JP2006153188A - Rolling bearing device for wheel support - Google Patents

Abstract

There is provided a rolling bearing device for supporting a wheel that has excellent static strength and fatigue strength, is not easily deformed or damaged even when a large load is applied, and is easy to manufacture because of excellent workability.
A hub wheel 2 of a wheel bearing rolling bearing device 1 has a carbon content of 0.35 mass% or more and 0.75 mass% or less, a silicon content of 0.5 mass% or less, and a manganese content. It is formed by subjecting an alloy steel having an amount of 0.8% by mass or less and a chromium content of 0.5% by mass or less to cold working with a processing rate of 30% or more. Moreover, this alloy steel satisfies the formula that 0.2% proof stress Ys (MPa) and Vickers hardness Hv are Ys> 2.3 × Hv. The hub wheel 2 is formed with a hardened layer 22 by induction hardening, and the Vickers hardness Hv of the other non-quenched portions is 220 or more and 300 or less.
[Selection] Figure 1

Description

  The present invention relates to a wheel bearing rolling bearing device that rotatably supports a wheel of an automobile or the like with respect to a suspension device.

  A rolling bearing device for supporting a wheel that supports a wheel of an automobile or the like rotatably with respect to a suspension device includes an inner member having a raceway surface on an outer peripheral surface, an outer member having a raceway surface on an inner peripheral surface, And a plurality of rolling elements arranged to be freely rollable between the raceway surface of the member and the raceway surface of the outer member. Further, a flange for attaching a wheel is provided on the outer peripheral surface of the inner member, and a flange for attaching a suspension device is provided on the outer peripheral surface of the outer member. Such wheel-supporting rolling bearing devices are being unitized, and the aforementioned flange has a structure integrated with an inner member and an outer member.

  The hub wheel (inner member) constituting the wheel support rolling bearing device is manufactured as follows using medium carbon steel for machine structural carbon steel such as S53C as a material. That is, after forming into a predetermined shape by hot forging, it is allowed to cool to produce an intermediate material having a structure in which pro-eutectoid ferrite and pearlite are combined, and turning, grinding, drilling, etc. are applied to this intermediate material Finish with.

  Since the raceway surface of the inner member and the raceway surface of the outer member are repeatedly loaded with high surface pressure from the rolling elements, hardening by induction hardening is necessary to ensure rolling fatigue life and prevent fretting of the fitting part. A layer is formed. On the other hand, most of the inner member and the outer member including the flange are not subjected to quenching and tempering in order to facilitate the work of cutting the support holes and screw holes. Used in the cooled state. However, these flanges are also required to have sufficient static strength and fatigue strength because a moment load is applied during wheel turning and wheel climbing.

Thus, the flanges are required to have the contradictory performance of excellent workability and sufficient strength. For this reason, conventionally, the above requirement has been met by a method such as increasing the thickness of the flange.
Moreover, in patent document 1, it respond | corresponds to the said request | requirement by giving induction hardening to the base part of a flange, and improving the fatigue strength of the base part of a flange. Furthermore, in patent document 2, the said request | requirement is responded by aiming at the strength improvement of a flange using the raw material which added the alloy element which contributes to strength improvement.
JP-A-11-51064 JP 2004-11025 A

As described above, the flange needs to have sufficient static strength and fatigue strength. However, although the method of Patent Document 1 can improve the fatigue strength of the root portion of the flange, the static strength of the flange is reduced. It was difficult to improve sufficiently. Moreover, since the deformation due to the heat treatment is large, there is a problem that the vibration of the flange is caused. Furthermore, the method of Patent Document 2 has a problem that it is expensive because the material is a special material.
On the other hand, with the recent demands for improving the fuel efficiency and running performance of automobiles, it has been studied to reduce the thickness of the flange. However, reducing the thickness of the flange means that the stress applied to the flange is increased, and there is a concern that the strength of the flange becomes insufficient and problems are likely to occur.

