JP2004149620A - Grease composition and grease-enclosed roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a grease composition which can inhibit further peeling of a white texture, and to provide a grease-enclosed roller bearing. <P>SOLUTION: The grease composition comprises a base oil, a thickening agent (preferably a specific diurea compound), and 0.5-10 mass%, based on the total grease amount, corrosion-proofing agent (preferably benzotriazole or its derivative), and the roller bearing encloses this grease composition. <P>COPYRIGHT: (C)2004,JPO

Description

【００１７】
式中、Ｒ_１は炭素数７〜１２の芳香族環含有炭化水素基、Ｒ_２は炭素数６〜１５の２価の芳香族環含有炭化水素基、Ｒ_３は炭素数８〜１２のアルキル基をそれぞれ示す。
【００１８】
また、一般式（１）〜（３）で表されるジウレア化合物は、［Ｒ_１のモル数／（Ｒ_１のモル数＋Ｒ_３のモル数）］値が０．５〜１．０となるように、好ましくは０．６〜１．０となるように混合され、グリース組成物全量に対して１０〜３０質量％の割合で配合される。この配合量が１０質量％未満ではグリース組成物が軟らかすぎて高温でのグリース漏れ等が懸念され、３０質量％を超えるとグリース組成物が硬すぎてトルクむらや低温時の異音発生の原因となる。
【００１９】
［腐食防止剤］
腐食防止剤は、金属表面に防食皮膜を形成させるものであれば全て使用することができるが、中でも窒素化合物、硫黄及び窒素を含む化合物等が好ましい。窒素化合物としてはＮ−Ｃ−Ｎ結合を持つ化合物が好ましく、ベンゾトリアゾール、ベンゾトリアゾール誘導体、イミダゾリン、ピリミジン等が挙げられる。硫黄及び窒素を含む化合物としてはＮ−Ｃ−Ｓ結合を持つ化合物が好ましく、１，３，４−チアジアゾールポリスルフィド、１，３，４−チアジアゾリル−２，５−ビスジアルキルジチオカルバメート、２−（アルキルジチオ）ベンゾイミダゾール等が挙げられる。その他にも、防食防止剤としてβ−（ｏ−カルボキシベンジルチオ）プロピオンニトリル、プロピオン酸、ジアルキルジチオリン酸塩等が使用できる。これらの中でも、ベンソトリアゾール及びベンソトリアゾール誘導体が、一般的な軸受材料である軸受鋼やＳＣｒ４２０等の肌焼き鋼等の表面に防食皮膜を形成しやすいことから好ましい。
【００２０】
これら防食防止剤は単独で、もしくは複数種を組み合わせて使用することができ、グリース組成物全量に対して０．５〜１０質量％、好ましくは０．５〜５質量％添加される。この添加量が０．５質量％未満では十分な防食皮膜を形成できず、１０質量％を超える場合は増分に見合う防食効果が得られないばかりか、焼付きが起こりやすくなる。
【００２１】
［防錆剤］
グリース組成物には、必要に応じて各種の添加剤が配合され得るが、中でも下記に示すナフテン酸塩やコハク酸誘導体から選ばれる防錆剤を添加することが好ましい。上記のように、腐食防止剤は内外輪や転動体の表面に防食皮膜を形成する。防錆剤も通常、金属表面に吸着して酸化を防止する保護膜を形成するため、金属に対する吸着性が腐食防止剤よりも強いと防食皮膜が形成されず、本発明の効果が損なわれてしまう。そこで、本発明では、腐食防止剤であるベンゾトリアゾールやベンゾトリアゾール誘導体に比べて金属表面への吸着性の低いナフテン酸塩やコハク酸誘導体を用いる。
【００２２】
（ナフテン酸塩）
ナフテン核を有する飽和カルボン酸塩であればよく、特に制約はない。主に、飽和単環カルボン酸塩Ｃ_ｎＨ_２ｎ−１ＣＯＯＭ、飽和複環カルボン酸塩Ｃ_ｎＨ_２ｎ−３ＣＯＯＭ、脂肪族カルボン酸塩Ｃ_ｎＨ_２ｎ＋１ＣＯＯＭ、及びこれらの誘導体が挙げられる。例えば、単環のカルボン酸塩では、以下を挙げることができる。
【００２３】
【化３】

【００２４】
上式中、Ｒ_４は炭化水素基を示しており、アルキル基、アルケニル基、アリール基、アルカリール基、アラルキル基等が挙げられる。また、Ｍは金属元素を示しており、Ｃｏ，Ｍｎ，Ｚｎ，Ａｌ，Ｃａ，Ｂａ，Ｌｉ，Ｍｇ，Ｃｕ等である。これらのナフテン酸塩は、単独でも適宜組み合わせて使用してもよい。
【００２５】
（コハク酸誘導体）
