JP5288725B2 - Grease composition and grease-filled bearing - Google Patents

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, severe use conditions such as high-speed rotation at high temperatures cause a problem in that specific peeling accompanied by a change in white structure occurs at an early stage on the rolling surface of the rolling bearing.
This specific exfoliation is different from the exfoliation from the inside of the rolling contact surface caused by normal metal fatigue, and is considered to be due to hydrogen embrittlement caused by hydrogen due to a fracture phenomenon that occurs from a relatively shallow surface of the rolling contact surface. Yes. 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 is known (see Patent Document 1). A method of adding bismuth dithiocarbamate to a grease composition is known (see Patent Document 2).
However, in recent years, electrical components and accessories in automobiles, motors in industrial machines, etc., are increasingly used in rolling bearings at high temperatures, such as frequent high-speed operation-sudden deceleration operation-rapid acceleration operation-sudden stop. The method of adding a passivating agent and bismuth dithiocarbamate has become inadequate as a measure for preventing the peeling phenomenon.
JP-A-3-210394 JP-A-2005-42102

  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 is a grease composition obtained by adding an additive to a base grease composed of a base oil and a thickener, and the additive contains at least an epoxy compound, The blending ratio is 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease.

The epoxy compound is at least one epoxy compound selected from bisphenol A type and bisphenol F type.
The thickener is a urea-based thickener.
Further, the base oil is at least one oil selected from alkyl diphenyl ether oil and poly-α-olefin oil.

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

  In the grease composition of the present invention, since an additive containing at least an epoxy compound is blended in a base grease composed of a base oil and a thickener, a peculiarity due to hydrogen embrittlement found in bearings used in automobiles and industrial machines. The occurrence of peeling can be suppressed, and the life of the grease-filled bearing can be extended.

  The grease-enclosed bearing of the present invention can effectively prevent specific peeling accompanied by a white structure change occurring on the rolling surface and has excellent bearing life. Therefore, an alternator, an electromagnetic clutch for a car air conditioner, an intermediate pulley, an electric fan motor, etc. It can be suitably used as a rolling bearing for automobile electrical parts, auxiliary machines, and the like.

As a result of diligent investigations on rolling bearings that can effectively prevent separation on the rolling surface due to hydrogen embrittlement, a rapid acceleration / deceleration test was conducted using a rolling bearing containing a grease composition containing an epoxy compound as an additive. As a result, it was found that the bearing life can be extended.
By blending an epoxy compound, it is considered that a coating of an epoxy polymer is generated on the bearing rolling surface by a catalytic action on a frictional wear surface or a new metal surface exposed by wear. This epoxy polymer coating formed on the rolling contact surface of the bearing suppresses the generation of hydrogen due to the decomposition of the grease composition and prevents unique peeling due to hydrogen embrittlement, which is thought to extend the life of the rolling bearing. . In particular, by setting the chemical structure and blending ratio of the epoxy compound to a predetermined value, the new metal surface exposed by frictional wear and the like can be covered without proceeding with the curing reaction between the epoxy compound and the urea-based thickener. It is done. The present invention is based on these findings.

化３および化７におけるＲは水素原子またはメチル基等のアルキル基を示す。また、化４および化７におけるｎは 1 以上の整数であり、好ましくは 1〜10、より好ましくは 1〜5 である。 The epoxy compound added to the grease composition of the present invention includes an epoxy compound known as an epoxy resin component generally used as an epoxy resin composition for liquid sealing. This epoxy compound may be either solid or liquid and may be used in combination. For example, novolak obtained by condensation or cocondensation of phenols and aldehydes such as glycidyl ether type epoxy resin and orthocresol novolak type epoxy resin obtained by reaction of bisphenol A, bisphenol F, bisphenol AD and the like with epichlorohydrin Epoxy resin novolac type epoxy resin, glycidyl ester type epoxy resin obtained by reaction of polybasic acid such as phthalic acid and dimer acid and epichlorohydrin, diaminodiphenylmethane, isocyanuric acid etc. glycidylamine obtained by reaction of epichlorohydrin Type epoxy resins, linear aliphatic epoxy resins obtained by oxidizing olefinic bonds with peracids such as peracetic acid, and alicyclic epoxy resins. These may be used alone or in combination of two or more. Among these, those represented by the following chemical formulas 1 to 7 are preferable. More preferably, it is a bisphenol A type epoxy compound represented by the following chemical formula 1 or a bisphenol F type epoxy compound represented by chemical formula 2 because of its good solubility.

R in Chemical Formula 3 and Chemical Formula 7 represents a hydrogen atom or an alkyl group such as a methyl group. Moreover, n in Chemical formula 4 and Chemical formula 7 is an integer of 1 or more, preferably 1 to 10, and more preferably 1 to 5.

  In the grease composition of the present invention, the compounding ratio of the epoxy compound is 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease composed of a base oil and a thickener described later. More preferably, it is 0.1 to 5 parts by weight. If the blending ratio of the epoxy compound is less than 0.05 parts by weight, peeling on the rolling surface due to hydrogen embrittlement cannot be effectively prevented. On the other hand, if the amount exceeds 10 parts by weight, the reaction between the epoxy compound and the urea-based thickener tends to occur, and the peeling prevention effect decreases.

