chain drives

1、第五章 Chain drives 鏈傳動(dòng)51 General considerations 概述52 Motion features of chain drives 鏈傳動(dòng)的運(yùn)動(dòng)特性 53 Design of roller chain drive 套筒滾子鏈設(shè)計(jì)計(jì)算 54 Forces in chain drive 鏈傳動(dòng)受力分析55 Replacement and tension of chain drive 鏈傳動(dòng)的布置與張緊 vCharacteristics and applications 特點(diǎn)和應(yīng)用vTypes of chain drives 鏈傳動(dòng)分類5-1 General con

2、siderations 概述1 、 Advantages 優(yōu)點(diǎn) In comparison to belt drive 與帶傳動(dòng)相比： Absence of slippage 無(wú)滑動(dòng) Smaller overall size 尺寸小 一、 Characteristics and applications特點(diǎn)和應(yīng)用Small tension force Small forces acting on the shaft 張緊力F0小壓軸力小 High efficiency 工作效率高，98Can be used under higher temperature and humidity 能在較高溫

3、度和濕度下工作 v In comparison to toothed drive Can be used for larger centre-to-centre distances 與齒輪傳動(dòng)相比： 中心距a可以很大（8m）2、 Drawbacks 缺點(diǎn) Used only for parallel shafts 只用于平行軸 The velocity of the chain is not constant Leading to larger impact, vibration and noise i瞬變化高速時(shí)沖擊、振動(dòng)、噪音大. 3、 Applications 應(yīng)用（ For low s

4、peed and severe operation condition 適用于低速，勝任惡劣工況）鏈傳動(dòng)在物料運(yùn)輸機(jī)械中的應(yīng)用曳引鏈在傳輸機(jī)械中的應(yīng)用起重鏈的應(yīng)用鏈傳動(dòng)在摩托車中的應(yīng)用鏈傳動(dòng)在工業(yè)加工機(jī)械中的應(yīng)用鏈傳動(dòng)在自行車上的應(yīng)用二、 Types of chain drives 鏈傳動(dòng)分類傳動(dòng)鏈：Power transmission chains 傳遞動(dòng)力Bushing chains 套筒鏈 ： Higher sliding speeds 、Severe wear Roller chains 套筒滾子鏈： Are extensively applied 應(yīng)用廣泛Silent chains

5、齒形鏈（無(wú)聲鏈）： Less noise 無(wú)噪音， High cost 價(jià)格高 Lifting chain 起重鏈： Suspending loads 提升重物 Hauling chain 曳引鏈： Carrying loads 移動(dòng)重物三、 Roller chains 套筒滾子鏈1、 Structure 結(jié)構(gòu)：Bushings 套筒4、 inside link plates內(nèi)鏈板1：Pin 銷軸3、 Outside link plates外鏈板2：Interference fit過(guò)盈配合Bushings 套筒、Rollers 滾子：Tolerance fit間隙配合The pin pass

6、through the bushings of adjacent links to form swivel joints 套筒、銷軸相對(duì)轉(zhuǎn)動(dòng)鏈節(jié)屈伸元件結(jié)構(gòu)圖 With an even number of links 鏈節(jié)數(shù)Lp是偶數(shù)： Large pitch 大節(jié)距 P： Cotter pins 開口銷Small pitch 小節(jié)距 P： Spring clamp 彈簧夾2、 Joints 接頭形式With an uneven number of links: Offset link 鏈節(jié)數(shù)Lp是奇數(shù)： 過(guò)渡鏈節(jié)（ Which, however, is weaker than the mai

7、n links. Therefore, designers try to use chains with an even number of links附加彎矩，導(dǎo)致鏈條抗拉強(qiáng)度下降，最好不用）52 Motion features of chain drives 鏈傳動(dòng)的運(yùn)動(dòng)特性vVariation in speed ratio 運(yùn)動(dòng)不均勻性vDynamic load 動(dòng)載荷vThe velocity of the chain and speed ratio is not constant upon uniform rotational speed of the small sprocket.

