Automotive engineers love to talk about electrically driven vehicles. Replacing the hundreds of rotating and reciprocating parts in an internal combustion engine with a simple electric motor promises plenty – greater reliability and precision for future cars, design freedom to move drive components away from the front of the car, and the possibility of getting rid of the exhaust system and other components.
In recent years, however, the growth of electrification in vehicles hasn’t been driven by Tesla’s Model S or Nissan’s Leaf. It has come from Ford’s F-150, General Motors’ Chevy Silverado, and Fiat Chrysler Automobiles’ Ram pickup lineup. To boost fuel economy, powertrain engineers have been stripping away every component that historically ran directly off the engine, replacing them with electrically driven ones – a trend that should accelerate as 2025 federal fuel economy mandates approach.
While the primary goal of electrified systems has been improving fuel economy, producers of the equipment say their components are also at the heart of new convenience and safety features and could someday power self-driving cars.
“Self-parking cars are the first step, and we’re seeing a lot more of those today,” says Horst Binning, CEO of German electrical automotive components supplier KSPG. “You can’t do any of that with mechanical systems. More and more components in the combustion engine will be electrified in the near future.”
Reducing engine loads
Cool features may be the future of electrical components, but the driver has been fuel economy. In addition to generating power to turn a car’s wheels, engines traditionally had to charge power brake pumps, water circulation systems for cooling, power steering pumps, and air-conditioning compressors. Giant serpentine belts pulled power from the engine to run all of those systems. Designers had to spec engines that were powerful enough to move the car’s metal and turn those belts to charge ancillary systems.
Frank Lubischer, global vice president of engineering and COO of Europe for steering specialist Nexteer Automotive, says the hydraulic power steering system alone was responsible for using up to 5% of the engine’s output. The parasitic losses of those systems quickly add up, forcing designers to up-size engines.
“With hydraulic power steering, you need constant oil circulation and pressure, but you really only need assistance from that system occasionally, typically at lower speeds and when turning from a stop,” Lubischer says.
Electrically powered steering systems can provide the same assist on demand, pulling power from the car’s electrical system only when extra turning power is needed. Then, as designers move enough of the load from the engine to the electrical system, manufacturers can shrink the vehicle’s engine, replacing V-6s with four-cylinder models. Engine downsizing has been a major trend in recent years with many mid-sized sedans – such as the Hyundai Sonata and Chevy Malibu – no longer offering V-6s.
Sizing up small systems
European automakers began replacing hydraulic steering systems with electrical ones in the late 1990s, a decade before the trend caught on in North America. Frank Lubischer, global vice president of engineering and COO of Europe for Nexteer Automotive, says U.S. automakers initially tried to adapt European systems, but that proved more challenging than initially thought.
“How do you apply a system developed for a subcompact or a compact car and make it work on a 1500-series pickup?” Lubischer asks.
European systems work for small vehicles, but when automakers began electrifying pickup steering, Nexteer had to create an all-new system. For Ford’s 2010 F-150, Nexteer abandoned belt-and-pulley-based car steering systems and developed a rack-and-ball-screw mechanism that could move the higher weights over the truck’s drive wheels. Lubischer says the company had to develop new hardening processes for the steel rack, new processes to grind and finish the ball screws, and precision-ground gears with 1µm accuracy tolerances.
“We had to upgrade every component, go to the best electric motors and most sophisticated gearing systems we’d ever used. And we had to stay on a 12V system. It would have been much easier to do if we could have pulled more power, but the standard is 12V,” Lubischer says.
Ford, General Motors, and Fiat Chrysler Automobiles all use Nexteer electrified power steering systems on their light-duty trucks, Lubischer adds.
Better fuel economy
Pulling ancillary systems off the engine is the first step in using electrification to boost fuel economy. Binning says further improvements come from the increased control that designers get from switching from mechanical-analog systems to computer-controlled digital electric ones.
Replacing mechanical water pumps and radiator fan belts with electrically motorized systems reduces engine load, and it allows companies to design cars that shut off their engines at red lights or when stopped in traffic. Start-stop systems, common in Europe and slowly making their way to North America, improve fuel economy by getting rid of idling. Computer controls within the car’s engine support the technology. However, Binning says such systems wouldn’t be possible without electric pumps.
“Right after the engine is turned off, it is still generating a lot of heat that needs to be displaced. That’s the role electrification is playing,” Binning says. “Within the next five years, there will be lots of changes in powertrains, but the U.S. is not going fully to e-mobility. There will be more electrification of cars, but not a significantly larger number of electric cars.”
Additional changes come from electrifying other components, which supports self-driving features and possibly the autonomous car. As Binning notes, self-parking features creeping down from high-end luxury cars to more mainstream vehicles have been the first applications, but more are on the way.
“Making vehicle systems electrical means making them digital. That’s where the control comes in. Once you have an electrically powered system routed to a computer system, the computer can activate and control that component,” Nexteer’s Lubischer says. Cars with adaptive cruise control use radar, laser systems, and other techniques to know where other vehicles and obstacles are on the road. If a driver fails to slow down to prevent a collision, car safety systems can activate the electrically powered brakes.
Lubischer says the car could also steer around the obstacle because the power steering system could support computer-control steering. He adds that such steering overrides aren’t likely until the auto industry figures out who would be legally liable if such as system were involved in an accident.
“Fully autonomous is going to take a lot of work, but some of the driver assistance systems seem more likely,” Lubischer adds. “At follow mode, if you’re stuck in traffic, crawling along at lower speeds, the car can already keep a safe distance from the vehicle in front of you and keep you in your lane.”
Even that basic system requires computers to control braking and steering, something that becomes more likely as electrification grows.
KSPG Automotive AG
About the author: Robert Schoenberger is the editor of TMV and can be reached at 216.393.0271 or firstname.lastname@example.org.