Hybrid driven: Toyota aims the 2004 Prius at a mass-market audience and gives us a glimpse of things to come

by John Peter

While the rest of the automotive world is struggling to make a business case for hybrids, Toyota Motor Company is making money. According to Toyota, the last few month's worth of the current generation Prius brought in a small profit (industry insiders say about $1,100 dollars per vehicle).

Toyota credits the profit to a savings in manufacturing costs, (The first generation Prius shared the Motomachi-Sumi, Japan, assembly line with Rav-4--the 2004 Prius will be built in Tsusumi on the same line with Camry) and the licensing of the technology to Nissan, who will buy transmissions and power electronics from Toyota, supplying its own Atkinson cycle engine. Nissan plans to sell 100,000 hybrid vehicles over a five-year period starting in 2006.

Dave Hermance, executive engineer environmental engineering says that Toyota has also had conversations with Ford, GM and DaimlerChrysler about the possible joint-use, joint-development and patent sharing of Toyota's hybrid technology.

"We had a technology, collaboration agreement with GM," says Hermance. "It hasn't yet generated a product and it might not. Our President (Fujio Cho) has said that Toyota is open to licensing this technology to anyone that wants to use it--obviously not for free."

It's the development of this technology that will continue to put money in the bank as the volume of hybrid electric vehicles (HEV) continues to climb. President Cho has said that Toyota has plans for global production of 300,000 HEVs a year by 2005-2006, with about half of those slated lot North America.

To reach those numbers, Toyota will need to sell hybrid technology to mainstream consumers. Enter, the second-generation 2004 Prius.

While the original car proved that hybrid technology made real-world sense, the 2004 Prius is designed to introduce the benefits of hybrid technology to a much larger audience.

The 2004 Prius (Prius II) is classified as a mid-size car by the E P A It has a six inch longer wheel-base and is five inches longer overall than the previous car. The biggest growth spurt comes in the interior where space is increased from 101 to 112 cubic feet. The sharply-styled interior has seats that fold flat into a bed ,and a 60-40 split folding rear seat that allows for storage of longer items while keeping a third passenger seat.

Though the '04 car is bigger, engineers managed to keep the weight gain to a minimum thanks to the extensive use of aluminum for the hood, rear hatch, front and rear bumper reinforcements and brake and suspension components. Prius II also features a lightweight plastic fuel tank and Toyota says that the greater reliance on the regenerative braking system allowed them to reduce the size of the front discs and go to a composite caliper.

The steel unibody has fascias made of recyclable TSOP plastic. Toyota refers to the design as a triangular monoform, which not only gives Prius its contemporary stylish look but a 0.26 coefficient of drag as well. The fifth-door design should appeal to European customers who have shied away from the previous generation car.

"The European arm of Toyota told us that the reason the '01 and '03 Prius didn't sell well in Europe had nothing to do with hybrid versus diesel," says Hermance. "The European market strongly demanded a hatchback."

The 1998 Prius concept, designed by Calty, was a hatchback, but the production car was changed to a sedan.

The ride is greatly improved by trading in the low rolling resistance tires for P185/65R15 all-weather radials mounted on aluminum alloy wheels.

while both Ford and Honda have decided to market hybrid technology as an option in standard production vehicles, Toyota will keep Prius unique.

"Part of the vision," says Hermance, "is that Prius will be a technology demonstration vehicle."

The '04 Prius is loaded with optional telematics goodies that are sure to whet the appetites of those interested in a vehicle like Prius. The Smart Entry/Smart Start system uses an embedded chip in the key fob to communicate with the vehicle enabling the lock, which opens when you touch the back of the door handle and allows you to start the vehicle without inserting a key.

There is also an optional Bluetooth-enabled hands-tree cell phone system and a 7-inch touch-sensitive LCD screen that displays standard features like the energy monitor, radio, HVAC controls and optional features such as Toyota's next-generation navigation system and the hands-free telephone functions. The power-flow screen now displays instantaneous fuel economy.

What North Americans won't get is a self-parking option and the electric-drive-only option that will be available on the Japanese car. The '04 Pius features true by-wire technology. Both throttle and shifter are full by-wire systems. Hermance says that the brake system is cooperative.

"When yon step on the brake pedal, you generate hydraulic pressure," Hermance says, "but it's not metered to the wheal cylinders until the computer decides that it needs hydraulic help." The system is designed to utilize the regenerative system as much as possible and cover the shortfall with the hydraulic brakes. In an emergency, the system will pass the hydraulic pressure on immediately.

The '04 Prius uses a new version of regenerative braking called electrically controlled braking. The system combines the benefits of ABS, electric brake distribution and brake sensors, increasing the regenerative capability of the system.

Another unique feature is the electric-inverter air conditioning. The compressor is driven by an integrally-mounted 3-phase 200 volt A/C electric motor allowing it to operate without the engine running at idle, increasing fuel efficiency and reducing emissions.

In addition to cooling the car in the summer, the system can also be used to defrost windows during the winter.

The heart of the 2004 Prius and the future of Toyota powertrain lie in the second generation Toyota Hybrid System now branded as Hybrid Synergy Drive.

The Toyota Hybrid System is a power split system, similar to the system Ford developed for the Escape and, according to Hermance, the same type of system that will be used in the 2005 Saturn view. Basically, the power split system takes an automatic transmission, (a sequentially-shifted automatic or a CVT) and provides it with two separate inputs, one for the electric system and one for the engine. The two functions are combined in the transmission providing the ability for either ICE, electric drive or optimally, the best of both worlds.

Engineers made several improvements to the Hybrid Synergy Drive system. Peak power to the motor was increased from 33Kw to 50Kw (a 50 percent increase) and torque was increased by about 15 percent to 400 Nm. Improved motor control improved mid-range torque by about 30 percent. Maximum speed has been increased to 6,700 rpm.

The generator was structurally increased allowing it to turn at a higher speed for a more aggressive control of the engine. The result was higher engine-off operation while still being able to start the engine. This also improved the balance between the electrical system and the engine system. A high-voltage converter boosts power to 500-volts allowing for the use of the more powerful motor and generator while maintaining the same current level.

"When you buy electronic components, you pay for the ability to carry current, not the ability to withstand voltage," says Hermance, "so if you reduce the current in the system, you can reduce the cost."

Because of the increased efficiency of the system, engineers were able to reduce the size of the power switching devices (the eight insulated bi-polar transistors in the power electronics) by about 20 percent.

"Not only is that a savings in cost and space," says Hermance, "it also increases efficiency because there's less heat rejection from the devices."

Engineers added the new circuits for the electric air conditioning and the high-voltage output while still maintaining the same size package.

The system runs off of Toyotas latest generation 200-volt nickel-metal hydride battery.