汽车车辆底盘外文文献翻译、中英文翻译、外文翻译

Chassis

Chassis include the clutch , the transmission, the drive shaft, the final drive assembly,

the front suspension, the rear suspension, the steering system ,the brake system, the wheels

and tires.

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 consists of the parts from the back of

the flywheel to the wheels . These parts include the clutch , the transmission ,the drive

shaft ,and the final drive assembly .

The clutch which includes the flywheel ,clutch disc , pressure plate , springs , pressure

plate cover and the linkage necessary to operate the clutch is a rotating mechanism between

the engine and the transmission . It operates through friction which comes from contact

between the parts . That is the reason why the clutch is called a friction mechanism . After

engagement, the clutch must continue to transmit all engine torque to transmission depending

on the friction without slippage . The clutch is also used to disengage the engine from the

drive train whenever the gears in the transmission are being shifted from gear ratio to

another .

To start the engine or shift the gears , the driver has to depress the clutch pedal with

the purpose of disengagement the transmission from the engine . At that time , the driven

members connected to the transmission input shaft are either stationary or rotating at a speed

that is slower of faster than the driving members connected to engine crankshaft . There is no

spring pressure on the clutch assembly parts . So there is no friction between the driving

members and driven members . As the driver lets loose the clutch pedal , spring pressure

increase on the clutch parts . Friction between the parts also increases . The pressure exerted

by the springs on the driven members is controlled by the driver through 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 pressure is applied , the speed

of the driving and driven members should be the same . At the moment , the clutch must act

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as a coupling device and transmit all engine power to the transmission , without slipping .

However , the transmission should be engaged to the engine gradually in order to

operate the car smoothly and minimize torsional shock on the drive train because an engine at

idle just develop little power . Otherwise , the driving members are connected with the driven

members too quickly and the engine would be stalled .

The flywheel is a major part of the clutch . The flywheel mounts to the engine‟s

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 as well . When the

clutch is applied , the flywheel transfers engine 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 .

The clutch disc fits between the flywheel and the pressure plate . The clutch disc has a

splined hub that fits over splines on the transmission input shaft . 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 – and – forth movement 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 and about the same

diameter as the clutch disc . One side of the pressure plate is machined smooth . This side will

press the clutch disc facing are against the flywheel . The outer side has shapes to facilitate

attachment of spring and release mechanism . The two primary types of pressure plate

assemblies are coil spring assembly and diaphragm spring .

In a coil spring clutch the pressure plate is backed by a number of coil springs and housed

with them in a pressed – steed cover bolted to the flywheel . The spring push against the

cover . Neither the driven plate nor the pressure plate is connected rigidly to the flywheel and

both can move either towards it o away . When the clutch pedal is depressed a thrust pad

riding on a carbon or ball thrust bearing is forced towards the flywheel . Levers pivoted so

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that they engage with the thrust pad at one end and the pressure plate tat the other end pull the

pressure plate back against its springs . This releases pressure on the driven plate

disconnecting the gearbox from the engine .

Diaphragm spring pressure plate assemblies are widely used in most modern cars . 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 slit into numerous fingers that act as release levers . When the clutch

assembly rotates with the engine these weights are flung outwards by centrifugal plate and

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 over the fulcrum ring

and its outer rim moves away from the flywheel . The retracting spring pulls the pressure plate

away from 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 over the pivot ring its outer rim forces the pressure

plate against the clutch disc so that the clutch 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 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 a cable or , more

commonly , by a hydraulic system . Either way , pushing the pedal down operates the

disengagement mechanism which puts pressure on the fingers of the clutch diaphragm via a

release bearing and causes the diaphragm to release the clutch plate . With a hydraulic

mechanism , the clutch pedal arm operates a piston in the clutch master cylinder . This forces

hydraulic fluid through a pipe to the cutch release cylinder where another operates the clutch

disengagement mechanism by a cable .

The other parts including the clutch fork , release bearing , bell – housing , bell housing

cover , and pilot bushing are needed to couple and uncouple the transmission . The clutch

fork , which connects to the linkage , actually operates the clutch . The release bearing fits

between the clutch fork and the pressure plate assembly . The bell housing covers the clutch

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assembly . The bell housing cover fastens to the bottom of the bell housing . This removable

cover allows a mechanic to inspect the clutch without removing the transmission and bell

housing . A pilot bushing fits into the back of the crankshaft and holds the transmission input

shaft .

TIC TRANSMISSION

The modern automatic transmission is by far , the most complicated mechanical component

in today‟s automobile . It is a type of transmission that sifts itself . A fluid coupling or torque

converter is used instead of a manually operated clutch to connect the transmission to the

engine .

There are two basic types of automatic transmission based on whether the vehicle is

rear wheel drive or front wheel drive . On a rear wheel drive car , the transmission is usually

mounted to the back of the engine and is located under the hump in the center of the

floorboard alongside the gas pedal position . A drive shaft connects the transmission to the

final drive which is located in the rear axle and is used to send power to the rear wheels .

Power flow on this system is simple and straight forward going 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 front wheel drive car , the transmission is usually combined with the final drive

to form what is called a transaxle . The engine on a front wheel drive car is usually mounted

sideways in the car with the transaxle tucked under it on the side of the engine facing the rear

of the car . Front axles are connected directly to the transaxle and provide power to front

wheels . In this example , power floes from the engine , through the torque converter to a

larger chain that sends the power through a 180 degree turn to the transmission that is along

side the engine . From there , the power is routed through the transmission to the final drive

where it is split and sent to the two front wheels through the drive axles .

There are a number of other arrangements including front drive vehicles where the

engine is mounted front to back instead of sideways and there are other systems that drive all

four wheels but the two systems described here are by far the most popular . A much less

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popular rear and is connected by a drive shaft to the torque converter which is still mounted

on the engine . This system is found on the new Corvette and is used in order to balance the

weight evenly between the front and rear wheels for improved performance and handling .

Another rear drive system mounts everything , the engine , transmission and final drive in the

rear . This rear engine arrangement is popular on the Porsche.

The modern automatic transmission consists of many components and systems that

designed to work together in a symphony of planetary gear sets , the hydraulic system, seals

and gaskets , the torque converter , the governor and the modulator or throttle cable 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

possible to describe these systems .

