JP2018048694A - Sintered bearing, and process of manufacture for the same - Google Patents
Sintered bearing, and process of manufacture for the same Download PDFInfo
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Abstract
Description
本発明は、焼結軸受およびその製造方法に関する。 The present invention relates to a sintered bearing and a manufacturing method thereof.
小型モータ用の軸受、例えばノート型パソコン等に装備されるファンモータ用の軸受としては、焼結金属製の軸受部材の内周面にヘリングボーン形状等に配列した複数の動圧発生溝を形成した流体動圧軸受を使用する場合が多い（特許文献１）。このように動圧発生溝を形成することで、軸の回転中は、動圧発生溝によって潤滑油が軸受面の軸方向一部領域に集められて動圧効果を生じ、この動圧効果によって回転する軸が軸受部材に対して非接触に支持される。 For small motor bearings, such as fan motor bearings installed in notebook computers, etc., multiple dynamic pressure generating grooves arranged in a herringbone shape etc. are formed on the inner peripheral surface of a sintered metal bearing member In many cases, a fluid dynamic pressure bearing is used (Patent Document 1). By forming the dynamic pressure generating groove in this way, during the rotation of the shaft, the lubricating oil is collected in a partial region in the axial direction of the bearing surface by the dynamic pressure generating groove to generate a dynamic pressure effect. The rotating shaft is supported in a non-contact manner with respect to the bearing member.
軸受部材の内周面の動圧発生溝は、例えば焼結体をサイジングする際に、コアピンの外周面に動圧発生溝の形状に対応した複数の凸部を形成し、サイジングに伴う加圧力で、焼結体の内周面をコアピンの外周面の凸部に食いつかせることで形成することができる。しかしながら、かかる工程では、動圧発生溝が焼結材料の塑性変形で形成されるため、塑性変形量のばらつきから、その精度確保には限界がある。 The dynamic pressure generating groove on the inner peripheral surface of the bearing member is formed by, for example, forming a plurality of convex portions corresponding to the shape of the dynamic pressure generating groove on the outer peripheral surface of the core pin when sizing the sintered body. Thus, the inner peripheral surface of the sintered body can be formed by biting the convex portion of the outer peripheral surface of the core pin. However, in such a process, since the dynamic pressure generating grooves are formed by plastic deformation of the sintered material, there is a limit to ensuring accuracy due to variations in the amount of plastic deformation.
その一方で、軸受面の粗大気孔を少なくすれば、油膜形成率が向上するため、動圧発生溝を省略しても十分な油膜剛性が得られると考えられる。そのため、動圧発生溝を有する流体動圧軸受を、そのような動圧発生溝を有しない、いわゆる真円軸受に置き換えることが可能となり、軸受装置の低コスト化を達成できると考えられる。 On the other hand, if the number of rough air holes on the bearing surface is reduced, the oil film formation rate is improved, so that it is considered that sufficient oil film rigidity can be obtained even if the dynamic pressure generating groove is omitted. For this reason, it is possible to replace the fluid dynamic pressure bearing having the dynamic pressure generating groove with a so-called perfect circle bearing having no such dynamic pressure generating groove, thereby achieving a reduction in cost of the bearing device.
そこで、本発明は、軸受面の粗大気孔を少なくし、表面開孔と内部気孔を微細化しかつ均質化した焼結軸受を提供することを目的とする。 SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sintered bearing in which rough air holes on the bearing surface are reduced, and surface openings and internal pores are refined and homogenized.
以上の目的を達成するため、本発明は、鉄粉の表面に第一銅粉を部分拡散により付着させた部分拡散合金粉と、第二銅粉と、銅よりも低融点の低融点金属粉とを含む圧紛体を焼結させてなる焼結軸受において、部分拡散合金粉の最大粒径が１０６μｍであり、前記部分拡散合金粉の第一銅粉の最大粒径が１０μｍ以下であることを特徴とするものである。 In order to achieve the above object, the present invention provides a partially diffusing alloy powder in which cuprous powder is adhered to the surface of iron powder by partial diffusion, a second copper powder, and a low melting point metal powder having a melting point lower than that of copper. In the sintered bearing formed by sintering a compact including the powder, the maximum particle size of the partial diffusion alloy powder is 106 μm, and the maximum particle size of the cuprous powder of the partial diffusion alloy powder is 10 μm or less. It is a feature.
本発明では、部分拡散合金粉および銅粉（第一銅粉）の最大粒径を制限しており、しかも当該銅粉の最大粒径を１０μｍ以下として銅粉を小粒径化している。従って、部分拡散合金粉の粒径を揃えることができ、これにより焼結後に粗大気孔を生じ難くすることができる。その一方で、原料粉の粒径が小さくなりすぎることはなく、圧紛体を成形する際の原料粉の流動性も良好なものとなる。 In the present invention, the maximum particle size of the partial diffusion alloy powder and the copper powder (the first copper powder) is limited, and the maximum particle size of the copper powder is set to 10 μm or less to reduce the copper powder. Therefore, it is possible to make the particle diameters of the partially diffused alloy powder uniform, thereby making it difficult to generate coarse air holes after sintering. On the other hand, the particle size of the raw material powder does not become too small, and the fluidity of the raw material powder when forming the compact is good.
第二銅粉を不規則形状で多孔質状にすれば、焼結後の焼結体を圧紛体よりも収縮させることができる。従って、焼結組織を緻密化して、粗大気孔の発生をさらに抑制することが可能となる。 If the cupric powder is made irregular and porous, the sintered body after sintering can be contracted more than the compact. Therefore, it becomes possible to densify the sintered structure and further suppress the generation of rough atmospheric pores.
