JP2006200700A - Rolling bearing device for supporting wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing device for supporting a wheel having excellent productivity and long service life and being light in weight. <P>SOLUTION: A hub wheel 2, an inner wheel 3, and an outer wheel 4 of the rolling bearing device 1 for supporting the wheel are formed by applying press machining or plastic working on alloy steel having content of carbon of 0.45 mass% or more and 0.6 mass% or less, content of silicon of 0.5 mass% or more and 0.8 mass% or less, content of manganese of 0.6 mass% or more and 1 mass% or less, and content of vanadium of 0.03 mass% or more and 1 mass% or less. This alloy steel satisfies the expression showing the relation of Vickers hardness Hv and limit compressibility X(%), X≥0.05×Hv+50. Hardened layers 22 formed by high frequency quenching are formed on the hub wheel 2 and the outer wheel 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wheel bearing rolling bearing device that rotatably supports a wheel of an automobile or the like with respect to a suspension device.

  A wheel-supporting rolling bearing device that supports a wheel of an automobile or the like so as to be rotatable with respect to a suspension device includes an inner member having a raceway surface on an outer peripheral surface, an outer member having a raceway surface on an inner peripheral surface, And a plurality of rolling elements arranged between the raceway surfaces so as to be freely rollable. Further, a flange for attaching a wheel is provided on the outer peripheral surface of the inner member, and a flange for attaching a suspension device is provided on the outer peripheral surface of the outer member. Such wheel-supporting rolling bearing devices are being unitized, and the aforementioned flange has a structure integrated with an inner member and an outer member.

In recent years, in order to improve the fuel efficiency and driving performance of automobiles, there has been an increasing demand for weight reduction of rolling bearing devices for supporting wheels. For example, further thinning of flanges for mounting wheels and suspension devices is also considered. However, when the flange is simply thinned, the stress applied to the flange increases, and there is a concern that the strength of the flange will be insufficient.
In particular, a bending stress is applied to the base portion of the flange provided on the member to which the wheel is attached while rotating. In addition, since a torsional stress is applied to the flange as the wheel rotates, fatigue failure may occur if sufficient strength against the flange cannot be secured.

  In addition, the flange is formed with a through hole through which a stud or bolt for attaching the wheel and the disk rotor is inserted. However, since the strength of the flange is reduced when the thickness is reduced, the stud and the stud are required to attach the wheel to the flange. When fastening a nut or fastening a bolt inserted through a through hole, there is also a concern that the peripheral portion of the through hole into which the base end portion of the stud of the flange is fitted is likely to be deformed.

  When the peripheral portion of the through hole is deformed, the perpendicularity of the disc rotor attached to the flange with respect to the rotation axis of the hub deteriorates. That is, both side surfaces of the disk rotor, which is the surface to be braked, should be perpendicular to the rotation axis of the hub. As a result, both side surfaces of the disk rotor are displaced in the axial direction with rotation, and vibration occurs. Even if the amplitude of vibration caused by such a cause is about several tens of μm, vibration called judder may occur during braking, resulting in a decrease in riding comfort. Therefore, when the flange is thinned to reduce the weight, sufficient fatigue strength, yield strength, etc. are indispensable in the non-quenched portion.

However, in the case of a member having a flange as described above, it is necessary to accurately process a through hole for inserting a stud or bolt for attaching a wheel or a suspension device. When the is increased, the workability is remarkably lowered and the productivity is greatly deteriorated.
From the above viewpoint, in the rolling bearing device for supporting a wheel, not only the raceway surface of the inner member and the raceway surface of the outer member that are subject to rolling fatigue, but also other non-quenched portions are sufficient after molding. High strength and workability are required.

  Generally, the strength of steel has a good correlation with hardness. For example, if the hardness after molding is improved using high carbon steel containing 0.7% by mass or more of carbon, the strength can be improved. Is possible. However, on the other hand, the workability is remarkably lowered, and the cost is inevitably increased. Also, in this case, in the caulking type wheel support rolling bearing device, the plastic workability of the caulking portion is lowered, and the caulking process itself becomes difficult.