1）Planetary gear sets

Automatic transmission contain many gears in various combinations . In a manual

transmission , gears slide along shafts as you move the shift lever from one position to

another , engaging various sizes gears as required in order to provide the correct gear ratio . In

an automatic transmission , how ever , the gears are never physically moved and are always

engaged to the same gears . This is accomplished through the use of planetary gear sets .

The basic planetary gear set consists of a sun gear , a ring and two or more planet

gears , all remaining in constant mesh . The planet gears are connected to each other through a

common carrier which allows the gears to spin on shafts called “pinions” which are attached

to the carrier .

One example of a way that this system can be used is by connecting the ring gear to

the input shaft coming from the engine , connecting the planet carrier to the output shaft , and

locking the sun gear so that it can‟t move . In this scenario , when we turn the ring gear , the

planets will “walk” along the sun gear ( which is held stationary ) causing the planet carrier to

turn the output shaft in the same direction as the input shaft but at a slower speed causing gear

reduction ( similar to a car in first gear ) .

If we unlock the sun gear and lock any two elements together , this will cause all three

elements to turn at the same speed so that to output shaft will turn at the same rate of speed as

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the input shaft . This is like a car that is third or high gear . Another way we can use a

planetary gear set is by locking the planet carrier from moving , then applying power to the

ring gear which will cause the sun gear to turn in opposite direction giving us reverse gear .

The illustration in Figure shows how the simple system described above would look in

an actual transmission . The input shaft is connected to the ring gear , the output shaft is

connected to the planet carrier which is also connected to a “Multi-disk” clutch pack . The sun

gear is connected to drum which is also connected to the other half of the clutch pack .

Surrounding the outside of the drum is a band that can be tightened around the drum when

required to prevent the drum with the attached sun gear from turning .

The clutch pack is used , in this instance , to lock the planet carrier with the sun gear

forcing both to turn at the same speed . If both the clutch pack and the band were released ,

the system would be in neutral . Turning the input shaft would turn the planet gears against

the sun gear , but since noting is holding the sun gear , it will just spin free and have no effect

on the output shaft . To place the unit in first gear , the band is applied to hold the sun gear

from moving . To shift from first to high gear , the band is released and the clutch is applied

causing the output shaft to turn at the same speed as the input shaft .

Many more combinations are possible using two or more planetary sets connected in

various way to provide the different forward speeds and reverse that are found in modern

automatic transmission .

2）Clutch pack

A clutch pack consists of alternating disks that fit inside a clutch drum . Half of the disks

are steel and have splines that fit into groves on the inside of the drum . The other half have a

friction material bonded to their surface and have splines on the inside edge that fit groves on

the outer surface of the adjoining hub . There is a piston inside the drum that is activated by

oil pressure at the appropriate time to squeeze the clutch pack together so that the two

components become locked and turn as one .

3）One-way Clutch

A one-way clutch ( also known as a “sprag” clutch ) is a device that will allow a component

such as ring gear to turn freely in one direction but not in the other . This effect is just like that

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bicycle , where the pedals will turn the wheel when pedaling forward , but will spin free when

pedaling backward .

A common place where a one-way clutch is used is in first gear when the shifter is in

the drive position . When you begin to accelerate from a stop , the transmission starts out in

first gear . But have you ever noticed what happens if you release the gas while it is still in

first gear ? The vehicle continues to coast as if you were in neutral . Now , shift into Low gear

instead of Drive . When you let go of the gas in this case , you will feel the engine slow you

down just like a standard shift car . The reason for this is that in Drive , one-way clutch is

used whereas in Low , a clutch pack or a band is used .

4）Torque Converter

On automatic transmission , the torque converter takes the place of the clutch found on

standard shift vehicles . It is there to allow the engine to continue running when the vehicle

comes to a stop . The principle behind a torque converter is like taking a fan that is plugged

into the wall and blowing air into another fan which is unplugged . If you grab the blade on

the unplugged fan , you are able to hold it from turning but as soon as you let go , it will begin

to speed up until it comes close to speed of the powered fan . The difference with a torque

converter is that instead of using air it used oil or transmission fluid , to be more precise .

A torque converter is a lager doughnut shaped device that is mounted between the

engine and the transmission . It consists of three internal elements that work together to

transmit power to the transmission . The three elements of the torque converter are the pump ,

the Turbine , and the Stator . The pump is mounted directly to the torque housing which in

turn is bolted directly to the engine‟s crankshaft and turns at engine speed . The turbine is

inside the housing and is connected directly to the input shaft of the transmission providing

power to move the vehicle . The stator is mounted to a one-way clutch so that it can spin

freely in one direction but not in the other . Each of the three elements has fins mounted in

them to precisely direct the flow of oil through the converter .

With the engine running , transmission fluid is pulled into the pump section and is

pushed outward by centrifugal force until it reaches the turbine section which stars it running .

The fluid continues in a circular motion back towards the center of the turbine where it enters

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the stator . If the turbine is moving considerably slower than the pump , the fluid will make

contact with the front of the stator fins which push the stator into the one way clutch and

prevent it from turning . With the stator stopped , the fluid is directed by the stator fins to

re-enter the pump at a “help” angle providing a torque increase . As the speed of the turbine

catches up with the pump , the fluid starts hitting the stator blades on the back-side causing

the stator to turn in the same direction as the pump and turbine . As the speed increase , all

three elements begin to turn at approximately the same speed . Sine the „80s , in order to

improve fuel economy , torque converters have been equipped with a lockup clutch which

locks the turbine to the pump as the vehicle reaches approximately 40-50 mph . This lockup is

controlled by computer and usually won‟t engage unless the transmission is in 3rd or 4th

gear .

