Power unit and saddle-riding type vehicle

A power unit to be mounted on a vehicle, the power unit comprising:

• an internal combustion engine including a crankshaft configured to output a rotational power of the internal combustion engine;
• a power generator connected to the crankshaft and configured to rotate, to regenerate electricity, and to output a rotational power;
• a transmission mechanism configured to perform a shift change operation during transmission of the rotational power output from at least one of the internal combustion engine and the power generator;
• and
• a battery configured to supply power to the power generator to assist drive thereof and to store power generated by the power generator;
• wherein
• the transmission mechanism includes:
• an output section configured to output the rotational power to a driving wheel as a driving force;
• and
• a clutch configured to transmit or disconnect the transmission of the rotational power from at least one of the internal combustion engine and the power generator to the output section;
• and
• the power generator is configured to store power in the battery or to supply power from the battery, during the shift change operation by the transmission mechanism, to drive the crankshaft to increase a torque of the crankshaft in a direction of increasing synchronization of a rotational speed of the crankshaft with a rotational speed of the crankshaft converted from a rotational speed of the output section based on a reduction ratio of the transmission mechanism or a target reduction ratio.