本発明によれば、軸受面を動圧発生溝のない円筒面状にした場合でも、十分な油膜剛性を確保し、高い油膜形成率を得ることが可能となる。従って、動圧発生溝を省略することが可能となり、そのような動圧発生溝を有する流体動圧軸受を使用する場合に比べて、軸受装置の低コスト化を図ることができる。 According to the present invention, even when the bearing surface is a cylindrical surface without a dynamic pressure generating groove, sufficient oil film rigidity can be ensured and a high oil film formation rate can be obtained. Therefore, the dynamic pressure generating groove can be omitted, and the cost of the bearing device can be reduced as compared with the case where a fluid dynamic pressure bearing having such a dynamic pressure generating groove is used.
また、本発明は、鉄粉の表面に第一銅粉を部分拡散により付着させた部分拡散合金粉と、第二銅粉と、銅よりも低融点の低融点金属粉とを含む圧紛体を焼結させて焼結軸受を製造する際に、部分拡散合金粉の最大粒径を１０６μｍとし、前記部分拡散合金粉の第一銅粉の最大粒径が１０μｍ以下にすることを特徴とする。この場合、第二銅粉として、不規則形状の多孔質銅粉を使用するのが好ましい。 In addition, the present invention provides a compact including a partial diffusion alloy powder in which a first copper powder is adhered to the surface of iron powder by partial diffusion, a second copper powder, and a low melting metal powder having a melting point lower than that of copper. When producing a sintered bearing by sintering, the maximum particle size of the partial diffusion alloy powder is set to 106 μm, and the maximum particle size of the cuprous powder of the partial diffusion alloy powder is set to 10 μm or less. In this case, it is preferable to use irregular-shaped porous copper powder as the second copper powder.
以上のように、本発明によれば、軸受面における粗大気孔を少なくして表面開孔を微細化しかつ均質化することができる。これにより、軸受面での圧力逃げが生じ難くなるため、高い油膜形成率を得ることが可能となる。 As described above, according to the present invention, the rough air holes on the bearing surface can be reduced, and the surface openings can be refined and homogenized. As a result, pressure escape at the bearing surface is unlikely to occur, and a high oil film formation rate can be obtained.
以下、本発明の実施の形態を図面に基づいて説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
図１に、情報機器、特に携帯電話やタブレット型端末等のモバイル機器に組み込まれる冷却用のファンモータを示す。このファンモータは、軸受装置１と、軸受装置１の軸部材２に装着されたロータ３と、ロータ３の外径端に取付けられた羽根４と、半径方向のギャップを介して対向させたステータコイル６ａおよびロータマグネット６ｂと、これらを収容するケーシング５とを備える。ステータコイル６ａは、軸受装置１の外周に取付けられ、ロータマグネット６ｂはロータ３の内周に取付けられる。ステータコイル６ａに通電することにより、ロータ３、羽根４、及び軸部材２が一体に回転し、これにより軸方向あるいは外径方向の気流が発生する。 FIG. 1 shows a cooling fan motor incorporated in an information device, particularly a mobile device such as a mobile phone or a tablet terminal. The fan motor includes a bearing device 1, a rotor 3 mounted on the shaft member 2 of the bearing device 1, a blade 4 attached to the outer diameter end of the rotor 3, and a stator opposed to each other through a radial gap. The coil 6a and the rotor magnet 6b are provided, and the casing 5 which accommodates these. The stator coil 6 a is attached to the outer periphery of the bearing device 1, and the rotor magnet 6 b is attached to the inner periphery of the rotor 3. By energizing the stator coil 6a, the rotor 3, the blades 4, and the shaft member 2 rotate together, thereby generating an axial or outer diameter airflow.
図２に示すように、軸受装置１は、軸部材２と、ハウジング７と、焼結軸受８と、シール部材９と、スラスト受け１０とを備える。 As shown in FIG. 2, the bearing device 1 includes a shaft member 2, a housing 7, a sintered bearing 8, a seal member 9, and a thrust receiver 10.
軸部材２は、ステンレス鋼等の金属材料で円柱状に形成されており、円筒状をなす焼結軸受８の内周面に挿入される。軸部材２は、軸受面となる焼結軸受８の内周面８ａでラジアル方向に回転自在に支持される。軸部材２の下端はハウジング７の底部７ｂに配置されたスラスト受け１０と接触しており、軸部材の回転時には、スラスト受け１０によって軸部材２がスラスト方向に支持される。ハウジング７は、略円筒状の側部７ａと、側部７ａの下方の開口部を閉塞する底部７ｂとを有する。側部７ａの外周面にケーシング５及びステータコイル６ａが固定され、側部７ａの内周面に軸受部材８が固定される。シール部材９は樹脂あるいは金属で環状に形成され、ハウジングの側部の内周面の上端部に固定されている。シール部材９の下側の端面が軸受部材８の上側端面と軸方向で当接している。シール部材９の内周面は軸部材２の外周面と半径方向で対向し、両者の間にはシール空間Ｓが形成されている。かかる軸受装置１では、少なくとも軸受部材８の内周面と軸部材２の外周面とで形成されるラジアル隙間が潤滑油で満たされる。この他、ハウジング７の内部空間を全て潤滑油で満たしてもよい（この場合、シール空間Ｓに油面が形成される）。 The shaft member 2 is formed in a cylindrical shape from a metal material such as stainless steel, and is inserted into the inner peripheral surface of the sintered bearing 8 having a cylindrical shape. The shaft member 2 is supported by the inner peripheral surface 8a of the sintered bearing 8 serving as a bearing surface so as to be rotatable in the radial direction. The lower end of the shaft member 2 is in contact with a thrust receiver 10 disposed on the bottom 7b of the housing 7, and the shaft member 2 is supported in the thrust direction by the thrust receiver 10 when the shaft member rotates. The housing 7 has a substantially cylindrical side portion 7a and a bottom portion 7b that closes an opening below the side portion 7a. The casing 5 and the stator coil 6a are fixed to the outer peripheral surface of the side portion 7a, and the bearing member 8 is fixed to the inner peripheral surface of the side portion 7a. The seal member 9 is formed in an annular shape with resin or metal, and is fixed to the upper end portion of the inner peripheral surface of the side portion of the housing. The lower end surface of the seal member 9 is in contact with the upper end surface of the bearing member 8 in the axial direction. The inner peripheral surface of the seal member 9 faces the outer peripheral surface of the shaft member 2 in the radial direction, and a seal space S is formed between them. In the bearing device 1, at least a radial gap formed between the inner peripheral surface of the bearing member 8 and the outer peripheral surface of the shaft member 2 is filled with the lubricating oil. In addition, the entire internal space of the housing 7 may be filled with lubricating oil (in this case, an oil surface is formed in the seal space S).
