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JP2004160783A - Injection molding method of molded article having thin part - Google Patents

Injection molding method of molded article having thin part Download PDF

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Publication number
JP2004160783A
JP2004160783A JP2002328121A JP2002328121A JP2004160783A JP 2004160783 A JP2004160783 A JP 2004160783A JP 2002328121 A JP2002328121 A JP 2002328121A JP 2002328121 A JP2002328121 A JP 2002328121A JP 2004160783 A JP2004160783 A JP 2004160783A
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Prior art keywords
cavity
thermoplastic resin
pressurized fluid
molten thermoplastic
mold
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JP2002328121A
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Japanese (ja)
Inventor
Yoshihiro Kayano
義弘 茅野
Shinji Kiboushi
真治 木坊子
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Mitsubishi Engineering Plastics Corp
Toyo Kagaku Co Ltd
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Mitsubishi Engineering Plastics Corp
Toyo Kagaku Co Ltd
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Abstract

【課題】薄肉部の強度低下や成形品の外観不良等を招くことの無い射出成形方法を提供する。
【解決手段】中空部を有する第１の厚肉部と第２の厚肉部との間に位置する中実の薄肉部を備えた成形品を、第１の厚肉部を成形すべき第１キャビティ部２１、第２の厚肉部を成形すべき第２キャビティ部２３、及び、薄肉部を成形すべき第３キャビティ部２５から構成されたキャビティを有し、第１キャビティ部２１に配置された溶融樹脂導入部１２及び加圧流体導入部１４、並びに、第３キャビティ部２５内で移動し得る可動コア部３０を備えた金型を使用して射出成形する方法は、可動コア部３０を後進端に位置せしめた状態でキャビティ内に溶融熱可塑性樹脂４０を射出し、次いで、キャビティ内の溶融熱可塑性樹脂４０の内部に加圧流体を導入した後、可動コア部３０を前進端へと移動させて、薄肉部を成形する各工程から成る。
【選択図】 図５The present invention provides an injection molding method that does not cause a decrease in strength of a thin portion or a defective appearance of a molded product.
A molded product having a solid thin portion located between a first thick portion having a hollow portion and a second thick portion is formed by molding a molded product having a first thick portion. It has a cavity composed of one cavity part 21, a second cavity part 23 for molding a second thick part, and a third cavity part 25 for molding a thin part, and is arranged in the first cavity part 21. The injection molding method using a mold having the melted resin introduction part 12 and the pressurized fluid introduction part 14 and the movable core part 30 movable in the third cavity part 25 is performed by using the movable core part 30. After the molten thermoplastic resin 40 is injected into the cavity with the is positioned at the backward end, and then a pressurized fluid is introduced into the molten thermoplastic resin 40 within the cavity, the movable core 30 is moved to the forward end. To form a thin portion.
[Selection diagram] FIG.

Description

【０００１】
【発明の属する技術分野】
本発明は、薄肉部を有する成形品の射出成形方法に関する。
【０００２】
【従来の技術】
溶融熱可塑性樹脂の射出成形に基づき成形品を成形する際、ひけや反りのない外観の美麗な成形品を得るための技術が、例えば、特開昭６３−２６８６１１号公報や特公平３−４７１７１号公報から周知である。これらの公報に開示された技術においては、金型に設けられたキャビティ内に溶融熱可塑性樹脂を射出してキャビティ内を溶融熱可塑性樹脂で充填し、次いで、加圧ガス等の加圧流体をキャビティ内の溶融熱可塑性樹脂内に導入して、中空部を有する成形品を得る。通常、成形品に厚肉部分を偏在させ、この厚肉部分に中空部を形成する。加圧流体は、金型に配設された加圧流体導入部から導入される。キャビティ内の溶融熱可塑性樹脂内に加圧流体を導入することによって、溶融熱可塑性樹脂が金型のキャビティ面に押し付けられる結果、成形品にひけや反りが発生することを効果的に防止することができる。
【０００３】
中空部の形成を確実なものとするために、中空部を形成すべきキャビティの部分に可動コア部を備えた金型が、例えば特開平４−２１２８２２号公報や特開平７−１６４４８６号公報から公知である。これらの技術においては、可動コア部を前進端に位置せしめた状態で、キャビティ内に溶融熱可塑性樹脂を射出する。そして、射出完了後、キャビティ内の溶融熱可塑性樹脂内に加圧流体を導入し、併せて、中空部を形成すべきキャビティの部分の体積を増加させるために可動コア部を後進端に移動させる。
【０００４】
【特許文献１】特開昭６３−２６８６１１号
【特許文献２】特公平３−４７１７１号
【特許文献３】特開平４−２１２８２２号
【特許文献４】特開平７−１６４４８６号
【特許文献５】特開平４−３３９６２４号
【特許文献６】米国特許第４４７４７１７号
【特許文献７】米国特許第５０４４９２４号
【特許文献８】米国特許第５９０８６４１号
【０００５】
【発明が解決しようとする課題】
しかしながら、特開昭６３−２６８６１１号公報や特公平３−４７１７１号公報に開示された技術を採用し、厚肉部と厚肉部との間に薄肉部が配置された成形品を成形する場合、一方の厚肉部を成形すべきキャビティの部分（便宜上、第１キャビティ部と呼ぶ）に溶融熱可塑性樹脂を射出したとき、薄肉部を成形すべきキャビティの部分（便宜上、第３キャビティ部と呼ぶ）における樹脂流動圧力損失が大きいために、第３キャビティ部を越えて他方の厚肉部を成形すべきキャビティの部分（便宜上、第２キャビティ部と呼ぶ）の一部に溶融熱可塑性樹脂が流入しない場合が多々ある。第１キャビティ部に加圧流体導入部を配設し、第１キャビティ部に射出された溶融熱可塑性樹脂の内部に加圧流体導入部を介して加圧流体を導入し、第１キャビティ部に存在する溶融熱可塑性樹脂を流動状態として、第３キャビティ部を越えて第２キャビティ部へと溶融熱可塑性樹脂を流入させる方法も考え得る。しかしながら、実際には、第３キャビティ部における樹脂流動圧力損失が大きいために、第２キャビティ部の一部に溶融熱可塑性樹脂を確実に流入させることは困難である。
【０００６】
このような現象は、第２キャビティ部に加圧流体導入部を配設し、第２キャビティ部からキャビティ内の溶融熱可塑性樹脂に加圧流体を導入することによって、第２キャビティ部に存在する溶融熱可塑性樹脂を流動させて、第２キャビティ部を溶融熱可塑性樹脂で十分に満たすことで、解決できるかもしれない。しかしながら、第３キャビティ部を越えて第１キャビティ部に存在する溶融熱可塑性樹脂の内部にも中空部を形成する必要があるが故に、第３キャビティ部に存在する溶融熱可塑性樹脂の内部にも中空部が形成されてしまい、成形品、特に、薄肉部の強度低下を招くといった問題が生じる。
【０００７】
更には、第３キャビティ部が存在するが故に、ヘジテーション（メルトフロントが一時的に停止する現象）によって生じるヘジテーションマークやフローマークが発生し、成形品の外観不良が多く生じる。また、ヘジテーションによってウエルドが薄肉部に形成されたり、一旦、固化した後にキャビティ内の熱可塑性樹脂が再流動するが故に、成形品の静的強度や疲労強度の低下を招く。
【０００８】
特に、薄肉部の強度低下は、薄肉部がヒンジ部として機能する場合、致命的である。
【０００９】
また、特開平４−２１２８２２号公報や特開平７−１６４４８６号公報に開示された技術にあっては、中空部を形成するために可動コア部が設けており、可動コア部が設けられたキャビティを用いて中実構造を有する薄肉部を確実に形成する技術に関しては何ら開示されていない。
【００１０】
従って、本発明の目的は、中空部を有する第１の厚肉部、中実あるいは中空部を有する第２の厚肉部、及び、第１の厚肉部と第２の厚肉部との間に位置する中実の薄肉部を有する成形品を、薄肉部の強度低下や成形品の外観不良等を招くこと無く、確実に成形し得る射出成形方法を提供することにある。
【００１１】
【課題を解決するための手段】
上記の目的を達成するための本発明の第１の態様に係る薄肉部を有する成形品の射出成形方法（以下、本発明の第１の態様に係る射出成形方法と呼ぶ）は、
（ａ）中空部を有する第１の厚肉部、
（ｂ）中実の第２の厚肉部、及び、
（ｃ）第１の厚肉部と第２の厚肉部との間に位置する中実の薄肉部、
を備えた成形品を、
▲１▼ 第１の厚肉部を成形すべき第１キャビティ部、第２の厚肉部を成形すべき第２キャビティ部、及び、薄肉部を成形すべき第３キャビティ部から構成されたキャビティを有し、
▲２▼ 第１キャビティ部に溶融熱可塑性樹脂が射出されるように配置された溶融樹脂導入部、
▲３▼ 第１キャビティ部に加圧流体が導入されるように配置された加圧流体導入部、及び、
▲４▼ 第３キャビティ部内で、成形品の薄肉部の厚さ方向に相当する方向に沿って前進端及び後進端の間で移動し得る可動コア部、
を備えた金型を使用して射出成形する方法であって、
（Ａ）可動コア部を後進端に位置せしめた状態で、溶融樹脂導入部を介してキャビティ内に溶融熱可塑性樹脂を射出する工程と、
（Ｂ）キャビティ内への溶融熱可塑性樹脂の射出中、若しくは、射出完了と同時に、若しくは、射出完了後、加圧流体導入部を介してキャビティ内の溶融熱可塑性樹脂の内部に加圧流体を導入し、第１キャビティ部を占める溶融熱可塑性樹脂の内部に中空部を形成する工程と、
（Ｃ）可動コア部を前進端へと移動させて、薄肉部を成形する工程、
を具備することを特徴とする。
【００１２】
上記の目的を達成するための本発明の第２の態様に係る薄肉部を有する成形品の射出成形方法（以下、本発明の第２の態様に係る射出成形方法と呼ぶ）は、第２の厚肉部に中空部を形成する点が、本発明の第１の態様に係る射出成形方法と異なっている。即ち、本発明の第２の態様に係る射出成形方法は、
（ａ）中空部を有する第１の厚肉部、
（ｂ）中空部を有する第２の厚肉部、及び、
（ｃ）第１の厚肉部と第２の厚肉部との間に位置する中実の薄肉部、
を備えた成形品を、
▲１▼ 第１の厚肉部を成形すべき第１キャビティ部、第２の厚肉部を成形すべき第２キャビティ部、及び、薄肉部を成形すべき第３キャビティ部から構成されたキャビティを有し、
▲２▼ 第１キャビティ部に溶融熱可塑性樹脂が射出されるように配置された溶融樹脂導入部、
▲３▼ 第１キャビティ部に加圧流体が導入されるように配置された加圧流体導入部、及び、
▲４▼ 第３キャビティ部内で、成形品の薄肉部の厚さ方向に相当する方向に沿って前進端及び後進端の間で移動し得る可動コア部、
を備えた金型を使用して射出成形する方法であって、
（Ａ）可動コア部を後進端に位置せしめた状態で、溶融樹脂導入部を介してキャビティ内に溶融熱可塑性樹脂を射出する工程と、
（Ｂ）キャビティ内への溶融熱可塑性樹脂の射出中、若しくは、射出完了と同時に、若しくは、射出完了後、加圧流体導入部を介してキャビティ内の溶融熱可塑性樹脂の内部に加圧流体を導入し、第１キャビティ部、第２キャビティ部及び第３キャビティ部を占める溶融熱可塑性樹脂の内部に中空部を形成する工程と、
（Ｃ）中空部内の加圧流体を排出する工程と、
（Ｄ）可動コア部を前進端へと移動させて、第３キャビティ部を占める溶融熱可塑性樹脂の内部に形成された中空部を無くし、中実の薄肉部を成形する工程、
を具備することを特徴とする。
【００１３】
上記の目的を達成するための本発明の第３の態様に係る薄肉部を有する成形品の射出成形方法（以下、本発明の第３の態様に係る射出成形方法と呼ぶ）は、本発明の第２の態様に係る射出成形方法と、加圧流体導入部の配置位置が異なる。
即ち、本発明の第３の態様に係る射出成形方法は、
（ａ）中空部を有する第１の厚肉部、
（ｂ）中空部を有する第２の厚肉部、及び、
（ｃ）第１の厚肉部と第２の厚肉部との間に位置する中実の薄肉部、
を備えた成形品を、
▲１▼ 第１の厚肉部を成形すべき第１キャビティ部、第２の厚肉部を成形すべき第２キャビティ部、及び、薄肉部を成形すべき第３キャビティ部から構成されたキャビティを有し、
▲２▼ 第１キャビティ部に溶融熱可塑性樹脂が射出されるように配置された溶融樹脂導入部、
▲３▼ 第２キャビティ部に加圧流体が導入されるように配置された加圧流体導入部、及び、
▲４▼ 第３キャビティ部内で、成形品の薄肉部の厚さ方向に相当する方向に沿って前進端及び後進端の間で移動し得る可動コア部、
を備えた金型を使用して射出成形する方法であって、
（Ａ）可動コア部を後進端に位置せしめた状態で、溶融樹脂導入部を介してキャビティ内に溶融熱可塑性樹脂を射出する工程と、
（Ｂ）キャビティ内への溶融熱可塑性樹脂の射出中、若しくは、射出完了と同時に、若しくは、射出完了後、加圧流体導入部を介してキャビティ内の溶融熱可塑性樹脂の内部に加圧流体を導入し、第１キャビティ部、第２キャビティ部及び第３キャビティ部を占める溶融熱可塑性樹脂の内部に中空部を形成する工程と、
（Ｃ）中空部内の加圧流体を排出する工程と、
（Ｄ）可動コア部を前進端へと移動させて、第３キャビティ部を占める溶融熱可塑性樹脂の内部に形成された中空部を無くし、中実の薄肉部を成形する工程、を具備することを特徴とする。
【００１４】
本発明の第１の態様〜第３の態様に係る射出成形方法（以下、これらを総称して、本発明の射出成形方法と略称する場合がある）において、キャビティ内に射出された溶融熱可塑性樹脂は、可動コア部が後進端に位置した状態にある第３キャビティ部内を流動する。即ち、この時点における第３キャビティ部の厚さ（成形品の薄肉部の厚さ方向に相当する金型キャビティ面間の距離）は厚い。従って、第３キャビティ部における樹脂流動圧力損失が小さく、第３キャビティ部内を溶融熱可塑性樹脂が容易に流動する結果、ヘジテーションが発生することが無く、フローマークも生じない。また、溶融熱可塑性樹脂が第２キャビティ部へ容易に流入するので、キャビティ全体を溶融熱可塑性樹脂によって確実に充満することができる。しかも、加圧流体によって所望の中空部が形成されるように、可動コア部の位置を調整することが可能である。ここで、溶融熱可塑性樹脂の「流動」とは、キャビティ内への溶融熱可塑性樹脂の射出時における溶融熱可塑性樹脂の流動だけでなく、キャビティ内の溶融熱可塑性樹脂の内部への加圧流体の導入による溶融熱可塑性樹脂の再流動をも含む概念である。
【００１５】
本発明の第１の態様に係る射出成形方法においては、前記工程（Ｃ）において、中空部内の加圧流体の一部を排出する構成とすることができる。尚、このような構成を、便宜上、本発明の第１Ａの態様に係る射出成形方法と呼ぶ。この場合、工程（Ｂ）において、加圧流体導入部を介してキャビティ内の溶融熱可塑性樹脂の内部に加圧流体を導入し、キャビティ内の溶融熱可塑性樹脂の内部に中空部を形成したとき、第１キャビティ部、第２キャビティ部及び第３キャビティ部は溶融熱可塑性樹脂で充満される。そして、工程（Ｃ）において可動コア部を前進端へと移動させて薄肉部を成形したとき、可動コア部の前進端への移動に伴い、第３キャビティ部内の溶融熱可塑性樹脂の一部は、第１キャビティ部へと押し出されるので、第１キャビティ部内の溶融熱可塑性樹脂の内部に形成された中空部の容積が減少する。その結果、第１キャビティ部内の溶融熱可塑性樹脂の内部に形成された中空部内に存在し、加圧流体導入部から加圧状態とされている加圧流体の一部は、加圧流体導入部から外部に排出される。
【００１６】
中空部は、加圧流体導入部を介して加圧状態とされている。それ故、第１キャビティ部内の溶融熱可塑性樹脂の内部に形成された中空部内に存在する加圧流体の一部が、加圧流体導入部の構造に依っては、加圧流体導入部から外部に排出され難い場合がある。このような場合、本発明の第１の態様に係る射出成形方法においては、前記工程（Ｂ）と工程（Ｃ）の間で、中空部内の加圧流体を排出する工程を更に具備する構成とすることが好ましい。尚、このような構成を、便宜上、本発明の第１Ｂの態様に係る射出成形方法と呼ぶ。
