JPH03220704A - Rotary transformer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a coil conductor such as a spiral conductor, a unit turns conductor, a short-circuit conductor, etc. made of a ceramic superelectric medium, or a coil conductor made of a ceramic superconductor, or a coil conductor such as a It relates to a rotary transformer on which a pattern conductor is formed,
When manufacturing a green body by injection molding a mixture of sinterable ferrite powder and a binder, a conductive layer made of a ceramic superconductor is inserted into the mold, and a spiral conductor or circuit pattern is formed on the surface. It is characterized in that it is formed by molding a green body, then degreasing and sintering.The coil molding and coil bonding processes are omitted, the circuit characteristics are greatly improved, and mass production is excellent. The present invention relates to a rotary transformer including a peripheral circuit in which circuit elements are directly mounted.

[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. Rotary transformers are also used as means for power transmission.

The rotary transformer has a rotating part rotor core and a stationary part stator core made of sintered ferrite and having an annular plate shape. In these cores, as shown in Fig. I4, a plurality of concentric coil grooves 2 are provided on one surface of an annular plate-shaped core l, and a plurality of concentric coil grooves 2 are provided in the coil grooves 2 to connect these with the outer periphery of the core. A diametrical arching groove 3 is provided.

As shown in the cross section of FIG. 15, the rotor core and stator core configured in this manner have a surface area of 10 to 703 μm on the surfaces of the rotor core 4 and stator core 5 provided with coil grooves 7 and 8, respectively. They are placed facing each other with a gap G between them. Each coil groove 7 and 8 has a rotor coil 9 with a predetermined number of turns. A stator coil 1o is wound and disposed, and its end portion is pulled out through a pull-out groove 3 and connected to the electric circuit and magnetic head of the VTR.

Conventionally, in order to arrange a coil conductor on sintered ferrite,
An annular plate-shaped core with multiple concentric coil grooves is set with a coil formed into a predetermined number of turns, which is a conductor with an insulating film on the outer periphery, in each groove, and adhesive is used to prevent the coil from falling off. The method is being used. However, when the sintered ferrite core is formed by powder pressing, especially
~In multi-channel types that use 14-channel coils or short-circuited conductors, there are many variations in groove width and roundness, making it difficult to set a coil of a constant size, and there are also variations in magnetic circuit characteristics. It has occurred. In order to improve these points, for example, grooves are added in post-processing using a diamond grinding wheel, etc., but this complicates the core manufacturing process and causes problems such as chipping. There was a point.

In order to deal with this point, the present inventors proposed a method of manufacturing a sintered ferrite core by injection molding method in Japanese Patent Application No. 63
It was proposed as No.-13571.

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 setting a coil formed with a predetermined number of turns in a groove and fixing it with adhesive. .

Also, JP-A-63-244789 and JP-A-63-2
As described in Japanese Patent No. 44790, although this is not a rotary transformer field, a method has been proposed in which a conductor pattern is formed on the surface by injection molding or pressure molding, and is deposited or transferred onto the surface. These are not applied to magnetic materials.

In addition, Japanese Patent Application Laid-open No. 64-31404, Japanese Patent Application Laid-open No. 62
-188303 and Japanese Patent Application Laid-open No. 159408/1983 disclose a technology using a rotary transformer core made of a mixture of ferrite and resin by injection molding, but these do not require degreasing of the green body. Since the magnetic material was used without being used, there was a problem with the performance of the magnetic material.

[Problem to be solved by the invention]

For forming a magnetic circuit and a conductor in such a sintered ferrite core by a simplified method, for example, Japanese Patent Application Laid-Open No. 62-2714.06 and Japanese Patent Application Laid-Open No. 63-5470
No. 7, Japanese Patent Application Laid-open No. 13310/1983, and the like have been proposed. However, methods such as embedding a printed coil in the groove of a sintered ferrite core in a later process, or forming a conductive metal layer in the groove of a sintered ferrite core and then sintering it, do not sinter the ferrite core in advance. This requires many steps such as gluing printed coils and applying conductive coating to the coils.

