【作者】 张健；

【导师】 杨玉虎； 常乐；

【作者基本信息】 天津大学 ， 机械工程， 2019， 硕士

【摘要】 面向自动机械对分度机构实现更高分度次数的工程需求,研究一种新型同轴式凸轮连杆分度机构。与现有分度机构相比,该机构具有结构紧凑,在输入轴转速相同时可实现更高分度次数的优点,具有重要的理论研究意义和工程应用价值。本文以上述同轴式凸轮连杆分度机构为对象,围绕其传动原理、动力学仿真及实验等方面开展系统的研究,旨在为机构的优化设计、性能提升提供理论依据。论文主要研究内容如下:首先,分析了机构的组成与传动原理,定义了该机构的工况参数和尺度参数,在此基础上建立了凸轮廓线方程,分析了不同参数对凸轮廓线几何形状的影响规律。推导了曲率半径与压力角、啮合角的解析表达式。建立了机构静力分析模型,分析了滚子与凸轮之间的碰撞力。其次,根据工况需求,在静力分析基础上,确定了样机尺度参数、结构参数。校核了各主要零部件的强度,建立了样机有限元模型。利用模态分析模块,分析了凸轮与滚子处于不同接触状态下的前4阶振型及其对应的固有频率,分别为输出盘扭转振动、输出盘两个方向平移振动及平行四边形连杆机构扭转振动。然后,考虑轴类与杆类构件、轴承、凸轮与滚子的接触等弹性因素,在ADAMS环境下建立了机构刚柔耦合动力学模型。仿真分析了杆长系数对动态响应的影响,得出停歇期输出盘扭转振动随杆长系数的增大呈现先减小后增大的趋势。同时,分析了不同运动规律对输出盘动态响应的影响,结果表明遵循修正正弦运动规律的分度凸轮机构具有最佳的动态精度。最后,结合实验样机搭建了机构动力学特性测试平台。采用单点激励-多点拾振的方法,测取了样机在一个分度周期内不同位置的固有频率。在切向位置布置测点,拾取了输出盘角加速度信号,并进行了频谱分析。结果表明,输出盘角加速度响应变化趋势与理论运动规律较为吻合,且其频谱与样机固有频率有限元仿真对应结果相近。此外,模态实验与有限元仿真结果的误差小于10%。上述结果验证了动力学模型的有效性。更多还原

【Abstract】 Aiming at the engineering requirements for the higher indexing rates,a novel indexing mechanism,named by coaxial cam-linkage indexing mechanism(CCIM),is developed.It has the advantages of compact structure,more indexing times compared with the current indexing mechanisms,which has important theoretical and engineering application value.The investigations on the transmission principle,dynamic simulation and experiment of CCIM are carried out in detail in this thesis.The outcomes lay theoretical foundation for the optimization design and performance improvement of the indexing mechanism.The main contents are listed as follows:Firstly,the composition and transmission principle of CCIM are analyzed,and the duty parameters and dimension parameters of CCIM are defined.The pitch curve equations are established,and its influence factors are also analyzed.Explicit formulae of curvature radius,pressure angle and meshing angle are derived.The static model is established and the collision force analysis is implemented between rollers and cams.Secondly,the prototype dimensional parameters and structural parameters are determined on the basis of static analysis,and the strength of relevant component is checked due to the working conditions.The finite element model(FEM)is established.The first-four mode shapes and corresponding frequencies during a period are analyzed by the modal analysis with the consideration of cam-roller contact status,The results indicate that the first-four mode shapes are the output wheel torsional vibration,the output wheel translational vibration and the quadrilateral linkages torsional vibration.Then,the rigid-flexible coupling dynamic model is established in ADAMS by considering the elastic factors,such as shafts and linkages,bearings,the contact between cams and rollers.The influence of the linkage coefficient on the dynamic response is investigated.During the dwell period,the torsional vibration of the output wheel firstly decreases and then increases with the increase of the linkage coefficient.At the same time,the influence of different motion laws on dynamic response of the output wheel is analyzed.The results indicate that CCIM following the modified sinusoidal(MS)motion law has the best dynamic precision.Finally,the dynamic test platform is built with the physical prototype.The single input/multi-output method is adopted to measure the natural frequencies at different positions during a period.The test points are arranged at the tangential position of the output wheel in the response experiment.The angular acceleration of the output wheel is picked up,and spectrum analysis is performed by Fast-Fourier-Transform(FFT).The results indicate that the angular acceleration responses tendency of the output wheel is consistent with theoretical motion law and its spectrum is close to the simulation results.The relative errors between the experiment and finite element analysis(FEA)is less than 10%.The validity of the dynamic model is confirmed by the mentioned results.更多还原