JP2001140866A - Fluid dynamic pressure bearing and spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the forming process of the dynamic grooves of a ring member and to reduce the product cost in a fluid dynamic pressure bearing having a flanged shaft constituted of the ring member formed with the thrust dynamic pressure grooves on the upper face and the lower face and the radial dynamic pressure grooves on the outer periphery respectively and a columnar member. SOLUTION: A blank ring 3a formed with annular notches W at edge sections is prepared in a preparation process (a). The radial dynamic pressure grooves G1 are formed on the blank ring 3a in a radial dynamic pressure groove forming process (b), The columnar member 2 is inserted into a half-machined ring 3b in a thrust dynamic pressure groove forming process (c), the half-machined ring 3b is arranged in a sizing ring H, a thrust groove machining die is set in a preparation stage, then the thrust groove machining die is pressed by a press machine, the thrust dynamic pressure grooves are formed on the upper face and the lower face of the half-machined ring 3b, and the pressing-in of the columnar member 2 is completed. The bulges of the edge portions of the half-machined ring 3b by pressing can be absorbed by the annular notches W, and the conventional post-process is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a ring member having thrust dynamic pressure grooves formed on its upper and lower surfaces and a radial dynamic pressure groove formed on its outer peripheral surface, respectively, and a cylindrical member press-fitted into the ring member. A fluid dynamic pressure bearing having a flanged shaft and a sleeve on which the flanged shaft is rotatably fitted as a basic constituent member, wherein a thrust dynamic pressure groove and a radial dynamic pressure groove are formed by an improved dynamic pressure groove machining process. The present invention relates to a fluid dynamic bearing having a formed ring member.

[0002]

2. Description of the Related Art A conventional fluid dynamic pressure bearing shown in FIG. 7 has a flanged shaft 1 formed by press-fitting a ring member 3 as a thrust member into a cylindrical member 2, and the flanged shaft 1 is rotatable. Stepped cylindrical sleeve 4 to be fitted
And an annular lid member 5 which also functions as a thrust holding member
It is composed of The minute gaps R1, R2, R3, R4 and R5 formed between these bearing components are filled with lubricating oil F. The tapered micro-gap S formed between the outer peripheral surface on the upper side of the cylindrical member 2 and the inner peripheral surface of the annular lid member 5 is formed by a lubricating oil F utilizing capillary action and surface tension.
Is a capillary seal that functions to prevent leakage to the outside. A radial dynamic pressure groove G1 such as a herringbone groove is formed on the lower outer peripheral surface of the cylindrical member 2, and the ring member 3
A spiral thrust dynamic pressure groove G2 such as a herringbone groove is formed on the upper surface and the lower surface, respectively.

[0003] With the rapid spread of portable electronic devices, there has been a demand for downsizing and weight reduction of a spindle motor as a rotary drive source thereof. As a result, fluid dynamic pressure bearings widely used for spindle motor bearings have been required to be further reduced in size and weight. Therefore, as shown in FIG. 6, a fluid motion including a flanged shaft 1 composed of a ring member 3 and a cylindrical member 2, a sleeve 4 for receiving the flanged shaft 1, and an annular lid member 5 also functioning as a thrust holding member. In the pressure bearing, spiral thrust dynamic pressure grooves G2 such as herringbone grooves are formed on the upper and lower surfaces of the ring member 3, and radial dynamic pressure grooves G1 such as herringbone grooves are formed on the outer peripheral surface of the ring member 3, respectively. Thin fluid dynamic pressure bearing formed by filling lubricating oil F into minute gaps R1, R2, R3, and R5 formed between the bearing component members and the thrust direction circulation hole Q provided in the ring member 3. Was developed.

Conventionally, a ring member 3 is provided with a thrust dynamic pressure groove G2.
Forming the radial dynamic pressure groove G1 by rolling or etching on the outer peripheral surface of a blank ring having a flat surface and a predetermined size, and forming the radial dynamic pressure groove G1. A thrust dynamic pressure groove forming step of pressing a groove machining die on both surfaces of the semi-processed ring on which a thrust dynamic pressure groove is formed, and a processed ring in which a radial dynamic pressure groove and a thrust dynamic pressure groove are formed. Three steps of a swelling adjustment step of cutting off the swelling of the edge portion were required. The radial dynamic pressure groove forming step and the thrust dynamic pressure groove forming step can be automated, but the bulge adjusting step has to be manually performed. For this reason, conventionally, there has been a problem that the ring member 3 cannot be machined in large quantities at low cost, and the cost of a thin fluid dynamic bearing cannot be reduced.

