EP0848392A1

EP0848392A1 - Encased magnetic core

Info

Publication number: EP0848392A1
Application number: EP96928693A
Authority: EP
Inventors: Norio c/o Mitsui Chemicals Inc. MATSUMOTO
Original assignee: Mitsui Chemicals Inc
Current assignee: Mitsui Chemicals Inc
Priority date: 1995-09-01
Filing date: 1996-08-29
Publication date: 1998-06-17
Also published as: WO1997009728A1; EP0848392A4; TW340946B; CA2230276A1

Abstract

The casing enclosed type magnetic core of the present invention is constructed by filling powders 13 at least partially in a space between a magnetic core and a casing when the magnetic core 11 is to be enclosed in the casing 12. The powders 13 are preferably nylon resin powders or silica powders having silicone oil adhered therearound.

Description

TECHNICAL FIELD

The present invention relates to a casing enclosed type magnetic core, for example, a casing enclosed type magnetic core which is used in a magnetic component for use in an electronic circuit.

BACKGROUND ART

In a magnetic component constructed by forming a coil produced by winding a wire round a magnetic core, a wire coated with an insulating film is used as the coil to prevent the coil from short-circuiting during the formation of the coil.

Since the magnetic core is harder than the insulating film formed on the wire, when the wire is wound round the magnetic core directly, the insulating film of the wire may be damaged and short-circuited during winding.

To prevent the insulating film from being damaged, the magnetic core is enclosed in a resin casing and then a coil is formed around the casing, or a coil is formed around a resin bobbin and then the bobbin is attached to the magnetic core.

Which method among the above should be used to protect the insulating film depends on the shape of the magnetic core of interest.

For example, in the case of a magnetic core composed of a magnetic alloy thin belt, the former method is employed because the shape of the magnetic core is almost annular.

Incidentally, when the magnetic core is enclosed in a casing, the magnetic core moves in the casing and collides with the wall of the casing during transportation if the magnetic core is not fixed in the casing.

When the magnetic core collides with the wall of the casing, it may be destroyed by stress applied to the magnetic core or the magnetic characteristics of the magnetic core may deteriorate.

Further, the impact may be transmitted to other component and exert a bad influence on the component.

Still further, a soldered portion of the coil may peel off due to the impact of the collision.

Therefore, in order to form a casing enclosed type magnetic core, the movement of the magnetic core in the casing must be prevented to ensure the reliability of the magnetic core as a magnetic component.

In this case, to prevent the movement of the magnetic core in the casing, it is conceivable to make the size of the inner wall of the casing the same as the outer size of the magnetic core.

However, when a core is formed by winding a wire round the casing enclosed type magnetic core, the casing may be deformed by the wound wire and stress may be applied to the magnetic core.

Further, since the magnetic core is in direct contact with the casing, the vibration of the magnetic core is easily transmitted to the casing and a big sound is generated when the magnetic core is excited.

For that reason, as conventional means for preventing the generation of a sound, a casing having an inner diameter larger than the outer size of the magnetic core is prepared and an adhesive is filled in or applied to a space between the casing and the magnetic core.

Meanwhile, when the casing is made much larger than the magnetic core, a magnetic flux in the space between the magnetic core and the casing must be taken into account.

Therefore, to produce the above casing enclosed type magnetic core, a casing slightly larger than a magnetic core is used.

As described above, by filling or applying an adhesive to the space between the magnetic core and the casing, the movement and vibration of the magnetic core in the casing are prevented from being transmitted to the casing.

However, when the adhesive is used and temperature inside the casing becomes higher than room temperature, the adhesive fixing the casing and the magnetic core expands.

Therefore, the vibration absorption power of the adhesive may be lost by a distortion caused by a volume increase due to the expansion of the adhesive depending on the amount of the adhesive filled or coated.

It is an object of the present invention to provide a casing enclosed type magnetic core which has high reliability as a magnetic component and makes a small sound.

