Toyota to launch hybrid Corona

By Russell Williamson

TOYOTA will become the first Japanese carmaker to launch a volume-production car fitted with a hybrid engine when its new Corona goes on sale about September.

The five-door Corona uses a petrol-electric engine and will initially only be available in Japan.

According to the company's executive vice president, Akhiro Wada, the hybrid engine has twice the economy of a petrol engine and produces just 10 percent of the emissions.

In an effort to cut urban pollution levels and reduce the reliance on fossil fuels for transport, most of the world's carmakers have been striving to develop electric and hybrid engines for cars.

Earlier this year, Honda released its electric Civic Ferio, while Toyota has an electric version of its small four wheel drive RAV4 on the market in Japan.

However, while pure electric vehicles offer the optimum solution to reducing pollution levels, a scarcity of recharging facilities and the high cost of batteries make them too impractical.

Wada said for electric vehicles to become viable enough to compete with traditional petrol-powered cars, the cost of batteries would need to fall by 90 percent.

As such, most carmakers are now turning to hybrid engines as a means of making cars more environmentally responsible.

The Toyota Hybrid System builds on the energy management system that the company first showed in its Prius concept car at the Tokyo motor show in 1995.

That car used a direct-injection four-cylinder engine combined with an electric motor/generator and a storage capacitor to improve fuel economy and provide a system for capturing braking energy.

The hybrid system takes this one step further and combines two distinct motive power sources.

A high-efficiency 1.5-liter four-cylinder petrol engine with variable valve timing provides the main power to the drive wheels.

Drive power also comes from an electric motor, which derives its power from a nickel-metal hybrid battery and an electric generator.

A power split device in the electronically controlled transmission allocates power from the petrol engine either directly to the wheels or to the electric generator.

The distribution of this power is controlled by the car's computer and depends on factors such as the amount of pressure on the accelerator, vehicle speed and battery charge.

The electrical power developed by the generator can then be used to drive the electric motor which, together with the power from the engine, helps drive the vehicle.

Under starting conditions or when the car is traveling at slow speeds, power to the car's drive wheels comes almost exclusively from the electric motor.

During normal operation, the power driving the car is balanced between both the petrol engine and the electric motor to provide the optimum efficiency.

Under full-throttle acceleration, power to the drive wheels is also supplemented by the battery.

In addition, power is also regenerated during deceleration and braking through the electric motor and fed back to the battery for storage.

Further efficiency is provided by the petrol engine completely cutting out when the vehicle is stopped at traffic lights or moving very slowly.

As in a conventional petrol-powered car, the battery does not need to be charged externally.

With the number of cars on the world's roads expected to reach nearly 400 million by 2005, the pressure is on manufacturers to come up with alternative means of powering these vehicles.

And in the short term, hybrid engines appear to be the most viable.