JP3023315B2 - Method for manufacturing permanent magnet structure and magnetic attachment for fixing denture - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic attachment used for fixing a denture in the field of dentistry.

[0002]

BACKGROUND OF THE INVENTION Magnetic attachments for fixing dentures
It is composed of a magnet assembly and a keeper. The magnet assembly has a permanent magnet and a yoke for guiding a magnetic flux generated from the permanent magnet to the keeper as basic components. This is opposed to a keeper made of a soft magnetic material, and the denture is fixed by magnetic attraction between the magnet assembly and the keeper. Conventionally, various types of magnetic attachments as shown in FIG. 2 have been studied (Kiuchi et al., "Analysis of Attraction Force of Closed Magnetic Circuit Type Magnetic Attachment," IEICE Technical Meeting,
SA-84-10 (1984), FIG. 2). In FIG. 2, 1
0 is a permanent magnet, 11 is a yoke made of a magnetic material, 12 is a keeper made of a magnetic material, (a) is a cup yoke type, (b), (c) and (d) are split pole types, (e) And (f) are called the sandwich type. In the cup yoke type shown in FIG. 2A, as shown in FIG. 5, the seal member facing the keeper 3 on the outside of the magnet has a concentric structure, and a disk yoke 4 made of a magnetic material is provided at the center of the seal member. The mainstream structure is a shield ring 5 made of a non-magnetic material. The magnetic flux from the magnet flows through a dotted path, and most of the magnetic flux passes through a disk yoke made of a magnetic material. Most of the suction force is generated at the opposing portions of the disk yoke, the cup yoke 2, and the keeper 3.

[0003]

The magnetic attachment of the cup yoke type shown in FIG. 5 has a practically sufficient suction force and is widely used at present. However, the magnetic attachment is used by being embedded in a denture. Therefore, it is clear that when demands for downsizing and large attraction force become stronger, it is desirable to further increase the efficiency of the magnetic circuit. Further, since the magnetic attachment is used in the oral cavity, it is required to have excellent corrosion resistance. In addition to using a material having excellent corrosion resistance as a case material, a permanent magnet is sealed in the case to prevent corrosion. Welding is used as a means for sealing a permanent magnet in a case, and Japanese Patent Publication No. 6-6128 discloses that a butt portion of a sandwich type magnetic attachment is adhered and sealed by laser welding.
Japanese Patent Application Laid-Open No. 4-227253 discloses that the butted portions of a cup yoke type magnetic attachment are adhered and sealed by seam welding. The permanent magnet is sealed by welding, but may cause stress corrosion cracking due to residual stress during welding. Therefore,
An object of the present invention is to improve the magnetic attraction force of a magnetic attachment and to prevent stress corrosion cracking due to residual stress in a welded portion of the magnetic attachment.

The present invention provides a permanent magnet including a case having an opening on one side, a permanent magnet housed in the case, and a seal member having at least a part of an austenitic alloy for sealing the case opening. A method for manufacturing a structure, comprising fixing a butted portion of a case and a seal member by welding and then performing a heat treatment. Further, the present invention comprises a case having an opening on one side, a permanent magnet housed inside the case, and a sealing member having at least a part of an austenitic alloy part for sealing the case opening, A magnet for fixing a denture, comprising: a butt portion of a seal member fixed by welding, and a permanent magnet structure having a columnar structure in at least a part of the weld portion; and a keeper made of a magnetic material. Attachment. In the present invention, performing the heat treatment after welding serves to alleviate the stress in the welded portion and also to improve the magnetic attraction force. The purpose of using austenitic stainless steel for the sealing member is to flow magnetic flux along the dotted line as shown in FIG. Austenitic stainless steel has a γ-phase austenitic structure in terms of metallography. The γ phase is a non-magnetic phase. This prevents the magnetic flux from short-circuiting at the butted portion of the case and the seal member, and allows the magnetic flux to efficiently pass from the permanent magnet structure to the keeper. However, when the butted portion is welded with a laser beam or the like and the seal member is remelted, rapid cooling of the seal member is likely to occur, and the solidification structure is not the original γ phase but the δ phase ferrite, which is a ferromagnetic layer. Easy to change into organization. As a result, the magnetic flux is short-circuited at the butted portion, and the magnetic attractive force is reduced. Therefore, annealing heat treatment is performed to return the seal member changed to the δ phase to the γ phase again. In addition, by simultaneously performing the heat treatment, it is possible to reduce the stress of the welded portion. The heat treatment is preferably performed in a reducing atmosphere to suppress precipitation of chromium. If the heat treatment temperature is 400 ° C. or higher, the stress in the welded portion can be relaxed.

