JP2003169453A - Rotor arrangement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotor arrangement wherein magnetic loss is reduced and cracking between magnets and a yoke which may be caused by thermal stress during use is prevented, and further the same effect is obtained even with rare-earth magnets large in a bonded area. <P>SOLUTION: The rotor arrangement is formed by brazing rare-earth amorphous sintered magnets 3 to the peripheral surface of a rotor core 1. The mating faces of the rare-earth amorphous sintered magnets 3 mated with the rotor core 1 are ground and etched. The mating faces and the peripheral surface of the rotor core are brazed via a cushioning member 2. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor device used for, for example, a rotor or a stator of a motor,
In particular, the present invention relates to a technique for improving the bonding strength between the sintered magnet and the rotor core that is the support thereof.

[0002]

2. Description of the Related Art Sintered magnets made of rare earth metals have excellent magnetic properties, and have recently occupy an important position as permanent magnets for motors. On the other hand, sintered magnets are hard and brittle, so when fixing them to the rotor core,
It is difficult to fix it by bolting which requires machining. In addition, there are technologies that cover the outer circumference of the sintered magnet with a resin or metal ring and fix it, and technology that winds Kevlar fiber around the outer circumference of the sintered magnet. And the manufacturing cost becomes high, which is not preferable. Further, although the sintered magnet and the rotor core have been joined with an adhesive, the adhesive has a limit in adhesive strength at high temperature. on the other hand,
The structure in which the sintered magnet is brazed to the outer peripheral surface of the rotor core has a small air gap, sufficient adhesive strength, and is advantageous in terms of cost.

However, in the structure in which the sintered magnet is brazed to the outer peripheral surface of the rotor core, at the time of cooling after brazing,
There is a drawback that thermal stress is generated due to the difference in linear expansion coefficient between the rotor core and the sintered magnet when the temperature is raised and lowered repeatedly when the rotor device is used, and cracks are likely to occur in the sintered magnet. Japanese Patent Application Laid-Open No. 9-102415 discloses a technique of joining a rare earth permanent magnet and a yoke with zinc or a zinc alloy. With this technology, the melting point of zinc is low, so
It is said that the difference in thermal expansion when the rare earth magnet and the yoke are joined is small, and cracks can be prevented from occurring at the joining interface during the cooling process.

[0004]

However, the above-described technique has a problem of cracking at the time of joining the magnet and the yoke, and cracks due to thermal stress during use of the rotor device that repeatedly raises and lowers the temperature are used. It does not prevent. Further, since zinc is made into a semi-molten state and diffused, there is a limit in the joint area, and for example, only a magnet having a size of about 10 mm square can be joined. Further, for a magnet having a larger joint area, the stress due to the difference in linear expansion coefficient between the magnet and the yoke cannot be relaxed, and the magnet may be damaged by thermal stress. Furthermore, the magnet surface is usually ground to ensure dimensional accuracy, but due to residual compressive stress generated in the surface layer of the magnet due to grinding, minute cracks are generated in the surface layer, It was the starting point of the crack.

Therefore, according to the present invention, the magnetic loss is small, and it is possible to prevent cracks due to thermal stress between the magnet and the yoke during use. It is an object of the present invention to provide a rotor device that can achieve the same effect with respect to a magnet.

[0006]

The rotor device of the present invention comprises:
A rotor device in which a sintered magnet is brazed to the outer peripheral surface of a rotor core, and after the joint surface of the sintered magnet with the rotor core is ground, an etching process is performed to cushion the joint surface and the outer peripheral surface of the rotor core. It is characterized in that it is brazed through a member.

In the rotor device having the above-mentioned structure, since the fine cracks caused by the processing strain caused by the grinding process are removed by performing the etching process, even if the thermal stress is generated, the sintered magnet is cracked. It is hard to enter. Moreover, since the joint surface of the sintered magnet and the outer peripheral surface of the rotor core are brazed via the cushioning member, the cushioning member absorbs the difference in linear expansion coefficient between the sintered magnet and the rotor core. The thermal stress generated in the sintered magnet can be reduced. As described above, in the rotor device of the present invention, the thermal stress is small in combination with the small number of starting points of cracking, so that cracking of the sintered magnet can be prevented.

