JP4572864B2 - Wheel support bearing unit outer member, wheel support bearing unit - Google Patents

Description

The present invention relates to a bearing unit for supporting a wheel (an outer member having a double row raceway groove and an outer member integrated with a flange, an inner ring, and a ball bearing).

  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. 8 is a cross-sectional view showing an example of a unitized wheel support bearing. This unit includes an inner member 1, an outer member 2, a ball 3, a cage 4, a first seal 5, a second seal 6, and a slinger 7, and the ball 3 rolls. Two rows of raceway grooves are provided.

  The inner member 1 has an inner ring 11 having two rows of raceway grooves, a hub 12 for fitting an axle, and a flange 13 for fixing the wheel side member 8. The inner member 1 includes a first member 1a and a second member 1b. The first member 1a is formed by integrally forming a portion of one inner ring raceway groove 11a of the inner ring 11, the hub 12 and the flange 13 (hub ring). The second member 1b is a ring-shaped member in which the other inner ring raceway groove 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 raceway grooves 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 support bearing unit so that it can withstand the severe use conditions in which water enters the 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 ball revolution direction is set within ± 15 °.

Further, in Patent Document 3 below, for the purpose of reducing the machining allowance of the raceway groove while improving the rolling life, the center of curvature of the raceway groove and the section of “fiber flow” are deposited. Are connected with a straight line, the tangent line of the raceway groove is drawn at the intersection with the raceway surface of this straight line, and the angle formed by the tangent line of the fiber flow at this intersection point and the tangent line of the raceway groove is defined as the “fiber flow angle”. It is described that this angle is 15 ° or less.
Japanese Patent No. 3123055 JP-A-8-42576 JP-A-2005-35513

  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 is a method different from patent documents 1-3, and it is a rolling bearing under the severe use conditions that water infiltrates inside. It is an object to prolong the life of the product.

In order to solve the above-mentioned problems, the present invention provides a wheel support bearing unit in which an outer ring and a flange having a double row raceway groove are integrally manufactured through a material forging process, and constitutes a wheel support bearing unit together with the inner ring and the ball. This is a bearing unit outer member that connects the tangent line at the ball contact point of the raceway groove in the cross section including the axis and the bend point of the forged streamline aligned with the direction of the bend of the track groove surface layer in the cross section . and the straight line indicating the direction of plastic flow curve is a line, or less angle of 90 ° 30 ° or more, when the length of the major axis of the contact ellipse between the raceway groove and the ball was 2A, in the cross section The plastic flow curve existing in the surface portion of the raceway groove provides a wheel support bearing unit outer member characterized by passing a position separated by 1.1 A or more from the contact point between the raceway groove and the ball. Further, a wheel support bearing unit comprising the outer member, an inner ring, and a ball is provided.

The present invention also includes an inner ring having a double row of raceway grooves, a hub for fitting an axle, and a flange for fixing a wheel side member, wherein at least one row of raceway grooves, the hub and the flange are integrally formed, and a material forging process A wheel support comprising an inner member manufactured through a forging process, an outer ring having a double row raceway groove and a flange for fixing a vehicle body side member, an outer member manufactured through a material forging process, and a ball. In the bearing unit for a bearing, at least one of the raceway groove of the inner ring and the raceway groove of the outer ring integrated with the flange is tangent to the ball contact point of the raceway groove in the cross section including the axis, and the raceway groove surface layer portion in the cross section The angle formed by the straight line indicating the direction of the plastic flow curve, which is a line connecting the bent points of the forged flow lines that are bent and arranged with directionality, is 30 ° or more and 90 ° or less. When the length of the long axis of the contact ellipse is 2A, the plastic flow curve existing on the surface of the raceway groove in the cross section passes a position 1.1A or more away from the contact point between the raceway groove and the ball. A wheel support bearing unit is provided.

  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 the materials. When the forging process is used, the more complex shapes of “double-row race ring” and “bearing member with a flange integrated with the race ring” (Near part) tends to appear on the surface of the raceway groove. The appearance of the core of the material on the surface of the raceway groove corrodes the cross section including the axis, and when observed with a stereomicroscope, a large number of forging lines are bent at the surface of the raceway groove and the directionality is changed. This can be confirmed by holding them in a line.

