Pivot assembly bearing device and disk drive device

Abstract

To provide a pivot assembly bearing device and a disk drive device to enable stable support of the pivot assembly bearing device to a housing.SOLUTION: At least two bearings (50), a cylindrical outer shaft (10) supporting the bearing 50 on an outer peripheral surface (11), and an inner side shaft (30) accommodated in the outer shaft (10) such that one end (32) extends from one opening portion (10a) of the outer shaft (10) are provided. The inner shaft (30) has a male threaded portion (32a) in at least a portion extending from the outer shaft (10).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a pivot assembly bearing device and a disk drive device.

Background Art

[0002] Conventionally, disk drive devices such as hard disk drives (HDDs) are known. A disk drive device rotates a magnetic disk at high speed, enabling high-speed access to a recording device. When the magnetic disk is rotated at high speed, problems such as noise and an increase in power consumption due to windage occur. Therefore, a technique for reducing windage by enclosing a gas having a lower density than air, for example, helium gas, in a disk device is known. A disk drive device includes a magnetic disk (recording disk), a head stack assembly that acts on the magnetic disk, and an actuator that drives the head stack assembly in a housing having a base member and a cover member.

[0003] A pivot assembly bearing device is used for the head stack assembly of a disk drive device. The pivot assembly bearing device is usually configured by inserting a pair of rolling bearings into a shaft (for example, Patent Document 1). The pivot assembly bearing device in Patent Document 1 has a pivot shaft fitted into a pin integrally formed on a base member, and a sleeve rotatably attached to the pivot shaft via a bearing. A cover member is placed on the pivot assembly bearing device, and a screw is inserted through the cover member so as to be screwed with the tip portion of the pin. That is, the pivot assembly bearing device described in Patent Document 1 is attached to the housing via a cover member and a screw in a state of being fitted into a pin formed on a base member.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] Incidentally, in recent years, there has been a trend towards increasing the number of magnetic disks housed in disk drive devices in order to increase their capacity. As the number of magnetic disks housed increases, for example, in the pivot assembly bearing device described in Patent Document 1, it becomes necessary to extend the pins, which are integrally formed with the base member, along the axial direction. As a result, the rigidity of the pins (housing) that support the pivot assembly bearing device decreases, and the load on the pins also increases, which could impair the stable support of the pivot assembly bearing device.

[0006] Therefore, the present invention has been made in view of the above problems, and aims to provide a technology that enables stable support of a pivot assembly bearing device to a housing. [Means for solving the problem]

[0007] To solve the above problems, the pivot assembly bearing device according to the present invention comprises at least two bearings, a cylindrical first shaft that supports the bearings on its outer circumferential surface, and a second shaft housed in the first shaft such that one end extends from one opening of the first shaft, wherein the second shaft has a male threaded portion at least in the portion extending from the first shaft. [Effects of the Invention]

[0008] According to the present invention, it becomes possible to mount the pivot assembly bearing device to the housing with high rigidity. [Brief explanation of the drawing]

[0009] [Figure 1] This is an exploded perspective view illustrating a disk drive device according to the first embodiment. [Figure 2]This is a longitudinal cross-sectional view of a pivot assembly bearing device for illustrating a pivot assembly bearing device according to the first embodiment. [Figure 3] This is a longitudinal cross-sectional view of the outer shaft of a pivot assembly bearing device according to the first embodiment. [Figure 4] This is a longitudinal cross-sectional view of the inner shaft of a pivot assembly bearing device according to the first embodiment. [Figure 5] This is a longitudinal cross-sectional view showing the pivot assembly bearing device according to the first embodiment in a state where it is fixed to the housing. [Figure 6] This is a longitudinal cross-sectional view showing the pivot assembly bearing device according to the second embodiment in a state where it is fixed to the base member. [Figure 7] This is a longitudinal cross-sectional view showing the pivot assembly bearing device according to the third embodiment in a state where it is fixed to the base member. [Figure 8] This is a longitudinal cross-sectional view showing the pivot assembly bearing device according to the fourth embodiment in a state where it is fixed to the base member. [Modes for carrying out the invention]

[0010] First, a general overview of a typical embodiment of the present invention will be given. In the following description, as an example, reference numerals on the drawings corresponding to the components of the invention are indicated in parentheses.

[0011] [1] The pivot assembly bearing device (1, 1A, 1B, 1C) according to this embodiment comprises at least two rolling bearings (50), a cylindrical outer shaft (10) that supports the rolling bearings (50) on its outer surface (11), and an inner shaft (30) housed in the outer shaft (10) such that its tip portion (32) extends from one opening (10a) of the outer shaft (10), wherein the inner shaft (30) has a male threaded portion (32a) at least at the tip portion (32) that extends from the outer shaft (10).

