JP2000260624A - Toroidal ferrite core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the seizure of ferrite cores at the time of burning by forming an upper face section and a lower face section of the ferrite core which is formed by an outer surface section, an inner surface section, the upper face section, and the lower face section, into a circular-arc projecting shape in a cross-sectional view. SOLUTION: A toroidal ferrite core 1 has an upper face 2 and a lower face 3, both of which are formed into a circular-arc projecting shape. About the dimensions, the outer diameter is 8 mm and the inner diameter is 4 mm and the height is 4 mm, for example. The height is the dimension of the highest part. The height of the circular-arc projecting part is 0.1 mm and is 2.5% of the height of the entire core. When such toroidal ferrite cores 1 are disposed loose in a burning case, they do not stick to each other due to their shape. If the height of the projection increases, the inductance of the core decreases. Accordingly, the height of the projection is at most 3 mm and should be 10% or below of the height of the entire core, When the cores are disposed loose in the burning case, the outer diameter of 20 mm or below is especially effective for preventing the attachment of the cores.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a toroidal ferrite core, and more particularly to a small toroidal ferrite core having a small outer diameter.

[0002]

2. Description of the Related Art Ferrite cores are formed by molding and firing soft ferrite materials such as MnZn-based ferrite materials and NiZn-based ferrite materials, and are used for various electric and electronic parts. Shapes and sizes also vary. Among them, the toroidal ferrite core has a winding wound on the core to form a coil, a transformer and the like.

[0003]

With the miniaturization of electric and electronic devices, small products are also required for ferrite cores. FIG. 3 is a perspective view of a conventional toroidal ferrite core, and FIG. 4 is a cross-sectional view taken along a plane passing through the center and parallel to an axial direction. The conventional toroidal ferrite core 31 has a small radius formed on the ridge,
Its cross-sectional shape was rectangular. For this reason, when the small toroidal ferrite cores 31 having a small outer diameter are stacked or placed separately in a firing case and fired, the upper surface 32 and the lower surface 33 come into contact with each other and are fired. For this reason, after the firing, it is necessary to separate the attached cores, and there has been a problem that a defective product is produced.

[0004] In view of the above, it is an object of the present invention to provide a small toroidal ferrite core having a small outer diameter, in which sticking during firing is prevented.

[0005]

According to the present invention, an outer diameter of 20 m is provided.
In the toroidal ferrite core of m or less, the shape of the upper surface and the lower surface in the cross-sectional shape formed by the outer diameter portion, the inner diameter portion, the upper surface portion, and the lower surface portion is a shape protruding in an arc shape. It is a characteristic toroidal ferrite core.

In the present invention, the projection length of the arc-shaped projection is 1 mm or less. Further, it is preferably 0.5 mm or less, more preferably 0.3 mm or less. Further, it is preferably 0.05 mm or more.

Further, in the present invention, the projection length of the arc-shaped projection is set to 10% or less of the height of the core. Further, it is preferably at most 5%.

The present invention also provides a toroidal ferrite core having an outer diameter of 10 mm or less, wherein the inner diameter is thicker than the outer diameter and the difference is 1 mm or less. .

Further, the present invention is characterized in that the thickness change portion has a curvature.

[0010]

FIG. 1 is a perspective view, partially in section, of an embodiment according to the present invention. FIG. 1 shows a cross section taken along a plane parallel to an axial direction passing through the center similarly to FIG. The toroidal ferrite core 1 of this embodiment has a shape protruding in an arc shape on the upper surface 2 and the lower surface 3. The dimensions of this example have an outer diameter of 8 mm, an inner diameter of 4 mm, and a height of 4 mm.
mm. The height is the highest dimension. At this time, the protruding length of the arc shape was 0.1 mm. The length of the protrusion is 2.5% of the height of the core.
It is. This protruding length is the dimension a shown in FIG. Due to this shape, when the pieces were placed in a firing case and fired, sticking of the toroidal ferrite cores did not occur. On the other hand, in the case of the conventional shape shown in FIGS.
At an incidence of about 10%, sticking occurred.

