Magnetic disk device

Abstract

To provide a magnetic disk device having five or more magnetic disks and being resistant to external shocks.SOLUTION: A magnetic disk device according to the embodiment includes a base, a magnetic disk, a head actuator, and a spindle motor. The base has a bottom wall having a second thickness and side walls. Five or more magnetic disks are provided in the base. The spindle motor is fixed to the bottom wall and has a sleeve having a first hole, a shaft through which the first hole is rotatably inserted, and a hub integrally and rotatably with the shaft. The hub has a first portion having an axial opening portion, a second portion extending from the outer peripheral portion of the lowermost surface of the first portion in a first direction from the magnetic disk toward the bottom wall, and a third portion extending from the lowermost surface of the second portion toward a second direction perpendicular to the first direction. The third portion has a first thickness, and a value obtained by dividing the second thickness by the first thickness is 1.89 or more.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] An embodiment of the present invention relates to a magnetic disk drive. [Background technology]

[0002] 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.

[0003] In order to obtain HDDs that are resistant to external shocks, the base thickness is designed to be thick while taking into consideration vibration characteristics. With the recent increase in capacity of HDDs, it has become difficult to obtain disk devices that are resistant to external shocks due to design restrictions on height dimensions with conventional shaft rotation type spindle motors. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 8,848,312 [Patent Document 2] U.S. Pat. No. 5,479,304 [Patent Document 3] JP 2004-166439 A Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a magnetic disk device that is equipped with five or more magnetic disks and is resistant to external shocks. [Means for solving the problem]

[0006] The magnetic disk device of the embodiment includes a base, a magnetic disk, a head actuator, and a spindle motor. The base has a bottom wall having a second thickness and a side wall erected along the peripheral portion of the bottom wall. Five or more magnetic disks are provided in the base, and the head actuator has a magnetic head supported to be freely movable.

[0007] 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 rotatable integrally with the shaft. The hub includes a first portion having an axial opening through which the upper end of the shaft is inserted, and a second portion extending from the outer periphery of the bottommost surface of the first portion in a first direction from the magnetic disk toward the bottom wall. The hub further includes a third portion extending from the bottommost surface of the second portion in a second direction perpendicular to the first direction and facing the bottom wall. The third portion has a first thickness, and a value obtained by dividing the second thickness by the first thickness is 1.89 or more.

[0008] Further, a magnetic disk device according to an embodiment includes a base having a bottom wall and a side wall extending along the periphery of the bottom wall, a top cover fixed to the side wall, and five or more magnetic disks provided within the base. The magnetic disk device includes a head actuator having a magnetic head and supporting the magnetic head movably, and a shaft rotating type spindle motor supporting the magnetic disks rotatably. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view of an HDD according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of the HDD taken along line AA′ shown in FIG. [Diagram 3] A graph showing the relationship between h2 / h1 and impact resistance. [Figure 4] FIG. 11 is a diagram showing a simulation result of vibration characteristics. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this description, common parts are denoted by common reference numerals throughout the drawings. Furthermore, the dimensional ratios of the drawings are not limited to the ratios shown in the drawings. Note that the present embodiment does not limit the present invention.

[0011] [First embodiment] As a magnetic disk device, a hard disk drive (HDD) according to a first embodiment will be described in detail below. Fig. 1 shows a perspective view of the HDD according to the first embodiment, and Fig. 2 shows a cross-sectional view taken along line A-A'.

[0012] (HDD structure) The HDD according to the first embodiment will be described with reference to Fig. 1. Fig. 1 shows a perspective view of the HDD according to the first embodiment.

[0013] As shown in Fig. 1, the HDD includes a housing 10, and includes a rectangular box-shaped base 200 with an open top, and a top cover 400. The base 200 includes a rectangular bottom wall 201 and a side wall 202 standing along the periphery of the bottom wall 201, and is molded as a single unit. The top cover 400 is sealed by being combined with the base 200 by a fastening member such as a plurality of screws. The top cover 400 and the base 200 may be sealed using a sealing method that uses an adhesive or a fitting mechanism other than screws or the like. The base 200 and the top cover 400 are made of a material such as aluminum or iron.

[0014] The base 200 accommodates a magnetic disk 11 that magnetically records and stores data, a spindle motor 100, and a head actuator 15. The spindle motor 100 rotatably supports the magnetic disk 11. The head actuator 15 movably supports a magnetic head 12 that moves over the surface of the magnetic disk 11 and detects and records changes in the magnetic pattern. The head actuator 15 also has a carriage 13 that supports the magnetic head 12, and a voice coil motor 14 that is used to control the position of the carriage 13. A printed circuit board (not shown) is screwed to the outer surface of a bottom wall 201 of the base 200, and this printed circuit board controls the operations of the spindle motor 100, the voice coil motor 14, and the magnetic head 12 via a board unit 16.

