JP2003065324A - Hydrodyanamic type bearing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent leakage of lubricant filled the inside of a housing toward the outside, to improve high speed rotation performance, and to reduce a cost. SOLUTION: A tapered surface 2a2 of a shaft part 2a faces an inside peripheral surface 10a of a sealing member 10 with a predetermined clearance. As a result, a taper shape sealing space S gradually expanding toward the outside is formed between the tapered surface 2a2 and the inside peripheral surface 10a. An inside space (including air bubbles inside a bearing member 8) of a housing 7 sealed by the sealing member 10 is filled with the lubricant and a fluid surface of the lubricant is located within the sealing space S.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure type bearing device. This bearing device is an information device such as an HDD or an F.
Magnetic disk device such as DD, CD-ROM, DVD-R
It is suitable for optical disk devices such as OM, spindle motors for magneto-optical disk devices such as MD and MO, polygon scanner motors for laser beam printers (LBP), or small motors for electric devices such as axial fans.

[0002]

2. Description of the Related Art In addition to high rotation accuracy,
Higher speed, lower cost and lower noise are required.
One of the components that determines the required performance is a bearing that supports the spindle of the motor, and in recent years, as this type of bearing, the use of a dynamic pressure type bearing having excellent characteristics in the required performance has been studied, Or actually used.

For example, in a dynamic pressure type bearing device incorporated in a spindle motor of a disk device such as an HDD, a radial bearing portion that rotatably supports a shaft member in a radial direction in a non-contact manner, and a shaft bearing member is rotatably supported in a thrust direction. A thrust bearing portion for contact support is provided, and as these bearing portions,
A dynamic pressure type bearing having a groove (dynamic pressure groove) for generating dynamic pressure on the bearing surface is used. The dynamic pressure groove of the radial bearing portion is formed on the inner peripheral surface of the housing or the bearing member or the outer peripheral surface of the shaft member, and the dynamic pressure groove of the thrust bearing portion uses the flange portion when the shaft member having the flange portion is used. Is formed on both end surfaces of the bearing or surfaces (faces of the bearing member, the bottom surface of the housing, and the like) opposed thereto.

[0004]

In the dynamic pressure type bearing device in which the shaft member and the bearing portion are housed in the housing and the internal space of the housing is filled with the lubricant, for example, a seal member is attached to the opening portion of the housing. The lubricant is prevented from leaking from the inside of the housing to the outside by applying an oil-repellent agent to the outflow path of the lubricant. However, due to the tendency of extremely high speed in the equipment field where this type of bearing device is used, higher high-speed rotation performance is required for the bearing device, and one of the measures to meet this requirement is lubrication. There has been a need for a sealing means that can more effectively prevent the agent from leaking to the outside.

An object of the present invention is to more effectively prevent the lubricant filled in the housing from leaking to the outside.

Another object of the present invention is to provide a dynamic pressure type bearing device which is superior in high speed rotation performance.

A further object of the present invention is to provide a lower cost hydrodynamic bearing device.

[0008]

In order to solve the above-mentioned problems, the present invention provides a housing having an opening at one end, a shaft member housed in the housing, and a dynamic pressure action of a lubricant generated in a radial bearing gap. A dynamic pressure type bearing device comprising a radial bearing portion for supporting a shaft member in a radial direction in a non-contact manner, and a seal member arranged in an opening of a housing,
There is a seal space between the inner peripheral surface of the seal member and the outer peripheral surface of the shaft member facing the seal member, and the seal space has a tapered shape that gradually expands toward the outside of the housing.
The interior space of the housing is filled with a lubricant, providing an arrangement in which the oil surface of the lubricant is in the seal space.

Since the oil surface of the lubricant is present in the seal space, the lubricant in the seal space is drawn in by the capillary force in the direction in which the seal space becomes narrow (inward direction of the housing). Therefore, leakage of the lubricant from the inside of the housing to the outside is effectively prevented.

