JP2012097780A - Fluid dynamic pressure bearing device, spindle motor, and disk drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce such an occurrence that a plate attached to a shaft warps to a sleeve side.SOLUTION: A fluid dynamic pressure bearing device 100 includes the shaft 110 arranged along the center axis, the sleeve 120, the plate 130, and a rotor hub 140. The shaft 110 has a small diameter portion 111, a middle diameter portion 112, and a large diameter portion 113 in order from an upper side. The sleeve 120 is attached to the large diameter portion 113. The plate 130 is arranged on the middle diameter portion 112, and has a first under surface 131a contacting the upper surface 113b of the large diameter portion 113 and a second under surface 131b extending outward radially from the first under surface 131a. The rotor hub 140 has a first contacting surface 140a to contact the plate 130. The upper surface 113b of the large diameter portion 113 has a second contacting surface 113c overlapping with the first contacting surface 140a in the axial direction and sandwiching the plate 130 together with the first contacting surface 140a.

Description

  The present invention relates to a fluid dynamic bearing device, a spindle motor, and a disk drive device.

  A hard disk device or an optical disk device is equipped with a motor that rotates the disk around a central axis. The motor has a rotating part, a stationary part, and a bearing device. The rotating part is rotated relative to the stationary part via the bearing device. In recent years, fluid dynamic bearing devices have been frequently used as bearing devices for motors. In the fluid dynamic pressure bearing device, lubricating oil is interposed between the shaft and the sleeve, and the shaft is rotated relative to the sleeve while being supported by the dynamic pressure of the lubricating oil.

As a prior art related to the invention of the present application, for example, there is one described in Patent Document 1. The motor described in Patent Document 1 includes a shaft that is supported by a sleeve and rotates, a hub coupled to the shaft, and a plate into which the shaft is inserted and coupled to the shaft. The plate is sandwiched from the axial direction by a step portion protruding in the radial direction of the shaft and the hub. Lubricating oil is filled between the plate and the sleeve, and constitutes a thrust bearing when the shaft rotates.
JP 2008-43193 A

  However, in the case of the motor, the surface that contacts the plate of the hub protrudes radially outward from the stepped portion of the shaft. For this reason, when the hub is inserted and the plate is fixed, or when an impact is applied to the hub, the surface of the hub that comes into contact with the plate is pressed from above and warped downward (sleeve side). There is a risk that. For this reason, the plate may come into contact with other members such as a sleeve, which may cause a problem.

  This invention is made | formed in view of such a subject, and it aims at providing the technique which reduces that the plate attached to the shaft warps to the sleeve side.

  In order to solve the above-described problems, a first invention of the present application is a fluid dynamic pressure bearing device, and includes a shaft disposed along a central axis extending vertically and a sleeve having an inner peripheral surface facing the shaft. A plate that is disposed on the upper side of the sleeve and extends in a radial direction from the outer peripheral surface of the shaft; a rotor hub that is disposed on the axially upper side of the plate and is fixed to the shaft; and the shaft and the sleeve And a lubricating fluid interposed between the sleeve and the plate, and the shaft includes, in order from the top, a small diameter portion, a medium diameter portion larger than the small diameter portion in the radial direction, and a radial direction. A large-diameter portion larger than the medium-diameter portion, an inner peripheral surface of the sleeve is opposed to the large-diameter portion of the shaft, and the plate is disposed on a radially outer side of the medium-diameter portion, A first lower surface in contact with the upper surface of the large-diameter portion, and a second lower surface extending radially outward from the first lower surface, wherein the rotor hub is fixed to the small-diameter portion, and the upper surface of the sleeve or the plate The second lower surface is provided with a dynamic pressure groove array for generating a dynamic pressure with respect to the lubricating fluid interposed between the sleeve and the plate, and the rotor hub is in contact with the plate. The upper surface of the large-diameter portion has a second contact surface that overlaps the first contact surface in the axial direction and sandwiches the plate with the first contact surface.

