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Automobile Steering System Passage A Steering System The steering system is one of those having the most significant influence on vehicle performance and reliability . Steering system including steering wheel , steering gears , linkages ,and other components is used to control the direction of a vehicle?s motion . There are a couple of different types of steering gears. The most common ones are rack-and-pinion and recirculating-ball steering gears. Rack-and-pinion Steering Rack-and-pinion steering is quickly becoming the most common type of steering on compact car , small truck and SUV in which the engine compartment space is limited. It is actually a pretty simple mechanism. The basic parts of a rack-and-pinion steering gear are shown in Fig.8-1. The steering wheel and steering shaft are connected to a pinion gear. The pinion gear is in mesh with a straight bar, called a rack that has teeth on one side. When the driver turns the steering wheel, the pinion gear turns, causing the rack to move. This movement, in turn, is connected to a linkage that moves the front wheels. The steering linkage consists of two inner tie rods and two tie rod ends. The inner tie rod ends are attached to the steering rack ends. The outer tie rod ends are attached to the suspension arms on the steering knuckles. Rubber boots are used to cover and protect the inner tie rod assemblies from road splash. An exploded view of the rack-and ?pinion steering system is shown in Fig.8-2. The pinion gear is attached to the steering shaft. When you turn the steering wheel, the gear spins, moving the rack. The tie rod at each end of the rack connects to the steering arm on the spindle. The rack-and-pinion gear-set does two things:It converts the rotational motion of the steering wheel into the linear motion needed to turn the wheels.It provides a gear reduction, making it e. Rack-and-pinion Steering Rack-and-pinion steering is quickly becoming the most common type of steering on compact car , small truck and SUV in which the engine compartment space is limited. It is actually a pretty simple mechanism. The basic parts of a rack-and-pinion steering gear are shown in Fig.8-1. The steering wheel and steering shaft are connected to a pinion gear. The pinion gear is in mesh with a straight bar, called a rack that has teeth on one side. When the driver turns the steering wheel, the pinion gear turns, causing the rack to move. This movement, in turn, is connected to a linkage that moves the front wheels. The steering linkage consists of two inner tie rods and two tie rod ends. The inner tie rod ends are attached to the steering rack ends. The outer tie rod ends are attached to the suspension arms on the steering knuckles. Rubber boots are used to cover and protect the inner tie rod assemblies from road splash. An exploded view of the rack-and ?pinion steering system is shown in Fig.8-2. The pinion gear is attached to the steering shaft. When you turn the steering wheel, the gear spins, moving the rack. The tie rod at

each end of the rack connects to the steering arm on the spindle. The rack-and-pinion gear-set does two things:It converts the rotational motion of the steering wheel into the linear motion needed to turn the wheels.It provides a gear reduction, making it easier to turn the wheels.On most cars, it takes three to four complete revolutions of the steering wheel to make the wheels turn from lock to lock (from far left to far right ).Recirculating-ball Steering Recirculating-ball steering is used on many trucks and SUVs today. The linkage that turns the wheels is slightly different then on a rack-and-pinion system. The larger and heavier the car, the more difficult it is to steer. Most large cars are equipped with a recirculating-ball steering gear. This type of steering gear is very low in friction and provides a good mechanical advantage for a heavy vehicle. The recirculating-ball steering gear consists of several parts contained in a steering gear housing. The steering gear shaft is connected to the steering wheel either directly or through some type of flexible joint. There is a worm gear on the end of the steering gear shaft. A pitman shaft is mounted in the housing in a position 90 to the worm gear. A ball nut rides on the worm gear and a gear on the pitman shaft, called the sector, is engaged with this nut. See Fig.8-3.Ball or roller bearings are used to support both ends of the worm gear and are adjustable to remove end or side play from the worm gear. The pitman shaft is supported by bushings, needle bearings, or a combination of the two, and provision is made to control the worm and pitman shaft clearance. All parts are enclosed in a cast housing that is partly filled with lubricant. Seals are used to prevent the entry of dirt or the loss of lubricant. Provision is made to bolt the steering gear housing to a rigid area, usually the frame. See Fig8-4.The ball nut has internal threads that are meshed to the threads of the worm with continuous rows of ball bearings are re-circulated through two outside loops, called ball guides.The sliding ball nut has tapered teeth cut on one face that mate with teeth on the sector. As the steering wheel is rotated, the nut is moved up or down on the worm. Because teeth on the nut are meshed with the teeth on the sector shaft to rotate and swing the steering linkage connected to it. See Fig.8-5.The recirculating-ball construction results in a friction-free contact between the nut and the worm. When the steering wheel is turned to the left, the ball bearings roll between the worm and the nut and work their way upward in the worm groove. When the ball bearings reach the top lf the nut, they enter two ball guides and are directed downward into the worm groove at a lower point. When the steering wheel is turned to the right, the ball bearings circulate in the opposite direction.Phrases and Expressions Steering system l?T?|

H a v e i n f l u e n c e o n ù[& . .

gq_íT S t e e r i n g w h e e l l?T?v

S t e e r i n g g e a r l?T:g R a c k - a n d - p i n i o n s t e e r i n g

? R e c i r u l a t i n g - b a l l ??n ??agl T ?:g…g

s t e e r i n g a_ˉs tl T ?:g…g? E n g i n e c o m p a r t m e n t ?S?R:g1? S t e e r i n g s h a f t l?Tt? P i n i o n g e a r \??n?