[0012] [2] In one embodiment of the pivot assembly bearing device (1, 1A, 1B, 1C) according to this embodiment, the outer shaft (10) has a protruding portion (17) that extends from the inner circumferential surface (15) such that it has an end face (17a) facing the other opening (10b) opposite to one opening (10a), and the inner shaft (30) has a protruding portion (33) that extends from the outer circumferential surface (31a) such that it has an end face (33a) facing the male thread portion (32a), and the outer shaft (10) and the inner shaft (30) are in contact with each other at the end faces (17a, 33a) of their respective protruding portions (17) and protruding portions (33).

[0013] [3] In one embodiment of the pivot assembly bearing device (1, 1A, 1B, 1C) according to this embodiment, the outer shaft (10) and the inner shaft (30) are in contact with each other at their protruding portions (17) and (33) between at least two rolling bearings (50) in the axial direction (X).

[0014] [4] In one embodiment of the pivot assembly bearing device (1, 1A, 1B, 1C) according to this embodiment, the difference between the coefficient of thermal expansion of the outer shaft (10) and the coefficient of thermal expansion of the inner shaft (30) is within 50%.

[0015] [5] The disk drive device (100) according to this embodiment comprises a pivot assembly bearing device (1, 1A, 1B, 1C) as described in any of [1] to [4] above, and a housing (110, 110A, 110B, 110C) that houses the pivot assembly bearing device (1, 1A, 1B, 1C), wherein the housing (110, 110A, 110B, 110C) has a hole (114) that engages with a male screw portion (32a).

[0016] [6] In one embodiment of the disk drive device (100) according to this embodiment, the hole (114) is a blind hole.

[0017] 〔7〕In one aspect of the disk drive device (100) according to the present embodiment, the housing (110, 110A, 110B, 110C) includes a base member (111) to which the pivot assembly bearing device (1, 1A, 1B, 1C) is attached via a male screw portion (32a), and at least one cover member (121) that is attached to the base member (111) and tightly closes the internal space (S) for housing the pivot assembly bearing device (1, 1A, 1B, 1C) from the outside. The internal space (S) is filled with a gas having a lower density than air.

[0018] 〔8〕In one aspect of the disk drive device (100) according to the present embodiment, the housing (110, 110A, 110B, 110C) includes at least nine magnetic disks (130).

[0019] 〔9〕In one aspect of the disk drive device (100) according to the present embodiment, the inner shaft (30) of the pivot assembly bearing device (1, 1A, 1B, 1C) has a female screw portion (34a) at the other end side, and at least one cover member (121) is attached to the pivot assembly bearing device (1, 1A, 1B, 1C) through the engagement between the female screw portion (34a) and the fastening member (B2).

[0020] 〔10〕In one aspect of the disk drive device (100) according to the present embodiment, the thickness of the housing (110, 110A, 110B, 110C) is greater than 1 inch.

[0021] Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that in the following description, the drawings are schematic, and it is necessary to pay attention to the fact that the dimensional relationships of each element, the ratios of each element, etc. may be different from the actual ones. There may also be parts where the dimensional relationships and ratios between the drawings are different from each other.

[0022] <First Embodiment> [Disk Drive Device] Figure 1 is an exploded perspective view illustrating the disk drive device 100 according to the present invention. The disk drive device 100 according to the first embodiment is a hard disk drive, for example, a helium-sealed hard disk drive. The disk drive device 100 according to the present invention comprises a pivot assembly bearing device 1 and a housing 110 that houses the pivot assembly bearing device 1, wherein the housing 110 has a hole 114 that engages with the pivot assembly bearing device 1. Specifically, the disk drive device 100 according to the present invention comprises a housing 110, a plurality of magnetic disks 130, and a head stack assembly 150, and the specific configuration of the disk drive device 100 will be described below.

[0023] (Enclosure) The housing 110 includes a base member 111, an inner cover member 121, and an outer cover member 125. The base member 111 is formed in a rectangular or substantially rectangular shape in plan view. The base member 111 is made of, for example, aluminum, and has a bottom wall portion 113 and a side wall portion 115. The bottom wall portion 113 and the side wall portion 115 define an internal space S for housing the magnetic disk 130 and head stack assembly 150, which will be described later. The base member 111 is open on the side opposite to the bottom wall portion 113. When the inner cover member 121 and the outer cover member 125 are attached to the base member 111, the internal space S is tightly closed to the outside by the inner cover member 121 and the outer cover member 125 and is filled with a gas with a density lower than air, such as helium gas.

