JP2009008200A - Fluid bearing device and spindle motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid bearing device capable of preventing leakage of filled lubricant while securing the sufficient length of a radial bearing part in a miniaturized and thinned bearing. <P>SOLUTION: The fluid bearing device is provided with a shaft, the sleeve rotatable to the shaft, a pair of seal members fixed to the shaft and forming thrust bearing parts between the sleeve and the seal members, annular projections formed on end faces of the sleeve, tapered capillary seal parts having an interface of lubricant, and a communication passage provided in the sleeve to connect the pair of thrust bearing parts with each other. Since a distance between the narrowest portion of the tapered capillary seal part and a rotating center shaft is set different from a distance between an opening part of the communication passage and the rotating center shaft, the fluid bearing device can secure the length of the radial bearing part and prevent leakage of the lubricant. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device used for a magnetic disk device or the like, and more particularly to the structure of a double-ended open type hydrodynamic bearing device.

  In recent years, hard disk drives (hereinafter referred to as HDDs) equipped with a spindle motor using a hydrodynamic bearing device that is superior in rotational accuracy and quietness in place of the conventionally used ball bearing device are It has been used in many home appliances other than personal computers.

  As a hydrodynamic bearing device used for a spindle motor used in this type of HDD, there are a hydrodynamic bearing device of one end opening type and a hydrodynamic bearing device of both end opening type. In particular, the both-end opening type hydrodynamic bearing device is superior to the single-end opening type hydrodynamic bearing device in terms of bearing rigidity and the like, and is therefore widely used for HDDs that require high reliability such as servers. .

  For example, there is a hydrodynamic bearing device disclosed in Patent Document 1 shown in FIG. The hydrodynamic bearing device 200 includes a shaft 201 having one end fixed to a base 203 and a radial bearing portion 206 (206a, 206b) formed between the shaft 201 and a sleeve rotatably attached to the shaft 201. 202 and a pair of seal members 204 (204a, 204b) that seal the lubricating fluid circulating in the bearing while forming a thrust bearing portion between the shaft 201 and the sleeve 202. Further, the sleeve 202 is formed with a first communication path 205 that allows the thrust bearing portions to communicate with each other. Further, the sleeve 202 is formed with a second communication passage 207 for communicating the communication passage 205 and the radial bearing portion 206, and two dynamic pressure generating portions (206 a, 206 b) formed in the radial bearing portion 205 are formed. ), The opening 207a of the second communication passage 207 is located.

  In this hydrodynamic bearing device, the radial bearing gap, the thrust bearing gap, the inner diameters of the first and second communication passages, and the shape of the radial dynamic pressure generating groove are set to predetermined dimensions and shapes, and in the direction of the arrow in FIG. A circulation flow is formed so that the lubricant flows.

  A technique for reducing the pressure in the vicinity of the seal portion and preventing the lubricant from leaking from the seal portion by forming such a circulating flow is disclosed.

Further, Patent Document 2 discloses that the sleeve 202 is positioned concentrically with the capillary seal portion 208 formed between the inclined surface 204 c formed on the seal member 204 and the inner peripheral surface 202 a of the sleeve 202. A plurality of communication paths 205 are provided, and the corners 204aa and 204bb of the seal members 204a and 204b facing the communication path 205 are cut larger than the other three corners of the remaining seal members 204a and 204b. . According to this configuration, since atmospheric pressure is easily transmitted to the lubricant, even if the lubricating oil is biased to one of the upper and lower openings of the bearing due to external impact or vibration, it quickly returns into the bearing. As a result, a technique for reducing leakage of lubricating oil is disclosed.
JP 2005-48890 A JP 2002-70849 A

  However, along with the miniaturization and thinning of the HDD, the axial length of the both-end opening type hydrodynamic bearing device must be shortened. In order to shorten the axial length, it is necessary to shorten the radial bearing portion or the capillary seal portion.

  In the prior art disclosed in Patent Document 1, since the communication path 207 must be secured between the two radial bearing portions, the required radial bearing portion length cannot be secured, and thus the radial bearing rigidity is reduced. This causes a problem that the shaft and the sleeve come into contact with each other at the radial bearing portion.

