JP6424983B2 - Iron-based sintered oil-impregnated bearing - Google Patents
Iron-based sintered oil-impregnated bearing Download PDFInfo
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- JP6424983B2 JP6424983B2 JP2018518068A JP2018518068A JP6424983B2 JP 6424983 B2 JP6424983 B2 JP 6424983B2 JP 2018518068 A JP2018518068 A JP 2018518068A JP 2018518068 A JP2018518068 A JP 2018518068A JP 6424983 B2 JP6424983 B2 JP 6424983B2
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims description 139
- 229910052742 iron Inorganic materials 0.000 title claims description 66
- 239000011148 porous material Substances 0.000 claims description 45
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 24
- 239000010949 copper Substances 0.000 claims description 23
- 230000002093 peripheral effect Effects 0.000 claims description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 12
- 229910052802 copper Inorganic materials 0.000 claims description 12
- 239000000203 mixture Substances 0.000 claims description 12
- 230000035699 permeability Effects 0.000 claims description 12
- 229910000859 α-Fe Inorganic materials 0.000 claims description 8
- 229910002804 graphite Inorganic materials 0.000 claims description 7
- 239000010439 graphite Substances 0.000 claims description 7
- 239000012535 impurity Substances 0.000 claims description 4
- 239000003921 oil Substances 0.000 description 29
- 239000010687 lubricating oil Substances 0.000 description 20
- 239000000843 powder Substances 0.000 description 16
- 239000002994 raw material Substances 0.000 description 15
- 239000002184 metal Substances 0.000 description 12
- 229910052751 metal Inorganic materials 0.000 description 12
- 238000005245 sintering Methods 0.000 description 11
- 239000002245 particle Substances 0.000 description 10
- 230000014759 maintenance of location Effects 0.000 description 9
- 238000004513 sizing Methods 0.000 description 8
- 238000012360 testing method Methods 0.000 description 6
- 239000011159 matrix material Substances 0.000 description 5
- 229910001562 pearlite Inorganic materials 0.000 description 5
- 229910045601 alloy Inorganic materials 0.000 description 4
- 239000000956 alloy Substances 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 230000001050 lubricating effect Effects 0.000 description 4
- 238000005461 lubrication Methods 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 3
- 230000006835 compression Effects 0.000 description 3
- 238000007906 compression Methods 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 3
- 239000010931 gold Substances 0.000 description 3
- 229910052737 gold Inorganic materials 0.000 description 3
- 239000000314 lubricant Substances 0.000 description 3
- 230000013011 mating Effects 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000013329 compounding Methods 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 239000002480 mineral oil Substances 0.000 description 2
- 235000010446 mineral oil Nutrition 0.000 description 2
- 239000011812 mixed powder Substances 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- XOOUIPVCVHRTMJ-UHFFFAOYSA-L zinc stearate Chemical compound [Zn+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O XOOUIPVCVHRTMJ-UHFFFAOYSA-L 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- IYRDVAUFQZOLSB-UHFFFAOYSA-N copper iron Chemical compound [Fe].[Cu] IYRDVAUFQZOLSB-UHFFFAOYSA-N 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- ALKZAGKDWUSJED-UHFFFAOYSA-N dinuclear copper ion Chemical compound [Cu].[Cu] ALKZAGKDWUSJED-UHFFFAOYSA-N 0.000 description 1
- 239000010696 ester oil Substances 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 150000002505 iron Chemical class 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000000116 mitigating effect Effects 0.000 description 1
- 229910021382 natural graphite Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical compound CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 102200082816 rs34868397 Human genes 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/02—Making ferrous alloys by powder metallurgy
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
- F16C33/02—Parts of sliding-contact bearings
- F16C33/04—Brasses; Bushes; Linings
- F16C33/06—Sliding surface mainly made of metal
- F16C33/12—Structural composition; Use of special materials or surface treatments, e.g. for rust-proofing
Description
本発明は、軸を支承するための内周面を有する鉄系焼結含油軸受に関し、特に、複写機の紙送りローラ等のような正逆に回転する軸を支承する軸受に適した鉄系焼結含油軸受に関する。 The present invention relates to an iron-based sintered oil-impregnated bearing having an inner circumferential surface for supporting a shaft, and in particular, an iron-based sintered oil bearing suitable for supporting a shaft rotating in forward and reverse directions such as a paper feed roller of a copying machine. The present invention relates to a sintered oil-impregnated bearing.
軸受には、従来から焼結合金製のものが多用されている。焼結合金は、含浸した潤滑油によって自己潤滑性を付与できる多孔質素材であるため、焼結含油軸受は、耐焼付き性と耐摩耗性が良好で、鉄や銅等を含む金属基地の焼結含油軸受が広く用いられている。近年、銅の価格が高騰しているため、鉄を主成分とする軸受のニーズが高まってきている。しかし、鉄を主成分とする軸受は、焼付き易く、また、相手部品であるシャフトを傷付け易いという欠点がある。特に、熱処理を施しておらず硬さが低いシャフトと組み合わせて、鉄を主成分とする軸受を用いる場合、上記の現象への対応が必要となる。 Conventionally, a bearing made of sintered alloy has been widely used. Since the sintered alloy is a porous material that can impart self-lubricity by means of the impregnated lubricating oil, the sintered oil-impregnated oil bearing is excellent in seizure resistance and wear resistance, and is a metal matrix containing iron, copper, etc. Oil-impregnated bearings are widely used. In recent years, as the price of copper has risen, the need for iron-based bearings has increased. However, iron-based bearings are prone to seizure and also have the disadvantage of being prone to damage to the shaft which is the mating part. In particular, when using an iron-based bearing in combination with a low-hardness shaft that has not been heat-treated, it is necessary to cope with the above phenomenon.
