JPS6151334B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a support device for a magnetic head used in an automatic tracking device of a video tape recorder, etc., which can displace the magnetic head in a predetermined direction.

For example, as shown in FIG. 1, this type of rotating magnetic head device 1 includes a rotating disk 2 that rotates in the direction of arrow A, and upper and lower drums 3 and 4 are disposed above and below this disk 2. The disk 2 is configured to be rotationally driven by a motor 5. The magnetic tape 6 is wound obliquely around each of the drums 3, 4, etc. within a winding angle range of approximately 180 degrees, and is driven to run in the direction of arrow B. In order to maintain a constant position of the magnetic tape 6 with respect to the rotary head device 1, an inclined stepped portion 9 and the like are provided on the guide poles 7, 8 and the outer periphery of the lower drum 4. Further, two magnetic heads are used, for example, and these are mounted on the rotary disk 2 at an angle of 180 degrees to each other, and the tip of the head tip 11 is connected to the outer circumferential surface 3a of each drum 3, 4, etc. By protruding slightly from the magnetic tape 4a and coming into sliding contact with the magnetic tape 6, video signals are recorded and reproduced.

With such a rotating magnetic head 1, a recording track T is formed on the magnetic tape 6 as shown in FIG.
are formed diagonally one after another. These recording tracks T are used when the magnetic tape 6 is driven to run at a steady speed in the direction of arrow B. During normal reproduction, the magnetic head 1 can trace the recording tracks T and reproduce the recorded signal. However, when the traveling speed of the magnetic tape 6 in the direction of arrow B is different from the steady speed during recording, such as when playing back as a still image called still playback or slow motion playback, etc. Due to the difference in tape speed during recording and playback, or due to the elongation of the magnetic tape 6, the locus of the head chip 11 deviates from the recording track T during playback as shown in FIG. In other words, tracking errors often occur, and the recorded signal can only be reproduced in a degraded form.

Conventionally, various methods have been used to correct such tracking errors, one of which is to correct the head chip 1 as shown in FIG.
1 is attached to an electro-mechanical transducer, for example, the tip 12a of the bimorph plate 12, and the base end 12b of the bimorph plate 12 is supported by the head base 13.
A device is known in which the device can be freely displaced in the direction of arrow C in the figure. Note that the direction of the arrow C is the same as the gap direction of the head chip 11.

The bimorph plate 12 consists of two plates 13 and 14 made of lead zirconate titanate (PbZrO ₂ -PbTiO ₂ ), which is a piezoelectric material, and a central reinforcing metal plate 15 that serves as an intermediate electrode, with the polarization directions of the two plates 13 and 14 being opposite to each other. Electrostrictive drive electrodes 16 and 17 are formed on the entire outer surfaces of each of the plates 13 and 14. Therefore, these two outer electrodes 1
When a voltage is applied between 6 and 17, the bimorph plate 12 maintains a constant displacement from the point P where it is fixed to the head base 13 to the displacement point Q at the tip where the head chip 11 is attached, as shown in the schematic diagram of FIG. It is uniformly curved and displaced with a radius of curvature of . The direction and amount of displacement of the head chip 11 are determined by the voltage application direction (polarity) and the applied voltage level.

By the way, as the bimorph plate 12 bends, the gap surface of the head tip 11 attached to the tip 12a of the bimorph plate 12 bends when the bimorph plate 12 is displaced.
The tip 12a of the magnetic tape 6 is oriented in a warped direction, causing an error in the angle of contact with the magnetic tape 6, and
The gap surface is pulled back in a direction away from the magnetic tape 6, resulting in a disadvantage that the contact pressure against the magnetic tape 6 is reduced.

Therefore, in view of these circumstances, the inventors of the present invention
A magnetic head device that uses a new drive for the bimorph plate to avoid errors in the angle of contact between the gap surface of the head chip and the magnetic tape, which were disadvantageous in conventional systems, and to improve contact pressure. This is what we are trying to provide.

