JPS5888802A - Permanent magnet erasing head - Google Patents

Abstract

PURPOSE:To increase the wear resistance and to reduce the deflected abrasion and the rubbing resistance for the titled erasing head, by sticking a rubbing surface member containing a glass material and a high-polymer material to the rubbing part of the erasing head to a recording medium. CONSTITUTION:The thickness of a recording medium is gradually reduced toward the outlet side from the inlet side. The Ba ferrite magnet plates 7-9 having the magnetization facilitating axes in the direction of thickness and nonmagnetic glass plates 10 and 11 are set alternately. At the same time, a soft magnetic matter 13 is provided to the head main body from the inlet side through the outlet side of a tape. As a result, the wear resistance is improved for a rubbing surface 1 along with the reduction of the deflected abrasion and the rubbing resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic erasing head used in magnetic recording/reproducing devices and the like.

Generally, as methods for erasing recording media such as magnetic tapes, there are known alternating current erasing methods, erasing methods using permanent magnets, and erasing methods that combine both.

Additionally, erasing methods using permanent magnets are broadly divided into saturation erasing type, which applies a saturated magnetic field to the recording medium, and gradual magnetic field type, which applies an inverted and gradually decreasing magnetic field to the recording medium running on the head surface. be done.

As described above, various erasing methods are known, but the erasing method using a permanent magnet is superior in that it does not require current for erasing, and it also reduces the residual magnetism after erasing to the vicinity of the magnetic neutral point. Gradual magnetic field type permanent magnet erase heads are superior to saturation erase types in that they can be demagnetized.

Conventionally known permanent magnet erasing heads of the gradually decreasing magnetic field type include the i
There is a permanent magnet erase head made of one piece of (barium) ferrite or Sr (strontium) ferrite, which has alternating magnetic poles of S and N poles magnetized on the recording medium sliding surface (1), and the recording medium entrance side (2) to the exit side (3
), the amount of magnetization is decreased toward 9J3, resulting in a gradually decreasing magnetic field distribution as shown in Figure 9J3.

However, in the case of this erase head, magnetization is usually carried out by changing the current applied to the magnetizer, but it is difficult to provide the desired amount of magnetization, and there are also variations in magnetization. It has the disadvantage that many of them cannot be manufactured.

On the other hand, the erasing head shown in Fig. 2 is a stack of several pre-magnetized magnet plates (4) of the same type, and each magnet plate (4) is placed on the recording medium entrance side (the second one). The amount of magnetization must be changed depending on what is used and what is used on the exit side (31, and furthermore, what is used in the intermediate part), so it has the disadvantage of being very time-consuming, and it also has the drawback that it is difficult to achieve the desired magnetization. This has the same drawback as the head shown in FIG. 1 in that it is difficult to adjust the magnetizing current to obtain the magnetic quantity.

Furthermore, in the erasing method using the head described above, there are cases where the desired characteristics cannot be obtained due to disturbances in the magnetic field intensity distribution as shown in Figure 6. This has disadvantages in that incomplete erasure or erasure spots occur, and noise may be generated or attempted during reproduction.

In Japanese Patent Application No. 56-24112 and Japanese Patent Application No. 56-36243 previously filed by the present applicant, a permanent magnet erasing head that does not cause the above-mentioned variations in magnetic field strength distribution and can easily obtain desired characteristics is disclosed. However, these are the fourth
As shown in the figure, there are several magnetic plates (71 (8
1 (9) and non-magnetic material QQq are arranged alternately in the running direction of the recording medium. 7) If the magnetic field strength is too strong, or if the non-magnetic material 00 is weak, the dotted line (6 In addition to the magnetic flux indicated by ), leakage magnetic flux appears from the N pole of the magnet plate (7) to the S pole of another magnet plate (8) (91), indicated by a dashed line.

Therefore, a phenomenon occurs in which the magnetic field strength of each S pole of the magnet plate +14) (9) is larger than the magnetic field strength of the N pole, and as a result, the magnetic field strength distribution measured along the sliding surface (1) As shown in Figure 6, the polarity shifts to the opposite polarity from the negative polarity, and the residual magnetism after erasing the magnetic tape cannot be demagnetized to the vicinity of the magnetic neutral point, resulting in incomplete erasure. There were cases where noise or distortion was observed during playback.

The present invention suppresses the deflection magnetic flux from the N pole of one magnet plate to the S pole of the other magnet plate in such a permanent magnet erase head of the gradually decreasing magnetic field type, and creates a permanent magnet having a good magnetic field strength distribution with alternating gradual decrease. A magnetic erase head is provided.

