JP2001140894A - Fluid bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the leaking of a lubricant over a long period and seizure between members and resulting wear, in a fluid bearing device in which a gap between a bearing member and a shaft member inserted in a bearing hole therein is filled with the lubricant. SOLUTION: At least either one of the inner peripheral surface of a sleeve 12 or the outer peripheral surface of a shaft 13 is covered with a monomolecular film 19. The lubricant 15 is adsorbed to the monomolecular film 19 and held in the gap 14 between the sleeve 14 and the shaft 13. Even if the sleeve 12 and the shaft 13 tend to make contact with each other because of an excessive force applied to the device, the monomolecular film 19 works as a strong solid lubricant to prevent seizure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing device used for a hard disk device, an optical disk rotating device, a video tape recorder and the like.

[0002]

2. Description of the Related Art Some conventional hydrodynamic bearing devices are used in a video tape recorder as shown in FIGS. In this hydrodynamic bearing device, a rotary cylinder 4A integrally formed with a sleeve 4 is rotatably mounted on a shaft 3 having both ends fixed to a lower fixed cylinder 1 and an upper fixed cylinder 2, and a concave portion 4B on the inner periphery of the rotary cylinder 4A. Within
A ring-shaped flange 5 externally fitted on the fixed shaft 3 and a ring-shaped thrust plate 6 are arranged. A motor rotor 7 is installed on the outer peripheral side of the rotary cylinder 4A. The motor stator 8 is attached.

In addition, one of the outer peripheral surface of the shaft 3 and the inner peripheral surface of the sleeve 4 (here, the inner peripheral surface of the sleeve 4A)
Radial side dynamic pressure generating groove 4C such as herringbone shape,
4D, and a thrust-side dynamic pressure generating groove 6A bent in a rectangular shape along the radial direction on one of the opposing surfaces of the flange 5 and the thrust plate 6 (here, the lower surface of the thrust plate 6).
And these radial-side dynamic pressure generating grooves 4C, 4D,
A gap 9 around the shaft 3 including the thrust-side dynamic pressure generating groove 6A is filled with a lubricant 10.

In such a hydrodynamic bearing device, a torque is generated in the motor rotor 7 by energizing the motor stator 8 to generate a rotating magnetic field, whereby the sleeve 4, the rotary cylinder 4 A, and the thrust plate 6 are connected to the shaft 3. Rotate around the axis. Then, at that time, with the rotation of the sleeve 4, the pumping action based on the herringbone shape works in the radial-side dynamic pressure generating grooves 4C and 4D, and the pressure of the lubricant 10 increases at the center of the herringbone shape.
The sleeve 4 is pressed in the radial direction, and rotates without contact with the shaft 3. Further, with the rotation of the flange 5 and the thrust plate 6 (in the direction of the arrow A), the lubricant 10 is applied to the bent portion 6B based on the bent shape in the thrust side dynamic pressure generating groove 6A.
Is transferred, and the pressure of the lubricant 10 increases at the bent portion 6 </ b> B, so that a floating force acts on the thrust plate 6, and the thrust plate 6 rotates without contact with the flange 5.

[0005]

However, in the conventional hydrodynamic bearing device as described above, when rotating or left for a long time, the shaft 3 is rotated as shown in FIGS.
The lubricant 10 tends to leak downward from the gap between the sleeve 4 and the sleeve 4. This is because, as shown in FIG. 7, the lubricant 10 is lightly repelled on the surface of the shaft 3 or the sleeve 4 and the contact angle θ
Is large and tends to leak out, and when an impact load is actually applied, it may spill as a drop 10A. Further, when an excessive force acts on the hydrodynamic bearing device, the shaft 3 and the sleeve 4 come into direct strong contact with each other, sometimes causing seizure.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a hydrodynamic bearing device that can prevent leakage of a lubricant and prevent seizure between members.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a first aspect of the present invention is a fluid bearing device in which a gap between a bearing member and a shaft member inserted into the bearing hole is filled with a lubricant. Wherein at least one of the inner peripheral surface of the bearing member and the outer peripheral surface of the shaft member is covered with a monomolecular film.

