JPH0426764B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Quantity Field] The present invention relates to a multipolar anisotropic cylindrical magnet used for field magnets of control motors used in various electronic equipment and industrial equipment, and the like. This relates to a manufacturing method.

[Prior Art] Many motors used to control various devices are used at a constant rotation speed, and in order to control the rotation speed at a constant speed, it is necessary to have a function that constantly detects the rotation speed and performs feedback control. be.

As a field magnet for this type of control motor,
For example, a magnet that is integrally molded by injection molding or the like, and whose axis of easy magnetization is arranged in two different directions and then magnetized in that direction
61008) has been proposed. FIG. 5 shows a sectional view of this field magnet. The magnet 30 is a magnet that is integrally molded from a mixture of magnet powder and an organic substance by a molding method such as an injection molding method, and has a flange portion 3 protruding from the outer periphery of the lower end of the ring portion 31 and the ring portion 32.
It consists of 2.

In the above magnet, the axis of easy magnetization of the magnet is located at the ring portion 31.
The magnets are arranged in the diametrical direction M ₁ and in the vertical direction M ₂ in the flange portion 32, respectively, and are magnetized in two directions, so that they serve as motor drive magnets and rotation detection magnets at the same time.

Furthermore, the magnet having the above structure is manufactured by, for example, a mold shown in FIG.
-Refer to No. 61008). This mold 33 can be divided into an upper mold 34 and a lower mold 35. A stepped cylindrical magnetic pole core 36 with a narrow upper diameter is provided at the center of the mold 33. An electromagnetic coil 37 is disposed on the outer circumferential side, and the electromagnetic coil 3
Mold members 38, 39, and 40 made of a ferromagnetic material are arranged around the electromagnetic coil 37 so that the magnetic flux induced by the magnetic flux 7 forms a path in the direction of the arrow shown in the figure. Furthermore, a non-magnetic material 41 is disposed within the mold member 39 between the electromagnetic coil 37 and the mold member 40 . Furthermore, a molding space 43 having the same shape as the flange ring shown in FIG. 5 is formed between the magnetic pole core 36, mold members 39, 40, and non-magnetic members 41, 42. The non-magnetic member 41 placed on the upper surface of the electromagnetic coil 37 serves to guide vertical magnetic flux to the flange portion 43b of the molding space 43 using the magnetic flux induced by the electromagnetic coil 37. On the other hand, the non-magnetic member 42 placed on the upper surface of the molding space 43 serves to guide the magnetic flux diametrically to the ring portion 43b of the molding space 43 using the magnetic flux rising in the center of the magnetic pole core 36. The molding die shown in FIG. 6 has the above-described configuration, so that magnetic fields are set in two directions within the same molding space 43.

[Problems to be Solved by the Invention] In the motor magnet described above, the axis of easy magnetization of the magnet is anisotropic in the diametrical direction in the ring portion and in the vertical direction in the flange portion. It is magnetized so that it has many magnetic poles on its anisotropic surface. Therefore, in this motor magnet, the axis of easy magnetization of the ferromagnetic powder does not match the direction of the lines of magnetic force inside the magnet after magnetization, and this internal magnetic structure is the most advantageous for obtaining high magnetic properties. There was a problem that it was not possible.

Further, in the above manufacturing method, since the electromagnetic coil is placed in the mold, there is a problem that the space for accommodating the electromagnetic coil becomes large, resulting in an increase in the size of the equipment.

An object of the present invention is to solve the problems of the prior art described above and to provide a multipolar anisotropic cylindrical magnet having high magnetic properties as a motor magnet.

Another object of the present invention is to provide a method for producing a multipolar anisotropic cylindrical magnet having predetermined magnetic properties using relatively simple equipment.

[Means for Solving the Problems] The present invention forms a plurality of magnetic poles having N poles and S poles alternately on each of at least two surfaces, and also forms an axis of easy magnetization of the ferromagnetic powder. N pole and S
This is a multipolar anisotropic cylindrical magnet characterized by being arranged along the direction of magnetic lines of force between the poles.

