JP3941239B2

JP3941239B2 - Constant velocity joint

Info

Publication number: JP3941239B2
Application number: JP18066898A
Authority: JP
Inventors: 重興嘉山
Original assignee: NSK Ltd
Current assignee: NSK Ltd
Priority date: 1998-06-26
Filing date: 1998-06-26
Publication date: 2007-07-04
Anticipated expiration: 2018-06-26
Also published as: JP2000018267A

Description

【０００１】
【発明の属する技術分野】
この発明に係る等速ジョイントは、例えば独立懸架式サスペンションに駆動輪を支持する為の転がり軸受ユニットに一体的に組み込み、トランスミッションから駆動輪に駆動力を伝達するのに利用する。
【０００２】
【従来の技術】
自動車のトランスミッションと、独立懸架式サスペンションにより支持した駆動輪との間には等速ジョイントを設けて、デファレンシャルギヤと駆動輪との相対変位や車輪に付与された舵角に拘らず、エンジンの駆動力を駆動輪に、全周に亙り同一角速度で伝達自在としている。この様な部分に使用される等速ジョイントとして従来から、例えば実開昭５７−１４５８２４〜５号公報、同５９−１８５４２５号公報、同６２−１２０２１号公報等に記載されたものが知られている。
【０００３】
この様な従来から知られた等速ジョイント１は、例えば図６〜８に示す様に、内輪２と外輪３との間の回転力伝達を６個のボール４、４を介して行なう様に構成している。上記内輪２は、トランスミッションにより回転駆動される一方の軸５の外端部に固定する。この為、上記内輪２の中心部には、この軸５の端部に形成した雄スプライン部を係合させる為のスプライン孔３１を設けている。又、上記外輪３は、駆動輪を結合する他方の軸６の内端部に固定する。上記内輪２の外周面２ａには、断面円弧形の内側係合溝７、７を６本、円周方向等間隔に、それぞれ円周方向に対し直角方向に形成している。又、上記外輪３の内周面３ａで、上記各内側係合溝７、７と対向する位置には、やはり断面円弧形の外側係合溝８、８を６本、円周方向に対し直角方向に形成している。
【０００４】
又、上記内輪２の外周面２ａと外輪３の内周面３ａとの間には、断面が円弧状で全体が円環状の保持器９を挟持している。この保持器９の円周方向６箇所位置で、上記内側、外側両係合溝７、８に整合する位置には、それぞれポケット１０、１０を形成し、各ポケット１０、１０の内側にそれぞれ１個ずつ、合計６個のボール４、４を保持している。これらのボール４、４は、それぞれ上記各ポケット１０、１０に保持された状態で、上記内側、外側両係合溝７、８に沿い転動自在である。
【０００５】
上記各ポケット１０、１０は図８に示す様に、円周方向に長い矩形とし、次述する軸交角αの変化に伴って、円周方向に隣り合うボール４、４同士の間隔が変化した場合でも、この変化を吸収できる様にしている。即ち、上記内側係合溝７、７の底面７ａ、７ａ同士の位置関係、並びに上記各外側係合溝８、８の底面８ａ、８ａ同士の位置関係は、図９に一点鎖線で示す様に、地球儀の経線の如き関係になっている。上記内輪２の中心軸と外輪３の中心軸とが一致している（軸交角α＝１８０°）場合に上記各ボール４、４は、図９に二点鎖線で示した、地球儀の赤道に対応する位置の近傍に存在する。これに対して、上記内輪２の中心軸と外輪３の中心軸とが不一致になる（軸交角α＜１８０°）と、等速ジョイント１の回転に伴って上記各ボール４、４が、図９の上下方向に往復変位（地球儀の北極方向と南極方向とに交互に変位）する。この結果、円周方向に隣り合うボール４、４同士の間隔が拡縮するので、上記各ポケット１０、１０を、それぞれ円周方向に長い矩形として、上記間隔の拡縮を行なえる様にしている。尚、上記内側係合溝７、７の底面７ａ、７ａと上記各外側係合溝８、８の底面８ａ、８ａとは、前述の説明から明らかな通り、互いに同心ではない。従って、上記経線に相当する線は、これら各係合溝７、８毎に、互いに少しずれた位置に存在する。
【０００６】
更に、図６に示す様に、前記一方の軸５と他方の軸６との変位に拘らず、上記各ボール４、４を、これら両軸５、６の軸交角α、即ち、上記一方の軸５の中心線ａと他方の軸６の中心線ｂとの交点ｏで両線ａ、ｂのなす角度αを二等分する、二等分面ｃ内に配置している。この為に、上記内側係合溝７、７の底面７ａ、７ａは、上記中心線ａ上で、上記交点ｏからｈだけ離れた点ｄを中心とする球面上に位置させ、上記外側係合溝８、８の底面８ａ、８ａは、上記中心線ｂ上で、上記交点ｏからｈだけ離れた点ｅを中心とする球面上に位置させている。但し、前記内輪２の外周面２ａ、外輪３の内周面３ａ、並びに前記保持器９の内外両周面は、それぞれ上記交点ｏを中心とする球面上に位置させて、上記内輪２の外周面２ａと保持器９の内周面との摺動、並びに外輪３の内周面３ａと保持器９の外周面との摺動を自在としている。
【０００７】
上述の様に構成する等速ジョイント１の場合、上記一方の軸５により内輪２を回転させると、この回転運動は６個のボール４、４を介して外輪３に伝達され、他方の軸６が回転する。両軸５、６同士の位置関係（上記軸交角α）が変化した場合には、上記各ボール４、４が内側、外側両係合溝７、８に沿って転動し、上記一方の軸５と他方の軸６との変位を許容する。
【０００８】
等速ジョイントの基本的な構造及び作用は上述の通りであるが、この様な等速ジョイントと、車輪を懸架装置に対して回転自在に支持する為の車輪用転がり軸受ユニットとを一体的に組み合わせる事が、近年研究されている。即ち、自動車の車輪を懸架装置に回転自在に支持する為には、外輪と内輪とを転動体を介して回転自在に組み合わせた車輪用転がり軸受ユニットを使用する。この様な車輪用転がり軸受ユニットと上述の様な等速ジョイントとを一体的に組み合わせれば、これら車輪用転がり軸受ユニットと等速ジョイントとを、全体として小型且つ軽量に構成できる。この様な車輪用転がり軸受ユニットと等速ジョイントとを一体的に組み合わせた、所謂第四世代のハブユニットと呼ばれる車輪用転がり軸受ユニットとして従来から、特開平７−３１７７５４号公報に記載されたものが知られている。
【０００９】
図１０は、この公報に記載された従来構造を示している。車両への組み付け状態で、懸架装置に支持した状態で回転しない外輪１１は、外周面にこの懸架装置に支持する為の第一の取付フランジ１２を、内周面に複列の外輪軌道１３、１３を、それぞれ有する。上記外輪１１の内側には、第一、第二の内輪部材１４、１５を組み合わせて成るハブ１６を配置している。このうちの第一の内輪部材１４は、外周面の一端寄り（図１０の左寄り）部分に車輪を支持する為の第二の取付フランジ１７を、同じく他端寄り（図１０の右寄り）部分に第一の内輪軌道１８を、それぞれ設けた円筒状に形成している。これに対して、上記第二の内輪部材１５は、一端部（図１０の左端部）を、上記第一の内輪部材１４を外嵌固定する為の円筒部１９とし、他端部（図１０の右端部）を等速ジョイント１ａの外輪３Ａとし、中間部外周面に第二の内輪軌道２０を設けている。そして、上記各外輪軌道１３、１３と上記第一、第二の内輪軌道１８、２０との間にそれぞれ複数個ずつの転動体２１、２１を設ける事により、上記外輪１１の内側に上記ハブ１６を、回転自在に支持している。
【００１０】
又、上記第一の内輪部材１４の内周面と上記第二の内輪部材１５の外周面との互いに整合する位置には、それぞれ係止溝２２、２３を形成すると共に、止め輪２４を、これら両係止溝２２、２３に掛け渡す状態で設けて、上記第一の内輪部材１４が上記第二の内輪部材１５から抜け出るのを防止している。更に、上記第二の内輪部材１５の一端面（図１０の左端面）外周縁部と、上記第一の内輪部材１４の内周面に形成した段部２５の内周縁部との間に溶接２６を施して、上記第一、第二の内輪部材１４、１５同士を結合固定している。
【００１１】
更に、上記外輪１１の両端開口部と上記ハブ１６の中間部外周面との間には、ステンレス鋼板等の金属製で略円筒状のカバー２７ａ、２７ｂと、ゴム、エラストマー等の弾性材製で円環状のシールリング２８ａ、２８ｂとを設けている。これらカバー２７ａ、２７ｂ及びシールリング２８ａ、２８ｂは、上記複数の転動体２１、２１を設置した部分と外部とを遮断し、この部分に存在するグリースが外部に漏出するのを防止すると共に、この部分に雨水、塵芥等の異物が侵入する事を防止する。又、上記第二の内輪部材１５の中間部内側には、この第二の内輪部材１５の内側を塞ぐ隔板部２９を設けて、この第二の内輪部材１５の剛性を確保すると共に、この第二の内輪部材１５の先端（図１０の左端）開口からこの第二の内輪部材１５の内側に入り込んだ異物が、前記等速ジョイント１ａ部分にまで達する事を防止している。尚、この等速ジョイント１ａは、前述の図６〜８に示した等速ジョイント１と同様に構成している。
【００１２】
上述の様に構成する車輪用転がり軸受ユニットを車両に組み付ける際には、第一の取付フランジ１２により外輪１１を懸架装置に支持し、第二の取付フランジ１７により駆動輪である車輪を第一の内輪部材１４に固定する。又、エンジンによりトランスミッションを介して回転駆動される、図示しない駆動軸の先端部を、等速ジョイント１ａを構成する内輪２の内側にスプライン係合させる。自動車の走行時には、この内輪２の回転を、複数のボール４、４を介して第二の内輪部材１５を含むハブ１６に伝達し、上記車輪を回転駆動する。
【００１３】
上述の様な第四世代のハブユニットをより小型化する為には、上記等速ジョイント１ａを構成する複数個のボール４、４の外接円の直径を小さくする事が有効である。そして、この外接円の直径を小さくする為、上記各ボール４、４の直径を小さくし、しかも上記等速ジョイント１ａにより伝達可能なトルクを確保する為には、上記ボール４、４の数を増やす必要がある。又、この様な事情によりボール４、４の数を増やした場合でも、これら各ボール４、４を保持する保持器９の耐久性を確保する為には、この保持器９に設けた複数のポケット１０、１０同士の間に存在する柱部３０、３０（図７、８、１１〜１４参照）の円周方向に亙る長さ寸法を確保する必要がある。何となれば、これら各柱部３０、３０の円周方向に亙る長さ寸法が不十分であると、上記保持器９の強度が不足し、長期間に亙る使用に伴って、上記各ポケット１０、１０の周縁部から亀裂等の損傷が発生する可能性が生じる為である。但し、これら各柱部３０、３０の長さ寸法を大きくする事は、ボール４、４との干渉防止の面から規制を受ける。即ち、第一として上記各ポケット１０、１０の円周方向に亙る長さは、上記等速ジョイント１ａをジョイント角（内輪２の中心軸と外輪３Ａの中心軸との位置関係が直線状態からずれた角度。図６に示した軸交角αの補角。）を付した状態で回転させた場合に、上記各ボール４、４が上記保持器９の円周方向に変位できる大きさである必要がある。又、第二として上記長さは、上記等速ジョイント１ａを組み立てるべく、内輪２と外輪３Ａと保持器９とを組み合わせた後、この保持器９、９のポケット１０、１０内に、上記各ボール４、４を組み込める大きさでなければならない。
