JP3558944B2 - Powder molding machine - Google Patents

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JP3558944B2
JP3558944B2 JP2000027785A JP2000027785A JP3558944B2 JP 3558944 B2 JP3558944 B2 JP 3558944B2 JP 2000027785 A JP2000027785 A JP 2000027785A JP 2000027785 A JP2000027785 A JP 2000027785A JP 3558944 B2 JP3558944 B2 JP 3558944B2
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pressure
pressing
pressing force
molding machine
roller
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JP2000301395A (en
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木 隆 鈴
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株式会社グローバル・ニュークリア・フュエル・ジャパン
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B30—PRESSES
    • B30B—PRESSES IN GENERAL
    • B30B11/00—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses
    • B30B11/02—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses using a ram exerting pressure on the material in a moulding space
    • B30B11/08—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses using a ram exerting pressure on the material in a moulding space co-operating with moulds carried by a turntable

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Press-Shaping Or Shaping Using Conveyers (AREA)
  • Powder Metallurgy (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、例えば原子燃料用の燃料ペレットの如き粉末冶金材料の成形を行う粉末成形機に関する。
【０００２】
【従来の技術】
一般に、上記燃料ペレットの如き粉末冶金材料の成形に際しては、ダイス内に供給された粉末を上下両パンチによって圧縮することが行われている。
【０００３】
図４は、上述の如き圧縮成形を行うための粉末成形機、特にロータリ型の粉末成形機の縦断面図であり、フレーム１とそのフレーム１の上方に設けられたスタンドフレーム２との間には竪シャフト３が立設されている。上記フレーム１の上面には上記竪シャフト３と同心状に竪シャフト油受４が固設されており、さらにその竪シャフト油受４の上方には、回転盤５が上記竪シャフト３に対して回転自在に装着されている。
【０００４】
上記回転盤５には、その外周部に、上部フランジ状部５ａ、中央フランジ状部５ｂ及び下部フランジ状部５ｃが一体に形成されており、中央フランジ状部５ｂには、図５に示すように、周方向に多数個のダイス６が設けられている。
【０００５】
また、上部フランジ状部５ａには、上記各ダイス６と同一軸線上にそれぞれ上パンチ７ａを保持する上パンチホルダー７が上下動可能に配設されており、下部フランジ状部５ｃにも各ダイス６と同一軸線上にそれぞれ下パンチ８ａを保持する下パンチホルダー８が上下動可能に配設され、さらに上記下部フランジ状部５ｃの外周に形成された歯車９に、適宜駆動機構によって駆動される駆動歯車１０が噛合されている。
【０００６】
