JPH05243066A - Fabrication of permanent magnet - Google Patents

Abstract

PURPOSE:To provide an annular permanent magnet with higher mass productivity in an automated line by carrying out molding by limiting a punch press surface configuration of a molding device in which a filter is placed, and partially polishing a resulting sintered structure of a different shape, and further removing an internal periphery burrs on the basis of time surface configuration of the filter. CONSTITUTION:There is employed a slurry in which powder of a permanent magnet material is dispersed in order to obtain an annular permanent magnet 1. The slurry is molded in a magnetic field in a wet atmosphere and is sintered into a sintered structure. The sintered structure 10 as a molded structure is of a cylindrical shape with its internal peripheral part more protruded than its external peripheral part. Upon molding, on one filter side end surface 11 in contact with a filter uneven configuration of the filter is transferred, and hence burrs 17 are formed on the internal and external peripheries of the filter side end surface 11. The internal periphery of the filter side end surface 11 of the sintered structure 10 is polished to remove the internal periphery burrs. Thus, the internal periphery burrs are removed with excellent mass-productivity in an automated line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an annular permanent magnet used in a magnetic circuit such as a speaker or a magnetron.

[0002]

2. Description of the Related Art An anisotropic oxide permanent magnet of magnetoplumbite such as Sr ferrite or Ba ferrite is known. It is formed into an annular shape and both end surfaces thereof are magnetized to produce a speaker or a magnetron. It is used for applications. Such an oxide permanent magnet is manufactured by wet-molding into an annular shape in a magnetic field and then sintering.

To form an oxide permanent magnet by wet molding, a slurry prepared by suspending oxide magnetic powder in a dispersion medium such as water is pumped and filled into the cavity of a molding die and pressed in a magnetic field. Molding is performed while removing the dispersion medium from the inside of the cavity. When removing the dispersion medium, a filter body such as a filter cloth is usually placed on one of the punches forming the cavity.

However, the concavo-convex shape of the filter body is transferred to the annular end surface on the filter body side of the thus obtained annular molded body, and in particular, the inner circumference and the outer circumference thereof are respectively inward and outward. A protruding burr will occur. If a sintered body is obtained from a molded body in which this burr particularly occurs on the inner circumference, a great obstacle occurs when mounting the magnet.

By the way, in recent years, in order to improve the mass productivity of such a permanent magnet and reduce the manufacturing cost thereof, its manufacture has been carried out in an unmanned automated manufacturing line. The burr on the outer periphery of the end surface of the molded body on the filter body side can be easily removed before firing by, for example, bringing a roller or the like into contact with the outer periphery of the molded body during transportation of the molded body.
However, it is difficult to remove the burrs on the inner circumference before firing, and it is almost difficult to use the automated line. For this reason, if the inner peripheral burr is to be removed before firing only by manual work, it takes time to remove it, and the yield is poor, which is a major obstacle to improving mass productivity and reducing costs. Is.

On the other hand, when sintering is performed in the presence of such inner peripheral burrs, naturally, burrs also occur in the sintered body. Polishing may be performed to remove the inner peripheral burr of the sintered body. However, as a method capable of mass-producing polishing on an automated line, it is inevitable to employ polishing of the end face on the filter body side or both upper and lower end faces.

However, the upper and lower end surfaces of the sintered body obtained from the molded body wet-molded by the usual method are planes parallel to each other, and in order to remove the inner peripheral burr, one end surface on the filter body side or There is no choice but to polish both end faces, which increases the polishing load, slows the processing speed, and reduces mass productivity.
The cost is high. Moreover, since the amount of polishing is large, the weight yield is poor, and chipping and chipping occur due to polishing on both the inner and outer peripheral edges, especially the outer peripheral edge, and the quantity yield is deteriorated, further increasing the cost.

[0008]

SUMMARY OF THE INVENTION The main object of the present invention is to provide a method for manufacturing an annular permanent magnet which has no inner peripheral burr, has very few defects, and can be mass-produced on an automated line with high productivity. is there.

