Magnetic disk device

Abstract

The invention provides a magnetic disk device which carries more than five magnetic disks and is resistant to external impact. According to one embodiment, a magnetic disk device includes a base, a magnetic disk, a head actuator, and a spindle motor. The base body has a bottom wall and a side wall, and the bottom wall has a second thickness. More than five magnetic disks are arranged in the base body. The spindle motor includes a sleeve fixed to the bottom wall and having a first hole, a shaft rotatably inserted through the first hole, and a hub integrally rotatable with the shaft. The hub has a first portion, a second portion, and a third portion, the first portion having a shaft opening, the second portion extending from a lowermost outer peripheral portion of the first portion in a second first direction, the first direction being a direction from the magnetic disk toward the bottom wall, and the third portion extending from a lowermost portion of the second portion in a second direction orthogonal to the first direction. The third portion has a first thickness, and the value obtained by dividing the second thickness by the first thickness is 1.89 or more.

Description

[0001] This application claims the priority of Japanese Patent Application No. 2023-164187 (filing date: September 27, 2023) as a basic application. The present application incorporates the entire contents of the basic application by reference. Technical Field

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

[0003] A hard disk drive (HDD) is a device for recording and storing data, and is composed of a magnetic disk, a head assembly required for reading and writing data, and a spindle motor that rotates the magnetic disk at high speed.

[0004] In order to obtain an HDD resistant to external impact, the base thickness is designed to be thick while considering vibration characteristics. Due to the large capacity of HDDs in recent years, the following problem has arisen in the conventional spindle motor of the shaft rotation method: it is difficult to obtain a disk device resistant to external impact due to the design restriction of the height dimension. Summary of the invention

[0005] An embodiment of the present invention provides a magnetic disk device that is resistant to external impact and that carries five or more magnetic disks.

[0006] The magnetic disk device of this embodiment comprises a base, a magnetic disk, a head actuator and a spindle motor, wherein the base comprises: a bottom wall having a second thickness; and a side wall erected along the peripheral edge of the bottom wall, the magnetic disk is arranged in five or more sheets in the base, the head actuator comprises a magnetic head supported to be movable, and the spindle motor comprises: a sleeve fixed to the bottom wall and having a first hole; a shaft inserted into the first hole in a rotatable state; and a hub rotatable integrally with the shaft. The hub comprises: a first part having a shaft opening portion through which the upper end portion of the shaft is inserted; a second part extending from the lowest outer peripheral portion of the first part toward a first direction, wherein the first direction is a direction from the magnetic disk toward the bottom wall; and a third part extending from the lowest portion of the second part toward a second direction orthogonal to the first direction, facing the bottom wall and having a first thickness, wherein in the third part, a value obtained by dividing the second thickness by the first thickness is greater than 1.89. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a perspective view of the HDD according to the first embodiment.

[0008] Figure 2 It is shown Figure 1 FIG. 1 is a cross-sectional view of the HDD taken along line AA′ shown.

[0009] Figure 3It is a graph showing the relationship between h2 / h1 and impact resistance.

[0010] Figure 4 It is a diagram showing the simulation results of vibration characteristics.

[0011] Description of Reference Numerals

[0012] 10 Housing

[0013] 11 Disk

[0014] 12 Magnetic Head

[0015] 13 Slide

[0016] 14 Voice Coil Motor

[0017] 15 Head actuator

[0018] 16 Base unit

[0019] 100 Spindle motor

[0020] 101 Axis

[0021] 102 Stator

[0022] 103 Coil

[0023] 105 Hub

[0024] 105a Part 1

[0025] 105b Part 2

[0026] 105c Part 3

[0027] 106 Fixture

[0028] 107 Threaded Parts

[0029] 108 Magnet

[0030] 109 Yoke

[0031] 110 Separator

[0032] 111 Sleeve

[0033] 112 Thrust plate

[0034] 113 Thrust bushing

[0035] 200 Matrix

[0036] 201 bottom wall

[0037] 202 Sidewall

[0038] 203 Cylinder

[0039] 204 base surface

[0040] 300 Hole 1

[0041] 301 Hole 2

[0042] 400 Top Cover

[0043] h1 1st thickness

[0044] h2 2nd thickness

[0045] H Height of the housing DETAILED DESCRIPTION

[0046] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the description, common reference numerals are used for common parts in all the accompanying drawings. In addition, the dimensional ratios of the accompanying drawings are not limited to the ratios shown in the drawings. In addition, this embodiment does not limit the present invention.

