JP2001247885A - Noise-reducing lubricating grease for rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricating grease made proof against softening due to shear during the rotation of a rolling bearing, not causing insufficient lubrication on the friction surface of a bearing lubricated with a lubricating grease, being capable of stably rolling at a low torque without noise, and having a prolonged life. SOLUTION: This noise-reducing lubricating grease for a rolling bearing is prepared by adding 5-15 wt.% thickener containing at least 5 wt.% lithium salt of a 12-24C hydroxy aliphatic acid to a base oil containing at least 30 wt.% ester oil having a kinematic viscosity of 10-100 mm2/s (at 40 deg.C) and a solubility parameter of 8.3-9.0. The grease is the one that does not deteriorate so much in the action of a rolling bearing when it is subjected to shearing action during e.g. the rotation of a rolling bearing because the affinity of the base oil for the thicker increases to a value higher than the requirements and can operate a rolling bearing in the state in which its acoustic characteristics, i.e., noise-reducing properties can be maintained for a long term.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricating grease for reducing the noise of a rolling bearing, and more particularly to a rolling bearing applicable to a rolling bearing incorporated in an electronic information recording / reproducing apparatus for recording and reproducing electronic information and the like. And a noise reducing lubricating grease.

[0002]

2. Description of the Related Art Magnetic recording / reproducing devices such as hard disk drives (HDDs) and video tape recorders (VTRs), printing devices such as laser beam printers (LBPs), compact disks (CDs) and CDs, which are storage media of personal computers. -Rolling bearings for recording / reproducing devices for electronic information or the like by optical means or other means such as ROM, digital video disk (DVD), DVD-ROM, etc., have low noise and low power consumption. In order to operate, those having excellent low torque properties and acoustic characteristics are required.

[0003] Conventionally, lubricating oil and lubricating grease have been used as lubricants for small-diameter rolling bearings called miniature bearings used in the above-described devices.

[0004] The cause of the noise generated in the rolling bearing mounted on such a recording / reproducing apparatus for electronic information or the like is as follows.
It is expected that the formation of a lubricating oil film on the sliding surface is inferior, and the bearing rotation torque often fluctuates simultaneously with the occurrence of noise.

Japanese Patent Application Laid-Open No. Hei 8-209176 discloses a grease composition which improves the acoustic characteristics of a bearing at a high temperature and extends the acoustic characteristics at a low speed rotation from a high temperature. A thickener comprising 40 to 100% by weight of a lithium salt of 12 to 24 fatty acids;
A grease composition comprising a base oil having a kinematic viscosity of 80 to 300 mm ² / s and containing an ester oil of 10% by weight or more and containing the thickener of 5% by weight or more and less than 20% by weight is disclosed. ing.

[0006]

However, in the conventional lubricating grease described above, the grease composition is softened by the shearing force applied by rotation in the rolling bearing, and the grease leaks out from the friction surface of the rolling bearing, and the initial lubrication grease leaks. May not be able to maintain the lubrication performance of

If lubricating grease flows out of the friction surface of the rotating rolling bearing and lubricating oil is insufficient, the rotational torque of the rolling bearing rapidly increases, and abnormal noise, which is noise, is generated from the friction surface.

As described above, in the conventional lubricating grease, there is a case where the lubricating oil is insufficient on the friction surface of the rotating rolling bearing. The precise mechanism of the information device reproducing device is also adversely affected, and a malfunction is likely to occur, and there is also a problem that the recorded information or the reproduced information of this type of device becomes unreliable.

Accordingly, an object of the present invention relating to a lubricating grease for a rolling bearing of the present invention is to solve the above-mentioned problem, to prevent the lubricating grease from softening due to shearing during rotation of the rolling bearing, and to provide a rolling bearing filled with lubricating grease. Another object of the present invention is to make it possible to rotate stably with low torque and without noise without causing insufficient lubrication on the friction surface, and to extend the life of the bearing.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a noise-reducing lubricating grease for a rolling bearing, wherein a base oil having a solubility parameter of 8.3 to 9.0 is replaced with a lithium fatty acid. It is a lubricating grease made of salt to increase the noise of rolling bearings.

