JP2005112902A - Grease composition and grease-sealed bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition which can effectively prevent the rolling surface of a grease-sealed bearing from peeling due to hydrogen embrittlement, and to provide a grease-sealed bearing. <P>SOLUTION: This grease composition comprising a base oil, a thickener and additives is characterized in that the additives comprise at least a molybdate and an organic acid salt. The molybdate is at least one molybdate selected from sodium molybdate, potassium molybdate and lithium molybdate. The organic acid is the sodium salt of an organic acid having a 1 to 20C carboxy group residue. The molybdate is contained in an amount of 0.01 to 5 wt.% based on the total amount of the grease composition, and the organic acid salt is contained in an amount of 5 to 70 wt.% based on the amount of the molybdate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a grease composition and the grease-filled bearing, and particularly for an alternator, an electromagnetic clutch for a car air conditioner, an intermediate pulley, an electric component such as an electric fan motor, a rolling bearing for an auxiliary machine, and a rolling bearing for a motor. The present invention relates to a grease composition and a grease-filled bearing in which the grease composition is sealed.

Electrical components and accessories in automobiles, motors in industrial machines, etc. are required to be downsized, high performance, and high output year by year, and usage conditions are becoming stricter. For these, rolling bearings are used, and grease is mainly used for lubrication. However, due to severe usage conditions, specific peeling accompanied with white structure change occurs early on the rolling surface of the rolling bearing, which is a problem.
This specific exfoliation is different from the exfoliation from the inside of the rolling contact surface caused by normal metal fatigue, and is a fracture phenomenon that occurs from a relatively shallow portion of the surface of the rolling contact surface and is considered to be hydrogen embrittlement caused by hydrogen.
As a method for preventing such a specific peeling phenomenon accompanied by a white tissue change that occurs at an early stage, for example, a method of adding a passivating agent to a grease composition has been reported (see Patent Document 1).
However, with the recent increase in the usage conditions of rolling bearings, sufficient measures cannot be taken with the method of adding a passivating agent.
JP-A-3-210394

  The present invention has been made to address such problems, and it is an object of the present invention to provide a grease composition capable of effectively preventing separation on a rolling surface due to hydrogen embrittlement in a grease-filled bearing and the grease-filled bearing. To do.

The grease composition of the present invention comprises a base oil and a thickener and an additive, and the additive contains at least a molybdate and an organic acid salt.
The molybdate is at least one molybdate selected from sodium molybdate, potassium molybdate and lithium molybdate.
In addition, the organic acid salt is a sodium salt of an organic acid having a carboxyl group residue having 1 to 20 carbon atoms.
The blending ratio of each component is 0.01 to 5% by weight of the molybdate with respect to the entire grease composition, and 5 to 70% by weight of the organic acid salt with respect to the addition amount of the molybdate. It is characterized by becoming.
The thickener is a urea-based thickener.

  The grease composition of the present invention is a grease composition used for a bearing portion, and the grease composition contains a molybdenum compound together with iron oxide on a frictional wear surface or a new ferrous metal surface exposed by wear in the bearing portion. It contains a molybdate capable of forming a film and an organic acid salt that promotes the formation of the film.

  The grease-enclosed bearing of the present invention is a bearing in which the above-described grease composition is encapsulated.

  Since the molybdate and organic acid salt are blended into the grease consisting of base oil and thickener, the occurrence of peculiar peeling due to hydrogen embrittlement found in bearings used in automobiles and industrial machinery can be suppressed. Extends the life of grease-filled bearings.

  By blending molybdate and organic acid salt, the molybdate decomposes and reacts on the frictional wear surface or the new metal surface exposed by wear, and a molybdenum compound film is formed on the bearing rolling surface along with iron oxide. Furthermore, by using both molybdate and organic acid salt, as a result of surface analysis, it was found that the oxide film was thicker and the molybdenum content was higher than when only molybdate was blended. Therefore, it is considered that the organic acid salt has an effect of promoting the generation of the iron oxide and molybdenum compound coating on the bearing rolling surface. The iron oxide and molybdenum compound coating formed on the rolling surface of the bearing can suppress the generation of hydrogen due to the decomposition of the grease and prevent unique peeling due to hydrogen embrittlement.

