JPS6327776B2 - - 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 υ. From this, it is determined by the relationship θ=sin ^-1 (60a/υ).

Therefore, in special playback such as still playback, low-speed playback, and high-speed playback where the magnetic tape running speed υ is different from that during recording, the video track inclination angle θ is different from that during recording, resulting in so-called track deviation and 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 reproduction signal by varying the angle θ of the video track along with the angle θ, so that an appropriate video track inclination angle θ appears even in special reproduction.

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.

As described above, the ring plate-shaped bonded piezoelectric element has unique advantages, but various measures are required to fix it. One problem is the width of the members that sandwich and fix the piezoelectric element from above and below. The piezoelectric element is made of a very fragile material, and if the relative positions of the upper and lower fixing members shift when it is fixed, a moment will act and cause it to break. This problem will now be explained in more detail using conventional examples shown in FIGS. 3 and 4.

The ring plate-shaped bonded piezoelectric element 2 has a convex portion 6
Springs 60, 62 are sandwiched between a piezoelectric element mounting base 48 having 8, 70 and a pair of pressing members 50, 52, and are integrated with the pressing members 50, 52.
It is pressed and fixed by the pressing force P generated by bending the .

As shown in FIG. 3, if the width W ₁ of the convex portions 68, 70 of the piezoelectric element mounting base 48 and the width W ₂ of the pressing members 50, 52 are equal and fixed without relative displacement, then Even during fixation, no moment is applied to the ring-plate bonded piezoelectric element 2, and there is no risk of it breaking.

However, as shown in FIG.
If W ₁ is smaller than the width W ₂ of the pressing members 50 and 52, or if the pressing members 50 and 52 are fixed at different positions, the pressing force P will act as a moment and the ring plate-shaped bonded piezoelectric element 2 will break. Become. Therefore, in the past, it was necessary to strictly control the machining accuracy of parts so that W ₁ and W ₂ were as equal as possible, and to use jigs during assembly to prevent relative positional deviations. This was a factor in increasing costs.

In view of the above points, the present invention does not require strict dimensional accuracy in the fixing member when fixing a ring plate-shaped bonded piezoelectric element, and does not require a jig during assembly. To provide a rotating magnetic head device that can be fixed without damaging the magnetic head.

Hereinafter, the present invention will be explained based on illustrated embodiments.

In FIG. 5, a lower cylinder 8 is fixed to a substrate 10, and has a magnetic tape guide portion 6 for guiding a magnetic tape 4 run by a known suitable magnetic tape running mechanism. Rotating axis 1
2 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 2 is provided on the upper part of the rotary shaft 12.
2 is press-fitted into the upper end surface 24, magnetic heads 26, 28 for recording and normal reproduction, magnetic heads 30, 32 for special reproduction, and a ring plate-shaped piezoelectric device as explained in FIGS. 1 and 2 are mounted. An upper cylinder unit 34 including the element 2 is fixed by a set screw 36.

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 through a conductive rotating disk 40 insulated and fixed to the upper cylinder unit 34 and a contact 42 insulated and fixed to the lower cylinder 8. It is designed to be carried out by

Further, the magnetic heads 26, 28, 30, 32
Signals are exchanged between the rotary transformer 44 and an amplifier (not shown). The detailed structure and assembly method of the upper cylinder unit 34 will be explained with reference to FIG. 6.

The above-mentioned recording and normal reproduction magnetic heads 26, 2
8 are attached to the upper cylinder 46 with machine screws 47, making an angle of 180 degrees with each other and having an appropriate amount of protrusion. In this case, the magnetic head 26,
The height of the upper cylinder 46 of 28 from the reference plane 49 is adjusted using spacers 27 and 29 so that it becomes a predetermined value.

On the other hand, the magnetic heads 30 and 32 for special reproduction are arranged on the same surface of the piezoelectric element 2 at an angle of 180 degrees to each other, and have a distance equal to the outer diameter of the upper cylinder 46 plus twice the required protrusion amount. Position and glue.

The piezoelectric element 2 includes a piezoelectric element mounting base 48 having convex portions 68 and 70, and a pair of pressing members 5.
The pressing member 5
0 and 52 are pressed and fixed by the spring force of springs 60 and 62 integrated with the 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,
The piezoelectric element unit 64 and the upper cylinder 46
After the special reproduction magnetic heads 30 and 32 are indexed at 180 degrees and the amount of protrusion is adjusted by aligning their centers, they are fixed with machine screws 66, and the cylinder unit 34 is completed.
The spacers 67 and 69 are used to set the heights of the special reproduction magnetic heads 30 and 32 to predetermined values.

Now, as mentioned above, when using the ring plate-shaped bonded piezoelectric element 2 as in this embodiment,
If there is a deviation in the dimensional accuracy of the width and relative position of the members that are clamped and fixed from above and below, there is a risk that the piezoelectric element 2 will break, so the dimensional accuracy of the width of the convex part of the fixed member must be strictly controlled. During assembly, it was necessary to use a jig and be careful not to cause relative positional deviation.

In this embodiment, the above problem is solved by providing a difference in the width of the convex portions of the upper and lower fixing members. Regarding this, Figures 7 and 8,
This will be explained in detail with reference to FIG.

