JP2013021191A - Bond magnet, manufacturing method therefor, and apparatus for manufacturing bond magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for extrusion-molding a bond magnet, which improves an orientation rate of the bond magnet.SOLUTION: An apparatus for manufacturing the bond magnet comprises: a plasticizing part 3 of melting a bond magnet composition composed of an anisotropic magnetic material and a resin, and subsequently extruding the bond magnet composition toward a front side; a gate part 21 which controls a flow of the bond resin composition having been melted in the plasticizing part; and a molding part 1 which has an orientation magnet 6 arranged therein for applying a magnetic field orienting the magnetic material, and also a cavity 19 for solidifying the melted bond resin composition. The gate part 21 has a plurality of flow paths formed by making flow paths 11 and 16 connected to the plasticizing part 3 branch toward the molding part 1, and a plurality of gates for connecting the flow paths and the cavity 19. The bond resin composition melted in the plasticizing part is filled in the cavity of the molding part from the plurality of the gates in a state that the bond resin composition is divided into a plurality of flows by the plurality of the flow paths.

Description

  The present invention relates to a method for manufacturing an anisotropic bonded magnet excellent in orientation rate and surface magnetic flux density by an extrusion molding method, a manufacturing apparatus therefor, and an anisotropic bonded magnet obtained by the extrusion molding method.

  A bonded magnet composed of a magnetic material and a resin as a binder of the magnetic material can be formed in a complicated shape as compared with a sintered magnet, and has excellent mechanical strength. Therefore, many bonded magnets are employed as electronic parts such as permanent magnet type synchronous motors such as DC motors and stepping motors, and magnet rolls for laser printers.

  By the way, the manufacturing method of such a bond magnet is divided roughly into three types, injection molding, compression molding, and extrusion molding.

  Among these manufacturing methods, the injection molding method is a method in which a bonded magnet composition composed of a magnetic material and a thermoplastic resin is heated in a cylinder of an injection molding machine to be in a molten and fluidized state, and a mold is formed using a plunger. In this method, the inside is filled and formed into a desired shape.

  The compression molding method is a method in which a bonded magnet composition composed of a magnetic material and a thermosetting resin is filled in a press mold and molded while being compressed.

  The processes of the compression molding method and the injection molding method described above have a certain cycle of filling a bonded magnet composition into a mold, molding and taking out a bonded magnet as a molded product, and the production is a so-called batch production. Therefore, its production speed is limited.

  In addition, injection molding and compression molding have a limit for molding a long and narrow molded product, a so-called long product. One reason for this is a problem in mold processing. Although the shape of the molded product is engraved in the mold, high-precision machining in the depth direction of the mold is very difficult. Another reason is a molding problem. In the case of compression molding, even if a long and narrow object is pressed, no pressure is transmitted to the middle of the molded product. Further, when a long product is molded by injection molding, the bonded magnet composition entering from the gate is cooled, resulting in a short shot (molding failure due to unfilled molding material).

  On the other hand, in the extrusion molding method, a bonded magnet composition composed of a magnetic material and a thermoplastic resin or a thermosetting resin is heated in a cylinder to be melted and fluidized. This is a method of forming a bond magnet composition into a desired shape while continuously supplying it to a mold. For this reason, the extrusion molding method is continuous with respect to the batch method of injection molding or compression molding, and thus the productivity is very excellent. Furthermore, since it can shape | mold continuously, the shaping | molding of the long product which was difficult by injection molding and compression molding becomes easy.

  Next, the magnetic material constituting the bonded magnet will be described. First, from the viewpoint of the raw material composition of the magnetic material, it is classified into a ferrite type and a rare earth type magnetic material. Ferrites are most popular because they have a long history and are inexpensive. However, the magnetic force is weaker than that of the rare earth system, and the magnetic force is insufficient when the molded product is small. Therefore, it is preferable to use a rare earth-based magnetic material for a small molded product.

