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1、Automobile Steering System 汽车转向系统Unit 8Passage APassage Al Has the most significant influence on vehicle Has the most significant influence on vehicle performance and reliability.performance and reliability.l Includes: Includes: steering wheelsteering wheel, , steering gearssteering gears, , linkage
2、slinkages, and other components, used to control the , and other components, used to control the direction of a vehicles motion.direction of a vehicles motion.l Two different types of steering gear: Two different types of steering gear: rack-and-rack-and-pinionpinion and and recirculating-ball steer
3、ing gears.recirculating-ball steering gears.Steering system Passage APassage ARack-and-pinion SteeringPassage APassage AlPretty simple mechanism.Pretty simple mechanism.lThe most common type of compact car, small truck The most common type of compact car, small truck and SUV in which the engine comp
4、artment space is and SUV in which the engine compartment space is limited.limited.lWhat are the basic parts of this system?What are the basic parts of this system? Steering wheelSteering wheel, , pinion gearpinion gear, , rackrack and and linkagelinkage. .http:/ APassage ARack-and-pinion SteeringPas
5、sage APassage Al The steering wheel and steering The steering wheel and steering shaft are connected to a shaft are connected to a pinion pinion geargear. The pinion gear is . The pinion gear is in mesh in mesh with with a straight bar, called a a straight bar, called a rackrack that has teeth on on
6、e side. When that has teeth on one side. When the driver turns the steering wheel, the driver turns the steering wheel, the pinion gears turns, causing the the pinion gears turns, causing the rack to move. This movement, in rack to move. This movement, in turn, is connected to a turn, is connected t
7、o a linkagelinkage that moves the front wheelsthat moves the front wheelshttp:/ APassage ARack-and-pinion SteeringPassage APassage AlThe steering linkage consists of two The steering linkage consists of two inner tie rods and two tie rod ends. inner tie rods and two tie rod ends. The former two are
8、attached to the The former two are attached to the steering rack ends, and the latter steering rack ends, and the latter two are attached to the suspension two are attached to the suspension arms on the steering knuckles.arms on the steering knuckles.lRubber boots are used to cover and Rubber boots
9、are used to cover and protect the inner tie rod assemblies protect the inner tie rod assemblies from road from road splashsplash. .lThe The exploded view exploded view of the system is of the system is shown in right figure.shown in right figure.http:/ APassage ARack-and-pinion SteeringPassage APass
10、age AlIt converts the rotational motion of the steering It converts the rotational motion of the steering wheel into the linear motion needed to turn the wheel into the linear motion needed to turn the wheels.wheels.lIt provides a gear reduction, making it easier to turn It provides a gear reduction
11、, making it easier to turn the wheels.the wheels.Two functions On most cars, it takes three to four complete On most cars, it takes three to four complete revolutionsrevolutions of the steering wheel to make the wheels of the steering wheel to make the wheels turn from lock to lock (from turn from l
12、ock to lock (from far left far left to to far rightfar right) )Passage APassage ARecirculating-ball steeringPassage APassage AlThe disadvantage of the rack-and-pinion system is: The disadvantage of the rack-and-pinion system is: As to the larger and heavier the car, the more difficult As to the larg
13、er and heavier the car, the more difficult it is to steer.it is to steer.lMost large cars are equipped with a Most large cars are equipped with a recirculatingrecirculating- -ballball steering gear, this type of steering gear is very steering gear, this type of steering gear is very low in friction
14、and provides a good mechanical low in friction and provides a good mechanical advantage for a heavy vehicle. advantage for a heavy vehicle. Passage APassage ARecirculating-ball steeringPassage APassage Ahttp:/ A worm gear worm gear is mounted on the is mounted on the end of the steering gear shaft.
