All modern cars are now equipped with a mechanism that has made driving more relaxing, power steering. Thanks to this device, a lower force must be applied to the steering wheel in order to turn the wheels. Let's find out how the power steering works and what are the differences between the electric and the hydraulic power steering.
Electric power steering
One of the benefits that every motorist appreciates of the power steering is the least force required to rotate the steering wheel. The power steering uses an external energy source whose function is to reduce the force needed to steer the wheels.
The benefits of power steering are particularly appreciated during the parking phase because, when the car is stationary, the tires generate greater friction with the ground than in the situations of motion and make it heavier to move the steering.
When it comes to electric power steering means a device that uses an electric motor connected to the steering column, and controlled by a control unit, through which is guided the action of the steered on the basis of the information coming from a sensor. With this system, you get a more accurate guide because the steering response depends on the speed of the car: the more it increases, the less the assistance of the power steering.
Thanks to the electric power steering you get greater energy savings compared to the hydraulic, both for the higher performance of the electric motor can be switched off in the absence of action steered.
In addition, in case of failure, the electric power steering immediately signals the problem by switching on a light on the instrument panel. In case of malfunction it will be possible to continue driving your car but, of course, the effort required to rotate the steering wheel will be higher.
Some cars also use power steering with dual drive. In House Fiat this device was adopted in 1999 on the occasion of the launch of the second series of the Point, and allows, by pressing a button on the dashboard marked with the inscription "city", to further reduce the force required to turn the steering wheel.
Hydraulic power steering
The hydraulic power steering was originally designed to be used on heavy vehicles, such as tractors or trucks, and then used on large-scale sedans.
This system is still widespread today even if the electric consideration has a greater application on the cars.
The hydraulic power steering is composed of an oil reservoir, a gear pump, which works at about 70 bar and is driven by the engine, a distributor with four lights, normally always closed, a control device of the vending machine, located in the steering column, in which there is a screw, a cylinder operator to the inside of which slides on a piston rod a piston that divides the cylinder into two chambers, and one end is connected to the steering linkages while at the other end is connected to the frame and a pressure relief valve to the stroke end of the steering column.
Hydraulic power steering works in the following way: with the wheel stopped, the oil sent from the pump to the distributor does not find access to the cylinder operator as the lights of the distributor are all closed, and back to the tank via a recovery tube, and when you make a steering rotation of the steering wheel controls the device which actuates the distributor connected to it, causing it to open two of the four "lights", which through a tube leading the oil in one of the two chambers of the cylinder operator.
This pressure increase in the chamber moves the plunger in the opposite direction, which thus acts on the wheel lever, and greatly facilitates the steering imposed by the steering wheel direction. When one chamber is filled, the other empty being connected to the recovery circuit. The pressure limiting Valve is operated only if and when the steering wheel runs to the end, and automatically brings the oil back to the recovery circuit without returning it to the cylinder.
Among the advantages of the hydraulic power steering, there is a greater driving feel compared to the electric one, while the negative sides of this device relate to the weight and the constant absorption of energy since the pump is always in function.