Tiếng anh cơ khí ô tô phần 2

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UNIT FOURTEEN

Engine Starting System

Ease of starting is one of the major performance char- acteristics of internal combustion engines To start such an en- gine, it is necessary to spin the engine crankshaft with sufficient speed for good mixing of air and fuel and adequate compression and ignition of the combustible charge The minimum speed with which the crankshaft of an engine should be rotated to ensure reliable starting of the engine is referred to as the cranking speed It depends on the en-gine type and starting conditions

The starting speed is 40 to 50 rpm for carburettor engines and 150 to 250 rpm for diesel engines Cranking the engine with a lower speed makes it more difficult for the engine to start, for in this case the charge has more time to escape through leaky joints and give off its heat of compression to the engine components, as a result of which both the pressure and temperature of the charge at the end of the compression stroke are reduced

Much effort is required to crank the engine during starting, since it is necessary to overcome friction in the moving engine components and the resistance offered by the charge being com- pressed This effort depends on the engine temperature, grow- ing higher with decreasing temperature, because of the increas- ing viscosity of lubricating oil

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combustion engines may be started by the following methods: hand starting, Eelectric starter motor, fgasoline en- gine, compressed-air motor, and compressed-air admission Hand starting depends on the muscle power of the operator to turn the crank handle hooked to the engine crankshaft or to tug at the starting rope wound around the engine flywheel In the early days of the automobile, it was necessary for the operator to start the engine with a hand crank tn other words, the driver had to insert a crank into the front of the engine and turn it by hand until the engine started operating This task required both skill and physical strength and made operation of the automobile very incon-venient for those who could not crank the engine More- over, without an electrical starting system, the early engines had design limitations in respect to displacement and compression ratio

Electric motor starting is the most common method used for starting automobile engines in 1910, Charles F Kettering be- gan to work on a practical electrical automotive starter The re- sulting system first appeared on the 1912 Cadillac; other manu- facturers quickly adopted it for their own passenger vehicles This resulted in an increase in the popularity and widespread use of automobiles

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from the battery, and it converts this energy into mechanical en- ergy, which transmits through the drive mechanism to the engine’s flywheel

The typical starting system has five components: battery, starting switch, battery cables, starter sole noid or switch, and starting motor The battery supplies electrical energy in the form of current flow for the starting circuit The starting motor can draw a large amount of current from the battery in order to turn the engine over The starter for a large V-s engine, for example, may require as much as 300 amperes of starting current

The starting system is convenient to operate and consider- ably eases the driver's work, but requires skilled maintenance and has only a small store of energy, which limits the number of possible starting attempts Many engines using an electric start- ing system are also provided with means for hand starting in case the storage battery or the starter motor should fail

To facilitate the starting of diesel engines under low-tempera- ture conditions, use is made of the compression release (decompressor) mechanism and heating devices

Most automotive engines have their starting systems con- trolled remotely, from the driver's cab Where an auxiliary en- gine is used for starting a diesel engine the auxiliary engine cranks the main one through a reduction gear referred to as the starting device

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when it fires and picks up speed, it automatically disengages the starting gears (Fig 13)

This starting method has the advantages of simplicity and of being able to start the diesel engine in extremely cold weather The warmjacket water from the gasoline engine can be used to preheat the main engine, and then the gasoline engine can turn it over as long as needed

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| -sturting-engine crank-shaft; 2-and 3-gears; 4-clutch lever; 5-reduc- tion-gear shaft, 6-and; 7-clutch driven and driving discs;8-ftvw' h881

ring (starte,) gear of diesel engine; 9-starter-gear; 10-automatic starter- gear release mechanism, | 1-starter-gear control lever

Compressedair admission The starting method most com- monly used on engines of moderate and large size is the com- pressed-air admission method The energy needed to start the engine is stored by compressing air into one or more tanks The compressed air is admitted through an automatic starting valve in the engine cylinder head when the piston is at top center at the start of power stroke The pressure of the air pushes the piston down and thus turns the engine over When the engine is turning fast enough, the injected fuel ignites and the engine runs on its own power, whereupon the air supply is cut off