8、 小鏈輪轉(zhuǎn)速1是常數(shù) 時(shí)，瞬時(shí)鏈速V和瞬時(shí)傳動(dòng)比i都是周期性變化的。一、 Variation in speed ratio運(yùn)動(dòng)不均勻性1、The chain velocity 瞬時(shí)鏈速V （為便于分析，設(shè)緊邊處于水平位置） The velocity of the joint of the link銷軸中心VA 1 R1 The velocity of chain 鏈速 V VAcos 1 R1 cos （The velocity of vertical motion of the chain 鏈條上下垂直運(yùn)動(dòng)速度V 1R1sin） 2sinRV2cosRV20VRV02sinRV2cosRV2

9、Z3602,2111max111min1min11maxo111max111min11o111Since angle varies, the chain velocity varies.周期性變化，導(dǎo)致V不均勻性2sinRV2cosRV20VRV02sinRV2cosRV2Z3602,2111max111min1min11maxo111max111min11o111振動(dòng)不平穩(wěn)，忽快忽慢忽上忽下，：加速下降：減速上升2, 0,02: 11VDeceleration in risingAcceleration in fallingWhen rising, the chain suddenly fa

10、lls and vice-versa Quick motion suddenly changes into slow motion and vice-versa Unsteady motion and vibration鏈速不均勻性11o1ZZ360Nun uniformity of the velocity for the chain2、 Instantaneous speed ratio 瞬時(shí)傳動(dòng)比 cosRcosRcosRV12211222i不均勻，變化212121constii Only at ： Z1 Z2 （ R1 R2 ） There is exactly a whole num

11、ber of links in the driving side of the chain只有當(dāng)Z1 Z2,緊邊長(zhǎng)度恰為P的整數(shù)倍時(shí)i121 （1 2） （，隨時(shí)相等）節(jié)距齒數(shù)）過(guò)鏈長(zhǎng)為（鏈輪轉(zhuǎn)一周，隨之轉(zhuǎn)）（PZZnniZPsm100060PnZ100060PnZV12212211Z3、Average velocity of the chain& average speed ratio 平均鏈速V和平均傳動(dòng)比 iWhen the sprocket turn 3600, the length of the chain running over the sprocket is zp. N

12、umber of teeth of a sprocketChain pitch二、 Dynamic load 動(dòng)載荷1、No uniformity of the motion Dynamic load 運(yùn)動(dòng)不均勻性動(dòng)載荷V，i，2 Periodic change Acceleration Dynamic load 周期性變化加速度動(dòng)載荷sinsin211RdtdRdtdVa2max111o21121max11112P2P2sinZ180sin2sin2，則時(shí)，aRRRav 1 P(Z1) It is favorable to select small pitch and large numbe

13、r of teeth from the point of view of decreasing dynamic load動(dòng)載荷宜采用小節(jié)距P大齒數(shù)Z12、Periodic change V周期性變化Cross vibration 橫向振動(dòng) Dynamic load 動(dòng)載荷3、Mesh impact Dynamic load 沖擊動(dòng)載荷 Impacts of the chain links on the sprocket teeth as new links come into engagement 鏈節(jié)進(jìn)入鏈輪時(shí)，以一定相對(duì) 速度相嚙合沖擊動(dòng)載荷constCCnqPU23In order to

14、 reduce impact為減小沖擊 Reduce 減小P，nReduce 減小q（ Mass per m 線密度）v Impact energy of motion 沖擊動(dòng)能53 Roller chain drive design 套筒滾子鏈設(shè)計(jì)計(jì)算vPrincipal parameters 參數(shù)選擇vTypes of failure 失效形式vLimit power curve and allowable power curve 極限功率曲線和許用功率曲線vDesign 設(shè)計(jì)計(jì)算1、i8（ Usually 23.5 ） i1Number of meshing teeth 嚙合齒數(shù) Wea

15、r of the sprocket 輪齒磨損 Shift outward upon the sprocket teeth profiles 跳鏈 1 120 i 23.5一、Principal parameters 參數(shù)選擇Nonuniformity of the motion and dynamics load運(yùn)動(dòng)不均勻性、動(dòng)載荷The links turn 增大鏈節(jié)相對(duì)轉(zhuǎn)角Power losses 功率損耗pressure increased acting on the pins增大鉸鏈承壓面壓強(qiáng)Wear 磨損 Z1 Z1 2、Z1，Z2Z1 9 Z1 f（i） Z2i Z1 120 Z2

16、 易跳鏈易跳鏈ddddZconst,PZ180sinPZ180sinPZ180sinPPooo Chain is easily fall 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

