JP6816079B2 - Vibration motor - Google Patents
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- JP6816079B2 JP6816079B2 JP2018183669A JP2018183669A JP6816079B2 JP 6816079 B2 JP6816079 B2 JP 6816079B2 JP 2018183669 A JP2018183669 A JP 2018183669A JP 2018183669 A JP2018183669 A JP 2018183669A JP 6816079 B2 JP6816079 B2 JP 6816079B2
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Description
本発明は、振動モータに関する。 The present invention relates to a vibration motor.
振動モータとは、例えば携帯電話等の携帯端末において、電話の着信やメールの受信等を報知するバイブレータとして機能するものであり、例えば錘（偏心錘）が取り付けられた軸をモータ部で回転させることにより、携帯端末全体を振動させ得る構造となっている。このような構造を採用した振動モータとして、軸を焼結軸受（焼結含油軸受）で支持するようにしたものがある（例えば、特許文献１，２）。 The vibration motor functions as a vibrator for notifying an incoming call or an email in a mobile terminal such as a mobile phone. For example, a shaft to which a weight (eccentric weight) is attached is rotated by a motor unit. As a result, the structure is such that the entire mobile terminal can be vibrated. As a vibration motor adopting such a structure, there is one in which the shaft is supported by a sintered bearing (sintered oil-impregnated bearing) (for example, Patent Documents 1 and 2).
図１に、焼結軸受を使用した振動モータの一構成例の要部を模式的に示す。図示例の振動モータ１では、モータ部Ｍの軸方向両側に突出させた軸３の両側を、内周に軸受面４ａを有する円筒状の焼結軸受４（４１，４２）で回転自在に支持している。軸３の一端には錘Ｗが設けられている。錘Ｗ側の焼結軸受４１は錘Ｗとモータ部Ｍの間に配置されており、この焼結軸受４１は、錘Ｗと反対側の焼結軸受４２よりも軸方向寸法（軸受面４ａの面積）が大きくなっている。二つの焼結軸受４（４１，４２）は、何れもハウジング２の内周に固定されている。この振動モータ１において、モータ部Ｍに通電され、軸３が回転すると、錘Ｗの影響を受けて軸３が軸受面４ａの全面に沿って振れ回りながら回転する。すなわち、この振動モータ１において、軸３は、その中心Ｏａを軸受中心（焼結軸受４の中心Ｏｂ）に対してあらゆる方向に偏心させた状態で回転する（図２参照）。 FIG. 1 schematically shows a main part of a configuration example of a vibration motor using a sintered bearing. In the vibration motor 1 of the illustrated example, both sides of the shaft 3 projecting from both sides in the axial direction of the motor portion M are rotatably supported by cylindrical sintered bearings 4 (41, 42) having bearing surfaces 4a on the inner circumference. doing. A weight W is provided at one end of the shaft 3. The sintered bearing 41 on the weight W side is arranged between the weight W and the motor portion M, and the sintered bearing 41 has an axial dimension (bearing surface 4a) more than the sintered bearing 42 on the opposite side of the weight W. Area) is getting bigger. The two sintered bearings 4 (41, 42) are both fixed to the inner circumference of the housing 2. In the vibration motor 1, when the motor portion M is energized and the shaft 3 rotates, the shaft 3 rotates while swinging along the entire surface of the bearing surface 4a under the influence of the weight W. That is, in the vibration motor 1, the shaft 3 rotates in a state where its center Oa is eccentric with respect to the bearing center (center Ob of the sintered bearing 4) in all directions (see FIG. 2).
近年、いわゆるスマートフォン等への搭載を考慮して、振動モータにはさらなる小型化が要請されている。振動モータを小型化した場合、モータパワーの増大には限界がある。そのような状況下でも所定の振動性能を確保するために、モータを高速回転化（１００００ｒｐｍ以上）し、あるいはアンバランス荷重を増大させることで対処しようとしており、焼結軸受の使用条件は一層過酷化する傾向にある。すなわち、振動モータでは、上述のとおり、軸が焼結軸受の軸受面全面に沿って振れ回ること、またアンバランス荷重により軸受面が軸に頻繁に叩かれる（軸受面に軸が頻繁に衝突する）ことなどから、焼結軸受の使用条件は通常用途の焼結軸受（例えば、スピンドルモータ用の焼結軸受）よりもただでさえ過酷であり、軸受面が摩耗し易い。そのため、所望の振動性能を確保するためにモータを高速回転化等すると、軸受面の摩耗が一層促進されることになり、回転変動が大きくなる。 In recent years, further miniaturization of vibration motors has been required in consideration of mounting on so-called smartphones and the like. When the vibration motor is miniaturized, there is a limit to the increase in motor power. Even under such circumstances, in order to ensure the specified vibration performance, we are trying to deal with it by increasing the motor speed (10000 rpm or more) or increasing the unbalanced load, and the operating conditions of the sintered bearing are even more severe. It tends to become. That is, in the vibration motor, as described above, the shaft swings around the entire bearing surface of the sintered bearing, and the bearing surface is frequently hit by the shaft due to the unbalanced load (the shaft frequently collides with the bearing surface). ) Therefore, the usage conditions of the sintered bearing are harsher than those of the sintered bearing for normal use (for example, the sintered bearing for a spindle motor), and the bearing surface is easily worn. Therefore, if the motor is rotated at a high speed in order to secure the desired vibration performance, the wear of the bearing surface is further promoted, and the rotation fluctuation becomes large.
また、所望の回転性能を発揮可能とするには、焼結軸受単体での軸受面精度のみならず、焼結軸受をハウジングの内周に固定した状態での軸受面精度も重要である。すなわち、焼結軸受の機械的強度（特に圧環強度）が不足していると、例えば焼結軸受をハウジングの内周に圧入を伴って挿入した際に、軸受面がハウジングの内周面形状に倣って変形し易くなる。焼結軸受の軸受面が変形した場合でも、サイジング等の形状修正加工を追加的に施せば軸受面を所定形状・精度に仕上げることができるが、加工工程が追加される分、製造コストが増大する。 Further, in order to be able to exhibit the desired rotational performance, not only the bearing surface accuracy of the sintered bearing alone but also the bearing surface accuracy of the sintered bearing fixed to the inner circumference of the housing is important. That is, if the mechanical strength (particularly the annular strength) of the sintered bearing is insufficient, for example, when the sintered bearing is inserted into the inner circumference of the housing with press fitting, the bearing surface becomes the shape of the inner peripheral surface of the housing. It becomes easy to be deformed accordingly. Even if the bearing surface of the sintered bearing is deformed, the bearing surface can be finished to a predetermined shape and accuracy by additionally performing shape correction processing such as sizing, but the manufacturing cost increases due to the addition of the processing process. To do.
また、特に携帯電話等の携帯端末で使用される振動モータには、携帯端末の落下に伴って大きな衝撃値が付加された場合でも、簡単に回転不能とならないような高い耐衝撃性が求められる。 In addition, vibration motors used in mobile terminals such as mobile phones are required to have high impact resistance so that they do not easily become inoperable even when a large impact value is applied as the mobile terminal falls. ..
そこで、本発明は、高い回転性能を長期間に亘って安定的に発揮することのできる振動モータを低コストに提供することを目的とする。 Therefore, an object of the present invention is to provide a vibration motor capable of stably exhibiting high rotational performance for a long period of time at low cost.
上記の目的を達成するために創案された本発明は、軸と、軸を回転駆動させるモータ部と、内周に軸受面を有し、軸を回転自在に支持する焼結軸受と、軸に設けられた錘と、焼結軸受を内周に圧入固定したハウジングとを備え、錘で軸を軸受中心に対して偏心回転させることにより振動が発生する振動モータであって、焼結軸受が、鉄を主成分とし、その次に銅を多く含む焼結体からなり、かつ３００ＭＰａ以上の圧環強度を有することを特徴とする。 The present invention, which was devised to achieve the above object, includes a shaft, a motor unit that rotationally drives the shaft, a sintered bearing having a bearing surface on the inner circumference and rotatably supporting the shaft, and a shaft. A vibration motor provided with a weight provided and a housing in which a sintered bearing is press-fitted and fixed to the inner circumference, and vibration is generated by rotating the shaft eccentrically with respect to the center of the bearing by the weight. It is characterized by being composed of a sintered body containing iron as a main component and then a large amount of copper, and having an annular strength of 300 MPa or more.
上記のように、本発明に係る振動モータでは、安価でありながら機械的強度に優れる鉄を主成分とし、軸との初期なじみ性等の摺動特性に優れた銅をその次に多く含む焼結体（鉄銅系の焼結体）からなる焼結軸受が使用される。このように、焼結軸受として、比較的安価でありながら、高強度で軸受面の耐摩耗性に優れたものが使用されるので、モータを高速回転化し、あるいはアンバランス荷重を増大させた場合であっても、特段のコスト増を招来することなく高い回転性能を確保することができる。特に、圧環強度が３００ＭＰａ以上の焼結軸受が使用されるので、焼結軸受をハウジング内周に圧入固定した場合でも、圧入に伴って軸受面が変形し、軸受面の真円度や円筒度などが低下するのを可及的に防止することができる。そのため、ハウジング内周に固定された焼結軸受に対し、軸受面を所定形状・精度に仕上げるための加工を追加的に実行する必要がなくなる。逆を言えば、簡便な固定手段である圧入を、ハウジングに対する焼結軸受の固定手段として問題なく採用することができる。また、焼結軸受が３００ＭＰａ以上の圧環強度を有していれば、振動モータを組み込んだ携帯端末が落下等し、振動モータ（焼結軸受）に大きな衝撃値が付加された場合でも、軸受面が変形等するのを可及的に防止することができる。以上から、本発明によれば、高い回転性能を長期間に亘って安定的に発揮することのできる振動モータを低コストに提供することができる。 As described above, in the vibration motor according to the present invention, the main component is iron, which is inexpensive but has excellent mechanical strength, and the firing contains the next largest amount of copper, which has excellent sliding characteristics such as initial compatibility with the shaft. Sintered bearings made of composites (iron-copper-based sintered bodies) are used. As described above, as the sintered bearing, a relatively inexpensive one having high strength and excellent wear resistance on the bearing surface is used. Therefore, when the motor is rotated at high speed or the unbalanced load is increased. Even so, high rotational performance can be ensured without causing a particular increase in cost. In particular, since a sintered bearing having an annular strength of 300 MPa or more is used, even when the sintered bearing is press-fitted and fixed to the inner circumference of the housing, the bearing surface is deformed by press-fitting, and the roundness and cylindricity of the bearing surface It is possible to prevent such a decrease as much as possible. Therefore, it is not necessary to additionally perform processing for finishing the bearing surface with a predetermined shape and accuracy for the sintered bearing fixed to the inner circumference of the housing. To put it the other way around, press-fitting, which is a simple fixing means, can be adopted without any problem as a fixing means for the sintered bearing to the housing. Further, if the sintered bearing has an annular strength of 300 MPa or more, the bearing surface even if a portable terminal incorporating the vibration motor falls or the like and a large impact value is applied to the vibration motor (sintered bearing). Can be prevented from being deformed as much as possible. From the above, according to the present invention, it is possible to provide a vibration motor capable of stably exhibiting high rotational performance for a long period of time at low cost.