Base oils that can be used in the present invention include mineral oils such as spindle oil, refrigerator oil, turbine oil, machine oil, dynamo oil, highly refined mineral oil, liquid paraffin, polybutene, GTL oil synthesized by the Fischer-Tropsch method, -Hydrocarbon synthetic oil such as α-olefin oil, alkylnaphthalene, alicyclic compound, etc., or natural oil, polyol ester oil, phosphate ester oil, polymer ester oil, aromatic ester oil, carbonate ester oil, diester oil And non-hydrocarbon synthetic oils such as polyglycol oil, silicone oil, polyphenyl ether oil, alkyldiphenyl ether oil, alkylbenzene oil, and fluorinated oil. These base oils can be used alone or in combination of two or more.
Among these, it is preferable to use alkyl diphenyl ether oil or poly-α-olefin oil excellent in heat resistance and lubricity.

Thickeners that can be used in the present invention include benton, silica gel, fluorine compounds, 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.
Of these, urea compounds are desirable in view of heat resistance, cost, and the like.

  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. In particular, in the present invention, it is preferable that the isocyanate compound is blended in an equal amount or more in order to prevent the free amino group from remaining.

  A diurea compound is obtained by reaction of a 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 base grease for blending the above epoxy compound and the like by blending a thickener such as a urea compound with the base oil can be obtained. A base grease using a urea compound as a thickener is prepared by reacting an isocyanate compound and an amine compound in a base oil.
The blending ratio of the thickener in 100 parts by weight of the base grease is 1 to 40 parts by weight, preferably 3 to 25 parts by weight. If the content of the thickener is less than 1 part by weight, the thickening effect will be reduced, making it difficult to make grease, and if it exceeds 40 parts by weight, the resulting base grease will be too hard and the desired effect will not be obtained. Become.

  In addition to the above epoxy compound, known additives for grease can be included as required. Examples of the additives include antioxidants such as organic zinc compounds and phenolic compounds, metal deactivators such as benzotriazole, viscosity index improvers such as polymethacrylate and polystyrene, and solid lubricants such as molybdenum disulfide and graphite. Rust preventives such as metal sulfonates and polyhydric alcohol esters, friction reducing agents such as organic molybdenum, oily agents such as esters and alcohols, and antiwear agents such as phosphorus compounds. 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. The grease composition 7 of the present invention is enclosed at least around the rolling element 4.

Examples 1 to 7
In half of the base oil shown in Table 1, 4,4′-diphenylmethane diisocyanate (trade name Millionate MT manufactured by Nippon Polyurethane Industry Co., Ltd., hereinafter referred to as MDI) was dissolved in the ratio shown in Table 1, and the rest A monoamine that is twice the equivalent of MDI was dissolved in half of the base oil. The respective blending ratios and types are shown in Table 1.
A solution in which monoamine was dissolved was added while stirring the solution in which MDI was dissolved, and then the reaction was continued for 30 minutes at 100 ° C. to 120 ° C. to produce a diurea compound in the base oil.
An epoxy compound and an antioxidant were added to this at the blending ratio shown in Table 1, 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 Table 1, the kinematic viscosity 30 mm ² / sec of Nippon Steel Chemical Co., trade name of Shin fluid 601 in the synthetic hydrocarbon oil is 40 ° C. was used as the base oil, kinematic viscosity alkyl ether oil at 40 ℃ 97 mm ² / Moresco high lube LB100 manufactured by Matsumura Oil Research Co., Ltd. was used. Moreover, the hindered phenol by Sumitomo Chemical Co., Ltd. was used for antioxidant.

  The obtained grease composition was subjected to a rapid acceleration / deceleration test. Test methods and test conditions are shown below. The results are shown in Table 1.

<Rapid acceleration / deceleration test>
An alternator, which is an example of an electrical accessory, was simulated, and the grease composition was sealed in a rolling bearing for rotating an inner ring that supports a rotating shaft, and a rapid acceleration / deceleration test was performed. The rapid acceleration / deceleration test conditions are as follows. The test was conducted. Then, abnormal peeling occurred in the bearing, and the time when the vibration of the vibration detector exceeded the set value and the generator stopped (peeling life time, h) was measured. The test was terminated after 500 hours.

Comparative Examples 1 to 3
In accordance with the method according to Example 1, the base grease was prepared by selecting the thickener and the base oil at the blending ratio shown in Table 1, and the additive was further 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 1.

  As shown in Table 1, in each example, all the rapid acceleration / deceleration tests showed excellent results of 470 hours or longer (peeling life time). This is considered to be because the specific exfoliation accompanied by the white texture change produced on the rolling surface could be effectively prevented by adding the epoxy compound at a predetermined ratio.

  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 excellent bearing life, automobiles such as alternators, electromagnetic clutches for car air conditioners, intermediate pulleys, electric fan motors, etc. It can be used for 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 (4)

A grease composition in which an additive is blended with a base grease comprising a base oil and a thickener,
The additive contains at least an epoxy compound, mixing ratio of the epoxy compound Ri 0.05 to 10 parts by weight der the base grease 100 parts by weight,
The grease composition, wherein the epoxy compound is at least one epoxy compound selected from bisphenol A type and bisphenol F type .   The grease composition according to claim 1, wherein the thickener is a urea thickener. The grease composition according to claim 1 or 2 , wherein the base oil is at least one oil selected from alkyl diphenyl ether oil and poly-α-olefin oil. 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 3 .

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