JP2002334498A - Servo pattern writing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a servo pattern writing device in which the center of the servo pattern written into a magnetic disk medium and the center of the magnetic disk medium are matched before the magnetic disk medium is loaded on the magnetic disk device. SOLUTION: The servo pattern writing device for writing the servo pattern in the magnetic disk medium 1 before the disk medium 1 is loaded on the magnetic disk device is provided with centering pins 8a-8c which radially project from the side surface of a spindle hub 4, abut on an inner peripheral surface of a medium hole 1-1 of the magnetic disk medium 1, and carry out centering by the air pressure, etc., supplied from a fluid channel 4b in the spindle hub 4 which supports the magnetic disk medium 1. By centering the medium hole 1-1 of the magnetic disk medium 1 on the rotation center of the spindle hub 4, the magnetic disk medium 1 is supported in the state where there is no eccentricity to the rotation center of the spindle hub 4 regardless of a bore tolerance of the hole 1-1 of the medium 1, and servo pattern writing is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo pattern writing technique, and more particularly to a technique effective when applied to a servo pattern writing step for writing a servo pattern on a magnetic disk medium before being incorporated into a product device. It is.

[0002]

2. Description of the Related Art Conventionally, servo information for positioning a head on a track of a disk medium is written on the disk medium (Servo Track Writer: S).
TW) is performed in a state where the disk medium is completely incorporated into the magnetic disk device. In this case, due to the vibration of the spindle and the head actuator at the time of writing, a vibration component overlaps the track of the servo track in the disk radial direction. State. For this reason, as a method for writing servo information with less error, a high-precision spindle motor is used in a single-plate state before being incorporated into a magnetic disk device on a magnetic disk medium, and the servo information is written in a state where vibration of a head actuator is suppressed. Japanese Patent Application Laid-Open No. 9-320002 discloses a method of writing servo information and incorporating it into a spindle of a magnetic disk device after writing servo information. As a method of recording a servo pattern before assembling it in a magnetic disk device, see Japanese Patent Application Laid-Open No. H08-07753.
There is also a method of recording a magnetic film with irregularities as disclosed in Japanese Patent Application Laid-Open No. 9-209.

[0003]

In the case of a manufacturing method in which servo information is recorded on a disk medium in a single-plate state, and after completion, the information is incorporated into a spindle of a magnetic disk drive, the rotation center of the disk medium when writing the servo information is required. It is necessary to make the rotation center coincide with the rotation center when assembling the device as much as possible.

However, in the method disclosed in Japanese Patent Application Laid-Open No. 9-320002, the contact surface between the spacer and the spindle hub is tapered, and the spacer is removed to secure a gap between the disk medium and the spindle hub. Although it is possible, the outer diameter of the spacer must match the inner diameter of the disk medium in order to position the disk medium at a position without eccentricity with respect to the rotation center of the spindle hub. Realization is difficult due to processing accuracy. Further, even if the outer diameter of the spacer and the inner diameter of the disk medium are made to coincide with each other, there is a technical problem that the position of the disk medium is shifted because the spacer is in contact with the disk medium when the spacer is removed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a magnetic disk drive in which servo information is recorded on a magnetic disk medium before being incorporated into the device and which is incorporated into the magnetic disk device after the recording is completed. It is an object of the present invention to provide a servo pattern writing technique capable of making the rotation center of a medium coincide with the rotation center when the medium is incorporated into a magnetic disk device.

Another object of the present invention is to improve the positioning accuracy in a magnetic disk device by using a servo pattern in a magnetic disk device manufacturing technique in which a servo pattern is written to a magnetic disk medium before being incorporated into the magnetic disk device. It is an object of the present invention to provide a servo pattern writing technique capable of performing the above.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method of manufacturing a magnetic disk drive, comprising the steps of writing a servo pattern on a magnetic disk medium and incorporating the magnetic disk medium with the servo pattern written into the magnetic disk drive. A servo pattern writing apparatus used to write a servo pattern on a magnetic disk medium, comprising: a spindle hub that is inserted into a medium hole opened in the center of the magnetic disk medium and drives the magnetic disk medium to rotate; and a rotating magnetic disk medium. And a centering mechanism provided on the spindle hub for centering the magnetic disk medium on the spindle hub.

