JP2002021858A - Wheel axle bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set surface hardness of a hub wheel end part caulking part before caulking in an optimized range. SOLUTION: This wheel axle bearing device provided with an outer wheel 4 is provided with double row raceways 10, 11, and attached to a vehicle body, a hub heel 1 having one raceway 5 of double row raceways 5, 9 facing to raceways 10, 11 on the outer wheel directly formed and having a wheel attached, an inner ring 2 fitted on a small diameter step part 8 of the hub wheel 1 and having another raceway 9 formed on the outer periphery, and double raw rolling elements 3 put between the raceways on the outer wheel 4, the hub wheel 1 and the inner ring 2, and integrated by caulking the end part of the hub wheel. The inner ring 2 is carbon steel containing 0.95 to 1.10 wt.% C and is hardened to a core part, the hub wheel 1 is carbon steel containing 0.5 to 0.8 wt.% C and has surface hardened layer 26 formed in the area from one raceway 5 to the small diameter step part 8, and surface hardness of a caulking part 21 of the hub wheel 1 before caulking is regulated in a range HRC 12 to 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel bearing device, and more particularly, to a wheel bearing device that rotatably supports a driving wheel or a driven wheel on a vehicle body.

[0002]

2. Description of the Related Art There are two types of wheel bearing devices for automobiles, one for a driven wheel and the other for a driving wheel. 129703). FIG. 1 is for driven wheels, and FIG. 2 is for drive wheels.
The rolling elements 3 in multiple rows and the outer ring 4 as an outer member are main components.

The hub wheel 1 has a track surface 5 on the outboard side formed on the outer peripheral surface thereof, and a wheel (not shown).
Is provided. Hub bolts 7 for fixing the wheel disc are provided at equal intervals in the circumferential direction of the flange 6. The inner ring 2 is fitted into a small-diameter stepped portion 8 formed on the outer peripheral surface of the hub wheel 1, and an inboard-side raceway surface 9 is formed on the outer peripheral surface of the inner ring 2. The inner ring 2 is press-fitted with an appropriate interference to prevent creep. Track surface 5 located on the outboard side of the vehicle and track surface 9 located on the inboard side of the vehicle
And constitute a double row of raceway surfaces.

The outer race 4 has a plurality of rows of raceways 10, 11 on its inner peripheral surface facing the raceways 5, 9 of the hub wheel 1 and the inner race 2.
And a flange (not shown) for attaching to a vehicle body. The double row rolling elements 3 are incorporated between the double row raceway surfaces 5 and 9 of the inner ring 2 and the double row raceway surfaces 10 and 11 of the outer ring 4. By crimping the inboard end of the hub wheel 1 as shown in the figure, the hub wheel 1 is attached to the inner ring 2.
Is fixed. By caulking the end of the hub wheel 1, the axial clearance of the bearing 17 is made negative, that is, a preload is applied. That is, the inner ring 2 is press-fitted into a state in which the inner ring 2 is abutted against the hub wheel 1, and is fitted to the hub wheel 1. At that time, it is measured whether or not the axial clearance is a preset value. ), The caulking load and the caulking amount are determined in advance, and caulking is performed.

In the case of the drive wheel shown in FIG. 2, the stem portion 14 of the joint outer ring 13 of the constant velocity universal joint 12 is inserted into the through hole 22 of the hub wheel 1 to be serrated (or splined) and fitted to the end. The bearing 17 and the constant velocity universal joint 12 are unitized by tightening the nut 16 to the formed male screw portion 15.

A seal 1 is provided at both ends of the wheel bearing device.
8 and 19 are mounted to prevent leakage of grease filled therein and intrusion of water or foreign matter from the outside. In the case of the driven wheel shown in FIG. 1, a cap 20 is used instead of the seal 19 located on the inboard side of the vehicle.
Is installed.

[0007]

The outer peripheral surface of the hub wheel 1 includes a raceway surface 5 on which the rolling elements 3 roll and a fitting surface and an abutting surface with the inner ring 2. Therefore, it is necessary to form a surface hardened layer having an appropriate hardness. On the other hand, by caulking the end of the small-diameter step portion 8 of the hub wheel 1, the inner ring 2
In order to fix the crimping, the crimping portion 21 is required to have ductility. Therefore, the crimping portion 21 must be set to an optimum surface hardness in consideration of workability, strength (rigidity), and the like. If there is no ductility due to the optimal surface hardness, the caulked portion 21 cannot be sufficiently caulked by springback or the like, and there is a possibility that the preload of the bearing 17 may be lost. Management becomes complicated.

Therefore, a wheel bearing device having a structure in which the inner ring 2 is fixed by caulking the end of the small-diameter stepped portion 8 of the hub wheel 1, that is, the wheel bearing device disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 11-129703. The surface hardness of the caulking portion 21 located at the end of the hub wheel 1 before caulking is Hv200 to 300,
That is, the Rockwell hardness is set to HRC 11.0 to 29.8.

In general, the surface hardness varies depending on the work hardening in the forging process, the heat history under the cooling condition after forging, or the material. The conventional example (Japanese Patent Laid-Open No. 11-1297)
No. 03), the upper limit of the surface hardness before crimping of the crimping portion 21 is Hv300 (HRC29.
In the case of 8), the variation in the axial clearance reduction amount of the bearing 17 is large, and the preload amount of the bearing 17 varies, so that the occurrence rate of defective products increases. Also, the lower limit Hv200
(HRC 11.0), there is a possibility that the strength of the caulked portion 21 may be reduced by stress generated by a moment load or the like received from the wheel.

In view of the above, the present invention has been proposed in view of the above problems, and an object of the present invention is to provide a wheel bearing device in which the surface hardness of a caulked portion before caulking is set to an optimum range. Is to do.

