JPH11218125A - Dynamic pressure bearing device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity of a dynamic pressure bearing device and reduce the cost of the device. SOLUTION: A bearing support frame body 12 and a bearing member 13 are fittingly fixed by insert forming. At the time of fittingly fixing both members 12, 13 to each other, both members 12, 13 are fittingly fixed to each other in an extremely easy process, omitting a conventional shrinkage fitting process itself requiring much time and labor, and dispensing with machining such as grinding and cutting to obtain tolerance dimensions for shrinkage fitting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing device in which a dynamic pressure is generated in a lubricating fluid and the rotating member is supported on a fixed member by the dynamic pressure of the lubricating fluid, and a method of manufacturing the same. About.

[0002]

2. Description of the Related Art In recent years, in various devices such as motors, various types of dynamic pressure bearing devices utilizing the dynamic pressure of a lubricating fluid such as oil or air have been studied and proposed so as to cope particularly with high-speed rotation. In this dynamic pressure bearing device, the dynamic pressure surface on the fixed member side and the dynamic pressure surface on the rotating member side are arranged to face each other, and a dynamic pressure generating groove is formed on at least one of the two opposing dynamic pressure surfaces. The lubricating fluid, such as oil or air, interposed between the opposing surfaces of the rotating member and the fixed member is pressurized by the pumping action of the dynamic pressure generating groove when the rotating member rotates, and the dynamic pressure action is increased. Then, the rotating member is held in a floating state by the dynamic pressure of the lubricating fluid, and the rotating member is supported for rotation.

In such a dynamic pressure bearing device, for example, as shown in FIG. 7, a sleeve-shaped bearing member 1 made of a stainless material or the like is provided with a holder portion provided on a frame 2 made of an aluminum material or the like. The third hole 4 is fitted and fixed by shrink fitting, for example. This bearing member 1
As shown in FIG. 7, when shrink-fitting is performed on the frame 2, a processing step on the left side of the drawing for the bearing sleeve 1 as a bearing member, and a processing step on the right side of the figure for the frame 2 as a bearing support frame. Are performed separately and in parallel.

That is, in the bearing sleeve (bearing member) shown in the left side of FIG. 8, a blank material as a material of the bearing sleeve is first subjected to an outer diameter centerless grinding for shrink fitting (step 1). Thereby, the outer diameter of the bearing sleeve 1 is formed within a predetermined dimensional tolerance. Next, the entire shape of the bearing sleeve 1 is cut (Step 2), and cutting powder and the like are washed away in a cleaning step (Step 3). At this time, in order to improve the reliability of the bearing device, the inventor of the present application has considered that an outer surface of the bearing sleeve 1 is subjected to a rust prevention treatment for preventing oxidation (step 4).

On the other hand, a frame (bearing support frame) 2 on the right side in the figure is formed by, for example, aluminum die casting. First, a hole 4 (FIG. 7) of a holder portion 3 for shrink fitting is formed.
Is formed into a predetermined tolerance dimension by cutting (step 5). Next, various surface processing is performed on the frame 2 (Step 6), and after the cutting powder and the like are washed away by washing (Step 7), the above-described bearing sleeve (bearing member) 1 is shrink-fitted (Step 6). Step 8). After the shrink fitting, a finish cutting step for eliminating an assembly error or the like is performed (step 9), and finally, cleaning is performed (step 10).

[0006]

However, in such a conventional hydrodynamic bearing device and its manufacturing method, as described above, the bearing sleeve (bearing member) 1 is fired on the frame (bearing support frame) 2. Because it is fitted and fixed, it has to go through complicated processes such as heating.
Many processes are required before and after the shrink fitting process. In particular, when a rust prevention process is to be performed, a great deal of labor is required, so that the productivity is not good and the cost must be increased.

Accordingly, the present invention enables a bearing member to be fitted and fixed to a bearing support frame in a simple process, thereby improving the productivity of the dynamic pressure bearing device and reducing the cost. It is an object of the present invention to provide a dynamic bearing device and a method of manufacturing the same.

[0008]

In order to achieve the above object, according to the present invention, a predetermined bearing support frame, a bearing member fitted and fixed to the bearing support frame, and A shaft member provided so as to be relatively rotatable between the bearing member and a dynamic pressure generating groove formed on at least one side of both opposed dynamic pressure surfaces provided on the bearing member and the shaft member; A lubricating fluid interposed between the opposed opposing dynamic pressure surfaces, and a dynamic pressure is generated in the lubricating fluid by a pressurizing action of the dynamic pressure generating groove, and the dynamic pressure causes the dynamic pressure between the bearing member and the shaft member. In a hydrodynamic bearing device that supports one of them in a floating state, the bearing support frame and the bearing member are:
Fitted and fixed by insert molding.

