JP4177191B2

JP4177191B2 - Closed forging device and closed forging method

Info

Publication number: JP4177191B2
Application number: JP2003201456A
Authority: JP
Inventors: 吉村　　隆志
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2003-07-25
Filing date: 2003-07-25
Publication date: 2008-11-05
Anticipated expiration: 2023-07-25
Also published as: JP2005040811A

Description

【０００１】
【発明の属する技術分野】
本発明は、冷間鍛造に代表されるような閉塞鍛造装置および閉塞鍛造方法に関し、特に前方押出しもしくは後方押出しを併用する閉塞鍛造装置および閉塞鍛造方法に関する。
【０００２】
【従来の技術】
この種の閉塞鍛造もしくは密閉鍛造に関する技術として例えば特許文献１に記載のものが知られている。
【０００３】
この従来の技術では、ダイス内に対向配置されることになる上下のパンチのうち上パンチ側を可動側として鍛造成形を行うにあたり、ダイスのインプレッションを上方側から順に大径部分、中径部分および小径部分とからなる段付き形状のものとし、中径部分と同等の大きさの素材を上記大径部分にセットした上で上下のパンチによりその素材を加圧して、素材に圧縮応力を加えながら小径部分側に押出し、さらなる加圧動作によりダイスと上下のパンチとで形成される閉空間内で素材を鍛造成形して所定形状の鍛造品とするものである。
【０００４】
【特許文献１】
特開平７−１１６７６４号公報（図１〜図３）
【０００５】
【発明が解決しようとする課題】
特許文献１に代表されるような従来の技術では、閉塞鍛造の特殊性として上パンチが下死点位置に達した瞬間に加圧力が急激に上昇する傾向にあり、型構造として相応の強度対策が講じられてはいても、鍛造品そのものの形状や大きさによっては型構造上十分な強度を確保できないことがある。例えば、素材として金属粉を焼結成形した予備成形体を用いて、それを冷間鍛造して所定形状に仕上げる焼結冷間鍛造品の場合にその傾向が強い。
【０００６】
そのため、成形しようとする鍛造品の形状によっては上パンチが下死点位置に達した瞬間に鍛造品を押し切ることになる加圧力を加減する必要があり、その結果として上パンチによって拘束されることになる鍛造品の上端面の加工精度もしくは形状精度が低下する。例えば、成形しようとする鍛造品の上端面を平坦に仕上げる必要がある場合でも、上記のように上パンチが下死点位置に達した瞬間の加圧力が制限されることにより、鍛造品の上端面を規定寸法通りの平坦面に仕上げることができないことになる。その結果、後工程にて機械加工等による仕上げ加工が必要となり、コストアップが余儀なくされることとなって好ましくない。
【０００７】
本発明はこのような課題に着目してなされたものであり、例えば上パンチが下死点位置に達した瞬間の加圧力が制限された場合でも、あたかもばりの発生を積極的に容認するばり出し鍛造（半分密閉鍛造）のように材料の一部が逃げ得る領域を確保しておくことで、鍛造品を確実に拘束して寸法精度の高い鍛造品を成形できるようにした閉塞鍛造装置および閉塞鍛造方法を提供しようとするものである。
【０００８】
【課題を解決するための手段】
請求項１に記載の発明は、少なくともダイスとこのダイス内に対向配置される一対の加圧パンチとで形成される閉空間内に素材を収容した上で、この素材を一対の加圧パンチにより加圧して前方押出しもしくは後方押出しの形態で鍛造品を成形するにあたり、ダイスの内周面に、鍛造品の成形末期にその鍛造品が収容されている閉空間と連通し且つ鍛造品のうち押出し方向側の端縁コーナー部が臨む逃げ凹部を形成し、この逃げ凹部のうち鍛造品の抜き取り方向側の端部をテーパ面としたことを特徴とする。
【０００９】
したがって、この構成のもとでは、成形初期段階では一対の加圧パンチによる加圧拘束力を受けて素材が前方押出しもしくは後方押出しの形態で押出し鍛造され、素材肉が閉空間内に充満するかたちで成形が進行する。その一方、成形末期の段階になると閉空間が微小な逃げ凹部と連通するようになり、最終的には素材肉の一部が逃げ凹部側にまで張り出すかたちで鍛造品の成形が完了する。すなわち、閉塞鍛造でありながらいずれか一方の加圧パンチがそのストローク限位置に達して鍛造品を押し切る段階では、その素材肉の一部が逃げ凹部側まで張り出すことにより、その押し切った時点での加圧力の極端に高くなることがないだけでなく、鍛造品を高精度に仕上げることができるようになる。
【００１０】
