JP3973074B2

JP3973074B2 - Sintered oil-impregnated bearing for electric motor and manufacturing method thereof

Info

Publication number: JP3973074B2
Application number: JP2001317713A
Authority: JP
Inventors: 元博宮坂
Original assignee: Hitachi Powdered Metals Co Ltd
Current assignee: Resonac Corp
Priority date: 2001-10-16
Filing date: 2001-10-16
Publication date: 2007-09-05
Anticipated expiration: 2021-10-16
Also published as: JP2003120674A

Description

【０００１】
【発明が属する技術分野】
この発明は、自動車等に電装される寒冷地環境で好適な電動機用焼結含油軸受及びその製造方法に関する。
【０００２】
【従来の技術】
自動車に電装される室内送風装置のフアンモータや座席駆動用モータのような電動機に使用される焼結含油軸受は、鉄系材料、銅系材料、鉄銅系材料などの選択肢の中から、鉄銅系材料が好ましいものとされている。これは銅合金の特徴である滑り特性、なじみ性、放熱性などと、鉄の特徴である比較的硬質、比較的低比重、安価などを兼ね備えているためである。このような焼結合金の鉄部分と銅部分の含有量はそれぞれ同量程度とされる。
【０００３】
【発明が解決しようとする課題】
上記した焼結含油軸受を用いた電動機は、温暖な環境下で運転したときは通常に稼働するが、例えば、零下２０℃とか零下３０℃のような寒冷地環境で運転すると、運転し始めたしばらくの間、鳴き音が発生するという問題があった。このような鳴き音の発生は、運転初期段階に摺動面の潤滑が不足している状態で起動されると、軸が振動しながら回転しているためと考えられるが、低温特性に優れていると言われている潤滑油に代えただけでは解決できなかった。また、この種の軸受には、潤滑油を蓄えておく含油フェルトを付設する構造（特開平７−２３１００１号、特開平９−１４００８５等）とされているが、軸受要素が複雑となり組立工数及び経費増となるためより簡素化したいという要望もある。
【０００４】
上述したような課題について、本発明者らは含油軸受構成等を工夫することにより解消可能なことを知見した。即ち、この発明は、低温環境で電動機を運転しても鳴き音が発生しない、含油率の比較的高い焼結含油軸受を提供することを目的としている。
【０００５】
【課題を解決するための手段】
上記目的を達成するために、この発明の電動機用焼結含油軸受は、軸受材料が焼結合金からなり、該焼結合金がＳｎ及びＰを含むＣｕ合金相とＦｅのフェライト相とが混在状態を呈した断面組織で、かつ気孔を除く合金に含める鉄粒子量が４５〜５３体積％であり、０．７質量％以下の黒鉛粒子を含有し、サイジングされた軸受内周表面に露出する鉄部の面積が２〜６％、有効多孔率２０〜３０％、及び軸受の通気度が６〜５０×１０^−１１ｃｍ^２であり、軸受内周面に粒子間或いは相の間の気孔に加えて鉄相内及び銅合金相内にも気孔が点在するとともに、気孔内には４０℃における動粘度で６１．２〜７４．８ｍｍ^２／ｓの合成油が含油されていることを特徴としている。
【０００６】
また、上記電動機用焼結含油軸受の製造方法としては、請求項２に記載のように、粒度が１４５メッシュ篩下の海綿状の還元鉄粉４２〜５０質量％、粒度が１４５メッシュ篩下で３５０メッシュ篩下のものが５０〜９０質量％である電解銅粉４１〜４３質量％、粒度が１００メッシュ篩下の箔状銅粉２〜１０質量％、錫粉１．４〜２．７質量％、Ｐ含有量が８〜９質量％のりん銅合金粉３〜５質量％、黒鉛粉０．７質量％以下、及び成形潤滑剤１質量％以下、を含む混合粉を用い、
前記混合粉を圧縮して密度５．３〜６．１ｇ／ｃｍ^３の範囲内の成形体を製作し、該成形体をりん銅合金粉が溶融する温度かつ７８０℃以下で焼結し、得られた焼結体をサイジングして密度５．８〜６．５ｇ／ｃｍ^３及び通気度６〜５０×１０^−１１ｃｍ^２のサイジング体にし、該サイジング体の気孔内に４０℃における動粘度が６１．２〜７４．８ｍｍ^２／ｓ（ｃＳｔ）の合成油を含油することを特徴としている。
【０００７】
以上の焼結含油軸受は、従来軸受の性状と摺動音等との関係について検討した次のような試験結果を基にしている。
