Leverkusen - Double clutch transmissions are currently a popular alternative to conventional automatic transmissions in cars. They enable highly dynamic acceleration thanks to quicker gear shifts without interrupting the tractive power and also reduce fuel consumption. A German sports car has now been equipped with the first double clutch transmission with a plastic oil pan. The plastic in question is Durethan AKV 35 H2.0 SR1 polyamide 66 from LANXESS, which is reinforced with 35 percent by weight glass fibers. “Use of our material coupled with the design flexibility and function integration capabilities of thermoplastics in general made it possible to create a very shallow oil pan. It would have been impossible to comply with the stringent requirements relating to installation space and to produce the complex geometry of the molded part using sheet steel,” explains Frank Krause, a LANXESS expert on the use of polyamide under-hood components. The oil pan is injection molded by IBS Filtran GmbH in Morsbach, Germany, and the fully assembled transmission is manufactured by ZF Getriebe GmbH in Friedrichshafen.

The oil pan has a height of just over 20 millimeters at its narrowest point. This gives the component a low inherent stiffness and increases the distortion tendency. “The challenge during the design and production process was therefore to minimize distortion in order to ensure that the component would retain its tightness throughout the vehicle’s life,” stated Krause. Excellent structural stiffness was also essential to enable the oil pan to absorb engine vibrations and shocks caused by potholes and to support the entire weight of the transmission during repair work.

Functions integrated directly by injection molding include the holder for the lifetime oil filter, the magnetic metal separator and the groove for the oil pan gasket. “Integrating functions lowers production costs and means much less subsequent assembly work. It also helps reduce the weight substantially,” notes Krause.

Durethan AKV 35 H2.0 SR1 has excellent resistance to chemicals, which is important for use in aggressive transmission oils. It also benefits from a low thermal aging tendency and therefore withstands high thermal stresses in continuous use with temperature peaks of 150 °C. This has been confirmed in aging tests over a period of more than 1,000 hours. The thermoplastic also produces smooth, homogeneous surfaces because, despite the high proportion of glass fibers it contains, these are barely visible. Further more, the polyamide 66 demonstrates excellent resistance to the chemicals encountered in vehicles on a daily basis such as oils, greases, road salt, battery acid and fuel.

LANXESS provided its cooperation partners IBS Filtran and ZF Getriebe GmbH with a great deal of support during development work on the transmission oil pan. Rheological calculations helped to minimize component distortion and develop an appropriate sprue concept for the injection mold. The component’s thermal expansion properties were also calculated and optimized. Simulation was used to determine the internal pressures to which the oil pan is subjected when the vehicle is moving and to analyze its sealing properties. The overall objective of LANXESS’s customer service is to help reduce the time to market for development partners’ products.