The opening of the starting valve is timed, directly or indi- rectly, by cams on the camshaft Usual starting air pressures on modern engines range from 250 to 300 psi TU MOI spin v quay compression ñ Sự nén ensure vt bảo đảm stroke 7 hanh trinh crank v quay trục resistance n sự can

admit v dua vao, hut vao introduce vé dua vao

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operator n hook v tug v wind v insert vt inconvenient a displacement n, practical a adopt vt popularity n widespread a generator n charge v replace vt perform v mechanical a typical a draw v ampere n considerably ad maintenance 1 facilitate vt remotely ad pinion n disengage vt simplicity a extremely ad người vận hành móc vào kéo quấn tròn ấn vào, chèn vào

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preheat v làm nóng trước enclose ví đặt vào moderate a điều hòa store vt cất giữ pressure 7Ø áp suất

whereupon ad và sau đó

directly ad trực tiếp

CUM TU UA THANH NGU

1 be referred to as duoc xem nhu la 2 depend on (upon) phụ thuộc vào

3 rpm = revolutions per minute số vòng quay/phút

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19 jacket water vỏ áo nước

20 cut off cắt đột ngột, cẮt ngang

CHU THICH RAI KHOA ————-—.s

Cranking the engine with a lower Speed makes it more diffi- cult for the engine to start, for in this case the charge has more time to escape through leaky joints and give off its heat of com- pression to the engine components, as a result of which both the pressure and temperature of the charge at the end of the com- pression stroke are reduced

Quay động cơ với một tốc độ thấp hơn làm cho động cơ khó khỏi động bởi vì trong trường hợp này không khí nạp có nhiều

thời gian thoát ra chỗ rò rÏ và làm mất nhiệt của việc hành trình nén đối với các bộ phận của động cơ vì vậy cả hai áp suất và nhiệt độ không khí nạp vào cuối hành trình nén bị giảm di

In other words, the driver had to insert a crank into the front of the engine and turn it by hand until the engine started operat- ing

Nói cách khác, người lái phải ấn vào một cần quay vào trong

đầu trước của động cơ và quay nó bằng tay cho đến khi động cơ

bắt đầu vận hành

Many engines using an electric Starting system are also pro- vided with means for hand Starting in case the storage battery or the starter motor should fail

Nhiều động cơ sử dụng hệ thống khởi động bằng điện cũng có phần khởi động bằng tay để khởi động trong trường hợp bình

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in case conj = lest trong trường hợp

The compressed air is admitted through an automatic start- ing valve in the engine cylinder head when the piston is at top center at the start of power stroke

Không khí nén được đưa vào qua một van khỏi động tự động

trong nắp xylanh động cơ piston ở tại điểm chết trên vào đầu hành trình sinh công RAI TAP I Dịch những cụm từ sau sang tiếng Việt: 1 Oo on oan fF 0œ»

transmit rotation to the diesel crankshaft disengage from the diesel flywheel ring gear _ automatic release mechanism

_ equip with a back-up starting mechanism _ impart rotation to the crankshaft

_ starting-engine drive gears

_as a result of friction between the components _ spin the starting-engine drive shaft

_the driven drum of the starting-engine drive clutch 10 free the shaft from the starting engine

41 the automatic starter-gear release mechanism 42 mesh with the flywheel ring gear

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14 disconnect the shaft from the Starting engine 15 the centrifugal force of the rotating flyweights 16 engage the drive pinion with the flywheel ring gear 17 allow the pinion to demesh from the flywheel 18 slide the drive gear into engagement with flywheel 19 absorb the shock of engagement

20 an electric motor desighed Specially for cranking internal 1

combustion engines

Điền vào chỗ trống 1 từ hoặc † cụm từ đúng nhất để hoàn thành câu:

The escape of air and the loss of heat both a lower

temperature at the end of compression A result from B result in

C give off D come back to

The starter solenoid iS _ operated heavy-duty switch A an electromagnetically B.an electrically

C.a hydraulically D an automatically

The solenoid switch Opens and closes the circuit between

the battery and _

A the engine B the generator C the Starting engine D cranking motor

The battery must Supply current flow to the starter

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in the modern automobile the starting switch is part of the keyed switch

A battery B ignition

C fuel D safety

Many solenoids also shift the cranking pinion into _ the flywheel ring gear

A mesh with B contact with C holding out against D touch with

The current producing the magnetic field in the windings _ the battery via the ignition switch

