JP2003191317A

JP2003191317A - Manufacturing method of plastic boot for constant velocity joint

Info

Publication number: JP2003191317A
Application number: JP2001398551A
Authority: JP
Inventors: Katsushi Saito; 克志齋藤; Eiichi Imazu; 栄一今津; Hiroshi Ono; 宏大野; Yoshikazu Tsujimoto; 芳和辻本
Original assignee: Toyo Tire and Rubber Co Ltd
Current assignee: Toyo Tire Corp
Priority date: 2001-12-27
Filing date: 2001-12-27
Publication date: 2003-07-08
Anticipated expiration: 2021-12-27
Also published as: JP3890466B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a plastic boot wherein a bellows part is molded in a prescribed shape and a product fault is reduced by preventing air leakage in blow molding so as to obtain a sufficient blowing pressure. <P>SOLUTION: The plastic boot for a constant velocity joint has a constitution wherein the inner periphery of a large-diameter-side fitting part 52 to be fitted to the outer periphery of an outer case 21 of the joint is formed in a noncircular shape corresponding to the outer periphery of the outer case 21 and a thick wall part 55 formed to be protuberant inward and a thin wall part 56 are formed alternately. In the manufacturing method of this boot, a molded parison 42 provided with a skirt part 57 being continuous along the outer peripheral end part of the large-diameter-side fitting part 52 is molded in molding. In forming, the large-diameter-side fitting part 52 and the skirt part 57 of the molded parison 42 are held between an inner mold 61 and a hollow mold 72 and subjected to blow forming. <P>COPYRIGHT: (C)2003,JPO

Description

【発明の詳細な説明】【０００１】【発明の属する技術分野】本発明は、入力側と出力側の
一方にトリポート、他方にアウターケースを備える等速
ジョイントにおいて使用される樹脂製ブーツの製造方法
に関するものである。【０００２】【従来の技術】車輌のドライブシャフト等に用いられる
等速ジョイントの一つとして、トリポートタイプのジョ
イントがあり、例えば前輪駆動自動車の駆動用に使用さ
れている。【０００３】このトリポートタイプの等速ジョイント
は、図７および図８に示すように、入力側と出力側の一
方のシャフト（１０）に、ローラ（１１）を持つ３本の
トラニオン（１２）を軸直角方向に突設して構成したト
リポート（１３）と、他方のシャフト（２０）の端部に
設けたアウターケース（２１）とからなり、アウターケ
ース（２１）はその内周に前記トリポート（１３）と対
応する軸方向の３本の摺動溝（２２）を有し、前記トリ
ポート（１３）のローラ（１１）が前記摺動溝（２２）
に嵌め合わされて、軸方向の摺動および両シャフトの角
度付けを可能にしながら、回転トルクを伝達できるよう
に構成されている。【０００４】この等速ジョイントにおいても、ジョイン
ト内部への塵埃や異物の侵入防止のために、一般にアウ
ターケース（２１）からトリポート（１３）側のシャフ
