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1、Chain Drives(鏈傳動),Terminology 1. Chains 鏈 2. Sprocket(Driving, Driven) 鏈輪,Chain transmits load in tension to and from sprocket.,Power transmission chains can be categorized as Roller chain Silent chain Engineering steel chain Detachable chain.,傳動鏈,起重鏈,牽引鏈,齒形鏈,,,鏈,滾子鏈,pins that pivot inside the rolle

2、r bushings. pins are press fitted into the pin link plates roller bushings are press fitted into roller link plates free-turning roller encircles each bushing to provide rolling engagement and contact with sprocket teeth,The distance between flexing joints in roller chain is the pitch(鏈節(jié)距), which is

3、 the basic designation for different chain sizes.,Roller chain,2.Joints (聯(lián)接鏈節(jié)),Axial positioning methods：,(Spring Pins)開口銷， 多用于大節(jié)距鏈,(Spring U board)彈簧卡片， 多用于小節(jié)距鏈,設(shè)計時，鏈節(jié)數(shù)以取為偶數(shù)(Even)為宜，這樣可避免使用過渡鏈節(jié)(Offset link bar)，因為過渡鏈節(jié)會使鏈的承載能力下降。,過渡鏈節(jié),3.滾子鏈的規(guī)格,標(biāo)記示例：,08A-186 GB1243.183,Multi-Strands roller chain,Doub

4、le-pitch roller chain,Because a given length of double-pitch chain contains only half as many pitches, it is lighter and less expensive than standard roller chain.,Another choice for high power transmission,Choice for long shaft distance transmission,Center guide chain,Side guide chain,Silent chain

5、(無聲鏈),Where the transmission of high power is the primary requirement, engineering steel drive chains offer many useful solutions.,Engineering steel chain(工程鏈),Standard types: heavy duty offset sidebar engineering steel roller chain heavy duty straight-sidebar roller-type conveyor chain,主要用于重型傳送裝置,A

6、dvantages detachable links can be separated at any joint without using special tools Detachable chain is low in cost and can transmit up to 25 hp at speeds to 350 fpm.,Detachable chain（可拆鏈）,Detachable link chains are fabricated with one-piece elements and can be press-formed from flat rolled steel,,

7、結(jié)構(gòu)簡單、可不用特殊工具安裝、拆卸,Chordal action (弦切現(xiàn)象或多邊形效應(yīng)),Characters of chain drive,二、瞬時速度和瞬時傳動比,鏈條鉸鏈A點的前進分速度：,上下運動分速度：,因為從動鏈輪的角速度為：,所以鏈傳動瞬時傳動比為：,當(dāng)主動鏈輪勻速轉(zhuǎn)動時，從動鏈輪的角速度以及鏈傳動的瞬時傳動比都是周期性變化的，因此鏈傳動不宜用于對運動精度有較高要求的場合。,由上述分析可知，鏈傳動中，鏈條的前進速度和上下抖動速度是周期性變化的，鏈輪的節(jié)距越大，齒數(shù)越少，鏈速的變化就越大。,Speed variation character,d=p/sin(180/z),Keep

8、 p constant，z d ,Elongation of chain after wearing,Design limitation of sprockets due to chordal action,For driving sprockets,For the same pitch， when Z decrease，power loss due to flexing increase，joints elements wear faster； For the same pitch, when Z decrease，D decreases，larger force must be susta

9、ined by chain to transmit the same power（2T/D）,Jump teeth occurs,For driven sprockets,通常限制鏈傳動的傳動比i6，推薦的傳動比i23.5。,為磨損均勻，Z應(yīng)取與鏈節(jié)數(shù)互為質(zhì)數(shù)的奇數(shù)。,Advantages of chain drives over belt drives are:, No slippage between chain and sprocket teeth. Negligible stretch, allowing chains to carry heavy loads. Long operat

10、ing life expectancy because flexure and friction contact occur between hardened bearing surfaces separated by an oil film. Operates in hostile environments such as high temperatures, high moisture or oily areas, dusty, dirty, and corrosive atmospheres, etc., especially if high alloy metals and other

11、 special materials are used. Long shelf life because metal chain ordinarily doesnt deteriorate with age and is unaffected by sun, reasonable ranges of heat, moisture, and oil. Certain types can be replaced without disturbing other components mounted on the same shafts as sprockets.,Drawbacks of chai

12、n drives that might affect drive system design are:, Noise is usually higher than with belts or gears, but silent chain drives are relatively quiet. Chain drives can elongate due to wearing of link and sprocket teeth contact surfaces. Chain flexibility is limited to a single plane whereas some belt

13、drives are not. Usually limited to somewhat lower-speed applications compared to belts or gears. Sprockets usually should be replaced because of wear when worn chain is replaced. V-belt sheaves exhibit very low wear.,Coiler drive,Drive for a roller-supported drum with a diameter of approx. 2 m and a

14、 length of 9 m,Roller conveyor,Board slitter saw,synchronously driven,Applications,Shaft center distance,In general, the preferred range of center distance for roller chain drives that allow adjustable center distances is 30 to 50 chain pitches. Roller chain drives with fixed centers should be limit

