JPS6151333B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic head support structure that is useful when applied to a magnetic head support structure of a rotating magnetic head device used in a video tape recorder, etc. This enables a magnetic head to accurately scan a recording track such as a video signal.

This type of rotating magnetic head device, for example, as shown in FIG. It has a motor 4 for driving. In the magnetic head device, the tip of the magnetic head 5, which is an electromagnetic transducer for performing magnetic recording and reproduction, slightly protrudes from the outer peripheral side of the upper and lower drums 2 and 3, so that the magnetic head 5 is located near the outer periphery of the upper drum 2. Installed in place. Moreover, the magnetic tape 1 is placed around the upper and lower drums 2, 3, etc.
It is wound into a shape and driven to run in the direction of arrow B. Further, guide poles 6, 7, etc. are provided in order to keep the position of the magnetic tape 1 constant with respect to the rotary head device. By bringing the magnetic head 5 and the magnetic tape 1 into sliding contact, video signals are recorded and reproduced.
When a desired video signal is recorded onto the magnetic tape 1 using such a rotating magnetic head device, a second video signal is recorded on the magnetic tape 1.
Recording tracks T as shown in the figure are sequentially formed obliquely. These recording tracks T are for when the magnetic tape 1 is driven to run at a steady speed _u0 in the direction of arrow B, and during normal playback, the magnetic head 5 moves on a straight line ₀ . , normal video signal playback can be performed. However, when the running speed of the magnetic tape 1 in the direction of the arrow B is different from the steady speed _u0 , such as during playback of still images (still playback) or slow motion playback, the trajectory of the magnetic head 5 is, for example, As shown by straight line ₁ in Fig. 2, the recording track T deviates from the recording track T. Further, in the case of quick motion reproduction, contrary to the above case, the trajectory of the magnetic head 5 deviates from one recording track, as shown by the straight line ₂ in FIG.

When performing still playback, slow motion playback, quick motion playback, etc., an electrostrictive drive mechanism using an electrostrictive element such as a so-called bimorph is used to compensate for the deviation of the magnetic head 5 from the recording track T. The following methods are used.
That is, as shown in FIG. 3, a magnetic head 5 is attached to a tip 12a of a bimorph plate 12 serving as an electrostrictive element, and a base end 12b of this bimorph plate 12 is supported by a head base 13. By displacing the bimorph plate 12 in the direction of the arrow X in FIG. 3 using a predetermined displacement input signal, the position of the magnetic head 5 is displaced and the head 5 is moved along the recording track T in the direction of the arrow C in FIG. Displace it in the transverse direction. Even in the case of different speed playback such as slow motion or quick motion, tracking correction is performed so that the locus of the magnetic head 5 becomes straight line ₀ in FIG.

By the way, in a one-head helical scan type video tape recorder that records and plays video signals with one rotating magnetic head, when performing n-times speed quick motion playback or 1/2 speed slow motion playback, the magnetic It is necessary for the head to perform a track jump at a period of one field of the recording track T or an integer multiple of one field. For example, when performing slow motion reproduction at 1/2 speed, one recording track T is repeatedly reproduced, so the magnetic head is moved from one recording track T to another.
A so-called track jump is required to return to the original recording track T that was reproduced once every two fields. Such a track jump operation of the magnetic head 5 must be performed within the blanking interval of the reproduced signal in order to prevent noise from occurring in the reproduced image. According to certain television signal recording and reproducing standards, the dropout period of the magnetic head is approximately 10 hours (horizontal scanning period).
(0.6 msec), it is desirable to completely complete the track jump of the magnetic head as described above during this time in order to obtain a stable reproduced image. For this purpose, the response of the electrostrictive drive mechanism that displaces the magnetic head must be at least 1 KHz in terms of frequency response. Various drive mechanisms have been proposed in the past to provide such high frequency response characteristics, but it has not yet been possible to obtain a sufficient jump speed, and the magnetic head cannot be moved near the beginning of the recording track after track jump. cannot follow the center position of the recording track, resulting in a large error in scanning the recording track. In addition, in other examples, electrostrictive drive mechanisms with frequency response characteristics of 1KHz or close to it have been proposed; I can't get sex. Therefore, it is not possible to compensate for tracking, which allows the magnetic head to follow the center position of the recording track, and the reproduced image becomes unstable.