DISCLOSURE OF THE INVENTION

A first feature of the present invention resides in a casing enclosed type magnetic core which comprises (a) a magnetic core, (b) a casing for containing the magnetic core, and (c) powders filled at least partially in a space between the magnetic core and the casing.

That is, the powders are filled in the space between the casing and the magnetic core to fix the casing and the magnetic core, prevent vibration absorption power from being lost by using an adhesive, and prevent and suppress the transmission of the vibration of the magnetic core to the casing.

In this case, the charging rate of the powders filled in the space between the magnetic core and the casing is, for example, 1 to 150%, preferably 10 to 150%, more preferably 10 to 120%, the most preferably 10 to 100%.

Incidentally, the charging rate of the powders is calculated from the following equation. charging rate (%) = mass of powders (g)/(volume of space [cm3] x bulk density of powders [g/cm3]) x 100

The bulk density of the powders [g/cm³] was measured in accordance with ASTM D1895-69.

Further, in the casing enclosed type magnetic core of the present invention, either magnetic or non-magnetic powders can be used.

Subsequently, a second feature of the present invention resides in a casing enclosed type magnetic core, wherein the maximum value of short diameter of the powder filled is in the range of 5 to 500 µm.

Incidentally, the maximum value of short diameter of the powder filled is particularly preferably in the range of 100 to 400 µm.

In this case, the short diameter of the powder is the diameter of the powder when the powder is spherical (having a circular section) and the shortest diameter of the powder when the powder does not have an indeterminate form like a powder having an elliptical section.

Next, a third feature of the present invention resides in a casing enclosed type magnetic core, wherein the powder is a nylon resin or silica having silicone oil adhered therearound.

It should be noted that, as the powder, there can be used the powder of a polyolefin such as polyethylene, polypropylene or polymethyl pentene, alumina powder, silicon dioxide powder or the like.

Next, a fourth feature of the present invention resides in a casing enclosed type magnetic core, wherein the casing has a closed structure.

Therefore, the casing enclosed type magnetic core of the present invention can insulate a sound generated by the vibration of the magnetic core by covering the magnetic core tightly with the casing.

Then, a fifth feature of the present invention resides in a casing enclosed type magnetic core, wherein the magnetic core is composed of an amorphous magnetic alloy thin belt.

Incidentally, this casing enclosed type magnetic core can be applied to magnetic cores made from various materials such as amorphous alloys (for example, Fe-based amorphous alloy), silicon steel, ferrite, dust and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a diagram showing the configuration of a casing enclosed type magnetic core of the present invention.

Fig. 2 is a diagram outlining a sound measurement test to be made on the casing enclosed type magnetic core.

Fig. 3 is a diagram showing the waveform of an excitation signal supplied to the coil at the time of the sound measurement test.

Fig. 4 is a table showing the test result of each casing enclosed type magnetic core.

Fig. 5 is a graph showing the sound level of each casing enclosed type magnetic core with respect to the charging rate of powders.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

[Embodiment 1]

First, a casing enclosed type magnetic core according to this embodiment will be outlined with reference to Fig. 1.

Here, Fig. 1 is a diagram showing the configuration of the casing enclosed type magnetic core of the present invention.

Then, the casing enclosed type magnetic core 10 according to this embodiment comprises a magnetic core 11,

casings

12₁ and 12₂, and powders 13 as shown in Fig. 1.

Next, the casing enclosed type magnetic core 10 is constructed by enclosing the magnetic core 11 in the casing 12 and filling the powders 13 in a space between the magnetic core and the casing.

Hereinafter, the constitution and performance of the casing enclosed type magnetic core according to this embodiment will be described with reference to Figs. 2 to 5.

In this case, Fig. 2 is a diagram outlining a sound measurement test to be made on the casing enclosed type magnetic core, Fig. 3 is a diagram showing the waveform of an excitation signal to be supplied to the coil at the time of the sound measurement test.

