JP2004308671A

JP2004308671A - Resin joint boot

Info

Publication number: JP2004308671A
Application number: JP2003098638A
Authority: JP
Inventors: Eiichi Imazu; 栄一今津; Takenori Oshita; 武範大下; Takeshi Ueda; 健上田; Hiroshi Ono; 宏大野
Original assignee: Toyo Tire and Rubber Co Ltd
Current assignee: Toyo Tire Corp
Priority date: 2003-04-01
Filing date: 2003-04-01
Publication date: 2004-11-04

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact resin joint boot excellent in durability. <P>SOLUTION: The resin joint boot is composed of a small diameter cylindrical part 12, a large diameter cylindrical part 14 and a bellows part 16 integrally connecting the small diameter cylindrical part 12 and the large cylindrical part 14. Each crest of a crest group 28 in the bellows part 16 near the small diameter cylindrical part is formed to have a height H1 to be lower than the height H2 of each crest of a crest group 30 near the large diameter cylindrical part. In the crest group 28 near the small diameter part 28, the each crest 24a, 24b, 24c are laid toward the side of the small diameter cylindrical part 12, and inclined surfaces 24a1, 24b1, 24c1 of a large diameter cylindrical part side of the each crest are formed substantially in parallel in a cross sectional shape along an axial direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、樹脂製ジョイントブーツに関し、詳しくは、自動車の等速ジョイントなどに用いられる蛇腹状の樹脂製ジョイントブーツに関する。
【０００２】
【従来の技術】
自動車や産業機械などの駆動シャフトのジョイントには、封入されているグリースを保持するため、あるいは塵埃等の進入を防ぐために、ジョイントブーツ（以下、単にブーツということもある。）が装着されている。
【０００３】
図４は、従来の樹脂製ジョイントブーツ１００の一例を示したものであり、図５は、その車両への装着状態を示した図である。このブーツ１００は、等速ジョイントの円筒形ハウジング部１に嵌着される大径筒部１０２と、該大径筒部１０２と離間して同軸的に配置されてシャフト２に嵌着される小径筒部１０４と、両者を一体に連結する蛇腹部１０６とからなり、熱可塑性エラストマーの射出ブロー成形等により一体に成形されている。大径筒部１０２と小径筒部１０４の外周面には、それぞれ固定用凹部１０８，１１０が設けられており、各凹部１０８，１１０にリング状の締付クランプ３，４を装着して外側から締め付けることにより、大径筒部１０２及び小径筒部１０４は、それぞれハウジング部１及びシャフト２の外周面に固定されるようになっている。
【０００４】
この種の樹脂製ジョイントブーツに関し、実開平６−８７７７６号公報及び特開平９−８９１０８号公報には、蛇腹部の圧縮側における大径筒部寄りの山同士の接触圧を低減してブーツの耐久性を向上するために、蛇腹部における小径筒部寄りの山群の各山の高さを大径筒部寄りの山群の各山の高さに比べて低く形成することが記載されている。そして、この構成により、広角度に屈曲変形した状態で回転させたときに、ブーツの圧縮側における小径筒部寄りの山群の展開長を小さくして、大径筒部寄りの山群の圧縮を助長させる働きを低減させ、もって、大径筒部寄りの山同士の接触圧を低減することができるとある。
【０００５】
しかしながら、上記のように単に小径筒部寄りの山群の高さを小さくするというだけでは、特に樹脂製ブーツを従来にもましてコンパクトにしようとしたときに、必ずしも十分な耐久性が確保できない場合がある。
【０００６】
また、従来、この種の樹脂製ジョイントブーツにおいては、広角度に屈曲変形した状態で回転させたときに、小径筒部においてその固定用凹部に亀裂が発生してしまう場合がある。これは、図６に示すように、小径筒部１０４では、広角度に屈曲変形させて回転したときに、隣接する蛇腹部１０６の端部１１２が矢印Ｘ０で示す方向に繰り返し変形を受けるため、それによる応力が固定用凹部１１０の蛇腹部側端部１１４に作用することによる。
