JP3034149B2 - Method for detecting offset of recording / reproducing head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an offset of a recording / reproducing head in a sector servo type magnetic disk drive.
Relates to the detection method, in particular, relates to an offset detecting method for accurately detecting the head position deviation amount at the time of on-track of the plurality of recording / reproducing heads (offset amount).

[0002]

2. Description of the Related Art Conventionally, in a magnetic disk device such as a hard disk device having a plurality of recording / reproducing heads,
The processing described below has been performed for each recording / reproducing head.

First, when detecting an offset amount between recording / reproducing heads, first, one (reference) recording / reading is performed.
A reproduction head is selected, the position of the reference recording / reproduction head is controlled using the servo burst information of the disk, and the on-track is executed.
The offset amount between the reference recording / reproducing head and the adjusted recording / reproducing head is detected by switching to the adjusted recording / reproducing head and reading the servo burst information of the disk by the adjusted recording / reproducing head. I was trying to do it.

Further, when switching from one recording / reproducing head (this is referred to as a current head) to another recording / reproducing head (this is referred to as a target head), a positional deviation between the two recording / reproducing heads is corrected. Is applied to a servo circuit for controlling the position of the recording / reproducing head from the servo information, that is, by applying an offset amount to offset the current position between the two recording / reproducing heads. The head is controlled to be on-track, and first, the target head is positioned on the correct (target) track. Then, after the head is on-track with the offset added, the recording / reproducing head is switched, and the application of the offset amount to the servo circuit is stopped. Thereby, at the time of recording / reproducing head switching,
The target head is almost on-track, and then fine adjustment is performed so that the target head is completely on-track.

[0005] Such a system is disclosed in, for example, Japanese Patent Laid-Open No. 2-2.
97703.

[0006]

However, in the known means for detecting the offset between the recording / reproducing heads, the width of each recording / reproducing head is shorter than the width of the servo burst information recorded on the disk. Therefore, depending on the magnitude of the value of the displacement, there is an area where the displacement of the adjusted recording / reproducing head cannot be accurately detected. That is, as shown in FIG. 6, when both ends of the adjusted recording / reproducing head 15 are displaced such that they enter only one of two servo burst information A and B adjacent to each other, When the reference recording / reproducing head is on track, the recording / reproducing head to be adjusted is located in a region D (this region is referred to as an incomplete detection region) in which the displacement cannot be accurately detected. Is simply switched to select the correct position of the adjusted recording / reproducing head (offset amount).
There is a problem that cannot be detected. In FIG. 6, reference numeral 18 denotes a track number described later, and reference numeral 19 denotes data and a rack.

[0007]

[0008] The present invention is intended to eliminate the problems described above, and its object is irrespective to the position offset amount of the recording / reproducing head can accurately detect the offset amount of the adjusted recording / reproducing head An object of the present invention is to provide an offset detection method.

[0009]

[0010]

In order to achieve the above object , the present invention has a plurality of recording / reproducing heads, and one of them is set as a reference recording / reproducing head to perform initial setting. In the magnetic disk drive, first, a reference recording / reproducing head is selected to perform on-track, and then, while the reference recording / reproducing head is on-track,
An adjusted recording / reproducing head different from the reference recording / reproducing head is switched and selected for a required time, and a first positional shift between the reference recording / reproducing head and the adjusted recording / reproducing head immediately after the switching is performed. Then, the adjusted recording / reproducing head is moved by the first positional deviation amount from a state where the reference recording / reproducing head is on-track, and the adjusted recording / reproducing head at that time is moved. Is measured as a second displacement amount, and the first displacement amount and the second displacement amount obtained here are measured as a second displacement amount. Means for detecting an offset amount between the reference recording / reproducing head and the adjusted recording / reproducing head based on

[0011]

[0012]

