Safety, driving pleasure, esthetics - when you drive a car, it is not just the steering wheel that has a major influence on the driving experience, but also the top column module that connects the steering wheel with the control unit. The French automotive supplier Valeo has now developed a top column module whose housing and levers are made of Basf’s engineering plastics Ultramid (PA) and Ultradur (PBT). It is around 20% lighter than the previous model and benefits from the outstanding surface finish, the good UV resistance and the excellent mechanics of the Basf materials. The top column module is used by the BMW Group in its vehicles with rear-wheel drive for the BMW 3 to 7 series.
The levers for the indicators and windshield wipers are noted for the particularly high-quality surface finish and stability of Ultramid B3EG10 SI. The surface polyamide, which is highly filled with 50% glass fibres, offers an ideal combination of mechanical and visual properties. It is therefore used in surface components which not only need to look attractive, but must also be extremely stable and UV-resistant. The material was originally developed for the furniture industry, where it is now used in numerous design and office chairs. Valeo carried out the tests on the resistance of car interior components in accordance with DIN EN ISO 1043-1/GS 93016.
The two-part core of the top column module is made of different Ultradur grades. The lower carrier housing made from Ultradur B 4300 G4, which is reinforced with 20% glass fibres, is manufactured by the company Buck Spritzgussteile Formenbau using the MuCell process. In this physical foaming process, nitrogen is added to the polymer melt during injection-moulding, which leads to the formation of a foam structure. As a result, the weight of the component is reduced by around ten percent and the dimensional stability is increased without any adverse effect on the high rigidity and excellent chemical resistance of the material. The upper top column module housing, on which the steering wheel is mounted, is made from the unreinforced PBT Ultradur B 4520. It is noted for its low water uptake and therefore high dimensional stability. Moreover, it combines an appealing surface finish with excellent dimensional stability at high temperatures. This well-balanced combination of properties is the basis for ensuring that the steering wheel can be mounted safely on the top column module.