JPH02110908A - Manufacture of toroidal coil - Google Patents

Abstract

PURPOSE:To manufacture the title toroidal coil at a low price in large quantities, and to obtain the manufacturing process having the accurate number of turns of winding and small fluctuations in the value of inductance by a method wherein a helical groove is formed on the outer circumferential surface of a ring-shaped ferrite element when a molding operation is conducted, and after a conductive film has been provided on the entire outer circumferential surface of said ferrite element, the conductive film on the region other than the helical groove is removed. CONSTITUTION:A helical groove 2 is formed on the outer circumferential surface of a ring- shaped ferrite element 1 when a molding operation is conducted, a conductive film 3 is provided on allover the outer circumference of said ferrite element 1, the conductive film 3 is removed from the region other than the helical groove 2, and a ringshaped core is formed. For example, the above-mentioned conductive film 3 is formed by providing non-electrolytic plating using the conductive material such as Ag, Ni, Cu and the like. Also, the conductive film 3 is removed by polishing the upper and the lower surfaces and the outer and the inner circumference of the ferrite element 1, or by conducting a barrel polishing operation. When the inductance of the toroidal coil is increased, the ferrite element is enlarged, or the width of the groove 2 is reduced, and the number of turns of winding is increased. Also, when the inductance is reduced, the above-mentioned procedures are conducted reversely.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a toroidal coil.

<Conventional technology> A conventional toroidal coil is constructed by using a ring-shaped element made of a magnetic material such as ferrite as a magnetic core, and winding a copper wire or the like around this magnetic core to obtain a completely closed magnetic circuit. Therefore, it has a large inductance value.

<Problems to be Solved by the Invention> By the way, when manually winding copper wire around the outer periphery of a ring-shaped element, the process is performed one by one, resulting in extremely poor work efficiency (and a significant increase in costs). There's a problem.

In addition, although it is not impossible to automatically wind copper wire using a machine, it is difficult to automatically wind a small ring-shaped element, and the element may crack. It is difficult to produce, and the automatic winding machine itself is also very expensive.

Furthermore, another method is to print the conductive material directly on the ferrite element, but it is very difficult to print the inside of the ring and it is impossible to mass produce it.

An object of the present invention is to provide a method for manufacturing a toroidal coil that can be manufactured inexpensively and in large quantities, has an accurate number of turns, and has small variations in inductance value, in order to solve the above-mentioned problems.

Means for Solving the Problems> In order to solve the above problems, the present invention forms a spiral groove on the outer peripheral surface of a ring-shaped ferrite element during molding, and coats the entire outer peripheral surface of the ferrite element with a conductive film. After that, the conductive film other than the spiral groove is removed to form a ring-shaped core.

Effect> When molding a ring-shaped ferrite element, a spiral groove is formed on the outer circumferential surface of the ferrite element, a conductive film is applied to the entire outer circumferential surface of the ferrite element by means of plating, etc., and then the inner circumference, outer circumference, upper and lower surfaces of the ferrite element are coated. The excess conductive film adhering to the part protruding from the spiral groove is removed to complete the ring-shaped toroidal coil.

<Example> Hereinafter, an example of the present invention will be described based on the accompanying drawings.

FIGS. 1 and 2 show a ring-shaped ferrite element 1, on which a spiral groove 2 is simultaneously formed on its outer peripheral surface during molding.

The ring-shaped ferrite element 1 is molded using a molding machine, a powder molding machine, etc., and is formed by forming a spiral groove 2.
A straight groove 2a provided on the outer peripheral surface, a straight groove 2b provided on the inner peripheral surface, and an inclined groove 2c spirally connecting the outer peripheral surface groove 2a and the inner peripheral surface groove 2b on the upper and lower surfaces. , 2d, and a starting point 2e and an ending point 2f of a spiral groove 2 are provided on one surface of the ring-shaped ferrite element 1.

The starting point 2e and the ending point 2f become lead-out portions when a toroidal coil is formed, and may be provided on any of the upper and lower surfaces, the outer circumferential surface, and the inner circumferential surface of the ferrite element 1.

As described above, the ferrite element 1 in which the spiral groove 2 is formed is fired at a temperature of 900 to 1400°C.

Next, a conductive film 3 is applied to the entire outer peripheral surface of the baked ferrite element 1 as shown in FIGS. 3 and 4.

The conductive film 3 is formed by electroless plating using a conductive material such as Ag, Ni, or Cu.

The ferrite element 1 whose entire outer peripheral surface is covered with a conductive film 3 is
Since it will not become a toroidal coil as it is, the conductive film 3 on the part of the outer peripheral surface of the ferrite element 1 that protrudes from the groove 2
remove.

The conductive film 3 can be removed by polishing or barrel polishing the upper and lower surfaces, outer circumference, and inner circumference of the ferrite element l. When the ferrite element 1 is exposed, the conductive film 3 remaining in the groove 2 becomes spiral and serves as a winding, completing a toroidal coil.

In addition, in the toroidal coil, if you want to make the inductance thicker, make the ferrite element thicker, or make the width of groove 2 smaller (and increase the number of windings, or if you want to make the inductance smaller, You can do the opposite.

In addition, the electroless plating that forms the conductive film 3 is usually 2 to 4 μm.
Since the conductive film 3 in the groove 2 is electrolytically plated on top of the conductive film 3 to increase the thickness of the conductive portion 3, the permissible current can be increased.

<Effects of the Invention> As described above, according to the present invention, a spiral groove is formed on the outer periphery of a ring-shaped ferrite element, a conductive film is applied to the entire outer peripheral surface of the ferrite element, and then the conductive film other than the spiral groove is formed. Since this is removed, toroidal coils with an accurate number of turns and small variations in inductance can be mass-produced at low cost.

In addition, since the conductive film does not protrude from the ferrite element, it is less susceptible to damage than those wrapped with copper wire, and since the conductor is drawn out on a part of the ferrite element, surface mounting is also possible. .

[Brief explanation of the drawings] Fig. 1 is a plan view of the ferrite element, Fig. 2 is the same (side view), Fig. 3 is a plan view of the ferrite element with a conductive film applied to the entire outer peripheral surface, Fig. 4 is the same A side view, FIG. 5 is a plan view in which the upper and lower surfaces, outer periphery, and inner periphery of the ferrite element shown in FIG. 3 are polished, and FIG. 6 is the same (plan view). Groove 2a. 2b... Straight groove portion C... Slanted groove portion 3... Conductive film

Claims (1)

[Claims] A spiral groove is formed on the outer peripheral surface of a ring-shaped ferrite element during molding, a conductive film is applied to the entire outer peripheral surface of this ferrite element, and then the conductive film other than the spiral groove is removed to form a ring-shaped core. A method for manufacturing a toroidal coil characterized by the following.