JP2001316687A - Lubricating oil for fluid bearing and fluid bearing using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricating oil for fluid bearings having excellent characteristics such as energy-saving properties and durability. SOLUTION: This lubricating oil for fluid bearings comprises an ester having a viscosity index of >=100, a total acid value of <=0.5 mgKOH/g and a hydroxyl value of <=20 mgKOH/g that is obtained from neopentyl glycol and at least one 6-12C monocarboxylic fatty acid and/or a derivative thereof. The monocarboxylic fatty acid is preferably a straight-chain saturated monocarboxylic fatty acid. Two or more monocarboxylic fatty acids are preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricating oil for a hydrodynamic bearing, a hydrodynamic bearing and a lubricating method of the hydrodynamic bearing using the lubricating oil. The present invention relates to a lubricating oil for a fluid bearing suitable for a fluid bearing.

[0002]

[Prior Art] Reducing the size and weight of audio equipment and personal computers,
The progress of capacity increase is remarkable. These electronic devices use various types of rotating devices, for example, rotating devices for driving a magnetic disk, an optical disk, an FD, a mini disk, a hard disk, a compact disk, a DVD, and the like. Are these improvements,
Another major reason is the improvement of bearings, which is indispensable for rotating devices. Fluid bearings consisting of a sleeve and a rotating shaft that face each other through lubricating oil do not have ball bearings, so they are excellent in miniaturization, weight reduction, quietness, economy, etc., and their use is expanded to audio equipment and personal computers. Is coming.

[0003] Lubricating oils or bearing fluids used in fluid bearings include neopentyl polyol esters, squalane and / or naphthenic mineral oils and greases of urea compound thickeners (JP-A-1-279117). JP-A No. 1-188592, which contains a fatty acid triester of trimethylolpropane as a base oil and contains a hindered phenolic antioxidant and a benzotriazole derivative.
Japanese Patent Application Laid-Open No. 1-225697), those containing a specific hindered phenolic antioxidant and an aromatic amine antioxidant in a specific ratio (Japanese Patent Application Laid-Open No. 1-225697), a specific monocarboxylic acid ester having a phenyl group, And / or those using a specific dicarboxylic acid ester as a base oil (JP-A-4-357318) and those using a simple composition as a base oil (Japanese Patent No. 2621)
No. 329), those containing a carbonic acid ester as a base oil and containing a sulfur-containing phenolic antioxidant and a zinc-based extreme pressure agent (Japanese Patent Application Laid-Open No. 8-34987), and those using a magnetic fluid (Japanese Patent Application Laid-Open No. 8-259977). JP-A-10-183159, and JP-A-10-183159, which use a phenolic antioxidant in a base oil containing a carbonate ester as a main component.

[0004]

It is expected that demands and demands for high-speed processing of a large amount of information and further downsizing of devices will increase in the future. In the past, power consumption of audio equipment and personal computers, etc., was not paid much attention because they were not so large.However, since the equipment can be made smaller by extending the life of the built-in battery or reducing its capacity, there is no need for energy saving. There are still strong ones. As described above, with the desire for high-speed processing of information and miniaturization of equipment, higher speed rotation of the fluid bearing is required. The energy loss in the bearing increases as the speed increases. However, the various lubricating oils or bearing fluids proposed above have high viscosities and have not been evaluated from the viewpoint of energy saving in bearings. Lubricating oils for hydrodynamic bearings have lubricating properties, deterioration stability (lifetime), sludge formation prevention, abrasion prevention and corrosion prevention, as well as energy saving performance and low evaporative lubrication. Oil is required to meet the demands for high-speed processing of information, compactness, and the like. In addition, as the size of the device is reduced, the durability of the device itself may be sacrificed, and the durability of the device may be affected by lubricating oil.

The present invention has been made to solve the above-mentioned problems, and provides a lubricating oil for a hydrodynamic bearing having not only low lubricity and deterioration stability but also particularly low evaporability and excellent performance such as energy saving and durability. The task is to provide. Another object of the present invention is to provide a fluid bearing and a method of lubricating the fluid bearing using the lubricating oil for the fluid bearing.