  As a material constituting the wheel-supporting rolling bearing device, structural carbon steel such as Japanese Industrial Standards S53C and SAE1055 is often used. Since the raceway surface of the inner member and the raceway surface of the outer member are repeatedly loaded with high surface pressure from the rolling elements, hardening by induction quenching is provided so as to have sufficient rolling fatigue life and wear resistance. A layer is formed. On the other hand, the part other than the raceway surface of the outer member and the part other than the raceway surface of the inner member were subjected to annealing and cold forming without performing hardening treatment such as quenching from the viewpoint of workability and the like. (In this specification, a portion in such a state is referred to as a “non-quenched portion”).

Patent Document 1 contains 0.5 to 0.7% by mass of carbon, 0.6 to 1.2% by mass of silicon, 0.6 to 1.0% by mass of manganese as alloy elements, and L calculated by the formula 11271C% + 5796Si% + 2665Mn% -6955 is 5000 or more, and H calculated by the formula 48.0C% + 5.7Si% + 11.5Mn% -16.2 is 23-25. A rolling part having excellent workability, fatigue strength, and rolling fatigue life is disclosed. However, only the hardness of the non-quenched part and the surface hardness of the hardened layer are mentioned.
JP 2002-363700 A

  Thus, the thing of patent document 1 does not fully satisfy both the intensity | strength and workability of a non-hardening part. In addition, since the rolling bearing device for supporting a wheel is subjected to rolling fatigue on the raceway surface of the inner member and the raceway surface of the outer member as in the case of a general rolling bearing, a sufficient rolling fatigue life is obtained in the hardened layer of the raceway surface. However, the thing of patent document 1 hardly considers about the rolling fatigue life of the hardened layer of a raceway surface.

Furthermore, in the case of a rolling bearing device for wheel support, the hardness, structure, and strength vary depending on the state of the material at the time of molding, so in order to improve the quality of the product, the molded wheel support It is also necessary to consider the hardness and microstructure of the rolling bearing device used.
Accordingly, an object of the present invention is to solve the above-described problems of the prior art and to provide a wheel support rolling bearing device that is lightweight and has a long life in addition to being excellent in productivity.

  In order to solve the above problems, the present invention has the following configuration. That is, the wheel support rolling bearing device according to claim 1 of the present invention includes an inner member having a raceway surface on an outer peripheral surface, and a raceway surface facing the raceway surface of the inner member. An outer member disposed outward, a plurality of rolling elements disposed so as to be freely rollable between the both raceway surfaces, and a wheel or a suspension device provided on at least one of the inner member and the outer member. A wheel support rolling bearing device in which one of the inner member and the outer member is a rotating wheel and the other is a fixed wheel, and at least one of the inner member and the outer member. One of the characteristics satisfies the following four conditions.

Condition 1: The carbon content is 0.45 mass% or more and 0.6 mass% or less, the silicon content is 0.5 mass% or more and 0.8 mass% or less, and the manganese content is 0.6 mass% or more. It is made of an alloy steel having a content of 1% by mass or less and a vanadium content of 0.03% by mass to 1% by mass.
Condition 2: Vickers hardness Hv and critical compression ratio X (%) of the alloy steel satisfy the expression X ≧ 0.05 × Hv + 50.
Condition 3: It is formed by press working or plastic working.
Condition 4: A hardened layer by induction hardening is formed on the raceway surface.

  With such a configuration, the inner member and the outer member have excellent static strength and fatigue strength, so that an excessive moment load and impact load are applied to the inner member and the outer member. Even when used under conditions, deformation hardly occurs. Therefore, it is not necessary to improve the strength by increasing the thickness or increasing the number of manufacturing steps. Moreover, since the workability of the alloy steel is excellent, the inner member and the outer member having the flange can be easily processed. Therefore, the wheel support rolling bearing device is easy to manufacture.

