JP2010089530A - Wheel bearing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provided a wheel bearing apparatus that limitedly increases hardness in serration or spline of an inner diameter surface coupled with a constant-velocity joint of a hub being a portion where sufficient strength and fatigue strength to resist high stress and repetitive stress are desired, and suppresses lowering of productivity caused by the increase of production steps. <P>SOLUTION: A base material of a hub 14 having a wheel mounting flange 17 has a standard structure obtained by hot forging of a steel material. A surface of the portion having the serration 21a or the spline SP in the inner diameter surface of a through-hole 21 of the hub 14 has a non-standard structure 30, and the non-standard structure is formed by laser hardening. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a bearing device for a wheel that has been improved in strength for passenger cars, freight cars, and the like.

In the wheel bearing device, there is a portion where the stress becomes high when the vehicle turns sharply. In particular, the strength of the portion where stress concentration occurs becomes a problem when the stress during the sudden turn increases.
In the wheel bearing device for driving wheel support, since the inner surface serration portion of the hub fitted with the stem portion of the constant velocity joint has a tooth shape, the valley portion may be highly stressed. By repeated fine deformation and displacement, the serration teeth of the hub and the constant velocity joint are worn and worn. By repeating these steps, cracks are generated in the valleys of the serration teeth, and durability is lowered. In addition, wear progresses, teeth wear out, and driving force cannot be transmitted.

  Therefore, an attempt was made to reinforce the inner diameter surface provided with the serration of the hub. Conventionally, this is not a measure for strengthening the serration part, but as a measure for strengthening the fatigue strength of the root part of the wheel mounting flange of the hub and the outer peripheral surface of the shaft part, high-frequency heat treatment is applied to the root part of the wheel mounting flange. A method of performing (for example, Patent Document 1) and a method of performing shot peening have been proposed (for example, Patent Document 2).

  However, in shot peening, work is limited due to the narrow inner diameter of the hub. In addition, in the high frequency heat treatment, there is a problem that the accuracy of teeth after heat treatment is deteriorated due to thermal strain, the built-in load of the constant velocity joint is increased, and play is generated. In the case of the method of increasing the hardness by refining the entire hub (for example, Patent Document 3), the number of processes is increased, and the overall workability, for example, machinability and cooling such as caulking is improved by increasing the hardness. The inter-workability may be reduced, and the slip torque may be reduced due to a decrease in the biting property of the hub bolt.

Accordingly, the present inventors have used a refrigerant to form serrations or splines formed on the inner diameter surface that are coupled to the constant velocity joint of the through hole of the hub that is hot during the process of hot forging the hub or at the end of the process. A method has been proposed in which a non-standard structure with increased hardness is obtained by cooling and self-recovery or recuperation holding tempering (for example, Patent Document 4).
JP 2004-182127 A JP 2005-145313 A JP-A-2005-003061 JP 2007-051749 A

  However, in the case of the technique disclosed in Patent Document 4 that uses forging heat, the scattered refrigerant reaches a portion other than the portion that is desired to be a non-standard structure, so that an undesired portion or a thin portion in the vicinity is also cured. Problems such as difficult to cut by turning. For example, it is conceivable that the thin portion hardens to 30 to 35 HRC and the life of the turning blade is reduced.

  The object of the present invention is to limit the hardness of serrations or splines on the inner diameter surface connected to the constant velocity joint of the hub, where sufficient strength and fatigue strength are desired for high stress and repeated stress. It is possible to provide a bearing device for a wheel that can reduce the decrease in productivity due to an increase in processes.

A wheel bearing device according to the present invention includes an inner member and an outer member that are rotatable with respect to each other via a double row of rolling elements, and the inner member includes a hub having a wheel mounting flange and a shaft of the hub. The hub has a through hole through which the stem portion of the joint member of the constant velocity joint is inserted, and the stem portion is formed on the inner diameter surface of the through hole. In a wheel bearing device having a serration or spline that meshes with a provided serration or spline,
The base material portion of the hub is a standard structure obtained by hot forging of a steel material, and the serration or spline formation portion on the inner diameter surface of the through hole of the hub is a non-standard structure portion, and the non-standard structure A structure | tissue is a structure | tissue obtained by laser hardening.

