JP6759389B2 - Sintered bearing - Google Patents
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- JP6759389B2 JP6759389B2 JP2019030396A JP2019030396A JP6759389B2 JP 6759389 B2 JP6759389 B2 JP 6759389B2 JP 2019030396 A JP2019030396 A JP 2019030396A JP 2019030396 A JP2019030396 A JP 2019030396A JP 6759389 B2 JP6759389 B2 JP 6759389B2
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本本発明は、焼結金属からなる焼結軸受に関する。 The present invention relates to a sintered bearing made of a sintered metal.
精密小型モータ用の軸受として、その優れた静粛性から焼結軸受が広く用いられている。この焼結軸受は、銅を主体とする銅系、鉄を主体とする鉄系、銅と鉄を主体とする銅鉄系に大別される。何れのタイプの焼結軸受も、通常はその多孔質組織の空孔に潤滑油を含浸させて使用される。例えば潤滑油を含浸させた銅鉄系の焼結軸受として、直径４５μｍ以下の銅系粉末を用い、かつ銅の比率や通油度を所定範囲に規定したものが公知である（特許文献１参照）。 Sintered bearings are widely used as bearings for precision small motors because of their excellent quietness. These sintered bearings are roughly classified into copper-based bearings mainly composed of copper, iron-based bearings mainly composed of iron, and copper-iron-based bearings mainly composed of copper and iron. Both types of sintered bearings are usually used by impregnating the pores of the porous structure with lubricating oil. For example, as a copper-iron-based sintered bearing impregnated with lubricating oil, a copper-based powder having a diameter of 45 μm or less is used, and the ratio of copper and the degree of oil permeability are specified within a predetermined range (see Patent Document 1). ).
ところで、焼結軸受の使用環境によっては、潤滑油を使用することが好ましくない場合がある。例えば、複写機や印刷機では、軸受から漏洩した潤滑油で紙を汚す可能性がある。また、自動車用電装部品では、軸受の周辺が高温となって潤滑油が短期間で劣化もしくは蒸散し、軸受性能を害する可能性がある。さらに潤滑油によって軸と軸受とが電気的に絶縁されることで生じる静電気の帯電が問題となる場合もある。 By the way, depending on the usage environment of the sintered bearing, it may not be preferable to use the lubricating oil. For example, in copiers and printing presses, the lubricating oil leaked from the bearings can stain the paper. Further, in electrical components for automobiles, the temperature around the bearing becomes high, and the lubricating oil may deteriorate or evaporate in a short period of time, which may impair the bearing performance. Further, the electrostatic charge generated by the electrical insulation between the shaft and the bearing by the lubricating oil may become a problem.
これら潤滑油を使用することが好ましくない用途では、潤滑油を含浸させていない、いわゆるドライタイプの焼結軸受（ドライ軸受）を用いることが考えられる。しかしながら、ドライ軸受ではどうしても潤滑不良が生じ易く、そのままでは回転数や荷重等の使用条件が大きく制約される。そこで、対策として、原料粉に配合される固体潤滑剤としての黒鉛の配合量を増やし、軸受自体の自己潤滑性能を強化することが考えられる。 In applications where it is not preferable to use these lubricating oils, it is conceivable to use so-called dry type sintered bearings (dry bearings) that are not impregnated with the lubricating oil. However, in dry bearings, poor lubrication is liable to occur, and as it is, usage conditions such as rotation speed and load are greatly restricted. Therefore, as a countermeasure, it is conceivable to increase the blending amount of graphite as a solid lubricant blended in the raw material powder to enhance the self-lubricating performance of the bearing itself.
しかしながら、黒鉛粉の比重や粒径は金属粉のそれらよりもかなり小さいため（例えば比重は金属粉の１／４程度である）、黒鉛の配合量を増やせば、それだけ原料粉全体の流動性が低下する。すなわち、原料粉を成形用の金型に充填し、これを圧縮して圧粉体を成形する際に、粉体の落下速度が不均一となり、偏析等による重量、寸法、密度等にバラツキを生じるおそれがある。また、原料粉を均一に混合することが難しく、このことも焼結体における偏析の発生を助長する。さらに黒鉛を多く含む原料粉は固まり難いので、圧粉体の強度が低下し、この結果、欠け、割れ、クラック等が発生し易くなる。 However, since the specific gravity and particle size of graphite powder are much smaller than those of metal powder (for example, the specific gravity is about 1/4 of that of metal powder), the more the amount of graphite compounded, the more fluid the raw material powder becomes. descend. That is, when the raw material powder is filled in a molding die and compressed to form a green compact, the falling speed of the powder becomes non-uniform, and the weight, size, density, etc. due to segregation etc. vary. May occur. In addition, it is difficult to uniformly mix the raw material powder, which also promotes the occurrence of segregation in the sintered body. Further, since the raw material powder containing a large amount of graphite is hard to solidify, the strength of the green compact is lowered, and as a result, chipping, cracking, cracking and the like are likely to occur.
