JP4084573B2

JP4084573B2 - Pressure vessel mirror part wrap part molding method

Info

Publication number: JP4084573B2
Application number: JP2002014506A
Authority: JP
Inventors: 伸雄笹岡
Original assignee: Central Motor Wheel Co Ltd
Current assignee: Central Motor Wheel Co Ltd
Priority date: 2002-01-23
Filing date: 2002-01-23
Publication date: 2008-04-30
Anticipated expiration: 2022-01-23
Also published as: JP2003214539A

Description

【０００１】
【発明の属する技術分野】
本発明は、気化ガス、液化ガス等を蓄える圧力容器の製造方法に関し、詳しくは、胴部と、その両筒口に接合される鏡部とからなる圧力容器の鏡部の製造方法に関するものである。
【０００２】
【従来の技術】
内部に気化ガス、液化ガス等を高圧で蓄える圧力容器としては、スチール鋼材、アルミニウム材、複合材等により構成されているものが知られている。なかでもスチール鋼製の圧力容器は、生産性の高さや低コスト等により多様な分野で使用されている。例えば、近年、環境問題として取り上げられる自動車の排出ガスの規制により、自動車用燃料にＬＰＧ（液化石油ガス）やＣＮＧ（圧縮天然ガス）等の使用が拡大しており、このようなＬＰＧやＣＮＧを蓄える高圧のガスタンクとして、圧力容器が一般的に用いられている。
【０００３】
このうちＬＰＧ等の高圧ガス用圧力容器としては、胴部を構成する円筒殻と、その両端筒口と夫々に接合する鏡部を構成する略半球殻とから構成されているものが広く用いられている。この構成の圧力容器の製造方法としては、平板を円筒状に円曲させて、その端部を溶接等で接合することにより円筒殻の胴部を形成し、平板をプレス加工して略半球殻の鏡部を形成し、該胴部の両端筒口に鏡部の開口を溶接等で接合するようにしていることが一般的である。
【０００４】
ここで、胴部と鏡部の接合部は、鏡部の開口周縁に形成した段差状のラップ部を、胴部の筒口周縁の内周面に該ラップ部の外周面が内嵌するように、胴部の両端筒口から嵌入する構造となっている。このような鏡部は、平板をプレス加工して所定形状の略半球殻を形成した後、この鏡部の開口周縁をへら絞りして、段差状のラップ部を形成するようにしていた。このへら絞り加工としては、例えば、鏡部を回転させて、周方向の一部領域で、内外両側から加工ロールで開口周縁を挟圧する方法等により行われる。さらに、このラップ部の開口周端縁を、鏡部中心軸に向かう内側に折り曲げて、ラップ部を胴部筒口に嵌入するガイドを形成しているものもある。
【０００５】
【発明が解決しようとする課題】
ところで、このような鏡部のラップ部では、へら絞り加工により、加工前に比して外径が縮小される（周長が短縮される）収縮変形を生じる。この収縮変形に伴い、材料のポアソン比に従って、へら絞り加工部位以外の部分に板厚の増加や延伸等の膨張変形が生じることとなる。ここで、上記したようにへら絞り加工を、鏡部を回転させて、周方向の一部領域で、内外両側から加工ロールで開口周縁を挟圧するようにしている場合にあっては、加工ロールで挟圧される加工部位に近接する開口周縁の周方向又は開口端方向に、膨張変形が生じることとなり得る。この膨張変形によって、ラップ部の板厚が増加することとなれば、ラップ部と胴部との溶接が不十分となることもあり得る。また、膨張変形によって、ラップ部が周方向に延伸することとなれば、ラップ部外径が所望の設定値より大きくなるか、又は部分的に延伸して周形状が異形となることにより、胴部の筒口への嵌合することが難しくなる。このような膨張変形は、材料の種類の違いだけでなく、同じ組成の材料でも構成する元素の組織配列によって、変形方向及び変形量が変化すると考えられるので、的確に予測することは極めて困難である。そのため、ラップ部外径が設定値より大きくなることを見越してへら絞り加工しても、適切な外径を有するラップ部を形成できず、ラップ部外径が小さくなりすぎれば、ラップ部を胴部の筒口に嵌合しても隙間を生じることとなり、胴部と鏡部とを適正に接合することが難しい。このように、胴部との嵌合部分であるラップ部の形状は、へら絞り加工によって成形寸法に比較的大きなバラツキを生じることとなっていた。特に、ラップ部外径が不安定となり、許容範囲を超える外径となると、不具合品となって使用できないことから、従来の鏡部の成形では不良率が高く、生産効率及び製造コストの面で非常に不利な状況となっていた。
【０００６】
さらに、上記のようにラップ部周端縁を内側に折り曲げて、胴部への嵌合ガイドを形成している成形方法にあっては、へら絞り加工による膨張変形が、開口端方向に進行することを折れ曲がった部分で妨げられる。そのため、胴部の内周面と嵌着する部分で膨張変形のほとんどを生じることとなるから、ラップ部の外径や板厚を一層不安定なものとすることとなっていた。
【０００７】
一方、このような圧力容器が自動車用のＬＰＧ容器として使用される場合にあって、スチール鋼製容器の軽量化への要求が強い。そのため、容器に使用する材料に高強度材料を用いることが提案されている。一般に圧力容器には、その内部に充填されたガス等によって内圧が負荷されるため、容器の外殻では引張力が働くこととなる。そのため、より高い引張強度を有する鋼材料を使用することにより、容器を薄肉化し、軽量化することが可能である。ところが、このような高引張強度の鋼材料（高張力鋼）は、同時に高耐力及び高弾性率を有していることから、変形し難く、かつ、加工後に変形が戻るスプリングバックが大きい。そのため、ラップ部のへら絞り加工では、上述した膨張変形に加え、強いスプリングバックを生じることとなるため、ラップ部の成形形状が一層不安定なものとなり、不良率が一層高くなるという問題が生じていた。而して、圧力容器の軽量化を進行させることに限界が生じていた。
【０００８】
本発明は、上記問題の解決を試みたものであって、胴部の両筒口に嵌入する鏡部のラップ部を、適切な形状で安定して成形することが可能である鏡部のラップ部成形方法を提供することを目的とするものである。
【０００９】
【課題を解決するための手段】
