JP2007022464A - Bearing device for wheels - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device for wheel improving a strength and fatigue strength of a wheel fixing flange or a vehicle body fixing flange against a high stress or a repetitive stress, and restricting a reduction in producvity caused by an increased number of steps. <P>SOLUTION: This invention is applied to a bearing device for wheel having an inner member 1 and an outer member 2 rotatable to each other through a plurality of rows of rollers 3 and having a wheel fixing flange 17 at a component, a hub 14, for example, constituting either an entire or a part of the inner member 1 or outer member 2. The component such as the hub 14 or the like having the wheel fixing flange 17 is a hot forging steel product. This component has a base material formed in normal texture and the surface off the wheel fixing flange 17 has a part 30 of non-normal texture. The non-normal texture is selected from fine ferrite-parlite texture, upper bainite texture, lower bainite structure and tempered martensite texture or a mixed texture of at least more than two types of textures. It is also applicable that the vehicle body fixing flange 12 of the outer member 2 is provided with a portion 30 of non-normal texture. <P>COPYRIGHT: (C)2007,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, stresses at the base of the wheel mounting flange of the hub increase when the vehicle turns suddenly. Therefore, in order to improve fatigue strength as a countermeasure against damage, there are a method of performing high-frequency heat treatment (for example, Patent Document 1) and a method of performing shot peening (for example, Patent Document 2) on the base of the flange. Further, in order to increase the fatigue strength, a method of tempering the entire part and increasing the hardness has been proposed (for example, Patent Document 3).

  FIG. 16 shows an example of a general manufacturing method of a hub in a conventional third generation type wheel bearing device. The bar material W0 shown in FIG. 6A is cut to a predetermined size to obtain a billet W1 that is a material of one hub (FIG. 5B). The billet W1 is a forging finish in which a plurality of processes (forging 1 pass, forging 2 passes, forging 3 passes) are gradually brought closer to the shape of the hub as a hot forging process, and the hub is roughly shaped in the final forging process. A product W4 is obtained (FIGS. (C) to (E)).

Forged finished product W4 is shot blasted for scale reduction, normalized or tempered as necessary (Fig. (F)), then turned (Fig. (G)), raceway surface, etc. Is subjected to high-frequency heat treatment ((H) in the figure). What is necessary is secondary turning of the flange surface, etc. ((I) in the figure). Thereafter, grinding is performed to finish the hub 14, and the wheel bearing device is assembled.
JP 2004-182127 A JP 2005-145313 A JP-A-2005-003061

  Conventional high-frequency heat treatment for improving fatigue strength may not be adopted depending on the part shape of the part to be treated. For example, the pilot part that guides the brake and the wheel protrudes from the side surface of the base part of the wheel mounting flange, the radius of curvature of the corner between the flange and the pilot part is small, or the pilot part is circled through the notch. In some cases, the shape is a claw distributed in the circumferential direction. In the case of such a shape, there is a problem that a part of the component becomes too hot locally due to high-frequency heating and melts away, so that high-frequency heat treatment cannot be performed.

In addition, in high-frequency heat treatment, shot peening, and the like, the number of processes increases, and the deflection accuracy of the flange may be deteriorated due to thermal strain or the like.
In the case of increasing the hardness by refining the entire part, the number of processes is increased and the overall workability (for example, machinability and cold workability such as caulking) decreases due to the increased hardness. In addition, slip torque may be reduced due to a decrease in the biting property of the hub bolt.

The above-mentioned problem is mainly a problem related to increasing the strength of the wheel mounting flange, but the same problem as described above also applies to the vehicle body mounting flange for mounting the wheel bearing device to a suspension device such as a knuckle of the vehicle body. There is.
As for the portion of the wheel bearing device attached to the vehicle body, it is desired to increase the hardness as a countermeasure against wear caused by fretting of members. Also in this case, there is a problem of overall workability due to an increase in the process and an increase in hardness in the high-frequency heat treatment and the tempering of the entire part.

  In the conventional method shown in FIG. 16, normalization or tempering is performed to improve the overall fatigue strength of the hub 14. In addition, since heating is performed again after forging is completed and cooled, energy consumption increases. There are cases where normalization and tempering are omitted, but if these are omitted, the crystal grains of the structure are large, the strength and toughness are lowered, and the fatigue strength is weak.

  In recent years, in order to improve fuel efficiency and reduce environmental impact, wheel bearing devices are also strongly desired to be smaller and lighter, and while maintaining fatigue strength and life, they are also smaller and lighter. It is necessary to plan.

An object of the present invention is to provide a wheel bearing device capable of improving the strength and fatigue strength of a wheel mounting flange against high stress and repeated stress, and suppressing a decrease in productivity due to an increase in processes. That is.
Another object of the present invention is to provide a wheel bearing device that can improve the strength and fatigue strength of a body mounting flange against high stress and repeated stress, and can suppress a decrease in productivity due to an increase in processes. Is to provide.
Still another object of the present invention is to provide a wheel bearing device in which the wear resistance of a portion to which a braking part or a suspension device is attached can be improved, and a decrease in productivity due to an increase in processes can be suppressed.

