JP2012183559A - Shaft member of rolling bearing for wheel and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a shaft member of a rolling bearing for a wheel capable of reducing cost by reducing the number of times of cold forging and a forging mold device needed for the cold forging.SOLUTION: An annealed shaft-shape raw material 61 is formed by annealing a shaft-shape raw material 60 comprising a structural carbon steel. A coated shaft-shape raw material 62 is formed by coating the surface of the annealed shaft-shape raw material 61 with lubricating agent. A cold forged article 64 integrally having a shaft part 10, a fitting shaft part 30, and a flange part 21 is formed by cold forging the coated shaft-shape raw material 62. A turned forged article 65 is formed by turning a part of the cold forged article 64. A heat treated forged article 66 by heat treating the turned forged article 65. The shaft member 1 of the rolling bearing for the wheel is formed by grinding the inner wheel track surface 18 in the outer peripheral surface of the shaft part 10 of the heat treated forged article 66.

Description

  The present invention relates to a shaft member of a rolling bearing device for a wheel and a manufacturing method thereof.

For example, Patent Document 1 discloses a method for manufacturing a shaft member of a rolling bearing device for a wheel.
In the method of manufacturing a shaft member disclosed in Patent Document 1, a blank 335 (see FIG. 6A) is used to form a material 336 (see FIG. 6C) with a cold working mold. A first step 21 for forming, and a second step 22 for forming the wheel mounting flange 332 from the material 336 using a closed forging die device. In addition, a lubrication process is performed before the blank material is charged in the first process, and a softening process and a lubrication process are performed before the second process 22.
In the first step, as shown in FIG. 6A, a solid round bar material (blank material) 335 is forward-extruded to form a shaft-shaped member 335a as shown in FIG. 6B. Is molded. Next, as shown in FIG. 6C, the material 336 is formed by heading the head of the shaft-shaped member 335 a and crushing it to substantially the same diameter as the outer diameter of the brake pilot 303.
In the second step 22, as shown in FIG. 6 (d), a wheel mounting flange is formed by extruding the material (molding material) 336 to the side perpendicular to the pushing direction using a closed forging die device. After forming 302 and the brake pilot (positioning cylinder portion) 303, as shown in FIG. 6E, the hub 331 is formed by drilling to form the shaft center hole 337. .
Moreover, the lubrication process before the 1st process 21 is a metal surface treatment called a phosphate membrane | film | coat process, for example. This phosphate film treatment is also called chemical conversion treatment or bond treatment. The purpose of the lubrication treatment is to reduce the friction generated between the mold and the material and facilitate plastic working without causing seizure.
Specifically, the lubrication treatment as the phosphate film treatment includes phosphate treatment, a degreasing step and scale removal (pickling) performed before the phosphate treatment, and a reaction type performed after the phosphate treatment. Processing such as soap lubrication.

JP 2008-194741 A

By the way, in the manufacturing method of the shaft member of the rolling bearing device for wheels disclosed in Patent Document 1, primary cold forging and secondary cold forging are sequentially performed in the first step 21, and tertiary cooling is performed in the second step 22. Inter-forging is performed.
That is, first, in the first step 21, a shaft-shaped member 335a (see FIG. 6B) is formed from the blank material 335 by primary cold forging. Further, a material 336 (see FIG. 6C) is formed from the shaft-like member 335a by secondary cold forging.
Thereafter, in the second step 22, the wheel mounting flange 302 and the brake pilot (positioning cylinder portion) 303 (see FIG. 6D) are formed from the material 336 by tertiary cold forging.
For this reason, primary, secondary, and tertiary cold forging are required, and many forging die apparatuses respectively corresponding to these primary, secondary, and tertiary cold forging are required, resulting in high costs.

  In view of the above problems, an object of the present invention is to provide a shaft member capable of reducing the cost by reducing the number of cold forgings and the forging die device required for cold forging, and a manufacturing method thereof.

