JP3609433B2

JP3609433B2 - Hollow injection molding method

Info

Publication number: JP3609433B2
Application number: JP8933792A
Authority: JP
Inventors: 茂生新宮; 保雄竹中; 勇樹森
Original assignee: Asahi Kasei Chemicals Corp
Current assignee: Asahi Kasei Chemicals Corp
Priority date: 1992-03-16
Filing date: 1992-03-16
Publication date: 2005-01-12
Anticipated expiration: 2020-01-12
Also published as: JPH05261748A

Description

【０００１】
【産業上の利用分野】
本発明は、金型キャビティ内に射出された溶融樹脂中に加圧流体を圧入することによって中空部を成形する中空射出成形方法に関する。特に、例えば自動車のバンパーやインストルメントパネル等のように、肉厚に変化を有していたり非対称の形状で大型の中空射出成形品の成形方法に関する。
【０００２】
【従来の技術】
従来、金型キャビティ内に射出された溶融樹脂中に加圧流体を圧入することで中空部を成形する中空射出成形方法が知られている（特公昭５７−１４９６８号公報）。
【０００３】
また、加圧流体を圧入するに際し、金型キャビティ内に開口する複数の加圧流体圧入口を設けて、この複数の加圧流体圧入口から同時に同じ圧力の加圧流体を圧入することも知られている。
【０００４】
【発明が解決しようとする課題】
しかしながら、金型キャビティ内に射出された溶融樹脂中に加圧流体を圧入する際に、必要な位置に確実に必要量の加圧流体を圧入しにくい問題がある。特に、成形すべき中空射出成形品が、厚さに変化を有し、非対称形状で大型になる程偏りのない加圧流体の圧入が行いにくい問題がある。この問題は、複数の加圧流体圧入口から加圧流体の圧入を行うことによってやや軽減される傾向にはあるが、これも十分な解決策とはなっていない。
【０００５】
必要な位置に必要量の加圧流体の圧入が行えない場合、所要の中空部を形成できないだけでなく、この中空部が形成できないことによって所謂ヒケを生じてしまい、中空射出成形品の品質を確保することが困難になる。
【０００６】
一方、実用に供される中空射出成形品は、一様な肉厚で対称形状のものはむしろまれで、肉厚に変化を有し、非対称形状のものがほとんどであり、しかも最近ではかなり大型の中空射出成形品の需要が増大している現状にある。
【０００７】
本発明は、このような現状に鑑みてなされたもので、肉厚に変化を有し、非対称形状で、しかも大型の中空射出成形品の成形に際しても、所要の位置に所要の大きさの中空部を確実に形成できるようにすることを目的とする。
【０００８】
【課題を解決するための手段及び作用】
本発明は、加圧流体の圧入状態に偏りを生じる原因が、金型キャビティ内に射出された溶融樹脂の圧力が一様ではない点にあることを見出したことによってなされたものである。
【０００９】
更に説明すると、金型キャビティ内に射出された溶融樹脂は圧力が一様ではなく、金型キャビティの部分によって高低の差を有する。
【００１０】
例えば、ゲートに近い部分に充填された溶融樹脂の圧力は一般的に高く、ゲートから離れるに従って、その流動抵抗によって溶融樹脂の圧力は低くなる傾向にある。特に、ゲート付近の金型キャビティ断面積が大きく、ゲートから離れた部分の金型キャビティ断面積が小さい時にはなおさらである。
【００１１】
このような溶融樹脂の状態下で加圧流体の圧入が行われるので、例え複数の加圧流体圧入口からの圧入を行っても、溶融樹脂の圧力が低い部分に開口する加圧流体圧入口から優先的に加圧流体が圧入され、これによって加圧流体の圧入状態に偏りを生じることになる。
【００１２】