[0009]

The above objects are achieved by the present invention described in (1) to (9) below. (1) A filter body is arranged on one punch, and an oxide permanent magnet material is wet-molded in a magnetic field in a cavity formed by this punch, a die, a core rod, and the other punch to obtain an annular molded body. At this time, the inner peripheral portion of the pressing surface of the punch in which the filter body is arranged is recessed from the outer peripheral portion to obtain a molded body in which the inner peripheral portion of the filter body side end surface is projected from the outer peripheral portion, and this molded body is By sintering, a sintered body is obtained in which the inner peripheral portion of the filter body side end surface is projected from the outer peripheral portion, and at least the inner peripheral portion of the sintered body of the filter body side end surface is polished to remove burrs on the inner periphery. Method for manufacturing a permanent magnet.

(2) The method for producing a permanent magnet according to the above (1), which conveys the outer peripheral surface of the sintered body while supporting the outer peripheral surface, and polishes both end surfaces between opposing grinders.

(3) The inner peripheral portion of the end surface on the side opposite to the filter body side is formed by making the inner peripheral portion of the pressing surface of the punch facing the punch in which the filter body is arranged protrude or recess from the outer peripheral portion. The permanent magnet according to (1) or (2) above, which is used to obtain a molded body in which the above is recessed or projected from the outer peripheral portion.

(4) The method for producing a permanent magnet according to any one of the above (1) to (3), wherein the outer peripheral burr of the compact is removed before the sintering.

(5) The filter body is disposed on the upper punch side having a drainage hole, and is brought into contact with the die and the core rod,
The method for producing a permanent magnet according to any one of (1) to (4) above, wherein the lower punch or the upper punch is pressed to form a slurry of an oxide permanent magnet material in a magnetic field.

(6) During the wet molding, the molded body is
The method for producing a permanent magnet according to any one of (1) to (5) above, wherein a magnetic field in an approximately axial direction is applied.

(7) In the above polishing, an unpolished portion is provided on the outer peripheral portion of the end face on the filter body side (1) to (6).
1. A method for manufacturing a permanent magnet according to any one of 1.

(8) The sintered body has an annular shape, and when the outer radius is Ro and the inner radius is Ri, a region of 0.2 (Ro-Ri) or more from the inner periphery is polished. 1)
A method for manufacturing a permanent magnet according to any one of (1) to (7).

(9) The method for producing a permanent magnet according to any one of the above (1) to (8), wherein the thickness of the permanent magnet is T and the thickness of the inner circumference is 0.01 T or more. ..

[0018]

According to the present invention, the inner peripheral portion of the pressing surface of the punch in which the filter body is arranged is recessed from the outer peripheral portion to form a molded body in which the inner peripheral portion of the end surface on the filter body side protrudes from the outer peripheral portion. Then, this is sintered to form a sintered body, and the inner peripheral portion thereof is polished to remove the inner peripheral burr. Since this polishing may be carried out, for example, by carrying the sintered body between opposed grinders, mass productivity is extremely high. Moreover, since it suffices to polish a predetermined region of the inner peripheral portion, the polishing load is remarkably reduced, the processing speed is increased, and the cost is reduced as compared with the case of polishing the entire surface. Further, since the polishing amount is reduced, the quantity yield and the weight yield due to chipping and chipping are remarkably improved, and the cost can be reduced in this respect as well.

In addition, Japanese Patent Laid-Open No. 61-54601 proposes a molded body having a chamfered end portion of the end surface on the side of the filter body, which prevents chipping and peeling during polishing. However, in this proposal, no attention was paid to the removal of inner peripheral burrs on an automated line, and even with a chamfered shape, burrs still occur, and the entire surface is polished to remove the inner peripheral burrs. There is no choice but to solve the above-mentioned cost increase. Further, the molded body of the present invention is different from the chamfering of this proposal because the inner peripheral portion of the molded body is projected.

As described above, conventionally, the shape of the punch pressing surface of the molding device for arranging the filter body is regulated to perform the molding, and the irregular shaped sintered body obtained from the molding is partially polished to obtain the surface of the filter body. There is no proposal to remove the inner peripheral burr based on the shape.

[0021]

[Specific Structure] The specific structure of the present invention will be described in detail below.