このような状況の下、下記特許文献1においては、鉄銅系焼結合金軸受に匹敵する耐焼付き性および相手部品への攻撃緩和性を有する鉄系焼結含油軸受が提案されている。この鉄系焼結含油軸受において、焼結合金の全体組成は、質量比で、Ｃｕ：２．０〜９．０％、Ｃ：１．５〜３．７％、残部：Ｆｅおよび不可避不純物からなる。軸受の内部は、フェライトが２０〜８５％（面積率）および残部がパーライトからなる鉄合金相中に、軸受の軸方向に対して交差する方向に延在する銅相、黒鉛相および気孔が分散する金属組織を有し、軸受面には、銅相が８〜４０％の面積率で露出する。 Under such circumstances, Patent Document 1 below proposes an iron-based sintered oil-impregnated oil bearing having seizure resistance and attack relaxation property to a counterpart part, which are comparable to iron-copper-based sintered alloy bearings. In this iron-based sintered oil-impregnated bearing, the overall composition of the sintered alloy is, by mass ratio, Cu: 2.0 to 9.0%, C: 1.5 to 3.7%, balance: Fe and unavoidable impurities Become. Inside the bearing, copper phase, graphite phase and pores extending in the direction intersecting with the axial direction of the bearing are dispersed in the iron alloy phase consisting of 20 to 85% (area ratio) of ferrite and the balance of pearlite In the bearing surface, the copper phase is exposed at an area ratio of 8 to 40%.
特許文献１の鉄系焼結軸受は、鉄銅系焼結含油軸受に匹敵する耐焼付き性および相手部品への攻撃緩和性を有すると共に、優れた耐摩耗性を有する。しかし、複写機の紙送りローラやヘッド駆動モータ等に適用すると、軸が正逆に回転し、正転及び逆転の各々における駆動時間が短いので、軸を支承する含油軸受において軸と軸受の間に良好な油膜を形成し難い。このような潤滑性の維持において厳しい動作環境にも対応が可能になるように油潤滑効果及び相手部品への攻撃緩和性が向上されれば、より広範な用途への適用が可能になる。
本発明は、経済的に有利な鉄系焼結含油軸受の油潤滑効果および相手部品への攻撃緩和性を更に向上させて、軸と軸受との間に形成される油膜の保持性に優れ、広範な用途への適用が可能な鉄系焼結含油軸受を提供することを目的とする。The iron-based sintered bearing of Patent Document 1 has excellent wear resistance as well as seizure resistance and attack relieving ability to a counterpart part comparable to that of a copper-copper-based sintered oil-impregnated bearing. However, when applied to a paper feed roller of a copying machine, a head drive motor, etc., the shaft rotates in forward and reverse directions, and the driving time in forward and reverse rotation is short. It is difficult to form a good oil film. If the oil lubrication effect and the attack mitigating property on the other part are improved so that it is possible to cope with a severe operating environment in maintaining such lubricity, application to wider applications becomes possible.
The present invention further improves the oil lubrication effect and the attack relieving property to the other parts of the economically advantageous iron-based sintered oil-impregnated bearing and is excellent in the retention of the oil film formed between the shaft and the bearing, An object of the present invention is to provide an iron-based sintered oil-impregnated bearing that can be applied to a wide range of applications.
本発明者らは、鉄系焼結含油軸受について、潤滑性の維持が難しい動作環境に対応するための検討を行った。この結果、潤滑油の供給能力を調整して、軸と含油軸受の間に油膜を維持し難い状況でも良好な潤滑特性を発揮できる含油軸受を実現し得ることを見出した。 The present inventors examined the iron-based sintered oil-impregnated oil bearing to cope with an operating environment in which it is difficult to maintain the lubricity. As a result, it has been found that it is possible to realize an oil-impregnated bearing capable of exhibiting good lubricating characteristics even in a situation where it is difficult to maintain an oil film between the shaft and the oil-impregnated bearing by adjusting the lubricating oil supply capacity.
本発明は、上記知見によるものであり、本発明の一態様によれば、鉄系焼結含油軸受は、軸を支持するための内周面を有する鉄系焼結軸受を有し、前記鉄系焼結軸受は、質量比で、２．０〜９．０％のＣｕ、０．５〜１．３％のＣ、残部のＦｅおよび不可避不純物からなる全体組成を有し、密度が５．３〜５．７Ｍｇ／ｍ3であって、通気度が７０〜２００×１０-11ｃｍ2であり、前記鉄系焼結軸受の内周面は、面積率で、８〜４０％の銅相、２５〜５５％の気孔、１〜５％の黒鉛相、および、残部の鉄基地からなり、前記鉄系焼結軸受の内周面において、全気孔の面積に対して、円相当径が７５μｍ以上である気孔が占める面積は７０％以上であり、円相当径が４５μｍ以上で７５μｍ未満である気孔が占める面積は０．１〜１０％であり、残りの面積は、円相当径が４５μｍ未満である気孔によって占められ、前記鉄基地は、面積率で２０％以上のフェライトを含む金属組織構造を有することを要旨とする。 The present invention is based on the above findings, and according to one aspect of the present invention, an iron-based sintered oil-impregnated bearing has an iron-based sintered bearing having an inner circumferential surface for supporting a shaft, the iron The sintered base bearing has an overall composition consisting of 2.0 to 9.0% of Cu, 0.5 to 1.3% of C, the balance of Fe and unavoidable impurities in mass ratio, and the density is 5.%. 3 to 5.7 Mg / m 3 , air permeability is 70 to 200 × 10 −11 cm 2 , and the inner peripheral surface of the iron-based sintered bearing has an area ratio of 8 to 40% of copper phase And 25 to 55% of pores, 1 to 5% of graphite phase, and the remaining iron base, and on the inner peripheral surface of the iron-based sintered bearing, the circle equivalent diameter is 75 μm with respect to the area of all pores. The area occupied by the above-described pores is 70% or more, and the area occupied by the pores having a circle equivalent diameter of 45 μm or more and less than 75 μm is 0.1 to 10%, Rino area is occupied by pore circle equivalent diameter is less than 45 [mu] m, wherein the iron base is summarized in that the area ratio with a metal structure structure containing 20% or more of ferrite.
