MISFIRE DETECTOR FOR ENGINE

PURPOSE:To detect the state of an misfire quickly and accurately with a simple construction, by using a decision circuit to determine the condition under which the cylinder internal pressure at the position ahead of upper dead point in the compression by a specified crank angle and that at the position behind it by the same angle therefrom are almost equal. CONSTITUTION:A specified crank angle alpha1 corresponding to a through hole 13 on a disc 15 and a specified angle alpha2 corresponding to a through hole 14 are set at the positions a specified angle beta ahead of the dead point in compression and the same angle behind it respectively. Especially, when the crank angle alpha2 is set near the crank angle at which the peak beta of the combustion pressure is generated, the cylinder internal pressure is detected at the peak betaof the combustion pressure as cylinder internal pressure P2. With such an arrangement, when the crank angles alpha1 and alpha2 are detected, a decision circuit 20 compares the internal pressures P1 and P2 and the same control is repeated until the P1 and P2 are almost equal. Thus, when the internal pressures P1 and P2 are found to be almost equal, the circuit 20 judges that the state of misfire exists.