JP2997091B2 - Fluid bearing device - Google Patents

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 rotary device such as a rotary cylinder in a magnetic recording device.

[0002]

2. Description of the Related Art In a hydrodynamic bearing device, a bearing fluid is interposed as a lubricant between a dynamic pressure generating surface of a shaft and a sleeve for receiving the shaft. In this case, a substance having a structure containing a polar group is used as a base oil of the lubricant in order to prevent the lubricant from flowing out under use conditions in which the lubricant is likely to flow out. Conventionally, diesters such as dioctyl adipate and dioctyl sebacate have been often used as such a base oil.

[0003]

The above-mentioned conventional diester-based lubricant can be used sufficiently under ordinary use conditions, but when the shaft rotates at a very high speed, about 10 ⁴ S ^{− Since the} temperature becomes high due to a large shear stress, when the operating atmosphere is high in humidity, deterioration mainly by hydrolysis occurs rapidly. For this reason, there have been problems that the viscosity of the lubricant changes, which adversely affects the lubrication characteristics, and that the constituent materials of the hydrodynamic bearing device corrode.

[0004] In view of such circumstances, the present invention provides a hydrodynamic bearing device that does not cause lubricant to flow out under use conditions such as high-speed rotation and has a stable lubricant even in a high-temperature and high-humidity environment. That is the task.

[0005]

In order to solve the above-mentioned problems, a hydrodynamic bearing device according to the present invention has a fluid interposed between a dynamic pressure generating surface of a shaft and a sleeve for receiving the shaft. Wherein the acid component is ω-
The monoester A comprising a monocarboxylic acid having a phenyl group at the 1-position and / or the acid component is in the α-position or α, α ′
A fluid having a base oil of diester B consisting of a dicarboxylic acid having an alkyl side chain at a position is used.

The present invention is applicable to both radial bearings and thrust bearings. The monocarboxylic acid used as the acid component of the monoester A, that is, the monocarboxylic acid having a phenyl group at the ω-1 position has a structure shown in the following (Chemical Formula 1). Further, dicarboxylic acid used as an acid component of diester B, ie, α-position or α,
The dicarboxylic acid having an alkyl side chain at the α'-position has a structure shown in the following (Formula 2).

[0007]

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[0008]

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In this case, the above-mentioned monoester A
Has at least one of octyl alcohol and 2-ethylhexyl alcohol as its alcohol component
Preferably, a seed is used. In addition, the above diester B
It is preferable to use 2-ethylhexyl alcohol as the alcohol component. These monoesters A
And diester B does not show much effect unless its total acid value is 1.5 mgKOH / g or less. Preferably, the total acid value is 0.7 mgKOH / g or less. Various known additives such as an antioxidant, an oiliness improver, an extreme pressure agent, and a rust inhibitor can be added to the bearing fluid used in the present invention, if necessary.

In the hydrodynamic bearing device according to the present invention, it is preferable that a groove is formed in a dynamic pressure generating surface of a shaft and / or a sleeve thereof.

[0011]

According to the present invention, a monoester A containing a monovalent novel fatty acid having a phenyl group at the ω-1 position as an acid component and / or a novel dicarboxylic acid having an alkyl side chain at the α-position or α, α′-position Diester B containing an acid as an acid component is used as a base oil of a bearing fluid. Since the acid component of this base oil has a phenyl group at the ω-1 position or an alkyl side chain at the α position, α, or α ′ position, the surface tension of the entire base oil is increased due to an increase in intermolecular attraction. Has improved,
The adsorbing power to the bearing constituent material is increased, and the outflow of the lubricant is easily prevented. In addition, the hydrolysis resistance is improved, and the deterioration hardly occurs even in a high temperature and high humidity environment.