It has been found that the work strain layer generated in the surface layer portion by the grinding process of the sintered magnet exists up to a depth of 20 to 30 μm from the surface. Therefore, the depth of the surface layer portion removed by etching is preferably 20 to 30 μm.
That is, it is desirable to remove all the work strain layer generated by the grinding work.

Further, conventionally, the sintered magnet has been plated to improve the corrosion resistance. However, when the plated sintered magnet and the rotor core are brazed via the cushioning member, the weakest peeling strength portion of the rotor device becomes the plating interface. That is, according to the study by the present inventors, the occurrence of cracks at the interface between the plating and the brazing filler metal has been confirmed due to the difference in linear expansion coefficient between the two. Also, there is no evidence that the brazing filler metal was blocked by plating and diffused into the sintered magnet,
It was also found that diffusion bonding between the two did not occur. further,
It has been confirmed that thermal stress is generated in the cooling process due to the difference in the linear expansion coefficient between the plating and the brazing material, and the structure of the surface of the sintered magnet is destroyed. Therefore, since a large centrifugal force acts on the rotor device due to high-speed rotation, plating should not be adopted, and in order to improve the corrosion resistance of the sintered magnet, the sintered magnet is sintered in the state of being bonded to the rotor core. It is desirable to coat the surface of the magnet with a resin.

Further, it is desirable that the cushioning member is made of stainless foam metal. When the cushioning member is a foam metal, the Young's modulus is small. Therefore, the cushioning member is easily deformed due to the difference in thermal expansion between the sintered magnet and the rotor core, and the thermal stress generated in both can be further reduced. In addition, since the foam metal is a stainless steel-based material, it has high elasticity limit and strength, and is not easily damaged even if large deformation occurs.

The stainless foam metal is preferably a magnetic material. As stainless steel magnetic material,
There are ferrite type and martensite type (SUS400 series). Since the buffer member made of these materials has the same magnetic properties as the sintered magnet, the magnetic flux increases and contributes to the improvement of the motor output. Further, it is desirable that the porosity of the stainless-steel foam metal is 50 to 90% in calculation. When the porosity is less than 50%, the Young's modulus is high,
It becomes impossible to absorb the difference in thermal expansion between the sintered magnet and the rotor core. Further, if the porosity exceeds 90%, the strength becomes insufficient.

Here, the rare earth metal sintered magnet has a property that when exposed to a high temperature, the metal structure changes and the magnet characteristics are affected. Therefore, it is desirable to use a brazing material having a relatively low liquidus generation temperature as the brazing material used for brazing. As such brazing material,
The content of the rare earth element RE is RE ≧ 50 atomic%, the content of Cu is 18 atomic% ≦ Cu <40 atomic%, and the content of the other alloy element AE is AE ≦ 20 atomic%.
E is Fe, Co, Ni, Ru, Rh, Pd, Os, I
r, Pt, Ag, Au, Zn, B, Al, Ga, In,
A rare earth alloy brazing material made of one or more selected from C, Si, Ge, Sn, Pb, P, Sb and Bi is suitable.

Rare earth elements RE, Cu and alloy elements AE
When the content of is specified as described above, the rare-earth element RE, Cu and the alloy element AE undergo a eutectic reaction under heating, so that the liquid phase generation temperature of the rare-earth alloy brazing material becomes relatively low. Since the liquid phase generated from the rare earth alloy brazing filler metal is highly active, the rare earth alloy brazing filler metal in the liquid phase state or the solid-liquid coexisting state exhibits good wettability with respect to the sintered magnet of the rare earth metal and diffuses. Manifest a phenomenon. In addition, the rare earth alloy brazing material exhibits good diffusivity with respect to the joined members made of various materials even in a solid state under heating. By using such a rare earth alloy brazing material, it is possible to firmly braze the sintered magnet of the rare earth metal and the buffer member at a relatively low temperature. In addition, since the rare earth alloy containing Cu becomes amorphous under the application of the liquid quenching method and the formability into a thin plate and the press punching workability are improved, it is more preferable to use the rare earth amorphous alloy brazing material. is there.