[0011]

According to a first aspect of the present invention, there is provided an outer member having a double-row raceway surface and having a flange attached to a vehicle body. A hub ring having a double-row raceway surface facing the raceway surface of the outer member, directly forming one of the double-row raceway surfaces, and having a flange to which a wheel is mounted; An inner member formed of an inner ring having the other raceway surface formed on the outer periphery, and an inner member formed of an inner race formed on the outer periphery of the outer member and the outer member and the inner member being interposed between the respective raceway surfaces. A double-row rolling element, the end of the hub wheel is swaged to integrate them inseparably, and the wheel is rotatably supported on the vehicle body. Quenched and hardened to the core at 0.95 to 1.10 wt%, Serial hub wheel, C is 0.5~0.8w
A surface hardened layer is formed in a region extending from the one raceway surface to the small diameter step portion with carbon steel of t%, and the surface hardness of the caulked portion of the hub wheel before caulking is determined by a Rockwell hardness HRC1.
It is characterized in that it is defined in the range of 2 to 25.

According to the first aspect of the present invention, the inner race having the inboard side raceway formed on the outer periphery has a C of 0.95 to 0.95.
Since the core portion is quenched and hardened at 1.10 wt%, and the raceway surface on the inboard side is a place where service life is severe, SUJ2 (specified in JIS G 4805 as high carbon chromium steel for bearings) C: 0.95 to 1.10 wt%) is preferable, and the strength surface and the rolling fatigue life can be improved.

[0013] Also, the hub wheel, C is 0.5 to 0.8 wt.
% Of carbon steel, the SUJ2 (C:
0.95 to 1.10 wt%) because the amount of carbon is smaller than
Improves workability (end caulking) and forms a hardened layer in the area extending from one raceway surface of the hub wheel to the small-diameter step, increasing hardness and improving rolling fatigue life. This prevents fretting on the mating surface.

In the hardened surface layer of the hub wheel, the raceway surface portion is required to have a life resistance because the rolling element rolls, and the shoulder surface of the small-diameter step portion of the hub wheel is a portion in contact with the inner ring. ,
Since the outer peripheral surface of the small-diameter step portion is a portion fitted with the inner ring, creep resistance and fretting resistance are required.

By setting the surface hardness of the caulked portion of the hub wheel before caulking to Rockwell hardness HRC 12 to 25, the hardness of the caulked portion can be controlled to an optimum range, and Preload management becomes easy, and a decrease in strength can be suppressed. In other words, if the surface hardness of the caulked portion is greater than HRC25 (Hv266), the variation in the amount of axial clearance reduction after caulking becomes large, and the preload amount of the bearing varies, resulting in a high incidence of defective products. Become. Conversely, the surface hardness of the caulked portion is HRC12
If it is smaller than (Hv196), the strength of the caulked portion may be reduced by the stress generated by the moment load received from the wheel.

According to a second aspect of the present invention, there is provided a seal provided with a seal lip which is attached to an end portion of the outer member on the outboard side and slidably contacts an outer peripheral surface of the hub wheel. It is characterized by extending to the seal sliding contact portion. In this case, the portion on the outboard side from the raceway surface of the hub wheel becomes a seal sliding contact portion having a surface on which the seal lip of the seal slides, and therefore wear resistance is required. It is desirable that the surface hardened layer described in claim 1 or 2 be formed by induction hardening (claim 10).

According to a third aspect of the present invention, in the hub wheel, C is 0.70% by weight or more and less than 0.80% by weight, and Si is 0.1% by weight or less.
50 wt% or more and 1.0 wt% or less, Mn is 0.10 w
t% or more and 2.0 wt% or less, Cr 0.40 wt% or more and 0.95 wt% or less, Al 0.050 wt% or less, O 0.0030 wt% or less, and the balance Fe
And a steel material having unavoidable impurities. By using such a steel material, the rolling fatigue life of the hub wheel can be further improved.

According to a fourth aspect of the present invention, in the inner ring, C is 0.8 to 1.2 wt% and Si is 0.4 to 1.0 wt%.
wt%, Cr is 0.2-1.2 wt%, Mn is 0.8-
It is formed from an alloy steel containing 1.5 wt%, and after carbonitriding, it is quenched from 830 to 870 ° C. to form a 160 to 1
It is desirable to temper to a temperature range of 90 ° C. to reduce the amount of retained austenite in the surface layer to 25 to 50%.

The inner ring is made of carburized steel having a C content of 0.15 to 0.40 wt%, a C content of 0.8 wt% or more, and a Rockwell hardness HRC5.
A surface hardened layer of at least 8 and Rockwell hardness HRC4
8 or more and a core having an HRC of less than 58, and the surface hardened layer has a retained austenite amount of 25 to 35%, a retained austenite structure of 5 μm or less, and a residual carbide amount of 10% or less. desirable.

According to the fourth and fifth aspects of the present invention, since the raceway surface on the inboard side of the double-row raceway surface is a place where service life is severe, the inner race formed with the raceway surface on the inboard side is formed. Is subjected to a predetermined heat treatment as a steel material having the above-described composition, whereby the rolling fatigue life can be further improved.

According to a sixth aspect of the present invention, a double row rolling element is incorporated between an outer member having a flange attached to a vehicle body and an inner member having a flange to which wheels are attached, and the inner member is rotated. A freely supported bearing portion, a joint outer ring provided at one end of the drive shaft and having a track groove formed on the inner peripheral surface, and a joint inner ring formed on the outer peripheral surface with a track groove opposed to the track groove of the joint outer ring. And a constant velocity universal joint comprising a ball incorporated between the track groove of the joint outer race and the track groove of the joint inner race, wherein the rotation of the joint outer race of the constant velocity universal joint is performed within the bearing. In the wheel bearing device, the serration portion to be fitted to the inner member of the bearing portion is formed by hardening and hardening, and the joint outer ring has a caulked portion at an end. And that Characterized in that defining the crimping previous surface hardness of the fastening portion in the range of Rockwell hardness HRC12～25.

According to a sixth aspect of the present invention, there is provided a wheel bearing device for a drive wheel including a bearing portion and a constant velocity universal joint portion, wherein the outer ring of the joint is fitted to an inner member of the bearing portion. Since the serrations are formed by hardening and hardening, the rigidity of the serrations can be ensured. Here, since a spline section can be employed instead of the serration section, the serration section means the serration section or the spline section. Further, a crimped portion is provided at an end of the joint outer ring, and the surface hardness of the crimped portion before crimping is determined by a Rockwell hardness HR.
As defined in the range of C12 to C25, similarly to the first aspect of the invention, the hardness of the caulked portion can be controlled to an optimal range, and the preload management of the bearing becomes easy,
A decrease in strength can be suppressed.

