JPS6030005B2 - magnetic erase head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic erase head used in a magnetic recording/reproducing device, and its purpose is to reduce even-order distortion and reduce noise. The purpose of the present invention is to provide an erasing head.

Generally, as methods for erasing signals from recording media such as magnetic tapes, there are known AC erasing methods, methods using direct current electromagnets, methods using permanent magnets, and methods using a combination of these methods.

Among those that use DC electromagnets and those that use permanent magnets, there are saturation erasing types that apply a saturated magnetic field to the recording medium, and gradually decreasing alternating magnetic field types that apply an inverted and gradually decreasing magnetic field to the recording medium running on the head surface. There is one. Conventionally, saturation erasing type erasing heads have been considered as those shown in Figs. 1 and 2. In Figs. It shows what was used.

The erasing head shown in FIG. 1 is composed of a magnetic material 2, a non-magnetic material 3, and a high permeability material 4, and the magnetic tape surface of the magnetic material 2 slides so that it becomes the north pole or the south pole. Magnetized perpendicular to the surface.

When the tape slides against the erasing head, about half its width is magnetized in one direction, and the signals on both the R and L tracks are erased. The high magnetic permeability material 4 suppresses the spread of magnetic flux from the magnet material 2 and prevents cross erasure over the upper half width of the magnetic tape. After erasing with a single-pole saturation erasing head having such a configuration, the tape is magnetized at point 30 or point 32 in FIG. 3 when viewed from the B-day curve of the tape. Therefore, when recording and reproducing are performed using a tape that has been saturated and magnetized and erased in this way, the magnetic tape is not demagnetized to the magnetic neutral point 31, so there are problems in that even-order distortion occurs and the noise level is high. . The erase head shown in FIG. 2 has a structure that mainly solves the problem of even order distortion of the unipolar saturation erase head described above, and has magnet materials 5, 6, 7, 8
, 9, a non-magnetic material 3, and a high magnetic permeability layer 4 are laminated. Among the above magnet materials 5 to 9, magnet materials 5, 7,
The set 9 and the set of magnets 6 and 8 are constructed so that the polarities of their tape sliding surfaces are mutually opposite polarities N, S, and N, as shown. With this configuration, for example, the center part of the R track of the tape 1 is magnetized by the S pole of the magnet material 6, and in terms of the B-day curve in FIG.
It is magnetized to 2. On the other hand, since both ends of the R track are magnetized by the N poles of the magnets 5 and 7, points 301 on the B-day curve in FIG. 3 are also magnetized. If the width of the magnet material 6 is about 1'2 of the R track width, even if the tape 1 slides slightly up and down, about half of the R track will be magnetized at 301 points, and the remaining about 301 points will be magnetized. Half is magnetized to point 32. Similarly, the L track of the tape 1 is magnetized by magnets 7, 8, and 9. When recording and reproducing using a tape magnetized as described above, even-order distortion generated from the tape portion magnetized at each point 30 and 32 is canceled out because they are in opposite phases to each other, and recording is performed at the standard level. The distortion rate during reproduction can be suppressed to 3% or less. However, the conventional erasing head described above has the runner-up point of having a large number of noise components. That is, this noise is generally referred to as DC erase noise, and becomes noticeable when there is a large variation in particle size of the tape or when the dispersibility of the particles is poor. In the above-mentioned saturation erasing method, the particles in the tape are saturated and magnetized with a constant magnetic field strength, so compared to the AC erasing method that erases the magnetic neutral point, it is greatly affected by particle size and dispersion, resulting in more noise. This was a major drawback. In other words, although the erasing head shown in FIG.
It also has the disadvantage of a lot of noise.On the other hand, the erasing head shown in FIG. 2 described above is good in terms of even-order distortion, but
It has the disadvantage of not being improved in terms of noise.