In order to solve the above-mentioned problems, the response of the electrostrictive drive mechanism should be made faster. That is, to describe the electrostrictive drive mechanism shown in FIG. 3, if the beam length L extending from the base end 12b to the tip 12a of the bimorph plate 12 supporting the magnetic head 5 is made sufficiently short, a fast response can be achieved. However, if the beam length L is shortened, a sufficient amount of displacement of the magnetic head 5 attached to the tip 12a of the beam cannot be obtained. Therefore, in order to simultaneously satisfy a faster response and a larger amount of displacement of the bimorph plate 12, the planar shape of the bimorph plate 12 is made thinner on the tip 12a side where the magnetic head 5 is attached, as shown in FIG. Further, the proximal end 12b supported by the head base 13 is formed into a substantially trapezoidal shape, or the distal end 12a is widened as shown in FIG.
From the base end 12b to both sides 12c and 12d
By making the plane shape tapered with a logarithmic curve or an arc similar to the logarithmic curve, both faster response and larger displacement can be improved to some extent.
Furthermore, the cross-sectional shape of the bimorph plate 12 is such that the proximal end 12b side is thick and the distal end 12a is thick.
Bimorph plate 1 for faster response if the sides are thinner
The rigidity of 2 itself can also be satisfied. However, the tip 12
When the base end 12b, which greatly contributes to the generation of the displacement a, is made thicker, the curvature due to the strain of the bimorph plate 12 obtained by electrostrictive driving with a predetermined input becomes smaller, and the displacement at the tip 12a can be made sufficiently large. Can not do it.

However, it is still not possible to simultaneously achieve a sufficiently high-speed response and a sufficiently satisfactory displacement by merely improving the plane or cross-sectional shape of the bimorph plate 12.

Therefore, the present invention makes the resonant frequency of the magnetic head support that supports and displaces the magnetic head sufficiently high, and enables high-speed recording track change or track jump of the magnetic head within an extremely short dropout period of the magnetic head. This was proposed for the purpose of providing a support structure for a magnetic head that enables response and sufficiently large displacement of the magnetic head.

Specific embodiments of the present invention will be described with reference to the drawings.

The magnetic head support 21 constituting the present invention is constructed by laminating a plurality of plate-shaped electrostrictive elements, which are mechanical transducer strain elements that expand and contract in response to a predetermined displacement input. As this plate-shaped electrostrictive element, a so-called bimorph plate P is used.
As shown in FIG. 8, this bimorph plate P has a piezoelectric material based on lead zirconate titanate on both sides of a central metal plate 22 which serves as an intermediate electrode and is made of titanium, horizontal copper, bronze, stainless steel, etc. The plate-shaped strain elements 23 and 24 formed with
Electrostrictive drive electrodes 25 and 26 are formed by coating and baking, for example, silver-containing glass frit on both sides of the electrode 24. Although each thickness is the same, the outer shape has the same width W of the bottom side 27 as shown in FIG.
A plurality of bimorph plates _P1 to _{P6, six} in this example, each having a different length L from the top to the tip 28 are prepared. In addition, when these bimorph plates P ₁ to _{P 6} are configured as the magnetic head support 21, their planar shape is tapered from the bottom portion 27 to the tip portion 28 in consideration of the response to electrostrictive drive and the displacement of the tip. Although it is formed in a trapezoidal shape, it is not limited to such a trapezoidal shape, but may be a triangular shape with a tapered tip or a rectangular shape with the same width from the base portion 27 to the tip portion 28.

