What Is Hydraulic Power Steering?

Power steering is necessary for most of the vehicles with increased demand for lighter control of the steering. Nowadays, Hydraulic power steering is a standard fitment in most vehicles. It provides lighter steering effort and easy maneuverability. Manufacturers employ power steering mainly to reduce the wheel turning efforts and to turn the sharp corners easily.

Power steering helps to negotiate the winding roads. It maneuvers the vehicle in confined spaces easily. It also offers some degree of resistance so that the driver gets the road feel and steering response. The road feel helps the driver to sense and predetermine the approach of front wheels. It visualizes the turning effort required to stabilize the vehicle body on turns, and in winds, etc.

Furthermore, to control a heavy vehicle with safety, particularly a loaded commercial vehicle, requires greater effort at the steering wheel. It should also be able to tackle wide variations of road surfaces and bumps and bounces. The use of large-section, low-pressure tires have greater road contact. So, they further magnify the steering efforts. Hence, manufacturers employ power-assisted steering on all types of vehicles i.e. cars, SUVs, and trucks alike.

Function:

Hydraulic power steering system consists of a steering gearbox, and an oil pump, a valve. It also includes a double-acting power cylinder, and a hydraulic oil reservoir. The system becomes active when the exertion of pressure on the steering wheel exceeds a predetermined value. When the driver turns the steering wheel, it, in turn, operates a valve. This valve directs the fluid to either side of the piston inside a cylinder to turn the wheels in the required direction. The valve directs the fluid back to the cylinder to prevent the tendency of the wheels to deflect when they run into an obstruction.

Operation:

Most designs provide a booster arrangement to turn the steering wheel shaft. This booster mechanism takes care of most of the work of the steering. Power steering employs compressed air, electrical mechanisms, and hydraulic pressure to run the steering shaft. However, most vehicles use a hydraulic pressure operated steering mechanism. Different manufacturers developed different types of the power steering system. They are Vicker’s system, Ross system, and Marks-Bendix. However, ‘Varmatic’ system is the most significant. They all work on the same principle and operate by pressurized hydraulic oil. Power steering system uses SAE 10W (or SAE 5W for temperatures below 120 degrees) for its operation.

Generally, manufacturers use two types of power steering gears. They are – Integral and Linkage booster type. The integral type controls and uses the hydraulic pressure directly within the steering gearbox housing. However, the booster type employs a hydraulic cylinder and control valve with conventional steering gearbox.

Furthermore, Hydraulic Power Steering system uses a belt driven pump to produce the necessary hydraulic pressure. The steering effort of the driver actuates the control valve. It allows the pressurized hydraulic oil to enter one side of the hydraulic cylinder, thereby pushing the piston to the other side. This causes the piston to move and forces the Pitman arm to the steering linkage and thereby the wheels.

Types of Hydraulic Power Steering Gears:

Nowadays, Power steering uses either hydraulic pressure or electric power assistance (epas) to operate the steering gear. Titan, ZF, and Rane are some of the leading manufacturers of steering gear components in the world.

Watch the Hydraulic Power Steering system in action:

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