JPH0370285B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating magnetic head fine moving device, and more particularly to a rotating magnetic head fine moving device that can always maintain a rotating magnetic head in the correct position during recording or reproduction.

2. Description of the Related Art Conventionally, as is well known, a piezoelectric bimorph has been used as a means for displacing a rotating magnetic head (video head) for variable speed playback, for example, in broadcasting VTRs and the like. However, the piezoelectric bimorph has the disadvantage that it cannot achieve a very large displacement due to limitations in strength and applied voltage. Another drawback was that displacement occurred due to temperature changes, etc.

Furthermore, in the piezoelectric bimorph, the rotating magnetic head is displaced by cantilever-like bending deformation, so if an attempt is made to obtain too large a displacement, the video head will not contact the magnetic tape surface at right angles.
Another drawback is that the so-called tilt angle increases, and the contact between the video head and the magnetic tape, that is, the head touch, deteriorates.

As a result, in order to displace the video head,
The method using a piezoelectric bimorph has the disadvantage that it is not possible to perform recording or reproduction to a sufficiently satisfactory degree.

An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art and to enable correct recording or reproduction by making it possible to greatly displace a rotating magnetic head, and to increase the tilt angle even when the magnetic head is largely displaced. To provide a rotating magnetic head fine movement device which can prevent the above problems and maintain good head touch.

In order to achieve the above object, the present invention provides an elastic plate whose both ends are fixed to the upper rotating cylinder and is movable in the direction of the rotation axis, and a rotating magnetic head is disposed at the tip of the central part. did.

In addition, in the present invention, in order to achieve the above object, a high magnetic permeability member is provided in the opposite direction (rotation axis direction) to the rotating magnetic head at the center of the elastic plate, and a certain amount of magnetic permeability is applied to the high magnetic permeability member. A high magnetic permeability material was fixed to the upper rotating cylinder so as to face each other across a gap to form a magnetic circuit, and an electromagnetic coil was attached to the high magnetic permeability material.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a bottom view when an embodiment of the rotating magnetic head fine movement device of the present invention is applied to an upper rotating cylinder of a two-head helical scan VTR.

In the figure, 1 and 2 are rotating magnetic heads; 3,
4 is a head holder, 5 and 6 are leaf springs as elastic plates, 7 and 8 are head bases, 9 and 10 are high magnetic permeability members, 11 is an upper rotating cylinder, 12 and 13 are set screws, and 41 and 42 are rotating magnetic heads. Height adjustment screws 1 and 2, and electrodes 51 and 52.

The rotating magnetic heads 1 and 2 are fixed to head holders 3 and 4, respectively. The head holders 3, 4 are preferably made of a material that is lightweight and provides good flatness, such as ceramic or plastic. Electrodes 51 and 52 provided on the head holders 3 and 4 are for relaying lead wires from the rotating magnetic heads 1 and 2.

The head holders 3 and 4 are respectively fixed to the lower surfaces of the center portions of leaf springs 5 and 6, which are approximately V-shaped as shown in the figure. Further, high magnetic permeability members 9 and 10 are fixed to the upper surfaces of the center portions of the leaf springs 5 and 6 on the opposite side from the rotating magnetic heads 1 and 2.

The high magnetic permeability members 9 and 10 are made of iron, soft ferrite, or the like. Furthermore, as shown in the figure, both ends of the leaf springs 5 and 6 are fixed to head bases 7 and 8, respectively.
3, it is fixed to the upper rotating cylinder 11.

As is clear from the above configuration, the rotating magnetic heads 1 and 2 are elastically supported by the leaf springs 5 and 6 with respect to the upper rotating cylinder 11, and are movable in the direction perpendicular to the plane of the paper of FIG. It's summery.

The height, 180° indexing and protrusion of the rotating magnetic heads 1 and 2 can be adjusted using the head bases 7 and 8.
This can be done in the same way as in the past by slightly moving or deforming the .

