JP6390442B2 - Magnetic particle removing method and magnetic particle removing apparatus - Google Patents

Description

  The present invention relates to a magnetic particle removing method and a magnetic particle removing apparatus for removing magnetic particles attached to the surface of a molded body formed by forming magnetic particles in a magnetic field.

  In the production of rare earth magnets and the like, compression molding is performed while applying a magnetic field to the magnetic material powder filled in the mold, so that anisotropy can be imparted to the magnet and a sintered magnet having high coercive force can be obtained. It is done. The molded body compression-molded in a magnetic field is taken out after demagnetization in the mold, but complete demagnetization is difficult, so the molded body has residual magnetism, Spilled magnetic powder existing on the lower mold surface and magnetic powder adsorbed on the upper mold surface are attracted and adhered. When this adhering magnetic powder is flowed to the subsequent process without completely removing it, (a) the adhering magnetic powder is burned during firing, or the sintered body is deformed if there is adhering magnetic powder on the contact surface with the sintering container, (b) Due to seized magnetic particles, the outer dimensions do not fit within the specified value and clogging occurs in the workpiece feeder of the grinding machine. (c) The seized magnetic particles cannot be removed by machining. Problems such as non-defective products occur, causing a reduction in production efficiency and dimensional defects.

  Japanese Patent Application Laid-Open No. 11-273978 (Patent Document 1) discloses a molded body in which magnetic powder is molded in a magnetic field, a pulsed vibration damping magnetic field is applied, and then an alternating magnetic field is applied to remove the magnetic powder on the surface of the molded body. A magnetic particle removal method is disclosed. The method described in Patent Document 1 is a method of removing magnetic particles, wherein magnetic powder is dropped from a molded body by generating an alternating magnetic field with a powder removal coil and moving the magnetic powder. However, in the method described in the cited document 1, in order to prevent the fallen magnetic powder from reattaching to the molded body, the powder removal coil must be disposed on the lower side of the molded body, and the magnetic powder on the upper side of the molded body is sufficient. May not be removed.

Japanese Patent Laid-Open No. 11-273978

  Therefore, an object of the present invention is to remove a magnetic powder once removed from the surface of the molded body formed by molding the magnetic powder in a magnetic field so that the magnetic powder once removed does not re-adhere to the molded body, and the removal for that purpose. Is to provide a device.

  As a result of diligent research in view of the above object, the present inventors attached to the surface of the molded body with a magnetic field that is generated by moving the permanent magnet relative to the molded body and changes in strength and direction over time. The peeled magnetic powder is peeled off, and the peeled magnetic powder is adsorbed by the permanent magnet, so that the peeled magnetic powder is prevented from reattaching to the molded body, and even the magnetic powder attached to the upper part of the molded body is efficiently removed. The inventors have found that this is possible and have come up with the present invention.

That is, the magnetic particle removing method of the present invention is
A magnetic powder removal method for removing unnecessary magnetic powder adhered to the surface of a molded body obtained by molding magnetic powder in a magnetic field,
By moving a plurality of arranged permanent magnets relative to the molded body, a magnetic field whose strength and direction change with time is applied to the molded body, and the magnetic powder adhering to the molded body is changed. It peels off by a magnetic field to be absorbed, and is attracted and removed by the permanent magnet.

  The time-varying magnetic field is preferably generated by arranging the permanent magnets in the circumferential direction so that the magnetic pole faces the molded body and rotating the permanent magnet around a central axis.

  The time-varying magnetic field is preferably generated by arranging the permanent magnets in a linear direction so that the magnetic pole faces the molded body and reciprocating the permanent magnets along the arrangement direction.

  It is preferable that the permanent magnet is arranged so that the magnetic pole surface coincides with one surface facing the molded body.

  The plurality of permanent magnets are preferably arranged such that magnetic poles having different polarities are alternately arranged.

  After adsorbing the magnetic powder by the permanent magnet, it is preferable to discard the adsorbed magnetic powder.

The magnetic particle removing apparatus of the present invention is
A magnetic particle removing device for removing unnecessary magnetic particles attached to the surface of a molded body obtained by molding magnetic particles in a magnetic field,
A powder removing plate having a plurality of permanent magnets, a relative moving means for relatively moving a plurality of magnets provided on the powder removing plate with respect to the molded body, and preventing magnetic powder from adhering directly to the powder removing plate And a cleaning mechanism.