  Further, in the prior art disclosed in Patent Document 2, the corners 204aa and 204bb of the seal members 204a and 204b must be cut off larger than the other three corners of the remaining seal members 204a and 204b. The length of the seal portion is shortened, the capillary effect is reduced, and the possibility that the lubricating fluid leaks increases.

  In other words, it is necessary to shorten the axial length of either the radial bearing portion or the capillary seal portion in order to reduce the size and thickness of the both-end opening type hydrodynamic bearing device, which is the performance required for the hydrodynamic bearing device. There has been a problem that either the radial bearing rigidity or the lubricating fluid leakage prevention structure must be sacrificed.

  In addition, as shown in FIG. 6, since the communication hole 205 is formed concentrically with the capillary seal portion 208, the external bearing / vibration in the axial direction is applied to the hydrodynamic bearing device to thereby form the sleeve. 202 moves up and down, and a sudden movement of the lubricating fluid occurs from the communication hole 205 toward the capillary seal portion 208. Before the lubricating fluid returns to the inside of the hydrodynamic bearing device, the lubricating fluid flows from the capillary seal portion 208. There was also a problem of leakage.

  The present invention solves the above-described problem. Even if the hydrodynamic bearing device is reduced in size and thickness, the required radial bearing rigidity is ensured, and even if a sudden external shock / vibration is applied, the lubricating fluid does not flow. It is an object of the present invention to provide a hydrodynamic bearing device having a double-end opening type that does not leak to the outside and can maintain the lubricating fluid in the hydrodynamic bearing device well for a long time.

  In order to solve the above-described conventional problems, the hydrodynamic bearing device of the present invention has a shaft and a bearing hole in which the shaft is disposed, and a radial bearing portion is formed between the outer peripheral surface of the shaft and the bearing hole. A sleeve that is rotatable with respect to the shaft, a pair of seal members that are fixed to the shaft and that form a thrust bearing portion between the sleeve, a cylindrical protrusion formed on the end surface of the sleeve, and a cylindrical shape A tapered capillary seal portion having a lubricating fluid interface provided between the inner peripheral surface of the protruding portion and the outer peripheral surface of the seal member, and a sleeve communicating between the pair of thrust bearing portions different from the bearing holes are provided. And a distance from the rotation center axis of the narrowest portion of the tapered capillary seal portion and the opening of the communication passage is different.

  Further, according to the present invention, a groove portion is formed radially outward from the thrust bearing portion on the end surface of the sleeve that is radially inward of the cylindrical projecting portion forming the thrust bearing portion, and the seal member Is characterized in that a protruding portion is formed in the groove via a gap.

  Furthermore, the position of the taper capillary seal portion and the position of the radial bearing portion overlap each other in the axial direction.

  With the above configuration, the taper capillary seal portion can be secured only in a necessary length without shortening the length of the radial bearing portion, so that a highly reliable seal configuration with high radial rigidity can be formed. .

  According to the hydrodynamic bearing device of the present invention, a sufficient radial bearing length can be secured even when the size and thickness of the hydrodynamic bearing device are reduced, and seal portions for preventing lubricant leakage are secured at both ends of the hydrodynamic bearing device. To provide a spindle motor equipped with a hydrodynamic bearing device with a double-ended opening type that can maintain a stable bearing performance over a long period of time even when sudden external shock or vibration is applied. Can do.

  Embodiments of a hydrodynamic bearing device and a spindle motor according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a sectional view of a spindle motor 1 equipped with a hydrodynamic bearing device 2 according to a first embodiment of the present invention. In the following description, for easy understanding, as shown in FIG. 1, the hub 42 side will be described as the upper side (upper side), the base 3 side will be the lower side (lower side), etc. Of course, it is not limited to.

[Entire configuration of spindle motor 1]
As shown in FIG. 1, the spindle motor 1 mainly includes a base 3, a rotor 4, a hydrodynamic bearing device 2, and a stator 5.

  The base 3 constitutes a fixed part of the spindle motor 1 and is a part of a housing of a recording / reproducing apparatus (HDD). The base 3 has a cylindrical portion 31, and one end of the shaft 32 of the fluid dynamic bearing device 2 is fixed inside the cylindrical portion 31.

