Electric Assist Is Proving to Be a New Power in Steering Systems
The hydraulic power-steering system--the norm on almost every passenger car and truck being built these days--appears destined to go the way of the solid rubber tire.
Several major suppliers of automotive systems have developed electric-assisted power-steering systems that are likely to make hydraulic systems--with their bulky pumps, power-draining drive pulleys and often-leaky hoses--obsolete.
In fact, some industry watchers say electric steering could be the norm by 2010.
But where several applications are in use in small cars in Europe and Asia and on two limited-production Honda models sold in the United States, domestic auto makers only now are venturing into the technology.
The first deal to supply electric steering for a U.S. auto company was announced this month by Delphi Automotive Systems Corp., the parts and systems developer spun off from General Motors Corp. in 1999.
Troy, Mich.-based Delphi won’t identify its client, but observers believe that it is former parent GM, and that the intended vehicle is a mainstream 2002 or 2003 model. GM would not comment.
Delphi, the world’s largest auto parts maker, says it also is deep in negotiations to provide electric steering for other domestic vehicles.
Additionally, Delphi rival TRW Inc. has said it has 17 contracts to provide or develop its electric steering system for auto makers around the globe. Japanese companies Koyo Seiko and Showa Denko also make electric steering--Showa supplies systems for Honda Motor Co.’s Acura NSX and Honda S2000 sports cars--and other major steering suppliers are developing systems too.
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Delphi, through its Saginaw Steering Systems unit, has been marketing its electric-assisted E-Steer system for more than two years in Europe. Fiat uses it on its Punto compact car and has sold more than 1 million vehicles equipped with E-Steer, says Brian Stainforth, Delphi’s engineering manager for electric steering.
Delphi also has announced a deal with Volkswagen, which plans to begin selling models with electric steering in Europe this summer.
Though an impressive accomplishment in an industry that often measures the speed of technological advances with a calendar rather than a clock, electric steering is an interim measure.
A further advancement still in early development is electronic steering, which would use wire-transmitted digital signals to relay the driver’s steering input to small motors at each wheel. The so-called steer-by-wire system would eliminate mechanical linkages between the driver and the vehicle’s wheels.
“Electric steering is the enabling technology for steer-by-wire,” Stainforth says.
Indeed, as auto makers push for more efficient, more user-friendly vehicles, technologies such as electric steering will become critical, says Nick Twork, a Michigan-based independent industry analyst working with AutoPacific Inc.
“It can help increase fuel efficiency and improve vehicle dynamics, especially when we get into full steer-by-wire and start linking it with systems like vehicle stability control,” he says.
There are two hurdles to widespread use of the systems, Twork says. The first is the need to redesign each vehicle to accept the new equipment. The second is the need to boost passenger vehicle electrical systems from the present 12-volt standard to 42-volt systems that can handle the demands of electric steering and all the other new electronics being jammed into cars and trucks.
Delphi’s present system uses the 12-volt architecture and thus is generally limited to light vehicles with small-diameter tires that require less force to turn.
Electric steering uses a small but powerful electric motor to augment the mechanical forces created when the driver moves the steering wheel.
E-Steer and other electric systems eliminate many elements of a hydraulic system: pumps, fluid reservoirs, hoses and the rubber-belt-and-pulley system that drives it all and saps engine power and fuel economy in the process.
Stainforth says E-Steer can add as much as 1.3 miles a gallon to a passenger vehicle’s fuel economy because its uses power only when the steering wheel is turned. A hydraulic system is a full-time parasite, draining engine power even when the vehicle is moving in a straight line.
By eliminating the hydraulic equipment, electric steering provides auto makers with an integrated system that can cut production costs. The estimated savings of $7 a vehicle doesn’t sound like much--until it is multiplied by the tens of millions of vehicles worldwide that could be equipped with electric steering each year.
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Because it has fewer parts and takes up less room than hydraulic systems, electric steering also gives designers and engineers more room under the hood with which to work. And for the driver, it can make steering easier, more responsive and more reliable.
The typical passenger vehicle’s engine, suspension and front sheet metal place 1,000 to 1,500 pounds of dead weight atop the wheels that a driver must move by turning the steering wheel--weight that is hardest to displace when the vehicle is moving slowly, as in a parking lot.
“There’s a lot friction on the tires as we try to swing a car around, and that’s when we appreciate a light touch,” Stainforth says. “Steering has to be able to turn a heavy load and turn it quickly.”
Electric systems also can be tuned: It is easy to reprogram the controller to make the sport coupe version of a car steer just a little quicker than the passenger sedan model or to boost power assist at low speeds, when it is needed most, and reduce it at high speeds, when a quick response could be dangerous.
The E-Steer system in the Fiat Punto has two driver-selected steering modes: “city” for lower speeds and lots of turning and “highway” for high-speed driving.
Electric motors and electronic controls for them are nothing new, so why isn’t electric steering old hat by now?
“True, we’ve had servomotors and some of the other bits and pieces for decades,” Stainforth says, noting that Delphi has been working on its system for 15 years. “But the technology in E-Steer is significantly different than the technology in your washing machine’s motor.”
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Times staff writer John O’Dell can be reached at john.odell@latimes.com.
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Steering Mechanics
Steering a car or truck requires the driver to turn front wheels glued to the road by half a ton or more of dead weight. Power steering makes the task easier, but today’s hydraulic systems can cut fuel economy and leak. Several automotive parts makers, including Delphi Automotive, have been developing electric power steering that eliminates the bulky, leak-prone parts while improving steering response.
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Electric
Delphi’s electric steerign system eliminates several bulky components found in a typical hyraulic power steering system. Because an electric motor does all the work, it keeps parts to a minimum:
1. Steering Column
2. Integrated electric motor and controller
3. Intermediate shaft
4. Rack-and-pinion gear
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Hydraulic
The system on most vehicles today uses several hoses, a pump and a fluid reservior. The parts take up room under the hood and add weight and complexity to the vehicle.
1. Steering column
2. Intermediate shaft
3. Rack-and-pinion gear
4. Power steering pump
5. Remote power steering fluid reservoir
6. Power steering hoses
7. Half-shaft axels (not shown in electric steering illustration above but common to all front-wheel drive vehicles)
Source:DelphiAutomotive