(1)軸受の有効多孔率自身は摺動音に大きな影響を与えない。
(2)軸受焼結合金の通気度は摺動音と関係がある。通気度と騒音レベルの関係は二次関数に近似していて、通気度が高いと騒音レベルも高くなる。
(3)含油している潤滑油の量が減少すると、騒音レベルが大きくなる。この場合、潤滑油が有効多孔率の半分以下になると、その増加が極度に大きくなる。
(4)潤滑油が充分に存在していれば、青銅系の軸受でも純鉄系の軸受でも騒音レベルに差が認められない。
(5)含油している潤滑油の量が減少したときは、純鉄系軸受が青銅系軸受より騒音レベルが大きくなる。
(6)潤滑油の粘度は、比較的高い方が騒音レベルが低くなる。
【０００８】
以上のような試験結果を踏まえ、発明の焼結含油軸受の構成、及びその構成を実現するための製造方法は、経験則から下記のような技術思想として導かれる。
(1)焼結合金は、銅合金相の中に鉄粒子が分散した複合組織とする。
(2)前記の体積割合つまり断面組織での割合は、両者の中間性質となるように約１：１の組織図形とする。
(3)軸受摺動面（内周面）は、鉄粒子の露出を少なくして銅合金面を主にすることにより軸摺動の初期なじみ性を良好にできるが、耐摩耗を考慮して鉄粒子の一部を所定程度まで露出点在させる。
(4)有効多孔率は、保油能を確保するためにできるだけ高めとする。
(5)軸受摺動面の油潤滑を確保するために、軸受内周面の気孔は、粒子間或いは相の間の比較的大きい気孔に加えて鉄相内及び銅合金相内にも気孔を点在する組織とする。
(6)軸受表面の露出鉄粒子を減少させるために、鉄粒子を銅合金で適度に包み込むものとし、原料に箔状の銅粉を使用する。
(7)鉄相及び銅合金層内に気孔を形成させるために、海綿状の還元鉄粉、及び粉末粒子径が小さい粉末の量が比較的多い銅粉を使用する。
(8)銅合金相は、比較的軟質なものとし、添加元素の数及び添加量の少ない材質とする。具体的にはＳｎとＰとする。
(9)有効多孔率及び強度を確保するために液相焼結とし、低融点の錫粉とりん銅合金を用いる。
(10)摺動の際の油潤滑を補完するため、混合粉の特性、合金強度、潤滑油の汚れがでない範囲で、固体潤滑物質を焼結合金に含有させる。
(11)軸受摺動面の気孔が残存するように、サイジングする。
(12)焼結合金は、有効多孔率が比較的大きい（密度が低め）割には、鉄相内及び銅合金相内に気孔を設けた組織図形とすることにより、通気度は比較的低い状態とし、摺動による油の過剰な染み出しを抑制する。
(13)潤滑油は、低温特性、熱安定性に優れると共に高温環境にも適合する合成油を選択する。
【０００９】
具体的には下記のような構成要件を具備することにより、上述した鳴き音が発生しない焼結含油軸受を得ることができる。
１．焼結合金に占める鉄粒子
鉄粒子は、海綿状をした還元鉄粉を用いることで、粒子中にも気孔を存在させる。鉄相は結合炭素を認めない軟質なフェライト組織とする。気孔を除く合金に占める鉄粒子量は４５〜５３体積％の範囲で銅合金相に分散させ、合金の骨組みを形成させる。粗大な鉄粒子が軸受表面に露出することがないように、鉄粉の粒度は、１４５メッシュ篩下とする。ここで、鉄粒子体積量４５〜５３％は、断面組織からみた鉄粒子の分布状態及び表面に露出する状態がほぼ同じになる範囲であり、この範囲外では後述する表面露出状態が確保できなくなる。この鉄粒子体積量４５〜５３％は、全体組織では４２〜５０質量％に相当する。
【００１０】
２．焼結合金に占める銅合金相
銅合金は、適度な硬さと強度のために、Ｃｕ−Ｓｎ−Ｐ系とする。このうち、Ｓｎは、錫粉の形で添加し、焼結により溶融させ、銅に拡散させる。銅合金系におけるＳｎ含有量は、青銅系としては少な目の３〜５質量％とする。これは全体組成では１．４〜２．７質量％に相当する。Ｐはりん銅合金粉の形で添加し、焼結中に溶融させ、銅に拡散させる。りん銅合金は、Ｐ含有量が二元系状態図の共析部分である８〜９質量％を用いる。これには、ＪＩＳＨ２５０１（１９７９）りん銅地金３種（記号：８ＰＣｕ）を採用することができる。りん銅合金粉の添加量は、焼結による液相発生量を考慮して銅合金系において６〜８質量％程度とする。これは、鉄粉を含む混合粉全体では３〜５質量％に相当する。また、Ｐ含有量は、銅合金系においては０．１８〜０．４質量％、全体組成では０．２４〜０．４５質量％に相当する。
【００１１】
