JP2021182591A - Powder magnetic core and its manufacturing method - Google Patents

Abstract

To provide a powder magnetic core that has both excellent corrosion resistance and excellent magnetic properties, and to provide a manufacturing method thereof.SOLUTION: A powder magnetic core includes a plurality of soft magnetic particles, a resin that has insulating properties and heat resistance and covers the surface of each soft magnetic particle, and a plurality of metal particles dispersed in the resin. The metal particles have a higher ionization tendency than the main components of soft magnetic particle. The metal particles are included in a lubricant mixed with the soft magnetic particles and the resin. The proportion of the metal stearate in the lubricant is 50% or more and less than 90%, and the content of the metal particles contained in the metal stearate is 1.3 wt.% or more and less than 2.3 wt.%.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a dust core and a method for producing the same.

In recent years, the spread of electrified vehicles has been rapidly increasing. Examples of the electrified vehicle include a hybrid vehicle (HEV: Hybrid Electric Vehicle), a plug-in hybrid electric vehicle (PHEV: Plug-in Hybrid Electric Vehicle), an electric vehicle (EV: Electric Vehicle), and the like. In such an electrified vehicle, in order to further improve fuel efficiency (electricity cost), it is required to reduce the size and weight of various electronic components and systems.

Further, driven by the expansion of the market for electrified vehicles, higher performance is required for soft magnetic particles used in choke coils, reactors, transformers, etc. and powder magnetic cores using them.

Further corrosion resistance is required for the dust core using soft magnetic particles in order to maintain high performance even when exposed to rain and wind for a long time.

For example, Patent Document 1 discloses a dust core using Fe (iron) -based soft magnetic particles. The configuration of the dust core will be described with reference to FIG. FIG. 2 is a diagram schematically showing a cross section of the dust core of Patent Document 1.

As shown in FIG. 2, the dust core of Patent Document 1 includes a plurality of Fe-based soft magnetic particles 1, a resin insulating layer 2 that covers the surfaces of each of the Fe-based soft magnetic particles 1, and an insulating layer. In addition to covering the surface of 2, it is provided with a resin rust preventive layer 4 containing a plurality of metal pieces 3. A combination of a plurality of Fe-based soft magnetic particles 1 and an insulating layer 2 is hereinafter referred to as a "molded body".

The dust core of Patent Document 1 described above is provided with a rust preventive layer 4 containing a plurality of metal pieces 3 to realize excellent corrosion resistance.

Further, since the metal piece 3 divides the pinhole extending in the thickness direction of the rust preventive layer 4, the rust preventive layer 4 having very few or no pinholes can be realized.

Further, since the metal piece 3 itself does not allow the rust-causing substance to permeate, it is possible to make the invasion path of the rust-causing substance in the rust-preventing layer 4 non-linear by dispersing the plurality of metal pieces 3 in the rust-preventing layer 4. can. Therefore, the intrusion route of the rust-causing substance becomes longer than the thickness of the rust-preventing layer 4, and it becomes difficult for the rust-causing substance to reach the molded body. As a result, the rust-causing substance adheres to the metal piece 3 before reaching the molded body and corrodes the metal piece 3, so that the generation of rust in the molded body can be suppressed.

Further, as shown in FIG. 2, the rust preventive layer 4 has a corner portion 4a and a flat portion 4b. The thickness of the corner portion 4a is 5 μm or more. The thickness of the flat portion 4b is about 1 to 100 times the thickness of the corner portion 4a.

Further, the shape of the metal piece 3 is a flaky shape or a particle shape. When the metal piece 3 is flaky, its thickness is 1 μm to 5 μm, its width is 5 μm to 20 μm, and its length is 5 μm to 20 μm. When the metal piece 3 is in the form of particles, its average particle size is 0.1 μm to 10 μm.

Japanese Unexamined Patent Publication No. 2014-72245

However, in the dust core of Patent Document 1, although excellent corrosion resistance is realized by the rust preventive layer, the packing rate of the soft magnetic particles is low, so that the relative magnetic permeability is lowered.