  The wheel bearing device of the present invention has an inner member and an outer member that are rotatable with respect to each other via a double row of rolling elements, and is a component that constitutes all or part of the inner member or the outer member. In the wheel bearing device having the wheel mounting flange, the part having the wheel mounting flange is a hot forged product of steel material, and the base material portion of this part is a standard structure, and the wheel mounting flange The surface has a non-standard structure, and the non-standard structure 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 is the above mixed structure.

The non-standard structure is, for example, a structure obtained by cooling during the hot forging process or at the end of the process for self-reheating or re-heating holding tempering.
Specifically, the fine ferrite / pearlite structure is obtained by partially cooling the part by immersing it in a coolant at the end of the hot forging step. Alternatively, when the hot forging process includes a plurality of forging processes, cooling is performed before the final forging process, and then the final forging process is performed. The tempered martensite structure is obtained by partially cooling the part to below the martensite start point at the end of the hot forging process and then performing reheat tempering. The upper bainite structure and the lower bainite structure are obtained by controlling to a predetermined cooling rate at the end of the hot forging step and cooling to about room temperature. The lower bainite structure can be obtained by lowering the cooling rate than that of the upper bainite structure.

  According to the wheel bearing device having this configuration, the following effects can be obtained. 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. Such refinement and increased hardness improve the fatigue strength of the non-standard structure part, and withstand higher stress amplitude, that is, higher strength than the wheel mounting flange made of only the standard structure. Can extend the life. 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.

Since the part of the non-standard structure is obtained by cooling during the hot forging process or at the end of the process, it is only necessary to add a simple process, and a decrease in productivity due to an increase in the process can be suppressed. Moreover, since the heat of hot forging is used, the energy used for the process for the structure modification can be reduced.
The non-standard part may be the entire surface of a part having a wheel mounting flange, but if it is only a necessary part of the wheel mounting flange or only a necessary part of the wheel mounting flange, workability such as machinability is reduced. Is minimized.

The non-standard tissue portion may be a root portion of the wheel mounting flange. Here, the root portion means not only the side surface of the wheel mounting flange but also the portion near the wheel mounting flange.
When the automobile is turning, for example, large-amplitude bending is repeatedly generated in the wheel mounting flange, and high stress is repeatedly generated in the root portion of the flange. When the root part of the wheel mounting flange has the above-mentioned non-standard structure against such high stress that occurs repeatedly, the strength and fatigue strength are improved by refining the structure and increasing the hardness. Generation of cracks at the root is suppressed. That is, the effect of crack generation → increased displacement of the wheel mounting flange → increase in vehicle vibration → damage of the wheel bearing device is suppressed, and the life is extended.

  The portion of the non-standard structure may be a side surface opposite to the wheel mounting surface of the wheel mounting flange. In the case of the side surface opposite to the wheel mounting surface of the wheel mounting flange, the root portion does not necessarily have to be a non-standard tissue portion. Also in this case, the strength and fatigue strength are improved with respect to the repeatedly generated high stress.

  The part of the non-standard structure may be both side surfaces or the entire surface of the wheel mounting flange. Brake discs are usually mounted on the wheel mounting surface of the wheel mounting flange, but due to the finer structure and increased hardness of the wheel mounting flange, the surface of the flange is worn by fretting with the brake disc. Is suppressed from worsening. Therefore, deterioration of the brake feeling, such as shudder and kickback, can be suppressed.

  The wheel bearing device according to the present invention may have any wheel mounting flange and can be applied to various types. For example, the inner member may be a hub and an inner ring fitted to the outer periphery of a shaft portion of the hub, and the component having the wheel mounting flange may be applied to a wheel bearing device that is the hub. it can. The hub in this case may be a hub that is independent of the finished product of a double-row bearing, for example.

Another wheel bearing device according to the present invention has an inner member and an outer member that are rotatable with respect to each other via a double row of rolling elements, and constitutes all or part of the inner member or the outer member. In a wheel bearing device having a body mounting flange as a part, the part having the body mounting flange is a hot forged product of steel, and the base material portion of this part is a standard structure and is used for body mounting. The flange surface has a non-standard structure, and the non-standard structure is 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. It is a mixed tissue of two or more types.
The non-standard structure is, for example, a structure obtained by cooling during the hot forging process or at the end of the process for self-reheating or re-heating holding tempering.

  Also in the vehicle body mounting flange for mounting on the vehicle body, high stress repeatedly occurs during the turning of the automobile and the like, similar to the wheel mounting flange. With respect to this repeated stress, the strength and fatigue strength of the non-standard structure are improved by refining the structure and increasing the hardness, and can withstand high stress amplitude and extend the life. Therefore, the size and weight can be reduced, the input weight for manufacturing the product can be reduced, and the cost can be reduced. In addition, since the non-standard structure portion is obtained by cooling during the hot forging process or at the end of the process, a simple process may be added, and a decrease in productivity due to an increase in the process can be suppressed. The part of the non-standard structure may be the entire surface of the part having the body mounting flange. However, if only a necessary part of the body mounting flange or only the necessary part of the body mounting flange is used, machinability and other workability deteriorates. Minimized.