[0024] The bottom wall portion 113 rotatably supports the magnetic disk 130, which will be described later, and also supports the head stack assembly 150, which will be described later. The bottom wall portion 113 has a hole 114 at a position that supports the pivot assembly bearing device 1 (see Figure 5). The hole 114 is formed as a blind hole that extends from the side of the internal space S to the outside. The hole 114 may also be a through hole. A female screw portion 114a is formed on the inner circumferential surface of the hole 114.

[0025] The side wall portion 115 is a part erected along the periphery of the bottom wall portion 113. The side wall portion 115 has a plurality of holes 116. Fastening members B1 such as screws, bolts, and pins, which are used to attach the inner cover member 121 (described later) to the base member 111, are inserted through the holes 116.

[0026] The inner cover member 121 is formed in the shape of a rectangular plate, for example, from aluminum or stainless steel. The inner cover member 121 has holes 122 and 123. Holes 122 are formed along the periphery of the inner cover member 121. When the inner cover member 121 is attached to the base member 111, the holes 122 in the inner cover member 121 and the holes 116 in the side wall portion 115 are aligned, and the fastening member B1 is inserted through both holes 122 and 116. Hole 123 is used to fix the inner cover member 121 to the pivot assembly bearing device 1, which will be described later. Hole 123 is formed in the recess 124.

[0027] The recess 124 is formed as a recess toward the base member 111 when the inner cover member 121 is fixed to the base member 111. The recess 124 has a horizontal portion 124a and an inclined portion 124b (see Figure 5). The horizontal portion 124a extends horizontally or substantially horizontally from the periphery of the hole 123. The horizontal portion 124a supports the heads of fastening members B2, such as screws, bolts, and pins, used to fix the inner cover member 121 to the pivot assembly bearing device 1. The inclined portion 124b extends diagonally from the horizontal portion 124a toward the outer cover member 125. The heads of the fastening members B2 are housed within the recess 124.

[0028] The outer cover member 125 is formed in the shape of a rectangular plate, for example, from aluminum. The outer cover member 125 is formed with planar dimensions that cover the inner cover member 121. The outer cover member 125 is welded to the inner cover member 121 around its entire periphery. As a result, the internal space S of the housing 110 is airtight to the outside, and leakage of the helium filling to the outside is suppressed.

[0029] (Magnetic disk) The housing 110 contains multiple magnetic disks 130 as recording media, preferably nine or more magnetic disks 130. A spindle motor 140 is provided on the bottom wall 113 of the housing 110. The spindle motor 140 supports and rotates the multiple magnetic disks 130. Each magnetic disk 130 has a magnetic recording layer on its upper and / or lower surface. Each magnetic disk 130 is coaxially fitted to the spindle motor 140. The magnetic disks 130 are rotated by the spindle motor 140 at a predetermined rotational speed. The number of magnetic disks 130 provided in the housing 110 is not particularly limited, and a single magnetic disk 130 may be housed in the housing 110.

[0030] (Head stack assembly) The head stack assembly 150 includes a magnetic head 151, a swing arm 153, an actuator 157, and a pivot assembly bearing device 1 according to the present invention. The magnetic head 151 records and reproduces information on the magnetic disk 130. The magnetic head 151 is supported by a swing arm 153 which is rotatably supported by the pivot assembly bearing device 1, which will be described later. The swing arm 153 is driven by the actuator 157. The swing arm 153 is supported by the pivot assembly bearing device 1 according to this embodiment so as to be able to swing parallel to the bottom wall portion 113 of the base member 111. A mounting hole 155 is formed in the base portion 154 of the swing arm 153. The pivot assembly bearing device 1 is press-fitted into the mounting hole 155.

[0031] <Pivot Assembly Bearing Device> Figure 2 is a longitudinal cross-sectional view of a pivot assembly bearing device 1 for illustrating the pivot assembly bearing device 1 according to the first embodiment. The pivot assembly bearing device 1 according to this embodiment comprises two rolling bearings 50, a cylindrical outer shaft (first shaft) 10 that supports the rolling bearings 50 on its outer circumferential surface 11, and an inner shaft (second shaft) 30 housed in the outer shaft 10 such that its tip (one end) 32 extends from one opening 10a of the outer shaft 10. The inner shaft 30 is characterized in that it has a male threaded portion 32a at least on the tip 32 extending from the outer shaft 10. The pivot assembly bearing device 1 according to this embodiment comprises an outer shaft 10, an inner shaft 30, a pair of rolling bearings 50, and a sleeve 70. The configuration of the pivot assembly bearing device 1 will be described in detail below.

[0032] Figure 3 is a longitudinal cross-sectional view of the outer shaft 10 of the pivot assembly bearing device 1 according to the first embodiment. The outer shaft 10 is a cylindrical member formed from, for example, stainless steel (SUS303, SUS304, SUS430F, etc.) and has openings 10a and 10b at both ends.

