JP2007228699A - Cylindrical magnet and its production process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylindrical magnet excellent in mechanical characteristics and magnetic characteristics in which the risk of damaging a molding during handling is low, and to provide its production process. <P>SOLUTION: A plurality of cylindrical magnet elements are bonded in the axial direction and the bonding surface between the magnet elements is non-planar in the cylindrical magnet. The production process of a cylindrical magnet comprises a first charging step for filling a cylindrical air gap provided in a female die with a first material containing first magnetic powder, a first press step for forming a first cylindrical green compact element by inserting a first cylindrical punch having a non-planar forward end face into the cylindrical air gap of the female die, a second charging step for filling a second material containing second magnetic powder on the first green compact element, and a second press step for forming a second cylindrical green compact element on the first green compact element by inserting a second cylindrical punch having a non-planar or planar forward end face into the air gap. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cylindrical magnet and a manufacturing method thereof, and more specifically, a cylindrical magnet in which a plurality of cylindrical magnet pieces whose axial height is relatively low are joined in the axial direction, and a manufacturing method thereof. About.

The bond magnet refers to a magnetic powder such as SmCo ₅ or Nd ₂ Fe ₁₄ B solidified with a resin. The resin used varies depending on the molding method. In general, a thermosetting resin is used in compression molding, and a thermoplastic resin is used in injection molding or extrusion molding. Further, the sintered magnet means a magnetic powder formed and sintered.
Sintered magnets require expensive equipment and have the disadvantage that they often require machining to be finished into a final product, but are characterized by a high energy product. On the other hand, the bond magnet has the disadvantage that the energy product becomes smaller as the filling rate of the magnetic powder becomes lower, but the process is relatively simple, and the final product shape can be obtained without machining. . Therefore, sintered magnets and bonded magnets are used for various purposes depending on the purpose.

Among the magnets, those having a cylindrical shape are used for rotors of various rotating devices such as servo motors and PM stepping motors. A cylindrical magnet is generally manufactured by pressing a raw material containing magnetic powder into a cylindrical shape, curing the resin, or sintering the magnetic powder.
In addition, the cylindrical magnet may be used alone as it is, but a plurality of cylindrical magnets may be used in combination in order to obtain a predetermined performance. Further, in order to obtain predetermined performance, a long cylindrical magnet having a relatively long axial length may be required. For this reason, various proposals have conventionally been made regarding methods for producing cylindrical magnets.

  For example, in Patent Document 1, a first raw material mixture containing magnet powder and resin is preliminarily compressed after filling into a cylindrical molding space, and a second raw material mixture containing nonmagnetic powder and resin is prepared. Pre-compressed after filling into the cylindrical molding space, pre-compressed after filling the first raw material mixture containing magnet powder and resin into the cylindrical molding space, and then higher than the pre-forming pressure Discloses a method of manufacturing a cylindrical bonded magnet that is compression molded. This document describes that a cylindrical bonded magnet in which a magnet part is bonded to both ends of a nonmagnetic part can be obtained by such a method.

  Patent Document 2 discloses a long ring magnet in which a plurality of ring magnets magnetized with two or more poles along the outer peripheral surface are bonded so that the same poles face each other in the axial direction. In the same document, when the thickness of the adhesive layer between the magnets is changed, the position of the low magnetic flux density region formed in the space near the outer periphery of the adhesive layer is moved closer to or away from the outer peripheral surface of the ring magnet. It describes what can be done.

  Further, Patent Document 3 discloses that when a magnetic alloy powder is molded in a magnetic field, the long radial magnet is formed by dividing it in the axial direction and sequentially stacking and forming it to form a long ring magnet compact. A method for manufacturing an isotropic ring magnet is disclosed. In the same document, when producing a long radial anisotropic ring magnet, it is described that the effect of radial orientation in magnetic field molding becomes significant when the height of the molded body molded at one time is reduced. Yes.

JP 2003-153504 A JP-A-2005-224021 Japanese Unexamined Patent Publication No. 09-233776

When there is room in the installation space of the cylindrical magnet and a magnet with a large maximum energy product is required, generally a cylindrical magnet with a relatively short axial length and a relatively thick wall Is used. On the other hand, in order to obtain a predetermined maximum energy product when there is not enough room for mounting the cylindrical magnet, a long length with a relatively thin wall thickness and a relatively long axial length. Cylindrical magnets are required.
However, in general, when a long molded body is press-molded, as the length of the molded body increases, the friction between the powders and the friction between the powder and the mold wall surface increase, and the distance from the punch increases. , The compressive force applied to the powder is reduced. As a result, the density of the molded body is highest at the portion close to the punch, and the density decreases as the distance from the punch increases. The non-uniform density causes a decrease in mechanical strength and magnetic properties of the cylindrical magnet.

