Hard disk drive device

Abstract

To provide an annular spacer that suppresses deterioration of flatness of a magnetic disk in a clamp fixed state and a hard disk device including the spacer.SOLUTION: Provided is an annular-shaped glass spacer 1 provided such that a main surface is in contact with a magnetic disk in a hard disk drive device, the spacer 1 having a pair of main surfaces 4, an inner circumferential surface 3, and an outer circumferential surface 2, in which a chamfered surface is present between each of the pair of main surfaces 4 and the outer circumferential surface 2, and at least a part of an outer circumferential region of at least one of the pair of main surfaces 4 has an inclined region 1A that is inclined toward the other main surface side in a radial direction from a center of the spacer 1 to the outer circumferential surface side.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an annular spacer that is provided so as to come into contact with a magnetic disk within a hard disk drive device, and to a hard disk drive device. [Background technology]

[0002] 2. Description of the Related Art With the recent rise of cloud computing, data centers for cloud computing are now using many hard disk drive devices (hereinafter also referred to as HDD devices) in order to increase storage capacity.

[0003] In HDD devices, annular spacers are provided between the magnetic disks in the HDD device to keep the magnetic disks apart. The spacers function to keep the magnetic disks from touching each other and to space the magnetic disks at predetermined positions with high precision. In an HDD device, spacers are sandwiched between multiple magnetic disks, and a spindle is passed through the inner holes of the magnetic disks and spacers to create a stack of magnetic disks and spacers. The stack is then pressed from one side with a clamping member, thereby fixing the magnetic disks and spacers in place.

[0004] For example, a glass spacer is known in which the average surface roughness of the portion in contact with the information recording medium substrate is 0.001 to 0.005 μm (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4136268 Summary of the Invention [Problem to be solved by the invention]

[0006] It has been found that in an HDD device in which a magnetic disk is fixed using the spacer described above, the flatness of the main surface of the magnetic disk closest to the clamp member is significantly deteriorated. This deterioration in flatness is undesirable because it makes the magnetic disk more likely to flutter when rotating at high speed. It is also undesirable because it makes the magnetic disk more likely to come into contact with the ramp member, which is the retreat area for the magnetic head.

[0007] SUMMARY OF THE PRESENTLY PREFERRED EMBODIMENTS The present invention has an object to provide a spacer for use in a hard disk drive device that suppresses deterioration of the flatness of a magnetic disk in a clamped state. [Means for solving the problem]

[0008] One aspect of the present invention is an annular spacer that is provided in a hard disk drive device so that its main surface is in contact with a magnetic disk. the spacer has a pair of main surfaces, an inner peripheral surface, and an outer peripheral surface, and a chamfered surface is provided between each of the pair of main surfaces and the outer peripheral surface; At least a portion of an outer circumferential region of at least one of the pair of main surfaces has an inclined region inclined toward the other main surface in a radial direction from the center of the spacer toward the outer circumferential surface.

[0009] The clearance of the inclined region inclined toward the other main surface is preferably 0.1 to 2 μm.

[0010] The inclined region is preferably a curved surface that is convex in a direction from the inside to the outside of the spacer. It is preferable that the thickness of the magnetic disk is 80% or less of the thickness of the spacer.

[0011] Preferably, the spacer material comprises glass.

[0012] It is preferable that the Young's modulus of the spacer is smaller than the Young's modulus of the substrate constituting the magnetic disk.

[0013] It is preferable that the spacer has a conductive film on its surface.

[0014] The magnetic disk preferably has a thickness of 0.55 mm or less.

[0015] Another aspect of the present invention is a hard disk drive device including the spacer and the magnetic disk.

