Coil-embedded dust core production process, and coil-embedded dust core

• US 20010016977A1
• Filed: 01/05/2001
• Published: 08/30/2001
• Est. Priority Date: 01/12/2000
• Status: Active Grant

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: Chou, Tsutomu, Suzuki, Tsuneo, Moro, Hideharu, Tamura, Jyunetsu, Sato, Sadaki
• Granted Patent: US 6,759,935 B2
• Time in Patent Office: Days
• US Class Current: 29/606
• CPC Class Codes: B22F 7/08 with one or more parts not made from powder B22F7/062 takes precedence
• CPC Class Codes: H01F 2017/046 helical coil made of flat wire, e.g. with smaller extension of wire cross section in the direction of the longitudinal axis
• CPC Class Codes: H01F 41/005 Impregnating or encapsulating insulating of windings H01F41/12
• CPC Class Codes: H01F 41/0246 Manufacturing of magnetic circuits by moulding or by pressing powder magnetic cores made by moulding or by pressing powder H01F27/255; soft magnetic particles H01F1/20, H01F1/36
• CPC Class Codes: Y10T 29/4902 Electromagnet, transformer or inductor
• CPC Class Codes: Y10T 29/49071 by winding or coiling
• CPC Class Codes: Y10T 29/49073 by assembling coil and core
• CPC Class Codes: Y10T 29/5313 Means to assemble electrical device

Abstract

The invention provides a process for producing a coil-embedded dust core by embedding a coil in magnetic powders comprising ferromagnetic metal particles coated with an insulating material. At the first compression molding step one portion of magnetic powders is filled in a molding die and then compression molded to form a lower core. At a coil positioning step the coil is positioned on the upper surface of the lower core in the molding die. At a coil embedding step another portion of magnetic powders is again filled in the molding die in such a way that the coil is embedded in these magnetic powders. At the second compression molding step pressure is applied to the lower core and coil in the direction of lamination thereof.

Claims

1. A process for producing a coil-embedded dust core by embedding a coil in magnetic powders comprising ferromagnetic metal particles coated with an insulating material, which includes:

a first compression molding step wherein one portion of magnetic powders is filled in a molding die and then compression molded to form a lower core,

a coil positioning step wherein said coil is positioned on an upper surface of said lower core in said molding die,

a coil embedding step wherein another portion of magnetic powders is again filled in said molding die in such a way that said coil is embedded in these magnetic powders, and

a second compression molding step wherein pressure is applied to said lower core and said coil in a direction of lamination thereof.

2. The coil-embedded dust core production process according to

claim 1

, which satisfies

1≦

P₂/P₁

where P₁ is a pressure applied at said first compression molding step and P₂ is a pressure applied at said second compression molding step.

3. The coil-embedded dust core production process according to

claim 1

, which satisfies

1<

P₂/P₁

where P₁ is a pressure applied at said first compression molding step and P₂ is a pressure applied at said second compression molding step.

4. The coil-embedded dust core production process according to

claim 1

, wherein:

said coil is a single-wound coil formed of a conductor wire of flat shape in section,

said conductor wire is wound in such a way that a major diameter direction of said flat section is perpendicular with respect to an axial direction of said coil,

said conductor wire is fixed at one end and another end with terminal electrodes, respectively, and

where said coil is positioned on the upper surface of said lower core, the terminal electrode located relatively near to said lower core is positioned on an upper surface of said conductor wire while the terminal electrode located relatively far away from said lower core is positioned on a lower surface of said conductor wire.

5. The coil-embedded dust core production process according to

claim 1

, wherein the upper surface of said lower core is provided with at least one protrusion that is located on an inner and/or outer periphery of said coil.

6. The coil-embedded dust core production process according to

claim 5

, wherein at least one of said protrusions, Ch≠

Dh/2, where Ch is a height of said protrusion, and Dh is a height of the coil-embedded dust core to be produced.

7. The coil-embedded dust core production process according to

claim 1

, wherein Bh≠

Dh/2, where Bh is a height of a surface of said lower core on which said coil is positioned, and Dh is a height of the coil-embedded dust core to be produced.

8. The coil-embedded dust core production process according to

claim 1

, wherein the ferromagnetic powders used comprises ferromagnetic metal particles where the number of ferromagnetic metal particles having a circularity of 0.5 or less as defined by the following equation (I) accounts for 20% or less of all ferromagnetic metal particles:

circularity=4π

S/L² 

 

(I)

where S is an area of a projected image of a particle, and L is a length of a profile of said projected image.

9. The coil-embedded dust core production process according to

claim 1

, wherein the ferromagnetic metal particles used are formed of an alloy composed primarily of Fe and Ni.

10. A coil-embedded dust core produced by the production process according to

claim 1

.