[0047] [First embodiment]

[0048] A hard disk drive (HDD) according to the first embodiment will be described in detail as a magnetic disk device. Figure 1 is a perspective view of a HDD according to the first embodiment. Figure 2 A cross-sectional view taken along line AA' is shown.

[0049] (Structure of HDD)

[0050] Reference Figure 1 The HDD according to the first embodiment will be described. Figure 1 A perspective view showing the HDD according to the first embodiment.

[0051] like Figure 1 As shown, the HDD includes a housing 10, a rectangular box-shaped base 200 with an upper opening, and a top cover 400. The base 200 includes a rectangular bottom wall 201 and a side wall 202 erected along the peripheral edge of the bottom wall 201, and is formed in one piece. The top cover 400 is sealed by combining with the base 200 by using a plurality of fastening members such as screws. In addition to screws, the top cover 400 and the base 200 can also be sealed by using an adhesive or an embedding mechanism. In addition, as the material of the base 200 and the top cover 400, for example, aluminum, iron, etc. are used.

[0052] A magnetic disk 11 for recording and storing data magnetically, a spindle motor 100, and a head actuator 15 are housed in the base 200. The spindle motor 100 supports the magnetic disk 11 so that it can rotate freely. In addition, the head actuator 15 supports the magnetic head 12 for moving on the surface of the magnetic disk 11 and detecting changes in the recorded magnetic pattern so that it can move freely. There is also a slide 13 for supporting the magnetic head 12 and a voice coil motor 14 for position control of the slide 13. A printed circuit board (not shown) is screwed on the outer surface of the bottom wall 201 of the base 200, and the printed circuit board controls the movement of the spindle motor 100, the voice coil motor 14, and the magnetic head 12 via the substrate unit 16.

[0053] The overall device height of the HDD, which is represented by the distance from the bottom of the bottom wall 201 to the top of the top cover 400, that is, the height (thickness) H of the housing 10 is formed to be 26.1 mm at most according to the HDD standard. In the spindle motor 100, five magnetic disks 11 are mounted via a partition 110 described later. The number of mounted magnetic disks 11 may be more than five. Each magnetic disk 11 is formed into a disk shape with a diameter of 96 mm, for example, but the diameter is not limited thereto, and may be, for example, 97 mm or more.

[0054] The direction from the magnetic disk 11 toward the bottom wall 201 is defined as the Z direction (first direction), the direction along the length direction of the HDD in a plane perpendicular to the Z direction is defined as the Y direction (second direction), and the direction perpendicular to the Z direction and the Y direction is defined as the X direction (third direction). In addition, for the sake of explanation, the direction from the bottom wall 201 toward the top cover 400 is defined as "up", and the opposite direction is defined as "down".

[0055] (Structure of Spindle Motor 100)

[0056] Figure 2 Shows Figure 1 The cross-sectional view of the HDD at the line AA' is shown. Figure 2 As shown, the spindle motor 100 used in the first embodiment has a non-rotating stator 102 and a coil 103 , and is an axially rotating structure including a shaft 101 serving as a rotating shaft and a hub 105 rotating integrally with the shaft 101 .