The permanent magnet 1 of the present invention is a magnetoplumbite type ferrite magnet, and has an annular shape as shown in FIG. One of the annular end faces of the permanent magnet 1 of the annular body (the upper side in the drawing) is the filter body side end face 11, and a part of this face, that is, the outer peripheral portion is usually the unpolished portion 14, so that the filter body has an uneven shape. The transferred pattern remains, while the inner peripheral portion is a polished portion 15 which is polished flat.

In order to obtain such a permanent magnet 1, a slurry in which a powder of a permanent magnet material is dispersed is used, a wet compaction is performed in a magnetic field to prepare a compact, and the compact is sintered to obtain a sintered compact. In the example shown in FIG. 2, the molded body and the sintered body 10 have a cylindrical shape, and the inner peripheral portion has a shape protruding from the outer peripheral portion. Then, during molding, the concavo-convex shape of the filter body is transferred to the one end surface 11 on the filter body side that contacts the filter body,
It has irregularities. Then, burrs 17 (only the inner peripheral portion is shown) are formed on the inner periphery and outer periphery of the end surface on the filter body side.

Such burr is generated as follows. That is, the slurry 100 is wet-molded in the cavity formed by the upper punch 21, the lower punch 25, the die 31, and the core rod 35 as shown in FIG. Is provided on the end face side of the upper punch 21). However, when arranging the filter body 7, the filter body is apt to bend or the like, and the upper punch 2
1 and the core rod 35 and the die 31 are likely to form a minute gap, and the slurry entering this portion causes burr. In particular, when the molding is performed on an automated line, the contact position between the die 31 and the upper punch 21 can be assembled with high accuracy, but the core rod 35 has an elongated thin diameter shape, so the vertical assembly accuracy must be deteriorated. In addition, the assembling accuracy deteriorates due to the material adhered to the filter and the material adhered to the rod even in the continuous molding. For this reason, especially in an automated line, the inner peripheral burr is often generated. The filter body 7 is arranged on the upper punch 21 side and is pressed by pressing the lower punch 25 or the upper punch 21. Therefore, the end surface 12 on the side opposite to the filter body 7 is pressed by, for example, the lower punch 25 to form a flat surface having no unevenness. On the other hand, in the example shown in FIG. 3, the upper punch 21,
The lower punch 25 has a shape in which the pressing surfaces 215, 255 are continuously inclined toward the inner circumference, and the inner circumference is recessed from the outer circumference. As a result, the formed body is the upper punch 2
1. Depending on the shape of the pressing surface of the lower punch 25, the inner peripheral portion of each pressing surface has a shape that continuously inclines and protrudes from the outer peripheral portion. As a result, the sintered body 10 obtained therefrom has a constant shape. Since it contracts at a contraction rate, it has a shape as shown in FIG. Then, the inner peripheral portion of the end surface 11 of the sintered body 10 on the filter body side is polished to remove the inner peripheral burr.

FIG. 3 shows an example of the molding apparatus. More specifically based on FIG. 3, a die 31 is supported by the support column 5, and the upper punch 21, the lower punch 25, and the core rod 35 are arranged on the die 31. A coil 8 is attached to the outer peripheral portion of the die 11, and both punches 21 and 25 are made magnetic so that the magnetic field can be oriented in the axial direction during molding. Now, the core rod 35 is fixedly arranged in the die 31. Also,
The upper punch 21 and the lower punch 25 are respectively in the cylinder 4
The upper punch 21 descends and comes into contact with the upper surface of the die 31, and the lower punch 14 ascends in the penetrating portion provided in the die 11 to perform pressure molding. I am supposed to do it. That is, the slurry of the oxide magnet powder includes the upper punch 21, the lower punch 25,
It is filled and molded in the cavity formed by the die 31 and the core rod 35.
A supply path (not shown) communicating with the cavity is formed in the die 31.

The upper punch 21 has a drain hole 6 for discharging the dispersion medium (water) pushed out from the slurry by pressurization.
1 is provided in plural numbers, and the drainage holes 61 are used as drainage paths 65.
Is in communication with. Further, the filter body 7 is provided on the upper punch 21 side.
Is installed, and only the dispersion medium is drained when pressurizing.
It has the function of pushing out into the cavity and stopping the magnet powder in the cavity. The filter body 7 is wound around rolls 71 and 75, and can be appropriately wound by rotating the rolls 71 and 75. Continuous molding is possible without changing the sheet each time. ing.