Therefore, in order to obtain a rotary transformer on which a coil conductor or a circuit pattern conductor is formed, the present inventors have developed a method of insert molding a conductive layer when injection molding a mixture of sinterable ferrite and a binder. proposed that the circuit formation process could be omitted. However, since the ferrite magnetic layer is filled between the conductors of the conductive layer used, there is a problem that the coupling coefficient as a rotary transformer decreases and the transmission efficiency decreases. In addition, when a circuit pattern is formed to mount an electric circuit on the surface of a rotary transformer, the conductor is in close contact with the magnetic material, and if the conductor is buried in the magnetic material, the circuit pattern may be distorted in the length direction. There was a problem that an inductance component was added. In addition to these problems, when the conductive layer is made of silver-palladium or silver-platinum, it has a high direct current resistance value, which varies depending on the conditions of the peripheral circuit to which it is connected, but is caused by this conductor resistance. The insertion loss was relatively large and the characteristics deteriorated.

The present invention has been made to solve the above problems, and its objects are to omit the step of forming a circuit pattern in the coil or its surrounding area, to prevent the coupling coefficient from decreasing, and to eliminate the need for a circuit pattern. An object of the present invention is to obtain a flat plate type rotary transformer in which a circuit can be mounted which does not easily have an inductance component and whose characteristics do not deteriorate due to heat generation.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a sintered ferrite rotary transformer in which a coil conductor or a circuit pattern conductor is formed in the groove or on the surface thereof, by injection molding a mixture of sintered ferrite and a binder. When obtaining a transgreen body, the conductor layer to be insert-molded is made of a ceramic superconductor and a nonmagnetic insulating layer is provided between the conductor layers, or a nonmagnetic insulator is provided between the conductor layer and magnetic ferrite. These are formed on release paper and inserted into a mold to form a rotary transgreen body with a conductor layer formed inside the groove or on the surface, which is then degreased and sintered. It is configured as a rotary transformer obtained by

[Effect]

In the sintered ferrite core on which the coil conductor according to the present invention is formed, the conductor layer is formed of a ceramic superconductor, so there is no reduction in the coupling coefficient and the transmission efficiency as a rotary lance. In particular, the transmission loss caused by the direct current resistance of the conductor is reduced, and the process of setting and gluing coils for circuit formation can be omitted, making it excellent in mass production.

Furthermore, since a circuit pattern can be formed on the ferrite surface, other circuit elements (for example, resistors, capacitors, inductors, etc.) can be directly mounted. Furthermore, since the circuit pattern conductor can be formed apart from the magnetic ferrite material, it is possible to form a pattern that is less likely to contain an inductance component.

〔Example〕

1 to 4 show first and second embodiments of a flat rotary transformer core in which a magnetic circuit according to the present invention is formed, and FIG. 1 is a perspective view of the first embodiment. , FIG. 2 is a perspective view of the second embodiment, and FIGS. 3 and 4 are sectional views taken along lines AA' and BB' in FIGS. 1 and 2, respectively.

In each figure, reference numeral 11 denotes a sintered ferrite core, a coil conductor layer 12 is provided on one side of the core 11, and an insulating layer 13 is provided between the coil conductor layers 12. In the first embodiment, the conductor layer 12 and the insulating layer 13 for the coil are placed in the groove formed in the sintered ferrite core l↓, and in the second embodiment, the conductor layer 12 and the insulating layer 3 are placed in the groove formed in the sintered ferrite core l↓. They are each formed flush with the surface of the ferrite core 11. Further, the coil conductors 12 are connected to the outside by using the through holes 4 in the first embodiment, and by the lead-out conductive layer 15 in the second embodiment.

In order to manufacture the sintered ferrite core 11 having the coil conductor layer 12 configured in this way, for example, as shown in FIG. Use what was given.

The release paper 19 is a plastic film such as polypropylene having a thickness of 10 to 300 ILm, or paper surface-treated with silicone or the like.

The conductor layer 12 is screen printed, spray printed, or spray coated using a paste made of a ceramic superconductor. , l@i layer 13 is essentially made of siliceous material, and is similarly formed by screen printing, spray printing, or spray coating after the conductor 512 is printed. Here, release paper 1
If the thickness of 9 is less than 15 μm, it becomes difficult to insert into a mold, while if it exceeds 300 μm, it becomes difficult to control the thickness of the green body.

The ceramic superconductor forming the conductor layer 12 is A-
It is a perovskite type compound consisting of B-CuO system,
A represents a group MA metal element such as La, Ce, Y, Yb, and Sc; B represents an alkaline earth metal element such as Sr and Ba; compounds, sulfides.

It is a mixture of compound powders such as carbonates and bromides, the above-mentioned compound powders of alkaline earth metal elements, and copper oxide powder, and is mixed and kneaded onto a paste using a resin such as acrylic resin or epoxy resin. The thickness of the conductor layer 12 is 0 to 200 μm, preferably 15 to 150 μm. If the thickness of the conductor layer 12 is less than 10 pm, the circuit will break, which is undesirable. On the other hand, if the thickness exceeds 200 Itm, it will be difficult to form a circuit on the release paper 19.

