Misfire detection in a spark ignition engine

#1. Field of the Invention

#The present invention relates generally to the detection of misfire in a spark ignition engine, and more particularly to the use of the ignition system in a spark ignition engine to detect the misfiring of the engine.

#2. Description of the Related Art

#Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.

#FIG. 1 is a graphical illustration of the secondary voltage rise and discharge of an ignition coil plotted against time;

#FIG. 2 is a graphical representation of a signal generated by a breakdown detector at the instant of the "breakdown" phase of a spark discharge;

#The present method of misfire detection disclosed herein is specifically explained in conjunction with the ignition system components described in U.S. Pat. No. 4,846,129, issued to Noble. Hereinafter, this patent will simply be referred to as the Noble patent. Reference to the Noble patent is not intended to imply that use of the present invention is strictly limited to implementation with the particular ignition components described therein. As one skilled in the art will appreciate, it is Applicants' belief that the present invention has broad applicability to a variety of ignition systems.

#The discussion which follows goes through the various steps and transfer functions which ultimately relate measurements of time-to-fire and breakdown voltage to the occurrence of misfire within a cylinder of an internal combustion engine. The determination of misfire according to this invention can be performed on an individual cylinder basis and over a wide range of rpm and load.

#Referring now to the drawings, FIG. 1 shows that an ignition coil has a predictable and repeatable secondary voltage rise characteristic (shown for both breakdown and non-breakdown situations). As illustrated by curve 10, the voltage at the secondary of the coil 58 increases with respect to time until the instant of breakdown discharge 12, whereupon it drops substantially, inducing a high current in the circuit and causing the formation of a spark across the gap of a spark plug 62. Curve 14, shown in dashed lines, represents the secondary voltage which would be observed absent any discharging event.