JP2004114851A

JP2004114851A - Wheel bearing device

Info

Publication number: JP2004114851A
Application number: JP2002281600A
Authority: JP
Inventors: Hideji Tajima; 田島　英児; Hitohiro Ozawa; 小澤　仁博
Original assignee: NTN Corp; NTN Toyo Bearing Co Ltd
Current assignee: NTN Corp
Priority date: 2002-09-26
Filing date: 2002-09-26
Publication date: 2004-04-15
Anticipated expiration: 2022-09-26
Also published as: JP4021293B2

Abstract

<P>PROBLEM TO BE SOLVED: To securely restrict fretting between a plastic deforming part of an outside joint member and an uneven part of a hub ring. <P>SOLUTION: The outside joint member 41 of a constant velocity universal joint 4 is engaged in the inner circumference of the hub ring 10, and the plastic deforming part 34 of the outside joint member 41 on the inner diameter side is plastically deformed in a diametrically enlarging direction, so that the uneven part 31 in the inner circumference of the hub ring 10 bites it to couple the hub ring 10 to the outside joint member 41. An outer circumference of the plastic deforming part 34 is rough-surfaced, with its surface roughness set in a range of Ra1.6-12.5. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
この発明は、自動車等の車両の車輪を支持するための車輪軸受装置に関するものである。
【０００２】
【従来の技術】
車輪軸受装置は、従動輪用と駆動輪用とに大別される。このうちで例えば駆動輪用の車輪軸受装置は、ハブ輪と、複列の軸受とからなるもので、さらにこれらと等速自在継手とをユニット化したものも存在する。
【０００３】
この駆動輪用の車輪軸受装置の一つに、軸受の複列のインナレースのうち、一方をハブ輪の外周に、他方を等速自在継手の外側継手部材の外周に形成したものがある。この種の軸受装置では、複列のインナレースの位置決め行うと共に、軸受内部に付与された予圧を保持するため、ハブ輪と等速自在継手とを結合する必要がある。近年では、軸方向スペースの有効活用や塑性変形部での剛性向上等の観点から、外側継手部材のステム部を拡径方向に塑性変形させ、これにハブ輪内周の凹凸部を食い込ませることで両者を結合する方法（以下、「拡径加締め」と呼ぶ）が提案されている（例えば特開２００１−１８６０５公報）。
【０００４】
この種の車輪軸受装置において、外側継手部材、およびハブ輪は、何れも鍛造成形される。鍛造後、外側継手部材にはステム部の外周やマウス部内周のトラック溝に研削が施される。また、ハブ輪には、鍛造後にその内周やインナレースに研削が施され、さらにブローチ加工等によって内周に凹凸部が形成される。従って、完成品では、塑性変形部の外周や凹凸部の表面（特に凸部の表面）には研削面が残っている。
【０００５】
【特許文献１】
特開２００１−１８６０５号公報
【０００６】
【発明が解決しようとする課題】
上記拡径加締めタイプの車輪軸受装置では、拡径方向の塑性変形後に外側継手部材の塑性変形部とハブ輪の凹凸部との間でフレッティングを生じる場合がある。フレッティングが進行すると、軸受の予圧の減少、軸力の低下を生じて製品機能が著しく低下する場合があるので、かかる不具合を回避できるような対策を講じることが望まれる。
【０００７】
一般的な機械部品でのフレッティング対策は、相対する二面間に潤滑剤等の低摩擦化物を介在させ、二面間の摩擦係数を減じる方向で行うものが多い。この対策に倣って、上記車輪軸受装置においても塑性変形部の外周面にボンデ処理を施し、その上で拡径加締めを行って耐久試験に供したところ、むしろ軸受装置の耐久寿命が低下することが明らかになった。
【０００８】
本発明は、以上の現象を考慮した上で、外側継手部材の塑性変形部とハブ輪の凹凸部との間のフレッティングを確実に抑制できる車輪軸受装置の提供を目的とする。
【０００９】
【課題を解決するための手段】
上記目的の達成のため、本発明にかかる車輪軸受装置は、内周に複列のアウタレースが形成された外方部材と、車輪取付けフランジを有するハブ輪、およびハブ輪の内周または外周に嵌合した嵌合部材を備え、外周に複列のインナレースが形成された内方部材と、アウタレースとインナレースとの間に介装された複列の転動体とを備え、ハブ輪と嵌合部材のうち、内径側の部材に、拡径方向に塑性変形される塑性変形部を設けると共に、外径側の部材に、拡径した塑性変形部に食い込む凹凸部を設けた車輪軸受装置において、塑性変形部の外周面または凹凸部の表面の少なくとも何れか一方を粗面化したものである。
【００１０】
上記車輪軸受装置においては、塑性変形後の塑性変形部に凹凸部が食い込んでいるため、本来はハブ輪と外側継手部材との間で滑りが生じることはない。しかしながら、塑性流動した塑性変形部の肉で凹凸部の凹部を全て充足することは難しいため、ハブ輪と外側継手部材との間に、回転トルク等に起因して微小な相対滑りを生じ、この微小滑りによって摩耗（フレッティング摩耗）を生じる場合がある。本発明は、粗面化によって二面間の摩擦係数を高め、これによって両面間で生じる微小滑りを規制するものである。
【００１１】
具体的に粗面化は、粗面化された部分の面粗さが、ＪＩＳに規定される中心線平均粗さでＲａ１．６以上（望ましくはＲａ３．２以上）となるように行われる。従来品では、塑性変形部の外周面や凹凸部の表面は研削面であるため、その面粗さは、Ｒａ０．２〜０．６３程度であったが、本願発明は、これよりも意図的に粗くしている。本発明者らの実験により、Ｒａが１．６よりも小さい場合は、顕著なフレッティング防止効果が期待できないことが明らかとなったため、これ以上の面粗さに設定した。
