JP4661409B2 - Bearing unit outer member, bearing unit - Google Patents

Description

  The present invention relates to 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.

  Patent Document 1 below discloses extending the life of a rolling bearing by setting the direction of the metal flow (forged streamline) of the inner ring and outer ring, which change depending on the conditions of the forging process, in a specific range. . Specifically, the maximum value of the angle of the metal flow with respect to the rotation axis in the cross section including the rotation axis is set to 10 ° or more and 50 ° or less. In order to make the metal flow angle within the above range, the material is hot forged in the radial direction, drilled, and then subjected to a step of expanding the diameter of the hole by cold rolling.

Patent Document 2 is configured such that a metal flow along the disk surface (a metal flow whose angle with respect to a tangent to the traction surface is 30 ° or less) exists on the traction surface of the input and output disks of the toroidal type continuously variable transmission. By doing so, it is described that the life is extended.
JP-A-8-42576 JP-A-11-190408

However, the techniques described in Patent Documents 1 and 2 are applied to an outer member in which an outer ring and a flange having a double-row track are integrated, an inner ring, and a bearing unit including a rolling element. However, there is a problem that a long life cannot be obtained under severe use conditions such as water entering inside.
INDUSTRIAL APPLICABILITY The present invention is used in a bearing unit including an outer member having a double row raceway and an outer ring integrated with a flange, an inner ring, and a rolling element under severe conditions such as water entering inside. It is an object to obtain a long life even in the case of failure.

In order to solve the foregoing problems, the present invention is the outer ring and the flange integrally with the trajectory of double row, a bearing unit outer member manufactured through the material of the forging step, have you to a cross section including the axis, It is a line connecting the vertices of the extremely bent forging line, and the plastic flow curve indicating the core of the material is present at a depth of 100 μm or more from the raceway surface, at the rolling element contact point of the raceway groove in the cross section. And an angle formed by the straight line indicating the plastic flow, which is a line indicating the direction of the plastic flow curve in the cross section , is 0 ° or more and 50 ° or less. . A bearing unit comprising the outer member, an inner ring, and rolling elements is provided.

Also, the inner ring having a raceway of the double row, hub fitted into the axle, and a flange for fixing a wheel-side member, at least one row of track and the hub and the flange are manufactured through integral to, material of the forging process A wheel support bearing unit comprising: an inner member, an outer ring having a double-row raceway, and a flange for fixing a vehicle body side member, and an outer member manufactured through a material forging process; and a rolling element. In addition, at least one of the inner ring raceway groove and the outer ring raceway groove integrated with the flange has a contact angle between the rolling element and the raceway groove in a cross section including the axis of −5 ° to +10 of the contact angle at the initial contact point. The plastic flow in the cross section exists at a depth of 100 μm or more from the raceway surface within the range of °, the tangent line at the contact point of the raceway groove in the cross section, and the straight line indicating the plastic flow in the cross section Angle of, Ru include those characterized in that 50 ° or less 0 ° or more.
According to this wheel support bearing unit, the contact angle between the rolling element and the raceway groove in the cross section including the axis is at the initial contact point for at least one of the raceway groove of the inner ring and the raceway groove of the outer ring integrated with the flange. In the range of −5 ° to + 10 ° of the contact angle, the position of the plastic flow indicating the core of the material is set to a depth of 100 μm or more from the raceway surface, and at the rolling element contact point of the raceway groove in the cross section. And the straight line indicating the plastic flow of the surface portion of the raceway groove in the cross section, the angle between 0 ° and 50 ° is less than the case where these conditions are not satisfied. It is possible to extend the life under severe use conditions such as infiltration.

  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. If 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 means that when the cross section including the axis is corroded and observed with a stereomicroscope, a large number of forged lines are extremely bent at the surface of the raceway groove and the directionality is changed. This can be confirmed by holding them in a line.

An example of the bearing unit outer member in this state is shown in FIG. 2 is a forged stream line, and FIG. 2B is an enlarged view of a portion A in FIG.
In the present invention, a line connecting the vertices of the extremely bent forging line _T is referred to as “plastic flow curve L _T ”, and a line indicating the direction thereof is referred to as “straight line L _S indicating plastic flow”. Here, since the core part (part near the center) of the material is more likely to have non-metallic inclusions (less clean) than the peripheral part, if the core part is present on the surface of the raceway groove, Peeling from the starting point is likely to occur.