【０００７】
【特許文献１】実開平６−８７７７６号公報
【０００８】
【特許文献２】特開平９−８９１０８号公報
【０００９】
【発明が解決しようとする課題】
本発明の目的は、コンパクトでありながら耐久性に優れる樹脂製ジョイントブーツを提供することにある。
【００１０】
【課題を解決するための手段】
本発明の樹脂製ジョイントブーツは、小径筒部と、大径筒部と、両者を一体に連結する蛇腹部とを備えてなる樹脂製ジョイントブーツにおいて、前記蛇腹部における小径筒部寄りの山群の各山の高さが大径筒部寄りの山群の各山の高さに比べて低く形成され、また、該小径筒部寄りの山群では、各山が小径筒部側に寝かされて、かつ各山の大径筒部側斜面が軸方向に沿った断面形状において互いに略平行に形成されたものである。
【００１１】
本発明のブーツでは、広角度に屈曲変形させたときに大きな応力が作用しやすい蛇腹部の大径筒部寄りの山群では各山の高さを確保して耐久性を維持しながら、小径筒部寄りの山群で各山の高さを低くしてコンパクト化を図ることができる。そして、特に、小径筒部寄りの山群において、各山を互いに略平行に小径筒部側に寝かせたことにより、ブーツ全体をコンパクト化した場合であっても、十分な耐久性を確保することが可能となる。
【００１２】
本発明のブーツにおいて、上記小径筒部寄りの山群の各山を小径筒部側に寝かせる際、各山の大径筒部側斜面の軸方向に対する傾斜角度は３０°以下であることが好ましく、より好ましくは１５°〜２５°の範囲内に設定することである。また、各山の大径筒部側斜面の断面形状を互いに略平行にする際、各山間での上記傾斜角度の差は１０°以下に設定されることが好ましく、より好ましくは５°以下である。
【００１３】
ところで、上記のように小径筒部寄りの山群において各山を互いに略平行に小径筒部側に寝かせた場合、これら小径筒部寄りの山群は圧縮方向に曲がりにくくなる。そのため、広角度に屈曲変形した状態で回転させたときに、小径筒部において固定用凹部の蛇腹部側端部に作用する応力が大きくなり、その部分の耐久性が悪化することが懸念される。そこで、小径筒部の外周面に設けた固定用凹部の蛇腹部側肩部に周方向に延びる切欠部を設けることにより、当該肩部のボリュームを低減して、該凹部の蛇腹部側の端部にかかる応力を緩和することができ、この部分での耐久性も確保することができる。
【００１４】
【発明の実施の形態】
以下、本発明の一実施形態に係る樹脂製ジョイントブーツ１０について図面に基づいて説明する。
【００１５】
本実施形態の樹脂製ジョイントブーツ１０は、自動車の等速ジョイントに装着される熱可塑性エラストマー樹脂製ブーツであり、図１に示すように、小径筒部１２と、該小径筒部１２と離間して同軸的に配置された大径筒部１４と、これら小径筒部１２と大径筒部１４を一体に連結する蛇腹部１６とからなる。
【００１６】
このブーツ１０のジョイントへの取付構造は、上記した図５に示す従来の構造と同様であり、従って、大径筒部１４は、等速ジョイントのハウジング部外周面に締付クランプによって外嵌固定される短円筒状をなしており、外周側にリング状の締付クランプを受け入れるための周方向に延びる固定用凹部１８を備える。また、小径筒部１２は、シャフトの外周面に締付クランプによって外嵌固定される短円筒状をなしており、外周側にはリング状の締付クランプを受け入れるための周方向に延びる固定用凹部２０を備える。なお、小径筒部１２は、大径筒部１４と同軸的に、即ち共通の中心線Ｏを持つように配置されている。
【００１７】
蛇腹部１６は、両端に口径差のある断面円形の蛇腹体であり、その内部にグリース封入空間２２を形成する。蛇腹部１６は、小径筒部１２側から順に第１山２４ａ、第１谷２６ａ、第２山２４ｂ、第２谷２６ｂ……というように、山と谷が交互に連続して形成された複数の山部及び谷部からなり、山部及び谷部の外径はそれぞれ、小径筒部１２から大径筒部１４へと順次に大きくなるように設定されている。山の数は５つ以上であることが好ましく、この実施形態では６つの山を備える６山６谷で構成されている。
【００１８】
蛇腹部１６は、大きく分けて小径筒部１２寄りの山群２８と大径筒部寄りの山群３０との２つの山群に形成されている。小径筒部１２寄りの山群２８には、小径筒部１２側から３山、即ち第１山２４ａ、第２山２４ｂ、第３山２４ｃが属する。また、大径筒部１４寄りの山群３０には、大径筒部１４側から３山、即ち第４山２４ｄ、第５山２４ｅ、第６山２４ｆが属する。なお、小径筒部寄りの山群２８は、蛇腹部が５山からなる場合には２山であることが好ましく、６山ないし７山からなる場合には３山であることが好ましい。
【００１９】
小径筒部寄りの山群２８では、各山２４ａ、２４ｂ、２４ｃの高さＨ１がいずれも大径筒部寄りの山群３０における各山２４ｄ、２４ｅ、２４ｆの高さＨ２に比べて低く形成されている。ここで、山の高さＨ１、Ｈ２とは、山の頂点とその両側の谷部の外周面側底点同士を結ぶ直線との距離をいう。
【００２０】