そこで本発明は、第１に、金型キャビティ内へ射出された溶融樹脂中へ、金型キャビティ内に開口する複数の加圧流体圧入口から加圧流体を圧入する中空射出成形方法において、加圧流体圧入時期と加圧流体圧入圧力を加圧流体圧入口毎に制御して、高い圧力の溶融樹脂が充填される金型キャビティ部分に開口する加圧流体圧入口からと、低い圧力の溶融樹脂が充填される金型キャビティ部分に開口する加圧流体圧入口からとの加圧流体の圧入を異なる加圧流体圧入時期及び異なる加圧流体圧入圧力で行うことを特徴とする中空射出成形方法を提供するものである。また、本発明は、第２に、金型キャビティ内へ射出された溶融樹脂中へ、金型キャビティ内に開口する複数の加圧流体圧入口から加圧流体を圧入する中空射出成形方法において、加圧流体圧入時期を加圧流体圧入口毎に制御して、高い圧力の溶融樹脂が充填される金型キャビティ部分に開口する加圧流体圧入口からの加圧流体圧入時期を、低い圧力の溶融樹脂が充填される金型キャビティ部分に開口する加圧流体圧入口からの加圧流体圧入時期より早くすることを特徴とする中空射出成形方法を提供すると共に、第３に、金型キャビティ内へ射出された溶融樹脂中へ、金型キャビティ内に開口する複数の加圧流体圧入口から加圧流体を圧入する中空射出成形方法において、加圧流体圧入圧力を加圧流体圧入口毎に制御して、高い圧力の溶融樹脂が充填される金型キャビティ部分に開口する加圧流体圧入口からの加圧流体圧入圧力を、低い圧力の溶融樹脂が充填される金型キャビティ部分に開口する加圧流体圧入口からの加圧流体圧入圧力より高くすることを特徴とする中空射出成形方法を提供するものである。
【００１３】
更に本発明を図１に基づいて説明する。
【００１４】
図１において、１は移動型１ａと固定型１ｂとからなる金型、２は移動型１ａと固定型１ｂ間に形成された金型キャビティ、３は射出ノズル、４はこの射出ノズル３に内蔵された加圧流体ノズル、５は制御装置、６は加圧流体発生装置、７は加圧流体源である。
【００１５】
射出ノズル３から射出された溶融樹脂は、ゲート８を介して金型キャビティ２内に充填されるもので、このゲート８は、加圧流体ノズル４から加圧流体を金型キャビティ２内の溶融樹脂に圧入するための加圧流体圧入口９ａを兼ねたものとなっている。
【００１６】
金型キャビティ２には、上記ゲート８でもある加圧流体圧入口９ａの他に、ゲート８から離れた位置にもうひとつの加圧流体圧入口９ｂが開口している。
【００１７】
この加圧流体圧入口９ａ，９ｂの設置位置は、中空部の形成位置に応じて適宜定めればよいが、特に成形すべき中空射出成形品が肉厚変化を有するものである時には、その厚肉部分（例えばボスやリブの形成箇所）に設けることが好ましい。また、溶融樹脂中に圧入された加圧流体の侵入方向を誘導するために、金型キャビティ２に溝状の誘導チャンネル（図示されていない）を設けた場合には、この誘導路に接続される位置に設けることが好ましい。
【００１８】
加圧流体圧入口９ａ，９ｂは、夫々供給路１０ａ，１０ｂを介して制御装置５に接続されている。この制御装置５は、各加圧流体圧入口９ａ，９ｂへの加圧流体の供給時期及び／又は供給する加圧流体の圧力を制御するものである。
【００１９】
制御装置５は、加圧流体発生装置６に接続されている。
【００２０】
加圧流体発生装置６は、コンプレッサー等の加圧機６ａと、蓄圧容器６ｂと、回収容器６ｃとを備えたもので、回収容器６ｃ及び／又は加圧流体源７から供給される加圧流体を加圧機６ａで昇圧し、この昇圧された加圧流体を蓄圧容器６ｂに蓄えるものである。
【００２１】
制御装置５は加圧流体発生装置６の蓄圧容器６ｂに接続されている。また、前記供給路１０ａ，１０ｂの途中には、夫々開閉弁１１ａ，１１ｂが介在した回収路１２ａ，１２ｂの一端が接続されており、この回収路１２ａ，１２ｂの他端は回収容器６ｃに接続されている。
【００２２】
まず、射出ノズル３から金型キャビティ２内に溶融樹脂を射出する。次いで、金型キャビティ２内の溶融樹脂に加圧流体を圧入する。
【００２３】
樹脂としては、一般の射出成形あるいは押出成形等に使用される熱可塑性樹脂全般を用いることができ、必要に応じて熱硬化性樹脂も使用できる。また、樹脂には必要に応じて各種添加剤を添加することができる。
【００２４】
加圧流体としては、常温常圧でガス状又は液状のもので、射出時の温度と圧力下において、使用樹脂と反応又は混合されないものが使用される。具体的には、例えば窒素ガス、炭酸ガス、空気、ヘリウムガス、水、グリセリン、流動パラフィン等であるが、窒素ガス、ヘリウムガス等の不活性ガスが好ましい。また、加圧流体の圧力は、一般的には１０〜５００ｋｇ／ｃｍ^２程度である。
【００２５】
加圧流体の圧入は、開閉弁１１ａ，１１ｂを閉じた状態で各加圧流体圧入口９ａ，９ｂを介して行われる。各加圧流体圧入口９ａ，９ｂからの圧入時期及び／又は圧入圧力が制御器５によって制御される。
【００２６】
即ち、各加圧流体圧入口９ａ，９ｂが開口している部分に充填された溶融樹脂の圧力が等しい時には、各加圧流体圧入口９ａ，９ｂから同時に同じ圧力の加圧流体を圧入することになるが、通常この溶融樹脂の圧力は金型キャビティ２の部分によって異なるので、各加圧流体圧入口９ａ，９ｂが開口している部分の溶融樹脂の圧力に応じて圧入時期及び／又は圧入圧力を制御する。
