JPS641844B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an erasing head device.

Structure of the conventional example and its problems The conventional example is shown in FIGS. 1 to 3. In other words, 1 is the main body of the magnetic erasing head device, 2 is its core, 3 is the recording/playback head, 4 is the core,
5 is a magnetic tape. As shown in FIG. 1, the core portion 2 of the conventional magnetic erase head device main body 1 is magnetized in an alternating and decreasing manner in the tape running direction (adjacent poles have opposite polarities, and the magnetization strength gradually decreases in the tape running direction). The magnetic tape 5 is subjected to an erasing magnetic field while running on the surface of the core portion 2 of the main body 1 of the magnet erasing head device, and the strength of the erasing magnetic field is roughly as shown in FIG. becomes. Due to this erasing magnetic field, the magnetic flux density of the magnetic tape 5 changes from _a1 to _a4 on the magnetization curve (B-H characteristic) and finally becomes the residual magnetic flux _BX , as shown in FIG. In other words, it is slightly DC magnetized. but,
Although it is possible to reduce the value of B _X by adjusting the amount of magnetization of each pole of the core part 2,
This is due to the fact that the magnetic layer of the tape is thick, the B-H characteristics differ between various tapes, and the tape contact pressure changes due to changes in tape running, which changes the space between the head and the tape. However, no matter how much the magnetization strength is adjusted, it is impossible to make _BX zero, and therefore, there is a drawback that erasure noise occurs when the magnetic tape 5 is reproduced due to the residual magnetization _BX .

On the other hand, FIG. 4 shows a so-called alternating current (AC) erase head device which applies an erase magnetic field generated by an alternating current erase current to a magnetic tape for zero erasure in order to eliminate the erase noise of the magnetic erase head device described above. In the figure, 6 is the main body of the AC erasing head device, 7 is its core part,
8 and 8' are left and right gap. In this conventional example, two gaps are provided in one head to perform double erasing in order to improve erasing efficiency, but even in such an AC erasing head device, the high coercive force tape cannot be completely used. Erasing requires a large amount of erasing power, and in portable tape recorders powered by batteries, such an AC erasing head device cannot be used due to battery life limitations.

On the other hand, it was considered that both heads were lined up so that DC cancellation was performed as shown in Fig. 1, and then AC cancellation was performed as shown in Fig. 4 (for example, in 1983,
−39548). This makes it possible to erase to zero with low power consumption.

However, the width erased by direct current is larger than the width erased by alternating current due to magnetic leakage, and therefore, of the residual magnetic flux density generated by DC erasure on the tape, a portion that is not erased by alternating current remains, causing the above-mentioned erasure noise. There was a drawback.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an erasing head device that can perform zero erasing with low power consumption and can prevent erasing noise.

Structure of the Invention The erasing head device of the present invention comprises magnet core portions that are arranged in a row in the tape running direction and have opposite polarities and whose magnetization strength gradually attenuates downstream in the tape running direction; The magnet core includes an AC erasing core part having a width larger than the width of the core part and disposed on the tape downstream side of the magnet core part. In other words, the power required for erasing is the power necessary to reduce the magnetic flux density to zero, which is sufficiently smaller than the residual saturation magnetic flux density, so that the power consumption is lower than that of the conventional technology. Furthermore, since the width of the AC erasing core part is made larger than the width of the magnet core part, the entire residual magnetic flux density generated by the magnet core part can be AC erased, so that erasure noise can be prevented.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention is shown in FIGS. 5 to 8. In other words, 9 is the main body of the erasing head device, 10 is a magnet core portion having a plurality of alternately different magnetic poles and gradually attenuated toward the downstream side of the tape, 11 is a shield plate, 12 is an AC erasing core portion, and 13 is a gap portion thereof. , 14 is its winding portion. In the tape running state shown in FIG. 5, the strength of the erasing magnetic field received by the magnetic tape 5 while it is running on the surfaces of the magnet core part 10 and the gap part 13 of the erasing head main body 9 is approximately 6. The values will be as shown in the figure. In FIG. 6, the magnetic field from H' ₁ to -H' ₄ is generated by the magnet core section 10,
As a result, similar to the conventional magnetic erase head device, the residual magnetic flux density of the magnetic tape 5 becomes as shown in FIG.
B′ _X. And since this B′ _X is a value sufficiently smaller than the saturation magnetic flux density of the magnetic tape,
As shown in FIG. 6, the magnetic tape 5 receives an alternating current magnetic field called H _AC due to the erase magnetic field generated in the gap portion 13 by passing a small alternating current erase current through the winding portion 14 of the alternating current erase core portion 12. As shown in FIG. 7, zero erasure is performed in the same manner as in the conventional AC erasure head device.

In this case, as shown in detail in FIG. 8, the width of the residual magnetic flux density generated by the magnet core 18 is the width of the magnet core 10 due to magnetic leakage of the magnet core 10.
Since it is wider than Wm, the width Wa of the AC erasing core section 12 is made larger than the width Wm correspondingly.

Effects of the Invention According to the erasing head device of the present invention, by providing a magnet core section and an AC erasing core section, zero erasing can be achieved with low power consumption, which is convenient when driven by battery power, and the magnet core section Since the width of the AC erasing core part is made larger than the width of the magnet core part, all of the residual magnetic flux density generated by the magnet core part can be erased by the AC erasing core part, which has the effect of preventing erasure noise. be.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the tape running state of a conventional magnetic erase head device, and Fig. 2 is a characteristic diagram showing the intensity of the erase magnetic field applied to the magnetic tape when the magnetic tape runs in front of the magnetic erase head device. , FIG. 3 is a magnetization curve diagram showing the process of change in the residual magnetic flux density of the magnetic tape at that time, FIG. 4 is a perspective view showing the tape running state of a conventional AC erasing head device, and FIG. FIG. 6 is a perspective view showing the tape running state of the erasing head device of the embodiment; FIG. 6 is a characteristic diagram showing the strength of the erasing magnetic field applied to the magnetic tape when the magnetic tape runs in front of the erasing head device;
FIG. 7 is a magnetization curve diagram showing the process of change in the residual magnetic flux density of the magnetic tape at that time, and FIG. 8 is a perspective view showing the core structure of the erasing head device. 10... Magnet core part, 12... AC erasing core part, Wm... Width of magnet core part 10, Wa... Width of AC erasing core part 12.

Claims (1)

[Claims] 1. Magnet core portions arranged in a row in the tape running direction, having mutually opposite polarities and having magnetization strength gradually attenuating downstream in the tape running direction, and having a width larger than the width of the magnet core portion. An erasing head device comprising: an AC erasing core section disposed on the tape downstream side of the magnet core section.