In the present invention, a line connecting bent points of forged flow lines that are bent and arranged with directionality is referred to as a “plastic flow curve”, and a line indicating the direction is referred to as a “straight line indicating the direction of the plastic flow curve”. . Here, since the core part of the material (part near the center) contains inclusions more easily than the peripheral part (the cleanliness of the steel is low), if the core part exists in the track groove surface layer part, Peeling from the starting point is likely to occur.

However, according to the present invention, even when the core portion of the material appears on the surface of the raceway groove (the range from the surface to the depth corresponding to the maximum shear stress depth), (1) “the direction of the plastic flow curve The angle (θ) between the straight line shown and the “tangent at the ball contact point of the raceway groove” is 30 ° to 90 °, and (2) the plastic flow curve is 1 from the contact point between the raceway groove and the ball. .. By satisfying the two conditions of passing through a position separated by 1 A or more (preferably 1.3 A or more), the presence rate of inclusions as a separation starting point is lower than when these conditions are not satisfied. Thus, the raceway grooves are less likely to be peeled off.
Specifically, since the inclusion that becomes the starting point of the separation exists along the forging line, by increasing the angle θ to 30 ° or more and 90 ° or less, compared to a case where it is smaller than this, The existence rate per area of the raceway groove of the inclusion becomes low.

  Further, as shown in FIG. 2, the plastic flow curve S satisfying the condition (2) exists outside the contact ellipse 25 in the surface layer portion of the raceway groove 21b, but does not satisfy the condition (2). The flow curve S ′ exists inside the contact ellipse 25 at the surface layer portion of the raceway groove 21b. In other words, “when the length of the long axis of the contact ellipse between the raceway groove and the ball is 2A, the plastic flow curve S passes through a position 1.1 A or more away from the contact point between the raceway groove and the ball”. Exists outside the contact ellipse 25 in the surface layer portion of the raceway groove 21b. And since a plastic flow curve is a line which shows the core part of a material with a high presence rate of inclusions, in the present invention, the plastic flow curve exists outside the contact ellipse so It is possible to reduce the presence rate of inclusions on the most loaded surface.

  In addition, when using a cylindrical material, the portion that is 40% of the radius from the center in the radial direction of the cylindrical material should be outside the contact ellipse between the raceway groove and the ball, or the carbon content of the material It is preferable that the sulfur content is 12 ppm or less and the sulfur content is 0.015% by mass or less from the viewpoint of reducing the presence rate of inclusions on the most loaded surface between the ball and the raceway groove.

According to the present invention, the material of the forging process the via the wheels produced supporting bearing unit outside the side member, the tangent of the ball contact point of the raceway groove in a cross section including the axis, raceway groove surface portion of the cross section The angle (θ) formed with a straight line indicating the direction of the plastic flow curve is 30 ° or more and 90 ° or less, and the plastic flow curve passes through a position separated by 1.1 A or more from the contact point between the raceway groove and the ball. by two conditions are satisfied that, in comparison with a case that does not meet these conditions, a longer wheel supporting bearing unit of life.

  According to the wheel support bearing unit of the present invention, at least one of the inner ring raceway groove and the outer ring raceway groove integrated with the flange, the tangent at the ball contact point of the raceway groove in the cross section including the axis line, and The angle (θ) formed with the straight line indicating the direction of the plastic flow curve of the track groove surface layer in the cross section is 30 ° or more and 90 ° or less, and the plastic flow curve is 1.1A or more from the contact point between the track groove and the ball. By satisfying the two conditions of passing through a distant position, it is possible to extend the life under severe use conditions in which water enters the interior, compared to the case where these conditions are not satisfied.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a cross-sectional view showing a bearing unit outer member of this embodiment. This sectional view shows only the left part of the section including the axis, and the right part is omitted.
The outer member 2 corresponds to the outer member 2 of the unitized wheel support bearing shown in FIG. 8, and includes an outer ring 21 having two rows of raceway grooves 21a and 21b, and a vehicle suspension system (vehicle body side member). The flange 22 in which the bolt hole 22a to be fixed is formed is integrally formed.
In this cross section, a plastic flow curve (a line connecting the bent points of the forging line T) S exists in the surface layer portion of the raceway groove 21b. A plastic flow curve does not exist in the surface layer portion of the groove (track groove) constituting the track groove 21a. Reference symbol P ₁ is a contact point between the raceway groove 21 a and the ball 3, and reference symbol P ₂ is a contact point between the raceway groove 21 b and the ball 3.

