JPH0836725A - Magnetic disk unit - Google Patents

Abstract

(57) [Summary] [Structure] The offset correction value calculation circuit 16 calculates an offset correction value at an arbitrary radial position according to the track number supplied from the position error signal calculation circuit 18.
The offset correction value from the offset correction value calculation circuit 16 and the offset amount from the offset detection circuit 14 are
It is supplied to the offset calculation circuit 15. The offset calculation circuit 15 calculates the track center offset amount of an arbitrary track. The track position correction circuit 13 calculates the position error signal calculation circuit 1 based on the calculation result of the offset calculation circuit 15.
8 is added, and the added value is subjected to PID processing.
This PID output is supplied to the support arm drive control circuit 22 via the amplifier 21. The support arm drive control circuit 22 controls the drive of a support arm having a reproducing head H _R and a recording head H _{W (} not shown) at its tip. [Effect] By making the track center offset close to zero, it is possible to minimize the track deviation at the time of reading and at the time of writing, and prevent the read error and the write error.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device in which a reproducing head and a recording head are separately provided on a rotary type supporting arm.

[0002]

2. Description of the Related Art Conventionally, as a head displacing means used in a magnetic disk device, a linear type for linearly moving a supporting arm to displace the head in the radial direction of the disk and a supporting arm are rotated to move the head to the disk. There is a rotary type that is displaced in the radial direction. At present, a rotary type is often used to reduce the size and weight of the device.

On the other hand, in recent years, a magnetoresistive head has been developed. This magnetoresistive head can obtain excellent reproduction sensitivity characteristics even with a narrow track width, and is suitable for increasing track density. Therefore, it is considered to use this magnetoresistive head in a magnetic disk device. However, this magnetoresistive head has no recording capability. Therefore, when the magnetoresistive head is used as a recording head in the magnetic disk device, it is necessary to prepare a winding type recording head. These two heads have a laminated structure and are called a so-called 2-gap head.

That is, in recent years, a magnetic disk apparatus adopts a rotary type support arm, and a rotary type head access mechanism in which a reproducing head and a recording head are separately attached to the support arm is used for high density recording. Playback is realized.

[0005]

By the way, in the magnetic disk drive using the so-called two-gap head, generally, during manufacturing, mask alignment accuracy or the like causes
The center lines of the recording head H _W and the reproducing head H _R are displaced as shown in FIG. 9B. Ideally, as shown in (A) of FIG. 9, the position of the center line C _R of the center line C _W and the read head H _R of the recording head H _W it is desirable to match. However, at the time of manufacture, a center offset δ is generated in the recording head H _W and the reproducing head H _R so that the center line C _W and the center line C _R are displaced as shown in FIG. 9B. I will end up. When this center offset δ is generated, the track center shift amount at the time of writing shown in FIG. 10, that is, the track center offset E _W is E _W = δ cos θ _s (1) Where θ _s is the skew angle.

Further, in a magnetic disk device having such a rotary type head access mechanism, the perpendicular line of the head and the track circumferential direction generally do not coincide with each other, and they intersect at a skew angle θ _S as shown in FIG. Therefore, a write / read center offset occurs due to the gap distance between the recording head H _W and the reproducing head H _R and the skew angle θ _S , which causes the track center offset e _w at the time of writing.
Occurs. This track center offset e _w is
As shown in FIG. 11, the rotation axis (pivot) 5 of the arm 50
1 and L ₁ the center distance between the spindle motor shaft 52, and the length L ₂ of the arm 50, the vent angle of the head theta _B, the recording head H _W the distance between the reproducing head H _R delta, track when the diameter is r, a _{e w = Δsinθ S = Δsin {} θ B + sin -1 ((r 2 + L 2 2 -L 1 2) / 2rL 2)} ··· (2).

By adding the track center offset E _W shown in the above equation (1) and the track center offset e _w shown in the above equation (2), the following (3)
The total track center offset E is calculated as shown in the equation.

E = E _W + e _w (3) That is, in the magnetic disk device using the so-called two-gap head, the track center offset E at the time of writing E caused by the mask alignment accuracy at the time of manufacturing _A total track center offset E, which is an addition value of _{W and} the track center offset e _w , which is generated when the perpendicular of the head gap and the track circumferential direction do not match, is generated.

The present invention has been made in view of the above circumstances, and minimizes the track deviation at the time of reading and at the time of writing by making the track center offset close to zero, and prevents a read error and a write error. It is an object of the present invention to provide a magnetic disk device that can be used.