The present invention solves these conventional drawbacks,
Three or more magnetic poles are provided leading and trailing to the magnetic recording medium, the first magnetic pole has a magnetic field strength sufficient to saturate the magnetic recording medium, and any magnetic pole other than the final magnetic pole following the first magnetic pole is provided. The second and subsequent magnetic poles have a weak magnetic field strength that is opposite to the preceding magnetic pole, and the final magnetic pole is divided into magnetic poles in the track width direction of the magnetic recording medium.

According to such a configuration, even-order distortion can of course be reduced, and an erasing head improved in terms of noise can also be provided. Embodiments of the magnetic erasing head of the present invention will be described below.

FIG. 4 shows an embodiment of the magnetic erasing head of the present invention. In FIG. 4, reference numeral 1 denotes a magnetic tape for compact cassettes or micro cassettes, the running direction of which is indicated by arrow 40, and the tape to be erased. The R and L tracks are indicated by symbols R and L, respectively. 41 is a non-magnetic material, which is in contact with a portion corresponding to about half the width of the non-erasing side of the tape.

42 is a shield plate for preventing cross erasing, and is made of a high magnetic permeability material such as permalloy.

43, 44, and 45 are a first magnetic pole, a second magnetic pole, and a final magnetic pole, respectively, and the first magnetic pole 43 has a height greater than the width of the magnetic tape 1 to be erased, and its magnetic field strength saturates the magnetic tape sufficiently. It has the value of

Like the first magnetic pole, the second magnetic pole 44 has a height greater than the width of the magnetic tape to be erased, has opposite polarity to the first magnetic pole, and has a magnetic pole strength smaller than that of the first magnetic pole and erased. It has a larger value than the coercive force of the magnetic tape. The final magnetic pole 45, which the tape finally comes into contact with, is composed of a plurality of magnetic poles in the width direction of the tape.
5 magnetic poles N, S 46, 47, 48, 49, 50
The strength of each of the magnetic poles 46 to 50 is approximately equal to or weaker than the strength of the second magnetic pole 44. The final magnetic pole 45 is made by stacking magnet materials that have been magnetized in advance, and forming N, S, N,
The magnetic pole of ...... is made to appear, or the magnetic material and the high magnetic permeability material are arranged alternately and magnetized, and the magnetic material is induced to the N pole, for example, to the tape sliding surface of the high magnetic permeability material. The magnetic pole is the south pole. Here, an example is shown in which a combination of high magnetic permeability materials 47, 49 and magnet materials 46, 48, 50 is used. Also, high magnetic permeability materials 47, 49
The thickness of the tape is approximately half the width of the R and L tracks of tape 1, and its position is at the center of each track, so even if the tape meanders up and down, the part corresponding to the front part of the track is the north pole, and the remaining part of the track is the north pole. S
It is configured to be magnetized at the poles. Therefore, the residual magnetization in the R and L tracks of the tape after erasing is oriented in a direction that cancels each other out, and the ratio is 1:1, which has the effect that even-order distortion does not occur.

In addition, the erase head configured with magnetic poles arranged as described above can be used for conventional saturation erase type erasing. It has the advantage of less DC erasure noise compared to the standard. The reason for this will be explained using FIGS. 5 and 6. FIG. 5 shows the B-day curve of the magnetic tape being erased, and FIG. 6 shows the magnetic field strength of each magnetic pole of the erasing head of this example. In FIG. 5, 51 is the magnetic field strength of the first magnetic pole 43, and 52 is the magnetic field strength of the second magnetic pole 44. 53 and 54 are respectively the final magnetic poles 4
5, 53 indicates the magnetic field strength at the tape sliding portion of the magnet materials 46, 48, and 50, and 54 indicates the magnetic field strength at the tape sliding portion of the high magnetic permeability material.