  Moreover, the magnetic material which comprises a bond magnet is classify | categorized into isotropic and anisotropy from the point of the expression mechanism of magnetism. An isotropic magnetic material exhibits an equivalent magnetic force in any direction. On the other hand, anisotropic magnetic materials can develop a strong magnetic force only in one direction. Therefore, when an anisotropic magnetic material is used as a bonded magnet, the magnetization direction of the particles of the magnetic material must be anisotropic with a certain direction. Such an operation is called orientation. This orientation can be broadly divided into two types: mechanical orientation and magnetic field orientation. “Mechanical orientation” is a method in which when a magnetic material is composed of plate-like particles, the plate-like particles are aligned in the thickness direction when pressure is applied to the plate-like particles from the outside. It is. When the plate-like particles have an easy magnetization axis in the thickness direction, the magnetic material particles can be mechanically oriented by this operation. On the other hand, “magnetic field orientation” means that particles are oriented by applying a magnetic field from the outside during molding. From the relationship between the particle shape and the direction of the easy axis of magnetization, mechanical orientation is possible with ferrite-based magnetic materials, but with rare-earth magnetic materials, it is limited to magnetic field orientation. When an anisotropic magnetic material is used, the orientation process is increased compared to when an isotropic magnetic material is used, so that molding becomes difficult, while magnetic force is higher than when an isotropic magnetic material is used. Become stronger. As a rare earth magnetic material, an isotropic magnetic material is widely used because it is easy to use, but anisotropy has been actively studied for miniaturization and energy saving of a motor.

JP-A-3-27906 JP-A-9-275028

  However, extrusion molding is advantageous in terms of productivity and molding of long products compared to compression molding and injection molding, but it is disadvantageous in terms of anisotropy. In the magnetic field orientation, a bonded magnet composition composed of a magnetic material and a resin component is heated and melted, and the easy magnetization axis of the magnetic material that can move freely under the orientation magnetic field is arranged in a desired direction, and the arrangement is maintained. In the case of a thermoplastic resin, it is cooled and solidified, and in the case of a thermosetting resin, it is carried out by heating and solidifying.

  In injection molding, thermoplastic resin is mainly used as a binder for magnetic materials, and a bonded magnet composition whose viscosity is sufficiently reduced by melting is injected into the cavity, and then cooled and solidified in the cavity as it is. Therefore, a bonded magnet molded product having a high orientation ratio can be obtained.

  In compression molding, a thermosetting resin is mainly used as a binder for the magnetic material, and heating and compression are performed while applying an orientation magnetic field to the bonded magnet composition filled in the mold. In the initial stage of heating, the viscosity of the resin decreases, and the particles of the magnetic material move along the orientation magnetic field. If the heating is continued as it is, the resin turns to curing, so that the particles of the magnetic material are fixed while maintaining the orientation.

  On the other hand, in the case of continuous extrusion, in order to sufficiently orient the magnetic material, the magnetic material is used for orientation while the magnetic material is under the influence of the orientation magnet, while the viscosity of the resin is reduced as much as possible. In order to fix the oriented magnetic material, it is necessary to raise the viscosity sufficiently and solidify it when it is removed from the influence of the magnet.

  In order to solve these problems, in the molding method disclosed in Patent Document 1, the temperature gradient in the presence of the magnet for orientation of the mold is obtained by combining members having different thermal conductivities in the configuration of the molding apparatus. By attaching it, the magnetic characteristics are improved. Further, in the molding method disclosed in Patent Document 2, the orientation rate of the bonded magnet is improved by arranging a plate-like obstacle in the middle of the flow path through which the molten bonded magnet composition passes. Yes. However, even with these molding methods, a molded product of a bonded magnet having sufficient magnetic properties has not been obtained.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a bonded magnet having a long length and excellent magnetic properties, which has been difficult with conventional molding techniques, by extrusion molding. There is.

  In order to achieve the above object, the present invention provides a bond in which a bonded magnet composition comprising an anisotropic magnetic material and a resin is melted and then solidified under a magnetic field for orienting the magnetic material and extruded. In the magnet manufacturing method, the melted bonded magnet composition is divided into a plurality of flows and filled in a cavity of a mold, and the magnetic field is applied.

  The magnetic material is preferably a Sm—Fe—N based magnetic material.

  The resin constituting the bonded magnet composition is preferably a thermoplastic resin.

  The bonded magnet is preferably formed in a cylindrical shape.

