How Power Steering Works

Power Steering (power-assisted steering) made a huge difference to driving when it was first invented in 1951.  It was first available on the Chrysler ‘Imperial’ in that year, and was called ‘Hydraglide’.

Power Steering can be either an electric or hydraulic based system.  The installation of power steering is a mechanical assist which makes steering a car lighter, easier and more precise with increased maneuverability.

Today this is a standard fitting in almost all four-wheeled vehicles, and it is something that we take for granted.  Power Steering is something that is only noticed when it isn’t there or it has broken down.

Hydraulic Power Steering

The hydraulic power steering system increases the steering wheel movement transmitted to the steered wheels on the vehicle (these are usually front wheels – a ‘front wheeled drive’ vehicle).

The necessary pressure would usually be generated from either a rotary vane pump or a generator which is run by the engine using a belt drive system.  A hydraulic cylinder then transmits the force to the steering gear, which, in its turn, steers the road wheels

The valves are controlled by the steering wheel movement, and they then control the flow to the cylinder. The more torque on the steering wheel, the more fluid allowed through, the more force applied to the steered wheels.  It is a basic transmission system.

The hydraulic pumps are positive-displacement pumps, which means that the flow rate is proportional to the rate of the engine:  The faster you are going the faster the steering operates.  This clearly would cause issues if unaddressed, so this is designed out by incorporating a flow-control valve and a restricting orifice along with a pressure relief valve – counteracting the ‘more speed = faster operation’ fault.

Should the Power Steering fail the steering will continue to work, but without the assistance for anyone operating the vehicle it will feel considerably heavier.

Electric Power Steering

In this, hi-tech solution, the assistance to the steered wheels is given by an electric motor rather than a hydraulic system.  This is a newer system, and is increasingly fitted to all vehicles.

The position and torque of the steering column in an electric power steering system is detected using sensors, this information, in turn is used by a computer model which applies assistive torque utilising the motor.   The motor can be attached to either the steering column or the steering gear.  The assistance canadjusted by engineers as it is completely variable dependent upon the road conditions or the vehicle and drive requirements – so can be effectively ‘tailor-made’ to suit the circumstances.

In electric Power Assisted Steering as a safety measure the  mechanical linkage is retained in case of failure.   In this case also the steering will feel considerably heavier without the assistance, and any failure will be immediately obvious.

Advantages of Electric Power Steering Over Hydraulic

Electrical systems are more fuel efficient as there is no constantly running, belt driven component.  There is also no hydraulic pump, with the attendant hydraulic hoses – always prone to leaks, and once the fluid is leaking pressure is lost and the pump starts to break down.

Electric Power Steering Systems incorporate electronic stability control, which gives instant variation to the torque assistance being applied.

How Power Steering Works

Power Steering is an assistive, long standing technology which increases the torque from the Steering Wheel moved by the driver and applies the increased torque to the steered wheels on the car.  If you are seeking to understand how power steering works on your individual vehicle then consult your manufacturer’s handbook.  If you have the traditional Hydraulic Power Steering fitted then include monitoring the fluid levels as part of your ongoing vehicle maintenance check.

 

 

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