JPH02284408A - Rotary transformer - Google Patents

Abstract

PURPOSE:To simplify the manufacturing process of a rotary transformer by contriving the shape and manufacturing method of the green body of the transformer at the time of injection molding a mixture of a sinterable ferrite and binder. CONSTITUTION:The green body of this rotary transformer formed with a conductor 14 for coil is manufactured when a mixture of a sinterable ferrite and binder is injection molded after a conductive layer pattern 13 in which the conductor 14 is formed on a releasable paper 15 is inserted into the cavity 22 of metallic molds for injection molding, with the conductive layer being faced to a fixed side metallic mold 18 end a mobile metallic mold 16 and intermediate plate 17 are closed. When the green body thus manufactured is degreased and sintered after the paper 15 is released, a flat plate type rotary transformer formed with the conductor for coil or a circuit pattern is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a rotary transformer in which a spiral conductor or a conductor for a circuit pattern is formed on the surface of sintered ferrite. When manufacturing a green body by injection molding a mixture with a binder, a conductive layer is injected into a mold, a rotary transgelin body with spiral conductors and circuit patterns formed on the surface is formed, and then degreased and baked. It is characterized by being tied together, and the coil forming and coil bonding processes are omitted.
Regarding the manufacturing method of rotary transformers that are excellent in mass production.
Ru.

[Conventional technology]

A rotary drum device of a rotary head type VTR uses a rotary transformer as a means for transmitting electric signals between a rotating part and a stationary part. A rotary transformer generally has a rotating part rotary core and a stationary part stator core in the shape of an annular plate made of sintered ferrite. These cores are annular plate-shaped cores 1 as shown in FIGS. 7 and 8.
A plurality of concentric coil grooves 2fJ'' are provided on one surface of the rotary core, and a radial pull-out groove 3 is provided in the coil groove 2 to connect these coil grooves to the outer periphery of the core. The rotor core 4 has coil grooves 7 and 8 as shown in the cross-sectional view of FIG. A rotor coil 9 and a stator coil 10 having a predetermined number of turns are wound around the grooves 7 and 8, and the ends thereof are drawn out through the lead-out groove 3 and connected to the electric circuit of the VTI and the magnetic head.

Conventionally, in order to form a coil conductor in sintered ferrite,
A method in which a coil is formed by forming a conductor with an insulating film on the outer periphery into a predetermined number of turns on an annular plate-shaped core having multiple concentric coil grooves, and is set in each port, and adhesive is used to prevent the coil from peeling off. is being carried out. However, when a sintered ferrite core is formed by powder pressing, there are many variations in groove diameter and roundness, especially in 4-7 channel coils and multi-channel types with short-circuit conductors. It was difficult to set the magnetic circuit, and variations occurred in the magnetic circuit characteristics. In order to improve this problem, for example, all grooves are added in post-processing using a diamond grinding wheel, but this complicates the core manufacturing process and causes problems such as chips. . The present inventors also proposed a method of manufacturing a sintered ferrite core by injection molding. In this case, the dimensional accuracy of the core was excellent, but in order to form a magnetic circuit, a complicated process was still required, such as placing a predetermined coil and fixing it with adhesive.

Also, JP-A No. 63-244789 and JP-A No. 63-244
As described in No. 790, a method of forming a conductive pattern on the surface by injection molding or pressure molding has been proposed, but there are performance problems in the case of magnetic materials.

[Problem to be solved by the invention]

As a method for forming a magnetic circuit in such a sintered ferrite core by a simplified method, for example, Japanese Patent Application Laid-Open No. 62-2
No. 71406, JP-A-63-54707 and JP-A-63
-13310 etc. have been proposed. However, by embedding the printed coil in the groove of the sintered ferrite core,
Many methods, such as forming a conductive metal layer in the grooves of a sintered ferrite core and sintering it, require that the ferrite core be sintered in advance, and then a printed coil is glued on top of it or a conductive coating is applied. process.

The inventors of the present invention have conducted extensive research into methods for obtaining rotary transformers on which coil conductors or circuit pattern conductors have been formed, and have found that when injection molding a mixture of sinterable ferrite and a binder, the shape of the rotary transformer green body and It has been found that by devising the manufacturing method, the step of forming the conductor can be omitted.

The present invention has been made based on the above knowledge, and on the facing side of a rotary transformer, a green body is formed with a coil conductor regardless of the shape of the groove portion, and is degreased and sintered to form a coil. To provide a flat plate type rotary transformer in which the step of forming a circuit pattern on the periphery of the transformer is omitted. In a method for manufacturing a sintered ferrite core having a surface formed with Insert a conductive layer on which the conductor is formed on the surface of the ferrite core, and use a rotary transformer green body in which the conductor surface and the ferrite surface are the same or the ferrite surface is slightly convex. The method of manufacturing a rotary transformer is characterized by molding, degreasing, and sintering.