According to the above means , first, for example, when the power of the magnetic disk drive is turned on, the reference recording / reproducing head is selected to perform on-track, and then the reference recording / reproducing is performed for a predetermined time. Head, and measures a first positional shift amount between the reference recording / reproducing head and the adjusted recording / reproducing head immediately after the switching, and then the reference recording / reproducing head is turned on-track. If the recording / reproducing head is adjusted, the adjusted recording / reproducing head is moved by the first positional deviation amount, and the position of the adjusted recording / reproducing head at that time and the originally adjusted recording / reproducing head are turned on. The reference recording / reproducing is performed by measuring a difference from a position to be tracked as a second displacement, and appropriately calculating the first displacement and the second displacement thus obtained. H The make accurate offset amount of the detection between the adjusted recording / reproducing head, and is stored stores the offset amount in the memory with. Therefore, the offset amount of the adjusted recording / reproducing head with respect to the reference recording / reproducing head is accurately detected, and the detection is performed without depending on the magnitude of the offset amount of the adjusted recording / reproducing head. be able to.

[0013]

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a method for detecting an offset of a recording / reproducing head according to the present invention.

In FIG. 1, 1 is a recording / reproducing head unit,
2 is a voice coil motor (VCM), 3 is a head selection circuit section, 4 is an offset amount detection section, 5 is a VCM drive current pattern generation section, 6 is a position servo control section, 7 is a seek control section, 8 is a VCM driver, 9 is a first memory, 10 is a second memory, 11 is a head switching command signal supply unit, 12 is a sector servo signal supply unit, 13 is a seek command signal supply unit, and 14 is a switching selection unit.

The recording / reproducing head section 1 includes a plurality of recording / reproducing heads, each of which opposes a disc (not shown), for example, a reference recording / reproducing head 1s and three adjusted recording / reproducing heads 1a, 1b, 1c. It is composed of Here, the recording / reproducing heads 1a and 1b are respectively disposed on one surface and the other surface of the first disk, and the recording / reproducing heads 1c and 1s are respectively disposed on one surface and the other surface of the second disk. The recording / reproducing heads face each other, and perform data recording / reproducing on the surfaces of the discs facing each other. The VCM 2 is driven by a current output from the VCM driver 8 and moves the recording / reproducing head unit 1 in the radial direction of a disk (not shown). The head selection circuit unit 3 selects one of the recording / reproducing heads 1a, 1b, 1c, and 1s by supplying the head switching command signal, and makes the selected recording / reproducing head usable. The offset amount detection unit 4 is configured to adjust the recording / reproducing heads 1a, 1a, 1
The offset amounts of b and 1c are detected. The VCM drive current pattern generation unit 5 determines a VCM drive current pattern corresponding to the amount of moving the recording / reproducing head unit 1 in an open loop, such as the offset amount detected by the offset amount detection unit 4, and sets the VCM drive current pattern as the VCM drive current pattern. The corresponding data is output as a digital value to the VCM driver 8 side. The position servo controller 6 controls the selected recording / reproducing head 1a, 1
b, 1c and 1s read the sector servo signals (track number 18 and servo burst information 1 of A and B shown in FIG. 6).
6, 17), and outputs a position control signal. The seek control unit 7 outputs a seek control signal when moving from the current track to the target track. Note that the position control and the seek control are closed loop controls. Although not shown, the VCM driver 8 has a D / A converter connected to its input side, and the VCM drive current pattern generator 5, the position servo controller 6, or the seek controller selected by the switching selector 14. An analog voltage after D / A conversion of one of the outputs of the unit 7 is input, and this analog voltage is converted into an analog current that actually flows, and VC
Supply to M2. The first memory 9 stores and stores the positional deviation amount and the offset amount measured by the offset amount detection unit 4, and records / reproduces the recording / reproducing heads 1a, 1b, 1c, and 1s.
When the reproducing head is switched, the reading is performed appropriately. The second memory 10 stores a VCM driving current pattern corresponding to the amount of movement of the recording / reproducing head unit 1 such as an offset amount in the form of a data table, and moves the recording / reproducing head unit 1 when the offset amount is corrected. At the time of the reading, the reading is performed appropriately. In this embodiment, the first memory 9 is a RAM and the second memory 9 is a second memory.
Is constituted by a ROM.

