JP2000268533A - Method and device for centering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make performable accurate centering by disposing plural groups of actuator pairs in positions opposite to respective disks, and setting timings butting the butting members of the actuators against the respective disks respectively different. SOLUTION: The distance from the tips of the rods 12B3 and 12D3 of actuators 10B3 and 10D3 to the peripheral edge of a disk 163 is set d1, and distances from the tips of rods 12B2, 12D2, 12B1 and 12D1 to the peripheral edges of disks 162 and 161 are set d1+dx and d1+2.dx. Thus, when the rods 12 are simultaneously started to be driven, for example, the order of rods 12B1 to 12B3 of butting against the disks 161 to 163 becomes the order of rods 12B3, 12B2 and 12B1, there is no variance in this order, no distortion occurs in a hub 14, and centering with good reproducibility can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centering method and an apparatus therefor, and more particularly to a centering method and an apparatus suitable for centering and attaching a disk of a magnetic disk drive to a shaft.

[0002]

2. Description of the Related Art Conventionally, servo track information is written on a disk which is a recording medium of a magnetic disk device. Normally, in a state where the magnetic disk device is assembled and completed, the head in the device is positioned by a length measuring device to write servo track information. However, this writing operation has the following problems.

First, since the servo track information is written using the head in the magnetic disk device, the accuracy of the servo track information cannot be improved. Therefore, it is difficult to cope with high density. Second, since all the heads of the magnetic disk drive are used to write the servo track information on all the disks, the operation takes time. Therefore, the cost for writing servo track information increases with mass production of disks.

In order to solve the first problem, there has been proposed a system in which servo track information is written on one disk using a dedicated servo track information writing device, and this disk is incorporated in a magnetic disk device. . In this method, since the servo track information is written on a large number of disks, each one of which is mounted on each magnetic disk device, the above-mentioned second problem is also solved at the same time.

However, in the conventional method, the eccentricity when the disk is mounted on the hub (shaft) of the servo track information writing device and the eccentricity when the disk on which the servo track information is written is mounted on the hub of the magnetic disk device. It becomes a problem. Generally, a gap of about 50 to 100 μm is provided between the hub and the center circular opening of the disc so that the fitting operation when the disc is mounted on the hub can be easily performed. If there is no eccentricity, there is an equal spacing between the hub and the disk opening. If eccentricity occurs in either the case where the disk is mounted on the writing device and the servo track information is written or the case where the disk is mounted on the magnetic disk device, when the disk is mounted on the magnetic disk device, the servo track information is not read. The written locus becomes eccentric with respect to the shaft of the disk device. For this reason, it is necessary to operate the head for writing / reading information eccentrically with respect to the shaft, which deteriorates the characteristics. Also, if the disk is installed eccentrically with respect to the shaft, when the shaft is rotated,
Vibration due to mounting eccentricity occurs, and the characteristics deteriorate.

In order to reduce the eccentricity, the above gap may be reduced. However, when the gap is reduced, the accuracy required for the parts is increased, which not only increases the cost but also causes a problem that the fitting operation becomes difficult.
This problem is not unique to the magnetic disk drive, but also occurs when the disk is mounted on a shaft and needs to be centered.

In order to mount the disk on the shaft without causing such mounting eccentricity, the present applicant has proposed the invention described in Japanese Patent Application No. Hei 10-187559. In the centering method proposed in this proposal, an actuator rod is applied to a disk, the state is detected, position information at that time is read, and centering is performed based on the position information. Further, by making the actuator unit multilayer, it is possible to center the multilayer disk.

[0008]

The case where the centering of a multilayer disc is performed by the above-mentioned conventional centering method will be considered. 1 and 2 show side views of an apparatus for centering three disks. By both sides of the actuator _{1B 1 ~1B 3, 1D 1 ~1D} 3 and rod of the front and rear actuators (not shown) in each layer, centering the disc 3 ₁ to 3 _3.

[0009] When centering the disc, the actuator 1B ₁ ~1B ₃ to the disk 3 ₁ to 3 _3, 1D
Abutted against the ₁ through 1d ₃ of the rod _{2B 1 ~2B 3, 2D 1 ~2D} 3, will determine the position to be centered based on the position where the right side of the rod 2B ₁ ~2B in particular trilayer Pay attention to the end of ₃ . In the case shown in FIG. 1, when abutting simultaneously the rod 2B ₁ ～2B ₃ to the disk 3 ₁ to 3 _3, the state in which the rod 2B _1, 2B ₂ is not abutted against the disc 3 _1, 3 _2, that is, the hub 4
Rod 2B ₃ of the third layer comes into contact with the disc 3 ₃ in a state where the undeflected.

