JPS59160821A - Manufacture of magnetic head - Google Patents

Abstract

PURPOSE:To eliminate the need to use a dummy block in chip cutting by working grooves in each core almost right angles to each gap surface and working grooves of proper depth almost right angles to said grooves, and thus forming projections. CONSTITUTION:Groove groups 5 and 11 are worked almost at right angles to gap surfaces 17 and 19 so that their groove bottom parts 34 and 35 connect front gap surfaces 17 and 19 and top core surfaces 36 and 37 together, and groove groups 8 and 14 are worked nearly at right angles to the gap surfaces 18 and 20 so that their groove bottom parts 38 and 39 connect back gap surfaces 18 and 20 and core bottom surfaces 40 and 41 together. Further, grooves 6, 9, 12, and 15 of proper depth are worked similarly on the gap surfaces 17, 19, 18, and 20 almost at right angles to those grooves 5, 10, 8, and 14, thus forming projection groups 7, 10, 13, and 16. Then, the core blocks 1 and 2 are opposed to each other to perform laser welding at the projectin parts and then perform wire saw cutting. Consequently, the core blocks 1 and 2 are cut straight and no cut surface zigzags.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of manufacturing a magnetic head used for audio, VTR, etc., using laser welding to join core blocks.

Conventional structure and its problems In recent years, with the advent of magnetic tapes with excellent magnetic properties such as metal tapes, magnetic heads made of metal magnetic materials with higher saturation magnetic flux density than ferrite materials have been developed. Magnetic heads are increasingly being used. The manufacturing method for magnetic heads made of ferrite materials is already an established technology, but in the case of metal magnetic materials, the bond between a pair of core blocks must be sufficiently strong with glass, as in the case of ferrite materials. It is not possible to perform the joining,
Recently, laser welding has begun to be used.

At that time, what should be fully considered is how to reduce the thermal residual stress in the weld, and if this is insufficient, for example, brittle materials such as sendust may cause cracks in the weld. Even if cranking does not occur in metallic magnetic materials that are highly tough or have a high degree of toughness, they still cause undesirable phenomena such as deterioration of gap length accuracy due to the influence of thermal residual stress.

Now, as shown in FIG. 1, a pair of core blocks 1.2 are butted against each other, and a laser beam 23.
Let us consider the case where laser welding is performed by irradiating 4. In this case, the weld generally has a diagonal shape,
When this part thermally contracts during the cooling process, the contraction is restrained by the surrounding base material and generates thermal residual stress, and near the interface between the molten part and the base material, the base material It is subjected to stress in the direction shown by . If the strength of the base metal and the strength of the welded part are insufficient, the area around the welded part cannot withstand this stress and cracks will occur. Alternatively, if the base metal strength and the strength of the welded part are sufficient, no crank will occur in the welded part, but the joint interface between the pair of core books 1 and 2 is exaggerated in Figure 3. As mentioned above, due to the bending moment caused by the stress mentioned above, the center part becomes wider and non-uniform.

In actual manufacturing of magnetic heads, this is undesirable as it leads to deterioration of gap length accuracy. Therefore, conventionally, in actual laser welding of magnetic hesode cores,
By forming protrusions on the core and welding the protrusions together, thermal residual stress is reduced.

That is, as shown in FIG. 4, when laser welding protrusions 7.1 whose cross-sectional area is approximately equal to the diameter of the laser beam 23 used for welding, the entire tip of the protrusion shown by diagonal lines is Since it becomes a molten part, this fused part is not constrained by the surroundings due to thermal contraction during the cooling process, so the occurrence of thermal stress is extremely small.

If laser welding is performed as described above, it is possible to perform welding with extremely low thermal residual stress, but in the conventional method of manufacturing a magnetic head, there have been various problems related to the method of forming the protrusions.

Hereinafter, the conventional manufacturing method and its problems will be explained in detail using Sendust's video head as an example.

