What is power steering? Electric & Hydraulic power steering system




What is power steering? 


Power steering is an automotive equipment or device that helps to turning the steering wheel easily. Power steering is powered by  hydraulic or electric actuators which attached with steering mechanism that turns the wheel left or right with less muscles force.It is also known as power assisted steering. Overall process is power steering system

Three types of power steering are most commonly used in automotive industries. All of these are discussed below

Rack and pinion steering


Rack and pinion steering
Rack and pinion steering are the most widely used
in small types of vehicles that consists of a rack and pinion gear. In this steering a pinion is connected perpendicularly with rack that is developed by tie rod mechanism. When steering wheel rotates pinion turns and creates a linear motion of the rack,connected with tie rods thus car wheels moves left or right. Rack and pinion system can move freely than worm gear and it takes more energy to drive.  

For larger pinion it is more difficult to turn and need less rotation of the steering wheel. In the big pinion, It is easier to turn but needs more rotates of steering wheel. 

Hydraulic power steering


Hydraulic power steering



Hydraulic power steering is more powerful than electric and rack and pinion power steering. Hydraulic fluid is pumped by hydraulic motor driven by the engine. If steering turns, fluids transferred  by the rotary valve housing to the piston and acts directly to the rack and pinion. Rotary valve is located between the pinion gear and steering gear input shaft. 


Hydraulic steering consists of these main parts 

  • Fluid reservoir or tank: Fluid reservoir stores the fluid inside it and supply to the hydraulic power steering system. 

  • Rotary valve: In the neutral position of the steering the rotary valve redirects the fluid to the pump. When steering wheel turns left or right fluid go to the hydraulic chamber of the steering rack thus vehicle wheels moves left or right.

  • Hydraulic pump: Hydraulic pump is connected to the engine through the belt. Pump creates the fluid force to create excessive power for the steering operation. 

  • Hydraulic chamber. Hydraulic fluid comes to hydraulic chamber through the rotary valve. Hydraulic chamber separated with two equal position and pistons separates each chamber. 



Electric power steering


Electric power steering

Electric power steering system is also called as EPS.It is an assistant type mechanism that makes more comfortable and accurate for driver to control the steering. A torque sensor is connected with torsion bar that generates signal to the ECU and finally ECU gives signal to the motor rotating directions and how slowly or fast will steering rotates? Electric power steering system used less energy from car engine than the hydraulic system and less maintenance needs in this system. 

Electric power steering consists of some components is listed below

  • Steering angle sensor

  • Torque sensor

  • Reduction gearbox

  • ECU

  • Vehicle speed sensor

  • Electric motor



Electro Hydraulic power steering



Image Source

EHPS system is used an electric motor (Not used belt driven hydraulic pump) to generate hydraulic pressure to move steering easily. Electro hydraulic power steering is also called EHPS. The main benefits of EPHS system is that it does not need the engine running to drive the hydraulic pump. EHPS consist of vane pump, two electric motors,steering gearbox and other electronics equipment that are installed in a single unit.

Hydraulic power steering vs electric power steering


Electric power steering system comparable cost is lower than hydraulic power steering system. Need continuous running of hydraulic pump to operate hydraulic power steering system that’s why fuel consumption increases for pump running. where electric power steering system needs to run the motor when needed.Fluid leakages are common issues for hydraulic power steering system.In the electric power steering system needs less maintenance.  

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