JPS6331215Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic head device used in an automatic tracking device of a video tape recorder, and more particularly to a magnetic head device that improves the contact between the tip of the head chip and the magnetic tape.

In a general rotary head type video tape recorder, when the tape speed is different from that during recording, such as during slow, still, quick, and reverse playback, the tracking locus of the magnetic head changes from one video track on the magnetic tape. Missing,
So-called guard band noise occurs. In order to remove such guard band noise, automatic tracking control is known in which the magnetic head itself is displaced in the track width direction to scan one video track during one tracking. There is.

An example of a rotating magnetic head device for a video tape recorder that enables such automatic tracking control is shown in FIG.

In FIG. 1, a rotating magnetic head device 1
has a rotating upper drum 2 and a fixed lower drum 3. The rotational drive shaft 4 connects the upper drum 2 and the motor 5, and the upper drum 2 is rotated by the motor 5 in the direction of arrow A in the figure at a rotational speed of 3600 rpm. The magnetic tape 6 is wound diagonally around the upper drum 2 and the fixed lower drum 3 at a winding angle of approximately 360 degrees, and is driven to run in the direction of arrow B in the figure.
A pair of guide poles 7 and 8 are provided to regulate the winding angle of the tape, and a tape guide stepped portion 9 is provided on the lower drum 3. Furthermore, the magnetic head device 10 basically has one magnetic head, and its head chip 1
1 is placed on a movable element such as a bimorph plate so as to slightly protrude from the outer peripheral surfaces 2a, 3a of each drum 2, 3. And this head tip 1
Video signals are recorded and reproduced by the leading end of the magnetic tape 6 coming into sliding contact with the magnetic tape 6.

When a video signal is recorded on the magnetic tape 6 by such a rotating magnetic head device 1, recording tracks T as schematically shown in FIG. 2 are sequentially formed obliquely. When reproducing the recorded magnetic tape 6 in a normal state, the magnetic tape 6 is driven to run in the direction of arrow B in the figure, and the head chip 11 scans over the recording track T in the direction of arrow C in the figure.

On the other hand, when the running speed of the magnetic tape 6 is different from that during recording, such as when playing back a still image called still playback, the head chip 11 moves as shown by the broken line in the figure unless some measure is taken. The head chip 11 is moved by the movable element, and the scanning trajectory L is moved along the recording track. So-called automatic tracking control is performed so as to follow T.

As an example of the configuration of a magnetic head device for performing such tracking control, the one shown in FIGS. 3 and 4, for example, is known. 3 and 4, the head chip 11 is attached to the electro-mechanical transducer, for example, the tip 12f of the bimorph plate 12, and the base end 12r of the bimorph plate 12 is attached to the head base 1.
By bonding the bimorph plate 12 to the platform-like protrusion 14 of No. 3 and fixedly supporting it to the upper drum 2 through the screw attachment hole 15, the head tip 11 can be bent in response to an electric signal. Middle arrow D
A device that can be freely displaced in any direction is known. Note that the direction of the arrow D is the head chip 11.
is the same as the gap direction of Further, 16 is a lead wire of the head chip 11, and 17 and 18 are lead wires of the bimorph plate 12.

The bimorph plate 12 is made of two plates 12a and 12b made of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ), which is a piezoelectric material, so that their polarization directions are opposite to each other, for example, in the direction of arrow P in FIG. As shown, it is constructed by bonding together through a central reinforcing metal plate 12m that serves as an intermediate electrode, and electrostrictive drive electrodes 1 are provided on both surfaces.
2c and 12d are formed. When a voltage is applied between these two outer electrodes, this bimorph plate 1
2 is the head tip 11 from the fixed end to the head base 13 as shown by the imaginary line in the schematic diagram of FIG.
The head tip 11 is uniformly curved and displaced with a constant radius of curvature from the fixed end to the displaceable end at which the head tip 11 is attached. In addition, head tip 11
The direction and amount of displacement are the direction of voltage application (polarity)
and the applied voltage.

By the way, as the bimorph plate 12 bends, as is clear from FIG.
The tip 12f of the gap is oriented in the direction of warping and does not touch the magnetic tape 6 perpendicularly, resulting in 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. As a result, the contact pressure against the magnetic tape 6 decreases. This resulted in poor contact with the magnetic tape 6, resulting in a disadvantage that the reproduction output voltage of the head was attenuated.