  The relative moving means is preferably means for rotating the powder removing plate made of the plurality of permanent magnets on a surface facing the molded body.

  The relative moving means is preferably means for causing the powder removing plate made of the plurality of permanent magnets to move straight on the surface facing the molded body.

  The method for removing magnetic particles of the present invention is a method in which magnetic particles attached to the surface of a molded body obtained by forming magnetic particles in a magnetic field are separated by a magnetic field whose strength and direction change, and the separated magnetic particles are adsorbed by a permanent magnet. Therefore, not only re-adhesion of the peeled magnetic powder to the molded body is prevented, but the peeled magnetic powder can be efficiently recovered without being scattered around.

  Since the magnetic particle removing apparatus of the present invention has both a function of peeling the magnetic powder adhered to the surface of the molded body and a function of adsorbing and removing the peeled magnetic powder, it adheres not only to the lower part of the molded body but also to the upper part of the molded body. It can also be preferably used to remove the magnetic powder.

It is a schematic diagram showing a state of relative movement between a magnetic field generated by a plurality of permanent magnets arranged so that magnetic poles having different polarities are alternately arranged and a molded body. FIG. 2A is a front view schematically showing an example of a means for generating a magnetic field whose intensity and direction change with time, and FIG. 3B is an AA cross section of FIG. It is a schematic diagram which shows another example of the means to generate | occur | produce the magnetic field from which intensity | strength and a direction change temporally. It is a schematic diagram which shows another example of the means to generate | occur | produce the magnetic field from which an intensity | strength and a direction change temporally. FIG. 4A is a front view schematically showing still another example of a means for generating a magnetic field whose intensity and direction change with time, and FIG. It is a schematic diagram for demonstrating the magnetic particle removal method of this invention. It is a schematic diagram for demonstrating the magnetic particle removal method of this invention.

[1] Magnetic powder removal method The magnetic powder removal method of the present invention for removing magnetic powder adhered to the surface of a molded body obtained by molding magnetic powder in a magnetic field is a plurality of permanent magnets arranged so that magnetic poles having different polarities are adjacent to each other. By moving the magnet relative to the molded body, a magnetic field whose strength and direction change with time is applied to the molded body, and the magnetic powder adhering to the molded body is vibrated by the changing magnetic field. While peeling, it is attracted and removed by the permanent magnet. More preferably, the plurality of permanent magnets are arranged so that magnetic poles having different polarities are alternately arranged.

  Examples of the means for generating a magnetic field whose strength and direction change with time include a method in which a plurality of permanent magnets in which magnetic poles having different polarities are alternately arranged are moved relative to the molded body. Here, it is most effective to arrange a plurality of permanent magnets so that magnetic poles having different polarities are alternately arranged, that is, in the order of N, S, N, S... It is not necessary to arrange them in such a manner that they have different polarities. For example, they may be arranged in the order of N, N, S, S, N, N, S, S,..., And the arrangement order is not particularly limited. The magnetic field generated by these methods becomes a rotating magnetic field that behaves so that the direction rotates as the plurality of permanent magnets and the molded body move relative to each other at a certain point on the surface of the molded body. Hereinafter, the case of a plurality of permanent magnets in which magnetic poles having different polarities are alternately arranged will be described with reference to FIG.

  For example, as shown in FIG. 1 (a), when the molded body is positioned directly above the permanent magnet M1, the surface F of the molded body C is at a point P on the surface F facing the permanent magnet M1 of the molded body C. An upward magnetic field orthogonal to is applied. Next, as shown in FIG. 1 (b), when the molded body C is relatively moved to an intermediate position between the permanent magnet M1 and the permanent magnet M2, the molded body C is at a point P on the surface F of the molded body C. A magnetic field in the right direction parallel to the surface F is applied. Furthermore, when the molded body C moves relative to the position directly above the permanent magnet M2, as shown in FIG. 1 (c), the point P on the surface F of the molded body C is perpendicular to the surface F of the molded body C. A downward magnetic field is applied. Furthermore, as shown in FIG.1 (d), when the molded body C is relatively moved to an intermediate position between the permanent magnet M2 and the permanent magnet M3, at a point P on the surface F of the molded body C, the molded body C A magnetic field in the left direction parallel to the plane F is applied. In this way, as shown in FIGS. 1 (a) to 1 (d), the molded body moves relative to the right as shown in FIGS. A magnetic field rotating clockwise is applied to.