また、金属粉間の結合強度を強化するために原料粉に錫を添加した場合、原料粉中の黒鉛の添加量が多いと、黒鉛が錫による金属粉の結合機能を阻害するため、焼結体の強度低下を招く。 Further, when tin is added to the raw material powder in order to strengthen the bond strength between the metal powders, if the amount of graphite added in the raw material powder is large, the graphite inhibits the binding function of the metal powder by tin, and thus sintering. It causes a decrease in the strength of the body.
本発明は、上記事情に鑑み、高強度で量産時の寸法や軸受性能のばらつきが小さい焼結軸受を提供することを目的とする。 In view of the above circumstances, an object of the present invention is to provide a sintered bearing having high strength and small variation in dimensions and bearing performance at the time of mass production.
本発明に係る焼結軸受は、黒鉛粉と金属粉とを含む原料粉を成形および焼結して得られた焼結軸受において、黒鉛粉として造粒粉が用いられ、かつ軸受面における遊離黒鉛の割合を面積比で２５％〜８０％としたことを特徴とするものである。原料粉として、銅粉、錫、および黒鉛粉を主成分とする混合粉末を用いることができる。 The sintered bearing according to the present invention is a sintered bearing obtained by molding and sintering raw material powder containing graphite powder and metal powder, in which granulated powder is used as the graphite powder and free graphite on the bearing surface. It is characterized in that the ratio of the above is 25% to 80% in terms of area ratio. As the raw material powder, a mixed powder containing copper powder, tin, and graphite powder as main components can be used.
このように軸受面における遊離黒鉛の割合を面積比で２５％〜８０％とすることで、軸受面における潤滑性が高まる。また、潤滑油を含浸させないドライな状態でも高い潤滑性を得ることができる。 By setting the ratio of free graphite on the bearing surface to 25% to 80% in terms of area ratio in this way, the lubricity on the bearing surface is enhanced. In addition, high lubricity can be obtained even in a dry state without impregnation with lubricating oil.
このように軸受面に多くの黒鉛を遊離させるため、黒鉛粉の配合量を既存品よりも増やす必要があるが、その場合でも黒鉛の造粒粉、すなわち黒鉛の微粉を造粒して大径化したものを使用することで、黒鉛粉１粒子当たりの重量を大きくすることができる。これにより１粒子当りの黒鉛粉と金属粉の重量差が小さくなるので、原料粉の流動性を向上させることができる。また、原料粉を均一混合も可能となる。従って、量産時の偏析による寸法や軸受性能のばらつきを小さくすることができ、かつ複雑な形状の軸受も製作可能となる。また、黒鉛の存在領域が集約されるため、多量の黒鉛が分散して存在する場合に比べ、圧粉体強度や焼結体強度を向上させることができる。 In order to release a large amount of graphite on the bearing surface in this way, it is necessary to increase the blending amount of graphite powder compared to existing products, but even in that case, graphite granulated powder, that is, graphite fine powder is granulated to have a large diameter. The weight per particle of graphite powder can be increased by using the graphite powder. As a result, the difference in weight between the graphite powder and the metal powder per particle is reduced, so that the fluidity of the raw material powder can be improved. In addition, the raw material powder can be uniformly mixed. Therefore, it is possible to reduce variations in dimensions and bearing performance due to segregation during mass production, and it is possible to manufacture bearings having complicated shapes. Further, since the region where graphite exists is concentrated, the powder compact strength and the sintered body strength can be improved as compared with the case where a large amount of graphite is dispersed and present.
上記構成においては、前記造粒粉の平均粒径を、６０μｍ〜５００μｍに設定するのが望ましい。 In the above configuration, it is desirable to set the average particle size of the granulated powder to 60 μm to 500 μm.
原料粉末における黒鉛の造粒粉の配合割合は、３重量％〜１５重量％にするのが望ましい。既存品では、上記の問題から黒鉛の配合割合は３重量％よりも小さくせざるを得なかったが、本発明によれば３重量％以上の黒鉛粉を配合することが可能となる。そのため、上記のとおり軸受面の広大な領域に黒鉛組織を形成することが可能となる。 It is desirable that the blending ratio of the graphite granulated powder in the raw material powder is 3% by weight to 15% by weight. In the existing product, the blending ratio of graphite had to be smaller than 3% by weight due to the above problem, but according to the present invention, it is possible to blend 3% by weight or more of graphite powder. Therefore, as described above, it is possible to form a graphite structure in a vast region of the bearing surface.
黒鉛の造粒粉の見かけ密度は、１．０ｇ／ｃｍ3以下とするのが望ましい。 The apparent density of graphite granulated powder is preferably 1.0 g / cm 3 or less.
本発明にかかる焼結軸受は、上記のとおり潤滑油を含浸させないドライ軸受として使用することができるが、潤滑油を含浸させる含油軸受としても使用することが可能である。 The sintered bearing according to the present invention can be used as a dry bearing that is not impregnated with lubricating oil as described above, but can also be used as an oil-impregnated bearing that is impregnated with lubricating oil.
