JP2009299759A - Wheel supporting rolling bearing unit - Google Patents

Wheel supporting rolling bearing unit Download PDF

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JP2009299759A
JP2009299759A JP2008153921A JP2008153921A JP2009299759A JP 2009299759 A JP2009299759 A JP 2009299759A JP 2008153921 A JP2008153921 A JP 2008153921A JP 2008153921 A JP2008153921 A JP 2008153921A JP 2009299759 A JP2009299759 A JP 2009299759A
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mass
balls
wheel
outer ring
ball
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Koki Yamada
紘樹 山田
Hideyuki Uyama
英幸 宇山
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NSK Ltd
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NSK Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/30—Parts of ball or roller bearings
    • F16C33/32—Balls
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C19/00—Bearings with rolling contact, for exclusively rotary movement
    • F16C19/02—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows
    • F16C19/14—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load
    • F16C19/18—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load with two or more rows of balls
    • F16C19/181—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load with two or more rows of balls with angular contact
    • F16C19/183—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load with two or more rows of balls with angular contact with two rows at opposite angles
    • F16C19/184—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load with two or more rows of balls with angular contact with two rows at opposite angles in O-arrangement
    • F16C19/186—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load with two or more rows of balls with angular contact with two rows at opposite angles in O-arrangement with three raceways provided integrally on parts other than race rings, e.g. third generation hubs
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2204/00—Metallic materials; Alloys
    • F16C2204/60—Ferrous alloys, e.g. steel alloys
    • F16C2204/64—Medium carbon steel, i.e. carbon content from 0.4 to 0,8 wt%

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Rolling Contact Bearings (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To secure sufficient durability, even when a service condition is severe, without causing damage and impression on a rolling surface of respective balls 20 and 20, even when excessive bearing pressure acts on the rolling surface of the balls 20 and 20, when the balls 20 and 20 run on a shoulder part of these respective tracks 11a, 11b, 17a and 17b, by improving a property of the balls 20 and 20 arranged between outer race raceway tracks 11a and 11b of a double row and inner race raceway tracks 17a and 17b of a double row. <P>SOLUTION: The balls 20 and 20 are subjected to carbonitriding processing or nitriding processing. The nitrogen concentration of a surface layer of the balls 20 and 20 is set to 0.2 mass% or more, and the area ratio of Si-Mn-based nitride existing on a surface of the balls 20 and 20 is set to 1%-10%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

この発明は、自動車の車輪を独立式の懸架装置に対して回転自在に支持する為の車輪支持用転がり軸受ユニットの改良に関する。具体的には、玉の転動面が外輪軌道或いは内輪軌道の肩部に乗り上げてこの転動面にエッジロードに基づく過大な面圧が作用した場合でも、この転動面を含む転がり接触部に、早期剥離等の損傷が発生しにくい、車輪支持用転がり軸受ユニットの実現を意図したものである。   The present invention relates to an improvement of a wheel bearing rolling bearing unit for rotatably supporting a vehicle wheel with respect to an independent suspension device. Specifically, even when the rolling surface of the ball rides on the shoulder of the outer ring raceway or the inner ring raceway and excessive surface pressure based on the edge load acts on this rolling contact surface, the rolling contact portion including this rolling contact surface In addition, it is intended to realize a rolling bearing unit for supporting a wheel that is unlikely to cause damage such as early peeling.

自動車の車輪を構成するホイール１、及び、制動用回転部材であって制動装置であるディスクブレーキを構成するロータ２は、例えば図１に示す様な構造により、独立懸架式の懸架装置を構成するナックル３に回転自在に支持している。上記図１及び後述する図２は、例えば特許文献１に記載された構造を示している。上記図１に示した構造では、上記ナックル３に形成した円形の支持孔４部分に、車輪支持用転がり軸受ユニット５を構成する、特許請求の範囲に記載した外輪相当部材である外輪６を、複数本のボルト７により固定している。一方、上記車輪支持用転がり軸受ユニット５を構成する、特許請求の範囲に記載した内輪相当部材であるハブ８に、上記ホイール１及びロータ２を、複数本のスタッド９とナット１０とにより結合固定している。又、上記外輪６の内周面には複列の外輪軌道１１ａ、１１ｂを、外周面には結合フランジ１２を、それぞれ形成している。この様な外輪６は、この結合フランジ１２を上記ナックル３に、上記各ボルト７で結合する事により、このナックル３に対し固定している。   A wheel 1 constituting a wheel of an automobile and a rotor 2 constituting a disc brake serving as a braking device, which is a braking rotating member, constitute an independent suspension system with a structure as shown in FIG. 1, for example. The knuckle 3 is rotatably supported. FIG. 1 and FIG. 2 described later show, for example, the structure described in Patent Document 1. In the structure shown in FIG. 1, the outer ring 6, which is a member corresponding to the outer ring described in the claims, is configured to form a wheel bearing rolling bearing unit 5 in the circular support hole 4 formed in the knuckle 3. It is fixed with a plurality of bolts 7. On the other hand, the wheel 1 and the rotor 2 are coupled and fixed to a hub 8 which constitutes the wheel bearing rolling bearing unit 5 and is an inner ring equivalent member described in claims by a plurality of studs 9 and nuts 10. is doing. Further, double-row outer ring raceways 11a and 11b are formed on the inner peripheral surface of the outer ring 6, and a coupling flange 12 is formed on the outer peripheral surface. Such an outer ring 6 is fixed to the knuckle 3 by connecting the connecting flange 12 to the knuckle 3 with the bolts 7.

又、上記ハブ８は、ハブ本体１３と内輪１４とから成る。このうちのハブ本体１３の外周面の一部で、上記外輪６の外端開口から突出した部分に、取付フランジ１５を形成している。尚、軸方向に関して「外」とは、自動車への組み付け状態で車両の幅方向外側となる、図１、２の左側を言う。反対に、自動車への組み付け状態で車両の幅方向中央側となる、図１、２の右側を、軸方向に関して「内」と言う。又、上記ハブ本体１３の外端部には、パイロット部と呼ばれる位置決め筒部１６を、このハブ本体１３と同心に設けている。上記ホイール１及びロータ２は、この位置決め筒部１６に外嵌する事により径方向の位置決めを図った状態で、上記取付フランジ１５の外側面に、上記各スタッド９とナット１０とにより結合固定している。   The hub 8 includes a hub body 13 and an inner ring 14. A mounting flange 15 is formed on a part of the outer peripheral surface of the hub main body 13 that protrudes from the outer end opening of the outer ring 6. Note that “outside” with respect to the axial direction refers to the left side of FIGS. On the other hand, the right side of FIGS. 1 and 2, which is the center side in the width direction of the vehicle in the assembled state in the automobile, is called “inside” in the axial direction. A positioning cylinder portion 16 called a pilot portion is provided concentrically with the hub body 13 at the outer end portion of the hub body 13. The wheel 1 and the rotor 2 are fixedly coupled to the outer surface of the mounting flange 15 by the studs 9 and the nuts 10 in a state in which the wheel 1 and the rotor 2 are externally fitted to the positioning cylinder portion 16 and positioned in the radial direction. ing.

又、上記ハブ本体１３の外周面の中間部に、上記複列の外輪軌道１１ａ、１１ｂのうちの外側の外輪軌道１１ａに対向する内輪軌道１７ａを、同じく内端部に小径段部１８を、それぞれ形成している。そして、この小径段部１８に、上記内輪１４を外嵌している。この内輪１４の外周面には、上記複列の外輪軌道１１ａ、１１ｂのうちの内側の外輪軌道１１ｂに対向する、内輪軌道１７ｂを形成している。この様な内輪１４は、上記ハブ本体１３の内端部を径方向外方に塑性変形させて形成したかしめ部１９により、このハブ本体１３に対し固定している。そして、上記両外輪軌道１１ａ、１１ｂと上記両内輪軌道１７ａ、１７ｂとの間に玉２０、２０を、それぞれ複数個ずつ転動自在に設けている。この状態でこれら各玉２０、２０は、上記両外輪軌道１１ａ、１１ｂと上記両内輪軌道１７ａ、１７ｂとに、両列同士の間で互いに逆方向で背面組み合わせ型の接触角を付与された状態で、転がり接触する。又、この状態で、上記各玉２０、２０に所定の予圧を付与している。この構成により前記ハブ８を前記外輪６の内径側に、がたつきなく、且つ、ラジアル荷重及びアキシアル荷重を支承しつつ回転可能に支持している。又、上記各玉２０、２０を設置した円筒状の空間の両端開口部は、それぞれシールリング２１ａ、２１ｂにより密閉している。   In addition, an inner ring raceway 17a facing the outer ring raceway 11a on the outer side of the double row outer ring raceways 11a, 11b is formed at an intermediate portion of the outer peripheral surface of the hub body 13, and a small-diameter step portion 18 is also provided at the inner end. Each is formed. The inner ring 14 is externally fitted to the small diameter step portion 18. An inner ring raceway 17b is formed on the outer peripheral surface of the inner ring 14 to face the inner outer ring raceway 11b of the double row outer ring raceways 11a and 11b. Such an inner ring 14 is fixed to the hub body 13 by a caulking portion 19 formed by plastically deforming the inner end portion of the hub body 13 radially outward. A plurality of balls 20, 20 are provided between the outer ring raceways 11a, 11b and the inner ring raceways 17a, 17b, respectively, so that they can roll. In this state, these balls 20, 20 are provided with a contact angle of a back combination type in the opposite direction between the two outer ring raceways 11a, 11b and the inner ring raceways 17a, 17b. In contact with rolling. In this state, a predetermined preload is applied to the balls 20 and 20. With this configuration, the hub 8 is supported on the inner diameter side of the outer ring 6 so as not to rattle and rotatably while supporting a radial load and an axial load. Further, both end openings of the cylindrical space in which the balls 20 and 20 are installed are sealed with seal rings 21a and 21b, respectively.