In addition, the method for manufacturing a multipolar anisotropic cylindrical magnet of the present invention includes a method for manufacturing a multipolar anisotropic cylindrical magnet.
A large number of permanent magnets with magnetic anisotropy in the circumferential direction and permanent magnets with magnetic anisotropy in the axial direction are arranged on the circumferential surface and the end face of the cylindrical cavity, respectively, via soft magnetic yokes. A multipolar static magnetic field having N and S poles alternately is formed on at least two surfaces of the cylindrical cavity, and a kneaded material containing ferromagnetic powder is injected into the cylindrical cavity for a predetermined period of time. It is characterized by performing orthogonal molding.

[Function] By using the cylindrical magnet as a multifaceted, multipolar anisotropic ring magnet, the magnetic structure inside the magnet of at least two magnetized surfaces is improved, and high magnetic properties can be easily ensured. The reason is as follows.

FIGS. 7a and 7b are diagrams schematically showing the easy axis of magnetization and the orientation state of ferromagnetic powder (ferrite particles) of a radial anisotropic magnet and a surface multipolar anisotropic magnet, respectively.

When magnetized so that N and S poles appear alternately on the same surface, magnetic flux lines φ flow from the S pole to the N pole inside the magnet, while lines of flux flow from the N pole to the S pole outside the magnet. Lines of magnetic flux flow towards.

In a radially anisotropic magnet, as shown in FIG. 7a, the axis of easy magnetization extends radially from the center of the magnet to the surface as indicated by arrows X in the figure. The plane perpendicular to this is the {0001} plane F of the ferrite particle. When the magnetizing magnetic field is extremely small, the magnetic flux line φ passes through the shortest magnetic path C connecting the north pole and the south pole, and magnetizes the magnet in this part. As the magnetizing magnetic field increases for a while, the magnetic flux lines φ gradually enter the inside of the magnet, and the magnetic flux lines φ also begin to flow in the magnetic paths D and E. If we divide the magnetic flux line vector φ→ flowing between the north and south poles into a component φ→r directed toward the center and a component φ→〓 perpendicular to this, a large magnetization energy is generated near A where φ→r effectively acts. However, only a low value of magnetic energy corresponding to the φ→〓 component can flow near the center B between the two poles. Therefore, even though the residual magnetic flux density is high, the surface magnetic flux density, which is directly related to motor performance, is low.

On the other hand, in the case of the surface multipolar anisotropic magnet according to the present invention, as shown in FIG. It has a structure in which an axis of easy magnetization is arranged in each direction. Therefore, it is possible to concentrate the magnetic energy of the ferrite particles in the direction of the magnetic flux lines as much as possible. Therefore, a magnetic circuit is constructed that can efficiently extract magnetic energy according to the residual magnetic flux density on each magnetic pole, so that a high surface magnetic flux density can be obtained.

Moreover, in the present invention, around the annular molding space,
A yoke of soft magnetic material and a permanent magnet are arranged so that adjacent magnetic poles with the yoke interposed therebetween have the same polarity. Therefore, if we take two permanent magnets whose N poles face each other via a yoke, the lines of magnetic flux flowing out from the two N poles repel each other, so they pass through the molding space and form the S of each permanent magnet. Return to the pole.
In this way, N poles and S poles are alternately formed on two or more surfaces of the molding space.

[Example] Fig. 1 is a diagram showing a cylindrical magnet according to an embodiment of the present invention, in which Fig. 1a is a plan view, and Fig. 1b is a first cylindrical magnet.
Figure 1c is a view of Figure 1b viewed from the _S1 direction, and Figure 1c is a view of Figure 1b viewed from the _S2 direction.

The cylindrical magnet 1 is formed by integrally molding a kneaded material containing ferromagnetic powder by a molding method such as injection molding, and consists of a ring part 2 and a flange part 3. In this cylindrical magnet, the inner peripheral surface of the ring portion 2 is alternately magnetized with N poles and S poles.
Here, the axis of easy magnetization of the ferromagnetic powder is Fig. 1c
Since the magnets are arranged along the direction of the lines of magnetic force inside the magnet, as shown by the broken line, a high surface magnetic flux density can be obtained. Further, the end face of the flange portion 3 is also magnetized with alternating north and south poles, as shown in FIG. 1a. Moreover, since the axis of easy magnetization of the ferromagnetic powder is arranged along the direction of the lines of magnetic force inside the magnet, as shown by the broken line in FIG. 1b, a high surface magnetic flux density can also be obtained at the flange portion 3.

