As a result of these thoughts, the concept of power steering was born in the 19th century. After the appearance of heavy-duty steam-powered buses on city streets, it became necessary to ease the workload of the drivers operating them. The search began for design solutions that would reduce the effort required to turn the steering wheel.
In 1925, Francis Deyes was one of the first to patent a hydraulic power steering system in the USA, and in 1933, General Motors was already planning to install it on its Cadillac car with a twelve-cylinder engine. By 1951, Chrysler had mastered the production of power steering and from that time on began equipping many of its models with it. The first manufacturer of passenger cars to offer the installation of power steering as an additional equipment model "519", was the company "Fiat". Currently, as a result of the appearance of front-wheel drive vehicles, the use of larger tires and weight, suspension with complicated kinematics, there is a need to use power steering even on small cars. As the name suggests, this device is based on the principle of hydraulics. The pressure in the system, filled with a special liquid, is created by a hydraulic pump driven by the engine crankshaft. The design includes a spool valve, which, when the steering wheel is turned, switches the fluid supply to one or another cavity, providing additional impact on the steering actuator (gearbox or rack). Initially, power steering designs were imperfect and had a number of drawbacks. For example, they reduced the effort required to control the car so much that the steering feedback was lost. Such systems were installed on cars up until the 80s. It is not difficult to imagine how dangerous it is to "overdo it" when manipulating the steering wheel while turning at high speed.
This is where the basic requirements that the power steering mechanism must meet follow. The goal is to make turning easy when maneuvering at low speeds and more noticeable in terms of steering force when driving at higher speeds, so that driving the car becomes as safe as possible.
With most power steering systems, the gain remains constant regardless of the vehicle speed. However, an increasing number of cars entering the market today are equipped with variable power assist systems, in which the power assist level changes depending on the speed of the car, ensuring precise and fast response when the car is cornering and the required force when maneuvering the car at low speeds.
One way to achieve this is to use a steering rack with a variable gear ratio. For this purpose, the pitch and diameter of the pitch circle of the teeth change along the length of the rack, while the pitch of the teeth on the gear remains constant. When the wheels of the car are set to move straight ahead, the steering gear ratio is equal to one and the gain is the smallest, but as the steering wheel approaches its extreme positions, the gear ratio increases and the force required to turn the wheels decreases. Computer-controlled power steering is also no longer something unusual. These steering systems process information from the vehicle's speedometer. Their operation is determined not only by the engine speed, but also by the vehicle speed. The computer microprocessor analyzes the signals coming from the sensor and calculates the required gain factor at each moment, which is realized using an electro-hydraulic converter.
The idea behind these systems is to take the best of both worlds - make the steering as light as possible at parking speeds, and reduce the power assistance when driving at high speeds so that the system operates almost like a conventional mechanical steering system without power assistance.
System maintenance
As a rule, the power steering mechanism is highly reliable and does not require complex maintenance during vehicle operation. Even if the power steering pump fails, the vehicle can continue to move, although turning the steering wheel in this case will require significantly more effort than even on a vehicle without power steering.
The most common cause of complete failure of the power steering is a broken pump drive belt. Check the condition of the belt regularly - it may be worn or loose. One of the signs of weak belt tension is the appearance of recoil (back push) on the steering wheel. This is usually most noticeable when the car is moving off and the wheels are turned all the way.
Maintain the proper level of fluid in the booster reservoir. When necessary, add only the fluid specified in the service manual. Please note that fluid intended for automatic transmissions cannot be used for all power steering systems. There are many different brands of liquids available on the market. The wrong fluid can ruin all the seals in the system.
Since the liquid is used not only as a working fluid of the hydraulic system, but also as a lubricant, it is very important that its level does not fall below the norm, otherwise the pump may fail. Also make sure the liquid is clean. Dirty or expired fluid will quickly destroy the pump and hydraulic system seals located on the rack and pinion mechanism, which will then require expensive repairs. Fluid replacement is rarely required. If you want to drain the fluid, you need to open the expansion tank cap, disconnect one of the system pipes and turn the steering wheel from side to side several times to squeeze the fluid out of the hydraulic system. There is usually no special hole for draining liquid. New fluid is added through the expansion tank. As a rule, this causes air locks to form in the hydraulic system, which impairs its functionality. They should be removed. The easiest way to do this is as follows. Start the engine, open the expansion tank cap and bleed the system by turning the steering wheel several times from one extreme position to the other. As the hydraulic system is pumped, the fluid level in the reservoir will decrease. Repeat this procedure until it stabilizes. After this, add liquid to the required level and close the lid, having first checked whether the ventilation hole is clogged (if it exists).
The most common failure of power steering systems is fluid leakage. Cars with such a defect usually fail technical inspection. Some older hydraulic systems were allowed to leak a small amount of fluid through bearings, shafts, etc., since it is virtually impossible to make them completely sealed. Regularly inspect the system units from all sides to promptly detect possible leaks from pipelines and fittings, as well as from loosely fastened pipelines and other parts.
Check to see if any tubes or hoses are rubbing against chassis or suspension components. A faulty hydraulic line can cause fluid to leak through the covers. When checking, turn the steering wheel from one extreme position to the other. Small leaks can often be repaired by adding commercially available sealing additives to the fluid. However, this will only be a short-term measure. If the pump is faulty, it can be repaired using a repair kit of new seals. Replacing the seals will do little to improve the pump if it is badly worn.
For those who like to do everything themselves, pump repair will not present any great difficulties. However, before installing the repaired pump on the car, it is advisable to test it on a stand. If you suspect that the pump is worn out, contact a power steering specialist to check its operating pressure and correctly diagnose the fault. Generally speaking, the numerous advantages of power steering far outweigh the problems created by its possible malfunctions. Once you have driven a car with a modern system, switch to a car without power steering and you will immediately "feel the difference."