JP3882109B2

JP3882109B2 - Manufacturing method of resin boot for constant velocity joint

Info

Publication number: JP3882109B2
Application number: JP2001398540A
Authority: JP
Inventors: 克志齋藤; 栄一今津; 宏大野; 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: 2007-02-14
Anticipated expiration: 2021-12-27
Also published as: JP2003191316A

Description

【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６および図７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１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（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、ブーツ（１）の１次成形パリソン（４０）が成形される。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（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。
【０００８】
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８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、空気は中空金型（７２）と内金型（６１）により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（４０）の内周部と内金型（６１）の間をに吹き込まれる。
【０００９】
前記蛇腹部（５４）の柔軟状態にある樹脂は、吹き込まれた空気のブロー圧力により前記中空金型（７２）内面に押し付けられ（図９）、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１０および図１１の径大側取付部（５２）の拡大図に示すように、上記パリソン（４０）と内金型（６１）の間に吹き込まれた空気は、前記中空金型（７２）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、これ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（６１）による径大側取付部（５２）の締め付け力が不足して、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（４０）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、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（５２）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】
本発明の目的は、上記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空気漏れを防止して充分なブロー圧力を得て蛇腹部を所定形状に成形し、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にある。
【００１４】
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り、１次成形で得られた成形パリソンを内金型と外金型とからなるブロー成形金型内で２次成形する際に、前記成形パリソンの前記径大側取付部を前記内金型と外金型との間に挟み、かつ前記外金型の内周部に設けた突起により前記径大側取付部の外周面を前記内金型の挟着部外周面に押圧しブロー成形する等速ジョイント用樹脂製ブーツの製造方法において、前記１次成形で前記径大側取付部の外周に周方向の凹部が形成され、２次成形で前記突起により前記凹部底面に幅狭の凹部を形成し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】
本発明によれば、外金型の内周部に設けた突起により前記径大側取付部が前記内金型の挟着面に圧着され空気漏れの通路を閉鎖し、金型内に吹き込まれた空気の漏れを防ぐことができ、充分なブロー圧力がパリソン内側に得られ蛇腹部を中空金型の内面形状に沿って完全に押し付けて樹脂ブーツを２次ブロー成形することができることに加えて、前記１次成形で前記径大側取付部の外周に周方向の凹部が形成され、２次成形で前記突起により前記周方向の凹部底面に幅狭の凹部を形成しブロー成形することにより、前記径大側取付部の内周部の内金型の外周面への圧着力が高まり、空気漏れの通路を完全に閉鎖することができるようになる。
【００１７】
【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。
【００１８】
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断面図であり、従来と同様の成形方法によるもので、すなわち、溶融樹脂が射出成型機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、ブーツ（１）の成形パリソン（４０）が１次成形される。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）が周方向に設けられている。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）は最終形状をなしていない。
【００１９】
図２は、インジェクションブロー成形法による２次成形用の金型断面図であり、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、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（４０）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。
【００２０】
図３および図４の径大側取付部分拡大図に示すように、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により固定されるための周方向の凹部（８）が形成され、中空金型（７２）の径大側取付部にそのための凸部（７３）が周方向に設けられている。
【００２１】
さらに、前記中空金型（７２）の径大側取付部分には、前記周方向の凹部（８）よりも幅狭の突起（７４）が周方向内周部に設けられ、前記凹部（８）底面に幅狭の凹部（７５）を形成するようになっている。
【００２２】
この中空金型（７２）の内周部に設けた突起（７４）により前記径大側取付部（５２）の外周面は内金型（６１）の挟着部（６２）に押圧され、前記径大側取付部（５２）が前記挟着部（６２）に圧着され、従来生じることのあったブロー成形時の空気漏れ通路となる隙間を閉鎖し、金型内に吹き込まれた空気の漏れを防ぐことができる。
【００２３】
上記突起（７４）の厚みは、前記締め付け部材固定用の凹部（８）の厚み１〜２ｍｍに対して０．５ｍｍ程度までが好ましい。突起厚みが０．５ｍｍを超えると、特に薄肉部（５６）において断面積が減少し剛性が低下しすぎたり、凹部（８）との段差が生じて逆に空気漏れを生じやすくなる。
【００２４】
これによって、パリソン（４０）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（５４）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。
【００２５】
上記突起（７４）は、中空金型（７２）の内周部の全周に渡って設けてもよいが、特に前記空気漏れの発生しやすい図５に示す薄肉部（５６）には少なくとも設ける必要がある。
【００２６】
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樹脂ブーツ（１）が得られる。
【００２７】
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。
【００２８】
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。
