JP2000315607A - Permanent magnet and fixing structure thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and inexpensively work through holes and to prevent the easy occurrence of chipping by setting a ratio between the diameter of the pierced through hole and the thickness of a sintered magnet body to be within a specified value range. SOLUTION: A permanent magnet 2 is the rare earth sintered magnet of Nd-Fe-B and a size is 56 mm×22 mm×9 mm. Through holes 5 whose diameters (d) are 6 mm are uniformly formed in right and left at an almost center part by piercing work. The ratio d/t of the thickness (t) of a sintered magnet body to the diameter (d) of the pierced through hole is about 0.7. Since the thickness of the arcuate sintered magnet body is limited on manufacture, it is about 2 to 25 mm. When the through holes are aimed to fasten/fix the magnets, fastening strength is sufficient for bolts inserted through the holes whose diameters are 3 to 10 mm. When the through hole is to be made in the rare earth sintered magnet by machining, d/t is set to be in the range of 0.1 to 5 from a factor in terms of a shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet used for various motors and generators, and more particularly to an arc-shaped or semi-circular (hereinafter, referred to as an arc-shaped) permanent magnet body. The present invention relates to a rare earth sintered permanent magnet having a through hole and a fixing structure using the permanent magnet.

[0002]

2. Description of the Related Art Conventionally, Sm-Co permanent magnets and R-Fe
The B-based permanent magnet is a magnet having a high energy product, and is generally manufactured by a powder sintering method. For example, Nd, F
Using e and B as raw materials, these are blended in a predetermined amount, and the blended raw materials are dissolved and poured into a mold to obtain an ingot. The obtained ingot is pulverized, the powder is pressed in a magnetic field, and the pressed body is sintered. After sintering, a predetermined heat treatment is performed to grind the surface and the like to obtain a sintered magnet body. In the above-described molding in a magnetic field, there are two types of molding: a vertical magnetic field molding in which the orientation applied magnetic field and the molding pressure direction are substantially parallel, and a horizontal magnetic field molding in which the orientation applied magnetic field and the molding pressure direction are substantially perpendicular. is there. Generally, the magnetic field orientation is better in the horizontal magnetic field molding than in the vertical magnetic field molding, and a sintered magnet with high magnetic properties can be obtained.

[0003] By the way, these Sm-Co system and R-Fe
-A rare earth sintered magnet containing a B-based rare earth element has a drawback that its cutting workability is extremely poor because it is very brittle. In reality, of the mechanical strength, the compressive strength is relatively high, so it is possible to perform grinding,
Since only a very low value was obtained for the tensile strength, it was difficult to perform drilling with a drill or the like. Therefore, the usual fixing means of the rare earth sintered magnet is based on an adhesive. For example, a relatively large rotating machine such as an eddy current type speed reducer in which a plurality of permanent magnets are attached around a rotor or the like to form a magnetic circuit. When a permanent magnet is fixed to a fixed member, a fixing structure in which the permanent magnet is fixed with an adhesive has generally been used.

However, it is very attractive to employ a rare earth sintered magnet and a mechanical fixing structure of an arc-shaped permanent magnet using a fastening member such as a bolt. Means for providing a through-hole by machining are also proposed. For example, Japanese Unexamined Patent Publication No.
According to 07691, it is disclosed that the screw mounting hole is made possible by drilling by electric discharge machining. Japanese Patent Application Laid-Open No. Hei 9-246026 does not describe a sintered magnet, but forms a RM-rich phase in a basic component of a raw material by performing a heat treatment after hot working such as hot rolling, and further forms an R-rich phase in a perforated portion. It is disclosed that the machinability is improved by setting the -M rich phase to a predetermined volume ratio.