In order to obtain a molded body of permanent magnets by the apparatus having such a structure, the upper punch 21 is operated by operating the cylinder 41.
Abutting the upper surface of the die 31 and lower punch 25
Is lowered to form a cavity for molding by the upper punch 21, the die 31, the core rod 35, and the lower punch 25, and the slurry of the magnet powder is pressure-fed and filled into the cavity. This pumping is performed from a supply path communicating with the cavity, and after this supply, the lower punch 25 moves up to pressurize the slurry. By this pressurization, the dispersion medium in the slurry is filtered by the filter body 7 and pushed out into the drainage hole 61 and discharged from the drainage port 65 to the outside, and the magnet powder is discharged by the upper punch 21 and the lower punch 25. It is squeezed to form a molded body 100 of a permanent magnet having a predetermined shape. Then, at the time of this molding, the surface uneven shape of the filter body 7 is transferred. Note that unlike the above, the upper punch 21 may be pressed.

As described above, the orientation magnetic field generated by the coil 8 is substantially in the axial direction, and the C-axis direction of the sintered body or the permanent magnet 1 obtained by partially polishing the sintered body is as shown in FIG. It is preferable to face the axial direction of the substantially annular body. However, in some cases, the C-axis direction may be inclined from the axial direction, and one end surface may form a ferromagnetic surface and the other end surface may form a ferromagnetic surface. The filter 7 may be of various types such as filter cloth and filter paper.

The molded body thus obtained is then sintered according to a conventional method. Prior to sintering, it is preferable to remove burrs on the outer peripheral portion of the end surface 11 on the filter body side. That is, after the molding is completed, the upper punch 21 is raised to open the cavity, and then the lower punch 25 is raised to take out the molded body from the apparatus and convey it. This transportation is preferably carried out while supporting the outer peripheral surface of the molded body, and by rotating this, a supporting roller for supporting and conveying the peripheral surface, or one end surface is supported and conveyed while the peripheral surface is supported. The outer peripheral burr can be easily removed by abutting the guide roller for guiding and the outer peripheral surface thereof.

Sintered body 10 obtained by the subsequent sintering
As shown in FIG. 2, as in the case of the molded body, the inner periphery of the end face 11 on the filter body side is inclined or warped so as to protrude from the outer periphery thereof. The inclination or the amount of warp can be changed according to the outer circumference radius Ro, the inner circumference radius Ri, the thickness T, etc. of the permanent magnet 1, but a normal permanent magnet size Ro = 10 to 1
When obtaining 10 mm, Ri = 5 to 55 mm, and T = 5 to 25 mm (see FIG. 1), the inclination amount represented by the difference in height between the outer peripheral edge and the inner peripheral edge of one end surface of the sintered body 10 is 0. 1 ~
4 mm, particularly about 0.2 to 2 mm, and the maximum height T'when the lower surface of the sintered body 10 is placed on a flat plate is T '/ T
It is preferable that ≦ 1.2, especially 1.02 ≦ T ′ / T ≦ 1.10. The end surface 12 on the side opposite to the filter body 7 may be a flat surface, but as shown in the figure, the end surface 12 on the side opposite to the filter body 7 projects toward the side opposite to the filter body 7,
If it is inclined, further curved, or, on the contrary, protrudes toward the filter body 7 side, inclined, and further curved, the polishing load at the time of polishing described below is reduced, and a more preferable result is obtained. Further, in the illustrated example, the end surface 11 on the filtering surface side and the end surface 12 on the opposite side are inclined with a constant inclination, but they are inclined or curved on a curved surface, or have a step. It is also possible to project the inner peripheral side with.

On the other hand, the surface shape of the filter body 7 is transferred to the filter body side end surface 11 of the sintered body 10. This transfer shape differs depending on the filter body 7, but when the filter body 7 more preferable in terms of the ability to remove the dispersion medium is used, the recess depth is about 0.05 to 0.2 mm. Then, as shown in FIG. 2, on the inner peripheral edge of the filter body side end surface 11,
There are burrs 17 that could not be removed by the automated line. The inner peripheral direction growth length of the burr 17 is generally 0.2 to 5
mm, the height of the burr 17 protruding upward is 0.05 to
It is about 0.3 mm.

