JP2007217521A - Grease composition and bearing containing grease - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition effectively preventing a rolling surface of a grease-containing bearing from flaking caused by hydrogen embrittlement, and the grease-containing bearing. <P>SOLUTION: The grease composition 7 is contained in the grease-containing bearing 1. The grease composition 7 is obtained by compounding an additive with a base grease comprising a base oil and a thickener, wherein the additive contains a hydroxide. The hydroxide is a metal hydroxide, particularly a metal hydroxide chosen from the group consisting of calcium hydroxide, aluminum hydroxide and magnesium hydroxide, and is compounded in an amount corresponding to 0.05-10 pts.wt. based on 100 pts.wt. base grease. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a grease composition and the grease-filled bearing, and particularly for alternators, electromagnetic clutches for car air conditioners, intermediate pulleys, electric motors such as electric fan motors, rolling bearings for auxiliary machines, and rolling bearings for motors. 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 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 contains a hydroxide, and the hydroxide The blending ratio is 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease.

  The hydroxide is a metal hydroxide, particularly at least one metal hydroxide selected from calcium hydroxide, aluminum hydroxide and magnesium hydroxide.

The thickener is a urea-based thickener.
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 is based on hydrogen embrittlement found in bearings used in automobiles and industrial machinery, because a hydroxide such as a metal hydroxide is blended with a base grease composed of a base oil and a thickener. The occurrence of peculiar 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 research on rolling bearings that can effectively prevent separation on the rolling surface due to hydrogen embrittlement, a rapid acceleration / deceleration test was conducted using rolling bearings filled with a grease composition containing hydroxide. As a result, it was found that the bearing life can be extended.
As a result of the surface analysis of the bearing rolling surface, the hydroxide reacts with the frictional wear surface or the newly formed metal surface exposed by wear, and an iron oxide film is formed on the bearing rolling surface. It was. By the action of the hydroxide, it becomes an alkaline environment, the metal surface is protected from corrosion, and the formation of the iron oxide film is promoted.
This iron oxide 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, and thus is considered to extend the life of the rolling bearing. The present invention is based on these findings.

Examples of the hydroxide added to the grease composition of the present invention include cobalt hydroxide, aluminum hydroxide, indium hydroxide, potassium hydroxide, calcium hydroxide, strontium hydroxide, lithium hydroxide, sodium hydroxide, and magnesium hydroxide. Metal hydroxides such as nickel hydroxide, iron hydroxide, copper hydroxide, zinc hydroxide and vanadium hydroxide, and inorganic hydroxides such as ammonium hydroxide.
Among the above hydroxides, metal hydroxides are particularly preferable because they are excellent in thermal durability, hardly decompose thermally, and have a high extreme pressure effect. These hydroxides may be added to the grease by mixing one type or two or more types.

  The mixing ratio of the hydroxide is 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease. If the blending ratio of the hydroxide 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.

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 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.
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.

A base grease for blending the above-mentioned hydroxide 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 effect of thickening will be reduced and it will be 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 a hydroxide, a known additive for grease can be contained as required. 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 thereof include solid lubricants, metal sulfonates, antirust agents such as 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 8
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 that was twice the 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, hydroxide and antioxidant were added 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 synthetic hydrocarbon oil used as the base oil is Shinflud 601 manufactured by Nippon Steel Chemical Co., Ltd. with a kinematic viscosity of 30 mm ² / sec at 40 ° C., and the alkyldiphenyl ether oil has a kinematic viscosity of 97 mm ² / sec at 40 ° C. Matsumura Oil Co., Ltd. and Moresco High Lube LB100 were used. As the antioxidant, hindered phenol manufactured by Sumitomo Chemical Co., Ltd. was used.

  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 such that the operating load is set to 1960 N and the rotation speed is 0 to 18000 rpm, and a current of 0.1 A flows in the test bearing. The test was conducted at Then, abnormal peeling occurred in the bearing, and the time when the vibration of the vibration detector exceeded the set value and the tester 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 400 hours or more (peeling life time). This is considered to be because the specific exfoliation accompanied with the white texture change produced on the rolling surface was effectively prevented by adding the hydroxide at a predetermined ratio.

  Since the grease composition of the present invention can effectively prevent specific peeling accompanied by a white structure change occurring on the rolling surface and has a long 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 (6)

  A grease composition comprising an additive and a base grease comprising a base oil and a thickener, wherein the additive contains a hydroxide, and the proportion of the hydroxide is 100 wt. A grease composition characterized by being 0.05 to 10 parts by weight with respect to parts.   The grease composition according to claim 1, wherein the hydroxide is a metal hydroxide.   The grease composition according to claim 2, wherein the metal hydroxide is at least one metal hydroxide selected from calcium hydroxide, aluminum hydroxide, and magnesium hydroxide.   The grease composition according to claim 1, 2 or 3, wherein the thickener is a urea-based thickener.   The grease composition according to any one of claims 1 to 4, wherein the base oil is at least one oil selected from alkyl diphenyl ether oils and poly-α-olefin oils.   6. 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 5.

Images