  This invention is a bonded magnet manufactured by the said manufacturing method, Comprising: It is a bonded magnet whose orientation rate is 70% or more.

  The present invention is a bonded magnet having an average surface magnetic flux density of 1100 G or more.

  The bonded magnet manufacturing apparatus according to the present invention melts a bonded magnet composition composed of an anisotropic magnetic material and a resin and then extrudes it forward, and melts at the plasticized portion. A molded part having a gate for controlling the flow of the bonded bond resin composition, an orientation magnet for applying a magnetic field for orienting the magnetic material, and a cavity for solidifying the molten bond resin composition In the bonded magnet manufacturing apparatus, the gate section includes a plurality of flow paths in which a flow path connected to the plasticizing section is branched toward the molding section, and the flow paths. And a plurality of gates connecting the cavities, and the bond resin composition melted in the plasticizing part is divided into a plurality of flows by the plurality of flow paths, Above from the gate Characterized in that it is filled into the cavity of the shaped part.

  It is preferable that the cavity has a cylindrical shape with a substantially concentric cross section, and the gate is a hole arranged side by side in the radial direction of the concentric circle.

  It is preferable that the gate and the orientation magnet are arranged so that a magnetic field for orienting the magnetic material is applied immediately after the molten bond resin composition passes through the gate.

  The present invention is a bonded magnet manufactured by the manufacturing apparatus, wherein the magnetic material is an Sm-Fe-N-based magnetic material, and the orientation ratio is 70% or more. .

  According to the present invention, it is possible to provide a bonded magnet that is long and excellent in surface magnetic flux density and orientation rate by an extrusion molding method.

FIG. 1 is a schematic cross-sectional view of a conventional bonded magnet manufacturing apparatus. FIG. 2 is a cross-sectional view in the AA direction in FIG. 3 is a cross-sectional view in the BB direction in FIG. FIG. 4 is a schematic cross-sectional view of a bonded magnet manufacturing apparatus according to an embodiment of the present invention. 5 is a cross-sectional view in the DD direction in FIG. 6 is a cross-sectional view in the EE direction in FIG. FIG. 7 is a cross-sectional view in the FF direction in FIG. FIG. 8 is a cross-sectional view in the FF direction of FIG. 4 in a molding portion according to another embodiment of the present invention. FIG. 9 is a cross-sectional view in the FF direction of FIG. 4 in a molding portion according to another embodiment of the present invention. FIG. 10 shows the measurement results of the surface magnetic flux density of the bonded magnet in one example of the present invention. FIG. 11 shows the measurement results of the surface magnetic flux density of the bonded magnet in one example of the present invention. FIG. 12 shows the measurement results of the surface magnetic flux density of the bonded magnet in one example of the present invention. FIG. 13 shows the measurement results of the surface magnetic flux density of the bonded magnet according to the comparative example of the present invention.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, the form shown below exemplifies a bonded magnet, a manufacturing method thereof, and a manufacturing apparatus for embodying the technical idea of the present invention, and the present invention relates to a bonded magnet, a manufacturing method thereof, and a bonded magnet. The manufacturing apparatus is not limited to the following.

  Further, the present specification by no means specifies the member shown in the claims as the member of the embodiment. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments are not intended to limit the scope of the present invention only to the description unless otherwise specified. It is just an example. Note that the size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation. Further, in the following description, the same name and reference sign indicate the same or the same members, and detailed description will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured such that a plurality of elements are constituted by the same member and the plurality of elements are shared by one member, and conversely, the function of one member is constituted by a plurality of members. It can also be realized by sharing.

  In the manufacturing method for forming an anisotropic bonded magnet by an extrusion molding method, in order to solve the above problems, the present inventors have made extensive studies, and as a result, a molded part that forms an end product shape by applying an orientation magnetic field. By filling the cavities with the magnet composition from a plurality of gates, the problems were solved and the present invention was completed.

  That is, in the present invention, a bonded magnet composition composed of an anisotropic rare earth magnetic material and a thermoplastic resin or a thermosetting resin is melted in a plasticizing part, and then cooled and solidified in a molding part to which an orientation magnetic field is applied. In a manufacturing method in which anisotropic bonded magnets are extruded by solidification by heating, the number of gates is a magnet composition having a gate for filling the cavity of the molded part with the bonded magnet composition, and the melted magnet composition in the plasticized part. After that, the bonded magnet composition is filled into the cavity of the molded part from the gate into the molded part to which the orientation magnetic field is applied.