The seal space can be constructed by providing a tapered surface on at least one of the outer peripheral surface of the shaft member and the inner peripheral surface of the seal member. When a taper surface is provided on the outer peripheral surface of the shaft member, the lubricant in the seal space receives centrifugal force when the shaft member rotates, and the seal space is narrowed along the taper surface (inward direction of the housing). Be pulled in (so-called centrifugal force seal). Therefore, in addition to the pulling action by the above-mentioned capillary force, there is also the pulling action by the centrifugal force, and the effect of preventing the lubricant from leaking out is further enhanced.

The taper angle θ of the tapered surface is 3 ° ≦ θ ≦ 2
It is preferable to set in the range of 5 °. If the taper angle θ of the taper surface is less than 3 °, the sealing effect due to the capillary force cannot be sufficiently obtained. For example, when the bearing device is in a horizontal position (the shaft member is in a horizontal state), due to the action of gravity,
There is a concern that the lubricant on the vertically lower side will be pushed out of the seal space and leak to the outside. On the other hand, the taper angle θ of the tapered surface is 2
If it exceeds 5 °, the space gap at the oil surface position of the lubricant becomes too large, and if a shock or the like is applied, the lubricant may be scattered to the outside.

The radial bearing portion may be formed directly on the inner peripheral surface of the housing, but it is preferably provided on a porous bearing member made of sintered metal. By impregnating the pores inside the bearing member with the lubricant, the amount of lubricant supplemented inside the housing can be increased, and the lubricant can be circulated between the inside and the outside of the bearing member. As a result, the lubricant does not deteriorate with time, and the excellent bearing function is maintained for a long period of time even when used at high speeds. Also, by using a porous bearing member,
The manufacturing cost can be reduced. For example, Japanese Patent Application Laid-Open No. 10-306827 (Japanese Patent Application No. 10-4)
No. 7973), a radial bearing portion can be easily formed at low cost on the inner peripheral surface of a porous bearing member material. Incidentally, Japanese Patent Laid-Open No. 10-3
In the manufacturing method described in No. 06827, a molding die having a molding portion corresponding to the shape of the dynamic pressure groove is inserted into the inner peripheral surface of the porous material, and a compressive force is applied to the porous material so that A dynamic pressure groove is formed on the inner peripheral surface of the porous material by pressing the peripheral surface of the mold. After forming the dynamic pressure groove, the molding die can be released from the inner peripheral surface of the porous material by utilizing the springback of the porous material by releasing the pressing force.

The shape of the dynamic pressure groove of the radial bearing portion is not particularly limited, but may be, for example, a herringbone shape. In that case, the dynamic pressure groove has an asymmetric shape in the axial direction and has a long axial length. The groove area can be located on the opening side of the housing. By making the dynamic pressure groove asymmetrical in the axial direction, a difference occurs in the pull-in force of the lubricant on both sides in the axial direction of the radial bearing portion. That is, the groove area having a long axial length has a large drawing force of the lubricant, and the groove area having a short axial length has a small drawing force of the lubricant.
Therefore, when the groove area having the long axial length is located on the opening side of the housing and the groove area having the short axial length is located on the inner side of the housing, the differential pressure of the pulling force of both groove areas causes the lubrication. The action of drawing the agent toward the inside of the housing occurs. This further enhances the effect of preventing the lubricant from leaking out.

In the above structure, when a plurality of radial bearing portions are arranged at intervals in the axial direction, a hollow groove can be provided on the outer peripheral surface of the shaft member facing the gap portion between the radial bearing portions. As a result, the gap between the spacing portion and the outer peripheral surface of the shaft member is made larger than the radial bearing gap,
The bearing torque can be reduced. Generally, the same effect is obtained by forming the above-mentioned spacing portion with a larger diameter than the radial bearing portion, but by providing a groove on the outer peripheral surface of the shaft member, the shape of the housing or bearing member can be simplified. There is an advantage that it can be realized. In particular, by making the gap between the radial bearings continuous with the groove bottom of the dynamic pressure groove of the radial bearing without any step, the radial bearing can be moved to the above gap and the gap can be changed from the radial bearing to the radial bearing. Since the lubricant is smoothly circulated, deterioration with time of the lubricant is less likely to occur.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 shows an example of the configuration of a spindle motor for information equipment in which a dynamic pressure type bearing device 1 according to this embodiment is incorporated. This spindle motor is used for a disk drive device such as an HDD, and includes a dynamic pressure type bearing device 1 that rotatably supports a shaft member 2 in a non-contact manner, a disk hub 3 mounted on the shaft member 2, and a radial direction. Motor stator 4 and motor rotor 5 facing each other through a gap
It has and. The stator 4 is attached to the outer circumference of the casing 6, and the rotor 5 is attached to the inner circumference of the disc hub 3. The housing 7 of the dynamic pressure type bearing device 1 is mounted on the inner circumference of the casing 6. The disk hub 3 holds one or a plurality of disks D such as magnetic disks. When the stator 4 is energized, the exciting force between the stator 4 and the rotor 5 causes the rotor 5 to rotate, whereby the disk hub 3
And the shaft member 2 rotates integrally.

