JPH0138734Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a double-gap erasing head, which suppresses temperature rise by reducing core loss and enables sufficient erasing of high coercive force magnetic tapes.

There are three types of erase heads based on the structure of the magnetic gap: single gap, semi-double gap, and double gap, as shown in FIGS. 1a, b, and c. Semi-double gap and double gap erasing heads aim to obtain a high erasing rate by erasing twice.
Among them, double gap provides a higher erasure rate. On the other hand, ferrite is often used as the core material of the erase head because of its heat generation. coercive force
For metal tapes exceeding 1000 (Oe), if ferrite is used for the core, a sufficient erasing rate cannot be obtained with a semi-double gap. On the other hand, in a double gap, since the total amount of magnetic flux flowing to both side cores flows through the center core, the center core is easily saturated, and the loss is large, resulting in large heat generation. As a countermeasure to this, there is a method of increasing the width of the center core, but it is necessary to take into account limitations such as the overall width of the head and the taping of the two gaps.

This invention was developed in view of the above-mentioned points, and its purpose is to provide an erasing head with a high erasing rate and little loss.

The invention will be explained below based on an example.

FIG. 2 shows an embodiment of the present invention. Basically, it has a double gap structure. Side cores 2 and 3 are provided on both sides of the center core 1, and side cores 2 and 3 are provided on both sides of the center core 1.
Then, wind the coils 4 and 5, respectively. The polarities of the two coils 4 and 5 connected in parallel are set so that the magnetic fluxes flowing through the center core 1 cancel each other out.

In both semi-double gap and double gap, the magnetic tape is subjected to the erasing magnetic field twice (Fig. 3a, b), but there is a large difference in erasing rate. This is not due to the direction of the erase fields in the two gaps, but is due to the rewriting phenomenon in the erase head. This is a phenomenon in which during the erasing process, the signal magnetic field on the tape that has not yet been sufficiently erased passes through the core and appears at the gear edge on the downstream side in the tape running direction, and the erased magnetic field becomes a bias and is rerecorded. . This phenomenon occurs more strongly in semi-double gaps than in double gaps, so that the elimination rate of semi-double gaps appears worse.

In the case of this invention, the erasing magnetic field is as shown in FIG. 3c, which is the same as in the case of a semi-double gap.
However, the signal magnetic field that is near the first gap G1 and has not yet been sufficiently erased does not appear at the downstream edge of the second gap G2 as in the case of a semi-double, but passes through the center core to the downstream edge of the first gap G1. Appears on the side edges. This is the same as the double gap case. Therefore, erasure by the second gap is completely performed without any re-recording phenomenon. However, as described above, the magnetomotive forces of the two coils cancel each other out at the center core, so almost no magnetic flux flows through the center core, so no loss occurs at the center core.

In addition, since the magnetic flux only crosses the front and rear parts of the center core, the width of the center core can be made extremely small compared to a normal double gap, which has the effect of reducing the overall width of the head. Since the gap interval is narrowed, the tape touch can be easily improved.

Figure 4 is a diagram showing the erase rate versus erase current, where curve A is the graph of the conventional semi-double method;
Curve B is a graph of the conventional double gap system and the double gap system according to this invention.

In the embodiment, the side cores 2 and 3 are constructed separately, but the side cores 2 and 3 may be constructed integrally.

As explained above, this invention consists of a center core and side cores on both sides of the center core, and in a double-gap erasing head where working gaps are formed on both sides of the center core, windings are connected in parallel to the side cores on both sides. The polarity of the two windings is configured so that their magnetomotive forces cancel each other out in the center core, so that the same high erasing rate as a normal double gap can be obtained, and the erasing magnetic field flows through the center core. Since there is no gap, the loss is low, and since the width of the center core can be made small, it is not only advantageous for miniaturization, but also because the gap between the two gaps is narrowed, the tape touch can be easily improved.

[Brief explanation of the drawing]

Figures 1a, b, and c are plan views showing conventional erasing heads, and Figure 2 is a diagram showing the erasing head of this invention.
Figures 3a and 3b are diagrams showing the magnetic flux near the gap in the conventional erasing head, Figure 3c is a diagram showing the magnetic flux near the gap in the erasing head of this invention, and Figure 4 is a diagram showing the erasure rate. It is. 1... Center core, 2, 3... Side core,
4, 5...Coil.

Claims (1)

[Scope of utility model registration request] In a double-gap erasure head, which is composed of a center core and side cores placed on both sides of the center core, and in which working gaps are formed on both sides of the center core, windings are connected in parallel to each of the side cores on both sides. 1. An erasing head characterized in that the wire is wound in such a manner that the polarity of the winding is such that the magnetomotive forces of the two cancel each other out in the center core.