JP2016050590A - Rotary equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide rotary equipment in which a bearing characteristic is improved and its rotational stability is superior.SOLUTION: This invention relates to rotary equipment comprising a fixed body; a rotary body rotatably supported at the fixed body; the first radial dynamic pressure generating groove having a herringbone shape arranged in at least one of the fixed body and the rotary body so as to generate a fluid dynamic pressure in a radial direction. The first radial dynamic pressure generating groove has, at an intermediate part protruding from both ends of the rotary body of a rotating axial direction in a circumferential direction, the first bent groove having a shallow and narrow region that is narrower than groove widths at both ends in a rotating axial direction and it has a groove depth that is shallower than a groove depth at both ends in the rotating axial direction.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a rotating device.

  For example, a fixed shaft, a radial bearing component that is rotatably supported around the fixed shaft, and a radial that is provided on the fixed shaft or the radial bearing component and generates dynamic pressure in the lubricating fluid filled in the gap A fluid dynamic pressure bearing having a dynamic pressure generating groove is known (see, for example, Patent Document 1).

JP 2011-47439 A

  In the fluid dynamic pressure bearing described above, the characteristics of the bearing such as rigidity and loss torque vary depending on the shape of the radial dynamic pressure generating groove that generates dynamic pressure in the lubricating fluid. For example, if the rigidity of the bearing is low, the rotation of the radial bearing constituent member may become unstable. Therefore, in order to improve the rotational stability of the fluid dynamic pressure bearing, it is necessary to optimize the shape of the radial dynamic pressure generating groove and improve the bearing characteristics such as rigidity.

  The present invention has been made in view of the above, and an object of the present invention is to provide a rotating device with improved bearing characteristics and excellent rotational stability.

  According to one aspect of the present invention, a fixed body, a rotating body rotatably supported by the fixed body, and at least one of the fixed body and the rotating body are provided to generate a fluid dynamic pressure in a radial direction. A rotating device including a herringbone-shaped first radial dynamic pressure generating groove, wherein the first radial dynamic pressure generating groove is formed at an intermediate portion protruding in the circumferential direction from both ends of the rotating body in the rotation axis direction. And a first bent groove having a shallow region in which the groove width in the circumferential direction is narrower than the groove width at both ends in the rotation axis direction and the groove depth is shallower than the groove depth at both ends in the rotation axis direction.

  According to the embodiment of the present invention, a rotating device having improved bearing characteristics and excellent rotational stability is provided.

1 is a perspective view illustrating a disk drive device according to an embodiment. It is sectional drawing which illustrates the bearing mechanism of the disk drive device which concerns on embodiment. It is a figure which illustrates the radial dynamic pressure generating groove | channel which concerns on embodiment. It is a figure which shows typically a mode that a cutting tool forms a micro groove | channel in a cutting device. It is an enlarged view which illustrates the 1st radial dynamic pressure generating groove in an embodiment. It is a figure explaining the bearing characteristic in a disc drive. It is a figure which illustrates the shape parameter of the 1st radial dynamic pressure generating groove. It is a figure which illustrates the shape parameter of the 1st radial dynamic pressure generating groove. It is a figure which illustrates the simulation result of the optimal groove ratio in an embodiment. It is a figure which illustrates the simulation result of the optimal groove depth in embodiment. It is a figure which illustrates the simulation result of the optimal inclination angle of the 1st radial dynamic pressure generating groove in an embodiment. It is a figure which illustrates the simulation result of the optimal inclination angle of the 2nd radial dynamic pressure generating groove in an embodiment. It is a figure which shows the shape of the 1st radial dynamic pressure generating groove | channel which concerns on Example 1. FIG. It is a figure which shows the shape of the 2nd radial dynamic pressure generating groove | channel which concerns on Example 1. FIG.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted. The dimensions of the members in each drawing are appropriately enlarged and reduced for easy understanding. In addition, in the drawings, some of the members that are not important for describing the embodiment are omitted.

  A disk drive device as a rotating device described below is equipped with a recording disk on which data is magnetically recorded, and is used as a hard disk drive or the like.

<Configuration of disk drive>
FIG. 1 is a perspective view illustrating a disk drive device 100 according to the embodiment. FIG. 1 shows a state in which the top cover 2 of the disk drive device 100 is removed for easy understanding. Further, for example, parts that are not important in explaining the present invention such as an electronic circuit are omitted.

  The disk drive device 100 according to the present embodiment includes a fixed body, a rotating body that rotates with respect to the fixed body, a recording disk 8 that is attached to the rotating body, and a data read / write unit 10. The fixed body includes a base 4, a top cover 2, and six screws 20. The rotating body includes a shaft 26, a hub 28, and a clamper 36, and is provided so as to be rotatable about a rotation axis R.

  In the following description, in the state where the top cover 2 is attached to the base 4, the top cover 2 side is described as the top and the base 4 side is described as the bottom. Further, the direction parallel to the rotation axis R of the rotating body is defined as the axial direction, the arbitrary direction passing through the rotation axis R on the plane perpendicular to the rotation axis R is defined as the radial direction, and the direction farther from the rotation axis R in the radial direction The direction closer to the rotation axis R will be described as the inner peripheral side. These notations do not limit the posture in which the disk drive device 100 is used, and the disk drive device 100 can be used in any posture.