  Moreover, this invention is a manufacturing method as described above, Comprising: It is a manufacturing method of the anisotropic bonded magnet which uses a Sm-Fe-N type magnetic material as a rare earth magnetic material. Thereby, it can be set as a bonded magnet with high surface magnetic flux density and orientation rate.

  Moreover, this invention is said manufacturing method, Comprising: It is a manufacturing method of the anisotropic bonded magnet whose shape of the shape | molded bonded magnet is a cylindrical shape. Thereby, it can be set as a cylindrical bond magnet with a high surface magnetic flux density and orientation rate.

  Moreover, this invention is an anisotropic bonded magnet manufactured by said method, Comprising: An anisotropic bonded magnet whose orientation rate is 70% or more.

  According to the structure of this invention, the elongate bond magnet excellent in the orientation rate and the surface magnetic flux density can be provided by extrusion molding.

  That is, the manufacturing method of the bonded magnet according to the present invention is an obstacle to the flow of the resin, although it is an extrusion molding in which it is preferable to smoothly fill the melted bond resin composition into the molded part. It is characterized by a unique device configuration having a simple gate part.

  That is, the present invention provides a bonded magnet composition at the moment of entering a molding part to which an orientation magnetic field is applied by filling the molding part with a molten magnet composition little by little from a plurality of gates formed in the gate part. Becomes sparse with respect to the molding space (cavity), so that the particles of the magnetic material easily move in the direction to be oriented. Therefore, the orientation rate of the bonded magnet can be remarkably increased, and a bonded magnet having a high surface magnetic flux density can be obtained.

  Hereinafter, an embodiment according to the present invention will be described in detail in comparison with a conventional example. However, the embodiment is an example for embodying the technical idea of the present invention, and the present invention is not limited to this embodiment and example. It is not limited.

  First, a conventional extrusion molding method will be described with reference to FIGS. As a conventional extrusion molding method, a method of forming a cylindrical bonded magnet using a thermoplastic resin as a binder of a magnetic material by extrusion molding will be described.

  The apparatus used for the conventional extrusion molding is roughly divided into a molding part 1, an inner die fixing part 2, and a plasticizing part 3, as shown in FIG. Each is provided with a heating device (not shown). The molding part 1 is composed of an outer die 4 and an inner die 5. The inner die fixing portion 2 includes an inner die fixing guide (spider) 8, a mandrel 9, and a barrel 10. Moreover, the plasticizing part 3 is comprised from the screw 12 and the barrel 13 for extruding the fuse | melted bond magnet composition ahead. Further, the outer die 4 has a magnet 6 for orientation.

  First, after the bonded magnet composition is melted in the plasticizing part 3, the bonded magnet composition is pushed out toward the inner die fixing part 2 by the screw 12 and becomes cylindrical in the flow path 11. Next, the melted bonded magnet composition enters the inner die fixing portion 2, and as shown in FIG. 2, the melted bonded magnet composition is formed by the flow path 14 formed by the through-hole having an arcuate cross section. The fluid of the object becomes three tile-like fluids, and further, the three tile-like fluids become one fluid again by the flow path 7 formed at the tip, and the inner die fixing portion 2 It is formed in a cylindrical shape from the outlet to the forming part 1. Thereafter, the molten fluid of the bonded magnet composition enters the molding part 1 and is formed by the orientation magnet 6 arranged so as to surround the cylindrical cavity of the molding part 1 as shown in FIG. The magnetic material contained in the bonded magnet composition is oriented in a desired orientation pattern by the applied magnetic field. The melted bonded magnet composition is cooled and solidified by a cooling device (not shown) from the time when it enters the molding part which is a mold for molding it to the time when it exits the molding part. A magnet can be obtained as a molded product.

  Next, a method for forming a cylindrical bonded magnet using the extrusion molding method of the present invention will be described with reference to FIGS.