6 and 7 are cross-sectional views showing different embodiments taken along line c-c' in FIG. is the conductor 71
This is to prevent the magnetic layer from entering between the layers 12 and 12, and may be the same or thicker than the conductor layer 12, or may cover the entire conductor layer 12. . This non-magnetic insulating layer 3 is a glassy insulating layer consisting essentially of silica, and contains alumina, lithium oxide, lead oxide, boron oxide, and alkaline earth metal oxides. Good too.

The release paper 19 with the non-magnetic insulating layer 13 provided between the conductor layers 12 in this way is placed inside the cavity of the injection mold shown in FIG. 8 so that the conductor M12 faces the fixed side metal 22. Insert and move the mold 20. After closing the intermediate mold 2↓, the rotary transgreen body 26 on which the coil conductor layer 12 and the like are formed is manufactured by injection molding a mixture of sinterable ferrite and a binder.

In the figure, 23 indicates a first spool, 24 indicates a runner, and 25 indicates a second spool.

The sinterable ferrite powder used to injection mold the green body 26 is calcined ferrite powder of nickel-zinc type, magnesium-zinc type, or manganese-zinc type, and its average grain size is 0.1 to 200 μm. can be used, but 0
．． 1 to 150 ILm is preferable, especially 0.1 to 150 ILm.
100 pm is preferred. In addition, the average diameter is 0.
If it is less than 1 μm, uniform dispersion during kneading becomes difficult;
The density after sintering decreases, and the magnetic property 2 mechanical strength decreases.

Examples of binders used include styrene polymers, ethylene polymers, propylene polymers, ethylene-vinyl acetate copolymers, alkynes (with a carbon number of 6 or less), and methacrylate-1 as a main component (50% by weight). % or more) (e.g. Pohe＼ riftyl methacrylate-1~, polyethyl methacrylate-1-), alkyl (carbon number 6 or less) acrylate as the main component (50% or more) copolymers (e.g. polymethyl methacrylate, polyethyl methacrylate,
Polybutyl acrylate-1-) is mentioned. The number average molecular weight of these synthetic resin binders measured by vapor pressure osmosis is preferably from 2,000 to 500,000, particularly preferably from 4,000 to 300,000.

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,
Form into pellets. The pellets are melted and injected into a mold by an injection device of an injection molding machine. The melt is the first
Spool 23. Runner 24. Via the second spool 25, the release paper 19 on which the coil conductor layer 12 (or circuit pattern conductor) is formed is inserted into the cavity (the molded part of the green body 26) from the pin gate 1- at the tip of the second spool. It is press-fitted and filled.

After the molten material is cooled and solidified, when the intermediate mold 21 and the movable mold 20 are moved, the rotary transformer green body 26 having a coil with an insulating layer 13 provided between the conductor layers on the surface or inside the groove moves. It remains in the mold 20 and is then released from the mold by ejecting a known ejection pin (not shown). Release paper 1 is removed from this separated green body 26.
After peeling 9, degreasing and sintering are performed to obtain a flat rotary transformer in which a coil in which an insulating layer 13 is provided between conductive layers 12 is formed.

Degreasing is carried out by raising the temperature of the atmosphere above room temperature until the binder is essentially gone, 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 to 100°C (preferably 1 to 80°C) per hour. Degreasing may also be carried out under atmospheric pressure (maximum 10 kg/cJ). The degreased rotary transformer is sintered according to methods practiced in the field of ferrite sintering. Sintering is done in the atmosphere.
or under an inert gas atmosphere such as argon or nitrogen
It is carried out in the range of 0-1200°C. In addition, the above degreasing,
The sintering process 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 on which the coil conductor or circuit pattern conductor of the present invention is formed is the same as that of the intended rotary 1
~It varies depending on the performance of the lance, but usually 0.5 to 50
In mm, the diameter is 10-150 mm, and the inner diameter is 3-50 mm.

FIG. 9 shows rotaries 1 to 1 manufactured by the method described above.
It is a sectional view showing l lances, and the rotor core 27 and the stator core 28, which are arranged opposite to each other with a predetermined gap G, each have a rotor coil conductor layer 12-A.
Also, a stator coil conductor layer work 2-B is arranged.

The number of channels is 2 to 14, and FIG. 10 shows an example of 9 channels. The conductor layer 12 corresponding to each channel is drawn out through the through hole 14 or the lead-out conductor layer 5 .