In the above configuration, when the power of a magnetic disk device, for example, a hard disk device is turned on, first, the head selection circuit section 3 first sets the reference recording / reproducing head 1s
And then the position servo controller 6 sends the reference recording / reproducing head 1s through the VCM driver 8 and the VCM 2.
Is supplied to control the reference recording / reproducing head 1s to perform on-track control. Immediately after the power is turned on, the track on the disk where the reference recording / reproducing head 1s is on-track is not determined, and it is unknown at which track the reference recording / reproducing head 1s is positioned first. On the other hand, the detection of the offset amount of each of the adjusted recording / reproducing heads 1a, 1b, 1c with respect to the reference recording / reproducing head 1s is performed on a track near the middle between the outermost track (cylinder) and the innermost track (cylinder). Is preferred. This is because the offset amount may be slightly different between the case where the offset amount is measured on the outermost track and the case where the offset amount is measured on the innermost track. This is because an average offset amount in all tracks (cylinders) can be detected. Therefore,
In order to measure the offset amount on the track near the middle,
It is necessary to move (seek) the on-track reference recording / reproducing head 1s to the center track of the disk. Therefore, following the previous operation, a seek command is added to the seek control unit 7 to make the reference recording / reproducing head 1s seek to the center track. Based on this command, the VCM 2 is driven, and the reference recording / reproducing is performed. The seek operation of the head 1s is performed. Thereafter, in order to make the reference recording / reproducing head 1s on-track on the center track, a sector servo signal detected by the reference recording / reproducing head 1s is supplied to the position servo controller 6, and the position servo controllers 6A, B The control signal is supplied to the VCM driver 8 so that the detection levels of the servo burst information are equal. Thereby, on-track to the center track of the reference recording / reproducing head 1s is performed. Subsequently, the head selection circuit unit 3 includes three adjusted recording / reproducing heads 1a, 1
b, 1c, for example, the recording / reproducing head 1a to be adjusted is switched and selected only for a short time (the time required to read another servo signal). Is a measurement of the temporary displacement (first displacement) of the adjusted recording / reproducing head 1a with respect to the reference recording / reproducing head 1s based on the track number and the servo burst information read by the adjusted recording / reproducing head 1a. Is performed, and the first displacement amount measured here is stored in the first memory 9. Specifically, the adjusted recording / reproducing head 1
a, the servo burst information of A (A burst) and the servo burst information of B (B burst) recorded on the disk are read eight times each, and the average value of the detection levels of both servo burst information is obtained. By calculating the difference, the first displacement amount is measured, and the first displacement amount is stored in the first memory 9 for subsequent processing. In addition, even if the adjusted recording / reproducing head 1a is displaced from the reference regular recording / reproducing head 1s by one track width or more, the adjusted recording / reproducing head 1a is controlled by the servo burst so that it can be detected. A track number (code recorded on a disk for each sector indicating a physical track address) is read together with the information (FIG. 6).
If this track number is not the track number indicating the center track, the first positional shift amount is measured in consideration of the shift amount corresponding to the difference between the track numbers. Next, the VCM drive current pattern generator 5 reads data corresponding to the VCM drive current pattern corresponding to the first displacement from the second memory 10, and reads this data via the switch selector 14. Side, and the VCM driver 8 supplies a current to the VCM 2 to move the position of the adjusted recording / reproducing head 1a (recording / reproducing head unit 1) to a position corresponding to the first positional deviation amount. Let it. After this movement is performed, the head selection circuit unit 3 switches and selects the reference recording / reproducing head 1s to the adjusted recording / reproducing head 1a, and subsequently, the offset amount detecting unit 4 returns to the adjusted recording / reproducing head 1a. / Reproducing head 1a
Read the servo burst information of A and B respectively,
By determining the difference between the detection levels of the two servo burst information, the current recording / reproducing head 1 (at the time of switching) can be obtained.
It is possible to know how much the position "a" is originally deviated from the position where the adjusted recording / reproducing head 1a should be on-track, and this deviation amount is measured as a second positional deviation amount. A required calculation (addition) is performed using the second displacement amount measured here and the first displacement amount already measured and stored in the first memory 9. The obtained offset amount is used as a reference recording / reproducing head 1
s is stored in the first memory 9 as a true offset amount of the adjusted recording / reproducing head 1a with respect to s.