Normally, when a magnet is magnetized and removed, the magnets that accumulate on the surface of the magnet generate a magnetic field in the opposite direction that demagnetizes the magnet. This is called a demagnetizing field, and by changing the dimensional ratio of the magnet, the residual magnetic flux density of the magnet plate can be changed.

The present invention is based on this principle, and by combining magnet plates with different magnet size ratios, a permanent magnet erase head with a gradually decreasing alternating magnetic flux distribution is obtained. By disposing a soft magnetic material on the side surface of the erasing head, the leakage t magnetic flux component is suppressed and the magnetic field strength distribution is made good.

Next, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 (See FIG. 7) FIG. 7 shows an I in which the thickness is gradually decreased from the inlet side to the outlet side of the recording medium and has an axis of easy magnetization in the thickness direction.
The main body of the head is made by laminating 1m ferrite magnet plates (7) (81 (91) and non-magnetic glass plates 00 gl in the horizontal direction alternately. Soft magnetic material (
).

When the soft magnetic material 0 is arranged in this way, the magnetic flux component shown by the dashed line υ' in Fig. 5 disappears, and only the magnetic flux straddles between adjacent magnetic poles as shown by the dotted line @. It became clear.

In addition, the magnetic flux density distribution measured along the recording medium sliding surface (1) shows an inverted rigid region magnetic field distribution as shown in Figure 9J8, and the magnetic field strength of the magnet plate (7) on the recording medium inlet side is Even if the magnet plate (7) has a strong
Good magnetic field distribution was obtained even when the thickness of 0 was small.

For this reason, by suppressing the N pole of the magnetic plate (7), that is, the first magnetic pole, with a soft magnetic material, the magnetic plate (7)
), the magnetic flux component indicated by the number d leading to the S pole of the magnet plate (81 (Ql), which is sequentially arranged on the recording medium exit side via the non-magnetic material aO (2), disappears and reaches the point 61 (6). This is because only the leakage magnetic flux shown in

Embodiment 2 (see FIG. 9) FIG. 9 shows the main body of the head in Embodiment 1,
A soft magnetic material is disposed only on the outside of the magnet plate (7) on the recording medium inlet side.

Due to the arrangement of the soft magnetic material (C) in this way, the N pole of the magnet plate (7) is substantially moved to the outer side of the recording medium entrance side (2) of the soft magnetic material (C), and as a result, As a result, the magnetic pole strength of the first pole becomes weaker. In other words, the first pole N
S between the pole and the magnet plate (81 (9)) sequentially arranged on the recording medium exit side through the non-magnetic material 00 (b) with respect to the magnet plate (7).
Since the poles become farther apart, the magnetic flux component indicated by the symbol - decreases, and the magnetic field strength distribution is improved as in the first embodiment.

Embodiment 3 (See FIG. 10) FIG. 10 shows the erasing head shown in Embodiment 2, in which a soft magnetic material α4 is further provided on the surface on the recording medium exit side.

In this embodiment, the S pole of the magnetic plate (9) on the recording medium exit side (3) moves to the surface of the soft magnetic material (B) that is in close contact with the magnetic plate (9), and the S pole moves from the first pole itself to The magnetic flux reaching the final pole will decrease. Therefore, the magnetic field strength at the final pole is
By appropriately setting the thickness of the soft magnetic material α4, it is possible to obtain a desired value.

Embodiment 4 (See FIG. 11) FIG. 11 shows the erase head shown in Embodiment 2 in which the soft magnetic material 0 is extended to the back surface of the head.

With this configuration, the magnetic poles (indicated by N in the figure) appearing on the surface of the soft magnetic material (b) are dispersed to the back of the head, and therefore, the magnetic poles (indicated by N in the figure) that appear on the surface of the soft magnetic material (b) are dispersed to the back of the head, and therefore, the magnetic poles (indicated by N in the figure) appear on the surface of the soft magnetic material (b). It becomes possible to suppress magnetic poles. That is, the magnetic flux indicated by the dashed line 1 in FIG. 5 is suppressed more than in the case of the head shown in the second embodiment.

In each of the above embodiments, the soft magnetic material (to) α4 may be made of a metal magnetic material such as sesodust or permalloy, or -Zn ferrite, and in these embodiments, the soft magnetic material Q3Q4 may be Although it forms a part of the recording medium sliding surface (1), the soft magnetic material tta (b) may be arranged only up to a position slightly recessed from the sliding surface (1). In other words, even when the soft magnetic material does not come into contact with a recording medium such as a tape, the same effect as described above can be achieved.