  According to the first exemplary invention of the present application, the shaft has a small-diameter portion smaller than the medium-diameter portion in the radial direction, the plate is disposed outside the medium-diameter portion, and the first contact surface and the second contact Hold it with the surface. Since the small-diameter portion is smaller than the medium-diameter portion in the radial direction, the position of the first contact surface that contacts the rotor hub plate can be moved radially inward, and the first contact surface and the second contact surface can be moved. It can be overlapped in the axial direction. Thereby, when the plate is sandwiched and fixed between the first contact surface and the second contact surface, the plate can be prevented from warping to the sleeve side.

It is a schematic sectional drawing of the fluid dynamic pressure bearing apparatus which concerns on one Embodiment. It is a longitudinal cross-sectional view of a disk drive device. FIG. 3 is a partially enlarged view showing an enlarged vicinity of an upper portion of a shaft shown in FIG. 2. It is a top view of a sleeve. It is the elements on larger scale which expanded and showed the adhesion part of the rotor hub and plate which concerns on a modification.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In the following, the direction along the central axis Q of the fluid dynamic bearing device is defined as the vertical direction, and the shape and positional relationship of each part will be described. However, this definition is merely for convenience of explanation, and does not limit the installation posture when the fluid dynamic bearing device, the spindle motor, and the disk drive device are mounted on an actual device.

<1. Fluid Dynamic Pressure Bearing Device According to One Embodiment>
FIG. 1 is a schematic cross-sectional view of a fluid dynamic bearing device 100 according to an embodiment. The fluid dynamic bearing device 100 includes a shaft 110, a sleeve 120, a plate 130, a rotor hub 140, and a lubricating fluid 150 arranged along a central axis Q that extends vertically. The sleeve 120 has an inner peripheral surface 120 a that faces the shaft 110. The plate 130 is disposed on the upper side of the sleeve 120 and extends radially outward from the outer peripheral surface 110 a of the shaft 110. The rotor hub 140 is disposed above the plate 130 in the axial direction (direction along the central axis Q) and is fixed to the shaft 110. The lubricating fluid 150 is interposed between the shaft 110 and the sleeve 120 and between the sleeve 120 and the plate 130. The lubricating fluid 150 is preferably a liquid, but is not limited to this and may be a gas.

  The shaft 110 has, in order from the top, a small diameter portion 111, a medium diameter portion 112 having a diameter d12 larger than the diameter d11 of the small diameter portion 111 in the radial direction, and a large diameter having a diameter d13 larger than the medium diameter portion 112 in the radial direction. Part 113 (d11 <d12 <d13). The inner peripheral surface 120 a of the sleeve 120 faces the outer peripheral surface 113 a of the large diameter portion 113. The plate 130 is disposed on the radially outer side of the medium diameter portion 112, and includes a first lower surface 131a that contacts the upper surface 113b of the large diameter portion 113, and a second lower surface 131b that extends radially outward from the first lower surface 131a. In the present embodiment, preferably, the first lower surface 131a and the second lower surface 131b are located on substantially the same plane in the radial direction. However, the first lower surface and the second lower surface do not have to be located on substantially the same plane.

  The rotor hub 140 is fixed to the small diameter portion 111. A guide or chamfering is applied to the lower end portion of the inner peripheral surface of the rotor hub 140. The upper surface 120b of the sleeve 120 is provided with a plurality of dynamic pressure grooves 161G that generate dynamic pressure with respect to the lubricating fluid interposed between the sleeve 120 and the plate 130. Note that the plurality of dynamic pressure grooves 161 </ b> G may be provided on the second lower surface 131 b of the plate 130. A plurality of dynamic pressure grooves 161 </ b> G may be provided on both the upper surface 120 b of the sleeve 120 and the second lower surface 131 b of the plate 30.

  The rotor hub 140 has a first contact surface 140 a that contacts a surface facing the upper side of the plate 130. The first contact surface 140a is disposed on the outside in the radial direction such as a guide or chamfering. The upper surface 113b of the large-diameter portion 113 includes a second contact surface 113c that overlaps the first contact surface 140a in the axial direction and sandwiches the plate 130 with the first contact surface 140a. In other words, the plate 130 is sandwiched between the first contact surface 140a and the second contact surface 113c that overlap in plan view. In the example shown in FIG. 1, the upper surface 113b and the second contact surface 113c are preferably substantially coincident. However, the upper surface 113b and the second contact surface 113c do not have to substantially coincide with each other. For example, the area of the upper surface 113b may be larger than the area of the first contact surface. May be provided.