The molybdate that can be used in the present invention is preferably a metal salt. Examples of the metal constituting the metal salt include sodium, potassium, lithium, magnesium, calcium, copper, zinc, barium and the like.
In the present invention, the metal that easily forms a film containing a molybdenum compound together with iron oxide reacts on the frictional wear surface or the newly formed iron-based metal surface exposed by wear in the bearing portion. Alkali metal salts of the salts are preferred. Suitable alkali metal molybdates include lithium molybdate, sodium molybdate or potassium molybdate, which can be used alone or as a mixture.

  The organic acid salt that can be used in the present invention can be any salt such as an aromatic organic acid, an aliphatic organic acid, or an alicyclic organic acid. As the organic acid, monobasic or polybasic organic acids can be used. Among these, an organic acid having a chemical structure having 1 to 20 carbon atoms is particularly preferable because it facilitates formation of a film containing a molybdenum compound.

  Specific examples of organic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, pelargonic acid, capric acid, undecyl acid, lauric acid, tridecylic acid, myristic acid, pentadecyl Monovalent saturated fatty acids such as acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid and arachidic acid, monounsaturated fatty acids such as acrylic acid, crotonic acid, undecylenic acid, oleic acid and gadoleic acid, malonic acid and methylmalon Divalent saturation such as acid, succinic acid, methyl succinic acid, dimethyl malonic acid, ethyl malonic acid, glutaric acid, adipic acid, dimethyl succinic acid, pimelic acid, tetramethyl succinic acid, suberic acid, azelaic acid, sebacic acid, brassic acid Divalent unsaturated fatty acids such as fatty acids, fumaric acid, maleic acid, oleic acid, tartaric acid, Fatty acid derivatives such as phosphate, benzoic acid, phthalic acid, trimellitic acid, and aromatic organic acids such as pyromellitic acid.

  The organic acid is preferably a metal salt, and a sodium salt is preferable among the metal salts. Preferred metal salts of organic acids include sodium benzoate, monosodium sebacate, disodium sebacate, monosodium succinate, and disodium succinate.

  Base oils that can be used in the present invention include mineral oils such as spindle oil, refrigerating machine oil, turbine oil, machine oil, dynamo oil, high-purity mineral oil, liquid paraffin, polybutene, poly-α-olefin, alkylnaphthalene, alicyclic compounds, etc. Hydrocarbon synthetic oil or natural oil, polyol ester oil, phosphate ester oil, polymer ester oil, aromatic ester oil, carbonate ester oil, diester oil, polyglycol oil, silicone oil, polyphenyl ether oil, alkyl diphenyl ether Non-hydrocarbon synthetic oils such as oil, alkylbenzene oil, and fluorinated oil can be used.

  Thickeners that can be used in the present invention include benton, silica gel, fluorine compound, lithium soap, lithium complex soap, strong lucium soap, calcium complex soap, aluminum soap, aluminum complex soap and other soaps, diurea compounds, polyurea compounds, etc. These urea compounds are mentioned. In consideration of heat resistance, cost, and the like, a urea compound is desirable.

  Examples of the urea compound include a diurea compound and a polyurea compound. A diurea compound is obtained by reaction of diisocyanate and a monoamine, for example. Examples of the diisocyanate include phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, hexane diisocyanate, etc., and monoamines include octylamine, dodecylamine, hexadecylamine, stearylamine, Examples include oleylamine, aniline, p-toluidine, cyclohexylamine and the like. The polyurea compound can be obtained, for example, by reacting diisocyanate with a monoamine or diamine. Examples of the diisocyanate and monoamine include those similar to those used for the production of the diurea compound. Examples of the diamine include ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, phenylenediamine, tolylenediamine, xylenediamine, And diaminodiphenylmethane.

