JP6173838B2 - Rolling elements and roller bearings - Google Patents

Description

  The present invention relates to a rolling element of a roller bearing and a roller bearing, for example, to a technique applied to a general industrial machine.

  Generally, a crowning is provided on a rolling surface of a rolling element made of a roller used in a roller bearing for the purpose of preventing bearing abnormality due to chamfered edge stress. However, in recent years, the load applied to the bearing tends to increase due to the downsizing and high performance of applications in which the bearing is used, and the amount of crowning drop is also increasing.

On the other hand, when the amount of drop of crowning increases, the inclination of the crowning tangent also increases, so that a corner is formed at the intersection of the crowning and the rolling element outer diameter straight portion. For this reason, the contact stress at the corners increases, and the bearing life may be reduced.
To solve this problem, as shown in FIG. 8, the corners are relaxed by a full crowning shape (Patent Document 1), and as shown in FIG. 9, the radius of curvature is increased toward the end face by a logarithmic curve shape (Patent Document). 2) and other measures are taken.

Japanese Utility Model Publication No. 4-95318 Japanese Patent No. 4429842

  However, in the above countermeasure, it is not clear how much crowning can be used to suppress the internal edge stress.

  An object of the present invention is to provide a rolling element and a roller bearing that can prevent a decrease in bearing life under heavy load conditions by clarifying the degree of corners that affect bearing life due to increased contact stress. It is to be.

The rolling element of the present invention has a roller shape, an end crowning portion is formed at the end of the outer roller rolling surface, and a portion of the roller rolling surface that is closer to the center than the end crowning portion has an outer diameter. In the rolling element used for roller bearings, it is a surface straight part or central crowning part,
In a cross section viewed along a plane including the roller-shaped roller axis, the roller includes a roller effective length Le that is an axial length of the roller rolling surface, and includes at least a part of the end crowning portion. Within an arbitrary range of 0.1 Le in the roller axial direction,
Arbitrary three points P1, P2, and P3 are taken out, and an angle θ formed by a straight line L1 connecting the points P1 and P2 and a straight line L2 connecting the points P1 and P3 is set to 179.7 ° or more. And

  In general, the outer diameter surface of the rolling element used in the roller bearing is provided with a crowning. However, if the amount of crowning drop at the chamfering position increases, The formed angle becomes smaller and an angle is generated at the intersection. Further, when the end crowning portion connects two arcs, if the radius of the first arc connected to the outer surface straight portion is increased, the first arc and the outer surface straight portion are formed. The angle can be increased. However, the angle formed by the first arc and the second arc is a small angle.

Therefore, in order to clarify the angle that affects the bearing life, the relationship between the angle and the rolling surface edge stress was examined.
Roller axial direction when the crowning width and the maximum drop amount (drop amount at the effective length position) are fixed, and the end crowning part shape is made, and each cylindrical roller is loaded under a specified condition. The surface pressure distribution was calculated. Then, an inversely proportional correlation was found between the angle of the corner on the roller rolling surface and the stress ratio. From this, it can be seen that the larger the angle of the corner portion, the smaller the generated stress and the less the influence on the bearing life. If the stress ratio exceeds α (α = 1.1, α times the maximum stress), there is a concern about the influence on the bearing life. The “stress ratio” is obtained by dividing the rolling surface edge stress value generated at the corner by the maximum stress value excluding edge stress (chamfer edge stress and rolling surface edge stress).

According to this configuration, any three points P1, P2, and P3 are taken out within an arbitrary range of 0.1 Le in the roller axial direction including at least a part of the end crowning portion in the region of the roller effective length Le, An angle θ formed by a straight line L1 connecting the points P1 and P2 and a straight line L2 connecting the points P1 and P3 is set to 179.7 ° or more. From the calculation results, if the angle θ of the corner is 179.7 ° or more, the stress ratio α is less than or equal to, so that it is possible to prevent a decrease in bearing life under heavy load conditions.
A point P1 forming an intersection of the outer diameter surface straight portion or the central crowning portion and the end crowning portion, an arbitrary point P2 on the outer diameter surface straight portion or the central crowning portion, and the end crowning portion You may take out arbitrary upper points P3.

The rolling element may be a cylindrical roller, a needle roller, a rod roller, or a tapered roller.
A roller bearing according to the present invention incorporates any of the rolling elements. By using the roller bearing in which any one of the rolling elements is incorporated, the internal edge stress can be suppressed and the bearing life can be prevented from being lowered. Therefore, the cost required for maintenance such as replacement of the bearing can be reduced.

