JP2001065569A - Hydrodynamic bearing - Google Patents

Abstract

(57) [Object] To provide a hydrodynamic bearing capable of preventing seizure at the time of contact between a shaft and a bearing sleeve and increasing load capacity. A hard solid lubricating film and micro dimples are formed on an outer surface of a shaft and / or an inner surface of a bearing sleeve which are processed from a base material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydrodynamic bearing. A shaft, a bearing sleeve, and a dynamic pressure generating groove formed in at least one of the shaft and a bearing for the shaft utilizing a dynamic pressure generated by a fluid flowing through the dynamic pressure generating groove between the shaft and the bearing sleeve; 2. Description of the Related Art A hydrodynamic fluid bearing for smooth rotation of a sleeve or smooth rotation of a shaft with respect to a bearing sleeve is used in a disk device, a deflection scanning device, and the like. The present invention relates to an improvement of such a hydrodynamic bearing.

[0002]

2. Description of the Related Art Various types of hydrodynamic bearings have been conventionally proposed (Japanese Patent Application Laid-Open Nos. 9-291932 and 10-2).
88221, JP-A-11-82486). However, these conventional proposals have inherent problems in hydrodynamic bearings, such as burn-in upon contact and insufficient load capacity. During high-speed rotation, a corresponding dynamic pressure is generated between the shaft and the bearing sleeve.In this case, if the load is small, the two will not contact and seize. In this case, if the load is large, both will come into contact with each other and burn.

[0003]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is that the conventional hydrodynamic bearing is inherent in the hydrodynamic bearing in which seizure and insufficient load capacity occur when the shaft and the bearing sleeve come into contact with each other. There is a problem.

[0004]

Means for Solving the Problems Thus, the present inventors have
As a result of research to solve the above problems, it is effective to form a hard solid lubricating film on the outer surface of the shaft and / or the inner surface of the bearing sleeve in order to prevent seizure at the time of contact. It is effective to form micro dimples on the outer surface of the shaft and / or the inner surface of the bearing sleeve in order to increase the frictional force. It has been found that it is important to achieve both the formation of a lubricating film and the formation of micro dimples.

That is, the present invention relates to a hydrodynamic bearing for generating a dynamic pressure in a fluid between a shaft and a bearing sleeve. The present invention relates to a hydrodynamic bearing formed by forming a lubricating film and micro dimples.

In the present invention, as the base material of the shaft, various metallic materials, usually, austenitic, ferriic or martensitic steel materials can be used. Shafts and bearing sleeves are obtained by machining parts from such a base material. In order to form a desired hard solid lubricating film and micro dimples on the outer surface of the shaft and / or the inner surface of the bearing sleeve, the base material is required. It is preferable to use a material having a relatively low hardness as a steel material,
It is more preferable to use a ferritic steel material of RB85 or less.

The hydrodynamic bearing according to the present invention has a hard solid lubricating film and micro dimples formed on the outer surface of the shaft and / or the inner surface of the bearing sleeve, which are processed from the above-described base material. As a hard solid lubricating film, D
An LC (diamond-like carbon) film, a TiC film, a TiN film, and the like can be mentioned. In order to form a hard solid lubricating film and a micro dimple as desired on the outer surface of the shaft and / or the inner surface of the bearing sleeve, TiN is used. Coatings are preferred. Although a known vapor phase plating method can be applied to the formation of such a hard solid lubricating film itself, it is preferable to apply a physical vapor phase plating method such as vacuum evaporation or sputtering when forming a TiN film. A well-known mechanical surface treatment method such as shot peening can be applied to the formation of the micro dimples.

The hard solid lubricating film and the micro dimples can be formed on either the outer surface of the shaft or the inner surface of the bearing sleeve, but are preferably formed on both. It is also possible to first form a micro dimple on the outer surface of the shaft and / or the inner surface of the bearing sleeve, and then form a hard solid lubricating film. Preferably, dimples are formed. In any case, this is for better prevention of burn-in at the time of contact and an increase in load capacity.

[0009]

FIG. 1 is a longitudinal sectional view schematically showing a spindle motor provided with a hydrodynamic bearing according to the present invention.
The shaft 21 is attached to the base 11, and flanges 31 and 32 are attached to upper and lower portions of the shaft 21. A bearing sleeve 41 is provided between the flange 31 and the flange 32 and surrounds the shaft 21.
1 is attached. The base 11 has yokes 61 and 62
Are mounted, and magnets 52 and 53 are mounted on inner surfaces of the hub 51 facing the yokes 61 and 62.