また、小径筒部寄りの山群２８では、各山２４ａ、２４ｂ、２４ｃが小径筒部１２側に寝かされ、かつ各山２４ａ、２４ｂ、２４ｃの大径筒部１４側斜面２４ａ１、２４ｂ１、２４ｃ１が軸方向に沿った断面形状（ブーツ中心線Ｏを通る断面形状）において互いに略平行に形成されている。すなわち、各山の大径筒部側斜面２４ａ１、２４ｂ１、２４ｃ１の軸方向に対する傾斜角度θ１、θ２、θ３がいずれも３０°以下、好ましくは１５°〜２５°に設定され、かつ、これら傾斜角度θ１、θ２、θ３の差（θ１〜θ３のうち最大の角度と最大の角度の差）が１０°以下、好ましくは５°以下に設定されている。具体的には、図１の実施形態では、θ１＝１９°、θ２＝２２°、θ３＝２０°に設定されている。
【００２１】
更に、上記山群２８における各山の小径筒部１２側斜面２４ａ２、２４ｂ２、２４ｃ２も、上記の大径筒部側斜面２４ａ１、２４ｂ１、２４ｃ１と同様、互いに略平行に形成されている。但し、これら小径筒部側斜面２４ａ２、２４ｂ２、２４ｃ２の傾斜角度は、大径筒部寄りの山群３０における各山２４ｄ、２４ｅ、２４ｆの小径筒部側斜面の傾斜角度と同程度か又はわずかに小さい程度に設定されており、従って、上記大径筒部側斜面の傾斜角度θ１、θ２、θ３よりも十分大きい。
【００２２】
小径筒部１２は、図２にその断面形状（ブーツ中心線Ｏを通る断面形状）が示されるように、外周面に締付クランプ４を受け入れるための固定用凹部２０を備えるとともに、内周面にシール用凸条３２を備える。
【００２３】
固定用凹部２０の軸方向両側の隅部２０ａ，２０ｂは湾曲面状に形成されている。また、固定用凹部２０の蛇腹部側隅部２０ａから上方、即ち半径方向外方に立ち上がった部分である蛇腹部側肩部２０ｃは全周にわたって切り欠かれており、これにより当該肩部２０ｃには周方向に延びる環状の切欠部３４が形成されている。
【００２４】
この切欠部３４は、小径筒部１２の外周面から半径方向内方に落ち込む縦面部３６と、該縦面部３６の内方端から固定用凹部２０の蛇腹部側壁面２０ｄに至る傾斜面部３８とからなる。傾斜面部３８は、縦面部３６の下端、即ち半径方向内方端から小径筒部１２の開口縁１２ａに向かって半径方向内方に傾斜しており、この実施形態では上記断面形状においてブーツ内側に向かって凸の湾曲面状に形成されている。
【００２５】
なお、この実施形態では切欠部３４に縦面部３６を設けているが、このような縦面部を設けることなく、小径筒部１２の外周面から固定用凹部２０の蛇腹部側壁面２０ｄにかけて単にテーパ面状又は湾曲面状に切り欠くことにより、切欠部３４を形成することもできる。
【００２６】
以上よりなる本実施形態のブーツ１０では、蛇腹部１６の大径筒部寄りの山群３０において各山２４ｄ、２４ｅ、２４ｆの高さを確保して耐久性を維持しながら、小径筒部寄りの山群２８で各山２４ａ、２４ｂ、２４ｃの高さを低くするとともに、これら各山２４ａ、２４ｂ、２４ｃを互いに略平行に小径筒部１２側に寝かせたことにより、ブーツ全体をコンパクト化した場合であっても、十分な耐久性を確保することが可能となる。
【００２７】
この点について詳述すると、図４に示すような従来のブーツ１００で、単に山谷の外径を小さくしてコンパクトを図った場合、蛇腹間の摩擦（蛇腹部の斜面同士の摩擦）やシャフトと谷部との摩擦などに起因する摩耗寿命が短くなって耐久性に劣ることになる。その原因は次のように考えられる。すなわち、図４に示す従来のブーツ１００では、蛇腹部１０６の５つの山がほぼ同形状であるため、これをブーツ単体で矢印Ｙで示す方向に屈曲変形させた場合、蛇腹部１０６の各山はほぼ均等に圧縮変形される。しかし、実際にジョイントに装着して屈曲変形させた場合には、図７に示すように、大径筒部寄りの山群１０６ａを中心に圧縮変形されることになる。このように従来のブーツ１００では、ジョイント装着時の屈曲形状がブーツ単体での屈曲形状と大きく異なるため、実際の使用時に大径筒部寄りの山群に不所望な応力が作用して、特にブーツをコンパクト化した場合に耐久性が劣ることになる。これに対し、本実施形態のブーツ１０では、小径筒部１２寄りの山群２８を上記のように形成したことにより、この部分が撓み変形しにくく、そのためブーツ単体で屈曲変形させた場合でも大径筒部寄りの山群３０を中心に圧縮変形される。従って、ブーツ単体での屈曲形状を、図３に示すジョイント装着時における屈曲形状に近づけることができるので、実際の使用時に大径筒部寄りの山群３０に作用する不所望な応力を抑制することができ、ブーツをコンパクトにした場合でも耐久性を確保することが可能となる。
【００２８】
以上の効果を確認するために、図１に示す実施形態のブーツ、図４に示す従来のブーツ、及び、図８に示す比較例のブーツ（従来のブーツで単に山谷の外径を小さくしてコンパクト化したブーツ）について比較実験を行った。
【００２９】
実験では、実施形態のブーツについては、最大外径Ｄ１を８７．１ｍｍ、第１山２４ａの外径Ｄ２を５０．１ｍｍ、軸方向寸法Ｌを１０６．９ｍｍとした。また、従来のブーツについては、最大外径Ｄ１を９１．４ｍｍ、第１山の外径Ｄ２を５７．１ｍｍ、軸方向寸法Ｌを１１５．９ｍｍとした。更に、比較例のブーツについては、最大外径Ｄ１を８８．０ｍｍ、第１山の外径Ｄ２を５３．０ｍｍ、軸方向寸法Ｌを１０８．０ｍｍとした。そして、ブーツ成形材料として熱可塑性エラストマーを用いて、各ブーツを成形し、得られたブーツについて耐久性を評価した。耐久性の評価は、各ブーツを等速ジョイントに組付け、雰囲気温度＝１００℃、ジョイント角＝４０°、回転数＝６００ｒ．ｐ．ｍ．として、高温雰囲気中での角度固定回転耐久試験により行った。結果を表１に示す。また、表１には、ブーツの重量及び内容積についても、従来のブーツを１００とした値を示した（値が小さいほど重量及び内容積が小さいことを示す）。
【００３０】
【表１】