軸受部材８は、主成分として鉄と銅を含む鉄銅系の焼結体で形成される。この焼結体は、各種粉末を混合した原料粉を金型に供給し、これを圧縮して圧紛体を成形した後、圧紛体を焼結することで製作される。本実施形態で使用する原料粉は、部分拡散合金粉と単体銅粉を主原料とし、これに低融点金属、および固体潤滑剤を配合した混合粉末である。以下、上記の各粉末について詳細に述べる。 The bearing member 8 is formed of a ferrous copper-based sintered body containing iron and copper as main components. This sintered body is manufactured by supplying raw powder mixed with various powders to a mold, compressing the raw powder to form a compact, and then sintering the compact. The raw material powder used in the present embodiment is a mixed powder in which a partial diffusion alloy powder and a single copper powder are used as main raw materials, and a low melting point metal and a solid lubricant are blended therein. Hereinafter, each of the above powders will be described in detail.
［部分拡散合金粉］
図３に示すように、部分拡散合金粉１１としては、核となる鉄粉１２の表面に、当該鉄粉より粒径の小さい銅粉１３（第一銅粉）を部分拡散により付着させたＦｅ−Ｃｕ部分拡散合金粉が使用される。この部分拡散合金粉１１の拡散部分はＦｅ−Ｃｕ合金を形成しており、この合金部分は鉄原子１２ａと銅原子１３ａとが相互に結合し、配列した結晶構造を有する。
[Partial diffusion alloy powder]
As shown in FIG. 3, as the partial diffusion alloy powder 11, Fe powder in which copper powder 13 (first copper powder) having a particle size smaller than the iron powder is adhered to the surface of the core iron powder 12 by partial diffusion. -Cu partial diffusion alloy powder is used. The diffusion portion of the partial diffusion alloy powder 11 forms an Fe—Cu alloy, and this alloy portion has a crystal structure in which iron atoms 12a and copper atoms 13a are bonded to each other and arranged.
部分拡散合金粉１１の鉄粉１２としては、還元鉄粉、アトマイズ鉄粉等を使用することができるが、本実施形態では還元鉄粉を使用する。還元鉄粉は、不規則形状で、かつ内部気孔を有する海綿状（多孔質状）をなす。還元鉄粉を使用することで、アトマイズ鉄粉を使用する場合に比べ、圧縮性を向上させて成形性を高めることができる。また、焼結後の鉄組織が多孔質状となるため、鉄組織中にも潤滑油を保有できるようになり、焼結体の保油性を向上できる利点も得られる。さらに鉄粉に対する銅粉の付着性が向上するため、銅濃度が均一な部分拡散合金粉を得ることができる。 As the iron powder 12 of the partial diffusion alloy powder 11, reduced iron powder, atomized iron powder, or the like can be used, but reduced iron powder is used in the present embodiment. The reduced iron powder has an irregular shape and a spongy (porous) shape having internal pores. By using reduced iron powder, compressibility can be improved and moldability can be improved as compared to the case of using atomized iron powder. Moreover, since the iron structure after sintering becomes porous, the lubricating oil can be held in the iron structure, and the oil retaining property of the sintered body can be improved. Furthermore, since the adhesiveness of the copper powder to the iron powder is improved, a partial diffusion alloy powder having a uniform copper concentration can be obtained.
また、部分拡散合金粉１１の核となる鉄粉１２としては、粒度１４５メッシュ以下の粉末が使用される。ここで「粒度１４５メッシュ」とは、目開きが１４５メッシュ（約１０６μｍ）の篩を通過させた粉末を意味する。従って、この場合の鉄粉の最大粒径は、１０６μｍとなる。「粒度１４５メッシュ以下」は粉末の粒度が１４５メッシュ以下であること、つまり粉末の最大粒径が１０６μｍ以下であることを意味する。なお、鉄粉１２の粒度は、２３０メッシュ（目開き６３μｍ、最大粒径６３μｍ）以下とするのがより好ましい。粉末の粒径は、例えばレーザー回析・散乱法で測定することができる（以下、同じ）。 Moreover, as the iron powder 12 used as the nucleus of the partial diffusion alloy powder 11, a powder with a particle size of 145 mesh or less is used. Here, “particle size 145 mesh” means a powder that has passed through a sieve having a mesh size of 145 mesh (about 106 μm). Accordingly, the maximum particle size of the iron powder in this case is 106 μm. “Particle size of 145 mesh or less” means that the particle size of the powder is 145 mesh or less, that is, the maximum particle size of the powder is 106 μm or less. The particle size of the iron powder 12 is more preferably 230 mesh (mesh size 63 μm, maximum particle size 63 μm) or less. The particle size of the powder can be measured, for example, by a laser diffraction / scattering method (hereinafter the same).