【００１７】
このような本発明の第１Ｂの態様に係る射出成形方法にあっては、工程（Ｃ）において可動コア部を前進端へと移動させて薄肉部を成形したとき、可動コア部の前進端への移動に伴い、第３キャビティ部内の溶融熱可塑性樹脂の一部は、第１キャビティ部へと押し出される。その結果、第１キャビティ部内の溶融熱可塑性樹脂の内部に形成された中空部の容積が減少するので、第１キャビティ部内の溶融熱可塑性樹脂の内部に形成された中空部内に存在する加圧流体は更に外部に排出される。
【００１８】
一方、本発明の第２の態様に係る射出成形方法にあっては、工程（Ｄ）において、可動コア部を前進端へと移動させて中実の薄肉部を成形したとき、可動コア部の前進端への移動に伴い、第３キャビティ部内の溶融熱可塑性樹脂の一部は、第１キャビティ部へと押し出される。その結果、第１キャビティ部内の溶融熱可塑性樹脂の内部に形成された中空部の容積が減少するので、第１キャビティ部内の溶融熱可塑性樹脂の内部に形成された中空部内に存在する加圧流体は更に外部に排出される。また、本発明の第３の態様に係る射出成形方法にあっては、工程（Ｄ）において、可動コア部を前進端へと移動させて中実の薄肉部を成形したとき、可動コア部の前進端への移動に伴い、第３キャビティ部内の溶融熱可塑性樹脂の一部は、第２キャビティ部へと押し出される。その結果、第２キャビティ部内の溶融熱可塑性樹脂の内部に形成された中空部の容積が減少するので、第２キャビティ部内の溶融熱可塑性樹脂の内部に形成された中空部内に存在する加圧流体は更に外部に排出される。
【００１９】
本発明の第１Ｂの態様に係る射出成形方法、あるいは又、本発明の第２の態様若しくは第３の態様に係る射出成形方法の工程（Ｃ）にあっては、中空部内の加圧流体を加圧流体導入部を介して外部に排出することができるし、あるいは又、加圧流体導入部の外周部を介して外部に排出することができる。これによって、中空部の圧力は大気圧となる。
【００２０】
本発明の第１Ａの態様に係る射出成形方法においては、工程（Ｃ）において、可動コア部を前進端へと移動させて薄肉部を成形するので、キャビティ内の熱可塑性樹脂は、薄肉部を成形することができる程度に柔軟性あるいは流動性を有している必要がある。
【００２１】
一方、本発明の第１Ｂの態様に係る射出成形方法においては、（Ｂ）と工程（Ｃ）の間で中空部内の加圧流体を排出し、その後、工程（Ｃ）において、可動コア部を前進端へと移動させて薄肉部を成形するので、キャビティ内の熱可塑性樹脂は、薄肉部を成形することができる程度に柔軟性あるいは流動性を有している必要があり、しかも、中空部内の加圧流体を排出したとき、中空部の形状を保持できる程度に固くなっている必要がある。また、本発明の第２の態様若しくは第３の態様に係る射出成形方法においては、工程（Ｃ）において、中空部内の加圧流体を排出し、工程（Ｄ）において、第３キャビティ部を占める溶融熱可塑性樹脂の内部に形成された中空部を無くし、中実の薄肉部を成形するので、キャビティ内の熱可塑性樹脂は、中実の薄肉部を成形することができる程度に柔軟性あるいは流動性を有している必要があり、しかも、中空部内の加圧流体を排出したとき、中空部の形状を保持できる程度に固くなっている必要がある。
【００２２】
本発明の射出成形方法にあっては、工程（Ｂ）において、加圧流体導入部を介してキャビティ内の溶融熱可塑性樹脂の内部に加圧流体を導入し、キャビティ内の溶融熱可塑性樹脂の内部に中空部を形成したとき、第１キャビティ部、第２キャビティ部及び第３キャビティ部は溶融熱可塑性樹脂で充満される。言い換えれば、加圧流体導入部を介してキャビティ内の溶融熱可塑性樹脂の内部に加圧流体を導入し、キャビティ内の溶融熱可塑性樹脂の内部に中空部を形成したとき、第１キャビティ部、第２キャビティ部及び第３キャビティ部が溶融熱可塑性樹脂で充満され、しかも、所望の中空部が形成されるように、キャビティ内に射出される溶融熱可塑性樹脂の量を決定する。
【００２３】
本発明の第１の態様に係る射出成形方法によって得られる成形品において、薄肉部近傍の第１の厚肉部の平均厚さをｔ１１、薄肉部近傍の第２の厚肉部の平均厚さをｔ１２、中実の薄肉部の平均厚さをｔ１３としたとき、０．１ｔ１１≦ｔ１３≦０．９ｔ１１、好ましくは０．４ｔ１１≦ｔ１３≦０．６ｔ１１を満足していることが望ましく、また、０．１ｔ１２≦ｔ１３≦０．９ｔ１２、好ましくは０．４ｔ１２≦ｔ１３≦０．６ｔ１２を満足していることが望ましい。
【００２４】
また、本発明の第２の態様若しくは第３の態様に係る射出成形方法によって得られる成形品において、薄肉部近傍の第１の厚肉部の平均厚さをｔ２１、薄肉部近傍の第２の厚肉部の平均厚さをｔ２２、中実の薄肉部の平均厚さをｔ２３としたとき、０．１ｔ２１≦ｔ２３≦０．９ｔ２１、好ましくは０．４ｔ２１≦ｔ２３≦０．６ｔ２１を満足していることが望ましく、また、０．１ｔ２２≦ｔ２３≦０．９ｔ２２、好ましくは０．４ｔ２２≦ｔ２３≦０．６ｔ２２を満足していることが望ましい。
【００２５】
本発明の第１の態様に係る射出成形方法において、可動コア部が後進端に位置するときの第３キャビティ部の厚さ（成形品の薄肉部の厚さ方向に相当する金型キャビティ面間の距離）をＴ１３Ｂ、可動コア部が前進端に位置するときの第３キャビティ部の厚さをＴ１３Ｆとしたとき、０．１≦Ｔ１３Ｆ／Ｔ１３Ｂ≦０．９、好ましくは、０．１≦Ｔ１３Ｆ／Ｔ１３Ｂ≦０．５を満足することが望ましい。
【００２６】
また、本発明の第２の態様若しくは第３の態様に係る射出成形方法において、可動コア部が後進端に位置するときの第３キャビティ部の厚さ（成形品の薄肉部の厚さ方向に相当する金型キャビティ面間の距離）をＴ２３Ｂ、可動コア部が前進端に位置するときの第３キャビティ部の厚さをＴ２３Ｆとしたとき、０．１≦Ｔ２３Ｆ／Ｔ２３Ｂ≦０．９、好ましくは、０．１≦Ｔ２３Ｆ／Ｔ２３Ｂ≦０．５を満足することが望ましい。
【００２７】
本発明の第１の態様に係る射出成形方法において、第３キャビティ部近傍の第１キャビティ部の平均厚さ（成形品の第１の厚肉部の厚さ方向に相当する金型キャビティ面間の平均距離）をＴ１１、第３キャビティ部近傍の第２キャビティ部の平均厚さ（成形品の第２の厚肉部の厚さ方向に相当する金型キャビティ面間の平均距離）をＴ１２としたとき、０．１Ｔ１１≦Ｔ１３Ｂ≦Ｔ１１、好ましくは０．５Ｔ１１≦Ｔ１３Ｂ≦Ｔ１１を満足し、且つ、０．１Ｔ１２≦Ｔ１３Ｂ≦Ｔ１２、好ましくは０．５Ｔ１２≦Ｔ１３Ｂ≦Ｔ１２を満足することが望ましい。
【００２８】
また、本発明の第２の態様若しくは第３の態様に係る射出成形方法において、第３キャビティ部近傍の第１キャビティ部の平均厚さ（成形品の第１の厚肉部の厚さ方向に相当する金型キャビティ面間の平均距離）をＴ２１、第３キャビティ部近傍の第２キャビティ部の平均厚さ（成形品の第２の厚肉部の厚さ方向に相当する金型キャビティ面間の平均距離）をＴ２２としたとき、０．１Ｔ２１≦Ｔ２３Ｂ≦Ｔ２１、好ましくは０．５Ｔ２１≦Ｔ２３Ｂ≦Ｔ２１を満足し、且つ、０．１Ｔ２２≦Ｔ２３Ｂ≦Ｔ２２、好ましくは０．５Ｔ２２≦Ｔ２３Ｂ≦Ｔ２２を満足することが望ましい。
【００２９】
これらの各種の構成を含む本発明の射出成形方法においては、前記工程（Ａ）において、キャビティ内に射出される溶融熱可塑性樹脂の量を、キャビティを完全には満たさない量とすることができ、あるいは又、キャビティを完全に満たす量とすることができる。
【００３０】
本発明の射出成形方法において使用する可動コア部の個数に特に制限はなく、１つの薄肉部を有する成形品を成形するために、１つの可動コア部を設置してもよいし、複数の可動コア部を設置してもよい。また、例えば、複数の薄肉部を成形品に設ける場合、その数だけ可動コア部を設置すればよい。更には、１つの可動コア部によって複数の薄肉部を形成することも可能である。後進端から前進端までの可動コア部の移動速度は一定であってもよいし、例えば、変化させてもよい。
【００３１】
本発明の射出成形方法にあっては、例えば、金型を、固定金型部と可動金型部から構成することができる。そして、この場合、成形すべき成形品の形状に依存して、可動コア部を、固定金型部側に配置してもよいし、可動金型部側に配置してもよいし、固定金型部側及び可動金型部側に配置してもよい。可動コア部の移動は、例えば、油圧シリンダーや空気圧シリンダー、電動モータを用いて行うことができる。
【００３２】
可動コア部の前後進を、射出成形機や加圧流体の供給装置から送出される制御信号に基づき制御することができる。可動コア部の前進端位置の制御は、所望する成形品の薄肉部の厚さに基づき決定すればよい。また、可動コア部の後進端位置の位置決めは、極めて簡単な機械的な位置制御、例えば、後退止めスリーブ、後退止めノックピン、後退止めブロック等を用いて行うことができる。
【００３３】
本発明の射出成形方法にあっては、成形すべき成形品の形状等に依存して、溶融樹脂導入部（所謂、ゲート部）の構造は、本質的に任意であり、例えば、ダイレクトゲート構造、サイドゲート構造、ジャンプゲート構造、ピンポイントゲート構造、トンネルゲート構造、リングゲート構造、ファンゲート構造、ディスクゲート構造、フラッシュゲート構造、タブゲート構造、フィルムゲート構造を例示することができる。
【００３４】
通常、熱可塑性樹脂を射出用シリンダー内で可塑化、溶融し、射出用シリンダーから、金型に設けられた溶融樹脂流路、溶融樹脂導入部を介してキャビティ内に溶融熱可塑性樹脂を射出する。ここで、溶融樹脂流路は、例えば、コールドランナータイプであってもよいし、ホットランナータイプであってもよい。
【００３５】
本発明の射出成形方法においては、加圧流体導入部は加圧流体導入ノズルから成り、加圧流体導入ノズルの先端部は第１キャビティ部内（第１キャビティ部を構成する金型キャビティ面近傍を含む）に位置し（本発明の第１の態様若しくは第２の態様に係る射出成形方法）、あるいは又、第２キャビティ部内（第２キャビティ部を構成する金型キャビティ面近傍を含む）に位置する構成（本発明の第３の態様に係る射出成形方法）とすることができるが、このような構成に限定するものではない。本発明の第１の態様若しくは第２の態様に係る射出成形方法にあっては、加圧流体導入部を、溶融樹脂導入部内部、あるいは、金型に設けられた溶融樹脂流路内に配置してもよいし、射出用シリンダーの先端部内に配置してもよい。
【００３６】
本発明の射出成形方法においては、キャビティ内の溶融熱可塑性樹脂への加圧流体の導入開始の時期は、キャビティ内への溶融熱可塑性樹脂の導入中、導入完了と同時、導入完了後のいずれであってもよい。キャビティ内の溶融熱可塑性樹脂への加圧流体の具体的な導入開始時期は、成形品の形状、使用する熱可塑性樹脂材料、成形条件等に依存するが、溶融熱可塑性樹脂のキャビティ内への導入開始から１秒乃至２０秒とすることが好ましいが、これに限定するものではない。加圧流体の導入開始時期の下限は、溶融熱可塑性樹脂をキャビティ内へ導入しながら、キャビティ内に加圧流体を導入する場合に、導入された加圧流体がキャビティ内の溶融熱可塑性樹脂と混ざり合うことがなくなるような時期とすればよい。一方、成形品の形状、使用する熱可塑性樹脂材料、成形条件等に依存するが、加圧流体の導入開始時期が６０秒を越えると、キャビティ内の溶融熱可塑性樹脂の固化によって加圧流体の導入が困難となる虞がある。
【００３７】
可動コア部を、キャビティ内に射出された溶融熱可塑性樹脂の流動が停止した後に、前進端に移動する。即ち、キャビティ内の溶融熱可塑性樹脂へ加圧流体が導入されてから或る時間が経過し、キャビティ内の溶融熱可塑性樹脂の流動が停止した後に、可動コア部の前進端への移動を開始する。可動コア部の前進端への移動開始は、第３キャビティ部内の熱可塑性樹脂の固化が完了する前である。従って、可動コア部の前進端への移動開示時期は、使用される熱可塑性樹脂の種類、成形条件、成形品の形状等に依存し、一義的に決定することはできないが、如何に遅くとも、金型を型開きする前には可動コア部を前進端に位置させる。
【００３８】
本発明の射出成形方法において使用される熱可塑性樹脂は、如何なる熱可塑性樹脂であってもよく、ポリカーボネート樹脂；ポリエチレン樹脂、ポリプロピレン樹脂等のオレフィン系樹脂；ポリスチレン樹脂、ＡＳ樹脂、ＡＢＳ樹脂、ＡＥＳ樹脂等のスチレン系樹脂；ＰＭＭＡ樹脂等のメタクリル系樹脂；ポリオキシメチレン（ポリアセタール）樹脂；ポリアミド６、ポリアミド６６、ポリアミドＭＸＤ等のポリアミド系樹脂；変性ポリフェニレンエーテル（ＰＰＥ）樹脂；ポリフェニレンサルファイド樹脂；ポリエチレンテレフタレート（ＰＥＴ）樹脂、ポリブチレンテレフタレート（ＰＢＴ）樹脂等のポリエステル系樹脂；液晶ポリマー等の熱可塑性樹脂、又は、これらの熱可塑性樹脂の少なくとも２種類以上の樹脂から成るポリマーアロイを挙げることができる。これらの熱可塑性樹脂には、剛性に代表される機械的特性、寸法安定性等を成形品に付与するために、例えば、ガラス繊維、ガラスフレーク、カーボン繊維、ウォラストナイト、ホウ酸アルミニウムウィスカー繊維、チタン酸カリウムウィスカー繊維、塩基性硫酸マグネシウムウィスカー繊維、珪酸カルシウムウィスカー繊維及び硫酸カルシウムウィスカー繊維から成る群から選択された少なくとも１種の材料から構成された無機繊維が含有されていてもよい。また、例えば安定剤、離型剤、紫外線吸収剤の有効発現量を熱可塑性樹脂に配合してもよい。
【００３９】
本発明の射出成形方法において、導入する加圧流体として、窒素ガス、炭酸ガス、空気、ヘリウムガス等常温でガス状の物質を使用することができるし、水等の液体や高圧下で液化したガスも使用可能である。
【００４０】
本発明の射出成形方法によって得られる成形品として、薄肉部がヒンジ部として機能する成形品（具体的には、例えば、蓋が一体成形された箱状成形品、ドアハンドルと、取付部を隠すためのカバーとが一体成形された成形品）、肉厚が極端に異なる成形品（具体的には、例えば、薄い取付部を有する筐体成形品）を挙げることができる。
【００４１】
【実施例】
以下、図面を参照して、実施例に基づき本発明を説明する。
【００４２】
（実施例１）
実施例１は、本発明の第１の態様に係る射出成形方法に関し、更に具体的には、可動コア部を前進端へと移動させて薄肉部を成形する際、中空部内の加圧流体の一部を排出する本発明の第１Ａの態様に係る射出成形方法に関する。
【００４３】
実施例１によって得られた成形品の模式的な平面図を図６の（Ａ）に示し、模式的な側面図を図６の（Ｂ）に示し、図６の（Ａ）の線Ｃ−Ｃに沿った模式的な断面図を図６の（Ｃ）に示す。
【００４４】
この成形品５０は、中空部５２を有する第１の厚肉部５１、中実の第２の厚肉部５３、及び、第１の厚肉部５１と第２の厚肉部５３との間に位置する中実の薄肉部５５から構成されている。成形品５０の幅（Ｗ）を２０ｍｍ、第１の厚肉部５１の長さ（Ｌ１）を４０ｍｍ、厚さ（ｔ１１）を５．０ｍｍ、第２の厚肉部５３の長さ（Ｌ２）を１５ｍｍ、厚さ（ｔ１２）を５．０ｍｍ、薄肉部５５の長さ（Ｌ３）を５．０ｍｍ、厚さ（ｔ１３）を１．０ｍｍとした。
【００４５】
実施例１において使用した金型の概念図を図１に示す。尚、図１にあっては、可動コア部３０が前進端に位置した状態を示す。
【００４６】
この金型は、固定金型部１０と可動金型部１１から構成されている。そして、金型は、成形品５０の第１の厚肉部５１を成形すべき第１キャビティ部２１、第２の厚肉部５３を成形すべき第２キャビティ部２３、及び、薄肉部５５を成形すべき第３キャビティ部２５から構成されたキャビティを有する。更には、金型は、溶融樹脂導入部（所謂ゲート部）１２、加圧流体導入部１４、及び、可動コア部３０を備えている。
【００４７】
溶融樹脂導入部１２は、第１キャビティ部２１に溶融熱可塑性樹脂４０が射出されるように固定金型部１０に配置されている。溶融樹脂導入部１２は、ダイレクトゲート構造を有し、図示しない射出用シリンダーと、固定金型部１０に設けられたスプルー及びコールドランナータイプの溶融樹脂流路１３を介して連通している。
【００４８】
加圧流体導入部１４は、第１キャビティ部２１に加圧流体が導入されるように可動金型部１１に配置されている。加圧流体導入部１４は、溶融樹脂に対しては逆止能力を有するが、加圧流体に対しては逆止能力を有さない、例えば、加圧流体導入部の先端が二重スリーブ構造あるいは細管構造を有する加圧流体導入部から構成されている。尚、このような構造を有する加圧流体導入部は、例えば、特開平４−３３９６２４号公報、米国特許第４４７４７１７号、米国特許第５０４４９２４号、米国特許第５９０８６４１号等に開示されている。可動金型部１１に取り付けられた加圧流体導入部１４の先端部は、第１キャビティ部２１内に突出している。また、加圧流体導入部１４は、配管１５を介して加圧流体源１６に接続されている。更には、加圧流体導入部１４は、図示しない加圧流体導入部移動手段（例えば、油圧シリンダーから成る）によって、前進端と後進端との間を移動可能である。加圧流体導入部１４が前進端に位置するとき、加圧流体導入部１４の先端部は、第１キャビティ部２１内に突出した状態となる。一方、加圧流体導入部１４が後進端に位置するとき、加圧流体導入部１４の先端部と金型との間には隙間が形成され、中空部内の加圧流体はこの隙間から大気中に開放され得る。
【００４９】
可動コア部３０は、第３キャビティ部２５内で、可動コア部移動手段である油圧シリンダー３１の作動によって、成形品５０の薄肉部５５の厚さ方向に相当する方向に沿って前進端及び後進端の間で移動し得る。
【００５０】
以下、金型等の概念図である図２〜図５を参照して、実施例１の射出成形方法を説明する。尚、実施例１にあっては、熱可塑性樹脂として、ポリカーボネート樹脂（三菱エンジニリングプラスチックス株式会社製、商品名：ユーピロンＳ３０００）を使用した。また、加圧流体として圧縮窒素ガス（圧力：１×１０７Ｐａ）を使用した。
【００５１】
金型に設けられたキャビティの形状は、図６に図示した成形品５０を成形できる寸法である。即ち、第３キャビティ部２５近傍の第１キャビティ部２１の平均厚さ（成形品５０の第１の厚肉部５１の厚さ方向に相当する金型キャビティ面間の平均距離）Ｔ１１は５．０ｍｍであり、第３キャビティ部２５近傍の第２キャビティ部２３の平均厚さ（成形品５０の第２の厚肉部５３の厚さ方向に相当する金型キャビティ面間の平均距離）Ｔ１２は５．０ｍｍである。また、可動コア部３０が後進端に位置するときの第３キャビティ部２５の厚さ（成形品５０の薄肉部５５の厚さ方向に相当する金型キャビティ面間の距離）Ｔ１３Ｂを５．０ｍｍとし、可動コア部３０が前進端に位置するときの第３キャビティ部２５の厚さＴ１３Ｆを１．０ｍｍとした。
【００５２】
［工程−１００］