On the other hand, it is also conceivable to provide a through-hole integrally when press-molding like a ring-shaped magnet. From this viewpoint, in the case of the vertical magnetic field molding, since the axis of easy magnetization (the axial direction of the through hole) of the molded body and the moving direction of the mold are the same, the core for forming the through hole ( By providing the core bar, the through-hole can be integrally formed. However, in the transverse magnetic field molding, which is advantageous because a molded body having high magnetic properties is obtained, since the axis of easy magnetization (the axial direction of the through hole) is orthogonal to the moving direction of the mold, it is not possible to integrally mold the through hole during molding. It can be said that it is difficult.

[0006]

However, even with a magnet molded body obtained by vertical magnetic field molding, some distortion occurs after sintering. In the case of the arc shape, distortion that varies in the vertical and horizontal directions occurs, and precise dimensional accuracy may not be obtained even for the through hole. In such a case, additional processing is required. On the other hand, since the sintered magnet formed by the transverse magnetic field has basically excellent magnetic properties as described above, it is desired to produce a permanent magnet having a through hole by the transverse magnetic field. However, in practice, the transverse magnetic field shaping is not realistic because it involves a drastic change of equipment in addition to the above-mentioned distortion problem. Of the two prior arts described above, the former proposes a solution to the problem from the working method, and the latter proposes a solution to the problem from the manufacturing method such as hot rolling and the specific phase morphology. Indeed, these may make it possible to machine through holes. However, on the other hand, it can be said that this is not a means that takes into account the problems of actual equipment and costs. Furthermore, it was not confirmed in the above-mentioned conventional example that the sintered magnet body could be perforated by machining.

In addition, in the case of the R—Fe—B sintered magnet, since the crystal grains are largely dropped during the processing, chipping (chipping) is apt to occur at the time of processing, and cracks and cracks are liable to occur therefrom. Further, at the time of drilling, an oxidation reaction occurs in the portion to be processed with a considerably high temperature. As a result, there is a problem that the magnetic properties are locally deteriorated. Further, in a structure in which a permanent magnet is fixed to a rotor or the like, a large electric motor or a rotating machine or the like remains uneasy about changes in environmental temperature and long-term reliability with only an adhesive. However, there is a problem in that it is not possible to reduce the size by separately providing a fixing bracket or the like.

Accordingly, the present invention is intended to solve these problems and is directed to an arc-shaped magnet excluding a ring-shaped magnet and a rare-earth sintered magnet. (Perforation processing) with a through hole provided. Permanent magnet that is easy to process the through hole at low cost and is less likely to cause chipping, etc., and fixing this permanent magnet directly to a fixed member such as a rotor or a stator. The purpose is to provide a structure.

[0009]

SUMMARY OF THE INVENTION The present invention is to solve these problems by first balancing the shape element between the permanent magnet main body and the through hole, and uses a conventional rare earth sintered magnet. However, it has been found that setting the ratio of the diameter of the through hole to the thickness of the magnet within a predetermined range is effective. That is, the present invention provides an RCo ₅ system, R ₂ C
o _17- based, R-Fe-B-based (R is one or two or more rare-earth elements including Y) sintered rare-earth magnets provided with through-holes by machining and drilling The ratio (d / t) between the diameter d of the through hole and the thickness t of the sintered magnet body is set to 0.
It is a permanent magnet in the range of 1 to 5, desirably, d / t of 0.4 to 2.

[0010] The present invention also relates to an RCo ₅ system, R ₂ Co
₁₇ or R-Fe-B (R is one or two or more rare earth elements including Y) A mixture of raw material powder for rare earth sintered magnet and mineral oil or synthetic oil And wet pressing with the powder oriented,
After sintering the obtained molded body, the sintered magnet body is provided with a through hole by machining, and the ratio (d) of the diameter d of the through hole to be bored and the thickness t of the sintered magnet body is obtained. / T) is 0.1 to
5 is a permanent magnet. Preferably, d
/ T is about 0.4 to 2. In this case, the raw material powder is mixed with a mineral oil or a synthetic oil and subjected to pressure forming after applying an orientation magnetic field. The grain boundaries are less likely to fall off.

