Magnetic disk drive and method for manufacturing the same

Abstract

This magnetic disk drive is provided with a plurality of magnetic disks 30 having the shape of a disk, spacers 80, a hub 90, a clamp 70, and a fastening member 72. The magnetic disk 30 has a through hole at a central part thereof. The spacer 80 has a through hole at a central part thereof, and is disposed between the magnetic disks 30. The hub 90 is inserted into the through holes of the magnetic disks 30 and the spacers 80. The clamp 70 presses and holds the magnetic disks 30 and the spacers 80. The fastening member 72 fastens the clamp 70 to the hub 90. The clamp 70 is fastened to the hub 90 by the fastening member 72 with a torque 5 cN∙m-45 cN∙m.

Description

[Technical field]

[0001] The present invention relates to a magnetic disk device and a method for manufacturing a magnetic disk device. [Background technology]

[0002] The spread of smartphones and smart home appliances has led to an increase in the amount of data used by individuals. This vast amount of data is then transmitted over the Internet and stored on magnetic disk devices (HDD: Hard Disk Drives) in data centers. In order to record such a large amount of data, there is a demand for magnetic disk devices with higher capacities.

[0003] For example, cited document 1 discloses a substrate for a magnetic recording medium, characterized in that a portion of at least one surface of a circular resin substrate having a through hole in the center is thicker a predetermined distance from the inner peripheral edge than a portion outside the predetermined distance, in order to reduce the thickness of a housing that houses the magnetic recording medium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-54254 A Summary of the Invention [Problem to be solved by the invention]

[0005] As an example of how to increase the capacity of magnetic disk drives, there is a technological trend to increase the number of magnetic disks mounted in the magnetic disk drive and expand the data area per magnetic disk drive. Since the dimensions of magnetic disk drives are regulated by standards, in order to increase the number of magnetic disks mounted, it is necessary to make some effort, such as reducing the thickness of the magnetic disks. If the thickness of the magnetic disk is reduced, the rigidity decreases, and the magnetic disk becomes more likely to deform when an impact is applied, such as when the HDD is dropped, and the shock resistance decreases. In other words, there is a dilemma between increasing the capacity of magnetic disk drives and the shock resistance of magnetic disk drives.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a magnetic disk device having excellent shock resistance and a large data capacity, and a method for manufacturing the magnetic disk device. [Means for solving the problem]

[0007] In order to achieve the above object, a magnetic disk device according to a first aspect of the present invention comprises: A plurality of disk-shaped magnetic disks each having a through hole in the center thereof; a spacer disposed between the magnetic disks and having a through hole in the center; a hub that is inserted into the through holes of the magnetic disk and the spacer; a clamp for pressing and holding the magnetic disk and the spacer; Fastening the clamp to the hub Multiple A fastening member, The clamp is Multiple The fastening member is fastened to the hub with a torque of 5 cN m or more and 45 cN m or less. 。

[0008] The clamp is Multiple It is preferable that the fastening member be fastened to the hub with a torque of 20 cN·m or more and 45 cN·m or less.

[0009] The clamp is Multiple It is preferable that the fastening member be fastened to the hub with a torque of 20 cN·m or more and 35 cN·m or less.

[0010] The magnetic disk has an inner diameter of 25 mm, an outer diameter of 95 mm to 97 mm, and a thickness of 0.35 mm to 0.635 mm. The spacer has an inner diameter of 25 mm, an outer diameter of 32 mm to 33 mm, and a thickness of 1.6 mm to 1.8 mm. Multiple The distance from the centre of the fastening member to the centre of the protrusion provided on the clamp is preferably 5 mm.

[0011] A first contact length in the radial direction between the magnetic disk and the clamp may be equal to or greater than half a second contact length in the radial direction between the magnetic disk and the spacer.

[0012] It is preferable to stack a plurality of the spacers between the magnetic disks.

[0013] It is preferable that a plurality of the spacers are stacked between the magnetic disk in contact with the clamp and the magnetic disk adjacent to this magnetic disk.

[0014] It is preferable that the thickness of the magnetic disk is 0.48 mm or less.

[0015] It is preferable that the thickness of the magnetic disk is 0.36 mm or less. The magnetic disk may include an aluminum alloy plate containing 1.0% by mass or more and 6.5% by mass or less of Mg, and further containing one or more of: 0.070% by mass or less of Cu, 0.60% by mass or less of Zn, 0.50% by mass or less of Fe, 0.50% by mass or less of Si, 0.20% by mass or less of Cr, 0.50% by mass or less of Mn, and 0.20% by mass or less of Zr, with the remainder being aluminum, unavoidable impurities, and other trace elements. The magnetic disk may comprise an aluminum alloy plate containing an essential element Fe and one or two of optional elements Mn and Ni, the total content of Fe, Mn and Ni being 1.00% by mass or more and 7.00% by mass or less, and further containing one or more of the following: Si: 14.0% by mass or less, Zn: 0.7% by mass or less, Cu: 1.0% by mass or less, Mg: 3.5% by mass or less, Cr: 0.30% by mass or less, Zr: 0.20% by mass or less, with the remainder being aluminum, unavoidable impurities and other trace elements. The magnetic disk is made of SiO 2 : 55% by mass or more and 70% by mass or less of the main component is Al 2 O 3 :25% by mass or less, Li 2 O: 12% by mass or less, Na 2 O: 12% by mass or less, K 2 O: 8% by mass or less, MgO: 7% by mass or less, CaO: 10% by mass or less, ZrO 2 :10% by mass or less, TiO 2 It is preferable that the aluminosilicate glass sheet contains one or more of 1 mass % or less of the above-mentioned elements, with the remainder being unavoidable impurities and other trace elements.

[0016] In order to achieve the above object, a method for manufacturing a magnetic disk drive according to a second aspect of the present invention includes the steps of: A plurality of disk-shaped magnetic disks each having a through hole in the center thereof; a spacer disposed between the magnetic disks and having a through hole in the center; a hub that is inserted into the through holes of the magnetic disk and the spacer; a clamp for pressing and holding the magnetic disk and the spacer; Fastening the clamp to the hub Multiple A method for manufacturing a magnetic disk drive including a fastening member, the method comprising the steps of: The clamp is tightened with a torque of 5cN·m to 45cN·m. Multiple A fastening step is provided for fastening the hub with a fastening member. Effect of the Invention

[0017] According to the present invention, it is possible to provide a magnetic disk device having excellent shock resistance and a large data capacity. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1A is a top view showing a magnetic disk device according to an embodiment, and FIG. 1B is a side view showing the magnetic disk device. [Diagram 2] 1 is a cross-sectional view showing a magnetic disk and a spacer included in a magnetic disk device according to an embodiment. [Diagram 3] 2 is an enlarged cross-sectional view showing a magnetic disk and a spacer included in the magnetic disk device according to the embodiment. FIG. [Figure 4] 11A and 11B are diagrams illustrating a state in which an impact is applied to a magnetic disk included in a magnetic disk device according to an embodiment. [Diagram 5] 13 is an enlarged cross-sectional view showing a magnetic disk and a spacer included in a magnetic disk device according to a modified example. [Figure 6] 13 is an enlarged cross-sectional view showing a magnetic disk and a spacer included in a magnetic disk device according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a magnetic disk device (HDD: Hard Disk Drive) according to an embodiment of the present invention will be described with reference to the drawings.