Each bimorph plate P ₁ to _{P 6} formed as described above
The magnetic head support 21 is constructed by laminating
It is constructed by stacking the longest first bimorph plate _P1 , which serves as a main electrostrictive element, with a magnetic head 5 attached to its tip, sandwiching other bimorph plates _P2 to _P6 , which serve as sub-electrostrictive elements. That is, the first bimorph plate P 1 having the longest length L ₁ is positioned in the center, and the second bimorph plate P ₂ having the second length L ₂ is stacked on one side of the first bimorph plate P ₁ and placed on the other side. overlaps the third bimorph plate P ₃ with the third length L ₃ , and
A fourth bimorph plate P4 having a fourth length _L4 is stacked on the bimorph plate _P2 , and a fifth bimorph plate _P4 having a fifth length _L5 is stacked on the third bimorph plate _P3 . Stack plate P ₅ and then add the fifth bimorph plate
A sixth bimorph plate P ₆ having a sixth length L ₆ is stacked on top of P ₅ , and the positions of the tips 28 are adjusted so that the bottom sides 27 of each bimorph plate P ₁ to _{P 5} coincide with each other. The layers are stacked in stages as shown in FIG. As described above, in the magnetic head support 21 constructed by laminating the bimorph plates P ₁ to _{P 6} , the lamination boundary surface 29 of each of the bimorph plates P ₁ to _{P 6} can slide without being fixed with any adhesive or the like. Leave it as a side. The magnetic head 5 is disposed at the center of the tip of the magnetic head support 21 by connecting a plurality of bimorph plates P _{1 to P 1} to the magnetic head support 21 .
The first bimorph plate P ₁ , which is the longest among the bimorph plates P ₆ , is attached to the tip 28 on one side of the bottom side in the figure so that at least the gap surface protrudes from the tip 28 . Further, the support body 21 includes each bimorph plate P ₁ to
The proximal end portion 30 of P ₆ with its base portion 27 aligned with the base end portion 30 is fixed to the supporting portions 31 so as to be sandwiched between the fixed supporting portions 31 formed in a pair. Note that the portion held by the fixed support portion 31 may be fixed with an adhesive or the like.

As shown in FIG. 7, the cross-sectional shape of the magnetic head support 21, which is constructed by laminating a plurality of bimorph plates P ₁ to P ₆ as described above, is thicker on the proximal end 30 side and thicker on the distal end 32 side.
The magnetic head 5 is formed into a tapered shape with thinner sides, and the magnetic head 5 is attached to the tapered tip 32.