[0033] The cross-sectional shape of the outer shaft 10 intersects the axis x passing through the center of the outer shaft 10 and is circular. The inner shaft 30, which will be described later, is inserted into the outer shaft 10 from the side of the opening 10b toward the side of the opening 10a. The outer shaft 10 supports the rolling bearing 50, which will be described later, on its outer circumferential surface 11. The outer shaft 10 has a flange portion 13 on its outer circumferential surface 11. The flange portion 13 is provided at the end of the outer shaft 10 on the side of the opening 10a and contacts the base member 111 when the pivot assembly bearing device 1 is attached to the base member 111. The flange portion 13 extends radially outward from the outer circumferential surface 11 and is provided around the entire circumference of the outer shaft 10 around the axis x.

[0034] The outer shaft 10 has a protruding portion (first projection) 17 on the inner circumferential surface 15 side. The protruding portion 17 is an annular portion that extends from the inner circumferential surface 15 toward the axis x along its entire circumference, and extends toward the opening 10a side from the middle or approximately middle position of the outer shaft 10 along the axis x. The protruding portion 17 is formed in an annular shape along the circumferential direction on the inner circumferential surface 15. On the side of the opening 10b relative to the protruding portion 17, there is a housing portion 19 for accommodating the protruding portion 33 of the inner shaft 30, which will be described later.

[0035] The inner diameter 17d of the protruding portion 17 of the outer shaft 10 is smaller than the inner diameter 19d of the housing portion 19. The outer shaft 10 houses the main body portion 31 of the inner shaft 30, which will be described later, in the protruding portion 17. The inner diameter 17d of the protruding portion 17 is slightly larger than the outer diameter 31D of the main body portion 31 of the inner shaft 30. The wall thickness of the protruding portion 17 of the outer shaft 10 is greater than the wall thickness of the housing portion 19.

[0036] The protruding portion 17 has an end face 17a facing the other opening 10b, which is opposite to the opening 10a. The end face 17a is a stepped surface formed by the difference between the inner diameter 17d of the outer shaft 10 in the protruding portion 17 and the inner diameter 19d of the outer shaft 10 in the housing portion 19. The end face 17a extends around the entire circumference of the inner circumferential surface 15 around the axis x. Multiple protruding portions 17 extending along the axis x may be provided on the inner circumferential surface 15 at predetermined intervals in the circumferential direction. The protruding portion 17 abuts against the inner shaft 30, which will be described later, at its end face 17a.

[0037] The housing section 19 is located on the side of the opening 10b relative to the protruding section 17 and accommodates the protruding section 33 of the inner shaft 30. The inner diameter 19d of the housing section 19 of the outer shaft 10 is slightly larger than the outer diameter 33D of the protruding section 33 of the inner shaft 30.

[0038] Figure 4 is a longitudinal cross-sectional view of the inner shaft 30 of the pivot assembly bearing device 1 according to the first embodiment. The inner shaft 30 is a rod-shaped member formed of, for example, stainless steel (SUS303, SUS304, SUS430F, etc.). The inner shaft 30 is housed in the outer shaft 10 coaxially or substantially coaxially with respect to the axis x. The cross-sectional shape of the inner shaft 30 intersecting the axis x is circular.

[0039] The inner shaft 30 has a main body portion 31 and an overhang portion (second projection) 33. The outer diameter 31D of the main body portion 31 is smaller than the outer diameter 33D of the overhang portion 33 and is inserted into the outer shaft 10 at the overhang portion 17 of the outer shaft 10. When the inner shaft 30 is housed in the outer shaft 10 (hereinafter also referred to as the "housed state"), the tip portion 32 of the main body portion 31 extends from the opening 10a of the outer shaft 10. The tip portion 32 is at least the portion exposed from the outer shaft 10, and a male threaded portion 32a is formed on the outer circumferential surface of the tip portion 32. In the housed state, the male threaded portion 32a at least partially overlaps with the inner circumferential surface 15 of the overhang portion 17 of the outer shaft 10 in the direction along the axis x (hereinafter also referred to as the "axial direction X"). The male threaded portion 32a is screwed into the female threaded portion 114a of the hole 114 formed in the bottom wall portion 113 of the base member 111.

[0040] The protruding portion 33 is a part that protrudes radially outward along its entire circumference from the outer peripheral surface 31a of the main body portion 31, and is a portion that is larger in diameter than the main body portion 31. In the housing state, the protruding portion 33 is housed in the housing portion 19 of the outer shaft 10. In the housing state, the inner shaft 30 is in contact with the protruding portion 17 of the outer shaft 10 at the protruding portion 33 and is supported from the side of the tip portion 32 in the axial direction X.

