Misfire detection apparatus for internal combustion engine

A misfire detection apparatus that is applied to a multi-cylinder internal combustion engine of which a crankshaft is connected to a power transmission destination via a damper, the misfire detection apparatus comprising an electronic control unit configured to execute:

• a crank-side acquisition process of acquiring a crank-side speed that is a rotation speed of the crankshaft in a small rotation angle range;
• a downstream-side acquisition process of acquiring a downstream-side speed that is a rotation speed of a portion of the damper, opposite from the crankshaft, in a small rotation angle range;
• a calculation process of calculating a torsion speed component based on a physical model of which an input is a difference between the crank-side speed and the downstream-side speed, the torsion speed component being a component due to torsion of the damper in the crank-side speed;
• and
• a determination process of determining whether there is a misfire in the internal combustion engine based on a determination speed variable that is a variable indicating a rotation speed of the crankshaft, from which the torsion speed component has been removed, wherein:
• the calculation process includes a correction process of correcting a value of a variable that is used in the physical model such that the value of the variable is reduced by an output value obtained by inputting time-series data of the variable to a finite-response low-pass filter,
• the physical model includes a first integral element of which an input is a value according to the difference, and a second integral element of which an input is a value according to an output value of the first integral element,
• the low-pass filter includes a first output-side filter that is a filter of which an input is time-series data of the output value of the first integral element, and
• the correction process includes a process of correcting the output value of the first integral element such that the output value of the first integral element is reduced by an output value of the first output-side filter.

A misfire detection apparatus that is applied to a multi-cylinder internal combustion engine of which a crankshaft is connected to a power transmission destination via a damper, the misfire detection apparatus comprising an electronic control unit configured to execute:

• a crank-side acquisition process of acquiring a crank-side speed that is a rotation speed of the crankshaft in a small rotation angle range;
• a downstream-side acquisition process of acquiring a downstream-side speed that is a rotation speed of a portion of the damper, opposite from the crankshaft, in a small rotation angle range;
• a calculation process of calculating a torsion speed component based on a physical model of which an input is a difference between the crank-side speed and the downstream-side speed, the torsion speed component being a component due to torsion of the damper in the crank-side speed;
• and
• a determination process of determining whether there is a misfire in the internal combustion engine based on a determination speed variable that is a variable indicating a rotation speed of the crankshaft, from which the torsion speed component has been removed, wherein:
• the calculation process includes a correction process of correcting a value of a variable that is used in the physical model such that the value of the variable is reduced by an output value obtained by inputting time-series data of the variable to a finite-response low-pass fitter,
• the physical model includes a first integral element of which an input is a value according to the difference, and a second integral element of which an input is a value according to an output value of the first integral element,
• the low-pass filter includes a second input-side filter that is a filter of which an input is time-series data of the value according to the output value of the first integral element, and
• the correction process includes a process of correcting the value according to the output value of the first integral element, which is an input of the second integral element, such that the value according to the output value of the first integral element is reduced by an output value of the second input-side filter.