On the other hand, according to the present invention, the position of the plastic flow indicating the core portion of the material is set to a depth of 100 μm or more from the raceway surface (d ≧ 100 μm in FIG. 2), and the raceway groove in the cross section including the axis line When the angle θ formed by the tangent L ₀ at the rolling element contact point P and the straight line L _S indicating the plastic flow in the cross section is not less than 0 ° and not more than 50 °, these conditions are not satisfied. In comparison, separation from the inclusions in the raceway grooves is less likely to occur. Further, it is preferable that the plastic flow is present at a position deeper than the depth corresponding to the maximum shear stress depth (2% of the rolling element diameter) from the raceway surface.

Further, in the case of a wheel support bearing unit, these conditions are as shown in FIG. 3, in which the contact angle between the rolling element 3 and the raceway groove 21b in the cross section is the contact angle (α) at the initial contact point (P ₀ ). ) In the range of −5 ° to + 10 °. The reason is that the contact angle changes due to the preload applied after assembly, and the contact angle increases due to the lateral G applied when the vehicle turns. FIG. 3A shows an initial contact point (a contact point between the raceway groove 21b and the rolling element 3 before applying the preload) P ₀ , and FIG. 3B shows a value at which the contact angle is at the initial contact point. A range A (range of contact points P _{1 to} P ₂ ) of (α) from −5 ° to + 10 ° is shown.

When the core portion of the material does not exist on the surface layer portion of the raceway groove (when d> 500 μm), there is no problem even if the angle θ exceeds 50 °, so the upper limit value of d is 500 μm.
Also, the bearing unit outer member outer ring and flange are integrated with the trajectory of the double row, in the method of manufacturing through the material of the forging process, the depth plastic flow from the raceway surface 100μm or more in a cross section including the axis The raceway groove is formed so that an angle formed between a tangent line at the contact point of the raceway groove in the cross section and a straight line indicating the plastic flow in the cross section is 0 ° or more and 50 ° or less. method of manufacturing a bearing unit outer member, characterized in that the cold rolling process before heat treatment prior to finish grinding Ru also listed.

According to this method, in a state before the heat treatment of the finish grinding before, as shown in FIG. 4 (a), the core portion in a state (material plastic flow curve L _T extends toward the raceway groove 21A orbit in the case of state) are emerging in the groove 21A, by expanding the diameter by cold rolling process the raceway groove 21A, as shown in FIG. 4 (b), the plastic flow curve L _T is track groove 21A curved It can be made to extend along. As a result, the angle θ formed by the tangent L ₀ at the rolling element contact point P of the raceway groove 21A and the straight line L _S indicating the plastic flow can be set to 0 ° or more and 50 ° or less.

  According to the present invention, the position of the plastic flow indicating the core portion of the material is set to a depth of 100 μm or more from the raceway surface, and the tangent line at the contact point of the raceway groove in the cross section including the axis line, By making the angle between the straight line indicating the plastic flow and 0 ° or more and 50 ° or less, the outer ring and the flange having the double-row track are integrated as compared with the case where these conditions are not satisfied. Separation starting from inclusions is unlikely to occur in the raceway grooves of the outer member.

Therefore, a long life can be obtained when the outer member, the inner ring, and the bearing unit including the rolling element are used under severe conditions such as water entering the inside .

Hereinafter, embodiments of the present invention will be described.
The bearing unit of this embodiment 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 raceways 21a and 21b. The outer ring 21 is provided with an outer member 2 in which a flange 22 is integrated, and a ball 3. The bearing unit has an inner diameter (d) of 38 mm, an outer diameter (D) of 73 mm, a width (B) of 40 mm, and an action point distance (K) of 65 mm. The diameter of the ball 3 is 11.1 mm.