More specifically, three or more centering pins for performing centering by pressing the inner end of the magnetic disk medium against a spindle hub for laminating a plurality of magnetic disk media and spacers are provided at the center of rotation of the spindle hub. By centering the magnetic disk medium, the magnetic disk medium can be mounted without eccentricity with respect to the rotation center of the spindle hub regardless of the inner diameter tolerance of the magnetic disk medium.

Further, the present invention is used for a method of manufacturing a magnetic disk drive, which includes a step of writing a servo pattern on a magnetic disk medium and a step of incorporating the magnetic disk medium with the servo pattern written into the magnetic disk drive. A servo pattern writing apparatus for writing the servo pattern on the magnetic disk medium, wherein the servo pattern writing apparatus is inserted into a medium hole and a spacer hole opened at the center of each of the magnetic disk medium and the spacer, and drives the magnetic disk medium to rotate. A spindle hub having an eccentric rotation center; servo pattern writing means for performing an operation of writing the servo pattern on the rotating magnetic disk medium; and an eccentric rotation center and a center of the spindle hub provided on the spindle hub. Diameter on the opposite side across the shaft Is obtained by a projection capable arranged positioning block, a structure including the.

More specifically, the spindle hub is mounted at a position eccentric from the rotation center of the spindle motor determined from the inner diameter tolerance of the magnetic disk medium and the mounting accuracy of the magnetic disk medium, and first, from the side of the eccentric rotation center. After the magnetic disk medium and the spacer are biased, the protrusion amount of the positioning block is set to a contact position with respect to the inner peripheral surface of the spacer hole of the biased spacer, and then the magnetic disk medium is pressed against the positioning block in the opposite direction. By shifting the magnetic disk medium to the contact position, the mounting accuracy of the magnetic disk medium to the spindle hub is suppressed within a predetermined range, and the magnetic disk medium is assembled.

[0011]

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

FIG. 1 is a conceptual diagram showing an example of the configuration of a servo pattern writing device according to an embodiment of the present invention. The servo pattern writing apparatus according to the present embodiment includes a centering mechanism for a magnetic disk medium as described below, and is used for a servo pattern writing apparatus used in a step of writing servo information before assembling the magnetic disk medium into the magnetic disk apparatus. This is an example.

As shown in FIG. 1, a servo pattern writing apparatus according to the present embodiment comprises a plurality of magnetic disk media 1, a head actuator mechanism 2 for reading and writing servo patterns on the magnetic disk media 1, a magnetic disk medium 1
A spindle motor 3 for rotating the spindle motor, a spindle hub 4 fixed to the spindle motor 3 and capable of attaching and detaching the magnetic disk medium 1 and the spacer 7, and a clamp 5 for fixing the magnetic disk medium 1 and the spacer 7 to the spindle hub 4. And a general control unit 6 for generating a servo pattern to be written on the magnetic disk medium 1 and controlling the spindle motor 3.

The head actuator mechanism 2 supports a plurality of heads 2a for writing a servo pattern on each recording surface of the magnetic disk medium 1, a plurality of arms 2b for supporting the head 2a, and a base end of the arm 2b. And an actuator 2c for controlling the positioning of the head 2a.

The servo pattern is written on the magnetic disk medium 1 by the servo pattern writing device as in the present embodiment, and then incorporated into the magnetic disk device.

