JPH0462804A - composite magnetic core - Google Patents

Abstract

PURPOSE:To achieve a high premeability, a large mechanical strength, and an improved durability even at a low-frequency range by enabling a thickness of a metal outer tube of a compound core to be reduced to a specific dimension in which a dust core consisting of a soft magnetic powder and an insulating material are filled. CONSTITUTION:An epoxy resin powder is added to a granular atomized iron powder and is fully mixed for enabling a mixed powder to be adjusted. Then, a stainless tube in which the mixed power is filled is set to a swaging machine, an outer surface of a stainless tube is forged in diameter direction from four directions while rotating for reducing the thickness to 0.1-1.5mm, thus obtaining a compound core 5 where a dust core 4 consisting of an atomized iron powder 2 and an epoxy resin powder 3 is formed in one piece within the stainless tube 1 as a metal outer tube.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a composite magnetic core and a method for manufacturing the same, and in particular, a composite magnetic core with high magnetic permeability and high mechanical strength and a method for manufacturing the same. Regarding.

(Prior Art) Laminated bodies or wound bodies of electromagnetic steel sheets have conventionally been used for relatively long magnetic cores used, for example, in ignition coils of engine ignition devices of automobiles. By the way, high-frequency excitation is required for ignition coils, etc., but because conventional magnetic steel cores have poor frequency characteristics,
There was a problem as shown below.

That is, when the ignition coil is subjected to high frequency excitation of several KHz or more, the magnetization characteristics deteriorate due to an increase in eddy current loss. This causes a problem in that the secondary voltage of the ignition coil decreases, making mis-sparking more likely.

In addition, when forming a magnetic core using a laminate of electromagnetic steel sheets, since the structure is such that rectangular electromagnetic steel sheet elements are laminated, it is practically difficult to form a magnetic core with a cross section or a circular shape. A cross section is used. Therefore, when winding a coil around a rectangular magnetic core to form an ignition coil, the coil comes into contact with the ridgeline of the magnetic core, making it easy to cut, and the enamel coating of the coil easily peels off, resulting in extremely poor winding properties. There is.

Furthermore, since a magnetic core with a rectangular cross section is generally housed in a cylindrical container and formed into an ignition coil or the like, it is difficult to increase the space factor of the magnetic core. Therefore,
This has the disadvantage that the volume of the coil, etc. that becomes the product increases, and the efficiency of utilization of the installation space decreases significantly.

Therefore, powder core walls have been widely used in recent years because they can be easily formed into a cylindrical shape to improve the winding properties and the space factor can be set to a large value.

Such powder magnetic cores are generally manufactured by press-molding a mixture of soft magnetic powder and an insulating binder.

Since the powder magnetic core manufactured in this way can have a large space factor, it is possible to make the device relatively compact.Secondly, even in the high frequency range, eddy current loss is small. Since soft magnetic powder is used, frequency characteristics are good.

(Problems to be Solved by the Invention) Such conventional powder magnetic cores are formed by mutually bonding magnetic material powder with a binder such as an insulating epoxy resin, and each binder part has a magnetic Because it is a gap, the magnetic permeability is unlikely to change significantly depending on the frequency. However, the magnetic permeability is generally low, especially 8~
A magnetic core used in a frequency range of about 1.2KH+ has a drawback of inferior magnetic properties compared to a conventional magnetic core formed by laminating electromagnetic steel sheets.

In addition, a common problem with powder magnetic cores is that powder magnetic cores are formed by fixing magnetic material powder with a binder, so they have low impact resistance and are susceptible to conditions such as external force or mechanical vibration. When used below,
There is a possibility that its reliability may deteriorate. This tendency becomes more pronounced as the magnetic core becomes longer.

The present invention has been made to solve the above problems, and provides a composite magnetic core that has high magnetic permeability even in a low frequency region, high mechanical strength, and excellent durability, and a method for manufacturing the same. With the goal.

[Structure of the invention]

(Means and effects for solving the problems) In order to achieve the object described in item 1, a composite magnetic core according to the present invention is a composite magnetic core in which a powder magnetic core made of soft magnetic powder and an insulating material is filled in a metal outer tube. , the composite magnetic core is characterized in that the wall thickness of the metal outer tube is set to 0.1 mm or more and 15 mm or less by diameter reduction, and the metal outer tube contains soft magnetic powder, a plurality of soft magnetic wires, and an insulating material. In the filled composite magnetic core, 0.
This is a composite magnetic core characterized by having a diameter of 1 mm or more and 1.5 mm or less.

Here, the powder magnetic core used in the present invention includes, for example, Fe powder,
Fe. i-series powder, Fe-A, j. Soft magnetic powder such as i-based powder, Fe-Ni-based powder, Fe-Co-based powder, etc. is fixed with an organic binder that is an insulating material.

