Search Auto-Repair-Questions

Wednesday, May 25, 2011

As automakers hunt for ways to boost fuel economy, many systems in gasoline-powered vehicles shift to electricity

2012 Buick Lacrosse Regenerative Braking
The lines separating electric vehicles, hybrids and conventional gasoline-powered vehicles are blurring as automakers add similar electric-powered features to all three.
Electric power steering, stop-start engine systems and electric-powered oil pumps are among the features originally intended for EVs and hybrids that are being adapted to gasoline-powered vehicles.
The goal: Improve fuel economy by cutting parasitic energy loss that occurs when vehicle accessories are powered by belt drives connected to the engine.
Gasoline-powered vehicles also are starting to get regenerative brakes, which convert kinetic energy into electricity to recharge the starter battery.
Among the leaders in the effort is BMW AG, which is rolling out these and other technologies under its EfficientDynamics fuel-saving program.
BMW has introduced electric-powered oil pumps, engine coolant pumps and steering systems. Now it plans to add regenerative brakes and stop-start systems to all its vehicles, and it is developing some gee-whiz computer controls to improve vehicle efficiency.
GM's approach
Mass-market automakers are taking a similar approach. General Motors, for instance, has improved its mild hybrid technology and reintroduced it as eAssist.
Features of eAssist, which will be available on the 2012 Buick LaCrosse and Regal and 2013 Chevrolet Malibu, include stop-start systems, and regenerative brakes that recharge a small lithium ion battery.
The lithium ion battery, in turn, provides power to the stop-start system, reducing the starter battery's workload. The separate starter battery on the three cars is a traditional 12-volt lead-acid unit.
When the vehicle accelerates, the lithium ion battery provides extra power to the wheels via a motor that doubles as the car's alternator and starter motor. A drive belt connects the alternator-starter to the crankshaft. The battery and alternator-starter alone cannot power the wheels; they only provide an assist.
To GM, eAssist is attractive because it is much cheaper to produce than a hybrid powertrain.

"Consumers want fuel economy," says Buick spokesman Nick Richards. "But the cost [of a full hybrid] holds them back. So we didn't redesign the entire vehicle around the powertrain."
The 2013 Malibu with eAssist gets an estimated 38 mpg on the highway, vs. 33 for the standard 2011 base Malibu.

These electrical devices have created demand for improved engine control units and sophisticated software to manage the electrical system.
Electric power
Here's a quick tour of key components in the electrification of the vehicle:

-- Stop-start systems. When the motorist stops the vehicle, the engine control unit automatically stops the engine, then restarts it when the driver lifts his foot off the brake. Stop-start can improve fuel economy from 4 to 10 percent. These systems typically require an upgraded starter motor and a more durable battery. Robert Bosch GmbH, Denso Corp. and Continental AG have developed stop-start components.
-- Electric power steering. Conventional power steering uses a hydraulic piston to exert the force needed to turn the wheels. The hydraulic system draws its energy from a belt drive connected to the engine. Electric power steering replaces the hydraulics with an electric motor mounted on the steering column or in the engine bay. Unlike a hydraulic system, the electric motor uses power only when the vehicle is turning. Electric power steering can improve fuel economy as much as 4 percent. Major suppliers include ZF Friedrichshafen AG, TRW Automotive Holdings Corp., Nexteer Automotive, Mando Corp., NSK Ltd., Denso Corp. and JTEKT Corp.

-- Electric-powered oil pumps and engine coolant pumps. BMW has designed an engine management system that regulates operation of the coolant and oil pumps, depending on engine conditions. These pumps draw power from electric motors rather than belt drives connected to the engine.

-- Electric parking brakes. An electric parking brake eliminates the need for a parking brake lever or pedal.

-- Regenerative brakes. These systems, mainstays of electric vehicles and hybrids, are starting to appear in conventional vehicles. They recharge the battery when the motorist steps on the brakes.

-- Upgraded batteries. To handle the increased load of electrical accessories, automakers are installing more durable 12-volt lead-acid batteries.

No comments:

Post a Comment