According to the second aspect of the present invention, the bearing member according to the first aspect is formed of an easily oxidizable material, and the exposed surface of the bearing member is coated with an oxidation resistant material. Insert molding is performed so as to be covered by the member.

Further, in the invention according to claim 3, the covering member made of the oxidation-resistant material according to claim 2 forms a part of the bearing support frame.

Furthermore, in the invention according to the fourth aspect, the covering member made of the oxidation resistant material according to the second aspect is unevenly fitted to the bearing member so as to prevent the coating member from falling off.

On the other hand, in the invention according to claim 5, the bearing member according to claim 1 is made of a metal material, and the bearing member and the bearing support frame are formed by insert die casting.

Further, in the invention according to claim 6, one of the bearing member and the shaft member according to claim 1 comprises a rotating member for holding a hard disk recording medium.

Further, according to the present invention, the predetermined bearing support frame, the bearing member fitted and fixed to the bearing support frame, and the bearing member can be relatively rotated. A shaft member provided, a dynamic pressure generating groove formed on at least one of the opposed dynamic pressure surfaces provided on the bearing member and the shaft member, and a lubricating fluid interposed between the opposed dynamic pressure surfaces. A dynamic pressure bearing for generating a dynamic pressure in the lubricating fluid by the pressurizing action of the dynamic pressure generating groove, and supporting one of the bearing member and the shaft member in a floating state by the dynamic pressure. In the method of manufacturing the device, by performing the shape processing of the bearing member from the blank material of the bearing member, by setting the bearing member obtained thereby in a molding die of the bearing support frame body and insert molding, Bearing member and bearing support It has a frame body to fit fixed.

According to the first or fifth or seventh aspect of the present invention, the time-consuming shrink-fitting step itself is omitted, and machining such as grinding and cutting for obtaining a tolerance dimension for shrink-fitting is performed. Is unnecessary, and the bearing support frame and the bearing member are fitted and fixed in a simple process.

According to the second aspect of the present invention, the provision of the covering member on the bearing member eliminates the need for rust-preventive treatment on the bearing member, thereby providing a simpler and less expensive fitting and fixing step.

At this time, if the covering member is formed as a part of the bearing support member as in the means of the third aspect, insert molding can be performed more efficiently.

Further, according to the means of the fourth aspect, the covering member is firmly held with respect to the bearing member, and good device durability can be obtained in addition to the above operation.

Such an operation is particularly effective for an apparatus using a hard disk recording medium such as the means described in claim 6.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a hydrodynamic bearing device according to the present invention is applied to a so-called shaft-rotating 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. 5 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 as a bearing support frame screwed to a fixed base (not shown), and a hollow cylindrical bearing holder 12 is provided at a substantially central portion of the frame 11. It is formed so as to stand up integrally, and a bearing sleeve 13 as a bearing member is fixed in the bearing holder 12.

At this time, the frame 11 as a bearing support frame integrally including the bearing holder 12 is formed of an oxidation resistant material, for example, various aluminum alloys, and the bearing sleeve 13 as a bearing member is It is formed from an easily oxidizable metal material. As the easily oxidizable metal material forming the bearing sleeve 13, for example, S
US430F and the like. Further, a magnetic steel material such as copper such as Cu-Sn-P-based alloy (phosphor bronze) or a copper-based alloy copper, or a nickel alloy having a lower thermal expansion coefficient than that of the copper alloy may be employed. Further, as a steel material that is a nickel alloy, Fe—Ni (invar), Fe—Ni—
There is Co (Super Invar).

The frame 11 including the bearing holder 12 and the bearing sleeve 13 are fitted and fixed by aluminum die-cast insert molding. Details of the structure and steps of fitting and fixing the bearing holder (bearing support frame) 12 and the bearing sleeve (bearing member) 13 by die-cast insert molding will be described later.

A stator core 14 is fitted on the outer peripheral surface of the bearing holder 12.
The winding 15 is wound around the salient pole portion.

In the inner hole of the bearing sleeve 13,
A rotating shaft 21 constituting the rotor set 2 is rotatably inserted. The rotating shaft 21 in the present embodiment is formed from a material such as stainless steel (SUS420J2), for example.

