JP4989083B2 - 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 comprising a base oil and a thickener, and the additive is at least selected from aluminum powder and an aluminum compound One aluminum-based additive is contained, and the mixing ratio of the aluminum-based additive is 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease.

The aluminum compound is at least one compound selected from aluminum carbonate and aluminum nitrate.
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.

  The grease composition of the present invention contains at least one aluminum-based additive selected from aluminum powder and an aluminum compound in a base grease composed of a base oil and a thickener, so that the bearing is used for automobiles and industrial machines. The occurrence of peculiar delamination due to hydrogen embrittlement, which can be seen in, can be suppressed, and the life of the grease-sealed 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 intensive investigations into methods that can effectively prevent peeling on the rolling surface due to hydrogen embrittlement for rolling bearings, a grease composition containing at least one aluminum-based additive selected from aluminum powder and aluminum compounds is enclosed. A rapid acceleration / deceleration test using the above-mentioned rolling bearings revealed that the bearing life can be extended.
The surface analysis of the bearing rolling surface shows that the aluminum compound reacts with the frictional wear surface or the new metal surface exposed by wear by forming an aluminum additive, and an aluminum coating is formed on the bearing rolling surface along with iron oxide. I understood the result.
This iron oxide and aluminum coating formed on the rolling 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. It is done. The present invention is based on these findings.

The aluminum-based additive added to the grease composition of the present invention is at least one selected from aluminum powder and an aluminum compound. Aluminum compounds include aluminum carbonate, aluminum sulfide, aluminum chloride, aluminum nitrate and its hydrate, aluminum sulfate, aluminum fluoride, aluminum bromide, aluminum iodide, aluminum oxide and its hydrate, aluminum hydroxide, selenium Aluminum fluoride, aluminum telluride, aluminum phosphate, aluminum phosphide, lithium aluminate, magnesium aluminate, aluminum selenate, aluminum titanate, aluminum zirconate and other inorganic aluminum, aluminum benzoate, aluminum citrate and other organic aluminum Is mentioned. These aluminum-based additives may be added to grease by mixing one type or two types.
Particularly preferable in the present invention is an aluminum powder having a high extreme pressure effect because it is excellent in heat resistance and hardly decomposes thermally.

The mixing ratio of the aluminum-based additive is 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease. That is, (1) when the aluminum additive is only aluminum powder, 0.05 to 10 parts by weight of aluminum powder with respect to 100 parts by weight of the base grease, and (2) when the aluminum additive is only aluminum compound, 0.05 to 10 parts by weight of aluminum compound per 100 parts by weight of grease, and (3) when aluminum additive is aluminum powder and aluminum compound, aluminum powder and aluminum compound are added to 100 parts by weight of base grease. Combine 0.05 to 10 parts by weight.
If the blending ratio of the aluminum additive is less than this 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.

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 Non-hydrocarbon synthetic oils such as polyglycol oil, silicone oil, polyphenyl ether oil, alkyldiphenyl ether oil, alkylbenzene oil, and fluorinated oil can be used.
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.

  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.

By adding a thickener such as a urea compound to the base oil, a base grease for blending the aluminum additive and the like 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 aluminum-based additive, a known grease additive may be included as necessary. Examples of the additives include antioxidants such as organic zinc compounds, amines, and phenolic compounds, metal deactivators such as benzotriazole, viscosity index improvers such as polymethacrylate and polystyrene, molybdenum disulfide, and graphite. Examples include solid lubricants, metal sulfonates, rust inhibitors such as polyhydric alcohol esters, friction reducers such as organic molybdenum, oil 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.

Example 1 , Example 2, Reference Examples 1-6
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) is dissolved in the proportion shown in Table 1, and the remaining half In this base oil, a monoamine having a double equivalent of MDI was dissolved. 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.
To this, an aluminum-based additive and an antioxidant were added in the proportions 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 HighLube LB100, a trade name of Matsumura Oil Co., sec. 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 load load on the pulley attached to the tip of the rotating shaft is set to 1960 N, the operating speed is set to 0 rpm to 18000 rpm, and a current of 0.1 A flows through the test bearing. 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
By a method according to Reference Example 1, a base grease was prepared by selecting a thickener and a base oil at a blending ratio shown in Table 1, and an additive was further blended to obtain a grease composition. The obtained grease composition was evaluated by conducting the same test as in Reference 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 400 hours or more (peeling life time). This is considered to be because the specific exfoliation accompanied by the white texture change that occurs on the rolling surface can be effectively prevented by adding the aluminum-based additive 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 comprising a base grease composed of a base oil and a thickener, and the additive contains at least one aluminum-based additive selected from aluminum carbonate and aluminum nitrate And a blending ratio of the aluminum-based additive is 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease.   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 .

Images