【００３１】
表１に示すように、従来のブーツを単にコンパクト化した比較例のブーツでは、耐久試験開始後２０時間にて蛇腹部の大径筒部寄りの谷部で疲労により破損した。これに対し、実施形態のブーツは、従来のブーツに比べて大幅にコンパクト化されたものでありながら、従来のブーツと同様、耐久試験開始後３０時間においても破損は見られず、耐久性の目標値を達成するものであった。
【００３２】
このようにジョイントブーツをコンパクトにすることは、ブーツ自体の軽量化だけでなく、内容積を減らして充填するグリース量を減らすことができ、そのためコスト削減とグリース重量に基づく軽量化にも寄与することができる。
【００３３】
また、上記した本実施形態のジョイントブーツ１０では、切欠部３４を設けたことにより、固定用凹部２０における蛇腹部側肩部２０ｃのボリュームが低減されている。そのため、図２に示すように蛇腹部１６の第１山２４ａに矢印Ｘで示す方向に繰り返し変形を付与した場合であっても、固定用凹部２０の蛇腹部側隅部２０ａにかかる応力が緩和される。従って、広角度に屈曲変形した状態で回転させたとしても、小径筒部１２においてその固定用凹部２０に亀裂が発生しにくく、よって、この部分の耐久性にも優れる。
【００３４】
この点を確認するために、図１に示す切欠部３４を設けたブーツと、切欠部３４を設けていないブーツとについて、有限要素法（ＦｉｎｉｔｅＥｌｅｍｅｎｔａｎａｌｙｓｉｓＭｅｔｈｏｄ）による解析（以下、ＦＥＭ解析という）を用いて、ジョイント角（ハウジング部の中心線とシャフトの中心線のなす角度）＝４０°に変形した場合における応力の分布についてシミュレーションを行った。結果は、切欠部３４のない場合、小径筒部における固定用凹部の蛇腹部側端部にかかる最大応力振幅値（蛇腹部側端部の断面Ｒに沿った方向に作用する主応力の振幅値）が１．１３３ｋｇ／ｍｍ^２であるのに対し、切欠部３４を設けた場合、該最大応力振幅値０．７４５ｋｇ／ｍｍ^２であり、低減されていた。
【００３５】
また、切欠部３４有りと無しのそれぞれについて、熱可塑性エラストマーを用いてブーツを成形し、得られた各ブーツについて、小径筒部での耐久性を評価する試験を行った。試験は、各ブーツを等速ジョイントに組付け、雰囲気温度＝１００℃、ジョイント角＝４０°、回転数＝６００ｒ．ｐ．ｍ．として行った。その結果、切欠部３４無しの場合、試験開始後２０時間にて小径筒部における固定用凹部の蛇腹部側隅部から破損したのに対し、切欠部３４有りの場合、試験開始後３０時間においても固定用凹部において破損が発生しなかった。
【００３６】
【発明の効果】
以上説明したように、本発明によれば、コンパクトでありながら耐久性に優れた樹脂製ジョイントブーツが得られる。
【図面の簡単な説明】
【図１】本発明の一実施形態に係る樹脂製ジョイントブーツの半断面半側面図である。
【図２】図１のＡ部拡大図である。
【図３】実施形態のブーツのＦＥＭ解析によるシミュレーション図（ジョイント角＝４０°）である。
【図４】従来の樹脂製ジョイントブーツの半断面半側面図である。
【図５】従来のブーツの等速ジョイントへの装着状態を示す断面図である。
【図６】従来のブーツにおける小径筒部の拡大断面図である。
【図７】従来のブーツのＦＥＭ解析によるシミュレーション図（ジョイント角＝４０°）である。
【図８】比較例のブーツの半断面半側面図である。
【符号の説明】
１０……樹脂製ジョイントブーツ
１２……小径筒部
１４……大径筒部
１６……蛇腹部
２０……固定用凹部
２４ａ１、２４ｂ１、２４ｃ１……小径筒部寄りの山群の大径筒部側斜面
２８……小径筒部寄りの山群
３０……大径筒部寄りの山群
３４……切欠部
Ｈ１……小径筒部寄りの山群の各山の高さ
Ｈ２……大径筒部寄りの山群の各山の高さ
θ１、θ２、θ３……大径筒部側斜面の傾斜角度[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a resin joint boot, and more particularly, to a bellows-shaped resin joint boot used for a constant velocity joint of an automobile or the like.
[0002]
[Prior art]
A joint boot (hereinafter, sometimes simply referred to as a boot) is attached to a joint of a drive shaft of an automobile, an industrial machine, or the like in order to hold grease enclosed therein or to prevent dust or the like from entering. .
[0003]
FIG. 4 shows an example of a conventional resin joint boot 100, and FIG. 5 is a diagram showing a state where the boot is mounted on a vehicle. The boot 100 has a large-diameter cylindrical portion 102 fitted to the cylindrical housing portion 1 of a constant velocity joint, and a small-diameter cylindrical member 102 coaxially arranged separately from the large-diameter cylindrical portion 102 and fitted to the shaft 2. It is composed of a cylindrical portion 104 and a bellows portion 106 for integrally connecting the two, and is integrally formed by injection blow molding of a thermoplastic elastomer. The outer peripheral surfaces of the large-diameter cylindrical portion 102 and the small-diameter cylindrical portion 104 are provided with fixing

