JPH08735Y2 - Magnetic core - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a magnetic core capable of reducing noise generated during operation.

[Conventional technology]

It is generally known that a magnetic core around which a coil is wound causes vibration when used in a mode in which a load is periodically turned on / off like a choke coil of a switching power supply. If the switching frequency is in the audible band, it may become noise and propagate to the surroundings, or vibrate surrounding parts to deteriorate the operating characteristics.

The above-mentioned sounding phenomenon has an ideal characteristic as a choke coil of a switching power supply for multiple outputs, that is, a magnetic circuit having a high inductance for a small DC superimposed current and a low inductance for a large DC superimposed current. There is a problem in that the higher the number, the greater the noise, and there is a dilemma in terms of performance and noise.

[Problems to be solved by the device]

However, when a slit is formed in the magnetic core, it is inevitable that the strength is lowered and resonance is likely to occur, thereby increasing vibration and noise.

Therefore, there is one in which the vicinity of the gap is fixed to reduce noise (Japanese Patent Application No. 61-55242). However, in the case where the vicinity of the gap is fixed, the noise reduction effect may vary depending on the fixing strength, and since the noise generated near the gap is suppressed after the fact, the effect is limited. .

The present invention has been made in view of the above matters, and an object thereof is to provide a magnetic core in which noise is significantly reduced.

[Means for solving the problem]

The present invention has the following configuration in order to solve the above technical problems.

That is, it is a magnetic core in which three or more annular magnetic cores are laminated, and at least one of the annular magnetic cores has a gap, and the magnetic cores on one side and the other side of the laminating direction are bordered by the center of the laminating direction. But the gaps are aligned so that they have a symmetric relationship,
When adjacent annular magnetic cores both have a gap, they are stacked so that the gap portions do not overlap each other, and when viewed comprehensively, the magnetic cores are configured to vibrate in the same phase to form a noise-reducing magnetic core.

And, in order to vibrate each magnetic core in phase, it is preferable that the dimensions of each magnetic core are matched,
Further, it is preferable that the respective magnetic cores are formed of the same material.

Furthermore, when the present invention is applied to a core formed by winding an amorphous metal ribbon, noise due to the performance of the amorphous material may be more preferably reduced.

Amorphous metals include Fe-B, Fe-BC, Fe-B
-Si, Fe-B-Si-C, Fe-B-Si-Cr, Fe-Co-B-Si, Fe-
Fe-based materials such as Ni-Mo-B, Co-B, Co-Fe-Si-B, Co-Fe-Ni-Mo
-B-Si, Co-Fe-Ni-B-Si, Co-Fe-Mn-B-Si, Co-Fe-M
Examples include Co-based materials such as n-Ni, Co-Mn-Ni-B-Si, and Co-Fe-Mn-Ni-B.

In addition to amorphous, Fe-based microcrystalline soft magnetic material such as Fe-Si-B-Cu-Nb-based alloy can be used.

[Action]

The noise of the magnetic core is generated because the distortion generated by the magnetostriction phenomenon of the magnetic core deforms the magnetic core in a specific mode.

On the other hand, since the sound wave that is noise is a wave, the density of pressure changes in space depending on the wavelength. Here, assuming that sound waves having the same wavelength and the same phase are radiated to a distant point at a certain two points, the sound pressure at the distant point is 2 if the distance between each of the two points and the distant point is equal.
It is the sum of the sound pressure emitted from the points. However, if the distance between each of the two points and the far point is not equal, the sound pressure at the far point has variability as a function of the phase difference, and the sound pressure becomes small due to the so-called interference effect.

Specifically, weaken each other in the direction in which the two sound sources are lined up,
The phenomenon of mutual strengthening occurs in the direction of the intermediate position of the sound source.

This kind of phase management should be finely adjusted depending on whether or not multiple magnetic cores have exactly the same vibration mode, high and low input frequencies, and other physical conditions. However, with the magnetic core having the gap formed as the boundary of the center in the stacking direction, on one side and the other side of the stacking direction,
If the gaps are aligned so that they are in a relative relationship, and there is a gap between adjacent annular magnetic cores, if the gaps are not overlapped, then the magnetic cores will vibrate in phase as a whole, It was possible to give directionality to the noise and to suppress the noise in actual use.

Further, since the mechanical strength is increased by polymerizing the magnetic core, resonance can be suppressed.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS.