[0016] Another aspect of the present invention is a hard disk drive device including ten or more magnetic disks and the spacer. The substrates of the magnetic disks are preferably made of glass. Effect of the Invention

[0017] The above-mentioned spacer can prevent the flatness of the magnetic disk from deteriorating when it is in a clamped state. [Brief description of the drawings]

[0018] [Figure 1] 1 is a perspective view of an external appearance of a magnetic disk spacer according to an embodiment of the present invention; [Diagram 2] 1A and 1B are diagrams illustrating the arrangement of a spacer and a magnetic disk according to an embodiment. [Diagram 3] 1 is a cross-sectional view of a main portion illustrating an example of the structure of an HDD device into which a spacer according to an embodiment is incorporated. [Figure 4] 4A to 4C are diagrams for explaining in detail the shape of the main surfaces of a spacer according to one embodiment. [Diagram 5] 1A and 1B are diagrams illustrating a state in which a magnetic disk is fixed by a top clamp in an HDD device. [Figure 6] 8 is a cross-sectional view of the spacer of the embodiment shown in FIG. 7 taken along line AA. [Figure 7] 1 is a view of a spacer according to an embodiment, viewed from one main surface side, in which the shaded area indicates an outer periphery region. [Figure 8] 3A to 3C are diagrams showing three examples of the shape of a main surface of a spacer according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The spacer of the present invention will be described in detail below. FIG. 1 is an external perspective view of a glass spacer (hereinafter simply referred to as a spacer) 1 of one embodiment, and FIG. 2 is a diagram illustrating the arrangement of the spacer 1 and a magnetic disk 5. FIG. 3 is a cross-sectional view of a main part illustrating an example of the structure of an HDD device in which the spacer 1 is incorporated. Materials of the spacer 1 described below include glass, but the spacer 1 is not necessarily limited to being made of glass. Other materials that can be used for the spacer 1 include metal materials such as stainless steel, titanium, aluminum, and aluminum alloys, and ceramics.

[0020] As shown in FIG. 2, the spacer 1 is assembled in an HDD device with the magnetic disks 5 and the spacers 1 stacked alternately. As shown in FIG. 3, a plurality of magnetic disks 5 are inserted into a rotating spindle 16 with the spacers 1 sandwiched between them, and the magnetic disks 5 are fixed to the spindle 16 by being pressed from above the stack of magnetic disks 5 and spacers 1 by a clamp member 12 fixed by a screw or the like, so that the magnetic disks 5 are attached at a predetermined interval. The clamp member 12 directly and locally presses the topmost magnetic disk 5 supported from below by the spacer 1. The clamp member 12 has a circular projection 14 for pressing the magnetic disk 5 provided around the central axis of the spindle 16. The cross section of the tip of the projection 14 in the radial direction of the clamp member is in the shape of a circular arc. In this way, the topmost magnetic disk 5 is pressed by the clamp member 12 and clamped. The entire stack is also clamped by the pressing force.

[0021] The spacer 1 described in the following embodiment is intended as a spacer provided between two magnetic disks 5 so as to be in contact with the magnetic disks 5.

[0022] As shown in Fig. 1, the spacer 1 has an annular shape and includes an outer peripheral surface 2, an inner peripheral surface 3, and opposing main surfaces 4. The pair of main surfaces are substantially parallel. The inner peripheral surface 3 and the outer peripheral surface 2 are substantially perpendicular to the pair of main surfaces 4. The surface of the spacer 1 may be appropriately provided with a chamfered surface (not shown). Here, "substantially parallel" means, for example, that the parallelism is 5 µm or less. Furthermore, "substantially perpendicular" means, for example, that the angle is 85 to 95 degrees. The inner peripheral surface 3 is a surface that comes into contact with the spindle 16 and is a wall surface that surrounds a hole having an inner diameter slightly larger than the outer diameter of the spindle 16 . The main surfaces 4 are the two surfaces that come into contact with the magnetic disk 5. The main surfaces 4 of the spacer 1 come into contact with the main surfaces of the magnetic disk 5 and fix the magnetic disk 5 by frictional force. The magnetic disk 5 fixed in this manner can be rotated at high speed by the rotation of the spindle 16, and magnetic information is read or written by a read / write magnetic head (not shown).

[0023] The clamp member 12 that presses and fixes the magnetic disks 5 is made of stainless steel, aluminum alloy, etc., because it has high mechanical strength and rigidity and is easy to process. In order to reliably press and fix the uppermost magnetic disk 5, a circular projection 14 extending in an arc shape is provided.