(base)
The base 4 includes a bottom plate portion 4 a that forms the bottom of the disk drive device 100, and an outer peripheral wall portion 4 b that is formed along the outer periphery of the bottom plate portion 4 a so as to surround the mounting area of the recording disk 8. Six screw holes 22 are provided on the upper surface 4 c of the outer peripheral wall 4 b, and the top cover 2 is fixed by screws 20 that are screwed into the screw holes 22.

  The base 4 is molded by die casting using, for example, an aluminum alloy. The base 4 may be formed by pressing from a steel plate, an aluminum plate, or the like. The base 4 is coated on the surface with a resin coating such as an epoxy resin in order to prevent the surface from peeling off. The surface of the base 4 may be plated with a metal material such as nickel or chromium instead of the resin coating.

(Data read / write part)
The data read / write unit 10 includes a swing arm 14, a voice coil motor 16, a pivot assembly 18, and a recording / reproducing head (not shown) attached to the tip of the swing arm 14.

  The pivot assembly 18 supports the swing arm 14 so as to be swingable around the head rotation axis S. The voice coil motor 16 moves the recording / reproducing head to a desired position on the recording disk 8. The recording / reproducing head records data on the recording disk 8 and reads data from the recording disk 8. The data read / write unit 10 is configured using a known technique for controlling the position of the head.

(Top cover)
The top cover 2 is fixed to the upper surface 4 c of the outer peripheral wall portion 4 b of the base 4 by six screws 20 that are screwed into the screw holes 22. A clean space 24 surrounded by the top cover 2, the bottom plate portion 4 a of the base 4, and the outer peripheral wall portion 4 b of the base 4 is filled with a gas from which particles have been removed. As the gas to be filled, for example, air, nitrogen, helium or hydrogen is used.

(Recording disc)
The recording disk 8 mounted on the disk drive device 100 is, for example, a glass 3.5-inch recording disk having a diameter of about 95 mm, and the center hole has a diameter of about 25 mm and a thickness of about 1.27 mm. 1.75 mm. In the disk drive device 100, four recording disks 8 are mounted on the hub 28.

<Configuration of bearing mechanism>
FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, and is a cross-sectional view illustrating a bearing mechanism of the disk drive device 100 according to the embodiment.

  The disk drive device 100 includes a shaft 26, an upper flange 27, a hub 28, a yoke 34, a magnet 35, and a clamper 36 as rotating bodies. Further, the base body 4, the plate 29, the stator core 40, the coil 42, the inner sleeve 31, and the outer sleeve 32 are provided as fixed bodies.

  Lubricant 92 is injected between the shaft 26, the inner sleeve 31 and the outer sleeve 32, and the rotating body including the hub 28 on which the recording disk 8 is mounted is centered on the rotation axis R on the fixed body including the base 4. Is supported rotatably.

(shaft)
The shaft 26 has a lower flange 26 a projecting annularly from the lower end to the outer peripheral side, a hub 28 is fixed to the upper end, and a cylindrical upper flange 27 is fixed to the lower side of the hub 28. The shaft 26 is provided so as to be rotatable about the rotation axis R together with the hub 28 and the upper flange 27.

  The shaft 26 is formed from a steel material such as stainless steel SUS420J2 by cutting or grinding. The shaft 26 may be integrally formed with the lower flange 26a as a single member, or may be configured as a separate part.

(Hub)
The hub 28 is formed in a substantially cup shape that is annular when viewed from above, and includes a shaft hole 28a, a protruding portion 28b, and a placement portion 28c. The hub 28 fixes and holds the recording disk 8 placed on the placement surface 28d of the placement portion 28c via the spacer 9, and rotates together with the shaft 26 fixed by press-fitting and bonding into the shaft hole 28a. Rotate around.

  The hub 28 is formed by cutting or pressing a steel material such as stainless steel SUS430 having soft magnetism. In addition, the hub 28 may be subjected to a surface layer forming process such as electroless nickel plating so that surface peeling is suppressed.

  The hub 28 may be formed from a single member. For example, each part may be configured as a separate part.

(Upper flange)
The upper flange 27 has an annular portion 27a that protrudes in an annular shape from the shaft 26 to the outer peripheral side, and a cylindrical portion 27b that protrudes downward from the outer peripheral end of the annular portion 27a, and is fixed by press-fitting and adhesion. Rotate with the shaft 26.

(Clamper)
The clamper 36 is an annular member, the center hole of which is fitted and fixed to the upper end portion of the hub 28, and the recording disk 8 that is stacked and placed via the spacer 9 is connected to the mounting portion 28 c of the hub 28. And fix between.

(yoke)
The yoke 34 is formed in a cylindrical shape by, for example, cutting or pressing from a steel material or the like having soft magnetism. The yoke 34 is fixed to the inner peripheral surface of the protruding portion 28b of the hub 28 by, for example, adhesion.

(magnet)
The magnet 35 is formed in a cylindrical shape, and is fixed to the inner peripheral surface of the yoke 34 by, for example, adhesion. The magnet 35 is, for example, a ferrite magnet material, a rare earth magnet material, or the like, and is formed including a resin such as polyamide as a binder. The magnet 35 may be formed by laminating, for example, a ferrite magnet layer and a rare earth magnet layer.

  The magnet 35 is provided with, for example, 12 magnetic poles in the circumferential direction of the inner circumferential surface, and is opposed to the outer circumferential surface of the salient pole provided in the stator core 40 in the radial direction via a gap.