According to a sixth aspect of the present invention, as in the seventh aspect of the present invention, the inner member comprises a hub wheel having a flange to which a wheel is mounted and a shoulder of a joint outer wheel. Of the double row raceway surfaces formed on the hub wheel, and the other raceway surface is formed directly on the outer diameter of the shoulder portion of the joint outer ring. It is possible to

The invention according to claim 8 is characterized in that the joint outer ring is made of carbon steel having a C content of 0.5 to 0.8 wt%, and a surface hardened layer is formed in a region extending from the other raceway surface to the serration portion. And Similar to the first aspect of the present invention, by forming the outer ring of the joint from carbon steel having C of 0.5 to 0.8 wt%,
Since the amount of carbon is smaller than that of SUJ2 (C: 0.95 to 1.10 wt%), the workability (end crimping) is improved, and further, from the other raceway surface of the joint outer ring to the serration portion. By forming the surface hardened layer in the region, the hardness can be increased and the rolling fatigue life can be improved. Of the hardened surface layer of the joint outer ring, the raceway surface is required to have long life because the rolling elements roll, and the serration is a part that fits with the inner member, so it is required to have wear resistance and rigidity. You.

According to a ninth aspect of the present invention, there is provided a seal which is mounted on the inboard end of the outer member and has a seal lip which is in sliding contact with the outer peripheral surface of the joint outer ring. It is characterized by extending to the seal sliding contact portion. In this case, the portion on the inboard side from the raceway surface of the joint outer ring becomes a seal sliding contact portion having a surface on which the seal lip of the seal slides, and therefore, wear resistance is required. The hardened surface layer described in claim 8 or 9 is desirably formed by induction hardening (claim 10).

According to an eleventh aspect of the present invention, the joint outer ring is
Is 0.70 wt% or more and less than 0.80 wt%, Si is 0.50 wt% or more and 1.0 wt% or less, and Mn is 0.1 wt% or less.
0 wt% or more and 2.0 wt% or less, Cr is 0.40 wt%
% To 0.95 wt% or less, Al is 0.050 wt%
Hereinafter, O contains 0.0030 wt% or less, and the balance is F
e and a steel material having unavoidable impurities. As in the third aspect of the invention, by using such a steel material, the rolling fatigue life of the outer race of the joint can be further improved.

According to a twelfth aspect of the present invention, in the motor vehicle wherein a brake rotor is mounted on a flange of the inner member,
When the brake rotor is rotated with reference to the outer member, the run-out width of the brake rotor is regulated to a standard value before the vehicle is assembled.

In general, in a wheel bearing device, when a run-out (axial run-out) occurs in a brake rotor attached to a flange of an inner member, it may cause vibration during braking from a high-speed running of an automobile. This causes uneven wear of the brake rotor and brake judder. In order to prevent uneven wear of the brake rotor and brake judder,
It is necessary to suppress the runout of the brake rotor. To suppress the runout of the brake rotor, not only the runout of the mounting surface of the brake rotor alone but also the flange runout, the axial runout of the bearing and the assembly error ( It is necessary to suppress misalignment and the like, and it is necessary to improve the accuracy of each component alone.

However, in addition to the runout of the mounting surface of the brake rotor alone, even if the flange runout, axial runout of the bearing, and assembly error (misalignment) are suppressed to improve the accuracy of each component alone, Because it is difficult to completely prevent uneven wear and brake judder, we focused on other factors that cause surface runout of the brake rotor other than improving the accuracy of each component alone.

As described above, by setting the surface hardness of the caulked portion before caulking to 12 to 25 HRC, the rigidity can be improved and no backlash occurs. As a result, the surface runout of the brake rotor is reduced. Can be suppressed. Since the run-out width of the brake rotor is regulated within the standard value before the assembly of the vehicle as in the invention of the twelfth aspect, troublesome run-out adjustment after the assembly of the brake rotor can be made unnecessary. Such a wheel bearing device with a brake rotor whose run-out width is regulated in advance is highly reliable, and the problem of surface run-out of the brake rotor is solved by directly using it at an automobile assembly plant. It is preferable that the standard value of the swing width of the brake rotor be 50 μm or less.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wheel bearing device according to the present invention will be described in detail below.

FIGS. 1 and 2 show an example of the structure of a wheel bearing device. 1 is for driven wheels, and FIG. 2 is for drive wheels. In each case, the main components are a hub wheel 1 and an inner ring 2, which are inner members, a double row rolling element 3, and an outer wheel 4 which is an outer member. As one of the elements, one raceway surface 5 of the double row raceway surfaces 5 and 9 is formed on the hub wheel 1, and the other raceway surface 9 is formed on the separate inner ring 2 fitted to the hub wheel 1. And a structure in which the inner ring 2 is fixed by caulking the end of the hub wheel 1.

The hub wheel 1 has a track surface 5 on the outboard side formed on the outer peripheral surface thereof and a wheel (not shown).
Is provided. Hub bolts 7 for fixing the wheel disc are provided at equal intervals in the circumferential direction of the flange 6. The inner ring 2 is fitted into a small-diameter stepped portion 8 formed on the outer peripheral surface of the hub wheel 1, and an inboard-side raceway surface 9 is formed on the outer peripheral surface of the inner ring 2. The inner ring 2 is press-fitted with an appropriate interference to prevent creep. Track surface 5 located on the outboard side of the vehicle and track surface 9 located on the inboard side of the vehicle
And constitute a double row of raceway surfaces.

The outer race 4 has multiple rows of raceways 10, 11 on its inner peripheral surface facing the raceways 5, 9 of the hub wheel 1 and the inner race 2.
And a flange (not shown) for attaching to a vehicle body. Double row rolling elements 3 are incorporated between double row raceway surfaces 5, 9 of hub wheel 1 and inner ring 2 and double row raceway surfaces 10, 11 of outer ring 4. Here, rolling element 3
As an example, a ball is used, but in the case of a wheel bearing device for an automobile having a large weight, a tapered roller can be used.

