JPH02236874A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To preclude malfunction due to a defect by inhibiting position control over a magnetic disk when the difference between the quantity of variation of position data from a servo head and the quantity of variation of position data on servo sectors provided on a data surface which are read out by a data head is larger than a specific value. CONSTITUTION:A magnetic disk 1 has data sectors 4 and servo sectors 5 for a position information signal and has a normal servo sector 5b, a defect 8, and a defect servo sector 5a. When data is recorded on and read out of a track 7, a position shift signal 12c(1) when the data head 101 passes the servo sector 5b of the track 7 is inputted to a processing circuit 16. Similarly, a position shift signal 12c(2) when the servo head 102 passes a place corresponding to the servo sector 5b of the track 7 is inputted to the processing circuit 16 and the position shifts of the signals (1) and (2) exceed a threshold value when the sector 5a has the defect 8. At this time, the defect is judged and a voice coil motor 28 is stopped from being driven.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic disk device used for information processing.

2. Description of the Related Art In recent years, magnetic disk drives have increased in capacity, and a so-called sector servo method, in which each data track is divided and a position reference signal is recorded, has begun to be used as a head positioning method. (For example, JP-A-51-81603) A conventional magnetic disk device of this type is schematically shown in FIG. 1 is a magnetic disk, and here three magnetic disks are provided. This magnetic disk 1 is fixed to a spindle 53 and rotated by a main shaft motor 53. Also, both sides of the magnetic disk 1 can be used, one of which is used as a servo surface 60, and the other surface is used as a data surface 61. A plurality of tracks are formed on the servo surface 60, and distance data from the center of the disk is stored in each track.

In order to read data stored on each side of the magnetic disk 1, magnetic heads 101 and 102 are provided for each side. 101 is a data head, and 102 is a servo head. Data head 101 and servo head 102
is held by a carriage 51, and this carriage 5
1 is moved in the diametrical direction of the magnetic disk 1 by a voice coil motor 27. A control unit 50 controls driving the voice coil motor 27 in accordance with servo data from the servo head 102 and data of servo sectors provided on the data surface.

In this method, servo signals are not recorded only on the servo surface as in the past, but servo sectors are also provided on all data surfaces, and the position signal read from the servo surface is added to the position signal of the servo sector on the data track. is superimposed to control head positioning.

FIG. 4 shows the data surface of the magnetic disk 1 using the sector servo system. The recording area of the data surface, that is, between concentric circles 2 and 3 shown in the figure, consists of a data sector 4 and a servo sector 5. Recording information is recorded in the data sector 4, and position signal information is recorded in the servo sector 5. This position signal information of the servo sector 5 is sent to the magnetic head 101 on the corresponding recording track.
used as a reference signal when positioning. Note 5
A indicates a defective servo sector, which will be described later, and 5b indicates a normal servo sector.

FIG. 3 is an enlarged view of the broken line portion of the recording area of the magnetic disk 1, and as the magnetic disk rotates, the recording tracks 6 and 7 move in the direction of the arrow in the figure relative to each data magnetic head. . Data sector 4 and servo sector 5
Information data and position information signals are recorded in the .

Problem to be Solved by the Invention However, in this case, as shown in FIG. 3, if there is a defect 8 in a certain servo sector 5a, the reference position indicated by the position information signal in that servo sector may be different from the actual center of the recording track 7. If the magnetic head deviates from its position, the servo system will operate as described above with a positioning error in the magnetic head, resulting in off-track, making it impossible to ensure the reliability of recorded and reproduced data. Normally, servo sector signals are recorded after the magnetic disk is fixed to the rotating shaft, so if a defect is found in the servo sector, the servo sector signal must be rewritten or the magnetic disk itself needs to be replaced, reducing productivity. down. That is, since servo signals are recorded not only on the servo surface but also on the data surface, all data surfaces are required to have the same signal quality as the servo surface, and specifications against defects become stricter.

In order to solve this problem, for example, Japanese Patent Laid-Open No. 59-218
678, when a defect 8 is found in an inspection after writing a position signal to a certain servo sector, a specific defect indication signal 10 is recorded in the erase zone 9 of the preceding servo sector 5b on the recording track 7. If this defect indication signal 10 is detected during reproduction of a servo sector signal, malfunctions due to defects in the servo sector can be avoided by, for example, preventing the servo circuit from operating with the signal from the servo sector that follows that servo sector. A method is proposed. However, in this case, an area is required to record the defect indication signal, and after the drive device is shipped,
For example, when a defect occurs in the servo sector area due to dust or the like, a similar off-track occurs.