射出成形機に備えられた射出用シリンダー（図示せず）内で、以下の表１に示す樹脂温度にて熱可塑性樹脂を可塑化、溶融した。そして、固定金型部１０と可動金型部１１を型締めし、油圧シリンダー３１の作動によって可動コア部３０を後進端に位置せしめた（図２参照）。図示しない加圧流体導入部移動手段に作動によって、加圧流体導入部１４は前進端に位置せしめられ、加圧流体導入部１４の先端部は、第１キャビティ部２１内に突出した状態となる。
【００５３】
［工程−１１０］
そして、以下の表１に示す金型温度、射出圧力にて、射出用シリンダーから、溶融樹脂流路１３、溶融樹脂導入部（ゲート部）１２を介してキャビティ内（より具体的には、第１キャビティ部２１内）に溶融熱可塑性樹脂４０を射出した（図３参照）。尚、キャビティ全体に導入した溶融熱可塑性樹脂４０の量をキャビティ全体の体積の７５％とした。
【００５４】
［表１］
樹脂温度：２９０゜Ｃ
金型温度：８０゜Ｃ
射出時間：４．０秒
射出圧力：６×１０７Ｐａ
（６００ｋｇｆ／ｃｍ２−Ｇ）
【００５５】
［工程−１２０］
溶融熱可塑性樹脂４０の射出開始から４．３秒後に、加圧流体源１６から、配管１５、加圧流体導入部１４を介してキャビティ内の溶融熱可塑性樹脂４０（より具体的には、第１キャビティ部２１内の溶融熱可塑性樹脂４０）の内部に加圧流体（圧力１×１０７Ｐａの加圧窒素ガス）を導入し、第１キャビティ部２１を占める溶融熱可塑性樹脂４０の内部に中空部５２を形成した（図４参照）。加圧流体の導入によって、キャビティ内の溶融熱可塑性樹脂４０は流動し、第１キャビティ部２１、第２キャビティ部２３及び第３キャビティ部２５は溶融熱可塑性樹脂４０で充満された。但し、中空部５２は、第１キャビティ部２１内に止まった。
【００５６】
［工程−１３０］
溶融熱可塑性樹脂４０の射出開始から９．３秒後に、油圧シリンダー３１を作動させて、可動コア部３０を後進端から前進端へと移動させ、薄肉部５５を成形した（図５参照）。可動コア部３０の移動量を４．０ｍｍとした。即ち、可動コア部３０が前進端に位置したときの、第３キャビティ部２５の厚さＴ１３Ｆ（成形品５０の薄肉部５５の厚さ方向に相当する金型キャビティ面間の距離）は１．０ｍｍである。移動速度を２ｍｍ／秒とした。可動コア部３０の前進端への移動に伴い、第３キャビティ部２５内の溶融熱可塑性樹脂４０の一部は、第１キャビティ部２１へと押し出された。その結果、第１キャビティ部２１内の溶融熱可塑性樹脂４０の内部に形成された中空部５２の容積が減少した。第１キャビティ部２１内の溶融熱可塑性樹脂４０の内部に形成された中空部５２内に存在し、加圧流体導入部１４から加圧状態とされている加圧流体の一部が、加圧流体導入部１４から外部に排出された。
【００５７】
［工程−１４０］
溶融熱可塑性樹脂４０の射出開始から３４．３秒後に、中空部５２内の加圧流体を加圧流体導入部１４を介して更に排出した。尚、中空部５２内が大気圧になった時点で、中空部５２内には大気圧の窒素ガスが残存し得る。
【００５８】
［工程−１５０］
溶融熱可塑性樹脂４０の射出開始から６４．３秒まで、キャビティ内の熱可塑性樹脂を冷却し、次いで、図示しない加圧流体導入部移動手段に作動によって加圧流体導入部１４を後進端に位置せしめた後、金型の型開きを行い、金型から成形品５０を取り出した。
【００５９】
得られた成形品５０の薄肉部５５には、ウエルド、ヘジテーションマーク、フローマーク等の外観不良は認められなかった。また、第１の厚肉部５１には所望の中空部５２が形成されており、更には、中実の薄肉部５５及び厚肉部５３が確実に形成されていた。
【００６０】
（比較例１）
比較例１においては、図１に示したように、可動コア部３０を予め前進端に固定した。そして、実施例１の［工程−１３０］、即ち、可動コア部３０を後進端から移動させる工程を実行すること無く、実施例１の［工程−１００］〜［工程−１２０］、［工程−１４０］〜［工程−１５０］を実行した。
【００６１】
その結果、第３キャビティ部２５における樹脂流動圧力損失が大きいために、加圧流体を導入することによっても、第２キャビティ部２３に溶融熱可塑性樹脂を十分に流入させることができず、第２キャビティ部２３において、熱可塑性樹脂の未充填部分が発生し、所望の成形品を得ることができなかった。
【００６２】
（実施例２）
実施例２は、実施例１の変形であり、本発明の第１Ｂの態様に係る射出成形方法に関する。実施例２においては、実施例１の［工程−１２０］の後に［工程−１４０］を実行し、次いで、［工程−１３０］を実行した。以下、実施例２の射出成形方法を、金型等の概念図である図２〜図４、図７及び図８を参照して説明する。尚、実施例２にあっては、熱可塑性樹脂、加圧流体として、実施例１と同じ熱可塑性樹脂、加圧流体を使用した。
【００６３】
［工程−２００］
先ず、実施例１の［工程−１００］と同様にして、熱可塑性樹脂を可塑化、溶融した。そして、固定金型部１０と可動金型部１１を型締めし、油圧シリンダー３１の作動によって可動コア部３０を後進端に位置せしめた。可動コア部３０が後進端に位置したときの、第３キャビティ部２５の厚さＴ１３Ｂ（成形品５０の薄肉部５５の厚さ方向に相当する金型キャビティ面間の距離）は５．０ｍｍである。図示しない加圧流体導入部移動手段に作動によって、加圧流体導入部１４は前進端に位置せしめられ、加圧流体導入部１４の先端部は、第１キャビティ部２１内に突出した状態となる（図２参照）。
【００６４】
［工程−２１０］
そして、実施例１の［工程−１１０］と同様にして、射出用シリンダーから、溶融樹脂流路１３、溶融樹脂導入部（ゲート部）１２を介してキャビティ内（より具体的には、第１キャビティ部２１内）に溶融熱可塑性樹脂４０を射出した（図３参照）。尚、キャビティ全体に導入した溶融熱可塑性樹脂４０の量をキャビティ全体の体積の７５％とし、射出時間を４．０秒とした。
【００６５】
［工程−２２０］
溶融熱可塑性樹脂４０の射出開始から４．３秒後に、実施例１の［工程−１２０］と同様にして、加圧流体導入部１４を介してキャビティ内の溶融熱可塑性樹脂４０（より具体的には、第１キャビティ部２１内の溶融熱可塑性樹脂４０）の内部に加圧流体（圧力１×１０７Ｐａの加圧窒素ガス）を導入し、第１キャビティ部２１を占める溶融熱可塑性樹脂４０の内部に中空部５２を形成した（図４参照）。加圧流体の導入によって、キャビティ内の溶融熱可塑性樹脂４０は流動し、第１キャビティ部２１、第２キャビティ部２３及び第３キャビティ部２５は溶融熱可塑性樹脂４０で充満された。但し、中空部５２は、第１キャビティ部２１内に止まった。
【００６６】
［工程−２３０］
溶融熱可塑性樹脂４０の射出開始から１４．３秒後に、図示しない加圧流体導入部移動手段に作動によって加圧流体導入部１４を後進端に位置せしめ、加圧流体導入部１４の先端部と金型との間に隙間を形成し、中空部５２内の加圧流体をこの隙間から大気中に排出した（図７参照）。尚、中空部５２内が大気圧になった時点で、中空部５２内には大気圧の窒素ガスが残存し得る。
【００６７】
［工程−２４０］
溶融熱可塑性樹脂４０の射出開始から１６．３秒後に、油圧シリンダー３１を作動させて、可動コア部３０を後進端から前進端へと移動させ、薄肉部５５を成形した（図８参照）。可動コア部３０の移動量は４．０ｍｍである。即ち、可動コア部３０が前進端に位置したときの、第３キャビティ部２５の厚さＴ１３Ｆ（成形品５０の薄肉部５５の厚さ方向に相当する金型キャビティ面間の距離）は１．０ｍｍである。移動速度を２ｍｍ／秒とした。可動コア部３０の前進端への移動に伴い、第３キャビティ部２５内の溶融熱可塑性樹脂４０の一部は、第１キャビティ部２１へと押し出された。その結果、第１キャビティ部２１内の熱可塑性樹脂の内部に形成された中空部５２の容積が減少した。第１キャビティ部２１内の熱可塑性樹脂の内部に形成された中空部５２内に存在する加圧流体の一部は、更に、加圧流体導入部１４の先端部と金型との間に隙間から大気中に排出された。
【００６８】
［工程−２５０］
溶融熱可塑性樹脂４０の射出開始から６４．３秒まで、キャビティ内の熱可塑性樹脂を冷却し、金型の型開きを行い、金型から成形品を取り出した。
【００６９】
得られた成形品５０の薄肉部５５には、ウエルド、ヘジテーションマーク、フローマーク等の外観不良は認められなかった。また、第１の厚肉部５１には所望の中空部５２が形成されており、更には、中実の薄肉部５５及び厚肉部５３が確実に形成されていた。
【００７０】
（実施例３）
実施例３も実施例１の変形である。実施例３にあっては、図９に金型の概念図を示すように、加圧流体導入部１１４は加圧流体導入ノズルから成り、その先端部は、溶融樹脂導入部１２の内部に配設されている。その他の構造は、実質的に、実施例１にて説明した金型と同じである。尚、実施例３においては、以下に説明する成形品を成形したので、第２キャビティ部２３Ａ，２３Ｂ、及び、第３キャビティ部２５Ａ，２５Ｂが、２つ設けられ、更には、２つの可動コア部３０Ａ，３０Ｂが配設されている。尚、図９にあっては、２つの可動コア部３０Ａ，３０Ｂが前進端に位置した状態を示す。
【００７１】
実施例３によって得られた成形品の模式的な平面図を図１４の（Ａ）に示し、模式的な側面図を図１４の（Ｂ）に示し、図１４の（Ａ）の線Ｃ−Ｃに沿った模式的な断面図を図１４の（Ｃ）に示す。
【００７２】
この成形品１５０は、中空部１５２を有する第１の厚肉部１５１、中実の２つの第２の厚肉部１５３Ａ，１５３Ａ、及び、第１の厚肉部１５１と第２の厚肉部１５３Ａ，１５３Ｂとの間に位置する２つの中実の薄肉部１５５Ａ，１５５Ｂから構成されている。成形品１５０の幅（Ｗ）を２０ｍｍ、第１の厚肉部１５１の長さ（Ｌ１）を４０ｍｍ、厚さ（ｔ１１）を５．０ｍｍ、第２の厚肉部１５３Ａ，１５３Ｂの長さ（Ｌ２）を１５ｍｍ、厚さ（ｔ１２）を５．０ｍｍ、薄肉部１５５Ａ，１５５Ｂの長さ（Ｌ３）を５．０ｍｍ、厚さ（ｔ１３）を１．０ｍｍとした。
【００７３】
また、金型に設けられたキャビティの形状は、図１４に図示した成形品１５０を成形できる寸法である。即ち、第３キャビティ部２５Ａ，２５Ｂ近傍の第１キャビティ部２１の平均厚さ（成形品１５０の第１の厚肉部１５１の厚さ方向に相当する金型キャビティ面間の平均距離）Ｔ１１は５．０ｍｍであり、第３キャビティ部２５Ａ，２５Ｂ近傍の第２キャビティ部２３Ａ，２３Ｂの平均厚さ（成形品１５０の第２の厚肉部１５３Ａ，１５３Ｂの厚さ方向に相当する金型キャビティ面間の平均距離）Ｔ１２は５．０ｍｍである。また、可動コア部３０Ａ，３０Ｂが後進端に位置するときの第３キャビティ部２５Ａ，２５Ｂの厚さ（成形品１５０の薄肉部１５５Ａ，１５５Ｂの厚さ方向に相当する金型キャビティ面間の距離）Ｔ１３Ｂを５．０ｍｍとし、可動コア部３０Ａ，３０Ｂが前進端に位置するときの第３キャビティ部２５Ａ，２５Ｂの厚さＴ１３Ｆを１．０ｍｍとした。
【００７４】
以下、金型等の概念図である図１０〜図１３を参照して、実施例３の射出成形方法を説明する。尚、実施例３にあっては、熱可塑性樹脂、加圧流体として、実施例１と同じ熱可塑性樹脂、加圧流体を使用した。
【００７５】
［工程−３００］
先ず、実施例１の［工程−１００］と同様にして、熱可塑性樹脂を可塑化、溶融した。そして、固定金型部１０と可動金型部１１を型締めし、油圧シリンダー３１Ａ，３１Ｂの作動によって可動コア部３０Ａ，３０Ｂを後進端に位置せしめた（図１０参照）。
【００７６】
［工程−３１０］
そして、実施例１の［工程−１１０］と同様にして、射出用シリンダーから、溶融樹脂流路１３、溶融樹脂導入部（ゲート部）１２を介してキャビティ内（より具体的には、第１キャビティ部２１内）に溶融熱可塑性樹脂４０を射出した（図１１参照）。尚、キャビティ全体に導入した溶融熱可塑性樹脂４０の量をキャビティ全体の体積の８０％とし、射出時間を７．０秒とした。
【００７７】
［工程−３２０］
次いで、実施例１の［工程−１２０］と同様にして、溶融熱可塑性樹脂４０の射出開始から７．３秒後に、加圧流体源１６から、配管１５、加圧流体導入部１１４を介してキャビティ内の溶融熱可塑性樹脂４０（より具体的には、第１キャビティ部２１内の溶融熱可塑性樹脂４０）の内部に加圧流体（圧力１×１０７Ｐａの加圧窒素ガス）を導入し、第１キャビティ部２１を占める溶融熱可塑性樹脂４０の内部に中空部１５２を形成した（図１２参照）。加圧流体の導入によって、キャビティ内の溶融熱可塑性樹脂４０は流動し、第１キャビティ部２１、第２キャビティ部２３Ａ，２３Ｂ及び第３キャビティ部２５Ａ，２５Ｂは溶融熱可塑性樹脂４０で充満された。但し、中空部１５２は、第１キャビティ部２１内に止まった。
【００７８】
［工程−３３０］
その後、実施例１の［工程−１３０］と同様にして、溶融熱可塑性樹脂４０の射出開始から１０．０秒後に、油圧シリンダー３１Ａ，３１Ｂを作動させて、可動コア部３０Ａ，３０Ｂを後進端から前進端へと移動させ、薄肉部１５５Ａ，１５５Ｂを成形した（図１３参照）。可動コア部３０Ａ，３０Ｂの移動量は４．０ｍｍである。即ち、可動コア部３０Ａ，３０Ｂが前進端に位置したときの、第３キャビティ部２５Ａ，２５Ｂの厚さＴ１３Ｆ（成形品の薄肉部の厚さ方向に相当する金型キャビティ面間の距離）は１．０ｍｍである。移動速度を２ｍｍ／秒とした。可動コア部３０Ａ，３０Ｂの前進端への移動に伴い、第３キャビティ部２５Ａ，２５Ｂ内の溶融熱可塑性樹脂４０の一部は、第１キャビティ部２１へと押し出された。その結果、第１キャビティ部２１内の溶融熱可塑性樹脂４０の内部に形成された中空部１５２の容積が減少した。第１キャビティ部２１内の溶融熱可塑性樹脂４０の内部に形成された中空部１５２内に存在し、加圧流体導入部１１４から加圧状態とされた加圧流体の一部は、加圧流体導入部１１４から外部に排出された。
【００７９】
［工程−３４０］
次いで、実施例１の［工程−１４０］と同様にして、溶融熱可塑性樹脂４０の射出開始から３７．３秒後に、中空部１５２内の加圧流体を加圧流体導入部１１４を介して排出した。尚、中空部１５２内が大気圧になった時点で、中空部１５２内には大気圧の窒素ガスが残存し得る。
【００８０】
［工程−３５０］
溶融熱可塑性樹脂４０の射出開始から６７．３秒まで、キャビティ内の熱可塑性樹脂を冷却し、その後、金型の型開きを行い、金型から成形品を取り出した。
【００８１】
得られた成形品１５０の薄肉部１５５Ａ，１５５Ｂには、ウエルド、ヘジテーションマーク、フローマーク等の外観不良は認められなかった。また、第１の厚肉部１５１には所望の中空部１５２が形成されており、更には、中実の薄肉部１５５Ａ，１５５Ｂ及び厚肉部１５３Ａ，１５３Ｂが確実に形成されていた。
【００８２】
尚、実施例３においては、実施例２にて説明した射出成形方法を適用することもできる。
【００８３】
（実施例４）
実施例４は、本発明の第２の態様に係る射出成形方法に関する。
【００８４】
実施例４によって得られた成形品５０の模式的な平面図を図１９の（Ａ）に示し、模式的な側面図を図１９の（Ｂ）に示し、図１９の（Ａ）の線Ｃ−Ｃに沿った模式的な断面図を図１９の（Ｃ）に示す。この成形品５０は、中空部５２を有する第１の厚肉部５１、中空部５４を有する第２の厚肉部５３、及び、第１の厚肉部５１と第２の厚肉部５３との間に位置する中実の薄肉部５５から構成されている。成形品５０の形状、寸法は、実施例１にて説明した成形品の形状、寸法と同じである。但し、第２の厚肉部５３にも中空部５４が形成されている点が異なる。即ち、成形品５０の幅（Ｗ）を２０ｍｍ、第１の厚肉部５１の長さ（Ｌ１）を４０ｍｍ、厚さ（ｔ２１）を５．０ｍｍ、第２の厚肉部５３の長さ（Ｌ２）を１５ｍｍ、厚さ（ｔ２２）を５．０ｍｍ、薄肉部５５の長さ（Ｌ３）を５．０ｍｍ、厚さ（ｔ２３）を１．０ｍｍとした。
【００８５】
実施例４において使用した金型は、実施例１にて説明した金型と同じ構造を有するので、詳細な説明は省略する。
【００８６】
金型に設けられたキャビティの形状は、図１９に図示した成形品５０を成形できる寸法である。即ち、第３キャビティ部２５近傍の第１キャビティ部２１の平均厚さ（成形品５０の第１の厚肉部５１の厚さ方向に相当する金型キャビティ面間の平均距離）Ｔ２１は５．０ｍｍであり、第３キャビティ部２５近傍の第２キャビティ部２３の平均厚さ（成形品５０の第２の厚肉部５３の厚さ方向に相当する金型キャビティ面間の平均距離）Ｔ２２は５．０ｍｍである。また、可動コア部３０が後進端に位置するときの第３キャビティ部２５の厚さ（成形品５０の薄肉部５５の厚さ方向に相当する金型キャビティ面間の距離）Ｔ２３Ｂを５．０ｍｍとし、可動コア部３０が前進端に位置するときの第３キャビティ部２５の厚さＴ２３Ｆを１．０ｍｍとした。尚、これらのＴ２１，Ｔ２２，Ｔ２３Ｂ，Ｔ２３Ｆに関しては、図１及び図２に示したＴ１１，Ｔ１２，Ｔ１３Ｂ，Ｔ１２３Ｆを、Ｔ２１，Ｔ２２，Ｔ２３Ｂ，Ｔ２３Ｆと読み替えればよい。
【００８７】
以下、金型等の概念図である図２、図１５〜図１８を参照して、実施例４の射出成形方法を説明する。尚、実施例４にあっては、熱可塑性樹脂、加圧流体として、実施例１にて説明した熱可塑性樹脂、加圧流体を使用した。
【００８８】
［工程−４００］
先ず、実施例１の［工程−１００］と同様にして、熱可塑性樹脂を可塑化、溶融した。そして、固定金型部１０と可動金型部１１を型締めし、油圧シリンダー３１の作動によって可動コア部３０を後進端に位置せしめた（図２参照）。図示しない加圧流体導入部移動手段に作動によって、加圧流体導入部１４は前進端に位置せしめられ、加圧流体導入部１４の先端部は、第１キャビティ部２１内に突出した状態となる。
【００８９】
［工程−４１０］
そして、実施例１の［工程−１１０］と同様にして、射出用シリンダーから、溶融樹脂流路１３、溶融樹脂導入部（ゲート部）１２を介してキャビティ内（より具体的には、第１キャビティ部２１内、第３キャビティ部２５内、及び、第２キャビティ部の一部内）に溶融熱可塑性樹脂４０を射出した（図１５参照）。尚、キャビティ全体に導入した溶融熱可塑性樹脂４０の量をキャビティ全体の体積の７０％とし、射出時間を３．４秒とした。
【００９０】
［工程−４２０］
溶融熱可塑性樹脂４０の射出開始から３．８秒後に、加圧流体源１６から、配管１５、加圧流体導入部１４を介してキャビティ内の溶融熱可塑性樹脂４０（より具体的には、第１キャビティ部２１内の溶融熱可塑性樹脂４０）の内部に加圧流体（圧力１×１０７Ｐａの加圧窒素ガス）を導入し、第１キャビティ部２１、第２キャビティ部２３及び第３キャビティ部２５を占める溶融熱可塑性樹脂４０の内部に中空部５２，５４，５６を形成した（図１６参照）。加圧流体の導入によって、キャビティ内の溶融熱可塑性樹脂４０は流動し、キャビティは溶融熱可塑性樹脂４０によって完全に充満された。
【００９１】
［工程−４３０］