Thus, it can be seen that sticking can be prevented by the present invention. If the arc-shaped projection is too large, it will cause a problem in later use. For example, the longer the protruding length, the more constant the core height, the smaller the effective cross-sectional area of the core, and the lower the inductance of the core. On the other hand, if the projection length is too small, the effect of projecting cannot be obtained. Therefore, the protrusion length is 1
mm or less, more preferably 0.5 mm or less,
It is more preferably 0.3 mm or less, and preferably about 0.1 mm. Further, it is preferably 0.05 mm or more. The protruding length is preferably 10% or less, more preferably 5% or less, and preferably about 1 to 3% with respect to the height of the core. In addition, this structure is particularly effective when the outer diameter of stacking the cores during firing or placing the cores in the firing case loosely is 20 mm or less, more preferably 10 mm or less, and even if it is too small. Since it is difficult to form, it is preferably about 2 mm or more.

FIG. 2 is a partially sectional perspective view of another embodiment according to the present invention. FIG. 2 shows a cross section taken along a plane parallel to the axial direction passing through the center similarly to FIGS. The toroidal ferrite core 11 of this embodiment has an inner diameter portion 15.
Is formed thicker than the outer diameter portion 14. The upper surface 12 and the lower surface 13 are formed so as to be gradually thicker toward the inner diameter portion 15 and have a curvature.
It preferably has a curvature, but may have a linear shape. The dimensions of this example have an outer diameter of 4 mm, an inner diameter of 2 mm,
Height is 2 mm. The height is the highest dimension. At this time, the difference in height between the outer diameter portion 14 and the inner diameter portion 15 was 0.12 mm. Due to this shape, the toroidal ferrite cores did not stick together when placed in a firing case and fired. On the other hand, FIG.
In the case of the conventional shape shown in FIG. 4, sticking occurred at an occurrence rate of about 6%.

Thus, it can be seen that the present invention can prevent sticking. If the difference between the height of the outer diameter portion and the height of the inner diameter portion is too large, there is a problem in later use. For example, if the difference is too large, the effective cross-sectional area of the core becomes small, and the inductance of the core decreases, and deformation due to molding density variation at the time of molding occurs. If the difference in height is too small, the effect is small and sticking occurs. Therefore, it is preferably 1 mm or less, more preferably 0.5 m
m or less, and the height of the outer diameter portion is 90 to 90% of the height of the inner diameter portion.
About 95% is preferable. Further, this structure has a shape that can cope with a case where the outer diameter is smaller than that of the embodiment of FIG.
Therefore, it is particularly effective when the outer diameter is 10 mm or less,
More preferably, it is 8 mm or less, more preferably, 4 mm or less.

According to the present invention, the shapes of the upper and lower surfaces of the toroidal ferrite core are minutely changed to prevent sticking during firing. If the change in shape is too large, the effective area of the core decreases, causing a decrease in inductance, and problems such as deformation due to molding density variation occur, but the present invention does not cause such problems. Sticking can be prevented. In addition, the above-described protruding shape may be formed over the entire surface from the outer diameter end to the inner diameter end, or a partly flat surface may be provided, and another part may be protruded. In this case, it is desirable that the plane portion is about 1/3 or less.

[0015]

According to the present invention, in a small toroidal ferrite core, sticking during firing can be prevented, and productivity can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view, partially in section, of an embodiment according to the present invention.

FIG. 2 is a partial sectional perspective view of another embodiment according to the present invention.

FIG. 3 is a perspective view of a conventional example.

FIG. 4 is a partial cross-sectional perspective view of a conventional example.

FIG. 5 is an explanatory diagram of one embodiment according to the present invention.

[Explanation of symbols]

 1,11 Toroidal ferrite core 2,12 Upper surface 3,13 Lower surface 14 Outer diameter 15 Inner diameter

Claims (5)

[Claims] 1. In a toroidal ferrite core having an outer diameter of 20 mm or less, the upper surface and the lower surface in a cross-sectional shape formed by an outer diameter portion, an inner diameter portion, an upper surface portion, and a lower surface portion are formed in an arc shape. A toroidal ferrite core characterized in that it has a shape to be formed. 2. The toroidal ferrite core according to claim 1, wherein a projection length of the arc-shaped projection is 1 mm or less. 3. A projection length of the arc-shaped projection is not more than 10% of a height of the core.
The toroidal ferrite core as described. 4. In a toroidal ferrite core having an outer diameter of 10 mm or less, an inner diameter portion is thicker than an outer diameter portion, and
A toroidal ferrite core having a difference of 1 mm or less. 5. The toroidal ferrite core according to claim 4, wherein the thickness change portion has a curvature.