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With ease

Man has always sought with a minimum of effort to get the maximum return. At first he was too lazy to walk - and there was a car. In a short time, "hardworking" humanity was horrified to find that even the fact to turn the steering wheel, the forces do not have to spend so little. And think how to alleviate their plight ...

As a result of these reflections in the XIX century was born the concept of the power steering. After appearing on the streets of heavy buses with a steam engine it was necessary to facilitate the work of the Governing drivers. Began search for constructive solutions to reduce stress by turning the steering wheel.

In 1925, the United States, Francis Davis one of the first patented the hydraulic power steering system, and in 1933 concern "General Motors" is already planned to install it on your car "Cadillac" with twelve-cylinder engine. By 1951, the company "Chrysler" has mastered the production of power steering systems, and since that time they started to equip many of its models. The first car manufacturer to offer the installation of the power steering as an option model "519" was the company "Fiat". Currently, as a result of front wheel drive cars, use larger tires and weight, with a sophisticated suspension kinematics there is the need for a power-assisted steering even in small cars. As the name implies, this device is based on the principle of using hydraulics. The pressure in the systems filled with a special liquid, created by the hydraulic pump driven by the engine crankshaft. The design of the spool valve is provided which, when turning the steering wheel switches the fluid in either chamber, providing additional impact on the steering actuator (gearbox or rail). The original design of the power steering were imperfect and had a number of shortcomings. For example, they reduce stress while driving so that the information content lost steering. These systems are installed on the car until the 80s. It is easy to imagine how dangerous it is "too far" in handling the wheel rotate at high speed.

From this it follows the basic requirements to be met by power-steering mechanism. The challenge is to make turning easy maneuvering at low speed and more tangible on the effort on the steering wheel while driving at a higher speed driving to become as safe as possible.

Most hydraulic actuators regardless of the vehicle speed gain remains constant. However, an increasing number of vehicles entering the market today, systems equipped with a variable gain amplifier whose degree of amplification has changed depending on the vehicle speed. They provide accurate and quick response when the vehicle is cornering and effort required for maneuvering the vehicle at low speed.

One way of achieving this is to use a steering rack with variable ratio gearing. For this purpose, the length of the rack is changed pitch and the diameter of the pitch circle of the teeth and the teeth on the pinion pitch remains constant. When the wheels of a vehicle are exposed to movement in the forward direction, steering ratio equal to one, and the least gain, but as it approaches the steering wheel to its extreme positions, the gear ratio increases, and the force required to rotate the wheels is reduced. Power steering, computer controlled, also ceases to be unusual. Such steering systems process information from the speedometer of the car. Their work depends not only on the engine speed, and vehicle speed. The microprocessor computer analyzes the signals coming from the sensor and calculates the time required for each gain, which is realized by means of an electrohydraulic transducer.

The idea of development of such systems: to take the best of both types of steering - at speeds typical for parking the car, make steering more easy, and when driving at high speed operation of the amplifier is reduced to the extent that the system worked nearly as well as conventional mechanical steering without the amplifier.