本発明は、上述の胴部を構成する円筒殻と、その両端筒口と夫々に接合する鏡部を構成する略半球殻とからなる圧力容器にあって、胴部の筒口周縁の内周面に、鏡部の開口周縁の外周面が内嵌するように、該鏡部の開口周縁に段差状のラップ部を形成する圧力容器鏡部のラップ部成形方法において、鏡部の開口周縁に、その外周面を、開口端に向かって薄肉化するように切削加工することにより縮径部を形成した後、該縮径部に連続する環状帯域を、鏡部の中心軸に向かって段差状にへら絞りして筒口内周面と嵌着することとなる嵌合周部を形成すると共に、縮径部を内側に向かって略湾曲状に押圧加工することにより、ラップ部を形成したことを特徴とする鏡部のラップ部成形方法である（請求項１）。ここで、ラップ部とは、鏡部の、胴部に嵌合される領域を示す。
【００１０】
このように、切削加工によって、鏡部の開口周縁に開口端に向かって薄肉化する縮径部を形成するようにしたことにより、この縮径部は、開口端に向かって徐々に剛性低下する剛性分布を有することとなる。これにより、その後の押圧加工によって、該縮径部がその剛性分布により、剛性が低い部分（開口端）から順に変形させることができるから、縮径部を容易に湾曲状とすることができ得る。さらには、この縮径部は外周面を切削することで形成するようにしているから、外側から内側に向かって実行する押圧加工によって、嵌合周部から連続する滑らかな湾曲状の縮径部を適切に形成でき得る。そして、嵌合周部を形成するための、縮径部と連続する環状帯域を段差状に加工するへら絞り加工と共に、この縮径部の押圧加工を実行するようにしたことにより、へら絞りによる収縮変形に伴って生じる膨張変形を、縮径部の開口端方向への延伸変形等に作用させるようにすることが可能となる。これにより、へら絞り加工によって生じる膨張変形が、嵌合周部の増肉変形や周長変形等に作用することを防止し得るから、嵌合周部の外径と肉厚とを精度良く安定して形成できるため、ラップ部の形状不良によって生じる鏡部の不具合品を著しく低減することが可能となる。而して鏡部の生産効率の向上と製造コストの低減が著しく進行するという優れた効果を生じる。
【００１１】
尚、このように形成した略湾曲状の縮径部は、ラップ部を胴部に嵌合する際の適切なガイドとなり得る。また、鏡部の開口周縁を切削加工して形成する縮径部は、その外周面を傾斜面や、傾斜曲面や、階段状面等の様々な形状に形成することができる。なかでも僅かに曲面となる傾斜曲面とすることにより、当該縮径部の剛性分布を一層滑らかにできるから、その後の押圧加工による湾曲状の形成が一層容易となると共に、押圧加工する加工冶具への負担を小さくすることができるため、好ましく用い得る。
【００１２】
上述した縮径部を略湾曲状とする押圧加工が、開口端方向に向かって鏡部の内側方向に傾斜する加圧斜面を、鏡部開口面に沿って押圧するものであること（請求項２）も提案される。ここで、加圧斜面は、開口端方向に向かって鏡部の内側に傾斜するものであり、押圧加工した際に、加圧斜面が縮径部の開口端に最初に接触するような角度となっていることが望ましい。これにより、押圧する加圧斜面が、まず縮径部の最も剛性の小さい開口端を押圧することで、ここが湾曲変形する。そして、引き続き押圧する加圧斜面は、開口端よりも厚肉である剛性の高い部分と接触することとなり、この部分が湾曲変形する。このように湾曲変形と、それに伴う加圧斜面が押圧する部分の移動とが、縮径部の厚肉方向に向かって順次連続して行われていくこととなるから、この押圧加工による縮径部の湾曲変形が適切に行われ、滑らかな湾曲状の縮径部を適切に形成し得る。また、縮径部にかかる押圧力が、当初開口端で鏡部凸に向かって斜め方向（加圧斜面に対し垂直方向）に強く作用していたものが、縮径部の湾曲変形と押圧部分の移動とによって徐々に開口面内方向への作用にも分散していくこととなる。これにより、開口端方向への延伸変形を妨げることもないから、へら絞り加工による膨張変形を、開口端方向に向かって順次適切に送り出すように導くことができ得る。
【００１３】
また、鏡部の外周端に面取り加工を施すと共に、該縮径部を略湾曲状にする押圧加工の加工初期では、該面取り部を押圧するようにしたこと（請求項３）も提案される。これにより押圧加工初期の加圧冶具と縮径部との接触による圧力を緩和することができるから、縮径部に亀裂や欠損等の損傷が生じることを防止できる。また、同時に加圧冶具にかかる反力（材料の弾性力）も軽減することとなり得るから、加圧冶具の寿命も延び、製造コストの低減に寄与でき得る。
【００１４】
かかる上述した本発明のラップ部成形方法によれば、ラップ部形状を所望のサイズで安定して形成することが可能となるから、圧力容器の軽量化を目的として、高強度材料を使用することも可能となる。而して、このような鏡部が、引張強度４９０Ｎ／ｍｍ²以上の高張力鋼により構成されるものであること（請求項４）もできる。かかる高張力鋼を使用した鏡部であっても、上述したように、へら絞り加工による収縮変形に伴って生じる膨張変形及びスプリングバックを、縮径部の押圧加工によって開口端方向への延伸変形等に作用させることができるから、嵌合周部の増肉変形や周長変形等を適切に防ぐことができる。而して、適正な形状の嵌合周部を安定して形成することができ、高張力鋼を使用することにより、鏡部の薄肉化が可能となり、圧力容器の軽量化が進む。尚、圧力容器の胴部にあっても、この高張力鋼を用いることによって、圧力容器の軽量化が一層進行でき得る。さらには、本発明のラップ部成形方法にあっては引張強度５４０Ｎ／ｍｍ²以上の高張力鋼を用いて、一層の軽量化を行うことも可能である。
【００１５】
【発明の実施の形態】
自動車用ＬＰＧ容器に本発明を適用した一実施例を説明する。
図１に、本発明にかかる鏡部４のラップ部成形方法により製造した鏡部４で構成された圧力容器１の断面図を示す。この圧力容器１は、円筒殻からなる胴部２の両筒口３，３に、鏡部４、４の開口５，５が嵌合された構造から成る。ここで、鏡部４，４には、本発明の要部にかかるラップ部７，７が形成されている。また、片方の鏡部４の凸頂部には、気化ガス、液化ガス等を注入又は排出するためのノズル６が配設されている。ここで、圧力容器１を構成する胴部２及び鏡部４，４は、後述するＪＩＳ規格に示される高張力鋼（ＳＧ３６５）を用いて成形している。
【００１６】
この圧力容器１の胴部２は、ＳＧ３６５の平板を、対向する二辺が合うように円曲して円筒状とし、この二辺を溶接等により接合することで形成される。ここで、胴部２は、その内周径が所望の寸法となるように整えられる。一方、鏡部４は、ＳＧ３６５の平板をプレス加工により略半球状に形成した後、開口縁に後述するラップ部成形方法によってラップ部７を形成して成形される。このラップ部７には、図２の拡大図のように、胴部２の内周面と嵌着する嵌合周部８と、該嵌合周部８と連続して開口端に向かって内側に湾曲する縮径部９とが配設される。尚、この縮径部９は、胴部２の筒口３にラップ部７を挿入する際のガイドの役目を有する。そして、この鏡部４のラップ部７を、胴部２に内嵌して、溶接等により鏡部４と胴部２とを接合し、圧力容器１が形成されることとなる。ここで、圧力容器１の接合に溶接を用いる場合としては、サブマージ溶接、アルタンガス溶接、炭酸ガス溶接等の様々な溶接方法を用いることが可能である。