For example, since the radial load applied between the axle and the wheel is transmitted to the flange provided on the outer peripheral surface of the hub wheel (inner member), if the strength of the flange is insufficient, the flange is elastically deformed. The amount can be so large that it cannot be ignored. If the amount of elastic deformation becomes large, damage to the base of the flange, such as cracks, or plastic deformation may occur with long-term use. There is a possibility that the sealing performance by the seal ring provided in the part may deteriorate.
Therefore, the present invention solves the problems of the prior art as described above, has excellent static strength and fatigue strength, is less likely to be deformed or damaged even when a large load is applied, and is easy to process. It is an object of the present invention to provide a wheel bearing rolling bearing device that is easy to manufacture because it is excellent.

  In order to solve the above problems, the present invention has the following configuration. That is, the wheel support rolling bearing device according to claim 1 of the present invention includes an inner member having a raceway surface on an outer peripheral surface, and a raceway surface facing the raceway surface of the inner member. An outer member disposed outward, and a plurality of rolling elements disposed so as to be freely rollable between the raceway surfaces, wherein one of the inner member and the outer member is a rotating wheel, In the wheel support rolling bearing device in which is a fixed wheel, at least one of the inner member and the outer member satisfies the following four conditions.

Condition 1: Carbon content is 0.35 mass% or more and 0.75 mass% or less, silicon content is 0.5 mass% or less, manganese content is 0.8 mass% or less, and chromium content is It is comprised with the alloy steel which is 0.5 mass% or less.
Condition 2: Molded by cold working with a working rate of 30% or more.
Condition 3: The Vickers hardness Hv of the non-quenched part other than the raceway surface is 220 or more and 300 or less.
Condition 4: 0.2% proof stress Ys (MPa) and Vickers hardness Hv of the alloy steel satisfy an expression of Ys> 2.3 × Hv.

Hereinafter, the rolling bearing device for supporting a wheel of the present invention will be described in detail focusing on the critical significance of each of the above-mentioned numerical values (content of alloying elements in alloy steel, Vickers hardness, etc.).
[Carbon content]
Carbon (C) is an element necessary for imparting strength and hardenability to the alloy steel. In order to reduce the manufacturing cost of the wheel bearing rolling bearing device and to obtain the same or higher performance as that produced by the conventional production method, the content in the alloy steel is set to 0.35% by mass or more. There is a need. However, if the content exceeds 0.75% by mass, the cold forgeability of the alloy steel may be reduced and the productivity may be deteriorated.

[About silicon content]
In addition to acting as a deoxidizer, silicon (Si) is an element having an effect of improving the rolling fatigue life by dissolving in a matrix. However, if the content in the alloy steel exceeds 0.5% by mass, the hardness after the spheroidization treatment becomes too high, and the machinability and the cutability of the alloy steel may be reduced.
[About manganese content]
Manganese (Mn) has the effect of improving the hardenability of the alloy steel. However, if the content in the alloy steel exceeds 0.8 mass%, the workability may be insufficient.

[Chromium content]
Chromium (Cr) has the effect of improving the hardenability of the alloy steel. Like Cr, it is more expensive than Mn, which is effective in improving hardenability, and may reduce the cold workability of the alloy steel, so Cr is preferably not added as much as possible. If it is difficult to ensure the necessary hardenability depending on the addition, a small amount of addition is necessary. For this reason, the Cr content needs to be 0.5% by mass or less.

[Conditions 3 and 4]
Since the wheel bearing rolling bearing device is loaded with a load applied from the wheel, a high 0.2% proof stress is required for the inner member and the outer member. In the present invention, “0.2% proof stress” means a stress with a residual stress strain of 0.2%. Since the 0.2% proof stress of alloy steel tends to be higher as it is harder, in order to make the 0.2% proof stress of the inner member and the outer member sufficient, the Vickers of the non-quenched part other than the raceway surface The hardness Hv needs to be 220 or more.

  However, if the alloy steel is too hard, the workability may be insufficient. Moreover, in the wheel bearing rolling bearing device used in an environment where water enters, if the alloy steel is too hard, there is a risk that delayed fracture will occur. For this reason, the Vickers hardness Hv of the non-quenched portion other than the raceway surface needs to be 300 or less. And it is necessary for the 0.2% proof stress Ys (MPa) and Vickers hardness Hv of the alloy steel to satisfy the formula of Ys> 2.3 × Hv.