As the alcohol component of the monoester A, trimethylolpropane and / or 2-ethylhexyl alcohol are used, or the diester B
When 2-ethylhexyl alcohol is used as the alcohol component, the hydrolysis resistance is further improved. In the present invention, if a groove is formed on the dynamic pressure generating surface of the shaft and / or the sleeve of the hydrodynamic bearing device, the holding force of the bearing fluid is improved, and the outflow of the lubricant is more easily prevented.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail, but the scope of the present invention is not limited to the following embodiments. FIG. 1 shows a first embodiment of the hydrodynamic bearing device according to the present invention. This is an example of a hydrodynamic bearing device combining a radial bearing and a thrust bearing. In the figure, 1 is a shaft, and 2 is a sleeve. Reference numeral 3 denotes a shaft stopper that is inserted into a groove provided on the shaft 1. Reference numeral 4 denotes a bearing fluid held between the shaft 1 and the dynamic pressure generating surface of the sleeve 2 in the thrust bearing portion by its own surface tension. It is. Reference numeral 5 denotes a thrust plate, and reference numeral 6 denotes a spiral dynamic pressure generating groove provided on the thrust plate 5. 7a and 7b are dynamic pressure generating grooves provided in the sleeve 2. 8 is the shaft 1 in the radial bearing portion
And the bearing fluid held between the dynamic pressure generating surfaces of the sleeve 2 and the sleeve 2 by its own surface tension.

FIG. 2 shows a second embodiment of the hydrodynamic bearing device according to the present invention. This is an example used as a recording rotary cylinder of a video tape recorder. In the figure, 10 is a shaft, and 11 is a sleeve. 1
Reference numeral 2 denotes a shaft stopper that is inserted into a groove provided on the shaft 10. Reference numeral 13 denotes a bearing fluid held between the shaft 10 and the dynamic pressure generating surface of the sleeve 11 in the thrust bearing portion by its own surface tension. Reference numeral 14 denotes a thrust plate, and reference numeral 15 denotes a spiral dynamic pressure generating groove provided on the thrust plate 14. 16a and 16b are dynamic pressure generating grooves provided in the sleeve 11. 17 is the shaft 10 in the radial bearing portion.
The bearing fluid is held between the dynamic pressure generating surfaces of the sleeve 11 and the sleeve 11 by its own surface tension. Reference numeral 18 denotes a lower cylinder that does not rotate, and 19 denotes an upper cylinder that rotates. Reference numeral 20 denotes a rotor magnet of a motor for rotating the upper cylinder 19, and reference numeral 21 denotes a stator.

In the first and second embodiments, the bearing fluids 4, 8, 13, and 17 have an acid component of ω-
The monoester A comprising a monocarboxylic acid having a phenyl group at the 1-position and / or the acid component is in the α-position or α, α ′
And a diester B comprising a dicarboxylic acid having an alkyl side chain at the base position. First of Monoester A
As a specific example of the following, the following chemical formula (3) using 7-phenyl-1-octanecarboxylic acid of n = 6 and R = H in the above chemical formula (1) as an acid component and octyl alcohol as an alcohol component. And octyl 7-phenyl-1-octanecarboxylate having the structure shown.

[0016]

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As a second specific example of the monoester A,
Using the above-mentioned 7-phenyl-1-octanecarboxylic acid as an acid component and 2-ethylhexyl alcohol as an alcohol component, it has the structure shown in the following chemical formula 4.
-Phenyl-1-octanecarboxylic acid-2-ethylhexyl ester.

[0018]

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As a third specific example of the monoester A,
N = 6 and R = 0CH in the above formula (1) as an acid component
7-phenyl-7-methoxy-1-octane having the structure shown in the following (Chemical Formula 5) using 7-phenyl-7-methoxy-1-octanecarboxylic acid of ₃ and 2-ethylhexyl alcohol as an alcohol component. Carboxylic acid-2-ethylhexyl ester is exemplified.

[0020]

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As a first specific example of the diester B, m = 5, R ¹ = H, R
^Using 1-methyl-1,7-heptanedicarboxylic acid of ² ＣＨCH ₃ and octyl alcohol as an alcohol component, 1-methyl- having a structure shown in the following chemical formula 6
1,7-heptanedicarboxylic acid-di-octyl ester.

[0022]

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As a second specific example of diester B, the following (Chem. 7) is used, in which the above-mentioned 1-methyl-1,7-heptanedicarboxylic acid is used as an acid component and 2-ethylhexyl alcohol is used as an alcohol component. 1-methyl-1,7-heptanedicarboxylic acid-di-2- having a structure
Ethylhexyl ester is mentioned.