An object of one aspect of the present disclosure is to provide a dust core having both excellent corrosion resistance and excellent magnetic properties, and a method for producing the same.

The dust core according to one aspect of the present disclosure includes a plurality of soft magnetic particles, a resin having insulating properties and heat resistance and covering the surface of each of the soft magnetic particles, and a plurality of particles dispersed in the resin. The metal particles have a greater tendency to ionize than the main component of the soft magnetic particles, and are contained in the metal particles, the soft magnetic particles, and a lubricant mixed with the resin. The proportion of the metal stearate in the lubricant is 50% or more and less than 90%, and the content of the metal particles contained in the metal stearate is 1.3 wt% or more and less than 2.3 wt%.

In the method for producing a dust core according to one aspect of the present disclosure, a step of producing soft magnetic particles, the soft magnetic particles, a resin, and a lubricant containing metal particles are mixed to produce granulated powder. A step of producing, a step of filling the granulated powder in a predetermined mold and pressure-molding to obtain a green compact, and a step of heating the green compact at a temperature at which the binder hardens. The metal particles have a greater tendency to ionize than the main component of the soft magnetic particles, and the metal particles are contained in the soft magnetic particles and the lubricant mixed with the resin, and in the lubricant. The proportion of the metal stearate is 50% or more and less than 90%, and the content of the metal particles contained in the metal stearate is 1.3 wt% or more and less than 2.3 wt%.

According to the present disclosure, both excellent corrosion resistance and excellent magnetic properties can be achieved at the same time.

The figure which shows typically the cross section of the dust core which concerns on embodiment of this disclosure. The figure which shows typically the cross section of the dust core of Patent Document 1.

Hereinafter, the dust core 100 according to the embodiment of the present disclosure will be described with reference to FIG. FIG. 1 is a diagram schematically showing a cross section of a dust core 100.

As shown in FIG. 1, the dust core 100 has soft magnetic particles 101, resin 102, and metal particles 103.

<Manufacturing method of soft magnetic particles 101>
The soft magnetic particles 101 can be produced, for example, by using an atomizing method, pulverization, a chemical reaction, or the like.

In the atomizing method, the surface irregularities of the soft magnetic particles 101 can be eliminated, and the shape of the soft magnetic particles 101 can be made substantially spherical. Therefore, it is possible to obtain a dust core 100 having a high filling rate of the soft magnetic particles 101. For this reason, it is preferable to produce the soft magnetic particles 101 by the atomizing method.

<Manufacturing method of dust core 100>
First, a plurality of soft magnetic particles 101 produced by the above-mentioned method, a resin 102 which is a binder having good insulating properties and high heat resistance, and a lubricant containing metal soap are mixed and granulated. Make powder. The metal soap contains a plurality of metal particles 103.

Next, the granulated powder is filled in a heat-resistant mold having a desired shape and pressure-molded to obtain a green compact. Then, the green compact is heated at a temperature at which the resin 102 is cured.

Through the above steps, a dust core 100 having a high relative magnetic permeability can be obtained. As shown in FIG. 1, the dust core 100 has a structure in which a plurality of soft magnetic particles 101 and a plurality of metal particles 103 are dispersed in a resin 102 that functions as an insulating layer.

<Soft magnetic particle 101>
As the soft magnetic particles 101, for example, pure iron powder, Fe-Si (silicon) alloy, sendust, permalloy, permendur and the like, as well as amorphous particles, nanocrystalline particles and the like can be used. can. Examples of the amorphous particles or nanocrystalline particles include Fe, Si, B (boron), C (carbon), P (phosphorus), Cu (copper), Co (cobalt), Ni (nickel), and Nb ( It may contain any one or more elements such as niobium), Al (aluminum), Cr (chromium), Ti (titanium), Ta (tantal), and Zr (zirconium).

The particle size of the soft magnetic particles 101 is preferably 10 μm or more and 30 μm or less. The reason is that the filling factor can be increased and excellent magnetic characteristics can be realized. When the particle size of the soft magnetic particles 101 is less than 10 μm, the soft magnetic particles 101 are aggregated, and the surface of each of the soft magnetic particles 101 cannot be covered with the resin 102, resulting in rust prevention. It will deteriorate.