また、部分拡散合金粉１１の銅粉１３（第一銅粉）としては、電解銅粉およびアトマイズ銅粉の双方が使用可能であるが、電解銅粉を使用するのがより好ましい。電解銅粉は一般に樹枝状であることから、銅粉１３として電解銅粉を使用することで、焼結時に焼結が進みやすくなる利点が得られる。また、部分拡散合金粉１１の銅粉１３の最大粒径は１０μｍ以下とする。なお、部分拡散合金粉１１におけるＣｕ粉の割合は、１０〜３０質量％（好ましくは１５質量％〜２５質量％）とする。 Moreover, as the copper powder 13 (first copper powder) of the partial diffusion alloy powder 11, both electrolytic copper powder and atomized copper powder can be used, but it is more preferable to use electrolytic copper powder. Since the electrolytic copper powder is generally dendritic, using the electrolytic copper powder as the copper powder 13 provides an advantage that the sintering easily proceeds during sintering. Moreover, the maximum particle diameter of the copper powder 13 of the partial diffusion alloy powder 11 is 10 μm or less. In addition, the ratio of Cu powder in the partial diffusion alloy powder 11 shall be 10-30 mass% (preferably 15 mass%-25 mass%).
以上に説明した部分拡散合金粉１１としては、粒度１４５メッシュ以下（最大粒径１０６μｍ）のものが使用される。 As the partial diffusion alloy powder 11 described above, those having a particle size of 145 mesh or less (maximum particle size 106 μm) are used.
［単体銅粉］
単体銅粉（第二銅粉）としては、図４に示すように、表面および内部の双方が多孔質となった銅粉（図４の白地中で黒く現れた部分が空孔を示す）が使用される。この多孔質の銅粉は、銅粉を焼鈍させることで得ることができる。単体銅粉の粒径は部分拡散合金粉における鉄粉１２と同程度であり、具体的には、粒度１４５メッシュ以下（最大粒径１０６μｍ以下）、より好ましくは２３０メッシュ以下（最大粒径６３μｍ以下）である。
[Single copper powder]
As the single copper powder (second copper powder), as shown in FIG. 4, copper powder whose surface and inside are both porous (the part that appears black in the white background in FIG. 4 shows voids) is used. used. This porous copper powder can be obtained by annealing the copper powder. The particle size of the single copper powder is about the same as that of the iron powder 12 in the partial diffusion alloy powder. Specifically, the particle size is 145 mesh or less (maximum particle size 106 μm or less), more preferably 230 mesh or less (maximum particle size 63 μm or less). ).
単体銅粉として、以上に述べた多孔質銅粉と、アスペクト比が例えば１３以上となるように扁平化させた箔状銅粉とを使用することもできる。箔状銅粉は圧紛体の成形時に表面に現れやすいため、軸受面を含む焼結体の表面を容易に銅膜で形成することができる。 As the single copper powder, the porous copper powder described above and the foil-like copper powder flattened so that the aspect ratio becomes, for example, 13 or more can also be used. Since the foil-like copper powder tends to appear on the surface when the compact is formed, the surface of the sintered body including the bearing surface can be easily formed with a copper film.
［低融点金属粉］
低融点金属粉は焼結時のバインダーとして添加される。低融点金属粉としては、融点が銅よりも低い金属粉、特に融点が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。本実施形態では、これらの中でも銅と鉄に拡散し易く、単粉で使用することが容易な錫粉、特にアトマイズ錫粉を使用する。低融点金属粉は焼結時に液相となって移動し、元の場所に空孔を形成する。従って、空孔を微細化するためにも低融点金属粉としては粒度が小さいもの、例えば粒度が２５０メッシュ以下（最大粒径６３μｍ以下）、好ましくは３５０メッシュ以下（最大粒径４５μｍ以下）のものを使用するのが好ましい。
[Low melting point metal powder]
The low melting point metal powder is added as a binder during sintering. As the low melting point metal powder, a metal powder having a melting point lower than that of copper, particularly a metal powder having a melting point of 700 ° C. or less, for example, powders of tin, zinc, phosphorus and the like are used. In the present embodiment, among these, tin powder, particularly atomized tin powder, which is easily diffused into copper and iron and can be easily used as a single powder, is used. The low-melting-point metal powder moves as a liquid phase during sintering and forms holes in the original place. Therefore, in order to refine the pores, the low melting point metal powder has a small particle size, for example, a particle size of 250 mesh or less (maximum particle size 63 μm or less), preferably 350 mesh or less (maximum particle size 45 μm or less). Is preferably used.
なお、銅と低融点金属を合金化させた合金化銅粉（例えば青銅粉）を使用することもできる。 An alloyed copper powder (for example, bronze powder) obtained by alloying copper and a low melting point metal can also be used.
［固体潤滑剤］
固体潤滑剤としては、黒鉛、二硫化モリブデン等の粉末を一種又は二種以上使用することができる。本実施形態では、コストを考えて黒鉛粉、特に鱗片状黒鉛粉を使用する。固体潤滑剤粉は軸受面８ａに露出することで、軸部材２との摺動を潤滑する役割を果たす。
[Solid lubricant]
As the solid lubricant, one or more powders such as graphite and molybdenum disulfide can be used. In the present embodiment, graphite powder, particularly scaly graphite powder is used in consideration of cost. The solid lubricant powder is exposed to the bearing surface 8a, and serves to lubricate sliding with the shaft member 2.