鉄を主成分とし、その次に銅を多く含む焼結体からなる焼結軸受は、例えば上記特許文献３に記載されているように、鉄粉に対し１０質量％以上３０質量％未満の銅を被覆してなり、粒度を８０メッシュ以下とした銅被覆鉄粉を圧粉・焼結することによって得ることができる。しかしながら、本発明者らが検証したところ、特許文献３に記載の焼結軸受を振動モータに使用した場合には、回転変動が大きくなることが明らかになった。これは、銅被覆鉄粉を圧粉・焼結して得られた焼結軸受では、鉄相（鉄組織）と銅相（銅組織）間のネック強度が低いため、軸受面が早期に摩耗したことに原因の一つがあると考えられる。 As described in Patent Document 3, for example, a sintered bearing made of a sintered body containing iron as a main component and then a large amount of copper is copper in an amount of 10% by mass or more and less than 30% by mass based on iron powder. It can be obtained by compacting and sintering copper-coated iron powder having a particle size of 80 mesh or less. However, as a result of verification by the present inventors, it has been clarified that when the sintered bearing described in Patent Document 3 is used for a vibration motor, the rotational fluctuation becomes large. This is because in a sintered bearing obtained by compacting and sintering copper-coated iron powder, the neck strength between the iron phase (iron structure) and the copper phase (copper structure) is low, so the bearing surface wears early. It is thought that there is one of the causes for what was done.
そこで、本発明では、焼結軸受として、鉄粉に銅粉を部分拡散させてなる部分拡散合金粉と、低融点金属粉と、固体潤滑剤粉とを含む原料粉末を成形し、焼結した焼結体を使用することとした。 Therefore, in the present invention, as a sintered bearing, a raw material powder containing a partially diffused alloy powder obtained by partially diffusing copper powder in iron powder, a low melting point metal powder, and a solid lubricant powder is molded and sintered. We decided to use a sintered body.
部分拡散合金粉では、銅粉の一部が鉄粉に拡散しているため、銅被覆鉄粉を使用する場合よりも焼結後の鉄組織と銅組織の間で高いネック強度が得られる。また、上記の構成によれば、成形後の焼結により、圧粉体に含まれる低融点金属粉が溶融する。低融点金属は銅に対して高いぬれ性を持つので、液相焼結により、隣り合う部分拡散合金粉の鉄組織と銅組織、あるいは銅組織同士を強固に結合させることができる。また、個々の部分拡散合金粉のうち、鉄粉の表面に銅粉の一部が拡散することでＦｅ−Ｃｕ合金が形成された部分には、溶融した低融点金属が拡散していくため、鉄組織と銅組織間のネック強度が一層高まる。これらのことから、焼結温度を低融点金属粉が溶融する温度（例えば７００〜９００℃）に設定した低温焼結でも軸受面の耐摩耗性に優れ、かつ３００ＭＰａ以上の圧環強度を有する高強度の焼結体（焼結軸受）を確実に得ることが可能となる。そして、軸受面の耐摩耗性が向上すれば、振動モータの回転変動を防止することができる。なお、この場合、原料粉末に含める部分拡散合金粉として、平均粒径５μｍ以上２０μｍ未満の銅粉が鉄粉に部分拡散し、かつ銅を１０〜３０質量％含有するものを使用するのが好ましい。 In the partially diffused alloy powder, since a part of the copper powder is diffused in the iron powder, a higher neck strength can be obtained between the iron structure after sintering and the copper structure than in the case of using the copper-coated iron powder. Further, according to the above configuration, the low melting point metal powder contained in the green compact is melted by sintering after molding. Since the low melting point metal has a high wettability with respect to copper, the iron structure and the copper structure of the adjacent partial diffusion alloy powders or the copper structures can be firmly bonded to each other by liquid phase sintering. Further, among the individual partial diffusion alloy powders, the molten low melting point metal diffuses to the portion where the Fe—Cu alloy is formed by the diffusion of a part of the copper powder on the surface of the iron powder. The neck strength between the iron structure and the copper structure is further increased. From these facts, high strength with excellent wear resistance of the bearing surface and an pressure ring strength of 300 MPa or more even in low temperature sintering in which the sintering temperature is set to the temperature at which the low melting point metal powder melts (for example, 700 to 900 ° C.). It is possible to reliably obtain a sintered body (sintered bearing) of the above. If the wear resistance of the bearing surface is improved, it is possible to prevent the rotation fluctuation of the vibration motor. In this case, as the partial diffusion alloy powder to be included in the raw material powder, it is preferable to use a partial diffusion alloy powder having an average particle size of 5 μm or more and less than 20 μm partially diffused into the iron powder and containing 10 to 30% by mass of copper. ..
本発明者らが鋭意検討を重ねた結果、原料粉末中に平均粒径１０６μｍを超える大粒径の部分拡散合金粉が含まれていると、焼結体の内部に粗大気孔が形成され易く、その結果、必要とされる軸受面の耐摩耗性や圧環強度等を確保できない場合があることが判明した。従って、部分拡散合金粉は、平均粒度１４５メッシュ以下（平均粒径１０６μｍ以下）のものを使用するのが好ましい。このような合金粉を使用することで、焼結後の金属組織（多孔質組織）が均一化され、多孔質組織中での粗大気孔の発生が抑制された焼結体を安定的に得ることができる。これにより、軸受面の耐摩耗性や軸受の圧環強度が一層向上した焼結軸受を安定的に得ることが可能となる。 As a result of diligent studies by the present inventors, if the raw material powder contains a partial diffusion alloy powder having a large particle size exceeding 106 μm on average, coarse air pores are likely to be formed inside the sintered body. As a result, it was found that the required wear resistance and annulus strength of the bearing surface may not be ensured. Therefore, it is preferable to use a partial diffusion alloy powder having an average particle size of 145 mesh or less (average particle size of 106 μm or less). By using such an alloy powder, the metal structure (porous structure) after sintering is made uniform, and a sintered body in which the generation of coarse air pores in the porous structure is suppressed can be stably obtained. Can be done. This makes it possible to stably obtain a sintered bearing in which the wear resistance of the bearing surface and the annular strength of the bearing are further improved.
上記の焼結軸受は、低融点金属粉として錫粉、固体潤滑剤粉として黒鉛粉を使用した原料粉末から得ることができる。この場合、焼結軸受は、Ｃｕを１０〜３０質量％、Ｓｎを０．５〜３．０質量％、Ｃを０．３〜１．５質量％含有し、残部を鉄および不可避的不純物とした焼結体で構成することができる。この構成では、ニッケル（Ｎｉ）やモリブデン（Ｍｏ）等の高価な材料を使用していないので、機械的強度および軸受面の耐摩耗性が高められた焼結軸受を低コストに得ることができる。そのため、回転変動が生じ難い高回転性能の振動モータを低コストに提供することができる。 The above sintered bearing can be obtained from a raw material powder using tin powder as a low melting point metal powder and graphite powder as a solid lubricant powder. In this case, the sintered bearing contains 10 to 30% by mass of Cu, 0.5 to 3.0% by mass of Sn, 0.3 to 1.5% by mass of C, and the balance is iron and unavoidable impurities. It can be composed of a sintered body. Since no expensive material such as nickel (Ni) or molybdenum (Mo) is used in this configuration, it is possible to obtain a sintered bearing having improved mechanical strength and wear resistance of the bearing surface at low cost. .. Therefore, it is possible to provide a vibration motor having high rotation performance, which is less likely to cause rotational fluctuation, at low cost.
焼結体の鉄組織を、軟質なフェライト相を主体として構成すれば、軸受面の軸に対する攻撃性を弱くすることができるので、軸の摩耗を抑制することが可能となる。フェライト相を主体とした鉄組織は、例えば鉄と炭素（黒鉛）が反応しない９００℃以下の温度で圧粉体を焼結することで得ることができる。 If the iron structure of the sintered body is mainly composed of a soft ferrite phase, the aggression of the bearing surface to the shaft can be weakened, so that wear of the shaft can be suppressed. An iron structure mainly composed of a ferrite phase can be obtained, for example, by sintering a green compact at a temperature of 900 ° C. or lower at which iron and carbon (graphite) do not react.
フェライト相を主体とする鉄組織には、その全てをフェライト相とした組織の他、フェライト相の粒界にフェライト相よりも硬質のパーライト相を存在させたような鉄組織も含まれる。このように、フェライト相の粒界にパーライト相を形成することで、鉄組織をフェライト相だけで構成する場合と比べ、軸受面の耐摩耗性を向上させることができる。軸の摩耗抑制と軸受面の耐摩耗性向上とを両立させるには、鉄組織に占めるフェライト相（αＦｅ）およびパーライト相（γＦｅ）の割合を、それぞれ、８０〜９５％および５〜２０％とする（αＦｅ：γＦｅ＝８０〜９５％：５〜２０％）のが好適である。なお、上記の割合は、例えば、焼結体の任意断面におけるフェライト相およびパーライト相それぞれの面積比率で求めることができる。 The iron structure mainly composed of a ferrite phase includes not only a structure in which all of them are ferrite phases but also an iron structure in which a pearlite phase harder than the ferrite phase is present at the grain boundaries of the ferrite phase. By forming the pearlite phase at the grain boundaries of the ferrite phase in this way, it is possible to improve the wear resistance of the bearing surface as compared with the case where the iron structure is composed of only the ferrite phase. In order to achieve both suppression of shaft wear and improved wear resistance of the bearing surface, the proportions of the ferrite phase (αFe) and pearlite phase (γFe) in the iron structure should be 80 to 95% and 5 to 20%, respectively. (ΑFe: γFe = 80 to 95%: 5 to 20%) is preferable. The above ratio can be obtained, for example, by the area ratio of the ferrite phase and the pearlite phase in an arbitrary cross section of the sintered body.