In order to solve the above-mentioned problem, a method of manufacturing a shaft member of a wheel rolling bearing device according to claim 1 of the present invention includes a shaft portion, a fitting shaft portion formed on one end side of the shaft portion, A method for manufacturing a shaft member of a rolling bearing device for a wheel having a flange portion positioned between a shaft portion and the fitting shaft portion and extending in an outer diameter direction,
An annealing process for forming an annealed shaft material by annealing a shaft material made of structural carbon steel,
A coating treatment process for forming a coated shaft material by coating a lubricant on the surface of the annealed shaft material;
Cold forging the film-treated shaft-shaped material to form a cold forging product integrally including the shaft portion, the fitting shaft portion, and the flange portion;
A turning process of turning a part of the cold forged product to form a turned forged product;
A heat treatment step of heat-treating the turned forged product to form a heat-treated forged product;
A polishing step of polishing the inner ring raceway surface on the outer peripheral surface of the shaft portion of the heat-treated forged product to form a shaft member.

According to the said structure, in the annealing treatment process of the coating process which is a pre-process of a cold forging process, the axial raw material (round bar material) which consists of structural carbon steel is heated at the temperature more than a transformation point. An annealed shaft material is formed by annealing. This annealed shaft material improves the ductility of the material.
Thereafter, in the coating treatment step, the surface of the annealed shaft-shaped material is coated with a lubricant (for example, a phosphate coating treatment) to form a coated shaft-shaped material. The frictional force generated between the forging mold and the material (material) is reduced by the lubricant film on the surface of the coated shaft-shaped material.
And since the film-treated shaft-shaped material that has undergone the above-described annealing treatment process and film treatment process becomes a material excellent in forgeability, in the subsequent cold forging process, the number of forgings is reduced, and the shaft portion and A cold forged product having the fitting shaft portion and the flange portion integrally can be easily formed.
As a result, it is possible to reduce the cost by reducing the number of cold forgings and the forging die device required for cold forging.
Thereafter, in the turning process, a part of the cold forged product is turned to form a turned forged product.
Furthermore, in the heat treatment process, the turned forged product is heat treated (quenched and tempered) to form a heat treated forged product, and in the polishing process, the inner ring raceway surface is polished on the outer peripheral surface of the shaft portion of the heat treated forged product. Thus, the shaft member is formed.

The manufacturing method of the shaft member of the rolling bearing device for wheels according to claim 2 is a manufacturing method of the shaft member of the rolling bearing device for wheels according to claim 1,
In the turning process, at least the lubricant film on the outer peripheral surface of the fitting shaft portion of the cold forged product is left without being turned.

According to the said structure, the contact between a fitting shaft part and the wheel (for example, aluminum alloy wheel) fitted by this fitting shaft part by the lubricant film which remain | survives on the outer peripheral surface of a fitting shaft part. It is possible to prevent dissimilar metal contact corrosion and sticking generated at the part.
As a result, it is not necessary to apply coating or wax application to the outer peripheral surface of the fitting shaft portion in order to prevent dissimilar metal contact corrosion.

The shaft member according to claim 3 is a shaft member manufactured by the method for manufacturing the shaft member of the wheel rolling bearing device according to claim 2,
A lubricant film is provided on the outer peripheral surface of the fitting shaft portion.

  According to the said structure, between a fitting shaft part and the wheel (for example, aluminum alloy wheel) fitted by this fitting shaft part by the lubricant film provided in the outer peripheral surface of the fitting shaft part It is possible to prevent dissimilar metal contact corrosion and sticking generated at the contact portion.

It is an axial direction sectional view showing the state where the shaft member manufactured by the manufacturing method of the shaft member of the rolling bearing device for wheels concerning Example 1 of this invention was assembled to the bearing device for wheels. FIG. 2 is a view taken along the arrow II in FIG. It is an axial direction sectional view showing an axis member similarly. It is an axial direction sectional view which expands and similarly shows a shaft part, a fitting shaft part, and a flange part of a shaft member. It is process drawing which shows the process of manufacturing the shaft member of the rolling bearing apparatus for wheels similarly from a shaft-shaped raw material, (A) of FIG. 5 shows a shaft-shaped raw material, and (B) of FIG. 5 is an annealed shaft-shaped raw material. (C) in FIG. 5 shows a shaft-treated shaft-shaped material, (D) in FIG. 5 shows a primary cold forged product, (E) in FIG. 5 shows a secondary cold forged product, (F) in FIG. 5 shows the forged product after turning, and (G) in FIG. 5 shows the forged product after heat treatment. It is explanatory drawing which shows the manufacturing method of the conventional shaft member.

