JPS634248B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating magnetic head device in which a magnetic head rotates within a drum, and in particular has a mechanism that uses electromagnetic force and a mechanism that uses a bimorph to swing the magnetic head. However, it is an object of the present invention to provide a rotating magnetic head device that can reproduce images of good quality even during extremely high-speed reproduction.

First, it has a pair of rotating azimuth magnetic heads.
The scanning state of a magnetic head on a recording track in a VTR device will be explained. The magnetic tape runs while attached diagonally to the circumferential surface of the drum over a predetermined angle, and during recording, recording tracks by the magnetic head of CH1 and recording tracks by the magnetic head of CH2 are alternately closely spaced on the tape. The tape is formed diagonally with respect to the longitudinal direction of the tape. 1st
In Figure A, the diagonal dot-dash line indicates the locus of the point that generates noise when crossed by the CH1 head (that is, the center line of the track adjacent to the recording track of the CH1 head), and the diagonal dashed line indicates the locus of the point that generates noise when crossed by the CH2 head. The locus of the points that occur (ie, the center line of the track adjacent to the recording track of the CH2 head) is shown.
Below, the former is the CH1 inhibitor line, and the latter is
This is called the CH2 inhibitor line. Figure 1A is
The inhibition lines of CH1 and CH2 are drawn consecutively. In the figure, "1" . . . indicates the recording order of the tracks, that is, the track number. CH1 on the right,
CH2 indicates a magnetic head that performs a reproducing operation during one track scanning period during reproduction.

During normal playback, the CH1 head scans the middle of the CH1 inhibit line, and the CH2 head scans the middle of the CH1 inhibit line.
Scan the middle of the CH2 inhibitor line. Therefore, the heads of CH1 and CH2 scan along the trajectory shown by the line, do not cross the inhibit line, and no noise is generated.

Further, in the figure, the line indicates the scanning locus of the magnetic head when the tape is transported in the forward direction at nine times the speed without displacing the magnetic head in the track width direction. From the figure, it can be seen that the CH2 head starts scanning from track ``7'', and the next CH1 head starts scanning from track ``16'', and from this it can be seen that the speed is 9 times faster in the forward direction. I understand.
Also, the line shows the head scanning locus during 7x speed reverse playback. Here, the line intersects with the inhibit line, and the reproduced image will be accompanied by noise.

To perform this special playback without noise,
In the case of 9x forward speed, the scanning trajectory of the head is as follows:
Line _a : In the case of 7x speed in the reverse direction, it is necessary to be as shown in line _a . To scan the head in this manner, it is necessary to displace the head in the track width direction during scanning. FIG. 1B shows the locus of displacement of one magnetic head for scanning the head as shown by line _a ,
Figure C shows the locus of displacement of the head for scanning along line _a . In both figures, the center line indicates the center rotation plane of the head. That is, in the former case, the CH1 head is displaced so that it is located four track pitches above the center position at the beginning of the track, and four track pitches below the center position at the end of the track, and in the latter case, On the contrary
The CH1 head is positioned four track pitches lower at the beginning of the track and is displaced four track pitches higher at the end.

In order to displace the rotating magnetic head as described above,
Conventionally, as means for swinging the CH1 and CH2 heads, there is a mechanism using electromagnetic force or a mechanism using bimorph. Mechanisms that utilize electromagnetic force are heavy, have poor frequency characteristics, and cannot provide high-speed response, so their scope of application is limited to high-speed playback at speeds close to the standard playback speed (for example, about 2 to 3 times faster).
If the speed is higher than that, noise will appear. Furthermore, when looking at mechanisms using bimorphs, there is no bimorph itself that can be put to practical use and exhibits a large amplitude. Therefore, with conventional rotating magnetic head devices, it has been impossible to perform reproduction at a speed extremely different from the standard reproduction speed, so-called ultra-high-speed reproduction, without noise.