【００２７】
図示される金型１においては、ゲート８から離れた位置にある加圧流体圧入口９ｂ部分の溶融樹脂に比して、ゲート８を兼ねる加圧流体圧入口９ａ部分の溶融樹脂の圧力の方が高く、加圧流体圧入口９ａからの加圧流体の圧入が、加圧流体圧入口９ｂからの加圧流体の圧入より行いにくくなるのが通常である。従って、（１）加圧流体圧入口９ａからの圧入を加圧流体圧入口９ｂからの圧入より早く開始する、（２）加圧流体圧入口９ａから圧入される加圧流体の圧力を加圧流体圧入口９ｂから圧入される加圧流体の圧力より高くする、（３）加圧流体圧入口９ａからの圧入を加圧流体圧入口９ｂからの圧入より早く開始し、かつ、加圧流体圧入口９ａから圧入される加圧流体の圧力を加圧流体圧入口９ｂから圧入される加圧流体の圧力より高くする、のいずれかの制御を行う。
【００２８】
加圧流体の圧入時期の制御は、加圧流体圧入口９ａ，９ｂへの加圧流体の供給を開閉制御する開閉弁（図示されていない）を制御器５に設け、その開放時期を調整することで行うことができる。また、圧入される加圧流体の圧力制御は、制御器５に圧力調整弁（図示されていない）を設け、この圧力調整弁で加圧流体圧入口９ａ，９ｂの供給される加圧流体の圧力を調整することで行うことができる。
【００２９】
このようにして加圧流体の圧入を行って所定の中空部を形成した後、各加圧流体圧入口９ａ，９ｂへの加圧流体の供給を止め、金型キャビティ２内の樹脂が十分冷却されてから、回収路１２ａ，１２ｂの開閉弁１１ａ，１１ｂを開放し、形成された中空部内の加圧流体を回収容器６ｃに回収する。そして、更に中空部内に残存する加圧流体を排出した後金型１を開いて、成形された中空射出成形品を取り出す。
【００３０】
上記方法によって得られる中空射出成形品は、金型キャビティ２内に射出された溶融樹脂中に、金型キャビティ２内に開口する複数の加圧流体圧入口９ａ，９ｂから、加圧流体圧入時期と圧入圧力の少なくとも一方を加圧流体圧入口毎に制御して加圧流体を圧入することによって形成された中空部を有するものとなる。
【００３１】
この中空射出成形品は、必要な位置に必要な大きさの中空部が形成されているので、ヒケのない良好な品質のものとなる。
【００３２】
本発明における制御は、上述のように、加圧流体圧入口９ａ，９ｂが開口する部分に充填される溶融樹脂の圧力に基づいて行うことが必要であるが、更に溶融樹脂の温度も加味して制御を行うことが好ましい。即ち、前述の圧力差による制御を温度に基づいて補正することが好ましい。
【００３３】
例えばゲート８から離れた位置に充填される溶融樹脂は、射出開始後直ちに充填されるゲート８付近の溶融樹脂に比して、冷却されながら流動した後に充填されたものであるために温度が低いのが通常である。また、加圧流体の圧入時期を遅らせた場合、その遅れた分冷却を受けることで溶融樹脂の温度は低くなる。温度の低い溶融樹脂は、温度の高い溶融樹脂に比して流動性が乏しく、その分加圧流体も圧入しにくい状態にある。
【００３４】
従って、溶融樹脂の圧力が一様の場合、温度の低い溶融樹脂が充填される部分に開口する加圧流体圧入口９ｂからの加圧流体の圧入は、温度の高い溶融樹脂が充填される部分に開口する加圧流体圧入口９ａに比して、早い時期に及び／又は高い圧力で行うのが好ましく、これに基づいて前述の圧力差による制御を補正することが好ましい。
【００３５】
更に本発明における制御は、加圧流体圧入口９ａから圧入される加圧流体によって形成されるべき中空部の大きさと、加圧流体圧入口９ｂから圧入される加圧流体によって形成されるべき中空部の大きさの相違に基づいて、前述の圧力差による制御を補正することが好ましい。
【００３６】
即ち、大きな中空部の形成が予定されている箇所への加圧流体の圧入は早い時期に及び／又は高い加圧流体で行い、中空部の形成を促すことが好ましく、逆に小さな中空部の形成が予定されている箇所への加圧流体の圧入は、遅い時期に及び／又は低い圧力の加圧流体で行い、中空部の形成を押え気味にすることが好ましいことから、これに基づいて前述の圧力差による制御を補正することが好ましい。
【００３７】
本発明における制御項目は、加圧流体の圧入時期及び／又は加圧流体の圧力であるが、更に加圧流体の圧入時間も加えて制御することが好ましい。即ち、加圧流体が圧入されにくい高い圧力の溶融樹脂が充填される部分への加圧流体の圧入時間は長くとり、加圧流体が圧入されやすい低い圧力の溶融樹脂が充填される部分への加圧流体の圧入時間は短くすることが好ましい。