  At this time, the magnetic field at the point P on the surface of the molded body C has a substantially constant strength when the interval between adjacent permanent magnets is small, but the strength between two adjacent permanent magnets when the distance is large. , The magnetic field varies in direction and intensity. Specific examples of these rotating magnetic field generating means will be described. In addition, these means in this invention are not limited to the example shown below.

(1) Rotating magnetic field generating means As means for moving a plurality of permanent magnets in which magnetic poles having different polarities are alternately arranged relative to the molded body, as shown in FIGS. 2 (a) and 2 (b) The powder removal plate 1 in which a plurality of permanent magnets 12a to 12f are arranged on the circumference of the disc 10 made of a nonmagnetic material at an equal distance from the center 11 is opposed to the molded body, and passes through the center 11. A means for rotating around an axis orthogonal to the disk 10 can be mentioned. The plurality of permanent magnets 12a to 12f are magnetized in a direction perpendicular to the disk 10, and are arranged such that adjacent permanent magnets (for example, the permanent magnet 12a and the permanent magnet 12b) have different polarities, and are molded. A rotating magnetic field can be generated in a direction facing the disc 10 by rotating the axis about the axis on the surface facing the body. The permanent magnets 12a to 12f are preferably arranged so as to be embedded in the recesses 13a to 13f provided in the disc 10.

  The period of the rotating magnetic field generated by rotating the magnetic powder plate may be appropriately set by a prior experiment or the like in consideration of the residual magnetism, the size, the adhesion amount of the magnetic powder, the time required for powder removal, etc. good. The same applies to the strength of the magnetic field generated by the magnet on the surface of the molded body.

  The principle of removing magnetic particles by moving the magnet relative to the compact will be described below. There is a case where magnetic powder is adsorbed on the molded body immediately after molding due to residual magnetism remaining in the molded body. The magnetic force generated in the molded body after molding by the orientation magnetic field during molding is usually reduced by demagnetization at the end of molding. However, a magnetic force may remain in the molded body due to insufficient demagnetization. Further, in some cases, magnet powder (magnetic powder) left during powder feeding may remain in the mold portion of the molding machine that performs the molding, and this magnetic powder is adsorbed by a molded body having residual magnetism. Although the molded body after demagnetization does not have such a large adsorbing force, the size of the adsorbed magnetic powder is as small as 10 μm or less and its mass is small, so it does not fall off naturally from the molded body.

  When a rotating magnetic field is applied to such magnetic particles, the magnetic particles vibrate or rotate due to the rotating magnetic field. Magnetic powder is a fine particle, but each has a north pole and a south pole, and in response to the change in the direction of the magnetic field from the outside, magnetization in the direction opposite to the direction of the external magnetic field is externally applied. Vibrates and / or rotates in a direction toward the magnetic field. At this time, if the magnetic powder attracting force to the compact is weakened and the magnetic field strength of the rotating magnetic field exceeds the attracting force with the magnetic powder compact, the magnetic powder leaves the compact and flies to the source of the rotating magnetic field. . When the generation source of the rotating magnetic field is a relative movement with respect to the magnet compact, the magnet generates a magnetic field by itself, so that the magnetic powder is adsorbed by the magnet. When the magnetic field generated by the magnet is sufficiently strong, the magnetic powder once adsorbed is rarely detached from the magnet.

  In the case of the present invention, this vibration and / or rotation and adsorption by a permanent magnet occur simultaneously, and this phenomenon is expressed as “peeling by a changing magnetic field and adsorption by the permanent magnet”.

  2 (a) and 2 (b) show an example of the powder removal plate 1 using circular permanent magnets 12a to 12f as viewed in the axial direction. However, as shown in FIG. The powder removal plate 1 may be configured by arranging the shape permanent magnets 14a to 14f in the same manner, or rectangular permanent magnets 15a and 15b are arranged with respect to the center 11 as shown in FIG. The powder removal plate 1 may be configured. In addition, the number of permanent magnets to be arranged is six in the configuration shown in FIGS. 2 (a) and 2 (b) and FIG. 3, and two in the configuration shown in FIG. 4, but is limited to these configurations. Is not to be done.