[0041] The protruding portion 33 faces the male threaded portion 32a of the tip portion 32 and has an end face 33a that faces the opening 10a of the outer shaft 10 when housed. The end face 33a is a stepped surface formed by the difference between the outer diameter 33D of the inner shaft 30 in the protruding portion 33 and the outer diameter 31D of the inner shaft 30 in the main body portion 31. The end face 33a extends around the entire circumference of the axis x. When housed, the end face 33a of the inner shaft 30 abuts the end face 17a of the outer shaft 10 in the axial direction X. The contact position between the outer shaft 10 and the inner shaft 30 is between a pair of rolling bearings 50, which will be described later, in the axial direction X, and does not overlap with the rolling bearings 50 in the axial direction X. Multiple protruding portions 33 extending along the axis x may be provided at predetermined intervals in the circumferential direction.

[0042] The protruding portion 33 has a blind hole 34. The blind hole 34 extends along the axis x from the opposite side of the tip portion 32 toward the tip portion 32. A female threaded portion 34a is formed on the inner circumferential surface of the blind hole 34. The fastening portion B2 that fixes the inner cover member 121 to the pivot assembly bearing device 1 engages with the female threaded portion 34a.

[0043] The rolling bearing 50 has an inner ring 51, an outer ring 53, and rolling elements 55. The rolling bearing 50 is installed between the outer shaft 10 and the cylindrical sleeve 70. Two rolling bearings 50 are mounted on the outer shaft 10 at a predetermined distance in the axial direction X. One rolling bearing 50 is mounted on the outer circumferential surface of the outer shaft 10 on the side of the opening 10a, and the other rolling bearing 50 is mounted on the outer circumferential surface of the outer shaft 10 on the side of the opening 10b.

[0044] The inner ring 51 is clearance-fitted to the outer shaft 10. An anaerobic adhesive (acrylic adhesive) may be applied between the inner surface of the inner ring 51 and the outer surface of the outer shaft 10. The outer ring 53 is clearance-fitted to the sleeve 70. The rolling element 55 is held so as to be able to roll between the inner ring 51 and the outer ring 53.

[0045] The sleeve 70, when the pivot assembly bearing device 1 is assembled, houses the rolling bearing 50 and is fitted onto the outer circumferential surface 11 of the outer shaft 10. The sleeve 70 has two recesses 71 formed in a concave shape on its inner circumferential surface. The recesses 71 extend in an annular shape in the circumferential direction. The recesses 71 are provided on both ends of the sleeve 70 in the axial direction X. A rolling bearing 50 is housed in each recess 71.

[0046] <Assembly process and fixing process to housing for pivot assembly bearing device> Next, the process of assembling the pivot assembly bearing device 1 according to this embodiment, and the process of fixing the assembled pivot assembly bearing device 1 to the housing 110 will be described. The sleeve 70, which houses the rolling bearings 50 in each recess 71, is fitted onto the outer shaft 10. Then, the inner shaft 30 is inserted from the side of the main body 31, from the side of the opening 10b of the outer shaft 10. The inner shaft 30 is inserted into the outer shaft 10 until the end face 33a of the protruding portion 33 abuts against the end face 17a of the protruding portion 17 of the outer shaft 10. In this way, the assembly process of the pivot assembly bearing device 1 is completed.

[0047] Figure 5 is a longitudinal cross-sectional view showing the pivot assembly bearing device 1 according to the first embodiment fixed to the housing 110. The assembled pivot assembly bearing device 1 is fixed to the housing 110. The pivot assembly bearing device 1 is brought close to the hole 114 formed in the bottom wall portion 113 of the base member 111. In the housing state, the tip portion 32 of the inner shaft 30 of the pivot assembly bearing device 1 protrudes from the outer shaft 10 on the side of the opening 10a. The male threaded portion 32a of the tip portion 32 of the inner shaft 30 exposed from the outer shaft 10 is inserted into the hole 114 of the base member 111, and the inner shaft 30 is rotated using a predetermined tool to screw the inner shaft 30 into the female threaded portion 114a.

[0048] Next, the inner cover member 121 and the outer cover member 125 are attached to the housing 110 to close the internal space S. The hole 122 of the inner cover member 121 is aligned with the hole 116 in the side wall portion 115 of the housing 110, and the hole 123 of the inner cover member 121 is aligned with the blind hole 34 in the protruding portion 33 of the inner shaft 30. Fastening members B1 and B2 are inserted through the respective holes 122, 116, 123, and 34 to fix the inner cover member 121 to the base member 111 and the pivot assembly bearing device 1. Finally, the outer cover member 125 is attached to the inner cover member 121 by welding along its edge.