[0015] The overall device height of the HDD, which is represented by the distance from the bottom surface of the bottom wall 201 to the top surface of the top cover 400, i.e., the height (thickness) H of the housing 10, is set to a maximum of 26.1 mm in accordance with the HDD standard. Five magnetic disks 11 are mounted on the spindle motor 100 via spacers 110, which will be described later. The number of magnetic disks 11 mounted may be five or more. Each magnetic disk 11 is formed in a disk shape having a diameter of, for example, 96 mm, but the diameter is not limited to this and may be, for example, 97 mm or more.

[0016] The direction from the magnetic disk 11 toward the bottom wall 201 is the Z direction (first direction), the direction along the longitudinal direction of the HDD in a plane perpendicular to the Z direction is the Y direction (second direction), and the direction perpendicular to the Z direction and the Y direction is the X direction (third direction). For the sake of explanation, the direction from the bottom wall 201 toward the top cover 400 is referred to as "up" and the opposite direction is referred to as "down".

[0017] (Structure of spindle motor 100) Fig. 2 shows a cross-sectional view of the HDD taken along line A-A' shown in Fig. 1. As shown in Fig. 2, the spindle motor 100 used in the first embodiment has a non-rotating stator 102 and coils 103, and has an axial rotation type structure equipped with a shaft 101 that serves as a rotating shaft, and a hub 105 that rotates integrally with the shaft 101.

[0018] The shaft 101 is set upright almost perpendicularly to a thrust bush 113 described later. The shaft 101 is inserted in a first hole 300 of the sleeve 111 in a freely rotatable state, and is supported by a bearing (not shown). The sleeve 111 is fixed to a second hole 301 of the bottom wall 201. A dynamic pressure bearing utilizing the fluid pressure of a lubricating fluid, a ball bearing, a Kegl roller bearing using a conical roller, or the like may be used between the shaft 101 and the sleeve 111. The above-mentioned first hole 300 and second hole 301 are referred to as holes even when other parts are inserted in the finished product.

[0019] On the other hand, in the fixed shaft type, the shaft 101 is fixed to the bottom wall 201 and further screwed to the top cover 400. In comparison with the rotating shaft type structure, the fixed shaft type differs in that the shaft 101 itself does not rotate, but the hub 105 rotates around the shaft 101.

[0020] 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 this cylindrical portion 203. The stator 102 is made of a magnetic material such as an electromagnetic steel sheet, and is provided with slits for winding the coil 103.

[0021] The hub 105, which is a rotating part of the spindle motor 100, is composed of a first part 105a, a second part 105b, and a third part 105c, and is integrally formed. In FIG. 2, the first part 105a and the third part 105c are indicated by dashed lines, and the second part 105b is indicated by a dashed line. The first part 105a has an axial opening into which the upper end of the shaft 101 is inserted. Here, the axial opening of the first part 105a is expressed as an axial opening even in a state in which the shaft 101 is inserted in the finished product. The second part 105b extends cylindrically in the Z direction from the outer periphery of the bottom surface of the first part 105a. The third part 105c extends on the XY plane from the bottom surface of the second part 105b toward the side wall 202.

[0022] A cylindrical yoke 109 is fixed to the inner peripheral surface of the second portion 105b. A similarly cylindrical magnet 108 is fixed to the yoke 109. The yoke 109 is made of a magnetic material and holds the magnet 108, thereby achieving stable rotation. The inner periphery of the magnet 108 is disposed opposite the outer periphery of the stator 102 with a gap therebetween.

[0023] When a driving current is supplied to the coil 103, a driving force is generated to rotate the magnet 108, and the hub 105, the magnet 108, and the yoke 109 rotate relative to the base 200, the stator 102, and the coil 103. This causes 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 to rotate. In this case, if the hub 105 is made of a magnetic material, the hub itself functions as the yoke, so the yoke 109 may be omitted.

[0024] 2, a thrust bush 113 is disposed so as to close the lower end opening of a cylindrical sleeve 111 fixed to a bottom wall 201. A cylindrical thrust plate 112 is provided on the thrust bush 113, and the shaft 101 is in contact with the inner circumference of the thrust plate 112. The thrust plate 112 receives the thrust force in the Z direction generated when the spindle motor 100 rotates. The thrust bush 113 distributes the force in the Z direction and supports the thrust plate 112 in receiving the thrust force. The thrust bush 113 is generally made of a low-friction material, enabling smooth rotation and control of axial force.