By the way, each of the bimorph plates P ₁ to _{P 6} constituting the magnetic head support 21 is polarized, for example, as shown by the arrows in FIG. That is, one strain element 23 of the first bimorph plate P ₁ is polarized downward in the figure, and the other strain element 24 is polarized upward in the _figure . One strain element 23 of the second bimorph plate P ₂ laminated on one side of the first bimorph plate P ₁
The other strain elements 24 are polarized in the opposite direction upward, and the other strain elements 24 are similarly polarized in the opposite direction.
Each strain element 23, ₂₄ of the third bimorph plate P3 laminated on the other side of the first bimorph plate _P1 is polarized in the same way as the second bimorph plate _P2 , and the fourth
and each strain element 23 of the fifth bimorph plates P ₄ and P ₅ ,
24 is polarized in the same way as the first bimorph plate _P1 , and each strain element 23, 24 of the sixth bimorph plate _P6
is polarized in the same way as the second and third bimorph plates P ₂ and P ₄ . That is, each bimorph plate P ₁ ~
The strain elements 23 and 24 of _P6 are polarized in opposite directions. By polarizing each of the bimorph plates P ₁ to _{P 6} stacked as described above, a simple connection as shown in FIG. 7 can be made. That is, one input terminal 33 is connected to the electrostrictive drive electrodes 25 and 26 of each of the bimorph plates P ₁ and P ₂ located at the lamination interface 29 of the first and second bimorph plates P ₁ to P ₂ .
The contact point of each bimorph plate P ₃ , which is located at the lamination interface 29 of the third and fifth bimorph plates P ₃ , P ₅ ,
Electrostrictive drive electrodes of each of the bimorph plates P 4 and P ₆ located at the contact point of the electrostrictive drive poles 25 and 26 of P ₅ and the lamination interface 29 of the fourth and sixth bimorph plates P _{4 and} P ₆ 25 and 26, and the other input terminal 3
4 is a contact point of the electrostrictive drive electrodes 25, 26 of each of the bimorph plates P ₁ , P ₃ located at the lamination interface 29 of the first and _third bimorph plates P 1 _, P 3;
The electrostrictive drive electrode 2 of the bimorph plates P ₂ and P ₄ is located at the laminated boundary surface 29 of the bimorph plates P ₂ and P ₄ .
5 and 26, one electrostrictive driving electrode 25 of the fifth bimorph plate _P5 and the other electrostrictive driving electrode ₂₆ of the other electrostrictive driving electrode _P6 of the sixth bimorph plate P6. connected to each contact. By connecting in this manner, drive voltages in the same direction are simultaneously applied to each of the bimorph plates _P1 to _P6 . Then, when a voltage is input as a predetermined displacement input to the head support 21 connected as described above, each bimorph plate
P ₁ to P ₆ curve in the same direction. For example, when a positive potential is input to the second input terminal 34, each of the bimorph plates P ₁ to P ₆ is polarized from the bottom portion 27 to the tip portion 28 as shown in FIG. Curve downward. The voltages input to the bimorph plates P ₁ to _{P 6} that curve in the same direction are at the same level, and the thicknesses of the bimorph plates P ₁ to P ₆ are also the same, so they all exhibit the same distortion rate. Therefore, the magnetic head 5 attached to the tip 28 of the first bimorph plate _P1 having the longest length _L1 can obtain the same amount of displacement as in the case of only the bimorph plate _P1 alone. Also all bimorph boards
When P ₁ to _{P 6} are curved, the stacked boundary surface 29 of each bimorph plate P ₁ to _{P 6} greatly contributes to the damping due to resonance of each bimorph plate P ₁ to _{P 6} . In other words, since the boundary surface 29 is not bonded and fixed but is a sliding surface, sliding motion occurs on the boundary surface 29 during electrostrictive driving, and absorbs the resonance vibration generated between each bimorph plate _P1 to _P6 . This is to do so.

Furthermore, the amount of displacement in the magnetic head support 21 and the tip 32 as a whole is the same as in the case of the longest first bimorph plate _P1 alone, but when looking at the resonance frequency due to electrostrictive drive, at least the above-mentioned displacement amount is obtained. This value is higher than that of the bimorph plate _P1 alone. Since the bimorph plates P ₁ and P ₆ constituting the magnetic head support 21 are wired as described above, if a predetermined displacement input is input, they will all be electrostrictively driven at the same time. In response to driving, bimorph plates with short beam lengths, that is, bimorph plates with a high resonance frequency respond instantaneously to voltages at the same level, and the response continues in the case of longer beams. That is, responses are made in order from the sixth bimorph plate P6 having the shortest length L to the shortest bimorph plate _P6 . The third and fifth bimorph plates P 3 and P ₅ located above the long first bimorph plate P ₁ of length L ₁ to which the magnetic head 5 is attached in FIGS. 7 and ₁₀ each have their own The second, fourth and sixth bimorph plates P ₂ , P 4 , P ₅ at the bottom of the figure act to press each bimorph plate having a high resonance frequency and having a length longer than its own which is lower _. act to attract each bimorph plate longer than its own above it with its own high resonant frequency. This attractive action is caused by the viscosity of a thin air film in a minute space created at the laminated interface 29, which is a sliding surface. Therefore, if the gap between the laminated interfaces 29 is structurally large, or in order to obtain stronger viscosity, a viscous material such as silicone grease or high-loss rubber may be inserted into the gap between the interfaces 29. good.
As the above-mentioned operation continues during electrostrictive driving, the other shorter bimorph plates P ₂ to _{P 6} press and attract the longest first bimorph plate P ₁ with length L ₁ . The resonant frequency of the first bimorph plate P ₁ is increased above that of itself. That is, the magnetic head support 2 is configured with a plurality of bimorph plates _P1 to _P6 .
1 is because the whole is electrostrictively driven as a whole, and the resonance frequency becomes close to the average of those of each of the bimorph plates _P1 to _P6 .

