JP2010245416A - Dc reactor bond magnet, method of manufacturing the same, and bond magnet source material powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC reactor bond magnet which can stabilize DC bias characteristics and reduce nose over a relatively long period of time. <P>SOLUTION: A bond magnet 20 has magnetic power 20a made by rapid quenching, first binders 20b for coupling of pieces of the magnetic power 20a therebetween, and second binders 20c filling air voids 22 generated upon compression molding. Preferably the first binders 20b are made of a thermosetting resin, and the second binders 20c are made of a thermoplastic resin having a melting temperature higher than the curing temperature of the thermosetting resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a bond magnet for a direct current reactor, a method for producing the same, and a raw material powder for a bond magnet.

  Conventionally, for example, in a voltage conversion circuit in a DC-DC converter or the like, a DC reactor is used as an inductance component. The DC reactor has various shapes of magnetic cores (cores) made of a soft magnetic material and the like, and a winding part (coil part) wound around the magnetic cores. The DC reactor is usually applied with a periodically changing current in a state where the DC is biased.

  This type of DC reactor is required to have a constant inductance over a relatively wide operating current range. This is because when the inductance varies, for example, a problem such as variation in the output DC voltage occurs.

  Therefore, conventionally, a gap has been formed in the magnetic core of the DC reactor for the purpose of satisfying the above requirements. This is because forming a gap in the magnetic core increases the magnetic resistance of the magnetic core and makes it difficult for magnetic saturation to occur, thereby improving the DC superposition characteristics of the DC reactor. Until now, an insulating material such as glass epoxy has been arranged in the gap as a gap material, but recently, a proposal has been made to arrange a bonded magnet in which magnetic powder is bonded with a binder.

  As a method for manufacturing the bonded magnet, for example, a compression molding method is widely known. The compression molding method is, for example, mixing magnetic powder made of sintered powder of rare earth magnet alloy and a binder such as epoxy resin or phenol resin, filling the raw material powder in a mold, compression molding, and binding the binder. Is used for the production of isotropic bonded magnets.

  In Patent Document 1, a ferrite-based magnetic material is added to a mixed resin of a thermosetting resin and a thermoplastic resin, preformed by a press or the like, and then heated while applying a magnetic field in a state where the thermoplastic resin is melted. A method for producing a magnetic anisotropic bonded magnet for curing a curable resin is disclosed.

JP 50-5899 A

  However, the prior art has room for improvement in the following points. That is, when sintered powder is used as the magnetic powder constituting the bonded magnet, if a relatively large coercive force is to be obtained, it is possible to secure a residual magnetic flux density necessary to generate a sufficient bias magnetic field. It becomes difficult and the direct current superimposition characteristics deteriorate.

  Therefore, it is conceivable to use a sintered powder having a coercive force necessary for practical use. However, in this case, a sufficient bias magnetic field cannot be generated, and noise increases when a DC reactor is used.

  According to the previous researches by the present inventor, when a super-quenched powder is applied instead of the sintered powder as the magnetic powder constituting the bonded magnet, it can contribute to the improvement of the DC superposition characteristics of the DC reactor and has a noise reduction effect. I know that there is.

  However, it has been newly found that, when exposed to a thermal environment exceeding 120 ° C. for a long time, the magnetic force of the bonded magnet decreases and the DC superposition characteristics of the DC reactor over a long period of time are likely to decrease. Furthermore, it was newly found that if the bonded magnet significantly expands due to significant thermal expansion, a gap is formed between the bonded magnet and the magnetic core, making it difficult to maintain the noise reduction effect over a long period of time. .

  The present invention has been made in view of the above circumstances, and the problem to be solved by the present invention is a bond for a DC reactor capable of stabilizing DC superposition characteristics and reducing noise over a relatively long period of time. It is to provide a magnet. Moreover, it is providing the manufacturing method which can obtain the said bonded magnet for DC reactors.

  In order to solve the above-described problems, a bonded magnet for a DC reactor according to the present invention is formed through compression molding, and binds between magnetic powder that has been milled using a super-quenching method and the magnetic powder. The gist is to have a first binder and a second binder that fills pores generated during the compression molding.

  Here, it is preferable that the first binder is a thermosetting resin, and the second binder is a thermoplastic resin having a melting temperature higher than a curing temperature of the thermosetting resin.

