Control device for internal combustion engine

A control device for an internal combustion engine, the control device comprising:

• a processor, and
• a memory storing programs that cause the processor to execute following processes (i) to (iii):
• (i) acquiring a sensor output value of an air-fuel ratio sensor installed in an exhaust passage of the internal combustion engine, the air-fuel ratio sensor including an element,
• (ii) detecting an air-fuel ratio by calculating an air-fuel ratio detection value based on the sensor output value and a gain, and
• (iii) executing a Proportional-Integral-Differential control as an air-fuel ratio feedback control based on the detected air-fuel ratio, wherein
• the program further causes the processor to
• start the processes (ii) and (iii) in a case where an element temperature of the air-fuel ratio sensor becomes equal to or higher than a predetermined activation temperature, and
• calculate the air-fuel ratio detection value during a period from when the processes (ii) and (iii) are started until a predetermined condition is satisfied, by setting the gain to a smaller value than a value of the gain after an elapse of the period, in a case where the sensor output value indicates that an air fuel ratio in the exhaust passage is richer than stoichiometric.