【００１２】
その一方で、粗面化された部分の面粗さがＲａ１２．５を超えると、所定の寸法公差が得られなくなるため、面粗さはＲａ１２．５以下、より好ましくはＲａ６．３以下とするのが望ましい。
【００１３】
粗面化によるフレッティング防止効果を高めるため、塑性変形部の外周面および凹凸部の表面は、低摩擦性の介在物を介在させることなく金属接触させるのが望ましい。
【００１４】
ここでいう「低摩擦性の介在物」は、塑性変形部の外周面と凹凸部の表面との間で、これらが金属接触する場合（一方または双方が熱処理による硬化層である場合も含む）よりも低い摩擦係数が得られるような介在物をいい、例えば潤滑油やグリースの油膜、固体潤滑被膜、ボンデ被膜やパーカー被膜等が該当する。
【００１５】
車輪軸受装置の具体的構成としては、上述のように嵌合部材を等速自在継手の外側継手部材としたものが考えられる。この場合、ハブ輪および外側継手部材の何れか一方が内径側の部材となり、拡径方向に塑性変形加工を受ける。他方は外径側の部材となる。何れの場合でも複列のインナレースは、ハブ輪および外側継手部材の各外周に形成することができる（図１および図５参照）。
【００１６】
他の具体的構成として、例えば嵌合部材をハブ輪に嵌合した内輪とすることが考えられる。この場合、複列のインナレースは、ハブ輪および内輪の各外周に形成することができ（図６参照）、あるいはハブ輪外周に嵌合した二つの内輪の各外周に形成することもできる（図７参照）。
【００１７】
【発明の実施の形態】
以下、本発明の実施形態を図１〜図７に基づいて説明する。
【００１８】
図１に本発明を適用した駆動輪用の車輪軸受装置の一例を示す。この車輪軸受装置は、ハブ輪１０と、軸受２０と、等速自在継手４０とをユニット化して構成される。なお、以下の説明では、車両に組み付けた状態で車両の外側寄りとなる側をアウトボード側といい（各図において図面左側）、車両の中央寄りとなる側をインボード側という（各図において図面右側）。
【００１９】
ハブ輪１０は軸心部に軸方向の貫通孔を有する中空状に形成される。ハブ輪１０のアウトボード側の端部には、車輪（図示せず）を取り付けるための車輪取付けフランジ１４が形成され、このフランジ１４の円周方向等間隔位置にホイールディスクを固定するためのハブボルト１５が植え込まれている。ハブ輪１０のフランジ１４よりもインボード側の外周面にアウトボード側のインナレース２７を形成してある。
【００２０】
等速自在継手４０は、ドライブシャフトからのトルクを内側継手部材４２およびトルク伝達ボール４３を介して外側継手部材４１に伝達する。外側継手部材４１の内周部には複数のトラック溝４１ａが形成されている。このトラック溝４１ａと内側継手部材４２の外周部に設けた複数のトラック溝４２ａとの協働で複数のボールトラックが形成され、各ボールトラックにトルク伝達ボール４３が配置される。各トルク伝達ボール４３は、ケージ４４によって同一平面内に保持されている（図５参照）。
【００２１】
外側継手部材４１は、ハブ輪１０の内周に嵌合した嵌合部材である。この外側継手部材４１は、一体に形成されたステム部４５とマウス部４６とを備え、ステム部４５にてハブ輪１０の内周に嵌合されている。マウス部４６の肩面４７がハブ輪１０のインボード側の端面と当接し、これにより、ハブ輪１０と外側継手部材４１の軸方向の位置決めがなされ、かつ、インナレース２７，２８間の寸法が規定される。マウス部４６の肩面４７寄りの外周面にインボード側のインナレース２８を形成してある。外側継手部材４１は、ステム部４５に、椀状のマウス部４６の底と連通した軸方向の貫通孔４８を設けることによって中空に形成されている。ステム部４５には、そのアウトボード側の軸端に後述する拡径加締めに際して外径側に塑性変形する塑性変形部３４が形成される。
【００２２】
外側継手部材４１の素材としては、Ｓ４０ＣやＳ５３Ｃを始め、炭素量０．３０〜０．６１の間の機械構造用炭素鋼（ＪＩＳに規定）が広く使用可能である。この他、重量％でＣを０．５〜０．７％、Ｓｉを０．６〜１．２％、Ｍｎを０．６〜１．０％含有すると共に、残部をＦｅおよび不可避的不純物とした鋼材も使用することができる。
【００２３】
外側継手部材４１には、上記素材の鍛造成形後、部分的に熱処理が施される。熱処理により硬化される部分は、図１にハッチングを付して表すように、肩面４７からインボード側のインナレース２８を経てシール２６のシールリップとの摺接面（シールランド）に至る領域と、マウス部４６内周の、トルク伝達ボールが転動するトラック溝４１ａの領域とであり、何れもＨＲｃ５８以上となるまで硬化される。熱処理としては、局部加熱ができ、硬化層深さの選定が自由であり、かつ硬化層以外への熱影響が少なく母材の性能を保持できる高周波焼入れが適当である。
【００２４】
これ以外の部分、特にステム部４５のうちで塑性変形部３４には、鍛造後も熱処理が施されない。これら未熱処理部のうち、塑性変形部３４の硬度は、拡径加締め時の加工性を考えると低いほど好ましいが、低すぎる場合は疲労耐久性の低下を招く。従って、塑性変形部３４は、ＨＲｃ１３以上２８以下、好ましくはＨＲｃ１８以上２５以下の硬度とするのが好ましい。
【００２５】
軸受２０は外方部材２１と複列の転動体２２とを含む。外方部材２１は車体（図示せず）に取り付けるためのフランジ２３を備え、内周面に複列の転動体２２が転動する複列のアウタレース２４を形成してある。ハブ輪１０のインナレース２７および外側継手部材４１のインナレース２８と外方部材２１の複列のアウタレース２４との間に複列の転動体２２が組み込まれている。ここでは転動体２２としてボールを使用した複列アンギュラ玉軸受の場合を図示してあるが、重量の嵩む自動車用の車輪軸受装置の場合には、転動体として円すいころを使用した複列円すいころ軸受を採用する場合もある。外方部材２１の両端開口部にはシール２５，２６が装着され、軸受内部に充填したグリースの漏洩ならびに外部からの水や異物の侵入を防止するようになっている。
【００２６】
ハブ輪１０の内周のうち、外側継手部材４１の塑性変形部３４外周との対向部分には凹凸部３１が形成される。凹凸部３１のインボード側には、ステム部４５の円筒状外周面と密着嵌合する嵌合面１６が形成されており、両者の嵌合によって車輪軸受装置に負荷された曲げモーメントが支持される構造になっている。
【００２７】
凹凸部３１の凹凸形状は任意であり、鍛造成形後のブローチ加工等によって例えばねじ形状やセレーション（スプラインも含む）形状、あるいは互いに平行な複数列の溝同士を交差させたアヤメローレット形状に形成される。このようにして形成された凹凸部３１は、熱処理によってＨＲｃ５８以上まで硬化される。
【００２８】
熱処理による硬化層は、図１にハッチングで示すように、ハブ輪１０内周の凹凸部３１の領域のみならず、ハブ輪１０外周の、シール２５のシールランドからインナレース２７を経てインボード側の端面に至る領域にも形成される。これらの熱処理は、上記と同様の理由から高周波焼入れにより行うのが望ましい。なお、図示のように双方の硬化層を非連続とすることにより、ハブ輪１０の焼き割れを生じにくくすることができる。