15、ed to about 30 pitches.,Minimum center distance must allow clearance between the teeth of the two sprockets.,Arc of chain engagement should not be less than 120 deg,中心距的合理選擇,General consideration for arrangement of chain drive design,Very long center distances cause excessive tension and may cause t

16、he chain to jump teeth. Long chains may need to be supported by guides or idlers.,Idler Sprocket,鏈傳動的合理布置,（1）Vertical plane,（2）Slope angle should be less than 45,（3）Keep slack side in the bottom side,General consideration for arrangement of chain drive design,Allowable Power for roller chain 鏈傳動的承載能

17、力,鏈傳動的承載能力是以鏈的強度和壽命為依據(jù)的。,1. 極限功率曲線,2.A系列套筒滾子鏈的實用功率曲線圖,實驗條件：單列,水平布置,載荷平穩(wěn), Z1=19, i=3, t=100P, th=15000h, P/P 3%,設(shè)計時可根據(jù)小鏈輪的轉(zhuǎn)速n1從圖中查出這種型號的鏈條允許傳遞的額定功率P0，額定功率曲線適合于鏈速v0.6m/s的場合。,當(dāng)鏈傳動實際工作條件與標(biāo)準(zhǔn)實驗條件不符時，應(yīng)考慮工作情況系數(shù)KA、鏈長、小鏈輪齒數(shù)、多排鏈等因素的影響。,額定功率曲線是在推薦的潤滑方式下得到的，當(dāng)不能滿足推薦的潤滑方式時，應(yīng)降低額定功率P0。,Pitch selection,人工定期潤滑滴油潤滑 油浴或

18、飛濺潤滑壓力噴油潤滑,推薦的潤滑方式,Recommended Lubrication method,三、鏈傳動主要參數(shù)的選擇,1鏈的節(jié)距和排數(shù),鏈條所能傳遞的功率P0可由下式確定,Pc=KAP(1031),(1030),式中 P0在特定條件下，單排鏈所能傳遞的功率(kW)（見圖1027）； Pc鏈傳動的計算功率(kW)； KA工況系數(shù)（表1012）； KZ小鏈輪齒數(shù)系數(shù)（表1013，當(dāng)工作在如圖1027所示的曲線頂點左側(cè)時（鏈板疲勞），查表中的KZ，當(dāng)工作在右側(cè)時（滾子套筒沖擊疲勞），查表中的KZ； KP多排鏈系數(shù)（表1014）； KL鏈長系數(shù)（圖1029），鏈板疲勞查曲線1，滾子套筒沖擊疲勞

19、查曲線2。,根據(jù)式（1030求出傳遞的功率，由圖1027查出合適的鏈號和鏈節(jié)距。,例10-2 設(shè)計如圖10-31所示的帶式運輸機傳動方案中的滾子鏈傳動。已知小鏈輪轉(zhuǎn)速n1=123r/min，傳動比i=3，傳遞功率P6.85kW，兩班制工作，中心距可調(diào)節(jié)，載荷平穩(wěn)。,解： 1選定鏈輪齒數(shù)z1、z2,初步假設(shè)鏈速v=0.63m/s，由表1015查得小鏈輪齒數(shù)z117，取z1=19，z2=iz1=319=57 (<120合適)。,2根據(jù)實用功率曲線，選鏈條型號,（1）初定中心距a0=40p，鏈節(jié)數(shù)LP為,取LP118節(jié)。由于中心距可調(diào)，可不算實際中心距。,估計，鏈條鏈板可能產(chǎn)生疲勞破壞。由表1013

20、查得KZ1.0，由表1014查得KP=1.0（初取單排鏈），由圖1029查得KL1.05，由表1012查得KA1.0。,該鏈條在實驗條件下所需傳遞的功率,由圖1027，按P06.52kW，n1=123r/min，選取鏈條型號為20A，p=31.75mm，且P0與n1交點在曲線頂點左側(cè)，確系鏈板疲勞破壞，估計正確。,3校核鏈速,與原假設(shè)v=0.63m/s范圍符合。,4計算鏈長和中心距,6.鏈條型號：20A1122 GB1243.183,5鏈輪結(jié)構(gòu)設(shè)計從略,中心距調(diào)整量,7計算作用在軸上的壓軸力,鏈傳動在安裝時，應(yīng)使鏈條受到一定的張緊力，張緊的目的主要是使松邊不致過松，以免影響鏈條正常退出嚙合和產(chǎn)生振動、跳齒或脫鏈現(xiàn)象。,1.工作拉力F,2.離心拉力Fc,3.垂度拉力Ff,式中 g重力加速度(m/s2)； a中心距（m）； f懸索垂度(m)； Kf垂度系數(shù),三、鏈傳動的受力分析和作用在軸上的載荷,作用在軸上的載荷FQ可近似地取為主動邊和從動邊總拉力之和，因離心拉力不作用在軸上，不應(yīng)計算在內(nèi)，由此得FQ=F+2Ff。又由于垂度拉力不大，故可近似取,