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1、精品学习资源原文：1.clutchCHASSIS欢迎下载精品学习资源The engine produces the power to drive the vehicle . The drive line or drive train transfer the power of the engine to the wheels . The drive train consistsof the parts from the back of the flywheel to the wheels . These parts include the clutch , the transmission ,
2、the drive shaft ,and the final drive assembly .Theclutchwhichincludestheflywheel,clutchdisc, pressureplate,springs , pressure plate cover and the linkage necessary to operate the clutchisarotatingmechanismbetweentheengineandthetransmission.It operates through friction which comes from contact betwee
3、n the parts . Thatisthereasonwhytheclutchiscalledafrictionmechanism.After engagement,theclutchmustcontinuetotransmitallenginetorqueto transmission depending on the friction without slippage . Theclutch is also used to disengage theengine from the drive train whenever thegears in the transmission are
4、 being shifted from gear ratio to another .To start the engine or shift the gears , the driver has to depress the clutchpedal with the purpose of disengagement the transmission from the engine .At that time , the driven members connected to the transmission input shaftare eitherstationaryor rotating
5、at a speed that is slowerof faster than the drivingmembersconnectedtoenginecrankshaft.Thereisnospring pressure on the clutchassembly parts .So there is no frictionbetween the drivingmembers and drivenmembers .As the driverlets loose the clutch pedal , springpressure increase on the clutchparts .Fric
6、tionbetween the partsalsoincreases . The pressureexertedby the springson the driven members is controlledby the driverthrough the clutch pedal and linkage. The positive engagement of the driving and driven members is made possible the friction between the surfaces of the members . When full spring p
7、ressure is applied , the speed of the driving and driven members should bethe same .Atthe moment, the clutchmust act as a couplingdeviceand transmit all engine power to the transmission , without slipping .欢迎下载精品学习资源However , the transmission should be engaged to the engine gradually in order to ope
8、rate the car smoothly and minimize torsional shock on the drivetrain because an engine at idle just develop little power . Otherwise , the driving members are connected with the driven members too quickly and theengine would be stalled .The flywheel is a major part of the clutch . The flywheel mount
9、s to the engine crankshaft and transmits engine torque to the clutch assembly . The flywheel , when coupled with the clutch disc and pressure plate makes and breaks the flow of power the engine to the transmission .The flywheel provides a mounting location for the clutch assembly aswell .When the cl
10、utchis applied, the flywheeltransfersengine torque to the clutch disc . Because of its weight , the flywheel helps to smooth engine operation . The flywheel also has a large ring gear at its outer edge , which engages with a pinion gear on the starter motor during engine cranking .Theclutchdisc fits
11、betweenthe flywheeland the pressure plate . Theclutch disc has a splined hub that fits over splines on the transmission inputshaft . A splined hub has grooves that match splines on the shaft . These splines fit in the grooves . Thus , the two parts held together . However , back C and C forth moveme
12、nt of the disc on the shaft is possible . Attached to the input shaft , the disc turns at the speed of the shaft .The clutch pressure plate is generally made of cast iron . It is round andabout the same diameter as the clutch disc . One side of the pressure plate is machined smooth . This side will
13、press the clutch disc facing are against the flywheel .The outer side has shapes to facilitateattachmentof springand release mechanism . The two primary types of pressure plate assemblies arecoil spring assembly and diaphragm spring .Ina coilspringclutchthe pressure plateis backed by a numberofcoil
14、springsand housed withthemin a pressed C steed coverboltedto the flywheel .The springpush against the cover .Neitherthe drivenplate nor the pressure plate is connectedrigidlyto the flywheeland both can move eithertowards ito away .When the clutchpedal is depressed a thrust pad欢迎下载精品学习资源ridingon a ca
15、rbon or ballthrustbearingis forcedtowardsthe flywheel . Leverspivotedso that they engage withthe thrustpad at one end and the pressureplatetatthe otherend pullthepressure platebackagainstits springs.Thisreleasespressureonthedrivenplatedisconnectingthe gearbox from the engine .Diaphragm spring pressu
16、re plate assemblies are widely used in most moderncars . The diaphragm spring is a single thin sheet of metal which yields when pressure is applied to it . When pressure is removed the metal spring back to its original shape . The center portion of the diaphragm spring is slitinto numerous fingers t
