Parking lock integration for electric axle drives by multi-objective design optimization

Abstract

Due to safety considerations, electric axle drives (e-drives) are often equipped with a parking lock system, which prevents vehicle movement while parking in redundancy with the parking brake. In order to integrate the parking lock into the e‑drive, various mounting positions inside the e‑drive are eligible, which have a direct influence on the e‑drive packaging. Furthermore, engaging the parking lock may happen at small vehicle velocities and while driving downhill, leading to high loads on the e‑drive components. These loads depend on the mounting position of the parking lock and have to be considered in the design phase to prevent failure of the system. That way, the designs of shafts, gear wheels and bearings of the gearbox are affected by the parking lock integration. A suboptimally integrated parking lock system can thus lead to undesirably high costs and reduced energy efficiency of the entire e‑drive—all alongside the packaging aspect. Consequently, finding the best suitable parking lock integration for a certain e‑drive is a complex task for the design engineers. To reduce the level of problem complexity, an established computer-based system design method for e‑drives by means of a multi-objective optimization is extended to be capable of considering the parking lock integration. The proposed method is applied to a case study and the impact of the parking lock on the optimality of an exemplary e‑drive system is shown.