The non-standard tissue portion may be a root portion of the vehicle body mounting flange. The root portion here means not only the flange for mounting the vehicle body but also the portion in the vicinity of this flange. The portion of the non-standard structure may be a side surface opposite to the vehicle body mounting surface of the vehicle body mounting flange. Further, the non-standard tissue portion may be on both side surfaces or the entire surface of the vehicle body mounting flange.
In the case of a flange for mounting on a vehicle body, as in the case of a flange for mounting on a wheel, a large repeated stress is generated at the root of the flange. Therefore, the strength and fatigue strength can be improved by using the non-standard structure at the root. The effect of life extension is obtained. Even when the side surface opposite to the vehicle body mounting surface of the vehicle body mounting flange is the non-standard structure, the effect of improving strength and fatigue strength and extending the life can be obtained. In the case where both side surfaces or the entire surface of the flange for mounting the vehicle body has the non-standard structure, fretting wear on the contact surface such as the flange and the knuckle can be suppressed by refining the structure and increasing the hardness of the non-standard structure.

Still another 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 double row rolling elements, and the outer member serves as a component on the vehicle body mounting side. In the apparatus, the part on the vehicle body mounting side is a hot forged product of steel, and this part has a non-standard structure on the outer diameter surface of the base material part having a standard structure, and the non-standard structure is One of a fine ferrite / pearlite structure, an upper bainite structure, a lower bainite structure, a tempered martensite structure, or a mixed structure of at least two of these structures, or during or during the hot forging process Finally, it is characterized in that it is a structure obtained by cooling and self-reheating or re-holding and tempering.
In the case of this configuration, since the outer diameter surface of the part on the vehicle body mounting side is the non-standard structure, fretting wear on the contact surface between the outer diameter surface and a knuckle or the like in the suspension device of the vehicle body is caused by the non-standard structure. It can be suppressed by refining the structure and increasing the hardness.

Still another wheel bearing device according to the present invention comprises the inner member and the outer member in a wheel bearing device having an inner member and an outer member that are rotatable with respect to each other via a double row of rolling elements. Any one of the parts is a hot forged product of steel, and this part has a standard structure in the base material portion and has a non-standard structure on the surface, and the non-standard structure includes a fine ferrite pearlite structure and an upper part. Any one of a bainite structure, a lower bainite structure, a tempered martensite structure, or at least a mixed structure of two or more of these structures, or by controlled cooling during the hot forging process or at the end of the process It is the obtained organization. This controlled cooling may be a method of partially bathing the refrigerant, or a method of cooling by controlling the cooling rate and the ambient temperature.
That is, the present invention is not limited to the flanges and the like, and the non-standard structure may be provided on the entire surface or a part of any part constituting the inner member and the outer member. By making the entire surface or any part that requires strength and wear resistance into the non-standard structure, the strength and fatigue strength can be improved, the life can be extended, or the wear resistance can be improved. It is done.

In the wheel bearing device of each configuration of the present invention, the hardness of the non-standard tissue portion and the standard tissue portion may be set as appropriate, for example, the non-standard tissue hardness is 20 to 40 HRC, The base material portion may have a hardness of 13 to 25 HRC.
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 of the base material hardness, in order to improve fatigue strength by increasing hardness. The upper limit of the hardness of the non-standard structure portion is preferably 40 HRC or less in order to ensure machinability.
The material used is carbon steel (C content 0.4 to 0.8%), but in the case of S53C, the hardness of the standard part 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.

  In the wheel bearing device of the present invention, a part having a wheel mounting flange is a hot forged product made of steel, and this part has a standard structure in the base material portion and a non-standard structure on the surface of the wheel mounting flange. The non-standard structure is any one of a fine ferrite / pearlite structure, an upper bainite structure, a lower bainite structure, a tempered martensite structure, or at least a mixed structure of two or more of these structures. Or, the non-standard structure is a structure obtained by cooling during self-recovery during the hot forging process or at the end of the process, or by recuperation holding and tempering. In addition, the refinement and hardness of the non-standard structure can improve the strength and fatigue strength of the wheel mounting flange, and suppress the decrease in productivity due to increased processes. Rukoto can.

  In another wheel bearing device according to the present invention, a part having a body mounting flange is a hot forged product made of steel, and this part has a base material portion having a standard structure and is not formed on the surface of the body mounting flange. It has a standard structure, and the non-standard structure is one of a fine ferrite / pearlite structure, an upper bainite structure, a lower bainite structure, a tempered martensite structure, or at least a mixture of two or more of these structures It is a structure, or the non-standard structure is a structure obtained by cooling at the end of the hot forging process or at the end of the process for self-reheating or reheating holding tempering. The strength and fatigue strength of the body mounting flange can be improved by reducing the structure of the non-standard structure and increasing the hardness against stress. It is possible to suppress the reduction of.

  In still another wheel bearing device according to the present invention, the part on the vehicle body mounting side is a hot forged product of steel, and this part has a standard structure in the base material portion and a non-standard structure on the outer diameter surface. The non-standard structure is a structure obtained by cooling during the hot forging process or at the end of the process for self-reheating or reheating holding tempering, or a fine ferrite pearlite structure, Since it is one of the upper bainite structure, the lower bainite structure, the tempered martensite structure, or at least a mixed structure of two or more of these structures, the outer diameter surface and the knuckle in the suspension device of the vehicle body, etc. The fretting wear on the contact surface can be suppressed by refining the non-standard structure and increasing the hardness, and the decrease in productivity due to an increase in processes can be suppressed.