更に、図示の例は、駆動輪（ＦＦ車の前輪、ＦＲ車及びＲＲ車の後輪、４ＷＤ車の全車輪）用の車輪支持用転がり軸受ユニット５である為、上記ハブ８の中心部に、スプライン孔２２を形成している。そして、このスプライン孔２２に、等速ジョイント用外輪２３の外端面に固設したスプライン軸２４を挿入している。これと共に、このスプライン軸２４の先端部にナット２５を螺合し、更に締め付ける事により、上記ハブ本体１３を、このナット２５と上記等速ジョイント用外輪２３との間に挟持している。   Furthermore, the illustrated example is a wheel bearing rolling bearing unit 5 for driving wheels (front wheels of FF vehicles, rear wheels of FR and RR vehicles, and all wheels of 4WD vehicles). The spline hole 22 is formed. A spline shaft 24 fixed to the outer end face of the constant velocity joint outer ring 23 is inserted into the spline hole 22. At the same time, a nut 25 is screwed onto the tip of the spline shaft 24 and further tightened, whereby the hub body 13 is sandwiched between the nut 25 and the constant velocity joint outer ring 23.

次に、図２は、従来から知られている車輪支持用転がり軸受ユニットの第２例として、従動輪（ＦＦ車の後輪、ＦＲ車及びＲＲ車の前輪）用のものを示している。この第２例の車輪支持用転がり軸受ユニット５ａは、従動輪用である為、ハブ８ａを構成するハブ本体１３ａの中心部にスプライン孔を設けていない。尚、図示の例では、内輪１４の内端面を、このハブ本体１３ａの内端部に設けたかしめ部１９により抑えているが、この内輪１４の内端面は、このハブ本体１３ａの内端部に螺合したナットにより抑える事もできる。この場合には、このハブ本体１３ａの内端部に、このナットを螺合する為の雄ねじ部を設ける。その他の部分の構造及び作用は、上述した第１例の車輪支持用転がり軸受ユニット５の場合と同様である。
尚、図示は省略するが、外輪相当部材を車輪と共に回転するハブとし、内輪相当部材を懸架装置に対し支持固定する静止側軌道輪とする車輪支持用転がり軸受ユニットも、例えば特許文献２に記載される等により、従来から広く知られている。 Next, FIG. 2 shows a second example of a conventionally known wheel support rolling bearing unit for a driven wheel (rear wheel of FF vehicle, front wheel of FR vehicle and RR vehicle). Since the wheel support rolling bearing unit 5a of the second example is for a driven wheel, a spline hole is not provided at the center of the hub body 13a constituting the hub 8a. In the illustrated example, the inner end surface of the inner ring 14 is suppressed by a caulking portion 19 provided at the inner end portion of the hub body 13a. It can also be suppressed by a nut screwed into the nut. In this case, a male screw portion for screwing the nut is provided at the inner end portion of the hub body 13a. The structure and operation of other parts are the same as those of the rolling bearing unit 5 for wheel support of the first example described above.
Although not shown in the drawings, a wheel support rolling bearing unit in which the outer ring equivalent member is a hub that rotates together with the wheel and the inner ring equivalent member is a stationary side race ring that is supported and fixed to the suspension device is also described in Patent Document 2, for example. For example, it has been widely known.

何れの構造の車輪支持用転がり軸受ユニット５、５ａにしても、各玉２０、２０に付与した予圧は、長期間に亙る使用に伴って次第に低下する。又、この予圧低下は、上記車輪支持用転がり軸受ユニット５、５ａを組み立てる際、或いはこの車輪支持用転がり軸受ユニット５、５ａを懸架装置に組み付ける際にミスアライメントがあった場合には、より著しくなる。何れにしても、上記車輪支持用転がり軸受ユニット５、５ａの剛性は、上記各玉２０、２０に付与されている予圧の低下に伴って低下する。そして、剛性が低下した上記車輪支持用転がり軸受ユニット５、５ａを組み付けた自動車が急旋回する等して、取付フランジ１５からハブ８、８ａに大きなモーメントが加わると、このモーメントを支承する側の列の玉２０、２０が、外輪軌道１１ａ（１１ｂ）及び内輪軌道１７ａ（１７ｂ）の正規位置から、これら両軌道１１ａ、１７ａ（１１ｂ、１７ｂ）の幅方向端部に存在する肩部に向けて変位する。   Regardless of the wheel bearing rolling bearing units 5 and 5a having any structure, the preload applied to the balls 20 and 20 gradually decreases with use over a long period of time. Further, this decrease in preload is more marked when there is a misalignment when assembling the wheel supporting rolling bearing units 5, 5a or when assembling the wheel supporting rolling bearing units 5, 5a to the suspension system. Become. In any case, the rigidity of the wheel bearing rolling bearing units 5 and 5a decreases as the preload applied to the balls 20 and 20 decreases. If a large moment is applied from the mounting flange 15 to the hubs 8 and 8a due to a sudden turn or the like of the automobile in which the wheel bearing rolling bearing units 5 and 5a with reduced rigidity are assembled, the side on which the moment is supported. The balls 20, 20 in a row are directed from the normal positions of the outer ring raceway 11 a (11 b) and the inner ring raceway 17 a (17 b) toward the shoulders present at the ends in the width direction of both the raceways 11 a, 17 a (11 b, 17 b). Displace.

そして、極端な場合には、上記各玉２０、２０がこの肩部に乗り上げる。この様にして、これら各玉２０、２０が上記両軌道１１ａ、１７ａ（１１ｂ、１７ｂ）の肩部に乗り上げると、これら各玉２０、２０の転動面に、エッジロードに基づく過大な面圧が作用して、これら各玉２０、２０の転動面に傷（玉乗り上げ傷）や圧痕が付く。そして、転動面に傷や圧痕が付いた玉２０、２０を組み込んだ、上記車輪支持用転がり軸受ユニット５、５ａをそのまま運転すると、これら各玉２０、２０の転動面の傷が拡がるだけでなく、上記両軌道１１ａ、１７ａ（１１ｂ、１７ｂ）迄もが傷付く。この結果、これら両軌道１１ａ、１７ａ（１１ｂ、１７ｂ）や上記各玉２０、２０の転動面に表面疲労型の剥離が発生する可能性が大きくなる等、上記車輪支持用転がり軸受ユニット５、５ａの耐久性が著しく損なわれる可能性がある。   In an extreme case, the balls 20 and 20 ride on the shoulders. In this manner, when these balls 20, 20 ride on the shoulders of both the tracks 11 a, 17 a (11 b, 17 b), excessive surface pressure based on the edge load is applied to the rolling surfaces of these balls 20, 20. Acts, and the rolling surfaces of these balls 20 and 20 have scratches (ball climbing scratches) and indentations. And if the said wheel support rolling bearing unit 5 and 5a which incorporated the ball | bowl 20 and 20 with a crack and an indentation on the rolling surface is drive | operated as it is, the damage | wound of the rolling surface of these each balls 20 and 20 will only spread. In addition, both the tracks 11a and 17a (11b and 17b) are damaged. As a result, there is a high possibility that surface fatigue type peeling will occur on the rolling surfaces of these raceways 11a, 17a (11b, 17b) and the balls 20, 20, and the wheel supporting rolling bearing unit 5, The durability of 5a may be significantly impaired.

上述の様な原因で発生する、車輪支持用転がり軸受ユニットの耐久性低下を防止する為に、前記特許文献２には、各軌道の断面形状（曲率半径）を工夫する事で、過大モーメントの作用時にも、各玉の転動面に作用する面圧の上昇を抑える構造が記載されている。但し、上記特許文献２に記載された様な、各軌道の断面形状を工夫するだけでは、未だ十分な耐久性向上効果を得られない。即ち、上記特許文献２に記載された構造によれば、過大モーメント作用時に於ける各玉の転動面の面圧上昇を抑えられるにしても、面圧上昇を完全になくす事は難しいので、これら各玉の転動面に玉乗り上げ傷や圧痕が付く可能性は残る。そこで、上記車輪支持用転がり軸受ユニットの耐久性をより向上させる為には、この車輪支持用転がり軸受ユニットの構成各部材の材料組成の工夫により、上記各玉の転動面に玉乗り上げ傷や圧痕が付いてしまった場合でも、上記表面疲労型の剥離を防止できる技術の実現が望まれる。   In order to prevent the deterioration of the durability of the rolling bearing unit for supporting a wheel, which is caused by the above-described causes, the above-mentioned Patent Document 2 discloses that an excessive moment is reduced by devising the cross-sectional shape (curvature radius) of each track. A structure that suppresses an increase in the surface pressure acting on the rolling surface of each ball is also described. However, it is not possible to obtain a sufficient durability improvement effect just by devising the cross-sectional shape of each track as described in Patent Document 2. That is, according to the structure described in Patent Document 2, it is difficult to completely eliminate the surface pressure increase even if the surface pressure increase of the rolling surface of each ball during the excessive moment action can be suppressed. There is still a possibility that the rolling surface of each of these balls may have a ball wound or indentation. Therefore, in order to further improve the durability of the wheel support rolling bearing unit, the ball rolling surface of each ball is damaged by devising the material composition of each member constituting the wheel support rolling bearing unit. Realization of a technique capable of preventing the surface fatigue-type peeling even when indentation has occurred is desired.