Therefore, the present inventors fixedly supported a head holder 19 made of carbon fiber or the like at the tips of two bimorph plates 12, 12, as shown in FIG. 5, and decided to support the head chip 11 with this holder 19. Therefore, the head chip 11 is moved in parallel in the direction of arrow D in the figure to avoid occurrence of an error in the angle of contact with the magnetic tape 6.

By the way, in order to widen the range of change in tape speed during playback, it is necessary to increase the sensitivity of the bimorph board, but in the configuration shown in Figure 5 above, due to the performance limitations of the bimorph board, it is necessary to increase the sensitivity of the bimorph board. I wasn't able to widen the range of modes very much.

The present invention further improves the prior art, and by arranging three or more bimorph plates in parallel, the overall rigidity is increased and the resonance frequency is increased without reducing the vibration sensitivity of the bimorph plates. A magnetic head device that is capable of increasing the height of the tape, thereby expanding the range of changes in tape speed during playback, and simplifying electrical connections between multiple bimorph plates or reducing the number of external lead wires. The purpose is to provide.

That is, the magnetic head device according to the present invention is characterized by at least three electro-mechanical transducers each using a piezoelectric plate having an electrode adhered to its surface, and the three or more electro-mechanical transducers. a plurality of spacers and a pair of support stands disposed parallel to each other; and at least three flat plates having substantially flexibility and protruding from and fixed to the respective tip ends of the electro-mechanical conversion element. A head support comprising a connecting member and a portion for connecting and fixing the tips of these flat connecting members to each other, and a head tip attached to the connecting and fixing portion of the head support, and the head tip is arranged parallel to each other. As electro-mechanical transducers, opposing surface electrodes of adjacent electro-mechanical transducers are arranged in such a way that opposing surface electrodes of adjacent electro-mechanical transducers are alternately arranged such that driving voltage is applied in the same direction and in the opposite direction with respect to the direction of bending displacement. By setting the potential, each electro-mechanical conversion element is configured to bend in the same direction in accordance with the drive voltage.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 6 is a side view schematically showing the first embodiment of the present invention, and the left and right directions in the figure are shortened. In FIG. 6, the three bimorph plates 21, 22, and 23 are constructed almost the same as the bimorph plate 12, but the polarization direction of the two piezoelectric plates 22a and 22b of the bimorph plate 22 (see FIG. The middle arrow P direction) is different from the others, and they each face the central reinforcing metal plate 22m that becomes the intermediate electrode. Since the other configurations are the same as the bimorph plate 12 shown in FIG. 3 etc., the same attached symbols a, b, . . . , etc. are given to the corresponding parts, and the explanation will be omitted.

These three bimorph plates 21, 22, 23
The proximal ends of the two are fixedly supported on a head base 31 or the like so that they are parallel to each other, and a spacer 32 is provided between the bimorph plates 21 and 22, and a spacer 32 is provided between the bimorph plates 22 and 23. Spacer 33
are arranged respectively. Furthermore, the electrical connections between the respective electrodes of these bimorph plates 21, 22, and 23 are such that all of them are displaced in the same direction and have the same amount of displacement in response to the bimorph drive signal. That is, a driving voltage of ±200V is applied to the electrode 21c of the first bimorph plate 21, and the electrode 2
1d, for example, a series circuit of a Zener diode 41 and a diode 42 with a Zener voltage of 39 V is inserted and connected from the electrode 21c to the intermediate electrode (center metal plate) 21m, and the electrode 21d is grounded.
A similar series circuit of a Zener diode 43 and a diode 44 is inserted and connected from there to the intermediate electrode 21m. Then, each electrode 23c, 23m, 23d of the third bimorph plate 23 is connected to each electrode 21 of the third bimorph plate 23.
c, 21m, and 21d, respectively. Since the polarization direction of the second bimorph plate 22 is opposite to that of the others, ±200V is applied to the electrode 22d,
While grounding the electrode 22c, the intermediate electrode 22m
A series circuit of a diode 45 and a zener diode 46 is connected to the intermediate electrode 22d.
A series circuit of a diode 47 and a Zener diode 48 is connected from m to electrode 22c, respectively. In this case, the mutually opposing electrodes 21d and 22c of the bimorph plates 21 and 22 are at the same ground potential, and the opposing electrodes 22d and 23c of the bimorph plates 22 and 23 are each at ±200V.
Therefore, if the spacers 32 and 33 are made of a conductive material and the equipotential electrodes are electrically connected, the four electrodes 21d, 22c, 22
The lead wires to d and 23c can be wired to two conductive spacers 32 and 33. In addition, the number of relay terminals such as terminal boards arranged on the head base 31 etc. is as follows.
As shown in FIG. 6, there are four pieces.

