JPS601620A - Rotary head device - Google Patents

Abstract

PURPOSE:To prevent the mistracking due to the natural oscillation by detecting the natural oscillation of a bimorph element and producing the electric signal corresponding to said natural oscillation in order to attenuate the natural oscillation. CONSTITUTION:A plan and a side view are shown for the periphery of the attachment part of a video head element of a rotary head device. A planar oscillation detecting piezoelectric element 7 is set on the center surface of a flat plate type bimorph containing a video head element 5 attached to a free end. The detection output of the element 7 is extracted in a rotary state. Therefore a brush ring system or a rotary transformer is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a rotary head device that can be incorporated into a video tape recorder or the like.

<Prior Art> Conventionally, a rotary head device was incorporated in a video tape recorder, and the magnetic head for reading magnetic signals was rotated in an oblique direction at the same time as the magnetic diso was running. Now, when using this reading method using a rotating head device, the pilot signal superimposed on the magnetic tape is detected, the positional deviation of the head itself is read, and the tracking of the head itself is adjusted based on the read signal. Ta.

FIG. 1(a) is a side sectional view of a conventional rotary head device, and FIG. 1(b) is a plan view thereof. I is upper 7 cylinder, 2
3 is a lower cylinder, 3 is a rotating shaft, 4 is a bimorph element fixed to the rotating shaft 3, and 5 is a video head element installed at the free end of the bimorph element 4. The bimorph element 4 moves up and down based on the above-mentioned positional deviation reading signal to control trunking of the video head element 5. FIG. 2(a) is a side view of the mounting area of the video head element 5, and FIG. 2(b) is a plan view thereof. Since the bimorph element 4 is flexible and can be freely bent at one end, a certain natural vibration is generated in the bimorph element 4 itself. Further, the magnitude and phase of the vibration vary in a complicated manner depending on the sliding condition between the video head element 5 and the magnetic tape. For this reason, even if the above-mentioned video head element 5 is tracked, mistrunking will occur due to the natural vibration of the bimorph element 4. This tendency has conventionally been developed by detecting the natural vibration of the bimorph element 4 and sending an electric signal corresponding to this natural vibration as a countermeasure against mistrunking such as 0 or more, which appears more prominently as the track width (track pinotine) of the magnetic tape becomes narrower. A device for applying a damping signal to the bimorph element 4 to attenuate vibrations has been proposed (Japanese Patent Publication No. 58-18686).
(see publication). FIG. 3 shows a device that takes measures against the above-mentioned mistracking. FIG. C) is a front view thereof and a diagram showing a connection configuration with a circuit.

In the device shown in the figure, the electrode 6 on one side of the bimorph element 4 is divided into two to form electrodes 6a and 6b. A portion corresponding to the electrode 6b serves as a bimorph vibration sensor that generates an electric signal A2 that suppresses the vibration of the bimorph element 4. The output of this bimorph vibration sensor is fed back to the bimorph drive circuit. However, in the device shown in FIG. 3, since the bimorph vibration sensor is formed from a part of the side of the bimorph element 4, the area occupied by the electrode 6a for driving the bimorph element 4 is reduced, and when the bimorph element 4 is driven, the tip of the bimorph element 4 is Azimuth loss occurred due to twisting.

Purpose of the present invention The present invention has been made to solve the above-mentioned conventional problems, and provides a structure for detecting the natural vibration of a bimorph element, generating an electric signal corresponding to this natural vibration, and attenuating the natural vibration. It is an object of the present invention to provide an apparatus that can carry out the displacement of a bimorph element in a well-balanced manner.

<Embodiment> An embodiment of the rotary head device according to the present invention will be described in detail below with reference to the drawings.

FIG. 4(a) is a plan view of the mounting area of the video head element of one embodiment of the rotary head device according to the present invention;
b) is a side view thereof and a diagram showing a connection configuration with a circuit. A flat piezoelectric element 7 for vibration detection is layered on the center surface of a flat bimorph element 4 having a video head element 5 at its free end.

The piezoelectric element 7 for vibration detection is preferably made of as thin and soft a material as possible so as not to interfere with the bending motion of the bimorph element 4. For example, polyfluorocvinylidene (PVDF) is suitable. The detection output of the piezoelectric element 7 for vibration detection is taken out in a rotating state, so a brush ring method or a rotary transformer is used.

FIG. 5 is a waveform diagram of each part of an embodiment of the rotary head device according to the present invention. (a) is the drive voltage waveform applied to the bimorph element 4 during high-speed pressure search, (b) is the displacement waveform of the video head element 5 based on the waveform (a) (including miscellaneous displacement components due to natural vibration of the bimorph element 4) , (c) is the detection signal waveform of the piezoelectric element 7 for vibration detection, (d) is the natural vibration waveform of the bimorph element 4, and (e) is the component that attenuates the miscellaneous displacement component due to the natural vibration of the bimorph element 4 (the above-mentioned bimorph element The corrected drive voltage waveform of the bimorph element 4, (f) is (
e) A displacement waveform of the video head element 5 when the noquimorph element 4 is driven based on the waveform. This (f
) By modifying the drive voltage waveform for the bimorph element 4 as shown in the waveform, the gutter element 5 can be tracked well in the video.

<Effects> According to the present invention as described above, the natural vibration component of the bimorph element can be attenuated, so mistrunking caused by the natural vibration of the bimorph element described above can be prevented. At this time, since the natural vibration of the bimorph element is read by the planar vibration detection piezoelectric element 7 layered on the central plane of the bimorph element, the presence of the detection piezoelectric element 7 causes the bimorph to Good tracking is possible without causing any hindrance to driving the element.

[Brief explanation of the drawing]

FIG. 1(a) is a side sectional view of a conventional rotating head device.
♂ (b) is a plan view of the same, Figure 2 (・) is a side view of the area around the conventional 1-de-orientation unit, (b) is a plan view of the same, and (c) is a front view of the same. and a diagram showing the connection configuration with the circuit,
FIG. 4(a) is a plan view of the mounting area of the video head element of one embodiment of the rotary head device according to the present invention;
1]) is a side view and a diagram showing the connection configuration with the circuit, and FIG. 5 is a waveform diagram. In the figure, 1: Upper cylinder 2: Lower cylinder 3 - Rotation axis 4: Bimorph element 5: Video head element 6: Electrode 7: Piezoelectric element for vibration detection Representative Patent attorney Aihiko Fukushi (and 2 others) No. 5 figure

Claims (1)

[Claims] 1. A rotatable flat bimorph element with one end fixed to a rotating shaft and the other end freely bendable, and a magnetic signal reading element installed at the free end of the bimorph element; a planar vibration-detecting piezoelectric element layered on the center surface of the bimorph element to read the natural vibration of the bimorph element; and a flat vibration-detecting piezoelectric element for attenuating the natural vibration of the bimorph element based on an output signal of the vibration-detecting piezoelectric element. A rotary head device comprising means for forming a drive signal.