【００２９】
内径側の部材としてのハブ輪１０と、嵌合部材としての外側継手部材４１とは、いわゆる拡径加締めにより一体に塑性結合される。すなわち、ハブ輪１０の内周に外側継手部材４１のステム部４５を嵌合した状態で、ステム部４５の塑性変形部３４を内径側から外径側に塑性変形させ、塑性変形部３４の外周を凹凸部３１に食い込ませてハブ輪１０と外側継手部材４１とを塑性的に結合する。これにより、インナレース２７，２８間の寸法が規定されて軸受２０内部に所定の予圧が付与される。塑性結合されたハブ輪１０と外側継手部材４１とは、外周に複列のインナレース２７、２８を有する内方部材２９を形成する。
【００３０】
加締めに際しては、上述のように凹凸部３１は高い硬度を備えるために潰れにくく、また、拡径側の塑性変形部３４は凹凸部３１に比べて低硬度で延性に富むために拡径代を大きくとってもステム部４５に加締め割れが生じにくい。従って、凹凸部３１を塑性変形部３４に深く食い込ませることができ、これによりハブ輪１０と外側継手部材４１の間で高い結合強度が確保される。
【００３１】
加締めは、例えば図２に示すように、外側継手部材４１のステム部４５内周の貫通孔４８に加締め治具（ポンチ）６０を挿入することによって行うことができる。加締め治具６０は、先端側（ステム部４５への挿入側）より順に小径円筒部６１、テーパ部６２、および大径円筒部６３を具備するもので、小径円筒部６１の外径寸法は加締め前の塑性変形部３４の内径寸法よりも小さく、大径円筒部６３の外径寸法は当該内径寸法よりも大きい。
【００３２】
加締めに際しては、外側継手部材４１をハブ輪１０の内周に挿入した状態で、車輪軸受装置が受け台６４上にセットされる。この時、車輪取付けフランジ１４のアウトボート側の端面が受け台６４の端面に支持される。ハブボルト１５は、受け台６４に設けたボルト穴６５に収容される。
【００３３】
この状態で加締め治具６０をインボード側から外側継手部材４１の貫通穴４８に押込む。これによりステム部４５の塑性変形部３４が加締め治具６０のテーパ面６２、さらには大径円筒部６３によって押し広げられ、拡径方向に塑性変形して外周面がハブ輪１０内周の凹凸部３１に食い込む。
【００３４】
この時、加締め治具６０の押込みに伴い、外側継手部材４１はアウトボード側に向けて押込み力を受ける。一方、受け台６４に支持されたハブ輪１０がこの押込み力に対抗するため、ハブ輪１０と外側継手部材４１との軸方向の当接部（外側継手部材４１の肩面４７とハブ輪１０のインボード側端面との当接部）には圧縮歪が生じる。これにより、アキシャル軸受隙間を負にして軸受２０に予圧を付与することができ、加締め結合の完了と同時に予圧設定を完了することが可能となる。同様の効果は、加締め結合する二部材間の当接部（軸方向の当接部）で圧縮歪を生じる方向に加締め治具６０を挿入することによって得られる。
【００３５】
塑性変形部３４の拡径加締めに際し、拡径量が一定量以下であると、凹凸部３１に対する塑性変形部３４の食い込み量が不足するので、塑性変形部３４の塑性変形前の内径寸法φｄ１’と塑性変形後の内径寸法φｄ１との比Δ（Δ＝φｄ１／φｄ１’）は、１．０５以上とするのが望ましい（φｄ１およびφｄ１’の図示は省略している）。その一方、拡径量が一定量以上であると、素材の延びが過大となって加締め割れ等の不具合を招く可能性があるので、上記比Δの上限値は、（塑性変形部３４の素材に含まれる炭素量によって異なるが）１．１４〜１．２０の範囲に設定するのが望ましい。
【００３６】
本発明にかかる車輪軸受装置では、外側継手部材４１の塑性変形部３４の外周面が従来品に比べて粗面化されている。粗面化する具体的手段としては、例えば鍛造・研削後の表面に化学的・物理的処理を施す方法や、鍛造・研削後の表面にサンドブラスト等の機械的処理を施す方法、あるいは、鍛造後の研削加工を省略し、当該外周面を鍛造肌（その後に熱処理されたものも含む）のままで使用する方法などが考えられる。研削加工を省略すれば、その分だけ加工コストを低廉化することができる。
【００３７】
この粗面化は、塑性変形部３４外周の面粗さがＲａ１．６〜１２．５の範囲、より好ましくはＲａ３．２〜６．３の範囲となるように行われる。塑性変形部３４外周の面粗さは、外側継手部材４１とハブ輪１０の加締め結合前に測定する他、加締め結合後であっても、図３に示すように、凹凸部３１の凸部３１ａが食い込んでいない塑性変形部３４の外周表面３４ａで測定することもできる。塑性変形部３４の表面では、凹凸部３１が食い込んでいない部分の面積が広いため、容易に面粗さを測定することができる。
【００３８】
以上の面粗さに設定することにより、凹凸部３１の表面と加締め結合前の塑性変形部３４の外周との間の摩擦係数を従来品のそれ（μ＝０．０８程度）に比べて大きく（例えば０．１８程度）することができる。図４は、当該摩擦係数が０．０８（比較品）および０．１８（本発明品）の車輪軸受装置について、耐久寿命の比較試験を行った結果を示すものである。図示からも明らかなように、本発明品は、従来品の約１．４倍程度の耐久寿命を備えており、本発明によるフレッティング抑制効果が実証された。なお、かかる効果を得るためには、当該摩擦係数を０．１以上に設定するのが望ましい。
【００３９】
摩擦係数を大きくするという観点から、塑性変形部３４の外周面および凹凸部３１の表面の間に油膜等の低摩擦性の介在物を介在させることは好ましくない。従って、両面間では、これらの介在物を存在させることなく金属接触させるのが望ましい。
【００４０】
粗面化は上述のように塑性変形部３４の外周で行う他、凹凸部３１の表面で行うこともできる。この場合の粗面化は、凹凸部３１を形成する前、すなわち凹凸部の形成領域がまだ平滑面である段階で行う他、可能であれば凹凸部３１の形成後に行っても良い。また、粗面化は、少なくとも加締め結合後に塑性変形部３４と接触する凸部３１ａの周辺（図３参照）で行われていれば足り、必ずしも凹凸部３１の全表面で行われている必要はない。もちろん塑性変形部３４の外周と凹凸部３１の双方を粗面化しても構わない。
【００４１】
なお、図１では、加締め部分において、ハブ輪１０を外径側に配置しているが、その逆に外側継手部材４１を外径側に配置した車輪軸受装置でも同様に本発明を適用することもできる（図５参照）。この場合、ハブ輪１０が内径側の部材となってそのインボード側に塑性変形部３４が形成され、外側継手部材４１がその外周に嵌合した嵌合部材となる。また、凹凸部３１は、外側継手部材４１の内周であってハブ輪の塑性変形部３４との対向領域に形成される。
【００４２】
以下、車輪軸受装置の他の実施形態を図６および図７に基づいて説明する。なお、両図において、図１に示す部材と機能が共通する部材には、同一の参照番号を付して重複説明を省略する。
【００４３】
図６は、ハブ輪１０と、ハブ輪１０の外周に嵌合した内輪５０とで内方部材２９を形成した実施形態である。内方部材２９のインナレース２７，２８のうち、アウトボード側のインナレース２７がハブ輪１０の外周に、インボード側のインナレース２８が内輪５０の外周にそれぞれ形成されている。