Below, the rolling bearing apparatus for wheel support of this invention is demonstrated in detail.
[Carbon content]
Carbon (C) is an element that is essential for ensuring the hardness of the non-quenched portion and the hardness of the hardened layer after quenching and tempering. Although 0.45 mass% or more is required from a viewpoint of rolling fatigue life, when too much, the hardness of a non-hardened part will become high too much and there exists a possibility that plastic workability may fall. Therefore, the C content in the alloy steel needs to be 0.45 mass% or more and 0.6 mass% or less.

[About silicon content]
Silicon (Si) acts as a deoxidizer during steelmaking and has the effect of improving the hardness and hardenability of the non-quenched part. In particular, after quenching and tempering, not only strengthens the martensite structure and improves the rolling fatigue life, but also in the non-quenched part, it dissolves in ferrite and improves the strength of the ferrite structure, yield strength and fatigue. Has the effect of increasing strength.
However, if there is too much Si, the hardness of the non-quenched part becomes too high, and the plastic workability at the time of molding and after molding may be reduced. Therefore, the Si content in the alloy steel needs to be 0.5 mass% or more and 0.8 mass% or less.

[About manganese content]
Manganese (Mn) acts as a deoxidizer like Si, and has the effect of improving the hardness and hardenability of the non-quenched part, so it is necessary to add 0.6 mass% or more. However, when there is too much Mn, the hardness of the non-quenched portion becomes too high, and the cold workability at the time of molding and after molding may be reduced. Therefore, the Mn content in the alloy steel needs to be 1% by mass or less.

[Vanadium content]
Vanadium (V) has a function of forming a stable carbide or carbonitride in alloy steel and effectively suppressing the growth of old austenite crystal grains during annealing and induction hardening. Yes. Further, by refining the prior austenite crystal grains, the ferrite is divided, and the balance between strength and workability is remarkably improved.
For this reason, V may be added as necessary, but in order to obtain the effect sufficiently, it is necessary to add 0.03% by mass or more. However, when V is too much, the hardness of the non-quenched portion becomes too high, and the cold workability at the time of molding and after molding may be deteriorated. Therefore, the V content in the alloy steel needs to be 1% by mass or less, and more preferably 0.5% by mass or less.

[Condition 2]
Plastic workability is expressed by deformation resistance and critical compressibility, and the deformation resistance and critical compressibility are affected by the alloy composition and structure of the material. In order to obtain good plastic workability, it is preferable to use a material having a low deformation resistance and a high critical compressibility. In general, deformation resistance depends on hardness, and a material having a high deformation resistance has a high hardness, and a material having a low deformation resistance has a low hardness. On the other hand, when the deformation resistance is too low, the hardness is generally lowered and the bearing device cannot be used.

Therefore, in the present invention, the upper limit of the hardness is set to Hv300, and attention is paid to the ratio between the hardness and the limit compressibility rather than the hardness itself. That is, the inner member and the outer member were made of alloy steel satisfying the formula where Vickers hardness Hv and critical compression ratio X (%) satisfy X ≧ 0.05 × Hv + 50. An alloy steel that satisfies the above formula has good plastic workability.
In addition, it is preferable that Vickers hardness Hv is 180 or more and 300 or less in a portion other than the raceway surface of the outer member and a portion other than the raceway surface of the inner member (non-quenched portion).

  In addition, since the critical compressibility and hardness are affected by the structure, the ferrite content in the alloy steel is 10% or more and 25% or less in area ratio, and is measured by the method defined in Japanese Industrial Standard JIS G0551. The austenite grain size is preferably 6 or more in terms of grain size number. More specifically, if the ferrite content in the non-quenched portion is large, there is a possibility that a problem may occur in terms of strength. Therefore, the area ratio is preferably 25% or less. In addition, in order for both the prior austenite crystal grains and the pro-eutectoid ferrite in the non-quenched part to be refined and the structure to be densified, the prior austenite crystal grain size in the non-quenched part is 6 or more in grain size number Is preferably 10% or more in terms of area ratio.

