초록 ▼

An apparatus and method are provided for detecting cylinder misfires in an internal combustion engine of a motor vehicle by digitally filtering out noise-related signals to improve the signal to noise ratio. Crankshaft rotation is sensed and crankshaft velocities are measured for each cylinder. Chan

An apparatus and method are provided for detecting cylinder misfires in an internal combustion engine of a motor vehicle by digitally filtering out noise-related signals to improve the signal to noise ratio. Crankshaft rotation is sensed and crankshaft velocities are measured for each cylinder. Changes in angular velocity are determined and correspond to each of a plurality of cylinder firing events. A window of consecutive changes in angular velocity are used with a digital filter. The digital filter contains filter coefficients which are determined from a frequency analysis for a given engine by distinguishing between actual misfire events and noise related event frequencies. From the analysis a cut off frequency between actual misfires and noise is determined which is then used to determine the filter coefficients. The digital filter generates a filter output for the current cylinder firing event and the filter output is preferably multiplied by a gain to provide a compensated filter output. The compensated filter output is compared to a threshold value and a misfire event is determined for the selected cylinder based on the comparison. A high pass filter may be employed to filter out low frequency noise-related signals such as those associated with a power train bobble. Similarly, a low pass filter can be used to filter out high frequency noise signals such as those associated with crankshaft torsional vibrations. Both high and low pass filters could be employed in the alternative by using a high pass filter at low engine speeds and a low pass at high engine speeds.

대표청구항 ▼

An apparatus for detecting misfire in individual cylinders of an internal combustion engine in a motor vehicle, comprising: means for sensing rotation of a crankshaft; measuring means connected to the sensing means for determining changes in angular velocity corresponding to each of a plurality of c

An apparatus for detecting misfire in individual cylinders of an internal combustion engine in a motor vehicle, comprising: means for sensing rotation of a crankshaft; measuring means connected to the sensing means for determining changes in angular velocity corresponding to each of a plurality of cylinder firings; frequency analysis means for analyzing a frequency response of the engine in a frequency domain and determining a cut-off frequency between misfire signals and noise related signals; digital filtering means for digitally filtering out noise related signals from the determined changes in angular velocity as a function of the cut-off frequency; and means for comparing an output of said digital filtering means with a threshold value to detect the occurrence of a misfire for a selected cylinder as a result of said comparison.