その上、先に述べたように鍛造品の一部である素材肉が逃げ凹部側まで張り出すことで、その張り出し部位に関するかぎりは鍛造品の形状は正規形状でないことになるものの、成形後の鍛造品が例えばノックアウト部材によって突き出される際に上記の張り出し部位がテーパ面によって矯正される。その結果、張り出し部が付帯している鍛造品の形状精度が高められることになる。
【００１１】
このように請求項１に記載の発明によれば、いずれか一方の加圧パンチがストローク限位置に達して鍛造品を押し切ることになる加圧力が制限された場合であっても、一対の加圧パンチによって鍛造品を確実に加圧拘束することができるから、拘束不足等を招くことなく鍛造品の寸法精度および形状精度が向上する。その結果、後工程にて機械加工等の仕上げ加工を行う必要がなくなり、工数削減とコストダウンを図ることができる。
【００１２】
また、逃げ凹部に対応する張り出し部が鍛造品に一旦は付帯することになるものの、その張り出し部はテーパ面によって矯正されることになるので、鍛造品の形状精度が向上する。
【００１４】
請求項２に記載の発明は、ダイスとこのダイス内に対向配置される一対の加圧パンチと、これらの加圧パンチを貫通するマンドレルとで形成される閉空間内に環状の素材を収容した上で、この素材を一対の加圧パンチにより加圧して前方押出しもしくは後方押出しの形態で鍛造品を成形するにあたり、前記マンドレルの外周面に、鍛造品の成形末期にその鍛造品が収容されている閉空間と連通し且つ鍛造品のうち押出し方向側の端縁コーナー部が臨む逃げ凹部を形成し、この逃げ凹部のうち鍛造品の抜き取り方向側の端部をテーパ面としたことを特徴とする。
【００１５】
この構成のもとでは、上記の軸穴の成形を司るマンドレルに先のダイス側と同様の逃げ凹部を形成してあるため、その軸穴についてダイス側の逃げ凹部と同様の機能が発揮される。
【００１６】
したがって、この請求項２に記載の発明によれば、鍛造品のうち特に逃げ凹部を設定した軸穴相当部の形状精度が向上する。
【００１７】
【発明の実施の形態】
図１以下の図面は本発明の好ましい実施の形態を示す図であり、図３に示すように素材として予め金属粉を焼結成形した予備成形体Ｐを用いて、それを冷間鍛造して図４に示すようないわゆる内歯車状の焼結冷間鍛造品Ｗを成形する場合の例を示している。なお、ここで使用する予備成形体Ｐは、例えば特開２００２−２７５５７２号公報および特開２００２−２９４３８８号公報等に記載のような特定の鉄基粉末成形用素材を用いた上で予備圧縮成形と予備焼結（仮焼結）とが施されたものを使用するものとする。
【００１８】
図３に示すように、素材（ブランク）としての予備成形体Ｐは、中心に段付き穴ｈを有する偏平円筒状もしくは円環状のものとして予め成形されている一方、その予備成形体Ｐから鍛造成形される鍛造品としての焼結冷間鍛造品Ｗは、図４に示すように略深皿状の本体部Ｂの内周にフランジ部Ｆ付きの軸穴Ｈを有していて、且つその本体部Ｂの内周面に内歯状の歯形部Ｇを有するものとして成形される。
【００１９】
鍛造装置としての金型は、図３に示すように、円筒状のインプレッションたる内周面１ａを有するダイス１のほか、対向配置された上下の加圧パンチ２，３、およびそれらの加圧パンチ２，３を貫通するマンドレル４およびノックアウトピン５等を主要素として構成される。ダイス１はスペーサ２１を介してパンチホルダ６に支持されている。下側の加圧パンチ３はマンドレル４のためのガイド穴３ａを有する円筒状のものであって、図４に示すようにノックアウトピン５とともに上方に突き出し可能ではあるものの、通常は図３に示すようにダイス１に内挿されながらパンチホルダ６に着座するかたちで支持されている。一方、上側の加圧パンチ２もマンドレル４のためのガイド穴２ａを有する円筒状のものであって、図示しないラムに固定支持されているとともに、鍛造成形時にはそのラムとともに下降して、下側の加圧パンチ３とともにダイス１に内挿される。これにより、図１に示すようにダイス１と上下の加圧パンチ２，３とにより閉塞鍛造のための閉空間Ｒが形成されて、焼結冷間鍛造品Ｗが成形される。
【００２０】
上側の加圧パンチ２は、図１から明らかなように、焼結冷間鍛造品Ｗのうち歯形部Ｇを含む本体部Ｂの内周面と上端面およびフランジ部Ｆの上端面の形状の成形を司るものであるから、その上側の加圧パンチ２の下端部には内外二段の段状部たるショルダー部７，８が形成されているとともに、それらショルダー部７，８にはさまれた突状部９の外周には上側の加圧パンチ２の円筒外周面よりも小径な外歯車状の歯形成形部１０が形成されている。
【００２１】