一方、上記下パンチホルダー８には、回転盤５から下方に突出している部分の外側に案内ローラ１１が装着されており、その案内ローラ１１が前記フレーム１上に周方向所定範囲にわたって配設された案内溝１２に係合されている。
【０００７】
また、上パンチホルダー７の前記回転盤５から上方に突出している部分の両側にも案内ローラ１３が装着され、上記回転盤５より上方位置において周方向所定範囲にわたって配設された案内溝１４に係合されている。
【０００８】
また、上記上パンチ７ａおよび下パンチ８ａをダイス６内に上下からそれぞれ挿入し、ダイス６内に供給された粉末原料を圧縮成形する加圧行程部においては、上パンチホルダー７の頂端及び下パンチホルダー８の下端にそれぞれ当接し、両パンチに加圧力を加える加圧ローラ１５及び１６がそれぞれ配設されている。上記加圧ローラ１５，１６を軸支する軸受部材１７，１８はスタンドフレーム２或はフレーム１に図示しない機構によって或範囲上下動のみ可能に設けられており、その軸受部材１７，１８の頂部或は底部とスタンドフレーム２或はフレーム１との間にはそれぞれシリンダ装置１７ａ，１８ａが介装されている。
【０００９】
なお、図４中の符号１９は粉末フィーダである。
【００１０】
しかして、粉末の圧縮成形に際しては、駆動歯車１０を介して回転盤５が回転せしめられ、それとともに所定位置に来たダイス６内に粉末フィーダ１９から粉末が供給される。そこで、上記回転盤５の回転に応じて、案内溝１２および案内ローラ１１を介して下パンチ８ａが所定の充填深さになるよう上動せしめられ、余分の粉末が除去されたのち、上パンチ７ａが次第に下降せしめられ、ダイス６内の粉末が上下両パンチ７ａ，８ａ間に挟持状態となる。このようにしてダイス６内の粉末を挟持状態としている上下パンチ７ａ，８ａが加圧ローラ１５，１６間に侵入すると、シリンダー装置１７ａ，１８ａにより所定の圧力が加えられた加圧ローラ１５，１６によって上下両パンチ７ａ，８ａが互いに接近する方向に押圧され、粉末の圧縮成形が行われる。このようにして加圧行程が終了すると、成形品を上下両パンチ７ａ，８ａによって挟持した状態で上下両パンチが上動せしめられ、下パンチ８ａの上面がダイス６の上面（ダイテーブル）と同一面となった時点で、上パンチ７ａがさらに上方に移動せしめられ、その後成形品の払い出しが行われる。以後同様にして、各ダイス６内で順次粉末の圧縮成形が行われる。
【００１１】
【発明が解決しようとする課題】
ところが、一般に粉末成形時は、ダイスの中で数ｔｏｎ／ｃｍ２ のオーダの圧力が成形品に加わっており、成形品をダイスから抜き出すと約１〜１．５％程度膨張する。
【００１２】
従って、成形終了後押し出し行程に入るとき急速に解圧すると成形品にクラック等の欠陥が発生する等の問題がある。
【００１３】
そこで成形品をダイス内から上下両パンチで挟持しながら押し出す押し出し行程中に、上記成形品に所定加圧力を維持させるため、上下両パンチの少なくとも一方にパンチに加圧力を加えるカム機構を設けるとともに、そのカム機構のカム体２２，２３を回転盤の回動方向に互いに分割された複数のカムによって構成せしめ、各カムの加圧用シリンダーの加圧力が順次小さくなるようにすることが提案されている（実公平２−４３５９５号公報）。
【００１４】
ところが、上述のように加圧用シリンダーによってカム機構に加圧力を加えるものにおいては、空気圧によってパンチに加圧力を加えるものであるため、粉末の充填量が変化した場合、その成型品の長さが変動し、その変動分だけ、パンチの位置が常に変位し、押圧力のバラツキがあり、押圧力を常に一定に保つことが困難であり、成形品のクラック等の発生を必ずしも十分に抑制することができない等の問題がある。
【００１５】
また、図６に示すように、加圧行程に於いて、回転方向に２つの加圧ローラ対を設け、第１の上下の加圧ローラ１５ａ，１６ａで本圧成形を行い、第２の上下の加圧ローラ１５ｂ，１６ｂで余圧成形を行うことで、急激な成形品の解圧を順次行うようにしたり、或は第１の上下の加圧ローラ１５ａ，１６ａで予定成形し、第２の上下の加圧ローラ１５ｂ，１６ｂで本圧成形を行うようにすることも提案されている。
【００１６】
しかし、このように複数対の加圧ローラを設けるものにおいても、所定の加圧力を維持させるには加圧ローラの位置調節が必要であり、その調節が困難であり、また構造も複雑となり、成形品のクラック等の発生を必ずしも十分に抑制することができない等の問題がある。
【００１７】
本発明は、このような点に鑑み、加圧成形直後の成形品に十分な押圧力を維持させ、成形品のクラック等の発生を十分抑制し成形品の歩留まりを向上し得るようにした粉末成形機を得ることを目的とする。
【００１８】
【課題を解決するための手段】
