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© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois.

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Presentation on theme: "© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois."— Presentation transcript:

1 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois by Russell Krick

2 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

3 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Functions of a steering system  Basic steering systems  Steering column assembly  Steering gear principles  Steering linkage (worm-type gearbox)  Manual rack-and-pinion steering (Continued)

4 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Integral-piston power steering system (linkage type)  External cylinder power steering (linkage type)  Power rack-and-pinion steering  Electronic steering assist  Four-wheel steering systems

5 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Provide precise control of the wheel direction  Maintain correct steering effort  Transmit road feel to the driver’s hands  Absorb most of the road shock going to the steering wheel  Allow for suspension action

6 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Two basic kinds of steering systems are in use today:  linkage (worm gear) steering systems  rack-and-pinion steering systems  Each may be operated manually or with power assist

7 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Steering Basic linkage steering Basic rack-and- pinion steering

8 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Consists of the steering wheel, steering shaft, column, ignition key mechanism, and sometimes, a flexible coupling and universal joint  Bolts to the underside of the dash  Sticks through the firewall and fastens to the steering gear

9 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Steering Column Components

10 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Locking Steering Wheel  When the ignition is off, the steering wheel cannot be turned  A rack and sector slide a steel pin into mesh with a slotted disc that is splined to the steering shaft  The pin locks the steering shaft to the column, preventing the steering wheel from being turned

11 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Locking Steering Wheel

12 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Collapsible Steering Column  Helps prevent driver chest and face injury during an auto accident  The column will crumple or slide together when forced forward during a collision  Several types are used:  steel mesh (crushing)  tube-and-ball (sliding)  shear capsule (break and slide)

13 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Collapsible Column Operation

14 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Tilt Steering Columns  A flex joint, or U-joint, allows the top half of the column and the steering wheel to be positioned at different angles  Manual tilt column  uses a lever on the steering column to unlock the flex joint so the wheel can be moved up and down

15 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Power Tilt Column  Uses a small electric motor, a control switch, and a gear mechanism to change the steering wheel angle or height  When the tilt switch is activated, current to the motor spins the small gears to move the steering column’s upper tube

16 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Memory Tilt Wheels  Use a tilt control module to “remember” more than one steering wheel position  A steering column sensor provides feedback so the module knows where the wheel is located  When the driver selects a switch position, the control module energizes the power tilt motor until the wheel has moved to the preprogrammed position

17 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Memory Tilt Wheel

18 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Power Tilt Gear Mechanism

19 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Two basic types of gear mechanisms are found in steering gearboxes:  worm gears  rack-and-pinion gears

20 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Gear Mechanisms

21 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Steering Gears Rack-and-pinion gear Worm steering gear

22 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Recirculating-Ball Gearbox  Normally used with a linkage steering system  Small steel balls circulate between the gear members to reduce friction

23 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Recirculating-Ball Gearbox

24 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Gearbox Components  Worm shaft  the input gear connected to the steering shaft  Sector shaft  the output gear from the steering gearbox  Ball nut  rides on the ball bearings and the worm gear

25 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Gearbox Components  Ball guides  route extra balls in and out from between the worm and ball nut  Adjusting nut  used to set worm shaft bearing preload  Adjusting screw  used to set the sector shaft clearance

26 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Gearbox Components

27 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Gearbox Ratio  Comparison between steering wheel rotation and sector shaft rotation  Ratios range from 15:1 to 24:1  Variable-ratio gearbox  changes the internal gear ratio as the wheels are turned away from center  Constant-ratio gearbox  has the same gear reduction from full left to full right

28 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Worm-and-Roller Steering Gearbox  Contains a roller that is mounted on the pinion shaft and meshes with the worm gear  The roller replaces the ball bearings and the ball nut used in the recirculating-ball gearbox

29 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Series of arms, rods, and ball sockets that connect the steering gearbox to the steering knuckles  Commonly called a parallelogram steering linkage