  In the hardened layer formed in the part including the raceway surface, sufficient surface hardness and hardened layer depth are required from the viewpoint of rolling fatigue life, but the quality of the hardened layer is the same as the quality of the non-quenched part. Similarly, the surface hardness of the hardened layer is preferably 650 to 780 in terms of Vickers hardness Hv in order to ensure a sufficient rolling fatigue life, although it depends on the induction hardening conditions and the like, and effective hardening of the hardened layer. The layer depth is preferably 1.5 mm or more.

  However, if an effective hardened layer depth greater than necessary is obtained, the workability is sacrificed due to the high hardenability of the alloy steel, and depending on the heating conditions, the crystal grains of the hardened layer become coarse. Therefore, the effective hardened layer depth is preferably 4 mm or less because the rolling fatigue life may be insufficient. In addition, if the old austenite crystal grains of the hardened layer are coarse, the rolling fatigue life may be insufficient. The particle size number is desirably 8 or more.

  The rolling bearing device for supporting a wheel of the present invention has excellent static strength and fatigue strength, and is not easily deformed even when a large load is applied. Moreover, since it is excellent in workability, in addition to being easy to manufacture, it is lightweight and has a long life.

  DESCRIPTION OF EMBODIMENTS Embodiments of a wheel bearing rolling bearing device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of an embodiment of a wheel bearing rolling bearing device according to the present invention. In the present embodiment, in a state where the wheel bearing rolling bearing device is attached to a vehicle such as an automobile, the portion facing the width direction outer side of the vehicle is referred to as an outer end side portion, and the portion facing the width direction center side Is referred to as an inner end portion. That is, in FIG. 1, the left side is the outer end side, and the right side is the inner end side.

  The wheel support rolling bearing device 1 of FIG. 1 includes a hub wheel 2, an inner ring 3, an outer ring 4, two rows of rolling elements 5, 5, and cages 6, 6 that hold the rolling elements 5. ing. Further, between the inner peripheral surface of the inner end side portion of the outer ring 4 and the outer peripheral surface of the inner end side portion of the inner ring 3, and the outer periphery of the inner peripheral surface of the outer end side portion of the outer ring 4 and the intermediate portion of the hub ring 2. Sealing devices 7a and 7b are provided between the surfaces.

Further, a wheel mounting flange 10 for supporting a wheel (not shown) is provided on the outer end side portion of the outer peripheral surface of the hub wheel 2. A suspension device mounting flange 13 is provided on the outer peripheral surface of the outer ring 4 at the end portion on the side away from the wheel mounting flange 10.
A cylindrical portion 11 having a small outer diameter is formed at the inner end side portion of the hub wheel 2. The inner ring 3 is press-fitted into the cylindrical portion 11, and the inner ring 3 and the hub wheel 2 are integrally fixed. In addition, what fixed the inner ring | wheel 3 and the hub ring | wheel 2 integrally is corresponded to the inner member which is the structural requirements of this invention, and the outer ring | wheel 4 is equivalent to the outer member which is the structural requirements of this invention.

  In the wheel support rolling bearing device 1, the hub wheel 2, the inner ring 3, and the outer ring 4 have a carbon content of 0.45 mass% to 0.6 mass% and a silicon content of 0.5 mass. % To 0.8% by mass, manganese content from 0.6% to 1% by mass, vanadium content from 0.03% to 1% by mass, the balance being iron and inevitable impurities It is composed of alloy steel, which is an element. Moreover, this alloy steel satisfies the formula where Vickers hardness Hv and critical compression ratio X (%) are X ≧ 0.05 × Hv + 50. The hub wheel 2, the inner ring 3, and the outer ring 4 are formed by subjecting the above alloy steel to press working or plastic working.