In FIG. 6, 1 and 2 are a pair of sendust core blocks, each having a winding groove 3 and 4 and a front gear 21.
It has surfaces 17, 19 and gap surfaces 18, 20. As shown in the figure, these core blocks 1゜2 include:
A group of protrusions 7° 13 are formed by a group of grooves 6 and 11 cut across the upper surface of the core by a thin rotary blade, and by grooves 6 and 12 cut to intersect with them at approximately right angles. Similarly, on the bottom surface of the core where the protrusions 10 and 16 are formed, opposing protrusions 10 and 16 are formed. Note that each protrusion is processed to have a cross-sectional area that is approximately the same as the laser beam diameter, as described in the explanation of FIG. Specifically, the length of one side of the protrusion is usually 0
．． After forming a glass thin film as a magnetic spacer on each gap surface of such core blocks 1 and 2 by vapor deposition, a jig (not shown) is used to separate the core blocks 1 and 2 as shown in FIG. are held in a pressed state to form a front gap portion 27 and a locking gear portion 2B. Reference numerals 21 and 22 indicate a glass thin film 0, and laser beams 23 and 24'iz are irradiated onto the opposing protrusion groups 7 and 13 and 1c10 and 16 to perform laser welding. At this time, as explained with reference to FIG. 4, almost no thermal stress is generated in the welded part, so no cracks occur and the gears and protrusions do not spread.

In this way, after laser welding is performed on the protrusions on the top and bottom surfaces of the core block, the joined core block is cut at a position including the welded protrusions to form a chip. As mentioned above, the core blocks are joined by microscopic laser welding, so a wire with low cutting resistance is often used to cut the chips.The principle of cutting with a zero wire saw is shown in Figure 7. As shown in Fig. 3, a group of wires 29 with a diameter of around 200 μm arranged at a constant interval d are reciprocated in the longitudinal direction of the wires, and the contact area between the wires 29 and the sample 3o is ground with fine abrasive particles mixed therein. The sample is gradually raised in the direction of the arrow while supplying liquid, and cutting is performed using parallel grooves shown by broken lines. When cutting the laser-joined core blocks 1 and 2 using this wire saw, conventionally, the groove groups 5 and 8 degrees 11.14 and the protrusion welds solidify into a roughly spherical shape when melted. In order to prevent the cut surface from meandering due to the roundness of the welded part, dummy blocks 31 and 32 must be placed on both sides of the core blocks 1 and 2 as shown in Figure 8. If not placed, approximately 1M in the longitudinal direction of core blocks 1 and 2.
At the beginning of the cutting process, some of the wire groups 29 with a wire diameter of around 200 μm stretched at regular intervals in the front and back are guided to the groove groups 5° 11 with different arrangement intervals, and the intervals are disturbed, and during the cutting process. Near the end of the process, the wire is guided by sliding on the surface of the welded part with the rounded f: vertebral protrusion, so the spacing between the wires is also disturbed. As a result, in chip cutting without a dummy block, the thickness of the chip changes in the vicinity of the welds or protrusions at both ends, as shown in FIG. 9, for example. Therefore, in order to eliminate such inconvenience, dummy blocks are arranged as shown in Fig. 8, and the cutting grooves to be machined on the dummy blocks 31 and 32 are aligned with the wire 2.
By disposing the guide wires 9 at both ends of the core blocks 1 and 2, disturbances in the wire spacing are prevented.

Naturally, since cutting is performed with a dummy block in this way, the cutting efficiency is poor and there is a lot of wasted material.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a magnetic head that can eliminate the above-mentioned drawbacks and can be performed without using dummy blocks.

Structure of the Invention The present invention provides a method in which a groove is formed in each core so that the groove bottom is approximately perpendicular to each gap surface so that the groove bottom connects the bank gap surface and the core bottom surface, or connects the front gap surface and the core top surface.
Furthermore, protrusions are formed by machining grooves of appropriate depth that are approximately perpendicular to these grooves, thereby providing a method of manufacturing a magnetic head that does not require a dummy block when cutting chips. It is.