  The rotor 4 is a rotating part of the spindle motor 1 and is driven to rotate by a rotational force generated by a magnetic circuit. The configuration of the rotor 4 will be described in detail later.

  As shown in FIG. 1, the hydrodynamic bearing device 2 is a device that supports the base 3 and the stator 5 in a relatively rotatable state. The hydrodynamic bearing device 2 will be described in detail later.

  The stator 5 constitutes a magnetic circuit together with a magnet 41 which will be described later, and is fixed to the outer peripheral portion of the cylindrical portion 31. The rotor 4 is rotationally driven with respect to the base 3 and the stator 5 by the rotational driving force generated by the magnetic circuit.

[Configuration of rotor 4]
As shown in FIG. 1, the rotor 4 has a magnet 41 and a hub 42.

  The rotor magnet 41 is an annular member disposed so as to face the outer peripheral side in the radial direction of the stator 5, and is fixed to the inner peripheral side of the hub 42.

  The hub 42 is a member to which a recording disk (not shown) is attached, and is fixed to the outer peripheral side of a sleeve 21 (see FIG. 2) described later by an adhesive or the like. The hub 42 has a hub body 43 and a disk mounting portion 44 as shown in FIG.

  The hub main body 43 is a cylindrical portion that supports the recording disk in the radial direction, and is fixed to the outer peripheral side of the sleeve 21. For example, two recording disks are inserted and arranged on the outer peripheral side of the hub body 43.

  The disc placement portion 44 is a portion for placing a recording disc, and is formed on the outer peripheral side of the lower end portion in the axial direction of the hub body 43. The recording disk includes, for example, a magnetic disk that can read and write information by an information access means (not shown).

[Configuration of fluid dynamic bearing device 2]
As shown in FIG. 2, the hydrodynamic bearing device 2 is a hydrodynamic bearing device that is open at both ends of the sleeve 21 and has a shaft 32 and a sleeve 21. The hydrodynamic bearing device 2 is a fixed shaft type hydrodynamic bearing device in which a rotating body rotates around a fixed shaft 32.

(shaft)
The shaft 32 is a member on the fixed side of the hydrodynamic bearing device 2, and a lower end portion in the axial direction is fixed to a hole 31 a formed inside the cylindrical portion 31 of the base 3. The shaft 32 has a shaft main body 32a, a first thrust flange 32b, and a second thrust flange 32c.

  The shaft main body 32 a is a columnar member that constitutes a main part of the shaft 32, and is disposed on the inner peripheral side of the sleeve 21 with a small gap between the sleeve 21.

  The first thrust flange 32b is, for example, an annular member that is press-fitted and bonded to the shaft main body 32a. The first thrust flange 32b is a first member of the sleeve 21 that faces the lower end surface in the axial direction of the sleeve 21 in the axial direction through a minute gap. It arrange | positions at the inner peripheral side of the cylindrical protrusion part 21b.

  As shown in FIG. 1, when the hydrodynamic bearing device 2 is attached to the base 3, an axially outer surface 32 bb of the first thrust flange 32 b is formed on the inner peripheral side of the cylindrical portion 31 of the base 3. By contacting the surface 31b, the axial height of the hydrodynamic bearing device 2 (disk mounting portion 44) can be easily positioned. The surface 32bb and the surface 31b on the outer side in the axial direction can be positioned. By adhering and fixing, the hydrodynamic bearing device can be firmly fixed to the base. Further, in order to more firmly fix the hydrodynamic bearing device to the base, an adhesive groove may be formed on the axially outer surface 32bb of the thrust flange 32b.

  The second thrust flange 32c is an annular member disposed on the opposite side of the sleeve 21 from the first thrust flange 32b in the axial direction. For example, the second thrust flange 32c is laser welded, press-fitted, bonded, or the like to the shaft body 32a. It is fixed. The second thrust flange 32c is disposed on the inner peripheral side of the second cylindrical projecting portion 21c of the sleeve 21 so as to face the axially upper end surface of the sleeve 21 in the axial direction through a minute gap.

  The first and second thrust flanges 32b and 32c are formed with thrust dynamic pressure generating grooves 72a and 73a on the surface facing the part of the sleeve 21 by etching or the like. The thrust dynamic pressure generating grooves 72a and 73a formed in the first and second thrust flanges 32b and 32c will be described in detail later.