【００１４】
この様な点を考慮しつつ、上記ボール４、４の数を６個よりも多くし、上記各柱部３０、３０の長さ寸法を大きくする構造として、特開平９−１７７８１４号公報には、図１１〜１４に示す様な等速ジョイント１ｂが記載されている。この公報に記載された等速ジョイント１ｂは、内輪２と外輪３との間の回転力伝達を８個のボール４、４を介して行なう様に構成している。そして、この公報に記載された構造の場合には、保持器９ａの円周方向８個所に、円周方向に亙る長さ寸法が大きいポケット１０ａ、１０ａと長さ寸法が短いポケット１０ｂ、１０ｂとを互いに等間隔に（分割ピッチ角を互いに等しくして）、且つ交互に配置している。これら２種類のポケット１０ａ、１０ｂのうち、長さ寸法が短いポケット１０ｂ、１０ｂは、ジョイント角を最大にしての上記等速ジョイント１ｂの使用状態でも、これら各ポケット１０ｂ、１０ｂの長さ方向両端部内側面とこれら各ポケット１０ｂ、１０ｂ内に保持されたボール４、４の転動面とが干渉しない大きさにしている。これに対して、長さ寸法が長いポケット１０ａ、１０ａは、上記各ポケット１０ｂ、１０ｂ内に上記各ボール４、４を組み込むべく、上記内輪２の中心軸と上記外輪３の中心軸とを、上記使用状態でのジョイント角の最大値を越えて傾斜させた状態でも、上記各ポケット１０ａ、１０ａの長さ方向両端部内側面と、既にこれら各ポケット１０ａ、１０ａ内に組み込んであるボール４、４とが干渉しない大きさにしている。
【００１５】
上述の様に構成される、前記特開平９−１７７８１４号公報に記載された等速ジョイントによれば、長さ寸法が長いポケット１０ａ、１０ａにボール４、４を組み込んだ後、長さ寸法が短いポケット１０ｂ、１０ｂ内にボールを組み込む事により、総てのポケット１０ａ、１０ｂ内にボール４、４を組み込める。即ち、これら各ポケット１０ａ、１０ｂ内にボール４、４を組み込む際には、図１４に示す様に、上記内輪２の中心軸と上記外輪３の中心軸とを、上記使用状態でのジョイント角の最大値を越えて傾斜させた状態で行なう。長さ寸法が長いポケット１０ａ、１０ａにボール４、４を組み込む際には、これら各ポケット１０ａ、１０ａの端部と、上記内輪２の外周面に形成した内側係合溝７、７の端部とが、上記ボール４、４の１個分以上整合する。従って、これら各ポケット１０ａ、１０ａ内へのボール４、４の組み込みを確実に行なえる。次いで、長さ寸法が短い４個のポケット１０ｂ、１０ｂ内にボール４、４を組み込むべく、上記内輪２の中心軸と上記外輪３の中心軸とを図１４に示す様に傾斜させると、既に上記長さ寸法が長いポケット１０ａ、１０ａ内に組み込んであるボール４、４が、図１３に鎖線矢印で示す様に、長さ寸法が短いポケット１０ｂ、１０ｂに近づく方向に、上記各ポケット１０ａ、１０ａ内で変位する。そして、上記長さ寸法が短い各ポケット１０ｂ、１０ｂの中央部と、上記内輪２の外周面に形成した内側係合溝７、７の端部とが整合する。従って、これら各ポケット１０ｂ、１０ｂ内へのボール４、４の組み込みを確実に行なえる。
【００１６】
更に、特開平９−３１７７８３号公報には、８個のボールを組み込んだ等速ジョイントに於いて、これら８個のボールのピッチ円直径Ｄ_P とこれら各ボールの直径Ｄ_B との関係、並びに、上記等速ジョイントを構成する外輪の外径Ｄ_O と内輪の中心部に形成したセレーション孔の内周面に形成した雌セレーションのピッチ円直径Ｄ_S との関係を規制する事が記載されている。即ち、この公報に記載された発明の場合には、３．３≦Ｄ_P ／Ｄ_B ≦５．０とし、２．５≦Ｄ_O ／Ｄ_S ≦３．５とするとしている。
【００１７】
【発明が解決しようとする課題】
上述した特開平９−３１７７８３号公報に記載された発明の様に、ボールのピッチ円直径Ｄ_P とボールの直径Ｄ_B との関係、並びに外輪の外径Ｄ_O と雌セレーションのピッチ円直径Ｄ_S との関係を規制するだけでは、等速ジョイントの強度・耐久性を確保しつつ小型化を図るには不十分である。特に、等速ジョイントのトルク容量を決める、セレーション孔の内周面に形成した雌セレーションのピッチ円直径Ｄ_S と、等速ジョイントの耐久性に大きな影響を与える上記ボールの直径Ｄ_B 、並びにボールのピッチ円直径Ｄ_P と各ボールの直径Ｄ_B との関係は、保持器に設けた柱部の強度を十分考慮した関係にしなければならない。
【００１８】
これに対して、仮に従来から一般的に実施されていた、６個のボールを組み込んだ等速ジョイントに対して、ボールの数を８個に増やす事により等速ジョイントを構成する外輪の外径を７％小型化する事を考えた場合、上記特開平９−３１７７８３号公報に記載された発明の様に、ボールのピッチ円直径Ｄ_P と各ボールの直径Ｄ_B との比を５．０とすると、各ボールの直径Ｄ_B が小さくなり過ぎて、ボールと外側係合溝及び内側係合溝の内側面との接触面圧が、６個のボールを組み込んだ等速ジョイントに比べて大幅に高くなり、耐久性を損なう。反対に、上記ボールのピッチ円直径Ｄ_P と各ボールの直径Ｄ_B との比を３．３とした場合には、各ボールの直径Ｄ_B が大きい為、保持器の柱部の長さが小さくなり、保持器の強度、耐久性が低下する。
【００１９】
又、上記特開平９−３１７７８３号公報に記載された発明では、外輪の外径Ｄ_O と内輪の中心部に形成したセレーション孔の内周面に形成した雌セレーションのピッチ円直径Ｄ_S との比を２．５〜３．５としているが、等速ジョイントを小型化するには、ボールのピッチ円直径Ｄ_P を内輪及び外輪に対して、どの位置に設定するかが重要である。更に、この場合に上記各ボールの直径Ｄ_B をどの程度に設定するかも重要である。
【００２０】
例えば、ボールのピッチ円直径Ｄ_P を大きくすれば、内輪の肉厚が大きくなって、内輪の強度並びに耐久性が高くなり、又、保持器の柱部の長さも大きくなって、保持器の強度並びに耐久性も高くなる。しかし外輪の肉厚が薄くなって、外輪の強度並びに耐久性が低下する。逆にボールのピッチ円直径Ｄ_P を小さくすれば、内輪の肉厚が薄くなり、内輪の強度並びに耐久性が低下し、又、保持器の柱部の長さも小さくなり保持器の強度並びに耐久性も低下する。
この様な事情に鑑みて本発明は、構成各部材の強度並びに耐久性を、現在一般的に使用されている、ボールを６個組み込んだ構造のものと同等に保ちつつ、等速ジョイントの小型化を実現すべく発明したものである。
【００２１】
【課題を解決する為の手段】
本発明の等速ジョイントは、前述した従来の等速ジョイントと同様に、中心部にセレーション孔を有する内輪と、この内輪の外周面の円周方向に互いに離隔した位置に存在する８個所に、それぞれ円周方向に対し直角方向に形成された断面円弧形の内側係合溝と、上記内輪の周囲に設けられた外輪と、この外輪の内周面で上記各内側係合溝と対向する位置に、円周方向に対し直角方向に形成された断面円弧形の外側係合溝と、上記内輪の外周面と外輪の内周面との間に挟持され、上記内側、外側両係合溝に整合する位置にそれぞれ円周方向に長い８個のポケットを形成した保持器と、これら各ポケットの内側に１個ずつ保持された状態で内側、外側両係合溝に沿う転動を自在とされた、８個のボールとから成り、これら各ボールを、上記内輪の中心軸と上記外輪の中心軸との軸交角を二等分し、これら両中心軸を含む平面に対し直交する二等分面内に配置している。
【００２２】
特に、本発明の等速ジョイントに於いては、上記８個のボールのピッチ円直径をＤ_Pとし、これら各ボールの直径をＤ_Bとし、上記セレーション孔の内周面に設けた雌セレーションのピッチ円直径をＤ_S とした場合に、３．５≦Ｄ_P／Ｄ_B≦３．９、２．０≦Ｄ_P／Ｄ_S≦２．２、０．５１≦Ｄ_B／Ｄ_S ≦０．６３の関係を何れも満たす。
更に、本発明の等速ジョイントに於いては、上記外輪の開口周縁部に、上記各外側係合溝と軸方向に連続する凹部を、全周に亙り設けている。そして、この凹部と上記外輪の軸方向内端面との連続部と、この凹部とこの外輪の内周面のうちで上記各外側係合溝同士の間部分に存在する肩面との連続部とを通過する、仮想円すい面の母線よりも径方向外方に、上記凹部と上記各外側係合溝の開口端縁部との連続部を配置している。
【００２３】
【作用】
上述の様に構成する本発明の等速ジョイントによれば、等速ジョイントの小型化を図るべく、ボールの数を従来一般的に実施されていた６個から８個に増やし、これら各ボールの直径を小さくした場合でも、保持器、内輪、外輪の強度並びに耐久性を、ボールを６個組み込んだ構造のものと同等に保つ事ができる。この様に、構成各部材の強度及び耐久性を確保しつつ等速ジョイントを小径化する事ができて、等速ジョイントとハブユニットの内輪とを一体化した、所謂第四世代のハブユニットの実用化が可能になる。
又、上記外輪の開口周縁部に、上記各外側係合溝と連続する凹部を全周に亙り設けている為、上記各ポケット内に上記各ボールを組み込む際に、これら各ボールと上記外輪の開口周縁部とが干渉する事を防止できる。従って、上記内輪とこの外輪との中心軸同士の変位量が比較的小さくても、上記各ポケット内への上記各ボールの組み込み作業を行なう事ができる。又、上記凹部の形状を上述の様に規制している為、ボール組み込み用治具と、上記各外側係合溝の開口端縁部とが当接する事を防止して、ボール組み込み作業の円滑化に寄与する事ができる。
【００２４】
尚、ボールのピッチ円直径Ｄ_P と、これら各ボールの直径Ｄ_B と、セレーション孔の内周面に設けた雌セレーションのピッチ円直径Ｄ_S との関係を上述の様に規制した理由は、次の通りである。
▲１▼ ３．５≦Ｄ_P ／Ｄ_B ≦３．９とした理由
ボールのピッチ円直径Ｄ_P に対して、これら各ボールの直径Ｄ_B を決める場合に、これら各ボールの直径Ｄ_B を大きくすれば、これら各ボールの転動面と内側係合溝及び外側係合溝の内側面との接触面圧を低く設定できる。但し、保持器に、このボールを組み込めるだけのポケットを設ける事を考慮しなければならない。特に、このポケットの内側で上記内側係合溝及び外側係合溝の間部分にボールを組み込む際、並びに等速ジョイントの運転時、ボールはポケットの中で周方向に移動するので、その分、ポケットの周方向に亙る長さを大きくしておく必要がある。従って、上記各ボールの直径Ｄ_B を大きくすれば、保持器の柱部の長さが小さくなり、保持器の強度が低下する。逆に上記各ボールの直径Ｄ_B を小さくすれば、保持器の柱部の長さを大きくでき、保持器の強度は向上するが、上記各ボールの転動面と内側係合溝及び外側係合溝の内側面との接触面圧が高くなり、これら内側係合溝及び外側係合溝を設けた内輪及び外輪の耐久性が低下する。下記の表１は、ボールのピッチ円直径Ｄ_P と各ボールの直径Ｄ_B との比（Ｄ_P ／Ｄ_B ）と、保持器の強度並びに上記各ボールの転動面と内側係合溝及び外側係合溝の内側面との接触面圧との関係を示したものである。
【００２５】
【表１】