(Stator core)
The stator core 40 has an annular ring portion in a top view and a plurality of salient poles extending from the annular portion to the radially outer peripheral side, and is fixed to the outer peripheral side of the protruding portion 4d of the base 4 by, for example, press-fitting. Yes. The stator core 40 is formed by, for example, integrating a plurality of laminated thin electromagnetic steel plates by caulking. The surface of the stator core 40 is provided with an insulating film by, for example, electrodeposition coating or powder coating. A coil 42 is wound around each salient pole of the stator core 40. The stator core 40 may be a solid core formed by solidifying magnetic powder such as a sintered body.

  When a three-phase substantially sinusoidal drive current is passed through the coil 42, a drive magnetic flux is generated along the salient poles of the stator core 40, and torque is generated by electromagnetic action with the magnetic flux of the magnetic poles of the magnet 35. Rotating drive.

(sleeve)
The inner sleeve 31 is a cylindrical member, and is fixed to the inner peripheral surface of the outer sleeve 32 by, for example, press-fitting and adhesion, and surrounds the upper flange 27 and the lower flange 26a of the shaft 26. The outer sleeve 32 is a cylindrical member surrounding the inner sleeve 31, and is fixed to the inner peripheral surface of the protruding portion 4d protruding from the bottom surface of the base 4 by press-fitting and bonding, for example.

  The inner sleeve 31 and the outer sleeve 32 are each formed in a substantially cylindrical shape by cutting, for example, from a steel material such as SUS430. The inner sleeve 31 and the outer sleeve 32 may be subjected to surface treatment such as electroless nickel plating after cutting a steel material such as SUS430 or a metal material such as brass. The inner sleeve 31 and the outer sleeve 32 may be integrally formed with a single member.

(plate)
The plate 29 is a disk-shaped member, and is fixed to the lower end of the outer sleeve 32 by press-fitting and bonding, for example. The plate 29 closes the lower end of the outer sleeve 32 and forms a space for accommodating the lower flange 26 a of the shaft 26 between the lower end of the inner sleeve 31.

(lubricant)
A lubricant 92 is injected into a predetermined gap between the shaft 26 and the upper flange 27 and the plate 29, the inner sleeve 31 and the outer sleeve 32. Lubricant 92 has phosphor added to base oil and emits light when irradiated with light of a predetermined wavelength. Therefore, lubricant 92 is easily detected when leaking from between members.

(Taper space)
A tapered space 118 is provided between the outer peripheral surface of the cylindrical portion 27 b of the upper flange 27 and the inner peripheral surface of the upper end portion 32 a of the outer sleeve 32. A gas-liquid interface 120 of the lubricant 92 is formed at the end. The taper space 118 functions as a seal portion that suppresses leakage of the lubricant 92 due to a capillary phenomenon.

(Radial dynamic pressure generating groove)
A first radial dynamic pressure generating groove 50 that generates a fluid dynamic pressure in the radial direction (radial direction) in the lubricant 92 when the shaft 26 and the hub 28 rotate, and a second radial dynamic groove 50 are formed on the inner peripheral surface of the inner sleeve 31. The dynamic pressure generating groove 55 is provided so as to be separated in the axial direction. The first radial dynamic pressure generating groove 50 and the second radial dynamic pressure generating groove 55 include a plurality of bent grooves 51 and 56 each having a herringbone shape as shown in FIG.

  One or more of the plurality of bent grooves 51 and 56 of the first radial dynamic pressure generating groove 50 and the second radial dynamic pressure generating groove 55 may be provided on the outer peripheral surface of the shaft 26.

  The first radial dynamic pressure generating groove 50 and the second radial dynamic pressure generating groove 55 are formed by a cutting apparatus having a cutting tool whose position is finely controlled using, for example, a piezoelectric element. In the cutting apparatus, the inner sleeve 31 is rotated while being held by a jig, and the cutting tool contacts the inner peripheral surface of the inner sleeve 31 and performs cutting while moving in the axial direction, whereby the first radial dynamic pressure is obtained. A generation groove 50 and a second radial dynamic pressure generation groove 55 are formed.

  FIG. 4 is a diagram schematically illustrating how the cutting tool 130 forms the minute groove 131 in the cutting apparatus.

  Since the inner sleeve 31 rotates while being held by the jig, the cutting tool 130 moves in the arrow direction relative to the inner sleeve 31 along the circumferential direction T as shown in FIG. Further, the cutting tool 130 is displaced in the vertical direction in FIG. 4 when an alternating electric field is applied to the piezoelectric element, and cuts a desired position on the inner peripheral surface of the rotating inner sleeve 31 to form the minute groove 131. To do.

  The width W perpendicular to the circumferential direction T of the minute groove 131 is formed in the range of 0.02 mm to 0.2 mm, for example. Further, the length Lg in the circumferential direction T of the minute groove 131 is formed in a range of 0.2 mm to 2 mm, for example, and the depth of the minute groove 131 is formed in a range of 3 μm to 50 μm, for example.

  FIG. 5 is an enlarged view illustrating the first radial dynamic pressure generating groove 50 in the embodiment.

  As shown in FIG. 5, the cutting tool 130 moves at a predetermined position along the circumferential direction T while moving at a predetermined pitch P in the X direction orthogonal to the circumferential direction T with respect to the rotating inner sleeve 31. The minute groove 131 is formed by cutting. The pitch P at which the cutting tool 130 moves is smaller than the width W of the minute groove 131, and the minute groove 131 is formed so as to overlap in the X direction. The first radial dynamic pressure generating groove 50 is formed by cutting the inner peripheral surface of the inner sleeve 31 such that the cutting tool 130 overlaps the plurality of minute grooves 131 extending in the circumferential direction T in the X direction. . Similarly to the first radial dynamic pressure generating groove 50, the second radial dynamic pressure generating groove 55 is formed by cutting a plurality of minute grooves 131 extending in the circumferential direction T so as to overlap in the X direction. .