  A raceway surface is formed on each of the axially intermediate portion of the outer peripheral surface of the hub wheel 2 and the outer peripheral surface of the inner ring 3. The raceway surface of the hub wheel 2 is the first inner raceway surface 20a, and the raceway surface of the inner ring 3 is the first. Two inner raceway surfaces 20b are provided. Further, a raceway surface facing both the inner raceway surfaces 20a and 20b is formed on the inner peripheral surface of the outer ring 4, and the raceway surface facing the first inner raceway surface 20a is the first outer raceway surface 21a and the second raceway surface. The track surface facing the second inner track surface 20b is a second outer track surface 21b. Further, a plurality of rolling elements 5 are freely rollable between the first inner raceway surface 20a and the first outer raceway surface 21a and between the second inner raceway surface 20b and the second outer raceway surface 21b. Is arranged. In the illustrated example, balls are used as the rolling elements, but rollers may be used depending on the application of the wheel bearing rolling bearing device 1 or the like.

  Further, high surface pressure is repeatedly applied from the rolling elements 5 to the first inner raceway surface 20a of the hub wheel 2, the second inner raceway surface 20b of the inner ring 3, and the first and second inner raceway surfaces 21a and 21b of the outer ring 4. The first inner raceway surface from the vicinity of the stepped portion 12 formed at the outer end of the cylindrical portion 11 in the outer peripheral surface of the hub wheel 2 so as to have sufficient rolling fatigue life and wear resistance. A hardened layer 22 is formed by induction hardening in a portion up to the vicinity of 20a and a portion of the inner peripheral surface of the outer ring 4 from the vicinity of the first outer raceway surface 21a to the vicinity of the second outer raceway surface 21b. Yes. The Vickers hardness Hv of this hardened layer 22 is 650 or more and 780 or less, and the prior austenite grain size measured by the method defined in Japanese Industrial Standard JIS G0551 is 6 or more in terms of grain size number.

  The portions of the hub wheel 2 and the outer ring 4 where the hardened layer 22 is not formed are not quenched, and the Vickers hardness Hv of the non-quenched portion is 180 or more and 300 or less. Further, the ferrite content is 10% or more and 25% or less in terms of area ratio, and the prior austenite grain size measured by the method defined in Japanese Industrial Standard JIS G0551 is 6 or more in grain size number. The inner ring 3 is subjected to carburizing or carbonitriding, quenching and tempering, and a hardened layer (not shown) is formed on the second inner raceway surface 20b by carburizing or carbonitriding.

  In order to assemble such a wheel support rolling bearing device 1 to an automobile, the suspension device mounting flange 13 is fixed to the suspension device, and the wheel is fixed to the wheel mounting flange 10. As a result, the wheel is supported rotatably by the wheel support rolling bearing device 1 with respect to the suspension device. That is, the inner ring 3 and the hub ring 2 that are integrally fixed are rotating wheels, and the outer ring 4 is a fixed ring.

  In such a wheel-supporting rolling bearing device 1, since the hub wheel 2 and the outer ring 4 have excellent static strength and fatigue strength, an excessive load (moment load or impact load) is applied to the flanges 10 and 13. Even if a load is applied, deformation hardly occurs. Therefore, it is not necessary to improve the strength by increasing the thickness or increasing the number of manufacturing steps. Moreover, since the workability of the alloy steel is excellent, the hub wheel 2 and the outer ring 4 having the flanges 10 and 13 can be easily processed. Therefore, the wheel support rolling bearing device 1 is easy to manufacture.