[0010]

In a magnetic disk drive according to the present invention, a reproducing head and a recording head are separately provided at the tip of a support arm whose base end side is rotatably supported, and the above-mentioned rotation of the support arm causes The reproducing head and the recording head are moved in a substantially radial direction of the disc, the servo signal recorded on the disc is picked up by the reproducing head, and the rotational position of the support arm is moved according to the picked-up servo signal. In a magnetic disk device for performing track servo by means of offset, an offset detecting means for detecting a write / read offset value at at least one radial position based on an output signal of the reproducing head, and an offset value detected by the offset detecting means. Offset calculating means for obtaining an offset value of an arbitrary track based on
The above problem is solved by having track position correcting means for correcting the track position at the time of writing or reading based on the calculation result of the offset calculating means.

Here, the offset detecting means detects the write / read offset value at at least one radial position based on the output signal of the reproducing head.
The at least one radial position means a single or a plurality of radial positions. Detecting at a single radial position means, for example, a case where there is a lookup table in advance and the offset value is detected by changing one coefficient.

In this case, the offset calculating means calculates an offset value of an arbitrary track from an offset correction value at an arbitrary radial position of the disk and a detected offset value of the offset detecting means.

The offset calculating means may calculate the offset value based on a value obtained by linearly approximating the plurality of offset values obtained by the offset detecting means.

Further, when the distance between the base end of the support arm and the center of rotation of the disk is L ₁ and the length of the support arm is L ₂ , the offset calculation means is L ₁ / L ₂
When 0.9 to 1.1, the offset value may be calculated based on the value obtained by linearly approximating the plurality of offset values obtained by the offset detecting means.

[0015]

The offset calculating means obtains the offset value of an arbitrary track based on the write / read offset value detected by the offset detecting means at at least one radial position. Then, the track position correcting means corrects the track position at the time of writing / reading based on the result of this calculation, so that the track center offset becomes close to zero to minimize the track deviation at the time of reading and writing, and the reading error. And, write error can be prevented.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a magnetic disk device according to the present invention will be described below with reference to the drawings. This embodiment is a magnetic disk device such as a hard disk device.
The schematic configuration is as shown in.

In FIG. 1, the base end of the support arm 1 is rotatably supported by a rotary shaft (pivot) 2. The rotation shaft 2 is rotated by the driving force of a motor (not shown) to control the position of the support arm 1. A slider body 3 is attached to the tip of the support arm 1. The slider body 3 is provided with a magnetoresistive reproducing head H _R and a winding recording head H _W. Reproducing head H _R and the recording head H _W are both located on the center line c ₁ of the support arms 1 spaced a predetermined distance, recording head H _W a forward position, a rear position the reproducing head H _R, respectively. And it is configured so that the reproducing head H _R and the recording head H _W at the innermost peripheral T ₁ position of the disk 4 is just a track to the track of both the servo signal. Thus, in another track recording head H _W and the read head H _R is just the track is located at the off-track position. Further, between the reproducing head H _R and the recording track H _W , the positional deviation of the center line occurs due to the mask alignment accuracy at the time of manufacturing as described above. Therefore, a track center shift, that is, a track center offset occurs between the reproducing head H _R and the recording track H _W.

In order to prevent the occurrence of such a track center offset, this embodiment has a track servo mechanism as shown in FIG. In FIG. 2, the output signal of the reproducing head H _R is supplied to the data detection circuit 12 and the track position correction circuit 13 via the amplifier 11.
The data detected by the data detection circuit 12 is supplied to a track center offset (hereinafter referred to as offset) detection circuit 14. The offset amount detected by the offset detection circuit 14 is supplied to a track center offset calculation circuit (hereinafter referred to as an offset calculation circuit) 15. The offset calculation circuit 15 is also supplied with an offset correction value from a track center offset correction value calculation circuit (hereinafter referred to as an offset correction value calculation circuit) 16.

As described above, the track position correction circuit 13
Also, the output signal of the reproducing head H _R is supplied via the amplifier 11. The track position correction circuit 13 includes a position signal generation circuit 17, a position error signal calculation circuit 18, an adder 19, and a proportional-integral-derivative (hereinafter referred to as PID) circuit 20.
It consists of and.