17、 of prime numbers.鏈節(jié)數(shù)Lp為偶數(shù)時(shí)，為均勻磨損， Z最好為質(zhì)數(shù)或不能整除鏈節(jié)數(shù)的數(shù)3、P（ pitch節(jié)距）P Size 尺寸Load carrying increases 承載能力增大Nonuniformity of the motion and dynamic load increase運(yùn)動(dòng)不均勻性、動(dòng)載荷增大v High speed and heavy load ： Small pitch and multiple- width chain drive 高速重載:小節(jié)距P多排v Low speed and light load ： Large pitch and si

18、ngle-width chain drive 低速重載:大節(jié)距P單排It is best practice to elect a chain with the minimum allowable pitch for the given load 節(jié)距P 盡量小，但排數(shù)34（均勻） a V不變時(shí)，單位時(shí)間內(nèi)同一鏈節(jié) 屈伸次數(shù)磨損 a 松邊上下顫動(dòng)，不平穩(wěn)4、Centre-to-centre distance 中心距a The number of the chain links 鏈節(jié)數(shù) Lpa（3050）P （amax80P）21221p)D(D4a12a2)DDLPLL（Lp（鏈條長(zhǎng)度用鏈節(jié)數(shù)表

19、示）LLpPaP)2ZZ(Pa22ZZLPZD21221P代入Lp Round The even number 偶數(shù)Lp Actual centre-to-centre distance實(shí)際中心距a21222121)2ZZ( 82ZZ2ZZ4PPPLLav二、 Types of failure 失效形式1、 Fatigue breakage of the chain 鏈條疲勞破壞 (chain plates, surfaces of the bushings and rollers)（鏈板、套筒和滾子表面）2、Wear of the hinge for the chain鏈條鉸鏈磨損Out o

20、ff sprocket 脫鏈 3、Seizure of the hinge for the chain 鏈條膠合（ At high speed 高速 ）4、 Overload breakage of the chain 鏈條過(guò)載拉斷5、Wear of the sprockets 鏈輪磨損v三、Limit power curve and allowable power curve 極限功率曲線和許用功率曲線v1 Limit of the wear failure 磨損破壞極限v2Limit of the fatigue failure of the chain plates 鏈板疲勞破壞極限v3

21、 Limit of the impact fatigue failure 套筒、滾子沖擊疲勞極限4 Limit of the seizure of the hinge between bushings and pins 套筒、銷軸膠合極限 5 Allowable power curve ,operating inside the range is safe許用傳動(dòng)功率曲線，在此范圍內(nèi)為安全區(qū).v6Wear breakage limit under poor lubrication and severe operating condition潤(rùn)滑不良、工作環(huán)境惡劣的磨損極限 Experiment

22、al conditions試驗(yàn)條件：Z119 Lp100Single-width單列Steady load載荷平穩(wěn)四、 Design 設(shè)計(jì)計(jì)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 實(shí)際工作中與上述試驗(yàn)條件不同時(shí)， 對(duì)工作功率P和許用功率P0進(jìn)行修正： KP KLoad factor 載荷系數(shù)Z119KZ（ Small

23、 sprocket tooth number factor 小鏈輪齒數(shù)系數(shù)）Lp100KL（ Chain length factor 鏈長(zhǎng)系數(shù)）多排鏈 KP（ Multiple-width chain factor 多排鏈系數(shù)）KZKLKPP0 Design criteria 設(shè)計(jì)依據(jù)： KPKZKLKPP0 0PLZPKKKKP2、V0.6m/s（ Low speed drive 低速傳動(dòng)）Principal failure is overload breakage ：主要失效形式過(guò)載拉斷Static strength check 靜強(qiáng)度校核7KFQZSPB安全系數(shù)Safety factor

24、緊邊總拉力單排鏈極限拉伸載荷鏈排數(shù)side driving of force totalTheFchain width -single of load BreakingQchain ofnumber width TheZPB 1、Useful load 工作拉力 F11000P/V 2、Centrifugal tension 離心拉力 F2qV2 5-4 Forces in the chain drives 鏈傳動(dòng)受力分析 3、Weight tension 垂度拉力F3 KfqgaFor a horizontal drive 水平傳動(dòng) ：Kf6For an angle of inclination of the drive to the horizontal up to 400 傾角40：Kf 2For a vertical drive 垂直傳動(dòng) ： Kf 1)(8142(33qgafaFaqgafF4、The total force of driving side緊邊總拉力 F F1+ F2+ F3 The