concave portions

108 and 110, respectively, and ring-shaped tightening

clamps

3 and 4 are attached to the

concave portions

108 and 110, respectively. By tightening, the large-diameter cylindrical portion 102 and the small-diameter cylindrical portion 104 are fixed to the outer peripheral surfaces of the housing portion 1 and the shaft 2, respectively.
[0004]
Regarding this type of resin joint boot, Japanese Utility Model Laid-Open Publication No. Hei 6-87776 and Japanese Patent Laid-Open Publication No. Hei 9-89108 disclose that the contact pressure between the peaks near the large-diameter cylindrical part on the compression side of the bellows part is reduced. In order to improve the durability, it is described that the height of each peak of the mountain group near the small-diameter cylindrical portion in the bellows portion is formed lower than the height of each mountain of the mountain group near the large-diameter cylindrical portion. I have. With this configuration, when the boot is rotated in a state of being bent and deformed at a wide angle, the development length of the mountains near the small-diameter cylinder on the compression side of the boot is reduced, and the compression of the mountains near the large-diameter cylinder is reduced. The contact pressure between the peaks near the large-diameter cylindrical portion can be reduced.
[0005]
However, simply reducing the height of the peaks near the small-diameter cylindrical portion as described above does not always ensure sufficient durability, especially when trying to make the resin boots more compact than ever before. There is.
[0006]
Conventionally, in a resin joint boot of this type, when it is rotated in a state of being bent and deformed at a wide angle, a crack may be generated in a fixing concave portion in a small-diameter cylindrical portion. This is because, as shown in FIG. 6, in the small-diameter cylindrical portion 104, the end portion 112 of the adjacent bellows portion 106 is repeatedly deformed in the direction indicated by the arrow X <b> 0 when being rotated while being bent at a wide angle, The resulting stress acts on the bellows-side end 114 of the fixing recess 110.
[0007]
[Patent Document 1] Japanese Utility Model Laid-Open No. 6-87776
[Patent Document 2] Japanese Patent Application Laid-Open No. 9-89108
[Problems to be solved by the invention]
An object of the present invention is to provide a resin joint boot that is compact and has excellent durability.
[0010]
[Means for Solving the Problems]
A resin joint boot according to the present invention is a resin joint boot including a small-diameter tubular portion, a large-diameter tubular portion, and a bellows portion integrally connecting the small-diameter tubular portion, wherein a mountain group near the small-diameter tubular portion in the bellows portion is provided. The height of each peak is formed to be lower than the height of each peak of the mountain group near the large-diameter cylindrical portion, and in the mountain group near the small-diameter cylindrical portion, each mountain lies on the small-diameter cylindrical portion side. In addition, the large-diameter cylindrical-portion-side slope of each mountain is formed substantially parallel to each other in a cross-sectional shape along the axial direction.
[0011]
In the boots of the present invention, a large diameter of the bellows near the large-diameter cylindrical portion on which a large stress is likely to act when bent and deformed at a wide angle secures the height of each peak and maintains durability while maintaining a small diameter. It is possible to reduce the height of each mountain in the mountain group near the cylinder, thereby achieving compactness. In particular, in the mountain group near the small-diameter cylindrical portion, by laying each mountain substantially parallel to each other on the small-diameter cylindrical portion side, sufficient durability is ensured even when the entire boot is made compact. Becomes possible.
[0012]
In the boot of the present invention, when each mountain of the mountain group near the small-diameter cylindrical portion is laid on the small-diameter cylindrical portion side, the inclination angle of the large-diameter cylindrical portion-side slope of each mountain with respect to the axial direction is preferably 30 ° or less. , More preferably within the range of 15 ° to 25 °. Further, when making the cross-sectional shapes of the large-diameter cylindrical portion side slopes of each mountain substantially parallel to each other, it is preferable that the difference of the above-mentioned tilt angle between each mountain is set to 10 ° or less, more preferably 5 ° or less. is there.
[0013]
By the way, when the peaks in the group of mountains near the small-diameter tube portion are laid on the small-diameter tube portion side substantially in parallel with each other, the mountains near the small-diameter tube portion are unlikely to bend in the compression direction. For this reason, when rotating in a state of being bent and deformed at a wide angle, the stress acting on the bellows-side end of the fixing concave portion in the small-diameter cylindrical portion becomes large, and there is a concern that the durability of that portion is deteriorated. . Therefore, by providing a notch extending in the circumferential direction at the bellows side shoulder of the fixing recess provided on the outer peripheral surface of the small diameter cylindrical portion, the volume of the shoulder is reduced, and the bellows side end of the recess is provided. The stress applied to the portion can be reduced, and the durability at this portion can be ensured.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a resin joint boot 10 according to an embodiment of the present invention will be described with reference to the drawings.
[0015]
The resin joint boot 10 of the present embodiment is a boot made of a thermoplastic elastomer resin mounted on a constant velocity joint of an automobile. As shown in FIG. And a large-diameter cylindrical portion 14 coaxially arranged, and a bellows portion 16 for integrally connecting the small-diameter cylindrical portion 12 and the large-diameter cylindrical portion 14.
[0016]
The mounting structure of the boot 10 to the joint is the same as the conventional structure shown in FIG. 5 described above. Therefore, the large-diameter cylindrical portion 14 is externally fixed to the outer peripheral surface of the housing portion of the constant velocity joint by a clamp. It has a fixing concave portion 18 extending in the circumferential direction for receiving a ring-shaped tightening clamp on the outer peripheral side. The small-diameter cylindrical portion 12 has a short cylindrical shape which is externally fitted and fixed to the outer peripheral surface of the shaft by a tightening clamp, and has a circumferentially extending fixing portion for receiving a ring-shaped tightening clamp on the outer peripheral side. A recess 20 is provided. The small-diameter cylindrical portion 12 is arranged coaxially with the large-diameter cylindrical portion 14, that is, so as to have a common center line O.
[0017]
The bellows portion 16 is a bellows body having a circular cross section with a difference in diameter at both ends, and forms a grease sealed space 22 therein. The bellows portion 16 includes a plurality of peaks and valleys formed alternately and continuously, such as a first peak 24a, a first valley 26a, a second peak 24b, a second valley 26b, in this order from the small-diameter cylindrical portion 12 side. The outer diameters of the peaks and valleys are set so as to gradually increase from the small-diameter cylindrical portion 12 to the large-diameter cylindrical portion 14, respectively. The number of peaks is preferably five or more. In this embodiment, the peaks are composed of six peaks and six valleys having six peaks.
[0018]
The bellows portion 16 is roughly divided into two mountain groups, a mountain group 28 near the small-diameter cylindrical portion 12 and a mountain group 30 near the large-diameter cylindrical portion. Three peaks, that is, a first peak 24a, a second peak 24b, and a third peak 24c, belong to the peak group 28 near the small-diameter tube portion 12 from the small-diameter tube portion 12 side. Also, three peaks, that is, a fourth peak 24d, a fifth peak 24e, and a sixth peak 24f, belong to the peak group 30 near the large-diameter tubular portion 14 from the large-diameter tubular portion 14 side. The number of peak groups 28 near the small-diameter cylindrical portion is preferably two when the bellows portion is composed of five peaks, and is preferably three when the bellows portion is composed of six or seven peaks.
[0019]
In the mountain group 28 closer to the small-diameter cylindrical portion, the height H1 of each of the