In the above explanation, a positive potential is input to the second input terminal 34, but if a positive potential is input to the first input terminal 33, the opposite displacement direction can be obtained with the same reverse operation as in the above case. Of course, it can be done.

The examples shown in FIGS. 7 and 10 use six bimorph plates P ₁ to P ₆ , but as shown in FIG. 11, four bimorph plates P ₁ to _{P 4} are used. A similar effect can be obtained even if the magnetic head support 21 is constructed using the same structure. In this case as well, each strain element 23, 24 of each bimorph plate _P1 to _P4 is
performs polarization in the same way as in the previous case. With this configuration, each of the above-mentioned bimorph plates located at the lamination interface 29 of the first and second bimorph plates P ₁ and P ₂
The contact point of the electrostrictive drive electrodes 25 and 26 of P ₁ and P ₂ , the third
and one and the other of the fourth bimorph plates P ₃ and P ₄ ,
That is, the electrostrictive drive electrodes 25 and 26 located at the outermost side of the magnetic head support 21 are grounded, and the input terminal 35 for the predetermined displacement signal is connected to the second and fourth electrodes.
The laminated boundary surface 29 of the bimorph plates P ₂ and P ₄ and the first
and the lamination interface 29 of the third bimorph plates P ₁ and P ₃
What is necessary is just to connect to the contact points of the electrostrictive drive electrodes 25, 26 and 25, 26 located respectively. If the wires are connected in this way, it can be driven with a single drive power source, and it can also be installed as the magnetic head support 21 on a rotating body of a video tape recorder without insulation.

Further, the effect obtained by combining the bimorph plates P as described above can be obtained by laminating two first and second bimorph plates P ₁ and P ₂ of different sizes, as shown in FIG. Obtained magnetic head support 2
You can get even 1. Also in this case, the first and second bimorph plates P ₁ and P ₂ are connected as shown by arrows in FIG.
The directions of polarization of the strain elements 23 and 24 constituting the plate are set to be opposite to each other, and the polarization of one strain element 23 and 24 of the first and second bimorph plates P ₁ and P ₂ facing each other and the other strain element 23 and 24 are Stack them so that they are in the same direction. Then, the input terminal 36 to which a predetermined displacement input is inputted may be connected as shown in FIG. 13. That is, four constant voltage diodes ZD ₁ ~
Using ZD ₄ and four diodes D ₁ to D ₄ , the constant voltage diode ZD and the diode D are set in opposite directions to each other, and these four sets constitute an anti-series circuit. Both ends of this anti-series circuit are grounded, and 2
A drive voltage input terminal 36 is connected to the intermediate position of each pair, and the connection point at the intermediate position is located at the lamination boundary surface ₂₉ of the first and second bimorph plates P ₁ and P ₂ . , P ₂ electrostrictive drive electrode 25,
first and second bimorph plates connected to the contacts of the input terminal 36 and at intermediate positions between the input terminal 36 and ground, respectively;
They are connected to the central metal plates 22 of P ₁ and P ₂ , that is, the intermediate electrodes, respectively. If the wiring and polarization are performed in this way, the magnetic head support 31 can be grounded without requiring insulation between the bimorph plates P ₁ and P ₂ , and the outermost bimorph plate 21 can be grounded. The electrostrictive drive electrodes 25 and 26 can be at ground potential, making it easy to attach the video tape recorder to a rotating body or the like.

