Multiphysics Investigations on the Dynamics of Differential Hypoid Gears

Abstract

Vehicular differential hypoid gears play an important role on the noise, vibration, and harshness (NVH) signature of the drivetrain system. Additionally, the generated friction between their mating teeth flanks under varying load-speed conditions is a source of power loss in a drivetrain while absorbing some of the vibration energy. This paper deals with the coupling between system dynamics and analytical tribology in multiphysics, multiscale analysis. Elastohydrodynamic lubrication (EHL) of elliptical point contact of partially conforming hypoid gear teeth pairs with non-Newtonian thermal shear of a thin lubricant film is considered, including boundary friction as the result of asperity interactions on the contiguous surfaces. Tooth contact analysis (TCA) has been used to obtain the input data required for such an analysis. The dynamic behavior and frictional losses of a differential hypoid gear pair under realistic operating conditions are therefore determined. The detailed analysis shows a strong link between NVH refinement and transmission efficiency, a finding not hitherto reported in literature.

Dynamics and efficiency of planetary gear sets for hybrid powertrains

“…The higher peak-to-peak oscillations translate to worsening NVH conditions. Another piece of information extracted from the DTE results is the ensuing teeth pair separation and any subsequent impacts [13,25]. As demonstrated by equation (6), DTE=0 is the threshold of this behaviour.…”

Tribodynamics of differential hypoid gears

“…The exact form for the particular variables is presented in (11). The model can be reduced to seven degrees of freedom, after eliminating the rigid body torsional mode (13).…”

“…Mass [M], damping [C] and stiffness [K] matrices are presented in detail in (11). The values of these matrices depend on the geometry and kinematics of the bearings and gear pair.…”

Effect of tapered roller bearing supports on the dynamic behaviour of hypoid gear pair differentials

“…Mohammadpour et al [24] presented a similar dynamic model to that of Karagiannis et al [22], but using the more appropriate lubricant film formula of Chittenden et al [25], which is applicable for elliptical contact footprint geometry of hypoid gear teeth pair with angled lubricant entrainment into the contact conjunction. Later Mohammadpur et al [26] used Evans and Johnson [27] tractive lubricant model subject to non-Newtonian shear, a condition which is commonplace in highly loaded hypoid gears. Their previous 2 degrees-of-freedom gear pair tribo-dynamics model [24] was extended to 8-DOF, including lateral vibrations of transmission shafts [26].…”

“…Later Mohammadpur et al [26] used Evans and Johnson [27] tractive lubricant model subject to non-Newtonian shear, a condition which is commonplace in highly loaded hypoid gears. Their previous 2 degrees-of-freedom gear pair tribo-dynamics model [24] was extended to 8-DOF, including lateral vibrations of transmission shafts [26].…”