A Passes on B comes from C is stored in D forms part of

The starter motor is energized _ a key-operated starter switch

A make use of B help through C as a means of D by means of

III Dịch những câu sau sang tiếng Việt:

1 In the case of diesel and dual-fuel engines, the cylinder charge, after being compressed, must be hot enough to ig- nite the oil fuel when it is injected at the top center

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3 The Bendix drive provides an automatic means of engag- ing the drive pinion with the flywheel ring gear for cranking the engine and for automatic disengagement of the starter pinion after the engine starts

4 One end of the sleeve is bolted to the Bendix drive spring, while the other end of the drive spring is keyed and bolted to the armature shaft through the drive head to anchor the assembly in place

5 The overrunning clutch starter uses a shift lever which slides the clutch and drive pinion assembly along the starter ar- mature shaft so that it can be engaged and disengaged with the flywheel ring gear

6 When the switch is turned to the “start” position, the mag- netic winding becomes connected to the battery so that the magnetic switches are operated and the circuit between the battery and the starter is completed

Ill Dịch những đoạn sau sang tiếng Việt:

The basic problems with the starter motor are as follows: the Starter motor fails to crank; the starter motor cranks slowly; the drive pinion clashes and grinds when being meshed with the flywheel ring gear

When you turn the ignition key to start and nothing happens, the first thing you probably think about is a dead battery You might be right, but before you check the battery, turn on the head- lights or dome light and try cranking If the lights do not come on, either the battery is dead ora connection is bad Check the con- nections at the battery, at the starter motor solenoid switch, and at the starter switch or relay If the lights go out as you try to crank, there may be a bad Connection at the battery The bad

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connection lets only a small current through-enough for the lights to go on But when you try to start, all the current goes to the starter motor because the motor has much less resistance than the lights Therefore, the lights go out Try wiggling the battery connections to see if this helps If the lights dim only slightly, the trouble probably is in the starter motor

If the starter motor cranks slowly and the engine does not start, the trouble is probably due to a discharged battery The battery does not have enough power to crank the engine fast enough for starting

LUYEN KY NANG ĐỤC HIẾU

Starting Motor

A reliable starting of the engine becomes possible when its crankshaft rotates at 60—80 rpm Such a speed is difficult to attain by manual cranking, therefore the engines are equipped with electric cranking motors called starting motors The starting or cranking motor itself is nothing but a device that converts elec- trical energy to mechanical energy in order to turn the engine over for starting The starter is a special type of electric motor designed to operate under great overloads and to produce high horsepower for its size However, the starter can only do this for a short period of time, since high current is necessary to operate the unit;this current flow creates considerable heat

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All starting motors are much the same in general design and operation, differing mainly in the type of drive mechanism used Basically, the starter motor consists of a housing, fields, arma- ture and brushes, end frames, and drive mechanism The starter housing, or frame, is a heavy cylindrical machined case that serves several functions This assembly encloses and protects the internal starter components from damage due to the entrance of moisture or other foreign materials In addition, the housing supports the field coils and forms a conducting path for the mag- netism produced by current passing through the coils Iron is a much better conductor of magnetic lines than air,

Field coils, along with their pole shoes, fit inside the iron starter housing or frame These components securely attach to the in- ner surface of this assembly by means of screws However, the field coils have a design that insulates them from the housing ‘but the coils connect to a terminal, protruding through the outer surface of the housing

The design of the field coils and pole pieces is such that they produce strong electromagnetic fields within the Starter itself, as current passes through the starter The field coils are formed by wrapping heavy insulated, flat copper strips around the pole shoes These Strips easily carry the heavy current flow needed for starting purpose

The field coils connect in series with armature winding through the starter brushes This design permits all the current passing through the field coil circuit also to flow through the armature windings

The armature is the only rotating component within the starter This device fits and operates between the drive and commutator end frames and the field windings When the starter is in opera-

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tions the current flowing through the armature produces a mag-

netic field in each of its conductors; the reaction between the

armature’s magnetic field and that produced by the field coils causes the armature to rotate

The armature itself consists of two main components (the armature windings and commutator) , which mount onto an ar-

mature shaft The armature windings are heavy, flat copper strips

instead of wire or cable, so that the windings can handle the heavy current flow The windings are made up of a number of coils of a single loop each The sides of these loops fit into slots within the armature core but are insulated from it Each slot con- tains the side of two coils