[0049] As described above, with the disk drive device 100 according to this embodiment, the pivot assembly bearing device 1 is fixed to the housing 110 by screwing the male threaded portion 32a of the inner shaft 30 into the hole 114 (female threaded portion 114a) of the base member 111, so that the pivot assembly bearing device 1 is fixed to the housing 110 with high rigidity.

[0050] Furthermore, the inner shaft 30 abuts against the end face 17a of the protruding portion 17 of the outer shaft 10 at the end face 33a of the protruding portion 33, pressing the outer shaft 10 against the bottom wall portion 113 along the axial direction X. This enables more rigid fixing of the pivot assembly bearing device 1 to the housing 110.

[0051] Furthermore, since the outer shaft 10 and the inner shaft 30 are in contact with each other in the axial direction X between the two rolling bearings 50, the stress caused by the contact between the outer shaft 10 and the inner shaft 30 acting on the rolling bearings 50 can be suppressed. This ensures the rotational accuracy of the rolling bearings 50.

[0052] Furthermore, the pivot assembly bearing device 1 is also fixed to the housing 110 by fastening member B2 from the side of the inner cover member 121. In other words, the pivot assembly bearing device 1 is fixed to the housing 110 at two points: the base member 111 and the inner cover member 121. In this state, the inner cover member 121 is in contact with the end face of the outer shaft 10 on the side of the opening 10b at the horizontal portion 124a of the recess 124. By screwing fastening member B2 into the female threaded portion 34a of the inner shaft 30, the inner shaft 30 and the outer shaft 10 are pressed toward the bottom wall portion 113 of the base member 111, and the outer shaft 10 is pressed toward the bottom wall portion 113 of the base member 111 via the inner cover member 121. This enables a more rigid fixing of the pivot assembly bearing device 1 to the housing 110.

[0053] Furthermore, since the outer shaft 10 and the inner shaft 30 are made of stainless steel, the difference in their coefficients of thermal expansion can be minimized. For example, it is preferable that the difference between the coefficient of thermal expansion of the outer shaft 10 and the coefficient of thermal expansion of the inner shaft 30 be within 50%. This makes it possible to minimize the difference in volume change between the outer shaft 10 and the inner shaft 30 when the disk drive unit 100 is driven, and to suppress changes in rigidity in fixing the pivot assembly bearing device 1 and the housing 110. Note that the outer shaft 10 and the inner shaft 30 may be made of different materials as long as the difference in their coefficients of thermal expansion is within 50%, but it is preferable that they be made of the same material.

[0054] Furthermore, the hole 114 formed in the bottom wall portion 113 of the base member 111 into which the tip portion 32 of the inner shaft 30 is inserted is formed as a blind hole, so that the helium filling the internal space S through the hole 114 does not leak out to the outside of the housing 110.

[0055] Furthermore, since the male threaded portion 32a of the tip portion 32 of the inner shaft 30 is formed on the entire portion of the tip portion 32 that is exposed from the outer shaft 10, a fastening force can be secured by screwing from the position where the outer shaft 10 and the base member 111 come into contact. This eliminates the need to consider the relief portion (the portion where the male threaded portion 32a is not formed) that occurs when forming the male threaded portion 32a on the main body portion 31, and the portion that does not screw with the female threaded portion 114a of the hole 114. Therefore, the proportion of the thickness of the bottom wall portion 113 of the base member 111 (thickness in the axial direction X) occupied by the hole 114 can be reduced. In addition, by increasing the gap between the hole 114 and the outer surface 113a of the bottom wall portion 113, it is possible to suppress leakage of gases such as helium gas, which have extremely small molecules and are filled in the internal space S, from the internal space S to the outside through casting defects that may occur during the manufacturing process of the base member 111.

[0056] Furthermore, the thickness of the disk drive unit 100 is, for example, greater than 1 inch. Here, "thickness of the disk drive unit 100" refers to the thickness of the housing 110, and corresponds to the height 100H between the outer surface 113a of the bottom wall portion 113 of the base member 111 in the housing 110 and the outer surface 125a of the outer cover member 125 in the axial direction X of the pivot assembly bearing device 1 (see Figure 5). According to the pivot assembly bearing device 1 of this embodiment, the inner shaft 30 is configured separately from the housing 110, and the pivot assembly bearing device 1 is fixed to the housing 110 via this inner shaft 30. As a result, even in disk drive units 100 with a large capacity, where the number of magnetic disks 130 is 9 or more, and the thickness of the housing 110 exceeds, for example, 1 inch or 2 inches, the pivot assembly bearing device 1 can be stably and rigidly fixed to the housing 110.

