Device and method for detecting misfire in engine

An engine misfire detection device comprising:

• a rotation speed sensor measuring a rotation speed of a supercharger,
• a sensor signal processing unit configured to:
• calculate a misfire index yt from a degree of change in the rotation speed of the supercharger measured by the rotation speed sensor;
• and
• determine a misfire in an engine when the calculated misfire index yt exceeds a pre-set determination value,
• wherein
• the misfire index calculating calculates the misfire index yt based on a decrease rate ΔNt of the rotation speed of the supercharger, the decrease rate ΔNt being calculated by using the following equation (1):
• ΔNt(tn)=[−1×{Nt(tn)−Nt(tn−1)}/Nt(tn−1)]×100 (1)
• where Nt(tn) is the rotation speed of the supercharger at a measurement time tn which any one of pistons included in the engine reaches a top dead center position, and Nt(tn−1) is a rotation speed of the supercharger at a measurement time tn−1 which another piston reaches a top dead center position, the measurement time tn−1 is one measurement time before tn.