【００２６】
この表１中、○印は可を、×印は不可を、それぞれ表している。又、保持器の強度は実験結果に基づくものであり、各ボールの転動面と内側係合溝及び外側係合溝の内側面との接触面圧は、計算により求めたものである。この接触面圧が４，２００ＭＰａ（４２８kgf/ mm²）を超えた場合には、等速ジョイントの運転を円滑に行なえないとして、×（不可）とした。即ち、等速ジョイントを構成する場合に一般的な、ＨRC６０〜６４程度に焼入硬化した鋼に、上記４，２００ＭＰａなる接触圧力を与えると、ボールと上記各内側面との永久変形量の和が、ボールの直径Ｄ_B のほぼ０．０００１倍となる。そして、この永久変形量の和がこの値を超えると、ボールの円滑な運動を妨げる様になる。そこで、上記した表１の結果から、ボールのピッチ円直径Ｄ_P と、これら各ボールの直径Ｄ_B との関係を、３．５≦Ｄ_P ／Ｄ_B ≦３．９とした。
【００２７】
▲２▼ ２．０≦Ｄ_P ／Ｄ_S ≦２．２とした理由
上記各ボールの直径Ｄ_B を小さくし、代りにボールの数を増やす事によって、等速ジョイントの小型化を図れるが、これら各ボールの直径Ｄ_B は無制限に小さくできる訳ではない。又、ボールのピッチ円直径Ｄ_P の設定範囲は、上記各ボールの直径Ｄ_B と、保持器に設ける柱部に必要とする長さとにより限定される。下記の表２は、ボールのピッチ円直径Ｄ_P と、セレーション孔の内周面に設けた雌セレーションのピッチ円直径Ｄ_S との比（Ｄ_P ／Ｄ_S ）と、上記各ボールの転動面と内側係合溝及び外側係合溝の内側面との接触面圧との関係を示したものである。
【００２８】
【表２】