コハク酸誘導体としては、具体的にそれぞれ以下の化合物を挙げることができる。例えば、コハク酸、アルキルコハク酸、アルキルコハク酸ハーフエステル、アルケニルコハク酸、アルケニルコハク酸ハーフエステル、コハク酸イミド等を挙げることができる。これらのコハク酸誘導体は、単独でも適宜組み合わせて使用してもよい。
【００２６】
上記のナフテン酸塩及びコハク酸誘導体は、それぞれ単独でもよいし、併用してもよい。単独使用及び併用の場合とも、その好ましい添加量は、グリース組成物全量に対して０．１〜１０質量％である。添加量がこれより少ないと、十分な防錆性を有することができず、これより多く含有するとグリースが軟化し、グリース漏れを発生させる恐れがあるため好ましくない。防錆性を確かにし、グリース漏れによる焼付き寿命を考慮するなら、グリース組成物全量に対して０．２５〜５質量％とすることが望ましい。
【００２７】
［その他の添加剤］
上記のグリース組成物には、更に各種性能を高めるために、例えば金属石けん、ベントン、シリカゲル等のゲル化剤；アミン系、フェノール系、イオウ系、チオリン亜鉛系等の酸化防止剤；塩素系、イオウ系、リン系、ジチオリン系亜鉛、有機モリブデン系等の極圧剤；脂肪酸、動植物油等の油性剤；ポリメタクリレート、ポリイソブチレン、ポリスチレン等の粘度指数向上剤等、通常グリース組成物に添加される各種の添加剤を添加してもよい。
【００２８】
これらの添加剤は単独もしくは複数種を組み合わせて使用することができ、また、その添加量は本発明の所期の目的を損なわない範囲であれば制限されるものではないが、通常グリース組成物全量に対して２０質量％以下添加することができる。
【００２９】
［製法］
上記のグリース組成物を調製する方法には特に制限はないが、一般的には基油中で増ちょう剤を反応させて得られる。尚、加熱時間や攪拌・混合時間等の製造条件は、使用する基油や増ちょう剤、腐食防止剤、その他の添加剤等により適宜設定される。また、腐食防止剤やその他の添加剤を添加した後に十分攪拌して均一に分散させる必要があるが、このときに加熱することも有効である。
【００３０】
また、このようにして調製されるグリース組成物のちょう度は、ＮＬＧＩ Ｎｏ．１〜３であることが望ましい。
【００３１】
（転がり軸受）
本発明は、上記のグリース組成物を封入した転がり軸受を提供する。但し、軸受の構造自体は制限されるものではなく、例えば図１に断面図として示される玉軸受１を例示することができる。この玉軸受１は、内輪１０と外輪１１との間に、保持器１２を介して複数の転動体である玉１３を転動自在に保持し、更に、内輪１０と外輪１１と玉１３とで形成される軸受空間Ｓに、上記のグリース組成物（図示せず）を充填し、シール部材１４により封止して構成されている。
【００３２】
このように構成される本発明のグリース封入転がり軸受は、封入したグリース組成物の白色組織剥離の抑制作用により、高温、高速、高荷重下で使用される部品用として好適となる。
【００３３】
【実施例】
以下に実施例を挙げて更に具体的に説明するが、本発明はこれにより何ら限定されるものではない。
【００３４】
（グリースＡの調製）
第１の容器に合成炭化水素油（ＰＡＯ）の半量とｐ−トルイジンとを入れ、７０〜８０℃に加温した。第２の容器にＰＡＯの半量とジフェニルメタンジイソシアネートとを入れ、７０〜８０℃に加温し、内容物を第１の容器に加えて攪拌した。反応熱のため反応物の温度は上昇するが、約３０分間この状態で攪拌を続け、反応を十分に行った後、昇温して１７０〜１８０℃で３０分間保持し、冷却した。その後、ベンゾトリアゾールを０．０５〜１２質量％となるように添加し、十分混練した後、ロールミルを通すことでグリースを得た。尚、何れのグリースにもナフテン酸亜鉛を２質量％の割合で添加してある。
【００３５】
（グリースＢの調製）
第１の容器にアルキルジフェニルエーテル油の半量及び、オクチルアミンとｐ−トルイジンとを両者の比率を変えて入れ、７０〜８０℃に加温した。第２の容器にアルキルジフェニルエーテル油の半量とジフェニルメタンジイソシアネートとを入れ、７０〜８０℃に加温し、内容物を第１の容器に加えて攪拌した。反応熱のため反応物の温度は上昇するが、約３０分間この状態で攪拌を続け、反応を十分に行った後、昇温して１７０〜１８０℃で３０分間保持し、冷却した。その後、ベンゾトリアゾールを１質量％添加し、十分混練した後、ロールミルを通すことでグリースを得た。尚、何れのグリースもコハク酸エステルを２質量％添加し、混和ちょう度をＮＬＧＩ Ｎｏ．２に調整した。
【００３６】
上記のグリースＡ及びグリースＢの配合を表１にまとめて示す。また、グリースＡ及びグリースＢを、下記に示す白色組織剥離試験及び焼付き寿命試験に供した。
【００３７】
【表１】

【００３８】
（白色組織剥離試験）