【００１７】
次に本発明にかかる、鏡部のラップ部成形方法について説明する。
ＪＩＳ規格Ｇ３１１６に示されるＳＧ３６５の高張力鋼の平板から鏡部４をプレス加工する。このＳＧ３６５は、約５４０Ｎ／ｍｍ²の引張強度、約３６５Ｎ／ｍｍ²の耐力を備える熱間圧延鋼板である。
この平板をプレス加工して得た略半球状の鏡部４を、外側の凹ドラム２１と、内側の凸ドラム２２とによって挟持して（図３参照）、所定の回転数で回転させる。そして、図４の拡大図に示すように、回転中の該鏡部４の開口周縁１０の外周面を切削バイト２７によって、開口端１２に向かって薄肉化するように切削加工する。この切削加工により形成した縮径部９は、その外面が外方向に若干膨らむ傾斜曲面となっている。この縮径部９は、開口端１２に向かって剛性が低下していく剛性分布を有する。また、この縮径部９の開口端１２の外面を切削して、面取り部１３を形成している。このような切削加工により、開口周縁１０に縮径部９を形成した鏡部４を得る。
【００１８】
その後、この鏡部４を、上記の切削加工の場合と同様に再び回転させる。ここで、回転する鏡部４の周方向一部域において、図５のように、加圧ロール２３により、縮径部９と連続する環状帯域１４を外側から押圧していき、内側に配された受けロール２４と共に該環状帯域１４を挟圧するへら絞り加工を実行する。これにより、環状帯域１４を段差状に成形し、胴部２の内周面と嵌着する嵌合周部８を形成する。そして、このへら絞り加工と共に、加圧ロール２３の下方に設けた、鏡部９の中心軸に向かって傾斜する加圧斜面２６を備えた斜圧ロール２５によって、縮径部９を押圧加工する。この押圧加工の加工初期では、加工ロール２３と共に斜圧ロール２５が開口５の面方向に沿って移動して、縮径部９の開口端１２に形成した面取り部１３を最初に押圧する。これにより、縮径部９の開口端１２付近、すなわち低剛性部分が内側方向に湾曲変形する。この湾曲変形により、斜圧ロール２５が押圧する縮径部９との接触部分が、縮径部９の厚肉方向に移動して、この接触部分付近を内側方向に湾曲変形する。これは、縮径部９の剛性が長さ方向で異なるから、剛性の低い開口端１２から順に、斜圧ロール２５による押圧と、湾曲変形とが連続して進行していくためである。而して、滑らかな湾曲状に変形した縮径部９を適切に形成でき得る。このようにして、嵌合周部８と縮径部９とからなるラップ部７を成形する。
【００１９】
次に、かかるラップ部７の成形方法により生じる作用につき説明する。
鏡部４のラップ部７の成形にあって、嵌合周部８を形成するへら絞り加工前に、縮径部９を形成し、該へら絞り加工と共に、縮径部９を略湾曲状とすることにより、へら絞り加工による収縮変形に伴って生じる膨張変形を縮径部９の長さ方向への延伸変形へ作用させることができ得る。詳しくは、へら絞り加工と押圧加工の前に、開口端１２に向かって薄肉化する傾斜曲面を備えた縮径部９を形成した後、へら絞り加工と共に、加圧斜面２６を備えた斜圧ロール２５で押圧加工することにより、縮径部９を略湾曲状とする連続的に行われる湾曲変形に伴って、へら絞り加工による膨張変形を、該縮径部９の長さ方向に順次効果的に送り出すように導き得る。このように、へら絞り加工により生じる膨張変形を、嵌合周部１０の板厚増加及び周長増加等に作用することが防止でき得る。また、このへら絞り加工によるスプリングバックも縮径部９へと作用させることが可能であるから、本実施例のＳＧ３６５のような高張力鋼を用いた場合にあっても、嵌合周部１０の板厚増加及び周長増加等を適正に防止でき得る。
【００２０】
かかるラップ成形方法により、鏡部４を成形した場合の嵌合周部１０の周長Ｌと製造個数Ｎとの関係を図６に例示する。ここで、嵌合周部１０の周長Ｌの設定値は１２００ｍｍである。１００個の鏡部４を製造した場合にあって、成形した各鏡部４の周長Ｌは１２００ｍｍから１２００．５ｍｍまでの０．５ｍｍの範囲内に収まっている。すなわち、この嵌合周部１０の外径誤差は０．１６ｍｍ以下であり、加工精度が極めて高いレベルで維持されて、安定的にラップ部７を成形していることが示されている。一方、比較例として、図７のように、同じ高張力鋼（ＳＧ３６５）を用い、鏡部ａの開口周縁ｂに縮径部を設けずに、本実施例と同様のへら絞り加工と押圧加工してラップ部ｃを成形した鏡部ａを製造した。この鏡部ａのラップ部ｃでは、嵌合周部ｄから開口端ｅに向かって、胴部との嵌合のガイドとなるように内側に屈曲されている。この比較例の鏡部ａを１００個製造した場合について、その嵌合周部ｄの周長Ｌと製造個数Ｎとの関係を図６に並記した。ここで、比較例の嵌合周部ｄの周長Ｌの設定値も、実施例と同じ１２００ｍｍである。しかし、１００個の製造における、嵌合周部ｄの周長Ｌは１１９８．５ｍｍから１２０４ｍｍまでの約５．５ｍｍの範囲にばらついている。そして、この嵌合周部ｄの外径誤差は約１．８ｍｍと大きく、かつ、バラツキも大きくなっており、ラップ部ｃの成形が不安定であることが示されている。また、この比較例では周長Ｌの許容範囲（１１９９．４〜１２００．６ｍｍ）に含まれる個数も少なく、不良率が高い。而して、本発明のラップ部成形方法では、所望の形状のラップ部７を有する鏡部４を精度良く安定して成形することが可能となる。これにより、鏡部４が胴部２と適切に嵌合させることができるから、鏡部４の製造にかかる不良率を著しく低減することが可能となり、生産効率を向上させ得ると共に、製造コストも低減できるという優れた効果が生じる。また、高張力鋼を適切に使用することができるから、圧力容器の薄肉化が可能となり、圧力容器の軽量化を一層進めることが可能となる。
【００２１】
また、このようなラップ部７の成形方法にあって、縮径部９の押圧加工を、加圧斜面２６を備えた斜圧ロール２５で行うようにしたことにより、斜圧ロール２５の加圧斜面２６が縮径部９から受ける反力（材料の弾性力）を緩和させることもできるから、この斜圧ロール２５の疲労寿命を著しく向上させ得る。これにより、斜圧ロール２５のメンテナンスや交換等により生じる費用も削減でき、製造コストの低減を一層進めることが可能となる。
【００２２】