ところで、図１〜２に示す様な車輪支持用転がり軸受ユニット５、５ａを構成する外輪６及びハブ本体１３、１３ａは、複雑な形状を鍛造により造る為の加工性や、各部の形状を仕上げる際の切削性を確保する為に、ＪＩＳ Ｇ ４０５１に規定されている機械構造用炭素鋼のうち、Ｓ５３Ｃ等の所謂中炭素鋼により造っている。そして、この中炭素鋼製の素材に鍛造加工を施して所定の形状とし、更に必要個所に旋削等の削り加工を施した後に、高周波焼き入れにより軌道面（外輪軌道１１ａ、１１ｂ、内輪軌道１７ａ、１７ｂ）部分の硬度を、各玉２０、２０の転動面との転がり接触により損傷しない程度に高くしている。尚、上記ハブ本体１３、１３ａの小径段部１８に外嵌固定する内輪１４は、ＪＩＳ Ｇ ４８０５に規定された高炭素クロム軸受鋼のうち、例えばＳＵＪ２により造り、全体を加熱した部材を焼き入れ油中に浸漬する、所謂ズブ焼き等の、一般的な焼き入れ・焼き戻し処理を施して、全体を硬化させている。   By the way, the outer ring 6 and the hub main bodies 13 and 13a constituting the wheel bearing rolling bearing units 5 and 5a as shown in FIGS. 1 and 2 finish workability for forming a complicated shape by forging and the shape of each part. In order to ensure the machinability, it is made of a so-called medium carbon steel such as S53C among the carbon steel for machine structure defined in JIS G 4051. Then, the medium carbon steel material is forged into a predetermined shape, and further subjected to machining such as turning at a required portion, and then subjected to induction hardening to raceway surfaces (outer ring raceways 11a and 11b, inner ring raceway 17a). 17b) The hardness of the portion is increased to such an extent that it is not damaged by rolling contact with the rolling surfaces of the balls 20 and 20. The inner ring 14 that is externally fitted and fixed to the small-diameter step portion 18 of the hub main body 13 or 13a is made of, for example, SUJ2 among high-carbon chromium bearing steels defined in JIS G 4805, and the whole heated member is quenched. The whole is hardened by applying a general quenching and tempering process such as so-called submerged soaking in oil.

上記外輪６及びハブ本体１３、１３ａを造る、上記Ｓ５３Ｃ等の中炭素鋼は、上記内輪１４を構成するＳＵＪ２等の軸受鋼に比べて、硬度が低く、残留オーステナイト量が少ない。硬度及び残留オーステナイト量は、表面の傷や圧痕による表面疲労に影響を及ぼす材料因子である。硬度に関しては、高い程表面に傷や圧痕が付きにくくなる。又、残留オーステナイトは、軟質な組織である為、表面に付いた傷や圧痕の周辺に発生する応力集中を緩和する。この為、残留オーステナイト量が多い程、剥離を抑制する事ができる。但し、残留オーステナイト量が多過ぎると、部材表面の硬度が低下する為、この残留オーステナイト量を多くする事に関しては、注意が必要である。   The medium carbon steel such as S53C that forms the outer ring 6 and the hub main bodies 13 and 13a is lower in hardness and less retained austenite than the bearing steel such as SUJ2 that constitutes the inner ring 14. Hardness and retained austenite amount are material factors that affect surface fatigue due to surface scratches and indentations. Regarding hardness, the higher the hardness, the less likely the surface is to be scratched or indented. Moreover, since retained austenite is a soft structure, it reduces stress concentration generated around scratches and indentations on the surface. For this reason, the larger the amount of retained austenite, the more the peeling can be suppressed. However, if the amount of retained austenite is too large, the hardness of the surface of the member will decrease, so care must be taken when increasing the amount of retained austenite.

上述の様な事情により、上記外輪６及びハブ本体１３、１３ａを造る、上記Ｓ５３Ｃ等の中炭素鋼は、上記一般的な焼き入れ・焼き戻し処理を施した、ＳＵＪ２等の軸受鋼に比べて、各玉２０、２０の転動面に付いた玉乗り上げ傷や圧痕を押し当てられる事による、表面疲労に対して不利である。これらの事を考慮すれば、前述の様な構造を有する車輪支持用転がり軸受ユニット５、５ａで、上記外輪６の内周面に形成した外輪軌道１１ａ、１１ｂ、及び、上記ハブ本体１３、１３ａの外周面に形成した内輪軌道１７ａの疲労寿命を確保する為には、玉２０、２０の転動面に、玉乗り上げ傷や圧痕が形成されない様にする事が重要になる。これら各玉２０、２０の転動面に玉乗り上げ傷や圧痕が形成されなければ、これら各玉２０、２０の転動面と転がり接触する、上記各軌道１１ａ、１１ｂ、１７ａ、１７ｂにも傷が付きにくくなり、これら各軌道１１ａ、１１ｂ、１７ａ、１７ｂや上記各玉２０、２０の転動面に表面疲労型の剥離が発生する可能性を低くできる。   Due to the circumstances as described above, the medium carbon steel such as S53C for producing the outer ring 6 and the hub main bodies 13 and 13a is compared with the bearing steel such as SUJ2 subjected to the general quenching and tempering treatment. The ball 20 and 20 are disadvantageous against surface fatigue due to being pressed against the ball climbing scratches and indentations on the rolling surfaces. If these are taken into consideration, the outer ring raceways 11a and 11b formed on the inner peripheral surface of the outer ring 6 and the hub main bodies 13 and 13a in the wheel bearing rolling bearing units 5 and 5a having the structure as described above. In order to ensure the fatigue life of the inner ring raceway 17a formed on the outer peripheral surface of the ball, it is important to prevent the balls 20 and 20 from rolling-up scratches and indentations on the rolling surfaces. If there are no ball landing scratches or indentations on the rolling surfaces of the balls 20, 20, the tracks 11a, 11b, 17a, 17b that are in rolling contact with the rolling surfaces of the balls 20, 20 are also scratched. And the possibility of occurrence of surface fatigue-type peeling on the rolling surfaces of the tracks 11a, 11b, 17a, 17b and the balls 20, 20 can be reduced.

特開２００７−１５２４１３号公報JP 2007-152413 A 特開平７−１６７１３８号公報JP 7-167138 A

本発明は、上述の様な事情に鑑みて、複列の外輪軌道と複列の内輪軌道との間に設けた各玉の性状を改良し、これら各玉がこれら各軌道の肩部に乗り上げて、これら各玉の転動面に過大面圧が作用した場合でも、これら各玉の転動面に傷や圧痕が付きにくい車輪支持用転がり軸受ユニットを実現すべく発明したものである。   In view of the circumstances as described above, the present invention improves the properties of each ball provided between the double row outer ring raceway and the double row inner ring raceway, and these balls ride on the shoulders of these raceways. Thus, the present invention has been invented to realize a wheel bearing rolling bearing unit in which even when an excessive surface pressure acts on the rolling surfaces of these balls, scratches and indentations are hardly formed on the rolling surfaces of these balls.

本発明の車輪支持用転がり軸受ユニットは、外輪相当部材と、内輪相当部材と、複数個の玉とを備える。
このうちの外輪相当部材は、内周面に、それぞれの断面形状が円弧形である複列の外輪軌道を有する。
又、上記内輪相当部材は、外周面に、それぞれの断面形状が円弧形である複列の内輪軌道を有する。
又、上記各玉は、上記両外輪軌道と上記両内輪軌道との間に、両列毎に複数個ずつ、これら両列同士の間で逆方向の接触角を付与された状態で、転動自在に設けられている。
更に、上記外輪相当部材と上記内輪相当部材とのうちの少なくとも一方の部材が中炭素鋼製であって、当該部材の周面に形成された複列の軌道部分が高周波熱処理により焼き入れ硬化されている。
そして、上記外輪相当部材と上記内輪相当部材とのうちの何れかの部材を、車輪を結合固定した状態でこの車輪と共に回転するハブとし、他方の部材を、懸架装置に対し支持固定する静止側軌道輪とする。 The wheel support rolling bearing unit of the present invention includes an outer ring equivalent member, an inner ring equivalent member, and a plurality of balls.
Out of these members, the outer ring equivalent member has a double row outer ring raceway having an arcuate cross section on the inner peripheral surface.
The inner ring equivalent member has a double-row inner ring raceway having an arc shape in cross section on the outer peripheral surface.
In addition, each of the balls rolls with a contact angle in the opposite direction between the both outer ring raceways and the inner ring raceways. It is provided freely.
Further, at least one of the outer ring equivalent member and the inner ring equivalent member is made of medium carbon steel, and the double-row track portion formed on the peripheral surface of the member is quenched and hardened by high-frequency heat treatment. ing.
One of the outer ring equivalent member and the inner ring equivalent member is a hub that rotates together with the wheel in a state where the wheel is coupled and fixed, and the other member is supported and fixed to the suspension device. It is a bearing ring.

