JP3358635B2 - Manufacturing method of flat type rotary transformer core - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary transformer installed in a rotary cylinder for recording and reproducing a magnetic tape of a VTR, and more particularly to a method of manufacturing a flat type rotary transformer core used for a rotary transformer. It is.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, a rotary transformer core of this kind is used in order to ensure the finished dimensions of the product shape shown in FIG. The sintered compact 3 obtained by sintering the powder compact formed by the powder press molding so as to have a thickness of about twice the thickness of the compact 3 is cut off by grinding to form the back surface on which the coil groove 1a and the lead groove 1b are formed.
The outer diameter and inner diameter were processed to obtain a flat or round rotary transformer core. However, when powder pressing was performed using the coil groove and the lead groove, the powder Non-uniform density occurs, and in the next step of sintering, uneven sintering of the sintered body occurs during sintering. After bonding, the back surface was ground thickly to obtain a rotary transformer core having the desired size.

[0003]

DISCLOSURE OF THE INVENTION The present invention relates to the deformation of swelling and warping in the surface direction of a sintered body due to uneven shrinkage that has occurred in the sintered body of a flat type rotary transformer core, and to the circumferential coil groove. In order to prevent the occurrence of irregular deformation of the diameter and the reduction of the yield of the finished product after sintering, and to obtain the outer diameter and inner diameter to satisfy the dimensional specifications of the product, the back surface has a large grinding allowance, the outer diameter and the inner diameter In order to eliminate the problems of increasing the manufacturing cost such as the need for grinding of the surface, it is necessary to reduce the grinding allowance and to obtain a method of manufacturing an inexpensive flat type rotary transformer core with good roundness and flatness. It is in.

[0004]

SUMMARY OF THE INVENTION In order to solve these problems, the present invention is directed to a method of manufacturing a rotary transformer core in order to improve the non-uniformity of green density, which is a cause of deformation of a sintered body. On the back surface on which the coil groove surface is formed, a dummy lead groove (dummy groove) is provided at an appropriate size at the time of compacting in a direction orthogonal to the lead groove formed on the coil groove surface, so that the dimension of the coil groove surface is increased. It is an object of the present invention to provide a method for manufacturing a rotary transformer core with improved dimensional accuracy by making the uniformity of the core.

That is, the present invention provides: A flat plate type provided with a plurality of circular coil grooves for arranging a plurality of circular coils on one surface of a flat part of a disc-shaped ferrite core and a lead groove for leading out the plurality of circular coils in a direction crossing the coil grooves. In the method for manufacturing a rotary transformer core, a dummy groove is provided in a direction perpendicular to the draw-out groove on the back surface of the surface on which the coil groove and the draw-out groove are provided at the time of compacting, and the dummy groove is sintered. This is a method for producing a flat rotary transformer core, which is characterized by grinding and removing.

[0006] 2. The dummy groove formed on the back surface of the coil groove and the drawing groove forming surface at right angles to the drawing groove has a groove width of 1 m.
m to 4 mm and groove depth from 0.45 mm to 1.8
2. The method for manufacturing a rotary transformer core according to the above item 1, wherein the diameter is mm.

[0007]

The both sides passing through the center of the disk of the rotary transformer core in the direction perpendicular to the drawing groove when forming the green compact on the mounting surface side of the coil groove and the circular coil formed with the drawing groove. By forming a dummy groove having an appropriate groove width and depth over the end, when the dummy groove does not exist, the warp deformation occurs so that the coil groove forming surface side becomes a convex surface. Reduce deformation. It is considered that the density of the green compact when the green compact having the dummy groove is compacted is increased along the surface where the dummy groove is formed by the mold entering the dummy groove portion, and the coil groove surface is increased. Since the dummy groove is formed perpendicular to the lead groove of the coil on the side, the deformation in the radial direction is made uniform, the roundness after sintering is improved, and the flatness is also improved. Note that the effect of the dummy groove is remarkably recognized even in the dummy groove having a width of 0.5 mm. However, the groove width may be reduced due to the risk of mold breakage due to the pressing force during compacting and durability due to abrasion. The minimum value may be as large as 1 mm, while the groove width of the dummy groove may be as large as 4 mm.

The depth of the dummy groove is determined by the size of the rotary transformer core, the coil groove depth, and the coil extraction groove depth. When the depth is less than 0.45 mm, the effect on warpage deformation (flatness) is obtained. Is small, but 0.45 mm to 1.8 mm has a large effect on warpage deformation. On the other hand, when the depth of the dummy groove is deep, the cutting allowance increases,
1.8 mm is sufficient.

[0009]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an example of a diagram showing a completed flat plate type rotary transformer core according to the present invention. The disk-shaped rotary transformer core 1 is provided with a plurality of coil grooves 1a concentrically on one surface and a lead groove 1b orthogonal to the coil grooves and extending from the center to the outer end face in the diameter direction. Rotary transformer cores vary in size, number of coil grooves, groove width, groove depth, and the like depending on the purpose of use. In this embodiment,
The outer diameter is 60 mm, the inner diameter is 14 mm, the thickness is 2.5 mm, the number of the coil grooves 1a is four, and the drawing groove 1b for drawing out the drawing wire of the circular coil housed in the coil groove is provided on the outer surface from the center direction. Was used.

The rotary transformer according to the present invention is a green compact formed by pressure-molding a soft magnetic material Ni-Zn ferrite powder into a shape as shown in FIG. On the back of the surface on which 1b was formed,
A sintered body 2 is prepared by sintering the compact of the present invention, in which a dummy groove 1c having a depth shallower than the grinding allowance is provided in a direction orthogonal to the extraction groove 1b for drawing out the coil end from the coil groove. The rotary transformer of the present invention is obtained by grinding off the formed surface side and finishing the product dimensions to a thickness of 2.5 mm.