溶融熱可塑性樹脂４０の射出開始から６．０秒後に、図示しない加圧流体導入部移動手段に作動によって加圧流体導入部１４を後進端に位置せしめ、加圧流体導入部１４の先端部と金型との間に隙間を形成し、中空部５２，５４，５６内の加圧流体をこの隙間から大気中に排出した（図１７参照）。尚、中空部５２，５４，５６内が大気圧になった時点で、中空部５２，５４，５６内には大気圧の窒素ガスが残存し得る。
【００９２】
［工程−４４０］
溶融熱可塑性樹脂４０の射出開始から８．０秒後に、油圧シリンダー３１を作動させて、可動コア部３０を後進端から前進端へと移動させて、第３キャビティ部２５を占める溶融熱可塑性樹脂４０の内部に形成された中空部５６を無くし、中実の薄肉部５５を成形した（図１８参照）。可動コア部３０の移動量は４．０ｍｍである。即ち、可動コア部３０が前進端に位置したときの、第３キャビティ部２５の厚さＴ２３Ｆ（成形品の薄肉部の厚さ方向に相当する金型キャビティ面間の距離）は１．０ｍｍである。移動速度を７ｍｍ／秒とした。可動コア部３０の前進端への移動に伴い、第３キャビティ部２５内の溶融熱可塑性樹脂４０の一部は、第１キャビティ部２１へと押し出された。その結果、第１キャビティ部２１内の溶融熱可塑性樹脂４０の内部に形成された中空部５２の容積が減少した。第１キャビティ部２１内の溶融熱可塑性樹脂４０の内部に形成された中空部５２内に存在した加圧流体の一部は、加圧流体導入部１４の先端部と金型との間に隙間から外部に排出された。
【００９３】
［工程−４５０］
溶融熱可塑性樹脂４０の射出開始から６３．４秒まで、キャビティ内の熱可塑性樹脂を冷却し、次いで、金型の型開きを行い、金型から成形品を取り出した。
【００９４】
得られた成形品５０の薄肉部５５には、ウエルド、ヘジテーションマーク、フローマーク等の外観不良は認められなかった。また、第１の厚肉部５１には所望の中空部５２が形成されており、更には、中実の薄肉部５５及び厚肉部５３が確実に形成されていた。
【００９５】
（実施例５）
実施例５は、本発明の第３の態様に係る射出成形方法に関する。
【００９６】
実施例５によって得られた成形品５０の模式的な平面図を図２６の（Ａ）に示し、模式的な側面図を図２６の（Ｂ）に示し、図２６の（Ａ）の線Ｃ−Ｃに沿った模式的な断面図を図２６の（Ｃ）に示す。この成形品５０は、中空部５２を有する第１の厚肉部５１、中空部５４を有する第２の厚肉部５３、及び、第１の厚肉部５１と第２の厚肉部５３との間に位置する中実の薄肉部５５から構成されている。成形品５０の形状、寸法は、実施例４にて説明した成形品の形状、寸法と同じである。但し、第２の厚肉部５３にも中空部５４が形成されている点が異なる。
【００９７】
実施例５において使用した金型の概念図を図２０に示す。尚、図２０にあっては、可動コア部３０が前進端に位置した状態を示す。この金型は、固定金型部１０と可動金型部１１から構成されている。そして、金型は、成形品５０の第１の厚肉部５１を成形すべき第１キャビティ部２１、第２の厚肉部５３を成形すべき第２キャビティ部２３、及び、薄肉部５５を成形すべき第３キャビティ部２５から構成されたキャビティを有する。更には、金型は、溶融樹脂導入部（所謂ゲート部）１２、加圧流体導入部２１４、及び、可動コア部３０を備えている。
【００９８】
溶融樹脂導入部１２は、第１キャビティ部２１に溶融熱可塑性樹脂４０が射出されるように固定金型部１０に配置されている。溶融樹脂導入部１２は、ダイレクトゲート構造を有し、図示しない射出用シリンダーと、固定金型部１０に設けられたスプルー及びコールドランナータイプの溶融樹脂流路１３を介して連通している。
【００９９】
加圧流体導入部２１４は、第２キャビティ部２３に加圧流体が導入されるように可動金型部１１に配置されている。加圧流体導入部２１４は、実施例１にて説明したと同様の構造を有する。
【０１００】
可動コア部３０は、第３キャビティ部２５内で、可動コア部移動手段である油圧シリンダー３１の作動によって、成形品５０の薄肉部５５の厚さ方向に相当する方向に沿って前進端及び後進端の間で移動し得る。
【０１０１】
金型に設けられたキャビティの形状は、図２６に図示した成形品５０を成形できる寸法である。即ち、第３キャビティ部２５近傍の第１キャビティ部２１の平均厚さ（成形品５０の第１の厚肉部５１の厚さ方向に相当する金型キャビティ面間の平均距離）Ｔ２１は５．０ｍｍであり、第３キャビティ部２５近傍の第２キャビティ部２３の平均厚さ（成形品５０の第２の厚肉部５３の厚さ方向に相当する金型キャビティ面間の平均距離）Ｔ２２は５．０ｍｍである。また、可動コア部３０が後進端に位置するときの第３キャビティ部２５の厚さ（成形品５０の薄肉部５５の厚さ方向に相当する金型キャビティ面間の距離）Ｔ２３Ｂを５．０ｍｍとし、可動コア部３０が前進端に位置するときの第３キャビティ部２５の厚さＴ２３Ｆを１．０ｍｍとした。
【０１０２】
以下、金型等の概念図である図２１〜図２５を参照して、実施例５の射出成形方法を説明する。尚、実施例５にあっては、熱可塑性樹脂、加圧流体として、実施例１にて説明した熱可塑性樹脂、加圧流体を使用した。
【０１０３】
［工程−５００］
先ず、実施例１の［工程−１００］と同様にして、熱可塑性樹脂を可塑化、溶融した。そして、固定金型部１０と可動金型部１１を型締めし、油圧シリンダー３１の作動によって可動コア部３０を後進端に位置せしめた（図２１参照）。可動コア部３０が後進端に位置したときの、第３キャビティ部２５の厚さＴ２３Ｂ（成形品５０の薄肉部５５の厚さ方向に相当する金型キャビティ面間の距離）は５．０ｍｍである。また、図示しない加圧流体導入部移動手段に作動によって、加圧流体導入部２１４は前進端に位置せしめられ、加圧流体導入部２１４の先端部は、第１キャビティ部２１内に突出した状態となる。
【０１０４】
［工程−５１０］
そして、実施例１の［工程−１１０］と同様にして、射出用シリンダーから、溶融樹脂流路１３、溶融樹脂導入部（ゲート部）１２を介してキャビティ内（より具体的には、第１キャビティ部２１内）に溶融熱可塑性樹脂４０を射出した（図２２参照）。尚、キャビティ全体に導入した溶融熱可塑性樹脂４０の量をキャビティ全体の体積の７０％とし、射出時間を３．４秒とした。
【０１０５】
［工程−５２０］
溶融熱可塑性樹脂４０の射出開始から３．８秒後に、加圧流体源１６から、配管１５、加圧流体導入部２１４を介してキャビティ内の溶融熱可塑性樹脂４０（より具体的には、第２キャビティ部２３内の溶融熱可塑性樹脂４０）の内部に加圧流体（圧力１×１０７Ｐａの加圧窒素ガス）を導入し、第１キャビティ部２１、第２キャビティ部２３及び第３キャビティ部２５を占める溶融熱可塑性樹脂４０の内部に中空部５２，５４，５６を形成した（図２３参照）。加圧流体の導入によって、キャビティ内の溶融熱可塑性樹脂４０は流動し、キャビティは溶融熱可塑性樹脂４０によって完全に充満された。
【０１０６】
［工程−５３０］
溶融熱可塑性樹脂４０の射出開始から８．８秒後に、図示しない加圧流体導入部移動手段に作動によって加圧流体導入部２１４を後進端に位置せしめ、加圧流体導入部２１４の先端部と金型との間に隙間を形成し、中空部５２，５４，５６内の加圧流体をこの隙間から大気中に排出した（図２４参照）。尚、中空部５２，５４，５６内が大気圧になった時点で、中空部５２，５４，５６内には大気圧の窒素ガスが残存し得る。
【０１０７】
［工程−５４０］
溶融熱可塑性樹脂４０の射出開始から１０．８秒後に、油圧シリンダー３１を作動させて、可動コア部３０を後進端から前進端へと移動させて、第３キャビティ部２５を占める溶融熱可塑性樹脂４０の内部に形成された中空部５６を無くし、中実の薄肉部５５を成形した（図２５参照）。可動コア部３０の移動量は４．０ｍｍである。即ち、可動コア部３０が前進端に位置したときの、第３キャビティ部２５の厚さＴ２３Ｆ（成形品の薄肉部の厚さ方向に相当する金型キャビティ面間の距離）は１．０ｍｍである。移動速度を２ｍｍ／秒とした。可動コア部３０の前進端への移動に伴い、第３キャビティ部２５内の溶融熱可塑性樹脂４０の一部は、第２キャビティ部２３へと押し出された。その結果、第２キャビティ部２５内の溶融熱可塑性樹脂４０の内部に形成された中空部５４の容積が減少した。第２キャビティ部２３内の溶融熱可塑性樹脂４０の内部に形成された中空部５４内に存在した加圧流体の一部は、加圧流体導入部２１４の先端部と金型との間に隙間から外部に排出された。
【０１０８】
［工程−５５０］
溶融熱可塑性樹脂４０の射出開始から６３．４秒まで、キャビティ内の熱可塑性樹脂を冷却し、次いで、金型の型開きを行い、金型から成形品を取り出した。
【０１０９】
得られた成形品５０の薄肉部５５には、ウエルド、ヘジテーションマーク、フローマーク等の外観不良は認められなかった。また、第１の厚肉部５１には所望の中空部５２が形成されており、更には、中実の薄肉部５５及び厚肉部５３が確実に形成されていた。
【０１１０】
（比較例２）
比較例２においては、図２０に示すように、可動コア部３０を予め前進端に固定した。そして、実施例５の［工程−５４０］、即ち、可動コア部３０を後進端から移動させる工程を実行すること無く、実施例５の［工程−５００］〜［工程−５３０］、［工程−５５０］を実行した。
【０１１１】
その結果、第３キャビティ部２５における樹脂流動圧力損失が大きいために、加圧流体を導入することによっても、第２キャビティ部２３に溶融熱可塑性樹脂を流入させることができず、第２キャビティ部２３において、熱可塑性樹脂の未充填部分が発生し、所望の成形品を得ることができなかった。
【０１１２】
以上、本発明を、好ましい実施例に基づき説明したが、本発明はこれらに限定されるものではない。実施例にて説明した使用熱可塑性樹脂、加圧流体、成形条件や金型の構造等は例示であり、適宜変更することができる。実施例１においては、薄肉部が１カ所あるいは２カ所、設けられた成形品の射出成形方法について説明したが、薄肉部の数はこれらに限定するものではない。
【０１１３】
【発明の効果】
本発明の射出成形方法にあっては、薄肉部を成形するに当たり、先ず、第３キャビティ部における成形品の薄肉部の厚さ方向に相当する金型キャビティ面間の距離を長くしておく。従って、第３キャビティ部における樹脂流動圧力損失を小さくすることができ、第３キャビティ部内を溶融熱可塑性樹脂が容易に流動する結果、ヘジテーションが発生することが無く、フローマークも生じない。また、溶融熱可塑性樹脂が第２キャビティ部へ容易に流入するので、キャビティ全体を溶融熱可塑性樹脂によって確実に充満することができる。従って、薄肉部の強度低下や成形品の外観不良等が生じることが無い。本発明の射出成形方法を、例えば、薄肉部がヒンジ部として機能する成形品の成形に適用すれば、高い強度（例えば静的強度や疲労強度）を有するヒンジ部を得ることができる。
【図面の簡単な説明】
【図１】図１は、実施例１において使用した金型の概念図である。
【図２】図２は、実施例１の射出成形方法を説明するための金型等の概念図である。
【図３】図３は、図２に引き続き、実施例１の射出成形方法を説明するための金型等の概念図である。
【図４】図４は、図３に引き続き、実施例１の射出成形方法を説明するための金型等の概念図である。
【図５】図５は、図４に引き続き、実施例１の射出成形方法を説明するための金型等の概念図である。
【図６】図６の（Ａ）、（Ｂ）及び（Ｃ）は、それぞれ、実施例１によって得られた成形品の模式的な平面図、模式的な側面図、及び、模式的な断面図である。
【図７】図７は、実施例２の射出成形方法を説明するための金型等の概念図である。
【図８】図８は、図７に引き続き、実施例２の射出成形方法を説明するための金型等の概念図である。
【図９】図９は、実施例３において使用した金型の概念図である。
【図１０】図１０は、実施例３の射出成形方法を説明するための金型等の概念図である。
【図１１】図１１は、図１０に引き続き。実施例３の射出成形方法を説明するための金型等の概念図である。
【図１２】図１２は、図１１に引き続き、実施例３の射出成形方法を説明するための金型等の概念図である。
【図１３】図１３は、図１２に引き続き、実施例３の射出成形方法を説明するための金型等の概念図である。
【図１４】図１４の（Ａ）、（Ｂ）及び（Ｃ）は、それぞれ、実施例３によって得られた成形品の模式的な平面図、模式的な側面図、及び、模式的な断面図である。
【図１５】図１５は、実施例４の射出成形方法を説明するための金型等の概念図である。
【図１６】図１６は、図１５に引き続き、実施例４の射出成形方法を説明するための金型等の概念図である。
【図１７】図１７は、図１６に引き続き、実施例４の射出成形方法を説明するための金型等の概念図である。
【図１８】図１８は、図１７に引き続き、実施例４の射出成形方法を説明するための金型等の概念図である。
【図１９】図１９の（Ａ）、（Ｂ）及び（Ｃ）は、それぞれ、実施例４によって得られた成形品の模式的な平面図、模式的な側面図、及び、模式的な断面図である。
【図２０】図２０は、実施例５において使用した金型の概念図である。
【図２１】図２１は、実施例５の射出成形方法を説明するための金型等の概念図である。
【図２２】図２２は、図２１に引き続き、実施例５の射出成形方法を説明するための金型等の概念図である。
【図２３】図２３は、図２２に引き続き、実施例５の射出成形方法を説明するための金型等の概念図である。
【図２４】図２４は、図２３に引き続き、実施例５の射出成形方法を説明するための金型等の概念図である。
【図２５】図２５は、図２４に引き続き、実施例５の射出成形方法を説明するための金型等の概念図である。
【図２６】図２６の（Ａ）、（Ｂ）及び（Ｃ）は、それぞれ、実施例５によって得られた成形品の模式的な平面図、模式的な側面図、及び、模式的な断面図である。
【符号の説明】
１０・・・固定金型部、１１・・・可動金型部、１２・・・溶融樹脂導入部、１３・・・溶融樹脂流路、１４，１１４，２１４・・・加圧流体導入部、１５・・・配管、１６・・・加圧流体源、２１・・・第１キャビティ部、２３，２３Ａ，２３Ｂ・・・第２キャビティ部、２５，２５Ａ，２５Ｂ・・・第３キャビティ部、３０，３０Ａ，３０Ｂ・・・可動コア部、３１，３１Ａ，３１Ｂ・・・油圧シリンダー、４０・・・溶融熱可塑性樹脂、５０，１５０・・・成形品、５１，１５１・・・第１の厚肉部、５２，５４，５６，１５２・・・中空部、５３，１５３Ａ，１５３Ｂ・・・第２の厚肉部、５５，１５５Ａ，１５５Ｂ・・・薄肉部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an injection molding method for a molded article having a thin portion.
[0002]
[Prior art]
When molding a molded article based on injection molding of a molten thermoplastic resin, techniques for obtaining a beautiful molded article having an appearance without sink marks and warpage are disclosed in, for example, JP-A-63-268611 and JP-B-3-47171. This is known from Japanese Patent Application Publication No. In the technology disclosed in these publications, a molten thermoplastic resin is injected into a cavity provided in a mold to fill the cavity with the molten thermoplastic resin, and then a pressurized fluid such as a pressurized gas is supplied. It is introduced into the molten thermoplastic resin in the cavity to obtain a molded article having a hollow portion. Usually, a thick part is unevenly distributed in a molded product, and a hollow part is formed in this thick part. The pressurized fluid is introduced from a pressurized fluid introduction unit provided in the mold. By introducing a pressurized fluid into the molten thermoplastic resin in the cavity, the molten thermoplastic resin is pressed against the cavity surface of the mold, thereby effectively preventing sinking and warping of the molded product. Can be.
[0003]
In order to ensure the formation of a hollow portion, a mold having a movable core portion in a cavity portion where a hollow portion is to be formed is disclosed in, for example, JP-A-4-212822 and JP-A-7-164486. It is known. In these techniques, the molten thermoplastic resin is injected into the cavity with the movable core positioned at the forward end. After the injection is completed, a pressurized fluid is introduced into the molten thermoplastic resin in the cavity, and at the same time, the movable core portion is moved to the backward end to increase the volume of the portion of the cavity where the hollow portion is to be formed. .