[0011] Here, the through-hole is provided with a counterbore portion in advance, and is drilled with a buffer member interposed therebetween, so that chipping is less likely to occur. In addition, if the drilling operation at this time is performed in a low oxygen atmosphere in a mineral oil or a synthetic oil or in an inert gas atmosphere, oxidation can be suppressed and deterioration of magnetic properties can be prevented. Further, even if the surface roughness Ra of the inner surface of the through-hole is set to 25 μm to 1.6 μm by selecting a tool and processing conditions, chipping is unlikely to occur, and plating and resin coating to be performed later can be easily applied. Finished neatly. It is desirable that a metal plating layer or a resin coating layer be provided on the outer surface of the magnet molded body including the inner diameter surface of the through-hole because corrosion resistance is improved and rust can be prevented.

The present invention utilizes a through hole directly formed in a permanent magnet as a bolt fastening hole. That is, a permanent magnet fixing structure in which the permanent magnet is directly attached to the fixed member by inserting a fastening member into a through hole provided in the permanent magnet and screwing it to a fixed member such as a rotor. is there. At this time, if a magnetic or non-magnetic protective cover that covers the permanent magnet is provided, the fastening is performed via the cover, so that the tightening force increases. The magnetic cover can reduce the ripple of the gap magnetic flux density waveform. Further, if the permanent magnet is fastened between the rotor and any of the fastening members via a buffer member such as a vibration absorbing member, the loosening of the bolt due to the rotational vibration is prevented.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an embodiment in which the permanent magnet of the present invention is used in an eddy current type speed reducer. FIG. 2 is a cross-sectional view illustrating an example in which a protective cover that covers the magnet is provided.

First, the eddy current type speed reducer will be described briefly. 2. Description of the Related Art Conventionally, a permanent magnet type eddy current type reduction device using a permanent magnet (hereinafter simply referred to as a retarder) has been known as a reduction braking device for a large vehicle. The outline of this retarder is as follows: a rotor attached to a rotating shaft such as a propeller shaft that works in conjunction with the rotation of a wheel; a permanent magnet attached to a fixed stator such as a body frame in close proximity to the rotor; It comprises a ferromagnetic plate interposed between magnets, and switches between braking and non-braking by changing the relative position between the permanent magnet and the ferromagnetic plate. Therefore, at the time of braking, the positions overlap and the rotor on the rotating side crosses the magnetic line of force of the permanent magnet on the fixed side, thereby generating an eddy current for braking the rotation of the rotor and applying a deceleration torque to the vehicle. Here, the permanent magnets are arranged adjacently in the circumferential direction on the stator side or the rotor side so that the polarities of the magnets are different from each other. Some of these fixing structures are made of adhesives, but the ambient temperature is 600
Since the temperature becomes as high as ° C., mechanical fastening means using fixing brackets are often used.

FIG. 3 shows an example in which this metal fitting is used. The permanent magnet 12 has an arc shape having a gently curved surface, and has engaging step portions 121 on both side surfaces. An engaging step 15 matching the engaging step 121 is provided between adjacent permanent magnets.
1 is provided with a fixture 15 made of a non-magnetic material. Therefore, the bolts 14 are inserted into the through holes 152 of the fixture 15 while combining the respective engagement step portions 121 and 151.
Are screwed onto a screw 131 to be formed on the stator 13 side, thereby fixing the two. With these retarders,
Naturally, a reduction in weight and size is desired, and therefore, a high-performance permanent magnet, that is, a rare-earth permanent magnet 12 is used. However, the fixing structure using the fixing bracket 15 as described above has a problem that the fixing bracket is large and heavy, and the effective magnetic flux amount is reduced.

