JPS6161173B2 - - 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 is capable of displacing a magnetic head in a predetermined direction. This invention relates to a head device with improved features.

In this type of rotating magnetic head device 1, as shown in FIG. 1, for example, a rotating drive shaft 2 connects an upper drum 3 and a motor 5.
As a result, the upper drum 3 is rotated in the direction of arrow A in the figure at a rotational speed of 3600 rpm. The magnetic tape 6 is diagonally placed around the upper drum 3 and the fixed lower drum 4.
It is wrapped at a wrapping angle of 360°, as shown by arrow B in the figure.
It is driven to travel in the direction. 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 4. The magnetic head device 10 basically has one magnetic head, and the head chip 11 is a movable element such as a bimorph plate that slightly protrudes from the outer peripheral surfaces 3a, 4a of each drum 3, 4. placed on top. The tip of this head chip 11 is connected to the magnetic tape 6.
Recording and playback of video signals are performed by slidingly contacting the device.

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. It will scan on a scanning locus l shown by . In such a state, as a matter of course, a high-quality reproduced image cannot be obtained, so a so-called tracking adjustment is performed by displacing the head chip 11 using the movable element so that its scanning locus follows the recording track T.

As an example of the configuration of such a tracking adjustment device, as shown in FIGS. 3 and 4, a head chip 1 is used.
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 glued to the platform-like protrusion 14 of the head base 13, and the screw attachment hole 1 is
It is known that the head tip 11 is fixedly supported on the upper drum 3 via the upper drum 3 so that the head tip 11 can be freely displaced in the direction of the arrow C in the figure when the bimorph plate 12 is bent in response to an electric signal. ing. Note that the direction of the arrow C is the same as the gap direction of the head chip 11. Further, 16 is a lead wire of the head chip 11, and 17 and 18 are lead wires of the bimorph plate 12.

The bimolk plate 12 is constructed by bonding two plates of lead zirconate titanate (PbZrO ₂ -PbTiO ₂ ), which is a piezoelectric material, with a central reinforcing metal plate interposed so that their polarization directions are opposite to each other. , electrostrictive driving electrodes are formed on the entire surface of both surfaces, and when a voltage is applied between these two outer electrodes, this bimorph plate 12 moves to the head base 13 as shown 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, the head tip 11
The direction and amount of displacement are the direction of voltage application (polarity)
and the applied voltage level.

By the way, as the bimorph plate 12 bends, as is clear from FIG.
The tip 12a of the gap is oriented in a warped direction, and does not touch the magnetic tape 6 perpendicularly, causing an error in the angle of contact with the magnetic tape 6, and the gap surface is pulled away from the magnetic tape 6. As a result, the contact pressure against the magnetic tape 6 decreases. As a result, the contact with the magnetic tape 6 becomes poor and the reproduced output voltage of the head is attenuated.

Therefore, the present inventors fixedly supported a rubber head holder 19 at the tips of two bimorph plates 12 and 120, as shown in FIG. 6, so that the head chip 11 was supported by this holder 19. This makes it possible to move the head chip more parallelly than when the head chip is supported by the single bimorph plate. However, if the head holder 19 is made of rubber as in the above-mentioned configuration, when the two bimorph plates 12 and 120 are displaced in the vertical direction in the figure, the direction of displacement is slightly The head chip 11 moves in the right angle direction, and there is therefore a risk that the image quality will deteriorate as jitter occurs during playback.

Therefore, in view of these circumstances, the inventors of the present invention
By adopting a new structure for supporting the head chip using a bimorph plate, it is possible to avoid errors in the angle of contact between the gap surface of the head chip and the magnetic tape, which were disadvantageous in the conventional system, and to reduce the contact pressure. The present invention aims to provide an improved magnetic head device.

That is, the magnetic head device of the present invention is an electric head device using a piezoelectric plate having electrodes adhered to its surface.
A pair of mechanical transducer elements were installed so that they were substantially parallel to each other, and each base end of each of these elements was fixedly supported, and a head support member made of a hard material was attached to the middle part of each tip. This is characterized in that both ends of the elastic member are connected and fixed.