In the rolling element design method of the present invention, a roller shape is formed, an end crowning portion is formed at an end of an outer roller rolling surface, and a portion of the roller rolling surface that is closer to the center than the end crowning portion. In the design method of the rolling element, the outer diameter surface straight part or the central crowning part is designed and the rolling element used for the roller bearing is designed.
In a cross section viewed along a plane including the roller-shaped roller axis, the roller includes a roller effective length Le that is an axial length of the roller rolling surface, and includes at least a part of the end crowning portion. Within an arbitrary range of 0.1 Le in the roller axial direction,
Arbitrary three points P1, P2, and P3 are taken out, and an angle θ formed by a straight line L1 connecting the points P1 and P2 and a straight line L2 connecting the points P1 and P3 is set to 179.7 ° or more. And

  According to this configuration, since the angle θ formed by the straight line L1 connecting the point P1 and the point P2 and the straight line L2 connecting the point P1 and the point P3 is 179.7 ° or more, the stress ratio α or less is obtained. A reduction in bearing life under heavy load conditions can be prevented.

  The rolling element of the present invention has a roller shape, an end crowning portion is formed at the end of the outer roller rolling surface, and a portion of the roller rolling surface that is closer to the center than the end crowning portion has an outer diameter. A roller that is a face straight portion or a central crowning portion, and is a roller body used in a roller bearing, and is a cross-section viewed along a plane including the roller-shaped roller shaft center and having an axial length of the roller rolling surface. Three arbitrary points P1, P2, and P3 are taken out within an arbitrary range of 0.1 Le in the roller axial direction including at least a part of the end crowning portion in the region of the effective length Le, and the points P1 and P2 Since the angle θ formed by the straight line L1 connecting the straight line L1 and the straight line L2 connecting the point P1 and the point P3 is 179.7 ° or more, the degree of the corner that affects the bearing life due to the increase in contact stress is clarified. Shaft under heavy load conditions It is possible to prevent a decrease in the service life.

It is a front view of a rolling element concerning a 1st embodiment of this invention. It is an expanded sectional view of the important section of the rolling element. It is a figure which shows the relationship between the angle in (phi) 12 mm x 14 mm, and internal edge stress. It is a figure which shows the relationship between the angle in (phi) 24 mm x 38 mm, and internal edge stress. It is an expanded sectional view of the important section of the rolling element concerning other embodiments of this invention. It is an expanded sectional view of the important section of the rolling element concerning other embodiments of this invention. It is sectional drawing of the roller bearing incorporating any rolling element of this invention. It is an expanded sectional view of the principal part of the rolling element of a prior art example. It is an expanded sectional view of the principal part of the rolling element of another conventional example.

  A rolling element according to a first embodiment of the present invention will be described with reference to FIGS. The rolling element of the embodiment is a “roller” used for a roller bearing, and the roller bearing is applied to, for example, a general industrial machine. However, the roller bearing may be applied to uses other than general industrial machines. In addition, the following description also includes the description about the design method of a rolling element.

  FIG. 1 is a front view of the roller 1 according to the embodiment. As shown in FIG. 1, in the roller 1 according to this embodiment, an outer roller rolling surface 1a is rolled to a raceway surface of inner and outer rings (not shown). The roller rolling surface 1a is an outer diameter straight portion 1aa having a central portion formed of a cylindrical surface, and end crowning portions 1ab are formed at both ends connected to the outer diameter straight portion 1aa. A chamfer 1c is provided between the roller rolling surface 1a and the roller end surfaces 1b on both axial sides.

  Generally, the outer diameter surface of the roller used in the roller bearing is provided with a crowning, but when the amount of crowning drop at the chamfering position increases, the outer diameter surface straight as shown in FIG. The angle θ formed by the portion 1aa and the end crowning portion 1ab is reduced, and an angle is generated at the intersection. Further, as shown in FIG. 5 described later, when the end crowning portion 1ab connects two arcs, if the radius R1 of the first arc connected to the outer diameter surface straight portion 1aa is increased, one of them is increased. The angle θ1 formed by the arc of the eye and the outer diameter surface straight portion 1aa can be increased. However, the angle θ2 formed by the first arc and the second arc connected to the arc becomes a small angle.