  The shaft 110 has a small diameter portion 111 smaller than the medium diameter portion 112 in the radial direction. The plate 130 is disposed outside the medium diameter portion 112 and is sandwiched between the first contact surface 140a and the second contact surface 113c. Here, since the small-diameter portion 111 is configured to be smaller than the medium-diameter portion 112 in the radial direction, the first contact surface 140a of the rotor hub 140 that comes into contact with the plate 130 obtains a predetermined contact area, and the position is radially inward. I can move. Thereby, the 1st contact surface 140a and the 2nd contact surface 113c can be piled up and down in the direction of an axis. Therefore, when the plate 130 is sandwiched between the first contact surface 140a and the second contact surface 113c, the plate 130 is stably held while reducing the warp to the sleeve 120 side. Moreover, even when it has a guide, a chamfering, etc. inside radial direction of the 1st contact surface 140a, the 1st contact surface 140a and the 2nd contact surface 113c can be piled up and down in the axial direction.

<2. More specific embodiment>
<2-1. Configuration of disk drive>
Subsequently, a more specific embodiment of the present invention will be described.

  FIG. 2 is a longitudinal sectional view of the disk drive device 1. FIG. 3 is a partially enlarged view showing the vicinity of the upper portion of the shaft 41 shown in FIG. The disk drive device 1 is a device that performs at least one of reading and writing of information with respect to the disk 12 while rotating the magnetic disk 12 (hereinafter simply referred to as “disk 12”). The disk drive device 1 includes a housing 11, two disks 12 and 12, an access unit 13, and a spindle motor 2.

  The housing 11 is a housing that accommodates the two disks 12 and 12, the access unit 13, and the spindle motor 2. The access unit 13 moves the head 13H along the recording surface of the disk 12 supported by the spindle motor 2, and executes at least one of reading and writing of information with respect to the disk 12.

<2-2. Spindle motor configuration>
The spindle motor 2 includes a stationary part 3 fixed to the housing 11 of the disk drive device 1 and a rotating part 4 that rotates around a central axis Q while supporting the disks 12 and 12.

  The stationary part 3 includes a base member 31, a stator core 32, a coil 33, and a stationary bearing unit 34.

  The base member 31 constitutes a part of the housing 11 of the disk drive device 1. However, the base member 31 and the housing 11 may be separate members fixed to each other. The base member 31 includes a flat plate portion 311 that expands in the radial direction, and a substantially cylindrical holder portion 312 that protrudes upward from the inner edge of the flat plate portion 311. The base member 31 is made of a metal such as an aluminum alloy, for example.

  The stator core 32 and the coil 33 are magnetic flux generators that generate magnetic flux in accordance with the drive current. The stator core 32 includes an annular core back 321 that is fixed to the outer peripheral surface of the holder portion 312 of the base member 31, and a plurality of teeth portions 322 that protrude radially outward from the core back 321. Yes. The stator core 32 is made of, for example, a laminated steel plate in which electromagnetic steel plates are laminated in the axial direction.

  Coil 33 includes a conductive wire wound around each tooth portion 322 of stator core 32. The coil 33 is connected to a power supply device (not shown) via a connector. When a drive current is applied to the coil 33 from the power supply device via the connector, a magnetic flux is generated in the tooth portion 322, and the rotating portion 4 is rotated about the central axis Q.

  The stationary bearing unit 34 supports the shaft 41 of the rotating unit 4 in a relatively rotatable state. A stationary bearing unit 34, a shaft 41, a rotor hub 42 and a plate 44, which will be described later, are connected to the fluid dynamic pressure bearing device 5 that connects the stationary portion 3 and the rotating portion 4 in a relatively rotatable state about the central axis Q. Constitute.

  The stationary bearing unit 34 includes a sleeve 341, a closing member 342, and a cap 343.