一方、上下の加圧パンチ２，３とともに上記の閉空間Ｒを形成することになるダイス１の内周面１ａおよびマンドレル４の外周面にはエアベント（空気抜き）を兼ねた微小深さの逃げ凹部１１，１２が環状溝の形態でその全周に形成されている。これらの逃げ凹部１１，１２の位置は、図３に示すように素材たる予備成形体Ｐを下パンチ３上の位置決め載置した状態で、予備成形体Ｐの外周側上端コーナー部および内周側上端コーナー部に近接するもこれらと干渉しないような位置であって、且つ図１に示すように上側の加圧パンチ２が下死点位置に達して焼結冷間鍛造品Ｗの成形が完了した状態では、その焼結冷間鍛造品Ｗの押出し方向側の端縁コーナー部すなわちの外周側上端コーナー部および内周側上端コーナー部がそれぞれ所定寸法だけ逃げ凹部１１，１２側に入り込むような位置に設定されている。
【００２２】
ここで、図２に拡大して示すように、ダイス１側の逃げ凹部１１の上下両端部はテーパ面１３ａ，１３ｂと曲率が例えばＲ１以上のアール面取り部１４ａ，１４ｂをもってダイス１のインプレッションたる内周面１ａに連続しているとともに、そのダイス１側の逃げ凹部１１の幅寸法Ｗ１を例えば１４ｍｍ程度に設定した場合、その深さＤは０．５±０．２ｍｍ程度に、テーパ面１３ａ，１３ｂの角度θは３０°程度にそれぞれ設定されている。同時に逃げ凹部１１の内隅部のアール面取り部１５ａ，１５ｂもアール面取り部１４ａ，１４ｂと同等の大きさに設定されている。ここで、マンドレル４側の逃げ凹部１２についてもダイス１側のものと同等の大きさのものとして形成されている。
【００２３】
このように構成された金型構造によれば、図３に示すように素材たる円環状の予備成形体Ｐを下側の加圧パンチ３の上に位置決め載置した上で上側の加圧パンチ２を下降させることで鍛造成形が開始される。
【００２４】
下降した上側の加圧パンチ２がダイス１に内挿されながら下側の加圧パンチ３とともに予備成形体Ｐを加圧拘束するようになると、焼結冷間鍛造品Ｗのための閉空間Ｒが形成されるとともに、その閉空間Ｒの容積が徐々に縮小されながら素材肉が歯形成形部１０を含む上側の加圧パンチ２の突状部９の形状になじむように予備成形体Ｐの塑性流動が開始され、いわゆる後方押出しの形態で鍛造成形が開始される。そして、成形初期段階では図１に示した焼結冷間鍛造品Ｗに近似した体積配分となるようにその塑性流動が進行することから、この段階では素材肉の一部がダイス１側およびマンドレル４側の逃げ凹部１１，１２に入り込むことはなく、予備成形Ｐに含まれる空気を追い出しつつ密閉された閉空間Ｒでの閉塞鍛造が進行する。
【００２５】
すなわち、図３の素材としての予備成形体Ｐの形状と図１の焼結冷間鍛造品Ｗの形状とを比較すると明らかなように、後方押出しによる予備成形体Ｐの塑性流動によって、上側の加圧パンチ２の押出し方向と逆方向に素材肉が徐々に略深皿状に隆起して、フランジ部Ｆ付きの軸穴Ｈと歯形部Ｇの鍛造成形が促進されるとともに予備成形体Ｐの密度が高くなる。
【００２６】
やがて、成形末期すなわち上側の加圧パンチ２が少なくともそのストローク限位置である下死点位置に達する直前になると、その成形完成度が高められて、素材たる予備成形体Ｐの形状が図１の焼結冷間鍛造品Ｗに近似したものとなることから、同図に示すように素材たる予備成形体Ｐ（焼結冷間鍛造品Ｗ）の外周側上端コーナー部および内周側上端コーナー部がそれぞれダイス１側およびマンドレル４側の逃げ凹部１１，１２に入り込むようになる。
【００２７】
そして、上側の加圧パンチ２が下死点位置に達すると、それをもって焼結冷間鍛造品Ｗの成形が完了したことになるのであるが、先の閉空間Ｒの体積が焼結冷間鍛造品Ｗの体積とほぼ等しいものとなって実質的に上下の加圧パンチ２，３が成形後の焼結冷間鍛造品Ｗを押し切るかたちとなることから、その瞬間に上下の加圧パンチ２，３が成形されたばかりの焼結冷間鍛造品Ｗに及ぼす加圧力が上昇する。その瞬間に、焼結冷間鍛造品Ｗの素材肉の逃げ場がない故に、図２に示すように、焼結冷間鍛造品Ｗの素材肉の一部すなわち成形されたばかりの焼結冷間鍛造品Ｗの外周側上端コーナー部および内周側上端コーナー部がそれぞれの逃げ凹部１１，１２側に張り出すようにしてわずかに膨出する。なお、その張り出し部を図２に符号Ｑで示す。これによって、焼結冷間鍛造品Ｗのうち歯形部Ｇ以外で上側の加圧パンチ２と接触している平坦部の加工精度が高められることになる。同時に、塑性流動によって焼結冷間鍛造品Ｗ内の空隙が減少することで焼結冷間鍛造品Ｗとしての密度も高められることになる。このように上側の加圧パンチ２が下死点位置に達した状態をもって焼結冷間鍛造品Ｗの成形が完了する。
【００２８】
上側の加圧パンチ２が下死点位置に達した以降は、図４に示すようにノックアウトピン５の上昇動作によって下側の加圧パンチ３と成形されたばかりの焼結冷間鍛造品Ｗとが上側の加圧パンチ２とともに上方に突き出される。この突き出し過程において、図２に示したように焼結冷間鍛造品Ｗのうち先に逃げ凹部１１，１２側に張り出した外周側上端コーナー部および内周側上端コーナー部の張り出し部Ｑが、各逃げ凹部１１，１２の上端部側（焼結冷間鍛造品Ｗの抜き取り方向側）のテーパ面１３ａとそれに連続するダイス１の内周面１ａやマンドレル４の外周面と順次摺接するかたちとなる。このため、テーパ面１３ａ等にて張り出し部Ｑが押し戻されるように矯正され、成形後の焼結冷間鍛造品Ｗには先の張り出し部Ｑの痕跡はほとんど残らないようになる。