Therefore, this problem can be solved by using the permanent magnet according to the present invention. That is,
In FIG. 1, a permanent magnet 2 is a rare earth sintered magnet of Nd—Fe—B, and its size is 56 mm × 22 mm × 9 m.
m (1 × B × t). In addition, a through hole 5 having a hole diameter (d) of 6 mm is formed in the substantially central portion evenly on the left and right sides by drilling. Therefore, the through hole 5 is formed as a bolt insertion hole, and a bolt (4) is inserted through a buffer member (not used in this embodiment) and the like, and is formed on the stator 3 side. It is screwed and fixed directly. At this time, a buffer member such as a spring material, a rubber material, or a synthetic resin material or a known vibration absorbing member is interposed between the bolt 4 and the permanent magnet 2 to disperse stress applied to the magnet.
It is also desirable to absorb vibrations and the like. Further, it is desirable to apply an adhesive to the threaded portion at the tip of the bolt to prevent the screw from loosening. The magnetizing may be performed in the state of the sintered magnet body, but in some cases, it is better to perform the magnetizing treatment after assembling in consideration of workability and equipment.

The ratio d / t of the thickness t of the sintered magnet body of this embodiment to the diameter d of the through hole to be drilled is about 0.7. The thickness of the arc-shaped sintered magnet body is approximately 2 to 25 m due to manufacturing limitations.
m. On the other hand, when the through hole is intended to fasten and fix the magnet, it is considered that a bolt having a diameter of 3 to 10 mm is sufficient for this kind of fastening strength. In the case where a through hole is to be drilled in such a rare earth sintered magnet by machining, it has been found that it is desirable to set d / t to be in the range of 0.1 to 5 due to geometrical factors. Was. More preferably, it is desirable to set the through-hole at about 0.4 to 2 to form the through-hole. Thus, the permanent magnet 2
, The permanent magnet 2 itself is large, and the gap 30 between the magnets can be suppressed as small as possible. Therefore, the magnetic force of the permanent magnet can be effectively used, and the weight and size can be reduced.

The sintered rare earth magnet of the present embodiment is N
d27.5%, Pr2.5%, Dy1.0%, B1.0
%, Nb 0.2%, Al 10.2%, Ga 0.1%, and the balance of the raw material powder for the R-Fe-B based rare earth sintered magnet of Fe is jet-milled, and this fine powder is mixed in mineral oil. The mixture was pressurized and injected into a mold cavity to which an orientation magnetic field was applied. After filling, the mixture was wet-molded by applying a molding pressure while applying an orientation magnetic field to obtain a press-formed body. The press-formed body is filtered, subjected to a demineralized oil treatment, and then sintered to obtain a sintered magnet body. In the case of a rare earth sintered magnet obtained through such a molding process, the orientation of the powder is in a fixed direction and is fine and uniform. This has the effect that hardly occurs.

FIG. 2 shows a fixing structure in which the permanent magnet of the present invention is directly fixed to the rotor side using bolts. The entire upper surface of the permanent magnet 6 is covered with a protective cover 7 and the bolts are fastened from above. It shows. The protective cover 7 may be made of a non-magnetic material or a magnetic material. However, a non-magnetic material such as rubber or resin material can provide a greater bolt tightening torque. In the case of a magnetic cover, it can be expected that the ripple of the gap magnetic flux density waveform is reduced. In the above embodiment, the through hole provided in the magnet is used as a bolt hole. However, for example, the through hole can be used as a hole for binding through a wire. Alternatively, a convex portion may be provided on the non-fixed member side, and the convex and concave portions of the through hole may be used as the positioning means by utilizing the concave / convex fitting.