In the example shown in FIG. 12, looking at the resonance frequency of the magnetic head support 21 to which the magnetic head 5 is attached, for example, assuming that the bottom portions 27 of the first and second bimorph plates P ₁ and P ₂ are 26 mm thick, are both 0.5 mm, the beam length L ₁ of the first bimorph plate P ₁ is 20 mm, and the width of its tip 28 is 3 mm.
mm, and the beam length L ₂ of the second bimorph plate P ₂
When the width of the tip 28 is 8 mm and the width of the tip 28 is 16 mm, the first
The inherent resonant frequency of the bimorph plate _P1 is 1050Hz,
The unique resonance frequency of the second bimorph plate _P2 is 3500Hz
However, an experimental result was obtained in which the resonant frequency of the support body 21 could be set to 1280 Hz by laminating the layers as described above. Note that the displacement of the tip 32 of the support body 21 was the same as in the case with _one first bimorph plate P.

As described above, the present invention is constructed by stacking a plurality of plate-shaped electromechanical transducers, and the main electrostrictive element has a magnetic head attached to one end that distorts according to an input signal and is fixed at the other end. and at least one sub-sheet having a length shorter than the main electrostrictive element, placed on the surface of the main electrostrictive element in the distortion direction, and fixed at the other end of the main electrostrictive element. an electrostrictive element, an input signal is supplied so that the main and sub electrostrictive elements are distorted in the same direction, and the magnetic head is displaceable with respect to the other ends of the main and sub electrostrictive elements. Therefore, it is an object of the present invention to provide a support structure for a magnetic head having a large displacement without reducing the displacement of the tip of the support, that is, the magnetic head attached to the tip, while increasing the resonance frequency as a magnetic head support. I can do it. Then, a quick response to a predetermined displacement input is possible, and if the present invention is applied to a rotating magnetic head device of a video tape recorder, track jumps can be performed quickly and accurately in cases such as playback at different speeds, and magnetic The scanning of the recording track by the head is stable, and an image without uneven reproduction can be obtained.

In the above description, a bimorph plate as an electro-mechanical transducer is used as the mechanical transducer, but other strain transducers that can expand and contract in response to a predetermined displacement input, such as magnetostrictive, thermostrictive, etc. transducers, may also be used. It may be configured using

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing a rotating magnetic head device used in a video tape recorder, FIG. 2 is a plan view showing a recording track on a magnetic tape, and FIG. 3 is a sectional view showing a conventional magnetic head support structure. be. 4 and 5 are plan views showing examples of conventional magnetic head supports, respectively, and FIG. 6 is a sectional view thereof. FIG. 7 is a sectional view showing an embodiment of the present invention, FIG. 8 is a sectional view showing a bimorph plate used in the present invention, and FIG. 9 is a sectional view showing a magnetic head support constituting the present invention. 10 is a plan view of each bimorph plate, and FIG. 10 is a sectional view showing the operating state of the above embodiment. FIG. 11 is a sectional view showing another embodiment of the invention, and FIG. 12 is a sectional view showing a further embodiment of the invention. P ₁ to P ₆ ... Bimorph plate, 21 ... Magnetic head support, 23, 24 ... Strain element, 25, 26 ...
Electrostrictive drive electrode, 27...bottom part of bimorph plate, 28...tip part of bimorph plate, 29...laminated boundary surface, 31...fixed support part.

Claims (1)

[Scope of Claims] 1. A main electrostrictive element, which is constructed by laminating a plurality of plate-shaped electromechanical transducers, and has a magnetic head attached to one end and fixed at the other end, which distorts according to an input signal; At least one or more sub-electrostrictive sheets having a length shorter than the main electrostrictive element, placed on the plane in the distortion direction of the main electrostrictive element, and fixed at the other end of the main electrostrictive element. an input signal is supplied so that the main and sub electrostrictive elements are distorted in the same direction, and the magnetic head is displaceable relative to the other ends of the main and sub electrostrictive elements. Features a magnetic head support structure.