<Lubricant>
Lubricants include, for example, metal soaps such as metal stearate and fatty acids such as aliphatic amides and fatty acid derivatives.

Examples of the metal stearate include lithium stearate, potassium stearate, calcium stearate, aluminum stearate, zinc stearate and the like.

When the proportion of the metal stearate in the lubricant is less than 50%, the proportion of the metal particles 103 present in the resin 102 is small, so that the rust preventive effect is low. On the other hand, when the proportion of the metal stearate in the lubricant is 90% or more, the fatty acid derivative is used in the step of curing the resin during the production of the green compact (the step of heating the green compact at the temperature at which the resin 102 is cured). The ratio of Therefore, since stearic acid containing the metal particles 103 does not seep into the soft magnetic particles 101 and the resin 102, the metal particles 103 cannot be contained in the resin 102.

When the proportion of the metal stearate in the lubricant is 50% or more and less than 90%, the fatty acid derivative is melted in the step of curing the resin at the time of producing the green compact, and the metal stearate seeps into the resin 102. As a result, the metal particles 103 enter into the resin 102, and the rust preventive effect is enhanced.

From the above, the proportion of metal stearate in the lubricant is preferably 50% or more and less than 90%.

Examples of the aliphatic amide include oleic acid amide, stearic acid amide, erucic acid amide, methylene bisstearic acid amide, ethylene bisstearic acid amide and the like.

When the proportion of the aliphatic amide in the lubricant is less than 5%, the amount of the aliphatic amide that dissolves out in the step of curing the resin at the time of producing the green compact is small. Therefore, diffusion of the metal particles 103 is unlikely to occur in the resin 102. On the other hand, when the proportion of the aliphatic amide in the lubricant is 25% or more, the metal particles 103 contained in the metal stearate are reduced, so that the rust preventive effect is reduced.

From the above, the proportion of the aliphatic amide in the lubricant is preferably 5% or more and less than 25%.

The fatty acid derivative is a long-chain fatty acid. Examples of the fatty acid derivative include fatty acid amides, fatty acid esters, fatty acid amines, and fatty acid chlorides.

When the proportion of the fatty acid derivative in the lubricant is less than 5%, the amount of the fatty acid derivative that dissolves out in the step of curing the resin at the time of producing the green compact is small. Therefore, diffusion of the metal particles 103 is unlikely to occur in the resin 102. On the other hand, when the ratio of the fatty acid derivative in the lubricant is 25% or more, the metal particles 103 contained in the metal stearate are reduced, so that the rust preventive effect is reduced.

From the above, the proportion of the fatty acid derivative in the lubricant is preferably 5% or more and less than 25%.

<Metal particles 103>
The metal particles 103 contained in the resin 102 are composed of a metal having a higher ionization tendency than iron. Therefore, the metal particles 103 are corroded before the soft magnetic particles 101. Therefore, the dust core 100 of the present embodiment can realize excellent corrosion resistance and rust prevention effect.

Examples of the metal particles 103 include particles composed of lithium, potassium, calcium, aluminum, zinc and the like.

The proportion of metal particles in the lubricant is preferably 10% or more and less than 50%.

As described above, in the manufacturing process of the dust core 100, the resin 102 and the lubricant containing the metal particles 103 are mixed to produce granulated powder. Therefore, as shown in FIG. 1, the metal particles 103 are evenly dispersed in the resin 102.

<Resin 102>
Examples of the resin 102 include an epoxy resin, a phenol resin, a silicone resin, a polyamide resin, a polyimide resin, and a polyamide-imide resin. Since these resins have good insulating properties and high heat resistance, it is possible to manufacture a dust core 100 having excellent molding strength.

The configuration and manufacturing method of the dust core 100 of the present embodiment have been described above.

Hereinafter, examples and comparative examples of the dust core 100 will be described.

First, Examples 1 and 2 and Comparative Example 1 will be described.