請求項１に係る発明は、 上下両パンチによる加圧力によって粉末を加圧成形するロータリ型の粉末成形機において、上記上下両パンチの少なくとも上パンチに加圧力を加える加圧ローラの上下位置移動に同期して上下動する加圧ローラ軸受部に、複数の皿バネを有する加圧補助装置を装着し、上記加圧補助装置の皿バネにより、加圧ローラの最大加圧点を通過した直後の上パンチに所定の押圧力を加え、成型品に所定加圧力を維持させるようにしたことを特徴とする。
【００１９】
請求項２に係る発明は、請求項１の発明において、上記加圧ローラ軸受部に設けられた加圧補助装置のシリンダ内に皿バネが配設され、その皿バネによる押圧力が、上記シリンダ内に上下動可能に収容されたピストン部材に固着されたカム体を介して、上パンチを保持する上パンチホルダに設けられている案内ローラに加えられるようにしたことを特徴とする。
【００２０】
また、請求項３に係る発明は、請求項１または２の発明において、加圧ローラの最大加圧点を通過した直後の加圧補助装置における押圧力が成型加圧力の５〜２０％になるように皿バネが組合わせられていることを特徴とする。
【００２１】
【発明の実施の形態】
以下、図１から図３を参照して本発明の一実施の形態について説明する。
【００２２】
尚、図中図４と同一部分については同一符号を付してその詳細な説明は省略する。
【００２３】
図１は、回転式粉末成形機の各成形行程を示す展開図であって、上パンチ７ａ及び下パンチ８ａがその移動方向に沿って設けられた案内溝１４，１２の如きガイドレール２０，２１に案内されて上下動し、加圧ローラ１５，１６によって粉末の加圧成形が行われる加圧行程Ａに引き続いて、成形品押し出し行程Ｂ、成形品払い出し行程Ｃ、粉末充填行程Ｄ、重量調整行程Ｅ、及び加圧準備行程Ｆが順次繰り返される。
【００２４】
ところで、加圧ローラ１５，１６による粉末の加圧行程Ａの終了直前位置から成形品押し出し行程Ｂ終了までの範囲Ｇにわたっては、上パンチホルダー７の案内ローラ１３ａに上方から係合し、上記上パンチホルダー７を介して上パンチ７ａにホールドダウン圧力を加える上部カム体２２が加圧ローラ１５に対して竪シャフト３と反対側すなわち外側方に設けられており、一方、加圧行程Ａの終了直前位置から成形品押し出し行程Ｂ間Ｈにおいては、下パンチホルダー８の上記外側方の案内ローラ１１ａに下方から係合し、下パンチ８ａにホールドアップ圧力を加える下部カム体２３が設けられている。
【００２５】
上記カム体２２は、両パンチ等を保持する回転盤５の回動方向に、５つのカム２２ａ，２２ｂ，２２ｃ，２２ｄ，２２ｅに分割されており、図２及び図３に示すように、各カム２２ａ，２２ｂ，２２ｃ，２２ｄ，２２ｅにそれぞれ圧力シリンダ２４ａ，２４ｂ，２４ｃ，２４ｄ，２４ｅのピストン２５ａ，２５ｂ，２５ｃ，２５ｄ，２５ｅが連結されている。一方下部カム体２３は、上記回転盤５の回動方向に３つのカム２３ａ，２３ｂ，２３ｃに分割されており、各カム２３ａ，２３ｂ，２３ｃにそれぞれ圧力シリンダのピストンが同様に連結されている。
【００２６】
上記構成は、従来の粉末成形機と同一であるが、本発明においては、図２及び図３に示すように、加圧ローラ１５に対して加圧ローラを支持するまたは同期して可動する軸受部１７に上パンチホルダ７に加圧力を加える加圧補助装置２６が設けられている。
【００２７】
すなわち、加圧ローラ１５に対して回転盤５の軸心側に位置し加圧ローラ１５の軸動作と同期する軸受部１７には、下方に開口するシリンダ２８が設けられており、そのシリンダ２８内には所定範囲だけ上下動可能にピストン部材２９が収容され、そのピストン部材２９とシリンダ２８頂壁内面との間に複数枚からなる皿バネ３０が介装されている。
【００２８】
上記ピストン部材２９の下面には、上部内側カム体３１が固着されており、その上部内側カム体３１が、加圧行程Ａの終了直前位置すなわち加圧ローラ１５の最大加圧を行う最下点位置から成型品押出し行程終了までの範囲にわたって、上パンチホルダー７の内側に装着された内側の案内ローラ１３ｂに上方から係合され、上記皿バネ３０の押圧力が上部内側カム体３１を介して上パンチホルダー７に装着された案内ローラ１３ｂに加えられるようになっている。
【００２９】
しかして、上下両パンチ７ａ，８ａが加圧行程の終了直前位置まで移動して来ると、上部カム体２２及び上部内側カム体３１がそれぞれ上パンチホルダー７の案内ローラ１３ａ或は１３ｂに係合し、両カム体により合成された押圧力が成形品に加わる。そして、成形品の押し出し行程終了まで、上記カム体２２，３１の形状に応じてその押圧力が順次小さくなる。
【００３０】
