Magnetic disk device

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, and a clamp 70. The magnetic disk 30 has a through hole at a central part thereof. The spacer 80 is disposed between the magnetic disks 30 and has a through hole at a central part thereof. 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. At a surface where the magnetic disk 30 is in contact with the spacer 80 or the clamp 70, the surface height of a top face of the magnetic disk 30 in contact with an outer peripheral portion of the spacer 80 or the clamp 70 is less than the surface height of the top face of the magnetic disk 30 in contact with an inner peripheral portion of the spacer 80 or the clamp 70.

Description

[Technical field]

[0001] The present invention relates to a magnetic disk drive. Place Regarding. [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 glass substrate for information recording media that is stably fixed to the hub of an SPM (spindle motor) and will not break even if a strong impact is applied to a magnetic disk recording device incorporating an SPM. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5392075 Summary of the Invention [Problem to be solved by the invention]

[0005] As an example of a method for realizing a high capacity magnetic disk device, there is a technological trend to increase the number of magnetic disks mounted in the magnetic disk device and expand the data area per magnetic disk device. Since the dimensions of the magnetic disk device are specified 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 disk. If the thickness of the magnetic disk is reduced, the rigidity decreases, and when an impact is applied, such as when the HDD is dropped, the magnetic disk becomes more likely to deform, and the shock resistance decreases. In other words, there is a dilemma between the high capacity of the magnetic disk device and the shock resistance of the magnetic disk device, and there is a demand for a magnetic disk device that has excellent shock resistance and high data capacity.

[0006] The present invention has been made in view of the above circumstances, and provides a magnetic disk drive having excellent shock resistance and a large data capacity. Place The purpose is to provide. [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, The thickness of the magnetic disk is 0.48 mm or less, At the surface where the magnetic disk contacts the spacer or the clamp, the plane height of the upper surface of the magnetic disk that contacts the outer periphery of the spacer or the clamp is lower than the plane height of the upper surface of the magnetic disk that contacts the inner periphery of the spacer or the clamp. Ku, An upper surface of at least one of the magnetic disks contacts the spacer or the clamp at an inner periphery of the magnetic disk, and a gap is formed between a lower surface of at least one of the magnetic disks and the spacer at an inner periphery of the magnetic disk. .

[0011] It is preferable that the thickness of the magnetic disk is 0.36 mm or less.

[0012] 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, The thickness of the magnetic disk is 0.48 mm or less, At a surface where the magnetic disk contacts the spacer or the clamp, a planar height of an upper surface of the magnetic disk that contacts an outer periphery of the spacer or the clamp is lower than a planar height of an upper surface of the magnetic disk that contacts an inner periphery of the spacer or the clamp, 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. 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, The thickness of the magnetic disk is 0.48 mm or less, At a surface where the magnetic disk contacts the spacer or the clamp, a planar height of an upper surface of the magnetic disk that contacts an outer periphery of the spacer or the clamp is lower than a planar height of an upper surface of the magnetic disk that contacts an inner periphery of the spacer or the clamp, 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. 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, The thickness of the magnetic disk is 0.48 mm or less, At a surface where the magnetic disk contacts the spacer or the clamp, a planar height of an upper surface of the magnetic disk that contacts an outer periphery of the spacer or the clamp is lower than a planar height of an upper surface of the magnetic disk that contacts an inner periphery of the spacer or the clamp, The magnetic disk preferably includes an aluminosilicate glass plate containing SiO2: 55% by mass or more and 70% by mass or less as a main component, one or more of Al2O3: 25% by mass or less, Li2O: 12% by mass or less, Na2O: 12% by mass or less, K2O: 8% by mass or less, MgO: 7% by mass or less, CaO: 10% by mass or less, ZrO2: 10% by mass or less, and TiO2: 1% by mass or less, with the remainder being unavoidable impurities and other trace elements. Effect of the Invention

[0013] According to the present invention, there is provided a magnetic disk drive having excellent shock resistance and high data capacity. Place can be provided. [Brief description of the drawings]

[0014] [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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic disk device (HDD: Hard Disk Drive) and a spacer according to an embodiment of the present invention will now be described with reference to the drawings.

[0016] 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 Figure 1 (A) and Figure 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 Figure 2.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] As shown in FIG. 2, 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.