FIG. 2 is an enlarged view of a portion of the raceway groove 21b of FIG. FIG. 2 shows a straight line L _S indicating the direction of the plastic flow curve S, a tangent line L ₁ at the ball contact point P ₂ of the raceway groove 21b, and an angle θ formed by these lines. In this example, the angle θ is 82.5 °.
In FIG. 2, a contact ellipse 25 of the raceway groove 21b with the ball 3 is projected and displayed on the upper side of the raceway groove 21b. The center of the contact ellipse 25 is a contact point P ₂ between the raceway groove 21b and the ball 3, and a straight line C indicating this point and straight lines H ₁ and H ₂ indicating both ends of the major axis 25a of the contact ellipse 25 are displayed. ing. When the length of the long axis 25a is 2A, the distances between the straight line C and the straight lines H ₁ and H ₂ are A.

In this example, the intersection point P _s of the track grooves 21b of the plastic flow curve S, the distance K between the ball contact point P ₂ of the raceway groove 21b has become K ₁ = 1.89A. That is, the plastic flow curve S passes through a position separated from the contact point P ₂ between the raceway groove 21b and the ball 3 by 1.89A.
Therefore, the outer member 2 satisfies the two conditions (30 ° ≦ θ ≦ 90 °, K ≧ 1.1A) of the present invention.
Note that plastic flow curve S shown in FIG. 2 by the two-dot chain line 'is the intersection P _S of the raceway groove _21b' distance K ₂ between the ball contact point P ₂ of the raceway groove 21b is turned 0.74A Yes. That is, the plastic flow curve S ′ passes through a position separated from the contact point P ₂ between the raceway groove 21b and the ball 3 by 0.74A.

A method for manufacturing the outer member 2 of FIG. 1 will be described with reference to FIG.
First, as shown to Fig.3 (a), a column-shaped raw material is prepared and it crushes from the axial direction both sides of a cylinder by an upsetting process. As a result, the state shown in FIG. Next, in the forging process, as shown in FIG. 3C, the flange 22, the outer ring 21, and the portion 23 connecting the portions 210 between the two raceways are formed into an integrated shape. Next, the connecting portion 23 is removed by a piercing punch process to obtain the shape shown in FIG. Next, as shown in FIG. 3E, raceway grooves 21a and 21b are formed by cold rolling.

And the outer member 2 from which angle (theta) differs can be obtained by changing the position of the flange 22 and the position of the connection part 23 in an axial direction, and the diameter expansion rate by cold rolling shaping | molding. Further, by changing the diameter of the cylindrical material to be used, it is possible to obtain the outer member 2 having a different orbital plane passing position (point P _s ) of the plastic flow curve S.

  A bearing unit corresponding to the embodiment of the present invention is shown in FIG. This figure is a cross-sectional view including the axis Z. This bearing unit has a shape in which a flange 22 is integrated with an outer ring 21 of a double-row angular ball bearing, and includes two inner rings 10a and 10b each provided with one row of raceways 11a and 11b, and two rows of raceway grooves 21a, The outer member 21 is provided with an outer member 21 having a flange 22 integrated with an outer ring 21 provided with 21b, and a ball 3. The bearing unit has an inner diameter (d) of 25 mm, an outer diameter (D) of 63.5 mm, a width (B) of 44.5 mm, and an action point distance (K) of 51 mm.

