JPH01253905A - Multiple-pole magnetizing permanent magnet - Google Patents

Abstract

PURPOSE:To improve magnetic flux density by performing multiple-pole magnetization on the surface of a magnet material body after uniformly magnetizing entire surface of the magnet material body previously. CONSTITUTION:First of all, a straight-line plate magnet material body 10 such as a sintered ferrite is uniformly magnetized in the direction of thickness so that N and S poles may appear on the upper and lower surfaces requiring a reinforced magnetic field. Then, an upper surface 11 of the straight-line plate magnet material body 10 is subject to multiple-pole magnetization and the N and S poles are formed alternately with magnetic pole array spaces D. Thus, also after the multiple-pole magnetization, magnetized part due to initial magnetization in the direction of thickness generates bias magnetic field, which is superposed onto the magnetic field of N and S poles by the multiple-pole magnetization. It allows an even reinforced magnetic field to be obtained at the N-pole side.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to a multi-pole mounting for a magnetic sensor used in combination with a magnetically sensitive element such as a Hall element, Hall IC, etc. for position and rotation detection. Concerning magnetic permanent magnets.

(Prior art) A multi-polar magnetized permanent magnet for a magnetic sensor has multi-pole magnetization on the surface of a diagonal magnet material, and utilizes a magnetic field with a component directed perpendicular to the surface to generate a Hall element, a Hall IC, etc. The magnetically sensitive element is activated. Conventional multi-polar magnetized permanent magnets of this type include a linear plate-shaped multi-polar magnetized permanent magnet shown in Pt58, a disc-shaped multi-polar magnetized permanent magnet shown in Fig. 19, and a Pt 10
There is a ring-shaped multi-polar magnetized permanent magnet shown in the figure, and a straight plate-shaped multi-polar magnetized permanent magnet shown in Fig. 8 is one in which Ni and S poles are alternately magnetized on the upper surface 1 of the magnet material (Fig. The disk-shaped multi-pole magnetized permanent magnet shown in FIG. 19 has a large number of alternating north and south poles magnetized on the upper surface 2 of the magnet material. Further, the ring-shaped multipolar magnetized permanent magnet shown in FIG. 10 has a large number of N poles and S poles alternately magnetized around the outer periphery 3 of the magnet material body (arrows in the figure indicate the direction of magnetic flux). As shown in FIG. 11, the surface magnetic flux density of the conventional multi-pole magnetized permanent magnets shown in FIGS. 8 to 10 is symmetrical on the north and south pole sides, and the maximum Magnetic flux density (peak value of magnetic flux density) B
n and the maximum magnetic flux density Bs on the S pole side are equal.

In order to increase the magnetic flux density on the surface of such a multipolar magnetized permanent magnet, when using the surface of a linear plate-shaped or disk-shaped magnet material p[, it is necessary to perform anisotropic orientation in the thickness direction,
When the outer circumferential surface of a ring-shaped object is used, polar anisotropic orientation is performed along the outer circumferential surface. In addition, the desired magnetic flux density was obtained by changing the magnet material to a rare earth magnet or the like with a high energy product.

(Problem to be solved by the invention) By the way, what about Hall elements and Hall ICs? When operating the magnet, a mechanical clearance (gap) is required between the magnetically sensitive part and the magnet surface so that both can perform relative movement. When designing a magnetic sensor, if this clearance can be increased, the range of applications of the magnetic sensor will be expanded. However, since the magnetic flux density decreases in inverse proportion to the clearance distance, if the clearance is too large, the magnetically sensitive element cannot be operated.

For example, sintered light magnets and rare earth magnets have weak mechanical strength, so when placed in places where functional strength measures are required, a protective cover is sometimes provided on the magnet surface using a resin mold or non-magnetic material. be. The thickness of this protective layer increases the clearance (which results in a decrease in magnetic properties).

In addition, ferrite magnets have a temperature characteristic of magnetic flux density of -0,
Because of 18%/gauss/'C, the magnetic flux density decreases as the temperature increases. For example, when used in magnetic sensors for automobiles, heat resistance of 150°C may be required, but even if the magnetic sensor operates at 20°C, the magnetic flux density decreases by approximately 20% at 150°C. As a result, the magnetic sensor may become inoperable.

Therefore, in order to compensate for the decrease in magnetic flux density under these conditions, it is necessary to select a magnet depending on the intended use. A magnet or the like will be used, but in any case this poses a problem in terms of cost.

In view of the above points, the present invention aims to provide a high-performance, low-cost method that can improve magnetic flux density without using magnetic materials with a high energy product (and without using a special manufacturing method such as polar anisotropic orientation). The purpose is to provide a multipolar magnetized permanent magnet.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides that after the entire magnet material body is magnetized uniformly in a -like manner in advance, multipolar magnetization is applied to the surface of the magnet material body. It is carried out.