  As FIG. 4 shows, the manufacturing apparatus concerning this invention is the same as that of the conventional manufacturing apparatus in the point which has the shaping | molding part 1 and the plasticization part 3. FIG. The manufacturing apparatus according to the present invention is different in that a gate portion 15 is used instead of the conventional inner die fixing portion 2. Here, a heating device (not shown) is attached to each of the plasticizing portion 3 and the gate portion 15. Further, as shown in FIGS. 5 and 6, a flow path 18 and a flow path 19 through which the melted bonded magnet composition passes are formed inside the gate portion 15.

  The shape and size of the flow channels 17 and 18 formed in the gate portion 15 of the present invention are not particularly limited, but the flow channels shown in FIGS. 4 to 7 will be described as an example.

  First, the bonded magnet composition is melted by heating in the plasticizing part 3, and the bonded magnet composition whose fluid is cylindrical in the flow path 11 of the magnet composition enters the gate part 15, 5 passes through the flow path 17 as shown in FIG. 5, and is first divided into two vertical directions (DD direction in FIG. 4). Thereafter, the bonded magnet composition flowing through each flow path is formed by a hole penetrating into the gate portion 15 as shown in FIG. The flow passes through the flow path 18, passes through the gate 21 that is the exit of the gate portion 15, and proceeds to the front molding portion 1. Next, the fluid of the bonded magnet composition is filled into a cylindrical cavity 19 formed in the molded part 1 as shown in FIG. At the same time, the magnetic material contained in the bonded magnet composition is formed into a cylindrical shape while being oriented in a desired orientation pattern by the magnetic field formed by the orientation magnet 6. The molten bonded magnet composition is cooled and solidified by a cooling device (not shown) before exiting from the molded part 1 to obtain a molded product as a cylindrical bonded magnet.

  Here, the major difference between the conventional manufacturing method and the present invention is that the fluid of the melted bonded magnet composition does not form a cylindrical shape before the orientation of the magnetic material.

  In the conventional manufacturing method, the melted bonded magnet composition fluid is already cylindrical before orientation, and the magnet composition is densely packed in the molding space. Therefore, even if the particles of the magnetic material try to move along the orientation magnetic field, the movement is limited.

  On the other hand, in the present invention, the cavity 19 of the molding part 1 is filled from a plurality of gates. 4 to 7 show an example of a manufacturing apparatus in which two gates 21 are formed in the gate portion 15. As shown in FIG. 4, the melted bonded magnet composition is gradually filled into the cavity 19 of the molded part 1 from the two gates 21 little by little. Therefore, compared with the conventional manufacturing method in which the melted bonded magnet composition is densely filled in the cavity, the manufacturing method according to the present invention reduces the density of the melted bonded magnet composition in the molding space. can do. In other words, according to the manufacturing method of the present invention, the magnetic material becomes easier to move and more oriented as compared with the conventional manufacturing method. The oriented magnetic material is gradually and densely packed in the molding space while maintaining the orientation state, and proceeds in the direction of the exit of the molding part while forming a cylindrical shape. As a result, a bonded magnet molded product having a high orientation rate and a high surface magnetic flux can be obtained.

  In the present invention, it is preferable that the gate and the magnet for orientation are arranged so that a magnetic field for orienting the magnetic material is applied immediately after the melted bond resin composition passes through the gate. This is because the orientation rate of the magnetic material can be improved. For example, as shown in FIG. 4, the gate portion 15 is such that the end surface of the gate portion 15 in which the gate 21 is opened and one end surface of the magnet for orientation arranged in the molded portion 1 are substantially the same surface. 15 and the molding part 1 are preferably arranged. Thereby, since the melted bond resin composition can receive the magnetic field from the magnet for orientation immediately after leaving the gate, the orientation ratio of the magnetic material can be improved.

  An orientation magnet is arranged in the molding part so as to surround the cavity. A permanent magnet is usually used as the orientation magnet. The material of the magnet used for the orientation permanent magnet 4 is preferably one having Br of 1T or more, and for example, a NdFeB sintered magnet can be used. When a magnet having a large magnetic force is used, the magnetic field for orientation generated in the cavity of the molded part becomes strong, and the surface magnetic flux density of the bonded magnet can be increased.