[Effect]

Since the sintered ferrite core on which the coil conductor according to the present invention is formed has the above manufacturing method, the step of bonding the coil into the groove of the ferrite core can be omitted, and it is excellent in mass production. .

Furthermore, since a circuit pattern is formed on the ferrite surface, other circuit elements (for example, resistors, capacitors, inductors, etc.) can be directly mounted.

〔Example〕

FIGS. 1 and 2 are a perspective view and a cross-sectional view showing an embodiment of a flat rotary transformer core in which a coil conductor according to the present invention is formed. Reference numeral 11 in the figure is a sintered ferrite core, and the ferrite surface is on the same plane as the conductive layer 12 forming the coil conductor. To manufacture a sintered ferrite core having a coil conductor configured as described above, a coil conductor 1 is placed on a release paper 15 shown in FIG.
A conductive layer pattern 13 formed with four conductive layer patterns is used.

Here, the release paper 15 is a plastic film such as polypropylene having a thickness of 10 to 300 μm, or paper surface-treated with silicon, etc., and the conductive layer is screen printed using a paste made of silver-palladium or silver-platinum. It is.

If the thickness of the release paper is less than 15 μm, it becomes difficult to insert it into a mold, while if it exceeds 600 μm, it becomes difficult to control the thickness of the green body. The content of silver in the conductive layer is 50-80% by weight, preferably 50-70%
% by weight, and the thickness of the conductor is 10200 μm, preferably 15-150 μm. If the silver content is less than 50% by weight, the resistance value will increase and the price will increase, creating a problem. On the other hand, if it exceeds 80% by weight, the conductor will melt during degreasing and sintering, causing deviation from the predetermined position. Further, if the thickness of the conductor is less than 10 μm, the direct current resistance becomes large, which is undesirable. On the other hand, if it exceeds 200 μm, it becomes difficult to form the conductor on the release paper. Further, FIG. 4 shows a cross section of the baton along the line AA', and FIG. 5 shows a cross section along the line B-B'.

FIG. 5, which is a BB' cross section of the pattern, is an enlarged sectional view of a portion corresponding to the lead-out groove, and 141 is a conductive layer corresponding to a concentric coil, and 14-2 is a lead-out coil. It is a conductive layer.

Further, 23 is an insulating layer made of glass, and 24 is a conductive layer for connecting the conductive layers 14-1.

The conductive pattern 13 with the conductor formed in this manner is inserted into the cavity 22 of the injection mold shown in FIG. 6 with the conductive layer facing the stationary mold 18, and then inserted into the movable mold 16. After closing the intermediate plate 17, a rotary transgreen body in which a coil conductor is formed is manufactured by injection molding a mixture of sinterable ferrite and a binder. The sinterable ferrite powder used for injection molding of the green body is calcined ferrite powder of nickel-zinc type, magnesilum-zinc type, or manganese-zinc type, and the average particle size can be 0.1-200 μm. is preferably 0.1-150 μm, particularly 0.1-1
00 μm is suitable. If the average diameter is less than 0.1 μm, uniform dispersion during kneading becomes difficult, the density after sintering decreases, and the magnetic properties 9 and mechanical strength decrease.

Examples of binders used include styrene polymers, ethylene polymers, propylene polymers, ethylene-vinyl acetate copolymers, and alkyl (carbon atoms of 6 or less) methacrylate as the main component (50% by weight or more). ) (e.g. polymethyl methacrylate, polyethyl methacrylate), copolymers whose main component is alkyl (6 or less carbon atoms) acrylate (50% by weight or more) (
Examples include polymethyl acrylate, polyethyl acrylate, polybutyl acrylate).

The number average molecular weight of these synthetic resin binders measured by vapor pressure osmosis is 2000-500,000, especially 4000-500,000.
300,000 is preferable. To mold a core green body using the above sinterable ferrite powder and binder, first mix the ferrite powder and binder in a predetermined ratio (usually 5 to 40 parts by weight of binder to 100 parts by weight of ferrite powder). Melt and knead and form into a pellet. The pellets are filled into an injection molding machine, melted, and injected into a mold. The melt is transferred to the first spool 19. Runner 20. Second spool 21
A conductive layer having a conductor for a coil or a conductor for a circuit pattern is press-fitted into the molded portion 22 of the rotary transformer green body through a pin gate forming the tip of the second spool. Cool and solidify,
When the intermediate mold 17 and the movable mold 16 are moved, the rotary transformer green body, on which the coil conductor and circuit pattern are formed, remains in the movable mold and is released from the mold by the oil used to eject the ejector pins. By peeling off the release paper 13 from the separated green body and then degreasing and sintering it, a flat plate rotary transformer on which a coil conductor or circuit pattern conductor is formed is obtained.

