Common Magnetic Circuit Structure
The use scenarios of NdFeB permanent magnets are roughly divided into adsorption, repulsion, induction, electromagnetic conversion, etc. In different applications, the requirements for magnetic fields are also different.
The space structure of 3C products is extremely limited, and at the same time requires high adsorption strength. The space structure does not allow the size of the magnet to increase, and the magnetic field strength needs to be increased through the magnetic circuit design;
In the occasion where magnetic field induction is required, the excessively divergent magnetic force lines will cause the Hall element to accidentally touch, and it is necessary to control the magnetic field range through the magnetic circuit design;
When one side of the magnet needs high adsorption strength and the other side needs to shield the magnetic field, the magnetic field strength on the shielding surface is too high will affect the use of electronic components, and it is also necessary to solve this problem through magnetic circuit design;
Occasions that require precise positioning effects, occasions that require a uniform magnetic field…etc.
In all the above cases, it is difficult to use a single magnet to achieve the use requirements, and when the price of rare earth is high, the volume and amount of the magnet will seriously affect the cost price of the product. Therefore, we can meet the adsorption conditions or use it normally. , Modify the magnetic circuit structure of the magnet to meet different usage scenarios, and reduce the amount of magnets to reduce costs.
Common magnetic circuits are roughly divided into HALBACH ARRAY array, multi-pole magnetic circuit, focusing magnetic circuit, adding magnetic permeable material, flexible transmission, single-sided magnetism, magnetic accumulation structure, etc. Let me introduce you one by one:
This is a nearly ideal structure in engineering, with the goal of producing the strongest magnetic field with the least amount of magnets. Due to the special magnetic circuit structure of the Halbach array, most of the magnetic field loops can circulate inside the magnetic device, thereby reducing magnetic flux leakage to achieve magnetic concentration, and realizing self-shielding effect in the non-working area. The optimized ring-shaped Halbach magnetic circuit design, non-working The lowest area can achieve 100% shielding. As can be seen from the figure, the direction of the magnetic force lines of the conventional magnetic circuit is symmetrical and divergent, while most of the magnetic force lines of the Halbach array are concentrated in the working area, so the magnetic attraction force can be improved.
Multi-pole magnetic circuit
The multi-pole magnetic circuit mainly utilizes the characteristic that the magnetic force line preferentially selects the nearest opposite pole to form a magnetic circuit. Compared with the ordinary unipolar magnet, the magnetic force line (magnetic field) of the multi-pole magnetic circuit is more concentrated on the surface, especially the more the number of poles is, the more obvious it is. There are two types of multi-pole magnetic circuit, one is the multi-pole magnetization method of one magnet, and the other is the adsorption method of multiple unipolar magnets. The difference between these two methods lies in the cost, but the actual functions are the same. The advantage of multi-pole magnetic circuit in small pitch adsorption is very obvious.
Focusing magnetic circuit
The focusing magnetic circuit uses a special magnetic circuit direction to gather the magnetic field in a small area, making the magnetic field in this area very strong, even reaching 1T, which is very helpful for accurate positioning and local induction.
Magnetically permeable material
The magnetically permeable material is to use the magnetic field circuit to preferentially select the path with the smallest reluctance. Using high magnetically permeable materials (SUS430, SPCC, DT4, etc.) Effect.
The characteristic of flexible transmission is non-contact flexible transmission through the attraction and repulsion formed by the magnet, small size, simple structure, torque can be changed according to the size of the magnet volume and air gap, and the adjustable space is large.
Single side magnetic
The single-sided magnet is characterized by shielding the polarity of one side of the magnet and retaining the polarity of the other side. The direct adsorption force is relatively large, but the magnetic force attenuates greatly with distance.
The characteristic of the form is that the magnets and iron yokes are arranged in opposite polarities. As the ratio between the thickness of the magnet and the thickness of the iron yoke increases, the thicker the thickness of the iron yoke, the smaller the divergence of the magnetic force lines. The magnetic-gathering structure can be flexibly designed according to the size of the air gap to achieve the optimal effect, which can effectively save magnets, and the magnetic field is evenly distributed along the iron yoke, but the disadvantage is that the assembly cost is high.