図１に示す構造を有し、内径φ１２ｍｍ、外径φ３７ｍｍ、幅１２ｍｍの接触ゴムシール付き深溝玉軸受に、グリースＡを０．９５ｇ封入して試験軸受とした。そして、図２に示す試験装置を用いて試験軸受の剥離発生確率を求めた。図示される試験装置は、試験軸受３１の内輪３２をシャフト３３の端部に嵌合させてナット３４で固定し、プーリ３５を介してエンジン（図示せず）からの回転を伝達される構成となっている。試験は、外輪回転速度１０００〜７０００ｍｉｎ^−１の繰り返し、室温、プーリ荷重１２００Ｎの条件で試験軸受３１を連続回転させ、５００時間を目標に行った。また、軸受内輪転走面に剥離が生じて振動が発生したとき、試験を終了した。試験は各１０例行い、下記式により剥離発生確率を算出した。
剥離発生確率＝（剥離発生数／試験数）×１００
【００３９】
（焼付き寿命試験）
図１に示す構造を有し、内径φ１７ｍｍ、外径φ５２ｍｍ、幅１６ｍｍの接触ゴムシール付き深溝玉軸受に、グリースＢを２．３ｇ封入して試験軸受とした。そして、図３に示す試験装置を用いて試験軸受の焼付き寿命を評価した。図示される試験装置は、回転用シャフト２０を一対の支持用軸受２２，２２で支持し、その中間部に試験軸受２１を装着し、更に全体を所定温度に維持できるように恒温容器（図示せず）に収容する構成となっている。試験は、シャフト２０を回転させて試験軸受２１を内輪回転速度２００００ｍｉｎ^−１、軸受外輪温度１７０℃、ラジアル荷重９８Ｎの条件で連続回転させ、焼付きが生じて軸受外輪温度が１８０℃以上に上昇したときに試験を終了し、それまでの時間を測定した。試験は各４例行い、平均時間が１０００時間以上を合格とした。
【００４０】
また、同様の焼付き寿命試験を、グリースＡを封入した試験軸受についても行った。
【００４１】
上記の白色組織試験の結果を図４に、焼付き寿命試験の結果を図５にそれぞれ示す。図４から、ベンゾトリアゾールの添加量が０．５〜１０質量％の範囲であれば、白色組織剥離の発生が少なく、また焼付き寿命も１０００時間を越えて良好であることがわかる。特に、ベンゾトリアゾールの添加量が０．５〜５質量％の範囲では、焼付き寿命が１２００時間以上と更に良好な結果が得られている。このことから、防食添加剤の添加量は０．５〜１０質量％、好ましくは０．５〜５質量％であることいえる。
【００４２】
また、図５から、ジウレア化合物における［Ｒ_１のモル数／（Ｒ_１のモル数＋Ｒ_３のモル数）］値が０．５０〜１．０の範囲であれば、焼付き寿命が１０００時間以上と良好になることがわかる。特に前記値が０．６〜１．０の範囲では焼付き寿命が１２００時間以上と更に良好な結果が得られている。このことから、ジウレア化合物における［Ｒ_１のモル数／（Ｒ_１のモル数＋Ｒ_３のモル数）］値は０．５０〜１．０、好ましくは０．６〜１．０であるといえる。
【００４３】
【発明の効果】
以上説明したように、本発明は、グリース封入転がり軸受の白色組織剥離の抑制効果及び高温焼付き性を従来に比べて格段に改善でき、特にオルタネータやカーエアコン用電磁クラッチ、中間プーリ、電動ファンモータ、水ポンプ等の自動車用電装部品、エンジン補機用の転がり軸受に好適に適用できる。
【図面の簡単な説明】
【図１】本発明の転がり軸受の一実施形態を示す断面図である。
【図２】実施例において、白色組剥離試験に用いた試験装置を示す概略断面図である。
【図３】実施例において、高温焼付き寿命試験に用いた試験装置を示す概略断面図である。
【図４】実施例で得られた、ベンゾトリアゾールの添加量と、剥離発生確率または焼付き寿命時間との関係を示すグラフである。
【図５】実施例でえられた、ジウレア化合物の［Ｒ_１のモル数／（Ｒ_１のモル数＋Ｒ_３のモル数）］値と焼付き寿命時間との関係を示すグラフである。
【符号の説明】
１ 玉軸受
１０ 内輪
１１ 外輪
１２ 保持器
１３ 玉
１４ シール[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a grease composition and a grease-enclosed rolling bearing. More specifically, parts used under high-temperature, high-speed, high-load conditions, such as automotive electrical components, alternators and intermediate pulleys that are engine accessories, electromagnetic clutches for car air conditioners, etc., or contact with water such as water pumps The present invention relates to a grease composition suitable for a rolling bearing incorporated in a component to be assembled, and a grease-enclosed rolling bearing as the rolling bearing.