以上に述べた原料粉の組成は、単体銅粉が１０質量％以上５０質量％以下（好ましくは２０質量％以上３０質量％以下）、低融点金属粉が１質量％〜４質量％、炭素が０．１〜１．５質量％であり、残りが部分拡散合金粉となる。原料粉には、必要に応じて各種成形助剤（例えば成形用潤滑剤）を添加してもよい。本実施形態では、上記の原料粉１００％に対して、成形用潤滑剤が０．１〜１．０質量％配合される。成形用潤滑剤として、例えば金属セッケン（ステアリン酸カルシウム等）やワックスを使用できる。但し、これらの成形用潤滑剤は、焼結により分解・消失して粗大気孔の要因となるため、成形用潤滑剤の使用量はなるべく抑えることが好ましい。 The composition of the raw material powder described above is such that the single copper powder is 10 mass% or more and 50 mass% or less (preferably 20 mass% or more and 30 mass% or less), the low melting metal powder is 1 mass% to 4 mass%, and the carbon is It is 0.1-1.5 mass%, and the remainder becomes a partial diffusion alloy powder. Various molding aids (for example, molding lubricants) may be added to the raw material powder as necessary. In the present embodiment, 0.1 to 1.0% by mass of a molding lubricant is blended with respect to 100% of the raw material powder. As the molding lubricant, for example, a metal soap (such as calcium stearate) or a wax can be used. However, since these molding lubricants are decomposed and disappeared by sintering and cause rough air holes, it is preferable to suppress the amount of molding lubricant used as much as possible.
上記の原料粉を金型の内部に充填し、圧縮することで圧紛体が成形される。その後、圧紛体を焼結することで、焼結体が得られる。焼結温度は、低融点金属の融点以上で、かつ銅の融点以下の温度とされ、具体的には７６０℃〜９００℃程度とする。圧紛体を焼結することにより、圧紛体中の錫粉が液相となって部分拡散合金粉の表面の銅粉（第一銅粉）や単体銅粉（第二銅粉）の表面を濡らすため、銅粒子同士や銅粒子と鉄粒子間の焼結が促進される。 A powder compact is formed by filling the raw material powder into the mold and compressing the powder. Then, a sintered compact is obtained by sintering a compact. The sintering temperature is set to a temperature not lower than the melting point of the low-melting point metal and not higher than the melting point of copper, specifically about 760 ° C. to 900 ° C. By sintering the compact, the tin powder in the compact becomes a liquid phase and wets the surface of the partially diffused alloy powder (copper powder) or single copper powder (second copper powder). Therefore, sintering between copper particles or between copper particles and iron particles is promoted.
この焼結体は、例えば密度６．０〜７．４ｇ／ｃｍ3（好ましくは６．９〜７．３ｇ／ｃｍ3）、内部空孔率が４〜２０％、好ましくは４〜１２％（より好ましくは５〜１１％）とされる。また、焼結体における各元素の含有量は、銅が３０質量％〜６０質量％、低融点金属が１質量％〜４質量％、炭素が０．１〜１．５質量％であり、残りが鉄となる。 This sintered body has, for example, a density of 6.0 to 7.4 g / cm 3 (preferably 6.9 to 7.3 g / cm 3 ) and an internal porosity of 4 to 20%, preferably 4 to 12% ( More preferably 5 to 11%). The content of each element in the sintered body is 30% to 60% by mass of copper, 1% to 4% by mass of low melting point metal, 0.1 to 1.5% by mass of carbon, and the rest Becomes iron.
この焼結体をサイジングにより整形することにより、軸受面の真円度を１μｍ以下まで高めることができる。その後、真空含浸等の手法で焼結体の内部空孔に潤滑油を含浸させることで、図２に示す焼結軸受８（焼結含油軸受）が完成する。潤滑油は、例えば４０℃における動粘度が１０〜２００ｍｍ2／ｓｅｃ、好ましくは１０〜６０ｍｍ2／ｓｅｃであり、かつ粘度指数が１００〜２５０であるものが使用される。 By shaping this sintered body by sizing, the roundness of the bearing surface can be increased to 1 μm or less. Then, the sintered bearing 8 (sintered oil-impregnated bearing) shown in FIG. 2 is completed by impregnating the internal pores of the sintered body with lubricating oil by a technique such as vacuum impregnation. For example, a lubricating oil having a kinematic viscosity at 40 ° C. of 10 to 200 mm 2 / sec, preferably 10 to 60 mm 2 / sec and a viscosity index of 100 to 250 is used.
この焼結体の焼結組織は、図５に示すように、部分拡散合金粉１１の鉄粉１２に由来するＦｅ組織１２’（散点模様で示す）の周囲に、部分拡散合金粉１１の銅粉１３に由来するＣｕ組織１３’（濃いグレーで示す）と、単体銅粉に由来する銅組織１４’（淡いグレーで示す）とが混在した形態をなす。これにより多くの鉄組織１２’が銅組織１３’，１４’で被覆された形態となるため、軸受面における鉄組織１２’の露出量を少なくすることができ、これにより焼結軸受８の初期なじみ性を向上させることができる。このように鉄組織の周囲を銅組織で覆った焼結組織は、鉄粉を銅めっきした銅被覆鉄粉を使用することでも得ることができるが、銅被覆鉄粉を使用した場合には、本発明で使用するＦｅ−Ｃｕ部分拡散合金粉に比べて、焼結後の銅組織と鉄組織間のネック強度が低下するため、焼結軸受の圧環強度が大幅に低下する。 As shown in FIG. 5, the sintered structure of the sintered body is formed around the Fe structure 12 ′ (indicated by a dotted pattern) derived from the iron powder 12 of the partial diffusion alloy powder 11. The Cu structure 13 ′ (shown in dark gray) derived from the copper powder 13 and the copper structure 14 ′ (shown in light gray) derived from the simple copper powder are mixed. As a result, a large amount of the iron structure 12 ′ is covered with the copper structures 13 ′ and 14 ′. Therefore, the exposure amount of the iron structure 12 ′ on the bearing surface can be reduced, and thereby the initial stage of the sintered bearing 8. Familiarity can be improved. As described above, the sintered structure in which the periphery of the iron structure is covered with the copper structure can be obtained by using the copper-coated iron powder obtained by copper plating the iron powder, but when the copper-coated iron powder is used, Compared to the Fe—Cu partially diffused alloy powder used in the present invention, the neck strength between the sintered copper structure and the iron structure is lowered, so that the crushing strength of the sintered bearing is greatly reduced.