Therefore, in order to clarify the angle that affects the bearing life, the relationship between the angle and the rolling surface edge stress was examined.
First, in a plurality of cylindrical rollers of φ12 mm × 14 mm, a plurality of end crowning shapes having a fixed crowning width and a maximum drop amount (drop amount at an effective length position) are prepared, and a bearing is provided for each cylindrical roller. The surface pressure distribution in the roller axial direction when the load was applied under the condition of 30% of the dynamic load rating Cr and misalignment: 2/1000 was calculated.
The calculation results are shown in FIG. 3 represents the angle θ of the corner portion on the roller rolling surface, and the vertical axis in FIG. 3 represents the stress ratio. “Stress ratio” = (Rolling surface edge stress value generated at corner) ÷ {Maximum stress value excluding edge stress (chamfer edge stress and rolling surface edge stress)}

  FIG. 4 shows the calculation results when the surface pressure distribution in the roller axial direction is calculated with a cylindrical roller of φ24 mm × 38 mm under the same conditions as described above. As shown in FIGS. 3 and 4, in any of the rollers, an inversely proportional correlation was found between the angle of the corner portion on the roller rolling surface and the stress ratio. From this, it can be seen that the larger the angle of the corner portion, the smaller the generated stress and the less the influence on the bearing life. On the other hand, if the stress ratio exceeds 1.1 (1.1 times the maximum stress), the bearing life may be affected.

The reason for the stress ratio 1.1 will be described.
The dynamic equivalent load P when calculating the life is proportional to the 0.5th power of the stress. Therefore, the life is proportional to the -10/3 power of the dynamic equivalent load P. As a result, in the region where the microscopic edge stands, when the stress increases by 10%, (√1.1) ⁽ −10/3 ⁾ = 0.85, and the lifetime decreases by 15%.
The above calculation is the life of the microscopic region, and when considered as the bearing life, the axial division width and the number of rolling elements are included in the calculation formula. The decrease is different from the above calculation.

  From the calculation results of FIG. 3 and FIG. 4, the stress ratio is 1.1 or less if the angle θ of the corner is 179.7 ° or more for both model numbers. That is, as shown in FIG. 1 and FIG. 2, the end of the roller effective length Le, which is the axial length of the roller rolling surface 1 a, in a cross section obtained by cutting the roller 1 along a plane including the roller axis La. The points P1, P2, and P3 are taken out within an arbitrary range of 0.1 Le in the roller axis direction including at least a part of the portion crowning portion 1ab, and the straight line L1 that connects the points P1 and P2, and the points P1 and P3 The angle θ formed by the straight line L2 connecting the two points to 179.7 ° or more.

  If the angle θ of the corner portion is 179.7 ° or more, the stress ratio is 1.1 or less, so that it is possible to prevent a decrease in bearing life under heavy load conditions. The point P1 is a point forming the intersection of the outer diameter surface straight portion 1aa and the end crowning portion 1ab, the point P2 is an arbitrary point on the outer diameter surface straight portion 1aa, and the point P3 is It is an arbitrary point on the end crowning portion 1ab. The intersection P1 between the outer diameter surface straight portion 1aa and the end crowning portion 1ab is preferably rounded. However, stress concentration occurs even in this case, so the angle θ needs to be 179.7 ° or more.

The reason for 0.1Le will be described.
In order to discuss the microscopic stress concentration, it is necessary to narrow the range of the three points that define the angle.

The range of 3 points needs to be narrower than the above, but if it is too narrow, there are the following problems.
・ Roughness and undulation components are included when the roller is actually measured to determine the angle formed by three points.
-It is difficult to produce a difference in drop amount at three points when actually measured (considering a measurement error, a drop amount difference of about 1 μm is necessary).
From the above, it was considered that a range of 3 points is required to be at least 0.1 Le.

Another embodiment will be described.
In the following description, the same reference numerals are given to the portions corresponding to the matters described in the preceding forms in each embodiment, and the overlapping description is omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those described in advance unless otherwise specified. The same effect is obtained from the same configuration. Not only the combination of the parts specifically described in each embodiment, but also the embodiments can be partially combined as long as the combination does not hinder.

  As shown in FIG. 5, also for the roller 1 having a plurality of (two in this example) end crowning portions, the angles θ1 and θ2 of the corner portions are set to 179.7 ° or more, respectively. In the roller 1 of this embodiment, first and second end crowning portions 1ac and 1ad are sequentially connected to the end portion of the outer diameter surface straight portion 1aa. Further, for example, the curvature radius R2 of the second end crowning portion 1ad is set larger than the curvature radius R1 of the first end crowning portion 1ac. The point P1 is a point that forms an intersection between the outer diameter surface straight portion 1aa and the first end crowning portion 1ac. The point P3 is an arbitrary point on the first end crowning portion 1ac.