[0004]
[Patent Document 1] JP-A-63-268611
[Patent Document 2] Japanese Patent Publication No. 3-47171
[Patent Document 3] JP-A-4-212822
[Patent Document 4] JP-A-7-164486
[Patent Document 5] JP-A-4-339624
[Patent Document 6] US Patent No. 4474717
[Patent Document 7] US Pat. No. 5,044,924
[Patent Document 8] US Pat. No. 5,908,641
[0005]
[Problems to be solved by the invention]
However, in the case of employing a technique disclosed in JP-A-63-268611 or JP-B-3-47171 to form a molded product in which a thin portion is disposed between thick portions. When the molten thermoplastic resin is injected into a portion of a cavity where one thick portion is to be molded (referred to as a first cavity portion for convenience), a portion of a cavity where a thin portion is to be molded (for convenience, a third cavity portion). ), The molten thermoplastic resin is applied to a part of the cavity (for convenience, called the second cavity) beyond the third cavity where the other thick part is to be molded. In many cases, it does not flow. A pressurized fluid introduction unit is provided in the first cavity portion, and a pressurized fluid is introduced into the molten thermoplastic resin injected into the first cavity portion via the pressurized fluid introduction portion. A method is also conceivable in which the existing molten thermoplastic resin is made to flow and the molten thermoplastic resin flows into the second cavity portion beyond the third cavity portion. However, in practice, since the resin flow pressure loss in the third cavity is large, it is difficult to reliably flow the molten thermoplastic resin into a part of the second cavity.
[0006]
Such a phenomenon exists in the second cavity portion by disposing the pressurized fluid introduction portion in the second cavity portion and introducing the pressurized fluid from the second cavity portion to the molten thermoplastic resin in the cavity. It may be possible to solve the problem by flowing the molten thermoplastic resin and sufficiently filling the second cavity portion with the molten thermoplastic resin. However, since it is necessary to form a hollow portion inside the molten thermoplastic resin existing in the first cavity portion beyond the third cavity portion, it is also necessary to form a hollow portion inside the molten thermoplastic resin existing in the third cavity portion. A hollow portion is formed, which causes a problem that the strength of a molded product, particularly, a thin portion is reduced.
[0007]
Further, since the third cavity exists, hesitation marks and flow marks generated by hesitation (a phenomenon in which the melt front temporarily stops) are generated, and the appearance of the molded article is often poor. Further, a weld is formed in a thin portion by hesitation, or the thermoplastic resin in the cavity reflows after being solidified once, so that the static strength and fatigue strength of the molded product are reduced.
[0008]
In particular, a decrease in the strength of the thin portion is fatal when the thin portion functions as a hinge portion.
[0009]
Further, in the technology disclosed in JP-A-4-212822 and JP-A-7-164486, a movable core portion is provided to form a hollow portion, and a cavity provided with the movable core portion is provided. There is no disclosure of a technique for reliably forming a thin-walled portion having a solid structure using the method.
[0010]
Accordingly, an object of the present invention is to provide a first thick portion having a hollow portion, a second thick portion having a solid or hollow portion, and the first thick portion and the second thick portion. It is an object of the present invention to provide an injection molding method capable of reliably molding a molded product having a solid thin portion located therebetween without causing a decrease in strength of the thin portion and poor appearance of the molded product.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, an injection molding method for a molded article having a thin portion according to the first aspect of the present invention (hereinafter, referred to as an injection molding method according to the first aspect of the present invention) is as follows.
(A) a first thick portion having a hollow portion,
(B) a solid second thick portion; and
(C) a solid thin portion located between the first thick portion and the second thick portion;
Moldings with
{Circle around (1)} A cavity composed of a first cavity portion for molding a first thick portion, a second cavity portion for molding a second thick portion, and a third cavity portion for molding a thin portion. Has,
{Circle around (2)} a molten resin introduction portion arranged so that the molten thermoplastic resin is injected into the first cavity portion;
(3) a pressurized fluid introduction unit disposed so as to introduce a pressurized fluid into the first cavity portion;
{Circle around (4)} a movable core portion which can move between a forward end and a reverse end along a direction corresponding to the thickness direction of the thin portion of the molded product in the third cavity portion;
A method of injection molding using a mold having
(A) a step of injecting a molten thermoplastic resin into a cavity through a molten resin introduction portion while the movable core portion is positioned at a backward end;
(B) During the injection of the molten thermoplastic resin into the cavity, at the same time as the completion of the injection, or after the injection is completed, the pressurized fluid is injected into the molten thermoplastic resin inside the cavity via the pressurized fluid introduction unit. Introducing and forming a hollow portion inside the molten thermoplastic resin occupying the first cavity portion;
(C) moving the movable core part to the forward end to form a thin part;
It is characterized by having.
[0012]
In order to achieve the above object, an injection molding method for a molded article having a thin portion according to the second aspect of the present invention (hereinafter, referred to as an injection molding method according to the second aspect of the present invention) is a second aspect. The point that a hollow portion is formed in the thick portion is different from the injection molding method according to the first aspect of the present invention. That is, the injection molding method according to the second aspect of the present invention comprises:
(A) a first thick portion having a hollow portion,
(B) a second thick portion having a hollow portion, and
(C) a solid thin portion located between the first thick portion and the second thick portion;
Moldings with
{Circle around (1)} A cavity composed of a first cavity portion for molding a first thick portion, a second cavity portion for molding a second thick portion, and a third cavity portion for molding a thin portion. Has,
{Circle around (2)} a molten resin introduction portion arranged so that the molten thermoplastic resin is injected into the first cavity portion;
(3) a pressurized fluid introduction unit disposed so as to introduce a pressurized fluid into the first cavity portion;
{Circle around (4)} a movable core portion which can move between a forward end and a reverse end along a direction corresponding to the thickness direction of the thin portion of the molded product in the third cavity portion;
A method of injection molding using a mold having
(A) a step of injecting a molten thermoplastic resin into a cavity through a molten resin introduction portion while the movable core portion is positioned at a backward end;
(B) During or after injection of the molten thermoplastic resin into the cavity, or after completion of the injection, the pressurized fluid is injected into the molten thermoplastic resin inside the cavity via the pressurized fluid introduction unit. Introducing, forming a hollow portion inside the molten thermoplastic resin occupying the first cavity portion, the second cavity portion, and the third cavity portion;
(C) a step of discharging the pressurized fluid in the hollow portion;
(D) moving the movable core portion to the forward end to eliminate a hollow portion formed inside the molten thermoplastic resin occupying the third cavity portion and form a solid thin portion;
It is characterized by having.
[0013]
In order to achieve the above object, the injection molding method for a molded article having a thin portion according to the third aspect of the present invention (hereinafter, referred to as the injection molding method according to the third aspect of the present invention) is the present invention. The arrangement position of the pressurized fluid introduction part is different from that of the injection molding method according to the second aspect.
That is, the injection molding method according to the third aspect of the present invention comprises:
(A) a first thick portion having a hollow portion,
(B) a second thick portion having a hollow portion, and
(C) a solid thin portion located between the first thick portion and the second thick portion;
Moldings with
{Circle around (1)} A cavity composed of a first cavity portion for molding a first thick portion, a second cavity portion for molding a second thick portion, and a third cavity portion for molding a thin portion. Has,
{Circle around (2)} a molten resin introduction portion arranged so that the molten thermoplastic resin is injected into the first cavity portion;
(3) a pressurized fluid introduction unit disposed so as to introduce a pressurized fluid into the second cavity portion;
{Circle around (4)} a movable core portion which can move between a forward end and a reverse end along a direction corresponding to the thickness direction of the thin portion of the molded product in the third cavity portion;
A method of injection molding using a mold having
(A) a step of injecting a molten thermoplastic resin into a cavity through a molten resin introduction portion while the movable core portion is positioned at a backward end;
(B) During or after injection of the molten thermoplastic resin into the cavity, or after completion of the injection, the pressurized fluid is injected into the molten thermoplastic resin inside the cavity via the pressurized fluid introduction unit. Introducing, forming a hollow portion inside the molten thermoplastic resin occupying the first cavity portion, the second cavity portion, and the third cavity portion;
(C) a step of discharging the pressurized fluid in the hollow portion;
(D) moving the movable core portion to the forward end to eliminate the hollow portion formed inside the molten thermoplastic resin occupying the third cavity portion and form a solid thin portion. It is characterized.
[0014]
In the injection molding method according to the first to third aspects of the present invention (hereinafter sometimes collectively referred to as the injection molding method of the present invention), molten thermoplastic resin injected into the cavity is used. The resin flows in the third cavity where the movable core is located at the backward end. That is, the thickness of the third cavity portion (the distance between the mold cavity surfaces corresponding to the thickness direction of the thin portion of the molded product) at this time is large. Therefore, the resin flow pressure loss in the third cavity is small, and the molten thermoplastic resin easily flows in the third cavity. As a result, hesitation does not occur and no flow mark occurs. Moreover, since the molten thermoplastic resin easily flows into the second cavity portion, the entire cavity can be reliably filled with the molten thermoplastic resin. In addition, it is possible to adjust the position of the movable core so that a desired hollow portion is formed by the pressurized fluid. Here, the “flow” of the molten thermoplastic resin means not only the flow of the molten thermoplastic resin during the injection of the molten thermoplastic resin into the cavity, but also the pressurized fluid into the molten thermoplastic resin inside the cavity. Is a concept including reflow of the molten thermoplastic resin due to the introduction of
[0015]
In the injection molding method according to the first aspect of the present invention, the step (C) may be configured to discharge a part of the pressurized fluid in the hollow portion. In addition, such a configuration is referred to as an injection molding method according to an embodiment 1A of the present invention for convenience. In this case, in the step (B), when a pressurized fluid is introduced into the molten thermoplastic resin in the cavity via the pressurized fluid introduction unit, and a hollow portion is formed in the molten thermoplastic resin in the cavity. The first, second, and third cavities are filled with a molten thermoplastic resin. Then, in the step (C), when the movable core portion is moved to the forward end to form the thin portion, a part of the molten thermoplastic resin in the third cavity portion is moved with the movement of the movable core portion to the forward end. , Is extruded into the first cavity portion, so that the volume of the hollow portion formed inside the molten thermoplastic resin in the first cavity portion is reduced. As a result, a part of the pressurized fluid existing in the hollow portion formed inside the molten thermoplastic resin in the first cavity portion and being in a pressurized state from the pressurized fluid introduction portion is partially compressed by the pressurized fluid introduction portion. Is discharged to the outside.
[0016]
The hollow portion is in a pressurized state via a pressurized fluid introduction unit. Therefore, a part of the pressurized fluid existing in the hollow portion formed inside the molten thermoplastic resin in the first cavity portion may be moved from the pressurized fluid introduction portion to the outside depending on the structure of the pressurized fluid introduction portion. May be difficult to discharge. In such a case, the injection molding method according to the first aspect of the present invention further includes a step of discharging the pressurized fluid in the hollow portion between the step (B) and the step (C). Is preferred. In addition, such a configuration is referred to as an injection molding method according to an embodiment 1B of the present invention for convenience.
[0017]
In the injection molding method according to the aspect 1B of the present invention, when the movable core portion is moved to the forward end in the step (C) to form the thin portion, the movable core portion is moved to the forward end of the movable core portion. As a result, a part of the molten thermoplastic resin in the third cavity is extruded into the first cavity. As a result, since the volume of the hollow portion formed inside the molten thermoplastic resin in the first cavity portion is reduced, the pressurized fluid existing in the hollow portion formed inside the molten thermoplastic resin in the first cavity portion is reduced. Is further discharged outside.
[0018]
On the other hand, in the injection molding method according to the second aspect of the present invention, in the step (D), when the movable core portion is moved to the forward end to form a solid thin portion, With the movement to the forward end, a part of the molten thermoplastic resin in the third cavity is extruded to the first cavity. As a result, since the volume of the hollow portion formed inside the molten thermoplastic resin in the first cavity portion is reduced, the pressurized fluid existing in the hollow portion formed inside the molten thermoplastic resin in the first cavity portion is reduced. Is further discharged outside. Further, in the injection molding method according to the third aspect of the present invention, in the step (D), when the movable core portion is moved to the forward end to form a solid thin portion, With the movement to the forward end, a part of the molten thermoplastic resin in the third cavity is extruded into the second cavity. As a result, since the volume of the hollow portion formed inside the molten thermoplastic resin in the second cavity portion is reduced, the pressurized fluid existing in the hollow portion formed inside the molten thermoplastic resin in the second cavity portion is reduced. Is further discharged outside.
[0019]
In the step (C) of the injection molding method according to the first aspect B of the present invention, or the injection molding method according to the second or third aspect of the present invention, the pressurized fluid in the hollow portion is removed. It can be discharged to the outside through the pressurized fluid introduction part, or can be discharged to the outside through the outer peripheral part of the pressurized fluid introduction part. Thereby, the pressure in the hollow portion becomes the atmospheric pressure.
[0020]
In the injection molding method according to the first aspect of the present invention, in the step (C), the movable core portion is moved to the forward end to form the thin portion, so that the thermoplastic resin in the cavity has the thin portion. It must have flexibility or fluidity to the extent that it can be molded.
[0021]
On the other hand, in the injection molding method according to the aspect 1B of the present invention, the pressurized fluid in the hollow portion is discharged between the step (B) and the step (C). Since the thin portion is formed by moving to the forward end, the thermoplastic resin in the cavity needs to have flexibility or fluidity such that the thin portion can be formed. When the pressurized fluid is discharged, it must be hard enough to maintain the shape of the hollow portion. In the injection molding method according to the second or third aspect of the present invention, the pressurized fluid in the hollow portion is discharged in the step (C), and the third cavity is occupied in the step (D). Since the hollow part formed inside the molten thermoplastic resin is eliminated and a solid thin part is molded, the thermoplastic resin in the cavity is flexible or fluid enough to form a solid thin part. It is necessary that the hollow part is hard enough to maintain the shape of the hollow part when the pressurized fluid in the hollow part is discharged.
[0022]
In the injection molding method of the present invention, in the step (B), a pressurized fluid is introduced into the molten thermoplastic resin in the cavity via the pressurized fluid introduction unit, and the molten thermoplastic resin in the cavity is introduced. When the hollow portion is formed inside, the first cavity portion, the second cavity portion, and the third cavity portion are filled with the molten thermoplastic resin. In other words, when a pressurized fluid is introduced into the molten thermoplastic resin in the cavity through the pressurized fluid introduction unit and a hollow portion is formed in the molten thermoplastic resin in the cavity, the first cavity portion, The amount of the molten thermoplastic resin injected into the cavity is determined so that the second cavity portion and the third cavity portion are filled with the molten thermoplastic resin and a desired hollow portion is formed.
[0023]
In the molded product obtained by the injection molding method according to the first aspect of the present invention, the average thickness of the first thick portion near the thin portion is represented by t. 11 , The average thickness of the second thick part near the thin part is t 12 , The average thickness of the solid thin part is t Thirteen 0.1t 11 ≤t Thirteen ≤0.9t 11 , Preferably 0.4t 11 ≤t Thirteen ≤0.6t 11 Is preferably satisfied, and 0.1 t 12 ≤t Thirteen ≤0.9t 12 , Preferably 0.4t 12 ≤t Thirteen ≤0.6t 12 It is desirable to satisfy.
[0024]
In the molded product obtained by the injection molding method according to the second or third aspect of the present invention, the average thickness of the first thick portion near the thin portion is represented by t. 21 , The average thickness of the second thick part near the thin part is t 22 , The average thickness of the solid thin part is t 23 0.1t 21 ≤t 23 ≤0.9t 21 , Preferably 0.4t 21 ≤t 23 ≤0.6t 21 Is preferably satisfied, and 0.1 t 22 ≤t 23 ≤0.9t 22 , Preferably 0.4t 22 ≤t 23 ≤0.6t 22 It is desirable to satisfy.
[0025]
In the injection molding method according to the first aspect of the present invention, the thickness of the third cavity portion when the movable core portion is located at the backward end (between the mold cavity surfaces corresponding to the thickness direction of the thin portion of the molded product). Distance) to T 13B , The thickness of the third cavity portion when the movable core portion is located at the forward end is T 13F And 0.1 ≦ T 13F / T 13B ≦ 0.9, preferably 0.1 ≦ T 13F / T 13B It is desirable to satisfy ≦ 0.5.
[0026]
Further, in the injection molding method according to the second or third aspect of the present invention, the thickness of the third cavity portion when the movable core portion is located at the backward end (in the thickness direction of the thin portion of the molded product). The distance between the corresponding mold cavity surfaces) is T 23B , The thickness of the third cavity portion when the movable core portion is located at the forward end is T 23F And 0.1 ≦ T 23F / T 23B ≦ 0.9, preferably 0.1 ≦ T 23F / T 23B It is desirable to satisfy ≦ 0.5.
[0027]
In the injection molding method according to the first aspect of the present invention, the average thickness of the first cavity portion near the third cavity portion (between the mold cavity surfaces corresponding to the thickness direction of the first thick portion of the molded product). Average distance) to T 11 , The average thickness of the second cavity portion near the third cavity portion (the average distance between the mold cavity surfaces corresponding to the thickness direction of the second thick portion of the molded product) is T 12 0.1T 11 ≤T 13B ≤T 11 , Preferably 0.5T 11 ≤T 13B ≤T 11 And 0.1T 12 ≤T 13B ≤T 12 , Preferably 0.5T 12 ≤T 13B ≤T 12 It is desirable to satisfy
[0028]
Further, in the injection molding method according to the second or third aspect of the present invention, the average thickness of the first cavity portion near the third cavity portion (in the thickness direction of the first thick portion of the molded product). The average distance between the corresponding mold cavity surfaces) is T 21 , The average thickness of the second cavity portion near the third cavity portion (the average distance between the mold cavity surfaces corresponding to the thickness direction of the second thick portion of the molded product) is T 22 0.1T 21 ≤T 23B ≤T 21 , Preferably 0.5T 21 ≤T 23B ≤T 21 And 0.1T 22 ≤T 23B ≤T 22 , Preferably 0.5T 22 ≤T 23B ≤T 22 It is desirable to satisfy
[0029]
In the injection molding method of the present invention including these various configurations, in the step (A), the amount of the molten thermoplastic resin injected into the cavity can be an amount that does not completely fill the cavity. Alternatively, the amount can completely fill the cavity.
[0030]
The number of movable core portions used in the injection molding method of the present invention is not particularly limited, and one movable core portion may be provided, or a plurality of movable core portions may be provided to mold a molded product having one thin portion. A core may be provided. Further, for example, when a plurality of thin portions are provided in a molded product, the movable core portions may be provided by the number thereof. Further, a plurality of thin portions can be formed by one movable core portion. The moving speed of the movable core portion from the backward end to the forward end may be constant, or may be changed, for example.
[0031]
In the injection molding method of the present invention, for example, the mold can be composed of a fixed mold part and a movable mold part. In this case, depending on the shape of the molded product to be molded, the movable core portion may be arranged on the fixed mold portion side, may be arranged on the movable mold portion side, or may be fixed mold portion. It may be arranged on the mold part side and the movable mold part side. The movement of the movable core portion can be performed using, for example, a hydraulic cylinder, a pneumatic cylinder, or an electric motor.
[0032]
The forward and backward movement of the movable core portion can be controlled based on a control signal sent from an injection molding machine or a pressurized fluid supply device. The control of the forward end position of the movable core portion may be determined based on the desired thickness of the thin portion of the molded product. Further, the positioning of the backward end position of the movable core portion can be performed by extremely simple mechanical position control, for example, by using a backstop sleeve, a backstop knock pin, a backstop block, or the like.
