JPS6232346Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a head support device in a recording/reproducing apparatus such as a VTR, and particularly to a head support device for forming a predetermined recording track on the recording medium by relative movement between the recording medium and the head. The present invention relates to a head moving device in a recording/reproducing apparatus which reproduces information recorded on the recording track.

Rotating head type helical scan type VTR
(video tape recorder), the angle of inclination of the wound tape with respect to the head drum,
Inclined recording tracks are formed on the magnetic tape depending on the tape running speed, the rotational speed of the rotary head, and the like. Therefore, when playing back a magnetic tape by running it at a speed different from the speed at which it was recorded, for example, still, slow motion, double speed,
When playing in various modes such as reverse,
The scanning locus of the head has a slope different from that of the recording track described above, causing the head to scan off the predetermined recording track. If the magnetic head scans off the predetermined recording track in this way, guard band noise and crosstalk will occur, which is undesirable. Therefore, in this type of VTR, a tracking correction means is required to ensure that the magnetic head correctly scans the recording track in various modes. As such tracking correction means, there is a magnetic head support device using an electro-mechanical conversion element, for example, a bimorph plate.

FIG. 1 shows the basic structure of such a bimorph plate. As shown in FIG. 1, a bimorph plate 1 includes a piezo ceramic element 4 having electrodes 2 and 3 adhered to both sides by silk printing or the like.
and a piezoceramic element 7 having electrodes 5, 6 adhered to both surfaces in the same manner. A shim 8 is bonded between the piezo ceramic elements 4 and 7 so that their polarization directions are opposite to each other as shown by the arrows in FIG. 5
are in contact with shim 8, respectively. The purpose of this shim 8 is to reinforce the bimorph board 1.
It is made of phosphor bronze, titanium alloy, carbon fiber, etc.

When a voltage is applied to such a bimorph plate 1 as shown in FIG. 2, the piezo ceramic element 4
Since an electric field is applied from the electrode 2 to the electrode 3 (in the direction opposite to the polarization direction), the ceramic element 4 is deformed in the direction of elongation as shown by the arrow in FIG. 2 due to the piezoelectric effect. do. Further, since an electric field is applied to the other ceramic element 7 in the direction from the electrode 5 to the electrode 6 (polarization direction), this ceramic element 7 is deformed in the direction of contraction. As a result, the bimorph plate 1 is bent as shown in FIG. 2, and the amount of deflection, that is, the amount of displacement of the free end of the bimorph plate 1, increases or decreases depending on the magnitude of the electric field applied to the ceramic elements 4, 7. Note that if the direction of the electric field is reversed, the direction of displacement will also be reversed.

As shown in FIGS. 2 to 4, one end of the bimorph plate 1 is cantilevered to the head mounting portion 16 of the rotating drum 9a of the rotating head drum 9, and a magnetic head 10 is attached to the free end of the bimorph plate 1. The magnetic head 10 is supported along the outer surface of the rotary head drum 9 so as to be movable (biasable) in the height direction of the drum 9. Furthermore, the fourth
In the figure, 9b is a fixed drum. Therefore, by appropriately adjusting the voltage applied to the bimorph plate 1 to control the amount of displacement of the magnetic head 10, the above-mentioned tracking correction becomes possible.

That is, as shown in FIG. 3, the magnetic tape 11 is helically wound around the outer peripheral surface of the rotary head drum 9 by a pair of tape guides 12 and 13 over an angle of approximately 340 degrees. This magnetic tape 11 is run at a speed of _V1 by a drive means not shown. On the other hand, the magnetic head 10 is attached to the rotating drum 9a of the rotating head drum 9 through the bimorph plate 1 as described above, and as shown in FIG. It protrudes slightly from the outer surface,
The magnetic tape 11 is rotated while running at a rotational speed of _V2 .
is in contact with. Therefore, when recording is performed with this apparatus, a large number of mutually parallel recording tracks _T1 are inclined at a predetermined angle with respect to the length direction of the magnetic tape 11, as shown in FIG. It is formed. Note that during normal playback, in which the magnetic tape 11 is run at the same speed _V1 as during recording, the magnetic head 10 correctly scans the recording track _T1 , and the magnetic head 10 moves along the recording track T1.
It never deviates from T ₁ .