【００４４】
この実施形態においては、ハブ輪１０のインボード側端部に形成した小径円筒部１９の外周に内輪５０が圧入されている。外側継手部材４１は、ハブ輪１０の内周に嵌合され、スプライン等のトルク伝達手段３７を介してハブ輪１０と結合され、かつ止め輪３８によってハブ輪１０に対して抜け止めされている。内輪５０のインボード側端面を外側継手部材４１の肩面４７と当接させ、かつアウトボード側の端面をハブ輪１０の肩面１８と当接させている。
【００４５】
この実施形態において、塑性変形部３４はハブ輪１０の小径円筒部１９に形成され、凹凸部３１は内輪５０の内周に形成されている（凹凸部３１の形成領域を×印で示す）。ハブ輪１０の塑性変形部３４を未熱処理部とし、これを拡径方向に塑性変形させることにより、塑性変形部３４の外周が内輪５０の凹凸部３１に食い込み、ハブ輪１０と内輪５０とが塑性的に結合される。この場合、ハブ輪１０が内径側の部材となり、内輪５０がハブ輪１０の外周に嵌合した嵌合部材となる。
【００４６】
図７は、ハブ輪１０と、ハブ輪１０の外周に嵌合した第一内輪５１および第二内輪５２とで内方部材２９を形成した実施形態である。内方部材２９のインナレース２７，２８は、何れも内輪５１，５２の外周にそれぞれ形成されている。図示しない外側継手部材は、ハブ輪１０の内周に嵌合され、ハブ輪１０とトルク伝達可能に結合される。
【００４７】
インボード側の第一内輪５１のインボード側端部には軸方向の延在部５３が形成され、その内周に凹凸部３１が形成されている。ハブ輪１０のインボード側端部の塑性変形部３４を未熱処理部とし、この部分を拡径方向に塑性変形させて凹凸部３１に食い込ませることにより、ハブ輪１０と内輪５１とが塑性的に結合される。この場合、ハブ輪１０が内径側の部材となり、内輪５１，５２がハブ輪１０の外周に嵌合した嵌合部材となる。
【００４８】
以上の図６および図７に示す何れの実施形態においても本発明を同様に適用することができる。
【００４９】
なお、図６および図７では、車輪軸受装置としてハブ輪１０、軸受２０、および外側継手部材をユニット化した駆動車輪用の車輪軸受装置を例示しているが、外側継手部材を含まず、ハブ輪１０と軸受２０とのみをユニット化した従動輪用の車輪軸受装置にも本発明を同様に適用することができる。
【００５０】
【発明の効果】
本発明によれば、塑性変形部の外周面または凹凸部の表面の少なくとも何れか一方を従来品より粗面化しているので、これらの二つの面の間で生じるフレッティングを抑制することができる。従って、車輪軸受装置の耐久寿命の向上を図ることができる。
【図面の簡単な説明】
【図１】本発明にかかる車輪軸受装置の一実施形態を示す断面図である。
【図２】上記車輪軸受装置の拡径加締め工程を示す断面図である。
【図３】加締め結合部の軸方向断面を拡大した図である。
【図４】従来品と本発明品の耐久寿命比較試験の結果を示す図である。
【図５】本発明にかかる車輪軸受装置の他の実施形態を示す断面図である。
【図６】本発明にかかる車輪軸受装置の他の実施形態を示す断面図である。
【図７】本発明にかかる車輪軸受装置の他の実施形態を示す断面図である。
【符号の説明】
１０　　ハブ輪
１４　　車輪取付けフランジ
２０　　軸受
２１　　外方部材
２２　　転動体
２４　　アウタレース
２７　　インナレース（アウトボード側）
２８　　インナレース（インボード側）
２９　　内方部材
３１　　凹凸部
３４　　塑性変形部
４０　　等速自在継手
４１　　外側継手部材
５０　　内輪
５１　　第一内輪
５２　　第二内輪[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wheel bearing device for supporting wheels of a vehicle such as an automobile.
[0002]
[Prior art]
Wheel bearing devices are roughly classified into those for driven wheels and those for driven wheels. Among them, for example, a wheel bearing device for a drive wheel includes a hub wheel and a double-row bearing, and there is also a device in which these and a constant velocity universal joint are unitized.
[0003]
As one of the wheel bearing devices for drive wheels, there is a wheel bearing device in which one of inner races of a double row of bearings is formed on the outer periphery of a hub wheel and the other is formed on the outer periphery of an outer joint member of a constant velocity universal joint. In this type of bearing device, it is necessary to couple the hub wheel and the constant velocity universal joint in order to position the double-row inner race and to hold the preload applied inside the bearing. In recent years, from the viewpoint of effective use of space in the axial direction and improvement of rigidity in plastically deformed portions, the stem of the outer joint member is plastically deformed in the radially expanding direction, and the unevenness of the inner periphery of the hub wheel is cut into this. (Hereinafter referred to as “diameter expansion caulking”) has been proposed (for example, Japanese Patent Application Laid-Open No. 2001-18605).