  Still another wheel bearing device according to the present invention is a hot forged product of steel material in which any component constituting the inner member and the outer member is a standard structure of the base material portion, The surface has a non-standard structure, and the non-standard structure 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 The above-mentioned mixed structure, or the structure obtained by controlled cooling at the end of the hot forging process or at the end of the process, improve the strength and fatigue strength by refining the structure and increasing the hardness of the non-standard structure. Or the wear resistance can be improved, and a decrease in productivity due to an increase in processes can be suppressed.

  In addition, in the wheel bearing device having the above-described configuration, the structure obtained by cooling at the end of the hot forging step may be cooled by reheating a normal hot forged product.

  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 formed 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 outer side in the vehicle width direction when attached to the vehicle body is referred to as the outboard side, and the side closer to the center in the vehicle width direction is referred to as the inboard 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. An inner ring fitting surface 16 having a step and a small diameter is provided at the inboard side end on the outer periphery of the shaft portion 14 a of the hub 14, and the inner ring 15 is fitted to the inner ring fitting surface 16. A through hole 21 through which a stem portion (not shown) of the outer ring of the constant velocity joint is inserted is provided at the center of the hub 14.

The hub 14 has a wheel mounting flange 17 on the outer periphery of the end on the outboard side of the shaft portion 14a. A hub bolt is inserted into each bolt press-fitting hole 18 provided at a plurality of locations in the circumferential direction of the wheel mounting flange 17. 19 is attached in a 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.

  In the wheel bearing device for driven wheels, as shown in FIG. 7, the hub 14 does not have the through hole 21 in the example of FIG. Further, in the wheel bearing device for the driven wheel in the example of FIG. 7, the inner ring 15 is connected to the hub 14 by a crimping portion 14 b in which the inboard side end of the shaft portion 14 a of the hub 14 is crimped to the outer diameter side. Are fixed in the axial direction.

  1, 2, and 7, the hub 14, the inner ring 15, and the outer member 2, which are parts constituting the inner member 1, are all hot forged products of steel materials. The surface of the root portion of the wheel mounting flange 17 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, for example, locally cooling the hub 14 by bathing a coolant during or at the end of the hot forging process. For example, fine ferrite pearlite Any one of a structure, an upper bainite structure, a lower bainite structure, and a tempered martensite structure, or at least a mixed structure of two or more of these structures.

FIG. 3 shows a hot forging process among the manufacturing processes of the hub 14, and FIG. 4 shows a manufacturing process after hot forging of the hub 14. 3 and 4 show the wheel bearing device for the driven wheel shown in FIG. 7 as an example, but the wheel bearing device for the drive wheel shown in FIG. It is the same.
As shown in FIG. 3A, a billet W1 as a material for one hub 14 is prepared by cutting a bar material (not shown) into a fixed size. This billet W1 passes through a plurality of processes as a hot forging process, here, a forging 1 pass, a forging 2 pass, and a forging 3 pass, and gradually approaches the shape of the hub. A forged finished product W4 having a rough shape of 14 is obtained ((B) to (D) in the figure).

  The forged finished product W4 is turned as shown in FIG. 4A, and the raceway surface 6 and the inner ring fitting surface 16 are subjected to high-frequency heat treatment (FIG. 4B). Thereafter, the raceway surface 6 and the like are ground ((D) in the figure). What is required is secondary turning of the surface of the wheel mounting flange 17 and the like before grinding ((C) in the figure). The hub 14 for which the raceway surface has been ground is assembled into a wheel bearing device (FIG. 5E).

  As shown in FIG. 3D, the portion 30 of the non-standard structure of the hub 14 is modified by partially blowing a coolant to the modification target portion at the end of the forging process, or FIG. After the forging process (forging 2 pass) before the final forging process (forging 3 pass) as shown in FIG.

  As the refrigerant, a liquid, its mist or gas, for example, oil, low temperature air or the like is used. Also, depending on the application, lubricants, media, rust preventives, etc. may be mixed in the refrigerant to reduce the scale by material lubrication / mold release effect, mold wear prevention, cooling effect, shot blasting after forging, etc. The omission, the antirust effect, etc. may be obtained.

At the time of blowing the refrigerant, the refrigerant may be blown while rotating the materials W3 and W4 serving as the hub 14 around the axis so that the cooling is uniformly performed on the entire circumference. Moreover, you may rotate a refrigerant | coolant spraying apparatus (not shown), without rotating the raw materials W3 and W4.
The coolant may be sprayed by using a ring-shaped cooling jacket (not shown) having a large number of ejection holes, or if the materials W3 and W4 to be the hub 14 are rotated, one nozzle is provided. It may be sprayed from.

  When rotating the materials W3 and W4 to be the hub 14 during cooling, either the vertical axis or the horizontal axis may be used. Also, the direction in which the refrigerant is ejected may be either upward or downward when the rotational vertical axis is used, and may be any direction other than the horizontal direction when the rotational horizontal axis is used. In addition, when cooling the internal diameter part which the internal diameter of the pilot part 20 of the hub 14 does not penetrate like the example of FIG. 7, it is good to spray upward so that a refrigerant | coolant may not accumulate.

