JPH0478112A - Composite magnetic core - Google Patents

Abstract

PURPOSE:To reduce magnetic gap, and improve magnetic characteristics, by providing compressed powder core composed of flat-shaped soft magnet alloy powder and insulator and a metal outer pipe accommodating said core, orientating the flat surface of the soft magnetic powder in the axial direction of the metal outer pipe, and constituting the soft magnetic alloy powder of Fe-Ni alloy. CONSTITUTION:Compressed powder core composed of flat-shaped soft magnetic alloy powder and insulator and a metal outer pipe accommodating said core are provided, and the flat surface of the soft magnetic alloy powder is orientated in the axial direction of the metal outer pipe. The soft magnetic alloy powder is Fe-Ni alloy composed of Ni equal to or larger than 60wt.% and equal to or smaller than 90wt.% and impurities which are inevitably contained. Fe equal to or smaller than 5wt.% which constitutes the soft magnetic alloy powder may be replaced by at least one of group IVa, group Va, and group VIa elements in the periodic table and Cu. The aspect ratio of soft magnetic alloy powder is desirably set larger than or equal to 5.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a composite magnetic core, particularly a composite magnetic core that is long and has a circular cross section,
It relates to a composite magnetic core that has excellent magnetic properties such as magnetic permeability and high mechanical strength.

(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 automobile engine ignition devices. By the way, high frequency excitation is required for ignition coils.
Conventional magnetic cores made of electromagnetic steel sheets have poor frequency characteristics and have the following problems.

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 and mis-sparking is likely to occur.

In addition, when forming a magnetic core with a laminate of electromagnetic steel sheets, since the structure is such that rectangular electromagnetic steel sheet elements are laminated, it is virtually difficult to form a magnetic core with a circular cross section. A cross section is used. Therefore, when forming an ignition coil by wrapping a coil once around a square magnetic core, 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.

Further, since a magnetic core having 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 overall volume of the coil as a product increases, resulting in a significant decrease in the efficiency of utilization of the arrangement space.

Therefore, powder magnetic cores, which can be easily formed into a cylindrical shape to improve winding properties and can have a large space factor, have been widely used in recent years.

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 equipment relatively compact, and even in the high frequency range, the eddy current loss is small. Since magnetic powder is used, frequency characteristics are good.

(Problems to be Solved by the Invention) Such conventional powder magnetic cores are formed by bonding granular magnetic material powder to each other with a binder such as an insulating epoxy resin, and each binder part has a magnetic Therefore, the magnetic permeability is unlikely to change significantly depending on the frequency.

However, magnetic permeability is generally low, and magnetic cores used particularly in the frequency range of about 8 to 12 KH2 have a drawback of inferior magnetic properties compared to magnetic cores formed by laminating conventional magnetic steel sheets.

In addition, since granular soft magnetic powder with an aspect ratio (the ratio of vertical and horizontal dimensions of the powder) close to 1 was generally used as magnetic material powder, when a long dust core was formed, there were many magnetic particles in the axial direction. Gaps are likely to form. Therefore, there is a problem that magnetic properties such as magnetic permeability are low.

This is a common problem with powder magnetic cores, but since powder magnetic cores are formed by simply fixing magnetic material powder with a binder, they have low impact resistance and are susceptible to external forces or mechanical vibrations. When used under such conditions, the reliability tends to decrease. This tendency becomes more pronounced as the magnetic core becomes longer.

In recent years, there has been a desire to downsize electrical equipment used in high frequency regions, and there is a need to further reduce iron loss and increase operating magnetic flux density.

The present invention was developed to solve the above problems, and has a long length with a circular cross section, excellent magnetic properties such as magnetic permeability even in a high frequency region, and high mechanical strength and durability. The purpose is to provide a composite magnetic core with excellent properties.

[Structure of the invention]

(Means and effects for solving the problems) In order to achieve the above object, a composite magnetic core according to the present invention includes a powder magnetic core made of a flat-shaped soft magnetic alloy powder and an insulating material, and a powder magnetic core that houses the powder magnetic core. the flat surface of the soft magnetic alloy powder is oriented in the axial direction of the metal outer tube, and the soft magnetic alloy powder contains 60% by weight or more and 90% by weight of Ni and unavoidable The Fe-Ni alloy is characterized by containing impurities.

Further, 5% by weight or less of Fe constituting the soft magnetic alloy powder may be replaced with at least one element selected from elements of Group IVa, Va, VTa, and Cu of the periodic table.

Further, the aspect ratio (ratio of the maximum length of the flat surface to the thickness) of the soft magnetic alloy powder is preferably set to 5 or more.