The coils connect to each other and to the commutator so that the current from the field coils tlows through all the armature windings at the same time This action creates a magnetic field around each armature winding, resulting in a repulsion force all around the conductor

The starting motor has two to six brushes These devices ride on the commutator segments; they carry the heavy current flow from the stationary field coils to the rotating armature wind-

ings via the commutator segments

The commutator end frame is a metal plate that bolts to the commutator end of the starter housing Depending on starter de- sign, this component has several functions In all cases, for ex-

ample, the end frame supports the commutator end of the arma- ture in a bushing Also, on many starter motors, the commutator

end frame also contains the holders that support the brushes

The drive housing, sometimes known as the drive end frame,

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this heavy iron component contains the mounting flange by which the starter motor attaches to the engine

To crank the engine, the starter has a drive for engaging the drive pinion of the starter with the flywheel ring gear The starter is cut in by the ignition switch The operating principle of the starter is based on the interaction between the magnetic fields induced in the field and armature windings when electric current is passed through them

The starter drive must engage the drive pinion with the fly- wheel only during starting of the engine After the engine starts, the pinion should be immediately disengaged from the flywheel ring gear, otherwise the latter will spin the drive pinion with a high speed and the armature winding turns may fly out of the slots under the effect of the centrifugal force

The automobile starters are remote-contralled and solenoid- operated The starter drive includes a solenoid relay, a solenoid with a pull-in winding and a hold-in winding, a shift lever, a spring, a splined sleeve and an overrunning clutch The pull-in winding is in series with the armature winding, while the hold-in winding is parallel with it

The overrunning clutch includes a driving sleeve sliding along the shaft splines and a driven sleeve with pinion and four wedge- shaped recesses The recesses accommodate rollers with spring and plungers When the driving sleeve starts rotating the rollers move into the narrow portion of the recesses and jam between the driving and driven sleeves If the driven sleeve is rotated

faster than the driving one, the rollers move to the wider portion

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ‘16 17 —— GHI CHÚ electric cranking motors nothing but

_ in between of at least 2 minutes _ dissipate into the air

other foreign materials electromagnetic fields armature windings

_ resulting in a repulsion force commutator segments

stationary field coils drive end frame

drive pinion of the starter flywheel ring gear

pull-in winding hold-in winding

wedge-shaped recesses

When the starter is in operation, the current flowing

causes the armature to rotate

18 After the engine starts, the pinion should be immediately

disengaged from the flywheel ring gear, otherwise the latter will

spin the drive pinion with a high speed and the armature winding

turns may fly out of the slots under the effect of the centrifugal

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UNIT FIFTEEN Automotive Chassis

Before we begin our studies of the chassis unit, we might take a quick look at the complete automobile it is made up of five basic parts, or components:

(1) The power plant or engine, which is the source of power that makes the car wheels rotate and the car move (This includes the electric, fuel, cooling, and lubricating systems.)

(2) The frame, which supports the engine, wheels, and body (3) The power train, which carries the power from the engine to the car wheels and which consists of the clutch, transmission, propeller shaft, differential, and gxles

(4) The car body

(5) The car-body accessories, which include the heater, lights, radio, windshield wiper, convertible-top raiser, and so on

Chassis, this french term was initially used to denote the frame part or main structure of a vehicle It is now extensively used to denote the complete vehicle except the body for the heavy ve- hicles having a separate body For light vehicles of mono con- struction types having body integral with the frame, it denotes the whole car excluding the additional fitment inside the body

All the major unit required,to propel the vehicle, direct its motion, stop it as well as permit to run smoothly over varying

road surface is known as chassis It is the main mounting for all

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car-riage unit and includs the instrument panel, hood and the cowl section sometimes as in case of a truck chassis It is the main machine portion l† includes the following components: (1 )Frame (2)Front suspension (3) steering mechanism (4) Wheels, axles, springs and shock absorbers (5)Engine, clutch and gear box (6)Pro-peller shaft (7)Radiator (8)Differential, half shaft and uni- versal joint (9)Brakes and braking system (10)Fuel tanks, petrol and hydraulic pipes, brake shafts and cables (11) Storage bat- tery (l2)Silencer (13)Car body (14)Car body accessories like

heater, lights, radio, windshield wiper, convertible raiser etc The chassis in general is equipped with a \|-beam construc- tion front axle For a good chassis design and for its good perfor- mances it must have fast pickup, strength, safety, durability, dependability, ease of control, quietness, speed, power, acces- sibility, economy of operation, low centre of gravity, stability, load clearance, braking ability, good springing, simplicity of lubrica- tion etc