Between the dynamic pressure surface formed on the inner peripheral wall surface of the bearing sleeve 13 and the dynamic pressure surface formed on the outer peripheral surface of the rotating shaft 21, a small opposing gap of several μm in the radial direction is formed. The minute opposing gap is filled with lubricating oil to form a radial dynamic pressure bearing. The bottom opening of the bearing holder 12 in the frame 11 is closed by a counter plate 16, and a dynamic pressure surface provided on the upper surface of the counter plate 16 in the drawing and a lower end of the rotating shaft 21 in the drawing. Between the attached thrust ring 23 and the dynamic pressure surface on the lower surface in the figure,
A minute facing gap of several μm is formed in the axial direction, and the minute facing gap is filled with lubricating oil to form a thrust dynamic pressure bearing.

Further, a minute opposing gap in the axial direction is similarly formed between the dynamic pressure surface on the upper surface of the thrust ring 23 and the dynamic pressure surface on the lower surface of the bearing sleeve 13. Lubricating oil is filled to form a thrust dynamic pressure bearing.

At least one of a pair of dynamic pressure surfaces constituting the radial dynamic pressure bearing and the thrust dynamic pressure bearing has, for example, a herringbone-shaped dynamic pressure generating groove 13a as shown in FIG. Are arranged so as to be annularly parallel to each other. During rotation, the lubricating fluid is pressurized by the pumping action of the dynamic pressure generating groove 13a to generate a dynamic pressure, and by the dynamic pressure generated in the lubricating fluid, Rotating shaft 21
Are axially supported in a floating state in the radial and thrust directions.

Returning to FIG. 5, a center hole of a hub 22 for supporting a predetermined hard disk recording medium (not shown) is fitted to the upper end of the rotating shaft 21 in the figure. The hub 22 has a substantially cylindrical body 22a on which the hard disk recording medium is mounted on the outer periphery, and the back 22 is provided on the inner peripheral wall of a skirt 22b provided at the lower edge of the body 22a. A drive magnet 22d is annularly mounted via a yoke 22c. The drive magnet 22d is disposed close to the above-described stator core 14 so as to annularly face the salient pole outer peripheral end face of the stator core 14.

On the other hand, the bearing holder 12 of the frame 11 constituting the bearing support frame and the bearing sleeve 13 as a bearing member described above are fitted and fixed by aluminum die-cast insert molding. In the aluminum die-cast insert molding, the bearing holder 12 made of the aluminum alloy, which is the oxidation-resistant material, covers the outer surface of the bearing sleeve 13 made of the easily oxidizable metal material, that is, the covering portion 12a covering substantially the entire surface exposed to the atmosphere. It is performed to have.

At this time, the covering portion 12a of the bearing holder 12 is fitted to the surface of the bearing sleeve 13 so as to prevent it from falling off in the axial direction. More specifically, an annular protrusion 12b is provided in a convex shape on the inner peripheral surface side of the covering portion 12a of the bearing holder 12, and an annular groove portion 13a is formed on the outer peripheral surface side of the bearing sleeve 13.
Are formed in a concave shape, and these are formed into a concave-convex fitting state by the aluminum die-cast insert molding described above, so that the covering portion 12a of the bearing holder 12 and
The bearing sleeve 13 is in a firmly fixed state.

Such insert die casting is performed, for example, as shown in FIG. First, the blank material of the bearing sleeve 13 prepared in advance is cut into a shape so as to be processed into the entire shape of the bearing sleeve 13 (step 1), and cutting powder or the like is flown in a cleaning process to make it a clean state (step 1). 2), the bearing sleeve 13 is
It is set at a predetermined position in a mold (not shown). At this time, the bearing sleeve 13 does not require highly accurate outer diameter grinding as in conventional shrink fitting.

In the present embodiment, when the blank material of the bearing sleeve 13 is set in a mold, the blank material of the bearing sleeve 13 is handled in a solid state without forming a center hole. A protruding portion having a predetermined shape is provided as a mold setting surface on an end surface (an upper end surface in FIG. 1) of a portion where a center hole is to be formed. This is because the coating portion 12 formed by insert die casting is formed.
(See FIG. 1) is due to the structure that covers the end surface of the bearing sleeve 13 almost completely. To achieve such a structure, a blank material for the bearing sleeve 13 is set in a mold. A set surface is required. The protruding portion having the mold setting surface is removed at the time of drilling after insert die casting.