したがって、成型品の押し出し行程開始直後においては、両カム体により合成された押圧力が形成品に加わることから、形成体には大きな力が加わり、スプリングバックの大きな粉末に対しホールドダウン力が作用し、成形体におけるクラックの発生がより抑制される。
【００３１】
すなわち、加圧ローラ１５の軸受部１７と前記シリンダ装置１７ａのピストンとの間にはローラ位置調整機構２７が設けられており、そのローラ位置調整機構２７により軸受部１７の上下位置を調整することにより最初に製作する成形体の高さから加圧ローラ１５の位置とカム体３１の位置が設定してある。したがって、ダイスに絶えず一定の粉末が挿入されれば、成形体の高さのバラツキは特に発生しないが、実際には粉末の流動性・嵩密度等各種条件から、常に一定量の粉末がダイス内に充填されるとは限らず、同一圧力で成形した場合には成形体の高さがばらつく。特に、充填量が少ない場合には、加圧行程においてシリンダ装置１７ａのピストンが押圧によって圧下され、加圧ローラ１５が若干下降した状態で粉末の加圧が行われる。したがって、従来のようにスタンドフレーム２に固設された圧力シリンダ２４ａのピストン２５ａ等によってカム体２２を上パンチに加えるようにしただけのものにおいては、圧力シリンダが一定位置にあるため加圧ローラ１５による加圧終了直後においては、カム体２２による上パンチホルダー７に対する押圧力が十分でなく、スプリングバッグによって成形体にクラックが生ずる可能性がある。
【００３２】
ところが、本発明においては皿バネ３０を有する加圧補助装置２６が軸受部１７に装着されているので、この加圧補助装置２６が加圧ローラ１５に追従して上下動する。したがって、上パンチホルダー７が加圧ローラ最下点を通過した直後に加圧補助装置２６が直ちに作動し、上述の如くカム体３１が十分上パンチホルダー７に作動するまでにタイムラグが生ずるようなことがなく、スプリングバックによって成形体にクラックが生ずることが確実に防止される。
【００３３】
ところで、上記上部内側カム体３１による押圧力は皿バネ３０の組合わせによって調節することができ、通常原子燃料の場合、３〜５ｔｏｎ／ｃｍ２ の加圧力の５〜２０％の圧力、すなわち約１５０〜８００ｋｇ／ｃｍ２ の圧力が成形体に加わるようにすることが好ましい。
【００３４】
なお、上記実施の形態においては上部内側カム体３１を設けたものを示したが、下パンチホルダー８の案内ローラ１１に係合する下部内側カム体を設けてもよい。
【００３５】
上記カム体の加圧力とクラックの発生頻度についての試験結果を表１に示す。
【表１】

Figure 0003558944
この表１に示すように、成形加圧力に対しなるべく高い圧力で成形直後の成形品を押さえながら、ダイスから抜き出すことによりクラックの発生が効果的に抑制されることが判る。そして、その押圧力は成形加圧力の５〜２０％が最適である。
【００３６】
【発明の効果】
以上説明したように、本発明は成形品をダイス内から上下両パンチで挟持しながら押し出す押し出し行程中に、上下両パンチの少なくとも上パンチに加圧力を加え、成形品に所定加圧力を維持させる複数の皿バネを有する加圧補助装置を設けたので、押し出し行程中の成形体に比較的高い圧力を加えた状態を維持することができ、押し出し行程時における急速な解圧によって成形体にクラックが発生することを防止することができる。しかも、上述のように加圧補助装置として皿バネを使用するのでスペース的制約も余り受けることがなく、加圧ローラの内側すなわち加圧ローラに対して回転盤軸心側に配置することができ、従来の押さえカム連続機構と併用して使用することができる。
【図面の簡単な説明】
【図１】本発明における粉末成形機の成形行程の展開図。
【図２】本発明の粉末成形機の押出行程時における成形体加圧装置部の縦断面図。
【図３】上部カム体部の平面図。
【図４】粉末成形機の概略構成を示す縦断面図。
【図５】ダイプレート部の平面図。
【図６】従来の一粉末成形機の成形行程の展開図。
【符号の説明】
５ 回転盤
６ ダイス
７ 上パンチホルダー
７ａ 上パンチ
８ 下パンチホルダー
９ 下パンチ
１１，１３，１３ａ，１３ｂ 案内ローラ
１５，１６ 加圧ローラ
１７，１８ 軸受部
２６ 加圧補助装置
２８ シリンダ
２９ ピストン部材
３０ 皿バネ
３１ 上部内側カム体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a powder molding machine for molding a powder metallurgy material such as a fuel pellet for a nuclear fuel.