On the other hand, the magnetic field intensity may be reversed so that the magnetic field strength at the sliding part 53 is made of a high magnetic permeability material and the sliding part 54 is made of a magnet material. The portion corresponding to the matter receives magnetic fields 51, 52, and 53, and the remaining portion corresponding to the matter receives the magnetic field 5.
, 52, 54. The magnetic tape has a magnetic field strength of 51,
52, 53, the magnetic tape is saturated by the magnetic field 51, no matter what residual magnetization there is in the initial state of the magnetic tape, resulting in a point 55 on the B-day curve, and then each magnetic field 52,
53, it passes through points 56, 57, 58, 59, and 60, and finally becomes the residual magnetization shown at point 61. On the other hand, each magnetic field 51
, 52, 54, points 55, 56, 57, 5
8, then returns to the vicinity of the third quadrant 57, and finally ends in the vicinity of the point 59. Therefore, when erasing with the erase head of this example, residual magnetization exists at points 61 and 59, and when erasing with the conventional erase head, residual magnetization exists at points 61 and 59.
32 (see FIG. 3). DC noise can be caused by uneven distribution of particles on the tape,
It becomes large when the particle size is significantly different in size, and the level becomes higher as the saturation magnetization state is approached. In the erase head of this example, the residual magnetization is reduced by 4.degree. as described above, so it has the advantage that the DC noise is 4.degree. smaller than the conventional saturation erase type magnetic head. Further, by setting the magnetic field strengths 52, 53, 54 of the second magnetic pole 44 and the final magnetic pole 45 to appropriate values, the residual magnetizations 61, 59 can be made even smaller. Furthermore, the erase head of this example has a residual magnetization of 61,5
Even if 9 does not approach zero, the values of residual magnetization 61 and 59 are 0 and -, respectively, so they cancel each other out, so even-order distortion is extremely unlikely to occur. It also has the same advantages as (see Figure 2). In addition, in the above explanation, the first, second, and final three
An example of an erase head with one magnetic pole was shown;
The present invention is not limited to magnetic poles, and it is also possible to realize an erase head having a magnetic pole configuration in which the magnetic field distribution is gradually decreasing except for the final magnetic pole, that is, an erase head having four or more poles.

As described above, according to the present invention, three or more magnetic poles are provided leading and trailing to a magnetic recording medium, and the first magnetic pole has a magnetic field strength sufficient to saturate the magnetic recording medium, and the first magnetic pole has a magnetic field strength sufficient to saturate the magnetic recording medium. A second pole other than the last pole following the first pole
The subsequent magnetic poles have a weak magnetic field strength due to their opposite magnetism to the preceding magnetic poles, and the final magnetic pole is divided into magnetic poles in the direction of the track of the magnetic recording medium, which reduces even-order distortion and significantly reduces noise. It has the advantage of being able to

[Brief explanation of the drawing]

Figures 1 and 2 are perspective views of the configuration of a conventional permanent magnet erasing head, Figure 3 is a B-day curve diagram of a magnetic tape showing residual magnetization after saturation erasing, and Figure 4 is a permanent magnet erasing head according to the present invention. A perspective view of the configuration of an embodiment of the head, FIG. 5 is a B-day curve diagram showing the state of the tape when subjected to magnetic field strength in the same head, and FIG. 6 is a distribution diagram of the magnetic field strength in the same head. It is. 1...magnetic tape, 42...high magnetic permeability material,
43, 44, 45... First, second, and final magnetic poles respectively, 46, 48, 50... Magnet material of the final magnetic pole, 47, 49... High magnetic permeability of the final magnetic pole. Material. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. Three or more magnetic poles are provided leading and trailing to the magnetic recording medium, and the first magnetic pole has a magnetic field strength sufficient to saturate the magnetic recording medium, and the first magnetic pole has a magnetic field strength sufficient to saturate the magnetic recording medium. A magnetic erasing head in which the second and subsequent magnetic poles other than the final magnetic pole that follow the magnetic pole have opposite polarity to the preceding magnetic pole and have a weak magnetic field strength, and the final magnetic pole is a divided magnetic pole in the track width direction. 2. The magnetic erasing head according to claim 1, wherein the final magnetic pole is made of a laminated structure in the width direction of the magnetic recording medium of a permanent magnet material and a high magnetic permeability material.