In order to solve this problem, a method of first producing a short cylindrical magnet and then adhering it in the axial direction is also conceivable. However, this method requires an adhesion step, and increases man-hours and costs.
On the other hand, the method of forming the raw material powder filling and forming in multiple stages is effective as a method for obtaining a uniform long shaped article having a high forming density. However, immediately after molding, the strength of the interface of the molded body is lower than the strength of the portion other than the interface of the molded body. Therefore, there exists a problem that a molded object tends to fracture | rupture at an interface during handling of a molded object.

The problem to be solved by the present invention is to provide a long cylindrical magnet excellent in mechanical characteristics and magnetic characteristics and a method for producing the same.
Another problem to be solved by the present invention is to provide a cylindrical magnet that is less likely to be damaged during handling of a molded body and a method for manufacturing the same.
Furthermore, another problem to be solved by the present invention is to provide a method of manufacturing a cylindrical magnet capable of manufacturing a cylindrical magnet having such characteristics without significantly increasing the number of steps and cost. There is.

In order to solve the above problems, a cylindrical magnet according to the present invention is characterized in that a plurality of cylindrical magnet pieces are joined in the axial direction, and a joining surface between the magnet pieces is non-planar. And
The cylindrical magnet manufacturing method according to the present invention includes a first filling step of filling a cylindrical gap provided in a female mold with a first raw material containing a first magnetic powder, and a tip surface thereof being non-planar. A cylindrical first punch is inserted into the female cylindrical gap to form a cylindrical first green compact piece; and Further, a second filling step of filling a second raw material further containing a second magnetic powder, and a cylindrical second punch whose tip surface is non-planar or flat are inserted into the gap, and the first pressure The gist of the present invention is to further include a second pressing step of forming a cylindrical second green compact piece on the powder piece.

  When press-molding a long cylindrical magnet, the green compact is divided into green compact pieces with relatively short axial lengths, and raw material filling and press-molding are performed for each green compact piece. When it is repeated, it is possible to obtain a long and uniform shaped body with a high density of the shaped body. At this time, if the shape of the interface of the green compact pieces is non-planar, the physical anchor effect increases and the interface strength between the green compact pieces increases. Therefore, there is little possibility that the molded body breaks at the interface of the green compact piece during handling. When the resulting molded body is cured or sintered with a resin, the green compact pieces become magnet pieces, and at the same time, the magnet pieces are firmly joined together, resulting in excellent mechanical strength and magnetic properties. A long cylindrical magnet is obtained.

Hereinafter, an embodiment of the present invention will be described in detail.
The cylindrical magnet according to the present invention is characterized in that a plurality of cylindrical magnet pieces are joined in the axial direction, and a joining surface between the magnet pieces is non-planar.
The cylindrical magnet may be a bonded magnet containing magnetic powder and a thermosetting resin, or may be a sintered magnet containing substantially only magnetic powder. When the cylindrical magnet is a bonded magnet, the plurality of magnet pieces are joined in the axial direction by a thermosetting resin contained in the magnet pieces. On the other hand, when the cylindrical magnet is a sintered magnet, the plurality of magnet pieces are joined in the axial direction by sintering.

The composition of the magnetic material contained in the cylindrical magnet is not particularly limited, and the present invention can be applied to any magnetic material. Specific examples of the magnetic material include SmCo ₅ , Nd ₂ Fe ₁₄ B, and SrO · nFe ₂ O ₃ . In the case where the cylindrical magnet is a bonded magnet, the type of thermosetting resin is not particularly limited. As the thermosetting resin, an epoxy resin, a phenol resin, a urea resin, a polyester resin, or the like is usually used.
The number of the magnet pieces constituting the cylindrical magnet is not particularly limited, and can be arbitrarily selected according to the purpose. The inner diameter and outer diameter of each magnet segment are the same in nature, but the height may be the same or may be different for each magnet segment. Furthermore, the composition of each magnet segment may be the same or may be different for each magnet segment.