The reasons for limiting each component and composition of the present invention will be explained below.

The soft magnetic alloy powder used in the composite magnetic core that is the object of the present invention has the following general formula: FeNl (
1) A powdered iron-nickel alloy having a composition expressed as 100-a a (60≦a≦90% by weight) is employed.

Here, in the above formula (1), Ni is effective in improving the saturation magnetic flux density, and in order to adjust the magnetostriction and magnetic anisotropy in the alloy with Fe and obtain excellent soft magnetic properties.
It is comprised in the range of 90% by weight. If the content is less than 60% by weight, the magnetostriction will increase, and if it exceeds 90% by weight, the saturation magnetic flux density will decrease. In order to obtain especially excellent soft magnetic properties, it is desirable to set the amount added in the range of 70 to 85% by weight.

Furthermore, Vla group, Va group, IVa group elements, and Cu are effective elements for improving soft magnetic properties, improving inductance values, and stabilizing magnetic properties against temperature changes. When the content exceeds 5% by weight, the saturation magnetic flux density becomes low, so the amount is set to 5% by weight or less. Preferably it is 1 to 4% by weight.

In addition, in the above Fe-Ni-based soft magnetic alloy powder, 0, S
Even if it contains trace amounts of unavoidable impurities such as those contained in ordinary Fe-based alloys, the effects of the present invention will not be impaired.

Moreover, the Fe-Ni based soft magnetic alloy powder used in the present invention is manufactured by, for example, a normal atomization method.

Note that the flatness of the soft magnetic alloy powder is adjusted by changing the crushing strength and crushing time.

The powder magnetic core used in the present invention is made of a mixture of soft magnetic powder having a flat shape and having a small coercive force prepared as described above, and an organic binder as an insulating material. It is compression molded using a press or the like.

Moreover, one of the features of the present invention is that, as the soft magnetic powder, in order to improve the magnetic properties, soft magnetic powder 1 having a particularly flat shape is used as shown in FIG. 4. The maximum length 1 of the flat surface with respect to the thickness t of this flat soft magnetic powder 1
When the aspect ratio R is the ratio of R, the value is set to 5 or more.

If the aspect ratio R is less than 5, the orientation described below will be degraded, and the magnetic properties will also be degraded. 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 facilitate winding around the powder magnetic core.
Further, the material thereof shall be appropriately selected 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. It becomes possible. Furthermore, by using a corrosion-resistant metal material such as stainless steel, it is possible to use the magnetic core under harsh conditions, and the mechanical strength of the entire magnetic core can also be improved.

Further, the powder magnetic core is filled into the metal outer tube so that the space factor with respect to the inner volume of the metal outer tube is 98% or more. Further, the packing density of the filled powder magnetic core is preferably 75% or more.

The above-mentioned space factor is calculated as the space factor for the internal volume of the metal outer tube of the powder magnetic core, which is calculated as the powder magnetic core is integrated. It shall be determined by the average value of the ratio of the area of the powder magnetic core to the area inside the outer tube in each cross section.

The fact that the space factor is less than 98% means that a space is formed between the metal outer tube and the powder magnetic core that causes a decrease in magnetic properties.

In other words, the space factor of the dust core should be 98% or more, preferably 1
By approaching 00%, the presence of the metal outer tube is prevented from becoming a factor in deteriorating the magnetic properties, and good magnetic properties can be obtained.

Moreover, the above-mentioned packing density is determined as the ratio (density ratio) of the density value of the soft magnetic powder actually filled in the outer tube to this density value, using the specific density of the soft magnetic powder as a reference.

If this packing density is less than 75%, the magnetic properties will deteriorate.

The composite magnetic core having the characteristics targeted by the present invention can be obtained by filling a metal outer tube with a mixture of flat-shaped soft magnetic powder and an insulating material, and then using a rolling machine or the like to remove the metal outer tube. By rolling and rolling from the circumferential direction or by hot isostatic pressing (HIP) treatment to reduce the diameter,
A powder magnetic core is formed in which the oblique plane of the soft magnetic powder is oriented in the axial direction of a metal outer tube, and the powder magnetic core and the metal outer tube are integrated.

As another manufacturing method, a mixture of flat-shaped soft magnetic powder and an insulating material is subjected to cold isostatic pressing (CIP) and compression molded, so that the flat plane of the soft magnetic powder is oriented in the longitudinal direction. A manufacturing method may also be used in which, after forming the powder magnetic core, the obtained powder magnetic core is loaded into a metal outer tube having a circular cross section and fixed integrally.

By using the swaging method, HIP treatment method, and CIP treatment method, it is possible to integrate the metal outer tube and the mixture with almost no voids between them, and at the same time It has a high packing density and can form a long powder magnetic core with a circular cross section.