ト（１０）の部分を覆うように適度に伸縮や曲げ変形が
可能な蛇腹状をなす樹脂製ブーツ（１）が設けられてい
る。【０００５】かかる樹脂製ブーツ（１）は、軸方向の一
端部が前記アウターケース（２１）の外周に嵌着されて
リング状バンド等の締付け部材（２５）により固定され
る径大の取付部（５２）として形成され、また他端部が
トリポート側のシャフト（１０）に固定される径小の取
付部（５３）として形成され、前記両取付部間の蛇腹部
（５４）とともに樹脂材料により一体に成形されてい
る。【０００６】ところで、前記アウターケース（２１）
は、図に示すように内周の摺動溝（２２）の配置に対応
して、外周形状も周方向に凹凸形状をなしており、その
ためこれに固定される樹脂ブーツ（１）は、組み付け状
態の安定性やシール性を確保するために、その内周を前
記アウターケース（２１）外周の形状に対応させて締め
付け固定することから、径大側取付部（５２）の内周
を、前記アウターケース（２１）外周の凹凸形状に対応
した形状をなし、内側への凸状をなす厚肉部（５５）と
薄肉部（５６）とが交互に形成されている。【０００７】従来、上記樹脂ブーツ（１）の一般的な成
形方法は、図９の金型概略断面図に示す射出成形法によ
り１次成形品のパリソン（４０）が成形される。すなわ
ち、溶融樹脂が射出成型機（８４）の先端部に設けられ
た射出ノズル（８１）から内金型（６１）と外金型（７
１）の間のキャビテー内に径小側取付部（５３）側から
射出され、樹脂ブーツ（１）の１次成形パリソン（４
０）が成形される。なお、前記内金型（６１）は、本体
（６２）と勘合リング（６３）とブーツ形成部（６４）
から構成されている。【０００８】この１次成形パリソン（４０）では、樹脂
ブーツ（１）の径小側取付部（５３）および径大側取付
部（５２）は所定形状に成形されるが、蛇腹部（５４）
は最終形状をなしたものではない。また、径大側取付部
（５２）にはアウターケースの外周に嵌着されてリング
状バンド等の締め付け部材（２５）により固定されるた
めの周方向の凹部（８）が形成され、外金型（７１）の
径大側取付部にそのための凸部（７３）が設けられてい
る次いで、上記成形パリソン（４０）は、１次成形後の柔
軟性を保ち内金型（６１）に装着されたままの状態で、
図１０に示すインジェクションブロー成形法による２次
ブロー成形用の外金型となる中空金型（７２）内に移動
され、空気入り口（８２）からブロー管（８３）を通じ
て金型内に空気が吹き込まれる。空気は中空金型（７
２）と内金型（６１）の嵌に挟まれ締め付けられた径大
側取付部（５２）を終端部として、パリソン先端部（４
１）からパリソン（４０）の内周部と内金型（６１）の
間に吹き込まれる。【０００９】柔軟状態にある蛇腹部（５４）の樹脂は、
吹き込まれた空気のブロー圧力により前記中空金型（７
２）内面に押し付けられ（図１１）、蛇腹部（５４）は
中空金型（７２）の内面に形成された蛇腹形状にブロー
成形され２次成形品が成形される。【００１０】ところが、図１２および図１３の径大側取
付部（５２）の拡大図に示すように、前記中空金型（７
２）と内金型（６１）によって締め付けられた径大側取
付部（５２）において、前記パリソン（４０）と前記内
金型（６１）の間にわずかの隙間（７９）を生じ、パリ
ソン（４０）と内金型（６１）の間に吹き込まれた空気
は、この隙間（７９）を通路として空気漏れを発生する
ことがある。これは、樹脂材料によるブーツの剛性がゴ
ム材に比べて高く、前記中空金型（７２）と内金型（６
１）の間に挟まれた径大側取付部（５２）の締め付け力
が不足して隙間（７９）を生じ、ブロー圧力による空気
漏れを発生するものである。【００１１】この空気漏れにより、前記パリソン（４
０）と内金型（６１）との間のブロー圧力が低下してパ
リソン（４０）を中空金型（７２）に押し付けるブロー
圧力が不足し、特に径大側取付部（５２）側の蛇腹部
（５４）に膨らみが不足した蛇腹部（５８）が発生し、
中でも第１山目に膨らみ不足が生じやすく所定の蛇腹形
状が得られず製品不良の原因となっている。【００１２】特に、上記空気漏れは、径大側取付部（５
２）の内周に交互に設けられた厚肉部（５５）と薄肉部
（５６）の内、厚みが薄く締め付け力の不足しがちな薄
肉部（５６）において前記隙間（７９）が生じやすく空
気漏れを発生しやすい。【００１３】【発明が解決しようとする課題】本発明は、上記問題に
鑑みてなされたものであり、トリポートタイプの等速ジ
ョイントに用いられる樹脂材料により一体成形して得ら
れる樹脂製ブーツの製造方法であり、特にブロー成形時
の径大側取付部からの空気漏れによる蛇腹部の膨らみ不
足を防止して所定形状の樹脂ブーツを成形することがで
き、製品不良の発生を低減することのできる樹脂製ブー
ツの製造方法を提供することを目的とする。【００１４】【課題を解決するための手段】本発明は、等速ジョイン
トのアウターケース外周に取付られる軸方向一端側の径
大側取付部と、トリポート側のシャフトに取り付けられ
