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FIRST 7-SPEED AUTOMATIC GEARBOX HAS SHIFT PLATE OF DUPONT ZYTEL
A shift plate made of DuPont Zytel nylon carries the fully integrated gear-change control system of DaimlerChrysler's trend-setting 7G-Tronic seven-speed automatic gearbox. The complex part, about 40 cm long and moulded to close tolerances, maintains its vital functional properties even though it works while immersed in gear oil at up to 140 °C. A flexible printed circuit, based on the DuPont Pyralux system, connects the electronics with the magnetic valves and with various sensors and floats which are also mounted on the shift plate. The entire module was developed and is supplied by Siemens VDO Automotive AG, Regensburg. Geiger technik, of Garmisch-Partenkirchen, supplies the shift plate. Zytel LM70G35 HSLX was identified as the optimal material for this demanding application. This heat-stabilised nylon 66, reinforced with 35 % glass fibre, has outstanding resistance to hot gear oil and all its aggressive additives. Thanks to its very good dimensional stability, the components of the electronic control unit work reliably independently of the operating temperature. The resin's combination of high stiffness and elasticity allows snap-fits to be integrally moulded into the part; it also meets Siemens VDO's requirement for laser-printability. Gerhard Lepsien, Key Account Manager at Geiger technik, comments: "We and DuPont were both involved in the module's development from the beginning. This meant that, at an early design stage, we could influence decisions affecting processing methods and parameters, and we could match the tool optimally with the part. DuPont helped us with mould-filling simulations and warpage analyses when evaluating various gating systems. As a result, we can respect very close tolerances without any difficulty, even though the part is a very large one." A flexible printed circuit carries the signals and currents between the control electronics and the gear connector, the sensors and the peripherally arranged magnetic valves. The flexible circuit is based on a Pyralux carrier laminate which is made up of a DuPont Kapton polyimide film, a high-temperature acrylic adhesive and a copper film. After etching, another insulating layer of Pyralux, made up of a second Kapton film with the same acrylic adhesive, is adhered under pressure onto the carrier laminate. In the electronics area, the back of this flexible circuit is laminated onto a rigid aluminium plate. To save space, the front is sealed directly onto the shift plate of Zytel. The film together with the shift plate thus forms an oil-proof housing for the electronics. DaimlerChrysler's 7G-Tronic seven-speed automatic gearbox has been standard equipment on Daimler-Chrysler's top-of-the-range eight-cylinder models since late 2003 and is now an option on certain models in the upper-medium range. It lowers fuel consumption, improves acceleration and produces faster bursts of speed than conventional 5-speed automatic gearboxes. Siemens VDO Automotive is a leading supplier of electronics, electricals and mechatronics to the automotive industry. As a development partner to the automotive industry the company makes products for the drive-train, motor-control electronics and fuel injection technology, helping to improve motor performance and reduce emissions. GEIGER technik GmbH, established in 1960, is an automotive industry supplier with about 1000 employees working in four plants in Germany. It has special competences in the production of injection-moulded and extrusion-blow-moulded parts for under-the-bonnet applications.
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