Next, the head selection circuit section 3 selects the reference recording / reproducing head 1s again, turns the reference recording / reproducing head 1s on the center track, and
The other one of the adjusted recording / reproducing heads 1a, 1b, 1c, for example, the adjusted recording / reproducing head 1b, is also switched and selected for a short period of time. 1a, measurement of the first positional deviation amount, storage in the first memory 9,
After the movement of the distance corresponding to the amount of the positional deviation and the measurement of the second amount of the positional deviation are performed, the calculation of the first amount of the positional deviation and the second amount of the positional deviation obtained here is carried out, whereby the adjusted recording / An accurate offset amount of the reproducing head 1b is obtained, and the offset amount is determined as an offset amount of the adjusted recording / reproducing head 1b with respect to the reference recording / reproducing head 1s.
To be stored.

Subsequently, similarly, the reference recording / reproducing head 1
In the state where s is on-track to the center track, the remaining one adjusted recording / reproducing head 1c is also switched and selected only for a short period of time, and in the same manner as described above, the second adjusted recording / reproducing head 1c is switched. Measurement of displacement amount of 1st, 1st
Is stored in the memory 9, the distance corresponding to the first displacement is measured, and the second displacement is measured. Then, the obtained first displacement and the second displacement are obtained. By calculation,
An accurate offset amount of the adjusted recording / reproducing head 1c is detected, and the detected offset amount is used as a reference recording / reproducing head 1c.
The first memory 9 stores and stores the offset amount of the adjusted recording / reproducing head 1c with respect to s.

FIG. 2 is a flowchart showing a processing procedure of the operation of the embodiment of the method for detecting the offset of the recording / reproducing head shown in FIG.

Hereinafter, using the flowchart shown in FIG.
An operation processing procedure for accurate offset detection will be described.

First, in step S1, the reference recording / reproduction head 1s is selected by the head selection circuit unit 3,
The seek controller 7 is provided to the VCM 2 via the VCM driver 8.
In addition, a control signal is supplied from the position servo control unit 6 to execute on-track of a track at the center (or near the center) of the reference recording / reproducing head 1s. Following, step S
2, the head selection circuit unit 3 controls one adjusted recording / reproducing head, for example, the adjusted recording / reproducing head 1a.
Is switched for a short period of time, that is, for a time necessary for the adjusted recording / reproducing head 1a to read the sector servo signal. Next, in step S3, when the switching of the adjusted recording / reproducing head 1a is selected, the adjusted recording / reproducing head 1s is adjusted based on the track number and the servo burst information read by the head 1a.
A temporary displacement amount of the reproducing head 1a, that is, a first displacement amount is measured, and the first displacement amount is stored in the first memory 9. Subsequently, in step S4, data corresponding to the VCM drive current pattern corresponding to the measured first displacement amount is transmitted from the VCM drive current pattern generation unit 5, and the current is set to V
It is supplied from the CM driver 8 to the VCM 2 and the adjusted recording /
The reproducing head 1a is moved by open loop control so as to eliminate the first positional deviation. Subsequently, in step S5, the difference between the position of the adjusted recording / reproducing head 1a after the movement and the position where the adjusted recording / reproducing head 1a should be on-track, that is, the second displacement amount is measured. You. Next, in step S6, the measured first
A required calculation is performed using the position shift amount and the second position shift amount, and the calculation result is used as the detected true offset amount of the adjusted recording / reproducing head 1a with respect to the reference recording / reproducing head 1s. It is stored in the memory 9.