These three bimorph plates 21, 22, 23
At the tip of each flexible portion 51,
52 and 53 are fixedly protruding and connected to each bimorph plate, the tips of these members 51, 52, and 53 are connected and fixed to each other, and the head chip 11 is attached and fixed to this connected and fixed part 56. These parts 5
1, 52, 53 and the connecting and fixing portion 56 may be formed by integral molding using an insulating material such as plastic. That is, in FIG. 6, the electrodes 21d, 22 at the tips of the bimorph plates 21, 22, 23
Since the members 51, 52, 53 are fixed to the surfaces d and 23d, each of these members 51, 5
It is necessary to provide insulation between the connecting and fixed portion 56 or at least one of the flexible members 51, 52, and 53 using an insulating material.
Therefore, the entire head support 50 may be integrally formed of plastic or the like, or the flexible members 51, 52, 53 may be made of an insulating material such as plastic, and the connecting and fixed portion 56 may be made of a conductive metal material. Alternatively, elastic flexible members 51, 52, 53 such as thin steel plates may be embedded in the connecting and fixing portion 56 such as plastic.

Here, the connecting fixed portion 56 of the head support 50
must be made of a rigid member so that it does not easily deform when the bimorph bends, and even if it is formed integrally from the same material,
The flexible members 51, 52, and 53 can be made thinner to provide flexibility (including elasticity), and the connecting and fixed portion 56 can be made thicker to provide rigidity. The head support is preferably made of light and strong material such as carbon fiber.

Note that, as shown by the imaginary line in FIG.
1, 52', and 53 are connected to the electrodes 21d, 22c, and 23d, which have the same ground potential, respectively.
The entire head support 50 can be integrally formed from a conductive material such as steel. In this case, each member 5
1, 52', 53 are made sufficiently thin so that each member 5
1, 52', and 53 should of course be made to bend easily.

According to the first embodiment of the present invention having the above configuration, even if the effective length l of the bimorph is lengthened in order to increase the deflection sensitivity of the bimorph, a plurality of (three in this example) bimorph plates 21 ,22,23
The structure in which these layers are stacked parallel to each other at a predetermined interval increases the overall rigidity and increases the resonant frequency, making it possible to have an extremely wide range of automatic tracking operations as described above, and to create high-performance video tapes. A magnetic head device for a recorder can be provided. Further, when the bimorph is deformed in a curved manner, the head tip 11 is moved in parallel in the direction of arrow D, and the error in the contact angle with the magnetic tape can be extremely reduced.
It is possible to prevent adverse effects such as image quality deterioration due to a reduction in the playback signal level. Furthermore, since the opposing electrodes between the bimorphs are configured to have equal potential, wiring of the lead wires can be simplified using a conductive spacer, and assembly can be easily performed. Also, during bimorph drive control, the adjacent bimorph plates 21 and 2
Since the opposing surface electrodes 21d and 22c, or 22d and 23c of the bimorph plates 2, 22, and 23 are at the same potential, electrically conductive spacers 32, 33 are used between the bimorph plates to connect leads for supplying driving voltage. Wiring can be simplified,
In addition to simplifying assembly, there is no risk of negative effects such as discharge or short circuit between the opposing electrodes, resulting in excellent reliability. In addition, the spacing between the bimorph plates can be extremely narrow (for example, 0.5mm
It is also easy to make the device smaller and thinner.

