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Innovative Fuel Tank Wins SPE's Grand Auto Design Prize
Twin sheet blow molding cuts weight and reduces emissions for new BMWs
Doug Smock, Contributing Editor -- Design News, November 21, 2008
A revolutionary new system for producing plastic fuel tanks is the grand winner of the 38th annual Automotive Innovation Awards Competition held by the Society of Plastics Engineers (SPE).
The twin-sheet blow molding system (TSBM) developed by Inergy Automotive Systems integrates components into a fuel tank during blow molding, reducing costs and emissions at the same time.
"This technology is the gateway to the next generation of plastic fuel systems, allowing much more complex fuel systems that met the strictest of performance and emissions standards," says Dave Hill, project engineer, Inergy Automotive Systems of Adrian, MI.
In the new process already in use in the BMW AG Series, sheets extrude between a central core and a mold. Core actions attach the components during initial sheet forming. The empty core is withdrawn and the mold is closed to join the formed sheets in a second blowing step. Components that can be attached to the core include baffles, gauges, valves, jet pumps, lines, fuel modules, and canisters.
TSBM replaces co-extrusion blow molding, which requires boring and welding of externally mounted components. "Weight savings are up to 10 percent compared to conventional blow molding," says Hill. "The Twin-Sheet Blow Molding process allows improved wall thickness control." There's an additional 10 percent savings through component simplification and reduction in finishing costs.
"More internal components mean fewer potential fuel leak paths," adds Hill. "Increased design flexibility provides increased tank capacity and driving range." Placing baffles within the tank also reduce noise.
Possibly most significantly, the internal placement of components also reduces emissions. "Permeation of the fuel system can be dramatically reduced compared to current tank systems at the same or lower cost," says hill. "The technology can meet all global evaporative emission standards."
The most important standard right now is in California, which is requiring vehicles to reduce their fuel emission by a factor of ten, to fewer than 54 mg per vehicle per day.
The key to the technology is the in-mold assembly. "We designed the tool so that it can be used with conventional blow molding machines," says Hill. Components are integrated using one of two innovative technologies. Internal welding is used for small components and internal riveting is used for larger components. Parts up to one kilogram can be inserted into the parison. The process also allows attachment of non-compatible materials, such as polyacteal to polyethylene.
The materials suppliers who participated in the technology development are Lyondell Basell, HDPE; Kurray, the EVOH barrier; and Mitsui for the adhesive.
Inergy is expecting to sell up to 3.4 million units of its system in2012 and will do so by increasing by half the number of new markets, in particular in Asia where its strategic clients are concentrated. Inergy is a 50/50 joint venture between Plastic Omnium and Solvay SA, and is a leading global Tier One supplier of complete plastic fuel systems and fluid storage technologies. It's headquartered in Paris and has 25 facilities located in 19 countries. In 2007, Inergy delivered 12.7 million fuel systems.
Other winners are:
- Body Exterior category: An integrated rocker molding/running board system used in the Ford Escape SUV
- Body Interior category: An integrated floor shifter / front console used in the Ford Flex.
- Chassis/Hardware/Powertrain: Injection molded oil pan for the Daimler AG C Class vehicles.
- Environmental: Soy foam automotive seat cushions for the Ford Mustang. Ford Mustang.
- Materials: Thermoplastic elastomer for slush molding of instrument panel skins in the Saab 9-7X SUV.
- Performance & Customization: Hood assembly with dual-weave carbon fiber composite in the Chevrolet Corvette ZR1 Sports Car.
- Process/Assembly/Enabling Technologies: A twin-sheet blow-molded fuel system in the BMW 7 series sedans. Also the grand prize winner.
- Safety: Polystyrene foam for head-impact protection in the Ford Focus.
Note: Design News Contributing Editor Doug Smock served as a member of the Blue Ribbon Judging Panel for the SPE Automotive design competition.
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Innovative Fuel Tank Wins SPE's Grand Auto Prize
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