5）Hydraulic System

The hydraulic system is a complex maze of passage and tubes that sends that sends

transmission fluid and under pressure to all parts of the transmission and torque converter

and . Transmission fluid serves a number of purpose including : shift control ,general

lubrication and transmission cooling . Unlike the engine ,which uses oil primary for

lubrication ,every aspect of a transmission „s function is dependant on a constant supply of

fluid is send pressure . In order to keep the transmission at normal operating temperature , a

portion of the fluid is send to through one of two steel tubes to a special chamber that is

submerged in anti-freeze in the radiator . Fluid passing through this chamber is cooled and

then returned to the transmission through the other steel tube . A typical transmission has an

avenge of ten quarts of fluid between the transmission , torque converter , and cooler tank , In

fact , most of the components of a transmission are constantly submerged in fluid including

the clutch packs and bands . The friction surfaces on these parts are designed to operate

properly only when they are submerged in oil .

6）Oil Pump

The transmission oil pump ( not to confused with the pump element inside the torque

converter ) is responsible for producing all the oil pressure that is required in the transmission .

The oil pump is mounted to front of the transmission case and is directly connected to a

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flange on the engine crankshaft , the pump will produce pressure whenever the engine is

running as there is a sufficient amount of transmission fluid available . The oil enters the

pump through a filter that is located at bottom of the transmission oil pan and travels up a

pickup tube directly to the oil pump . The oil is then sent , under pressure to the pressure

regulator , the valve body and the rest of the components , as required .

7）Valve Body

The valve body is the control center of the automatic transmission . It contains a maze

of channels and passages that direct hydraulic fluid to the numerous valves which when

activate the appropriate clutch pack of band servo to smoothly shift to the appropriate gear for

each driving situation . Each of the many valves in the valve body has a specific purpose and

is named for that function . For example the 2-3 shift valve activates the 2nd gear up-shift or

the 3-2 shift timing valve which determines when a downshift should occur .

The most important valve and the one that you have direct control over is the manual

valve. The manual valve is directly connected to the gear shift handle and covers and

uncovers various passages depending on what position the gear shift is paced in . When you

place the gear shift in Drive , for instance , the manual valve directs fluid to the clutch pack

( s ) that activates 1st gear . It also sets up to monitor vehicle speed and throttle position so

that it can determine the optimal time and the force for the 1-2 shift . On computer controlled

transmission , you will also have electrical solenoids that are mounted in the valve body to

direct fluid to the appropriate clutch packs or bands under computer control to more precisely

control shift points .

8）Seals and Gaskets

An automatic transmission has many seals and gaskets to control the flow of

hydraulic fluid and to keep it from leaking out . There are two main external seals : the front

seal and the rear seal . The front seal seals the point where the torque converter mounts to the

transmission case . This seal allows fluid to freely move from the converter to the

transmission but keeps the fluid from leaking out . The rear seal keeps fluid from leaking past

the output shaft .

A seal is usually made of rubber ( similar to the rubber in a windshield wiper blade )

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and is used to keep oil from leaking past a moving part such as a spinning shaft . In some

cases , the rubber is assisted by a spring that holds he rubber in close contact with the

spinning shaft .

A gasket is a type of seal used to seal two stationary parts that are fasted together .

Some common gasket materials are : paper , cork , rubber , silicone and soft metal .

Aside from the main seals , there are also a number of other seals and gasket that vary from

transmission to transmission . A common example is the rubber O-ring that seals the shaft for

the shift control lever . This is the shaft that you move when you manipulate the gear shifter .

Another example that is common to most transmission is the oil pan gasket . In fact , seals are

required anywhere that a device needs to pass through the transmission case with each one

being a potential source for leaks .

9）Computer Controls

The computer uses sensors on the engine and transmission to detect such things as

throttle position , vehicle speed , engine speed , engine load , stop light switch position , etc .

to control exact shift points as well as how soft or firm the shift should be . Some

computerized transmission even learn your driving style and constantly adapt to it so that

every shift is timed precisely when you would need it .

Because of computer controls , sports models are coming out with the ability to take

manual control of the transmission as through it were a stick shift lever through a special gate ,

then tapping it in one direction or the other in order to up-shift at will . The computer

monitors this activity to make sure that the driver dose not select a gear that could over speed

the engine and damage it .

Another advantage to these “ smart” transmission is that they have a self diagnostic

mode which can detect a problem early on and warn you with an indicator light on the dash .

A technician can then plug test equipment in and retrieve a list of trouble codes that will help

pinpoint where the problem is .

3．The Differential System

When a vehicle is cornered the inner wheel moves through a shorter distance than the

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outer wheel . This means that the inner wheel must slow down and the outer wheel must

speed up . During this period it is desirable that each driving maintains its driving action . The

differential performs these two tasks . The principle of the bevel type differential can 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 inner disc

will now move through a smaller distance ;this will cause the lever to pivot about its center

which will prize forward the outer disc to give it a greater movement . This action shows that

the torque applied to each driving wheel is always equal – hence the differential is sometimes

called a torque equalizer .

4．Brake System

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 into thermal ( heat ) . When stepping on the brakes , the

driver commands 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 .

The brake system is composed of the following basic components : the “master cylinder”

which is located under the hood , and is directly connected to the brake pedal , converts driver

foot‟s mechanical pressure into hydraulic pressure . 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 system . “Shoes” and “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 or drum

brakes in the rear connected by a system of tubes and hoses that link the brake at each wheel

to the master cylinder .

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Stepping on the brake pedal , a plunger is actually been pushing against in the master

cylinder which forces hydraulic oil ( brake fluid ) through a series of tubes and hoses to the

braking unit at each wheel . Since hydraulic fluid ( or any fluid for that matter ) cannot be

compressed , pushing fluid through 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 it started with . It is very

important 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 the system must be bled to remove the air . There are “bleeder screws” at

each wheel and caliper for 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 brake pads against the disk

( rotor ) which is attached to the wheel , forcing it to slow down or stop . This process is

similar to the wheel ,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 the pads and shoes to

eventually wear out and require replacement .

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 cause you to have a spongy pedal and the car will be hard

to stop ) .

The brake fluid 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 drops noticeably over a short period of time or goes down to about two

thirds full , have your brakes checked as soon as possible . Keep the reservoir covered expect

for the amount of time you need to fill it and never leave a can of brake fluid uncovered .

Brake fluid must maintain a very high boiling point . Exposure to air will cause the fluid to

absorb moisture which will lower that boiling point .

