Battery Switch Technology


Friday, January 22, 2010

Hybrid Electric Car Technology

2010 Toyota Prius Hybrid Electric Car Technology Exposed

Yountville, Calif. The eagerly awaited details of the 2010 Toyota Pruis are slowly emerging. We already provided an overview of the car after it was revealed at the Detroit Auto Show. Last week, we were in Napa Valley, where Toyota released technical details what will make this vehicle hum (but not too loudly). –Larry Webster
The Engine

Mechanically, the biggest changes for the most popular hybrid electric on the market are in the engine room. The 1.5-liter gas engine is out in favor of a 1.8-liter unit. This larger engine still operates with the late-intake-valve-closing Atkinson cycle, and it produces more lower-end torque. This engine also operates at lower speeds, a fuel-saving move that offsets the larger displacement. There is an electrically operated water pump, which allowed engineers to remove the drive belt and the accompanying parasitic loss from the motor. As before, the crankshaft is offset in relation to the cylinders to reduce friction.

Engine coolant circulates to a heat exchanger that encircles the exhaust just downstream of the catalytic converter. This feature heats the engine up sooner, so it can be warmed up and turned off promptly. Also, it provides quick cabin heat. An aggressive exhaust-gas recirculation system employs cooled exhaust gas that's pumped into the cylinders. The inert gas replaces the intake charge, reducing exhaust-gas temperature and pumping losses.

The Transmission

The Hybrid Synergy drive system uses the same planetary Continuously Variable Transmission as before, but with a new twist. The main electric motor drive, called MG2, was downsized and produces less torque (153 lb-ft versus 295). But a reduction gear-set that connects it to the gearbox allows the MG2 to spin to 13,500 rpm, 7100 higher than before. Consequently, it makes 80 peak horsepower, 13 greater than before. The smaller, lighter MG2 and other refinements in the drive system yielded a 66-pound weight saving.

The Battery

A nickel-metal-hydride battery pack returns. It's been shrunk slightly, but a more effective cooling system allowed a peak output rise from 25 kilowatts to 27 (battery voltage remains at 201.6 volts). The inverter converter has been improved—it's slightly smaller—and provides up to 600 volts of AC current, a 100-volt jump. Toyota has also added a feature many Prius buyers have been waiting for—an electric-only button. Pressing this button on the dash prevents the gas engine from starting until the battery is depleted. Electric-only mileage, however, is slight—on average, a mile. For longer battery-powered runs, we'll have to wait for the rumored plug-in version; it should appear within two years.

Horsepower and Fuel Economy

The total maximum output of the engine and electric motor is 134 hp, 20 higher than before. That should drop the 0-to-60-mph sprint by about a second to 9.5 seconds. Despite the increased pace, the fuel economy has been improved, jumping from 48/45 city/highway to 50/49.

That fuel economy increase is all the more incredible considering that the new car weighs about 110 pounds more, a consequence of meeting tougher crash regulations. For sure, the car's aerodynamics play a role in increasing the on-road efficiency. Airflow around the Prius is carefully managed with flat underside panels, bumper-mounted air deflectors, and that gently sloping rear hatch. The drag coefficient has been reduced to only 0.25.

High-Tech Extras

Toyota left some of the most high-tech stuff outside of the mechanicals. Buyers can opt for the Lane Keep Assist system that detects when the car goes out of a lane and automatically nudges the steering wheel to stay on course. A pre-collision system works in conjunction with radar cruise control to avoid an impending collision by applying the brakes. An optional roof-mounted solar panel powers the fan and keeps a parked Prius cool, reducing the draw on the air conditioning. The new Prius can even Parallel Park itself with the Intelligent Parking Assist. There are also items we're not used to seeing in hybrids, such as leather, power and heated seats, voice-activated navigation and Bluetooth connectivity.

Prices have not yet been released, but expect the base Prius to start around $24,500. Fully loaded, we wouldn't be surprised to see the Prius clear 30 grand.

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