JP2516360B2 - Method and apparatus for writing servo information on magnetic disk - Google Patents

Description

The present invention relates to a method and apparatus for writing AGC servo information on a magnetic disk.

[Prior Art] In a small-sized magnetic disk device used as a storage device of a computer, a step motor having a simpler mechanism is used in place of a conventional voice coil motor, and a servo function (data A surface servo system) has been developed in which a highly accurate operation is performed to increase the storage density and increase the capacity. As the servo function, there is an AGC servo for making the peak value of the read signal of each code read by the magnetic head constant. This will be described below.

In FIG. 3 (a), the clock code C is recorded in a certain range in the circumferential direction by the clock magnetic head H _{1 at} an appropriate position on the magnetic disk D. Also, an index IDX indicating the reference position of the track T provided on the magnetic disk D
Subsequently, a servo information band A is provided on the front head of each track, and servo information is recorded on the servo information band A by the data magnetic head H ₂ . The clock code C is erased because it is unnecessary after the servo information is recorded in the band A.

FIG. 6B shows the band A developed, in which the AGC servo information A ₁ is recorded in the radial direction over each track T immediately after the IDX, and another servo information A ₂ is recorded following A _1. . The A ₂ and other control codes and data codes are all recorded in a fixed range along the center line of the track T to prevent crosstalk between adjacent tracks. On the other hand, AGC servo information (hereinafter simply referred to as servo information) A ₁ needs to accurately indicate the magnitude of the read signal at any position of the magnetic head. Recording is performed continuously without gaps by moving one half of the pitch. However, depending on the writing method, the recording of A ₁ is not continuous, and a drop of the read signal occurs at this discontinuous portion, so that the AGC may not operate properly. 4 (a) and 4 (b) illustrate a method of recording servo information A ₁ on a magnetic disk. When the magnetic disk rotates in the direction of arrow R in FIG. 4 (a), the center of the magnetic head H is The center line r or the boundary line b of the track T is scanned. In this case, if the direction of the working gap g (azimuth) of the magnetic head is in the direction of the tangent line of the track B along which the magnetic head moves between tracks, the recorded servo information M is recorded.
Is a continuous line that coincides with the locus B, as shown in FIG. However, if the azimuth direction is different from the tangent line, recording will not continue. This is shown in FIGS. 5 (a) and 5 (b). In the figure (a), the azimuth direction of the gap g forms an angle θ with respect to the tangent to the locus B, and the recorded servo information is M ₁ , M ₂ , Inclined and discontinuous like M ₃ . When reading such discontinuous servo information, there are variations in the positioning of the magnetic head due to expansion and contraction due to the temperature of the magnetic disk, or variations in the azimuth angle θ. I don't know.

As a method of eliminating such discontinuity, the inventor of the present application has made a patent application "writing method for disk type recording medium (Japanese Patent Laid-Open No. 63-18510)". The gist of the invention is to geometrically analyze the trajectory of the magnetic head, calculate the shift amount of each writing position, and correct the phase of the write signal of the magnetic head corresponding to the shift amount. However, actually, in addition to the calculated shift amount, there are variations in the positioning of the magnetic head and variations in the azimuth angle θ due to the expansion and contraction of the magnetic disk due to the above-mentioned temperature change. Can not be corrected. Therefore, there is a need for a method and apparatus for correcting these variations and writing continuous servo information.

[Object of the Invention] In the servo information of the conventional magnetic disk described above, in order to eliminate the instability of the read signal due to the positioning of the magnetic head and the variation of the azimuth angle of the magnetic head, the servo information is continuously transmitted. An object of the present invention is to provide a method and apparatus for writing servo information on a magnetic disk that can be recorded as lines.

[Means for Solving the Problems] The feature of the servo information writing method of the magnetic disk of the present invention for achieving such an object is that the magnetic disk next to the index code that is the starting point of the track of the magnetic disk is In the writing of servo information used for automatic adjustment of the read signal level, which is continuously provided over the entire range of the data track in the radial direction, at the first write position on the arbitrary track or the center line between the tracks. The phase of the read signal with respect to the signal of the index code obtained by reading the written servo information at the first writing position, and the second servo information which is adjacent to the servo information at a distance ½ of the track pitch from the first writing position. The phase difference ΔΦ between the read signal and the index code signal read at the write position However, the first
The phase of the write signal of the servo information with respect to the signal of the index code at the write position of the second write position by delaying or advancing the phase of the write signal with respect to the signal of the index code at the second write position. Servo information is written to.