(Examples 1 and 2)
As the soft magnetic particles 101, water atomized powder of Fe-6.5Si manufactured by TIZ Advanced Alloy and having a particle size of 30 μm was used. As the resin 102, a silicone resin was used.

A water atomizing powder, a silicone resin, and a lubricant containing zinc soap were mixed and granulated to prepare a granulated powder. An insulating film may be formed before granulation.

As the lubricant, a lubricant containing zinc stearate was used. The content of zinc stearate was 1.5 wt% in Example 1 and 2.5 wt% in Example 2. Further, zinc soap having a ratio of zinc particles (an example of metal particles 103) of 10% was used. The content of zinc particles contained in zinc stearate was 1.3 wt% in Example 1 and 2.3 wt% in Example 2.

Next, the granulated powders of Examples 1 and 2 were put into a mold, and pressure molding was performed at a ^{pressure of 4 tons / cm 2 using a press machine.} As a result, the green compact of Example 1 and the green compact of Example 2 were produced.

Then, the relative magnetic permeability at a frequency of 100 kHz was measured for each of the green compacts of Examples 1 and 2 using an impedance analyzer.

(Comparative Example 1)
The above-mentioned water atomizing powder and a silicone resin were mixed and granulated to prepare a granulated powder. That is, the above-mentioned lubricant is not added to this granulated powder.

Next, the granulated powder was put into a mold and pressure-molded at a pressure of 4 tons / cm ² using a press machine to prepare a green compact.

The relative magnetic permeability of the green compact was measured at a frequency of 100 kHz using an impedance analyzer.

<Rust prevention evaluation test>
Environmental test (inner temperature 85 ° C., humidity 85% RH), which is a general rust prevention test, for each powder magnetic core manufactured based on the powders of Examples 1, 2 and Comparative Example 1. Was performed, and rust prevention evaluation was performed. The results are shown in Table 1.

As shown in Table 1, in Example 1 and Example 2, rust did not occur in the dust core even after 1000 hours (hours) after the start of the environmental test. On the other hand, in Comparative Example 1, rust occurred on the dust core 24 hours after the start of the environmental test.

Therefore, it was demonstrated that the dust cores of Examples 1 and 2 are superior in corrosion resistance to the powder cores of Comparative Example 1.

Further, as shown in Table 1, when the relative magnetic permeability of Comparative Example 1 was used as a reference, the relative magnetic permeability of Example 1 was + 6%, and the relative magnetic permeability of Example 2 was −17%.

Therefore, it was demonstrated that the specific magnetic permeability of the powder magnetic core of Example 1 is higher than the specific magnetic permeability of the powder magnetic core of Comparative Example 1. Further, it was demonstrated that the relative magnetic permeability of the dust core of Example 2 was lower than that of Comparative Example 1.

In Example 1, the reason why the specific magnetic permeability is improved is that the soft magnetic particles are densely filled in the dust core (molded body) by the addition of the lubricant, and the filling rate is improved.

Further, in Example 2, the reason why the relative magnetic permeability is lowered is as follows. In the step of heating the powder compact, the melted lubricant flows out from the inside of the powder magnetic core, so that a cavity from which the lubricant has escaped is generated inside the powder magnetic core.

As the amount of the lubricant added during granulation increases, the number of cavities inside the dust core increases, and the filling rate of the soft magnetic particles in the dust core decreases. In other words, when the amount of lubricant added increases above a certain level, the decrease in filling rate due to the increase in cavities described above outweighs the improvement in filling rate due to the addition of lubricant, and the relative magnetic permeability decreases. It is probable that it was done.

From the above, it can be said that the dust core of Example 1 in which the content of zinc particles contained in zinc stearate is 1.3 wt% can realize both excellent corrosion resistance and excellent magnetic properties.

The comparison results of Examples 1, 2 and Comparative Example 1 have been described above.

Next, Example 3 and Comparative Example 2 will be described.