Next, in step S7, it is determined whether or not the offset amounts of all the adjusted recording / reproducing heads 1a, 1b, 1c have been detected and stored in the first memory 9. Perform all adjustment records /
When the determination of the offset amounts of the reproducing heads 1a, 1b, and 1c and the storage in the first memory 9 have been completed (Y)
On the other hand, when the series of operation processing is completed, and the detection of the offset amount and the storage in the first memory 9 have not been completed yet (N), the process returns to step S2, and again.
The recording / reproducing heads 1a, 1b to be switched and selected.
1c is changed so that the processing after step S1 is repeated.

In the offset detection method described above,
Only one reference recording / reproducing head 1s is determined,
Although the offset amounts of the reproducing heads 1a, 1b, and 1c are all determined with respect to the reference recording / reproducing head 1s, the present invention is not limited to such a method. For example, when calculating the offset amount of the recording / reproducing head 1a, the offset amount is calculated based on the recording / reproducing head 1s, and then the offset amount of the recording / reproducing head 1b is calculated based on the recording / reproducing head 1a. Asked, as well,
Recording / reproducing head 1 based on recording / reproducing head 1b
The offset amount of c may be obtained. In short, it is measured how much the four recording / reproducing heads 1a, 1b, 1c, and 1s are offset from each other, and if the offset amount is stored in the first memory 9, the offset amount is calculated. For example, the offset amounts of the recording / reproducing head 1c with respect to the recording / reproducing head 1a can be obtained, and these offset amounts can be used at the time of offset correction described later.

In the case described above, all the adjusted recording /
Although the detection of the offset amounts of the reproducing heads 1a, 1b, and 1c and the storage and storage in the first memory 9 have been described as being performed when the power of the hard disk device is turned on, the detection of the offset amounts and the first The storage in the memory 9 is not limited to being performed when the power supply of the hard disk device is turned on. For example, the first memory 9 is formed of a non-volatile EEPROM, not a RAM, and is performed when the hard disk device is shipped. You may do so.

As described above, according to the present embodiment, the adjusted recording / reproducing heads 1a, 1b, which detect the offset amount,
1c is switched and selected for a short time, the first positional deviation amount of the recording / reproducing heads 1a, 1b and 1c selected and switched is measured, and further, the first positional deviation amount is eliminated. The adjusted recording / reproducing heads 1a, 1b, 1
After moving c, the second displacement of the adjusted recording / reproducing heads 1a, 1b, 1c from the original on-track position is measured, and the first displacement and the measured first displacement are measured here. Since the offset amount is detected from the second displacement amount, an accurate offset amount can be accurately obtained.

FIG. 3 is a current waveform diagram showing an example of a VCM driving current pattern supplied to the VCM when correcting the offset between the two recording / reproducing heads when switching between the recording / reproducing heads. FIG. 4 is an explanatory diagram showing a part of storage contents stored in advance in a second memory in the form of a data table in order to generate the VCM drive current pattern.

FIG. 3A shows a VCM driving current pattern in a case where a relatively short distance is required to correct the offset amount between the recording / reproducing heads. The current pattern simply consists of positive and negative pulse currents of relatively small amplitude.
(B) is a VCM drive current pattern in the case where it is necessary to move a medium distance during the correction, and the VCM drive current pattern at this time is a pulse whose amplitude changes in two stages for both positive and negative polarities. It consists of current. (C) is a VCM drive current pattern when it is necessary to move a relatively long distance at the time of the correction, and the amplitude of the VCM drive current pattern at this time changes in three stages for both positive and negative polarities. It consists of a pulse current. In this case, the positive pulse current forms a moving acceleration portion of the recording / reproducing head, and the negative pulse current forms a moving deceleration portion of the recording / reproducing head.

In FIG. 4, the left column indicates the distance that the recording / reproducing head should move when correcting the offset amount of the recording / reproducing head, and the distance depends on the length of the moving distance. , 0, 4, 8, ..., 24, 28, 3
2,..., 504, 508, 512 are classified into 128 levels, and the right column is a VCM drive current pattern corresponding to each of the 128 levels indicating the distance to be moved. Represents the number of steps in which the amplitude of the pulse current changes in each polarity.
, Indicate the amplitude value of the pulse current.

