JP2010006198A - Bearing device for wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device for a wheel capable of restraining deterioration in productivity caused by an increase in the number of processes by limitedly increasing hardness in a nut seat surface of a hub which is a part where strength and fatigue strength are required against high stress and repetitive stress. <P>SOLUTION: In this bearing device for the wheel, the hub 14 has a through-hole 21 for inserting a stem 32a of a joint member 32 of a constant velocity universal joint 31 in a central part, and the opening peripheral edge of the through-hole 21 in an outboard side end surface of the hub 14 becomes a seat surface 35 contacting with a nut 33 or a washer 34 attached to a male screw on the tip of the stem 32a so as to be threaded. A base material of the hub 14 is a standard structure, and a nut seat surface 35 of the hub 14 is formed as a part 30 of a nonstandard structure, and the nonstandard structure is formed as a structure formed by laser quenching. <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 for supporting the driving wheel for rotating the inner ring, a through hole through which the stem portion of the joint member of the constant velocity joint is inserted is provided at the center of the hub. The opening peripheral edge of the through-hole on the end face of the hub on the outboard side becomes a seat surface to which a nut screwed to the male screw portion at the tip of the stem portion or a washer laid under the nut comes into contact.
This seating surface is finished by machining, but has a countersink shape at the boundary with the forging skin. The corner between the countersink and the peripheral surface of the countersink becomes a high-stress part when the automobile turns, which may cause a decrease in durability. That is, the periphery of the counterbore portion is near the root portion of the wheel mounting flange, but the root portion of the wheel mounting flange is stressed by a large amplitude runout in the wheel mounting flange during a sharp turn of the automobile. Becomes larger. The corner portion of the countersink portion is likely to cause stress concentration and becomes high stress when the automobile turns.
Moreover, the seating surface of the nut may be worn by fretting with the nut, which may lead to a decrease in axial force that couples the constant velocity joint.

  Therefore, an attempt was made to reinforce the periphery of the seat surface in the hub. Conventionally, it is not a reinforcement measure around the seat surface, but as a measure for strengthening the fatigue strength of the base part of the pilot part that guides the wheel and braking parts of the hub, a high frequency is applied to the root part of the wheel mounting flange. Methods for performing heat treatment (for example, Patent Document 1) and methods for performing shot peening (for example, Patent Document 2) have been proposed, and it is conceivable to apply these methods.

  The high-frequency heat treatment described above may not be adopted depending on the part shape of the part to be treated. In other words, when applied to a countersink that serves as a seating surface of a nut for constant velocity joint coupling of a hub, if the radius of curvature of the corner between the bottom surface and the peripheral surface of the countersink is small, it is partially caused by high-frequency heating. However, there are cases in which the treatment cannot be performed due to problems such as melting locally due to excessively high temperature.

In addition, in the high frequency heat treatment, the deflection accuracy of the flange may be deteriorated due to thermal strain or the like. In shot peening, when processing recesses such as the seating surface, the media accumulates according to the processing, so that the media does not reach the surface of the processing location, and media removal may be required multiple times. is there.
In order to increase the fatigue strength, there is a method of tempering the entire part and increasing the hardness (for example, Patent Document 3). However, the entire workability (for example, machinability and cooling such as caulking) is improved by increasing the hardness. Inter-workability) may decrease, and slip torque may decrease due to a decrease in the biting property of the hub bolt.

Therefore, the present inventors cooled a part of the hub (the seat surface) in red hot with a refrigerant during the hot forging process of the hub or at the end of the process, so that self-recuperation or recuperation holding tempering is performed. Thus, a method of obtaining a non-standard structure that increases the hardness in the portion has been proposed (for example, Patent Document 4).
JP 2004-182127 A JP 2005-145313 A JP-A-2005-003061 JP 2007-38805 A

  However, in the case of the technique disclosed in Patent Document 4 that uses forging heat, the refrigerant extends to a portion other than the portion desired to be a non-standard structure, and other thin portions such as an undesired portion and a hub pilot portion are cured. However, problems such as difficulty in cutting by subsequent turning occur. For example, in the hub pilot part which is a thin part, the whole is hardened to 30 to 35 HRC, and the life of the turning blade is reduced.

  The object of the present invention is to increase the hardness of the nut seat surface of the hub, which is a part where sufficient strength and fatigue strength are desired against high stress and repeated stress, and increase productivity by increasing the number of processes. It is an object to provide a wheel bearing device in which a decrease in the rotation is suppressed.