Therefore, the present invention is designed to perform ultra-high-speed reproduction without noise, and one embodiment thereof will be described below with reference to the drawings.

FIG. 2A is a longitudinal sectional view of one embodiment of the rotating magnetic head device according to the present invention, and FIG. 2B is a bottom view showing the upper rotating drum and the swing mechanism.

In each figure, a rotating magnetic head device 1 consists of a lower stationary drum 2 and an upper rotating drum assembly 3, around which a magnetic tape 4 runs. The rotating shaft 5 is rotatably supported by a bearing 6, and a base plate 7 is fitted and fixed thereto.

The rotating drum assembly 3 includes a rotating drum main body 8,
It consists of a rotating yoke (oscillating body) 9 and a leaf spring 10. The rotating drum main body 8 is screwed to the base plate 7 while being fitted onto the rotating shaft 5. The rotating yoke 9 has its center hole loosely fitted into the rotating shaft 5, and
It is supported by a leaf spring 10 on the lower surface side of the rotating drum main body 8 . As a result, the rotating yoke 9 rotates integrally with the rotating drum main body 8, and swings ( seesaw) exercise. The diametrically opposite sides of the rotating yoke 9 are yoke portions 9a, 9b, to which permanent magnet pieces 12a, 12b are fixed.

The electromagnetic drive mechanism 11 includes the yoke portions 9a and 9b.
The drive coil 13 is fitted into the magnetic field formed inside. The drive coil 13 is wound around a coil frame 14 fixed to the lower drum 2.

Reference numerals 15a and 15b are bimorph elements each in the form of a relatively long narrow strip, which are disposed in the same direction as the arms of the rotating yoke 9, and are mounted on the rotating yoke 9. That is, the bimorph elements 15a and 15b are
One end of the fixing member 1 is placed near the center hole of the yoke 9.
It is fixed by 6a and 16b, and when it bends, the other end side is displaced in the vertical direction. A magnetic head 17 is attached to the other end of the bimorph elements 15a and 15b.
a and 17b are fixed facing the circumferential surface of the drum.

As a result, the magnetic heads 17a and 17b rotate integrally with the rotating drum body 8, and the electromagnetic drive mechanism 1
1 and the bimorph elements 15a, 15b, the magnetic heads 17a, 17b are oscillated in the direction of the rotation axis of the rotary drum body 8 to which they are attached.

Next, the operation of the apparatus having the above configuration during ultra-high-speed reproduction operation will be explained with reference to FIGS. 3A and 3B.

Drum pulses are applied to the first drive circuit 20 and the second drive circuit 21, and the first drive circuit 20 outputs, for example, a sinusoidal current. Electromagnetic drive mechanism 1
1 is operated by being supplied with this sine wave current, and the rotating yoke 9 is mounted on the bimorph element 15.
a, 15b and magnetic heads 17a, 17b. Here, the rotating yoke 9 etc. are heavy and have poor frequency characteristics of swing, and the magnetic heads 17a, 17
b undergoes a rocking displacement as shown by the graph line in FIG. 3A. Although this displacement trajectory approximates the ideal triangular wave-shaped swinging displacement trajectory of the head shown by the graph line in the same figure, it has an error with respect to this, and if this continues, noise will appear in the reproduced image. appear. Therefore,
In the present invention, this error can be reduced by using the bimorph elements 15a, 1.
5b is used for correction.

That is, the second drive circuit 21 outputs a signal with a waveform (this waveform has a predetermined shape) corresponding to the above-mentioned error, and this signal is output to the slip ring 18.
The bimorph element, which is applied to the bimorph elements 15a and 15b through the magnetic head and which supports the magnetic head during reproduction, bends vertically. As a result, the magnetic head 17
a and 17b are added to the displacement caused by the swinging of the rotating yoke 9 and are further displaced (FIG. 3B shows the displacement of the heads 17a and 17b caused by the bimorph elements 15a and 15b).
), the above error is corrected, and the displacement trajectory is the ideal displacement trajectory, that is, the magnetic head 1.
The magnetic head 1 when the centers of the magnetic heads 7a and 17b scan the center of the track recorded on the magnetic tape 4.
This corresponds to the displacement locus of 7a and 17b.
Therefore, the magnetic heads 17a and 17b are, for example, the first
Scanning will be performed along line _a in figure A.

