【作者】 王阳；

【导师】 闫振华；

【作者基本信息】 吉林大学 ， 机械设计及理论， 2023， 硕士

【摘要】 汽车是大批量生产的行业,公差设计一方面影响着系统的功能、性能,另一方面影响着制造成本。汽车座椅与车身之间的装配问题是众多公差设计问题中的一个典型,一直受到汽车座椅和车身行业的重视。汽车座椅骨架和车身骨架的制造工艺主要是冲压和焊接,零部件精度较低,因此座椅与车身之间的装配精度设计是个难点。如果座椅和车身的相关公差规范的过于严格,将导致制造成本过高甚至工艺能力达不到要求,另一方面,如果规范的过于宽松,又可能导致无法装配,或装配的质量差,甚至影响碰撞安全性。本论文针对该问题进行了研究,主要内容如下:1)孔销浮动的建模与分析孔销浮动是座椅与车身公差设计问题中的一个主要问题,本文在第2章首先在仅考虑尺寸公差的情况下将孔销浮动问题通过运动学模型表示出来,建立了曲柄滑块模型,并给出了数学模型,通过数学方法求出了孔销浮动导致的误差范围。接下来,进一步考虑了添加位置公差和采用最大实体要求对孔销浮动问题的影响,对数学模型进行了相应的优化。最后给出了一个简单的装配模型作为应用案例,对该方法进行了详细的解释说明。2)基于运动学模型方法的汽车座椅与车身装配的公差分析对汽车座椅和车身进行了公差规范。影响座椅与车身装配的误差有两部分,一部分是孔销浮动导致的装配误差,另一部分是安装孔相对于定位基准的制造误差。装配误差可以通过前面推导的运动学模型进行求解,制造误差可以由安装孔的位置度得到。将制造误差与基于几何模型得到的装配误差耦合即得到总的误差范围,使其与安装螺栓截面进行比较,便可确定装配结果。之后又分别讨论了座椅安装孔与车身安装孔位置度均采用最大实体要求和车身次定位孔添加位置度并采用最大实体要求两种情况下的误差范围以及装配情况。3)基于矢量环法的汽车座椅与车身装配的公差分析在确定了汽车座椅与车身装配的总误差范围后,还需要讨论各设计变量对安装孔误差的影响效果。因此建立了矢量环方程,并求出了各组成环(设计变量)的灵敏度。因为考虑孔销浮动的影响,所以需要分情况讨论建立矢量环方程,之后得到不同情况下的灵敏度矩阵并做出分析。接下来利用灵敏度矩阵,通过公差累积分析模型对各组成环的公差进行了分析。然后,利用公差分析软件CETOL对汽车座椅与车身装配进行了三维公差分析,得到了公差分析结果以及灵敏度、贡献度。4)汽车座椅与车身装配的公差优化介绍了基于合作博弈的公差优化方法。建立了公差成本模型,包括制造成本模型和质量损失成本模型。并以公差成本模型和几何产品质量为目标函数,公差值为变量,以企业的加工能力及现有的工业制造水平作为约束条件建立公差优化模型。合作博弈优化模型由三部分组成,即博弈方,效用以及策略。将公差成本与几何产品质量作为博弈方,通过模糊聚类理论将公差设计变量进行分组,并求出效用矩阵,再利用Shapley值方法求解优化模型,得到最优效用组合。通过最后得到的不同策略组合下的效用及二范数图发现,当公差值取最小或最大时,只能单方面满足产品质量或生产成本最优,只有当二范数最小时才能够得到二者均最优的结果,最后给出了结论:传统的单目标优化并不能得到最优解,只能得到较优解。更多还原

【Abstract】 Automobile is a mass production industry,tolerance design on the one hand affects the function and performance of the system,on the other hand affects the manufacturing cost.The assembly problem between car seat and body is a typical tolerance design problem,which is paid more attention by car seat and body industry.The manufacturing process of car seat frame is mainly stamping and welding,the precision of parts is low,and the manufacturing precision of the body is also low,so the assembly precision design between the seat and the body is difficult.If the relevant tolerance specifications of the seat and body are too strict,the manufacturing cost will be too high or even the process capacity will not meet the requirements.On the other hand,if the specification is too loose,it may lead to the failure of assembly,or the poor quality of assembly,and even affect the collision safety.This paper studies this problem,and the main contents are as follows:1)Modeling and analysis of hole pin floatingThe tolerance problem of orifice pin floating is expressed by geometric model,the crank slider model is established,and the error range caused by orifice pin floating is calculated by mathematical method,and a mathematical model is given.After that,the change of mathematical model of dowel pin and hole when the position degree is added and the change of mathematical model when the maximum entity requirement is applied to the reference element is discussed.Finally,a simple assembly model is given to illustrate the application of this method.2)Tolerance analysis of seat and body assembly based on geometric model methodThe tolerances of car seat and car body are regulated.The assembly error of seat and body is divided into two parts,one is the assembly error caused by the floating hole pin,and the other is the manufacturing error of the mounting hole relative to the positioning reference.The assembly error can be solved by using the geometric model derived above,and the manufacturing error is the position degree of the mounting hole.By coupling the calculated assembly error with the manufacturing error,the total assembly error can be obtained,and then the assembly result can be determined by comparing it with the section of mounting bolt.Then,the variation of error range is discussed respectively when the position of mounting hole adopts the principle of maximum entity and when the position of sub-positioning hole of body is added and the maximum entity requirement is adopted.3)Tolerance analysis of car seat and body assembly based on vector ring methodAfter determining the total error range of car seat and body assembly,it is necessary to discuss the effect of each design variable on the error of mounting hole.Therefore,the vector ring equation is established and the sensitivity matrix of each component ring is obtained.Considering the floating factor of the hole pin,the vector ring equation needs to be established by case discussion,and the sensitivity matrix under different cases is obtained.Then the sensitivity matrix is used to analyze the tolerance of each component ring through the tolerance accumulation analysis model.In the end,the tolerance analysis software is introduced,and the three-dimensional tolerance analysis of car seat and body assembly is carried out by using it.The tolerance analysis results,sensitivity and contribution analysis results are obtained,and the explanation is given.4)Tolerance optimization of car seat and body assemblyThe tolerance optimization method based on cooperative game is introduced.The tolerance cost model is established,including manufacturing cost model and quality loss cost model.Taking the tolerance cost model and geometric product quality as the objective function and the tolerance value as the variable,the tolerance optimization model was established with the enterprise’s processing capacity and the existing industrial manufacturing level as the constraint conditions.The cooperative game optimization model is composed of three parts,namely,game player,utility and strategy.Taking tolerance cost and geometric product quality as game parties,the tolerance design variables were grouped by fuzzy clustering theory,and the utility matrix was obtained.Then Shapley value method was used to solve the optimization model,and the optimal utility combination was obtained.更多还原