  By cutting using such a cutting device, the first radial dynamic pressure generating groove 50 and the second radial dynamic pressure generating groove 55 are formed in desired shapes with high dimensional accuracy.

(Thrust dynamic pressure generating groove)
As shown in FIG. 2, on the upper surface of the lower flange 26a of the shaft 26, the fluid dynamic pressure in the thrust direction (axial direction) is applied to the lubricant 92 when the shaft 26 rotates relative to the plate 29, the inner sleeve 31 and the like. A first thrust dynamic pressure generating groove 60 to be generated is provided. The first thrust dynamic pressure generating groove 60 is composed of, for example, a plurality of grooves having a herringbone shape or a spiral shape. The first thrust dynamic pressure generating groove 60 may be provided on the lower surface of the inner sleeve 31.

  Further, a second thrust dynamic pressure generating groove for generating a fluid dynamic pressure in the thrust direction in the lubricant 92 when the shaft 26 rotates with respect to the plate 29, the inner sleeve 31, and the like is formed on the lower surface of the lower flange 26a of the shaft 26. 65 is provided. The second thrust dynamic pressure generating groove 65 is constituted by a plurality of grooves having a herringbone shape or a spiral shape, for example. The second thrust dynamic pressure generation groove 65 may be provided on the upper surface of the plate 29.

  Similar to the first radial dynamic pressure generating groove 50 and the second radial dynamic pressure generating groove 55, the first thrust dynamic pressure generating groove 60 and the second thrust dynamic pressure generating groove 65 are minute grooves cut by the cutting tool 130. It may be formed.

  When the shaft 26 and the hub 28 are rotated with respect to the plate 29, the inner sleeve 31, and the like, the shaft 26 and the hub 28 are moved to the plate 29, the inner sleeve 31, and the fluid dynamic pressure in the radial direction and the thrust direction generated in the lubricant 92. The outer sleeve 32 is supported in a non-contact state.

<Bearing characteristics>
FIG. 6 is a diagram for explaining the bearing characteristics in the disk drive device 100. FIG. 6 is an XY cross section orthogonal to the rotation axis R, and the shaft 26 and the inner sleeve 31 are schematically depicted. In FIG. 6, the shaft 26 is drawn in a cylindrical shape.

  As shown in FIG. 6, when the shaft 26 is displaced by δx in the X direction from the position indicated by the broken line to the position indicated by the solid line, a force Fx in the X direction is applied to the shaft 26 to return to the original position. Further, the shaft 26 is affected by the dynamic pressure of the lubricant 92 generated by the first radial dynamic pressure generating groove 50 and the second radial dynamic pressure generating groove 55 formed on the inner peripheral surface of the inner sleeve 31, A force Fy in the Y direction perpendicular to the X direction works.

  Thus, the rigidity of the bearing that generates the force Fx in the X direction when the shaft 26 is displaced by δx in the X direction is defined as Kxx (= Fx / δx). In the following description, the term “bearing rigidity” refers to Kxx. The characteristic of the bearing that generates the force Fy in the Y direction is assumed to be Kxy (= Fy / δx). Further, the attenuation in the X direction due to the presence of the lubricant 92 between the shaft 26 and the inner sleeve 31 is defined as Cxx.

  At this time, if the bearing stiffness Kxx is large, the displacement of the shaft 26 in the X direction is suppressed, and the rotation of the hub 28 is kept stable. If the bearing characteristic Kxy is small, the displacement of the shaft 26 in the Y direction is suppressed, and the rotation of the hub 28 is kept stable. Further, if the bearing damping Cxx is small, mechanical resonance is suppressed. Further, when the torque cross of the bearing is reduced, the current consumption of the rotating device is reduced.

(simulation)
The above-described bearing characteristics such as rigidity Kxx, characteristic Kxy, damping Cxx, and torque cross are lubricated by the first radial dynamic pressure generating groove 50 and the second radial dynamic pressure generating groove 55 formed on the inner peripheral surface of the inner sleeve 31. It changes according to the dynamic pressure of the agent 92.

  Therefore, the shape of the radial dynamic pressure generating groove in which the bearing characteristics such as the bearing stiffness Kxx, the characteristic Kxy, the damping Cxx, and the torque cross are optimized is obtained by first to third simulations described below.

  7 and 8 are diagrams illustrating the shape parameters of the first radial dynamic pressure generating groove 50 used in the simulation.

  Here, as shown in FIG. 7, the axial length of the first radial dynamic pressure generating groove 50 is L, and the circumferential direction of the bent groove 51 at both ends in the axial direction of the first radial dynamic pressure generating groove 50 is set. The groove width is Weg, and the groove interval in the circumferential direction is Wel. The circumferential groove width of the bent portion provided near the center in the axial direction of the first radial dynamic pressure generating groove 50 is Wcg, and the circumferential groove interval is Wcl.

  Furthermore, the groove depth at both ends of the bent groove 51 is De, the groove depth at the center is Dc, and the outer line and the circumferential direction on the side protruding from the bent portion to the end of the bent groove 51 are in the circumferential direction. An angle formed is defined as an inclination angle A1.

