JPH04267308A - Focused orientation type polar anisotropic disclike magnet and magnetic orienting mold - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a focused orientation type polar anisotropic disc magnet suitable for use as a permanent magnet for a flat motor, and a magnetic field orientation mold suitable for molding the magnet. This is an attempt to improve the surface magnetic field on the working surface of a disc-shaped magnet.

0002

2. Description of the Related Art Conventionally, a flat type motor such as a spindle motor for a floppy disk or a hard disk or a capstan motor for a VTR has a disk-shaped permanent magnet 101 which is axially magnetized in the thickness direction, as shown in FIG. is used. However, with respect to the area of the disc-shaped magnet 101, the stator coil 102
Since the area of the magnet is small, that is, the effective area of action of the magnet on the stator coil is small, it cannot be said that the magnetized surface is used effectively. Therefore, the torque obtained was not sufficient considering the size of the magnet used. In the figure, number 103 is the upper case, 104
is a back yoke, 105 is a bush, 106 is a shaft, and 107 is a lower case.

0003

SUMMARY OF THE INVENTION The present invention advantageously solves the above problems by effectively concentrating magnetic flux only on the substantial working surface of a disc-shaped magnet, thereby reducing the surface magnetic field on the working surface. The purpose of the present invention is to propose a focused orientation type polar anisotropic disc-shaped magnet that can improve torque when used as a flat type motor, together with a magnetic field orientation mold suitable for manufacturing the magnet.

In other words, the present invention provides a disc-shaped magnet having one of the front and back surfaces as a working surface, in which the direction of orientation of magnetic powder particles in a cross section including the central axis of the disc-shaped magnet is in the track on the working surface side of the magnet. Focused orientation type polar anisotropic disc shape in which the direction of orientation of the magnetic particles in a cross section including the center circle of the central ring region is along the direction of the lines of magnetic force in the case of polar anisotropic magnetization. It is a magnet (first invention).

The present invention also provides a magnetic field orientation mold that has a disc-shaped cavity and applies a magnetic field to a magnetic material introduced into the cavity to orient magnetic particles in the material in the thickness direction. A magnetically oriented mold in which an annular region narrower than the track width is defined on one of the upper and lower surfaces by a permanent magnet around the central ring of the cavity track, while the remaining region is defined by a non-magnetic material. (Second invention).

Further, the present invention provides a magnetic field orientation mold that has a disc-shaped cavity and applies a magnetic field to a magnetic material introduced into the cavity to orient magnetic particles in the material in the thickness direction. For one of the upper and lower surfaces, at least the entire surface of the track is partitioned with a main pole of ferromagnetic material,
On the other side, an annular region narrower than the track width is defined around the center ring of the cavity track by a permanent magnet, while the remaining region is defined by a non-magnetic material, and the back surface of the permanent magnet is made of ferromagnetic material. A magnetic field orientation mold comprising arranging an auxiliary pole of material and joining the main pole and the auxiliary pole with the same ferromagnetic material to form a closed magnetic path (third invention)
It is.

[0007]

[Operation] In this invention, the magnetic circuit of the molding die is modified to effectively control the orientation direction of magnetic particles in the magnet material, thereby improving the surface magnetic field on the substantial working surface of the disc-shaped magnet. Plan. Specifically, for an annular region on either the upper or lower surface of the cavity, centered around the center ring of the cavity track and narrower than the track width, a permanent magnet polarized in the circumferential direction by polar anisotropic magnetization is used. By dividing the remaining region with a non-magnetic material, the lines of magnetic force inside the cavity are polarized anisotropically and focused on the central ring region of the permanent magnet side track.

[0008] With regard to the magnetic material charged into the cavity in this way, the orientation direction of the magnetic particles is aligned in the direction of the magnetic lines of force, that is, in the longitudinal section including the central axis of the magnet, the magnetic particles are focused on the central ring region of the permanent magnet side track. Therefore, the magnetic flux after magnetization can be narrowed into a donut shape, and the cross section including the center circle of the central ring can be aligned with the direction of the lines of magnetic force when polar anisotropic magnetization is performed. As a result, the surface magnetic field on the substantially working surface of the magnet, which is polar anisotropic, can be significantly improved.

