2. STEERING SYSTEM
Steering is the term applied to the collection of components,
linkages, etc. which will allow a vehicle to follow the desired
direction.
An automobile is steered with the help of steering gears and
linkages, which transfer the motion of the hand operated
steering wheel to the pivoted front wheel hubs via steering
column.
The other parts that are used for steering a vehicle are steering
wheel pads, steering shafts, steering boxes, steering arms and
steering stabilizers. These parts are made of durable materials
like stainless steel, iron, aluminum, copper, magnesium,
titanium, platinum, rubber, and plastics.
3. NEEDS OF STEERING SYSTEM
It should multiply the turning effort applied on the steering
wheel by the driver.
It should be to a certain extent irreversible. In other words, the
shocks of the road surface encountered by the wheels should
not be transmitted to the driver’s hands.
The mechanism should have self rightening effect i.e., when the
driver releases the steering wheel after negotiating the turn, the
wheel should try to achieve straight ahead position.
4. Functionof Steering System
•Control of front wheel (sometimes
rearwheel) direction.
• Transmit road feel (slight steering
wheel pull caused by the road surface)
to thedrivers hand.
•Maintain correctamount of effort
needed to turn thewheels.
•Absorb mostof theshock going to the
steering wheel as the tire hits holes
and bumps in the road.
•Allow for suspensionaction.
5. LAYOUT OF A STEERING SYSTEM
A typical steering systemconsistsof
Steering wheel
Steering shaft
Steering gear box
Pitman arm
Drag link
Steering knuckle arm,
Tie rod
Track rod arm
7. Turning the Car (when turning, front wheelsdon’t point the same direction)
•Inside wheel turns at a smallerradius, hence the inside wheel turns at a
steeperangle then theoutside wheel.
9. Linkage Steering System (Worm Gear) Parts
•Steering Wheel – used by thedriver to rotatea
steering shaft that passes through the steering
column.
•Steering Shaft – transfers turning motion from
thesteering wheel to the steering gearbox.
•Steering Column – supports the steering column
and steering shaft.
10. STEERING GEARS
The steering gear is a device for converting the rotary motion
of the steering wheel into straight line motion of the linkage
with a mechanical advantage.
If the steering wheel is connected directly to the steering
linkage it would require a great effort to move the front
wheels. Therefore, to assist the driver, a reduction system is
used having a steering ratio.
Most useful steering gear system are as follows:
1) Recirculation ball type steering gear.
2) Rack-and-pinion steering.
3) Hydraulic power steering.
11. RECIRCULATING BALL TYPE
STEERING GEAR
🗸It consists of a worm at the end of steering rod. A nut is mounted on the
worm with two sets of balls is the grooves of the worm, in between the nut
and, the worm. The balls reduce the friction during the movement of the nut
on the worm. The nut has a number of teeth on outside, which mesh with
the teeth on a worm wheel sector, on which is further mounted the drop arm.
🗸When the steering wheel is turned, the balls in the worm roll in the grooves
and cause the nut to travel along the length of the worm. The balls, which
are in 2 sets, are recirculated through the guides. The movement of the nut
causes the wheel sector to turn at an angle and actuate the link rod through
the drop arm, resulting in the desired steering of the wheels. The end play of
the worm can be adjusted by means of the adjuster nut provided.
🗸To compensate for the wear of the teeth on the nut and the worm, the two
have to be brought nearer bodily. To achieve this, the teeth on the nut are
made tapered in the plane perpendicular to the plane of Figure.
13. Linkage Steering System (Worm Gear) Parts
•Steering Gearbox) – changes turning motion
into a straight-line motion to the leftorright.
•Steering gear box ratios range from 15:1 to
24:1 (with 15:1, thewormgearturns 15 times
to turn theselectorshaftonce).
•Steering linkage – connects the steering
gearboxto thesteering knucklesand wheels.
14. RACK-AND-PINION STEERING
Rack-and-pinion steering is quickly becoming the most common type of
steering on cars, small trucks and SUVs.
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.
Arack-and-pinion gear set is enclosed in a metal tube, with each end of the
rack protruding from the tube. A rod, called a tie rod, connects to each end
of the rack. 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.
15. 🗸Some cars have variable-ratio steering, which uses a rack-and-pinion gear
set that has a different tooth pitch (number of teeth per inch) in the
center than it has on the outside. This makes the car respond quickly
when starting a turn (the rack is near the center), and also reduces effort
near the wheel's turning limits.
17. Basic Rack-and-Pinion Steering
•Pinion Gear- rotated by the steering wheel and steering shaft; it’s teeth mesh
with the teeth on the rack.
•Rack- long steel barwith teeth along one section; slides sidewaysas the pinion
gearturns.
19. Basic Rack-and-Pinion Steering
•Partof rack contains a piston
•Two fluid ports, one on each side.
•Thesidewith high pressurepushes the piston to the
oppositeside (turning thewheel).