  As another means for moving the permanent magnet relative to the molded body, as shown in FIGS. 5 (a) and 5 (b), on the plate 20 made of a non-magnetic material, orthogonal to the plate 20. And a means for reciprocating the plate 20 in the X-axis direction with a dust removing plate 2 in which a plurality of permanent magnets 21a to 21f magnetized in the direction to be aligned in a line in the X-axis direction. The plurality of permanent magnets 21a to 21f are arranged so that adjacent permanent magnets (for example, the permanent magnet 21a and the permanent magnet 21b) have different polarities, and the plate 20 is reciprocated in the A-axis direction. A rotating magnetic field can be generated in a direction facing the plate 20. The permanent magnets 21a to 21f are preferably configured so that the length in the X-axis direction is shorter than the length in the direction parallel to the surface of the plate 20 and perpendicular to the X-axis. The permanent magnets 21a to 21f are preferably arranged so as to be embedded in the recesses 22a to 22f provided in the plate 20.

(2) Procedure for removing magnetic particles The procedure for removing magnetic particles will be described using a means for generating a rotating magnetic field by the rotation of the dust removing plate 1 shown in FIG. 2 (hereinafter sometimes simply referred to as magnetic field generating means). . As shown in FIG. 6 (a), the powder removing plate 1 can be disposed on the upper part and the lower part of the molded body 101. The dust removing plates 100a and 100b are accommodated in non-magnetic cases 104a and 104b so as to be rotatable around the shafts 111a and 111b. The powder removal plate 100a disposed on the upper portion of the molded body 101 mainly peels and adsorbs the magnetic powder 102a on the upper surface 101a of the molded body, and the powder removal plate 100b disposed on the lower portion of the molded body 101 mainly includes the magnetic powder 102b on the lower surface 101b of the molded body. Is peeled off and adsorbed. The partition plates 103a and 103b are arranged between the cases 104a and 104b housing the powder removal plates 100a and 100b and the molded bodies 101a and 101b, and the magnetic powders 102a and 102b adsorbed by the powder removal plates 100a and 100b can be easily removed. It is preferable to have a cleaning mechanism that can do this.

  First, as shown in FIG. 6 (a), the compact 101 is brought close to the powder removal plate 100a, and a rotating magnetic field is generated by rotating the disc 10 of the powder removal plate 100a around the axis 111a. The magnetic powder 102a adhering to the upper surface 101a is peeled off. At this time, the molded body 101 is preferably disposed so as to face the rotating permanent magnets 21a to 21f. As shown in FIG. 6B, the magnetic powder 102a peeled off from the upper surface 101a of the molded body 101 is adsorbed on the circumference where the permanent magnets 12a to 12f (indicated by 112a and 112b in FIG. 6) are arranged. After the magnetic powder 102a on the upper surface 101a of the molded body 101 is completely peeled off, the rotation of the disk 10 of the powder removing plate 100a may be stopped.For example, the magnetic powder 102a adhered to a plurality of molded bodies 101 continuously may be removed. When removing, it is not always necessary to stop the rotation of the disc 10 of the powder removing plate 100a. At this time, by arranging the partition plate 103a between the molded body 101 and the powder removal plate 100a, the separated magnetic powder 102a is not directly attracted to the permanent magnets 12a to 12f constituting the powder removal plate 100a, and the partition plate 103a. Adsorb.

  Next, as shown in FIG. 6 (c), the molded body 101 from which the magnetic powder 102a adhering to the upper surface 101a has been removed is brought close to the powder removal plate 100b, and similar to the removal of the magnetic powder 102a adhering to the upper surface 101a. Then, the magnetic powder 102b attached to the lower surface 101b of the molded body 101 is peeled off by the rotating magnetic field generated by rotating the disc 10 of the powder removing plate 100b, and the permanent magnets 12a to 12f constituting the powder removing plate 100b are used. It is adsorbed via the partition plate 103b. On the other hand, the powder removal plate 100a and the partition plate 103a that have adsorbed the magnetic powder 102a adhering to the molded body upper surface 101a are retracted to a position where they do not interfere with the powder removal plate 100b.

  As shown in FIGS. 6 (d) and 6 (e), the magnetic powders 102a and 102b adsorbed by the powder removal plate 100a / partition plate 103a and the powder removal plate 100b / partition plate 103b exclude the partition plates 103a and 103b. It can be easily removed by separating from the powder plates 100a and 100b and tilting.

