摘 要

本文为市面上存在的一款电动汽车设计一款兼具动力性与经济性的二速电动汽车变速器。电动汽车变速器在作用上与传统汽车基本是相同的，在驾驶员对外界环境进行观察判断后，根据个人和驾驶的需求，改变电动机输出到车轮的转速和转矩，来改变汽车的工况来适合路况。不同的是，电动汽车的倒挡是通过电机反转来实现的倒挡工作的，而不是通过变换为倒车档位。变速器对于电动汽车来说十分重要，是电动汽车上的重要组件。良好的动力性与经济性是电动汽车变速器的基本要求也是重要要求。而在设计时，同时也要考虑电动汽变速器的尺寸以及是否方便维修等方面的，成本是否合理，能不能与相应的车辆相匹配。本文将对一款电动汽车进行变速器进行总体的设计并进行仿真，以获得更好的动力性与经济性，来达到更好的设计效果。

Catalog

Abstract 2

Chapter1. Introduction 4

1.1 Background 4

1.2 Brief introduction of electric vehicle 5

1.3 Characteristics of electric vehicle transmission 5

1.4 Research status at home and abroad 5

Chapter2.Transmission Design for Electric Vehicles 6

2.1 Electric Vehicle Parameters and Design Objectives 7

2.2 Design of Drive Ratio for Electric Vehicles 9

2.3 Simulation of Two-speed Transmission 10

Chapter3. Confirmation of transmission shaft related parameters 12

（1）Calculation of Center Distance 12

(2)Selection of Outline Dimensions 13

(3)Gear parameters 15

Chapter4.Gear strength calculation 16

Chapter5．Determine the size of the shaft 19

Chapter6．Selection of shift mechanism 21

Chapter7．Selection of synchronizer 23

Chapter8．Summary 25

Reference......................................................................................................................26

Thanks..........................................................................................................................27

Chapter1. Introduction

• 1. Background

With the development of society today, more and more people have their own cars.However, as a non-renewable energy, oil consumption has been accelerating rapidly, which has caused a series of problems, including oil price increase, environmental problems caused by emissions, safety problems of accelerated oil extraction and war around oil competition.So more and more countries have begun to invest in the development of new energy vehicles. The main research directions include various fuel cell electric vehicles, pure electric vehicles and hybrid electric vehicles.Electric vehicle is becoming more and more important to modern society. Although there are some problems such as immature technology, it is undeniable that electric vehicle is the main direction of future automobile.As an important part of electric vehicle, the transmission of electric vehicle is used to change the torque output from motor to drive shaft and wheel according to driver's judgment and operation to the external environment, so that electric vehicle can be operated under appropriate conditions, and then make electric vehicle obtain good power and economy.Therefore, many scholars have carried out research and achieved very good results.In China, new energy vehicles have also been greatly supported and subsidized by the state.When we buy new energy vehicles in our country, we will enjoy the subsidies granted by the state and the exemption from purchase tax. In addition, our government is also vigorously building new charging stakes to bring convenience to the users of electric vehicles.Therefore, it is very important for electric vehicles to study how to design a better transmission.As the representative industry of the industry, the automobile industry is the industry that integrates the traditional industry. The level of the automobile industry deeply represents the industrial level of a country. Due to the small gap in starting time between the countries, the electric vehicle is also the only step for China to catch up with or even surpass the western countries in the automobile industry. The rise and fall of the electric vehicle also affects China's international industry.Therefore, the development of electric vehicles is very important to China.

1.2.Brief introduction of electric vehicle

Electric vehicle (EV) is a relatively new type of vehicle. The definition of EV is that it uses battery as energy source, generates driving force by electric motor, drives power to the wheel by transmission overload to drive the EV to run on electricity, and conforms to national safety regulations.Compared with traditional vehicles, electric vehicles as new energy vehicles have unmatched advantages over traditional vehicles. The main advantages of electric vehicles are as follows:

(1) No pollution and noise will be produced.Electric vehicles use electric motors, so they do not produce exhaust gas when working and do not produce exhaust pollution when working.Therefore, the use of electric vehicles can greatly reduce the environmental pollution problems in cities.Motor noise is also less than internal combustion engines.The promotion and use of electric vehicles can greatly alleviate the environmental problems caused by noise and air pollution in the city and improve the quality of life in the city.

(2) Higher energy efficiency.According to the research of different scholars in different countries, pure electric vehicle has higher energy utilization ratio than traditional internal combustion engine vehicle.Conventional cars use about 18 percent energy efficiency, while electric vehicles use about 22 percent energy efficiency.Under urban conditions, vehicles often face traffic jams and stop-and-go, in which case, electric vehicles are far superior to traditional vehicles.Electric vehicles do not consume electricity when they stop driving, and due to the existence of a brake recovery system, some of the energy lost during braking can be recovered when the electric vehicle is braked.On the other hand, conventional vehicles, whether parking or starting brakes, have energy consumption.Electric vehicles also consume less at idle speed and are more suitable for today's urban conditions.

(3) Simple structure.Compared with traditional internal combustion vehicle, electric vehicle has simple structure due to simple driving mechanism structure and other reasons.Maintenance is simpler because of its simple structure.At the same time, the electric vehicle is simpler than the traditional vehicle operation and reduces the operator's operation difficulty.

1.3.Characteristics of electric vehicle transmission