JP2006250317A - Rolling bearing and bearing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prolong the lifetime of a rolling bearing using a method focusing on the flow of a material in deformation of the material at the time of forging. <P>SOLUTION: The facial layer part of the rolling element contacting surface of each raceway groove 21a/21b of an outer ring 21 is formed only from the part of a columnar material outside the position as 40% of its radius from the center in the radial direction. Therein the angle θ formed between the tangent L and a straight line A<SB>1</SB>should lie between 0° and 60°, including the limits, where the tangent L is of the raceway groove 21a/21b formed at the rolling element contacting point P in the section including the axis while the straight line A<SB>1</SB>exhibits the direction of the grain flow T<SB>1</SB>in forging on the most facial side of the raceway groove 21a/21b on the section. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rolling bearing and a bearing unit (an outer member in which an outer ring having a double-row raceway and a flange are integrated, an inner ring, and a bearing provided with rolling elements).

  In recent years, in order to improve the fuel efficiency of automobiles, unitization of wheel support bearings for the purpose of weight reduction has been advanced. FIG. 1 is a cross-sectional view showing an example of a unitized wheel support bearing. This unit is composed of an inner member 1, an outer member 2, a ball (rolling element) 3, a cage 4, a first seal 5, a second seal 6, and a slinger 7. Has two rows of rolling tracks.

  The inner member 1 includes an inner ring 11 having two rows of tracks, a hub 12 that fits an axle, and a flange 13 that fixes the wheel side member 8. The inner member 1 includes a first member 1a and a second member 1b. The first member 1a is a member in which one inner ring raceway 11a portion of the inner ring 11, the hub 12 and the flange 13 are integrally formed (hub ring). The second member 1b is a ring-shaped member in which the other inner ring raceway 11b is formed, and is externally fitted to the first member 1a.

The outer member 2 is formed integrally with an outer ring 21 having two rows of raceways 21a and 21b and a flange 22 in which a bolt hole 22a for fixing a vehicle suspension device (vehicle body side member) is formed.
The inner member 1 and the outer member 2 having such a complicated shape are conventionally made of a medium carbon steel containing about 0.5% by mass of carbon, and after being processed into a predetermined shape by hot forging, It is manufactured by hardening the surface layer of the raceway groove by induction hardening.

  In addition, there is an increasing demand for improving the life of the wheel supporting bearing unit so that it can withstand severe use conditions such as water entering inside. There are two methods to meet this requirement: a method using a material made of steel containing a specific alloy component and a method using a material made of steel with a high degree of cleanliness. There are problems such as productivity reduction and cost increase.

On the other hand, the following Patent Documents 1 and 2 disclose that the life of the rolling bearing is extended by setting the direction of the metal flow (forged streamline) that changes depending on the conditions of the forging process within a specific range. Has been. In patent document 1, the maximum value of the angle with respect to the said rotating shaft of the metal flow in the cross section containing a rotating shaft is set to 10 degrees or more and 50 degrees or less. In patent document 2, the angle of the metal flow with respect to the revolution direction of the rolling element is set within ± 15 °.
Japanese Patent No. 3123055 JP-A-8-42576

  Although this invention is a method which paid its attention to the flow of the material accompanying the raw material deformation | transformation at the time of forging, it makes it a subject to lengthen the lifetime of a rolling bearing by the method different from patent document 1 and 2. FIG.

  In order to solve the above problems, the present invention is manufactured through a forging process of a cylindrical material, and the surface layer portion (for example, a range from the surface to the maximum shear stress depth) of the rolling element contact surface of the raceway groove is the circle. The columnar material is formed only in the radial direction of the columnar material at a portion outside the position that is 40% of the radius from the center, and is tangent to the rolling element contact point of the raceway groove in the section including the axis, and the most surface side of the track groove in the section An angle ring formed by a straight line indicating the direction of the forged flow line is 0 ° or more and 60 ° or less. Moreover, the rolling bearing provided with this bearing ring is provided.