That is, in the magnetic head support device of the present invention, a head chip is attached to the tip of a plate made of piezoelectric material bonded in two layers, and the base end is fixed, and at least half of the base end side to be fixed is fixed. A drive electrode is provided in the part so that the bending action is performed by supplying an AC drive voltage to this electrode, and a part on the tip side is provided with a drive electrode such that both plates forming the above two layers extend in the same direction. The present invention is characterized in that it has an electrode structure, and the driving voltage is supplied to the electrode through a rectifying means.

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 5 shows an embodiment of the present invention, in which the bimorph plate 12 has its base end 12b fixedly supported by a fixed part such as a head base 13 provided in a rotating magnetic head device. It is mounted as a cantilevered beam. The bimorph plate 12 includes two plates 14a and 14b made of a piezoelectric material such as lead zirconate titanate (PbZrO ₂ -PbTiO ₂ ), which are connected to the base end 12.
In the half part on the b side, that is, the part 12B on the proximal end side of the bimorph plate 12, the central reinforcing metal plate 15, which also serves as an intermediate electrode, is interposed, and the remaining half part on the distal end 12a side, that is, the bimorph plate 12 At the tip side portion 12A, adhesive etc. 1 is applied without using such a metal plate 15.
8 are integrally bonded together. Electrostrictive drive electrodes 16 and 17 are formed on each outer surface of the bimorph plate 12 corresponding to the proximal end portion 12B, that is, the portion in which the central reinforcing metal plate 15 serving as the intermediate electrode is interposed. has been done. Further, on both outer surfaces of the distal end portion 12A of the bimorph plate 12, the bimorph plate 12
Which plate body 14a, 1 made of piezoelectric material constitutes
The electrodes 19 and 20 are formed to be spaced apart from the electrodes 16 and 17 so that the electrodes 4b also extend in the same direction.

In this example, one connection terminal 21a of the power source 21 is connected to the reinforcing metal plate 15 serving as the intermediate electrode, and each of the drive electrodes 16, 1
The other connecting terminal 21b of the power source 21 is connected to 7, so that a desired voltage can be applied in a desired polar direction between the intermediate electrode constituted by the central reinforcing metal plate 15 and each of the electrodes 16 and 17. There is.

Further, one connection terminal 21a and the other connection terminal 21b of the power source 21 are connected to input terminals 22a and 22b of a full-wave rectifier 22, and output terminals 2c and 22d of this rectifier 22 are connected to the electrodes 19 and 20. ing. Note that 23 is a resistor, which connects one output terminal 22c of the rectifier 22 and one electrode 2.
0 and the other output terminal 22d of the rectifier 22
and the other electrode 19, and is interposed so as to compensate for the quick response of the bimorph plate 12 even when the bias voltage changes quickly.

Therefore, when electricity is applied between the electrodes 16 and 17 for electrostrictive driving from the power supply 21, the bimorph plate 12 has a portion 12B on the base end side where these electrodes 16 and 17 are provided at the level of the applied voltage. and is warped and bent depending on the direction of application. At this time, since the power source 21 is connected to the electrodes 19 and 20 via the rectifier 22, a direct current corresponding to the AC drive voltage supplied between the electrostrictive drive electrodes 16 and 17 is generated. A voltage is applied, thereby extending each of the plates 14a, 14b in accordance with the warping of the proximal portion 12B.