The wheel bearing device of 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 the hub. An inner ring fitted to the outer periphery of the shaft portion, the hub has a through-hole through which a stem portion of a joint member of a constant velocity joint is inserted in the center portion, and the through-hole in the end surface on the outboard side of the hub In the wheel bearing device in which the opening peripheral edge of the hole is a seating surface that comes into contact with a nut or washer that is screwed to the male screw portion at the tip of the stem portion,
The base material part of the hub is a standard structure, the seating surface of the hub is a part of a non-standard structure, and the non-standard structure is a structure obtained by laser quenching.

According to the wheel bearing device having this configuration, the following effects can be obtained. Since the periphery of the seating surface (nut seating surface) where the nut for constant velocity joint connection on the end face of the hub contacts is near the root of the wheel mounting flange, there is a large amplitude deflection in the wheel mounting flange when the vehicle turns. When it occurs repeatedly, high stress is repeatedly generated. Since the seating surface is a part of a non-standard structure against such repeated high stress, strength and fatigue strength are improved by refining the structure and increasing hardness, and cracks occur from the periphery of the seating surface. Occurrence is suppressed. That is, the action of crack generation → increased displacement of the wheel mounting flange → increased vibration of the vehicle → damage of the wheel bearing device 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. Accordingly, 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, fretting wear on the seating surface due to contact with the nut is suppressed, and a decrease in the tightening axial force of the nut due to the wear is suppressed.

  The part of the non-standard structure is obtained by laser quenching in particular, so that even if the radius of curvature of the corner between the bottom surface and the peripheral surface of the countersunk portion is small, a part of the non-standard texture is locally heated. To prevent becoming too much, it will not melt away. In addition, since only the seating surface of the hub can be limited and heat-treated by laser quenching, it is possible to maintain the deflection accuracy and the like of the wheel mounting flange with high accuracy. When the non-standard structure is limited to the seating surface only, unlike the case where the entire surface of the hub is a non-standard structure, workability such as machinability and caulking is minimized. Can be suppressed. Therefore, most of the hub other than the seating surface 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.

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 seating surface is composed of a bottom surface of a countersink portion provided on an end surface on the outboard side of the hub, and the seating surface extends over the periphery of a corner between the bottom surface of the countersink portion and the peripheral surface of the countersink portion. A non-standard organization part may be provided.
In particular, when the seating surface is the bottom surface of the countersink portion, high stress is repeatedly generated at the corner between the bottom surface of the countersink portion and the peripheral surface. However, with respect to such high stress that repeatedly occurs, if the seat surface and the portion extending around the corner between the bottom surface and the peripheral surface of the countersunk portion are the non-standard structure, By increasing the hardness and increasing the hardness, the strength and fatigue strength are improved, and the occurrence of cracks from the periphery of the seating surface such as the corner between the bottom surface of the countersink and the peripheral surface is suppressed.

  The hub and the inner ring may have respective rows of raceway surfaces. In addition, the hub does not have a raceway surface, the inner ring is plural, and each inner ring has a double row raceway surface, that is, the hub is independent from a finished bearing product composed of double row bearings. It may be a hub of parts.

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.
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. The lower limit of the hardness of the non-standard structure portion is preferably 20 HRC or more, preferably 25 HRC or more, which is about the center value 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 amount: 0.4 to 0.8 wt%) 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.

  The depth of the non-standard tissue is preferably 0.1 mm or more and 1.5 mm or less. When the depth of the non-standard tissue is less than 0.1 mm, the non-standard tissue is too thin and the effect cannot be expected. In addition, if the depth of the non-standard tissue is larger than 1.5 mm, the laser irradiation time becomes long to obtain a deep non-standard tissue, so that the part other than the irradiation range is heated and the irradiation range is not easily cooled after irradiation. Problems such as a decrease in hardness, deterioration of the structure, and deterioration of accuracy such as vibration 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.

The wheel bearing device of 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 the hub. An inner ring fitted to the outer periphery of the shaft portion, the hub has a through-hole through which a stem portion of a joint member of a constant velocity joint is inserted in the center portion, and the through-hole in the end surface on the outboard side of the hub In the wheel bearing device in which the opening peripheral edge of the hole is a seating surface that comes into contact with a nut or washer that is screwed to the male screw portion at the tip of the stem portion,
Since the base material part of the hub is a standard structure, the seating surface of the hub is a part of a non-standard structure, and the non-standard structure is a structure obtained by laser quenching. On the other hand, the hub seating surface, which is a part where strength and fatigue strength are desired, can be increased in hardness to a limited extent, and a decrease in productivity due to an increase in processes can be suppressed.

