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。     

基于运动仿真的凸轮机构参数逆向CAD方法

提出了利用机构运动仿真和实测模型获取平面盘形凸轮从动件运动规律和动程角等运动参数,再利用这些运动参数和有关结构尺寸,重新解析设计的逆向CAD方法,给出了在Pro/E软件平台上实现凸轮机构运动仿真和获取机构运动参数的过程.应用实例证明该方法高效直观,所设计的凸轮机构精度高,可直接用于生产.     

Machining of plate cam profiles on CNC machine tools using a highly integrated part programming system

The concept of NC (Numerical Control) and CNC (Computerised Numerical Control) in machine tools has contributed a great deal to automation and flexibility in manufacturing. In small/medium batch manufacturing, machining of complex contours with conventional machining is neither economical nor accurate. These can be achieved on a CNC machining centre more economically. The can machining system is designed to provide the necessary CNC program blocks for machining the plate cam profiles. The cam profiles can be defined by geometric curves, by follower motion or through a set of points. A promising new concept for approximating the tool path close to the defined cam profile, within the specified tolerance, has been proposed. The CLIP algorithm, presented in this paper, automatically chooses the best of the available interpolations (e.g. linear and circular interpolations) for selecting the intermediate points on the profile to guide the cutter for machining the profile. It provides the minimum number of intermediate points. This module can also be used for machining the elliptical profiles and pockets. The cam module, with little modification, is also used for machining the scroll threads of any pitch.     

The effect of cam profile errors and system flexibility on cam mechanism outputL'effet des erreurs de profil des cames et de la flexibilite du systeme sur son fonctionnement

An investigation of the effects of machining errors in the contact surfaces of a cam mechanism together with all possible system flexibility errors is carried out by simulation. An 11 degree of freedom dynamic model of a cam follower system including its drive system was selected, and the dynamic simulation is combined with a stochastic simulation of the random nature of the machining tolerances which have a considerable effect on the actual output. Jump phenomena, the preloading of the retaining spring, variations in angular velocity, characteristics of the various motion curves, flexibility of the various components, non-roundness of cam shaft bearings, non-concentricity of the base circle and machining tolerance on both cam profile and follower are all taken into account, and an analytical method to calculate the spring constant between cam and follower considering Hertzian contact is developed.The lengthy simulation program is handled on a mini-computer by utilizing suitable numerical methods and overlay techniques resulting in a continuous simulation of the effects of all input errors in a cam-mechanism. The effects of tolerance and flexibility errors are examined separately as well as in combination.     

用于加工弧面凸轮轮廓曲面的NURBS插补方法

在分析弧面凸轮轮廓曲面上加工刀痕产生的原因,以及对分度机构性能影响的基础上,提出了用NURBS样条插补凸轮从动件运动规律曲线的思想方法.通过对NURBS样条插补改进算法的深入分析,得出了进一步校正满足加工步长条件的NURBS样条参数增量的算式.同时对插补前弧面凸轮从动件运动规律曲线的修正、NURBS插补误差和插补过程的实现进行了计算与分析.结果表明,采用文中给出的方法,能显著提高弧面凸轮轮廓面的加工精度.     

Mechanical error analysis of disk cam mechanisms with a flat-faced follower

By employing the concept of equivalent linkage, this paper presents an analytical method for analyzing the mechanical errors of disk cam mechanisms with a flat-faced follower. The resulting error equations do not really involve the location of the curvature center of the cam profile, and locating the curvature center of the cam profile is not essential. The resulting errors are significantly affected by the pressure angle, and the smaller pressure angle will result in the smaller mechanical error. In the worst case, owing to the joined effects of various design parameters, the accuracy of the follower motion may degrade considerably. For the oscillating follower case, all acceleration error functions have a sudden change at every beginning and at every end of the motion even though the theoretical follower displacement is cycloidal motion.     

基于B样条的弧面分度凸轮的设计与制造技术

介绍了一种新的基于B样条曲线的弧面分度凸轮集成设计与制造技术,给出了两种构造凸轮从动件运动特征曲线的方法--优化设计法和拟合法.讨论了用它们构造凸轮运动曲线的特点和注意事项,提出了用B样条插补加工弧面分度凸轮的方法,并开发了相应的设备,给出了实验结果.     

