JPS6233316A - Permanent magnet erasure head - Google Patents

Abstract

PURPOSE:To reduce head detaching noise by scattering a soft magnetic member coated by fine powder hard magnetic member and nonmagnetic member alternately and adjacently to a magnetic tape slide face so as to make the magnetic field strength of the magnetic member strong at the tape intake and weak at the tape exit for magnetization. CONSTITUTION:Let the X, Y axes of the coordinate system be within the slide face of a tape and the Z axis be perpendiclar to this paper, then the distribution of the magnetic field strength Hz going vertically from the slide face of an erasure head is shown in characteristic 9. The absolute value of the magnetic field in the X direction of this erasure head is decreased gradually while being alternated. The distance between the magnetic poles of N and S regions depends on grain diameter of the hard magnetic member 1 and the soft magnetic member 2. The magnetizing state in this case is shown in characteristics 10-12. That is, the distribution viewed in the Y direction at X=a is shown in the characteris tic 10, the characteristics 11, 12 correspond respectively to the coordinate at X=b, c and the absolute value of the alternate magnetic field in the X direction of this erasure head is decreased gradually and the distribution in the Y direc tion shows an alternate magnetization with equal absolute value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to permanent magnet erase heads for use in magnetic recording devices.

2. Description of the Related Art In general, there are methods for erasing magnetic recording media such as magnetic tapes, including alternating current erasing methods, methods using permanent magnets, and methods using a combination of these methods. Furthermore, among those that use permanent magnets, there are those of the saturation erase type that apply a saturation magnetic field to the recording medium to erase the signal, and those that use a gradually decreasing alternating magnetic field that apply an inverted and gradually decreasing magnetic field to the recording medium running on the head surface. The present invention relates to a permanent magnetic field erase head of the gradually decreasing alternating field type.

A conventional permanent magnet erase head with a gradually decreasing alternating magnetic field is shown in Fig. 6 (
&), a magnetic material 7 is placed on the tape sliding surface of the magnetic head.
The magnetic material 7 is magnetized so that the magnetic field gradually decreases in order to form multiple poles such as N and S poles, and when the magnetic tape passes over the magnet material T, it becomes a pseudo alternating current magnetic tape. It is to be erased.

FIG. 6 (bl) shows the magnetic field strength distribution 8 of the erasing head applied to the magnetic tape.

Problems to be Solved by the Invention However, since such conventional erasing heads are quasi-alternating current, they have the advantage of having a superior S/N ratio compared to the saturation erasing type. In the pseudo AC type, there is a limit to the number of alternating magnetic poles that can be taken due to the convenience of processing technology and magnetization technology, and the distance between the N pole and S pole is 0.3
The limit is about 0.4 MM.

Therefore, if the magnetic properties of the magnetic tape to be erased are different, or if the contact with the magnetic tape becomes uneven, the magnetic tape will not be erased to the magnetic neutral point as shown in Figure 6. , the DC residual magnetization m remains.

However, FIG. 6 shows the B-H curve of the magnetic tape.

Therefore, the magnetic tape finally reaches the point of DC residual magnetization m while drawing a minor loop as shown by the arrow in Figure 6, so that the magnetic neutral point of the magnetic tape after erasing, that is, the DC residual magnetization m is zero. In order to achieve this value, it is extremely difficult to set the magnetic field distribution of the erase head for erase heads with a small number of alternating magnetic poles, and even slight fluctuations in the contact state with the magnetic tape can affect the magnetic field applied to the magnetic tape. Generally, the strength is different, and DC residual magnetization m remains.

When recording and reproducing are performed using a magnetic tape in which such DC residual magnetization remains, there is a major drawback in that a large amount of even-order distortion occurs.

Furthermore, when a multi-pole magnetized erase head is used and a stop operation is performed from the erase state, the erase head instantly retreats and detaches from the magnetic tape. It has the disadvantage that a large noise (hereinafter this noise will be referred to as head detachment noise) is generated instantaneously during reproduction.

The present invention solves the above-mentioned problems of conventional heads, and brings the residual magnetization after erasing closer to the magnetic neutral point to significantly reduce the occurrence of even-order distortion. The purpose of the present invention is to provide a permanent magnet erase head that can significantly reduce head detachment noise caused by.