部分拡散合金粉（Ｆｅ−Ｃｕ部分拡散合金粉）を構成する鉄粉としては、還元鉄粉を使用することができる。鉄粉としては、還元鉄粉以外にも、例えばアトマイズ鉄粉を使用することもできるが、還元鉄粉は内部気孔を有する海綿状（多孔質状）をなすことから、アトマイズ鉄粉に比べて粉末が柔らかく、圧縮成形性に優れる。そのため、低密度でも圧粉体強度を高めることができ、圧粉体の欠けや割れの発生を防止することができる。また、還元鉄粉は、上記のとおり海綿状をなすことから、アトマイズ鉄粉に比べて保油性に優れる利点も有する。 As the iron powder constituting the partially diffused alloy powder (Fe—Cu partially diffused alloy powder), reduced iron powder can be used. As the iron powder, for example, atomized iron powder can be used in addition to the reduced iron powder, but since the reduced iron powder is spongy (porous) with internal pores, it is compared with the atomized iron powder. The powder is soft and has excellent compression moldability. Therefore, the strength of the green compact can be increased even at a low density, and the occurrence of chipping or cracking of the green compact can be prevented. Further, since the reduced iron powder has a spongy shape as described above, it also has an advantage of being superior in oil retention property as compared with the atomized iron powder.
上記構成において、焼結体の表層部の気孔率、特に軸受面を含む表層部の気孔率は５〜２０％とするのが好ましい。なお、ここでいう表層部とは、表面から深さ１００μｍに至るまでの領域である。 In the above configuration, the porosity of the surface layer portion of the sintered body, particularly the porosity of the surface layer portion including the bearing surface, is preferably 5 to 20%. The surface layer portion referred to here is a region from the surface to a depth of 100 μm.
焼結軸受は、焼結体の内部気孔に潤滑油を含浸させたいわゆる焼結含油軸受とすることができ、この場合、潤滑油としては、４０℃の動粘度が１０〜５０ｍｍ2／ｓの範囲内にあるものが好ましく使用される。軸受隙間に形成される油膜の剛性を確保しつつ、回転トルクの上昇を抑えるためである。なお、焼結体に含浸させる油としては、４０℃の動粘度が１０〜５０ｍｍ2／ｓの範囲内にある油（潤滑油）を基油とした液状グリースを採用しても良い。 The sintered bearing can be a so-called sintered oil-impregnated bearing in which the internal pores of the sintered body are impregnated with lubricating oil. In this case, the lubricating oil has a kinematic viscosity of 10 to 50 mm 2 / s at 40 ° C. Those within the range are preferably used. This is to suppress an increase in rotational torque while ensuring the rigidity of the oil film formed in the bearing gap. As the oil to be impregnated in the sintered body, a liquid grease using an oil (lubricating oil) having a kinematic viscosity at 40 ° C. in the range of 10 to 50 mm 2 / s may be adopted.
上記構成の振動モータにおいて、焼結軸受はモータ部の軸方向両側に配置することができる。この場合、モータ部の軸方向両側に配置した焼結軸受のうち、一方側の焼結軸受を錘とモータ部の間に配置し、かつこの一方側の焼結軸受の軸方向寸法を、他方側の焼結軸受の軸方向寸法よりも大きくすることができる。このようにすれば、上記一方側の焼結軸受の軸受面面積を大きく設定することができるので、相対的に大きなアンバランス荷重が作用する錘に近接した側において軸支能力を高めることができる。その一方、相対的に小さなアンバランス荷重が作用する上記他方側の焼結軸受では、その軸受面面積を小さく設定することができるので、振動モータ全体としての回転トルクの増大を抑制することができる。 In the vibration motor having the above configuration, the sintered bearings can be arranged on both sides in the axial direction of the motor portion. In this case, among the sintered bearings arranged on both sides in the axial direction of the motor portion, the sintered bearing on one side is arranged between the weight and the motor portion, and the axial dimension of the sintered bearing on one side is set to the other. It can be larger than the axial dimension of the side sintered bearing. By doing so, the bearing surface area of the sintered bearing on one side can be set large, so that the shaft support capacity can be increased on the side close to the weight on which a relatively large unbalanced load acts. .. On the other hand, in the sintered bearing on the other side on which a relatively small unbalanced load acts, the bearing surface area can be set small, so that an increase in rotational torque of the vibration motor as a whole can be suppressed. ..
以上に示すように、本発明によれば、モータを高速回転化し、あるいはアンバランス荷重を増大させた場合であっても、高い回転性能を長期間に亘って安定的に発揮することのできる振動モータを低コストに提供することができる。 As described above, according to the present invention, vibration capable of stably exhibiting high rotational performance over a long period of time even when the motor is rotated at high speed or the unbalanced load is increased. The motor can be provided at low cost.
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.
本発明の一実施形態に係る振動モータを、図１を援用して説明する。図示例の振動モータ１は、軸３と、図示しないロータマグネットおよびステータコイル等を有し、軸３を１００００ｒｐｍ以上の回転数で回転駆動させ得るモータ部Ｍと、モータ部Ｍの軸方向両側に配置され、内周に軸受面４ａを有するリング状の焼結軸受４（４１，４２）と、金属又は樹脂材料で略円筒状に形成され、内周にモータ部Ｍおよび焼結軸受４（４１，４２）を保持した円筒状のハウジング２とを備える。軸３は、ステンレス鋼等の金属材料で形成され、ここでは直径２ｍｍ以下（好ましくは１．０ｍｍ以下）のものが使用される。軸３の一端には錘Ｗが一体又は別体に設けられており、本実施形態の錘Ｗは、その中心を軸３の中心に対して偏心させるようにして軸３の一端に取り付け固定されている。また、焼結軸受４（４１，４２）は、ハウジング２の内周に圧入固定されている。軸３の外周面３ａと焼結軸受４の軸受面４ａとの間に形成される隙間（軸受隙間）の隙間幅は、例えば片側（半径値）で４μｍ程度に設定されている。焼結軸受４の内部気孔には、４０℃の動粘度が１０〜５０ｍｍ2／ｓの範囲内にある潤滑油が含浸されている。焼結軸受４の内部気孔には、上記の潤滑油に替えて、４０℃の動粘度が１０〜５０ｍｍ2／ｓの範囲内にある油（潤滑油）を基油としたグリースを含浸させても良い。 The vibration motor according to the embodiment of the present invention will be described with reference to FIG. The vibration motor 1 of the illustrated example has a shaft 3, a rotor magnet, a stator coil, and the like (not shown), and is capable of rotationally driving the shaft 3 at a rotation speed of 10,000 rpm or more. A ring-shaped sintered bearing 4 (41, 42) having a bearing surface 4a on the inner circumference and a substantially cylindrical shape made of a metal or resin material, and a motor portion M and a sintered bearing 4 (41) arranged on the inner circumference. , 42) is provided with a cylindrical housing 2. The shaft 3 is made of a metal material such as stainless steel, and here, a shaft 3 having a diameter of 2 mm or less (preferably 1.0 mm or less) is used. A weight W is integrally or separately provided at one end of the shaft 3, and the weight W of the present embodiment is attached and fixed to one end of the shaft 3 so that the center thereof is eccentric with respect to the center of the shaft 3. ing. Further, the sintered bearings 4 (41, 42) are press-fitted and fixed to the inner circumference of the housing 2. The gap width of the gap (bearing gap) formed between the outer peripheral surface 3a of the shaft 3 and the bearing surface 4a of the sintered bearing 4 is set to, for example, about 4 μm on one side (radius value). The internal pores of the sintered bearing 4 are impregnated with lubricating oil having a kinematic viscosity at 40 ° C. in the range of 10 to 50 mm 2 / s. Instead of the above lubricating oil, the internal pores of the sintered bearing 4 are impregnated with grease based on an oil (lubricating oil) having a kinematic viscosity of 10 to 50 mm 2 / s at 40 ° C. Is also good.
以上の構成を有する振動モータ１において、モータ部Ｍに通電され、軸３が回転駆動されると、焼結軸受４の内部気孔に保持された潤滑油が温度上昇に伴って軸受面４ａに滲み出す。この滲み出した潤滑油によって、対向する軸３の外周面３ａと焼結軸受４の軸受面４ａとの間の軸受隙間に油膜が形成され、軸３が焼結軸受４によって回転自在に支持される。なお、軸３は、その一端に偏心固定された錘Ｗの影響を受けることにより、軸受面４ａの全面に沿って振れ回りながら回転する。すなわち、軸３は、図２に示すように、その中心Ｏａを焼結軸受４（４１，４２）の中心Ｏｂに対してあらゆる方向に偏心させた状態で回転する。これに伴い、モータ部Ｍに振動が生じ、この振動がモータ部Ｍを内周に保持したハウジング２（モータの躯体）に伝わることにより、振動モータ１が全体として振動する。 In the vibration motor 1 having the above configuration, when the motor portion M is energized and the shaft 3 is rotationally driven, the lubricating oil held in the internal pores of the sintered bearing 4 seeps into the bearing surface 4a as the temperature rises. put out. The exuded lubricating oil forms an oil film in the bearing gap between the outer peripheral surface 3a of the opposing shaft 3 and the bearing surface 4a of the sintered bearing 4, and the shaft 3 is rotatably supported by the sintered bearing 4. Ru. The shaft 3 rotates while swinging along the entire surface of the bearing surface 4a due to the influence of the weight W eccentrically fixed to one end thereof. That is, as shown in FIG. 2, the shaft 3 rotates in a state where its center Oa is eccentric with respect to the center Ob of the sintered bearings 4 (41, 42) in all directions. Along with this, vibration is generated in the motor unit M, and this vibration is transmitted to the housing 2 (motor skeleton) holding the motor unit M on the inner circumference, so that the vibration motor 1 vibrates as a whole.
本実施形態では、二つの焼結軸受４１，４２の軸方向寸法（軸受面４ａの面積）および径方向の厚さを相互に異ならせている。具体的には、錘Ｗに近い側の焼結軸受４１（錘Ｗとモータ部Ｍの間に配置された焼結軸受４１）の軸受面４ａの面積を、錘Ｗから遠い側の焼結軸受４２の軸受面４ａの面積よりも大きく設定している。これは、錘Ｗに近い側では、錘Ｗから遠い側よりも大きなアンバランス荷重が軸３に作用するため、軸受面４ａの面積拡大を通じて軸３の支持能力向上を図る一方、錘Ｗから遠い側では、錘Ｗに近い側ほどの支持能力を必要としないため、軸受面４ａの面積を小さくして低トルク化を図るためである。なお、同一の焼結軸受４をモータ部Ｍの軸方向両側に配置し、これら２つの焼結軸受４で軸３を回転自在に支持するようにしても構わない。 In this embodiment, the axial dimensions (area of the bearing surface 4a) and the radial thickness of the two sintered bearings 41 and 42 are different from each other. Specifically, the area of the bearing surface 4a of the sintered bearing 41 (sintered bearing 41 arranged between the weight W and the motor portion M) on the side closer to the weight W is the sintered bearing on the side farther from the weight W. It is set larger than the area of the bearing surface 4a of 42. This is because on the side closer to the weight W, a larger unbalanced load acts on the shaft 3 than on the side farther from the weight W, so that the support capacity of the shaft 3 is improved by expanding the area of the bearing surface 4a, while it is far from the weight W. On the side, the support capacity as close to the weight W as is not required, so that the area of the bearing surface 4a is reduced to reduce the torque. The same sintered bearings 4 may be arranged on both sides of the motor portion M in the axial direction, and the shaft 3 may be rotatably supported by these two sintered bearings 4.