このような本発明にあって、鏡部４の開口周縁１０を切削加工して形成する縮径部９としては、上記の実施例のように、開口端１２に向かって僅かに膨らむ傾斜曲面の他、略ストレート面となる傾斜面、又は、階段状に段階的に薄肉化していくような外面等とすることも可能である。このような外面形状に切削加工した縮径部９にあっても、その後の押圧加工によって、本発明の作用効果を適切に発揮し得る略湾曲状の縮径部９を成形することができ得る。
【００２３】
また、略湾曲状の縮径部９を形成する押圧加工にあって、斜圧ロール２６の加圧面を、上記実施例の加圧斜面２６とする場合の他、面外方向に凸状としたり、僅かに凹状とする等の加圧曲面とすることも可能である。斜圧ロール２６がこのような加圧曲面を備えることにより、縮径部９から受ける反力を一層緩和することができるから、斜圧ロール２６の疲労寿命の向上に寄与でき得る。
【００２４】
かかる本発明は上記実施例に限定されるものではなく、この発明の主旨を逸脱しない範囲において様々な形態で実施し得るものである。また、本発明は自動車用ＬＰＧ容器だけでなく、胴部２に鏡部４を嵌合してなる構成を具備する他の圧力容器１にも適用可能である。
【００２５】
【発明の効果】
このように本発明は、圧力容器鏡部のラップ部を、切削加工により開口周縁に、その外周面を開口端に向かって薄肉化する縮径部を形成した後、該縮径部と連続する環状帯域を段差状に加工するへら絞り加工により嵌合周部を形成すると共に、該縮径部を押圧加工により略湾曲状に変形させるようして、成形するようにした成形方法（請求項１）である。かかる成形方法にあっては、切削加工により縮径部を開口端に向かって徐々に剛性低下する剛性分布を有するものとし、押圧加工により該縮径部を剛性の低い部分から順次連続して湾曲変形するようにしたことにより、へら絞りによる収縮変形に伴って生じる膨張変形を、該縮径部の開口端方向への延伸変形等に作用させることができるから、嵌合周部の増肉変形や周長変形等を防止でき、嵌合周部の外径と肉厚を精度良く安定して成形することが可能となる。而して、ラップ部の形状不良によって生じる鏡部の不良率を著しく低減することができ、鏡部の生産効率の向上と製造コストの低減を著しく進めることができるという優れた効果を生じる。
【００２６】
また、縮径部を略湾曲状とする押圧加工が、開口端方向に向かって鏡部の内側方向に傾斜する加圧斜面を、鏡部開口面に沿って押圧するものとした場合（請求項２）にあっては、押圧する加圧斜面が、縮径部の湾曲変形に伴って、縮径部の最も剛性の小さい開口端から順に縮径部の厚肉方向に向かって移動することとなるから、縮径部が開口端から順次連続して湾曲変形し、滑らかな湾曲状の縮径部を適切に形成し得る。これにより、へら絞り加工により生じる膨張変形を開口端方向に向かって適切に作用させることができる。
【００２７】
また、鏡部の外周端に面取り加工を施すと共に、該縮径部を略湾曲状にする押圧加工の加工初期では、該面取り部を押圧するようにした場合（請求項３）にあっては、押圧加工初期の加圧冶具と縮径部との接触による圧力を緩和できるから、縮径部に損傷が生じることを防止できる。また、加圧冶具にかかる反力（材料の弾性力）も軽減できるから、加圧冶具の疲労寿命が向上し、製造コストの低減に寄与でき得る。
【００２８】
このような本発明のラップ部成形方法によれば、ラップ部形状を精度良く安定して形成することが可能となるから、圧力容器の軽量化を目的として、高強度材料を使用することも可能となる（請求項１の効果）。これにより、鏡部が、引張強度４９０Ｎ／ｍｍ²以上の高張力鋼により構成されるものとした場合（請求項４）にあって、へら絞り加工により生じる膨張変形及び、高張力鋼の強いスプリングバックを、縮径部の開口端方向への延伸変形等に作用させることができるから、嵌合周部の増肉変形や周長変形等を適切に防ぐことができる。而して、高張力鋼を使用することによって、鏡部の薄肉化が可能となるから、圧力容器の軽量化を一層進めることができ得る。
【図面の簡単な説明】
【図１】本発明による鏡部４から成る圧力容器１の縦断面図である。
【図２】鏡部４と胴部２との接合部分の拡大断面図である。
【図３】ラップ部７の成形における鏡部４の挟持状態を表す状態図である。
【図４】本発明にかかる縮径部９の切削加工を表す説明図である。
【図５】本発明にかかるへら絞り加工と押圧加工を表す説明図である。
【図６】本発明の効果を示す周長Ｌと製造個数Ｎとの測定図である。
【図７】従来のラップ部成形方法による鏡部ａの拡大断面図である。
【符号の説明】
１圧力容器
２胴部
４鏡部
７ラップ部
８嵌合周部
９縮径部
１０開口周縁
１２開口端
１３面取り部
１４環状帯域[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a pressure vessel that stores vaporized gas, liquefied gas, and the like, and more particularly, to a method of manufacturing a mirror portion of a pressure vessel that includes a body portion and a mirror portion that is joined to both cylinder ports. .
[0002]
[Prior art]
Known pressure vessels that store vaporized gas, liquefied gas, and the like at high pressures are made of steel, aluminum, composite materials, and the like. Among them, steel steel pressure vessels are used in various fields due to high productivity and low cost. For example, in recent years, the use of LPG (liquefied petroleum gas) and CNG (compressed natural gas) as fuel for automobiles has been expanded due to regulations on automobile exhaust gas, which is taken up as an environmental problem. A pressure vessel is generally used as a high-pressure gas tank for storing.