An embodiment of the present invention will be described below with reference to FIG.

First, as shown in FIG. 7a, the two bimorph plates 12, 120 are fixedly supported at their base ends 12b, 120b on the head base 13 so as to be substantially parallel to each other. Further, at each tip 12a, 120a of each bimorph plate 12, 120, a plate spring 20, such as a phosphor bronze plate, is bent into a U-shape as an elastic member and connects each bent piece 20a, 20b. Fixed. A head holder 22 made of, for example, Bakelite or other hard material is fixedly held at the midway portion 20c of the leaf spring 20.

In this example, the head chip 11 is attached to a head attachment step 22a formed on the right side of the holder 22 in the drawing.

The present invention can also be applied to a multi-head type head device in which a plurality of head chips (not shown) are attached to the head holder 22.

In the above configuration, each of the bimorph plates 12,
By applying a voltage in the same direction between the electrodes 120 (not shown), if the tips 12a, 120a of each bimorph plate are bent downward in the figure as shown in FIG. 7b, for example, the bimorph plate Leaf spring 2 connected and fixed to the tip of 12,120
Since the plate spring 20 is integrally fixedly connected to the middle part of the bimorph plate 12 through the hard head holder 22, the plate spring 20 is connected to each bimorph plate 12,
When the bimorph plates 12 and 120 are bent, the head holder 22 is accurately displaced in the vertical direction in FIG. will be moved exactly to
The state of contact with the magnetic tape is also stabilized.

FIG. 8 shows the bimorph plates 12, 120 shown in FIG. 7b in a state where their tips are bent so that they are displaced downward in the figure.
120 is an enlarged view of the vicinity of the tip. In this example, the leaf spring 20 includes bent pieces 20 at both upper and lower ends in the figure.
a and 20b are connected and fixed to the upper bimorph plate 12 on the lower side in the figure, and to the lower bimorph plate 120 on the upper side in the figure in a superposed state. Therefore, the bimorph plate 12,
120, the middle part 20 of this leaf spring 20
The part 20 joined to the hard head holder 22 of c.
Since the portion d is integrated with the holder 22, it is not bent, and the free portions 20e and 20f, which are continuous on both upper and lower sides in the figure, of the portion 20d are bent as shown in FIG. That is, in the illustrated case, the upper free portion 20e is displaced so as to protrude more forward than the distal end surface 12c of the upper bimorph plate 12, and the lower free portion 20e
f is displaced so as to be pulled back to the rear side of the distal end surface 120c of the lower bimorph plate 120. This is because the bimorph plates 12 and 120 are bent in the same direction, causing a shift in the connection and fixing position of the spring 20 with each of the bimorph plates 12 and 120. Then, the middle part 2 of the leaf spring 20 is
Due to the occurrence of deflection of the free portions 20e and 20f at 0c, the head chip 11 is attached to this midway portion and is bonded to the hard head holder 22 that is integrated with the portion 20d that does not cause the above-described deflection.
is displaced in parallel due to deflection of the bimorph plates 12, 120 due to curvature in the vertical direction in the figure.

In addition, FIG. 9 shows each bimorph plate 1 of the plate spring 20.
This figure shows another embodiment in which the state of connection and attachment to the 2, 120 is modified to a state different from that of the embodiment shown in FIG. 8 above.

That is, in this example, the bent pieces 20a and 20b located on both the upper and lower sides in the figure of the leaf spring 20 are bonded and fixed to each outer surface near the tip of each bimorph plate 12, 120 so as to overlap. . In this example, in order to allow the free portions 20e and 20f of the midway portion 20c of the leaf spring 20 to be sufficiently bent in the front-rear direction when each bimorph plate 12 and 120 is bent, the tip edge 12c of each bimorph plate 12 and 120 is , 120c are configured to form inclined surfaces. As a result, the midway portion 20c of the leaf spring 20 can bend around the bent portions 20g, 20h when each bimorph plate 12, 120 bends, and the parallel displacement of the hard head holder 22 can be sufficiently realized. be.

