JPH02284409A - 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] [Field of Industrial Application] The present invention relates to a rotary lance having a spiral conductor, a unit number of turns conductor, a short circuit conductor, or a circuit pattern conductor formed on the surface of sintered ferrite. , when manufacturing a green body by injection molding a mixture of sinterable ferrite powder and a binder, a conductive layer is inserted into the mold and a green body with spiral conductors and circuit patterns formed on the surface is formed. The present invention relates to a rotary transformer which is characterized in that it is then degreased and sintered, eliminates the coil forming and coil bonding steps, and is excellent in mass production.

[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.

The rotary transformer has a rotating part rotary core and a stationary part stator core, which are made of sintered ferrite and have an annular plate shape. As shown in FIGS. 7 and 8, these cores are provided with a plurality of concentric coil grooves 2 on the force side of the annular plate-shaped core 1, and these coil grooves 2 are arranged around the outer periphery of the core. A radial pull-out groove 3 is provided.

The rotary core and stator core configured in this way have coil grooves 7 and 8 as shown in a cross-sectional view in FIG.
The surfaces of the rotor core 4 and stator core 5, which are provided with , this end portion is pulled out through the pull-out groove 3 and connected to the electric circuit and magnetic head of the VTR.

Conventionally, in order to form a coil conductor in sintered ferrite,
A conductor with an annular plate-shaped core having multiple concentric coil grooves and an insulating film on the outer periphery, and a coil formed into a predetermined number of turns, is inserted into each port, and the coil is peeled off using adhesive. Measures are being taken to prevent this. However, when the sintered ferrite core is formed by powder pressing, especially 4-
In multi-channel types with 14-channel coils and short-circuit conductors, there are many variations in groove width and roundness, making it difficult to set coils of a constant size, and variations in magnetic circuit characteristics occur. There is. 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, complicated steps were still required, such as setting a prescribed coil and fixing it with adhesive.

Also, JP-A-63-244789 and JP-A-63-2
As described in Japanese Patent No. 44790, 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 that the invention sought to solve]

For example, JP-A-62-271406, JP-A-63-54707, and JP-A-63-1 disclose magnetic circuits and conductors formed on such a sintered ferrite core by a simplified method. Publication No. .331.0 and the like have been proposed. However, for methods such as embedding the coil in the groove of a sintered ferrite core or forming a conductive metal layer in the groove of the sintered ferrite core and further sintering, the ferrite core must be sintered in advance. There is a need,
Second, it requires many steps such as adhering the coil and applying conductive coating.

The inventors of the present invention have conducted extensive research into methods for obtaining rotary lances on which coil conductors or circuit pattern conductors are formed. It has been found that by devising the shape of the green body and the manufacturing method, it is possible to obtain a rotary 1 Herance in which the circuit formation process is omitted.

The present invention was made based on the findings described in section 2. In a rotary lance in which a coil conductor or a circuit pattern conductor is provided in a concentric groove portion, a conductive layer is insert-molded to form a conductive layer inside the groove. By molding, degreasing, and sintering a rotary transformer green body with a through hole penetrating in the thickness direction, it is possible to obtain a flat rotary transformer in which the process of forming a circuit pattern on the coil or its surrounding area is omitted. purpose.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a sintered ferrite 1-rotary 1-lance in which a coil conductor or a circuit pattern conductor is formed in a groove.
When obtaining a rotary transformer green body by injection molding a mixture of - and a binder, a conductive layer on which a coil conductor or a circuit pattern conductor is formed on a release paper is inserted into a mold, and grooves are inserted into the mold. This rotary transformer is characterized in that it is formed by molding a rotary transformer green body having a conductor layer formed therein and having through holes extending through the thickness thereof, and then degreasing and sintering the green body.

[Effect]

Since the sintered ferrite core on which the coil conductor according to the present invention is formed has the above-mentioned characteristics, the process of setting and bonding the coil in the groove of the ferrite core can be omitted, and it is excellent in mass production. .

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

〔Example〕

1 and 2 are a perspective view and a cross-sectional view showing an embodiment of a flat rotary transformer core in which a magnetic circuit and a conductor according to the present invention are formed.