Further, as the above-mentioned soft magnetic powder, in order to improve the magnetic properties, it is particularly preferable to use a soft magnetic powder having a flat shape. When the aspect ratio R is the ratio of the maximum length 1 of the flat surface to the thickness t of the flat soft magnetic powder, it is desirable to set the value to 5 or more. If the aspect ratio R is less than 5, the orientation will be lowered and the magnetic properties will also be lowered.

In order to achieve a particularly remarkable effect of improving magnetic properties, it is desirable to set the aspect ratio to 20 or more.

Note that the aspect ratio of the soft magnetic powder produced by the crushing operation is adjusted by appropriately changing the crushing strength and crushing time of the soft magnetic material pieces serving as the raw material.

In addition, the metal outer tube preferably has a circular cross section in order to make the winding around the powder magnetic core more comfortable.
In addition, the 10A qualities shall be selected as appropriate depending on the intended use. For example, by using an outer tube made of soft magnetic material, the magnetic properties can be further improved, and by using a soft magnetic material different from the soft magnetic material filled inside, intermediate magnetic properties can be imparted. is also possible. In addition, by using a corrosion-resistant metal such as stainless steel + A material, it is possible to use it under severe conditions, and it is also possible to improve the mechanical strength.

The thickness of the metal outer tube has a great effect on the mechanical strength of the composite magnetic core, the difficulty of the manufacturing process, and the magnetic properties.
A powder magnetic core is filled inside, and in order to maintain its mechanical strength and suppress deterioration of magnetic properties, it is
It is set in a very thin range of less than mm. If the thickness of the metal outer tube is less than 0.1 mm, the function of the metal outer tube to firmly hold the powder magnetic core will be insufficient, the mechanical strength of the composite magnetic core will be low, and the durability and reliability of the magnetic core will decrease. At the same time, rolling and finishing operations in the manufacturing process described later become difficult. On the other hand, the thickness of the metal outer tube is 1.
If it exceeds 5 mm, the mechanical strength is significantly improved, but the cross-sectional area of the powder core filled inside the outer tube is relatively reduced compared to a composite magnetic core that does not use an outer tube. , the magnetic properties of the composite magnetic core as a whole deteriorate. Therefore, the thickness of the metal outer tube is 0. It is set in the range of 1 to 1.5 mm. For this reason, it is desirable that the metal for forming the outer tube has high mechanical strength and excellent corrosion resistance; specifically, stainless steel and the like are preferred.

In addition, the soft magnetic wire is arranged along the axial direction inside the metal outer tube in order to increase the magnetic permeability of the magnetic core, and is preferably made of the same material as the soft magnetic powder described above.
Different materials can also be used depending on the application. The soft magnetic wire may be insulated in advance, but depending on the use of the magnetic core, the manufacturing method, or the content ratio of the wire inside the magnetic core, it may not be necessary to insulate it in advance. For example, insulation may be inevitably achieved by mixing an insulating material and soft magnetic powder. Further, as the above-mentioned insulating coating material, it is possible to use various insulating materials including organic resin-based ones.

Examples of the shape of this soft magnetic wire include a normal cylindrical wire. These soft magnetic wires can be coated with insulation on their surfaces, then bundled together and filled with soft magnetic powder and insulation material into a metal outer tube, or coated with soft magnetic powder without insulation coating. Another method is to disperse and fill them together with the insulating material.

The soft magnetic wire integrated with the powder magnetic core can have a good wedge effect by increasing the proportion of the soft magnetic wire in the powder magnetic core.

The composite magnetic core having the characteristics targeted by the present invention can be produced by filling a metal outer tube with a soft magnetic powder and an insulating material, or a mixture of these and a soft magnetic wire, and then inserting the metal outer tube into a swaging machine, for example. The mixture filled in the metal outer tube is manufactured by rolling and rolling from the circumferential direction using a metal tube to reduce the diameter. However, this diameter reduction process is not limited to rolling, and may be any method that reduces the diameter of the metal outer tube using an external force. For example, hot isostatic pressing (HI)
It is also possible to reduce the diameter by cold isostatic pressing (CI P) or cold isostatic pressing (CI P).

According to the composite magnetic core containing the soft magnetic wire according to the above configuration,
Because soft magnetic wire rods with almost no magnetic gaps are arranged along the axial direction inside the metal outer tube, the magnetic core has a particularly low It is possible to relatively increase the magnetic permeability in the frequency domain.

In addition, since the dust core is protected by a metal outer tube with a very thin thickness, the mechanical strength of the core as a whole is increased, and it has excellent durability even when used under harsh conditions. Reliability can be maintained. In particular, by setting the thickness of the metal outer tube in the range of 0.1 to 1.5 mm,
A high-strength composite magnetic core can be obtained without deteriorating magnetic properties.