According to the wheel bearing device having this configuration, the following effects can be obtained. Since the serrations or splines on the hub's inner surface are toothed, the troughs may become highly stressed due to the moment load acting on the hub when the car is turning, etc. By repeated deformation and displacement, the serration teeth of the hub and the constant velocity joint are worn and worn.
However, if the inner surface where the serrations or splines of the hub are formed with the non-standard structure against such high stresses that occur repeatedly, the strength and fatigue strength are reduced due to the refinement of the structure and the increase in hardness. And cracking from the serration or spline root is suppressed. That is, the operation of crack generation → increase in displacement of the stress generation site → vibration extension of crack → damage of the hub is suppressed, and the life is extended. Therefore, it can be reduced in size and weight as compared with a wheel bearing device having a normal standard structure. Therefore, the input weight for manufacturing the wheel bearing device can be reduced, the cost can be reduced, and it can be provided at a low cost. Further, since the wheel bearing device is light, the weight of the automobile can be reduced, and the fuel consumption can be improved.
Furthermore, since the hardness is increased by the non-standard structure, abrasion of serrations or splines is prevented. For this reason, it is possible to prevent the teeth from being worn and the driving force from being transmitted.

  The portion of the non-standard structure is obtained by laser quenching in particular, so that it is possible to prevent a part of the hub from becoming too hot locally and solve problems such as melting. Also, only the inner diameter surface of the through hole, which is the target location in the hub, can be locally heat treated by laser quenching to increase the hardness, so that the wheel mounting flange runout accuracy etc. can be maintained with high accuracy. Is possible. If the non-standard texture portion is limited to the inner diameter surface of the through hole, unlike the case where the entire hub surface is non-standard texture, workability such as machinability and caulking properties is reduced. Is minimized.

  Therefore, most of the hub other than the inner diameter surface of the through hole is not hardened, and grinding after the heat treatment can be easily and quickly performed. Therefore, the number of processing steps can be reduced and the cycle time per product can be improved as compared with the conventional one. In other words, it is possible to suppress a decrease in productivity due to an increase in the number of processes compared to the conventional one. In addition, the life of a grinding wheel or the like can be extended, and the manufacturing cost can be reduced. Further, unlike shot peening, an optical fiber cable or the like can be easily passed through the through hole even if the inner diameter of the through hole of the hub is narrow. Therefore, it becomes possible to irradiate a predetermined place on the inner diameter surface of the through hole with the laser beam.

The non-standard structure, which is a structure obtained by laser quenching, is one of a fine ferrite / pearlite structure, an upper bainite structure, a lower bainite structure, a tempered martensite structure, or at least two of these structures It may be a mixed tissue.
Any of the above-mentioned fine ferrite / pearlite structure, upper bainite structure, lower bainite structure, tempered martensite structure, or at least a non-standard structure such as a mixed structure of two or more of these structures is standard. Compared with the base material portion made of the structure, the structure is fine and the hardness is equal to or higher than that. This refinement and increased hardness improves the fatigue strength of the non-standard structure part, and can withstand higher stress amplitude, that is, higher strength and longer life compared to a hub consisting only of a normal standard structure. Can be Therefore, it can be reduced in size and weight as compared with a wheel bearing device having a normal standard structure. Therefore, the input weight for manufacturing the wheel bearing device can be reduced, the cost can be reduced, and it can be provided at a low cost. Further, since the wheel bearing device is light, the weight of the automobile can be reduced, and the fuel consumption can be improved.

  The hub and the inner ring may have respective rows of raceway surfaces. The hub may have no raceway surface, and the inner ring may have a double row raceway surface, that is, the hub may be a hub of a component independent of a finished bearing composed of double row bearings.

