JPH0235365B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention displaces a rotating magnetic head device, particularly a rotating magnetic head, of a magnetic recording/reproducing device (including devices without a recording function) such as a video tape recorder in a direction perpendicular to its rotation locus. The present invention relates to a rotating magnetic head device which is particularly adapted to obtain a good reproduction signal.

In the case of a helical scan rotary head type magnetic recording/reproducing device, the angle θ (video track inclination angle) that the video track recorded on the magnetic tape makes with respect to the upper and lower ends of the magnetic tape is determined by the video track pitch a and the magnetic tape running speed V. From this, it is determined by the relationship θ=sin ^-1 (60a/V).

Therefore, in the case of special playback such as still playback, low-speed playback, and high-speed playback, where the magnetic tape running speed V is different from that during recording, the video track inclination angle θ is different from that during recording, resulting in so-called track deviation, causing track misalignment. Even if a wide read-only magnetic head is provided separately from a recording magnetic head, it is impossible to obtain a perfect read signal.

In order to improve this drawback, a piezoelectric element is interposed between the rotating magnetic head and the rotating shaft, and electrical energy related to the video track inclination angle θ is applied to the piezoelectric element to change the height position of the rotating magnetic head over time. A proposal has been made to obtain a perfect playback signal by changing the tilt angle .theta. and making an appropriate video track tilt angle .theta. appear even in special playback.

In this case, the height direction displacement y of the rotating magnetic head
has the following relationship with the length l of the piezoelectric element from the fixed part and the applied voltage E.

y=kl ² E Here, k is a constant determined by the piezoelectric constant and thickness of the piezoelectric element.

As is clear from the above equation, in order to obtain a large displacement with a low voltage, it is necessary to make the length of the piezoelectric element from the fixed part as long as possible. In particular, in home video tape recorders and the like, it is desired that the operating voltage be low in terms of power consumption and safety.

The present invention uses a ring plate-shaped bonded piezoelectric element in order to make the effective length of the piezoelectric element as long as possible. Here, an example of the electrode form and driving form of the ring plate-shaped bonded piezoelectric element will be described with reference to FIGS. 1 and 2.

The ring plate-shaped bonded piezoelectric element 2 is constructed by bonding two hollow disk-shaped piezoelectric element plates 101 and 102 with an adhesive so that their polarization axes are in the same direction. The electrode on this bonding surface is divided into an electrode 103 and an electrode 104. Now, the electrode 105 and the electrode 106 are connected so that they are electrically conductive, and the drive source 10 is connected between them and the electrode 103 or the electrode 104.
7 and 108, one of the two piezoelectric element plates 101 and 102 will expand and the other will contract, resulting in bending deformation of the piezoelectric element.

In addition, as described above, the piezoelectric element 2 has electrodes on the bonding surface separated into electrodes 103 and 104, so although it is a single piezoelectric element in shape, it is driven by the drive sources 107 and 108. It operates as two piezoelectric elements that can be driven separately. That is, the height positions of the two rotating magnetic heads can be controlled separately.

However, such a ring plate-shaped piezoelectric element has one unique problem. This is because the two piezoelectric elements, which can be driven separately, are integrated in shape, so if the fixing method is incomplete, the two piezoelectric elements can be driven separately.
There is a problem in that the movement of one piezoelectric element leaks to the other, interfering with accurate operation.

In view of the above points, the present invention is a rotating head type magnetic recording and reproducing device having a structure in which a ring plate-shaped piezoelectric element is stably fixed in order to accurately displace a rotating magnetic head during special reproduction and obtain a good reproduction signal. The present invention provides a rotating magnetic head device for use in a magnetic field.

Hereinafter, the present invention will be explained based on illustrated embodiments. In FIG. 3, a lower cylinder 8 having a magnetic tape guide portion 6 for guiding a magnetic tape 4 run by a suitable well-known magnetic tape running mechanism is fixed to a substrate 10.

The rotating shaft 12 is rotatably supported by the housing portion 14 of the lower cylinder 8 by ball bearings 16a, 16b, and a magnet rotor 18 is attached to the lower part thereof. A stator core 20 having stator windings is disposed facing inside the magnet rotor 18, and the rotating shaft 12 is rotated at a predetermined number of rotations by a brushless DC motor constituted by the stator core 20. .