Here, when assembling the magnetic disk medium 1 into the hub of the magnetic disk device, the inner diameter of the magnetic disk medium 1 and the outer diameter of the hub of the magnetic disk device are in contact at some region on the circumference. When the hub of the magnetic disk device is deformed due to heating / cooling or shock input, a force generated at a contact portion between the hub of the magnetic disk device and the magnetic disk medium 1 causes non-isotropic deformation of the magnetic disk medium 1. This may cause the positioning accuracy to deteriorate. Therefore, when assembling the magnetic disk medium 1 into the hub of the magnetic disk device, the magnetic disk medium 1 is centered with respect to the rotation center of the hub of the magnetic disk device, and disk clamping is performed.

Therefore, in the servo pattern writing apparatus, it is necessary to suppress the occurrence of eccentricity after the magnetic disk device is assembled by writing the servo pattern while the magnetic disk medium 1 is centered.

FIGS. 2A and 2B are a sectional view and a top view showing one embodiment of the configuration of a spindle hub having a centering mechanism according to the present embodiment.

As shown in FIG. 2, a plurality of centering pins 8a to 8c for centering the magnetic disk medium 1 are provided inside the spindle hub 4.
Are provided so as to be radially displaceable in the radial direction so as to be able to protrude from the outer peripheral surface. The storage cavity 4a of the spindle hub 4 in which each of the centering pins 8a to 8c is stored,
The inner end side communicates with a fluid passage 4b formed in the axial direction of the spindle hub 4.

Then, by supplying air to the fluid passage 4b, the outer ends of the centering pins 8a to 8b protrude, and the centering pins 8a to 8b protrude from the inner peripheral surface of the medium hole 1-1 through which the spindle hub 4 of the magnetic disk medium 1 is inserted. By pressing in contact, the magnetic disk medium 1 before clamping can be moved to a radially uniform position without eccentricity with respect to the rotation center of the spindle hub 4.

Here, as shown in the top view of FIG. 2B, the centering pins 8a to 8c are installed at three or more radially uniform arrangement angles, thereby enabling a stable centering operation. After the centering operation is completed, the magnetic disk medium 1 is fixed by the clamp 5 and then the fluid path 4b
And only the centering pins 8a to 8c can be drawn into the storage cavity 4a in a direction opposite to that during the centering operation. Thereby, when the spindle motor 3 is rotated, the centering pins 8a to 8c can be prevented from contacting the inner peripheral surface of the medium hole 1-1 of the magnetic disk medium 1, and vibration and distortion of the magnetic disk medium 1 in the outer peripheral direction can be prevented. Can be suppressed.

FIG. 3 is a sectional view showing a modification of the configuration of the spindle hub having the centering mechanism according to the present embodiment. When a plurality of magnetic disk media 1a to 1e are inserted into the spindle hub 4, the centering pins 8a are arranged at intervals of the arrangement pitch of the magnetic disk media 1 in the axial direction of the spindle hub 4 for each magnetic disk medium 1. ~
8n are provided radially at three or more locations, and air is supplied from the fluid passage 4b to the storage cavity 4a inside the spindle hub 4 so that all the magnetic disk media 1 are simultaneously adjusted to the inner diameter tolerance of each magnetic disk medium 1. Centering. Here, the fluid passage 4b inside the spindle hub 4 may be divided for each centering pin 8a to 8n corresponding to each magnetic disk medium 1 as shown in FIG.

In each of the fluid passages 4b divided as shown in FIG. 4, centering pin control valves 9a to 9e are provided at positions respectively in contact with the inner ends of the sets of centering pins 8a to 8n. The centering pin control valves 9a to 9e are pushed up when air is supplied to the inside of the centering pin 8b.
The position of the centering pins 8a to 8n may be controlled so as to perform centering. When a centering pin control valve is used, a plurality of supply ports for air supplied to the fluid passage 4b may be provided for each centering pin control valve. Here, the shapes of the centering pin control valves 9a to 9e are centering pins 8a to 8e corresponding to the respective magnetic disk media 1.
In order to make the amount of movement of n equal, it is desirable to use a spherical centering pin control valve 9-1 as illustrated in FIG. 4 or a conical centering pin control valve 9-1 as illustrated in FIG.