  The present invention is also a bearing ring member in which a bearing ring having a double-row raceway and a flange are integrally manufactured through a forging process of a cylindrical material, and the surface layer portion of the rolling element contact surface of the raceway groove is The cylindrical material is formed only in a portion outside the position that is 40% of the radius from the center in the radial direction, and the contact angle between the rolling element and the raceway groove in the cross section including the axis is −5 of the contact angle at the initial contact point. In the range of ° to + 10 °, the angle formed by the tangent line at the contact point of the raceway groove in the cross section and the straight line indicating the direction of the forging line on the most surface side of the raceway groove in the cross section is 0. Provided is a bearing ring member characterized by having an angle of from 60 ° to 60 °. Moreover, the bearing unit provided with this bearing ring member is provided.

  The present invention also includes an inner ring having a double-row track, a hub for fitting an axle, and a flange for fixing a wheel-side member, and at least one row of the track, the hub and the flange are integrally formed through a material forging process. A wheel support bearing comprising a manufactured inner member, an outer member having a double-row track and a flange for fixing a vehicle body side member, an outer member manufactured through a material forging process, and a rolling element. In the unit, at least one of the member in which the raceway of the inner member, the hub and the flange are integrated, and the outer member has a surface layer portion of the raceway contact surface of the raceway groove from the center in the radial direction of the cylindrical material. In the range where the contact angle between the rolling element and the raceway groove in the cross section including the axis is −5 ° to + 10 ° of the contact angle at the initial contact point, formed only at a portion outside the position that is 40% of the radius, Cross section The angle formed between the tangent line at the contact point of the raceway groove in the rolling groove and the straight line indicating the direction of the forging line on the most surface side of the raceway groove in the cross section is 0 ° or more and 60 ° or less. Provided is a wheel support bearing unit.

  The present invention also provides a method for manufacturing a bearing ring of a rolling bearing through a forging step of a cylindrical material, wherein the surface layer portion of the rolling element contact surface of the raceway groove is 40% of the radius from the center in the radial direction of the cylindrical material. A tangent line at the rolling element contact point of the raceway groove in the cross section including the axis, and a straight line indicating the direction of the forging line on the outermost surface side of the raceway groove in the cross section. Provided is a method for manufacturing a bearing ring, wherein forging conditions are set so that an angle formed is not less than 0 ° and not more than 60 °.

When comparing a double-row bearing ring with a single-row bearing ring, or when comparing a bearing member with a flange integrated with the bearing ring and a bearing member with only a bearing ring without a flange, these are circular. When manufactured through the forging process of a columnar material, the more complex shapes of “double-row bearing ring” and “bearing member with a flange integrated with the bearing ring” are the core of the material in the forging process. (A portion near the center) is likely to appear on the surface of the raceway groove.
Here, since the core part of the material (part near the center) is more likely to have non-metallic inclusions (less clean) than the peripheral part, if the core part exists in the track groove surface layer part, Peeling from the starting point is likely to occur.

  According to the present invention, the surface layer portion of the rolling element contact surface of the raceway groove is formed only at a portion outside the position that is 40% of the radius from the center in the radial direction of the cylindrical material. It is difficult for inclusions to be present in the surface layer portion. In addition, the angle formed by the tangent line at the contact point of the raceway groove in the cross section including the axis and the straight line indicating the direction of the flow line on the most surface side of the raceway groove in the cross section is 0 ° to 60 °. For this reason, it is difficult for the raceway groove to peel off as compared with the case where the angle exceeds 60 °.

  According to the present invention, the surface layer portion of the rolling element contact surface of the raceway groove of the raceway ring (outer member) manufactured through the forging process of the columnar material is set to 40% of the radius from the center in the radial direction of the columnar material. A tangent line at the contact point of the raceway groove in the cross section including the axis, and a straight line indicating the direction of the forging line on the outermost surface side of the raceway groove in the cross section. By making the formed angle between 0 ° and 60 °, the life of the rolling bearing (bearing unit) can be extended.

  According to the wheel support bearing unit of the present invention, at least one of the inner member raceway, the member in which the hub and the flange are integrated, and the outer member manufactured through the forging process of the columnar material, the raceway groove rolling is performed. The surface layer portion of the moving body contact surface is formed only at a portion outside the position that is 40% of the radius from the center in the radial direction of the cylindrical material, and the tangent line at the rolling element contact point of the raceway groove in the cross section including the axis line The angle formed by the straight line indicating the direction of the forging line on the most surface side of the raceway groove in the cross section is set to 0 ° or more and 60 ° or less, so that it can be used under severe usage conditions such as water entering inside. The lifetime can be extended.