  The sleeve 341 has a substantially cylindrical shape and surrounds the outer peripheral surface of the shaft 41. The sleeve 341 is disposed inside the holder portion 312 of the base member 31. The sleeve 341 is made of, for example, a metal such as stainless steel or a copper alloy.

  FIG. 4 is a top view of the sleeve 341. On the upper surface of the sleeve 341, a thrust bearing surface 341S in which a plurality of dynamic pressure grooves 341G are arranged is provided. As the shaft 41 rotates, dynamic pressure is generated in the lubricating oil 51 interposed between the upper surface of the sleeve 341 and the lower surface (second lower surface 444) of the plate 44, thereby forming a thrust bearing.

  Returning to FIG. 2, the closing member 342 is formed in a substantially disk shape and is disposed below the shaft 41. The closing member 342 closes the lower part of the sleeve 341.

  The cap 343 is attached to the upper part of the sleeve 341. As shown in FIG. 3, the cap 343 has a lower surface 343 a that faces the upper surface 441 of the plate 44, and an inner side surface 343 b that faces the outer surface 442 of the plate 44.

  Next, the configuration of the rotating unit 4 of the spindle motor 2 will be described. The rotating unit 4 includes a shaft 41, a rotor hub 42, a rotor magnet 43, and a plate 44.

  The shaft 41 is disposed along a central axis Q that extends vertically. As shown in FIG. 3, the shaft 41 includes, in order from the top, a small diameter portion 411 having a diameter d1, a medium diameter portion 412 having a diameter d2, and a large diameter portion 413 having a diameter d3 (d1 <d2 <D3).

  The shaft 41 is rotatably supported with respect to the stationary bearing unit 34 in a state where the shaft 41 is inserted into a bearing hole disposed in the center of the sleeve 341. At this time, the inner peripheral surface 341 a of the sleeve 341 faces the outer peripheral surface 413 a of the large-diameter portion 413 of the shaft 41. The upper surface 413 b of the large diameter part 413 has a second contact surface 413 c that contacts the plate 44.

  Although not shown, a plurality of radial dynamic pressures that generate dynamic pressure in the lubricating fluid (the lubricating oil 51 in this embodiment) interposed between the shaft 41 and the sleeve 341 are provided on the outer peripheral surface 413a of the large-diameter portion 413. Grooves are arranged. The radial dynamic pressure groove is a so-called herringbone groove. When the shaft 41 rotates, the lubricating oil is pressurized by the radial dynamic pressure groove array, and the shaft 41 rotates while being supported along the radial direction by the dynamic pressure generated in the lubricating oil 51. Note that the plurality of radial dynamic pressure grooves may be disposed on the inner peripheral surface 341 a of the sleeve 341 facing the outer peripheral surface 413 a of the large diameter portion 413.

  The rotor hub 42 is fixed to the shaft 41 and rotates together with the shaft 41. The rotor hub 42 has a shape that extends radially outward around the central axis Q. The rotor hub 42 has a joint portion 421, a body portion 422, and a cylindrical portion 423. The joint portion 421 is fixed to the small diameter portion 411 of the shaft 41 by means such as press fitting, shrink fitting, welding, or an adhesive. The body portion 422 spreads outward from the joint portion 421 in the radial direction. The cylindrical portion 423 hangs from the outer peripheral edge of the body portion 422. The rotor hub 42 has a first contact surface 421 a that contacts the plate 44.

  The rotor magnet 43 is attached to the inner peripheral surface of the cylindrical portion 423 of the rotor hub 42. The rotor magnet 43 has an annular shape centered on the central axis Q. The inner peripheral surface of the rotor magnet 43 faces the outer peripheral surface of the plurality of teeth portions 322 of the stator core 32 in the radial direction. The inner peripheral surface of the rotor magnet 43 is a magnetic curved surface in which N poles and S poles are alternately arranged.

  The plate 44 is disposed on the upper side of the sleeve 341 and has a disk shape extending in the radial direction from the outer peripheral surface of the medium diameter portion 412 of the shaft 41. The plate 44 has a first lower surface 443 that contacts the upper surface 413b of the large-diameter portion 413, and a second lower surface 444 that extends radially outward from the first lower surface 443.