特に、本発明の車輪支持用転がり軸受ユニットに於いては、上記各玉に、浸炭窒化処理又は窒化処理を施している。そして、これら各玉の表面層の窒素濃度を０．２質量％以上とし、且つ、これら各玉の表面に存在する、Ｓｉ及びＭｎを含有した窒化物であるＳｉ−Ｍｎ系窒化物の面積率を、１％以上、１０％未満としている。
尚、上記中炭素鋼の組成として、具体的には、請求項２に記載した発明の様に、Ｃを０．４８質量％以上、０．６０質量％以下、Ｓｉを０．１５質量％以上、０．３５質量％以下、Ｍｎを０．６０質量％以上、０．９０質量％以下、Ｃｒを０．１０質量％以上、０．５０質量％以下含むものが、好ましく使用できる。 In particular, in the rolling bearing unit for supporting a wheel according to the present invention, each of the balls is subjected to carbonitriding or nitriding. And the nitrogen concentration of the surface layer of each of these balls is 0.2% by mass or more, and the area ratio of Si-Mn nitride that is a nitride containing Si and Mn present on the surface of each of these balls Is 1% or more and less than 10%.
In addition, as the composition of the medium carbon steel, specifically, as in the invention described in claim 2, C is 0.48 mass% or more, 0.60 mass% or less, and Si is 0.15 mass% or more. 0.35% by mass or less, Mn containing 0.60% by mass or more and 0.90% by mass or less, and Cr containing 0.10% by mass or more and 0.50% by mass or less can be preferably used.

又、上述の様な本発明を実施する場合に好ましくは、請求項３に記載した発明の様に、上記各玉として、Ｓｉを０．３質量％以上、２．２質量％以下、Ｍｎを０．３質量％以上、２．０質量％以下含有し、Ｓｉの含有量とＭｎの含有量との比Ｓｉ／Ｍｎが５以下である鋼に、浸炭窒化焼き入れ及び焼き戻しを含む熱処理を施す事により造られたものを使用する。
又、上述の様な本発明を実施する場合に好ましくは、請求項４に記載した発明の様に、上記各玉の表面の残留オーステナイト量を０〜１５容量％とし、表面（転動面）の硬度をＨｖ７８０以上とする。
更に、上述の様な本発明を実施する場合に好ましくは、請求項５に記載した発明の様に、上記各玉として、表面に、平均粒径｛（長径＋短径）／２｝が０．０５〜１μｍのＳｉ−Ｍｎ系窒化物が、３７５μｍ2 中に１００個以上存在するものを使用する。 Further, when the present invention as described above is carried out, preferably, as in the invention described in claim 3, as each of the balls, Si is 0.3 mass% or more, 2.2 mass% or less, and Mn is Heat treatment including carbonitriding and quenching and tempering is performed on steel containing 0.3% by mass or more and 2.0% by mass or less, and the ratio Si / Mn of Si content to Mn content is 5 or less. Use what was made by applying.
Further, when carrying out the present invention as described above, preferably, the amount of retained austenite on the surface of each ball is set to 0 to 15% by volume as in the invention described in claim 4, and the surface (rolling surface) The hardness is set to Hv780 or more.
Further, when carrying out the present invention as described above, preferably, as in the invention described in claim 5, the average particle size {(major axis + minor axis) / 2} is 0 on the surface as each of the balls. The thing which 100 or more Si-Mn type | system | group nitride of 0.05-1 micrometer exists in 375 micrometer 2 is used.

上述の様に構成する本発明の車輪支持用転がり軸受ユニットによれば、各玉の圧砕強度が高くなるので、これら各玉が外輪軌道或いは内輪軌道の肩部に乗り上げて、これら各玉の転動面に過大面圧が作用した場合でも、これら各玉の転動面に傷や圧痕が付きにくくなる。そして、玉の乗り上げ傷や圧痕に起因する、上記外輪軌道及び上記内輪軌道の表面疲労による寿命低下を抑制できる。
以下に、各部の性状を前述の様に規制した理由に就いて説明する。 According to the wheel support rolling bearing unit of the present invention configured as described above, the crushing strength of each ball is increased, so that each ball rides on the shoulder of the outer ring raceway or the inner ring raceway, and Even when excessive surface pressure is applied to the moving surface, the rolling surfaces of these balls are less likely to be damaged or indented. And the life fall by the surface fatigue of the said outer ring track | truck and the said inner ring track | truck resulting from the riding-up wound and indentation of a ball | bowl can be suppressed.
The reason why the properties of each part are regulated as described above will be described below.

［各玉の表面層の窒素濃度及びＳｉ−Ｍｎ系窒化物の面積率］
Ｓｉ（けい素）及びＭｎ（マンガン）を含有する鋼の窒素濃度を増加させると、微細で高硬度なＳｉ−Ｍｎ系窒化物が析出し、表層部が強化される。上記各玉の転動面に傷や圧痕が付きにくく（圧砕強度を確保）すべく、これら各玉の転動面に十分な量の、微細で高硬度なＳｉ−Ｍｎ系窒化物を析出させる為には、窒素濃度を０．２質量％以上確保する必要がある。 [Nitrogen concentration of surface layer of each ball and area ratio of Si-Mn nitride]
When the nitrogen concentration of the steel containing Si (silicon) and Mn (manganese) is increased, fine and hard Si-Mn nitride is precipitated, and the surface layer portion is strengthened. A sufficient amount of fine and hard Si—Mn nitride is deposited on the rolling surface of each ball so that the rolling surface of each ball is not easily damaged or indented (to ensure crushing strength). Therefore, it is necessary to secure a nitrogen concentration of 0.2% by mass or more.

又、上記圧砕強度を十分に向上させる為には、上記各玉の転動面に析出しているＳｉ−Ｍｎ系窒化物の量を、面積率で１％以上確保する必要がある。但し、上記各玉の転動面に析出しているＳｉ−Ｍｎ系窒化物の量が多過ぎると、これら各玉の転動面の硬度が高くなり過ぎて、これら各玉の、熱処理後に於ける研削性が低下する可能性があるだけでなく、靭性が低下して割れが生じる可能性がある。これら研削性及び靱性の低下を、実用上問題ない程度に抑える為には、上記各玉の転動面に析出しているＳｉ−Ｍｎ系窒化物の量を、面積率で１０％以下に抑える必要がある。   Further, in order to sufficiently improve the crushing strength, it is necessary to secure the amount of Si—Mn nitride deposited on the rolling surface of each ball in an area ratio of 1% or more. However, if the amount of Si-Mn nitride deposited on the rolling surface of each ball is too large, the hardness of the rolling surface of each ball will become too high, In addition to the possibility that the grindability is reduced, the toughness is reduced and cracking may occur. In order to suppress these deteriorations in grindability and toughness to such an extent that there is no practical problem, the amount of Si—Mn nitride deposited on the rolling surface of each ball is suppressed to 10% or less in terms of area ratio. There is a need.

［各玉を構成する鋼中のＳｉの含有量］
Ｓｉは、製鋼時に脱酸剤として作用すると共に、鋼の焼き戻し軟化抵抗性を高める作用も有する為、上記各玉の硬度を確保する為に必要である。この様な作用を十分に得る為には、Ｓｉの含有量を、０．１５質量％以上確保する必要がある。更に、Ｓｉの含有量が多い程、軟窒化処理や浸炭処理に伴って、上記各玉の表層部（転動面）の窒素濃度や炭素濃度が高くなる。そして、前述した様に、これら各玉の表層部を強化する為に十分な量のＳｉ−Ｍｎ系窒化物を析出させる為には、Ｓｉの含有量を、０．３質量％以上確保する必要がある。
但し、Ｓｉの含有量が多過ぎると、得られた玉の靭性が低下したり、芯部への窒素の拡散が阻害されて、玉全体としての硬度を確保しにくくなるで、Ｓｉの含有量の上限値を２．２質量％とする事が好ましい。 [Si content in steel constituting each ball]
Si acts as a deoxidizer during steel making and also has an effect of increasing the temper softening resistance of the steel, so it is necessary to ensure the hardness of each ball. In order to sufficiently obtain such an action, it is necessary to secure a Si content of 0.15% by mass or more. Furthermore, as the Si content increases, the nitrogen concentration and the carbon concentration of the surface layer portion (rolling surface) of each ball increase with the soft nitriding treatment or the carburizing treatment. As described above, in order to precipitate a sufficient amount of Si-Mn nitride to strengthen the surface layer of each ball, it is necessary to secure a Si content of 0.3% by mass or more. There is.
However, if the Si content is too large, the toughness of the obtained ball will be reduced, or the diffusion of nitrogen into the core will be hindered, making it difficult to ensure the hardness of the entire ball. The upper limit of the amount is preferably 2.2% by mass.

［各玉を構成する鋼中のＭｎの含有量］
Ｍｎは、製鋼時に脱酸剤として作用すると共に、鋼の焼き入れ性を高める作用を有する。この様な作用を十分に得る為には、Ｍｎの含有量を０．１質量％以上確保する必要がある。更に、前述した様に、上記各玉の表層部を強化する為に十分な量のＳｉ−Ｍｎ系窒化物を析出させる為には、Ｍｎの含有量を０．３質量％以上確保する必要がある。
但し、Ｍｎの含有量が多過ぎると、鋼の鍛造性や切削性が低下したり、鋼中の不純物であるＳ（硫黄）やＰ（燐）と介在物を形成し、得られた玉の強度を低下させる可能性がある事から、Ｍｎの含有量の上限値を２．０質量％とする事が好ましい。 [Mn content in steel constituting each ball]
Mn acts as a deoxidizer during steelmaking and has the effect of enhancing the hardenability of the steel. In order to sufficiently obtain such an action, it is necessary to secure a Mn content of 0.1% by mass or more. Furthermore, as described above, in order to precipitate a sufficient amount of Si-Mn nitride to strengthen the surface layer of each ball, it is necessary to secure a Mn content of 0.3% by mass or more. is there.
However, if the content of Mn is too large, the forgeability and machinability of the steel are reduced, or inclusions are formed with S (sulfur) and P (phosphorus) which are impurities in the steel. Since there is a possibility of lowering the strength, the upper limit of the Mn content is preferably set to 2.0% by mass.

