JPH10225052A - Motor with dynamic pressure bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide longer service life with a simple and low-cost structure by satisfactorily preventing an adhesive from being peeled off. SOLUTION: As an adhesive for jointing a bearing member 22 to a bearing retainer 21, an elastic adhesive having an elongation larger than a difference in thermal expansion between the bearing member 22 and the bearing retainer 21 is used, and an adhesive pool 21g for permitting the elongation of the elastic adhesive quantitatively is formed. It is thus possible to conduct complete absorption of the above stress by the elongation of the elastic adhesive, even after a shearing force is received by a shift between the bearing member 22 and the bearing retainer 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor provided with a dynamic pressure bearing device for generating a dynamic pressure in a lubricant and supporting the shaft and the bearing member so as to be able to rotate relative to each other by the dynamic pressure.

[0002]

2. Description of the Related Art In recent years, various types of dynamic pressure bearing devices utilizing the dynamic pressure of a lubricant such as oil have been studied and proposed, particularly for motors adapted to high-speed rotation. In this hydrodynamic bearing device, a shaft-side hydrodynamic bearing surface circumferentially opposed to the shaft is provided;
A dynamic pressure generating groove is formed on at least one of the dynamic pressure bearing surfaces on the bearing member side, and a predetermined oil or the like interposed between the opposed dynamic pressure bearing surfaces of the shaft and the bearing member. The lubricant is pressurized by the pumping action of the dynamic pressure generating groove when the two members rotate relative to each other, and the rotating member is supported for rotation by the dynamic pressure of the lubricant.

On the other hand, a bearing holder such as a disk hub is fixedly used for a bearing member of a motor provided with such a dynamic pressure bearing device. The bearing holder is usually fitted to the bearing member with a clearance tolerance of a clearance fit having a relatively wide gap, and is made of epoxy resin or the like in the clearance between the shaft and the bearing member. A sufficient amount of a thermosetting adhesive is filled, so that the two members are integrally joined.

[0004]

However, the above-mentioned adhesive for joining the conventional bearing member and the bearing holder is not suitable for use in various heating steps during the manufacturing process or due to a change in the operating temperature environment during the use of the motor. In some cases, a stress is generated to cause a peeling phenomenon from the bonding interface. Then, a minute gap is formed at the part where the adhesive is peeled off, and the lubricant in the bearing portion oozes out due to the capillary force of the minute gap, causing oil leakage and oil scattering, thereby causing a problem in the device. May cause contamination.

[0005] Such a problem of peeling of the adhesive becomes remarkable especially when the bearing member and the bearing holder are formed of different materials (materials). In other words, if the materials of the two members are different from each other, and if the linear expansion coefficients of the two members are different, the thermal environment of the two members changes and the displacement of the joints of the two members occurs. In particular, a shear force acts on the adhesive due to an axial displacement, and the shearing force easily causes the adhesive peeling phenomenon as described above.

Therefore, the present invention has a simple and low-cost structure, and can prolong the service life of the bearing member and the bearing holder while effectively preventing the adhesive from peeling off. It is an object of the present invention to provide a motor provided with a hydrodynamic bearing device.

[0007]

In order to achieve the above object, a motor provided with a hydrodynamic bearing device according to the present invention comprises a shaft and a bearing provided to rotate relative to the shaft. Member, and a bearing holder integrally joined to the bearing member with an adhesive, and a lubricant filled between the opposed bearing surfaces of the shaft and the bearing member is provided on the both bearing surfaces. In a motor including a dynamic pressure bearing device in which the shaft and the bearing member are supported so as to be relatively rotatable by being pressurized by a dynamic pressure generating groove formed on at least one side, the adhesive may include: It is made of an elastic adhesive having an elongation larger than a difference in thermal expansion between the bearing member and the bearing holder, and allows the elastic adhesive to extend at a joint between the bearing member and the bearing holder. Adhesive pool is provided That.