鉄系焼結含油軸受の潤滑性が、厳しい動作環境においても維持可能になり、正逆に回転する軸を支承して短時間で回転動作を反転させるような油膜を維持し難い用途でも良好な潤滑特性を発揮し得る格別な効果を有するので、鉄系焼結含油軸受の適用範囲を、複写機の紙送りローラやヘッド駆動モータ等へ拡大することができる。 The lubricity of iron-based sintered oil-impregnated bearings can be maintained even in a severe operating environment, and it is also good for applications where it is difficult to maintain an oil film that supports rotating shafts in reverse and reverse rotation operation in a short time Since it has a remarkable effect that can exhibit lubricating characteristics, the application range of the iron-based sintered oil-impregnated bearing can be expanded to the paper feed roller of a copying machine, a head drive motor, and the like.
鉄系焼結含油軸受における油潤滑性および相手部品への攻撃緩和性を更に向上させる手法として、摺動面（つまり、軸受内周面）に潤滑油を供給する供給能力と、摺動面での油膜の保持性とを両立させることが肝要である。回転軸が正逆の両方に回転して正転及び逆転の駆動時間が短い動作環境においては、軸受内周面と軸との間に形成される油膜が保持し難いので、潤滑油の供給を強化するようにバランスを移行すると油膜を保持し易くなると考えられる。これに従って、潤滑油の供給能力に直結する焼結軸受の通気度および密度が特定される。更に、軸受内周面に露出する気孔の状態に着目して、内周面への潤滑油の供給と油膜保持とを両立し易い気孔径の分布が特定される。このようにして、軸受の使用環境に応じて、潤滑油の供給能力と油膜保持との両立が可能な通気度及び気孔径分布を有するように焼結軸受の金属組織構造が設計される。
［鉄系焼結含油軸受の全体組成および軸受内周面の金属組織］
本発明の鉄系焼結含油軸受は、全体組成が、質量比で、Ｃｕ：２．０〜９．０％、Ｃ：０．５〜１．３％、残部：Ｆｅおよび不可避不純物からなる鉄系焼結軸受を主体として有する。鉄系焼結軸受は、鉄粉、銅粉及び炭素粉を上記組成割合で混合し、必要に応じてステアリン酸塩等の成形潤滑剤を配合して混合粉末を用意し、これを成形用の原料粉末として用いて軸受の形状に圧粉成形して、成形した圧粉体を焼結することによって得られる。鉄系焼結軸受に潤滑油を含浸させて得られる鉄系焼結含油軸受は、内周面において回転軸を支持して軸受けとして機能する。As a method to further improve the oil lubricity and attack relieving property of the iron-based sintered oil-impregnated bearing, the supply ability to supply lubricating oil to the sliding surface (that is, the inner peripheral surface of the bearing) and the sliding surface It is important to make it compatible with the oil film retention of In an operating environment where the rotating shaft rotates in both forward and reverse directions and the forward and reverse drive time is short, the oil film formed between the bearing inner circumferential surface and the shaft is difficult to hold, so supply of lubricating oil It is thought that shifting the balance to strengthen the oil film makes it easier to hold the oil film. In accordance with this, the air permeability and density of the sintered bearing that is directly linked to the lubricating oil supply capacity are identified. Furthermore, focusing on the state of the pores exposed on the bearing inner circumferential surface, the distribution of the pore diameter that easily achieves both the supply of the lubricating oil to the inner circumferential surface and the oil film retention is specified. In this way, the metallographic structure of the sintered bearing is designed to have the air permeability and the pore size distribution that can achieve both the lubricating oil supply capability and the oil film retention, depending on the use environment of the bearing.
[Overall composition of iron-based sintered oil-impregnated oil bearing and metallographic structure of inner surface of bearing]
In the iron-based sintered oil-impregnated bearing of the present invention, the entire composition is, in mass ratio, Cu: 2.0 to 9.0%, C: 0.5 to 1.3%, balance: iron and unavoidable impurities Based on sintered bearings. Iron-based sintered bearings are prepared by mixing iron powder, copper powder and carbon powder in the above composition ratio, compounding a forming lubricant such as stearate as required, and preparing a mixed powder. It is obtained by compacting the raw material powder into the shape of a bearing and sintering the formed green compact. The iron-based sintered oil-impregnated bearing obtained by impregnating the iron-based sintered bearing with the lubricating oil supports the rotary shaft on the inner circumferential surface and functions as a bearing.
鉄系焼結軸受は、鉄基地によって構成され、鉄基地は、フェライト相とパーライト相の混合組織構造またはフェライトの単相組織構造である。鉄系焼結軸受において、鉄基地中にパーライト相よりも硬さの低いフェライト相が多く分散すると、相手部品の攻撃を緩和する上で有利である。この観点から、本発明においては、鉄系焼結軸受の鉄基地におけるフェライト相の面積率が２０％以上となるように、原料粉末調製時の配合によって焼結軸受の組成を上記の範囲に調整する。鉄基地の原料である鉄粉として還元鉄粉が用いられ、７５〜１５０μｍ程度の平均粒径のものが良好に使用され、特に１００μｍ程度のものが好適である。 The iron-based sintered bearing is constituted by an iron base, and the iron base is a mixed structure structure of a ferrite phase and a pearlite phase or a single phase structure of ferrite. In the iron-based sintered bearing, if a large amount of ferrite phase having a hardness lower than that of the pearlite phase is dispersed in the iron base, it is advantageous for alleviating the attack of the mating part. From this point of view, in the present invention, the composition of the sintered bearing is adjusted to the above range by the compounding at the time of preparation of the raw material powder so that the area ratio of the ferrite phase in the iron base of the iron based sintered bearing is 20% or more. Do. As iron powder which is a raw material of iron base, reduced iron powder is used, one having an average particle diameter of about 75 to 150 μm is favorably used, and one having about 100 μm is particularly preferable.