[0006]

According to the present invention, a viscosity index of at least 100 obtained from neopentyl glycol and at least one monovalent fatty acid having 6 to 12 carbon atoms and / or a derivative thereof, and a total acid value of 0.5 mgKOH / It is a lubricating oil for hydrodynamic bearings composed of esters having a hydroxyl value of 20 mgKOH / g or less. Here, the at least one monovalent fatty acid and / or a derivative thereof is preferably two or more monovalent fatty acids and / or a derivative thereof. It is preferably a linear saturated monovalent fatty acid and / or a derivative thereof.

Further, the lubricating oil for a hydrodynamic bearing preferably contains 0.1 to 5.0 mass% of a polyhydric alcohol partial ester compound, a polyhydric alcohol partial ether compound, or a mixture thereof. Is preferably a compound having at least two hydroxyl groups. Further, the lubricating oil for a hydrodynamic bearing preferably contains 0.05 to 5.0 mass% of benzotriazole and / or a derivative thereof, a phenolic antioxidant, an epoxy compound, a carbodiimide compound and / or a phosphoric ester. .

The present invention also relates to a fluid bearing comprising a shaft and a sleeve, wherein the fluid bearing is filled with the lubricating oil for a fluid bearing. Lubrication method.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The base oil used in the lubricating oil for hydrodynamic bearings of the present invention is an ester obtained by reacting neopentyl glycol with a monovalent fatty acid having 6 to 12 carbon atoms or a derivative thereof. It is preferable to use a saturated fatty acid containing no unsaturated bond from the viewpoint of chemical stability and heat resistance, as the monovalent fatty acid or a derivative thereof (hereinafter, simply referred to as a fatty acid including a derivative unless otherwise specified). An ester with a monovalent fatty acid having 5 or less carbon atoms has a low viscosity, and it is difficult to obtain sufficient rigidity to support a fluid bearing portion, and is not preferable in durability. On the other hand, an ester with a monovalent fatty acid having 13 or more carbon atoms has a high viscosity, increases resistance during rotation, and does not provide good energy-saving properties.

[0010] As the fatty acid, any of a branched fatty acid and a linear fatty acid can be used. With respect to the lubricating oil for hydrodynamic bearings of the present invention, diesters composed of branched fatty acids are preferred for hydrolysis, while diesters of linear fatty acids are more preferred because of their good lubricity and high viscosity index. Naturally, diesters of neopentyl glycol having both acyl groups from branched fatty acids and straight-chain fatty acids having these properties can also be preferably used.
As the fatty acid, either a saturated fatty acid or an unsaturated fatty acid can be used, but a saturated fatty acid is preferred from the viewpoint of stability and the like.

As the saturated monovalent fatty acid having 6 to 12 carbon atoms,
Specifically, caproic acid, enanthic acid, 2-ethylpentanoic acid, 2-methylhexanoic acid, caprylic acid, 2-ethylhexanoic acid, pelargonic acid, 3,5,5-trimethylhexanoic acid, capric acid, isodecanoic acid , Undecylic acid, lauric acid or a mixed acid thereof, and those obtained from neopentyl glycol esters having a viscosity index of 100 or more. Above all,
Caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid or a mixed acid thereof is preferred. As the derivative of the saturated monovalent fatty acid, the above compound and a compound having 1 carbon atom
And esters with 4 lower alcohols, acid anhydrides and chlorides. Among them, chloride produces a corrosive chlorine compound as a by-product during ester synthesis, and removal and purification of chlorine are troublesome. It is preferred to use lower alcohol esters, especially acid anhydrides. The synthesis of neopentyl glycol ester can be carried out from neopentyl glycol and the above fatty acid, ester of lower alcohol of the fatty acid, acid anhydride or chloride by a known esterification reaction or transesterification reaction.