[0020] The magnetic disk device 100 of this embodiment is a box-shaped recording and reproducing device, and includes a housing 10, a base 20, a plurality of magnetic disks 30 arranged in a stack, a head stack assembly 40, a voice coil motor 50, a ramp road 60, a clamp 70, and necessary members such as a spindle motor and a circuit board (not shown) as shown in Figures 1(A) and 1(B).The magnetic disk device 100 also includes a plurality of spacers 80 arranged between the plurality of magnetic disks 30, and a hub 90 that rotates the plurality of magnetic disks 30 around a rotation axis Z as shown in Figures 2 and 3.

[0021] Returning to Fig. 1, the dimensions of the magnetic disk device 100 are determined by a common standard, and for example, 3.5-inch magnetic disk devices conforming to the SFF-8301 standard are preferably used for data centers. This standard stipulates that the height H of the housing 10 is 26.1 mm, the width W is 101.6 mm, and the depth D is 147 mm.

[0022] The housing 10 is generally made of metal and has a cubic box shape with one side open, and contains a base 20, a magnetic disk 30, a head stack assembly 40, a voice coil motor 50, a ramp road 60, a clamp 70, and necessary components such as a spindle motor and a circuit board, which are sealed by a top cover not shown.

[0023] The base 20 is disposed at the bottom of the housing 10, and is a portion on which the voice coil motor 50, the spindle motor, the circuit board, etc. are mounted. The base 20 and the housing 10 are often integrated.

[0024] As shown in Figs. 2 and 3, the magnetic disk 30 is a disk-shaped medium having a through hole in the center for magnetically recording information, and is composed of a substrate, an underlayer, a magnetic layer, a protective layer, and a lubricant layer, and rotates around a rotation axis Z. As a magnetic recording method, a perpendicular magnetic recording method (PMR: Perpendicular Magnetic Recording) or a shingled magnetic recording method (SMR: Shingled Magnetic Recording) is preferably used. To achieve a higher capacity, technologies such as a heat assisted magnetic recording method (HAMR: Heat Assisted Magnetic Recording) and a microwave assisted magnetic recording method (MAMR: Microwave Assisted Magnetic Recording) have been developed. As a substrate, an aluminum alloy substrate or a glass substrate is preferably used. Details of the aluminum alloy substrate and the glass substrate will be described later.

[0025] The thickness Td of the magnetic disk 30 is preferably 0.2 mm or more, more preferably 0.35 mm or more. The thickness Td of the magnetic disk 30 is 1.75 mm or less, more preferably 0.635 mm or less, even more preferably 0.50 mm or less, particularly preferably 0.48 mm or less, and even more particularly preferably 0.36 mm or less. The outer diameter 2×Rd of the magnetic disk 30 is preferably 95 mm or more and 97 mm or less, and the inner diameter is 25 mm. The number N of the magnetic disks 30 included in the magnetic disk device 100 of this embodiment is preferably 8 sheets or more and 16 sheets or less. As an example of realizing a high capacity of the magnetic disk device 100, there is a technique of increasing the number of magnetic disks 30 mounted and expanding the data area per magnetic disk device 100. However, as described above, the dimensions of the magnetic disk device 100 are determined by standards, and the space in which the magnetic disks 30 are mounted is limited. Therefore, in order to increase the number of magnetic disks 30 that can be mounted, the thickness of the magnetic disks 30 is reduced.

[0026] Returning to Fig. 1, the head stack assembly 40 has an arm 41 and a head unit 42 attached to the tip of the arm 41. When recording by HAMR, a laser element is mounted on the head unit 42, and when storing by MAMR, a microwave generating element is mounted on the head unit 42.

[0027] The voice coil motor 50 is a drive motor that rotates the head stack assembly 40 .

[0028] The ramp road 60 is a resin part that is mounted at a position closest to the magnetic disk 30 on the outer periphery of the magnetic disk 30 for the purpose of retracting the head portion 42 when the magnetic disk device 100 is not in operation.

[0029] The clamp 70 is made of a non-ferromagnetic metal such as an aluminum alloy, and has a protrusion 71 that contacts the magnetic disk 30 on a surface facing the upper surface of the magnetic disk 30 as shown in FIG. 2 and FIG. 3, and presses and holds the magnetic disks 30 and the spacer 80 against the hub 90. The clamp 70 may further have a coating such as Ni-P plating on its surface. The magnetic disk 30 is fixed by the clamp 70 by pressing the protrusion 71 of the clamp 70 into contact with the upper surface of the magnetic disk 30. The magnetic disk 30 is prevented from coming off when the magnetic disk 30 is rotated at high speed and data is processed. The clamp 70 is fixed to the hub 90 by a fastening member 72. For example, a screw or a hex lobe (six-pointed star) screw is used as the fastening member 72. The pitch of the fastening member 72 is normal and has a pitch of 0.4 mm. The fastening member 72 is made of stainless steel or the like. The first contact length L1 in the radial direction between the magnetic disk 30 and the protrusion 71 is preferably at least half the second contact length L2 in the radial direction between the magnetic disk 30 and the spacer 80. In the radial direction, the distance L3 from the center of the fastening member 72 that fixes the clamp 70 to the center of the protrusion 71 is preferably 4.0 to 6.5 mm. Also, the hole diameter d1 of the clamp 70 for receiving the fastening member 72 is preferably 2.0 to 3.5 mm. And the height t1 of the protrusion 71 is preferably 0.1 to 0.5 mm.

[0030] The spacer 80 is a ring-shaped thin plate and is disposed between the multiple magnetic disks 30. By disposing the spacer 80 between the multiple magnetic disks 30, the magnetic disks 30 are firmly fixed to the hub 90 of the spindle motor by the clamp 70. The role of the spacer 80 is to ensure the spacing between the multiple magnetic disks 30 and to transmit the rotational driving force of the hub 90 to the magnetic disks 30 that are not in direct contact with the hub 90 or the clamp 70 by coming into close contact with the magnetic disks 30.