  The wheel-supporting rolling bearing device of the present invention has excellent static strength and fatigue strength, is not easily deformed or damaged even when a large load is applied, and is easy to manufacture because of excellent workability.

  DESCRIPTION OF EMBODIMENTS Embodiments of a wheel bearing rolling bearing device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of an embodiment of a wheel bearing rolling bearing device according to the present invention. In the present embodiment, in a state where the wheel bearing rolling bearing device is attached to a vehicle such as an automobile, the portion facing the width direction outer side of the vehicle is referred to as an outer end side portion, and the portion facing the width direction center side Is referred to as an inner end portion. That is, in FIG. 1, the left side is the outer end side, and the right side is the inner end side.

  The wheel support rolling bearing device 1 of FIG. 1 includes a hub wheel 2, an inner ring 3, an outer ring 4, two rows of rolling elements 5, 5, and cages 6, 6 that hold the rolling elements 5. ing. Further, between the inner peripheral surface of the inner end side portion of the outer ring 4 and the outer peripheral surface of the inner end side portion of the inner ring 3, and the outer periphery of the inner peripheral surface of the outer end side portion of the outer ring 4 and the intermediate portion of the hub ring 2. Sealing devices 7a and 7b are provided between the surfaces.

Further, a wheel mounting flange 10 for supporting a wheel (not shown) is provided on the outer end side portion of the outer peripheral surface of the hub wheel 2. A suspension device mounting flange 13 is provided on the outer peripheral surface of the outer ring 4 at the end portion on the side away from the wheel mounting flange 10.
A cylindrical portion 11 having a small outer diameter is formed at the inner end side portion of the hub wheel 2. The inner ring 3 is press-fitted into the cylindrical portion 11, and the inner ring 3 and the hub wheel 2 are integrally fixed. In addition, what fixed the inner ring | wheel 3 and the hub ring | wheel 2 integrally is corresponded to the inner member which is the structural requirements of this invention, and the outer ring | wheel 4 is equivalent to the outer member which is the structural requirements of this invention.

  A raceway surface is formed on each of the axially intermediate portion of the outer peripheral surface of the hub wheel 2 and the outer peripheral surface of the inner ring 3. The raceway surface of the hub wheel 2 is the first inner raceway surface 20a, and the raceway surface of the inner ring 3 is the first. Two inner raceway surfaces 20b are provided. Further, a raceway surface facing both the inner raceway surfaces 20a and 20b is formed on the inner peripheral surface of the outer ring 4, and the raceway surface facing the first inner raceway surface 20a is the first outer raceway surface 21a and the second raceway surface. The track surface facing the second inner track surface 20b is a second outer track surface 21b. Further, a plurality of rolling elements 5 are freely rollable between the first inner raceway surface 20a and the first outer raceway surface 21a and between the second inner raceway surface 20b and the second outer raceway surface 21b. Is arranged. In the illustrated example, balls are used as the rolling elements, but rollers may be used depending on the application of the wheel bearing rolling bearing device 1 or the like.

  Of the outer peripheral surface of the hub wheel 2, the portion from the vicinity of the stepped portion 12 formed at the outer end of the cylindrical portion 11 to the vicinity of the first inner raceway surface 20 a and the inner peripheral surface of the outer ring 4, A hardened layer 22 by induction hardening is formed in a portion from the vicinity of the one outer raceway surface 21a to the vicinity of the second outer raceway surface 21b. The portions of the hub wheel 2 and the outer ring 4 where the hardened layer 22 is not formed are not quenched, and the Vickers hardness Hv of the non-quenched portion is 220 or more and 300 or less. The inner ring 3 is subjected to carburizing or carbonitriding, quenching and tempering, and a hardened layer (not shown) is formed on the second inner raceway surface 20b by carburizing or carbonitriding.

  In order to assemble such a wheel support rolling bearing device 1 to an automobile, the suspension device mounting flange 13 is fixed to the suspension device, and the wheel is fixed to the wheel mounting flange 10. As a result, the wheel is supported rotatably by the wheel support rolling bearing device 1 with respect to the suspension device. That is, the inner ring 3 and the hub ring 2 that are integrally fixed are rotating wheels, and the outer ring 4 is a fixed ring.