The magnetic core 11 used in the casing enclosed type magnetic core is obtained by heating at about 470°C a roll having an outer diameter of 27.0 mm, an inner diameter of 15.0 mm and a height of 10.0 mm of a Fe-based amorphous magnetic alloy thin belt (manufactured by Allied Signal Co. of the US, trade name: Metglas 2605S-2, [composition Fe₇₈B₁₃Si₉ (%)]) containing Si and B.

The casing 12 is a casing having an outer diameter of 27.7 mm, an inner diameter of 14.7 mm and a height of 10.3 mm (all are the sizes of the inner casing) (manufactured by Toray Industries, Inc., trade name: TORAYCON 1184G-30).

Further, two kinds of powders are used such as the powders 13 filled in the space between the magnetic core 11 and the casing 12 are composed of nylon resin powders having a maximum value of short diameter of 180 µm (manufactured by Sumitomo Seika Co., trade name: Flolon) and silica powders having a maximum value of short diameter of 300 µm and silicone oil adhered therearound (manufactured by Toray Dow Corning Silicone Co., trade name: Trefil).

Then, several casing enclosed type magnetic cores having different charging rates of powders using the above materials were fabricated.

Thereafter, a coil was formed by making 31 turns of a magnetic wire having a diameter of 1.0 mm⊘ around each of the magnetic cores provided by the above process to prepare evaluation samples.

Then, a fixation test for evaluating reliability as a magnetic component and a sound measuring test were made on each of the evaluation samples. The methods of the above tests will be described in detail hereinunder.

First, the fixation test was carried out by holding the case enclosed type magnetic core with hand and strongly shaking it in a direction parallel to the section of the laminate of the magnetic core. When the movement of the magnetic core was felt, the magnetic core was judged as defective.

Subsequently, the sound measuring test was carried out by measuring the level of a sound generated by the casing enclosed type magnetic core 10 when an excitation signal was supplied to the coil 15 formed around the casing enclosed type magnetic core 10 as shown in Fig. 2 by a microphone 21 installed at a position 200 mm away from the center of the casing enclosed type magnetic core 10.

Thereafter, a sound pressure level having a central frequency of 1/3 octave band measured by the microphone 21 of 10 kHz is taken as a sound level and whether the casing enclosed type magnetic core passes the sound measuring test is judged based on whether the sound level thereof is 45.0 dB or lower.

This target value of 45.0 dB is determined based on a sound level which is apparently perceived to be a lower sound than 58.0 dB, the sound level of a casing enclosed type magnetic core using an adhesive.

Incidentally, the excitation signal to be supplied to the coil 15 is a sweep sinusoidal wave having a frequency of 500 to 20,000 Hz which changes at a current value of 0 to 6A as shown in Fig. 3.

Further, evaluation on each sample was carried out mainly at room temperature and part of the samples were evaluated at a high temperature of 110°C.

The evaluation results of the casing enclosed type magnetic cores will be now described with reference to Figs. 4 and 5.

In this case, Fig. 4 is a table showing the evaluation results of each sample and Fig. 5 is a diagram showing the relationship between the sound level of each sample and charging rate for each type of powders.

As shown in Fig. 4, out of 10 prepared samples, Samples 1 to 3 used nylon resin powders and Samples 4 to 10 used silica powders having silicone oil adhered therearound.

First, the fixation test was made on Sample 1 and the sound level thereof was measured based on a nylon resin powder charging rate calculated from the above equation of 10.6%.

As a result, the sample passed the fixation test and the sound level thereof was found to be 34.9 dB, lower than the target value.

Subsequently, the fixation test was then made on Sample 2 at room temperature and a high temperature of 110°C and the sound level thereof was measured based on a nylon resin powder charging rate of 24.5%.

As a result, the sample passed the fixation test at room temperature and a high temperature of 110°C and the sound level thereof was found to be 35.9 dB, lower than the target value.

The fixation test was also made on Sample 3 and the sound level thereof was measured based on a nylon resin powder charging rate of 49.7%.

As a result, the sample passed the fixation test and the sound level thereof was found to be 43.5 dB, lower than the target value.

