ChainDriveNew 機械設計 英文教案_重大

1、Chain Drives(鏈傳動)Terminology1. Chains 鏈2. Sprocket(Driving, Driven) 鏈輪Chain transmits load in tension to and from sprocket.Power transmission chains can be categorized asRoller chainSilent chain Engineering steel chainDetachable chain.傳動鏈 起重鏈 牽引鏈 齒形鏈 鏈滾子鏈 pins that pivot inside the roller bushings.p

2、ins are press fitted into the pin link platesroller bushings are press fitted into roller link platesfree-turning roller encircles each bushing to provide rolling engagement and contact with sprocket teethThe distance between flexing joints in roller chain is the pitch(鏈節(jié)距), which is the basic desig

3、nation for different chain sizes.Roller chain2.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 標記示例： 08A-186 GB1243.183 Multi-Strands roller chainDouble-pitch roller chainBecaus

4、e 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 transmissionChoice for long shaft distance transmissionCenter guide chainSide guide chainSilent chain (無聲鏈)Where the transmission of hi

5、gh 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 chainheavy duty straight-sidebar roller-type conveyor chain主要用于重型傳送裝置Advantagesdetachable links can be separat

6、ed at any joint without using special toolsDetachable 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,結構簡單、可不用特殊工具安裝、拆卸Chordal action (弦切現(xiàn)象或多邊形效應)C

7、haracters 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：當主動鏈輪勻速轉動時，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 characterd=p/sin(180/z) Keep p constant，z d Elongation of chain after wearingDesign

8、limitation of sprockets due to chordal actionFor driving sprocketsFor 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 sustained by chain to transmit the same power（2T/D）Jump teeth occ

9、ursFor driven sprockets通常限制鏈傳動的傳動比i6，推薦的傳動比i。 為磨損均勻，Z應取與鏈節(jié)數(shù)互為質數(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 operating life expectancy because flexure and friction contact occur betwe

10、en 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 special materials are used. Long shelf life because metal chain ordi

11、narily 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 chain drives that might affect drive system design are: Noise is usually h

12、igher 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 drives are not. Usually limited to somewhat lower-speed applications co

13、mpared 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 driveDrive for a roller-supported drum with a diameter of approx. 2 m and a length of 9 mRoller conveyorBoard slitter sawsynchronously drivenApplica

14、tionsShaft center distanceIn 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 limited to about 30 pitches.Minimum center distance must allow clearance between the

15、 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 designVery long center distances cause excessive tension and may cause the chain to jump teeth.Long chains may need to be supported by guides or idlers.Idle

16、r 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 sideGeneral consideration for arrangement of chain drive designAllowable Power for roller chain鏈傳動的承載能力 鏈傳動的承載能力是以鏈的強度和壽命為依據的。 1. 極限功率曲線 0由鏈板疲勞強度限定由滾子、套筒沖擊疲勞強度限定由銷軸和套筒膠合限定額定功率P0/kW小鏈輪轉速n1 /(r/min

17、)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%設計時可根據小鏈輪的轉速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的場合。當鏈傳動實際工作條件與標準實驗條件不符時，應考慮工作情況系數(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，當不能滿足推薦的潤滑方式時，應降低額定功率P0。Pitch selection人工定期潤滑滴油潤滑油浴或飛濺潤滑壓力噴油潤滑 推薦的潤滑方式Recommended Lubrication method三、鏈

18、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，當工作在如圖1027所示的曲線頂點左側時（鏈板疲勞），查表中的KZ，當工作在右側時（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，滾子套筒沖擊疲勞查曲線2。 根據式（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。已知小鏈輪轉速n1=123r/min，傳動比i=3，傳遞功率P，兩班制工作，中心距可調節(jié)，載荷平穩(wěn)。 解