  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 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 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 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 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 35, the step surface 32 b of the joint member 32 is pressed against the width 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 includes a bottom surface 36 b 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 of the countersink portion 36, that is, the bottom surface 36b and the peripheral surface 36c are turning 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 that are parts constituting the inner member 1 are all hot forged products of steel, and among these, the seat surface 35 of the hub 14 and its periphery are non-standard. It is a part 30 of the tissue. The non-standard tissue portion 30 is provided from the seat surface 35 to the periphery of the corner portion 36a between the bottom surface 36b and the peripheral surface 36c of the countersink portion 36 constituting the seat surface 35. Thereby, the peripheral surface 36c of the counterbore part 36 is also 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 steel material used as the material is 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 bearing surface 35 and the periphery of the hub 14 subjected to the turning process are hardened by laser hardening.

  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. However, the oscillation wavelength is not necessarily limited to 808 nm. It is also possible to laser quench one workpiece using semiconductor lasers with different oscillation wavelengths.
Since the wavelength of the semiconductor laser light is visible light, the reflectance on the processed surface is low, and there is an advantage that laser processing is possible even at low output. 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 reduce 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 number of steps. It becomes possible to plan.
Laser hardening can be performed by using a mirror system including at least one of a microlens array, a condensing lens, a beam splitter, and the like together with a semiconductor laser. When a workpiece is laser-quenched using such a mirror system, the energy loss of laser light can be reduced. In addition, when a predetermined machining surface is sequentially laser-quenched by controlling the mirror system, a moving mechanism for moving the laser head nozzle or the like relative to the workpiece can be omitted. In this case, the facility cost can be reduced.

In this laser hardening, in order to improve the strength and fatigue strength at the base portion of the wheel mounting flange 17, that is, the seat surface 35 of the hub 14 and the periphery thereof, the surface hardness of the hardening range (non-standard tissue portion 30) is 40 HRC. It is made to become above. When toughness is required, it is desirable to perform high-temperature tempering before induction quenching of the raceway surface or the like so that the surface hardness in the curing range is 20 to 40 HRC. The base material portion of the hub 14 has a standard structure, and the hardness of the base material portion is 13 to 25 HRC. 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 to 40 HRC, but the strength and fatigue strength such as rigidity are higher than the case of exceeding 40 HRC. Inferior. When improving strength and fatigue strength, and when toughness is required, the depth of the non-standard structure is desirably 0.1 mm or more and 1.5 mm or less.
Thereafter, induction hardening is performed from the seal land 5 to the inner ring fitting surface 16 including the raceway surface 6 and tempered. 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, when the concave portion 37 is designed deeply and the distance between the seal land 5 or the raceway surface 6 and the seat surface 35 is short, it is preferable to perform laser quenching after induction quenching. When the seal land 5 or the raceway surface 6 and the seat surface 35 are close to each other, if the laser quenching to the seat surface 35 is performed first, the heat caused by the induction quenching of the seal land 5 or the raceway surface 6 or the like performed later on the laser quenching portion. Tempering will occur at a high temperature, and the hardness of the laser-quenched portion may decrease. For this reason, the hardness of the laser-quenched portion can be ensured by performing induction hardening with a wide heat-affected range first and laser hardening with a narrow heat-affected range later. 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 periphery of the seat surface 35 with which the nut 33 for constant velocity joint connection on the end face of the hub 14 contacts is near the root of the wheel mounting flange 17, the wheel mounting flange 17 bends with a large amplitude when the vehicle turns. When this occurs repeatedly, high stress is repeatedly generated. In particular, when the seat surface 35 is the bottom surface 36b of the countersink portion 36, high stress is repeatedly generated at the corner portion 36a between the bottom surface 36b of the countersink portion 36 and the peripheral surface 36c.

  However, with respect to the high stress repeatedly generated, the portion extending around the corner surface 36a and the corner portion 36a of the countersink portion 36 is the non-standard tissue portion 30. The strength and fatigue strength are improved by increasing the hardness and the hardness, and the occurrence of cracks from the periphery of the seating surface 35 such as the corner 36a of the countersink portion 36 is suppressed. That is, the action of crack generation → increased displacement of the wheel mounting flange 17 → increased vibration of the vehicle → damage of the wheel bearing device is suppressed, thereby extending the life.

That is, the fine ferrite pearlite structure, the upper bainite structure, the lower bainite structure, any of the tempered martensite structure, or at least a portion of the non-standard structure of the mixed structure of two or more of these structures, Compared to the base material portion made of the standard structure, the structure is fine and the hardness is equal to or higher than that. 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. Accordingly, 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 of the seat surface 35 is increased by the non-standard structure, fretting wear of the seat surface 35 due to contact with the nut 33 is suppressed, and a decrease in the tightening axial force of the nut 33 due to the wear is suppressed. The

  Since the non-standard tissue portion 30 is obtained by laser quenching in particular, even if the radius of curvature of the corner portion 36a between the bottom surface 36b and the peripheral surface 36c of the countersink portion 36 is small, a part of the non-standard tissue portion 30 is obtained. It prevents the temperature from becoming too high locally, and does not melt. That is, in the present embodiment, when laser quenching the non-standard tissue portion 30, for example, as shown in FIG. 3, the laser head nozzle LN is moved to the bottom surface 36 b, the corner portion 36 a, and the peripheral portion of the counterbore portion 36. It moves along the surface 36c. In this case, at least one of the output of the laser beam, the defocus amount, and the oscillation mode may be changed. In any case, only the seat surface 35 and the periphery thereof in the hub 14 are laser hardened in a limited manner, and most of the hub 14 other than the seat surface 35 and the like is not laser hardened. Thereby, for example, it is possible to prevent the pilot portion 20 and the like from becoming too high, and to solve problems such as a part of the pilot portion 20 being melted.