  Further, the bonded magnet for a DC reactor includes the magnetic powder: 80 to 96% by mass, the first binder: 2 to 15% by mass, and the second binder: 5% by mass or less (excluding 0). It is preferable to contain.

  A method for manufacturing a bonded magnet for a direct current reactor according to the present invention includes a raw material preparation step of preparing a raw material powder containing magnetic powder milled using a super rapid cooling method, a first binder, and a second binder, After forming the basic shape by compression molding the raw material powder to obtain a compression molded body, and connecting the magnetic powder in the compression molded body with a first binder, the pores generated during the compression molding are The gist of the present invention is to have a pore closing step of filling with a second binder.

  Here, the first binder is preferably a thermosetting resin, and the second binder is preferably a thermoplastic resin having a melting temperature higher than the curing temperature of the thermosetting resin.

  In the raw material powder, the first binder is preferably coated around the magnetic powder, and the second binder is preferably powdery.

  The raw material powder for bonded magnets according to the present invention is milled using a super-quenching method, and the melting temperature is higher than the curing temperature of the magnetic powder coated with a thermosetting resin and the thermosetting resin. It contains a thermoplastic resin powder having a gist.

  The bonded magnet for a direct current reactor according to the present invention includes a magnetic powder milled using a super-quenching method, a first binder that bonds magnetic powder, and a second binder that fills pores generated during compression molding. Have. Therefore, even when exposed to a thermal environment exceeding 120 ° C. for a relatively long time, it is possible to stabilize the DC superposition characteristics of the DC reactor and reduce the noise. This is presumably due to the following reasons.

  That is, generally, since the compression-molded body is powder-molded, the molded body necessarily includes several percent of pores. The air present in the pores advances the oxidation of the magnetic powder from the inside of the magnet. Therefore, the magnetic force is reduced, and as a result, the direct current superimposition characteristic is reduced. Furthermore, the air in the pores thermally expands at a high temperature and generates an expansion stress, causing a magnet shape change. Further, the above-described oxidation of the magnetic powder also causes volume expansion of the magnetic powder itself, which is not preferable for suppressing the change in the magnet shape.

  In this respect, the bonded magnet for a DC reactor according to the present invention has a basic shape that is obtained by combining the magnetic powders milled using the ultra-quenching method with the first binder, and the pores generated at the time of compression molding Is filled with a second binder. For this reason, it is considered that the oxidation of the magnetic powder made of the ultra-quenched powder is suppressed by the air in the pores, so that the magnetic force is less likely to be lowered, and the DC superposition characteristics can be stabilized over a long period of time. In addition, since the expansion of air in the pores is suppressed, the change in the magnet shape is suppressed, and it becomes difficult to generate a gap between the bonded magnet and the magnetic core, and it is possible to reduce noise over a long period of time. it is conceivable that.

  Here, when the first binder is a thermosetting resin and the second binder is a thermoplastic resin having a melting temperature higher than the curing temperature of the thermosetting resin, the magnetic Since the pores can be closed with the thermoplastic resin after the basic shape is formed with the powder and the thermosetting resin, the magnet shape is excellent in stability and pore closing property.

  Moreover, when the magnetic powder, the 1st binder, and the 2nd binder contain a specific amount, it is excellent in balance of magnet performance, magnet shape, magnet strength, and magnet appearance.

  According to the method for manufacturing a bonded magnet for a direct current reactor according to the present invention, a raw material powder including magnetic powder, first binder, and second binder that has been milled using a superquenching method is prepared and prepared. A raw material powder is compression-molded to form a compression-molded body, and the magnetic powder in the molded compression-molded body is bonded by a first binder to form a basic shape. Fill with a binder. Therefore, a bonded magnet having the above-described configuration can be obtained.

  Here, when the first binder is a thermosetting resin and the second binder is a thermoplastic resin having a melting temperature higher than the curing temperature of the thermosetting resin, the thermosetting resin is used. Is hardened first to form a basic shape with magnetic powder and a thermosetting resin, then set to a temperature higher than the curing temperature of the thermosetting resin, and the pores are blocked by melting the thermoplastic resin. be able to. Therefore, it becomes easy to obtain a bonded magnet having excellent magnet shape stability and pore blockage.