図示は省略しているが、焼結軸受４の内部気孔に含浸させた潤滑油がハウジング２の外部に漏れ出し、あるいは飛散するのを防止するため、振動モータ１にはハウジング２の開口部をシールするシール部材を設けても良い。 Although not shown, the vibration motor 1 is provided with an opening of the housing 2 in order to prevent the lubricating oil impregnated in the internal pores of the sintered bearing 4 from leaking or scattering to the outside of the housing 2. A sealing member for sealing may be provided.
以上で説明した焼結軸受４は、鉄を主成分とし、その次に銅を多く含む（Ｃｕ：１０〜３０質量％）鉄銅系の焼結体からなり、かつ３００ＭＰａ以上の圧環強度を有する。このような焼結軸受４（焼結体）は、主に（Ａ）原料粉末生成工程、（Ｂ）成形工程、および（Ｃ）焼結工程、を順に経て製造される。以下、上記（Ａ）〜（Ｃ）の各工程について詳細に説明する。なお、二つの焼結軸受４（４１，４２）は、軸受面４ａの面積が相互に異なるだけで、その他の構造は実質的に同一であり、同じ製造工程を経て製造される。 The sintered bearing 4 described above is made of an iron-copper-based sintered body containing iron as a main component and then a large amount of copper (Cu: 10 to 30% by mass), and has an annular strength of 300 MPa or more. .. Such a sintered bearing 4 (sintered body) is mainly manufactured through (A) a raw material powder producing step, (B) a molding step, and (C) a sintering step in this order. Hereinafter, each of the above steps (A) to (C) will be described in detail. The two sintered bearings 4 (41, 42) are manufactured through the same manufacturing process, except that the areas of the bearing surfaces 4a are different from each other and the other structures are substantially the same.
（Ａ）原料粉末混合工程
この工程では、後述する複数種の粉末を混合することにより、焼結軸受４の作製用材料である原料粉末を均一化する。本実施形態で使用する原料粉末は、部分拡散合金粉を主原料とし、これに低融点金属粉および固体潤滑剤粉を配合した混合粉末である。この原料粉末には、必要に応じて各種成形潤滑剤（例えば、離型性向上のための潤滑剤）を添加しても良い。以下、上記の各粉末について詳細に述べる。
(A) Raw Material Powder Mixing Step In this step, the raw material powder, which is a material for manufacturing the sintered bearing 4, is made uniform by mixing a plurality of types of powders described later. The raw material powder used in the present embodiment is a mixed powder in which a partial diffusion alloy powder is used as a main raw material, and a low melting point metal powder and a solid lubricant powder are mixed therein. Various molding lubricants (for example, lubricants for improving releasability) may be added to the raw material powder, if necessary. Hereinafter, each of the above powders will be described in detail.
［部分拡散合金粉］
図４に示すように、部分拡散合金粉１１としては、鉄粉１２の表面に銅粉１３を部分拡散させたＦｅ−Ｃｕ部分拡散合金粉が使用され、本実施形態では、鉄粉１２の表面に、鉄粉１２よりも平均粒径が小さい多数の銅粉１３を部分拡散させた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、図４中の部分拡大図に示すように、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。部分拡散合金粉１１は、１４５メッシュの篩の網目は通過可能な粒子、すなわち平均粒度１４５メッシュ以下（平均粒径１０６μｍ以下）の粒子のみが使用される。
[Partial diffusion alloy powder]
As shown in FIG. 4, as the partial diffusion alloy powder 11, Fe—Cu partial diffusion alloy powder in which copper powder 13 is partially diffused on the surface of iron powder 12 is used. In the present embodiment, the surface of iron powder 12 is used. In addition, Fe-Cu partially diffused alloy powder in which a large number of copper powders 13 having an average particle size smaller than that of iron powder 12 are partially diffused is used. The diffused portion of the partially diffused alloy powder 11 forms an Fe—Cu alloy, and as shown in the partially enlarged view in FIG. 4, the alloy portion is arranged with iron atoms 12a and copper atoms 13a bonded to each other. It has a crystal structure. As the partial diffusion alloy powder 11, only particles that can pass through the mesh of the 145 mesh sieve, that is, particles having an average particle size of 145 mesh or less (average particle size of 106 μm or less) are used.
なお、粉末はその粒径が小さくなるほど見掛密度が下がり、浮遊し易くなる。そのため、原料粉末中に小粒径の部分拡散合金粉１１が多く含まれていると、後述する成形工程において成形金型（キャビティ）に対する原料粉末の充填性が低下し、所定形状・密度の圧粉体を安定的に得ることが難しくなる。具体的には、粒径４５μｍ以下の粒子を２５質量％以上含んだ部分拡散合金粉１１を使用した場合に、上記の問題が生じ易くなることを本発明者らは見出した。従って、部分拡散合金粉１１としては、平均粒度１４５メッシュ以下（平均粒径１０６μｍ以下）で、かつ平均粒度３５０メッシュ（平均粒径４５μｍ）以下の粒子を２５質量％以上含まないものを選択使用するのが望ましい。平均粒径は、粒子群にレーザ光を照射し、そこから発せられる回析・散乱光の強度分布パターンから計算によって粒度分布、さらには平均粒径を求めるレーザ回析散乱法（例えば株式会社島津製作所製のＳＡＬＤ３１０００を用いる）により測定することができる（以下に述べる粉末の平均粒径も同様の方法で測定することができる）。 The smaller the particle size of the powder, the lower the apparent density and the easier it is to float. Therefore, if the raw material powder contains a large amount of the partially diffused alloy powder 11 having a small particle size, the filling property of the raw material powder in the molding die (cavity) is lowered in the molding process described later, and the pressure of the predetermined shape and density is reduced. It becomes difficult to obtain powder stably. Specifically, the present inventors have found that the above problems are likely to occur when the partially diffused alloy powder 11 containing particles having a particle size of 45 μm or less is used in an amount of 25% by mass or more. Therefore, as the partial diffusion alloy powder 11, a powder having an average particle size of 145 mesh or less (average particle size 106 μm or less) and containing 25% by mass or more of particles having an average particle size of 350 mesh (average particle size 45 μm) or less is selectively used. Is desirable. The average particle size is determined by a laser diffraction / scattering method (for example, Shimadzu Co., Ltd.) in which a group of particles is irradiated with laser light and the particle size distribution is calculated from the intensity distribution pattern of the diffraction / scattered light emitted from the particle group, and the average particle size is obtained. It can be measured by (using SALD31000 manufactured by Mfg. Co., Ltd.) (the average particle size of the powder described below can also be measured by the same method).
上記の部分拡散合金粉１１を構成する鉄粉１２としては、還元鉄粉、アトマイズ鉄粉等、公知の鉄粉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、球形に近似した不規則形状で、かつ内部気孔を有する海綿状（多孔質状）であるから、海綿鉄粉とも称される。使用する鉄粉１２は、平均粒径２０μｍ〜１０６μｍのものが好ましく、平均粒径３８μｍ〜７５μｍのものが一層好ましい。 As the iron powder 12 constituting the partial diffusion alloy powder 11, known iron powder such as reduced iron powder and atomized iron powder can be used, but in the present embodiment, the reduced iron powder is used. Reduced iron powder is also called sponge iron powder because it has an irregular shape similar to a sphere and is spongy (porous) with internal pores. The iron powder 12 to be used preferably has an average particle size of 20 μm to 106 μm, and more preferably an average particle size of 38 μm to 75 μm.
また、部分拡散合金粉１１を構成する銅粉１３としては、汎用されている不規則形状や樹枝状の銅粉が広く使用可能であり、例えば、電解銅粉、アトマイズ銅粉等が用いられる。本実施形態では、表面に多数の凹凸を有すると共に、粒子全体として球形に近似した不規則形状をなし、成形性に優れたアトマイズ銅粉を使用している。銅粉１３としては、鉄粉１２よりも小粒径のものが使用され、具体的には平均粒径５μｍ以上２０μｍ以下（好ましくは２０μｍ未満）のものが使用される。なお、個々の部分拡散合金粉１１におけるＣｕの割合は１０〜３０質量％（好ましくは２２〜２６質量％）であり、後述する焼結工程で得られる焼結体４”における銅の含有量（厳密には、焼結体４”がＳｎやＣを含まないとした場合における銅の含有量）と同じである。つまり、本実施形態において、原料粉末には単体の銅粉や鉄粉を配合しない。原料粉末には、単体の銅粉や鉄粉を配合しても構わないが、単体の銅粉を配合すると、軸受面４ａの耐摩耗性向上（軸受面４ａの高強度化）を図ることが難しくなる。そのため、例えば軸３が回転するのに伴って軸受面４ａに軸３が衝突した際などに、軸受面４ａに圧痕（凹み）が形成され易くなる。また、単体の鉄粉を配合すると、所望の圧環強度を有する焼結体４”（焼結軸受４）を得ることが難しくなる。従って、原料粉末には、単体の銅粉や鉄粉を配合しないのが好ましい。 Further, as the copper powder 13 constituting the partial diffusion alloy powder 11, general-purpose irregular-shaped or dendritic copper powder can be widely used, and for example, electrolytic copper powder, atomized copper powder, or the like is used. In the present embodiment, atomized copper powder is used, which has a large number of irregularities on the surface, has an irregular shape similar to a spherical shape as a whole particle, and has excellent moldability. As the copper powder 13, a copper powder having a particle size smaller than that of the iron powder 12 is used, and specifically, a copper powder having an average particle size of 5 μm or more and 20 μm or less (preferably less than 20 μm) is used. The proportion of Cu in the individual partial diffusion alloy powder 11 is 10 to 30% by mass (preferably 22 to 26% by mass), and the copper content in the sintered body 4 "obtained in the sintering step described later (preferably 22 to 26% by mass). Strictly speaking, it is the same as the copper content when the sintered body 4 "does not contain Sn or C). That is, in the present embodiment, the raw material powder does not contain a single copper powder or iron powder. A single copper powder or iron powder may be added to the raw material powder, but if a single copper powder is added, the wear resistance of the bearing surface 4a can be improved (the bearing surface 4a has a higher strength). It gets harder. Therefore, for example, when the shaft 3 collides with the bearing surface 4a as the shaft 3 rotates, indentations (dents) are likely to be formed on the bearing surface 4a. Further, when a single iron powder is blended, it becomes difficult to obtain a sintered body 4 "(sintered bearing 4) having a desired annular strength. Therefore, a single copper powder or iron powder is blended in the raw material powder. It is preferable not to do so.