Means for Solving the Problem In order to solve this problem, the present invention solves the problem by changing the amount of change in position data from the servo head and the amount of change in the position data read by the data head of the servo sector provided on the data surface. The apparatus further includes a control means for inhibiting position control of the carriage holding the servo head and the data head when the difference between the servo head and the data head is greater than a predetermined value.

Effect: With this configuration, if a servo sector on a data plane is defective, the incorrect position data obtained from it will be much different from the position data obtained from the previous servo sector, and the amount of change in position data from the servo plane will be much larger. Since there is a difference, position control of the carriage in that case is prevented.

Embodiment A magnetic disk drive according to an embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Note that the outline of the magnetic disk device in this embodiment is almost the same as that shown in FIG. 5, so a description thereof will be omitted. FIG. 1 is a diagram showing the inside and surroundings of a control section 50 of a magnetic disk device according to an embodiment of the present invention. FIG. 2 is a plan view showing data sectors and servo sectors of the data surface medium of the magnetic disk 1 of this embodiment. In Figures 1 and 2,
Items with the same symbol indicate the same signal. In FIG. 2, the same numbers as in FIG. 3 indicate the same components as in the conventional structure.

In FIG. 1, a servo signal read from the servo surface of the magnetic disk 1 by the servo head 102 is amplified by the servo amplifier 21, converted into a servo surface position deviation signal 22a by the servo surface position signal detection circuit 22, and Signal 23b is separated. Timing generation circuit 14
sends a timing signal 14d for detecting the digit 1 information of the servo sector 5 shown in FIG. 2 to the data surface position signal detection circuit 12 from the clock signal 23b. On the other hand, a data signal read from the data surface of the data medium of the magnetic disk 1 by the data head 101 is amplified by the data amplifier 11 and sent to the data surface position signal detection circuit 12 and a data processing circuit (not shown). In the data surface position signal detection circuit 12, the position information signal from the data surface is converted into a position signal 12c proportional to the amount of positional deviation of the data head at the timing of a timing generation circuit 14d.
The data plane is sent to the A/D converter 15. Data side A/D
The converter 15 converts the analog positional deviation signal 1 2 c obtained by the data surface position signal detection circuit 12 into a digital signal 1
5e, and sends data surface positional deviation information 15e to the processing circuit 16.

Further, the servo surface position deviation signal 22a detected by the servo surface position signal detection circuit 22 is transmitted to the servo surface A/D converter 24.
Then, the analog servo surface position deviation signal 22a is converted into a digital signal 24g and input to the processing circuit 16. The processing circuit 16 detects a servo surface position deviation signal 24g of the servo surface A/D converter 24 and the data surface A/D using a detection means that detects a defect in the servo sector of the data surface from the position information of the data surface and the servo surface, which will be described later. The data plane positional deviation signal 15e of the converter 15 is subtracted, and the relative positional deviation signal 16 is obtained.
h to the D/A converter 2 until the next servo sector 5 arrives.
Send on 5th. The D/A converter 25 converts the digital signal of the relative positional deviation signal 16h between the data surface and the servo surface position information into an analog signal, and outputs the analog signal to the adder 26. In the adder 26, the servo surface positional deviation signal 22a and the relative positional deviation signal 16h are added together, and sent to a servo circuit section 27 including phase compensation, etc., and positioning control is performed by driving the voice coil moke 28.

Here, the detection means for detecting a defect in the servo sector of the data surface from the position information of the data surface and the servo surface is the processing circuit 1.
6 is the data surface change amount 12 which is the difference between the data surface position deviation signal 15e(2) of the data surface A/D converter 15 on the data surface and the data surface position deviation signal 15e(1) of the preceding servo sector; Servo surface A/ on servo surface
Servo surface position deviation signal 24g (2) of D converter 24 and servo surface position deviation signal 2 of the preceding servo sector
From the servo change I1i 1, which is the difference from 4g (1),
Calculate the difference i2-i1 in the amount of change, and if the absolute value is within a certain threshold (for example, a value of 1/4 of the track width),
The positional deviation signal of the servo sector on the data surface is enabled, and if the value exceeds a certain threshold value, it is assumed that the servo sector on the data surface is defective, and the data surface position information and servo surface position are determined based on the data surface position signal due to the defect. The relative positional deviation signal 16h of information is not output.