  A mode for carrying out the present invention will be described in accordance with an embodiment.

A first embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, a shaft member (sometimes called a hub wheel) 1 employed in a wheel bearing device (wheel hub unit) is formed on a shaft portion 10 and one end side of the shaft portion 10. A fitting shaft portion 30 having a diameter larger than that of the shaft portion 10 and into which a center hole of a wheel (not shown) is fitted, a flange base portion 23 positioned between the shaft portion 10 and the fitting shaft portion 30, and the flange A plurality of flange portions 21 radially extending in the outer diameter direction are integrally provided on the outer peripheral surface of the base portion 23.

Further, in the first embodiment, the shaft portion 10 of the shaft member 1 is formed in a stepped shaft shape in which the flange portion 21 side has a large diameter and the distal end side has a small diameter, and the outer peripheral surface of the large diameter portion 11 of the shaft portion 10. Is formed with one inner ring raceway surface 18 of a double row angular ball bearing 41 as a rolling bearing.
An inner ring body 42 having the other inner ring raceway surface 44 on the outer peripheral surface is fitted into the outer peripheral surface of the small diameter portion 12 of the shaft portion 10. Furthermore, an end shaft portion 15 having the same diameter as that of the small diameter portion 12 extends from the tip portion of the shaft portion 10. The inner ring body 42 is fixed to the outer peripheral surface of the small-diameter portion 12 by caulking the distal end portion of the end shaft portion 15 radially outward to form the caulking portion 17.

An outer ring member 45 is disposed on the outer peripheral surface of the shaft portion 10 of the shaft member 1 while maintaining an annular space.
Outer ring raceway surfaces 46 and 47 corresponding to the inner ring raceway surfaces 18 and 44 of the shaft member 1 are formed on the inner peripheral surface of the outer ring member 45 at predetermined intervals in the axial direction. Between the inner ring raceway surfaces 18 and 44 and the outer ring raceway surfaces 46 and 47, a plurality of rolling elements (balls) 50 and 51 are held by cages 52 and 53, respectively, so that they can roll. Is done.
It should be noted that the end shaft portion 15 of the shaft portion 10 is caulked to the plurality of rolling elements (balls) 50 and 51 disposed between the inner ring raceway surfaces 18 and 44 and the outer ring raceway surfaces 46 and 47. A required axial preload is applied based on the caulking force when forming the portion 17.
In addition, a vehicle body side flange 48 is integrally formed at the axially central portion of the outer peripheral surface of the outer ring member 45. The vehicle body side flange 48 is fastened to a mounting surface of a vehicle body side member such as a knuckle or a carrier supported by a vehicle suspension device (not shown) with a bolt.
Further, a seal member 56 is press-fitted and assembled to the inner peripheral surface of one end portion of the outer ring member 45, and the tip end portion of the lip 58 of the seal member 56 is formed adjacent to the shoulder portion of the inner ring raceway surface 18 of the shaft member 1. The seal surface 19 is slidably contacted.

The plurality of flange portions 21 are provided with bolt holes 24 through which hub bolts 27 for fastening the wheels are arranged by press fitting. Further, the rotor support surface 22 is formed as a flat surface on one side surface (the surface facing the brake rotor 55) of the flange portion 21.
Further, the fitting shaft portion 30 is formed with a brake rotor fitting portion 31 corresponding to the brake rotor 55 on the flange portion 21 side, and corresponds to the wheel with a slightly smaller diameter than the brake rotor fitting portion 31 on the tip side. A wheel fitting portion 32 is formed.
Further, a forged recess 35 by cold forging, which will be described in detail later, is formed on the end surface of the center portion of the fitting shaft portion 30.