The offset correction value calculation circuit 16 calculates an offset correction value at an arbitrary radial position according to the track number supplied from the position error signal calculation circuit 18. The offset correction value from the offset correction value calculation circuit 16 and the offset amount from the offset detection circuit 14 are supplied to the offset calculation circuit 15, as described above. Then, the offset calculation circuit 15 calculates the track center offset amount of an arbitrary track,
It is supplied to the adder 19. Therefore, the track position correction circuit 13 causes the adder 19 to add the calculation result of the position error signal calculation circuit 18 to the calculation result of the offset calculation circuit 15, and causes the PID circuit 20 to perform proportional integration. The output signal of the PID circuit 20 is supplied to the support arm drive control circuit 22 via the amplifier 21. The support arm drive control circuit 22 controls the drive of a support arm having a reproducing head H _R and a recording head H _{W (} not shown) at its tip.

The offset detection circuit 14 detects write / read offset amounts at a plurality of radial positions. The offset detection circuit 14 detects the write / read offset amount at a timing after the magnetic disk device is powered on, and the detected value is recorded in the memory section. An example of the detection method performed by the offset detection circuit 4 will be described below.

First, three or more tracks in which the guard band in the data zone is not a recess are continuously formed on the magnetic disk 4, for example, at a specific radius. The numbers of these three tracks are n-1, n, and n + 1. Here, the servo zone is formed similarly to other tracks.

Next, recording / reproducing is performed on an actual drive using this magnetic disk 4. That is, first, a position signal is detected from the servo zone via the reproducing head, and the reproducing head H _R is tracked to the nth track based on this signal. At this time, the recording head (not shown) offsets and tracks by an unknown value E shown in the equation (3). In this state, a specific digital signal with a CRC code is recorded in the data area. After that, the reproducing head H _R is slightly offset, for example, 0.05 T _P (track pitch), and reading for one track is performed. And C at that track position
Measure the number of blocks with no RC error.

The above is repeated tens of times, for example, C at each track position when off-tracking ± 1 track.
The number of blocks without RC error is measured and the data is stored. FIG. 3 shows the characteristics of the data table of the track center offset amount vs. the number of blocks that pass the CRC, which is the stored data. In FIG. 3, this characteristic graph is, in principle, symmetrical about the track center.
To obtain the track center from this data table, for example, the average offset of the number of blocks that pass the CRC is calculated. This is the total track center offset E (= e _w + E _W ... (3) of the recording head with respect to the reproducing head.
The detected value E _N in the n-th track of the equation) is represented.

The offset correction value calculation circuit 16 is a position error signal calculation circuit 1 of a track position correction circuit 13, which will be described later.
The offset correction values at all the radial positions are calculated based on the position error signal supplied from 8. An example of the calculation method performed by the offset correction value calculation circuit 16 will be described below.

[0026] as shown in FIG. 10, center distance L _1, the length L ₂ of the arm 50, the skew angle theta _S of the head of the pivot shaft 51 and the spindle motor shaft 52 of the arm 50,
Head vent angle θ _B , recording head H _W and reproducing head H _R
The distance Δ between them is a known value that can be grasped at each design stage. Therefore, these values can be written in advance in a ROM (not shown). Also, the track diameter r
Have a one-to-one correspondence with track numbers. Therefore, the track center offset e _w shown in the above equation (2) can be calculated using the central processing unit (CPU) or digital signal processing unit (DSP),
It is possible to calculate the offset correction value for each track. Alternatively, the offset correction value for the track number may be calculated in advance based on the equation (2), and this may be stored in the ROM as a table.

The offset calculation circuit 15 calculates the offset amount of all tracks from the detected offset amount of the offset detection circuit 14 and the offset correction value of the offset correction value calculation circuit 16. An example of the calculation method performed by the offset calculation circuit 15 will be described below.

The detection value E _N in the nth track detected by the offset detection circuit 14, the offset correction value e _wN in the nth track calculated by the offset correction value calculation circuit 16, and E _W shown in the above equation (1) The offset correction value E _{WN on} the n-th track is expressed as E _N = e _wN + E _WN from the above equation (3). When the skew angle θ _S is small, E _WN ≈
Since δ is almost constant, the k-th value calculated by the above-described calculation method
Using the offset correction value e _wk in the track,
The offset amount E (k) on the track is E (k) = e _wk + E _WN .

The track position correction circuit 13 corrects the track position at the time of writing based on the calculation result of the offset calculation circuit 15. The track position correction performed by the track position correction circuit 13 will be described below. The position here means an address. Therefore, before describing the track position correction circuit 13, a disk on which a magnetic disk device records and reproduces information signals will be first described.

This disc has a format as shown in FIG. In FIG. 4, the disk 4 is provided with a large number of tracks T having different radii around the center of rotation, and a servo portion 25 is provided at an angular track T position one radius up at equal intervals. In such a disk 4, the servo section 25 and the subsequent data section 26 form one sector, and several tens of sectors are provided in one track.