Ｃｕ（銅）は、焼結時に軟質な銅相として鉄基地中に分散して、鉄系焼結含油軸受の馴染み性、相手材攻撃性の緩和に寄与する。しかし、全体組成中のＣｕ量が増加すると、その分、原料コストが増加する。このため、本発明の鉄系焼結含油軸受においては、軸受の内周面付近に銅粉末が集中するように、圧粉体の成形に関して前記特許文献１の技術を利用する。具体的には、Ｃｕを扁平状の銅粉の形態で導入することによって、原料粉末がダイキャビティ内を落下する際に、コアロッドの周囲に扁平状の銅粉がまとわり付いて、コアロッドに銅粉が張り付いた状態となる。従って、ダイキャビティ内の原料粉末を圧粉成形すると、圧粉体の内周面に銅粉が集中的に存在する。つまり、Ｃｕ原料として扁平状の銅粉を用いると、原料粉末に含まれるＣｕ量が少なくても、軸受内周面に露出する銅相の量を確保することが可能である。従って、全体組成中のＣｕ量が少なくても、摺動特性が求められる軸受内周面に露出する銅相の量が軸受内部に比べて多くなるので、軸受内部及び全体組成中のＣｕ量を削減して原料費用を抑制しつつ銅による馴染み性を享受することができる。このように、特許文献１の技術を利用することにより、鉄系焼結軸受の全体組成中のＣｕ量が質量比で２．０〜９．０％であっても、内周面においては、銅相が内周面全体に対して面積率で８〜４０％の範囲となるように、鉄系焼結含油軸受を調製することができる。扁平状の銅粉は、粒径が２０〜１５０μｍ程度のものを好適に用いることができる。粒径が小さい銅粉は、鉄粒子間の間隙に入り易く、過大な銅粉は、コアロッド周囲に遍在し難くなる。粒子径と厚さとの比は、２．５〜２０程度であると好適である。 Cu (copper) is dispersed in the iron base as a soft copper phase at the time of sintering, and contributes to the compatibility of the iron-based sintered oil-impregnated bearing and the alleviation to the attack of the mating material. However, when the amount of Cu in the overall composition increases, the cost of the raw material correspondingly increases. For this reason, in the iron-based sintered oil-impregnated bearing of the present invention, the technology of Patent Document 1 is used for forming a green compact so that the copper powder is concentrated in the vicinity of the inner peripheral surface of the bearing. Specifically, by introducing Cu in the form of a flat copper powder, the flat copper powder wraps around the core rod when the raw material powder falls in the die cavity, and It will be in the state where copper powder stuck. Therefore, when the raw material powder in the die cavity is compacted, copper powder is intensively present on the inner peripheral surface of the green compact. That is, when flat copper powder is used as the Cu raw material, even if the amount of Cu contained in the raw material powder is small, it is possible to secure the amount of the copper phase exposed on the inner peripheral surface of the bearing. Therefore, even if the amount of Cu in the overall composition is small, the amount of copper phase exposed on the inner surface of the bearing where the sliding characteristics are required is larger than that in the bearing. It is possible to enjoy the familiarity with copper while reducing the raw material cost by reducing it. Thus, by utilizing the technology of Patent Document 1, even if the amount of Cu in the overall composition of the iron-based sintered bearing is 2.0 to 9.0% by mass ratio, on the inner circumferential surface, The iron-based sintered oil-impregnated bearing can be prepared such that the area ratio of the copper phase to the entire inner circumferential surface is 8 to 40%. As the flat copper powder, one having a particle diameter of about 20 to 150 μm can be suitably used. Copper powder having a small particle size is likely to enter the interstices between iron particles, and excessive copper powder is less likely to be ubiquitous around the core rod. The ratio of particle diameter to thickness is preferably about 2.5 to 20.
Ｃ(炭素）は、焼結時に一部が鉄基地に拡散して鉄基地中のパーライト相の形成に寄与し、残部は固体潤滑剤として機能しつつ遊離黒鉛相として金属組織中（主として気孔中）に分散し、内周面において軸との摩擦を緩和する。この効果を得るため、軸受内周面に露出する黒鉛相の量が内周面に対する面積率で１％以上になるように、全体組成におけるＣ量は０．５質量％以上に設定される。一方、複写機等の紙送りローラやプリンタヘッド駆動モータ等においては、支承する軸が正逆両方に回転して正転及び逆転の各駆動時間が短く、このような用途においては、軸との摩擦によって軸受内周面から黒鉛が脱落し易い。故に、軸受内周面に露出する黒鉛相の量が軸受内周面に対する面積率で５％以下になるように、全体組成におけるＣ量を１．３質量％以下に制限する。平均粒径が４０〜８０μｍ程度の黒鉛粉末を使用すると、基地への拡散や摺動特性等の点において好適である。 C (carbon) partially diffuses to the iron matrix during sintering to contribute to the formation of the pearlite phase in the iron matrix, and the remaining portion functions as a solid lubricant and as a free graphite phase in the metal structure (mainly in the pores) To disperse the friction with the shaft on the inner circumferential surface. In order to obtain this effect, the amount of C in the overall composition is set to 0.5 mass% or more so that the amount of the graphite phase exposed to the inner peripheral surface of the bearing is 1% or more in area ratio to the inner peripheral surface. On the other hand, in a paper feed roller such as a copying machine, a printer head drive motor, etc., the supporting shaft rotates in both forward and reverse directions, and each driving time of forward rotation and reverse rotation is short. Graphite is likely to fall off the bearing inner circumferential surface due to friction. Therefore, the amount of C in the entire composition is limited to 1.3 mass% or less so that the amount of the graphite phase exposed to the bearing inner circumferential surface is 5% or less in area ratio to the bearing inner circumferential surface. Use of a graphite powder having an average particle diameter of about 40 to 80 μm is preferable in terms of diffusion to a base, sliding characteristics, and the like.
