四川交通职业技术学院毕业设计
目 录
第1章 绪 论 ··················································································································· 1
1.1 选题的目的和意义 ·································································································· 1
1.2 国内外的研究现状 ·································································································· 1 1.3 设计研究的主要内容 ······························································································ 3 第2章 曲柄连杆机构受力分析 ··························································································· 4
2.1 曲柄连杆机构的类型及方案选择 ·········································································· 4 2.2 曲柄连杆机构运动学 ······························································································ 4
2.1.1 活塞位移 ······································································································· 5 2.1.2 活塞的速度 ··································································································· 6 2.1.3 活塞的加速度 ······························································································· 6 2.2 曲柄连杆机构中的作用力 ······················································································ 7
2.2.1 气缸内工质的作用力 ··················································································· 7 2.2.2 机构的惯性力 ······························································································· 7 2.3 本章小结 ················································································································ 14 第3章 活塞组的设计 ········································································································· 15
3.1 活塞的设计 ············································································································ 15
3.1.1 活塞的工作条件和设计要求 ····································································· 15 3.1.2 活塞的材料 ································································································· 16 3.1.3 活塞头部的设计 ························································································· 16 3.1.4 活塞裙部的设计 ······················································································· 21 3.2 活塞销的设计 ······································································································· 23
3.2.1 活塞销的结构、材料 ··············································································· 23 3.2.2 活塞销强度和刚度计算 ··········································································· 23 3.3 活塞销座 ··············································································································· 24
3.3.1 活塞销座结构设计 ··················································································· 24 3.3.2 验算比压力 ······························································································· 24 3.4 活塞环设计及计算 ······························································································· 25
3.4.1 活塞环形状及主要尺寸设计 ··································································· 25 3.4.2 活塞环强度校核 ······················································································· 25 3.5 本章小结 ··············································································································· 26 第４章 连杆组的设计 ········································································································· 27
4.1 连杆的设计 ··········································································································· 27
4.1.1 连杆的工作情况、设计要求和材料选用 ··············································· 27 4.1.2 连杆长度的确定 ······················································································· 27 4.1.3 连杆小头的结构设计与强度、刚度计算 ··············································· 27 4.1.4 连杆杆身的结构设计与强度计算 ··························································· 30 4.1.5 连杆大头的结构设计与强度、刚度计算 ··············································· 33
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四川交通职业技术学院毕业设计
4.2 连杆螺栓的设计 ···································································································· 35
4.2.1 连杆螺栓的工作负荷与预紧力 ································································· 35 4.2.2 连杆螺栓的屈服强度校核和疲劳计算 ····················································· 35 4.3 本章小结 ················································································································ 36 第5章 曲轴的设计 ············································································································· 37
5.1 曲轴的结构型式和材料的选择 ············································································ 37
5.1.1 曲轴的工作条件和设计要求 ····································································· 37 5.1.2 曲轴的结构型式 ························································································· 37 5.1.3 曲轴的材料 ································································································· 37 5.2 曲轴的主要尺寸的确定和结构细节设计 ···························································· 38
5.2.1 曲柄销的直径和长度 ················································································· 38 5.2.2 主轴颈的直径和长度 ················································································· 38 5.2.3 曲柄 ············································································································· 39 5.2.4 平衡重 ········································································································· 39 5.2.5 油孔的位置和尺寸 ····················································································· 40 5.2.6 曲轴两端的结构 ························································································· 40 5.2.7 曲轴的止推 ································································································· 40 5.3 曲轴的疲劳强度校核 ···························································································· 41
5.3.1 作用于单元曲拐上的力和力矩 ································································· 41 5.3.2 名义应力的计算 ························································································· 45 5.4 本章小结 ················································································································ 47 第6章 曲柄连杆机构的创建 ····························································································· 48
