Learn more about the various technologies used in Toyota's hybrid vehicles
World's top level input/output to weight ratio - light weight
In addition to being light-weight, the high power output nickel metal hydride (Ni-MH) battery used in the Toyota hybrid technology provides a high input/output to weight ratio. (power output in relation to weight)
The cooling system for the battery cells including the cooling duct is optimized, while components such as the system main relay are designed for reduction in size and weight.
Furthermore, the system maintains the battery charge at a constant level at all times by monitoring and computing the cumulative amount of discharge under acceleration, and recharging by regenerative braking or with surplus power under normal running conditions.
The hybrid battery (traction battery) has a limited service life. The lifespan of the hybrid battery (traction battery) can change in accordance with driving style and driving conditions.
The gas/petrol engine used in Toyota hybrid technology is more energy-efficient, producing higher output than conventional gas/petrol engines.
The new (2009) Prius' 1.8L 2ZR-FXE high-expansion-ratio Atkinson cycle engine replaces the former 1.5L 1NZ-FXE. The wealth of torque created by an increased displacement decreases the engine rpm during high-speed cruising. Further improvements in fuel efficiency have been achieved through the following new mechanisms.
Electric water pump
The water pump is now driven by electricity from the battery. Elimination of the drive belt decreases mechanical loss, and the flow of the coolant can be controlled even more precisely according to the vehicle's conditions.
Exhaust heat recirculation system
This system utilizes exhaust heat -what used to go wasted- for the heater and to warm up the engine, allowing quicker heater and engine warmups.
Flow volume of the exhaust gas is controlled carefully by the electric EGR valve and is channeled into the intake manifold, alleviating negative pressure in the manifold and decreasing pumping loss in the engine. Cooling the exhaust gas with the EGR cooler actualizes large volume EGR.
Roller rocker arm
The valve train system features roller rocker arms, decreasing friction loss in valve movements.
Maximum power output: 73kW(99PS)/5,200 rpm
Maximum torque: 142N･m(14.5kgf･m)/4,000 rpm
Employing synchronous A/C motor for compact packaging, light weight and high efficiency
Toyota's hybrid technology uses synchronous A/C motors, which can efficiently produce strong torque up into the high revolution ranges and provide freedom to control motor revolutions and torque. Toyota has also succeeded in making electric motors more compact, light-weight and efficient, for smoother starts/acceleration.
- 3-phase A/C
- Optimum control of the angle between rotating magnetic field and rotor magnets
- Permanent rotor magnets positioned in the ideal V-figure configuration
Max. output:60 kW (82PS)
Max. torque:207 N・m (21.1 kgf・m)
*The figures are for Prius manufactured to Japanese market specification.
Splitting power produced by the gas/petrol engine between the drive train and the generator
The power splitting device distributes the power produced by the gas/petrol engine to the drive train and to the generator. To divide the power efficiently, it uses a planetary gear consisting of a ring gear, pinion gears, a sun gear and a planetary carrier.
1. The rotating axle of the planetary carrier is directly connected to the gas/petrol engine and rotates the perimeter ring gear and the sun gear inside via the pinion gears.
2. The rotating axle of the ring gear is directly connected to the electric motors, and thus transfers the driving power to the wheels. The axle of the sun gear is directly connected to the generator and converts the power produced by the gas/petrol engine into electric energy.
Reuse of kinetic energy by using the electric motors to regenerate electricity
Toyota's hybrid technology can reuse kinetic energy by using its electric motors to regenerate electricity in what is called "regenerative braking".
Normally, electric motors are turned by passing an electric current through it. However, if some outside force is used to turn the electric motors, it functions as a generator and produces electricity. This makes it possible to employ the rotational force of the driving axle to turn the electric motors, thus regenerating electric energy for storage in the battery and simultaneously slowing the car with the regenerative resistance of the electric motors.
The system coordinates regenerative braking and the braking operation of the conventional hydraulic brakes so that kinetic energy, which is normally discarded as friction heat when braking, can be collected for later reuse in normal driving mode.
Typically, driving in city traffic entails a cycle of acceleration followed by deceleration. The energy recovery ratio under these driving conditions can therefore be quite high.
To take advantage of this situation, the system proactively uses regenerative braking when running the car in the low speed range. Taking the Prius as an example, the system can save the energy equivalent of 1? of gas/petrol while running in city traffic for 100 km.
High speed rotation for higher maximum power output
As with electric motors, Toyota's hybrid technology uses a synchronous AC generator capable of high speed axial rotation, realizing substantial electrical power while the car is running in the mid-speed range.
Toyota has put together the ideal generator, high output electric motor and gas/petrol engine combination to enhance low to mid-speed range acceleration.
The new Prius (2009) has a more compact, light-weight design realized through centralized winding of the coils.
Toyota's hybrid technology is equipped with a Power Control Unit that consists of an inverter, a Voltage-Boosting Converter and an AC/DC converter to run the car on electric motors.
The inverter converts DC supplied by the battery to AC to turn the electric motors and to use in the generator. Conversely, it converts AC generated by the electric motors and the generator into DC to recharge the battery. Direct cooling of switching device is featured in the new (2009) Prius, improving cooling efficiency and enabling inverter downsizing and weight reduction.
The Voltage-Boosting Converter steplessly increases the normal 201.6 V DC supply voltage to a maximum of 650 V to feed the electric motors and the generator as required. This means more power can be generated from a small current to bring out high performance from the high output motors, enhancing overall system efficiency. It also means that the inverter could be made smaller and lighter.
The DC/DC converter steps down the 201.6 V supply voltage from the battery to 12 V, to be used by ancillary systems and electronic devices like the ECU.
Reduction gear amplifies torque from the electric motors
Toyota's hybrid technology incorporates the newly developed reduction gear. The reduction gear is designed to reduce the high rpm of the front electric motors so that the power produced can be transferred to the wheels, with the added benefit of torque amplification, i.e. with greater power.This torque amplification effect, coupled with higher revving capability of the front electric motors, combines to provide seamless acceleration at will.