【００３８】
本発明において加圧流体圧入口９ａ，９ｂは、図示されるような２箇所に限られず、３箇所以上としてもよく、成形すべき中空射出成形品の大きさ、形状等に応じて定めればよい。また、図示されるように、ゲート８を兼ねる加圧流体圧入口９ａを有する場合、一般にこのゲート８を兼ねる加圧流体圧入口９ａ付近の溶融樹脂は他の加圧流体圧入口９ｂ付近の溶融樹脂より圧力が高くなるので、ゲートを兼ねる加圧流体圧入口９ａからの加圧流体の圧入は、それ以外の加圧流体圧入口９ｂからの加圧流体の圧入に比して、早い時期及び／又は高い圧力で行われることになる。
【００３９】
【実施例】
実施例１
図２〜図４に示されるような自動車のインストルメントパネルを成形した。
【００４０】
図２において、矢印Ａは図１におけるゲート８を兼ねる加圧流体圧入口９ａからの溶融樹脂充填方向及び加圧流体圧入方向を示し、矢印Ｂは図１における加圧流体圧入口９ｂからの加圧流体圧入方向を示す。また、１３ａ，１３ｂは、圧入された加圧流体の侵入方向を誘導するために形成された厚肉部分である誘導チャンネル部である。
【００４１】複合ポリプロピレン（旭化成工業社製「ロイマーＱＴＤ２４２Ｅ」）を、２２０℃で溶融させて１０秒間射出し、４０℃の温度に調整された金型内の矢印Ａに相当する部分から充填した。
【００４２】
上記溶融樹脂の充填が完了してから０．１秒後に、金型の矢印Ａに相当する部分から圧力１５０ｋｇ／ｃｍ^２の窒素ガスを圧入すると共に、溶融樹脂の充填が完了してから１秒後に、圧力１７５ｋｇ／ｃｍ^２の窒素ガスを、金型の矢印Ｂに相当する部分から圧入した。尚、窒素ガスの圧力は、溶融樹脂の温度及び形成すべき中空部の大きさを考慮して定めた。
【００４３】
金型内の樹脂を冷却した後、形成された中空部内の窒素ガスを排出し、金型を開放して、成形されたインストルメントパネルを取り出したところ、誘導チャンネル部１３ａ，１３ｂのほぼ全域に中空部が形成され、更にこの誘導チャンネル部１３ａ，１３ｂが連結されたボス、リブ等の厚肉部にも中空部が形成されており、ヒケの発生は観察されなかった。
【００４４】
また、このインストルメントパネルを１２０℃の環境温度にさらして耐熱性を調べたところ、変形が極めて少なく、良好な耐熱性が確認された。
【００４５】
比較例１
溶融樹脂の充填が完了してから０．１秒後に、矢印Ａ及びＢに相当する部分から同時に１５０ｋｇ／ｃｍ^２の圧力の窒素ガスを圧入した以外実施例１と同様にしてインストルメントパネルの成形を行った。
【００４６】
得られたインストルメントパネルは、特に金型のゲート側に位置する誘導チャンネル部１３ａの両端部分に中空部が形成されておらず、この部分にヒケが観察された。
【００４７】
【発明の効果】
本発明は以上説明した通りのものであり、肉厚変化を有し、非対称形状で大型の製品でもヒケのない良好な品質を維持することができ、特に近年需要の高まっている自動車のインストルメントパネル、バンパー等の大型製品の製造に極めて有益なものである。
【図面の簡単な説明】
【図１】本発明の説明図である。
【図２】実施例で成形した自動車のインストルメントパネルの説明図である。
【図３】図２におけるＩＩＩ−ＩＩＩ断面図である。
【図４】図２におけるＩＶ−ＩＶ断面図である。
【符号の説明】
１金型
１ａ移動型
１ｂ固定型
２金型キャビティ
３射出ノズル
４加圧流体ノズル
５制御装置
６加圧流体発生装置
６ａ加圧機
６ｂ蓄圧容器
６ｃ回収容器
７加圧流体源
８ゲート
９ａ，９ｂ加圧流体圧入口
１０ａ，１０ｂ供給路
１１ａ，１１ｂ開閉弁
１２ａ，１２ｂ回収路
１３ａ，１３ｂ誘導チャンネル部[0001]
[Industrial application fields]
The present invention relates to a hollow injection-molding method for molding a hollow portion by forcing pressurized fluid into the molten resin injected into the mold cavity. In particular, for example, as in automobiles bumpers and instrument panels, it relates to a molding method of a large hollow injection-molded article in the form of an asymmetric or have a change in wall thickness.
