景德镇陶瓷学院机械原理.ppt

Mechanisms and Machine Theory 机械原理,Chapter 1 Introduction,1.1 Study Object (对象) Mechanisms and Machine Theory,Machine(机器) Mechanism(机构),Study structure of internal combustion engine(内燃机) first.,1. Cylinder 缸体 or Frame 机架,2. Piston 活塞 3. Coupler 连杆 4. Crank 曲柄 4. Pinion 小齿轮 4”. Flywheel飞轮 5. Gear 大齿轮 5. Inlet cam进气凸轮 5”.Outlet cam排气凸轮 6. Inlet valve进气阀 7. Outlet valve排气阀,Slider-crank mechanism 曲柄滑块机构,能实现预期的机械运动的系统，并可用来完成有用的机械功或转换机械能。,Gear mechanism 齿轮机构,Cam mechanism 凸轮机构,This is a structural block diagram (结构框图) of internal combustion engine（内燃机）,Machine element(零件) is a basic element（元素） of manufacture（制造）, e.g. coupler body, big-end cover, nuts（螺母）, bolts（螺栓） etc. .,Link(构件) is a basic element in kinematic analysis(运动分析). It may be a rigid(刚性的) structure of some machine elements.,For example, coupler is the rigid assembly(装配体) of the coupler body, big-end cover, nuts, and bolts.,The crank 4, the pinion 4, the flywheel 4, and the keys(键), form another link.,The gear 5, the cam shaft(轴) (including the two cams 5 and 5”) , and the key form a third link.,In the study of kinematics(运动学), we are concerned only with the motion of links(构件), not of individual(单个) machine elements(零件).,Mechanism(机构) is a system of links(构件) which can transform(转换) or transmit(传递) force and motion.,Slider-crank Gear Cam mechanism mechanism mechanism 曲柄滑块机构 齿轮机构 凸轮机构,The function of the gear mechanism is to change the direction and speed of rotation.,The function of the slider-crank mechanism is to transform the reciprocation(往复移动) of the piston 2 into the rotation of the crank 4.,Mechanism(机构) is a basic system of links(构件) which can transform(转换) or transmit(传递) force and motion.,The function of the cam mechanism is to transform the continuous rotation of the cam into a regular reciprocation of the follower.,Many practical machines contain more than one mechanism while many simple machines are composed(组成) of only one basic mechanism. The term machinery (机械) is used to cover both mechanisms and machines.,Machine(机器) is a mechanical system which can transmit or transform energy, materials or information.,The study object of this book is machinery.,一般认为机器的研究重点是机械功和机械能的问题；而机构的研究重点是在其结构、运动和力作用等基本方面。,（1）人为的实物的组合体。 （2）各构件之间都具有确定的相对运动。 （3）能够完成有用的机械功或转换机械能。 凡同时具备以上3个特征的实物组合体就称为机器。机构具有机器的前两个特征。 从结构和运动的观点来看，两者之间并无区别。因此，常用“机械”一词作为它们的总称。,Other machines: the shaping machine .,Composition(组成) of machine 从功能和系统的角度来看，机器一般主要由五部分组成。,1.2 Study Content ： Most machines, even very complicated(复杂的) ones, are built up from only a few types of commonly used mechanisms, such as slider-crank mechanisms, gear mechanisms, cam mechanisms etc. This situation(情形) is similar to the combinations(组合) of the seven-piece puzzle(七巧板).,The most content of this book is for “analysis(分析)” and “synthesis(综合)” of some commonly used mechanisms.,Difference between “synthesis(综合)” and “design” : Dimensions(尺寸) affecting(影响) the motion of the mechanism are called kinematics dimensions(运动学尺寸).,Distance LAB between the centres of the two holes in the coupler is the only kinematics dimension.,Difference between “synthesis(综合)” and “design” : Dimensions(尺寸) affecting(影响) the motion of the mechanism are called kinematics dimensions(运动学尺寸).,The radius of the hole is not a kinematics dimension!,“Synthesis (综合)” is the process of determining only the kinematics dimensions of a mechanism required to produce a particular (特定的) motion.,“Design” is the process of prescribing the sizes, shapes, material compositions(成分), arrangements of parts, calculations of strength(强度), methods of production etc.,1.3 Purpose It is hoped that, after studying this textbook, the student will grasp(掌握) the basic theory and obtain the basic knowledge and skills(技能) needed in mechanisms synthe