“The joining surface between the magnet elements is non-planar” means that all the surfaces constituting the interface between the magnet elements are not on the same plane.
As a non-planar joining surface, specifically,
(1) A joining surface in which the shape of the axial cross section (a cross section when the magnet element is cut by a plane passing through the central axis) is stepped
(2) A joint surface having a tapered axial cross-section,
(3) A joint surface having a wedge-shaped axial cross-section,
(4) The shape of the circumferential cross section (the cross section when the cylindrical surface obtained by cutting the magnet element along the circumferential direction at a certain distance from the central axis is developed in a plane) is A joint surface that is serrated (regularly or irregularly uneven along the circumferential direction),
and so on.
In this case, the height and width of the staircase joint surface, the taper angle of the taper joint surface, the wedge apex angle of the wedge joint surface, the concave and convex shape of the serrated joint surface, the concave and convex period, etc. are particularly limited. It can be arbitrarily selected depending on the purpose.

Next, the manufacturing method of the cylindrical magnet which concerns on this invention is demonstrated.
The manufacturing method of the cylindrical magnet which concerns on the 1st Embodiment of this invention is a manufacturing method of a bonded magnet, Comprising: A 1st filling process, a 1st press process, a 2nd filling process, and a 2nd press process And a heat treatment step.

The first filling step is a step of filling the first raw material containing the first magnetic powder into a cylindrical gap provided in the female mold.
In the case of a bonded magnet, the first raw material includes a thermosetting resin in addition to the first magnetic powder. The composition of the first magnetic powder is not particularly limited, and the various magnetic materials described above can be used. Further, the first raw material may contain other components (for example, a metal soap-based lubricant such as calcium stearate) as necessary.
The addition amount of the thermosetting resin is selected in accordance with the average particle size and particle size distribution of the raw material powder, the characteristics required for the cylindrical magnet, and the like. Usually, about 2 to 4 wt% of a thermosetting resin is added to the first raw material.
The height of the magnet segment is determined by the filling amount of the first raw material into the gap and the molding pressure. Therefore, the optimal filling amount of the first raw material in the gap is selected according to work efficiency, characteristics required of the molded body, and the like.

The first pressing step is a step of inserting a cylindrical first punch whose tip surface is non-planar into a female cylindrical gap to form a cylindrical first green compact piece.
The shape of the tip surface of the first punch determines the interface shape between the green compact pieces (magnet pieces). Specifically, as the shape of the tip surface of the first punch,
(1) A tip surface having a stepped axial cross section,
(2) A tip surface having a tapered axial cross-section,
(3) A tip surface having a wedge-shaped axial cross section;
(4) A tip surface having a sawtooth shape in the circumferential cross section;
and so on.
The shape of the tip surface of a punch (hereinafter referred to as “lower punch”) inserted into the gap from the direction opposite to the first punch may be planar or non-planar. good.

The first punch may be an integrated type or a divided type in which a plurality of parts are combined. In particular, when the shape of the axial cross section of the tip surface of the first punch is stepped, the first punch is divided into an inner diameter side punch and an outer diameter side punch, and the inner diameter side punch and the outer diameter side punch are independent from each other. A split type that can be moved is preferable. Use of such a divided first punch has an advantage that the height of the step portion can be arbitrarily changed by changing the relative positions of the inner diameter side punch and the outer diameter side punch.
The molding pressure in the first pressing step is not particularly limited and can be arbitrarily selected according to the purpose. For example, the first green compact piece may be molded at a molding pressure (hereinafter referred to as “set pressure”) at which a molding density required for the molded body is obtained, or molded at a pressure lower than the set pressure ( (Preliminary molding). Further, the molding may be molding in a magnetic field in which molding is performed while applying a magnetic field.
After the formation of the first green compact piece, the first punch and the lower punch are simultaneously lowered downward to move the first green compact piece downward of the female die, and above the first green compact piece. In addition, a gap necessary for adding the raw material is formed.

The second filling step is a step of filling the second raw material further containing the second magnetic powder on the first green compact piece.
When manufacturing the long cylindrical magnet which has the same composition, the thing of the same composition as the 1st raw material and the 1st magnetic powder is used for the 2nd raw material and the 2nd magnetic powder, respectively. On the other hand, when it is desired to change the characteristics depending on the part, the second raw material and the second magnetic material may have different compositions from the first raw material and the first magnetic material, respectively. In addition, when the second filling step and the second pressing step are repeated a plurality of times, the second raw material may have the same composition or may be different for each second green compact piece. Since the other points regarding the second raw material and the second magnetic powder contained therein are the same as those in the first filling step, description thereof will be omitted.

