Power Steering Systems Explained
Power steering is a system for reducing the steering effort on cars by using an external power source to assist in turning the wheels. Power steering was invented in the 1920s by Francis W. Davis and George Jessup in Waltham, Massachusetts. Chrysler Corporation introduced the first commercially available power steering system on the 1951 Chrysler Imperial under the name Hydraguide.
Hydraulic systems
Most power steering systems work by using a belt driven pump to provide hydraulic pressure to the system. This hydraulic pressure is generated by a rotary-vane pump which is driven by the vehicle's engine. As the speed of the engine increases, the pressure in the hydraulic fluid also increases, hence a relief valve is incorporated into the system to allow excess pressure to be bled away.
While the power steering is not being used, i.e. driving in a straight line, twin hydraulic lines provide equal pressure to both sides of the steering wheel gear. When torque is applied to the steering wheel, the hydraulic lines provide unequal pressures and hence assist in turning the wheels in the intended direction.
Some more modern implementations of hydraulic systems also include an electronic pressure valve which can reduce the hydraulic pressure of the power steering lines as the vehicle's speed increases (Variable assist power steering)
Electric systems
Electric Power Steering, uses completely electric components. Sensors detect the motion and torque of the steering column and a computer applies assisted power via electric motors. This allows varying amounts of assistance to be applied depending on driving conditions.
In contrast to hydraulic systems, with an electric system the "communication" is only one way. The steering wheel transmits forces to the front wheels assisted by the motors, but the forces on the front wheels are not transmitted back through the motors to the steering wheel. Electric-only systems thus do not provide as much feedback to the driver, a criticism commonly expressed as a lack of steering "feeling".
Electric power steering (EPS) is designed to use an electric motor to provide directional control to the driver of a vehicle. Most EPS systems have variable assist, which allows for more assistance as the speed of a vehicle decreases and less assistance from the system during high-speed situations. This functionality requires a delicate balance of power and control that has only been available to manufacturers in recent years. The EPS system is replacing the hydraulic steering system and is destined to soon become mainstream among automotive manufacturers.
Electric power steering systems do not require engine power to operate. Thus, a vehicle equipped with an EPS system may achieve an estimated three percent greater fuel economy than the same vehicle with conventional hydraulic power steering. As an added benefit, more of the engine's power is transmitted to its intended location > the wheels.
Electro-hydraulic systems
So called "hybrid" systems use the same hydraulic assist technology as standard systems, with the hydraulic pressure being provided by an electric motor instead of a belt driven one.
Maintaining your steering system
How do you properly maintain your power steering system? The best thing you can do for your power steering is have the fluid flushed every 2 years. Just like your brake fluid , power steering fluid will retain and absorb moisture in the system. This will cause the fluid to break down and will cause corrosion in the system . Keeping the fluid fresh and clean will also keep the seals and gaskets conditioned and will help avoid costly leaks and repairs. Ask YourAutoAdvisor for more tips and advice on how to maintain your steering system properly. Our expert help can save you money on repair bills and maintenance.
