JPH10199730A - Inductance device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain inductance required even at the time of a large current by making small the reduction of inductance by a method wherein at least a part of a winding core portion of a drum core is coated with a material having higher saturation magnetic flux density than a magnetic body, and windings are applied thereon. SOLUTION: Ferrite is molded on a resinous base 15, and a drum core 11 to which windings 12 are applied is mounted, and a ring core 13 is disposed surrounding the drum core 11. A magnetic path is formed of the drum core 11 and ring core 13. And then a winding core portion of the drum core 11 is coated with the magnetic body 14. As for a material of this magnetic body 14, a material having a larger saturation magnetic flux density than ferrite forming the drum core 11 such as iron, permalloy, etc., is used. Further, even if the entire winding core is coated, it may be coated also partly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an inductance device, and more particularly to an improvement of a core of an inductance device suitable for use in a choke coil for a DC-DC converter.

[0002]

2. Description of the Related Art A choke coil used in a DC-DC converter or the like has a large inductance value when a flowing current is small, and a constant inductance value is obtained without saturation of a core when the current increases. It is desirable. The inductance value at the time of a large current may be smaller than the initial value.

FIG. 3 is a front sectional view of a conventional inductance device using a ferrite drum core and a ring core. A drum core 31 provided with a winding 32 by molding and firing ferrite on a resin base 35 is mounted, and a ring core 33 is arranged around the drum core 31. Thus, a magnetic path is formed by the drum core 31 and the ring core 33.

In order to increase the inductance value,
It is necessary to narrow the gap G1 between the drum core 31 and the ring core 33. However, when the gap G1 is narrowed, as shown by the curve 46 in FIG. 4, the core is saturated with an increase in the current, and the inductance is rapidly reduced. When the gap G1 is increased, the curve 47 in FIG.
Sufficient inductance cannot be obtained from the beginning.
In any case, they will be out of the use area indicated by hatching in FIG.

[0005]

SUMMARY OF THE INVENTION The present invention seeks to obtain an inductance device which does not easily saturate even when a large current flows. The required inductance can be obtained even at a large current by reducing the decrease in inductance. An inductance device is provided.

[0006]

According to the present invention, a magnetic material having a high saturation magnetic flux density is added to a magnetic material core.
This is to solve the above problem.

That is, in an inductance device in which magnetic cores are arranged at intervals around a magnetic drum core, at least a part of the core of the drum core is covered with a material having a higher saturation magnetic flux density than the magnetic material. , In which a winding is applied thereon.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A part or the whole of a core portion of a wire of a drum core made of a magnetic material such as ferrite is covered with a magnetic material having better saturation characteristics than a material of a drum core such as iron or permalloy. The wire is wound on it. Even if the winding core of the core such as ferrite is saturated, the magnetic material such as iron or permalloy still remains in a non-saturated state, whereby a predetermined inductance value is obtained.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a front sectional view showing an embodiment of the present invention. It has basically the same structure as the above-mentioned conventional inductance device. Drum core 11 with ferrite molded on resin base 15 and wound 32
A ring core 13 is arranged around 11. Thus, a magnetic path is formed by the drum core 11 and the ring core 13.

In the inductance device according to the present invention, the core of the drum core 11 is covered with the magnetic material 14. As a material of the ferromagnetic body 14, a material having a higher saturation magnetic flux density than ferrite forming the drum core 11, such as iron or permalloy, is used.

The characteristics of the inductance device in which the winding core is covered with the magnetic material as described above will be described with reference to FIG.
At the time of a small current, the same high inductance value as the conventional one can be obtained. As the current increases, the inductance value changes, as shown by curve 28 in FIG. However, as compared to the change of the conventional inductance device indicated by the curve 26 shown by the broken line in FIG. It is possible to limit the decrease in the inductance value in a range that falls within the use range 29 indicated by hatching in FIG.

As described above, any material having a higher saturation magnetic flux density than the material of the core may be used for the magnetic material covering the core of the core. A band-shaped magnetic material may be wound around a winding core, or a U-shaped core may be fitted. Further, the winding core may be entirely covered or only a part thereof may be covered.

[0014]

According to the present invention, it is possible to prevent a decrease in inductance due to core saturation even at a large current, and it is suitable for a choke coil for a DC-DC converter which can be used with a wide range of current values. An inductance device is obtained.

Further, since the magnetic material is merely added to the winding core, the number of manufacturing steps is slightly increased, and the increase in the manufacturing cost can be minimized.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of characteristics of an inductance device according to the present invention.

FIG. 3 is a front sectional view showing an example of a conventional inductance device.

FIG. 4 is a diagram illustrating characteristics of a conventional inductance device.

[Explanation of symbols]

 11, 31: Drum core 12, 22: Winding 13, 33: Ring core 14: Magnetic material (high flux saturation density material)

Claims (4)

[Claims] 1. An inductance device in which a magnetic core is arranged around a magnetic drum core at an interval.
An inductance device, wherein at least a part of a core portion of a drum core is covered with a material having a higher saturation magnetic flux density than the magnetic material, and a winding is applied thereon. 2. An inductance device in which a magnetic core forming a magnetic path is disposed close to a flange of a magnetic drum core, wherein at least a part of a winding core of the drum core has a saturation magnetic flux density lower than that of the magnetic material. An inductance device characterized by being covered with a high material and being wound thereon. 3. An inductance device in which a ferrite magnetic core is arranged at intervals around a ferrite magnetic drum core, wherein at least a part of the core of the drum core is made of a material having a higher saturation magnetic flux density than the ferrite magnetic material. An inductance device characterized by being covered with a wire and being wound thereon. 4. An inductance device having a magnetic core forming a magnetic path close to a core for winding a wire, wherein at least a part of the core of the core for winding the wire has a saturation flux higher than that of the magnetic material. Covered with dense material,
An inductance device having a winding wound thereon.