For example, when the offset amount corresponds to a distance to be moved at the level of 8, a pulse current having only a step having an amplitude value of 11 for both positive and negative polarities is used as a VCM drive current pattern. In other words, when the offset amount corresponds to a distance to be moved at a level of 28, both the positive and negative polarities have a stage consisting of an amplitude value 6 first and a stage consisting of an amplitude value 9 next. The pulse current is used as a VCM drive current pattern, and the offset amount is 50
In the case where the distance corresponds to the distance to be moved at the level of 8, the pulse having both the positive and negative polarities has a phase consisting of the amplitude value 10 first, a phase consisting of the following amplitude value 18, and a phase consisting of the subsequent amplitude value 13. This means that the current is used as the VCM drive current pattern, and even when the distance corresponds to a distance to be moved at another level, it is exactly the same as the above-described case.

Here, only the VCM drive current pattern that generates a positive pulse current is stored and stored in the second memory 10. What is necessary is just to invert the value of the positive polarity pulse current read from the memory 10. Note that this second
The data table stored in the memory 10 of
In step S4 of the flowchart shown in FIG. 2 described above, it is also used when the adjusted recording / reproducing head 1a (1b, 1c) is moved by the first positional deviation amount.

FIG . 3 and FIG.
The offset correction of the recording / playback head is performed as follows.
It is.

First, in this embodiment, when the power of a magnetic disk device such as a hard disk device is turned on in advance, the other recording / reproducing heads 1a, 1b with respect to the (reference) recording / reproducing head 1s by the offset detection method described above. , 1
It is assumed that the offset amount of c has been detected and that the offset amount is stored in the first memory 9. As shown in FIG. 4, a large number of levels, for example, 128, are previously stored in the second memory 10 in correspondence with various moving distances of the recording / reproducing head for which the offset amount is to be corrected. VCM drive current patterns of different levels are stored and stored. The reason why 128 levels are prepared in this way is to control the movement of the recording / reproducing head very finely by open loop control.

When the recording / reproducing head 1s is selected, if a head switching command signal for switching to the recording / reproducing head 1a is supplied to the head switching command signal supply section 11, for example, The switching command signal is supplied to the head selection circuit unit 3 and the offset amount detection unit 4. At this time, in response to the head switching command signal, the offset amount detecting unit 4 determines the recording / reproducing head 1s before switching and the recording / reproducing after switching based on the offset amount stored in the first memory 9. The amount of offset from the head 1a, that is, the distance to be moved by the recording / reproducing head 1a (recording / reproducing head unit 1) is obtained (calculated).

Next, the VCM drive current pattern generator 5
After the offset amount (distance to be moved) is obtained, the offset amount (distance to be moved) is set to any of the 128 levels stored in the second memory 10. If the level is determined to be applicable, and a level corresponding to the offset amount (distance to be moved) is determined, data of the VCM drive current pattern corresponding to the level is read from the data table of the second memory 10.

Subsequently, based on the head switching command signal, the head selection circuit section 3 selects the head to be used by switching from the recording / reproducing head 1s to the recording / reproducing head 1a. Digital data corresponding to the VCM drive current pattern read from the second memory 10 is sent from the VCM drive current pattern generator 5 to the VCM driver 8 via the switching selector 14, and the VCM driver 8 Positive and negative pulse current is VC
M2. At this time, the recording / reproducing head 1a
Is accelerated stepwise or non-stepwise by the positive pulse current supplied to the VCM 2 to quickly move toward the center of the target track, and then move to the center of the target track. When approaching, this time VCM2
The motor is decelerated stepwise or non-stepwise by the negative pulse current supplied to the target track, and the movement control is performed such that the track just stops at the center position of the target track. During the movement control, the position of the recording / reproducing head 1a is not corrected by the sector servo signal. That is, this movement control is performed by open loop control.