【００２９】
そして、成形されたばかりの焼結冷間鍛造品Ｗが図４のようにダイス１から完全に突き出されるのと相前後して、例えば上側の加圧パンチ２に内蔵された図外の上側のノックアウトピンが突き出し動作することにより、焼結冷間鍛造品Ｗは上側の加圧パンチ２からも離型されて下側の加圧パンチ３上に残されることになる。
【００３０】
このように本実施の形態によれば、金型構造の強度が成形対象となる焼結冷間鍛造品Ｗの形状等の制約から十分に確保できない場合であっても、上側の加圧パンチ２が下死点位置に達して焼結冷間鍛造品Ｗを押し切った瞬間の加圧力を極端に大きくすることなく、寸法精度および形状精度に優れた焼結冷間鍛造品Ｗを成形することが可能となる。
【００３１】
ここで、上記の実施の形態では、素材として焼結予備成形体Ｐを用いて焼結冷間鍛造品Ｗを冷間鍛造成形する場合を例にとって説明したが、下記のように本発明の主旨を逸脱しない範囲内で他の実施の形態として種々変更することは可能である。
【００３２】
（１）焼結鍛造以外の通常の鍛造のほか、温間や熱間の各鍛造方式にも適用することができる。
【００３３】
（２）上記の実施の形態では、下側の加圧パンチ３に対向する上側の加圧パンチ２の接近移動により後方押出しの形態で鍛造品Ｗを成形するものについて説明したが、前方押出しの形態としても本発明を同様に適用することができる。
【００３４】
（３）成形後の焼結冷間鍛造品Ｗを上側の加圧パンチ２から離型させる手段として、例えば上側の加圧パンチ２を複数の筒状の構造体からなる複合構造として、筒状の構造体同士の相対移動により上側の加圧パンチ２から焼結冷間鍛造品Ｗを突き出すようにしてもよい。
【００３５】
（４）ダイス１の内周面１ａおよびマンドレル４の外周面に形成される逃げ凹部１１，１２は、その全周面に形成される溝状のものに代えて、周方向に部分的に形成してもよい。
【００３６】
また、各請求項に記載したもの以外の本発明の主要な構成をその作用効果とともに記載すれば次のとおりである。
【００３７】
（５）請求項１〜３のいずれかの記載を前提として、閉空間Ｒに収容される素材Ｐは環状のものであってその素材Ｐの中心部をマンドレル４が貫通するようになっていて、成形後の鍛造品である焼結冷間鍛造品Ｗは軸穴Ｈを有する深皿状の本体部Ｂの内周面に内歯状の歯形部Ｇが形成されているものであることを特徴とする閉塞鍛造装置。
【００３８】
この構成のもとでは、環状の素材Ｐから、軸穴Ｈを有する深皿状の本体部Ｂの内周面に内歯状の歯形部Ｇが形成された鍛造品としての焼結冷間鍛造品Ｗが成形されることになる。
【００３９】
したがって、軸穴Ｈと歯形部Ｇを有する鍛造品としての焼結冷間鍛造品Ｗを高精度に仕上げることができることから、後工程にて機械加工等の仕上げ加工を行う必要がなくなり、工数削減とコストダウンを図ることができる。
【００４０】
（６）少なくともいずれか一方のパンチ２の加圧面の内外周には段状のショルダー部７，８が形成されていることを特徴とする請求項１〜３のいずれかに記載の閉塞鍛造装置。
【００４１】
この構成のもとでは、鍛造品としての焼結冷間鍛造品Ｗの上端面がより強固に拘束される。したがって、鍛造品である焼結冷間鍛造品Ｗの上端面の加工精度が一段と向上する。
【図面の簡単な説明】
【図１】本発明の好ましい実施の形態を示す図で、閉塞鍛造用の金型構造において成形が完了した瞬間の状態を示す要部拡大断面図。
【図２】図１のＡ部拡大説明図。
【図３】図１の金型構造において成形が開始される前の状態を示す要部拡大断面図。
【図４】同じく図１の金型構造において成形後の焼結冷間鍛造品が突き出され状態を示す要部拡大断面図。
【符号の説明】
１…ダイス
１ａ…内周面
２…上側の加圧パンチ
３…下側の加圧パンチ
４…マンドレル
１０…歯形成形部
１１，１２…逃げ凹部
１３ａ，１３ｂ…テーパ面
Ｂ…本体部
Ｇ…歯形部
Ｈ…軸穴
Ｐ…予備成形体（素材）
Ｒ…閉空間
Ｗ…焼結冷間鍛造品（鍛造品）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a closed forging device and a closed forging method as typified by cold forging, and more particularly to a closed forging device and a closed forging method that use forward extrusion or backward extrusion together.
