JPH0345282Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a magnetic recording/reproducing device that uses a metal magnetic tape as a recording medium, in which a metal magnetic material is adhered to a base material by vapor deposition or sputtering, and includes an erasing head and a metal magnetic tape. The purpose is to reduce and eliminate the effects of static electricity generated by sliding.

Generally, the core containing the tape sliding surface of a recording/playback head or a playback-only audio head is grounded to a shield case surrounding it.
When these heads are installed in a magnetic recording/reproducing device, the shield cases of these heads are grounded to the magnetic recording/reproducing device, so the cores of these heads, including the tape sliding surface, are not connected to the magnetic recording/reproducing device. Grounded.

The reason for taking such measures is as follows.
That is, when the tape slides over these heads, static electricity is randomly generated between the magnetic tape and the core. If the core is not grounded, this randomly generated static electricity will appear as noise in the playback output of the head. If the core is grounded, the potential of the core is constant and no noise is generated.

In contrast, the core of the erase head is not grounded. Even if static electricity is generated and accumulated in the erase head core due to the sliding between the erase head core and the magnetic tape, the erase current is extremely large compared to the reproduced signal, so it hardly affects the erase performance. Also, in VTRs, the core of the rotating video playback head is grounded.

Furthermore, it never occurred to me that noise could be removed simply by grounding the playback head, and that grounding the eraser head would be necessary since the eraser head is physically separated from the playback head.

Thus, in the past, there was no need to ground the core of the erase head. However, recently, magnetic recording and reproducing devices have been put into practical use that use metal magnetic tapes made by attaching a magnetic metal material such as cobalt or nickel to a base by vapor deposition or sputtering.In this case, the core of the reproducing head is grounded. It was also found that noise would occur if the core of the erase head was not grounded.

This is due to the following reason. Conventional magnetic tape has γ
Whether it is -Fe ₂ O ₃ , Co-added γ-Fe ₂ O ₃ tape, or alloy powder tape, these magnetic powders are mixed with a non-conductive binder and applied to a base such as polyethylene terephthalate. Ta.
Therefore, the electrical conductivity of the magnetic surface side of these conventional coated magnetic tapes was quite low.

In other words, the resistance of conventional magnetic tape is 1×10 ⁸
~ ⁹ Ω/sq (“Digital Magnetic Recording” by Makoto Kizawa, Showa
Published by Shokodo in 1954, P179), and the above 1×10 ⁸ ~ ⁹
Ω/sq is 10cm between the erase head and playback head, and the magnetic tape width is 1cm, then the resistance value is 1×
¹⁰⁹ to ¹⁰ Ω.

On the other hand, a metal magnetic tape on which metal is deposited by vapor deposition or sputtering does not contain a binder, so its magnetic surface side has considerably high conductivity.

For this reason, irregular static electricity generated between the metal magnetic tape and the erase head is transmitted to the playback head through the conductive metal magnetic tape, and appears as noise in the playback output.

When a conventional coated magnetic tape is used, its resistance value is much larger than that of a metal magnetic tape, and the irregular static electricity generated is not transmitted to the reproducing head. In addition, coated magnetic tapes are usually mixed with carbon black as an antistatic agent to adjust the resistance value, so they do not charge (``Digital Magnetic Recording'' by Makoto Kizawa, published by Shokodo in 1978).
P179).

The present invention provides a magnetic recording and reproducing apparatus that uses such a metal magnetic tape and is capable of reducing noise caused by static electricity.

Figure 1 shows one embodiment of the present invention, and the second
The figure is a sectional view of the core portion of FIG. 1.

Note that the diagram is extremely simplified so that it can be used for either audio or video, and therefore does not disclose a specific configuration when there are multiple channels, but is highly conceptualized.

It is composed of side cores 1 and 2, a main center core 3 magnetically connected to the side cores 1 and 2 through a back core 10, and sub center cores 4 and 5 interposed between the main center core 3 and the side cores 1 and 2, respectively. . Therefore, the gaps for generating the erasing magnetic field are the gaps 6, 7, and 7 between the side cores 1 and 2, the sub center cores 4 and 5, and the main center core 3
There are a total of 4 pieces, 8 and 9. 16 is a winding for exciting the erase head. The erasing head is fixed to a conductive chassis 13 of the magnetic recording/reproducing device through a conductive insert 12.

The inclusion 12 has the same cross-sectional shape as the head core shown in FIG.
Between 14 and inclusion 12 and chassis 13
Since both of them are electrically conductive and in close contact with each other by mechanical bonding such as conductive adhesive or screws, the side cores 1 and 2, which are the cores on which the metal magnetic tape slides, the main center core 3, and the sub center cores 4 and 5.
Both are electrically connected to the chassis 13. The inclusion 12 is of course also non-magnetic, for example aluminum, in order to retain its function as an erase head.

The degree of conduction varies depending on the core material. When the core including these tape sliding surfaces is made of sendust or a metal material such as iron or cobalt-based amorphous, the resistance between the core surface and the chassis 13 can be 10 ohms or less.

In addition, when the core is made of polycrystalline ferrite, Mn-Zn ferrite is used, and the resistivity of this Mn-Zn ferrite is about several tens of Ωcm (National Technical Report
DEC.1976P.764Table8). Considering that the size of the erasing head is about 1 cm ³ , the resistance between the core surface and the chassis 13 can be reduced to about several tens of ohms or less.

With this level of resistance, the static electricity generated inside the core of the erase head due to sliding between the metal magnetic tape and the erase head will hardly accumulate.
It is considered that the erase head and the chassis 13 are always at the same potential, and the noise is no longer generated.

The inclusion 12 is required to contact the side cores 1 and 2, the main center core 3, and the sub center cores 4 and 5, but is not required to contact the back core 10. Further, in this embodiment, a 4-gap case is shown, but the same applies to a 3-gap or 2-gap case in which one or two of the sub center cores 4 and 5 are missing.

As described above, according to the present invention, the entire core of the erasing head, including the tape sliding surface, can be grounded to the chassis of the magnetic recording/reproducing device. Even when used, there is no noise caused by static electricity, and signals with a good S/N ratio can be reproduced.

[Brief explanation of the drawing]

Figure 1 is a front view showing one embodiment of the present invention;
The figure is a sectional view of the same. 1, 2...Side core, 3...Main center core,
4, 5... Sub center core, 6, 7, 8, 9... Gap, 10... Back core, 12... Inclusion,
16... Winding wire.

Claims (1)

[Scope of utility model registration request] A metal magnetic tape in which a metal magnetic substance is adhered to a base material by vapor deposition or sputtering,
an erasing head for erasing the metal magnetic tape; and a magnetic core constituting the erasing head, one end of which is electrically connected to at least the magnetic core that contacts the metal magnetic tape, and the other end electrically connected to a chassis. 1. A magnetic recording and reproducing device using a metal magnetic tape, characterized in that it is equipped with a conductive material.