Servotronic - what is this device in the car?

Perhaps, one of the most useful inventions in the automotive industry is the power steering. Thanks to him, the driver can easily control the steering wheel, especially when maneuvers at low speed. Today there are several types of such amplifiers. This is a hydraulic and electrical system. But among other things, they can be equipped with additional functions. One of them is servotronic. What is it - we will consider right now.

Where did it come from?

This function appeared relatively recently. Belongs the idea of creating a servotronic system for BMW. What is this element, we will consider further. In the 85th year at the exhibition "Motorshow" in Amsterdam was BMW BMW M5 in the 34th body. The machine was not only a powerful engine, but also excellent controllability. In particular, many journalists noted the responsiveness of the helm. On the spot it could be scrolled with one finger. However, at speed, it becomes incredibly hard. This provided the machine with excellent stability at high speeds. It was the first power amplifier with this function. They called this system servotronic.

What it is? Characteristic

Servotronic - an electronic system that allows you to adjust the gain on the steering wheel, depending on the speed of the car. The system serves for comfort and control.

What cars are installed?

Initially servotronic appeared on the 34th BMW. Further, this technology was adopted by other manufacturers. This is Volkswagen, Porsche and Volvo. Servotronic was also installed on the Audi. What is servotronic, we already know. But it is worth noting that in addition to it there are also analogues (for example, the active steering system). We'll talk about it a little later.

How does it work

Rake steering with servotronic almost does not differ from usual. The exception is all kinds of sensors and control unit. Conditionally servotronic can be divided into two parts - informative and executive. To read the data, the system provides input sensors:

• Power steering.
• Steering angle (for vehicles with ESP system).

With their help, the system determines the position of the rudder relative to the angle of rotation of the front wheels. Also in the system there is a Hall sensor. He informs about the position of the crankshaft in the engine. A speedometer sensor transmits data on the current speed of the machine. Thus, several signals are sent to the control unit at once. Then the system processes this information and sets a certain algorithm of operation to the actuators. These include a back-action chamber with a slide valve and a piston. To regulate the pressure of the hydraulic fluid, the system has a servotronic solenoid valve. What is this element? It interacts with the servotronic unit. When turning the rudder, a fluid is passed through the slide valve to the cylinder of the hydraulic booster. The latter begins to act on the mechanism of turning the wheel. At the same time, a signal is sent to the solenoid valve. It opens and the liquid fills the camera back. Thus, the pressure in the cylinder drops. The reverse action piston locks the spool. Gain on the steering wheel increases.

With the falling speed of the car, the valve closes. When parking, it is closed at all, which makes it possible to easily rotate the steering wheel in place. As soon as the speed exceeds 20 kilometers per hour, the valve gradually opens. The driver needs to make more effort to rotate than usual. That is, servotronic operation is based on the throttling of hydraulic fluid in the GUR system by opening or closing the solenoid valve. In this case, the unit regularly receives signals and the current vehicle speed and the position of the steering wheel itself. The servotronic control unit is usually located at the glove box.

Malfunctions

This system is highly reliable, so the malfunctions are minimized. If there are any problems, a corresponding light bulb is displayed on the instrument panel. Thus, the system may not supply power to the servotronic sensor (terminals are oxidized or broken), or to the unit itself. Probably, the fuse has overheated in the system. In the event of system failure, the driver will immediately notice changes in the behavior of the car. The relay with servotronic will be controlled as usual, with the GUR. At high speeds, the steering wheel will be as light as small ones. Because of this, the car will be less stable on the road.

Active Steering System AFS

It is a servotronic analog. What is this system? It is a unit operating from a planetary gearbox. The latter is equipped with an electric motor. Usually it is put on cars with ЭУРом. So, the gearbox with the motor is mounted on the steering shaft. The system has its own control unit, which, like the servotronic, receives signals from various sensors. On their basis, the electronics takes measures to adjust the gear ratio between the steering wheel and the wheels of the machine. With increasing speed, this number increases. The steering wheel becomes more rigid. The system automatically selects the appropriate gear ratio and can change it every second. Thus, the fundamental difference between AFS and servotronic is the method for controlling forces. In the first case, the reducer with an electric motor is sensed, in the second case there is an electromagnetic valve that controls the flow and pressure of the hydraulic fluid. AFS has many advantages. So, the system is able not only to make management more stringent, but also to prevent an emergency situation. In the case of a car skid, the electronics evaluate the situation thanks to the sensors and automatically rotate the wheels to a certain angle.