In the case of the drive wheel shown in FIG. 2, the stem portion 14 of the joint outer ring 13 of the constant velocity universal joint portion 12 is inserted into the through hole 22 of the hub wheel 1 which is an inner member, and fitted at the serration portion. The outer ring 4, the hub wheel 1, and the inner ring 2 are tightened by tightening a nut 16 to a male screw portion 15 formed at the end.
And the constant velocity universal joint 12 are unitized. The constant velocity universal joint portion 12 is provided at one end of a drive shaft (not shown), and has a joint outer ring 13 having a track groove formed on an inner peripheral surface thereof and a track groove facing the track groove of the joint outer ring 13 having an outer peripheral surface. It comprises a joint inner ring (not shown) formed on the surface, and a ball (not shown) incorporated between the track groove of the joint outer ring 13 and the track groove of the joint inner ring.

As another embodiment of the wheel bearing device for a drive wheel, there is one having a structure shown in FIG. The wheel bearing device of this embodiment does not have a separate inner ring 2 unlike the embodiment of FIG. 2 described above. That is, of the multiple rows of raceway surfaces 5 and 9, the raceway surface 9 on the inboard side is formed directly on the shoulder 25 of the joint outer race 13 of the constant velocity universal joint 12.

Seals 18 and 19 are provided at both ends of the bearing portion 17 to prevent leakage of grease filled therein and intrusion of water and foreign matter from the outside. In the case of the driven wheel shown in FIG. 1, a cap 20 is attached instead of the seal 19.

In the embodiment shown in FIGS. 1 and 2, the inner ring 2 is fixed to the hub wheel 1 by caulking the end of the small-diameter step portion 8 located on the inboard side of the hub wheel 1 as shown in the figure. ing. In the case of the embodiment shown in FIG. 3, the hub wheel 1 is fixed to the joint outer ring 13 by caulking the end of the stem portion 14 of the joint outer ring 13 as illustrated. This caulking not only causes the end of the hub wheel 1 or the joint outer ring 13 to be plastically deformed radially outward by pressing with a cylindrical punch or the like, but also forms irregularities on the end of the hub wheel 1 or the joint outer ring 13. Alternatively, the end may be expanded radially outward and plastically deformed.

In the wheel bearing device for a driven wheel shown in FIG.
Although the case where the end for caulking is formed by providing the recess 23 in the solid hub wheel 1 is illustrated, the hub wheel itself may be hollow. Conversely, in the driving wheel bearing device of FIG. 3, the case where the end of the hollow stem portion 14 is swaged is illustrated. However, by providing a recess in the solid stem portion, the swaging is performed. Can also be formed. As the number of hollow spaces increases, the weight can be reduced and the heat radiation effect can be obtained, which is advantageous in that the durability of the bearing is improved.

In the embodiment shown in FIGS. 1 and 2, the outer peripheral surface of the hub wheel 1 on which the seal lip of the seal 18 mounted on the outboard side end of the outer ring 4 slides, that is, from the seal sliding contact portion to the raceway surface 5. The surface hardened layer 26 is formed in a region extending to the small-diameter stepped portion 8 through the step. On the other hand, in the embodiment of FIG. 3, a seal 19 attached to the inboard end of the outer race 4 is provided.
The surface hardened layer 2 is formed on the outer peripheral surface of the shoulder portion 25 of the joint outer ring 13 with which the seal lip slides, that is, in the region extending from the seal sliding contact portion through the raceway surface 9 to the serration portion 27 of the stem portion 14.
6 is formed.

When the respective portions of the surface hardened layer 26 are indicated by a to d, the a portion is a seal lip portion where the seal lips of the seals 18 and 19 are slidably contacted, and therefore, wear resistance is required. b
Since the portion is the raceway surface 5 on which the rolling element 3 rolls, the life resistance is required. The portion c is a portion that comes into contact with the inner ring 2 and d
Since the portion is a portion that fits with the inner ring 2 or the hub wheel 1,
Creep resistance and fretting resistance are required. In addition, since the part e is the caulked part 21, ductility is required.

The heat treatment for forming the surface hardened layer 26 is preferably induction hardening. The high-frequency heat treatment as the surface hardening treatment makes it possible to freely select the hardened layer 26 by effectively utilizing the characteristics of the induction heating, to impart abrasion resistance and improve the fatigue strength. Induction heating is a method in which electric energy is directly converted into heat energy in a metal using electromagnetic induction to generate heat, and high-frequency heat treatment using this method has many features. In particular, since local heating can be performed, the depth of the hardened layer can be freely selected, and control can be performed so as not to significantly affect a portion other than the hardened layer, so that the performance of the base material can be maintained. Therefore, the desired hardened layer 26 can be formed in the regions of the ad portions, and the e portion can be left as an unquenched base material.

On the other hand, as described above, since the swaged portion 21 at the end of the hub wheel 1 or the joint outer ring 13 is required to have ductility, the swaged portion 21 is considered in consideration of workability and strength (rigidity). To the optimum surface hardness. If there is no ductility due to the optimum surface hardness, the caulked portion 21 cannot be sufficiently caulked by springback or the like, and the bearing portion 1
There is a risk that the preload may be lost at 7, and the man-hours and management for complicated crimping are complicated.

From such a viewpoint, the surface hardness of the caulked portion 21 before caulking is defined as Rockwell hardness HRC12 to 25,
That is, Hvs 204 to 266 are set. This allows
Preload management of the bearing portion 17 becomes easy, and a decrease in strength can be suppressed. In some cases, heat treatment such as annealing and tempering is performed to control the surface hardness of the caulked portion within a predetermined range.