［低融点金属粉］
低融点金属粉としては、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。本実施形態では、これらの中でも銅と鉄に拡散し易く（相性が良く）、単粉で使用できる錫粉１４（図６参照）、特にアトマイズ錫粉を使用する。錫粉（アトマイズ錫粉）１４としては、平均粒径５〜６３μｍのものが好ましく使用され、平均粒径２０〜４５μｍのものが一層好ましく使用される。
[Low melting point metal powder]
As the low melting point metal powder, 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. In the present embodiment, among these, tin powder 14 (see FIG. 6) that easily diffuses into copper and iron (good compatibility) and can be used as a single powder, particularly atomized tin powder is used. As the tin powder (atomized tin powder) 14, those having an average particle size of 5 to 63 μm are preferably used, and those having an average particle size of 20 to 45 μm are more preferably 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。
[Solid lubricant]
As the solid lubricant, one or more powders such as graphite and molybdenum disulfide can be used. In this embodiment, graphite powder, particularly scaly graphite powder, is used in consideration of cost.
（Ｂ）成形工程
成形工程では、図５（ａ）（ｂ）に示すような成形金型２０を使用して上記の原料粉末１０を圧縮することにより、図１等に示す焼結軸受４に近似した形状（略完成品形状）の圧粉体４’を得る。成形金型２０は、主要な構成として、同軸配置されたコア２１、上下パンチ２２，２３およびダイ２４を有する。成形金型２０は、例えばカム式成形プレス機のダイセットにセットされる。
(B) Molding step In the molding step, the raw material powder 10 is compressed by using the molding die 20 as shown in FIGS. 5A and 5B to form the sintered bearing 4 shown in FIG. 1 and the like. A green compact 4'with an approximate shape (substantially finished product shape) is obtained. The molding die 20 has a core 21, upper and lower punches 22, 23 and a die 24 arranged coaxially as a main configuration. The molding die 20 is set in, for example, a die set of a cam-type molding press.
上記構成の成形金型２０において、コア２１、下パンチ２３およびダイ２４で画成されるキャビティ２５内に原料粉末１０を充填してから、上パンチ２２を下パンチ２３に対して相対的に接近移動させ、原料粉末１０を適当な加圧力（成形すべき圧粉体の形状や大きさに応じて設定される）で圧縮すると、圧粉体４’が成形される。そして、上パンチ２２を上昇移動させると共に下パンチ２３を上昇移動させ、圧粉体４’をキャビティ２５外に抜き出す。図６に模式的に示すように、圧粉体４’では、部分拡散合金粉１１、錫粉１４および黒鉛粉（図示せず）が均一に分散している。本実施形態で使用している部分拡散合金粉１１は、鉄粉１２として還元鉄粉を使用しているため、アトマイズ鉄粉を使用した部分拡散合金粉に比べて粉末が柔らかく、圧縮成形性に優れる。そのため、低密度でも圧粉体４’の強度を高めることができ、圧粉体４’の欠けや割れの発生を防止することができる。 In the molding die 20 having the above configuration, the raw material powder 10 is filled in the cavity 25 defined by the core 21, the lower punch 23, and the die 24, and then the upper punch 22 is relatively close to the lower punch 23. When the raw material powder 10 is moved and compressed with an appropriate pressing force (set according to the shape and size of the green compact to be molded), the green compact 4'is formed. Then, the upper punch 22 is moved upward and the lower punch 23 is moved upward to pull out the green compact 4'out of the cavity 25. As schematically shown in FIG. 6, in the green compact 4', the partial diffusion alloy powder 11, the tin powder 14, and the graphite powder (not shown) are uniformly dispersed. Since the partially diffused alloy powder 11 used in the present embodiment uses reduced iron powder as the iron powder 12, the powder is softer than the partially diffused alloy powder using atomized iron powder, and has excellent compression moldability. Excellent. Therefore, the strength of the green compact 4'can be increased even at a low density, and the occurrence of chipping or cracking of the green compact 4'can be prevented.
（Ｃ）焼結工程
焼結工程では、圧粉体４’を焼結し、焼結体を得る。焼結条件は、黒鉛（黒鉛粉）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。鉄−炭素の平衡状態では、７２３℃に変態点があり、これを超えると鉄と炭素の反応が開始されて鉄組織中にパーライト相（γＦｅ）が生成されるが、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）が生成される。パーライト相（γＦｅ）は高硬度（ＨＶ３００以上）で相手材に対する攻撃性が強いため、焼結軸受４の鉄組織中に過剰にパーライト相（γＦｅ）が存在すると、軸３の摩耗を進行させるおそれがある。また、一般的な焼結軸受の製造工程では、ブタン、プロパン等の液化石油ガスと空気を混合してＮｉ触媒で熱分解させた吸熱型ガス（ＲＸガス）の雰囲気下で圧粉体を加熱・焼結させる場合が多い。しかしながら、吸熱型ガスでは炭素が拡散して圧粉体の表面を硬化させるおそれがあり、上記同様の問題が生じ易くなる。
(C) Sintering step In the sintering step, the green compact 4'is sintered to obtain a sintered body. The sintering conditions are such that carbon contained in graphite (graphite powder) does not react with iron (carbon diffusion does not occur). In the iron-carbon equilibrium state, there is a transformation point at 723 ° C, and beyond this, the reaction between iron and carbon is started and a pearlite phase (γFe) is generated in the iron structure, but in sintering, it is 900 ° C. After that, the reaction between carbon (graphite) and iron begins, and the pearlite phase (γFe) is generated. Since the pearlite phase (γFe) has a high hardness (HV300 or more) and is highly aggressive against the mating material, if the pearlite phase (γFe) is excessively present in the iron structure of the sintered bearing 4, the shaft 3 may be worn. There is. Further, in the general manufacturing process of a sintered bearing, the green compact is heated in the atmosphere of a heat absorbing gas (RX gas) obtained by mixing liquefied petroleum gas such as butane and propane and air and pyrolyzing it with a Ni catalyst.・ In many cases, it is sintered. However, in the endothermic gas, carbon may diffuse to harden the surface of the green compact, and the same problem as described above is likely to occur.
以上の観点から、圧粉体４’は９００℃以下、具体的には８００℃（好ましくは８２０℃）以上８８０℃以下で加熱する（低温焼結）。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。このような焼結条件であれば、原料粉末で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質のフェライト相（ＨＶ２００以下）となる。原料粉末に流体潤滑材等の各種成形潤滑剤を含めていた場合、成形潤滑剤は焼結に伴って揮散する。 From the above viewpoint, the green compact 4'is heated at 900 ° C. or lower, specifically 800 ° C. (preferably 820 ° C.) or higher and 880 ° C. or lower (low temperature sintering). The sintering atmosphere is a carbon-free gas atmosphere (hydrogen gas, nitrogen gas, argon gas, etc.) or a vacuum. Under such sintering conditions, 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 (HV200 or less). When various molding lubricants such as a fluid lubricant are contained in the raw material powder, the molding lubricant volatilizes with sintering.
鉄組織は、その全てをフェライト相（αＦｅ）で形成する他、図７に示すように、フェライト相αＦｅとパーライト相γＦｅの二相組織にすることもできる。これにより、フェライト相αＦｅよりも硬質のパーライト相γＦｅが軸受面４ａの耐摩耗性向上に寄与し、高面圧下での軸受面４ａの摩耗を抑制して軸受寿命を向上させることができる。但し、パーライト相γＦｅの存在割合が過剰となり、フェライト相αＦｅと同等の割合になると、パーライトによる軸３に対する攻撃性が増して軸３が摩耗しやすくなる。これを防止するため、図７に示すように、パーライト相γＦｅはフェライト相αＦｅの粒界に存在（点在）する程度に抑える。ここでいう「粒界」は、粉末粒子間に形成される粒界の他、粉末粒子中に形成される結晶粒界の双方を意味する。鉄組織をフェライト相αＦｅとパーライト相γＦｅの二相組織で形成する場合、鉄組織に占めるフェライト相αＦｅおよびパーライト相γＦｅの割合は、焼結体の任意断面における面積比で、それぞれ、８０〜９５％および５〜２０％（αＦｅ：γＦｅ＝８０〜９５％：５〜２０％）程度とするのが望ましい。これにより、軸３の摩耗抑制と軸受面の耐摩耗性向上とを両立させることができる。 The iron structure may be entirely formed of a ferrite phase (αFe), or may have a two-phase structure of a ferrite phase αFe and a pearlite phase γFe as shown in FIG. As a result, the pearlite phase γFe, which is harder than the ferrite phase αFe, contributes to the improvement of the wear resistance of the bearing surface 4a, and the wear of the bearing surface 4a under high surface pressure can be suppressed to improve the bearing life. However, when the abundance ratio of the pearlite phase γFe becomes excessive and becomes the same ratio as that of the ferrite phase αFe, the aggression of the pearlite to the shaft 3 increases and the shaft 3 is easily worn. In order to prevent this, as shown in FIG. 7, the pearlite phase γFe is suppressed to the extent that it is present (spotted) at the grain boundaries of the ferrite phase αFe. The "grain boundary" here means both the grain boundary formed between the powder particles and the crystal grain boundary formed in the powder particles. When the iron structure is formed by a two-phase structure of a ferrite phase αFe and a pearlite phase γFe, the ratio of the ferrite phase αFe and the pearlite phase γFe to the iron structure is the area ratio in an arbitrary cross section of the sintered body, which is 80 to 95, respectively. % And 5 to 20% (αFe: γFe = 80 to 95%: 5 to 20%). As a result, it is possible to achieve both suppression of wear of the shaft 3 and improvement of wear resistance of the bearing surface.
パーライト相γＦｅの析出量は、主に焼結温度と雰囲気ガスに依存する。従って、上記のようにパーライト相γＦｅをフェライト相αＦｅの粒界に存在させるためには、焼結温度を８２０℃〜９００℃程度に上げ、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γＦｅを形成することができる。なお、上記のとおり、９００℃を超える温度で圧粉体４’を焼結すると、黒鉛（炭素）が鉄と反応してパーライト相γＦｅが形成されるので、圧粉体４’は９００℃以下で焼結するのが好ましい。 The amount of pearlite phase γFe deposited depends mainly on the sintering temperature and the atmospheric gas. Therefore, in order to allow the pearlite phase γFe to exist at the grain boundaries of the ferrite phase αFe as described above, the sintering temperature is raised to about 820 ° C to 900 ° C, and a gas containing carbon as the atmosphere inside the furnace, for example, natural gas or Sinter using a heat absorbing gas (RX gas). As a result, carbon contained in the gas diffuses into iron during sintering, and a pearlite phase γFe can be formed. As described above, when the green compact 4'is sintered at a temperature exceeding 900 ° C., graphite (carbon) reacts with iron to form a pearlite phase γFe, so that the green compact 4'is 900 ° C. or lower. It is preferable to sinter with.
