Automotive Steering Systems Overview

Steering System

• Steering is the collection of components and linkages allowing a vehicle to follow a desired direction
• Automobiles use steering gears and linkages to transfer hand-operated steering wheel movement to the front wheel hubs via the steering column
• Other steering parts include steering wheel pads, shafts, boxes, arms, and stabilizers

Needs of Steering

• Steering should multiply the driver's turning effort
• It should be mostly irreversible, so road shocks aren't transferred to the driver's hands
• Steering mechanisms should have self-rightening, releasing the steering wheel after turning

Function of Steering

• Controls front wheel (sometimes rear wheel) direction
• Transfers road feel (slight steering wheel pull caused by road surface) to the driver
• Maintains the correct amount of effort needed to turn wheels
• Absorbs most of the shocks from the road surface impacting the steering wheel

Layout of a Steering System

• A typical steering system includes a steering wheel, steering shaft, steering gear box, pitman arm, drag link, steering knuckle arm, and track rod arm

Turning the Car

• When turning, the front wheels don't point in the same direction
• The inner wheel travels a shorter distance than the outer wheel

Linkages Steering System

• Linkages (worm gear system) transfer the driver's steering wheel rotation to the steering shaft, through the steering column, and then to the steering gear box
• The steering column supports both the steering column and steering shaft

Steering Gears

• Steering gears convert the steering wheel's rotary motion into a straight-line motion for the linkage with mechanical advantage
• If the steering wheel connected directly to the linkage, more effort would be required to turn the wheels
• A reduction system (steering ratio) is used to assist the driver

Most Useful Steering Gear Systems

• Recirculation ball type steering gear transmits rotary motion from the steering wheel to the piston, along with rack-and-pinion steering, consisting of a rack along its length, and a pinion gear connected to the steering wheel
• Hydraulic power steering utilizes a hydraulic system to multiply the force applied to the steering wheel, making it easier to use

Linkage Steering System (Worm Gear Parts)

• Steering systems (worm gear parts, steering gearbox) transform the turning motion into a straight-line left or right motion
• Steering gearbox ratios generally range from 15:1 to 24:1 (with 15:1, the worm gear turns 15 times to turn the selector shaft once)
• The steering linkage connects the steering gearbox to the steering knuckles and wheels

Basic Rack-and-Pinion Steering

• Gear housing holds the pinion gear and the rack
• Tie rods connect the rack with steering knuckles

Steering Linkage

• Pitman arms transfer gearbox motion to the steering linkage
• Pitman arms are splined to the gearbox

Differential Axle in a Vehicle

• The differential is an integral part of all four-wheel vehicles
• It allows the wheels to turn at different speeds, necessary when a vehicle turns.

Parts of Differential System

• Pinion drive gear transfers power from the drive shaft to the ring gear
• Ring gear transfers power to the differential case assembly
• Spider gears are at the heart of the differential
• Differential case assembly holds and houses the gear drive axels
• Rear drive axel transfers torque from the differential assembly to the drive wheels

Working of Differential System

• When turning, inner and outer wheels travel different distances
• During a right turn, the inner wheels travel a shorter distance than the outer ones