る径小側取付部と、前記両取付部間の蛇腹部とが樹脂材
料により一体に成形され、前記径大側取付部の内周が前
記アウターケース外周に対応した非円形形状をなし、内
側への凸状をなす厚肉部と薄肉部とが交互に形成されて
なる等速ジョイント用樹脂製ブーツの製造方法におい
て、１次成形で前記径大側取付部の外周端部に沿って連
続するスカート部を設けた成形パリソンを成形し、２次
成形において前記成形パリソンの前記径大側取付部およ
び前記スカート部を前記内金型と外金型との間に挟みブ
ロー成形することを特徴とする等速ジョイント用樹脂製
ブーツの製造方法である。【００１５】本発明の等速ジョイント用樹脂製ブーツの
製造方法では、１次成形で得られた径大側取付部の外周
端部に沿って連続するスカート部を設けた成形パリソン
を、２次成形の内金型と外金型とからなるブロー成形金
型内に移動し、成形パリソンの径大側取付部およびスカ
ート部を内金型と外金型との間に挟みブロー成形するも
のであるので、径大側取付部と内金型との間に締め付け
不足による空気の通路となる隙間が生じても、外金型と
内金型の間に挟まれ締め付けられた径大側取付部の外周
端部に沿って連続するスカート部が前記空気の通路を閉
塞し、ブロー成形時の空気漏れを防ぐことができる。【００１６】【発明の実施の形態】次に本発明の実施の形態を図面に
示す実施例に基づいて説明する。【００１７】図１〜図５は本発明にかかる樹脂製ブーツ
（１）の成形方法の１実施例を示すもので、図１は射出
成形法による１次成形パリソンを成形する金型概略断面
図である。図に示すように、溶融樹脂が射出成型機（８
４）の先端部に設けられた射出ノズル（８１）から内金
型（６１）と外金型（７１）の間のキャビテー内に径小
側取付部（５３）側から射出され、樹脂ブーツ（１）の
成形パリソン（４２）が１次成形される。【００１８】前記内金型（６１）は、本体（６２）と勘
合リング（６５）とブーツ形成部（６４）とから構成さ
れ、勘合リング（６５）のパリソン（４２）側の外周部
には径大側取付部（５２）の外周端部に沿って連続する
スカート部（５７）を形成するための径小部（６６）が
設けら、図６に示す樹脂ブーツ部分断面図のように、径
大側取付部（５２）の外周端部に沿って連続するスカー
ト部（５７）が１次成形により形成される。【００１９】また、径大側取付部（５２）にはアウター
ケースの外周に嵌着されてリング状バンド等の締め付け
部材（２５）により固定されるための周方向の凹部
（８）が形成され、外金型（７１）の径大側取付部にそ
のための凸部（７３）が設けられているこの１次成形パリソン（４２）では、樹脂ブーツ（１）
の径小側取付部（５３）および径大側取付部（５２）は
所定形状に成形されるが、蛇腹部（５４）は最終形状を
なしたものではない。【００２０】図２は、インジェクションブロー成形法に
よる２次成形用の金型概略断面図であり、上記成形パリ
ソン（４２）は、１次成形後の柔軟性を保ち内金型（６
１）に装着された状態で、図に示すようにブロー成形用
の中空金型（７２）内に移動され、空気入り口（８２）
からブロー管（８３）を通じて金型内に空気が吹き込ま
れる。空気は中空金型（７２）と内金型（６１）により
外周部を締め付けられた径大側取付部（５２）を終端部
としてパリソン先端部（４１）からパリソン（４２）の
内周部と内金型（６１）の間を通過して径大側取付部
（５２）に向かって吹き込まれる。【００２１】図３および図４の径大側取付部（５２）の
部分拡大図に示すように、径大側取付部（５２）は内金
型（６１）と中空金型（７２）との間に挟まれ締め付け
られているものの、パリソン（４２）と内金型（６１）
の間にわずかの隙間（７９）を生じ、パリソン（４２）
と内金型（６１）の間に吹き込まれた空気は、この隙間
（７９）を通路として空気漏れを発生しようとする。こ
れは、従来と同じ理由で、樹脂材料によるブーツの剛性
がゴム材に比べて高く、前記中空金型（７２）と内金型
（６１）の間に挟まれた径大側取付部（５２）の締め付
け力が不足して隙間（７９）を生じるものである。【００２２】しかし、本実施形態によれば、１次成形に
より形成された径大側取付部（５２）の外周端部に沿っ
て連続して設けられたスカート部（５７）が、中空金型
（７２）と内金型を構成する勘合リング（６５）との間
に挟まれ締め付けられているため、上記の隙間（７９）
から続く空気の通路を閉塞し、ブロー成形時の空気漏れ
を防止して、２次ブロー成形を行うことができる。【００２３】また、上記空気の通路の閉塞が完全なもの
でない場合でも、スカート部（５７）を追加することで
空気の通路が延長され、空気が漏れる前にブロー圧力に
よって蛇腹部（５４）を膨らませ中空金型（７２）内面
に押し付け所定形状に成形することができる。【００２４】上記スカート部（５７）の形状は、長さが
径大側取付部（５２）の外周端部から１０〜３０ｍｍの
範囲が好ましく、１５ｍｍ程度がより好ましい。また、
厚みは０．５〜１．５ｍｍの範囲が好ましく、１ｍｍ程
