Hydraulic Power Steering

Hydraulic power steering, also referred as HPS, is a hydraulic system, which helps in reducing the steering effort on vehicles. In other words, hydraulic pressure is used on the steering so that the wheels are turned without much effort. Almost all modern cars have hydraulic power steering as it provides for easier driving control of the car, besides maintaining stability. Hydraulic power steering is mostly used because it reduces the steering effort on cars. Such power steering, by using an external power source help in turning the wheels.

How does Hydraulic Power Steering Works?

The steering wheel is provided pressure with the help of hydraulic fluid. The steering wheel moves a spring loaded valve. The valve is moved in the direction in which you put pressure on the wheel. This lets the hydraulic pressure to move the wheels. The hydraulic power for the steering is provided by a rotary-vane pump, which is driven by the car's engine. As the vanes spin, hydraulic fluid is pulled from the return line at low pressure and at high pressure, as the speed of the engine increases, the pressure in the hydraulic fluid also increases. When force is applied to the steering wheel, the hydraulic lines provide unequal pressures and this results in turning the wheels in the required direction. Modern implementations of hydraulic systems also include an electronic pressure valve. This reduces the hydraulic pressure of the power steering lines as the speed of the vehicle increases.

Hydraulic Power Steering Components

The hydraulic power steering consist of the following :

• Controlled pressure distributor case
• Steer torque detector
• Hydraulic booster pump
• Tank with a working liquid
• Connection hoses
• Belt driven pump
• Rotary vane pump

Electro-Hydraulic Power Systems

Electro-hydraulic power steering systems (EHPS), also referred as “hybrid” systems, use the same hydraulic technology as standard systems, but here the hydraulic pressure is provided by a pump driven by an electric motor instead of belt-driven by the engine.

Difference Between Hydraulic Power Steering and Electric Power Steering

Electric Power Steering systems use electric components with no hydraulic systems at all. A hydraulic power steering as discussed uses hydraulic pressure which is supplied by an engine-driven pump to help the motion of turning the steering wheel. Electric power steering is considered to be more efficient than the hydraulic power steering, since the electric power steering motor only needs to provide help when the steering wheel is turned, whereas the hydraulic pump must run continuously. In electronic power steering , the assistance provided depends on the vehicle type, road speed, and even driver preference. There is no leakage and disposal of hydraulic power steering fluid. In HPS, the hydraulic assistance stops working if the engine stops.