Interiors: Battle of the Bulk
By rethinking designs and working toward more efficient solutions, seats will be major contributors to vehicle downsizing and lightweighting.
According to Thomas Gould, Design Director, Industrial Design; North American Automotive Experience at Johnson Controls: “There was a lot of movement toward smaller vehicles with the first spike in gas prices a few years ago, and it showed people didn’t want to compromise. They just wanted a smaller vehicle.” This trend will continue as automakers struggle to meet the new fuel economy requirements. The question then becomes: How?
“If I can take 50 mm out of the seatback,” says Gould, “I can pull that sliver out of the entire vehicle.” Taking this slice out, however, requires cooperation between supplier and OEM at the earliest stages. Otherwise you end up with a vehicle that is lighter and more fuel-efficient, but that is unappealing to the buyer.” Enter Eric Michalak. He has the ridicu-lously long title of Senior Manager New Technologies, Complete Seat, JIT and Safety Experience. He’s also a member of Johnson Controls’ Technology and Advanced Development (TAD) group. That unit created the “Comfort Thin” seat.
Currently under intense scrutiny by automakers globally, this seat concept is built around Johnson Controls’ proven modular seat structure, and is designed to be adaptable for multiple applications and use in all rows of a vehicle. It uses decades’ old mattress technology—individually pocketed coil springs—to reduce seatback thickness to 33 mm through its centerline. (Moving to a unique seat structure would bring this down to about 25 mm.)
Though each coil spring can be easily compressed between thumb and forefinger, distributing the occupant load across rows of springs provides the proper support and lets the seat contour to the user’s back. This makes it feel safe despite its shallow dimensions. Because the coils are positioned in a grid pattern, the spring rates can be changed by rows, allowing for personalization. “I can give you a different seat contour just by changing the springs,” says Michalak. The grid pattern also makes it relatively simple to quickly prototype a new design, or to construct the same basic seat with different comfort characteristics and trim between models, platforms or even across an OEM’s entire lineup. And the springs (30 to 35 mm in diameter in the back with 15- to 17-mm coils along the bolster and top) are sequestered inside individual pockets made from permeable polypropylene.
A rigid plastic seatback provides a solid base to which the pockets are high-frequency welded. This provides a stiff surface for a pneumatic lumbar support that can be smaller than normal because it does not have to compress seat foam before it moves forward, which saves both weight and money. Further, the seatback can be molded with integral channels that flow air through the individual pockets (the blower would just have to clip on the seatback). Seat heaters, instead of sitting on top of the foam, would sit on the base and radiate heat upward through the individual pockets. “Not only is this more com-fortable and more like the forced air system in a house,” says Michalak, “it reduces the number of parts and increases quality because you aren’t flexing the heating elements.” Also, because the back and pockets are made from similar materials, the seatback can be recycled in a single-stream process once extraneous items like the lumbar support and heating element are removed. A magnet separates the metal from the plastic.
The Comfort Thin’s unique seatback design has another advantage. It drops the H-point by 27 mm by letting the occupant sit further in the seat, and less on top of it. This creates the opportunity to reduce the length of the lower cushion. Says Michalak: “If we get in early enough, we can take these dimensions out of the cabin, or leave them in the cabin with a lighter seat that offers its own add-on effects through-out the vehicle. Either way, vehicle energy consumption goes down.”
And they have other ideas related to reducing the size and space of seats without sacrificing comfort. For example, there’s the Slim Stow seat, which has a slightly different twist on the way people think about seats: It is about sitting in the seat rather than on it. Intended to replace the current folding rear seat design in full-size pickups, the Slim Stow is lighter and takes up 33% less space than traditional designs. The seat’s tubular upper frame structure contains the child seat attachment points and side bolsters, while the folding lower portion surprisingly has 50% more foam than usual in comfort areas. “The kinematics of this design do a number of things,” says Gould. “They allow the folded seat to stow behind the C-pillar, increasing the load floor space available. Plus, it moves the seatback down 100 mm in its stowed position.” This gets the FMVSS 202A-compliant headrests pretty much out of the line of vision.
In order to get the occupant to sit in the seat rather than on it, the center portion of the seat gently drops below the level of the bolsters. All of this movement is done without the use of assist springs. “It’s all counterbalanced,” says Gould, “and the seating area is balanced to the weight of the occupant so that it feels natural when you sit down.” The Slim Stow was designed for weight and space savings and, at a minimum, cost neutrality. It currently uses 30% fewer materials than a conventional seat, and could be combined with the pocketed coil design of the Comfort Thin to create a hybrid seat that not only folds more compactly, but which reduces the size of the deployed seat. This would help automakers reduce the size and weight of their most profitable vehicles without hurting their capability, things which are also important to consumers.
Further refinements will come in other areas, like smaller, lighter, more powerful adjustment motors and the use of touchscreen menus for seat adjustments instead of buttons and switches. Even things that were tagged and sewn in (e.g. the labels for the seat-mounted airbags, tether, etc.) can be put right into the trim patterns, eliminating a part. “There are things we can do with stitching and trim,” says Gould, “that give us decorative stitching on a surface, including construction sews as part of the seat design, high-frequency welding and embossing for a different look, and laser etching the surface layer. We even have a leather substitute that looks like the real thing, but weighs a lot less and is more environmentally friendly in terms of how it is produced.”
With the proper lead time and inte-gration into the vehicle development cycle, it’s unlikely that future vehicle buyers will give up any of the comfort and convenience they have come to expect or notice the bulk that is missing.
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