(Function) When magnetizing the surface of a permanent magnet with N and S poles alternately,
The magnetization strength of both poles is equal, but in a magnetic sensor that uses only one magnetic field on the north or south pole side when operating a magnetically sensitive element, the north and south poles are equally magnetized. It can be used even if it is not. Therefore, if only the magnetic pole side on which the magnetically sensitive element is to be operated can be more strongly magnetized, it is not necessary to use a magnetic material with a high energy product. However, if this is carried out with only one multi-pole magnetization process, it is possible to weaken the magnetization strength of one of the magnetic poles, but it is impossible to magnetize it even more strongly. be.

On the other hand, as shown in Figure 12, if the magnetization magnitudes of the multi-pole N and S poles are +M and -M, and the external magnetic field is 4, then the strength of the magnetic field inside the magnet is are +M, -M
It becomes a composite magnetic field of H and H, and since the magnetization directions of the N and S poles are opposite, a forward-reverse relationship occurs between the magnetic field H and
Due to the effect of the bias magnetic field, the magnetic flux density becomes uneven on the magnet surface, and as a result, the magnetization strength of the north and south poles becomes variable. That is, N on the top surface of the magnet in FIG.
Magnetic flux density Bn-H+M at the pole, magnetic flux density B at the S pole
s=HM, and as a result, the surface magnetic flux density has an asymmetrical waveform on the north pole side and the south pole side to which the bias magnetic field is applied, as shown in FIG.

In the present invention, instead of the above-mentioned external magnetic field H, the entire magnet material is uniformly magnetized in advance in a direction that requires a strong magnetic field, and then the surface of the magnet material is multi-poled. After magnetization, a bias magnetic field is generated by the magnetized part due to initial magnetization, which is superimposed on the magnetic field generated by multi-pole magnetization in the subsequent process, thereby creating a strong magnetic field on either the N pole or S pole side. I'm trying to get it.

(Example) Hereinafter, an example of a multipolar magnetized permanent magnet according to the present invention will be described with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, in which a linear plate-shaped multipolar magnetized permanent magnet is constructed. First, as shown in FIG. 2A, a linear plate-shaped magnet material body 10 made of sintered ferrite or the like is magnetized in a negative direction in the 1γ direction. In the illustrated case, the orientation is such that the north pole appears on the top surface, which requires a strong magnetic field, and the south pole appears on the bottom surface.

Next, as shown in Fig. 1(B), the upper surface 1 of the linear plate-shaped magnet material body is
1, and the magnetic pole arrangement interval D''c is formed to alternately form N poles and S poles (arrows in the figure indicate the direction of magnetic flux).

In the case of this 11th embodiment, the magnetized portion due to the initial magnetization in the thickness direction (portion near the middle or bottom of the linear plate-shaped magnet material body) remaining after multipolar magnetization generates a bias magnetic field, which is generated by the multipolar magnetization. The magnetic field is superimposed on the N-pole and S-pole magnetic fields due to magnetization, and as a result, a stronger magnetic field is obtained on the N-pole side in the case shown.

Note that if the thickness L of the linear plate-shaped magnet material is less than 1/3 of the magnetic pole arrangement interval, the magnetization in the thickness direction initially performed will be canceled by the magnetizing magnetic field during multi-pole magnetization. , the effect of magnetic bias cannot be obtained)a FIG. 2 shows a second embodiment of the present invention, in which a disk-shaped multipolar magnetized permanent magnet is constructed. First, as shown in FIG.
A negative magnetization is applied to the material in the thickness direction. In the illustrated case, the orientation is such that the north pole appears on the top surface, which requires a strong magnetic field, and the south pole appears on the bottom surface.

Next, as shown in FIG. 2(B), the surface 13 of the disc-shaped magnet material body is magnetized with multiple poles to form alternating north and south poles.

In the case of this second embodiment, the magnetized portion due to the initial magnetization in the thickness direction (portion near the middle or lower surface of the disk-shaped magnet material body) that remains after multipole magnetization generates a bias magnetic field, which causes the multipolar magnetization. The magnetic field is superimposed on the N-pole and S-pole magnetic fields due to magnetization, and as a result, a stronger magnetic field is obtained on the N-pole side in the case shown. However, in this case as well, if the thickness t of the disk-shaped magnet material is 1/3 or less of the magnetic pole arrangement interval, the initial magnetization in the thickness direction is canceled by the magnetizing magnetic field during multi-pole magnetization. Figure 3 shows a third embodiment of the present invention, in which a ring-shaped multipolar magnetized permanent magnet is constructed. First, as shown in FIG. 2A, a ring-shaped magnet material body 1.1 made of sintered 7-elite or the like is magnetized in a negative manner in the radial direction. In the illustrated case, the direction is such that the north pole appears on the outer peripheral surface, which requires a strong magnetic field, and the south pole appears on the inner peripheral surface.