In an embodiment, the depth of the dummy groove is set to 0 m.
m, 0.45 mm, 0.9 mm, 1.35 mm, 1.8
0mm, groove width 0.5mm to 5mm after sintering
In the range of 1 mm, 20 samples were prepared at 1 mm intervals under one condition, and the measurement was performed after grinding to a thickness of 2.5 mm. Using Ni-Zn-based ferrite with an initial relative magnetic permeability of 700, granulate powder having an average particle size of 0.5 μm, and press at 1.5 ton / cm ² for compaction. Get the body,
Sintered in air at 1100 ° C for 2 hours, thickness is about 5mm
Was obtained, and the back surface of the coil groove forming surface of the sintered body was ground to a thickness of 2.5 mm. In the typical groove width of the obtained sintered body, the roundness of the outer diameter and the inner diameter indicating the amount of deformation (difference between the maximum value and the minimum value from the true circle) and the warpage deformation (plate thickness) (The difference from the height from the surface plate when placed on the surface plate) was measured. The results are shown in Table 1 and FIG. 3. The dummy groove has a groove width of 2 mm and a groove depth of 0.45 mm, 0.9 mm.
FIG. 3 is a characteristic diagram showing a relationship between roundness and warpage when 0 mm, 1.35 mm, and 1.8 mm. However, the depth of the coil groove at this time is 0.90 mm, and the depth of the lead groove is 1.35 mm.

[0012]

[Table 1]

Particularly, the roundness of the inner diameter greatly depends on the change in the depth of the dummy groove. When the dummy groove width is 2 mm and the dummy groove depth is 0.45 mm, the inner diameter roundness is 0 mm. Also, the warp deformation shows a characteristic that the deviation becomes smaller in any groove width as compared with the conventional case where there is no dummy groove. When the groove width is 1 mm to 4 mm, the dummy groove depth is 0.9 mm to 1.35 mm. At the time of (1), the warpage deformation was 0.04 mm to 0.07 mm, which was 1/4 of the conventional manufacturing method without the dummy groove. Even when the width of the dummy groove not shown in Table 1 was 0.5 mm or 5 mm, a remarkable effect on the warpage was recognized. From the above results, by providing a dummy groove at the time of compacting on the back surface on which the coil groove and the lead groove according to the present invention are formed, the density distribution of the compact can be made uniform,
Therefore, the shrinkage of the sintered body after sintering can be made much more uniform than before.

The rotary transformer core 10 has a width of 2 mm and a depth of 0.90 mm in the embodiment.
As a result of manufacturing and finishing 00 products, the processing yield is
10% higher than before, and 67
%, And a rotary transformer core with good flatness and roundness can be provided with good yield. In addition, in the manufacturing method of the present invention, the size of the rotary transformer core is shown in the example in which a rotary transformer core having an outer diameter of 60 mm is used. It has been confirmed that the method can be applied, and for larger or smaller types, the groove width, depth, etc. of the dummy grooves may be appropriately selected so as to match the size of the rotary transformer core.

[0015]

As described above, according to the present invention,
Roundness is achieved by forming a dummy groove in the direction perpendicular to the extraction groove on the back surface where the coil groove and the extraction groove are formed at the time of compacting, and grinding and removing the dummy groove after sintering to form a rotary transformer core. It is possible to provide a flat type rotary transformer core with the advantage that the outer diameter and the inner diameter at the time of finish molding are small, the warpage is small, the dimensional accuracy is good, that is, the yield is good and the manufacturing can be performed at low cost. became.

[Brief description of the drawings]

FIG. 1 is a view showing a flat type rotary transformer core;
1 (a) is a plan view, and FIG. 1 (b) is an AA of FIG. 1 (a).
FIG. 1 (c) is a rear view.

2A and 2B are views showing the shape of the rotary transformer core of the present invention after sintering, FIG. 2A is a plan view, and FIG. 2B is a sectional view taken along line BB of FIG. 2A. In addition, the line GG indicates a surface on which the dummy groove 1c side is ground and removed. FIG. 2C is a rear view.

FIG. 3 is a characteristic diagram showing the relationship between the roundness of the outer diameter and the inner diameter and the amount of warpage deformation and the depth of the dummy groove when the dummy groove width of the rotary transformer core of the present invention is 2.0 mm.

4 (a) is a plan view showing a shape of a conventional rotary transformer core after sintering, and FIG. 4 (b) is a view showing FIG.
FIG. 4A is a cross-sectional view taken along the line CC, and FIG.

[Description of Signs] 1 Rotary transformer core 1a Coil groove 1b Lead-out groove 1c Dummy groove 2 Sintered body obtained by sintering compacted body of the present invention 3 Sintered body obtained by sintering conventional compacted body D Outer diameter Roundness E Inner diameter roundness F Warpage deformation

Claims (1)

(57) [Claims] 1. A flat ferrite core having a flat part on one side,
In a method for manufacturing a flat type rotary transformer core having a plurality of circular coil grooves for arranging a plurality of circular coils and a drawing groove for drawing out a drawing line of the plurality of circular coils in a direction intersecting with the coil grooves, a method of compacting powder is provided. A flat plate type rotary, wherein a dummy groove is arranged in a direction orthogonal to the extraction groove on the back surface of the surface on which the coil groove and the extraction groove are arranged, and the dummy groove is ground and removed after sintering. Method of manufacturing transformer core.