第八章 链传动

1、第八章 Chain drives 链传动81 General considerations 概述82 Motion features of chain drives 链传动的运动特性 83 Design of roller chain drive 套筒滚子链设计计算 84 Forces in chain drive 链传动受力分析85 Replacement and tension of chain drive 链传动的布置与张紧 vCharacteristics and applications 特点和应用vTypes of chain drives 链传动分类8-1 General con

2、siderations 概述1 、 Advantages 优点 In comparison to belt drive 与带传动相比： Absence of slippage 无滑动 Smaller overall size 尺寸小 一、 Characteristics and applications特点和应用Small tension force Small forces acting on the shaft 张紧力F0小压轴力小 High efficiency 工作效率高，98Can be used under higher temperature and humidity 能在较高温

3、度和湿度下工作 v In comparison to toothed drive Can be used for larger centre-to-centre distances 与齿轮传动相比： 中心距a可以很大（8m）2、 Drawbacks 缺点 Used only for parallel shafts 只用于平行轴 The velocity of the chain is not constant Leading to larger impact, vibration and noise i瞬变化高速时冲击、振动、噪音大. 3、 Applications 应用（ For low s

4、peed and severe operation condition 适用于低速，胜任恶劣工况）二、 Types of chain drives 链传动分类传动链：Power transmission chains 传递动力Bushing chains 套筒链 ： Higher sliding speeds 、Severe wear Roller chains 套筒滚子链： Are extensively applied 应用广泛Silent chains 齿形链（无声链）： Less noise 无噪音， High cost 价格高 Lifting chain 起重链： Suspendin

5、g loads 提升重物 Hauling chain 曳引链： Carrying loads 移动重物三、 Roller chains 套筒滚子链1、 Structure 结构：Bushings 套筒4、 inside link plates内链板1：Pin 销轴3、 Outside link plates外链板2：Interference fit过盈配合Bushings 套筒、Rollers 滚子：Tolerance fit间隙配合The pin pass through the bushings of adjacent links to form swivel joints 套筒、销轴相对

6、转动链节屈伸元件结构图 With an even number of links 链节数Lp是偶数： Large pitch 大节距 P： Cotter pins 开口销Small pitch 小节距 P： Spring clamp 弹簧夹2、 Joints 接头形式With an uneven number of links: Offset link 链节数Lp是奇数： 过渡链节（ Which, however, is weaker than the main links. Therefore, designers try to use chains with an even number

7、of links附加弯矩，导致链条抗拉强度下降，最好不用）82 Motion features of chain drives 链传动的运动特性vVariation in speed ratio 运动不均匀性vDynamic load 动载荷vThe velocity of the chain and speed ratio is not constant upon uniform rotational speed of the small sprocket. 小链轮转速1是常数 时，瞬时链速V和瞬时传动比i都是周期性变化的。一、 Variation in speed ratio运动不均匀性1

8、、The chain velocity 瞬时链速V （为便于分析，设紧边处于水平位置） The velocity of the joint of the link销轴中心VA 1 R1 The velocity of chain 链速 V VAcos 1 R1 cos （The velocity of vertical motion of the chain 链条上下垂直运动速度V 1R1sin） 2sinRV2cosRV20VRV02sinRV2cosRV2Z3602,2111max111min1min11maxo111max111min11o111Since angle varies, t

9、he chain velocity varies.周期性变化，导致V不均匀性2sinRV2cosRV20VRV02sinRV2cosRV2Z3602,2111max111min1min11maxo111max111min11o111振动不平稳，忽快忽慢忽上忽下，：加速下降：减速上升2, 0,02: 11VDeceleration in risingAcceleration in fallingWhen rising, the chain suddenly falls and vice-versa Quick motion suddenly changes into slow motion an

10、d vice-versa Unsteady motion and vibration链速不均匀性11o1ZZ360Nun uniformity of the velocity for the chain2、 Instantaneous speed ratio 瞬时传动比 cosRcosRcosRV12211222i不均匀，变化212121constii Only at ： Z1 Z2 （ R1 R2 ） There is exactly a whole number of links in the driving side of the chain只有当Z1 Z2,紧边长度恰为P的整数倍时i1

11、21 （1 2） （，随时相等）节距齿数）过链长为（链轮转一周，随之转）（PZZnniZPsm100060PnZ100060PnZV12212211Z3、Average velocity of the chain& average speed ratio 平均链速V和平均传动比 iWhen the sprocket turn 3600, the length of the chain running over the sprocket is zp. Number of teeth of a sprocketChain pitch二、 Dynamic load 动载荷1、No unifo

12、rmity of the motion Dynamic load 运动不均匀性动载荷V，i，2 Periodic change Acceleration Dynamic load 周期性变化加速度动载荷sinsin211RdtdRdtdVa2max111o21121max11112P2P2sinZ180sin2sin2，则时，aRRRav 1 P(Z1) It is favorable to select small pitch and large number of teeth from the point of view of decreasing dynamic load动载荷宜采用小节