[0005]

FIG. 1 is a schematic sectional view of a magnetic attachment according to the present invention. In FIG. 1, 1 is a permanent magnet, 2 is a case, 3 is a keeper, 6 is a seal member, and includes a shield plate 4 and a seal ring 5.
The permanent magnet 1 has Nd of a maximum energy product of 45 MGOe.
SUS447 having a magnetic flux density Bs of 1.28T was used for the case, the shield plate and the keeper using an FeB-based magnet.
SUS with large magnetic resistance for shield ring using J1
316L was used. In FIG. 1, the butted portion between the case and the shield ring and the butted portion between the shield ring and the shield plate were laser-welded.

(Example 1) A permanent magnet structure having the same structure as that shown in FIG. 1 was prepared by using a permanent magnet having an outer diameter of 3.0 mm and a height of 1.3 mm (an outer diameter of 2.3 mm and a height of 0.5 mm). Use), a magnetic attachment for dentures having an outer diameter of 3.0 mm and a height of 0.8 mm of the keeper was prepared, and a repeated load test of a welded portion with and without heat treatment and a measurement of suction force were performed. The heat treatment was performed in an inert atmosphere at 900 ° C for 2 hours and at 460 ° C.
A two-stage heat treatment of × 1 hr was performed. The repeated weight test is
A weight of 50 kg was applied to the welded portion, and the number of occurrences of cracks was measured. In the repeated load test, the permanent magnet structure without heat treatment cracked after 2,000,000 times, and the permanent magnet structure after heat treatment cracked after 3,000,000 times. From this, it has practically sufficient durability with or without heat treatment, but by performing heat treatment,
It was found that the durability was improved and the reliability was excellent. Further, in the measurement of the suction force, the suction force without heat treatment was 292 gf, and the suction force with heat treatment was 323 gf. It was found that the heat treatment improved the suction force. Welds before and after heat treatment (A in FIG. 1)
Part) was observed (× 400) by SEM, and FIG.
As shown in FIG. FIG. 3 shows the structure of the weld before heat treatment (after laser welding), and FIG. 4 shows the structure of the weld after heat treatment. 3 and 4 that the heat treatment forms a columnar structure.

(Embodiment 2) A permanent magnet having a structure similar to that of FIG. 1 and having an outer diameter of 4.5 mm and a height of 1.3 mm (a permanent magnet having an outer diameter of 3.5 mm and a height of 0.5 mm) was used. Use), a magnetic attachment for dentures having an outer diameter of 4.5 mm and a height of 0.8 mm of the keeper was prepared, and the suction force with and without heat treatment was measured. 732 g of suction force without heat treatment
f, and the suction force when subjected to a heat treatment at 700 ° C. for 3 hours in an inert atmosphere was 776 gf. Example 1
Repeated load tests were performed in the same manner as in Example 1. As a result, it was found that the attachment after heat treatment did not crack even if the number of attachments exceeded 3 million, and that good durability was obtained.

According to the present invention, the stress at the welded portion of the magnetic attachment can be removed, the durability can be improved, and the magnetic attraction between the magnet structure and the keeper can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a magnetic attachment according to the present invention.

FIG. 2 is a schematic cross-sectional view of various conventional magnetic attachments.

FIG. 3 is a metallographic photograph of a welded section of a permanent magnet structure before heat treatment.

FIG. 4 is a metallographic photograph of a cross section of a welded portion of a permanent magnet structure after heat treatment.

FIG. 5 is a schematic sectional view of a cup yoke type magnetic attachment.

[Explanation of symbols]

1 permanent magnet, 2 case, 3 keeper, 4 shield plate, 5 seal ring, 6 seal member

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-227253 (JP, A) JP-A-5-132719 (JP, A) JP-A-5-69178 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) A61C 13/235 A61C 8/00

Claims (2)

(57) [Claims] 1. A case having an opening on one side, and a case
Seals the permanent magnet housed inside and the case opening
Having at least a part of an austenitic alloy part for
Consists of a sealing member, butts the case and the sealing member
Is fixed by weldingAnd at least the welds
Also have a columnar structure in partA permanent magnet structure and a keeper made of magnetic material,  Magnetic attachment for fixing a denture,
Chimento. 2. A case having an opening on one side, a permanent magnet housed inside the case, and sealing the case opening.
A method of manufacturing a permanent magnet structure comprising a seal member having at least a part of an austenitic alloy portion for fixing a butt portion between a case and a seal member by welding and then performing a heat treatment. A method for manufacturing a permanent magnet structure.