[0002]
[Prior art]
The spread of FF vehicles for the purpose of reducing the size and weight of automobiles and the demand for larger living spaces have forced the reduction of engine room space, and electric components such as alternators, intermediate pulleys, electromagnetic clutches for car air conditioners, and water pumps.・ The size and weight of engine accessories are being further reduced, and these parts are also required to have higher performance and higher output.However, a reduction in output is inevitable due to downsizing. For example, alternators In the case of electromagnetic clutches for car air conditioners, the increase in speed compensates for the decrease in output, and the speed of idler pulleys increases accordingly. Further, the demand for improved quietness increases the sealing of the engine room and promotes a high temperature in the engine room. Therefore, these parts also need to withstand high temperatures.
[0003]
As described above, these parts are used under high temperatures, high speeds and high loads.In the rolling bearings to be incorporated, the inner and outer rings and the rolling elements come into contact with each other at a high surface pressure, and the surface of the metal has a new surface. Is easy to occur. Since the newly formed metal surface has a high activity, the encapsulated grease is decomposed to generate hydrogen, and this hydrogen penetrates into the bearing steel to induce white structure change peeling (hereinafter referred to as "white structure peeling") due to hydrogen embrittlement. Sometimes.
[0004]
In addition, since these parts are often installed in the lower part of the engine room, the bearings are apt to be exposed to muddy water and rainwater that jump up from the road surface during traveling. It is also susceptible to water ingress. Although the infiltration of water can be suppressed to some extent by mounting a contact rubber seal on the bearing, it is not yet possible to completely prevent water from entering. Further, since the engine of the automobile repeatedly starts and stops, when the temperature inside the housing of the bearing decreases and reaches the dew point when the engine is stopped, moisture in the surrounding air condenses to form water droplets. It may adhere to the bearings or mix into the lubricating agent such as grease. Hydrogen may also be generated by such moisture, and white tissue peeling similar to that described above will occur.
[0005]
In order to suppress such white-texture detachment, a special rust inhibitor is added to the encapsulated grease (for example, see Patent Literature 1 and Patent Literature 2), and a special steel material is used as a bearing material (for example, see Patent Literature 2). 3) and other measures have been taken.
[Patent Document 1]
JP 2001-234935 A (pages 2 to 4)
[Patent Document 2]
JP-A-2002-121577 (pages 2 to 3)
[Patent Document 3]
JP-A-2002-21856 (pages 2 to 3)
[0006]
[Problems to be solved by the invention]
As described above, white rolling has become a new important issue in rolling bearings incorporated into automotive electrical components and engine accessories, but the conventional countermeasures have a sufficient suppression effect depending on the use conditions. May not be obtained.
[0007]
Therefore, the present invention is expected to further increase the high temperature and high load in the future, grease composition that can further suppress the white structure peeling, as well as further suppress the occurrence of white structure peeling, especially for automobiles An object of the present invention is to provide a grease-sealed rolling bearing suitable for electrical components, engine accessories, and the like.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a grease composition containing a base oil and a thickener, and containing a corrosion inhibitor in an amount of 0.5 to 10% by mass based on the total amount of grease, and an inner ring. A grease-enclosed rolling bearing characterized in that a plurality of rolling elements are rotatably held by a retainer between the rolling element and an outer ring, and the grease composition is filled and sealed with a seal member. .
[0009]
Corrosion inhibitors form corrosion protection films on metal surfaces to prevent corrosion. Therefore, in the case of a rolling bearing, the inner and outer rings and the surfaces of the rolling elements are protected by this anticorrosion film, and the generation of a new metal surface is suppressed, and as a result, the generation of hydrogen due to the decomposition of grease is also suppressed, and the peeling of white tissue is suppressed. Prevent occurrence.