  In the wheel support rolling bearing device 1, the hub wheel 2, the inner ring 3, and the outer ring 4 have a carbon content of 0.35 mass% to 0.75 mass% and a silicon content of 0.5 mass. % Or less, manganese content is 0.8 mass% or less, chromium content is 0.5 mass% or less, and the balance is composed of iron and alloy steel which is an inevitable impurity element. Moreover, this alloy steel satisfies the formula that 0.2% proof stress Ys (MPa) and Vickers hardness Hv are Ys> 2.3 × Hv. The hub wheel 2, the inner ring 3, and the outer ring 4 are formed by subjecting the above alloy steel to cold working with a working rate (cold working rate) of 30% or more.

  In such a wheel-supporting rolling bearing device 1, since the hub wheel 2 and the outer ring 4 have excellent static strength and fatigue strength, an excessive load (moment load or impact load) is applied to the flanges 10 and 13. Even if it is loaded, deformation and damage (cracking, etc.) hardly occur. Therefore, it is not necessary to improve the strength by increasing the thickness or increasing the number of manufacturing steps. Moreover, since the workability of the alloy steel is excellent, the hub wheel 2 and the outer ring 4 having the flanges 10 and 13 can be easily processed. Therefore, the wheel support rolling bearing device 1 is easy to manufacture.

  Below, an example of the manufacturing method of the above-mentioned hub wheel 2 is demonstrated, referring FIG. First, after heating the above-mentioned rolled steel sheet made of alloy steel to the A1 transformation point or higher, it is annealed by cooling to a temperature below the A1 transformation point at a cooling rate of 5 to 30 ° C./h. Next, the disk-shaped material obtained by punching the rolled steel sheet (see (a) of FIG. 2) is deep-drawn and formed into a bowl shape (see (b) of FIG. 2). A through hole was formed in the bottom (see (c) of FIG. 2). And after shape | molding in the shape of the hub wheel 2 (refer FIG.2 (d)), the bolt hole was provided in the flange by piercing (refer (e) of FIG. 2). Since the alloy steel described above is excellent in workability, it is easy to form with such a high workability. Further, by forming by cold forging, it can be formed with much higher precision than conventional forming by hot forging, so that cutting can be omitted. Thus, the strength of the non-quenched portion is improved and the manufacturing cost is reduced.

The outer peripheral surface including the raceway surface of the obtained hub wheel 2 was subjected to induction hardening and tempering to form a hardened layer 22, and then grinding and superfinishing or superfinishing alone were performed to complete the hub wheel 2.
When the inner ring 3 and the outer ring 4 are manufactured in the same manner as the hub ring 2 and are assembled, the wheel bearing rolling bearing device 1 can be obtained.
〔Example〕
Hereinafter, the present invention will be described more specifically with reference to examples. The cold workability of the alloy steel having the composition as shown in Table 1 was evaluated. The evaluation method will be described below.

A columnar test piece having a diameter of 60 mm and a height of 90 mm was produced by press molding from an alloy steel annealed under the following conditions.
Annealing conditions: After heating at 720 to 850 ° C. for 0.5 to 1 h, cool to 650 to 700 ° C. at a cooling rate of 5 to 20 ° C./h, and further air cool to room temperature.
The cold workability was evaluated by the cracking limit strain in the upsetting test, which is one of the guidelines for evaluating the pressure during cracking and cracking limit. The above-mentioned test piece was upset, and the height Hf of the test piece in which the occurrence of cracks was confirmed by visual observation was measured. Then, the limit upsetting ratio was calculated from the formula {(H0−Hf) / H0} × 100 from Hf and the initial height H0 (90 mm) of the test piece.

  3 to 6 show the relationship between the content of C, Si, Mn, and Cr in the alloy steel and the limit upsetting rate. FIG. 3 shows that the lower the carbon content, the higher the limit upsetting rate and the better the cold workability. If the carbon content exceeds 0.75% by mass, the limit upsetting rate is remarkably low, so that cold workability is low and cracking may occur during cold forging. Similarly, from FIGS. 4 to 6, in order to avoid cracks during cold forging, the Si content is 0.5 mass% or less, the Mn content is 0.8 mass% or less, and the Cr content is It is understood that it is necessary to set the content to 0.5% by mass or less.