When centering pin control valves 9a to 9e are used, both ends are hemispherical as shown in FIG. 4 or FIG. 6 ( a) a spherical centering pin 8-1 as shown in FIG. 6A, or a spherical body 8-2a on the centering pin control valves 9a to 9e side and a cylinder 8-2b on the magnetic disk medium 1 side as shown in FIG. It is preferable that the centering pin 8-2 is formed as follows. When the centering pin control valves 9a to 9e are not used, it is preferable that the centering pin is spherical, cylindrical, or a cylinder whose both ends are hemispherical.

When a plurality of magnetic disk media 1 are inserted, the position of the centering pin 8 is shifted due to the stacking tolerance, and if the centering pin 8 comes into contact with the spacer 7, the inner diameter of the spacer hole 7-1 of the spacer 7 is changed. Is larger than the inner diameter of the medium hole 1-1 of the magnetic disk medium 1, the centering method of the present embodiment can be applied.

At this time, the shape of the outer end of the centering pin 8 in contact with the inner peripheral surface of the medium hole 1-1 of the magnetic disk medium 1 is such that the surface of the centering pin 8 in contact with the inner peripheral end of the magnetic disk medium 1 is
It is necessary to have a flat shape so as not to interfere with the adjacent magnetic disk medium 1 and the spacer 7.

The centering pin control valves 9a to 9e
When using the centering pin control valves 9a to 9e
Is set so that air is sucked when the spindle motor 3 rotates and the centering pins 8a to 8n are drawn into the spindle hub 4 so as not to contact the inner peripheral surface of the medium hole 1-1 of the magnetic disk medium 1. Needs to be smaller than the diameter of the fluid passage 4b.

FIGS. 7A and 7B are a sectional view and a top view showing another modified example of the configuration of the spindle hub having the centering mechanism according to the present embodiment.

As shown in FIG. 7, in this modification, centering pins 8 corresponding to the respective magnetic disk media 1a-1b are provided.
a to 8f are radially arranged at equal intervals in the circumferential direction, and when a plurality of magnetic disk media 1a to 1b are inserted into the spindle hub 4, as shown in FIG. A set of centering pins 8a to 8f corresponding to 1b is circumferentially shifted for each magnetic disk medium.
Thereby, the spacers 7a can be arranged closer to each other without concern about interference between the sets of centering pins 8a to 8f in the axial direction of the spindle hub 4.
7b to be thinned, and a plurality of magnetic disk media 1a-1b
Are densely stacked, the required height of the spindle hub 4 is reduced, so that the effect of the spindle hub 4 falling down in the axial direction can be reduced.

In the above-described embodiment, the magnetic disk medium 1 is shifted before performing the centering operation.
Thereafter, a centering operation may be performed.

According to the above-described embodiment, the centering is performed by contacting the inner peripheral surface of the medium hole 1-1 of the magnetic disk medium 1 with the spindle hub 4 on which the plurality of magnetic disk media 1 and the spacers 7 are stacked. A plurality of centering pins 8a to 8n are radially provided at three or more locations to center the magnetic disk medium 1 at the center of rotation of the spindle hub 4 so that the inner diameter tolerance of the medium hole 1-1 of the magnetic disk medium 1 is small or large. Irrespective of the above, the magnetic disk medium 1 is supported without any eccentricity with respect to the rotation center of the spindle hub 4, and the servo pattern can be written.

As a result, when the magnetic disk medium 1 is incorporated in the magnetic disk device in a later step, the medium hole 1-1 of the magnetic disk medium 1 is centered at the rotation center of the spindle hub of the magnetic disk device. Thus, the center of rotation of the spindle hub of the magnetic disk device exactly matches the center of the track of the servo pattern, and it is possible to prevent various troubles when the centers of the two do not match.

