JP2001032828A - Dynamic pressure type bearing and spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small dynamic pressure type bearing capable of generating higher dynamic pressure. SOLUTION: The depth of each dynamic pressure generating groove 11 is made to be gradually shallowed from an entrance toward a return point. As a result, the flow velocity at the return point 11A is higher than that at the entrance of the groove 11. Thus, higher dynamic pressure can be efficiently generated, compared with conventional configuration where the depth of the groove is not changed along the passage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of drawing a liquid with a rotation into a groove formed on either a rotating surface or a stationary surface facing the rotating surface and receiving a load by dynamic pressure generated by the liquid. And a spindle motor using the same.

[0002]

2. Description of the Related Art A shaft portion and a bearing portion for supporting the shaft portion are provided, and a dynamic pressure generating groove is formed on one of opposing surfaces thereof.
A liquid dynamic pressure type bearing that forms a layer of high-pressure lubricating oil etc. in a minute gap between the two when the shaft rotates, and realizes non-contact rotation of the shaft, is a bearing for spindle motors such as hard disk drives. It is used as

A dynamic pressure generating groove formed in a conventional dynamic pressure type bearing is generally of a spiral pattern or a herringbone pattern, but in either pattern, it follows the flow of liquid flowing therethrough. This is realized by forming a groove having a predetermined constant depth.

[0004]

In the case where the liquid is pressurized in such a dynamic pressure generating groove with its rotation, the liquid for generating the dynamic pressure often uses an oil-based liquid. ,
Since the liquid is an incompressible liquid, the pressure of the liquid flowing into the dynamic pressure generating groove increases along the streamline. In particular, in the case of a spiral pattern, the groove width becomes narrower along the streamline, so that a larger dynamic pressure can be generated.

[0005] By the way, the demand for miniaturization of various devices in the related art has increased, and thus a problem has arisen that a required dynamic pressure must be generated using a narrower area than in the related art. SUMMARY OF THE INVENTION An object of the present invention is to provide a dynamic pressure bearing having high dynamic pressure generation efficiency and a spindle motor using the same, which can solve the above-mentioned problems in the prior art.

[0006]

According to the present invention, there is provided, in accordance with the present invention, a shaft having a shaft and a bearing for supporting the shaft, wherein a pressure is generated on one of opposing surfaces thereof. In a dynamic pressure bearing in which a dynamic pressure generating groove for pressurizing a liquid is formed, a configuration is proposed in which the groove depth of the dynamic pressure generating groove is gradually reduced along a streamline of the pressure generating liquid. .

The pressure-generating liquid held between the shaft and the bearing is drawn into the dynamic pressure-generating groove by the relative rotational movement of the two. The pattern of the dynamic pressure generating groove may be an arbitrary pattern such as a spiral or herringbone. Then, the pressure generating liquid flows through the dynamic pressure generating groove by a streamline according to the groove pattern of the dynamic pressure generating groove, but since the depth of the dynamic pressure generating groove becomes shallower from the inlet to the inner side by the streamline,
As a whole, the pressure of the pressure generating liquid in the dynamic pressure generating groove is increased, and a higher dynamic pressure can be efficiently generated.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing an example of an embodiment of a dynamic pressure bearing according to the present invention. The dynamic pressure bearing shown in FIG. 1 is obtained by applying the present invention to a ring-shaped dynamic pressure bearing. The dynamic pressure bearing 1 includes a shaft body 2
Shaft 4 formed by fixing ring 3 to end 2A by press-fitting
And a bearing portion 5 for supporting the shaft portion 4.
The ring 3 of the shaft portion 4 rotatably housed in the concave portion 6A of the main body 6 comes out of the concave portion 6A and is pressed by the disc-shaped thrust pressing member 7.

Axial dynamic pressure generating grooves G1 and G2 are formed on the upper surface 3A and lower surface 3B of the ring 3, respectively, and a radial dynamic pressure generating groove G3 is formed on the peripheral surface 3C of the ring 3. Lubricating oil for generating dynamic pressure is held between the shaft portion 4 and the bearing portion 5. Therefore, when the shaft portion 4 rotates, an axial space is formed between the upper surface 3 </ b> A and the disc-shaped thrust holding member 7. Axial dynamic pressure is generated by the dynamic pressure generating groove G1, and axial dynamic pressure is generated by the axial dynamic pressure generating groove G2 between the lower surface 3B and the bottom surface of the recess 6A.
A radial dynamic body is generated between the peripheral surface 3C and the inner peripheral surface of the recess 6A by the radial dynamic pressure generating groove G3. As a result, an axial dynamic pressure bearing and a radial dynamic pressure bearing, which are high-pressure lubricating oil layers, are formed between the shaft portion 2 and the bearing portion 5, and the shaft portion 2 can rotate in a non-contact manner.