[0010]
Further, the corrosion inhibitor has an effect of preventing oxidation of grease, destruction of oxidizing substances, suppression of corrosive oxidation products, and the like. The grease is oxidatively degraded, so that the decomposition of the lubricant is accelerated and low molecular substances are generated. Particularly in automotive electrical components and engine accessories, bearings are used under high temperatures and high loads, which promotes the production of low-molecular substances and further promotes decomposition into lower-molecular substances, which leads to hydrogen Is more likely to occur. The corrosion inhibitor also prevents such grease from being oxidized and deteriorated at the same time, so that the more severe the conditions of use, the more remarkably the effect of suppressing the separation of the white structure as compared with the conventional case.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail. First, the grease composition of the present invention will be described.
[0012]
(Grease composition)
[Base oil]
The base oil to be used is not particularly limited, and all oils usually used as base oils for lubricating oils can be used. The kinematic viscosity at 40 ° C. is preferably 10 to 400 mm ² / preferably in order to avoid generation of abnormal noise at low temperature startup due to insufficient low temperature fluidity of the grease and seizure caused by difficulty in forming an oil film at high temperature. The base oil is preferably 20 to 250 mm ² / sec, more preferably 20 to 250 mm ² / sec, and still more preferably 40 to 150 mm ² / sec.
[0013]
Specific examples of the type of base oil include mineral oil-based, synthetic oil-based, and natural oil-based lubricating oils. As the mineral oil-based lubricating oil, those obtained by purifying mineral oil by appropriately combining vacuum distillation, solvent removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay refining, hydrorefining, and the like are suitable. Examples of the synthetic oil-based lubricating oil include a hydrocarbon-based oil, an aromatic-based oil, an ester-based oil, and an ether-based oil. Examples of the hydrocarbon-based oil include normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, poly-α-olefin such as 1-decene and ethylene co-oligomer, and hydrides thereof. Examples of the aromatic oil include alkylbenzenes such as monoalkylbenzene and dialkylbenzene, and alkylnaphthalenes such as monoalkylnaphthalene, dialkylnaphthalene, and polyalkylnaphthalene. Examples of ester oils include dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, diester oils such as methyl acetyl sinolate, or trioctyl trimellitate, Aromatic ester oils such as tridecyl trimellitate and tetraoctyl pyromellitate, and polyols such as trimethylolpropane caprylate, trimethylolpropaneperargonate, pentaerythritol-2-ethylhexanoate, and pentaerythritol belargonate Ester oils, and complex ester oils, which are oligoesters of a polyhydric alcohol and a mixed fatty acid of a dibasic acid / monobasic acid, and the like are also included. Examples of the ether oil include polyglycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, and polypropylene glycol monoether, and monoalkyl triphenyl ethers, alkyl diphenyl ethers, dialkyl diphenyl ethers, pentaphenyl ethers, tetraphenyl ethers, and monoalkyl tetraalkyl ethers. And phenyl ether oils such as phenyl ether and dialkyltetraphenyl ether. Other synthetic lubricating oils include tricresyl phosphate, silicone oil, perfluoroalkyl ether and the like. Examples of the natural oil-based lubricating oil include oils and fats such as beef tallow, lard, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, palm kernel oil, and hydrides thereof. These base oils can be used alone or as a mixture, and are adjusted to the preferable kinematic viscosity described above.
[0014]
[Thickener]
The thickener is not particularly limited as long as it forms a gel structure and has a function of retaining the above-described base oil in the gel structure. Specifically, metal soaps including Li, Na, and the like, metal soaps such as composite metal soaps selected from Li, Na, Ba, and Ca, and benton, silica gel, urea compounds, urea / urethane compounds, urethane compounds, and the like Non-soaps can be appropriately selected and used, but urea compounds, urea / urethane compounds, urethane compounds and mixtures thereof are desirable in view of obtaining a strong oil film and heat resistance of the grease composition. Specific examples of the urea compound, urea / urethane compound, and urethane compound include a diurea compound, a triurea compound, a tetraurea compound, a polyurea compound, a urea / urethane compound, a diurethane compound, and a mixture thereof. Particularly, a diurea compound, a urea / urethane compound, a diurethane compound and a mixture thereof are preferable, and it is particularly preferable to mix a diurea compound.
[0015]
In order to further improve the high-temperature stability, it is preferable to use a diurea compound represented by the following formulas (1) to (3) as a thickener. These diurea compounds are particularly excellent in heat resistance and can be used even at a high temperature close to 180 ° C.