However, when playing back while running the magnetic tape 11 at a speed slower than V ₁ , for example in slow motion (V=V _1/2 , V _1/3 , etc.) or still motion (V=0) mode, , the scanning locus of the magnetic head 10 as shown by the dotted line in FIG.
The inclination angle of _T2 becomes larger than the inclination angle of recording track _T1 . As a result, the recording track _T1 and the scanning locus of the magnetic head 10 no longer match, resulting in guard band noise and crosstalk. Therefore, by applying an appropriate voltage to the bimorph plate 1 supporting the magnetic head 10 and deforming the bimorph plate 1, the magnetic head 10 can be deformed.
If it is displaced as shown in FIG. 2, it is possible to scan the predetermined recording track _T1 without deviating from it.

Further, even when the running speed of the magnetic tape 11 is faster than _V1 , tracking correction is performed by deforming the bimorph plate 1. That is, for example, in triple speed playback mode (V=3V ₁ ),
As shown by the chain line in FIG. 3, the magnetic head 10
The inclination angle of the scanning trajectory _T3 becomes smaller than the inclination angle of the recording track _T1 . Therefore, in this case as well, the bimorph plate 1 can be appropriately deformed to match the recording track _T1 .

However, in a so-called reverse playback mode in which the magnetic tape 11 is played by running in the opposite direction to that during normal playback (for example, V=-
2V ₁ ), the inclination angle of the scanning locus T ₄ of the magnetic head 10 becomes much larger than the inclination angle of the recording track T ₁ as shown by the two-dot chain line in FIG.
Therefore, in order to match the scanning locus of the magnetic head 10 with the recording track _T1 during this reverse reproduction mode, it is necessary to make a fairly wide movement. Furthermore, as the reverse speed or double speed increases, it is necessary to move the magnetic head 10 over a wider range. Other than making the protrusion length l ₁ (see Figs. 2 and 3) sufficiently long to the cantilevered portion, or applying an excessive voltage to the bimorph plate 1 to cause the bimorph plate 1 to bend greatly. There was no way. However, when the length _l1 is increased, the natural resonance frequency ₀ inevitably decreases, and as a result, the response speed becomes slower, and as a result, it is not possible to sufficiently jump between track pitches within the flyback operation time. Can not. For this reason,
In reality, the protrusion length l ₁ is subject to significant restrictions due to its relationship with the natural resonance frequency _{of 0} , and cannot be made very long. Furthermore, if the bimorph plate 1 is bent significantly, the piezo ceramic elements 4 and 7 may crack or even be damaged.

The present invention was devised in view of the above-mentioned actual situation, and is intended for use in a recording/reproducing apparatus which is configured to allow a large head deflection (displacement distance) without reducing the natural resonance frequency ₀ . It is intended to provide a support device.

The following is a sixth example of applying the present invention to a head support device in a helical scan type VTR.
This will be explained with reference to FIGS. In addition, Figure 6~
In FIG. 10, parts common to those in FIGS. 1 and 2 are given the same reference numerals and their explanations will be omitted.

First, FIG. 6 shows a first embodiment of the present invention, and the head support device of this embodiment includes the bimorph plate 1 and magnetic head 10 as described above, and one end of the bimorph plate 1. It is composed of a pair of monomorph plates 18 and 19 that are held and supported. This monomorph board 18 consists of a piezo ceramic element 22, on both sides of which electrodes 20, 21 are adhered by silk printing, baking, etc., and a shim 23, which is bonded to the electrode 21 with an adhesive or the like. Similarly, the monomorph plate 19 is a piezoelectric plate with electrodes 24 and 25 adhered to both sides by silk printing or the like.
It consists of a ceramic element 26 and a shim 27 bonded to the electrode 24 with adhesive or the like. The pair of monomorph plates 18 and 19 are arranged substantially parallel to each other at a predetermined interval, and one end thereof is attached to the mounting portion 16 of the rotating drum 9a described above.
It is supported cantilevered by. Note that the shims 23 and 27 of the monomorph plates 18 and 19 are arranged to face each other.

