Shift characteristics of a bilateral Harpoon-shift synchronizer for electric vehicles equipped with clutchless AMTs. (1st February 2021) - Mo, Wenwei
Highlights: A new concept of bilateral Harpoon-shift synchronizer for electric vehicles is proposed. Small axial shifting force is required during engagement of bilateral Harpoon shift. A detailed multi-body dynamic model is built to figure out the interacting ways between the engaging-related parts. Chamfer angle and torque spring stiffness are optimized to reduce shifting shocks. Abstract: This paper introduces a new concept of bilateral Harpoon-shift synchronizer for electric vehicles (EVs) equipped with multi-speed clutchless automated manual transmissions (CLAMTs), aiming to improve the shifting quality and efficiency. In addition, it overcomes some of the biggest issues of conventional counterparts, including friction loss and wear. To investigate the engaging performance of the proposed synchronizer comprehensively, a detailed and original multi-body dynamic model of the bilateral Harpoon shift is developed to capture the synchronizer's transient behavior during engagement. In the model, the engaging process is defined as six stages, and it can simulate the interactions between the engaging-related parts. Then a model of EV powertrain system, which integrates the synchronizer model, is established to analyze the gearshift vibrations, allowing to evaluate the engaging performance of the bilateral Harpoon shift in terms of shifting shocks. Also, to guarantee a smooth gear change, torque and speed profiles are designed based on a modified step function for the motor torque control and active speed synchronization. Based on the integrated model, the effects of the torque spring stiffness and tooth chamfer angle on the shifting shocks are comprehensively analyzed, and then the optimized values of these two significant parameters are obtained through quantitative analysis. Results show that the proposed synchronizer is able to achieve high quality shifting for EVs and meanwhile overcome the friction-related drawbacks of traditional synchronizers. Besides, it greatly simplifies the shift control strategy due to its special engaging mechanism.