JPS59175002A - Erasion head - Google Patents

Abstract

PURPOSE:To attenuate gradually the magnetomotive force of a magnet in a simple and highly accurate way by providing a prescribed polished part to a tape rubbing surface of a head and then setting a spacer on said polished part. CONSTITUTION:Plural (three) magnets 12 having magnetizing directions inverted alternately are set side by side with prescribed spaces along a tape rubbing surface forming a prescribed curved surface of a head main body 11. A part of the tape rubbing surface of the main body 11 is polished at the tape flow-out side, and the length of the magnet 12 is adjusted at said polished part. Thus the magnetomotive force is gradually attenuated in comparison with the magnet 12 at the tape flow-in side. An epoxy inorganic adhesive, glass, ferrite, etc. is provided on the polished surface as a spacer 13. Then the surface of the spacer 13 is formed into the same curved surface as the original tape rubbing surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an erasing head (C) used for erasing magnetization of a magnetic recording medium, such as a magnetic tape.

There are two methods for demagnetizing magnetic tape in tape recorders and the like: an alternating current erasing method that uses a gradually decreasing alternating current magnetic field, and a direct current erasing method that uses a magnet or a direct current magnetic field.

Among these methods, the AC cancellation method applies a gradually decreasing AC magnetic field a to the magnetic tape to converge the hysteresis loop b of the tape magnetic material to zero, thereby reducing the magnetization in the tape to zero. It is a strained product.

This cross-current erasing method has the advantage that the magnetization after erasing becomes zero, so there is less erasing noise, but on the other hand, it has the disadvantage that the efficiency is poor because the core loss in the erasing head is large because high frequencies are used.

On the other hand, in the DC cancellation method, as shown in Figure 2, the magnetic field a in one direction is
is added to the magnetic tape, and the magnetic tape is magnetized to saturation at a predetermined point C on the hysteresis loop b.

This DC erasing method has the advantage that there is little core loss because it uses direct current, and it does not require any current at all if a magnet is used. This method has the disadvantage that it causes unevenness and that erasure noise is likely to occur due to fluctuations in the contact state between the tape and the head. .

Conventionally, as shown in FIG. 3, when a plurality of magnets 2 whose magnetized directions are alternately reversed along the tape sliding surface l of the head body l are arranged, the length dimensions of these magnets 2 are adjusted in order. A so-called multi-pole attenuation type erasing head/JS has been developed, in which the magnetomotive force is sequentially attenuated along the tape running direction, and the magnetization of the magnetic tape is reversed and attenuated in the same way as in the AC extinction method. There is.

This method combines the advantages of AC and DC elimination methods, and can be expected to provide good erasure.

However, in reality, with such an erasing head, it is extremely difficult to magnetize the plurality of magnets 2 arranged in parallel so that the magnetomotive force is gradually reversed and attenuated. 82. Residual magnetization on the hysteresis loop C is caused by variations in the reversal magnetic field shown by al and bl, variations in magnetization, and variations in the contact between the tape and the head. b
This has the disadvantage that large fluctuations of 2Φ occur, and these are the cause of generation of erasure noise.

This invention was made to eliminate the above-mentioned drawbacks.
It is an object of the present invention to provide an erasing head which can be magnetized so that the magnetomotive force of a plurality of magnets arranged in parallel can be easily and sequentially attenuated with high precision, and which can obtain good magnetic characteristics.

An embodiment of the present invention will be described below with reference to the drawings.

i@5 In the figure, 11 is a head body, and this body 11 includes a plurality of (three in the illustrated example) magnets 1 whose magnetization directions are alternately reversed Cζ along a tape sliding surface forming a predetermined curved surface.
2 are arranged in parallel at predetermined intervals.

In addition, the head main body 11 has the tape outflow side portion of the tape sliding contact surface polished, and the length dimension of the magnet 12 at this polished portion is adjusted to sequentially attenuate the magnetomotive force compared to the tape inflow side magnet 12#. ing. In this case, the magnetomotive force of magnet 12 on the tape outflow side is the tape holding force Hc.
lζ so that it is near ζ.

On the other hand, if a spacer 13 is provided on the polished surface of the head body 11, for example, an epoxy adhesive, m-horizontal adhesive, glass, ferrite, etc., the surface of the spacer 13 is formed into the same curved surface as the initial tape sliding surface. are doing.