度がより好ましい。【００２５】長さが１０ｍｍ未満では上記締め付け力が
偏り空気漏れ防止が充分でなく、また３０ｍｍを超えて
も効果は向上しない。また、厚みは０．５ｍｍ未満であ
ると締め付け効果が得られず、１．５ｍｍを超えると逆
にスカート部に隙間が生じやすくなる。【００２６】これによって、パリソン（４２）と内金型
（６１）の間は密閉状態が維持され、充分なブロー圧力
がパリソン内側にかかり、柔軟状態にある蛇腹部（５
４）の樹脂を中空金型（７２）の内面形状に沿って完全
に押し付けることができ（図５）、蛇腹部（５４）は中
空金型（７２）の内面に形成された蛇腹形状にブロー成
形され所定の形状を有する樹脂ブーツ（１）が成形され
る。【００２７】なお、上記スカート部（５７）は、径大側
取付部（５２）の外周端部の全周に渡って設けるのが好
ましい。【００２８】上記２次ブロー成形後のブーツは中空金型
（７２）および内金型（６１）から離型され、径小側取
付部（５３）の先端密閉部分が切り取られ、図６の部分
断面図に示す樹脂ブーツ（１）が得られる。なお、スカ
ート部（５７）は、樹脂ブーツ（１）をジョイントに取
付ける際には通常切り取り使用されるが、取付け時やジ
ョイント使用時に支障がなければ残しておいてもよい。【００２９】また、前記径大側取付部（５２）の内周に
は、１条もしくは複数条のシール用凸部（７６）が設け
られてもよい。このシール用凸部（７６）としては、図
４の実施例のように断面台形の凸部（７７）の両側端部
に凸条（７６ｂ）を設けたもの、図３のように、１もし
くは複数状の凸条（７６ａ）を設けたもの等、種々の形
態による実施が可能であり、該凸部（７６）が圧縮され
ることで、シール状態を良好に保持できる。【００３０】なお、前記樹脂材料としては、熱可塑性エ
ラストマー樹脂、中でも鉱物油あるいは植物油を配合し
たものが好ましい。これにより、広角度に屈曲変位して
連続回転させても、擦過音等の異音の発生を抑制でき
る。またシール性や耐久性も良好に確保できる。さらに
前記熱可塑性エラストマー樹脂として、脂肪酸アミドを
配合したもの、あるいはポリエーテルを配合したものを
用いることもできる。【００３１】【発明の効果】上記したように本発明による樹脂ブーツ
の製造方法では、径大側取付部の外周端部に沿って連続
して設けられたスカート部が、２次ブロー成形時に中空
金型と内金型を構成する勘合リングとの間に挟まれ締め
付けられて、成形パリソンと内金型の間に生じる隙間か
ら続く空気の通路を閉塞し、ブロー成形時の空気漏れを
防止してブロー成形を行うことができ、また、上記空気
の通路の閉塞が完全なものでない場合でも、スカート部
を追加することで空気の通路が延長され、空気が漏れる
前にブロー圧力によって樹脂製ブーツの蛇腹部を膨らま
せ中空金型内面に押し付け所定形状に成形することがで
きるので、製品不良の発生を大きく低減することができ
る。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a resin boot used in a constant velocity joint having a tripod on one of an input side and an output side and an outer case on the other side. It is about. 2. Description of the Related Art As one of constant velocity joints used for a drive shaft of a vehicle, there is a tripod type joint, for example, used for driving a front wheel drive automobile. As shown in FIGS. 7 and 8, this tripod type constant velocity joint has three trunnions (12) having rollers (11) on one shaft (10) on the input side and the output side. And an outer case (21) provided at the end of the other shaft (20). The outer case (21) is provided on the inner periphery thereof with the tripod (13). (13) has three sliding grooves (22) in the axial direction corresponding thereto, and the roller (11) of the tripod (13) is provided with the sliding grooves (22).