上述のように調製した原料粉末をダイキャビティ内で軸受の形状に圧粉成形して得られる圧粉体を焼結することによって、鉄系焼結軸受が得られる。焼結温度は、９５０〜１０３０℃程度に設定することが好ましく、焼結温度が低いと、鉄基地中のフェライトの量が過剰になって硬さが不足し、軸受として用いた時の摩耗量が増加する。焼結温度が高いと、パーライトの量が増えて過度に硬くなり、軸受として用いた時の軸の摩耗量が増加して、軸受自体の摩耗量も増加する。焼結雰囲気ガスとしては、水素／窒素混合ガス、分解アンモニアガス、変成ガスなどの非酸化性ガスが用いられる。得られた鉄系焼結軸受は、適宜サイジングを施して潤滑油を含浸させることによって、鉄系焼結含油軸受を得ることができる。
［鉄系焼結軸受の密度および通気度］
焼結含油軸受は、焼結軸受の通気度（permeability、単位：１Ｄ(darcy)≒１０-12ｍ2＝１０-8ｃｍ2）が高いほど、潤滑油の供給能力が高くなるが、その一方で、通気度が高過ぎると、軸と軸受内周面の間に形成される油膜の圧力がリークし易くなり、保油性が悪化して良好な潤滑特性を得ることができなくなる。このため、焼結軸受の通気度は、好適な潤滑油の供給と油膜の圧力が得られるように、用途に応じて調整することが肝要である。これは、焼結軸受の密度によって調整することができる。正逆に回転する軸を支承し、正転及び逆転の各駆動時間が短い動作環境の用途においては、密度が５．３〜５．７Ｍｇ／ｍ3、通気度が７０〜２００×１０-11ｃｍ2の範囲になるように焼結軸受を調製するとよい。焼結軸受の密度は、成形用キャビティに投入する原料粉末の充填量を変化させて圧粉成形時の圧縮率を調整することによって、所望の値に調節することができる。An iron-based sintered bearing is obtained by sintering a green compact obtained by compacting the raw material powder prepared as described above into a bearing shape in a die cavity. The sintering temperature is preferably set to about 950 to 1030 ° C. When the sintering temperature is low, the amount of ferrite in the iron base becomes excessive and the hardness is insufficient, and the amount of wear when used as a bearing Will increase. When the sintering temperature is high, the amount of pearlite increases and the material becomes excessively hard, and the amount of wear of the shaft when used as a bearing increases and the amount of wear of the bearing itself also increases. As a sintering atmosphere gas, a non-oxidizing gas such as a hydrogen / nitrogen mixed gas, a decomposition ammonia gas, or a conversion gas is used. The iron-based sintered oil-impregnated bearing can be obtained by appropriately sizing the obtained iron-based sintered bearing and impregnating the lubricating oil.
[Density and air permeability of iron-based sintered bearings]
In sintered oil-impregnated bearings, the higher the air permeability of sintered bearings (unit: 1D (darcy) 10 10 -12 m 2 = 10 -8 cm 2 ), the higher the lubricating oil supply capacity, but on the other hand However, if the air permeability is too high, the pressure of the oil film formed between the shaft and the inner circumferential surface of the bearing tends to leak, and the oil retention deteriorates, making it impossible to obtain good lubricating characteristics. For this reason, it is important to adjust the air permeability of the sintered bearing according to the application so as to obtain a suitable lubricating oil supply and oil film pressure. This can be adjusted by the density of the sintered bearing. For applications in operating environments that support rotating shafts in forward and reverse directions and short forward and reverse drive times, the density is 5.3 to 5.7 Mg / m 3 and the air permeability is 70 to 200 × 10 -11 The sintered bearing may be prepared to be in the range of cm 2 . The density of the sintered bearing can be adjusted to a desired value by changing the filling amount of the raw material powder charged into the molding cavity to adjust the compression ratio at the time of compacting.
正逆に回転する軸を支承し、正転及び逆転の各駆動時間が短い動作環境の用途における潤滑特性をさらに向上させるには、軸受内周面に形成される気孔が、軸受内周面に対する面積率で２５〜５５％であるように焼結軸受を調製することが好ましい。このために、原料として使用する粉末の粒度分布の調整、及び、焼結後の最終圧縮加工（サイジング、コイニング）を利用することができ、最終圧縮加工によって表面に開口する気孔を縮小することができる。 In order to further improve the lubrication characteristics in operating environment applications in which the forward and reverse rotating shafts are supported and the forward and reverse drive times are short, pores formed in the inner circumferential surface of the bearing against the inner circumferential surface of the bearing The sintered bearing is preferably prepared to have an area ratio of 25 to 55%. For this purpose, adjustment of the particle size distribution of the powder used as a raw material, and final compression processing (sizing, coining) after sintering can be used to reduce pores opened on the surface by final compression processing. it can.
［鉄系焼結含油軸受の気孔の大きさ及びその量］
上記の密度および通気度とも関連するが、鉄系焼結含油軸受において、大きな気孔は潤滑油の供給能力に寄与するが、同時に、保油性においては不利に作用し、良好な潤滑特性の維持が難しくなる。一方、鉄基地中に分散する小さな気孔は、軸受内周面における含油能力を高め、軸と軸受内周面に形成される油膜の保油性向上に寄与する。[Size and amount of pores in iron-based sintered oil-impregnated bearings]
Although related to the above density and air permeability, in iron-based sintered oil-impregnated bearings, large pores contribute to the ability to supply lubricating oil, but at the same time adversely affect oil retention and maintain good lubricating properties. It becomes difficult. On the other hand, the small pores dispersed in the iron matrix enhance the oil-retaining ability on the inner circumferential surface of the bearing, and contribute to the improvement of the oil retention of the oil film formed on the shaft and the inner circumferential surface of the bearing.