銅粉は電解銅粉と箔状銅粉とを用いる。前者の電解銅粉は比較的微粉（サブシーブ粉の含有量が多い粉末）を用いる。このことで焼結体の銅合金相中に微細な気孔を形成させる。このような電解銅粉の粒度は、１４５メッシュ篩下であって３５０メッシュ篩下のものが５０〜８０質量％である電解銅粉が好ましく、市販の電解銅粉では、例えば福田金属箔粉工業製ＣＥ２５及びＣＥ１５が該当する。電解銅粉の添加量は、銅粉全量４５〜５１質量％のうち約８０〜９５％である４１〜４３質量％とする。また、後者の箔状銅粉は全銅粉量のうち、重量で１／２０〜１／５（５〜２０質量％）を用いる。箔状の銅粉は摺動面に露出する銅合金相を多くする。その結果、前記した摺動面に露出する鉄粒子の面積を適度に抑える効果がある。粒度は１００メッシュ篩下のものを用いる。
【００１２】
３．軸受断面組織と軸受摺動表面の状況
軸受の断面組織は、鉄相と銅合金相が面積で約１：１の割合で混合していて、粒子間に比較的大きな気孔、各相内に比較的小さい気孔が分散している。また、表層部は、鉄粒子の一部が軸受表面に露出した状態である。サイジングされた軸受内周表面は、気孔が一般的な焼結合金と同様に金属粒子間の気孔（凹部）と、金属部の特に銅合金部に細かな気孔が観察される状態であり、摺動面の気孔の面積は約５〜２０％程度とする。また、軸受内周表面の金属面は、大部分が銅合金面で、鉄が斑点状に露出しており、鉄の露出面積は２〜６面積％とする。これは、顕微鏡で観察したとき、面積０．２ｍｍ^２の視野内に平均直径が約３０μｍの鉄が約１０〜２５個観察される状態に相当する。このような表面は、銅合金面が主体で、間隔を置いて鉄で補強した図形を呈しており、粒子間の比較的大きな気孔と共に粒子にも比較的小さい気孔が存在して、それぞれ含油機能がある状態である。
【００１３】
４．固体潤滑物質
潤滑の点からは、含浸油の潤滑を補完するために黒鉛粒子を含有させることができる。この含有量は全体組成で０．７質量％以下とする。黒鉛の含有は、油潤滑不足のときに摩擦軽減するが、多量の含有は、合金の強度を低下させ、高い有効多孔率にするのを阻害し、使用中に潤滑油中に混合すると、潤滑性能を悪くするおそれがある。
【００１４】
５．焼結温度
焼結条件は、錫粉及びりん銅合金粉が溶融する温度以上とし、焼結による密度上昇が０．１〜０．２ｇ／ｃｍ^３程度になる温度と時間とする。焼結温度は７２０〜７８０℃である。
【００１５】
６．密度、有効多孔率及び通気度
有効多孔率は、焼結合金の強度が設計値を満足すると共に、含油フェルト等の補油手段を使用しなくて済むように、含油能が多い領域とし、２０〜３０％とする。この値は密度が５．８〜６．５ｇ／ｃｍ^３に相当する。また、通気度は、原料粉に海綿状の還元鉄粉と、粒度の比較的細かい銅粉及び箔状の銅粉を用いていることにより、密度及び有効多孔率に対して、通気度合として比較的低い状態の焼結合金となる。密度５．８〜６．５ｇ／ｃｍ^３に対応する通気度は６〜５０×１０^−１１ｃｍ^２（×１０^−３ｄａｒｃｙ）である。
【００１６】
７．潤滑油
潤滑油は、低温に対応できると共に高温においても適応するような合成油とし、粘度グレードがＩＳＯＶＧ６８相当のものを用いる。これは、４０℃における動粘度が６１．２〜７４．８ｍｍ^２／ｓ（ｃＳｔ）である。この合成油は、潤滑特性、低温特性、熱安定性に優れる基油のＰＡＯ（ポリ−α−オレフイン）、及び油性向上剤であるエステルを主成分とするものが好ましい。このような合成油に該当する市販品としては、例えば、商品名アンデロール４６５（アンデロールジャパン製）、商品名オールタイムＪ−６５２（ＮＯＫクリューバ社製）等が挙げられる。
【００１７】
【実施例】
次に、発明を適用した実施例により説明する。この実施例は、上記した焼結含油軸受の製造方法及び製作された焼結含油軸受の物性について調べ、比較例と対比した例である。ここでは発明の実施例及び比較例を、混合粉末の製作、粉末成形、焼結、サイジング、含油の各処理、製作された焼結含油軸受の物性、性能試験の順に述べる。
【００１８】
１．混合粉末の製作
（実施例）
原料粉末は、下記の(1)〜(6)を使用し、混合した。各原料粉末の配合割合は質量で、鉄粉４５％、電解銅粉４４％、箔状銅粉４．５％、錫粉２％、りん銅合金粉４％、黒鉛粉０．５％である。また、成形潤滑剤であるステアリン酸亜鉛粉は追加で０．５％を添加した。
(1)鉄粉：同和鉄粉製、名称ＤＮＣ−１８０、粒度１４５メッシュ篩下
(2)電解銅粉：福田金属箔粉工業製、名称ＣＥ−２５、１４５メッシュ篩下で３５０メッシュ篩下のものが８０〜９０質量％
(3)箔状銅粉：福田金属箔粉工業製、名称Ｃｕ−Ｓ−１００、１００メッシュ篩下で３５０メッシュ篩下のものが３５〜５５質量％
(4)錫粉：日本アトマイズ加工製、名称Ｓｎ−３２５
(5)りん銅合金粉：福田金属箔粉工業製、名称８Ｐ−Ｃｕ−Ａｔ−２００