Furthermore, one end of the bimorph plate 1 is inserted between the free ends of the monomorph plates 18 and 19 and is rigidly fixed with an adhesive. In other words,
One end of this bimorph plate 1 is connected to the monomorph plate 1.
It is supported in a cantilevered state by being sandwiched between the free ends of 8 and 19. That is, the portion of the bimorph plate 1 on the fixed end side of the electrodes 2 and 6 is the monomorph plate 18,
It is adhesively fixed to the free end side portions of the shims 23 and 27 of No. 19. A magnetic head 10 is adhesively fixed to the free end of the bimorph plate 1. As is clear from FIGS. 6 and 7, there is a space 3 between the cantilevered end surface 29 of the bimorph plate 1 and the wall surface 16a of the head mounting portion 16.
0 is set.

Further, as shown by arrows in FIG. 6, the polarization directions of the piezoceramic elements 4 and 7 of the bimorph plate 1 are opposite to each other, while the polarization directions of the piezoceramic elements 2 of the monomorph plates 18 and 19 are opposite to each other.
The polarization directions of 2 and 26 are also opposite to each other. The polarization directions of the piezoceramic element 4 of the bimorph plate 1 and the piezoceramic element 22 of the monomorph plate 18 are opposite to each other. The polarization directions are also opposite to each other.

Although not shown in the drawings, the piezo ceramic elements 4, 7, 22, and 26 each have a predetermined direction so that the bimorph plate 1 and the monomorph plates 18, 19 are deflected (deformed) in the same direction. It is configured so that an electric field can be applied to it. That is, when the magnetic head 10 is displaced (moved) downward as shown in FIG. 7, the piezo ceramic elements 4 of the bimorph plate 1 and the monomorph plate 18
and 22 from electrodes 2 and 20 to electrodes 3 and 21
As a result, these piezoceramic elements 4, 22 are deformed in the direction of elongation as shown by the arrows in FIG. Meanwhile, at the same time, the piezo ceramic elements 7 and 2 of the bimorph plate 1 and the monomorph plate 19
6 is applied with an electric field directed from electrodes 5 and 24 to electrodes 6 and 25, respectively, and as a result, these piezo ceramic elements 7 and 26 are deformed in the direction of contraction as shown by the arrows in FIG. ing. Therefore, the displacement distance of the free end of the bimorph plate 1 and thus the magnetic head 10 is only the displacement distance due to the deformation of the protruding portion of the bimorph plate 1 from the free ends of the monomorph plates 18 and 19 (the portion indicated by l in FIG. 6). The wall surface 16a of the mounting portion 16
The protruding parts of the monomorph plates 18 and 19 from
This is the sum of the increase caused by the deformation of the portion (indicated by L in the figure).

That is, at this time, the free ends of the monomorph plates 18, 19 are displaced downward by a distance α in FIG. Furthermore, as described above, since this device is provided with the space 30, the bimorph plate 1 and the monomorph plate 1
The bimorph plate 1 is supported by the pair of monomorph plates 18 and 19 at a certain angle with respect to the horizontal plane at the portion where the bimorph plates 8 and 19 overlap each other, that is, the bonded portion (cantilevered portion). Therefore, the distance is the sum of the displacement distance α of the free ends of the monomorph plates 18 and 19 (see FIG. 7) and the displacement distance of the free ends of the bimorph plate 1 due to the bimorph plate 1 being angled as described above. This is added to the displacement distance due to the deformation of the bimorph plate 1 itself.

In addition, the bimorph plate 1 at the time of deformation as described above
The radius of curvature r ₁ of the monomorph plates 18 and 19 and the radius of curvature r ₂ of the monomorph plates 18 and 19 are configured so that r ₁ <r ₂ in consideration of the rigidity of the head support and the vibration sensitivity of the magnetic head 10. Also, monomorph plates 18, 19
is constructed to have considerably higher rigidity than the bimorph plate 1.

On the other hand, when moving the magnetic head 10 upward, an electric field in the opposite direction to that in the above case is applied to the piezo
It may be added to the ceramic elements 4, 7, 22, and 26. Further, the magnitude of the deflection of the magnetic head 10 is controlled by adjusting the magnitude of the electric field applied to these piezo ceramic elements 4, 7, 22, and 26.