[0002]
[Prior art]
Conventionally, a hollow injection molding method is known in which a hollow portion is formed by press-fitting a pressurized fluid into a molten resin injected into a mold cavity (Japanese Patent Publication No. 57-14968).
[0003]
It is also known that when pressurizing a pressurized fluid, a plurality of pressurized fluid pressure inlets opened in the mold cavity are provided, and pressurized fluid of the same pressure is simultaneously injected from the plurality of pressurized fluid pressure inlets. It has been.
[0004]
[Problems to be solved by the invention]
However, when pressurizing the pressurized fluid into the molten resin injected into the mold cavity, there is a problem that it is difficult to reliably press the required amount of the pressurized fluid into the required position. In particular, there is a problem that a hollow injection molded product to be molded has a change in thickness, and it is difficult to pressurize a pressurized fluid with no deviation as it becomes asymmetrical and large in size. This problem tends to be alleviated by pressurizing pressurized fluid from a plurality of pressurized fluid pressure inlets, but this is also not a sufficient solution.
[0005]
If the required amount of pressurized fluid cannot be injected at the required position, not only the required hollow part cannot be formed, but also the hollow part cannot be formed, so-called sinks occur, and the quality of the hollow injection molded product is reduced. It becomes difficult to secure.
[0006]
On the other hand, hollow injection-molded products that are put into practical use are rarely those with a uniform wall thickness and symmetrical shape, but have a change in the wall thickness, are mostly asymmetrical shapes, and are recently quite large. The demand for hollow injection molded products is increasing.
[0007]
The present invention has been made in view of such a situation, and has a change in thickness, an asymmetric shape, and a hollow of a required size at a required position even when molding a large hollow injection molded product. It is an object to ensure that the portion can be formed.
[0008]
[Means and Actions for Solving the Problems]
The present invention has been made by finding that the cause of the bias in the press-fitted state of the pressurized fluid is that the pressure of the molten resin injected into the mold cavity is not uniform.
[0009]
More specifically, the pressure of the molten resin injected into the mold cavity is not uniform, and there is a difference in height between the mold cavity portions.
[0010]
For example, the pressure of the molten resin filled in the portion close to the gate is generally high, and the pressure of the molten resin tends to decrease due to the flow resistance as the distance from the gate increases. This is especially true when the mold cavity cross-sectional area near the gate is large and the mold cavity cross-sectional area away from the gate is small.
[0011]
Since pressurization of the pressurized fluid is performed under such a state of the molten resin, even if the pressurization from a plurality of pressurized fluid pressure inlets is performed, the pressurized fluid pressure inlet that opens to a portion where the pressure of the molten resin is low Therefore, the pressurized fluid is press-fitted preferentially, thereby causing a bias in the press-fitted state of the pressurized fluid.
[0012]
In view of this, the present invention provides a first aspect of a hollow injection molding method in which pressurized fluid is injected into a molten resin injected into a mold cavity from a plurality of pressurized fluid inlets that open into the mold cavity. By controlling the pressure fluid injection timing and the pressure fluid injection pressure for each pressure fluid pressure inlet, the low pressure melting from the pressure fluid inlet opening into the mold cavity filled with the high pressure molten resin A hollow injection molding method characterized in that pressurization of pressurized fluid from a pressurized fluid pressure inlet opening in a mold cavity portion filled with resin is performed at different pressurized fluid pressure injection times and different pressurized fluid pressure pressures. Is to provide. Second, the present invention relates to a hollow injection molding method in which pressurized fluid is pressed into a molten resin injected into a mold cavity from a plurality of pressurized fluid pressure inlets opened in the mold cavity. The pressurized fluid injection timing is controlled for each pressurized fluid injection port, and the pressurized fluid injection timing from the pressurized fluid injection port that opens to the mold cavity filled with high-pressure molten resin is set to a low pressure. Provided is a hollow injection molding method characterized in that the pressurization fluid press-in timing from the pressurization fluid press-in opening opening into the mold cavity portion filled with the molten resin is provided, and thirdly, in the mold cavity In a hollow injection molding method in which pressurized fluid is injected from a plurality of pressurized fluid pressure inlets that open into the mold cavity into the molten resin injected into the mold, the pressurized fluid pressure is controlled for each pressurized fluid pressure inlet. A high pressure molten tree Pressurized fluid injection pressure from the pressurized fluid pressure inlet that opens into the mold cavity portion filled with the pressure is pressurized from the pressurized fluid pressure inlet that opens into the mold cavity portion filled with the low pressure molten resin. A hollow injection molding method characterized in that the pressure is higher than the fluid press-fitting pressure .
[0013]
Further, the present invention will be described with reference to FIG.
[0014]
In FIG. 1, 1 is a mold composed of a movable mold 1a and a fixed mold 1b, 2 is a mold cavity formed between the movable mold 1a and the fixed mold 1b, 3 is an injection nozzle, and 4 is built in the injection nozzle 3. The pressurized fluid nozzle 5 is a control device, 6 is a pressurized fluid generator, and 7 is a pressurized fluid source.