FIG. 2 is a plan view of an axial dynamic pressure generating groove G1 formed in the ring 3, and FIG. 3 is a sectional view taken along line AA of FIG. As can be seen from FIGS. 2 and 3, the groove pattern of the axial dynamic pressure generation groove G1 is a herringbone,
The axial dynamic pressure generating groove G1 has a large number of rectangular grooves 1
1 is formed in alignment with the upper surface 3A of the ring 3. The grooves 11 are formed such that the groove width at the entrance is a1 and the groove width at the turning point 11A is a2 (<a1). Then, as shown in FIG. 3, the depth of the groove gradually becomes shallower from the inlet to the turning point along the center line of the groove serving as the lubricating oil flow path. In the present embodiment, the groove depth at each entrance is d1, and the groove depth at the turning point 11A is d2 (<d1). The same applies to all the grooves 11.

Since the axial dynamic pressure generating groove G1 is configured as described above, when the shaft portion 4 and the bearing portion 5 rotate relatively, the upper surface 3A of the ring 3 and the rear surface 7A of the disc-shaped thrust holding member 7 are formed. 2 flows into each groove 11 of the axial dynamic pressure generating groove G1, and the lubricating oil flows along each groove 11 in a direction indicated by an arrow X in FIG. As is clear from the above, in each groove 11,
The groove cross-sectional area at the entrance is a1 × d1, and the groove cross-sectional area at the turning point 11A is a2 × d2. Here, a1
× d1> a2 × d2, and the compressibility of the lubricating oil is negligible. Therefore, between the lubricating oil flow velocity V1 at the inlet of the groove 11 and the lubricating oil flow velocity V2 at the turning point 11A, V1 = r × V2 where r = (a1 × d1) / (a2 × d2). The relationship is established.

That is, the flow velocity at the turning point 11A is higher than the flow velocity at the entrance of each groove 11, and as a result, compared with the conventional configuration (d1 = d2) in which the groove depth is not changed along the flow path. Higher dynamic pressure can be efficiently generated in a small area. Therefore, ring 3
If the area of the upper surface 3A is the same, the generated dynamic pressure can be made larger. Further, if the required dynamic pressure is the same, the area of the upper surface 3A can be smaller, and the size of the dynamic pressure bearing can be reduced.

Although the axial dynamic pressure generating groove G1 has been described in detail above, the axial dynamic pressure generating groove G2 is completely the same, so that the description of the configuration and effects of the axial dynamic pressure generating groove G2 will be omitted. Although the groove pattern of the axial dynamic pressure generating grooves G1 and G2 is a herringbone in the present embodiment, the groove depth is gradually increased along the flow path of the lubricating oil by using another groove pattern, for example, a spiral. Of course, a similar effect can be obtained even if the depth is reduced.

FIG. 4 shows a radial dynamic pressure generating groove G3 formed on the peripheral surface 3C of the ring 3. As shown in FIG. In the present embodiment, the radial dynamic pressure generating groove G3 is formed so that a large number of grooves 12 having a substantially constant width are aligned above and below the peripheral surface 3C of the ring 3, and the pattern of the grooves 12 is the same as that of the herringbone. Has become. As shown in FIG. 5, the groove 12
The depth of the groove is deepest at the entrance 12a, gradually becomes shallower toward the groove depth 12b, and becomes the shallowest at the groove depth 12b.