[0008] According to the motor having such a dynamic pressure bearing device, the adhesive for joining the bearing member and the bearing holder is subjected to stress caused by thermal influence, particularly, the bonding between the bearing member and the bearing holder. Even when a shearing force is applied due to the gap between them, the above-mentioned stress is absorbed by the elasticity of the adhesive. At this time, since a sufficient amount of the adhesive is secured in the adhesive reservoir,
The amount of elongation of the adhesive will also be sufficiently ensured, and therefore, stress such as shear generated due to displacement between the bearing member and the bearing holder will be completely absorbed by the elasticity of the adhesive, The conventional adhesive peeling phenomenon can be prevented well.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a so-called fixed-end-shaft HDD spindle motor will be described in detail with reference to the drawings. First, the overall structure of the HDD spindle motor shown in FIG. 1 will be described. This HDD spindle motor includes a stator set 1 as a fixed member and a rotating member assembled to the stator set 1 from above in the figure. And a rotor set 2. The stator set 1 has a frame 11 screwed to a fixed base (not shown), and a fixed shaft 12 erected substantially at the center of the frame 11 moves upward in the figure. Extending. This fixed shaft 1
2 are screwed to a fixed base (not shown).

The frame 11 has a hollow cylindrical support holder 13, and a stator core 14 is fitted around the outer periphery of the support holder 13. A winding 15 is wound around the salient pole portion of the stator core 14.

On the other hand, the rotor set 2 has a disk hub 21 as a bearing holder for supporting a predetermined recording medium (not shown).
Is connected to the fixed shaft 1 via a substantially hollow cylindrical radial bearing member 22 attached to the center of the disk hub 21.
2 is rotatably supported on the outer peripheral side.

The disk hub 21 has a substantially cylindrical body 2 on which a magnetic recording medium such as a magnetic disk is mounted on the outer periphery.
1a and a drive magnet 21c on the inner peripheral side of the body 21a via a back yoke 21b.
Are mounted in an annular shape. This drive magnet 21c
Are arranged close to each other so as to annularly face the outer peripheral end surface of the stator core 14 described above.

The disk hub 21 is made of an aluminum alloy member. An outer peripheral portion of a radial bearing member 22 made of stainless steel is fitted into a mounting hole 21d formed in a center portion of the disk hub 21 with a shrink fit. Fitted with Hameyai tolerance. As described above, the two members 21 and 22 are used.
Is mounted with a shrink-fitting tolerance so that positioning in the radial direction is particularly performed.

Further, as shown in particular in FIG.
A positioning step 21e is formed at the upper end of the mounting hole 21d of the disk hub 21 in the drawing, with the inner peripheral wall protruding toward the center by a predetermined amount. The illustrated lower end surface 21f of the positioning step 21e is formed with a predetermined accuracy so as to form a contact surface perpendicular to the axial direction, and the illustrated lower contact surface 21f of the positioning step 21e is formed.
The illustrated upper end face of the radial bearing member 22 is abutted against the above. This allows the radial bearing member 22 to have a predetermined right angle while being positioned in the axial direction.

Further, at the bottom corner of the abutting surface 21f of the positioning step 21e, an adhesive reservoir 21g is provided.
Is provided. An adhesive for adhering the radial bearing member 22 and the disk hub 21 is filled in the adhesive reservoir 21g, and the outer peripheral joint surface of the radial bearing member 22 and the disk are filled with the adhesive. The inner peripheral side joining surface of the hub 21 is integrally joined.
The reason why the adhesive reservoir 21g is provided at the root corner of the abutting surface 21f in the positioning step 21e is that the adhesive reservoir 21g is provided at the joint between the radial bearing member 22 and the disk hub 21 by the amount of thermal relative displacement. Is the smallest part, whereby the amount of deformation of the adhesive is minimized, and the reliability of bonding is increased.

