Disk device

Abstract

An embodiment provides a disk device capable of increasing the number of recording media that can be set. According to the embodiment, the disk device includes: a housing having a bottom wall and a cover opposite to the bottom wall; a plurality of magnetic recording media (18) rotatably arranged in the housing and coaxially spaced and stacked at predetermined intervals; and a plurality of spacer rings (66) respectively arranged between adjacent magnetic recording media. At least one of the uppermost magnetic recording medium (18U) adjacent to the cover and the lowermost magnetic recording medium (18L) adjacent to the bottom wall has a substrate with higher rigidity than substrates of other magnetic recording media, and the spacer ring connected to the magnetic recording medium having the substrate with higher rigidity has a thermal expansion coefficient different from the thermal expansion coefficients of the other spacer rings.

Description

[0001] This application claims the priority of Japanese Patent Application No. 2020-138035 (filing date: August 18, 2020) as a basic application. The present application incorporates all the contents of the basic application by reference. Technical Field

[0002] An embodiment of the present invention relates to a disk device. Background Art

[0003] As a disk device, for example, a hard disk drive (HDD) includes: a plurality of magnetic recording media (disks) rotatably arranged in a housing, a plurality of magnetic heads for reading and writing information on the disks, and a head actuator for supporting the magnetic heads so that they can move relative to the disks.

[0004] In recent years, disk devices have been increasing in number and thinning due to higher capacity. Due to the thinning, the deflection of the disk during drop impact increases, and there is a concern of failures caused by slopes or contact between the head and the disk. Summary of the invention

[0005] An embodiment of the present invention provides a disk device having improved shock resistance.

[0006] According to an embodiment, a disk device comprises: a housing having a bottom wall and a cover opposite to the bottom wall; a plurality of magnetic recording media coaxially spaced apart from each other in a stacked manner in the housing; and a plurality of spacer rings respectively arranged between adjacent magnetic recording media. At least one of the uppermost magnetic recording medium adjacent to the cover and the lowermost magnetic recording medium adjacent to the bottom wall has a substrate having higher rigidity than substrates of other magnetic recording media, and the spacer ring connected to the magnetic recording medium having the substrate having higher rigidity has a thermal expansion coefficient different from the thermal expansion coefficients of the other spacer rings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is an exploded perspective view showing the top cover of the hard disk drive (HDD) according to the first embodiment in an exploded state.

[0008] Figure 2 is a cross-sectional view of the HDD.

[0009] Figure 3 This is a cross-sectional view showing an enlarged view of a magnetic head and a magnetic disk in the HDD.

[0010] Figure 4 It is a cross-sectional view schematically showing a magnetic disk and a spindle motor in the HDD.

[0011] Figure 5It is a cross-sectional view schematically showing a magnetic disk and a spindle motor in a HDD according to a second embodiment.

[0012] Figure 6 It is a cross-sectional view schematically showing a magnetic disk and a spindle motor in a HDD according to a third embodiment.

[0013] Figure 7 It is a diagram showing a combination of materials for forming a magnetic disk, a spacer, and a spindle motor in an HDD according to a fourth embodiment.

[0014] Figure 8 It is a diagram showing a combination of materials for forming a magnetic disk, a spacer, and a spindle motor in an HDD according to a fifth embodiment.

[0015] Fig. 9 It is a diagram showing a combination of materials for forming a magnetic disk, a spacer, and a spindle motor in an HDD according to a sixth embodiment.

[0016] Fig.10 It is a diagram showing a combination of materials for forming a magnetic disk, a spacer, and a spindle motor in an HDD according to a seventh embodiment. DETAILED DESCRIPTION

[0017] Hereinafter, a disk device according to an embodiment will be described with reference to the drawings.

[0018] In addition, the disclosure is only an example, and appropriate and easily conceivable changes that maintain the gist of the invention by a person skilled in the art are of course included in the scope of the present invention. In addition, the drawings sometimes schematically show the size and shape of each part compared to the actual form in order to make the description clearer, but this is only an example and does not limit the interpretation of the present invention. In addition, in this specification and each figure, the same reference numerals are given to the same elements as those already described in the figures that have appeared, and the detailed description is sometimes appropriately omitted.