  Further, as shown in FIG. 8, G is a clearance in the radial direction between the inner peripheral surface of the inner sleeve 31 and the outer peripheral surface of the shaft 26.

(First simulation)
In the first simulation, the ratio of the length L in the axial direction of the first radial dynamic pressure generating groove 50 to the distance r from the rotation axis R in the region including the bent portion is the bearing ratio L / r. Further, the ratio (Wcg / Wcl) of the groove width Wcg and the groove interval Wcl at the bent portion of the first radial dynamic pressure generating groove 50 is the bent portion groove ratio GprC, and the groove width at both ends of the first radial dynamic pressure generating groove 50. The ratio (Weg / Wel) between Weg and groove interval Wel is the end groove ratio GprE. When the groove ratio is 50% or more, the ratio of the groove widths Wcg and Weg between the adjacent bent grooves 51 is more than half, and when it is less than 50%, it is less than half. Yes. In the first simulation, in the first radial dynamic pressure generating groove 50, a parameter that maximizes the rigidity Kxx was obtained under the condition that the torque cross is constant.

  FIG. 9A shows the result of the first simulation in which the optimum groove ratio (vertical axis) at which the rigidity Kxx is maximized with respect to the bearing ratio L / r (horizontal axis) when the gap G is 2 μm. It is a graph. In the graph of FIG. 9A, the plot group 902 is the bent groove ratio GprC, and the plot group 904 is the end groove ratio GprE.

  From the graph shown in FIG. 9A, in the first radial dynamic pressure generating groove 50, when the bearing ratio L / r is small, the groove ratio GprC of the bent portion is large and the groove ratio GprE of both ends is small. Thus, it was found that the bearing stiffness Kxx is maximized. Further, the first radial dynamic pressure generating groove 50 is formed such that when the bearing ratio L / r is large, the groove ratio GprC of the bent portion is small and the groove ratio GprE of both ends is large. It has been found that the bearing stiffness Kxx is maximized.

  In the graph of FIG. 9A, the approximate expression of the groove ratio GprC of the bent portion of the first radial dynamic pressure generating groove 50 and the approximate expression of the groove ratio GprE of both ends have a bearing ratio L / r of about 1. 05, at a point where the groove ratio Gpr is about 50%.

  Thus, in the first radial dynamic pressure generating groove 50, when the bearing ratio L / r is less than 1.05, the bent portion groove ratio GprC generally indicated by the plot group 902 is larger than 50%, and the plot group 904 When the end groove ratio GprE indicated by is smaller than 50%, the bearing stiffness Kxx is maximized. That is, in this case, when the groove width Wcg of the bent portion is larger than the groove width Wcg of the both ends, the first radial dynamic pressure generating groove 50 has the maximum bearing rigidity Kxx. More specifically, when the bearing ratio L / r is less than 1.05, the bent portion groove ratio GprC of the first radial dynamic pressure generating groove 50 is 50% to 90%, and the end groove ratio GprE is 10%. It is preferably ˜50%.

  Further, the first radial dynamic pressure generating groove 50 has a bent portion groove ratio GprC generally indicated by the plot group 902 smaller than 50% when the bearing ratio L / r is 1.05 or more, and is indicated by the plot group 904. When the end groove ratio GprE is 50% or more, the bearing stiffness Kxx is maximized. That is, in this case, when the groove width Wcg of the bent portion is smaller than the groove width Wcg of both ends, the first radial dynamic pressure generating groove 50 has the maximum bearing rigidity Kxx. More specifically, when the bearing ratio L / r is 1.05 or more, the bending portion groove ratio GprC of the first radial dynamic pressure generating groove 50 is 10% to 50%, and the end groove ratio GprE is 50%. It is preferable that it is -80%.

  FIG. 9B is a graph showing the result of the first simulation in which the optimum groove ratios GprC and GprE at which the rigidity Kxx is maximized with respect to the bearing ratio L / r when the gap G is 4 μm are obtained. FIG. 9C is a graph showing the results of the first simulation in which optimum groove ratios GprC and GprE at which the rigidity Kxx is maximized with respect to the bearing ratio L / r when the gap G is 6 μm are obtained. . As shown in FIGS. 9B and 9C, the relationship between the bearing ratio L / r and the groove ratios GprC and GprE is shown in FIG. 9A regardless of whether the gap G is 4 μm or 6 μm. ) Is almost the same as when the gap G is 2 μm.

(Second simulation)
In the second simulation, for the first radial dynamic pressure generating groove 50, the optimum bent groove depth Dc and end groove depth De at which the bearing stiffness Kxx is maximized with respect to the bearing ratio L / r are respectively determined as gaps. It calculated | required as ratio Dc / G, De / G with G. The graph of FIG. 10 shows a plot group 906 representing the optimum bent portion groove depth ratio Dc / G with respect to the bearing ratio L / r and the optimum end groove depth ratio De in the range where the gap G is 2 μm to 6 μm. A plot group 908 representing / G is shown.