  In the raw material powder, when the first binder is coated around the magnetic powder and the second binder is powdery, the magnetic powder is easily bonded by the first binder. Therefore, the basic shape can be easily maintained, and the second binder is appropriately dispersed in the raw material powder, so that the pores can be easily filled.

  The raw material powder for bonded magnets according to the present invention is milled using a super-quenching method, and the melting temperature is higher than the curing temperature of the magnetic powder coated with a thermosetting resin and the thermosetting resin. And a thermoplastic resin powder having. Therefore, it can be suitably used as a raw material powder prepared by the method for manufacturing a bonded magnet according to the present invention.

It is the figure which showed typically the cross section of the bond magnet for DC reactors which concerns on this invention. It is the figure which showed typically the cross section of the compression molding obtained by compression-molding the prepared raw material powder. It is the figure which showed typically schematic structure of the direct current reactor produced in the Example. It is a figure which shows the general | schematic measuring method of the direct current | flow superimposition characteristic of the direct current reactor produced in the Example. It is the figure which showed the relationship between the magnetic field strength AT (DC) and the AL value (μH / N ² , H: inductance, N: number of turns) indicating the inductance per turn of the winding number, (a) Is data at the beginning of use, and (b) is data after 30,000 hours of use at 130 ° C. It is the figure which showed the relationship between magnetic field intensity | strength AT (DC) and JIS-A noise (dB), (a) is the data of the use initial stage, (b) is after 30,000 hours use at 130 degreeC. It is data.

  Hereinafter, a bonded magnet for a DC reactor according to an embodiment of the present invention (hereinafter sometimes referred to as “the present bonded magnet”) and a manufacturing method for a bonded magnet for a DC reactor (hereinafter referred to as “the present manufacturing method”). ), And the raw material powder for bonded magnet (hereinafter sometimes referred to as “the present raw material powder”) will be described in detail.

1. This bond magnet This bond magnet is applied to a direct current reactor and is magnetically isotropic. Usually, the DC reactor has a magnetic core (core) and a winding portion (coil portion) in which a winding is wound around the magnetic core for at least one turn.

  Specific examples of the magnetic core material include an Fe electromagnetic steel sheet, an amorphous electromagnetic steel sheet, and a dust core containing Si of several percent (for example, 1% by mass or more). Moreover, as a shape of a magnetic core, a substantially cyclic | annular form, a substantially E shape, a substantially U shape etc. can be illustrated, for example.

  The magnetic core has a gap in the magnetic path. This bonded magnet is disposed as a gap material in the gap of the magnetic core. At this time, the present bonded magnet is disposed in the gap so as to generate a magnetic flux in the opposite direction to the magnetic flux generated by the winding portion.

  In the DC reactor, the gap length is not particularly limited. However, if the gap length is too small, the desired DC superposition characteristics tend to be difficult to obtain. On the other hand, if the gap length is too large, the total magnetic permeability in the magnetic path is lowered, and it is difficult to obtain a desired inductance value. The gap length is appropriately set in consideration of these.

  Therefore, the magnet shape of the present bonded magnet is determined according to the shape of the gap of the DC reactor and is not particularly limited. Examples of the magnet shape of the present bond magnet include a rectangular parallelepiped shape, a cubic shape, a columnar shape, a cylindrical shape, a rectangular tube shape, and a spherical shape.

  FIG. 1 schematically shows a cross section of the bonded magnet. As illustrated in FIG. 1, the bonded magnet 20 includes at least a magnetic powder 20a, a first binder 20b, and a second binder 20c.

  In the present bonded magnet, the magnetic powder is milled using a super rapid cooling method. The ultra-quick cooling method is generally a super-quenched powder by bringing a melted magnet component into contact with a cooled rotating roll (single roll, etc.), rapidly solidifying it, and performing pulverization, classification, etc. as necessary. Is the way to get.

  When the sintered powder that undergoes a high-temperature sintering process during milling is compared with the above ultra-cooled powder, the sintered powder has coarse crystal grains due to sintering, whereas the ultra-quenched powder is crystallized by ultra-quenching. There are differences in microstructure such as fine grains. In addition, the ultra-quenched powder tends to be in the form of flakes, ribbons, etc. due to its production method.

  The ultra-quenched powder has less decrease in coercive force in a relatively high temperature environment as compared with the sintered powder. This is because, since the crystal grains are fine, even if one crystal grain is reversed in magnetization, the crystal grain boundary located outside the crystal grains prevents the magnetization reversal from propagating, and all the crystal grains are completely reversed in magnetization. It is presumed that this is because it is difficult to get up.