[0004]
In this type of wheel bearing device, the outer joint member and the hub wheel are all forged. After forging, the outer joint member is ground on track grooves on the outer periphery of the stem portion and the inner periphery of the mouth portion. After forging, the inner periphery and inner race of the hub wheel are subjected to grinding, and an uneven portion is formed on the inner periphery by broaching or the like. Therefore, in the finished product, the ground surface remains on the outer periphery of the plastic deformation portion and the surface of the uneven portion (particularly, the surface of the convex portion).
[0005]
[Patent Document 1]
JP 2001-18605 A
[Problems to be solved by the invention]
In the above-described enlarged diameter caulking type wheel bearing device, fretting may occur between the plastically deformed portion of the outer joint member and the uneven portion of the hub wheel after the plastic deformation in the radially enlarged direction. If fretting progresses, the preload of the bearing may decrease and the axial force may decrease, resulting in a significant decrease in product function. Therefore, it is desirable to take measures to avoid such a problem.
[0007]
Fretting countermeasures in general mechanical parts are often performed in a direction in which a low-friction material such as a lubricant is interposed between two opposing surfaces to reduce the friction coefficient between the two surfaces. Following this measure, in the above-mentioned wheel bearing device, the outer peripheral surface of the plastically deformed portion is subjected to a bond treatment, and then subjected to a diameter expansion caulking and subjected to a durability test, but rather the durability life of the bearing device is reduced. It became clear.
[0008]
An object of the present invention is to provide a wheel bearing device that can reliably suppress fretting between a plastically deformed portion of an outer joint member and a concave and convex portion of a hub wheel in consideration of the above phenomenon.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a wheel bearing device according to the present invention has an outer member having a double row outer race formed on an inner periphery thereof, a hub wheel having a wheel mounting flange, and an inner or outer periphery of the hub wheel. An inner member in which a double row of inner races are formed on the outer periphery, and a double row of rolling elements interposed between the outer race and the inner race, and are fitted with the hub wheel. Among the members, in the wheel bearing device provided with a plastically deformed portion that is plastically deformed in the radially expanding direction on the member on the inner diameter side, and a concave and convex portion that bites into the expanded plastically deformed portion on the outer diameter member. At least one of the outer peripheral surface of the plastic deformation portion and the surface of the uneven portion is roughened.
[0010]
In the above-described wheel bearing device, since the uneven portion has penetrated into the plastically deformed portion after the plastic deformation, slippage does not originally occur between the hub wheel and the outer joint member. However, since it is difficult to completely fill the recesses of the uneven portion with the flesh of the plastically deformed portion that has undergone plastic flow, a slight relative slip occurs between the hub wheel and the outer joint member due to rotational torque and the like. Wear (fretting wear) may occur due to microslip. In the present invention, the coefficient of friction between two surfaces is increased by roughening, thereby restricting micro-slip generated between both surfaces.
[0011]
Specifically, the roughening is performed so that the surface roughness of the roughened portion is Ra 1.6 or more (preferably Ra 3.2 or more) as a center line average roughness specified in JIS. In the conventional product, since the outer peripheral surface of the plastic deformation portion and the surface of the uneven portion are ground surfaces, the surface roughness was about Ra 0.2 to 0.63, but the present invention is more intentional. It is coarse. Experiments by the present inventors have revealed that when Ra is smaller than 1.6, a remarkable fretting prevention effect cannot be expected. Therefore, the surface roughness was set to be higher than this.
[0012]
On the other hand, when the surface roughness of the roughened portion exceeds Ra12.5, a predetermined dimensional tolerance cannot be obtained, so that the surface roughness is Ra12.5 or less, more preferably Ra6.3 or less. It is desirable.
[0013]
In order to enhance the fretting prevention effect due to the roughening, it is desirable that the outer peripheral surface of the plastically deformed portion and the surface of the uneven portion be brought into metal contact without inclusion of a low-friction inclusion.
[0014]
The term "low friction inclusions" used herein refers to a case where the outer peripheral surface of the plastically deformed portion and the surface of the uneven portion are in metal contact with each other (including a case where one or both are hardened layers by heat treatment). Inclusions with which a lower coefficient of friction can be obtained, such as an oil film of lubricating oil or grease, a solid lubricating film, a bond film, a Parker film, and the like.
[0015]
As a specific configuration of the wheel bearing device, it is conceivable that the fitting member is the outer joint member of the constant velocity universal joint as described above. In this case, one of the hub wheel and the outer joint member becomes a member on the inner diameter side, and undergoes plastic deformation processing in the radially increasing direction. The other is a member on the outer diameter side. In any case, a double-row inner race can be formed on each outer periphery of the hub wheel and the outer joint member (see FIGS. 1 and 5).
[0016]
As another specific configuration, for example, the fitting member may be an inner ring fitted to the hub wheel. In this case, the inner race of the double row can be formed on each outer circumference of the hub wheel and the inner ring (see FIG. 6), or can be formed on each outer circumference of two inner rings fitted to the outer circumference of the hub wheel (see FIG. 6). (See FIG. 7).
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0018]
FIG. 1 shows an example of a wheel bearing device for a drive wheel to which the present invention is applied. This wheel bearing device is configured by unitizing a hub wheel 10, a bearing 20, and a constant velocity universal joint 40. In the following description, the side closer to the outside of the vehicle when assembled to the vehicle is referred to as an outboard side (left side in each drawing), and the side closer to the center of the vehicle is referred to as an inboard side (in each drawing). Right side of the drawing).
[0019]
The hub wheel 10 is formed in a hollow shape having an axial through hole at an axis portion. A wheel mounting flange 14 for mounting a wheel (not shown) is formed at an end of the hub wheel 10 on the outboard side, and a hub bolt for fixing a wheel disc at circumferentially equal positions on the flange 14. 15 are implanted. An outer race 27 on the outboard side is formed on the outer peripheral surface on the inboard side of the flange 14 of the hub wheel 10.
[0020]
The constant velocity universal joint 40 transmits the torque from the drive shaft to the outer joint member 41 via the inner joint member 42 and the torque transmitting ball 43. A plurality of track grooves 41a are formed in the inner peripheral portion of the outer joint member 41. A plurality of ball tracks are formed in cooperation with the track grooves 41a and the plurality of track grooves 42a provided on the outer peripheral portion of the inner joint member 42, and the torque transmission balls 43 are arranged on each of the ball tracks. Each torque transmission ball 43 is held in the same plane by a cage 44 (see FIG. 5).