[0024] Fig. 4 is a diagram for explaining in detail the cross-sectional shape of the main surface 4 of the spacer 1 (cross-sectional shape cut along the radial direction of the spacer 1). In the example shown in Fig. 4, the inclination of the inclined surface (inclined region or inclined portion) 1A described below is emphasized. Here, the terms inclined surface, inclined region, and inclined portion refer to a portion that exists in at least a part of the outer circumferential region of at least one of the pair of main surfaces 4 and is inclined toward the other main surface 4 in the radial direction from the center of the spacer 1 toward the outer circumferential surface side. A part of the main surface 4 on at least one side of the spacer 1 is inclined as an inclined surface 1A, which is inclined so that the height of the surface of the spacer 1 gradually decreases toward the corner between the main surface 4 and the outer peripheral surface 2 of the spacer 1. In other words, the inclined surface 1A is inclined so that the thickness of the spacer 1 decreases. The inclined surface 1A is inclined so as to move away from the magnetic disk 5. The inclined surface 1A is inclined so as to approach the main surface 4 on the other side of the spacer 1 toward the corner. In the example shown in FIG. 4, the inclined surface 1A is provided on the upper main surface 4, but the inclined surface 1A may be provided on both the upper and lower main surfaces 4.

[0025] The reason for providing the inclined surface 1A from a certain radial position on the main surface 4 toward the outer circumferential surface 2 is to suppress deterioration of flatness due to warping of the magnetic disk 5 when the magnetic disk 5 is pressed and fixed by the clamp member 12. Figure 5 is a cross-sectional view illustrating the fixed state of the magnetic disk 5 by the clamp member 12. When a conventional spacer 1 without an inclined surface 1A is used, the magnetic disk 5 is pressed by the protrusion 14 and warps upward as shown by the dotted line in FIG. 5. This is considered to occur due to the following mechanism. That is, in recent years, the magnetic disk 5 has become a relatively thin plate material, so that the localized pressing force from the tip of the arc-shaped protrusion 14 is not diffused to the magnetic disk 5, and the pressing force of the protrusion 14 is transmitted to the spacer 1. As a result, the portion of the main surface 4 of the spacer 1 directly below the tip of the protrusion 14 (the central peripheral portion of the main surface 4) is locally recessed due to the pressing force from the protrusion 14, and the shape of the main surface 4 is deformed so that the portion on the outer peripheral side from the recessed portion (the outer peripheral region of the main surface 4) rises upward. It is considered that the magnetic disk 5 sandwiched between the spacer 1 and the clamp member 12 warps upward as shown by the dotted line in accordance with this deformation of the main surface 4.

[0026] In contrast, in the spacer 1 of the embodiment, as shown in FIG. 4, a part of the main surface 4 is an inclined surface 1A inclined so that the thickness of the spacer 1 becomes thinner toward the corner between the main surface 4 and the outer peripheral surface 2 of the spacer 1. Therefore, even if the part of the main surface 4 (the middle peripheral region of the main surface 4) receiving the pressing force of the protrusion 14 is locally recessed, the part on the outer peripheral surface side relative to this part (the outer peripheral region of the main surface 4) does not rise upward from the recessed part. That is, the recess of the main surface 4 due to the pressing force of the protrusion 14 can be offset. In other words, in anticipation of the deformation of the main surface 4 receiving the force of the protrusion 14, the part of the main surface 4 on the outer peripheral surface 2 side relative to the part receiving the force of the protrusion 14 is an inclined surface 1A inclined so that the thickness of the spacer 1 becomes thinner, so that the part on the outer peripheral surface 2 side does not rise upward. Therefore, the magnetic disk 5 does not warp upward as shown by the dotted line in FIG. 5. In other words, the inclined surface 1A is inclined so as to move away from the magnetic disk 5 toward the corner between the main surface 4 and the outer peripheral surface 2 of the spacer 1.

[0027] FIG. 6 is a cross-sectional view of a spacer having a chamfered surface between the main surface and the outer circumferential surface. FIG. 7 is a view of a spacer having an annular shape as viewed from one main surface side, and FIG. 6 is a cross-sectional view of the spacer shown in FIG. 7 along the line AA. In FIG. 7, the shaded area is the outer circumferential region of the main surface, and at least a part of the outer circumferential region has an inclined region 1A (as described above, in this specification, it may be called an "inclined surface", "inclined portion", etc.) inclined toward the other main surface side in the radial direction from the center of the spacer toward the outer circumferential surface side. On the other hand, the spacer shown in FIG. 6 has an outer circumferential surface 2, an inner circumferential surface 3, and a main surface 4 facing each other, and a chamfered surface 6 is present between the main surface 4 and the outer circumferential surface 2. As shown in FIG. 6, a chamfered surface 6A may be present between the main surface 4 and the inner circumferential surface 3.