【００２９】
この表中、○印は可を、×印は不可を、それぞれ表している。ちなみに、現在一般的に使用されている、６個のボールを組み込んだ一般的な等速ジョイントの場合、上記比Ｄ_P ／Ｄ_S は、２．２〜２．４程度である。従って、この比Ｄ_P ／Ｄ_S が２．２を越えた場合には、ボールの数を６個から８個に増やす事による小型化を図れない。
そこで、この様な表２の結果から、ボールのピッチ円直径Ｄ_P と、セレーション孔の内周面に設けた雌セレーションのピッチ円直径Ｄ_S との関係を、２．０≦Ｄ_P ／Ｄ_S ≦２．２とした。
【００３０】
▲３▼ ０．５１≦Ｄ_B ／Ｄ_S ≦０．６３とした理由
ボールのピッチ円直径がＤ_P 、各ボールの直径がＤ_B 、セレーション孔の内周面に設けた雌セレーションのピッチ円直径がＤ_S であり、
３．５≦Ｄ_P ／Ｄ_B ≦３．９ −−− （１）
２．０≦Ｄ_P ／Ｄ_S ≦２．２ −−− （２）
であるから、（１）式より
Ｄ_P ／３．９≦Ｄ_B ≦Ｄ_P ／３．５ −−− （３）
（２）式より、
Ｄ_P ／２．２≦Ｄ_S ≦Ｄ_P ／２．０ −−− （４）
（３）、（４）式より、
２．０／３．９≦Ｄ_B ／Ｄ_S ≦２．２／３．５
０．５１≦Ｄ_B ／Ｄ_S ≦０．６３
となる。
【００３１】
【発明の実施の形態】
図１〜５は、本発明の実施の形態の１例として、本発明を第四世代のハブユニットを構成する等速ジョイントに適用した状態を示している。懸架装置に支持した状態で回転しない外輪１１は、外周面にこの懸架装置に支持する為の第一の取付フランジ１２を、内周面に複列の外輪軌道１３、１３を、それぞれ有する。上記外輪１１の内径側には、ハブ本体３２と内輪３３とから成るハブ３４を、この外輪１１と同心に配置している。このハブ３４の外周面で上記各外輪軌道１３、１３に対向する部分には、それぞれ第一、第二の内輪軌道１８、２０を設けている。これら両内輪軌道１８、２０のうち、第一の内輪軌道１８は、上記ハブ本体３２の中間部外周面に直接形成している。又、このハブ本体３２の中間部のうち、上記第一の内輪軌道１８を形成した部分よりも内端寄り（図１の右端寄り）部分に、上記内輪３３を外嵌している。上記第二の内輪軌道２０は、この内輪３３の外周面に形成している。そして、上記各外輪軌道１３、１３と上記第一、第二の内輪軌道１８、２０との間に、それぞれ複数個ずつの転動体２１、２１を転動自在に設ける事により、上記外輪１１の内側に上記ハブ３４を、回転自在に支持している。
【００３２】
図示の例の場合には、上述の様に、上記第一の内輪軌道１８を上記ハブ本体３２の外周面に直接形成する事により、この第一の内輪軌道１８の直径を、上記内輪３３の外周面に形成した第二の内輪軌道２０の直径よりも小さくしている。又、この様に第一の内輪軌道１８の直径を第二の内輪軌道２０の直径よりも小さくした事に伴い、上記第一の内輪軌道１８と対向する外側（自動車への組み付け状態で幅方向外側となる側を言い、図１の左側）の外輪軌道１３の直径を、内側（自動車への組み付け状態で幅方向中央側となる側を言い、図１の右側）の外輪軌道１３の直径よりも小さくしている。更に、この外側の外輪軌道１３を形成した、外輪１１の外半部の外径を、上記内側の外輪軌道１３を形成した部分である、上記外輪１１の内半部の外径よりも小さくしている。又、図示の例では、この様に第一の内輪軌道１８及び外側の外輪軌道１３の直径を小さくした事に伴い、これら第一の内輪軌道１８と外側の外輪軌道１３との間に設ける転動体２１、２１の数を、上記第二の内輪軌道２０と内側の外輪軌道１３との間に設ける転動体２１、２１の数よりも少なくしている。
【００３３】
又、上記ハブ本体３２の外端部外周面には、このハブ本体３２に車輪を支持固定する為の第二の取付フランジ１７を、このハブ本体３２と一体に設けており、この第二の取付フランジ１７に、上記車輪を結合する為の複数本のスタッド３５の基端部を固定している。図示の例の場合にこれら複数本のスタッド３５のピッチ円直径は、上述の様に外輪１１の外半部の外径を、同じく内半部の外径よりも小さくした分だけ（上記各スタッド３５の頭部３６が上記外輪１１の外端部外周面と干渉しない程度に）小さくしている。尚、上記ハブ本体３２の外周面のうちで、上記第一の内輪軌道１８を形成した部分よりも軸方向内方に存在する部分の直径は、この第一の内輪軌道１８に対応する転動体２１、２１の内接円の直径よりも小さくしている。この理由は、車輪用転がり軸受ユニットの組み立て時に、外輪１１の外端部内周面に形成した外輪軌道１３の内径側に複数の転動体２１、２１を組み付けると共に、上記外輪１１の外端部内周面にシールリング３７を内嵌固定した状態で、この外輪１１の内径側に上記ハブ本体３２を挿入自在とする為である。又、上記ハブ本体３２の中間部外周面で、上記第一の内輪軌道１８と上記内輪３３を外嵌した部分との間部分には、全周に亙り凹溝状の肉盗み部３８を形成して、上記ハブ本体３２の軽量化を図っている。
【００３４】
又、上記ハブ本体３２に外嵌した内輪３３が軸方向内端側にずれ動くのを防止して、上記各外輪軌道１３、１３と上記第一、第二の内輪軌道１８、２０との間にそれぞれ複数個ずつ転動自在に設けた、上記各転動体２１、２１に付与した予圧を適正値に保持すべく、上記ハブ本体３２の外周面内端寄り部分に全周に亙り形成した係止凹溝３９に、止め輪４０を係止している。この止め輪４０は、それぞれが半円弧状である、１対の止め輪素子により構成している。この様な止め輪４０は、上記各転動体２１、２１に適正な予圧を付与すべく、上記内輪３３を上記ハブ本体３２に対して軸方向外方に押圧しつつ、その内周縁部を上記係止凹溝３９に係合させる。上記内輪３３を軸方向外方に押圧している力を解除した状態でも上記各転動体２１、２１に適正な予圧を付与したままにすべく、上記止め輪４０として、適切な厚さ寸法を有するものを選択使用する。即ち、上記止め輪４０として、厚さ寸法が僅かずつ異なるものを複数種類用意し、上記係止凹溝３９の溝幅等、転がり軸受ユニットの構成各部材の寸法との関係で適切な厚さ寸法を有する止め輪４０を選択し、上記係止凹溝３９に係合させる。従って、この止め輪４０を係止凹溝３９に係止すれば、上記押圧している力を解除しても、上記内輪３３が軸方向内端側にずれ動くのを防止して、上記各転動体２１、２１に適切な予圧を付与したままに保持できる。
【００３５】
又、上記止め輪４０を構成する１対の止め輪素子が直径方向外方に変位し、この止め輪４０が上記係止凹溝３９から不用意に抜け落ちる事を防止すべく、この止め輪４０の周囲に、間座４１の一部を配置している。この間座４１は、上記ハブ本体３２の内端部分に設けた、等速ジョイント用の外輪４２により構成する、本発明の対象である等速ジョイント１ｃ内に、雨水、塵芥等の異物が入り込むのを防止する為のブーツ４３の外端部を外嵌支持する為のものである。又、前記外輪１１の外端部内周面と上記ハブ本体３２の中間部外周面との間には前記シールリング３７を、上記外輪１１の内端部内周面と前記内輪３３の内端部外周面との間には組み合わせシールリング４４を、それぞれ設けて、前記複数の転動体２１、２１を設置した空間４５の両端開口部を塞いでいる。
【００３６】
更に、上記ハブ本体３２の内端部で、上記内輪３３と上記ブーツ４３の外端部とを外嵌した部分は、上述の様に、等速ジョイント１ｃの外輪となる外輪４２としている。この外輪４２の内周面の円周方向に関して等間隔位置には、それぞれ断面形状が円弧形である８本の外側係合溝８、８を、それぞれ円周方向に対し直角方向（図１の左右方向）に形成している。又、上記外輪４２の内側には、この外輪４２と共にツェッパ型の上記等速ジョイント１ｃを構成する為の、内輪２を配置している。そして、この内輪２の外周面に８本の内側係合溝７、７を、それぞれ円周方向に対し直角方向に、やはり円周方向に亙り等間隔に形成している。そして、これら各内側係合溝７、７と上記各外側係合溝８、８との間に、これら各係合溝７、８毎に１個ずつ、合計８個のボール４、４を、保持器９ａのポケット１０ａ、１０ｂ内に保持した状態で転動自在に設けている。更に、上記内輪２の中心部には、スプライン孔３１を軸方向に亙り形成している。自動車への組み付け状態でこのスプライン孔３１には、図示しない駆動軸の端部をスプライン係合させ、上記内輪２及び上記８個のボール４、４を介して、上記ハブ本体３２を回転駆動自在とする。
【００３７】
上記保持器９ａには、前述の図１１〜１４に示した従来構造の場合と同様に、円周方向の長さ寸法が互いに異なる２種類のポケット１０ａ、１０ｂを、円周方向に亙って交互に設けている。即ち、円周方向に亙る長さが大きいポケット１０ａ、１０ａを９０度置きに配置し、円周方向に関して、これら長さが大きいポケット１０ａ、１０ａ同士の中間位置に、円周方向に関する長さが小さいポケット１０ｂ、１０ｂを配置している。
【００３８】
又、図示の例では、上記外輪４２の開口周縁部に、上記各外側係合溝８、８と軸方向に連続する凹部４６を、全周に亙り形成している。上記各ポケット１０ａ、１０ｂ内にボール４、４を組み込む際には、上記凹部４６が、図４に示す様に、これら各ボール４、４と上記外輪４２の開口周縁部との干渉を防止する。従って、図示の例の場合には、内輪２と外輪４２との中心軸ａ、ｂ（図６）同士の変位量が比較的小さくても、上記各ポケット１０ａ、１０ｂ内へのボール４、４の組み込み作業を行なえる。
【００３９】
又、上記凹部４６の形状は、以下の様に規制している。即ち、この凹部４６と前記外輪４２の軸方向内端面との連続部（図５に示す位置Ａ）と、この凹部４６とこの外輪４２の内周面のうちで上記各外側係合溝８、８同士の間部分に存在する肩面４８との連続部（図５に示す位置Ｂ）とを通過する、仮想円すい面の母線よりも径方向外方に、上記凹部４６と上記各外側係合溝８、８の開口端縁部との連続部（図５に示す位置Ｃ）を配置している。この様な形状を有する上記凹部４６は、ボール組み込み用治具を構成するシャフト４７（図５）と、上記外側係合溝８、８の開口端縁部とが当接する事を防止して、ボール組み込み作業の円滑化に寄与する。即ち、上記各ポケット１０ａ、１０ｂ内にボール４、４を組み込む際には、上記ボール組み込み用治具のシャフト４７を上記内輪２のスプライン孔３１内に挿入し、この内輪２を揺動変位させる。この際、上記シャフト４７の外周面が、円周方向に亙って凹凸部を構成する、上記外側係合溝８、８の開口端縁部に当接すると、上記シャフト４７を操作する作業者に違和感を与える。これに対して本例の場合には、上記凹部４６を設ける事により、上記開口端縁部と上記シャフト４７の外周面とが当接する事を防止している。即ち、上記外輪４２に対して上記シャフト４７を大きく傾斜させた場合にこのシャフト４７の外周面は、上記凹部４６の開口周縁部に当接する。この開口周縁部は全周に亙って滑らかに連続するので、上記シャフト４７を操作する作業者に違和感を与える事はなく、作業の円滑化に寄与する。
【００４０】
各部を上述の様に構成する本発明の等速ジョイント１ｃに於いては、前記８個のボール４、４のピッチ円直径Ｄ_P と、これら各ボール４、４の直径Ｄ_B と、前記セレーション孔の内周面に設けた雌セレーションのピッチ円直径Ｄ_S との関係を、３．５≦Ｄ_P ／Ｄ_B ≦３．９、２．０≦Ｄ_P ／Ｄ_S ≦２．２、０．５１≦Ｄ_B ／Ｄ_S ≦０．６３としている。
【００４１】
上述の様に構成する本例の等速ジョイント１ｃを組み込んだ車輪用転がり軸受ユニットにより、車輪を懸架装置に対して回転自在に支持する作用は、前述した従来の等速ジョイントを組み込んだ車輪用転がり軸受ユニットの場合と同様である。又、本発明の等速ジョイント１ｃによれば、等速ジョイント１ｃの小型化を図るべく、ボール４、４の数を従来一般的に実施されていた６個から８個に増やし、これら各ボール４、４の直径を小さくした場合でも、保持器９ｂ、内輪２、外輪４２の強度並びに耐久性を、ボールを６個組み込んだ構造のものと同等に保つ事ができる。この様に、構成各部材の強度及び耐久性を確保しつつ等速ジョイント１ｃを小径化する事ができて、等速ジョイント１ｃと車輪用転がり軸受ユニットを構成するハブ本体３２とを一体化した、所謂第四世代のハブユニットの実用化が可能になる。
【００４２】
即ち、本発明の等速ジョイント１ｃを組み込んだ車輪用転がり軸受ユニットの場合には、この等速ジョイント１ｃを構成する内側、外側両係合溝７、８の数を８本とし、上記ボール４、４の数を８個としているので、車輪用転がり軸受ユニットの使用に伴う、ハブ３４と内輪２との間でのトルク伝達時に、上記等速ジョイント１ｃを構成する各ボール４、４毎に加わる負荷の大きさを、前述の図６〜７に示した従来構造の場合よりも小さくできる。従って、その分だけ、上記各ボール４、４の外径を小さくして、環状に配置したこれら各ボール４、４の外接円の直径、並びに上記複数の外側係合溝８、８の外接円の直径を小さくできる。そして、この様に外側係合溝８、８の外接円の直径を小さくした分、車輪用転がり軸受ユニットの外径寸法を小さくして、装置全体の小型・軽量化を図れる。しかも、上述の様に、構成各部材の強度並びに耐久性を確保できる。
【００４３】
特に、図示の例の様に、上記各外側係合溝８、８の外半部を前記第二の内輪軌道２０の内径側に配置すれば、車輪用転がり軸受ユニットの外径寸法だけでなく軸方向寸法も小さくして、装置全体の小型・軽量化をより有効に図れる。この様な本例の構造は、転がり軸受ユニット本体を構成する第二の内輪軌道２０を、上記各外側係合溝８、８よりも大径にせざるを得ず、上記転がり軸受ユニット本体の外径寸法が大きくなる。この様な本例の構造では、上記ボール４、４の数を６個から８個に増やして、その分ボール４、４の外径を小さくし、上記転がり軸受ユニットの外径寸法を小さくできる本発明の効果が、特に大きくなる。
【００４４】
更に、図示の例の場合には、前述した様に、外側の転動体列を構成する各転動体２１、２１のピッチ円直径を小さくする事により、外輪１１の外半部の外径を小さくできる。そして、この外輪１１の外半部の外径を小さくした分だけ、ハブ本体３２の外周面に設けた第二の取付フランジ１７に固定した複数のスタッド３５のピッチ円直径を小さくできる。従って、上記ハブ本体３２の軸方向寸法を大きくする事なく、上記スタッド３５を支持固定する上記第二の取付フランジ１７の外径を小さくして、車輪用転がり軸受ユニットの小型・軽量化を、更に有効に図れる。
【００４５】
尚、上述の様に、外側の転動体列を構成する各転動体２１、２１のピッチ円直径を内側の転動体列を構成する各転動体２１、２１のピッチ円直径よりも小さくする事に伴い、外側の転動体列部分の基本動定格荷重が内側の転動体列部分の基本動定格荷重よりも小さくなる。従って、両列に加わる荷重が同じであれば、外側の転動体列部分の寿命が内側の転動体列部分の寿命よりも短くなる。これに対して、一般的な自動車では、外側の転動体列部分に加わる荷重は内側の転動体列部分に加わる荷重よりも小さい。この為、上記両列部分の寿命をほぼ同じにする設計が容易になって、無駄のない設計が可能になる。尚、図示の例では、転動体２１、２１として玉を使用しているが、重量の嵩む自動車用の転がり軸受ユニットの場合には、転動体としてテーパころを使用する場合もある。本発明は、勿論、この様に転動体としてテーパころを使用する転がり軸受ユニットにも適用可能である。
【００４６】
【発明の効果】
本発明の等速ジョイントは、以上に述べた通り構成され作用するので、回転力伝達用のボールの数を８個とする事により外径を小さくできる構造で、しかも構成各部材の強度並びに耐久性を確保できる。従って、第四世代のハブユニットと呼ばれる、等速ジョイントを一体的に組み込んだ車輪用転がり軸受ユニットの小型・軽量化を、十分な耐久性を確保しつつ実現できる。
【図面の簡単な説明】
【図１】本発明の等速ジョイントを組み込んだ車輪用転がり軸受ユニットの１例を示す断面図。
【図２】図１のＡ−Ａ断面図。
【図３】保持器とボールとを取り出して図２と同方向から見た断面図。
【図４】等速ジョイントの保持器を、ボールの組み込みが可能な程度にまで外輪に対して傾斜させた状態を示す断面図。
【図５】等速ジョイントの保持器をボールの組み込みが可能な程度にまで外輪に対して傾斜させた状態で、組み込み用治具のシャフトと外輪との関係を示す断面図。
【図６】従来の等速ジョイントの第１例を、ジョイント角を付与した状態で示す断面図。
【図７】同じくジョイント角を付与しない状態で示す、図６のＢ−Ｂ断面に相当する図。
【図８】保持器の一部を外周側から見た図。
【図９】内側、外側両係合溝の底面の位置関係を示す模式図。
【図１０】等速ジョイントを一体的に組み込んだ車輪用転がり軸受ユニットの１例を示す断面図。
【図１１】従来の等速ジョイントの第２例を、ジョイント角を付与しない状態で示す断面図。
【図１２】図１１のＣ−Ｃ断面図。
【図１３】従来構造の第２例に組み込む保持器の断面図。
【図１４】保持器にボールを組み込むべく、内輪と外輪とを所定方向に変位させた状態を示す断面図。
【符号の説明】
１、１ａ、１ｂ、１ｃ等速ジョイント
２内輪
２ａ外周面
３、３Ａ外輪
３ａ内周面
４ボール
５軸
６軸
７内側係合溝
７ａ底面
８外側係合溝
８ａ底面
９、９ａ保持器
１０、１０ａ、１０ｂポケット
１１外輪
１２第一の取付フランジ
１３外輪軌道
１４第一の内輪部材
１５第二の内輪部材
１６ハブ
１７第二の取付フランジ
１８第一の内輪軌道
１９円筒部
２０第二の内輪軌道
２１転動体
２２係止溝
２３係止溝
２４止め輪
２５段部
２６溶接
２７ａ、２７ｂカバー
２８ａ、２８ｂシールリング
２９隔板部
３０柱部
３１スプライン孔
３２ハブ本体
３３内輪
３４ハブ
３５スタッド
３６頭部
３７シールリング
３８肉盗み部
３９係止凹溝
４０止め輪
４１間座
４２外輪
４３ブーツ
４４組み合わせシールリング
４５空間
４６凹部
４７シャフト
４８肩面 [0001]
BACKGROUND OF THE INVENTION
The constant velocity joint according to the present invention is incorporated, for example, in a rolling bearing unit for supporting a driving wheel in an independent suspension type suspension, and used to transmit a driving force from the transmission to the driving wheel.
[0002]
[Prior art]
A constant velocity joint is provided between the transmission of the automobile and the drive wheel supported by the independent suspension, and the engine is driven regardless of the relative displacement between the differential gear and the drive wheel and the steering angle applied to the wheel. Force can be transmitted to the drive wheel at the same angular velocity over the entire circumference. Conventionally, constant velocity joints used in such parts are known, for example, those described in Japanese Utility Model Laid-Open Nos. 57-145824-5, 59-185425, 62-12021, etc. Yes.
[0003]
Such a conventionally known constant velocity joint 1 is configured to transmit the rotational force between the inner ring 2 and the outer ring 3 through six

balls

4, 4 as shown in FIGS. It is composed. The inner ring 2 is fixed to the outer end portion of one shaft 5 that is rotationally driven by a transmission. For this reason, the center of the inner ring 2 has this shaft.

