Did you ever think, how the steering of your car controls the entire movement? You might have known that the steering mechanism what we recently use are called power steering and it includes two types: electric and hydraulic. With a power steering mechanism, a driver can control the heading of their car by applying a minimum steering effort and at the same time, it will supply a relevant amount of road feel to the driver. High axle weight, larger tire cross-sections, and front wheel drive of most of the passenger vehicles made power steering a necessary safety feature of every vehicle.
Electric power steering system(EPAS) and Hydraulic power steering system(HPAS) are the two important types of power steering system available. Among them, the automobile industry widely uses hydraulic power steering system because of its handling ease and stability. In the HPAS system, it will add a certain amount of torque to the applied torque and reduces the effort for automobile wheel turning operation. By adapting a hydraulic power steering, you can smoothly and comfortably maneuver the vehicle, regardless of its size or weight. EPAS systems are more energy efficient than hydraulic steering system but are limited to small and medium-sized automobiles. Also, electronic power steering systems are smaller and lighter than hydraulic systems. Understanding general details related to widely used and popular hydraulic power steering system will help to troubleshoot and maintain the system for reducing expensive damage. We can discuss more details on HPAS system here.
Usually, an HPAS system uses rack and pinion driver control mechanism with a constant flow-controlled pump. This method provides lighter weight and precise control over the vehicle. Another driver control mechanism currently used in HPAS system is steering gearbox. This mechanism is highly durable and is designed for rough usage. So, SUV’s and truck applications use this steering gear box driver control mechanism.
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Hydraulic Power Steering Working
The hydraulic power steering system is a closed loop system that uses pressurized hydraulic fluids for changing the wheel angle of front wheels based on steering angle. It contains a hydraulic pump driven by a belt, valves, cylinder, reservoir and a driver control mechanism(rack & pinion/steering gearboxes).
Here, we can discuss the working of the hydraulic system using rack and pinion driver control mechanism. A rack is a metal bar connected between the front wheels and the pinion is a small gear with teeth placed inside the housing. The pinion is meshed with the rack for providing precise steering. The rack and pinion steering will convert the rotational motion of steering wheel to the linear motion of front wheels. Also, it provides gear reduction.
Both the front wheels are connected to the rack with two separate tie rods on each end. The steering wheel and pinion are connected together with a steering shaft and the rotation of the steering wheel will move the rack to the preferred direction. This movement will help to turn the vehicle wheels.
The above are the basic rack and pinion steering working.
How hydraulics work in this power steering system?
When the driver rotates the steering wheel, the belt and pulley arrangement of the engine will pull fluid from the reservoir to pump. The hydraulic pump will pressurize this fluid and will release it through hydraulic fluid lines towards the rack. The rack has a piston and cylinder arrangement. The cylinder has two openings on either side of the piston and the openings are connected with the hydraulic fluid lines. When the high-pressure fluid is fed to any of the openings, the piston will move towards the opposite direction along with the rack. This will generate a smooth and precise linear motion of the front wheels.
Also, Read: Hydraulic Fluid Properties