对心滚子移动从动件盘形凸轮机构的接触应力

当工作载荷较大时,凸轮表面和从动件端部的接触疲劳破坏就成为凸轮机构失效的主要形式之一。但在有关凸轮的教科书中,对接触应力的计算过程论述较少。本文详细分析了对心滚子移动从动件盘形凸轮机构接触应力的计算方法,并给出具体计算例题。     

Radius of Curvature and Entraining Velocity of Cam Follower Mechanisms

A general procedure for determining the equivalent radius of curvature and entraining velocity of various oscillating and reciprocating cam and follower mechanisms has been developed. This procedure requires as input the motion of the follower, i.e., the lift curve, the angular velocity of the cam and the basic geometry of the cam and follower mechanism. The radius of curvature of the cam at the point of contact was determined using the method of kinematic coefficients. A vector loop superimposed on the cam and follower was used to determine the entraining velocity of the mechanism at the point of contact.     

多圆弧凸轮接触点位置的计算机辅助求解

提出了一种简单有效的多圆弧凸轮机构瞬时接触点位置的计算机辅助求解方法,它通过分析凸轮与从动件的瞬时接触公法线与圆弧区域界线之间的相对关系来判断任一瞬时凸轮与从动件的接触点的位置、接触点处的曲率半径和曲率中心的位置,据此,可对凸轮机构进行高副低代和运动分析。该方法对于直动、摆动、尖顶、滚子、平底从动件凸轮机构均适用。应用被建议的方法对含平底摆动从动件圆弧凸轮的多功能家用缝纫机送料机构进行了运动分析及动态仿真,验证了该方法的有效性。     

设计盘形凸轮廓线的相对速度法

提出了一种利用凸轮与从动件的相对速度设计盘形凸轮轮廓的新方法，该方法基于从动件和支承绕凸轮轴线反转的原理，利用从动件上的接触线或者滚子轴线相对固定凸轮的速度和凸轮与从动件的几何关系设计盘 形凸轮轮廓，应用该方法导出了四种不同类型凸轮机构的凸轮廓线的解析表达式，并给出了对应的设计实例。     

弧面凸轮廓面三坐标机测量与传动质量评价

在分析了弧面凸轮廓面数学模型的基础上,利用三坐标测量机对弧面凸轮廓面进行了等径点位测量,并提出了一种逐点比较法,将所有的测量数据用于确定凸轮坐标系与测量坐标系的位置关系。用非均匀B样条曲线拟合所有凸轮坐标系中的点坐标数据,由拟合曲线和滚子共轭运动的啮合方程求解实际共轭运动,从而评价弧面凸轮廓面的传动质量。最后,通过一个检测实例验证了该算法的正确性和可行性。     

A computer-aided method for optimum design of plate cam-size avoiding undercutting and separation phenomena—II: Design nomogramsEine rechnergestützte methode zur konstruktion optimaler kurvengetriebe ohne unterschnitt und anheben der rolle. Teil 2: Konstruktionsnomogramme

This study presents design nomograms which make it easy for the cam designer to estimate the limiting value of the investigated parameter which can be applied to a plate cam follower system, as long as the maximum contact stress between the cam and follower during both rise and return strokes of cam revolution can be determined. The undesirable phenomena of the undercutting of cam profile and the separation between the cam and the follower are taken into consideration. Moreover, these design nomograms give correlations between the investigated parameters and the optimum plate cam size and also are used to study the influence of an investigated parameter on this size. The optimum plate cam size is the combination of cam base circle radius and the amount of cam follower offset, and satisfies the suggested design procedure which is based on taking the contact stress as a design criterion. The investigated parameters are dynamic, kinematic, geometric and material. A brief discussion on using the suggested design procedure to design the size of plate cam is described. For a numerical example, the presented design nomograms are for reciprocating cam-roller-follower which operated by parabolic plate cam.     