Various components of the motor vehicle, i.e.engine, car body, wheels etc are required to be supported These are SUP- ported ona rigid structure providing a skeleton to hold the com- ponents together A separate chassis usually composed of steel girders of channel or box section with welded cross members and body supports is generally used

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power assembly and transmission, the engine is connected to the clutch and transmission which are futher connected to final drive gears ttrough the propeller shafts and tmiversal joints They are enclosed in a housing bolted to the rear axle spring attached to the frame through the rear springs The chassis frame and the mits attached to it are suctxwted on the wheels and tyre assem- blies through front and rear suspension systeiim without abnor- mally raising the frame or transmitting shocks to the frame due to road irregularitles

A chassis in general is required to carry the weight of the vehicle and its passengers ;to withstand the engine and trans- mission torques thrust, accelerating and braking torque; to resist the effect of centrifugal forces ten car -noting a curve; and to withstand bending and twisting stresses due to the fluctuating of rear and front axles For these purposes the chassis frame is made up of two side members constructed either of charnel or boxsettiofls and welded or riveted to the horizontal members To permit sufficient movement of the steering wheels, the frames taper inwards at the front or the taper starting at the rear runs for the full length of the vehicle To allow for the vertical movement of the rear axles, the side members also sweep upwards

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In comparison to heavier solid rectangular sections, a slightly deeper or box section provides the same resistance to bending The main factor governing the strength of the tubular section is the distance between the top com-pression member and the lower tension member For drilling a hole in the chassis frame either to reduce the weight or attach some component to it, it should be located in a low-stress region or thé neutral axis To avoid break- ing of a beam at the centre due to the stress being greatest at this point, the beam should be provided either the same deep section throughout or a varying depth sections in comparison to stress

The design of the frame should be such as to give clear- ance for bump movement of axles and steering movement of the front wheels for which the pressed steel channel section side members are up swept over the axles and inswept at the front By varying the depths of the section according to the stress re- quirements, the bending of the side members can be resisted

A cruciform or X type bracing riveted to plate at the centre is used to prevent the lozenging of the frame But this type of frame is weak in torsion and has to take up many stresses resulting in cracking of certain body panels, rattling and movement between door and pillar

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bending 7 uén cong torsion n sự xoắn comparatively ad s0 với rectangular a hình chữ nhật neutral 4 trung hòa bump ñ sự va đập cruciform a dạng chữ thập bracing n gia cường thâm

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CHU THICH RAI KHOA

For light vehicles of mono construction types having body integral with the frame, it denotes the whole car excluding the additional fitment inside the body

Đối với các xe vận tải nhẹ với các kiểu cấu tạo đơn giản có

phần thân gắn liền với khung xe, nó chỉ ra rằng toàn bộ xe loại

trừ phần thiết bị thêm vào đều ở bên trong xe

To avoid breaking of a beam at the centre due to the stress being greatest at this point, the beam should be provided either same deep section throughout or a varying depth sections in comparison to stress

Để tránh gãy một thanh tại tâm do lực nén vượt lên cao, tại điểm này thanh phải được chế tạo sao cho hoặc có cùng mặi cắt hoặc các mặt cắt thay đổi theo lực nén

being greatest at this point cao nhất tại điểm này

DÑI TP

I Dich những cụm từ sau sang tiếng Việt:

a in addition to resisting the distorting forces the design of chassis frame

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7 consist of two longitudinal or side members 8 connect the spring and running boards 9 oncross-members of the frame

10 protect the body from engine vibrations

II Tìm 1 từ thích hợp nhất với định nghĩa trong 4 từ được cho dưới

đây:

1 framework of a vehicle without a body and finders A mounting B chassis

C driver’s cabin D wagon

2 portion of body between engine compartmeni and driver, which ordinarily contains instruments used by operator