Immediately after the movement of the recording / reproducing head 1a ends, the recording / reproducing head is switched to a known tracking control state, that is, closed loop control using a sector servo signal by the position servo controller 6. The on-track of 1a is executed. After the on-track is executed, the recording / reproducing head 1a can record (write) and reproduce (read) information on the disk.

The above description has been made on the operation when the recording / reproducing head 1s is switched to the recording / reproducing head 1a by the head switching command signal, but the other recording / reproducing heads 1b and 1c are switched. The operation when selecting is exactly the same as the operation described above. The operation when the recording / reproducing head 1a is switched to the recording / reproducing head 1b is the same as that described above, but the method of obtaining the offset amount is slightly different. . That is, the first memory 9 stores the other recording / reproducing heads 1a, 1b, 1 with respect to the recording / reproducing head 1s.
Since the offset amount of c is stored and stored, the offset amount between the recording / reproducing heads 1a and 1b is determined by the offset amount of the recording / reproducing head 1a with respect to the recording / reproducing head 1s and the recording / reproducing with respect to the recording / reproducing head 1s. Head 1
It can be obtained by taking the difference from the offset amount of b, and this difference is the distance to be moved. Note that the other methods of obtaining the offset amount between the recording / reproducing heads are the same, and further description will be omitted.

[0040] Subsequently, FIG. 5, there is provided a recording / reproducing head shown in FIG. 1 is a flow chart showing an example of a processing procedure of the operation for offset correction.

Hereinafter, according to the flowchart shown in FIG.
An operation processing procedure for offset correction will be described.

First, in step S 8, a (reference) adjustment recording / reproducing head which is measured in advance by supplying a head switching command signal to the offset amount detection unit 4 and stored in the first memory 9. From the offset amounts of the other recording / reproducing heads 1a, 1b, 1c with respect to 1s,
Recording / reproducing head before switching, for example, head 1s, and recording / reproducing head after switching, for example, head 1a
Is calculated (the distance to be moved). Continue,
In step S9, the VCM drive current pattern corresponding to the level of the calculated offset amount (distance to be moved) is selected, and the selected VCM drive current pattern data is read. Next, in step S10, switching to a recording / reproducing head, for example, head 1a, is selected based on a head switching command signal to the head selection circuit unit 3. In the subsequent step S11, a pulse current of positive / negative polarity corresponding to the read VCM drive current pattern is supplied to the VCM2,
Thereby, the recording / reproducing head 1a (recording / reproducing head unit 1) is moved. Next, in step S12, tracking control for the recording / reproducing head 1a is performed, and the recording / reproducing head 1a is turned on-track.
This series of processing procedures ends.

In the description of the offset correction method, the process of selecting the switching of the recording / reproducing head in step S10 is performed after selecting and reading the VCM drive current pattern in step S9, and then moving the recording / reproducing head in step S11. Although the process is performed before the process, the recording / reproducing head switching selection process may be performed at any time before the tracking control in step S12. For example, before step S8, that is, the head switching command signal May be performed immediately after the recording / reproducing head unit 1 is moved in step S11.

Further, in the above description, the level of the offset amount between the recording / reproducing heads is set to 1 as shown in FIG.
Although the case of dividing into 28 ways is described, the way of dividing is merely an example and is not limited to 128 ways of dividing.

[0045] The method of the number of stages of the setting in the VCM driving current pattern corresponding to the level of the offset amount in the description, and, for the method of the size of the set of their current value, can be carried out appropriately set However, the present invention is not limited to the setting method shown in FIG.

In the block diagram shown in FIG. 1, the offset detector 4, the VCM drive current pattern generator 5, and the like have been described as separate components, but these components, ie, the offset detector, 4, VCM
The drive current pattern generator 5, the position servo controller 6, the seek controller 7, the first memory 9, the second memory 10, and the switching selector 14 can be constituted by a single-chip microprocessor. In that case, the microprocessor may be programmed so as to execute the flowcharts shown in FIGS.