The hardness of the non-standard structure portion may be 20 HRC or more and 40 HRC or less, and the hardness of the standard structure of the base material portion may be 13 HRC or more and 25 HRC or less. When the hardness of the portion of the non-standard structure is 20 HRC or more and 40 HRC or less, the toughness is excellent. In this case, the hardness of the portion of the non-standard structure is set to 20 HRC or more and 40 HRC or less by high temperature tempering.
The lower limit of the hardness of the non-standard structure is preferably 20 HRC or more, preferably 25 HRC or more, which is about the center of the base material hardness, in order to improve fatigue strength by increasing the hardness. The material used for the hub is carbon steel (C content 0.4 to 0.8%) or the like, but in the case of S53C or the like, the hardness of the standard structure portion is 13 to 25 HRC. In the case of performing cold working such as caulking, or taking into account the portion into which the hub bolt is press-fitted, it is preferable that the maximum is 25 HRC.
The hardness of the non-standard structure portion may be 40 HRC or more, and the hardness of the standard structure of the base material portion may be 13 HRC or more and 25 HRC or less. When the hardness of the non-standard structure is 40 HRC or more, strength such as rigidity and fatigue strength can be improved.
In addition, if the hardness of the non-standard structure is less than 20 HRC, the strength and fatigue strength are insufficient, and the toughness is excellent in the range of 20 HRC or more and 40 HRC or less, but the strength and fatigue such as rigidity are higher than those in the case of exceeding 40 HRC. The strength is inferior.

  The depth of the non-standard tissue is preferably 0.1 mm or more and 1.5 mm or less. In the case of 0.1 mm or less, the non-standard structure is too thin and the effect cannot be expected. Further, if the thickness is 1.5 mm or more, the laser irradiation time is long to obtain a deep non-standard structure. Therefore, the part other than the irradiation range is heated, and the irradiation range is less likely to be rapidly cooled after the irradiation. Problems such as deterioration in accuracy such as runout of the wheel mounting flange are likely to occur.

The non-standard structure which is a structure obtained by laser quenching may be a structure obtained by quenching using YAG laser light. According to the YAG laser beam, the wavelength of the laser beam can be shortened, the permeability is excellent, and the workpiece can be processed deeply.
Further, the non-standard structure that is a structure obtained by laser quenching may be a structure obtained by quenching using a semiconductor laser beam. Since the semiconductor laser has high energy conversion efficiency, a large-scale cooling mechanism is unnecessary, and a mirror system is not required. Further, since the wavelength of the semiconductor laser light is visible light, there is an advantage that the laser processing is possible even at a low output since the reflectance on the processing surface is low. In addition, since the intensity distribution of the laser beam can be rectangular, large area quenching can be performed efficiently. Therefore, it is possible to further shorten the time required for laser quenching per workpiece, and to reduce the number of man-hours, as compared with the case using the YAG laser beam or the infrared laser beam. In addition, since the laser output can be reduced as compared with YAG laser light or the like, the energy cost can be reduced. In addition, when the non-standard structure is a structure obtained by quenching using a semiconductor laser beam, it is not necessary to apply an absorbent for increasing the absorption of the laser beam to the workpiece, thereby reducing the man-hour. It becomes possible to plan. It is also possible to perform laser hardening using a mirror system together with a semiconductor laser.

A wheel bearing device according to the present invention includes an inner member and an outer member that are rotatable with respect to each other via a double row of rolling elements, and the inner member includes a hub having a wheel mounting flange and a shaft of the hub. The hub has a through hole through which the stem portion of the joint member of the constant velocity joint is inserted, and the stem portion is formed on the inner diameter surface of the through hole. In a wheel bearing device having a serration or spline that meshes with a provided serration or spline,
The base material portion of the hub is a standard structure obtained by hot forging of a steel material, and the serration or spline formation portion on the inner diameter surface of the through hole of the hub is a non-standard structure portion, and the non-standard structure Since the structure is a structure obtained by laser quenching, the serration or spline of the inner diameter surface coupled to the constant velocity joint of the hub can be hardened to a limited extent against high stress and repeated stress, and the process Reduced productivity due to increase.

