The goal of reducing fuel consumption and CO2-Emission is leading to turbo-charged combustion engines that deliver high torque at low speeds (down speeding). To meet NVH requirements damper technologies such as DMF (Dual Mass Flywheel) are established, leading to reduced space for the clutch system. Specific measures need to be considered if switching over from SMF (Single Mass Flywheel) to DMF [8]. Doing so has an impact on thermal behavior of the clutch system, for example due to reduced and different distribution of thermal masses and heat transfer to the surroundings. Taking these trends into account, clutch systems within vehicle powertrains are facing challenges to meet requirements e.g. clutch life, cost targets and space limitation. The clutch development process must also ensure delivery of a clutch system that meets requirements taking boundary conditions such as load cycles and driver behavior into account.
Relevant load cycles are derived based on feedback and analysis of driver behavior under varying road and traffic conditions. For example, one relevant load cycle is the overriding of the clutch in 1st or 2nd gear in dense traffic condition that causes high thermal clutch load due to heat energy generated at the clutch frictional surfaces. This heat energy is relevant for lifetime or can even destroy the clutch/clutch system if not considered properly within the clutch development process.
These load cycles are the input for a simulation based clutch optimization. The virtual optimization process is taking aspects such as thermal and lifetime performance for the given boundary conditions of the system, the available installation space, materials (i.e. friction facing), part geometry and of course the costs into account. This process is based on analytical calculations, thermal and thermal-mechanical simulation and CAD modelling. Recent development in thermal-mechanical simulation methods allow a more application-specific consideration of the thermal behavior of the system, also in the early design phase.
To validate simulation results, physical tests were carried out; 1st gear repeat vehicle launches on a gradient and 2nd gear launches on a flat road which includes temperature measurements to determine the rise in temperature until a certain number of cycles is reached. In this paper, the approach for clutch optimization is shown based on the analysis of two different clutch sets of the same size including experimental results based on vehicle measurements.