Table 1 below shows the distance K and the angle θ between the ball contact point P ₂ of the raceway groove 21b of the outer member 2 and the point P _S (intersection of the raceway groove 21b of the plastic flow curve) for this bearing unit. The life of each value was examined. As an outer ring for the test bearing, an outer ring 20a having a shape shown in FIG. 5 was produced. In the outer ring 20, the flange 22 of the outer member 2 is removed to form a double row outer ring 21 shown in FIG. 4B, and then the outer ring 21 is divided into two equal parts in the axial direction (cut along the line H). Can be obtained.

  First, as shown in FIG. 3A, a columnar material made of SUJ2 having a diameter of 50 to 70 mm and an axial dimension of 70 mm was prepared. Next, using a 2500 ton press (manufactured by Kurimoto Iron Works), this material is placed between the upper and lower molds with the axial direction set to the vertical direction, and the axial dimension becomes 30 to 40 mm at 1150 to 1200 ° C. The upsetting process was performed by squeezing until the state shown in FIG.

Next, as shown in FIG.3 (c), the outer ring | wheel 21, the flange 22, and the part 23 which connected the part 210 between both raceway grooves were shape | molded by the forge process. Next, the connecting portion 23 was removed by a piercing punch process to obtain the shape shown in FIG. Next, as shown in FIG. 3E, cold rolling is performed to form the tracks 21a and 21b, the inner diameter N ₁ at both ends is set to 50 mm, and the inner diameter N ₂ at the middle is set to 41 mm. The outer member 2 was expanded to 66 mm, thereby forming the outer member 2.

Next, after removing the flange 22 by turning, the groove shapes of the raceway grooves 21a and 21b were adjusted by turning. Next, after induction hardening, a tempering treatment was performed at 180 ° C. for 2 hours to make the surface hardness HRC59. Next, each dimension including the groove shape of the raceway grooves 21a and 21b was made accurate by grinding.
In order to change the angle θ, the conditions of the forging process in FIG. 3C and the diameter expansion rate by cold rolling forming in FIG. Further, the raceway passage position (point P _s ) of the plastic flow curve S changes due to the difference in diameter of the cylindrical material used.

As a result, a double row outer ring 21 shown in FIG. 4B was obtained, and the outer ring 21 was divided into two equal parts (cut along the line H) in the axial direction by electric discharge machining. In this state, for each of the outer rings 20a divided in half, the cross section including the axis Z is corroded and observed with a stereomicroscope, the state of the streamline at the surface layer portion of the raceway groove is examined, and the plastic flow curve S is drawn. The angle θ and the distance K were measured. The results are also shown in Table 1 below.
When the actual outer member 2 is manufactured, the flange 22 is not removed after the shape shown in FIG. 3 (e), and the groove shapes of the raceway grooves 21a and 21b are adjusted by turning, and then induction hardening is performed. And tempering.

  As the ball 3 for the test bearing, a product made of SUJ2 and subjected to normal heat treatment was used, and the inner ring 10a was produced by the following method. First, a columnar material (diameter 50 mm × axial dimension 1 m) made of Sanyo Special Steel's high cleanliness SUJ2 steel was cut into 42 mm in the axial direction and then turned into an inner ring shape by turning. Next, after quenching by heating to 840 ° C. and cooling, tempering treatment was performed at 180 ° C. for 2 hours to make the surface hardness HRC61. Next, grinding was performed so that each dimension including the groove shape of the raceway groove 11a was an accurate dimension.

The life test of this test bearing was performed 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 10a. 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 (8820 N) applied from above the rotating shaft J.
In addition, the testing machine used in this test constantly measures the vibration generated in the test bearing with a vibrometer, and when the measured value of the vibrometer exceeds a certain value due to separation on the raceway surface of the outer ring 20a, the rotation is stopped. The time from the start of rotation to the stop is recorded. The time until the rotation stopped was defined as the life of the test bearing.

In addition, 10 bearings were prepared for each sample and tested, and the L10 life was examined. Then, by dividing the L10 life of No. 1-24 by the L10 life of No. 1 with θ = 0 and K = 1.1A, the “life ratio” is set to “1” as the L10 life of No. 1. " The results are also shown in Table 1 below. In Table 1, numerical values deviating from the configuration of the present invention are underlined. A case where neither θ nor K is underlined corresponds to an example of the present invention, and a case where either one is underlined corresponds to a comparative example.
The results are summarized in a graph (FIG. 6) showing the relationship between θ and the L10 life and a graph (FIG. 7) showing the relationship between “K / A” and the L10 life.