5

A spline hole 31 is provided for engaging a male spline portion formed at the end portion. The outer ring 3 is fixed to the inner end portion of the other shaft 6 to which the driving wheel is coupled. On the outer peripheral surface 2a of the inner ring 2, six

inner engagement grooves

7, 7 having an arc cross section are formed at equal intervals in the circumferential direction, respectively, at right angles to the circumferential direction. Further, on the inner peripheral surface 3a of the outer ring 3, there are six

outer engagement grooves

8, 8 having a circular arc shape in the circumferential direction at positions facing the

inner engagement grooves

7, 7. It is formed in a perpendicular direction.
[0004]
Further, between the outer peripheral surface 2a of the inner ring 2 and the inner peripheral surface 3a of the outer ring 3, a cage 9 having a circular cross section and an annular shape is sandwiched.

Pockets

10 and 10 are formed at positions corresponding to the inner and outer

engaging grooves

7 and 8 at six positions in the circumferential direction of the retainer 9, respectively, and 1 inside each

pocket

10 and 10. A total of six

balls

4, 4 are held one by one. The

balls

4 and 4 can roll along the inner and outer

engaging grooves

7 and 8 while being held in the

pockets

10 and 10, respectively.
[0005]
As shown in FIG. 8, each of the

pockets

10 and 10 has a rectangular shape that is long in the circumferential direction, and the interval between the

balls

4 and 4 that are adjacent to each other in the circumferential direction has changed in accordance with the change in the axis crossing angle α described below. Even so, this change is absorbed. That is, the positional relationship between the

bottom surfaces

7a and 7a of the

inner engagement grooves

7 and 7 and the positional relationship between the bottom surfaces 8a and 8a of the

outer engagement grooves

8 and 8 are as shown by a one-dot chain line in FIG. The relationship is like a meridian of the globe. When the center axis of the inner ring 2 and the center axis of the outer ring 3 coincide with each other (axis crossing angle α = 180 °), the

balls

4, 4 are located on the equator of the globe shown by a two-dot chain line in FIG. It exists in the vicinity of the corresponding position. On the other hand, when the central axis of the inner ring 2 and the central axis of the outer ring 3 do not coincide with each other (the axis crossing angle α <180 °), the

balls

4 and 4 are moved as the constant velocity joint 1 rotates. 9 is reciprocated in the vertical direction (displaced alternately in the north and south pole directions of the globe). As a result, the interval between the

balls

4, 4 adjacent to each other in the circumferential direction expands / contracts, so that the

pockets

10, 10 are each formed into a rectangle that is long in the circumferential direction so that the interval can be expanded / contracted. The

bottom surfaces

7a and 7a of the

inner engagement grooves

7 and 7 and the bottom surfaces 8a and 8a of the

outer engagement grooves

8 and 8 are not concentric with each other, as is apparent from the above description. Accordingly, a line corresponding to the meridian exists at a position slightly deviated from each other for each of the

engagement grooves

7 and 8.
[0006]
Further, as shown in FIG. 6, regardless of the displacement between the one shaft 5 and the other shaft 6, the

balls

4, 4 are moved to the axis crossing angle α between the two shafts 5, 6, that is, The angle a formed by the two lines a and b is bisected at the intersection o between the center line a of the shaft 5 and the center line b of the other shaft 6. For this purpose, the

bottom surfaces

7a, 7a of the

inner engagement grooves

7, 7 are positioned on a spherical surface centered on a point d separated from the intersection o by h on the center line a. The bottom surfaces 8a and 8a of the

grooves

8 and 8 are positioned on a spherical surface centered on a point e that is separated from the intersection o by h on the center line b. However, the outer peripheral surface 2a of the inner ring 2, the inner peripheral surface 3a of the outer ring 3, and both inner and outer peripheral surfaces of the retainer 9 are positioned on a spherical surface centering on the intersection point o, respectively, The sliding between the surface 2 a and the inner peripheral surface of the cage 9 and the sliding between the inner peripheral surface 3 a of the outer ring 3 and the outer peripheral surface of the cage 9 are made free.
[0007]
In the case of the constant velocity joint 1 configured as described above, when the inner ring 2 is rotated by the one shaft 5, this rotational motion is transmitted to the outer ring 3 via the six

balls

4, 4, and the other shaft 6 Rotates. When the positional relationship between the shafts 5 and 6 (the above-mentioned axis crossing angle α) changes, the

balls

4 and 4 roll along the inner and outer

engaging grooves

7 and 8 and the one shaft 5 and the other shaft 6 are allowed to be displaced.
[0008]
Although the basic structure and operation of the constant velocity joint are as described above, such a constant velocity joint and a wheel rolling bearing unit for supporting the wheel rotatably with respect to the suspension device are integrated. Combining has been studied in recent years. That is, in order to rotatably support a vehicle wheel on a suspension device, a wheel rolling bearing unit in which an outer ring and an inner ring are rotatably combined via a rolling element is used. If such a wheel rolling bearing unit and a constant velocity joint as described above are combined together, the wheel rolling bearing unit for a wheel and the constant velocity joint can be made small and light as a whole. Conventionally, such a wheel rolling bearing unit for a wheel called a fourth generation hub unit, in which a wheel rolling bearing unit for a wheel and a constant velocity joint are integrally combined, is described in JP-A-7-317754. It has been known.
[0009]
FIG. 10 shows a conventional structure described in this publication. The outer ring 11 that does not rotate while being supported by the suspension device when assembled to the vehicle has a first mounting flange 12 for supporting the suspension device on the outer peripheral surface and a double row outer ring raceway 13 on the inner peripheral surface. 13 respectively. A hub 16 formed by combining the first and second

inner ring members

14 and 15 is disposed inside the outer ring 11. Of these, the first inner ring member 14 has a second mounting flange 17 for supporting the wheel on one end portion (left side in FIG. 10) of the outer peripheral surface, and on the other end portion (right side in FIG. 10). The first inner ring raceway 18 is formed in a cylindrical shape provided. On the other hand, the second inner ring member 15 has one end portion (left end portion in FIG. 10) as a cylindrical portion 19 for fitting and fixing the first inner ring member 14 to the other end portion (FIG. 10). Is the outer ring 3A of the constant velocity joint 1a, and the second inner ring raceway 20 is provided on the outer peripheral surface of the intermediate part. Then, by providing a plurality of

rolling elements

21 and 21 between the

outer ring raceways

13 and 13 and the first and second

inner ring raceways

18 and 20, the hub 16 is provided inside the outer ring 11. Is supported rotatably.
[0010]
Further,

locking grooves

22 and 23 are formed at positions where the inner peripheral surface of the first inner ring member 14 and the outer peripheral surface of the second inner ring member 15 are aligned with each other, and a retaining ring 24 is provided. The first inner ring member 14 is prevented from slipping out of the second inner ring member 15 by being provided in a state of being hung over both the

locking grooves

22 and 23. Further, welding is performed between the outer peripheral edge of one end surface (left end surface in FIG. 10) of the second inner ring member 15 and the inner peripheral edge of the step portion 25 formed on the inner peripheral surface of the first inner ring member 14. 26, the first and second

inner ring members

14, 15 are coupled and fixed together.
[0011]
Further, between the opening portions at both ends of the outer ring 11 and the outer peripheral surface of the intermediate portion of the hub 16 are made of a metal and substantially cylindrical cover 27a, 27b such as a stainless steel plate, and an elastic material such as rubber or elastomer. Annular seal rings 28a and 28b are provided. The covers 27a and 27b and the seal rings 28a and 28b block the portion where the plurality of rolling

elements

21 and 21 are installed from the outside, and prevent the grease existing in the portion from leaking outside. Prevents foreign matter such as rainwater and dust from entering the area. In addition, a partition plate portion 29 that closes the inside of the second inner ring member 15 is provided inside the intermediate portion of the second inner ring member 15 to ensure the rigidity of the second inner ring member 15 and Foreign matter that has entered the inside of the second inner ring member 15 from the opening (left end in FIG. 10) of the second inner ring member 15 is prevented from reaching the constant velocity joint 1a. The constant velocity joint 1a is configured in the same manner as the constant velocity joint 1 shown in FIGS.
[0012]
When the rolling bearing unit for a wheel configured as described above is assembled to a vehicle, the outer ring 11 is supported on the suspension device by the first mounting flange 12, and the wheel as the driving wheel is first supported by the second mounting flange 17. The inner ring member 14 is fixed. Further, the tip of a drive shaft (not shown) that is rotationally driven by the engine via the transmission is spline-engaged with the inner side of the inner ring 2 constituting the constant velocity joint 1a. During traveling of the automobile, the rotation of the inner ring 2 is transmitted to the hub 16 including the second inner ring member 15 through the plurality of

balls

4 and 4 to drive the wheels to rotate.
[0013]
In order to reduce the size of the fourth generation hub unit as described above, it is effective to reduce the diameter of the circumscribed circle of the plurality of

balls

4 and 4 constituting the constant velocity joint 1a. In order to reduce the diameter of the circumscribed circle, the diameter of each of the

balls

4 and 4 is reduced, and in order to secure a torque that can be transmitted by the constant velocity joint 1a, the number of the

balls

4 and 4 is set. Need to increase. Further, even when the number of

balls

4 and 4 is increased due to such circumstances, in order to ensure the durability of the cage 9 that holds the

balls

4 and 4, a plurality of balls 9 provided in the cage 9 are provided. It is necessary to ensure the length of the column portions 30 and 30 (see FIGS. 7, 8 and 11 to 14) existing between the

pockets

10 and 10 in the circumferential direction. If the length of the

pillars

30 and 30 extending in the circumferential direction is insufficient, the strength of the retainer 9 is insufficient, and the pockets 10 are used with use over a long period of time. This is because there is a possibility that damage such as cracks may occur from the peripheral portion of the ten. However, increasing the length of each of the

pillars

30 and 30 is restricted from the viewpoint of preventing interference with the

balls

4 and 4. That is, the length of the

pockets

10 and 10 in the circumferential direction is that the constant velocity joint 1a has a joint angle (the positional relationship between the central axis of the inner ring 2 and the central axis of the outer ring 3A is deviated from a linear state). The

balls

4 and 4 need to be large enough to be displaced in the circumferential direction of the cage 9 when rotated in a state of being supplemented with the axis crossing angle α shown in FIG. There is. Secondly, the above-mentioned length is determined by combining the inner ring 2, the outer ring 3 </ b> A and the cage 9 in order to assemble the constant velocity joint 1 a. It must be large enough to accommodate the

balls

4 and 4.
[0014]
In consideration of these points, Japanese Patent Application Laid-Open No. 9-177814 discloses a structure in which the number of the

