Transmission ratio controller and method for determining transmission ratio

A transmission ratio controller including circuitry, the circuitry comprising:

• a transmission ratio calculator configured to calculate a transmission ratio of a transmission mechanism in accordance with a state of an internal combustion engine;
• and
• a monitor configured to monitor the transmission ratio calculated by the transmission ratio calculator, wherein
• the state of the internal combustion engine is specified based on a specified parameter,
• the transmission ratio calculator is configured to calculate the transmission ratio using a first transmission ratio map when the specified parameter satisfies a first condition,
• the transmission ratio calculator is configured to calculate the transmission ratio using a second transmission ratio map that differs from the first transmission ratio map when the specified parameter satisfies a second condition,
• the first condition and the second condition are not simultaneously satisfied,
• when the specified parameter satisfies the first condition, the internal combustion engine is in a first state,
• when it is assumed that the specified parameter satisfies the second condition, the internal combustion engine is in a second state,
• the first state and the second state are identical except for the specified parameter,
• the monitor is configured to calculate a hypothetical transmission ratio using the second transmission ratio map based on the second state when the internal combustion engine is in the first state, and
• on a condition that the transmission ratio calculated when the internal combustion engine is in the first state differs from the hypothetical transmission ratio by a predetermined reference value or greater, the monitor is configured to determine that the internal combustion engine is in a situation in which the transmission ratio has a possibility of differing in accordance with the specified parameter.