[0028] In one embodiment, the inclined region 1A is preferably a curved surface that is convex from the inside to the outside of the spacer. By forming the inclined region 1A in such a shape, the shape of the main surface 4 that is deformed by the pressing force of the protrusion 14 can be maintained almost horizontal without curving upward or downward. The clearance D of the inclined region 1A before receiving the force of the protrusion 14 (the amount of change in the position in the thickness direction from the start position S of the inclined surface 1A on the inner peripheral surface 3 side to the end position of the inclined region 1A on the outer peripheral surface 2 side. However, the inclined region is only a part of the main surface and is not included in the chamfered surface) is, for example, 2.0 μm or less. If the clearance D exceeds 2.0 μm, it may take time to manufacture the spacer 1, and the production cost may increase. From the same viewpoint, the clearance D is more preferably 1.5 μm or less. Moreover, the clearance D is preferably 0.1 μm or more. If the clearance D is less than 0.1 μm, the effect of suppressing the deterioration of the flatness of the magnetic disk 5 in the clamped fixed state may be reduced.

[0029] When the length of the main surface of the spacer 1 along the radial direction from the center of the annular shape of the spacer 1 is L (L is also called the width of the main surface of the spacer 1), the start position S of the inclined surface 1A is preferably located at a position that is radially separated from the edge position of the outer peripheral surface of the main surface by a distance of 20% or more of the length L. If the start position S of the inclined surface 1A is located at a position radially separated from the edge position of the outer peripheral surface of the main surface by less than 20% of the length L, the effect of suppressing deterioration of the flatness of the magnetic disk 5 in the clamped state may be reduced. 8 is a cross-sectional view illustrating examples of the shape of the main surface 4 of the spacer 1. Three representative examples of the shape (cross-sectional view) of the outer circumferential region of the main surface 4 are shown in Fig. 8. In each drawing, the inclination of the inclined surface is emphasized, and the chamfered surface 6 is not shown. The main surface of the spacer 1 has an inclined surface such that the height of the surface of the spacer 1 gradually decreases (or the thickness of the spacer 1 gradually decreases) toward the corner between the main surface 4 and the outer peripheral surface 2 (or, in the case where a chamfered surface 6 is present between the main surface 4 and the outer peripheral surface 2, toward the corner between the main surface 4 and the chamfered surface 6), which is referred to as a "rounded edge shape" (see Figures 4 and 8(a)). If there is another inclined surface on the main surface of the spacer 1 whose surface height decreases toward the inner circumferential surface 3 (i.e., if the radial cross-sectional shape of the main surface is an upwardly convex arc shape. Hereinafter, this will be referred to as an arc-shaped shape. See FIG. 8(b)), the start position S of the inclined surface 1A can be the apex position of the upwardly convex arc in the thickness direction of the spacer. Note that if there are multiple upwardly convex arc shapes on the profile of the radial main surface, the highest position in the thickness direction of the spacer can be the start position S of the inclined surface 1A. Furthermore, when the shape of the main surface of the spacer 1, when viewed in radial cross section, monotonically decreases from the edge on the inner circumferential surface side to the edge on the outer circumferential surface side (including the case where the shape decreases non-linearly but monotonically. Hereinafter, this will be referred to as a "substantially linear shape." See Figure 8(c)), the starting position S of the inclined surface 1A can be the edge on the inner circumferential surface side on the main surface.

