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

Abstract

The spread of all-electric drives is steadily increasing in all sectors of road transport. Due to the constantly increasing demands on efficiency and performance by legislation and customers, it is necessary to continuously push the system limits of the powertrains. This paper presents an approach that performs an initial thermal system analysis based on a first gearbox configuration and efficiency calculation. Here, the componentwise loss calculation is used to identify thermal hotspots within the gearbox stage. The basis of this analysis is the thermal network method. For the approach, the gearbox elements gear, bearing, shaft, seal and housing are broken down into standard thermal elements to be created automatically for any subsequent gearbox configuration. The linking of these elements to each other is also standardised and automated comparably. An extensive simulation study is carried out using the smoothed particle hydrodynamics method to consider the load point-dependent oil distribution, which enables an initial estimate of the oil distribution. The thermal network filled in this way is then solved on a time-step basis, allowing dynamic load cases to be considered. The quality of the method is validated within the paper using the VW ID 3 gearbox as an example. Due to the use of a series gearbox, the validation was carried out on the basis of the accessible housing temperatures. These already show good convergence of the method compared to other existing approaches, which reinforces the necessity of conducting further experimental studies.