JPH09229055A - Dynamic pressure bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To escape static electricity accumulated on a rotary shaft to a housing. SOLUTION: This dynamic bearing is provided with radial holes 13, 14 drilled inward in the radial direction on the cylindrical face 1A of a rotary shaft 1. Steel balls 15, 16 are slidably inserted into the radial holes 13, 14. When the rotary shaft 1 is rotated, the steel balls 15, 16 are slided outward in the radial direction by centrifugal force, and contacted with the inner circumferential face 3B of a housing 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a dynamic pressure bearing used for a D (hard disk drive) spindle motor or the like.

[0002]

2. Description of the Related Art Conventionally, as this type of dynamic pressure bearing, HD
Some are built into the D spindle motor. In this dynamic pressure bearing, the rotary shaft and the housing do not come into contact with each other during rotation, and only the fluid for generating the dynamic pressure is interposed between the rotary shaft and the housing. Therefore, this dynamic pressure bearing is particularly suitable for supporting a rotating shaft that rotates at a high speed.

However, in the above dynamic pressure bearing, since static electricity cannot be released from the rotary shaft to the housing, there is a problem that the magnetic head of the HDD is damaged by the static electricity accumulated on the rotary shaft.

When a rolling bearing is used instead of the dynamic pressure bearing, static electricity accumulated on the rotating shaft can escape to the housing side through balls, so that the magnetic head is not damaged. Since the frictional resistance of the balls, especially the torque loss due to the static frictional resistance is large as compared with the dynamic pressure bearing, it is not suitable for supporting the shaft of a precision machine such as an HDD rotating at high speed.

[0005]

Therefore, an object of the present invention is to maintain the advantage of being suitable for high-speed rotation,
An object of the present invention is to provide a dynamic pressure bearing capable of releasing static electricity accumulated on the rotating shaft to the housing.

[0006]

In order to achieve the above object, the invention of claim 1 is such that a radial supporting dynamic pressure groove is formed on the cylindrical surface of the rotating shaft or on the inner peripheral surface of the housing facing the cylindrical surface. In the dynamic pressure bearing, at a position separated from the radial support dynamic pressure groove by a predetermined distance in the axial direction,
It is characterized in that a radial hole is bored inward in the radial direction on the cylindrical surface of the rotary shaft, and a conductor is inserted into the radial hole so as to be slidable in the radial direction.

According to the first aspect of the present invention, when the rotary shaft rotates, the radial supporting dynamic pressure groove generates a dynamic pressure in the fluid between the cylindrical surface of the rotary shaft and the inner peripheral surface of the housing. And supports the rotating shaft in the radial direction with respect to the housing.

At this time, the electric conductor inserted in the radial hole of the rotary shaft receives a centrifugal force due to the rotation, slides radially outward, and protrudes from the cylindrical surface to the inner peripheral surface of the housing. Contact. Then, static electricity transferred from the rotating shaft to the conductor is transferred from the conductor to the housing. This allows static electricity to escape from the rotary shaft to the housing.

According to a second aspect of the present invention, in the dynamic pressure bearing according to the first aspect, the radial hole is radially inside the cylindrical surface due to the weight of the conductor when the rotary shaft is stationary. It is characterized by being shaped so that it can be immersed in one direction.

Therefore, according to the second aspect of the invention, since the conductor does not contact the inner peripheral surface of the housing when the rotating shaft is stationary, increase in the starting resistance can be avoided.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the embodiments shown in the drawings.

[First Embodiment] FIG. 1 shows a first embodiment of a dynamic pressure bearing of the present invention. The first embodiment includes a rotary shaft 1 and a housing 2. The housing 2 has a tubular portion 3 and a bottom plate 5 fixed to an end surface 3A of the tubular portion 3. Radial supporting dynamic pressure grooves 8 and 10 are formed in bearing surfaces 6 and 7 of an inner peripheral surface 3B of the cylindrical portion 3 facing the cylindrical surface 1A of the rotating shaft 1. The dynamic pressure grooves 8 and 10 are axially separated from each other by a predetermined distance. A large diameter surface 11 having a larger diameter than the bearing surfaces 6 and 7 is formed between the dynamic pressure grooves 8 and 10.

On the other hand, an axial supporting dynamic pressure groove 12 is formed on the inner surface 5A of the bottom plate 5 facing the axial end surface 1B of the rotary shaft 1.

Radial holes 13 and 14 are bored inward in the cylindrical surface 1A of the rotary shaft 1 at a position facing the large diameter surface 11 of the housing 2. The radial holes 13 and 14 are out of phase with each other by about 180 ° in the circumferential direction. Further, the radial holes 13 and 14 are inclined so as to approach the end surface 1B inward in the radial direction.

Steel balls 15 and 16 are slidably inserted into the inclined radial holes 13 and 14, respectively.