Therefore, when this cylindrical magnet 1 is incorporated into the above-mentioned motor, the motor performance, especially the detection accuracy of the rotation speed, can be improved. Furthermore, in the above cylindrical magnet, the motor performance remains the same even if the surface magnetic flux density is the same or different between the inner circumferential surface of the ring portion and the end surface of the flange portion.

Next, embodiments of the manufacturing method of the present invention will be described with reference to the attached drawings.

FIG. 2 is a sectional view showing an example of a mold used in the manufacturing method of the present invention.

The mold 4 has a fixed mold 5, a movable mold 6, and annular bodies 7 and 8. The annular body 7 is provided on the core 10, and the annular body 8 is provided on the fixed mold 5, and is in contact with the movable mold 6 via a non-magnetic disc 24. Fixed type 5,
A cylindrical space formed by the movable mold 6, the annular bodies 7 and 8, and the core receiving plate 9 is a magnet molding cavity 11.
It is. The annular bodies 7 and 8 are surrounded by a non-magnetic backup member 12, a core 10, and a movable mold 6. A fixed mold fixing plate 13 is provided on the fixed mold 5, and a nozzle opening 14 is formed on the fixed mold fixing plate 13. The sprue 15 below the nozzle opening 14 passes through the fixed mold fixing plate 13 and the fixed mold 5, and connects to the cylindrical cavity 1 via the runner 16.
It is connected to 1.

The movable mold 6 is fixed to a lower plate 18 via a spacer block 17. The movable mold 6 has a vertical hole opening into a cylindrical cavity 11, through which a projecting pin 19 is vertically movable. The ejecting pin 19 is fixed to the ejecting pin fixing upper plate 20, and the rod 22 connected to the center of the lower surface of the lower plate 21 fixed to the upper plate 20 is connected to the center hole 2 of the lower plate 18.
3 through the piston of the cylinder (not shown)
is connected to.

FIG. 3a shows the structure of the annular body 7 and the core 10 in detail in a cross-sectional view. The non-magnetic core 10 has a large number of protrusions 24a, 24b, 24c, . . . on its outer surface. Permanent magnets 25a, 2 are placed in the grooves between each protrusion.
5b, 25c,... are accommodated. Interposed between each permanent magnet are yokes 26a, 26b, 26c, . . . made of a soft magnetic material such as mild steel, pure iron, or permenda. Permanent magnet 2 constituting the annular body 7
5a, 25b, 25c, ... and yokes 26a, 26
A non-magnetic sleeve 2 is provided on the outer peripheral surface of b, 26c,...
7 is provided.

FIG. 3b similarly shows the structure of the annular body 8, sprue 15, and runner 16 in detail.

A permanent magnet 28 is attached to the non-magnetic backup member 12.
a, 28b, 28c, .
9a, 29b, 29c, . . . are interposed. In each of the annular bodies 7, 8, as shown in FIG. 3, the permanent magnets are arranged such that adjacent pairs of opposing magnetic poles have the same polarity. For example, if we pay attention to the permanent magnets 25b and 25c, the yoke 2 between them
Since both N poles are in contact with 6b, the magnetic flux flowing out from both N poles tends to flow into the S pole through the yoke 26b. Therefore, the tip of the yoke 26b becomes the north pole. By the same principle, the adjacent yoke 26
The tip of c becomes the south pole. In this way, at the tips of the yokes 26a, 26b, 26c,...
Magnetic poles of opposite polarity appear alternately like N, S, etc. That is, a multipolar static magnetic field is formed on the surface of the molding space 11 by the alternating magnetic poles of the permanent magnet and the soft magnetic yoke. Molding space 11 according to the same principle
In this case, it becomes possible to simultaneously obtain a multipolar static magnetic field from the annular body 8.

In a preferred embodiment of the invention, a magnetic field strength of 3000 Oe or more is required to achieve sufficient orientation. This permanent magnet needs to have a high residual magnetic flux density in order to form an extremely large number of magnetic poles at small intervals on the magnet surface. For this purpose, rare earth magnets such as samarium/cobalt magnets and neodymium/iron/boron magnets are desirable. These rare earth magnets have a residual magnetic flux density Br of 8500G or more, preferably 10000G or more (for example, in
50100, Japanese Patent Application Laid-open No. 58-142507) The shape and dimensions of the permanent magnet and yoke that make up the magnetic circuit of the mold are determined according to the number of poles of the anisotropic cylindrical magnet to be manufactured and the required magnetic properties. , can be set appropriately using an analysis method such as the finite element method.

