摘 要

新世纪以来,我国新能源汽车的保有量和汽车销售量逐年的上升,使得了我国的石油化工业对外的依存度逐年大幅上升,节能降耗已刻不容缓。但是迫于一些发达国家对新能源汽车保有量和燃油的消耗量逐渐增加和降低的政策和要求,各大新能源汽车制造厂商纷纷着手抓紧了对于新能源电动汽车尤其特别是电动汽车的技术研制与生产推广,电动汽车的市场销量正逐渐增加和上升^[8]。与目前传统的燃油电动汽车的轻量化相比,电动汽车目前所需要使用的混合动力电池的比能量比燃油的比能量小很多^[9],且混合动力电池的能量引入大幅增加了电动汽车的重量和整车使用质量,这样就使得新能源电动汽车的平均续航行驶里程已经远不如于传统的燃油电动汽车,加快对新能源电动汽车的技术轻量化推进已经显得十分迫切。因此本文进一步提出了纯电动商用燃油汽车电驱桥壳结构有限元的分析和电动汽车轻量化有限元设计这一重要研究课题^[2]。

本文首先对目前我国正在发展中所面对的严峻的汽车能源短缺问题和安全性进行了简要的介绍。通过分析纯电动汽车的基本性能结构,得出其显著的优势和缺点不足^[10]。其优势之处在于电动汽车可以显著地缓解因为汽车不可再生能源(如天然石油等)的急速增长和使用带来的汽车能源短缺的严重问题^[11],并且电动汽车可以有效地积极响应目前全球最大规模的提倡节能环保的电动汽车号召,极大的程度上可以降低因为电动汽车的行驶过快而带来的汽车尾气严重污染的问题^[12]。其缺点在于与市场上传统的燃油驱动汽车的优点相比^[13],电动汽车目前所需要使用的混合动力电池的比能量比传统燃油的比能量小很多^[3],且混合动力电池的使用和引入大幅程度地增加了电动汽车的重量和整车使用质量,这些都使得目前电动汽车的续航里程和重量上远不如市场上传统的燃油驱动汽车^[14]。为了有效解决这些严峻的问题,常见的解决思路之一就是对其驱动桥的结构进行轻量化的设计,改变其需要使用的材料,在完全符合其使用安全要求的情况下减轻其重量^[15]。

其次,由某纯电动汽车驱动桥的有限元扫描件公司使用三维的建模分析软件solidworks建立了汽车驱动桥的三维有限元模型。在这个三维模型中,运用了同轴一体化的设计思想^[1],将汽车电机零部件放置在中间,其他汽车零部件则直接放置在两边。为了进一步提高对有限元模型分析的效率,在建立各种汽车零部件三维有限元模型时,将对有限元分析的结果造成影响较小的汽车油管支架、纵摆臂驱动支架、减震器支架全部删除,同时为了大限度地保证驱动桥有限元相关分析的精度,保留了驱动支架及桥壳各部件的倒圆角。将已经建模完成的三维驱动桥模型直接导入ansys通过有限元相关分析处理软件的有限元相关分析处理接口^[4],得到了对应的驱动桥有限元相关分析模型。在有限元建模的整个过程之中,虽然为了之后的分析和计算方便,对模型的结构进行了一些小的改造,但是整体上来说,整个驱动桥的模型还是完全符合了原本驱动桥的基本设计和结构。

之后,根据已经成功构建了的纯电动汽车的驱动桥三维有限元模型和数据导入了已经完成的驱动桥有限元模型,对其在4种工况下的典型动力使用工况下的驱动桥进行了强度和桥壳以及刚度的分析。四种的极限典型工况分别是:纯电动汽车不平衡的路面冲击载荷的作用在驱动桥壳(极限工况一);汽车最大的侧向驱动力在高速行驶下的一体化后桥电驱动作用在后桥的桥壳(极限工况二);纯电动汽车受最大紧急制动时的一体化后桥驱动桥壳(极限工况三);汽车发动机受最大侧向制动力时的一体化后桥电驱动的作用在后桥桥壳(极限工况四)^[5]。经过进一步的分析,4种典型工况下的驱动桥桥壳都很好地满足了强度和刚度的要求,基本我们可以明确认为该工况下驱动桥的桥壳都能够在任何一个现实的汽车使用工况下正常地工作。