(6)黒鉛粉：日本黒鉛工業製、名称ＣＰＢ
（比較例）
原料粉末は、下記の(1)〜(4)を使用し、混合した。各原料粉末の配合割合は質量で、鉄粉４８％、電解銅粉４８％、錫粉３．５％、黒鉛粉０．５％である。また、成形潤滑剤のステアリン酸亜鉛粉は実施例と同じく追加で０．５％を添加した。
(1)鉄粉：ヘガネス製、名称ＮＣ１００−２４、粒度８０メッシュ篩下
(2)電解銅粉：福田金属箔粉工業製、名称ＣＥ−５６、８０メッシュ篩下で３５０メッシュ篩下のものが１５％
(3)錫粉：日本アトマイズ加工製、名称Ｓｎ−３２５
(4)黒鉛粉：日本黒鉛工業製、名称ＣＰＢ
【００１９】
２．粉末成形
（実施例及び比較例）前記各混合粉を金型で軸受形状に圧縮成形した。成形体密度は６．０ｇ／ｃｍ^３に設定した。
【００２０】
３．焼結
（実施例及び比較例）前記粉末成形された各圧粉成形体は、水素ガスと窒素ガスの混合ガス中、温度７６０℃で焼結した。
【００２１】
４．サイジング
（実施例及び比較例）前記各焼結体のサイジングはネガティブサイジングで行った。軸受内径金属面の塑性変形は、塑性流動による封孔が進まない程度とした。なお、発明方法としては、圧粉成形時の密度を５．３〜６．１ｇ／ｃｍ^３の範囲内に設定し、焼結によって密度５．５〜６．２ｇ／ｃｍ^３まで上昇し、サイジングによって密度５．８〜６．５ｇ／ｃｍ^３まで上げることにより、有効多孔率が２０〜３０％の範囲内となるようにすることが好ましい。
【００２２】
５．含油
（実施例及び比較例）前記各サイジング体には、含油処理として商品名アンデロール４６５（アンデロールジャパン製）を真空含浸させた。
【００２３】
６．焼結含油軸受の物性など
以上の条件で製作された実施例と比較例の各焼結含油軸受の性状は下記の通りである。
(1)密度は実施例及び比較例のもの共に６．２ｇ／ｃｍ^３であった。
(2)通気度は、実施例のものが２０×１０^−１１ｃｍ^２（×１０^−３ｄａｒｃｙ）、比較例のものが６０×１０^−１１ｃｍ^２（×１０^−３ｄａｒｃｙ）であった。
(3)有効多孔率は実施例及び比較例のもの共に２５％であった。
(4)含油率は実施例及び比較例のもの共に２５％であった。
(5)軸受内周面の金属面面積は、実施例のものが９０％であり、比較例のものが６５％であった。
(6)実施例のものは軸受内周面の露出鉄粒子の面積が３％であった。比較例のものは軸受内周面の銅合金部と鉄部の面積として、鉄部面積が金属表面の２０％であった。
(7)実施例のものは軸受内周面の露出気孔状態として、気孔面積が１０％で、金属粒子間の気孔の他に銅合金部粒子表面に小さい気孔が認められた。比較例のものは軸受内周面の露出気孔状態として、気孔面積が３５％で、金属粒子間の気孔が主で、銅合金部に気孔が少なく平滑となっていた。
【００２４】
７．電動機の低温稼働試験
評価方法は、上記の実施例と比較例の焼結含油軸受を電動機のモータシャフト軸用として装着し、該電動機を零下３０℃に冷却した後、その温度環境で運転したときに騒音発生の有無を調べた実装試験である。電動機は、シャフト軸直径８ｍｍで、滑り速度が０．８ｍ／ｓ、ＰＶ値が０．０８ＭＰａ・ｍ／ｓである。試験結果は、実施例の焼結含油軸受を用いると、鳴き音が運転初期から発生しないが、比較例の焼結含油軸受を用いると鳴き音が発生し、発明品の優位性が顕著に認められた。
【００２５】
このように、軸受構成としては、摺動面が銅合金相と鉄相及び気孔が適度に分散した状態で、有効多孔率が比較的多く、通気度が比較的低い焼結合金とし、低温特性に優れ動粘度が比較的高い潤滑油とを組み合わせることで、低温環境の運転で鳴き音を発生しない電動機用軸受要素が実現される。
【００２６】
【発明の効果】
以上説明したように、この発明は、焼結含油軸受構成及びその製造方法を工夫することにより、例えば、零下３０℃程度の寒冷地で使用される電動機の運転初期段階での鳴き音を発生させず、適用電動機の品質及び信頼性を向上することができる。[0001]
[Technical field to which the invention belongs]
The present invention relates to a sintered oil impregnated bearing for an electric motor suitable for a cold region environment electrically mounted on an automobile or the like and a method for manufacturing the same.