The adhesive is made of a predetermined elastic adhesive, and has an elongation larger than a difference in thermal expansion between the radial bearing member 22 and the disk hub 21 as a bearing holder. As described above, the radial bearing member 22
Is formed of an aluminum alloy material, while a relatively large difference in thermal expansion is generated between these two members. Is filled with an elastic adhesive having an elongation larger than the difference in thermal expansion between the two members.
The elastic adhesive is configured to be allowed to expand by the amount stored in the adhesive reservoir 21g described above.

As the elastic adhesive in the present embodiment,
An ultraviolet curing type and an anaerobic curing type are used, and a curing at room temperature by using a primer (curing accelerator) in combination is used. The elastic adhesive in the present embodiment has a viscosity of 1000 cp (at 25
° C) and the elongation is 150%
Is adopted.

As shown in FIG. 1, the radial bearing member 22 has a pair of dynamic pressure bearing portions 22a and 22b arranged in parallel in the axial direction (vertical direction in the drawing) at predetermined intervals. . The pair of radial dynamic pressure bearing portions 22
The inner peripheral surfaces of the radial dynamic pressure bearing portions 22a, 22b are opposed to the outer peripheral surface of the fixed shaft 12 with a gap of several μm. On at least one side of the surface, for example, a herringbone-shaped radial dynamic pressure generating groove is formed in a concave shape so as to be annularly juxtaposed. A predetermined lubricant 24 made of oil, a magnetic fluid, or the like is interposed between the two opposing surfaces. When the disk hub 21 rotates, the lubricant 24 is pumped by the radial dynamic pressure generating groove. The pressure is increased to generate a dynamic pressure, and the disk hub 21 is axially supported in the radial direction by the dynamic pressure generated by the lubricant 24.

The fixed shaft 12 is made of a material obtained by heat-treating stainless steel. Two fixed thrust hydrodynamic bearings are provided at the end of the fixed shaft 12 (upper end in the figure). A ring-shaped thrust plate (retaining ring) 16 constituting the portions 16a and 16b is fixed. The two thrust dynamic pressure bearing portions 16a and 16b constituted by the thrust plate 16 are disposed adjacent to the upper side in the drawing of the radial dynamic pressure bearing member 22 disposed in the upper side in the drawing.

That is, the illustrated lower surface of the thrust plate 16 is disposed so as to face the illustrated upper surface of the radial dynamic pressure bearing member 22, and the illustrated upper surface of the thrust plate 16 is The thrust holding plate 25 screwed to the central portion is disposed so as to face the lower end surface in the drawing, and the thrust dynamic pressure bearing portion 16a,
On both end surfaces in the axial direction of the thrust plate 16 constituting 16b,
For example, herringbone-shaped grooves for generating thrust dynamic pressure are each formed in an annular shape.

The space between the opposing surfaces of the thrust plate 16 and the radial dynamic pressure bearing member 22 and the thrust plate 1
Each of the gaps between the first and second thrust holding plates 25 and the opposing surfaces is filled with the lubricant 24 in the radial dynamic pressure bearing portions 22a and 22b so as to be continuous.
When the disk hub 21 rotates, the lubricant 24 is pressurized by the pumping action of the thrust dynamic pressure generating groove to generate a dynamic pressure, and the dynamic pressure generated by the lubricant 24 causes the disk hub 21 to rotate in the thrust direction. It is configured to be supported.

That is, a thrust dynamic pressure bearing portion 16b is disposed on the inner peripheral side of the adhesive reservoir 21g provided on the positioning step portion 21e of the disk hub 21, and the lubricant 24 Is satisfied. In addition,
The joint between the thrust holding plate 25 and the disk hub 21 is joined by an adhesive so as to form a completely sealed structure before the injection of the lubricant 24, whereby good sealing performance with respect to the lubricant 24 is ensured. I have. The adhesive filled in the joint is continuously and continuously filled over the entire periphery of the joint by the capillary force of an annular guide groove (not shown) formed in the joint. This completes the closed structure.

