The linear motor can be considered as a deformation of the rotating motor in terms of structure. It can be seen as a rotating motor that is split along its radial direction and then flattened. With the rapid development of automatic control technology and microcomputers, higher requirements have been put forward for the positioning accuracy of various types of automatic control systems. In this case, the traditional rotating motor plus a set of linear motion driving devices composed of transformation mechanisms have been far from meeting the requirements of modern control systems. For this reason, many countries in the world are studying, developing and applying linear Motors, making the application of linear Motors more and more extensive.
Compared with the rotary motor, the linear motor has the following main characteristics: First, the structure is simple. Since the linear motor does not need to turn the rotational motion into an additional device for linear motion, the structure of the system itself is greatly simplified, and the weight and volume are greatly reduced.; Second, the positioning accuracy is high. Where a linear motion is required, the linear motor can achieve direct transmission, thus eliminating various positioning errors brought about by the middle link. Therefore, the positioning accuracy is high, such as the use of microcomputer control. It can also greatly improve the positioning accuracy of the entire system; Third, the response speed, high sensitivity, and good portability. It is easy for a linear motor to use magnetic levitation to support its movers, thus making it always maintain a certain air gap between the movers and the stators without contact, which eliminates the contact friction between the movers and the movers. Therefore, the sensitivity, rapidity and automaticity of the system are greatly improved. Fourth, work safety and reliability, long life. The linear motor can achieve no contact transmission force, and the mechanical friction loss is almost zero, so there are fewer faults and no maintenance, so it is safe and reliable to work and has a long life.
Linear motors are mainly used in three aspects: First, they are used in automatic control systems. The second is as a long-term continuous operation of the driving motor; Third, it is applied to devices that require a short time and a short distance to provide huge linear motion energy.
The high-speed maglev train maglev train is the most typical example of the practical application of linear Motors. The United States, Britain, Japan, France, Germany, Canada and other countries are developing linear suspension trains, of which Japan has made the fastest progress.
The world's first elevator driven by a linear motor was installed in the Wanshi Building in Toshima, Tokyo, Japan, in April 1990. The elevator has a load of 600kg and a speed of 105m/min, raising the height to 22.9 M. Because there is no tracer unit for a linear motor driven elevator, the computer room at the top of the building can be omitted. If the height of the building increases to about 1,000 meters, it is necessary to use a steel-free rope elevator. This elevator is driven by a linear motor with high temperature superconductivity technology. The coil is installed in the shaft and the car is equipped with a high-performance permanent magnet material. Like a maglev train, Use radio waves or optical control technology to control.
When an ultra-high-speed motor rotates beyond a certain limit, the motor using rolling bearings will produce sintering and damage. A linear suspension motor(electromagnetic bearing) has been developed abroad to use suspension technology to levitate the motor's movers in the air. The mechanical contact and friction resistance between the mover and the stator are eliminated. The speed can reach 25,000 to 100,000 r/min, and it is widely used in high-speed motors and high-speed spindle components. For example, the 5-axis controllable electromagnetic high-speed spindle for multi-process automatic numerical control lathes recently developed by Aikawa Corporation of Japan adopts two radial electromagnetic bearings and one axial thrust electromagnetic bearing, which can withstand the load of the machine tool on Renyifangxiang. In the middle of the shaft, in addition to the high-speed motor, it is also equipped with a tool automatic exchange mechanism suitable for multi-process automatic numerical control lathes.