, So as to be able to transmit rotational torque while enabling sliding in the axial direction and angulation of both shafts. [0004] Also in this constant velocity joint, in order to prevent dust and foreign matter from entering the inside of the joint, generally, it is appropriately expanded and contracted so as to cover a portion of the shaft (10) from the outer case (21) to the tripod (13). A bellows-shaped resin boot (1) that can be bent and deformed is provided. The resin boot (1) has a large-diameter mounting portion which is fitted at one end in the axial direction to the outer periphery of the outer case (21) and is fixed by a fastening member (25) such as a ring-shaped band. (52), and the other end is formed as a small-diameter mounting portion (53) fixed to the tripod-side shaft (10), and is formed of a resin material together with the bellows portion (54) between the mounting portions. It is molded integrally. The outer case (21)
As shown in the figure, the outer peripheral shape also has an irregular shape in the circumferential direction corresponding to the arrangement of the inner peripheral sliding groove (22), and therefore, the resin boot (1) fixed thereto is assembled. In order to secure the stability of the state and the sealing performance, the inner circumference is tightened and fixed in accordance with the outer circumference of the outer case (21). The outer case (21) has a shape corresponding to the irregular shape of the outer periphery, and has thick portions (55) and thin portions (56) which are convex inward and formed alternately. Conventionally, as a general method for molding the resin boot (1), a parison (40) as a primary molded product is molded by an injection molding method shown in a schematic sectional view of a mold in FIG. That is, the molten resin is supplied from the injection nozzle (81) provided at the tip of the injection molding machine (84) to the inner mold (61) and the outer mold (7).
1) is injected from the small-diameter mounting portion (53) side into the cavity and the primary molding parison (4) of the resin boot (1) is injected.
0) is molded. The inner die (61) includes a main body (62), a fitting ring (63), and a boot forming part (64).
It is composed of In the primary molded parison (40), the small-diameter side mounting portion (53) and the large-diameter side mounting portion (52) of the resin boot (1) are formed into a predetermined shape, but the bellows portion (54).
Is not the final shape. The large-diameter mounting portion (52) is provided with a circumferential recess (8) that is fitted to the outer periphery of the outer case and fixed by a fastening member (25) such as a ring-shaped band. The large-diameter side mounting portion of the mold (71) is provided with a convex portion (73) for that purpose. Then, the molded parison (40) is attached to the inner mold (61) while maintaining the flexibility after the primary molding. As it was done,
It is moved into a hollow mold (72) which is an outer mold for secondary blow molding by the injection blow molding method shown in FIG. 10, and air is blown into the mold from an air inlet (82) through a blow pipe (83). It is. Air is a hollow mold (7
The parison tip (4) is terminated with the large-diameter-side mounting portion (52) clamped between the fitting of the inner mold (2) and the inner mold (61).
1) is blown between the inner periphery of the parison (40) and the inner mold (61). The resin of the bellows portion (54) in the soft state is
The hollow mold (7) is blown by the blow pressure of the blown air.
2) It is pressed against the inner surface (FIG. 11), and the bellows portion (54) is blow-molded into the bellows shape formed on the inner surface of the hollow mold (72) to form a secondary molded product. However, as shown in an enlarged view of the large-diameter side mounting portion (52) in FIG. 12 and FIG.
In the large-diameter mounting portion (52) fastened by the inner mold (2) and the inner mold (61), a slight gap (79) is generated between the parison (40) and the inner mold (61), and the parison ( The air blown between the inner mold 40 and the inner mold 61 may cause air leakage through the gap 79 as a passage. This is because the rigidity of the boot made of the resin material is higher than that of the rubber material, and the hollow mold (72) and the inner mold (6) are used.
The gap (79) is generated due to insufficient tightening force of the large-diameter mounting portion (52) sandwiched between 1), thereby causing air leakage due to blow pressure. The air leak causes the parison (4)
0) and the blow pressure between the inner mold (61) is reduced and the blow pressure for pressing the parison (40) against the hollow mold (72) is insufficient. In particular, the bellows on the large-diameter side mounting portion (52) side. A bellows (58) with insufficient bulge occurs in the part (54),
Above all, the first peak is likely to be insufficiently swollen, and a predetermined bellows shape cannot be obtained, which causes a product defect. In particular, the air leakage is caused by the large-diameter mounting portion (5).