［各玉を構成する鋼中のＳｉの含有量とＭｎの含有量との比Ｓｉ／Ｍｎ］
Ｓｉ−Ｍｎ系窒化物は、焼き戻しによる窒化物とは異なり、Ｍｎを取り込みながらＮ（窒素）がＳｉと反応して形成される。従って、鋼中のＳｉの含有量に対してＭｎの含有量が少ないと、Ｎを十分に拡散させても、Ｓｉ−Ｍｎ系窒化物の析出が促進されない。この為、Ｓｉの含有量が０．３質量％以上、２．２質量％以下、Ｍｎの含有量が０．３質量％以上、２．０質量％以下である鋼に、圧砕強度、耐摩耗性、耐焼付き性を何れも向上させる事に関して効果を有する量（面積率が１％以上１０％未満）のＳｉ−Ｍｎ系窒化物を析出させる為には、上記比Ｓｉ／Ｍｎを、５以下に抑える（Ｍｎに対するＳｉの量を確保する）事が好ましい。 [Ratio Si / Mn between Si content and Mn content in steel constituting each ball]
Unlike nitrides obtained by tempering, Si—Mn nitride is formed by reacting N (nitrogen) with Si while incorporating Mn. Therefore, if the Mn content is less than the Si content in the steel, precipitation of Si—Mn nitride is not promoted even if N is sufficiently diffused. For this reason, a steel having a Si content of 0.3% by mass or more and 2.2% by mass or less and a Mn content of 0.3% by mass or more and 2.0% by mass or less has a crushing strength and wear resistance. In order to precipitate Si-Mn nitride in an amount (area ratio is 1% or more and less than 10%) that has an effect on improving both the property and seizure resistance, the ratio Si / Mn is 5 or less. It is preferable to keep it at a minimum (to ensure the amount of Si relative to Mn).

［各玉の表面の残留オーステナイト量及び表面硬度］
これら各玉の表面硬度が低いと、これら各玉が何れかの軌道の肩部に乗り上げた場合に、これら各玉の転動面（表面）に、傷や圧痕が付き易くなる。そこで、これら各玉の表面の硬度をＨｖ７８０以上確保して、上記乗り上げが発生した場合にも、これら傷や圧痕が形成されにくくする事が好ましい。
一方、残留オーステナイトは、軟質な組織である為、表面に付いた傷や圧痕の周辺に発生する応力集中を緩和する。この為、残留オーステナイト量が多い方が、これら傷や圧痕が転動面の剥離に繋がる事を抑制できる。但し、この残留オーステナイト量が多過ぎると、上記各玉の転動面の硬度が低下したり、これら各玉の形状安定性が損なわれる為、残留オーステナイト量を１５容量％以下に抑える事が好ましい。 [Amount of retained austenite and surface hardness on the surface of each ball]
If the surface hardness of each of these balls is low, when each of these balls rides on the shoulder portion of any track, the rolling surface (surface) of each of these balls is likely to be damaged or indented. Therefore, it is preferable that the hardness of the surface of each ball is ensured to be Hv780 or more, and these scratches and indentations are not easily formed even when the above-mentioned climbing occurs.
On the other hand, since retained austenite is a soft structure, it relieves stress concentration generated around scratches and indentations on the surface. For this reason, the one where there is much residual austenite can suppress that these cracks and indentations lead to peeling of a rolling surface. However, if the amount of retained austenite is too large, the hardness of the rolling surface of each ball is reduced or the shape stability of each ball is impaired, so it is preferable to keep the amount of retained austenite to 15% by volume or less. .

［各玉の表面のＳｉ−Ｍｎ系窒化物の大きさと個数］
各玉の転動面に存在する窒化物は、前述の通り、これら各玉の転動面を強化するが、平均粒径が１μｍを超える程に大きな窒化物は、材料の強化にあまり寄与しない。細かい窒化物が分散して均等に存在している方が、上記各玉の転動面を強化する面からは効果がある。この理由は、析出強化の理論上、析出物粒子間の距離が小さい（短い）程、強化能が優れる事による。従って、上記各玉の転動面に析出しているＳｉ−Ｍｎ系窒化物の面積率が同じであっても、析出粒子数が多ければ、相対的に粒子間距離が短くなり、上記各玉の転動面が強化される。これらの事を、製造工程と合わせて考慮すれば、Ｓｉ−Ｍｎ系窒化物の面積率を前述した理由で１〜１０％の範囲に規制する事を前提とし、このＳｉ−Ｍｎ系窒化物の平均粒径を、０．０５〜１μｍの範囲に規制して、個々のＳｉ−Ｍｎ系窒化物を微細にして個数を増やす事が好ましい。具体的には、面積３７５μｍ2 の範囲で、平均粒径｛（長径＋短径）／２｝が０．０５〜１μｍであるＳｉ−Ｍｎ系窒化物が１００個以上存在する事が好ましい。 [Size and number of Si-Mn nitrides on the surface of each ball]
As described above, the nitride existing on the rolling surface of each ball reinforces the rolling surface of each of these balls, but a nitride having an average particle size exceeding 1 μm does not contribute much to the strengthening of the material. . From the viewpoint of strengthening the rolling surface of each ball, it is more effective that fine nitrides are dispersed and present uniformly. The reason for this is that the strengthening ability is superior as the distance between the precipitate particles is smaller (shorter) in theory of precipitation strengthening. Therefore, even if the area ratio of the Si-Mn nitride deposited on the rolling surface of each ball is the same, the larger the number of precipitated particles, the shorter the inter-particle distance becomes. The rolling surface of is strengthened. If these are considered together with the manufacturing process, it is assumed that the area ratio of the Si—Mn nitride is restricted to a range of 1 to 10% for the above-described reason, It is preferable that the average particle diameter is regulated within a range of 0.05 to 1 μm, and the number of Si—Mn nitrides is made finer and the number thereof is increased. Specifically, it is preferable that 100 or more Si—Mn nitrides having an average particle size {(major axis + minor axis) / 2} of 0.05 to 1 μm exist in an area of 375 μm 2 .

［上述した条件を満たすＳｉ−Ｍｎ系窒化物を得る為の熱処理プロセス］
上述した条件を満たすＳｉ−Ｍｎ系窒化物を得る為の熱処理プロセスは、特に限定しないが、例えば、前述した組成を有する鋼に次の様な手順で熱処理を施す事により、上記条件を満たすＳｉ−Ｍｎ系窒化物を得られる。
先ず、浸炭窒化処理を、８００〜８７０℃で２〜８時間施す。必要な浸炭窒化処理を施す為には、８００℃以上の処理温度が必要な反面、処理温度が８７０℃を越えると、窒化物が粗大化して、微細な（平均粒径が１μｍ以下の）Ｓｉ−Ｍｎ系窒化物の個数が減少する。又、窒素の固溶限も大きくなる為、窒化物の量が少なくなり、所望の面積率を得られなくなる。
又、浸炭窒化処理工程の初期から、Ｒｘガスとエンリッチガスとアンモニアガスとの混合ガス雰囲気とし、ＣＰ値は１．２以上、アンモニアガスの流量はＲｘガスの流量の１／５以上にする。更に、浸炭窒化後の焼き入れは、油温６０〜１２０℃の範囲で行う。焼き入れ時の熱衝撃を抑えて、歩留りを確保する為には、６０℃以上での焼き入れが必要であるが、焼き入れ温度が１２０℃よりも高いと、十分な硬度を得られない。又、焼き戻しは１６０〜２７０℃の範囲で行う。この温度は、必要な硬度を確保し、且つ、転動面の残留オーステナイト量を前述した適正範囲に収める為に規制する。 [Heat treatment process for obtaining Si-Mn nitride satisfying the above conditions]
The heat treatment process for obtaining the Si—Mn nitride satisfying the above conditions is not particularly limited. For example, by performing heat treatment on the steel having the above-described composition in the following procedure, -Mn nitride can be obtained.
First, carbonitriding is performed at 800 to 870 ° C. for 2 to 8 hours. In order to perform the necessary carbonitriding treatment, a treatment temperature of 800 ° C. or higher is necessary, but when the treatment temperature exceeds 870 ° C., the nitride becomes coarse and fine (average particle size is 1 μm or less) Si. -The number of Mn nitrides decreases. Further, since the solid solubility limit of nitrogen is increased, the amount of nitride is reduced, and a desired area ratio cannot be obtained.
Further, from the initial stage of the carbonitriding process, a mixed gas atmosphere of Rx gas, enriched gas and ammonia gas is set, the CP value is 1.2 or more, and the flow rate of ammonia gas is 1/5 or more of the flow rate of Rx gas. Furthermore, quenching after carbonitriding is performed in the oil temperature range of 60 to 120 ° C. In order to suppress the thermal shock at the time of quenching and secure the yield, quenching at 60 ° C. or higher is necessary. However, if the quenching temperature is higher than 120 ° C., sufficient hardness cannot be obtained. Tempering is performed in the range of 160 to 270 ° C. This temperature is regulated to ensure the necessary hardness and to keep the amount of retained austenite on the rolling surface within the above-mentioned appropriate range.

