Chapter机械.ppt

含义：主动件连续运动时，从动件周期性的出现停歇状态的机构。 应用于：生产线的转位机构，步进机构计数装置、轻工机械 类型 Ratchet mechanism 棘轮机构 geneva wheel槽轮机构 intermittent gearing/ incomplete gearing不完全齿轮机构 凸轮间歇机构 2 type of ratchet mechanism Outside-ratchet mechanism Inside-ratchet mechanism 1 Double-driver ratchet mechanism双动式棘轮机构 Hook shape pawl 钩头棘爪C91T6-2B Straight-shape pawl 直形棘爪C91T6-2A 2 Rotate pawl/ rotating ratchet mechanism 可变向棘轮机构 The wheel can obtain the intermittent motion of counter clockwise direction and clockwise rotation 棘轮可实现逆时针和顺时针的间歇运动 3 Friction ratchet mechanism摩擦式棘轮机构 4 Overrun ratchet mechanism 超越式棘轮机构 2 working condition棘爪工作条件 图6-6 略 选定齿数z和按照强度要求确定模数m。 公式计算： 顶圆直径 D=mz 齿 高 h=0.75m 齿 顶 厚 a=m 齿槽夹角 θ=60°或55° 棘爪长度 L=2πm 齿顶 D 、齿根D-2h 按z等分齿顶圆A’、C…… 弦A’B=a=m △ CO’B为等角 △, ∠O’BC =∠O’CB = 90 – θ O’ 以O’、O’B交齿根圆E,连CE、BE 一.槽轮机构的工作原理 Coefficient of motion of Geneva wheel mechanism运动特性系数 When the driving plate rotates one circle, the ratio of the time tm of wheel and the time t of plate is known as the coefficient of motion of Gevena mechanism, using τ to represent it. τ=tm/t 在一个运动循环内，槽轮的运动时间对拨盘的运动时间的比值称为运动特性系数。 attention 1 For the τ should be greater than zero, the number Z of radial slots of outer wheel is greater or equal to 3. τ 0，z=3 2 the τis always less than 0.5. The running time of the wheel will be always less than the stillness time. τ 0.5, 运动时间tm〈静止时间ts 3 z=3, 有较大的振动和冲击，很少应用 K pins on plate If there are k pins on plate 如果拨盘上装有k个均匀分布的圆销, τ=k(z-2)/2z For the value of τshould be less than or equal to 1,(τ=1,否则不能实现间歇运动 ) K=2z/(z-2) Number of slots z 3, 4-5, =6 Number of pins n 1-5, 1-3, 1-2 Generally, z=4-8 常取z为4-8 6.3 intermittent gearing/ incomplete gearing不完全齿轮机构 There is one tooth or not all teeth made on the driving wheel. 主动轮为只有一个或几个齿的不完全齿轮。 Locking arc锁住弧 In the period of cease of driven wheel, both wheels provide locking arc to prevent the driven wheel from