balls

4 and 4 is larger than six and the lengths of the

pillars

30 and 30 are increased. The constant velocity joint 1b as shown to FIGS. 11-14 is described. The constant velocity joint 1b described in this publication is configured to transmit the rotational force between the inner ring 2 and the outer ring 3 through eight

balls

4 and 4. In the case of the structure described in this publication, pockets 10a and 10a having a large length in the circumferential direction and pockets 10b and 10b having a short length are provided at eight locations in the circumferential direction of the cage 9a. Are arranged at equal intervals (with equal division pitch angles) and alternately. Of these two types of pockets 10a and 10b, the

pockets

10b and 10b having a short length are both ends in the longitudinal direction of the

pockets

10b and 10b even when the constant velocity joint 1b is used with the joint angle being maximized. The inner side surface and the rolling surfaces of the

balls

4 and 4 held in the

pockets

10b and 10b are set so as not to interfere with each other. On the other hand, the pockets 10a and 10a having a long length have a central axis of the inner ring 2 and a central axis of the outer ring 3 in order to incorporate the

balls

4 and 4 into the

pockets

10b and 10b. Even in a state where the joint angle is inclined beyond the maximum value of the joint angle in the use state, the inner surfaces of both ends in the longitudinal direction of the pockets 10a, 10a and the

balls

4, 4 already incorporated in the pockets 10a, 10a. The size is such that it does not interfere with.
[0015]
According to the constant velocity joint described in JP-A-9-177814, which is configured as described above, after the

balls

4 and 4 are assembled in the pockets 10a and 10a having long lengths, the length dimensions are By incorporating the balls into the

short pockets

10b and 10b, the

balls

4 and 4 can be incorporated into all the pockets 10a and 10b. That is, when the

balls

4 and 4 are assembled in the pockets 10a and 10b, as shown in FIG. 14, the center angle of the inner ring 2 and the center axis of the outer ring 3 are set to the joint angle in the use state. It is performed in a state of being inclined beyond the maximum value of. When the

balls

4 and 4 are assembled into the pockets 10a and 10a having a long length, the end portions of the pockets 10a and 10a and the end portions of the

inner engagement grooves

7 and 7 formed on the outer peripheral surface of the inner ring 2 are used. Match one or more of the

balls

4, 4. Therefore, it is possible to reliably incorporate the

balls

4 and 4 into the pockets 10a and 10a. Next, when the central axis of the inner ring 2 and the central axis of the outer ring 3 are inclined as shown in FIG. 14 in order to incorporate the

balls

4 and 4 into the four

pockets

10b and 10b having a short length, The

balls

4 and 4 incorporated in the pockets 10a and 10a having long lengths are arranged in the direction approaching the

pockets

10b and 10b having short lengths as shown by chain line arrows in FIG. Displace within 10a. And the center part of each

pocket

10b, 10b with a short said length dimension and the edge part of the inner

side engagement grooves

7 and 7 formed in the outer peripheral surface of the said inner ring | wheel 2 align. Therefore, it is possible to reliably incorporate the

balls

4 and 4 into the

pockets

10b and 10b.
[0016]
Further, JP-A-9-317783 discloses a pitch circle diameter D of eight balls in a constant velocity joint incorporating eight balls._P And the diameter D of each of these balls_B And the outer diameter D of the outer ring constituting the constant velocity joint._O The pitch circle diameter D of the female serration formed on the inner peripheral surface of the serration hole formed at the center of the inner ring_S It regulates the relationship between That is, in the case of the invention described in this publication, 3.3 ≦ D_P / D_B ≦ 5.0, 2.5 ≦ D_O / D_S ≦ 3.5.
[0017]
[Problems to be solved by the invention]
As in the invention described in Japanese Patent Laid-Open No. 9-317783, the pitch circle diameter D of the ball_P And ball diameter D_B And the outer diameter D of the outer ring_O And female serration pitch circle diameter D_S Is not sufficient to reduce the size while ensuring the strength and durability of the constant velocity joint. In particular, the pitch diameter D of the female serration formed on the inner peripheral surface of the serration hole, which determines the torque capacity of the constant velocity joint._S And the diameter D of the ball, which greatly affects the durability of the constant velocity joint_B , As well as the pitch circle diameter D of the ball_P And the diameter D of each ball_B The relationship between and should be a relationship that fully considers the strength of the pillar provided in the cage.
[0018]
On the other hand, the outer diameter of the outer ring constituting the constant velocity joint is increased by increasing the number of balls to eight compared to the constant velocity joint in which six balls are incorporated, which has been generally performed conventionally. Is considered to be downsized by 7%, the pitch circle diameter D of the ball as in the invention described in the above-mentioned JP-A-9-317783._P And the diameter D of each ball_B If the ratio to the diameter is 5.0, the diameter D of each ball_B Becomes too small, the contact surface pressure between the ball and the inner surface of the outer engagement groove and the inner engagement groove is significantly higher than that of a constant velocity joint incorporating six balls, which impairs durability. On the contrary, the pitch circle diameter D of the ball_P And the diameter D of each ball_B When the ratio to the diameter is 3.3, the diameter D of each ball_B Therefore, the length of the cage column is reduced, and the strength and durability of the cage are reduced.
[0019]
Further, in the invention described in the above-mentioned JP-A-9-317783, the outer diameter D of the outer ring_O The pitch circle diameter D of the female serration formed on the inner peripheral surface of the serration hole formed at the center of the inner ring_S However, in order to reduce the constant velocity joint, the pitch circle diameter D of the ball_P It is important to set the position with respect to the inner ring and the outer ring. Further, in this case, the diameter D of each of the above balls_B It is also important how much to set.
[0020]
For example, the pitch circle diameter D of the ball_P Increasing the thickness of the inner ring increases the strength and durability of the inner ring, and increases the length of the pillar portion of the cage, thereby increasing the strength and durability of the cage. However, the thickness of the outer ring is reduced, and the strength and durability of the outer ring are reduced. Conversely, the pitch circle diameter D of the ball_P By reducing the thickness of the inner ring, the thickness of the inner ring is reduced, the strength and durability of the inner ring are lowered, and the length of the pillar portion of the cage is also reduced, so that the strength and durability of the cage are also lowered.
In view of such circumstances, the present invention is a small-sized constant velocity joint while maintaining the strength and durability of each constituent member equal to that of a structure in which six balls are generally used. It was invented in order to realize this.
[0021]
[Means for solving the problems]
The constant velocity joint of the present invention is similar to the conventional constant velocity joint described above, in the inner ring having a serration hole in the central portion, and at eight positions that are separated from each other in the circumferential direction of the outer circumferential surface of the inner ring. An inner engagement groove having an arc cross section formed in a direction perpendicular to the circumferential direction, an outer ring provided around the inner ring, and each inner engagement groove on the inner circumferential surface of the outer ring. The outer engagement groove having a circular arc cross section formed at a position perpendicular to the circumferential direction at a position, and sandwiched between the outer peripheral surface of the inner ring and the inner peripheral surface of the outer ring. A cage that has eight pockets that are long in the circumferential direction at positions that align with the grooves, and can be rolled along both the inner and outer engagement grooves while one pocket is held inside each pocket. And each of these balls is connected to the inner ring. The axis intersection angle between the central axis and the central axis of the outer ring bisecting are arranged on the bisecting plane perpendicular to the plane containing these two central axes.
[0022]
  In particular, in the constant velocity joint of the present invention, the pitch circle diameter of the eight balls is set to D._PAnd the diameter of each of these balls is D_BThe pitch circle diameter of the female serration provided on the inner peripheral surface of the serration hole is D_S  If 3.5 ≦ D_P/ D_B≦ 3.9, 2.0 ≦ D_P/ D_S≦ 2.2, 0.51 ≦ D_B/ D_S  All of the relations ≦ 0.63 are satisfied.
  Furthermore, in the constant velocity joint of the present invention, the outer circumferential edge of the outer ring is provided with a concave portion continuous with the outer engaging grooves in the axial direction over the entire circumference. And the continuous part of this recessed part and the axial direction inner end surface of the said outer ring | wheel, and the continuous part of this recessed part and the shoulder surface which exists in the part between each said outer engagement groove | channel among the inner peripheral surfaces of this outer ring | wheel The continuous part of the said recessed part and the opening edge part of each said outer engagement groove | channel is arrange | positioned in radial direction outward rather than the bus line of the virtual conical surface which passes through.
[0023]
[Action]
  According to the constant velocity joint of the present invention configured as described above, in order to reduce the size of the constant velocity joint, the number of balls is increased from six to eight, which has been generally practiced in the past. Even when the diameter is reduced, the strength and durability of the cage, inner ring, and outer ring can be kept equal to those of a structure in which six balls are incorporated. In this way, the constant velocity joint can be reduced in diameter while ensuring the strength and durability of the constituent members, and the so-called fourth generation hub unit in which the constant velocity joint and the inner ring of the hub unit are integrated. Practical application becomes possible.
  In addition, since the outer periphery of the opening of the outer ring is provided with a recess that is continuous with the outer engagement grooves on the entire circumference, when the balls are assembled in the pockets, Interference with the peripheral edge of the opening can be prevented. Therefore, even if the displacement between the central axes of the inner ring and the outer ring is relatively small, the work of assembling the balls into the pockets can be performed. In addition, since the shape of the concave portion is regulated as described above, the ball mounting jig and the opening edge of each outer engagement groove are prevented from coming into contact with each other so that the ball mounting operation is smooth. Can contribute to the development.
[0024]
The pitch circle diameter D of the ball_P And the diameter D of each of these balls_B And the pitch circle diameter D of the female serration provided on the inner peripheral surface of the serration hole._S The reason for regulating the relationship with the above is as follows.
▲ 1 ▼ 3.5 ≦ D_P / D_B Reason for ≦ 3.9
Ball pitch circle diameter D_P The diameter D of each of these balls_B The diameter D of each of these balls_B Is increased, the contact surface pressure between the rolling surfaces of these balls and the inner surfaces of the inner and outer engaging grooves can be set low. However, it must be considered that the cage is provided with a pocket that can accommodate the ball. In particular, when the ball is incorporated inside the pocket between the inner engagement groove and the outer engagement groove, and when the constant velocity joint is operated, the ball moves in the circumferential direction in the pocket. It is necessary to increase the length of the pocket in the circumferential direction. Therefore, the diameter D of each ball_B If is increased, the length of the pillar portion of the cage is reduced, and the strength of the cage is reduced. Conversely, the diameter D of each ball_B If the length of the cage is reduced, the length of the cage pillar can be increased and the strength of the cage is improved. However, the contact surfaces of the rolling surfaces of the balls and the inner surfaces of the inner and outer engagement grooves are as follows. The pressure is increased, and the durability of the inner ring and the outer ring provided with the inner engagement groove and the outer engagement groove is lowered. Table 1 below shows the pitch circle diameter D of the ball._P And the diameter D of each ball_B Ratio (D_P / D_B ) And the strength of the cage and the contact surface pressure between the rolling surface of each ball and the inner surfaces of the inner and outer engaging grooves.
[0025]
[Table 1]