[0002]
[Prior art]
As a technique related to this type of closed forging or closed forging, for example, one described in Patent Document 1 is known.
[0003]
In this conventional technique, when performing forging with the upper punch side of the upper and lower punches to be opposed to each other in the die as the movable side, the impressions of the die are increased in order from the upper side to the large diameter part, the medium diameter part, and While having a stepped shape consisting of a small diameter part, set the material of the same size as the medium diameter part in the above large diameter part and pressurizing the material with the upper and lower punches, applying compressive stress to the material The material is forged in a closed space formed by a die and upper and lower punches by a further pressurizing operation, and the material is forged into a predetermined shape.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-116764 (FIGS. 1 to 3)
[0005]
[Problems to be solved by the invention]
In the conventional technology represented by Patent Document 1, as a special feature of the closed forging, the pressing force tends to increase suddenly at the moment when the upper punch reaches the bottom dead center position. However, depending on the shape and size of the forged product itself, sufficient strength may not be ensured in terms of the mold structure. For example, this tendency is strong in the case of a sintered cold forged product in which a preform formed by sintering metal powder as a raw material is cold-forged and finished into a predetermined shape.
[0006]
Therefore, depending on the shape of the forged product to be molded, it is necessary to adjust the pressure that pushes the forged product at the moment when the upper punch reaches the bottom dead center position. As a result, it is restrained by the upper punch. The processing accuracy or shape accuracy of the upper end surface of the forging product becomes lower. For example, even if it is necessary to finish the upper end surface of a forged product to be formed flat, the pressing force at the moment when the upper punch reaches the bottom dead center position is limited as described above. The end surface cannot be finished to a flat surface as specified. As a result, finishing processing by machining or the like is required in the subsequent process, which is not preferable because the cost is inevitably increased.
[0007]
The present invention has been made paying attention to such a problem. For example, even when the pressing force at the moment when the upper punch reaches the bottom dead center position is limited, the occurrence of flashing is positively accepted. A closed forging device that secures an area in which a part of the material can escape as in forging forging (half-sealing forging), so that the forging can be reliably restrained and a forging with high dimensional accuracy can be formed, and An object is to provide a closed forging method .
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, a material is accommodated in a closed space formed by at least a die and a pair of pressure punches disposed opposite to each other in the die, and then the material is separated by a pair of pressure punches. When forming a forged product in the form of forward extrusion or backward extrusion under pressure, the inner peripheral surface of the die communicates with the closed space in which the forged product is accommodated at the end of the forged product and is extruded out of the forged product. A relief recess that faces an end edge corner portion on the direction side is formed, and an end portion on the extraction direction side of the forged product is formed as a tapered surface in the relief recess.
[0009]
Therefore, under this configuration, in the initial stage of molding, the material is subjected to pressure restraint force by a pair of pressure punches, the material is extruded and forged in the form of forward extrusion or backward extrusion, and the material meat fills the closed space. The molding proceeds. On the other hand, at the final stage of molding, the closed space comes into communication with the minute relief recess, and finally the forging is completed in a form in which a part of the material meat protrudes to the relief recess side. That is, at the stage where either one of the pressure punches reaches its stroke limit position and pushes the forged product while it is closed forging, when a part of the material meat projects to the escape recess side, In addition to not being extremely high, the forging can be finished with high accuracy.
[0010]
In addition, as described above, the material meat that is a part of the forged product is projected to the relief recess side, so that the shape of the forged product is not a regular shape as far as the projecting part is concerned, When the forged product is protruded by, for example, a knockout member, the protruding portion is corrected by the tapered surface. As a result, the shape accuracy of the forged product attached with the overhanging portion is improved.
[0011]
Thus, according to the first aspect of the present invention, even when one of the pressure punches reaches the stroke limit position and the pressing force that pushes the forged product is limited, a pair of pressurizing punches are limited. Since the forged product can be reliably pressure-restrained by the pressure punch, the dimensional accuracy and shape accuracy of the forged product can be improved without causing insufficient restraint. As a result, there is no need to perform finishing such as machining in the subsequent process, and man-hours can be reduced and costs can be reduced.
[0012]
Further, although the overhanging portion corresponding to the relief recess is once attached to the forged product, the overhanging portion is corrected by the tapered surface, so that the shape accuracy of the forging product is improved.
[0014]
According to the second aspect of the present invention , an annular material is accommodated in a closed space formed by a die, a pair of pressure punches disposed opposite to each other in the die, and a mandrel penetrating the pressure punches. In the above, when the forged product is molded in the form of forward extrusion or backward extrusion by pressing the material with a pair of pressure punches , the forged product is accommodated on the outer peripheral surface of the mandrel at the final stage of the forged product. edge corners of the extrusion direction of the closed space and communicating with and forgings there are formed a relief recess facing, and wherein an end portion of the extraction direction of the forged product of the relief recess has a tapered surface To do.