On the other hand, in the case shown in FIG.
Do 2B₁, 2B_TwoRod 2B _ThreeIs against the disk
Since the butting starts at the same time when approaching,
Disk 3₁, 3_TwoRod 2B₁, 2B_TwoIs disk 3
₁, 3_TwoThe hub 4 is pressed against
The rod 2B of the third layer is bent in the direction of the arrow._ThreeBut di
Disc 3_ThreeHit. Thus, butting of the rod
The timing of the hub 4 changes
And reduce the centering accuracy due to the variation
Problem.

The present invention has been made in view of the above points, and it is possible to prevent a plurality of abutting members from abutting on each disk at the same time, and perform accurate centering without variation in deflection of a hub at the time of abutting. It is an object of the present invention to provide a centering method and a device therefor.

[0012]

According to a first aspect of the present invention, there is provided a pair of actuators having abutment members arranged at positions facing each other with respect to a plurality of disks inserted through a hub and abutting against the outer periphery of the disks. Has a plurality of sets,
In the centering device for centering each of the plurality of disks, the timing at which the abutting member of the actuator abuts each of the plurality of disks is made different.

As described above, since the timing at which the abutment member of the actuator abuts on each of the plurality of disks is made different, it is possible to prevent the plurality of abutment members from abutting on each disk at the same time, and to prevent the hub from being abutted when the abutment members abut. Accurate centering can be performed without variation in deflection. The invention according to claim 2 has a plurality of pairs of actuators having abutment members disposed at positions facing each other with respect to each of the plurality of disks inserted through the hub and abutting against the outer periphery of the disks, and In the centering method of centering each disk,
The timing at which the striking member of the actuator strikes each of the plurality of disks is different for each disk.

As described above, the timing at which the abutting member of the actuator abuts against each of the plurality of disks is made different, so that a plurality of abutting members are prevented from abutting on each disk at the same time. Accurate centering can be performed without variation in deflection. According to a third aspect of the present invention, in the centering method according to the second aspect, the separation distance of the abutting member of the actuator with respect to each of the plurality of disks at the start of centering is different for each disk.

As described above, since the separation distance of the abutting member of the actuator for each of the plurality of disks is made different for each disk, even if the abutment for centering the plurality of disks is started simultaneously, the abutment of each actuator is started. The timing at which the member strikes each disk is different and different. According to a fourth aspect of the present invention, in the centering method according to the third aspect, a separation distance of the abutting member of the actuator with respect to each of the plurality of disks at the start of centering is based on the abutting member of each actuator. It is determined based on the detection value at the time of hitting the disk.

As described above, the separation distance of the abutting member with respect to each of the plurality of disks is determined based on the detection value when the abutting member of each actuator abuts against the reference disk. , The distance between the abutting member of the actuator and the distance can be accurately determined. According to a fifth aspect of the present invention, in the centering method according to the second aspect, a position at which the abutting member of the actuator abuts each of the plurality of disks at the time of centering is shifted by a specified amount from the centering position.

As described above, the centering center can be corrected by shifting the position at which the abutment member abuts against each of the plurality of disks by a specified amount from the centering position. According to a sixth aspect of the present invention, in the centering method according to the fifth aspect, when the actuators are arranged with a phase difference according to each of the plurality of disks, the specified amount is determined based on the phase difference. decide.

As described above, when the actuator is arranged with a phase difference according to each of the plurality of disks, the actuator is arranged with a phase difference to determine the specified amount based on the phase difference. Can respond to.

[0019]

3 and 4 are a plan view and a side view of an embodiment of a centering device according to the present invention. In FIG. 3, the centering device has four disks per disk.
Actuators 10A, 10B, 10C, and 10D.
D has rods 12A, 12B, 12 as abutting members.
C and 12D are provided. The rods 12A and 12C oppose each other with the hub 14 and the disc 16 interposed therebetween,
B and 12D are similarly opposed. Rods 12A and 12
C is movable in the y-axis direction, and rods 12B and 12D
Is movable in the x-axis direction orthogonal to the y-axis. Rod 1
The tips of 2 </ b> A to 12 </ b> D can contact the outer periphery of the disk 16. By using these four rods 12A to 12D, the centering position of the disk 16 with respect to the hub 14 is detected, and the centering is executed. The hub 14 is set on a shaft of the centering device.