[0031] Regarding the thickness Ts of the spacer 80, the narrower the interval between the magnetic disks 30, the more magnetic disks 30 can be mounted in a limited space, which is preferable, but the surface of the magnetic disk 30 needs a space for operating the head stack assembly 40. In particular, in the above-mentioned high-capacity technologies of HAMR and MAMR, when recording by HAMR, a laser element needs to be mounted on the head unit 42, and when storing by MAMR, a microwave generating element needs to be mounted on the head unit 42, and it is not easy to miniaturize the head stack assembly 40. The interval between the magnetic disks 30, i.e., the thickness Ts of the spacer, needs to be at least 1 mm or more, preferably 1.5 mm, and more preferably 1.6 mm or more. In order to mount as many magnetic disks 30 as possible in the magnetic disk device 100, the thickness Ts of the spacer is preferably 1.8 mm or less.

[0032] The shape of the spacer 80 is preferably such that the flatness of both surfaces of the spacer 80 is small. Furthermore, it is preferable that the boundaries between the surface of the spacer 80 and the inner and outer periphery end faces (hereinafter, the inner and outer periphery of the spacer) are chamfered for the purpose of removing burrs, etc. This is because there is a concern that burrs on the inner and outer periphery of the spacer 80 may come into contact with the magnetic disk 30 and cause scratches when the magnetic disk 30 and the spacer 80 are laminated.

[0033] The material of the spacer 80 is preferably selected from materials that reduce the difference in thermal expansion coefficient between the spacer 80 and the magnetic disk 30. If the difference in thermal expansion coefficient between the two is large, the spacer 80 and the surface of the magnetic disk 30 may be misaligned when the environmental temperature during operation of the magnetic disk device 100 changes, causing read / write errors. When the magnetic disk 30 is made of an aluminum alloy substrate, the spacer 80 is preferably made of aluminum. When the magnetic disk 30 is made of a glass substrate, the spacer 80 is preferably made of glass, stainless steel, titanium, or the like. Furthermore, in order to prevent the magnetic disk 30 and the spacer 80 from being charged, the spacer 80 is preferably conductive. When glass is used for the spacer 80, it is preferable that the glass spacer 80 has a metal film such as Ni-P plating on its surface and side.

[0034] A case where a plurality of magnetic disks 30 are mounted in the magnetic disk device 100 will be described. As shown in Fig. 2 and Fig. 3, the outer radius of the magnetic disk is Rd, the thickness of the magnetic disk is Td, the outer radius of the spacer is Rso, the thickness of the spacer 80 is Ts, and the stack height of the magnetic disks and the spacer is T. The inner diameter of the magnetic disk 30 and the inner diameter of the spacer 80 are equal, and the inner radius of the magnetic disk = the inner radius of the spacer Rsi. The inner diameter of the magnetic disk 30 and the inner diameter 2Rsi of the spacer 80 are, for example, 25 mm. The outer diameter 2Rso of the spacer 80 is preferably 32 mm or more and 33 mm or less.

[0035] Here, consider a magnetic disk device 100 in which the height H of the housing 10 conforming to SFF-8301 is 26.1 mm. When N magnetic disks 30 with a thickness Td and (N-1) spacers 80 with a thickness Ts are alternately stacked in the magnetic disk device 100, the stacking height T = N x Td + (N-1) x Ts must be less than 26.1 mm. However, since the magnetic disk device 100 includes components such as a base 20, a circuit board, a spindle motor, a clamp 70, a hub 90, and a top cover in addition to the magnetic disks 30 and spacers 80, the stacking height T of the magnetic disks 30 and spacers 80 is preferably 20 mm or less, and more preferably 19 mm or less. As described above, the lower limit of the thickness Td of the magnetic disk 30 is 0.3 mm, the lower limit of the thickness Ts of the spacer 80 is 1 mm, and the upper limit of the stacking height T of the magnetic disks 30 and the spacer 80 is 20 mm, so the upper limit of the number N of magnetic disks 30 is 16. In order to achieve a high capacity of the magnetic disk device 100, the number N of magnetic disks 30 is preferably 8 or more.

[0036] Hub 90 is made of a non-ferromagnetic metal such as an aluminum alloy, has a cylindrical small diameter portion 91 and a large diameter portion 92 connected in the direction of rotation axis Z, and rotates by a spindle motor about rotation axis Z as its central axis. The diameter of small diameter portion 91 is the same as the inner diameter of magnetic disk 30 and the inner diameter 2Rsi of spacer 80. Large diameter portion 92, together with clamp 70, sandwiches and fixes magnetic disk 30 and spacer 80.

[0037] As described above, the magnetic disk 30 is a disk-shaped medium for magnetically recording information, and is composed of a substrate, an underlayer, a magnetic layer, a protective layer, and a lubricating layer. An aluminum alloy substrate or a glass substrate is preferably used as the substrate.

[0038] (Aluminum alloy substrate) For the aluminum alloy substrate, an Al-Mg based alloy such as the conventionally used JIS 5086 alloy is preferably used due to its high strength, or an Al-Fe based alloy is preferably used due to its high rigidity.

[0039] Specifically, the Al-Mg alloy is an aluminum alloy containing 1.0 to 6.5 mass% Mg, and further containing one or more of 0.070 mass% or less Cu, 0.60 mass% or less Zn, 0.50 mass% or less Fe, 0.50 mass% or less Si, 0.20 mass% or less Cr, 0.50 mass% or less Mn, and 0.20 mass% or less Zr, with the balance being aluminum, inevitable impurities, and other trace elements. Examples of other trace elements include Be, Sr, etc., and the effects of the present disclosure are not hindered as long as each is 0.1 mass% or less.

[0040] The Al-Fe alloy is an aluminum alloy containing one or two of the essential element Fe and the optional elements Mn and Ni, with the total content of these Fe, Mn and Ni being 1.00 to 7.00 mass%, and further containing one or more of the following: Si: 14.0 mass% or less, Zn: 0.7 mass% or less, Cu: 1.0 mass% or less, Mg: 3.5 mass% or less, Cr: 0.30 mass% or less, and Zr: 0.20 mass% or less, with the balance being aluminum, unavoidable impurities and other trace elements. Examples of other trace elements include Be, Sr, etc., and as long as each is 0.1 mass% or less, the effect of the present disclosure is not hindered.

[0041] Next, a method for producing the aluminum alloy substrate will be described.

[0042] First, an ingot is produced by semi-continuous casting, and then hot-rolled and cold-rolled to produce a plate material of a desired thickness. Alternatively, a plate material is produced by continuous casting, and then cold-rolled to produce a plate material of a desired thickness. The ingot may be heat-treated to homogenize the structure. The plate material may be heat-treated before, during, or after cold rolling to improve workability.