The surface hardness of the caulked portion 21 is HRC25 (H
v266) (for example, in the case of HRC28), the variation in the amount of axial clearance reduction after crimping becomes large, and the preload amount of the bearing portion 17 varies, so that the occurrence rate of defective products increases. For example, FIG.
3 shows the relationship between the surface hardness of No. 1 and the amount of reduction in axial clearance. In particular, as shown in FIG.
When the surface hardness of the bearing 17 is HRC28 (conventional range), the variation of the axial clearance reduction amount becomes large,
The preload amount varies, and the yield is greatly reduced.

On the other hand, as shown in the figure, when the surface hardness of the caulked portion 21 before the caulking is in the range of HRC 12 to 25, it is apparent that the variation of the axial clearance reduction amount is small. Yes, the yield can be improved.
FIG. 5 shows the surface hardness of the caulked portion 21 before caulking is H.
In the wheel bearing device shown in FIGS. 1 and 2 with RC12 to RC25, the relationship between the pushing amount of the inner ring 2 and the axial clearance reduction amount is shown. Also in this case, the variation of the axial clearance reduction amount with respect to the pushing amount of the inner ring 2 is small.

Conversely, the surface hardness of the caulked portion 21 is HRC1
2 (Hv204), the caulked portion 2 is formed by the stress generated by the moment load received from the wheel.
1 may be reduced in strength. For example, FIG. 6 shows the relationship between the surface hardness of the crimped portion 21 and the breaking load.
It shows the strength. As is clear from this figure, when the surface hardness of the crimped portion 21 is less than HRC12, the breaking load is 250 kN or less, indicating that the strength of the crimped portion 21 is low.

In the embodiment shown in FIGS. 1 and 2, the inner race 2 having the raceway surface 9 on the inboard side formed on the outer periphery has a C of 0.95 to 1.10 wt% and is hardened to the core by hardening. Since the raceway surface 9 on the inboard side is a place where service life is severe, JIS G
SUJ2 (C: 0.95 to 1.1) specified in 4805
0 wt%), and the strength surface and the rolling fatigue life can be improved.

The hub wheel 1 in the embodiment of FIGS. 1 and 2 and the joint outer ring 13 in the embodiment of FIG.
Since C is formed from 0.5 to 0.8 wt% carbon steel, the workability (edge crimping) is reduced by the carbon amount smaller than SUJ2 (C: 0.95 to 1.10 wt%). ) Is improved. C is required to be 0.5 wt% or more in order to improve strength, wear resistance and rolling fatigue life, and 0.8
If the content is more than wt%, the workability, machinability and toughness are reduced, so that the upper limit is set.

In the case of the conventionally used S53C (medium carbon steel), if the hub wheel 1 and the joint outer ring 13 are allowed to cool after forging, their surface hardness is about Rockwell hardness HRC10 to 30. Where C is 0.5-
When 0.8 wt% carbon steel is used, the surface hardness after forging exceeds the Rockwell hardness HRC30. Therefore, the surface hardness is further increased by performing heat treatment such as annealing and tempering to increase the Rockwell hardness. It is necessary to use HRC12 to 25.

In the hub wheel 1 or the joint outer ring 13, the content of C is 0.70% by weight or more and less than 0.80% by weight, and the content of Si is 0.1% by weight or less.
50 wt% or more and 1.0 wt% or less, Mn is 0.10 w
t% or more and 2.0 wt% or less, Cr 0.40 wt% or more and 0.95 wt% or less, Al 0.050 wt% or less, O 0.0030 wt% or less, and the balance Fe
And a steel material having unavoidable impurities. By using such a steel material, the rolling fatigue life of the hub wheel 1 or the joint outer ring 13 can be further improved.

C is required to be at least 0.70 wt% in order to further improve the strength, wear resistance and rolling fatigue life, and if it exceeds 0.80 wt%, as described above, the workability and machinability are reduced. This is set as the upper limit from the viewpoint that the properties and toughness are reduced.

In addition to deoxidation, Si is necessary as an element for improving the rolling fatigue life. When the content is less than 0.50 wt%, this effect is small.
If added in excess of 0 wt%, machinability and workability will be significantly reduced, so this is made the upper limit.

Mn enhances the toughness by improving the hardenability of the steel, and effectively contributes to the improvement of the rolling fatigue life. However, if it is less than 0.10 wt%, the effect of this addition is poor, while if it exceeds 2.0 wt%, machinability, toughness and workability are significantly reduced. Therefore, Mn is set in the range of 0.10 to 2.0 wt%, and preferably in the range of 0.50 to 1.20 wt%.

Cr enhances the hardenability of the steel, improves the strength and toughness, and has a content of 0.40 watts.
Below t%, these effects are small, while 0.95 w
If it exceeds t%, it becomes impossible to omit diffusion annealing due to the relationship with other elements. The effect of Cr is 0.80
wt%, it is almost saturated, and above 0.80 wt%, other elements,
Particularly, depending on the relationship between the amount of C and the amount of Si, a giant carbide is easily generated at the time of melting. Therefore, Cr is 0.40
0.95 wt% range, preferably 0.40 to
The range is 0.80 wt%.

Al is added as a deoxidizing agent, and combines with O to form hard oxide-based inclusions, thereby reducing the rolling fatigue life. Therefore, it is desirable to be as low as possible, and the upper limit is 0.050 wt%. Further, O combines with Al to form hard oxide-based nonmetallic inclusions, so that the rolling fatigue life is reduced. Therefore,
It is desirable that the amount is as small as possible, and the upper limit is 0.0030 wt%.

Since the raceway surface 9 on the inboard side of the double row raceway surfaces 5 and 9 is a place where service life is severe, the separate inner ring 2 on which the raceway surface 9 on the inboard side is formed. Is subjected to a predetermined heat treatment as a steel material having the following composition, whereby the rolling fatigue life can be further improved.

First, a separate inner ring 2 on which the inboard-side raceway surface 9 is formed is set so that C is 0.8 to 1.2 wt%.
0.4 to 1.0 wt% of Si, 0.2 to 1.2 watts of Cr
t%, Mn is formed from an alloy steel containing 0.8 to 1.5 wt%, and after carbonitriding, quenched from 830 to 870 ° C and tempered to a temperature range of 160 to 190 ° C,
The retained austenite in the surface layer portion is set to 25 to 50%.