[0057] Next, other embodiments will be described using Figures 6 to 8. Note that parts identical to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0058] <Second Embodiment> Figure 6 is a longitudinal cross-sectional view showing the pivot assembly bearing device 1A according to the second embodiment fixed to the base member 111. The disk drive device according to the second embodiment comprises the pivot assembly bearing device 1A and the base member 111 to which the pivot assembly bearing device 1A is fixed.

[0059] The bottom wall portion 113 of the base member 111 has a protrusion 117 at a position that supports the pivot assembly bearing device 1. The protrusion 117 is formed convexly from the inner surface 113b of the bottom wall portion 113 toward the pivot assembly bearing device 1A. The protrusion 117 is formed in a circular shape in plan view. When the pivot assembly bearing device 1A is fixed to the bottom wall portion 113 of the base member 111, the protrusion 117 enters the recess 20 of the outer shaft 10, which will be described later.

[0060] A hole 114 is formed in the protrusion 117. The hole 114 is formed concentrically or substantially concentrically with the protrusion 117. The hole 114 is formed as a blind hole extending from the inner surface 113b to the outer surface 113a. The hole 114 may also be a through hole. A female threaded portion 114a is formed on the inner circumferential surface of the hole 114.

[0061] The pivot assembly bearing device 1A comprises an outer shaft 10, an inner shaft 30, a pair of rolling bearings 50, and a sleeve 70. The outer shaft 10 has a recess 20 in a protruding portion 17 on the side of the opening 10a. The recess 20 is formed concave along the axis x on the side of the opening 10a and is formed concentrically or substantially concentrically with respect to the axis x. The recess 20 is formed in a circular shape in plan view, and its inner diameter 20d is slightly larger than the outer diameter 117D of the protruding portion 117.

[0062] The disk drive device according to the second embodiment provides the same effects as the disk drive device 100 according to the first embodiment. Since the base member 111 has a protrusion 117 and the pivot assembly bearing device 1A has a recess 20 on the outer shaft 10, when fixing the pivot assembly bearing device 1A to the base member 111, the protrusion 117 can be inserted into the recess 20, making it easy to position the pivot assembly bearing device 1A relative to the base member 111.

[0063] Furthermore, since a hole 114 is formed in the protrusion 117 of the base member 111, the starting position of the hole 114 can be set higher than the inner surface 113b of the bottom wall portion 113 by the amount that the protrusion 117 protrudes. In other words, the gap between the hole 114 and the outer surface 113a of the bottom wall portion 113 can be increased, and the helium filling the internal space S can be reliably prevented from seeping out through the hole 114.

[0064] <Third Embodiment> Figure 7 is a longitudinal cross-sectional view showing the pivot assembly bearing device 1B fixed to the base member 111 in the third embodiment. The disk drive device according to the third embodiment comprises a pivot assembly bearing device 1B and a base member 111 to which the pivot assembly bearing device 1B is fixed.

[0065] The bottom wall portion 113 of the base member 111 has a recess 118 at a position that supports the pivot assembly bearing device 1. The recess 118 is formed in a concave shape from the inner surface 113b to the outer surface 113a of the bottom wall portion 113. The recess 118 is formed in a circular shape in plan view. When the pivot assembly bearing device 1B is fixed to the base member 111, the protrusion 22 of the outer shaft 10, which will be described later, enters into the recess 118.

[0066] A hole 114 is formed in the recess 118. The hole 114 is formed concentrically or substantially concentrically in the recess 118. The hole 114 is formed as a blind hole extending from the inner surface 113b to the outer surface 113a. The hole 114 may also be a through hole. A female threaded portion 114a is formed on the inner circumferential surface of the hole 114.

[0067] The pivot assembly bearing device 1B comprises an outer shaft 10, an inner shaft 30, a pair of rolling bearings 50, and a sleeve 70. The outer shaft 10 has a protrusion 22 on the side of the opening 10a. The protrusion 22 is formed convexly on the side of the opening 10a and is formed concentrically or substantially concentrically with respect to the axis x. The protrusion 22 is formed in a circular shape in plan view, and its outer diameter 22D is slightly smaller than the inner diameter 118d of the recess 118.

[0068] The disk drive device according to the third embodiment provides the same effects as the disk drive device 100 according to the first embodiment. Since the base member 111 has a recess 118 and the pivot assembly bearing device 1B has a protrusion 22 on the outer shaft 10, the positioning of the pivot assembly bearing device 1B relative to the base member 111 can be easily performed by inserting the protrusion 22 into the recess 118 when fixing the pivot assembly bearing device 1B to the base member 111.