FIG. 2 shows a dynamic pressure type bearing device 1.
The hydrodynamic bearing device 1 includes a bottomed cylindrical housing 7 having an opening 7a at one end, a cylindrical bearing member 8 fixed to the inner peripheral surface of the housing 7, a shaft member 2, and a housing 7.
The seal member 10 fixed to the opening 7a of the above is used as a main component.

The housing 7 is made of a soft metal material such as brass and has a cylindrical side portion 7b and a bottom portion 7c. A spiral dynamic pressure groove 7c2 shown in FIG. 4, for example, is formed in a region of the inner bottom surface 7c1 of the bottom portion 7c which will be the thrust bearing surface. In this embodiment, the housing 7 has the side portion 7b and the bottom portion 7c as separate structures, and the lid-shaped member serving as the bottom portion 7c is fixed to the opening of the other end of the bottom portion 7b by caulking, adhering or the like. However, the side portion 7b and the bottom portion 7c may be integrated.

The shaft member 2 is made of, for example, stainless steel (SU
S420J2) and the like, the shaft portion 2a and the flange portion 2 integrally or separately provided at the lower end of the shaft portion 2a.
and b. On the outer peripheral surface of the shaft portion 2a, the recessed groove 2
a1 and a tapered surface 2a2 are provided. The taper surface 2a2 has a taper angle θ in a direction in which the diameter is gradually reduced upward in FIG. A cylindrical surface 2a3 is provided continuously upward from the tapered surface 2a2.

The bearing member 8 is formed of, for example, a porous material, particularly a sintered metal containing copper as a main component, and the pores inside thereof are impregnated with lubricating oil or lubricating grease to form an oil-impregnated bearing.
Two upper and lower radial bearing surfaces R1 and R2 are provided on the inner peripheral surface 8a of the bearing member 8, and the radial bearing surfaces R1 and R2 are axially separated from each other with a gap R3 interposed therebetween.

As shown in FIG. 3, the radial bearing surface R1 is provided with a herringbone-shaped dynamic pressure groove, for example, a first region in which a plurality of dynamic pressure grooves 8a1 inclined in one axial direction are arranged in the circumferential direction. m1, a second region m2 in which a plurality of dynamic pressure grooves 8a2 inclined in the other axial direction are arranged in the circumferential direction,
It is composed of an annular portion n between the region m1 and the second region m2. The axial length of the first region m1 is larger than that of the second region m2, and the dynamic pressure groove 8a1 of the first region m1 and the dynamic pressure groove 8a2 of the second region m2 are axially asymmetrical with respect to the annular portion n. It has become. In addition, the first region m1 having a long axial length is
In the figure, it is located on the upper side (the opening 7a side of the housing 7),
A second region m2 having a short axial length is located on the lower side (on the bottom portion 7c side of the housing 7) in the figure. Radial bearing surface R
Similarly, 2 also includes a herringbone-shaped dynamic pressure groove, and a plurality of dynamic pressure grooves 8a3 inclined in one axial direction are arranged in the first region m1 ′ in the circumferential direction and inclined in the other axial direction. The second region m in which the plurality of dynamic pressure grooves 8a4 are arranged in the circumferential direction.
2'and an annular portion n'between the first region m1 'and the second region m2'. The axial length of the first region m1 ′ is larger than that of the second region m2 ′, and the dynamic pressure groove 8 of the first region m1 ′ is formed.
a3 and the dynamic pressure groove 8a4 in the second region m2 ′ form an annular portion n ′.
It has an axially asymmetrical shape with respect to. Further, the first region m1 ′ having a long axial length is located on the upper side (on the side of the opening 7a of the housing 7) in the figure, and the second region m2 ′ having a short axial length is on the lower side in the figure ( It is located on the bottom portion 7c side of the housing 7.

