机械原理版lecture1机构与机器理论

Mechanisms

and

Machine

Theory机构与机器理论(机械原理)Ye

ZhongheM.R.

SmithLan

Zhaohui叶仲和:83717031,Chapter

1Introduction1.1

Study

Object(对象):Machinery(机械)(1)Machine

andMechanism(机构):Studystructureofinternal

combustionengine(内燃机)first.1.

Cylinder缸体orFrame

机架Piston

活塞Coupler连杆Crank曲柄4’.Pinion

小齿轮4”.

Flywheel飞轮Gear

大齿轮5’.Inlet

cam进气凸轮

5”.Outlet

cam排气凸轮Inlet

valve进气阀Outlet

valve排气阀Slider-crank

mechanism曲柄滑块机构Piston

2Coupler

3Frame

1Crank

4Gear

mechanism齿轮机构Piston

2Coupler

3Frame

1Crank

4Frame

1Pinion4'Gear5Cam

mechanism凸轮机构Piston

2Coupler

3Frame

1Crank

4Frame

1Pinion4'Gear5Frame

1Follower6Follower7Frame

1Cam5'Cam

5"This

is

a

structuralblock

diagram

(结构框图)of

internal

combustionengine（内燃机）.Piston

2Coupler

3Frame

1Crank

4Frame

1Pinion4'Gear5Frame

1Follower6Follower7Frame

1Cam5'Cam

5"Machine

element(零件)is

abasic

of

manufacture(制造),e.g.coupler

body(连杆体),big-endcover,nuts(螺母),bolts(螺栓)etc.

.Link(构件)is

a

basicelement

in

kinematicanalysis(运动分析).Itmay

be

a

rigid(刚性的)structureofsomemachineelements.For

example,coupler

istherigidassembly(装配体)ofthecouplerbody,big-end

cover,nuts,andbolts.The

crank4,thepinion

4¢,theflywheel

4†,andthekeys(键),formanotherlink.The

gear

5,

thecam

shaft(轴)(including

the

twocams

5’

and

5”),andthe

key

form

a

thirdlink.Inthestudyofkinematics(运动学),we

areconcerned

only

with

the

motion

of

links(构件),not

of

individual(单个)machine

elements(零件).Manymachine

elements

onelinkMechanism(机构)is

asystemoflinks(构件)which

can

transform(转换)or

transmit(传递)force

andmotion.Piston

2Frame

1Coupler

3Frame

1Frame

1Follower6Follower7Frame

1Crank

4Pinion4'Gear5Cam5'Cam

5"Slider-crankmechanism曲柄滑块机构Gearmechanism齿轮机构Cammechanism凸轮机构Piston

2Coupler

3Frame

1Frame

1Follower6Frame

1Crank

4Pinion4'Gear5Cam5'Cam

5"

Follower7Frame

1The

function

of

the

slider-crank

mechanism

is

totransform

the

reciprocation(往复移动)of

thepiston2intotherotationofthecrank4.Piston

2Coupler

3Frame

1Frame

1Follower6Frame

1Crank

4Pinion4'Gear5Cam5'Cam

5"

Follower7Frame

1The

functionofthe

gearmechanism

istochange

the

direction

and

speed

of

rotation.Piston

2Coupler

3Frame

1Frame

1Follower6Frame

1Crank

4Pinion4'Gear5Cam5'Cam

5"

Follower7Frame

1The

functionofthe

cam

mechanism

istotransformthecontinuous

rotationofthecaminto

a

regularreciprocationofthe

follower.Piston

2Coupler

3Frame

1Frame

1Follower6Frame

1Crank

4Pinion4'Gear5Cam5'Cam

5"

Follower7Frame

1Machine(机器)

is a

mechanical

systemwhich

can

transmitor

transform

energy,materials

or

information.Many

practical

machines

contain

more

thanone

mechanism

while

manysimple

machines

are

composed(组成)of

only

one

basicmechanism.The

term

†machinery†(机械)is

usedto

cover

both

mechanisms

and

machines.The

studyobjectofthisbookis

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。人为的实物的组合体。各构件之间都具有确定的相对运动。 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。操纵系统和控制系统传动系统动力系统执行系统框架支撑系统1.2

Study

Content

：Mostmachines,evenverycomplicated(复杂的)

ones,

are

built

up

fromonly

a

few

typesofcommonly

used

mechanisms,

such

as

slider-

crank

mechanisms,

gear

mechanisms,

cam

mechanisms

etc. This

situation(情形)

is

similarto

thecombinations(组合)

of

the

seven-piecepuzzle(七巧板).Themostcontentofthisbookisfor“analysis(分析)”and“synthesis(综合)”of

somecommonlyusedmechanisms.AB(b)Distance

betweenthe

centres

of

thetwo

holes

in

thecoupler

isthe

onlykinematicsdimension.Differencebetween“synthesis(综合)”and“design”:Dimensions(尺寸)affecting(影响)themotion

of

the

mechanism

are

called

kinematicsdimensions(运动学尺寸).The

radius

of

thehole

is

not

akinematicsdimension!!!!!Differencebetween“synthesis(综合)”and“design”:Dimensions(尺寸)affecting(影响)themotion

of

the

mechanism

are

called

kinematicsdimensions(运动学尺寸).AB(b)“Synthesis

(综合)”is

the

process

ofdetermining

only

the

kinematicsdimensionsof

a

mechanism

required

to

produce

aparticular

(特定的)motion.“Design”is

the

process

of

prescribing

thesizes,shapes,material

compositions(成分),arrangements

of

parts,

calculations

ofstrength(强度),methods

of

production

etc.虽然综合仅仅是设计的一小步，但却是很重要的一步。综合又可细分为结构综合(或类型综合)、尺寸综合等步骤，其中类型综合是极具创造性的工作。1.3

PurposeItishopedthat,afterstudyingthistextbook,the

student

willgrasp(掌握)the

basic

theory

andobtaintheba