ChainDriveNew 机械设计 英文教案_重大

1、Chain Drives(链传动)Terminology1. Chains 链2. Sprocket(Driving, Driven) 链轮Chain transmits load in tension to and from sprocket.Power transmission chains can be categorized asRoller chainSilent chain Engineering steel chainDetachable chain.传动链 起重链 牵引链 齿形链 链滚子链 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(链节距), which is the basic desig

3、nation for different chain sizes.Roller chain2.Joints (联接链节)Axial positioning methods：(Spring Pins)开口销，多用于大节距链(Spring U board)弹簧卡片，多用于小节距链设计时，链节数以取为偶数(Even)为宜，这样可避免使用过渡链节(Offset link bar)，因为过渡链节会使链的承载能力下降。过渡链节3.滚子链的规格 标记示例： 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 (无声链)Where the transmission of hi

5、gh power is the primary requirement, engineering steel drive chains offer many useful solutions.Engineering steel chain(工程链)Standard types:heavy duty offset sidebar engineering steel roller chainheavy duty straight-sidebar roller-type conveyor chain主要用于重型传送装置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（可拆链）Detachable link chains are fabricated with one-piece elements and can be press-formed from flat rolled steel,结构简单、可不用特殊工具安装、拆卸Chordal action (弦切现象或多边形效应)C

7、haracters of chain drive二、瞬时速度和瞬时传动比链条铰链A点的前进分速度：上下运动分速度：因为从动链轮的角速度为：所以链传动瞬时传动比为：当主动链轮匀速转动时，从动链轮的角速度以及链传动的瞬时传动比都是周期性变化的，因此链传动不宜用于对运动精度有较高要求的场合。由上述分析可知，链传动中，链条的前进速度和上下抖动速度是周期性变化的，链轮的节距越大，齿数越少，链速的变化就越大。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通常限制链传动的传动比i6，推荐的传动比i。 为磨损均匀，Z应取与链节数互为质数的奇数。 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中心距的合理选择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链传动的合理布置（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链传动的承载能力 链传动的承载能力是以链的强度和寿命为依据的。 1. 极限功率曲线 0由链板疲劳强度限定由滚子、套筒冲击疲劳强度限定由销轴和套筒胶合限定额定功率P0/kW小链轮转速n1 /(r/min

17、)系列套筒滚子链的实用功率曲线图实验条件：单列,水平布置,载荷平稳, Z1=19, i=3, t=100P, th=15000h, P/P 3%设计时可根据小链轮的转速n1从图中查出这种型号的链条允许传递的额定功率P0，额定功率曲线适合于链速的场合。当链传动实际工作条件与标准实验条件不符时，应考虑工作情况系数KA、链长、小链轮齿数、多排链等因素的影响。额定功率曲线是在推荐的润滑方式下得到的，当不能满足推荐的润滑方式时，应降低额定功率P0。Pitch selection人工定期润滑滴油润滑油浴或飞溅润滑压力喷油润滑 推荐的润滑方式Recommended Lubrication method三、链

18、传动主要参数的选择 1链的节距和排数 链条所能传递的功率P0可由下式确定 Pc=KAP(1031) (1030) 式中 P0在特定条件下，单排链所能传递的功率(kW)（见图1027）；Pc链传动的计算功率(kW)；KA工况系数（表1012）；KZ小链轮齿数系数（表1013，当工作在如图1027所示的曲线顶点左侧时（链板疲劳），查表中的KZ，当工作在右侧时（滚子套筒冲击疲劳），查表中的KZ；KP多排链系数（表1014）；KL链长系数（图1029），链板疲劳查曲线1，滚子套筒冲击疲劳查曲线2。 根据式（1030求出传递的功率，由图1027查出合适的链号和链节距。 例10-2 设计如图10-31所示的带式运输机传动方案中的滚子链传动。已知小链轮转速n1=123r/min，传动比i=3，传递功率P，两班制工作，中心距可调节，载荷平稳。 解