The gap R3 faces the recessed groove 2a1 of the shaft 2a, and the gap between them is larger than the radial bearing gap. In addition, the gap portion R3 has a groove bottom of the dynamic pressure groove 8a2 of the radial bearing surface R1 and a dynamic pressure groove 8 of the radial bearing surface R2.
It is continuous with the groove bottom of a3 without any step.

A circumferential groove 8b1 is formed on the upper end surface 8b of the bearing member 8 as a mark for identifying the vertical direction. A spiral dynamic pressure groove 8c1 is formed on the lower end surface 8c of the bearing member 8.

The radial bearing surfaces R1 and R2 and the gap R3 of the bearing member 8 are, for example, disclosed in Japanese Patent Laid-Open No. 10-
Molding can be easily performed at low cost by using the manufacturing method described in Japanese Patent Application No. 306827 (Japanese Patent Application No. 10-47973). For example, for a cylindrical bearing member material, a molding die (core rod) having molding portions corresponding to the shapes of the radial bearing surfaces R1, R2 and the spacing portion R3 is used, and the radial bearing surfaces R1, R2 and the spacing portion R3 are used. Can be simultaneously molded. Further, after molding, the molding die (core rod) can be released by utilizing the spring back of the bearing member material.

As shown in FIG. 1, the seal member 10 is annular, and is press-fitted into the inner peripheral surface of the opening 7a of the housing 7,
It is fixed by means such as adhesion. In this embodiment, the inner peripheral surface 10a of the seal member 10 is formed in a cylindrical shape, and the lower end surface 10b of the seal member 10 is the upper end surface 8 of the bearing member 8.
It is in contact with b.

The shaft portion 2a of the shaft member 2 is inserted into the inner peripheral surface 8a of the bearing member 8, and the flange portion 2b is housed in the space between the lower end surface 8c of the bearing member 8 and the inner bottom surface 7c1 of the housing 7. To be done. Radial bearing surfaces R1 and R2 of the bearing member 8
Respectively face the outer peripheral surface of the shaft portion 2a via a radial bearing gap. Further, the lower end surface 8c of the bearing member 8 faces the upper end surface of the flange portion 2b via a thrust bearing gap, and the inner bottom surface 7c1 of the housing 7 (a region where the dynamic pressure groove 7c2 is formed) of the flange portion 2b. It faces the lower end face with a thrust bearing gap. The slim portion 2 of the shaft portion 2a
A gap larger than the radial bearing gap is provided between a1 and the gap R3 of the bearing member 8.

The tapered surface 2a2 of the shaft portion 2a is the seal member 1.
0 is opposed to the inner peripheral surface 10a through a predetermined gap, thereby forming a taper-shaped seal space S between the both, which gradually expands in the outer direction of the housing 7 (upward in the figure). To be done. A lubricant (lubricant oil) is filled in the internal space of the housing 7 (including the pores inside the bearing member 8) sealed by the seal member 10, and the oil surface of the lubricant is in the seal space S. The volume of the seal space S is set to be larger than the volume change amount of the lubricant filled in the internal space of the housing 7 due to the temperature change within the operating temperature range. As a result, even if the volume of the lubricant changes due to the temperature change, the oil level of the lubricant can be constantly maintained in the seal space S.

