JPH0143363B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic head support device for supporting a magnetic head of a rotating magnetic head device used in a video tape recorder or the like. A magnetic head is supported using an electrostrictive transducer element which is made by joining two layers of ferroelectric materials and generates bending displacement by utilizing the expansion and contraction of the plate-like material due to the electrostrictive phenomenon of the ferroelectric material. .

[Conventional technology]

Conventionally, a rotary magnetic head device 1 used in a video tape recorder has a rotary magnetic head device 1, as shown in FIG.
It has a rotary disk 2 that rotates in the direction, and upper and lower drums 3 and 4 fixed to the chassis of the video tape recorder are disposed above and below the rotary disk 2. The motor 5 rotates the rotary disk 2. The magnetic tape 6 is placed around the upper and lower drums 3, 4, etc.
It is wound diagonally within an angle range of 180 degrees and is operated 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, guide poles 7, 8, a stepped portion 9 of the lower drum 4, etc. are provided. Further, two magnetic heads are provided, for example, and these are mounted on the rotary disk 2 at an angle of 180 degrees to each other. The tip of the head chip 11 of the magnetic head slightly protrudes from the outer peripheral surface of the upper and lower drums 3, 4, etc., and comes into sliding contact with the magnetic tape 6, thereby recording and reproducing video signals.

By the magnetic head rotating in this manner, recording tracks T are sequentially formed diagonally on the magnetic tape 6 as shown in FIG. These recording tracks T indicate that the magnetic tape 6 is moving at a steady speed _v0 as shown by arrow B.
During normal playback, the head chip 11 moves along a straight line ₁₀ to reproduce a normal video signal.

However, when the running speed of the magnetic tape 6 in the direction of arrow B is different from the steady speed v ₀ , such as when playing still images (still playback) or slow motion playback, which is a different speed playback, the head chip 11
For example, the movement trajectory of is 1, such as the straight line 1 ₁ in Figure 2.
It falls off the record track T of the book. In order to compensate for such a deviation from the recording track T,
The electrostrictive conversion element is constructed by bonding two layers of plate-like bodies made of ferroelectric material and generating bending displacement by utilizing the expansion and contraction of the plate-like body due to the electrostrictive phenomenon of the ferroelectric material. A magnetic head support device is known that uses a head support plate to displace the head chip 11 in the direction of arrow C in FIGS. 1 and 2.

As a magnetic head support device using a head support plate formed as described above, for example, one constructed as shown in FIG. 3 is known.

What is shown in FIG. 3 is the head chip 11.
is attached to the platform part 14 of the head base, which is attached to the rotary disk 2, which is a rotating body, with the mounting screws 12.
It is supported by being attached to the tip of a head support plate 15 whose base end is fixed with adhesive. In this way, the head support plate 15, which is attached as a cantilever with only the base end supported, is electrostrictively driven by a predetermined electric signal, so that the head chip 11 moves in the direction of the arrow in FIGS. 1 and 2. It is configured to compensate for the deviation from the recording track T by being displaced in the C direction.

[Problem that the invention seeks to solve]

By the way, with the above configuration, head chip 1
The conventional head support plate 15 supporting the head 1 includes two plate-shaped bodies 16 and 17 made of a ferroelectric material such as lead zirconate titanate, and a central metal plate serving as a reinforcing plate that also serves as an intermediate electrode. These plate-shaped bodies 16, 1
For example, silver-containing glass frit or the like is coated and baked on both surfaces of the electrostrictive drive electrodes 18, 7.
19 is formed. Since the electrostrictive drive electrodes 18 and 19 are formed in this way, the head chip 1
1 is attached on one electrostrictive drive electrode 18. Therefore, a predetermined insulation treatment is performed between the head chip 11 and one of the electrostrictive drive electrodes 18. Then, when the head support plate 15, which has electrostrictive drive electrodes 18 and 19 formed on both surfaces of the plate bodies 16 and 17, is electrostrictively driven by a predetermined electric signal, the head support plate 15 becomes as shown in FIG. As shown in the schematic diagram, a fixed point P ₀ is a support for the head base 13.
It is uniformly curved in a curve shown by symbol A with a constant radius of curvature R from the tip to the displacement point Q, which is the tip where the head tip 11 is attached. As a result, the gap surface of the head chip 11 attached to the tip of the head support plate 15 faces in the curved direction of the tip of the head support plate 15.
Then, the gap surface of the head chip 11 does not come into close contact with the recording surface of the magnetic tape 6 that is running while being wound around the upper and lower drums 3 and 4, and the error in the angle of contact with the recording surface becomes significant. The head chip 11 will no longer be able to accurately trace the recorded track.

