| 摘要 |
PROBLEM TO BE SOLVED: To provide a misfire judgment method of an internal combustion engine free to easily and inexpensively perform without using a pressure seating type pressure sensor and capable of carrying out misfier judgment high in precision and favorable in reproducibility. SOLUTION: Cylinder internal pressure of the internal combustion engine on which a spark plug is mounted is measured by the pressure sensor (seating type pressure sensor) provided on a mounting seat of the spark plug. First pressure measuring time is specified in a period before a top dead center in which a crank angle reaches the top dead center after an air intake valve is closed, a measured value of the cylinder internal pressure at the first pressure measuring time is specified as P1 , second pressure measuring time is specified in a period after the top dead center in which an exhaust valve opens after the crank angle reaches the top dead center, and the measured value of the cylinder internal pressure at the second pressure measuring time is specified as P2 . Additionally, corrective measuring time is set in the period before the top dead center and before ignition time, a cylinder internal pressure measuring value at the corrective measuring time is specified as a corrected pressure value P0 , and values which the corrected pressure value P0 is respectively deducted from the pressure measuring values P1 and P2 are specified as P1 ' and P2 '. Thereafter, the misfier judgment of the internal combustion engine is carried out in accordance with a ratio of these P1 ' to P2 '.
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