JPH10184667A - Thrust dynamic pressure bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thrust dynamic pressure bearing that can suppress the damage of the outer peripheral parts of the thrust receiving surface and thrust bearing surface by making both these surface hard to come in contact even in case of conical motion being generated to a shaft part. SOLUTION: Either one (41, for instance) of the thrust bearing surface 41 provided at a bearing 4 and the thrust receiving face 33 provided at a shaft part 3 is inclined in a direction of enlarging a clearance (s) between the thrust bearing surface 41 and the thrust receiving surface 33 on the radially outside of a top part 42a of a herringbone groove 42.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thrust dynamic pressure bearing most suitable for a spindle used in a device such as a magnetic disk drive, a video tape recorder, a digital audio tape recorder and the like.

[0002]

2. Description of the Related Art A thrust dynamic pressure bearing basically includes a lubricating oil, grease or the like between a thrust bearing surface provided on a bearing portion and a thrust bearing surface of a shaft portion opposed to the thrust bearing surface. By filling the lubricant and rotating the shaft, a dynamic pressure is generated in the lubricant by a pumping action of a dynamic pressure generating groove formed in at least one of the thrust bearing surface and the thrust receiving surface. The shaft is supported in the axial direction.

FIG. 5 shows an example of a conventional thrust dynamic pressure bearing used for a spindle.
In this thrust dynamic pressure bearing, the shaft portion 1 is formed from a spindle 11 and a flange 12 provided at one end of the spindle 11, and one end surface 13 of the flange 12 acts as a thrust receiving surface. 13
A plurality of herringbone grooves 22 for generating dynamic pressure are formed on the thrust bearing surface 21 of the bearing portion 2 facing the bearing. Then, a lubricant (not shown) is filled between the flange 12 and the bearing portion 2, and by the rotation of the shaft portion 1, a dynamic pressure is generated in the lubricant so that the shaft portion 1 is moved as shown in FIG. As shown in the figure, the shaft 1 is supported.

[0004]

By the way, when the spindle 11, that is, the shaft portion 1 is used in a hard disk drive and has many disks, for example, the shaft portion 1 has a conical motion during rotation. Easy to do. When the shaft portion 1 makes a conical motion, the thrust bearing surface 13 is inclined as shown in FIG. 6B, and the edge thereof comes into contact with the outer peripheral portion of the thrust bearing surface 21 of the bearing portion 2 (so-called one-side contact). . Therefore, there is a problem that the outer peripheral portions of the thrust surfaces 13 and 21 are gradually worn and damaged. Further, when the thrust bearing surface 13 and the thrust bearing surface 21 are in contact with each other and there is no gap between the two surfaces, there is also a problem that the dynamic pressure is not generated and the thrust load capacity is reduced.

Accordingly, an object of the present invention is to provide a thrust thrust bearing which makes it difficult for the thrust bearing surface to come into contact with the thrust bearing surface even if conical motion occurs in the shaft portion, thereby suppressing damage to the outer peripheral portion of these surfaces. It is to provide a dynamic pressure bearing.

[0006]

In order to achieve the above object, a thrust dynamic pressure bearing according to the present invention has a thrust bearing surface provided on a bearing portion opposed to a thrust receiving surface provided on a shaft portion. In a thrust dynamic pressure bearing in which at least one of the bearing surface and the thrust receiving surface has a herringbone groove for generating dynamic pressure, and between the thrust bearing surface and the thrust receiving surface, a lubricant is filled. Either the thrust bearing surface or the thrust receiving surface is a radially outer surface than the top of the herringbone groove, and an inclined surface inclined in a direction in which a gap between the thrust bearing surface and the thrust receiving surface expands. It is characterized by becoming.

The operation of the thrust dynamic pressure bearing having the above configuration will be described with reference to FIG. 3 in a case where the thrust receiving surface has the herringbone groove and the inclined surface. 3A shows a state in which the shaft is rotating without tilting, FIG. 3B shows a state in which the shaft is tilted during rotation, and FIG. 3C shows a state in which the shaft is further tilted and makes contact with the bearing. FIG. As shown in FIG. 3A, when the shaft rotates, the lubricant between the thrust bearing surface and the thrust bearing surface is sucked into the herringbone groove by the pumping action of the herringbone groove for generating dynamic pressure. The groove portion radially outward from the top of the herringbone groove sucks the lubricant from the outer peripheral side toward the inner peripheral side, and the groove portion radially inward from the top of the herringbone groove receives the lubricant. Inhale from the inner circumference to the outer circumference. In this way, the lubricant is sucked into the herringbone groove, so that a dynamic pressure is generated in the lubricant, and the shaft part floats. As a result, a gap is formed between the thrust bearing surface and the thrust bearing surface.
The gap at this time is constant radially inward from the top of the herringbone groove, but becomes larger outward from the top of the herringbone groove in the radial direction. Then, as shown in FIG. 3 (B), when the thrust receiving surface is inclined from the top of the herringbone groove to a point where the gap d1 on the radially outer side and the gap d2 on the radially inner side are substantially equal, the herringbone groove Since the balance of the pumping action between the radially inner portion and the radially outer portion from the top is improved, the generated dynamic pressure is well balanced. As a result, it is possible to prevent the thrust load capacity from being extremely reduced even when the shaft portion is in a conical motion.

