Apparatus and method for detecting misfire in internal combustion engine

A misfire detection apparatus for an internal combustion engine having a plurality of cylinders, wherein the apparatus selects three of the cylinders that are consecutively ignited as subjects of misfire detection, and defines the selected cylinders as a first subject cylinder, a second subject cylinder, and a third subject cylinder in an order of ignition, wherein the apparatus is capable of detecting three types of misfire including a single-cylinder misfire, in which a misfire occurs only in the first subject cylinder, a consecutive-two-cylinder misfire, in which a misfire occurs in the first and second subject cylinders, and an intermittent-two-cylinder misfire, in which a misfire occurs in the first and third subject cylinders, the apparatus comprising:

• a computer, wherein the computer obtains a rotation fluctuation amount of the engine at each of the first to third subject cylinders;
• wherein the computer determines whether a misfire is occurring in the first subject cylinder based on the rotation fluctuation amount at the first subject cylinder;
• wherein, when it is determined that a misfire is occurring in the first subject cylinder, the computer determines whether the type of the occurring misfire is a single-cylinder misfire based on the rotation fluctuation amount at the second subject cylinder and the rotation fluctuation amount at the third subject cylinder;
• and
• wherein, when it is determined that the type of the occurring misfire is not a single-cylinder misfire, the computer determines whether the type of the occurring misfire is a consecutive-two-cylinder misfire or an intermittent-two-cylinder misfire based on the rotation fluctuation amount at the second subject cylinder and the rotation fluctuation amount at the third subject cylinder.

A misfire detection method for an internal combustion engine having a plurality of cylinders, the method comprising:

• selecting three of the cylinders that are consecutively ignited as subjects of misfire detection, and defining the selected cylinders as a first subject cylinder, a second subject cylinder, and a third subject cylinder in an order of ignition;
• and
• determining a occurring misfire to be one of three types of misfire including a single-cylinder misfire, in which a misfire occurs only in the first subject cylinder, a consecutive-two-cylinder misfire, in which a misfire occurs in the first and second subject cylinders, and an intermittent-two-cylinder misfire, in which a misfire occurs in the first and third subject cylinders, wherein the determining of the misfire type includes:
• obtaining a rotation fluctuation amount of the engine at each of the first to third subject cylinders;
• determining whether a misfire is occurring in the first subject cylinder based on the rotation fluctuation amount at the first subject cylinder;
• determining whether the type of the occurring misfire is a single-cylinder misfire based on the rotation fluctuation amount at the second subject cylinder and the rotation fluctuation amount at the third subject cylinder when it is determined that the misfire is occurring in the first subject cylinder;
• and
• determining whether the type of the occurring misfire is a consecutive-two-cylinder misfire or an intermittent-two-cylinder misfire based on the rotation fluctuation amount at the second subject cylinder and the rotation fluctuation amount at the third subject cylinder when it is determined that the type of the occurring misfire is not a single-cylinder misfire.