  The method of holding the materials W3 and W4 that will become the hub 14 during cooling may be as long as it does not hinder the cooling part from being uniformly cooled, holding the shaft part 14a, holding the outer diameter part of the wheel mounting flange 17, The outer diameter portion of the pilot portion 20 may be retained. When the hub 14 has a through hole 21 at the center as in the case of driving wheels, the hub 14 may be centered and held using the through hole 21 as a guide.

By cooling, the structure of the non-standard structure portion 30 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 two or more of these structures. As shown in FIG. 5, the mixed structure can be selected depending on the cooling method.
In FIG. 5, the horizontal axis indicates the passage of time, and the vertical axis indicates the temperature. In the figure, A ₃ is the temperature that becomes the A ₃ transformation point, and A ₁ is the temperature that becomes the A ₁ transformation point. M _s is a martensite start point (hereinafter referred to as “M _s point”), and M _f is a martensite finish point (hereinafter referred to as “M _f point”).
The steel material used as the material is carbon steel having a C content of 0.4 to 0.8%, such as S53C.

5, as shown by the curve (0), when simply cooled from forging the component temperature T1 (A greater than ₃ transformation point), the standard organization is a tissue of the conventional forging, that is, a ferrite-pearlite structure.

  Curve (1) is a cooling curve when a fine ferrite / pearlite structure is obtained as a non-standard structure. Until the end of the hot forging process, that is, until the hot forging is finished and cooling, the component (material) to be reformed is partially cooled by being exposed to a coolant as shown in FIG. By limiting the cooling time and allowing self-recuperation after cooling, a fine ferrite and pearlite structure can be obtained as the non-standard structure. The fine ferrite pearlite structure is a structure obtained by normalization, that is, a normalization structure.

  Curve (2) shows another cooling curve when a fine ferrite / pearlite structure is obtained as a non-standard structure. In this case, as shown in FIG. 3, when the hot forging process is composed of a plurality of forging processes, the component (material W3) is placed before the final forging process (FIG. 3D) (FIG. 3C). ) Is partially or wholly cooled, and then the final forging step (FIG. 3D) is performed. The final forging step is performed during the self-recuperation after the cooling. Thus, by adding one of the forging steps after cooling, dynamic strain is given and a fine ferrite / pearlite structure is obtained.

Curves (3) and (4) show cooling curves when a tempered martensite structure, which is a tempered structure, is obtained as a non-standard structure. At the end of the hot forging process, the part is partially cooled to a range below the M _s point and above the M _f point, and then reheated and tempered within a predetermined temperature range, thereby providing a tempered structure as a non-standard structure. That is, a tempered martensite structure is obtained. When the recuperating and tempering temperature is about 500 to 600 ° C., the structure becomes sorbite. When the recuperating and tempering temperature is about 350 to 400 ° C., the structure becomes troostite.

  Curves (5) and (6) show the cooling curves when upper bainite and lower bainite are obtained as non-standard structures, respectively. At the end of the hot forging process, as a controlled cooling, the structure becomes upper bainite by cooling slightly slower than the quenching cooling rate (cooling rate generated by martensite). When quenching is performed at a cooling rate slower than the cooling rate, the structure becomes lower bainite.

  Although various cooling methods have been described with reference to FIG. 5, when the non-standard tissue portion 30 is locally provided, such as the root portion of the wheel mounting flange 17 in the example of FIG. Of the cooling methods indicated by (1) to (6), the methods indicated by curves (1) to (4) are preferred. When the entire surface of the part is the non-standard texture portion 30, the method shown in the cooling curves (5) and (6) may be used.

  According to the wheel bearing device of this configuration, the following effects can be obtained. The surface portion 30 of the root portion of the wheel mounting flange 17 is a non-standard structure, and the non-standard structure is one of a fine ferrite / pearlite structure, an upper bainite structure, a lower bainite structure, a tempered martensite structure, or Since at least two or more of these structures are mixed, the strength of the root portion of the wheel mounting flange 17 is improved, and a long life is obtained. That is, when the automobile turns, for example, a large amplitude flexure is repeatedly generated in the wheel mounting flange 17, and high stress is repeatedly generated in the root portion of the flange 17. When the surface portion 30 of the root portion of the wheel mounting flange 17 is the above-described non-standard structure, the structure is fine compared to the base material portion made of the standard structure, for such high stress that repeatedly occurs, Further, the hardness is equal to or higher than that, and the fatigue strength is improved by refining the structure and increasing the hardness. Therefore, compared with a wheel mounting flange made of only a normal standard structure, the strength is increased, it can withstand a high stress amplitude, and cracks are prevented from occurring at the root portion of the wheel mounting flange 17, thereby extending the service life. it can. 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 and the life is extended.

  As a result, it is possible to reduce the size and weight compared to the wheel bearing device of the normal standard structure, thus reducing the input weight of the product manufacturing of the wheel bearing device, reducing the cost, and providing it at a low cost. It becomes possible to do.

Since the non-standard-structure portion 30 is obtained by cooling during the hot forging process or at the end of the process, it is only necessary to add a simple process, and a decrease in productivity due to an increase in the process can be suppressed. For example, the process can be simplified as compared with the case of normalizing or tempering. Moreover, since the heat of hot forging is used, the energy used for the process for the structure modification can be reduced. Unlike the high-frequency heat treatment, even if the radius of curvature of the corner between the wheel mounting flange 17 and the pilot portion 20 is small, the reforming process can be performed without causing problems such as burnout due to overheating.
Since the non-standard structure portion 30 is a part of the wheel mounting flange 17, a decrease in workability such as machinability can be minimized.