[0025] The third portion 105c of the hub 105 is a hub flange, and functions as a holder for the magnetic disks 11. As shown in Fig. 2, the magnetic disks 11 are mounted on the third portion 105c, and five of the magnetic disks 11 can be mounted via spacers 110. Furthermore, the number of magnetic disks 11 mounted may be five or more depending on the application. The uppermost magnetic disk 11 is fixed to the hub 105 by a clamp 106 attached to the top surface of the hub 105 by a screw 107.

[0026] In the spindle motor 100 according to the first embodiment, the first thickness h1 in the Z direction of the third portion 105c, which is the hub flange, is 1.89 mm. The second thickness h2, which is expressed as 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 (h2 / h1) obtained by dividing the second thickness h2 by the first thickness h1 is 2.28.

[0027] In the HDD having the axial rotation type spindle motor 100 of the present invention and having five or more magnetic disks 11 mounted thereon, it is necessary to ensure a sufficient thickness of the second thickness h2 in order to obtain sufficient shock resistance. If the second thickness h2 is thin, the elastic deformation of the bottom wall 201 increases when an impact is received. This leads to damage to functional components such as the spindle motor 100 and the head actuator 15. However, the device height H of the HDD according to this embodiment is a maximum of 26.1 mm according to the standard, and there is a limit to the space in the height direction. Furthermore, if the thickness of the first thickness h1 of the third portion 105c, which is the hub flange, is not ensured to a certain extent, the deformation of the magnetic disk increases. Therefore, when five or more magnetic disks 11 are mounted, adjustment of the dimensions of the first thickness h1 and the second thickness h2 becomes important in a design that ensures reliability.

[0028] (Effects of the First Embodiment) Usually, when there are many magnetic disks 11, the mounting area of ​​the magnetic disks 11 in the height direction is large, making it difficult to secure a sufficient second thickness h2 to obtain shock resistance. In this case, a fixed-shaft type spindle motor is often used. A fixed-shaft type spindle motor has a structure in which both the upper and lower parts of the shaft are fixed and the rotating part rotates around the fixed shaft, and external shocks and vibrations are not easily transmitted directly to the shaft, so it generally has excellent shock resistance and vibration characteristics.

[0029] On the other hand, the fixed-shaft spindle motor has more components and a more complicated mechanism than the rotating-shaft spindle motor 100. In this embodiment, the rotating-shaft spindle motor 100 is used, which has fewer components and can reduce assembly labor compared to the fixed-shaft spindle motor, and is expected to have a cost advantage of about 30%. Furthermore, it is no longer necessary to use the fixed-shaft and rotating-shaft methods depending on the number of magnetic disks to be mounted, which leads to a shortened development period and reduced labor costs through the use of common parts. From the above, by adopting the configuration of this embodiment, it is possible to realize a large number of HDDs at low cost.

[0030] Figure 3 shows the relationship between h2 / h1 and shock resistance. A shock resistance test was conducted on a disk device with five magnetic disks 11 under three conditions of h2 / h1. The horizontal axis is h2 / h1 and the vertical axis is the shock value, and the graph shows an approximation curve obtained by plotting the shock value at which the HDD was destroyed. The general product specification value required for HDDs on the market is about 250G, and Figure 3 shows that h2 / h1 is 1.89 times when the product specification value is 250G. Therefore, the product specification value of 250G can be achieved by setting the h2 / h1 value to 1.89 or more.

[0031] 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, so that h2 / h1 is 2.28, which has a margin of 50 G relative to the product specification value of 250 G and provides sufficient impact resistance.

[0032] In order to achieve the general product standard value of 250G, the value of h2 / h1 should be 1.89 or more, and is not limited to 2.28. To achieve a safer product standard value of 300G or more impact resistance, it is preferable that h2 / h1 be 2.28 or more.