When the shaft member 2 rotates, dynamic pressure of the lubricant is generated in the radial bearing gap, and the shaft portion 2a of the shaft member 2 rotates in the radial direction by the oil film of the lubricant formed in the radial bearing gap. Freely supported by non-contact. As a result, a radial bearing portion that rotatably supports the shaft member 2 in the radial direction in a non-contact manner is configured. At the same time, a dynamic pressure of the lubricant is generated in the thrust bearing gap, and the flange portion 2b of the shaft member 2 is rotatably supported in both thrust directions in a non-contact manner by an oil film of lubricating oil formed in the thrust bearing gap. . As a result, a thrust bearing portion that rotatably supports the shaft member 2 in the thrust direction in a non-contact manner is configured.

Further, since there is an oil surface of the lubricant in the seal space S, the lubricant in the seal space S is narrowed by the capillary force (inward direction of the housing 7: downward direction). Be drawn towards. Therefore, leakage of the lubricant from the inside of the housing 7 to the outside is effectively prevented. Further, by providing the tapered surface 2a2 on the outer peripheral surface of the shaft portion 2a, when the shaft member 2 rotates, the lubricant in the seal space S receives a centrifugal force, and the tapered surface 2a
2 in the direction in which the seal space S becomes narrower (the housing 7
Inward direction: downward). Therefore,
In addition to the pulling action by the above-mentioned capillary force, there is also the pulling action by the centrifugal force, so that the effect of preventing the lubricant from leaking out is further enhanced.

Here, the taper angle θ of the taper surface 2a2 of the shaft portion 2a is preferably set within the range of 3 ° ≦ θ ≦ 25 ° for the reason described above.

Further, in this embodiment, the dynamic pressure grooves (8a1 and 8a2, 8a3 and 8a) on the radial bearing surfaces R1 and R2 are used.
4) has an axially asymmetrical shape, and the groove regions (m1, m1 ′) having a long axial length are formed in the opening 7a of the housing 7.
Since it is located on the side (upper side), the following effects are also obtained. That is, particularly in the radial bearing surface R1 on the opening 7a side (upper side) of the housing 7, the groove region m1 having a longer axial length is formed on the opening 7a side (upper side) of the housing 7.
Is located in the groove area m1 having a long axial length due to the differential pressure of the lubricant drawing force, and the groove area m2 having a short axial length has a large lubricant drawing force. The effect of drawing the lubricant in the seal space S toward the inside (downward) of the housing 7 is obtained. This further enhances the effect of preventing the lubricant from leaking out.

The lubricant is drawn toward the inside by the spiral dynamic pressure grooves 8c1 and 7c2 provided on the lower end surface 8c of the bearing member 8 and the inner bottom surface 7c1 of the housing 7. Generated pressure,
This upward pressure is balanced by the downward pressure difference on the radial bearing surface R1 and the same downward pressure difference on the radial bearing surface R2.

By applying an oil repellent to at least one of the outer peripheral surface of the shaft portion 2a adjacent to the seal space S and the surface of the seal member 10, the effect of preventing the lubricant from leaking can be further enhanced. In the example shown in an enlarged manner in FIG. 2B, a partial region of the cylindrical surface 2a3 located above the tapered surface 2a2 of the shaft portion 2a, and the seal member 10.
The oil repellent agent f is applied to the inner diameter side region (the region indicated by the broken line in the figure) of the upper end surface 10c of the.

The tapered surface forming the tapered seal space may be provided on the inner peripheral surface of the seal member 10. Alternatively, it may be provided on both the inner peripheral surface of the seal member 10 and the outer peripheral surface of the shaft portion 2a.

[0035]

The present invention has the following effects.

(1) Since the oil surface of the lubricant is present in the tapered seal space, the lubricant in the seal space is drawn in by the capillary force in the direction in which the seal space becomes narrower (inward direction of the housing). . Therefore, leakage of the lubricant from the inside of the housing to the outside is effectively prevented.

(2) A sufficient sealing effect can be obtained by setting the taper angle θ of the tapered surface facing the sealing space to 3 ° ≦ θ ≦ 25 °.

(3) By providing the radial bearing portion on the porous bearing member made of sintered metal, the pores inside the bearing member can be impregnated with the lubricant, so that the lubricant inside the housing is supplemented. The amount of oil increases,
Circulation of the lubricant is also performed between the inside and the outside of the bearing member. Therefore, the deterioration of the lubricant inside the housing with time is small, and the excellent bearing function is maintained for a long time even when used at high speed rotation. Further, by using the porous bearing member, it is possible to mold the radial bearing portion easily and at low cost.