Hereinafter, embodiments of the present invention will be described.
In this embodiment, the outer member 2 of the wheel supporting bearing unit of FIG. 1 was produced by the method shown in FIG. Thereby, the surface layer part (range from the surface to the maximum shear stress depth) of the rolling element contact surface of the raceway grooves 21a and 21b of the outer ring 21 is outside the position where the radial direction of the cylindrical material is 40% of the radius. The part was formed only. Further, as shown in FIG. 3, the tangent line L at the rolling element contact point P of the raceway grooves 21a and 21b in the cross section including the axis line and the forging line T ₁ on the most surface side of the raceway grooves 21a and 21b in the cross section. The angle (θ) formed with the straight line A ₁ indicating the direction was set to 0 ° to 60 °.

  In the method of FIG. 2, first, as shown in FIG. 2A, a columnar material is prepared and crushed from both sides in the axial direction of the column by an upsetting process. As a result, the state shown in FIG. Next, as shown in FIG. 2C, the flange 22, the outer ring 21, and the portion 23 connecting the portions 210 between the two tracks are formed into an integrated shape by a forging process. Next, the connecting portion 23 is removed by a piercing punch process to obtain the shape shown in FIG.

  2, by adjusting the ratio of the diameter and length of the material in the upsetting process and adjusting the formation position and thickness of the portion 23 in the forging process, etc., the raceway grooves 21a, The surface layer portion of the rolling element contact surface of 21b is formed only in a portion outside the position that is 40% of the radius from the center in the radial direction of the cylindrical material, and the angle θ is 0 ° or more and 60 ° or less. Can be.

Since the wheel support bearing unit of FIG. 1 is used with a preload applied, the contact angle varies depending on the amount of preload. Therefore, the range in which the angle θ is 0 ° or more and 60 ° or less is shown in FIG. as shown in), the initial contact point (contact point between the raceway grooves 21b and the rolling element 3 before applying a preload) not only the position of P _0, as shown in FIG. 4 (b), the contact angle is an initial A range A (range of contact points P _{1 to} P ₂ ) in which the value (α) at the contact point is −5 ° to + 10 ° is preferable.

Here, when the distribution state of inclusions in the radial direction of the columnar material (diameter 130 mm) made of SUJ2 was examined, the graph shown in FIG. 5 was obtained. The horizontal axis “material radial position (%)” of this graph is the ratio of the distance from the center O in the radial direction K of the cylindrical material to the radius, as shown in FIG. The vertical axis “number of inclusions (pieces)” in this graph is the number of inclusions having a diameter of 10 μm or more existing in the observation area of 300 mm ² , and the inclusions at each radial position of the cylindrical material are actually measured with an optical microscope. The results obtained by observing a plurality of times until the total observation area reaches 300 mm ² so that the observation regions do not overlap are shown.
As can be seen from the graph of FIG. 5, the surface layer portion of the rolling element contact surface of the raceway groove is formed only at a portion outside the position that is 40% of the radius from the center in the radial direction of the cylindrical material. The inclusion density in the part is remarkably lowered, and peeling starting from the inclusion becomes difficult to occur.

  A life test using a test bearing was performed by the method shown in FIG. The test bearing is a flat washer type thrust bearing including an inner ring 10, an outer ring 20, and balls 30. The inner ring 10 is a disk-shaped member having a center hole 10a into which the rotation shaft J is fitted, and a raceway groove 10b is formed on the disk surface. The outer ring 20 is formed in a disk shape having the same diameter as the inner ring 10 and is not provided with a raceway groove. Therefore, in the outer ring 20, the ball 30 contacts the flat disk surface. Both end positions (range of the raceway surface) of the surface with which the ball 30 of the outer ring 20 contacts are indicated by “M”.

As the outer ring 20, test pieces having the configurations of Nos. 1 to 10 shown in Table 1 were produced by the following method.
First, a columnar material made of SUJ2 but having different oxygen (O) content and sulfur (S) content in steel and having a forged line perpendicular to the axial direction was prepared. Next, a disk-shaped test piece was cut out from the cylindrical material by the following method.
A method of cutting out the test piece will be described with reference to FIG. In FIG. 8, the forging line is indicated by “T” and the cylindrical material is indicated by “E ₁ ” and “E ₂ ”. Table 1 shows the ratio (D / R) of the angle θ to the radius R of the angle D and the distance D from the center O in the radial direction K of the cylindrical material at the end of the raceway surface (point M). Changed. When θ = 0, both end points “M” are at the same position in the radial direction K, but when θ ≠ 0, they are at different positions. Therefore, the ratio (D / R) in the case of θ ≠ 0 is a value at a position (point M ₁ ) closest to the material center on the track surface.

