Detailed Loss Modelling of Vehicle Gearboxes

Abstract

Drag torques of gearboxes are an important part of the overall losses in today's vehicle drive trains. From measurements it is well known that overall drag torques of vehicle gearboxes vary significantly over the range of operating points and speeds, depending on the interaction of the losses of the single gearbox elements like bearings, gearings, etc. Because today's vehicle emission regulations are becoming stricter and stricter "drag torque design" of gearboxes will be even more important in the future. Prediction of losses helps to save cost (e.g. drag torque measurements), speeds up the development and allows to assess many concepts in short time. We collected detailed semi-analytical drag models for the common gearbox components from literature and from manufacturer information and implemented them in a Modelica library. This library contains models for radial shaft seals, rotary unions, synchronizers, multi-disc clutches, helical gearings, planetary gearings, various kinds of bearings, lubrication systems and lubricant characteristics. Using this library drag torques of any vehicle gearbox may be computed for any operating condition (engaged gear, speed, torque, temperature). Simulation results for a 7 speed double clutch transmission show good correlation with measurements.

Vehicle subsystems' energy losses and model-based approach for fuel efficiency estimation towards an integrated optimisation

“…The manual transmission (MT) modelling considers both single-stage and double-stage layouts, components size and geometry are established depending on transmission type, maximum torque, number of gears and ratios. Energy losses in MT are defined by quite standard formulations, as for ICE, many studies and research activities have already provided enough accurate estimation of dissipative contributions among almost all gearbox components (Pelchen, 2002;Heingartner and Mba, 2003;Gronitzki, 2006;Höhn et al, 2007Höhn et al, , 2009Schlegel et al, 2009;Stahl and Michaelis, 2012;Kolekar, 2013;Gorla et al, 2014;Organisciak et al, 2015;Stahl and Sonawane, 2015). Losses for MT can be therefore obtained as…”

“…where µ is the coefficient of friction between gears and depends on the transmitted force F bt , gear width b and roughness R a , pitch sum speed v ∑c and circle diameter ρ redC , oil type X L and viscosity η, H is a correction factor depending on gear ratio τ, number of teeth z, helix angle β and contact ratio ε, while T and ω are input shaft torque and rotating speed (equations from (Schlegel et al, 2009)); gear fluid drag is split into air and oil dependencies and further parameters required to evaluate these contributions are gear base and addendum circle diameters d b and d a , gear module m,oil density ρ and input shaft rotating speed N in rpm (equations from (Schlegel et al, 2009;Heingartner and Mba, 2003); bearings losses depends on sliding and rolling resistance coefficients µ bear and f 0,bear , force acting on bearings F bear , bearings diameter d bear and oil kinematic viscosity v; synchronisers losses require to define synchroniser axial length L ax , cone discs gap h gap and diameter d synchro (equations from Stahl and Sonawane (2015)).…”

Vehicle subsystems' energy losses and model-based approach for fuel efficiency estimation towards an integrated optimisation

“…The manual transmission (MT) modelling considers both single-stage and double-stage layouts, components size and geometry are established depending on transmission type, maximum torque, number of gears and ratios. Energy losses in MT are defined by quite standard formulations, as for ICE, many studies and research activities have already provided enough accurate estimation of dissipative contributions among almost all gearbox components (Pelchen, 2002;Heingartner and Mba, 2003;Gronitzki, 2006;Höhn et al, 2007Höhn et al, , 2009Schlegel et al, 2009;Stahl and Michaelis, 2012;Kolekar, 2013;Gorla et al, 2014;Organisciak et al, 2015;Stahl and Sonawane, 2015). Losses for MT can be therefore obtained as where Z, L, SS, R and S are respectively gears, bearings, shaft seals and synchronisers losses and P and O refer to load-dependent and load-independent contributions.…”

Effect of bearing thermally induced preload on the efficiency of automotive manual transmission under RDE

“…3 Nevertheless, due to the experimental nature of this research approach, the influencing factors of gearbox efficiency are often summarized to the types of gears used in gearboxes or even the type of transmission, as well as the type of vehicle itself. 4 Another approach on estimating transmission efficiency has been the categorization of the different types of loses that occur both on the gears and the bearings of manual transmissions. Experimental tests have been conducted in order for this categorization as well as the proposed most dominant loss sources to be verified.…”