[0026]
In Table 1, a circle mark represents “OK” and a cross mark represents “not possible”. The strength of the cage is based on the experimental results, and the contact surface pressure between the rolling surface of each ball and the inner surfaces of the inner and outer engaging grooves is obtained by calculation. This contact surface pressure is4,200MPa (428 kgf / mm²), The constant velocity joint could not be operated smoothly. That is, in the case of forming a constant velocity joint, the steel hardened and hardened to about HRC 60 to 64 is used.4,200When a contact pressure of MPa is applied, the sum of the permanent deformation amounts of the ball and each of the inner surfaces is the diameter D of the ball._B Is approximately 0.0001 times greater than AndThisIf the sum of the amount of permanent deformation exceeds this value, smooth movement of the ball will be hindered. Therefore, from the results of Table 1 above, the pitch circle diameter D of the ball_P And the diameter D of each of these balls_B And the relationship 3.5 ≦ D_P / D_B ≦ 3.9.
[0027]
(2) 2.0 ≦ D_P / D_S Reason for ≦ 2.2
Diameter D of each ball above_B The constant velocity joint can be miniaturized by reducing the diameter and increasing the number of balls instead._B Can't be made infinitely small. Also, the pitch circle diameter D of the ball_P The setting range is the diameter D of each ball._B And the length required for the pillar portion provided in the cage. Table 2 below shows the pitch circle diameter D of the ball._P And the pitch circle diameter D of the female serration provided on the inner peripheral surface of the serration hole._S Ratio (D_P / D_S ) And the contact surface pressure between the rolling surface of each of the balls and the inner surfaces of the inner and outer engaging grooves.
[0028]
[Table 2]

[0029]
In this table, a circle indicates yes and a cross indicates not. Incidentally, in the case of a general constant velocity joint that incorporates six balls, which is generally used at present, the above ratio D_P / D_S Is about 2.2 to 2.4. Therefore, this ratio D_P / D_S When the value exceeds 2.2, the size cannot be reduced by increasing the number of balls from six to eight.
Therefore, from the results of Table 2, the pitch circle diameter D of the ball_P And the pitch circle diameter D of the female serration provided on the inner peripheral surface of the serration hole._S And the relationship 2.0 ≦ D_P / D_S ≦ 2.2.
[0030]
(3) 0.51 ≦ D_B / D_S Reason for ≦ 0.63
The pitch circle diameter of the ball is D_P , The diameter of each ball is D_B The pitch circle diameter of the female serration provided on the inner peripheral surface of the serration hole is D_S And
3.5 ≦ D_P / D_B ≦ 3.9 −−− (1)
2.0 ≦ D_P / D_S ≦ 2.2 −−− (2)
Therefore, from equation (1)
D_P /3.9≦D_B ≦ D_P /3.5 --- (3)
From equation (2)
D_P /2.2≦D_S ≦ D_P /2.0 ---- (4)
From equations (3) and (4),
2.0 / 3.9 ≦ D_B / D_S ≦ 2.2 / 3.5
0.51 ≦ D_B / D_S ≦ 0.63
It becomes.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
1 to 5 show a state in which the present invention is applied to a constant velocity joint constituting a fourth generation hub unit as an example of an embodiment of the present invention. The outer ring 11 that does not rotate while being supported by the suspension device has a first mounting flange 12 for supporting the suspension device on the outer peripheral surface, and double-row

outer ring raceways

13 and 13 on the inner peripheral surface. On the inner diameter side of the outer ring 11, a hub 34 including a hub body 32 and an inner ring 33 is disposed concentrically with the outer ring 11. First and second

inner ring raceways

18 and 20 are provided on portions of the outer peripheral surface of the hub 34 facing the

outer ring raceways

13 and 13, respectively. Of these

inner ring raceways

18 and 20, the first inner ring raceway 18 is formed directly on the outer peripheral surface of the intermediate portion of the hub body 32. Further, the inner ring 33 is externally fitted to a portion closer to the inner end than the portion where the first inner ring raceway 18 is formed in the intermediate portion of the hub body 32 (closer to the right end in FIG. 1). The second inner ring raceway 20 is formed on the outer peripheral surface of the inner ring 33. A plurality of rolling

elements

21, 21 are provided between the

outer ring raceways

13, 13 and the first and second

inner ring raceways

18, 20, respectively. The hub 34 is rotatably supported on the inner side.
[0032]
In the case of the illustrated example, as described above, the first inner ring raceway 18 is formed directly on the outer peripheral surface of the hub main body 32, so that the diameter of the first inner ring raceway 18 is changed to that of the inner ring 33. The diameter of the second inner ring raceway 20 formed on the outer peripheral surface is made smaller. Further, as the diameter of the first inner ring raceway 18 is made smaller than the diameter of the second inner ring raceway 20 in this way, the outer side facing the first inner ring raceway 18 (in the width direction in the assembled state to the automobile) The diameter of the outer ring raceway 13 on the outside side (left side in FIG. 1) is larger than the diameter of the outer ring raceway 13 on the inside (right side in FIG. 1 on the right side in FIG. 1). Is also small. Further, the outer diameter of the outer half portion of the outer ring 11 that forms the outer ring raceway 13 on the outside is made smaller than the outer diameter of the inner half portion of the outer ring 11 that is the portion where the inner outer ring raceway 13 is formed. ing. Further, in the example shown in the drawing, as the diameters of the first inner ring raceway 18 and the outer outer ring raceway 13 are reduced in this way, the rolling provided between the first inner ring raceway 18 and the outer outer ring raceway 13 is reduced. The number of moving

bodies

21 and 21 is smaller than the number of

rolling elements

21 and 21 provided between the second inner ring raceway 20 and the inner outer ring raceway 13.
[0033]
A second mounting flange 17 for supporting and fixing a wheel to the hub body 32 is provided integrally with the hub body 32 on the outer peripheral surface of the outer end portion of the hub body 32. A base end portion of a plurality of studs 35 for connecting the wheel is fixed to the mounting flange 17. In the case of the illustrated example, the pitch circle diameter of the plurality of studs 35 is equal to the outer diameter of the outer half of the outer ring 11 smaller than the outer diameter of the inner half as described above (each of the studs described above). The 35 heads 36 are made small (so as not to interfere with the outer peripheral surface of the outer end of the outer ring 11). Of the outer peripheral surface of the hub main body 32, the diameter of the portion existing in the axial direction from the portion where the first inner ring raceway 18 is formed is the rolling element corresponding to the first inner ring raceway 18. 21 and 21 are smaller than the diameter of the inscribed circle. This is because, when the rolling bearing unit for the wheel is assembled, a plurality of rolling

elements

21 and 21 are assembled on the inner diameter side of the outer ring raceway 13 formed on the inner peripheral surface of the outer ring 11, and the inner periphery of the outer ring 11 is assembled. This is because the hub main body 32 can be inserted into the inner diameter side of the outer ring 11 with the seal ring 37 fitted and fixed to the surface. Further, on the outer peripheral surface of the intermediate portion of the hub main body 32, a groove stealing portion 38 having a groove shape is formed over the entire circumference between the first inner ring raceway 18 and the portion where the inner ring 33 is externally fitted. Thus, the hub body 32 is reduced in weight.
[0034]
Further, the inner ring 33 fitted on the hub main body 32 is prevented from moving to the inner end side in the axial direction, so that the

outer ring raceways

13 and 13 and the first and second inner ring raceways 18,20In order to keep the preload applied to each of the rolling

elements

21 and 21 provided in a freely movable manner at a proper value, the hub main body 32 has an entire inner periphery near the inner end of the outer peripheral surface. The retaining ring 40 is locked in the formed locking groove 39. The retaining ring 40 is constituted by a pair of retaining ring elements each having a semicircular arc shape. Such a retaining ring 40 presses the inner ring 33 against the hub body 32 in the axial direction so as to apply an appropriate preload to each of the rolling

elements

21, 21, and the inner peripheral edge of the inner ring 33 is Engage with the locking groove 39. In order to keep an appropriate preload applied to the rolling

elements

21 and 21 even in a state in which the force pressing the inner ring 33 outward in the axial direction is released, an appropriate thickness dimension is set as the retaining ring 40. Select what you have. That is, as the retaining ring 40, a plurality of types having slightly different thickness dimensions are prepared, and the appropriate thickness is determined in relation to the dimensions of the constituent members of the rolling bearing unit, such as the groove width of the locking groove 39. A retaining ring 40 having a size is selected and engaged with the locking groove 39. Therefore, when the retaining ring 40 is locked in the locking groove 39, the inner ring 33 is prevented from moving toward the inner end side in the axial direction even when the pressing force is released, and The rolling

elements

21 and 21 can be held with an appropriate preload applied.
[0035]
Further, in order to prevent the pair of retaining ring elements constituting the retaining ring 40 from displacing outward in the diametrical direction, the retaining ring 40 is inadvertently falling out of the retaining groove 39. A part of the spacer 41 is arranged around the. The spacer 41 is formed by a constant velocity joint outer ring 42 provided at the inner end portion of the hub body 32, and foreign matter such as rainwater and dust enters the constant velocity joint 1c that is the subject of the present invention. This is for externally supporting the outer end portion of the boot 43 for preventing the above-described problem. Further, the seal ring 37 is provided between the outer peripheral surface of the outer end of the outer ring 11 and the outer peripheral surface of the intermediate portion of the hub body 32, and the inner peripheral surface of the inner end of the outer ring 11 and the outer periphery of the inner end of the inner ring 33. A combination seal ring 44 is provided between the two surfaces, and both ends of the space 45 in which the plurality of rolling

elements

21 and 21 are installed are closed.
[0036]
Further, the portion of the inner end portion of the hub main body 32 where the inner ring 33 and the outer end portion of the boot 43 are externally fitted is the outer ring 42 that becomes the outer ring of the constant velocity joint 1c as described above. Eight

outer engagement grooves

8 and 8 each having a circular cross-sectional shape are arranged at right angles to the circumferential direction (FIG. 1) at equal intervals with respect to the circumferential direction of the inner circumferential surface of the outer ring 42. Left and right direction). Further, an inner ring 2 for constituting the Rzeppa type constant velocity joint 1c together with the outer ring 42 is disposed inside the outer ring 42. Then, eight

inner engagement grooves

7, 7 are formed on the outer peripheral surface of the inner ring 2 in a direction perpendicular to the circumferential direction and also in the circumferential direction at equal intervals. And between these

inner engagement grooves

7, 7 and the

outer engagement grooves

8, 8, one for each of the

engagement grooves

7, 8, a total of eight

balls

4, 4, It is provided so as to be able to roll while being held in the pockets 10a and 10b of the cage 9a. Further, a spline hole 31 is formed in the center portion of the inner ring 2 in the axial direction. The spline hole 31 is spline-engaged with an end portion of a drive shaft (not shown) in an assembled state in an automobile, and the hub main body 32 can be driven to rotate via the inner ring 2 and the eight

balls

4, 4. And
[0037]
As in the case of the conventional structure shown in FIGS. 11 to 14 described above, the retainer 9a has two types of pockets 10a and 10b having different circumferential lengths extending in the circumferential direction. It is provided alternately. That is, the pockets 10a and 10a having a large length in the circumferential direction are arranged every 90 degrees, and the length in the circumferential direction is set at an intermediate position between the pockets 10a and 10a having a large length in the circumferential direction.