[0015]
The molten resin injected from the injection nozzle 3 is filled into the mold cavity 2 through the gate 8, and the gate 8 melts the pressurized fluid from the pressurized fluid nozzle 4 in the mold cavity 2. It also serves as a pressurized fluid pressure inlet 9a for press-fitting into the resin.
[0016]
In the mold cavity 2, in addition to the pressurized fluid pressure inlet 9 a which is also the gate 8, another pressurized fluid pressure inlet 9 b is opened at a position away from the gate 8.
[0017]
The installation positions of the pressurized fluid pressure inlets 9a and 9b may be appropriately determined according to the formation position of the hollow portion, but when the hollow injection molded product to be molded has a change in thickness, its thickness It is preferable to provide it in a meat part (for example, a location where a boss or rib is formed). In addition, when a groove-shaped guide channel (not shown) is provided in the mold cavity 2 in order to guide the penetration direction of the pressurized fluid press-fitted into the molten resin, it is connected to this guide path. It is preferable to provide at the position.
[0018]
The pressurized fluid pressure inlets 9a and 9b are connected to the control device 5 via supply paths 10a and 10b, respectively. The control device 5 controls the supply timing of pressurized fluid to the pressurized fluid pressure inlets 9a and 9b and / or the pressure of the pressurized fluid to be supplied.
[0019]
The control device 5 is connected to the pressurized fluid generator 6.
[0020]
The pressurized fluid generator 6 includes a pressurizer 6a such as a compressor, a pressure accumulating container 6b, and a recovery container 6c, and the pressurized fluid supplied from the recovery container 6c and / or the pressurized fluid source 7 is supplied. The pressure is increased by the pressurizer 6a, and this pressurized fluid is stored in the accumulator 6b.
[0021]
The control device 5 is connected to the pressure accumulating vessel 6 b of the pressurized fluid generator 6. In addition, one end of the recovery paths 12a and 12b with the on-off valves 11a and 11b interposed is connected to the supply paths 10a and 10b, respectively, and the other end of the recovery paths 12a and 12b is connected to the recovery container 6c. Has been.
[0022]
First, molten resin is injected from the injection nozzle 3 into the mold cavity 2. Next, a pressurized fluid is pressed into the molten resin in the mold cavity 2.
[0023]
As the resin, general thermoplastic resins used in general injection molding or extrusion molding can be used, and a thermosetting resin can also be used as necessary. Various additives can be added to the resin as necessary.
[0024]
As the pressurized fluid, one that is gaseous or liquid at normal temperature and pressure and that does not react or mix with the resin used under the temperature and pressure at the time of injection is used. Specific examples include nitrogen gas, carbon dioxide gas, air, helium gas, water, glycerin, liquid paraffin, and the like, but inert gases such as nitrogen gas and helium gas are preferable. The pressure of the pressurized fluid is generally about 10 to 500 kg / cm ² .
[0025]
Pressurization of the pressurized fluid is performed through the pressurized fluid pressure inlets 9a and 9b with the on-off valves 11a and 11b being closed. The controller 5 controls the press-fitting timing and / or press-fitting pressure from the pressurized fluid pressure inlets 9 a and 9 b.
[0026]
That is, when the pressure of the molten resin filled in the portions where the pressurized fluid pressure inlets 9a and 9b are open is equal, the pressurized fluid of the same pressure is simultaneously injected from the pressurized fluid pressure inlets 9a and 9b. However, since the pressure of the molten resin usually varies depending on the portion of the mold cavity 2, the press-fitting time and / or press-fitting is performed according to the pressure of the molten resin in the portion where the pressurized fluid pressure inlets 9 a and 9 b are opened. Control the pressure.
[0027]
In the illustrated mold 1, the pressure of the molten resin at the pressurized fluid pressure inlet 9 a portion also serving as the gate 8 is higher than the molten resin at the pressurized fluid pressure inlet 9 b portion located away from the gate 8. In general, the pressurization of the pressurized fluid from the pressurized fluid pressure inlet 9a is more difficult than the pressurization of the pressurized fluid from the pressurized fluid pressure inlet 9b. Therefore, (1) the press-fitting from the pressurized fluid pressure inlet 9a is started earlier than the press-fitting from the pressurized fluid pressure inlet 9b. (2) the pressure of the pressurized fluid to be pressed from the pressurized fluid pressure inlet 9a is increased. (3) The press-fitting from the pressurized fluid pressure inlet 9a is started earlier than the press-fitting from the pressurized fluid pressure inlet 9b, and the pressurized fluid pressure is increased. Any control of making the pressure of the pressurized fluid press-fitted from the inlet 9a higher than the pressure of the pressurized fluid press-fitted from the pressurized fluid pressure inlet 9b is performed.
