吉林大学机械原理双语课件5.cams and design.ppt

The motion manners of the follower： Polynomials can be used to approximate any function. solution：choose ml, Plot the displacement diagram. s O O K B0 (C0) -w1 120° 30° 120° 90° C5 C4 C3 C2 C1 C9 C8 C7 C6 1 2 3 6 7 8 5 4 9 1 2 3 4 5 6 7 8 (B9) B8 B7 B6 B5 B4 B3 B2 B1 Pitch curve Cam profile 2.Graphical synthesis of plate cam with translating flat-faced follower(平底从动件盘形凸轮廓线设计) Follower motion law, radius of the prime circle r0 are given as below. Cam rotate clockwise in ω1.Construct the cam profile. 180° 360° 0° s r0 w1 d Solution: choose ml and plot the displacement diagram. 180° 360° 0° s -w1 r0 w1 3.Plate cam with oscillating knife-edge/roller follower(摆动尖顶从动件盘形凸轮廓线设计) Follower motion law, radius of the prime circle r0 are given as below. The follower pivot O1O2 is a and the length of follower O2B0 is L .Cam rotate clockwise in w1.Construct the cam profile. 0° 180° 360° a L O1 O2 B0 y ymax d 30° r0 w1 30° d ymax Solution: choose scale my=1°/mm, Plot the angular displacement diagram. -w1 7 0 1 2 3 4 5 6 8 9 10 O2(1) O2(2) O2(3) O2(4) O2(5) O2(6) O2(7) O2(8) O2(9) B0 O1 O2 w1 B1 B2 B3 B4 B5 B6 B7 B8 B9 A F F” F’ v2 F’— useful component force F’’—harmful component force F’=Fcosa F’’=Fsina OR F=F’tana (1)F’ is a constant, a?, F” ?, mechanisms for efficiency↓; (2)a ? ?, mechanisms will be self-locking. (3)amax≤[a]. 5.4 Determination of elementary dimensions of cam mechanism 5.4.1 Pressure angle and forces of cam mechanism (凸轮机构基本尺寸的确定) Translating follower [a]=30° Oscillating follower [a]=35°~45° Force closure [a]=70°~80° Form closure [a] is the same as rise e O1 A w1 r0 5.4.2 Determination of radius of cam prime circle P --- instant center of velocity a --- pressure angle （kinfe-edge or roller follower） s0 s n n t t P a * (第5章 凸轮机构及其设计） Chapter 5 Cam mechanisms and design 1 2 3 5.1 Application and types of cam mechanisms (凸轮机构的类型和应用) w 1 2 3 5.1.1 Composition and applications (1)A cam(driving link) 具有曲线轮廓或凹槽的构件,是主动件, 通常等速转