本発明によれば、軸受面の潤滑性を向上させることができる。また、量産時でも偏析による軸受性能や寸法精度のばらつきを抑制することができ、かつ圧粉体や焼結体の強度を向上させることができる。また、複雑な形状を有する焼結軸受を製作することも可能となり、軸受形状の自由度が高まる。 According to the present invention, the lubricity of the bearing surface can be improved. Further, even at the time of mass production, it is possible to suppress variations in bearing performance and dimensional accuracy due to segregation, and it is possible to improve the strength of the green compact and the sintered body. Further, it becomes possible to manufacture a sintered bearing having a complicated shape, and the degree of freedom in the bearing shape is increased.
以下、本発明を実施するための形態について図面に基づき説明する。 Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
図１に示すように、本実施形態では、焼結軸受１は、内周に軸受面１ａを有する円筒状に形成される。この焼結軸受１の内周にステンレス鋼等からなる軸２を挿入し、その状態で軸を回転させ、あるいは焼結軸受１を回転させると、軸２の外周面が焼結軸受１の軸受面１ａによって回転自在に支持される。 As shown in FIG. 1, in the present embodiment, the sintered bearing 1 is formed in a cylindrical shape having a bearing surface 1a on the inner circumference. When a shaft 2 made of stainless steel or the like is inserted into the inner circumference of the sintered bearing 1 and the shaft is rotated in that state or the sintered bearing 1 is rotated, the outer peripheral surface of the shaft 2 becomes the bearing of the sintered bearing 1. It is rotatably supported by the surface 1a.
本発明の焼結軸受１は、各種粉末を混合した原料粉を金型に充填し、これを圧縮して圧粉体を成形した後、圧粉体を焼結することで形成される。 The sintered bearing 1 of the present invention is formed by filling a mold with a raw material powder in which various powders are mixed, compressing the raw material powder to form a green compact, and then sintering the green compact.
本実施形態の焼結軸受１は、いわゆる銅鉄系と呼ばれるものであり、原料粉として、銅粉、鉄粉、低融点金属粉、および黒鉛粉を主成分とする混合粉末が用いられる。この混合粉末には、必要に応じて各種成形助剤、例えば離型性向上のための潤滑剤（金属セッケン等）が添加される。以下、焼結軸受１の実施形態について、その原料粉末および製造手順を詳細に述べる。 The sintered bearing 1 of the present embodiment is a so-called copper-iron type, and as a raw material powder, a mixed powder containing copper powder, iron powder, low melting point metal powder, and graphite powder as main components is used. Various molding aids, for example, lubricants for improving releasability (metal soap, etc.) are added to the mixed powder as needed. Hereinafter, the raw material powder and the manufacturing procedure of the sintered bearing 1 embodiment will be described in detail.
［銅粉］
銅粉としては、焼結軸受用として汎用されている球状や樹枝状の銅粉が広く使用可能であるが、本実施形態では、電解粉又は水アトマイズ粉が用いられる。なお、これらの混合粉も使用可能である。銅粉の平均粒径は、例えば４０μｍ〜１６０μｍとし、見かけ密度は、例えば１．５〜３．０ｇ／ｃｍ3とする。見かけ密度の定義は、JIS Z 8901の規定に準じる（以下、同じ）。銅粉として扁平銅粉を使用することもできる。
[Copper powder]
As the copper powder, spherical or dendritic copper powder, which is widely used for sintered bearings, can be widely used, but in the present embodiment, electrolytic powder or water atomizing powder is used. In addition, these mixed powders can also be used. The average particle size of the copper powder is, for example, 40 μm to 160 μm, and the apparent density is, for example, 1.5 to 3.0 g / cm 3 . The definition of apparent density conforms to the provisions of JIS Z 8901 (hereinafter the same). Flat copper powder can also be used as the copper powder.
［鉄粉］
鉄粉としては、還元鉄粉、水アトマイズ鉄粉等の公知の粉末が広く使用可能であるが、本実施形態では、還元鉄粉を使用する。還元鉄粉は、略球形でありながら不規則形状でかつ多孔質状をなし、表面に微小な凹凸を有する海綿状となることから、海綿鉄粉とも呼ばれる。鉄粉としては、例えば、平均粒径６０μｍ〜２００μｍ、見かけ密度２．０〜３．０ｇ／ｃｍ3のものを使用する。なお、鉄粉に含まれる酸素量は０．２重量％以下とする。
[Iron powder]
As the iron powder, known powders such as reduced iron powder and water atomized iron powder can be widely used, but in the present embodiment, reduced iron powder is used. The reduced iron powder is also called sponge iron powder because it is substantially spherical but irregularly shaped and porous, and has a spongy shape with minute irregularities on the surface. As the iron powder, for example, one having an average particle size of 60 μm to 200 μm and an apparent density of 2.0 to 3.0 g / cm 3 is used. The amount of oxygen contained in the iron powder shall be 0.2% by weight or less.