[0028]
The pressurization timing of the pressurized fluid is controlled by providing an opening / closing valve (not shown) for controlling the supply of the pressurized fluid to the pressurized fluid pressure inlets 9a and 9b in the controller 5, and adjusting the opening timing. Can be done. In addition, the pressure control of the pressurized fluid to be press-fitted is provided with a pressure regulating valve (not shown) in the controller 5, and the pressurized fluid supplied to the pressurized fluid pressure inlets 9a and 9b by this pressure regulating valve. This can be done by adjusting the pressure.
[0029]
After pressurizing the pressurized fluid in this way to form a predetermined hollow portion, supply of the pressurized fluid to the pressurized fluid pressure inlets 9a and 9b is stopped, and the resin in the mold cavity 2 is sufficiently cooled. After that, the on-off valves 11a and 11b of the recovery paths 12a and 12b are opened, and the pressurized fluid in the formed hollow portion is recovered in the recovery container 6c. Further, after the pressurized fluid remaining in the hollow portion is discharged, the mold 1 is opened, and the molded hollow injection molded product is taken out.
[0030]
The hollow injection-molded product obtained by the above method is used to pressurize the pressurized fluid into the molten resin injected into the mold cavity 2 from the plurality of pressurized fluid pressure inlets 9a and 9b opened in the mold cavity 2. And a hollow portion formed by press-fitting a pressurized fluid by controlling at least one of the press-fitting pressure for each pressurized fluid pressure inlet.
[0031]
Since this hollow injection molded product has a hollow portion of a necessary size at a required position, it has a good quality without sink.
[0032]
As described above, the control in the present invention needs to be performed based on the pressure of the molten resin filled in the portions where the pressurized fluid pressure inlets 9a and 9b are opened. It is preferable to perform control. That is, it is preferable to correct the control based on the pressure difference based on the temperature.
[0033]
For example, the molten resin filled at a position away from the gate 8 is lower in temperature because it is filled after flowing while being cooled than the molten resin near the gate 8 that is filled immediately after the start of injection. It is normal. Further, when the pressurization timing of the pressurized fluid is delayed, the temperature of the molten resin is lowered by receiving the cooling for the delay. The molten resin having a low temperature is poor in fluidity as compared with the molten resin having a high temperature, and the pressurized fluid is also difficult to press.
[0034]
Therefore, when the pressure of the molten resin is uniform, the pressurization of the pressurized fluid from the pressurized fluid pressure inlet 9b that opens to the portion filled with the low temperature molten resin is the portion where the high temperature molten resin is filled. Compared with the pressurized fluid pressure inlet 9a that opens at a high pressure, it is preferably performed at an earlier time and / or at a higher pressure, and based on this, it is preferable to correct the control by the pressure difference.
[0035]
Further, in the control of the present invention, the size of the hollow portion to be formed by the pressurized fluid injected from the pressurized fluid pressure inlet 9a and the hollow to be formed by the pressurized fluid injected from the pressurized fluid pressure inlet 9b are controlled. It is preferable to correct the control based on the pressure difference described above based on the difference in size of the portions.
[0036]
That is, it is preferable that the pressurization of the pressurized fluid to the place where the formation of the large hollow portion is planned is performed at an early stage and / or with a high pressurized fluid to promote the formation of the hollow portion. Based on this, it is preferable that the pressurization of the pressurized fluid to the place where the formation is planned is performed at a later time and / or with a low-pressure pressurization fluid to make the formation of the hollow part a pressing feeling. It is preferable to correct the control based on the pressure difference.
[0037]
The control item in the present invention is the pressurization timing of the pressurized fluid and / or the pressure of the pressurized fluid, but it is preferable to control by adding the pressurization time of the pressurized fluid. That is, the pressurization time of the pressurized fluid to the portion filled with the high pressure molten resin that is difficult to pressurize the pressurized fluid is long, and the portion to be filled with the low pressure molten resin where the pressurized fluid is easy to be injected is filled. It is preferable to shorten the press-fitting time of the pressurized fluid.
[0038]
In the present invention, the pressurized fluid pressure inlets 9a and 9b are not limited to two as shown, but may be three or more as long as they are determined according to the size, shape, etc. of the hollow injection molded product to be molded. Good. Further, as shown in the figure, when the pressurized fluid pressure inlet 9a also serving as the gate 8 is provided, generally, the molten resin near the pressurized fluid pressure inlet 9a also serving as the gate 8 is melted near the other pressurized fluid pressure inlet 9b. Since the pressure is higher than that of the resin, the pressurization of the pressurization fluid from the pressurization fluid pressure inlet 9a that also serves as the gate is performed earlier than the pressurization of the pressurization fluid from the other pressurization fluid pressurization inlet 9b. It will be done at high pressure.
[0039]
【Example】
Example 1
An automobile instrument panel as shown in FIGS. 2 to 4 was molded.