  Below, an example of the manufacturing method of the above-mentioned hub wheel 2 is demonstrated, referring FIG. First, the above-described rolled steel sheet made of alloy steel is heated to the A1 transformation point or higher, and then cooled to a temperature below the A1 transformation point and annealed. Next, the disk-shaped material obtained by punching the rolled steel sheet (see (a) of FIG. 2) is deep-drawn and formed into a bowl shape (see (b) of FIG. 2). A through hole was formed in the bottom (see (c) of FIG. 2). And after shape | molding in the shape of the hub wheel 2 (refer FIG.2 (d)), the bolt hole was provided in the flange by piercing (refer (e) of FIG. 2). Since the alloy steel described above has good plastic workability, it is easy to form such a high workability. Further, by forming by cold forging, it can be formed with much higher precision than conventional forming by hot forging, so that cutting can be omitted. Thus, the strength of the non-quenched portion is improved and the manufacturing cost is reduced.

The outer peripheral surface including the raceway surface of the obtained hub wheel 2 was subjected to induction hardening and tempering to form a hardened layer 22, and then grinding and superfinishing or superfinishing alone were performed to complete the hub wheel 2.
When the inner ring 3 and the outer ring 4 are manufactured in the same manner as the hub ring 2 and are assembled, the wheel bearing rolling bearing device 1 can be obtained.
〔Example〕
Hereinafter, the present invention will be described more specifically with reference to examples. The cold workability of the alloy steels having the compositions shown in Tables 1 and 2 was evaluated based on the critical compression ratio. Further, the physical properties of the non-quenched part were evaluated by the prior austenite grain size, ferrite content, hardness, yield strength, and fatigue strength. The evaluation method will be described below.

A material cut out from a bar made of alloy steel was cut and annealed under the following conditions to prepare a cylindrical test piece having a diameter of 60 mm and a height of 90 mm.
Annealing conditions: The temperature was raised from room temperature to a temperature higher than the A1 transformation point (760 to 820 ° C.) over 2 to 4 hours, held at that temperature for 1 to 4 hours, and then the temperature below the A1 transformation point (680 to 720). C.) over 1 to 4 hours and held at that temperature for 2 to 10 hours. Then, the furnace was cooled to 660 to 700 ° C. for 2 to 6 hours and further to 480 to 520 ° C. for 5 to 15 hours, and then cooled to room temperature.

  The critical compressibility was calculated from the pressure during cold forging and the crack initiation limit strain in the upsetting test which is one of the guidelines for evaluation of crack initiation limit. That is, the above-mentioned test piece was upset, and the height Hf of the test piece in which the occurrence of cracks was confirmed by visual observation was measured. Then, the critical compression ratio was calculated from Hf and the initial height H0 (90 mm) of the test piece according to the formula {(H0−Hf) / H0} × 100.

  Further, the hardness of the non-quenched part is obtained by cutting out the smooth part of the flange of the hub wheel (made of alloy steel shown in Tables 1 and 2) of the wheel bearing rolling bearing device 1 as shown in FIG. After embedding, the cut surface was finished and polished with emery paper, and then measured using a Vickers hardness tester. Further, after etching the same surface as the surface where the hardness was measured with a picral corrosion solution, the content (area ratio) of pro-eutectoid ferrite and the prior austenite grain size were measured by performing microstructure observation and image processing.

Furthermore, the yield strength of the non-quenched part was measured using a JIS 14A test piece (diameter 8.5 mm) cut out from the flange of the hub wheel. Further, the fatigue strength of the non-quenched part was measured using an Ono type rotating bending fatigue tester. The test conditions are a rotation speed of 3700 min ⁻¹ and a rotation speed of 10 ⁷ cycles. The test piece used was a No. 1-8 test piece specified in JIS Z2271, which was cut out from the flange of the hub wheel.

  Each evaluation result is shown in Tables 3 and 4. As can be seen from Tables 3 and 4, since the prior austenite grains and proeutectoid ferrite are refined by suitable alloy components, each of the examples has cold workability (critical compressibility) and strength (yield strength, fatigue). The balance with (strength) was excellent. The relationship between hardness and critical compressibility is shown in the graph of FIG. 3, and the relationship between hardness and fatigue strength is shown in the graph of FIG. As can be seen from the graphs, when the hardness is the same, both the cold workability and the fatigue strength were superior to the comparative example.