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The brake fluid travels from the master cylinder to the wheels through a series of steel

tubes and reinforced rubber hoses . Rubber hoses are only used in places that require

flexibility , such as at the front wheels , which move up and down as well as steer . The rest of

the system uses non-corrosive seamless steel tubing with special fittings at attachment points .

If a steel line requires a repair , the best procedure is to replace the complete line . If this is nit

practical , a line can be repaired using special splice fittings that are made for brake system

repair . You must never use brass “compression” fittings or copper tubing repair a brake

system . They are dangerous and illegal .

Other Components in the Hydraulic System

1）Proportioning Valve or Equalizer Valve

These valves are mounted between the master cylinder and the rear wheels . They are

designed to adjust the pressure between the front and the rear brakes depending on how hard

you are stopping . The shorter you stop , the more of the vehicle‟s weight is transferred to the

front wheels , in some cases , causing the rear to lift and the front to dive . These valves are

designed to direct more pressure to the front and less pressure to the harder you stop . This

minimizes the chance of premature lockup at the rear wheels .

2）Pressure Differential Valve

This valve is usually mounted just below the master and is responsible for turning the brake

warning light on when it detects a malfunction . It measures the pressure from the two

sections of the master cylinder and compares them . Since it is mounted ahead of the

proportioning or equalizer valve , the two pressure it detects should be equal . If it detects a

difference , it means that there is probably a brake fluid leak somewhere in the system .

3）Combination Valve

The Combination valve is simply a proportioning valve and a pressure differential valve

that is combine into one unit .

The parking brake system controls the rear brakes through a series of steel cables that are

connected to either a hand lever or a foot pedal . The ideal is that the system is fully

mechanical and completely bypasses the hydraulic system so that the vehicle can be brought

to a stop even if there is a total brake failure .

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5．Steering System

Basic Parts of Steering System

The steering converts the steering –wheel rotary motion into a turn motion of the

steered wheels of the vehicle .

The basic steering system in most cars is the same . The steering gear of steering box

is the heart of the steering system .This is usually next to the engine . A shaft extends from the

back of the steering gear . This shaft is connected to the steering column or steering shaft .

The steering wheel is at the top of the steering column . Another shaft comes from the bottom

of the steering gear . This shaft connects to the arms , rods , and links . This parts assembly ,

called the steering linkage , connects the steering gear to the parts at the wheels . The wheels

and tires mount to the steering knuckles , As shown in fig , the knuckles are pivoted at the top

and bottom . Thus , the wheels and rites can turn from side top side .

While the steering system may look complicated , it works quite simply . When a

driver drives a car straight down the road , the steering gear is centered . The gear holds the

linkage centered so that the wheels and tires point straight ahead . When the driver turns the

steering wheel , the steering shaft rotates and the steering gear moves toward that side . The

shaft coming out the bottom of the steering gear turns , as well . When the shaft turns , it pulls

the linkage to one side and makes the steering knuckles turn slightly about their pivot points .

Thus , the steering knuckle , spindle , wheels , and tires turn to one side , causing the car to

turn .

The type of steering layout depends on the suspension system . The beam axle used on

heavy commercial vehicle has a king pin fitted at each end of the axle and this pin is the pivot

which allows the wheels to be steered . Cars have independent suspension and this system has

ball joints to allow for wheel movement .

Types of Steering System

A steering box must have the following qualities :

1) no play in the straight-ahead position

2)low friction , resulting in high efficiency

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3)high rigidity ,

4)read justability

For these reasons , these are several different types of steering gears . However ,

there are only two types of steering systems : manual steering systems and power steering

systems . In the manual type , the driver dose all the work of turning the steering wheel ,

steering gear , wheels and tires . In the power , hydraulic fluid assists the operation so that

driver effort is reduced .

On today‟s cars , two types of steering systems commonly are used to provide steering

control :

1) recirculating ball

2) rack and pinion

Either of these two types of steering mechanisms may be a fully mechanical systems or a

power –assisted system .

6． Front Suspension

The front suspension is more complicated than the rear suspension . This is because the

front wheels must move in several different directions . The wheels must move up and down

with the suspension and turn left to right with the steering . Since the car goes in the direction

in which the front wheels point , the alignment of the front wheels is important . The wheels

must point in just the right direction for the car to move straight down the road and turn

properly .

Modern cars uses an independent front suspension . In this system , each wheel mounts

separately to the frame and has its own individual spring and shock absorber . Thus , the

wheels act independently of one another . When one wheel hits a bump or hole in the road ,

the other wheel dose no9t deflect .

Front Wheel Alignment

As a car moves down the high-way , the suspension moves the front wheels up and down .

At the same time , the steering mechanism moves the front wheels , sometimes to make turns

and sometimes to make the travel straight . The angular relationship between the wheels and

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suspension parts during this motion is the front-end geometry . Since the geometry can

change the alignment of front wheels is adjustable . You can change the adjustment to

compensate for spring sag .

The alignment of the front wheels affects the operation of a car . Poor alignment ca make

a car pull to one side and stop the front wheels from returning to the straight-ahead position

after a turn . The three normally adjustable angles are caster , camber , and toe .

1)Caster

Caster is the forward or backward of spindle or steering the knuckle at the top when

viewed from the side . Forward tilt is negative caster and backward tilt positive caster . Caster

is measured in the number of degrees that it is forward or backward from true vertical and is

adjustable on many vehicle .

2) Kingpin Angle

The kingpin angle is the inclination of the steering axis relative to the longitudinal

plane , measured in the transverse plane of the vehicle . Kingpin angle is 2°-16°and

determines the steering aligning torque in conjunction with steering offset and wheel caster .

It is measured only with the vehicle loaded .

3) Camber

Camber is the inward or outward tilt of the wheel at the top . Inward tilt is negative

camber and outward tilt is positive camber . The tilt of the wheel is measured inn degrees and

is adjustable on many vehicles .

4) Toe-in

Toe-in specifies the degree to which non-parallel front wheels are closer together at

the front than at th e rear ; measured at the edges of the rims at the wheel center height . front

non-driven wheels , toe-in is approximately 2-3 mm , and between 3mm and-2mm for driven

wheels . Toe-in reduces the tendency of the wheels to shimmy .

