Ignition timing control device for internal combustion engine

An ignition timing control device for an internal combustion engine configured to use a fuel containing alcohol, the internal combustion engine including

• a fuel injection valve,
• a delivery pipe configured to supply the fuel to the fuel injection valve,
• a fuel pipe configured to communicate with the delivery pipe,
• a fuel tank, and
• an alcohol concentration sensor provided to one of the fuel pipe and the fuel tank, the alcohol concentration sensor being configured to detect a concentration of alcohol in the fuel,
• the ignition timing control device comprising
• an electronic control unit configured to:
• acquire an operating state of the internal combustion engine;
• acquire the concentration of alcohol in the fuel based on the alcohol concentration detected with the alcohol concentration sensor;
• calculate a reference ignition timing of the internal combustion engine based on the operating state;
• calculate an advance correction amount of an ignition timing such that an advance amount of the ignition timing increases more as the alcohol concentration is higher;
• set a target ignition timing of the internal combustion engine based on the reference ignition timing and the advance correction amount;
• determine, based on change in the alcohol concentration, whether or not the fuel injected from the fuel injection valve starts to switch from a first fuel to a second fuel higher in the alcohol concentration than the first fuel;
• determine whether or not the first fuel remaining in the fuel pipe and the delivery pipe is consumed and switching from the first fuel to the second fuel is completed;
• restrict the advance correction amount, during a period from a time when the start of the switching is determined to a time when the completion of the switching is determined, to an advance correction amount corresponding to the alcohol concentration of the first fuel or lower;
• and
• cancel restriction of the advance correction amount after the completion of the switching is determined.