The numerical values corresponding to the plot group 906 and the plot group 908 are shown below.
L / r = 0.25 Dc / G = 1.08 De / G = 1.86 Dc / De = 58%
L / r = 0.50 Dc / G = 1.33 De / G = 2.48 Dc / De = 54%
L / r = 0.75 Dc / G = 0.85 De / G = 2.23 Dc / De = 38%
L / r = 1.00 Dc / G = 1.04 De / G = 2.01 Dc / De = 52%
L / r = 1.25 Dc / G = 1.05 De / G = 1.91 Dc / De = 55%
L / r = 1.50 Dc / G = 0.91 De / G = 1.89 Dc / De = 48%
L / r = 1.75 Dc / G = 0.89 De / G = 2.02 Dc / De = 44%
L / r = 2.00 Dc / G = 0.73 De / G = 1.98 Dc / De = 37%
L / r = 2.25 Dc / G = 0.77 De / G = 2.14 Dc / De = 36%
L / r = 2.50 Dc / G = 0.51 De / G = 2.02 Dc / De = 25%
L / r = 2.75 Dc / G = 0.50 De / G = 2.11 Dc / De = 24%
L / r = 3.00 Dc / G = 0.69 De / G = 2.00 Dc / De = 35%
As described above, in the result of the second simulation, when the bearing ratio L / r is in the range of 0.25 to 3, the bending portion groove depth ratio Dc / G is distributed from 0.5 to 1.33, and the center value. Was about 0.9. Similarly, when the bearing ratio L / r is in the range of 0.25 to 3, the end groove depth ratio De / G is distributed from 1.86 to 2.48, and the center value is about 2.1. . As described above, from the result of the second simulation, when the bearing ratio L / r is in the range of 0.25 to 3, the groove depth ratio Dc / G at the bent portion is smaller than the groove depth ratio De / G at both ends. Occasionally, it has been found that the bearing stiffness Kxx is maximized. That is, in the first radial dynamic pressure generating groove 50, when the groove depth Dc of the bent portion is smaller than the groove depth De of both ends, the bearing rigidity Kxx is maximized.

  In the first simulation and the second simulation described above, the result of the first radial dynamic pressure generating groove 50 has been described, but the same applies to the second radial dynamic pressure generating groove 55.

(Third simulation)
As a third simulation, first, under the conditions shown below, the angle formed by the outer line on the side projecting in the circumferential direction from the bent portion to the end portion of the bent groove 51 of the first radial dynamic pressure generating groove 50 and the circumferential direction. The relationship between a certain inclination angle A1 and the bearing stiffness Kxx was determined. In the simulation, the distance r from the rotation center of the region including the bent portion of the bent groove 51 of the first radial dynamic pressure generating groove 50 is 2 mm, and the axial length L of the first radial dynamic pressure generating groove 50 is 2.6 mm. Went.

Bearing ratio L / r: 1.3 (≧ 1.05)
Bending groove ratio GprC = 44 [%]
End groove ratio GprE = 62 [%]
Bending groove depth Dc = 3.0 [μm]
End groove depth De = 6.1 [μm]
Bent groove depth Dc / end groove depth De = 49 [%]
FIG. 11 is a graph plotting the relationship between the inclination angle A1 obtained by the third simulation and the bearing stiffness Kxx. As shown in FIG. 11, it was found that the inclination angle A1 is about 23.8 ° and the bearing stiffness Kxx is maximized. For example, the range of 13 ° or more and 40 ° or less where the stiffness Kxx increases is a preferable range.

  In addition, under the conditions shown below, an inclination angle A2 that is an angle formed by the outer circumferential line of the second radial dynamic pressure generating groove 55 that protrudes in the circumferential direction from the bent portion to the end of the bent groove 56 and the circumferential direction, The relationship with the bearing stiffness Kxx was determined. In the simulation, the distance r from the rotation center of the region including the bent portion of the bent groove 56 of the second radial dynamic pressure generating groove 55 is 2 mm, and the axial length L of the second radial dynamic pressure generating groove 55 is 1.6 mm. Went.

Bearing ratio L / r: 0.8 (<1.05)
Bent groove ratio GprC = 57 [%]
End groove ratio GprE = 45 [%]
Bending groove depth Dc = 3.3 [μm]
End groove depth De = 6.8 [μm]
Bent groove depth Dc / end groove depth De = 49 [%]
FIG. 12 is a graph plotting the relationship between the inclination angle A2 obtained by the third simulation and the bearing stiffness Kxx. As shown in FIG. 12, it was found that the inclination angle A2 is about 19.9 °, and the bearing stiffness Kxx is maximized. For example, the range of 12 ° to 35 ° at which the stiffness Kxx increases is a preferable range.

[Example 1]
Next, the shapes of the first radial dynamic pressure generating groove 50 and the second radial dynamic pressure generating groove 55 in the disk drive device 100 according to the first embodiment will be described. The first radial dynamic pressure generating groove 50 and the second radial dynamic pressure generating groove 55 of the disk drive device 100 according to the first embodiment have the following shape parameters.

(1st radial dynamic pressure generating groove)
Distance r from center of rotation: 2.0 [mm]
Axial length L: 2.6 [mm]
Bearing ratio L / r: 1.3 (≧ 1.05)
Bending groove ratio GprC = 44 [%]
End groove ratio GprE = 62 [%]
Bending groove depth Dc = 3.0 [μm]
End groove depth De = 6.1 [μm]
Bent groove depth Dc / end groove depth De = 49 [%]
Inclination angle A1 = 23.8 [deg]
FIG. 13 is a diagram illustrating the first radial dynamic pressure generating groove 50 in the first embodiment. As shown in FIG. 13, in the first radial dynamic pressure generating groove 50, the groove width Wcg of the bent portion of each bent groove 51 is smaller (narrower) than the groove width Weg at both ends, and the groove depth Dc of the bent portion is set. It is formed to be smaller (shallow) than the groove depth De at both ends. As described above, each of the bent grooves 51 of the first radial dynamic pressure generating groove 50 has a shallow region 52 where the groove width is narrower than both ends and the groove depth is shallower at the portion including the bent portion.