Therefore, the present invention reduces the contact angle error between the magnetic tape 6 and the head chip 11 as described above when performing tracking correction, so that a stable reproduced image can be reliably obtained. This was proposed for the purpose of facilitating installation, improving the mechanical strength of the head support, providing greater freedom in the selection of materials, and improving high-speed response through electrostrictive drive. .

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention joins a plate-shaped ferroelectric material to both sides of a portion of an intermediate electrode from the base end to a position a predetermined distance away from the tip. A strain drive electrode is provided on a ferroelectric material, and a material lighter and more rigid than the ferroelectric material is bonded to a predetermined portion of the intermediate electrode to which the plate-shaped ferroelectric material is not bonded to form a head support. , a magnetic head is attached to the tip of the head support.

[Effect]

The present invention relates to a strain drive electrode provided on a plate-shaped ferroelectric material bonded to both sides of a portion of an intermediate electrode constituting a head support from its base end to a position a predetermined distance away from its tip. When a driving current is supplied, the head support is deflected and displaces the magnetic head attached to its tip. At this time, since the ferroelectric material is bonded only halfway from the base end of the intermediate electrode, the tip of the head support is translated in parallel without being deflected. Furthermore, on the tip side of the head support plate where the ferroelectric material is not bonded,
Since a material that is lighter and more rigid than the above ferroelectric material is bonded, the weight of the head support plate can be reduced and its mechanical strength improved, and an improvement in high-speed response due to electrostrictive drive can be achieved. Ru.

[Example] Hereinafter, specific examples of the present invention will be described with reference to the drawings.

FIGS. 5 and 6 show a magnetic head support device to which the present invention is applied, and this support device also includes a head support plate configured as an electrostrictive transducer, similar to the conventional device described above. 31 is a fixing means 32, such as a head base, whose base end is attached to the rotating body of the rotating magnetic head device or to the rotating body.
It is mounted as a cantilever supported on the The head support plate 31 has a central metal plate 30 formed entirely of a ferroelectric material such as lead zirconate titanate on both sides of a substantially triangular central metal plate 30 with a tapered tip that serves as a reinforcing plate that also serves as an intermediate electrode. It is constructed by joining two plate-like bodies 33 and 34 formed into a substantially trapezoidal shape with an adhesive or the like. These plate-like bodies 33 and 34 extend from the wide proximal end of the central metal plate 30 toward the distal end at a predetermined distance apart, and in this embodiment, the plate-like bodies 33 and 34 are 1/1/1 of the total length of the central metal plate 30.
It is joined over a range of 2. On the plate-like bodies 33 and 34 formed of the above-mentioned ferroelectric material, an electrostrictive drive electrode 3 is provided which drives the plate-like bodies 33 and 34 in a strain manner.
5 and 36 are provided. The head support plate 31 configured in this manner has a proximal end portion 37 on both surfaces thereof extending from near the proximal end where the electrostrictive driving electrodes 35 and 36 serve as supporting portions for the fixing means 32 to the central portion.
is formed. That is, the electrostrictive drive electrode 35,
36 is formed at approximately 1/2 of the central portion from the base end of the head support plate 31. In addition, at the distal end portion of the central metal plate 30 to which the plate-like bodies 33 and 34 are not joined, lightweight synthetic resin plates 41 and 42, which are lighter and more rigid than the ferroelectric material, are used.
are joined.

The head chip 3 constituting the magnetic head
8 is attached by a method such as bonding with adhesive, with the gap-formed tip protruding from the tip of the central metal plate 30 which faces outward from the tips of the synthetic resin plates 41, 42.

In this way, if the electrostrictive drive electrodes 35 and 36 are provided only at the base end 37 without forming an electrostrictive drive electrode at the distal end of the head support plate 31, the head support plate 31 can be moved by a predetermined electric signal. When electrostrictively driven, only the base end portion 37 is strain-driven without driving the distal end portion 39.

Here, using FIG. 4 mentioned above, the displacement of the tips of the head tips 11 and 38 between the conventional type and the type according to the present invention will be compared.

Note that the head support plate 15 constituting the conventional device
The length from the fixed point P ₀ to the displacement point Q is the same for the head support plate 31 constituting the present invention.

In the conventional device, the head support plate 15 is electrostrictively driven by a predetermined electric signal.
As described above, it is uniformly curved with a constant radius of curvature R from the fixed point P ₀ to the displacement point Q as shown by the symbol A. On the other hand, in the device of the present invention, when driven with a voltage at the same level as the electric signal, the head support plate 31 is connected to the electrostrictive drive electrode 3.
The radius of curvature R is the same as that of the conventional one only from the base end 37 where electrodes 5 and 36 are formed, that is, from the fixed point P ₀ to the intermediate point q that is the tip of the electrodes 35 and 36.
It is curved with . Further, the tip portion 39 on which the electrostrictive drive electrode is not formed is not strain-driven and is linearly extended in the tangential direction from the intermediate point q. The head support plate 3 constituting the present invention
1 is displaced along a curve as shown by symbol B in FIG.