In the present invention, at least one of the joints between the sintered magnet, the rotor core and the cushioning member may be brazed, and the other joining means is optional. For example,
Form the bolt holes when compacting the sintered magnet.
The bolt inserted through the bolt hole may be screwed into the cushioning member. Similarly, the buffer member can be bolted to the soft magnetic material. Any joining means can be brazing. In addition, shrink fitting, cold fitting, welding, etc. are also applicable.

Brazing of the sintered magnet and the buffer member and / or
Alternatively, the brazing between the cushioning member and the rotor core can be partially performed at one or a plurality of locations. By performing such brazing, the thermal expansion of the buffer member does not significantly affect the sintered magnet and the rotor core, and the thermal stress acting on them can be further reduced. Such a partial brazing structure is effective when the buffer member has a linear expansion coefficient close to that of the rotor core and the difference in linear expansion coefficient between the buffer member and the sintered magnet is large. Therefore, when the difference in linear thermal expansion coefficient between the buffer member and the sintered magnet or rotor core is small, there is no problem even if the entire surface is brazed. Further, in the above configuration, it is also possible to dispose the cushioning member at one or a plurality of positions according to the brazing material and braze each cushioning member to the sintered magnet or the rotor core. However, in this case, since the area of the buffer member becomes small, it is necessary to correct the magnetic characteristics by devising the shapes of the sintered magnet and the soft magnetic material.

[0016]

1 (A) and 1 (B) are views of a rotor, which is an embodiment of a rotor device, as viewed in the axial direction.
FIG. 1 (A) shows that the outer circumference of the rotor core 1 is flatly formed at four locations along the circumferential direction, and the sintered magnets 3 are laminated on the flat portion with the foam metal 2 interposed therebetween. The brazing material 4 is used for this. In FIG. 1 (B), recesses are formed at four locations on the outer circumference of the yoke 1 along the circumferential direction, and sintered magnets 3 are laminated in the recesses in the same manner as in FIG. 1 (A). These rotor devices are generally SPM (Surface Perm
anent magnet).

FIG. 2 is a diagram showing a manufacturing process of the rotor device of the embodiment. First, a powder of a rare earth metal is compacted into a magnet shape, and after sintering, aging for strain relief is performed.
Next, the joint surface of the sintered magnet with the rotor core is ground to be flat, and then the magnet is etched. As a result, the work strain layer generated by the grinding work is removed.
Next, the sintered magnet is brazed to the outer periphery of the rotor core via a cushioning member to produce a rotor assembly.

Next, the rotor assembly is washed, and its mounting portion and screw portion are masked and coated with resin. The resin in this case is preferably an epoxy resin which is more excellent in corrosion resistance than a polyimide resin or the like. Then, it is baked using a far infrared lamp or the like (for example, 18
The rotor device is completed at 0 ° C. for 1 hour).

[0019]

EXAMPLES The present invention will be described in more detail below with reference to examples.
Reveal Soft magnetic material composed of S35C as rotor core
(Linear expansion coefficient: 11.7 × 10 ^-6/ ℃, Young's modulus: 2
1000 kgf / mm^Two) Is 50 mm long, 21 mm wide,
It was processed to have a thickness of 25 mm. This soft magnetic material has a length of 1
Amorphous composite of 7 mm, width 17 mm, thickness 0.1 mm
Brazing filler metal (Nd₇₀-Cu₇₀-Al₅) 3 layers
17 mm in height, 17 mm in width, 0.6 in thickness
9 mm SUS410L foam metal (coefficient of linear expansion: 1
7.3 x 10^-6/ ° C, Young's modulus: 500 kgf / mm
^Two, Porosity: 84.8%, tensile strength: about 0.79 kgf
/ Mm^Two) Are overlaid. Above this foam metal
2 pieces of the same amorphous alloy brazing material are stacked,
Grinding on the top 41 mm long, 34 mm wide, and 6 mm thick
After that, it was etched with a solution containing nitric acid as the main component.
Rare earth amorphous sintered magnet (without plating)
Number: -0.8 x 10^-6/ ° C, Young's modulus: 16000k
gf / mm^Two, Tensile strength: 7.5 kgf / mm^Two) Heavy
I put it together. FIG. 3 shows such a laminate,
Reference numeral 1 is a soft magnetic material, 2 is a foam metal, 3 is a rare earth amorph
As sintered magnet, 4 is a brazing material of amorphous alloy.