(Sleeve 21)
The sleeve 21 is a cylindrical member on the rotational side that is symmetrical in the vertical direction and is included in the hydrodynamic bearing device 2, and is a cylindrical member that is disposed so as to be rotatable relative to the shaft 32. The sleeve 21 is formed in a cylindrical shape having a communication hole 22e, which will be described later, by assembling the inner sleeve 23 having a plurality of D-cut portions formed on the outer peripheral surface thereof by press-fitting (inserting) into the outer sleeve 24. Forming part. Specifically, as described above, the sleeve 21 includes the inner sleeve 23 and the outer sleeve 24, and includes a plurality of radial dynamic pressure generating grooves 71a and 71b, a first cylindrical protruding portion 21b, and a second It has a cylindrical protrusion 21c and a plurality of communication holes 22e. The inner sleeve 23 and the outer sleeve 24 are formed of a copper-based alloy, and are each press-fitted and fixed together after being blanked independently. Thereafter, medium machining, precision machining, and radial dynamic pressure groove machining are performed, and after measuring the inner diameter shape, electroless Ni phosphor plating is performed by a predetermined thickness (about 1 to 10 μm thickness).

  The radial dynamic pressure generating grooves 71a and 71b are herringbone-shaped grooves formed on the inner peripheral surface of the sleeve 21 and arranged uniformly in the circumferential direction. An annular recess (not shown) formed on the inner peripheral side of the sleeve 21 is formed between the radial dynamic pressure generating grooves 71a and 71b.

  The first and second cylindrical protruding portions 21b and 21c are cylindrical portions in which the outer peripheral portions of both ends of the sleeve 21 protrude outward in the axial direction. First and second thrust flanges 32b and 32c are arranged on the inner peripheral portions of the first and second cylindrical projecting portions 21b and 21c. Therefore, the first and second cylindrical projecting portions 21b and 21c are arranged. The inner diameter is set larger than the inner diameter of the sleeve 21.

The communication holes 22e are formed between the inner sleeve 23 and the outer sleeve 24, and are equally disposed in the circumferential direction, for example, so as to penetrate the sleeve 21 in the axial direction.
A lubricating fluid 46 is filled between the shaft 32 and the sleeve 21. Further, between the first thrust flange 32b and the first cylindrical protruding portion 21b and between the second thrust flange 32c and the second cylindrical protruding portion 21c, taper capillary seal portions 48a and 48b described later are provided. Is formed.

  In the hydrodynamic bearing device 2, the radial bearing portion 71 that supports the rotor 4 in the radial direction is configured by the sleeve 21 having the radial dynamic pressure generating grooves 71a and 71b, the shaft 32, and the lubricating fluid 46 interposed therebetween. . The first thrust bearing portion 72 that supports the rotor 4 in the axial direction is constituted by a first thrust flange 32b having a thrust dynamic pressure generating groove 72a, a sleeve 21, and a lubricating fluid 46 interposed therebetween. Further, the second thrust bearing portion 73 that supports the rotor 4 in the axial direction is constituted by a second thrust flange 32c having a thrust dynamic pressure generating groove 73a, a sleeve 21, and a lubricating fluid 46 interposed therebetween.

  Here, when the rotation-side member (sleeve 21 or the like) rotates relative to the fixed-side member (shaft 32 or the like), the radial direction and the axial direction of the shaft 32 in the bearing portions 71, 72, and 73 respectively. A support force (dynamic pressure) is generated in a state where a predetermined gap is left between the rotation side member and the member. Thus, the rotation of the spindle motor 1 can be efficiently started with the rotation-side member and the fixed-side member in a non-contact state.

  As described above, the hydrodynamic pressure flows into the radial dynamic pressure generating grooves 71a and 71b and the thrust dynamic pressure generating grooves 72a and 73a into the gap formed between the shaft 32 and the sleeve 21 constituting the hydrodynamic bearing device 2. Is filled with a lubricating oil 46.