30 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Steering Linkage

31 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Steering Linkage  Pitman arm  transfers gearbox motion to the steering linkage  Center link (relay rod)  a steel bar that connects the right and left sides of the steering linkage

32 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Steering Linkage  Idler arm  supports the end of the center link on the passenger side  Tie-rod assemblies  fasten the center link to the steering knuckles  ball sockets are used on both ends  a toe adjustment sleeve allows length change for alignment

33 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Ball Sockets  Provide for motion in all directions between two connected parts  Some have a grease fitting, allowing lubrication  Others are sealed units  Used in pitman arms, idler arms, and tie-rods

34 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Ball Sockets A. Idler arm B. Tie-rod end C. Tie-rod inner end D. Tie-rod (rack- and-pinion)

35 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

36 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Rack-and-Pinion Steering

37 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Steering Gear  Consists of a pinion shaft, rack, thrust spring, bearings, seals, and a gear housing  Bolts to the frame or unibody structure  Rubber bushing mounts help absorb road shock

38 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Steering Gear

39 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Steering Gear  When the pinion shaft turns, the pinion gear acts on the rack gear  The rack slides sideways, moving the tie- rods and the front wheels

40 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Tie-Rod Assemblies  Connect the ends of the rack with the steering knuckles  Rubber dust boots fit over the inner ball sockets to keep out road dirt and water

41 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Power Steering Systems  Most systems use an engine-driven pump and a hydraulic system to assist steering action  An electric motor in the rack may be used to provide power assist

42 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Basic Power Steering

43 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Basic Operation  Pressure from the oil pump is used to operate a piston-and-cylinder assembly  When the control valve routes oil pressure into one end of the piston, the piston slides in its cylinder  Piston movement helps move steering system components

44 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Types of Power Steering  There are three main types of power steering systems:  integral-piston linkage system  rack-and-pinion system  external cylinder power steering system

45 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Integral-Piston Linkage

46 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Rack-and-Pinion

47 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only External Cylinder

48 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Power Rack-and-Pinion

49 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Power Steering Pump  Engine-driven pump that produces the hydraulic pressure for steering system operation  Driven by a belt or directly off the back of the camshaft  The power steering fluid reservoir may be formed as part of the body or as a separate container

50 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Pump and System

51 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Pump Types

52 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Slipper-Type Pump

53 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Vane-Type Pump Operation

54 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Pressure-Relief Valve  Used in a power steering system to control the maximum oil pressure  Prevents system damage by limiting pressure  A relief valve opens when the steering wheel is turned to the full-left or full- right position

55 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Pressure-Relief Valve

56 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Power Steering Hoses  High-pressure, hydraulic, rubber hoses that connect the power steering pump and the gearbox or power cylinder  One line serves as the pressure feed line  One line serves as a return line to the reservoir  Metal lines may be used where vibration or movement is not a problem

57 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  The hydraulic piston is mounted in the steering gearbox housing  System components:  power steering pump  hydraulic lines  integral power-assist gearbox

58 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Integral Power Steering Gearbox  Contains a conventional worm-and- sector gear, a hydraulic piston, and a flow-direction valve  Two valve designs are commonly used:  spool valve  rotary valve

59 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Spool Valve-Type Gear

60 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Spool Valve Operation  When the steering wheel is turned, the pivot lever moves the spool valve so pressure enters a power chamber  Pressure forces the power piston left or right, helping to turn the sector shaft  As the power piston strokes, oil from the other power chamber is vented through the spool valve back to the reservoir

61 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Rotary Valve Operation  Rotary valve-type steering boxes have a small torsion bar to detect steering wheel turning direction and turning effort  When the steering wheel is turned, the torsion bar twists and turns the rotary valve  Rotary valve directs pressure to the correct side of the power piston

62 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Integral Gear Operation Driving straight ahead

63 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Integral Gear Operation Right turn

64 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Integral Gear Operation Left turn