In order to perform the life test of this bearing unit by the method shown in FIG. 6, the inner ring 10a and the outer ring 20a of the test bearing shown in FIG. 6 were produced by the following method.
The inner ring 10a was produced by the method shown in FIG.
First, as shown to Fig.7 (a), the column-shaped raw material (diameter 35mm x axial direction dimension 40mm) made from the high cleanliness SUJ2 steel of Sanyo special steel was prepared. Next, using a 2500 ton press (manufactured by Kurimoto Iron Works), place this material between the upper and lower molds with the axial direction up and down and press at 1100 to 1200 ° C. until the axial dimension is 27 mm. By crushing, an upsetting process was performed to obtain a state shown in FIG.

Next, as shown in FIG. 7C, the inner ring 10a was formed into a shape in which one end in the axial direction was closed by a forging process. Next, the closed portion 13 was removed by a piercing punch process to obtain the shape shown in FIG.
Next, after quenching by heating to 840 ° C. for 1 hour and cooling, a 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 track 11a was an accurate dimension.

The manufacturing method of the outer ring 20a is as follows. First, the outer member 2 of FIG. 5 is produced by the method shown in FIG.
That is, as shown in FIG. 8A, a columnar material made of S53CG having a diameter of 50 mm and an axial dimension of 80 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 is 45 to 47 mm at 1100 to 1200 ° C. The upsetting process was performed by squeezing until the state shown in FIG. Up to this step, all the samples are performed under the same conditions. By changing the following forging process and cold rolling conditions for each sample, the flow of the forging line is changed, and the angle θ and the distance d are changed. I let you.

Next, as shown in FIG. 8 (c), the flange 22, the outer ring 21, and the portion 23 connecting the portions 210 between the two tracks were formed into an integrated shape by a forging process. Next, the connecting portion 23 was removed by a piercing punch process to obtain the shape shown in FIG.
Next, after removing the flange 22 by turning, the groove shapes of the tracks 21a and 21b were adjusted by turning. Next, after subjecting some samples to cold rolling, other samples were subjected to induction hardening without performing cold rolling. Next, 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 tracks 21a and 21b was made accurate by grinding. As a result, a double row outer ring 21 shown in FIG. 9 was obtained.

Next, the double-row outer ring 21 shown in FIG. 9 was divided into two equal parts (cut along line H) in the axial direction by electric discharge machining. The portion on the raceway 21a side is the outer ring 20a of the test bearing. Note that when the actual outer member 2 is manufactured, the flange 22 is not removed after the shape shown in FIG. After adjusting the groove shapes of the tracks 21a and 21b, induction hardening and tempering treatment is performed.

The obtained inner ring 10a and outer ring 20a were cut along a plane including the axis Z to expose a cross section including the axis Z. This cross section was first corroded with a saturated picric acid aqueous solution, then further corroded with a liquid obtained by mixing a small amount of ferric chloride in a saturated picric acid aqueous solution, and then the cross section was observed with a stereomicroscope. Based on this micrograph, draw a metal flows T appearing in the cross section of the inner ring 10a and the outer ring 20a, painted plastic flow curve L _T on the basis of the grain flow T.

As a result, the inner ring 10a, the plastic flow curves L _T exists in the vicinity of the thickness direction center, the raceway grooves 11a to a depth of 500μm were not present.
The outer ring 20a, so plastic flow curve L _T to the vicinity of the surface layer portion of the raceway groove 21a is present, as shown in FIG. 4 (b), the "plastic flow is a line indicating the direction of plastic flow curve L _T The straight line L _S "and the tangent line L ₀ at the rolling element contact point P of the raceway groove 21a (21A) are drawn, and the angle θ between the straight line L _S indicating the plastic flow and the tangent line L ₀ is measured. Further, as the existence depth d of the plastic flow, the distance between the rolling element contact point P of the raceway groove 21a (21A) and the intersection point Q between the normal H of the point P and the straight line L _S was measured. The results are shown in Table 1 below.