この観点から、本発明の鉄系焼結含油軸受においては、潤滑油の供給のための大きな気孔の量と、鉄基地中に分散する小さな気孔の量を調整して、潤滑油の供給能力と保油性のバランスをとることが好ましい。この点に関し、本発明では、気孔の大きさを円相当径（面積円相当径：Heywood径）によって評価する。円相当径は、測定される面積と等しい面積を有する真円に変換した時の真円の直径であり、光学顕微鏡によって観察した画像に基づいて、市販の画像分析ソフトウエアを用いて決定することができる。具体的には、大きな気孔、すなわち、円相当径が７５μｍ以上である気孔が、軸受内周面に露出する気孔全体の面積に対して７０％以上となり、残部の気孔は、小さい気孔、すなわち、円相当径が７５μｍ未満の気孔であることが好ましい。 From this point of view, in the iron-based sintered oil-impregnated bearing of the present invention, the amount of large pores for supplying the lubricating oil and the amount of small pores dispersed in the iron matrix are adjusted to provide the lubricating oil supply capability and It is preferable to balance the oil retention. In this regard, in the present invention, the size of the pores is evaluated by the circle equivalent diameter (area circle equivalent diameter: Heywood diameter). The equivalent circle diameter is the diameter of a true circle when converted to a true circle having an area equal to the area to be measured, and is determined using commercially available image analysis software based on an image observed by an optical microscope. Can. Specifically, large pores, ie, pores having a circle equivalent diameter of 75 μm or more, account for 70% or more of the area of the entire pores exposed on the bearing inner circumferential surface, and the remaining pores are small pores, ie, It is preferable that the pores have an equivalent circle diameter of less than 75 μm.
本発明の鉄系焼結含油軸受において、鉄系焼結含油軸受は、円相当径が７５μｍ以上である気孔が気孔全体の面積に対して７０％以上を占め、円相当径が４５μｍ以上且つ７５μｍ未満である気孔が気孔全体の面積に対して０．１〜１０％を占め、残部の気孔面積を円相当径が４５μｍ未満である気孔が占めることが好ましい。
鉄系焼結軸受に含浸する潤滑油は、用途及び動作環境を勘案して各種潤滑油から適宜選択して使用することができ、例えば、鉱物油、合成炭化水素油、エステル油などから１種又は２種以上を組み合わせて使用して良い。概して、ＩＳＯ粘度グレードがＶＧ５０〜１５０の潤滑油が好適に用いられる。In the iron-based sintered oil-impregnated bearing of the present invention, in the iron-based sintered oil-impregnated bearing, the pores having a circle equivalent diameter of 75 μm or more occupy 70% or more of the area of the whole pores, and the circle equivalent diameter is 45 μm or more and 75 μm It is preferable that the pores having less than the area occupy 0.1 to 10% of the area of the whole pores, and the pores having the equivalent circle diameter be less than 45 μm.
The lubricating oil to be impregnated into the iron-based sintered bearing can be appropriately selected and used from various lubricating oils in consideration of the application and the operating environment. For example, mineral oil, synthetic hydrocarbon oil, ester oil etc. Or you may use combining 2 or more types. In general, lubricating oils of ISO viscosity grade VG 50-150 are preferably used.
以下、本発明を実施例によりさらに詳細に説明する。 Hereinafter, the present invention will be described in more detail by way of examples.
（１）軸受の作製
鉄系焼結軸受を作製するために、下記の粉末を用意した。
１．鉱石還元鉄粉（平均粒径：１００μｍ）
２．銅箔粉（平均粒径：５０μｍ）
３．天然黒鉛粉（平均粒径：６０μｍ）
４．ステアリン酸亜鉛(1) Production of Bearing In order to produce an iron-based sintered bearing, the following powder was prepared.
1. Ore reduced iron powder (average particle size: 100 μm)
2. Copper foil powder (average particle size: 50 μm)
3. Natural graphite powder (average particle size: 60 μm)
4. Zinc stearate
上記の鉄粉末９３．５質量部に、銅粉５質量部、黒鉛粉１．５質量部を添加し、これらを合わせた１００質量部の混合粉末に対して、成形潤滑剤としてステアリン酸亜鉛粉末０．６質量部を添加して混合することにより、原料粉末を用意した。 5 parts by mass of copper powder and 1.5 parts by mass of graphite powder were added to 93.5 parts by mass of the above iron powder, and zinc stearate powder as a forming lubricant was used with respect to 100 parts by mass of the mixed powder Raw material powder was prepared by adding and mixing 0.6 mass part.