[0030] The clearance D can be measured, for example, by an optical interferometer. Specifically, it can be measured, for example, by a flatness tester FT-17 manufactured by NIDEK Corporation. After acquiring shape data of the main surface of the spacer 1, the cross-sectional shape in the radial direction of the spacer 1 is analyzed (i.e., the height data of the spacer main surface along any radial direction is displayed as a cross-sectional view and analyzed), and the heights at the start position S of the inclined surface 1A and the end position (the boundary between the main surface and the chamfered surface on the outer periphery) of the inclined surface 1A are measured, and the difference in the thickness direction (the difference in the respective heights) is calculated. This measurement is repeated every 90 degrees with the center of the spacer 1 as the reference to acquire four data, and the average value of these data can be regarded as the clearance D of one main surface. As described later, when grinding or polishing the main surface of the spacer 1 in the same manner as in the manufacture of a magnetic disk substrate, a double-sided simultaneous processing device is basically used, so that the clearance D of each of the pair of main surfaces is almost the same. In addition, in the individual radial profile data, there are cases where the outer peripheral region of the main surface does not sink, and the position of the edge on the outer peripheral side on the main surface is the highest. In such cases, the above-mentioned amount of allowance may be calculated by assigning an opposite sign to the amount of allowance. For example, the height of the edge on the outer peripheral side and the lowest height on the main surface profile are obtained, the difference between the two in the thickness direction is calculated, and the opposite sign to the above-mentioned amount of allowance may be assigned. In this way, it is possible to calculate together with other amount of allowance data, so that the average amount of allowance for the main surface 4 can be correctly grasped. The inclination angle of such inclined surface 1A with respect to the horizontal portion of the main surface 4 is, for example, 0 degrees to 5 degrees or less, and the inclined surface 1A is different from a chamfered surface having an inclination angle of, for example, 20 degrees or more.

[0031] According to an embodiment, the thickness of the magnetic disk 5 mounted on the HDD together with the spacer 1 is preferably 80% or less of the thickness of the spacer 1. The thickness of the magnetic disk 5 is more preferably 70% or less of the thickness of the spacer 1, and even more preferably 50% or less. As the thickness of the magnetic disk 5 becomes thinner, the pressing force of the clamp member 12 penetrates the magnetic disk 5 and easily affects the spacer 1, so that the surface of the spacer 1 is more likely to deform into a concave shape around the part that receives the pressing force. When the spacer 1 deforms into a concave shape, the magnetic disk 5 follows suit and bends significantly. Then, the outer peripheral edge of the magnetic disk 5 is displaced from a predetermined position in the plate thickness direction, causing problems such as contact with a ramp. However, by using the spacer 1 of this embodiment, the concaveness of the spacer 1 can be offset in the above case, so that bending of the magnetic disk 5 can be suitably prevented. That is, warping of the magnetic disk 5 can be suppressed. The thickness of the spacer 1 is, for example, 0.5 to 3 mm, and the thickness of the magnetic disk 5 is, for example, 0.2 to 0.8 mm. There is no particular restriction on the substrate material of the magnetic disk 5, but for example, a glass substrate or an aluminum alloy substrate can be used. Among these, a glass substrate is more preferable from the viewpoint of the effect of the spacer 1 being high due to its relatively high rigidity.

[0032] According to an embodiment, the Young's modulus of the spacer 1 is preferably smaller than that of the substrate constituting the magnetic disk 5. This allows the local pressure from the clamp member 12 to be easily transmitted to the spacer 1 without deforming or damaging the magnetic disk 5, and the portion of the main surface of the spacer 1 that receives the pressure from the clamp member 12 is easily recessed, which prevents the main surface of the spacer 1 from being recessed. In other words, the spacer 1 can easily receive the pressure and deform the shape of the inclined surface 1A to a horizontal surface. The Young's modulus of the spacer 1 is, for example, 60 to 200 [GPa], and the Young's modulus of the substrate constituting the magnetic disk 5 is, for example, 70 to 110 [GPa]. When amorphous glass is used as the material of the spacer 1, the Young's modulus of the spacer 1 is preferably, for example, 60 to 100 [GPa].

[0033] The material of the spacer 1 is not particularly limited, and when glass is used as the material, examples of the material include aluminosilicate glass, soda-lime glass, soda aluminosilicate glass, aluminoborosilicate glass, boron silicate glass, quartz glass, and crystallized glass. Among these, amorphous glass is preferable because it is easy to increase the smoothness of the surface of the spacer 1 and is relatively easy to process. As the aluminosilicate glass, for example, amorphous glass containing silicon dioxide (SiO2): 59 to 63 mass%, aluminum oxide (Al2O3): 5 to 16 mass%, lithium oxide (Li2O): 2 to 10 mass%, sodium oxide (Na2O): 2 to 12 mass%, and zirconium oxide (ZrO2): 0 to 5 mass% can be used. The soda-lime glass may be, for example, amorphous glass containing 65 to 75 mass % SiO2, 1 to 6 mass % Al2O3, 2 to 7 mass % CaO, 5 to 17 mass % Na2O, and 0 to 5 mass % ZrO2.