peaks

24a, 24b, 24c is formed to be lower than the height H2 of each

mountain

24d, 24e, 24f in the mountain group 30 closer to the large-diameter cylindrical portion. Have been. Here, the peak heights H1 and H2 refer to the distance between the peak of the peak and the straight line connecting the bottom points on the outer peripheral surface of the valleys on both sides thereof.
[0020]
In the mountain group 28 near the small-diameter cylindrical portion, the

peaks

24a, 24b, and 24c are laid on the small-diameter cylindrical portion 12 side, and the slopes 24a1, 24b1 of the

peaks

24a, 24b, and 24c on the large-diameter cylindrical portion 14 side. 24c1 are formed substantially parallel to each other in a cross-sectional shape along the axial direction (a cross-sectional shape passing through the boot center line O). That is, the inclination angles θ1, θ2, θ3 of the large-diameter cylindrical portion side slopes 24a1, 24b1, 24c1 of each mountain with respect to the axial direction are all set to 30 ° or less, preferably 15 ° to 25 °, and these inclination angles are set. The difference between θ1, θ2, and θ3 (the difference between the maximum angle and the maximum angle among θ1 to θ3) is set to 10 ° or less, preferably 5 ° or less. Specifically, in the embodiment of FIG. 1, θ1 = 19 °, θ2 = 22 °, and θ3 = 20 °.
[0021]
Further, the slopes 24a2, 24b2, 24c2 on the small-diameter cylindrical portion 12 side of each mountain in the mountain group 28 are also formed substantially parallel to each other, similarly to the above-described large-diameter cylindrical portion-side slopes 24a1, 24b1, 24c1. However, the inclination angles of the small-diameter cylinder-side slopes 24a2, 24b2, and 24c2 are approximately the same as or slightly smaller than the inclination angles of the small-diameter cylinder-side slopes of the

