The purpose of this project is the rear suspension design of the Model 1070 electric truck. The significance is to study the advantages of using electric energy as an energy source on trucks and the impact on the overall layout of trucks. Using the electric vehicles have these following advantages: (1) Essentially zero emissions, in the driving process, the car uses electrical energy, no exhaust emissions, no pollution to the environment; (2) The energy efficiency of electric vehicles is higher than that of fuel vehicles; 3) Only use a single electric energy source, thus eliminating the need for engines, transmissions, fuel tanks and other systems. The structure is relatively simple; (4) The noise is relatively small; (5) The car can be charged when the electricity at the low peak and the power generation equipment fully utilized. However, electric cars also face some problems at this stage. For example, (1) the cruising range is relatively short; (2) the use of batteries and motor controllers is costly; (3) the battery life is short, and it takes a long time to replace the charging; (4) the charging time is long, especially new The charging infrastructure for energy vehicles is not perfect^[2]. Although China’s light electric trucks started late, but they have always been national plans. These include the state’s subsidy policies for new energy vehicles over the past few years and so on, all of which indicate the good prospects for the development of new energy vehicles^[3][4].

In the past few years, pure electric trucks in the United States have developed in varying degrees in both heavy and light areas. The speed has been significantly improved, and the endurance capacity has been somewhat insufficient. Recently, at MWC2017, American automaker Ford released a new concept unmanned electric truck. In addition to being unmanned, this concept truck can be used as a landing platform for drones to send goods to places where transport is not possible^[5]. Purely electric trucks are limited by charging time and cruising range. Currently, they are mainly used for point-to-point short-distance transportation. They cannot yet truly replace the internal-combustion engine trucks and meet the requirements for long-distance transportation. Despite this, several major truck brands in Europe have introduced pure electric products, which shows that the application of pure electric trucks has become a trend within the industry and cannot be overlooked. Previous online shopping giant Amazon plans to launch drone delivery service. London, United Kingdom, plans to test unmanned truck delivery next year to provide 24-hour delivery service, thereby reducing the number of road vehicles during heavy traffic hours and alleviating traffic congestion^[6]. And our neighboring country, Japan, is the first country in the world to begin the development of hybrid cars and realize industrialization. Hybrid power technology is a necessary part of the shift from a single engine drive to a purely electric drive, which can significantly reduce fuel consumption and reduce carbon emissions. It is also the key direction of technological development in various countries. As for the field of pure electric vehicles, Japan mainly uses small and light trucks as the mainstream market^[7].

For the use of electric energy as a power source to drive trucks, then for the entire vehicle layout, there must be a difference in the layout of the vehicle to an ordinary fuel truck. For example, the current automobile frame structure is characterized by strong speciality and high quality, which is not suitable for light-duty electric vehicles. It is necessary to reduce the frame quality when designing, and it is necessary to arrange the power battery and the car wiring conveniently^[8]. Or when placing the damper on the rear suspension, it should be as close to the wheel center as possible to ensure uniform force^[9].

2. 研究的基本内容与方案

Here I choose Dong Feng pure electric truck EQ1070TTBEV as a reference to design. The type of suspension has two types which are non-independent suspension and independent suspension on two-axle vehicles. The characteristic of the non-independent suspension structure is that the left and right wheels are connected by a steel shaft and are connected to the frame (or body) through a suspension. A typical representative is a longitudinal leaf spring suspension. Compared with independent suspension, its advantages are simple structure, reliable work, convenient maintenance and low cost. When the wheel moves up and down, the wheel alignment changes little, and the tire wears less. Therefore, the non-independent suspension is mainly used for commercial trucks, front and rear wheels of city buses, and rear wheels of some passenger cars. So in summary, we designed the rear suspension of the truck using the structure of leaf spring non-independent suspension^[10][11].

Suspension design can be divided into structural form and main parameter selection stage and detailed design stage, and sometimes it must be repeated. Because the suspension parameters affect more vehicle characteristics and involve the arrangement of other assemblies, it is generally necessary to consider and determine them in a comprehensive manner. The establishment of the vehicle leaf spring model is a very important step in the design of the rear suspension. Use the three-dimensional software CATIA to establish the geometric model of the component and finally exports it to Auto CAD^[12][13]. Including the design and calculation for the rear suspension shock absorber is also a very important step in the entire design^[14]. After the corresponding 3d modeling is completed, appropriate finite element analysis can be made for some elements^[15]. The final 2D drawing should include individual parts drawings for each component and the overall assembly drawing for the rear suspension. At the same time write the design specification, find the problem in time to correct.

[1] Camilla Barbarossa,Patrick De Pelsmacker,Ingrid Moons. Personal Values, Green Self-identity and Electric Car Adoption[J]. Ecological Economics,2017,140.

[2] Wang Hao, Li Ping. Research on the Construction of China's New Energy Vehicle Charging Infrastructure Industry[J]. Automotive Industry Research, 2017(01):4-9.

[3] Ye Qiyun. On the subsidy policy for new energy pure electric vehicles and trucks[J]. Light Vehicle Technology, 2017(06):50-53.