According to the above configuration, a specific portion of each molecule constituting the monomolecular film is firmly entangled with the inner peripheral surface of the bearing member (and / or the outer peripheral surface of the shaft member, hereinafter omitted) by covalent bond or the like, Since the lubricant is adsorbed to the other part of each molecule by its affinity, the contact angle of the lubricant with the inner peripheral surface of the bearing member is reduced. This means that the wettability of the inner peripheral surface of the bearing member is improved. Also, at this time, the lubricant penetrates into the gaps between the molecules constituting the monomolecular film, so that the contact area between the lubricant and the monomolecular film increases, and the adsorbing force of the lubricant on the monomolecular film is extremely large. Become. For this reason, the lubricant does not spill out or seep out from the bearing gap. Further, since the monomolecular film is firmly fixed to the inner peripheral surface of the bearing member as described above, even if an excessive force is applied to the device and the bearing member and the shaft member are likely to come into contact with each other, the monomolecular film is strong. Acts as a solid lubricant and does not cause seizure.

According to a second aspect of the present invention, in the configuration of the first aspect, the monomolecular film is formed of a carboxylic acid, an aminosilane,
It is characterized in that any one of polyacrylic acid is formed as a material. The monomolecular film is obtained by dissolving the above-described material in an appropriate solvent such as an organic solvent such as benzene, developing the washed bearing member or shaft member on the surface thereof, and evaporating the solvent.
And the like.

Preferred carboxylic acids include those having 1 to 3 carbon atoms.
There are zero, saturated or unsaturated, linear or cyclic, aliphatic or aromatic hydrocarbon skeletons and carboxylic acids with one to three carboxyl groups. Aminosilanes include aminosilane compounds such as polysilanes and monosilanes having one or more amino groups at terminals and / or other sites.

The polyacrylic acid includes homopolymers of acrylic acid and alkyl acrylate (alkyl has 10 or less carbon atoms) homopolymers and copolymers thereof. A monomolecular film made of these materials can be firmly attached to the surface of the metal material constituting the bearing member or the shaft member by covalent bonding or the like. It exhibits good characteristics for bearing devices, such as a low coefficient of friction when combined and excellent non-adhesion properties. In addition, when a charging voltage is applied between the bearing member and the shaft member, the monomolecular film may generate a repulsive force between the two surfaces to reduce the friction coefficient.

According to a third aspect of the present invention, in the configuration of the first aspect, a dynamic pressure generating groove for increasing the pressure of the lubricant is formed on at least one of the inner peripheral surface of the bearing member and the outer peripheral surface of the shaft member. Features. According to the above configuration, the lubricant is transferred to the dynamic pressure generating groove and the pressure of the lubricant increases with the rotation of the bearing member or the shaft member, but the lubricant is held by the monomolecular film as described above at that time. Therefore, the radial pressing force of the lubricant is increased, and the bearing member and the shaft member are reliably maintained in a non-contact state.

[0013]

(Embodiment 1) Hereinafter, a hydrodynamic bearing device according to Embodiment 1 of the present invention will be described with reference to FIGS. This hydrodynamic bearing device can constitute a part of the hydrodynamic bearing device described above with reference to FIG.

In FIG. 1, a shaft 13 is inserted into a sleeve 12 having a bearing hole 11, and the sleeve 12 and the shaft 1 are inserted.
A lubricant 15 is injected into a gap 14 between the lubricant 3 and the lubricant 3. The sleeve 12 and the shaft 13 are made of a metal material such as SUS, and the lubricant 15 is selected from fluorine oil (perfluoropolyether), ester oil, olefin oil, mineral oil, and the like.

Herringbone-shaped dynamic pressure generating grooves 16 and 17 are formed on the outer peripheral surface of the shaft 13. Reference numeral 18 denotes a lubricant reservoir. A monomolecular film 19 made of polyacrylic acid or the like is formed on the inner peripheral surface of the sleeve 12. In the above-described hydrodynamic bearing device, when the sleeve 12 is rotated by a motor or the like (not shown), a pumping action based on the herringbone shape acts on the dynamic pressure generating grooves 16 and 17 with the rotation of the sleeve 12, thereby forming the herringbone shape. The pressure of the lubricant 15 rises at the center of the sleeve 13, and the sleeve 15 is pressed in the radial direction by the lubricant 15, and the sleeve 12 rotates without contact with the shaft 13.