A urea compound is obtained by reacting an isocyanate compound and an amine compound. In order not to leave a reactive free radical, the isocyanate group of the isocyanate compound and the amino group of the amine compound are preferably blended so as to be approximately equivalent.
Base grease for blending various compounding agents by blending a urea compound with a base oil can be obtained. The base grease is produced by reacting an isocyanate compound and an amine compound in a base oil.

  The blending ratio of the thickener to the base grease is 1 to 40% by weight, preferably 3 to 25% by weight, based on the whole base grease. If the content of the thickener is less than 1% by weight, the thickening effect is reduced, making it difficult to make grease. If the content exceeds 40% by weight, the obtained base grease becomes too hard and the desired effect is difficult to obtain. Become.

  The blending ratio of molybdate and organic acid salt is 0.01-5% by weight of molybdate and the amount of molybdate added to the entire grease composition composed of the base grease and various compounding agents. On the other hand, the organic acid salt is blended in an amount of 5 to 70% by weight. If the blending ratio of molybdate and organic acid salt is less than the above blending range, peeling on the rolling surface due to hydrogen embrittlement cannot be effectively prevented. Moreover, even if it exceeds the said range, the peeling prevention effect does not improve any more.

  In addition to a mixed compounding agent of molybdate and organic acid salt, a known additive for grease can be contained as necessary. Examples of the additives include organic zinc compounds, amine-based, phenol-based, sulfur-based antioxidants, metal deactivators such as benzotriazole, polymethacrylate, polystyrene and other viscosity index improvers, molybdenum disulfide, graphite. Examples thereof include solid lubricants such as metal sulfonates, rust preventives such as polyhydric alcohol esters, friction reducing agents such as organic molybdenum, oily agents such as esters and alcohols, and phosphorus-based antiwear agents. These can be added alone or in combination of two or more.

  Since the grease composition of the present invention can suppress the occurrence of peculiar peeling due to hydrogen embrittlement, the life of the grease-sealed bearing can be improved. For this reason, ball bearings, cylindrical roller bearings, tapered roller bearings, spherical roller bearings, needle roller bearings, thrust cylindrical roller bearings, thrust tapered roller bearings, thrust needle roller bearings, thrust spherical roller bearings, etc. Can be used as grease.

A bearing in which the grease composition of the present invention is enclosed will be described with reference to FIG. FIG. 1 is a cross-sectional view of a deep groove ball bearing.
In the grease-filled bearing 1, an inner ring 2 having an inner ring rolling surface 2a on the outer peripheral surface and an outer ring 3 having an outer ring rolling surface 3a on the inner peripheral surface are arranged concentrically, and the inner ring rolling surface 2a and the outer ring rolling surface 3a are arranged. A plurality of rolling elements 4 are arranged between the two. The cage 5 is configured to hold the plurality of rolling elements 4, and the seal member 6 is fixed to the outer ring 3 or the like. A grease composition 7 is enclosed at least around the rolling element 4.

Examples 1-13
4,4-Diphenylmethane diisocyanate (MDI) is dissolved in half of the base oil shown in Table 1 and Table 2 in the proportions shown in Table 1 and Table 2, and 4,4-diphenylmethane is dissolved in the remaining half of the base oil. A monoamine that was twice the equivalent of diisocyanate was dissolved. The respective blending ratios and types are as shown in Tables 1 and 2.
A solution in which monoamine is dissolved is added while stirring the solution in which 4,4-diphenylmethane diisocyanate is dissolved, and then the reaction is continued at 100 to 120 ° C. for 30 minutes to form a diurea compound in the base oil. It was.
To this, molybdate, organic acid salt and antioxidant were added at the blending ratios shown in Tables 1 and 2, and the mixture was further stirred at 100 to 120 ° C. for 10 minutes. Thereafter, the mixture was cooled and homogenized with three rolls to obtain a grease composition.