[0033]
In the injection molding method of the present invention, the structure of the molten resin introduction part (so-called gate part) is essentially arbitrary depending on the shape of the molded article to be molded, and for example, a direct gate structure , Side gate structure, jump gate structure, pinpoint gate structure, tunnel gate structure, ring gate structure, fan gate structure, disk gate structure, flash gate structure, tab gate structure, and film gate structure.
[0034]
Usually, the thermoplastic resin is plasticized and melted in the injection cylinder, and the molten thermoplastic resin is injected from the injection cylinder into the cavity through the molten resin flow path and the molten resin introduction portion provided in the mold. . Here, the molten resin flow path may be, for example, a cold runner type or a hot runner type.
[0035]
In the injection molding method according to the present invention, the pressurized fluid introduction unit includes a pressurized fluid introduction nozzle, and the tip of the pressurized fluid introduction nozzle is located inside the first cavity (in the vicinity of the mold cavity surface forming the first cavity). (Including the injection molding method according to the first or second aspect of the present invention) or in the second cavity (including the vicinity of the mold cavity surface forming the second cavity). (The injection molding method according to the third aspect of the present invention), but the present invention is not limited to such a configuration. In the injection molding method according to the first aspect or the second aspect of the present invention, the pressurized fluid introduction section is disposed inside the molten resin introduction section or inside the molten resin flow path provided in the mold. It may be arranged in the tip of the injection cylinder.
[0036]
In the injection molding method of the present invention, the timing of starting the introduction of the pressurized fluid into the molten thermoplastic resin in the cavity is either during the introduction of the molten thermoplastic resin into the cavity, simultaneously with the completion of the introduction, or after the completion of the introduction. It may be. The specific time to start the introduction of the pressurized fluid into the molten thermoplastic resin in the cavity depends on the shape of the molded product, the thermoplastic resin material used, the molding conditions, etc., but the molten thermoplastic resin is introduced into the cavity. The time is preferably 1 second to 20 seconds from the start of introduction, but is not limited thereto. The lower limit of the introduction start time of the pressurized fluid is that when the pressurized fluid is introduced into the cavity while the molten thermoplastic resin is introduced into the cavity, the introduced pressurized fluid and the molten thermoplastic resin in the cavity are not introduced. It may be a time when mixing does not occur. On the other hand, depending on the shape of the molded product, the thermoplastic resin material to be used, the molding conditions, etc., when the introduction start time of the pressurized fluid exceeds 60 seconds, the solidification of the molten thermoplastic resin in the cavity causes the pressurized fluid to be removed. There is a possibility that introduction becomes difficult.
[0037]
The movable core moves to the forward end after the flow of the molten thermoplastic resin injected into the cavity is stopped. That is, after a certain time has elapsed since the pressurized fluid was introduced into the molten thermoplastic resin in the cavity and the flow of the molten thermoplastic resin in the cavity was stopped, the movable core started moving to the forward end. I do. The movement of the movable core to the forward end is started before the solidification of the thermoplastic resin in the third cavity is completed. Therefore, the disclosure timing of the movement of the movable core portion to the forward end depends on the type of the thermoplastic resin used, the molding conditions, the shape of the molded product, and the like, and cannot be determined uniquely, but no matter how late, Before opening the mold, the movable core is positioned at the forward end.
[0038]
The thermoplastic resin used in the injection molding method of the present invention may be any thermoplastic resin, such as a polycarbonate resin; an olefin resin such as a polyethylene resin and a polypropylene resin; a polystyrene resin, an AS resin, an ABS resin, and an AES resin. Styrene resins such as PMMA resins; methacrylic resins such as PMMA resins; polyoxymethylene (polyacetal) resins; polyamide resins such as polyamide 6, polyamide 66 and polyamide MXD; modified polyphenylene ether (PPE) resins; polyphenylene sulfide resins; (PET) resin, polyester resin such as polybutylene terephthalate (PBT) resin; thermoplastic resin such as liquid crystal polymer, or polymer resin comprising at least two or more kinds of these thermoplastic resins. Lee can be mentioned. In order to impart mechanical properties represented by rigidity, dimensional stability, etc. to the molded article, these thermoplastic resins include, for example, glass fiber, glass flake, carbon fiber, wollastonite, aluminum borate whisker fiber And inorganic fibers made of at least one material selected from the group consisting of potassium titanate whisker fibers, basic magnesium sulfate whisker fibers, calcium silicate whisker fibers, and calcium sulfate whisker fibers. Further, for example, an effective expression amount of a stabilizer, a release agent, and an ultraviolet absorber may be blended in the thermoplastic resin.
[0039]
In the injection molding method of the present invention, as the pressurized fluid to be introduced, a gaseous substance such as nitrogen gas, carbon dioxide gas, air, helium gas or the like can be used at normal temperature, and liquid such as water or liquefied under high pressure can be used. Gas can also be used.
[0040]
As a molded product obtained by the injection molding method of the present invention, a molded product in which a thin portion functions as a hinge portion (specifically, for example, a box-shaped molded product in which a lid is integrally molded, a door handle, and a cover for hiding an attachment portion) (A molded product in which a cover is integrally molded) and a molded product having an extremely different wall thickness (specifically, for example, a casing molded product having a thin mounting portion).
[0041]
【Example】
Hereinafter, the present invention will be described based on embodiments with reference to the drawings.
[0042]
(Example 1)
Example 1 Example 1 relates to the injection molding method according to the first aspect of the present invention. More specifically, when the movable core portion is moved to the forward end to form the thin portion, the pressurized fluid in the hollow portion is formed. The present invention relates to an injection molding method according to the first aspect of the present invention, in which a part is discharged.
[0043]
A schematic plan view of the molded article obtained in Example 1 is shown in FIG. 6A, a schematic side view is shown in FIG. 6B, and a line C- in FIG. FIG. 6C shows a schematic cross-sectional view along the line C.
[0044]
The molded product 50 includes a first thick portion 51 having a hollow portion 52, a solid second thick portion 53, and a portion between the first thick portion 51 and the second thick portion 53. Is formed of a solid thin portion 55 located at The width (W) of the molded product 50 is 20 mm, and the length (L) of the first thick portion 51 is 1 ) Is 40 mm and the thickness (t 11 ) Is 5.0 mm and the length (L 2 ) Is 15 mm and the thickness (t 12 ) Is 5.0 mm and the length (L 3 ) Is 5.0 mm and the thickness (t Thirteen ) Was set to 1.0 mm.
[0045]
FIG. 1 shows a conceptual diagram of the mold used in the first embodiment. Note that FIG. 1 shows a state in which the movable core unit 30 is located at the forward end.
[0046]
This mold includes a fixed mold section 10 and a movable mold section 11. Then, the mold includes the first cavity portion 21 for molding the first thick portion 51 of the molded product 50, the second cavity portion 23 for molding the second thick portion 53, and the thin portion 55. It has a cavity composed of the third cavity part 25 to be molded. Further, the mold includes a molten resin introduction part (a so-called gate part) 12, a pressurized fluid introduction part 14, and a movable core part 30.
[0047]
The molten resin introduction part 12 is arranged in the fixed mold part 10 so that the molten thermoplastic resin 40 is injected into the first cavity part 21. The molten resin introduction section 12 has a direct gate structure, and communicates with an injection cylinder (not shown) via a sprue provided in the fixed mold section 10 and a cold runner type molten resin flow path 13.
[0048]
The pressurized fluid introduction part 14 is arranged in the movable mold part 11 so that the pressurized fluid is introduced into the first cavity 21. The pressurized fluid introduction unit 14 has a non-return capability for molten resin, but does not have a non-return capability for the pressurized fluid. Alternatively, it is composed of a pressurized fluid introduction part having a thin tube structure. The pressurized fluid introducing section having such a structure is disclosed in, for example, JP-A-4-339624, U.S. Pat. No. 4,474,717, U.S. Pat. No. 5,044,924, and U.S. Pat. No. 5,908,641. The distal end of the pressurized fluid introduction unit 14 attached to the movable mold unit 11 projects into the first cavity 21. The pressurized fluid introduction unit 14 is connected to a pressurized fluid source 16 via a pipe 15. Further, the pressurized fluid introduction unit 14 is movable between a forward end and a rearward end by a pressurized fluid introduction unit moving unit (for example, composed of a hydraulic cylinder) not shown. When the pressurized fluid introduction unit 14 is located at the forward end, the distal end of the pressurized fluid introduction unit 14 projects into the first cavity 21. On the other hand, when the pressurized fluid introduction unit 14 is located at the rearward end, a gap is formed between the tip of the pressurized fluid introduction unit 14 and the mold, and the pressurized fluid in the hollow portion flows from the gap to the atmosphere. Can be opened to
[0049]
The movable core portion 30 moves forward and backward in the third cavity portion 25 along the direction corresponding to the thickness direction of the thin portion 55 of the molded product 50 by the operation of the hydraulic cylinder 31 serving as the movable core portion moving means. Can move between the edges.
[0050]
Hereinafter, the injection molding method of the first embodiment will be described with reference to FIGS. 2 to 5 which are conceptual views of a mold and the like. In addition, in Example 1, a polycarbonate resin (trade name: Iupilon S3000, manufactured by Mitsubishi Engineering-Plastics Corporation) was used as the thermoplastic resin. Also, a compressed nitrogen gas (pressure: 1 × 10 7 Pa) was used.
[0051]
The shape of the cavity provided in the mold is a size that can mold the molded product 50 shown in FIG. That is, the average thickness of the first cavity portion 21 near the third cavity portion 25 (the average distance between the mold cavity surfaces corresponding to the thickness direction of the first thick portion 51 of the molded product 50) T 11 Is 5.0 mm, and the average thickness of the second cavity portion 23 near the third cavity portion 25 (the average distance between the mold cavity surfaces corresponding to the thickness direction of the second thick portion 53 of the molded product 50) ) T 12 Is 5.0 mm. Further, the thickness of the third cavity portion 25 when the movable core portion 30 is located at the backward end (the distance between the mold cavity surfaces corresponding to the thickness direction of the thin portion 55 of the molded product 50) T 13B Is set to 5.0 mm, and the thickness T of the third cavity portion 25 when the movable core portion 30 is located at the forward end. 13F Was set to 1.0 mm.
[0052]
[Step-100]
The thermoplastic resin was plasticized and melted at the resin temperature shown in Table 1 below in an injection cylinder (not shown) provided in the injection molding machine. Then, the fixed mold part 10 and the movable mold part 11 were clamped, and the movable core part 30 was positioned at the backward end by the operation of the hydraulic cylinder 31 (see FIG. 2). The pressurized fluid introduction unit 14 is positioned at the forward end by the operation of the pressurized fluid introduction unit moving means (not shown), and the distal end of the pressurized fluid introduction unit 14 projects into the first cavity 21. .
[0053]
[Step-110]
Then, at the mold temperature and injection pressure shown in Table 1 below, from the injection cylinder, through the molten resin flow path 13 and the molten resin introduction part (gate part) 12, the inside of the cavity (more specifically, The molten thermoplastic resin 40 was injected into one cavity portion 21) (see FIG. 3). The amount of the molten thermoplastic resin 40 introduced into the entire cavity was set to 75% of the volume of the entire cavity.
[0054]
[Table 1]
Resin temperature: 290 ° C
Mold temperature: 80 ° C
Injection time: 4.0 seconds
Injection pressure: 6 × 10 7 Pa
(600kgf / cm 2 -G)
[0055]
[Step-120]
4.3 seconds after the start of the injection of the molten thermoplastic resin 40, the molten thermoplastic resin 40 (more specifically, the molten thermoplastic resin 40 in the cavity) from the pressurized fluid source 16 via the pipe 15 and the pressurized fluid introduction unit 14. A pressurized fluid (pressure 1 × 10 4) is placed inside the molten thermoplastic resin 40 in one cavity 21. 7 A pressurized nitrogen gas of Pa) was introduced to form a hollow portion 52 inside the molten thermoplastic resin 40 occupying the first cavity portion 21 (see FIG. 4). The introduction of the pressurized fluid caused the molten thermoplastic resin 40 in the cavity to flow, and the first cavity portion 21, the second cavity portion 23, and the third cavity portion 25 were filled with the molten thermoplastic resin 40. However, the hollow portion 52 stopped in the first cavity portion 21.
[0056]
[Step-130]
9.3 seconds after the start of the injection of the molten thermoplastic resin 40, the hydraulic cylinder 31 was operated to move the movable core portion 30 from the backward end to the forward end, thereby forming the thin portion 55 (see FIG. 5). The moving amount of the movable core part 30 was 4.0 mm. That is, the thickness T of the third cavity 25 when the movable core 30 is located at the forward end. 13F (The distance between the mold cavity surfaces corresponding to the thickness direction of the thin portion 55 of the molded product 50) is 1.0 mm. The moving speed was 2 mm / sec. With the movement of the movable core portion 30 to the forward end, a part of the molten thermoplastic resin 40 in the third cavity portion 25 was pushed out to the first cavity portion 21. As a result, the volume of the hollow portion 52 formed inside the molten thermoplastic resin 40 in the first cavity portion 21 has been reduced. A part of the pressurized fluid that exists in the hollow portion 52 formed inside the molten thermoplastic resin 40 in the first cavity portion 21 and is in a pressurized state from the pressurized fluid introduction portion 14 is pressurized. The fluid was discharged from the fluid inlet 14 to the outside.
[0057]
[Step-140]
34.3 seconds after the start of the injection of the molten thermoplastic resin 40, the pressurized fluid in the hollow portion 52 was further discharged through the pressurized fluid introduction portion 14. At the time when the inside of the hollow portion 52 reaches the atmospheric pressure, nitrogen gas at the atmospheric pressure may remain in the hollow portion 52.
[0058]
[Step-150]
The thermoplastic resin in the cavity is cooled until 64.3 seconds from the start of the injection of the molten thermoplastic resin 40, and then the pressurized fluid introduction unit 14 is moved to the backward end by operating a pressurized fluid introduction unit moving means (not shown). After that, the mold was opened, and the molded product 50 was taken out of the mold.
[0059]
No defective appearance such as welds, hesitation marks, and flow marks was observed in the thin portion 55 of the obtained molded product 50. Further, a desired hollow portion 52 is formed in the first thick portion 51, and a solid thin portion 55 and a thick portion 53 are surely formed.
[0060]
(Comparative Example 1)
In Comparative Example 1, as shown in FIG. 1, the movable core portion 30 was fixed to the advance end in advance. Then, [Step-130] of the first embodiment, that is, [Step-100] to [Step-120], [Step-130] of the first embodiment without executing the step of moving the movable core portion 30 from the backward end. 140] to [Step-150].
[0061]
As a result, since the resin flow pressure loss in the third cavity portion 25 is large, the molten thermoplastic resin cannot be sufficiently caused to flow into the second cavity portion 23 even by introducing the pressurized fluid. Unfilled portions of the thermoplastic resin were generated in the cavity portion 23, and a desired molded product could not be obtained.
[0062]
(Example 2)
Example 2 is a modification of Example 1 and relates to the injection molding method according to the 1B embodiment of the present invention. In Example 2, [Step-140] was executed after [Step-120] in Example 1, and then [Step-130] was executed. Hereinafter, the injection molding method of Example 2 will be described with reference to FIGS. 2 to 4, 7 and 8 which are conceptual diagrams of a mold and the like. In Example 2, the same thermoplastic resin and pressurized fluid as in Example 1 were used as the thermoplastic resin and pressurized fluid.
[0063]
[Step-200]
First, the thermoplastic resin was plasticized and melted in the same manner as in [Step-100] of Example 1. Then, the fixed mold part 10 and the movable mold part 11 were clamped, and the movable core part 30 was positioned at the backward end by the operation of the hydraulic cylinder 31. The thickness T of the third cavity portion 25 when the movable core portion 30 is located at the backward end. 13B (The distance between the mold cavity surfaces corresponding to the thickness direction of the thin portion 55 of the molded product 50) is 5.0 mm. The pressurized fluid introduction unit 14 is positioned at the forward end by the operation of the pressurized fluid introduction unit moving means (not shown), and the distal end of the pressurized fluid introduction unit 14 projects into the first cavity 21. (See FIG. 2).
[0064]
[Step-210]
Then, in the same manner as in [Step-110] of Example 1, from the injection cylinder, through the molten resin flow path 13 and the molten resin introduction portion (gate portion) 12, the inside of the cavity (more specifically, the first The molten thermoplastic resin 40 was injected into the cavity 21) (see FIG. 3). In addition, the amount of the molten thermoplastic resin 40 introduced into the entire cavity was 75% of the volume of the entire cavity, and the injection time was 4.0 seconds.
[0065]
[Step-220]
4.3 seconds after the start of injection of the molten thermoplastic resin 40, the molten thermoplastic resin 40 in the cavity (more specifically, through the pressurized fluid introduction portion 14) in the same manner as in [Step-120] of Example 1 The pressurized fluid (pressure 1 × 10 4) is placed inside the molten thermoplastic resin 40 in the first cavity 21. 7 A pressurized nitrogen gas of Pa) was introduced to form a hollow portion 52 inside the molten thermoplastic resin 40 occupying the first cavity portion 21 (see FIG. 4). The introduction of the pressurized fluid caused the molten thermoplastic resin 40 in the cavity to flow, and the first cavity portion 21, the second cavity portion 23, and the third cavity portion 25 were filled with the molten thermoplastic resin 40. However, the hollow portion 52 stopped in the first cavity portion 21.
[0066]
[Step-230]
14.3 seconds after the start of the injection of the molten thermoplastic resin 40, the pressurized fluid introduction unit 14 is moved to the backward end by the operation of the pressurized fluid introduction unit moving means (not shown). A gap was formed between the mold and the mold, and the pressurized fluid in the hollow portion 52 was discharged into the atmosphere from the gap (see FIG. 7). At the time when the inside of the hollow portion 52 reaches the atmospheric pressure, nitrogen gas at the atmospheric pressure may remain in the hollow portion 52.
[0067]
[Step-240]
16.3 seconds after the start of the injection of the molten thermoplastic resin 40, the hydraulic cylinder 31 was operated to move the movable core portion 30 from the backward end to the forward end, thereby forming the thin portion 55 (see FIG. 8). The amount of movement of the movable core 30 is 4.0 mm. That is, the thickness T of the third cavity 25 when the movable core 30 is located at the forward end. 13F (The distance between the mold cavity surfaces corresponding to the thickness direction of the thin portion 55 of the molded product 50) is 1.0 mm. The moving speed was 2 mm / sec. With the movement of the movable core portion 30 to the forward end, a part of the molten thermoplastic resin 40 in the third cavity portion 25 was extruded to the first cavity portion 21. As a result, the volume of the hollow portion 52 formed inside the thermoplastic resin in the first cavity portion 21 has been reduced. A part of the pressurized fluid present in the hollow portion 52 formed inside the thermoplastic resin in the first cavity portion 21 further has a gap between the tip of the pressurized fluid introduction portion 14 and the mold. Was released into the atmosphere.
[0068]
[Step-250]
The thermoplastic resin in the cavity was cooled until 64.3 seconds from the start of injection of the molten thermoplastic resin 40, the mold was opened, and the molded product was taken out of the mold.
