JPS628845B2 - - 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.

Conventionally, in a rotating head type magnetic recording/reproducing device, the rotating magnetic head has been fixed to the rotating shaft via a metallic disk or strip block so as not to move during operation.

Therefore, the rotation locus of the rotating magnetic head formed a completely flat surface perpendicular to the center of the rotation axis.

On the other hand, the running of a magnetic tape, on which signals are recorded and reproduced by being scanned by a rotating magnetic head, is considerably undulating from an ideal straight line due to a number of reasons, including the linearity of the magnetic tape guide. It is becoming. As a result, especially when the recording device and the playback device are different, the state of the running undulation of the magnetic tape is different, causing so-called track deviation.
There was a fear that a defective reproduction signal would occur.

In order to improve this drawback, a rotating magnetic head height variable means made of a piezoelectric element is interposed between the rotating magnetic head and the rotating shaft, and electric energy associated with the running undulation state of the magnetic tape is applied to the piezoelectric element. However, a device for displacing a rotating magnetic head has been proposed.

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 v.

y=kl ² v Here, k is a constant determined from 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 desirable and necessary to use a low voltage from the viewpoint of power consumption and safety.

In view of the above points, the present invention aims at displacing the rotary magnetic head in response to the undulations of the running of the magnetic tape and obtaining a good reproduction signal. A rotating magnetic head device for a head type magnetic recording/reproducing device is provided.

Hereinafter, the present invention will be explained based on illustrated embodiments. In FIG. 1, a lower cylinder 6 is fixed to a substrate 8, and has a magnetic tape guide portion 4 for guiding a magnetic tape 2 run by a known suitable magnetic tape running mechanism.

The upper cylinder 10 has a cylinder receiver 1 fixed to the cylinder 6 such that a slight gap 12 is formed between the upper cylinder 10 and the lower cylinder 6 at the outer circumference.
It is fixed at 4.

Reference numeral 20 denotes a rotary shaft rotatably supported by the housing portion 16 of the lower cylinder 6 by ball bearings 18a and 18b, and a pulley 22 is fixed to the lower part of the shaft by a set screw 24.
It is rotated at a predetermined number of rotations by a belt 26 from a drive motor (not shown).

Further, a rotary disk 28 is fixed to the upper part of the rotary shaft 20 by a set screw 30, and two magnetic heads 38 and 40 are mounted on the upper end surface 32 of the rotary disk 28 at an angle of 180 degrees, as shown in the top view in FIG. A disk-shaped bonded piezoelectric element 52 constituting the rotating magnetic head height variable means is bonded at an angle of .
The magnetic heads 38, 40 are fixed by a set screw 44 at a position forming an angle of approximately 90° with the magnetic heads 38, 40 such that the magnetic heads 38, 40 are located in the gap 12. Here, the disk shape refers to a disk body without a hole in the center, or if there is a hole in the center, the outer diameter/inner diameter is 2.6 or more.

Therefore, by rotating the magnetic heads 38 and 40 to scan the magnetic tape 2, recording or reproduction of signals is performed.

The electrical energy is supplied to the bonded piezoelectric element 52 through a conductive rotary disk 46 insulated and fixed to the rotary disk 28 and a contactor 48 insulated and fixed to the upper cylinder 10. It is configured to be carried out by.

Further, a rotary transformer 50 is used for receiving and receiving signals between the magnetic heads 38 and 40 and an amplifier (not shown).
It is done through.

Here, the bonded piezoelectric element 52 will be explained in more detail with reference to FIGS. 3 and 4.
As shown in FIG. 3, the bonded piezoelectric element 52 is made by bonding two disk-shaped piezoelectric element plates 101 and 102 with an outer diameter/inner diameter of 2.6 or more with adhesive so that their polarization axes are in the same direction. It is configured.
When the electrodes 103 and 104 of the bonded piezoelectric element are electrically connected and a voltage is applied between them and the electrode 105, one of the two piezoelectric element plates 101 and 102 expands. , the other one contracts, so that the piezoelectric element as a whole undergoes bending deformation as shown in FIG.