17、hat act as release levers . When the clutch assembly rotates with the engine these weights are flung outwards by centrifugal plateand cause the levers to press against the pressure plate . During disengagement of the clutch the fingers are moved forward by the release bearing . The spring pivots ove
18、r the fulcrum ring and its outer rim moves away from the flywheel . The retracting spring pulls the pressure plate awayfrom the clutch plate thus disengaging the clutch .When engaged the release bearing and the fingers of the diaphragm spring move towards the transmission . As the diaphragm pivots o
19、ver the pivot ringits outer rim forces the pressure plate against the clutch disc so that theclutch plate is engaged to flywheel .The advantages of a diaphragm type pressure plate assembly are its compactness , lower weight , fewer moving parts , less effort to engage , reduces rotational imbalance
20、by providing a balanced force around the pressure plate and less chances of clutch slippage .The clutch pedal is connected to the disengagement mechanism either by acable or , more commonly , by a hydraulic system . Either way , pushing thepedal down operates the disengagementmechanism whichputs pre
21、ssure on the fingersof the clutchdiaphragmviaa release bearingand causes the diaphragmto release the clutchplate .Witha hydraulicmechanism, the clutch pedal arm operates a piston in the clutch master cylinder . This forces hydraulicfluidthrougha pipe to the cutchrelease cylinderwhere another欢迎下载精品学习
22、资源operates the clutch disengagement mechanism by a cable . The other parts including the clutch fork , release bearing , bellC housing ,欢迎下载精品学习资源bell housing cover , and pilot bushing are needed to couple and uncouple the transmission. The clutchfork, whichconnectsto the linkage, actually operates
23、the clutch . The release bearing fits between the clutch fork and the pressure plate assembly . The bell housing coversthe clutch assembly . The bell housing cover fastens to the bottom of the bell housing . This removablecover allows a mechanic to inspect the clutch without removing the transmissio
24、n and bell housing . A pilot bushing fits into the back of the crankshaft and holds the transmission input shaft .2 automatic transmissionThemodernautomatictransmissionisbyfar,themostcomplicated mechanicalcomponentin today.s automobile .It is a type of transmission that siftsitself .A fluidcouplingo
25、r torqueconverteris used insteadof a manually operated clutch to connect the transmission to the engine .There are two basic types of automatictransmissionbased on whetherthe vehicle is rear wheel drive or front wheel drive . On a rear wheel drive car ,the transmission is usually mounted to the back
26、 of the engine and is locatedunderthe humpinthe centerofthefloorboardalongsidethe gas pedal position . A drive shaft connects the transmission to the final drive which islocated in the rear axle and is used to send power to the rear wheels . Powerflow on this system is simple and straight forward go
27、ing from the engine , through the torque converter , then trough the transmission and drive shaft until it reaches the final drive where it is split and sent to the two rear transmission .On a frontwheel drivecar , the transmissionis usually combinedwiththefinaldrive to formwhat is called a transaxl
28、e .The engine on a frontwheel drivecar is usuallymountedsidewaysin the car withthe transaxletuc ked under it on the side of the engine facing the rear of the car . Front axles are connecteddirectlyto the transaxleand providepowerto frontwheels .In this example , power floes from the engine , through
29、 the torque converter to欢迎下载精品学习资源a largerchainthatsends thepowerthrougha180degreeturntothe transmission that is along side the engine . From there , the power is routed throughthe transmissionto the finaldrivewhere it is splitand sent to the two front wheels through the drive axles .Thereare a numb
30、er of otherarrangementsincludingfrontdrivevehicleswhere the engine is mounted front to back instead of sideways and there areother systems that drive all fourwheels but the two systems described here are by far the most popular . A much less popular rear and is connected by adriveshaft to the torque
31、 converterwhichis stillmountedon the engine . This system is found on the new Corvette and is used in order to balance the weightevenly between the frontand rear wheels for improvedperformance and handling .Anotherrear drivesystem mounts everything, the engine , transmissionand finaldriveinthe rear
32、.Thisrear enginearrangementis popular on the Porsche.Themodernautomatictransmissionconsistsofmanycomponentsand systems that designed to work together in a symphony of planetary gear sets ,the hydraulic system, seals and gaskets , the torque converter , the governorand the modulator or throttle cable