  Examples of the method for attaching the plate 44 to the medium diameter portion 412 include a method of press-fitting the ring-shaped plate 44 into the medium diameter portion 412. The inner diameter of the plate 44 is larger than the diameter d1 of the small diameter portion 411. Further, the inner diameter of the plate 44 is preferably the same as or slightly smaller than the diameter d2 of the medium diameter portion 412. Since the diameter d1 of the small diameter part 411 is smaller than the diameter d2 of the medium diameter part 412, the outer surface of the small diameter part 411 and the inner peripheral surface of the plate 44 are damaged when the plate 44 is press-fitted into the medium diameter part 412. Can be suppressed. Therefore, the rotor hub 42 and the plate 44 can be fixed to the shaft 41 with high accuracy. The attachment method of the plate 44 is not limited to press-fitting, and can be fixed by means such as shrink fitting, welding, or an adhesive.

  The plate 44 is made of, for example, stainless steel or a copper alloy. Since the diameter d1 of the small diameter portion 411 is smaller than the diameter d2 of the medium diameter portion 412, the through hole of the plate 44 can be easily passed through the small diameter portion 411 when the plate 44 is press-fitted into the medium diameter portion 412. . For this reason, generation | occurrence | production of the curvature of the plate 44 which consists of stainless steel or a copper alloy is reduced.

  The plate 44 may be made of ceramics. Ceramics are more susceptible to brittle fracture when stresses higher than the material strength are applied, compared to metals such as stainless steel and copper alloys. As described above, the through hole of the plate 44 can be easily passed through the small diameter portion 411. For this reason, when the plate 44 is formed of ceramics, occurrence of chipping or cracking of the plate 44 is reduced.

  Note that the material of the plate 44 is not limited to that described above, and may be formed of other materials.

  The plate 44 is sandwiched between the first contact surface 421a and the second contact surface 413c. The first contact surface 421a and the second contact surface 413c have portions that overlap in the axial direction. The plate 44 is stably held in the axial direction by the overlapping portion of the first contact surface 421a and the second contact surface 413c.

  In plan view, the radially outer end of the first contact surface 421a preferably overlaps the second contact surface 413c in the axial direction. Thereby, it can suppress that the plate 44 warps to the sleeve 341 side.

  In particular, in the example shown in FIG. 3, the position of the radially outer end of the first contact surface 421a and the position of the radially outer end of the second contact surface 413c substantially coincide with each other in the axial direction. For this reason, when the plate 44 is sandwiched between the first contact surface 421a and the second contact surface 413c, the plate 44 can be held in a balanced manner by the first contact surface 421a and the second contact surface 413c. It is possible to suppress warping of either one.

  Further, the axial length of the medium diameter portion 412 is preferably shorter than the axial length of the inner peripheral surface of the plate 44. Thereby, a gap having a length d4 is provided between the rotor hub 42 and the medium diameter portion 412 in the axial direction. According to this, since the rotor hub 42 is suppressed from contacting the upper surface of the medium diameter portion 412, the rotor hub 42 can be reliably brought into contact with the plate 44. Thereby, the plate 44 can be reliably pinched by the 1st contact surface 421a and the 2nd contact surface 413c, and it hold | maintains stably.

  Further, d5 (= d2-d1) is preferably shorter than d6 (= d3-d2). d5 indicates the length of the portion where the medium diameter portion 412 protrudes in the radial direction with respect to the small diameter portion 411. d6 indicates the length of the portion where the large diameter portion 413 protrudes in the radial direction with respect to the medium diameter portion 412. With this configuration, the plate 44 can be satisfactorily fixed between the first contact surface 421a and the second contact surface 413c while ensuring the radial thickness of the small diameter portion 411. For example, the shaft 41 may have a bolt screw hole for coupling to the housing 11 formed therein. In such a case, the required strength can be ensured by securing the thickness of the small diameter portion 411. Therefore, when the rotor hub 42 is fixed to the small diameter portion 411, the deformation of the small diameter portion 411 can be prevented.

