Not a Perfect Circle with ID2®: Oval Sprocket Technology in Belt Drives Extends Life(Oct 31,2005)

It sounds like a paradox: Although the belt pulley developed by automotive supplier INA Schaeffler KG may be "out of round" because it has oval sintered wheels, the ID2® technology used here results in extended operating life for the belt drive. The rediscovered oval technology reduces vibrations and has a positive effect on acoustics. Toothed belts are used to drive the camshaft in around 75% of European engines. Reasons for this wide use include the simplicity of the drive and flexible belt guidance, low friction and low costs. Core components such as the sprocket and the toothed belt must meet the usual requirements in engine manufacture – an engine life of around 240,000 km, temperatures of up to 150 °C as well as small design spaces, low weight and acoustic neutrality. The fact that accessories have to be driven as well and that stop-and-go traffic is on the rise also contributes to increased stress on the components, particularly the toothed belt. Reducing forces and vibrations significantly relieves stress on belt drives and their components and ultimately saves drivers money. Engineers at INA in Herzogenaurach focus on improving the sprocket, which is the toothed drive wheel or output wheel. This represents an important step towards increasing the operating life. Developments are based on a general change in the shape of the wheel. Experts have turned the round sprocket into an oval sintered sprocket that will be launched as the ID2® system. Using an oval belt pulley to ensure the drive runs smoothly? What sounds like a paradox is in fact an important contribution to compensating tensile forces in the toothed belt. Installing the oval ID2® results in nearly constant belt tension, and force peaks in the belt drive components are reduced by up to 40%. This also has an impact on the camshaft drive. The camshaft vibration angle can be reduced by up to 60%. The difference between a round sprocket and an oval ID2® sprocket is just a few millimeters. The DINA® simulation software system is the basis for this development. The software can be combined with system tests to analyze the stress on the entire system and the resulting vibration impact. "Reduced stress on the components means that the components can be downsized, which in turn means that costs are reduced. If dimensions remain unchanged, the operating life of the entire system can be increased considerably", says Ralf Walter, Manager of Belt Drive Systems Development at INA-Schaeffler KG. End customers, i. e. drivers, will be able to save money as a result of the extended operating life of the belt, which means longer replacement intervals compared to standard designs. Experts are very interested in this innovation developed in Herzogenaurach. INA engineers are already working with customers on a large number of projects, including customers in Asia, where one out of two cars is delivered with a toothed belt. One question remains: Will ID2® also be used in chain drive applications? It is certainly possible to benefit from oval wheel technology in these applications, and engineers at INA are already working on initial projects.