A misfire determination period is set to a predetermined range of a crank angle. A CPU performs: a calculation process of calculating an average value of a torque of an output shaft of an internal combustion engine in the misfire determination period; a misfire determining process of determining that a misfire has occurred when the calculated average value is less than a prescribed threshold value; and a process of setting the whole misfire determination period to a period in a positive torque range which is a range of a crank angle at which the torque of the output shaft is equal to or greater than zero at the time of normal combustion in which a misfire does not occur.

A misfire determination period is set to a predetermined range of a crank angle. A CPU performs: a calculation process of calculating an average value of a torque of an output shaft of an internal combustion engine in the misfire determination period; a misfire determining process of determining that a misfire has occurred when the calculated average value is less than a prescribed threshold value; and a process of setting the whole misfire determination period to a period in a positive torque range which is a range of a crank angle at which the torque of the output shaft is equal to or greater than zero at the time of normal combustion in which a misfire does not occur.

A motor noise detecting device according to an embodiment of the present disclosure includes a signal sensing part for sensing an acoustic signal generated from an object to be tested, a data acquisition part for receiving the acoustic signal sensed by the signal sensing part and converting it into an acoustic digital signal, and a data analysis part for receiving and analyzing the acoustic digital signal to perform a detection on whether the object to be tested is abnormal. In addition, the signal sensing part includes an AE (Acoustic Emission) sensor for sensing an elastic wave included in the acoustic signal, and the data analysis part generates result data of analyzing the acoustic digital signal, analyzes the generated result data through a pre-learned model, and detects whether the object to be tested is abnormal.

Systems and methods determining a presence or absence of engine misfire at low engine load are disclosed. In one example, the presence or absence of engine misfire is based on a fuel target error value and an exhaust temperature error. Operation of an engine may be adjusted when engine misfire is detected.

A control apparatus, which is for an internal combustion engine with a spark plug having a center electrode and a ground electrode disposed so as to form a spark discharge gap therebetween, includes a voltage applying section for applying a voltage to the spark discharge gap, a constant-voltage path including a constant-voltage element parallel-connected to the spark discharge gap of the spark plug for preventing the spark discharge gap from being applied with a voltage higher than a set voltage, and an operation control circuit for controlling an operating condition of the internal combustion engine. The operation control circuit is configured to measure a current-flowing time during which a current flows through the constant-voltage path when a voltage higher than the set voltage is applied to the constant-voltage path, and change the operating condition of the internal combustion engine in accordance with the measured current-flowing time.

A control apparatus, which is for an internal combustion engine with a spark plug having a center electrode and a ground electrode disposed so as to form a spark discharge gap therebetween, includes a voltage applying section for applying a voltage to the spark discharge gap, a constant-voltage path including a constant-voltage element parallel-connected to the spark discharge gap of the spark plug for preventing the spark discharge gap from being applied with a voltage higher than a set voltage, and an operation control circuit for controlling an operating condition of the internal combustion engine. The operation control circuit is configured to measure a current-flowing time during which a current flows through the constant-voltage path when a voltage higher than the set voltage is applied to the constant-voltage path, and change the operating condition of the internal combustion engine in accordance with the measured current-flowing time.

A misfire determination device of an engine in which explosion occurs at unequal intervals, the engine including a plurality of cylinders and a crankshaft which is angularly displaced at a different angle between expansion strokes, is configured to calculate generated torque correlation amount correlated with generated torque, based on an angular position signal of the crankshaft, and perform misfire determination, based on an average value of the generated torque correlation amount in an interval less than one cycle of the engine, at an angular position of the crankshaft which is different from an angular position of the crankshaft at an ignition timing.

A misfire determination device of an engine in which explosion occurs at unequal intervals, the engine including a plurality of cylinders and a crankshaft which is angularly displaced at a different angle between expansion strokes, is configured to calculate generated torque correlation amount correlated with generated torque, based on an angular position signal of the crankshaft, and perform misfire determination, based on an average value of the generated torque correlation amount in an interval less than one cycle of the engine, at an angular position of the crankshaft which is different from an angular position of the crankshaft at an ignition timing.

A state detection system for an internal combustion engine is provided. Rotation waveform variables include information on a difference between cylinders in the rotational speed of a crankshaft during periods in which the respective cylinders generate combustion torque. An obtainment process obtains a value of the rotation waveform variables and a value of a road surface state variable based on an output of a sensor that detects a state of the road surface. A selection process selects, from a plurality of types of mapping data stored in the storage device, the mapping data that is associated with the road surface state variable as the detection mapping. A determination process determines whether the engine is in a predetermined operating state based on an output value of the selected detection mapping that takes the rotation waveform variables as inputs.

A state detection system for an internal combustion engine is provided. Rotation waveform variables include information on a difference between cylinders in the rotational speed of a crankshaft during periods in which the respective cylinders generate combustion torque. An obtainment process obtains a value of the rotation waveform variables and a value of a road surface state variable based on an output of a sensor that detects a state of the road surface. A selection process selects, from a plurality of types of mapping data stored in the storage device, the mapping data that is associated with the road surface state variable as the detection mapping. A determination process determines whether the engine is in a predetermined operating state based on an output value of the selected detection mapping that takes the rotation waveform variables as inputs.