FIG. 7 is a top view of the piezoelectric element mounting base 48, in which a pair of convex portions 68 and 70 are provided at symmetrical positions with respect to the center of the piezoelectric element mounting base 48, and the outer and inner edges thereof are as described above. The outer diameter and the inner diameter of the piezoelectric element 2 are approximately equal to each other, and the straight line A connecting the ridges 72 and 74 is parallel to the straight line B connecting the ridges 76 and 78.

Further, 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.

8a and 8b are a side view and a bottom view of a pair of fixing members 61, 63, and FIG.
63 are the pressing members 50, 52 and the springs 60, 62.
and the pressing members 50, 52 are connected to the springs 60, 62.
It is constructed by placing the parts together at approximately the center of the parts, or by integrating them by means such as adhesion. At both ends of the springs 60 and 62, there are holes 81 opposite to the female threaded portions 79 of the piezoelectric element mounting base 48.
is provided.

FIG. 9 is a side view of the piezoelectric element 2 fixed by the piezoelectric element mounting base 48 shown in FIG. 7 and the pair of fixing members 61 and 63 shown in FIG. 8.

In this embodiment, by tightening the two small screws 54, the pressing members 50, 52 are automatically moved approximately to the convex portions 68, 70 of the piezoelectric element mounting base 48 without using any jig. The width of the pressing members 50 and 52 can be made to face directly above each other.
W ₂ is connected to the convex portions 68 and 70 of the piezoelectric element mounting base 48.
Since the width W ₁ is smaller than the width W 1 of the convex portions 68 and 70, even if their center positions deviate by the dimension e, if the deviation is within the range of e<W ₁ −W ₂ /2, there will be an extreme As long as there is no protrusion, the pressing force P acts on the same upper and lower positions, so the pressing force P acts as a moment and the piezoelectric element 2 does not break as in the conventional example shown in FIG.

Also, the maximum value of e, which is the accumulated dimensional tolerance of each part.
If W ₁ −W ₂ is designed to be larger than twice e _nax , there is no need to use a jig during assembly. Even if W ₁ −W ₂ is designed to be large, if it is made too large, the piezoelectric element 2
In FIG. 9, the difference between the sensitivity when displacing in the _Y1 direction and the sensitivity when displacing in the _Y2 direction becomes large, and the drive circuit for the piezoelectric element 2 becomes complicated, so _W1- There is a natural limit to the value of W ₂ . In this example, in the case of a ring-plate bonded piezoelectric element with an outer diameter of 44.5 mm and an inner diameter of 32.3 mm, W ₁ = 4 mm, W ₂
= 3.5mm, and W ₁ −W ₂ = 0.5mm.

As is clear from the above description, according to the present invention, when installing a ring-plate bonded piezoelectric element, there is no need to strictly control the dimensions of each component, and there is no need to use a special jig. will not occur. Therefore, the assembly yield can be significantly improved and the assembly time can be shortened compared to the conventional example, and the present invention is particularly useful as a rotary magnetic head device for household magnetic recording and reproducing devices produced in large quantities.

It should be noted that the piezoelectric element used in the present invention is not limited to the shape shown in the drawings, and may be modified or have any similar shape as long as it has the same function as the piezoelectric element.

[Brief explanation of the drawing]

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 Figs. 3 and 4 are conventional examples of bonded piezoelectric elements. FIG. 5 is a side sectional view of an embodiment of the present invention, FIG. 6 is an exploded perspective view of essential parts of the embodiment, and FIG. 7 is a side view of the main part showing the mounting state of the piezoelectric element. 8a and b are side views and bottom views of a fixing member that can be used in the same embodiment, and FIG. 9 shows the mounting state of the bonded piezoelectric element in the same embodiment. FIG. 3 is a side view of main parts. 2... Ring plate-shaped bonded piezoelectric element, 4...
Magnetic tape, 8... Lower cylinder, 12... Rotating shaft, 26, 28... Magnetic head for recording and normal reproduction, 30, 32... Magnetic head for special reproduction, 3
4... Upper cylinder unit, 46... Upper cylinder, 48... Piezoelectric element mounting base, 50, 52... Pressing member, 54... Machine screw, 60, 62... Spring,
61, 63...fixing member, 64...piezoelectric element unit, 68, 70...convex portion.

Claims (1)

[Claims] 1. 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 rotating shaft that rotatably supports the plurality of rotating magnetic heads; and a rotating shaft that supports the plurality of rotating magnetic heads in a longitudinal direction of the rotating shaft according to an applied voltage. a ring plate-shaped bonded piezoelectric element that is displaced by a ring plate, and a piezoelectric element fixing means that fixes the bonded piezoelectric element to the rotating shaft, and the piezoelectric element fixing means has a first and a piezoelectric element mounting base having a second convex portion;
The piezoelectric element mounting base includes a pair of fixing members comprising a pressing member and a spring for sandwiching and press-fixing the bonded piezoelectric element in cooperation with the first and second convex portions of the piezoelectric element mounting base; The width of the pressing member is made smaller than the width of the first and second convex portions of the piezoelectric element mount, and the pressure member passes through the first and second convex portions of the piezoelectric element mount and the first and second A rotating magnetic head characterized in that the piezoelectric element mounting base and the pair of fixing members are fastened at at least two points each on two straight lines perpendicular to the straight line connecting the convex portions of the rotary magnetic head. Device.