The servo pattern of the servo section 25 is shown in FIG.
Shown in

In FIG. 5, the servo head 25 has a sector head portion ST in which a sector start signal is recorded at the head thereof, and address portions AD1 and AD2 in which track addresses are recorded are provided behind the sector head portion ST. Immediately before the address portion AD1, a burst signal area X in which a burst signal indicating an odd track is recorded,
Immediately before the address portion AD2, there are provided burst signal areas Y in which burst signals indicating even tracks are recorded. Then, the burst signal area X
And the level of the burst signal region Y are compared, and the address of AD1 is adopted when X> Y, and the address of AD2 is adopted when X <Y, whereby the track address is detected. When X = Y, it is recognized that the reproducing head H _R is located in the middle of the tracks. Also, the address part A
A, B, and C signals are recorded behind D1 and AD2.
Section, B section, and C section, and at different positions from A section and B section,
Further, it is provided at a position slightly away from the track center line c ₂ and is provided integrally with the A portion and the B portion of the adjacent tracks. The section C is provided continuously to the adjacent tracks, and is configured to pick up the reproducing head H _R regardless of the course of scanning.
Then, (A−B) / C is calculated, and the value FA corresponding to the off-track amount from the track center line c ₂ is calculated as shown in FIG.
The fine address FA is detected by calculating. In FIG. 6, TP indicates a track pitch and TW indicates a track width. By combining the track address and the fine address, the current address of the reproducing head H _R can be known.

The track position correcting circuit 13 corrects the track position of the head on the disk 4 having such a format. The track correction circuit 13 includes the position signal generation circuit 17, the position error signal calculation circuit 18, the adder 19 and the PID circuit 20 as described above.

The position signal generation circuit 17 extracts a track address and a fine address, which are position signals, from the output signal of the reproducing head H _R via the amplifier 11 and generates a current address from these addresses. Specifically, the position signal generation circuit 17 calculates the fine address by calculating (A−B) / C as described above, and the value (0 ± 1) is calculated by an A / D converter (not shown). It is converted into a digital value divided into 100, for example. The track address and the fine address are added by an adder (not shown) to obtain the current address.

The position error signal calculation circuit 18 supplies an address difference, which is a position error signal obtained by subtracting the present address from a target address supplied from the other, to the adder 19 and calculates the track number as an offset correction value calculation circuit. Supply to 16.

The adder 19 adds the address difference to the offset amount of an arbitrary track from the offset calculation circuit 15 and outputs it to the PID circuit 20. The PID output from the PID circuit 20 is supplied to the support arm drive control circuit 22 via the amplifier 21. The support arm drive control circuit 22 controls the drive of a support arm having a reproducing head H _R and a recording head H _{W (} not shown) at its tip.

As described above, in the magnetic disk device of this embodiment, the offset, that is, the track center offset, can be brought close to zero, the track shift at the time of reading and writing can be minimized, and the read error and the write error can be prevented. be able to.

The magnetic disk drive according to the present invention is
The present invention is not limited to the above embodiment, but may be applied to the following magnetic disk device. This magnetic disk device will be described below as another embodiment.

The schematic structure of the magnetic disk device of the other embodiment is similar to that of the magnetic disk device shown in FIG. The magnetic disk drive of the other embodiment has a track servo mechanism as shown in FIG. 7 in order to prevent the occurrence of the track center offset. The track servo mechanism of the magnetic disk device of the other embodiment differs from the track servo mechanism shown in FIG. 2 in that the offset calculation circuit 23 adopts a calculation method by linear interpolation to calculate the offset amount of all tracks. This is the point of calculation. That is, the offset calculation circuit 23 calculates the offset value based on the value obtained by linearly approximating the plurality of offset values obtained by the offset detection circuit 14. As a calculation method by linear interpolation,
There are a linear interpolation method for the radial position r and a linear interpolation method for the track number k.

As a linear interpolation method for the radial position r,
The offset amount of all tracks is calculated from a straight line passing through the points (r ₀ , E ₀ ) and the points (r _n , E _n ) on the (r, E) plane. In this case, the straight line E (r) passing through the two points is: E (r) = {(E _n −E ₀ ) r / (r _n −r ₀ )} + {(E ₀ r _n −E _n r ₀ ) / (R _n −r ₀ )} (4) Here, the relationship between the track number and the radial position can be stored in advance in the ROM as a table, for example. Specifically, first, the radial position rk of the track number k to be obtained is obtained from the ROM table. Next, rk is substituted for r in the equation (4) to calculate E (rk).