[0016]
Embedded image

[0017]
In the formula, R ₁ is an aromatic ring-containing hydrocarbon group having 7 to 12 carbon atoms, R ₂ is a divalent aromatic ring-containing hydrocarbon group having 6 to 15 carbon atoms, and R ₃ is an alkyl group having 8 to 12 carbon atoms. The groups are respectively shown.
[0018]
In general formula (1) to the diurea compounds represented by (3), _{[R 1} of moles / _{(R 1} molar number + number of moles of _{R 3)]} value is 0.5 to 1.0 Thus, it is preferably mixed so as to be 0.6 to 1.0, and is mixed at a ratio of 10 to 30% by mass based on the total amount of the grease composition. If the amount is less than 10% by mass, the grease composition is too soft, which may cause grease leakage at a high temperature. If the amount exceeds 30% by mass, the grease composition is too hard to cause uneven torque and noise at low temperatures. It becomes.
[0019]
[Corrosion inhibitor]
Any corrosion inhibitor can be used as long as it forms an anticorrosive film on a metal surface, and among them, a nitrogen compound, a compound containing sulfur and nitrogen and the like are preferable. As the nitrogen compound, a compound having an N—C—N bond is preferable, and examples thereof include benzotriazole, benzotriazole derivatives, imidazoline, and pyrimidine. As the compound containing sulfur and nitrogen, a compound having an N—C—S bond is preferable, and 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bisdialkyldithiocarbamate, 2- (alkyl Dithio) benzimidazole and the like. In addition, β- (o-carboxybenzylthio) propionnitrile, propionic acid, dialkyldithiophosphate and the like can be used as anticorrosion inhibitors. Among these, benzosotriazole and benzotriazole derivatives are preferable because they easily form an anticorrosion film on the surface of a common bearing material such as bearing steel or case hardening steel such as SCr420.
[0020]
These anticorrosion inhibitors can be used alone or in combination of two or more, and are added in an amount of 0.5 to 10% by mass, preferably 0.5 to 5% by mass based on the total amount of the grease composition. If the addition amount is less than 0.5% by mass, a sufficient anticorrosion film cannot be formed, and if it exceeds 10% by mass, not only an anticorrosion effect commensurate with the increase cannot be obtained, but also seizure tends to occur.
[0021]
[anti-rust]
Various additives may be added to the grease composition as needed. Among them, it is preferable to add a rust inhibitor selected from the following naphthenates and succinic acid derivatives. As described above, the corrosion inhibitor forms an anticorrosion film on the surfaces of the inner and outer rings and the rolling elements. Rust preventive agents also usually form a protective film that adsorbs to the metal surface to prevent oxidation, so if the metal's adsorbability is stronger than the corrosion inhibitor, no anticorrosive film is formed and the effects of the present invention are impaired. I will. Therefore, in the present invention, a naphthenate or a succinic acid derivative having a lower adsorptivity to a metal surface than benzotriazole or a benzotriazole derivative which is a corrosion inhibitor is used.
[0022]
(Naphthenate)
Any saturated carboxylate having a naphthene nucleus may be used, and there is no particular limitation. Mainly saturated monocyclic carboxylate _C n _H 2n-1 COOM, saturated double ring carboxylates _C n _H 2n-3 COOM, aliphatic carboxylates _C n _H 2n + 1 COOM, and derivatives thereof. For example, for a monocyclic carboxylate, the following can be mentioned.
[0023]
Embedded image

[0024]
In the above formula, R ₄ represents a hydrocarbon group, and examples thereof include an alkyl group, an alkenyl group, an aryl group, an alkaryl group, and an aralkyl group. M represents a metal element, such as Co, Mn, Zn, Al, Ca, Ba, Li, Mg, and Cu. These naphthenates may be used alone or in appropriate combination.
[0025]
(Succinic acid derivative)
Specific examples of the succinic acid derivative include the following compounds. For example, succinic acid, alkyl succinic acid, alkyl succinic acid half ester, alkenyl succinic acid, alkenyl succinic acid half ester, succinimide and the like can be mentioned. These succinic acid derivatives may be used alone or in appropriate combination.
[0026]
The above naphthenate and succinic acid derivative may be used alone or in combination. When used alone or in combination, the preferable addition amount is 0.1 to 10% by mass based on the total amount of the grease composition. If the amount is less than this, sufficient rust-preventing properties cannot be obtained, and if the amount is more than that, the grease is softened, which may cause grease leakage. In order to ensure rust prevention and to consider the seizure life due to grease leakage, it is desirable that the content be 0.25 to 5% by mass based on the total amount of the grease composition.