[0069]
No defective appearance such as welds, hesitation marks, and flow marks was observed in the thin portion 55 of the obtained molded product 50. Further, a desired hollow portion 52 is formed in the first thick portion 51, and a solid thin portion 55 and a thick portion 53 are surely formed.
[0070]
(Example 3)
The third embodiment is also a modification of the first embodiment. In the third embodiment, as shown in the conceptual view of the mold in FIG. 9, the pressurized fluid introduction unit 114 is formed of a pressurized fluid introduction nozzle, and the tip is disposed inside the molten resin introduction unit 12. Is established. Other structures are substantially the same as the mold described in the first embodiment. In the third embodiment, since the molded article described below is molded, two second cavities 23A and 23B and three third cavities 25A and 25B are provided, and two movable cores are further provided. Parts 30A and 30B are provided. Note that FIG. 9 shows a state where the two movable core portions 30A and 30B are located at the forward end.
[0071]
A schematic plan view of the molded article obtained in Example 3 is shown in FIG. 14A, a schematic side view is shown in FIG. 14B, and a line C- in FIG. FIG. 14C shows a schematic cross-sectional view along C.
[0072]
The molded article 150 includes a first thick portion 151 having a hollow portion 152, two solid second thick portions 153A, 153A, and a first thick portion 151 and a second thick portion. 153A, 153B and two solid thin portions 155A, 155B. The width (W) of the molded product 150 is 20 mm, and the length (L) of the first thick portion 151 is 1 ) Is 40 mm and the thickness (t 11 ) Is 5.0 mm and the length (L) of the second thick portions 153A and 153B is 2 ) Is 15 mm and the thickness (t 12 ) Is 5.0 mm and the length of the thin portions 155A, 155B (L 3 ) Is 5.0 mm and the thickness (t Thirteen ) Was set to 1.0 mm.
[0073]
In addition, the shape of the cavity provided in the mold is a size that can mold the molded product 150 shown in FIG. That is, the average thickness of the first cavity portion 21 near the third cavity portions 25A and 25B (the average distance between the mold cavity surfaces corresponding to the thickness direction of the first thick portion 151 of the molded product 150) T 11 Is 5.0 mm, and the average thickness of the second cavities 23A and 23B near the third cavities 25A and 25B (the mold corresponding to the thickness direction of the second thick portions 153A and 153B of the molded product 150). Average distance between cavity surfaces) T 12 Is 5.0 mm. The thickness of the third cavities 25A and 25B when the movable cores 30A and 30B are located at the backward end (the distance between the mold cavity surfaces corresponding to the thickness direction of the thin portions 155A and 155B of the molded product 150). ) T 13B Is set to 5.0 mm, and the thickness T of the third cavity portions 25A, 25B when the movable core portions 30A, 30B are located at the forward end. 13F Was set to 1.0 mm.
[0074]
Hereinafter, the injection molding method of the third embodiment will be described with reference to FIGS. 10 to 13 which are conceptual diagrams of a mold and the like. In Example 3, the same thermoplastic resin and pressurized fluid as in Example 1 were used as the thermoplastic resin and pressurized fluid.
[0075]
[Step-300]
First, the thermoplastic resin was plasticized and melted in the same manner as in [Step-100] of Example 1. Then, the fixed mold part 10 and the movable mold part 11 were clamped, and the movable core parts 30A, 30B were positioned at the backward end by the operation of the hydraulic cylinders 31A, 31B (see FIG. 10).
[0076]
[Step-310]
Then, in the same manner as in [Step-110] of Example 1, from the injection cylinder, through the molten resin flow path 13 and the molten resin introduction portion (gate portion) 12, the inside of the cavity (more specifically, the first The molten thermoplastic resin 40 was injected into the cavity 21) (see FIG. 11). The amount of the molten thermoplastic resin 40 introduced into the entire cavity was set to 80% of the volume of the entire cavity, and the injection time was set to 7.0 seconds.
[0077]
[Step-320]
Then, in the same manner as in [Step-120] of Example 1, 7.3 seconds after the start of the injection of the molten thermoplastic resin 40, from the pressurized fluid source 16 via the pipe 15, the pressurized fluid introduction unit 114. A pressurized fluid (pressure 1 × 10 4) is placed inside the molten thermoplastic resin 40 (more specifically, the molten thermoplastic resin 40 7 A pressurized nitrogen gas (Pa) was introduced to form a hollow portion 152 inside the molten thermoplastic resin 40 occupying the first cavity portion 21 (see FIG. 12). Due to the introduction of the pressurized fluid, the molten thermoplastic resin 40 in the cavity flows, and the first cavity portion 21, the second cavity portions 23A and 23B, and the third cavity portions 25A and 25B are filled with the molten thermoplastic resin 40. . However, the hollow portion 152 stopped in the first cavity portion 21.
[0078]
[Step-330]
Thereafter, in the same manner as in [Step-130] of Example 1, 10.0 seconds after the start of injection of the molten thermoplastic resin 40, the hydraulic cylinders 31A and 31B are operated to move the movable core portions 30A and 30B to the backward end. To the forward end to form the thin portions 155A and 155B (see FIG. 13). The amount of movement of the movable core portions 30A, 30B is 4.0 mm. That is, the thickness T of the third cavity portions 25A, 25B when the movable core portions 30A, 30B are located at the forward end. 13F (The distance between the mold cavity surfaces corresponding to the thickness direction of the thin portion of the molded product) is 1.0 mm. The moving speed was 2 mm / sec. With the movement of the movable core portions 30A, 30B to the forward end, a part of the molten thermoplastic resin 40 in the third cavity portions 25A, 25B was extruded to the first cavity portion 21. As a result, the volume of the hollow portion 152 formed inside the molten thermoplastic resin 40 in the first cavity portion 21 has been reduced. A part of the pressurized fluid existing in the hollow portion 152 formed inside the molten thermoplastic resin 40 in the first cavity portion 21 and brought into a pressurized state from the pressurized fluid introduction portion 114 is part of the pressurized fluid. It was discharged from the introduction unit 114 to the outside.
[0079]
[Step-340]
Then, in the same manner as in [Step-140] of Example 1, after 37.3 seconds from the start of the injection of the molten thermoplastic resin 40, the pressurized fluid in the hollow portion 152 is discharged through the pressurized fluid introduction unit 114. did. At the time when the inside of the hollow portion 152 reaches the atmospheric pressure, nitrogen gas at the atmospheric pressure may remain in the hollow portion 152.
[0080]
[Step-350]
The thermoplastic resin in the cavity was cooled until 67.3 seconds from the start of injection of the molten thermoplastic resin 40, and then the mold was opened, and the molded product was taken out of the mold.
[0081]
In the thin portions 155A and 155B of the obtained molded article 150, no defective appearance such as weld, hesitation mark, flow mark, etc. was observed. Further, a desired hollow portion 152 is formed in the first thick portion 151, and solid thin portions 155A and 155B and thick portions 153A and 153B are surely formed.
[0082]
In the third embodiment, the injection molding method described in the second embodiment can be applied.
[0083]
(Example 4)
Example 4 relates to an injection molding method according to the second aspect of the present invention.
[0084]
FIG. 19A shows a schematic plan view of the molded product 50 obtained in Example 4, FIG. 19B shows a schematic side view thereof, and FIG. 19A shows a line C. FIG. 19C shows a schematic cross-sectional view along the line -C. The molded product 50 includes a first thick portion 51 having a hollow portion 52, a second thick portion 53 having a hollow portion 54, and a first thick portion 51 and a second thick portion 53. And a solid thin portion 55 located between the two. The shape and size of the molded product 50 are the same as the shape and size of the molded product described in the first embodiment. However, the difference is that the hollow portion 54 is also formed in the second thick portion 53. That is, the width (W) of the molded product 50 is 20 mm, and the length (L) of the first thick portion 51 is 1 ) Is 40 mm and the thickness (t 21 ) Is 5.0 mm and the length (L 2 ) Is 15 mm and the thickness (t 22 ) Is 5.0 mm and the length (L 3 ) Is 5.0 mm and the thickness (t 23 ) Was set to 1.0 mm.
[0085]
Since the mold used in the fourth embodiment has the same structure as the mold described in the first embodiment, detailed description will be omitted.
[0086]
The shape of the cavity provided in the mold is a size that can mold the molded product 50 shown in FIG. That is, the average thickness of the first cavity portion 21 near the third cavity portion 25 (the average distance between the mold cavity surfaces corresponding to the thickness direction of the first thick portion 51 of the molded product 50) T 21 Is 5.0 mm, and the average thickness of the second cavity portion 23 near the third cavity portion 25 (the average distance between the mold cavity surfaces corresponding to the thickness direction of the second thick portion 53 of the molded product 50) ) T 22 Is 5.0 mm. Further, the thickness of the third cavity portion 25 when the movable core portion 30 is located at the backward end (the distance between the mold cavity surfaces corresponding to the thickness direction of the thin portion 55 of the molded product 50) T 23B Is set to 5.0 mm, and the thickness T of the third cavity portion 25 when the movable core portion 30 is located at the forward end. 23F Was set to 1.0 mm. In addition, these T 21 , T 22 , T 23B , T 23F As for T, the T shown in FIG. 1 and FIG. 11 , T 12 , T 13B , T 123F And T 21 , T 22 , T 23B , T 23F Should be read as
[0087]
Hereinafter, the injection molding method of the fourth embodiment will be described with reference to FIGS. 2 and 15 to 18 which are conceptual views of a mold and the like. In Example 4, the thermoplastic resin and the pressurized fluid described in Example 1 were used as the thermoplastic resin and the pressurized fluid.
[0088]
[Step-400]
First, the thermoplastic resin was plasticized and melted in the same manner as in [Step-100] of Example 1. Then, the fixed mold part 10 and the movable mold part 11 were clamped, and the movable core part 30 was positioned at the backward end by the operation of the hydraulic cylinder 31 (see FIG. 2). The pressurized fluid introduction unit 14 is positioned at the forward end by the operation of the pressurized fluid introduction unit moving means (not shown), and the distal end of the pressurized fluid introduction unit 14 projects into the first cavity 21. .
[0089]
[Step-410]
Then, in the same manner as in [Step-110] of Example 1, from the injection cylinder, through the molten resin flow path 13 and the molten resin introduction portion (gate portion) 12, the inside of the cavity (more specifically, the first The molten thermoplastic resin 40 was injected into the cavity 21, the third cavity 25, and a part of the second cavity (see FIG. 15). The amount of the molten thermoplastic resin 40 introduced into the entire cavity was set to 70% of the volume of the entire cavity, and the injection time was set to 3.4 seconds.
[0090]
[Step-420]
3.8 seconds after the start of injection of the molten thermoplastic resin 40, the molten thermoplastic resin 40 (more specifically, from the pressurized fluid source 16) in the cavity from the pressurized fluid source 16 via the pipe 15 and the pressurized fluid introduction unit 14. A pressurized fluid (pressure 1 × 10 4) is placed inside the molten thermoplastic resin 40 in one cavity 21. 7 (Pressurized nitrogen gas of Pa) was introduced to form hollow portions 52, 54, 56 inside the molten thermoplastic resin 40 occupying the first cavity portion 21, the second cavity portion 23, and the third cavity portion 25 (FIG. 16). Due to the introduction of the pressurized fluid, the molten thermoplastic resin 40 in the cavity flowed, and the cavity was completely filled with the molten thermoplastic resin 40.
[0091]
[Step-430]
6.0 seconds after the start of injection of the molten thermoplastic resin 40, the pressurized fluid introduction unit 14 is positioned at the backward end by operation of a pressurized fluid introduction unit moving means (not shown), and the distal end of the pressurized fluid introduction unit 14 A gap was formed between the mold and the mold, and the pressurized fluid in the hollow portions 52, 54, and 56 was discharged into the atmosphere from the gap (see FIG. 17). At the time when the pressure in the hollow portions 52, 54, 56 becomes atmospheric pressure, nitrogen gas at atmospheric pressure may remain in the hollow portions 52, 54, 56.
[0092]
[Step-440]
8.0 seconds after the start of injection of the molten thermoplastic resin 40, the hydraulic cylinder 31 is operated to move the movable core portion 30 from the backward end to the forward end, and the molten thermoplastic resin occupying the third cavity portion 25 The hollow portion 56 formed inside the 40 was eliminated, and a solid thin portion 55 was formed (see FIG. 18). The amount of movement of the movable core 30 is 4.0 mm. That is, the thickness T of the third cavity 25 when the movable core 30 is located at the forward end. 23F (The distance between the mold cavity surfaces corresponding to the thickness direction of the thin portion of the molded product) is 1.0 mm. The moving speed was 7 mm / sec. With the movement of the movable core portion 30 to the forward end, a part of the molten thermoplastic resin 40 in the third cavity portion 25 was pushed out to the first cavity portion 21. As a result, the volume of the hollow portion 52 formed inside the molten thermoplastic resin 40 in the first cavity portion 21 has been reduced. A part of the pressurized fluid existing in the hollow part 52 formed inside the molten thermoplastic resin 40 in the first cavity part 21 has a gap between the tip of the pressurized fluid introduction part 14 and the mold. Was discharged to the outside.
[0093]
[Step-450]
The thermoplastic resin in the cavity was cooled until 63.4 seconds from the start of injection of the molten thermoplastic resin 40, then the mold was opened, and the molded product was taken out of the mold.
[0094]
No defective appearance such as welds, hesitation marks, and flow marks was observed in the thin portion 55 of the obtained molded product 50. Further, a desired hollow portion 52 is formed in the first thick portion 51, and a solid thin portion 55 and a thick portion 53 are surely formed.
[0095]
(Example 5)
Example 5 Example 5 relates to the injection molding method according to the third aspect of the present invention.
[0096]
FIG. 26A shows a schematic plan view of the molded product 50 obtained in Example 5, FIG. 26B shows a schematic side view thereof, and FIG. 26A shows a line C. FIG. 26C shows a schematic cross-sectional view along the line -C. The molded product 50 includes a first thick portion 51 having a hollow portion 52, a second thick portion 53 having a hollow portion 54, and a first thick portion 51 and a second thick portion 53. And a solid thin portion 55 located between the two. The shape and dimensions of the molded product 50 are the same as the shapes and dimensions of the molded product described in the fourth embodiment. However, the difference is that the hollow portion 54 is also formed in the second thick portion 53.
[0097]
FIG. 20 shows a conceptual diagram of the mold used in the fifth embodiment. Note that FIG. 20 shows a state in which the movable core unit 30 is located at the forward end. This mold includes a fixed mold section 10 and a movable mold section 11. Then, the mold includes the first cavity portion 21 for molding the first thick portion 51 of the molded product 50, the second cavity portion 23 for molding the second thick portion 53, and the thin portion 55. It has a cavity composed of the third cavity part 25 to be molded. Further, the mold includes a molten resin introduction section (a so-called gate section) 12, a pressurized fluid introduction section 214, and a movable core section 30.
[0098]
The molten resin introduction part 12 is arranged in the fixed mold part 10 so that the molten thermoplastic resin 40 is injected into the first cavity part 21. The molten resin introduction section 12 has a direct gate structure, and communicates with an injection cylinder (not shown) via a sprue provided in the fixed mold section 10 and a cold runner type molten resin flow path 13.
[0099]
The pressurized fluid introduction part 214 is arranged in the movable mold part 11 so that the pressurized fluid is introduced into the second cavity part 23. The pressurized fluid introduction unit 214 has the same structure as that described in the first embodiment.
[0100]
The movable core portion 30 moves forward and backward in the third cavity portion 25 along the direction corresponding to the thickness direction of the thin portion 55 of the molded product 50 by the operation of the hydraulic cylinder 31 serving as the movable core portion moving means. Can move between the edges.
[0101]
The shape of the cavity provided in the mold is a size that allows the molded product 50 shown in FIG. 26 to be molded. That is, the average thickness of the first cavity portion 21 near the third cavity portion 25 (the average distance between the mold cavity surfaces corresponding to the thickness direction of the first thick portion 51 of the molded product 50) T 21 Is 5.0 mm, and the average thickness of the second cavity portion 23 near the third cavity portion 25 (the average distance between the mold cavity surfaces corresponding to the thickness direction of the second thick portion 53 of the molded product 50) ) T 22 Is 5.0 mm. Further, the thickness of the third cavity portion 25 when the movable core portion 30 is located at the backward end (the distance between the mold cavity surfaces corresponding to the thickness direction of the thin portion 55 of the molded product 50) T 23B Is set to 5.0 mm, and the thickness T of the third cavity portion 25 when the movable core portion 30 is located at the forward end. 23F Was set to 1.0 mm.
[0102]
Hereinafter, the injection molding method of the fifth embodiment will be described with reference to FIGS. 21 to 25 which are conceptual diagrams of a mold and the like. In Example 5, the thermoplastic resin and the pressurized fluid described in Example 1 were used as the thermoplastic resin and the pressurized fluid.
[0103]
[Step-500]
First, the thermoplastic resin was plasticized and melted in the same manner as in [Step-100] of Example 1. Then, the fixed mold part 10 and the movable mold part 11 were clamped, and the movable core part 30 was positioned at the backward end by the operation of the hydraulic cylinder 31 (see FIG. 21). The thickness T of the third cavity portion 25 when the movable core portion 30 is located at the backward end. 23B (The distance between the mold cavity surfaces corresponding to the thickness direction of the thin portion 55 of the molded product 50) is 5.0 mm. The pressurized fluid introduction unit 214 is positioned at the forward end by the operation of the pressurized fluid introduction unit moving means (not shown), and the distal end of the pressurized fluid introduction unit 214 projects into the first cavity 21. It becomes.
[0104]
[Step-510]
Then, in the same manner as in [Step-110] of Example 1, from the injection cylinder, through the molten resin flow path 13 and the molten resin introduction portion (gate portion) 12, the inside of the cavity (more specifically, the first The molten thermoplastic resin 40 was injected into the cavity 21) (see FIG. 22). The amount of the molten thermoplastic resin 40 introduced into the entire cavity was set to 70% of the volume of the entire cavity, and the injection time was set to 3.4 seconds.
[0105]
[Step-520]
3.8 seconds after the start of injection of the molten thermoplastic resin 40, the molten thermoplastic resin 40 (more specifically, from the pressurized fluid source 16) in the cavity from the pressurized fluid source 16 via the pipe 15 and the pressurized fluid introduction unit 214. 2 A pressurized fluid (pressure 1 × 10 2) is set inside the molten thermoplastic resin 40 in the cavity 23. 7 (Pressurized nitrogen gas of Pa) was introduced to form hollow portions 52, 54, 56 inside the molten thermoplastic resin 40 occupying the first cavity portion 21, the second cavity portion 23, and the third cavity portion 25 (FIG. 23). Due to the introduction of the pressurized fluid, the molten thermoplastic resin 40 in the cavity flowed, and the cavity was completely filled with the molten thermoplastic resin 40.
[0106]
[Step-530]
8.8 seconds after the start of the injection of the molten thermoplastic resin 40, the pressurized fluid introduction unit 214 is moved to the rearward end by the operation of the pressurized fluid introduction unit moving means (not shown). A gap was formed between the mold and the mold, and the pressurized fluid in the hollow portions 52, 54, and 56 was discharged into the atmosphere from the gap (see FIG. 24). At the time when the pressure in the hollow portions 52, 54, 56 becomes atmospheric pressure, nitrogen gas at atmospheric pressure may remain in the hollow portions 52, 54, 56.