7．Rear Suspension

The purpose of the rear suspension is to support the weight of the rear of the vehicle . As

with the front suspension , this system contributes to the stability and ride of the vehicle .

Rear suspension may be of the solid axle or independent design . Many cars have solid axle

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rear suspension . Either design may have different kinds of springs , including torsion bars .

However , the coil spring and leaf spring types are most popular .

8．Wheels and Tires

To maintain grip when a vehicle is traveling at speed over a bumpy surface , a wheel

must be light in weight . Also it must be strong , cheap to produce , easy to clan and simple to

remove .

Wheels

The structure of the wheel is shown in Fig . The rim is made in one piece , with the

wheel center welded or riveted to it . Most modern vehicles use the drop center type . This

drop center provides a well for tire bead to drop into for tire removal . A slight hump at the

head ledge holds the tire in place should it go flat while driving .

tires

Tires are important to your safety and comfort . They transmit the driving and

braking power to the road . The car‟s directional control , road-ability and riding comfort are

greatly dependent on the tires . Tires should be selected and maintained with great care .

There are two basic types of tires – those with inner tubes and those without ( called

“tubeless” tires ) . Most modern automobile tires are of the tubeless type . Truck and bus tire

are usually of the tube type .

Tires are made of several layers of nylon , rayon , or polyester fabric bonded together

with belts of rayon , fiberglass , or steel cord . The rubber used in tires is a blend of natural

and synthetic rubber .

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底盘

底盘包括：离合器、变速器、传动轴、主减速器、前悬架、后悬架、制动系、转向系、车轮和轮胎。

1．离合器

发动机产生的动力是用来驱动汽车。传递过程把发动机动力传递到车轮，驱动力从发动机后面的飞轮输入到车轮，这些组成包括：离合器、变速器、传动轴、主减速器。

离合器的组成包括：飞轮、从动盘、压盘、弹簧、离合器盖、操纵部分。离合器是发动机和变速器之间的一个机构，它是通过摩擦来传递动力的，这就是为什么说离合器被称为摩擦机构。经过接触，离合器要传送发动机发出的功率而且没有损失。它还可以切断发动机转矩，便于换挡。

启动发动机或是传动轴旋转时，驾驶员踏下离合器踏板，目的是使离合器分离。此时，主动部分接到变速器输入轴是静止或旋转时，速度可以从高到低的通过主动部分传递到发动机曲轴上。没有瘫痪的压力作用于主动部分，住、从动之间就没有动力的传递，由于驾驶员松开离合器踏板，弹簧的压力作用于从动部分，两者的摩擦力也谁之增强，施加的压力，由于弹簧压力推动压盘而产生。全部弹簧的压力足够大，此时主从动部分的速度就是一样。目前，离合器作为耦合装置和传递发动机全部功率，而不打滑。

不过变速器与发动机之间的连接，尽量减少扭矩传递的损失，因为发动机在怠速或刚刚启动能耗低，否则，主从动部分，发动机不能被启动。

飞轮是离合器的一个主要部分，从发动机曲轴上输出的扭矩传递到飞轮上，经离合器输出。飞轮，从动盘，把发动机的功率输送到变速器上。

飞轮提供了离合器的一个安装位置，以便于和离合器配合，由于他的重量重，所以惯性大，有助于发动机的工作，飞轮还有一个大齿圈在外缘上，与启动马达的小齿轮相啮合，用来启动发动机。

离合器的从动盘在飞轮和压力板之间。它的中间有一个内花键与变速器输入轴相配合，变速器输入轴也有花键，它们相配合，因此，两部分就固定在一起。然而，离合器从动盘就只能轴向移动这就是输入轴与从动盘一起转动。

离合器压盘是由铸铁做的，它是圆的，直径与从动盘相同，压盘为了便于安装，一

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方以飞轮相对，它的设计以便于谈话的压缩和伸展。两种主要类型的离合器是：周边弹簧离合器和膜片离合器。一个弹簧离合器是由若干螺旋弹簧和安置。当离合器踏板踏下时，分离轴承就产生一个力推动分离杠杆，压缩弹簧，切断了发动机与变速器之间的动力传递。

膜片弹簧离合器多用于现代的汽车。膜片弹簧是一个单一的薄板金属的变形产生压力的，当压力去出后金属弹簧回大原来的形状。中心部分是做成手指壮充当分离杠杆，当离合器与发动机旋转时离心力的作用不会使压紧力减小，在离合器工作状态时，膜片也处于压紧状态，当分离轴承压膜片时，离合器分离。

当分离轴承及向变速器方向移动时，此时，膜片推动压盘运动，离合器就结合，转速跟发动机的相同。

它的优点是：膜片弹簧的压力在使用过程中变化小，重量轻，转动惯量小，降低了转动的不平稳，为压板提供了一个压紧力，不易使离合器打滑。

离合器踏板通过拉线连来使离合器分离，而更常用的是，由一个液压系统的辅助。无论那种方式，踏下踏板时使分离的力，通过分离轴承到膜片上手指状的分量杠杆上，使离合器分离。液压机构中，离合器踏板后设有一个活塞称为离合器主缸，这迫使液压油通过观点通向工作缸，到离合器上没有拉。

其它包括：离合器叉、分离轴承、离合器盖、离合器壳、飞轮、变速器输入轴，实际上这些都是便于控制离合器。分离轴承在离合器叉和压盘之间，离合器盖装离合器的零件。离合器壳主要是，把变速器、发动机、离合器连接在一起，使得变速器输入轴与发动机曲轴在同一轴线上。

2．自动变速器

对于现代的汽车，自动变速器是一个复杂的组件，这种传递动力的方式，是液力变矩期充当离合器来连接发动机和变速器。

两个基本类型的自动变速器基于该车辆是否是前驱动或后驱动。对发动机前置后驱动的汽车，变速器通常安装在发动机后底盘中心与油门配合。变速器输出轴连接到后桥，把发动机的动力传递到后轮，动力传输系统是直线的，从发动机，通过液力变矩器、变速器、传动轴、最后直接到到达车轮。