  Moreover, the bonded magnet obtained by extrusion molding as described above may be subjected to a magnetizing step if necessary. By performing the magnetization, the surface magnetic flux density becomes higher.

  An anisotropic magnetic material can be applied to the magnetic material that can be used in the present invention. Examples of anisotropic magnetic materials include ferrite, Sm—Co, Nd—Fe—B, and Sm—Fe—N. The above magnetic materials can be used alone or in combination of two or more. Moreover, you may perform an oxidation-resistant process and a coupling process to a magnetic material as needed.

  The resin as the binder of the magnetic material in the present invention is not particularly limited, and both a thermoplastic resin and a thermosetting resin can be used. Of these, thermoplastic resins are preferred in terms of moldability and magnetic properties. For example, thermoplastic resins such as polypropylene, polyethylene, polyvinyl chloride, polyester, polyamide, polycarbonate, polyphenylene sulfide, and acrylic resin, thermoplastic elastomers such as ester and polyamide, or heat such as epoxy and phenol A curable resin can be used.

  Although the blending ratio of the magnetic material and the resin depends on the type of the resin, it is desirable that the ratio of the magnetic material to the entire bonded magnet composition is 40 to 75 Vol%. Further, an antioxidant, a lubricant and the like can be further mixed.

  Examples according to the present invention will be described in detail below. Needless to say, the present invention is not limited to the following examples.

1. Production of anisotropic bonded magnet <Example 1>
(Preparation of magnetic material)
An anisotropic Sm—Fe—N magnetic material (average particle diameter of 3 μm) is used as the magnetic material.

(Preparation of magnet composition)
The Sm—Fe—N based magnetic material is surface-treated with ethyl silicate and a silane coupling agent. 9137 g of the Sm—Fe—N magnetic material subjected to the surface treatment and 863 g of 12 nylon are mixed with a mixer. The obtained mixed powder is kneaded at 220 ° C. using a biaxial kneader, cooled, and then cut into an appropriate size to obtain a bonded magnet composition.

(Extrusion molding)
4 to 7 are schematic views of the manufacturing apparatus according to the present embodiment. The present embodiment will be described in more detail with reference to these drawings.

  The bonded magnet manufacturing apparatus according to the present embodiment includes a plasticizing part 3 that melts a bonded magnet composition composed of an anisotropic magnetic material and a resin and then extrudes it forward with a screw 12. A gate unit 15 for controlling the flow of the bond resin composition melted in the conversion unit 3 and an orientation magnet 6 for applying a magnetic field for orienting the magnetic material are disposed, and the melted bond resin composition And a molded part 1 having a cavity 19 for solidifying the bonded magnet.

  Here, the gate portion 15 is formed in the molding portion 1 with two passages in which one passage connected to the plasticizing portion 3 is branched toward the molding portion 1. It has a cavity 19 that is a molding space and two gates 21 that connect the two flow paths. Two gates 21 of this embodiment are formed at the outlet of the gate portion 15. That is, the cavity 19 has a cylindrical shape with a substantially concentric cross section, and the gate 21 is a hole arranged in two in the radial direction of the concentric circle when viewed from the exit direction of the cavity 19.

  In such a manufacturing apparatus, the bond resin composition melted in the plasticizing part 3 is divided into two-handed flow by two flow paths formed in the gate part 15, and is directly supplied to the outlet of the gate part 15. The cavity 19 of the molding part 1 is filled from the two formed gates.

  In this embodiment, the bonded magnet composition is formed into a final product shape by a cavity 19 having an annular cross-sectional shape composed of the inner peripheral surface of the outer die 4 and the outer peripheral surface of the inner die 5 shown in FIG. The dimensions of the annular cross section are an outer diameter of 25 mm and an inner diameter of 23 mm. The bonded magnet composition prepared and prepared above is charged from the hopper of the extruder. The bonded magnet composition is heated and melted by the screw part 3 and sent to the front gate part 15. In this gate portion 15, the bonded magnet composition is divided into two flow paths by the flow paths 17 and 18 shown in FIGS. The bonded magnet composition is filled into the cavity 19 of the molded part 1 through two gates, and is formed into a cylindrical shape while the magnetic material particles are oriented by the magnetic field of the orientation magnet 6 arranged as shown in FIG. Modeled. The molten bond resin composition is cooled and solidified at the exit of the cavity by a cooling device (not shown). In this way, a molded product of a cylindrical anisotropic bonded magnet can be continuously obtained.

