfire of said selected cylinder firing by performing a first comparison in response to said deviation of acceleration and the expected torque corresponding to said selected cylinder firing. - View Dependent Claims (24, 25, 26)
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Specification