[0019] (First embodiment)

[0020] A hard disk drive (HDD) according to the first embodiment will be described in detail as the disk device.

[0021] Figure 1 This is an exploded perspective view of the HDD according to the embodiment, shown with the cover removed.

[0022] like Figure 1As shown, the HDD has a rectangular housing 10. The housing 10 has a rectangular box-shaped base 12 with an opening on the top and a cover (top cover) 14. The base 12 has a rectangular bottom wall 12a and a side wall 12b erected along the periphery of the bottom wall 12a, and is integrally formed of, for example, aluminum. The cover 14 is formed into a rectangular plate shape, for example, from stainless steel. The cover 14 is screwed to the side wall 12b of the base 12 by a plurality of screws 13, and the upper opening of the base 12 is airtightly closed.

[0023] A plurality of (for example, 10) magnetic disks 18 and a spindle motor 19 that supports and rotates the magnetic disks 18 are provided in the housing 10 as disk-shaped magnetic recording media. The spindle motor 19 is disposed on the bottom wall 12a. Each magnetic disk 18 has, for example, a substrate formed in a disk shape with a diameter of 95 mm (3.5 inches) and made of a non-magnetic body (for example, glass or aluminum) and a magnetic recording layer formed on the upper and lower surfaces of the substrate. Each magnetic disk 18 is coaxially fitted to a hub of the spindle motor 19 described later and is clamped by a clamp spring 20. Thus, the 10 magnetic disks 18 are coaxially stacked at predetermined intervals and supported in a state of being positioned parallel to the bottom wall 12a of the base 12. The magnetic disk 18 is rotated in the direction of arrow B at a predetermined rotation speed by the spindle motor 19. In addition, the number of magnetic disks 18 mounted is not limited to 10, and may be set to be less than 9, more than 10, and less than 12.

[0024] A plurality of magnetic heads 17 for recording and reproducing information on a magnetic disk 18 and an actuator assembly 22 for supporting the magnetic heads 17 so as to be movable relative to the magnetic disk 18 are provided in the housing 10. In addition, a voice coil motor (VCM) 24 for rotating and positioning the actuator assembly 22, a ramp loading mechanism 25 for holding the magnetic head 17 at an unloading position away from the magnetic disk 18 when the magnetic head 17 moves to the outermost periphery of the magnetic disk 18, a substrate unit (FPC unit) 21 on which electronic components such as a conversion connector are mounted, and a spoiler 70 are provided in the housing 10. The ramp loading mechanism 25 has a ramp 80 provided on the bottom wall 12a and located near the outer periphery of the magnetic disk 18, and a protrusion to be described later provided on the actuator assembly 22.

[0025] A printed circuit board 27 is screwed onto the outer surface of the bottom wall 12 a of the base 12 . The printed circuit board 27 constitutes a control unit that controls the operation of the spindle motor 19 and controls the operations of the VCM 24 and the magnetic head 17 via the board unit 21 .

[0026] The actuator assembly 22 includes an actuator block 29, a plurality of arms 32 extending in the same direction from the actuator block 29, and a head gimbal assembly (HGA) 30 mounted on the extending end of each arm 32. The actuator block 29 is rotatably supported by a support shaft (pivot) 28 erected on the bottom wall 12a via a unit bearing. Each HGA 30 includes a suspension (load beam) 26 extending from the arm 32, and a flexible member (wiring member) 28 (see FIG. 1 ) disposed on the load beam 26 and the arm 32. Figure 3 ) and the magnetic head 17 mounted on the universal joint portion 41 of the flexible member 28.

[0027] The head actuator assembly 22 further includes a support frame (not shown) extending from the actuator block 29 in a direction opposite to the arm 32, and a voice coil mounted on the support frame. The voice coil is located between a pair of yokes 37 provided on the bottom wall 12a, and together with the yokes 37 and a magnet fixed to one of the yokes 37, forms a VCM 24.

[0028] The FPC unit 21 has a main body 21a formed by a flexible printed circuit substrate, and the main body 21a is fixed to the bottom wall 12a of the base 12. Electronic components such as a conversion connector are installed on the main body 21a. The conversion connector penetrates the bottom wall 12a and is connected to the printed circuit substrate 27. The FPC unit 21 has a relay flexible printed circuit substrate (hereinafter referred to as a relay FPC) 21b extending from the main body 21a. The extended end of the relay FPC21b is installed on the side (installation surface) of the actuator block 29. The extended end of the relay FPC21b is electrically connected to the magnetic head 17 via the aforementioned flexure 28.

[0029] The ramp loading mechanism 25 includes a ramp 80 provided on the bottom wall 12a and located near the outer periphery of the magnetic disk 18, and a protrusion 35 provided at the front end of each load beam 26 (see FIG. Figure 3 When the magnetic head 17 moves to the outermost periphery of the magnetic disk 18 , the protrusion 35 of the load beam 26 climbs up the slope 80 , and the magnetic head 17 is held in the unloading position away from the magnetic disk 18 .

[0030] Figure 2 1 is a cross-sectional view of the HDD. As shown in the figure, in one example, the spindle motor 19 includes a pivot 60 erected substantially perpendicular to the bottom wall 12a, a cylindrical rotating shaft 62 supported rotatably around the pivot 60, a substantially cylindrical hub 64 coaxially fixed around the rotating shaft 62, a stator coil SC fixed to the bottom wall 12a and arranged around the rotating shaft 62, and a cylindrical magnet M mounted on the inner circumference of the hub 64 and facing the stator coil SC. The hub 64 includes an outer circumferential surface coaxially positioned with the pivot 60 and an annular flange 65 integrally formed at the lower end (end on the bottom wall 12a side) of the outer circumferential surface.

[0031] The magnetic disk 18 is engaged with the outer peripheral surface of the shaft hub 64 in a state where the shaft hub 64 is inserted into the inner hole thereof. In addition, an annular spacer ring 66 is mounted on the outer peripheral surface of the shaft hub 64, and the spacer ring 66 is sandwiched between two adjacent magnetic disks 18. A plurality of magnetic disks 18 and a plurality of spacer rings 66 are sequentially arranged on the flange 65 of the shaft hub 64, and are mounted on the shaft hub 64 in an alternately overlapping state. By pressing the inner peripheral portions of the plurality of magnetic disks 18 and the spacer rings 66 toward the flange 65 side using a clamp spring 20 mounted on the upper end of the shaft hub 64, the plurality of magnetic disks 18 are spaced apart from each other by a predetermined interval and fixed in a stacked state. The lower surface and inner peripheral portion of the lowest magnetic disk 18 abut against the flange 65 of the shaft hub 64. The clamp spring 20 abuts against the upper surface and inner peripheral portion of the uppermost magnetic disk 18. Thus, the ten magnetic disks 18 are supported in parallel with each other and substantially in parallel with the bottom wall 12 a at predetermined intervals, and are supported so as to be rotatable integrally with the rotating shaft 62 and the hub 64 .

[0032] The height (thickness) H of the housing 10 is formed to be less than 26.1 mm at most according to the 3.5-inch HDD specification. The plate thickness T of each disk 18 is formed to be 0.35 to 0.635 mm, and is set to 0.5 mm in this embodiment. The interval d (equivalent to the thickness of the interval ring) between two adjacent disks 18 is formed to be about 1.2 to 1.5 mm. The stacking height h of the entire disk (the height from the lower surface of the lowest disk 18 to the upper surface of the uppermost disk 18) is set to 18.356 mm in this embodiment.

[0033] Figure 3 This is a side view schematically showing an enlarged view of a magnetic head and a magnetic disk of an HDD.

[0034] As shown in the figure, the magnetic disk 18 has a substrate 101 formed into a disc shape and made of a non-magnetic body. A soft magnetic layer 102 as a base layer and a magnetic recording layer 103 and a protective film 104 of its upper layer are sequentially stacked on the upper surface and lower surface of the substrate 101. The magnetic disk 18 is rotated in the direction of arrow B at a predetermined speed by a spindle motor 19.