［内輪相当部材及び外輪相当部材を構成する中炭素鋼中のＣの含有量］
Ｃ（炭素）は、鋼自体の硬度及び強度を高める作用を有する事に加えて、鋼の焼き入れ性を高める作用も有する。これらの作用により、上記内輪相当部材或いは上記外輪相当部材として、必要な硬度及び強度を確保する為には、上記中炭素鋼中のＣの含有量を、０．４８質量％以上確保する事が好ましい。但し、Ｃの含有量が多過ぎると、鍛造性や切削性を低下させるので、この含有量の上限を０．６０質量％とする事が好ましい。 [Content of C in medium carbon steel constituting inner ring equivalent member and outer ring equivalent member]
C (carbon) has the effect of enhancing the hardenability of the steel in addition to the effect of increasing the hardness and strength of the steel itself. With these actions, in order to ensure the necessary hardness and strength as the inner ring equivalent member or the outer ring equivalent member, it is possible to ensure the content of C in the medium carbon steel to be 0.48% by mass or more. preferable. However, if the content of C is too large, forgeability and machinability are deteriorated, so the upper limit of this content is preferably 0.60% by mass.

［内輪相当部材及び外輪相当部材を構成する中炭素鋼中のＳｉ、Ｍｎの含有量］
これらＳｉ及びＭｎは、前述した、各玉を構成する鋼中にこれらＳｉ及びＭｎを含有させるのとほぼ同様の理由で添加する。但し、各玉の場合とは異なり、表面にＳｉ−Ｍｎ系窒化物を析出させる事は意図していない。又、上記内輪相当部材及び上記外輪相当部材は、上記各玉に比べて、靱性の低下に伴う弊害が表れ易い。この為、Ｓｉ及びＭｎの何れに関しても、含有量の上限値を、上記各玉の場合よりも低く抑えている。
即ち、Ｓｉは、製鋼時に於ける脱酸剤として作用させると共に、焼き戻し時の軟化抵抗性を高める作用も発揮させる為に０．１５質量％以上含有させるが、鋼の靭性の低下を抑える為に、含有量の上限値を０．３５質量％とする事が好ましい。
又、Ｍｎは、製鋼時に於ける脱酸剤として作用させると共に、鋼の焼き入れ性を高める作用も発揮させる為に、０．６質量％以上含有させるが、鋼の鍛造性や切削性の低下を抑えると共に、ＳやＰと介在物を形成する事を抑える為に、含有量の上限値を０．９質量％とする事が好ましい。 [Contents of Si and Mn in the medium carbon steel constituting the inner ring equivalent member and the outer ring equivalent member]
These Si and Mn are added for substantially the same reason as described above in which these Si and Mn are contained in the steel constituting each ball. However, unlike the case of each ball, it is not intended to deposit Si—Mn nitride on the surface. Further, the inner ring equivalent member and the outer ring equivalent member are more likely to have a harmful effect due to a decrease in toughness than the respective balls. For this reason, the upper limit of content is restrained lower than the case of each said ball about both Si and Mn.
That is, Si acts as a deoxidizer during steel making and is also contained in an amount of 0.15% by mass or more in order to exert an effect of increasing softening resistance during tempering, but to suppress a decrease in steel toughness. Further, the upper limit of the content is preferably 0.35% by mass.
In addition, Mn is added in an amount of 0.6% by mass or more in order to make it act as a deoxidizer during steel making and also to enhance the hardenability of the steel, but it decreases the forgeability and machinability of the steel. In order to suppress the formation of inclusions with S and P, the upper limit of the content is preferably set to 0.9% by mass.

［内輪相当部材及び外輪相当部材を構成する中炭素鋼中のＣｒの含有量］
Ｃｒ（クロム）は、鋼の焼き入れ性を高める作用を有する為、内輪軌道或いは外輪軌道の表面硬度を高くする為に含有させるが、この作用を十分に得る為には、Ｃｒの含有量を０．１０質量％以上確保する必要がある。但し、Ｃｒの含有量が多過ぎると、鍛造性や切削性を低下させるので、Ｃｒの含有量の上限値を０．５０質量％とする事が好ましい。 [Cr content in medium carbon steel constituting inner ring equivalent member and outer ring equivalent member]
Since Cr (chromium) has the effect of enhancing the hardenability of steel, it is included in order to increase the surface hardness of the inner ring raceway or outer ring raceway. In order to obtain this effect sufficiently, the Cr content must be increased. It is necessary to ensure 0.10% by mass or more. However, if the Cr content is too large, forgeability and machinability are deteriorated, so the upper limit of the Cr content is preferably 0.50% by mass.

本発明の特徴は、車輪支持用転がり軸受ユニットを構成する、外輪相当部材と、内輪相当部材と、複数個の玉との性状を適正に規制して、これら外輪相当部材と内輪相当部材との間に大きなモーメントが作用し、上記各玉が外輪軌道或いは内輪軌道の肩部に乗り上げた場合にも、これら各玉の転動面に傷が付きにくくする事により、厳しい使用条件下でも優れた耐久性を確保できる車輪支持用転がり軸受ユニットを実現する点にある。
図面に表れる車輪支持用転がり軸受ユニットの構造に就いては、前述の図１〜２に示した構造を含め、従来から知られている各種車輪支持用転がり軸受ユニットと同様である。就いては、具体的構造に就いての図示並びに説明は省略する。尚、外輪相当部材を車輪と共に回転するハブとし、内輪相当部材を懸架装置に対し支持固定する静止側軌道輪とする車輪支持用転がり軸受ユニットも、本発明の対象となる。 A feature of the present invention is that the outer ring equivalent member, the inner ring equivalent member, and the plurality of balls constituting the wheel support rolling bearing unit are appropriately regulated and the outer ring equivalent member and the inner ring equivalent member Even when a large moment acts between them and each ball rides on the shoulder of the outer ring raceway or inner ring raceway, the rolling surface of each ball is less likely to be scratched, making it excellent even under severe usage conditions. It is in the point which implement | achieves the rolling bearing unit for wheel support which can ensure durability.
The structure of the wheel-supporting rolling bearing unit shown in the drawings is the same as that of various conventionally-known wheel-supporting rolling bearing units including the structure shown in FIGS. Therefore, illustration and description of a specific structure are omitted. Note that a wheel bearing rolling bearing unit that uses a member that corresponds to the outer ring as a hub that rotates together with the wheel and a stationary side ring that supports and fixes the member corresponding to the inner ring as to the suspension device is also an object of the present invention.

本発明の効果を確認する為に行った実験に就いて説明する。この実験は、前述の図２に示した構造を有する車輪支持用転がり軸受ユニット５ａを使用した、転がり疲労試験として行った。使用した車輪支持用転がり軸受ユニット５ａを構成する各玉２０、２０のピッチ円直径（ＰＣＤ）は４６．６mm、両列同士の間のピッチは３２mm、両列の玉２０、２０の数はそれぞれ１３個ずつ、これら各玉２０、２０の直径は１０．３１９mmとした。又、ハブ本体１３ａと共にハブ８ａを構成する内輪１４は、下記の表１に示す組成を有する、高炭素クロム軸受鋼２種（ＳＵＪ２）を使用し、焼き入れ（ずぶ焼き）・焼き戻しの後に周知の研削加工を施して造った。尚、各表中には、鋼を構成する元素のうち、Ｆｅ以外の重要なものを記載してある。各鋼に関して、上記各表に記載されていないものは、Ｆｅ及び不可避不純物、乃至は、本発明の作用・効果に影響を及ぼさない、微量元素である。

Figure 2009299759
An experiment conducted for confirming the effect of the present invention will be described. This experiment was conducted as a rolling fatigue test using the wheel-supporting rolling bearing unit 5a having the structure shown in FIG. The pitch diameter (PCD) of the balls 20 and 20 constituting the wheel bearing rolling bearing unit 5a used is 46.6 mm, the pitch between the rows is 32 mm, and the number of balls 20 and 20 in both rows is respectively Each of these balls 20, 20 had a diameter of 10.319 mm. Further, the inner ring 14 constituting the hub 8a together with the hub main body 13a uses high carbon chrome bearing steel type 2 (SUJ2) having the composition shown in Table 1 below, and after quenching (tempering) and tempering. Made with known grinding. In each table, important elements other than Fe among elements constituting steel are described. Regarding each steel, those not described in the above tables are Fe and unavoidable impurities, or trace elements that do not affect the functions and effects of the present invention.
Figure 2009299759

外輪６及び上記ハブ本体１３ａは、下記の表２又は表３に示した組成を有する中炭素鋼により造り、各軌道面（外輪軌道１１ａ、１１ｂ、内輪軌道１７ａ、１７ｂ）を含む周面部分に高周波焼き入れ・焼き戻しを施す事により、上記各軌道面を含む周面部分に表面硬化層を形成した。焼き入れにより硬化させた表面部分の硬度はＨｖ６８０〜７５０であり、焼き入れされていない（生のままである）内部の硬度は、Ｈｖ２００〜２５０である。

Figure 2009299759
Figure 2009299759
 The outer ring 6 and the hub body 13a are made of medium carbon steel having the composition shown in Table 2 or Table 3 below, and on the peripheral surface portion including each raceway surface (outer ring raceways 11a, 11b, inner ring raceways 17a, 17b). By performing induction hardening and tempering, a hardened surface layer was formed on the peripheral surface portion including each of the raceway surfaces. The hardness of the surface portion hardened by quenching is Hv 680-750, and the hardness of the unquenched (raw) interior is Hv 200-250.
Figure 2009299759
Figure 2009299759

一方、前記各玉２０、２０は、下記の表４、５に示した組成を有する鋼製の素材に鍛造加工を施してから、周知の切削加工及び研削加工に加えて、前述した条件で浸炭窒化処理を施す事により造った。

Figure 2009299759
Figure 2009299759
 On the other hand, the balls 20, 20 are carburized under the above-described conditions in addition to the known cutting and grinding processes after forging a steel material having the composition shown in Tables 4 and 5 below. It was made by nitriding.
Figure 2009299759
Figure 2009299759

転がり疲労試験の試験条件は、下記の通り、２種類の試験（試験１、試験２）を行った。
(1) 試験１：玉２０、２０のみを変化させた転がり疲労試験
この試験では、外輪６及びハブ本体１３ａは、本発明の技術的範囲に属する、前記表２に示す組成を有する鋼により造ったものを使用した。
(2) 試験２：外輪６及びハブ本体１３ａを変化させた転がり疲労試験
この試験では、各玉２０、２０は、本発明の技術的範囲に属する、前記表５に示す組成を有する鋼により造ったものを使用した。 The test conditions of the rolling fatigue test were two types of tests (Test 1 and Test 2) as follows.
(1) Test 1: Rolling fatigue test with only balls 20 and 20 changed In this test, the outer ring 6 and the hub body 13a are made of steel having the composition shown in Table 2 belonging to the technical scope of the present invention. Used.
(2) Test 2: Rolling fatigue test with outer ring 6 and hub body 13a changed In this test, each ball 20, 20 is made of steel having the composition shown in Table 5 belonging to the technical scope of the present invention. Used.