The environment in which lubricating oils for hydrodynamic bearings are used due to the spread of audio equipment and personal computers is equivalent to that of home electric appliances, and the use range must be considered from -20 to 60 ° C. To enable use under such conditions, excellent low-temperature properties are required so that sufficient fluidity can be obtained even at low temperatures. Neopentyl glycol esters are preferred because esters obtained using two or more saturated monovalent fatty acids having different chemical structures have good low-temperature fluidity. For example,
When two types of fatty acids are used, there are three types of esters, one of which has only one fatty acid bonded, the other has only one fatty acid bonded, and the other has both fatty acids bonded one by one.
An ester mixture containing esters of different chemical structures will be obtained. Such an ester mixture is
It is considered that the low-temperature fluidity is improved as compared with an ester having only a single chemical structure, because the crystallinity is lost.

The ester used for the lubricating oil of the present invention has a viscosity index of 100 or more. The viscosity index of the ester tends to increase as the acyl group is linear and the number of carbon atoms increases. Therefore, as long as necessary viscosity, low-temperature fluidity and lubricity can be ensured, a fatty acid having a large number of carbon atoms and a large proportion of linear chains is used, and the mixing ratio of the branched fatty acid is 50% by weight.
Hereinafter, it is preferable to use a mixed acid of 40% or less. In particular, when only linear mixed fatty acids are used, a high viscosity index, good lubricating property can be secured, and since it has a high viscosity index, the viscosity becomes low at low temperatures and energy saving becomes possible. Since it can be secured, lubricity becomes good.

The lubricating oil for a hydrodynamic bearing of the present invention has a total acid value of O.O.
Use an ester having a hydroxyl value of 5 mgKOH / g or less and a hydroxyl value of 20 mgKOH / g or less. The total acid value is important for ensuring corrosion resistance, abrasion resistance and stability, and is preferably 0.3 mgKOH / g or less. Further, the hydroxyl value is preferably 5 mgKOH / g or less from the viewpoint of improving moisture absorption resistance and stability. Esters having such properties can be obtained by sufficiently performing an esterification reaction and then appropriately purifying the ester by a known method.

Further, the water contained in the ester is a substance involved in the hydrolysis, and the ash can be a catalyst for promoting the hydrolysis or a substance causing sludge generation. The water content is preferably 500 ppm or less, more preferably 100 ppm or less, and the ash content is preferably 10 ppm or less, more preferably 1 ppm or less. Water can be removed by, for example, heat distillation, heat vacuum distillation, or blowing of an inert gas, and ash can be removed by an adsorption treatment. In order to reduce ash, it is also effective to carry out ester synthesis without a catalyst. By doing so, ester hydrolysis and sludge generation are minimized, and highly stable esters can be obtained, so that the deterioration stability of lubricating oils for hydrodynamic bearings is improved, and long-term stability and long life are achieved. Can be achieved.

The lubricating oil of the present invention may contain various additives in addition to the above-mentioned neopentyl glycol ester as a base oil in order to improve practical performance. Examples of such additives include fatty acid monoester compounds and / or monoether compounds of polyhydric alcohols, benzotriazole and / or derivatives thereof.
Further, a phenolic antioxidant, an epoxy compound, a carbodiimide compound, or a phosphate ester
It is also effective to mix species or two or more species.

The fatty acid monoesters and monoethers of polyhydric alcohols have two or more hydroxyl groups.
It is a polyhydric alcohol derivative in which at least two hydrocarbon groups are added by an ether bond or an ester bond, and is used as an oil agent. The polyhydric alcohol derivative is adsorbed on one bearing metal (for example, a shaft) at a hydroxyl group portion, and the hydrocarbon group extending from the ether bond or the ester bond prevents contact with the other bearing metal (for example, a sleeve). Therefore, it is considered that the lubricating action is improved. Such a polyhydric alcohol derivative can be obtained by a condensation reaction of a polyhydric alcohol having 3 to 6 hydroxyl groups with a monool having 10 to 22 carbon atoms or a monovalent fatty acid. Here, as the polyhydric alcohol, specifically, glycerin, trimethylolpropane, diglycerin, erythritol, pentaerythritol, triglycerin, sorbitol,
Mannitol and the like are particularly preferable, and trihydric alcohol is particularly preferable, and glycerin is particularly preferable. Further, a monovalent fatty acid that forms a partial ester with a polyhydric alcohol is
Those having 14 to 20 carbon atoms are more preferable, and specific examples include myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, and erucic acid. Examples of the monool that forms a partial ether with a polyhydric alcohol include monohydric alcohols corresponding to these acids.
Oleic acid and oleyl alcohol are particularly preferred, and glycerin monooleate or glycerin monooleyl ether is particularly preferred as the compound of the polyhydric alcohol derivative.