The diameter of the cylindrical material used depends on the diameter of the test piece and θ. In the example shown in FIG. 8A, a test piece of θ = 55 ° and H = 50% cannot be cut out from this cylindrical material E _1, but for example, as shown in FIG. if Jo material E _2, can be cut out.
Next, each cut specimen was heated at 830 to 850 ° C. for 0.5 to 1 hour and then quenched with oil, and then subjected to tempering treatment at 160 to 200 ° C. for 2 hours to obtain surface hardness. Was set to HRC61 or higher.

The inner ring 10 and the ball 3 were made of SUJ2 and subjected to normal heat treatment. Also, four balls 3 were used, and the ball 3 had a PCD (pitch circle diameter) of 38.5 mm.
And the life test of this test bearing was done by the method shown in FIG. First, the test bearing is placed in the container Y with the rotary shaft J attached to the inner ring 10. In this state, the liquid E in which 5% by mass of water is mixed with the lubricating oil “VG10” is placed in the container Y so that the entire test bearing is immersed in the liquid E. Next, the rotating shaft J is rotated at a speed of 1000 min ⁻¹ with an axial load Pa (2940 N) applied from above the rotating shaft J. Then, the time until peeling occurred was examined, and this time was converted into the number of stress repetitions, and the number of stress repetitions (cycle) was defined as the life (rolling fatigue life).

  The results are also shown in Table 1 below. Moreover, from this result, the graph which shows the relationship between the ratio (D / R) of an outer ring | wheel and a lifetime was created using the data of No. 1-4 and No. 6-9 whose angle (theta) is 60 degrees or less. . This graph is shown in FIG. Furthermore, from this result, a graph showing the relationship between the angle θ of the outer ring and the life was created using the data of Nos. 3 to 10 with the ratio (D / R) exceeding 40%. This graph is shown in FIG.

  Moreover, from this result, the oxygen content in the steel and the life of the outer ring were obtained using the data of No. 3-4 and No. 6-9, in which the angle θ was 60 ° or less and the ratio (D / R) exceeded 40%. A graph showing the relationship between This graph is shown in FIG. Furthermore, from this result, using the data of No. 3-4 and No. 6-9 where the angle θ is 60 ° or less and the ratio (D / R) exceeds 40%, the sulfur content in the steel of the outer ring and A graph showing the relationship with the service life was created. This graph is shown in FIG.

As can be seen from the graph of FIG. 9, the larger the outer ring ratio (D / R), that is, the raceway surface of the outer ring is formed not only from the core part of the cylindrical material but from the peripheral part side, Long life. In particular, when the ratio (D / R) is 43% or more, the lifetime is 1.7 × 10 ⁷ cycles or more, but when the ratio (D / R) is 36% or less, the lifetime is 0.48 × 10 ^7. It was below cycle.
As can be seen from the graph of FIG. 10, the smaller the outer ring θ is, the longer the life is. In particular, when θ is 55 ° or less, the lifetime is 1.7 × 10 ⁷ cycles or more, but when θ is 65 ° or more, the lifetime is 0.77 × 10 ⁷ cycles or less.
As can be seen from the graphs of FIGS. 11 and 12, the life becomes longer as the oxygen content in steel and sulfur content in steel of the outer ring are lower.

