Hybrid vehicle control method and hybrid vehicle control device

A hybrid vehicle control device for controlling a hybrid vehicle, the hybrid vehicle control device comprising:

• an internal combustion engine;
• an electric power generation motor connected to the internal combustion engine via a gear mechanism to generate power when the internal combustion engine is in a firing state;
• a braking force amplification device configured to amplify brake pedal depressing force using an intake negative pressure of the internal combustion engine;
• and
• a control unit configured to control the internal combustion engine and the electric power generation motor,
• the control unit being programmed to;
• set a rotational speed threshold value as an engine rotational speed at which a continuous gear tooth striking sound occurring in the gear mechanism does not occur in the gear mechanism or at which an operating noise of the internal combustion engine is louder than the continuous gear tooth striking sound in the firing state,
• generate a negative pressure while maintaining the engine rotational speed when a negative pressure generation request exists in the firing state and the engine rotational speed is equal to or greater than the rotational speed threshold value, and
• generate the negative pressure after switching from the firing state to a motoring state when the negative pressure generation request exists in the firing state and the engine rotational speed is less than the rotational speed threshold value, the motoring state being a state in which the internal combustion engine is rotated by the electric power generation motor.