Next, as shown in FIG. 3(B), the outer circumferential surface 15 of the ring-shaped magnet material body is magnetized with multiple poles to alternately form N and S poles.

In the case of this third embodiment, the magnetized portion due to the initial radial magnetization that remains even after multi-pole magnetization (the middle or inner peripheral surface portion of the ring-shaped magnet material body) generates a bias magnetic field, and this The magnetic field is superimposed on the N-pole and S-pole magnetic fields on the outer peripheral surface due to polar magnetization, and as a result, a stronger magnetic field is obtained on the N-pole side in the illustrated case. However, in this case as well, if the radial thickness Lr of the ring-shaped magnet material body is 1/3 or less of the magnetic pole arrangement interval, the initial radial magnetization due to the magnetizing magnetic field during multi-pole magnetization will be They are canceled out, and the effect of magnetic bias cannot be obtained.

FIG. 4 shows the relationship between the clearance and the magnetic flux density when the disk-shaped multipolar magnetized permanent magnet of the second embodiment is constructed.

However, the disk-shaped magnet material body used is B.
r (4200 Hauss), t, Hc (29500e)
It has the following characteristics, outer diameter 90+am, inner diameter 60mm, thickness 4
alI11, and the thickness direction is the easy magnetization direction. Here, (A) in the same figure shows the magnetic flux density on the upper and lower surfaces when the disk-shaped magnet material body is magnetized in -like m1 steps in the thickness direction, and is measured at a clearance of Oml. Figure (B) shows the magnetic flux density when one of the upper and lower surfaces of the disc-shaped magnet material body is subjected to tiS two-stage Vf1 magnetization, that is, multi-pole magnetization (72 poles), and the clearance O
mm, 0.5mm.

The cases of 1.0III11.2.01 are shown respectively.

As shown in Fig. 1 (B), regardless of the size of the clearance, the effect of the bias magnetic field caused by the magnetization due to the stepwise magnetization of Pt51 appears, and a strong magnetic field is obtained on the N pole side. , 0m16, the maximum magnetic flux density of the north pole is about 300 gauss, which is sufficient to operate the magnetically sensitive element.

On the other hand, Fig. 5 shows a disc-shaped multi-pole magnetized permanent magnet obtained by performing only multi-pole magnetization (72 poles) using a disc-shaped magnet material body having the same characteristics and dimensions as the Pt44 magnet material. The relationship between clearance and magnetic flux density is shown below. In this case, the effect of the bias magnetic field cannot be obtained, and the clearance 2.0LIII7 has a maximum magnetic flux density of 200
gauss and cannot operate the magnetically sensitive element.

Figure ttS6 shows the relationship between the clearance and magnetic flux density when a disc-shaped multipolar magnetized permanent magnet of the j@2 embodiment is constructed, and the thickness of the disc-shaped magnet material body is 4111 in Figure 4.
This is a case of changing from 111 to 811II11. There are no changes to the properties or dimensions of the magnet material other than the thickness.

Here, (A) in the same figure shows the magnetic flux density on the upper and lower surfaces when #IJ1 step magnetization is performed uniformly in the thickness direction of the disk-shaped magnet material body, and is measured at a clearance Owm.

In the same figure (B), one of the upper and lower surfaces of the disk-shaped magnet material body is magnetized in f52 steps, that is, multi-pole magnetized (7 poles).
2) is applied, and the clearance is 0a.
oo, 0.5111111% 1, 0mm.

The case of 2.0+n+o is shown respectively. As shown in FIG. 6(B), by increasing the thickness of the magnet material body, f
It can be seen that the bias magnetic field caused by magnetization by the i1 stage magnetization can be increased. Further, by changing the thickness t of the disk-shaped magnet material in a size range larger than ⅓ of the magnetic pole arrangement interval, it is possible to freely adjust the magnitude of the bias magnetic field.

Figure 7 shows the clearance distance from the magnet surface and the maximum magnetic flux density (magnetic flux (peak value of density). In the figure, curve A is an isotropic sintered 7-magnitude light magnet that has been subjected to conventional multi-pole magnetization. Array interval 3.5
The 0 curve opening, which is magnetized with 36 poles at a pitch of The same is true for curve A. In the case of multi-pole magnetized permanent magnets with these curves A and 1, the magnet material is cheap and easy to manufacture, but if the clearance is 2.0III1 or more, it will fall below the expected operating level (230 gauss) of the magnetically sensitive element and will not be sensitive. The magnetic element cannot be activated.

In addition, curve C is a polar-anisotropic oriented sintered ferrite magnet that has been subjected to conventional multi-pole magnetization, and the magnet shape and number of poles are the same as curve A. This magnet uses only conventional neodymium/iron/boron plastic magnets with conventional multi-pole magnetization, and the magnet shape and number of poles are the same as those for curve A.