对于发动机前置前轮驱动的汽车，变速器通常和差速器装在一起。对于前驱动的汽车，变速器安装在发动机一侧，前车轴直接连接到差速器上，把动力传递给前轮。在这

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个布置中，动力来自于发动机，通过液力变矩器、变速器输出的动力通过了一个180度大转弯，经过变速器沿发动机侧边通过传动轴输出到前轮。

还有其它的一些布置，发动机前置前驱动，发动机横向布置，装设一个分动器可以实现四轮驱动。但这种形式目前是最常用的：发动机中置后驱动，可以使重量均匀的分布在前、后轮之间，改善了操作性能；发动机后置后驱动，发动机、变速器、驱动轮都在后方，这种后置式的发动机的安排，是最满意的。

现代的自动变速器包括了许多组件和系统的协同工作，有行星齿轮组、液压系统、密封件和垫圈、变矩器、调节器、节气门拉线、计算机控制这些都是多年来由机械式演变过来的。这用简单、通用的解释，描述一下这些系统。

1）行星齿轮组

自动变速器箱体内有很多齿轮，有各种不同的组合，在一个变速箱内，齿轮的滑动沿轴线从一个位置到另一个位置，对各种大小齿轮的要求，有正确的传动比。在一个自动变速箱，至始至终，不是齿轮的机械移动来达到这一点的，通过行星齿轮组来完成。

基本的行星齿轮组成由一个太阳轮、一个齿圈、并且有两个或两个以上的行星齿轮，全部齿轮都是常啮合。行星齿轮的相互联系通过一个共同的载体，使齿轮相互啮合在一起。

一个传递方式，这个系统可以从发动机的输出连接到齿圈作为主动件，连接行星轮作为从动件，并锁定太阳轮，使起不能转动。在这情况下，当我们把齿圈、行星齿轮，沿太阳轮转动，主动件与从动件就同向转动，从动件的转速慢，齿轮减速就类似汽车的一挡。

如果解开太阳轮和锁定其它两个元素，这就会使这三个要素以同样的速度转动，齿轮的传动就类似于汽车是第三或高挡位。另一个方式是，把行星架锁定，使太阳轮作为主动轮，齿圈作为从动件，这时它们的转动方向就相反，就类似以汽车的到挡。

上面所说的，在实际的传动过程是如何控制。齿圈为输入轴，行星架为输出轴，都是通过盘式离合器控制。太阳轮一个单向离合器，一个制动器，当制动器作用时，太阳轮只能从一个方向转动。

在这情况下，离合器的使用，锁定行星架与太阳轮迫使它们以相同的转速转动。如果它们的离合器和制动器都被释放，该系统在自由状态。变速器的行星齿轮组太阳轮是自由的，比输出动力。在一挡位，制动器制动太阳轮跟随转动，从第一挡到高挡制动器

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释放和离合器使用到输入轴，它们以同一个速度转动。

使用两个或两个以上的行星齿轮组以各种方式连接，可提供不同的前进速度和扭矩，普遍的使用以现代的自动变速器。

2）片式离合器

片式离合器主要由若干交替排列的离合器盘和离合器片组成。每片离合器盘上有伸出的突线，勾住离合器鼓，以输入轴连接。离合器片内的键槽与离合器壳互相啮合，离合器壳与中间轴键槽连接，中间轴又与后行星排内齿圈用键槽连接。因此，离合器盘和离合器片分别与输入轴和湖行星排内齿圈连接。操作离合器的活塞安装以离合器鼓上，离合器鼓亦称做为活塞缸。

3）单向离合器

单向离合器是一种只可以使元件在一个方向转动，如把齿圈自由在一贯方向，而不能反向转动，这种作用就象是，自行车踏板转动时，可以带动车轮转动，当车轮转动或向另一个方向转动是自由的

一个单向离合器用于一挡时，在驱动方向是，当从停止开始加速，在第一个齿轮输出动力，如果继续加速，不在一挡位？汽车继续加速，他就是一个方向自由的。此时，单向离合器不在输出动力，当车速慢下来时，转速慢，它就可以起作用。这一个现象由于，在提供力的时候它才起作用，在高速时，是自由的。

4）液力变矩器

对于自动变速器，液力变矩器取代离合器装于车上。它的作用是：当车停下来，发动机还可以继续运转。传递扭矩的原理，比如，把一个风扇吹向另一个，另一个不用插电也能跟它一起转动，如果你压住扇片，它就不会转动，但你一放手，它就开始加速，直到速度接近动力风扇。它们两者的差异就是：变矩器不是利用空气，而是利用油液，以使他的传递更加准确。

液力变矩器是一个较大的盆壮装置，安装在发动机与变速器之间。它包含三个部件，协同工作，为变速器提供动力，液力变矩器的三要素是：泵论、涡轮、导轮，泵论是通过螺栓直接安装在发动机的曲轴上，转速与发动机的相同，涡轮连接到变速器的输入轴上，为汽车提供动力，导轮上装有一个单向离合器，使他只可以在一个方向转动，而在另一方被固定，每一个要素之间通过液流传递扭矩。

发动机启动后，输入轴开始旋转，带动泵轮旋转，因旋转产生的离心力使泵轮叶片

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间的液流沿叶片从外缘向外甩出；接着又由于泵轮和涡轮转速差引起泵轮叶片外缘与涡轮叶片外缘产生了压力差，液流从液压高的泵轮叶片外缘流进涡轮叶片外缘，同时，泵轮的旋转也使得其叶片带动液流随工作轮旋转，这一旋转就使液流流进涡轮时方向改变，从而冲击涡轮叶片推动涡轮绕泵轮同一方向旋转。从涡轮流出的液流进入固定不动的导轮，经导轮叶片改变方向后回流至泵轮。如果涡轮的速度大大低于泵轮转素时，导轮仍锁住不动。导轮停止，液流通过导轮时重新进入泵轮，促使泵轮旋转起到扭矩增大的作用。由于泵轮和导轮的转速增加，液流开始改变方向流向泵轮叶片背面，也可以产生增矩的作用。由于车速的提高，这三要素句以相同的转速旋转，为了提高燃油经济性，在液力变矩器上装了一个锁止离合器，车速达到40—50英里的时候，锁止离合器就把三要素连为一体，这种控制是计算机控制。