[0002]
[Prior art]
Generally, when molding a powder metallurgy material such as the above-mentioned fuel pellet, the powder supplied into the die is compressed by both upper and lower punches.
[0003]
FIG. 4 is a vertical sectional view of a powder molding machine for performing the above-described compression molding, particularly a rotary-type powder molding machine, in which a frame 1 and a stand frame 2 provided above the frame 1 are provided. Has a vertical shaft 3 erected. A vertical shaft oil receiver 4 is fixedly mounted on the upper surface of the frame 1 concentrically with the vertical shaft 3, and above the vertical shaft oil receiver 4, a turntable 5 is provided with respect to the vertical shaft 3. It is mounted rotatably.
[0004]
The rotary disk 5 has an upper flange portion 5a, a central flange portion 5b, and a lower flange portion 5c integrally formed on the outer peripheral portion thereof, and the central flange portion 5b has, as shown in FIG. Are provided with a large number of dies 6 in the circumferential direction.
[0005]
An upper punch holder 7 for holding an upper punch 7a on the same axis as each of the dies 6 is provided on the upper flange-like portion 5a so as to be movable up and down. A lower punch holder 8 for holding a lower punch 8a on the same axis as that of the lower flange 6 is disposed so as to be vertically movable, and is further driven by a driving mechanism as appropriate to a gear 9 formed on the outer periphery of the lower flange-like portion 5c. The drive gear 10 is meshed.
[0006]
On the other hand, a guide roller 11 is mounted on the lower punch holder 8 outside a portion protruding downward from the turntable 5, and the guide roller 11 is disposed on the frame 1 over a predetermined range in the circumferential direction. In the guide groove 12.
[0007]
Guide rollers 13 are also mounted on both sides of a portion of the upper punch holder 7 projecting upward from the rotary disk 5, and are provided in guide grooves 14 provided over a predetermined range in the circumferential direction at a position above the rotary disk 5. Is engaged.
[0008]
Further, the upper punch 7a and the lower punch 8a are respectively inserted into the die 6 from above and below, and the top end of the upper punch holder 7 and the lower punch Pressing rollers 15 and 16 are provided, which abut against the lower ends of the holders 8 and apply pressure to both punches, respectively. The bearing members 17 and 18 for supporting the pressure rollers 15 and 16 are provided on the stand frame 2 or the frame 1 by a mechanism (not shown) so that the bearing members 17 and 18 can only move up and down within a certain range. The cylinder devices 17a and 18a are interposed between the bottom and the stand frame 2 or the frame 1, respectively.
[0009]
Reference numeral 19 in FIG. 4 denotes a powder feeder.
[0010]
When the powder is compacted, the rotating disk 5 is rotated via the drive gear 10, and the powder is supplied from the powder feeder 19 into the die 6 at a predetermined position. Therefore, the lower punch 8a is moved upward through the guide groove 12 and the guide roller 11 so as to have a predetermined filling depth in accordance with the rotation of the turntable 5, and after the excess powder is removed, the upper punch 8a is removed. 7a is gradually lowered, and the powder in the die 6 is sandwiched between the upper and lower punches 7a, 8a. In this way, when the upper and lower punches 7a and 8a holding the powder in the die 6 between the pressing rollers 15 and 16 enter the pressing rollers 15, 16 to which predetermined pressure is applied by the cylinder devices 17a and 18a. Thus, the upper and lower punches 7a, 8a are pressed in directions approaching each other, and compression molding of the powder is performed. When the pressing process is completed in this manner, the upper and lower punches are moved upward while the molded product is held between the upper and lower punches 7a and 8a, and the upper surface of the lower punch 8a is the same as the upper surface (die table) of the die 6. At this point, the upper punch 7a is moved further upward, and then the molded product is paid out. Thereafter, in the same manner, the compression molding of the powder is sequentially performed in each die 6.
[0011]
[Problems to be solved by the invention]
However, in general, at the time of powder molding, a pressure of the order of several tons / cm 2 is applied to the molded product in the die, and when the molded product is extracted from the die, it expands by about 1 to 1.5%.
[0012]
Accordingly, if the pressure is rapidly released when the extrusion process is started after the completion of molding, there are problems such as occurrence of defects such as cracks in the molded product.