Means for Solving the Problems In order to solve the above problems, the permanent magnet erasing head of the present invention uses a soft magnetic material coated with a finely powdered hard magnetic material and a non-magnetic material on the magnetic tape sliding surface. , are distributed alternately and adjacent to each other, and the magnetic material is configured such that the magnetic field strength of the magnetic material is strong at the entrance side of the magnetic tape and weakly magnetized at the exit side of the magnetic tape.

Effect of the present invention With the above-described configuration and magnetization method, the N region and the S region are alternately and adjacently coated with a finely powdered hard magnetic material and a non-magnetic material on the operating surface of the erase head. It is made of soft magnetic material, and by magnetizing the magnetic field strength in each N region or S region to be strong on the entrance side of the magnetic tape and weak on the exit side, the magnetic tape is coated with fine powder hard magnetic material and non-magnetic material. The number of alternating magnetic poles is increased by forming a gradually decreasing alternating magnetic field in the tape running direction and an alternating magnetic field in the tape width direction with the distance between the soft magnetic materials. The S/N ratio is superior to that of . Furthermore, since multipolarization is also performed in the tape width direction, even if the magnetized backbone is transferred to the magnetic tape, when the magnetic flux is reproduced by the playback head, the magnetic fluxes entering the playback head have components in opposite directions, so they cancel each other out. Head detachment noise due to the transferred pattern can be reduced, and since the direct current components of magnetization remaining on the magnetic tape after erasing become opposite components to each other within the magnetic tape track, even-order distortion does not occur.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1(&) shows the structure of a permanent magnet erase head in one embodiment of the present invention.

In Figure 1, 1 is, for example, samarium cobalt...
Hard magnetic material such as strontium ferrite, 2 is for example iron, permendur, permalloy, Mn-Zn
A soft magnetic material such as ferrite, and 3 are non-magnetic materials such as plastics, ceramics, and glass.

Note that the hard magnetic material 1 is in the form of fine powder, and the soft magnetic material 2 is in the form of a rod (or may be a round rod, a square rod, or a needle).

It is spherical and its diameter is 30 μm to 150 μm. It is cam rank.

Furthermore, the soft magnetic material 2 is coated with a non-magnetic material 3 and thoroughly mixed with the hard magnetic material 1, and after being subjected to a coupling treatment with a coupling agent, the tape has good sliding properties and a smooth surface. Binder 4 with good surface after polishing
(For example, nylon.

polypropylene, etc.) and then molded.

In addition, by performing molding in a magnetic field, the hard magnetic material 2
is oriented perpendicular to the erase head operating plane.

Furthermore, hard magnetic material 1. The soft magnetic material 2 coated with the non-magnetic material 3 may be sufficiently mixed and fixed with an adhesive (eg, epoxy, acrylic, etc.).

Next, FIG. 2 is a magnetization strength distribution diagram, in which the horizontal axis represents the tape position with respect to the erasing head, with the entrance side in the tape running direction being 0 and the exit side being E, and the vertical axis is the magnetization strength. The magnetization strength is strong on the entrance side in the tape running direction and weak on the exit side. After magnetization, the magnetization pattern on the operating surface of the erase head is such that the hard magnetic material 1 is the magnetic pole in the magnetization direction, and the soft magnetic material 2 is the magnetic pole in the magnetization direction.
A magnetic polarity opposite to that of the hard magnetic material 1 is induced. Therefore, when the hard magnetic material 1 is magnetized to the N region, the soft magnetic material 2 is induced to the opposite S region.

Note that arrow C indicates the tape width direction.

The operation of the permanent magnet erase head constructed as described above will be described below.

First, the case where the magnetized state is viewed in the tape running direction indicated by arrow A will be described below. As shown in Figure 3, the coordinate system X,
When the Y-axis is set within the sliding surface of the tape and the Z-axis is set perpendicular to the plane of the paper, the distribution of the magnetic field strength H2 perpendicular to the sliding surface of the erasing head is as shown in characteristic 9 in Figure 4(a). It has become. In this manner, in the present erase head, the absolute value of the magnetic field alternates and gradually decreases in the X direction. At this time, the distance between the magnetic poles of each N region and S region is determined by the grain sizes of the hard magnetic material 1 and the soft magnetic material 2.

