平面四杆机构的运动特性planarlinkagemechanisms主讲人：周会娜

目录CONTENTS1234曲柄存在的条件Conditionsfortheexistenceofacrank急回运动和行程速比系数Quickreturnmovementandtravelspeedratiocoefficient压力角和传动角Pressureangleandtransmissionangle死点位置Dead-centerposition

1曲柄存在的条件ConditionsfortheexistenceofacrankONE

铰链四杆机构的三种基本形式的区别在于连架杆是否为曲柄。Thedifferencebetweenthethreebasicformsofhingefourbarmechanismsliesinwhethertheconnectingrodisacrank.曲柄摇杆机构Crank-rockermechanism空间连杆机构Spatiallinkage一、曲柄存在的条件1.Conditionsfortheexistenceofacrank双曲柄机构Doublecrankmechanism

曲柄摇杆机构:1根连架杆能作整周360°回转。Crankrockermechanism:Oneconnectingrodcanrotate360°throughouttheentirecycle.曲柄摇杆机构Crankrockermechanism一、曲柄存在的条件1.Conditionsfortheexistenceofacrank

双曲柄机构:2根连架杆能作整周360°回转。Doublecrankmechanism:Twoconnectingrodscanrotate360°throughouttheentirecycle.双曲柄机构Doublecrankmechanism一、曲柄存在的条件1.Conditionsfortheexistenceofacrank

双摇杆机构:连架杆均无法作整周360°回转。Doublerockermechanism:Eventheframerodcannotrotate360°throughouttheentirecycle.双摇杆机构Doublerockermechanism一、曲柄存在的条件1.Conditionsfortheexistenceofacrank

一、曲柄存在的条件1.Conditionsfortheexistenceofacrankcrank-rockermechanism曲柄摇杆机构Doublecrankmechanism双曲柄机构double-rockermechanism双摇杆机构

曲柄存在的条件：Conditionsfortheexistenceofacrank:?杆长之和条件：最短杆与最长杆长度之和小于或等于其它两杆长度之和。Theconditionforthesumofpolelengthsisthatthesumofthelengthsoftheshortestandlongestpolesislessthanorequaltothesumofthelengthsoftheothertwopoles.?最短杆条件：连架和机架中必有一杆是最短杆。Shortestpoleconditionisthattheremustbeonepoleintherackandframethatistheshortestpole.一、曲柄存在的条件1.Conditionsfortheexistenceofacrank

判断由不同杆作机架时四杆机构类型的方法：Themethodtodeterminethetypeoffourbarmechanismwhenusingdifferentrodsastheframe:一、曲柄存在的条件1.ConditionsfortheexistenceofacrankYNa、b、c、d(杆长a≤b≤c≤d)双摇杆机构Double-rockermechanisma+d≤b+c以最短杆相邻杆为机架Usingtheshortestadjacentpoleastheframe曲柄摇杆机构