[0043] Next, the plate material prepared as described above is punched by a press machine to prepare a disk-shaped blank having the desired inner and outer diameter dimensions. After that, in order to reduce the flatness of the blank, the blanks are stacked on each other, and a load is applied to the stacked blanks, followed by a heat treatment.

[0044] Next, the inner and outer diameters of the blank are cut using a lathe to produce a T-sub with the desired inner and outer diameters and a chamfered portion of the desired length. The surfaces of both sides of the blank may then be cut to produce a T-sub with the desired thickness. The T-sub may then be heat-treated to remove any distortion that may have occurred inside the material due to the cutting process.

[0045] Next, the surfaces of both sides of the T-sub are ground with a grinding machine to produce a G-sub of the desired thickness. The G-sub may then be heat-treated to remove any distortion caused by grinding inside the material.

[0046] Next, the M sub is produced by depositing plating of the desired thickness on all surfaces of the G sub, including the surface, sides, and chamfered surfaces. First, the G sub is pretreated to improve plating adhesion. Then, plating is performed. Ni-P electroless plating is preferably used for plating. Furthermore, the M sub may be heat-treated to remove internal stress from the Ni-P electroless plating.

[0047] Next, the surfaces of both sides of the M sub are polished with a polishing machine to produce a substrate of the desired thickness, i.e., an aluminum alloy substrate. The lower limit of the thickness of the aluminum alloy substrate produced by this method is 0.3 mm. This is due to the thickness of a part called a carrier that holds the aluminum alloy substrate when polishing with a polishing machine. The thickness of the carrier can be selected as long as it is equal to or greater than the thickness of the aluminum alloy substrate to be processed, but if the carrier is too thin, it will lack strength and will be damaged during polishing. From the viewpoint of carrier strength, the thickness of the carrier is preferably 0.3 mm or more. Therefore, the lower limit of the thickness of the aluminum alloy substrate to be processed is 0.3 mm. Note that the carrier is preferably made of resin such as aramid resin or epoxy resin. In order to improve strength, fibrous reinforcing materials such as carbon fiber or glass fiber may be included.

[0048] Next, an underlayer, a magnetic layer, a protective layer, and a lubricating layer are formed on the surface of the aluminum alloy substrate, thereby obtaining a magnetic disk 30.

[0049] (Glass substrate) Aluminosilicate glass is preferably used as the glass substrate because of its high hardness. Specifically, aluminosilicate glass contains SiO2: 55 to 70 mass% as a main component, and one or more of Al2O3: 25 mass% or less, Li2O: 12 mass% or less, Na2O: 12 mass% or less, K2O: 8 mass% or less, MgO: 7 mass% or less, CaO: 10 mass% or less, ZrO2: 10 mass% or less, and TiO2: 1 mass% or less, with the balance being unavoidable impurities and other trace elements.

[0050] Next, a method for manufacturing the glass substrate will be described.

[0051] First, a glass material prepared to have a predetermined chemical composition is melted, and the molten mass is press-molded from both sides by a direct press method to produce a glass blank having a desired thickness. The method for producing the glass blank is not limited to the direct press method, and may also be a float method, a fusion method, a redraw method, or the like.

[0052] Next, this glass original plate is cored into an annular shape, and the inner and outer diameter portions are polished to obtain an annular glass plate having the desired inner diameter, outer diameter, and chamfer length.

[0053] Next, both surfaces of this annular glass plate are ground by a grinding machine to obtain an annular glass substrate having a desired plate thickness and flatness.

[0054] Further, both surfaces of the annular glass substrate are polished by a polishing machine to produce a substrate having a desired thickness, i.e., a glass substrate. During the polishing process, a chemical strengthening treatment using a sodium nitrate solution, potassium nitrate solution, or the like may be performed.

[0055] The lower limit of the thickness of the glass substrate produced by this method is 0.3 mm. This is due to the thickness of a part called a carrier that holds the glass substrate when polishing with a polishing machine. The thickness of the carrier can be selected as long as it is equal to or greater than the thickness of the glass substrate to be processed, but if the carrier is too thin, it will lack strength and will be broken during polishing. From the viewpoint of carrier strength, the thickness of the carrier is preferably 0.3 mm or more. Therefore, the lower limit of the thickness of the glass substrate to be processed is 0.3 mm. Note that carriers made of resins such as aramid resins and epoxy resins are preferably used. To improve strength, fibrous reinforcing materials such as carbon fibers and glass fibers may be included.

[0056] (shock resistance) When the magnetic disk device 100 receives an external impact, as shown in FIG. 4, the magnetic disk 30 is deflected, and the magnetic disk 30 collides with, for example, the ramp road 60. As described above, the ramp road 60 is a resin part mounted at a position closest to the magnetic disk 30 on the outer periphery side of the magnetic disk 30 for the purpose of retracting the head unit 42 when the magnetic disk device 100 is not in operation. When the magnetic disk 30 collides with the ramp road 60, a part of the ramp road 60 is chipped, generating foreign matter, or the magnetic disk 30 is scratched, causing a failure. The higher the rigidity of the magnetic disk 30, the smaller the amount of deflection and the lower the probability of failure. In other words, the higher the rigidity of the magnetic disk 30, the higher the impact resistance.

[0057] (Fluttering resistance) During operation of the magnetic disk device 100, the magnetic disk 30 rotates at high speed. The rotation speed is, for example, 7200 rpm. When the magnetic disk 30 rotates at high speed, turbulence occurs in the gas inside the magnetic disk device 30, causing the magnetic disk 30 to vibrate. This vibration phenomenon is called fluttering. When the magnetic disk 30 vibrates, the position accuracy of the head portion 42 decreases, causing a read error. The higher the rigidity of the magnetic disk 30, the smaller the amount of vibration and the lower the probability of a read error. In other words, the higher the rigidity of the magnetic disk 30, the better the fluttering resistance. Note that a technique is known in which the magnetic disk device 100 is filled with helium instead of air in order to reduce the turbulence of the gas inside the magnetic disk device 100.

[0058] (Magnetic disk rigidity) The shock resistance of the magnetic disk 30 is indicated by the magnitude of the deflection of the magnetic disk 30 when the magnetic disk 30 is subjected to acceleration due to a shock. The fluttering resistance of the magnetic disk 30 is indicated by the magnitude of the deflection of the magnetic disk 30 when the magnetic disk 30 is subjected to turbulent gas flow generated by the magnetic disk 30 rotating at high speed. In other words, the shock resistance and fluttering resistance of the magnetic disk 30 are determined by whether the magnetic disk 30 is prone to deflection or not.

