Powertrain layout shows cross section of engine and drive units. Generator Motor Engine Power-split device Reduction gears Drive shaft.

Starting from rest/light load If the engine is in the low-efficiency zone—vehicle is starting from rest, moving at very low speed, or descending a slight gradient—the fuel supply is cut or the engine is stopped and the electric motor drives the vehicle (A).

Full-throttle acceleration During full-throttle acceleration, power is also supplied from the battery to augment the drive power (A).

Deceleration/braking During deceleration and braking, kinetic energy from the wheels passes through the electric motor, which functions as a generator (A). Recovered energy is stored in the battery.

Battery charging The battery is regulated to maintain a constant charge. When the charge is low, the electric generator routes power to charge the battery (D).

Normal driving Engine power is divided by the power-split device, one route directly powering the wheels (B) and the other operating the electric generator. Electricity from the generator runs the electric motor to assist with powering the wheels (C). The system controls the ratio of these paths to optimize efficiency.

Return to Toyota readies gasoline/electric hybrid system.