[0027]
[Other additives]
In order to further enhance various performances, the above-mentioned grease composition includes, for example, gelling agents such as metal soap, benton, and silica gel; antioxidants such as amine-based, phenol-based, sulfur-based, and zinc thiophosphorus-based; Extreme pressure agents such as sulfur-based, phosphorus-based, dithiophosphorus-based zinc, and organic molybdenum-based agents; oil-based agents such as fatty acids, animal and vegetable oils; viscosity index improvers such as polymethacrylate, polyisobutylene, and polystyrene; usually added to grease compositions Various additives may be added.
[0028]
These additives can be used alone or in combination of two or more, and the amount of addition is not limited as long as the intended purpose of the present invention is not impaired, but usually the grease composition It can be added in an amount of 20% by mass or less based on the total amount.
[0029]
[Production method]
The method for preparing the above grease composition is not particularly limited, but is generally obtained by reacting a thickener in a base oil. The production conditions such as heating time, stirring and mixing time are appropriately set depending on the base oil, thickener, corrosion inhibitor, other additives and the like used. Further, it is necessary to sufficiently stir and uniformly disperse after adding the corrosion inhibitor and other additives, and heating at this time is also effective.
[0030]
The consistency of the grease composition thus prepared is determined by NLGI No. Desirably, it is 1-3.
[0031]
(Rolling bearing)
The present invention provides a rolling bearing enclosing the above grease composition. However, the structure of the bearing itself is not limited, and for example, a ball bearing 1 shown in a sectional view in FIG. 1 can be exemplified. The ball bearing 1 holds a plurality of balls 13, which are rolling elements, between an inner ring 10 and an outer ring 11 via a retainer 12 so as to freely roll. The formed bearing space S is filled with the above-mentioned grease composition (not shown) and sealed with a seal member 14.
[0032]
The grease-enclosed rolling bearing of the present invention configured as described above is suitable for components used at high temperatures, high speeds, and under high loads due to the action of suppressing the white structure of the encapsulated grease composition.
[0033]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.
[0034]
(Preparation of grease A)
A first container was charged with half the amount of synthetic hydrocarbon oil (PAO) and p-toluidine, and heated to 70 to 80 ° C. Half the amount of PAO and diphenylmethane diisocyanate were placed in a second container, heated to 70 to 80 ° C., and the contents were added to the first container and stirred. Although the temperature of the reaction product increased due to the heat of the reaction, stirring was continued in this state for about 30 minutes, and after the reaction was sufficiently performed, the temperature was raised and maintained at 170 to 180 ° C. for 30 minutes, followed by cooling. Thereafter, benzotriazole was added to a concentration of 0.05 to 12% by mass, kneaded sufficiently, and then passed through a roll mill to obtain grease. In addition, zinc naphthenate was added to each grease at a ratio of 2% by mass.
[0035]
(Preparation of grease B)
In a first container, half of the alkyl diphenyl ether oil and octylamine and p-toluidine were added at different ratios, and heated to 70 to 80 ° C. Half of the alkyl diphenyl ether oil and diphenylmethane diisocyanate were placed in a second container, heated to 70 to 80 ° C., and the contents were added to the first container and stirred. Although the temperature of the reaction product increased due to the heat of the reaction, stirring was continued in this state for about 30 minutes, and after the reaction was sufficiently performed, the temperature was raised and maintained at 170 to 180 ° C. for 30 minutes, followed by cooling. Thereafter, benzotriazole was added in an amount of 1% by mass, kneaded sufficiently, and then passed through a roll mill to obtain grease. Each grease was added with 2% by mass of a succinic acid ester, and was adjusted to NLGI No. Adjusted to 2.
[0036]
Table 1 shows the composition of grease A and grease B. Further, grease A and grease B were subjected to the following white structure peeling test and seizure life test.
[0037]
[Table 1]

[0038]
(White tissue peel test)
0.95 g of grease A was sealed in a deep groove ball bearing with a contact rubber seal having a structure shown in FIG. 1 and having an inner diameter of 12 mm, an outer diameter of 37 mm, and a width of 12 mm to form a test bearing. Then, the peeling occurrence probability of the test bearing was determined using the test apparatus shown in FIG. The illustrated test apparatus has a configuration in which an inner ring 32 of a test bearing 31 is fitted to an end of a shaft 33 and fixed with a nut 34, and rotation from an engine (not shown) is transmitted via a pulley 35. Has become. In the test, the test bearing 31 was continuously rotated under the conditions of an outer ring rotation speed of 1000 to 7000 min ^-1 and room temperature and a pulley load of 1200 N, and was performed for a target of 500 hours. The test was terminated when peeling occurred on the bearing inner ring rolling surface and vibration occurred. The test was performed for each of 10 cases, and the peeling occurrence probability was calculated by the following equation.