According to the head support device configured in this way,
The bimorph plate 1 is supported at one end by monomorph plates 18 and 19, which are a type of electro-mechanical conversion element, and the magnetic head 10 is supported and fixed on the free end of the bimorph plate 1.
Since the magnetic heads 8 and 19 are biased (deformed) in the same direction, the deflection of the magnetic head 10 can be made larger than in the conventional case. That is _, in the case of the conventional head support device as shown in FIG.
However, in the head support device of this embodiment, the monomorph plates 18 and 19 are biased in the same direction as the bimorph plate 1, and the bimorph plate 1 is biased against the pair of monomorph plates at their bonded portions (overlapping portions). Since the plates 18 and 19 are tilted by a certain angle with respect to the horizontal plane, the deformation of the protruding length L of these monomorph plates 18 and 19 affects the deflection of the magnetic head 10 as described above. This is because it will contribute to
To explain this using specific numerical values, if the protrusion length l of the bimorph plate 1 is approximately 16 to 18 mm and the protrusion length L of the monomorph plates 18 and 19 is 9 to 11 mm, the displacement distance of the magnetic head 10 is compared to the conventional head support device as shown in Figure 2.
It is possible to increase it to about 1.6 times. For this reason, even if the protruding length l of the bimorph plate 1 is set to the conventional length, for example, 720 mm can be achieved without applying an excessive voltage.
Since a displacement distance of about .mu. (conventionally about 460 .mu.) can be achieved, it is fully possible to perform reverse 1x to 3x speed modes.

In addition, since it is possible to sufficiently displace the free end of the bimorph plate 1 and thus the magnetic head 10 by applying a relatively small voltage compared to the conventional case, the vibration sensitivity of the magnetic head can be greatly improved. Can be done.

On the other hand, despite having such advantages,
Since the monomorph plates 18 and 19 are constructed to have considerably higher rigidity than the bimorph plate 1,
Substantial natural resonance frequency of the head support means consisting of bimorph plate 1 and monomorph plates 18, 19
₀ is uniquely determined only by the protrusion length l of the bimorph plate 1, and there is no risk that this ₀ will drop, so the response speed of the magnetic head 10 will not change. By appropriately selecting the protrusion length l of the bimorph plate 1 and the protrusion length L of the monomorph plates 18 and 19, the displacement distance (runout) of the magnetic head 10 can be further increased and the natural resonance frequency ₀ can be further increased. is also possible.

Furthermore, compared to the conventional head support device in which the bimorph plate 1 is supported by the mounting portion 16, in the head support device of this embodiment, the bimorph plate 1 is supported flexibly by the monomorph plates 18 and 19. Therefore, stress concentration at point A in FIG. 7 when the bimorph plate 1 deforms is alleviated. Also, the curvature half r ₁ of the bimorph plate 4 and the monomorph plate 18,
Since the radius of curvature r ₂ of 19 is configured to satisfy r ₁ <r ₂ , the stress at point B in FIG. 7 is also small. As a result, the stress at the points A and B is relaxed, so that the crack resistance of the bimorph plate 1 and the piezo ceramic elements 4, 7, 22, and 26 is improved, and cracking and breakage can be effectively prevented. In addition, bimorph plate 1 and monomorph plate 18, 1
9 and 9 are made of the same material, there is no risk that only the bimorph plate 1 will bend due to thermal expansion or contraction due to temperature changes and the magnetic head 10 will be deflected. is always held in a fixed position. Therefore, there is no change in the characteristics of the head support device due to temperature changes.

Next, a second embodiment of the present invention will be described with reference to FIG. 8. In this embodiment, instead of the monomorph plates 18 and 19, a pair of bimorph plates 32,
33 is used. Note that the pair of bimorph plates 32 and 33 may be obtained by cutting the previously described bimorph plate 1 into short pieces.

Even with this configuration, if an appropriate electric field is applied to each bimorph plate 1, 32, 33 to bias (deflect) them in the same direction,
Exactly the same effects as in the first embodiment described above can be obtained.

Next, a third embodiment of the present invention will be described with reference to FIG. 9. In this embodiment, two sets of devices configured as shown in FIG. 6 are used.
The sets of devices are arranged parallel to each other. The free ends of the pair of bimorph plates 1 are connected to each other by a head support member 35 having a U-shaped cross section. That is, both arm portions 3 of this head support member 35
5a and 35b have some elasticity, and both arm portions 35a and 35b are adhered to the free end of the bimorph plate 1, respectively. The magnetic head 10 is adhesively fixed to the head support member 35, so that the magnetic head 10 is substantially attached to the free end of the bimorph plate 1.