Small pockets

10b and 10b are arranged.
[0038]
In the illustrated example, the outer peripheral edge of the outer ring 42The outer

engaging grooves

8 and 8 are continuous in the axial direction.A recess 46 is formed over the entire circumference. When the

balls

4 and 4 are assembled in the pockets 10a and 10b, the concave portion 46 prevents interference between the

balls

4 and 4 and the outer peripheral edge of the outer ring 42 as shown in FIG. . Therefore, in the case of the illustrated example, even if the displacement amount between the central axes a and b (FIG. 6) of the inner ring 2 and the outer ring 42 is relatively small, the

balls

4 and 4 into the pockets 10a and 10b. Can be built in.
[0039]
The shape of the recess 46 is regulated as follows. That is, each of the outer engagement grooves 8 among the continuous portion (position A shown in FIG. 5) between the concave portion 46 and the inner end surface in the axial direction of the outer ring 42 and the inner peripheral surface of the concave portion 46 and the outer ring 42. The recessed portion 46 and each outer engagement are radially outward from the generatrix of the virtual conical surface passing through the continuous portion (position B shown in FIG. 5) with the shoulder surface 48 that exists between the eight. The continuous part (position C shown in FIG. 5) with the opening edge part of the groove |

channels

8 and 8 is arrange | positioned. Have such a shapeThe recess 46 includes a shaft 47 (FIG. 5) constituting a ball mounting jig,the aboveThis prevents the

outer engagement grooves

8 and 8 from coming into contact with the opening edge portions, thereby contributing to the smooth operation of assembling the ball. That is, when the

balls

4 and 4 are assembled in the pockets 10a and 10b, the shaft 47 of the ball mounting jig is inserted into the spline hole 31 of the inner ring 2, and the inner ring 2 is oscillated and displaced. . At this time, an operator who operates the shaft 47 when the outer peripheral surface of the shaft 47 comes into contact with the opening end edge of the

outer engagement grooves

8 and 8 that form a concavo-convex portion in the circumferential direction. Give a sense of incongruity. On the other hand, in the case of this example, by providing the recess 46, the opening edge and the outer peripheral surface of the shaft 47 are prevented from coming into contact with each other. That is, when the shaft 47 is largely inclined with respect to the outer ring 42, the outer peripheral surface of the shaft 47 abuts on the opening peripheral edge of the recess 46. Since the peripheral edge of the opening is smoothly continuous over the entire circumference, the operator who operates the shaft 47 does not feel uncomfortable and contributes to smooth operation.
[0040]
In the constant velocity joint 1c of the present invention in which each part is configured as described above, the pitch circle diameter D of the eight

balls

4, 4 is as follows._P And the diameter D of each of these

balls

4 and 4_B And the pitch circle diameter D of the female serration provided on the inner peripheral surface of the serration hole._S And the relationship 3.5 ≦ D_P / D_B ≦ 3.9, 2.0 ≦ D_P / D_S ≦ 2.2, 0.51 ≦ D_B / D_S ≦ 0.63.
[0041]
The wheel rolling bearing unit incorporating the constant velocity joint 1c of the present example configured as described above supports the wheel rotatably with respect to the suspension device, for the wheel incorporating the conventional constant velocity joint described above. The same as the case of the rolling bearing unit. Further, according to the constant velocity joint 1c of the present invention, in order to reduce the size of the constant velocity joint 1c, the number of

balls

4, 4 is increased from six to eight, which has been generally practiced in the past. Even when the diameters of 4 and 4 are reduced, the strength and durability of the cage 9b, the inner ring 2, and the outer ring 42 can be kept equal to those of a structure in which six balls are incorporated. In this way, the constant velocity joint 1c can be reduced in diameter while ensuring the strength and durability of the constituent members, and the constant velocity joint 1c and the hub body 32 constituting the wheel rolling bearing unit are integrated. In other words, the so-called fourth generation hub unit can be put into practical use.
[0042]
That is, in the case of the wheel rolling bearing unit incorporating the constant velocity joint 1c of the present invention, the number of the inner and outer

engaging grooves

7 and 8 constituting the constant velocity joint 1c is eight, and the ball 4 Since the number of 4 is eight, each of the

balls

4 and 4 constituting the constant velocity joint 1c at the time of torque transmission between the hub 34 and the inner ring 2 due to the use of the wheel rolling bearing unit. The magnitude of the applied load can be made smaller than in the case of the conventional structure shown in FIGS. Accordingly, the outer diameter of each of the

balls

4 and 4 is reduced by that amount, and the diameter of the circumscribed circle of each of the

balls

4 and 4 arranged in an annular shape, and the circumscribed circle of the plurality of outer

engaging grooves

8 and 8. Can be made smaller in diameter. Further, by reducing the diameter of the circumscribed circle of the outer

engaging grooves

8 and 8 in this way, the outer diameter of the wheel rolling bearing unit can be reduced, and the overall apparatus can be reduced in size and weight. In addition, as described above, the strength and durability of each constituent member can be ensured.
[0043]
In particular, if the outer half of each of the

outer engagement grooves

8, 8 is arranged on the inner diameter side of the second inner ring raceway 20 as in the illustrated example, not only the outer diameter dimension of the wheel rolling bearing unit is provided. By reducing the axial dimension, the entire device can be made more compact and lighter. In such a structure of this example, the second inner ring raceway 20 constituting the rolling bearing unit main body must be made larger in diameter than the outer

engaging grooves

8, 8. The diameter is increased. In the structure of this example, the number of the

balls

4 and 4 is increased from 6 to 8, and the outer diameter of the

balls

4 and 4 can be reduced accordingly, and the outer diameter of the rolling bearing unit can be reduced. The effect of the present invention is particularly great.
[0044]
Further, in the case of the illustrated example, as described above, the outer diameter of the outer half of the outer ring 11 is reduced by reducing the pitch circle diameter of the rolling

elements

21 and 21 constituting the outer rolling element row. it can. The pitch circle diameter of the plurality of studs 35 fixed to the second mounting flange 17 provided on the outer peripheral surface of the hub main body 32 can be reduced by the amount that the outer diameter of the outer half of the outer ring 11 is reduced. Therefore, the outside diameter of the second mounting flange 17 for supporting and fixing the stud 35 is reduced without increasing the axial dimension of the hub body 32, thereby reducing the size and weight of the wheel rolling bearing unit. Furthermore, it can be achieved effectively.
[0045]
As described above, the pitch circle diameter of the rolling

elements

21 and 21 constituting the outer rolling element row is made smaller than the pitch circle diameter of the rolling

elements

21 and 21 constituting the inner rolling element row. Accordingly, the basic dynamic load rating of the outer rolling element row portion is smaller than the basic dynamic load rating of the inner rolling element row portion. Therefore, if the load applied to both rows is the same, the life of the outer rolling element row portion is shorter than that of the inner rolling element row portion. In contrast, in a general automobile, the load applied to the outer rolling element row portion is smaller than the load applied to the inner rolling element row portion. For this reason, the design which makes the lifetime of the both row portions substantially the same becomes easy, and the design without waste becomes possible. In the illustrated example, balls are used as the rolling

elements

21, 21, but in the case of a rolling bearing unit for automobiles that is heavy in weight, tapered rollers may be used as the rolling elements. Of course, the present invention can also be applied to a rolling bearing unit that uses a tapered roller as a rolling element.
[0046]
【The invention's effect】
Since the constant velocity joint of the present invention is configured and operates as described above, the structure can reduce the outer diameter by setting the number of balls for transmitting rotational force to eight, and the strength and durability of each component. Can be secured. Therefore, it is possible to realize a reduction in size and weight of a rolling bearing unit for a wheel integrated with a constant velocity joint, which is called a fourth generation hub unit, while ensuring sufficient durability.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of a rolling bearing unit for a wheel incorporating a constant velocity joint according to the present invention.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
3 is a sectional view of the cage and the ball taken out and viewed from the same direction as FIG.
FIG. 4 is a cross-sectional view showing a state in which a cage of a constant velocity joint is inclined with respect to an outer ring to such an extent that a ball can be incorporated.
FIG. 5 is a cross-sectional view showing the relationship between the shaft of the assembling jig and the outer ring in a state where the cage of the constant velocity joint is inclined with respect to the outer ring to such an extent that the ball can be incorporated.
FIG. 6 is a sectional view showing a first example of a conventional constant velocity joint in a state where a joint angle is given.
FIG. 7 is a view corresponding to the BB cross section of FIG. 6, similarly showing a state where no joint angle is given.
FIG. 8 is a view of a part of the cage as viewed from the outer peripheral side.
FIG. 9 is a schematic diagram showing the positional relationship between the bottom surfaces of both the inner and outer engagement grooves.
FIG. 10 is a sectional view showing an example of a rolling bearing unit for a wheel in which a constant velocity joint is integrated.
FIG. 11 is a sectional view showing a second example of a conventional constant velocity joint in a state where no joint angle is given.
12 is a cross-sectional view taken along the line CC of FIG.
FIG. 13 is a cross-sectional view of a cage incorporated in the second example of the conventional structure.
FIG. 14 is a cross-sectional view showing a state where an inner ring and an outer ring are displaced in a predetermined direction in order to incorporate a ball into the cage.
[Explanation of symbols]
    1, 1a, 1b, 1c constant velocity joint
    2 inner ring
    2a Outer peripheral surface
    3, 3A Outer ring
    3a Inner peripheral surface
    4 balls
    5 axes
    6 axes
    7 Inner engagement groove
    7a Bottom
    8 Outer engagement groove
    8a Bottom
    9, 9a Cage
  10, 10a, 10b pocket
  11 Outer ring
  12 First mounting flange
  13 Outer ring raceway
  14 First inner ring member
  15 Second inner ring member
  16 Hub
  17 Second mounting flange
  18 First inner ring raceway
  19 Cylindrical part
  20 Second inner ring raceway
  21 Rolling elements
  22 Locking groove
  23 Locking groove
  24 retaining ring
  25 steps
  26 Welding
  27a, 27b cover
  28a, 28b Seal ring
  29 Separator
  30 pillars
  31 Spline hole
  32 Hub body
  33 inner ring
  34 Hub
  35 Stud
  36 heads
  37 Seal ring
  38 Meat Stealing Club
  39 Locking groove
  40 retaining ring
  41 spacer
  42 Outer ring
  43 Boots
  44 Combination seal ring
  45 space
  46 recess
  47 Shaft
  48    Shoulder

Claims

An inner ring having a serration hole in the center, and an inner ring having an arc cross section formed at a right angle with respect to the circumferential direction at eight locations on the outer circumferential surface of the inner ring that are separated from each other in the circumferential direction. A cross-section arc shape formed in a direction perpendicular to the circumferential direction at a position facing the inner engagement grooves on the inner peripheral surface of the outer ring and the outer ring provided around the inner ring and the inner ring Eight pockets that are sandwiched between the outer engagement groove and the outer peripheral surface of the inner ring and the inner peripheral surface of the outer ring and that are aligned with both the inner and outer engagement grooves are formed in the circumferential direction. The cage is composed of eight balls, one of which is held inside each of the pockets, and can freely roll along both the inner and outer engaging grooves. The angle of intersection between the center axis of the outer ring and the center axis of the outer ring is divided into two equal parts. In a constant velocity joint arranged on the bisecting plane orthogonal to free plane, the pitch circle diameter of the eight balls as D _P, these diameter of each ball and D _B, among the serration hole When the pitch circle diameter of the female serration provided on the peripheral surface is D _S , 3.5 ≦ D _P / D _B ≦ 3.9, 2.0 ≦ D _P / D _S ≦ 2.2, 0.51 ≦ D _B / D _S ≦ 0.63 is satisfied , and the outer circumferential edge of the outer ring is provided with a concave portion continuous in the axial direction with the outer engagement groove. And a continuous portion of the outer ring with respect to the axial inner end surface, and a continuous portion of the recess and the shoulder surface existing in the portion between the outer engagement grooves among the inner peripheral surface of the outer ring, A continuous portion between the concave portion and the opening edge of each outer engagement groove is disposed radially outward from the generatrix of the virtual conical surface. Constant velocity joint, wherein a thing.