When the inner ring 2 has a C content of 0.8 to 1.2 wt%
The reason for the high carbon content is to harden the surface layer basically by quenching and tempering. 0.2-1.2 wt% Cr
When Cr is less than 0.2 wt%, carbides are not formed and the hardness of the surface layer is insufficient, and when it exceeds 1.2 wt%, carbides become coarse and become a starting point of peeling, and the life is likely to be short. Because.

Si stably increases the retained austenite in the surface layer to 25% or more, imparts temper softening resistance,
This is because 0.4 wt% or more is required to ensure heat resistance, but if it exceeds 1.0 wt%, enrichment of nitrogen and carbon from the surface to the surface layer portion in the course of carbonitriding is hindered.

Mn is used for quenching up to the core while ensuring quenchability. In this embodiment, Mn is an element for stabilizing retained austenite in the quenching process and the tempering process to increase residual austenite in the surface layer. A large amount of Mn
The addition of C causes deterioration in workability and causes sintering cracking and embrittlement.

When the inner race 2 is formed from an alloy steel having such a composition and carbonitriding is performed, the nitrogen content of the surface layer increases, and the Ms point of the surface layer decreases as compared with the core portion. The untransformed austenite is more in the surface layer than in the core. Since nitrogen is high in the surface layer and the quenching start temperature (austenitizing temperature) is increased to 830 to 870 ° C., the residual austenite in the surface layer can be easily increased to 25% or more. In order to stably increase the retained austenite, the quenching end temperature is increased to about 100 ° C, preferably 90 to 120 ° C. In this quenching process, the martensitic transformation of the nitrogen-enriched surface portion starts later than the inside, and the amount of the transformation is smaller than the inside, so that residual compressive stress is formed in the surface portion.

The quenching start temperature (austenitizing temperature)
Is 830 to 870 ° C., which is higher than that of ordinary quenched and tempered steel, so that the crack sensitivity value accompanying quenching becomes large. Therefore, it is desirable to set the cooling capacity in the range of 300 to 150 ° C. in the quenching process to 0.2 cm ⁻¹ or less and control the cooling rate in the martensitic transformation process.

In the carbonitriding process, carbonitriding is usually performed in a high-temperature gas obtained by adding ammonia to a carburizing or reducing gas. In this case, the carbonitriding is performed in a temperature range of 830 to 870 ° C. Immediately quenched in oil under the above conditions.

As the heat treatment method in this embodiment, the tempering temperature after quenching is set to a relatively low temperature of 160 to 190 ° C., the decomposition of residual austenite in the tempering process is suppressed, and the residual austenite in the surface layer is reduced to 25 to The range is 50%. The higher the retained austenite in this range, the better the rolling fatigue life under lubricating conditions with the inclusion of foreign matter, but on the other hand, the lower the surface hardness and the lower the wear resistance, so the residual austenite in the surface layer is A range of 25 to 30% is preferred. On the other hand, since the core is tempered at a low temperature of 190 ° C. or lower, usually about 15 to 20% of retained austenite remains.

Secondly, the raceway surface 9 on the inboard side is formed on a separate inner ring 2 made of carburized steel having a carbon content of 0.15 to 0.40% by weight. Amount 0.
8% by weight or more and a surface hardened layer having a Rockwell hardness of HRC58 or more and a core part having a Rockwell hardness of HRC48 or more and less than HRC58, and the surface hardened layer has a residual austenite amount of 25 to 35%. The size of the retained austenite structure is 5 μm or less, and the amount of residual carbide is 10% or less.

The steel material has a C content of 0.15 to 0.40 wt%.
Structural carbon steel or structural low alloy steel (JIS G
Clean steel such as SCr430 specified in 4104 or SCM430 specified in JIS G 4105) is used. After being formed into the inner ring 2, it is carburized to 0.80 wt% or more, and
A carburized layer for obtaining the surface hardened layer characteristics is formed by a quenching and tempering treatment described later.

After carburizing, quenching and tempering are performed to adjust the surface hardened layer to a residual austenite amount of 25 to 35%, a residual austenite structure size of 5 μm or less, and a carbonized material of 10% or less, and perform a super finish. A track surface 9 is formed.

The surface hardened layer is composed of a tempered martensite phase, a residual austenite phase and a residual carbide.
The amount of retained austenite is indicated by volume%. The reason for setting the amount of retained austenite to 25 to 35% is to impart toughness to a hardened surface hardened layer to prevent plastic deformation due to surface injection of solid foreign matter of lubricating oil. Buffers stress generation. If the amount of retained austenite is less than 25%, it is not sufficient to buffer the generation of stress due to plastic deformation. If the amount of retained austenite exceeds 35%, plastic deformation is large and surface roughness is undesirably deteriorated.

The size of the retained austenite structure is a size represented by the diameter of a circle having an area equivalent to the area of one austenite structure on the sample-polished etched surface under microscopic observation. The following is to secure the number of retained austenite phases contained in the foreign matter indentation in order to cope with the incorporation of minute foreign matter, to relieve the stress of foreign matter press-fitting, and to prevent cracks on the surface layer.

The residual carbide is mainly a quenched residue of a carbide not dissolved in the austenite phase at the time of quenching and heating. The reason why the amount of the residual carbide is set to 10% or less is to increase the amount of solute carbon in the tempered martensite phase, thereby increasing the strength of the matrix and the effect of compressive stress on the inside of the surface layer under the pressure of foreign matter. And tempering resistance is imparted to the matrix to prevent the hardened layer from softening due to a rise in temperature during use, thereby ensuring a rolling life under severe use conditions.

The structure of such a hardened surface layer is formed by heat treatment after carburization. To adjust the carburized layer to 0.8 wt% or more, the carbon potential in the carburizing atmosphere is set to 0.8 wt% or more and carburizing is performed for a predetermined time. In the carburizing step, after heating in a carburizing atmosphere (usually accompanied by a diffusion treatment), quenching in oil cooling (carburizing and quenching) is performed, followed by secondary quenching and tempering. The secondary quenching temperature is 82
Adjusted to the range of 0 to 870 ° C., 250 ° C. or less, especially 2
Tempering at a temperature below 00 ° C.

