Abstract: In a compound power-split hybrid powertrain, the performance and fuel efficiency can be further enhanced by engaging and braking the power-split device and power components. To meet the high torque demands of commercial vehicles, traditional wet clutches require an increased number of friction plates and larger size, leading to higher costs and drag losses. In contrast, mechanical clutches are compact and can handle high torque, but they generate friction losses during overrunning, failing to meet the needs of hybrid commercial vehicles for controllable directional locking and bidirectional non-contact freedom. A multi-mode non-contact selectable one-way clutch is designed. This clutch can operate in three modes: forward locking, reverse locking, and bi-directional freewheeling, offering a high torque capacity while avoiding drag and friction losses. The static behavior and mode-switching processes of the multi-mode non-contact selectable one-way clutch are analyzed, and an optimization model was developed with the objectives of increasing the load-bearing torque, reducing transient impacts and achieving a compact and lightweight design, a multi-objective optimization decision-making approach that combines non-dominated sorting genetic algorithm Ⅱ(NSGA2), constrained ordered weighted averaging(COWA) operator, and technique for order preference by similarity to ideal solution (TOPSIS) method is proposed. When compared to initial solution, this optimization method leads to a 23.5% increase in load-bearing torque, a 13.7% reduction in idling angle, and a 0.5% decrease in the volume of key components. A hybrid transmission is mounted on a test bench for mode switching test. The results of the bench test confirm the feasibility of the design method. This study provides valuable insights for the design of high-torque multi-mode non-contact selectable one-way clutch.

Key words: selectable one-way clutch, mode switching, power-split hybrid transmission, multi-objective optimization