TRW, EPS Achieve Fusion

When the all-new '10 Ford Fusion arrives in showrooms this spring, prospective buyers are bound to notice the redesigned front end, sportier look, wider stance, more-powerful engines, enhanced safety features and spiffy ice-blue dashboard lighting.

But less obvious will be a significant switch to full electric power steering from a conventional hydraulically driven configuration. That's exactly what TRW Automotive wants — for consumers to find the Fusion's new EPS inspires just as much confidence and exhibits the same responsiveness and maneuverability as the old system.

“The key is to make it transparent to the end user, whether they're driving electric power steering or hydraulic steering,” says Sanjay Singh, TRW's director-rack drive electric steering. “The system should have a very natural feel to the driver's hand, and not be numb like some of the older generations of EPS.”

TRW's new “belt-drive” EPS is standard on '10 Fusions (and '10 Mercury Milans) powered by a 2.5L 4-cyl. or a 3.0L V-6. A more powerful 3.5L V-6 in the new Fusion (and '10 Lincoln MKZ) is paired with hydraulic steering.

Ford's move to EPS on its high-volume, lower-midsize sedan coincides with the auto industry's zealous push to boost fuel efficiency.

TRW says its belt-drive EPS — also known as “rack-drive” because of the motor's placement directly on the steering rack — reduces fuel consumption and carbon-dioxide emissions up to 10% compared with conventional hydraulic steering, which requires a pump driven off a pulley attached to the engine.

Hydraulic steering systems draw energy whenever the engine is running, even if the vehicle is standing still or going in a straight line on the highway.

The belt-drive system consumes electricity only when the steering wheel is turned. Assist power is applied directly to the steering rack with a belt and ball-nut mechanism.

The system requires no hydraulic pump, hoses or fluid, saving packaging space in the engine bay, simplifying installation at the vehicle assembly plant and reducing potential warranty claims.

By way of comparison, TRW says conventional hydraulic steering consumes fuel at a rate of 0.35 L/100 km driven, while EPS requires an infinitesimal 0.02 L/100 km. That translates to a gain of almost 1 mpg.

The fuel-economy boost is most evident on the highway, when steering inputs are minimal. “The maximum power you're using is in the parking-lot conditions,” Singh says. “Other than that, the power requirements are low.”

The switch to EPS surely factors into Ford's marketing of the new Fusion's “unsurpassed 4-cyl. gasoline fuel economy.”

Ford recently announced the 2.5L I-4 in the new Fusion will achieve 23/34 mpg (10.2-6.9 L/100 km) city/highway, a 16% improvement over the smaller, less-powerful 2.3L I-4, paired with hydraulic steering.

TRW says the Fusion represents the supplier's first launch worldwide for the belt-drive EPS. Production began late last year, and another program is slated to begin this spring, Singh says. Including the Fusion program, TRW plans to launch four belt-drive EPS programs by the end of 2010.

In 2009, Singh says he expects about 200,000 vehicles on the road with the belt-drive system.

EPS comes from several suppliers in many configurations, most of them designed for overseas vehicles smaller than the Fusion. The smaller the vehicle, the less power required to turn the wheels.

TRW was first to market in 1998 with electrically powered hydraulic steering, which uses an electric motor to decouple the steering pump from the engine. A power pack linked to a conventional rack-and-pinion gear provides steering assist on demand, while reducing fuel consumption.

The supplier has more than 13 million EPHS systems in the field. EPHS was supposed to be a waypoint until completely dry EPS systems take hold.

But EPHS continues to be viable in the market because of its packaging flexibility and application across a variety of vehicle segments. Plus, EPHS can deliver fuel savings over conventional hydraulic steering of up to 3% versus 3.5% for?pure EPS.

TRW claims to be the world's No.2 producer of steering systems, behind Japan's JTEKT Corp.

TRW has served the A- and B-segments with a low-cost EPS system that mounts a motor controller directly to the steering column. A torque sensor on the column detects steering inputs and sends a signal to the controller, which drives a motor that turns the wheels.

The new, more robust belt-drive system is designed for slightly larger C- and D-segment vehicles with higher power requirements. Beyond that, for heavier vehicles such as SUVs and minivans, TRW steers its customers to its latest-generation EPHS.

Despite a depressed vehicle market, TRW is gearing up for steady volume increases of its belt-drive EPS in North America and Europe.

By 2011, TRW expects annual production of about 900,000 units. By 2014, TRW plans to produce about 1.8 million belt-drive steering systems annually, says Frank Lubischer, TRW's vice president-steering engineering.

TRW already manufactures more than 1 million column-mounted EPS systems annually, with more than 5 million units on the road currently, Singh says.

Lubischer says TRW is quoting some vehicle programs that will cover up to 3 million units for a single platform.

TRW assembles most of its column-mounted systems at plants in Europe, but Singh says the supplier will launch its first low-volume program in North America within a few years.

TRW recently launched a column-drive steering system for the Ford Fiesta in Europe, and that system will be on the B-car when it arrives in the U.S.

Europe and Asia have embraced EPS earlier than the U.S., primarily with column-drive systems, because those regions prefer smaller cars that are better suited for this technology.

Singh expects the market to need both the column- and belt-drive systems for the foreseeable future, and that one technology will not supplant the other.

The column-drive system can deliver assist forces of up to 10 kilonewtons, while the belt-drive system is capable of up to 13 kilonewtons.

Singh declines to say how much of a price premium the belt-drive EPS carries over hydraulic steering but says the simpler installation at the vehicle plant and improved fuel efficiency are well worth it, especially as new emissions requirements are bearing down.

A major challenge with the belt-drive program was eliminating noises that were common with earlier EPS systems.

“It should not have any electrical or mechanical noises peculiar to EPS,” Singh says. “You don't want customers saying, ‘I've never heard these noises before with my hydraulic steering.’”

A test drive of the new steering system on a prototype Fusion finds it surprisingly quiet during all types of maneuvers.

“At high speed, we want to make sure the system has enough power…so you can avoid a deer or an obstacle in a safe manner,” Singh says.

TRW is producing the belt-drive system for North America at its plant in Queretaro, Mexico. Singh says the company plans to add more capacity in Mexico and Europe to produce the belt-drive system.

Most hybrid-electric vehicles already use some form of electric power steering because of the low fuel consumption, and Lubischer expects that trend to continue.

“Otherwise, you would have to run a permanent parasitic loss through an engine that you keep running, to do hydraulics,” he says. “That doesn't really make sense.”

Lubischer sees a bleak future for conventional hydraulic steering as fuel-economy demands stiffen. He says converting hydraulic steering plants to EPS is not that difficult.

Even BMW AG, often regarded as the benchmark for its precise, on-center steering feel, is migrating away from hydraulics, he says.

“They are going there. They understand it,” Lubischer says of BMW. “I think they are like everyone else, going full-speed into electric steering.”

Year-Old Steering, Driveline Supplier JTEKT Off to Fast Start
subscribers.WardsAuto.com/ar/jtekt_fast_start/

Electric Steering Nearing Hydraulic Parity
subscribers.WardsAuto.com/ar/electric_steering_hydraulic/