(Second radial dynamic pressure generating groove)
Distance r from center of rotation: 2.0 [mm]
Axial length L: 1.6 [mm]
Bearing ratio L / r: 0.8 (<1.05)
Bent groove ratio GprC = 57 [%]
End groove ratio GprE = 45 [%]
Bending groove depth Dc = 3.3 [μm]
End groove depth De = 6.8 [μm]
Bent groove depth Dc / end groove depth De = 49 [%]
Inclination angle A2 = 19.9 [deg]
FIG. 14 is a diagram illustrating the second radial dynamic pressure generating groove 55 in the first embodiment. As shown in FIG. 14, in the second radial dynamic pressure generating groove 55, the groove width Wcg of the bent portion of each bent groove 56 is larger (wider) than the groove width Weg at both ends, and the groove depth Dc of the bent portion is set. It is formed to be smaller (shallow) than the groove depth De at both ends. As described above, each of the bent grooves 56 of the second radial dynamic pressure generating groove 55 has a shallow wide region 57 having a groove width wider than the both end portions and a shallow groove depth in a portion including the bent portion.

[Comparative Example 1]
The shapes of the first radial dynamic pressure generating groove and the second radial dynamic pressure generating groove in the disk drive device according to Comparative Example 1 will be described. The first radial dynamic pressure generating groove and the second radial dynamic pressure generating groove of the disk drive device according to Comparative Example 1 have the following shape parameters.

(1st radial dynamic pressure generating groove)
Distance r from center of rotation: 2.0 [mm]
Axial length L: 2.6 [mm]
Bearing ratio L / r: 1.3 (≧ 1.05)
Bent groove ratio GprC = 37 [%]
End groove ratio GprE = 37 [%]
Bending portion groove depth Dc = 6.0 [μm]
End groove depth De = 6.0 [μm]
Bending portion groove depth Dc / end portion groove depth De = 100 [%]
Inclination angle A = 15.0 [deg]
(Second radial dynamic pressure generating groove)
Distance r from center of rotation: 2.0 [mm]
Axial length L: 1.6 [mm]
Bearing ratio L / r: 0.8 (<1.05)
Bent groove ratio GprC = 37 [%]
End groove ratio GprE = 37 [%]
Bending portion groove depth Dc = 6.0 [μm]
End groove depth De = 6.0 [μm]
Bending portion groove depth Dc / end portion groove depth De = 100 [%]
Inclination angle A = 15.0 [deg]
As described above, in the first radial dynamic pressure generating groove and the second radial dynamic pressure generating groove in Comparative Example 1, the groove width and the groove depth of each bent groove are formed uniformly.

  In the configurations of the above-described Example 1 and Comparative Example 1, the results of obtaining the bearing characteristics by simulation are shown below.

[Bearing characteristics of Example 1]
(1st radial dynamic pressure generating groove)
Rigidity Kxx (N / μm): 72.6
Characteristic Kxy (N / μm): 64.7
Attenuation Cxx (N · s / m): 226923
Torcross (N · μm): 3811
(Second radial dynamic pressure generating groove)
Rigidity Kxx (N / μm): 30.6
Characteristic Kxy (N / μm): 20.0
Attenuation Cxx (N · s / m): 68235
Torcross (N · μm): 2359
[Bearing characteristics of Comparative Example 1]
(1st radial dynamic pressure generating groove)
Rigidity Kxx (N / μm): 57.5
Characteristic Kxy (N / μm): 92.6
Attenuation Cxx (N · s / m): 314129
Torcross (N · μm): 4062
(Second radial dynamic pressure generating groove)
Rigidity Kxx (N / μm): 27.2
Characteristic Kxy (N / μm): 26.8
Attenuation Cxx (N · s / m): 90072
Torcross (N · μm): 2500
As described above, the rigidity Kxx of the first radial dynamic pressure generating groove 50 in the first embodiment is greater than the rigidity Kxx of the first radial dynamic pressure generating groove in the first comparative example. Further, the rigidity Kxx of the second radial dynamic pressure generating groove 55 in the first embodiment is larger than the rigidity Kxx of the second radial dynamic pressure generating groove in the first comparative example.

  Further, the characteristic Kxy of the first radial dynamic pressure generating groove 50 in Example 1 is smaller than the characteristic Kxy of the first radial dynamic pressure generating groove in Comparative Example 1. Similarly, the characteristic Kxy of the second radial dynamic pressure generating groove 55 in Example 1 is smaller than the characteristic Kxy of the second radial dynamic pressure generating groove in Comparative Example 1.

  Further, the attenuation Cxx of the first radial dynamic pressure generating groove 50 in the first embodiment is smaller than the attenuation Cxx of the first radial dynamic pressure generating groove in the first comparative example. Similarly, the attenuation Cxx of the second radial dynamic pressure generating groove 55 in Example 1 is smaller than the attenuation Cxx of the second radial dynamic pressure generating groove in Comparative Example 1.