peaks

24d, 24e, and 24f in the mountain group 30 near the large-diameter cylinder. Therefore, it is sufficiently larger than the inclination angles θ1, θ2, and θ3 of the large-diameter cylindrical-portion-side inclined surface.
[0022]
The small-diameter cylindrical portion 12 is provided with a fixing recess 20 for receiving the tightening clamp 4 on an outer peripheral surface and an inner peripheral surface as shown in a sectional shape (a sectional shape passing through the boot center line O) in FIG. Is provided with a ridge 32 for sealing.
[0023]
The

corner portions

20a and 20b on both sides in the axial direction of the fixing concave portion 20 are formed in a curved surface shape. In addition, the bellows side shoulder 20c, which is a portion that rises upward from the bellows side corner 20a of the fixing concave portion 20, that is, the portion that rises outward in the radial direction, is cut out over the entire circumference, thereby forming the shoulder 20c. Is formed with an annular cutout 34 extending in the circumferential direction.
[0024]
The notch portion 34 includes a vertical surface portion 36 that falls radially inward from the outer peripheral surface of the small-diameter cylindrical portion 12, an inclined surface portion 38 that extends from an inner end of the vertical surface portion 36 to the bellows side wall surface 20 d of the fixing recess 20. Consists of The inclined surface portion 38 is inclined radially inward from the lower end of the vertical surface portion 36, that is, from the radially inner end to the opening edge 12a of the small-diameter cylindrical portion 12, and in this embodiment, in the cross-sectional shape described above, inside the boot. It is formed in the shape of a convex curved surface.
[0025]
In this embodiment, the notch portion 34 is provided with the vertical surface portion 36. However, without providing such a vertical surface portion, a taper is simply provided from the outer peripheral surface of the small-diameter cylindrical portion 12 to the bellows side wall surface 20d of the fixing concave portion 20. The notch 34 can also be formed by cutting out in a plane or curved plane.
[0026]
In the boot 10 of the present embodiment configured as described above, the

peaks

24d, 24e, and 24f of the peaks 30 near the large-diameter cylindrical portion of the bellows portion 16 are secured and the durability is maintained while maintaining the height of the

peaks

24d, 24e, and 24f. The height of each of the

peaks

24a, 24b, and 24c is reduced in the peak group 28, and the

peaks

24a, 24b, and 24c are laid on the small-diameter tube portion 12 side substantially in parallel with each other, so that the entire boot is made compact. Even in this case, sufficient durability can be ensured.
[0027]
This point will be described in detail. In the conventional boot 100 shown in FIG. 4, when the outer diameters of the peaks and valleys are simply reduced to achieve compactness, friction between the bellows (friction between the slopes of the bellows) and shaft and The wear life resulting from friction with the valleys is shortened, resulting in poor durability. The cause is considered as follows. That is, in the conventional boot 100 shown in FIG. 4, since the five peaks of the bellows portion 106 have substantially the same shape, when these are bent and deformed in the direction indicated by the arrow Y by the boot alone, each peak of the bellows portion 106 is deformed. Are almost uniformly compressed and deformed. However, when it is actually attached to a joint and bent and deformed, as shown in FIG. 7, it is compressed and deformed around the mountain group 106 a near the large-diameter cylindrical portion. As described above, in the conventional boot 100, since the bent shape at the time of mounting the joint is significantly different from the bent shape of the boot alone, undesired stress acts on the peaks near the large-diameter cylindrical portion during actual use, and particularly, If the boots are made compact, the durability will be poor. On the other hand, in the boot 10 of the present embodiment, since the peaks 28 near the small-diameter cylindrical portion 12 are formed as described above, this portion is unlikely to be flexibly deformed. It is compressed and deformed around the mountain group 30 near the cylindrical portion. Therefore, the bent shape of the boot alone can be made close to the bent shape at the time of mounting the joint shown in FIG. 3, thereby suppressing an undesired stress acting on the mountain group 30 near the large-diameter cylindrical portion during actual use. Therefore, durability can be ensured even when the boot is made compact.
[0028]
In order to confirm the above effects, the boot of the embodiment shown in FIG. 1, the conventional boot shown in FIG. 4, and the boot of the comparative example shown in FIG. A comparative experiment was performed on a compact boot.
[0029]
In the experiment, regarding the boot of the embodiment, the maximum outer diameter D1 was 87.1 mm, the outer diameter D2 of the first peak 24a was 50.1 mm, and the axial dimension L was 106.9 mm. Further, for the conventional boot, the maximum outer diameter D1 was 91.4 mm, the outer diameter D2 of the first mountain was 57.1 mm, and the axial dimension L was 115.9 mm. Further, with respect to the boot of the comparative example, the maximum outer diameter D1 was 88.0 mm, the outer diameter D2 of the first mountain was 53.0 mm, and the axial dimension L was 108.0 mm. Each boot was molded using a thermoplastic elastomer as a boot molding material, and the resulting boots were evaluated for durability. The durability was evaluated by assembling each boot to a constant velocity joint, ambient temperature = 100 ° C., joint angle = 40 °, rotation speed = 600 rpm. p. m. The test was performed by an angle fixed rotation endurance test in a high temperature atmosphere. Table 1 shows the results. Table 1 also shows the weight and the internal volume of the boot, assuming that the conventional boot is 100 (the smaller the value, the smaller the weight and the internal volume).
[0030]
[Table 1]

