Everyone knows that magnets have a propertyattract metals. Also one magnet can attract the other. But the interaction between them is not limited only to attraction, they can repel each other. The matter at the poles of the magnet - opposite poles attract, the same poles - repel. This property is the basis of all electric motors, and quite powerful.
There is also such a thing as levitation forthe action of the magnetic field, when the object placed over the magnet (having a pole similar to it) hangs in space. This effect was applied in practice in the so-called magnetic bearing.
An electromagnetic type device in whichThe rotating shaft (rotor) is supported in the stationary part (stator) by the forces of the magnetic flux, called the magnetic bearing. When the mechanism is in operation, it is influenced by physical forces that tend to displace the axis. To overcome them, the magnetic bearing is equipped with a monitoring system that monitors the load and provides a control signal for the magnetic flux. Magnets, in turn, are stronger or weaker on the rotor, keeping it in a central position.
The magnetic bearing has found wide application inindustry. These are mainly powerful turbomachines. Due to the absence of friction and, accordingly, the need to use lubricants, the reliability of machines is greatly increased. The wear of the knots is practically not observed. Also, the quality of dynamic characteristics is increased and the efficiency is increased.
A magnetic bearing, where a force field is createdwith the help of electromagnets, is called active. Electromagnets positional are located in the bearing stator, the rotor is represented by a metal shaft. The entire system that ensures the retention of the shaft in the unit is called the active magnetic suspension (AMP). It has a complex structure and consists of two parts:
Magnetic bearings on permanent magnets areRotor shaft holding systems that do not use a control circuit that includes feedback. Levitation is carried out only due to the forces of high-energy permanent magnets.
The disadvantage of such a suspension is the needthe use of a mechanical stop, which leads to friction and reduced reliability of the system. The magnetic emphasis in the technical sense is not yet realized in this scheme. Therefore, in practice, a passive bearing is used infrequently. There is a patented model, for example, Nikolayev's suspension, which has not yet been replicated.
The term "magnetic hub bearing" refers toto the ASB system, which is widely used in modern cars. The ASB bearing is characterized by the built-in wheel speed sensor inside. This sensor is an active device embedded in the bearing shim. It is built on the basis of a magnetic ring, on which the poles of the element that reads the change in the magnetic flux alternate.
When the bearing rotates, a constantThe change in the magnetic field produced by the magnetic ring. The sensor records this change by forming a signal. Then the signal enters the microprocessor. Thanks to it, such systems as ABS and ESP work. They are already correcting the work of the car. ESP is responsible for electronic stabilization, ABS regulates the rotation of the wheels, the level of pressure in the system is braking. It monitors the operation of the steering system, acceleration in the lateral direction, and also corrects the operation of the transmission and the engine.
The main plus of the ASB bearing isIt is possible to control the speed of rotation even at very low rpm. At the same time, the overall dimensions of the hub are improved, the mounting of the bearing is simplified.
The simplest magnetic bearing by one's own handsto make it simple. It is not suitable for practical use, but it clearly demonstrates the possibilities of magnetic force. To do this, you need four neodymium magnets of the same diameter, two magnets of a slightly smaller diameter, a shaft, for example a piece of plastic tube, and a stop, for example a glass half-liter can. Magnets of smaller diameter with the help of hot melt are fixed to the ends of the tube in such a way that a coil appears. In the middle of one of these magnets, a plastic ball is glued from the outside. The same poles should look outwards. Four magnets with the same poles up are decomposed in pairs at a distance of the length of the tube segment. The rotor is placed over the lying magnets and on the side where the plastic ball is glued, prop it with a plastic jar. Here is the magnetic bearing and is ready.