[0015]
Under this arrangement, since the mandrel Le responsible for forming the axial bore is formed ahead of the die side and the same relief recesses, same function as the die side of the escape recess is exhibited for the shaft hole The
[0016]
Therefore, according to the second aspect of the present invention, the shape accuracy of the shaft hole equivalent portion in which the relief recess is set in the forged product is improved.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
1 and the following drawings show a preferred embodiment of the present invention. As shown in FIG. 3, a preform P obtained by sintering metal powder in advance as a raw material is used and cold forged. The example in the case of shape | molding what is called an internal gear-shaped sintered cold forging product W as shown in FIG. 4 is shown. The preform P used here is a precompression molding after using a specific iron-based powder molding material as described in, for example, JP-A Nos. 2002-275572 and 2002-294388. And pre-sintered (pre-sintered).
[0018]
As shown in FIG. 3, the preform P as a raw material (blank) is preliminarily molded as a flat cylindrical shape or an annular shape having a stepped hole h at the center. A sintered cold forged product W as a forged product to be formed has a shaft hole H with a flange portion F on the inner periphery of a substantially deep dish-shaped main body portion B as shown in FIG. The body part B is molded as having an internal tooth-shaped part G on the inner peripheral surface thereof.
[0019]
As shown in FIG. 3, a die as a forging device includes a die 1 having an inner peripheral surface 1a which is a cylindrical impression, upper and lower pressure punches 2 and 3 arranged opposite to each other, and pressure punches thereof. The mandrel 4 and the knockout pin 5 passing through 2 and 3 are configured as main elements. The die 1 is supported by the punch holder 6 via the spacer 21. The lower pressure punch 3 has a cylindrical shape having a guide hole 3a for the mandrel 4 and can protrude upward together with the knockout pin 5 as shown in FIG. Thus, it is supported in the form of being seated on the punch holder 6 while being inserted into the die 1. On the other hand, the upper pressure punch 2 has a cylindrical shape having a guide hole 2a for the mandrel 4 and is fixedly supported by a ram (not shown). The pressure punch 3 is inserted into the die 1. Thereby, as shown in FIG. 1, the closed space R for closed forging is formed by the die 1 and the upper and lower pressure punches 2 and 3, and the sintered cold forged product W is formed.
[0020]
As is apparent from FIG. 1, the upper pressure punch 2 has a shape of the inner peripheral surface and upper end surface of the main body portion B including the tooth profile portion G of the sintered cold forged product W and the upper end surface of the flange portion F. Since it controls the molding, shoulder portions 7 and 8 are formed at the lower end portion of the pressure punch 2 on the upper side, and the inner and outer stepped portions are sandwiched between the shoulder portions 7 and 8. On the outer periphery of the protruding portion 9, an external gear-like tooth forming portion 10 having a smaller diameter than the cylindrical outer peripheral surface of the upper pressure punch 2 is formed.
[0021]
On the other hand, on the inner peripheral surface 1a of the die 1 and the outer peripheral surface of the mandrel 4 that form the closed space R together with the upper and lower pressure punches 2 and 3, a relief recess with a minute depth that also serves as an air vent (air venting). 11 and 12 are formed on the entire circumference in the form of an annular groove. The positions of these relief recesses 11 and 12 are as shown in FIG. 3 in a state in which the preform P, which is a material, is positioned on the lower punch 3 and placed on the outer peripheral side upper corner and the inner periphery of the preform P. The position close to the upper corner but does not interfere with them, and the upper pressure punch 2 reaches the bottom dead center position as shown in FIG. 1, and the forming of the sintered cold forged product W is completed. as to the state, the edge corner portion viz the outer peripheral side upper corner portion of the extrusion direction and the inner peripheral side upper corner portion of the sintered cold forged product W is Komu enters the respective recess 11, 12 side relief by a predetermined distance Is set to the correct position.
[0022]
Here, as shown in an enlarged view in FIG. 2, the upper and lower end portions of the relief recess 11 on the die 1 side are tapered surfaces 13a and 13b and rounded chamfered portions 14a and 14b having a curvature of, for example, R1 or more. When the width dimension W1 of the relief recess 11 on the die 1 side is set to about 14 mm, for example, the depth D is about 0.5 ± 0.2 mm, and the taper surface 13a, The angle θ of 13b is set to about 30 °. At the same time, the rounded chamfered portions 15a and 15b at the inner corners of the escape recess 11 are also set to the same size as the rounded chamfered portions 14a and 14b. Here, the relief recess 12 on the mandrel 4 side is also formed to have the same size as that on the die 1 side.
[0023]
According to the mold structure configured as described above, an annular preform P as a raw material is positioned and placed on the lower pressure punch 3 as shown in FIG. Forging is started by lowering 2.
[0024]
When the lowered upper pressure punch 2 is inserted into the die 1 and pressurizes the preform P together with the lower pressure punch 3, the closed space R for the sintered cold forging W Is formed, and the plasticity of the preform P is adjusted so that the material meat conforms to the shape of the protruding portion 9 of the upper pressure punch 2 including the tooth forming portion 10 while the volume of the closed space R is gradually reduced. Flow is started and forging is started in the form of so-called backward extrusion. At the initial stage of molding, the plastic flow proceeds so that the volume distribution approximates to the sintered cold forged product W shown in FIG. 1. Therefore, at this stage, a part of the raw material meat is on the die 1 side and the mandrel. The four-side relief recesses 11 and 12 do not enter, and the closed forging in the sealed closed space R proceeds while driving out the air contained in the preform P.