試験１、試験２共に、予め車輪支持用転がり軸受ユニット５ａを組み立てた状態で、各玉２０、２０の転動面（表面）に玉乗り上げ傷を形成しておき、これら各玉２０、２０を使用して、以下に示す試験条件で寿命試験を行った。この玉乗り上げ傷を付ける作業は、上記車輪支持用転がり軸受ユニット５ａを単体で水平面に（回転中心軸を鉛直方向に向け）固定して、上記ハブ本体１３ａに、５ｋＮの荷重（一方向荷重）を１０秒間負荷し、その後この荷重を除く行程を１サイクルとし、上記各玉２０、２０の転動面を各軌道の肩部へ乗り上げさせてから、再び正規の位置に戻した。この様な作業を２０サイクル繰り返す事により、上記各玉２０、２０に乗り上げ傷を形成した。   In both Test 1 and Test 2, in the state where the wheel bearing rolling bearing unit 5a is assembled in advance, a ball climbing scratch is formed on the rolling surface (surface) of each ball 20, 20, and each of these balls 20, 20 is In use, a life test was conducted under the test conditions shown below. The operation of scratching the ball is carried out by fixing the wheel-supporting rolling bearing unit 5a as a single unit on a horizontal surface (with the rotation center axis in the vertical direction) and applying a load of 5 kN (one-way load) to the hub body 13a. Was applied for 10 seconds, and then the process of removing this load was set as one cycle, the rolling surfaces of the balls 20 and 20 were run on the shoulders of the tracks, and then returned to the normal position again. By repeating such an operation for 20 cycles, the balls 20 and 20 were climbed to form scratches.

次いで、上記各玉２０、２０に乗り上げ傷を形成した、上記車輪支持用転がり軸受ユニット５ａに、次の条件で、上記(1)(2)に記載した転がり疲労試験を施した。
ラジアル荷重 ： ６５００Ｎ
アキシアル荷重 ： ３９００Ｎ
ハブ８ａの回転速度 ： １０００min-1
この条件で、回転試験機に振動計を取り付け、振動値が初期振動値の３倍になった時点を寿命とした。尚、上記両荷重は、乗り上げが発生しない様に、それぞれの方向等を規制した。
この様な条件で行った、前述した試験１の転がり疲労試験の結果を、各試料の組成、性状等と共に、前記表４に示した。試験結果を表す寿命は、それぞれ５個ずつの試料（車輪支持用転がり軸受ユニット５ａ）に就いての試験結果から、累積破損確率５０％に対応する寿命（以下、Ｌ５０寿命と呼ぶ）を求めた。そして、一般的に用いられているＳＵＪ２製の玉２０、２０を組み込んだ、比較例ＯのＬ５０寿命を１．０として、それとの比で表している。 Next, the rolling fatigue test described in the above (1) and (2) was performed on the wheel bearing rolling bearing unit 5a on which the balls 20 and 20 were run and formed scratches under the following conditions.
Radial load: 6500N
Axial load: 3900N
Rotational speed of hub 8a: 1000min -1
Under this condition, a vibration meter was attached to the rotation tester, and the time when the vibration value became three times the initial vibration value was regarded as the life. In addition, each direction etc. were controlled so that the above-mentioned both loads might not get on.
The results of the rolling fatigue test in Test 1 described above under these conditions are shown in Table 4 together with the composition and properties of each sample. The life representing the test results was obtained from the test results for each of the five samples (roller bearing unit 5a for supporting the wheel), and the life corresponding to a cumulative failure probability of 50% (hereinafter referred to as L50 life). . Then, the L50 life of Comparative Example O incorporating the generally used SUJ2 balls 20 and 20 is 1.0, and the ratio is expressed as a ratio to that.

上記表４に記載した、本発明の技術的範囲に属する８種類の試料（実施例Ａ〜Ｈ）と、本発明の技術的範囲からは外れる７種類の試料（比較例Ｉ〜Ｏ）のうち、実施例Ａ〜Ｈに就いては、鋼の組成、Ｓｉ／Ｍｎ比、窒素濃度、窒化物（Ｓｉ−Ｍｎ系窒化物）面積率、窒化物（Ｓｉ−Ｍｎ系窒化物）の個数、残留オーステナイト量、硬度が、総て前述した本発明（好ましいとした範囲を含む）の技術的範囲内にある。この為、上記各玉２０、２０の圧砕強度が高く、玉乗り上げが起こった場合でも、これら各玉２０、２０に傷や圧痕が付きにくく、寿命が長い。又、これら各玉２０、２０にサブゼロ処理を施す事により、更に寿命が延長する事が分かる。   Among the eight types of samples (Examples A to H) belonging to the technical scope of the present invention described in Table 4 above and the seven types of samples (Comparative Examples I to O) outside the technical scope of the present invention In Examples A to H, the steel composition, Si / Mn ratio, nitrogen concentration, area ratio of nitride (Si—Mn nitride), number of nitrides (Si—Mn nitride), residual The austenite amount and hardness are all within the technical scope of the present invention (including the preferred range) described above. For this reason, the crushing strength of each of the balls 20 and 20 is high, and even when the balls run up, the balls 20 and 20 are hardly scratched or indented and have a long life. It can also be seen that the life is further extended by subjecting these balls 20 and 20 to sub-zero treatment.

これに対して、比較例Ｉ、Ｊは、焼き戻し温度が低い為、残留オーステナイト量が本発明の技術的範囲よりも多く、その為に、玉乗り上げ傷が付き易く、寿命が短い。
又、比較例Ｋは、ＳＵＪ２に浸炭窒化処理を施したもので、Ｓｉの含有量が本発明の技術的範囲よりも少ない。この為、窒化物面積率が低く、しかも窒化物の個数が少ない事からも分かる様に、上記各玉２０、２０の転動面に十分な量のＳｉ−Ｍｎ系窒化物が析出せず、寿命が短い。
又、比較例Ｌは、ＳＵＪ２に浸炭窒化処理を施した場合で、Ｍｎの含有量が本発明の技術的範囲よりも少ない。この為、上記比較例Ｋの場合と同様に、上記各玉２０、２０の表面に、十分な量のＳｉ−Ｍｎ系窒化物を析出していない。しかも、焼き戻し温度が低い為、硬度も低くなっている。この結果、寿命が短い。
又、比較例Ｍは、上記各玉２０、２０の組成に関しては、本発明の技術的範囲内にあるが、比Ｓｉ／Ｍｎが高く、窒化物面積率が低い事と窒化物の個数が少ない事とから分かる様に、上記各玉２０、２０の転動面に十分な量のＳｉ−Ｍｎ系窒化物を析出させられず、寿命が短い。
又、比較例Ｎは、上記各玉２０、２０の組成及び比Ｓｉ／Ｍｎは本発明の技術的範囲内にあるが、窒素濃度が低い為、窒化物面積率が低い事と窒化物の個数が少ない事とから分かる様に、十分な量のＳｉ−Ｍｎ系窒化物を析出させる事ができず、寿命が短い。 On the other hand, Comparative Examples I and J have a low tempering temperature, so that the amount of retained austenite is larger than the technical range of the present invention, and therefore, the ball climbing damage is likely to occur and the life is short.
In Comparative Example K, SUJ2 was subjected to carbonitriding, and the Si content was less than the technical scope of the present invention. Therefore, as can be seen from the fact that the nitride area ratio is low and the number of nitrides is small, a sufficient amount of Si—Mn nitride is not deposited on the rolling surfaces of the balls 20, 20. Life is short.
Moreover, the comparative example L is a case where the carbonitriding process is performed on SUJ2, and the Mn content is less than the technical scope of the present invention. For this reason, as in the case of Comparative Example K, a sufficient amount of Si—Mn nitride is not deposited on the surfaces of the balls 20 and 20. Moreover, since the tempering temperature is low, the hardness is also low. As a result, the lifetime is short.
Further, Comparative Example M is within the technical scope of the present invention with respect to the composition of the balls 20 and 20 described above, but the ratio Si / Mn is high, the nitride area ratio is low, and the number of nitrides is small. As can be seen from the above, a sufficient amount of Si—Mn nitride cannot be deposited on the rolling surfaces of the balls 20 and 20 and the life is short.
In Comparative Example N, the composition of each of the balls 20 and 20 and the ratio Si / Mn are within the technical scope of the present invention. However, since the nitrogen concentration is low, the nitride area ratio is low and the number of nitrides. As can be seen from the fact that the amount of Si—Mn is small, a sufficient amount of Si—Mn nitride cannot be deposited, and the lifetime is short.

