JP2016092317A - Ferrite core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferrite core which inhibits harmful effect caused by burrs of a gap and prevents chips of an end part of the gap even when formed into a substantially C shape.SOLUTION: A ferrite core is formed into a substantially C shape by forming a gap 130 in a core body 110 having a substantially toroidal shape. The gap 130 is formed at a thin wall part 120 formed into a shape thinner than the other portion. A clearance dimension G of the gap 130 is set so as to be smaller than a lateral width dimension of the thin wall part 120. The thin wall part 120 is recessed from an inner peripheral surface and an outer peripheral surface of the core body 110.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a ferrite core having an adjustable saturation current value.

When the conventional toroidal ferrite core is used in the differential mode, it is saturated when several amperes are superimposed, and as a result, the noise reduction effect is lost. Therefore, a core of Fe—Si material (ferrosilicon) is used as one that does not saturate even when a large current is superimposed. Unlike the ferrite core, the Fe-Si core has a low magnetic permeability, so that a large current is not superimposed and does not saturate.
However, the Fe—Si core has a problem that the noise reduction effect is also low because of its low impedance.

  In view of this, Japanese Patent Application Laid-Open No. 07-2015579 proposes a ferrite core that has a high noise reduction effect and does not saturate even when a large current is superimposed, by making the core body made of ferrite substantially C-shaped.

Japanese Patent Application Laid-Open No. 07-2015579

However, since this substantially C-shaped ferrite core cuts the core body obtained by firing in a radial direction with a processing machine such as a diamond cutter to form a gap, burrs are generated at the end of the gap. There was a case. The burrs may cause damage to signal lines inserted inside the ferrite core and various signal lines existing outside the ferrite core.
When removing the burr after forming the gap in an attempt to remove such adverse effects of the burr, the end of the gap may be lost due to the brittleness of the ferrite core.

  The present invention was devised in view of the above circumstances, and even if it is a substantially C-shaped ferrite core, there is no adverse effect of gap burr, and the end of the gap is not chipped. The purpose is to provide.

  In the ferrite core according to the present invention, a gap is formed in a substantially C-shape by forming a gap in a substantially toroidal core body, and the gap is formed in a thin portion formed thinner than other portions.

  Since the ferrite core according to the present invention is a substantially C-shaped ferrite core in which a gap is formed, a ferrite core having an optimum saturation magnetic flux density can be obtained by changing the width dimension of the gap. In addition, since the gap is formed in a thin portion, even if burrs are generated when the gap is formed, various signal lines are not damaged by the burrs. For this reason, since it is not necessary to remove burrs, chipping at the end of the gap caused by removing burrs does not occur.

It is drawing of the ferrite core which concerns on embodiment of this invention, Comprising: The figure (A) is a schematic plan view, The figure (B) is a schematic sectional view on the AA line. It is a schematic plan view before the gap formation of the ferrite core which concerns on embodiment of this invention. 1 is a schematic perspective view of a ferrite core according to an embodiment of the present invention. FIG. 3 is a schematic enlarged plan view around the gap of the ferrite core according to the embodiment of the present invention. It is a graph which shows the relationship between the external magnetic field density and magnetic flux density by the difference in the dimension of the gap of the ferrite core which concerns on embodiment of this invention. It is a graph which shows the relationship between the frequency and impedance by the difference in the gap of the ferrite core which concerns on embodiment of this invention. It is a general BH curve of a ferrite core. It is a schematic perspective view of the ferrite core which concerns on other embodiment of this invention.

  A ferrite core 100 according to an embodiment of the present invention is a ferrite core formed in a substantially C shape by forming a gap 130 in a substantially toroidal core body 110, and the gap 130 is formed thinner than other portions. The thin-walled portion 120 is formed.

  The ferrite core 100 is formed by firing as a core body 110 in which the gap 130 is not formed, and the ferrite core 100 is completed by forming the gap 130 in the core body 110.

The core body 110 before the gap 130 is formed is formed in a substantially toroidal shape as shown in FIG. The core body 110 is different from a conventional general one, that is, a toroidal shape, in that a thin portion 120 is formed.
If the dimension from the center point O of the core body 110 to the inner peripheral surface 111 of the other part other than the thin part 120 is A and the dimension from the outer peripheral surface 112 is B, the thickness dimension of the part is B−A. . On the other hand, when the dimension from the center point O to the inner peripheral surface 121 of the thin portion 120 is a and the dimension from the outer peripheral surface 122 is b, the width dimension of the thin portion 120 is ba.
Moreover, it is set so that B−A> ba.
That is, the thin portion 120 is formed by being recessed from the inner peripheral surface 111 and the outer peripheral surface 112 of the core body 110.
Further, the width of the thin portion 120 is W, and the thickness of the core body 110 is D.

An example of the dimension of each part is given.
A (dimension from the center point O to the inner peripheral surface 111) = 7.4 mm
B (dimension from the center point O to the outer peripheral surface 112) = 13.35 mm
a (Dimension from the center point O to the inner peripheral surface 121 of the thin portion 120) = 8.4 mm
b (dimension from the center point O to the outer peripheral surface 122 of the thin portion 120) = 12.3 mm
A-a (recessed dimension on the inner peripheral surface 121 side of the thin portion 120) = 1.0 mm
B−b (recess dimension on the outer peripheral surface 122 side of the thin portion 120) = 1.05 mm
W (width dimension of thin portion 120) = 2.0 mm
D (thickness dimension) = 11.2 mm

  A gap 130 is formed in the thin portion 120 of the core body 110 configured as described above. The gap 130 is formed using, for example, a diamond cutter. In addition, since the gap 130 must be formed in the thin part 120, the gap 130 is formed in a state where the core body 110 is fitted in a jig whose setting position is constant.