[0002]
[Prior art]
Sintered oil-impregnated bearings used in electric motors such as fan motors for indoor air blowers and seat drive motors that are electrically mounted on automobiles are available in iron, copper, and iron-copper materials. Copper-based materials are preferred. This is because the copper alloy has the sliding characteristics, the conformability, the heat dissipation, etc., which are the characteristics of the copper alloy, and the relatively hard, relatively low specific gravity, low cost, etc., which are the characteristics of the iron. The contents of the iron portion and the copper portion of such a sintered alloy are about the same amount.
[0003]
[Problems to be solved by the invention]
The electric motor using the sintered oil-impregnated bearing described above normally operates when operated in a warm environment. For example, when operated in a cold region such as below 20 ° C or below 30 ° C, the electric motor started to operate. There was a problem that a squeal was generated for a while. The generation of such squeals is thought to be due to the shaft rotating with vibration when it is started in the initial stage of operation when the sliding surface is insufficiently lubricated. It was not possible to solve the problem simply by replacing the lubricating oil that was said to be present. In addition, this type of bearing has an oil-impregnated felt for storing lubricating oil (JP 7-23001A, JP 9-140085, etc.). There is also a desire to simplify it because it increases costs.
[0004]
The present inventors have found that the problems described above can be solved by devising the oil-impregnated bearing configuration and the like. That is, an object of the present invention is to provide a sintered oil-impregnated bearing having a relatively high oil content that does not generate squeal even when the electric motor is operated in a low temperature environment.
[0005]
[Means for Solving the Problems]
To achieve the above object, an electric motor for oil-impregnated sintered bearing of the invention, the bearing material consists of sintered alloy, ferrite phase and the mixed-in Cu alloy phase and Fe containing said sintered alloy is Sn and P The amount of iron particles included in an alloy excluding pores is 45 to 53% by volume and contains 0.7% by mass or less of graphite particles and is exposed to the sized bearing inner peripheral surface. The area of the iron part is 2 to 6%, the effective porosity is 20 to 30%, and the air permeability of the bearing is 6 to 50 × 10 ⁻¹¹ cm ² , and pores between particles or phases are formed on the inner peripheral surface of the bearing. In addition, pores are scattered in the iron phase and the copper alloy phase, and synthetic oil having a kinematic viscosity at 40 ° C. of 61.2 to 74.8 mm ² / s is contained in the pores. It is said.
[0006]
Moreover, as a manufacturing method of the said sintered oil-impregnated bearing for electric motors, as described in Claim 2, 42-50 mass% of spongy reduced iron powder with a particle size of 145 mesh sieve, and a particle size of 145 mesh sieve Electrolytic copper powder 41-43% by mass of 50-90% by mass under 350 mesh sieve, 2-10% by mass of foil-like copper powder under 100 mesh sieve, 1.4-2.7% tin powder %, A mixed powder containing 3 to 5% by weight of phosphor copper alloy powder having a P content of 8 to 9% by weight, 0.7% by weight or less of graphite powder, and 1% by weight or less of molding lubricant,
The mixed powder is compressed to produce a molded body having a density in the range of 5.3 to 6.1 g / cm ³ , and the molded body is sintered at a temperature at which the phosphor copper alloy powder melts and 780 ° C. or less. The obtained sintered body was sized to obtain a sizing body having a density of 5.8 to 6.5 g / cm ³ and an air permeability of 6 to 50 × 10 ⁻¹¹ cm ² , and a kinematic viscosity at 40 ° C. in the pores of the sizing body. It is characterized by containing 61.2 to 74.8 mm ² / s (cSt) synthetic oil.
[0007]
The sintered oil-impregnated bearing described above is based on the following test results obtained by examining the relationship between the properties of the conventional bearing and the sliding sound.
(1) The effective porosity of the bearing itself does not significantly affect the sliding noise.
(2) The air permeability of the sintered bearing alloy is related to the sliding noise. The relationship between the air permeability and the noise level approximates a quadratic function, and the higher the air permeability, the higher the noise level.
(3) When the amount of lubricating oil is reduced, the noise level increases. In this case, when the lubricating oil becomes less than half of the effective porosity, the increase becomes extremely large.
(4) If there is enough lubricant, no difference in noise level will be observed between bronze bearings and pure iron bearings.
(5) When the amount of lubricating oil containing oil decreases, pure iron bearings have a higher noise level than bronze bearings.
(6) The higher the viscosity of the lubricating oil, the lower the noise level.
[0008]
Based on the test results as described above, the configuration of the sintered oil-impregnated bearing of the invention and the manufacturing method for realizing the configuration are derived from the empirical rule as the following technical idea.
(1) The sintered alloy has a composite structure in which iron particles are dispersed in a copper alloy phase.
(2) The volume ratio, that is, the ratio in the cross-sectional structure, is a structure figure of about 1: 1 so as to be an intermediate property between the two.
(3) The bearing sliding surface (inner peripheral surface) can improve the initial conformability of the shaft sliding by reducing the exposure of iron particles and mainly using the copper alloy surface, but considering wear resistance. Part of the iron particles are scattered to a predetermined extent.
(4) The effective porosity should be as high as possible to ensure oil retention.
(5) In order to ensure oil lubrication of the bearing sliding surface, the pores on the inner peripheral surface of the bearing have pores in the iron phase and copper alloy phase in addition to the relatively large pores between particles or phases. The organization is scattered.