[0021]
The outer joint member 41 is a fitting member fitted to the inner periphery of the hub wheel 10. The outer joint member 41 includes a stem portion 45 and a mouth portion 46 that are integrally formed, and is fitted to the inner periphery of the hub wheel 10 at the stem portion 45. The shoulder surface 47 of the mouth portion 46 is in contact with the end surface on the inboard side of the hub wheel 10, whereby the hub wheel 10 and the outer joint member 41 are axially positioned, and the dimension between the inner races 27 and 28. Is defined. An inner race 28 on the inboard side is formed on the outer peripheral surface of the mouth portion 46 near the shoulder surface 47. The outer joint member 41 is formed hollow by providing a stem portion 45 with an axial through hole 48 communicating with the bottom of the bowl-shaped mouth portion 46. The stem portion 45 has a plastically deformable portion 34 that is plastically deformed to the outer diameter side at the time of expanding diameter caulking described later, at the shaft end on the outboard side.
[0022]
As a material of the outer joint member 41, carbon steel for machine structure (defined in JIS) having a carbon amount of 0.30 to 0.61, including S40C and S53C, can be widely used. In addition, 0.5 to 0.7% of C, 0.6 to 1.2% of Si, and 0.6 to 1.0% of Mn are contained by weight%, and the balance is Fe and unavoidable impurities. Steel materials can also be used.
[0023]
After forging the above material, the outer joint member 41 is partially subjected to heat treatment. As shown by hatching in FIG. 1, the portion cured by the heat treatment is a region extending from the shoulder surface 47 to the sliding contact surface (seal land) with the seal lip of the seal 26 through the inner race 28 on the inboard side. And the area of the track groove 41a on the inner periphery of the mouth 46 where the torque transmitting ball rolls, both of which are cured until the HRc becomes 58 or more. As the heat treatment, induction hardening, which can perform local heating, can freely select the depth of the hardened layer, and has little heat influence on portions other than the hardened layer and can maintain the performance of the base material, is suitable.
[0024]
The other parts, especially the plastically deformed part 34 in the stem part 45, are not subjected to heat treatment even after forging. The hardness of the plastically deformed portion 34 among these unheated portions is preferably as low as possible in view of the workability at the time of expanding and caulking, but if too low, the fatigue durability is reduced. Therefore, the plastically deformed portion 34 preferably has a hardness of HRc 13 or more and 28 or less, preferably HRc 18 or more and 25 or less.
[0025]
The bearing 20 includes an outer member 21 and double-row rolling elements 22. The outer member 21 has a flange 23 for attaching to a vehicle body (not shown), and has a double-row outer race 24 on which the double-row rolling elements 22 roll on the inner peripheral surface. A double row rolling element 22 is incorporated between the inner race 27 of the hub wheel 10 and the inner race 28 of the outer joint member 41 and the double row outer race 24 of the outer member 21. Here, the case of a double row angular ball bearing using balls as the rolling elements 22 is shown, but in the case of a wheel bearing device for a heavy automobile, a double row tapered roller using tapered rollers as rolling elements. Bearings may be employed. Seals 25 and 26 are attached to both ends of the outer member 21 to prevent leakage of grease filled in the inside of the bearing and intrusion of water or foreign matter from the outside.
[0026]
In the inner circumference of the hub wheel 10, an uneven portion 31 is formed at a portion facing the outer circumference of the plastic deformation portion 34 of the outer joint member 41. On the inboard side of the concave / convex portion 31, a fitting surface 16 that fits tightly with the cylindrical outer peripheral surface of the stem portion 45 is formed, and a bending moment applied to the wheel bearing device by the fitting of the two is supported. The structure is
[0027]
The concavo-convex shape of the concavo-convex portion 31 is arbitrary, and is formed into, for example, a screw shape, a serration (including spline) shape, or an iris knurled shape in which a plurality of parallel rows of grooves are intersected by broaching or the like after forging. You. The uneven portion 31 formed in this manner is hardened to HRc 58 or more by heat treatment.
[0028]
As shown by hatching in FIG. 1, the hardened layer formed by the heat treatment is formed not only in the region of the uneven portion 31 on the inner periphery of the hub wheel 10 but also on the inboard side of the outer periphery of the hub wheel 10 from the seal land of the seal 25 via the inner race 27. Is formed also in a region reaching the end face of the substrate. These heat treatments are desirably performed by induction hardening for the same reason as described above. By making both the hardened layers discontinuous as shown in the figure, it is possible to make the hub wheel 10 less likely to cause a burning crack.
[0029]
The hub wheel 10 as a member on the inner diameter side and the outer joint member 41 as a fitting member are integrally plastically coupled by so-called diameter-enlarging caulking. That is, with the stem portion 45 of the outer joint member 41 fitted to the inner periphery of the hub wheel 10, the plastic deformation portion 34 of the stem portion 45 is plastically deformed from the inner diameter side to the outer diameter side. The hub wheel 10 and the outer joint member 41 are plastically connected to each other. Thereby, the dimension between the inner races 27 and 28 is defined, and a predetermined preload is applied inside the bearing 20. The hub wheel 10 and the outer joint member 41 that are plastically connected form an inner member 29 having double rows of inner races 27 and 28 on the outer periphery.
[0030]
At the time of caulking, the uneven portion 31 has a high hardness as described above, so that it is not easily crushed, and the plastic deformation portion 34 on the enlarged diameter side has a lower hardness and is more ductile than the uneven portion 31, so that the diameter expansion margin is required. Even if it is large, crimping cracks are less likely to occur in the stem portion 45. Therefore, the uneven portion 31 can be deeply penetrated into the plastically deformed portion 34, so that a high coupling strength between the hub wheel 10 and the outer joint member 41 is secured.
[0031]
The caulking can be performed, for example, by inserting a caulking jig (punch) 60 into the through hole 48 on the inner periphery of the stem 45 of the outer joint member 41 as shown in FIG. The caulking jig 60 includes a small-diameter cylindrical portion 61, a tapered portion 62, and a large-diameter cylindrical portion 63 in this order from the distal end side (the insertion side into the stem portion 45). The inner diameter of the plastically deformed portion 34 before crimping is smaller than the inner diameter of the large diameter cylindrical portion 63.
[0032]
In caulking, the wheel bearing device is set on the cradle 64 with the outer joint member 41 inserted into the inner periphery of the hub wheel 10. At this time, the end surface of the wheel mounting flange 14 on the outboard side is supported by the end surface of the cradle 64. The hub bolt 15 is housed in a bolt hole 65 provided in the receiving base 64.