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an example of a wheel bearing device, and this example is applied to a third generation type driving wheel support. This wheel bearing device has an inner member 1 and an outer member 2 that are rotatable with respect to each other via a double row of rolling elements 3, and the rolling elements 3 are held by a cage 4 for each row. The term “double row” as used herein refers to two or more rows and may be three or more rows, but in the illustrated example, it is two rows. The inner member 1 and the outer member 2 have double-row raceway surfaces 6 and 7 and raceway surfaces 8 and 9, respectively. This wheel bearing device is a double-row angular contact ball bearing type, the rolling elements 3 are made of balls, and the raceway surfaces 6 and 7 are formed so that the contact angles are outward. Both ends of the bearing space between the inner member 1 and the outer member 2 are sealed with seals 10 and 11.

  The outer member 2 is composed of a single integral part, and a vehicle body mounting flange 12 is provided at an arbitrary position in the width direction. The outer diameter surface portion of the outer member 2 closer to the inboard side than the vehicle body mounting flange 12 is a surface to which a knuckle (not shown) serving as a suspension device of the vehicle body is fitted. In this specification, the side closer to the outside in the vehicle width direction when attached to the vehicle body is referred to as the outboard side (left side in FIG. 1), and the side closer to the center in the vehicle width direction is referred to as the inboard side (see FIG. 1 right side). At a plurality of locations in the circumferential direction of the vehicle body mounting flange 12, vehicle body mounting holes 13 including bolt insertion holes or screw holes are provided. The material of the outer member 2 is, for example, carbon steel having a C content of 0.4 wt% or more and 0.8 wt% or less, such as S53C. However, the steel material used as a raw material is not limited to S53C.

  The inner member 1 is composed of two parts, a hub 14 and an inner ring 15 fitted to the outer periphery of the inboard side end of the shaft portion 14a of the hub 14. The hub 14 and the inner ring 15 are formed with the raceway surfaces 6 and 7 on the inner member 1 side, respectively. An inner ring fitting surface 16 having a step and a small diameter is provided on the inboard side end on the outer periphery of the shaft portion 14a of the hub 14, and the inner ring 15 is press-fitted to the inner ring fitting surface 16 with a squeeze. Match. The material of the inner ring 15 is, for example, high carbon chrome bearing steel such as SUJ2. However, the steel material used as a raw material is not limited to SUJ2.

The hub 14 has wheel mounting flanges 17 on the outer periphery of the end of the outboard side of the shaft portion 14a, and hub bolts 19 are inserted into the hub bolt holes 18 provided at a plurality of locations in the circumferential direction of the wheel mounting flanges 17. Is installed in the press-fit state.
An annular pilot portion 20 concentric with the hub 14 protrudes from the base portion of the wheel mounting flange 17 of the hub 14. The pilot portion 20 includes a brake pilot 20a serving as a portion for guiding a brake disc that is attached to the side surface on the outboard side of the wheel mounting flange 17, and a wheel pilot 20b that protrudes further to the outboard side than the brake pilot 20a. Consists of. The pilot unit 20 may be divided into a plurality of portions provided with notches at a plurality of locations in the circumferential direction.

At the center of the hub 14, a through hole 21 is provided through which the stem portion 32 a of the outer ring serving as one joint member 32 of the constant velocity joint 31 is inserted. The stem portion 32a is formed of a serration shaft, and the inner surface of the through hole 21 is provided with a serration 21a that meshes with the serration of the stem portion 32a except for the vicinity of the end on the inboard side. The stem portion 32a may be a spline shaft, and the spline SP may be provided instead of the serration 21a of the hub 14.
The opening peripheral edge of the through-hole 21 on the end surface of the hub 14 on the outboard side becomes a seat surface 35 with which a nut 33 screwed on the male screw portion at the tip of the stem portion 32a or a washer 34 laid under the nut 33 comes into contact. By tightening the nut 33, the step surface 32 b of the joint member 32 is pressed against the end surface of the inner ring 15, and the wheel bearing device and the constant velocity joint 31 are coupled.

The seat surface 35 of the hub 14 is a bottom surface of the counterbore portion 36. A concave portion 37 is provided on the inner surface side of the pilot portion 20 on the end surface on the outboard side of the hub 14, and the counterbore portion 36 is provided on the bottom portion of the concave portion 37. Due to the formation of the recess 37, the pilot portion 20 has a cylindrical shape.
The inner surface of the recess 37 is a forged skin or a turning surface, and the inner surface, that is, the bottom surface and the peripheral surface of the countersink portion 36 are turned surfaces. The counterbore part 36 is not limited to a deeply formed part as shown in the drawing, but may be a part having a depth to the extent that the forged skin portion is cut away.