As described above, according to the present embodiment , the recording /
The levels of various offset amounts between the reproducing heads are stored and stored in the second memory 10 in the form of a voice coil motor driving current pattern table that changes stepwise or non-stepwise, and the switching of the recording / reproducing head 1a is selected. At this time, the offset amount between the recording / reproducing head before and after the switching is calculated, and the level of the offset amount in the second memory 10 corresponding to the calculated offset amount is used as a VCM drive current pattern. Reading, supplying the read VCM drive current pattern, that is, a stepwise or non-stepwise pulse current having a magnitude corresponding to the level of the offset amount, to the VCM2, and in the open-loop control, the recording / reproducing head unit 1 is moved, it takes a considerable time to move the recording / reproducing head. No quick, you can correct an offset amount of time accurately recording / reproducing head switching.

[0048]

As described above, according to the present invention,
The adjusted recording / reproducing head for detecting the offset amount is switched and selected for a predetermined time, and the first positional deviation amount of the switched selected recording / reproducing head with respect to the reference recording / reproducing head 1s is measured. Subsequently, after moving the adjusted recording / reproducing head so as to eliminate the first positional deviation amount, this time, the position of the adjusted recording / reproducing head after movement and the original adjusted recording / reproducing head are changed. The difference from the position at which the head is to be on-track is measured as a second displacement amount, and the offset amount is detected from the first displacement amount and the second displacement amount measured here. Therefore, there is an effect that an accurate offset amount can be accurately obtained.

[0049]

[Brief description of the drawings]

1 is a block diagram used to perform an embodiment of the offset detection method of the recording / reproducing head according to the present invention.

FIG. 2 is a flowchart showing a processing procedure of an operation of the embodiment of the offset detecting method of the recording / reproducing head shown in FIG. 1;

FIG. 3 is a current waveform diagram showing an example of a VCM driving current pattern supplied to a VCM when correcting an offset amount between the two recording / reproducing heads when switching between the recording / reproducing heads.

FIG. 4 is an explanatory diagram showing a part of storage contents stored in a memory in advance in a data table in order to generate the VCM drive current pattern shown in FIG. 3;

In the recording / reproducing head shown in FIG. 5 FIG. 1 is a flow <br/> chart showing an example of a processing procedure of the operation for offset correction.

FIG. 6 is an explanatory diagram showing a pattern of a sector servo signal recorded on a disk and a positional deviation amount detected by a position of a recording / reproducing head on the pattern.

[Description of Signs] 1 Recording / reproducing head unit 1a to 1c Adjusted recording / reproducing head 1s Reference recording / reproducing head 2 Voice coil motor (VCM) 3 Head selection circuit unit 4 Offset amount detecting unit 5 VCM driving current pattern generating unit Reference Signs List 6 position servo control unit 7 seek control unit 8 VCM driver 9 first memory 10 second memory 11 head switching command signal supply unit 12 sector servo signal supply unit 13 seek command signal supply unit 14 switching selection unit 15 A burst 16 B burst 17 Track number

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 21/10

Claims (3)

(57) [Claims] 1. A magnetic disk drive having a plurality of recording / reproducing heads and setting one of them as a reference recording / reproducing head for initial setting, first selects a reference recording / reproducing head. To perform on-track, and then, with the reference recording / reproducing head on-track,
An adjusted recording / reproducing head different from the reference recording / reproducing head is switched and selected for a required time, and a first positional shift between the reference recording / reproducing head and the adjusted recording / reproducing head immediately after the switching is performed. Then, the adjusted recording / reproducing head is moved by the first positional deviation amount from a state where the reference recording / reproducing head is on-track, and the adjusted recording / reproducing head at that time is moved. Is measured as a second displacement amount, and the first displacement amount and the second displacement amount obtained here are measured as a second displacement amount. A method for detecting an offset amount between the reference recording / reproducing head and the adjusted recording / reproducing head based on the following formula: 2. The recording / reproducing head according to claim 1, wherein the detection of the offset amount of the adjusted recording / reproducing head with respect to the reference recording / reproducing head is performed at least when the power of the magnetic disk drive is turned on. Offset detection method. 3. The method according to claim 1, wherein the detected offset amount is stored in a memory.