In the case of the multi-pole magnetized permanent magnet shown in curve C and II, even if the clearance is 2.0++ m, it exceeds the expected operating level of the magnetically sensitive element (230 Hauss) and the magnetically sensitive element can be activated, but a special manufacturing method is required. In either case, the cost is high because it requires expensive magnet materials.

Curve E shows a multi-polar magnetized permanent magnet according to the present invention using isotropic sintered 7-magnitude light magnets, and the magnet shape and number of poles are the same as curve A. The multi-pole magnetized permanent magnet according to the present invention is constructed using a radially anisotropic sintered ferrite magnet for curve A, and the magnet shape and number of poles are the same as for curve A.

The multi-polar magnetized permanent magnet according to the present invention has the expected operating level (230 gauss) of the magnetically sensitive element even when the clearance is 2.0IIII as shown in curves E and I.
However, the magnet material is inexpensive and easy to manufacture.

Although FIG. 7 shows an example in which the present invention is applied to a sintered ferrite magnet, the present invention can also be applied to other magnet materials (such as ferrite powder mixed with plastic). It is clear that there is.

(Effects of the Invention) As explained above, according to the multipolar magnetized permanent magnet of the present invention, after uniformly magnetizing the entire magnet material in advance,
By magnetizing the surface of the magnetic material with multiple poles,
Magnetic flux density can be improved without using expensive magnetic materials with a high energy product, or without using a special manufacturing method for polar anisotropically oriented magnets. In addition, regarding the stability of the maximum magnetic flux density of each magnetic pole, by uniformly magnetizing in the first stage and saturating the multi-pole magnetization in the second stage, it is relatively easy to achieve a uniform magnetic flux with little variation. It can be the density. Furthermore, by changing the thickness of the magnet that is magnetized in the first stage within a range that is larger than 1/3 of the magnetic pole arrangement interval, it is possible to increase the
It is possible to freely adjust the magnitude of the bias magnetic field.

[Brief explanation of the drawing]

FIG. 1(A) is a perspective view showing the first embodiment of a multipolar magnetized permanent magnet according to the present invention, and shows the first stage of magnetization, and FIG. 1(B) is a perspective view of the second stage of magnetization in the first embodiment. Figure 2 (A) is a perspective view showing the Pt52 embodiment of the present invention and shows the first stage magnetization, and Figure 2 (B) shows the second stage magnetization in the second embodiment. FIG. 3(A) is a perspective view showing the third embodiment of the present invention and shows the first stage magnetization, and FIG. 3(B) is a perspective view of the third embodiment of the present invention.
A perspective view showing the second stage magnetization in the t43 example, fX
Figure S4 is of the present invention! The Pt5s diagram is a waveform diagram showing the relationship between clearance and magnetic flux density in the case of Example 52, the Pt5s diagram is a waveform diagram showing the relationship between clearance and magnetic flux density in the case of a conventional multipolar magnetized permanent magnet, and the PIS6 diagram is a waveform diagram showing the relationship between the clearance and magnetic flux density in the case of the conventional multipolar magnetized permanent magnet. A waveform diagram showing the relationship between the clearance and the magnetic flux density when the thickness of the magnet material body is increased in the second embodiment. Figure 7 shows the relationship between the clearance and the maximum magnetic flux density in the case of various magnet materials and manufacturing methods. Graphs, Figure 8 is a perspective view showing the first conventional example of a multipolar magnetized permanent magnet, Figure 9 is a waveform diagram of magnetic flux density on the magnet surface in the case of a stone, and Figure 12 is a waveform diagram of the magnetic flux density when an external magnetic field is present. FIG. 13, which is an explanatory diagram showing the relationship between the external magnetic field and the magnetization within the magnet, is a waveform diagram of the magnetic flux density on the magnet surface in the case of FIG. 12. DESCRIPTION OF SYMBOLS 10... Straight plate-shaped magnet material body, 12... Disc-shaped magnet material body, 14... Ring-shaped magnet material body, D...
Magnetic pole arrangement spacing, t, tr...thickness. Figure 3 @Yurufuugeikan @Horiyakariiba/Shoichi Clearance (Saki) Figure 8 Figure 9 Figure 10 Figure 11 Figure I Figure 12 Figure 13

Claims (3)

[Claims] (1) A multipolar magnetized permanent magnet characterized in that after the entire magnetic material body is uniformly magnetized in advance, the surface of the magnetic material body is magnetized with multiple poles. (2) Claim 1, wherein the magnet material body is sintered ferrite.
Multipolar magnetized permanent magnet as described. (3) The multipolar magnetized permanent magnet according to claim 1, wherein the magnet material is a composite ferrite obtained by mixing ferrite powder into plastic.