Processing conditions for drilling a through hole are also one of the requirements. In the present embodiment, for example, a basic condition of a rotation speed of a drill: 300 to 400 rpm, a feed speed: 0.05 mm / rotation, and a drill tip angle: 125 ° is given. The feed speed needs to be set considerably lower than that of ordinary steel materials, and the drill tip angle is wider than usual. Also, when processing through holes, it is better to feed them several times instead of drilling all at once.In addition, a counterbore part is provided in advance, and chipping is performed by drilling from the counterbore side. Perforation is performed with less. In addition, when a non-magnetic cover such as a rubber material as shown in FIG. 2 is covered in advance and the cover is pierced while pressing the cover, chipping is less likely to occur. Also, the drilling work at this time,
It is more preferable to carry out the treatment in a low oxygen atmosphere in a mineral oil or a synthetic oil or in an inert gas atmosphere. By doing so, it is possible to suppress oxidation and prevent deterioration of magnetic characteristics. The surface roughness Ra of the inner diameter surface of the through hole is 25.
By setting the thickness to be from μm to 1.6 μm, plating and resin coating to be performed later can be easily applied and finished cleanly. If a metal plating layer or a resin coating layer is provided on the outer surface of the magnet molded body including the inner diameter surface of the through hole, corrosion resistance may be improved and rust may be prevented.

The permanent magnet and the fixing structure of the present invention are devices which require reliability and safety at low and high speed rotation, and are suitable for applications where the weight and size of the device are desired to be reduced. Like the speed reduction mechanism of a hoist,
It is effective when used for a drive motor of a railway vehicle, an electric vehicle, or the like.

[0022]

According to the present invention, in a rare earth sintered magnet having an arc shape, a through hole can be formed by machining by selecting the optimum value of the thickness and the dimensional relationship of the through hole to be machined. Became a magnet. At this time, it can be processed so as not to cause chipping or the like.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a fixing structure using a permanent magnet of the present invention in an eddy current type speed reducer.

FIG. 2 is a schematic sectional view showing another embodiment provided with a cover.

FIG. 3 is a perspective view showing a mounting structure of a permanent magnet of a conventional eddy current type speed reducer.

[Explanation of symbols]

 1: Fixing structure of permanent magnet 2, 6: Permanent magnet 3: Stator 4: Fastening member (bolt) 5: Through hole 7: Protective cover 8: Rotor

Claims (9)

[Claims] 1. A rare-earth sintered magnet having a through-hole formed by machining, wherein a ratio (d / t) of a diameter d of the through-hole to be drilled to a thickness t of the sintered magnet body is 0.1. Permanent magnets characterized by being 1 to 5. 2. RCo ₅ system, R ₂ Co ₁₇ system, R—Fe
-Apply an orientation magnetic field to a mixture of any of the B-based (R is one or more of the rare-earth elements including Y) rare-earth-based sintered magnet raw material powder and mineral oil or synthetic oil to form a powder. After being wet-molded while being oriented, and sintering the obtained molded body, the sintered magnet body is provided with a through hole by machining. A permanent magnet having a ratio (d / t) to the thickness t of 0.1 to 5. 3. The permanent magnet according to claim 1, wherein the through hole is formed by providing a counterbore. 4. The permanent magnet according to claim 1, wherein the through hole is formed with a buffer member interposed therebetween. 5. The permanent magnet according to claim 1, wherein the perforation is performed in a low oxygen atmosphere in a mineral oil or a synthetic oil or in an inert gas atmosphere. 6. A surface roughness Ra of an inner diameter surface of the through hole.
The permanent magnet according to claim 1, wherein (center line average roughness) is 25 μm to 1.6 μm. 7. A permanent magnet is directly attached to a fixed member by inserting a fastening member into a through hole provided in the permanent magnet according to claim 1 and screwing the fixing member to the fixed member. A permanent magnet fixing structure. 8. A magnetic or non-magnetic protective cover for covering the permanent magnet is provided, and the permanent magnet is directly attached to the member to be fixed by screwing on the protective cover with a fastening member. The permanent magnet fixing structure according to claim 7, wherein 9. The fixing device according to claim 7, wherein the permanent magnet is directly attached to the fixed member via a buffer member between the permanent magnet and one of the fixed member and the fastening member. Fixed structure of permanent magnet.