Then, the frame 11 is die-cast with aluminum by injecting a molten aluminum alloy into the cavity in the mold (step 3). In forming the frame 11 as well, it is not necessary to perform highly accurate hole inner diameter processing on the frame as in the case of performing conventional shrink fitting.

The bearing sleeve 13 is fitted and fixed to the bearing holder 12 of the frame 11 by such insert aluminum die-casting. Processing (step 4) and finish cutting (step 5) are performed, and finally cleaning is performed (step 6). At this time, almost the entire outer surface of the bearing sleeve 13 is entirely covered with the oxidation-resistant coating portion 1 by the above-described aluminum die-cast insert molding.
Since it is covered with 2a, it is not necessary to perform a conventional rust prevention treatment.

As described above, according to the dynamic pressure bearing device and the method of manufacturing the same according to the present embodiment, the bearing holder 12 of the frame 11 as the bearing support frame and the bearing sleeve 13 as the bearing member are fitted. In fixing, the troublesome shrink-fitting process itself as in the related art is omitted, and processing such as grinding and cutting to obtain a tolerance dimension for performing shrink-fitting is not required. Both members are fitted and fixed.

Further, in the apparatus of the present embodiment, since the bearing sleeve 13 is provided with the covering member 12a made of an oxidation-resistant material, it is not necessary to perform a rust-proofing treatment on the bearing sleeve 13, so that the fitting and fixing process can be more simplified. Has been obtained.

At this time, if the covering member 12a is formed as a part of the bearing holder 12 as in the apparatus of the present embodiment, insert aluminum die-casting can be performed more efficiently. Further, at this time, in the apparatus of the present embodiment, the covering portion 12a of the bearing holder 12 and the surface of the bearing sleeve 13 are fitted into the concave and convex so as to be in a firmly fixed state, and are prevented from falling off in the axial direction. Therefore, in addition to the above-described effects, good device durability can be obtained.

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, as described above, the bearing holder 1
In the case where the second covering portion 12a is provided on the surface of the bearing sleeve 13, as shown in FIG. 2, a step portion 13c provided on the end face (the upper end face in the drawing) of the bearing sleeve 13 is provided.
It is also possible to insert-mold a structure in which the covering portion 12a of the bearing holder 12 is engaged with the reference surface of the bearing holder 12 such that the covering portion 12a comes into contact with the reference surface. By doing so, the mold can be set in a state after the blank material of the bearing sleeve 13 has been subjected to the hole processing, and a more secure engagement mode can be obtained.

In this case, if a hole is made after insert molding before blanking the blank material of the bearing sleeve 13, as shown in FIG. The abutment reference surface for the portion 12a may not be provided.

Further, as shown in FIG. 4, the center portion 1 on the end face (the upper end face in the figure) of the bearing sleeve 13 is formed.
It is also possible to adopt a structure in which 3d is formed so as not to be covered by the covering portion 12a, and an oil repellent or the like is applied thereto.

Further, the dynamic pressure generating groove in the dynamic bearing device to which the present invention is applied is not limited to the herringbone shape as in the above-described embodiment, but may have other various shapes. The present invention can be similarly applied to grooves for generating dynamic pressure.

Further, in the above-described embodiment, the present invention is applied to a so-called rotary shaft type motor, but the present invention can be similarly applied to a fixed shaft type motor.

Further, the present invention can be similarly applied to a dynamic pressure bearing device used other than the above-mentioned HDD motor, and uses air and other various fluids in addition to oil as lubricating fluid. The present invention can be similarly applied to those used.

[0045]

As described above, claim 1 or 5 or 7
The described invention, by fitting and fixing the bearing support frame body and the bearing member by insert molding, when fitting and fixing both members, while omitting the troublesome shrink fitting process itself as in the past, This eliminates the need for grinding, cutting, etc., which provide tolerance dimensions for shrink fitting, and fits and fixes both members in an extremely simple process. It is possible to greatly improve the cost and reduce the cost of the apparatus.

According to a second aspect of the present invention, a coating member made of an oxidation-resistant material is provided on a bearing member.
Since the bearing member does not need to be subjected to rust prevention treatment and can be fitted and fixed more easily and inexpensively, the above-described effects can be further improved.

In this case, according to the third aspect of the present invention, the insert member is formed as a part of the bearing support member so that insert molding can be performed more efficiently. Can be improved.