[0107]
[Step-540]
10.8 seconds after the start of injection of the molten thermoplastic resin 40, the hydraulic cylinder 31 is operated to move the movable core portion 30 from the backward end to the forward end, and the molten thermoplastic resin occupying the third cavity portion 25. The hollow portion 56 formed inside the 40 was eliminated, and a solid thin portion 55 was formed (see FIG. 25). The amount of movement of the movable core 30 is 4.0 mm. That is, the thickness T of the third cavity 25 when the movable core 30 is located at the forward end. 23F (The distance between the mold cavity surfaces corresponding to the thickness direction of the thin portion of the molded product) is 1.0 mm. The moving speed was 2 mm / sec. With the movement of the movable core portion 30 to the forward end, a part of the molten thermoplastic resin 40 in the third cavity portion 25 was pushed out to the second cavity portion 23. As a result, the volume of the hollow portion 54 formed inside the molten thermoplastic resin 40 in the second cavity portion 25 has been reduced. A part of the pressurized fluid present in the hollow portion 54 formed inside the molten thermoplastic resin 40 in the second cavity portion 23 has a gap between the tip of the pressurized fluid introduction portion 214 and the mold. Was discharged to the outside.
[0108]
[Step-550]
The thermoplastic resin in the cavity was cooled until 63.4 seconds from the start of injection of the molten thermoplastic resin 40, then the mold was opened, and the molded product was taken out of the mold.
[0109]
No defective appearance such as welds, hesitation marks, and flow marks was observed in the thin portion 55 of the obtained molded product 50. Further, a desired hollow portion 52 is formed in the first thick portion 51, and a solid thin portion 55 and a thick portion 53 are surely formed.
[0110]
(Comparative Example 2)
In Comparative Example 2, as shown in FIG. 20, the movable core portion 30 was fixed to the advance end in advance. Then, [Step-540] of the fifth embodiment, that is, [Step-500] to [Step-530], [Step-540] of the fifth embodiment without executing the step of moving the movable core unit 30 from the backward end. 550].
[0111]
As a result, since the resin flow pressure loss in the third cavity 25 is large, even if the pressurized fluid is introduced, the molten thermoplastic resin cannot flow into the second cavity 23, and the second cavity 23 In No. 23, an unfilled portion of the thermoplastic resin was generated, and a desired molded product could not be obtained.
[0112]
Although the present invention has been described based on the preferred embodiments, the present invention is not limited to these embodiments. The thermoplastic resin used, the pressurized fluid, the molding conditions, the structure of the mold, and the like described in the examples are merely examples, and can be appropriately changed. In the first embodiment, the injection molding method of the molded article provided with one or two thin portions is described, but the number of thin portions is not limited to these.
[0113]
【The invention's effect】
In the injection molding method of the present invention, in molding the thin portion, first, the distance between the mold cavity surfaces corresponding to the thickness direction of the thin portion of the molded product in the third cavity is increased. Therefore, the resin flow pressure loss in the third cavity can be reduced, and the molten thermoplastic resin easily flows in the third cavity. As a result, hesitation does not occur and no flow mark occurs. Moreover, since the molten thermoplastic resin easily flows into the second cavity portion, the entire cavity can be reliably filled with the molten thermoplastic resin. Therefore, the strength of the thin portion is not reduced and the appearance of the molded product is not deteriorated. If the injection molding method of the present invention is applied to, for example, molding of a molded product in which a thin portion functions as a hinge portion, a hinge portion having high strength (for example, static strength or fatigue strength) can be obtained.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a mold used in Example 1.
FIG. 2 is a conceptual diagram of a mold and the like for describing an injection molding method according to a first embodiment.
FIG. 3 is a conceptual diagram of a mold and the like for explaining the injection molding method of Example 1, following FIG. 2;
FIG. 4 is a conceptual diagram of a mold and the like for explaining the injection molding method of Example 1, following FIG. 3;
FIG. 5 is a conceptual diagram of a mold and the like for explaining the injection molding method of Example 1, following FIG. 4;
6 (A), 6 (B) and 6 (C) are a schematic plan view, a schematic side view, and a schematic cross section of a molded product obtained in Example 1, respectively. FIG.
FIG. 7 is a conceptual diagram of a mold and the like for explaining an injection molding method according to a second embodiment.
FIG. 8 is a conceptual diagram of a mold and the like for explaining the injection molding method of the second embodiment, following FIG. 7;
FIG. 9 is a conceptual diagram of a mold used in Example 3.
FIG. 10 is a conceptual diagram of a mold and the like for explaining an injection molding method according to a third embodiment.
FIG. 11 is a continuation of FIG. 10; It is a conceptual diagram of a metal mold | die etc. for demonstrating the injection molding method of Example 3.
FIG. 12 is a conceptual diagram of a mold and the like for explaining an injection molding method according to a third embodiment, following FIG. 11;
FIG. 13 is a conceptual diagram of a mold and the like for explaining the injection molding method of the third embodiment, following FIG. 12;
14A, 14B, and 14C are a schematic plan view, a schematic side view, and a schematic cross section of a molded product obtained in Example 3, respectively. FIG.
FIG. 15 is a conceptual diagram of a mold and the like for explaining an injection molding method according to a fourth embodiment.
FIG. 16 is a conceptual diagram of a mold and the like for explaining the injection molding method of the fourth embodiment, following FIG.
FIG. 17 is a conceptual diagram of a mold and the like for explaining the injection molding method of the fourth embodiment, following FIG. 16;
FIG. 18 is a conceptual diagram of a mold and the like for explaining the injection molding method of the fourth embodiment, following FIG. 17;
19 (A), (B) and (C) are a schematic plan view, a schematic side view, and a schematic cross section of a molded product obtained in Example 4, respectively. FIG.
FIG. 20 is a conceptual diagram of a mold used in Example 5.
FIG. 21 is a conceptual diagram of a mold and the like for describing an injection molding method according to a fifth embodiment.
FIG. 22 is a conceptual diagram of a mold and the like for explaining the injection molding method of the fifth embodiment, following FIG. 21;
FIG. 23 is a conceptual diagram of a mold and the like for explaining the injection molding method of the fifth embodiment, following FIG. 22;
FIG. 24 is a conceptual diagram of a mold and the like for explaining the injection molding method of Example 5, following FIG. 23;
FIG. 25 is a conceptual diagram of a mold and the like for explaining the injection molding method of Example 5, following FIG. 24;
26A, 26B, and 26C are a schematic plan view, a schematic side view, and a schematic cross section of a molded product obtained in Example 5, respectively. FIG.
[Explanation of symbols]
10: fixed mold part, 11: movable mold part, 12: molten resin introduction part, 13: molten resin flow path, 14, 114, 214 ... pressurized fluid introduction part, 15 ... piping, 16 ... pressurized fluid source, 21 ... first cavity part, 23, 23A, 23B ... second cavity part, 25, 25A, 25B ... third cavity part, 30, 30A, 30B ... movable core part, 31, 31A, 31B ... hydraulic cylinder, 40 ... molten thermoplastic resin, 50, 150 ... molded product, 51, 151 ... first Thick portion, 52, 54, 56, 152 ... hollow portion, 53, 153A, 153B ... second thick portion, 55, 155A, 155B ... thin portion

Claims (5)

（ａ）中空部を有する第１の厚肉部、
（ｂ）中実の第２の厚肉部、及び、
（ｃ）第１の厚肉部と第２の厚肉部との間に位置する中実の薄肉部、
を備えた成形品を、
▲１▼ 第１の厚肉部を成形すべき第１キャビティ部、第２の厚肉部を成形すべき第２キャビティ部、及び、薄肉部を成形すべき第３キャビティ部から構成されたキャビティを有し、
▲２▼ 第１キャビティ部に溶融熱可塑性樹脂が射出されるように配置された溶融樹脂導入部、
▲３▼ 第１キャビティ部に加圧流体が導入されるように配置された加圧流体導入部、及び、
▲４▼ 第３キャビティ部内で、成形品の薄肉部の厚さ方向に相当する方向に沿って前進端及び後進端の間で移動し得る可動コア部、
を備えた金型を使用して射出成形する方法であって、
（Ａ）可動コア部を後進端に位置せしめた状態で、溶融樹脂導入部を介してキャビティ内に溶融熱可塑性樹脂を射出する工程と、
（Ｂ）キャビティ内への溶融熱可塑性樹脂の射出中、若しくは、射出完了と同時に、若しくは、射出完了後、加圧流体導入部を介してキャビティ内の溶融熱可塑性樹脂の内部に加圧流体を導入し、第１キャビティ部を占める溶融熱可塑性樹脂の内部に中空部を形成する工程と、
（Ｃ）可動コア部を前進端へと移動させて、薄肉部を成形する工程、
を具備することを特徴とする薄肉部を有する成形品の射出成形方法。(A) a first thick portion having a hollow portion,
(B) a solid second thick portion; and
(C) a solid thin portion located between the first thick portion and the second thick portion;
Moldings with
{Circle around (1)} A cavity composed of a first cavity portion for molding a first thick portion, a second cavity portion for molding a second thick portion, and a third cavity portion for molding a thin portion. Has,
{Circle around (2)} a molten resin introduction portion arranged so that the molten thermoplastic resin is injected into the first cavity portion;
(3) a pressurized fluid introduction unit disposed so as to introduce a pressurized fluid into the first cavity portion;
{Circle around (4)} a movable core portion which can move between a forward end and a reverse end along a direction corresponding to the thickness direction of the thin portion of the molded product in the third cavity portion;
A method of injection molding using a mold having
(A) a step of injecting a molten thermoplastic resin into a cavity through a molten resin introduction portion while the movable core portion is positioned at a backward end;
(B) During the injection of the molten thermoplastic resin into the cavity, at the same time as the completion of the injection, or after the injection is completed, the pressurized fluid is injected into the molten thermoplastic resin inside the cavity via the pressurized fluid introduction unit. Introducing and forming a hollow portion inside the molten thermoplastic resin occupying the first cavity portion;
(C) moving the movable core part to the forward end to form a thin part;
A method for injection-molding a molded article having a thin portion, characterized by comprising: 前記工程（Ｃ）において、中空部内の加圧流体の一部を排出することを特徴とする請求項１に記載の薄肉部を有する成形品の射出成形方法。2. The method according to claim 1, wherein a part of the pressurized fluid in the hollow portion is discharged in the step (C). 前記工程（Ｂ）と工程（Ｃ）の間で、中空部内の加圧流体を排出する工程を更に具備することを特徴とする請求項１に記載の薄肉部を有する成形品の射出成形方法。The method according to claim 1, further comprising a step of discharging the pressurized fluid in the hollow portion between the step (B) and the step (C). （ａ）中空部を有する第１の厚肉部、
（ｂ）中空部を有する第２の厚肉部、及び、
（ｃ）第１の厚肉部と第２の厚肉部との間に位置する中実の薄肉部、
を備えた成形品を、
▲１▼ 第１の厚肉部を成形すべき第１キャビティ部、第２の厚肉部を成形すべき第２キャビティ部、及び、薄肉部を成形すべき第３キャビティ部から構成されたキャビティを有し、
▲２▼ 第１キャビティ部に溶融熱可塑性樹脂が射出されるように配置された溶融樹脂導入部、
▲３▼ 第１キャビティ部に加圧流体が導入されるように配置された加圧流体導入部、及び、
▲４▼ 第３キャビティ部内で、成形品の薄肉部の厚さ方向に相当する方向に沿って前進端及び後進端の間で移動し得る可動コア部、
を備えた金型を使用して射出成形する方法であって、
（Ａ）可動コア部を後進端に位置せしめた状態で、溶融樹脂導入部を介してキャビティ内に溶融熱可塑性樹脂を射出する工程と、
（Ｂ）キャビティ内への溶融熱可塑性樹脂の射出中、若しくは、射出完了と同時に、若しくは、射出完了後、加圧流体導入部を介してキャビティ内の溶融熱可塑性樹脂の内部に加圧流体を導入し、第１キャビティ部、第２キャビティ部及び第３キャビティ部を占める溶融熱可塑性樹脂の内部に中空部を形成する工程と、
（Ｃ）中空部内の加圧流体を排出する工程と、
（Ｄ）可動コア部を前進端へと移動させて、第３キャビティ部を占める溶融熱可塑性樹脂の内部に形成された中空部を無くし、中実の薄肉部を成形する工程、
を具備することを特徴とする薄肉部を有する成形品の射出成形方法。(A) a first thick portion having a hollow portion,
(B) a second thick portion having a hollow portion, and
(C) a solid thin portion located between the first thick portion and the second thick portion;
Moldings with
{Circle around (1)} A cavity composed of a first cavity portion for molding a first thick portion, a second cavity portion for molding a second thick portion, and a third cavity portion for molding a thin portion. Has,
{Circle around (2)} a molten resin introduction portion arranged so that the molten thermoplastic resin is injected into the first cavity portion;
(3) a pressurized fluid introduction unit disposed so as to introduce a pressurized fluid into the first cavity portion;
{Circle around (4)} a movable core portion which can move between a forward end and a reverse end along a direction corresponding to the thickness direction of the thin portion of the molded product in the third cavity portion;
A method of injection molding using a mold having
(A) a step of injecting a molten thermoplastic resin into a cavity through a molten resin introduction portion while the movable core portion is positioned at a backward end;
(B) During or after injection of the molten thermoplastic resin into the cavity, or after completion of the injection, the pressurized fluid is injected into the molten thermoplastic resin inside the cavity via the pressurized fluid introduction unit. Introducing, forming a hollow portion inside the molten thermoplastic resin occupying the first cavity portion, the second cavity portion, and the third cavity portion;
(C) a step of discharging the pressurized fluid in the hollow portion;
(D) moving the movable core portion to the forward end to eliminate a hollow portion formed inside the molten thermoplastic resin occupying the third cavity portion and form a solid thin portion;
A method for injection-molding a molded article having a thin portion, characterized by comprising: （ａ）中空部を有する第１の厚肉部、
（ｂ）中空部を有する第２の厚肉部、及び、
（ｃ）第１の厚肉部と第２の厚肉部との間に位置する中実の薄肉部、
を備えた成形品を、
▲１▼ 第１の厚肉部を成形すべき第１キャビティ部、第２の厚肉部を成形すべき第２キャビティ部、及び、薄肉部を成形すべき第３キャビティ部から構成されたキャビティを有し、
▲２▼ 第１キャビティ部に溶融熱可塑性樹脂が射出されるように配置された溶融樹脂導入部、
▲３▼ 第２キャビティ部に加圧流体が導入されるように配置された加圧流体導入部、及び、
▲４▼ 第３キャビティ部内で、成形品の薄肉部の厚さ方向に相当する方向に沿って前進端及び後進端の間で移動し得る可動コア部、
を備えた金型を使用して射出成形する方法であって、
（Ａ）可動コア部を後進端に位置せしめた状態で、溶融樹脂導入部を介してキャビティ内に溶融熱可塑性樹脂を射出する工程と、
（Ｂ）キャビティ内への溶融熱可塑性樹脂の射出中、若しくは、射出完了と同時に、若しくは、射出完了後、加圧流体導入部を介してキャビティ内の溶融熱可塑性樹脂の内部に加圧流体を導入し、第１キャビティ部、第２キャビティ部及び第３キャビティ部を占める溶融熱可塑性樹脂の内部に中空部を形成する工程と、
（Ｃ）中空部内の加圧流体を排出する工程と、
（Ｄ）可動コア部を前進端へと移動させて、第３キャビティ部を占める溶融熱可塑性樹脂の内部に形成された中空部を無くし、中実の薄肉部を成形する工程、
を具備することを特徴とする薄肉部を有する成形品の射出成形方法。(A) a first thick portion having a hollow portion,
(B) a second thick portion having a hollow portion, and
(C) a solid thin portion located between the first thick portion and the second thick portion;
Moldings with
{Circle around (1)} A cavity composed of a first cavity portion for molding a first thick portion, a second cavity portion for molding a second thick portion, and a third cavity portion for molding a thin portion. Has,
{Circle around (2)} a molten resin introduction portion arranged so that the molten thermoplastic resin is injected into the first cavity portion;
(3) a pressurized fluid introduction unit disposed so as to introduce a pressurized fluid into the second cavity portion;
{Circle around (4)} a movable core portion which can move between a forward end and a reverse end along a direction corresponding to the thickness direction of the thin portion of the molded product in the third cavity portion;
A method of injection molding using a mold having
(A) a step of injecting a molten thermoplastic resin into a cavity through a molten resin introduction portion while the movable core portion is positioned at a backward end;
(B) During or after injection of the molten thermoplastic resin into the cavity, or after completion of the injection, the pressurized fluid is injected into the molten thermoplastic resin inside the cavity via the pressurized fluid introduction unit. Introducing, forming a hollow portion inside the molten thermoplastic resin occupying the first cavity portion, the second cavity portion, and the third cavity portion;
(C) a step of discharging the pressurized fluid in the hollow portion;
(D) moving the movable core portion to the forward end to eliminate a hollow portion formed inside the molten thermoplastic resin occupying the third cavity portion and form a solid thin portion;
A method for injection-molding a molded article having a thin portion, characterized by comprising:
JP2002328121A 2002-11-12 2002-11-12 Injection molding method of molded article having thin part Pending JP2004160783A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011040186A1 (en) * 2009-09-30 2011-04-07 コニカミノルタオプト株式会社 Device for manufacturing resin molded articles for use in optical elements, and method for manufacturing optical elements
WO2021037768A1 (en) * 2019-08-23 2021-03-04 Intersurgical Ag Respiratory interface device and method of manufacturing a sealing member for a respiratory interface device
WO2022038245A1 (en) * 2020-08-21 2022-02-24 Intersurgical Ag Improvements relating to sealing members
KR20220140169A (en) * 2021-04-09 2022-10-18 재영아이텍 주식회사 Water injection type injection molding product and injection molding product with thick mass portion

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011040186A1 (en) * 2009-09-30 2011-04-07 コニカミノルタオプト株式会社 Device for manufacturing resin molded articles for use in optical elements, and method for manufacturing optical elements
EP2484507A4 (en) * 2009-09-30 2014-06-11 Konica Minolta Opto Inc Device for manufacturing resin molded articles for use in optical elements, and method for manufacturing optical elements
JP5737181B2 (en) * 2009-09-30 2015-06-17 コニカミノルタ株式会社 Optical element resin molded product manufacturing apparatus and optical element manufacturing method
WO2021037768A1 (en) * 2019-08-23 2021-03-04 Intersurgical Ag Respiratory interface device and method of manufacturing a sealing member for a respiratory interface device
CN114641331A (en) * 2019-08-23 2022-06-17 英特外科股份公司 Respiratory interface device and method of making a sealing member for a respiratory interface device
WO2022038245A1 (en) * 2020-08-21 2022-02-24 Intersurgical Ag Improvements relating to sealing members
GB2598158B (en) * 2020-08-21 2025-02-12 Intersurgical Ag Improvements relating to sealing members
KR20220140169A (en) * 2021-04-09 2022-10-18 재영아이텍 주식회사 Water injection type injection molding product and injection molding product with thick mass portion
KR102481334B1 (en) * 2021-04-09 2023-01-02 재영아이텍 주식회사 Injection molding product with thick mass portion

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