[0021] The thickness Td of the magnetic disk 30 is preferably 0.2 mm or more and 1.75 mm or less, more preferably 0.2 mm or more and 0.50 mm or less, even more preferably 0.2 mm or more and 0.48 mm or less, and particularly preferably 0.2 mm or more and 0.36 mm or less. The outer diameter 2×Rd of the magnetic disk 30 is preferably 95 mm or 97 mm, 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 to be mounted, the thickness of the magnetic disks 30 is made thin.

[0022] 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.

[0023] The voice coil motor 50 is a drive motor that rotates the head stack assembly 40 .

[0024] 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.

[0025] As shown in FIG. 2, the clamp 70 has a protrusion 71 that contacts the magnetic disk 30 on a surface facing the upper surface of the magnetic disk 30, and presses and holds the magnetic disks 30 and the spacer 80 against the hub 90 to fix them. The magnetic disk 30 is fixed by the clamp 70 by pressing the protrusion 71 of the clamp 70 against 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 by clamping the inner diameter side part of the upper surface of the magnetic disk 30 by the protrusion 71. The clamp 70 is fixed to the hub 90 by a fastening member 72. For example, a screw or a hex lobe screw of T6 to T8 size is used as the fastening member 72. The bolt diameter used is M2 or the like.

[0026] 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 contacting and adhering to the magnetic disks 30. For this reason, it is desirable for the shape of the spacer 80 to have small flatness on both surfaces of the spacer 80.

[0027] 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 space to operate 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 or more, and more preferably 1.6 mm or more.

[0028] As shown in FIG. 3, the spacer 80 desirably has a chamfered portion 81 at the boundary between the surface and the inner and outer periphery end faces (hereinafter, the inner and outer periphery of the spacer) for the purpose of removing burrs, etc. This is because there is a concern that burrs at the inner and outer periphery of the spacer 80 may contact the magnetic disk 30 and cause scratches when the magnetic disk 30 and the spacer 80 are stacked. If the outer radius of the spacer 80 is Rso, the inner radius of the spacer 80 is Rsi, the length of the chamfered portion 81 at the outer periphery of the spacer 80 is Lso, the length of the chamfered portion 82 at the inner periphery of the spacer 80 is Lsi, the outer radius of the contact portion 83 between the spacer 80 and the magnetic disk is Rsso, and the inner radius of the contact portion 83 between the spacer 80 and the magnetic disk 30 is Rssi, then Rsso=Rso-Lso and Rssi=Rsi+Lsi. The length Rst of the contact portion 83 in the radial direction is Rst=Rsso-Rssi. The contact portion 83 is the portion where the spacer 80 contacts the magnetic disk 30. Since the chamfered portions 81, 82 of the spacer 80 do not contribute to contact with the magnetic disk 30 and do not contribute to the role of transmitting the rotational driving force of the hub 90 to the magnetic disk 30, it is preferable that the lengths Lso, Lsi of the chamfered portions 81, 82 of the spacer 80 be as small as possible, specifically, 0.1 mm or less.

[0029] The material for forming the spacer 80 is preferably selected from materials that have a small 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, when the environmental temperature during operation of the magnetic disk 30 device changes, the spacer 80 and the surface of the magnetic disk 30 will be misaligned, 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 surface and side of the glass spacer 80 are provided with a metal film such as Ni-P plating.

[0030] 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, 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 disk 30 and the spacer 80 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 of the spacer 80, 2 x Rsi, is, for example, 25 mm. Moreover, the outer diameter of the spacer 80, 2 x Rso, is preferably 32 mm or more and 65 mm or less. This allows the data area in the magnetic disk device 100 to be expanded while maintaining the shock resistance and fluttering resistance of the magnetic disk device 100.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] (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.

[0035] 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.

[0036] 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.

[0037] Next, a method for producing the aluminum alloy substrate will be described.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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 the grinding process inside the material.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] (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.

[0046] Next, a method for manufacturing the glass substrate will be described.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] Furthermore, 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.

[0051] 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.

[0052] (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.

[0053] (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 read / write errors. In other words, the higher the rigidity of the magnetic disk 30, the better the fluttering resistance. Note that a technology 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.

[0054] (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.

