No matter what the final Corporate Average Fuel Economy (CAFE) numbers turn out to be, every piece that goes into future vehicles will be scrutinized for weight savings and performance improvements. That includes the interior, particularly the seats. “As vehicles shrink over the next few years,” says David Kingston, executive director, Complete Seat Product & Business Planning, Johnson Controls Automotive Experience (Plymouth, MI; http://www.johnsoncontrols.com), “the challenge is fitting the occupant and saving some room without adversely affecting comfort.” From a seating perspective, 65% to 70% of the weight of a seat is in its structure. Therefore, as Kingston says, “If you don’t take it out there, you won’t be getting much out elsewhere.”
Accordingly, Johnson Controls has begun using continuous laser welding to add strength while reducing the thickness of the steel in seat side members from 1.2 mm to 0.7 mm. In addition, it is integrating smaller motors into the seats, using parts integration to eliminate brackets—up to 1.0 lb. per seat in a recent design—and the associated manufacturing costs, creating new mechanisms with lower mass and better packaging, as well as introducing more esoteric weight saving items like thin-wall headrest tubes. This, however, may not be enough in some applications. These hybrid aluminum/steel structures will put steel only where it is needed for strength, while larger, pricier vehicles walking the mileage tightrope may find themselves incorporating custom solutions that use magnesium and composites. Says Kingston: “It will take a systems approach.” He explains that this is much like the one employed to meet tougher seatback recliner standards, to save weight, and meet tougher safety standards (the recliners, frames and mechanisms were integrated in a laser welded high-strength steel structure), and this will lead to the use of even smaller motors, tracks, and mechanism in the future.
However, there is another way in which seating is being asked to reduce overall vehicle weight. By making seats thinner, OEMs can remove an equivalent slice out of a vehicle’s structure without adversely affecting the couple distance—measured from the centerline of the occupants’ H- point from one row to the next—between each row of seats. In many cases, that means taking foam out, but doing so requires a new formulation so comfort isn’t compromised. Johnson Controls claims its VibraTech foam not only can be tailored to a vehicle’s ride characteristics and offer up to a 40% improvement in road vibration absorption—it’s used in the Lexus RX330 crossover—but can allow cut foam depth to be reduced from 50 mm to 30 mm without reducing comfort levels. Yet this is only part of the equation. The perception of room—as Boeing found out with its work on the interior of its new 787 jetliner—is almost as important to the comfort equation as the room itself.
“Putting a flat, park bench-like seat in a vehicle is a recipe for disaster,” says Kingston, “because people equate bolstering and contour with comfort.” So it designed its first row Slim Seat around tubular steel, VibraTech foam, and a new lumbar support design to create a thin cross-section seatback that liberates fully 50 mm of knee room in the second row. “That gives the OEM the choice of moving the middle row up that amount and taking a 50-mm slice of mass out of the vehicle, or taking a smaller slice and improving knee room,” says Kingston. Shown at the Frankfurt Motor Show in its i3 concept car, it was paired with a second row seat whose split lower cushion folds flat against the rear seatback to provide increased cargo room in the passenger compartment, as well as space under the seats for hidden small item storage. It’s this flexibility that has intrigued a number of OEMs interested in giving buyers full-scale space in a smaller—and lighter—overall package.
One thing that might make the job easier for seat suppliers is a shift to an “inside-out” design approach where the vehicle is designed around an interior package adapted to the mechanical and other requirements of the vehicle as it is engineered. And though this ideal is unlikely to be reached, Kingston says recent moves toward earlier involvement in the layout and design process have allowed suppliers to reach better compromises in terms of weight, space, flexibility, and consumer acceptance. “The consumer doesn’t care what compromises you had to make,” he says, “just that you made the right ones in terms of comfort and convenience. That’s the real mass reduction challenge."