Process for detecting a misfire in an internal combustion engine and system for carrying out said process
First Claim
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1. A method for detecting a misfire in one or more cylinders of an internal combustion engine, comprising the steps of:
- generating a sampled signal by sampling an exhaust gas pressure during at least one engine cycle at a sampling frequency proportional to rotational speed of a crankshaft;
analyzing said sampled signal in the frequency domain by means of a Fourier transform;
calculating a misfire index from said analysis;
comparing said index with at least one threshold value; and
identifying a misfire based on said comparison of said index with said at least one threshold value.
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Abstract
A process for detecting a misfire in one or more cylinders of an internal combustion engine, including sampling the exhaust gas pressure values during at least one engine cycle at a sampling frequency proportional to the crankshaft rotational speed, analyzing the sampled signal in the frequency domain, calculating a misfire index from the analysis, comparing the index with one or more threshold values, and identifying a misfire based on the comparison of the index with the threshold values.
46 Citations
14 Claims
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1. A method for detecting a misfire in one or more cylinders of an internal combustion engine, comprising the steps of:
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generating a sampled signal by sampling an exhaust gas pressure during at least one engine cycle at a sampling frequency proportional to rotational speed of a crankshaft;
analyzing said sampled signal in the frequency domain by means of a Fourier transform;
calculating a misfire index from said analysis;
comparing said index with at least one threshold value; and
identifying a misfire based on said comparison of said index with said at least one threshold value. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An apparatus for detecting a misfire in one or more cylinders of an internal combustion engine, comprising:
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at least one sensor for detecting a pressure in an exhaust pipe;
at least one sensor for detecting a rotation of a crankshaft;
said sensors being connected to at least one control unit, said control unit comprising;
means for producing a converted signal by performing analogue-to-digital conversion of a signal from said sensor for detecting exhaust pipe pressure;
means for producing a sampled signal by sampling said converted signal, wherein a sampling frequency is proportional to a rotational speed of the crankshaft;
memory means for storing said sampled signal; and
means for analyzing said sampled signal in the frequency domain by means of a Fourier transform, calculating a misfire index from said analysis, comprising said index with at least one threshold value, and identifying a misfire based on said comparison of said index with said at least one threshold value. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A car comprising an apparatus for detecting a misfire in one or more engine cylinders of an internal combustion engine, said apparatus comprising:
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at least one sensor for detecting a pressure in an exhaust pipe;
at least one sensor for detecting a rotation of a crankshaft;
said sensors being connected to at least one control unit, said control unit comprising;
means for producing a converted signal by performing analogue-to-digital conversion of a signal from said sensor for detecting exhaust pipe pressure;
means for producing a sampled signal by sampling said converted signal, wherein a sampling frequency is proportional to a rotational speed of the crankshaft;
memory means for storing said sampled signal; and
means for analyzing said sampled signal in the frequency domain by means of a Fourier transform, calculating a misfire index from said analysis, comparing said index with at least one threshold value, and identifying a misfire based on said comparison of said index with said at least one threshold value.
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Specification