  Lubrication is provided between the shaft 41 and the sleeve 341, between the sleeve 341 and the plate 44, between the plate 44 and the cap 343, and the communication hole 341H penetrating the upper and lower surfaces of the sleeve 341. Oil 51 is filled. The filling spaces of the lubricating oil 51 communicate with each other, and the lubricating oil 51 can freely flow.

  As shown in FIG. 3, the gap between the inner surface 343 b of the cap 343 and the outer surface 442 of the plate 44 is continuous with the gap between the sleeve 341 and the plate 44. Further, the gap between the lower surface 343 a of the cap 343 and the upper surface 441 of the plate 44 is continuous with the gap between the inner side surface 343 b of the cap 343 and the outer side surface 442 of the plate 44. The gap between the inner surface 343b of the cap 343 and the outer surface 442 of the plate 44 and the gap between the lower surface 343a of the cap 343 and the upper surface 441 of the plate 44 are continuously filled with the lubricating oil 51. Is done. The lower surface 343a of the cap 343 includes an inclined surface. The gap between the inclined surface and the upper surface 441 of the plate 44 gradually increases toward the inner side in the radial direction. The interface 51 </ b> B of the lubricating oil 51 is located in the gap between the lower surface 343 a of the cap 343 and the upper surface 441 of the plate 44. The interface 51B faces inward in the radial direction. Since the interface 51B of the lubricating oil 51 has a meniscus shape due to the action of surface tension, the lubricating oil 51 is prevented from leaking out of the stationary bearing unit 34. That is, the seal portion 52 is configured by the lower surface 343 a of the cap 343 and the upper surface 441 of the plate 44. Note that the seal portion 52 may be configured by inclining the upper surface 441 of the plate 44 to widen the gap between the plate 44 and the cap 343.

  In the present embodiment, by providing the small diameter portion 411, the first contact surface 421a of the rotor hub 42 that sandwiches the plate 44 can be disposed on the radially inner side. Thereby, since the seal portion 52 can be configured to be relatively long in the radial direction, the fluid dynamic pressure bearing device 5 can be thinned while increasing the storage amount of the lubricating oil 51. For example, the gap between the upper surface 441 of the plate 44 and the lower surface 343a of the cap 343 may be configured with substantially constant dimensions.

  As the lubricating oil 51, for example, an oil mainly composed of an ester such as a polyol ester oil or a diester oil is used. Note that the inside of the stationary bearing unit 34 may be filled with a lubricating fluid such as a gas.

<3. Modification>
As mentioned above, although exemplary embodiment of this invention was described, this invention is not limited to said embodiment.

  FIG. 5 is a partially enlarged view showing the rotor hub 42, the plate 44, and the bonded portion in an enlarged manner according to a modification. In the example shown in FIG. 5, an adhesive 61 is used when fixing between the rotor hub 42 and the plate 44. As shown in FIG. 5, an adhesive holder 62 may be provided in which the gap with the plate increases from the radially outer end of the first contact surface 421 a of the rotor hub 42 toward the radially outer side. When the adhesive 61 is applied by the adhesive 61, it can be suppressed that the liquid-state adhesive 61 flows into the fluid dynamic bearing device 5.

  The present invention can also be applied to a spindle motor for rotating optical disks other than magnetic disks. However, spindle motors for magnetic disks are required to have particularly high performance with respect to rotational characteristics. Therefore, the technical significance of applying the present invention to a spindle motor for a magnetic disk is great.

  The present invention can be used for a fluid dynamic bearing device, a spindle motor, and a disk drive device.

DESCRIPTION OF SYMBOLS 1 Disk drive device 100,5 Fluid dynamic pressure bearing apparatus 11 Housing 110,41 Shaft 110a Outer peripheral surface 111,411 Small diameter part 112,412 Medium diameter part 113,413 Large diameter part 113a, 413a Outer surface 113b, 413b Upper surface 113c, 413c Second contact surface 12 Disc 120, 341 Sleeve 120a, 341a Inner peripheral surface 120b Upper surface 13 Access portion 130, 44 Plate 113a, 443 First lower surface 131b, 444 Second lower surface 140, 42 Rotor hub 140a, 421a First contact surface 150 Lubrication Fluid 161G, 341G Dynamic pressure groove 2 Spindle motor 20 Sleeve 3 Stationary part 30 Plate 32 Stator core 33 Coil 341a Inner peripheral surface 341S Dynamic pressure generating surface 343 Cap 343a Lower surface 343b Inner side surface 4 times Part 43 rotor magnet 51 lubricating oil 52 seal portion 61 adhesive 62 adhesive holding portion Q central axis D11 to D13, d1 to d3 diameter d4~d6 length