Further, in the embodiment shown in FIG. 6, the bimorph plate 12 has an intermediate electrode between the plates 14a and 14b made of piezoelectric material at a proximal portion 12B and a distal portion 1.
They are formed in each part of 2A. That is, 15 indicates each plate body 14a, 1 on the proximal end side.
It is a metal plate that constitutes an intermediate electrode between 4b, and 15
a is a metal plate constituting an intermediate electrode between the respective plates 14a and 14b on the tip side; each of these metal plates 15,
15a are spaced apart from each other in the middle. In this case, one of the electrostrictive drive electrodes 16 and 17 is grounded, and the other 17 is connected to the power source 21. In addition, the input terminals 22a, 2 of the full-wave rectifier 22
2b has one 22a connected to the power source 21 and the other 22b grounded, one 22c of the output terminals 22c and 22d of this rectifier 22 connected to the metal plate 15a which becomes the intermediate electrode on the tip side, and the other 22d connected to the electrode. 19 and 20.
Further, between the output terminals 22c and 2 of the rectifier 22,
A resistor 23 is connected to 2d.

Therefore, in both cases shown in FIGS. 5 and 6 above, when a voltage is applied in a predetermined direction and at a predetermined level between the electrostrictive drive electrodes 16 and 17 on the base end 12b side of the bimorph plate 12, the As shown in FIG. 7, the base end portion 12B of the bimorph plate 12 undergoes a curvature deformation in a desired direction by a desired amount of curvature in response to this voltage. Therefore, the tip 12 of the bimorph plate 12
The head chip 11 supported at point a is displaced in accordance with the above-mentioned curved deformation, and the tracking error with respect to the recording track is corrected. Moreover, in the present invention, at this time, a predetermined DC bias corresponding to the electrostrictive drive voltage level is applied between the electrodes 19 and 20 on the tip 12a side of the bimorph plate 12, so that the bimorph plate 1
The tip end portion 12A of the head tip 2 extends in the direction of arrow D, that is, toward the surface of the magnetic tape 6, and the head tip 11 is always placed in sliding contact with the magnetic tape 6 with a stable contact pressure. be.

As is clear from the explanation of FIGS. 5 to 7 above, in the present invention, a normal electrode is used up to about half the length of the fixed end of the bimorph plate attached to the head base, and the tip end beyond that is used as a normal electrode. The section is adapted to apply a rectified driving voltage to the electrodes such that the two piezoelectric materials extend in the length direction. As a result, the greater the bending caused by driving, the greater the elongation, and the distance between the magnetic tape and the head chip can be kept unchanged. Therefore, the contact of the head chip with the magnetic tape caused by the curved deformation of the bimorph plate can be improved, and a contact state with constant contact pressure can be realized. Moreover, since the electrodes used to cause deflection in the bimorph plate extend to half of the fixed end side, there is less curvature-like bending at the tip end, and the error in the contact angle of the head tip against the magnetic tape can be kept to a minimum. There is.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view schematically showing the magnetic head device. FIG. 2 is a plan view schematically showing recording tracks on the magnetic tape surface. Third
The figure is a schematic side view showing a conventional example, and FIG. 4 is a side view schematically showing the operating state. FIG. 5 is a schematic circuit diagram showing one embodiment of the invention, FIG. 6 is a schematic circuit diagram showing another embodiment of the invention, and FIG. 7 is a side view schematically showing the operating state of the invention. be. 11...Head tip, 12...Bimorph plate, 12a...Tip of bimorph plate, 12b...
Proximal end of bimorph plate, 12A... distal end portion of bimorph plate, 12B... proximal end portion of bimorph plate, 13... head base, 14a, 14b...
Plate body made of piezoelectric material constituting a bimorph plate, 15
...Central reinforcing metal plate constituting the intermediate electrode, 16,
17...Electrostrictive drive electrode, 18...Adhesive, 1
9, 20...electrode, 21...power supply, 22...full wave rectifier.

Claims (1)

[Claims] 1 A head tip is attached to the tip of a plate made of piezoelectric material bonded in two layers, and the proximal end is fixed, and a drive electrode is provided on at least half of the proximal end to be fixed, and this electrode The bending operation is performed by supplying a driving voltage to the electrode, and the tip side has an electrode structure such that both plates of the two layers extend in the same direction, and this electrode is supplied with the driving voltage. A support device for a magnetic head, characterized in that the magnetic head is supplied via a full-wave rectifier.