The apparatus of FIG. 3 is particularly suitable for injection molding of composite magnets. Such injection molding can be performed as follows.

First, mix the ferromagnetic powder and resin at about 250℃~
The sprue 15 is injected through the nozzle port 14 at a temperature of about 350°C and a pressure of about 600 Kg/cm ² to about 1000 Kg/cm ² .
The liquid is injected into the cylindrical cavity 11 via the runner 16.

After cooling, the anisotropically molded composite magnet is moved downward through the movable mold 6, and the rod 22 is pushed up by the piston (not shown) of the cylinder, and the protruding pin 1
By raising the core 9, it can be separated from the core 10 and recovered. Subsequently, the ejecting pin 19 is returned to its original position and the movable mold 6 is raised to restore the cylindrical cavity 11 and perform the next molding cycle. The obtained composite magnet is magnetized in the same direction as the anisotropy direction.

In the case of molding the above composite magnet, as ferromagnetic powder
Ferrite powder such as Ba ferrite and Sr ferrite, alnico magnet powder, Fe-Cr-Co magnet powder, rare earth cobalt magnet powder, etc. can be used. As resins, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer,
Thermoplastic resins such as polyethylene and polyamide can be used. The blending ratio of ferromagnetic powder and resin needs to be 60% by weight or more from the viewpoint of magnetic properties, but if it exceeds 90% by weight, molding becomes difficult. In order to improve moldability, a small amount (several percent by weight) of a lubricant such as polyethylene or calcium stearate may be added. Further, in order to improve the wettability between the ferromagnetic powder and the resin, the ferromagnetic powder can be coated with an organic silicon compound, an organic titanate compound, or the like.

In addition to the injection molding of the composite magnet described above, the present invention is also applicable to extrusion molding thereof and wet molding of ferrite and the like.

Wet molding is about 50% of the powder of magnetic material such as ferrite.
-70% by weight, about 0.01 to about 0.2% by weight of a binder such as polyvinyl alcohol or methyl cellulose, and about 30 to 50% by weight of a solvent such as water to form a slurry, and the slurry is poured into the mold of the present invention. In this case, multipolar anisotropy is performed in the above-mentioned multipolar static magnetic field.

The present invention will be explained in more detail using the following specific examples.

Ferrite particles (Sr・
1.35 kg of nylon 12 (3014U, manufactured by Ube Industries) was added to 7.65 kg of 6Fe ₂ O ₃ ), premixed using a Henschel mixer, and then hot-cut at a temperature of 235° C. using a twin-screw extruder to create pellets.

The pellets were put into a molding machine equipped with the mold shown in Figure 3, and heated to 80°C at a temperature of 290℃ and a pressure of 800Kg/ ^cm2.
The mixture was injected into a cavity 11 in a mold heated to .degree. C., and then cooled and solidified. The dimensions inside the cavity were an inner diameter of 40 mm, an outer diameter of 46 mm, and a length of 10 mm, and the flange part had an outer diameter of 48 mm and a flange part thickness of 1.5 mm. Each permanent magnet for generating a multipolar static magnetic field is a samarium cobalt magnet (Hitachi Metals H-30CH), Br10600G, Hc9000Oe, and the yoke is
SS41 material was used.

The magnetic field strength on each magnetic pole appearing on the inner peripheral surface of the cavity 11 was about 40,000 Oe. In this embodiment, 18 permanent magnets were used on the inner peripheral surface of the cavity 11, and 24 permanent magnets were used on the flange surface of the cavity 11, so there were 18 permanent magnets in the space of the cavity 11.
It has a multipolar static magnetic field with 24 poles and 24 poles at the same time.