[0013]
Therefore, in order to maintain a predetermined pressing force on the molded product during the extrusion process in which the molded product is sandwiched between the dies and extruded by the upper and lower punches, at least one of the upper and lower punches is provided with a cam mechanism for applying a pressing force to the punch. It has been proposed that the cam bodies 22 and 23 of the cam mechanism are constituted by a plurality of cams which are divided from each other in the rotating direction of the turntable so that the pressing force of the pressurizing cylinder of each cam is gradually reduced. (Japanese Utility Model Publication No. 2-35955).
[0014]
However, as described above, when the pressing force is applied to the cam mechanism by the pressurizing cylinder, the pressing force is applied to the punch by air pressure. Fluctuates, the position of the punch is constantly displaced by the amount of the fluctuation, there is variation in the pressing force, it is difficult to keep the pressing force constant, and it is necessary to sufficiently suppress the occurrence of cracks and the like in the molded product There are problems such as not being able to do.
[0015]
Also, as shown in FIG. 6, in the pressing step, two pressure roller pairs are provided in the rotating direction, and the first upper and lower pressure rollers 15a and 16a perform the main pressure forming, and the second upper and lower pressure rollers. The pressure rollers 15b and 16b are used to carry out excess pressure forming, so that the pressure of the molded product is suddenly released, or the first upper and lower pressing rollers 15a and 16a are used to form the second product and the second pressurizing roller is used to form the second product. It has also been proposed to perform the main pressure molding with the upper and lower pressure rollers 15b, 16b.
[0016]
However, even in the case of providing a plurality of pairs of pressure rollers as described above, it is necessary to adjust the position of the pressure roller in order to maintain a predetermined pressure, it is difficult to adjust the position, and the structure is complicated, There are problems such as the occurrence of cracks and the like in the molded product cannot always be sufficiently suppressed.
[0017]
In view of the foregoing, the present invention has been made to maintain a sufficient pressing force on a molded product immediately after pressure molding, and to sufficiently suppress the occurrence of cracks and the like in the molded product and improve the yield of the molded product. The purpose is to obtain a molding machine.
[0018]
[Means for Solving the Problems]
An invention according to claim 1 is a rotary-type powder molding machine that press-molds powder by pressing force of both upper and lower punches, wherein the pressing roller applies a pressing force to at least the upper punch of the upper and lower punches by moving the pressing roller up and down. A pressure assist device having a plurality of disc springs is mounted on the pressure roller bearing that moves up and down in synchronization with the pressure assist device, and the disc spring of the pressure assist device immediately after passing the maximum pressure point of the pressure roller. A predetermined pressing force is applied to the upper punch to maintain a predetermined pressing force on the molded product.
[0019]
According to a second aspect of the present invention, in the first aspect of the present invention, a disc spring is provided in a cylinder of the pressure assist device provided in the pressure roller bearing, and a pressing force of the disc spring is applied to the cylinder. It is characterized by being added to a guide roller provided on an upper punch holder for holding an upper punch via a cam body fixed to a piston member housed therein so as to be vertically movable.
[0020]
According to a third aspect of the present invention, in the first or second aspect of the invention, the pressing force of the pressing auxiliary device immediately after passing the maximum pressing point of the pressing roller is 5 to 20% of the molding pressure. And a disc spring is combined.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0022]
In the figure, the same parts as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0023]
FIG. 1 is an exploded view showing each molding process of a rotary powder molding machine, in which guide rails 20, 21 such as guide grooves 14, 12 provided with an upper punch 7a and a lower punch 8a along the moving direction. , And moves up and down, following the pressing process A in which the powder is pressed by the pressing rollers 15 and 16, followed by a molded product extruding process B, a molded product discharging process C, a powder filling process D, and weight adjustment. Step E and pressurization preparation step F are sequentially repeated.
[0024]
By the way, over a range G from a position immediately before the end of the powder pressing process A by the pressing rollers 15 and 16 to the end of the molded product extruding process B, the upper roller is engaged with the guide roller 13a of the upper punch holder 7 from above. An upper cam body 22 for applying a hold-down pressure to the upper punch 7a via the punch holder 7 is provided on the side opposite to the vertical shaft 3 with respect to the pressing roller 15, that is, on the outer side. In the period H during the extrusion process B from the immediately preceding position, a lower cam body 23 is provided which engages the guide roller 11a on the outer side of the lower punch holder 8 from below and applies a hold-up pressure to the lower punch 8a. .
