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STEERING SYSTEM

STEERING SYSTEMSteering 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.

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 drivers 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.

Function of Steering SystemControl of front wheel (sometimes rear wheel) direction.Maintain correct amount of effort needed to turn the wheels.Transmit road feel (slight steering wheel pull caused by the road surface) to the drivers hand.Absorb most of the shock going to the steering wheel as the tire hits holes and bumps in the road.Allow for suspension action.

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LAYOUT OF A STEERING SYSTEM A typical steering system consists of Steering wheelSteering shaft Steering gear box Pitman armDrag link Steering knuckle arm, Tie rod Track rod arm

Tire rodSteering armDrag linkPitman armGearbox

Turning the Car (when turning, front wheels dont point the same direction)

Inside wheel turns at a smaller radius, hence the inside wheel turns at a steeper angle then the outside wheel.

Linkage Steering System (Worm Gear)

Linkage Steering System (Worm Gear) PartsSteering Wheel used by the driver to rotate a steering shaft that passes through the steering column.

Steering Shaft transfers turning motion from the steering wheel to the steering gearbox.

Steering Column supports the steering column and steering shaft.

STEERING GEARSThe 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.

RECIRCULATING BALL TYPE STEERING GEARIt 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.

RECIRCULATING BALL TYPE STEERING GEAR

Linkage Steering System (Worm Gear) PartsSteering Gearbox) changes turning motion into a straight-line motion to the left or right.

Steering gear box ratios range from 15:1 to 24:1 (with 15:1, the worm gear turns 15 times to turn the selector shaft once). Steering linkage connects the steering gearbox to the steering knuckles and wheels.

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.

A rack-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.

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.

Basic Rack-and-Pinion Steering

Basic Rack-and-Pinion Steering

Pinion Gear- rotated by the steering wheel and steering shaft; its teeth mesh with the teeth on the rack.Rack- long steel bar with teeth along one section; slides sideways as the pinion gear turns.

Basic Rack-and-Pinion Steering

Gear Housing- holds the pinion gear and rack.Tie-rods- connects the rack with steering knuckles.

Basic Rack-and-Pinion Steering

Part of rack contains a pistonTwo fluid ports, one on each side.The side with high pressure pushes the piston to the opposite side (turning the wheel).

Steering Linkage

Pitman Arm transfers gearbox motion to the steering linkage.Pitman arm is splined to the gearbox.

Steering Linkage

Center Link (Relay Rod) steel bar connects the right and left side of the steering linkage.Connects to Pitman arm, Tie rod ends, and Idler arm.

Steering Linkage

Idler Arm supports the end of the center link on the passenger side of the vehicle.Bolts to the vehicles frame.

If worn, will cause excessive steering play.

Steering Linkage

Tie-Rod Assemblies: Two tie-rod assemblies are used to fasten the center link to steering knuckles.Assembly is consist of inner tie-rod end, outer tie-rod end,and a toe adjustment sleeve.

Be sure to check the toe setting after replacing the tie-rod ends.

Steering Linkage

Rack-and-pinion outer tie-rod end is similar to the regular tie-rod end, but the inner tie-rod end sits inside the rack assembly.

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 detectorControlled pressure distributor caseHydraulic booster pumpTank with a working liquidConnection 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

Power Steering normally use an engine driven pump and a hydraulic system to assist steering action.

Three major types of power steering systems:Integral-piston linkage system.External power steering system.Rack-and-pinion systemIntegral power piston.External power piston.Integral Rack-and-pinion system is the most common.

Power steering pump is driven by the engine produces the hydraulic pressure for steering system operation.Four basic pumps:Roller pump.Vane pump.Slipper pump.Gear pump.

Steering System Diagnosis Steering Wheel Play is the most common problem.Should not be able to turn the steering wheel more than 1 (33mm) without causing movement of the front wheels.

Move the wheel side-to-side, should have no play.

Steering System Diagnosis Hard Steering (steering wheel requires excessive turning effort)Low power steering fluid.Pump belt broken or slipping.

Steering System NoiseBelt squeal is a loud screeching sound produced by a worn belt.Power steering pump noise is usually a loud whine that only occurs when the steering wheel is turned.Low fluid level and air in the system.Check fluid with engine turned off.

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