[0003]
Among these, as a pressure vessel for high-pressure gas such as LPG, a container composed of a cylindrical shell constituting a body part and a substantially hemispherical shell constituting a mirror part joined to both ends of the cylindrical shell is widely used. Yes. As a method of manufacturing a pressure vessel having this structure, a flat plate is bent into a cylindrical shape, and its end is joined by welding or the like to form a cylindrical shell body, and the flat plate is pressed to form a substantially hemispherical shell. In general, the mirror part is formed, and the opening of the mirror part is joined to the both ends of the barrel part by welding or the like.
[0004]
Here, the joint part between the body part and the mirror part is such that the step-shaped lap part formed at the opening periphery of the mirror part is fitted into the inner peripheral surface of the periphery of the barrel opening of the body part so that the outer peripheral surface of the wrap part fits inside. It has a structure that is fitted from both ends of the barrel. In such a mirror part, a flat plate is pressed to form a substantially hemispherical shell having a predetermined shape, and then the opening peripheral edge of the mirror part is narrowed down to form a stepped lap part. The spatula drawing is performed by, for example, a method in which a mirror portion is rotated and the peripheral edge of the opening is clamped by a processing roll from both inside and outside in a partial region in the circumferential direction. Further, there is a type in which the opening peripheral edge of the wrap portion is bent inward toward the central axis of the mirror portion to form a guide for fitting the wrap portion into the barrel tube opening.
[0005]
[Problems to be solved by the invention]
By the way, in such a lapping part of the mirror part, the outer diameter is reduced (peripheral length is shortened) due to the spatula drawing process as compared with that before the process. Accompanying this shrinkage deformation, expansion deformation such as increase in plate thickness or stretching occurs in a portion other than the spatula drawing portion in accordance with the Poisson's ratio of the material. Here, as described above, when the spatula drawing process is performed, the mirror is rotated, and the peripheral edge of the opening is sandwiched between the inner and outer sides by a processing roll in a partial region in the circumferential direction. Expansion deformation may occur in the circumferential direction or the opening end direction of the peripheral edge of the opening that is close to the processing site to be clamped. If the plate thickness of the lap portion increases due to this expansion deformation, the lap portion and the body portion may be insufficiently welded. Also, if the wrap portion is stretched in the circumferential direction due to expansion deformation, the outer diameter of the wrap portion becomes larger than a desired set value, or the circumferential shape becomes irregular due to partial stretching. It becomes difficult to fit the part into the tube opening. Such expansion deformation is considered to be difficult to predict accurately because the deformation direction and amount of deformation are considered to change depending on not only the difference in the type of material but also the structural arrangement of the elements comprising the material of the same composition. is there. For this reason, even if the outer diameter of the lap portion is larger than the set value, even if the lap portion is drawn with a spatula, a wrap portion having an appropriate outer diameter cannot be formed. Even if fitted to the cylindrical opening of the part, a gap is generated, and it is difficult to properly join the body part and the mirror part. As described above, the shape of the lap portion, which is a fitting portion with the body portion, causes a relatively large variation in the molding dimension by spatula drawing. In particular, if the outer diameter of the lap part becomes unstable and the outer diameter exceeds the allowable range, it can not be used as a defective product, so the defective rate is high in conventional mirror part molding, and in terms of production efficiency and manufacturing cost It was a very disadvantageous situation.
[0006]
Further, in the molding method in which the peripheral edge of the wrap portion is bent inward as described above to form the fitting guide to the trunk portion, the expansion deformation due to the spatula drawing progresses in the direction of the opening end. It is disturbed at the bent part. For this reason, most of the expansion and deformation occurs at the portion fitted to the inner peripheral surface of the body portion, so that the outer diameter and the plate thickness of the wrap portion are further unstable.
[0007]
On the other hand, when such a pressure vessel is used as an LPG vessel for automobiles, there is a strong demand for weight reduction of a steel steel vessel. Therefore, it has been proposed to use a high-strength material for the material used for the container. In general, since an internal pressure is applied to a pressure vessel by a gas or the like filled therein, a tensile force acts on the outer shell of the vessel. Therefore, by using a steel material having a higher tensile strength, the container can be made thinner and lighter. However, such a high tensile strength steel material (high tensile steel) has a high yield strength and a high elastic modulus at the same time, so that it is difficult to be deformed and has a large spring back to which the deformation returns after processing. Therefore, in the spatula drawing of the lap portion, in addition to the above-described expansion deformation, a strong spring back is generated, so that the molding shape of the wrap portion becomes more unstable and the defect rate becomes higher. It was. Thus, there has been a limit to the progress of weight reduction of the pressure vessel.
[0008]
The present invention is an attempt to solve the above-mentioned problem, and the wrap portion of the mirror portion that can be stably molded with an appropriate shape into the wrap portion of the mirror portion that is fitted into both the cylinder ports of the trunk portion. The object is to provide a molding method.
[0009]
[Means for Solving the Problems]
The present invention is a pressure vessel comprising a cylindrical shell that constitutes the above-mentioned body part, and a substantially hemispherical shell that constitutes a mirror part that is joined to both ends of the cylindrical shell. In the method for forming a pressure vessel mirror wrap portion in which the stepped wrap portion is formed on the opening periphery of the mirror portion so that the outer peripheral surface of the opening periphery of the mirror portion is fitted, After forming the reduced diameter portion by cutting the outer peripheral surface so as to be thinned toward the opening end, the annular band continuing to the reduced diameter portion is stepped in a stepped shape toward the central axis of the mirror portion. A wrap portion is formed by forming a fitting peripheral portion that is to be squeezed and fitted to the inner peripheral surface of the tube opening and pressing the reduced diameter portion in a substantially curved shape toward the inside. This is a method for forming a mirror part wrap part (claim 1). Here, the wrap portion indicates a region of the mirror portion that is fitted to the body portion.
[0010]
Thus, by forming a reduced diameter portion that becomes thinner toward the opening end on the opening periphery of the mirror portion by cutting, the rigidity of the reduced diameter portion gradually decreases toward the opening end. It will have a stiffness distribution. Thereby, since the reduced diameter portion can be deformed in order from the portion having the lower rigidity (opening end) by the rigidity distribution by subsequent pressing, the reduced diameter portion can be easily curved. . Furthermore, since this reduced diameter portion is formed by cutting the outer peripheral surface, a smooth curved reduced diameter portion continuous from the fitting peripheral portion by pressing performed from the outside to the inside. Can be formed appropriately. And by forming the fitting peripheral portion with a spatula drawing process that processes the annular zone continuous with the reduced diameter portion into a stepped shape, the pressing process of the reduced diameter portion is executed, so that It is possible to cause the expansion deformation caused by the contraction deformation to act on the extension deformation in the opening end direction of the reduced diameter portion. As a result, expansion deformation caused by spatula drawing can be prevented from acting on thickening deformation, circumferential length deformation, etc. of the fitting peripheral part, so that the outer diameter and wall thickness of the fitting peripheral part can be accurately and stably maintained. Therefore, it is possible to remarkably reduce the defective product of the mirror part caused by the defective shape of the wrap part. Thus, an excellent effect is achieved in that the production efficiency of the mirror part is improved and the manufacturing cost is significantly reduced.