As a linear interpolation method for the track number k, points (0, E ₀ ) and points (n, E _n ) on the (k, E) plane are used.
The offset amount of all tracks is calculated from the straight line passing through. In this case, the straight line E (r) passing through the above two points is E (r) = {(E _n −E ₀ ) k / n} + E ₀ (5) The track number k to be obtained from this equation (5)
To calculate E (k).

Further, when the distance between the base end of the support arm 1 and the center of rotation of the disk is L ₁ and the length of the support arm is L ₂ , the offset calculation circuit 15 is L ₁
When / L ₂ is 0.9 to 1.1, the offset amount may be calculated based on the value obtained by linearly approximating the plurality of offset values obtained by the offset detection circuit 14. This L ₁ / L ₂ value of 0.9 to 1.1 indicates a tracking error of ± 0.
It is a value that can be suppressed within the range of 1 (μm).

[0043]

In the magnetic disk device according to the present invention, the reproducing head and the recording head are separately provided at the tip of the supporting arm whose base end side is rotatably supported, and the reproducing head and the recording head are rotated by the rotation of the supporting arm. The recording head is moved in a substantially radial direction of the disk, the servo signal recorded on the disk is picked up by the reproducing head, and the rotational position of the support arm is moved according to the picked up servo signal to perform the track servo. In the magnetic disk device to perform,
Offset detecting means for detecting a write / read offset value at at least one radial position based on the output signal of the reproducing head, and an offset value of an arbitrary track based on the offset value detected by the offset detecting means. Since there is an offset calculating means to be obtained and a track position correcting means for correcting the track position at the time of writing or reading based on the calculation result of the above offset calculating means, by making the track center offset close to zero, reading and writing can be performed. It is possible to minimize the track deviation at the time and prevent read error and write error.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a magnetic disk device according to an embodiment of the present invention.

FIG. 2 is a block circuit diagram of a track servo mechanism of a magnetic disk device.

FIG. 3 is a characteristic diagram of a data table of a track center offset amount vs. the number of blocks that pass a CRC, for explaining a detection method of an offset detection circuit.

FIG. 4 is a format diagram of a disc.

FIG. 5 is a servo pattern diagram of a servo unit of the disk.

FIG. 6 is an off-track characteristic diagram of a fine address servo.

FIG. 7 is a block circuit diagram of a track servo mechanism of a magnetic disk device according to another embodiment of the present invention.

FIG. 8 is a diagram showing a tracking error when L ₁ / L ₂ is 0.9 to 1.1.

FIG. 9 is a diagram for explaining a center offset at the time of manufacturing.

FIG. 10 is a diagram for explaining skew angle and write / read track center shift.

FIG. 11 is a diagram for explaining a write / read center offset derived from a gap distance between a recording head H _W and a reproducing head H _R and a skew angle θ _S.

[Explanation of symbols]

 13 Track Position Correction Circuit 14 Offset Detection Circuit 15 Offset Calculation Circuit 16 Offset Correction Value Calculation Circuit 17 Position Signal Generation Circuit 18 Position Error Signal Calculation Circuit 19 Adder 20 Proportional Integral Differentiation Circuit

Claims (4)

[Claims] 1. A reproducing head and a recording head are separately provided at the tip of a supporting arm whose base end side is rotatably supported, and the reproducing arm and the recording head are rotated substantially in the radial direction of a disk by the rotation of the supporting arm. Move, pick up the servo signal recorded on this disc with the above reproducing head,
In a magnetic disk device that performs track servo by moving the rotational position of the support arm according to the picked-up servo signal, a write / read offset value is set at at least one radial position based on the output signal of the reproducing head. Offset detection means for detecting, offset calculation means for obtaining an offset value of an arbitrary track based on the offset value detected by the offset detection means, and track position at the time of writing or reading based on the calculation result of the offset calculation means And a track position correcting means for correcting the magnetic field. 2. The offset calculating means calculates an offset value of an arbitrary track from an offset correction value at an arbitrary radial position of the disk and a detected offset value of the offset detecting means.
The magnetic disk device described. 3. The offset calculating means calculates the offset value based on a value obtained by linearly approximating a plurality of offset values obtained by the offset detecting means. Magnetic disk device. 4. The offset calculating means sets a distance between a base end of the support arm and a rotation center of the disk by L ₁ ,
When the length of the support arm is L _2, and when L ₁ / L ₂ is 0.9 to 1.1, a plurality of offset values obtained by the offset detection means are linearly approximated and obtained. The magnetic disk device according to claim 1, wherein the offset value is calculated based on the value.