[0005]

SUMMARY OF THE INVENTION An object to be solved by the present invention is to provide a ring member having thrust dynamic pressure grooves formed on its upper and lower surfaces and a radial dynamic pressure groove formed on its outer peripheral surface, respectively. In a fluid dynamic pressure bearing having a flanged shaft composed of a press-fitted cylindrical member and a sleeve into which the flanged shaft is rotatably fitted, a thrust dynamic pressure groove and a radial dynamic pressure are formed on the ring member. An object of the present invention is to reduce a product cost by shortening a groove forming process for forming a groove and performing automation.

[0006]

In order to solve the above-mentioned problems, a thrust dynamic pressure groove is formed on an upper surface and a lower surface thereof, and a radial dynamic pressure groove is formed on an outer peripheral surface of the ring member. In a fluid dynamic pressure bearing having a flanged shaft composed of a cylindrical member and a sleeve on which the flanged shaft is rotatably fitted as a basic component, a radial dynamic pressure is formed on the outer peripheral surface by rolling or etching. A semi-processed ring having a groove formed therein was arranged in a sizing ring, and a groove forming die was pressed on both surfaces thereof to form a thrust dynamic pressure groove to process the ring member.

A flanged shaft comprising a ring member having thrust dynamic pressure grooves formed on its upper and lower surfaces and radial dynamic pressure grooves formed on its outer peripheral surface, respectively, and a cylindrical member press-fitted into the ring member. In a manufacturing process of a fluid dynamic bearing in which a flanged shaft is rotatably fitted as a basic constituent member and air pockets are formed at boundaries between a thrust bearing gap and a radial bearing gap, an edge thereof is formed. A semi-processed ring in which a circular cut with a right angle or an acute angle is formed in the section and a radial dynamic pressure groove is formed on the outer peripheral surface by rolling or etching is arranged in a sizing ring, and groove processing dies are formed on both surfaces thereof. The ring member was processed by pressing to form a thrust dynamic pressure groove.

Further, in the semi-processed ring having the radial dynamic pressure grooves formed therein, a thrust dynamic pressure groove is formed after the cylindrical member constituting the shaft with flange is inserted, thereby eliminating the step of press-fitting the cylindrical member. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fluid dynamic pressure bearing according to an embodiment of the present invention shown in a longitudinal sectional view in FIG. 1 receives a flanged shaft 1 comprising a ring member 3 and a cylindrical member 2, and receives the flanged shaft 1. It is composed of a sleeve 4 and an annular lid member 5 which also functions as a thrust holding member. A spiral thrust dynamic pressure groove G2 such as a herringbone groove is formed on the upper and lower surfaces of the ring member 3, and a radial dynamic pressure groove G such as a herringbone groove is formed on the outer peripheral surface thereof.
1 are formed respectively. Further, minute gaps R1, R2, R3, and R formed between these bearing components.
5 and a plurality of thrust direction circulation holes Q provided in the ring member 3 are filled with lubricating oil F. Column member 2
The tapered minute gap S formed between the outer peripheral surface on the upper side and the inner peripheral surface of the annular lid member 5 is a capillary which functions so as not to leak the lubricating oil F to the outside by utilizing capillary action and surface tension. It is a seal.

At the upper and lower edges of the ring member 3, annular notches W for air pockets are respectively formed. The cross section of the annular notch W is a right angle as shown in FIG. 2A or an acute angle as shown in FIG. 2B.

By the way, the thrust dynamic pressure groove is formed in the ring member 3.
The dynamic pressure distribution of the conventional fluid dynamic bearing shown in FIG. 7 in which the radial dynamic pressure grooves are formed in the cylindrical member 2 is shown in FIG.
As shown in (a), the thrust dynamic pressure is generated on the upper and lower surfaces of the ring member 3, and the radial dynamic pressure is generated on the lower outer peripheral surface of the cylindrical member 2.