  Thus, since the ultra-quenched powder has a small decrease in coercive force at high temperature, it can maintain a high residual magnetic flux density in a relatively low temperature environment such as room temperature, as compared with sintered powder. Therefore, by adopting the ultra-quenched powder as the magnetic powder, the magnet is difficult to be thermally demagnetized, and the bias effect of the winding magnetic flux by the magnet magnetic flux is increased, which is advantageous for noise reduction.

  Various rare earth alloys can be suitably used as the magnetic material constituting the magnetic powder. Specific examples of the rare earth alloy include, for example, R-X1-X2 alloys (provided that R: one or more rare earth elements selected from Nd, Pr, Dy, Tb and Ho, X1: 1 type or 2 types selected from Fe and Co, 1 type or 2 types selected from X2: B and C), Sm—Fe—N alloys, Sm—Co alloys, etc. are used as suitable ones. Can do.

  Preferably, an Nd—Fe—B alloy, an Sm—Fe—N alloy, an Sm—Co alloy, or the like is preferably used from the viewpoint of having a relatively high saturation magnetization and a strong magnetic force. it can. In particular, Sm—Fe—N alloys and Sm—Co alloys are useful because they are excellent in corrosion resistance and heat resistance. In addition, the said magnetic powder may consist of 1 type of powders, and may consist of the combination of 2 or more types of different powders.

  The average particle size of the magnetic powder is preferably 10 to 500 μm, more preferably 100 to 300 μm, from the viewpoint of improving the packing density. In addition, the said average particle diameter can be measured by observation with a scanning electron microscope (SEM).

  In the present bonded magnet, the first binder bonds the magnetic powder. Therefore, a magnet-shaped basic shape is held by the magnetic powder and the first binder.

  As a material for the first binder, for example, various thermosetting resins can be applied. Examples of the thermosetting resin include various imide resins such as polyamideimide, bismaleimide triazine, and maleimide, epoxy resins, and phenol resins. These may be contained alone or in combination of two or more. Of these, an imide resin is preferable.

  Here, this bonded magnet is formed through compression molding. In general, since compression molding is powder molding, the compression molded body necessarily includes several percent of pores. As shown in FIG. 1, in the present bonded magnet 20, the pores 22 generated during compression molding are filled with the second binder 20c.

  However, the present bonded magnet may have a small number of pores that are not filled with the second binder within the range not impairing the gist of the present invention. This is because it is difficult in manufacturing to completely block all pores.

  As a material for the second binder, for example, various thermoplastic resins can be applied. As the thermoplastic resin, a thermoplastic resin having a melting temperature higher than the curing temperature of the thermosetting resin can be suitably used. At the time of magnet production, the pores can be closed by melting the thermoplastic resin after forming the basic shape with magnetic powder and thermosetting resin, so there are advantages such as excellent magnet shape stability and pore closing properties Because.

  However, the melting temperature is selected to be lower than the deterioration temperature of the thermosetting resin. More preferably, the difference between the curing temperature of the thermosetting resin and the melting temperature of the thermoplastic resin is 10 ° C. or more from the viewpoint of heat resistance and the like. From the viewpoint of preventing oxidative degradation of the magnetic powder, the curing temperature of the thermosetting resin and the melting temperature of the thermoplastic resin are preferably 300 ° C. or lower.

  The curing temperature of the thermosetting resin and the melting temperature of the thermoplastic resin can be measured with a thermal analyzer (DSC).

  Examples of the thermoplastic resin include polyamide imide, polyether sulfone, polybenzimidazole, polyvinylidene fluoride, aromatic polyamide, polyether imide, and the like. These may be contained alone or in combination of two or more.

  Of these, polyamide imide and polyether sulfone are preferable.

  The present bonded magnet preferably contains magnetic powder: 80 to 96% by mass, first binder: 2 to 15% by mass, and second binder: 5% by mass or less (excluding 0). This is because if the ratio of each component is within the above range, the balance of magnet performance, magnet shape, magnet strength, magnet appearance, etc. is excellent.