Degreasing is carried out by raising the temperature of the atmosphere above room temperature until the binder essentially disappears, but it may also be carried out in the atmosphere, under vacuum, or in an atmosphere of an inert gas such as argon or nitrogen. The maximum temperature for degreasing is usually 200°C or higher, but the rate of increase is usually 1-100°C (preferably 1-80°C) per hour.

Degreasing may also be carried out under pressure (maximum 10V).

The degreased rotary transformer is sintered according to methods practiced in the field of ferrite sintering. Sintering is carried out in the air or in an inert gas atmosphere such as argon or nitrogen at a temperature in the range of 700-1200°C. The above degreasing and sintering steps may be performed continuously or in separate steps. Furthermore, the rotary transformer obtained in this way, on which a coil or circuit pattern is formed, can be ground to improve its surface precision. The thickness of the rotary transformer in which the coil and circuit turns of the present invention are formed varies depending on the intended performance of the rotary transformer.
Usually Q, 5-50m, diameter io-60mm, inner diameter 3-25B. The number of channels is 2-11, and FIG. 10 shows an example of 9 channels. The conductor layer corresponding to each channel is drawn out at the end using an insulating layer as shown in FIG. However, each lead-out conductive layer is omitted.

〔effect〕

As described above, since the low retransformer according to the present invention on which the coil, short-circuit conductor, and circuit pattern are formed is manufactured by the above-described manufacturing method, it is possible to form the conductor in the manufacturing process of the sintered ferrite core. This eliminates the process of inserting the coil and gluing it together, and in terms of transmission characteristics, the occupation ratio of the coil conductor to the groove is extremely high, making it possible to create a stable product with little transmission loss, even if it is equipped with an amplifier or switching circuit. It has many advantages such as being small and inexpensive to manufacture.

[Brief explanation of drawings]

1 and 2 show one embodiment of a rotary transformer according to the present invention, with FIG. 1 being a perspective view and FIG. 2 being a longitudinal sectional view of FIG. 1. 6 and 5 show the conductive layer pattern formed on the release paper inserted into the mold, FIG. 6 is a perspective view, and FIG. 4 is a sectional view taken along the line A-A' in FIG. 6. , Figure 5 is the third
It is a sectional view taken along the line BB' in the figure. Figure 6 shows the rotary transgreen body and spool with release paper and conductive layer with the mold closed. FIG. 3 is a longitudinal cross-sectional view showing the positional relationship of runners. FIG. 7 is a plan view of a conventional two-groove sintered ferrite core. FIG. 8 is a longitudinal sectional view showing an example of a conventional rotary transformer. FIG. 9 is a longitudinal sectional view showing an example of a rotary transformer according to the present invention. FIG. 10 is a plan view of a multi-channel type ferrite core according to the present invention. 11 to 16 show another embodiment of the present invention in which elements are mounted on the side opposite to the coil surface, FIG. 11 is a plan view showing a circuit pattern diagram on the core surface, and FIG. 12 11 is a plan view showing circuit elements mounted on the pattern shown in FIG. 11, and FIG. 13 is a side view thereof. 1: Sintered ferrite core 2: Coil groove 6: Pull-out groove 4: Rotor core 5 Ni stake-core 6: Gap 7: Rotor coil groove 8 Ni cheater coil groove 9: Rotor coil 10 Ni cheater coil 11: Coil conductor or integral Rotary transformer 12: conductive layer circuit 13: conductive layer pattern 14: conductive layer 14-1: coil part conductive layer 14-2: drawer part conductive layer 15: release paper 16: moving mold 17: intermediate mold 18 : Fixed mold 19: First spool 20: Runner 21: Second spool 22 integral body 26: Insulating layer 24: Conductive layer connecting the coil parts 25: Rotrans with integrated conductor for rotor 26: For stator RO transformer with integrated conductor 61: Inductance element 32: Integrated circuit 36: Chip type resistance element 64: Chip type capacitor Figure 2

Claims (3)

[Claims] 1. When injection molding a mixture of sinterable ferrite and binder, a spiral conductor, a unit number of turns conductor,
A rotary transformer characterized in that a conductive layer on which a short-circuit conductor or a circuit pattern conductor is formed is inserted, a rotary transformer green body with the conductor formed on the surface is formed, and then degreased and sintered. 2. 2. The method for manufacturing a rotary transformer according to claim 1, wherein the conductive layer is made of a metal consisting of silver-palladium or silver-platinum. 3. A rotating magnetic head device using the rotary transformer according to claims 1 and 2 above.