Abstract: A misfire determination apparatus includes first to third obtaining units, a calculator, and a determination unit. The first obtaining unit is configured to obtain actual engine rotation number of an engine. The engine is coupled, via a torsion element, to side of an axle coupled to an electric motor in a torque transmittable manner. The second obtaining unit is configured to obtain motor rotation number of the electric motor. The calculator is configured to calculate calculated engine rotation number of the engine on the basis of the motor rotation number and a total gear ratio between the electric motor and the engine. The third obtaining unit is configured to obtain a rotation deviation between the actual and the calculated engine rotation numbers. The determination unit is configured to execute misfire determination of the engine by determining the engine as being misfiring when the rotation deviation exceeds a determination threshold.

Abstract: A misfire determination apparatus includes first to third obtaining units, a calculator, and a determination unit. The first obtaining unit is configured to obtain actual engine rotation number of an engine. The engine is coupled, via a torsion element, to side of an axle coupled to an electric motor in a torque transmittable manner. The second obtaining unit is configured to obtain motor rotation number of the electric motor. The calculator is configured to calculate calculated engine rotation number of the engine on the basis of the motor rotation number and a total gear ratio between the electric motor and the engine. The third obtaining unit is configured to obtain a rotation deviation between the actual and the calculated engine rotation numbers. The determination unit is configured to execute misfire determination of the engine by determining the engine as being misfiring when the rotation deviation exceeds a determination threshold.

Abstract: A misfire detection device for an engine having cylinders includes: a crank angle detector that detects an angular position of a crankshaft; a rotational speed calculator that calculates a rotational speed of the crankshaft on the basis of an output from the crank angle detector; and a misfire detector that obtains a difference between a rotational speed of the crankshaft in a combustion process in a diagnosis target cylinder and a rotational speed of the crankshaft in a combustion process in a last cylinder whose ignition order is immediately before the diagnosis target cylinder, and carries out a misfire detection by using a diagnostic value set on the basis of the difference.