In FIG. 4, the hub 14 is fitted through the central circular openings of the _three disks 16 _{1 to} 16 ₃ . The actuator 10B _1, 10D ₁ is provided corresponding to the disk 16 of the _first layer, the actuator 10B ₂ corresponding to the disk 16 of the _second layer, 10D ₂
Is provided, the actuator 10B ₃ corresponding to the disk 16 ₃ of the third layer, 10D ₃ are al provided.

In the present invention, the disks 16 _{1 to} 16
For the same time line ₃ of centering, during the centering start distance from the tip of the actuator 10B _1, the rod 12B ₁ of 10D _1, 12D ₁ of the first layer to the peripheral edge of the disk 16 ₁ is a predetermined value d1, the second Rods 12B ₂ , 12D of actuators 10B ₂ , 10D _{2 in} layers
Distance from the _second distal end to the periphery of the disk 16 ₂ d
1 + dx, and the third-layer actuator 10B ₃ , 1
0D ₃ of the rod 12B _3, the distance from the tip of the 12D ₃ to the periphery of the disk 16 ₃ is a d1 + 2 · dx.

Here, the centering method will be described with reference to FIG. First, the rod 12 of the actuator 10A
A is moved in the positive direction of the y-axis and is pressed against the disk 16, and when it is hit at that time, the position Y1 of the actuator 10A on the rod 12A is obtained. Thereafter, the rod 12A of the actuator 10A is moved in the negative direction of the y-axis to temporarily separate from the disk 16, and the rod 12C of the actuator 10C is moved in the negative direction of the y-axis to hit the disk 16.

In this state, the rod 12A of the actuator 10A is moved in the positive direction of the y-axis and is pressed against the disk 16, so that the
The position Y2 of the rod A of A is obtained. Using the positions Y1 and Y2, a position Y3 =
(Y1 + Y2) / 2 is obtained, and the rod 12A of the actuator 10A is moved to that position. Thereafter, the actuator 10 is brought into contact with the disk 16 in this state.
The rod 12C of C is moved.

Next, the rod 12 of the actuator 10D
D is moved in the positive direction of the x-axis, pressed against the disk 16, and when it strikes at that time, the position X1 of the actuator 10D on the rod 12D is determined. Thereafter, the rod 12D of the actuator 10D is moved in the negative direction of the x-axis to temporarily separate from the disk 16, and then the rod 12B of the actuator 10B is moved in the negative direction of the x-axis and pressed against the disk 16.

In this state, the rod 12D of the actuator 10D is moved in the positive direction of the x-axis, pressed against the disk 16, and
The position X2 of the rod 12D of D is obtained. Using the positions X1 and X2, a position X3 =
(X1 + X2) / 2 is obtained, and the rod 12D of the actuator 10D is moved to that position. Thereafter, the actuator 10 is brought into contact with the disk 16 in this state.
The rod B of B is moved.

Thus, the centering is completed.
The above operation is performed simultaneously on all of the first, second and third layers. Before the centering is started, the rod of each actuator stands by at a position distant from the disk 16 to some extent. At this time, as shown in FIG. 4, each rod is set to be shifted by the distance dx for each layer. Therefore, when the drive start for simultaneously abutting the rod of the actuator of all layers, each layer of the rod (e.g., 12B ₁ to 12
The order in which B ₃ ) strikes the disk is as follows: the rods 12B ₃ in the _third layer, the rods 12B ₂ in the _second layer, and the rods 1 in the first layer.
2B ₁ order, this order does not vary,
At the time when the rod 12B ₂ of the second layer strikes, the rod 12B ₃ of the third layer has finished striking and does not press the disk 16 _3, and when the rod 12B ₁ of the first layer strikes, the rod 12B of the second layer has struck. _{Since the} disk ₂ does not press the disk 16 ₂ after the abutment, the hub 14 does not bend and the centering can be performed with good reproducibility.