[0024]

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As a third specific example of the diester B, m = 4 and R ¹ =
Using 1-methyl-1,6-hexanedicarboxylic acid of H, R ² ＣＨCH ₃ and using 2-ethylhexyl alcohol as an alcohol component, 1-methyl-1,6 having a structure shown in the following chemical formula 8 -Hexanedicarboxylic acid-di-
2-ethylhexyl ester is exemplified.

[0026]

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As a fourth specific example of diester B, as the acid component, m = 5 and R ¹化 C
Using 1,7-di-methyl-1,7-heptanedicarboxylic acid of H ₃ , R ² ＣＨCH ₃ ,
Examples thereof include 1,7-di-methyl-1,7-heptanedicarboxylic acid-di-2-ethylhexyl ester having the structure shown in the following (Chemical Formula 9) using ethylhexyl alcohol.

[0028]

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-Comparison between Example and Comparative Example- In using a hydrodynamic bearing device having the structure shown in FIG. 2 as a recording rotary cylinder of a video tape recorder, the following chemical formulas (3) and (4) were used as bearing fluids. Examples 1 to 4 using lubricants each having a base oil of the monoester A shown and the diester B shown in the above (Chem. 6) and (Chem. 8)
And a comparative example using a lubricant having dioctyl adipate as a base oil, the respective performances were compared.

Each lubricant was prepared by adding the following additives to the above base oil at the following compounding ratios. Pentaerythrityl-tetrakis [3-3,5-di-t-butyl-4-hydroxyphenyl] propionate 0.3 wt% Methyl benzotriazole 0.1 wt% In this case, the fluid bearing devices of Examples and Comparative Examples are compared. Was continuously rotated at 5000 rpm in an environment of 60 ° C. and 90%, the condition was observed, and the time until failure occurred was measured. When abrasion powder was generated due to corrosion and rotation unevenness occurred in the hydrodynamic bearing device, it was determined that "defective". In each hydrodynamic bearing device, the shear stress applied to the lubricant was about 2 × 10 ⁴ S ⁻¹ . The measurement results are as follows. Example 1 2800 hours Example 2 3200 hours Example 3 2900 hours Example 4 3300 hours Comparative example 1500 hours From the above comparison, it can be seen that the example is superior to the comparative example and the operation is stable for a long time. .

[0031]

The hydrodynamic bearing device according to the present invention is configured as described above, so that the lubricant hardly flows out and the reliability is high even in a high temperature and high humidity environment.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a hydrodynamic bearing device according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the hydrodynamic bearing device according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 shaft 2 sleeve 3 shaft retaining 4 thrust bearing fluid 5 thrust plate 6 spiral dynamic pressure generating groove 7a dynamic pressure generating groove 7b dynamic pressure generating groove 8 radial bearing fluid 9 bracket 10 shaft 11 sleeve 12 shaft retainer 13 thrust Bearing fluid 14 Thrust plate 15 Spiral type dynamic pressure generating groove 16a Dynamic pressure generating groove 16b Dynamic pressure generating groove 17 Radial bearing fluid 18 Lower cylinder 19 Upper cylinder 20 Stator 21 Rotor magnet

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Noriyoshi Miyoshi 2-86-3 Karuri, Habikino-shi, Osaka Prefecture Habikino Royal Heights 405 (72) Inventor Masashi Uehata 3-chome, Higashiyamahonshinmachi, Yao-shi, Osaka No.23, No.4 (58) Fields investigated (Int. Cl. ⁷ , DB name) F16C 17/02

Claims (4)

(57) [Claims] 1. A fluid bearing device in which a fluid is interposed between dynamic pressure generating surfaces of a shaft and a sleeve for receiving the shaft.
As the fluid, a monoester A in which the acid component is composed of a monocarboxylic acid having a phenyl group at the ω-1 position and / or a diester B in which the acid component is composed of a dicarboxylic acid having an alkyl side chain at the α-position or α, α′-position A fluid bearing device characterized by using a fluid based on oil. 2. The hydrodynamic bearing device according to claim 1, wherein the alcohol component of the monoester A is at least one of octyl alcohol and 2-ethylhexyl alcohol. 3. The hydrodynamic bearing device according to claim 1, wherein the alcohol component of the diester B is 2-ethylhexyl alcohol. 4. The hydrodynamic bearing device according to claim 1, wherein a groove is formed in a dynamic pressure generating surface of the shaft and / or the sleeve.