[0011]
In addition, the substantially curved reduced diameter part formed in this way can become an appropriate guide at the time of fitting a wrap part to a trunk | drum. Further, the reduced diameter portion formed by cutting the peripheral edge of the opening of the mirror portion can have an outer peripheral surface formed in various shapes such as an inclined surface, an inclined curved surface, and a stepped surface. In particular, by making the inclined curved surface a slightly curved surface, the rigidity distribution of the reduced diameter portion can be made smoother, so that it becomes easier to form a curved shape by subsequent pressing, and to a processing jig for pressing. This can be preferably used because it can reduce the burden of.
[0012]
The pressing process for making the reduced diameter portion substantially curved as described above presses the pressure slope inclined toward the inner side of the mirror portion toward the opening end direction along the mirror opening surface. 2) is also proposed. Here, the pressure inclined surface is inclined inward of the mirror portion toward the opening end direction, and when pressed, the angle at which the pressure inclined surface first contacts the opening end of the reduced diameter portion is set. It is desirable that As a result, the pressure slope to be pressed first presses the opening end having the smallest rigidity of the reduced diameter portion, so that this is curved and deformed. Then, the pressure slope to be continuously pressed comes into contact with a highly rigid portion that is thicker than the opening end, and this portion is curved and deformed. As described above, the bending deformation and the movement of the portion pressed by the pressure inclined surface are successively performed in the direction of the thickness of the reduced diameter portion. The curved deformation of the part is appropriately performed, and a smooth curved reduced diameter part can be appropriately formed. In addition, the pressing force applied to the reduced diameter portion was strongly acting in the oblique direction (perpendicular to the pressure slope) at the opening end at the initial opening end. As a result of this movement, the action in the in-plane direction is gradually dispersed. Thereby, since it does not disturb the extending | stretching deformation | transformation to an opening end direction, the expansion deformation | transformation by a spatula drawing process can be guide | induced so that it may send out appropriately sequentially toward an opening end direction.
[0013]
Further, it is proposed that the chamfered portion is pressed at the initial stage of the pressing process in which the outer peripheral end of the mirror portion is chamfered and the reduced diameter portion is substantially curved. . As a result, it is possible to relieve the pressure caused by the contact between the pressure jig at the initial stage of pressing and the reduced diameter portion, and therefore it is possible to prevent the reduced diameter portion from being damaged such as cracks and defects. At the same time, the reaction force (elastic force of the material) applied to the pressure jig can be reduced, so that the life of the pressure jig can be extended and the manufacturing cost can be reduced.
[0014]
According to the above-described method for forming a lap part of the present invention, it is possible to stably form the wrap part shape at a desired size, so that a high-strength material is used for the purpose of reducing the weight of the pressure vessel. Is also possible. Thus, such a mirror part can be made of high-tensile steel having a tensile strength of 490 N / mm ² or more (Claim 4). Even in a mirror part using such high-strength steel, as described above, expansion deformation and springback caused by contraction deformation due to spatula drawing processing are applied to the opening end direction by deformation processing of the reduced diameter portion. Therefore, it is possible to appropriately prevent the thickening deformation and the circumferential length deformation of the fitting peripheral portion. Thus, a fitting peripheral portion having an appropriate shape can be stably formed, and the use of high-strength steel makes it possible to reduce the thickness of the mirror portion and to reduce the weight of the pressure vessel. In addition, even if it exists in the trunk | drum of a pressure vessel, weight reduction of a pressure vessel can further advance by using this high tensile steel. Furthermore, in the lapping part forming method of the present invention, it is possible to further reduce the weight by using high-tensile steel having a tensile strength of 540 N / mm ² or more.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment in which the present invention is applied to an automotive LPG container will be described.
In FIG. 1, sectional drawing of the pressure vessel 1 comprised by the mirror part 4 manufactured with the lapping part shaping | molding method of the mirror part 4 concerning this invention is shown. The pressure vessel 1 has a structure in which the openings 5 and 5 of the mirror parts 4 and 4 are fitted to both the cylinder ports 3 and 3 of the body part 2 made of a cylindrical shell. Here, the mirror parts 4 and 4 are formed with wrap parts 7 and 7 according to the main part of the present invention. In addition, a nozzle 6 for injecting or discharging vaporized gas, liquefied gas, or the like is disposed on the convex top of one mirror unit 4. Here, the trunk | drum 2 and the mirror parts 4 and 4 which comprise the pressure vessel 1 are shape | molded using the high-tensile steel (SG365) shown by the JIS specification mentioned later.
[0016]
The body portion 2 of the pressure vessel 1 is formed by rounding a flat plate of SG365 into a cylindrical shape so that two opposite sides meet each other, and joining the two sides by welding or the like. Here, the trunk | drum 2 is prepared so that the internal peripheral diameter may become a desired dimension. On the other hand, the mirror part 4 is formed by forming a flat plate of SG365 into a substantially hemispherical shape by pressing, and then forming a wrap part 7 on the opening edge by a wrap part forming method described later. As shown in the enlarged view of FIG. 2, the wrap portion 7 has a fitting peripheral portion 8 fitted to the inner peripheral surface of the body portion 2 and an inner side toward the opening end continuously from the fitting peripheral portion 8. And a reduced-diameter portion 9 that is curved. The reduced diameter portion 9 serves as a guide when the wrap portion 7 is inserted into the tube port 3 of the body portion 2. And the wrap part 7 of this mirror part 4 is fitted in the trunk | drum 2, and the mirror part 4 and the trunk | drum 2 are joined by welding etc., and the pressure vessel 1 will be formed. Here, when welding is used for joining the pressure vessel 1, various welding methods such as submerged welding, altan gas welding, and carbon dioxide gas welding can be used.
[0017]
Next, a method for forming the lap portion of the mirror portion according to the present invention will be described.
The mirror part 4 is pressed from a flat plate of high-strength steel of SG365 shown in JIS standard G3116. The SG365 has a tensile strength of about 540N / mm ^2, a hot rolled steel sheet having a yield strength of about 365N / mm ^2.