[0057] The shaft 101 is erected substantially vertically on a thrust bushing 113 described later. The shaft 101 is inserted into the first hole 300 of the sleeve 111 in a rotatable state and supported by a bearing not shown. The sleeve 111 is fixed to the second hole 301 of the bottom wall 201. In addition, a dynamic pressure bearing using fluid pressure of a lubricating fluid, a ball bearing, a linear roller bearing using a tapered roller, etc. may be used between the shaft 101 and the sleeve 111. The first hole 300 and the second hole 301 described above are expressed as holes even when other components are inserted in the finished product.

[0058] On the other hand, in the shaft fixing method, the shaft 101 is fixed to the bottom wall 201 and screwed to the top cover 400. The shaft fixing method is different from the shaft rotating method in that the shaft 101 itself does not rotate but the hub 105 rotates around the shaft 101.

[0059] A cylindrical portion 203 extending in the Z direction is formed in the second hole 301 of the bottom wall 201, and the stator 102 is fixed to the outer periphery of the cylindrical portion 203. The stator 102 is made of a magnetic material such as an electromagnetic steel plate, and has a slit for winding the coil 103.

[0060] The hub 105 as the rotating part of the spindle motor 100 is composed of a first portion 105a, a second portion 105b, and a third portion 105c, and is formed integrally. Figure 2 , the first part 105a and the third part 105c are shown by dotted lines, and the second part 105b is shown by dotted lines. The first part 105a has a shaft opening through which the upper end of the shaft 101 is inserted. Here, the shaft opening of the first part 105a is also expressed as the shaft opening in the state where the shaft 101 is inserted in the finished product. The second part 105b extends in the Z direction in a cylindrical shape from the bottom outer peripheral part of the first part 105a. The third part 105c extends from the bottom of the second part 105b toward the side wall 202 on the XY plane.

[0061] A cylindrical yoke 109 is fixed to the inner peripheral surface of the second portion 105b. A cylindrical magnet 108 is fixed to the yoke 109. The yoke 109 is made of a magnetic material and holds the magnet 108 to obtain stable rotation. In addition, the inner periphery of the magnet 108 is arranged opposite to the outer periphery of the stator 102 with a gap therebetween.

[0062] When a driving current is supplied to the coil 103, a driving force for rotating the magnet 108 is exerted, and the hub 105, the magnet 108, and the yoke 109 rotate relative to the base 200, the stator 102, and the coil 103. As a result, the magnetic disk 11 mounted on the outer periphery of the first portion 105a and the outer periphery of the second portion 105b of the hub 105 can be rotated. At this time, when the hub 105 is formed of a magnetic material, the hub itself functions as a yoke, and therefore the yoke 109 can be omitted.

[0063] in addition, Figure 2The spindle motor 100 shown is provided with a thrust bushing 113 to close the lower end opening of a cylindrical sleeve 111 fixed to the bottom wall 201. A cylindrical thrust disk 112 is provided on the thrust bushing 113, and the shaft 101 contacts the inner periphery of the thrust disk 112. The thrust in the Z direction generated when the spindle motor 100 rotates is borne by the thrust disk 112. The thrust bushing 113 disperses the force in the Z direction and supports the thrust disk 112 to bear the thrust. The thrust bushing 113 is generally made of a low-friction material, and can achieve smooth rotation and control of axial force.

[0064] The third portion 105c of the hub 105 is a hub flange, and functions as a holding portion for the magnetic disk 11. Figure 2 As shown, the third part 105c is equipped with a magnetic disk 11, and five magnetic disks 11 can be mounted through a spacer 110. In addition, the number of magnetic disks 11 mounted may be more than five depending on the application. The uppermost magnetic disk 11 is fixed to the hub 105 by a clamp 106 mounted on the hub 105 using a screw 107.

[0065] In the spindle motor 100 according to the first embodiment, the first thickness h1 of the third portion 105c as the hub flange in the Z direction is 1.89 mm. The second thickness h2 represented by the distance from the base surface 204 facing the third portion 105c to the outside of the bottom wall 201 is designed to be 4.3 mm, and the value obtained by dividing the second thickness h2 by the first thickness h1 (h2 / h1) is 2.28.