As described above, a lubricating grease using a base oil having a predetermined solubility parameter and employing a fatty acid lithium salt as a thickener has a higher affinity for the base oil and the thickener than required, so that Even if the lubricating grease is subjected to a shearing action during the rotation of the bearing, the action of the thickener does not decrease so much, and the softening of the lubricating grease is suppressed.

[0012] Therefore, the lubricating grease is less likely to scatter from the sealed rolling bearings, does not run out of lubricating oil even after a long-term use, and does not deteriorate the oil film formation. A lubricating grease capable of operating a rolling bearing while maintaining the acoustic characteristics of the present invention.

In order to further ensure the above-mentioned effects, a base oil having a solubility parameter of 8.3 to 9.0 has a carbon number of 12 to 9.0.
It is preferable to provide a noise reducing lubricating grease for a rolling bearing, which comprises a thickener containing 5% by weight or more of the 24 hydroxy fatty acid lithium salt.

Similarly, in order to further ensure the above-mentioned effect, a kinematic viscosity at 40 ° C. of 10 to 100 mm ²
/ S, a base oil containing 30% by weight or more of an ester oil having a solubility parameter of 8.3 to 9.0 and a thickener containing 5 to 15% by weight of a lithium salt of a hydroxy fatty acid having 12 to 24 carbon atoms is 5 to 15%. It is preferable to use a noise reducing lubricating grease for rolling bearings, which is blended by weight.

Kinematic viscosity at 40 ° C. is 10 to 100 mm
^In the lubricating grease employing a ² / s base oil, the lubricating oil (base oil) supplied to the friction surface from the grease has a predetermined kinematic viscosity and forms a lubricating oil film of a required thickness on the friction surface, It improves the lubrication of the rolling bearing in a high-speed rotation state and stabilizes the rotation torque in a low state.

A lubricating grease using a lithium hydroxy fatty acid salt having about 12 to 24 carbon atoms as a thickener,
It becomes a lubricating grease having a stable consistency at a high temperature, and the above-mentioned action is stabilized even under a high temperature condition.

As described above, the rolling bearing (such as a grease-filled rolling bearing for an electronic information recording / reproducing device) in which lubricating grease is sealed according to the present invention is hardly scattered or leaks out of the lubricating grease, and flows in the bearing. And stable rotation with low torque and no noise even at high speed without lubrication shortage.

Further, noise of the grease-enclosed rolling bearing is prevented, the life of the rolling bearing is extended, and malfunction of the recording / reproducing apparatus such as electronic information at the time of recording / reproducing information is prevented.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Rolling bearings for which lubricating grease is used in the invention according to each claim of the present application are:
Usually, a number of rolling elements composed of "rollers" or "balls" are arranged between an inner ring and an outer ring, and are rolling bearings that support the rotating shaft in a radial direction or a thrust direction or in both directions. The spacing between them is arranged by a cage. Incidentally, a recording / reproducing apparatus for electronic information or the like usually has an inner diameter of a bearing of less than 10 mm and an outer diameter of 3 to 10 mm.
In many cases, a rolling bearing of about 30 mm is used, and a bearing called a miniature bearing is also included in such a bearing.

The base oil of the lubricating grease used in the invention according to each claim of the present application may have a solubility parameter of 8.3 to 9.0, and may be a poly-α-olefin oil (also referred to as PAO oil). Synthetic hydrocarbon oils, ester oils, ether oils and other known lubricating oils can be used without limitation. As a rolling bearing in a recording / reproducing apparatus for electronic information, etc., it is assumed that the rolling bearing is used under high-speed rotation conditions exceeding, for example, 10,000 rpm and may be heated to about 70 ° C. A base oil having heat resistance at temperature is used.

Here, the solubility parameter (δ) is Sm
According to all [PASmall, J. Appl. Chem., 3,71 (1953)], the molecular attraction force (Fi) calculated from the constituent groups such as the atoms or atomic groups constituting the molecule and the bond type is applied to the molecule. The additive properties of each Fi are recognized, and can be calculated by the following equation 1.

