Slide 10 The Toyota Hybrid System - the Transmission  

• The generator, the motor, and an epicylic power-split device provide two paths for the engine power.

• (The MIRA-Giles transmission, from the 1950's, used a power-split system with two hydrostatic machines).

• These components act as a Continuously Variable Transmission (CVT) between two limiting ratios.

• 72 per cent of the power goes via the mechanical path, and only 28 per cent via the electrical path.

• This greatly reduces the size of the electrical machines, and increases the overall efficiency.

• Even so, the electrics have their own liquid cooling system, independent of the engine.

• No clutch or torque converter is required, since the motor gives maximum torque at very low speeds.

• This transmission ensures that the optimum engine speeds and throttle openings are always used.

• 'Neutral' and 'Reverse' are effected electrically, while 'B' gives additional engine braking.

• Automatic transmission is an inherent feature of the THS, and involves very low losses.

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