上記原料粉末を、円管形状のキャビティに投入して、円筒形の内周面を有する円管状の圧粉体に圧縮成形し、得られた圧粉体の焼結およびサイジングを行って、鉄系焼結軸受を得た。焼結は、分解アンモニアガス雰囲気中、１０００℃に加熱して行い、サイジングは、通常の方法により、内周面において塑性流動による封孔が進まない程度に行った。なお、５．１〜５．９Ｍｇ／ｍ３の範囲で密度が異なる同一寸法の焼結軸受を作成するために、軸受の密度の中央値を５．５Ｍｇ／ｍ３とし、有効多孔率の中央値を２９％とする条件に基づいて、成形時の加圧動作を設定し、表1に示す密度になるように、キャビティへ充填する原料粉末の量を調整して、試料番号１〜４の焼結含油軸受を作製した。また、試料番号６〜１４の焼結含油軸受試料は、軸受の密度は５．５Ｍｇ／ｍ３一定とし、サイジング時に軸受の内径へのサイジングピンの当て代を変えて作製した。各試料番号について、測定用及び試験用に複数の焼結軸受試料を作製した。
そして、焼結軸受の気孔に潤滑油（鉱物油 粘度グレードＩＳＯ ＶＧ６８）を含浸させて、試料番号１〜１４の焼結含油軸受試料を得て、試験用試料として以下の試験に用いた。The raw material powder is charged into a circular tube-shaped cavity, compression-molded into a cylindrical tubular green compact having a cylindrical inner peripheral surface, and sintering and sizing of the obtained green compact are carried out to obtain iron. The system sintered bearing was obtained. Sintering was performed by heating to 1000 ° C. in a decomposition ammonia gas atmosphere, and sizing was performed by an ordinary method to such an extent that sealing by plastic flow did not proceed on the inner peripheral surface. In order to density in a range of 5.1~5.9Mg / m 3 to create a sintered bearing different identical sizes, the median of the density of the bearing and 5.5 mg / m 3, the center of the effective porosity The pressing operation at the time of molding is set based on the condition that the value is 29%, and the amount of the raw material powder to be filled in the cavity is adjusted to obtain the density shown in Table 1, A sintered oil-impregnated bearing was made. The sintered oil-impregnated bearing samples of sample numbers 6 to 14 were prepared with the density of the bearings kept constant at 5.5 Mg / m 3 and the sizing allowance of the inner diameter of the bearings was changed at the time of sizing. For each sample number, a plurality of sintered bearing samples were prepared for measurement and testing.
Then, the pores of the sintered bearing were impregnated with lubricating oil (mineral oil viscosity grade ISO VG68) to obtain sintered oil-impregnated bearing samples of sample numbers 1 to 14, and used as test samples in the following test.
（２）評価
各試料番号について、サイジング前の焼結体の通気度を測定し、サイジング後に軸受を軸方向に分割して、内周面を光学顕微鏡により観察し、画像分析ソフトウエア（イノテック株式会社製Quick Grain Standard Video）を用いて、内周面の画像から気孔の面積率を求めた。更に、画像中の各気孔について、各気孔の面積から円相当径を算出し、算出した円相当径に基づいて気孔の分布割合を決定した。
また、試験用の焼結含油軸受試料を、軸方向が水平になるようにハウジングに取り付けた。更に、モータを回転軸が水平になるように設置して、高周波焼き入れした炭素鋼Ｓ４５Ｃ製のシャフトをモータの回転軸に取り付けた。このシャフトを、ハウジングに取り付けた焼結含油軸受試料の内径に隙間を持たせて挿入し、ハウジングに鉛直方向の荷重を与えた状態でシャフトを正逆回転させて軸受試験を行った。軸受試験では、シャフトの回転数を３０００ｒｐｍとし、負荷面圧を１ＭＰａとして２０分の運転を行い、運転終了後の摩擦係数を測定した。試料番号１〜４の焼結含油軸受試料の評価結果を表１に、試料番号５〜１４の焼結含油軸受試料の評価結果を表２に示す。(2) Evaluation For each sample number, measure the air permeability of the sintered body before sizing, divide the bearing in the axial direction after sizing, observe the inner peripheral surface with an optical microscope, image analysis software (Inotech Co., Ltd. The area ratio of the pores was determined from the image of the inner peripheral surface using a company-made Quick Grain Standard Video). Furthermore, for each pore in the image, the circle equivalent diameter was calculated from the area of each pore, and the pore distribution ratio was determined based on the calculated circle equivalent diameter.
In addition, a sintered oil-impregnated bearing sample for test was attached to the housing so that the axial direction was horizontal. Furthermore, the motor was installed so that the rotating shaft was horizontal, and a shaft made of induction hardened carbon steel S45C was attached to the rotating shaft of the motor. The shaft was inserted into the sintered oil-impregnated bearing sample attached to the housing with a clearance, and the load was applied to the housing in the vertical direction, and the shaft was rotated forward and reverse to conduct a bearing test. In the bearing test, the rotational speed of the shaft was 3000 rpm, the load surface pressure was 1 MPa, and the operation was performed for 20 minutes, and the coefficient of friction after the operation was measured. The evaluation results of the sintered oil-impregnated bearing samples of sample numbers 1 to 4 are shown in Table 1, and the evaluation results of the sintered oil-impregnated bearing samples of sample numbers 5 to 14 are shown in Table 2.
表１の試料番号１〜４の焼結含油軸受試料の結果より、試料番号２、３の焼結含油軸受試料は、いずれも摩擦係数が０．１１〜０．１２の低い範囲に収まり、金属接触の発生が防止されている。これに対し、試料番号１および４の焼結含油軸受試料は、いずれも０．１６以上となっており、金属接触が発生しているものと考えられる。つまり、試料番号２，３においては、潤滑油の供給と油膜保持のバランスが良好であると言える。従って、密度を５．３〜５．７Ｍｇ／ｍ３、通気度を７０〜２００×１０−１１ｃｍ２の範囲に設定することで、金属接触の発生を抑制し、摩擦係数を低減することができる。From the results of the sintered oil-impregnated bearing samples of sample numbers 1 to 4 in Table 1, the sintered oil-impregnated bearing samples of sample numbers 2 and 3 all have friction coefficients falling within a low range of 0.11 to 0.12, and metals The occurrence of contact is prevented. On the other hand, the sintered oil-impregnated bearing samples of sample numbers 1 and 4 are all 0.16 or more, and it is considered that metal contact occurs. That is, in sample numbers 2 and 3, it can be said that the balance between the supply of lubricating oil and the holding of the oil film is good. Therefore, by setting the density in the range of 5.3 to 5.7 Mg / m 3 and the air permeability in the range of 70 to 200 × 10 −11 cm 2 , the occurrence of metal contact can be suppressed and the coefficient of friction can be reduced. it can.