Δ = ρΣFi / M (Equation 1) (where, ρ is density and M is molecular weight.) The above-mentioned molar attraction force (Fi) is expressed by Hoy [KLHoy, J. Pai.
nt Technol., 42, 76 (1970) etc.] for each atomic group as shown in Table 1 below. The unit of Fi is [(cal / cm ³ ) ^1/2 mole].

[0023]

[Table 1]

Examples of the base oil having such a solubility parameter within a predetermined range include ester oil and ether oil.

Examples of the type of ester oil include diester oil obtained by reacting a dibasic acid and an alcohol, and aromatic ester oil obtained by reacting an aromatic tribasic acid or an aromatic tetrabasic acid with an alcohol. And polyol ester oils obtained from the reaction of polyhydric alcohols and monobasic acids.

As diester oils, dioctyl adipate (DOA), diisobutyl adipate (DIB),
Examples include dibutyl adipate (DBA), dioctyl azelate (DOZ), dibutyl sebacate (DBS), dioctyl sebacate (DOS), and the like.

Examples of the aromatic ester oil include trioctyl trimellitate (TOTM), tridecyl trimellitate, tetraoctyl pyromellitate and the like.

Examples of the polyol ester oil include those obtained by reacting a polyhydric alcohol shown below with a monobasic acid. The monobasic acid to be reacted with the polyhydric alcohol may be used alone or in combination. Further, a polyhydric alcohol and a dibasic acid / monobasic acid may be used as a complex ester of a mixed fatty acid and an oligoester.

Examples of polyhydric alcohol esters include trimethylolpropane (TMP), pentaerythritol (PE), dipentaerythritol (DPE), neopentyl glycol (NPG), and 2-methyl-2-propyl-1,3-propane. Diol (MPPD) and the like.

The monobasic acid is mainly a monovalent fatty acid having 4 to 18 carbon atoms, and specific examples thereof include acetic acid, valeric acid,
Caproic acid, caprylic acid, enanthic acid, pelargonic acid,
Capric acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, tallow acid, stearic acid, caproleic acid, undecylenic acid, lindelic acid, tuzic acid, fisthenic acid, myristoleic acid, palmitoleic acid, petroseric acid, oleic acid, Examples include elaidic acid, ascrepic acid, vaccenic acid, sorbic acid, linoleic acid, linolenic acid, sabininic acid, and ricinoleic acid.

Other ether oils as base oils include C _{12 of} diphenyl, triphenyl and tetraphenyl.
Of -C ₂₀ (di) phenyl ether oil in which the alkyl group is introduced is preferred.

Preferred conditions for the kinematic viscosity of the base oil used in the present invention are 10 mm ² / s or more at 40 ° C. 40
With a base oil having a kinematic viscosity at 10 ° C. of less than 10 mm ² / s, a lubricating oil film is not sufficiently formed in the initial stage of bearing rotation, and the lubricating oil film is likely to be interrupted. The upper limit of the kinematic viscosity at 40 ° C. of the base oil used in the present invention is 200 at 40 ° C. in consideration of the torque of the rotating shaft.
mm ² / s or less, preferably 150 mm ² / s or less (4
0 ° C.), more preferably 100 mm ² / s or less (40
° C).

The thickener used in the grease of the present invention is a lithium salt of a fatty acid, also called lithium soap, and preferably a lithium salt of a hydroxy fatty acid having 12 to 24 carbon atoms.

Specific examples of the lithium soap include lithium laurate (C ₁₂ ), lithium myristate (C ₁₄ ),
Palmitic acid (C ₁₆₎ lithium, heptadecanoic acid (C ₁₇₎
Lithium, lithium stearate (C ₁₈ ), lithium arachidate (C ₂₀ ), lithium behenate (C ₂₂ ), lithium lignoceric acid (C ₂₄ ), lithium tallow fatty acid, 9
Lithium-hydroxystearate, lithium 10-hydroxystearate, lithium 12-hydroxystearate, lithium 9,10-hydroxystearate, lithium ricinoleate, lithium ricinoelaidate and the like.

Among these, particularly preferred lithium soaps are lithium stearate and lithium 12-hydroxystearate. A thickener containing 5% by weight or more of such a lithium soap is used in an amount of 5 to 20% by weight based on the total amount of grease. It is preferable to mix them.