Here, when looking at the contact angles of the tips of the head chips 11 and 38 to the magnetic tape 6 in the conventional type and the present invention, it is found that from the fixed point P ₀ of the head support plate 15 used in the conventional type to the displacement point Q. If the angle corresponding to the extending circular arc is 2θ, then the angle corresponding to the curved circular arc of the head support plate 31 used in the present invention, that is, the circular arc from the fixed point P ₀ to the intermediate point q is θ. Therefore, the contact angle of the head chip 38 attached to the tip 39 extending tangentially from the tip of the arc with respect to the magnetic tape 6 is also θ.

Also, the amount of displacement of each of the head support plates 15 and 31 from the inoperative position (X-axis in FIG. 4) is compared.

Displacement h (2θ) of the conventional head support plate 15
From the following equation, h(2θ)≒Rθ/2×sinθ≒Rθ ² /2 ∴h(2θ)≒2Rθ ² The amount of displacement of the head support plate 31 constituting the present invention
From the following formula, hχ becomes h(χ)≒3/2Rθ・sinθ≒3/2Rθ ² , and comparing the two, ∴h(χ)/h(2θ)≒3/2・Rθ ² /2・Rθ ² = 3
/4.

From the above-mentioned relationship, if the total lengths of the head support plates 15 and 31 are made the same, the electrostrictive drive electrode will be reduced by 1/2.
2. In other words, even if 1/2 of the tip 39 to which the head chip 38 constituting the magnetic head is attached is not driven in a distorted manner, the displacement of the tip remains by 1/4, whereas the head tip 38 relative to the magnetic tape is Since it is attached to the tip of the head support plate 31 where the strain drive electrode is not formed, there is no need to insulate the head chip 38 and the electrode. Furthermore, since there is no need to form an electrode, the weight can be reduced by at least the weight of the electrode conventionally formed at the tip, and high-speed response when strain-driven is improved. Furthermore, if the electrostrictive drive is reduced, the capacitance is reduced and the structure of the drive circuit becomes easier. Further, since the head tip 38 is attached to the tip portion which is not subjected to electrostrictive driving, it is easy to bond with an adhesive or the like, and the bonded state is also stable and reliable.

In addition, since the head support plate 31 is formed into a substantially trapezoidal shape as shown in FIG. can be made smaller.
That is, the mass of the distal end can be reduced while the bending displacement force of the proximal end 37 is kept relatively strong, and the high-speed response when the head support plate 31 is strain-driven is improved. Furthermore, as mentioned above, since there is no electrostrictive drive electrode at the tip,
Compared to the conventional case in which an electrostrictive drive electrode is also provided at the tip, the tip can be made lighter by the weight of the electrostrictive drive electrode. Therefore,
The head support plate 31 constituting the present invention has a substantially trapezoidal shape to reduce the weight of the tip, and the synergistic effect of not providing an electrode at the tip allows the head support plate 31 to be strain-driven when driven. High-speed response is greatly improved.

Furthermore, when the head support plate 31 is displaced in the direction of arrow D in FIG. 6, the upper limit of the frequency is determined by the natural frequency of the head support plate 31.

Next, we will discuss the natural frequency of the head support plate in which only the base end is supported.

The mass of the head support plate is distributed over the entire head support plate, but to simplify the explanation, consider an ideal system in which the mass is concentrated at the center of gravity P of the head support plate.

Head support plate 3 with width W and length L shown in FIG. 7a
₁ , the distance from the fixing means 32 to the center of gravity P is _la , and the spring constant of the head support plate 31 at this time is Ka, then the natural frequency _{ω a is} K=K _a /M _a ......(1) (However, K is a constant of proportionality).

Next, a case where only the width of the head support plate 31 shown in FIG. 7a is reduced to 1/2 will be explained using FIG. 7b. In this case, since the width W is set to 1/2, the mass of the head support plate 31 is 1/2 M _a , the distance from the fixing means 32 to the center of gravity P is l, and the spring constant of the head support plate 31 is approximately 1/2 K _a becomes.

Therefore, the natural frequency ω _b is approximately K1/2K _a /1/2M _a =KK _a /M _a (2).

As can be seen from equations (1) and (2) above, when only the width of the head support plate is halved, the natural frequencies are almost the same.