Ｆｅ−Ｃｕ部分拡散合金粉の製造過程において、鉄粉１２および銅粉１３の最大粒径を上記のように制限していない場合、たとえこれら鉄粉１２や銅粉１３の平均粒径が上記最大粒径と近い値であったとしても、粒径の大きい鉄粉や銅粉も混入した状態で部分拡散合金粉が製造されることになる。そのため、図６に模式的に示すように、粒径の大きい鉄粉と銅粉が一体化された粒子（粗大粒子）が相当量形成される。このような粗大粒子が集合した状態で焼結されれば、粒子間の隙間が大きくなるため、焼結後に粗大気孔を生じることになる。 In the production process of the Fe—Cu partial diffusion alloy powder, when the maximum particle diameters of the iron powder 12 and the copper powder 13 are not limited as described above, the average particle diameter of the iron powder 12 and the copper powder 13 is the maximum. Even if it is a value close to the particle size, the partial diffusion alloy powder is produced in a state where iron powder and copper powder having a large particle size are also mixed. Therefore, as schematically shown in FIG. 6, a considerable amount of particles (coarse particles) in which iron powder and copper powder having a large particle diameter are integrated are formed. If sintering is performed in a state where such coarse particles are aggregated, gaps between the particles become large, and thus coarse air holes are generated after sintering.
これに対し、本発明では、銅粉１３、さらに部分拡散合金粉の最大粒径を制限しており、しかも銅粉１３の最大粒径が部分拡散合金粉１２の最大粒径よりもかなり小さい。従って、部分拡散合金粉の粒度分布がシャープな形となる（部分拡散合金の粒径が揃った状態となる）。その一方で、原料粉の粒径が小さくなりすぎることはなく、粉末の状態での流動性も良好なものとなる。そのため、焼結後に粗大気孔を生じ難くなり、焼結組織中の空孔を微細化かつ均質化することができる。 On the other hand, in the present invention, the maximum particle size of the copper powder 13 and further the partial diffusion alloy powder is limited, and the maximum particle size of the copper powder 13 is considerably smaller than the maximum particle size of the partial diffusion alloy powder 12. Therefore, the particle size distribution of the partial diffusion alloy powder is sharp (the particle size of the partial diffusion alloy is uniform). On the other hand, the particle size of the raw material powder does not become too small, and the fluidity in the powder state is also good. Therefore, it becomes difficult to produce rough atmospheric holes after sintering, and the pores in the sintered structure can be refined and homogenized.
加えて、本発明では単体銅粉として多孔質銅粉を使用している。本発明者らの検証によれば、多孔質の銅粉（多孔質のＣｕ−Ｓｎ合金粉も含む）を使用することで、焼結後の焼結体は圧紛体よりも収縮することが明らかになった。具体的には圧紛体に対する焼結体の寸法変化率が、内径寸法および外径寸法とも０．９９５〜０．９９９程度となった。これは、多孔質の銅粉が焼結時に周辺の銅粒子（部分拡散合金粉の銅粉および他の多孔質銅粉）を引き付ける作用を奏するためと考えられる。これに対し、多孔質ではない銅粉を使用した既存の銅鉄系焼結体では、焼結時には圧紛体の状態よりも膨張するのが通例である。このように焼結時に焼結体が収縮することで、焼結組織が緻密化されるため、粗大気孔の発生をさらに確実に抑制することが可能となる。 In addition, in the present invention, porous copper powder is used as the single copper powder. According to the verification by the present inventors, it is clear that the sintered body after sintering contracts more than the powder body by using porous copper powder (including porous Cu-Sn alloy powder). Became. Specifically, the dimensional change rate of the sintered body relative to the compact was about 0.995 to 0.999 for both the inner diameter dimension and the outer diameter dimension. This is presumably because the porous copper powder acts to attract peripheral copper particles (partial diffusion alloy powder copper powder and other porous copper powder) during sintering. On the other hand, in the existing copper iron-based sintered body using copper powder that is not porous, it is usual that the sintered body expands more than the state of the compact during sintering. Since the sintered body shrinks during the sintering as described above, the sintered structure is densified, so that it is possible to more reliably suppress the generation of rough atmospheric holes.
これらの作用を通じて、各表面気孔の面積を０．００５ｍｍ2以下とした焼結体を得ることができ、粗大気孔の発生を防止することが可能となる。因みに、軸受面の表面開孔率は、面積比で４％以上１５％以下となる。また、焼結体における通油度は０．０５〜０．０２５ｇ/１０分となる。ここでいう「通油度」は、多孔質のワークが、その多孔質組織を介してどの程度潤滑油を流通させることができるのかを定量的に示すためのパラメータ［単位：ｇ／１０ｍｉｎ］である。通油度は、室温（２６〜２７℃）環境下で円筒状試験体の内周孔を０．４ＭＰａの加圧力を負荷しながら潤滑油で満たし、試験体の外径面に開口した表面開孔から滲み出して滴下した油を採取することで求めることができる。 Through these actions, a sintered body having an area of each surface pore of 0.005 mm 2 or less can be obtained, and generation of rough atmospheric pores can be prevented. Incidentally, the surface area ratio of the bearing surface is 4% or more and 15% or less in terms of area ratio. Moreover, the oil penetration degree in a sintered compact will be 0.05-0.025 g / 10min. The “oil permeability” here is a parameter [unit: g / 10 min] for quantitatively indicating how much lubricating oil can circulate through the porous structure of the porous work. is there. The degree of oil penetration is determined by filling the inner peripheral hole of the cylindrical specimen with lubricating oil while applying a pressure of 0.4 MPa under a room temperature (26-27 ° C.) environment, and opening the surface of the specimen on the outer diameter surface. It can be determined by collecting the oil that has oozed out of the hole and dropped.