The polyhydric alcohol derivative may be appropriately mixed in an effective amount for exhibiting the effect, and the mixing amount is not particularly limited.
It is preferable to mix so as to contain 0.1 to 5.0% by mass, and more preferably about 0.5 to 5.0% by mass. Further, the partial (particularly, mono) ether and the partial (particularly, mono) ester of the polyhydric alcohol may be used alone, a plurality of compounds may be used, or a mixture thereof may be used.

As benzotriazole and / or a derivative thereof, a compound represented by the following general formula (1) is preferably used.

Embedded image In the formula, R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a hydrogen atom or a group having 0 to 20 carbon atoms containing a nitrogen atom and / or an oxygen atom. Benzotriazole derivatives are preferred because they improve the wear resistance of copper,
It is preferred that R ₂ is a group containing 10 to 20 carbon atoms containing a nitrogen atom.

Further, benzotriazole and / or a derivative thereof is 0.1 to 5.0 based on the entire lubricating oil for a hydrodynamic bearing.
It is preferable to mix them so that they are contained in an amount of about 0.5 to 5.0% by mass. If the addition amount is small, the effect of the wear resistance of copper is not particularly obtained, and if it is too large, not only the effect corresponding to the addition amount is not obtained, but also sludge formation may be caused in some cases, which is not preferable.

As phenolic antioxidants, 2,6
-Di-t-butylphenol, 2,6-di-t-butyl-
4-methylphenol, 2,6-di-t-butyl-4-
Ethylphenol, 2,6-di-t-butyl-4-nbutylphenol (ethyl 744), 4,4 ′ methylenebis (2,6-di-t-butylphenol), 2,2′-thiobis (4-methyl- 6-t-butylphenol) and the like. Also, an amine antioxidant may be used,
In particular, the combined use can significantly improve the oxidation stability.

As the epoxy compound, a phenylglycidyl ether type epoxy compound, an alkyl glycidyl ether type epoxy compound, a glycidyl ester type epoxy compound, an alicyclic epoxy compound, an epoxidized fatty acid monoester, an epoxidized vegetable oil or the like is used alone or in combination. Can be used. Preferred among these epoxy compounds are alkyl glycidyl ether type epoxy compounds, glycidyl ester type epoxy compounds, alicyclic epoxy compounds and epoxidized fatty acid monoesters. Among them, alkyl glycidyl ether type epoxy compound, glycidyl ester type epoxy compound,
Alicyclic epoxy compounds or mixtures thereof are more preferred. By adding these epoxy compounds, the stability of the substrate, especially the hydrolysis stability, is greatly improved.

The carbodiimide compound is a compound represented by the following general formula (2).

## STR2 ## _{R 3 -N = C = N-} R 4 (2) wherein, R ₃ and R ₄ is a hydrocarbon group containing hydrogen or a hydrocarbon group or a nitrogen and / or oxygen,, R ₃ And R ₄ may be the same or different.
In the general formula (2), preferably, R ₃ and R ₄ are hydrogen, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, and 6 to 6 carbon atoms.
18 aromatic hydrocarbon group and aromatic-aliphatic hydrocarbon group. Specifically, alkyl groups such as hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, 2-methylbutyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl and dodecyl, propenyl, butenyl ,
Alkenyl groups such as isobutenyl, pentenyl, 2-ethylhexenyl, octenyl, cyclopentyl, cyclohexyl, methylcyclopentyl, cycloalkyl groups such as ethylcyclopentyl, phenyl, aryl groups such as naphthyl, trail, isopropylphenyl, diisopropylphenyl, triisopropylphenyl, Compounds containing an aryl group such as alkyl-substituted phenyl such as nonylphenyl and an aralkyl group such as benzyl and phenethyl as R ₃ and R ₄ can be mentioned. The carbodiimide compound has a function as an acid scavenger and improves hydrolytic stability.