?;N¨R??n? S t e e r i n g l i n k a g e l?T O¨R:g…g T i e r o d *jébFg I n n e r t i e r o d e n d *jébFg…Q￥c4Y O u t e r t i e r o d e n d *jébFg Y￥c4Y S t e e r i n g a r m l?T?? L o c k t o l o c k ?l?T?v ?;`TVl?Wpe G e a r r e d u c t i o n ??n??Q-? M e c h a n i c a l a d v a n t a g e :g°hHeêv

S U V ( s p o r t u t i l i t y v e h i c l e ) Y(u?[?f?

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B a l l b e a r i n g tt??b E n d p l a y

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B a l l g u i d e a_ˉs tü[h? N e w W o r d s p e r f o r m a n c e n . '`y€

?Hey€ r e l i a b i l i t y n . ?S`?'` l i n k a g e n . `gFg:g…g

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?…?Y t h r e a d n . o?1~ l o o p n . ˉsTV?? t a p e r e d

a d j . %?SO…v E X E R C I S E 1 D e c i d e w h e t h e r t h e

f o l l o w i n

g s t a t e m e n t s a r e t r u e o r f a l s e

a c c o r d i n g t o t h e p a s s a g e . T h e s t e e r i n g

s y s t e m i s u s u a l l y u s e d t o c o n t r o l t h e

d i r

e c t i o n o

f a v e h i c l e s m o t i o n . W hen the driver

turns the steering wheel, the pinion gear turns, causing the linkage to move.We are completely sure that it takes three complete revolutions of the steering wheel to

make the wheels turn from far left to far right on most cars.Recirculating-ball steering is widely used on many trucks and SUVs, which provides a good mechanical advantage for heavy vehicle.The purpose of seals is to prevent the entry of dirt

or the loss of lubricant.When the steering wheel is turned to the left, the ball

bear i n g s c i r c u l a t e i n t h e o p p o s i t e

d i r

e c t i o n . E X E R C I S E 2 T r a n s l a t e t h e

f o l l o w i n

g p

h r a s e s

i n t o c h i n e s e o r

e n g l i s h . r a c k - a n d - p i n i o n

s t e e r i n g l?Tt? r e c i r c u l a t i n g - b a l l

s t e e r i n g l?T?v i n n e r t i e r o d e n d l?T?? o u t e r

t i e r o d e n d l?T:g m e c h a n i c a l

a d v a n t a g e l?T?| E X E R C I S E 3 F i l l in the blanks with the suitable words or phrases given below, changing the form where necessary. influence

upon, steering arm, steering wheel, ball nut, steering gear, move up and down,

consist of, rack-and-pinion steering 1. The steering system is one of those

having the most significant vehicle performance and reliability. 2. The converts the rotaty motion of the steering wheel into straight-line motion. 3. The is mounted on the upper end of the steering shaft. 4. The manual steering system steering wheel and column, a manual gearbox and pitman arm, etc. 5. The balls must

roll in the grooves inside the . 6. As the worm rotates, the balls cause

the nut to along the worm.7. The gear is used mostly on

smaller car.8. The movement is carried through the rods to the at the

front wheels.EXERCISE 4Match the following English phrases in Column A equivalents

in Column B. 1. steering wheel A. Dispositions of a vehicle are transferred to the

part that interacts with the external medium 2. worm gear B. a small cogwheel

that is engaged by a rack 3. roller bearing C. the toothed wheel of this gear;

a worm wheel 4. steering gear D. a wheel that controls steering, as in a vehicle 5.

pinion gear E. a system of interconnected machine elements, such as rods, springs,

and pivots 6. linkage F. a bearing to reduce friction between machine

parts EXERCISE 5Translate the chinses given in t h e b r a c k e t s i n t o

e n g l i s h 1 . S t e e r i n g s y s t e m m a i n l y

?è??N

i n c l u d e s ?l T?v 0l T:g 0`gFg:g…g?TvQ?N?

?. 2 . I n t h e p i t m a n a r m s y s t e m , t h e

m o v e m e n t i n s i d e t h e s t e e r i n g b o x ??Ol?TGd??t?êSl?TGd???el? ? 3 . T h e s t e e r i n g

l i n k a g e i s s o d e s i g n e d a s t o

?2?bk}lf?l??S?ef?n?§O?n ?. 4 . F o r t h e p e r s o n a l s a f e t y o f t h e d r i v e r a n d p a s s e n g e r s o f

\O(u ?. 5 .

t h e c a r , ?l T:gw @wí? ‰ (v)

T w o t y p e s o f s t e e r i n g s y s t e m s r e u s u a l l y u s e d o n c a r s : ?Kb¨Rl T?|?~?T?R?Rl T?|?~? P a s s a g e B p o w e r s t e e r i n g P o w e r s t e e r i n g i n a r e c i r c u l a t i n g - b a l l system works similarly to a rack-and-pinion system. A power- steering system should assist the driver only when he is exerting force on the steeringwheel (such as when starting

a turn). When the driver is not exerting force (such as when driving in a straight line ),the system shouldn?t provide any assist.There are a couple of key components in power steering in addition to the rack-and pioin or recirculating-ball mechanism. See Fig.8-6 Pump The hydraulic power for the steering is provided by a rotary-vane pump. See Fig. 8-7.This pump is driven by the car?s engine via a belt and pulley. It contains a retractable vanes that spin inside an oval chamber.As the vanes spin, they pull hydraulic fliud from the return line at low pressure and force

it into the outlet at high pressure. The amount of flow provided by the pump depends on the car?s engine speed. The pump mustprovided adequate flow when the engine is idling. As a result, the pump moves much more fluid than necessary when the engine

is running at faster speeds.The pump contains a pressure-relief valve to make sure that the pressure does not get too high, especially at high engine speeds when so much fluid is being pumped. Rotary Valve The device that senses the force on the steering wheel is called the rotary valve. The key to the rotary valve

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