Further, a rotary disk 22 is press-fitted into the upper part of the rotary shaft 12, and on its upper end surface 24 there are recording and normal reproduction magnetic heads 26, 28 and special reproduction magnetic heads 30, 32, as shown in FIG. Second
The upper cylinder unit 34, which is equipped with the ring plate-shaped piezoelectric element 2 as explained in the figure, is attached to the set screw 36.
Fixed by

At this time, the magnetic heads 26, 28, 30, 3
2 is a slight gap 3 formed between the lower cylinder 8 and the upper cylinder unit 34.
8.

Therefore, the magnetic heads 26, 28, 30, 3
2 is rotated to scan the magnetic tape 4, thereby recording or reproducing signals.

The electrical energy is supplied to the piezoelectric element 2 by means of a contactor 42 insulated and fixed to the lower cylinder 8 of the conductive rotary disk 0 insulated and fixed to the cylinder unit 34. It is designed to be carried out with

Further, the magnetic heads 26, 28, 30, 32
Signals are exchanged between the rotary transformer 44 and an amplifier (not shown).

The detailed structure of the cylinder unit 34 will be explained with reference to FIG. 4.

The above-mentioned recording and normal reproduction magnetic heads 26, 2
8 are attached to the upper cylinder 46 by machine screws 47, making an angle of 180 degrees with each other and having an appropriate protrusion amount.

On the other hand, the magnetic heads 30 and 32 for special reproduction are positioned and bonded on the same surface of the piezoelectric element 2 at an angle of 180 degrees to each other and protrude from the outer periphery of the upper cylinder 46 by an appropriate amount. The piezoelectric element 2 includes a piezoelectric element mounting base 48 each having a convex portion and a pair of fixing members 5.
0 and 52 are sandwiched together and fixed by tightening with machine screws 54.

Further, the pair of fixing members 50, 5
An adhesive is injected through holes 60, 62 provided in the convex portions 56, 58 of 2, and the fixing members 50, 52 and the piezoelectric element 2 are adhesively fixed to form a piezoelectric element unit 64. Then, this piezoelectric element unit 64 is placed on the upper cylinder 46 so that the special reproduction magnetic heads 30 and 32 form an angle of approximately 90 degrees with the recording and normal reproduction magnetic heads 26 and 28. By aligning the centers of the piezoelectric element unit 64 and the upper cylinder 46, the special reproduction magnetic heads 30, 2 are indexed at a 180° angle and the amount of protrusion is adjusted. Upper cylinder unit 3
This is the completion of step 4.

Now, as mentioned above, when using the ring plate-shaped piezoelectric element 2 like the one in this embodiment, there is a possibility that operation interference between the piezoelectric elements on both sides will have an adverse effect on the reproduced image, and the fixing structure of the piezoelectric element may be affected. requires some ingenuity.

The fixing structure of the piezoelectric element in this example will be explained in more detail with reference to FIG. 5 and FIGS. 6a and 6b.

A pair of convex portions 68, 7 of the piezoelectric element mounting base 48
0 is provided at a symmetrical position with respect to the center of the piezoelectric element mounting base 48, and its outer diameter and inner diameter are approximately equal to the outer diameter and inner diameter of the piezoelectric element 2, respectively.
The straight line A connecting the ridges 72 and 74 and the straight line B connecting the ridges 76 and 78 are shaped to be parallel to each other.

Furthermore, the piezoelectric element mounting base 48 has a ridge 72 and a ridge 7 that pass through the center of the pair of convex portions 68 and 70.
Two pairs of female threaded portions 79 are provided at positions symmetrical to the convex portion on two straight lines C and D perpendicular to the straight line A connecting the two.

On the other hand, the pair of fixing members 50 and 52 have protrusions 56 and 58 approximately in the same shape and dimensions as the pair of protrusions 68 and 70 of the piezoelectric element mounting base 48, located approximately in the center thereof.
However, holes 81 are provided on both sides of the convex portions 56 and 58, respectively, to face the female threaded portion 79.

Furthermore, approximately at the center of the convex portions 56 and 58,
Grooves 80, 82 and holes 60, 62 are provided.

When the piezoelectric element 2 is inserted between the piezoelectric element mounting base 48 and the pair of fixing members 50, 52 and tightened with the machine screws 54, all the tightening force is applied to the ridges 72, 74, 76, 78. acts uniformly over the entire length (the pair of fixing members 5
The same is true for the ridges of the convex portions 56 and 58 of 0 and 52).As a result, the piezoelectric element 2 is tightened uniformly from its inner circumference to its outer circumference, resulting in the most stable fixation. The fixing portion can prevent vibrations from propagating from one piezoelectric element to the other, and can minimize operational interference.