That is, for example, when adjusting the height of the rotating magnetic heads 1 and 2, the height of the rotating magnetic heads 1 and 2 is adjusted.
This is done by attaching the height adjustment screws 41 and 42 of No. 2 to the upper rotating cylinder 11, for example, so as to press the head bases 7 and 8 from above (see Fig. 4), and adjusting the degree of screwing. be able to.

Figure 2 shows the upper rotating cylinder 11 shown in Figure 1.
FIG. 2 is a sectional view taken along the - line. In the figure, 14 to 17 are electromagnetic coils, 18 and 19 are yokes, 22 to 25 are pins, and 44 and 45 are magnetic shield plates. Further, FIG. 3 is a plan view of the upper rotating cylinder 11. In the same figure, 53, 54
indicates a holder. In addition, in FIGS. 2 and 3, the same parts and equivalent parts as in FIG. 1 are indicated by the same reference numerals.

As is clear from FIGS. 2 and 3, the pins 22 and 23 are separated by a certain gap for the high magnetic permeability member 9, and the pins 22 and 23 are separated by a certain gap for the high magnetic permeability member 10. Separate the pin 24,
25 are respectively arranged on the upper rotating cylinder 11.

The pins 22 and 23 are fixed by a holder 53, and the pins 24 and 25 are fixed by a holder 54, respectively.

The holders 53 and 54 are made of non-magnetic material,
It is screwed to the upper rotating cylinder 11. Further, the upper parts of the pins 22 and 23 are connected to a yoke 18, and the upper parts of the pins 24 and 25 are connected to a yoke 19.
Each is connected. Note that the yoke 1
8, 19 and pins 22-25 are made of high magnetic permeability material.

Furthermore, electromagnetic coils 14 and 15 are wound around the pins 22 and 23, respectively, and electromagnetic coils 16 and 17 are wound around the pins 24 and 25, respectively.
Therefore, the high magnetic permeability member 9, the pins 22, 23 and the yoke 18, and the high magnetic permeability member 10, the pin 2
4, 25 and the yoke 19 constitute independent magnetic circuits.

FIG. 4 is a sectional view of a rotating magnetic head device having an upper rotating cylinder 11 using a rotating magnetic head fine movement device according to an embodiment of the present invention.

In the same figure, 28 is a lower fixed cylinder, 29
is a disk, 30 is a shaft (rotating shaft), 31 is an upper bearing, 32 is a lower bearing, 33 is a rotary transformer, 34 is a 3-channel slip ring, 35
is a 3 channel brush. Note that the same parts and equivalent parts as in FIG. 1 are indicated by the same reference numerals.

The lower fixed cylinder 28 is provided with an upper bearing 31 and a lower bearing 32, which support the shaft 30. A disk 29 is fixed to the shaft 30 by a method such as press-fitting, and the upper rotating cylinder 11, as shown in the figure,
It is screwed to the disk 29. Incidentally, the transmission and reception of signals to and from the rotating magnetic heads 1 and 2 is performed by a rotary transformer 33, as is well known.

In addition, pin 2 that constitutes the magnetic circuit described above
Electromagnetic coils 14 and 15 wound around 2 and 23
and electromagnetic coils 16 and 1 wound around pins 24 and 25, which also constitute the other magnetic circuit.
7 are connected in series or in parallel.

Therefore, the number of lead wires from the electromagnetic coils 14 to 17 is four. However, one of the lead wires of each pair can be shared, so even with a total of three lead wires, it is possible to
Current can be supplied to these electromagnetic coils 14-17.

Therefore, in order to supply current to the electromagnetic coils 14 to 17, the three-channel slip ring 3
4 is fixed to the disk 29. Furthermore, three-channel brushes 35 are fixedly arranged.

As can be understood from the above description, when a DC voltage is supplied to each of the electromagnetic coils 14, 15 and 16, 17 via the brush 35 and the slip ring 34, the pins 22, 23 and the high magnetic permeability member 9 , and the gap portions of the pins 24, 25 and the high magnetic permeability member 10, a certain attractive force acts on them.