[0025]
The cam body 22 is divided into five cams 22a, 22b, 22c, 22d, and 22e in the direction of rotation of the rotary disk 5 that holds both punches and the like. As shown in FIGS. The pistons 25a, 25b, 25c, 25d, 25e of the pressure cylinders 24a, 24b, 24c, 24d, 24e are connected to the cams 22a, 22b, 22c, 22d, 22e, respectively. On the other hand, the lower cam body 23 is divided into three cams 23a, 23b, and 23c in the rotation direction of the rotary disk 5, and the pistons of the pressure cylinders are similarly connected to the respective cams 23a, 23b, and 23c. .
[0026]
The above configuration is the same as that of the conventional powder molding machine. However, in the present invention, as shown in FIGS. The section 17 is provided with a pressure assisting device 26 for applying a pressing force to the upper punch holder 7.
[0027]
That is, the bearing portion 17 which is located on the shaft center side of the rotating disk 5 with respect to the pressure roller 15 and is synchronized with the axial operation of the pressure roller 15 is provided with a cylinder 28 which opens downward. A piston member 29 is accommodated therein so as to be able to move up and down by a predetermined range, and a plurality of disc springs 30 are interposed between the piston member 29 and the inner surface of the top wall of the cylinder 28.
[0028]
An upper inner cam body 31 is fixed to the lower surface of the piston member 29, and the upper inner cam body 31 is located at a position immediately before the end of the pressing stroke A, that is, a lowermost point at which the pressing roller 15 performs maximum pressing. Over the range from the position to the end of the molded product extruding process, it is engaged from above with the inner guide roller 13b mounted inside the upper punch holder 7, and the pressing force of the disc spring 30 is applied via the upper inner cam body 31. It is designed to be added to a guide roller 13b mounted on the upper punch holder 7.
[0029]
When the upper and lower punches 7a, 8a have moved to positions immediately before the end of the pressing stroke, the upper cam body 22 and the upper inner cam body 31 engage the guide rollers 13a or 13b of the upper punch holder 7, respectively. Then, the pressing force synthesized by the two cam bodies is applied to the molded product. Until the extrusion process of the molded product is completed, the pressing force is gradually reduced according to the shape of the cam bodies 22 and 31.
[0030]
Therefore, immediately after the start of the extrusion process of the molded product, the pressing force synthesized by the two cam bodies is applied to the formed product, so that a large force is applied to the formed product and a hold-down force acts on the powder having a large springback. However, generation of cracks in the molded body is further suppressed.
[0031]
That is, a roller position adjusting mechanism 27 is provided between the bearing 17 of the pressure roller 15 and the piston of the cylinder device 17a, and the vertical position of the bearing 17 is adjusted by the roller position adjusting mechanism 27. Thus, the position of the pressure roller 15 and the position of the cam body 31 are set based on the height of the molded body to be manufactured first. Therefore, if a certain amount of powder is constantly inserted into the die, there is no particular variation in the height of the compact, but in fact, due to various conditions such as the fluidity and bulk density of the powder, a certain amount of powder always remains in the die. Is not always filled, and when molded under the same pressure, the height of the molded body varies. In particular, when the filling amount is small, the piston of the cylinder device 17a is pressed down by the pressing in the pressing process, and the powder is pressed while the pressing roller 15 is slightly lowered. Therefore, in the conventional apparatus in which the cam body 22 is simply applied to the upper punch by the piston 25a of the pressure cylinder 24a fixed to the stand frame 2, since the pressure cylinder is at a fixed position, Immediately after the pressurization by 15, the pressing force of the cam body 22 against the upper punch holder 7 is not sufficient, and there is a possibility that cracks may occur in the formed body due to the spring bag.
[0032]
However, in the present invention, since the pressure assisting device 26 having the disc spring 30 is mounted on the bearing 17, the pressure assisting device 26 moves up and down following the pressure roller 15. Therefore, immediately after the upper punch holder 7 has passed the lowermost point of the pressure roller, the pressure assisting device 26 is immediately activated, and a time lag occurs until the cam body 31 operates sufficiently on the upper punch holder 7 as described above. Thus, cracks in the molded body due to springback are reliably prevented.
[0033]
By the way, the pressing force by the upper inner cam body 31 can be adjusted by a combination of the disc springs 30. In the case of normal nuclear fuel, 5 to 20% of the pressing force of 3 to 5 ton / cm 2 , that is, about Preferably, a pressure of 150 to 800 kg / cm 2 is applied to the compact.
[0034]
In the above embodiment, the upper inner cam body 31 is provided, but a lower inner cam body that engages with the guide roller 11 of the lower punch holder 8 may be provided.