  When removing the magnetic powder 102a adhering to the axial end surface of the cylindrical molded body 101 using a means for generating a rotating magnetic field, the axial end surface of the cylindrical molded body 101 is removed as shown in FIG. It may be arranged so as to face the rotating powder removing plate 100a, or the powder removal may be performed, or as shown in FIG. 7 (b), the side surface of the cylindrical molded body 101 faces the rotating powder removing plate 100a. You may arrange | position so that powder removal may be performed.

  6 and 7, a cylindrical molded body is used. However, the present invention is not limited to this, and can be applied to a magnet having a rectangular parallelepiped shape, a tile shape (bow shape), or a columnar shape, and is not dependent on the shape of the magnet. Applicable.

[2] Magnetic particle removing device The magnetic particle removing device of the present invention is a magnetic particle removing device for removing unnecessary magnetic particles adhering to the surface of a molded body obtained by forming magnetic particles in a magnetic field, A powder removing plate having a magnet; a relative moving means for moving the powder removing plate relative to the molded body; and a cleaning mechanism for preventing magnetic powder from directly adhering to the powder removing plate. The powder removal plate, the relative movement means, and the cleaning mechanism are as described above.

1, 2, ... Powder removal plate
10 ... disc
11 ・ ・ ・ Center
12a-12f ... Permanent magnet
13a-13f
14a ~ 14f ・ ・ ・ Permanent magnet
15a, 15b ・ ・ ・ Permanent magnet
20 ... board
21a ~ 21f ・ ・ ・ Permanent magnet
22a-22f ... hollow
100a, 100b ・ ・ ・ Powder removal plate
101 ... Molded body
101a ・ ・ ・ Top surface
101b ・ ・ ・ Lower surface
102a, 102b ・ ・ ・ Magnetic powder
103a, 103b ・ ・ ・ Partition plate
104a, 104b ・ ・ ・ Case
111a ... axis
112a, 112b ・ ・ ・ Permanent magnet

Claims (9)

A magnetic powder removal method for removing unnecessary magnetic powder adhered to the surface of a molded body obtained by molding magnetic powder in a magnetic field,
By moving a plurality of arranged permanent magnets relative to the molded body, a magnetic field whose strength and direction change with time is applied to the molded body, and the magnetic powder adhering to the molded body is changed. A magnetic particle removing method, wherein the magnetic powder is peeled off by a magnetic field to be removed and adsorbed and removed by the permanent magnet.   2. The magnetic particle removing method according to claim 1, wherein the time-varying magnetic field is formed by arranging the permanent magnets in a circumferential direction so that a magnetic pole surface faces the molded body, and rotating the permanent magnets around a central axis. A method for removing magnetic particles, characterized in that it is generated by   2. The magnetic particle removing method according to claim 1, wherein the time-varying magnetic field is obtained by arranging the permanent magnets in a linear direction so that a magnetic pole surface faces the molded body, and the permanent magnets along the arranging direction. A method for removing magnetic particles, characterized in that the magnetic particles are generated by reciprocating.   4. The magnetic particle removing method according to claim 2, wherein the permanent magnet is arranged so that the magnetic pole surface coincides with one surface facing the molded body.   5. The magnetic particle removal method according to claim 2, wherein the plurality of permanent magnets are arranged such that magnetic poles having different polarities are alternately arranged.   6. The method for removing magnetic particles according to claim 1, wherein after adsorbing the magnetic particles by the permanent magnet, the adsorbed magnetic particles are discarded. A magnetic particle removing device for removing unnecessary magnetic particles attached to the surface of a molded body obtained by molding magnetic particles in a magnetic field,
A powder removal plate having a plurality of permanent magnets, a relative movement means for moving the plurality of permanent magnets provided on the powder removal plate relative to the molded body, and the magnetic powder directly attached to the powder removal plate A magnetic particle removing apparatus comprising a cleaning mechanism for blocking.   8. The magnetic particle removing apparatus according to claim 7, wherein the relative moving means is means for rotating the powder removing plate made of the plurality of permanent magnets on a surface facing the molded body. .   8. The magnetic particle removing apparatus according to claim 7, wherein the relative moving means is a means for causing the powder removing plate made of the plurality of permanent magnets to linearly move on a surface facing the molded body. .

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