A thin stopper plate 27 is provided on the upper end surface of the thrust pressing plate 25 and the lower end surface of the thrust dynamic pressure bearing 22 from outside (upper and lower sides in the figure) via an absorbent cloth 26. The absorbent cloth 26
The stopper plate 27 prevents the lubricant 24 from scattering outside even in the worst case.

Further, the two radial dynamic pressure bearing portions 22a and 22b and the two thrust dynamic pressure bearing portions 16 described above are provided.
a, 16b are arranged side by side so as to define a series of bearing spaces extending in the axial direction.
a, 16b, 22a, and 22b, the fixed shaft 12 and the rotating members 22b, 2
Capillary seal portions 3 each having a narrow gap with 5
1a and 31b are the four dynamic pressure bearings 16a and 16
b, 22a, 22b are provided so as to sandwich them from both sides in the axial direction.

Each of these capillary seal portions 31a, 31b
Of these, the lower capillary seal portion 31b shown in the figure is provided in a part of the radial dynamic pressure bearing portion 22b arranged on the lower side in the figure, and more specifically, the radial dynamic pressure bearing portion 2b.
The narrow gap between the inner peripheral wall of the outer end portion in the axial direction (the lower end portion in the drawing) of 2b and the outer peripheral surface of the fixed shaft 12 is gradually expanded toward the outer side in the lower axial direction in the drawing to open. Is formed. Further, the capillary seal portion 31a on the upper side of the figure is
Thrust holding plate 2 constituting thrust dynamic pressure bearing portion 16a
5 and a fixed gap between the fixed shaft 12 and the inner peripheral wall of the aforementioned thrust holding plate 25 and the fixed shaft 12.
Is formed so as to gradually expand and open outward in the axial direction on the upper side in the figure.

Further, a lubricant injection portion 32 is provided on the outer side in the axial direction (upper side in the figure) of the above-described upper capillary seal portion 31a in the axial direction so as to be continuous with the capillary seal portion 31a. ing. The lubricant injection portion 32 is formed of an enlarged gap that is continuous with the narrow gap that constitutes the capillary seal portion 31a, and the inner peripheral wall of the thrust holding plate 25 facing the fixed shaft 12 is sealed with a capillary seal. It is formed by inclining at an opening angle larger than the inclined wall constituting the portion 31a. The capacity in the gap of the lubricant injection part 32 is set to be larger than the capacity of the bearing space connecting the two capillary seal parts 31a and 31b described above, whereby the total amount of the lubricant 24 is once reduced. Then, the lubricant is injected into the lubricant injection section 32 in a vacuum state, and thereafter, the inside of the bearing space (the lower side in the figure) is filled by capillary force.

When the lubricant 24 is injected, a sealing material such as an O-ring is detachably attached to the capillary seal portion 31b side, and the lubricant is injected from the lubricant injection portion 32 in a vacuum state. After that, the bearing space can be filled with the lubricant by the atmospheric pressure by opening to the atmosphere.

On the other hand, the aforementioned radial dynamic pressure bearing portion 22
A lubricant reservoir 33 is provided in a portion between the shafts a and 22b in the axial direction to enlarge a gap with the fixed shaft 12 by depressing an inner peripheral surface of the radial dynamic pressure bearing member 22 to an outer peripheral side. I have.

According to the motor according to the embodiment, the adhesive for joining the radial dynamic pressure bearing member 22 and the disk hub 21 as the bearing holder is subjected to stress due to thermal influence, particularly to radial dynamic force. Even when a shearing force due to a displacement between the pressure bearing member 22 and the disk hub 21 is received, the above-mentioned stress is absorbed by the elasticity of the adhesive.

Since a sufficient amount of the elastic adhesive at this time is secured in the adhesive reservoir 21g, a sufficient amount of elongation of the adhesive is also ensured. A stress such as a shear caused by a shift between the disk hub 21 as a bearing member and the disk hub 21 is:
The adhesive is completely absorbed by the elasticity of the elastic adhesive, so that the conventional adhesive peeling phenomenon can be prevented well.