By the way, such a disc-shaped magnet is sometimes used with a back yoke attached thereto, and in this case, it is preferable to insert mold a ferromagnetic material to serve as the back yoke. Therefore, when manufacturing a disc-shaped magnet used as described above, in the above-mentioned molding die, an auxiliary pole made of ferromagnetic material is arranged on the back side of the permanent magnet, and a ferromagnetic material is also used for the opposing surface. as the main pole,
Preferably, the main pole and the auxiliary pole are joined together using a ferromagnetic material to form a closed magnetic path.

FIGS. 1A and 1B show a comparison of a disc-shaped magnet in which magnetic powder particles are oriented according to the present invention and a disc-shaped magnet in which the particles are oriented according to the conventional method. As is clear from the figure, while there is wasted magnetic flux in the conventional magnet shown in FIG. 1(b), in the inventive magnet shown in FIG. 1(a), all the magnetic flux is effectively It is focused on the surface and used effectively, thus obtaining a higher surface magnetic field.

The orientation angle of the magnetic powder particles indicated by α in FIG. 1 is preferably about 10 to 70 degrees, preferably about 20 to 60 degrees. This is because if the orientation angle α is smaller than 10°, the effect of improving the surface magnetic field will be poor, while if it is larger than 70°, the effective surface area on which the surface magnetic field will appear will be significantly narrowed, and it will be reduced depending on the magnet's intrinsic coercive force. This is because it may become magnetic.

As the disc-shaped magnet of the present invention, both synthetic resin magnets and sintered magnets can be used. For example, as magnetic powder for synthetic resin magnets and sintered magnets, any conventionally known magnetic powder can be used, such as ferrite magnetic powder, alnico magnetic powder, and rare earth magnetic powder such as samarium-cobalt magnetic powder and neodymium-iron-boron magnetic powder. Regarding the particle shape, it is preferable that the average particle diameter is about 1.5 μm and the compressed density is 3.20 or more.

[0013] As for the synthetic resin, any conventionally known synthetic resin can be used, and representative examples thereof are as follows. Polyamide-based synthetic resins such as polyamide-6 and polyamide-12. Single or copolymerized vinyl-based synthetic resins such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polymethyl methacrylate, polystyrene, polyethylene, and polypropylene. Synthetic resins such as polyurethane, silicone, polycarbonate, PBT, PET, polyetheretherketone, chlorinated polyethylene and Hypalon. Rubbers such as propylene, neoprene, styrene butadiene and acrylonitrile butadiene. Epoxy resin. Phenolic synthetic resin. Further, the blending ratio of the magnetic powder and the synthetic resin as the binder is desirably about 60 to 70 vol% of the magnetic powder. In addition, it goes without saying that conventionally used plasticizers, antioxidants, surface treatment agents, and the like can be used in appropriate amounts depending on the purpose.

Next, the magnetically oriented mold according to the present invention will be explained. FIG. 2 schematically shows a preferred example of a magnetically oriented mold for injection molding according to the present invention. In the figure, number 1 is a cavity provided in the die 2, 3 is a main pole, and 4 is a permanent magnet. The area of the magnet 4 is smaller than the area of the cavity 1, that is, it has a disk shape with an area equal to the center ring of the track, that is, the effective usable area for mounting the motor. As the permanent magnet 4, a so-called polar anisotropic magnet is used, which is polarized alternately N, S, N, S, etc. along the circumference of the disk, as shown in FIG. 5 is an auxiliary pole, and this auxiliary pole 5 has the same area as the permanent magnet 4. Furthermore, 6 is a fixed plate, 7 is a movable plate, 8 is a nozzle touch, 9 is a spool, 10 is an ejection pin, 11 is an ejection plate, and 12 is a cavity plate.

If not only the die 2 and the cavity plate 12 but also the main pole 3 and the auxiliary pole 5 are made of non-magnetic material,
The molding die according to the second invention has one main pole 3 and an auxiliary pole 5.
If the die 2 and the cavity plate 12 are made of a ferromagnetic material and the die 2 and the cavity plate 12 are made of a non-magnetic material, a closed magnetic path can be easily formed and the molding die according to the third invention can be obtained. In this case, it is desirable that the ejector pin 10 is made of ferromagnetic material.