【００２９】
【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、１次成形で得られた成形パリソンを内金型と外金型とからなるブロー成形金型内で２次成形する際に、前記成形パリソンの前記径大側取付部を前記内金型と外金型との間に挟み、かつ前記外金型の内周部に設けた突起により前記径大側取付部の外周面を前記内金型の挟着部外周面に押圧しブロー成形するものであり、２次ブロー成形時の径大側取付部における空気漏れを防止し、１次成形パリソンと内金型の間に充分なブロー圧力を得て柔軟状態にある樹脂を中空金型に押し付け所定の蛇腹形状を有する樹脂ブーツを成形することができ、製品不良の発生を大きく低減することができる。
【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】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７】前図のＸ−Ｘ線の断面図である。
【図８】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９】従来の２次ブロー成形時の金型概略断面図である。
【図１０】同上ブーツの径大側取付部（厚肉部）の拡大図である。
【図１１】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）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
（６２）挟着部
（７４）突起[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a resin boot used in a constant velocity joint including a tripart on one of an input side and an output side and an outer case on the other side.
[0002]
[Prior art]
One of the constant velocity joints used for vehicle drive shafts and the like is a triport type joint, which is used, for example, for driving a front-wheel drive automobile.
[0003]
As shown in FIGS. 6 and 7, 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. A triport (13) projecting in the direction and an outer case (21) provided at the end of the other shaft (20), and the outer case (21) is formed on the inner periphery of the triport (13). And the three sliding grooves (22) in the axial direction corresponding to the roller, and the roller (11) of the tripod (13) is fitted into the sliding groove (22), so that the axial sliding and both shafts The rotation torque can be transmitted while the angle can be angled.
[0004]
Also in this constant velocity joint, in order to prevent dust and foreign matter from entering the inside of the joint, it is generally stretched and bent appropriately to cover the portion of the shaft (10) on the tripod (13) side from the outer case (21). A resin boot (1) having an accordion-like shape is provided.
[0005]
The resin boot (1) has a large-diameter attachment portion (52) in which one end portion in the axial direction is fitted to the outer periphery of the outer case (21) and is fixed by a fastening member (25) such as a ring-shaped band. And the other end is formed as a small-diameter mounting portion (53) fixed to the tripod shaft (10), and is integrally formed with a resin material together with the bellows portion (54) between the mounting portions. Has been.
[0006]
By the way, the outer case (21) has an irregular shape in the circumferential direction corresponding to the arrangement of the inner peripheral sliding groove (22) as shown in the figure, and is therefore fixed to this. Since the inner periphery of the boot (1) is fastened in accordance with the shape of the outer periphery of the outer case in order to ensure the stability and sealing performance in the assembled state, The periphery has a shape corresponding to the uneven shape on the outer periphery of the outer case (21), and thick portions (55) and thin portions (56) that are convex inward are alternately formed.
[0007]
Conventionally, as a general molding method of 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 small-diameter side mounting portion (53) is formed in the cavity between the inner die (61) and the outer die (71) from the injection nozzle (81) provided at the tip of the injection molding machine (84). ) Side and the primary molding parison (40) of the boot (1) is molded. The large-diameter mounting portion (52) is formed 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 convex part (73) for it is provided in the large diameter side attaching part of 71). In this 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 molded into a predetermined shape, but the bellows portion (54) is the final shape. It was not made.