FIGS. 8A and 8B show the configuration of a servo pattern writing apparatus according to another embodiment of the present invention.
FIG. 3 is a conceptual diagram showing an example of a method of aligning a magnetic disk medium using the same in a process order.

As shown in FIG. 8, in the positioning method according to the present embodiment, the spindle hub 4 is moved from the rotation center 3a of the spindle motor 3 to the inner diameter tolerance of the magnetic disk medium 1 and the mounting accuracy of the magnetic disk medium 1 (required eccentricity). ), A position shifted by an eccentricity 13 determined from
m). The spindle hub 4 has a central shaft 4
A movable positioning block 12 is provided on a side surface opposite to the rotation center 3a via z. Although not particularly shown, the positioning block 12 is displaced radially outward from the side surface of the spindle hub 4 and displaced in the opposite direction drawn into the spindle hub 4 by the same air pressure as the above-mentioned centering pin. Has become possible.

The positioning amount of the positioning block 12 (projection amount from the side of the spindle hub 4) is
Inner diameter 11 of spacer hole 7-1 determined from mounting position of
Stipulated.

Since the spacer 7 is used repeatedly, only a small number of the spacers 7 need to be manufactured, and the dimensional tolerance of the inner diameter 11 of the spacer hole 7-1 is reduced (for example, +0 to 20 μm).
Is possible. On the other hand, the magnetic disk medium 1 is mass-produced, and it is difficult to reduce the dimensional tolerance of the inner diameter 10 of the medium hole 1-1 due to cost and other restrictions. It is larger than the tolerance (for example, +0 to 50 μm).

Hereinafter, an example of a centering method by the servo pattern writing apparatus according to the present embodiment will be described.

First, as exemplified in FIG. 8A, the magnetic disk medium 1 and the spacer 7 inserted into the spindle hub 4 are placed on a line connecting the eccentric rotation center 3a and the center axis 4z of the spindle hub 4. Then, the medium is offset in the direction (direction A) from the rotation center 3a toward the central axis 4z, and the medium hole 1-
1 and the inner peripheral surface of the spacer hole 7-1 are connected to the spindle hub 4
, And in this state, the positioning block 12 on the opposite side is protruded to abut on the inner peripheral surface of the spacer hole 7-1. FIG. 8A shows the state up to this point.

Thereafter, as illustrated in FIG.
The magnetic disk medium 1 is offset in the direction (direction B) opposite to the above-described direction A, and the medium hole 1-1 on the opposite side to the above-described offset is shifted.
1 is brought into contact with the positioning block 12 which is stopped by contacting the inner peripheral surface of the spacer hole 7-1. At this time, since the tolerance of the inner diameter 10 of the magnetic disk medium 1 is larger than the tolerance of the inner diameter 11 of the spacer 7, the center of the magnetic disk medium 1 is aligned with the center axis 4 z of the spindle hub 4 in this direction B offset. And stops at a position closer to the eccentric rotation center 3a. Then, the positioning block 12
To the original position inside the spindle hub 4.

As a result, the inner diameter of the magnetic disk medium 10
The gap between the spindle hub 4 and the positioning block 12 (the amount of protrusion from the side surface of the spindle hub 4, ie, the dimensional tolerance of the inner diameter 11 of the spacer hole 7-1) is the minimum, and the maximum is the medium hole of the magnetic disk medium 1. A value obtained by subtracting the shift amount (the dimensional tolerance of the inner diameter 11 of the spacer hole 7-1) from the dimensional tolerance of the inner diameter 10 of 1-1 is obtained, and the mounting accuracy of the magnetic disk medium 1 is kept within a predetermined range. It becomes possible to install the medium 1.

