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 misfire detecting system for an engine of a vehicle that detects a misfire of the engine is provided. The system includes a sensor configured to detect a wheel speed of the vehicle, a load adjustment device configured to adjust a load of the engine, and a processor. The processor determines whether a wheel slip has occurred by examining whether a change rate of the wheel speed is equal to or greater than a determination reference value, when determining whether the wheel slip has occurred, limits a determination of the misfire of the engine by adjusting the determination reference value higher or lower based on corresponding increases or decreases in a requested load, by applying the adjusted determination reference value, determines that wheel slip has occurred, and based on the wheel slip determination, determines that the misfire has occurred.

A CPU substitutes a difference between a crank-side speed that is a rotation speed of a crankshaft and a downstream-side speed that is a speed of a portion, opposite from the crankshaft, in a damper into a differential speed. The CPU calculates a torsion angle through a process of integrating the differential speed. The CPU calculates a torsion speed component that is a speed component of the crankshaft due to torsion of the damper based on a process of integrating a value obtained by multiplying the torsion angle by an elastic modulus, and calculates a time that is a variable indicating a speed of the crankshaft, used to determine a misfire, based on the torsion speed component. The CPU subtracts a value obtained by subtracting an output value of the integrating process, applied to a finite response low-pass filter process, from the output value.

A CPU substitutes a difference between a crank-side speed that is a rotation speed of a crankshaft and a downstream-side speed that is a speed of a portion, opposite from the crankshaft, in a damper into a differential speed. The CPU calculates a torsion speed component that is a speed component of the crankshaft due to torsion of the damper based on a physical model of which an input is the differential speed, and calculates a time that is a variable indicating a speed of the crankshaft, used to determine a misfire, based on the torsion speed component. The CPU delays acquisition time of the downstream-side speed used to calculate the differential speed, with respect to acquisition time of the crank-side speed according to the rotation speed of the crankshaft.

An individual cylinder air-fuel ratio estimation of estimating an air-fuel ratio of an individual cylinder is performed on a sensed value of an air-fuel ratio sensor set in an exhaust gas collection part of an engine, and an individual cylinder air-fuel ratio control of controlling the air-fuel ratio of the individual cylinder is performed in such a way that a variation in the air-fuel ratio between the cylinders becomes small on the basis of an estimated air-fuel ratio of the individual cylinder. Further, it is determined whether or not a misfire of the engine is caused and when it is determined that the misfire of the engine is caused, the individual cylinder air-fuel ratio estimation and the individual cylinder air-fuel ratio control are stopped and an individual cylinder correction value by the individual cylinder air-fuel ratio control is reset. In this way, it is possible to avoid the individual cylinder air-fuel ratio control from being performed continuously as usual in a state where the air-fuel ratio of the individual cylinder cannot be controlled correctly due to the effect of the misfire.

The control device for an internal combustion engine disclosed in the present application is a control device that determines the presence or absence of misfire based on an angle detection cycle calculated from an output signal of an angle sensor, the control device includes an arithmetic processing device and a storage device, the control device is configured so that the storage device stores the angle detection cycle calculated in a misfire detection threshold value comparison section after the reference angle section as a threshold value comparison target cycle and is configured such that the arithmetic processing device determines the presence or absence of misfire based on the misfire detection threshold value cycle calculated based on the reference detection cycle and the threshold value comparison target cycle, thereby it becomes possible to accurately determine the presence or absence of misfire in the control device for the internal combustion engine.

A misfire detecting system for an engine of a vehicle that detects a misfire of the engine is provided, which includes a processor. The processor determines whether a misfire has occurred by examining whether a fluctuation of a crank angle of the engine is equal to or greater than a determination reference value, acquires a value relating to a density of intake air introduced into the engine, and adjusts the determination reference value according to the value related to the density.

An electronic control unit sets a misfire determination threshold to a first value in the cylinder injection mode, and sets the misfire determination threshold to a second value smaller than the first value in the port injection mode, and determines that a misfire occurs in the engine when a rotation fluctuation of the engine is larger than the misfire determination threshold. In a case where the cylinder injection mode is changed to the port injection mode, when a predetermined period has elapsed from the change, the electronic control unit changes the misfire determination threshold from the first value to the second value.

A vehicle drive system includes an internal combustion engine, a clutch, an engine rotation speed detector, an output shaft rotation speed detector, and a processor. The internal combustion engine includes cylinders and a crankshaft. The clutch is connected to the crankshaft via a torsion element and includes an output shaft. The engine rotation speed detector detects a crankshaft rotation speed. The output shaft rotation speed detector detects an output shaft rotation speed. The processor is configured to calculate a torque generated in each of the cylinders based on the crankshaft rotation speed. The processor is configured to decrease transmission torque of the clutch so that a difference between the crankshaft rotation speed and the output shaft rotation speed to be a target value when misfiring occurs. The processor is configured to identify a misfiring cylinder among the cylinders based on the torque calculated while the transmission torque is decreased.

This invention relates to an engine for a vehicle using alternative fuel, preferably gas, comprising an engine (5) having a spark ignited ignition system (2) wherein said ignition system (2) includes misfire detection by means of a sensor device (4) providing information to a control system (20), connected to or within said ignition system (2), and wherein said combustion includes diluted operation to optimize emissions wherein said sensor device (4) includes an ion sensing measurement means (40) arranged to measure an ion current in said engine (5) and that said ignition system (2) has a built-in function to detect misfiring through an analysis of the ion current of the engine (5) during combustion.