Of the thick part (55) and the thin part (56) provided alternately on the inner circumference of 2), the gap (79) is easily generated in the thin part (56) where the thickness is small and the tightening force tends to be insufficient. Air leaks easily occur. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in consideration of a resin boot obtained by integrally molding a resin material used for a tripod constant velocity joint. It is a manufacturing method, in which a resin boot having a predetermined shape can be formed by preventing insufficient bellows from swelling due to air leakage from a large-diameter side mounting portion during blow molding, thereby reducing the occurrence of product defects. It is an object of the present invention to provide a method for manufacturing a resin boot that can be manufactured. SUMMARY OF THE INVENTION The present invention is directed to a large-diameter mounting portion at one axial end attached to the outer periphery of an outer case of a constant velocity joint, and a small-diameter mounting portion mounted to a tripod shaft. And the bellows portion between the two mounting portions are integrally formed of a resin material, and the inner circumference of the large-diameter mounting portion has a non-circular shape corresponding to the outer case outer circumference, and has a convex shape inward. In a method of manufacturing a resin boot for a constant velocity joint in which a thick portion and a thin portion are alternately formed, a skirt portion that is continuous along an outer peripheral end portion of the large-diameter side mounting portion is provided by primary molding. For a constant velocity joint, a molded parison is molded, and in the secondary molding, the large-diameter mounting portion and the skirt portion of the molded parison are sandwiched between the inner mold and the outer mold and blow molded. Resin boots Is a manufacturing method. In the method of manufacturing a resin boot for a constant velocity joint according to the present invention, a molded parison provided with a continuous skirt portion along the outer peripheral end of the large-diameter side mounting portion obtained by the primary molding is used for the secondary molding. It moves into the blow molding mold consisting of the inner mold and the outer mold for molding, and inserts the large-diameter side mounting part and the skirt part of the molded parison between the inner mold and the outer mold to perform blow molding. Therefore, even if there is a gap between the large-diameter side mounting portion and the inner die that becomes an air passage due to insufficient tightening, the large-diameter side mounting portion clamped between the outer die and the inner die is tightened. A skirt portion continuous along the outer peripheral end of the airtight member closes the air passage, so that air leakage during blow molding can be prevented. Next, an embodiment of the present invention will be described with reference to an embodiment shown in the drawings. 1 to 5 show one embodiment of a method for molding a resin boot (1) according to the present invention. FIG. 1 is a schematic sectional view of a mold for molding a primary molded parison by an injection molding method. It is. As shown in the figure, the molten resin is injected into an injection molding machine (8
The injection nozzle (81) provided at the tip of (4) is injected into the cavity between the inner mold (61) and the outer mold (71) from the small-diameter mounting part (53) side, and the resin boot ( The molded parison (42) of 1) is primarily molded. The inner mold (61) comprises a main body (62), a fitting ring (65) and a boot forming part (64), and the outer periphery of the fitting ring (65) on the parison (42) side is provided. A small diameter portion (66) for forming a continuous skirt portion (57) along the outer peripheral end of the large diameter side mounting portion (52) is provided, as shown in the resin boot partial sectional view shown in FIG. A skirt portion (57) continuous along the outer peripheral end of the large-diameter attachment portion (52) is formed by primary molding. The large-diameter mounting portion (52) has a circumferential recess (8) which is fitted to the outer periphery of the outer case and is fixed by a fastening member (25) such as a ring-shaped band. In the primary molding parison (42) in which the convex portion (73) for the large-diameter mounting portion of the outer mold (71) is provided, the resin boot (1)
The small-diameter side mounting portion (53) and the large-diameter side mounting portion (52) are formed into a predetermined shape, but the bellows portion (54) does not have the final shape. FIG. 2 is a schematic sectional view of a mold for secondary molding by the injection blow molding method. The molded parison (42) maintains the flexibility after the primary molding, and the inner mold (6).
In the state of being attached to 1), it is moved into a hollow mold (72) for blow molding as shown in the figure, and the air inlet (82).
Air is blown into the mold through the blow pipe (83). The air flows from the parison tip (41) to the inner periphery of the parison (42) with the large-diameter side mounting portion (52) whose outer periphery is tightened by the hollow mold (72) and the inner mold (61) as the end. The air is blown toward the larger-diameter mounting portion (52) through the space between the inner molds (61). As shown in the partial enlarged view of the large-diameter mounting portion (52) in FIGS. 3 and 4, the large-diameter mounting portion (52) is provided between the inner die (61) and the hollow die (72). The parison (42) and the inner mold (61) are sandwiched and tightened.
