JPS6356602B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an erasing head used in a magnetic recording/reproducing device that has excellent erasing characteristics even for high coercivity recording media.

Ferrite erasing heads, which are currently widely used due to their excellent core loss characteristics, wear resistance, and productivity, are suitable for high-retention recording media such as metal powder tapes, which are being put into practical use for high-density recording. On the other hand, since the saturation magnetic flux density (B _s ) of the core is low, the erase characteristics are insufficient.

In order to solve this problem, there is an erasing head shown in FIG. 1 in which only the core portion facing the recording medium is made of sendust material and the remaining portion is made of ferrite. In FIG. 1, 1 is a head cap, 2 is a sendust core, 3 is a ferrite core, 4 is an excitation ferrite core, and 5 is a head winding. However, in such an erasing head, the gap portion sendust core and ferrite core must be made using techniques such as adhesive bonding, which poses many production difficulties. Furthermore, with this method, it is not possible to sufficiently reduce the cross-sectional area of the sendust core portion perpendicular to the magnetic path. Eddy current losses at high frequencies such as cancellation signals are significant;
Core heat generation occurs. Furthermore, sendust material is softer than ferrite, and such a structure is unfavorable from the standpoint of head wear.

In order to eliminate these technical drawbacks, a head was proposed in which a thin film of sendust or the like having a high _Bs was formed on both sides of the gap of a ferrite core, as shown in FIG. However, in this case,
Since high B _s films are placed on both sides of the gap, the magnetic flux concentrates only in this area, resulting in a steep magnetic field distribution, which is not desirable as an erase head.
In Figure 2, the reference numbers 1 to 5 are
The same numbers and the same parts in the figure are shown, and 6 is the sendust film.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an erasing head which does not have these disadvantages and is highly efficient and has excellent erasing properties, wear resistance and productivity.

In order to achieve the above object, the erase head according to the present invention has a magnetic head in which a pair of cores made of metal oxide magnetic material are butted against each other to form an operating gap. The gist is to have a magnetic film with high magnetic permeability at saturation magnetic flux density.

That is, in the present invention, if one of the pair of cores forming the gap is made of a material with a sufficiently high B _s and the other is made of a material with a relatively small B _s , the magnetic flux is dispersed and a large magnetic field is spread over a wide range. This is based on the knowledge of the present inventors that it is possible to obtain satisfactory erasing characteristics by forming an opaque film. Sendust etc. can be used as a material with high B _s .

The present invention will be explained in more detail below using examples with reference to the accompanying drawings, but these are merely illustrative, and it goes without saying that various modifications and improvements may be made without going beyond the scope of the present invention. It is.

FIG. 3 shows a perspective view of an erasing head in one embodiment of the invention. In this embodiment, the cores of the excitation part and the gap part are vertically butted against each other to form a closed magnetic path. In the figure, 9 and 9' are front cores, 10 is an excitation core, and 11 is a winding. Each core is MnZn sintered ferrite and B _s
It is 400 Gauss. The gap butting surface of the core is mirror polished. 8 is front core 9
A magnetic film such as sendust film is uniformly formed on the mirror-finished surface and core recess by sputtering method.
In this embodiment, Sendust with a coercive force (H _c ) of 0.5 Oersted and B _s of 8000 Gauss is used.
The cross section perpendicular to the magnetic flux of the thin film core formed to a thickness of 10 μm has a structure in which the cross-sectional area when cut at the end point of the ferrite core decreases toward the gap joint surface, and during this time the magnetic flux is narrowed and the density increases. was confirmed to have sufficient properties for the purpose of the present invention. Further, the bond between the sendust film and the ferrite was sufficient both magnetically and physically. The length of the head gap 7 is 20 μm.

FIG. 4 is a perspective view of an erasing head in another embodiment of the invention. In this embodiment, the sendust film is sputtered only on the head gap abutting surfaces. This erase head has the same magnetic flux throttling effect and almost the same erase performance as the erase head shown in Figure 3, but since there is no sendust core film in the recess, the glass conventionally used in ferrite is used in the recess. It is possible to adopt a gap forming technique in which the gap is poured into the gap.

These erase heads according to the present invention differ from conventional erase heads in manufacturing only in that a thin sendust film is attached to the surface of the substrate used.
Therefore, since the sendust film does not have the difficulty of processing like the conventional sendust core bulk, the conventional ferrite processing process can be used as is, and the productivity is almost the same as that in the ferrite head processing process. It's still the same. Furthermore, satisfactory performance can be obtained even if other oxide magnetic materials are used for the substrate. Regarding the head structure,
The structure shown in FIGS. 3 and 4 is not necessarily required, and the present invention can also be applied to a case where a closed magnetic circuit is formed using only two cores.

4.75 cm/s using the erasing head according to the invention
The erasing characteristics of an 80 Hz, 250 pwb/mm signal recorded on metal tape (H _c = 980 Oersted) at a tape speed of
55 dB to -60 dB, which was 5 to 15 dB better than the conventional erase head (the erase head shown in Figs. 1 and 2).Also, there was almost no heat generation in the core.The erase head according to the present invention The superiority of the erasing characteristics is thought to be due to the large spread of H in the same magnetic field, and therefore the large number of cycles of the erasing magnetic field that is applied to one point on the tape during erasing, and the experimental results also support this idea. Therefore, the erasing head according to the present invention is effective for high S/N recording and reproducing apparatuses that use high _Hc tapes such as metal tapes.

[Brief explanation of the drawing]

1 and 2 are perspective views of a conventional erasing head, and FIGS. 3 and 4 are perspective views of an erasing head according to the present invention. 7...Head gap, 8...Magnetic film, 9,
9'...Front core, 10...Exciting core, 11
...Winding, 13...C-shaped core.

Claims (1)

[Claims] 1. In an erasing head in which a pair of cores made of metal oxide magnetic material are butted against each other to form an operating gap, a magnetic film with high saturation magnetic flux density and high magnetic permeability is provided on at least the gap surface on one core side. ,
An erasing head characterized in that the gap depth regulating surface formed by the film is configured to face the head sliding surface and obliquely intersect with the gap surface.