このように本発明によれば、軸受面に生じる粗大気孔をなくし（表面気孔の最大面積が０．００５ｍｍ2）、表面開孔の大きさを均一化することができる。これにより軸受面８ａでの圧力逃げを抑制して油膜形成率を高めることができるため、低速回転および高速回転を問わず、高い油膜剛性を確保して軸を安定的に支持することが可能となる。そのため、動圧発生溝を有しない真円軸受の形態であっても、動圧発生溝付きの焼結軸受と同等の軸受性能を得ることができ、動圧発生溝付き焼結軸受の代替え品として用いることが可能となる。特に動圧溝付きの焼結軸受では、周速５ｍ／ｍｉｎ以下の領域では、動圧効果が十分得られないために使用が困難となるが、本発明の焼結軸受であれば、周速５ｍ／ｍｉｎ以下の低速領域でも安定して軸を支持できるメリットが得られる。 As described above, according to the present invention, the rough air holes generated on the bearing surface can be eliminated (the maximum area of the surface air holes is 0.005 mm 2 ), and the size of the surface holes can be made uniform. As a result, the pressure relief at the bearing surface 8a can be suppressed and the oil film formation rate can be increased. Therefore, it is possible to stably support the shaft while ensuring high oil film rigidity regardless of low-speed rotation or high-speed rotation. Become. Therefore, even in the form of a perfect circle bearing without a dynamic pressure generating groove, it is possible to obtain the same bearing performance as a sintered bearing with a dynamic pressure generating groove, which is an alternative to a sintered bearing with a dynamic pressure generating groove. Can be used. In particular, a sintered bearing with a dynamic pressure groove is difficult to use because the dynamic pressure effect is not sufficiently obtained in a region where the peripheral speed is 5 m / min or less. There is an advantage that the shaft can be stably supported even in a low speed region of 5 m / min or less.
また、図６に示す粗大粒子では、銅粉の体積に比べて拡散接合部の面積が小さくなるため、両者の接合強度が低下する。そのため、部分拡散合金粉を篩掛けした際には、その衝撃で銅粒子が鉄粒子から脱落し易くなる。この場合、原料粉中には小粒径の単体銅粉が多数混入した状態となるため、原料粉の流動性が低下し、銅の偏析を招く要因となる。これに対し、本願発明では、部分拡散合金粉の製造に使用する銅粉１３の最大粒径を制限しているため、部分拡散合金粉は総じて図３に示すように形態を有する。この場合、銅粉１３の体積に比べて拡散接合部の面積が相対的に大きくなるため、鉄粉１２と銅粉１３の接合強度が高まる。従って、篩掛けを行った際にも銅粉が脱落し難くなり、上記の弊害を防止することができる。 Moreover, in the coarse particle shown in FIG. 6, since the area of a diffusion junction part becomes small compared with the volume of copper powder, both joint strength falls. Therefore, when the partial diffusion alloy powder is sieved, the copper particles are easily dropped from the iron particles by the impact. In this case, since a large amount of single copper powder having a small particle size is mixed in the raw material powder, the fluidity of the raw material powder is lowered, which causes segregation of copper. On the other hand, in this invention, since the maximum particle size of the copper powder 13 used for manufacture of a partial diffusion alloy powder is restrict | limited, a partial diffusion alloy powder has a form as shown in FIG. In this case, since the area of the diffusion bonding portion is relatively larger than the volume of the copper powder 13, the bonding strength between the iron powder 12 and the copper powder 13 is increased. Therefore, it is difficult for the copper powder to fall off even when sieving, and the above-described adverse effects can be prevented.
図７に本発明品と比較品の油膜形成率の測定結果を示す。なお、比較品としては、１００メッシュ以下の鉄粉を核とする銅被覆鉄粉を用いた焼結軸受を用いている。 FIG. 7 shows the measurement results of the oil film formation rate of the product of the present invention and the comparative product. As a comparative product, a sintered bearing using copper-coated iron powder having iron powder of 100 mesh or less as a core is used.
油膜形成率は、図８に示す回路を使用し、サンプルとして軸と焼結軸受を組み合わせたものをセットした上で電圧を測定することにより求めている。検出電圧が０［Ｖ］であれば油膜形成率は０％であり、検出電圧が電源電圧と等しければ油膜形成率は１００％である。油膜形成率１００％は軸と焼結軸受が非接触状態にあることを意味し、油膜形成率０％は軸と焼結軸受が接触したことを意味する。図７の横軸は、時間を表す。測定条件として、軸の回転数は２０００ｍｉｎ-1、軸のスラスト荷重は０．２Ｎに設定している。 The oil film formation rate is obtained by using the circuit shown in FIG. 8 and measuring a voltage after setting a combination of a shaft and a sintered bearing as a sample. If the detection voltage is 0 [V], the oil film formation rate is 0%, and if the detection voltage is equal to the power supply voltage, the oil film formation rate is 100%. An oil film formation rate of 100% means that the shaft and the sintered bearing are in a non-contact state, and an oil film formation rate of 0% means that the shaft and the sintered bearing are in contact. The horizontal axis in FIG. 7 represents time. As measurement conditions, the rotational speed of the shaft is set to 2000 min −1 , and the thrust load of the shaft is set to 0.2N.