[0033] FIG. 4 shows an example of the simulation results of vibration characteristics when the number of magnetic disks 11 mounted is three and five. In FIG. 4, the dashed line shows the simulation results of the first embodiment in which the number of magnetic disks 11 is five, and the solid line shows the simulation results of an HDD in which the number of magnetic disks 11 is three. Normally, as the number of magnetic disks 11 mounted increases, there is concern that the vibration characteristics will deteriorate. This is because the mass distribution becomes off the central axis of the structure, and the rotation speed is not distributed evenly, resulting in a problem with rotation balance. Therefore, by ensuring a sufficient second thickness h2, the effects of rotation balance can be reduced and stable vibration characteristics can be obtained. In the HDD in this embodiment in which five magnetic disks 11 are mounted, as shown in FIG. 4, the acceleration of 1 G (9.8 m / s 2 ) was smaller than that of a conventional HDD equipped with three magnetic disks 11. This shows that the HDD of this embodiment can obtain stable vibration characteristics even if the number of mounted magnetic disks is increased.

[0034] Furthermore, when five or more magnetic disks 11 are mounted, the distance between the magnetic disks 11 becomes narrow, so it is also important to evaluate the amount of deformation of the magnetic disks 11 during HDD operation. In the HDD according to the first embodiment of the present invention, the amount of deformation of the magnetic disks 11 during HDD operation was measured. As a result, it was confirmed that the amount of deformation was approximately the same as the amount of deformation of the magnetic disks 11 in a conventional HDD, and that this amount of deformation does not affect the writing and reading of data.

[0035] As described above in detail, in the HDD according to the first embodiment, the second thickness h2 and the first thickness h1 are set so that the value obtained by dividing the second thickness h2 by the first thickness h1 is 1.89 times or more, thereby obtaining sufficient shock resistance. Furthermore, the evaluation results show that there is no effect on the vibration characteristics and the deformation amount of the magnetic disk. As a result, in a 3.5-inch HDD using a axial rotation type spindle motor 100 and with a maximum height (thickness) H of the housing 10 of 26.1 mm, five or more magnetic disks 11 can be mounted, thereby realizing a large capacity.

[0036] Although the embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the invention and its equivalents described in the claims. [Explanation of symbols]

[0037] 10. Chassis 11 Magnetic Disks 12 Magnetic head 13 Carriage 14 Voice coil motor 15 Head Actuator 16 Circuit Board Unit 100 Spindle motor 101 Shaft 102 Stator 103 Coil 105 Hub 105a Part 1 105b Part 2 105c Part 3 106 Clamp 107 Screw 108 Magnet 109 York 110 Spacer 111 Sleeve 112 Thrust plate 113 Thrust Bush 200 base 201 Bottom wall 202 Side wall 203 Cylindrical part 204 Base surface 300 First Hole 301 Second Hole 400 Top cover h1 First thickness h2 Second thickness H Height of the housing

Claims

1. With the base, A magnetic disk; A head actuator; A spindle motor; Equipped with The base is a bottom wall having a second thickness; A side wall extending along a peripheral portion of the bottom wall; having Five or more of the magnetic disks are provided in the base, the head actuator has a movably supported magnetic head, The spindle motor is a sleeve secured to the bottom wall and having a first aperture; a shaft rotatably inserted through the first hole; A hub that is rotatable integrally with the shaft; having The hub includes: a first portion having an axial opening through which an upper end of the shaft is inserted; a second portion extending from a bottom outer periphery of the first portion in a first direction from the magnetic disk toward the bottom wall; a third portion extending from a lowermost surface of the second portion toward a second direction perpendicular to the first direction, facing the bottom wall, and having a first thickness; having A magnetic disk drive in which the third portion has a value obtained by dividing the second thickness by the first thickness of 1.89 or more.

2. 2. The magnetic disk drive according to claim 1, wherein a value obtained by dividing the second thickness by the first thickness is equal to or greater than 2.

28.

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

4. 3. The magnetic disk drive according to claim 1, wherein the first thickness is 1.89 mm or more.

5. a top cover secured to the side wall; 3. The magnetic disk drive according to claim 1, wherein a height from the lowermost surface of said bottom wall to the uppermost surface of said top cover is 26.2 mm or less.

6. the base further comprises a second hole; 3. The magnetic disk drive according to claim 1, wherein the sleeve is fixed to the second hole.

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

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

9. A clamp is further provided on the upper surface of the hub.

3. The magnetic disk drive according to claim 1, wherein the magnetic disk is provided between the third portion and the clamp via a spacer.

10. A base having a bottom wall and a side wall extending along a peripheral portion of the bottom wall; A top cover fixed to the side wall; Five or more magnetic disks disposed within the base; a head actuator having a magnetic head and movably supporting the magnetic head; a spindle motor that supports the magnetic disk so as to be freely rotatable, and a magnetic disk device that includes a rotating shaft type spindle motor.

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