JPS63225902A - Method for erasing by rotary magnetic head - Google Patents

Abstract

PURPOSE:To reduce an unerased area on a magnetic tape and to prevent a trouble due to over-recording at the time of reproduction from being generated, by permitting an erasure current to flow even in a prescribed time which gives no effect on a rotary magnetic head on the other side without limiting the erasing period of the magnetic tape only in one revolution of the head. CONSTITUTION:The rotary magnetic heads A-H1...B-H2 commonly used for recording and reproduction are arranged on the rotary drum D of the rotary magnetic head keeping a prescribed angle, and a rotary erasure head FE-H is arranged. Also, the magnetic tape T is wound across the drum D at an angle >=270 deg.. On a rotary transformer for the magnetic head, a rotary side and a fixed side coil parts RL and SL are formed respectively, and the heads A-H1 and B-H1 are connected to the coupling coils LA and LB of the coil part SL, and the heads A-H1 and B-H1 to the coupling coils LA1 and LB2, and the head FE-H is connected to a coupling coil LE provided between both coils. And the erasing period is not limited to one revolution of the head, and the erasure current is permitted to flow in the prescribed time which gives no influence on the head on the other side, then, the unerased area on the tape can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an erasing method using a rotating magnetic head, which is useful when erasing information on a magnetic tape recorded by a helical scan method using a flying erase head. be.

[Summary of the invention]

In particular, the present invention provides an erasing method in which information is recorded by a magnetic recording device equipped with a large number of rotating magnetic heads of four or more, and then the recorded information is erased by one wide rotating erasing head. The present invention provides an erasing method in which the unerased area is reduced by passing an erasing current through the head for a predetermined period even after one rotation.

[Conventional technology]

A helical scan magnetic recording (reproduction) device is usually equipped with a rotating magnetic head that forms recording tracks diagonally on the tape, and also applies an erasing magnetic field along the diagonal recording tracks. It is known to have a rotary erasing head that can do this.

Figure 4 shows two rotating magnetic heads A-H, B-H and one
The figure shows a rotating drum D equipped with two rotating erase heads FE-H (flying erase heads), on which a magnetic tape T is attached (guide bosses) C1, G2.
It is guided by and wrapped at an angle of 180° or more.

When information is recorded using such a rotating magnetic head,
As shown in FIG. 5, a recording track A is formed diagonally on the magnetic tape T by a first rotating magnetic head A-H, and then a recording track A is formed diagonally on the magnetic tape T by a second rotating magnetic head B-H. It is known that recording tracks B are formed alternately in the sections.

Further, for such a recording track, the rotary erasing head FE-H located between the first and second rotary magnetic heads A-H and B-H is arranged as shown in FIG.
Since the rotary erasing head FE-H comes into contact with the magnetic tape T at the first . If the drum is placed at a drum position h higher than the second rotating magnetic disks A-H and B-H, the erase area will be shown by diagonal lines, and data will be recorded in the areas of tracks A and H in one rotation. You can erase the information you have.

However, the first. Since the mounting position is set to be h higher than the second rotating magnetic heads A-H1 and B-H, there is an unerased area θH in the initial portions of tracks A and B.
A small amount of E (white part) remains.

In this case, if this unerased area is small, it will not cause much of a problem, but as the number of rotating magnetic heads increases, this unerased area will become larger and will affect the next recording information.

Figures 6 and 7 show four rotating magnetic heads A-HII.
This shows an example in which A-H2, B-11, and B-B2 are provided, and the rotating erase head FE-H is provided between the rotating magnetic heads B-H and A-Hl.

In this case, the recording track of the magnetic tape T is recorded by three rotations of the rotary drum D, as shown in FIG.

A2. Four tracks lined up with Bl and B2 are formed, and PO, PI, P2... are the erase head FE-.
H indicates the position where magnetic tape T contacts.