[0025]
That is, as is clear when comparing the shape of the preform P as the raw material of FIG. 3 and the shape of the sintered cold forged product W of FIG. The material meat gradually rises in a substantially deep dish shape in the direction opposite to the direction in which the pressure punch 2 is pushed out, and the forging of the shaft hole H with the flange portion F and the tooth profile portion G is promoted and the preform P is formed. Density increases.
[0026]
Eventually, at the end of molding, that is, just before the upper pressure punch 2 reaches at least the bottom dead center position, which is the stroke limit position, the molding completeness is increased, and the shape of the preform P as the material is shown in FIG. Since it is similar to the sintered cold forged product W, as shown in the figure, the outer peripheral side upper end corner portion and the inner peripheral side upper end corner portion of the preform P (sintered cold forged product W) as the material Enters the recesses 11 and 12 on the die 1 side and the mandrel 4 side, respectively.
[0027]
Then, when the upper pressure punch 2 reaches the bottom dead center position, the forming of the sintered cold forged product W has been completed. Since the upper and lower pressure punches 2 and 3 are substantially equal to the volume of the forged product W, the upper and lower pressure punches 2 and 3 are pushed through the sintered cold forged product W after forming. The pressurizing force exerted on the cold forging product W which has just been formed 2 and 3 is increased. At that moment, since there is no escape from the raw material meat of the sintered cold forged product W, as shown in FIG. 2, a part of the raw material meat of the sintered cold forged product W, that is, the sintered cold forged just formed. The outer peripheral side upper end corner portion and the inner peripheral side upper end corner portion of the product W slightly bulge out so as to protrude toward the respective escape recesses 11 and 12. In addition, the overhang | projection part is shown with the code | symbol Q in FIG. As a result, the processing accuracy of the flat portion of the sintered cold forged product W that is in contact with the upper pressure punch 2 other than the tooth profile portion G is increased. At the same time, the density of the sintered cold forged product W is increased by reducing the voids in the sintered cold forged product W due to plastic flow. In this way, the molding of the sintered cold forged product W is completed when the upper pressure punch 2 has reached the bottom dead center position.
[0028]
After the upper pressure punch 2 reaches the bottom dead center position, as shown in FIG. 4, the sintered cold forging W just formed with the lower pressure punch 3 by the raising operation of the knockout pin 5, Is protruded upward together with the upper pressure punch 2 . In this projecting process, as shown in FIG. 2, the outer peripheral side upper end corner portion and the projecting portion Q of the inner peripheral upper end corner portion, which are first projected to the relief recesses 11 and 12 side of the sintered cold forged product W, A taper surface 13a on the upper end side of each of the relief recesses 11 and 12 (on the drawing direction side of the sintered cold forged product W), and a shape that sequentially slides on the inner peripheral surface 1a of the die 1 and the outer peripheral surface of the mandrel 4 Become. For this reason, it corrects so that the overhang | projection part Q may be pushed back by the taper surface 13a etc., and the trace of the previous overhang | projection part Q will remain in the sintering cold forging W after shaping | molding.
[0029]
Then, just before the sintered cold forged product W just formed is protruded completely from the die 1 as shown in FIG. 4, for example, on the upper side of the upper side, not shown, incorporated in the upper pressure punch 2. When the knockout pin protrudes, the sintered cold forged product W is released from the upper pressure punch 2 and is left on the lower pressure punch 3.
[0030]
As described above, according to the present embodiment, even when the strength of the mold structure cannot be sufficiently ensured due to restrictions such as the shape of the sintered cold forged product W to be molded, the upper pressure punch 2 It is possible to form a sintered cold forged product W having excellent dimensional accuracy and shape accuracy without excessively increasing the pressing force at the moment when it reaches the bottom dead center position and pushes down the sintered cold forged product W. It becomes possible.
[0031]
Here, in the above-described embodiment, the case where the cold forging of the sintered cold forged product W is cold forged using the sintered preform P as a raw material has been described as an example, but the gist of the present invention is as follows. Various modifications can be made as other embodiments without departing from the scope of the present invention.
[0032]
(1) In addition to normal forging other than sintering forging, it can also be applied to warm and hot forging methods.
[0033]
(2) In the above-described embodiment, the forging product W is formed in the form of backward extrusion by the close movement of the upper pressure punch 2 facing the lower pressure punch 3. The present invention can be similarly applied as a form.
[0034]
(3) As a means for releasing the sintered cold forged product W after molding from the upper pressure punch 2, for example, the upper pressure punch 2 is formed into a cylindrical shape as a composite structure composed of a plurality of cylindrical structures. The sintered cold forging product W may be protruded from the upper pressure punch 2 by relative movement of the structures.
[0035]
(4) The relief recesses 11 and 12 formed on the inner peripheral surface 1a of the die 1 and the outer peripheral surface of the mandrel 4 are partially formed in the circumferential direction instead of the groove-shaped one formed on the entire peripheral surface. May be.