In the hydrodynamic bearing having the above structure, when the rotary shaft 1 rotates with respect to the housing 2, the hydrodynamic groove 8 and the bearing surface 7 of the bearing surface 6 formed on the inner peripheral surface 3B of the tubular portion 3 of the housing 2 are formed. The dynamic pressure groove 10 generates a dynamic pressure in the fluid existing between the rotary shaft 1 and the housing 2 to support the rotary shaft 1 in the radial direction with respect to the housing 2. On the other hand, the axial supporting dynamic pressure groove 12 formed in the bottom plate 5 of the housing 2 generates a dynamic pressure in the fluid to support the rotary shaft 1 in the axial direction with respect to the housing 2.

At this time, the balls 15 and 16 inserted into the radial holes 13 and 14 of the rotary shaft 1 are subjected to centrifugal force due to the rotation and slid outward in the radial direction to project from the cylindrical surface 1A. , Contacts the inner peripheral surface 3B of the tubular portion 3 of the housing 2. Then, the static electricity transferred from the rotating shaft 1 to the balls 15 and 16 is transferred from the balls 15 and 16 to the tube portion 3. As a result, static electricity can be released from the rotary shaft 1 to the housing 2. Therefore, according to this embodiment, H
When used in a DD spindle motor, it is possible to prevent the magnetic head connected to the rotary shaft 1 from being damaged by static electricity. Further, since only centrifugal force acts on the balls 15 and 16 at the time of rotation, the torque required for rotation is hardly increased by the frictional resistance due to contact with the housing 2.

According to this embodiment, the rotary shaft 1
At rest, the balls 15 and 16 have slanted radial holes 13
And 14 inward in the radial direction, and the cylindrical surface 1A
More immersive. Therefore, when the rotary shaft 1 is stationary,
Since the balls 15 and 16 do not come into contact with the inner peripheral surface 3B of the tubular portion 3 of the housing 2, it is possible to avoid an increase in starting resistance.

Second Embodiment Next, FIG. 2 shows a second embodiment of the dynamic pressure bearing of the invention. The second embodiment constitutes a spindle motor of HDD. This embodiment includes a rotary shaft 21 and a housing 22. One end portion 21A in the axial direction of the rotary shaft 21 is fitted and fixed in the central hole 24A of the lid portion 24 of the outer cylinder 23. A rotor 29 is fixed to the inner peripheral surface 23A of the outer cylinder 23.

On the other hand, the housing 22 has a rotary shaft 21.
It has a tubular portion 25 that surrounds the outer periphery, a lid portion 26 that is fixed to an end surface 25A of the tubular portion 25, and a bearing plate 27 that is fixed to an inner surface 26A of the lid portion 26. The bearing plate 27 has an end surface 21B of the large-diameter end 21B of the rotary shaft 21.
-1 is facing. Then, the inner surface 2 of the bearing plate 27
An axial supporting dynamic pressure groove 35 is formed in 7A. Then, the outer peripheral surface 2 of the tubular portion 25 of the housing 22
5B, the stator 2 is placed so as to face the rotor 29.
8 is fixed. A bottom plate 30 is fitted and fixed to the outer peripheral surfaces of the tubular portion 25 and the lid portion 26. The bottom plate 30 has a larger diameter than the outer cylinder 23.

The tubular portion 25 of the housing 22
Has radial bearing surfaces 31 and 32 axially separated by a predetermined dimension from the inner peripheral surface 25C. Radial bearing dynamic pressure grooves 33 and 34 are formed in the radial bearing surfaces 31 and 32. Further, the large-diameter inner peripheral surface 25D of the tubular portion 25 is opposed to the large-diameter end portion 21B of the rotary shaft 21. The large-diameter end portion 21B has radial holes 38 and 40 bored inward from the cylindrical surface 37 in the radial direction. The radial holes 38, 40 are formed in the end face 21B-
It is inclined to approach 1. Further, the two radial holes 38, 40 are out of phase with each other by about 180 ° in the circumferential direction. Steel balls 41 and 42 are inserted into the radial holes 38 and 40. The balls 41 and 42 can freely slide in the radial holes 38 and 40 in the radial direction.

According to the above embodiment, when the rotor 29 rotates with respect to the stator 28, the rotary shaft 21 rotates with respect to the housing 22, and the dynamic pressure grooves 33, 3 for radial support are provided.
4 generates a dynamic pressure in the radial direction, and supports the rotary shaft 21 in the radial direction with respect to the housing 22. At the same time, the axial supporting dynamic pressure groove 35 generates a dynamic pressure in the axial direction,
The rotating shaft 21 is axially supported with respect to the housing 22.