The substantially hemispherical mirror part 4 obtained by pressing the flat plate is sandwiched between the outer concave drum 21 and the inner convex drum 22 (see FIG. 3) and rotated at a predetermined rotational speed. Then, as shown in the enlarged view of FIG. 4, the outer peripheral surface of the opening peripheral edge 10 of the rotating mirror part 4 is cut by the cutting tool 27 so as to become thinner toward the opening end 12. The reduced diameter portion 9 formed by this cutting is an inclined curved surface whose outer surface slightly swells outward. The reduced diameter portion 9 has a rigidity distribution in which the rigidity decreases toward the opening end 12. Further, a chamfered portion 13 is formed by cutting the outer surface of the opening end 12 of the reduced diameter portion 9. By such a cutting process, the mirror part 4 in which the reduced diameter part 9 is formed on the opening peripheral edge 10 is obtained.
[0018]
Then, this mirror part 4 is rotated again similarly to the case of said cutting. Here, in a partial region in the circumferential direction of the rotating mirror part 4, as shown in FIG. 5, the pressure zone 23 presses the annular zone 14 continuous with the reduced diameter part 9 from the outside and is arranged on the inside. A spatula drawing process is performed to clamp the annular zone 14 together with the receiving roll 24. Thereby, the annular zone 14 is formed in a step shape, and the fitting peripheral portion 8 that fits with the inner peripheral surface of the body portion 2 is formed. Then, along with this spatula drawing, the reduced diameter portion 9 is pressed by an oblique pressure roll 25 provided below the pressure roll 23 and provided with a pressure slope 26 inclined toward the central axis of the mirror portion 9. . At the initial stage of the pressing process, the oblique pressure roll 25 moves along the surface direction of the opening 5 together with the processing roll 23 to first press the chamfered portion 13 formed at the opening end 12 of the reduced diameter portion 9. As a result, the vicinity of the opening end 12 of the reduced diameter portion 9, that is, the low rigidity portion is curved and deformed inward. By this bending deformation, the contact portion with the reduced diameter portion 9 pressed by the oblique pressure roll 25 moves in the thickness direction of the reduced diameter portion 9, and the vicinity of this contact portion is bent and deformed in the inner direction. This is because, since the rigidity of the reduced diameter portion 9 is different in the length direction, pressing by the oblique pressure roll 25 and bending deformation proceed sequentially from the opening end 12 having low rigidity. Thus, the reduced diameter portion 9 deformed into a smooth curved shape can be appropriately formed. In this way, the wrap portion 7 including the fitting peripheral portion 8 and the reduced diameter portion 9 is formed.
[0019]
Next, an effect caused by the molding method of the wrap portion 7 will be described.
In forming the wrap part 7 of the mirror part 4, the reduced diameter part 9 is formed before the spatula drawing process for forming the fitting peripheral part 8, and the reduced diameter part 9 is made substantially curved along with the spatula drawing process. By doing so, the expansion deformation caused by the contraction deformation by the spatula drawing process can be applied to the extension deformation in the length direction of the reduced diameter portion 9. Specifically, after the reduced diameter portion 9 having the inclined curved surface that becomes thinner toward the opening end 12 is formed before the spatula drawing process and the pressing process, the slant pressure including the pressure inclined surface 26 together with the spatula drawing process. By pressing with the roll 25, the expansion deformation by the spatula drawing process is sequentially effected in the length direction of the reduced diameter portion 9 along with the continuously deformed deformation that makes the reduced diameter portion 9 substantially curved. Can be sent out. As described above, it is possible to prevent the expansion deformation caused by the spatula drawing process from acting on the increase in the plate thickness and the increase in the peripheral length of the fitting peripheral portion 10. Further, since the spring back by the spatula drawing process can also be applied to the reduced diameter portion 9, even when a high strength steel such as SG365 of this embodiment is used, the fitting peripheral portion 10 It is possible to appropriately prevent an increase in plate thickness and circumference.
[0020]
FIG. 6 illustrates the relationship between the peripheral length L of the fitting peripheral portion 10 and the production number N when the mirror portion 4 is formed by such a lap forming method. Here, the set value of the peripheral length L of the fitting peripheral portion 10 is 1200 mm. When 100 mirror parts 4 are manufactured, the peripheral length L of each molded mirror part 4 is within a range of 0.5 mm from 1200 mm to 1200.5 mm. That is, the outer diameter error of the fitting peripheral portion 10 is 0.16 mm or less, and it is shown that the processing accuracy is maintained at a very high level and the wrap portion 7 is stably formed. On the other hand, as a comparative example, as shown in FIG. 7, the same high-strength steel (SG365) is used, and a spatula drawing process and a pressing process similar to those of this embodiment are performed without providing a reduced diameter part at the opening peripheral edge b of the mirror part a. Thus, a mirror part a in which the wrap part c was formed was manufactured. The wrap portion c of the mirror portion a is bent inward from the fitting peripheral portion d toward the opening end e so as to serve as a guide for fitting with the body portion. When 100 mirror parts a of this comparative example were manufactured, the relationship between the peripheral length L of the fitting peripheral part d and the number N of manufactured parts is shown in FIG. Here, the set value of the peripheral length L of the fitting peripheral portion d of the comparative example is also 1200 mm, which is the same as that of the example. However, the peripheral length L of the fitting peripheral portion d in the manufacture of 100 pieces varies in a range of about 5.5 mm from 118.5 mm to 1204 mm. And the outer diameter error of this fitting peripheral part d is as large as about 1.8 mm, and the dispersion | variation is also large, and it is shown that shaping | molding of the lap | wrap part c is unstable. Moreover, in this comparative example, the number contained in the permissible range (1199.4 to 1200.6 mm) of the circumferential length L is small, and the defect rate is high. Thus, according to the lap part forming method of the present invention, the mirror part 4 having the wrap part 7 having a desired shape can be accurately and stably formed. Thereby, since the mirror part 4 can be appropriately fitted to the body part 2, it is possible to remarkably reduce the defect rate for manufacturing the mirror part 4 and to improve the production efficiency and the manufacturing cost. An excellent effect that it can be reduced occurs. Moreover, since high-tensile steel can be used appropriately, the pressure vessel can be made thinner and the pressure vessel can be further reduced in weight.
[0021]
Further, in such a method of forming the wrap portion 7, the pressure processing of the inclined pressure roll 25 is performed by pressing the reduced diameter portion 9 with the oblique pressure roll 25 having the pressure inclined surface 26. Since the reaction force (elastic force of the material) received by the inclined surface 26 from the reduced diameter portion 9 can be reduced, the fatigue life of the oblique pressure roll 25 can be remarkably improved. Thereby, expenses caused by maintenance and replacement of the oblique pressure roll 25 can be reduced, and the manufacturing cost can be further reduced.