In the second pressing step, a cylindrical second punch whose tip surface is non-planar or flat is inserted into the gap, and further on the first green compact piece, a cylindrical second green compact element is inserted. This is a step of forming a piece.
The second filling step and the second pressing step are repeated a plurality of times as necessary. When the second green compact piece formed in the second pressing step is not the green compact piece formed last, a cylindrical punch whose tip surface is non-planar is used for the second punch. In this case, the second punch may have the same shape as the first punch, or may have a different shape.
On the other hand, when the second green compact piece is a green compact piece to be formed last, the second punch may be a cylindrical punch whose tip surface is non-planar, or its tip. A cylindrical punch having a flat surface may be used. In particular, when the above-described split type punch is used as the second punch, a molded body (pressure-free) in which the interface shape between the green compact pieces is stepped and the end face shape is flat without performing punch replacement. A unit of powder pieces) is obtained. Since the other points regarding the second punch are the same as those of the first punch, the description thereof is omitted.

The molding pressure in the second pressing step is selected optimally according to the purpose. For example, when the second green compact piece formed in the second pressing step is not formed last, the forming pressure may be a set pressure or may be lower than the set pressure.
On the other hand, when the second green compact piece is formed last, the forming is performed at a set pressure. As a result, the green compacts are firmly bonded to each other, and at the same time, a molded body having a target molding density is obtained.
If the second green compact piece is not formed last, the second green compact piece is lowered by simultaneously lowering the first punch and the lower punch after the second green compact piece is formed. It moves below a female type | mold, and the space | gap required in order to add a raw material is formed above the 2nd green compact piece. Thereafter, the filling and forming of the raw material are repeated as many times as necessary.
On the other hand, when the second green compact piece is formed last, the lower punch is raised after the second green compact piece is formed, and the formed body is taken out from the female die.

  FIG. 1 is a schematic cross-sectional view of an integrated first punch (and second punch) and a molded body formed using the first punch. In FIG. 1A, the first punch 10 is an integral cylindrical punch having an axial cross-sectional shape that is stepped. When the filling and pressing of the raw material are repeated a plurality of times using such a first punch 10, as shown in FIG. 1B, the first green compact piece 12a and the second green compact piece A molded body 12 in which 12b to 12n are joined in the axial direction and the interface between the green compact pieces is stepped is obtained. In this case, the upper end surface of the molded body 12 is stepped.

  FIG. 2 is a schematic cross-sectional view of a split-type first punch (and second punch) and a molded body formed using the first punch. In FIG. 2A, the first punch 20 is divided into an inner diameter side punch 20a and an outer diameter side punch 20b so that the inner diameter side punch 20a and the outer diameter side punch 20b can move independently. It has become. When the filling and pressing of the raw material are repeated a plurality of times using such a first punch 20, as shown in FIG. 2 (b), the first green compact piece 22a and the second green compact piece A molded body 22 in which 22b to 22n are joined in the axial direction and the interface between the green compact pieces is stepped is obtained. In this case, when pressing the green compact piece 22n at the top, if the tip surface of the first punch 20 is made flat, the upper end surface of the compact 22 is flat as shown in FIG. Can be.

The heat treatment step is a step of heating the molded body composed of the combined body of the first green compact piece and the second green compact piece to cure the thermosetting resin after the second pressing step.
The heat treatment is usually performed by holding the green compact at 170 to 190 ° C. for about 2 to 20 minutes, although it depends on the size of the thermosetting resin used and the molded body. When heat treatment is performed, the green compact becomes a magnet piece by curing the thermosetting resin, and at the same time, the plurality of magnet pieces are axially moved by the thermosetting resin contained in the magnet piece. To form a cylindrical magnet.

Next, the manufacturing method of the cylindrical magnet which concerns on the 2nd Embodiment of this invention is demonstrated. The method for manufacturing a cylindrical magnet according to the present embodiment is a method for manufacturing a sintered magnet, and includes a first filling step, a first pressing step, a second filling step, a second pressing step, and sintering. Process.
When manufacturing a sintered magnet, the raw material contains substantially only magnetic powder. Other components (for example, a lubricant, a sintering aid, etc.) are added to the raw material as necessary. Since the other points regarding the first filling step, the first pressing step, the second filling step, and the second pressing step are the same as those in the first embodiment, the description thereof is omitted.