[0069] <Fourth Embodiment> Figure 8 is a longitudinal cross-sectional view showing the pivot assembly bearing device 1C according to the fourth embodiment fixed to the base member 111. The disk drive device according to the fourth embodiment comprises a pivot assembly bearing device 1C and a base member 111 to which the pivot assembly bearing device 1C is fixed.

[0070] The pivot assembly bearing device 1C comprises an outer shaft 10, an inner shaft 30, a pair of rolling bearings 50, and a sleeve 70. The inner shaft 30 has a flange portion 13C on the side of the opening 10b.

[0071] The disk drive device according to the fourth embodiment provides the same effects as the disk drive device 100 according to the first embodiment. Furthermore, since the outer shaft 10 has a flange portion 13C on the side of the opening 10b, the horizontal portion 124a of the inner cover member 121 rests on the flange portion 13C. As a result, for example, the contact area with the inner cover member 121 can be made larger at the flange portion 13C compared to the contact area between the end face of the outer shaft 10 on the side of the opening 10b and the inner cover member 121 in the first to third embodiments, enabling stable pressing of the outer shaft 10 against the base member 111 by the inner cover member 121.

[0072] <Other> Although preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and includes all aspects included in the concept and claims of the present invention. Furthermore, each configuration may be selectively combined as appropriate to achieve at least some of the above-described problems and effects. Also, for example, the shape, material, arrangement, size, etc. of each component in the above embodiments may be appropriately changed depending on the specific use of the present invention. For example, in the above embodiments, two rolling bearings 50 were provided, but three or more rolling bearings 50 may be provided. In this case, the contact position between the outer shaft 10 and the inner shaft 30 should be between the two outermost rolling bearings 50 in the axial direction X, but it is preferable that they do not overlap with any of the rolling bearings 50 in a radial view.

[0073] Furthermore, although the disk drive device 100 according to the above embodiment was helium-filled, it is not necessary for helium to be sealed in the internal space S.

[0074] Furthermore, although the thickness of the disk drive unit 100 or the housing 110 in the above embodiment was greater than 1 inch, the thickness of the disk drive unit 100 or the housing 110 is not particularly limited. For example, the configuration of the disk drive unit 100 in the above embodiment can also be applied to disk drive units having a thickness of 1 inch or less. [Explanation of symbols]

[0075] 1, 1A, 1B, 1C... Pivot Assembly Bearing Device 10...Outer shaft (first shaft), 10a, 10b...Opening, 15...Inner circumferential surface, 17...Protruding part (first projection), 17a...End face, 30...Inner shaft (second shaft), 31a...Outer surface, 32...Tip (one end), 32a...Male threaded portion, 33...Protruding portion (second projection), 33a...End face, 34...Hole, 34a...Female threaded portion, 50...Rolling bearing 100...Disk drive unit, 110...Housing, 111...Base member, 121...Inner cover member (cover member), 114a...Female screw part, 130...Magnetic disk

Claims

1. At least two bearings and A cylindrical first shaft that supports the bearing on its outer surface, A second shaft is housed in the first shaft such that one end extends from one opening of the first shaft, Equipped with, The second shaft has a male threaded portion at least in the portion extending from the first shaft, The first shaft has a first projection that protrudes from its inner circumferential surface such that it has an end face facing the other opening opposite to the first opening, The second shaft has a second projection that protrudes from its outer circumferential surface, having an end face that faces the male threaded portion. The first shaft and the second shaft are in contact with each other at the end faces of the first and second projections, respectively. The first shaft and the second shaft are in contact with each other in the axial direction at the first projection and the second projection between the at least two bearings. A pivot assembly bearing device characterized by the following features.

2. The pivot assembly bearing device according to claim 1, characterized in that the difference between the coefficient of thermal expansion of the first shaft and the coefficient of thermal expansion of the second shaft is within 50%.

3. The pivot assembly bearing device according to claim 1, A housing for the pivot assembly bearing device, Equipped with, The housing has a hole that engages with the male screw portion. A disk drive device characterized by the following features.

4. The disk drive device according to claim 3, characterized in that the aforementioned hole is a blind hole.

5. The housing comprises a base member to which the pivot assembly bearing device is attached via the male threaded portion, and at least one cover member attached to the base member to tightly close the space housing the pivot assembly bearing device to the outside. The aforementioned space is filled with a gas that is less dense than air. The disk drive device according to feature 3.

6. The disk drive device according to claim 3, characterized in that the housing comprises at least nine magnetic disks.

7. The second shaft of the pivot assembly bearing device has a female threaded portion on the other end. The at least one cover member is attached to the pivot assembly bearing device via the engagement of the female screw portion and the fastening member. The disk drive device according to feature 5.

8. The disk drive device according to claim 5, characterized in that the thickness of the housing is greater than 1 inch.

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