At this time, since the lubricant 15 is held in the gap 14 by the action of the monomolecular film 19, the sleeve 12
And the shaft 13 are reliably maintained in a non-contact state. Even when the sleeve 12 and the shaft 13 are likely to come into contact with each other due to an excessive force applied to the device, the seizure does not occur because the monomolecular film 19 serves as a strong solid lubricant. This is because, as shown in FIGS. 2 and 3, the monomolecular film 19 (having a thickness t
(About 2 to 20 nanometers), the anchor portion 20A of each molecule 20 does not become firmly entangled with the inner peripheral surface of the sleeve 12 by a covalent bond or the like and peels off. Due to the affinity, the contact angle γ of the lubricant 15 with respect to the inner peripheral surface of the sleeve 12 is reduced as shown in the drawing, that is, the wettability of the inner peripheral surface of the sleeve 12 is improved. Moreover,
Since the lubricant 15 penetrates into the gaps between the molecules 20,
The contact area between each molecule 20 and the lubricant 15 becomes large, and the adsorbing force of the lubricant 15 to the monomolecular film 19 becomes very large. For this reason, the lubricant 15 does not spill from the gap 14 or bleed out. (Embodiment 2) In the hydrodynamic bearing device according to Embodiment 2 of the present invention, as shown in FIG. 4, monomolecular films 19 and 21 are formed on the inner peripheral surface of the sleeve 12 and the outer peripheral surface of the shaft 13, respectively. Have been. Thereby, the lubricant 15 is more reliably held in the gap 14 than in the bearing device of the first embodiment, the non-contact state between the sleeve 12 and the shaft 13 is maintained, and the seizure resistance is improved.

The same effect as in the first embodiment can be obtained by forming a monomolecular film only on the outer peripheral surface of the shaft 13. It is also possible to form a monomolecular film only below the inner peripheral surface of the bearing member or the outer peripheral surface of the shaft member. Further, the dynamic pressure generating groove may be formed as needed, and may be formed only on the inner peripheral surface of the sleeve 12 or may be formed on the inner peripheral surface of the sleeve 12 and the shaft 13.
May be formed on both of the outer peripheral surfaces.

[0018]

As described above, according to the present invention, by forming a monomolecular film on at least one of the inner peripheral surface of the bearing member and the outer peripheral surface of the shaft member, the space between the bearing member and the shaft member is filled. This can prevent the lubricant from leaking, and can provide a high effect by the lubricant and can improve the seizure resistance. Further, since the recording medium is not stained due to the leakage of the lubricant, the operation error of the recording medium can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a hydrodynamic bearing device according to Embodiment 1 of the present invention.

FIG. 2 is a partially enlarged sectional view of the hydrodynamic bearing device shown in FIG.

FIG. 3 is a schematic view illustrating the operation of a monomolecular film in the hydrodynamic bearing device shown in FIG.

FIG. 4 is a partially enlarged sectional view of a hydrodynamic bearing device according to Embodiment 2 of the present invention.

FIG. 5 is a cross-sectional view showing a schematic overall configuration of a conventional hydrodynamic bearing device.

6 is a partially enlarged sectional view of the hydrodynamic bearing device shown in FIG.

7 is a partially enlarged cross-sectional view illustrating leakage of lubricant in the hydrodynamic bearing device shown in FIG.

FIG. 8 is a schematic diagram illustrating leakage of lubricant in the hydrodynamic bearing device shown in FIG. 1;

[Explanation of symbols]

 11 Bearing hole 12 Sleeve (bearing member) 13 Shaft (shaft member) 14 Clearance 15 Lubricant 16, 17 Dynamic pressure generating groove 19 Monolayer 21 Monolayer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI theme coat ゛ (reference) C10M 107/28 C10M 107/28 C10N 40:02 C10N 40:02 F-term (reference) 3J011 AA07 CA02 CA05 JA02 KA02 MA02 MA24 QA02 RA03 SE10 4H104 BB14A BJ01A CB07A CD04A LA03 PA01 PA04 QA12

Claims (3)

[Claims] 1. A hydrodynamic bearing device in which a lubricant is filled in a gap between a bearing member and a shaft member inserted into the bearing hole, wherein at least one of an inner peripheral surface of the bearing member and an outer peripheral surface of the shaft member is a single molecule. A hydrodynamic bearing device characterized by being covered with a membrane. 2. The hydrodynamic bearing device according to claim 1, wherein the monomolecular film is formed of any one of carboxylic acid, aminosilane, and polyacrylic acid. 3. The hydrodynamic bearing device according to claim 1, wherein a dynamic pressure generating groove for increasing the pressure of the lubricant is formed on at least one of the inner peripheral surface of the bearing member and the outer peripheral surface of the shaft member.