FIG. 2 is a partially enlarged view showing the hydrodynamic bearing of FIG. The hydrodynamic bearing includes a shaft 21 and a bearing sleeve 41 surrounding the shaft 21. A plurality of dynamic pressure generating grooves 22 are formed on the outer peripheral surface of the shaft 21, and a gap 71 is provided between the shaft 21 and the bearing sleeve 41. Axis 2
When the bearing sleeve 41 rotates around the shaft 21 with the shaft 1 as a fixed shaft, the air supplied to the gap 71
, A dynamic pressure is generated.
1, so that the bearing sleeve 41 can rotate smoothly.

In the hydrodynamic bearing shown in FIGS. 1 and 2,
A hard solid lubricating film 23 and many micro dimples 24 are formed on the outer peripheral surface of the shaft 21, and a hard solid lubricating film 42 and many micro dimples 43 are also formed on the inner peripheral surface of the bearing sleeve 41. 1 and 2
The hydrodynamic bearing shown in FIG.
Are hardened lubricating films 23 and 42 made of TiN.
After forming hard solid lubricating films 23 and 42 by vacuum evaporation on the outer peripheral surface of the shaft 21 and the inner peripheral surface of the bearing sleeve 41, the micro dimples 2 are formed by shot peening.
4, 43 are formed.

Four types of hydrodynamic bearings shown in Table 1 were produced. In each case, the other conditions are the same, and the description is omitted.
A hard solid lubricating film is formed on the outer surface of the shaft and the inner surface of the bearing sleeve by vacuum evaporation to form TiN
A film is formed, and micro dimples are formed by shot peening. For these four types of hydrodynamic bearings, when air was used as the fluid, Ti
Table 1 shows the effect of reducing the frictional force by forming the N film and the effect of increasing the dynamic pressure by forming the micro dimples. Example 2 in Table 1 corresponds to the hydrodynamic fluid bearing described above with reference to FIGS. 1 and 2, but a decrease in frictional force means that seizure during contact is correspondingly prevented, and an increase in dynamic pressure means a load. This means increasing the capacity accordingly.

[0013]

[Table 1]

In Table 1, A: martensitic steel material of HRC58 B: ferritic steel material of HRB78 TiN → WPC: When a TiN film is formed first and then micro dimples are formed WPC → TiN: First When a micro dimple is formed and then a TiN film is formed. Friction force reduction effect:
；: When the frictional force becomes 50% or more and less than 70%, Δ;
When the friction force is 70% or more and less than 90% Dynamic pressure increasing effect: Based on the absence of micro dimples, ◎: When the dynamic pressure is increased by 100% or more, ○: Dynamic pressure is 50% or more and less than 100% If increased, Δ; dynamic pressure is 3
0% or more and less than 50%

[0015]

As is apparent from the above description, the present invention as described above has the effects of preventing seizure at the time of contact between the shaft and the bearing sleeve and increasing the load capacity.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing a spindle motor provided with a hydrodynamic bearing according to the present invention.

FIG. 2 is a partially enlarged view showing the hydrodynamic bearing of FIG. 1;

[Explanation of symbols]

21 ··· shaft, 22 ··· dynamic pressure generating groove, 23, 42 ··· hard solid lubricating film, 24, 43 ··· micro dimple, 4
1. Bearing sleeve, 51. Hub, 52, 53. Magnet, 61, 62 .. Yoke

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J011 AA07 AA10 AA11 BA02 CA02 CA05 DA01 DA02 JA02 KA02 LA05 MA03 QA03 RA01 SB01 SB02

Claims (4)

[Claims] In a hydrodynamic bearing for generating a dynamic pressure in a fluid between a shaft and a bearing sleeve, a hard solid lubricating film is formed on an outer surface of the shaft processed from a base material and / or an inner surface of the bearing sleeve. A hydrodynamic bearing comprising micro dimples. 2. The hydrodynamic bearing according to claim 1, wherein the base material is a steel material having an HRB of 85 or less. 3. The hydrodynamic bearing according to claim 1, wherein the hard solid lubricating film is a TiN film. 4. The hydrodynamic bearing according to claim 1, wherein the micro dimples are formed after forming the hard solid lubricating film.