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. It 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 surroundings.
Taking these trends into account, clutch systems within vehicle
power-trains are facing challenges to meet requirements e.g. clutch
life, cost targets and space limitation. Clutch development process
must ensure to deliver 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
& an analysis of driver behavior under varying road and traffic
conditions. For example, one relevant load cycle is overriding of
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
even destroys the clutch/clutch system if not considered properly.
These load cycles are 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 lining), part geometry and of course the
costs into account. This process is based on analytical
calculations, thermal and thermal-mechanical simulations and CAD
modelling. Recent development in thermal-mechanical simulation
methods allows a more application-specific consideration of the
thermal behavior of the system, also in the early design phase. It
makes possible to consider the influence of the surface
temperatures, dynamic tapering, cushion deflection under various
load scenarios. These scenarios can be defined for multiple driving
conditions (including already discussed 1st and 2nd gear launches),
thus thermal optimization is more oriented to real vehicle
application. To validate simulation results physical tests were
carried out, 1st gear repeat restart on gradient and 2nd gear march
off on flat road which includes temperature measurement to
determine the rise in temperature until certain number of cycles.
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.