Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1997-06-11
2001-01-09
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603210, C029S603120, C360S125020
Reexamination Certificate
active
06170150
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing a magnetic head for a magnetic recording and playback device with which it is possible to record with high density, for example, a video tape recorder (VTR) an da digital audio tape recorder (R-DAT) and so on.
2. Description of the Prior Art
For example, in order to record with high density, it is necessary to make track patterns recorded on magnetic recording medial small. As a method for it, there is the so-called guard bandless recording method in which recording takes place without providing a guard band.
However, as there is no guard band between tracks in the guard bandless recording method, so-called adjacent cross talk which is caused when a magnetic head traces (playbacks) a signal of an adjacent recording track.
Referring to a magnetic head loaded into a home VTR, as shown in
FIG. 2
, this magnetic head is usually used for both recording and playback, thus, head width (width of a gap) HW of a playback head is formed larger than a recording track pitch in order to ensure compatibility of playback.
Therefore, in case of playback of a recording pattern without a guard band by the magnetic head loaded to the home VTR, an overlap portion G
1
of the magnetic gap occurs picks up a signal of a recording track TB adjacent a track TA and the adjacent cross talk is caused.
In a conventional magnetic head, in playing back of an azimuth recorded signal in case of, for example, the home digital VTR, obtained error rates varied from − one figure to + figure even if the playback C/N had been fixed, and the magnetic recording and playback device such as the home digital VTR to which the magnetic head was loaded at the lower limit of variation had to be designed.
Further, the conventional magnetic head had a problem that it was not possible to obtain the error rate enough to play back due to shortage of C/N in recording for a long time that, for example, standard tape feeding speed of the home VTR was two third of usual speed and video tape playback time was 1.5 times of usual time.
On the other hand, it is known that as a track pitch which is a pitch of a pattern recorded on a magnetic tape with high density recording, effect of the adjacent cross talk is larger and it causes degradation of S/N and the error rate.
Therefore, in order to control the effect of adjacent cross talk in playback of in the conventional magnetic head, it is considered that an angle of a track width adjusting groove is formed vertical to a surface opposite to a magnetic gap.
However, the magnetic head having the form is not preferable in point of recording and playback because a cross section of a magnetic core in the neighborhood of a magnetic gap.
Further, in a conventional method for producing the magnetic head, projections for forming the magnetic gap of a pair of magnetic core half bodies are not perfectly matched to both ends, and displacement of the ends of the projections for forming the magnetic gap of a pair of magnetic core half bodies occurs. Though it is known that this displace causes the adjacent cross talk, it is not clear that relation between the displacement and the adjacent cross talk.
Therefore, by forming, for example, the angle of the track width adjusting groove large, that is to say, the V-type groove of a large angle, it is considered to match to the both ends of the projection for forming the magnetic gap of a pair of magnetic core half bodies as perfectly as possible.
However, when making the angle of the track width adjusting groove large, the method for producing the conventional magnetic head had a problem that process yield was remarkably degradated to match the magnetic gap only at the edge of the track width adjusting groove.
The present invention was proposed considering the conventional technical problem and an object of the present invention is provide a magnetic head producing method for producing a magnetic head that is possible to control effect of adjacent cross talk less with the good process yield.
SUMMARY OF THE INVENTION
The inventors of the present invention studied in earnest for solving the foregoing problem, and as a result, found that it is possible to control the effect of adjacent cross talk by adjusting the amount of displacement and a direction of track width of a magnetic gap and a method for producing a magnetic head to make the amount of displacement and the direction of the track width of the magnetic gap fixed.
That is to say, though the inventors of the present invention obtained the results of the experiment, as shown in
FIGS. 5 and 6
, we examined the results of the experiment in detail and determined that is possible to realize the following action and effect.
First, in cases where displacement of the magnetic gap occurs, there are two cases. One of them, as shown in
FIG. 4
, is where the direction of the central line F caused by displacement of ends of projections for the magnetic gap of a pair of magnetic core half bodies is nearly in the direction of the azimuth angle of a recording track TA and an adjacent recording track TB, and the other, as shown in
FIG. 3
, is where the direction of the central line F caused by displacement of ends of projections for the magnetic gap of a pair of magnetic core half bodies is far from the direction of the azimuth angle of the recording track TA and the adjacent recording track TB.
The problem of the relation between the direction F of the bisector of an opening angle
0
by displacement G
1
of the magnetic gap g and an angle of azimuth recording of the adjacent recording track, in the case of
FIG. 3
, “displacement of the magnetic gap in the positive direction,” and in the case of
FIG. 4
, “displacement of the magnetic gap in the negative direction,” is described next.
At the part G
2
that head width (width of the gap) HW of a playback head is to the recording track TB, a signal of the track TA found by the normal magnetic gap is picked up, and a signal of the adjacent recording track TB is not picked up in order to scan the so-called reverse azimuth.
Examining the effect of the adjacent cross talk in both cases, in case of the displacement of the magnetic gap in the positive direction, as shown in
FIG. 5
, it is understood that the effect of the adjacent cross talk is small.
On the other hand, in case of the displacement of the magnetic gap in the negative direction, as shown in
FIG. 6
, it is understood that the effect of the adjacent cross talk is large.
Here, FIG.
5
and
FIG. 6
are characteristic graph views showing how error rates are changed by the adjacent cross talk when the displacement of the magnetic gap occur. Further, FIG.
5
and
FIG. 6
show when the azimuth angles of the magnetic head are +20 degree and −20 degree. Plots (vertical lines) as shown in FIG.
5
and
FIG. 6
are results measured by whether there was the effect of the adjacent cross talk or not. The lower part of the vertical lines are the plots of the parts where there was no cross talk effect and the upper parts of the vertical lines are the plots of the parts where there was the effect of cross talk. Therefore, the shorter the length of the vertical lines is, the less the effect of the cross talk.
In adjacent pattern components picked up by the normal magnetic gap g, high frequency parts are controlled by azimuth loss, however, in the adjacent pattern by the displacement of the magnetic gap, it is almost impossible to expect azimuth loss in case of displacement of the magnetic gap in one direction. Actually, at high frequencies, there is the case that is 5 dB higher than amount of the displacement picked up from the normal magnetic gap. Therefore, in a system in which a low-pass component is not used for detecting a signal as, for example, as a signal of a partial response class 4, leakage from the adjacent track of comparatively high frequency can adversely affect detection of the signal.
As a result, though it is preferable to produce so that the displacement of the magnetic gap
Hoshi Kazuhiro
Ogata Seiichi
Saito Tadashi
Sonnenschein Nath & Rosenthal
Sony Corporation
Tugbang A. Dexter
Young Lee
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