It is sectional drawing which shows an example of the bearing for wheel support unitized. It is a figure explaining the preparation methods of the bearing unit outside member of the present invention. The angle (θ) formed by the tangent line L at the rolling element contact point P of the raceway groove in the cross section including the axis and the straight line A ₁ indicating the direction of the forging line T ₁ on the outermost surface side of the raceway groove in the cross section is described. FIG. It is a figure explaining the range of the contact angle which makes angle (theta) of an outer ring | wheel 0 to 30 degrees. It is a graph which shows the distribution state of the inclusion in the radial direction of a cylindrical raw material. It is a figure explaining the horizontal axis | shaft of FIG. 5 "the radial direction position (%) of a raw material". It is a figure explaining the life test done in the Example. It is a figure explaining how to cut out the test piece produced in the Example. It is the graph which put together the data of the life test done in the Example in the relationship between the ratio (D / R) of an outer ring, and a life. It is the graph which put together the data of the life test performed in the Example in the relationship between (theta) of an outer ring | wheel and a lifetime. It is a graph which put together the data of the life test done in the Example in the relationship between the oxygen content rate in the steel of an outer ring | wheel, and a lifetime. It is a graph which put together the data of the life test done in the Example in the relationship between the sulfur content rate in the steel of an outer ring | wheel, and a lifetime.

Explanation of symbols

1 Inner member 1a First member (hub wheel)
DESCRIPTION OF SYMBOLS 1b 2nd member 11b Inner ring track 11 Inner ring 12 Hub 13 Flange 2 Outer member 21 Outer ring 21a Track groove 21b Track groove 22a Bolt hole for fixing a suspension device (vehicle body side member) 22 Flange 3 Ball (rolling element)
4 Cage 5 First seal 6 Second seal 7 Slinger 8 Wheel-side member A ₁ Straight line indicating the direction of T ₁ L Tangent line of raceway groove at contact point L _S0 Linear translation line indicating plastic flow K circle Radial direction of columnar material P Contact point P ₀ Initial contact point P ₁ contact point P ₂ contact point T Forging flow line T ₁ Forging flow line on the most surface side θ Angle formed by straight line A ₁ and tangent line L

Claims (6)

It is manufactured through a forging process of a columnar material, and the surface layer portion of the contact surface of the raceway groove is formed only at a portion outside the position that is 40% of the radius from the center in the radial direction of the columnar material,
The angle formed between the tangent line at the contact point of the raceway groove in the cross section including the axis and the straight line indicating the direction of the forging line on the most surface side of the raceway groove in the cross section is 0 ° or more and 60 ° or less. Rolling bearing raceway characterized by that.   A rolling bearing comprising the bearing ring according to claim 1. A bearing ring member having a double row raceway and a flange integrally manufactured through a forging process of a cylindrical material,
The surface layer portion of the rolling element contact surface of the raceway groove is formed only in a portion outside the position that is 40% of the radius from the center in the radial direction of the cylindrical material,
In the range where the contact angle between the rolling element and the raceway groove in the cross section including the axis is -5 ° to + 10 ° of the contact angle at the initial contact point, the tangent line at the contact point of the rolling groove in the cross section, A bearing ring member characterized in that an angle formed by a straight line indicating a direction of a forging line on the most surface side of a raceway groove in a cross section is 0 ° or more and 60 ° or less.   A bearing unit comprising the bearing ring member according to claim 3. An inner ring having a double-row track, a hub for fitting an axle, and a flange for fixing a wheel side member. At least one row of the track, the hub and the flange are integrally manufactured through a forging process of a cylindrical material. An inner member;
An outer member having a double row track and a flange that fixes the vehicle body side member are integrally formed through a forging process of a columnar material; and
Rolling elements,
In a wheel support bearing unit comprising:
At least one of the member in which the track of the inner member, the hub and the flange are integrated, and the outer member are:
The surface layer portion of the rolling element contact surface of the raceway groove is formed only at a portion outside the position that is 40% of the radius from the center in the radial direction of the cylindrical material,
In the range where the contact angle between the rolling element and the raceway groove in the cross section including the axis is -5 ° to + 10 ° of the contact angle at the initial contact point, the tangent line at the contact point of the rolling groove in the cross section, A wheel support bearing unit, characterized in that an angle formed by a straight line indicating a direction of a forging line on the most surface side of the raceway groove in a cross section is 0 ° or more and 60 ° or less. In the method of manufacturing a bearing ring for a rolling bearing through a forging process of a cylindrical material,
The surface layer portion of the rolling element contact surface of the raceway groove is formed only in a portion outside the position that is 40% of the radius from the center in the radial direction of the cylindrical material,
The angle formed between the tangent line at the contact point of the raceway groove in the cross section including the axis and the straight line indicating the direction of the forged flow line on the most surface side of the raceway groove in the cross section is 0 ° to 60 °. The forging conditions are set as described above.

Images