<First Embodiment> A first embodiment will be described with reference to FIG. The magnetic core 1 is
By winding a thin plate of amorphous metal Fe ₇₈ Si ₉ B ₁₃ (atomic%), the outer diameter is 25 mm and the inner diameter is 15 m.
m, an annular core with a thickness of 10 mm from the upper surface to the lower surface. The cross section thereof is square and has an outer peripheral surface 5 and an inner peripheral surface 6, and a first side surface (upper surface) 2 that connects the respective edges of the outer peripheral surface 5 and the inner peripheral surface 6 to each other. And the outer peripheral surface 5
And a second side surface (lower surface) 4 that connects the other edges of the inner peripheral surface 6 to each other. The first side surface 2 and the second side surface 4 of the magnetic core 1 are flat surfaces. Further, the gap 3 is formed at one location in the radial direction and has a width of 0.8 mm.

One magnetic core 1 having the same shape as the two magnetic cores 1 having no gap was prepared, and the core having no gap was laminated so as to be sandwiched by the magnetic cores 1 having the gap 3.

The magnetic cores 1 on both sides were provided with the position of the gap 3 such that the position of the gap 3 was 0 ° on the circumference of the core.

As a result, the magnetic cores 1 on both sides have a symmetrical relationship with respect to the magnetic core in the center.

Each magnetic core 1 is an adhesive (Trade name: Three Bond, 120
7) glued together.

The experimental results of noise when used as a choke coil for a switching power supply will be described below with reference to FIG.

FIG. 2 is a graph showing the relationship between the magnetic flux density at a frequency of 10 KHz and the sound pressure level of noise when excited with a multiple sine wave (frequency range, output electrification is constant at 1 to 20 KHz).
Dotted lines B, C, and D are sound pressure levels when the two magnetic cores 1 are used alone, and a solid line A is the magnetic core of this embodiment. When the magnetic core 1 is used alone, the noise linearly increases with the increase of the magnetic flux, and the magnetic core 1 shown by C shows 63 dB at 200 gauss and the magnetic core 1 shown by B shows 67 dB. 65 dB for magnetic core 1 indicated by D
Has become.

In the magnetic core of the present embodiment, the noise linearly increases as the magnetic flux increases in the range of 50 gauss to 100 gauss.
When it exceeds 100 gauss, the increase in noise is greatly suppressed, and for example, it is suppressed to about 57 dB at 200 gauss.

This value is about 5 to 10 dB lower than the noise of each magnetic core alone at 200 Gauss, and noise is suppressed.

In this way, high-frequency noise that is offensive to the ears is reduced, and noise generation is suppressed especially at high input (high magnetic flux density), so that the use environment can be favorably maintained.

<Other Embodiments> As shown in FIG. 3, a magnetic core having a gap 3 is sandwiched between magnetic cores having no gap, and as shown in FIG. 4, three magnetic cores having a gap 3 are provided. Overlap
An example is one in which the gaps 3 of the cores on both sides are aligned at 0 degrees on the circumference, and the gap 3 of the center core is set at a position of 180 degrees on the circumference.

In addition, according to the present invention, the noise reduction as described above can be expected by stacking layers in a symmetrical relationship.

[Effect of device]

According to the present invention, with the above configuration, it is possible to reduce the noise that can efficiently cancel the noise generated by each magnetic core.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention, FIG. 1 is a perspective view of the first embodiment, FIG. 2 is a graph showing the relationship between magnetic flux density and noise, and FIGS. 3 and 4 FIG. 6 is a perspective view showing another example. 1 ... magnetic core, 2 ... first side surface, 3 ... gap,
4 ... second side surface, 5 ... outer peripheral surface, 6 ... inner peripheral surface.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area H01F 27/24 H

Claims (3)

[Scope of utility model registration request] 1. A magnetic core in which three or more annular magnetic cores are laminated, and at least one of the annular magnetic cores has a gap, and one side and the other side of the laminating direction are separated from each other with the center of the laminating direction as a boundary. When the magnetic cores are aligned so that the gaps are symmetrical and the adjacent annular magnetic cores have gaps, the magnetic cores are stacked so that the gaps do not overlap each other, and when viewed comprehensively, the magnetic cores are A magnetic core configured to vibrate in phase. 2. The magnetic core according to claim 1, wherein the respective magnetic cores are formed of the same material. 3. The magnetic core according to claim 1, wherein the magnetic core is formed by winding an amorphous metal ribbon.