As a result, the high magnetic permeability members 9 and 10 are subjected to an upward force, so that the leaf springs 5 and 6 fixed to the high magnetic permeability members 9 and 10 are bent upward. As a result, the rotating magnetic heads 1 and 2, which are respectively linked to the leaf springs 5 and 6, are also displaced upwardly.

Next, the operation of the rotating magnetic head fine movement device according to one embodiment of the present invention will be described.

First, the initial heights of the rotating magnetic heads 1 and 2 of the rotating magnetic head device can be set at correct positions (reference positions) by adjusting the applied DC voltage as described above. Note that during recording, the rotating magnetic heads 1 and 2 are fixed at this reference position from beginning to end.

Next, correction during reproduction of the rotating magnetic heads 1 and 2 will be described. Rotating magnetic head 1, 2
Correction during scanning is performed using the electromagnetic coils 14, 1 described above.
This is done by applying an alternating voltage to terminals 5, 16, and 17.

That is, the electromagnetic coils 14, 15 and 1
When an alternating voltage is applied to the high magnetic permeability member 9 and 17, an attractive force that increases or decreases according to the applied alternating voltage
and 10 respectively. As a result, the bending of the leaf springs 5, 6 fixing the high magnetic permeability members 9, 10 changes. As a result, the leaf spring 5,
Rotating magnetic heads 1 and 2 attached to 6
is displaced upward and downward (in the direction perpendicular to the plane of paper in FIG. 1) centering on the reference position.

Therefore, during reproduction, the positional deviation of the rotating magnetic heads 1 and 2 with respect to the recording track is detected by conventionally well-known means, and a corresponding alternating voltage for correction is applied to the electromagnetic coils 14 to 17.
By applying the same voltage to the rotating magnetic heads 1 and 2, the rotating magnetic heads 1 and 2 can always be corrected to the correct position for reproduction.

In the rotating magnetic head fine movement device of this embodiment, as described above, by applying DC and/or AC voltage to the electromagnetic coils 14 to 17, the rotating magnetic heads 1 and 2 are displaced via the magnetic circuit. Therefore, there is a concern that leakage magnetic flux from the magnetic circuit may affect the rotating magnetic heads 1 and 2.

However, in this embodiment, as described above, since the rotating magnetic head and the magnetic circuit are arranged in opposite directions with respect to the widthwise center of the central portions of the leaf springs 5 and 6, the leakage occurs. The influence of magnetic flux can be reduced.

Further, as shown in FIG. 2, if magnetic shield plates 44 and 45 are provided on the upper rotating cylinder 11,
Furthermore, since the influence of leakage magnetic flux can be reduced, no particular problem arises.

Note that the adverse effects of the leakage magnetic flux are generally more significant during recording than during reproduction. Therefore, in order to avoid the adverse effects of magnetic flux leakage during recording, the positions of the rotating magnetic heads 1 and 2 are not adjusted by passing DC current through the magnetic coils 14 to 17 as described above. This can be done using only the aforementioned adjustment screws 41, 42 (see Figures 1 and 4).

Furthermore, if the adverse effects of the leakage magnetic flux do not pose a problem, a permanent magnet may be inserted into the magnetic circuit instead of setting the reference position by passing a direct current through the magnetic coils 14 to 17.

In this case, the above-mentioned permanent magnets may be inserted between the yokes 18 and 19 (see FIG. 3), but in order to further reduce the influence on the rotating magnetic heads 1 and 2, As shown in FIG. 5, it is preferable to arrange the permanent magnets 55 and 56 on the rotating shaft side.

In addition, in FIG. 5, 57 to 60 indicate yokes made of high magnetic permeability material. In addition, the same parts and equivalent parts as in FIG. 3 are indicated by the same reference numerals.

Next, according to this embodiment, the rotating magnetic head 1,
The following describes how the tilt angle of No. 2 is reduced and, as a result, it is possible to maintain good head touch.

In this embodiment, as described above, the leaf springs 5, 6
The rotating magnetic heads 1, 2 are supported at both ends of the plate springs 5, 6 through the head holders 3, 4 at the center of the leaf springs 5, 6.
are placed.