The sintering step is a step of heating the compact made of a combination of the first green compact piece and the second green compact piece to sinter the magnetic powder.
As the sintering conditions, optimum conditions are selected according to the composition of the magnetic powder. Sintering is usually performed by holding the green compact in an inert atmosphere at 1100-1300 ° C. for 1-2 hours. When the green compact is heated under appropriate conditions, each green compact piece is sintered into a magnet piece, and at the same time, the magnet pieces are joined in the axial direction by sintering to form a cylindrical magnet.

Next, the operation of the cylindrical magnet and the manufacturing method thereof according to the present invention will be described.
In general, when a long shaped body is press-molded, the density tends to be non-uniform as the length of the shaped body increases. Further, in order to press-mold a long shaped body, it is usually necessary to use a large mold capable of forming a void having a height several times its height. Furthermore, since there is an upper limit to the stroke of the press machine, there is a limit to the length of the molded body that can be molded by one press.

On the other hand, when a long cylindrical magnet is press-molded, the compact is divided into green compact pieces having a relatively short axial length, and raw material filling and When the press molding is repeated, a long and uniform shaped body having a high density of the shaped body is obtained. In addition, since filling and pressing are repeated a plurality of times, a relatively long molded body can be easily formed even when using a relatively small mold or a press machine having a relatively short stroke. Can be produced.
If the shape of the interface between the green compact pieces is non-planar at the time of molding, the physical anchor effect increases and the interface strength between the green compact pieces increases. Therefore, there is little possibility that the molded body breaks at the interface of the green compact piece during handling. When the resulting molded body is cured or sintered with a resin, the green compact pieces become magnet pieces, and at the same time, the magnet pieces are firmly joined together, resulting in excellent mechanical strength and magnetic properties. A long cylindrical magnet is obtained.

  The embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention.

  The cylindrical magnet and the manufacturing method thereof according to the present invention can be used as a rotor magnet for various rotating devices such as a servo motor and a PM stepping motor and a manufacturing method thereof.

FIG. 1A is a cross-sectional view of an integrated punch having a stepwise axial cross section at its tip, and FIG. 1B is a molding formed using the punch shown in FIG. It is sectional drawing of a body. FIG. 2A is a cross-sectional view of a split punch having a stepwise axial cross section at its tip, and FIG. 2B is a molding formed using the punch shown in FIG. It is sectional drawing of a body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 1st punch 12 molded object 12a 1st green compact piece 12b-12n 2nd green compact piece

Claims (10)

A plurality of cylindrical magnet pieces are joined in the axial direction,
A cylindrical magnet having a non-planar joining surface between the magnet pieces.   The bonded magnet according to claim 1, wherein the joining surface between the magnet pieces has a stepped shape in an axial cross section. The magnet piece includes magnetic powder and a thermosetting resin,
The cylindrical magnet according to claim 1, wherein the plurality of magnet pieces are joined in the axial direction by the thermosetting resin contained in the magnet pieces.   The cylindrical magnet according to claim 1 or 2, wherein the plurality of magnet pieces are joined in the axial direction by sintering. A first filling step of filling a first raw material containing the first magnetic powder into a cylindrical gap provided in the female mold;
A first pressing step of inserting a cylindrical first punch whose front end surface is non-planar into the female cylindrical gap to form a cylindrical first green compact piece;
A second filling step of filling a second raw material further containing a second magnetic powder on the first green compact piece;
A cylindrical second punch whose front end surface is non-planar or flat is inserted into the gap to form a second cylindrical green compact piece on the first green compact piece. A second pressing step;
The manufacturing method of the cylindrical magnet provided with.   The cylinder according to claim 5, wherein the second filling step and the second pressing step of forming the second green compact piece using the second punch having a non-planar tip surface are repeated a plurality of times. Of manufacturing a magnet.   7. The method for manufacturing a cylindrical magnet according to claim 5, wherein tips of the first punch and the second punch have a stepped shape in an axial cross section. The first punch and the second punch are divided into an inner diameter side punch and an outer diameter side punch,
The method for manufacturing a bonded magnet according to claim 7, wherein each of the inner diameter side punch and the outer diameter side punch can move independently. The first raw material and the second raw material include a thermosetting resin,
After the second pressing step, the method further comprises a heat treatment step of heating a molded body composed of a combination of the first green compact piece and the second green compact piece to cure the thermosetting resin. Item 9. A method for producing a cylindrical magnet according to any one of Items 5 to 8. The method further comprises a sintering step of heating the molded body composed of a combination of the first green compact piece and the second green compact piece after the second pressing step to sinter the magnetic powder. Item 9. A method for producing a cylindrical magnet according to any one of Items 5 to 8.

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