[0059] (Torque when tightening the clamp) The clamp 70 is fastened to the hub 90 by the fastening member 72 with a torque of 5 cN·m to 45 cN·m. As the fastening member 72, a hex lobe screw of T6 to T8 size or the like is preferably used. The bolt diameter is M2 or the like. The upper limit of the torque when fastening is 45 cN·m, preferably 40 cN·m, and more preferably 35 cN·m. By setting the upper limit of the torque when fastening to these values, the impact resistance of the magnetic disk device 100 can be improved. In detail, by setting the upper limit of the torque when fastening to these values, it is possible to prevent a gap from being generated in a part of the contact portion between the magnetic disk 30 and the spacer 80. By preventing a gap from being generated in a part of the contact portion between the magnetic disk 30 and the spacer 80, even if an impact is applied to the magnetic disk device 100 from the outside, the magnetic disk 30 is prevented from being deformed, and the magnetic disk device 100 has excellent impact resistance. On the other hand, the lower limit of the torque when fastening is 5 cN·m, preferably 20 cN·m, and more preferably 25 cN·m. When the torque when fastening is within these values, the magnetic disk 30 and the spacer 80 can be sufficiently fastened together. If the lower limit of the torque when fastening is less than 5 cN·m, the fastening member 72 may come loose.

[0060] (Ratio of first contact length L1 to second contact length L2) The first contact length L1 between the magnetic disk 30 and the clamp 70 in the radial direction is preferably at least half the second contact length L2 between the magnetic disk 30 and the spacer 80 in the radial direction. By making the first contact length L1 / second contact length L2 at least half, the impact resistance can be improved. By making the first contact length L1 / second contact length L2 at least half, the contact portion between the magnetic disk 30 and the clamp 70 is large, and the gap between the magnetic disk 30 and the clamp 70 can be reduced. By making the gap smaller, even if an impact is applied to the magnetic disk device 100 from the outside, the magnetic disk 30 can be prevented from being deformed, and the magnetic disk device 100 has excellent impact resistance. Therefore, the first contact length L1 / second contact length L2 is preferably at least half, and more preferably at least 0.9. From the viewpoint of impact resistance, it is preferable that the first contact length L1 / second contact length L2 is closer to 1.0. However, the closer it is to 1.0, the heavier the clamp becomes, so it is preferable to set the upper limit at around 0.95.

[0061] (Method of manufacturing a magnetic disk device) In the method for manufacturing a magnetic disk device, as shown in FIG. 2, in the arranging step, the magnetic disks 30 and the spacers 80 are arranged on the hub 90, and in the fastening step, the clamp 70 is fastened to the hub 90 by the fastening member 72 with a torque of 5 cN·m or more and 45 cN·m or less. In detail, in the arranging step, the magnetic disks 30 and the spacers 80 are arranged on the hub 90 in an alternating stacked manner. In the fastening step, the clamp 70 is placed on the hub 90 on which the magnetic disks 30 and the spacers 80 are arranged, and the clamp 70 is fastened to the hub 90 by using a hex lobe screw as the fastening member 72. In this way, the magnetic disks 30 and the spacers 80 are fixed to the hub 90. In the fastening step, the upper limit of the torque when fastening the clamp 70 by the fastening member 72 is 45 cN·m, preferably 40 cN·m, and more preferably 35 cN·m, as described above. Also, the lower limit of the torque is 5 cN·m, preferably 20 cN·m, and more preferably 25 cN·m. In Fig. 1, six fastening members 72 are used for fastening, but it is preferable that all of them be fastened with the same torque. The fastening torque can be adjusted, for example, with a Kanon idling torque driver manufactured by Nakamura Seisakusho Co., Ltd. The fastening torque can be measured, for example, with a torque driver manufactured by Tohnichi Seisakusho Co., Ltd.

[0062] As described above, according to the magnetic disk device 100 of the present embodiment, by appropriately adjusting the torque when fastening the clamp 70, it is possible to improve the shock resistance without reducing the recording area, and therefore it is possible to provide a 3.5-inch magnetic disk device equipped with a magnetic disk made of an aluminum alloy substrate and a glass substrate, which has excellent shock resistance and high data capacity. In addition, the first contact length L1 in the radial direction between the magnetic disk 30 and the clamp 70 is at least half the second contact length L2 in the radial direction between the magnetic disk 30 and the spacer 80, so that the magnetic disk device 100 can improve the shock resistance without reducing the recording area. By installing the magnetic disk device 100 in a data center, it is possible to contribute to increasing the capacity of the data center. In addition, the idea of ​​the present embodiment, in which the shock resistance can be improved without reducing the recording area by appropriately adjusting the torque when fastening the clamp 70 or by making the first contact length L1 at least half the second contact length L2, can be applied not only to the 3.5-inch magnetic disk device 100 but also to magnetic disk devices 100 of any size. The type of magnetic disk 30 is not limited to the magnetic disk 30 made of an aluminum alloy substrate or a glass substrate, but the present invention can be applied to any type of magnetic disk 30.

[0063] (Modification) In the above embodiment, an example in which the spacers 80 are arranged between the magnetic disks 30 without overlapping each other has been described. The spacers 80 may be stacked in a plurality of sheets as shown in FIG. 5. Usually, one spacer 80 is placed between the magnetic disks 30, but by stacking two or more spacers, the impact resistance can be improved. It is better to have more spacers 80, but if there are too many, the number of magnetic disks 30 that can be mounted will be reduced, so the upper limit is three. Also, as shown in FIG. 6, if the number of all spacers 80 is two or more, the number of magnetic disks 30 that can be mounted will be reduced, so it is preferable to have two or more spacers 80 only for the spacer 80 that contacts the topmost magnetic disk 30 (the magnetic disk 30 that contacts the clamp 70), which is likely to be deformed. It is also effective to increase the thickness Ts of the spacer 80, but in that case, the design of the spacer 80 needs to be changed, which is not practical, so it is preferable to stack a plurality of spacers 80.

[0064] In the above embodiment, an example has been described in which the magnetic disk device 100 is a 3.5-inch magnetic disk device, but the magnetic disk device 100 may be a device other than a 3.5-inch magnetic disk device, for example, a 2.5-inch magnetic disk device. EXAMPLES

[0065] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these.

[0066] (The clamping torque and the amount of deflection of the magnetic disk when fastening the clamp) As the magnetic disk substrate 31, a plated aluminum alloy substrate having the composition shown in Table 1 and a glass substrate having the composition shown in Table 2 were prepared. The substrate size was an inner diameter of 25 mm, an outer diameter of 97 mm, and a plate thickness of 0.50 mm. The spacer 80 was made of aluminum and had an inner diameter of 25 mm, an outer diameter of 32 mm, and a thickness of 1.7 mm. The clamp 70 used had a distance L3 from the center of the fastening member 72 shown in FIG. 3 to the center of the protrusion 71 of 5 mm, a hole diameter d1 of the clamp 70 for inserting the fastening member 72 shown in FIG. 3 of 2 mm, and a height t1 of the protrusion 71 shown in FIG. 3 of 0.2 mm. As the fastening member 72, a T6 size hex lobe screw with a bolt diameter of M2 was used.