[0031]
As shown in Table 1, the boot of the comparative example in which the conventional boot was simply made compact was damaged by fatigue in the valley near the large-diameter cylindrical portion of the bellows portion 20 hours after the start of the durability test. On the other hand, the boot of the embodiment is much more compact than the conventional boot, but does not show any damage even 30 hours after the start of the durability test, similarly to the conventional boot. The target was achieved.
[0032]
Making the joint boot compact in this way not only reduces the weight of the boot itself, but also reduces the amount of grease to be filled by reducing the internal volume, thus contributing to cost reduction and weight reduction based on grease weight. be able to.
[0033]
In addition, in the joint boot 10 of the above-described embodiment, the provision of the notch 34 reduces the volume of the bellows-side shoulder 20 c in the fixing recess 20. Therefore, even when the first peak 24a of the bellows 16 is repeatedly deformed in the direction indicated by the arrow X as shown in FIG. 2, the stress applied to the bellows-side corner 20a of the fixing recess 20 is reduced. Is done. Therefore, even if the rotation is performed in a state of being bent and deformed at a wide angle, the fixing recess 20 in the small-diameter cylindrical portion 12 is less likely to crack, and thus the durability of this portion is also excellent.
[0034]
In order to confirm this point, an analysis using a finite element analysis method (hereinafter, referred to as FEM analysis) is performed on a boot provided with the notch 34 and a boot not provided with the notch 34 shown in FIG. Was used to simulate the distribution of stress when the joint angle (the angle between the center line of the housing part and the center line of the shaft) = 40 °. As a result, when there is no notch 34, the maximum stress amplitude value applied to the bellows side end of the fixing concave portion in the small-diameter cylindrical portion (the amplitude value of the main stress acting in the direction along the section R of the bellows side end) ) Is 1.133 kg / mm ² , whereas when the notch 34 is provided, the maximum stress amplitude value is 0.745 kg / mm ^2, which is reduced.
[0035]
In addition, a boot was formed using a thermoplastic elastomer with and without the notch 34, and a test was performed to evaluate the durability of the obtained boot in a small-diameter cylindrical portion. In the test, each boot was assembled on a constant velocity joint, the ambient temperature was 100 ° C., the joint angle was 40 °, and the number of revolutions was 600 rpm. p. m. Went as. As a result, in the case where there was no notch 34, it was damaged from the bellows side corner of the fixing concave portion in the small-diameter cylindrical portion 20 hours after the start of the test, whereas in the case where there was the notch 34, it was 30 hours after the start of the test. No damage occurred in the fixing recess.
[0036]
【The invention's effect】
As described above, according to the present invention, a resin joint boot excellent in durability while being compact can be obtained.
[Brief description of the drawings]
FIG. 1 is a half sectional half side view of a resin joint boot according to an embodiment of the present invention.
FIG. 2 is an enlarged view of a portion A in FIG.
FIG. 3 is a simulation diagram (joint angle = 40 °) of the boot of the embodiment by FEM analysis.
FIG. 4 is a half sectional half side view of a conventional resin joint boot.
FIG. 5 is a cross-sectional view showing a conventional boot attached to a constant velocity joint.
FIG. 6 is an enlarged cross-sectional view of a small-diameter cylindrical portion of a conventional boot.
FIG. 7 is a simulation diagram (joint angle = 40 °) of a conventional boot by FEM analysis.
FIG. 8 is a half sectional half side view of a boot of a comparative example.
[Explanation of symbols]
10 resin joint boot 12 small-diameter cylindrical portion 14 large-diameter cylindrical portion 16 bellows 20 fixing recesses 24a1, 24b1, 24c1 large-diameter cylindrical portion near the small-diameter cylindrical portion Side slope 28 Mountain group 30 near the small-diameter cylinder portion Mountain group 34 near the large-diameter cylinder portion Notch H1 Height of each mountain of the mountain group near the small-diameter cylinder portion H2 Large-diameter cylinder Heights θ1, θ2, θ3 of the peaks of the mountain group near the slope: the inclination angle of the large-diameter cylinder-side slope

Claims

In a resin joint boot including a small-diameter tubular portion, a large-diameter tubular portion, and a bellows portion that integrally connects the two,
The height of each mountain of the mountain group near the small-diameter cylindrical portion in the bellows portion is formed lower than the height of each mountain of the mountain group near the large-diameter cylindrical portion,
In the mountain group near the small-diameter cylindrical portion, each mountain is laid on the small-diameter cylindrical portion side, and the large-diameter cylindrical portion-side slope of each mountain is formed substantially parallel to each other in a cross-sectional shape along the axial direction. Resin joint boots characterized by that.

In the mountain group near the small-diameter cylinder portion, the inclination angle of each mountain with respect to the axial direction of the large-diameter cylinder-side slope is set to 30 ° or less, and the difference between the inclination angles of each mountain portion is 10 ° or less. The resin joint boot according to claim 1, wherein:

The resin joint boot according to claim 1, wherein a fixing recess is provided on an outer peripheral surface of the small-diameter tubular portion, and a notch extending in a circumferential direction is provided on a bellows-side shoulder of the recess.