chaindrives解答.ppt

第五章 Chain drives 链传动;Characteristics and applications 特点和应用 Types of chain drives 链传动分类;1 、 Advantages 优点 ★ In comparison to belt drive 与带传动相比： ① Absence of slippage 无滑动 ② Smaller overall size 尺寸小 ;③Small tension force →Small forces acting on the shaft 张紧力F0小→压轴力小 ④High efficiency 工作效率高，η≈98％ ⑤Can be used under higher temperature and humidity 能在较高温度和湿度下工作 ;★ In comparison to toothed drive Can be used for larger centre-to-centre distances 与齿轮传动相比： 中心距a可以很大（8m）;2、 Drawbacks 缺点 ① Used only for parallel shafts 只用于平行轴 ② The velocity of the chain is not constant → Leading to larger impact, vibration and noise i瞬变化→高速时冲击、振动、噪音大. ;3、 Applications 应用;链传动在物料运输机械中的应用;曳引链???传输机械中的应用;起重链的应用;链传动在摩托车中的应用;链传动在工业加工机械中的应用;;二、 Types of chain drives 链传动分类;② Lifting chain 起重链： Suspending loads 提升重物 ③ Hauling chain 曳引链： Carrying loads 移动重物 ;三、 Roller chains 套筒滚子链;Bushings 套筒、 Rollers 滚子：;;; With an even number of links 链节数Lp是偶数： ;With an uneven number of links: Offset link 链节数Lp是奇数： 过渡链节;BACK;§5－2 Motion features of chain drives 链传动的运动特性;The velocity of the chain and speed ratio is not constant upon uniform rotational speed of the small sprocket. 小链轮转速ω1是常数 时，瞬时链速V和瞬时传动比i都是周期性变化的。;1、The chain velocity 瞬时链速V （为便于分析，设紧边处于水平位置） ① The velocity of the joint of the link 销轴中心VA＝ ω1 R1 ② The velocity of chain 链速 V＝ VAcosβ＝ ω1 R1 cosβ （The velocity of vertical motion of the chain 链条上下垂直运动速度 V′＝ ω 1R1sinβ） ;;;③ ;;;;;;⑤;2、 Instantaneous speed ratio 瞬时传动比;③ Only at ： Z1＝ Z2 （ R1＝ R2 ） There is exactly a whole number of links in the driving side of the chain 只有当Z1＝ Z2,紧边长度恰为P的整数倍时;3、Average velocity of the chain average speed ratio 平均链速V和平均传动比 i;二、 Dynamic load 动载荷;①;③ ω1↑ P↑(Z1↓) → It is favorable to select small pitch and large number of teeth from the point of view of decreasing dynamic load 动载荷↑宜采用小节距P大齿数Z1 ;;3、Mesh impact→ Dyn