表２の試料番号５〜８の焼結含油軸受試料の結果より、試料番号６、７の焼結含油軸受試料は、いずれも摩擦係数が０．１２〜０．１３の低い範囲に収まり、金属接触の発生が防止されているが、試料番号５および８の焼結含油軸受試料は、いずれも０．１７以上となっており、金属接触が発生しているものと考えられる。このように気孔の面積率が２５〜５５％の範囲にある焼結軸受では、潤滑油の供給及び油膜保持が良好であり、金接接触の発生が好適に抑制され、摩擦係数を低減することができる。 According to the results of the sintered oil-impregnated bearing samples of sample numbers 5 to 8 in Table 2, the sintered oil-impregnated bearing samples of sample numbers 6 and 7 all have friction coefficients falling within a low range of 0.12 to 0.13, and metals Although the occurrence of the contact is prevented, it is considered that the sintered oil-impregnated bearing samples of sample Nos. 5 and 8 both have a value of 0.17 or more, and metal contact has occurred. Thus, in the sintered bearing having the area ratio of pores in the range of 25 to 55%, the supply of lubricating oil and the retention of the oil film are good, and the occurrence of the gold contact is suitably suppressed to reduce the friction coefficient. Can.
表２の試料番号９〜１０の焼結含油軸受試料の結果より、試料番号１０の焼結含油軸受試料は、摩擦係数が０．１３と低く、金属接触の発生が防止されているが、試料番号０９の焼結含油軸受試料は、０．１７となっており、金属接触が発生しているものと考えられる。このように、内周面において円相当径が７５μｍ以上の大きい気孔が面積率で全気孔の７０％以上を占める焼結軸受では、金接接触の発生が好適に抑制され、摩擦係数を低減することができる。 From the results of the sintered oil-impregnated bearing samples of sample Nos. 9 to 10 in Table 2, the sintered oil-impregnated bearing sample of sample No. 10 has a low coefficient of friction of 0.13 and the occurrence of metal contact is prevented, but the samples The sintered oil-impregnated bearing sample of No. 09 is 0.17, and it is considered that metal contact occurs. Thus, in the sintered bearing in which the large pores having a circle equivalent diameter of 75 μm or more occupy 70% or more of the total pores in the inner peripheral surface in the area ratio, the generation of the gold contact is suitably suppressed and the friction coefficient is reduced. be able to.
表２の試料番号１１〜１４の結果より、試料番号１２および１３の焼結含油軸受試料は、摩擦係数が０．１２〜０．１３と低くなっており、金属接触の発生が防止されているが、試料番号１１および１４の焼結含油軸受試料は、０．１６と高くなっており、金属接触が発生しているものと考えられる。このように、円相当径が４５〜７５μｍの中程度の大きさの気孔が、面積率で、全気孔の０．１〜１０％を占める焼結軸受では、金接接触の発生が好適に抑制され、摩擦係数を低減することができる。 From the results of sample numbers 11 to 14 in Table 2, the sintered oil-impregnated bearing samples of sample numbers 12 and 13 have a low coefficient of friction of 0.12 to 0.13, and the occurrence of metal contact is prevented However, the sintered oil-impregnated bearing samples of sample numbers 11 and 14 are as high as 0.16, and it is considered that metal contact is occurring. Thus, in the sintered bearing in which the medium-sized pores having a circle-equivalent diameter of 45 to 75 μm occupy 0.1 to 10% of the total pores in terms of area ratio, the occurrence of gold contact is suitably suppressed And the coefficient of friction can be reduced.
正逆に回転する軸を支承し、短時間の駆動で反転するような、軸と含油軸受の間に良好な油膜を形成し難い用途においても、良好な潤滑特性を発揮するので、複写機等の紙送りローラや、ヘッド駆動モータ等のような厳しい動作環境で使用される軸受に適用可能である。 It exhibits good lubrication characteristics even in applications where it is difficult to form a good oil film between the shaft and the oil-impregnated bearing, such as supporting a rotating shaft in forward and reverse directions and reversing in a short time drive. The present invention is applicable to bearings used in severe operating environments such as paper feed rollers of the above, and head drive motors.
Claims (1)
前記鉄系焼結軸受は、質量比で、２．０〜９．０％のＣｕ、０．５〜１．３％のＣ、残部のＦｅおよび不可避不純物からなる全体組成を有し、密度が５．３〜５．７Ｍｇ／ｍ3であって、通気度が７０〜２００×１０-11ｃｍ2であり、
前記鉄系焼結軸受の内周面は、面積率で、８〜４０％の銅相、２５〜５５％の気孔、１〜５％の黒鉛相、および、残部の鉄基地からなり、
前記鉄系焼結軸受の内周面において、全気孔の面積に対して、円相当径が７５μｍ以上である気孔が占める面積は７０％以上であり、円相当径が４５μｍ以上で７５μｍ未満である気孔が占める面積は０．１〜１０％であり、残りの面積は、円相当径が４５μｍ未満である気孔によって占められ、
前記鉄基地は、面積率で２０％以上のフェライトを含む金属組織構造を有する鉄系焼結含油軸受。 Having an iron-based sintered bearing having an inner circumferential surface for supporting the shaft;
The iron-based sintered bearing has an overall composition consisting of 2.0 to 9.0% of Cu, 0.5 to 1.3% of C, the balance of Fe and unavoidable impurities in mass ratio, and the density is 5.3 to 5.7 Mg / m 3 , and the air permeability is 70 to 200 × 10 -11 cm 2 ,
The inner peripheral surface of the iron-based sintered bearing is composed of 8 to 40% copper phase, 25 to 55% pores, 1 to 5% graphite phase, and the balance iron base in area ratio,
In the inner peripheral surface of the iron-based sintered bearing, the area occupied by pores having a circle equivalent diameter of 75 μm or more is 70% or more with respect to the area of all pores, and the circle equivalent diameter is 45 μm or more and less than 75 μm. The area occupied by the pores is 0.1 to 10%, and the remaining area is occupied by the pores whose circle equivalent diameter is less than 45 μm,
The iron-based sintered oil-impregnated bearing having a metallographic structure containing ferrite of 20% or more by area ratio.
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