An internal combustion engine (1) includes: an exhaust gas recirculation unit equipped with an exhaust gas recirculation control valve (9); a crank angle sensor (11) that detects an indicated mean effective pressure fluctuation rate (cPi) as an indicator of combustion stability of the internal combustion engine (1); and a controller (10) that corrects the EGR rate of the exhaust gas recirculation unit based on the combustion stability. The controller (10) is configured to: increase-correct the EGR rate by a predetermined amount when the state where the indicated mean effective pressure fluctuation rate (cPi) is lower than a threshold value continues for a predetermined number of cycles; and decrease-correct the EGR rate by a predetermined amount immediately when the indicated mean effective pressure fluctuation rate (cPi) is higher than or equal to the threshold value.

Method for identifying cylinders of an internal combustion engine which are subjected to misfire during operation, comprising a step of determining whether the engine is subjected to a misfire condition; a step of measuring vibrations generated upon operating the engine; and a step of identifying at least one cylinder subjected to a misfire in dependence on the measured vibrations.

A drive train abnormality determination device for a straddled vehicle that includes a drive train having a rotator. The drive train abnormality determination device includes an angle signal output unit that periodically outputs an angle signal in accordance with rotation of the rotator, a rotator rotation speed fluctuation physical quantity acquisition unit that acquires a quantity related to a fluctuation in a rotation speed of the rotator, based on the angle signal from the angle signal output unit, a rough road determination unit that determines whether a distribution state or pattern satisfies a predetermined rough road condition, a continuity determination unit that determines whether the rough road condition is continuously satisfied, and a drive train abnormality determination unit that determines, responsive to a determination by the continuity determination unit that the rough road condition is continuously satisfied, that the drive train has an abnormality in its functioning.

A CPU determines that there is a misfire when a relative magnitude of a rotation fluctuation amount ΔT30[0] related to a cylinder subject to the determination in relation to a rotation fluctuation amounts ΔT30[4] of the previous combustion cycle is greater than or equal to the determination value Δth. However, during the execution of a catalyst warm-up process, the CPU uses, in the comparison, the relative magnitude of the rotation fluctuation amount ΔT30[0] in relation to the average ΔT30ave[0] of the smallest five of the rotation fluctuation amounts ΔT30[4] to ΔT30[40] from the past ten combustion cycles.

Time required by a crankshaft to rotate 30° CA from a compression top dead center is defined as time T30. A CPU calculates a rotation fluctuation amount ΔT30 related to a cylinder subject to determination of a misfire by subtracting a value related to a cylinder in which a compression top dead center occurred immediately before the cylinder subject to the determination from a value related to the subject to the determination. The rotation fluctuation amount ΔT30 that corresponds to a cylinder in which a combustion operation is stopped is used as a reference value ΔT30ref. When a combustion operation is performed, it is determined that there is a misfire if the absolute value of the difference between the rotation fluctuation amount ΔT30 and the reference value ΔT30ref is less than or equal to a determination value Δth.

A misfire detection device executes a deactivating process that deactivates combustion control for air-fuel mixture in one or some of cylinders and a deactivating process that determines whether a misfire has occurred. The determining process determines whether a misfire has occurred by evaluating a magnitude of a rotation fluctuation amount using a determination value independent from the rotation fluctuation amount. The determining process includes a deactivation-related setting process that sets a different determination value for each of first and second cylinders when the deactivating process is executed. The deactivating process has not been executed in the first and second cylinders. The rotation fluctuation amount is a change amount of an instantaneous speed variable. The instantaneous speed variable indicates a speed in a case in which a crankshaft rotates in a rotation angle region that is less than or equal to an occurrence interval of a compression top dead center.

A control system includes a first control device and a second control device. The second control device transmits, to the first control device, a resonance influence torque or a first motor rotation angle speed, and information acquisition timing, which is an acquisition timing of the first motor rotation angle speed. The first control device calculates an engine inertia torque based on an engine rotation angle speed. The first control device selects the resonance influence torque based on the first motor rotation angle speed acquired at a predetermined derivation timing, based on the received information acquisition timing, and derives, as an engine torque, a sum of the resonance influence torque and the engine inertia torque, calculated based on the engine rotation angle speed derived at the predetermined derivation timing.

A misfire detection device and method for an internal combustion engine are provided. A deactivating process deactivates combustion control for air-fuel mixture in a deactivated cylinder. An instantaneous speed variable indicates a speed in a case where a crankshaft rotates by a specific angle. The specific angle of the first instantaneous speed variable is a first angle. The specific angle of the second instantaneous speed variable is a second angle greater than the first angle. A second determining process determines whether a misfire has occurred from a magnitude of a rotation fluctuation amount of a subject of determination, instead of a relative magnitude of the rotation fluctuation amount of the subject of the determination relative to a reference rotation fluctuation amount, when the reference rotation fluctuation amount is a rotation fluctuation amount of the deactivated cylinder during the execution of the deactivating process.

A diagnostic system and method that (a) that uses models indicative of both successful firing and skips to determine if cylinders of a skip fire controlled internal combustion engine have successfully fired or successfully skipped and (b) uses filtered exhaust gas pressure readings for detecting faults associated with EGR systems and/or turbocharger systems.

A CPU performs a regeneration process for a GPF by stopping combustion control of cylinder #1 and causing an air-fuel ratio of an air-fuel mixture in the other cylinders to be richer. The CPU calculates a rotational fluctuation amount which is used to detect random misfires in which a misfire rate in a predetermined period is equal to or greater than a predetermined proportion by calculating a difference in time et3txdh in which a crank shaft rotates by 30°CA. At the time of performing the regeneration process, the CPU calculates the rotational fluctuation amount based on a value obtained by removing an influence of torsion of a damper from the time et3txdh. When the influence of torsion is removed, 0.5th-order rotation and harmonics thereof are selectively used using a filter process.