JP2003042143A - Hydrodynamic pressure bearing and spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fix a holding ring to a cylindrical opened end portion of a stepped sleeve with a single bag-shaped dead-end so that the holding ring and a thrust ring of a flanged shaft are aligned in parallel with each other, in the hydrodynamic pressure bearing in which the flanged shaft having the thrust ring, the stepped sleeve with a single bag-shaped dead-end, and the holding ring are major structural components. SOLUTION: The hydrodynamic pressure bearing is comprised of the flanged shaft 1, the stepped sleeve with a single bag-shaped dead-end forming a small- diameter cylinder portion, a large-diameter cylinder portion, and the cylindrical opened end portion in order, the holding ring 5 press-fitted the cylindrical opened end portion of the stepped sleeve 4 with a single bag-shaped dead-end by mating upper-end faces of both members each other, lubricating oil filled in a minute gap including a thrust gap and radial gap formed among these structural members, and a dynamic pressure generating groove arranged in the thrust gap and radial gap. Further, a connecting portion (w) between the holding ring 5 and the sleeve is jointed by means of slant-directional welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid dynamic pressure bearing having a flanged shaft, a one-sided bag-like stepped sleeve and a retaining ring as main components, and a rotor supported on a stator by the fluid dynamic pressure bearing. Regarding spindle motor,
Particularly, it relates to a structure for fixing the pressing ring to the cylindrical open end of the one-sided bag-like stepped sleeve.

[0002]

2. Description of the Related Art A spindle motor in which a rotor is supported on a stator by a fluid dynamic bearing mainly composed of a flanged shaft, a one-sided bag-like sleeve and a retaining ring is disclosed in, for example, Japanese Patent Laid-Open No. 11-218128. It is disclosed. FIG. 5 is a cross-sectional view of the spindle motor disclosed in the above patent publication, exaggeratingly showing a minute gap including a thrust gap and a radial gap.

In the spindle motor shown in FIG. 5, the rotor includes a cup-shaped hub 6 having a cylindrical skirt portion 6a and a boss portion 6b, and a rotor magnet 7 attached to the inner peripheral surface of the cylindrical skirt portion 6a. Further, the stator includes a base substrate 9 and a stator coil 8 attached to the outer peripheral surface of the sleeve 4 of the fluid dynamic bearing standing on the base substrate 9.

A fluid dynamic bearing for rotatably supporting the rotor on the stator comprises a thrust ring portion 3 and a column portion 2.
Shaft with flange 1 and cylindrical open end 4c
Single bag shaped stepped sleeve 4 having a pressure and a presser ring 5 press-fitted and fixed to the cylindrical open end 4c of the single bag shaped stepped sleeve 4.
And are the main constituent members.

The single bag stepped sleeve 4 has a small diameter cylindrical portion 4a formed on the closed end side thereof and a cylindrical open end portion 4c.
A large diameter cylindrical portion 4b is formed between the small diameter cylindrical portion 4a and the small diameter cylindrical portion 4a. When the flanged shaft 1 is inserted into the single bag-shaped stepped sleeve 4, the lower outer peripheral surface of the cylindrical portion 2 of the flanged shaft 1 faces the inner peripheral surface of the small diameter cylindrical portion 4a, and these surfaces form a radial gap. It is formed. A radial dynamic pressure generating groove G1 such as a herringbone groove is provided on the lower outer peripheral surface of the cylindrical portion 2 of the flanged shaft 1.

When the shaft with flange 1 is inserted into the one-bag stepped sleeve 4 and the pressing ring 5 is press-fitted and fixed to the cylindrical open end 4c of the one-bag stepped sleeve 4, the upper surface 3a of the thrust ring and the presser foot are pressed. The lower surface 5a of the ring 5 faces each other, and these surfaces form a first thrust gap. Further, the lower surface of the thrust ring and the surface of the step portion, which is the boundary surface between the large-diameter cylindrical portion and the small-diameter cylindrical portion, face each other, and these surfaces form a second thrust gap. The thrust dynamic pressure generating groove G2 as shown in FIG. 6 is provided on the upper and lower surfaces of the thrust ring 3.

Then, a radial gap formed between the main bearing constituent members of the shaft with flange 1, the stepped sleeve 4 having a single bag shape, and the pressing ring 5 and a minute gap including the first thrust gap and the second thrust gap, and Lubricating oil is filled in a minute gap formed between the inner peripheral surface of the pressing ring and the outer peripheral surface of the boss portion 6b of the cup-shaped hub 6.

By the way, in the fluid dynamic bearing having the above-mentioned structure, the pressing ring 5 is arranged in a single bag shape so that the lower surface 5a of the pressing ring 5 and the upper surface 3a of the thrust ring 3 of the shaft with flange 1 are parallel to each other. It is necessary to press-fit and fix it to the cylindrical open end of the attached sleeve 4. If the upper surface 3a of the thrust ring 3 of the flanged shaft 1 is not parallel and inclined, there is a problem that the thrust clearance is changed or shaft runout occurs during rotation.

