§5 Belt drives 带传动§5-1 General considerations 概述§5-2 Belt drive theoretical basis 带传动理论基础§5-3 V-Belt drive design 带传动设计（V带）§5-4 Tension device of the belt drive 张紧装置Belt drive design example 带传动设计实例§5-1 General considerations ★特点和应用Characteristics and applications of the belt drive ★分类Types of the belt drive★带的结构、型号和长度Composition、section and length of the V－belt一、特点和应用1 、优点2 、缺点3、Applications二、TypesStandard V-beltFlat belt Multiple V belt Toothed-belt drive三、Composition、section and length of the belt带的结构、型号和长度1.普通V带Standard V-belt2.平形带Flat-belt3.多楔带Multiple V belt drive4.同步齿形带Toothed belt drive1. Standard V-belt 普通V带2、Flat-belt 平形带3、多楔带Multiple V belt drive4、toothed belt drive 同步齿形带§2-2Belt drive theoretical basis 带传动理论基础★受力分析Forces in belts★应力分析Stresses in belts★带的滑动现象Creep and slipping of the belt ★失效形式和计算准则Types of failure & design criteria ★承载能力确定Load-carrying capacity一、Forces in belts In no-load operation In load operationLoose sides Tight sides1、带传递的力2、有效拉力F e 由带和轮之间接触弧上摩擦力的总和F f 承受P1000F F F F 21e e ＝－＝＝两边拉力差有效拉力fe F F ＝3、F e ↑→ F f ↑，始终保证F e ＝F f 。
然而，在一定条件下，F f 有一极限值F f max 。
当F e > F f max 时，导致打滑失效。
4.F emax calculation （开始打滑时，F 1、F 2之间关系）()2μemax emax 022μμemax emax 01αα20emax μ2emax 02emax 0q υ1F 2F F F q υ1F 2F F F 11q υF 2F q υ2F F q υ2F F 3+-+-++--=⇓⎪⎭⎫ ⎝⎛--=⎪⎭⎫ ⎝⎛-+αααμμαe e e e e e ＝－＝＝＝此时：）打滑时：（二、应力分析Stresses in belts⎪⎪⎩⎪⎪⎨⎧→=→→=→)1σ2σ(22σ2)2σ1σ(11σ1.1由带绕过大轮时，拉应力由带绕过小轮时，拉应力拉应力A F F A F F Tensile stress As the belt runs over the driven pulley, tensile stress changes from σ2to σ1.As the belt runs over the driving pulley, tensile stress changes from σ1to σ22. 离心应力Centrifugal stress)/kg q (d αq υR υ)q(Rd αdC 22m ：==①带沿弧面运动，微段d l 产生离心力dC ：As the belt runs over arc of the pulley, centrifugal force dC is acting on an elementary arc d l .。
）中包含，，＝中包含，（作用于全带长，＝＝③离心应力：作用于整个带长离心拉力发生于圆周部分离心力（离心拉力）＝＝②根据力平衡关系：：产生离心力段①带沿弧面运动，微弧c 212c 212c c c 2c 2c 22σσσq υF F F A q υA F F dC q υF 2αd 2αd s in d αq υ2αd s in F 2)/kg q (d αq υR υ)αq(Rd dC Cσ⎩⎨⎧⇓⎪⎭⎫ ⎝⎛≈==m d dl Take into account the condition of static equilibrium ②根据力平衡关系：Centrifugal tensile force . . Centrifugal tensile force F c acting on the arc parts and straight portions of the belt Centrifugal force dC acting on the arc parts on the belt。
）中包含，，＝中包含，（作用于全带长，＝＝③离心应力：作用于整个带长离心拉力发生于圆周部分离心力（离心拉力）＝c 212c 212c c c 2c σσσq υF F F Aq υA F F dC q υF 222σ⎩⎨⎧⇓⎭⎝Centrifugal stressCentrifugal stress σc acts on every part of the belt.**Because F c is contained in F 1or F 2, σc is contained in σ1or σ2.Centrifugal stress σc acts on every part of the belt.F c is a part of both F 1and F 2, while σc is a part of σ1and σ22b 1b b b σσσD2c E σ>∴↑⇒↓=D 3. 弯曲应力The bending stress（发生于带与带轮接触的圆弧部分）Acting on the arc of contact on the pulley4. The total stressThe total stress in the belt is equal to the sum of the bending stress plus the tensile stress which contains the centrifugal stress .Maximum stress is at the point where the tight side of the belt runs onto the smaller driving pulley.4. 总应力：等于拉应力（包括离心应力）与弯曲应力之和；最大应力发生于紧边进入小带轮处。
b1c αμαμb12αμαμb11b11max σσ1e Fe A 1σq υ1e Fe A 1σAF σσσ++⎪⎪⎭⎫ ⎝⎛-=+⎪⎪⎭⎫ ⎝⎛+-=+=+=三、带的滑动现象Creep and slipping of the belt1.带的弹性滑动Creep of the belt （固有的、不可避免的正常现象）21121212211υυυυεεεεA σεA σε>⎪⎨⎧<→→>⎪⎪⎩⎪⎪⎨⎧带滑动（逐渐缩短），沿轮面带绕过主动轮：②＝松边应变：＝紧边应变：①The tight side strain The loose side strainThe operation of an elastic belt is associated with creep of the belt on the pulleys .It is inevitable.As the belt runs over the driving pulley, the belt becomes shortened and creeps along the pulley. As the belt runs over the driven pulley, the belt is elongated and creeps along the pulley.212121212122υυυυεευυεεεεA σε>⎪⎩⎪⎨⎧>→→<→→>⎪⎪⎩⎨带带滑动（逐渐伸长），沿轮面带绕过从动轮：滑动（逐渐缩短），沿轮面带绕过主动轮：②＝松边应变：①由于带的弹性和拉力差引起的带与带轮之间的滑动，称为弹性滑动。
The creep of the belt on the pulleys is caused by elasticity of the belt and the difference between tensile forces of the tight and the loose sides. It is known as the elastic slip.Results of the creep: a. efficiency drops.b. belt wear.c. temperature of the belt grows.d. the speed ratio is not precise.③后果：a. 效率降低；b. 带磨损；c. 带温升高；d. v 2<v 1传动比不准确％）～一般为21(111πππυυυε121212112211121i D D n n D D D n D n D n -=-=-=-=从动轮相对于主动轮的圆周速度相对降低率称为滑动率：The relative creep factor is ：2. 打滑Slip（过载失效，必须避免）(It is a kind of failure. And it should be avoided）带在带轮上全面滑动，导致带严重磨损、带的运动处于不稳定状态，这种现象称为打滑。
.③α1< α2打滑发生在小带轮处Slip occurs on smaller pulley四、失效形式和计算准则Types of failure & design criteria1. 失效形式Types of failure ：打滑、带疲劳破坏Slip fatigue failure2. 计算准则design criteria：在不打滑前提下，具有一定的疲劳强度和寿命。