  The obtained molded product of the cylindrical bonded magnet is an anisotropic cylindrical bonded magnet having an outer diameter of 25 mm, an inner diameter of 23 mm, a wall thickness of 1 mm, and an outer periphery of 12 poles.

<Example 2>
(Preparation of magnetic material)
The same magnetic material as in Example 1 is used.
(Preparation of magnet composition)
Using the same magnetic material as in Example 1, the same bonded magnet composition as in Example 1 is produced.
(Extrusion molding)
Extrusion molding was performed in the same manner as in Example 1 except that four gates were formed at the exit of the gate part of Example 1. FIG. 8 shows a cross-sectional view of the gate of this example as viewed from the exit of the molding part. As shown in FIG. 8, the gate of this embodiment is formed as four holes at equal intervals along the circumference of the bottom surface of the cylindrical cavity.

<Example 3>
(Preparation of magnetic material)
The same magnetic material as in Example 1 is used.
(Preparation of magnet composition)
Using the same magnetic material as in Example 1, the same bonded magnet composition as in Example 1 is produced.
(Extrusion molding)
Extrusion molding was performed in the same manner as in Example 1 except that six gates were formed at the exit of the gate part of Example 1. FIG. 9 shows a cross-sectional view of the gate of this example as viewed from the exit of the molding part. As shown in FIG. 9, the gate of this embodiment is formed as six holes at equal intervals along the circumference of the bottom surface of the cylindrical cavity.

<Comparative Example 1>
(Preparation of magnetic material)
The same magnetic material as in Example 1 is used.
(Preparation of magnet composition)
Using the same magnetic material as in Example 1, the same magnet composition as in Example 1 is produced.
(Extrusion molding)
1 to 3 are schematic views of an extrusion mold used in Comparative Example 1. FIG. The gate portion 15 of the first embodiment is changed to the inner die fixing portion 2. Extrusion is carried out in the same manner as in Example 1, but it has already been formed into a cylindrical shape after passing through the inner die fixing part, and when the bonded magnet composition enters the forming part, it is cylindrical. This is a difference from 1.
The shape of the obtained bonded magnet molded product is the same as that of Example 1, and is an anisotropic cylindrical bonded magnet having an outer diameter of 25 mm, an inner diameter of 23 mm, a wall thickness of 1 mm, and an outer periphery of 12 poles.

2. Evaluation of anisotropic bonded magnet (Measurement of surface magnetic flux density)
The bonded magnets obtained in Example 1 and Comparative Example 1 were cut to a height of 20 mm, and the surface magnetic flux density on the outer periphery of the cylindrical bonded magnet was measured with a magnet analyzer. The measurement was performed by fixing a cylindrical bonded magnet as a molded product to a 360 ° rotating stage of a magnet analyzer, bringing the probe into contact with the center of the side surface of the cylindrical bonded magnet, and rotating the stage 360 °.

  10 shows the surface magnetic flux density of the bonded magnet of Example 1, FIG. 11 shows the surface magnetic flux density of the bonded magnet of Example 2, and FIG. 12 shows the surface magnetic flux density of the bonded magnet of Example 3. FIG. 13 shows the surface magnetic flux density of the bonded magnet of Comparative Example 1. Furthermore, the average value of the surface magnetic flux density of each Example and Comparative Example is shown in Table 1 below.

  According to these measurement results, it can be seen that the surface magnetic flux is improved as the number of gates is smaller. Further, it can be seen that the surface magnetic flux density is higher than that of the comparative example in any of the examples regardless of the number of gates.

(Measurement of orientation rate)
In order to measure the orientation ratio of each example and comparative example, the pole portion of the bonded magnet is cut into 1 mm square. This is magnetized with an air-core coil. At this time, the orientation direction is aligned with the direction of the magnetic field generated by the magnetizing coil. The magnetization magnetic field was about 30 kOe. The residual magnetization σr of the magnetized bonded magnet was measured with a VSM (vibrating sample magnetometer).