The stabilization of retained austenite in the martensitic transformation process at the time of secondary quenching contributes, in addition to the chemical composition of the raw material, to C and N in the carburized layer which can be provided in the heat treatment step. , Austenitizing temperature contributes. On the other hand, the carbide after the martensitic transformation is exclusively undissolved cementite at the austenitizing temperature, and therefore, the amount of carbide is Fe-F at the austenitizing temperature.
It is largely determined by the excess carbon amount from the carbon amount on the e ₃ C phase diagram Acm line. For other elements, N reduces carbides.

When the carburized layer is selected to have a C content of 0.8 to 1.0 wt%, the secondary quenching temperature is adjusted to a range of 820 to 870 ° C., and tempering is performed at a temperature of 200 ° C. or less, whereby the amount of retained austenite is reduced. And the size of the retained austenite structure is 5 μm or less. Since the secondary quenching temperature stabilizes austenite as the temperature increases, if the temperature exceeds 870 ° C., the amount of retained austenite increases and the retained austenite structure becomes coarse. On the other hand, when the temperature is 820 ° C. or less, the amount of retained austenite is reduced to 25% or less.

The surface hardened layer can also be realized by performing a carbonitriding treatment on the carburized layer. In this case, after carburizing and quenching, instead of the above-described secondary quenching, quenching is performed immediately after carbonitriding. Increasing the nitrogen in the carburized layer increases the amount of solute carbon, thereby reducing the amount of residual carbides. However, it stabilizes austenite.
The temperature is lowered to 00 to 840 ° C., and the size and amount of the structure of the retained austenite after quenching are adjusted to the above-mentioned predetermined range. Thus, the austenitizing temperature is set to 800 to 840.
Even when the temperature is lowered to 0 ° C., an increase in nitrogen in the carburized layer increases the amount of solute carbon in austenite and decreases the amount of residual carbide, so that the amount of residual carbide can be reduced to 10% or less. In addition, as a method of adjusting the amount of retained austenite, sub-zero treatment or high-temperature tempering may be performed.

In the wheel bearing device of each embodiment, the brake rotor 2 is attached to the flange 6 provided on the hub wheel 1.
4 and the brake rotor 2
When the wheel 4 is rotated, the run-out width of the brake rotor 24 is regulated to a standard value before the vehicle is assembled. As described above, the surface hardness of the caulked portion 21 before caulking is 12 to
By using 25HRC, the rigidity can be improved and no backlash occurs. As a result, the runout of the brake rotor 24 can be suppressed, and the troublesome runout adjustment after assembling the brake rotor is not required. it can. Such a wheel bearing device with a brake rotor whose run-out width is regulated in advance has high reliability, and the problem of surface run-out of the brake rotor 24 is solved by directly using it at an automobile assembly plant. The standard value of the run-out width of the brake rotor 24 is 50 μm or less, preferably 30 μm or less.

In order to prevent the occurrence of brake judder, it is necessary that the runout of the brake rotor 24 be, for example, 50 μm or less, preferably 30 μm or less in a state where the bearing device is assembled. For example, in order to restrict the runout of the brake rotor 24 to within a standard value in a state where the wheel bearing device with the brake rotor is assembled, the outer ring 4 of the bearing portion 17 is fixed to a measuring table (not shown), and the fixing is performed. The hub wheel 1 is rotated once with reference to the outer ring 4 and the swing width of the brake rotor 24 fixed to the flange 6 at that time is measured by applying a measuring instrument (not shown) such as a dial gauge to the brake rotor 24. It can be performed by measuring. Before assembling the wheel bearing device, that is, before assembling the hub wheel 1 and the bearing 17, the brake rotor 2 is attached to the flange 6 of the hub wheel 1.
4 may be fixed, and the runout of the brake rotor 24 may be regulated within a standard value with reference to the rotation axis of the hub wheel 1.

[0078]

According to the present invention, the surface hardness of the caulked portion before caulking is set to Rockwell hardness HRC12 to 25, so that the hardness of the caulked portion can be reduced from the viewpoint of preload control and strength of the bearing portion. It can be controlled to the optimal range.
That is, it is possible to suppress the variation in the reduction amount of the axial clearance after caulking, and it becomes easy to control the preload of the bearing portion. Further, the strength of the caulked portion can be improved by the stress generated by the moment load received from the wheel, and a high-quality wheel bearing device can be provided in terms of strength and life, and its practical value is large.

[Brief description of the drawings]

FIG. 1 is a partially omitted cross-sectional view showing a structural example of a wheel bearing device for a driven wheel for explaining a conventional example and an embodiment of the present invention.

FIG. 2 is a partially omitted cross-sectional view showing a structural example of a wheel bearing device for a drive wheel for describing a conventional example and an embodiment of the present invention.

FIG. 3 is a partially omitted sectional view showing a structural example of another embodiment of a wheel bearing device for a drive wheel.

FIG. 4 is a characteristic diagram showing a relationship between the surface hardness of a caulked portion and an axial clearance reduction amount.

FIG. 5 is a characteristic diagram showing the relationship between the amount of inner ring pushing and the amount of axial clearance reduction.