焼結後、焼結体４”にサイジングを施し、焼結体４"を仕上がり形状・寸法に仕上げた後、この焼結体４”の内部気孔に真空含浸等の手法で潤滑油を含浸させると、図１に示す焼結軸受４が完成する。焼結体４”の内部気孔に含浸させる潤滑油は、上述のとおり低粘度のもの、具体的には４０℃の動粘度が１０〜５０ｍｍ2／ｓの潤滑油（例えば合成炭化水素系潤滑油）が使用される。軸受隙間に形成される油膜の剛性を確保しつつ、回転トルクの上昇を抑えるためである。なお、焼結体４”の内部気孔には、上記の潤滑油に替えて、４０℃の動粘度が１０〜５０ｍｍ2／ｓの潤滑油を基油としたグリースを含浸させても良い。また、サイジングは必要に応じて施せば足り、必ずしも施す必要はない。 After sintering, the sintered body 4 "is sized, the sintered body 4" is finished into a finished shape and dimensions, and then the internal pores of the sintered body 4 "are impregnated with lubricating oil by a method such as vacuum impregnation. The sintered bearing 4 shown in FIG. 1 is completed. The lubricating oil impregnated in the internal pores of the sintered body 4 "has a low viscosity as described above, specifically, a kinematic viscosity at 40 ° C. of 10 to 50 mm. A 2 / s lubricant (eg, synthetic hydrocarbon-based lubricant) is used. This is to suppress an increase in rotational torque while ensuring the rigidity of the oil film formed in the bearing gap. The internal pores of the sintered body 4 "may be impregnated with grease based on a lubricating oil having a kinematic viscosity of 10 to 50 mm 2 / s at 40 ° C. instead of the above-mentioned lubricating oil. , Sizing should be done as needed, not necessarily.
以上のようにして得られた焼結体４”（焼結軸受４）は、Ｃｕを１０〜３０質量％（好ましくは２２〜２６質量％）、Ｓｎを０．５〜３．０質量％（好ましくは１．０〜３．０質量％）、Ｃを０．３〜１．５質量％（好ましくは０．５〜１．０質量％）含有し、残部が鉄および不可避的不純物からなる。そして、圧粉体４’の焼結温度を銅の融点（１０８３℃）よりも遥かに低温の９００℃以下とした上記の焼結条件であれば、圧粉体４’に含まれる（部分拡散合金粉１１を構成する）銅粉１３は溶融せず、従って、焼結に伴って銅が鉄（鉄組織）中に拡散しない。そのため、焼結体４”の表面（軸受面４ａ）には青銅相を含む適量の銅組織が形成されている。また、軸受面４ａには遊離黒鉛も露出している。そのため、軸３との初期なじみ性が良好で、軸受面４ａの摩擦係数も小さいものとなる。原料粉末に占める錫粉の配合割合を増やせば焼結体４”の機械的強度が高まるが、Ｓｎの量が過剰となると粗大気孔が増えるため、上記の配合割合（Ｃｕの配合割合に対して１０％程度の配合割合）としている。 The sintered body 4 "(sintered bearing 4) obtained as described above contains 10 to 30% by mass (preferably 22 to 26% by mass) of Cu and 0.5 to 3.0% by mass (preferably 22 to 26% by mass) of Sn. It contains preferably 1.0 to 3.0% by mass), 0.3 to 1.5% by mass (preferably 0.5 to 1.0% by mass) of C, and the balance is composed of iron and unavoidable impurities. Then, under the above-mentioned sintering conditions in which the sintering temperature of the green compact 4'is 900 ° C. or lower, which is much lower than the melting point of copper (1083 ° C.), it is included in the green compact 4'(partial diffusion). The copper powder 13 (which constitutes the alloy powder 11) does not melt, and therefore copper does not diffuse into the iron (iron structure) with the sintering. Therefore, the surface (bearing surface 4a) of the sintered body 4 ”is formed. An appropriate amount of copper structure including the bronze phase is formed. Free graphite is also exposed on the bearing surface 4a. Therefore, the initial compatibility with the shaft 3 is good, and the friction coefficient of the bearing surface 4a is also small. Increasing the blending ratio of tin powder in the raw material powder increases the mechanical strength of the sintered body 4 ", but if the amount of Sn is excessive, the crude air pores increase, so the above blending ratio (relative to the blending ratio of Cu) The mixing ratio is about 10%).
焼結体４”には、鉄を主成分とする鉄組織および銅からなる銅組織が形成される。本実施形態では、原料粉末に鉄粉単体や銅粉単体が添加されておらず、添加されているにしても微量であるので、焼結体４”の全ての鉄組織および銅組織が部分拡散合金粉１１を主体として形成される。部分拡散合金粉では、銅粉の一部が鉄粉に拡散しているため、焼結後の鉄組織と銅組織の間で高いネック強度を得ることができる。また、焼結時には、圧粉体４’中の錫粉１４が溶融し、部分拡散合金粉１１に含まれる銅粉１３の表面を濡らす。これに伴い、液相焼結が進行し、図７に示すように、隣り合う部分拡散合金粉１１の鉄組織と銅組織、あるいは銅組織同士を結合する青銅相（Ｃｕ−Ｓｎ）１６が形成される。また、個々の部分拡散合金粉１１のうち、鉄粉１２の表面に銅粉１３の一部が拡散してＦｅ−Ｃｕ合金が形成された部分には、溶融したＳｎが拡散してＦｅ−Ｃｕ−Ｓｎ合金（合金相）１７が形成されるため、焼結体４”を構成する鉄組織と銅組織間のネック強度が一層高くなる。そのため、上述したような低温条件での焼結でも高い圧環強度、具体的には３００ＭＰａ以上の圧環強度を得ることができる。また、軸受面４ａを硬くして軸受面４ａの耐摩耗性を向上させることもできる。なお、図７においては、フェライト相αＦｅやパーライト相γＦｅなどを色の濃淡で表現している。具体的には、フェライト相αＦｅ→青銅相１６→Ｆｅ−Ｃｕ―Ｓｎ合金１７→パーライト相γＦｅの順に色を濃くしている。 An iron structure containing iron as a main component and a copper structure composed of copper are formed in the sintered body 4 ”. In the present embodiment, iron powder alone or copper powder alone is not added to the raw material powder, and is added. Even if it is, since it is a very small amount, all the iron structure and the copper structure of the sintered body 4 "are formed mainly of the partial diffusion alloy powder 11. In the partially diffused alloy powder, since a part of the copper powder is diffused in the iron powder, a high neck strength can be obtained between the iron structure and the copper structure after sintering. Further, at the time of sintering, the tin powder 14 in the green compact 4'melts and wets the surface of the copper powder 13 contained in the partial diffusion alloy powder 11. Along with this, liquid phase sintering progresses, and as shown in FIG. 7, a bronze phase (Cu—Sn) 16 that bonds the iron structure and the copper structure of the adjacent partial diffusion alloy powders 11 or the copper structures is formed. Will be done. Further, among the individual partial diffusion alloy powders 11, the molten Sn diffuses to the portion where a part of the copper powder 13 diffuses on the surface of the iron powder 12 to form the Fe—Cu alloy, and Fe—Cu. Since the −Sn alloy (alloy phase) 17 is formed, the neck strength between the iron structure and the copper structure constituting the sintered body 4 ”is further increased. Therefore, the sintering under low temperature conditions as described above is also high. An pressure ring strength, specifically, an pressure ring strength of 300 MPa or more can be obtained. Further, the bearing surface 4a can be hardened to improve the abrasion resistance of the bearing surface 4a. In FIG. 7, the ferrite phase can be obtained. αFe, the pearlite phase γFe, and the like are represented by shades of color. Specifically, the colors are darkened in the order of ferrite phase αFe → bronze phase 16 → Fe—Cu—Sn alloy 17 → pearlite phase γFe.
また、部分拡散合金粉１１として、平均粒度１４５メッシュ以下（平均粒径１０６μｍ以下）の粉末を使用しているので、焼結体４”の組織を均一化して粗大気孔の生成を防止することができる。そのため、焼結体４”を高密度化して圧環強度や軸受面４ａの耐摩耗性をさらに高めることができる。 Further, since the powder having an average particle size of 145 mesh or less (average particle size of 106 μm or less) is used as the partial diffusion alloy powder 11, the structure of the sintered body 4 ”can be made uniform and the formation of coarse air pores can be prevented. Therefore, it is possible to increase the density of the sintered body 4 "and further improve the annular strength and the wear resistance of the bearing surface 4a.
以上に示すように、本実施形態の焼結体４”は３００ＭＰａ以上の圧環強度を有しており、この圧環強度の値は、既存の銅鉄系焼結体のそれに比べて２倍以上の値である。また、本実施形態の焼結体４”の密度は６．８±０．３ｇ／ｃｍ3となり、既存の銅鉄系焼結体の密度（６．６ｇ／ｃｍ3程度）よりも高密度となる。既存の銅鉄系焼結体でも圧粉体の成形工程で高圧縮することで高密度化することは可能であるが、このようにすると、内部の流体潤滑剤が焼結時に燃焼できずにガス化するため、表層部の気孔が粗大化してしまう。本発明では圧粉体の成形時に高圧縮する必要はなく、そのような不具合を防止することができる。 As shown above, the sintered body 4 "of the present embodiment has an annulus strength of 300 MPa or more, and the value of the annulus strength is more than twice that of the existing copper-iron sintered body. the value. Further, from the density of the sintered body 4 "of the present embodiment is 6.8 ± 0.3g / cm 3, and the density of the existing copper iron-based sintered body (about 6.6 g / cm 3) Is also dense. Even with existing copper-iron sintered bodies, it is possible to increase the density by high compression in the powder molding process, but in this way, the fluid lubricant inside cannot be burned during sintering. Since it is gasified, the pores on the surface layer become coarse. In the present invention, it is not necessary to highly compress the green compact at the time of molding, and such a defect can be prevented.
このように焼結体４”を高密度化させる一方で、含油率を１５ｖｏｌ％以上にすることができ、既存の銅鉄系焼結軸受と同程度の含油率を確保できる。これは、主に部分拡散合金粉１１を構成する鉄粉１２として、海綿状をなし、保油性に優れた還元鉄粉を使用していることに由来する。この場合、焼結体４”に含浸させた潤滑油は、焼結組織の粒子間に形成された気孔だけでなく、還元鉄粉が有する気孔にも保持される。 While increasing the density of the sintered body 4 "in this way, the oil content can be increased to 15 vol% or more, and the same level of oil content as the existing copper-iron-based sintered bearing can be secured. This is because reduced iron powder, which has a spongy shape and is excellent in oil retention, is used as the iron powder 12 constituting the partially diffused alloy powder 11. In this case, the lubricant impregnated in the sintered body 4 ”is used. The oil is retained not only in the pores formed between the particles of the sintered structure but also in the pores of the reduced iron powder.