用有限元法研究蜗杆副轮齿承载状况

本文将文献[1]提出弹性接触问题的二维有限元混合法推广到三维问题,并用FORTRAN算法语言编制了计算机源程序,将有限元法用于蜗杆副轮齿的强度分析。计算了在P=2000N的外载荷作用下,ψ1＝0°所对应的接触线上产生的接触内力及其分布、蜗杆副的综合刚度分布,以及蜗轮齿面上ψ1＝-40°、0°、50°三条接触线上的刚度分布。计算结果指出,在接触线上载荷的分布呈“U”形。     

一种新型凸轮机构—凹圆弧底从动件盘形凸轮机构的设计（一）

本文根据赫兹应力理论，提出一种凹圆弧底从动件的盘形凸轮机构。这种机构能够显著提高凸轮高副的接触强度，降低磨损，延长寿命，较之传统的凸轮机构更加适应高速重载的要求。本文就这种新型凸轮机构的理论基础与凸轮轮廓曲线的设计步骤进行了详细论述。     

凸轮机构中凸轮廓线设计的新方法

为确保从动件输出端的准确运动规律、减少高速运动时的冲击,建立凸轮机构的动力学系统模型和相应方程,导出从动件输出端的运动规律下凸轮与从动件接触处的运动规律,以此为依据设计了凸轮轮廓曲线,并讨论了机构工作频率对凸轮廓线的影响,为设计高速凸轮机构提供了可靠的依据。     

Predictions of cam follower wear in diesel engines

The rate of wear of cam followers in a valve train system is mainly a function of contact stress between the cam and the follower, sliding velocity and hydrodynamic film thickness between the two mating surfaces. The problem of surface fatigue wear becomes severe as the contact between cam and follower exceeds the plasticity limit of material. It finally leads to an increase in valve lash and loss of engine performance. The wear is minimised by reducing the coefficient of friction and by minimizing the compressive stress.In this paper, an attempt has been made to estimate the wear of followers quantitatively. The profile of followers resulting from steady and non-catastropic wear processes is computed by combining a linear wear relation and an elasto-hydrodynamic or boundary lubrication transition model with kinematic analysis. The finite element analysis, AVL TYCON simulation program and classical methodology have been effectively used to predict the follower wear. The model was validated on all types of followers widely varying in size, brake mean effective pressure and speed. The predicted wear profiles exhibit satisfactory agreement with experimental observations. At the end of the paper, a design guideline for designing a cam follower for low wear rate is given.     

具有响应与强度约束的凸轮机构动态设计

以滚子从动件平面凸轮机机构为分析对象，结合从动件相对变形理论，提出了输出响应限制与构件强度约束相结合的凸轮机构动态设计与修改方法，并从理论上进行了阐述。最后，通过一实例对不同频率比λ、不同摆臂截面形状及截面积下的摆臂最大变形、最大弯应力及凸轮与转子间最大压应力进行了数值计算，为凸轮机构动态设计与修改，提供了一种理论依据及具体的实现方法。     

基于ADAMS的共轭凸轮机构仿真分析

本文以凸轮摆式剪切机中的凸轮剪切机构为研究对象,对摆动从动件共轭凸轮机构进行理论分析,在3维CAD 软件Solidworks中建立凸轮机构模型。以ADAMS的碰撞仿真理论为基础,对机构进行动力学仿真分析,得出凸轮与摆杆之间接触力、凸轮主轴所受力以及凸轮与摆杆之间间隙随凸轮转动的变化规律曲线,并对凸轮与摆杆之间的共轭情况进行了分析。本文对摆动从动件共轭凸轮机构的合理设计和结构参数的优化设计具有一定的参考价值。     

Transient elastohydrodynamic lubrication film thickness in sliding and rolling line contacts

The contact behavior between cam and follower is greatly influenced by the kinematics and dynamics of the whole valve train system. This is the reason that both shape and thickness of the fluid film in the contact gap are mainly determined by applied loads and relative contact speeds as well as the curvatures of contacting elements. Most of the studies about lubricant film behavior between cam and follower have been performed without a consideration of transient effects in the contact gap. For the computational difficulties of transient effects, most contact conditions such as relative contacting speeds have been regarded as quasi-steady state during the whole operating cycle. In this work, in order to obtain stable convergence, a multigrid multi-level method is used for the computation of load capacity in the lubricant film. Nonlinear valve spring dynamics are also considered in the same way as Hanachi’s. From the computational results, transient EHL film thicknesses under the conditions of different contact geometries are computed for a pushrod type valve train system during an engine cycle. Several results show the squeeze film effect, which is generally not found with conventional EHL computations of the cam and follower contact. The results are also compared with those by the Dowson-Hamrock (D-H) formula, which does not consider the dynamic film effect. Without the dynamic film effect as in D-H’s formula, the minimum film thickness is highly dependent on the entraining lubricant velocity, whereas the minimum film thickness including the squeeze film effect is dependent on the applied load.     