At this time, the above two balls 41, 4
2 receives the centrifugal force, moves radially outward in the radial holes 38, 40, projects from the cylindrical surface 37, and contacts the large-diameter inner peripheral surface 25D of the cylindrical portion 25. Then, the static electricity accumulated on the rotating shaft 21 moves from the balls 41 and 42 to the housing 22, and further moves from the housing 22 to the bottom plate 30. Therefore, static electricity can be released from the rotary shaft 21, and the magnetic head mounted on the outer peripheral surface of the outer cylinder 23.
It is possible to prevent damage (not shown). At this time, the balls 41, 42 only slightly contact the inner peripheral surface 25D by the centrifugal force, so that the rotation of the rotary shaft 21 is hardly hindered. Further, when the rotation of the rotary shaft 21 is stopped, the balls 41 and 42 are inclined with respect to the radial holes 38 and 4.
It moves inward in the radial direction along 0, and is recessed inward in the radial direction with respect to the cylindrical surface 37. Therefore, the balls 41 and 42 do not increase the torque required for activation.

As described above, according to this embodiment, the static electricity generated on the rotary shaft 21 can be easily utilized by utilizing the rotation of the rotary shaft 21 without impairing the original characteristic of the dynamic pressure bearing that is suitable for high speed rotation. Can be removed.

Although the steel balls are used as the conductors in the first and second embodiments, the conductors of the present invention are not limited to the steel balls, but may be made of aluminum alloy or copper. Or it may be a titanium ball. Furthermore, the conductor may be made of conductive ceramic. Further, the conductor may be a resin sphere coated with a metal film. Furthermore, the conductor is not limited to the spherical shape, and may have any shape. Further, in the above-mentioned embodiment, two radial holes are provided at positions symmetrical with respect to the rotation axis, but only one radial hole may be provided. However, it is better to provide a plurality of radial holes at symmetrical positions for better balance during rotation.

[0026]

As is clear from the above, in the dynamic pressure bearing of the first aspect of the invention, the radial support dynamic pressure groove is formed on the cylindrical surface of the rotary shaft or on the inner peripheral surface of the housing facing the cylindrical surface. In the dynamic pressure bearing, a radial hole is bored inward in the radial direction in the cylindrical surface of the rotary shaft at a position axially separated from the radial support dynamic pressure groove by a predetermined distance. The conductor is inserted in the radial hole so as to be slidable in the radial direction.

Therefore, according to the first aspect of the present invention, when the rotary shaft rotates, the conductor inserted in the radial hole of the rotary shaft receives the centrifugal force due to the rotation and slides radially outward. Since it projects from the cylindrical surface and contacts the inner peripheral surface of the housing, static electricity can be released to the housing from the rotating shaft through the conductor.

Further, since the above-mentioned electric conductor is only in contact with the housing by receiving the centrifugal force, this contact resistance hardly increases the torque required for rotation.

The invention according to claim 2 is the dynamic pressure bearing according to claim 1, wherein the radial hole is located inside the radial surface more than the cylindrical surface due to the weight of the conductor when the rotating shaft is stationary. It is shaped so that you can immerse yourself in it.

Therefore, according to the second aspect of the present invention, when the rotary shaft is stationary, the conductor does not contact the inner peripheral surface of the housing, so that increase in the starting resistance can be avoided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a dynamic pressure bearing of the present invention.

FIG. 2 is a cross-sectional view showing a spindle motor of an HDD as a second embodiment of the dynamic pressure bearing of the present invention.

[Explanation of symbols]

1 ... Rotating shaft, 2 ... Housing, 3 ... Cylindrical part, 3A ... End surface,
3B ... inner peripheral surface, 5 ... bottom plate, 5A ... inner surface, 6,7 ... bearing surface, 8,10 ... radial support dynamic pressure groove, 11 ... large diameter surface,
12 ... Axial supporting dynamic pressure groove, 13, 14 ... Radial hole, 15, 16 ... Steel ball, 21 ... Rotating shaft, 22 ... Housing, 23 ... Outer cylinder, 24 ... Lid part, 24A ... Central hole, Two
5 ... Cylindrical portion, 25A ... End surface, 26 ... Lid portion, 26A ... Inner surface,
27 ... Bearing plate, 28 ... Stator, 30 ... Bottom plate, 31, 3
2 ... Radial bearing surface, 33, 34 ... Radial support dynamic pressure groove, 35 ... Axial support dynamic pressure groove, 37 ... Cylindrical surface, 3
8, 40 ... Radial holes, 41, 42 ... Steel balls.

Claims (2)

[Claims] 1. A dynamic pressure bearing having a radial support dynamic pressure groove formed on a cylindrical surface of a rotary shaft or on an inner peripheral surface of a housing facing the cylindrical surface, wherein the radial support dynamic pressure groove defines a predetermined axial direction. At a position separated by a distance of, a radial hole is bored inward in the cylindrical surface of the rotary shaft, and a conductor is slidably inserted in the radial hole in the radial hole. A dynamic pressure bearing characterized in that 2. The dynamic pressure bearing according to claim 1, wherein the radial hole has a shape such that when the rotary shaft is stationary, the conductor is dented radially inward from the cylindrical surface by its own weight. A dynamic pressure bearing characterized by being made.