JPS5845668A - Dynamic tracking method for magnetic disc recording and reproducing device - Google Patents

Abstract

PURPOSE:To make a magnetic head follow a track, even if shift exists between the track and the magnetic head due to the eccentricity of a disc, by displacing the position of the magnetic head by an amount represented by the amount of eccentricity of the magnetic disc. CONSTITUTION:A track D recorded with a radius gamma0 in using a point A as a center is turned around a point B, and reproduction is performed with a magnetic head fixed to a point C apart from the point B by the distance gamma0. Then, a distance delta between the points A and B is the eccentricity and a distance between the point C and a point E represents a track shift (x). In this case, the track shift (x) is a value obtd. by subtracting a distance BE from the distance gamma0 and is expressed as the product of a distance delta and costheta. Since the angle theta is originated from the revolution of a magnetic disc rotating motor, the magnetic head can accurately follow the track by providing the displacement of deltacostheta to the head in synchronizing with the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dynamic tracking method in a magnetic disk recording/reproducing device.Conventional magnetic disks are widely used along with magnetic tapes as information recording media. In a magnetic disk, information can be recorded as changes in the magnetization state on a magnetic disk in concentric tracks by a magnetic head, and the information can be reproduced by the magnetic head as needed.

Incidentally, magnetic disk recording and reproducing devices generally require disk compatibility, and for this purpose, the four noises, rotational speeds, and recording and reproducing methods of the disks are standardized. However, in the case of magnetic disks, the position of the magnetic head and the trunk on the disk may vary due to eccentricity of the axis of the motor that rotates the disk, or manufacturing or assembly errors between the disk and magnetic head depending on the device, even in the same device. As a result, the level of the playback signal changes and the content of the retrieved information changes, resulting in a change in the sound quality in the case of sound or a change in the image quality (especially in the case of color images). In this case, there is a problem that the color tone) changes.

Conventionally, the following methods were used: (1) information was recorded on a magnetic disk once in a wide trunk, then both sides of the track disappeared to form a narrow ring track, and playback was performed using a wide magnetic head; 2) A method of recording signals for correcting track deviation on both sides of the recording track,
(3) Six methods have been proposed to improve the manufacturing precision of related parts of the device without reducing the eccentricity between the magnetic head and the track. However, the above method (1) requires an erasing head, the above method (2) requires a complicated configuration of the recording circuit, the above method (3) has manufacturing limitations, and (z) Method (2) each has its own problems, such as the inability to increase trunk density.

In view of the above points, the present invention is designed so that the position of the magnetic head of a magnetic disk rotating at an angular velocity ω is displaced by 6 points, which is expressed by δ and θ (where δ is the eccentricity N of the magnetic disk). It is.

The present invention will be explained below with reference to the drawings.

In a magnetic disk recording/reproducing device, misalignment between a track on the disk and a magnetic head is mainly due to eccentricity of the disk. That is, in FIG. 1, the radius r is centered at point A. Track D recorded at point B is rotated synchronously from point B to r. If the magnetic head fixed at the string crossing point C is not used for reproduction, the distance δ between points A and B is the eccentricity,
The distance from point C to point E is calculated as track deviation X.

X = ro BE - δ θ Because, roCOXψ - BEcmθ 1 δ rosin ψ = BEsln θ , ・5 planes - δ - θ 1, n - "knee 77" - 7 - ear os
”#)kir −δ匪θ (','ro)δ)θ
Since this is caused by the rotation of the motor for rotating the magnetic disk, if a displacement of δ to θ is applied to the head in synchronization with the motor, the magnetic head will accurately follow the track.

FIG. 2 is a schematic diagram of the magnetic head moving mechanism, in which 1 is a motor for rotating the magnetic disk, 2 is a disk placed on a disk 3 rotated by motor I, and 4 is information recorded on the disk 2. or a magnetic head for reproducing, 5 a head displacement element such as a viezo element for displacing the magnetic head 4;
7 is a head mounting part, and 7 is a head moving mechanism consisting of a step motor, a whistle coil, etc.

FIG. 3 shows the sixth embodiment of the present invention using the above-mentioned magnetic head moving mechanism.
1 shows an embodiment of a tracking circuit for implementing a tracking method. In the figure, 8 indicates 6 circuits that do not detect the envelope of the signal reproduced by the magnetic head 4, and 9
6f detects that the frequency of the envelope of the reproduced signal coincides with the rotational frequency @fr of the disk, the detection circuit 1
0 is the envelope frequency or the disk rotation frequency 117
Detects that If has reached twice fr, that is, 2fr2
f. Detection circuit. Both of these detection circuits 9 and 10 are composed of band-pass filters. 11 is f,
Based on the output signals from the detection circuit 9 and the 2fr inspection circuit 10, the phase controller) CI-512, kk controller 1
3. Switching element 14, full finger signal output to head moving mechanism 7; 6 system controller; 15 is a drive circuit configured by oscillation gain; phase and IJR width are controlled by output of phase controller 12 and output of amplitude controller 13; sends the controlled output to the head displacement element 5.