粗大気孔は特に焼結体４”の表層部（焼結体表面から深さ１００μｍに至るまでの領域）で生じやすいが、以上のようにして得られた焼結体４”であれば、上記のように表層部における粗大気孔の発生を防止して表層部の高密度化を図ることができる。具体的には、表層部の気孔率を、５〜２０％にすることができる。この気孔率は、例えば焼結体４”の任意断面における気孔部の面積比率を画像解析することで求めることができる。 Coarse air pores are particularly likely to occur in the surface layer portion of the sintered body 4 "(the region from the surface of the sintered body to a depth of 100 μm), but the sintered body 4" obtained as described above is described above. As described above, it is possible to prevent the generation of coarse air pores in the surface layer portion and increase the density of the surface layer portion. Specifically, the porosity of the surface layer portion can be set to 5 to 20%. This porosity can be obtained, for example, by image analysis of the area ratio of the pores in an arbitrary cross section of the sintered body 4 ".
このように表層部が高密度化されることで軸受面４ａの表面開孔率も小さくなる。具体的には、軸受面４ａの表面開孔率を５％以上２０％以下の範囲内に設定することができる。なお、表面開孔率が５％を下回ると、軸受隙間に必要十分量の潤滑油を滲み出させることが難しくなり、焼結軸受としてのメリットを得ることができない。 By increasing the density of the surface layer portion in this way, the surface aperture ratio of the bearing surface 4a also decreases. Specifically, the surface aperture ratio of the bearing surface 4a can be set within the range of 5% or more and 20% or less. If the surface aperture ratio is less than 5%, it becomes difficult to exude a necessary and sufficient amount of lubricating oil into the bearing gap, and the merit of the sintered bearing cannot be obtained.
また、この焼結体４”を得るための原料粉末として、鉄粉１２の表面に銅粉１３を部分拡散させた部分拡散合金粉１１を主原料としたものを使用しているため、既存の鉄銅系焼結軸受で問題となる銅の偏析を防止することができる。また、この焼結体４”であれば、ＮｉやＭｏ等の高価な金属粉末を使用することなく機械的強度を向上させることができるので、焼結軸受４の低コスト化も達成される。 Further, as the raw material powder for obtaining the sintered body 4 ”, the existing raw material is the partial diffusion alloy powder 11 in which the copper powder 13 is partially diffused on the surface of the iron powder 12. It is possible to prevent segregation of copper, which is a problem in iron-copper-based sintered bearings. Further, with this sintered body 4 ", mechanical strength can be increased without using expensive metal powders such as Ni and Mo. Since it can be improved, the cost of the sintered bearing 4 can be reduced.
以上で説明したように、本発明に係る振動モータ１で使用する焼結軸受４は高い圧環強度（３００ＭＰａ以上の圧環強度）を有するため、図１に示すようにハウジング２の内周に圧入固定した場合でも、軸受面４ａがハウジング２の内周面形状に倣って変形することがなく、固定後も軸受面４ａの真円度や円筒度等を安定的に維持することができる。そのため、ハウジング２の内周に焼結軸受４を圧入固定した後、軸受面４ａを適正形状・精度に仕上げるためにサイジング等の形状修正加工を追加的に実行することなく、所望の真円度（例えば３μｍ以下の真円度）を得ることができる。また、焼結軸受４が３００ＭＰａ以上の圧環強度を有していれば、焼結軸受４を組み込んだ振動モータ１（ひいては振動モータ１を備えた携帯端末等）が落下等することにより軸受面４ａに大きな衝撃値が付加された場合でも、軸受面４ａの変形を可及的に防止することができる。 As described above, since the sintered bearing 4 used in the vibration motor 1 according to the present invention has a high annular strength (an annular strength of 300 MPa or more), it is press-fitted and fixed to the inner circumference of the housing 2 as shown in FIG. Even in this case, the bearing surface 4a does not deform following the shape of the inner peripheral surface of the housing 2, and the roundness, cylindricity, and the like of the bearing surface 4a can be stably maintained even after fixing. Therefore, after the sintered bearing 4 is press-fitted and fixed to the inner circumference of the housing 2, the desired roundness is obtained without additionally performing shape correction processing such as sizing in order to finish the bearing surface 4a to an appropriate shape and accuracy. (For example, roundness of 3 μm or less) can be obtained. Further, if the sintered bearing 4 has an annular strength of 300 MPa or more, the bearing surface 4a is caused by the vibration motor 1 incorporating the sintered bearing 4 (by extension, a portable terminal or the like equipped with the vibration motor 1) falling or the like. Even when a large impact value is applied to the bearing surface 4a, deformation of the bearing surface 4a can be prevented as much as possible.
また、以上で述べたように、（１）焼結軸受４を構成する焼結体４”が鉄を主成分とし、しかもその多孔質組織における鉄組織と銅組織間のネック強度、および銅組織同士のネック強度が高いために軸受面４ａが高硬度化されていること、（２）焼結軸受４は、粗大気孔が少ない均一で緻密な多孔質組織を有すること、（３）軸受面４ａに銅組織（青銅相）や遊離黒鉛が露出していること、などの種々の要因により、軸受面４ａは高い耐摩耗性を有する。そのため、軸受面４ａの全面に沿って軸３が振れ回り、あるいは軸３が軸受面４ａに頻繁に衝突したとしても、軸受面４ａの摩耗や損傷が抑えられる。従って、本発明によれば、高い回転性能を長期間に亘って発揮することのできる振動モータ１を低コストに提供することができる。 Further, as described above, (1) the sintered body 4 "constituting the sintered bearing 4 contains iron as a main component, and the neck strength between the iron structure and the copper structure in the porous structure and the copper structure. The bearing surface 4a has a high hardness due to the high neck strength of each other, (2) the sintered bearing 4 has a uniform and dense porous structure with few coarse air holes, and (3) the bearing surface 4a. The bearing surface 4a has high wear resistance due to various factors such as the copper structure (bronze phase) and the exposed free graphite. Therefore, the shaft 3 swings around the entire surface of the bearing surface 4a. Or, even if the shaft 3 frequently collides with the bearing surface 4a, wear and damage of the bearing surface 4a can be suppressed. Therefore, according to the present invention, vibration capable of exhibiting high rotational performance for a long period of time can be exhibited. The motor 1 can be provided at low cost.
ここで、参考までに、特許文献１に記載の技術手段に係る焼結軸受（以下、「銅被覆鉄粉軸受」という）の表層部の顕微鏡写真を図８に示す。図８と、本実施形態に係る振動モータ１で使用している焼結軸受４の表層部の顕微鏡写真（図３参照）とを比較すると、本実施形態に係る焼結軸受４は、銅被覆鉄粉軸受に比べて表層部の多孔質組織が緻密であることが理解される。実際、本実施形態に係る焼結軸受４の表層部の気孔率は１３．６％だったのに対し、銅被覆鉄粉軸受の表層部の気孔率は２５．５％程度であった。このような差を生じた要因として、銅被覆鉄粉では鉄粉に銅膜が密着しているにすぎず、鉄組織と銅組織の間のネック強度が不足していることが挙げられる。 Here, for reference, FIG. 8 shows a micrograph of the surface layer portion of the sintered bearing (hereinafter, referred to as “copper-coated iron powder bearing”) according to the technical means described in Patent Document 1. Comparing FIG. 8 with a photomicrograph (see FIG. 3) of the surface layer portion of the sintered bearing 4 used in the vibration motor 1 according to the present embodiment, the sintered bearing 4 according to the present embodiment is coated with copper. It is understood that the porous structure of the surface layer is denser than that of the iron powder bearing. In fact, the porosity of the surface layer portion of the sintered bearing 4 according to the present embodiment was 13.6%, whereas the porosity of the surface layer portion of the copper-coated iron powder bearing was about 25.5%. One of the factors that caused such a difference is that in the copper-coated iron powder, the copper film is only in close contact with the iron powder, and the neck strength between the iron structure and the copper structure is insufficient.
以上、本発明の一実施形態に係る振動モータ１について説明を行ったが、本発明の実施の形態は上述のものに限られない。 Although the vibration motor 1 according to the embodiment of the present invention has been described above, the embodiment of the present invention is not limited to the above.
例えば、焼結軸受４の鉄組織や銅組織の全てを部分拡散合金粉だけで形成する場合を説明したが、原料粉末に単体鉄粉および単体銅粉のうちどちらか一方または双方を添加し、鉄組織や銅組織の一部を単体鉄粉や単体銅粉で形成することもできる。この場合、最低限の耐摩耗性、強度、および摺動特性を確保するため、原料粉末における部分拡散合金粉の割合は５０質量％以上にするのが好ましい。また、この場合、原料粉末中の固体潤滑剤粉の配合割合は０．３〜１．５質量％が適量である。さらに原料粉末における低融点金属粉の配合割合は０．５〜５．０質量％とする。この配合割合は原料粉末中における銅粉の総量（部分拡散合金粉中の銅粉と別途添加された単体銅粉の和）の１０質量％程度に設定するのが好ましい。原料粉末の残部が単体鉄粉もしくは単体銅粉（あるいは双方の単体粉）、および不可避的不純物で形成されることになる。 For example, the case where all the iron structure and copper structure of the sintered bearing 4 are formed only by the partial diffusion alloy powder has been described. However, one or both of the single iron powder and the single copper powder are added to the raw material powder, and the powder is added. A part of the iron structure or the copper structure can also be formed of a single iron powder or a single copper powder. In this case, in order to secure the minimum wear resistance, strength, and sliding characteristics, the ratio of the partial diffusion alloy powder in the raw material powder is preferably 50% by mass or more. Further, in this case, the appropriate amount of the solid lubricant powder in the raw material powder is 0.3 to 1.5% by mass. Further, the blending ratio of the low melting point metal powder in the raw material powder is 0.5 to 5.0% by mass. This blending ratio is preferably set to about 10% by mass of the total amount of copper powder in the raw material powder (the sum of the copper powder in the partial diffusion alloy powder and the single copper powder added separately). The balance of the raw material powder will be formed by elemental iron powder or elemental copper powder (or both elemental powders), and unavoidable impurities.
