偏置直动从动件圆盘凸轮的设计和特性分析

Design and characteristics analysis of circular disk cam with offset translating follower

圆盘凸轮机构特性值的理论分析目前少见,影响其动力学性能评判和适用场合的确定。详细研究了偏置直动从动件圆盘凸轮的运动学和动力学特性,获得了从动件的位移、速度、加速度、跃度、跳度和压力角,以及最大无量纲速度、最大无量纲加速度、最大无量纲跃度和最大无量纲转矩这4个主要的动力学特性值的精确计算式、求解方法和曲线图。根据计算结果,可判断该机构与特性值有关的动力学性能的优劣和适用场合。给出了在满足压力角和尺寸约束下通过求解非线性方程组来设计机构尺寸的一种方法及其实例。研究结果显示:1)压力角约束构成的设计可行域是一个由若干条直线围成的凸多边形; 2)行程速比系数小于3; 3)特性值只决定于各构件的相对长度; 4)凸轮偏心率是特性值的最敏感参数; 5)若凸轮偏心率和从动件偏距率变小,则机构性能趋好; 6)该机构无任何冲击且特性值小,因而动力学性能优异,可用于高速场合。

Theoretical analyses for characteristic values of circular disk cams are rare,affecting the evaluation for dynamic performances and suitable application occasions of these mechanisms. By a detailed research on kinematics and dynamic characteristics of circular disk cam with offset translating follower,the accurate formulas,solving methods and diagrams of the follower’s displacement,velocity,acceleration,jerk,jump,pressure angle,as well as four of major dynamic characteristics which are maximum dimensionless velocity,maximum dimensionless acceleration,maximum dimensionless jerk and maximum dimensionless torque were obtained. According to results of the numerical calculation,advantages and disadvantages of the dynamic performances related to the characteristic values,and the suitable application occasions,can be judged. A method and an example for designing the sizes of the mechanism by solving the nonlinear equations with the constraints of the pressure angle and sizes is given. Results of above study show that: 1) the feasible design region formed by the pressure angle constraints is a convex polygon surrounded by several straight lines;2) the coefficient of travel speed variation is less than 3;3) the characteristic values are determined only by relative the lengths of mechanism’s each member;4) the cam’s eccentricity is the most sensitive parameter for characteristic values;5) if the cam’s eccentricity or the follower’s offset rate decreases,the performances of the mechanism usually become better;6) this mechanism has small characteristic values and no any impact in motion,so its dynamic performances are excellent. It can be used for high speed.