The hub 14, inner ring 15, and outer member 2, which are parts constituting the inner member 1, are all hot forged products of steel materials. Among these, the hub 14 is a serration 21 a on the inner diameter surface of the through hole 21. The surface portion of the portion provided with is a non-standard tissue portion 30. The base material portion of the hub 14 has a standard structure.
The non-standard structure of the non-standard structure portion 30 is a structure obtained by laser quenching, for example, any one of fine ferrite / pearlite structure, upper bainite structure, lower bainite structure, tempered martensite structure, or at least these. It is assumed that two or more types of mixed tissues are mixed. In each of the following embodiments, the non-standard tissue portion 30 is a tissue obtained by laser quenching even when not specifically described.

The manufacturing process of the hub 14 is performed, for example, in the order of forging → turning → laser quenching → high frequency quenching of the raceway surface → tempering → grinding → assembly.
That is, the material of the hub 14 is made into a forged finished product by hot forging, and the forged finished product is turned. The surface portion of the hub 14 on which the serration 21a of the hub 14 that has been turned is provided is hardened by laser hardening. The steel material used as the material is, for example, carbon steel having a C content of 0.4% wt to 0.8 wt%, such as S53C. However, the steel material used as a raw material is not limited to S53C.

  As shown in FIG. 3, laser quenching involves quenching and curing the surface layer of a target location by irradiating a location where a high energy laser beam is desired to be cured, and self-quenching after heating. Here, a YAG laser beam is used as the laser beam, and the surface layer on the processed surface is cured without being melted by adjusting its output, defocus amount L1, feed speed, and oscillation mode. As the oscillation form of the laser light, there are a system for continuously oscillating the laser light and a system for intermittently oscillating the laser light. The defocus amount L1 is a value that once focuses the focal point f1 of the condenser lens on the surface S1 of the curing target location, and separates the laser head nozzle LN of the YAG laser oscillator from the surface S1 of the curing target location. In this way, the laser head nozzle LN is separated from the portion to be cured, and the laser light condensed by the lens or the like is irradiated on the surface S1 of the portion to be cured with the focus f1 slightly removed. In this case, the spot diameter of the laser beam on the surface S1 of the portion to be cured becomes larger than when the surface S1 is irradiated with the focal point f1 of the laser beam, and heat is applied substantially uniformly to a relatively wide surface of the portion to be cured. be able to. Therefore, the time required for laser quenching per workpiece can be shortened, and the number of man-hours can be reduced.

  When YAG laser light is used, the wavelength of the laser light can be as short as 1.06 μm, for example, and it has excellent permeability and can be processed deeply. However, the wavelength of the laser beam is not limited to 1.06 μm. Further, the laser beam generated by the YAG laser oscillator may be guided to the laser head nozzle LN by an optical fiber cable (not shown). In this case, it is desirable to arrange the laser head nozzle LN at a predetermined angle α (α is, for example, 5 degrees) with respect to the traveling direction L2. In this case, it is possible to prevent the laser light emitted from the optical fiber cable from being reflected by the metal surface and the reflected light from reentering the optical fiber cable. Therefore, the optical fiber cable can be protected.

  Further, when adjusting the laser beam feeding speed, for example, the laser head nozzle LN may be attached to the tip of a robot arm (not shown). The moving speed can be adjusted by moving the robot arm relative to the portion to be cured. Note that laser hardening may be performed by moving the workpiece relative to the fixed laser head nozzle LN. It is also possible to apply a semiconductor laser as an alternative to the YAG laser. When using a semiconductor laser beam, a laser beam having a wavelength of, for example, 808 nm can be used.