33、 and computer controls that has evolved over the years into what many mechanical inclined individuals consider to be an art from . Here try to used simple , generic explanation where possibleto describe these systems .3 The Differential SystemWhen a vehicle is cornered the inner wheel moves through
34、a shorter distance than the outer wheel . This means that the inner wheel must slow down and the outer wheel must speed up . During this period it is desirablethat each driving maintains its driving action . The differential performs these two tasks . The principle of the bevel type differential can
35、 be seen if the unit is considered as two discs and a lever .When the vehicle is traveling straight , the lever will divide the diving force equally and both discs will move the same amount .When the vehicle corners , the driving will still be divided equally but the欢迎下载精品学习资源innerdisc willnow move
36、througha smallerdistance；this willcause the lever to pivot about its center which will prize forward the outer disc to giveita greater movement .This actionshows that the torque appliedto each欢迎下载精品学习资源driving wheel is always equal torque equalizer .4 Brake SystemC hence the differential is sometime
37、s called a欢迎下载精品学习资源The breaking system is the most important system in cars . If the brakes fail , the result can be disastrous . Brakes are actually energy conversion devices , which convert the kinetic energy momentum of the vehicle intothermal heat . When stepping on the brakes , the driver comm
38、ands a stopping force ten times as powerful as the force that puts the car in motion .The braking system can exert thousands of pounds of pressure on each of the four brakes .Thebrake system iscomposedofthe followingbasiccomponents: the master cylinder. which is located under the hood , and is direc
39、tly connectedto the brake pedal , converts driver foots mechanical pressure into hydraulicpressure . Steel brake lines. and flexible brake hoses.connect the master cylinder to the slave cylinders. located at each wheel . Brake fluid , specially designed to work in extreme condition , fills the syste
40、m . Shoesand Pads are pushed by the salve cylinders to contact the drum and rotors thus causing drag , which hopefully slows the car .The typical brake system consists of disk brakes in front and either disk ordrum brakes in the rear connected by a system of tubes and hoses that link the brake at ea
41、ch wheel to the master cylinder .Stepping on the brake pedal , a plunger is actually been pushing against inthe master cylinder which forces hydraulic oil brake fluid through a series of tubes and hoses to the braking unit at each wheel . Since hydraulicfluid or any fluid for that matter cannot be c
42、ompressed , pushing fluidthrough a pipe is just like pushing a steel bar through pipe . Unlike a steel bar , however , fluid can be directed through many twists and turns on its way to its destination , arriving with the exact same motion and pressure that欢迎下载精品学习资源it started with . It is very impor
43、tant that the fluid is pure liquid and that there are no air bubbles in it . Air can compress , which causes a sponginess to the pedal and severely reduced braking efficiency . If air is suspected , then thesystem must be bled to remove the air .There are bleeder screws at each wheel and caliper for
44、 this purpose .On a disk brakes , the fluid from the master cylinder is forced into a caliper where it pressure against a piston . The piton , in-turn , squeezes two brakepads against the disk rotor whichis attached to the wheel , forcingit toslow down or stop . This process is similarto the wheel ,
45、causing the wheel to stop . In either case , the friction surface of the pads on a disk brake system , on the shoes on a drum brake convert the forward motion of the vehicle into heat . Heat is what causes the friction surfaces lining of thepads and shoes to eventually wear out and require replaceme
46、nt .Brake fluid is a special oil that has specifics properties . It is designed to withstand cold temperatures without thickening as well as very high temperatures without boiling . If the brake fluid should boil , it will causeyou to have a spongy pedal and the car will be hard to stop .The brake f
47、luid reservoir is on top of the master cylinder . Most cars today have a transparent reservoir so that you can see the level without opening the cover . The brake fluid lever will drop slightly as the brake pads wear .This is a normal condition and no cause for concern . If the lever dropsnoticeably over a short period of time or goes down to about two thirds full ,have your brakes checked as soon as possib