Next, a case where only the length of the head support plate 31 shown in FIG. 7a is reduced to 1/2 will be explained using FIG. 7c.

In this case, since only the length is halved, the mass of the head support plate 31 is 1/2 _Ma , the distance from the fixing means 32 to the center of gravity P is 1/2 _la , and the spring constant of the head support plate 31 is approximately It becomes 2K _a .

Therefore, the natural frequency ω _c is approximately K2K _a /1/2M _a =2KK _a /M _a (3).

As can be seen from equations (1) and (3) above, if only the length of the head support plate 31 is halved, the natural frequency will approximately double.

As mentioned above, in order to increase the natural frequency of the rectangular head support plate 31 as shown in FIG. 7a,
As shown in Figure 7b, this cannot be achieved even by changing the width.
As shown in FIG. 7c, if the length is shortened, the amount of displacement during strain driving becomes small, and the required amount of displacement may not be satisfied, which is not preferable.

Next, a shape for increasing the natural frequency without changing the length L of the head support plate 31 will be explained.

When the head support plate 31 shown in FIG. 7a is formed into a triangular shape whose width becomes narrower from the base end 37a to the distal end 39a, as shown in FIG. 7d,
The length from the base end 37a to the tip 39a is L, the width of the base end 37a is W, and the mass of the head support plate 31 is 1/2.
M _a , the distance from the fixing means 32 to the center of gravity P is 2/3l _a
It is. If the spring constant at this time is K _d , the natural frequency ω _d is KK _d /1/2M _a (4).

Here, the width of the head support plate 31 from the base end 37a to the center of gravity P is always 1/2W or more, and the distance from the base end 37a to the center of gravity P is less than l _a , so the spring constant K _d is K _d ＞1/2K _a ......(5).

Therefore, from equations (1), (2), and (5), ω _d >ω _a (6).

As can be seen from the above, by making the head support plate 31 substantially triangular or trapezoidal, it is possible to change the displacement amount of the tip portion 39 without changing the length L of the head support plate 31. It is possible to increase the natural frequency without

In this way, by making the head support plate 31 substantially triangular or trapezoidal in shape, and by not providing an electrostrictive drive electrode on the tip 39, the amount of displacement of the tip 39 can be made relatively large. It is possible to improve the high-speed response while maintaining the same, and furthermore, it is possible to reduce the contact angle error between the head chip 38 and the magnetic tape.

In the embodiment of the present invention described above, the electrostrictive drive electrodes 35 and 36 are located at the base end 3 of the entire length of the head support plate 31.
As mentioned above, by forming the part at 1/2 of 7, the amount of displacement is reduced by 25% compared to the conventional one.
This decrease in displacement can be overcome by increasing the total length of the head support plate 31 by 15%.

Further, in the above embodiment, the head support plate 31 is formed into a substantially triangular shape. It may be formed into a rectangular shape because it can reduce its weight and improve its mechanical strength, and improve high-speed response due to electrostrictive drive.

〔Effect of the invention〕

As described above, in the present invention, a ferroelectric material is bonded only to the middle part from the base end of the intermediate electrode, and a material that is lighter and more rigid than the ferroelectric material is bonded to the tip side where the ferroelectric material is not bonded. Since the head support body is configured by the head support plate, the magnetic head attached to the tip of the head support plate can be moved and displaced in parallel, and the weight of the head support plate can be reduced.
Mechanical strength can be improved by the material bonded to the tip side, and high-speed response can be improved by electrostrictive driving.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing a rotating magnetic head device used in a video tape recorder;
This figure 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 device. FIG. 4 is an explanatory view schematically showing the operating states of a conventional support device and a support device according to the present invention. FIG. 5 is a schematic plan view of the support device according to the present invention, and FIG. 6 is a sectional view thereof. FIGS. 7a, b, c and d are schematic diagrams comparing the characteristics of different shapes of the head support plate. 31... Head support plate, 33, 34... Plate-shaped body, 3
5, 36...Electrostrictive drive electrode, 37... Base end portion of head support plate, 38... Head chip, 41, 42... Lightweight synthetic resin plate.

Claims (1)

[Scope of Claims] 1. A plate-shaped ferroelectric material is bonded to both sides of a portion of the intermediate electrode from the base end to a position a predetermined distance away from the tip, and the plate-shaped ferroelectric material is bonded to the plate-shaped ferroelectric material for strain driving. an electrode is provided, and a material lighter and more rigid than the ferroelectric material is bonded to a predetermined portion of the intermediate electrode to which the plate-shaped ferroelectric material is not bonded to form a head support; a tip of the head support; A magnetic head support device characterized in that a magnetic head is attached to a portion of the magnetic head.