On the other hand, both the thrust dynamic pressure groove and the radial dynamic pressure groove are formed in the ring member 3, and the dynamic dynamic bearing of the present invention shown in FIG. 1 and the conventional fluid dynamic bearing shown in FIG. In the pressure distribution, as shown in FIG. 5B, the thrust dynamic pressure is generated on the upper and lower surfaces of the ring member 3 and the radial dynamic pressure is generated on the outer peripheral surface of the ring member 3. Therefore, at the boundary between the thrust bearing gap R1 and the radial bearing gap R2 and at the boundary between the thrust bearing gap R3 and the radial bearing gap R2, a negative pressure (a pressure lower than the atmospheric pressure) and oil shortage are likely to occur. If negative pressure occurs or oil runs out,
The fluid dynamic bearing cannot maintain smooth rotation, and in some cases, the shaft may come into contact with the sleeve and seize. By the way, the lubricating oil F contains bubbles, though slightly. This bubble is compressed during high speed rotation,
Caught in the air pocket. Then, since the compressible air serves as a damper, no negative pressure is generated at the boundary between the bearing gaps. As described above, the air pocket functions to catch air bubbles existing in the minute gap, to prevent air bubbles from being included in the moving lubricant, and to prevent oil from running out in the bearing gap. . In addition, the lubricating agent is applied to the surface of the annular notch W, so that air bubbles can be easily caught in the air pocket.

Conventionally, it has been difficult to form an air pocket in a fluid dynamic bearing provided with a flanged shaft in which both a thrust dynamic pressure groove and a radial dynamic pressure groove are formed in a ring member 3. By using the method of processing the ring member 3 described with reference to FIG. 1, an effective air pocket is formed in the fluid dynamic bearing of FIG.

FIG. 3 shows a process of forming the flanged shaft 1 including a step of forming a thrust dynamic pressure groove and a radial dynamic pressure groove in the ring member 3 employed in the fluid dynamic pressure bearing according to the present invention. This shows a processing step of the flanged shaft 1 which does not require the press-fitting step of the cylindrical member 2. The dynamic pressure groove forming step includes three steps: a preparation step (a), a radial dynamic pressure groove forming step (b), and a thrust dynamic pressure groove forming step (c). In the preparation step (a), a blank ring 3a is formed by cutting annular notches W (not shown) as shown in FIG. next,
In the radial dynamic pressure groove forming step (b), the blank ring 3
A radial dynamic pressure groove G1 is formed by rolling or etching on the outer peripheral surface of a. Subsequently, in the thrust dynamic pressure groove forming step (c), there is a preparation stage before the thrust dynamic pressure groove forming stage. That is, the step of inserting the cylindrical member 2 into the ring hole of the semi-processed ring 3b in which the radial dynamic pressure groove G1 is formed, the step of disposing the semi-processed ring 3b into which the cylindrical member 2 is inserted in the sizing ring H, This is a step of setting a pair of dies for processing a thrust groove (not shown) on the upper surface and the lower surface. After this preparatory stage, the thrust groove processing die is pressed in the direction of the arrow by a press machine (not shown) to form thrust dynamic pressure grooves on the upper and lower surfaces of the semi-processed ring 3b.

Pressing causes the semi-finished ring 3b to expand in the radial direction. However, the outer diameter direction is restricted by the sizing ring H and the inner diameter direction is restricted by the columnar member 2. Then, pressure escapes to the upper and lower edge portions of the semi-processed ring 3b, and this portion slightly expands. However, since an annular cutout W is formed at the edge portion, the annular cutout W absorbs a swelling due to the pressing pressure. By absorbing the bulge, the size of the annular notch W is reduced by that amount, but since the bulge is formed to the predetermined size from the beginning, the function of the air pocket is not impaired. Since the cylindrical member 2 is pressed in the radial direction from the semi-finished ring 3b, the cylindrical member 2 is pressed into the semi-finished ring 3b. In this case, there is also an advantage that the cylindrical member 2 is press-fitted into the ring member 3 with a good perpendicularity.