Note that the signals reproduced by the magnetic heads 17a and 17b are taken out to the outside via a rotary transformer 19.

Therefore, the magnetic heads 17a and 17b are displaced with a large amplitude by the electromagnetic drive mechanism 11, and in addition to this, they are also displaced with high speed and small amplitude by the bimorph elements 15a and 15b, and as a result, they are displaced with a large amplitude and high speed. Scanning follows an ideal trajectory, and ultra-high-speed playback is performed well with no noise bars.

Furthermore, since the bimorph elements 15a and 15b are used, the heads 17a and 17b can be displaced at high speed, so that the magnetic heads can be displaced to follow track bending as required. Furthermore, bimorph elements 15a, 1
It is also possible to detect track bending by repeatedly bending the magnetic head 5b at a high frequency and reciprocating the magnetic heads 17a and 17b up and down at a high frequency.

Note that during high-speed playback at a speed several times the standard playback speed, only the electromagnetic drive mechanism 11 operates, so that playback is performed without noise bars appearing.

As described above, the rotating magnetic head device of the present invention has a structure in which the rotating magnetic head is attached to the tip of a bimorph, and the base side of the bimorph is supported by a rocking body that swings under the action of electromagnetic force. , the error with respect to the displacement trajectory of the magnetic head when the magnetic head is oscillatedly displaced in the direction of the rotational axis of the drum by the oscillator and scans with its center aligned with the center of the track recorded on the magnetic tape is calculated as a bimorph. Since it is displaced by , it has the advantage that it is possible to reproduce images without noise bars even during ultra-high-speed reproduction, which is used when searching for a predetermined position on a tape.

[Brief explanation of the drawing]

Figure 1A is a diagram that continuously draws the inhibition lines of CH1 and CH2 heads and shows the scanning locus of the heads, and Figures B and C are the oscillating displacements of the magnetic head during high-speed playback in the forward and reverse directions, respectively. FIG. 2A is a diagram showing the locus, and FIG.
3A is a bottom view of the upper rotating drum assembly, FIG. 3A is a diagram showing the displacement locus of the magnetic head due to the electromagnetic drive mechanism together with an ideal displacement locus, and FIG. 3B is a diagram showing the displacement locus of the magnetic head due to the bimorph element. be. DESCRIPTION OF SYMBOLS 1...Rotating magnetic head device, 2...Lower fixed drum, 3...Upper rotating drum assembly, 4...
Magnetic tape, 5... Rotating shaft, 9... Rotating yoke,
10...Plate spring, 11...Electromagnetic drive mechanism, 12
a, 12b... Magnet piece, 13... Drive coil, 1
5a, 15b...bimorph element, 16a, 16
b...Fixing member, 17a, 17b...Magnetic head, 20, 21...Drive circuit.

Claims (1)

[Claims] 1. In a rotating magnetic head device in which a magnetic head rotates within a drum around which a magnetic tape runs, being swingably supported in the direction of the rotational axis of the drum, the rotating magnetic head is attached to the tip of a bimorph. The base side of the bimorph is supported by an oscillating body that oscillates under the action of electromagnetic force, and a signal is sent to the oscillating body so that the center of the magnetic head scans the center of the track recorded on the magnetic tape during variable speed reproduction. A current is applied to cause the magnetic head to oscillate, and a signal current is applied to the bimorph to cause the magnetic head to swing so as to eliminate an error between the actual trajectory of the magnetic head displaced by the oscillator and the center of the track. A rotating magnetic head device characterized in that it is configured to cause displacement.