[0034] The glass material from which the spacer 1 is made may be obtained by any method, such as cutting a plate glass manufactured by a float method or a down-draw method into a circular shape, forming molten glass by a press method, or slicing a glass tube manufactured by a tube drawing method into an appropriate length. The end face (outer or inner peripheral surface) and main surface of the circular glass thus formed may be ground (including chamfering) and polished in the same manner as in manufacturing a magnetic disk substrate. The method of grinding and polishing the end face is not particularly limited, and may be ground or polished by a formed grinding wheel containing diamond abrasive grains of #80 to #1000. The grinding and polishing of the end face may also be performed using an abrasive brush or a polishing pad. Furthermore, the grinding and polishing of the end face may be performed chemically using an etching solution containing hydrofluoric acid or hydrofluoric silicic acid. The inclined surface 1A of the main surface 4 may be formed by grinding or polishing the main surface 4, or by using both of these. For example, in the polishing process, by using a slurry containing alumina or silica abrasive grains and a suede-type polishing pad made of soft polyurethane foam, the above-mentioned removal amount D can be increased. On the other hand, by using a slurry containing cerium abrasive grains and a suede-type polishing pad, the peripheral region of the main surface can be warped upward. Furthermore, by changing or combining the concentration of the slurry, the hardness of the polishing pad, and other conditions, it is possible to obtain a flat main surface without an inclined surface, or to adjust the starting position S of the inclined surface.

[0035] The dimensions of the annular spacer 1 may be changed as appropriate depending on the specifications of the HDD to be mounted, but for a nominal 3.5-inch HDD device, the outer diameter is, for example, 30 to 34 mm, the inner diameter is, for example, 25 mm, and the thickness is, for example, 0.5 to 3 mm. If a chamfered surface (on the inner or outer circumferential surface side) is provided, the angle of the chamfered surface with respect to the main surface is, for example, 20 to 70 degrees, and the radial width of the main surface is, for example, 50 to 500 μm. The shape of the chamfered surface may be straight or curved when viewed in radial cross section. The dimensions of the magnetic disk 5 may also be changed as appropriate depending on the specifications of the HDD to be installed, but if it is intended for a nominal 3.5-inch HDD device, the outer diameter is, for example, 85 to 100 mm, the inner diameter is, for example, 25 mm, and the thickness is, for example, 0.2 to 0.8 mm.

[0036] According to an embodiment, it is preferable that a conductive film is provided on the surface of the spacer 1. Examples of materials for the conductive film include nickel alloys such as nickel phosphorus (NiP), tin oxide (SnO2), zinc oxide (ZnO), titanium oxide, FTO in which tin oxide is doped with fluorine, and AZO in which zinc oxide is doped with aluminum oxide (Al2O3). By providing a conductive film on the surface of the spacer 1 in this manner, static electricity charged on the magnetic disk 5 can be discharged from the spacer 1 to the outside via the metal spindle 16, and the adsorption of foreign matter and fine particles due to static electricity charged on the magnetic disk 5 in the HDD device can be reduced. In addition, dust generation from the surface of the base material of the spacer 1 can also be prevented. The base material of the spacer 1 having the conductive film may be made of glass, ceramics, or metal.

[0037] According to one embodiment, the thickness of the magnetic disk 5 to be mounted in the HDD together with the spacer 1 is preferably 0.55 mm or less. In the case of a magnetic disk 5 having a thickness of 0.55 mm or less, the pressing force of the clamp member 12 is likely to penetrate the magnetic disk 5 and affect the spacer 1, so that the surface of the spacer 1 is likely to deform into a concave shape around the part receiving the pressing force. Furthermore, since the magnetic disk 5 has a thin plate thickness, it is likely to conform to the concave shape of the spacer 1. As a result, the magnetic disk 5 is likely to bend. However, even in this case, the spacer 1 having the above-mentioned inclined surface 1A is preferable because it can suppress or even prevent the above-mentioned bending.