[0008] Even if the shaft portion is unfortunately tilted further than the state shown in FIG. 3 (B) and its thrust bearing surface comes into contact with the thrust bearing surface (one side contact), thanks to the inclined surface, As shown in FIG. 3 (C), they come into surface contact (region c), and the contact area is smaller than that of the conventional thrust dynamic pressure bearing in which only the edge of the thrust bearing surface is in contact with the thrust bearing surface. Will increase significantly. As a result, the occurrence of damage on the thrust bearing surface and the outer peripheral portion of the thrust receiving surface is suppressed.

[0009] The above operation of the present invention is applicable to the case where the herringbone groove and the inclined surface are provided on the thrust bearing surface and the thrust bearing surface, respectively, or conversely, the thrust bearing surface and the thrust bearing surface. Even when each is formed, and when both the herringbone groove and the inclined surface are formed only on the thrust receiving surface, also, the herringbone groove is formed between the thrust bearing surface and the thrust receiving surface. The same applies to the case where both the thrust bearing surface and the thrust bearing surface are formed on one of the thrust bearing surface and the thrust bearing surface.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments.

FIG. 1 shows a thrust dynamic pressure bearing according to an embodiment of the present invention. As shown in FIG. 1A, the rotatable shaft portion 3 includes a shaft 31 and a flange 32 provided at one end of the shaft 31, and the flange 32 is opposed to the bearing portion 4. One end surface 33 of the flange 32 and the surface 41 of the bearing portion 4 facing the end surface 33 function as a thrust bearing surface and a thrust bearing surface, respectively. The space between the flange 32 and the bearing portion 4 is filled with a lubricant (not shown) such as oil or grease.

The thrust bearing surface 41 of the bearing 4 is
As shown in FIG. 1B, a plurality of herringbone grooves 42 for generating dynamic pressure are formed at predetermined intervals in the circumferential direction. Further, the thrust bearing surface 41 has an inclined surface 41a radially outside the top 42a of the herringbone groove 42. The inclined surface 41a is inclined so that the bearing gap s, that is, the gap s between the thrust bearing surface 41 and the thrust receiving surface 33, becomes wider radially outward from the top 42a of the herringbone groove 42. The gap s between the thrust bearing surface 41 and the thrust receiving surface 33 is usually set to about 7 μm. Also,
The amount of inclination of the inclined surface 41a varies depending on the assumed amount of inclination due to the conical movement of the shaft portion 3. However, usually, the angle between the thrust bearing surface 41 and the outer peripheral edge of the inclined surface 41a (the bearing portion 4) is about 1 to 3 μm. To make a drop.

In the above-described thrust dynamic pressure bearing, when the shaft portion 3 rotates, the lubricant between the thrust bearing surface 33 and the thrust bearing surface 41 is pushed into the herringbone groove 42 by the pumping action of the herringbone groove 42. Therefore, a dynamic pressure is generated in the lubricant, and the shaft portion 3 is axially supported by the dynamic pressure.

Here, the shaft 3 is inclined during the rotation of the shaft 3, and the size of the bearing gap s radially outward from the top 42a of the herringbone groove 42 (see d1 in FIG. 3B). ) And the size of the bearing gap s on the inner side in the radial direction (FIG. 3).
When the thrust receiving surface 33 inclines to a point where (d2) of (B) is substantially equal, the pumping action balance between the radially inner portion 42b and the radially outer portion 42c from the top portion 42a of the herringbone groove 42 is balanced. Therefore, the balance of the generated dynamic pressure is also improved. As a result, it is possible to prevent the thrust load capacity from being extremely reduced even when the shaft portion 3 is in a conical motion.

Further, even if a conical motion occurs in the shaft portion 3, the thrust bearing surface 33 becomes the thrust bearing surface 41.
Even if the outer peripheral portion contacts the outer peripheral portion,
a, the thrust receiving surface 33 and the inclined surface 41a of the thrust bearing surface 41 come into surface contact (FIG. 3C).
C)). Therefore, only the edge of the thrust bearing surface contacts the thrust bearing surface (see FIG. 6).
The contact area is greatly increased as compared with the conventional thrust dynamic pressure bearing. As a result, the occurrence of damage on the outer peripheral portions of the thrust bearing surface 41 and the thrust receiving surface 33 is suppressed.