Reference numeral 11 in the figure is a sintered ferrite core, which includes a conductive layer 12 forming a coil conductor on the bottom surface of the groove of the core, a coil conductor support layer 14 supporting the conductor layer in the center, and a through hole 13.
is formed. 1-1 and 1-3 are enlarged perspective views of the through hole 13, and the expanded conductor support layer is the place where the conductor layer for the central coil of the conductor layer of 2 tan or more is located. The conductor is drawn out through the through hole 13 by various methods. As an example of the drawing method, an enlarged sectional view is shown in FIG. 1(g) to FIG.
5 to the conductor layer and then pulling it out from the through hole, using conductive paste 16 to connect it to the conductor layer and pulling it out on both sides of the through hole, and opening a hole in the center of the end of the coil using a pull out pin 17. Method of pulling out from the through hole (the upper end of the pin is soldered to the end of the coil) and the conductive layer 1 of the present invention
8 is inserted into both sides of the through hole and pulled out from the through hole. When soldering to a conductor layer using these lead-out coils or pins, attach the coil or pin after sintering, and when using conductive paste, apply it to the green body and then degrease and sinter as described below to make it conductive again. When using layer inserter l~, the coil can be drawn out by inserting the conductor layer l~ during green body molding and performing degreasing and sintering as described later. To manufacture a sintered ferrite core having a coil conductor configured in this manner, a conductive layer pattern 19 on which a coil conductor 20 is formed on a release paper 21 shown in FIG. 3 is used. Here, the release paper 21 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 will be difficult to insert the mold into the mold.
If it exceeds 0 Pm, 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 110-200% by weight.
7z, preferably 115-150IL. If the silver content is less than 50% by weight, the DC resistance value will increase and the price will increase, causing problems. On the other hand, if it exceeds 80% by weight, the conductor will melt during degreasing and sintering, causing it to shift from the specified 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 Pm, it becomes difficult to form a conductor circuit pattern on the release paper. In addition, Fig. 4 shows the pattern A-A of Fig. 3.
'Shows a cross section. The conductive layer pattern 19 on which the conductor was formed in this way is placed on the protrusion inside the cavity of the injection mold shown in FIG. After closing the movable mold 23 and intermediate plate 22, a mixture of sinterable ferrite and binder is injection molded to form a coil conductor on the bottom of the groove, and a through hole is formed in the thickness direction. A rotary transgreen body is manufactured.

The sinterable ferrite powder used for injection molding of the green body is calcined ferrite powder of nickel-zinc type, magnesium-zinc type, or manganese-zinc type, and its average particle size is 0.1-200 μm. Can be used but 0.1-
150μm is preferable, especially 0.11-1O0p
Preferably. If the average diameter is less than 0.1 μm, uniform dispersion during kneading becomes difficult, the density after compaction decreases, and the magnetic properties and mechanical strength decrease.

Examples of binders used include styrene polymers, ethylene polymers, propylene polymers, ethylene-vinyl acetate copolymers, alkyl (carbon atoms of 6 or less) methacrylate-1- as the main component (50 (wt% or more) copolymers (e.g. polymethyl methacrylate 1~.polyethyl methacrylate), alkyl (carbon number 6 or less)
Copolymers containing acrylate-1 as the main component (50% by weight or more) (e.g., polymethyl acrylate-1, polyethyl acrylate-1, polybutyl acrylate). Vapor pressure osmosis method for these synthetic m-lipid binders. The number average molecular weight measured by
-300,000 is preferred. In order to mold a green body for the core using sinterable Ferrai 1 powder and a binder, first mix the Ferrite powder and the binder in a predetermined ratio (usually the binder is mixed with 100 parts by weight of Ferrai 1 powder). The mixture is melt-kneaded and formed into a pellet shape.

These pellets 1 to 1 are filled into an injection molding machine, melted, and injected into a mold. The melt is transferred to the first spool 25, the runner 26, the second
A mold forming the spool 27 is filled, and a conductive layer having a coil conductor or a circuit pattern conductor is inserted into the molded portion 28 of the rotary transformer green body by a pin gage 1 forming the tip of the second spool.

At this time, a pin 29 provided on the intermediate mold 22 forms a through hole penetrating in the thickness direction inside the groove of the green body. After cooling and solidifying, the intermediate mold 22 and the movable mold 23 are moved, and the rotary transformer green body with the coil conductor formed inside the groove remains in the movable mold, and is released by ejecting the ejection pin. . By peeling off the release paper 21 from the separated green body or degreasing and sintering with the release paper still present, a flat rotary transformer having a coil conductor or a circuit pattern conductor formed thereon can be obtained. Degreasing is carried out by raising the temperature of the atmosphere by 1" above room temperature until the binder and release paper are removed from the wood, but the atmosphere is air.

It may be carried out under vacuum or in an atmosphere of an inert gas such as argon or nitrogen. The maximum temperature for degreasing is usually 200
0C or higher, but the rate of rise is usually 1-1 per hour.
00°C (preferably 1-80°C).

Degreasing may also be carried out under pressure (up to 10 kg/cm2). Degreased rotary 1-lance is ferrai 1
- sintered according to methods practiced in the field of sintering. The sintering is carried out at a temperature in the range of 7001.200° C. in the air or in an atmosphere of an inert gas such as alcon or nitrogen. The degreasing and sintering steps may be performed continuously or in separate steps. Furthermore, the rotary 1~ on which coils and circuit patterns were formed, obtained in this way.
The lance can also be ground to improve surface accuracy.