A cowl B cab

C carrage D coach

3 Aconnection for transmitting power from a driving to a driven shaft through an angle

A clutch B differential

C universal joint D release mechanism

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A strong beam, usually of iron or steel, which supports the smaller beams

A bracing B girder C channel bar D panel

Il Dich nhifng cau sau sang tiéng Viét:

1 This frame construction, nowadays used in most of the motor cars is sometimes known as chassisless, unitary, mono- coque or integral construction

The frame is extremely rigid and strong so that it can with- stand the shock blows, twists, vibrations, and other strains to which it is put on the road

If the frame absorbs part of the forces resulting from a front- End collision, then these absorbed forces will not be car- ried tc the passengers

The structure is also free from shake on rough roads, an increased life of door locks, hinges and many other small parts along with a reduced body rattle

The stress taken by the panel affects the thickness of the material of structural members like sills, rails and pillars which are about 1.1 mm thick with panneis like roof of 0 9 mm thickness

The cost of major repairs to the body of an integral chassis construction vehicle is quite high although the shock to the passengers is reduced due to absorption of collision impact

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IV Dịch đoạn văn sau sang tiếng Việt:

The car wheels are suspended on springs that support the weight of the vehicle The springs absorb road shock as the wheels encounter holes or bumps and prevent, to a large extent, any consequent jarring action or up-and-down motion from be- ing carried through the frame and body Springs are coil type, leaf type, torsion bar or rod or air suspension The coil spring is a heavy steel coil The weight of the frame and body puts an initial compression on the spring The spring will further compress when the wheel passes over an obstruction in the road

The leaf spring has been made in a number of forms, but the one that has been most commonly used is the semielliptical type The leaf spring is made up of a series of flat plates, or leaves, of graduated length, one on top of another The spring assembly acts as a flexible beam and is usually fastened at the two ends to the car frame and at the center to the wheel axle some cars have used only one leaf spring at the rear and one at the front, each spring supporting two wheels With this design, the center of the spring is attached to the frame, and each end of the spring supports a wheel.The action is similar on all leaf springs When the wheel encounters a bump, the spring bends up-ward to ab- sorb the blow When the wheel drops into a hole, the spring bends downward Thus, the leaf spring does the same job as the coil spring in the vehicle

LUYEN KY NANG DOC HIEU

Type of classis Frames

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are used It suppots the engine body, wheels arid power train members It is made of box tubular and channel members care- fully shaped, welded or riveted together It is reinforced by cross members and made extremely rigid and strong to withstand shock blows, twists, vibrations and other strains of the road In order to make the motor evhicle safer to drive, frames have been re- designed in recent years to absorb crash force resulting from a front-end collision Holes and notches are provided in the frame and part of the collision forces absorbed causes collapse of front end of the frame without allowing the forces to be carried to the passengers Similarly to prevent noise and vibration in herent in the engine operation from passing to the engine frame and thence to the occupants of the car, the engine is insulated from the frame by certain type of rubber pad or washer at the end point of sup- port (which may be three or four)

Two rubber mountings at the front and a singie, long, narrow rubber mounting pad is provided at the rear Further to avoid metal to metal contact, engine mounting lugs are inserted in the rubber and the mounting bolts are passed through them There are in general two common types of chassis frame construc- tions-the conventional frame construction and integral or frameless construction

in conventional frame construction, generally the power unit of a motor vehicle is connected with the transmission The struc- tural frame fitted to the axles through the suspension system carries the power unit The body and the cables are jointed to the frame by means of bolts and nuts or by welding

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Chassis, a french term was initially used to denote the frame part or main structure of a vehicle It is now extensively used to denote the complete vehicie except the body for heavy vehicle with separate body For light vehicles of mono construction types having body integral with the frame, it denotes the whole car excluding the additional fitment in side the body

For making a motor vehicle to be self-propelling unit for mov- ing safely on the road the power unit, transmission system, steer- ing and brakes are included in the vehicle These units com- bined together are known as the chassis

The height of the chassis is increased or decreased depend- ing upon the techniques of mounting the chassis frame to the axle At the ends of the axles, suitable tyres and wheels are fitted for moving it on the road