In Tables 1 and 2, the alkyl diphenyl ether oil used as the base oil is LB100 under the trade name of Matsumura Oil Co., Ltd., synthetic hydrocarbon oil is Shinflud 601 under the trade name of Nippon Steel Chemical Co., and polyol ester is the trade name of Kao Corporation. Kaolube 268 was used respectively. As the mineral oil, a paraffinic mineral oil having a kinematic viscosity of 30.7 mm ² / s (40 ° C.) was used.
As the antioxidant, alkylated diphenylamine was used.

  The obtained grease composition was subjected to a high-temperature high-speed test, a rapid acceleration / deceleration test, and a blending penetration measurement according to Japanese Industrial Standards. Test methods and test conditions are shown below. The results are shown in Tables 1 and 2.

High-temperature high-speed test Rolling bearing (6204) is filled with 1.8 g of the grease composition obtained in each example, and the bearing outer ring outer diameter is 180 ° C, radial load is 67N, and axial load is 67N. Rotated with, and measured the time to burn-in.

Rapid Acceleration / Deceleration Test A rapid acceleration / deceleration test was performed on a rolling bearing with internal rotation that supports the rotating shaft of an alternator, which is an example of an electrical accessory. The rapid acceleration / deceleration test conditions were set such that the load applied to the pulley attached to the tip of the rotating shaft was 3234N and the rotational speed was 0 to 18000rpm. Then, abnormal peeling occurred in the bearing, and the time when the generator stopped when the vibration of the vibration detector exceeded the set value was measured.

Examples 14 and 15
Li-12-hydroxystearate was added to the base oil shown in Table 2, and dissolved by heating at 200 ° C. with stirring. In addition, each compounding ratio is as Table 2. Thereafter, the mixture was cooled, molybdate, organic acid salt and antioxidant were added at the blending ratio shown in Table 2, and homogenized with three rolls to obtain a grease composition. The grease composition was subjected to a high-temperature high-speed test and a rapid acceleration / deceleration test in the same manner as in Example 1. However, considering the heat resistance of Li soap grease, the high-temperature high-speed test was conducted at 150 ° C.

Comparative Examples 1-6
By the method according to Example 1, the thickener and base oil were selected at the blending ratios shown in Table 2 to adjust the base grease, and further additives were blended to obtain a grease composition. The obtained grease composition was evaluated by performing the same test as in Example 1. The results are shown in Table 2.

  As shown in Table 1 and Table 2, each example can effectively prevent specific peeling accompanied with a white texture change occurring on the rolling surface, and thus is excellent in a high-temperature high-speed test and a rapid acceleration / deceleration test. All the rapid acceleration / deceleration tests in each example showed 300 hours or more.

  Since the grease composition of the present invention can effectively prevent specific peeling accompanied with a white structure change occurring on the rolling surface and has a long bearing life, it can be used for alternators, car air conditioner electromagnetic clutches, intermediate pullers, electric fan motors, etc. It can be used for automotive electrical parts, rolling bearings for auxiliary machines, and motor bearings.

It is sectional drawing of a deep groove ball bearing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Grease-filled bearing 2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Seal member 7 Grease composition

Claims (7)

A grease composition comprising a base oil and a thickener and an additive, wherein the additive contains at least a molybdate and an organic acid salt. The grease composition according to claim 1, wherein the molybdate is at least one molybdate selected from sodium molybdate, potassium molybdate, and lithium molybdate. The grease composition according to claim 1 or 2, wherein the organic acid salt is a sodium salt of an organic acid having 1 to 20 carbon atoms. The molybdate is 0.01 to 5% by weight based on the entire grease composition, and the organic acid salt is blended in an amount of 5 to 70% by weight based on the amount of the molybdate added. The grease composition according to claim 1, claim 2 or claim 3. The grease composition according to claim 1, wherein the thickener is a urea-based thickener. A grease composition for use in a bearing portion, the grease composition comprising a molybdate capable of forming a film containing a molybdenum compound together with iron oxide on a frictional wear surface or a new ferrous metal surface exposed by wear in the bearing portion; A grease composition comprising an organic acid salt that promotes the formation of the film. A grease-enclosed bearing in which a grease composition is encapsulated, wherein the grease composition is the grease composition according to any one of claims 1 to 6.

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