JPH0123875B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sector signal forming method, and more particularly to a sector signal forming method for positioning a head in a sector servo type magnetic disk device.

Recently, as a positioning method for magnetic disk devices,
A so-called sector servo method has been considered in which the data head is accurately positioned on the data track by compensating for the effects of temperature off-track and the like.

This method is a type of self-servo method in which a position signal is written on the data surface, and the data head itself detects and controls the position. Due to its characteristics, this method requires the data head itself to generate a position signal. In contrast, commonly used data heads have a core width that is considerably narrower than their track pitch. The reason for this is that the core width must have a sufficient margin due to the influence of signal crosstalk or off-track.

FIG. 1 is a diagram for explaining a conventional sector signal forming method. Tracks are provided on the recording medium surface of a magnetic disk so as to be orthogonal to the radial direction (arrow), and sector areas are provided to record sector position signals as shown in the figure, mixed with the data area where information is to be recorded. There is. Two types of signals, A and B, are written in the sector area by data head 1.
Since the core width CW of the data head 1 is narrower than the track width TW, there is a no-signal area between the signal A and the signal B where no sector signal exists.

Figure 2 shows the voltage waveforms of signal A and signal B (second
Figure A) and the waveform of their voltage difference (Figure 2B).The position of the data head is controlled so that the voltage difference between signal A and signal B becomes zero; The linear range L is quite narrow (2CW-TW).

On the other hand, gain control (AGC) is used to compensate for the voltage waveform of the reproduced signal in the radial direction of the magnetic disk surface.
In this case, the sum of the voltages of signal A and signal B is generally controlled to be constant. Figure 3 is a diagram showing the voltage waveforms of signal A and signal B (Figure 3A) and the waveform of the voltage sum of signal A and signal B (Figure 3B). It fluctuates greatly.

An object of the present invention is to widen the range in which the difference in reproduction voltage between two types of signals formed in a sector area is linear;
Furthermore, it is an object of the present invention to provide a sector signal forming method in which the sum of the reproduced voltages is constant over the entire track width.

The method of the present invention is characterized in that the data head is moved by a pitch smaller than the core width of the data head, and the sector signal is overwritten (OVER WRITE) to form the sector signal.

FIGS. 4 and 5 are diagrams for explaining one embodiment of the method of the present invention. First, signal A is written into the sector area using data head 1 (FIG. 4A). Next, signal B is written at a pitch of half the track width TW/2, which is smaller than the core width CW of data head 1 (FIG. 4B). At this time, signal A
Width overlapped with signal B (CW-TW/2)
The signal B is erased by the newly written signal B, but this kind of redundant writing is usually called overwrite.
Furthermore, the head is moved at a pitch of half the track width TW/2 and signal B is written (FIG. 4c). In this way, signals A and B can be written in the sector area without gaps (FIG. 5).

FIG. 6 shows reproduced waveforms A of signals A and B, and waveform B of the voltage difference between them. In this case, the linear region L of the voltage difference becomes CW, which is wider by TW-CW than the linear region 2CW-TW in the conventional case shown in FIG. In other words, the track pitch TW is 30μm,
When the core width CW of the head is 22 μm, the linear region is larger in the embodiment of the present invention than in the conventional case.
Wider by TW-CW=8μm. On the other hand, the sum of the voltages of signal A and signal B becomes almost constant as shown in Figure 7, and there is no voltage fluctuation in the adjacent track area as shown in the conventional example in Figure 3, which is advantageous for gain control. It can be said that this is a signal forming method.

As explained above, the present invention provides sector servo signals.
By overwriting, it is possible to eliminate the no-signal area due to the difference in track pitch and core width.This allows for a wider controllable range of head position, and also allows for tracking control when applying gain control. Since the signal amplitude does not change each time it crosses, a stable position signal can be obtained, which is highly effective in precisely positioning the head.

[Brief explanation of drawings]

1 to 3 are diagrams for explaining the conventional method, and FIGS. 4 to 7 are diagrams for explaining the method of the present invention. 1 is the data head.

Claims (1)

[Claims] 1. In a method of forming a sector position signal by mixing data on the data surface of a magnetic disk using a data head, the data head is moved in bits smaller than the core width of the data head, and the sector signal is formed by superimposing the data head. A sector signal forming method characterized by: