Bulk temperature prediction of a two-speed automatic transmission for electric vehicles using thermal network method and experimental validation

Abstract

Nowadays, the development of electric vehicle equipped with a two-speed automatic transmission has become a hotspot. As well known, the automatic transmission operates with power loss including gear meshing loss, bearing loss, and oil churning loss. This paper focuses on the bulk temperature prediction of a two-speed automatic transmission using thermal network method. An integrated model, including an efficiency model and a heat balance model, is proposed, which makes it possible to predict power loss, bulk temperature, and temperature distributions under different conditions. In the efficiency model, each part of power losses from gear meshes is studied to calculate the summation of mechanical power losses in the transmission, including losses of gear meshing, bearing and oil churning. In the heat balance model, the entire gearbox is divided into elements with a uniform temperature connected by thermal resistances which account for conduction, convection, and radiation, based upon the first law of thermodynamics for transient conditions. The effectiveness of bulk temperature prediction using thermal network method is validated by the comparison between simulation results and the experimental data. Consequently, this study on heat transfer characteristics, thermal characteristics, and bulk temperature prediction of the two-speed automatic transmission has significant academic and application values.

Efficiency and heat balance calculation of worm gears

“…They used a specific TNM for heat balance calculations, which correspond closely to the measurements. Further approaches to using TNMs for heat balance and temperature calculations with regard to gearboxes can be found in [26] for worm gears, [14] for hypoid gears, [4,11,19] for spur gears, [6,42] for planetary gears and [38] for helical gears.…”

“…Rearranging and using Eq. (19) with Eq. (18) and putting it into the context of a thermal network with n nodes, an expression for the temperature calculation of each node can be formulated:…”

Method for thermal evaluation of automotive gearbox packages taking into account load point-dependent oil distribution

“…Determining critical thermal conditions in gearboxes is crucial for preventing material failures [10,15,17]. The thermal network method is an option to achieve this with a compromise of calculation time and calculation accuracy.…”

Calculating component temperatures in gearboxes for transient operation conditions

“…The TNM is used for heat balance and temperature calculation of gearboxes. For example, the TNM was applied by Funck [12], Changenet et al [3] and Liu et al [23] on spur gears; Monz [27] and Paschold et al [32] on worm gears; Fossier et al [11] on hypoid gears; Chen et al [4], Durand de Gevigney et al [8] and Xiao et al [47] on planetary gears and Sucker [43] on crossed helical gears. All these studies refer to steady state operation conditions, where it is:…”