FIG. 6 shows another embodiment of the present invention. This embodiment is obtained by increasing the number of non-standard tissue portions 30 in the first embodiment described with reference to FIGS. In this embodiment, the entire range of both side surfaces of the wheel mounting flange 17 of the hub 14 and the range extending from the side surface on the outboard side of the wheel mounting flange 17 to the outer peripheral surface of the brake pilot 20a at the root portion thereof are non-standard. It is a part 30 of the organization.
Further, the entire side surface on the outboard side, which is the side surface opposite to the side surface on the vehicle body mounting side of the vehicle body mounting flange 12 in the outer member 2, and the outer member 2 on the outboard side from the vehicle body mounting flange 12. The range extending over the entire outer diameter surface of the non-standard tissue portion 30. Furthermore, the surface of the root portion on the side surface on the inboard side that is the side surface on the vehicle body mounting side of the vehicle body mounting flange 12 is a non-standard tissue portion 30.

  As in the case of the hub 14, these non-standard texture portions 30 are portions where the non-standard texture has been obtained by being partially cooled with a coolant during or at the end of the hot forging process. The non-standard organization is the same as each example given in the first embodiment. Other configurations are the same as those of the first embodiment.

  In the case of this configuration, since the entire side surfaces of the wheel mounting flange 17 are the non-standard portion 30, the entire wheel mounting flange 17 has a higher strength and a longer life. In addition, a brake disk (not shown) is attached to the side surface of the wheel mounting flange 17 on the outboard side which is the wheel mounting surface, but the structure of the surface of the wheel mounting flange 17 is refined and the hardness is increased. Further, it is possible to prevent the surface accuracy from being deteriorated due to wear of the flange surface due to fretting with the brake disk. Therefore, deterioration of the brake feeling, such as shudder and kickback, can be suppressed.

Also in the vehicle body mounting flange 12 of the outer member 2, a large amplitude of flexure is repeatedly generated during turning of the automobile, and high stress is repeatedly generated at the root portion of the flange 12. However, in this embodiment, the non-standard tissue portion 30 is provided on the entire base portion of the vehicle body mounting flange 12 and the side surface on the outboard side. The strength of 30 and fatigue strength are improved, it can withstand high stress amplitude, and the life can be extended. Therefore, the wheel bearing device can be further reduced in size and weight, the input weight for manufacturing the product can be reduced, and the cost can be reduced.
In this embodiment, the non-standard tissue portion 30 of each part may be selectively provided with any one or a plurality of portions 30 in any combination.

FIG. 7 shows the wheel bearing device in the embodiment of FIG. 1 for supporting a driven wheel. In this embodiment, as described above, the hub 14 does not have the through hole 21 in the embodiment of FIG. The inner ring 15 is fixed in the axial direction with respect to the hub 14 by a caulking portion 14b in which the inboard side end of the shaft portion 14a of the hub 14 is caulked to the outer diameter side.
In the embodiment of FIG. 7, the non-standard tissue portion 30 may be only the surface of the root portion of the wheel mounting flange 17 as shown in FIG. Further, as shown in FIG. 6A, similarly to the example of FIG. 6, the entire surface of both side surfaces of the wheel mounting flange 17 and each part of the outer member 2 similar to the example of FIG. A portion 30 may be provided.
The effect of providing the non-standard tissue portion 30 is the same as the example of FIG. Further, in the case of the wheel bearing device having the crimping portion 14b as shown in FIG. If the standard tissue portion 30 is obtained, the caulking portion 14b is not hardened and does not hinder the caulking work.

8 to 15 each show another embodiment of the present invention. In each figure, (A) and (B) show examples in which the portions where the non-standard tissue portions 30 are provided are different. Also in each of these embodiments, by providing the non-standard structure portion 30, strength and fatigue strength can be improved by refining the structure and increasing the hardness, and the life can be extended, or fretting wear can be achieved by increasing the hardness. Can be reduced.
In each of these embodiments, the matters other than those specifically described are the same as those of the first embodiment described with reference to FIGS. Moreover, in each of these embodiments, when there are a plurality of non-standard tissue portions 30 in a plurality of locations, the non-standard tissue portions 30 of each portion are selected as one or a plurality of portions 30 in any combination. It may be provided.

The wheel bearing device of FIG. 8 is of a tapered roller bearing type for supporting a drive wheel, 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 an inner ring 15. The inner ring 15 is provided for each row. The outer member 2 is composed of a single component.
FIG. 4B shows an example in which the root portion of the wheel mounting flange 17 of the hub 14 is a non-standard tissue portion 30. 6A is similar to the example of FIG. 6 in that the outer diameter from both side surfaces of the wheel mounting flange 17 and the side surface on the outboard side, which is the side surface of the outer member 2 on the side opposite to the vehicle body mounting side of the vehicle body mounting flange 12. A non-standard tissue portion 30 is provided at the portion extending over the surface and at the root portion of the side surface on the inboard side of the vehicle body mounting flange 12.

  FIG. 9 shows the wheel bearing device in the example of FIG. 8 for supporting the driven wheel, and the hub 14 does not have the central through hole 21. Further, the inner ring 15 is fixed to the hub 14 by a caulking portion 14 b of the hub 14. Other configurations are the same as the example of FIG.