Furthermore, the case where there is a defect will be described in detail below. In FIG. 2, as already explained, 4 is a data sector, 5 is a servo sector for position information signals, 5b is a normal servo sector, 8 is a defective servo sector, and 5a is a defective servo sector. explain.

Data surface position deviation signal 12c when the data head 101 passes through the servo sector 5b of track 7 of the data medium
(1) is connected to the digital signal 15e (1) on the data side A/D.
The data surface position deviation signal 12c(2) converted by the converter 15 and passed through the servo sector 5a is converted into a digital signal 15e(2) by the data surface A/D converter 15, and each value thereof is processed. Take in the circuit 16. Similarly, when the servo head 102 passes through a location corresponding to the servo sector 5b of the track 7 of the servo medium, the servo surface position deviation signal 22a (1) is the digital signal 24g (1
) is converted by the servo surface A/D converter 24 and passes through the servo sector 5a. The servo surface position deviation signal 22a (
2) is the digital signal 24g (2) is the servo surface A/D
It is converted by a converter 24, and each value is input into a processing circuit 16. The processing circuit 16 receives a data surface position shift signal 15e.
(2) and the data surface change amount i2 which is the difference between the positional deviation signal 15e (1) from the data surface 61 of the preceding servo sector and the servo surface positional deviation signal 24g (2) on the servo surface 60; When i2-i1 is calculated from the servo change amount 11 which is the difference from the servo surface position deviation signal 24g (1) of the preceding servo sector, if there is a defect in the servo sector 5a, the value will be greater than the threshold value.
It is determined that there is a defect in the servo sector on the data surface, and the relative positional deviation signal 16h is not changed. In this way, there is no risk that the voice coil motor 28 will be erroneously driven by the data plane position information signal from the defective servo sector.
Correct positioning can be performed.

In this embodiment, a microcomputer is used as the processing circuit 16, but it goes without saying that a configuration using only hardware is also possible. In addition, in this embodiment, if the difference between the data surface variation amount 12 and the servo surface variation amount i1 is equal to or greater than the threshold value, the relative positional deviation signal 16h is not changed. It was configured to be controlled by a relative position shift signal in the sector, but the servo sector 5
The relative positional deviation signal 16h may be output by using the servo surface positional deviation signal on the non-defective track a (for example, 6).

Furthermore, as a method for detecting defects, the configuration is such that a comparison is made with the previous sector, but it may also be compared with the average value of the rate of change of a plurality of previous sectors.

Effects of the Invention As explained above, the present invention provides a magnetic head when the difference between the amount of change in the position data from the servo head and the amount of change in the position data read by the data head of the servo sector provided on the data surface is greater than or equal to a predetermined value. Therefore, even if there is a defect in the sabot sector on the data surface, it is possible to prevent malfunction of position control based on the defect.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a magnetic disk device according to an embodiment of the present invention, FIG. 2 is a plan view showing data sectors and servo sectors of the data surface medium of this embodiment, and FIG. 3 is a plan view showing conventional data sectors and servo sectors. FIG. 4 is a plan view showing the data surface of the magnetic disk, and FIG. 5 is a schematic diagram of the magnetic disk device. 1...Magnetic disk, 4...Data sector, 5...
・Servo sector, 5a...Defective servo sector, 6, 7
. . . Recording track, 8 . . . Defect portion, 9 . . Erase zone, 10 .
...Servo surface position signal detection circuit. Name of agent: Patent attorney Shigetaka Awano and one other person (Himisaki FNj)

Claims (1)

[Scope of Claims] A servo disk having a servo surface storing position data, a data storage area held coaxially with the servo disk and divided into a plurality of parts, and position data stored between the data storage areas. a carriage holding a data disk having a servo sector; a servo head for reading position data on the servo disk; and a data head for reading data on the data disk; position data from the servo head; a position control means for controlling the position of the carriage based on the position data of the servo sector from the head; and a difference between the amount of change in the position data from the servo head and the amount of change in the position data of the servo sector from the data head. A magnetic disk drive comprising: control means for preventing the control means from controlling the position of the carriage when the position of the carriage is greater than or equal to a predetermined value.