Furthermore, according to the present invention, by reducing the diameter of a metal outer tube filled with a mixture of soft magnetic powder, an insulating material, and a soft magnetic wire, by applying an external force such as rolling. Therefore, it is possible to easily manufacture a composite magnetic core having a circular cross section with excellent windability.

In addition, by reducing the diameter using external force in this rolling method, it is possible to firmly integrate the metal outer tube, soft magnetic wire, and dust core without forming any gaps between them. It is possible to sufficiently increase the packing density of the powder magnetic core.

(Examples) Next, the composite magnetic core of the present invention will be described in more detail with reference to the following examples.

Examples 1 and 2, Comparative Example]. , 2 As Example 1, granular atomized iron powder (average particle size 80μ
1% by weight of epoxy resin powder (average particle size 50 μm)
) was added and thoroughly mixed to prepare a mixed powder.

On the other hand, as a metal outer tube, the outer diameter is 15 mm, the inner diameter is 14 mm,
Two stainless steel tubes each having a length of 300 mm were prepared, and after filling one of the two stainless steel tubes with the mixed powder, the openings at both ends of the stainless steel tubes were sealed with silicone rubber.

Next, set the stainless steel tube filled with the above mixed powder in the suction machine, and while rotating the stainless steel tube,
By rolling the outer surface of the stainless steel tube in the radial direction from all sides to reduce the diameter to an outer diameter of 8.0 mm and an inner diameter of 6.8 mm, a stainless steel tube 1 as a metal outer tube as shown in Fig. 1 is obtained. A composite magnetic core 5 (in which a powder magnetic core 4 made of atomized iron powder 2 and epoxy resin powder 3 is integrated and filled)
Example 1) was obtained. In addition, a Fe wire with a diameter of 0.3 mm and a length of 300 mm was coated with an insulating coating made of epoxy resin.
Several wire rods were prepared. Then, the bundled Fe wires are arranged along the central axis direction of the other stainless steel tube, and after the mixed powder is filled around the bundle of Fe wires, the openings at both ends of the stainless steel tube are sealed with silicone rubber. did. Next, rolling was carried out in the same manner as in the manufacturing process of Example], and the diameter was reduced to 8.0 mm in outer diameter and 6.8 mm in inner diameter.
Stainless steel pipe 1 as a metal outer pipe as shown in Fig. 2
-Fe as a soft magnetic wire material with an insulating coating 6 formed therein;
A composite magnetic core 8 (Example 2) in which the wire rod 7 and the powder magnetic core 4 were integrated and filled was obtained. The powder magnetic core 4 is composed of atomized iron powder 2 as a soft magnetic powder and epoxy resin powder 3 as an insulating phase.

The F disposed in the center of the composite magnetic core 8 obtained in this way
The occupation ratio of the e-line 1''7 to the internal volume of the stainless steel tube was measured and found to be 89%.

In order to evaluate the magnetic properties of the obtained composite magnetic cores 5 and 8, the initial magnetic permeability μ in AC was measured using an aCL CR meter, while a bending test was conducted to evaluate the mechanical strength. provided.

On the other hand, as comparative example 1, as shown in FIG.
Non-oriented electrical steel sheet (S
A large number of thin plates 9 formed in step 14) are laminated with an insulating layer interposed therebetween, and 3. 8mmX 3. 3mm x 100mm
A conventional magnetic core ↑0 having the dimensions was manufactured and subjected to characteristic evaluation.

Further, as Comparative Example 2, the mixture of the atomized iron powder and resin powder prepared in Examples 1 and 2 was press-molded to have a rectangular cross section as shown in FIG.
X 3. A powder magnetic core 11 having dimensions of 8 mm x ]-00 mm was manufactured and subjected to characteristic evaluation.

The measurement results of the magnetic properties and mechanical strength of the magnetic cores of Examples 1 and 2 and Comparative Example 1.2 obtained in this way are shown in the following 1.
Shown in the table.

As is clear from the measurement results in Table 1, the composite magnetic core according to Example 1 has a small decrease in μ in the high frequency region, unlike the conventional magnetic steel core according to the comparative example.
Furthermore, it was found that the composite C magnetic core according to Example 2 has high magnetic permeability even in the low frequency range because it is equipped with Fe wire.

On the other hand, regarding the strength characteristics, the bending strength of the magnetic core of Comparative Example 2, which was measured using only the powder magnetic core, was 7 kgy''' m.
Although rA is small, according to the composite magnetic core of Example), the mechanical strength is 4.
It will rise to about twice as much.

Furthermore, when the composite magnetic core of Example 1 was formed into a coil by applying primary and secondary windings and its operating characteristics were investigated, it was found that KH
Even with excitation in the z order, there was no significant voltage drop on the secondary winding side, and no mechanical noise was observed.