Further, the magnetic disk servo information writing device of the present invention which achieves the above object is characterized by a first read / write circuit having a first magnetic head for reading an index code and a clock code provided on the magnetic disk. , A clock generator for generating an index pulse and a clock pulse obtained corresponding to the index code and the clock code by the read signal of the first read / write circuit, and a servo information used for automatic adjustment of the read signal level. Second to write / read
A second read / write circuit having a magnetic head, a phase ΔΦ1 of the read signal of the servo information at the first write position of an arbitrary track or the center line between the tracks with respect to the index pulse, and the second magnetic head. The phase ΔΦ2 with respect to the index pulse of the read signal for reading the servo information written at the first write position at the adjacent second write position that is ½ of the track pitch away from the first write position is detected. The phase detection circuit and the phase ΔΦ1 are stored and the phase ΔΦ1 is stored.
A storage / calculation circuit that calculates a phase difference ΔΦ by subtracting the phase ΔΦ1 from 2 and a servo at the second write position with respect to the phase of the write signal with respect to the index pulse at which the servo information is written at the first write position. And a timing circuit for generating a write timing signal for delaying or advancing the phase of the write signal with respect to the index pulse for writing information.

[Operation] In the magnetic disk servo information writing method and the writing apparatus according to the present invention, the servo information written at an arbitrary track or an intermediate position thereof is read, and then the magnetic head is moved from that position to two minutes of the track pitch. The same servo information as above is read out and the phase difference ΔΦ between both read signals is detected. next,
At the moved position, the servo information is written by the write signal delayed or advanced by ΔΦ from the phase of the write signal before the movement, and there is no discontinuity in the servo information due to the positioning of the magnetic head or the variation of the azimuth angle. , Are continuously written.

[Embodiment] FIGS. 1A and 1B are diagrams for explaining a phase difference of a read signal waveform with respect to an azimuth angle θ of a magnetic head which is a basis of a servo information writing method for a magnetic disk according to the present invention. . It is assumed that the direction of the action gap g of the magnetic head H forms an azimuth angle θ with respect to the tangent line of the movement locus B of the magnetic head, and the magnetic disk rotates in the direction of arrow R. Read signal center line r ₁ magnetic head H at the top has read the recording M ₁ of the servo information A ₁ written self at position (i) of any of the track T _1, as shown in FIG. (B), the index Waveform (b) phase ΔΦ _{1 with} respect to IDX
However, at the position (b) where the magnetic head has moved by half the track pitch, the same recording M ₁ is read earlier and the waveform Δ becomes a phase ΔΦ _{2 and} advances by the phase difference ΔΦ. However, there is a delay when the azimuth angle θ is in the opposite direction to the figure. Here, the record M ₁ has a length that enables reading at adjacent positions separated by a half pitch.

In the present invention, the recording M ₁ is read at the position (a), then the magnetic head H is moved to the adjacent position, the same recording M ₁ is read at the position (b), and the phase difference ΔΦ between them is detected. Next, at this position (b), change the phase of the write signal by Δ
Φ is corrected and M ₂ is recorded and continuously recorded. The record M ₂ ′ shown by the dotted line is the case where the phase ΔΦ is not corrected. Thereafter, the same phase correction is sequentially performed, and writing is performed so that the recordings M ₁ , M _2, ... Are continuous over the entire surface of the magnetic disk.

FIG. 2 is a schematic block diagram of an embodiment of a magnetic disk servo information writing method and apparatus according to the present invention. In the figure, the first magnetic head 1a of the first read / write circuit 1 writes a clock code in an appropriate area other than the servo information band on the data surface. Then, the magnetic head 1a reads the index IDX and the clock signal and inputs them to the clock pulse generator 2 to generate the index pulse and the clock pulse. On the other hand, the second read / write circuit 4
The magnetic head 4a first writes servo information at an arbitrary first writing position (center line of tracks or center line between tracks), and then the servo information is written to the magnetic head.
Read by 4a, the read signal is the peak detection circuit
The peak of the waveform is detected by 5a and applied to the phase detection circuit 5, where the phase difference ΔΦ ₁ with the index pulse is detected by the clock pulse, and this is temporarily stored in the memory / arithmetic circuit 6. Then, the second magnetic head 4a moves to the adjacent second writing position at a distance of 1/2 of the track pitch to read the above servo information, and the read signal has a peak detected by the peak detection circuit 5a. Is given to the phase detection circuit 5, where the phase difference ΔΦ ₂ with the index pulse is detected by the clock pulse,
It is stored in the memory / arithmetic circuit 6.

It should be noted that the phases ΔΦ ₁ and ΔΦ ₂ from the index pulse to the generation of the read signals of waveforms (a) and (b) are based on the index IDX as shown in FIG. As can be understood from the relationship between the position of the code C and the index IDX and the waveform diagram of FIG. 1 (b), one rotation is generated from the generation of the index pulse generated by detecting the index IDX to the generation of the next index pulse ( Since it is 1 cycle), that is, 360 °, it represents the amount of positional deviation at the rotational position of the generation position from the generation of this index pulse to the peak position of each read signal. This can be easily obtained by counting the number of clock pulses.