[0035] Each HGA 30 of the actuator assembly 22 includes a load beam 26 extending from an arm 32, a flexure 28 disposed on the load beam 26 and the arm 32, and a magnetic head 17 mounted on a gimbal portion 41 of the flexure 28. A protrusion 35 extends from the front end of the load beam 26.

[0036] The magnetic head 17 is a floating head, and has a slider 42 of a substantially rectangular parallelepiped shape and a head 43 formed at the end of the outflow end side of the slider 42. The slider 42 is formed of, for example, a sintered body of aluminum oxide and titanium carbide (aluminum-titanium-carbon alloy), and the head 43 is formed of a multilayer film, which constitutes a write element and a read element. The head 43 is electrically connected to the head IC and the control unit (printed circuit board 27) via the wiring of the flexible member 28.

[0037] The slider 15 has a substantially rectangular disk facing surface (ABS) SA facing the surface of the magnetic disk 18. The magnetic head 17 is maintained in a state of floating a predetermined amount from the surface of the magnetic disk 18 by air flow C generated between the disk surface and the disk facing surface SA due to the rotation of the magnetic disk 18.

[0038] Figure 4 It is a cross-sectional view schematically showing a magnetic disk and a spindle motor in an HDD.

[0039] When an impact is applied to the HDD, the impact amplitude of the uppermost disk 18 (the disk closest to the top cover) and the lowermost disk 18 (the disk closest to the base bottom wall) pressed on one side by the clamp spring 20 or the flange 65 of the hub may be larger than that of the intermediate disk 18 pressed widely from both above and below by the spacer ring 66. Therefore, the intermediate disk 18 uses the aluminum substrate 101, while at least one of the uppermost and lowermost disks 18 uses a substrate 101 made of a material different from that of the intermediate disk 18, that is, a material with high rigidity.

[0040] like Figure 4 As shown, according to this embodiment, the topmost magnetic disk 18U uses a substrate 101 formed of a material (e.g., glass) having a higher rigidity than aluminum. In one example, the glass substrate uses a glass substrate having a Young's modulus that is 15% higher than that of an aluminum substrate and a lower density than that of an aluminum substrate. The other magnetic disks 18 use a substrate 101 formed of aluminum.

[0041] In addition, if the material of the substrate 101 is different, the eccentricity of the magnetic disk 18 may increase due to the difference in thermal expansion coefficient between the adjacent spacer ring 66 and the clamp spring 20. Therefore, according to the present embodiment, the other spacer rings 66 are formed of aluminum, and the uppermost spacer ring 66U and the clamp spring 20 that are in contact with the uppermost magnetic disk 18U are formed of a material different from that of the other spacer rings 66 (specifically, a material having a thermal expansion coefficient intermediate between aluminum and glass). As such a material, for example, stainless steel, titanium, glass, etc. can be used.

[0042] As described above, according to the first embodiment, by using the top magnetic disk 18U as a magnetic disk using a glass substrate with high rigidity, the vibration of the magnetic disk when the HDD is impacted can be reduced, thereby improving the impact resistance of the HDD. At the same time, by using the spacer ring 66U and the clamp spring 20 formed of a material with a small difference in thermal expansion coefficient with the glass substrate, the increase in the eccentricity of the top magnetic disk 18U can be suppressed. In addition, at least the spacer ring 66U of the spacer ring 66U and the clamp spring 20 can be formed of the material with a small difference in thermal expansion coefficient, and the clamp spring 20 can also be formed of aluminum.

[0043] As described above, according to the first embodiment, it is possible to provide a magnetic disk device having improved shock resistance.

[0044] Next, the disk structure of the HDD of other embodiments will be described. In the other embodiments described below, the same reference numerals are given to the same parts as the first embodiment, and the detailed description thereof is omitted or simplified, and the description will focus on the parts different from the first embodiment.

[0045] (Second embodiment)

[0046] Figure 5 It is a cross-sectional view schematically showing a magnetic disk and a spindle motor in a HDD according to a second embodiment.

