第八章 鏈傳動(dòng)幻燈片.ppt

1、第八章 Chain drives 鏈傳動(dòng),81 General considerations 概述 82 Motion features of chain drives 鏈傳動(dòng)的運(yùn)動(dòng)特性 83 Design of roller chain drive 套筒滾子鏈設(shè)計(jì)計(jì)算 84 Forces in chain drive 鏈傳動(dòng)受力分析 85 Replacement and tension of chain drive 鏈傳動(dòng)的布置與張緊,Characteristics and applications 特點(diǎn)和應(yīng)用 Types of chain drives 鏈傳動(dòng)分類,8-1 General

2、considerations 概述,回總目錄,1 、 Advantages 優(yōu)點(diǎn) In comparison to belt drive 與帶傳動(dòng)相比： Absence of slippage 無滑動(dòng) Smaller overall size 尺寸小,一、 Characteristics and applications特點(diǎn)和應(yīng)用,BACK,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，98 Can be used under higher temperature an

3、d humidity 能在較高溫度和濕度下工作, 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、 Applicatio

4、ns 應(yīng)用,（ For low speed and severe operation condition 適用于低速，勝任惡劣工況）,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 齒形鏈（無聲鏈）： Less noise 無噪音， High cost 價(jià)格高,BACK, L

5、ifting 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 過盈配合,Bushings 套筒、 Rollers 滾子：,Tolerance fit 間隙配合,The pin pass through the bushings of adjace

6、nt links to form swivel joints 套筒、銷軸相對轉(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)： 過渡鏈節(jié),（ Which, however, is weaker than the main links. Therefore, desi

7、gners 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）,BACK,82 Motion features of chain drives 鏈傳動(dòng)的運(yùn)動(dòng)特性,Variation in speed ratio 運(yùn)動(dòng)不均勻性 Dynamic load 動(dòng)載荷,回總目錄,The velocity of the chain and speed ratio is not constant upon uniform rotational speed of the small sprocket. 小鏈輪轉(zhuǎn)速1是常數(shù)

8、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,BACK,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）,Since angle varies, the chain vel

9、ocity varies. 周期性變化，導(dǎo)致V不均勻性,Deceleration in rising,Acceleration in falling,When rising, the chain suddenly falls and vice-versa,Quick motion suddenly changes into slow motion and vice-versa,Unsteady motion and vibration,Nun uniformity of the velocity for the chain,2、 Instantaneous speed ratio 瞬時(shí)傳動(dòng)比,

10、 , Only at ： Z1 Z2 （ R1 R2 ） There is exactly a whole number of links in the driving side of the chain 只有當(dāng)Z1 Z2,緊邊長度恰為P的整數(shù)倍時(shí),i121 （1 2）,（，隨時(shí)相等）,3、Average velocity of the chain& average speed ratio 平均鏈速V和平均傳動(dòng)比 i,When the sprocket turn 3600, the length of the chain running over the sprocket is zp.,Num

11、ber of teeth of a sprocket,Chain pitch,BACK,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,BACK, 1 P(Z1) It is favorable to select small pitch and large number of teeth from the point of view of decreasing dynamic

12、load 動(dòng)載荷宜采用小節(jié)距P大齒數(shù)Z1,2、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 速度相嚙合沖擊動(dòng)載荷,In order to reduce impact為減小沖擊,Reduce 減小P，n Reduce 減小q （ Mass per m 線密度）,Imp

13、act energy of motion 沖擊動(dòng)能,BACK,83 Roller chain drive design 套筒滾子鏈設(shè)計(jì)計(jì)算,Principal parameters 參數(shù)選擇 Types of failure 失效形式 Limit power curve and allowable power curve 極限功率曲線和許用功率曲線 Design 設(shè)計(jì)計(jì)算,回總目錄,1、i8（ Usually 23.5 ） i1Number of meshing teeth 嚙合齒數(shù) Wear of the sprocket 輪齒磨損 Shift outward upon the sprock

14、et 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，Z2,Z1 9 Z1 f（i）, Z2i Z1 120 Z2 易跳鏈,Chain is easily fall out off sprocke

15、t,When 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. 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 c

16、arrying 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,High speed and heavy load ： Small pitch and multiple- width chain drive 高速重載:小節(jié)距P多排 Low speed and light load ： Large pitch and single-width chain drive 低速重載:大節(jié)距P單排,It is best practice to elect a chain with th

17、e 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) Lp a（3050）P （amax80P）,Lp（鏈條長度用鏈節(jié)數(shù)表示）LLpP,Lp Round The even number 偶數(shù)Lp Actual centre-to-centre distance實(shí)際中心距a,二、 Types of failure 失效形

18、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 off 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 鏈條過載拉斷 5、Wear of the sprockets 鏈輪磨損,三

19、、Limit power curve and allowable power curve 極限功率曲線和許用功率曲線,1 Limit of the wear failure 磨損破壞極限 2Limit of the fatigue failure of the chain plates 鏈板疲勞破壞極限 3 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 ,

20、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).,6Wear breakage limit under poor lubrication and severe operating condition 潤滑不良、工作環(huán)境惡劣的磨損極限,Experimental conditions 試驗(yàn)條件： Z119 Lp100 Single-width 單列 Steady load 載荷平穩(wěn),四、 Design 設(shè)計(jì)計(jì)算,1、The power which can be transmitted by a chain drive under actu

21、al 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 sprocket tooth number factor 小鏈輪齒數(shù)系數(shù)） Lp100KL（ Chain length factor 鏈長系數(shù)） 多排鏈 KP（ Multiple-width chain factor 多排鏈系數(shù)）,KZKLKPP0,Design cr

22、iteria 設(shè)計(jì)依據(jù)： KPKZKLKPP0,2、V0.6m/s（ Low speed drive 低速傳動(dòng)） Principal failure is overload breakage ： 主要失效形式過載拉斷,Static strength check 靜強(qiáng)度校核,Safety factor,1、Useful load 工作拉力 F11000P/V,2、Centrifugal tension 離心拉力 F2qV2,8-4 Forces in the chain drives 鏈傳動(dòng)受力分析,3、Weight tension 垂度拉力F3 Kfqga,For a horizontal drive 水平傳動(dòng) ：Kf6 For an angle of inclination of the drive to the horizontal up to 400 傾角40：Kf 2 For a vertical drive 垂直傳動(dòng) ： Kf 1,4、The total force of driving side 緊邊總拉力 F F1+ F2+ F3 The total force of driven side 松邊總拉力 F F2+ F3,The force acting on