In this way, as shown in Figure 1, the inner circumferential surface of the ring part is made 18-pole anisotropic, and the end face of the flange part is given 24-pole anisotropy. A cylindrical magnet was obtained that also served as a detection magnet. This magnet is placed in a coil-type magnetizing device with a known structure having 24 magnetic poles and 18 magnetic poles,
Magnetization was performed in the same direction as the anisotropic direction using a magnetic field of 8000 Oe. When the surface magnetic flux density of the obtained cylindrical magnet was measured, as shown in Figure 4a, the average of the 18 poles on the inner peripheral surface of the magnet was 1500G, and as shown in Figure 4b, it was 24G at the magnet flange. at the average of the poles
It was 1200G.

On the other hand, in a magnet integrally molded with the same shape and the same material as the above, as disclosed in JP-A No. 59-61008, the ring part has a radial direction and the flange part has a different axis of easy magnetization from the axial direction. In the case of a cylindrical magnet arranged in two directions and obtained by magnetizing as shown above, the average of 18 poles on the inner peripheral surface of the magnet is 1000G, and the average of 24 poles on the magnet flange is about 800G. Ta.

Although the present invention has been described based on examples, various changes can be made without departing from the spirit of the invention. For example, although the cavity 11 is completely cylindrical in the embodiment, it can also be an incomplete cylinder such as a semi-cylindrical shape depending on the use of the magnet.

Further, in the embodiment, various combinations of the multipole static magnetic field on the inner circumferential surface of the cavity 11, on the outer circumferential surface of the cavity 11, on both end surfaces, and on each cavity surface are also possible.

[Effects of the Invention] According to the present invention, by having at least two surfaces in which the axis of easy magnetization of the ferromagnetic powder coincides with the direction of the lines of magnetic force inside the magnet after magnetization in an integrally molded ring magnet, the magnetic properties are improved compared to conventional ones. It is possible to obtain a cylindrical magnet that is significantly improved and functions as both a motor drive magnet and a rotation detection magnet at the same time.
Therefore, by incorporating this magnet into the motor, the motor's performance, precision, and
Smaller size and lighter weight can be achieved. Further, according to the manufacturing method of the present invention, a mold having a magnetic circuit using permanent magnets is used without using an electromagnetic coil, so that it is possible to significantly downsize the equipment.

[Brief explanation of drawings]

Figures 1a, b, and c are views showing an embodiment of a cylindrical magnet according to the present invention, Figure 2 is a cross-sectional view of a mold for manufacturing the cylindrical magnet according to the present invention, and Figure 3 a is a Z ₁ - Z ₁ sectional view of Fig. 2, and Fig. 3 b is a cross-sectional view of Fig. 2.
_4a and _4b are diagrams showing the surface magnetic flux density distribution waveforms of the inner peripheral surface and end surface of the cylindrical magnet according to the present invention, respectively, and FIG. FIG. 6 is a cross-sectional view of a mold for manufacturing the cylindrical magnet of FIG. 5, and FIGS. It is a schematic diagram showing a state. 1: Cylindrical magnet, 2: Ring part, 3: Flange part.

Claims (1)

[Claims] 1. A cylindrical magnet obtained by molding and magnetizing a kneaded material containing at least ferromagnetic powder in a magnetic field, which has N poles and S poles alternately on at least two surfaces. 1. A multipolar anisotropic cylindrical magnet, characterized in that the ferromagnetic powder has a plurality of magnetic poles, and the axis of easy magnetization of the ferromagnetic powder is arranged along the direction of the line of magnetic force between the north pole and the south pole. 2. The multipolar anisotropic cylindrical magnet according to claim 1, wherein each surface has substantially the same magnetic properties. 3. The multipolar anisotropic cylindrical magnet according to claim 1, wherein each surface has different magnetic properties. 4. In a method for manufacturing a multipolar anisotropic cylindrical magnet by molding a kneaded material mainly composed of ferromagnetic powder in a magnetic field, facing at least two surfaces around a cylindrical cavity of a mold, A large number of permanent magnets magnetized in the circumferential direction or axial direction are arranged through soft magnetic yokes so that the opposing magnetic poles of adjacent permanent magnets have the same polarity, and N poles are alternately placed on each of the surfaces. A method for producing a multipolar anisotropic cylindrical magnet, characterized in that a multipolar static magnetic field having a south pole and a south pole is formed, and the kneaded material is injected into the cylindrical cavity and anisotropically formed for a predetermined period of time. .