Misfire detection in an internal combustion engine

Apparatus for detecting misfires occurring during individual cylinder firings of a multi-cylinder combustion engine comprising:

• 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.

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;
• 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.

Apparatus for detecting misfires occurring during individual cylinder firings of a multi-cylinder combustion engine comprising:

• 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.