In this laser hardening, in order to improve the strength and fatigue strength at the location where the serrations 21a of the hub 14 are provided, the surface hardness of the hardening range (non-standard structure portion 30) is set to 40 HRC or more. When toughness is required, it is desirable to perform high-temperature tempering prior to induction hardening of the raceway surface or the like so that the surface hardness in the hardening range is 20 HRC or more and 40 HRC or less. The base material portion of the hub 14 is a standard structure portion, and the hardness of the base material portion is 13 HRC or more and 25 HRC or less. When the hardness of the non-standard structure is less than 20 HRC, the strength and fatigue strength are insufficient, and the toughness is excellent in the range of 20 HRC or more and 40 HRC or less. Is inferior.
Thereafter, induction hardening is performed on the raceway surface 6, the inner ring fitting surface 16, the contact surface of the seal 10, etc., and tempering is performed. Thereafter, the raceway surface 6 and the like are ground, and the hub 14 that has been ground is assembled to the wheel bearing device.

  In the manufacturing process of the hub 14, the order of laser hardening and induction hardening may be reversed. In particular, in the case where the distance between the raceway surface 6 of the hub 14 and the inner ring fitting surface 16 and the surface portion where the serration 21a is provided on the inner diameter surface of the through hole 21 is short, laser quenching is performed after induction hardening of the raceway surface 6 and the like. Good to do. When the distance between the raceway surface 6 and the inner ring fitting surface 16 and the surface portion where the serration 21a is provided on the inner diameter surface of the through hole 21 is short, the surface portion of the inner diameter surface of the through hole 21 where the serration 21a is provided. If laser quenching is performed first, heat by induction quenching of the raceway surface 6 and the like performed later will temper the laser quenching portion at a high temperature, and the hardness of the laser quenching portion will decrease. Therefore, the hardness of the laser-quenched portion (the surface portion where the serration 21a is provided on the inner diameter surface of the through-hole 21) is performed by first performing induction hardening with a wide heat-affected range and then performing laser quenching with a narrow heat-affected range. Can be secured. Tempering is performed by heating with a laser beam whose output, defocus amount, and feed rate are adjusted, whether the hub 14 is put into a heating furnace for overall heating or high-frequency heating. It may be tempered.

According to the wheel bearing device of this configuration, the following effects can be obtained. Since the serrations 21a are formed on the inner diameter surface of the hub 14 in a tooth shape, the trough portion may become highly stressed due to a moment load acting on the hub 14 when the vehicle is turning, etc. Due to repeated fine deformation / displacement, the teeth of the serrations 21a of the hub 14 and the constant velocity joint 31 are rubbed and worn.
However, if the inner diameter surface on which the serrations 21a of the hub 14 are formed as the non-standard structure portion 30 with respect to such high stress that repeatedly occurs, the strength and fatigue are reduced due to the refinement of the structure and the increase in hardness. Strength improves and it is suppressed that a crack generate | occur | produces from the root of the serration 21a. That is, the action of crack generation → increase in displacement of the stress generation site → extension of crack → breakage of the hub is suppressed and the life is extended.

That is, any one of the fine ferrite pearlite structure, the upper bainite structure, the lower bainite structure, and the tempered martensite structure, or at least the non-standard structure portion 30 of the mixed structure of two or more of these structures is The structure is finer and the hardness is equal to or higher than that of the base material portion made of the standard structure. By such structure refinement and hardness increase, the strength and fatigue strength of the non-standard structure part are improved, and it withstands high stress amplitude, that is, increased in strength, compared to a hub consisting only of a normal standard structure, Long life can be achieved. Therefore, it can be reduced in size and weight as compared with a wheel bearing device having a normal standard structure. Therefore, the input weight for manufacturing the wheel bearing device can be reduced, the cost can be reduced, and it can be provided at a low cost. Further, since the wheel bearing device is light, the weight of the automobile can be reduced, and the fuel consumption can be improved.
Further, since the hardness is increased by the non-standard structure, the serration 21a is prevented from being worn. For this reason, it is possible to prevent the teeth from being worn and the driving force from being transmitted.