The grease of the present invention may contain known additives such as a rust preventive, an antioxidant, an extreme pressure additive and a wear inhibitor so as not to impair the intended purpose.

Incidentally, rust preventives include metal salts of organic sulfonic acids and esters, among which organic sulfonic acid salts include metal salts such as dinonylnaphthalene sulfonic acid and heavy alkylbenzene sulfonic acid. Specific examples include calcium sulfonate, barium sulfonate, sodium sulfonate and the like.

Examples of the esters include sorbitan monolaurate, sorbitan trilaurate, sorbitan monostearate, and sorbitan monooleate, which are partial esters of polybasic carboxylic acids and polyhydric alcohols of sorbitan derivatives.

As the antioxidant, a nitrogen-containing compound-based antioxidant and a phenol-based antioxidant may be used alone or in combination. Examples of the nitrogen compound-based antioxidant include phenyl α-naphthylamine, diphenylamine, phenylenediamine, oleylamidoamine, and phenothiazine. Examples of the phenolic antioxidant include p-tert-butylphenisalicylate, 2,6-di-tert-butyl-p-phenylphenol, and the like.

[0040]

Examples and Comparative Examples [Examples 1 to 4, Comparative Examples 1 to 4]
4] Base oils used in Examples and Comparative Examples are summarized below,
Table 2 shows the content (% by weight) of each component when the lubricating grease composition was 100% by weight. The numbers in parentheses in Table 2 correspond to the types of base oil. (1) Ester oil (manufactured by FMC: Leolube DOS) (2) Ester oil (manufactured by NOF Corporation: UNISTAR H310)
R) (3) Ester oil (FMC: Leo Lube LPE60)
2) (4) PAO oil (Nippon Steel Chemical Co., Ltd .: Shinfluid 40)
1) (5) PAO oil (Nippon Steel Chemical Co., Ltd .: Shinfluid 60)
1) (6) PAO oil (Nippon Steel Chemical Co., Ltd .: Shinfluid 80)
1) (7) Ether oil (Matsumura Oil Laboratories: Moresco Hi-Lube LB15) (8) Ether oil (Matsumura Oil Research Laboratories: Moresco High-Lube LB100) A thickener and an additive (antioxidant) were mixed while heating in a container, and in a state where these were completely dissolved, the solution was brought into contact with an iron plate cooled with liquid nitrogen and rapidly cooled to produce a lubricating grease.

Physical properties evaluation tests were performed on the obtained lubricating grease under the following conditions. These results are also shown in Table 2.

[Evaluation of bearing acoustic characteristics]
84 bearings (deep groove ball bearings, dimensions: inner diameter 4mm, outer diameter 9m
m), the two bearings were mounted on one spindle, and the spindle was driven to rotate at a bearing rotation speed of 20,000 rpm, an ambient temperature of 100 ° C., and an axial load of 0.8 kgf. Under this rotation condition, JI
The noise value (dBA) was measured every 100 hours in accordance with SB1548-1960. 42d noise level at each measurement
When it was less than BA, the bearing was again rotated under the same conditions as above, and the noise value after 100 hours was measured. Then, the measurement was repeated under the same conditions until the noise value reached 42 dBA, and the number of hours until the noise value reached 42 dBA was examined. The results were evaluated on a four-point scale as described below, and the results are indicated by symbols in Table 2.印: Time to reach 42 dBA is 800 hours or more ○: Time to reach 42 dBA is 500 hours or more 8
Less than 00 hours △: Time to reach 42 dBA is 300 hours or more 5
Less than 00 hours x mark: Time to reach 42 dBA is less than 300 hours

[Evaluation of Softening Property of Lubricating Grease] A 6204 bearing (deep groove ball bearing, dimensions: inner diameter 20 mm, outer diameter 47 mm) filled with lubricating grease was rotated at 10,000 rpm.
Atmosphere at room temperature, axial load 39.2N (= 4kg
Rotated continuously for 4 hours in f).

Thereafter, the lubricating grease was die-cut into a column having a diameter of 3 mm and a height of 2 mm. The column-shaped grease was placed on a horizontal surface, and a transparent plate was placed on the upper end surface, and 100 g of the transparent grease was placed thereon.
And crushed the lubricating grease for 5 seconds. Then, the length and width of the lubricating grease which was removed in a circular shape by removing the weight was measured, and an estimated value of the penetration was calculated using a conversion table of the penetration previously prepared.