[0008]
Next, the molded parison (40) is kept outside the secondary blow molding by the injection blow molding method shown in FIG. 8 while maintaining the flexibility after the primary molding and being attached to the inner mold (61). It is moved into a hollow mold (72) to be a mold, and air is blown into the mold from the air inlet (82) through the blow pipe (83), and the air is blown into the hollow mold (72) and the inner mold (61). ) And the large diameter side attachment portion (52) tightened by) is blown between the inner periphery of the parison (40) and the inner mold (61) from the parison tip (41).
[0009]
The resin in the flexible state of the bellows part (54) is pressed against the inner surface of the hollow mold (72) by the blowing pressure of the blown air (FIG. 9), and the bellows part (54) is hollow mold (72). A secondary molded product is formed by blow molding into a bellows shape formed on the inner surface.
[0010]
However, as shown in the enlarged views of the large-diameter side mounting portion (52) in FIGS. 10 and 11, the air blown between the parison (40) and the inner mold (61) is the hollow mold ( 72) and the large-diameter side mounting portion (52) tightened by the inner mold (61), a slight gap (79) is generated between the parison (40) and the inner mold (61). Air leakage may occur 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 clamping force of the large-diameter side mounting portion (52) by the hollow mold (72) and the inner mold (61) is insufficient, and the blow pressure It causes air leaks.
[0011]
Due to this air leakage, the blow pressure between the parison (40) and the inner mold (61) is lowered, and the blow pressure for pressing the parison (40) against the hollow mold (72) is insufficient. A bellows portion (58) with insufficient swelling occurs in the bellows portion (54) on the mounting portion (52) side, and a predetermined bellows shape cannot be obtained, causing a product defect.
[0012]
In particular, the above-mentioned air leak is a thin-walled thin-walled portion (55) and a thin-walled portion (56) provided alternately on the inner periphery of the large-diameter mounting portion (52), which are thin and tend to have insufficient tightening force. The gap (79) is likely to occur in the portion (56), and air leakage is likely to occur.
[0013]
[Problems to be solved by the invention]
An object of the present invention is made in view of the above, and is a method for manufacturing a resin boot obtained by integrally molding a resin material used in a triport type constant velocity joint, and in particular, air during blow molding An object of the present invention is to provide a method of manufacturing a resin boot that can prevent leakage and obtain a sufficient blow pressure to form a bellows portion into a predetermined shape, thereby reducing the occurrence of product defects.
[0014]
The present invention comprises a large-diameter side attachment portion on one axial end side attached to the outer periphery of the outer case of a constant velocity joint, a small-diameter side attachment portion attached to a triport-side shaft, and a bellows portion between the two attachment portions. It is integrally molded from a resin material, the inner circumference of the large-diameter side mounting portion has a non-circular shape corresponding to the outer circumference of the outer case, and thick and thin portions that are convex inward are alternately formed. Te becomes, when the secondary molding in the blow molding mold comprising a molding parison obtained in the primary molding and a inner die and the outer die, the said large-diameter-side mounting portion of the parison deposit Blow molding is performed by pressing the outer peripheral surface of the large-diameter side mounting portion against the outer peripheral surface of the sandwiched portion of the inner mold by a protrusion provided between the mold and the outer mold and provided on the inner peripheral portion of the outer mold. In the method of manufacturing a resin boot for a constant velocity joint, in the primary molding, A resin boot for a constant velocity joint, characterized in that a recess in the circumferential direction is formed on the outer periphery of the large-diameter side mounting portion, and a narrow recess is formed on the bottom surface of the recess by the projection in the secondary molding and blow molding is performed. It is a manufacturing method.
[0015]
According to the present invention, the large-diameter side mounting portion is pressed against the clamping surface of the inner mold by the protrusion provided on the inner peripheral portion of the outer mold, and the air leakage passage is closed and blown into the mold. In addition to being able to prevent leakage of air, a sufficient blow pressure can be obtained inside the parison, the bellows can be completely pressed along the inner surface shape of the hollow mold, and the resin boot can be subjected to secondary blow molding In the primary molding, a circumferential recess is formed on the outer periphery of the large-diameter side attachment portion, and in the secondary molding, a narrow recess is formed on the bottom surface of the circumferential recess by the projection, and then blow molding is performed. The pressure-bonding force to the outer peripheral surface of the inner mold at the inner peripheral portion of the large-diameter side attachment portion is increased, and the air leakage passage can be completely closed .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described based on examples shown in the drawings.