Probability of peeling = (number of peelings / number of tests) × 100
[0039]
(Seizure life test)
2.3 g of grease B was sealed in a deep groove ball bearing with a contact rubber seal having a structure shown in FIG. 1 having an inner diameter of 17 mm, an outer diameter of 52 mm, and a width of 16 mm to form a test bearing. Then, the seizing life of the test bearing was evaluated using the test device shown in FIG. The illustrated test apparatus supports a rotating shaft 20 with a pair of supporting bearings 22, 22, mounts a test bearing 21 in an intermediate portion thereof, and further maintains a constant temperature vessel (not shown) so that the whole can be maintained at a predetermined temperature. ). In the test, the shaft 20 is rotated to continuously rotate the test bearing 21 under the conditions of an inner ring rotation speed of 20000 min ⁻¹ , a bearing outer ring temperature of 170 ° C., and a radial load of 98 N. Seizure occurs, and the bearing outer ring temperature rises to 180 ° C. or more. When the test was completed, the test was terminated, and the time until that was measured. The test was performed for each of four cases, and an average time of 1,000 hours or more was regarded as a pass.
[0040]
The same seizure life test was also performed on a test bearing in which grease A was sealed.
[0041]
FIG. 4 shows the results of the white structure test, and FIG. 5 shows the results of the seizure life test. From FIG. 4, it can be seen that when the amount of benzotriazole added is in the range of 0.5 to 10% by mass, the occurrence of white structure peeling is small, and the seizure life is good over 1000 hours. In particular, when the addition amount of benzotriazole is in the range of 0.5 to 5% by mass, a better result is obtained in which the seizure life is 1200 hours or more. From this, it can be said that the amount of the anticorrosion additive is 0.5 to 10% by mass, preferably 0.5 to 5% by mass.
[0042]
From FIG. 5, if the value of [moles of R ₁ / (moles of R ₁ + moles of R ₃ )] in the diurea compound is in the range of 0.50 to 1.0, the seizure life is 1000 hours. It turns out that it becomes favorable with the above. In particular, when the value is in the range of 0.6 to 1.0, an even better result is obtained in which the seizure life is 1200 hours or more. From this, it can be said that the value of [the number of moles of R ₁ / (the number of moles of R ₁ + the number of moles of R ₃ )] in the diurea compound is 0.50 to 1.0, preferably 0.6 to 1.0. .
[0043]
【The invention's effect】
INDUSTRIAL APPLICABILITY As described above, the present invention can significantly improve the effect of suppressing the separation of the white structure and the high-temperature seizure of the grease-enclosed rolling bearing as compared with the related art. It can be suitably applied to electric parts for automobiles such as motors and water pumps, and rolling bearings for engine accessories.
[Brief description of the drawings]
FIG. 1 is a sectional view showing one embodiment of a rolling bearing of the present invention.
FIG. 2 is a schematic cross-sectional view showing a test apparatus used in a white assembly peel test in Examples.
FIG. 3 is a schematic sectional view showing a test apparatus used in a high-temperature seizure life test in Examples.
FIG. 4 is a graph showing the relationship between the amount of benzotriazole added and the probability of occurrence of peeling or the seizure life time obtained in Examples.
[5] was example in the examples is a graph showing the relationship between [R ₁ of moles / (R ₁ molar number + number of moles of R _3)] value and the seizure life time of the diurea compounds.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ball bearing 10 Inner ring 11 Outer ring 12 Cage 13 Ball 14 Seal

Claims (5)

A grease composition comprising a base oil and a thickener, and containing a corrosion inhibitor in an amount of 0.5 to 10% by mass based on the total amount of the grease. The grease composition according to claim 1, wherein the corrosion inhibitor is benzotriazole or a derivative thereof. As the thickener, a diurea compound represented by the following general formulas (1) to (3) may be prepared by adding [R ₁ mole / (R ₁ mole + R ₃ mole)] to a value of 0.50 to 0.50. The grease composition according to claim 1, wherein the grease is added in an amount of 10 to 30% by mass based on the total amount of the grease so as to be 1.0.

(In the formula, R ₁ is an aromatic ring-containing hydrocarbon group having 7 to 12 carbon atoms, R ₂ is a divalent aromatic ring-containing hydrocarbon group having 6 to 15 carbon atoms, and R ₃ is a C 8 to 12 carbon atom. Represents an alkyl group.) The grease composition according to any one of claims 1 to 3, further comprising at least one rust inhibitor selected from a naphthenate and a succinic acid derivative. A plurality of rolling elements are rotatably held by a retainer between an inner ring and an outer ring, and the grease composition according to any one of claims 1 to 4 is filled and sealed with a seal member. A grease-filled rolling bearing characterized by the following.

Images