The thickness of the rotary l-lance on which the coil conductor or circuit pattern conductor of the present invention is formed varies depending on the performance of the intended rotary transformer, but is usually 0.5-50 mm.
The diameter is 10-150 mm and the inner diameter is 3-
It is 50111111. The thickness of the coil conductor support layer at the center of the through hole is 0, 2-1, 0 n.
wn, and the size of the through hole is 0.5-5.0nn in diameter.
It is. The number of channels is 2-14, and an example of 14 channels is shown in FIG. 1-0. The conductor layer corresponding to each channel is drawn out according to the example shown in FIGS. 1-(g) to 1-(&). However, FIG. 10 shows an example in which short-circuit conductors are arranged at the 3rd, 6th, 8th, and 10th grooves from the inner diameter side.

〔Effect of the invention〕

As described above, since the rotary transformer according to the present invention on which the coil, short-circuit conductor, and circuit pattern are formed has the above-mentioned characteristics, 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, 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 compact and inexpensive to manufacture.

[Brief explanation of drawings]

1 and 2 show one embodiment of a rotary transformer according to the present invention, FIG. 1 (α) is a perspective view, and FIG. 2 is a vertical section taken along line A-A' in FIG. It is a diagram. FIG. 1(b) to FIG. 1(,7) are partially enlarged views of the through hole,
FIG. 1(I)) is a perspective view, FIG. 1(c) is a plan view, and FIG. 1(d) is a sectional view. Fig. 1(d) to Fig. 1(&) are partially enlarged views of the through hole showing the method of drawing out the conductor, and Fig. 1(g) shows the case where another drawing coil is used. f) shows the case where a conductive paste is used, FIG. 1 (>) shows the case where a pull-out pin is used, and FIG. 1 (1L) shows the case where the conductive layer pattern of the present invention is used. 3 and 4 show the conductive layer pattern formed on the release paper inserted into the mold, FIG. 3 is a perspective view, and FIG. 4 is a sectional view taken along the line A-A' in FIG. 3. It is. FIG. 5 is a vertical sectional view showing the positional relationship of the rotary transgreen body having a release paper and a conductive layer, the spool, and the runner, with the mold closed and FIG. 6 with the mold opened. FIG. 7 is a plan view of a conventional two-groove sintered ferrite core, and FIG. 8 is a longitudinal sectional view showing an example of a conventional rotary transformer. Further, FIG. 9 is a cross-sectional view showing an example of the rotary transformer of the present invention, and FIGS. 10 (cL) and (b) are a plan view and a cross-sectional view of a multi-channel type ferrite core according to the present invention. Figures 11 to 13 show another embodiment of the present invention in which a circuit pattern is formed on the core surface opposite to the coil surface and circuit elements are mounted on it, and Figure 11 shows the core surface. FIG. 12 is a plan view showing circuit elements mounted on the pattern of FIG. 11, and FIG. 13 is a side view thereof. 1...Sintered ferrite core, 2...Coil groove, 3...
- Pull-out groove, 4... Rotor core, 5... Stator core, 6... Gap, 7... Rotor coil groove, 8
...Stator coil groove, 9...Rotor coil, 1
0: Stator coil, 11: Rotary with integrated circuit 1 to lance, 12: Conductive layer, 13: Through hole, 14: Conductor layer support layer for coil, 15: Extraction coil, 16: Conductive paste Layer, 17...Drawer pin, 1
8... Lead-out conductive layer, 19... Conductive layer pattern, 20
... Conductive layer, 21 - Release paper, 22 ... Intermediate mold, 2
3... Moving mold, 24... Fixed mold, 25 ・First
Spool, 26... Runner, 27... Second spool, 28... Green body, 29... Pin pin for making through holes, 30... Rotary transformer with integrated rotor conductor, 31... ...Rotary transformer with integrated stator conductor, 32...Rotor conductor,
33... Stator conductor, 34... Inductance element, 35... Integrated circuit, 36... Chip type resistor element, 37... Chip type capacitor, 38... Chip type diode. No. 70 (α) Yu / Ward 87 Ryo (d) Taku / Usuko / Ki / 2 Takul Bacteria No. 50 A40 Akira Ryo 8 Usu

Claims (4)

[Claims] 1. In a method of insert molding a conductive layer on which a spiral conductor, unit number of turns conductor, short-circuit conductor, or circuit pattern conductor is formed, after the conductive layer is set in a mold, a mixture of sinterable ferrite and a binder is A rotary transformer characterized by injection molding, molding a rotary transformer green body with through holes extending through the thickness, and then degreasing and sintering the body. 2. 2. The rotary transformer according to claim 1, wherein the conductive layer is formed with a release paper interposed therebetween. 3. 3. The rotary transformer according to claim 1, wherein the conductive layer is made of a metal consisting of silver-palladium or silver-platinum. 4. A rotary magnetic head device using the rotary transformer according to any one of claims 1 to 3.