Next, an embodiment in which the present invention is applied to a shaft rotation type HDD spindle motor will be described. In the embodiment of the shaft rotation type HDD spindle motor shown in FIG. 3, a motor frame 41 as a fixing member is used.
A radial bearing member 42 is fixed to an inner peripheral portion of a substantially hollow cylindrical bearing holder 43 erected at a substantially central portion of the radial bearing member 42. A rotating shaft 52 is attached to the inner peripheral portion of the radial bearing member 42.
Are rotatably mounted via a lubricant not shown.

The bearing holder 43, which constitutes a bearing holder, is made of an aluminum alloy member, and has a stator core 44 on the outer periphery of the bearing holder 43.
Is held, and an outer peripheral portion of a radial bearing member 42 made of a stainless material is fitted in a mounting hole 43d formed in a central portion of the bearing holder 43 with a loose fit tolerance. Thus, both members 4
The positioning in the radial direction is performed by mounting the 2, 43 with shrink fit.

At the lower end of the mounting hole 43d in the bearing holder 43 as shown in the figure, a positioning step 43e slightly protruding from the inner peripheral wall toward the center is formed. The illustrated upper end surface of the positioning step 43e is formed with a predetermined accuracy so as to form a contact surface 43f perpendicular to the axial direction, and the radial bearing member 42 described above is formed with respect to the contact surface 43f. The illustrated lower end surface is abutted. This allows the radial bearing member 42 to be positioned in the axial direction and to have a predetermined perpendicularity.

Further, similarly to the above-described embodiment, an adhesive reservoir 43g is provided at the root corner of the abutting surface 43f provided on the positioning step 43e of the bearing holder 43. The adhesive reservoir 43g is filled with an elastic adhesive for adhering the radial bearing member 42 and the bearing holder 43. The elastic adhesive allows the adhesive reservoir 43g to be in contact with the outer peripheral joining surface of the radial bearing member 42. And the inner peripheral surface of the bearing holder 43 are integrally joined.
In this case, the elastic adhesive is applied to the radial bearing member 42.
And the bearing holder 43 as a bearing holder has an elongation larger than the difference in thermal expansion between the two, and the elongation of the elastic adhesive is quantitatively allowed by the adhesive reservoir 43g.

In this embodiment, in addition to the adhesive reservoir 43g, two adhesive reservoirs 43h and 43j in which the inner peripheral side wall surface of the bearing holder 42 is depressed to the outer peripheral side.
Are provided at the joint between the bearing holder 42 and the radial bearing member 43.

The disk hub 51 in this embodiment is
The rotating shaft 52 is fixed to the upper end in the figure. A thrust plate (retaining ring) 56 is fixed to a lower end portion of the rotary shaft 52 shown in the figure, and a lower end of the rotary shaft 52 is rotatably received by a thrust receiving plate 55. The rotary shaft 52 is supported in the axial direction by a thrust bearing portion constituted by the above members. In such an embodiment, the same operation and effect as in the above-described embodiment can be obtained.

Further, in the embodiment shown in FIG. 4, when joining both members of the bearing member 61 and the bearing holding member 62, both of the two members 61 and 62 are the same as in the above-described embodiment. No positioning step is provided. The adhesive reservoir 63 in this case is arranged at the axial center of the bearing holder 62. This is because the thermal relative displacement between the bearing member 61 and the bearing holder 62 occurs around the central portion in the axial direction, and the central portion in the axial direction, which is the center of the thermal relative displacement, has an adhesive. By disposing the pool portion 63, the amount of deformation of the elastic adhesive can be minimized, and the reliability of bonding can be increased.

Although the embodiments of the present invention made by the inventor have been specifically described above, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say.

For example, in each of the above embodiments, the bearing member and the bearing holder are firmly fixed by the shrink fit, so that the positioning in the radial direction is strictly maintained. It is not necessary to set it as a clearance fit. However, in this case, it is necessary that the squeeze tolerance is set to such an extent that the positioning of the two members does not hinder the thickness of the adhesive filling the gap.