［低融点金属粉］
低融点金属粉は、焼結温度よりも低融点の金属粉であり、本発明では、融点が７００℃以下の金属粉、例えば錫、亜鉛、リン等の粉末が使用される。この中でも焼結時の蒸散が少ない錫が好ましい。また、錫粉としてはアトマイズ粉を使用する。これら低融点金属粉は、融点が７００℃以下で焼結温度よりも低融点であり、また、焼結時の蒸散が少ない。錫粉は、銅に対して高いぬれ性を持つため、原料粉に配合することで、焼結時に、液相焼結と固相焼結が進行し、鉄組織と銅組織や銅組織同士の結合強度が強化される。
[Low melting point metal powder]
The low melting point metal powder is a metal powder having a melting point lower than the sintering temperature, and in the present invention, a metal powder having a melting point of 700 ° C. or lower, for example, a powder of tin, zinc, phosphorus or the like is used. Of these, tin, which has less transpiration during sintering, is preferable. In addition, atomized powder is used as the tin powder. These low melting point metal powders have a melting point of 700 ° C. or lower, which is lower than the sintering temperature, and have less transpiration during sintering. Since tin powder has a high wettability with respect to copper, by blending it with the raw material powder, liquid phase sintering and solid phase sintering proceed at the time of sintering, and the iron structure and the copper structure or the copper structure are separated from each other. Bond strength is strengthened.
［黒鉛粉］
黒鉛粉としては、黒鉛の微粉を造粒し、大径化させた黒鉛造粒粉が使用される。微粉としては、鱗状又は球状の天然黒鉛粉で、平均粒径が４０μｍ以下のものを用いる。造粒後の黒鉛粉は、平均粒径６０μｍ〜５００μｍの範囲とし、見かけ密度は１．０ｇ／ｃｍ3以下とする。造粒のためのバインダとしては、例えばフェノール樹脂を使用する。バインダの量は、黒鉛微粉に対して５重量％〜１５重量％とするのが望ましい。
[Graphite powder]
As the graphite powder, graphite granulated powder obtained by granulating fine graphite powder and increasing the diameter is used. As the fine powder, a scale-like or spherical natural graphite powder having an average particle size of 40 μm or less is used. The graphite powder after granulation has an average particle size in the range of 60 μm to 500 μm, and an apparent density of 1.0 g / cm 3 or less. As the binder for granulation, for example, a phenol resin is used. The amount of the binder is preferably 5% by weight to 15% by weight with respect to the graphite fine powder.
［配合比］
上記各粉末を公知の混合機で均一に混合することで原料粉が得られる。原料粉に対する黒鉛粉の配合割合は３重量％〜１５重量％とする（望ましくは５重量％〜１２重量％）。原料粉における低融点金属粉の配合割合は任意に定めることができ、例えば１重量％〜４重量％とする。鉄粉と銅粉の配合割合は、軸受の使用条件やコストを勘案して任意に定めることができる。
[Mixing ratio]
Raw material powder can be obtained by uniformly mixing each of the above powders with a known mixer. The mixing ratio of the graphite powder to the raw material powder is 3% by weight to 15% by weight (preferably 5% by weight to 12% by weight). The blending ratio of the low melting point metal powder in the raw material powder can be arbitrarily determined, and is, for example, 1% by weight to 4% by weight. The mixing ratio of iron powder and copper powder can be arbitrarily determined in consideration of the bearing usage conditions and cost.
［成形］
混合後の原料粉は成形機の金型３に供給される。図２に示すように、金型３は、コア３ａ、ダイ３ｂ、上パンチ３ｃ、および下パンチ３ｄからなり、これらによって区画されたキャビティに原料粉末が充填される。上下パンチ３ｃ，３ｄを接近させて原料粉体を圧縮すると、原料粉末が、コア３ａの外周面、ダイ３ｂの内周面、上パンチ３ｃの端面、および下パンチ３ｄの端面からなる成形面によって成形され、焼結軸受１に対応した形状（本実施形態では円筒状）の圧粉体４が得られる。
[Molding]
The raw material powder after mixing is supplied to the mold 3 of the molding machine. As shown in FIG. 2, the mold 3 includes a core 3a, a die 3b, an upper punch 3c, and a lower punch 3d, and the cavity defined by these is filled with the raw material powder. When the upper and lower punches 3c and 3d are brought close to each other to compress the raw material powder, the raw material powder is formed by a molding surface consisting of an outer peripheral surface of the core 3a, an inner peripheral surface of the die 3b, an end surface of the upper punch 3c, and an end surface of the lower punch 3d. A green compact 4 having a shape corresponding to the sintered bearing 1 (cylindrical in the present embodiment) is obtained.