5）液压系统

液压系统是一个复杂的迷宫壮通道，液流压力控制变速器扭矩的输出，。液流有若干用途，包括：换挡控制、润滑、冷却。不象发动机，它只用来润滑，每一个流动，是依赖于不断提供的液体压力。为了使油液在一个正常的温度工作，部分液流从散热器中流过以便散热。液体通过此通道被冷却，然后返回到传输通道。液里变矩器和散热器，是用来给液流散热的。事实上大部分的摩擦表面都淹没在油液中，比如：离合器盘、离合器片，也能正常的工作。

6）油泵

油泵主要是负责提供油液传输过程中的压力，油泵安装在前面的泵轮上，并且以发动机的曲轴相连，当发动机转动时，带动油泵运转，产生压力，提供足够的油。油进入油泵时通过一个空气滤清器，安装在油底壳的底部。压力调节器、调压阀、压力修正阀调节后送到各个管路。

7）阀体

阀体是自动变速器的控制中心。它包含一个迷宫壮的通道输送液压油，在每一个工况下控制离合器和其它伺服机构，顺利的控制齿轮传动情况。

最重要的阀门一个直接控制的手动阀。手动阀是直接连接到齿轮变速箱里面的，根据它所在位置打开或关闭各种通道，控制换挡节奏。用齿轮变速传动来举例说明，监控车辆的速度和油门的位置，以便它能确定最佳的换挡时间，。计算机的控制，通过电磁阀控制油压压力，控制离合器或制动器，以更精确的控制换挡点。

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8）密封垫和垫圈

一个自动变速器有许多的密封件和垫圈，以控制流动的液压油，使它不外泄。主要有两个外部密封垫：前油封和后油封。前油封安装到变速器的变矩器，这使得油底壳到变矩器的油液能自由流动，而不外泄。后密封垫使游液不泄漏到输出轴。

密封垫通常用橡胶（类似汽车挡风玻璃雨刮器叶片），它是用来保持不泄漏到其它部分，如旋转轴。在有的情况下，用一个弹簧和橡胶在一起，如用在花键轴。

垫圈是一种用来密封两个固定部分，使其连接在一起。一些常见的衬垫材料是：硬纸、软木、橡胶、有机硅和软金属。

除了主要的密封垫，也有一些其它的密封垫和垫片，因使用条件而定，有的从轴到轴的连接。一个常见的例子是橡胶O型密封圈用来密封换的挡轴。就是说，你所操作的边速杠在转动时，另一个例子是大部分常见的油底壳垫片，事实上，密封垫是随时进行更换，防止油不泄漏。

9）计算机控制

计算机控制是利用传感器对发动机和变速器提取数据，因为节气门位置、汽车行驶速度、发动机转速、发动机负荷等是变数。利用这些数据可以精确控制换挡点，以便换挡平顺。一些电脑数据，能了解行驶条件，并不断的适应行驶条件的变化，使汽车稳定的行驶。

由于计算机的控制，通过一个特殊的元素代替了手动控制，在每一个工况都是安全的。计算机的控制，确保发动机转速不至于过高而使发动机损坏。

另一个好处是，这些精确的数据输入系统，有一个自诊断系统，以便能使我们及时的发现问题，当有问题时，故障指示灯就闪烁。维修人员就可以根据检测设备检测出的故障码，很快的找到问题所在部位。

3．差速器

当车辆转弯时，内侧车轮要比外侧车轮所走路线短，也就是说，内车轮必须放慢、外车轮必须加快。此时，驾驶员控制行驶方向，差速器来实现此功能。从差速器的形状可以看出，就相当于两个膜片的作用。

当车辆直线行驶时，两个车轮以相同的速度转动。

当车转弯时，扭矩会平分，但内车轮通过较小的距离，车轮成为一个支点，为外车轮提供一个扭矩，使外车轮转快。转矩分配到每一个驱动轮是相等的，是扭矩等分特性。

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4．制动系统

在汽车上，制动系统是最主要的系统。如果制动失效，其结果只能是灾难性的。制动器是一个能量转换装置，因为它是将机械能转化为热能，制动时，驾驶员踏下踏板，强大的制动里把车停住，每4次制动，制动系统就会产生千磅的压力。

制动系统由以下几个部分组成，“主缸”位于发动机下面，并直接连接到制动踏板，驾驶员踏下制动踏板，将机械压力转换为液压力，设在每一个车轮上的“轮缸”通过制动软管连接到主缸。制动液，是经过特别的设计，填补了该系统在极端情况下的工作。“蹄”、“鼓”是由轮缸推动蹄与鼓接触，从而产生摩擦阻力，使车速慢下来。

典型的制动系统是，前轮是盘式，后轮是鼓式，通过软管把主缸的压力传递到制动器上。

踏下制动踏板是，柱塞就推动主缸的制动液，通过一系列的软管流向每一个车轮的制动器。由于液体不能被压缩，推动液体通过管道就像是钢性的材料通过管道。有别于钢体，然而液体可直接通过许多曲折和反复的管道到达目的地，与开始哟相同的速度和压力。液流是纯液体，不能有气泡，这一点非常重要。空气可以压缩，最后会造成压力的下降，降低了制动效能。如果管路有气泡，那么必须排除，在每一个车轮上的制动器都装有“排气螺栓”以排除气泡。

对盘式制动器，液流从主缸送入到制动盘的卡钳的活塞上产生压力，使活塞移动，使卡钳对盘产生摩擦阻力，迫使车速放慢。这种制动系统就比鼓式的要好，因为它的散热性比较好。由于表面间的摩擦，会使制动蹄片磨损，当磨损到一定程度时就应该更换。

制动液是一种具有特殊性质的油，在寒冷的条件下，流动性要好，在非常高的温度下不沸腾。（如果制动液沸腾，就会使制动管路有气泡，汽车就难以停止。）

制动主缸是主要的，大多数汽车有一个视液窗，在不开封油箱的情况下，能看到液面的高低。由于制动蹄片的磨损，制动液面会有所下降。这是一个正常的情况，不到最低位都没有问题。如果在较短的时间内下降明显或下降到约三分之二处，应该对制动系统进行检查，使制动液保持在一个高度范围内。制动液必须有一个非常高的沸点，暴露在空气中会吸收水分，这样沸点就会降低。