As is clear from the above description, the sizing ring H is a metal protection ring for protecting the ring so that the outer diameter of the ring does not change even when a pressing pressure is applied. Therefore, the inner diameter of the sizing ring H used in the thrust dynamic pressure groove forming step (c) in FIG. 3 is slightly larger than the outer diameter of the semi-finished ring 3b, and the thickness thereof is the same as that of the semi-finished ring 3b. Things. Also,
The thrust groove processing die is a general die in which projections having the same pattern as the thrust groove are formed on the surface thereof. Further, press machines are also common.

A flanged shaft 1 comprising a ring member 3 having a thrust dynamic pressure groove G2 and a radial dynamic pressure groove G1 formed through the above-described steps, and a cylindrical member 2 pressed into the ring member 3 is shown in FIG. Is as shown in the perspective view.

According to the dynamic pressure groove forming step of FIG. 3, the radial dynamic pressure grooves and the thrust dynamic pressure grooves can be formed in the blank ring without inserting the cylindrical member into the semi-finished ring.
In this case, in the preparation step (a), a blank ring 3a having a predetermined size is prepared. In this case, it does not matter whether the blank ring has the annular notch W. Next, in the radial dynamic pressure groove forming step (b), a radial dynamic pressure groove G1 is formed on the outer peripheral surface of the blank ring 3a by rolling or etching.
Subsequently, in the thrust dynamic pressure groove forming step (c), there is a preparation stage before the thrust dynamic pressure groove forming stage. That is, the step of arranging the semi-finished ring 3b in the sizing ring H and the step of setting a pair of dies for thrust groove processing (not shown) on the upper and lower surfaces thereof. After this preparation stage,
A thrust groove processing die is pressed in the direction of the arrow by a press (not shown) to form thrust dynamic pressure grooves G2 on the upper surface and the lower surface of the semi-finished ring 3b. By pressing, the semi-finished ring 3b expands in the radial direction. However, the outer diameter direction is restricted by the sizing ring H. Thus, the semi-processed ring 3b slightly expands in the unrestricted inner diameter direction. Therefore, the swelling of the edge portion of the semi-processed ring 3b which occurred in the conventional dynamic pressure groove forming process without using the sizing ring is eliminated. Although the inner diameter direction slightly expands, the reduction of the inner diameter due to the expansion does not hinder the press-fitting of the cylindrical member 2 by determining the inner diameter of the blank ring, that is, the size of the ring hole.

The thin small-sized spindle motor in which the rotor is rotatably supported on the stator by the above-mentioned fluid dynamic bearing is configured such that the cup-shaped hub 6 is a part of the rotor and the sleeve 4 is a part of the stator. I have. That is, a stator coil is disposed on the outer peripheral surface of the sleeve 4 fixed at a predetermined position on the motor substrate, and a rotor magnet is disposed on the inner peripheral surface of the cup-shaped hub 6. When an exciting current is supplied to the stator coil, the rotor supported by the fluid dynamic bearing rotates due to electromagnetic interaction between the exciting current and the magnetic field of the rotor magnet. I do. The cup-shaped hub 6 on which a rotating body such as a magnetic disk is mounted is formed integrally with the cylindrical member 2 of the flanged shaft 1 in FIG.
These may be manufactured separately.

[0020]

According to the present invention, a sizing ring is used, and a semi-processed ring having radial dynamic pressure grooves formed on the outer peripheral surface thereof by rolling or etching is arranged in the sizing ring, and grooves are formed on both surfaces thereof. The die is pressed to form a thrust dynamic pressure groove. Therefore, the edge of the semi-processed ring does not expand after the formation of the thrust dynamic pressure groove, and the post-process is not required, so that the manufacturing process of the ring member can be shortened. For this reason, the conventional manual post-process is eliminated, so that the manufacturing process is automated, and a large number of fluid dynamic bearings can be provided at low cost.