In addition, as soft magnetic powder, soft magnetic powder with a large aspect ratio or a flat shape is used, and the swaging process, H1P
When the treatment or CIP treatment is performed, the diameter of the mixture of soft magnetic powders etc. is gradually reduced, so that each soft magnetic powder is oriented in its oblique plane or in the axial direction and densified. . At this time, if the aspect ratio of the soft magnetic powder is less than 5, the orientation will be insufficient.

According to the composite magnetic core having the above configuration, soft magnetic powder having a flat shape with a large aspect ratio and excellent magnetic properties is used as a constituent material, and the flat surface is oriented in the axial direction to achieve high density. A powder magnetic core is formed. Therefore, compared to a conventional dust core made of soft magnetic powder with a small aspect ratio, the magnetic gap formed between the powder particles arranged in the axial direction is greatly reduced, and the magnetic properties are greatly improved. .

Furthermore, since the powder magnetic core is protected by the metal outer tube, the strength of the magnetic core as a whole is increased, and excellent durability and reliability can be maintained even when used under harsh conditions.

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

Examples 1 to 7, Comparative Examples 1 to 4 As Examples 1 to 7, alloy powders having the compositions shown in the left column of Table 1 were prepared by an atomization method, the obtained powders were pulverized, and further 1 By heat-treating in hydrogen for an hour, a flat Fe--Ni based soft magnetic alloy powder having an average particle size of 80 to 120 μm and an aspect ratio (1/l) of 90 was obtained.

Next, 1% by weight of epoxy resin powder having an average particle size of 50 μm was added to each soft magnetic alloy powder and thoroughly mixed to prepare a uniform mixture.

On the other hand, as a metal outer tube, a stainless steel tube with a circular cross section of 15 m in outer diameter, 13 m in inner diameter, and 300 m in length was prepared, and after filling the above mixture into the stainless steel tube, the openings at both ends of the stainless steel tube were sealed with silicone rubber. It stopped.

Next, set the stainless steel tube filled with the above mixture in the suction machine, and while rotating the stainless steel tube,
The outer surface of the stainless steel pipe was rolled in the radial direction from all sides to reduce the outer diameter to 8 mm and the inner diameter to 5.4 mm.
A composite magnetic core 4 was obtained in which a powder magnetic core 3 was filled in a stainless steel tube 2 as a metal outer tube as shown in the figure. The powder magnetic core 3 includes atomized alloy powder 1 as soft magnetic alloy powder,
It consists of epoxy resin powder 5 as an insulating material.

Note that the space factors of the composite magnetic cores 4 of Examples 1 to 7 are all 98.0 to 99.5%, and the packing density is 88.0.
The range was 88.7%.

Then, in order to evaluate the magnetic properties of the obtained composite magnetic core, the initial magnetic permeability μ in alternating current was measured using an LCR meter using O 2 , while a bending test was conducted to evaluate the mechanical strength.

On the other hand, as Comparative Example 1, granular atomized iron powder having the same composition as the soft magnetic powder used in Example 1, an average particle size of 80 μm, and an aspect ratio of 1.2 was used.
A mixture was prepared by adding 1% by weight of 0 μm epoxy resin powder. Then, the obtained mixture was subjected to the same manufacturing process as in Example 1 to manufacture a composite magnetic core.

In addition, as Comparative Example 2, the mixture prepared in Example 1 was compression molded to form a 3.8 mm x 3° 8 nm x 1 piece as shown in Figure 2.
Conventional powder magnetic core 3a having a square cross section with dimensions of 00 mm
was manufactured. The packing density of this powder magnetic core 3a is 89.
It was 0%. Further, the dimensions of this powder magnetic core 3a were selected as the maximum dimensions that can be inserted into the stainless steel pipe (inner diameter 5.4 HD) reduced in diameter in Example 1.

Next, the obtained powder magnetic core 3a was subjected to a bending test, and inserted into a stainless steel tube with an outer diameter of 8-1 and an inner diameter of 5.4 cm to form a composite magnetic core, and the magnetic properties were measured and evaluated in the same manner as in Example 1. I did it.

On the other hand, as comparative example 3, as shown in Fig. 3, the height was 3°8 mm.
, width 100, thickness 0.35 mm non-oriented electrical steel plate (S
A conventional laminated magnetic core 7 having dimensions of 3.8 mm x 3.8 mm x 100 mm was manufactured by laminating a large number of thin plates 6 formed in step 14) with insulating layers interposed therebetween, and was subjected to characteristic evaluation.