Further, according to the present invention, the cover member of the bearing member and the air-exposed surface of the bearing support frame are fitted to each other in an uneven manner so as to be in a firmly fixed state, thereby preventing the bearing member from falling off in the axial direction. Therefore, in addition to the effects described above, the durability of the device can be improved.

The above-described effect is particularly effective for an apparatus using the hard disk recording medium according to the sixth aspect, and a great effect can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view showing a state in which a frame and a bearing sleeve of an HDD spindle motor having a dynamic pressure bearing device according to an embodiment of the present invention are fitted and fixed.

FIG. 2 is a partial cross-sectional explanatory view showing a fitted state of a frame and a bearing sleeve in another embodiment of the present invention.

FIG. 3 is a partial cross-sectional explanatory view showing a fitted and fixed state of a frame and a bearing sleeve according to still another embodiment of the present invention.

FIG. 4 is a partial cross-sectional explanatory view showing a fitted and fixed state of a frame and a bearing sleeve according to still another embodiment of the present invention.

FIG. 5 shows an HDD provided with a hydrodynamic bearing device to which the present invention is applied.
FIG. 2 is an explanatory cross-sectional view illustrating an entire structure of a spindle motor.

FIG. 6 is a flowchart showing a process of fitting and fixing the frame and the bearing sleeve of the dynamic pressure bearing device according to the present invention.

FIG. 7 is an explanatory cross-sectional view showing a state in which a frame and a bearing sleeve of an HDD spindle motor having a conventional dynamic pressure bearing device are fitted and fixed.

FIG. 8 is a flowchart showing a process of fitting and fixing a frame and a bearing sleeve of a conventional hydrodynamic bearing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stator set 2 Rotor set 11 Frame (bearing support frame) 12 Bearing holder (bearing support frame) 12a Covering part 12b Annular protrusion 13 Bearing sleeve (bearing member) 13b Annular groove 21 Rotary shaft 22 Hard disk recording medium supporting hub

Continued on the front page (72) Inventor Shinji Ota 14-888 Ako, Komagane City, Nagano Prefecture Inside the Sankyo Seiki Seisakusho Komagane Plant

Claims (7)

[Claims] A shaft member provided so as to be relatively rotatable between a predetermined bearing support frame, a bearing member fitted and fixed to the bearing support frame, and a bearing member; A dynamic pressure generating groove formed on at least one of the opposed dynamic pressure surfaces provided on the bearing member and the shaft member; and a lubricating fluid interposed between the opposed dynamic pressure surfaces. A dynamic pressure bearing device that generates a dynamic pressure in a lubricating fluid by a pressurizing action of a generation groove and supports one of the bearing member and the shaft member in a floating state by the dynamic pressure. A dynamic pressure bearing device characterized in that the bearing and the bearing member are fitted and fixed by insert molding. 2. The bearing member according to claim 1, wherein said bearing member is formed of an easily oxidizable material, and insert molding is performed such that an exposed surface of said bearing member is covered with a coating member made of an oxidation resistant material. A hydrodynamic bearing device characterized by being made. 3. A hydrodynamic bearing device, wherein the covering member made of the oxidation-resistant material according to claim 2 forms a part of a bearing support frame. 4. A hydrodynamic bearing device, wherein the covering member made of the oxidation-resistant material according to claim 2 is fitted into the bearing member so as to prevent the coating member from falling off. 5. The dynamic pressure bearing device according to claim 1, wherein the bearing member according to claim 1 is made of a metal material, and the bearing member and the bearing support frame are formed by insert die casting. 6. A hydrodynamic bearing device, wherein one of the bearing member and the shaft member according to claim 1 comprises a rotating member for holding a hard disk recording medium. 7. A predetermined bearing support frame, a bearing member fitted and fixed to the bearing support frame, a shaft member provided so as to be relatively rotatable between the bearing member, and A dynamic pressure generating groove formed on at least one of the opposed dynamic pressure surfaces provided on the bearing member and the shaft member; and a lubricating fluid interposed between the opposed dynamic pressure surfaces. A method for producing a dynamic pressure bearing device in which a dynamic pressure is generated in a lubricating fluid by a pressurizing action of a generating groove and one of the bearing member and the shaft member is supported in a floating state by the dynamic pressure, The shape of the bearing member is processed from a blank material of the member, and the bearing member obtained thereby is set in a molding die of the bearing support frame body and insert-molded, whereby the bearing member and the bearing support frame body are formed. To be fixed Method of manufacturing a dynamic pressure bearing device, characterized in that.