Since the radial dynamic pressure generating groove G3 is configured as described above, when the shaft portion 4 and the bearing portion 5 rotate relatively, the gap between the peripheral surface 3C of the ring 3 and the peripheral surface of the concave portion 6A is formed. 4 flows into each groove 12 of the radial dynamic pressure generating groove G3, and the lubricating oil flows along each groove 12 in a direction indicated by an arrow Y or Z in FIG. Radial dynamic pressure generating groove G
Also in the case of No. 3, similarly to the case of the axial dynamic pressure generating grooves G1 and G2, the cross-sectional area of the inlet 12a of each groove is the largest, the cross-sectional area of the groove depth 12b is the smallest, and the cross-sectional area of the groove is Since the flow rate is gradually reduced from the inlet 12 to the groove depth 12b, the flow speed at the groove depth 12b is faster than the flow speed at the inlet 12a of the groove 12, and as a result, the groove depth changes along the flow path. Higher dynamic pressure can be efficiently generated in a smaller area as compared with the conventional configuration in which no dynamic pressure is applied.

Therefore, when the area of the peripheral surface 3C of the ring 3 is the same, the generated radial dynamic pressure can be made larger. In addition, if the required radial dynamic pressure is the same, the area of the peripheral surface 3C may be smaller, and the size of the dynamic pressure bearing can be reduced. FIG.
FIG. 2 is a cross-sectional view showing an example of an embodiment of a spindle motor configured using the dynamic pressure bearing 1 shown in FIG. The spindle motor 21 has a dynamic pressure bearing 1 shown in FIG. That is, the bearing body 6 of the dynamic pressure bearing 1 is formed integrally with the base 22. A hub 23 is fixed to the shaft body 2 of the dynamic pressure bearing 1, and a rotor magnet 24 attached to the hub 23 and a stator coil 25 attached to the base 22 face each other with a small gap.

Since the spindle motor 21 is configured as described above, when a current flows through the stator coil 25, the hub 23 rotatably supported by the dynamic pressure bearing 1 is provided.
Can be rotated. In this case, since the dynamic pressure bearing 1 is configured as described above, the dynamic pressure generation efficiency is high, the shaft rigidity can be sufficiently increased even with a small size, and the device can be downsized. For this reason, by attaching a magnetic disk to the hub 23 by a known appropriate means, the magnetic disk can be rotated very stably even in a small size, and extremely high-density magnetic recording and reading can be performed by a small device. be able to.

[0018]

According to the present invention, as described above, the dynamic pressure generation efficiency can be increased, so that the area required for forming the dynamic pressure grooves can be reduced, and the dynamic pressure type can be reduced without lowering the shaft rigidity. The size of the bearing can be reduced. Further, if the area for forming the dynamic pressure bearing is the same, a higher dynamic pressure can be generated.

Further, by using the dynamic pressure bearing according to the present invention, a compact and highly stable spindle motor can be realized, and a compact and high-performance magnetic disk device can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an embodiment of a dynamic pressure bearing according to the present invention.

FIG. 2 is a plan view of an axial dynamic pressure generating groove formed in the ring of FIG. 1;

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a side view of the ring of FIG. 1;

FIG. 5 is a sectional view taken along line BB of FIG. 4;

FIG. 6 is a sectional view showing an example of an embodiment of a spindle motor configured using the dynamic pressure bearing shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing 2 Shaft main body 3 Ring 4 Shaft part 5 Bearing part 11 Groove 11A Turning point G1, G2 Axial dynamic pressure generating groove G3 Radial dynamic pressure generating groove a1, a2 Groove width d1, d2 Groove depth

Continued on the front page (72) Inventor Atsushi Ota 1-8-1, Nakase, Mihama-ku, Chiba-shi, Chiba Inside Seiko Instruments Inc. (72) Inventor Koji Nitori 1-8-1, Nakase, Mihama-ku, Chiba-shi, Chiba Seiko Instruments Inc. F term in the company (reference) 3J011 AA10 AA11 BA03 BA04 BA08 CA03 JA02 KA02 KA03 MA02 5H605 BB05 BB19 CC04 EB03 EB06 EB28 5H607 BB14 BB17 CC01 DD08 DD14 FF12 GG01 GG02 GG12

Claims (2)

[Claims] 1. A dynamic pressure bearing having a shaft portion and a bearing portion for supporting the shaft portion, wherein a dynamic pressure generating groove for pressurizing a pressure generating liquid is formed on one of opposing surfaces thereof. A dynamic pressure bearing wherein the depth of the dynamic pressure generating groove is gradually reduced along a streamline of the pressure generating liquid. 2. A spindle motor comprising the dynamic pressure bearing according to claim 1.