With each head positional relationship like this, one rotary erasing head F
When erasing four recording tracks by one rotation of E-H, the erasing track width is set to be four tracks as described above, and the other rotating magnetic heads A-H1, A- It is necessary to provide the drum at a higher position than H2°B - H1 and B - H2.

Incidentally, in the rotary transformer for supplying signals to each of the rotating heads, the coupling coil connects, for example, B-B2 . of the rotating magnetic head from the inside. A-B2
．． LB2. for FE-H, B-Hl, A-B2. Li
It is preferable that the coupling coil of the erasing head be located in the center so that it becomes 2, LEF, Let, and LAI.

This is because by using a rotary transformer with coupling coils in this order, there is an effect that the erasing coupling coil LEF can be used as a short ring during playback.For example, when track B2 is being played back, Sometimes A-Hl and B-H of a rotating magnetic head
This is because it is possible to prevent the signal reproduced from l from becoming a crossstroke and being output to the reproduction circuit.

[Problem that the invention seeks to solve]

However, since the rotating erase head attached to these four rotating magnetic heads is required to erase four tracks of recorded information in one rotation, the width of the erase head is limited to the width of each rotating magnetic head. It is required that the gap width be about four times larger than the gap width of the rotary magnetic heads A-H1, A-H2, B-Hl, and B-B2. It becomes necessary.

Therefore, the erasing area of the tape that is erased with one rotation of the erasing head becomes as shown by the diagonal lines in Figure 7, and is even larger than when the angle θHE of the unerased area (white area) is 2 heads. .

By the way, according to actual measurements, the rotation angle θHF of this unerased area is 2.4° in the case of the NTSC system and 4.00° in the case of the PAL system, and in the case of the 8mm video format, PCM data is transferred to this unerased area. A preamble area may be included.

Then, newly recorded data is superimposed on this unerased data, causing problems during playback.

[Means for solving problems]

The present invention has been made in view of these problems, and aims to provide an erasing method that reduces the unerased area to an area that does not affect the next recorded information, and which shortens the erasing period. The erasing current is made to flow not only during one revolution of the erasing head but also during a predetermined period that does not affect other rotating magnetic heads.

[Effect]

Since the period during which the erasing current is applied is extended by utilizing the period during which there is no problem with recording by other rotating magnetic heads,
The unerased area of the magnetic tape can be made narrower than before.

〔Example〕

FIG. 1 shows an embodiment of a rotating drum and a rotary transformer to which the erasing method using a rotating magnetic head of the present invention is applied.

In this figure, A-H+, A-B2. B-Hl, B-
As mentioned above, B2 is a recording/reproducing rotary magnetic head (hereinafter simply referred to as a magnetic head) arranged at an angle of 90° on the rotary drum D, and FE-H is a rotary erasing head (hereinafter simply referred to as a magnetic head).
T is a magnetic tape wound around a rotating drum D at an angle (2π-α).

Also, RL is the rotating side coil part of the rotary transformer, SL
indicates the fixed side coil portions of the a-Tali transformer, and these coil portions are equipped with magnetic heald B-H concentrically from the inside.
Coupling coil LB2 for magnetic head A-H2, coupling coil L^2 for magnetic head A-H2, coupling coil LE for erase head FE-H, coupling coil LB+ for magnetic head B-H1, coupling coil L for magnetic head A-H,
^1 is provided in a ring shape.

A magnetic tape T formed by such a rotating magnetic head
If the upper recording track is designed with the drum diameter, number of rotations, and tape speed set to predetermined values, the format will be such that four recording tracks A lt A 2 + Bl, B2 are lined up in order in three revolutions as shown in Figure 2. For each track, there are 8
The video signal can be sequentially recorded in the remaining portion of the M signal.

Further, during reproduction, by short-circuiting the erasing coupling coil LE on the fixed side using, for example, the switch S1, the coupling coil LE can be used as a short ring.