FIG. 6 is a characteristic diagram showing a relationship between the surface hardness of a crimped portion and a breaking load.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inner member (hub ring) 2 Inner member (inner ring) 3 Rolling element 4 Outer member (outer ring) 6 Flange 8 Small diameter step part 5, 9 Track surface 10, 11 Track surface 12 Constant velocity universal joint 13 Joint outer ring 17 Bearing part 18, 19 Seal 21 Caulking part 24 Brake rotor 25 Shoulder part 26 Surface hardened layer 27 Serration part

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C22C 38/38 C22C 38/38 F16B 4/00 F16B 4/00 Q F16C 19/18 F16C 19/18 33/62 33 / 62 F16D 3/20 F16D 3/20 Z (72) Inventor Katsuhiko Nishio 1578 Higashikaizuka, Iwata-shi, Shizuoka Prefecture Inside (72) Inventor Masaru Sera 1578 Higashikaizuka, Iwata-shi, Shizuoka Prefecture F-term inside Nthie Nu Co., Ltd. (Reference) 3J101 AA02 AA43 AA54 AA62 AA72 BA53 DA02 DA03 EA03 FA31 FA44 GA03 4K042 AA22 BA03 CA06 DA01 DA02 DA06 DC02

Claims (13)

[Claims] An outer member having a double-row raceway surface and having a flange attached to a vehicle body, and a double-row raceway surface facing the raceway surface of the outer member are formed, and the double-row raceway is formed. One of the surfaces is formed directly on the raceway surface, and is fitted to a hub wheel having a flange to which the wheel is mounted, and a small-diameter step formed on the outer peripheral surface of the hub wheel, and the other raceway surface is formed on the outer periphery. An inner member comprising an inner ring, and a plurality of rows of rolling elements interposed between respective raceway surfaces of the outer member and the inner member, and the ends of the hub wheel are swaged to separate them. A wheel bearing device that rotatably supports the wheel on a vehicle body, wherein the inner ring is quenched and hardened to a core at a C of 0.95 to 1.10 wt%, and the hub wheel has a C of 0 0.5-0.8
A surface hardened layer is formed in a region extending from the one raceway surface to the small-diameter step portion with carbon steel of wt%, and the surface hardness of the caulked portion of the hub wheel before caulking is determined by Rockwell hardness HRC.
A wheel bearing device defined in the range of 12 to 25. 2. A seal mounted on an outboard side end of the outer member and provided with a seal lip sliding on an outer peripheral surface of a hub wheel, wherein a surface hardened layer of the hub wheel extends to a seal sliding portion. The wheel bearing device according to claim 1, wherein the wheel bearing device extends. 3. The hub wheel has a C content of 0.70 wt% or more and less than 0.80 wt%, a Si content of 0.50 wt% or more and 1.0 wt% or less, and a Mn content of 0.10 wt% or more and 2.0 wt% or less.
0.95 wt% when Cr is 0.40 wt% or more.
% Or less, Al is 0.050 wt% or less, and O is 0.003% or less.
3. The wheel bearing device according to claim 1, wherein the wheel bearing device contains 0 wt% or less, and the balance is formed of a steel material having Fe and unavoidable impurities. 4. 4. The inner ring has C of 0.8 to 1.2 wt.
%, 0.4 to 1.0 wt% of Si, and 0.2 to 1% of Cr.
It is formed of alloy steel containing 2 wt% and Mn containing 0.8 to 1.5 wt%, and after carbonitriding, 830 to 870 ° C.
The wheel bearing device according to any one of claims 1 to 3, wherein the quenched steel is tempered to a temperature range of 160 to 190C to reduce the amount of retained austenite in the surface layer to 25 to 50%. 5. The inner ring has a C of 0.15 to 0.40 w.
a carburized steel of t%, C is 0.8 wt% or more, and has a surface hardened layer having a Rockwell hardness of HRC58 or more, and a core having a Rockwell hardness of HRC48 or more and less than HRC58. The layer has a retained austenite content of 25 to 35% and a retained austenite structure of 5 μm in size.
The wheel bearing device according to any one of claims 1 to 4, wherein m and the residual carbide amount are 10% or less. 6. A bearing having a double-row rolling element incorporated between an outer member having a flange attached to a vehicle body and an inner member having a flange to which wheels are attached, and rotatably supporting the inner member. A joint outer ring provided at one end of the drive shaft and having a track groove formed on an inner peripheral surface; a joint inner ring formed with an outer peripheral surface having a track groove facing the track groove of the joint outer ring; and the joint outer ring And a constant velocity universal joint composed of a ball incorporated between the track groove of the joint inner race and a track groove of the joint inner race. The rotation of the joint outer race of the constant velocity universal joint is transmitted to the inner member of the bearing. In the wheel bearing device according to (1), the outer ring of the joint is formed by quenching and hardening a serration portion fitted to an inner member of the bearing portion, and has a caulked portion at an end portion, and has a caulked portion. Crimping of parts Wheel bearing apparatus being characterized in that defined in the range of Rockwell hardness HRC12~25 the surface hardness of the. 7. The inner member comprises a hub wheel having a flange to which a wheel is mounted, and a shoulder of a joint outer wheel.
The raceway surface of the double row formed on the inner member is formed directly on the hub wheel and the other raceway surface is formed directly on the outer diameter of the shoulder of the joint outer race. Item 7. The wheel bearing device according to item 6. 8. The joint outer ring has a C of 0.5 to 0.8 w.
The wheel bearing device according to claim 7, wherein a surface hardened layer is formed in a region extending from the other raceway surface to the serration portion using t% of carbon steel. 9. A seal mounted on an inboard end of the outer member and provided with a seal lip that slides on an outer peripheral surface of the joint outer ring, wherein a surface hardened layer of the joint outer ring extends to a seal sliding contact portion. 9. The wheel bearing device according to claim 8, wherein the wheel bearing device extends. 10. The wheel bearing device according to claim 1, wherein the surface hardened layer is formed by induction hardening. 11. The joint outer ring has a C content of 0.70 wt%.
Above is less than 0.80 wt%, Si is more than 0.50 wt% and less than 1.0 wt%, and Mn is more than 0.10 wt%.
0.95w at 0wt% or less and Cr at 0.40wt% or more
t% or less, Al is 0.050 wt% or less, O is 0.00
The wheel bearing device according to any one of claims 6 to 10, wherein the wheel bearing device contains 30 wt% or less, and the balance is made of a steel material having Fe and unavoidable impurities. 12. When the brake rotor is mounted on the flange of the inner member, when the brake rotor is rotated with reference to the outer member, the swing width of the brake rotor is set to a value before assembly of the vehicle. The wheel bearing device according to any one of claims 1 to 11, wherein the wheel bearing device is regulated within a standard value. 13. The wheel bearing device according to claim 12, wherein the standard value is set to 50 μm or less.