図７からも明らかなように、比較品は軸と焼結軸受が頻繁に接触していると考えられるのに対し、本発明品はほぼ非接触状態が維持されている。従って、比較品と比べ、本発明品の方がより良好な油膜形成率を得られることが確認された。 As is clear from FIG. 7, the comparative product is considered to be in frequent contact between the shaft and the sintered bearing, whereas the product of the present invention is maintained in a substantially non-contact state. Therefore, it was confirmed that the product of the present invention can obtain a better oil film formation rate than the comparative product.
以上、本発明に係る焼結軸受の使用例としてファンモータを例示したが、本発明にかかる焼結軸受の適用対象はこれに限定されず、種々の用途に使用することができる。 As mentioned above, although the fan motor was illustrated as a usage example of the sintered bearing which concerns on this invention, the application object of the sintered bearing concerning this invention is not limited to this, It can be used for various uses.
また、焼結軸受８の軸受面８ａの内周面に動圧発生溝を形成しない場合を説明したが、必要に応じて軸受面８ａに複数の動圧発生溝を形成することができる。動圧発生溝は軸２の外周面に形成することもできる。 Moreover, although the case where the dynamic pressure generating groove is not formed on the inner peripheral surface of the bearing surface 8a of the sintered bearing 8 has been described, a plurality of dynamic pressure generating grooves can be formed on the bearing surface 8a as necessary. The dynamic pressure generating groove can also be formed on the outer peripheral surface of the shaft 2.
１ 軸受装置
２ 軸部材
８ 焼結軸受
８ａ 内周面（軸受面）
１１ 部分拡散合金粉
１２ 鉄粉
１３ 銅粉
DESCRIPTION OF SYMBOLS 1 Bearing apparatus 2 Shaft member 8 Sintered bearing 8a Inner peripheral surface (bearing surface)
11 Partially diffused alloy powder 12 Iron powder 13 Copper powder
Claims (5)
部分拡散合金粉の最大粒径が１０６μｍであり、前記部分拡散合金粉の第一銅粉の最大粒径が１０μｍ以下であることを特徴とする焼結軸受。 Baked by sintering a powder body comprising a partially diffused alloy powder in which cuprous powder is adhered to the surface of iron powder by partial diffusion, a second copper powder, and a low melting point metal powder having a melting point lower than that of copper. In connection bearings,
A sintered bearing characterized in that the maximum particle size of the partial diffusion alloy powder is 106 μm, and the maximum particle size of the cuprous powder of the partial diffusion alloy powder is 10 μm or less.
部分拡散合金粉の最大粒径を１０６μｍとし、前記部分拡散合金粉の第一銅粉の最大粒径が１０μｍ以下であることを特徴とする焼結軸受の製造方法。 Sintering by sintering a powder body containing a partially diffused alloy powder in which cuprous powder is adhered to the surface of the iron powder by partial diffusion, a second copper powder, and a low melting point metal powder having a melting point lower than that of copper When manufacturing bearings,
A method for producing a sintered bearing, wherein the maximum particle size of the partial diffusion alloy powder is 106 μm, and the maximum particle size of the cuprous powder of the partial diffusion alloy powder is 10 μm or less.
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
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| JP2016184290A JP6836364B2 (en) | 2016-09-21 | 2016-09-21 | Sintered bearings and their manufacturing methods |
| KR1020197009979A KR102331498B1 (en) | 2016-09-08 | 2017-09-07 | Sintered bearing and its manufacturing method |
| DE112017004520.7T DE112017004520T5 (en) | 2016-09-08 | 2017-09-07 | Sintered bearing and process for its production |
| US16/329,256 US20190186532A1 (en) | 2016-09-08 | 2017-09-07 | Sintered bearing and process for producing same |
| PCT/JP2017/032364 WO2018047923A1 (en) | 2016-09-08 | 2017-09-07 | Sintered bearing and process for producing same |
| CN201780054247.3A CN109890539B (en) | 2016-09-08 | 2017-09-07 | Sintered bearing and method for manufacturing same |
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| JP2016184290A JP6836364B2 (en) | 2016-09-21 | 2016-09-21 | Sintered bearings and their manufacturing methods |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2019183868A (en) * | 2018-04-03 | 2019-10-24 | Ntn株式会社 | Sintered oil-containing bearing, fluid dynamic pressure bearing device and method for manufacturing sintered oil-containing bearing |
| CN114833341A (en) * | 2022-05-07 | 2022-08-02 | 成都惠灵丰金刚石钻头有限公司 | Sintering process of diamond bearing |
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| JP2015092097A (en) * | 2013-10-03 | 2015-05-14 | Ntn株式会社 | Sintered bearing and its manufacturing method |
| JP2015137660A (en) * | 2014-01-20 | 2015-07-30 | Ntn株式会社 | sintered bearing |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2015092097A (en) * | 2013-10-03 | 2015-05-14 | Ntn株式会社 | Sintered bearing and its manufacturing method |
| JP2015137660A (en) * | 2014-01-20 | 2015-07-30 | Ntn株式会社 | sintered bearing |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2019183868A (en) * | 2018-04-03 | 2019-10-24 | Ntn株式会社 | Sintered oil-containing bearing, fluid dynamic pressure bearing device and method for manufacturing sintered oil-containing bearing |
| CN114833341A (en) * | 2022-05-07 | 2022-08-02 | 成都惠灵丰金刚石钻头有限公司 | Sintering process of diamond bearing |
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