[0016] As the ferromagnetic material, S55C, S5
Carbon steels such as 0C and S40C, die steels such as SKD11 and SKD61, other materials such as pamendur and pure iron can be used, but it is more advantageous to perform surface hardening treatment to improve wear resistance. On the other hand, non-magnetic materials include stainless steel,
Copper-beryllium alloy, high manganese steel, bronze, brass, non-magnetic super steel N-7, etc. are advantageously suitable, and it is advantageous to subject these to surface hardening treatment to improve wear resistance, if necessary.

Now, when synthetic resin magnet material is introduced into the disc-shaped cavity 1 by injection molding into the mold shown in FIG. 2, regardless of whether a closed magnetic path is formed, the lines of magnetic force inside the disc-shaped cavity 1 In the vertical section including the central axis of cavity 1, the light is focused on the central ring region of the cavity track, and in the cross section including the center circle of the central ring, it is transmitted along the direction of the lines of magnetic force when polar anisotropic magnetization is performed. Therefore, the magnetic particles in the magnet material are also oriented along the direction of the lines of magnetic force, and thus a polar anisotropic focusing type disc-shaped magnet as shown in FIG. 4 is obtained.

From the perspective of the mold magnetic circuit, on the permanent magnet side where the magnetic flux is to be narrowed, the magnet width is made narrower than the cavity width around the center ring of the track on that side, while the magnet width is made narrower than the cavity width on the opposite wide area main On the pole side, it is important that the width of the magnetic pole be equal to or wider than the cavity width.

Further, in consideration of the case where the disk-shaped magnet is later incorporated into a motor, it is preferable to have a so-called donut shape with a hollow hole, but such a hollow hole is not necessarily an essential requirement in the present invention.

[0020] The case where an injection molding mold is mainly used as the molding mold has been explained above, but if the necessary parts of the magnetic circuit mold are changed to other molding molds, a compression molding mold can be used. You can also do that. FIG. 5 schematically shows a preferred example of a compression molding mold. In the place shown in the same figure, number 13
14 is the upper punch, 15 is the die (non-magnetic material)
, 16 is a core (non-magnetic material), and 17 is a molded body. As shown in FIG. 6, the upper punch 13 has a permanent magnet 19 covered with a non-magnetic material under the upper punch seat 18.
It has a structure in which And upper punch seat part 1
8. If the lower punch 14 is made of a non-magnetic material, the molding die according to the second invention will be obtained.On the other hand, if the upper punch seat 18 and the lower punch 14 are made of ferromagnetic material, the molding die will be obtained according to the third invention. Becomes a mold.

By using the above-mentioned mold, a polar anisotropic permanent magnet having magnetic powder orientation as shown in FIG. 7 can be obtained.

[0022]

[Example] A closed magnetic path forming type injection mold (mold A) shown in Fig. 2 and a closed magnetic path non forming type compression molding mold (mold B) shown in Fig. 5 are provided. A disk-shaped magnet having the dimensions shown in FIG. 8 was molded using a magnetic field orientation molding machine under the following conditions. Raw materials: Magnetic powder particles Ferrite magnetic powder (magnetoplumbite strontium ferrite with average particle size of 1.5 μm) - Synthetic resin: Polyamide 12 - Plasticizer: TTS (isopropyl triisostearoyl titanate)

[0023] Blend/Blend A (Plamag blend) Magnetic powder: 66 vol% Polyamide 12
: 33 vol% TTS : 1 vol% ・Blend B (sintering mixture) Magnetic powder: 40 wt% Water: 60 wt%

Molding conditions/injection molding conditions Pellet composition used: Composition A Injection cylinder temperature: 300°C Mold temperature: 100°C Injection pressure
: 1800 kg/cm2 Excitation time : Constant cooling time : 15 seconds injection cycle
: 30 seconds/Compression molding conditions Raw materials used: Formulation B Water removal method: Injection method Excitation method: Vertical magnetic field molding Molding temperature: 20°C Firing temperature: 1250°C

Table 1 shows the results of an investigation of the surface magnetic field and starting torque (motor characteristics) of the disc-shaped magnet thus obtained after magnetization.