[0067] [Table 1]

[0068] [Table 2]

[0069] Next, as shown in FIG. 4, the magnetic disk substrate 31 was fixed to the hub 90 by the spacer 80 and the clamp 70, and they were placed in an impact test device. The fastening torque when fixing the magnetic disk substrate 31 of Examples 1 to 9 and Comparative Examples 1 to 5 is shown in Table 1, and the fastening torque when fixing the magnetic disk substrate 31 of Examples 10 to 11 and Comparative Example 6 is shown in Table 2. The fastening torque was adjusted with a Kanon idling torque driver manufactured by Nakamura Seisakusho Co., Ltd. The torque was measured with a torque driver manufactured by Tohnichi Seisakusho Co., Ltd. The deflection amount due to the impact at the outer peripheral position of the magnetic disk substrate 31 (distance r1 from the substrate center: 44.2 mm) and the inner peripheral position of the magnetic disk substrate 31 (distance r2 from the substrate center: 23 mm) was measured by applying an impact with an acceleration of 55 to 60 G and an action time of 2.7 to 3.0 ms using a capacitance distance sensor.

[0070] The difference between the deflection amount at the outer peripheral position and the inner peripheral position ("deflection amount at the outer peripheral position" - "deflection amount at the inner peripheral position") was calculated, and the maximum absolute value was divided by the acceleration ("maximum absolute value of the difference in deflection amount" / "acceleration", hereafter referred to as maximum deflection amount). Measurement was performed once for each sample. After that, the maximum deflection amount of Comparative Examples 1 to 4 and 6 with a fastening torque of 50 cN·m was set as 100%, and the relative value of the maximum deflection amount of each fastening torque of Examples 1 to 11, which have the same composition, was obtained. The relative value of the maximum deflection amount was obtained based on Comparative Example 1 for Examples 1 to 2, Comparative Example 2 for Examples 3 to 4, Comparative Example 3 for Examples 5 to 6, Comparative Example 4 for Examples 7 to 9, and Comparative Example 6 for Examples 10 to 11. The relative value of the maximum deflection amount of Comparative Example 5 was obtained based on the maximum deflection amount of Comparative Example 4 as 100%. In Comparative Example 5, the fastening torque was 60 cN·m, so the relative value of the maximum deflection was larger than that of Comparative Example 4, where the fastening torque was 50 cN·m. The relative values ​​of the maximum deflection calculated as described above are shown in Tables 1 and 2. Referring to Tables 1 and 2, the fastening torques of Examples 1 to 11 were 10 to 40 cN·m, and the relative values ​​of the maximum deflection of Examples 1 to 11 were less than 100% of the corresponding Comparative Examples 1 to 4 and 6. As described above, it was found that when the fastening torque was 10 to 40 cN·m, the relative value of the maximum deflection was smaller than when the fastening torque was 50 cN·m.

[0071] Next, an aluminum alloy substrate having the composition shown in Table 3 was prepared as a magnetic disk substrate 31. The substrate size was an inner diameter of 25 mm, an outer diameter of 97 mm, and a plate thickness of 0.35 mm, and a substrate having a plate thickness different from that of the aluminum alloy substrate in Table 1 was prepared. The spacer 80 in Examples 12 and 13 and Comparative Example 7 was made of aluminum and had an inner diameter of 25 mm, an outer diameter of 32 mm, and a thickness of 1.7 mm, the spacer 80 in Examples 14 and 15 and Comparative Example 8 was made of aluminum and had an inner diameter of 25 mm, an outer diameter of 32 mm, and a thickness of 1.6 mm, and the spacer 80 in Examples 16 to 18 and Comparative Examples 9 and 10 was made of aluminum and had an inner diameter of 25 mm, an outer diameter of 33 mm, and a thickness of 1.8 mm. 3, the clamp 70 used had a distance L3 from the center of the fastening member 72 to the center of the protrusion 71 of 5 mm, a hole diameter d1 of the clamp 70 for inserting the fastening member 72 of 2 mm, and a height t1 of the protrusion 71 of 0.2 mm. The fastening member 72 had a bolt diameter of M2, and a T6 size hex lobe screw was used.

[0072] [Table 3]

[0073] Next, as shown in FIG. 4, the magnetic disk substrate 31 was fixed to the hub 90 with the spacer 80 and the clamp 70, and they were placed in an impact test device. The fastening torque when fixing the magnetic disk substrate 31 of Examples 12 to 18 and Comparative Examples 7 to 10 is shown in Table 3. The fastening torque was adjusted with a Kanon idling torque driver manufactured by Nakamura Seisakusho Co., Ltd. In addition, torque was measured with a torque driver manufactured by Tohnichi Seisakusho Co., Ltd. In addition, the deflection amount due to impact at the outer peripheral position of the magnetic disk substrate 31 (distance r1 from the substrate center: 44.2 mm) and the inner peripheral position of the magnetic disk substrate 31 (distance r2 from the substrate center: 23 mm) was measured by applying an impact with acceleration of 31 to 33 G and action time of 3.6 to 3.85 ms using a capacitance distance sensor.

[0074] The difference between the deflection amount at the outer peripheral position and the inner peripheral position ("deflection amount at the outer peripheral position" - "deflection amount at the inner peripheral position") was calculated, and the maximum absolute value was divided by the acceleration ("maximum absolute value of the difference in deflection amount" / "acceleration", hereafter referred to as maximum deflection amount). Measurement was performed once for each sample. After that, the relative value of the maximum deflection amount for each fastening torque of Examples 12 to 18 was obtained by setting the maximum deflection amount of Comparative Examples 7 to 9, which has a fastening torque of 50 cN·m, as 100%. The relative value of the maximum deflection amount was obtained based on Comparative Example 7 for Examples 12 and 13, Comparative Example 8 for Examples 14 and 15, and Comparative Example 9 for Examples 16 to 18. The relative value of the maximum deflection amount of Comparative Example 10 was obtained by setting the maximum deflection amount of Comparative Example 9 as 100%. Since the fastening torque of Comparative Example 10 is 60 cN·m, the relative value of the maximum deflection amount was larger than that of Comparative Example 9, which has a fastening torque of 50 cN·m. As described above, it was found that when the fastening torque was 10 to 40 cN·m, the relative value of the maximum deflection was smaller than when the fastening torque was 50 cN·m.