[0047] As shown in the figure, according to this embodiment, the bottom magnetic disk 18L uses a substrate 101 formed of a material (e.g., glass) having a higher rigidity than aluminum. In one example, the glass substrate uses a glass substrate having a Young's modulus that is 15% higher than that of an aluminum substrate and a lower density than that of an aluminum substrate. The other magnetic disks 18 use a substrate 101 formed of aluminum.

[0048] In addition, the other spacer rings 66 and the clamp spring 20 are formed of aluminum, whereas the lowest spacer ring 66L and the hub 64 (at least the flange 65) that are in contact with the lowest magnetic disk 18L are formed of a material different from that of the other spacer rings 66 (specifically, a material having a thermal expansion coefficient intermediate between aluminum and glass). As such a material, for example, stainless steel, titanium, glass, or the like can be used.

[0049] As described above, according to the second embodiment, by making the bottom magnetic disk 18L a magnetic disk using a glass substrate with high rigidity, the vibration of the magnetic disk when the HDD is impacted can be reduced, thereby improving the impact resistance of the HDD. At the same time, by using the spacer ring 66L and the flange 65 formed of a material with a small difference in thermal expansion coefficient from the glass substrate, the increase in the eccentricity of the bottom magnetic disk 18L can be suppressed.

[0050] In addition, at least the spacer ring 66L of the spacer ring 66L and the flange 65 may be formed of the material having a small difference in thermal expansion coefficient, and the flange 65 and the hub may be formed of aluminum.

[0051] As described above, according to the second embodiment, a magnetic disk device having improved shock resistance can be obtained.

[0052] (Third embodiment)

[0053] Figure 6 It is a cross-sectional view schematically showing a magnetic disk and a spindle motor in a HDD according to a third embodiment.

[0054] As shown in the figure, according to this embodiment, the topmost magnetic disk 18U and the bottommost magnetic disk 18L use a substrate 101 formed of a material having higher rigidity than aluminum (e.g., glass). In one example, the glass substrate uses a glass substrate having a Young's modulus that is 15% higher than that of an aluminum substrate and a density that is lower than that of an aluminum substrate. The other magnetic disks 18 in the middle use a substrate 101 formed of aluminum.

[0055] The other intermediate spacer ring 66 is made of aluminum, whereas the uppermost spacer ring 66U and the clamp spring 20 connected to the uppermost magnetic disk 18U, and the lowermost spacer ring 66L and the hub 64 (at least the flange 65) connected to the lowermost magnetic disk 18L are made of a material having a thermal expansion coefficient intermediate between aluminum and glass. For example, stainless steel, titanium, glass, and the like can be used as such a material.

[0056] As described above, according to the third embodiment, by using the uppermost magnetic disk 18U and the lowermost magnetic disk 18L as magnetic disks using a highly rigid glass substrate, it is possible to reduce vibration of the magnetic disks when the HDD receives an impact, thereby improving the impact resistance of the HDD.

[0057] The drop impact test was carried out using the HDD of this embodiment, and compared with the HDD of the comparative example in which all disks used aluminum substrates. The HDD was dropped under the conditions of 50-70G, and the write / read test of the entire surface of the disk was carried out after the impact to compare the extent of the impact that it could withstand. As a result, the HDD equipped with only the disk of the aluminum substrate failed the write / read test under the conditions of 60G. In contrast, the HDD with the top and bottom disks using glass substrates passed the test under the conditions of 60G, confirming the improvement of impact resistance.

[0058] Furthermore, according to the present embodiment, by using the spacer rings 66U, 66L, the clamp spring 20, and the flange 65 formed of a material having a small difference in thermal expansion coefficient with the glass substrate, it is possible to suppress an increase in the eccentricity of the uppermost magnetic disk 18U and the lowermost magnetic disk 18L. In addition, at least the spacer rings 66U, 66L among the spacer rings 66U, 66L, the clamp spring 20, and the flange 65 may be formed of the material having a small difference in thermal expansion coefficient, and the spacer ring 66 and the flange 65 may also be formed of aluminum.

[0059] As described above, according to the third embodiment, it is possible to obtain a magnetic disk device having improved shock resistance.

[0060] Figure 7 This is a diagram showing a first example of the combination of materials for forming each component in the first, second, and third embodiments described above.