The centering start position is determined by detecting the abutting position of each actuator with a reference disk before the centering is performed, and acquiring the position. Move to position. FIGS. 5A and 5B are diagrams for explaining the driving of the actuator and the abutment of the rod against the disk. FIG. 5A shows a state before the rod 12B abuts against the disk 16, and FIG. 5B shows a state where the rod 12B abuts against the disk 16 so that the center circular opening of the disk 16 is Shows a state in which it is in contact with.

Each actuator is connected to a computer 26,
The driving is controlled by a control board 28, a counter board 30, and a driver board 32. Computer 2
6 controls the control board 28 according to a program for realizing the operation described with reference to FIG.
The counter board 30 is provided with each actuator (1 in FIG. 5).
0B), an encoder pulse from an encoder built in the actuator 10B is detected, and the rotational position of the motor built in the actuator 10B, that is, the position of the rod 12B is detected. The encoder pulse is also used by the computer 26 to determine whether the rod 12B has come into contact with the disk 16.

The control board 28 drives the driver board 32 in response to a command from the computer 26.
The driver board 32 outputs a pulse signal to the motor in the actuator 10B to rotate the motor. For example, the computer 26 instructs the control board 28 to cause the actuator 10B to move the rod 12B in the positive x-axis direction. The control board 28
An appropriate nearest target position is set, and the driver board 32 is driven to drive the motor of the actuator 10B. As a result, the rod 12B starts moving in the positive direction of the x-axis.
Thereafter, the control board 28 continuously updates the latest target position.

The computer 26 monitors the latest target position output from the control board 28 to the driver device 32 and the current position of the rod 12B output from the counter board 30, and determines whether the difference between the two is within a predetermined range. Always judge. If it is less than the predetermined range, it indicates that the rod 12B is moving toward the nearest target position. The driver board 32 controls the actuator 12B according to an instruction from the control board 28. Further, it receives an encoder pulse from the actuator 12B and outputs it to the counter board 30. Counter board 3
0 counts the encoder pulses from the actuator 12B to detect the position of each rod 12B.

The actuator 12B includes a linear actuator and an encoder. The linear actuator has a motor and a linear guide mechanism. Rotational movement of the motor is converted to linear movement by the linear guide mechanism, and the rod 12
B moves linearly. The encoder detects the rotational position of the motor. Since the rotational motion of the motor and the linear motion of the rod 12B have a linear relationship, the rotational position of the motor indicates the position of the rod 12B (coordinates on the x-axis). The other actuators 12A to 12D have the same configuration.

Incidentally, the detection that the rod 12B has come into contact with the disk 16 is performed by detecting the nearest target position and the rod 12B.
Is compared with a predetermined threshold value, that is, the difference between the actual movement position, ie, the output count value of the encoder. While the rod 12B is being moved by driving, the difference between the sequentially updated latest target position and the output count value of the encoder is equal to or smaller than a predetermined value. On the other hand, when the rod stops, the nearest target position is sequentially updated, so that the above-mentioned difference increases sharply. Thus, for example, if the threshold is 1
The pulse is set to 00 pulses, and when the difference exceeds 100 pulses, it is determined that the rod has stopped. By stopping the driving of the motor of the actuator 10B when the stop state of the rod 12B is detected, it is possible to prevent the rod 12B from forcibly pressing the disk 16.

Next, the processing for determining the centering start position of the rod of each actuator will be described with reference to the flowchart of FIG. Before each actuator is actually centered, it strikes against each actuator using a reference disk. In FIG. 6, first, in step S10, 0 is set to a layer number I and a channel (Ch) number J for distinguishing each actuator, and initialization is performed. Next, the process proceeds to step S12 to obtain an approximate abutting position of the disk. Steps S13 to S15 explain step S12 in detail.

In step S13, the actuator of the I layer J channel (I = 0, J = 0 indicates the first layer actuator 10A, J = 1 indicates the actuator 10B, J =
2 is actuator 10C, J = 3 is actuator 1
(Corresponding to 0D) to drive the rod against the disk 16. Then, after obtaining the count value output by the encoder of the actuator at that time in step S14, the actuator is driven to retract the rod from the disk 16 in step S15.