［焼結］
その後、圧粉体４は焼結炉にて焼結される。焼結条件は、黒鉛に含まれる炭素が鉄と反応しない（炭素の拡散が生じない）条件とする。焼結では９００℃を超えてから炭素（黒鉛）と鉄の反応が始まり、パーライト相γＦｅが生じる。パーライト相γＦｅが生じると、軸受面１ａに遊離する黒鉛組織の量が減少し、本発明の目的を達成できない。また、パーライト相γＦｅは硬い組織（ＨＶ３００以上）で相手材に対する攻撃性が強いため、過剰にパーライト相が析出すると軸２の摩耗を進行させるおそれがある。
[Sintering]
After that, the green compact 4 is sintered in a sintering furnace. The sintering conditions are such that carbon contained in graphite does not react with iron (carbon diffusion does not occur). In sintering, the reaction between carbon (graphite) and iron starts after the temperature exceeds 900 ° C., and a pearlite phase γFe is generated. When the pearlite phase γFe is generated, the amount of graphite structure freed on the bearing surface 1a is reduced, and the object of the present invention cannot be achieved. Further, since the pearlite phase γFe has a hard structure (HV300 or more) and has strong aggression against the mating material, excessive precipitation of the pearlite phase may promote wear of the shaft 2.
また、従来の焼結軸受の製造工程では、焼結雰囲気として、液化石油ガス（ブタン、プロパン等）と空気を混合してＮｉ触媒で熱分解させた吸熱型ガス（ＲＸガス）を使用する場合が多い。しかしながら、吸熱型ガス（ＲＸガス）では炭素が拡散して表面を硬化させるおそれがある。 Further, in the conventional manufacturing process of a sintered bearing, an endothermic gas (RX gas) obtained by mixing liquefied petroleum gas (butane, propane, etc.) and air and thermally decomposing it with a Ni catalyst is used as the sintering atmosphere. There are many. However, in the endothermic gas (RX gas), carbon may diffuse and harden the surface.
以上の観点から、本実施形態では、焼結は９００℃以下の低温焼結、具体的には７００℃（望ましくは７６０℃）〜８４０℃の焼結温度とする。また、焼結雰囲気は、炭素を含有しないガス雰囲気（水素ガス、窒素ガス、アルゴンガス等）あるいは真空とする。これらの対策により、原料粉では炭素と鉄の反応が生じず、従って焼結後の鉄組織は全て軟らかいフェライト相αＦｅ（ＨＶ２００以下）となる。焼結に伴い、各種成形助剤は焼結体内部から揮散する。 From the above viewpoint, in the present embodiment, the sintering is performed at a low temperature of 900 ° C. or lower, specifically, a sintering temperature of 700 ° C. (preferably 760 ° C.) to 840 ° C. The sintering atmosphere is a carbon-free gas atmosphere (hydrogen gas, nitrogen gas, argon gas, etc.) or a vacuum. With these measures, the reaction between carbon and iron does not occur in the raw material powder, and therefore the iron structure after sintering becomes a soft ferrite phase αFe (HV200 or less). With sintering, various molding aids volatilize from the inside of the sintered body.
なお、パーライト相（γＦｅ）がフェライト相（αＦｅ）の粒界に点在する程度であれば、軸２に対する攻撃性はそれほど高まらず、その一方で軸受面１ａの摩耗を抑制する効果を得ることができる。ここでいう「粒界」は、フェライト相の間やフェライト相と他の粒子との間に形成される粒界の他、フェライト相中の結晶粒界の双方を意味する。このような態様でパーライト相をフェライト相の粒界に存在させるためには、焼結温度を上記例示よりも上げて８２０℃〜９００℃とし、かつ炉内雰囲気として炭素を含むガス、例えば天然ガスや吸熱型ガス（ＲＸガス）を用いて焼結する。これにより、焼結時にはガスに含まれる炭素が鉄に拡散し、パーライト相を形成することができる。 If the pearlite phase (γFe) is scattered around the grain boundaries of the ferrite phase (αFe), the aggression against the shaft 2 is not so high, and on the other hand, the effect of suppressing the wear of the bearing surface 1a is obtained. Can be done. The "grain boundaries" here mean both grain boundaries formed between the ferrite phases and between the ferrite phase and other particles, as well as crystal grain boundaries in the ferrite phase. In order to allow the pearlite phase to exist at the grain boundaries of the ferrite phase in such an embodiment, the sintering temperature is raised from the above example to 820 ° C to 900 ° C, and a gas containing carbon as the atmosphere inside the furnace, for example, natural gas. Or heat-absorbing gas (RX gas) is used for sintering. As a result, carbon contained in the gas diffuses into iron during sintering, and a pearlite phase can be formed.
以上に述べた焼結工程を経ることで、多孔質の焼結体が得られる。この焼結体にサイジングを施すことにより、図１に示す焼結軸受１が完成する。本実施形態の焼結軸受はドライ軸受として使用されるので、サイジング後における潤滑油の含浸は行われない。上記のように、焼結時に炭素と鉄を反応させず、鉄組織を軟質のフェライト相にすることにより、サイジング時に焼結体が塑性流動を生じやすくなり、高精度のサイジングを行うことができる。 By going through the sintering process described above, a porous sintered body can be obtained. By sizing the sintered body, the sintered bearing 1 shown in FIG. 1 is completed. Since the sintered bearing of this embodiment is used as a dry bearing, it is not impregnated with lubricating oil after sizing. As described above, by making the iron structure a soft ferrite phase without reacting carbon and iron during sintering, the sintered body tends to generate plastic flow during sizing, and high-precision sizing can be performed. ..