[0038] In an HDD device having such a spacer 1 and magnetic disks 5, the more the number of magnetic disks 5 mounted, the more the pressing force of the clamp member 12 needs to be increased to fix the magnetic disks 5. For this reason, in a conventional spacer without an inclined surface 1A, the more the number of magnetic disks 5 mounted increases, the more the magnetic disks 5 warp. However, by using a spacer 1 having an inclined surface 1A, the magnetic disks 5 are less likely to warp even if the pressing force of the clamp member 12 is increased. In this respect, the spacer 1 having the inclined surface 1A functions effectively in an HDD device having nine or more magnetic disks 5 mounted. Furthermore, in an HDD device having ten or more magnetic disks mounted, the use of the spacer 1 having the inclined surface 1A is even more effective. Furthermore, in an HDD device having eleven or more magnetic disks mounted, the use of the spacer 1 having the inclined surface 1A is even more effective.

[0039] 4, a part of the main surface 4 of the spacer 1 is an inclined surface 1A that is inclined so that the thickness of the spacer 1 becomes thinner toward the corner between the main surface 4 and the outer peripheral surface 2, and the part on the inner peripheral surface side of the inclined surface 1A extending toward the outer peripheral surface side is a horizontal surface with no inclination. However, instead of a horizontal surface, the spacer 1 may be an inclined surface that is inclined so that the thickness of the spacer 1 becomes thinner from the starting position of the inclined surface 1A toward the corner between the main surface 4 and the inner peripheral surface 3. In this case, the starting position S of the inclined surface 1A is the place that protrudes most upward.

[0040] One modified example of the present invention is an annular spacer that is provided in a hard disk drive device so that its main surface comes into contact with a magnetic disk. The main surface on at least one side of the spacer has a slope that is inclined away from the magnetic disk toward a corner between the main surface and the outer peripheral surface of the spacer in a portion of the main surface. In other words, the main surface on at least one side of the spacer has a slope that is inclined toward a corner between the main surface and the outer peripheral surface of the spacer in a portion of the main surface so as to approach the main surface on the other side of the spacer. Here, the "corner" refers to the edge between the main surface and the chamfered surface when there is a chamfered surface between the main surface and the outer peripheral surface.

[0041] Yet another modification of the present invention is an annular spacer provided in a hard disk drive device with a main surface in contact with a magnetic disk, wherein the main surface on at least one side of the spacer is an inclined surface that is inclined in part so that the thickness of the spacer becomes thinner toward a corner between the main surface and the outer circumferential surface of the spacer. EXAMPLES

[0042] Using an HDD equipped with nine magnetic disks, the relationship between the clearance D of the outer peripheral region of the main surface of the spacer and the change in flatness (warping) of the magnetic disk (the one fixed at the top) before and after clamping was investigated. Specifically, the top magnetic disk and the spacer immediately below were removed from the spindle of the HDD, and the flatness of the removed magnetic disk was measured. Next, an arbitrary spacer for which the clearance D was measured was attached to the spindle with the surface for which the clearance was measured facing up, followed by the magnetic disk whose flatness had been previously measured being attached to the spindle, and finally clamping was performed using a clamp member, and the flatness of the top surface of the magnetic disk was measured in this state. Anything that would interfere with the measurement (such as a ramp member) was removed from the HDD in advance. The flatness (warping) of the magnetic disk was measured as the maximum height difference on the surface of the magnetic disk using Optiflat manufactured by Phase Shift Technology.

[0043] The specifications of the spacer and magnetic disk are as follows: Spacer: Made of amorphous glass (Young's modulus: 72 GPa), outer diameter 32 mm, inner diameter 25 mm, plate thickness 1.8 mm, chamfered surface has a radial length of 250 μm on both the inner and outer circumference sides and an angle of 45 degrees with respect to the inner and outer circumference surfaces. The width L of the main surface is 3.0 mm. By adjusting the manufacturing conditions of the spacers in various ways, spacers with various clearance amounts D of the inclined surfaces were manufactured. Magnetic disk: A magnetic film etc. is formed on a glass substrate. The Young's modulus of the glass substrate is 80 GPa, the diameter is 97 mm, the inner diameter is 25 mm, and the plate thickness is 0.5 mm.