Next, such a sintered body 10 is polished. The polishing may be preferably partial polishing of at least only the end surface 11 on the filter body side, but if the polishing is carried out while the sintered body 10 is continuously transported, a very preferable result in mass production can be obtained. As shown in the drawing, it is preferable to simultaneously polish the end surface 11 on the filter body side and the end surface 12 on the opposite side thereof, as indicated by the alternate long and short dash line.

FIG. 4 illustrates such a preferred polishing process. In FIG. 4, a pair of grinders 91 and 95, which rotate in opposite directions, are arranged opposite to each other with a gap corresponding to the final thickness T of the permanent magnet 1 interposed therebetween. And
In order to make the radial direction of the sintered body 10 vertical, b in the figure
It may be conveyed in the same direction and polished on both sides. In the case of the sintered body 10 as shown in FIG. 2, since both end surfaces are inclined in the same direction, the sintered body 10 is sharpened by the grinders 91 and 95 as compared with the case of polishing an annular body having no warp. The amount of polishing is remarkably small, the weight yield is remarkably improved, and the processing speed is extremely high.

In such a case, when polishing, 0.2 (Ro-Ri) from the inner circumference at the end face 11 on the filter body side.
It is preferable to polish the above area (polishing portion 15).
If the area of the polishing portion 15 is too small, the effect of removing burrs becomes ineffective. In addition, the contact area with the yoke of the speaker or magnetron becomes small, and the amount of surface effect magnetic flux decreases. However, if the area of the polishing portion 15 is too wide, the polishing load becomes large, and if the entire area is polished and the area of the polishing portion reaches the outer peripheral edge, chipping or chipping is likely to occur at the outer peripheral edge. Furthermore, the weight yield also decreases due to the increase in the polishing amount. Generally, for example, the size of the yoke of the speaker is set to an outer diameter smaller than the outer diameter of the magnet, and even if the area of the polishing portion 15 is larger than the outer diameter of the yoke, the change in the effective magnetic flux amount is small. Therefore, it is preferable that the area of the polishing portion 15 is set to the yoke outer diameter or less, more preferably 0.95 Ro or less, and particularly 0.9 Ro or less to eliminate these disadvantages.

On the other hand, the polishing thickness ΔT is the total thickness T of the permanent magnet.
On the other hand, it is preferable that ΔT / T ≧ 0.01. Thereby, the inner peripheral burr can be effectively removed. However, ΔT
If too large, the same inconvenience as described above will occur, so it is preferable to set ΔT / T ≦ 0.1. Since the permanent magnet 1 shown in FIG. 3 is subjected to the above-mentioned double-side polishing, the end face opposite to the filter body is polished from the outer peripheral side with the same polishing allowance as above.

[0036]

According to the present invention, the inner peripheral burr can be removed with extremely high mass productivity by using it in an automated line by simply changing the molding apparatus. At this time, the polishing load is remarkably reduced, and the processing speed is remarkably improved. In addition, chipping and chipping are prevented, the quantity and weight yield are improved, and the manufacturing cost is remarkably reduced.

The present inventors conducted various experiments in order to confirm such effects. One example is shown below.

Experimental Example Using the apparatus shown in FIG. 3, the inner peripheral sides of the pressing surfaces 215, 255 of the upper punch 21 and the lower punch 25 are continuously recessed to make 40
Sr ferrite was molded in a wet magnetic field at a pressure of 0 kg / cm ² . Then, it sintered at 1240 degreeC. The orientation magnetic field was in the axial direction. The sintered body 10 had an outer diameter of 2Ro = 70 mm and an inner diameter of 2Ri = 32 mm, and the filter body-side end surface 11 had irregularities having recesses having a depth of 0.1 mm. The inner peripheral height of the sintered body 10 was 10.6 mm, and the outer peripheral height was 9.6 mm.

