Power steering is a system where the steering effort is reduced by using some components. In the power steering system, hydraulic oil is used to deliver the power in the system. In this article, I will discuss what is power steering in a car and the types of power steering used in a car.
What is Power Steering in A Car
The increased use of large-section low-pressure balloon tires has aggravated the steering problem due to the greater contact area between the tire and the ground. The driver requires a greater force to be exerted on the steering wheel for steering the heavy vehicle or heavily loaded commercial vehicle, especially when the vehicle has to take a sharp turn.
Power steering makes it easier to turn sharp corners. It is fitted not only to heavy commercial vehicles but also to heavy and medium-weight cars. It is usually arranged to be operative when the effort at the steering wheel exceeds a pre-determined value. When this effort is excluded, a valve directs the working fluid to the appropriate side of the power cylinder, and this results in the steered wheels being turned in the desired direction.
The working fluid is a high-quality lubricating oil having a viscosity rating equivalent to ASE low for normal conditions. The actual amount of assistance given depends upon the resistance offered to the movement of the road wheels.
Types of Power Steering
There are usually two general types of power steering systems-
- Integral Power Steering, in which the power operating assembly is part of the steering gear.
- Linkage Power Steering, in which the power opening assembly is a part of the linkage.
All these types are discussed below-
#1. Integral Power Steering
The integral power steering is designed to receive power assistance only when the effort at the steering wheel rim exceeds 1 kg and is up to 2.5 kg. It consists of a worm and ball bearing nut steering gear with a hydraulic rack piston, concentric with the worm shaft, which can aid in moving the nut in either direction using hydraulic pressure.
A reaction contract valve is linked to the worm shaft thrust bearing through a link and actuator lever. Any moment of the thrust bearing causes the control valve to move which opens and closes the oil passage between the valve body and the housing of the gear and pinion assembly.
Working of Integral Power Steering
Fig. shows an Integral power steering system with steering linkage, mounted on a motor vehicle. The working of the integral power steering during a right tum is shown in Fig. 33.26. When the vehicle is going straight ahead, the oil flows from the pump, through the open center of the valves, and back to the reservoir.
It also flows into the areas on both sides of the rack piston to act as a lubricant and to cushion the road shocks. These areas are sometimes called “power cylinders”. When the vehicle is turned to the right, the reaction of the wheels, steering linkage, pitman shaft sector, and ball nut to the turning of the worm causes the worm to move downward to the left slightly.
The movement forces the worm against the thrust bearing and causes the actuating lever and control valve links to move the control valve to the position shown in Fig. The fluid passage to the right tum cylinder is broadened, while that to the left tum cylinder is made narrower.
Thus, the fluid flow from the pump is restricted and pump pressure is built up to exert sufficient pressure on the right tum side of the rack position, helping the ball nut in the right tum direction. The fluid in the left tum power cylinder is forced to return to the pump reservoir through the return line.
When the vehicle has to take a left tum, an opposite reaction of the worm causes the fluid to enter the left tum power cylinder in greater volume and to empty the right tum cylinder. This reaction causes the rack piston and ball nut to move in the left-turn direction.
#2. Linkage Power Steering
In this type of power steering, the power cylinder is not a part of the steering gear. The power cylinder is connected to the steering linkage. The valve assembly is inclined in the steering linkage, either as a separate assembly or integrally with the power cylinder. The power assistance is applied directly to the steering linkage.
Working of Linkage Power Steering
In a neutral position, that is, when the vehicle is running straight ahead, a spool valve in the control valve assembly is held in the center position through a centering spring. The oil flows to both sides of the position in the power cylinder and around the valve bands and returns to the pump reservoir.
When the vehicle is taking a left turn and the force on the wheel exceeds 2 kg, the pitman’s arm moves the spool control valve with sufficient force to overcome the pressure of the centering spring so that the valve slides to the right-hand side of the valve body.
In this position, it connects the left-hand side of the power cylinder to the return line leading to the pump reservoir and directs oil pressure to the right-hand side of the power cylinder. This causes the cylinder housing to move to the right, which moves the relay rod to the right to turn the wheels to the left.
When the vehicle is taking a right tum, the conditions are reversed and the relay rod is forced to turn the wheels to the right.
Conclusion on What is Power Steering in a Car
Power steering is a system in a car that assists the driver in turning the wheels by applying hydraulic or electric power. Its primary purpose is to make steering easier, especially at low speeds and when parking. This power steering helps the driver to put less effort when turning the wheel. There are two types of power steering used in automobile cars. In this article, the types of power steering system is discussed along with the working principle.
Frequently Asked Questions(FAQ’S)
How does power steering work?
Traditional power steering systems use a hydraulic pump to pressurize power steering fluid, which assists in turning the wheels. Electric Power Steering (EPS) systems use an electric motor to provide assistance based on sensors detecting steering wheel input.
Why is power steering important?
Power steering is important because it reduces the physical effort needed to steer a vehicle, making driving more comfortable and less fatiguing. It enhances maneuverability, especially in tight spaces, and improves overall vehicle control.
How do I know if my power steering is failing?
Signs of power steering failure may include difficulty turning the steering wheel, whining noise when turning, or fluid leaks. If you experience these symptoms, it’s advisable to have your power steering system checked by a professional.
Is electric power steering more fuel-efficient?
Yes, electric power steering (EPS) is generally more fuel-efficient than hydraulic power steering (HPS) because the electric motor only assists when needed, whereas hydraulic systems operate continuously.