本発明では、上記のように原料粉における黒鉛粉の配合割合を３重量％以上としているので、軸受面１ａに黒鉛組織を面積比で２５％以上の割合で形成することができる。そのため、軸受面１ａの自己潤滑性を高めて、軸受の潤滑性能と導電性を向上させることができ、高速回転や高荷重の条件下でも高い耐久寿命を有する焼結軸受を提供することができる。また、潤滑油を多孔質組織に含浸させないドライ軸受としての使用も可能となり、複写機や印刷機（例えばマグロール）、自動車用電装部品、家庭用電化製品、高真空機器等において、潤滑油が使用できない部位にも使用することが可能となる。なお、軸受面１ａに遊離する黒鉛組織の面積が過剰になると、軸受面１ａの強度低下を招くため、面積比の上限は８０％とする。 In the present invention, since the blending ratio of the graphite powder in the raw material powder is 3% by weight or more as described above, the graphite structure can be formed on the bearing surface 1a at a ratio of 25% or more in terms of area ratio. Therefore, the self-lubricating property of the bearing surface 1a can be enhanced to improve the lubrication performance and conductivity of the bearing, and it is possible to provide a sintered bearing having a long durable life even under conditions of high speed rotation and high load. .. It can also be used as a dry bearing that does not impregnate the porous structure with lubricating oil, and it is used in copiers and printing machines (for example, Magroll), electrical components for automobiles, household appliances, high vacuum equipment, etc. It can be used for parts that cannot be used. If the area of the graphite structure freed on the bearing surface 1a becomes excessive, the strength of the bearing surface 1a is lowered, so the upper limit of the area ratio is set to 80%.
なお、軸受面１ａにおける面積比の測定は画像解析により行うことができる。この画像解析は、例えば次のように行う。
（１）金属顕微鏡（（株）ニコン製ＥＣＬＩＰＳＥ ＭＥ６００）で撮影（１００倍）。
（２）画像取得は（株）ニコン製Ｄｉｇｉｔａｌ Ｓｉｇａｈｔ ＤＳ−Ｕ３で行う。
（３）画像処理は（株）ニコンインストルメンツカンパニー製ＮＩＳ−Ｅｌｅｍｅｎｔｓ Ｄで行う。
（４）デジタル画像解析ソフト（イノテック（株）製Ｑｕｉｃｋ Ｇｒａｉｎ）で黒鉛の面積比率を算出する。
The area ratio on the bearing surface 1a can be measured by image analysis. This image analysis is performed, for example, as follows.
(1) Photographed with a metallurgical microscope (ECLIPSE ME600 manufactured by Nikon Corporation) (100x).
(2) Image acquisition is performed by Digital Sigate DS-U3 manufactured by Nikon Corporation.
(3) Image processing is performed by NIS-Elements D manufactured by Nikon Instruments Company, Inc.
(4) Calculate the area ratio of graphite with digital image analysis software (Quick Grain manufactured by Innotek Co., Ltd.).
更に、本発明では黒鉛粉として造粒粉を使用しているので、黒鉛粉１粒子当たりの重量を大きくすることができる。これにより１粒子当りの黒鉛粉と金属粉の重量差が小さくなるので、原料粉の流動性を向上させることができる。また、原料粉を均一混合も可能となる。従って、量産時の偏析による寸法や軸受性能のばらつきを小さくすることができ、かつかつ複雑な形状の軸受も製作可能となる。また、多孔質組織において黒鉛の存在領域が集約されるため、多量の黒鉛が分散して存在する場合に比べ、圧粉体強度や焼結体強度を向上させることができる Further, since the granulated powder is used as the graphite powder in the present invention, the weight per particle of the graphite powder can be increased. As a result, the difference in weight between the graphite powder and the metal powder per particle is reduced, so that the fluidity of the raw material powder can be improved. In addition, the raw material powder can be uniformly mixed. Therefore, it is possible to reduce variations in dimensions and bearing performance due to segregation during mass production, and it is possible to manufacture bearings having complicated shapes. Further, since the region where graphite exists is concentrated in the porous structure, the powder compact strength and the sintered body strength can be improved as compared with the case where a large amount of graphite is dispersed and present.
なお、以上の説明では、焼結軸受の例示として、金属粉として銅粉、鉄粉、および低融点金属粉を使用する銅鉄系を挙げたが、本発明はこれに限られず、金属粉として銅粉と低融点金属粉を使用する銅系焼結軸受や、金属粉として鉄粉と微量の銅粉を使用する鉄系焼結軸受にも同様に適用することができる。 In the above description, as an example of the sintered bearing, a copper iron system using copper powder, iron powder, and low melting point metal powder as the metal powder has been mentioned, but the present invention is not limited to this, and the metal powder is not limited to this. The same can be applied to a copper-based sintered bearing that uses copper powder and a low melting point metal powder, and an iron-based sintered bearing that uses iron powder and a small amount of copper powder as the metal powder.