[0033]
In this state, the crimping jig 60 is pushed into the through hole 48 of the outer joint member 41 from the inboard side. As a result, the plastically deformed portion 34 of the stem portion 45 is expanded by the tapered surface 62 of the caulking jig 60 and further by the large-diameter cylindrical portion 63, and is plastically deformed in the radially expanding direction so that the outer peripheral surface is formed on the inner periphery of the hub wheel 10. It digs into the uneven part 31.
[0034]
At this time, as the crimping jig 60 is pushed, the outer joint member 41 receives a pushing force toward the outboard side. On the other hand, since the hub wheel 10 supported by the cradle 64 opposes this pushing force, an axial contact portion between the hub wheel 10 and the outer joint member 41 (the shoulder surface 47 of the outer joint member 41 and the hub wheel 10). (Abutting portion with the end face on the inboard side) has a compressive strain. As a result, a preload can be applied to the bearing 20 with the axial bearing gap being negative, and the preload setting can be completed simultaneously with the completion of the caulking connection. A similar effect can be obtained by inserting the crimping jig 60 in a direction in which a compressive strain is generated at a contact portion (a contact portion in the axial direction) between the two members to be crimped and joined.
[0035]
When the diameter expansion of the plastic deformation portion 34 is caulked, if the diameter expansion amount is equal to or less than a certain amount, the amount of the plastic deformation portion 34 biting into the uneven portion 31 is insufficient, so the inner diameter dimension φd1 of the plastic deformation portion 34 before the plastic deformation. It is desirable that the ratio Δ (Δ = φd1 / φd1 ′) between '′ and the inner diameter dimension φd1 after plastic deformation is 1.05 or more (φd1 and φd1 ′ are not shown). On the other hand, if the diameter expansion amount is equal to or more than a certain amount, the elongation of the material becomes excessive, which may cause a problem such as caulking cracking. It is desirable to set it in the range of 1.14 to 1.20 (depending on the amount of carbon contained in the material).
[0036]
In the wheel bearing device according to the present invention, the outer peripheral surface of the plastic deformation portion 34 of the outer joint member 41 is roughened as compared with a conventional product. As a specific means for roughening, for example, a method of performing a chemical or physical treatment on the surface after forging or grinding, a method of performing a mechanical treatment such as sandblasting on the surface after forging or grinding, or A method of omitting the grinding process and using the outer peripheral surface with a forged surface (including those heat-treated afterwards) can be considered. If the grinding process is omitted, the processing cost can be reduced accordingly.
[0037]
This roughening is performed so that the surface roughness of the outer periphery of the plastic deformation portion 34 is in the range of Ra 1.6 to 12.5, more preferably in the range of Ra 3.2 to 6.3. The surface roughness of the outer periphery of the plastic deformation portion 34 is measured before the outer joint member 41 and the hub wheel 10 are crimped together, and even after the crimping connection, as shown in FIG. The measurement can also be performed on the outer peripheral surface 34a of the plastically deformed portion 34 in which the portion 31a has not penetrated. On the surface of the plastic deformation portion 34, the area of the portion where the uneven portion 31 does not bite is large, so that the surface roughness can be easily measured.
[0038]
By setting the surface roughness as described above, the friction coefficient between the surface of the uneven portion 31 and the outer periphery of the plastically deformed portion 34 before the crimping connection is compared with that of the conventional product (μ = 0.08). It can be large (for example, about 0.18). FIG. 4 shows the results of a comparative test of the durability life of the wheel bearing devices having the friction coefficients of 0.08 (comparative product) and 0.18 (product of the present invention). As is clear from the drawing, the product of the present invention has a durable life of about 1.4 times that of the conventional product, and the fretting suppression effect of the present invention has been demonstrated. In order to obtain such an effect, it is desirable to set the coefficient of friction to 0.1 or more.
[0039]
From the viewpoint of increasing the friction coefficient, it is not preferable to interpose a low-friction inclusion such as an oil film between the outer peripheral surface of the plastic deformation portion 34 and the surface of the uneven portion 31. Therefore, it is desirable to make metal contact between both surfaces without the presence of these inclusions.
[0040]
The surface roughening may be performed on the outer surface of the plastic deformation portion 34 as described above, or may be performed on the surface of the uneven portion 31. In this case, the surface roughening may be performed before forming the uneven portion 31, that is, at a stage where the formation region of the uneven portion is still a smooth surface, or may be performed after the formation of the uneven portion 31 if possible. Further, it is sufficient that the surface roughening is performed at least around the convex portion 31a that comes into contact with the plastic deformation portion 34 after the crimping connection (see FIG. 3), and it is necessary to perform the surface roughening necessarily. There is no. Of course, both the outer periphery of the plastic deformation portion 34 and the uneven portion 31 may be roughened.
[0041]
In FIG. 1, the hub wheel 10 is arranged on the outer diameter side in the swaged portion, but the present invention is similarly applied to a wheel bearing device in which the outer joint member 41 is arranged on the outer diameter side. (See FIG. 5). In this case, the hub wheel 10 becomes a member on the inner diameter side, the plastic deformation portion 34 is formed on the inboard side, and the outer joint member 41 becomes a fitting member fitted on the outer periphery. The uneven portion 31 is formed on the inner periphery of the outer joint member 41 in a region facing the plastic deformation portion 34 of the hub wheel.
[0042]
Hereinafter, another embodiment of the wheel bearing device will be described with reference to FIGS. 6 and 7. In both figures, members having the same functions as the members shown in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.
[0043]
FIG. 6 shows an embodiment in which the inner member 29 is formed by the hub wheel 10 and the inner ring 50 fitted on the outer periphery of the hub wheel 10. Of the inner races 27 of the inner member 29, the outer race 27 on the outboard side is formed on the outer periphery of the hub wheel 10, and the inner race 28 on the inboard side is formed on the outer periphery of the inner ring 50.
[0044]
In this embodiment, the inner ring 50 is press-fitted to the outer periphery of the small-diameter cylindrical portion 19 formed at the inboard end of the hub wheel 10. The outer joint member 41 is fitted to the inner periphery of the hub wheel 10, is coupled to the hub wheel 10 via a torque transmission means 37 such as a spline, and is prevented from being removed from the hub wheel 10 by a retaining ring 38. . The inboard end surface of the inner race 50 is in contact with the shoulder surface 47 of the outer joint member 41, and the outboard end surface is in contact with the shoulder surface 18 of the hub wheel 10.
