JPS6338420Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a magnetic head mechanism for a video tape recorder that is capable of adjusting the contact pressure of the magnetic head in contact with a magnetic tape.

[Background technology and its problems]

Conventional methods for adjusting the contact pressure of the magnetic head in contact with the magnetic tape include: 1. Applying centrifugal force to the magnetic head by rotating a rotating cylinder, bending a spring material and protruding the magnetic head from the surface of the rotating cylinder. 2) A method is proposed in which a magnetic head is attached to the tip of the bimorph, a voltage is applied to the bimorph, and the electrostrictive effect of the bimorph causes the magnetic head to protrude from the surface of the rotating cylinder.

As shown in FIG. 1, the above magnetic head function 1 is achieved by attaching the magnetic head 1 to one end of the spring material 2,
The other end of this spring material 2 is fixed to a rotating cylinder 4 via a fixing member 3. Therefore, when the rotating cylinder 4 rotates, the magnetic head 1 bends the spring material 2 due to the centrifugal force, and the tip of the magnetic head 1 protrudes from the surface of the rotating cylinder 4 and fixed cylinder 5 and comes into contact with the magnetic tape. do.

In order to maintain a constant contact pressure between the magnetic head 1 in contact with the magnetic tape, this mechanism requires high mechanical properties of the component materials, precision of the individual components (especially the spring material 2), and precision of assembly of the components, making it expensive. There's a problem.

As shown in FIG. 2, in the second magnetic head mechanism, the magnetic head 1 is fixed to the tip of a bimorph 6, and the bimorph 6 is fixed to a rotating cylinder 4 via a fixing member 3. Therefore, when a voltage is applied to the bimorph 6, the electrostrictive effect of the bimorph 6 causes the tip of the magnetic head 1 to protrude from the surfaces of the rotary cylinder 4 and fixed cylinder 5 and come into contact with the magnetic tape.

Although this mechanism requires less parts and assembly accuracy than the magnetic head mechanism 1 above, the bimorph 6
is a cantilever type, and it is difficult to strongly oppose the tape pressure, so there is a problem that it is difficult to maintain the contact pressure against the tape at a constant value due to the bimorph force. .

[Purpose of invention]

This idea was made in view of the above points, and is easy to assemble and inexpensive.
Another object of the present invention is to provide a magnetic head mechanism for a video tape recorder that can easily maintain contact pressure and can adjust the contact pressure.

[Summary of the idea]

In order to achieve the above-mentioned purpose, this invention consists of sequentially laminating piezoelectric ceramic plates with electrodes on the front and back sides to form a laminated ceramic plate, attaching a magnetic head to one end of the laminated ceramic plate in the stacking direction, and rotating the other end. The tip of the magnetic head is fixed to a cylinder or rotating head base, and by applying a predetermined voltage between each electrode, the tip of the magnetic head protrudes a predetermined length from the surface of the rotating cylinder or fixed cylinder, and the magnetic head is attached to the magnetic tape with stable contact pressure. This makes it possible to contact the

〔Example〕

This invention will be explained below based on the drawings.

3a, b, and c are manufacturing process diagrams of a laminated ceramic plate, and FIG. 4 is a perspective view showing a magnetic head mechanism of a video tape recorder according to an embodiment of the invention.

First, as shown in FIG. 3, piezoelectric ceramic plates 12 provided with electrodes 11 on the front and back sides are successively laminated and cut into appropriate dimensions to form a laminated ceramic plate 13. Next, as shown in FIG. 4, a head mounting base 14 is attached to one end in the lamination direction of the laminated ceramic plate 13 cut to an appropriate size, the magnetic head 1 is fixed to this head mounting base 14, and the laminated ceramic plate The other end in the stacking direction of 13 is attached to the rotating cylinder 4 via the fixing members 3 and 15. Then, the electrodes 11, 11 of each piezoelectric ceramic plate 12 described above are
The voltage of the power supply 16 is applied to the part corresponding to the variable resistor 1.
Adjust with step 7 and apply.

When the magnetic head mechanism is configured as described above, each piezoelectric ceramic plate 12 is caused to elongate in the stacking direction of the laminated ceramic plates 13 due to the piezoelectric effect of the voltage applied from the power source 16, which is approximately proportional to the applied voltage. For example, the laminated ceramic plate 13 made by laminating 50 piezoelectric ceramic plates 12 with a thickness of 250 μm is approximately
An electric field of 10KV/cm causes an elongation of approximately 30μm. In addition, the laminated ceramic plate 13, which is made by laminating 70 piezoelectric ceramic plates 12 with a thickness of 300 μm, has an electric field of -
As for the elongation characteristics, an electric field of 10 KV/cm causes an elongation of approximately 50 μm.

By the way, when an external pressure is applied to the laminated ceramic plate 13 while a voltage is applied to the laminated ceramic plate 13, the elongation changes as shown in the yield strength-displacement characteristics shown in FIG. 6a.

However, since the contact pressure at which the magnetic head 1 comes into contact with the magnetic tape is about 40 g at most, there is almost no influence from external pressure.

