Abstract

Abstract This paper proposes a novel synchronizer ‘Harpoon-Shift’ aiming at improving the comfort and efficiency of gearbox, meanwhile, simplifying the shifting control strategy for multi-speed electric vehicles. It will overcome one of the biggest shortcomings of traditional synchronizer system with frictional cone clutch. Experiment is established to investigate the torque and speed responses during the engagement of gears pairs. Then, based on previous testing results, the relationship of the peak torque and minimum speed difference to implement gear shifting with various spring coefficients is investigated. In addition, a mathematical model of the Harpoon-Shift system is developed to simulate the engagement process. The simulation results of system transient responses are validated against the data measured on testing rig. The model is then improved to study the impact of the rotating inertia, speed and speed difference on the torsional vibration and required time of engagement. Both of the simulation and experimental results show the significant improvement of proposed synchronizer to conventional cone clutch synchronizer.

Highlights

  • The application of multi-speed transmissions in electric vehicles (EVs) continues to grow as a result of improved performance and driving efficiency in comparison to single speed EVs [1]

  • The motor 2 and gearbox provide a simulated load representing the whole vehicle inertia, for these tests the input side of the test unit is held at constant speed and the output side of the test unit is synchronised to the input with the Harpoon-shift mechanism

  • A novel synchronizer, namely Harpoon-shift, for electric vehicles is presented and a mathematical model of the synchronization mechanism is developed in this paper

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Summary

Introduction

The application of multi-speed transmissions in electric vehicles (EVs) continues to grow as a result of improved performance and driving efficiency in comparison to single speed EVs [1]. Shifting and gear selection is performed with the use of friction clutches, a result of both limited controllability and high inertia of combustion engines. These friction elements are a major source of inefficiency in multi-speed gearboxes [2,3,4]. As electric motors are significantly more controllable that their conventional counterparts, as evidenced by paper such as [5,6,7], reliance on inefficient friction elements can be reduced, and even eliminated This has resulted in the development of shift control strategies that rely on motor control rather than friction based strategies [8,9,10]. As shown in [11] these strategies cannot entirely eliminate the need for torsional vibration absorption during clutch lockup

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