As described above, according to the present embodiment, the spindle hub 4 is eccentric from the rotation center 3a of the spindle motor 3 determined from the dimensional tolerance of the inner diameter 10 of the magnetic disk medium 1 and the mounting accuracy of the magnetic disk medium 1. And the spindle hub 4 is provided with a positioning block 12 for defining the stop position of the return biasing operation of the magnetic disk medium 1 by the offset eccentricity of the spacer 7 so that the spindle hub 4 moves in the opposite direction. By performing the two offset operations, the mounting accuracy of the magnetic disk medium 1 to the spindle hub 4 is kept within a predetermined range, and the inner diameter 1 of the magnetic disk medium 1 is reduced.
It is possible to support the center of 0 as coincident with the rotation center 3a of the spindle motor 3 as possible.

As a result, when the magnetic disk medium 1 is incorporated in the magnetic disk device in a later step, the medium hole 1-1 of the magnetic disk medium 1 is centered on the rotation center of the spindle hub of the magnetic disk device. Thus, the center of rotation of the spindle hub of the magnetic disk device exactly matches the center of the track of the servo pattern, and it is possible to prevent various troubles when the centers of the two do not match.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments and can be variously modified without departing from the gist thereof. Needless to say, there is.

[0044]

According to the present invention, in a method of manufacturing a magnetic disk device for recording servo information on a magnetic disk medium before being incorporated in the device and after completing the recording, a method for writing servo information is described. The rotation center of the magnetic disk medium and the rotation center at the time of assembling into the magnetic disk device can be matched as much as possible.
The effect is obtained.

According to the present invention, there is provided a magnetic disk drive manufacturing technique in which a servo pattern is written to a magnetic disk medium before being incorporated into the magnetic disk drive.
The effect that the positioning accuracy in the magnetic disk device by the servo pattern can be improved can be obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of a configuration of a servo pattern writing device according to an embodiment of the present invention.

FIGS. 2A and 2B are a cross-sectional view and a top view showing an embodiment of the configuration of a spindle hub having a centering mechanism according to an embodiment of the present invention.

FIG. 3 is a sectional view showing a modification of the configuration of a spindle hub having a centering mechanism according to an embodiment of the present invention.

FIG. 4 is a sectional view showing still another modification of the configuration of the spindle hub having the centering mechanism according to the embodiment of the present invention.

FIG. 5 is a sectional view showing still another modification of the configuration of the spindle hub having the centering mechanism according to the embodiment of the present invention.

FIGS. 6A and 6B are cross-sectional views showing still another modified example of the configuration of a spindle hub having a centering mechanism according to an embodiment of the present invention.

FIGS. 7A and 7B are a cross-sectional view and a top view showing another modified example of the configuration of a spindle hub having a centering mechanism according to an embodiment of the present invention.

FIGS. 8A and 8B are conceptual diagrams showing an example of a configuration of a servo pattern writing apparatus according to another embodiment of the present invention and a method of aligning a magnetic disk medium using the apparatus in the order of steps. It is.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic disk medium, 1a-1e ... Magnetic disk medium, 1-1 ... Medium hole, 2 ... Head actuator mechanism part, 2a ... Head, 2b ... Arm, 2c ... Actuator, 3 ... Spindle motor, 3a ... Rotation center, 4. Spindle hub 4a Storage cavity 4b Fluid passage 4z
... Central axis, 5 ... Clamp, 6 ... Overall control unit, 7 ... Spacer, 7a-7b ... Spacer, 7-1 ... Spacer hole, 8 ...
Centering pins, 8a to 8n: Centering pins, 8
-1: Centering pin, 8-2: Centering pin,
8-2a: sphere, 8-2b: cylinder, 9-1: centering pin control valve, 9a to 9e: centering pin control valve,
10: inner diameter of magnetic disk medium, 11: inner diameter of spacer, 12: positioning block, 13: eccentricity

Continuing from the front page (72) Inventor Shizuo Yamazaki 2880 Kozu, Odawara-shi, Kanagawa Pref.Hitachi, Ltd.Storage Division (72) Inventor Yoichi Kusaya 781 Nakai-cho, Nakaicho, Ashigara-gun, Kanagawa Prefecture F-term in Hitachi Computer Equipment Co., Ltd. (Reference) 5D096 WW02 5D109 DA14 DA18 5D138 UA20 UA22 UA24