凸轮机构综合与分析的接触条件法

以从动件与凸轮轮廓必须保持直接接触的约束条件建立位置方程,再通过位置方程对凸轮转角的求导,导出了轮廓极径的一、二阶导数与从动件类速度和类加速度之间的关系方程;利用上述方程,根据已知的凸轮轮廓,确定出从动件运动量的变化规律,并按照取定的从动件运动规律,导出了凸轮的轮廓方程和曲率半径等参量。     

偏心凸轮副时变乏油润滑数值分析

为研究乏油条件下偏心凸轮副的润滑状态,基于凸轮-挺杆机构建立时变乏油润滑模型,探究一个周期内6个典型瞬时(60°、120°、180°、240°、300°、360°)的压力和油膜厚度变化规律,并分析不同凸轮旋转角度下转速、初始载荷和润滑油黏度等参数对接触区润滑状态的影响。结果表明：当凸轮转至180°时,膜厚最小,压力最大,乏油状况最严重;限量供油下最小膜厚出现在凸轮转角为180°时,但是凸轮转角为0°时乏油速度最快,乏油程度更深;增大凸轮旋转速度时乏油速度更快,乏油程度更深;相同供油条件下,润滑油黏度越高使得接触区乏油情况越严重,乏油速度更快,乏油程度更深;载荷对接触区的润滑状态的影响较小,只在凸轮转角为0°接触区卷吸速度最大时,能够体现出载荷对接触区润滑状态的影响。     

Disk cam mechanisms with a translating follower having symmetrical double rollers

This paper proposes a novel translating follower that has symmetrical double rollers and also demonstrates how to design such a cam mechanism. Two identical rollers are symmetrically mounted on opposite sides of the follower. The two rollers will take turns to contact the cam when the cam rotates. The application of this follower can greatly reduce the pressure angle on both the rising and the falling motions of the follower. It may also reduce the induced forces.     

用最优控制理论设计高速凸轮-从动杆系统

本文将最优控制理论用于高速凸轮-从动杆系统的设计,对凸轮-从动杆系统存在着众多而又相互矛盾的设计要求,本文提出的性能指标泛函对众多的设计要求都有显著效果,该优化设计法与传统的多项式设计方法相比较,使最大接触力、接触应力以及能量损失分别减小了19%、10%及17%,同时使凸轮-从动杆分离的凸轮工作转速提高6%。在减小压力角、凸轮曲率以及从动杆力等重要性能方面也有显著改善。     

船用柴油机凸轮动态摩擦学分析及型线优化设计*

柴油机配气凸轮工作环境较为恶劣,工作过程中配合界面间载荷、速度及曲率半径等工况周期性变化,导致润滑接触条件苛刻,磨损情况恶劣。以某船用柴油机配气凸轮机构典型工况为算例,针对凸轮-挺柱常见的磨损问题,研究凸轮-挺柱动态接触特性;采用余弦-等速段和高次五项式对凸轮型线进行优化设计,并对凸轮-挺柱副动态接触及弹流润滑状态进行数值分析。结果表明:原凸轮磨损的原因是凸轮-挺柱副在运动周期内动态接触应力出现明显波动,最大值超过许用应力值;经型线优化设计后,凸轮-挺柱动态接触应力降到许用值以下,改善了动态接触特性,凸轮型线具有较好的润滑特性,运行过程中可保持较稳定的油膜润滑状态;凸轮转速和接触载荷的改变会直接影响凸轮-挺柱的润滑状态,尤其是随凸轮转速增大,润滑膜厚增大,压力减小,润滑接触状态明显改善。     

按许用压力角设计最小尺寸的摆动从动杆平面凸轮的解析法

关于按许用压力角设计最小尺寸的摆动从动杆平面凸轮机构的课题,至今未获得圆满解决。作者按微分几何的包络原理导出限制这种凸轮最小尺寸的界线方程式,据此可在电子计算机上图象显示凸轮轴心的容许区域或者直接计算其最小基圆半径和摆杆长度。文中将这种方法应用于锁合凸轮、槽道凸轮及共轭凸轮。     

旋转控制头密封胶芯性能三维有限元分析与结构优化

为提升带压起下钻过程中旋转控制头胶芯密封性能,基于虚功原理得到动态密封过程的有限元控制方程,并进行橡胶单轴压缩试验确立胶芯变形过程中的Yeoh本构模型;运用ABAQUS试验平台建立胶芯三维有限元模型,通过模拟起下钻过程中胶芯动态密封过程,得出密封面上受力分布规律;研究胶芯内锥角、外锥角、内径等结构参数对密封性能的影响....