  In the present embodiment, as shown in FIG. 2, for the purpose of preventing the filled lubricating fluid 46 from leaking while ensuring a sufficient radial bearing portion length in a downsized / thinned bearing. The first and second thrust flanges 32b and 32c are formed with projecting portions 32bd and 32cd extending toward the sleeve 21 on the outer peripheral portion, and the sleeve 21 has an annular recess 24a in which the projecting portions 32bd and 32cd are disposed. -24b is formed.

This will be described in more detail with reference to FIG.
FIG. 3 is an enlarged view of the tapered capillary seal portion 48b of the hydrodynamic bearing device 2 in FIG. The second thrust flange 32c has an annular plate-like portion 32d and a protruding portion 32e protruding inward in the axial direction.

  The second thrust flange 32c is configured such that the inner peripheral surface 32dd of the annular plate-shaped portion 32d is press-fitted into the shaft in a state where the inner peripheral side surface of the annular plate-shaped portion 32d is in contact with the stepped portion 32aa formed on the shaft. It is fixed by bonding. In this embodiment, press-fit adhesive fixing is used, but fixing may be performed using a method such as laser welding fixing, adhesive fixing, or press-fit fixing.

  A herringbone-shaped dynamic pressure generating groove 73a is formed by an etching method on a surface 32bd of the annular plate-shaped portion 32d facing the end surface 23b of the sleeve 21. The dynamic pressure generating groove 73a may have a spiral shape, or may be formed by a method such as cutting or pressing.

  In addition, the annular plate-like portion 32d is also a portion forming the second thrust bearing portion 73, and the minute gap must be made of a highly rigid material with high accuracy and less distortion. It is made of a material such as stainless steel or iron-based material.

  The protruding portion 32e of the second thrust flange 32c is formed on the outer peripheral portion of the annular plate-shaped portion 32d, and is arranged so that the outer peripheral surface 32ee of the protruding portion 32e faces the cylindrical protruding portion 21b of the sleeve 21. Has been. The gap formed between the cylindrical protruding portion 21b and the outer peripheral surface 32ee is formed with an inclined surface on the outer peripheral surface 32eb so that the gap increases toward the outer side in the axial direction, and the tapered capillary seal portion 48b is formed. Has been.

  Since the protruding portion 32e does not form the second thrust bearing portion 73, the material thereof may be an easily moldable material such as resin.

  In addition, the annular plate-like portion 32d and the protrusion 32e forming the second thrust flange 32c are formed by pressing the annular plate-like portion 32d, and the protrusion 32e is provided by insert molding.

  On the other hand, a communication hole 22e and an annular recess 24a are formed in the end surface 23b of the sleeve 21 that faces the second thrust flange 32c in the axial direction.

  The communication hole 22e is formed between the outer sleeve 24 and the inner sleeve 23, and communicates the first thrust bearing portion 72 and the second thrust bearing portion 73. The opening 22ee of the communication hole 22e is formed on the end surface 23b of the inner sleeve 23 facing the annular plate-like portion 32d, and is located radially outward from the second thrust dynamic pressure generating groove 73a.

  The annular recess 24a is formed on the end surface of the outer sleeve 24 radially inward from the cylindrical protrusion 21b. In the annular recess 24a, the protruding portion 32e of the second thrust flange is disposed so as to be positioned via the gaps A, B, and C shown in FIG.

  The outer peripheral surface 32ee of the protruding portion 32e of the second thrust flange 32c, the cylindrical protruding portion 21b of the sleeve 21, the tapered capillary seal portion 48b formed by the annular recess 24a, and the portion where the gap A is formed, The radial bearing portion 71 formed between the inner peripheral surface 23c of the sleeve 21 (inner sleeve 23) and the shaft outer peripheral surface 32z is disposed so as to overlap in the axial direction. That is, since the axial length of the radial bearing portion 71 can be set regardless of the axial length of the tapered capillary seal portion 48b, a more optimal radial bearing portion length can be secured. It becomes possible to ensure more optimal bearing rigidity.

  In addition to the inclined surface 32eb and the cylindrical protrusion 21 formed on the outer peripheral surface 32ee of the second thrust flange 32c, a tapered capillary seal portion is also formed between the inclined surface 32eb and the annular recess 24a. Therefore, even if the interface changes due to expansion or contraction of the lubricating fluid 46, the capillary effect can be sufficiently retained.

