Nexteer’s eccentric rack bearing reduces EPS systems’ noise and friction, important factors in a vehicle’s perceived quality. Click to enlarge.

Electric power steering specialist Nexteer Automotive has developed a polyamide eccentric rack bearing that has superior NVH (noise, vibration and harshness) performance compared to conventional yoke-style bearings. It will help vehicle manufacturers improve the feel and noise of electric power steering (EPS) systems in vehicles of all sizes.

The need to cut CO₂ is making electric power steering a key technology. According to Nexteer, replacing hydraulic steering with an on-demand electrically powered system can reduce a vehicle’s CO₂ emissions by 5-6 g/km. The technology can contribute significantly to an automaker’s CO₂ reduction targets for 2015 when the European Commission is due to levy steep penalties.

However, as manufacturers improve their vehicles’ efficiency they must also maintain excellent steering feel. Steering friction is a key factor in this, determining the purity of the feedback. A system with lower friction makes the drive feel more assured, communicating what’s happening at the contact patch to the driver’s fingertips and allowing them to place the car on the road more precisely.

Controlling lash, the play between mating components, in EPS systems is a significant part of our advanced development work. A balance between tight tolerances and low friction is what gives steering systems a feeling of directness. The new bearing’s reduced friction ensures that feel is not lost in the system; it also noticeably improves steering noise. As vehicle manufacturers create more premium models for new market segments and reduce vehicle weights, it will help to ensure the perceived quality of vehicles continues to meet customers’ expectations for their brand.

The bearing is the result of our close cooperation with scientists at materials specialists that produced a premium polyamide grade that displays excellent dimensional properties across all operating temperatures. It then underwent countless painstaking iterations to produce a mechanical design that is both simple and robust. It has to absorb shocks and be insensitive to moisture.

—Paul Poirel, Nexteer’s chief product engineer, Europe

Nexteer’s solution eliminates traditional yoke-style bearings that use a spring-loaded bushing to protect against lash, but which can resonate, creating rattles and other NVH problems. Nexteer’s polyamide bearing makes the steering system quieter, more durable and easier to package. Reducing the friction also makes it quicker and easier to fine-tune the system to suit customers’ requirements.

Nexteer is the only Tier One supplier focused entirely on the development of electric power steering systems. It has the industry’s broadest EPS portfolio, offering systems that can benefit every class of passenger vehicle from city cars to luxury limousines and SUVs.

Nexteer is receiving considerable interest in the development. Our eccentric rack bearing recently entered production in the EPS system for the premium B-segment Citroën DS3. The eccentric rack bearing is compatible with all our EPS systems that are based on a rack and pinion gear, whether it’s single-pinion, dual-pinion or belt-drive. We expect other applications to follow.

—Laurent Bresson, Nexteer Automotive’s Executive Director, Europe

Nexteer recently invested more than €40 million (US$52 million) to upgrade its state-of-the-art factory in Poland as part of its preparations for EPS contracts with PSA Peugeot Citroën. It supplies the Citroën C3 and DS3, benchmark vehicles in their class.

Capstone HEV truck solution. Source: Capstone. Click to enlarge.

Capstone Turbine Corporation has initiated a demonstration project with a major US manufacturer of Class 5 through Class 8 heavy duty trucks that will utilize a Capstone 65 kW microturbine as a range extender in a hybrid electric drive system. In June, Capstone released configurations of the C30 (30 kW) microturbine as a range extender meeting California Air Resources Board (CARB) requirements for New On-Road Heavy-Duty Engines for Urban Bus – Hybrid service with no aftertreatment.(Earlier post.)

This truck will be the first to take advantage of the complete Capstone Drive Solution, which includes the Capstone microturbine along with liquid cooled power electronics, permanent magnet traction drive motor and vehicle power control system.

The electric hybrid vehicle market is in a significant growth phase, with essentially every manufacturer of trucks, buses and automobiles looking for the right solution to serve their customers. Capstone’s microturbine technology offers many benefits for these applications, including our extremely low emission levels that meet the most stringent CARB and EPA 2010 requirements without any exhaust after-treatment.

I am pleased that a major OEM in the heavy duty truck market is investing its time and resources to demonstrate the Capstone Drive Solution and that the demonstration will include getting this vehicle in the hands of some of their key customers as well.

—Darren Jamison, Capstone President and CEO

Capstone’s HEV drive system. Source: Capstone. Click to enlarge.

The Capstone Drive Solution will make it easier for vehicle manufacturers to integrate microturbines into a series hybrid electric drivetrain. As part of a recent joint development agreement with CalMotors, the Capstone HEV product offering will now include inverter drives, traction motors and a vehicle power control module that will seamlessly integrate with Capstone 30kW and 65kW microturbines.

The inverters and traction motors are mobile hardened versions of the proven Parker Hannifin industrial motor drive products. (Earlier post.) The Capstone microturbines are able to operate on traditional liquid fuels such as diesel and biodiesel but can also utilize alternative fuels such as natural gas without sacrificing efficiency.