[0018]
1 to 5 show one embodiment of a method for molding a resin boot (1) according to the present invention. FIG. 1 is a sectional view of a mold for molding a primary molding parison by an injection molding method. In other words, the molten resin has a diameter in the cavity between the inner mold (61) and the outer mold (71) from the injection nozzle (81) provided at the tip of the injection molding machine. Injection is performed from the small side attachment portion (53) side, and the molding parison (40) of the boot (1) is primarily molded. The large-diameter side mounting portion (52) is formed with a circumferential recess (8) that is fitted to the outer periphery of the outer case and fixed by a fastening member such as a ring-shaped band. A convex portion (73) therefor is provided in the circumferential direction on the large diameter side mounting portion. In the primary molding parison (40), the small diameter side mounting portion (53) and the large side mounting portion (52) of the resin boot (1) are molded into a predetermined shape, while the bellows portion (54) has a final shape. Not done.
[0019]
FIG. 2 is a sectional view of a mold for secondary molding by the injection blow molding method, and the molded parison (40) is attached to the inner mold (61) while maintaining flexibility after the primary molding. As shown in the figure, it is moved into a blow mold (72) and blown into the mold through the blow pipe (83) from the air inlet (82), and the air is blown into the hollow mold (72). Between the inner periphery of the parison (40) and the inner mold (61) from the parison tip (41), with the large-diameter side mounting portion (52) tightened at the outer periphery by the inner die (61). Is blown toward the large-diameter side attachment portion (52).
[0020]
As shown in the enlarged view of the large-diameter side attachment in FIGS. 3 and 4, the large-diameter side attachment portion (52) is fitted on the outer periphery of the outer case and is fixed by a fastening member such as a ring-shaped band. A concave portion (8) in the circumferential direction is formed, and a convex portion (73) therefor is provided in the circumferential direction on the large diameter side attachment portion of the hollow mold (72).
[0021]
Furthermore, a protrusion (74) having a narrower width than the circumferential recess (8) is provided on the inner peripheral portion in the circumferential direction on the large diameter side attachment portion of the hollow mold (72), and the recess (8) A narrow recess (75) is formed on the bottom surface.
[0022]
The outer peripheral surface of the large-diameter side attachment portion (52) is pressed against the clamping portion (62) of the inner die (61) by the projection (74) provided on the inner peripheral portion of the hollow die (72), The large-diameter side mounting portion (52) is pressure-bonded to the sandwiching portion (62) to close a gap serving as an air leakage path at the time of blow molding, which has conventionally occurred, and leakage of air blown into the mold Can be prevented.
[0023]
The thickness of the protrusion (74) is preferably up to about 0.5 mm with respect to the thickness of 1-2 mm of the recess (8) for fixing the fastening member. When the thickness of the protrusion exceeds 0.5 mm, the cross-sectional area is reduced particularly in the thin portion (56), the rigidity is excessively lowered, or a step with the concave portion (8) is generated, and air leakage tends to occur.
[0024]
As a result, a sealed state is maintained between the parison (40) and the inner mold (61), and a sufficient blow pressure is applied to the inside of the parison, so that the resin of the bellows part (54) in a flexible state is transferred to the hollow mold (72 ) (FIG. 5), and the bellows portion (54) is blow-molded into a bellows shape formed on the inner surface of the hollow mold (72) and has a predetermined shape ( 1) is formed.
[0025]
The protrusion (74) may be provided over the entire circumference of the inner periphery of the hollow mold (72), but at least provided in the thin part (56) shown in FIG. There is a need.
[0026]
The boot after the secondary blow molding is released from the hollow mold (72) and the inner mold (61), and the tip sealed portion of the small diameter side mounting portion (53) is cut off to obtain the resin boot (1). .
