JPS63317917A - Degaussing method for magnetic head - Google Patents

Abstract

PURPOSE:To degauss a magnetic head to prevent the degradation of S/N due to head magnetization by gradually attenuating a recording current at the time of switching plural magnetic heads to one another. CONSTITUTION:In a device where plural magnetic heads are switched to one another to record and reproduced a signal, the recording current is gradually attenuated after contacting between the magnetic head and a tape is terminated. Thus, about 5MHz AC magnetic field which is gradually attenuated is applied to the core of the magnetic head, and magnetization of the magnetic head is erased by AC and is attenuated. Consequently, the degradation of S/N due to head magnetization is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application in Industry-1-] The present invention relates to a demagnetizing force method for a magnetic head, which demagnetizes the magnetic head during non-recording.

[Prior Art] FIG. 2 is a diagram showing a schematic configuration of a main part of a recording system of a VTR in a two-way system in which a tape is wound at 180° around a rotation ram. In Figure 2, ■ is a signal input terminal, 2
a, 2b, recording amplifier, 3a.

3b is a switching circuit, and 4a and 4b are magnetic heads. In the so-called 180° winding two-head type VTR,
Since the two magnetic heads perform recording alternately, it is necessary to switch the recording current of the two magnetic spatulas.

FIG. 3 is a timing chart showing the conventional recording current switching timing, and FIG. 3(a) shows a 30Hz signal (hereinafter referred to as 30PG) that switches between high level and low level every 1760 seconds in synchronization with the rotation of the rotating drum. FIG. 5B shows the envelope of the recording current for the 11ch (channel) magnetic head, and FIG. 1C shows the envelope of the recording current for the 2nd channel magnetic head. Here, 30 pages
To explain the relationship between G and the phase of each recording current in the case of FIG. 3, conventionally, regarding recording current switching timing,
It is only required that the envelope be flat in the 180° section where the magnetic head contacts the tape, and no consideration has been given to other sections. Therefore, there was no built-in function for demagnetizing the magnetic head when it was not recording.

[Problems to be solved by the invention] As mentioned above, in conventional VTRs, the magnetic head is
Since the magnetic head is left in a magnetized state due to the immediately previous recording information signal, it is difficult to magnetize the magnetic head in this magnetized state with a new information signal for recording due to the influence of the residual magnetic field from the previous signal. Unfortunately, as a result, it was difficult to record information signals faithfully.

The present invention has been made to solve these problems, and provides a method for demagnetizing each magnetic head during non-recording without adding any new mechanism to a conventional VTR. With the goal.

[Means for Solving the Problems] In order to achieve the object described above, the magnetic head degaussing method of the present invention gradually attenuates the recording current when switching the magnetic head, thereby degaussing the magnetic head. This method involves demagnetizing the magnet.

[Function] By carrying out the method described in the following two sections, the demagnetization method of the present invention can demagnetize the magnetic head without adding any structural additions, thereby preventing a decrease in S due to magnetization of the head.

[Embodiment] FIG. 1 is a waveform diagram showing an envelope of a recording current for magnetizing each magnetic spatula l=' according to an embodiment of the present invention. When the contact between the magnetic head and the magnetic tape ends, the recording current is gradually attenuated as shown in FIG. For example, in a consumer VTR, the recording current is 5 MHz.
Nearby alternating current signals are dominant, and by gradually attenuating the recording current applied immediately before each magnetic head is switched to a non-recording state, the core of the magnetic head receives a gradually attenuating frequency of about 5 MHz. An alternating current magnetic field of 100 mL is applied, and the magnetic head is demagnetized by alternating current and attenuated.

Incidentally, in the present invention, by gradually attenuating the recording current,
The purpose is to demagnetize the magnetic head, and the shape of the attenuation curve does not have to be a straight line as shown in FIG. 1, but can be arbitrary. Further, the decay time is also arbitrary. Furthermore, although the above embodiment is applied to a two-head type VTR in which a tape is wound 180 degrees around a drum, the VTR has a plurality of recording heads and records signals by switching between the heads.
Of course, the present invention can be applied to TR regardless of the number of heads and the angle of 9 turns.

[Effects of the Invention] As explained above, the present invention can demagnetize the magnetic head by gradually attenuating the recording current at the timing of switching the recording current, thereby reducing S/
A decrease in N can be prevented.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram showing the envelope of the recording current for magnetizing each magnetic head, which is an embodiment of the present invention.
The figure shows the schematic configuration of the main parts of the recording system of a VTR in a two-head system in which a tape is wound 180 degrees around a rotating drum.
FIG. 3 is a timing chart showing conventional recording current switching timing. In the figure. 2a, 2b=recording amplifier 3a, 3b switching circuit 4a, 4b: magnetic head

Claims (1)

[Claims] A magnetic recording and reproducing device that records or reproduces information signals by alternately switching a plurality of magnetic heads, characterized in that when switching the magnetic heads, the magnetic heads are demagnetized by gradually attenuating the recording current. A method for demagnetizing a magnetic head.