かかる構成では、単体鉄粉や単体銅粉の配合量を変更することにより、部分拡散合金粉を使用することで得られる耐摩耗性、高強度、および良好な摺動特性を維持しつつ、軸受特性を調整することが可能となる。例えば単体鉄粉を添加すれば、部分拡散合金粉の使用量減による低コスト化を図りつつ軸受の耐摩耗性を高めることができ、単体銅粉を添加すれば摺動特性をさらに改善することができる。そのため、各種用途に適合した焼結軸受の開発コストを低廉化することができ、焼結軸受の多品種少量生産にも対応可能となる。 In such a configuration, by changing the blending amount of the elemental iron powder or the elemental copper powder, the bearing can maintain the wear resistance, high strength, and good sliding characteristics obtained by using the partial diffusion alloy powder. It is possible to adjust the characteristics. For example, if elemental iron powder is added, the wear resistance of the bearing can be improved while reducing the cost by reducing the amount of partial diffusion alloy powder used, and if elemental copper powder is added, the sliding characteristics can be further improved. Can be done. Therefore, the development cost of the sintered bearing suitable for various applications can be reduced, and it is possible to cope with the high-mix low-volume production of the sintered bearing.
また、圧粉体４’を圧縮成形する際には、成形金型２０および原料粉末１０の少なくとも一方を加熱した状態で圧粉体４’を圧縮成形する、いわゆる温間成形法や、成形金型２０の成形面（キャビティ２５の画成面）に潤滑剤を塗布した状態で圧粉体４’を圧縮成形する金型潤滑成形法を採用しても良い。このような方法を採用すれば、圧粉体４’を一層精度良く成形することができる。 Further, when the green compact 4'is compression-molded, a so-called warm molding method in which the green compact 4'is compression-molded while at least one of the molding die 20 and the raw material powder 10 is heated, or a molding die A mold lubrication molding method may be adopted in which the green compact 4'is compression-molded with the lubricant applied to the molding surface of the mold 20 (the drawing surface of the cavity 25). If such a method is adopted, the green compact 4'can be molded with higher accuracy.
さらに、軸受隙間を介して対向する焼結軸受４の軸受面４ａあるいは軸３の外周面３ａには、動圧溝等の動圧発生部を設けることもできる。このようにすれば、軸受隙間に形成される油膜の剛性を高めることができるので回転精度を一層高めることができる。 Further, a dynamic pressure generating portion such as a dynamic pressure groove may be provided on the bearing surface 4a of the sintered bearing 4 facing the bearing gap or the outer peripheral surface 3a of the shaft 3. By doing so, the rigidity of the oil film formed in the bearing gap can be increased, so that the rotation accuracy can be further improved.
１ 振動モータ
２ ハウジング
３ 軸
４ 焼結軸受
４’ 圧粉体
４” 焼結体
４ａ 軸受面
１０ 原料粉末
１１ 部分拡散合金粉
１２ 鉄粉
１３ 銅粉
１４ 錫粉（低融点金属粉）
１６ 青銅相
１７ Ｆｅ−Ｃｕ−Ｓｎ合金
２０ 成形金型
αＦｅ フェライト相
γＦｅ パーライト相
Ｍ モータ部
Ｗ 錘
1 Vibration motor 2 Housing 3 Shaft 4 Sintered bearing 4'Compact powder 4 "Sintered body 4a Bearing surface 10 Raw material powder 11 Partial diffusion alloy powder 12 Iron powder 13 Copper powder 14 Tin powder (low melting point metal powder)
16 Bronze phase 17 Fe-Cu-Sn alloy 20 Molding mold αFe ferrite phase γFe pearlite phase M Motor part W weight
Claims (15)
前記焼結軸受が、鉄を主成分とし、その次に銅を多く含む焼結体からなり、
前記焼結体がさらに低融点の元素として錫を含有し、残部を固体潤滑剤および不可避的不純物とし、
前記焼結体が、鉄粉の表面に、該鉄粉よりも小粒径でかつ平均粒径が５μｍ以上２０μｍ以下の複数の銅粉を部分拡散させてなり、銅の含有量が１０〜３０質量％の部分拡散合金粉と、前記低融点の元素の粉末と、固体潤滑剤粉とを含む原料粉末を成形し、銅の融点よりも低温で焼結して形成され、
前記焼結体の銅源として、前記部分拡散合金粉の銅粉のみが用いられたことを特徴とする振動モータ。 The shaft, the motor unit that drives the shaft to rotate, the sintered bearing that has a bearing surface on the inner circumference and supports the shaft rotatably, the weight provided on the shaft, and the sintered bearing are press-fitted and fixed to the inner circumference. It is a vibration motor that is equipped with a housing and generates vibration by eccentrically rotating the shaft with respect to the center of the bearing with a weight.
The sintered bearing is composed of a sintered body containing iron as a main component and then a large amount of copper.
The sintered body further contains tin as a low melting point element, and the balance is a solid lubricant and unavoidable impurities.
The sintered body is formed by partially diffusing a plurality of copper powders having a particle size smaller than that of the iron powder and an average particle size of 5 μm or more and 20 μm or less on the surface of the iron powder, and the copper content is 10 to 30. A raw material powder containing a mass% partial diffusion alloy powder, the low melting point element powder, and a solid lubricant powder is molded and sintered at a temperature lower than the copper melting point .
A vibration motor characterized in that only the copper powder of the partial diffusion alloy powder was used as the copper source of the sintered body .
前記焼結軸受が、鉄を主成分とし、その次に銅を多く含む焼結体からなり、The sintered bearing is composed of a sintered body containing iron as a main component and then a large amount of copper.
前記焼結体がさらに低融点の元素として錫を含有し、残部を固体潤滑剤および不可避的不純物とし、The sintered body further contains tin as a low melting point element, and the balance is a solid lubricant and unavoidable impurities.
前記焼結体が、鉄粉の表面に、該鉄粉よりも小粒径でかつ平均粒径が５μｍ以上２０μｍ以下の複数の銅粉を部分拡散させてなり、銅の含有量が１０〜３０質量％の部分拡散合金粉と、前記低融点の元素の粉末と、固体潤滑剤粉と、単体銅粉とを含む原料粉末を成形し、銅の融点よりも低温で焼結して形成され、The sintered body is formed by partially diffusing a plurality of copper powders having a particle size smaller than that of the iron powder and an average particle size of 5 μm or more and 20 μm or less on the surface of the iron powder, and the copper content is 10 to 30. A raw material powder containing a mass% partial diffusion alloy powder, the low melting point element powder, a solid lubricant powder, and a single copper powder is molded and sintered at a temperature lower than the copper melting point.
前記焼結体の銅源として、前記部分拡散合金粉の銅粉および前記単体銅粉のみが用いられたことを特徴とする振動モータ。A vibration motor characterized in that only the copper powder of the partial diffusion alloy powder and the single copper powder were used as the copper source of the sintered body.
焼結軸受が、鉄を主成分とし、その次に銅を多く含む焼結体からなり、
前記焼結体がさらに低融点の元素として錫を含有し、残部を固体潤滑剤および不可避的不純物とし、
前記焼結体が、鉄粉の表面に、該鉄粉よりも小粒径でかつ平均粒径が５μｍ以上２０μｍ以下の複数の銅粉を拡散させてなり、銅の含有量が１０〜３０質量％の部分拡散合金粉と、前記低融点の元素の粉末と、固体潤滑剤粉とを含む原料粉末を成形し、銅の融点よりも低温で焼結して形成され、
前記焼結体が、前記部分拡散合金粉の焼結で形成された鉄組織と銅組織とを有し、前記銅組織の一部が前記鉄組織に拡散しており、前記銅組織同士が前記元素で結合され、
前記焼結体の銅源として、前記部分拡散合金粉の銅粉のみが用いられたことを特徴とする振動モータ。 The shaft, the motor unit that drives the shaft to rotate, the sintered bearing that has a bearing surface on the inner circumference and supports the shaft rotatably, the weight provided on the shaft, and the sintered bearing are press-fitted and fixed to the inner circumference. It is a vibration motor that is equipped with a housing and generates vibration by eccentrically rotating the shaft with respect to the center of the bearing with a weight.
Sintered bearings consist of a sintered body containing iron as the main component and then copper as the main component.
The sintered body further contains tin as a low melting point element, and the balance is a solid lubricant and unavoidable impurities.
The sintered body is formed by diffusing a plurality of copper powders having a particle size smaller than that of the iron powder and an average particle size of 5 μm or more and 20 μm or less on the surface of the iron powder, and the copper content is 10 to 30 mass. A raw material powder containing % partial diffusion alloy powder , the low melting point element powder, and a solid lubricant powder is molded and sintered at a temperature lower than the copper melting point.
The sintered body has an iron structure and a copper structure formed by sintering the partial diffusion alloy powder , a part of the copper structure is diffused into the iron structure, and the copper structures are said to each other. Combined with elements,
A vibration motor characterized in that only the copper powder of the partial diffusion alloy powder was used as the copper source of the sintered body .
前記焼結軸受が、鉄を主成分とし、その次に銅を多く含む焼結体からなり、
前記焼結体がさらに低融点の元素として錫を含有し、残部を固体潤滑剤および不可避的不純物とし、
前記焼結体が、鉄粉の表面に、該鉄粉よりも小粒径でかつ平均粒径が５μｍ以上２０μｍ以下の複数の銅粉を部分拡散させてなり、銅の含有量が１０〜３０質量％の部分拡散合金粉と、前記低融点の元素の粉末と、固体潤滑剤粉と、単体銅粉とを含む原料粉末を成形し、銅の融点よりも低温で焼結して形成され、
前記焼結体が、前記部分拡散合金粉の焼結で形成された第一鉄組織および第一銅組織と、前記単体銅粉の焼結で形成された第二銅組織とを有し、前記第一銅組織同士が前記元素で結合され、
前記焼結体の銅源として、前記部分拡散合金粉の銅粉および前記単体銅粉のみが用いられたことを特徴とする振動モータ。 The shaft, the motor unit that drives the shaft to rotate, the sintered bearing that has a bearing surface on the inner circumference and supports the shaft rotatably, the weight provided on the shaft, and the sintered bearing are press-fitted and fixed to the inner circumference. It is a vibration motor that is equipped with a housing and generates vibration by eccentrically rotating the shaft with respect to the center of the bearing with a weight.
The sintered bearing is composed of a sintered body containing iron as a main component and then a large amount of copper.
The sintered body further contains tin as a low melting point element, and the balance is a solid lubricant and unavoidable impurities.
The sintered body is formed by partially diffusing a plurality of copper powders having a particle size smaller than that of the iron powder and an average particle size of 5 μm or more and 20 μm or less on the surface of the iron powder, and the copper content is 10 to 30. A raw material powder containing a mass% partial diffusion alloy powder , the low melting point element powder, a solid lubricant powder, and a single copper powder is molded and sintered at a temperature lower than the copper melting point.
The sintered body has a ferrous structure and a cuprous structure formed by sintering the partial diffusion alloy powder , and a cupric structure formed by sintering the elemental copper powder. The cuprous structures are bonded to each other by the element ,
A vibration motor characterized in that only the copper powder of the partial diffusion alloy powder and the single copper powder were used as the copper source of the sintered body .
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