(6) In order to reduce the exposed iron particles on the bearing surface, iron particles shall be appropriately wrapped with a copper alloy, and foil-like copper powder shall be used as a raw material.
(7) In order to form pores in the iron phase and the copper alloy layer, spongy reduced iron powder and copper powder having a relatively large amount of powder having a small powder particle size are used.
(8) The copper alloy phase should be relatively soft and should be made of a material with a small number and amount of additive elements. Specifically, Sn and P are assumed.
(9) Liquid phase sintering is used to ensure effective porosity and strength, and low melting point tin powder and phosphor copper alloy are used.
(10) In order to supplement oil lubrication during sliding, a solid lubricating material is included in the sintered alloy within the range where the characteristics of the mixed powder, the alloy strength, and the contamination of the lubricating oil are not present.
(11) Sizing so that the pores on the bearing sliding surface remain.
(12) Sintered alloys have a relatively low air permeability by having pores in the iron phase and copper alloy phase for a relatively large effective porosity (low density). To prevent excessive oil seepage due to sliding.
(13) For the lubricating oil, select a synthetic oil that is excellent in low temperature characteristics and thermal stability and that is compatible with high temperature environments.
[0009]
Specifically, a sintered oil-impregnated bearing that does not generate the above-described squealing noise can be obtained by having the following structural requirements.
1. Iron particles in the sintered alloy The iron particles cause pores to exist in the particles by using sponge-like reduced iron powder. The iron phase has a soft ferrite structure with no bonded carbon. The amount of iron particles in the alloy excluding pores is dispersed in the copper alloy phase in the range of 45 to 53% by volume to form an alloy framework. The particle size of the iron powder is under a 145 mesh screen so that coarse iron particles are not exposed on the bearing surface. Here, the iron particle volume of 45 to 53% is a range in which the distribution state of the iron particles viewed from the cross-sectional structure and the state exposed on the surface are substantially the same, and outside this range, the surface exposed state described later cannot be secured. . The iron particle volume of 45 to 53% corresponds to 42 to 50% by mass in the entire structure.
[0010]
2. The copper alloy phase copper alloy occupying in the sintered alloy is made of Cu-Sn-P system for appropriate hardness and strength. Of these, Sn is added in the form of tin powder, melted by sintering, and diffused into copper. The Sn content in the copper alloy system is 3 to 5% by mass, which is the smallest for the bronze system. This corresponds to 1.4 to 2.7% by mass in the total composition. P is added in the form of phosphor copper alloy powder, melted during sintering, and diffused into copper. The phosphorous copper alloy uses 8 to 9 mass% in which the P content is the eutectoid part of the binary phase diagram. For this, three types of JIS H2501 (1979) phosphor copper ingots (symbol: 8PCu) can be employed. The addition amount of the phosphor copper alloy powder is about 6 to 8% by mass in the copper alloy system in consideration of the amount of liquid phase generated by sintering. This corresponds to 3 to 5% by mass in the entire mixed powder containing iron powder. Further, the P content corresponds to 0.18 to 0.4 mass% in the copper alloy system and 0.24 to 0.45 mass% in the overall composition.
[0011]
Copper powder uses electrolytic copper powder and foil-like copper powder. The former electrolytic copper powder uses a relatively fine powder (a powder with a high content of sub-sieve powder). As a result, fine pores are formed in the copper alloy phase of the sintered body. The particle size of such electrolytic copper powder is preferably an electrolytic copper powder having a mesh size of 145 mesh sieve and 50 to 80% by mass of 350 mesh sieve. CE25 and CE15 manufactured are applicable. The addition amount of the electrolytic copper powder is 41 to 43% by mass, which is about 80 to 95% of the total copper powder of 45 to 51% by mass. Moreover, the latter foil-like copper powder uses 1 / 20-1 / 5 (5-20 mass%) by weight among the total copper powder amount. The foil-like copper powder increases the copper alloy phase exposed on the sliding surface. As a result, there is an effect of moderately suppressing the area of the iron particles exposed on the sliding surface. The particle size is 100 mesh sieve.
[0012]
3. Bearing cross-sectional structure and bearing sliding surface The cross-sectional structure of the bearing is such that the iron phase and the copper alloy phase are mixed in a ratio of about 1: 1 by area. Small pores are dispersed. Further, the surface layer portion is in a state in which some of the iron particles are exposed on the bearing surface. The sized bearing inner peripheral surface is a state in which pores are observed between metal particles (recesses) and fine pores are observed in the metal part, particularly the copper alloy part, like a general sintered alloy. The area of the pores on the moving surface is about 5 to 20%. The metal surface on the inner peripheral surface of the bearing is mostly a copper alloy surface, and iron is exposed in spots, and the exposed area of iron is 2 to 6% by area. This corresponds to a state in which about 10 to 25 irons having an average diameter of about 30 μm are observed in a visual field having an area of 0.2 mm ² when observed with a microscope. Such a surface is mainly composed of a copper alloy surface and presents a figure reinforced with iron at intervals, and there are relatively small pores in the particles as well as relatively large pores between the particles. There is a state.