[0027]
Further, one or more sealing protrusions (76) may be provided on the inner periphery of the large-diameter side attachment portion (52). As the convex portion for sealing (76), as shown in the embodiment of FIG. 4, a convex portion (76b) is provided at both end portions of the convex portion (77) having a trapezoidal cross section. Various forms such as those provided with a plurality of protruding ridges (76a) can be implemented, and the protruding state (76) can be compressed to maintain a good sealing state.
[0028]
In addition, as said resin material, what mix | blended thermoplastic elastomer resin, especially mineral oil or vegetable oil is preferable. Thereby, even if it is bent and displaced at a wide angle and continuously rotated, it is possible to suppress the generation of abnormal noise such as scratching noise. In addition, good sealing and durability can be secured. Further, as the thermoplastic elastomer resin, those containing a fatty acid amide or those containing a polyether can also be used.
[0029]
【The invention's effect】
As described above, in the method for manufacturing a resin boot according to the present invention, when the molding parison obtained by the primary molding is secondarily molded in the blow molding mold composed of the inner mold and the outer mold, the molding parison is formed. The outer diameter surface of the large-diameter side mounting portion is sandwiched between the inner mold and the outer mold, and the outer peripheral surface of the large-diameter side mounting portion is formed by the protrusion provided on the inner peripheral portion of the outer mold. Is pressed against the outer peripheral surface of the sandwiched portion and blow-molded to prevent air leakage at the large-diameter side mounting portion during the secondary blow molding and to provide a sufficient blow pressure between the primary molding parison and the inner mold. As a result, a resin boot having a predetermined bellows shape can be molded by pressing the resin in a flexible state against the hollow mold, and the occurrence of product defects can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a mold for primary molding of a resin boot showing an embodiment according to the present invention.
FIG. 2 is a schematic cross-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 attachment portion (thick portion) of the boot.
FIG. 4 is an enlarged view of a large diameter side attachment portion (thin wall 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 longitudinal sectional view of the resin boot attached to a joint.
FIG. 7 is a cross-sectional view taken along line XX in the previous figure.
FIG. 8 is a schematic sectional view of a mold for secondary molding of a conventional resin boot.
FIG. 9 is a schematic sectional view of a mold at the time of conventional secondary blow molding.
FIG. 10 is an enlarged view of the large-diameter side attachment portion (thick portion) of the boot.
FIG. 11 is an enlarged view of a large diameter side attachment portion (thin wall portion) of the boot.
[Explanation of symbols]
(1) Boot (8) Tightening recess (10) (20) Shaft (12) Trunnion (13) Triport (21) Outer case (22) Sliding groove (40) Molded parison (52) Large diameter side mounting part (55 ) Thick part (56) Thin part (53) Small diameter side attachment part (54) Bellows part (62) Clamping part (74) Projection

Claims

A large-diameter side attachment portion on one end in the axial direction attached to the outer case outer periphery of the constant velocity joint, a small-diameter side attachment portion attached to the triport shaft, and a bellows portion between the two attachment portions are integrated with a resin material. The inner periphery of the large-diameter side mounting portion has a non-circular shape corresponding to the outer periphery of the outer case, and thick and thin portions that are convex inward are formed alternately ,
When the molding parison obtained by the primary molding is secondarily molded in a blow molding mold composed of an inner mold and an outer mold, the large-diameter side mounting portion of the molding parison is separated from the inner mold and the outer mold. Constant velocity with which the outer peripheral surface of the large-diameter side mounting portion is pressed against the outer peripheral surface of the sandwiched portion of the inner mold by a projection provided between the inner mold and the inner peripheral portion of the outer mold. In the manufacturing method of resin boots for joints,
A constant-speed recess is formed in the outer periphery of the large-diameter mounting portion in the primary molding, and a narrow recess is formed in the bottom surface of the recess by the protrusion in the secondary molding, and is blow-molded. Manufacturing method of resin boots for joints.