Next, the magnetized state when viewed in the width direction of the magnetic tape will be described. The magnetized state in this case is shown in FIG. 4(b).

(0), (d) (7) Characteristics 10.11.12.

In other words, the distribution seen in the Y direction of X=a is shown in Figure 4 (b
), characteristics 11 and 12 correspond to the positions of X=b and c, respectively. In this way, the main erase head
In the Y direction, the absolute value of the alternating magnetic field gradually decreases, and if you look at the distribution in the Y direction, you will see alternating magnetization with equal absolute values.

When erasing a tape using the magnetized erase head described above, the tape becomes a multi-pole magnetized erase head with gradually decreasing alternating magnetization in the tape running direction, and erases near the magnetic neutral point, resulting in excellent S/N. . Furthermore, in the tape width direction, a multi-pole magnetized erase head with alternating magnetization of equal absolute value receives the magnetic fields of the N area and the S area on the recording/reproducing track, and after passing through the gradually decreasing alternating magnetic field, the residual magnetization of the tape disappears. B) With respect to the magnetic neutral point of the f curve, residual magnetization points of opposite polarity remain in the N region and S region within the track.

As described above, when the erasing head of the present invention is used, the residual magnetization acts complementarily within the track, and the apparent residual magnetization becomes zero. As a result, if the erasing head of the present invention is used, even-order distortion due to recording and reproduction will not occur. On the other hand, regarding the head detachment noise that occurs when the playback head reproduces the pattern transferred on the tape, the magnetic flux flowing into the rad core for reproduction cancels each other out wherever the playback head is on the transferred pattern, so the head detachment noise is significant. Decrease.

Effects of the Invention The erasing head of the present invention has an N area and an S area on the operating surface of the erasing head.
The N and S regions are arranged alternately and the adjacent N and S regions are made of a soft magnetic material coated with a finely powdered hard magnetic material and a non-magnetic material. It is strongly magnetized on the inlet side and weakly magnetized on the outlet side. Therefore, head detachment noise caused by the transfer pattern remaining on the tape when the erasing head detaches from the tape can be significantly reduced. Furthermore, even if there is residual magnetization in the erased tape, this erase head remains at the remanent magnetization point of opposite polarity in the N area and S area within the track width, the apparent residual magnetization becomes zero, and even-order distortion during recording and reproduction is reduced. This has the effect of preventing this from occurring. Furthermore, since the magnetic pole strength gradually decreases from the tape inlet side to the tape outlet side, the tape to be erased receives a gradually decreasing alternating magnetic field, and as with alternating current erasing, an erasing characteristic with good S/N ratio can be obtained.

Furthermore, in the present invention, since a soft magnetic material coated with a non-magnetic material is used, the distance over which the magnetic flux acts on the tape is longer than when the tape is not coated with a non-magnetic material. This makes it difficult to malfunction even when the surface roughness of the tape operating surface of the erasing head is rough, and good erasing characteristics can be obtained without being affected by mechanical errors in the tape running system.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a permanent magnet erase head according to an embodiment of the present invention, FIG. 2 is a diagram of its magnetization strength distribution, and FIG. 3 is an explanation of the permanent magnet erase head according to an embodiment of the present invention. Figures 4(a) to 4(d) are magnetic field strength distribution diagrams, Figure 5 (2L) is a diagram of the configuration of a conventional erase head, and Figure 6
Figure (b) is the magnetic field strength distribution diagram, and Figure 6 is the B-
It is an H curve characteristic diagram. 1... Hard magnetic material, 2... Soft magnetic material, 3... Non-magnetic material. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 Prisoner Figure 5 Figure 6

Claims (1)

[Claims] On the operating surface of the erase head, N regions and S regions are formed alternately and adjacent N regions and S regions are formed of a soft magnetic material coated with a finely powdered hard magnetic material and a nonmagnetic material, and each N of
A permanent magnet erasing head configured such that the magnetic field strength is strong on the tape entrance side and weakly magnetized on the tape exit side in the area or S area.