Next, a method of manufacturing the shaft member of the wheel rolling bearing device according to the first embodiment will be described with reference to FIGS.
The manufacturing method of the shaft member of the wheel rolling bearing device according to the first embodiment includes an annealing process, a coating process, a cold forging process, a turning process, a heat treatment process, and a polishing process. .
First, prior to the annealing treatment step, a structural carbon steel round bar material having a carbon content of about 0.5% such as S45C, S50C, S55C, etc. is cut into a predetermined length to form a shaft-shaped material 60 (FIG. 5). (See (A)).
In the annealing process, the shaft-shaped material 60 is heated at a temperature equal to or higher than the transformation point, preferably about 20 ° C. to 70 ° C. higher than the transformation point temperature.
As a result, the carbon component in the shaft-shaped material 60 is spheroidized and spheroidized and annealed to form the annealed shaft-shaped material 61 (see FIG. 5B). This annealed shaft material 61 improves the ductility of the material itself.

Next, in the coating processing step, the surface of the annealed shaft material 61 is coated with a lubricant to form the coated shaft material 62 having the lubricant coating 36 (see FIG. 5C).
For example, a coated shaft material 62 having a lubricant film (phosphate film) 36 is formed by applying phosphate as a lubricant to the surface of the annealed shaft material 61.
The frictional force generated between the cold forging die and the material (material) is reduced by the lubricant film 36 on the surface of the coated shaft-shaped material 62.
The coated shaft material 62 that has undergone the annealing process and the coating process described above is a material excellent in cold forgeability.

The cold forging process includes a primary cold forging process and a secondary cold forging process.
In the primary cold forging process, the forged die 62 (not shown) for forward extrusion of cold forging is used to forwardly extrude the coated shaft-shaped raw material 62, whereby the shaft portion (large diameter portion 11, small diameter). Portion 12 and end shaft portion 15), intermediate shaft portion (forming a part of flange base portion 23 and fitting shaft portion 30) 20, fitting shaft portion (in this state, forged recess 35 and brake rotor) 30 is formed), and a primary cold forging product 63 is manufactured by forward extrusion of cold forging (see FIG. 5D).

  Next, in the secondary cold forging step, a forged recess 35 is formed on the end face of the central portion of the fitting shaft portion 30 of the primary cold forged product 63 by using a forging die device (not shown) for cold forging side extrusion. A plurality of flange portions 21 are formed radially on the outer peripheral surface of the intermediate shaft portion (flange base portion 23) 20 positioned between the shaft portion 10 and the fitting shaft portion 30 to form a secondary cold forged product 64. (See FIG. 5E).

In the turning process, a part of the secondary cold forged product 64, for example, the rotor support surface 22 on one side of the flange portion 21 and the end surface 33 of the fitting shaft portion 30 are turned, and the bolt hole 24 is formed in the flange portion 21. Is drilled to form a turned forged product 65 (see FIG. 5F).
In this turning process, at least the lubricant coating 36 of the wheel fitting portion 32 of the fitting shaft portion 30 of the secondary cold forged product 64 is left without being turned.
Further, in the first embodiment, as shown in FIG. 4, the side surface opposite to the rotor support surface 22 of the flange portion 21, the seal surface 19 formed adjacent to the shoulder portion of the inner ring raceway surface 18, and the forged recess 35. The lubricant film 36 is left without being turned on the surface of the shaft 10 and the end face 15 of the shaft 10 at the end of the shaft 10. Then, the turning range is reduced by the amount of the lubricant film 36 left, and turning is facilitated.

  Next, in the heat treatment (quenching, tempering) step, the inner ring raceway surface 18 of the shaft portion 10 of the turned forged product 65 as shown in the shaded portion of FIG. 3, FIG. 4, and FIG. And a part of the large-diameter portion 11 adjacent to the inner ring raceway surface 18, the outer peripheral surface of the small-diameter portion 12, and the step surface between the large-diameter portion 11 and the small-diameter portion 12 are induction-quenched and then baked. By returning, the heat-treated forged product 66 having the toughness necessary as the shaft member of the wheel rolling bearing device is formed while maintaining the necessary hardness for the inner ring raceway surface and the like.

  Finally, in the polishing step, the surface of the heat-treated portion including the inner ring raceway surface 18 of the heat-treated forged product 66 (the surface of the shaded portion shown in FIG. 3, FIG. 4 and FIG. 5G) is polished. The shaft member 1 is formed.

