For the first time in Europe, a polymer bracket (molded in DuPont™ Zytel® nylon) is used to secure the ‘hot-ends’ of exhaust systems to the underside of a car.
anvisgroup of Bad Soden-Salmünster, Germany, working in cooperation with Volkswagen, has developed the first catalytic converter bracket for cars to be made from an engineering thermoplastic.
Due to its position – in close proximity to the engine where temperatures of up to 175°C, high static and dynamic forces, moisture and chemicals combine – steel plates had previously been considered irreplaceable for such applications.
Yet anvisgroup has proven the opposite by developing an innovative, two-component bracket based on glass-fiber reinforced DuPont™ Zytel® nylon and rubber. Since mid-2006, the design has proven itself at the ‘hot end’ of exhaust systems on all new vehicles belonging to Volkswagen’s so-called Golf platform (PQ35).
Manufacture of the newly-designed bracket starts with the injection-molding of the cross-bar in DuPont™ Zytel® nylon resin. During a second production phase, the rubber bearings, either made from EPDM (for diesel and smaller petrol engines) or the more heat-resistant silicon rubber VMQ (high-performance petrol engines) are molded on. Finally the aluminum bushings, required to secure the bracket, are assembled by force fitting. Mounted between the exhaust manifold and the catalytic converter, the two-component part provides flexible and attenuating support for the exhaust system in the x-direction, while absorbing static and dynamic loads in the y- and z-directions. Thus it prevents, for example, the exhaust system from jolting forward in the event of a sudden deceleration, which could otherwise damage the sensitive, flexible metal bellows that decouples load change movements and vibrations between the engine and the exhaust system.
Comprehensive testing, carried out by anvisgroup, showed that Zytel® 70G35HSL, a hydrolysis-stabilized PA66 with 35 wt. % glass fibers, can meet OEM requirements for dependability for the entire lifecycle of the vehicle. “The component was subjected to the kind of extreme conditions that you would only experience in real life if you were to drive a car and heavy trailer uphill on a potholed road for hundreds of kilometers,” comments Gerhard Heckmann, product group manager for exhaust system mountings and decouplings at anvisgroup. “Our test results confirmed that, even then, the cross-bar made of glass-fiber reinforced Zytel® continues to perform faultlessly. Indeed the new catalytic converter bracket offers high levels of safety over its entire lifetime.”
In addition, the new design offers further decisive benefits: Firstly, the polymer component weighs only 165g and is therefore considerably lighter than its metal counterpart, which comes in at 300g. Secondly, it provides the opportunity for cost-efficiencies during manufacture because, for example, surface protection is no longer required to prevent corrosion. “With the completion of this project we have been able to implement the first polymer mounting for the ‘hot end’ of the exhaust module. Hence there is nothing to prevent the development of a polymer alternative for the ‘cold end’ as well,” concludes Heckmann.
anvisgroup develops innovative functional solutions for vehicle dynamics, comfort and safety. Its product portfolio includes chassis components, power-plant suspension systems, exhaust system mountings and decoupling elements/TMD. As a global innovator of acoustic- and vibration-control solutions for the entire vehicle, anvisgroup and its 2200 employees achieved a global turnover of 260 million Euros in 2006.