Examples of the phosphoric acid ester include tricresyl phosphate, triphenyl phosphate, cresyl diphenyl phosphate, diphenyl hydrogen phosphate, 2-ethylhexyl diphenyl phosphate, etc., and tricresyl phosphate and triphenyl phosphate are more preferable. . By adding a phosphate ester, the wear resistance of iron can be significantly improved.

The phenolic antioxidant, the epoxy compound, the carbodiimide compound, and the phosphoric acid ester preferably contain one or more selected from them. In the present invention, the amount of these additives is not particularly limited.However, even when a plurality of additives are blended, for each additive, 0.05 to 0.5% of the total amount of the lubricating oil for a fluid bearing. What is necessary is just to mix so that it may contain 5.0 mass%. If the addition amount is too small, there is no effect, and if it is too large, the characteristics of the base oil are not utilized and sludge is formed, which is not preferable.

The hydrodynamic bearing of the present invention is characterized by using the above-mentioned lubricating oil for hydrodynamic bearing. Especially if it is a fluid bearing that does not have a mechanism such as a ball bearing, but consists of a sleeve and a shaft, and the spacing is maintained so that the lubricant contained between them does not directly contact each other, It is not limited. In the fluid bearing of the present invention, a dynamic pressure generating groove is provided on one or both of the rotating shaft and the sleeve, and the rotating shaft is supported by dynamic pressure. Also includes hydrodynamic bearings, etc., in which a thrust plate is provided to produce.

In the fluid bearing, the sleeve and the rotating shaft or the sleeve and the thrust plate are in partial or full contact with each other because dynamic pressure is not generated when the fluid bearing is not rotating. Because of this, contact and non-contact are repeated, metal wear of the sleeve, rotating shaft or sleeve and thrust plate may occur, and seizure may occur due to temporary contact during rotation. It maintains high-speed rotation stability and quietness (durability) over a long period of time due to its properties, lubricity, anticorrosion, and sludge formation resistance, and exhibits excellent energy savings especially at high speeds. Accordingly, since the fluid bearing of the present invention enables reduction of power consumption due to higher speed and energy saving, OA equipment equipped with this fluid bearing is required to be more compact in addition to high-speed rotation stability and quietness. Or a longer life.

Further, the present invention is a method for lubricating a fluid bearing, wherein the fluid bearing is lubricated with the lubricant for a fluid bearing defined above. As already described, by filling and lubricating the fluid bearing lubricating oil into the fluid bearing, high-speed rotation stability and quietness are maintained for a long time, and excellent energy saving and long life are achieved. Can be.

[0029]

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited at all by the following examples.

(Embodiment I) FIG. 1 shows a specific example of a preferred fluid bearing for loading and using the lubricating oil for a fluid bearing of the present invention. It is sectional drawing which shows typically the schematic structure of the motor equipped with the fluid bearing. In FIG. 1, the motor 1 is
The bracket 2 includes a shaft 4 whose one end is externally fixed to a central opening of the bracket 2, and a rotor 6 rotatably held relative to the shaft 4. A stator 12 is fixed to the bracket 2, and generates a rotational driving force between the bracket 12 and a rotor magnet 10 provided on the rotor 6 so as to face the stator 12.