[0055] (Plane height of magnetic disk) At the surface where the magnetic disk 30 and the spacer 80 contact, as shown in FIG. 3, the planar height H1 of the top surface of the magnetic disk 30 that contacts the outer periphery of the spacer 80 is lower than the planar height H2 of the top surface of the magnetic disk 30 that contacts the inner periphery of the spacer 80. The planar heights H1 and H2 are measured, for example, based on the contact portion 83. Note that, in the magnetic disk 30 arranged at the top, at the surface where the magnetic disk 30 and the clamp 70 contact, the planar height H1 of the top surface of the magnetic disk 30 that contacts the outer periphery of the clamp 70 is lower than the planar height H2 of the top surface of the magnetic disk 30 that contacts the inner periphery of the clamp 70. Note that the top surface of the magnetic disk 30 refers to the surface close to the clamp 70. Preferably, at least in the magnetic disk 30 arranged at the top, the planar height H1 is lower than the planar height H2 at the surface where the magnetic disk 30 and the clamp 70 contact. More preferably, the magnetic disks 30, which are more than half the total number of the magnetic disks 30 mounted, have a planar height H1 lower than the planar height H2 at the surface where the magnetic disks 30 and the spacer 80 contact. More preferably, all the magnetic disks 30 have a planar height H1 lower than the planar height H2 at the surface where the magnetic disks 30 and the spacer 80 contact. By defining the planar height H1 and planar height H2 of the upper surface of the magnetic disks 30 as described above, it is possible to improve the impact resistance. If the planar height H1 of the magnetic disks 30 in contact with the outer periphery of the spacer 80 is higher than the planar height H2 of the magnetic disks 30 in contact with the inner periphery of the spacer 80, the gap between the outer periphery of the spacer 80 and the lower surface of the magnetic disks 30 becomes large when fastened. In this state, when an impact is applied from the bottom up to the magnetic disk device 100 from the outside, the magnetic disks 30 are significantly deformed, and the impact resistance decreases. On the other hand, if the planar height H1 of the magnetic disk in contact with the outer periphery of the spacer 80 is lower than the planar height H2 of the magnetic disk 30 in contact with the inner periphery of the spacer 80, the gap between the outer periphery of the spacer 80 and the underside of the magnetic disk 30 becomes small when fastened. In this state, when an impact is applied from below to above to the magnetic disk device 100 from the outside, the magnetic disk 30 comes into contact with the spacer 80 immediately because the gap is small, which has the effect of preventing the magnetic disk 30 from being significantly deformed, and improves impact resistance.In addition, when the magnetic disk device 100 is dropped with the top side facing up, an impact is applied from the bottom up to the magnetic disk device 100. Therefore, it is considered that the probability that an impact is applied from the bottom up to the magnetic disk device 100 is higher than the probability that an impact is applied from the top down to the magnetic disk device 100. Therefore, excellent impact resistance can be obtained by making the planar height H1 of the magnetic disk 30 lower than the planar height H2. The difference (H1-H2) between the planar height H1 of the magnetic disk in contact with the outer periphery of the spacer 80 and the planar height H2 of the magnetic disk in contact with the inner periphery of the spacer 80 is preferably -3.0 μm or less, and more preferably -4.0 μm or less. Although there is no particular lower limit, it is about -15 μm.

[0056] (Method of manufacturing a magnetic disk device) A method for manufacturing the magnetic disk device 100 includes the steps of measuring a planar height H1 of the upper surface of the magnetic disk 30 in contact with the outer periphery of the spacer 80 and a planar height H2 of the upper surface of the magnetic disk 30 in contact with the inner periphery of the spacer 80; inserting the magnetic disk 30 and the spacer 80 into the hub 90 in an arrangement such that the planar height H1 of the upper surface of the magnetic disk 30 in contact with the outer periphery of the spacer 80 is lower than the planar height H2 of the upper surface of the magnetic disk 30 in contact with the inner periphery of the spacer 80; and fixing the magnetic disk 30 and the spacer 80 to the hub 90 with a clamp 70.