Therefore, in the test using nylon resin powders, all the samples had a sound level of 45.0 dB or lower which was lower than the target value.

Then, the fixation test was made on Sample 4 at room temperature and a high temperature of 110°C and the sound level thereof was measured based on a silica powder charging rate of 30.0%.

The fixation test was also made on Sample 5 and the sound level thereof was measured based on a silica powder charging rate of 50.0%.

As a result, the sample passed the fixation test and the sound level thereof was found to be 32.8 dB, lower than the target value.

Then, the fixation test was made on Sample 6 and the sound level thereof was measured based on a silica powder charging rate of 60.0%.

As a result, the sample passed the fixation test and the sound level thereof was found to be 32.9 dB, lower than the target value.

Next, the fixation test was made on Sample 7 and the sound level thereof was measured based on a silica powder charging rate of 70.0%.

As a result, the sample passed the fixation test and the sound level thereof was found to be 32.1 dB, lower than the target value.

The fixation test was further made on Sample 8 and the sound level thereof was measured based on a silica powder charging rate of 80.0%.

As a result, the sample passed the fixation test and the sound level thereof was found to be 36.2 dB, lower than the target value.

The fixation test was further made on Sample 9 and the sound level thereof was measured based on a silica powder charging rate of 90.0%.

As a result, the sample passed the fixation test and the sound level thereof was found to be 32.3 dB, lower than the target value.

It should be noted that the fixation test was further made on Sample 10 and the sound level thereof was measured based on a silica powder charging rate of 100.0%.

As a result, the sample passed the fixation test and the sound level thereof was found to be 34.3 dB, lower than the target value.

Therefore, in the test using silica powders, all the samples had a sound level of 45.0 dB or lower which was lower than the target value.

That is, it was found that a sound generated from the magnetic core and the movement of the magnetic core in the casing can be suppressed by filling powders in the space between the magnetic core and the casing.

As described above, when the powders are filled in the space between he magnetic core and the casing, a casing enclosed type magnetic core having high reliability as a magnetic component and making a sound small can be obtained.

Further, as is obvious from the results of a test made on Sample 2 and Sample 4 at a temperature of 110°C, the casing enclosed type magnetic core can be used stably at a high temperature.

Also, as is evident from the evaluation results of the samples, the powder charging rate is preferably in the range of 1 to 150%, more preferably 10 to 150%, much more preferably 10 to 120%, the most preferably 10 to 100%.

The maximum value of short diameter of the powder used in the present invention is preferably in the range of 5 to 500 µm, particularly preferably 100 to 400 µm.

Industrial Feasibility

Since the casing enclosed type magnetic core of the present invention is able to prevent or suppress the movement of the magnetic core in the casing and the transmission of the vibration of the magnetic core to the casing, a casing enclosed type magnetic core making a sound small during use and having high reliability as a magnetic component can be obtained.

Further, since the casing enclosed type magnetic core of the present invention does not use an adhesive, its vibration absorption power is not lost even when it is used at high temperatures.

For that reason, according to the present invention, a casing enclosed type magnetic core having a wider usable temperature range than the conventional casing enclosed type magnetic core can be obtained.

Claims

A casing enclosed type magnetic core comprising:

(a) a magnetic core;

(b) a casing for housing the magnetic core; and

(c) powders filled at least partially in a space between the magnetic core and the casing.
The casing enclosed type magnetic core as set forth in claim 1, the maximum value of short diameter of the powder is in the range of 5 to 500 µm.
The casing enclosed type magnetic core as set forth in claim 1 or 2, the powder is made from a nylon resin.
The casing enclosed type magnetic core as set forth in claim 1 or 2, the powder is silica having silicone oil adhered therearound.
The casing enclosed type magnetic core as set forth in any one of claims 1 to 4, the casing has a closed structure.
The casing enclosed type magnetic core as set forth in any one of claims 1 to 5, the magnetic core is composed of an amorphous magnetic alloy thin belt.