The method of manufacturing the shaft member of the wheel rolling bearing device according to the first embodiment is configured as described above.
Therefore, in the annealing process step, which is a pre-process of the coating process, which is a pre-process of the cold forging process (primary and secondary cold forging process), from a round bar of structural carbon steel such as S45C, S50C, S55C, etc. The shaft-shaped material 60 is heated at a temperature equal to or higher than the transformation point and annealed to form the annealed shaft-shaped material 61 with improved material ductility.
Thereafter, in the coating treatment step, the surface of the annealed shaft material 61 is coated with a lubricant film 36 that reduces the frictional force generated between the cold forging mold and the coated shaft material 62 is formed. .
As a result, the coated shaft material 62 becomes a material excellent in forgeability.
For this reason, in the subsequent cold forging process, the number of forgings can be reduced as compared with a manufacturing method that requires primary, secondary, and tertiary cold forging described in Patent Document 1.
In the first embodiment, the shaft portion 10, the fitting shaft portion 30, and the plurality of flange portions 21 are integrally formed by two cold forging steps of the primary cold forging step and the secondary cold forging step. A cold forging product (secondary cold forging product 64) can be easily formed.
As a result, it is possible to reduce the cost by reducing the number of cold forgings and the forging die device required for cold forging.

Further, in the turning process, at least the lubricant coating 36 of the wheel fitting portion 32 of the fitting shaft portion 30 of the cold forged product (secondary cold forged product 64) is left without being turned. And by the lubricant film 36 remaining on the outer peripheral surface of the wheel fitting portion 32, the wheel fitting portion 32 and a wheel (for example, an aluminum alloy wheel) fitted to the wheel fitting portion 32, It is possible to prevent dissimilar metal contact corrosion and sticking occurring at the contact portion between the two.
As a result, the outer peripheral surface of the wheel fitting portion 32 is not required to be coated or waxed to prevent foreign metal contact corrosion.

  Further, in the shaft member 1 manufactured by the method for manufacturing the shaft member of the wheel rolling bearing device according to the first embodiment, the lubricant film 36 is provided on the outer peripheral surface of the wheel fitting portion 32 of the fitting shaft portion 30. Therefore, it is possible to prevent dissimilar metal contact corrosion and sticking occurring at the contact portion between the wheels (for example, an aluminum alloy wheel).

  In addition, this invention is not limited to the said Example 1, In the range which does not deviate from the summary of this invention, it can also implement with a various form.

DESCRIPTION OF SYMBOLS 1 Shaft member 10 Shaft part 18 Inner ring raceway surface 21 Flange part 30 Fitting shaft part 32 Wheel fitting part 36 Lubricant coating 41 Angular contact ball bearing (rolling bearing)
42 Inner ring body 44 Inner ring raceway surface 60 Shaft material 61 Annealed shaft material 62 Coated shaft material 63 Primary cold forged product 64 Secondary cold forged product 65 Turned forged product 66 Forged product after heat treatment

Claims (3)

For a wheel having a shaft portion, a fitting shaft portion formed on one end side of the shaft portion, and a flange portion positioned between the shaft portion and the fitting shaft portion and extending in the outer diameter direction A method of manufacturing a shaft member of a rolling bearing device,
An annealing process for forming an annealed shaft material by annealing a shaft material made of structural carbon steel,
A coating treatment process for forming a coated shaft material by coating a lubricant on the surface of the annealed shaft material;
Cold forging the film-treated shaft-shaped material to form a cold forging product integrally including the shaft portion, the fitting shaft portion, and the flange portion;
A turning process of turning a part of the cold forged product to form a turned forged product;
A heat treatment step of heat-treating the turned forged product to form a heat-treated forged product;
A method of manufacturing a shaft member of a rolling bearing device for a wheel, comprising: a polishing step of polishing an inner ring raceway surface on an outer peripheral surface of a shaft portion of the heat-treated forged product to form a shaft member. It is a manufacturing method of the shaft member of the rolling bearing device for wheels according to claim 1,
A method of manufacturing a shaft member of a rolling bearing device for a wheel, characterized in that, in the turning process, the lubricant film on at least the outer peripheral surface of the fitting shaft portion of the cold forged product is left without being turned. It is a shaft member manufactured by the manufacturing method of the shaft member of the rolling bearing device for wheels according to claim 2,
A shaft member for a rolling bearing device for a wheel, wherein a lubricant film is provided on an outer peripheral surface of the fitting shaft portion.

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