The non-standard tissue portion 30 is obtained in particular by laser quenching. If the portion of the non-standard structure is obtained by conventional high-frequency heat treatment, the formation portion of the serration 21a on the inner diameter surface of the hub 14 has a tooth shape, so that part of the serration 21a is locally hot. Problems such as melting out too much can occur. On the other hand, in the present embodiment, when the non-standard tissue portion 30 is laser-quenched, for example, as shown in FIG. 3, the laser head nozzle LN is positioned at or near the serration 21a. When moved relatively, at least one of the output of the laser beam, the defocus amount, and the oscillation mode is changed. Thereby, it is possible to prevent the serrations 21a from becoming too high, and solve problems such as the serrations 21a being melted.
Further, if the non-standard texture portion is obtained by conventional high-frequency heat treatment, most of the wheel mounting flange 17 is heat-treated, and the deflection accuracy of the wheel mounting flange 17 is deteriorated due to thermal strain or the like. Can occur. On the other hand, in the present embodiment, only the inner diameter surface of the target through-hole 21 in the hub 14 can be heat-treated by being limited by laser quenching, so that the deflection accuracy of the wheel mounting flange 17 can be improved. High accuracy can be maintained. Therefore, the deflection accuracy of the brake disc attached to the side surface on the outboard side of the wheel mounting flange 17 can be maintained with high accuracy.
Further, when the entire hub 14 is tempered to increase the fatigue strength, the workability of the entire hub 14 is reduced due to the increased hardness. However, in the present embodiment, only the target portion of the wheel mounting flange 17 is provided. Is made into a non-standard tissue portion 30 by laser quenching limitedly. Therefore, only the inner diameter surface of the through-hole 21 having a non-standard structure can be limited in hardness. Unlike the case where the entire surface of the hub 14 is made of a non-standard structure, deterioration of workability such as machinability and caulking properties can be minimized.

  Therefore, most of the hub 14 other than the inner diameter surface of the through hole 21 is not hardened, and grinding processing after the heat treatment can be easily and quickly performed. Therefore, the number of processing steps can be reduced and the cycle time per product can be improved as compared with the conventional one. In other words, it is possible to suppress a decrease in productivity due to an increase in the number of processes compared to the conventional one. In addition, the life of a grinding wheel or the like can be extended, and the manufacturing cost can be reduced. Further, unlike shot peening, an optical fiber cable or the like can be easily passed through the through hole 21 even if the inner diameter of the through hole 21 of the hub 14 is narrow. Accordingly, it is possible to irradiate a predetermined portion of the inner diameter surface of the through hole 21 with laser light.

Another embodiment of the present invention will be described with reference to the drawings.
In the following description, the same reference numerals are given to portions corresponding to the matters described in the preceding forms in each embodiment, and overlapping description may be omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those described in the preceding section. Not only the combination of the parts specifically described in each embodiment, but also the embodiments can be partially combined as long as the combination does not hinder.

4 to 6 show other embodiments, respectively. Also in each of these embodiments, the formation portion of the serration 21a on the inner diameter surface of the through hole 21 of the hub 14 is a non-standard tissue portion 30, and the non-standard tissue is a tissue obtained by laser quenching. Strengthening and fatigue strength are improved by extending the structure of the non-standard structure portion 30 and increasing the hardness, thereby extending the life. Further, the wear of the serration 21a is reduced by increasing the hardness of the portion where the serration 21a is formed.
In addition, in each of these embodiments, except for the matters specifically described, it is the same as the embodiment described with reference to FIGS.

  The wheel bearing device of FIG. 4 is of a tapered roller bearing type for driving wheel support, and the inner member 1 is a double row in which the inner member 1 is fitted to the outer periphery of the hub 14 and the shaft portion 14a of the hub 14. It consists of an inner ring 15. The inner ring 15 is provided for each row. The outer member 2 is composed of a single component and has a vehicle body mounting flange 12. According to this embodiment, there exists an effect similar to the wheel bearing apparatus of FIG.

  The wheel bearing device shown in FIG. 5 is of an angular ball bearing type for supporting a driving wheel. Like the wheel bearing device shown in FIG. 4, the inner member 1 includes a hub 14 and a shaft portion of the hub 14. It consists of a double-row inner ring 15 fitted to the outer periphery of 14a. The outer member 2 is composed of one integral part, and does not have the vehicle body mounting flange 12 in the example of FIG. 1 and has a cylindrical surface throughout. The material of the outer member 2 of this embodiment is, for example, high carbon chrome bearing steel such as SUJ2. However, the steel material used as a raw material is not limited to SUJ2. In this example, the two inner rings 15 have the same size. According to this embodiment, there exists an effect similar to the wheel bearing apparatus of FIG.