Therefore, since the protrusion length of the magnetic head 1 from the rotating cylinder 4 can be determined by the voltage applied to the laminated ceramic plate 13, the contact pressure can be maintained better than in the case using the bimorph shown in FIG. 2 described above. will be carried out reliably.

In other words, in the case of Fig. 2, when external pressure is applied with voltage applied as shown in Fig. 6b, the bimorph changes greatly with an external force of several tens of grams due to its proof force-displacement characteristics, and the contact pressure with the tape is sufficient. I can't take it. On the other hand, in the case of the present invention, it is made of laminated ceramic plates and utilizes the force in the lamination direction, so it can withstand large external forces and maintains the protrusion amount of the head, that is, the contact pressure, constant. be able to.

In addition, in the conventional example shown in Fig. 1 or 2, the head is supported in a cantilever type, so when the amount of protrusion of the head is changed, the contact angle θ between the head and the tape is changed as shown by the dotted line in Fig. 6c. As shown in the figure, the head characteristics change, but in the case of the present invention, such drawbacks are also eliminated.

By the way, as can be understood from the characteristic diagram in FIG. 5, the laminated ceramic plate 13 generally has hysteresis characteristics, and even if the electric field is removed after elongation occurs by applying electrolysis, elongation remains as residual strain, so this property For example, the magnetic head structure of the present invention can be attached to a rotating drum using this method, and then the magnetic head can be attached in such a manner that the magnetic head protrudes from the rotating cylinder 4 by a predetermined length with the electric field removed.

Furthermore, when residual strain occurs in the piezoelectric ceramic plate 12, the piezoelectric ceramic plate 12 is in a polarized state, and a voltage is output due to the electrostrictive effect in response to the contact pressure of the magnetic head. If this voltage is detected and the fixing member 15 shown in FIG. It becomes possible to control the mounting position and change the amount of protrusion so that the optimum contact pressure can always be applied to the magnetic head.

FIG. 7 is a perspective view showing another embodiment of this invention, in which a bimorph 18 for pressure detection is inserted between the laminated ceramic plate 13 and the fixing member 15.

When the magnetic head mechanism is configured as in the embodiment shown in FIG. 7, the protruding length of the magnetic head 1 can be adjusted by the voltage applied to the laminated ceramic plate 13 as described above, and the magnetic head in contact with the magnetic tape can be Depending on the contact pressure of the head 1, an electromotive force signal due to the piezoelectric effect is obtained from the bimorph 18. Therefore, if the contact pressure is insufficient due to the signal from the bimorph 18, the voltage applied to the laminated ceramic plate 13 is increased by a control circuit (not shown).
In the opposite case, the applied voltage can be reduced to automatically adjust the contact pressure to an optimal value.

Although the head mount 14 was used in the above embodiment, it may be omitted. Further, although the laminated ceramic plate 13 is fixed to the rotary cylinder 4, it may be fixed to a rotary head base or the like that rotates similarly to the rotary cylinder 4.

[Effect of idea]

As explained above, in the magnetic head mechanism of the video tape recorder of this invention, piezoelectric ceramic plates having electrodes on the front and back sides are successively laminated to form a laminated ceramic plate, and a magnetic head is attached to one end of the laminated ceramic plate in the laminating direction. At the same time, since the other end is fixed to a rotating cylinder or the like and a predetermined voltage is applied to each electrode, the protrusion length of the magnetic head due to the piezoelectric effect of the piezoelectric ceramic plate can be adjusted by the applied voltage. Furthermore, since the magnetic head is attached in the direction of lamination of the laminated ceramic, the contact pressure with the tape is reliably maintained. Furthermore, since the precision of the component parts is not required so much, there is an advantage that assembly is simple and manufacturing is possible at low cost.

[Brief explanation of drawings]

1 and 2 are perspective views showing the magnetic head mechanism of a conventional video tape recorder, and FIGS. 3a, b,
Fig. 4 is a perspective view showing the magnetic head mechanism of a video tape recorder according to an embodiment of this invention, Fig. 5 is a characteristic diagram of electric field-elongation, and Fig. 6 a is a diagram of the manufacturing process of a laminated ceramic plate. The proof force-displacement characteristic diagram of the invented magnetic head mechanism, Fig. 6b is the proof force-displacement characteristic diagram of the conventional magnetic head mechanism, Fig. 6c.
7 is an explanatory view showing the inclination of the magnetic head, and FIG. 7 is a perspective view showing another embodiment of this invention. In the figure, 1 is a magnetic head, 4 is a rotating cylinder, and 5 is a magnetic head.
11 is a fixed cylinder, 11 is an electrode, 12 is a piezoelectric ceramic plate, 13 is a laminated ceramic plate, 15 is a fixed member, 16 is a power source, 17 is a variable resistor, and 18 is a bimorph.

Claims (1)

[Scope of utility model registration request] Piezoelectric ceramic plates each having electrodes on the front and back sides are laminated one after another to form a laminated ceramic plate. A magnetic head is attached to one end of the laminated ceramic plate in the lamination direction, and the other end is fixed to a rotating cylinder or a rotating head base, and between each of the electrodes. 1. A magnetic head mechanism for a video tape recorder, characterized in that the magnetic head mechanism is configured such that a predetermined voltage can be applied to the magnetic head.