Example 5 (See Figure 12) Figure 12 shows the recording medium sliding surface of the erasing head of Example 1.
A glass layer M was layered as a sliding surface member, and good results were obtained in this example as well as in the previous examples.

Similar effects were obtained when such a sliding IT1 member was used in the erasing heads shown in FIGS. 2-4.

In each of the above embodiments, a case has been described in which magnetic plates and non-magnetic plates are alternately laminated, but the same applies to the erasing head previously shown in Japanese Patent Application No. 56-36243 with 8 axes by the present applicant. It is applicable.

Incidentally, as the magnetic plate used in the erasing head in the present invention,
samarium, cobal) magnets, 8R iron alloy magnets, alnico magnets, or samarium and cobalt alloy powders kneaded with ethylene and vinyl acetate copolymer, then molded in a magnetic field and demagnetized, or the above-mentioned IA type magnets. A similar effect was obtained even when the magnet plates were laminated in combination with magnet plates, shaped into a predetermined shape, and magnetized.

Furthermore, similar results were obtained when a metal material such as a brass plate or a polymer material such as polyacetal resin was used as the nonmagnetic material.

Further, similar results can be obtained even if a non-magnetic metal material such as alumina or a polymer material such as polyacetal resin is used as the sliding surface member O, and the present invention can be satisfied.

In each of the above embodiments, the case where three magnet plates were used was explained, but the number may be any number, and even if there are more magnet plates, the same alternating demagnetization field distribution as in the above embodiments can be obtained. I got it.

As described above, in the present invention, a plurality of permanent magnet plates and non-magnetic plates of varying thickness are arranged alternately in the running direction of the recording medium, so that a reversal gradually decreasing magnetic field is obtained by one magnetization. Since this relates to a permanent magnet erase head characterized in that a soft magnetic material is disposed on the erase head side at least on the entrance side and the exit side of the recording medium, it is different from the conventional one. It has the advantage that the magnetic field intensity distribution is less disturbed than the permanent magnet erase head, and the desired performance can be easily and stably obtained, and is of extremely great industrial value.

In addition, by attaching a sliding surface member made of glass material, polymeric material, etc. to the recording medium exit side of the erasing head,
It has significantly better abrasion resistance than those that are not attached.
Furthermore, it has the advantage that uneven wear and sliding resistance can be reduced, and performance deterioration is significantly reduced.

° 4. Brief description of the drawings Figure 1 is a simplified front view of a conventional permanent magnet erasing head made of an integrated magnet, Figure 112 is a simplified front view of a conventional permanent magnet erasing head made of a plurality of stacked magnet plates, Figure 3 is a magnetic field strength distribution diagram, Figure 4 is a simplified front view of a permanent magnet erasing head made up of multiple permanent magnet plates and non-magnetic plates laminated, and Figure 5 is a diagram of the magnetic field strength distribution.
6 is a magnetic field strength distribution diagram of the erasing head shown in FIG. 5, and FIGS. 7FXJ to 12 show five embodiments of the present invention. 7 is a simplified front view of Example 1, FIG. 8 is a magnetic field strength distribution diagram of the permanent magnet erasing head of the present invention, and FIG. 9 is a simplified front view of Example 2. 1! The JIO diagram is a simplified front view of Example 3, Figure 11 is a simplified front view of Example 4, and Figure 11 is a simplified front view of Example 4.
FIG. 2 is a simplified front view of Example 5.

(1) Stripped recording medium sliding surface, (2+ is recording medium entrance side,
(32 is on the recording medium exit side, (4) is a magnet plate, (5) is near the recording medium entrance, t61 is near the recording medium exit, (7) ~
(9) is a magnetic plate with different thickness, 0 (10υ is a non-magnetic material,
02Oi is leakage magnetic flux, (13Q41 is a soft magnetic material, and aQ is a sliding surface member.

Fig. 1.7 Fig. 2 'Goj　r'1 the law of nature

Claims (1)

[Claims] ■ A permanent magnet in which a plurality of permanent magnet plates and rotating magnetic plates of varying thickness are arranged alternately in the running direction of the recording medium so that a reversal and gradually decreasing magnetic field is obtained by one magnetization. 1. A permanent magnet erase head, characterized in that a soft magnetic material is disposed on at least the side surface of the erase head on the entrance side on the entrance side and the exit side of a recording medium. ■ In the above permanent magnet erase heads with different thicknesses,
2. The permanent magnet erasing head according to claim 1, wherein the thickness direction is the direction of easy magnetization. (2) A permanent magnet erasing head according to claim 1, characterized in that a sliding surface member made of metal material, glass material, or polymeric material is attached to the recording medium sliding surface.