6.1 对Pro/E软件基本功能的介绍 ············································································· 48 6.2 活塞的创建 ············································································································ 48
6.2.1 活塞的特点分析 ························································································· 48 6.2.2 活塞的建模思路 ························································································· 48 6.2.3 活塞的建模步骤 ························································································· 48 6.3 连杆的创建 ············································································································ 50
6.3.1 连杆的特点分析 ························································································· 50 6.3.2 连杆的建模思路 ························································································· 50 6.3.3 连杆体的建模步骤 ····················································································· 50 6.3.4 连杆盖的建模 ····························································································· 52 6.4 曲轴的创建 ············································································································ 52
6.4.1 曲轴的特点分析 ························································································· 52 6.4.2 曲轴的建模思路 ························································································· 52 6.4.3 曲轴的建模步骤 ························································································· 52 6.5 曲柄连杆机构其它零件的创建 ············································································ 54
6.5.1 活塞销的创建 ····························································································· 54 6.5.2 活塞销卡环的创建 ····················································································· 55 6.5.3 连杆小头衬套的创建 ················································································· 55 6.5.4 大头轴瓦的创建 ························································································· 55 6.5.5 连杆螺栓的创建 ························································································· 55 6.6 本章小结 ················································································································ 56
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四川交通职业技术学院毕业设计
第7章 曲柄连杆机构运动分析 ························································································· 57
7.1 活塞及连杆的装配 ································································································ 57
7.1.1 组件装配的分析与思路 ············································································· 57 7.1.2 活塞组件装配步骤 ····················································································· 57 7.1.3 连杆组件的装配步骤 ················································································· 58 7.2 定义曲轴连杆的连接 ···························································································· 59 7.3 定义伺服电动机 ···································································································· 60 7.4 建立运动分析 ········································································································ 60 7.5 进行干涉检验与视频制作 ···················································································· 61 7.6 获取分析结果 ········································································································ 62 7.7 对结果的分析 ········································································································ 64 7.8 本章小结 ················································································································ 64 结 论 ······························································································································· 65 参考文献 ······························································································································· 66 致 谢 ······························································································································· 67 附 录 ······························································································································· 68
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四川交通职业技术学院毕业设计
摘 要
本文以捷达EA113汽油机的相关参数作为参考，对四缸汽油机的曲柄连杆机构的主要零部件进行了结构设计计算，并对曲柄连杆机构进行了有关运动学和动力学的理论分析与计算机仿真分析。
首先，以运动学和动力学的理论知识为依据，对曲柄连杆机构的运动规律以及在运动中的受力等问题进行详尽的分析，并得到了精确的分析结果。其次分别对活塞组、连杆组以及曲轴进行详细的结构设计，并进行了结构强度和刚度的校核。再次，应用三维CAD软件：Pro/Engineer建立了曲柄连杆机构各零部件的几何模型，在此工作的基础上，利用Pro/E软件的装配功能，将曲柄连杆机构的各组成零件装配成活塞组件、连杆组件和曲轴组件，然后利用Pro/E软件的机构分析模块(Pro/Mechanism)，建立曲柄连杆机构的多刚体动力学模型，进行运动学分析和动力学分析模拟，研究了在不考虑外力作用并使曲轴保持匀速转动的情况下，活塞和连杆的运动规律以及曲柄连杆机构的运动包络。仿真结果的分析表明，仿真结果与发动机的实际工作状况基本一致，文章介绍的仿真方法为曲柄连杆机构的选型、优化设计提供了一种新思路。
关键词：发动机；曲柄连杆机构；受力分析；仿真建模；运动分析；Pro/E
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四川交通职业技术学院毕业设计
第1章 绪 论
1.1 选题的目的和意义
曲柄连杆机构是发动机的传递运动和动力的机构，通过它把活塞的往复直线运动转变为曲轴的旋转运动而输出动力。因此，曲柄连杆机构是发动机中主要的受力部件，其工作可靠性就决定了发动机工作的可靠性。随着发动机强化指标的不断提高，机构的工作条件更加复杂。在多种周期性变化载荷的作用下，如何在设计过程中保证机构具有足够的疲劳强度和刚度及良好的动静态力学特性成为曲柄连杆机构设计的关键性问题[1]。
通过设计，确定发动机曲柄连杆机构的总体结构和零部件结构，包括必要的结构尺寸确定、运动学和动力学分析、材料的选取等，以满足实际生产的需要。
在传统的设计模式中，为了满足设计的需要须进行大量的数值计算，同时为了满足产品的使用性能，须进行强度、刚度、稳定性及可靠性等方面的设计和校核计算，同时要满足校核计算，还需要对曲柄连杆机构进行动力学分析。
为了真实全面地了解机构在实际运行工况下的力学特性，本文采用了多体动力学仿真技术，针对机构进行了实时的，高精度的动力学响应分析与计算，因此本研究所采用的高效、实时分析技术对提高分析精度，提高设计水平具有重要意义，而且可以更直观清晰地了解曲柄连杆机构在运行过程中的受力状态，便于进行精确计算，对进一步研究发动机的平衡与振动、发动机增压的改造等均有较为实用的应用价值。
1.2 国内外的研究现状
多刚体动力学模拟是近十年发展起来的机械计算机模拟技术，提供了在设计过程中对设计方案进行分析和优化的有效手段，在机械设计领域获得越来越广泛的应用。它是利用计算机建造的模型对实际系统进行实验研究，将分析的方法用于模拟实验，充分利用已有的基本物理原理，采用与实际物理系统实验相似的研究方法，在计算机上运行仿真实验。目前多刚体动力学模拟软件主要有Pro/Mechanics，Working model 3D，ADAMS等。多刚体动力学模拟软件的最大优点在于分析过程中无需编写复杂仿真程序，在产品的设计分析时无需进行样机的生产和试验。对内燃机产品的部件装配进行机构运动仿真，可校核部件运动轨迹，及时发现运动干涉；对部件装配进行动力学仿真，可校核机构受力情况；根据机构运动约束及保证性能最优的目标进行机构设计优化，可最大限度地满足性能要求，对设计提供指导和修正[2]。目前国内大学和企业已经已进行了机构运动、动力学仿真方面的研究和局部应用，能在设计初期及时发现内燃机曲柄连杆机构干涉，校核配气机构运动、动力学性能等，为设计人员提供了基本的设计依据[3-4]。
目前国内外对发动机曲柄连杆机构的动力学分析的方法很多，而且已经完善和成熟。其中机
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