[0035]
Table 1 shows test results on the pressing force of the cam body and the frequency of occurrence of cracks.
[Table 1]
Figure 0003558944
As shown in Table 1, it can be seen that the generation of cracks is effectively suppressed by removing the molded product immediately after molding with a pressure as high as possible with respect to the molding pressure and extracting the molded product from the die. The pressing force is optimally 5 to 20% of the molding pressure.
[0036]
【The invention's effect】
As described above, the present invention applies a pressing force to at least the upper punches of the upper and lower punches during the extrusion process of extruding the molded product from the inside of the die while holding the molded product between the upper and lower punches, thereby maintaining a predetermined pressing force on the molded product. Since the pressure assisting device having a plurality of disc springs is provided, it is possible to maintain a state in which a relatively high pressure is applied to the compact during the extrusion process, and the compact is cracked by the rapid pressure release during the extrusion process. Can be prevented from occurring. In addition, since a coned disc spring is used as the pressure assisting device as described above, there is not much space restriction, and the pressure assisting device can be disposed inside the pressure roller, that is, on the rotating disk axis side with respect to the pressure roller. It can be used in combination with a conventional pressing cam continuous mechanism.
[Brief description of the drawings]
FIG. 1 is a development view of a molding process of a powder molding machine according to the present invention.
FIG. 2 is a longitudinal sectional view of a compact pressing device during the extrusion process of the powder compacting machine of the present invention.
FIG. 3 is a plan view of an upper cam body.
FIG. 4 is a longitudinal sectional view showing a schematic configuration of a powder molding machine.
FIG. 5 is a plan view of a die plate portion.
FIG. 6 is a development view of a molding process of a conventional powder molding machine.
[Explanation of symbols]
5 Rotating disk 6 Die 7 Upper punch holder 7a Upper punch 8 Lower punch holder 9 Lower punch 11, 13, 13a, 13b Guide rollers 15, 16 Pressure rollers 17, 18 Bearing unit 26 Pressure assist device 28 Cylinder 29 Piston member 30 Disc spring 31 Upper inner cam body

Claims (3)

上下両パンチによる加圧力によって粉末を加圧成形するロータリ型の粉末成形機において、上記上下両パンチの少なくとも上パンチに加圧力を加える加圧ローラの上下位置移動に同期して上下動する加圧ローラ軸受部に、複数の皿バネを有する加圧補助装置を装着し、上記加圧補助装置の皿バネにより、加圧ローラの最大加圧点を通過した直後の上パンチに所定の押圧力を加え、成型品に所定加圧力を維持させるようにしたことを特徴とする粉末成形機。In a rotary-type powder molding machine that pressurizes and forms powder by the pressing force of both upper and lower punches, pressurization that moves up and down in synchronization with the vertical position movement of a pressing roller that applies a pressing force to at least the upper punch of the upper and lower punches A pressure assisting device having a plurality of disc springs is mounted on the roller bearing, and a predetermined pressing force is applied to the upper punch immediately after passing the maximum pressing point of the pressure roller by the disc spring of the pressure assisting device. In addition, a powder molding machine characterized by maintaining a predetermined pressure on a molded product . 上記加圧ローラ軸受部に設けられた加圧補助装置のシリンダ内に皿バネが配設され、その皿バネによる押圧力が、上記シリンダ内に上下動可能に収容されたピストン部材に固着されたカム体を介して、上パンチを保持する上パンチホルダに設けられている案内ローラに加えられるようにしたことを特徴とする、請求項１記載の粉末成型機。 A disc spring is disposed in a cylinder of the pressure assist device provided in the pressure roller bearing , and the pressing force of the disc spring is fixed to a piston member housed vertically in the cylinder. 2. The powder molding machine according to claim 1, wherein the powder molding machine is adapted to be added to a guide roller provided on an upper punch holder for holding the upper punch via a cam body . 加圧ローラの最大加圧点を通過した直後の加圧補助装置における押圧力が成型加圧力の５〜２０％になるように皿バネが組合わせられていることを特徴とする、請求項１または２記載の粉末成型機。2. A disk spring is combined so that the pressing force of the pressing auxiliary device immediately after passing through the maximum pressing point of the pressing roller is 5 to 20% of the molding pressure. Or the powder molding machine according to 2.
JP2000027785A 1999-02-09 2000-02-04 Powder molding machine Expired - Fee Related JP3558944B2 (en)

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