Are you sitting comfortably?01 January 2011
Ryan Borroff discovers in there needs to be a fundamental rethink in seating design and materials
The worldwide trend is towards smaller, more fuel-efficient cars. Yet consumer expectations of space and comfort remain the same. The pressure is on automotive seating engineers to develop seats that are lighter, thinner and less complex, while offering similar comfort and safety levels.
It's a tough challenge made tougher, considering end-of-life recycling requirements and the need to use more eco-friendly materials. But, despite seats representing almost 40% of the weight of a vehicle interior, the evolution of seat design appears slow. Does there need to be a fundamental rethink in automotive seat engineering?
Not necessarily, says Karl Henn, engineering manager, global seating systems, Lear Corporation. "Lighter and thinner seats get a lot of press. This is because mass and thickness are easy to measure. Suppliers are being pushed hard to meet increasingly aggressive mass targets, but there is no sudden revolution – just a gradual trend to thinner and lighter seats. The real frontier is in what the end consumer experiences: in craftsmanship, seating comfort and feature usability, in being able to use seat functions intuitively."
These are not traditional areas of working for engineers, and the trend now is towards a closer collaboration between seat engineers and vehicle designers. If there is a revolution, says Henn, it is in the design engineering process: "From an engineering perspective, this fundamental rethink is beginning. Engineers like measurables, but the seats we need to be engineering now are craftsmanship and comfort focused, which are not easy to measure.
The challenge is to find a way to objectively determine how comfortable a seat is and the same with craftsmanship or features usability; to get engineers cross-trained into these types of disciplines, so that we can confidently measure factors such as defining what comfort means.
"Better understanding of seat engineering means we can deal with these issues at the design stage, using robust processes to deal with integration challenges. By using anthropometric data, we have been able to develop comfort and safety features into parts that were serving other functions as well, while lowering mass and making the manufacturing process easier. Now we have to ensure that most of the major parts in a seat fulfil more than one role. For example, our Dynamic Environmental Comfort System (DECS) weighs up to 50% less than other systems. We couldn't do that ten years ago."
The focus is on removing foam and reducing components, either by design or in the manufacturing process. Johnson Controls has been focusing on the seat construction process. The company has adapted a high-frequency welding process to enable designs and imprints to be applied to seating trim covers.
"Usually, the cover of a car seat may comprise anything from a dozen to over 50 parts that are usually found in the central panels of the seat surface and in the backrests," explains Marc Van-Soolingen, senior design manager, seating, consumer
& market research, Johnson Controls Automotive Experience. "The traditional method is to weave these designs into the material panels by a flat-bed or round-knit process, before they are filled with a layer of foam and backed with facing material into a complete seat cover. HF welding simplifies manufacturing, as the covers can be created in a single colour, since all of the design elements are applied at a later stage. This technology [means] new colours and designs [can be introduced] to the vehicles in a cost-effective way."
So what about the environment? Some suppliers are already using alternative eco materials in vehicle seats. Lear and Magna Seating have soy-based foam products in production vehicles, though their use has been questioned for competing with food supply resources. Suppliers are looking at developing foam materials from recycled product. Magna Seating is using a new technology to create renewed polyol – the key raw material used in polyurethane foam – from old car seat cushions. The material is now used in the seats of the 2011 Jeep Grand Cherokee.
Meanwhile, Faurecia may yet have shown a future direction for vehicle seating by eliminating foam altogether. Seen in its Light Attitude concept car, its Sustainable Comfort Seat uses two sheets of injection-moulded thermoplastic polyurethane, instead of foam. What would normally be the metal seat frame structure has been replaced by injection-moulded nylon and a long-glass-fibre structural frame. As the head restraints have also been injection moulded, there is no steel or foam used there either. The result is reduced weight and thinner seats.
For tomorrow's car seats, the evolution will continue by using new, non-ferrous materials for structural elements and by the gradual improvement of the seat design through materials commonisation and consolidation. The thin, sculpted seats seen in concept vehicles may yet begin to appear in production vehicles, but "tomorrow's seats will see much more focus on craftsmanship and brand differentiation in the interior", says Henn. "I am not convinced seats will look a great deal different over the next five years or so."
After all, this is an evolution, not a revolution.
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