A disk-shaped upper thrust plate 4a and a lower thrust plate 4b projecting radially outward are provided on the upper and lower portions of the shaft 4, and a gas intervening portion 22 is provided on the outer surface of the shaft between these thrust plates. Are formed. On the other hand, the rotor 6 has a rotor hub 6a on which the recording disk D is mounted on the outer peripheral portion thereof and a shaft 4 which is located on the inner peripheral side of the rotor 6 through a minute gap in which the lubricating oil 8 is held.
And a sleeve 6b supported by the Further, the sleeve 6b is provided with an upper counter plate 7a and a lower counter plate 7b so as to cover the outer sides of the upper and lower thrust plates.

An opposing sleeve 6b extends from the outer peripheral portion of the shaft 4 adjacent to the upper portion of the gas intervening portion 22 provided at the center of the shaft 4 to the lower surface, the outer peripheral surface, and the outer peripheral portion of the upper thrust plate. A small gap is formed between the upper part of the inner peripheral portion through hole 6c and the lower surface of the upper counter plate 7a, and the lubricating oil 8 is held. A spiral groove 14 for generating a dynamic pressure in the lubricating oil 8 with the rotation of the rotor 6 is formed on the lower surface of the upper thrust plate 4a to generate a supporting force for holding the rotor portion in the axial direction when the motor rotates. At the same time, the lubricant 8 is pushed back in the direction of arrow A. Further sleeve 6b
An unbalanced herringbone-shaped groove 24 is formed in the lubricating oil holding portion on the upper inner surface of the inner peripheral portion through hole 6c to generate a supporting force for holding the rotor portion in the radial direction when the motor rotates, and at the same time, to supply the lubricating oil 8 Push up in the direction of arrow B.

Due to the dynamic pressure of the lubricating oil 8 generated by these grooves, the pressure distribution generated in the lubricating oil 8 in the minute gap is highest at the inner peripheral portion P on the lower surface of the upper thrust plate 4a. As a result, even if the air dissolved in the lubricating oil 8 becomes air bubbles, the air bubbles are diffused out of the inner peripheral portion P and are eliminated, and the air gap between the lower gas intervening portion 22 or the lower surface of the upper counter plate 7a is formed. To the department. These voids are released to the atmosphere directly or through the outside air communication holes 20, and the air bubbles are released to the outside air, thereby realizing a fluid bearing structure with no lubricating oil leakage and high supporting force.

Similar structures of the minute gaps, grooves, and lubricating oil holding portions are formed upside down on the lower thrust plate 4b and the lower counter plate 7b from below the gas intervening portion 22 provided at the center of the shaft 4. The rotor portion is more stably supported by the lower dynamic pressure bearing portion. Further, in the fluid bearing of this structure, the upper and lower counter plates 7a and 7b effectively prevent the lubricating oil 8 from spreading in the outer peripheral direction due to the rotational centrifugal force even at a high speed of about 20,000 revolutions per minute. By using the lubricating oil for a hydrodynamic bearing according to the present invention, higher speed and more stable rotation can be realized.

(Example II) Various lubricating oils for hydrodynamic bearings were trial-produced, filled into a motor having the above hydrodynamic bearing structure shown in FIG. 1 and actually driven, and tested in the following manner. Was evaluated.

The following esters (A to E and H), mineral oil (F), and alkylbenzene (G) were used as base materials for the lubricating oil for hydrodynamic bearings. A: Ester of neopentyl glycol (NPG) and n-C ₉ acid B: NPG, n-C ₉ acid (50 mol%) and n-C ₁₀ acid (50
Esuaru with mixed acid of mol%) C: NPG and, n-C ₁₀ acid (95 mol%) and n-C ₁₂ acid (5
mol :) mixed acid D: ester of pentaerythritol and nC ₅ acid E: ester of trimethylolpropane and 2-ethylhexanoic acid F: paraffinic mineral oil G: alkylbenzene H: NPG and 2- Mixed ester of 72% by mass of an ester with ethylhexanoic acid and 28% by mass of an ester of pentaerythritol with 2-ethylhexanoic acid

The following additives were used. I: glycerin monooleyl ether J: benzotriazole derivative represented by the following general formula (3)