[0057] The process of measuring the planar heights H1 and H2 is carried out as follows. The planar heights H1 and H2 are expressed as the peak height and valley depth of the entire surface of the magnetic disk 30 relative to a certain reference plane (0 μm). In FIG. 3, the spacer 80 arranged below is illustrated as a reference plane. The planar height H1 of the magnetic disk 30 in contact with the outer periphery of the spacer 80 is calculated by measuring the height difference in the circumferential direction at the position of the magnetic disk 30 in contact with the outer periphery of the spacer 80 (for example, the position of the outer radius Rsso) after measuring the planar height of the entire substrate, and calculating the maximum peak height or maximum valley depth. The planar height H2 of the magnetic disk in contact with the inner periphery of the spacer 80 is calculated by measuring the height difference in the circumferential direction at the position of the magnetic disk 30 in contact with the inner periphery of the spacer 80 (for example, the position of the inner radius Rssi) after measuring the planar height of the entire substrate, and calculating the maximum peak height or maximum valley depth. Here, the maximum peak height is the highest value in the outer or inner circumference, and the maximum valley depth is the lowest value in the outer or inner circumference. When the maximum peak height in the inner circumference is greater than the maximum valley depth in the outer circumference, the difference between H1 (maximum valley depth) and H2 (maximum peak height) is expressed as H1-H2, and when this value is smaller than 0 μm, the planar height H1 of the magnetic disk 30 in contact with the outer circumference of the spacer 80 is defined as being lower than the planar height H2 of the magnetic disk 30 in contact with the inner circumference of the spacer 80. When the maximum peak height in the outer circumference is greater than the maximum valley depth in the inner circumference, the difference between H1 (maximum peak height) and H2 (maximum valley depth) is expressed as H1-H2, and the planar height H1 of the magnetic disk 30 in contact with the outer circumference of the spacer 80 is defined as being higher than the planar height H2 of the magnetic disk 30 in contact with the inner circumference of the spacer 80. When the planar height H1 is higher than the planar height H2, the thickness of the magnetic disk 30 is constant, so that when the magnetic disk 30 is turned over and measured, the planar height H1 is lower than the planar height H2.

[0058] Next, the process of inserting the magnetic disk 30 and the spacer 80 into the hub 90 will be described. In the process of measuring the planar heights H1 and H2, if the measured planar height H1 is lower than the planar height H2, the magnetic disk 30 is inserted into the hub 90 in its current state. If the measured planar height H1 is higher than the planar height H2, the magnetic disk 30 is turned over and inserted into the hub 90. The magnetic disk 30 and the spacer 80 are then fixed to the hub 90 by the clamp 70.

[0059] As described above, according to the magnetic disk device 100 of the present embodiment, the planar height H1 of the upper surface of the magnetic disk 30 in contact with the outer periphery of the spacer 80 is lower than the planar height H2 of the upper surface of the magnetic disk 30 in contact with the inner periphery of the spacer 80, so that the impact resistance can be improved without reducing the recording area, and a 3.5-inch magnetic disk device having excellent impact resistance and high data capacity can be provided. 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 planar height H1 of the upper surface of the magnetic disk 30 in contact with the outer periphery of the spacer 80 is lower than the planar height H2 of the upper surface of the magnetic disk 30 in contact with the inner periphery of the spacer 80, 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 the magnetic disk 30 is not limited to the magnetic disk 30 made of an aluminum alloy substrate or a glass substrate, and can be applied to any type of magnetic disk 30.

[0060] (Modification) 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

[0061] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these.

[0062] (First embodiment) 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 size of the magnetic disk substrate 31 was an inner diameter of 25 mm, an outer diameter of 97 mm, and a plate thickness of 0.50 mm. The difference (H1-H2) between the planar height H1 of the magnetic disk substrate 31 in contact with the outer periphery of the spacer 80 of the magnetic disk substrate 31 and the planar height H2 of the magnetic disk substrate 31 in contact with the inner periphery of the spacer 80 is shown in Table 1 for Examples 1 to 8 and Comparative Examples 1 to 8, and in Table 2 for Examples 9 to 10 and Comparative Examples 9 to 10. For Examples 1 to 10, the measurements of H1 and H2 were performed on the front surface (surface A) as shown in FIG. 3. H1 was measured at the outer radius Rsso=15.8 (tolerance +0, -0.5 mm) of the contact portion between the spacer 80 and the magnetic disk substrate 31. H2 was measured at an inner radius Rssi=12.7 (tolerance +0.5, -0 mm) of the contact portion between the spacer 80 and the magnetic disk substrate 31. The flat heights H1 and H2 were measured using a non-contact flatness measuring machine (MESA) (manufactured by ZyGO).

[0063] [Table 1]

[0064] [Table 2]

[0065] Next, as shown in Fig. 4, for example, surface A of the magnetic disk substrate 31 was placed on top (the side closer to the clamp 70 shown in Fig. 2 in the Z direction is the top), and the spacer 80 and the clamp 70 were used to fix the magnetic disk substrate 31 to the hub 90, and the deflection caused by the impact at the outer periphery of the magnetic disk substrate 31 (distance r1 from the substrate center: 44.2 mm) and the inner periphery of the magnetic disk substrate 31 (distance r2 from the substrate center: 23 mm) was measured by applying an impact from bottom to top with an acceleration of 55 to 60 G and an action time of 2.7 to 3.0 ms using a capacitance-type distance sensor. The spacer 80 used was made of aluminum, had an outer diameter of 32 mm, an inner diameter of 25 mm, and a thickness of 1.7 mm.