  As described above, since the first radial dynamic pressure generating groove 50 and the second radial dynamic pressure generating groove 55 in the first embodiment have the bearing stiffness Kxx larger than that of the first comparative example, the displacement of the shaft 26 in the X direction is suppressed. Thus, the rotation of the hub 28 is kept more stable. Further, in the first radial dynamic pressure generating groove 50 and the second radial dynamic pressure generating groove 55 in the first embodiment, the characteristics Kxy and the damping Cxx are smaller than those in the first comparative example, the torque loss is reduced, and the bearing characteristics are improved. I understand that.

  As described above, under the condition that the bearing ratio (L / r) is 1.05 or more, the radial dynamic pressure generating groove has a groove width Wcg of the bent portion that is narrower than the groove width Weg of both ends, and By having a bent groove including a shallow narrow region where the groove depth Dc is shallower than the groove depth De at both ends, the bearing characteristics are improved and the rotational stability is improved. On the condition that the bearing ratio (L / r) is less than 1.05, the radial dynamic pressure generating groove has a groove width Wcg at the bent portion wider than the groove width Weg at both ends, and the groove depth Dc at the bent portion is By having a bent groove including a shallow wide area shallower than the groove depth De at both ends, the bearing characteristics are improved and the rotational stability is improved.

  Although the rotating device according to the embodiment has been described above, the present invention is not limited to the above embodiment, and various modifications and improvements can be made within the scope of the present invention.

26 Shaft 28 Hub 31 Inner sleeve 32 Outer sleeve 50 First radial dynamic pressure generating grooves 51, 56 Bending groove 52 Shallow area 55 Second radial dynamic pressure generating groove 57 Shallow area 60 First thrust dynamic pressure generating groove 65 Second Thrust dynamic pressure generating groove 100 Disk drive device (rotary equipment)

Claims (13)

A fixed body,
A rotating body rotatably supported by the fixed body;
A rotating device including a herringbone-shaped first radial dynamic pressure generating groove that is provided on at least one of the fixed body and the rotating body and generates a fluid dynamic pressure in a radial direction;
The first radial dynamic pressure generating groove has a groove width in the circumferential direction that is narrower than a groove width at both end parts in the rotation axis direction at an intermediate part protruding in the circumferential direction from both ends in the rotation axis direction of the rotating body. A rotating device comprising a first bent groove having a shallow narrow region whose depth is shallower than the groove depth at both ends in the rotation axis direction. The first bent groove is characterized in that a length L1 in the rotation axis direction and a distance r1 from the rotation center of the rotating body in the shallow narrow region satisfy a relationship of L1 / r1 ≧ 1.05. The rotating device according to claim 1. The first bent groove is characterized in that a circumferential groove width Weg1 at both ends and a circumferential groove interval Wel1 at both ends satisfy a relationship of 0.5 <Weg1 / Wel1 <0.8. The rotating device according to claim 1 or 2. In the first bent groove, the circumferential groove width Wcg1 in the shallow narrow region and the circumferential groove interval Wcl1 in the shallow narrow region satisfy a relationship of 0.1 <Wcg / Wcl <0.5. The rotating device according to any one of claims 1 to 3, wherein: The first bent groove is characterized in that an angle A1 formed by a circumferential line protruding in the circumferential direction from the shallow narrow region to the end portion and the circumferential direction is 13 ° ≦ A1 ≦ 40 °. Item 5. The rotating device according to any one of Items 1 to 4. A herringbone-shaped second that is provided on at least one of the fixed body and the rotating body, is spaced apart from the first radial dynamic pressure generating groove in the rotation axis direction, and generates a fluid dynamic pressure in the radial direction. Including a radial dynamic pressure generating groove,
The second radial dynamic pressure generating groove has a groove width in a circumferential direction wider than a groove width at both ends in the rotation axis direction and a groove depth at an intermediate portion protruding in the circumferential direction from both ends in the rotation axis direction. 6. The rotating device according to claim 1, further comprising a second bent groove having a shallow wide area shallower than a groove depth at both ends in the rotation axis direction. The second bent groove is characterized in that a length L2 in the rotation axis direction and a distance r2 from the rotation center of the rotating body in the shallow region satisfy a relationship of L1 / r1 <1.05. The rotating device according to claim 6. The second bent groove is characterized in that the circumferential groove width Weg2 at both ends and the circumferential groove interval Wel2 at both ends satisfy the relationship of 0.1 <Weg1 / Wel1 <0.5. The rotating device according to claim 6 or 7. In the second bent groove, a circumferential groove width Wcg2 in the shallow wide region and a circumferential groove interval Wcl2 in the shallow wide region satisfy a relationship of 0.5 <Wcg / Wcl <0.9. The rotating device according to any one of claims 6 to 8, wherein The second bent groove is characterized in that an angle A2 formed by a circumferential line extending in a circumferential direction from the shallow wide region to an end portion and a circumferential direction satisfy 12 ° ≦ A2 ≦ 35 °. Item 10. The rotating device according to any one of Items 6 to 9. 11. The rotating device according to claim 6, wherein at least one of the shallow narrow region and the shallow wide region is formed of a plurality of minute grooves extending in a circumferential direction. A thrust dynamic pressure generating groove provided on at least one of the fixed body and the rotating body and generating a fluid dynamic pressure in a thrust direction;
The rotation according to any one of claims 6 to 11, wherein the shallow narrow region and the shallow wide region are provided closer to a rotation center of the rotating body than the thrust dynamic pressure generating groove. machine. The rotating body includes a hub on which a recording disk is mounted,
The rotating device according to any one of claims 6 to 12, wherein the shallow narrow region and the shallow wide region are provided in a region where the hub exists in the rotation axis direction.

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