Steering System

1. © 2012 Delmar, Cengage Learning
Steering Fundamentals
Chapter 65

2. © 2012 Delmar, Cengage Learning
Objectives
• List the parts of steering systems
• Describe the principles of operation of steering
systems
• Compare linkage systems to rack and pinion
• Describe how power steering systems operate

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Steering Systems
• Steering system works with the suspension
system
– Components
• Steering gear
• Steering linkage
• Steering wheel
• Steering column
• Styles of steering
– Gear box and parallelogram linkage
– Long rack with linkage extending from ends

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Steering Gears
• Common types
– Recirculating ball and nut steering gear
– Rack and pinion steering gear
• Steering ratio
– Amount of steering wheel rotation
• Steering wheel turned all the way in one direction:
stops against a lock
• Turning radius
– Amount of space required for a vehicle to turn
around

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Recirculating Ball and Nut
Steering Gear
• Sector gear meshes with ball nut
– Ball nut rides on bearings on the worm shaft
• Provides smooth steering feel
– Ball nut has curved channels
– Steering shaft has bearing channels
• Balls rotate and recirculate through tubes

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Rack-and-Pinion Steering
• Characteristics
– End of steering shaft has a pinion gear
• Meshes with the rack gear
– Lighter and easier to install than standard
steering gears
– Often has a faster ratio
– More easily damaged when front wheels hit a
curb or rock
– Transmit more road shock

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Steering Linkage
• Steering gear is connected to wheels by
steering linkage
• Parts vary depending on design
– Tie-rods
– Steering arms
– Steering-knuckle
• Parallelogram steering design
– Most popular
– Used with long and short arm suspension

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Parallelogram Steering Linkage
• Recirculating ball gear uses parallelogram
steering
– Name comes from parallelogram shape made by
steering linkage during a turn
• Characteristics
– Tie-rods on each side connected by center link
– Pitman arm connects steering box to center link
– Idler arm supports center link on passenger side

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10. © 2012 Delmar, Cengage Learning
Ball Sockets
• Ball sockets connect steering linkage parts
– Allow parts to rotate during a turn
– Pivot as the steering deflects during a bump

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Tie Rods
• Tie-rod ends attached to pivot points at front
wheels
– Transmit motion from steering wheel to front
wheels
– Maintain correct front wheel toe
• Threaded adjusting sleeve connects inner and
outer tie-rods
– Right-hand thread on one end
• Left-hand on other

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13. © 2012 Delmar, Cengage Learning
Steering Arm
• Tie-rods attach to front wheels at steering arms
– Steering arm is attached to steering knuckle
• Includes spindle
• During a turn
– Inside wheel must turn sharper than outside
wheel
• Steering arms angled inward
– Ackerman angle
– Toe-out-on-turns

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15. © 2012 Delmar, Cengage Learning
Rack-and-Pinion Steering
Linkage
• Rack and pinion: less complicated
– Two tie-rods come out of steering rack
– Conventional tie-rod end ball sockets on outer
ends
– Inner tie-rod ends are ball sockets enclosed in
rubber bellows or boots
• Steering damper
– Minimizes effect of road shocks to steering wheel

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Steering Column
• Steering wheel splined to steering shaft located
in center of steering column
– Locknut retains steering wheel to shaft
• Shaft supported by bearings at top and bottom of
column
• Tilt columns allow driver to adjust steering
wheel angle
– Air bags are installed on steering wheel
– There is flexible coupling between steering shaft
and splined input shaft of steering gear

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18. © 2012 Delmar, Cengage Learning
Power Steering
• Steering systems on most cars today are power
assisted
– Some manual units are still made
• Most power steering is hydraulic
– Pressure supplied from crankshaft by belt-driven
pump

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Power Steering Pump
• Steering pump driven by crankshaft belt
supplies hydraulic pressure to assist steering
– Power steering pump types: roller, vane, and
slipper
• Operation
– Pump develops more flow at higher speeds
– Flow control valve is almost always working
– Requires considerable horsepower to operate

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Types of Power Steering
• Power steering is either rack-and-pinion or
conventional recirculating ball and nut units
– Most power steering systems are integral
• Recirculating ball power steering
– Gear boxes use pivot lever or torsion bar acting
on spool valve
• Rack-and-pinion systems
– Fluid is directed to a chamber on either side of
the rack

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22. © 2012 Delmar, Cengage Learning
Electronically Controlled
Variable Effort Power Steering
• Reasonable speed: fixed power assist not
necessary
– Late-model vehicles: vehicle speed determines
amount of power assist
– Pump-controlled units: actuator solenoid
changes fluid flow
– Steering gear–controlled steering assist: boost is
sensed by module
– Four-wheel steering systems: improve handling

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24. © 2012 Delmar, Cengage Learning
Electronically Controlled
Steering Systems
• Can be “steering-by-wire” or mechanically
connected using electro-hydraulic steering gear
– AFS system changes between low and high
speed steering assist
• Electric motor–powered steering systems use a
rack-and-pinion steering gear
• Electric power steering improves fuel economy
– Controls amount of assist by regulating current
• Planetary gear active steering
– Input is sun gear and output is planetary carrier

25. © 2012 Delmar, Cengage Learning