Next, the process proceeds to step S18, where a centering start position is calculated from the obtained count value. Thereafter, in step S18, it is determined whether or not the value of J is less than the total number M of channels (M = 4 in FIG. 5). If J <M, the value of J is incremented by 1 in step S20, and step S20 is performed. Proceed to S12. By the way, at the time of J = 0,1,
Since the actuators 10A and 10B have just been butted, the centering start position calculated in step S16 is a meaningless value.
In step S16 when the actuators 10C and 10D are abutted at time 3, the correct centering start position shown in FIG. 4 (the distance d1 + 2 · d in the first layer).
x) is calculated.

On the other hand, if J.gtoreq.M, since the abutment of the actuator for one layer has been completed, the flow advances to step S22. In step S22, it is determined whether the value of I is less than the total number of layers N (N = 3 in FIG. 5). If I <N, the value of I is incremented by 1 in step S24, and The value is set to 0 and the process proceeds to step S12. Thereby, the butting operation of each actuator of the next layer is performed. In the second layer shown in FIG. 4, the separation distance d1 + dx is calculated as the centering start position, and in the third layer, the separation distance d1 is calculated as the centering start position.
Thereafter, when the abutting operation of all the actuators of all the layers is completed, I ≧ N is satisfied in step S22, and this processing ends.

As described above, the separation distance of the abutting member with respect to each of the plurality of disks is determined based on the detection value when the abutting member of each actuator abuts against the reference disk. , The distance between the abutting member of the actuator and the distance can be accurately determined. After the centering of the disk 16, when the disk 16 is fastened and fixed to the hub 14, a displacement may occur due to the fastening. In such a case, the disk 16 is centered in consideration of the offset for correcting the above-mentioned deviation. This will be described with reference to FIG. The position information to be centered is determined from the information obtained by the abutment of each of the actuators 10A to 10D, and the centering taking into account the offset is performed by changing the value by the amount by which the centering center is to be moved (correction amount). .

For example, although the disk 16 shown by the solid line in FIG. 7 is the accurate centering position by the abutment of the actuator, as shown by the two-dot line, the disk 16 is offset by the distance δ in the negative direction of the x-axis. If it is desired, the position of the rod 12B of the actuator 10B positioned at the final stage of centering is moved in the negative direction of the x-axis by a distance δ from the position where accurate centering is performed. If the other operations are executed in the same manner as the conventional centering procedure, centering in consideration of the offset can be performed.

The actuator of each layer is simply multiplied as it is.
When multiple layers are stacked, depending on the height of the actuator,
Therefore, the distance between the multi-layered disks is regulated, and the
There is a problem that impact cannot be achieved. Therefore,
As shown in FIG. 8, the third layer actuator 10A_Three,
10B_Three, 10C_Three, 10D_ThreeAgainst the second layer
10A_Two, 10B_Two, 10C _Two, 10D_TwoOne
It is shifted by a fixed angle phase difference θ. This allows
When viewed from the side, the actuators of the third and second layers are part
It will be in a partially overlapping state. In FIG. 8, the second
Layer actuator 10A_Two, 10B_Two, 10C_Two, 1
0D_TwoIn contrast, the first layer actuator 10A₁, 10
B₁, 10C₁, 10D ₁Also has a constant angle of phase difference -θ
By displacing them, the actuation of the third layer and the first layer
The waiters are completely overlapped.

In such a case, offset centering is performed in consideration of the phase difference θ of each layer. For example, when it is desired to center the disks 16 _{1 to} 16 ₃ of all layers offset by the distance δ in the angular direction of the x-axis similarly to FIG. 7, the actuators 10A ₂ and 10B ₂ which perform centering positioning of two layers are respectively provided. On the other hand, δ × cos θ,
The centering may be performed by moving extra by δ × sin θ.

The present invention is not limited to a magnetic disk device, but is also suitable for application to, for example, a magneto-optical disk device, and is not limited to the above embodiment.

[0042]

As described above, the first aspect of the present invention provides
The timing at which the striking member of the actuator strikes each of the plurality of disks is made different. in this way,
Since the timing at which the abutting member of the actuator abuts each of the plurality of disks is different, it is possible to prevent a plurality of abutting members from abutting on each disk at the same time. Centering can be performed.

According to a second aspect of the present invention, the timing at which the abutment member of the actuator abuts against a plurality of disks is different for each disk. As described above, since the timing at which the abutting member of the actuator abuts on each of the plurality of disks is made different, it is possible to prevent the plurality of abutting members from abutting on each disk at the same time, and the variation in the bending of the hub when the abutting members abut. Accurate centering can be performed without any trouble.