  The remanent magnetization of Example 1 was σr1 = 100 emu / g. When this raw material magnetic material is 100% oriented, the residual magnetization is σr0 = 128 emu / g, so the orientation rate was σr1 / σr0 = 78%. The residual magnetizations of Example 2, Example 3, and Comparative Example 1 were σr2 = 95 emu / g, σr3 = 90 emu / g, and σr3 = 80 emu / g, respectively. Therefore, the orientation rates of Example 2, Example 3, and Comparative Example 1 were 74%, 70%, and 63%, respectively. These results are summarized in Table 1.

  From the measurement results of the surface magnetic flux density and the orientation ratio, it can be seen that by using the extrusion method of the present invention, the orientation ratio of the magnetic material in the magnet composition can be increased, and as a result, the surface magnetic flux density of the bonded magnet can be increased. .

  The present invention can provide an anisotropic bonded magnet having a long length and a high surface magnetic flux density continuously with high productivity. In the case of a cylindrical magnet, a motor part such as a brushless motor, particularly a long bond magnet, can be used as a magnet roll for a laser printer, and can contribute to reduction in size, weight, and energy saving.

  DESCRIPTION OF SYMBOLS 1 ... Molding part, 2 ... Inner die fixing part, 3 ... Plasticization part, 4 ... Outer die, 5 ... Inner die, 6 ... Magnet for orientation, 7, 11, 14, 16, 18, 20 ... flow path of bonded magnet composition, 8 ... inner die fixing guide, 9 ... mandrel, 10, 13, 17 ... barrel, 12 ... screw, 15 ... Gate part, 19 ... Cavity, 21 ... Gate.

Claims (10)

In the method of manufacturing a bonded magnet, after melting a bonded magnet composition composed of an anisotropic magnetic material and a resin, solidifying the magnetic material under a magnetic field that orients the magnetic material and performing extrusion molding.
A method for producing a bonded magnet, comprising: filling a molten mold magnet flow into a cavity of a mold in a state where the flow of the bonded magnet composition is divided into a plurality, and applying the magnetic field.   The method for manufacturing a bonded magnet according to claim 1, wherein the magnetic material is an Sm—Fe—N based magnetic material.   The method for producing a bonded magnet according to claim 1 or 2, wherein the resin constituting the bonded magnet composition is a thermoplastic resin.   The manufacturing method of the bonded magnet as described in any one of Claim 1 to 3 with which the said bonded magnet is shape | molded by cylindrical shape.   The bonded magnet manufactured by the manufacturing method as described in any one of Claim 1 to 4, Comprising: An orientation rate is 70% or more, The bonded magnet characterized by the above-mentioned.   The bonded magnet according to claim 5, wherein the average value of the surface magnetic flux density is 1100 G or more. After a bonded magnet composition composed of an anisotropic magnetic material and a resin is melted, a plasticized part that is extruded forward, and a flow of the bond resin composition melted at the plasticized part is controlled. A bonded magnet for performing extrusion molding, comprising: a gate portion; and a molding portion in which an orientation magnet for applying a magnetic field for orienting the magnetic material is disposed, and a molding portion having a cavity for solidifying the molten bond resin composition. In the manufacturing equipment of
The gate portion includes a plurality of flow passages in which a flow passage connected to the plasticizing portion is branched toward the molding portion, and a plurality of gates connecting the flow passages and the cavity. Have
The bond resin composition melted in the plasticizing part is filled into a cavity of the molding part from the plurality of gates in a state of being divided into a plurality of flows by the plurality of flow paths. Bond magnet manufacturing equipment.   The bonded magnet manufacturing apparatus according to claim 7, wherein the cavity has a cylindrical shape having a substantially concentric cross section, and the gates are two holes arranged side by side in a radial direction of the concentric circle.   The gate and the orientation magnet are arranged so that a magnetic field for orienting the magnetic material is applied immediately after the melted bond resin composition passes through the gate. Bond magnet manufacturing equipment.   10. A bonded magnet manufactured by the bonded magnet manufacturing apparatus according to claim 7, wherein the magnetic material is an Sm—Fe—N-based magnetic material, and the orientation ratio is 70% or more. Bond magnet characterized by being.

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