Misfire detection device for internal combustion engine, misfire detection system for internal combustion engine, data analysis device, and controller for internal combustion engine

A misfire detection device for an internal combustion engine, comprising:

• memory circuitry;
• and
• processor circuitry, wherein
• the memory circuitry is configured to store mapping data that defines a mapping that takes rotation durations as inputs to output probabilities that a misfire has occurred in cylinders of the internal combustion engine, the mapping including a neural network having an intermediate layer, and a softmax function which normalizes outputs of the neural network so that a sum of the probabilities of misfires is equal to 1,
• the processor circuitry is configured to perform:
• an obtainment process that obtains the rotation durations based on a detection value of a sensor that detects rotational behavior of a crankshaft of the internal combustion engine;
• a determination process that determines presence or absence of a misfire based on an output of the mapping by inputting parameters correlated positively with the probabilities that a misfire has occurred into the softmax function to obtain the probabilities that a misfire has occurred, and comparing a maximum value of the probabilities that a misfire has occurred to a threshold value;
• and
• a response process that, when the determination process determines that a misfire has occurred, operates predetermined hardware to respond to a situation where the misfire has occurred,
• the mapping outputs a probability that a misfire has occurred in at least one cylinder, and the mapping data is data that has been learned by machine learning.