  More specifically, it is easy to improve the magnet performance by setting the lower limit of the magnetic powder to 80% by mass or more. On the other hand, when the upper limit of the magnetic powder is 96% by mass or less, it becomes easy to ensure moldability at the time of production. More preferably, magnetic powder is good in the range of 90-96 mass%.

  Moreover, it becomes easy to improve magnet strength by making the minimum of a 1st binder into 2 mass% or more. On the other hand, by setting the upper limit of the first binder to 15% by mass or less, it becomes easy to secure the magnetic powder ratio, and it is easy to improve the magnetic characteristics. More preferably, a 1st binder is good in the range of 2-4 mass%.

  In addition, by setting the upper limit of the second binder to 5% by mass or less, the second binder is difficult to be exposed on the magnet surface more than necessary, and the appearance of the magnet is easily maintained. More preferably, the second binder is 2% by mass or less.

  In addition, the content rate of the magnetic powder and binder contained in this bond magnet can be investigated by burning out a binder in an inert gas. In addition, the content and type of the binder component is such that each binder component is extracted from the present bond magnet using an appropriate solvent, FT-IR (infrared absorption spectrum), NMR (nuclear magnetic resonance), etc. It is possible to investigate by conducting the analysis.

2. This manufacturing method This manufacturing method has at least a raw material preparation process, a shaping | molding process, and a pore obstruction | occlusion process. Hereinafter, each process is demonstrated in order.

(Raw material preparation process)
The raw material preparation step is a step of preparing a raw material powder containing magnetic powder milled using a rapid quenching method, a first binder, and a second binder.

  The raw material powder may be prepared by itself or supplied from another source. In addition, since the kind of each component, content, etc. in the said raw material powder are based on the description mentioned above in "1. this bond magnet", detailed description here is abbreviate | omitted.

  Here, in this raw material preparation step, it is preferable to prepare a mixed powder containing magnetic powder having a first binder coated around it and a powdery second binder as the raw material powder. In the pore closing step, the magnetic powder is easily bonded by the first binder, so that the basic shape is easily maintained, and the second binder is appropriately dispersed in the raw material powder, so that the pores are easily filled. Because it becomes.

  More preferably, in the raw material preparation step, as the raw material powder, a magnetic powder that has been milled using a super-quenching method and is coated with a thermosetting resin (uncured) around it, and the thermosetting resin It is preferable to prepare a mixed powder (this raw material powder) containing a thermoplastic resin powder having a melting temperature higher than the curing temperature. This is because there are advantages such as easy formation of the structure of the present bonded magnet.

  In the raw material powder, the magnetic powder may be subjected to a surface treatment such as a coupling treatment with a silane coupling agent or the like. In addition, the raw material powder may contain one or more kinds of various additives such as a solid lubricant (stearic acid compound).

(Molding process)
The main forming step is a step of compression-molding the raw material powder to obtain a compression-molded body. FIG. 2 schematically shows a cross-section of a compression molded body obtained by compression molding the prepared raw material powder. When the prepared raw material powder is compacted by a press molding method or the like, pores 22 of about several percent are generated in the compact as shown in FIG. Since air is present in the pores 22, this causes oxidation of the magnetic powder 20 a and thermal expansion. In this manufacturing method, the pores 22 are closed in the next step.

(Porosity block process)
In the pore closing step, the magnetic powder in the compression molded body obtained in the molding step is joined with a first binder to form a basic shape, and then the pores generated during the compression molding are formed with the second binder. It is a process of filling.

  Specifically, first, the first binder is hardened first, and a magnet shape is formed by the magnetic powder and the first binder. At this stage, there are relatively many pores generated during compression molding.

  The method of solidifying the first binder varies depending on the binder material. For example, when the first binder is a thermosetting resin, the compression molded body may be heated in the vicinity of the curing temperature of the thermosetting resin. . Examples of the heating means include a far-red furnace. Heating by a far-red furnace is preferable because it has advantages such as rapidness and radiation heating.

  Next, while maintaining the basic shape, the pores are closed with the second binder to relatively reduce the pores in which air exists. Although the pores are preferably completely closed, it is difficult to manufacture the pores completely. Therefore, pores that are not blocked by the second binder may exist within a range that does not impair the spirit of the present invention, and the purpose of the pore closing step can be achieved.

  The method for closing the pores varies depending on the material of the second binder. For example, when the second binder is a thermoplastic resin, the compression-molded body having a basic shape is close to the melting temperature of the thermoplastic resin. Just heat it.

