TOYOTA'S REVOLUTIONARY HYBRID GASOLINE/ELECTRIC PRIUS:
A REAL CAR IN EVERY WAY. . .ONLY SMARTER
The Toyota Prius represents a breakthrough in the combination of an efficient, powerful gasoline-fueled internal combustion engine and a clean, quiet electric motor driving a stylish, roomy four-door, five-passenger sedan.
When Prius goes on sale in the U.S. beginning in mid-2000, plans call for the vehicle to be available through Toyota dealers nationwide. As with all other Toyota and Lexus products, Prius will be available for either purchase or lease. Target pricing for the vehicle will be comparable to similar-sized vehicles such as Corolla or Camry.
Prius was launched initially in Japan in December, 1997, and was greeted with excitement by Japanese consumers. During that first year, the vehicle was so popular that production was increased three separate times to keep up with demand.
The electronic controls that make up the Toyota Hybrid System (THS) allow Prius to run on either electricity or gasoline alone, or a combination of both. The ratio of power provided by each system is constantly monitored, depending on speed and load, to keep the vehicle in its most efficient operating mode.
Based on Japanese-market testing and certification, Prius achieves nearly double the fuel efficiency of conventional gasoline-powered vehicles (when measured in the Japanese 10-15 test mode), resulting in fuel economy of 66 miles per gallon (mpg) and over 850 miles on a single 13.2 gallon tank of gasoline. The development target for the U.S.-market Prius is approximately 60 mpg.
Because of the system-s efficiency, exhaust emissions also are reduced drastically. Again, based on Japanese regulations and standards, carbon dioxide (CO2) emissions are reduced by 50 percent, while carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) emissions are reduced by about 90 percent. Toyota engineers are striving to have the U.S.-market vehicle comply with the upcoming California Super Ultra Low Emission Vehicle (SULEV) standard. SULEV is approximately 75 percent cleaner than the strictest existing standard, Ultra Low Emission Vehicle (ULEV).
Prius' main power is provided by an efficient 1.5-liter gasoline engine. Peak power for the engine is 58 horsepower at 4,000 rpm, with peak torque of 75 lb./ft. also reached at 4,000 rpm. The engine is equipped with Lexus-like variable valve timing which helps maximize efficiency and minimize emissions.
Engine revs are limited to 4,000 rpm, allowing internal parts to be built lighter. In addition, the crankshaft has a smaller diameter, piston rings have lower tension and the valve spring load is less, when compared to standard higher-revving engines. These advances result in a large reduction in friction loss, which also translates into increased efficiency.
The electric motor is a permanent-magnet design which needs no maintenance as its no-touch internal componentry never wears. It produces its maximum power of 30 kilowatts (40 horsepower) from 940-2,000 rpm, and maximum torque of 31.1 kg-m (225 lb./ft.) from 0-940 rpm.
Operation of the THS is seamless and virtually imperceptible to driver and passengers. Its five main modes are:
1. When pulling away from a stop or under a light load, only the electric motor powers the vehicles.
2. In normal driving, power from the gasoline engine is divided by a power-split device between the wheels and the electric generator. The generator runs the electric motor to provide additional power to the wheels.
3. Under full-throttle acceleration, the electric motor is supplemented by power from the batteries.
4. During deceleration or braking, the motor functions as a generator to recharge the batteries. The batteries never need to be recharged from an external source. The gasoline engine also shuts down, creating zero exhaust emissions and using no fuel.
5. The battery is regulated to maintain a constant charge. When the charge is low, the electric generator routes power to charge the battery.
The key to the system is a power-split device in the transmission which sends engine power either directly to the wheels or to the electric generator controlling the electric motor or battery state-of-charge. The power-split device uses a planetary gear to constantly vary the amount of power supplied from the engine to either the wheels or the generator. The electronically controlled transmission smoothly adjusts the rates of revolution of the gasoline engine, electric generator and electric motor to accommodate for acceleration and deceleration.
The engine is kept within its most efficient speed and torque range as much as possible to maximize fuel efficiency. When the engine falls out of this range, such as when the vehicle is pulling away from a stop, descending a slight grade or moving very slowly, fuel is cut off and the engine is stopped. In this mode, initial move-off power is supplied by the electric motor as it produces 100 percent of its maximum torque immediately off of idle. When power requirements change, the engine is started by the generator and the electric motor is used to supplement acceleration.
To further boost system efficiency, Prius is fitted with a regenerative braking system. When the vehicle is coasting or the brakes are applied, the motor is turned into a generator, capturing energy that would normally be lost as heat or kinetic energy and transforming it into electricity to recharge the batteries. The system is particularly effective during stop-and-go driving.
Prius was styled at Calty Design Research, Toyota's southern California design studio in Newport Beach. It combines the short overhangs and large, relatively upright cabin necessary for a newly designed city vehicle.
Inside, Prius' high front and rear seating positions make for easy ingress and egress, as well as offering good visibility. The instruments are centered high on the dashboard at the base of the windshield making it easier for the driver to change eye-focus from the road to the dash. The audio system is located below the instrument cluster, as is a 5.8-inch wide multi-function monitor which shows the condition and energy flow of the hybrid drive system and also can be used for a navigation system display.
Safety also was key in the development of Prius. Driver- and passenger-side airbag supplemental restraint systems (SRS) are standard, as are adjustable shoulder anchor-points for the front seatbelts. Incorporating Toyota's Passive Safety Body technology, Prius was designed to meet or exceed each and every known and foreseeable worldwide crash-safety standard.
Suspension components include MacPherson struts in the front and incorporate an L-beam lower control arm. The rear is fitted with a torsion-beam axle with toe-control links, which allows for a large trunk and rear seat capacity while not sacrificing ride or handling compliance. Front disc brakes are teamed with rear drums, and an anti-lock system (ABS) is standard.
CONTACT: Jeremy Barnes - 310-618-4782