[0061] According to the first example, in a HDD having an aluminum motor hub 64, an aluminum clamp spring 20, and a magnetic disk 18 having an aluminum substrate, a glass substrate is used for the topmost and bottommost disks 18U (18L), or only one of them. The glass substrate has a Young's modulus that is 15% or more higher than that of the aluminum substrate and a density that is lower than that of the aluminum substrate. An aluminum-based spacer ring is used for the intermediate layer spacer ring 66, and a stainless steel-based, titanium-based, or glass-based spacer ring having a thermal expansion coefficient different from that of the aluminum-based one is used for the topmost and bottommost or one of them spacer rings 66U, 66U adjacent to the glass substrate.

[0062] Figure 8 This is a diagram showing a second example of the combination of materials for forming each component in the above-mentioned first, second, and third embodiments.

[0063] According to the second example, in a HDD having an aluminum motor hub 64, an aluminum clamp spring 20, and a magnetic disk 18 using an aluminum substrate (aluminum material 1), the topmost and bottommost magnetic disks 18U (18L) or only one of them use an aluminum substrate (aluminum material 2) of a different material. The aluminum substrate (aluminum material 2) uses an aluminum substrate having a Young's modulus higher than that of the aluminum substrate (aluminum material 1) by more than 8% and a density difference of less than 5%. The intermediate layer spacer ring 66 uses aluminum (aluminum material 3), and the topmost and bottommost or one of them spacer rings 66U (66L) adjacent to the magnetic disk 18U (18L) of the aluminum substrate (aluminum material 2) uses an aluminum (aluminum material 4) having a thermal expansion coefficient different from that of the aluminum material 3.

[0064] Fig. 9 It is a diagram showing a third example of the combination of materials for forming each component in the above-mentioned first, second, and third embodiments.

[0065] According to the third example, in an HDD having a stainless steel motor hub 64, a stainless steel clamp spring 20, and a magnetic disk 18 using an aluminum substrate, a glass substrate is used for the topmost and bottommost or only one of the magnetic disks 18U (18L). The glass substrate uses a glass substrate having a Young's modulus higher than that of the aluminum substrate by 15% or more and a density lower than that of the aluminum substrate. The intermediate layer spacer ring 66 uses an aluminum material, and the topmost and bottommost or either of the spacer rings 66U (66L) adjacent to the magnetic disk 18U (18L) of the glass substrate uses a stainless steel, titanium, or glass material having a thermal expansion coefficient different from that of the aluminum material.

[0066] Fig.10 This is a diagram showing a fourth example of the combination of materials for forming each component.

[0067] According to the fourth example, in an HDD having a stainless steel motor hub 64, a stainless steel clamp spring 20, and a magnetic disk 18 of a glass substrate (glass material 1), a glass substrate (glass material 2) of a different material is used for the topmost and bottommost magnetic disks 18U (18L) or only one of them. The glass substrate (glass material 2) uses a glass substrate having a Young's modulus higher than that of the glass substrate (glass material 1) by 8% or more and a density difference of less than 5%. The intermediate layer spacer ring 66 uses stainless steel, titanium, or glass (material 3), and the topmost and bottommost or any one of them spacer rings 66U, 66L adjacent to the magnetic disk 18U (18L) of the glass substrate (glass material 2) uses stainless steel, titanium, or glass (material 4) having a thermal expansion coefficient different from that of material 3.

[0068] In any combination of the first to fourth examples described above, the same operational effects as those of the first to third embodiments described above can be obtained.

[0069] (Fourth embodiment)

[0070] According to the fourth embodiment, in an HDD having a plurality of (for example, 10) magnetic disks 18 using an aluminum substrate or a glass substrate, the topmost and bottommost or only one of the magnetic disks 18U (18L) is a magnetic disk having a substrate thickness different from that of the substrates of the other magnetic disks 18. For example, the substrate of the topmost and bottommost or only one of the magnetic disks 18U (18L) uses a substrate that is +20 to 30% thicker than the substrate thickness of the other magnetic disks 18. In one example, the thickness of the magnetic disk 18 in the middle layer is set to 0.5 mm, and the thickness of the topmost and bottommost magnetic disks 18U and 18L is set to 0.635 mm. The material of each constituent member can be applied to any of the above-mentioned examples 1 to 4. The substrates of all magnetic disks can also be set to aluminum substrates, or the substrates of all magnetic disks can be set to glass substrates.