As can be seen from the graph of FIG. 6, when the angle θ of the outer member is 30 ° or more, the life ratio is 2.0 or more, whereas when it is less than 30 °, the life ratio is less than 1.5. there were. As can be seen from the graph of FIG. 7, the life ratio is 2.0 or more when “K / A” ≧ 1.1, whereas the life ratio is “K / A” ≦ 1.0. It was less than 1.5.
Therefore, the bearing unit corresponding to the embodiment of the present invention has a longer life under severe use conditions in which water enters the interior than the bearing unit corresponding to the comparative example.

It is sectional drawing which shows one Embodiment of the bearing unit outer member of this invention. It is the figure which expanded the part of the track groove 21b of FIG. It is a figure explaining the preparation methods of the bearing unit outside member of the present invention. It is sectional drawing which shows the bearing unit used as the basis of the test bearing produced in the Example. It is a figure explaining the life test done in the Example. It is the graph which put together the data of the life test done in the Example in the relationship between angle (theta) of an outer member, and L10 life. It is the graph which put together the data of the life test performed in the Example in the relationship between "K / A" of an outer member, and L10 life. It is sectional drawing which shows an example of the bearing unit for wheel support reduced in weight.

Explanation of symbols

1 Inner member 1a First member (hub wheel)
1b Second member 11b Inner ring raceway groove 11 Inner ring 12 Hub 13 Flange 2 Outer member 21 Outer ring 21a Raceway groove 21b Raceway groove 22a Bolt hole for fixing the suspension device (vehicle body side member) 22 Flange 25 Contact ellipse 25a Long axis of contact ellipse 3 ball 4 cage 5 first seal 6 second seal 7 slinger 8 wheel-side member Ls tangent raceway grooves in a straight line L ₁ contact point indicating the direction of plastic flow curve S plastic flow curve P ₁ contact point P ₂ Angle between contact point θ L ₁ and Ls

Claims (3)

The outer ring and the flange having the double row raceway grooves are manufactured integrally through a forging process of the material, and are a wheel support bearing unit outer member that constitutes a wheel support bearing unit together with the inner ring and the ball,
The direction of the plastic flow curve, which is the line connecting the tangent line at the ball contact point of the raceway groove in the cross section including the axis and the bending point of the forged flow line aligned with the direction of the bend of the track groove surface layer in the cross section The angle formed by the straight line indicating is 30 ° or more and 90 ° or less,
When the length of the long axis of the contact ellipse between the raceway groove and the ball is 2A, the plastic flow curve existing in the raceway groove surface layer portion in the cross section is 1.1 A or more from the contact point between the raceway groove and the ball. A wheel support bearing unit outer member characterized by passing through a distant position. A wheel support bearing unit comprising the outer member according to claim 1 , an inner ring and a ball . An inner ring having a double row raceway groove, a hub for fitting an axle, and a flange for fixing a wheel side member, and at least one row of the raceway groove, the hub and the flange are integrally manufactured through a material forging process. An inner member;
An outer member having a double row raceway groove and a flange for fixing the vehicle body side member are integrally formed, and an outer member manufactured through a forging process of the material ,
With the ball,
Te wheel supporting bearing unit odor with a
At least one of the inner ring raceway groove and the outer ring raceway groove integrated with the flange,
The direction of the plastic flow curve, which is the line connecting the tangent line at the ball contact point of the raceway groove in the cross section including the axis and the bending point of the forged flow line aligned with the direction of the bend of the track groove surface layer in the cross section The angle formed by the straight line indicating is 30 ° or more and 90 ° or less,
When the length of the long axis of the contact ellipse between the raceway groove and the ball is 2A, the plastic flow curve existing in the raceway groove surface layer portion in the cross section is 1.1 A or more from the contact point between the raceway groove and the ball. wheel supporting bearing unit, which comprises passing the distant position.

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