  In the wheel bearing device of FIG. 6, the inner member 1 includes a hub 14 and a double-row inner ring 15 fitted to the outer periphery of the shaft portion 14 a of the hub 14. The inner ring 15 is provided for each row, and the inner ring 15 on the inboard side is larger in thickness and axial dimension than the inner ring 15 on the outboard side. The inner ring 15 is fixed to the hub 14 in the axial direction by a caulking portion 14 b provided on the hub 14. The outer member 2 is composed of one integral part, and the outer diameter surface is a cylindrical surface throughout, and does not have the vehicle body mounting flange 12 in the example of FIG. The wheel bearing device according to the embodiment of FIG. 6 also has the same effects as the wheel bearing device of FIG.

It is sectional drawing of the wheel bearing apparatus which concerns on 1st Embodiment of this invention. It is sectional drawing of the hub of the bearing apparatus for wheels. It is a figure showing the example which carries out laser hardening of the principal part of the hub, (a) is a sectional view seen by cutting the principal part of the hub with an axial plane, (b) is a radial plane with the principal part of the hub It is sectional drawing seen by cut | disconnecting. It is sectional drawing of the wheel bearing apparatus which concerns on 2nd Embodiment of this invention. It is sectional drawing of the wheel bearing apparatus which concerns on 3rd Embodiment of this invention. It is sectional drawing of the wheel bearing apparatus which concerns on 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inner member 2 ... Outer member 3 ... Rolling body 6-9 ... Track surface 14 ... Hub 14a ... Shaft part 15 ... Inner ring 17 ... Wheel mounting flange 21 ... Through-hole 21a ... Serration 30 ... It becomes a non-standard structure. Portion 31 ... Constant velocity joint 32 ... Joint member 32a ... Stem portion SP ... Spline

Claims (8)

An inner member and an outer member that are rotatable with respect to each other via a double row of rolling elements, and the inner member is fitted to a hub having a wheel mounting flange and an outer periphery of a shaft portion of the hub. A serration that consists of two inner rings, and the hub has a through hole through which the stem portion of the joint member of the constant velocity joint is inserted at the center, and the serration or spline provided in the stem portion on the inner diameter surface of the through hole Or in a wheel bearing device having a spline,
The base material portion of the hub is a standard structure obtained by hot forging of a steel material, and the serration or spline formation portion on the inner diameter surface of the through hole of the hub is a non-standard structure portion, and the non-standard structure The wheel bearing apparatus whose structure is a structure | tissue obtained by laser hardening.   The non-standard structure which is a structure obtained by laser quenching according to claim 1 is any one of a fine ferrite / pearlite structure, an upper bainite structure, a lower bainite structure, a tempered martensite structure, or at least of these structures. A wheel bearing device which is a mixed structure of two or more of them.   3. The wheel bearing device according to claim 1, wherein the hub and the inner ring have raceways in each row.   The wheel bearing device according to claim 1 or 2, wherein the hub does not have a raceway surface, and the inner ring has a double row raceway surface.   The wheel bearing device according to any one of claims 1 to 4, wherein the hardness of the non-standard structure portion is 20 HRC or more and 40 HRC or less, and the hardness of the standard structure of the base material portion is 13 HRC or more and 25 HRC or less.   5. The wheel bearing device according to claim 1, wherein the hardness of the non-standard structure portion is 40 HRC or more and the hardness of the standard structure of the base material portion is 13 HRC or more and 25 HRC or less.   The wheel bearing device according to any one of claims 1 to 6, wherein the non-standard structure that is a structure obtained by laser quenching is a structure obtained by quenching using a YAG laser beam.   The wheel bearing device according to any one of claims 1 to 6, wherein the non-standard structure, which is a structure obtained by laser quenching, is a structure obtained by quenching using a semiconductor laser beam.

Images