According to the experimental results of the present inventors, it has become clear that in such a structure, the swing angle of the heads 1 and 2 can be made extremely small compared to the case where a conventional cantilevered piezoelectric bimorph is used.

Furthermore, in this embodiment, the leaf spring 5,
As described above, the phase relationship between the parts that generate the force for bending the leaf springs 5 and 6, that is, the high magnetic permeability members 9 and 10, and the rotating magnetic heads 1 and 2 is centered in the width direction of the central parts of the leaf springs 5 and 6. are arranged in opposite directions.

In other words, the positions of the high magnetic permeability members 9 and 10 are shifted from the center of the central portion of the leaf springs 5 and 6 in the width direction in the rotation axis direction. Therefore, when an attractive force in the direction of the arrow shown in FIG. 6 acts on the high magnetic permeability members 9 and 10, the leaf springs 5 and 6 are deformed as shown by solid lines.

That is, if the high magnetic permeability members 9, 10
is located at the center of the central portion of the leaf springs 5, 6, the leaf springs 5, 6 are deformed as shown by the broken lines, but the mounting positions of the high magnetic permeability members 9, 10 are As mentioned above, since it is offset from the center of the central portion, it is deformed as shown by the solid line.

As a result, the tilt angles of the rotating magnetic heads 1 and 2 hardly matter, and the heads 1 and 2 can come into contact with the magnetic tape surface at a substantially right angle.

As is clear from the above description, in the present invention,
In order to perform recording or reproduction correctly, the rotary magnetic head can be largely displaced, and even when the magnetic head is largely displaced, it is possible to substantially prevent the occurrence of a tilt angle.

Furthermore, the present invention has the advantage that the rotating magnetic head can be displaced with an extremely low voltage compared to the case where a conventional piezoelectric bimorph is used. Although the present invention uses an electromagnet to displace the rotating magnetic head, the adverse effect of leakage magnetic flux on the rotating magnetic head does not pose a particular problem as described above.

[Brief explanation of drawings]

Figure 1 shows two rotating magnetic head fine movement devices of the present invention.
A bottom view showing an embodiment applied to an upper rotating cylinder of a head helical scan VTR, FIG. 2 is a sectional view thereof, FIG. 3 is a plan view thereof, and FIG. sectional view of a rotating magnetic head device with an upper rotating cylinder 11;
FIG. 5 is a plan view showing another embodiment of the upper rotary cylinder 11 shown in FIG. 1, and FIG. 6 is an explanatory side view of the essential parts of the rotating magnetic head fine movement device of the present invention. 1, 2... Rotating magnetic head, 5, 6... Leaf spring, 9, 10... High magnetic permeability member, 11... Upper rotating cylinder, 14-17... Electromagnetic coil, 18,
19 and 57-60... York, 22-25...
...Pin, 55, 56...Permanent magnet.

Claims (1)

[Scope of Claims] 1. A rotating magnetic head fine movement device for displacing a rotating magnetic head, which rotates with the rotation of a rotating body to scan a magnetic tape, to a desired position in the direction of the rotation axis,
an elastic plate whose both ends are fixed to the rotating body and whose central part is movable in the direction of the rotation axis; the rotating magnetic head disposed at the tip of the central part of the elastic plate; and the central part of the elastic plate. a magnetic circuit made of a high magnetic permeability material fixed to the rotating body so as to face the high magnetic permeability member and facing the high magnetic permeability member with a certain gap therebetween; 1. A rotating magnetic head fine movement device comprising: an electromagnetic coil wound in a high magnetic permeability material of a circuit, and displacing the rotating magnetic head to a desired position by energizing the electromagnetic coil. 2. Claim 1, characterized in that the magnetic circuit including the high magnetic permeability member is disposed in the central portion of the elastic plate on the side opposite to the rotating magnetic head, that is, on the side close to the rotating shaft. Rotating magnetic head fine movement device as described in .