20. Steering Linkage
Pitman Arm transfersgearbox motion to thesteering linkage.
•Pitman arm is splined to thegearbox.
21. Steering Linkage
Center Link (Relay Rod) steel barconnects the rightand
left side of the steering linkage.
•Connects to Pitman arm, Tie rod ends, and Idlerarm.
22. Steering Linkage
IdlerArm supports theend of thecenter link on
the passengersideof thevehicle.
•Bolts to thevehicle’s frame.
•If worn, will causeexcessive steering play.
23. Steering Linkage
Tie-Rod Assemblies: Two tie-rod assembliesare used
to fasten thecenter link tosteering knuckles.
•Assemblyis consist of inner tie-rod end, outer tie-rod end,
and a toeadjustment sleeve.
•Be sure tocheck the toe setting after replacing the
tie-rod ends.
25. ⚫ HYDRAULIC POWER STEERING : is a hydraulic system for reducing
the steering effort on vehicles by using hydraulic pressure to assist in
turning the wheels. It is intended to provide for easier driving direction
control of the car while preserving "feedback", stability and unambiguity of
the trajectory specified. The steering booster is arranged so that should the
booster fail, the steering will continue to work (although the wheel will feel
heavier).
The steering booster consists of the following basic elements:
🗸Steer torque detector
🗸Controlled pressure distributor case
🗸Hydraulic booster pump
🗸Tank with a working liquid
🗸Connection hoses
The working liquid, also called "hydraulic fluid" or "oil", is the medium by
which pressure is transmitted. Common working liquids are based on
mineral oil. For pressure restriction in the pump there is a restrictive valve,
which is adjusted on different cars in a range from 7 to 13 MPa.
HYDRAULIC POWER STEERING
26.
27. Power Steering normally usean engine driven pump and a hydraulic
system toassiststeering action.
Three majortypes of powersteering systems:
•Integral-piston linkage system.
•External powersteering system.
•Rack-and-pinion system
•Integral power piston.
•External power piston.
Integral Rack-and-pinion system
is the mostcommon.
28. Powersteering pump is driven by theengine produces the hydraulic
pressure forsteering systemoperation.
Four basicpumps:
•Rollerpump.
•Vane pump.
•Slipper pump.
•Gearpump.
29. Steering System Diagnosis
Steering Wheel Play is the mostcommon problem.
Should not beable to turn thesteering wheel
more than 1 ½’’ (33mm) without causing
movement of the front wheels.
Move thewheel side-to-side,
should have no play.
30. Steering System Diagnosis
Hard Steering (steering wheel requires excessive turning effort)
•Low powersteering fluid.
•Pump belt brokenorslipping.
Steering System Noise
•Belt squeal is a loud screeching sound produced byaworn belt.
•Power steering pump noise is usuallya loud whine that onlyoccurswhen
thesteering wheel is turned.
•Low fluid level and air in the system.
Check fluid with engine turned off.
32. CASTER ANGLE
Angle between vertical line and
centre line of king pin
FUNCTIONS
◾ SELF CENTRING
ACTION
◾ STRAIGHT LINE
STABILITY
◾ EXCESSIVE CASTER
MAKES STEERING
HEAVIER, LESS
RESPONSIVE AND
INCREASED EFFORT
34. ANGLE BETWEEN VERTICLE LINE AND
KINGPIN CENTRE LINE (From F.V.)
FUNCTIONS
◾ HELPS IN
STEERING
RETURNABILITY
AFTER A TURN IS
COMPLETED
◾ REDUCES
STEERING EFFORT
◾ REDUCES TIRE
WEAR
37. Angle between Geometric line
and Thrust Line
◾ OCCURS WHEN REAR
WHEEL HAS
IMPROPER
ALIGNMENT
◾ EFFECTS DIRECTION
OF TRAVEL BY
CAUSING PULL IN THE
DIRECTION AWAY
FROM THRUST LINE
FUNCTIONS
38. Turning circle radius = (track/2) + (wheelbase/
sin(average steer angle))
The turning circle of a car is the diameter
of the circle described by the outside
wheels when turning on full lock.
39. ◾ SYSTEM AUTOMATICALLY STEERS THE REAR
WHEELS ACCORDING TO SPEED OF VEHICLE
AND STEERING ANGLE.
◾ USED IN MILITARY, OFF ROAD VEHICLES,
BUSES, TRUCKS AND LARGE VAHICLS
◾ INCREASES HANDLING AND
STABILITY
◾ REDUCES TURNING RADIUS
40.
41. ◾ VEHICLE STEERS BY POWER ASSIST
FROM EXTERNAL SOURCE OTHER
THAN DRIVER’S EFFORT
◾ HELPS IN STEERING OF HEAVY
VEHICLES
◾ INCREASES THE STEERING RATIO
AND REDUCES DRIVER’S EFFORT
◾ TWO MAJOR TYPES – HPS AND EPS