Next, the above laminated body was placed in a vacuum furnace and the inside was evacuated to 10 ^-4 torr. Before vacuum evacuation, the inside of the vacuum furnace was kept at 1000 ° C. for 5 hours to release impurities adhering to the inner wall and prevent oxidation of the brazing material. Next, the heating rate of the vacuum furnace is set to raise the temperature inside the furnace to 500 ° C. in 60 minutes, and at that temperature, 1
After holding for 3 minutes, it was held at 475 ° C. for 40 minutes, and then gradually cooled.

4 and 5 are photomicrographs of a cross section of a sample in which the soft magnetic material 1, the foamed metal 2, and the rare earth amorphous sintered magnet 3 are bonded to each other by the brazing material 4 as described above. Further, FIG. 6 is a micrograph of a cross section of a sample manufactured under the same conditions as above except that etching was not performed. In the sample shown in FIG. 6, fine cracks are generated in the vicinity of the interface of the rare earth amorphous sintered magnet 3 due to the processing strain of the grinding process. However, in the sample obtained by etching the rare earth amorphous sintered magnet 3, as shown in FIGS. 4 and 5, no cracks were observed near the interface of the rare earth amorphous sintered magnet 3.

Next, FIG. 7 is a photograph of a cross section showing the effect of etching on the ground rare earth amorphous sintered magnet. In FIG. 7A, etching is performed for 3 minutes, and in this state, a processing strained layer due to grinding remains. In (2), etching is further performed for 1 minute. In this state, the work strained layer is removed, and a drop mark remains. In (3), etching was performed for 2 minutes, and the unevenness of the dropout marks was rounded.
In (4), additional etching is further performed for 3 minutes, and gentle unevenness is formed. In (5), additional etching is performed for 4 minutes, and the surface condition is almost the same as in (4). From the above results, (3)
It is considered that the etching may be performed up to the above condition. Therefore, it is considered appropriate that the etching time is 4 to 5 minutes.

[0023]

As described above, in the present invention,
The magnetic loss is small, and it is possible to prevent cracks due to thermal stress generated between the magnet and the yoke during use. In addition, the same effect can be obtained for rare earth magnets with a large bonding area. Obtainable.

[Brief description of drawings]

1A and 1B are views of a rotor device according to an embodiment of the present invention as viewed from an axial direction.

FIG. 2 is a diagram showing a manufacturing process of the rotor device according to the embodiment of the present invention.

FIG. 3 is a perspective view showing a rotor device according to an embodiment of the present invention.

FIG. 4 is a micrograph showing a cross section of a rotor device according to an example of the present invention.

FIG. 5 is a micrograph showing a cross section of a rotor device according to an example of the present invention.

FIG. 6 is a micrograph showing a cross section of a rotor device of a comparative example.

7 (1) to (5) are micrographs showing a cross section of a rare earth amorphous sintered magnet that has been subjected to an etching treatment in Examples of the present invention.

[Explanation of symbols]

1 Soft magnetic material (rotor core) 2 foam metal 3 Amorphous sintered magnet 4 brazing material

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H02K 1/27 501 H02K 1/27 501G (72) Inventor Yoichi Nakahara 1-4-1, Wako-shi, Saitama Prefecture No. 5 F002 AA08 AB07 AC02 AE08 5H622 CA02 CA07 CA13 CB04 CB05 DD02 PP04 PP19 QA06 QA08

Claims (4)

[Claims] 1. A rotor device in which a sintered magnet is brazed to an outer peripheral surface of a rotor core, wherein a bonding surface of the sintered magnet with the rotor core is ground, and then an etching process is performed to perform the etching. A rotor device in which the outer peripheral surface of the rotor core is brazed via a cushioning member. 2. The rotor device according to claim 1, wherein a surface of the sintered magnet is coated with a resin in a state where the sintered magnet is bonded to the rotor core. 3. The rotor device according to claim 1, wherein the cushioning member is made of stainless foam metal. 4. The processing strained layer due to the grinding process is removed by the etching.
4. The rotor device according to any one of 3 above.