The conditions for evaluating the motor characteristics are as follows.・Magnet outer diameter: 60mm Inner diameter: 20mm Thickness: 4mm Magnetization: 8 poles ・Coil phase: 3 phases 6 coils Number of turns: 140 Turns/coil resistance: 15 ohms/coil ・Drive method 3-phase bipolar voltage: 12V Current: 400 mA (200 mA/phase)

[0027]

[Table 1]

As is clear from the table, by using the magnetic field orientation molding machine according to the present invention and focusing the magnetic particles in the disc-shaped magnet onto the central ring region of the track on the working surface side, the surface magnetic field on the working surface can be greatly increased. It has been possible to improve the torque characteristics, and excellent torque characteristics have been obtained.

[0029]

Thus, according to the present invention, the magnetic particles in the disc-shaped magnet material can be effectively oriented to the central ring region of the track on the working surface side, and as a result, the surface on the working surface of the permanent magnet after magnetization can be effectively oriented. The magnetic field can be significantly improved compared to the conventional method.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a comparison of the magnetic particle orientations of disc-shaped magnets manufactured according to the present invention and a conventional method.

FIG. 2 is a schematic diagram of a magnetically oriented mold for injection molding according to the present invention.

FIG. 3 is a diagram showing the polarization state of a permanent magnet.

FIG. 4 is a diagram showing the direction of magnetic lines of force of magnetic powder particles after magnetization of a polar anisotropic focusing type disc-shaped magnet obtained according to the present invention.

FIG. 5 is a schematic diagram of a magnetically oriented mold for compression molding according to the present invention.

FIG. 6 is a diagram showing the structure of an upper punch of a compression molding mold.

FIG. 7 is a diagram showing the orientation state of magnetic powder particles in a molded body.

FIG. 8 is a diagram showing the dimensions and shape of a disc-shaped magnet produced in an example.

FIG. 9 is an exploded view of the flat motor.

[Explanation of symbols]

1 Cavity 2 Die 3 Main pole 4 Permanent magnet 5 Auxiliary pole 6 Fixed plate 7. Moving board 8 Nozzle touch 9 Spool 10 Eject pin 11　Extrusion plate 12 Cavity plate 13 Upper punch 14 Lower punch 15 Die 16 core 17 Molded object 18 Upper punch seat 19 Permanent magnet 101 Permanent magnet 102 Stator coil 103 Upper case 104 Back yoke 105 Bush 106 Shaft 106 Lower case

Claims (3)

[Claims] Claim 1: In a disc-shaped magnet having one of the front and back surfaces as an active surface, the orientation direction of magnetic powder particles in a cross section including the central axis of the disc-shaped magnet is in the central ring region of the track on the active surface side of the magnet. A focused orientation type polar anisotropic disk-shaped magnet in which the direction of orientation of magnetic powder particles in a cross section including the center circle of the central ring region is along the direction of the lines of magnetic force when polar anisotropic magnetization is performed. 2. A magnetic field orientation mold that has a disc-shaped cavity and applies a magnetic field to a magnetic material introduced into the cavity to orient the magnetic particles in the material in the thickness direction, the mold comprising: A magnetically oriented mold characterized in that, on either side, an annular region narrower than the track width is defined by a permanent magnet around the central ring of the cavity track, while the remaining region is defined by a non-magnetic material. . 3. A magnetic field orientation mold that has a disc-shaped cavity and applies a magnetic field to a magnetic material introduced into the cavity to orient the magnetic particles in the material in the thickness direction, wherein On one side, at least the entire surface of the track is divided by a main pole made of ferromagnetic material, and on the other side, an annular region narrower than the track width is divided around the central ring of the cavity track using permanent magnets. The area is divided using a non-magnetic material, and an auxiliary pole made of a ferromagnetic material is arranged on the back side of the permanent magnet, and the main pole and the auxiliary pole are also joined using a ferromagnetic material to form a closed magnetic path. A magnetic field orientation mold featuring: