JPS58195102A - Magnetic head position detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position detection device for detecting the position of a magnetic head used in a small magnetic recording/reproducing device.

FIG. 1 shows a magnetic rad movement device used in a conventional magnetic recording/reproducing device. A conventional example will be explained below with reference to FIG. The magnetic recording and reproducing device used in this example records and reproduces video signals.
The explanation will proceed assuming that it is used for playback. The magnetic sheet 1 is attached to the shaft of a magnetic sheet rotating motor (not shown) by holding the sheet 11, and is rotated at 5600 rpm in order to record one field of video signals per rotation.

A head moving motor 2 moves the magnetic head 9 in the radial direction of the magnetic sheet 1. When the head moving motor 2 rotates, the drive gear 3. The driven gear 4 rotates, and the drive screw 6 directly connected to the driven gear 4 rotates. When the drive screw 6 rotates, the head holder 7 moves due to the rotation of the screw thread. Head holder 7
A head mounting plate 8 is fixed to the head mounting plate 8.
A magnetic head 9 is attached to. Therefore, the magnetic head 9 moves together with the head holder 7.

Note that the bearing 5 is provided to hold the drive screw 6 and the driven gear 4, and the one-turn stopper 10 is provided.

This is provided to prevent the head holder 7 from shifting or rotating.

The magnetic head 9 moves the magnetic sheet 1 in the radial direction by the above-described operation, but in order to make the magnetic sheet 1 compatible, tracking must be performed. For example, the total movement of magnetism/rad1 is 4Ill11.
If 50 field signals are recorded during that time, the track pitch will be 80 μm. As a means for moving the magnetic head 9 by 80 μm, a Nockles motor is used as the head moving motor 2, and a drive gear 3. The backlash of the magnetic head moving mechanism system consisting of the driven gear 4° drive screw 6 and head holder 7 is removed, and the pulse motor's 1. The rotation angle is controlled by the number of driving pulses, and the magnetic
Kasumi [This method does not move the Rad 9) (only by the Luss motor drive Hals) (the rotation angle of the Luss motor is controlled), and the position of the magnetic head 9 cannot be detected accurately.
Therefore, since a magnetic head moving mechanism without backlash is required, it is difficult to design a single mechanism system. In addition, since the position of the magnetic head 9 cannot be detected, a switch (not shown) that detects that the magnetic head 9 is at the innermost circumference of recording C of the magnetic sheet 1, and a switch that detects that it is at the outer circumference position. At least two switches were required.

On the other hand, as a method for detecting minute displacements as in this example,
There are various methods, such as a method using a differential transformer and a method using Magnescale, but these methods have drawbacks such as the large size of the detection device and the increased load on the magnetic head feeding mechanism, so they cannot be used easily. Further, with an optical method using a photodiode or the like, it is difficult to detect a pitch of 80 μm.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art.
j, form 1 oath single composition arrangement, magnetic% ``-y)'' f
)1□1[Detect the position 8''(-1'6 j 5 K t, ?,: '1°0 position to magnetism)' The purpose is to provide a 1km detection device.

In the present invention, the magnetic head is provided with a movable electrode that moves together with the magnetic head and a fixed electrode that does not move.

The amount of movement of the magnetic head is detected as a change in capacitance, and the position of the magnetic head is detected.

Furthermore, the position of the magnetic head is detected using an oscillation circuit whose oscillation frequency changes due to minute changes in capacitance, and a servo is applied to the magnetic head moving mechanism to move the magnetic head to the correct position.

The present invention will be explained below using examples. FIG. 2 shows an embodiment of the present invention. Similar to the first example, FIG. 2 shows the magnetic head and its moving mechanism. The difference from the conventional example shown in FIG. 1 is that a movable electrode 12 that moves together with the head holder 7 and a fixed electrode 15 that does not move with respect to the head holder 7 are provided. When the head moving motor 2 rotates, the drive gear 5. The drive screw 6 rotates via the driven gear 4, and the head holder 7 moves. The head holder 7 has a head mounting plate 8. A magnetic head 9 is attached as well as a moving electrode 12,
As the head holder 7 moves, the moving electrode 12 moves.

Reference numeral 15 denotes a fixed electrode that does not move, and the movable electrode 12 moves in and out between the two electrodes 13 and 15.

When the head holder 7 moves, the movable electrode 12 moves, so the capacitance of the capacitor composed of the movable electrode 12 and the fixed electrode 16 changes. Since the moving distance of the magnetic head 9 and the moving distance of the moving electrode 12 are the same, the position of the magnetic head 9 can be detected by detecting the capacitance k of the capacitor described above.

FIG. 3 is a sectional view of the moving electrode section and the fixed electrode section. #
! In FIG. 3, the moving direction of the magnetic head 9 is perpendicular to the plane of the paper. The moving electrode 12 mounted on the head holder 7 moves together with the magnetic head 9. Moving electrode 12
moves between fixed electrodes 15 as shown in FIG. Note that 14 is a fixed base, which is a plate that serves as a base on which the fixed electrode 13, a motor for rotating the magnetic sheet, etc. are attached.

FIG. 4 is a diagram showing the relationship between moving electrodes and fixed electrodes. The direction of movement of the magnetic field 9 in FIG. 4 is parallel to one sheet of paper, as indicated by an arrow 15. Figure 4(a) shows
A case is shown in which the movable electrode 12 and the fixed electrode 13 are one layer. FIG. 4 (61) is an example of a three-layer structure so that the change in electrostatic sensitivity increases with respect to the amount of movement of the moving electrode 12.

FIG. 5 is a block diagram when a capacitance change is detected and a servo is applied to the magnetic head moving mechanism to perform one-position control. The operation shown in FIG. 5 will be explained. Reference numeral 16 denotes a detection oscillator, which is an oscillator whose oscillation frequency changes according to a change in capacitance between the moving electrode 12 and the fixed electrode 13. Reference numeral 18 denotes a reference oscillator, and in the case of one reference oscillator, a crystal oscillator 17 is used to keep the oscillation frequency constant. Reference numeral 19 denotes a head position setting device, which is arbitrarily set by the person operating the apparatus. In this example, a variable resistor is generally set. The position setting device 19 sets the setting counter 20 . Change the output value of.

First, we will explain the magnetic head position display operation.
-4 exclusive. 7. The output of the detection excavator 16 is counted by the counter 21.
5 7L, 7□23;・1:・11-months, U. The characteristics of the 6° detection oscillator are shown below. When the position of the magnetic head 9 is on the first track among 50 tracks, the frequency is 11.
and when it is on the 50th track, the frequency f
Excavation at 5o. Frequency 11 is 1oILHz, 8Il
*Assuming that f5a is 500jL#z, counter 2
If 1 is set to '/10000, counter 21
If the output frequency is displayed as is on the display 24, the position of the magnetic head 9 will be displayed.

Next, the position setting operation of the magnetic head 9 will be explained. The value of the setting counter 20 is changed by the position setting device 19. The oscillator 18 generates a constant frequency, which is input to the program counter 22. The count number of the program counter 22 is configured to change depending on the value of the setting counter 2o. For example, if the frequency of the reference oscillator 18 is IMtlz, when you want to set the first track, the count number of the program counter 22 't
/'1o6, and if you want to set it to the 50th track, set the setting color /2 so that it becomes '/2x1o'*.
Kara by 0,'! >Set the number of peaks. Now, as I explained earlier about the 11'\rad positioning operation, magnetic/\
When the trad 9 is at the 1 address, a signal with a frequency of 1H2 is output from the color/receiver 21, and when it is at the 5011 address, a signal with a frequency of 50 Hz is output. On the other hand, the program counter 22 outputs a signal with a frequency of 1H2 when it wants to set address 1, and a signal with a frequency of 50 Hz when it wants to set it to address 50.

By comparing these two frequencies with the comparator 24, an output corresponding to the deviation between the set value and the detected position of the magnetic head 9 can be obtained. If this output is amplified by the driver 25 and the head moving motor 2 is driven, the position of the magnetic head 9 can be set correctly.On the other hand, the position of the magnetic head 9 can be detected.

It is also possible to detect the innermost circumference and the position of the innermost circumference where the magnetic head 9 deviates from the recording surface of the magnetic sheet 1.
This eliminates the need for two position switches.

As described above, according to the present invention, the position of the magnetic head can be detected with a small, light storage, and simple configuration without increasing the load on the magnetic head moving device.

[Brief explanation of the drawing]

Figure 1 is a front view of a conventional magnetic head moving device;
The figure is a front view of a magnetic head moving device incorporating a position detecting device according to the present invention, FIG. 6 is a sectional view showing the structure of the electrode section of the position detecting device according to the present invention, and FIG. FIG. 5 is a sectional view of a main part of a fixed electrode section, and FIG. 5 is a block diagram of a position control circuit of a magnetic head moving device. The tlE6 diagram is a diagram showing the characteristics of the detection oscillator. 2...Recording medium. 7...Head holder. 8...Head mounting plate. 9...Magnetic head. 12...Moving electrode. 13...Fixed electrode. 16...Detection oscillator. '3'1 Figure 1 2 years old O 3 z 4th mouth (b) 2 years old 5 Figure 3 ) O 6 Figure a ki...do Oa1

Claims (1)

[Claims] 1. In a magnetic recording and reproducing device that moves a magnetic head, records a signal on a recording element, and reproduces the signal, a magnetic head that is fixed integrally with the magnetic head and moves together with the magnetic head. with moving electrodes. A fixed electrode placed opposite the moving electrode. 1. A position detection device for a magnetic head, comprising means for detecting a change in capacitance between a moving electrode and a fixed electrode. 2.41I In the magnetic head position detection device according to claim 1, the means for detecting a change in capacitance comprises:
A magnetic head position detection device characterized by being an oscillator whose oscillation frequency changes according to a change in capacitance between a moving electrode and a fixed electrode.