Further, as can be seen from Tables 3 and 4, when the hardness was the same, the example was superior in yield strength to the comparative example, and the ferrite content was a suitable amount. And since the yield strength of 500 MPa and 10 ⁷ cycle fatigue strength of 400 MPa can be sufficiently achieved without significantly reducing the cold workability (limit compressibility), the cold workability of the wheel bearing rolling bearing device and It is advantageous for weight reduction.

Next, a rotation test was conducted on the wheel-supporting rolling bearing device, and its life was evaluated. At that time, fix the suspension mounting flange provided on the outer peripheral surface of the outer ring, apply a load to the wheel mounting flange provided on the outer peripheral surface of the hub wheel, and perform a rotation test under the following conditions. It was. Then, the occurrence of flaking was detected by measuring the vibration of the hub ring and the outer ring, and the life was evaluated by the total number of revolutions until flaking occurred on the raceway surface of the inner ring or the raceway surface of the outer ring. The results are shown in Tables 5 and 6. Further, the relationship between the surface hardness Hv and the life of the hardened layer is shown in the graph of FIG. 5, and the relationship between the prior austenite crystal grain size and the life of the hardened layer is shown in the graph of FIG. The life values shown in Tables 5 and 6 and FIGS. 5 and 6 are relative values when the life of Comparative Example 23 is 1.
Radial load: 7000N
Axial load: 5000N
Rotational speed: 300 min ^-1

  As can be seen from Tables 5 and 6 and FIGS. 5 and 6, the wheel support rolling bearing device of the example had a longer life than the wheel support rolling bearing device of the comparative example.

It is sectional drawing which shows the structure of one Embodiment of the rolling bearing apparatus for wheel support which concerns on this invention. It is a figure explaining the manufacturing method of a hub ring. It is a graph which shows the relationship between the hardness of a non-hardened part, and a limit compression rate. It is a graph which shows the relationship between the hardness of a non-hardened part, and fatigue strength. It is a graph which shows the relationship between the surface hardness Hv of a hardened layer, and the lifetime of the rolling bearing apparatus for wheel support. It is a graph which shows the relationship between the old austenite grain size of a hardened layer, and the lifetime of the rolling bearing apparatus for wheel support.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rolling bearing apparatus for wheel support 2 Hub wheel 3 Inner ring 4 Outer ring 5 Rolling element 10 Wheel mounting flange 13 Suspension apparatus mounting flange 20a First inner raceway surface 20b Second inner raceway surface 21a First outer raceway surface 21b Second outer race Raceway 22 Hardened layer

Claims (1)

An inner member having a raceway surface on the outer peripheral surface, an outer member having a raceway surface opposite to the raceway surface of the inner member, and disposed on the outer side of the inner member, and a roll between the raceway surfaces. A plurality of rolling elements arranged movably and a flange provided on at least one of the inner member and the outer member to which a wheel or a suspension device is attached; and the inner member and the outer member In a wheel support rolling bearing device in which one of them is a rotating wheel and the other is a fixed wheel, at least one of the inner member and the outer member satisfies the following four conditions: Rolling bearing device.
Condition 1: The carbon content is 0.45 mass% or more and 0.6 mass% or less, the silicon content is 0.5 mass% or more and 0.8 mass% or less, and the manganese content is 0.6 mass% or more. It is made of an alloy steel having a content of 1% by mass or less and a vanadium content of 0.03% by mass to 1% by mass. Condition 2: Vickers hardness Hv and critical compression ratio X (%) of the alloy steel satisfy the expression X ≧ 0.05 × Hv + 50.
Condition 3: It is formed by press working or plastic working.
Condition 4: A hardened layer by induction hardening is formed on the raceway surface.

Images