更に、前記表３に、前記外輪６及び前記ハブ本体１３ａを構成する鋼の組成及び焼き入れ方法と共に、前述した試験２の転がり疲労試験の結果を示した。
上記表３の記載から分かる様に、本発明の技術的範囲に属する実施例ａ〜ｉに就いては、上記外輪６及び上記ハブ本体１３ａを構成する鋼の組成が本発明の技術的範囲内にある為、寿命が長い。
これに対して、上記外輪６及び上記ハブ本体１３ａを構成する鋼の組成が本発明の技術的範囲からは外れる、比較例ｊ〜ｍに就いては、上記外輪６及び上記ハブ本体１３ａの強度を十分に得られず、寿命が短い。 Further, Table 3 shows the results of the rolling fatigue test in Test 2 described above, together with the composition of steel constituting the outer ring 6 and the hub main body 13a and the quenching method.
As can be seen from the description in Table 3 above, in Examples a to i belonging to the technical scope of the present invention, the composition of the steel constituting the outer ring 6 and the hub body 13a is within the technical scope of the present invention. Therefore, the life is long.
On the other hand, in the comparative examples j to m in which the composition of the steel constituting the outer ring 6 and the hub main body 13a is out of the technical scope of the present invention, the strength of the outer ring 6 and the hub main body 13a. Cannot be obtained sufficiently, and the lifetime is short.

本発明の対象となる車輪支持用転がり軸受ユニットの第１例を、懸架装置に組み付けた状態で示す断面図。Sectional drawing which shows the 1st example of the rolling bearing unit for wheel support used as the object of this invention in the state assembled | attached to the suspension apparatus. 同第２例を単体で示す断面図。Sectional drawing which shows the said 2nd example single-piece | unit.

符号の説明Explanation of symbols

１ ホイール
２ ロータ
３ ナックル
４ 支持孔
５、５ａ 車輪支持用ハブユニット
６ 外輪
７ ボルト
８、８ａ ハブ
９ スタッド
１０ ナット
１１ａ、１１ｂ 外輪軌道
１２ 結合フランジ
１３、１３ａ ハブ本体
１４ 内輪
１５ 取付フランジ
１６ 位置決め筒部
１７ａ、１７ｂ 内輪軌道
１８ 小径段部
１９ かしめ部
２０ 玉
２１ａ、２１ｂ シールリング
２２ スプライン孔
２３ 等速ジョイント用外輪
２４ スプライン軸
２５ ナット DESCRIPTION OF SYMBOLS 1 Wheel 2 Rotor 3 Knuckle 4 Support hole 5, 5a Wheel support hub unit 6 Outer ring 7 Bolt 8, 8a Hub 9 Stud 10 Nut 11a, 11b Outer ring track 12 Coupling flange 13, 13a Hub body 14 Inner ring 15 Mounting flange 16 Positioning cylinder Part 17a, 17b Inner ring raceway 18 Small diameter step part 19 Caulking part 20 Ball 21a, 21b Seal ring 22 Spline hole 23 Outer ring for constant velocity joint 24 Spline shaft 25 Nut

Claims (5)

内周面に、それぞれの断面形状が円弧形である複列の外輪軌道を有する外輪相当部材と、外周面に、それぞれの断面形状が円弧形である複列の内輪軌道を有する内輪相当部材と、これら両内輪軌道と上記両外輪軌道との間に、両列毎に複数個ずつ、これら両列同士の間で逆方向の接触角を付与された状態で転動自在に設けられた玉とを備え、上記外輪相当部材と上記内輪相当部材とのうちの少なくとも一方の部材が中炭素鋼製であって、当該部材の周面に形成された複列の軌道部分が高周波熱処理により焼き入れ硬化されており、上記外輪相当部材と上記内輪相当部材とのうちの何れかの部材を、車輪を結合固定した状態でこの車輪と共に回転するハブとし、他方の部材を、懸架装置に対し支持固定する静止側軌道輪とする車輪支持用転がり軸受ユニットに於いて、上記各玉が、浸炭窒化処理又は窒化処理が施されたものであり、これら各玉の表面層の窒素濃度が０．２質量％以上であり、且つ、これら各玉の表面に存在する、Ｓｉ及びＭｎを含有した窒化物であるＳｉ−Ｍｎ系窒化物の面積率が、１％以上、１０％未満である事を特徴とする車輪支持用転がり軸受ユニット。   An outer ring equivalent member having a double row outer ring raceway having an arc shape on the inner peripheral surface, and an inner ring equivalent having a double row inner ring raceway having an arc shape on the outer peripheral surface. A plurality of members are provided between the inner ring raceways and the outer ring raceways for each row, and are provided so as to be freely rollable with a contact angle in the opposite direction between the rows. And at least one of the outer ring equivalent member and the inner ring equivalent member is made of medium carbon steel, and the double-row track portion formed on the peripheral surface of the member is baked by high-frequency heat treatment. One of the outer ring equivalent member and the inner ring equivalent member is a hub that rotates together with the wheel while the wheel is coupled and fixed, and the other member is supported by the suspension device. Wheel-supporting rolling with fixed stationary raceway In the receiving unit, each of the balls is subjected to carbonitriding or nitriding treatment, and the nitrogen concentration of the surface layer of each of these balls is 0.2% by mass or more. A rolling bearing unit for supporting a wheel, wherein an area ratio of Si-Mn nitride, which is a nitride containing Si and Mn, existing on a surface is 1% or more and less than 10%. 中炭素鋼が、Ｃを０．４８質量％以上、０．６０質量％以下、Ｓｉを０．１５質量％以上、０．３５質量％以下、Ｍｎを０．６０質量％以上、０．９０質量％以下、Ｃｒを０．１０質量％以上、０．５０質量％以下含むものである、請求項１に記載した車輪支持用転がり軸受ユニット。   Medium carbon steel has C of 0.48 mass% or more and 0.60 mass% or less, Si of 0.15 mass% or more and 0.35 mass% or less, Mn of 0.60 mass% or more, 0.90 mass% %, The rolling bearing unit for wheel support according to claim 1, which contains not less than 0.10 mass% and not more than 0.10 mass% and not more than 0.50 mass%. 各玉が、Ｓｉを０．３質量％以上、２．２質量％以下、Ｍｎを０．３質量％以上、２．０質量％以下含有し、Ｓｉの含有量とＭｎの含有量との比Ｓｉ／Ｍｎが５以下である鋼に、浸炭窒化焼き入れ及び焼き戻しを含む熱処理を施す事により造られたものである、請求項１〜２のうちの何れか１項に記載した車輪支持用転がり軸受ユニット。   Each ball contains 0.3% by mass or more and 2.2% by mass or less of Si, 0.3% by mass or more and 2.0% by mass or less of Mn, and the ratio between the Si content and the Mn content The wheel support according to any one of claims 1 to 2, wherein the steel having a Si / Mn of 5 or less is produced by subjecting a steel including carbonitriding and quenching and tempering to a heat treatment. Rolling bearing unit. 各玉の表面の残留オーステナイト量が０〜１５容量％で、表面硬度がＨｖ７８０以上である、請求項１〜３のうちの何れか１項に記載した車輪支持用転がり軸受ユニット。   The rolling bearing unit for wheel support according to any one of claims 1 to 3, wherein the amount of retained austenite on the surface of each ball is 0 to 15% by volume and the surface hardness is Hv780 or more. 各玉の表面に、平均粒径が０．０５〜１μｍのＳｉ−Ｍｎ系窒化物が、３７５μｍ2 中に１００個以上存在する、請求項１〜４のうちの何れか１項に記載した車輪支持用転がり軸受ユニット。 The wheel according to any one of claims 1 to 4, wherein 100 or more Si-Mn nitrides having an average particle diameter of 0.05 to 1 µm are present on the surface of each ball in 375 µm 2. Rolling bearing unit for support.
JP2008153921A 2008-06-12 2008-06-12 Wheel supporting rolling bearing unit Pending JP2009299759A (en)

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EP2412835A1 (en) * 2009-03-25 2012-02-01 NTN Corporation Bearing parts, rolling bearing, and process for production of bearing parts
WO2014122970A1 (en) * 2013-02-08 2014-08-14 Ntn株式会社 Bearing component and rolling bearing
CN110724812A (en) * 2019-10-10 2020-01-24 邯郸钢铁集团有限责任公司 Method for eliminating furnace roller indentation defect of continuous annealing furnace

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JP2004052997A (en) * 2002-05-30 2004-02-19 Nsk Ltd Rolling device and manufacturing method
JP2005282854A (en) * 2004-03-03 2005-10-13 Nsk Ltd Rolling bearing
JP2007269099A (en) * 2006-03-30 2007-10-18 Ntn Corp Bearing device for wheel
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Publication number Priority date Publication date Assignee Title
EP2412835A1 (en) * 2009-03-25 2012-02-01 NTN Corporation Bearing parts, rolling bearing, and process for production of bearing parts
EP2412835A4 (en) * 2009-03-25 2013-03-27 Ntn Toyo Bearing Co Ltd Bearing parts, rolling bearing, and process for production of bearing parts
US8714831B2 (en) 2009-03-25 2014-05-06 Ntn Corporation Bearing component, rolling bearing, and method for producing bearing component
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CN105074246A (en) * 2013-02-08 2015-11-18 Ntn株式会社 Bearing component and rolling bearing
CN110724812A (en) * 2019-10-10 2020-01-24 邯郸钢铁集团有限责任公司 Method for eliminating furnace roller indentation defect of continuous annealing furnace
CN110724812B (en) * 2019-10-10 2021-03-09 邯郸钢铁集团有限责任公司 Method for eliminating furnace roller indentation defect of continuous annealing furnace

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