  A means of firing the core body 110 that has been formed in advance corresponding to the gap 130 from the time of firing is also conceivable, but if the material corresponding to the gap 130 is formed during firing, the entire core body 110 is distorted. There is a fear. For this reason, it is desirable to first fire the core body 110 without the gap 130 and then form the gap 130 in the thin portion 120 of the core body 110.

  Even if the gap 130 is formed using a diamond cutter, a burr 140 may inevitably occur at the end of the gap 130 as shown in FIG. However, even if the burrs 140 are generated, the burrs 140 are contained in the thin-walled portion 120, so that signal lines inserted into the ferrite core 100 and various signal lines existing outside the ferrite core 100 are used. There is a much lower risk of damage.

  Needless to say, the gap 130 is not limited to the diamond cutter described above, and may be formed by other equipment such as a laser cutter or an ultrasonic cutter.

The gap dimension G (see FIGS. 1 and 3 etc.) of the gap 130 of the ferrite core 100 in which each part is formed with the dimensions described above is 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, FIG. 5 shows the relationship between the external magnetic field strength and the magnetic flux density in the case of 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, and 1.0 mm. For comparison, FIG. 5 also shows the case where there is no gap 130 (that is, the gap dimension G of the gap 130 is 0.0 mm).
This reveals that the formation of the gap 130 can increase the intensity of the external magnetic field that reaches saturation, that is, the saturation current value. Moreover, it can be seen that as the dimension of the gap 130 increases, the inclination becomes gentler and the value of the external magnetic field intensity reaching the saturation magnetic flux density increases.
That is, by forming the gap 130, the ferrite core 100 can be made more difficult to be saturated, and the external magnetic field strength reaching the saturation magnetic flux density can be controlled by changing the gap dimension G of the gap 130. Will be able to.

The external magnetic field strength reaching the saturation magnetic flux density can be controlled by changing the gap dimension G of the gap 130 for the following reason.
The ferrite core generally has a magnetic saturation characteristic as shown in FIG. That is, when an external magnetic field exceeding the saturation magnetic flux density of the ferrite core 100 is applied, the magnetic characteristics are lost and the noise reduction effect is completely lost.
In order to suppress magnetic saturation, it is necessary to smooth the BH curve, that is, to reduce the magnetic permeability μ. As a result, the impedance of the ferrite core 100 is reduced, and the magnetic field strength reaching the saturation magnetic flux density can be further increased.

By providing the gap 130 in the ferrite core 100, an air layer having a magnetic permeability of 1 is provided in the magnetic flux of the ferrite core 100, and the magnetic permeability of the entire magnetic path can be reduced. That is, the BH curve can be made smooth.
The magnetic permeability of the entire magnetic path depends on the thickness of the air layer, that is, the gap size G of the gap 130. The greater the thickness of the air layer, that is, the greater the gap dimension G of the gap 130, the lower the permeability of the entire magnetic path and the lower the impedance. For this reason, even if there is a large current superposition, magnetic saturation does not occur.
Conversely, the smaller the thickness of the air layer provided in the magnetic flux of the ferrite core 100, that is, the smaller the gap dimension G of the gap 130, the more the permeability of the entire magnetic path is the ferrite core when the gap 130 is not formed. Is close to the magnetic permeability, i.e., becomes larger, and the impedance becomes higher. For this reason, even when a small current is superimposed, magnetic saturation occurs.

In the above-described Fe—Si material (ferrosilicon), several material grades are determined in advance, and the value of the external magnetic field strength reaching the saturation magnetic flux density is uniquely determined by the grade. In addition, a magnetic permeability larger than that corresponding to the gap dimension G of the gap 130 of the ferrite core 100 corresponding to 1.0 mm cannot be obtained.
On the other hand, with the ferrite core 100 having the gap 130 formed therein, as described above, the external magnetic field strength reaching the saturation magnetic flux density can be adjusted by changing the gap dimension G of the gap 130. There is.
Note that the slope shown in FIG. 5 is proportional to the impedance (see FIG. 6).

  In the above-described embodiment, the dimensions of each part of the ferrite core 100 are specified, but the present invention is not limited to this, and it goes without saying that various dimensions can be taken as necessary.

  In addition, the substantially C shape in the present specification includes not only the substantially torus shape shown in FIG. 1 and the like but also the shape shown in FIG.

100 Ferrite core 110 Core body 120 Thin portion 130 Gap G (Gap) gap size

Claims (3)

  A ferrite core, wherein a gap is formed in a substantially C shape by forming a gap in a substantially toroidal core body, wherein the gap is formed in a thin part formed thinner than other parts.   The ferrite core according to claim 1, wherein a gap dimension of the gap is set smaller than a width dimension of the thin portion.   The ferrite core according to claim 1, wherein the thin portion is formed by being recessed from an inner peripheral surface and an outer peripheral surface of the core body.

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