  Examples of the heating means include a far-red furnace. A far-infrared furnace is preferable from the viewpoint of being quick and capable of radiant heating.

  In this pore closing step, for example, the first binder may be cured by changing the set temperature in the far-red furnace and providing a temperature distribution in the furnace, and then the second binder may be melted. Alternatively, the first binder may be cured and once cooled, and then heated again to melt the second binder.

  According to the present pore closing step, after the magnet shape is determined by the magnetic powder and the first binder, the second binder is filled into the pores generated at the time of compression molding, and the air present in the pores is pushed out, The pores are blocked.

  Then, if the obtained molded body is magnetized, the present bonded magnet can be obtained.

  Although the present manufacturing method has been described above, the present manufacturing method may have other processes such as a deburring process, a cleaning process, and a painting process as necessary.

Hereinafter, the present invention will be described more specifically with reference to examples.
1. Bond magnet for DC reactor (gap material)
Example 1
<Preparation of raw material powder>
Nd: 30.4 mass%, Fe: 62.0 mass%, Co: 6.00 mass%, B: 0.91 mass%, Ga: 0.56 mass%, unavoidable impurities 0.13 mass% Each raw material was weighed so as to have an alloy composition, and each weighed raw material was heated and melted to obtain a molten alloy. The obtained alloy melt was rapidly cooled and solidified using a single roll ultra-rapid cooling method, and magnetic powder (average particle size 200 μm) composed of the above magnet alloy composition was milled. The roll peripheral speed was 25 m / s.

  Next, after the obtained magnetic powder was subjected to silane coupling treatment, uncured polyamideimide (PAI, curing temperature: about 230 ° C.) was coated around the magnetic powder as a first binder.

  Next, magnetic powder coated with polyamideimide as the first binder and polyethersulfone (PES, melting temperature: about 260 ° C.) powder as the second binder were mixed to obtain a raw material powder. The proportion of each component in the raw material powder is 95% by mass of magnetic powder, 3.3% by mass of polyamideimide as the first binder, and 0.7% by mass of polyethersulfone as the second binder. . The remaining 1% by mass is lithium stearate, a coupling agent and the like.

<Molding of compression molding>
The prepared raw material powder was compression-molded into a rectangular parallelepiped shape having a width W of 16 mm, a height H of 25 mm, and a thickness t of 1 mm using a press molding method at room temperature.

<Curing and pore blocking>
The obtained compression-molded body was heated at 240 ° C. for 10 minutes in the atmosphere using a far-red furnace to bond the magnetic powder in the compression-molded body with polyamideimide, thereby forming the basic shape of the magnet. .

  Next, the heating temperature was set to 270 ° C., and heating was performed in the same atmosphere for 10 minutes to melt the polyether sulfone, and the pores generated during compression molding were filled with the polyether sulfone.

  Next, the obtained unmagnetized molded body was magnetized in a pulse magnetic field.

  As described above, a DC reactor bond magnet (width W: 16 mm) having magnetic powder milled using the ultra-quenching method, polyamideimide that bonds the magnetic powder, and polyether sulfone that fills pores generated during compression molding. A rectangular parallelepiped shape having a height H of 25 mm and a thickness t of 1 mm.

(Comparative Example 1)
In Example 1, a magnetic powder coated with an epoxy resin as a first binder without using a second binder is a raw material powder (magnetic powder: 97% by mass, epoxy resin as a first binder: 3% by mass) For the direct current reactor according to Comparative Example 1, except that the first binder was heated and cured to form the basic shape of the magnet, and then the magnet was magnetized without further heating. A bonded magnet was produced.

2. Insulator for DC reactor (gap material)
(Comparative Example 2)
A glass epoxy resin body formed into a rectangular parallelepiped shape having a width W: 16 mm, a height H: 25 mm, and a thickness t: 1 mm was used as a gap material according to Comparative Example 2.

(Comparative Example 3)
A glass epoxy resin body formed into a rectangular parallelepiped shape having a width W: 16 mm, a height H: 30 mm, and a thickness t: 1 mm was used as a gap material according to Comparative Example 3.

(Comparative Example 4)
A glass epoxy resin body formed into a rectangular parallelepiped shape having a width W: 16 mm, a height H: 35 mm, and a thickness t: 1 mm was used as a gap material according to Comparative Example 4.