Embedded image K: 2,6-di-t-butyl-4-methylphenol L: 2-ethylhexyl glycidyl ether M: tricresyl phosphate N: bis (diisopropylphenyl) carbodiimide

The lubricating oils for hydrodynamic bearings of the present invention (Examples 1 to 8) were prepared by blending the NPG ester base materials (A to C) and additives as shown in Table 1. The oils of Examples 1 and 2 do not contain additives, and Examples 3 to 8 show that the additives of I to N are contained in the amount in parentheses as shown in the column of additives in Table 1. Was blended. Further, lubricating oils for hydrodynamic bearings of Comparative Examples (Comparative Examples 1 to 5) were prepared using the base materials D to H. In addition, none of the lubricating oils for hydrodynamic bearings of the comparative examples contained any additives.

[0039]

[Table 1]

With respect to the prepared oils of Examples 1 to 8 and Comparative Examples 1 to 4, the physical properties of the oils were measured, and the oil was loaded on an actual fluid bearing and subjected to an acceleration test to evaluate its practical performance. The physical property measurement and the performance evaluation test were performed by the following methods.

(1) Evaporation amount: It was determined from the amount of weight loss when kept at 120 ° C. for 12 hours by matured gravimetric analysis (TG method). (2) Kinematic viscosity and viscosity index: According to JIS K 2283, the kinematic viscosity was measured using a Canon-Fenske viscometer and the viscosity index was calculated. (3) Hydroxyl value: Measured according to JIS K0070. (4) Total acid value: Measured according to JIS K 2514. (5) Moisture: Measured according to the Karl Fischer coulometric titration method of JIS K 2275. (6) Ash: Measured according to JIS K 2272. However, it was assumed that measurement could be performed up to the unit of ppm.

(7) NRRO test failure rate (durability):
For each sample, a motor 5 having the hydrodynamic bearing structure of FIG.
It is mounted on a table and accelerated by an intermittent operation in which the motor is started / stopped repeatedly at a temperature of 80 ° C, and non-repeatable run-out (NRRO) is measured to improve durability. The effect of lubricating oil on it was evaluated. At this time, the driving / stopping of the motor is performed by driving the motor (ON) as shown in FIG.
OO rpm), drive it after holding it (0N)
After 30 seconds, the motor was stopped (OFF), and after 30 seconds, the operation of driving the motor again (0N) was repeated. In the evaluation, the NRRO value was measured at the time of 10,000 and 20,000 intermittent times, and the case where the NRRO value exceeded 0.05 μm was determined to be defective, and the number of motors determined to be defective was determined for the sample oil. Expressed as a percentage of the total number of motors used (5).
In addition, when it clearly shows a sign exceeding 0.05 μm, it is measured even when it does not reach 10,000 or 20,000 times.
A case where the thickness exceeds μm is also regarded as defective.

(8) Energy saving: Using the same motor as that used for evaluating the NRRO test failure rate (durability), the current flowing through the motor was measured to evaluate the energy saving. That is, Examples 1 to 5 and Comparative Examples 2 and 5
Was loaded into the fluid bearing of the motor, and the current value was measured with an ammeter set between the DC power supply and the motor. The test was performed under the conditions of a motor rotation speed of 10,000 rpm, no load, an outside air temperature of the motor of 0 ° C. and 40 ° C.

Table 2 shows test results of physical property measurement and durability evaluation.
Table 3 shows the test results of the energy saving evaluation.

[0045]

[Table 2]

From Table 2, it can be seen that the lubricating oils of Examples 1 to 8 have a small amount of evaporation and the defect rate of the NRRO test is not a problem, and can be used effectively as a lubricating oil for hydrodynamic bearings. Understand. On the other hand, although Comparative Examples 1 and 2 have a small amount of evaporation, the failure rate of the NRRO test is large, and Comparative Examples 3 to 5 cannot be used practically because the amount of evaporation is too large.