[0013]
4). From the standpoint of solid lubricant lubrication, graphite particles can be included to supplement the lubrication of the impregnating oil. This content shall be 0.7 mass% or less by the whole composition. The graphite content reduces friction when oil lubrication is insufficient, but a large amount reduces the strength of the alloy and hinders high effective porosity. May degrade performance.
[0014]
5). Sintering temperature Sintering conditions are set to a temperature at which the tin powder and phosphorous copper alloy powder are melted or higher, and a temperature and time at which the density increase due to sintering is about 0.1 to 0.2 g / cm ³ . The sintering temperature is 720-780 ° C.
[0015]
6). Density, effective porosity, and air permeability Effective porosity is a region having a high oil impregnation capacity so that the strength of the sintered alloy satisfies the design value and it is not necessary to use an oil replenishing means such as an oil impregnated felt. -30%. This value corresponds to a density of 5.8 to 6.5 g / cm ³ . In addition, the air permeability is compared as the air permeability for density and effective porosity by using sponge-like reduced iron powder, relatively fine copper powder and foil-like copper powder as raw material powder. It becomes a low-temperature sintered alloy. The air permeability corresponding to the density of 5.8 to 6.5 g / cm ³ is 6 to 50 × 10 ⁻¹¹ cm ² (× 10 ⁻³ darcy).
[0016]
7). As the lubricating oil, a synthetic oil that can cope with a low temperature and can be adapted at a high temperature is used, and a viscosity grade equivalent to ISO VG 68 is used. This has a kinematic viscosity at 40 ° C. of 61.2 to 74.8 mm ² / s (cSt). This synthetic oil is preferably composed mainly of a base oil PAO (poly-α-olefin) having excellent lubrication characteristics, low-temperature characteristics and thermal stability, and an ester which is an oiliness improver. As a commercial item applicable to such a synthetic oil, brand name Anderol 465 (made by Anderol Japan), brand name all-time J-652 (made by NOK Kluuba), etc. are mentioned, for example.
[0017]
【Example】
Next, an embodiment to which the invention is applied will be described. In this example, the manufacturing method of the above-described sintered oil-impregnated bearing and the physical properties of the manufactured sintered oil-impregnated bearing were examined and compared with the comparative example. Here, examples and comparative examples of the invention will be described in the order of production of mixed powder, powder molding, sintering, sizing and oil impregnation, physical properties of the manufactured oil impregnated bearing, and performance test.
[0018]
1. Production of mixed powder (Example)
The raw material powder was mixed using the following (1) to (6). The blending ratio of each raw material powder is 45% iron powder, 44% electrolytic copper powder, 4.5% foil copper powder, 2% tin powder, 4% phosphorous copper alloy powder, and 0.5% graphite powder. . In addition, 0.5% of zinc stearate powder, which is a molding lubricant, was added.
(1) Iron powder: Dowa iron powder, name DNC-180, particle size 145 mesh under sieve
(2) Electrolytic copper powder: manufactured by Fukuda Metal Foil Powder Industry, name CE-25, under 145 mesh sieve and under 350 mesh sieve is 80-90% by mass
(3) Foil-like copper powder: manufactured by Fukuda Metal Foil Powder Industry, name Cu-S-100, 100 mesh sieve and 350 mesh sieve, 35 to 55 mass%
(4) Tin powder: manufactured by Nippon Atomizing, name Sn-325
(5) Phosphor copper alloy powder: manufactured by Fukuda Metal Foil Powder Industry, name 8P-Cu-At-200
(6) Graphite powder: manufactured by Nippon Graphite Industry, name CPB
(Comparative example)
The raw material powder was mixed using the following (1) to (4). The mixing ratio of each raw material powder is 48% iron powder, 48% electrolytic copper powder, 3.5% tin powder, and 0.5% graphite powder. Further, 0.5% of zinc stearate powder as a molding lubricant was added in the same manner as in the examples.
(1) Iron powder: Made by Höganäs, name NC100-24, particle size 80 mesh sieve
(2) Electrolytic copper powder: manufactured by Fukuda Metal Foil Powder Industry, name CE-56, 80 mesh sieve and 350 mesh sieve 15%
(3) Tin powder: manufactured by Nippon Atomizing, name Sn-325
(4) Graphite powder: manufactured by Nippon Graphite Industry, name CPB
[0019]
2. Powder Molding (Examples and Comparative Examples) Each of the mixed powders was compression molded into a bearing shape using a mold. The compact density was set to 6.0 g / cm ³ .
[0020]
3. Sintering (Examples and Comparative Examples) Each powder compact formed by powder molding was sintered at a temperature of 760 ° C. in a mixed gas of hydrogen gas and nitrogen gas.
[0021]
4). Sizing (Examples and Comparative Examples) Sizing of each sintered body was performed by negative sizing. The plastic deformation of the metal inner surface of the bearing was such that the sealing due to plastic flow did not progress. Incidentally, as an invention method sets the density during compacting in the range of 5.3~6.1g / cm ^3, raised by sintering to a density 5.5~6.2g / cm ^3, the sizing Thus, it is preferable to increase the density to 5.8 to 6.5 g / cm ³ so that the effective porosity falls within the range of 20 to 30%.