[0066] The amount of deflection caused by the impact at the outer and inner peripheral positions of the magnetic disk substrate 31 was actually measured, and the difference between the amount of deflection at the outer and inner peripheral positions ("outer peripheral deflection amount" - "inner peripheral deflection amount") 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 the maximum deflection amount).

[0067] Example 1 is a case where the measurement was performed with the A side facing up, and Comparative Example 1 is a case where the B side, which is the back side of the magnetic disk substrate 31, the same as in Example 1, was facing up. Example 1 and Comparative Example 1 were each measured three times. Comparative Examples 2 to 10 are cases where the measurement was performed with the B side, which is the back side of the magnetic disk substrate 31, the same as in Examples 2 to 10, facing up. Similarly, Examples 2 to 10 and Comparative Examples 2 to 10 were each measured three times. Thereafter, the average value of the maximum deflection amounts of a total of six times in Example 1 and Comparative Example 1 was calculated, and this average value was set as 100%, and the average value of the relative values ​​of the maximum deflection amounts measured three times in Example 1 and the average value of the relative values ​​of the maximum deflection amounts measured three times in Comparative Example 1 were each calculated. As for Examples 2 to 10, the maximum deflection amounts of the average values ​​of Examples 2 to 10 and Comparative Examples 2 to 10 were set as 100%, and the relative values ​​of the maximum deflection amounts of Examples 2 to 10 and Comparative Examples 2 to 10 were calculated. If the maximum deflection of the magnetic disk substrate 31 due to 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 failure. The smaller the maximum deflection of the substrate, the better the impact resistance.

[0068] (Second Example) As the magnetic disk substrate 31, aluminum alloy substrates with different thicknesses were produced, with the composition shown in Example 1 of Table 1. The size of the magnetic disk substrate 31 was an inner diameter of 25 mm, an outer diameter of 97 mm, and a thickness of 0.35 mm. Table 3 shows the difference (H1-H2) between the planar height H1 of the magnetic disk substrate 31 in contact with the outer periphery of the spacer 80 of the magnetic disk substrate 31 and the planar height H2 of the magnetic disk substrate 31 in contact with the inner periphery of the spacer 80 for Example 11 and Comparative Example 11. Measurements of H1 and H2 were carried out in the same manner as in the first example described above.

[0069] [Table 3]

[0070] Next, as shown in Fig. 4, for example, surface A of the magnetic disk substrate 31 was placed on top (the side closer to the clamp 70 shown in Fig. 2 in the Z direction is the top), and the spacer 80 and the clamp 70 were used to fix the magnetic disk substrate 31 to the hub 90, and the deflection caused by 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 from bottom to top with an acceleration of 31 to 33 G and an action time of 3.6 to 3.85 ms using a capacitance-type distance sensor. The spacer 80 used was made of aluminum, had an outer diameter of 32 mm, an inner diameter of 25 mm, and a thickness of 1.7 mm.

[0071] The amount of deflection caused by the impact at the outer and inner peripheral positions of the magnetic disk substrate 31 was actually measured, and the difference between the amount of deflection at the outer and inner peripheral positions ("outer peripheral deflection amount" - "inner peripheral deflection amount") 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 the maximum deflection amount).

[0072] Example 11 is a case where the measurement was performed with the A side facing up, and Comparative Example 11 is a case where the B side, which is the back side of the magnetic disk substrate 31, the same as in Example 11, was facing up. Example 11 and Comparative Example 11 were each measured three times. Comparative Example 11 is a case where the measurement was performed with the B side, which is the back side of the magnetic disk substrate 31, the same as in Example 11, facing up. Then, the average value of Example 11 and Comparative Example 11 was calculated, and the maximum deflection amount of the average value of Example 11 and Comparative Example 11 was set to 100%, and the relative value of the maximum deflection amount of Example 11 and Comparative Example 11 was obtained. Note that if the maximum deflection amount of the magnetic disk substrate 31 due to impact is large, it will collide strongly with a component in the magnetic disk device, for example, a ramp road, and a part of the ramp road will be chipped, generating foreign matter, or the magnetic disk will be scratched, causing a failure. The smaller the maximum deflection amount of the substrate, the better the impact resistance.