Therefore, if the running undulation of the magnetic tape is detected and electrical energy corresponding to the amount is applied to the bonded piezoelectric element to change the height of the magnetic head, deterioration of the reproduced signal due to so-called track deviation can be prevented. can be completely eliminated, and a very good reproduced signal can be obtained.

Now, as mentioned above, in order to lower the voltage applied to the piezoelectric element and increase the displacement in the height direction of the rotating magnetic head, it is necessary to increase the length from the fixed part of the piezoelectric element to the rotating magnetic head. There is.

Therefore, in this embodiment, the bonded piezoelectric element 52 is attached to the rotary disk 28 at a position where the two magnetic heads 38 and 40, which are bonded at an angle of 180 degrees, form an angle of approximately 90 degrees. It is fixed at

With such a structure, the effective length of the piezoelectric element becomes l shown in FIG. The maximum possible size of a structure in which two magnetic heads are bonded together can be revealed. Furthermore, when considering the bonded piezoelectric element as a cantilever supported by two fixed points 44,
If the outside diameter is the same, a disk shape with a small inner diameter will generate less stress for the same external force than a circular shape with a large inner diameter, so there is less risk of breakage and it can be used stably for a long period of time. It has great effects.

As is clear from the above description, according to the present invention, since the effective length of the piezoelectric element can be maximized, a large height displacement of the rotating magnetic head can be obtained with a low voltage, and it is particularly compact and This device is very useful as a rotating magnetic head device for a household magnetic recording/reproducing device that requires a low power consumption type.

Note that the piezoelectric element used in the present invention is not limited to the shape and structure shown in the drawings. An element having a structure provided with electrodes, or an element having a structure in which one piezoelectric element plate and a non-piezoelectric member (for example, a metal plate) are bonded together can also be used.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing one embodiment of the present invention, FIG. 2 is a top view of the bonded piezoelectric element portion in the same embodiment, and FIGS. 3 and 4 are the bonded piezoelectric elements in the same embodiment. FIG. 3 is a cross-sectional view for explaining the structure and operation. 2... Magnetic tape, 4... Magnetic tape guide section, 6... Lower cylinder, 8... Substrate, 10... Upper cylinder, 18a, 18b... Ball bearing, 20... Rotating shaft, 28... Rotating disk ,3
8, 40... Magnetic head, 44... Set screw, 52
... Bonded piezoelectric element, 101, 102 ... Piezoelectric element plate, 103, 104, 105 ... Electrode.

Claims (1)

[Scope of Claims] 1. A tape guide cylinder capable of guiding travel by winding a magnetic tape around its outer periphery, and for recording signals on the magnetic tape wrapped around the tape guide cylinder or reproducing signals from the magnetic tape. A rotating magnetic head, a rotating shaft that rotatably supports the rotating magnetic head, and two members having the rotating magnetic head on the surface and having different amounts of expansion and contraction when electric energy is applied are bonded together. ,
The rotary magnetic head height variable means is configured to cause bending deformation in the length direction of the rotating shaft as a whole due to the difference in the amount of expansion and contraction of these members, and the rotary magnetic head height variable means is configured to be circular. A rotating magnetic head device, characterized in that the rotating magnetic head has a plate shape and is fixed to the rotating shaft at a position forming an angle of approximately 90 degrees with respect to the center of the rotating shaft. 2. In the statement of claim 1, the rotating magnetic head height variable means is made by bonding two piezoelectric element plates together, and when one piezoelectric element plate expands, the other piezoelectric element plate contracts, and the height of the rotating magnetic head changes as a whole. is a rotating magnetic head device characterized by using a type of bonded piezoelectric element that causes bending deformation. 3. A rotating magnetic head as set forth in claim 1, characterized in that the rotating magnetic head height variable means uses a structure in which a piezoelectric element plate and a metal plate are bonded together. Device.