次に、本発明の実施品（以下、本発明品と記す）について、造粒黒鉛粉を使用しない従来品と比較して説明する。この本発明品と従来品は、上記実施形態とは異なり、銅系焼結軸受である。 Next, the product of the present invention (hereinafter referred to as the product of the present invention) will be described in comparison with the conventional product that does not use granulated graphite powder. The product of the present invention and the conventional product are copper-based sintered bearings, unlike the above-described embodiment.
図３は焼結軸受１の軸受面１ａを拡大した顕微鏡写真であり、（Ａ）図が本発明品を、（Ｂ）図が従来品を示す。両図において、明部が銅組織（Ｓｎとの合金部分も含む）を示し、暗部が黒鉛組織を示す。微細な暗部は、表面に開口した空孔である。本発明品では従来品よりも黒鉛の分布量が多くなっていることが分かる。また、本発明品では、黒鉛が均一に分散していることも理解できる。ちなみに、（Ａ）図における黒鉛の面積比は７８％であり、（Ｂ）図における黒鉛の面積比は２８％である。なお、この面積比率を測定するための画像解析は、上述の機器と方法を使用した。 FIG. 3 is an enlarged micrograph of the bearing surface 1a of the sintered bearing 1, in which FIG. 3A shows the product of the present invention and FIG. 3B shows the conventional product. In both figures, the bright part shows the copper structure (including the alloy part with Sn), and the dark part shows the graphite structure. The fine dark part is a hole opened on the surface. It can be seen that the product of the present invention has a larger distribution amount of graphite than the conventional product. It can also be understood that in the product of the present invention, graphite is uniformly dispersed. Incidentally, the area ratio of graphite in the figure (A) is 78%, and the area ratio of graphite in the figure (B) is 28%. The above-mentioned equipment and method were used for the image analysis for measuring this area ratio.
図４は、圧粉体の強さを評価するために行ったラトラ試験の結果を示す。ここで、ラトラ試験とは、金属圧粉体のラトラ試験法（日本粉末冶金工業会規格：ＪＳＰＭ標準４−６９）に基づいて測定を行い、得られる測定結果から算出する値を用いて、試験片(圧紛体)の崩壊のしやすさ(圧紛体の強さを数値化)を求める方法で、得られるラトラ値が低い方が圧紛体は強い。図４から分かるように、本発明品は、従来品よりラトラ値が低いので、圧紛体の強度が優れ、欠け、割れ等を抑制できる。 FIG. 4 shows the results of a rattra test performed to evaluate the strength of the green compact. Here, the ratra test is a test using a value calculated from the measurement results obtained by measuring based on the ratra test method for metallic green powder (Japan Powder Metallurgy Industry Association standard: JSPM standard 4-69). A method for determining the ease of disintegration of a piece (powder) (quantifying the strength of the powder). The lower the ratra value obtained, the stronger the powder. As can be seen from FIG. 4, since the product of the present invention has a lower rattle value than the conventional product, the strength of the powder compact is excellent, and chipping, cracking, etc. can be suppressed.
図５は、圧粉体の強さを評価するために測定した圧環強さを示す。図５から分かるように、本発明品は、従来品より圧環強さが大きいため、圧紛体の強度が優れ、欠け、割れ等を抑制できる。 FIG. 5 shows the annular strength measured to evaluate the strength of the green compact. As can be seen from FIG. 5, since the product of the present invention has a higher ring strength than the conventional product, the strength of the powder compact is excellent, and chipping, cracking, etc. can be suppressed.
図６は、成形重量のばらつきを評価するために測定した成形重量の最大値、平均値、最小値を示す。図６から分かるように、本発明品は、従来品より成形重量の最大値と最小値との差が小さく、成形重量のばらつきが小さい。 FIG. 6 shows the maximum value, the average value, and the minimum value of the molding weight measured in order to evaluate the variation in the molding weight. As can be seen from FIG. 6, the product of the present invention has a smaller difference between the maximum value and the minimum value of the molding weight than the conventional product, and the variation in the molding weight is small.
図７は、圧粉体長さのばらつきを評価するために測定した圧粉体長さの平均値、最小値を示す。図７から分かるように、本発明品は、従来品より圧粉体長さの最大値と最小値との差が小さく、圧粉体長さのばらつきが小さい。 FIG. 7 shows the average value and the minimum value of the green compact length measured for evaluating the variation in the green compact length. As can be seen from FIG. 7, the product of the present invention has a smaller difference between the maximum value and the minimum value of the green compact length than the conventional product, and the variation in the green compact length is small.
図８は、以下の条件での運転後の軸受内径面の摩耗量を示す。また、同条件の運転での摩擦係数の変化を図９に示す。
周速：Ｖ＝７ｍ／ｍｉｎ
面圧：Ｐ＝２ＭＰａ
温度：１００℃
試験軸：ＳＵＳ４２０Ｊ２（ＨＲＣ＝５０、Ｒａ＝０．４μｍ）
隙間：１５μｍ
FIG. 8 shows the amount of wear on the inner diameter surface of the bearing after operation under the following conditions. Further, FIG. 9 shows a change in the coefficient of friction during operation under the same conditions.