[0022]
5). Oil impregnation (Examples and Comparative Examples) Each sizing body was impregnated with a trade name Anderol 465 (manufactured by Anderol Japan) as an oil impregnation treatment.
[0023]
6). The properties of the sintered oil-impregnated bearings of Examples and Comparative Examples manufactured under the above conditions such as the properties of the sintered oil-impregnated bearing are as follows.
(1) The density was 6.2 g / cm ³ in both Examples and Comparative Examples.
(2) The air permeability was 20 × 10 ⁻¹¹ cm ² (× 10 ⁻³ darcy) in the example, and 60 × 10 ⁻¹¹ cm ² (× 10 ⁻³ darcy) in the comparative example.
(3) The effective porosity was 25% in both Examples and Comparative Examples.
(4) The oil content was 25% in both Examples and Comparative Examples.
(5) The metal surface area of the bearing inner peripheral surface was 90% in the example and 65% in the comparative example.
(6) In the example, the exposed iron particle area on the inner peripheral surface of the bearing was 3%. In the comparative example, the area of the copper alloy part and the iron part on the inner peripheral surface of the bearing was 20% of the metal surface.
(7) In the examples, the exposed pores on the inner peripheral surface of the bearing had a pore area of 10%, and in addition to the pores between the metal particles, small pores were observed on the surface of the copper alloy part particles. The comparative example had an exposed pore state on the inner peripheral surface of the bearing, with a pore area of 35%, mainly pores between metal particles, and smooth with few pores in the copper alloy part.
[0024]
7). The low temperature operation test evaluation method of the electric motor is the case where the sintered oil-impregnated bearings of the above-mentioned examples and comparative examples are mounted for the motor shaft of the electric motor, and the motor is cooled to below 30 ° C. and then operated in that temperature environment. This is a mounting test that examined the presence or absence of noise generation. The electric motor has a shaft shaft diameter of 8 mm, a sliding speed of 0.8 m / s, and a PV value of 0.08 MPa · m / s. The test results show that when the sintered oil-impregnated bearing of the example is used, no squeal is generated from the beginning of operation, but when the sintered oil-impregnated bearing of the comparative example is used, a squeal is generated and the superiority of the invention product is remarkably recognized. It was.
[0025]
As described above, the bearing structure is a sintered alloy in which the sliding surface has a copper alloy phase, an iron phase, and pores appropriately dispersed, and has a relatively large effective porosity and a relatively low air permeability. In combination with a lubricating oil having an excellent kinematic viscosity and a relatively high kinematic viscosity, an electric motor bearing element that does not generate squealing noise during low temperature operation is realized.
[0026]
【The invention's effect】
As described above, the present invention generates a squealing sound at the initial stage of operation of an electric motor used in a cold region of about 30 ° C., for example, by devising a sintered oil-impregnated bearing configuration and a manufacturing method thereof. Therefore, the quality and reliability of the applied motor can be improved.

Claims

Bearing material consists sintered alloy, in said sintered alloy is cross tissue and ferrite phase of the Cu alloy phase and Fe exhibited mixed-state containing Sn and P, and the amount of iron particles including alloys excluding pores 45 to 53% by volume , containing 0.7% by mass or less of graphite particles, the area of the iron part exposed to the sized bearing inner peripheral surface is 2 to 6%, the effective porosity is 20 to 30%, and The air permeability of the bearing is 6 to 50 × 10 ⁻¹¹ cm ² , and pores are scattered in the iron phase and the copper alloy phase in addition to the pores between particles or phases on the inner peripheral surface of the bearing, A sintered oil-impregnated bearing for an electric motor, wherein a synthetic oil having a kinematic viscosity at 40 ° C. of 61.2 to 74.8 mm ² / s is contained in the pores.

42 to 50% by mass of spongy reduced iron powder having a particle size of 145 mesh sieve, 41 to 43% by mass of electrolytic copper powder having a particle size of 50 to 90% by mass of 145 mesh sieve and 350 mesh sieve, particle size Is 2 to 10% by mass of foil-like copper powder under 100 mesh sieve, 1.4 to 2.7% by mass of tin powder, 3 to 5% by mass of phosphorous copper alloy powder having a P content of 8 to 9% by mass, graphite powder Using mixed powder containing 0.7% by mass or less and molding lubricant 1% by mass or less,
The mixed powder is compressed to produce a molded body having a density in the range of 5.3 to 6.1 g / cm ³ , and the molded body is sintered at a temperature at which the phosphor copper alloy powder melts and 780 ° C. or less. The obtained sintered body was sized to obtain a sizing body having a density of 5.8 to 6.5 g / cm ³ and an air permeability of 6 to 50 × 10 ⁻¹¹ cm ² , and a kinematic viscosity at 40 ° C. in the pores of the sizing body. A method for producing a sintered oil-impregnated bearing for an electric motor, comprising impregnating a synthetic oil of 61.2 to 74.8 mm ² / s.