The chassis frame is used on most of the vehicles except the light vehicles and certain special vehicles For different types of vehicles, the constructional details are different and varying

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In case the chassis frame construction is to be used for cars, it is tapered in at the front to provide sufficient steering lock and swept upwards at the rear for providing axle clearance

For forming the structure of the automobile it is fitted to ax- les It is manufactured and fabricated separately Plain rectan- gular shaped chassis frames were the earliest to be used on motor vehicles Two length of side members having channel or shallow U-section steel are used to construct them Cross mem- bers of similar section or tubular section are used to reinforce and inter connect the length of side member On heavy motor vehicles, these chassis frame having cross members either bolted or riveted to the side members for easy removal or dismantling are used In this form they are also known as built-up chassis frame

On light and faster vehicles, due to the higher load speeds, built-up type are unfit to use as such Certain modifications are required to be carried in them An inswept is provided to the frame by keeping the front ends of the side members closer to each other between the front wheels This modification helps to make steering easy and efficient by providing a wider steering lock for turning the front wheels

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purpose this chassis frame was further modified The modified form known as cruciform bracing type has the flanges running along inside the channels of the side members forming a box section The cross members were fabricated from two long chan- nel section bars shaped into a wide V At the apexes they were fastened together by means of plates riveted or welded to the upper and lower flanges

The ends of the side members were attached to the either by a weld or rivet joint along with gusset plates or reinforcement plates in between to the side members

For commercial vehicles with relatively low volume produc- tion it has advantages of strong chassis of small proportional weight sufficient to carry the considerable pay loads, provision for fitting a variety of bodies to the same chassis, localised acci- dent damage which is easy to repair in comparison to the inte- gral chassis further by using two size of chassis and detailed alteration propeller shaft controls etc both long and short wheel base version of the same vehicle can be produced (HI CHÚ 1 power train members front-end collision rubber mountings engine mounting lugs

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8 in case

9 plain rectangular shaped chassis frames 10 shallow U-section steel

11 built-up chassis frame 12 as such

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UNIT SIXTEEN

The Clutches

A clutch is a friction device used to connect and discon- nect a driving force from a driven member In automotive ap- plications, it is used in conjunction with an engine flywheel to provide smooth engagement and disengagement of the en- gine and manual transmission

Since an internal combustion engine develops little power or torque at low rpm, it must gain speed before it will move the vehicle However, if a rapidly rotating engine is suddenly con- nected to the drive line of a stationary vehicle, a violent shock will result

So gradual application of load, along with some slowing of engine speed, is needed to provide reasonable and comfortable starts In vehicles equipped with a manual transmission, this is accomplished by means of a mechanical clutch

The clutch utilizes friction for its operation The main parts of the clutch are a pressure plate, and a driven disk The pressure plate is coupled with the flywheel, while the driven disk is fitted to the transmission input shaft The pressure plate is pressed to the disk by the springs so that the torque is transmitted owing to friction forces from the engine to the input shaft of the transmis- sion Smooth engagement is ensured by slipping of the disk be- fore a full pressure is applied

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plate and driven disks are dry in contrast to oil-bath clutches in which the plate and disks operate in a bath of oil It is called “springloaded” because the pressure plate and the driven disk are always pressed to each other by springs and are released only for a time to shift gears or to brake the automobile

In addition to the plate and disk, the clutch includes a cover, release levers, a release yoke, pressure springs and a control linkage The clutch cover is a steel stamping bolted to the fly- wheel The release levers are secured in-side the cover on the supporting bolts The outer ends of the release levers are articu- lated to the pressure plate Sucha construction allows the pres- sure plate to approach the cover or move away from it., all the time rotating with the flywheel The springs spaced around the circumference between the pressure plate and the clutch cover clamp the driven disk between the pressure plate and the fly- wheel

The springs are installed with the aid of projections and sock- ets provided on the cover and pressure plate The pressure plate sockets have thermal-insulation gaskets for protecting the springs against overheating

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support assembly is shifted back by the return spring thus releas- ing the release levers so that the pressure plate is forced by its springs towards the flywheel to clamp the driven disk and en- gage the clutch (Fig 14)

Fig 14 Clutch release mechanism

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housing accommodates pneumatic, hydraulic and servo plung- ers, When the clutch pedal is pushed, the fluid pressure from the main cylinder is transmitted through the pipelines and hoses to the hydraulic and servo plungers of the pneumatic booster