In the conventional fluid dynamic pressure bearing shown in FIG. 5, the surface facing the outer peripheral surface of the pressing ring 5, that is, the inner peripheral surface of the cylindrical open end 4c of the one-bag stepped sleeve 4 is vertical. The apex of the inner peripheral surface is an acute angle, and the thickness of the pressing ring 5 is larger than the depth of the inner peripheral surface of the cylindrical open end 4c.

For this reason, when the pressing ring 5 is press-fitted and fixed to the cylindrical open end of the one-bag stepped sleeve 4, the pressing ring 5 is deformed by the stress of the sleeve. Further, since stress acts on the lower side of the pressing ring 5, the pressing ring 5 is deformed in a direction in which the pressing ring 5 floats on the inner diameter side at the abutting surface of the cylindrical open end portion 4c. Due to such a cause, the conventional fluid dynamic bearing has a problem that the lower surface 5a of the pressing ring 5 and the upper surface 3a of the thrust ring 3 of the flanged shaft 1 may not be parallel to each other. Further, there is a work-related cause that the pressing ring 5 is tilted when press-fitting.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a fluid dynamic bearing including a shaft with a flange having a thrust ring, a stepped sleeve having a one-sided bag, and a retaining ring as main components. The pressing ring is fixed to the cylindrical open end of the single bag-shaped stepped sleeve so that the thrust ring of the flanged shaft becomes parallel.

[0012]

In order to solve the above problems, a flanged shaft having a thrust ring portion and a cylindrical portion, a small diameter cylindrical portion, a large diameter cylindrical portion and a cylindrical open end portion are formed in order. A one-bag shaped stepped sleeve, a holding ring press-fitted into the cylindrical open end of the sleeve with the upper end surfaces of both members aligned, and a minute gap including thrust gaps and radial gaps formed between these constituent members. In the fluid dynamic pressure bearing including the lubricating oil sealed in, and the dynamic pressure generating groove provided in the thrust gap and the radial gap, the pressing ring is fixed to the sleeve by oblique welding.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a spindle motor according to an embodiment of the present invention, in which a minute clearance including a thrust clearance and a radial clearance is exaggeratedly shown.

In the spindle motor shown in FIG. 1, the rotor includes a cup-shaped hub 6 having a cylindrical skirt portion 6a and a boss portion 6b, and a rotor magnet 7 attached to the inner peripheral surface of the cylindrical skirt portion 6a. Further, the stator includes a base substrate 9 and a stator coil 8 attached to the outer peripheral surface of the sleeve 4 of the fluid dynamic bearing standing on the base substrate 9.

The fluid dynamic bearing for rotatably supporting the rotor on the stator is composed of a thrust ring portion 3 and a column portion 2.
Shaft with flange 1 and cylindrical open end 4c
Single bag shaped stepped sleeve 4 having a pressure and a presser ring 5 press-fitted and fixed to the cylindrical open end 4c of the single bag shaped stepped sleeve 4.
And are the main constituent members.

The single bag-shaped stepped sleeve 4 has a small diameter cylindrical portion 4a formed on the closed end side thereof and a cylindrical open end portion 4c.
A large diameter cylindrical portion 4b is formed between the small diameter cylindrical portion 4a and the small diameter cylindrical portion 4a. When the flanged shaft 1 is inserted into the single bag-shaped stepped sleeve 4, the lower outer peripheral surface of the cylindrical portion 2 of the flanged shaft 1 faces the inner peripheral surface of the small diameter cylindrical portion 4a, and these surfaces form a radial gap. It is formed. A radial dynamic pressure generating groove G1 such as a herringbone groove is provided on the lower outer peripheral surface of the cylindrical portion 2 of the flanged shaft 1.

When the flanged shaft 1 is inserted into the one-bag shaped stepped sleeve 4 and the pressing ring 5 is press-fitted and fixed to the cylindrical open end 4c of the one-bag shaped stepped sleeve 4, the upper surface 3a of the thrust ring and the presser foot are pressed. The lower surface 5a of the ring 5 faces each other, and these surfaces form a first thrust gap. Further, the lower surface of the thrust ring and the surface of the step portion, which is the boundary surface between the large-diameter cylindrical portion and the small-diameter cylindrical portion, face each other, and these surfaces form a second thrust gap. The thrust dynamic pressure generating groove G2 as shown in FIG. 6 is provided on the upper and lower surfaces of the thrust ring 3.

Then, a radial clearance, a first clearance, and a minute clearance including a second thrust clearance formed between the main bearing constituent members of the flanged shaft 1, the one-sided bag-shaped sleeve 4, and the pressing ring 5, and Lubricating oil is filled in a minute gap formed between the inner peripheral surface of the pressing ring and the outer peripheral surface of the boss portion 6b of the cup-shaped hub 6.