Claims (5)

[Claims] 1. A method for manufacturing a magnetic disk drive, comprising: writing a servo pattern on a magnetic disk medium; and incorporating the magnetic disk medium on which the servo pattern is written into a magnetic disk drive. A servo pattern writing apparatus for writing the servo pattern on a medium, comprising: a spindle hub that is inserted into a medium hole opened in a central portion of the magnetic disk medium and drives the magnetic disk medium to rotate; A servo pattern writing device, comprising: servo pattern writing means for writing the servo pattern; and a centering mechanism provided on the spindle hub for centering the magnetic disk medium with respect to the spindle hub. 2. The servo pattern writing device according to claim 1, wherein the centering mechanism is radially displaceable inside the spindle hub at a position facing an inner peripheral surface of the medium hole of the magnetic disk medium. A plurality of radially arranged centering pins, and a fluid passage communicating with an inner end of the storage cavity of the centering pin, wherein the centering pin is protruded by pressurization of the fluid passage to allow the centering pin to protrude. A first configuration for performing an operation of performing the centering by making contact with a peripheral surface, and an operation of pulling the centering pin into the spindle hub by suction to the fluid passage; the medium hole of the magnetic disk medium; A plurality of centers radially displaceable radially inside the spindle hub at positions facing the inner peripheral surface of the spindle hub; A fluid passage communicating with an inner end of the centering pin storage cavity, and a pin drive piece provided in the fluid passage in contact with the inner end of the centering pin, wherein the fluid An operation of performing the centering by displacing the pin driving piece in the axial direction of the spindle hub by pressurizing the passage, projecting the centering pin and making contact with the inner peripheral surface of the medium hole, and the fluid passage A second configuration for performing an operation of pulling the centering pin into the spindle hub by suction to the spindle hub. 3. The servo pattern writing device according to claim 2, wherein a plurality of the magnetic disk media are stacked on the spindle hub in the axial direction, and correspond to the media holes of each of the magnetic disk media. A plurality of sets of the centering pins arranged at the set positions are arranged so as to be shifted from each other in a circumferential direction of the spindle hub. 4. A method for manufacturing a magnetic disk device, comprising: writing a servo pattern on a magnetic disk medium; and incorporating the magnetic disk medium on which the servo pattern is written into a magnetic disk device. A servo pattern writing apparatus for writing the servo pattern on a medium, wherein the medium is inserted into a medium hole and a spacer hole opened at a central portion of each of the magnetic disk medium and the spacer, and drives the magnetic disk medium to rotate, and An eccentric spindle hub; servo pattern writing means for performing an operation of writing the servo pattern on the rotating magnetic disk medium; and a eccentric rotation center and a central axis of the spindle hub provided on the spindle hub. Radially projectable on opposite side A servo pattern writing device, comprising: a positioning block arranged. 5. The servo pattern writing device according to claim 4, wherein the servo pattern writing device is provided at a central portion of the spacer according to an inner diameter tolerance of the magnetic disk medium and an eccentric amount of the spindle hub determined from a mounting accuracy of the magnetic disk medium. The inner diameter of the spacer is determined so that the manufacturing tolerance of the diameter of the spacer hole is smaller than the manufacturing tolerance of the diameter of the spindle hub, and the magnetic disk medium incorporated in the spindle hub is positioned in the positioning block. A step of offsetting the inner periphery of the medium hole and the spacer hole to the outer periphery of the spindle hub by offsetting from a direction opposite to the disposition position; and Projecting; and, from the direction of the arrangement position of the positioning block, the inner circumference of the medium hole is positioned at the position. A step of biasing the magnetic disk medium until the magnetic disk medium comes into contact with the block, and a step of retracting the positioning block into the spindle hub. A servo pattern writing device for performing centering.