Method of and system for detecting misfire in internal combustion engine
First Claim
1. A method of detecting misfiring condition of a spark-ignition internal combustion engine, comprising sensing the exhaust noises of the engine and producing a continuous signal wave having an exhaust-noise frequency variable as a function of and in correspondence with the detected exhaust noises, the signal wave having a frequency spectrum having peak values one of which appears at a fundamental frequency component of the wave irrespective of firing conditions in the engine and the others of which appear at certain fractional harmonics of the fundamental frequency component when a misfire takes place in the engine, detecting the output speed of the engine and producing an engine-speed signal variable with the detected engine output speed, and analyzing said signal wave with respect to the fundamental frequency component of the wave and said fractional harmonics on the basis of said engine-speed signal for detecting existence of a misfiring condition, if any, of the engine from the relationship between the respective spectrum amplitudes of the frequency spectrum of the signal wave at the fundamental frequency component and the fractional harmonics thereof.
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Abstract
A method of and a system for detecting a misfire caused in a spark-ignition internal combustion engine, characterized by producing a signal wave having a frequency variable with the frequency of exhaust noises of the engine and a signal variable with the output speed of the engine and analyzing the frequency characteristics of the signal wave on the basis of the signal representative of the engine output speed.
39 Citations
12 Claims
- 1. A method of detecting misfiring condition of a spark-ignition internal combustion engine, comprising sensing the exhaust noises of the engine and producing a continuous signal wave having an exhaust-noise frequency variable as a function of and in correspondence with the detected exhaust noises, the signal wave having a frequency spectrum having peak values one of which appears at a fundamental frequency component of the wave irrespective of firing conditions in the engine and the others of which appear at certain fractional harmonics of the fundamental frequency component when a misfire takes place in the engine, detecting the output speed of the engine and producing an engine-speed signal variable with the detected engine output speed, and analyzing said signal wave with respect to the fundamental frequency component of the wave and said fractional harmonics on the basis of said engine-speed signal for detecting existence of a misfiring condition, if any, of the engine from the relationship between the respective spectrum amplitudes of the frequency spectrum of the signal wave at the fundamental frequency component and the fractional harmonics thereof.
- 7. A misfire detecting system for a spark-ignition internal combustion engine, comprising an electroacoustic transducer for sensing the exhaust noises of the engine and producing a continuous signal wave having an exhaust-noise frequency which varies with the detected exhaust noises, the signal wave having a frequency spectrum having peak values one of which appears at a fundamental frequency component of the wave irrespective of firing conditions in the engine and the other of which appears at certain fractional harmonics of the fundamental frequency component when a misfire takes place in the engine, engine-speed detecting means for detecting the output speed of the engine and producing an engine-speed signal which is variable with the detected output speed of the engine, and frequency analyzing means for analyzing said signal wave with respect to the fundamental frequency component of the wave and said fractional harmonics thereof on the basis of said engine-speed signal for thereby detecting misfiring conditions, if any, of the engine from the relationship between the respective amplitudes of the frequency spectrum of the signal wave at said fundamental frequency component and said fractional harmonics.
Specification