A slight gap (79) between the parison (42)
The air blown between the inner mold (61) and the inner mold (61) tends to cause air leakage through the gap (79). This is because, for the same reason as in the prior art, the rigidity of the boot made of the resin material is higher than that of the rubber material, and the large-diameter mounting portion (52) sandwiched between the hollow mold (72) and the inner mold (61). The gap (79) is generated due to insufficient tightening force. However, according to this embodiment, the skirt portion (57) provided continuously along the outer peripheral end of the large-diameter mounting portion (52) formed by primary molding is a hollow mold. (72) and the fitting ring (65) that constitutes the inner mold, and are clamped.
The air passage following the air flow is closed, and air leakage during blow molding can be prevented, so that secondary blow molding can be performed. Even when the air passage is not completely closed, the air passage is extended by adding the skirt portion (57), and the bellows portion (54) is blown by the blow pressure before the air leaks. It can be expanded and pressed against the inner surface of the hollow mold (72) to form a predetermined shape. The shape of the skirt portion (57) is preferably such that the length is in the range of 10 to 30 mm from the outer peripheral end of the large-diameter mounting portion (52), and more preferably about 15 mm. Also,
The thickness is preferably in the range of 0.5 to 1.5 mm, more preferably about 1 mm. If the length is less than 10 mm, the above-mentioned tightening force is unbalanced and air leakage is not sufficiently prevented, and if it exceeds 30 mm, the effect is not improved. If the thickness is less than 0.5 mm, a tightening effect cannot be obtained, and if the thickness exceeds 1.5 mm, a gap is easily formed in the skirt. As a result, a sealed state is maintained between the parison (42) and the inner mold (61), a sufficient blow pressure is applied to the inner side of the parison, and the bellows (5) is in a soft state.
The resin of 4) can be completely pressed along the inner surface shape of the hollow mold (72) (FIG. 5), and the bellows portion (54) is blown into the bellows shape formed on the inner surface of the hollow mold (72). A molded resin boot (1) having a predetermined shape is formed. The skirt portion (57) is preferably provided over the entire outer peripheral end of the large-diameter mounting portion (52). The boot after the secondary blow-molding is released from the hollow mold (72) and the inner mold (61), and the closed end of the small-diameter side mounting portion (53) is cut off. The resin boot (1) shown in the sectional view is obtained. The skirt portion (57) is usually cut off when the resin boot (1) is attached to the joint, but may be left as long as it does not hinder the attachment or use of the joint. Further, one or a plurality of sealing projections (76) may be provided on the inner periphery of the large-diameter mounting portion (52). As the convex portion (76) for sealing, a convex portion (77b) provided on both side ends of a convex portion (77) having a trapezoidal cross section as in the embodiment of FIG. Various forms, such as those provided with a plurality of ridges (76a), can be implemented. By compressing the ridges (76), a good sealing state can be maintained. The resin material is preferably a thermoplastic elastomer resin, especially one containing a mineral oil or a vegetable oil. This makes it possible to suppress the occurrence of abnormal noise such as rubbing noise even when the bending rotation is performed at a wide angle and continuous rotation is performed. Also, good sealing properties and durability can be ensured. Further, as the thermoplastic elastomer resin, a resin compounded with a fatty acid amide or a compound compounded with a polyether can also be used. As described above, in the method for manufacturing a resin boot according to the present invention, the skirt portion provided continuously along the outer peripheral end of the large-diameter mounting portion is hollow during secondary blow molding. It is sandwiched and tightened between the mold and the mating ring that constitutes the inner mold to block the air passage that continues from the gap created between the molding parison and the inner mold, preventing air leakage during blow molding. Even if the air passage is not completely closed, the addition of the skirt extends the air passage and allows the resin boot to be blown by the blow pressure before the air leaks. Since the bellows portion can be expanded and pressed against the inner surface of the hollow mold to be formed into a predetermined shape, occurrence of product defects can be greatly reduced.