Next, the operation of the tracking circuit will be explained.

Let us now consider a case in which, among two trunks M and N (the radius of the rack N is smaller than the radius of the trunk M) recorded concentrically on the disk, track M is played back and then the track is moved to track N.

Assuming that tracks M and N are eccentric, if this is expanded in the scanning direction, track M
, N are sinusoidal. The output of the envelope detection circuit 8 when the magnetic head 4 crosses the track N in the direction of the arrow is as shown in the same figure. The output waveform is shown step by step while moving to the center position of N (indicated by a broken line).

f. The detection circuit 9 detects from the output of the envelope detection circuit 8 that the frequency of the envelope of the reproduced signal matches the rotational wave number of the disk.
The movement of the magnetic head 4 by the head moving mechanism 7 is temporarily stopped via the system controller 1], and the drive circuit 5 is controlled by the phase controller 12 via the system controller 11. In this case, the magnetic head 4
It is also possible to adjust the phase while A) is still moving, without temporarily stopping it. After that, the magnetic head 4 is moved toward e toward the center of the track N, and from the output of the envelope detection circuit 8, the 21r detection circuit 10 determines that the frequency of the envelope of the reproduced signal matches twice the rotational frequency of the disk. In order to detect this, the system controller 11 causes the head moving mechanism 7 to stop the movement 1 of the magnetic head 4, and at the same time, switches the switching element 14 to contact bK. Amplitude controller: Do not apply a gradually increasing 16 DC voltage from the controller 13 to the head displacement element 5. As a result, the magnetic head 4 is slightly displaced from the center of the trunk B toward the scoop track M. While the magnetic head 4 is displaced in this way, the envelope of the reproduction M of the magnetic head 4 is detected by the envelope detection circuit 8. It is detected that the output frequency of the envelope detection circuit 8 matches the rotational frequency of the disk. When the fr detection circuit 9 detects it again, the DC voltage output from the amplitude controller 13 via the system controller 11 is switched to the contact a of the switching element 14 along with the bold line.
The bolded meandering current pressure value is not applied to the drive circuit 15. As a result, the drive circuit 5 is applied from the phase and amplitude controller 13 that are aligned in phase 1.
It oscillates with an amplitude determined by the current voltage, and the oscillation multiplier is applied to the piezo element 6 by the head displacement element 5. After that, I started regular tracking.

In this way, the deviation occurs between track N and magnetic head 4 during playback.
When the shield deviates by that much, the magnetic head 4 follows the tail of the track N and is displaced 1-B, so the level of the reproduced signal hardly changes.

As discussed above, in the present invention, in a magnetic disk recording/reproducing device, the eccentricity of the disk is δ, the rotational angle of the disk is ω, and the age of the magnetic head is δ.
■Since the displacement is made by the amount represented by θ, the magnetic head can follow the track even if there is a misalignment between the track and the magnetic head due to eccentricity of the disk, and a nearly constant reproduction output can always be obtained. According to the above, an erasing head for erasing the image information of a wide track recorded in the past is not necessary, the circuit configuration does not make sense, and the viscosity of the device during manufacturing and assembly is not necessary. It is possible to improve the quality of the reproduced output '1' without limiting the limits.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram without explaining the basis of the tracking method according to the present invention, Fig. 2 is a route diagram of the moving mechanism of the magnetic head, and Fig. 3 is an illustration of the actual application of the tracking method according to the present invention. FIG. 4 is a waveform diagram of the reproduction output signal for each head as the magnetic head and the tracking circuit move. DESCRIPTION OF SYMBOLS 1...Magnetic disk rotation motor, 2...Disk, 3...Disc, 4...Magnetic head, 5...Head displacement element, 6...Head mounting part, 7...Head Movement mechanism, 8...Envelope detection circuit, 9...Fr detection circuit, 10...2fr Prevention 1fil FMt, 1
DESCRIPTION OF SYMBOLS 1... System controller, 12... Phase controller, ]3... Amplitude controller, 14... Switching element, ]5... Drive circuit. Patent applicant: Roku Konishi Photo Industry Co., Ltd. Agent: Hiroshi Suzuki, patent attorney Figure 1 Figure 2

Claims (1)

[Claims] In a magnetic disk recording reproduction method in which a magnetic disk rotating at an angular velocity ω is reproduced by a magnetic head, the position of the magnetic head is expressed by δ＼ω1 (where δ is the eccentricity of the magnetic disk) and is displaced by six fingers. A dynamic dragging method characterized by