Claims (12)

A shaft disposed along a central axis extending vertically;
A sleeve having an inner peripheral surface facing the shaft;
A plate disposed above the sleeve and extending radially from the outer peripheral surface of the shaft;
A rotor hub disposed on the axially upper side of the plate and fixed to the shaft;
A lubricating fluid interposed between the shaft and the sleeve and between the sleeve and the plate;
With
The shaft, in order from the top, has a small diameter portion, a medium diameter portion larger than the small diameter portion in the radial direction, and a large diameter portion larger than the medium diameter portion in the radial direction,
The inner peripheral surface of the sleeve is opposed to the large diameter portion of the shaft,
The plate is disposed on the radially outer side of the medium diameter portion, and has a first lower surface that contacts the upper surface of the large diameter portion, and a second lower surface that extends radially outward from the first lower surface,
The rotor hub is fixed to the small diameter portion,
The upper surface of the sleeve or the second lower surface of the plate is provided with a dynamic pressure groove array for generating a dynamic pressure with respect to the lubricating fluid interposed between the sleeve and the plate,
The rotor hub has a first contact surface that contacts the plate;
The upper surface of the large-diameter portion has a second contact surface that overlaps the first contact surface in the axial direction and sandwiches the plate with the first contact surface. The fluid dynamic bearing device according to claim 1,
A fluid dynamic bearing device in which a radially outer end portion of the first contact surface overlaps the second contact surface in the axial direction in a plan view. In the fluid dynamic pressure bearing device according to claim 2,
A fluid dynamic bearing device in which a radially outer end portion of the first contact surface and a radially outer end portion of the second contact surface substantially coincide with each other in an axial direction in a plan view. In the fluid dynamic pressure bearing device according to any one of claims 1 to 3,
A fluid dynamic bearing device having a gap between the rotor hub and the medium diameter portion with respect to a central axis direction. In the fluid dynamic pressure bearing device according to any one of claims 1 to 4,
A fluid dynamic bearing device in which the plate is press-fitted into the medium diameter portion. In the fluid dynamic bearing device according to claim 5,
A fluid dynamic bearing device in which the plate is made of stainless steel or copper alloy. In the fluid dynamic bearing device according to claim 5,
A fluid dynamic bearing device in which the plate is made of ceramics. The hydrodynamic bearing device according to any one of claims 1 to 7,
A cap having a lower surface facing the upper surface of the plate and an inner surface facing the outer surface of the plate;
A seal portion that increases as the gap between the cap and the plate moves radially inward;
Further including
A fluid dynamic bearing device in which the lubricating fluid is continuously interposed between the shaft and the sleeve, between the sleeve and the plate, and between the plate and the cap. In the fluid dynamic bearing device according to any one of claims 1 to 8,
A fluid dynamic bearing device, wherein a length of a portion of the medium diameter portion protruding from the small diameter portion is shorter than a length of a portion of the large diameter portion protruding from the medium diameter portion. In the fluid dynamic bearing device according to any one of claims 1 to 9,
An adhesive is interposed between the first contact surface and the upper surface of the plate,
The fluid dynamic bearing device according to claim 1, wherein the first contact surface includes an adhesive holding portion in which a gap between the first contact surface and the plate increases from a radially outer end of the first contact surface toward a radially outer side. A stationary part;
A rotating part that is rotatably supported by the stationary part via the fluid dynamic bearing device according to any one of claims 1 to 10,
A rotation drive unit that rotates the rotating unit with respect to the stationary unit;
Including spindle motor. A spindle motor according to claim 11;
An access unit that performs at least one of reading and writing of information with respect to the disk supported by the rotating unit of the spindle motor;
A housing for housing the spindle motor and the access unit;
A disk drive device comprising:

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