[0073] It was found that when the planar height H1 of the magnetic disk substrate 31 in contact with the outer periphery of the spacer 80 is lower than the planar height H2 of the magnetic disk substrate 31 in contact with the inner periphery of the spacer 80, the maximum deflection amount of the magnetic disk substrate is small and the impact resistance is good. In particular, it was found that the impact resistance is further improved when the difference (H1-H2) between the planar height H1 of the magnetic disk substrate 31 in contact with the outer periphery of the spacer 80 and the planar height H2 of the magnetic disk substrate 31 in contact with the inner periphery of the spacer 80 is -3.0 μm or less. It was also found that even when the plate thickness is 0.35 mm, the maximum deflection amount of the magnetic disk substrate is small and the impact resistance is good when the planar height H1 is lower than the planar height H2, as in the case of a plate thickness of 0.50 mm. As a result, it is considered that the maximum deflection amount of the magnetic disk substrate is small and the impact resistance is good when the planar height H1 is lower than the planar height H2 regardless of the plate thickness. On the other hand, when the planar height H1 of the magnetic disk substrate 31 in contact with the outer periphery of the spacer 80 was higher than the planar height H2 of the magnetic disk substrate 31 in contact with the inner periphery of the spacer 80, the maximum deflection amount was large and the impact resistance was poor.

[0074] As described above, it has been found that the impact resistance can be improved while maintaining the thickness of the magnetic disk substrate 31 by making the planar height H1 of the upper surface of the magnetic disk substrate 31 in contact with the outer periphery of the spacer 80 lower than the planar height H2 of the upper surface of the magnetic disk substrate 31 in contact with the inner periphery of the spacer 80. Note that the magnetic disk substrate 31 differs from the magnetic disk 30 in that it does not include a magnetic layer, etc., but is considered to be equivalent to the magnetic disk 30 in terms of impact resistance, etc.

[0075] 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.

[0076] This application is based on Japanese Patent Application No. 2021-035203, filed on March 5, 2021. The entire specification, claims, and drawings of Japanese Patent Application No. 2021-035203 are incorporated herein by reference. [Explanation of symbols]

[0077] 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 81, 82 Chamfered part 83 Contact Part 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 Rssi Inner radius Rso Rsso 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, The thickness of the magnetic disk is 0.48 mm or less, At a surface where the magnetic disk contacts the spacer or the clamp, a planar height of an upper surface of the magnetic disk that contacts an outer periphery of the spacer or the clamp is lower than a planar height of an upper surface of the magnetic disk that contacts an inner periphery of the spacer or the clamp, an upper surface of at least one of the magnetic disks contacts the spacer or the clamp at an inner periphery of the magnetic disk, and a gap is formed between a lower surface of at least one of the magnetic disks and the spacer at an inner periphery of the magnetic disk; A magnetic disk device comprising:

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

2. The magnetic disk drive according to claim 1.

3. A plurality of disk-shaped magnetic disks each having a through hole in the center; 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, The thickness of the magnetic disk is 0.48 mm or less, At a surface where the magnetic disk contacts the spacer or the clamp, a planar height of an upper surface of the magnetic disk that contacts an outer periphery of the spacer or the clamp is lower than a planar height of an upper surface of the magnetic disk that contacts an inner periphery of the spacer or the clamp, 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. A magnetic disk device comprising:

4. A plurality of disk-shaped magnetic disks each having a through hole in the center; 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, The thickness of the magnetic disk is 0.48 mm or less, At a surface where the magnetic disk contacts the spacer or the clamp, a planar height of an upper surface of the magnetic disk that contacts an outer periphery of the spacer or the clamp is lower than a planar height of an upper surface of the magnetic disk that contacts an inner periphery of the spacer or the clamp, 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. A magnetic disk device comprising:

5. A plurality of disk-shaped magnetic disks each having a through hole in the center; 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, The thickness of the magnetic disk is 0.48 mm or less, At a surface where the magnetic disk contacts the spacer or the clamp, a planar height of an upper surface of the magnetic disk that contacts an outer periphery of the spacer or the clamp is lower than a planar height of an upper surface of the magnetic disk that contacts an inner periphery of the spacer or the clamp, 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; A magnetic disk device comprising:

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