[0071] As described above, by increasing the thickness of the substrate of the topmost or bottommost disk 18U (18L) or either one of them, the rigidity of the disk 18U (18L) is increased, and the vibration of the disk when the HDD is impacted can be reduced, thereby improving the impact resistance of the HDD.

[0072] The present invention is not limited to the above-mentioned embodiments as it is, and the constituent elements can be deformed and concretized in the implementation stage without departing from the scope of its purpose. In addition, various inventions can be formed by appropriate combinations of multiple constituent elements disclosed in the above-mentioned embodiments. For example, some constituent elements can also be deleted from all the constituent elements shown in the embodiments. Moreover, the constituent elements in different embodiments can also be appropriately combined.

[0073] For example, the number of magnetic disks to be installed is not limited to 10, but may be 9 or less, or may be increased to 11 or 12. The material of each component is not limited to the above-mentioned embodiments or examples, and can be appropriately selected and changed.

Claims

1. A disk device comprising: A housing having a bottom wall and a cover opposite to the bottom wall; a plurality of magnetic recording media coaxially stacked and spaced apart from each other by a predetermined interval within the housing; and A plurality of spacer rings are respectively arranged between adjacent magnetic recording media, At least one of the uppermost magnetic recording medium adjacent to the cover and the lowermost magnetic recording medium adjacent to the bottom wall has a substrate having higher rigidity than substrates of other magnetic recording media. The spacer ring in contact with the magnetic recording medium having the highly rigid substrate has a thermal expansion coefficient different from that of other spacer rings.

2. The disk device according to claim 1, The topmost magnetic recording medium and the bottommost magnetic recording medium have substrates with higher rigidity than substrates of other magnetic recording media, and the spacer ring connected to the topmost magnetic recording medium and the spacer ring connected to the bottommost magnetic recording medium have thermal expansion coefficients different from those of other spacer rings.

3. The disk device according to claim 1, The highly rigid substrate is formed of a material different from a material used to form the substrate of the other magnetic recording medium.

4. The disk device according to claim 3, The spacer ring in contact with the substrate with high rigidity has a thermal expansion coefficient that is intermediate between the thermal expansion coefficient of the substrate with high rigidity and the thermal expansion coefficient of the substrate of the other magnetic recording medium.

5. The disk device according to claim 4, The substrate having high rigidity is composed of a glass substrate, and the substrate of the other magnetic recording medium is composed of an aluminum substrate.

6. The disk device according to claim 3, The thickness of the substrate having high rigidity is greater than the thickness of the substrate of the other magnetic recording medium.

7. The disk device according to claim 1, The plate thickness of the substrate having high rigidity is greater than the plate thickness of the substrate of the other magnetic recording medium.

8. The disk device according to claim 1, It also comprises: a spindle motor, which is arranged on the bottom wall, has a freely rotatable hub engaged with the multiple magnetic recording media and the multiple spacer rings, and an annular flange which is arranged at the end of the bottom wall side of the hub and carries the bottom magnetic recording medium; and a clamping spring, which is fixed to the end of the cover side of the hub and is pressed against the top magnetic recording medium, at least one of the clamping spring and the flange has a thermal expansion coefficient different from the thermal expansion coefficient of the other spacer rings.

9. The disk device according to claim 2, It also comprises: a spindle motor, which is arranged on the bottom wall and has a freely rotatable hub engaged with the multiple magnetic recording media and the multiple spacer rings, and an annular flange which is arranged at the end of the bottom wall side of the hub and carries the bottom magnetic recording medium; and a clamping spring, which is fixed to the end of the cover side of the hub and is pressed against the top magnetic recording medium, the clamping spring and the flange having a thermal expansion coefficient different from the thermal expansion coefficient of the other spacer rings.

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