[0022]
In the present invention, the reduced diameter portion 9 formed by cutting the opening periphery 10 of the mirror portion 4 is an inclined curved surface that slightly swells toward the opening end 12 as in the above embodiment. In addition, it is also possible to use an inclined surface that is a substantially straight surface, or an outer surface that is gradually thinned stepwise. Even in the reduced-diameter portion 9 cut into such an outer surface shape, the substantially curved reduced-diameter portion 9 that can appropriately exhibit the effects of the present invention can be formed by subsequent pressing. .
[0023]
Further, in the pressing process for forming the substantially curved reduced diameter portion 9, the pressure surface of the oblique pressure roll 26 may be convex in the out-of-plane direction in addition to the pressure inclined surface 26 of the above embodiment. It is also possible to use a pressure curved surface such as a slightly concave shape. By providing the pressure roll 26 with such a pressure curved surface, the reaction force received from the reduced diameter portion 9 can be further relaxed, which can contribute to an improvement in the fatigue life of the pressure roll 26.
[0024]
The present invention is not limited to the above embodiments, and can be implemented in various forms without departing from the gist of the present invention. The present invention can be applied not only to an automobile LPG container but also to other pressure containers 1 having a configuration in which a mirror part 4 is fitted to a body part 2.
[0025]
【The invention's effect】
As described above, in the present invention, after the lap portion of the pressure vessel mirror portion is formed on the peripheral edge of the opening by cutting, and the reduced diameter portion whose outer peripheral surface is thinned toward the opening end is formed, it is continuous with the reduced diameter portion. A molding method in which a fitting peripheral portion is formed by a spatula drawing process for processing the annular zone into a step shape, and the reduced diameter portion is deformed into a substantially curved shape by a pressing process (Claim 1). ). In this molding method, the reduced diameter portion has a rigidity distribution that gradually decreases in rigidity toward the opening end by cutting, and the reduced diameter portion is sequentially bent from the low rigidity portion by pressing. As a result of the deformation, the expansion deformation caused by the contraction deformation due to the spatula can be applied to the expansion deformation in the direction of the opening end of the reduced diameter portion. Further, it is possible to prevent deformation of the circumference and the like, and it is possible to accurately and stably mold the outer diameter and thickness of the fitting circumferential portion. Thus, it is possible to remarkably reduce the defect rate of the mirror part caused by the shape defect of the lap part, and to produce an excellent effect that the production efficiency of the mirror part can be improved and the manufacturing cost can be significantly reduced.
[0026]
Further, when the pressing process for making the reduced diameter portion substantially curved presses the pressure inclined surface inclined inward of the mirror portion toward the opening end direction along the mirror opening surface (claim). In 2), the pressure inclined surface to be pressed moves in the thickness direction of the reduced diameter portion in order from the opening end having the smallest rigidity of the reduced diameter portion, along with the curved deformation of the reduced diameter portion. Therefore, the reduced diameter portion can be successively curved and deformed sequentially from the opening end, and a smooth curved reduced diameter portion can be appropriately formed. Thereby, the expansion deformation caused by the spatula drawing process can be appropriately applied toward the opening end direction.
[0027]
In addition, when chamfering is performed on the outer peripheral end of the mirror portion and the chamfered portion is pressed at the initial stage of the pressing process in which the reduced diameter portion is substantially curved, (Claim 3) Since the pressure caused by the contact between the pressure jig at the initial stage of pressing and the reduced diameter portion can be relieved, it is possible to prevent the reduced diameter portion from being damaged. In addition, since the reaction force (elastic force of the material) applied to the pressure jig can be reduced, the fatigue life of the pressure jig can be improved, and the manufacturing cost can be reduced.
[0028]
According to such a method for forming a lap part of the present invention, it is possible to form the wrap part shape with high accuracy and stability, and it is also possible to use a high-strength material for the purpose of reducing the weight of the pressure vessel. (Effect of claim 1). Thus, when the mirror part is made of high-tensile steel having a tensile strength of 490 N / mm ² or more (Claim 4), expansion deformation caused by spatula drawing and a strong spring of high-tensile steel Since the back can be applied to stretching deformation and the like in the opening end direction of the reduced diameter portion, it is possible to appropriately prevent thickness increase deformation and circumferential length deformation of the fitting peripheral portion. Thus, the use of high-strength steel makes it possible to reduce the thickness of the mirror part, and thus the weight of the pressure vessel can be further reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a pressure vessel 1 comprising a mirror part 4 according to the present invention.
FIG. 2 is an enlarged cross-sectional view of a joint portion between a mirror part 4 and a body part 2;
FIG. 3 is a state diagram showing a holding state of the mirror part 4 in the molding of the wrap part 7;
FIG. 4 is an explanatory diagram showing cutting of the reduced diameter portion 9 according to the present invention.
FIG. 5 is an explanatory view showing a spatula drawing process and a pressing process according to the present invention.
FIG. 6 is a measurement diagram of a circumferential length L and a production number N showing the effect of the present invention.
FIG. 7 is an enlarged cross-sectional view of a mirror part a by a conventional wrap part forming method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pressure vessel 2 trunk | drum 4 mirror part 7 lap | wrap part 8 fitting circumference part 9 diameter reducing part 10 opening periphery 12 opening end 13 chamfering part 14 annular zone

Claims

A pressure vessel comprising a cylindrical shell constituting a body part and a substantially hemispherical shell constituting a mirror part respectively joined to the cylindrical ports at both ends thereof; In the method of forming the wrap portion of the pressure vessel mirror portion that forms a stepped wrap portion on the opening periphery of the mirror portion so that the outer peripheral surface of the mirror portion is fitted inside,
After forming the reduced diameter portion by cutting the outer peripheral surface of the mirror portion on the outer periphery of the mirror portion so as to become thinner toward the opening end,
The annular zone continuous to the reduced diameter portion is narrowed down stepwise toward the central axis of the mirror portion to form a fitting peripheral portion that is to be fitted to the inner peripheral surface of the tube opening, and the reduced diameter portion is A method for forming a wrap portion for a pressure vessel mirror portion, wherein the wrap portion is formed by pressing in a substantially curved shape toward the inside.

The pressing process for making the reduced diameter portion substantially curved presses a pressure slope inclined in the inner direction of the mirror portion toward the opening end direction along the mirror opening surface. Item 2. A method for forming a lap portion of a pressure vessel mirror portion according to Item 1.

The chamfering process is performed on the peripheral edge of the outer peripheral surface of the mirror part, and the chamfered part is pressed in the initial stage of the pressing process in which the reduced diameter part is substantially curved. The method for forming a lap portion of a pressure vessel mirror portion according to claim 2.

The method of forming a lap portion for a pressure vessel mirror portion according to any one of claims 1 to 3, wherein the mirror portion is made of high-tensile steel having a tensile strength of 490 N / mm ² or more.