In addition, in the above-mentioned embodiment, an example was shown in which the rotor coil and the stator coil were embedded in the sintered ferrite core 11, but as shown in FIGS. 11 to 13,
Circuit pattern conductors 12' may be formed on release paper 19 at predetermined intervals using a similar method and buried on the side opposite to the coil installation surface of the core. An inductance element 31 is placed on the ferrite core 11'. Integrated circuit 32. Chip type resistance element 33° Chip type capacitor 34. It becomes possible to directly mount the chip type diode 35 and the like.

〔Effect of the invention〕

As described above, since the rotary transformer on which the coil conductor and circuit pattern according to the present invention are formed has the above characteristics, the conductor can be formed in the manufacturing process of the sintered ferrite core, and the coil conductor can be formed in the process of manufacturing the sintered ferrite core. In addition to omitting the insertion and gluing steps, cold, L7, −
1c By using a cooling device that uses liquid nitrogen or the like as a cooling medium, there is no decrease in the coupling coefficient, and in terms of transmission characteristics, the occupancy ratio of the coil conductor to the groove is very high, so the coupling coefficient is high, and the direct current resistance of the conductor is low. Stable products with significantly less loss due to rotary transformers can be manufactured compactly and inexpensively by incorporating amplifiers and switching circuits, and are suitable for high-bandwidth use because the circuit pattern attached to the outside of the rotary transformer is less likely to contain inductance components. It has many advantages such as being suitable for

[Brief explanation of drawings]

FIGS. 1 to 4 show the first part of the rotary transformer according to the present invention. A second embodiment is shown, and FIG. 1 is a perspective view of the first embodiment,
Figure 2 is a perspective view of the second embodiment, Figure 3 is A-A in Figure 1.
Figure 4 is a cross-sectional view taken along the line B-B' in Figure 2. Figures 5 to 7 are diagrams showing the conductive layer pattern formed on the release paper inserted into the mold. , FIG. 5 is a perspective view thereof, FIGS. 6 and 7 are sectional views showing different embodiments along the line c-c' in FIG. 5, and FIG. 8 is a mold ``'']
Fig. 9 is a sectional view showing an example of the rotary transformer according to the present invention, and Fig. 10 is a plan view showing the rotary 1 to lance compatible with 9 channels according to the present invention. , FIGS. 11 to 13 relate to the third embodiment of the present invention,
Fig. 11 is an explanatory diagram showing the shape of the circuit pattern conductor that is closely attached to the core side, Fig. 12 is a plan view showing the mounted components, Fig. 13 is a side view of the sintered ferrite core, Fig. 14, and FIG. 15 relates to a conventional example, FIG. 4 is a plan view of a ferrite core, and FIG. 15 is a sectional view of a rotary transformer. 1... Sintered ferrite core, 2... Coil groove, 3... Pull-out groove, 4...
・Rotor core, 5...Stator core, G...
・Gap, 7, 8...Coil groove, 9...Rotor coil, 10...Stator coil, 11.11'...Sintered ferrite core, 12...
Conductor layer for coil, 12'... Conductor layer for circuit pattern, ) 13... Insulating layer, 14... Through hole, 15...-
drawer part conductive layer, 19... release paper, 20... moving mold, 21...
...Intermediate mold, 22...Fixed mold, 23...
First spool, 24... Runner 25... Second spool, 26... Green body, 27... Rotor core, 28... Stator core, 31... Inductance element, 32... Integration Circuit, 33... Chip type resistance element, 34... Chip type capacitor 35... Chip type diode. 2nd bar 6th bar ≦ 5th Akira

Claims (5)

[Claims] 1. A coil medium or a circuit pattern medium and a nonmagnetic insulating layer are inserted into injection molding of a mixture of sinterable ferrite and a binder to obtain a green body on which a conductive layer is adhered. A rotary transformer obtained by degreasing and sintering a rotary transformer, wherein the conductor layer is formed using a ceramic superconductor. 2. 2. The rotary transformer according to claim 1, further comprising a nonmagnetic insulating layer made of vitreous material essentially consisting of silica and provided between the conductor layers and/or around the conductor layers. 3. 3. The rotary transformer according to claim 1, wherein the conductive layer and the insulating layer are formed on a release paper and are subjected to insert injection molding. 4. 4. The rotary transformer according to claim 1, wherein the rotary transformer is used in a rotating magnetic head device. 5. 4. The rotary transformer according to claim 1, wherein the rotary transformer is used in a power transmission device.