The present invention can be similarly applied to various motors other than the HDD motor described above.

[0041]

As described above, according to the present invention, as the adhesive for joining the bearing member and the bearing holder, an elastic adhesive having an elongation greater than the thermal expansion difference between the bearing member and the bearing holder is used. Adopted and provided with an adhesive reservoir that allows the elastic adhesive to elongate quantitatively, when subjected to stress due to thermal effects, especially shear force due to displacement between the bearing member and the bearing holder Even, since the above-mentioned stress is completely absorbed by the elongation of the elastic adhesive, with a simple and low-cost structure, it is possible to prevent the conventional adhesive peeling phenomenon well. The life can be extended, and the reliability of the motor including the dynamic bearing device can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory view showing an example of a fixed-shaft HDD spindle motor including a hydrodynamic bearing device according to an embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing a boundary portion between a radial bearing portion and a thrust bearing portion in FIG.

FIG. 3 is a half cross-sectional explanatory view showing a half of a shaft rotation type HDD spindle motor including a dynamic pressure bearing device according to another embodiment of the present invention.

FIG. 4 is an explanatory partial cross-sectional view showing a part of a hydrodynamic bearing device according to still another embodiment of the present invention in an enlarged manner.

[Explanation of symbols]

 Reference Signs List 12 fixed shaft 16 thrust plate 21 disk hub (bearing holder) 21e positioning step 21f abutting surface 21g adhesive reservoir 22 radial bearing member 24 lubricant 25 thrust holding plate 42 radial bearing member 43 bearing holder 43e positioning step 43f projection For the time being 43g Adhesive reservoir 51 Disk hub (bearing holder) 52 Rotary shaft

Claims (7)

[Claims] 1. A bearing, comprising: a shaft; a bearing member provided to rotate relative to the shaft; and a bearing holder integrally joined to the bearing member by an adhesive. The lubricant filled between the opposed bearing surfaces of the shaft and the bearing member is pressurized by the dynamic pressure generating grooves formed on at least one of the two bearing surfaces, so that the shaft and the bearing member are relatively moved. In a motor having a hydrodynamic bearing device rotatably supported, the adhesive is made of an elastic adhesive having an elongation larger than a thermal expansion difference between the bearing member and the bearing holder, A motor equipped with a hydrodynamic bearing device, characterized in that a joint portion between the bearing member and the bearing holder is provided with an adhesive reservoir for permitting quantitative expansion of the elastic adhesive. 2. A motor having a hydrodynamic bearing device, wherein the adhesive according to claim 1 is filled in a joint between a bearing member and a bearing holder. 3. The bearing holder according to claim 1, further comprising a disk hub joined to an outer peripheral portion of the bearing member, wherein the disk hub is formed of an aluminum member that holds the disk body. Motor equipped with a dynamic pressure bearing device. 4. A motor provided with a hydrodynamic bearing device, wherein the bearing holder according to claim 1 is a frame-side bearing holder for holding a stator core. 5. A motor provided with a hydrodynamic bearing device, wherein the bearing member and the bearing holder according to claim 1 are joined to each other with a shrink-fitting tolerance. 6. The adhesive reservoir according to claim 1, wherein the adhesive reservoir is provided at a joint between the bearing member and the bearing holder at a position where the thermal relative displacement between the two members is the smallest. Motor with dynamic pressure bearing device. 7. The bearing member according to claim 1, wherein the bearing member is formed of a cylindrical body, a bearing holder is fixed to an outer peripheral side of the bearing member, and the shaft end surface of the bearing member is attached to the bearing holder. An abutting positioning step is formed, lubricant is filled so as to reach at least the positioning step of the bearing holder from between the opposed bearing surfaces of the shaft and the bearing member, and the adhesive reservoir is formed of A motor provided with a hydrodynamic bearing device, which is provided at a root corner of a positioning step of a bearing holder.