The vast majority of cars manufactured these days (around 80%) have power steering fitted – what is it? Power steering is actually ‘power assisted steering system’ which makes steering the car easier by reducing the effort needed from the driver to turn the wheels.
The power steering can use hydraulic or intermediate electrical devices to magnify the force from the steering wheel and this makes maneuvering easier, and smoother whilst also much less labor intensive for the driver.
- It makes driving the vehicle appreciably easier.
- It improves safety – improving both vehicle response and precision steering.
- Easier steering at lower speeds. Maneuvering at low speeds is difficult without power steering assistance.
- Stability on the uneven road surface – less of the wheel movement is transferred to the steering wheel.
- The steering wheel returns to a ‘neutral’ position automatically.
The three different types of power steering systems.
In a hydraulic system, the hydraulic pump is driven by both the engine and the hydraulic cylinders. This is used to multiply the input force which then makes steering the front wheels ‘lighter’ for the driver
The pressure is applied onto the steering gear by highly compressed hydraulic fluid found within the hydraulic cylinder.
With the electro-hydraulic system the rotary hydraulic pump, normally driven by the engine, is replaced with a hydraulic pump which is driven via an electric motor.
This is also known as the ‘hybrid power steering system’ as it utilizes both electric and hydraulic components.
This brings us to bang up-to-date to the latest system. With Electronic the hydraulic system is replaced with electric sensors and motors. The force then is not provided by hydraulics, but a motor which is battery driven and the torque is controlled by sensors that detect the position of the steering column in the vehicle. Very clever stuff. This gives the best and most responsive result, and so is the system most used in modern vehicles.
- Steering mechanism. This is generally a rack and pinion system where the rotational movement of the steering wheel converts to the transverse motion of the wears by a set of meshed gears, ‘rack’ that provide the transverse motion alongside a rotational movement provided by the ‘pinion’.
- These are the constraints that provide the motion between 2 different components – the ‘links’. Within power steering, the tie-rods connect the ‘rack’ to the wheel and transfer the transverse motion from the rack across to the wheel.
- This can be any of the above three methods.
- Steering wheel. The round item you hold and turn to effect the change throughout the system.
How it works.
The three differently powered systems all work differently.
With a hydraulic system, the input force is multiplied using – hydraulics. This involves a hydraulic cylinder – rotator pump – hydraulic lines – hydraulic fluid under compression – coupling mechanism that then couples it to the rack in the steering system.
The vehicle driver rotates the steering wheel which makes the engine fire the hydraulic pump which then pumps the compressed hydraulic fluid through the lines.
This compressed fluid goes into the hydraulic cylinder and causes pressure to be applied over the cylinder’s piston.
The newly pressurised piston moves from one end to the other end generating more movement and forcing more fluid through the lines. The input force from the driver is therefore multiplied.
The fluid applies pressure, through the coupling mechanism, to the attached pinion and the force I then transposed to the rack gear and steering of the front wheels is effected.
Hybrid (Semi Hydraulic System)
There is no hydraulic pump in this system – it utilizes an electric pump which is more reliable and less prone to breakdown. The rest of the system functions in exactly the same way as a hydraulic system.
The electric motor as the above example provides the power here.
The driver turns the steering wheel and the electronic sensors attached to the steering read the input and send information to the control unit of the vehicle.
The ECU analyses the input and sends a voltage signal to the electric motor whose gear is in mesh with the pinion gear.
The motor produces the particular torque required according to the value of the voltage received.
The gear starts transmitting the torque requested to the pinion gear, which applies it to the rack.
The rack move, which is transmitted through to the front wheels which turn.
The three power steering systems work in much the same way to magnify the driver’s movements with the steering wheel and apply them to the steering of the car. With some knowledge of how a power steering system works you can effect repairs, ensure adequate maintenance, and gain a better understanding of how your power steering system steers your car.