[0047]

[Table 3]

From Table 3, it can be seen that the lubricating oils of Examples
In any case of ° C., the value of the current is small (particularly, the lubricating oil of Example 2 has a higher viscosity than that of Comparative Example 5, but the value of the current is small). In a DC circuit, the power to turn the motor is proportional to the current. It can be said that power consumption is low and energy saving is high. Further, in Examples 4 and 5, although the viscosity was higher than that in Example 1, the current value was low and the effect of the additive was confirmed.

[0049]

According to the present invention, the viscosity index obtained from neopentyl glycol and a monovalent fatty acid having 6 to 12 carbon atoms is 100 or more, the total acid value is 0.5 mgKOH / g or less, and the hydroxyl value is 20 mgKOH / g.
It is a lubricating oil for a hydrodynamic bearing characterized by comprising the following esters, and because it is a hydrodynamic bearing using the lubricating oil for a hydrodynamic bearing and a method of lubricating the hydrodynamic bearing, excellent energy saving and durability can be obtained. The present invention can be suitably used particularly for a rotating device of an electronic device whose speed and speed have been reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a schematic configuration of a motor equipped with a fluid bearing.

FIG. 2 is a chart schematically showing a drive / stop pattern in an intermittent operation of a motor in an acceleration test for evaluating the practical performance of a lubricating oil for a hydrodynamic bearing.

[Explanation of symbols]

 Reference Signs List 1 motor 4 shaft 4a upper thrust plate 4b lower thrust plate 6b sleeve

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C10M 129/76 C10M 129/76 133/22 133/22 133/38 133/38 137/04 137/04 171 / 00 171/00 F16C 33/10 F16C 33/10 Z // C10N 20:00 C10N 20:00 Z 20:02 20:02 30:00 30:00 Z 40:02 40:02 (72) Inventor Takahashi Nitto 3-17-35 Niisonanami, Toda City, Saitama Prefecture Japan Energy Co., Ltd. (72) Inventor Keiji Matsumoto 10 Nishitogoku Tsutsumi-cho, Niikyo-ku, Kyoto, Kyoto, Japan Nidec Central Research Laboratory (72) Inventor Kyoko Yokoyama F-term (reference) 3J011 JA02 MA22 4H104 BB05C BB08C BB09C BB32C BB34A BB35C BE16C BE26C BH03C EA02A EA22A LA20 PA01

Claims (7)

[Claims] 1. The method according to claim 1, wherein the neopentyl glycol and at least one
A monovalent fatty acid having 6 to 12 carbon atoms and / or a derivative thereof having a viscosity index of 100 or more, a total acid value of 0.5 mgKOH / g or less, and a hydroxyl value of 20 mgKOH / g or less. Features Lubricating oil for hydrodynamic bearings. 2. The lubricating oil for a hydrodynamic bearing according to claim 1, wherein the at least one monovalent fatty acid and / or a derivative thereof is two or more monovalent fatty acids and / or a derivative thereof. 3. The monovalent fatty acid and / or a derivative thereof is a linear saturated monovalent fatty acid and / or a derivative thereof.
Or the lubricating oil for a hydrodynamic bearing according to 2. 4. A polyhydric alcohol partial ester compound having at least two hydroxyl groups and at least one ester bond or a polyhydric alcohol partial ether having at least two hydroxyl groups and at least one ether bond 0.1 to 5.0 mass% of the compound or a mixture thereof,
The lubricating oil for a hydrodynamic bearing according to any one of claims 1 to 3, which contains 0.1 to 5.0% by mass of benzotriazole and / or a derivative thereof (b). 5. One or more kinds selected from phenolic antioxidants, epoxy compounds, carbodiimide compounds and phosphoric acid esters, each in a range of 0.05 to 5.
The lubricating oil for a hydrodynamic bearing according to any one of claims 1 to 4, which contains O wt%. 6. A fluid bearing comprising a shaft and a sleeve, wherein the lubricating oil according to claim 1 is used. 7. The hydrodynamic bearing according to claim 6, wherein
A lubricating method for a hydrodynamic bearing, characterized by using the lubricating oil for a hydrodynamic bearing according to any one of (1) to (5).