(Comparative Example 5)
A glass epoxy resin body formed into a rectangular parallelepiped shape having a width W: 16 mm, a height H: 40 mm, and a thickness t: 1 mm was used as a gap material according to Comparative Example 5.

3. Production of DC Reactor A pair of cut cores (magnetic path cross section: 25 mm × 16 mm, average magnetic path length: 227 mm, semi-annular shape) laminated with Fe plates (thickness 0.1 mm) containing 6.5 mass% Si. The gap material according to Example 1 and Comparative Examples 1 to 5 was bonded to the gap so as to form a 1 mm wide gap (Example 1 and Comparative Example 1 were bonded magnets, and Comparative Examples 2 to 5 were insulators) ) Were inserted and joined to produce a substantially annular magnetic core.

  Next, a winding was wound around the gap of the magnetic core (50 turns) to form a winding part.

  Thereby, the direct current reactor which concerns on Example 1 and Comparative Examples 1-5 was produced. FIG. 3 shows a schematic configuration of the DC reactor manufactured as described above.

  The DC reactor 10 is formed in a gap 12 formed between two substantially U-shaped cut cores (magnetic cores) 11a and 11b facing each other in the vertical direction as viewed in FIG. 3 and the two facing cut cores 11a and 11b. The bonded magnet 20 is inserted and bonded to the outer periphery of the bonded magnet 20, and winding portions 31a and 31b are wound around the outer periphery of the bonded magnet 20.

  The bond magnet 20 is a rectangular parallelepiped having a predetermined width W, height H (not shown in a direction perpendicular to the paper surface), and thickness t. Moreover, the magnetic flux (broken line arrow in FIG. 3) which arises by each winding part 31a, 31b is a direction opposite to the magnetic flux (solid line arrow in FIG. 3) by the bond magnet 20. FIG.

4). Evaluation and Consideration Using each DC reactor produced, AL value indicating the inductance per turn of the initial winding and AL value indicating the inductance per turn of the winding after 30,000 hours of use at 130 ° C. Was measured.

  FIG. 4 shows an outline of a method for measuring the DC superposition characteristics. That is, as shown in FIG. 4, a DC power source 100 (manufactured by Kikusui Electronics Co., Ltd., PAS series), a DC ammeter 102, an AC cut reactor 104 (manufactured by IPEC Co., Ltd.), an LCR meter 106 (HIROKI Corporation) 3522), DC cut film capacitor 108 (Fuji Electric Manufacturing Co., Ltd., “UD630106”, TYPE TME). Next, the LCR meter 106 was set to the constant current mode and the frequency was set to 10 kHz. Next, the measurement sample S (each DC reactor produced, winding: 50 turns <winding cross-sectional shape 2 mm × 4 mm>) was connected, and the DC power supply 100 was adjusted so that the DC ammeter 102 had each set current (AT = Set current x number of turns). Next, the L value of the LCR meter 106 was read. This L value is a value synthesized with the AC cut reactor 104. Subsequently, the L value of the measurement sample S was calculated by (L value of AC cut reactor 104 × L value of LCR meter 106) / (L value of AC cut reactor 104−L value of LCR meter 106).

FIG. 5 shows the relationship between the magnetic field strength AT (DC) and the AL value (μH / N ² , H: inductance, N: number of turns) indicating the inductance per turn of the winding.

  Moreover, using each produced DC reactor, the JIS-A noise in the initial stage and the JIS-A noise after being used at 130 ° C. for 30,000 hours were measured. The measurement method and measurement conditions are as follows.

  Various DC reactors are hung from above in a soundproof box that is blocked from external vibrations, and current is applied by winding the winding around the cut core so that the vibration of the soundproof box does not interfere. (Input: DC variable + ripple [triangular wave 6.0 App (ampere peak to peak)]). And the noise meter was arrange | positioned in the position 100 mm away from the cut core surface, and the noise which generate | occur | produces from various DC reactors with the noise meter was measured. The dimensions inside the soundproof box were 500 mm × 500 mm × 500 mm. The temperature in the soundproof box was 130 ° C.

