Almost every modern vehicle is now are equipped with some form of Power Steering and it is something that we have all become used to. Without Power Assisted Steering it becomes very difficult to turn the Steering Wheel from side to side, especially while sitting stationary. Power Steering has been fitted to vehicles for many years and has made driving overall a much more enjoyable experience and also a lot safer.
Although the Power Steering System is a Closed Circuit which has Fluid forced through the system by the Power Steering Pump, over time the fluid will wear and the lubricating properties will begin to deteriorate. With every service we suggest that you replace the Power Steering Fluid by draining the reservoir and replacing the fluid. By doing this new fluid is constantly being flushed throughout the system helping to remove any harmful build ups and also keep the steering as light as possible. Changing the fluid is a fairly simple process that only takes a few minutes to do, but by doing this you’re extending the overall life span of the components in the Power Steering System such as the Power Steering Pump and Also Power Steering Rack.
There are 2 different styles of Power Steering, One being a hydraulic system and the other is electronic. The Hydraulic System is the more common system which has been by all vehicle manufacturers for many years and now in more recent times Electronically Assisted Power Steering has been introduced.
Here’s a brief explanation on how the Hydraulic System operates –
The Hydraulic system is fitted with a Power Steering Reservoir, Power Steering Pump, High Pressure Power Steering Line and Also a Power Steering Rack. A Basic Explanation of how it works is: When the engine is running fluid is being forced through the system by the Power Steering Pump which is being driven by the engine, While turning the steering wheel the Power Steering Fluid being forced by the pump applies additional pressure to assist in turning the Steering Rack in the desired Direction. Once this fluid passes through the Power Steering rack it returns back to the reservoir where it continues to be circulated back through the system.
Here’s a brief explanation on how the electronic System Operates –
The electronic Power Steering System does not rely on any fluid or pump driven by the engine to assist with Steering, Instead this system relies entirely on voltage being provided to an electronic motor attached to the steering. There are several sensors which are constantly reading the position of the steering wheel and also the steering shaft. When turning the wheel these sensors determine the direction in which the wheel has been turned and subsequently activate an electronic motor on the side of the steering rack. This electronic motor then is signalled by computer control on how much assistance to provide as a result of signals sent from the Vehicles Steering Control Module.
History of the Power Steering System.
The first known power steering system was made in the late 1800s but very little is known about it. In the early 1900s an electric device was added to a 5 ton truck in an attempt to reduce the effort for turning. Commercially the motor vehicle industry was set on a new path when In 1951 the Chrysler Corporation brought out power steering on the “Chrysler Imperial” followed by Cadillac in 1952, from this point on adapting the same basic hydraulic system over the next three decades adding to the desire for luxury and easier safe driving until today when almost no commercially manufactured vehicle has power steering. The addition more recently in vehicles toward front wheel drive, much wider tyres and radial in application, heavier vehicles and 4wd automobiles, multiply the effort to turn the steering wheel and allowing a far greater sensitivity or harsher feel of the road back to the driver, this almost makes it mandatory for a manufacturer to have power steering.
Development of Power Steering Systems
In the middle of the century a hydraulic power steering system consisted of a rotary pump driven by the engine via vee belt from the crankshaft. This pump was usually a rotary vane type which fed hydraulic fluid under pressure to a double acting hydraulic cylinder attached to the steering arm assembly or tie rod system that is directly connected to the wheels. Connected to the steering column would be control valves which would when turning the wheel increase the hydraulic pressure, or in essence vary the pressure from the pump to the ram as needed, compensating for the greater external forces on the suspension and wheels. Hydraulic systems are “positive displacement” type systems and therefore the faster the engine goes the greater the pressure produced, this obviously isn’t conducive to driving so the pressure from the pump is controlled by by a restricting orifice to restrict or make constant the amount of fluid needed and a flow control valve re directs the resultant fluid back to the reservoir, Incorporated in the system is also a pressure relief valve to stop any over pressurising of the system , this also diverts any excess back to the reservoir.
The next move was to replace the double acting piston arrangement to the steering box being hydraulically controlled and the in the latter part of the 20th century the development of the “rack and pinion” steering control. These developments give us a far more safe, precise and sensitive steering control of our automobiles.
All of this is constantly being developed with the introduction of “variable assist power steering” developed by Citroen of France, this is articulated as “speed sensitive steering” where the steering pressure is constant at any speed and the the steering wheel moves at a constant to the hydraulic activated cylinder added to this it also incorporates an application that gives the fell of returning the wheel to centre after turning into a corner. General motors offered an option the standard range of Pontiac vehicles of “variable ratio power steering, ever the ongoing development of steering development.
Accompanied with this was the Electro hydraulic systems also known as “hybrid” where the normal pump driven by the engine was now driven by an electric motor, devoid of engine revs making the pressure constant. In 1992 Toyota manufactured the MR2 with this type of system and in 1994 VW did the same with the Golf, since then many manufactures have adopted the same approach.
Development continues with a more sophisticated Electric system where an electric motor assists the steering mechanism rather than a hydraulic pump drive by the engine. This motor is controlled by sensors detecting the position and pressure on the steering.
It’s naturally implied that electric systems have an advantage over engine driven types particularly for fuel efficiency and the ability to be controlled by computer with sensors giving information about driving conditions and all the surrounding circumstances coupled with the fact there are no hydraulic hose and fluid controlled issues to be considered.