13、距P大齿数Z12、Periodic change V周期性变化Cross vibration 横向振动 Dynamic load 动载荷3、Mesh impact Dynamic load 冲击动载荷 Impacts of the chain links on the sprocket teeth as new links come into engagement 链节进入链轮时，以一定相对 速度相啮合冲击动载荷constCCnqPU23In order to reduce impact为减小冲击 Reduce 减小P，nReduce 减小q（ Mass per m 线密度）v Impact

14、energy of motion 冲击动能83 Roller chain drive design 套筒滚子链设计计算vPrincipal parameters 参数选择vTypes of failure 失效形式vLimit power curve and allowable power curve 极限功率曲线和许用功率曲线vDesign 设计计算1、i8（ Usually 23.5 ） i1Number of meshing teeth 啮合齿数 Wear of the sprocket 轮齿磨损 Shift outward upon the sprocket teeth profile

15、s 跳链 1 120 i 23.5一、Principal parameters 参数选择Nonuniformity of the motion and dynamics load运动不均匀性、动载荷The links turn 增大链节相对转角Power losses 功率损耗pressure increased acting on the pins增大铰链承压面压强Wear 磨损 Z1 Z1 2、Z1，Z2Z1 9 Z1 f（i） Z2i Z1 120 Z2 易跳链易跳链ddddZconst,PZ180sinPZ180sinPZ180sinPPooo Chain is easily fall

16、 out off sprocketWhen the number of the chain links is the even number，In order to facilitate more uniform wear, It is preferable to select an uneven number of teeth for the sprockets or to select the number of teeth from the series of prime numbers.链节数Lp为偶数时，为均匀磨损， Z最好为质数或不能整除链节数的数3、P（ pitch节距）P Si

17、ze 尺寸Load carrying increases 承载能力增大Nonuniformity of the motion and dynamic load increase运动不均匀性、动载荷增大v High speed and heavy load ： Small pitch and multiple- width chain drive 高速重载:小节距P多排v Low speed and light load ： Large pitch and single-width chain drive 低速重载:大节距P单排It is best practice to elect a cha

18、in with the minimum allowable pitch for the given load 节距P 尽量小，但排数34（均匀） a V不变时，单位时间内同一链节 屈伸次数磨损 a 松边上下颤动，不平稳4、Centre-to-centre distance 中心距a The number of the chain links 链节数 Lpa（3050）P （amax80P）21221p)D(D4a12a2)DDLPLL（Lp（链条长度用链节数表示）LLpPaP)2ZZ(Pa22ZZLPZD21221P代入Lp Round The even number 偶数Lp Actual

19、centre-to-centre distance实际中心距a21222121)2ZZ( 82ZZ2ZZ4PPPLLav二、 Types of failure 失效形式1、 Fatigue breakage of the chain 链条疲劳破坏 (chain plates, surfaces of the bushings and rollers)（链板、套筒和滚子表面）2、Wear of the hinge for the chain链条铰链磨损Out off sprocket 脱链 3、Seizure of the hinge for the chain 链条胶合（ At high sp

20、eed 高速 ）4、 Overload breakage of the chain 链条过载拉断5、Wear of the sprockets 链轮磨损v三、Limit power curve and allowable power curve 极限功率曲线和许用功率曲线v1 Limit of the wear failure 磨损破坏极限v2Limit of the fatigue failure of the chain plates 链板疲劳破坏极限v3 Limit of the impact fatigue failure 套筒、滚子冲击疲劳极限4 Limit of the seizu

21、re of the hinge between bushings and pins 套筒、销轴胶合极限 5 Allowable power curve ,operating inside the range is safe许用传动功率曲线，在此范围内为安全区.v6Wear breakage limit under poor lubrication and severe operating condition润滑不良、工作环境恶劣的磨损极限 Experimental conditions试验条件：Z119 Lp100Single-width单列Steady load载荷平稳四、 Design 设

22、计计算v1、The power which can be transmitted by a chain drive under actual working conditions is determined by multiplying the tabular value by the correction factors 实际工作中与上述试验条件不同时， 对工作功率P和许用功率P0进行修正： KP KLoad factor 载荷系数Z119KZ（ Small sprocket tooth number factor 小链轮齿数系数）Lp100KL（ Chain length factor 链

23、长系数）多排链 KP（ Multiple-width chain factor 多排链系数）KZKLKPP0 Design criteria 设计依据： KPKZKLKPP0 0PLZPKKKKP2、V0.6m/s（ Low speed drive 低速传动）Principal failure is overload breakage ：主要失效形式过载拉断Static strength check 静强度校核7KFQZSPB安全系数Safety factor紧边总拉力单排链极限拉伸载荷链排数side driving of force totalTheFchain width -single

24、of load BreakingQchain ofnumber width TheZPB 1、Useful load 工作拉力 F11000P/V 2、Centrifugal tension 离心拉力 F2qV2 8-4 Forces in the chain drives 链传动受力分析 3、Weight tension 垂度拉力F3 KfqgaFor a horizontal drive 水平传动 ：Kf6For an angle of inclination of the drive to the horizontal up to 400 倾角40：Kf 2For a vertical drive 垂直传动 ： Kf 1)(8142(33qgafaFaqgafF4、The total force of driving side紧边总拉力 F F1+ F2+ F3 T