[0066] In order to obtain sufficient impact resistance, an HDD having a spindle motor 100 of the shaft rotation method of the present invention and equipped with more than 5 magnetic disks 11 needs to ensure a sufficient wall thickness of the second thickness h2. If the second thickness h2 is thin, the elastic deformation of the bottom wall 201 will increase when impacted. This will cause damage to functional components such as the spindle motor 100 and the head actuator 15. However, the device height H of the HDD involved in this embodiment is a maximum of 26.1 mm according to the standard, and there is a limitation on the space in the height direction. Moreover, if the wall thickness of the first thickness h1 of the third part 105c serving as the hub flange is not ensured to a certain extent, the deformation of the magnetic disk will increase. Therefore, in the case of carrying more than 5 magnetic disks 11, the adjustment of the dimensions of the first thickness h1 and the second thickness h2 is important in designing to ensure reliability.

[0067] (Effects of the First Embodiment)

[0068] Generally, when there are multiple disks 11, the mounting area of ​​the disks 11 in the height direction is large, so it is difficult to fully ensure the second thickness h2 to obtain impact resistance. In this case, it is common to use a spindle motor with an axis fixed. The spindle motor with an axis fixed is a structure in which both the upper and lower parts of the axis are fixed, and the rotating part rotates around the fixed axis. It is difficult for external impact and vibration to be directly transmitted to the axis, so it is usually excellent in impact resistance and vibration characteristics.

[0069] On the other hand, the spindle motor of the fixed axis type has more components and a complicated structure compared with the spindle motor 100 of the rotating axis type. In the present embodiment, the spindle motor 100 of the rotating axis type has fewer components than the spindle motor of the fixed axis type, and can also reduce the assembly man-hours, so it is expected that there will be a cost advantage of about 30%. In addition, there is no need to distinguish between the fixed axis type and the rotating axis type according to the number of disks to be mounted, so it is also helpful to shorten the development time and reduce labor costs by commonizing components. According to the above, by adopting the structure of this embodiment, it is possible to realize multiple HDDs at a low cost.

[0070] Figure 3 The relationship between h2 / h1 and impact resistance is shown. In a disk device with 5 disks 11, h2 / h1 was tested for impact resistance under 3 conditions. The graph shows an approximate curve obtained by plotting the impact value of HDD destruction with h2 / h1 on the horizontal axis and the impact value on the vertical axis. The standard value required for HDDs circulating on the market is usually around 250G. Figure 3 , h2 / h1 is 1.89 times when the product standard value is 250G. Therefore, by making the value of h2 / h1 1.89 or more, the product standard value of 250G can be achieved.

[0071] In the spindle motor 100 of the first embodiment, the first thickness h1 is 1.89 mm and the second thickness h2 is 4.3 mm. Therefore, h2 / h1 is 2.28, which has a margin of 50 G with respect to the product standard value of 250 G, and is a specification capable of obtaining sufficient impact resistance.

[0072] In order to achieve a normal product standard value of 250G, the value of h2 / h1 may be 1.89 or more and is not limited to 2.28. In order to have an impact resistance of 300G or more as a safer product standard value, h2 / h1 is preferably 2.28 or more.

[0073] Figure 4 An example of simulation results of vibration characteristics when the number of magnetic disks 11 mounted is 3 and 5 is shown. Figure 4In the figure, the dotted line shows the simulation result of the first embodiment with five disks 11, and the solid line shows the simulation result of the HDD with three disks 11. Generally, when the number of disks 11 mounted increases, the vibration characteristics may decrease. This is because there will be problems with rotational balance caused by the mass distribution that deviates from the central axis of the structure and the uneven distribution of the rotational speed. Therefore, by fully ensuring the second thickness h2, the influence of the rotational balance can be reduced and stable vibration characteristics can be obtained. In the HDD equipped with five disks 11 in this embodiment, as shown in FIG. Figure 4 As shown, the acceleration is 1G (9.8m / s 2 ) is smaller than that of the conventional HDD equipped with three magnetic disks 11. This shows that even if the number of magnetic disks mounted increases, a stable vibration characteristic can be obtained in the HDD of this embodiment.

