A proper steering system mechanism is necessary to effectively control the vehicle with safety during its entire speed range without much effort. It should also be able to tackle wide variations of road surfaces and bumps and bounces to the vehicle.
Moreover, it is the basic feature of the vehicle to be steered straight and maintained at that position or turned at the driver’s will without s/he putting much efforts to do so. It is also necessary that the moving vehicle is under driver’s perfect control in order to avoid an accident.
To control the vehicle properly, the driver should be able to:
the vehicle in different directions so that it does not go off course.
its speed in order to move the vehicle as necessary.
it down or stop it slowly or suddenly without drifting.
The accelerator, gears, and brakes control the vehicle movement while the steering system provides directional changes to the moving vehicle. In addition to directing the vehicle in a particular direction, the steering system must be arranged geometrically. The wheels must roll freely without slipping or causing any friction. Besides, the steering must be light, stable, and with some degree of self-adjusting ability.
Steering mechanism must avoid tire slippage while the vehicle makes a turn. To achieve this, each wheel must roll on an arc which has a common center with the arcs of the other wheels of the vehicle. To make each front wheel move about its own pivot (around the kingpin or ball joints), it is necessary to turn the inner wheel through a larger angle than the outer wheel. This arrangement makes the two front wheels ”toe-out” slightly while making a turn which is known as ‘Akerman Principle’ or ‘Akerman System’.
The function of the steering system is to convert the rotary movement of the steering wheel into an angular turning of the front wheels. It also multiplies the driver’s effort by leverage or mechanical advantage so that it makes easier to turn the wheels. Steering knuckles carry the front wheels that run on the ball or tapered roller bearings. Hence, the steering system also must absorb some part of road shocks and prevent them from transmitting to the driver.
When the driver turns the steering wheel, it transmits the resulting motion to a steering tube. This tube rotates inside the steering column and transmits the motion further to the steering gear-set fitted at the end of the steering tube. Steering gear set changes the direction of motion and multiplies the twisting force according to the gear ratio. The output or roller shaft rotates and moves the Pitman arm. It further transmits the motion to the steering knuckle thru’ the relay rod, the idler arm, tie rods, and steering arms.
The conventional steering system has following components:
Moreover, thepower steering system is an advanced type of steering gear mechanism which uses either hydraulic pressure or electric power assistance (EPAS) to operate the steering gear. ZF is one of the leading manufacturers of steering gear components in the world.