[0040]
In FIG. 2, an arrow A indicates the direction of filling the molten resin and the direction of pressurized fluid injection from the pressurized fluid pressure inlet 9a that also serves as the gate 8 in FIG. 1, and the arrow B indicates the pressure from the pressurized fluid pressure inlet 9b in FIG. Indicates the direction of pressurized fluid injection. Reference numerals 13a and 13b denote guide channel portions which are thick portions formed to guide the intrusion direction of the pressurized fluid.
[0041] The composite polypropylene (Asahi Chemical Industry Co., Ltd. "Roima QTD242E") was melted at 220 ° C. by injection for 10 sec, was charged from a portion corresponding to the arrow A in the mold which is adjusted to a temperature of 40 ° C..
[0042]
0.1 seconds after the filling of the molten resin is completed, nitrogen gas having a pressure of 150 kg / cm ² is injected from the portion corresponding to the arrow A of the mold, and 1 second after the filling of the molten resin is completed. Later, nitrogen gas having a pressure of 175 kg / cm ² was injected from the portion corresponding to the arrow B of the mold. The nitrogen gas pressure was determined in consideration of the temperature of the molten resin and the size of the hollow portion to be formed.
[0043]
After cooling the resin in the mold, the nitrogen gas in the formed hollow part is discharged, the mold is opened, and the molded instrument panel is taken out, and almost all of the induction channel parts 13a and 13b are taken out. A hollow portion was formed, and a hollow portion was also formed in a thick portion such as a boss or a rib to which the guide channel portions 13a and 13b were connected, and no occurrence of sink marks was observed.
[0044]
Further, when this instrument panel was exposed to an environmental temperature of 120 ° C. and examined for heat resistance, deformation was extremely small and good heat resistance was confirmed.
[0045]
Comparative Example 1
Molding of an instrument panel in the same manner as in Example 1 except that nitrogen gas having a pressure of 150 kg / cm ² was simultaneously injected from the portions corresponding to arrows A and B 0.1 seconds after the filling of the molten resin was completed. Went.
[0046]
In the obtained instrument panel, hollow portions were not formed at both end portions of the guide channel portion 13a located on the gate side of the mold, and sink marks were observed at these portions.
[0047]
【The invention's effect】
The present invention is as described above, has a change in thickness, can maintain a good quality without a sink even in a large shape product with an asymmetric shape, and in particular, an automobile instrument that has been in increasing demand in recent years. It is extremely useful for manufacturing large products such as panels and bumpers.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of the present invention.
FIG. 2 is an explanatory view of an automotive instrument panel molded in an example.
3 is a cross-sectional view taken along line III-III in FIG.
4 is a cross-sectional view taken along the line IV-IV in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Mold 1a Moving mold 1b Fixed mold 2 Mold cavity 3 Injection nozzle 4 Pressurized fluid nozzle 5 Control device 6 Pressurized fluid generator 6a Pressurizer 6b Accumulation container 6c Recovery container 7 Pressurized fluid source 8 Gates 9a, 9b Pressure fluid pressure inlets 10a and 10b Supply passages 11a and 11b On-off valves 12a and 12b Recovery passages 13a and 13b Guide channel portions

Claims

In a hollow injection molding method in which pressurized fluid is injected into a molten resin injected into a mold cavity from a plurality of pressurized fluid pressure inlets that open into the mold cavity, the pressurized fluid injection timing and the pressurized fluid injection Mold cavity part filled with low pressure molten resin from pressure fluid pressure inlet opening to mold cavity part filled with high pressure molten resin by controlling the pressure for each pressurized fluid pressure inlet A hollow injection molding method, wherein pressurization of a pressurized fluid from a pressurized fluid pressure inlet opening at a different pressure is performed at different pressurized fluid pressurization timings and different pressurized fluid pressurization pressures.

In a hollow injection molding method in which pressurized fluid is pressed into a molten resin injected into a mold cavity from a plurality of pressurized fluid pressure inlets that open into the mold cavity, Mold cavity part filled with low pressure molten resin, the timing of pressurizing fluid pressure from the pressurized fluid pressure inlet opening to the mold cavity part filled with high pressure molten resin, controlled for each inlet A hollow injection molding method characterized in that it is made earlier than the pressurizing fluid press-fitting time from the pressurizing fluid pressurizing inlet opening.

In a hollow injection molding method in which pressurized fluid is pressed into a molten resin injected into a mold cavity from a plurality of pressurized fluid pressure inlets that open into the mold cavity, the pressurized fluid pressurizing pressure is set to the pressurized fluid pressure. Mold cavity part filled with low-pressure molten resin, pressurizing fluid injection pressure from pressurized fluid pressure inlet opening to mold cavity part filled with high-pressure molten resin controlled for each inlet A hollow injection molding method characterized in that the pressure is higher than the pressurizing fluid pressurizing pressure from the pressurizing fluid pressurizing inlet opening.