  Further, a point P4 forming an intersection of the first end crowning portion 1ac and the second end crowning portion 1ad and an arbitrary point P5 on the second end crowning portion 1ad are taken out. Similarly to the above-described embodiment, the angle θ1 formed by the straight line L1 connecting the points P1 and P2 and the straight line L2 connecting the points P1 and P3 is set to 179.7 ° or more. Furthermore, since the angle θ2 formed by the straight line L3 connecting the point 4 and the point P3 and the straight line L4 connecting the point P4 and the point P5 is 179.7 ° or more, the stress ratio becomes 1.1 or less. It is possible to prevent a decrease in life.

In each said embodiment, although the center side part from the edge part crowning part in a roller rolling surface is made into the outer-diameter surface straight part, it is not limited to this example. For example, as shown in FIG. 6, the central portion of the roller rolling surface 1a is a central crowning portion 1ae having a radius of curvature R3, and an end crowning portion 1ab having a radius of curvature R4 is formed in the central crowning portion 1ae. It is good also as a structure which connects. Also in this case, by setting the angle θ3 formed by the straight line L1 and the straight line L2 to 179.7 ° or more, the stress ratio becomes 1.1 or less, so that a reduction in bearing life can be prevented.
The present invention may be applied to a crowning composed of a single line or a plurality of straight lines or arcs, and does not depend on the crowning shape.

FIG. 7 is a cross-sectional view of a roller bearing incorporating the rolling element according to any of the above embodiments.
The roller bearing includes an inner ring 2, an outer ring 3, a plurality of rollers 1 interposed between the raceway surfaces 2a and 3a of the inner and outer rings 2 and 3, and a cage that holds the rollers 1 at regular intervals in the circumferential direction. 4. By incorporating any one of the above rolling elements into the roller bearing, the internal edge stress can be suppressed and the bearing life can be prevented from decreasing, so that the cost required for maintenance such as replacement of the bearing can be reduced.
The rollers may be needle rollers, rod rollers, or tapered rollers.
The three points P1, P2, and P3 may be arbitrarily set within the range of 0.1 Le in the roller axial direction in the region of the roller effective length Le. For example, three points P1, P2, and P3 may be set on the outer diameter surface straight portion. In that case, the angle θ formed by the three points is 180 °, which satisfies the requirement of 179.7 ° or more.

DESCRIPTION OF SYMBOLS 1 ... Roller 1a ... Roller rolling surface 1aa ... Outer diameter surface straight part 1ab ... End part crowning part 1ae ... Central crowning part

Claims (5)

An end crowning portion is formed at the end of the outer peripheral roller rolling surface, and a portion on the center side of the roller rolling surface with respect to the end crowning portion is an outer diameter straight portion or a central crowning portion. In rolling elements used in roller bearings,
In a cross section viewed along a plane including the roller-shaped roller axis, the roller includes a roller effective length Le that is an axial length of the roller rolling surface, and includes at least a part of the end crowning portion. Within an arbitrary range of 0.1 Le in the roller axial direction,
Arbitrary three points P1, P2, and P3 are taken out, and an angle θ formed by a straight line L1 connecting the points P1 and P2 and a straight line L2 connecting the points P1 and P3 is set to 179.7 ° or more. Rolling element.   2. The rolling element according to claim 1, wherein a point P <b> 1 that forms an intersection of the outer diameter surface straight portion or the central crowning portion and the end crowning portion, and an arbitrary point on the outer diameter surface straight portion or the central crowning portion. A rolling element that extracts a point P2 and an arbitrary point P3 on the end crowning portion.   The rolling element according to claim 1 or 2, wherein the rolling element is a cylindrical roller, a needle roller, a bar roller, or a tapered roller.   A roller bearing incorporating the rolling element according to any one of claims 1 to 3. An end crowning portion is formed at the end of the outer peripheral roller rolling surface, and a portion on the center side of the roller rolling surface with respect to the end crowning portion is an outer diameter straight portion or a central crowning portion. In the rolling element design method for designing rolling elements used in roller bearings,
In a cross section viewed along a plane including the roller-shaped roller axis, the roller includes a roller effective length Le that is an axial length of the roller rolling surface, and includes at least a part of the end crowning portion. Within an arbitrary range of 0.1 Le in the roller axial direction,
Arbitrary three points P1, P2, and P3 are taken out, and an angle θ formed by a straight line L1 connecting the points P1 and P2 and a straight line L2 connecting the points P1 and P3 is set to 179.7 ° or more. The rolling element design method.

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