In this case, the erasing head that produces 75) force is constructed using a magnetomotive force that alternately reverses the celadon direction along the tape sliding surface that forms a curved surface of radius R, as shown in FIG. 6, 1a). A head main body 11 is prepared in which a plurality of equal magnets 12 (three in the illustrated example) are arranged side by side at a predetermined interval. Then, as shown in FIG.
Polished into a curved or flat surface.

The length of the magnets 1-12 is made smaller than that of the magnet 121 on the open inflow side so that the magnetomotive force thereof is gradually attenuated along the tape outflow direction.

Thereafter, a non-magnetic spacer 13 is placed on the surface 1114, and the surface of the spacer 13 is polished into a curved surface having the same radius as the initial sliding contact surface of the tape, thereby completing the erasing head.

Therefore, in the erasing head constructed as described above, a plurality of magnets arranged in parallel along the tape sliding surface are initially magnetized to the same strength.

By polishing the tape exit side, the magnetomotive force is gradually attenuated in the tape exit direction, so compared to conventional multi-pole magnets that are magnetized in a multi-pole attenuation type from the beginning, each magnet has the desired effect. Not only can the magnetomotive force of

In addition, the strength of the magnetic field on the tape outflow side can be appropriately set by polishing. As a result, good performance characteristics with less erasing noise can be expected when erasing the magnetization of the magnetic tape. In addition, since a spacer is provided on the polished surface and this spacer surface is made to have the same curved surface as the initial tape sliding contact surface, it is possible to eliminate fluctuations in the contact of the magnetic tape1, thereby reducing residual magnetization after erasing. Fluctuations can be prevented, and the generation of erasure noise caused by this can also be prevented.

Nanami (Here, we investigated the output and distortion rate of the erasing head of this invention and the conventional erasing head when an IKHz signal was recorded and played back on the tape after erasing by changing the DC bias current at the time of recording. The results shown in Figs. 7 and 8 were obtained.In other words, in the erasing head of the present invention, as shown in Fig. 7, the output a, the distortion rate l, and the DC bias are close to zero cancellation. A current of about 20μ8 is suitable for t&, whereas with a conventional erasing head, the output a and mold distortion rate are as shown in Figure 8, and the optimum DC bias current is about 100μ8 for saturation erasure. Ta.

On the other hand, when we analyzed the frequency components of the erasure noise during no-signal recording and playback (magnetic erasure (1, recording with AC bias or DC bias and then playing back), the erasing head of the present invention was as shown in FIG. 9. As shown in Figure εα10, it was also found that the erase noise a at low and medium frequencies of 50 Hz to 2 KH2 is significantly smaller and approaches the pulse erase noise b compared to the conventional erase head.

Note that the present invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications without changing the gist. For example, in the above embodiment, the case where there are three magnets is described, but any number of magnets may be used as long as it is two or more.

[Brief explanation of the drawing]

Figures 1 and 2 are characteristic diagrams for explaining the erasing methods of different conventional erase heads, Figure 3 is a schematic <4 diagram showing a conventional four-duck erase head, and Figure 4 is a Characteristic diagrams of the erasing head; Figure 5 is a schematic diagram showing an embodiment of the erasing head of the present invention; Figure 6 is a schematic diagram illustrating the manufacturing process of the erasing head; 7 to 1O1 are for comparing the characteristics of the erasing head of the present invention and the conventional erasing head.
The figure shows the characteristics of the erasing head of the present invention, and FIGS. 8 and 10 show the characteristics of the conventional erasing head. 1.11...Head body 2,12...Magnet 13...Spacer sister 1 Fig. 2 Fig. 3 @5 Fig. 6 Fig. (a) Fig. 7 JA; Rin G〃no)

Claims (1)

[Claims] +11 A head body in which a plurality of magnets whose magnetization directions are alternately reversed are arranged in parallel along a curved tape sliding contact surface, and a tape outlet side portion of the tape sliding contact surface is formed. An erasing head characterized by comprising: a polishing portion that sequentially attenuates the magnetomotive force of the magnet in this portion; and a spacer provided on the polishing portion and formed to have the same curved surface as the tape sliding surface. 2) The erasing head according to claim 1, wherein the polishing portion is formed in a curved or planar shape with a radius R1 (〉㇠) relative to the curved radius of the tape sliding surface. 3) The erasing head according to claim 1flR or claim 2, wherein the spacer is made of adhesive, glass, or ferrite.