More specifically, a noise measuring device composed of the following devices was connected to a data recorder (external device), and the noise value and current value were measured.
[Components of noise measurement equipment]
Function generator: manufactured by HIOKI (model 7070)
AC power amplifier: manufactured by NF (model 4520)
Step-up transformer: manufactured by NF High frequency CT: manufactured by HIOKI (model 9275)
Sound level meter: RION (model NL-20)
[Dimensions: 500mm x 500mm x 500mm]
Noise / vibration measurement unit: BK, PULSE acoustic vibration analysis device Ripple frequency during measurement: 10 kHz

  FIG. 6 shows the relationship between the magnetic field strength AT (DC) and JIS-A noise (dB).

  5 and 6, the following can be understood. That is, as shown in FIG. 5, the direct current reactors according to Comparative Examples 2 to 5 using the gap material (insulator) according to Comparative Examples 2 to 5 are both changed in inductance after the initial use and after long-term use. I can't see it. This is because there is no change in the characteristics and shape of the magnet after long-term use.

  Next, when the DC reactor according to Comparative Example 1 using the gap material (bonded magnet) according to Comparative Example 1 is exposed to a thermal environment of 130 ° C. for a long time, the inductance is reduced and the DC superimposition characteristics are not good. You can see that it is stable. This is because in the gap material according to Comparative Example 1, the pores generated at the time of compression molding are not filled with the thermoplastic resin at all, so that the magnetic powder is oxidized from the inside of the magnet and the magnetic force is reduced.

  Moreover, when the direct-current reactor which concerns on the comparative example 1 is exposed to a 130 degreeC thermal environment for a long period of time, it turns out that a noise becomes large. This is because the shape of the gap material changed due to the thermal expansion of the air in the pores (specifically, the magnet swelled in the direction perpendicular to the magnetic path), and a gap was created between the gap material and the magnetic core. It is.

  On the other hand, in the DC reactor according to Example 1, the basic shape is maintained by bonding between the magnetic powders with the thermosetting resin as the first binder, and the pores generated during the compression molding are the second binder. The gap material (bonded magnet) according to Example 1 filled with the thermoplastic resin is used. Therefore, it can be seen that even when exposed to a thermal environment of 130 ° C. for a long period of time, the stability of the DC superimposition characteristic and the low noise characteristic are excellent.

  As described above, the DC reactor bonded magnet, the manufacturing method thereof, and the raw material powder for bonded magnet according to the present invention have been described. However, the present invention is not limited to the above embodiment and examples, and the gist of the present invention is described. Various modifications are possible without departing from the scope.

10 DC reactors 11a, 11b Cut core (magnetic core)
12 Gap 20 Bonded magnet 20a Magnetic powder 20b First binder 20c Second binder 22 Pore 30 Winding 31a, 31b Winding part

Claims (7)

A direct-current reactor bonded magnet formed through compression molding,
Magnetic powder milled using a rapid quenching method;
A first binder that bonds between the magnetic powders;
A second binder that fills pores generated during the compression molding;
A bonded magnet for a direct current reactor, comprising: The first binder is a thermosetting resin,
2. The direct current reactor bond magnet according to claim 1, wherein the second binder is a thermoplastic resin having a melting temperature higher than a curing temperature of the thermosetting resin. The magnetic powder: 80 to 96% by mass,
The first binder: 2 to 15% by mass,
3. The bonded magnet for a direct current reactor according to claim 1, wherein the second binder contains 5% by mass or less (excluding 0). A raw material preparation step of preparing a raw material powder containing magnetic powder milled using a super rapid cooling method, a first binder, and a second binder;
A molding step of compressing the raw material powder to obtain a compression molded body,
A pore closing step of filling the pores generated during the compression molding with a second binder after forming a basic shape by joining the magnetic powder in the compression molded body with a first binder,
A method for producing a bonded magnet for a direct current reactor, comprising: The first binder is a thermosetting resin,
The method for producing a bond magnet for a DC reactor according to claim 4, wherein the second binder is a thermoplastic resin having a melting temperature higher than a curing temperature of the thermosetting resin. In the raw material powder,
The first binder is coated around the magnetic powder,
The method for producing a bonded magnet for a direct current reactor according to claim 4 or 5, wherein the second binder is powdery. Magnetic powder that has been milled using a super-quenching method and is coated with a thermosetting resin,
A raw material powder for a bond magnet, comprising: a thermoplastic resin powder having a melting temperature higher than a curing temperature of the thermosetting resin.

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