According to a third aspect of the present invention, the separation distance of the abutment member of the actuator with respect to each of the plurality of disks at the start of centering is different for each disk. As described above, since the separation distance of the abutting member of the actuator with respect to each of the plurality of disks is made different for each disk, the abutting members of each of the actuators have their respective abutting members even if the abutment for centering the plurality of disks is started simultaneously. The timing of hitting the disc is shifted and different.

According to a fourth aspect of the present invention, the distance between the abutting members of the actuators with respect to each of the plurality of disks at the start of centering is determined when the abutting members of the actuators abut against a reference disk. Is determined based on the detected value of In this manner, the separation distance of the abutting member with respect to each of the plurality of disks is determined based on the detection value when the abutting member of each actuator abuts against the reference disk, so that the actuator of each of the plurality of disks is The separation distance of the abutting member can be accurately determined.

According to a fifth aspect of the present invention, the positions at which the abutment members of the actuators abut against the plurality of disks during centering are shifted by a specified amount from the centering positions. In this manner, the centering center can be corrected by shifting the position at which the abutting member abuts each of the plurality of disks from the centering position by the specified amount.

According to a sixth aspect of the present invention, when the actuators are arranged with a phase difference corresponding to each of a plurality of disks, the designated amount is determined based on the phase difference. Thus, when the actuator is arranged with a phase difference according to each of the plurality of disks,
Since the specified amount is determined based on the phase difference, it is possible to cope with the fact that the actuators are arranged with a phase difference.

[Brief description of the drawings]

FIG. 1 is a side view of a conventional apparatus for centering three disks.

FIG. 2 is a side view of a conventional apparatus for centering three disks.

FIG. 3 is a plan view of one embodiment of the centering device of the present invention.

FIG. 4 is a side view of an embodiment of the centering device of the present invention.

FIG. 5 is a diagram for explaining driving of an actuator of the present invention and abutment of a rod against a disk.

FIG. 6 is a flowchart of a process for determining a centering start position of a rod of each actuator.

FIG. 7 is a diagram for explaining a method of performing centering in consideration of an offset according to the present invention.

FIG. 8 is a plan view of a centering device in which third-layer and second-layer actuators are arranged at a certain angle.

[Explanation of symbols]

10A, 10B, 10C, 10D, 10B ₁ , 10
_{D 1, 10B 2, 10D 2} , 10B 3, 10D 3 actuators 12A, 12B, 12C, 12D, 12B 1, 12
D ₁ , 12B ₂ , 12D ₂ , 12B ₃ , 12D ₃ rod 14 hub 16, 16 _{1 to} 16 ₃ disk 26 computer 28 control board 30 counter board 32 driver board

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Nakamura 4-1-1 Ueodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Takao Hirahara 4-chome, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture No. 1 Inside Fujitsu Limited

Claims (6)

[Claims] 1. A plurality of pairs of actuators having abutment members arranged at positions facing each other with respect to each of a plurality of disks inserted through a hub and abutting against the outer periphery of the disks, and centering each of the plurality of disks. A centering device, wherein the timing at which the abutment member of the actuator abuts each of the plurality of disks is different. 2. A plurality of pairs of actuators having abutment members arranged at positions facing each other with respect to each of the plurality of disks inserted through the hub and abutting against the outer periphery of the disks, and centering each of the plurality of disks. A centering method, wherein the timing at which the abutting member of the actuator abuts each of the plurality of disks is different for each disk. 3. The centering method according to claim 2, wherein the separation distance of the abutting member of the actuator with respect to each of the plurality of disks at the start of centering is different for each disk. 4. The centering method according to claim 3, wherein a distance between the abutment member of the actuator with respect to each of the plurality of disks at the start of centering is:
A centering method characterized in that it is determined based on a detection value obtained when an abutment member of each actuator abuts against a reference disk. 5. The centering method according to claim 2, wherein a position at which the abutment member of the actuator is brought into contact with each of the plurality of disks at the time of centering is shifted by a specified amount from the centering position. 6. The centering method according to claim 5, wherein when the actuators are arranged with a phase difference in accordance with each of the plurality of disks, determining the specified amount based on the phase difference. Characteristic centering method.