In addition, as Comparative Example 4, the same process as Examples 1 to 7 was carried out using soft magnetic alloy powder that deviated from the composition range of the soft magnetic alloy material or the range specified in the present invention as shown in the left column of Table 1. Composite magnetic cores with the same dimensions were prepared.

Table 1 shows the measurement results of the initial magnetic permeability μ and C in alternating current and the bending strength of the composite magnetic cores of Examples 1 to 7 and Comparative Examples 1 to 4 thus obtained.

[Margin below]

As is clear from the measurement results in Table 1, the composite magnetic cores according to Examples 1 to 7 are different from the conventional composite magnetic core (comparative example) formed using granular atomized iron powder with a small aspect ratio as soft magnetic powder. Compared to 1), the magnetic gap in the axial direction is small because the flat atomized iron powder with excellent soft magnetism and a large aspect ratio is oriented in the axial direction. Therefore, high magnetic permeability can be obtained even in a high frequency region.

Regarding magnetic flux density, the composite magnetic cores according to Examples 1 to 7 obtained the same results as the magnetic core made of magnetic steel sheets (Comparative Example 3), whereas the magnetic core according to Comparative Example 2 was due to the presence of air gaps in the tube. It was down about 35%.

Furthermore, regarding the strength characteristics, the flexural strength of the core of Comparative Example 2, which was measured using only the powder magnetic core, was as low as 7 kg/-; For example, since the stainless steel pipe functions as a reinforcing member, the mechanical strength increases by about four times. In addition, the powder magnetic cores 3.3a inserted into the stainless steel tube 2 as in Examples 1 to 7 and Comparative Example 2 can be used for a long period of time because the powder magnetic cores 3, 3a are protected by the two stainless steel tubes. Even after the powder magnetic cores 3, 3a were cracked or chipped, it was demonstrated that the durability was significantly improved.

Furthermore, the composite magnetic cores of Examples 1 to 7 were formed into coils by applying primary and secondary windings, and the operating characteristics were investigated.
Even with excitation on the order of KHz, there was almost no voltage drop on the secondary winding side, and no mechanical noise was observed.

〔Effect of the invention〕

As explained above, according to the composite magnetic core according to the present invention, soft magnetic powder having excellent soft magnetic properties and a flat shape with a large aspect ratio is used as a constituent material, and this flat surface is oriented in the axial direction. A high-density dust core is formed. Therefore, compared to conventional powder magnetic cores made of soft magnetic powder with a small aspect ratio, the magnetic gap formed between the powder particles arranged in the axial direction is significantly reduced, and the magnetic properties are significantly improved. .

Furthermore, since the powder magnetic core is protected by the metal outer tube, the strength of the magnetic core as a whole is increased, and excellent durability and reliability can be maintained even when used under harsh conditions.

Further, according to the structure of the composite magnetic core according to the present invention, the metal outer tube filled with a mixture of soft magnetic powder and an insulating material is subjected to swaging, HIP treatment, or CIP treatment, so that the axial direction inside the metal outer tube is It is possible to easily manufacture a high-density magnetic core body in which the flat planes of soft magnetic powder are oriented, and in particular, it is possible to easily manufacture a composite magnetic core having a circular cross section with excellent windability.

1...Atomized alloy powder (soft magnetic powder), 2...Stainless steel tube (metal outer tube), 3.3a...Powder magnetic core, 4.
... Composite magnetic core, 5... Epoxy resin powder (insulating material),
6... Thin plate, 7... Laminated magnetic core.

Ro Ganjin agent Hatano long

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an embodiment of the composite magnetic core according to the present invention, Fig. 2 is a perspective view showing a conventional powder magnetic core having a square cross section, and Fig. 3 is a conventional powder magnetic core formed by laminating electromagnetic steel plates. FIG. 4 is a perspective view showing the outer shape of the soft magnetic powder.

Claims (3)

[Claims] 1. A powder magnetic core made of a flat-shaped soft magnetic alloy powder and an insulating material, and a metal outer tube housing the powder magnetic core, wherein the flat surface of the soft magnetic alloy powder is aligned with the axis of the metal outer tube. The soft magnetic alloy powder has a content of 60% by weight.
A composite magnetic core characterized in that it is an Fe-Ni alloy comprising 90% by weight or less of Ni and impurities unavoidably included. 2. Claim 1 characterized in that 5% by weight or less of Fe constituting the soft magnetic alloy powder is replaced with at least one element selected from Group IVa, Va, and VIa elements of the periodic table and Cu. Composite magnetic core as described. 3. 3. The composite magnetic core according to claim 1, wherein the soft magnetic alloy powder has an aspect ratio (ratio of the maximum length of the flat surface to the thickness) of 5 or more.