65 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  The power cylinder is commonly bolted to the frame and the center link  The control valve may be located in the gearbox or on the steering linkage

66 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only External Cylinder Power Steering

67 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Uses hydraulic pressure to assist the driver in moving the rack and the front wheels

68 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Power Rack-and- Pinion Steering

69 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Power Rack-and- Pinion Steering

70 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Power Cylinder and Piston  Power cylinder  precisely machined tube that accepts the power piston  Power piston  formed by attaching a hydraulic piston to the center of the rack  Routing oil pressure into either end of the power cylinder causes piston movement

71 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Power Rack-and- Pinion (Rotary Control Valve)

72 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Control Valves  Rotary control valve  operated by a torsion shaft connected to the pinion gear  Spool control valve  operated by the thrust action of the pinion shaft that occurs when the pinion gear is rotated against the rack gear

73 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Power Rack-and- Pinion (Spool Control Valve)

74 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only System Operation  When the steering wheel is turned, vehicle weight causes the front tires to resist turning, moving the control valve  Movement of the control valve aligns specific oil passages internally  Pump pressure forces oil through the control valve to the power cylinder  Pressure acts on the power piston, pushing the rack and the front wheels

75 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only High Speed Operation Little valve movement, low power assist

76 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Low Speed Operation More valve movement, high power assist

77 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Uses a small electric motor to help move the rack-and-pinion gearbox  The motor is mounted inside the rack housing and acts on the steering rack

78 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Electronic Assist Rack-and-Pinion Lighter and more compact than a hydraulic system

79 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Electronic Assist Operation  A steering control module (computer) electronically reacts to steering pressure  The module operates the electric motor in the rack assembly to help the driver steer the wheels  The module can reverse motor rotation and alter motor speed as needed

80 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Proportional Power Steering  Senses vehicle speed and steering load to ensure adequate road feel  Increases steering effort at higher speeds for more road feel  Lowers steering effort at lower speeds to ease maneuvering

81 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Low Speed Operation  A computer-controlled electromagnet is used to alter the operation of the stub shaft, torsion bar, and rotary control valve  At low speeds, the computer sends current through the electromagnet in one direction to help attract and pull on the stub shaft and torsion bar, increasing valve output pressure

82 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only High Speed Operation  At high speeds, the computer reverses electrical flow through the electromagnet  The valve output pressure decreases, reducing assist, and increasing steering effort for better road feel

83 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Proportional Steering In this system, a computer, a vehicle speed sensor, and a solenoid control hydraulic pressure

84 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only In a four-wheel steering system, all four wheels change direction to improve handling, stability, feel, and maneuverability

85 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Four-Wheel Steering System

86 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Four-Wheel Steering In a gentle turn, the wheels pivot in the same direction

87 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Four-Wheel Steering In a sharp turn, the wheels pivot back and then turn in opposite directions

88 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Mechanical System  Uses a special front rack-and-pinion gearbox with a transfer box  The transfer box operates a long shaft that extends back to the rear rack  When the front wheels are turned, the shaft rotates to turn the rear wheels

89 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Hydraulic System  Uses a conventional power rack-and- pinion steering system up front  Hydraulic lines extend back to a rear power steering pump, which is driven by the differential  Depending on vehicle speed, the rear pump forces fluid under pressure into a control valve

90 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Hydraulic System  When a specific road speed is reached, the control valve can then operate the rear steering system  The rear rack is connected by tie-rods to the rear suspension trailing arms  When activated, the rear rack shifts the trailing arms to steer the rear wheels

91 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Electronic System  An electronic system is speed-sensitive  An electric-motor-driven power rack (rear actuator) acts on the rear wheels using a recirculating-ball drive and mechanical links  The rear-wheel steering angles are computer controlled

92 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Electronic System

93 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Electronic System Operation  The computer analyzes signals from angle sensors in the front steering and signals from wheel speed sensors in the anti-lock brake system  The rear actuator is energized by the computer to move the rear wheels as needed

94 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Rear Actuator


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