Examples 3 to 6, Comparative Examples 3 to 6 Next, as Examples 3 to G, the mixed powder prepared in Example 1 was filled into stainless steel tubes having various outer diameters, and then a sway sink man was used. The outer diameter of each stainless steel tube was reduced to 8 mm by rolling and rolling, and the wall thickness d of each stainless steel tube was reduced to 0.
．． 1mm, 0. 5mm, 10mm, 1
．． A composite magnetic core with a thickness of 5 mm was prepared, and the initial permeability μ and anti-C can strength in AC were measured in the same manner as in Example 1.

On the other hand, in Comparative Examples 3 to 6, the wall thickness d of the stainless steel pipes was 0. 1. 7+nm, 2. 0mm, 2
．． A magnetic core set to 3m+n was prepared, and its magnetic properties and strength properties were measured in the same manner as in Examples 3 to 6, and the results shown in FIG. 5 were obtained.

As is clear from the results shown in Fig. 5, the composite core of Comparative Example 3 without the stainless steel pipe (d = 0) has a small bending strength of 7 kg/mrA and has low strength characteristics, but the initial permeability μ is big. On the other hand, in the composite cores of Comparative Examples 4 to 6 in which the wall thickness d of the stainless steel tube was set large, the bending strength increased rapidly, but the cross-sectional area of the powder core decreased relatively. , the magnetic properties will deteriorate. Then, the wall thickness d of the stainless steel pipe is 0
．． According to the composite magnetic cores of Examples 2 to 5, which are set in the range of 1 to 1.5 mm, it is possible to simultaneously satisfy magnetic feelability and strength characteristics.

〔Effect of the invention〕

As explained above, according to the composite magnetic core according to the present invention, the powder magnetic core is protected by a metal outer tube having an appropriate thickness, so the mechanical strength of the magnetic core as a whole is increased and it can withstand harsh conditions. It maintains excellent durability and reliability even when used in

Especially the metal outer tube j9. The size is 0.1 to 1-. By setting the thickness in the range of 5 mm, a high-strength composite magnetic core can be obtained without deteriorating the magnetic properties.

In addition, because the soft magnetic wire material with no magnetic gap is arranged along the axial direction inside the metal outer tube, it is particularly effective at low frequencies compared to conventional magnetic cores that consist only of dust cores with many caps. It is possible to relatively increase the magnetic permeability in the region.

Furthermore, according to the present invention, a mixed powder of soft magnetic powder and an insulating material,
Further, by rolling a metal outer tube filled with soft magnetic wire, a composite magnetic core having a circular cross section with excellent winding properties can be easily manufactured in one piece.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of a composite magnetic core according to the present invention, FIG. 2 is a perspective view showing another embodiment of the composite magnetic core according to the present invention, and FIG.
The figure is a perspective view showing the shape of a conventional magnetic core formed by laminating electronic steel plates, and Figure 4 is a perspective view showing a conventional powder magnetic core formed by pressure forming a mixture of magnetic powder and insulating material. , FIG. 5 is a graph showing the correlation between the initial magnetic permeability over the wall thickness and the bending strength of the metal outer tube. 1...Stainless steel tube (metal outer tube), 2...Atomized iron powder (soft magnetic powder), 3...Epoxy resin powder (insulating material), 4...Powder magnetic core, 5...Composite magnetic core , 6... Insulation coating, 7... Fe wire (soft magnetic wire), 8... Composite magnetic core, 9... Thin plate, 10... Magnetic core, 11... Powder magnetic core.

Claims (6)

[Claims] 1. In a composite magnetic core in which a metal outer tube is filled with a dust core made of soft magnetic powder and an insulating material, the wall thickness of the metal outer tube is set to 0.1 mm or more and 1.5 mm or less by diameter reduction. A composite magnetic core featuring 2. 2. The composite magnetic core according to claim 1, wherein the soft magnetic powder has a flat shape, and the direction of the flat surface is oriented in the longitudinal direction of the metal outer tube. 3. The composite magnetic core according to claim 1, wherein the metal outer tube is a stainless steel tube. 4. In a composite magnetic core in which a metal outer tube is filled with soft magnetic powder, a plurality of soft magnetic wires, and an insulating material, the wall thickness of the metal outer tube is set to 0.1 mm or more and 1.5 mm or less by diameter reduction. A composite magnetic core characterized by: 5. 5. The composite magnetic core according to claim 4, wherein the soft magnetic powder has a flat shape, and the soft magnetic powder and the plurality of soft magnetic wires are oriented in the longitudinal direction of the metal outer tube. 6. 5. The composite magnetic core according to claim 4, wherein the metal outer tube is a stainless steel tube.