(Example 3)
The soft magnetic particles 101 were obtained by melting an Fe-based alloy composition by high-frequency heating or the like to prepare a thin band (which may be a thin section) of an amorphous layer by a liquid quenching method, and crushing the thin band. Grinded powder was used. The particle size of this pulverized powder was 15 μm. As the resin 102, a silicone resin was used.

The pulverized powder, the silicone resin, and the lubricant containing zinc soap were mixed and granulated to prepare a granulated powder. An insulating film may be formed before granulation.

The content of zinc stearate contained in the zinc soap was 1.5 wt%. In addition, zinc soap was used in which the proportion of zinc particles contained in zinc stearate was 10%. The content of zinc particles contained in zinc stearate was 1.3 wt%.

Next, the granulated powder was put into a mold and pressure-molded at a pressure of 4 tons / cm ² using a press machine to prepare a green compact.

The relative magnetic permeability of the green compact was measured at a frequency of 100 kHz using an impedance analyzer.

(Comparative Example 2)
The above-mentioned pulverized powder and a silicone resin were mixed and granulated to prepare a granulated powder. That is, the above-mentioned lubricant is not added to this granulated powder.

Next, the granulated powder was put into a mold and pressure-molded at a pressure of 4 tons / cm ² using a press machine to prepare a green compact.

The relative magnetic permeability of the green compact was measured at a frequency of 100 kHz using an impedance analyzer.

<Rust prevention evaluation test>
An environmental test (inner temperature 85 ° C., humidity 85% RH), which is a general rust prevention test, was performed on each of the powder magnetic cores manufactured based on the powders of Example 3 and Comparative Example 2. , Rust prevention evaluation was performed. The results are shown in Table 2.

As shown in Table 2, in Example 3, rust did not occur in the dust core even after 1000 hours (hours) after the start of the environmental test. On the other hand, in Comparative Example 2, rust occurred on the dust core 24 hours after the start of the environmental test.

Therefore, it was demonstrated that the dust core of Example 3 is superior in corrosion resistance to the powder core of Comparative Example 2.

Further, as shown in Table 2, the relative magnetic permeability of Example 3 was + 8% when the relative magnetic permeability of Comparative Example 2 was used as a reference.

Therefore, it was demonstrated that the specific magnetic permeability of the powder magnetic core of Example 3 is higher than the specific magnetic permeability of the powder magnetic core of Comparative Example 2.

Therefore, even when the above-mentioned pulverized powder is used as the soft magnetic particle 101, the content of the zinc particles contained in the zinc stearate is 1. If it is 3 wt%, it can be said that a dust core having both excellent corrosion resistance and excellent magnetic characteristics can be realized.

Further, when TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) analysis was performed on the cross section of the dust core of Example 3, even if the content of zinc stearate was very small, the zinc element inside the dust core was found. Was detected.

On the other hand, when TOF-SIMS analysis was performed on the cross section of the dust core of Comparative Example 2, no zinc element was detected inside the powder core.

Therefore, in Example 3, it is considered that zinc detected by TOF-SIMS contributes to the reason why the dust core does not rust even after 1000 hours after the start of the environmental test.

The zinc particles contained in the metal soap of the lubricant are widely dispersed in the dust core through the granulation process. Further, the metal soap is melted and becomes liquid by the pressure of the subsequent molding press process and the curing heat treatment process.

Therefore, the zinc particles in the melted metal soap seep out from the inside of the dust core to the surface and diffuse. Zinc spread inside and on the surface of the dust core has a higher ionization tendency than iron, which is the main component of soft magnetic particles, and thus exhibits a high rust preventive effect.

Specifically, this rust preventive action is the following two types of actions.
(1) Zinc reacts with oxygen to form a film of zinc oxide, which makes it difficult for oxygen and water to pass through and prevents iron from corroding. (2) Zinc precedes iron to water. Sacrificial anticorrosion action to prevent iron corrosion by dissolving in and ionizing

By setting the content of zinc particles contained in zinc stearate to 1.3 wt% or more and less than 2.0 wt%, corrosion resistance can be improved, zinc particles dispersed in the resin increase, and relative magnetic permeability is improved. can.