In the spindle motor disclosed in FIG. 1,
The fluid dynamic bearing has a joint structure different from that of the conventional fluid dynamic bearing shown in FIG. That is, in the fluid dynamic bearing according to the present invention, a joining structure is employed in which the single bag shaped stepped sleeve 4 and the pressing ring are joined by oblique welding.

In more detail, referring to FIG. 2, the flanged shaft 1 is inserted into the single bag-shaped stepped sleeve 4, and the pressing ring 5 is inserted into the cylindrical open end of the single bag-shaped stepped sleeve 4. Indicates the status.

In the fluid dynamic bearing subassembly of FIG.
As shown in FIG. 3 (A), the welding is performed by irradiating the contact portion between the two members with laser light for a short time from the oblique direction of the arrow. The portion where the laser light is irradiated and welded is the annular contact portion w between the pressing ring 5 and the single bag-shaped stepped sleeve 4.

According to such oblique welding, as shown in FIG.
As shown in, the amount of strain generated in the pressing ring 5 is small, and tilting and tilting with respect to the sleeve 4 are almost eliminated. Therefore, in the fluid dynamic bearing subassembly of FIG. 2, when the holding ring 5 is joined to the sleeve 4 by oblique welding, the holding ring 5 is fixed to the cylindrical open end of the sleeve 4 without being deformed or tilted. To be done. Therefore, the parallelism between the pressing ring 5 and the thrust ring 2 of the flanged shaft 1 is reliably maintained.

Incidentally, comparing the oblique welding shown in FIG. 3 with the conventional vertical welding shown in FIG. 4, it can be seen that the thermal stresses of the two are different. That is, in the conventional vertical welding, since the thermal stress is applied perpendicularly to the joint portion of the parts, the pressing ring 5 is easily distorted or tilted with respect to the sleeve 4.
On the other hand, in the oblique welding, since the thermal stress is applied obliquely to the joint portion of the components, the amount of distortion of the pressing ring 5 or inclination of the pressing ring 5 becomes very small.

According to the present invention, in a fluid dynamic bearing including a flanged shaft having a thrust ring, a one-sided bag-like stepped sleeve and a pressing ring as main components, the pressing ring and the flanged shaft are parallel to each other. As described above, the pressing ring can be fixed to the cylindrical open end of the one-sided stepped sleeve by welding. Since it is fixed by diagonal welding, the presser ring does not deform,
Therefore, in the spindle motor provided with this fluid dynamic pressure bearing, the shaft runout due to the deformation of the pressing ring disappeared.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a spindle motor according to an embodiment of the present invention in which a minute gap is exaggeratedly shown.

FIG. 2 is a sectional view of a subassembly of a fluid dynamic bearing portion according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of oblique welding in which a laser beam is applied to a component joint portion from an oblique direction.

FIG. 4 is an explanatory diagram of vertical welding in which laser light is emitted from a vertical direction to a component joint.

FIG. 5 is a cross-sectional view of a conventional spindle motor in which a minute gap is exaggeratedly shown.

FIG. 6 is a plan view of a thrust ring in which a thrust dynamic pressure generating groove G2 is formed.

[Explanation of symbols]

1 Shaft with flange 2 column 3 thrust ring 4 Single bag step sleeve 4c Cylindrical open end 5 Presser ring 6 cup-shaped hub 6a Cylindrical skirt part 6b Boss 7 rotor magnet 8 Stator coil 9 Base substrate G1 radial dynamic pressure generating groove G2 thrust dynamic pressure generating groove w Welded joint

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ryoji Yoneyama             1-8 Nakase, Nakase, Mihama-ku, Chiba City, Chiba Prefecture             Ico Instruments Co., Ltd. F-term (reference) 3J011 AA01 BA04 BA08 CA02 DA02                       JA02 KA02 KA03 KA05                 5H605 AA00 AA04 BB05 BB19 CC04                       CC05 EB01 EB03 EB21 GG02                 5H607 AA04 BB01 BB14 BB17 CC01                       DD01 DD02 DD03 DD16 GG01                       GG03 GG12 GG15 GG25 JJ04                 5H615 AA01 BB01 BB14 PP01 PP02                       PP24 PP25 PP28 SS17                 5H621 AA00 GB00 HH01 JK17 JK19

Claims (2)

[Claims] 1. A flanged shaft having a thrust ring portion and a cylindrical portion, a single bag shaped stepped sleeve in which a small diameter cylindrical portion, a large diameter cylindrical portion and a cylindrical open end are formed in order, and a cylinder of the sleeve. The press-fitting ring that press-fits the upper end surfaces of both members to the cylindrical open end, lubricating oil enclosed in a minute gap including thrust gaps and radial gaps formed between these component members, and the thrust gap. A fluid dynamic bearing comprising a dynamic pressure generating groove provided in a radial gap, wherein the joint between the pressing ring and the sleeve is joined by oblique welding. 2. A spindle motor in which a rotor is rotatably supported by a stator by the fluid dynamic pressure bearing of claim 1.