Electric power steering systems currently are used only on very small or very exotic cars, but their fuel-saving benefits will be hitting the automotive mainstream soon, say officials atCorp.'s Saginaw Div.
The steering system and component supplier introduced two new electric power steering systems at the North American Auto Show and says the most sophisticated all-electric version is scheduled to appear on a 1997 1/2 model vehicle of a "major customer." Officials won't reveal details, but hint the vehicle will be built by a European automaker because fuel prices are so much higher there.
More applications are scheduled from 1998 through 2000. GM Europe might be a good guess as the first user, but Saginaw has 60% of the world hydraulic steering pump market and sells to every major OEM -- so it's not a sure bet.
Saginaw General Manager Donald L. Runkle says the primary benefit of an electric power steering system is fuel economy; it can provide a 1 mpg to 1.5 mpg improvement by eliminating parasitic power losses. That's equivalent to taking 300 lbs. (136 kg) of mass from a Saturn-size car, he says.
Completely electric systems are easy to install because they eliminate the complex hoses and fittings of hydraulics and can be incorporated into modules, he adds.
Even so, electrics are more expensive and don't steer like conventional hydraulic systems. Saginaw engineers now are working to make the electrics so easy to install that lower assembly costs will offset the higher electric component costs. "Our target is to bring them to market at the same price as hydraulics, and we're within shouting distance," says William R. Herren, Saginaw's general director -- sales, marketing & planning.
The other problem -- providing a strong "on-center" feel to the steering wheel when going straight and making the wheel spin back to center after making a hard turn as with a hydraulic system -- has been solved with new technology, assures Chief Engineer Dr. Aly A. Badawy.
The only full-time electric power steering system now in use is in the exotic Acura NSX sports car. However, "part time" systems that provide power assist only for parking have been used since 1986 in Asia for very small vehicles. What sets the Saginaw systems apart is that they work full-time and are designed for larger compact cars. The systems can be configured in several different ways and can use conventional or brushless electric motors. However, Saginaw engineers favor the brushless motors because they believe they offer better long-term durability.
The two systems introduced at the show are Saginaw's E-H-Steer (electro-hydraulic) and E-Steer (fully electric). The E-H uses an electric motor to drive the hydraulic power steering pump. This frees the vehicle's engine from parasitic power losses normally required to drive the pump and improves fuel economy. Because the E-H system does not depend on the engine for its power, the electric motor and pump can be installed anywhere in the vehicle, freeing up valuable space in the engine compartment or simplifying installation.
The mid-engine Pontiac Fiero, which could not accommodate a traditional power steering system, was scheduled to be equipped with an early version of this system but was pulled out of production before it could happen. GM's Impact electric car currently uses a Saginaw E-H system.
The more sophisticated E-Steer system offers all the advantages of E-H-Steer but eliminates the hydraulic pump and hoses altogether by using an electric motor to directly assist steering. It senses driver torque on the steering shaft, compares it to vehicle speed and then provides the appropriate amount of assist with the electric motor.