The wheel bearing device of FIG. 10 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 an inner ring 15. The inner ring 15 is provided for each row, and the inner ring 15 on the inboard side may have a larger 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.
FIG. 4B shows an example in which the root portion of the wheel mounting flange 17 of the hub 14 is a non-standard tissue portion 30. In FIG. 4A, both side surfaces of the wheel mounting flange 17 and the outer diameter surface of the outer member 2 are non-standard tissue portions 30.
When the outer diameter surface of the outer member 2 is a non-standard tissue portion 30 as shown in FIG. 5A, a knuckle (not shown) for fixing the outer member 2 and the outer member 2 Fretting wear on the fitting surface is suppressed by the high hardness of the non-standard texture portion 30 on the outer diameter surface.

  FIG. 11 shows the wheel bearing device in the example of FIG. 10 for supporting the driven wheel, and the hub 14 does not have the central through-hole 21. Other configurations are the same as those in the example of FIG.

  The wheel bearing device of FIG. 12 includes the hub 14 and a double row of inner rings 15 fitted on the outer periphery of the shaft portion 14a of the hub 14 as in the wheel bearing device of FIG. . 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 15 are the same size, and the inner ring 15 is fixed in the axial direction to the hub 14 by a constant velocity joint (not shown) coupled to the hub 14 without caulking. Is called. The non-standard tissue portion 30 is the same as the example of FIG.

The wheel bearing device of FIG. 13 is of the second generation type inner ring rotating type, and the outer member 2 has a vehicle body mounting flange 12. The inner member 1 includes the double row inner ring 15 and the inner ring 15. A hub (not shown) for fitting the inner ring 15 to the outer periphery of the shaft portion is formed. The hub has a wheel mounting flange as in the example of FIG.
In the example of FIG. 5A, non-standard tissue portions 30 are provided from both side surfaces of the vehicle body mounting flange 12 of the outer member 2 to the outer diameter surface.
In the example of FIG. 5B, a non-standard tissue portion 30 is provided at the root of the vehicle body mounting flange 12.
The hub (not shown) to which the inner ring 15 is fitted may be provided with a non-standard tissue portion 30 on the root portion or both side surfaces of the wheel mounting flange 17 as in the example of FIG.

The wheel bearing device of FIG. 14 is of a fourth generation type, and the inner member 1 is composed of a hub 14 and a joint outer ring 32 which is one joint member of the constant velocity joint 31. The joint outer ring 32 is formed with raceway surfaces 6 and 7 in each row. The outer member 2 is made of one component and has a vehicle body mounting flange 12.
FIG. 4B shows an example in which the root portion of the wheel mounting flange 17 of the hub 14 is a non-standard tissue portion 30. FIG. 4A shows an example in which the non-standard tissue portions 30 are formed from both side surfaces of the wheel mounting flange 17 and from both side surfaces of the vehicle body mounting flange 12 to the outer diameter surface of the outer member 2.

The wheel bearing device of FIG. 15 is of the second generation type outer ring rotating type, and the inner member 1 is composed of double rows of inner rings 15. The outer member 2 has a wheel mounting flange 17 and a pilot portion 20.
FIG. 5B shows an example in which the root portion of the wheel mounting flange 17 of the outer member 2 is a non-standard tissue portion 30. FIG. 3A shows an example in which both side surfaces of the wheel mounting flange 17 and the outer diameter surface of the outer member 2 are non-standard tissue portions 30.

  In each of the above-described embodiments, the non-standard tissue portion 30 is partially provided on the surface of the parts constituting the inner member 1 or the outer member 2. The entire surface of the parts constituting the member 2, such as the hub 14 and the outer member 2, may be used as the non-standard tissue portion 30.

  In addition, what was obtained by cooling the last of a hot forging process in each said embodiment may cool what heated the normal hot forging goods.

It is sectional drawing which shows 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 process explanatory drawing of the forge process of the hub of the bearing apparatus for wheels. It is process explanatory drawing of the process after the forge of the hub of the bearing apparatus for wheels. It is explanatory drawing of the cooling curve which obtains various non-standard structure | tissues of the hot forged components. It is a fragmentary sectional view of the bearing device for wheels concerning other embodiments of this invention. It is sectional drawing of the wheel bearing apparatus which concerns on further another embodiment of this invention, and the fragmentary sectional view of the modification. It is sectional drawing of the wheel bearing apparatus which concerns on further another embodiment of this invention, and the fragmentary sectional view of the modification. It is sectional drawing of the wheel bearing apparatus which concerns on further another embodiment of this invention, and the fragmentary sectional view of the modification. It is sectional drawing of the wheel bearing apparatus which concerns on further another embodiment of this invention, and the fragmentary sectional view of the modification. It is sectional drawing of the wheel bearing apparatus which concerns on further another embodiment of this invention, and the fragmentary sectional view of the modification. It is sectional drawing of the wheel bearing apparatus which concerns on further another embodiment of this invention, and the fragmentary sectional view of the modification. It is sectional drawing of the wheel bearing apparatus which concerns on further another embodiment of this invention, and sectional drawing of the modification. It is sectional drawing of the wheel bearing apparatus which concerns on further another embodiment of this invention, and the fragmentary sectional view of the modification. It is sectional drawing of the wheel bearing apparatus which concerns on further another embodiment of this invention, and sectional drawing of the modification. It is process explanatory drawing which shows the forge process of the hub of the conventional wheel bearing apparatus, and a subsequent process.