Next, in the memory / arithmetic circuit 6, the phase difference ΔΦ ₂ −ΔΦ
₁ = ΔΦ is calculated, and the calculated value of ΔΦ is transferred to the timing generation circuit 3. In the timing generation circuit 3, the write timing signal of the servo information is generated by the index pulse, the clock pulse and the phase difference ΔΦ, whereby the phase of the write signal is delayed by ΔΦ from that at the first writing position or advanced. On the other hand, at the second write position, servo information is written by the second magnetic head 4a. In this case, the delay or advance is automatically performed by the same process according to whether the value of ΔΦ is positive or negative. In the above, for convenience, an arbitrary track or a position in the middle of the track is set as the first writing position. However, in actuality, the track is started from the first track and sequentially moved to the adjacent positions, and the above is performed for all tracks. Is written and continuous servo information A ₁ is recorded.

[Effects of the Invention] As is clear from the above description, according to the method and apparatus for writing servo information on a magnetic disk of the present invention, since AGC servo information is continuously recorded,
Regardless of the variation in positioning of the magnetic head due to the expansion and contraction due to the temperature of the magnetic disk, or the presence or absence of variation in the azimuth angle, the read signal at that position is accurately read regardless of the position of the magnetic head.
There are significant effects that contribute to stable operation of the magnetic disk device.

[Brief description of drawings]

1 (a) and 1 (b) show a method of writing servo information on a magnetic disk according to the present invention and a method of making a phase difference of a read signal generated by an azimuth angle of a magnetic head and AGC servo information continuous. FIG. 2 is a schematic block diagram of an embodiment of a magnetic disk servo information writing system and a writing apparatus according to the present invention, and FIGS. 3 (a) and 3 (b) are
4A and 4B are explanatory views of a servo information band provided on the data surface of the magnetic disk, FIGS. 4A and 4B are explanatory diagrams of a recording method of AGC servo information, and FIGS. 5A and 5B are magnetic It is a figure explaining the discontinuity of AGC servo information which arises with the azimuth angle of a head. 1 ... First read / write circuit, 1a ... First magnetic head, 2 ... Clock pulse generation circuit, 3 ... Timing circuit, 4 ... Second read / write circuit, 4a ... Second Magnetic head, 5 ... Phase detection circuit, 5a ... Peak detection circuit, 6 ... Memory / operation circuit. D ... magnetic disk, IDX ... index, A ... servo information band, C ... clock code, T ... track, H ... magnetic head, M ... information recording, g ... gap, R ... rotation Direction, ΔΦ …… Phase difference, θ …… Azimuth angle.

Claims (2)

(57) [Claims] 1. Automatic adjustment of a read signal level continuously provided over the entire range of a data track in the radial direction of the magnetic disk next to the index code which is the starting point of the track of the magnetic disk. In writing the servo information to be used, the servo information written at the first writing position on an arbitrary track or the center line between the tracks is read and the phase of the read signal with respect to the signal of the index code read at the first writing position. ,
Detecting a phase difference ΔΦ between the servo information and the phase of the read signal with respect to the signal of the index code read at the second writing position adjacent to the first writing position by ½ of the track pitch, and The phase difference ΔΦ delays or advances the phase of the write signal of the servo information with respect to the signal of the index code at the first writing position with respect to the phase of the write signal with respect to the signal of the index code at the second writing position. And writing servo information to the second write position. 2. A first read / write circuit having a first magnetic head for reading an index code and a clock code provided on a magnetic disk, and the index code and the index code by a read signal of the first read / write circuit. Second read having a clock generator for generating index pulses and clock pulses obtained corresponding to respective clock codes, and a second magnetic head for writing / reading servo information used for automatic adjustment of read signal level / Write circuit, a phase ΔΦ1 of the read signal of the servo information at the first write position of the center line between arbitrary tracks or tracks with respect to the index pulse, and the second magnetic head from the first write position. Adjacent second write separated by half the track pitch A phase detection circuit for respectively detecting a phase ΔΦ2 of the read signal for reading the servo information written at the first writing position at the position with respect to the index pulse; and storing the phase ΔΦ1 to obtain the phase ΔΦ1 from the phase ΔΦ2. Phase difference subtracted
A memory / arithmetic circuit for calculating Φ; and a servo information write operation at the second write position with respect to a phase of a write signal with respect to the index pulse at which servo information write operation is performed at the first write position. The phase of the write signal with respect to the index pulse is defined as the phase difference Δ
A servo information writing apparatus for a magnetic disk, comprising: a timing circuit that generates a write timing signal that delays or advances the phase.