设计平面凸轮轮廓的新方法

提出了设计平面凸轮轮廓的相对运动法,这是一种适用于各种平面凸轮轮廓设计的通用方法。利用从动件相对凸轮运动的相对速度、相对加速度和从动件的表面法线确定平面凸轮的轮廓方程、压力角和曲率半径是该方法的基本原理。通过建立基于反转原理的通用模型、坐标系和齐次坐标变换技术,导出了平面凸轮的轮廓方程、压力角和曲率半径的一般表达式。该推导过程不仅适用于手工完成,而且为平面凸轮轮廓设计的智能化、自动化打下了基础。根据设计的自动推导和求解策略,用C++和OpenGL语言开发了计算机辅助设计程序实现了平面凸轮轮廓设计和机构运动仿真的自动化。最后,给出了设计和仿真实例。     

Pro/E阵列功能在圆锥滚子从动件圆柱凸轮建模中的应用

圆锥滚子摆动从动件圆柱凸轮的轮廓曲面是复杂的空间曲面,设计繁琐且很难用常规的制图方法绘制。根据布尔运算原理和啮合过程中滚子与凸轮的相对运动关系,在分析圆锥滚子摆动从动件圆柱凸轮工作原理的基础之上,提出一种生成圆锥滚子摆动从动件圆柱凸轮造型的新方法。利用Pro/E提供的强大阵列功能和关系式,给出了方便快速地求出凸轮啮合廓面的过程,实现了圆柱凸轮的三维数字化精确建模和系列化设计。该方法易于为一般工程技术人员所掌握,也可应用于其它机械零件三维实体参数化造型。     

基于组件技术的凸轮从动件运动规律反求研究

研究了从CATIA数字模型中获取凸轮轮廓曲线上离散点坐标的方法,并以这些离散点及凸轮机构基本尺寸为依据,提出了反求机构从动件的运动规律的方法。利用CATIA提供的COM功能,结合其自带的V5AutomationAPI函数开发了反求从动件的运动规律算法及程序,并对反求所得结果与理论结果进行了误差分析,研究表明提出方法是准确的和适用的。     

行星分度凸轮机构凸轮理论廓线的几何性质

通过对行星分度凸轮机构凸轮理论廓线的连续性、正则性和自交现象等几何性质的分析，确定了从动性运动规律、变位系数和分度数对凸轮廓线设计的影响，建立了机构参数选取的几何约束条件。     

圆柱分度凸轮单侧面加工及误差计算方法研究

应用空间啮合原理和旋转变换矩阵理论，推导了圆锥滚子从动件圆柱分度凸轮的理论工作廓面方程及单侧面加工凸轮实际工作廓面方程；廓面采取单侧面加工时，给出了刀具误差对凸轮廓面法向误差影响的精确计算方法和近似计算方法，解决了空间凸轮廓面误差计算的难题，进一步完善了圆柱分度凸轮机构的设计和制造理论。     

Stochastic error analysis in cam mechanisms

A probabilistic method is outlined for obtaining the variances in displacement, velocity and acceleration of followers in cam mechanisms for any given manufacturing tolerance on the cam profile. A follower motion equation is obtained by expansion in a Taylor series and considered in both linear and second-order terms. The equation is analyzed with random variables for the kinematic displacement, velocity and acceleration of the follower employing stochiastic techniques including finite differences and the maximum likelihood method. A general computer program allows the designer to obtain projected output errors for any commonly used disc cam type, and an example of one of these is included.     

平底从动件盘形凸轮机构的研究

根据已知凸轮机构运动简图，提出了凸轮轮廓参数确定平底从动件运动规律的分析算法，建立了相应的代数算式；并在此基础上，导出了根据预定的从动件运动规律确定凸轮轮廓参数的代数算式；并验证了算法的正确性。     

滚子从动件盘形凸轮机构的运动分析

针对滚子从动件盘形凸轮机构，根据凸轮机构运动简图和凸轮实际廓线测量值，导出了确定从动件的位移、速度、加速度及其机构压力角的计算公式，并用实例验证了计算公式的正确性。     

基于UG NX6.0的弧面分度凸轮三维实体建模与仿真加工

以弧面分度凸轮工作轮廓面方程为基础,基于UGNX6.0和MATLAB提出了弧面分度凸轮空间轮廓曲面三维实体建模的一种新方法,通过UG运动仿真对建模结果进行分析验证,同时运用UG数控加工模块对弧面分度凸轮的加工刀轨进行了模拟,为空间凸轮机构的设计与数控加工提供了参考依据。     

空间凸轮数控加工刀具误差对凸轮轮廓法向误差影响的计算方法

空间凸轮的计算机数控 (CNC)加工是现在最为常用的一种加工方法 ,而仿形加工中靠模凸轮的加工也是采用该法进行的 ,粗加工时采用比滚子直径小一些的刀具 ,精加工时就必须使用与滚子直径相同的刀具 ,本文给出了刀具尺寸误差 ΔR对凸轮轮廓法向误差 Δn影响的计算方法及规律     

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.     

基于ADAMS的凸轮机构设计及运动仿真分析

用大型运动学和动力学分析软件ADAMS完成尖顶直动从动件盘形凸轮机构设计和实体造型,并对其进行运动分析和仿真,缩短了凸轮的设计周期并提高了设计质量,为凸轮机构的设计分析提供一种有效的新方法.     

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.