Then, the adjacent track A21 of recording track A, for example.
There is an advantage in that it is possible to prevent the reproduced signal picked up from B2 from being induced into the adjacent coupling coil at the rotary transformer and deteriorating the S/N ratio.

By the way, during recording, each magnetic head A Hl, A-H2, B-H1+B is activated at the timing shown in FIG.
- supply recording currents IA, 2A, IB, and 2B to B2;
4 recording tracks A I + A 2 at T (3 rotations)
+ B 1 + B 2 are sequentially formed. At this time, when an erase current is applied to the erasing head FE-H during the period indicated by diagonal lines (■), the four tracks in the lower left diagonally shaded area indicated by (■) in FIG. The recorded information (AI, A2
．． Bl, B2) can be recorded.

However, as mentioned above, since the erasing head FE-H contacts the magnetic tape T at the P1 position, many unerased areas remain at the beginning of the track. However, in the erasing method of the present invention, as shown in FIG. Erasing head FE-H rotates once (
The erasing current is also controlled to flow during the period (angle θ[)) from the position (P2) where it contacts the magnetic tape T in the second rotation after IT).

Then, the lower right diagonally lined area indicated by the area ``■'' in FIG. 2 is also erased, so that the unerased area can be further narrowed.

Note that during the period when the recording current is being supplied to the magnetic heads A-H2 and B-H, the erasing current cannot be supplied because the erasing current leaks to these heads via the coupling coil. , magnetic heads B-H2, A-H, the coupling coil LBl is closed by closing the two switches S2 in FIG.
+L^2 operates as a sigot ring, and it is possible to prevent erasing current from being induced from the rotary transformer to the coupling coils L^I and LB2.

In this way, in the erasing method of the present invention, after the region (■) of one stroke (IST) erased by one revolution of the erasing head, the erasing current is also applied during the initial period (angle θE) of the second revolution. Therefore, it is possible to roughly erase the area marked "■" and to narrow the remaining area when rewriting recorded information.

Therefore, especially in the case of 8 mm video, there is an effect that the data recorded in the initial part of the track can be rewritten without errors.

In the above embodiment, four rotary heads were explained, but even when four or more rotary heads are used,
It goes without saying that the erasing method of the present invention is useful.

Note that the period during which the erasing head is not in contact with the magnetic tape (
It goes without saying that the erasing current may also be applied during the period of angle α) (between the regions ■ and ■).

〔Effect of the invention〕

As explained above, the present invention is particularly applicable to a magnetic recording apparatus equipped with four or more rotating magnetic heads and a rotating magnetic head that simultaneously erases the number of recording tracks formed by the rotating magnetic heads. Since the second erasing current is turned off at the timing of , the unerased area of the magnetic tape can be narrowed.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a rotating drum and rotary transformer showing an embodiment of the erasing method of the present invention, Fig. 2 is a pattern diagram showing recording tracks and erasing areas on the tape, and Fig. 3 is a diagram showing the supply to each magnetic head. 4 is an illustration of a rotating drum with two heads, FIG. 5 is a pattern diagram of a recording track with the head of FIG. 4, and FIG. 6 is an explanation of a rotating drum with four heads. 7 is a pattern diagram of the recording track by the head of FIG. 6. In the figure, A-
H1, A-H21B-H1, B-H2 are rotating magnetic heads, FE-H is a rotating erasing head, and RL and SL are coupling coil portions of a rotary transformer.

Claims (1)

[Claims] A tape is wound around a rotating drum having an angle of at least 270° and having at least four or more rotating magnetic heads and an erasing head provided with a gap width for erasing information on tracks recorded by each of the rotating magnetic heads. In the magnetic recording device that is in contact with the tape, an erase current for one stroke is supplied to the erase head during rewriting, and an erase current is further supplied for an initial predetermined period when the erase head contacts the tape again. An erasing method using a rotating magnetic head, characterized in that the unerased area of a track is reduced.