[0044] <Drop-off amount D> Four pieces of data were obtained at 90° intervals on one main surface of one spacer, and the average value was calculated. The sign of the allowance D is defined as follows: When the main surface profile slopes toward the other main surface as it approaches the outer circumferential surface (i.e., has a descending shape) (i.e., in the case of the spacer of the present invention), it is considered positive, and conversely, when it becomes higher as it approaches the outer circumferential surface and the outer circumferential edge is the highest, it is considered negative.

[0045] <Change in flatness> The flatness of a magnetic disk is generally greater after clamping than before clamping, but the opposite is also true in some cases, so the change in flatness is shown as an absolute value. If the change in flatness is 4 μm or less, it can be used, if it is 3 μm or less it is preferably usable, and if it is 2.5 μm or less it is more preferably usable.

[0046] [Table 1]

[0047] As shown in the above results, it was found that by setting the clearance amount D to more than 0 (positive), the amount of change in flatness can be reduced to 4 μm or less. It was also found that by setting the clearance amount D to 0.1 to 2.0 μm, the amount of change in flatness can be reduced to 3 μm or less. It was also found that by setting the clearance amount D to 0.1 to 1.5 μm, the amount of change in flatness can be reduced to 2.5 μm or less.

[0048] The spacer and hard disk drive device of the present invention have been described in detail above, but the present invention is not limited to the above-mentioned embodiments and examples, and various improvements and modifications may of course be made within the scope that does not deviate from the gist of the present invention. [Explanation of symbols]

[0049] 1 Glass Spacer 1A Slope 2 Outer surface 3 Inner surface 4 Main surface 5. Magnetic Disk 10. Hard disk drive device 12 Clamping member 14 protrusions 16 Spindle 18 Rotational Axis

Claims

1. A hard disk drive device, The hard disk drive includes ten or more magnetic disks, and an annular spacer disposed in the hard disk drive such that a main surface of the spacer is in contact with any one of the magnetic disks, the spacer has a pair of main surfaces, an inner peripheral surface, and an outer peripheral surface, and a chamfered surface is provided between each of the pair of main surfaces and the outer peripheral surface; A hard disk drive device, wherein at least one of the pair of main surfaces has an inclined region inclined toward the other main surface in a radial direction from the center of the spacer toward the outer circumferential surface, within at least a part of the outer circumferential region within the range of the main surface.

2. A hard disk drive device as described in claim 1, wherein the clearance of the inclined region inclined toward the other main surface of the spacer is 0.1 to 2 μm.

3. A hard disk drive device, The hard disk drive includes ten or more magnetic disks, and an annular spacer disposed in the hard disk drive such that a main surface of the spacer is in contact with any one of the magnetic disks, the spacer has a pair of main surfaces, an inner peripheral surface, and an outer peripheral surface, and a chamfered surface is provided between each of the pair of main surfaces and the outer peripheral surface; A hard disk drive device, wherein at least one of the pair of main surfaces has a portion within the range of the main surface and at least a part of the outer circumferential region, the radial cross-sectional shape from the center of the spacer toward the outer circumferential surface side being an upwardly convex arc.

4. 4. The hard disk drive device according to claim 3, wherein in a cross-sectional shape of the main surface, a difference in height in the thickness direction of the spacer between a vertex position in the thickness direction of the spacer on the upwardly convex arc and an edge on the outer circumferential surface side of the main surface is 0.1 to 2 μm.

5. 5. The hard disk drive device according to claim 1, wherein the magnetic disk has a thickness of 0.55 mm or less.

6. A hard disk drive device described in any one of claims 1 to 5, wherein a material of the spacer includes any one of glass, stainless steel, titanium, aluminum, aluminum alloy, and ceramics.

7. 7. The hard disk drive device according to claim 1, wherein a substrate of the magnetic disk is made of glass.

8. 8. The hard disk drive device according to claim 1, wherein the Young's modulus of the spacer is smaller than the Young's modulus of a substrate that constitutes the magnetic disk.

9. 9. The hard disk drive device according to claim 1, wherein the spacer has a conductive film on a surface thereof.

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