最后，对已经验证了强度和刚度达标的驱动桥桥壳进行轻量化设计^[6]。根据轻量化设计的一般思路，驱动桥的轻量化一般采用的是更换材料和变更链接方式这两种方法。本文中，采用更换材料的方法，将原本的材料钢材更换成更加轻盈的铝合金材料。经过验证，更换成铝合金材料之后的驱动桥桥壳仍然满足使用要求。故轻量化设计符合设计要求^[7]。

关键词： 纯电动汽车，驱动桥，有限元分析，轻量化

Abstract

Since the beginning of the new century, China's car ownership and sales volume have been increasing year by year, making China's oil dependence on the outside increased year by year. Under the pressure of the country's requirements of gradually reducing the consumption of automobile fuel, the major automobile manufacturers have seized on the development and promotion of new energy vehicles, especially electric vehicles, and the sales of electric vehicles are gradually rising. Compared with the traditional fuel vehicles, the specific energy of the power battery used by electric vehicles is much smaller than that of the fuel. Moreover, the introduction of batteries has greatly increased the vehicle's overall quality, which makes the range of electric vehicles far less than that of traditional fuel vehicles. it is urgent to speed up the lightweight of electric vehicles. Therefore, the finite element analysis and lightweight design of electric drive axle housing for pure electric commercial vehicles are presented in this paper.

This paper first gives a brief introduction to the serious energy problem that China is facing. Through the analysis of the basic structure of pure electric vehicle, its significant advantages and disadvantages are obtained. The advantage is that it can significantly alleviate the problem of energy shortage caused by the rapid use of non-renewable energy (such as oil), and it can actively respond to the call of energy conservation and environmental protection on a global scale, and greatly reduce the exhaust pollution caused by vehicle driving. The disadvantage is that compared with traditional fuel cars, electric cars currently use much less specific energy of power batteries than fuel cars, and the introduction of batteries has greatly increased the vehicle's overall quality, which makes the range of electric cars far less than that of traditional fuel cars. In order to solve these problems, the common idea is to design the drive axle with light weight, change the materials used, and reduce the weight in accordance with the use requirements.

Secondly, the 3d model of the drive axle of a pure electric vehicle was established by using the 3d modeling software solidworks. In this model, using the idea of coaxial integration, the motor is placed in the middle and the other parts are placed on both sides. In order to improve the efficiency of finite element analysis, the tubing bracket, longitudinal swing arm bracket and shock absorber bracket which have little influence on the analysis results will be removed when the three-dimensional model of each part is built. At the same time, in order to ensure the accuracy of finite element analysis, the rounded corners of each part of the drive axle housing will be retained. The completed 3d model is imported into the correlation analysis interface of ansys finite element analysis software to obtain the corresponding finite element model. In the process of modeling, although some modifications were made to the model for the convenience of calculation afterwards, on the whole, the whole model still conforms to the basic structure of the original drive axle.

Then, according to the three-dimensional model of the drive axle of the pure electric vehicle that has been built and the finite element model that has been imported, the strength and stiffness of the drive axle are analyzed under four typical working conditions. The four ultimate working conditions are as follows: the impact load on the uneven road surface is acted on the bridge housing (working condition 1); The rear axle housing with integrated electric drive under the maximum driving force of the vehicle (working condition 2); The integrated rear axle housing in emergency braking (working condition 3); The integrated electric drive rear axle housing of the vehicle under the maximum lateral force (working condition 4). After analysis, the drive axle housing under four typical working conditions all meet the requirements of strength and stiffness, and it can be basically considered that the drive axle housing can work normally under any practical working conditions.

Finally, the light weight design of the drive axle housing has been carried out. According to the general idea of light weight design, the light weight of drive axle generally adopts the two methods of changing the material and changing the link mode. In this paper, the method of material replacement will be used to replace the original material steel into a more lightweight aluminum alloy material. After verification, the driving axle housing still meets the requirements after being replaced with aluminum alloy. Therefore, the lightweight design meets the design requirements.

Key Words: Pure electric vehicle, drive axle, finite element analysis, lightweight

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