[0045]
In this embodiment, the plastic deformation portion 34 is formed on the small-diameter cylindrical portion 19 of the hub wheel 10, and the uneven portion 31 is formed on the inner periphery of the inner ring 50 (the area where the uneven portion 31 is formed is indicated by a cross). The plastically deformed portion 34 of the hub wheel 10 is an unheated portion, and the plastically deformed portion is plastically deformed in the radially expanding direction, so that the outer periphery of the plastically deformed portion 34 bites into the uneven portion 31 of the inner ring 50, and the hub wheel 10 and the inner ring 50 Plastically bonded. In this case, the hub wheel 10 is a member on the inner diameter side, and the inner ring 50 is a fitting member fitted on the outer periphery of the hub wheel 10.
[0046]
FIG. 7 shows an embodiment in which the inner member 29 is formed by the hub wheel 10 and the first inner ring 51 and the second inner ring 52 fitted on the outer periphery of the hub wheel 10. The inner races 27 and 28 of the inner member 29 are both formed on the outer periphery of the inner rings 51 and 52, respectively. An outer joint member (not shown) is fitted to the inner periphery of the hub wheel 10 and is coupled to the hub wheel 10 so as to be able to transmit torque.
[0047]
An axially extending portion 53 is formed at an inboard end of the first inner race 51 on the inboard side, and an uneven portion 31 is formed on the inner periphery thereof. The plastic deformation portion 34 at the inboard end of the hub wheel 10 is an unheated portion, and this portion is plastically deformed in the radially expanding direction and bites into the uneven portion 31 so that the hub wheel 10 and the inner ring 51 are plastically deformed. Is combined with In this case, the hub wheel 10 is a member on the inner diameter side, and the inner rings 51 and 52 are fitting members fitted on the outer periphery of the hub wheel 10.
[0048]
The present invention can be similarly applied to any of the embodiments shown in FIG. 6 and FIG.
[0049]
6 and 7 illustrate a wheel bearing device for a drive wheel in which the hub wheel 10, the bearing 20, and the outer joint member are unitized as the wheel bearing device. The present invention can be similarly applied to a wheel bearing device for a driven wheel in which only the wheel 10 and the bearing 20 are unitized.
[0050]
【The invention's effect】
According to the present invention, since at least one of the outer peripheral surface of the plastically deformed portion and the surface of the uneven portion is roughened compared to the conventional product, fretting generated between these two surfaces can be suppressed. . Therefore, the durability life of the wheel bearing device can be improved.
[Brief description of the drawings]
FIG. 1 is a sectional view showing one embodiment of a wheel bearing device according to the present invention.
FIG. 2 is a cross-sectional view showing a step of expanding and caulking the wheel bearing device.
FIG. 3 is an enlarged view of an axial cross section of a caulked joint.
FIG. 4 is a view showing the results of a durability life comparison test between a conventional product and a product of the present invention.
FIG. 5 is a sectional view showing another embodiment of the wheel bearing device according to the present invention.
FIG. 6 is a sectional view showing another embodiment of the wheel bearing device according to the present invention.
FIG. 7 is a sectional view showing another embodiment of the wheel bearing device according to the present invention.
[Explanation of symbols]
Reference Signs List 10 hub wheel 14 wheel mounting flange 20 bearing 21 outer member 22 rolling element 24 outer race 27 inner race (outboard side)
28 Inner race (inboard side)
29 inner member 31 uneven portion 34 plastic deformation portion 40 constant velocity universal joint 41 outer joint member 50 inner ring 51 first inner ring 52 second inner ring

Claims

内周に複列のアウタレースが形成された外方部材と、
車輪取付けフランジを有するハブ輪、およびハブ輪の内周または外周に嵌合した嵌合部材を備え、外周に複列のインナレースが形成された内方部材と、
アウタレースとインナレースとの間に介装された複列の転動体と
を備え、ハブ輪と嵌合部材のうち、内径側の部材に、拡径方向に塑性変形される塑性変形部を設けると共に、外径側の部材に、拡径した塑性変形部に食い込む凹凸部を設けた車輪軸受装置において、
塑性変形部の外周面または凹凸部の表面の少なくとも何れか一方が粗面化されていることを特徴とする車輪軸受装置。An outer member having a double-row outer race formed on the inner periphery,
A hub wheel having a wheel mounting flange, and a fitting member fitted to the inner or outer periphery of the hub wheel, an inner member having a double row inner race formed on the outer periphery,
A double-row rolling element interposed between the outer race and the inner race, and, among the hub wheel and the fitting member, a member on the inner diameter side is provided with a plastic deformation portion that is plastically deformed in the diameter increasing direction. In a wheel bearing device provided with an uneven portion that bites into the expanded plastic deformation portion on the outer diameter side member,
A wheel bearing device wherein at least one of an outer peripheral surface of a plastic deformation portion and a surface of an uneven portion is roughened.

粗面化された部分の面粗さがＲａ１．６以上である請求項１記載の車輪軸受装置。The wheel bearing device according to claim 1, wherein the surface roughness of the roughened portion is Ra 1.6 or more.

粗面化された部分の面粗さがＲａ１２．５以下である請求項１または２記載の車輪軸受装置。3. The wheel bearing device according to claim 1, wherein the surface roughness of the roughened portion is Ra12.5 or less.

嵌合部材が等速自在継手の外側継手部材であり、複列のインナレースが、ハブ輪および外側継手部材の各外周に形成されている請求項１〜３何れか記載の車輪軸受装置。The wheel bearing device according to any one of claims 1 to 3, wherein the fitting member is an outer joint member of a constant velocity universal joint, and a double-row inner race is formed on each outer periphery of the hub wheel and the outer joint member.

嵌合部材が、ハブ輪の外周に嵌合した内輪である請求項１〜３何れか記載の車輪軸受装置。The wheel bearing device according to any one of claims 1 to 3, wherein the fitting member is an inner ring fitted on the outer periphery of the hub wheel.

複列のインナレースが、ハブ輪および内輪の各外周に形成されている請求項５記載の車輪軸受装置。The wheel bearing device according to claim 5, wherein a double-row inner race is formed on each outer periphery of the hub wheel and the inner ring.

複列のインナレースが、ハブ輪外周に嵌合した二つの内輪の各外周に形成されている請求項５記載の車輪軸受装置。The wheel bearing device according to claim 5, wherein a double-row inner race is formed on each outer periphery of the two inner races fitted on the outer periphery of the hub wheel.