[0074] In addition, when more than five disks 11 are mounted, the distance between the disks 11 becomes narrow, so it is also important to evaluate the deformation amount of the disks 11 when the HDD is in operation. In the HDD involved in the first embodiment of the invention of this application, the deformation amount of the disks 11 when the HDD is in operation was measured. As a result, it was confirmed that the deformation amount was the same as the deformation amount of the disks 11 in the conventional HDD and had no effect on the writing and reading of data.

[0075] As described in detail above, in the HDD involved in the first embodiment, by setting the second thickness h2 and the first thickness h1 so that the value obtained by dividing the second thickness h2 by the first thickness h1 becomes 1.89 times or more, sufficient impact resistance can be obtained. Moreover, the evaluation results show that there is no influence on the vibration characteristics and the deformation amount of the magnetic disk. Thus, in a 3.5-inch HDD with a spindle motor 100 using an axial rotation method and a maximum height (thickness) H of the housing 10 of 26.1 mm, more than 5 magnetic disks 11 can be mounted, and large capacity can be achieved.

[0076] The embodiments of the invention of this application have been described, but the embodiments are provided as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their variations are included in the scope and gist of the invention, and are included in the invention described in the claims and the scope of their equivalents.

Claims

1. A magnetic disk device comprising: matrix; disk; Head actuator; as well as Spindle motor, The substrate has: a bottom wall having a second thickness; and a side wall erected along the peripheral edge of the bottom wall, The magnetic disks are provided with more than 5 disks in the base. The head actuator includes a magnetic head supported so as to be movable. The spindle motor has: a sleeve fixed to the bottom wall and having a first hole; a shaft rotatably inserted into the first hole; and a hub rotatable integrally with the shaft, The hub has: a first portion having a shaft opening through which the upper end of the shaft is inserted; a second portion extending from the lowermost outer peripheral portion of the first portion toward a first direction, wherein the first direction is a direction from the magnetic disk toward the bottom wall; as well as a third portion extending from the bottom of the second portion toward a second direction orthogonal to the first direction, facing the bottom wall and having a first thickness, In the third portion, a value obtained by dividing the second thickness by the first thickness is 1.89 or more.

2. The magnetic disk device according to claim 1, The value obtained by dividing the second thickness by the first thickness is 2.28 or more.

3. The magnetic disk device according to claim 1 or 2, The first thickness and the second thickness are thicknesses in the first direction, In the first direction, the third portion is provided between the bottom wall and the magnetic disk.

4. The magnetic disk device according to claim 1 or 2, The first thickness is greater than or equal to 1.89 mm.

5. The magnetic disk device according to claim 1 or 2, characterized in that: It also has a top cover fixed to the side wall, The height from the bottom of the bottom wall to the top of the top cover is set to 26.2 mm or less.

6. The magnetic disk device according to claim 1 or 2, The substrate further comprises a second hole, The sleeve is fixed to the second hole.

7. The magnetic disk device according to claim 6, The second hole further includes a cylindrical portion extending in the first direction, and a coil provided on the stator is fixed to an outer circumference of the cylindrical portion.

8. The magnetic disk device according to claim 7, further comprising: a magnet disposed between the second portion and the coil; and A yoke is provided between the magnet and the second portion.

9. The magnetic disk device according to claim 1 or 2, A clamp is also provided on the upper surface of the hub. The magnetic disk is disposed between the third portion and the clamp via a spacer.

10. A magnetic disk device comprising: A base body having a bottom wall and a side wall erected along a peripheral edge of the bottom wall; a top cover fixed to the side wall; 5 or more magnetic disks, which are arranged in the base; A head actuator having a magnetic head and supporting the magnetic head so as to be movable; as well as A shaft rotation type spindle motor supports the magnetic disk so as to be rotatable.

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