This demonstration project is the first of several vehicle applications we are working on that will use the new Capstone Drive Solution. The other projects include Class 4 commercial trucks and Class 8 tractors and utilize both new OEM applications like this one and retrofits to existing vehicles. We are also pursuing marine applications for both auxiliary power and propulsion. Our new Capstone Drive Solution offering will open a lot of opportunities for electric drive systems where our ultra-low emissions and high efficiency have an advantage over more traditional prime movers.

—Jim Crouse, Executive VP of Sales and Marketing

Controlling soot from fossil fuels and solid biofuels may be a faster method of reducing Arctic ice loss and global warming than other options, including controlling CH₄ or CO₂, although all controls are needed, according to a new study by Dr. Mark Z. Jacobson at Stanford University.

Results of the study suggest that soot is second only to carbon dioxide in contributing to global warming. However, climate models to date have mischaracterized the effects of soot in the atmosphere, according to Jacobson, director of Stanford’s Atmosphere/Energy Program. Because of that, soot’s contribution to global warming has been ignored completely in national and international global warming policy legislation, he said.

Controlling soot may be the only method of significantly slowing Arctic warming within the next two decades. We have to start taking its effects into account in planning our mitigation efforts and the sooner we start making changes, the better.

—Mark Jacobson

The study will be published this week in Journal of Geophysical Research (Atmospheres). Jacobson used a computer model of global climate, air pollution and weather that he developed over the last 20 years and updated to include additional atmospheric processes to analyze how soot can heat clouds, snow and ice.

Soot—black and brown particles that absorb solar radiation—comes from two types of sources: fossil fuels such as diesel, coal, gasoline, jet fuel; and solid biofuels such as wood, manure, dung, and other solid biomass used for home heating and cooking around the world.

Jacobson found that the combination of the two types of soot is the second-leading cause of global warming after carbon dioxide. That ranks the effects of soot ahead of methane, an important greenhouse gas. He also found that soot emissions kill more than 1.5 million people prematurely worldwide each year, and afflicts millions more with respiratory illness, cardiovascular disease, and asthma, mostly in the developing world where biofuels are used for home heating and cooking.

Jacobson found that eliminating soot produced by the burning of fossil fuel and solid biofuel could reduce warming above parts of the Arctic Circle in the next fifteen years by up to 1.7 degrees Celsius (3 degrees Fahrenheit). For perspective, net warming in the Arctic has been at least 2.5 degrees Celsius (4.5 degrees Fahrenheit) over the last century and is expected to warm significantly more in the future if nothing is done.

Soot lingers in the atmosphere for only a few weeks before being washed out, so a reduction in soot output would start slowing the pace of global warming almost immediately. Greenhouse gases, in contrast, typically persist in the atmosphere for decades—some up to a century or more—creating a considerable time lag between when emissions are cut and when the results become apparent.

The most immediate, effective and low-cost way to reduce soot emissions is to put particle traps on vehicles, diesel trucks, buses, and construction equipment. Particle traps filter out soot particles from exhaust fumes. Soot could be further reduced by converting vehicles to run on renewable electric power.

Jacobson found that although fossil fuel soot contributed more to global warming, biofuel-derived soot caused about eight times the number of deaths. Providing electricity to rural developing areas, thereby reducing usage of solid biofuels for home heating and cooking, would have major health benefits, he said. Soot from fossil fuels contains more black carbon than soot produced by burning biofuels, which is why there is a difference in warming impact.

Black carbon is highly efficient at absorbing solar radiation in the atmosphere, just like a black shirt on a sunny day. Black carbon converts sunlight to heat and radiates it back to the air around it. This is different from greenhouse gases, which primarily trap heat that rises from the Earth’s surface. Black carbon can also absorb light reflecting from the surface, which helps make it such a potent warming agent.

Warming of the air by any chemical, including soot, enhances natural surface emissions of water vapor [e.g., Dessler et al., 2008] and methane [Schutz et al., 1990; Anisimov, 2007] and chemical production of ozone in already-polluted locations [Jacobson, 2008b]. These three gases are all greenhouse gases, and ozone is a surface air pollutant. Warmer temperatures due to soot and other components also increase emissions of ozone and particulate matter precursors, including biogenic organic gases [e.g., Guenther et al., 1995] and NO. As such it is important to investigate whether controlling soot may reduce not only temperatures and primary particles, but also

secondary air pollutant gases and particles.

—Jacobson, J. Geophys. Res.

Black carbon has an especially potent warming effect over the Arctic. When black carbon is present in the air over snow or ice, sunlight can hit the black carbon on its way towards Earth, and also hit it as light reflects off the ice and heads back towards space. Black carbon also lands on the snow, darkening the surface and enhancing melting.

There is a big concern that if the Arctic melts, it will be a tipping point for the Earth’s climate because the reflective sea ice will be replaced by a much darker, heat absorbing, ocean below. Once the sea ice is gone, it is really hard to regenerate because there is not an efficient mechanism to cool the ocean down in the short term.

—Mark Jacobson

Jacobson is a senior fellow at the Woods Institute for the Environment. This work was supported by grants from the US Environmental Protection Agency, NASA, the NASA high-end computing program, and the National Science Foundation.

Resources

• Mark Z. Jacobson. Short-term effects of Controlling Fossil-Fuel Soot, Biofuel Soot and Gases, and Methane on Climate, Arctic Ice, and Air Pollution Health. J. Geophys. Res., In Press.

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