JPH0442476A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To ensure magnetic head positioning accuracy by using two kinds of magnetic head positioning information in different frequency and performing a magnetic head positioning control in order to make the amplitude of a beat signal zero. CONSTITUTION:Two kinds of magnetic head positioning control information 3a and 3b in different frequency is written every other track pitch in a positioning control information area 2 by shifting 1/2 track pitch from a track position in the radial direction. Then, the magnetic head positioning control is performed in order to make the amplitude of the beat signal zero by using two kinds of different frequencies as the magnetic head positioning information. By this method, lowering of the positioning control accuracy due to signal amplitude fluctuation is suppressed, thus ensuring the magnetic head positioning accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic disk drive, and particularly relates to a method for controlling the positioning of a magnetic head of a magnetic disk drive.

[Conventional technology]

With the miniaturization and increase in capacity of magnetic disk devices, positioning information has been stored on the data recording surface and read out to perform positioning of the magnetic head. In this case, as shown in FIG. 2, a positioning control information area 12 is provided on the information recording track 11, and A
ol) A circuit gain adjustment area 14, and positioning information areas 15 and 16 in which positioning control information 13 is written alternately at every other track, shifted by 172 track pitches in the radial direction in opposite directions from the track position. And A
After setting the AGC gain so that a constant amplitude is obtained in the GC circuit gain adjustment area 14, the AGC fixed gain 14 is set.
Readout information 18a in which the AGC gain is fixed in 17 and the signals of positioning information areas 15 and 16 are amplified by AGC
and 18b, positioning IIJ control is performed so that the amplitudes of the positioning information 15 and 16 are equal.

[Problem to be solved by the invention]

The above-mentioned conventional method for controlling positioning by writing positioning information on the data recording surface uses an AGC circuit to obtain a predetermined amplitude level, but as capacity increases, the density of information recording tracks increases. In order to secure a guard band width to suppress the influence on adjacent tracks when writing information, the ratio of the track width of the magnetic head to the information recording track pitch becomes smaller. The amplitude of the read signal for positioning control information becomes smaller, the positioning accuracy decreases, and in some cases, an information read error may occur.
If the fixed gain function of the AGC circuit malfunctions, as shown in read information 18blC, if the magnetic head is on the correct track, the amplitude of the positioning information area 16 will be as shown by the dotted line, but if the amplitude of the positioning information areas 15 and 16 is By controlling the positioning so that they are equal, a positioning error occurs by the amplitude shown by the solid line and the dotted line in the magnetic head positioning information area 16, and in severe cases, there is a drawback that a similar information reading error occurs.

An object of the present invention is to provide a magnetic disk device with improved positioning control information for a magnetic head.

[Means to solve the problem]

The magnetic disk device of the present invention includes a magnetic head positioning control information area at least once per revolution on a track on a data recording surface, and detects the read signal amplitude of the positioning control information area to obtain magnetic head positioning information. In a magnetic disk drive, positioning control tIIl information of two types of magnetic heads with different frequencies is written in the positioning control information area at every other track pitch by shifting 172 track pitches in the radial direction from the track position, and It is characterized in that the positioning of the magnetic head is controlled so as to obtain a point where the amplitude of the information read signal becomes zero.

[Effect]

Two different frequencies are used instead of the AGC gain as magnetic head positioning information, and the magnetic head positioning is controlled so that the amplitude of the beat signal becomes zero.
Compared to the conventional method, a decrease in positioning accuracy due to signal amplitude fluctuations is suppressed, and since an AGC circuit is not required, the positioning accuracy of the magnetic head can be guaranteed.

(Example) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the physical positional relationship and readout information of signals in a positioning control information area according to an embodiment of the present invention.

Figure 1 shows the positioning control information area [2] provided in the information recording track 1 on the data recording surface, and the positioning control information 3a drawn in every 1 track pitch in the radial direction from the information recording track by 172 track pitches. and 3b,
Furthermore, readout information 4 read out on the information distribution track is shown. The positioning control information 3a and 3b are written at two different frequencies f3a and f3b.

When this positioning tlIjtIIl information 3a and 3b is read on the information recording track number n, the read information va4 in the positioning control information area 2 is the positioning control information 3a.
The amplitude of the beat frequency (l f3a-f3b I) period is the difference between the frequency f3a of , and the frequency f3b of the same <3b, and the amplitude of the read information 4 becomes zero for each beat period. Also, the magnetic head is set to information recording track number Mn-1 or n.
When shifted in the +i direction, the amplitude of the read information 4 does not become zero in the beat period.

In this case, the positioning correction of the magnetic head is performed in the IJ direction where the minimum amplitude of the readout information 4 is smaller, and the magnetic head is adjusted so that a point where the amplitude of the readout signal 4 in the positioning III control information area 2 becomes zero is obtained. By performing positioning control, the magnetic head is correctly positioned on the information recording track IS n. Note that the amplitude of the read signal 4 does not necessarily have to be zero, as long as it does not exceed the minimum amplitude value of the read signal 8 obtained when the magnetic head positioning accuracy error tolerance specific to each magnetic disk @ stomach is within the allowable range. Of course, the amplitude value is determined experimentally and statistically for each magnetic disk device.

〔Effect of the invention〕

As explained above, the present invention uses two types of magnetic head positioning information of different frequencies to control the positioning of the magnetic head so that the amplitude of the beat signal becomes zero. Decrease in positioning control efficiency due to amplitude fluctuations is suppressed, and since the AGC circuit is not used, the positioning accuracy of the magnetic head can be guaranteed, information read errors and destruction can be prevented, and the reliability of the magnetic disk drive can be improved. Since the AGC circuit is improved and an AGC circuit is not required, there is an effect of cost reduction.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the physical positional relationship and readout information of signals in a positioning control information area according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating signals and others in a conventional positioning control information area. 1... Information recording track, 2... Positioning tUa information area, 3a, 3b... Positioning control information, 4... Read information.

Claims (1)

[Claims] 1. A magnetic head positioning control information area is provided at least once per revolution on a track on a data recording surface, and the read signal amplitude of the positioning control information area is detected to obtain magnetic head positioning information. In the magnetic disk drive, positioning control information for two different magnetic heads of different frequencies is written in the positioning control information area at intervals of 1/2 track pitch in the radial direction from the track position; A magnetic disk device characterized in that positioning control of a magnetic head is performed so as to obtain a point where the amplitude of a read signal of control information becomes zero.