In the embodiment shown in FIG. 1, the thrust bearing surface 41 has an inclined surface 41a and a herringbone groove 4a.
2, the inclined surface 33a may be formed on the thrust receiving surface 33 as shown in FIG. In this case, the inclination direction of the inclined surface 33a is opposite to that of the inclined surface 41a shown in FIG. 1, and rises from the top 42a of the herringbone groove 42 formed on the thrust bearing surface 41 to the outside in the radial direction. It is inclined to be.

In the embodiment shown in FIGS. 1 and 2, the herringbone groove is provided on the thrust bearing surface 41, but may be provided on the thrust receiving surface 33. Further, it can be provided on both the thrust bearing surface 41 and the thrust receiving surface 33.

The present invention is not limited to the thrust dynamic pressure bearing in which the shaft 3 is composed of the shaft 31 and the flange 32 provided at one end thereof as shown in FIGS.
As shown in FIG. 4, a thrust hydrodynamic bearing in which a flange 52 is provided at an end portion of a shaft 51 and a housing 6 surrounding the flange 52 serving as a bearing portion is provided,
As shown in (B), it is needless to say that the present invention can be applied to a thrust dynamic pressure bearing or the like in which the shaft portion 7 has no flange. In the thrust dynamic pressure bearing shown in FIG. 4A, both end surfaces 53 and 54 of the flange 52 are inclined surfaces 53a and 53, respectively.
4a. In the thrust dynamic pressure bearing shown in FIG. 4B, the end surface 71 of the shaft portion 7 has an inclined surface 71a. In these figures, the herringbone groove is omitted to simplify the drawings.

[0019]

As is apparent from the above description, in the thrust dynamic pressure bearing of the present invention, either one of the thrust bearing surface provided on the bearing portion or the thrust bearing surface provided on the shaft portion is provided between the thrust bearing surface and the thrust bearing surface. At an outer side in the radial direction from the top of the herringbone groove provided on at least one of the receiving surfaces, an inclined surface is inclined in a direction in which a gap between these surfaces expands. Therefore, when the shaft portion is tilted, it is possible to improve the balance of the gap between the outside and the inside in the radial direction with the top portion as the center, and the inside of the herringbone groove portion and the outside portion in the radial direction with respect to the top portion in the radial direction. The balance of the pumping action with the herringbone groove can be improved. Therefore, the generated dynamic pressure can be well-balanced, and even if the shaft is in a conical motion,
Extreme reduction of the thrust load capacity can be prevented.

Further, the gap between the thrust bearing surface and the thrust bearing surface is increased from the top of the herringbone groove to the outer peripheral portion by virtue of the inclined surface. In this case, even if the shaft portion is tilted so that the edge of the thrust bearing surface contacts the thrust bearing surface, the thrust bearing surface does not contact the thrust bearing surface. Even if the shaft portion is further inclined and the thrust bearing surface comes into contact with the thrust bearing surface, the two surfaces come into surface contact thanks to the inclined surface.
That is, according to the present invention, the contact area when the thrust bearing surface comes into contact with the thrust bearing surface can be greatly increased as compared with the related art. Therefore, occurrence of damage on the thrust bearing surface and the outer peripheral portion of the thrust receiving surface can be suppressed.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a thrust dynamic pressure bearing of the present invention, wherein (A) is a cross-sectional view of the thrust dynamic pressure bearing,
(B) shows a thrust bearing surface of the thrust dynamic pressure bearing.

FIG. 2 shows another embodiment of the present invention.

FIG. 3 is a diagram illustrating the operation of the present invention.

FIG. 4 is a view showing another embodiment of a thrust dynamic pressure bearing to which the present invention can be applied.

FIG. 5 is a view showing a conventional thrust dynamic pressure bearing.

FIG. 6 is a diagram showing a state in which the thrust receiving surface is inclined and hits the thrust bearing surface in the thrust dynamic pressure bearing of FIG. 5;

[Explanation of symbols]

3, 7: Shaft, 4, 6: Bearing, 33, 53, 54, 7
1 ... thrust receiving surface, 33a, 41a, 53a, 54
a, 71a: inclined surface, 41: thrust bearing surface, 42:
Herringbone groove.

Claims (1)

[Claims] 1. A thrust bearing surface provided on a bearing portion opposes a thrust receiving surface provided on a shaft portion, and at least one of the thrust bearing surface and the thrust receiving surface has a herringbone groove for generating dynamic pressure. Further, in the thrust dynamic pressure bearing in which a lubricant is filled between the thrust bearing surface and the thrust receiving surface, one of the thrust bearing surface and the thrust receiving surface is formed of the herringbone groove. A thrust dynamic pressure bearing characterized in that a radially outer side of the top portion has an inclined surface inclined in a direction in which a gap between the thrust bearing surface and the thrust receiving surface increases.