  Next, a hub ring was produced from the alloy steel shown in Table 1 as described above, and a flange deformation test was performed to evaluate the deformation resistance of the hub ring. The method of the flange deformation test will be described below. Using the hub bolt and nut, the brake rotor and the wheel were fastened to the wheel mounting flange of the hub wheel with a force of 100 N · m. After removing the nut, measure the amount of deformation of the flange surface at a position 10 mm outward and 10 mm inward from the PCD position of the bolt hole of the hub bolt. Based on the maximum flange deformation shown in FIG. The deformation resistance was obtained.

  As a result of the flange deformation test, the cold working rate at the time of producing the hub ring, the Vickers hardness Hv of the non-quenched portion of the hub ring, the ratio Ys of 0.2% proof stress Ys (MPa) and Vickers hardness Hv / Hv is summarized in Table 2. The deformation resistance shown in Table 2 is shown as a relative value when the deformation resistance of the hub wheel of Comparative Example 5 manufactured by the conventional method is 1. Here, the conventional manufacturing method of the hub wheel is to form an annealed material by hot forging, and then perform turning, induction hardening, grinding, and polishing.

  As can be seen from the graph of FIG. 8, when the carbon content was less than 0.35 mass%, the deformation resistance was low (that is, the deformation amount of the flange surface was large). Further, as can be seen from the graph of FIG. 9, the deformation resistance was low when the processing rate was less than 30%. Furthermore, as can be seen from the graph of FIG. 10, the deformation resistance was low when the Vickers hardness Hv of the non-quenched portion was less than 220. Furthermore, as can be seen from the graph of FIG. 11, when Ys / Hv was 2.3 or less, the deformation resistance was low.

It is sectional drawing which shows the structure of one Embodiment of the rolling bearing apparatus for wheel support which concerns on this invention. It is a figure explaining the manufacturing method of a hub ring. It is a graph which shows the relationship between content of carbon in alloy steel, and a limit upsetting rate. It is a graph which shows the relationship between content of silicon in alloy steel, and a limit upsetting rate. It is a graph which shows the relationship between content of manganese in alloy steel, and a limit upsetting rate. It is a graph which shows the relationship between content of chromium in alloy steel, and a limit upsetting rate. It is a figure explaining the maximum flange deformation amount. It is a graph which shows the relationship between content of carbon in alloy steel, and deformation resistance. It is a graph which shows the relationship between a cold work rate and deformation resistance. It is a graph which shows the relationship between the Vickers hardness Hv of a non-hardening part, and deformation resistance. It is a graph which shows the relationship between Ys / Hv and deformation resistance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rolling bearing apparatus for wheel support 2 Hub wheel 3 Inner ring 4 Outer ring 5 Rolling element 10 Wheel mounting flange 13 Suspension apparatus mounting flange 20a First inner raceway surface 20b Second inner raceway surface 21a First outer raceway surface 21b Second outer race Raceway 22 Hardened layer

Claims (1)

An inner member having a raceway surface on an outer peripheral surface, an outer member having a raceway surface opposite to the raceway surface of the inner member, and arranged on the outer side of the inner member, and a roll between the raceway surfaces. A rolling bearing device for supporting a wheel, wherein one of the inner member and the outer member is a rotating wheel, and the other is a fixed wheel. And at least one of the outer members satisfies the following four conditions: a rolling bearing device for supporting a wheel.
Condition 1: Carbon content is 0.35 mass% or more and 0.75 mass% or less, silicon content is 0.5 mass% or less, manganese content is 0.8 mass% or less, and chromium content is It is comprised with the alloy steel which is 0.5 mass% or less.
Condition 2: Molded by cold working with a working rate of 30% or more.
Condition 3: The Vickers hardness Hv of the non-quenched part other than the raceway surface is 220 or more and 300 or less.
Condition 4: 0.2% proof stress Ys (MPa) and Vickers hardness Hv of the alloy steel satisfy an expression of Ys> 2.3 × Hv.

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