[0036]
Moreover, it will be as follows if the main structures of this invention other than what was described in each claim are described with the effect.
[0037]
(5) On the premise of the description in any one of claims 1 to 3, the material P accommodated in the closed space R is annular, and the mandrel 4 penetrates through the center of the material P. The sintered cold forged product W, which is a forged product after molding, is one in which an internal tooth-shaped tooth profile G is formed on the inner peripheral surface of a deep dish-shaped main body B having a shaft hole H. A closed forging device.
[0038]
Under this configuration, sintered cold forging as a forged product in which an internal tooth profile G is formed on the inner peripheral surface of a deep dish-shaped main body B having a shaft hole H from an annular material P. The product W is molded.
[0039]
Therefore, since the sintered cold forged product W as the forged product having the shaft hole H and the tooth profile G can be finished with high accuracy, it is not necessary to perform finishing such as machining in the subsequent process, thereby reducing the man-hours. And cost reduction.
[0040]
(6) The closed forging device according to any one of claims 1 to 3, wherein stepped shoulder portions 7 and 8 are formed on the inner and outer peripheries of the pressing surface of at least one of the punches 2. .
[0041]
Under this configuration, the upper end surface of the sintered cold forged product W as the forged product is more firmly restrained. Therefore, the processing accuracy of the upper end surface of the sintered cold forged product W, which is a forged product, is further improved.
[Brief description of the drawings]
FIG. 1 is a view showing a preferred embodiment of the present invention and is an enlarged cross-sectional view of a main part showing a state at the moment when molding is completed in a mold structure for closed forging.
FIG. 2 is an enlarged explanatory view of a part A in FIG.
3 is an enlarged cross-sectional view of a main part showing a state before molding is started in the mold structure of FIG. 1;
4 is an enlarged cross-sectional view of a relevant part showing a state in which a sintered cold forged product after molding is protruded in the mold structure of FIG. 1; FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Dies 1a ... Inner peripheral surface 2 ... Upper pressure punch 3 ... Lower pressure punch 4 ... Mandrel 10 ... Tooth formation part 11, 12 ... Relief recess
13a, 13b ... tapered surface B ... main body G ... tooth profile H ... shaft hole P ... preliminary body (material)
R ... Closed space W ... Sintered cold forged product (forged product)

Claims

A material is accommodated in a closed space formed by at least a die and a pair of pressure punches disposed opposite to each other in the die, and then the material is pressed by a pair of pressure punches to be extruded forward or backward. A closed forging device for forming a forged product in a form,
Formed on the inner peripheral surface of the die is a relief recess that communicates with the closed space in which the forged product is accommodated at the end of the forging product and faces the edge corner of the forged product on the extrusion direction side. Of these, a closed forging device characterized in that the end of the forged product on the extraction direction side is a tapered surface.

An annular material is accommodated in a closed space formed by a die, a pair of pressure punches arranged opposite to each other in the die, and a mandrel penetrating these pressure punches, and the material is then added to a pair. A closed forging device that forms a forged product in the form of forward extrusion or backward extrusion by pressing with a pressure punch,
Wherein the outer peripheral surface of the mandrel to form a closed space and communicating with and relief recess end edge corner portion of the extrusion direction side faces of the forged product to which the forged product is accommodated in the molded end of the forgings, the relief recess Of these , a closed forging device characterized in that the end of the forged product on the extraction direction side is a tapered surface .

A material is accommodated in a closed space formed by a die and a pair of pressure punches arranged opposite to each other in the die, and the material is pressurized by a pair of pressure punches to be extruded forward or backward. A closed forging method for forming a forged product with
On the inner peripheral surface of the die, a relief recess is formed which communicates with the closed space in which the forged product is accommodated at the end of the forged product and faces the edge corner portion on the extrusion direction side of the forged product. Of the relief recess, the end of the forging product in the direction of extraction is set as a tapered surface,
While forming the forged product by pressurizing and restraining the material by the pair of pressure punches, the edge corner portion on the extrusion direction side of the forged product is projected into the escape recess at the end of the molding,
A closed forging method characterized in that when the molded forged product is extracted, an edge corner portion on the extrusion direction side that protrudes into the relief recess is corrected so as to be pushed back by a tapered surface of the relief recess.

An annular material is accommodated in a closed space formed by a die, a pair of pressure punches disposed opposite to each other in the die, and a mandrel penetrating the pressure punches, and then the material is added to the pair of pressure punches. A closed forging method in which a forged product is formed in the form of forward extrusion or backward extrusion by pressing with a pressure punch,
On the outer peripheral surface of the mandrel, a relief recess is formed which communicates with a closed space in which the forged product is accommodated at the end of the forged product and faces an edge corner portion on the extrusion direction side of the forged product. Leave the end of the forged product on the side of the forging product as a tapered surface,
While forming the forged product by pressurizing and restraining the material by the pair of pressure punches, the edge corner portion on the extrusion direction side of the forged product is projected into the escape recess at the end of the molding,
A closed forging method characterized in that when the molded forged product is extracted, an edge corner portion on the extrusion direction side protruding from the relief recess is corrected so as to be pushed back by a tapered surface of the relief recess.