Peripheral speed: V = 7m / min
Surface pressure: P = 2 MPa
Temperature: 100 ° C
Test axis: SUS420J2 (HRC = 50, Ra = 0.4 μm)
Gap: 15 μm
図８から分かるように、本発明品は、従来品に比較して、軸受内径面の摩耗量を抑制することができる。また、図９から分かるように、１０ｍｉｎ経過後では、本発明品は、従来品と比較して、摩擦係数を抑制することができる。 As can be seen from FIG. 8, the product of the present invention can suppress the amount of wear on the inner diameter surface of the bearing as compared with the conventional product. Further, as can be seen from FIG. 9, after 10 minutes have passed, the product of the present invention can suppress the friction coefficient as compared with the conventional product.
以上の説明では、焼結軸受として軸の回転運動を支持する軸受を例示したが、本発明にかかる焼結軸受は、軸等の摺動部材の直線運動を支持するいわゆるリニア軸受としても使用することができる。また、本発明の焼結軸受は、潤滑油を含浸させないドライ軸受として使用するだけでなく、サイジング後に潤滑油を含浸させる含油軸受としても使用することができる。 In the above description, a bearing that supports the rotational movement of the shaft is illustrated as a sintered bearing, but the sintered bearing according to the present invention is also used as a so-called linear bearing that supports the linear movement of a sliding member such as a shaft. be able to. Further, the sintered bearing of the present invention can be used not only as a dry bearing that is not impregnated with lubricating oil, but also as an oil-impregnated bearing that is impregnated with lubricating oil after sizing.
１ 焼結軸受
１ａ 軸受面
２ 軸
３ 金型
４ 圧粉体
1 Sintered bearing 1a Bearing surface 2 Shaft 3 Mold 4 Powder powder
Claims (5)
黒鉛粉として鱗状の黒鉛粉を造粒した造粒粉が用いられ、かつ軸受面における、前記黒鉛粉から生じた遊離黒鉛の割合を面積比で２８％よりも大きく、８０％以下とし、
前記造粒のためのバインダの量を、前記黒鉛粉に対して５重量％〜１５重量％としたことを特徴とする焼結軸受。 In a sintered bearing obtained by molding a raw material powder containing graphite powder and metal powder with a mold and then sintering the raw material powder.
As the graphite powder, a granulated powder obtained by granulating scale-like graphite powder is used, and the ratio of free graphite generated from the graphite powder on the bearing surface is set to 80% or less , which is larger than 28% in terms of area ratio.
A sintered bearing characterized in that the amount of the binder for granulation is 5% by weight to 15% by weight with respect to the graphite powder .
黒鉛粉として鱗状の黒鉛粉を造粒した造粒粉が用いられ、かつ軸受面における、前記黒鉛粉から生じた遊離黒鉛の割合を面積比で２８％よりも大きく、８０％以下とし、
前記造粒のためのバインダの量を、前記黒鉛粉に対して５重量％〜１５重量％とし、潤滑油を含侵させずに使用されることを特徴とする焼結軸受。 In a sintered bearing obtained by molding a raw material powder containing graphite powder and metal powder with a mold and then sintering the raw material powder.
As the graphite powder, a granulated powder obtained by granulating scale-like graphite powder is used, and the ratio of free graphite generated from the graphite powder on the bearing surface is set to 80% or less , which is larger than 28% in terms of area ratio.
A sintered bearing characterized in that the amount of the binder for granulation is 5% by weight to 15% by weight with respect to the graphite powder, and the bearing is used without impregnation with lubricating oil.
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| JPS5763653A (en) * | 1980-10-06 | 1982-04-17 | Hitachi Chem Co Ltd | Wear resistant brass alloy |
| JPS5773149A (en) * | 1980-10-24 | 1982-05-07 | Hitachi Chem Co Ltd | Wear resistant brass alloy |
| JPS57123951A (en) * | 1981-01-10 | 1982-08-02 | Hitachi Chem Co Ltd | Aluminum alloy containing dispersed graphite and lead |
| JPH0621140B2 (en) * | 1986-08-14 | 1994-03-23 | リグナイト株式会社 | Method for producing graphite / phenol resin granules |
| JPH0238540A (en) * | 1988-07-29 | 1990-02-07 | Komatsu Ltd | Production of nongreased sliding material |
| JPH11117044A (en) * | 1997-10-13 | 1999-04-27 | Mitsubishi Materials Corp | Bearing made of free-graphite-precipitation-type ferrous sintered material, excellent in initial conformability |
| JP2000199028A (en) * | 1998-12-28 | 2000-07-18 | Rubutekku:Kk | Self-lubricating sintered composite material |
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| JP3932274B2 (en) * | 2002-08-06 | 2007-06-20 | 三菱マテリアルＰｍｇ株式会社 | Sintered Cu alloy bearing for recirculation exhaust gas flow control valve of EGR type internal combustion engine showing excellent wear resistance under high temperature environment |
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