With the apparatus shown in FIG. 3, the inner peripheral side of the end face 11 on the filter body side of both end faces of this sintered body 10 and the end face 12 on the opposite side end face.
The outer peripheral side of the was polished. The polishing allowance was ΔR = 11 mm, Δt = 0.3 mm on one side, and the permanent magnet (A) had a total thickness T = 10 mm.

On the other hand, for comparison, the pressing surfaces 215 and 255 of the upper punch 21 and the lower punch 25 are flat surfaces, and molding is carried out in a magnetic field in the axial direction, and molding and sintering are carried out in the same manner as above. It has a transfer shape of the filter surface on the end surface of
A parallel annular sintered body with Ro = 70 mm and Ri = 32 mm was obtained. Next, the both surfaces were entirely polished with a stock removal having a thickness of 0.4 mm to obtain a permanent magnet B.

In both cases, the sintered body 10 had burrs having a width of 0.2 to 3 mm and a height of 0.2 mm at the inner peripheral edge of the end surface on the filter body side, which were all removed by the above polishing. We were able to. However, in the permanent magnet A, as compared with the comparative permanent magnet B, the processing speed was increased by 15%, the occurrence rate of chipping and chipping was reduced by 5%, and the polishing amount was halved.

From the above, the effect of the present invention is clear.

[Brief description of drawings]

FIG. 1 is a sectional view showing a permanent magnet of the present invention.

FIG. 2 is a sectional view showing a sintered body according to the present invention.

FIG. 3 is a sectional view showing an apparatus used for wet molding of the present invention.

FIG. 4 is a perspective view showing an apparatus used for polishing of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Permanent magnet 10 Sintered body 100 Slurry 11 Filter body side end surface 14 Unpolished part 15, 16 Polished part 17 Burr 21 Upper punch 25 Lower punch 31 Die 35 Core rod 7 Filter 8 Coil 91, 95 Grinder

Claims (9)

[Claims] 1. A ring-shaped molded body in which a filter body is arranged in one punch, and an oxide permanent magnet material is wet-molded in a magnetic field in a cavity formed by this punch, a die, a core rod, and the other punch. To obtain a molded body in which the inner peripheral portion of the pressing surface of the punch in which the filter body is arranged is recessed from the outer peripheral portion to project the inner peripheral portion of the filter body side end surface from the outer peripheral portion. The body is sintered to obtain a sintered body in which the inner peripheral portion of the filter-side end surface protrudes from the outer peripheral portion, and at least the inner peripheral portion of the filter-body-side end surface of this sintered body is polished to form an inner peripheral burr. A method for manufacturing a permanent magnet for removing a magnet. 2. The method for producing a permanent magnet according to claim 1, wherein the sintered body is conveyed while being supported on the outer peripheral surface thereof, and both end surfaces thereof are polished between the grinders facing each other. 3. The inner peripheral portion of the end surface on the side opposite to the filter body side is formed by protruding or recessing the inner peripheral portion of the pressing surface of the punch facing the punch in which the filter body is arranged from the outer peripheral portion. The permanent magnet according to claim 1 or 2, wherein a molded body which is recessed or protruded from the outer peripheral portion is obtained. 4. The method for producing a permanent magnet according to claim 1, wherein an outer peripheral burr of the compact is removed before the sintering. 5. The filter body is arranged on the side of the upper punch having a drainage hole, is brought into contact with a die and a core rod, and the lower punch or the upper punch is pressed to apply a slurry of an oxide permanent magnet material in a magnetic field. The method for manufacturing a permanent magnet according to claim 1, wherein the permanent magnet is molded. 6. The method for producing a permanent magnet according to claim 1, wherein a magnetic field in an approximately axial direction is applied to the molded body during the wet molding. 7. The method for producing a permanent magnet according to claim 1, wherein an unpolished portion is provided on the outer peripheral portion of the end surface on the filter body side during the polishing. 8. The sintered body has an annular shape, and when the outer circumference radius is Ro and the inner circumference radius is Ri, 0.2 from the inner circumference.
8. A region of (Ro-Ri) or more is polished,
1. A method for manufacturing a permanent magnet according to any one of 1. 9. The method for producing a permanent magnet according to claim 1, wherein a thickness of 0.01 T or more on the inner circumference is polished, where T is the thickness of the permanent magnet.