制动液压缸的压力，由主缸通过一系列的钢管和橡胶软管传输而来的，有很好的灵活性，如在前驱动的汽车中，车轮的上升或下降，以及转弯。其余的地方都使用耐腐蚀性的钢油管，如果有裂纹，必须进行修理，用与与原来一样材料的更换，绝不能利用软

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金属来修复，那样做是很危险。

制动液压系统的组件

1）平衡阀

这些阀门安装在主缸与轮缸之间。它们是调节前后轮之间系统油压的大小，当你紧急停车时，更多的重量会转移到前轮，在某些情况下，造成前桥下沉失去方向的稳定性，这些阀门的设计，自动分配前后压力，给你更容易的停车，也减少了由于后轮的重量减轻，使后轮过早的抱死。

2）压差阀

此阀通常安装于管路上，当它检查到压力故障时，点亮刹车警示灯。它调节压力，把主缸的压力分两路输出，并比较大小。因为它是安装在均衡阀后，它输出的压力是相等的。如果它检查压力的差异，有可能大是系统某处的制动液泄漏。

3）组合阀

它是一个比例阀和压差阀，组合在一起的整体。

驻车制动系统控制后桥车轮，最理想的是，完全机械或机械与液压控制，如果某个制动失效，也可以使车停住。

5．转向系统

转向系统的基本组成：转向操纵机构、转向器和转向传动机构三大部分组成。

当汽车转向时，驾驶员对转向盘施加一个转向力矩，带动转向器、车轮转过一个角度，实现转向。

基本的转向系统，大多数汽车都是一样的。转向器是转向系统的核心，从转向盘施加转向力矩通过转向轴和连轴器输入到转向器，在经过左、右横拉杆传递给固定一两侧转向节上的左、右转向节臂，使转向节和它所支撑的转向轮绕主销轴线偏转一定角度，实现转向。

转向器必须具备以下特性：

1） 直线行驶特性

2） 高传动效率

3） 高刚性

4） 自动回正能力

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由于这些理由，有几种不同的转向器。但是，也只有两种转向系统：机械转向系统和动力转向系统。机械转向系统以驾驶员的体力作为转向能源，其中所以的传力件都是机械的。动力转向系统是兼用驾驶员体力和发动机的动力作为转向能源，减少了驾驶员的体力消耗。

对现代的汽车，转向系统常用的转向器：

1） 循环球式转向器

2） 齿轮齿条式转向器

无论是那种类型的转向器，可以采用机械或动力转向系统。

6．前悬架

前悬架比后悬架更加复杂，这是因为前轮在几个不同的方向转动，车轮向上、向下运动并且还会向左、向右转动。由于汽车要改变行驶方向，汽车的前轮是非常重要的，在短短的时间里正确的指导方向，保证汽车直线或转弯行驶。

现代汽车使用的都是独立前悬架，在这一个体系中，每一个车轮都安装在单独的车架上，并有自己单独的减震器。因此，车轮它都是独自转动，当一个车轮在突起或沟槽里，另一个车轮不偏转。

前轮定位

转向桥在保证汽车转向功能的同时，应使转向论有自动回正的作用，以保证汽车稳定的直线行驶功能。即当在遇到外力作用发生偏转时，一旦作用的外力消失，应能自动的回到原来的直线行驶位置。这种自动回正作用是转向轮的定位参数来保证实现的。就是使车轮和悬架系统零件之间的角关系来控制，它们之间的角关系会改变，可以调整弹性零件来改变。

前轮对行驶的汽车影响是非常大，转向轮、主销、前轴之间的安装应具有一定精确的相对位置。这些转向轮的定位参数有：主销后倾角、主销内倾角、前轮外倾角和前轮前束。

1） 主销后倾角

使主销在汽车的纵向平面内向后有一个倾角，即主轴线和地面垂直线在汽车纵向平面内的夹角，保证了汽车直线行驶时的方向稳定性。

2） 主销内倾角

主销在汽车的横向平面内向内倾斜一个角度，一般在2~16度。

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3） 前轮外倾角

前轮外倾角是通过车轮中心的汽车横向平面与车轮平面的交线与地面垂线之间的夹角。补偿汽车满载时车轮内倾的趋势，以减少轮胎的偏磨损和轮毂轴承的受力分布合理。

4） 前轮前束

前束表明，在某个程度上车轮是平衡的。在前方、后方测量轮辋边缘在车轮中心的长度，不是前桥驱动的汽车，前束大约在2~3毫米之间，抵消车轮外倾带来轮胎横向滑磨的不良后果。

7．后悬架

后悬架是车辆支持重量的核心，与前悬架相比，用来承受重量，后悬架系统，大多数是非独立悬架，有较多的钢板，有个种不同的弹簧，包括扭杆弹簧、螺旋弹簧和钢板弹簧，其中螺旋弹簧和钢板弹簧是最常用。

8．车轮和轮胎

车在不平坦的路面上行驶时，也应该具有良好的附着力，车轮的重量要轻，强度要大，价格要低，便于更换。

车轮

车轮是介于轮胎和车轴之间承受负荷的组件，通常由两个主要部件轮辋和轮辐组成。轮辋是在车轮上安置和支撑轮胎的部件，轮辐是在车轮上介于车轴和轮辋之间的部件，它们通过焊接或铆接在一起。现在的大多数汽车使用深槽轮辋，这轮辋结构简单，刚度大，质量较小，与轮胎的接触面大。

轮胎

对于汽车的安全性和舒适性，轮胎是很重要的，它还要保证车轮和路面间有良好的附着性，以提高汽车的牵引性、制动性和通过性，承受汽车的重力，并传递其他方向的里和力矩。

轮胎有良种基本类型，有内胎和无内胎的。现代化的汽车大多是无内胎，卡车和公共汽车有内胎的。

轮胎由数层尼龙，粘胶，涤纶织物，人造玻璃纤维或钢丝帘布层组合而成。橡胶轮胎，是用天然合成的橡胶制成的。

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