Next, FIG. 7 shows a second embodiment of the present invention,
An example is shown in which four bimorph plates 61, 62, 63, and 64 are used. In this case, the polarization direction P of the first and third bimorph plates 61 and 63 is
It is the same as the bimorph plate 22 in the middle position in the figure,
The polarization directions of the second and fourth bimorph plates 62 and 64 are the same as those of the bimorph plates 21 and 23 shown in FIG. 6 and the bimorph plate 12 shown in FIG. 3, etc. In addition, each flexible member 7 of the head support body 70 is attached and fixed to the tip of each bimorph plate 61, 62, 63, 64.
1, 72, 73, and 74 are electrodes 61c, respectively.
62d, 63c, and 64d, and since the voltages applied to these electrodes change at equal potential, the head support 70 can be formed integrally of steel or the like. In this case, each member 71
74 need to be formed sufficiently thin so that they can be bent when each bimorph plate 61 to 64 is deformed. In addition, each spacer 32, 33, 34
Since the electrodes facing each other with a space therebetween have the same potential, it goes without saying that the lead wiring can be simplified by using a conductive material. Another configuration is the sixth
Since it is similar to the figure, corresponding parts are given the same reference numerals and explanations will be omitted.

According to this second embodiment, as in the first embodiment, it is possible to avoid the occurrence of an error in the contact angle of the head to the tape, thereby preventing image quality deterioration, and increasing the resonant frequency without reducing the vibration sensitivity of the bimorph. This not only improves the automatic tracking function but also simplifies the wiring.

Next, FIG. 8 shows a third embodiment of the present invention,
An example is shown in which four bimorph plates 81, 82, 83, and 84 having the same structure including the polarization direction are used. In this third embodiment, only two sets of Zener diodes and diodes are required, and the number of terminals such as a terminal block is only three. Further, even if the entire head support body 90 is integrally formed of a conductive material such as steel, the flexible members 91, 92, 93, and 94 can be arranged at equal intervals. However, each spacer 36, 37, 38 is made of an insulating material, and each bimorph plate 91, 92, 9
The distance between 3 and 94 must be set somewhat wide (for example, about 2 mm) in consideration of air discharge.
The other configurations are the same as those of the first and second embodiments.

According to the third embodiment, it is possible to avoid occurrence of an error in the contact angle of the head to the tape, and to increase the resonant frequency without reducing the vibration sensitivity of the bimorph. Furthermore, as an advantage of this embodiment, since it is sufficient to use a plurality of bimorph plates having the same structure, the number of types of parts can be reduced, which is convenient for handling and storage. In addition, there are two sets of Zener diodes and diodes (to drive one bimorph board).
This reduces the number of parts. Furthermore, a conductive material can be used for the head support, and a compact head support with the necessary strength can be constructed using steel.

[Brief explanation of the drawing]

Fig. 1 is an external perspective view schematically showing an example of a rotating magnetic head device, Fig. 2 is a plan view schematically showing a recording track on a magnetic tape, and Fig. 3 is a specific example of a conventional magnetic head device. 4th enlarged perspective view showing
The figure is also a schematic side view. FIG. 5 is a schematic side view showing an example of the prior art of the present invention. FIG. 6 is a side view schematically showing the first embodiment of the present invention. FIG. 7 is a side view schematically showing a second embodiment of the present invention. FIG. 8 is a side view schematically showing a third embodiment of the present invention. 11... Head chip, 21, 22, 23, 6
1, 62, 63, 64, 81, 82, 83, 84
... Bimorph board, 31 ... Head base, 32,
33, 34, 36, 37, 38...Spacer, 5
0,70,90...Head support, 51,52,
53, 71, 72, 73, 74, 91, 92, 9
3,94...Flexible member, 56,76,96...
Connecting fixed part.

Claims (1)

[Claims for Utility Model Registration] At least three electro-mechanical transducers using piezoelectric plates having electrodes adhered to their surfaces; and at least three electro-mechanical transducers arranged in parallel to each other. a plurality of spacers and a pair of support stands disposed in the electro-mechanical transducer; at least three plate-like connecting members having substantially flexibility and protruding from and fixed to the respective tips of the electro-mechanical transducer; a head support consisting of a portion that connects and fixes the tips of flat plate-like connecting members to each other; and a head chip that is attached to the connecting and fixing portion of the head support, and the electro-mechanical converter that is arranged parallel to each other. Elements are alternately arranged such that the driving voltage is applied in the same direction and in the opposite direction with respect to the direction of bending displacement, so that the potentials of opposing surface electrodes of adjacent electromechanical transducer elements are equalized. A magnetic head device characterized in that the electro-mechanical transducers are configured to bend in the same direction depending on the drive voltage.