Further, in the fluid dynamic bearing according to the present invention, the upper and lower edges of the blank ring are provided with annular notches having a right angle or an acute angle in cross section, and the thrust dynamic pressure grooves are formed in the above-described steps. The air pockets can be easily formed, and therefore the manufacturing cost of the fluid dynamic bearing having the air pockets can be reduced. In this case, after the cylindrical member is inserted into the semi-processed ring having the radial dynamic pressure grooves formed therein, the thrust dynamic pressure grooves are formed on both surfaces thereof. Shaft formation can be performed simultaneously. Therefore, the step of press-fitting the cylindrical member into the ring member becomes unnecessary, and the manufacturing process can be further shortened.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of a fluid dynamic bearing according to the present invention.

FIG. 2 is a cross-sectional view of a part of a ring member having an annular notch.
Indicates an annular notch having a sharp cross section.

FIG. 3 is a view showing a dynamic pressure groove processing step.

FIG. 4 is a perspective view of a flanged shaft having a ring member in which a thrust dynamic pressure groove and a radial dynamic pressure groove are respectively formed.

5A and 5B are diagrams showing a dynamic pressure distribution of a fluid dynamic pressure bearing. FIG. 5A shows a dynamic pressure of a fluid dynamic bearing in which a thrust dynamic pressure groove is formed in a ring member and a radial dynamic pressure groove is formed in a cylindrical member. (B) shows the dynamic pressure distribution of the fluid dynamic pressure bearing in which both the thrust dynamic pressure groove and the radial dynamic pressure groove are formed in the ring member.

FIG. 6 is a longitudinal sectional view of a conventional fluid dynamic pressure bearing in which both a thrust dynamic pressure groove and a radial dynamic pressure groove are formed in a ring member.

FIG. 7 is a longitudinal sectional view of a conventional fluid dynamic bearing in which a thrust dynamic pressure groove is formed in a ring member and a radial dynamic pressure groove is formed in a cylindrical member.

[Explanation of symbols]

 Reference Signs List 1 shaft with flange 2 cylindrical member 3 ring member 4 sleeve 5 annular lid member 6 cup-shaped hub F lubricating oil G1 radial dynamic pressure groove G2 thrust dynamic pressure groove H sizing ring Q1, Q2 lubrication oil circulation holes R1, R2, R3, R4, R5 Small gap S Tapered small gap (capillary seal) W Annular notch

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J011 AA20 BA04 BA08 CA02 DA02 JA02 KA02 KA03 LA05 MA12 PA03 SB01 5H607 BB01 CC01 FF12 GG01 GG02 GG09 GG12 GG14

Claims (4)

[Claims] 1. A flanged shaft comprising: a ring member having thrust dynamic pressure grooves formed on its upper and lower surfaces and radial dynamic pressure grooves formed on its outer peripheral surface; and a cylindrical member press-fitted into the ring member. In a fluid dynamic bearing in which a flanged shaft is rotatably fitted with a sleeve as a basic constituent member, the ring member is semi-processed in which a radial dynamic pressure groove is formed on the outer peripheral surface by rolling or etching. A fluid dynamic pressure bearing characterized in that a ring is disposed in a sizing ring, and a thrust dynamic pressure groove is formed by pressing a groove forming die on both surfaces thereof. 2. A flanged shaft comprising a ring member having thrust dynamic pressure grooves formed on the upper and lower surfaces thereof and a radial dynamic pressure groove formed on its outer peripheral surface, respectively, and a cylindrical member press-fitted into the ring member. In a fluid dynamic pressure bearing in which a flanged shaft is rotatably fitted as a basic component and an air pocket is formed at a boundary portion between a thrust bearing gap and a radial bearing gap, the ring member includes: A semi-processed ring in which a circular cut with a right angle or an acute angle is formed at the edge and a radial dynamic pressure groove is formed on the outer peripheral surface by rolling or etching is arranged in a sizing ring, and grooves for forming grooves are formed on both surfaces thereof. Wherein a thrust dynamic pressure groove is formed by pressing the fluid dynamic pressure bearing. 3. The semi-processed ring in which the radial dynamic pressure grooves are formed is disposed in a sizing ring after the cylindrical member is inserted, and a groove forming die is pressed on both surfaces thereof to form a thrust dynamic pressure groove. The fluid dynamic pressure bearing according to claim 1, wherein the fluid dynamic bearing is formed. 4. A spindle motor in which a rotor is rotatably supported on a stator by the fluid dynamic pressure bearing according to claim 1.