  In addition, since only the seating surface 35 and the like of the hub 14 can be subjected to heat treatment by limiting by laser quenching, it is possible to maintain the deflection accuracy of the wheel mounting flange 17 with high accuracy. When the non-standard structure portion 30 is in a limited range of only the seating surface 35 and the like, unlike the case where the entire surface of the hub 14 is a non-standard structure, workability such as machinability and caulking properties is improved. Degradation is minimized. Therefore, most of the hub 14 other than the seating surface 35 and the like is not cured, and grinding processing after tempering 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.

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, a non-standard tissue portion 30 is provided around the seat surface 35 in contact with the constant velocity joint coupling nut 33 or the washer 34 on the end surface of the hub 14, and the non-standard tissue is obtained by laser quenching. Organization. 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, fretting wear is reduced by increasing the hardness of the seating surface 35, and a reduction in the axial force of the nut 33 is suppressed.
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 an angular ball 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 inner rings 15a and 15b. The inner rings 15a and 15b are provided for each row, and the inner ring 15b on the inboard side may have a larger thickness and axial dimension than the inner ring 15a on the outboard side. The inner rings 15 a and 15 b are fixed to the hub 14 in the axial direction by caulking portions 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. According to this embodiment, there exists an effect similar to the wheel bearing apparatus of FIG.
In this embodiment, the entire recess 37 is turned and the countersunk portion of the seating surface 35 is not provided, but a countersink portion may be provided as in the embodiment of FIG.

  The wheel bearing device of FIG. 5 is similar to the wheel bearing device of FIG. 4 in that the inner member 1 includes a hub 14 and double row inner rings 15a and 15b fitted to the outer periphery of the shaft portion 14a of the hub 14. Consists of. The outer member 2 is composed of one integral part, and does not have the vehicle body mounting flange 12. In this example, the two inner rings 15a and 15b have the same size. According to this embodiment, there exists an effect similar to the wheel bearing apparatus of FIG.

  The wheel bearing device of FIG. 6 is of a tapered roller bearing type for driving wheel support, and the inner member 1 is a double row in which the hub 14 and the outer periphery of the shaft portion 14a of the hub 14 are fitted. It consists of inner rings 15a and 15b. The inner rings 15a and 15b are provided for each row. The outer member 2 is composed of a single component. 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. 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 elements 6-9 ... Raceway surface 14 ... Hub 14a ... Shaft part 15 ... Inner ring 17 ... Wheel mounting flange 21 ... Through-hole 30 ... Non-standard structure part 31 ... Constant velocity joint 32 ... Joint member 32a ... Stem portion 33 ... Nut 35 ... Seat surface 36 ... Counter-sink portion 36a ... Corner portion 36b ... Bottom surface 36c ... Circumferential surface

Claims (9)

The inner ring includes an inner member and an outer member that are rotatable relative 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. The hub has a through-hole through which the stem portion of the joint member of the constant velocity joint is inserted, and the peripheral edge of the through-hole on the end surface of the hub on the outboard side is In the wheel bearing device that serves as a seating surface in contact with a nut or washer screwed to the male screw portion at the tip,
A wheel bearing device in which a base material portion of the hub is a standard structure, the seating surface of the hub is a non-standard structure portion, and the non-standard structure is a structure 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 seating surface according to claim 1 or 2, wherein the seating surface comprises a bottom surface of a countersink portion provided on an end surface of the hub on the outboard side, and the space between the bottom surface of the countersink portion and the peripheral surface of the countersink portion. The wheel bearing apparatus which provided the part of the said non-standard structure | tissue over the circumference | surroundings of the corner of this.   4. The wheel bearing device according to claim 1, wherein each of the hub and the inner ring has a row of raceway surfaces. 5.   The wheel bearing device according to any one of claims 1 to 3, 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 5, 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.   The wheel bearing device according to any one of claims 1 to 5, 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 7, wherein the non-standard structure, which 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 7, wherein the non-standard structure, which is a structure obtained by laser hardening, is a structure obtained by hardening using a semiconductor laser beam.

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