According to the head support device configured in this way,
When the bimorph plate 1 and the monomorph plates 18 and 19 are deformed, as shown in FIG. 10, the magnetic head 10 is translated in parallel from the position shown in FIG. 9 due to the elasticity of both arms 35a and 35b of the head support member 35. It turns out. Therefore, the magnetic head 10 can be moved parallel to the recording surface of the magnetic tape, and the abutment angle of the magnetic head 10 with respect to the recording surface can be maintained in a preferable state. As a result,
As in the case of the previously described embodiments, the deflection of the magnetic head 10 can be increased to a large extent, and since there is no spacing loss at the contact surface between the magnetic tape and the magnetic head 10, noise during double speed or reverse playback mode can be reduced. can be reduced, and reproduction characteristics can be improved.

Note that two sets of devices as shown in FIG. 8 may be used and configured in the same manner as in the case of FIG. 9, and even with this configuration, the above-mentioned effects can be obtained.

As described above, the present invention provides a first pair of electromechanical transducers (for example, monomorph plates 18 and 19, bimorph plates 32 and 3
3) and a second electro-mechanical conversion element (for example, bimorph plate 1), one end of which is held between the free ends of the first pair of electro-mechanical conversion elements.
and a head (e.g., magnetic head 10) attached to the free end of the second electro-mechanical transducer, and applies an electric field in a predetermined direction to the first and second electro-mechanical transducers. The heads are moved by biasing them in the same direction. Therefore, according to the head support device of the present invention, the displacement distance of the free end of the second electro-mechanical transducer is determined by the deflection (deformation) of the second electro-mechanical transducer and the first pair of electro-mechanical transducers. Due to the synergistic effect with the bias of the conversion element,
It can be longer than the conventional one (for example, 1.6 times), and as a result, the deflection of the head can be increased. Therefore, for example, reverse playback operations at 1x to 3x speed and other high speed playback operations are possible.

Furthermore, if the second electro-mechanical transducer is configured to have considerably higher rigidity than the second electro-mechanical transducer, the response speed can be changed without lowering the natural resonance frequency ₀ of the device. This makes it possible to increase the vibration of the head without any noise, making it possible to achieve noiseless playback during double-speed playback. Moreover,
Since the stress that acts upon deformation of the first and second elements described above is dispersed to the fulcrums of each of these elements, there is also the advantage that crack resistance is improved.

[Brief explanation of the drawing]

1 to 5 are for explaining a conventional head support device in which a magnetic head is supported by a bimorph plate, and FIG. 1 is a side view showing the structure of the bimorph plate, and FIG. Fig. 2 is a side view of the main part of a head support device using this bimorph plate, Fig. 3 is a plan view of the main part of the rotating head drum of this device, Fig. 4 is a front view of this rotary head drum, and Fig. 5 is a recording track. FIG. 2 is a plan view of a magnetic tape. 6 to 10 show an embodiment in which the present invention is applied to a head support device for a helical scan type VTR. 6 and 7 show a first embodiment of the present invention, in which FIG. 6 is a side view of the head support device, and FIG. 7 is a side view showing the state of the head support device during operation. , FIG. 8 is a side view of a head support device showing a second embodiment of the present invention, and FIGS. 9 and 10 show a third embodiment of the present invention, in which FIG. FIG. 10 is a side view of the head support device showing a state in which the head support device is in operation. In addition, in the symbols used in the drawings, 1...
... Bimorph plate as second electro-mechanical conversion element, 10 ... Magnetic head, 16 ... Mounting part, 1
8, 19...A monomorph plate serving as a first electro-mechanical conversion element, 32, 33...A bimorph plate serving as a first electro-mechanical conversion element.

Claims (1)

[Scope of utility model registration request] In a recording and reproducing apparatus that forms a predetermined recording track on the recording medium or reproduces information recorded on this recording track by relative movement between the recording medium and the head, each head is supported on a cantilever. a first pair of electro-mechanical conversion elements; a second electro-mechanical conversion element, one end of which is held between the free ends of the first pair of electro-mechanical conversion elements; a head attached to the free end of the electro-mechanical transducer;
A head in a recording/reproducing apparatus, characterized in that the head is moved by applying an electric field in a predetermined direction to the first and second electromechanical transducers to bias them in the same direction. Support device.