[0075] Next, an aluminum alloy substrate having the composition shown in Table 4 and a glass substrate having the composition shown in Table 5 were prepared as the magnetic disk substrate 31. The aluminum alloy substrate had an inner diameter of 25 mm, an outer diameter of 95 mm, and a plate thickness of 0.635 mm, while the glass substrate had an inner diameter of 25 mm, an outer diameter of 97 mm, and a plate thickness of 0.5 mm. The spacer 80 was made of aluminum and had an inner diameter of 25 mm, an outer diameter of 32 mm, and a thickness of 1.6 mm. As shown in FIG. 3, the clamp 70 had a distance L3 from the center of the fastening member 72 to the center of the protrusion 71 of 5 mm, a hole diameter d1 of the clamp 70 for inserting the fastening member 72 of 2 mm, and a height t1 of the protrusion 71 of 0.2 mm. The fastening member 72 had a bolt diameter of M2, and a T6 size hex lobe screw was used.

[0076] [Table 4]

[0077] [Table 5]

[0078] Next, as shown in FIG. 4, the magnetic disk substrate 31 was fixed to the hub 90 by the spacer 80 and the clamp 70, and they were placed in an impact test device. The fastening torque when fixing the magnetic disk substrate 31 of Examples 19 and 20 and Comparative Example 11 is shown in Table 4, and the fastening torque when fixing the magnetic disk substrate 31 of Examples 21, 22 and Comparative Example 12 is shown in Table 5. The fastening torque was adjusted with a Kanon idling torque driver manufactured by Nakamura Seisakusho Co., Ltd. In addition, the torque was measured with a torque driver manufactured by Tohnichi Seisakusho Co., Ltd. In addition, the deflection amount due to the impact at the outer peripheral position of the magnetic disk substrate 31 (distance r1 from the substrate center: 44.2 mm) and the inner peripheral position of the magnetic disk substrate 31 (distance r2 from the substrate center: 23 mm) was measured by applying an impact with an acceleration of 51 to 56 G and an action time of 2.7 to 3.0 ms using a capacitance distance sensor.

[0079] The difference in the amount of deflection between the outer peripheral position and the inner peripheral position ("amount of deflection at the outer peripheral position" - "amount of deflection at the inner peripheral position") was calculated, and the maximum absolute value was divided by the acceleration ("maximum absolute value of the difference in the amount of deflection" / "acceleration", hereafter referred to as the maximum deflection). Measurement was performed once for each sample. After that, the relative values ​​of the maximum deflection for each fastening torque of Examples 19 to 22 were calculated, with the maximum deflection for Comparative Examples 11 and 12, which had a fastening torque of 50 cN·m, being set to 100%. The relative values ​​of the maximum deflection for Examples 19 and 20 were calculated based on Comparative Example 11, and for Examples 21 and 22, based on Comparative Example 12. As described above, it was found that the relative values ​​of the maximum deflection were smaller when the fastening torque was 30 to 40 cN·m than when the fastening torque was 50 cN·m.

[0080] If the maximum deflection of the magnetic disk substrate 31 due to an impact is large, it may collide strongly with components in the magnetic disk device, such as the ramp road, causing part of the ramp road to chip off and generate foreign matter, or the magnetic disk to be scratched, resulting in a breakdown. The smaller the maximum deflection of the magnetic disk substrate 31, the better the impact resistance.

[0081] (Ratio of first contact length L1 to second contact length L2) The fastening torque was set to 40 cN·m, and the magnetic disk substrate 31 was fixed to the hub 90 by the spacer 80 and the clamp 70 while changing L1 / L2 as shown in Tables 6 and 7. The magnetic disk substrate 31 was fixed to the hub 90 by the spacer 80 and the clamp 70, and the magnetic disk substrate 31 was placed in the same impact test device as above, and the same test was performed. After that, the maximum deflection of Comparative Examples 13 to 15 with L1 / L2 of 0.06 was set as 100%, and the relative values ​​of the maximum deflection of Examples 23 to 25 with L1 / L2 of 1.00 were obtained. The relative values ​​of the maximum deflection of Example 23 were obtained based on Comparative Example 13, that of Example 24 was obtained based on Comparative Example 14, and that of Example 25 was obtained based on Comparative Example 15. Examples 23 to 25 have the same composition as the corresponding Comparative Examples 13 to 15. The relative values ​​of the maximum deflection obtained as described above are shown in Tables 6 and 7. Referring to Tables 6 and 7, the relative values ​​of the maximum deflection of Examples 23 to 25 are smaller than 100% of the corresponding Comparative Examples 13 to 15. The relative values ​​of the maximum deflection amounts of Examples 23 to 25 in which L1 / L2 is 1.00 are smaller than the relative values ​​of the maximum deflection amounts of Comparative Examples 13 to 15 in which L1 / L2 is 0.06, and it is understood that Examples 23 to 25 have good impact resistance.

[0082] [Table 6]

[0083] [Table 7]

[0084] (Number of spacers) As shown in Tables 8 and 9, the fastening torque was set to 40 cN·m, L1 / L2 was set to 1.00, and the number of spacers 80 was changed, and the magnetic disk substrate 31 was fixed to the hub 90 by the spacers 80 and the clamp 70, which were then placed in the same impact test device as above, and the same test was performed. After that, the maximum deflection amount of Comparative Examples 16 to 18, which had one spacer 80, was set to 100%, and the relative values ​​of the maximum deflection amount of Examples 26 to 28, which had two spacers 80, were obtained. The relative values ​​of the maximum deflection amount of Example 26 were obtained based on Comparative Example 16, the relative values ​​of the maximum deflection amount of Example 27 were obtained based on Comparative Example 17, and the relative values ​​of the maximum deflection amount of Example 28 were obtained based on Comparative Example 18. The compositions of Examples 26 to 28 are the same as those of the corresponding Comparative Examples 16 to 18. The relative values ​​of the maximum deflection amount obtained in the above manner are shown in Tables 8 and 9. Referring to Tables 8 and 9, the relative values ​​of the maximum deflection amounts of Examples 26 to 28, which have two spacers 80, are less than 100% compared to the corresponding Comparative Examples 16 to 18, which have one spacer 80, and it is clear that Examples 26 to 28 have good impact resistance.