When the content of zinc particles contained in zinc stearate is less than 1.3 wt%, the proportion of zinc particles dispersed in the resin is small, so that the rust preventive effect is small. On the other hand, when the content of zinc particles contained in zinc stearate is 2.0 wt% or more, the proportion of zinc particles in the dust core increases, so that the filling rate of the soft magnetic particles decreases and the soft magnetism occurs. The original magnetic properties of body particles cannot be maintained.

<Effect>
The dust core 100 of the present embodiment is dispersed in a plurality of soft magnetic particles 101, a resin 102 having insulating properties and heat resistance and covering the surface of each of the soft magnetic particles 101, and the resin 102. The metal particles 103 include a plurality of metal particles 103, and the metal particles 103 have a greater tendency to ionize than the main component of the soft magnetic particles 101, and the metal particles 103 are used as a lubricant mixed with the soft magnetic particles 101 and the resin 102. The proportion of the metal stearate contained in the lubricant is 50% or more and less than 90%, and the content of the metal particles 103 contained in the metal stearate is 1.3 wt% or more and less than 2.3 wt%. It is characterized by that.

Therefore, in the dust core 100, the metal particles 103 corrode before the soft magnetic particles 101, so that the soft magnetic particles 101 do not corrode. Therefore, the dust core 100 has excellent corrosion resistance. As a result, the magnetic component using the dust core 100 can be used for a long period of time even in an environment of high temperature and high humidity or in an environment exposed to rain and wind.

Further, in the dust core 100, the metal particles 103 play a role as a lubricant, so that the filling rate of the soft magnetic particles 101 is improved. Therefore, the dust core 100 has a high relative permeability.

From the above, the dust core 100 of the present embodiment can have both excellent corrosion resistance and excellent magnetic properties.

It should be noted that the present disclosure is not limited to the description of the above embodiment, and various modifications can be made without departing from the spirit of the present embodiment.

The dust core of the present disclosure and the method for producing the same can provide a dust core having improved corrosion resistance (rust resistance) and magnetic properties (specific magnetic permeability). As a result, it is possible to provide a dust core provided with soft magnetic particles used in inductors such as high-performance choke coils, reactors, and transformers.

1 Fe-based soft magnetic material particles 2 Insulation layer 3 Metal pieces 4 Rust-proof layer 4a Square part 4b Flat part 100 Powder magnetic core 101 Soft magnetic material particles 102 Resin 103 Metal particles

Claims (5)

With multiple soft magnetic particles,
A resin that has insulating properties and heat resistance and covers the surface of each of the soft magnetic particles,
Containing a plurality of metal particles dispersed in the resin,
The metal particles have a higher ionization tendency than the main component of the soft magnetic particles.
The metal particles are contained in the soft magnetic particles and the lubricant mixed with the resin.
The proportion of metal stearate in the lubricant is 50% or more and less than 90%.
The content of the metal particles contained in the metal stearate is 1.3 wt% or more and less than 2.3 wt%.
Powder magnetic core. The average particle size of the soft magnetic particles is 10 μm or more and 30 μm or less.
The dust core according to claim 1. The metal particles are particles composed of lithium, potassium, calcium, aluminum, or zinc.
The dust core according to claim 1 or 2. The resin is an epoxy resin, a phenol resin, a silicone resin, a polyamide resin, a polyimide resin, or a polyamide-imide resin.
The dust core according to any one of claims 1 to 3. The process of producing soft magnetic particles and
A step of mixing the soft magnetic particles, a resin, and a lubricant containing metal particles to prepare a granulated powder.
A step of filling a predetermined mold with the granulated powder and pressure molding to obtain a green compact.
Including a step of heating the green compact at a temperature at which the binder hardens.
The metal particles have a higher ionization tendency than the main component of the soft magnetic particles.
The metal particles are contained in the soft magnetic particles and the lubricant mixed with the resin.
The proportion of metal stearate in the lubricant is 50% or more and less than 90%.
The content of the metal particles contained in the metal stearate is 1.3 wt% or more and less than 2.3 wt%.
A method for manufacturing a dust core.

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