Using one kind of inner ring 10a thus obtained, 35 kinds of outer rings 20a having different θ and d as shown in Table 1, and one kind of ball 3 made of SUJ2 and subjected to normal heat treatment, Ten test bearings shown in FIG. 6 were each assembled with sample Nos. 1-35.
In the test method shown in FIG. 6, first, the test bearing is placed in the container Y with the rotating 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 test machine used in this test constantly measures the vibration generated in the test bearing with a vibration meter, and when the measured value of the vibration meter exceeds a certain value due to the separation in the raceway groove 21a of the outer ring 20a, the rotation is stopped. At the same time, the time from the start to the end of rotation is recorded. The time until the rotation stop was examined for the life of the test bearing and the L ₁₀ life. Furthermore, each sample of the L ₁₀ life was divided by No. 2 of L ₁₀ life was calculated to "L ₁₀ life ratio". The results are also shown in Table 1 below.

Further, by using those d ≧ 100 [mu] m among the obtained data are summarized in the relationship between the angle θ and the L ₁₀ life ratio of the outer ring 20a. This graph is shown in FIG. Furthermore, using those 0 ≦ θ ≦ 50 ° of the obtained data, the distance d (the depth from the raceway surface of the plastic flow) of the outer ring 20a and are summarized in the relationship between the L ₁₀ life. This graph is shown in FIG.

As can be seen from the graphs in Table 1 and FIG. 10, when the outer ring distance d is 100 μm or more, the outer ring angle θ is 0 to 50 °, and the life is 2.2 to 8.2 times that of No. 2. However, when the angle θ of the outer ring is 55 ° or more, the life is 0.9 to 1.1 times that of No. 2.
As can be seen from the graphs of Table 1 and FIG. 11, when the outer ring angle θ is 0 to 50 °, the outer ring distance d is 100 μm or more, and the life is 2.2 to 8.2 times that of No. 2. Although the outer ring distance d is 90 μm or less, the lifetime is 0.5 to 1.1 times that of No. 2.
Further, it can be seen from the graph of FIG. 11 that when the distance d is equal to or greater than 100 μm and the distance d is the same, the life can be extended as the angle θ decreases.

It is sectional drawing which shows an example of the bearing unit for wheel support reduced in size and weight. It is sectional drawing explaining the depth from the track surface of a plastic flow curve, the line which shows a plastic flow, and a plastic flow. It is a figure explaining the range of the contact angle which makes the depth from the track surface of a plastic flow 100 micrometers or more and makes angle (theta) 0 degrees or more and 50 degrees or less. It is sectional drawing explaining the effect | action and angle (theta) by a cold rolling process. It is sectional drawing which shows the bearing unit of embodiment. It is a figure explaining the life test performed in embodiment. It is a figure explaining the production method of the inner ring | wheel of the bearing unit employ | adopted by embodiment. It is a figure explaining the production methods of the outer member of the bearing unit employ | adopted by embodiment. It is sectional drawing which shows the state which removed the flange from the outer side member of the bearing unit of FIG. The data of life tests conducted in the embodiment (d ≧ 100 [mu] m), is a graph summarizing the relationship between the angle θ and the L ₁₀ life ratio of the outer ring (outer member). The data of life tests conducted in embodiments (0 ≦ θ ≦ 50 °) , is a graph summarizing the relationship of the outer ring depth from the raceway surface of the plastic flow of the (outer member) (d) and the L ₁₀ life .

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 Ls Straight line indicating plastic flow L ₀ Tangent line of raceway groove at contact point T Forging line L _T plastic flow curve P Initial contact point P ₀ Contact point P ₁ Contact point P ₂ Contact point θ Angle between tangent L ₀ and straight line Ls indicating plastic flow

Claims (2)

An outer ring and a flange having a double row raceway are integrally formed through a forging process of a material, and are bearing unit outer members.
And have you to a cross section including the axis, a line connecting the vertices of extreme bent grain flows, plastic flow curve showing the core portion of the material is present from the raceway surface to a depth of more than 100 [mu] m, in the cross-section An angle formed by a tangent line at a contact point of the raceway groove with a rolling element and a straight line indicating a plastic flow, which is a line indicating the direction of the plastic flow curve in the cross section , is 0 ° or more and 50 ° or less. Bearing unit outer member to be used. A bearing unit comprising the outer member according to claim 1, an inner ring, and rolling elements .

Images