[0085] [Table 8]

[0086] [Table 9]

[0087] As described above, by setting the fastening torque when fastening the clamp 70 to the above value, the impact resistance can be improved while the thickness of the magnetic disk substrate 31 remains the same. This is shown by the above embodiment using aluminum alloy substrates and glass substrates with plate thicknesses of 0.35 mm, 0.50 mm, and 0.635 mm and outer diameters of 95 mm and 97 mm, and spacers with thicknesses of 1.6 mm, 1.7 mm, and 1.8 mm and outer diameters of 32 mm and 33 mm. Also, by setting the ratio of the first contact length L1 to the second contact length L2 to the above value, the impact resistance can be improved while the fastening torque and the thickness of the magnetic disk substrate 31 remain the same. Also, by setting the number of spacers 80 to two, the impact resistance can be improved while the fastening torque, L1 / L2, and the thickness of the magnetic disk substrate 31 remain the same. The magnetic disk substrate 31 is different from the magnetic disk 30 in that it does not have a magnetic layer, but it is considered to be equivalent to the magnetic disk 30 in terms of impact resistance, etc. Therefore, it was found that by setting the fastening torque and L1 / L2 to the above-mentioned values, or by using two spacers 80, it is possible to provide a magnetic disk drive having excellent shock resistance and a large data capacity.

[0088] The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present invention. The above-described embodiments are for the purpose of explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is indicated by the claims, not the embodiments. Various modifications made within the scope of the claims and the scope of the invention equivalent thereto are considered to be within the scope of the present invention.

[0089] This application is based on Japanese Patent Application No. 2021-046121, filed on March 19, 2021. The entire specification, claims, and drawings of Japanese Patent Application No. 2021-046121 are incorporated herein by reference. [Explanation of symbols]

[0090] 10. Chassis 20 Foundations 30 Magnetic Disk 31 Magnetic disk substrates 40 Head stack assembly 41 Arm 42 Head section 50 Voice coil motor 60 Ramp Road 70 Clamp 71 Protrusion 72 Fastening members 80 Spacer 90 Hub 91 Small diameter section 92 Large diameter section 100 Magnetic disk device D Depth W width H Height N number of sheets Z Rotation Axis Rd outer radius Td, Ts thickness T stack height Rsi inner radius Rso outer radius

Claims

1. A plurality of disk-shaped magnetic disks each having a through hole in the center thereof; a spacer disposed between the magnetic disks and having a through hole in the center; a hub that is inserted into the through holes of the magnetic disk and the spacer; a clamp for pressing and holding the magnetic disk and the spacer; a plurality of fastening members fastening the clamp to the hub, The clamp is fastened to the hub by the multiple fastening members with a torque of 5 cN·m or more and 45 cN·m or less. A magnetic disk device comprising:

2. The clamp is fastened to the hub by the multiple fastening members with a torque of 20 cN·m or more and 45 cN·m or less.

2. The magnetic disk drive according to claim 1.

3. The clamp is fastened to the hub by the multiple fastening members with a torque of 20 cN·m or more and 35 cN·m or less.

2. The magnetic disk drive according to claim 1.

4. The magnetic disk has an inner diameter of 25 mm, an outer diameter of 95 mm to 97 mm, and a plate thickness of 0.35 mm to 0.635 mm, the spacer has an inner diameter of 25 mm, an outer diameter of 32 mm to 33 mm, and a thickness of 1.6 mm to 1.8 mm, and the distance from the center of the multiple fastening members to the center of the protrusion provided on the clamp is 5 mm.

4. The magnetic disk drive according to claim 1, wherein the magnetic disk drive is a disk drive having a plurality of magnetic disks.

5. a first contact length in a radial direction between the magnetic disk and the clamp is equal to or greater than half a second contact length in a radial direction between the magnetic disk and the spacer; 5. The magnetic disk drive according to claim 1, wherein the magnetic disk drive is a disk drive having a plurality of magnetic disks.

6. A plurality of the spacers are stacked between the magnetic disks.

6. The magnetic disk drive according to claim 1, wherein the magnetic disk drive is a magnetic disk drive having a plurality of magnetic disks.

7. a plurality of the spacers are stacked between the magnetic disk in contact with the clamp and the magnetic disk adjacent to the magnetic disk; 6. The magnetic disk drive according to claim 1, wherein the magnetic disk drive is a magnetic disk drive having a plurality of magnetic disks.

8. The thickness of the magnetic disk is 0.48 mm or less.

8. The magnetic disk drive according to claim 1, wherein the magnetic disk drive is a magnetic disk drive having a plurality of magnetic disks.

9. The thickness of the magnetic disk is 0.36 mm or less.

8. The magnetic disk drive according to claim 1, wherein the magnetic disk drive is a magnetic disk drive having a plurality of magnetic disks.

10. The magnetic disk includes an aluminum alloy plate containing Mg: 1.0% by mass or more and 6.5% by mass or less, and further containing one or more of Cu: 0.070% by mass or less, Zn: 0.60% by mass or less, Fe: 0.50% by mass or less, Si: 0.50% by mass or less, Cr: 0.20% by mass or less, Mn: 0.50% by mass or less, and Zr: 0.20% by mass or less, with the remainder being aluminum, unavoidable impurities, and other trace elements.

10. The magnetic disk drive according to claim 1, wherein the magnetic disk drive is a magnetic disk drive having a plurality of magnetic disks.

11. The magnetic disk includes an aluminum alloy plate containing an essential element Fe and one or two of optional elements Mn and Ni, the total content of which is 1.00% by mass or more and 7.00% by mass or less, and further containing one or more of the following: Si: 14.0% by mass or less, Zn: 0.7% by mass or less, Cu: 1.0% by mass or less, Mg: 3.5% by mass or less, Cr: 0.30% by mass or less, and Zr: 0.20% by mass or less, with the balance being aluminum, unavoidable impurities, and other trace elements.

10. The magnetic disk drive according to claim 1, wherein the magnetic disk drive is a magnetic disk drive having a plurality of magnetic disks.

12. The magnetic disk is made of SiO ２ : 55% by mass or more and 70% by mass or less as a main component, Al ２ O ３ : 25% by mass or less, Li ２ O: 12% by mass or less, Na ２ O: 12% by mass or less, K ２ O: 8% by mass or less, MgO: 7% by mass or less, CaO: 10% by mass or less, ZrO ２ : 10% by mass or less, TiO ２ : An aluminosilicate glass plate containing one or more of 1 mass% or less of each of the above elements, with the remainder being unavoidable impurities and other trace elements; 10. The magnetic disk drive according to claim 1, wherein the magnetic disk drive is a magnetic disk drive having a plurality of magnetic disks.

13. A plurality of disk-shaped magnetic disks each having a through hole in the center thereof; a spacer disposed between the magnetic disks and having a through hole in the center; a hub that is inserted into the through holes of the magnetic disk and the spacer; a clamp for pressing and holding the magnetic disk and the spacer; a plurality of fastening members for fastening the clamp to the hub, a fastening step of fastening the clamp to the hub with the plurality of fastening members with a torque of 5 cN·m or more and 45 cN·m or less.

23. A method for manufacturing a magnetic disk drive comprising the steps of:

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