DN Staff

September 25, 2006

6 Min Read
Engine, Transmission Controls Push Forward

The powertrain, the first application for microcontrollers in cars, has jumped on the makeover bandwagon popularized on numerous TV shows. Electronic controls have been fine tuned so much over the past few decades that observers have said that it wouldn't evolve much, partially because automakers don't like to change critical engine or transmission components.

But automotive engineers have redoubled their efforts to conserve fuel and improve performance. They're devising new techniques for conventional engines while also pushing new technologies such as hybrids and fuel cells, which by itself adds competition to spark further developments for gasoline engines.

Innovation for emerging hybrid and fuel cell controls is expected, but the wide focus on new techniques for conventional engines is surprising many. "A lot of people thought the powertrain market was just going to grow with car volumes, but there's a dramatic increase with newer engine concepts like variable valve timing and other applications that require significantly more electronic content," says Peter Schulmeyer, director of strategy and marketing for Freescale.

New technologies such as cylinder deactivation are seeing adoption as engine controllers increase their functionality. But there's also a strong focus on fine-tuning technologies such as variable valve timing, which has been around for decades but is continuing to expand from luxury vehicles into the mainstream and pickups.

Fuel injection has also been around for years, but it's also seeing significant improvement. Siemens VDO is touting a system that uses piezo-actuated direct injection to conserve fuel. "Compared with a conventional port injection, Piezo Direct Injection helps reduce fuel consumption by 20 percent, depending on the total level of system integration," says Mike Crane, Siemens VDO's director of powertrain gasoline systems. The injectors, management system, software and fuel pump are all changed to bring this improvement, he adds.

Injectors are also a focus in the push to make diesel engines more popular in the U.S. while reducing emissions to meet tighter regulations in Europe. Delphi Diesel Systems is offering a common rail system that offers five injections, which helps control emissions.

The more injections there are, the more tightly they must be monitored. "Tolerances are very tight, if the amount of fuel injected is too high, fuel consumption goes up, and if it's too low, noise increases," said Detlev Schoeppe, engineering director for Delphi, based in Kokomo, IN.

Transmission Transition

While smaller vehicles made in Japan shift to continuously variable transmission, the high torque used in many American-designed vehicles make that impractical. But that doesn't mean change isn't coming.

Some observers predict that the drive for fuel economy will prompt U.S. carmakers to shift to six-speed automatic transmissions, which offer from 3 to 8 percent better mileage than four speeds. That means transmissions will need more than the four to six solenoids used to help control fluid flow so the clutches work properly.

"In six speeds, you need one PWM and as many as seven constant current of variable force solenoids," says Joe Funyak, global product marketing manager of transmission ICs at Infineon Technologies AG of San Jose, CA. The chipmaker is marketing controllers that manage these solenoids with accuracy of around 2 percent, far better than the 5 percent accuracy now in broad use.

Another aspect of this new focus on powertrains is networking. Today's vehicles have a growing number of CAN networks, prompting engineers to look at techniques that let them consolidate networks. As faster, more capable networks enter the vehicle, engineers are expected to do more to link powertrains and other synergistic applications to gain even more benefits.

Currently, most such efforts focus around FlexRay, which is now starting to see use in applications that require more bandwidth than the ubiquitous CAN bus offers. FlexRay provides their determinism and fault tolerance needed for mission critical applications like drive by wire technologies and powertrains. The knowledge base created by using FlexRay in safety and other areas will help provide openings for the technology, while this usage will also help build the volumes needed to lower costs. Freescale already offers a controller and other companies like austriamicrosystems of Unterpremstaetten, Austria, which next month will unveil its AS8221 high-speed transceiver, are entering the market as interest from automakers grows.

Hybrid Growth

While linking braking, engine and transmission systems together is still emerging in gasoline-powered vehicles, the clean slate offered by hybrid vehicles let them take the lead in this emerging technology. Integration is integral in battery management.

"In hybrids, you're integrating braking and the powertrain," says Larry Burns, GM's vice president of R&D and Strategic Planning. Batteries are charged by braking, he adds.

Hybrid sales are a small fraction of the auto market, but many electronic system and component suppliers are racing to develop techniques that reduce the $3,000-$5,000 cost premium that comes with the many added parts needed to trim fuel consumption. Batteries are the single largest pricing component, so they're getting plenty of focus. IGBTs are also under intense scrutiny. "IGBT modules are large and expensive," says Bob Schumacher, advanced product development and business strategy, Delphi Electronics & Safety division. The company is now offering a module that employs flip chip technologies, providing significant size and cost reductions compared to conventional wire-bonding techniques.

Toyota, which owns a large percentage of the U.S. hybrid market, is pushing the technology to further extend its dominance and set the stage for the next predicted changeover in energy sources. "Hybridization is not only a significant improvement for internal combustion engine power systems, it's also a critical enabler for fuel cell systems," says Dave Hermance, executive engineer for Toyota Advanced Technology Vehicles.

Another challenge is to keep IGBT's cool. Some hybrids employ a separate radiator for them. Infineon is focusing on eliminating that. "We have a junction temperature of 175 degrees C, so we can utilize the engine's coolant," says Sayeed Ahmed, Hybrid Drives marketing manager at Infineon.

Hybrid challenges extend far beyond electronic technologies, even drawing attention from insurance companies like State Farm. Noting that there are already more than 328,000 hybrid vehicles in the United States, the insurer recently established the Auto Design and Extrication Forum. Among its goals are to protect firemen and other first responders of the unique challenges presented by high voltage technologies in hybrids.

Hydraulic Hybrid

While batteries are presently the preferred alternative power source, heavy duty vehicle developers are exploring the use of hydraulics for power. The U.S. Environmental Protection Agency (EPA) teamed up with the U.S. Army, UPS, International Truck and Engine Corp. and Eaton Corp., altering a UPS truck so it uses hydraulic energy to launch the truck, providing substantial fuel savings over conventional driving. "Stored energy basically turns the hydraulic pump into a motor," said Ken Rasmussen, Eaton's global engineering manager.

The hydraulic hybrid diesel urban delivery vehicle stores energy in a hydraulic accumulator, building pressure during braking. Initial tests in the spring showed a 60 to 70 percent improvement in fuel economy and more than a 40 percent reduction in carbon dioxide emissions compared to a conventional UPS vehicle.

However, there are still issues that must be resolved. A key one is that accumulators develop very high pressure, raising safety concerns if hoses or other components break.

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