Explanation of symbols

1 ... inner member 2 ... outer member (component)
3 ... rolling elements 6-9 ... raceway surface 12 ... body mounting flange 14 ... hub (component)
14a ... Shaft part 14b ... Clamping part 15 ... Inner ring (parts)
17 ... Wheel mounting flange 20 ... Pilot part 30 ... Non-standard structure part 31 ... Constant velocity joint 32 ... Joint outer ring (parts)

Claims (14)

  For a wheel having an inner member and an outer member that are rotatable with respect to each other via a double row of rolling elements, and a wheel mounting flange on a part of the inner member or the outer member. In the bearing device, the part having the wheel mounting flange is a hot forged product of steel, and this part has a standard structure in the base material part and has a non-standard structure on the surface of the wheel mounting flange. The non-standard structure is any one of a fine ferrite / pearlite structure, an upper bainite structure, a lower bainite structure, a tempered martensite structure, or a mixed structure of at least two of these structures. Wheel bearing device.   For a wheel having an inner member and an outer member that are rotatable with respect to each other via a double row of rolling elements, and a wheel mounting flange on a part of the inner member or the outer member. In the bearing device, the part having the wheel mounting flange is a hot forged product of steel, and this part has a standard structure in the base material part and has a non-standard structure on the surface of the wheel mounting flange. The wheel bearing device according to claim 1, wherein the non-standard structure is a structure obtained by cooling and self-reheating in the hot forging process or at the end of the process, or by performing recuperation holding and tempering.   The wheel bearing device according to claim 1 or 2, wherein the non-standard structure portion is a root portion of the wheel mounting flange.   3. The wheel bearing device according to claim 1, wherein the non-standard structure portion is a side surface opposite to a wheel mounting surface of the wheel mounting flange.   3. The wheel bearing device according to claim 1, wherein the portion of the non-standard structure is the both side surfaces or the entire surface of the wheel mounting flange.   6. The hub according to claim 1, wherein the inner member is a hub and an inner ring fitted to an outer periphery of a shaft portion of the hub, and the component having the wheel mounting flange is the hub. Is a wheel bearing device.   For a wheel having an inner member and an outer member that are rotatable with respect to each other via a double row of rolling elements, and a part that constitutes all or part of the inner member or the outer member, and a vehicle body mounting flange. In the bearing device, the part having the vehicle body mounting flange is a hot forged product of steel, and the part has a standard structure on the base material part and has a non-standard structure on the surface of the body mounting flange, The non-standard structure is any one of a fine ferrite / pearlite structure, an upper bainite structure, a lower bainite structure, a tempered martensite structure, or a mixed structure of at least two of these structures. Wheel bearing device.   For a wheel having an inner member and an outer member that are rotatable with respect to each other via a double row of rolling elements, and a part that constitutes all or part of the inner member or the outer member, and a vehicle body mounting flange. In the bearing device, the part having the vehicle body mounting flange is a hot forged product of steel, and the part has a standard structure on the base material part and has a non-standard structure on the surface of the body mounting flange, The wheel bearing device according to claim 1, wherein the non-standard structure is a structure obtained by cooling and self-reheating in the hot forging process or at the end of the process, or by performing recuperation holding and tempering.   9. The wheel bearing device according to claim 7, wherein the portion of the non-standard structure is a root portion of the vehicle body mounting flange.   9. The wheel bearing device according to claim 7, wherein the portion of the non-standard structure is a side surface opposite to the vehicle body mounting surface of the vehicle body mounting flange.   9. The wheel bearing device according to claim 7, wherein the portion of the non-standard structure is the both side surfaces or the entire surface of the vehicle body mounting flange.   In a wheel bearing device having an inner member and an outer member that are rotatable relative to each other via a double row of rolling elements, wherein the outer member is a vehicle body mounting side component, the vehicle body mounting side component is a steel material. This part is a hot forged product of which the base material portion has a standard structure and has a non-standard structure on the outer diameter surface, and the non-standard structure includes a fine ferrite / pearlite structure, an upper bainite structure, and a lower bainite structure. Any one of the structures, tempered martensite structures, or at least a mixed structure of two or more of these structures, or cooled during the hot forging process or at the end of the process to be self-reheated or recovered. A wheel bearing device characterized by being a structure obtained by heat-holding and tempering.   In a wheel bearing device having an inner member and an outer member that are rotatable relative to each other via a double row of rolling elements, any one of the inner member and the outer member is a hot forged product of steel. Yes, this part has a base structure with a standard structure and a non-standard structure on the surface, and the non-standard structure includes a fine ferrite / pearlite structure, an upper bainite structure, a lower bainite structure, and a tempered martensite structure. Or at least two of these structures, or a structure obtained by controlling the cooling rate and temperature during the hot forging process or at the end of the process. A wheel bearing device.   14. The wheel bearing device according to claim 1, wherein the non-standard tissue portion has a hardness of 20 to 40 HRC and the base material portion has a hardness of 13 to 25 HRC.

Images