Further, the leaf spring 20 as an elastic member illustrated in each of the above embodiments was formed by bending a single phosphor bronze plate into a U-shape. Alternatively, two leaf springs 20 and 21 bent into a U-shape as shown in FIG. 10 may be used. That is, in the example shown in FIG. 10, one bent piece 20a of one U-shaped leaf spring 20 is connected and fixed to the upper bimorph plate 12, and one bent piece 21a of the other U-shaped leaf spring 21 is connected and fixed to the upper bimorph plate 12. The hard head holder 22 is connected and fixed to the lower bimorph plate 120, and is further interposed between the other bent piece 20b of the one U-shaped leaf spring 20 and the other bent piece 21b of the other U-shaped leaf spring 21. I am trying to connect and fix it so that it is fixed. Even with this configuration, the same effects as in the above embodiment can be achieved.

Furthermore, although not shown, the hard head holder 22 portion may be formed integrally with the leaf springs 20 and 21 using a highly elastic material such as phosphor bronze or carbon fiber. good. Then, as in each of the above embodiments, the leaf spring 20,
21 is a bimorph plate 12, 120 as shown in the figure.
If the springs 20 and 21 are connected in such a way that the thickness direction coincides with the direction of curvature of the bimorph plates 12 and 120, the strength will be strong in the width direction of the springs 20 and 21, that is, the direction perpendicular to the direction of curvature of the bimorph plates 12 and 120. Accurate movement of the head tip 11 in the vertical direction can be further ensured.

As described above, in the present invention, a leaf spring such as a phosphor bronze plate is connected to the tips of two bimorph plates, and the middle part of this spring is rigidly connected and fixed via a hard holder. Since the head tip is adhesively supported by a hard connecting part constructed as shown in FIG. has no angle and can always make plane contact.
As a result, spacing loss can be eliminated, a stable contact state can be obtained, and the intended purpose can be fully achieved.

Furthermore, in the present invention, voltages in the same direction are applied to the two bimorph plates, so there is no deterioration in runout, and compared to a case where the entire length of the head support section is made of bimorph plates, the tip of the bimorph plate is Since it is lightweight, the natural frequency can be improved. Furthermore, since the leaf spring extends in a U-shape at the tips of the two bimorph plates, elastic energy is more likely to be dissipated when the leaf spring bends, so the resonance Q value is higher than that of a single bimorph plate structure. can be kept small. Therefore, there is no need to specifically provide a damper member for absorbing vibrations at the tip of the bimorph plate.

Furthermore, the present invention provides, in place of the bimorph plate,
It is also possible to use the monomorph plate as an electro-mechanical conversion element.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing an example of a conventional rotating magnetic head device, FIG. 2 is a plan view schematically showing a recording track of a magnetic tape, and FIG. 3 is an example of a conventional head support device. FIG. 4 is a schematic side view, and FIG. 5 is a schematic side view for explaining the deflection state of the bimorph plate. FIG. 6 is a side view showing the schematic structure of the head device which is the premise of the present invention. FIG. 7 and subsequent drawings are drawings for explaining the present invention. FIG. 7 is a schematic side view showing one embodiment, in which a shows a bimorph plate in a resting state, and b shows a bimorph board in a swinging state. FIG. 8 is a partially enlarged view showing another embodiment, in which a is a perspective view and b is a side view. FIG. 9 is a partially enlarged view showing still another embodiment, in which a is a perspective view and b is a side view. FIG. 10 is a partially enlarged view showing still another embodiment, in which a is a perspective view and b is a perspective view.
is a side view. DESCRIPTION OF SYMBOLS 11... Head chip, 12, 120... Bimorph plate, 20, 21... Leaf spring, 22... Hard head holder.

Claims (1)

[Claims] 1. An electro-mechanical transducer using a piezoelectric plate with electrodes adhered to its surface is provided so that a pair of the elements are substantially parallel to each other, each base end of each of these elements is fixedly supported, and 1. A magnetic head device characterized in that both ends of an elastic member having a head support member made of a hard material attached to the middle part of each tip are connected and fixed.