From the estimated value of the penetration of the lubricating grease subjected to the shearing in the rolling bearing as described above, the estimated value of the penetration of the lubricating grease obtained under the same conditions before the start of the test is subtracted. The difference between these values is also shown in Table 2 as a change in the estimated value of the penetration. The results were evaluated on a four-point scale as described below. It can be evaluated that the larger the difference value, the softer the lubricating grease.印: Change in the estimated value of the penetration value is less than 30 ○: Change in the estimated value of the penetration value is 30 or more and less than 60 △: Change in the estimated value of the penetration value is 60 or more and less than 90 X: Admix Changes in the estimated value of consistency are 90 or more

[0046]

[Table 2]

As is clear from the results shown in Table 2, the lubricating greases of Comparative Examples 1 to 4 which did not employ a base oil having a solubility parameter within a predetermined range exhibited 42 dBA when the test time was less than 300 hours or less than 500 hours. Noise generated from the bearings, the lubricating grease softens due to the shearing applied during rotation in such a relatively short operating time, and the lubricating grease scatters due to centrifugal force during rotation, resulting in a sufficient lubricating oil film on the friction surface. Was not formed.

On the other hand, the lubricating greases of Examples 1 to 4 using a base oil having a solubility parameter within a predetermined range,
The time when the noise value of the bearing reached 42 dBA was 500 hours or more, and the rolling bearing could be smoothly rotated without generating noise even if the rolling bearing rotated continuously received a long time.

Therefore, such lubricating grease is
It has been recognized that the life of the rolling bearing is prolonged, the malfunction and noise of the recording / reproducing apparatus for electronic information and the like are suppressed, and the service life is prolonged.

Further, when this lubricating grease is sealed in a rolling bearing used for a recording / reproducing apparatus for electronic information, etc., the lubricating grease does not cause insufficient lubrication when rotating at high speed, and rotates at a stable low torque without generating noise. A grease-sealed rolling bearing for a recording / reproducing apparatus for electronic information, which hardly causes errors in reading and writing of electronic information.

[0051]

As described above, the invention relating to the noise reducing grease of a rolling bearing according to the present invention is based on ester oil having a solubility parameter in a predetermined range as a base oil and a thickener comprising a fatty acid lithium salt in the base oil. The lubricating grease contains a base oil and a thickener, which has a very high affinity for lubricating grease. Therefore, there is an advantage that even if the rolling bearing is rotated at high speed, the rolling bearing can be reliably rotated with low noise for a long time.

The noise-reducing lubricating grease of a rolling bearing, in which a thickener comprising a lithium salt of a fatty acid having 12 to 24 carbon atoms is blended in an amount of 5% by weight or more, can surely obtain the above advantages.

The kinematic viscosity at 40 ° C. is 10 to 10
The lubricating grease employing a base oil of 0 mm ² / s,
The lubricating oil supplied from the grease to the friction surface has a predetermined kinematic viscosity, forms a lubricating oil film of the required thickness on the friction surface, improves the lubricity of the rolling bearing in high-speed rotation, and reduces the rotational torque. Has the advantage of stabilizing.

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Claims (3)

[Claims] 1. A noise reducing lubricating grease for a rolling bearing obtained by increasing a base oil having a solubility parameter of 8.3 to 9.0 with a lithium fatty acid salt. 2. A noise reducing effect of a rolling bearing comprising a base oil having a solubility parameter of 8.3 to 9.0 and a thickener containing 5% by weight or more of a lithium salt of hydroxy fatty acid having 12 to 24 carbon atoms. Lubricating grease. 3. A kinematic viscosity at 40 ° C. of 10 to 100 m
A base oil containing at least 30% by weight of an ester oil having a solubility parameter of 8.3 to 9.0 at m ² / s and having a carbon number of 12 to 2
4. A noise reducing lubricating grease for a rolling bearing, comprising 5 to 20% by weight of a thickener containing 5% by weight or more of a lithium salt of a hydroxy fatty acid.