【図面の簡単な説明】【図１】本発明にかかわる１実施例を示す樹脂製ブーツ
の１次成形の金型概略断面図である。【図２】本発明にかかわる１実施例を示す樹脂製ブーツ
の２次成形の金型概略断面図である。【図３】同上ブーツの径大側取付部（厚肉部）の拡大図
である。【図４】同上ブーツの径大側取付部（薄肉部）の拡大図
である。【図５】本発明にかかわる２次ブロー成形時の金型概略
断面図である。【図６】本発明にかかわる樹脂製ブーツの部分断面図で
ある。【図７】樹脂製ブーツのジョイントに取付けた状態の縦
断面図である。【図８】前図のＸ−Ｘ線の断面図である。【図９】従来の樹脂製ブーツの１次成形の金型概略断面
図である。【図１０】従来の樹脂製ブーツの２次成形の金型概略断
面図である。【図１１】従来の２次ブロー成形時の金型概略断面図で
ある。【図１２】同上ブーツの径大側取付部（厚肉部）の拡大
図である。【図１３】同上ブーツの径大側取付部（薄肉部）の拡大
図である。【符号の説明】（１）ブーツ（８）締め付け凹部（１０）（２０）シャフト（１２）トラニオン（１３）トリポート（２１）アウターケース（２２）摺動溝（４０）（４２）成形パリソン（５２）径大側取付部（５５）厚肉部（５６）薄肉部（５３）径小側取付部（５４）蛇腹部（５７）スカート部（６１）内金型（６２）内金型本体（６３）（６５）勘合リング（６４）ブーツ形成部（７１）外金型（７２）中空金型BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view of a mold for primary molding of a resin boot showing one embodiment according to the present invention. FIG. 2 is a schematic sectional view of a mold for secondary molding of a resin boot showing one embodiment according to the present invention. FIG. 3 is an enlarged view of a large-diameter side mounting portion (thick portion) of the boot. FIG. 4 is an enlarged view of a large-diameter mounting portion (thin portion) of the boot. FIG. 5 is a schematic sectional view of a mold at the time of secondary blow molding according to the present invention. FIG. 6 is a partial cross-sectional view of a resin boot according to the present invention. FIG. 7 is a vertical cross-sectional view of a state of being attached to a joint of a resin boot. FIG. 8 is a cross-sectional view taken along line XX of the preceding figure. FIG. 9 is a schematic sectional view of a mold for primary molding of a conventional resin boot. FIG. 10 is a schematic sectional view of a mold for secondary molding of a conventional resin boot. FIG. 11 is a schematic sectional view of a mold at the time of conventional secondary blow molding. FIG. 12 is an enlarged view of a large-diameter mounting portion (thick portion) of the boot. FIG. 13 is an enlarged view of a large-diameter mounting portion (thin portion) of the boot. [Description of Signs] (1) Boot (8) Tightening recess (10) (20) Shaft (12) Trunnion (13) Tripport (21) Outer case (22) Sliding groove (40) (42) Molded parison (52) Large-diameter mounting part (55) Thick part (56) Thin-wall part (53) Small-diameter mounting part (54) Bellows part (57) Skirt part (61) Inner die (62) Inner die body (63) ) (65) Fitting ring (64) Boot forming part (71) Outer die (72) Hollow die

───────────────────────────────────────────────────── フロントページの続き (72)発明者大野宏大阪府大阪市西区江戸堀１丁目17番18号東洋ゴム工業株式会社内 (72)発明者辻本芳和大阪府大阪市西区江戸堀１丁目17番18号東洋ゴム工業株式会社内Ｆターム(参考） 4F208 AG05 AG10 AG22 AG24 AG28 LA01 LA02 LA08 LB01 LG04 LG14 LG19 LG28 LJ01 LJ08 LN01 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Ohno 1-17-18 Edobori, Nishi-ku, Osaka-shi, Osaka Toyo Tire & Rubber Co., Ltd. (72) Inventor Yoshikazu Tsujimoto 1-17-18 Edobori, Nishi-ku, Osaka-shi, Osaka Toyo Tire & Rubber Co., Ltd. F term (reference) 4F208 AG05 AG10 AG22 AG24 AG28 LA01 LA02 LA08 LB01 LG04 LG14 LG19 LG28 LJ01 LJ08 LN01

Claims

Claims: 1. A large-diameter mounting portion at one axial end mounted on the outer periphery of an outer case of a constant velocity joint, a small-diameter mounting portion mounted to a tripod shaft, and both mounting portions. The bellows portion between the portions is integrally formed of a resin material, and the inner periphery of the large-diameter mounting portion has a non-circular shape corresponding to the outer case outer periphery, and has a thick portion and a thin portion that are convex inward. And a method of manufacturing a resin boot for a constant velocity joint in which a part is formed alternately, wherein a molded parison provided with a continuous skirt portion along an outer peripheral end portion of the large-diameter side mounting portion is formed by primary molding. And manufacturing the resin boot for a constant velocity joint by sandwiching the large-diameter mounting portion and the skirt portion of the molded parison between the inner mold and the outer mold in the secondary molding and performing blow molding. Method.