The servo arrangement is intended for automatic change of the air pressure in the pneumatic cylinder proportionally to the force applied to the pedal The plunger moves with the dia- phragm, the outlet valve closes and the inlet valve opens thus admitting the compressed air to the Pneumatic plunger piston The forces created by the pneu-matic and hydraulic plungers are added together and are applied through the push rod to the release yoke shaft lever, the lever turns the shaft and the re- lease yoke, thus disengaging the clutch After the clutch pedal is released, the outlet valve opens and the inlet closes Under the action of the springs the pistons return the plungers to the initial position and the air from the cylinder is let out to the atmosphere Automatic clutches were used in certain U S and European cars American Motors’ “E-Stick” clutch eliminated the need for physical operation of the clutch pedal A German car maker en- gineered an automatic clutch system called “Hydrak”, which con- sisted of a fluid flywheel con-nected to a single, dry disk clutch

In the “E-Stick” set up, the pressure plate levers “engage”the clutch disk rather than”release” them Also, the clutch remains disengaged until a servo unit is applied by oil pressure when the shift lever is placed “in gear” with the engine running

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device controls engagement of the mechanical clutch, depend- ing on whether the rear axle is in traction or is pushed by car momentum

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hydraulically ad pedal n depress ví booster n hose n servo ñ proportionally ad initial a European a.; n physical a engineer vt., ; 7 setup n bridge vt traction n momentum n roller n vedge vt in conjunction with 1 2 along 3 pressure plate 4 be coupled with 5 be fitted to 6 owing to 7 thuộc thủy lực bàn đạp Ấn xuống, ép xylanh trợ lực ống dẫn bằng cao su hay vật liệu déo phần trợ lực cân xứng, tỉ lệ

ban đầu đầu (thuậc) Châu Âu thuộc vật lý thiết kế, Kỹ sư SỰ đưa ra, sự tạo dựng bắt, nối Sự lôi, sự kéo xung lượng, động lượng con lăn

chèn vào, nên, chêm

CUM TU VA THANH NGU _ ————— ee

liên kết với

the0, cùng với, song Song với đĩa ép

được ghép với, được nối với

được ăn khóp với

nhờ có, do bởi

8 dry Spring - loaded clutch l hợp được tải lò xo khô, ly hợp ma sát

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8 in contrast to để tương phản với 9 a release yoke gdp điều khiển

10 control linkage cần điều khiển

11 with the aid of Với sự trợ giúp của 12 thermal-insuation gasket đệm kín cách nhiệt 13 let out ra ngoài

CHU THICH RAI KHOA

The pressure plate is pressed to the disk by the springs so that the torque is transmitted owing to friction forces from the engine to the input shaft of the transmission

Địa ép bị ép vào đĩa ma sát bởi các lò xo để momen xoắn

được truyền nhờ có lực ma sát từ động cơ đến trục sơ cấp của

hộp số

transmit from to truyền từ đến

The springs spaced around the circumference between the pressure plate and the clutch cover clamp the driven disk be- tween the pressure plate and the flywheel

Các lò xo được đặi cách nhau xung quanh đường tròn giữa đĩa ép và kẹp vỏ ly hợp đĩa bị động giữa địa ép và bánh đà

spaced around được đặt xung quanh

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Khi tốc độ động cơ tang lên các con lăn chèn vào các chỗ của chúng giữa đa ép và vỏ ly hợp để ly hợp xoay càng nhanh thì lực ép đã dùng ở đĩa ép và đĩa ma sát càng lón the faste the greater càng nhanh càng lón ĐI TẬP

I Bịch những cum tw sau sang tiếng Việt:

1 transmit maximum torque of the engine without the occurrence of sudden jerks be able to engage gradually and positively in case of high speed vehicle clutches the noise produced during the transmission

2 3 4 5

6 occupy minimum amount of space 7 reduce effective clampling load 8 the power developed by the engine 9 avoid damage to the transmission

10 be fitted, between the engine and the gear-box

lÏ Chon 1 ti phil hop nhat dé hoan thanh các câu sau:

1 To drive the wheels of the automobile the power developed

by the engine must _to them

A transmit B be transmitted