Furthermore, the grooves 80 and 82 allow for more stable fixation.

Furthermore, holes 60 provided in the convex portions 56, 58,
If adhesive is injected from 62, it will not only help in fixing, but also connect the convex portions 56, 58 and the piezoelectric element 2.
By filling the gap between the two and preventing dust from entering the fixed part, stability can be further increased.

As is clear from the above description, according to the present invention, the ring plate-shaped piezoelectric element can be stably fixed, so that the magnetic heads attached to it can be accurately displaced without mutual interference. As a result, a good reproduced signal can be obtained.

Note that the bonded piezoelectric element used in the present invention is not limited to the shape shown in the drawings, and any modification or similar shape may be used as long as it has the same function as the piezoelectric element.

[Brief explanation of drawings]

FIG. 1 is a top view of an example of a bonded piezoelectric element that can be used in the present invention, FIG. 2 is a configuration diagram for explaining an example of its driving form, and FIG. 3 is a side cross-section of an example of the present invention. Figure 4 is an exploded perspective view of essential parts of the same embodiment, Figure 5 is a top view of a piezoelectric element mount that can be used in the same embodiment, and Figures 6 a and b are fixings that can be used in the same embodiment. FIG. 3 is a top view and a side view of the plate. 2... Piezoelectric element, 4... Magnetic tape, 8... Lower cylinder, 12... Rotating shaft, 30, 32... Magnetic head for special reproduction, 48... Piezoelectric element mounting base, 5
0, 52... Fixing member, 54... Machine screw, 56,
58... Protrusion, 60, 62... Hole, 64... Piezoelectric element unit, 68, 70... Protrusion, 72, 7
4,76,78...Ring, 79...Female thread part, 8
0,82...groove, 81...hole.

Claims (1)

[Scope of Claims] 1. A tape guide cylinder capable of guiding travel by wrapping a magnetic tape around its outer periphery, and for recording signals on or reproducing signals from the magnetic tape wound around the tape guide cylinder. a plurality of rotating magnetic heads, a rotating shaft that rotatably supports the plurality of rotating magnetic heads, and the plurality of rotating magnetic heads, and the rotating magnetic head is arranged in the longitudinal direction of the rotating shaft. A ring plate-shaped bonded piezoelectric element to enable displacement,
piezoelectric element fixing means for fixing the bonded piezoelectric element to the rotating shaft; The structure includes a pair of fixing members having a convex portion approximately in the center for sandwiching the bonded piezoelectric element in cooperation with the convex portion, and the second fixing member passes through the two convex portions of the piezoelectric element mounting base. A rotating magnetic head device characterized in that the piezoelectric element mounting base and the pair of fixing members are fastened together on two straight lines perpendicular to a straight line connecting the convex portions of the parts. 2. In the description of claim 1, the two convex portions of the piezoelectric element mounting base and the ridges of the convex portions of the pair of fixing members that are in contact with the bonded piezoelectric element are perpendicular to the two straight lines. A rotating magnetic head device characterized in that it is formed of straight lines. 3. The rotating magnetic head device according to claim 2, wherein the protrusions of the pair of fixing members are provided with through holes for injecting an adhesive. 4. A tape guide cylinder around which a magnetic tape can be wound to guide its travel, and a plurality of rotating magnets for recording signals on or reproducing signals from the magnetic tape wound around the tape guide cylinder. a rotary shaft rotatably supporting the plurality of rotary magnetic heads; and a rotary magnetic head for displacing the rotary magnetic heads in the longitudinal direction of the rotary shaft. A ring plate-shaped bonded piezoelectric element,
piezoelectric element fixing means for fixing the bonded piezoelectric element to the rotating shaft; The fixing member includes a pair of fixing members having a protrusion substantially in the center for cooperating with a protrusion to sandwich the bonded piezoelectric element, and a groove is provided in the protrusion of the pair of fixing members, and the piezoelectric element mounting base and the pair of fixing members are connected on two straight lines that pass through the two convex portions of the piezoelectric element mounting base and are perpendicular to a straight line that connects the two convex portions. A rotating magnetic head device characterized in that it is configured to be fastened.