DESCRIPTION OF THE EMBODIMENTS FIG. 10 shows the shape of a core block in the first embodiment of the present invention, and the same reference numerals as those in FIG. 5 are given the same numbers. Figure 11 shows these core blocks 1 and 2.
2 shows a cross section at plane 33 across groove 5.11. 11th
As shown in the figure, the groove group 5.11 has its groove bottom 34.35
is the front gap surface 17.19 and the core top surface 36.37
'(i: so that the grooves 8, 141d, and their groove bottoms 38.39 connect the bank gap surface 18.20 and the core bottom surface 40° 41, and are approximately perpendicular to each gap surface. In the case of Fig. 1, grooves 6, 9, 12, and 15 of appropriate depth are formed to intersect these grooves at approximately right angles 9 and are parallel to the gap surfaces 17, 19, 18° 20. Processed in the same manner as above, protrusion groups 7, 10, 13
, 16 are formed. Thereafter, the core blocks 1 and 2 are faced to each other, and the protrusions are laser welded, and then wire cutting is performed. At this time, since there are no grooves on the upper surfaces of the core blocks 1 and 2 as in the conventional case, the wire group 29 stretched at a constant interval can be stretched while maintaining the interval, as shown in Fig. 12. Cut the tops of core blocks 1 and 2. After that, the wire starts to come into contact with the rounded surface of the welded part of the protrusion whose height has become somewhat lower during welding, when the wire is cut to a depth of about 200 μm, which is approximately equal to the wire diameter. However, at this time, the wire is already guided on both sides of the protrusion weld by the grooves that have been cut and are spaced at intervals equal to the wire spacing;
In addition, the wire guide grooves are much closer together than when using a conventional dummy block, so the wire that comes into contact with the rounded surface of the weld will not slip on that surface and will move through the core block 1. .2 can be cut straight, and the cut surface will not meander.

Note that the chip obtained with the front gap end and back gap end welded in this manner is attached to the unit base 42 as shown in FIG. After this, the welded portion at the end of the front gap is removed by grinding with a lapping tape, and the tape sliding surface 43 is polished to form a magnetic heel tip.

In addition, in this embodiment, the front gap end,
Laser welding was performed at both ends of the pack gap to join the pair of core blocks, but other suitable joining means were applied to one end, and laser welding was performed at either the end of the back gap or the end of the front gap. Of course, it is also possible to perform either one of them. In that case, it is of course only necessary to form it at the end of the gap surface where laser welding is performed.

Effects of the Invention As is clear from the above explanation, the F3AK of the present invention does not require a dummy block when cutting core block chips, improving cutting efficiency, and since the materials are much closer together than before, the cut surface The flatness of the plate is also greatly improved. To give concrete numerical values, in the above example, in the actual manufacturing process, it is possible to shorten the cutting time from 4 hours to 2 hours, and the flatness of the cut surface can be reduced from about 10 μm to 5 μm.
It improved to about m. In this way, the present invention has significant effects as a method of manufacturing a magnetic head.

[Brief explanation of the drawings] A diagram showing the spread of the interface due to thermal residual stress in core block welding, Figure 4 is an illustration of protrusion welding, Figure 5 is a diagram of the conventional core shape, and Figure 6 Figure 6 shows the state in which the core of Figure 6 is being laser welded. Figure 7 is an explanatory diagram of the wire saw. FIG. 8 is a diagram showing a state in which a conventional core is cut with a wire saw, FIG. 9 is a diagram showing a chip cut from a conventional core without a dummy block, and FIG. 10 is a diagram showing a method of manufacturing a magnetic head according to an embodiment of the present invention. Diagram showing the shape of the core,
FIG. 11 is a sectional view of the core shown in FIG. 10, FIG. 12 is a diagram of the core shown in FIG. 10 being cut with a wire saw after laser welding, and FIG. 13 is a front view of the chip according to the embodiment of the present invention. FIG. 6 is a state diagram in which the laser welded portion at the end of the gap is removed and a tape sliding surface is formed. 1.2...-core block, 5, 6, 8, 9, 1
1. 12.14.15... Groove, 7, 10, 13.1
6... Protrusion, 23.24... Laser beam. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 26 301 \26 Figure 5 Figure 7 Figure 9 Figure 1O

Claims (2)

[Claims] (1) After making a pair of core blocks face each other to form a front gap portion and a pack gap portion, and laser welding at least one of the front gap end portion or the pack gap end portion, this , in each core, create a groove approximately perpendicular to each gap surface so that the groove bottom connects the bank gap surface and the core bottom surface, or connects the front gap surface and the core top surface, and is approximately equal to the laser beam diameter. These grooves formed on each core face each other in a predetermined facing state of each core, and intersect with the grooves at approximately right angles and have a gap between them. By machining a groove of an appropriate depth approximately parallel to the surface, a protrusion formed by this groove and the aforementioned groove is provided on each core, and the groove formed in this way is formed on each core. A method of manufacturing a magnetic head in which opposing projections are laser welded and the chip is cut so that the welded part is included in the chip. (2) The method for manufacturing a magnetic head according to claim 1, wherein the core block material is a metal magnetic material.