15、end of the steering gear shaft. And a And a pitman shaft pitman shaft is mounted is mounted in the housing in a position 90in the housing in a position 90to to the worm gear.the worm gear.lA A ball nut ball nut rides on the worm rides on the worm gear and a gear on the pitman gear and a gear on the
16、pitman shaft, called shaft, called the sectorthe sector, is , is engaged with this nut.engaged with this nut.lThe The steering shaft steering shaft is connected to the is connected to the steering wheel steering wheel either directly or through some type of flexible joint.either directly or through
17、some type of flexible joint.Passage APassage ARecirculating-ball steeringPassage APassage Ahttp:/ lThe recirculating-ball construction results in a friction-free The recirculating-ball construction results in a friction-free contact between the nut and the worm. When the steering contact between the
18、 nut and the worm. When the steering wheel is turned to the left, the ball bearings roll between the wheel is turned to the left, the ball bearings roll between the worm and the nut and work their way upward in the worm worm and the nut and work their way upward in the worm groove. groove. l lWhen t
19、he ball bearings reach the top When the ball bearings reach the top of the nut, they enter two ball guides of the nut, they enter two ball guides and are directed down-ward into the and are directed down-ward into the worm groove at a lower point. When worm groove at a lower point. When the steering
20、 wheel is turned to the the steering wheel is turned to the right, the ball bearings circulate in the right, the ball bearings circulate in the opposite direction.opposite direction.Passage APassage ANew words （生词）22.22. Performance Performance23.23. Reliability Reliability24.24. Linkage Linkage25.2
21、5. Rack Rack26.26. Splash Splash27.27. Pitman Pitman28.28. Bushing Bushing29.29. Sector Sector30.30. Thread Thread31.31. Tapered Tapered32.32. Steering wheel Steering wheel33.33. Steering shaft Steering shaft34.34. Steering gear Steering gear35.35. Steering arm Steering arm36.36. Tie rod Tie rod37.3
22、7. Mechanical advantage Mechanical advantage38.38. Flexible joint Flexible joint39.39. Needle bearing Needle bearing40.40. Roller bearing Roller bearing41.41. Ball guide Ball guidePassage APassage AClassworkPage 89, Paragraph 2-3Passage BPassage BPower SteeringlPower steering in a Power steering in
23、a recirculatingrecirculating-ball system works -ball system works similarly to a rack-and-pinion system. A power-similarly to a rack-and-pinion system. A power-steering system should assist the driver only when steering system should assist the driver only when he is exerting force on the steering w
24、heel. When he is exerting force on the steering wheel. When the driver is not exerting force, the system shouldnt the driver is not exerting force, the system shouldnt provide any assist. provide any assist. Passage BPassage BPower SteeringlProvides the hydraulic power for the steering by a Provides
25、 the hydraulic power for the steering by a rotary-vane pumprotary-vane pump. .lDriven by the cars engine Driven by the cars engine viavia a belt and pulley. a belt and pulley.lContains a set of Contains a set of retractableretractable vanes that spin inside vanes that spin inside an an oval chambero
26、val chamber. .lThe amount of fluid provided by the pump depends The amount of fluid provided by the pump depends on the cars engine speed. So the adequate flow on the cars engine speed. So the adequate flow must be provided even the engine is in idling. As a must be provided even the engine is in id
27、ling. As a result, the pump result, the pump provides more fluid than provides more fluid than necessary when the engine is running at faster necessary when the engine is running at faster speeds.speeds.PumpPassage BPassage BPower SteeringlThe device senses the force on the steering wheel.The device
28、 senses the force on the steering wheel.lThe key to it is The key to it is a torsion bara torsion bar. .lThe top of the bar is connected to the steering wheel, The top of the bar is connected to the steering wheel, and the bottom of the bar is connected to the pinion or and the bottom of the bar is
29、connected to the pinion or worm gear.worm gear.lWhen the steering wheel is not being turned, both When the steering wheel is not being turned, both hydraulic lines provide the hydraulic lines provide the samesame amount of pressure amount of pressure to the steering gear. But if the to the steering
30、gear. But if the spool valve spool valve is turned is turned one way or the other, ports open up to provide high-one way or the other, ports open up to provide high-pressure fluid to the appropriate line.pressure fluid to the appropriate line.Rotary valvePassage BPassage BPower SteeringlSince the po
31、wer-steering pump runs constantly, Since the power-steering pump runs constantly, pumping fluid all the time, it wastes horsepower. This pumping fluid all the time, it wastes horsepower. This results in results in reducing fuel economyreducing fuel economy. .lSeveral Several innovationsinnovations t
32、hat will improve fuel economy, that will improve fuel economy, such as the “steer-by-wire” or “drive-by-wire” system.such as the “steer-by-wire” or “drive-by-wire” system.lThis system completely eliminate the This system completely eliminate the mechanical mechanical connectionconnection in steering
33、 system, replacing it with a in steering system, replacing it with a purely electronic control system. (EPS)purely electronic control system. (EPS)lThis development can This development can free up free up space in the engine space in the engine compartment by eliminating the steering shaft. And it
34、compartment by eliminating the steering shaft. And it can also can also reduce vibration reduce vibration inside the car.inside the car.The future/development of power steering Passage APassage ANew words （生词）1.1. Assist Assist2.2. Exert Exert3.3. Pulley Pulley4.4. Retractable Retractable5.5. Vane V
35、ane6.6. Oval Oval7.7. Adequate Adequate8.8. Innovation Innovation9.9. Motorize Motorize10.10. Feedback Feedback11.11. Decade Decade12.12. Power steering Power steering13.13. Rotary vane pump Rotary vane pump14.14. Hydraulic fluid Hydraulic fluid15.15. Pressure-relief valve Pressure-relief valve16.16
36、. Rotary valve Rotary valve17.17. Torsion bar Torsion bar18.18. Spool-valve assembly Spool-valve assembly19.19. Drawing board Drawing board20.20. Steer-by-wire system Steer-by-wire system21.21. Drive-by-wire system Drive-by-wire system西华大学XIHUA UNIVERSITYXIHUA UNIVERSITY交通与汽车工程学院交通与汽车工程学院Faculty of
37、Faculty of Transportation and Transportation and Automotive EngineeringAutomotive Engineering Homework1.Review the new words and expressions2.Exercise 3,4,5西华大学XIHUA UNIVERSITYXIHUA UNIVERSITY交通与汽车工程学院交通与汽车工程学院Faculty of Faculty of Transportation and Transportation and Automotive EngineeringAutomotive Engineering Thanks