  Further, even if the lubricating fluid 46 is held in the gaps B and C formed by the protruding portion 32e of the second thrust flange 32c and the annular concave portion 24a, even if the lubricating fluid 46 in the tapered capillary seal portion 48b evaporates. Since the interface 46a of the lubricating fluid 46 does not immediately reach the bearing portion or the communication hole 22e, it is possible to prevent air bubbles from being mixed into the bearing gap and to prolong the life of the bearing. Reliability is improved.

  Further, since the opening 22ee of the communication hole 22e is formed radially inward from the taper capillary seal portion 48b, external shock and vibration are applied to the hydrodynamic bearing device, and the taper capillary is passed through the communication hole 22e. Even if an abrupt lubricating fluid flow toward the seal portion 48b occurs, the abrupt flow of the lubricating fluid 46 is divided because the gaps A, B, and C are formed, and the taper capillary seal portion 46b It is difficult to transmit to the interface 46a, and leakage of the lubricating fluid 46 can be prevented.

  The present invention can be widely applied to a hydrodynamic bearing device having a lubricating fluid therein, for example, mounted on a spindle motor for HDD, a spindle motor for high-density optical disk, or the like.

Sectional drawing of the spindle motor carrying the hydrodynamic bearing apparatus in Embodiment 1 of this invention Sectional drawing of the hydrodynamic bearing apparatus in Embodiment 1 of this invention The expanded sectional view of the taper capillary seal part of the fluid dynamic bearing device in Embodiment 1 of the present invention Cross-sectional view of a spindle motor equipped with a conventional hydrodynamic bearing device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spindle motor 2,200 Fluid dynamic bearing apparatus 21,202 Sleeve 21b, 21c Cylindrical protrusion part 22e Communication hole 23 Inner sleeve 24 Outer sleeve 24a, 24b Annular recessed part 3, 203 Base 31 Cylindrical part 31a Hole 32, 201 Shaft 32a Shaft Main body 32b, 32c Thrust flange 32d Annular plate-like portion 32e Protruding portion 4 Rotor 41 Magnet 42 Hub 43 Hub main body 44 Disc mounting portion 46 Lubricating fluid 48a, 48b Tapered capillary seal portion 5 Stator 71, 206 Radial bearing portion 71a, 71b, 72a, 73a Dynamic pressure generating groove 72, 73 Thrust bearing portion 202a Inner peripheral surface 204, 204a, 204b Seal member 204c Inclined surface 204aa, 204bb Corner portion 205, 207 Communication passage 207a Opening 208 the capillary seal part

Claims (6)

A shaft,
A sleeve that has a bearing hole in which the shaft is disposed, and that is rotatable with respect to the shaft in which a radial bearing portion is formed between an outer peripheral surface of the shaft and the bearing hole;
A pair of seal members fixed to the shaft and forming a thrust bearing portion with the sleeve;
A cylindrical protrusion formed on the end surface of the sleeve;
A tapered capillary seal portion having an interface of the lubricating fluid provided between an inner peripheral surface of the cylindrical protrusion and an outer peripheral surface of the seal member;
A communication path provided in the sleeve that communicates between the thrust bearing portions different from the bearing hole, and
A hydrodynamic bearing device, wherein a distance from a rotation center axis of a narrowest portion of the tapered capillary seal portion and an opening portion of the communication path is different.   On the end surface of the sleeve that is radially inward of the cylindrical projecting portion forming the thrust bearing portion, a groove portion is formed radially outward from the thrust bearing portion. The hydrodynamic bearing device according to claim 1, wherein a protrusion is disposed in the groove with a gap.   The hydrodynamic bearing device according to claim 2, wherein a position of the tapered capillary seal portion and a position of the radial bearing portion overlap in an axial direction.   The said sealing member which has the said protrusion part, The said protrusion part is a resin material, Other parts are metal materials, such as stainless steel, It is manufactured by insert molding, The Claims 1-3 characterized by the above-mentioned. The hydrodynamic bearing device described.   The hydrodynamic bearing device according to claim 1, wherein one of the pair of seal members is integrally formed with the shaft. A spindle motor comprising the hydrodynamic bearing device according to claim 1.