(4) By making the dynamic pressure groove of the radial bearing portion into a herringbone shape and having an asymmetrical shape in the axial direction and having a groove area having a long axial length on the opening side of the housing, The effect of preventing lubricant from leaking out can be further enhanced.

(5) When a plurality of radial bearing portions are arranged at intervals in the axial direction, a hollow groove is provided on the outer peripheral surface of the shaft member to simplify the shape of the housing or the bearing member and reduce the manufacturing cost. It can be reduced.

(6) By making the gap between the radial bearings continuous with the groove bottom of the dynamic pressure groove of the radial bearing without any step, from the radial bearing to the gap described above,
The lubricant is smoothly circulated from the gap portion to the radial bearing portion. Therefore, the deterioration of the lubricant inside the housing with time is small, and the excellent bearing function is maintained for a long time even when used at high speed rotation.

[Brief description of drawings]

FIG. 1 is a sectional view of a spindle motor having a dynamic pressure type bearing device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a dynamic pressure type bearing device according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of the bearing member {FIG. 3 (a)} and a view showing the lower end face {FIG. 3 (b)}.

FIG. 4 is a diagram showing an inner bottom surface of a housing.

[Explanation of symbols]

1 Dynamic pressure bearing device 2 shaft members 2a Shaft 2a2 taper surface 2b Flange part 7 housing 8 Bearing members R1 radial bearing R2 radial bearing R3 spacing part 8a1 dynamic pressure groove 8a2 dynamic pressure groove 8a3 dynamic pressure groove 8a4 dynamic pressure groove 10 Seal member 10a inner peripheral surface S seal space

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3J011 AA04 BA06 CA02 DA01                 3J016 AA01 AA02 AA03 BB23 CA02                 5H605 AA02 AA03 BB05 BB19 CC02                       CC04 CC05 DD05 DD16 EB03                       EB13 EB21 EB23 EB28 GG21                 5H607 AA05 AA06 BB01 BB14 BB17                       CC01 DD01 DD02 DD03 DD09                       DD16 GG01 GG03 GG12 GG15                       GG25 GG28 KK10

Claims (6)

[Claims] 1. A housing having an opening at one end, a shaft member housed in the housing, and a radial bearing portion for supporting the shaft member in the radial direction in a non-contact manner by a dynamic pressure action of a lubricant generated in a radial bearing gap. And a seal member arranged in the opening of the housing, wherein a seal space is provided between an inner peripheral surface of the seal member and an outer peripheral surface of the shaft member facing the inner peripheral surface. The seal space has a taper shape that gradually expands toward the outside of the housing, the interior space of the housing is filled with a lubricant, and the oil surface of the lubricant is in the seal space. A dynamic pressure type bearing device characterized by the above. 2. At least one of the outer peripheral surface of the shaft member and the inner peripheral surface of the seal member facing the seal space is a tapered surface, and the taper angle θ of the tapered surface is 3 °.
The dynamic pressure type bearing device according to claim 1, wherein ≦ θ ≦ 25 °. 3. The dynamic pressure type bearing device according to claim 1, wherein the radial bearing portion is provided on a porous bearing member made of sintered metal. 4. The radial bearing portion has a herringbone-shaped dynamic pressure groove, and the dynamic pressure groove has an axially asymmetric shape, and a groove region having a long axial length is provided on the opening side of the housing. The hydrodynamic bearing device according to claim 1, wherein the hydrodynamic bearing device is located. 5. A plurality of the radial bearing portions are arranged at intervals in the axial direction, and a hollow groove is provided on the outer peripheral surface of the shaft member facing the gap portion between the radial bearing portions. The dynamic pressure type bearing device according to claim 1, which is characterized in that. 6. A dynamic pressure type bearing device according to claim 5, wherein the gap between the radial bearing portions is continuous with the groove bottom of the dynamic pressure groove of the radial bearing portion without any step. .