Non-elliptical contact profile for roller bearings

Abstract

A roller bearing comprises: an inner race; an outer race; and a roller arranged between and in contact with the inner race and the outer race. The bearing has a flange (31, 131) on the inner race at one axial end and a flange (21, 121) on the outer race at the opposite axial end. One of the flanges and / or the end of the roller comprises at least one main section (53, 153) in the middle of two additional sections (52, 152; 54, 154). The main section merges tangentially with the two additional sections and has a first curvature that is different from the corresponding curvatures of the two additional sections. A non-elliptical contact footprint can be obtained by a compound profile at the contact location between the roller end and the mating flange surface.

Description

[0001] Related Applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 490,392, filed April 26, 2017, and U.S. Provisional Patent Application No. 62 / 519,464, filed June 14, 2017, the contents of both applications are hereby incorporated herein by reference. Technical Field

[0003] The present invention relates to bearings, and more particularly to roller bearings. Background Art

[0004] Radial cylindrical bearings are mainly used to support a large amount of radial loads. However, modern applications require that such bearings also support a certain amount of axial loads. In these cases, the roller ends and mating surfaces on the inner and outer flanges of the bearing rings must be properly designed to produce a desirable contact footprint to control contact stress and friction. Prior art designs (such as those disclosed in US 6,530,693 B1 and US 6,997,616 B2) propose molded roller ends that result in an elliptical contact portion or footprint between the roller ends and the flange surface. The shape of the contact ellipse is determined by the main radius at the center of the contact and is independent of the contact load. The size of the contact ellipse increases with increasing contact load. To prevent the contact footprint from having an undesirable interaction (e.g., truncation) with the edge of the flange surface generated by the undercut and the outer diameter or inner diameter surface geometry (which results in severe edge stress), the contact ellipse is designed so that its semi-major axis is located in the circumferential direction. However, under light loads, when the perimeter of the contact ellipse is away from the edge of the flange face, the shape of the contact footprint ellipse may not be the most desirable for controlling contact stresses. Summary of the invention

[0005] A first aspect of the invention provides a profile at a roller end and / or mating flange surface that produces a non-elliptical footprint at the contact between the roller end and the mating flange surface. In another aspect, the invention provides a profile on a roller end face and / or flange surface that includes multiple radii of curvature. Yet another aspect of the invention is to produce a profile that includes a multi-segment profile portion on a roller end and / or flange surface, wherein each profile segment is tangent to at least one of the adjacent profile segments. Yet another aspect of the invention is to produce a profile on a roller end face and / or flange surface that includes a segment of a logarithmic profile in the contact portion.

[0006] More specifically, in one embodiment, the present invention provides a roller bearing, comprising: an inner race; an outer race; and a roller, which is arranged between and in contact with the inner race and the outer race. The bearing has a flange on the inner race at one axial end and a flange on the outer race at the opposite axial end. The roller has a formed roller end, which includes at least one main section in the middle of two additional sections. The main section blends tangentially with the two additional sections, and the main section has a first curvature that is different from the corresponding curvatures of the two additional sections.

[0007] In another embodiment, the present invention provides a roller bearing, comprising: an inner race; an outer race; and a roller, which is arranged between and in contact with the inner race and the outer race. The bearing has a flange on the inner race at one axial end and a flange on the outer race at the opposite axial end. At least one of the flanges is formed to include at least one main section in the middle of two additional sections. The main section is tangentially fused to the two additional sections, and the main section has a first curvature that is different from the corresponding curvatures of the two additional sections.

[0008] In yet another embodiment, the present invention provides a roller bearing comprising: an inner race; an outer race; and a roller disposed between and in contact with the inner race and the outer race. The bearing has a flange on the inner race at one axial end and a flange on the outer race at the opposite axial end. At least one of the flanges or the end of the roller has a profile comprising a main section having a reference point C defining a contact position between the roller and the flange, the main section having a continuously varying radius of curvature that decreases as the distance from the reference point C increases. In many embodiments, the reference point C may be at the center of the main section, but this need not be the case.

[0009] Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a partially cutaway perspective view of a rolling element bearing embodying the present invention.

[0011] Figure 2 yes Figure 1 A three-dimensional view of the rolling elements of a rolling element bearing.

[0012] Figure 3 yes Figure 2 Schematic diagram of a rolling element illustrating a portion of the curved end face profile.

[0013] Figure 4 Schematically illustrates Figure 3 The contact footprint between the rolling element and the mating flange surface of the rolling element bearing.

[0014] Figure 5 An alternative embodiment of the invention is schematically depicted, wherein the roller end profile is spherical and the mating flange surface has at least three profile segments.

[0015] Figure 6 Another alternative embodiment of the invention is schematically depicted, wherein the roller end profile is conical and the mating flange surface has at least three profile segments.

[0016] Figure 7 is a partially cutaway perspective view of another rolling element bearing embodying the present invention.

[0017] Figure 8 yes Figure 7 A three-dimensional view of the rolling elements of a rolling element bearing.

[0018] Fig. 9 yes Figure 8 Schematic diagram of a rolling element illustrating a portion of the curved end face profile.

[0019] Fig.10 yes Fig. 9 An enlarged partial view of a schematic diagram of .

[0020] Fig.11 is a graphical view that shows Fig. 9 The curved end face is a portion of the curved portion of the profile.

[0021] Fig.12 Schematically illustrates Fig. 9 The contact footprint between the rolling element and the mating flange surface of the rolling element bearing.

[0022] Fig.13 Another alternative embodiment of the invention is schematically depicted, wherein the roller end profile is conical and the mating flange surface has at least three profile segments, wherein at least one segment is part of a logarithmic curve. DETAILED DESCRIPTION

[0023] Before any embodiments of the invention are explained in detail, it will be understood that the invention is not limited in its application to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways.

[0024] refer to Figure 1The roller bearing or rolling element bearing 10 of the present invention comprises: an outer ring 20; an inner ring 30; and a set of rollers 40 arranged between and in rolling contact with the outer ring 20 and the inner ring 30. Although the illustrated embodiment shows a cylindrical roller bearing (with cylindrical rollers), the present invention can also be applied to tapered roller bearings, spherical roller bearings and possibly needle roller bearings. The outer ring 20 includes at least one radially inwardly extending flange 21 at one end of a raceway 22 defined on the outer ring 20. In the illustrated embodiment, the outer ring 20 includes two radially inwardly extending flanges 21. Each flange 21 includes a flange surface 23 facing axially inwardly toward the raceway 22.

[0025] The inner ring 30 includes at least one radially outwardly extending flange 31 at one axial end of a raceway 32 defined on the inner ring 30. The flange 31 includes a flange surface 33 facing the raceway 32 axially inwardly.

[0026] Each roller 40 has two end faces 41a and 41b and an outer diameter surface 46 that engages and rolls on raceways 22, 32. The end faces 41a, 41b can be made substantially symmetrical about a central radial plane of the roller 40 (a plane perpendicular to the roller axis), but this need not be the case.

[0027] refer to Figure 2 and Figure 3 Each end face 41a, 41b comprises a curved profile 45 defined by a rotation axis 47 passing through the roller 40 (see Figure 3 ). The curved profile 45 is formed by a plurality of segments 51, 52, 53, 54 and 55, such as in Figure 2 and Figure 3 It will be understood that Figure 3 4, for simplicity and clarity, only the lower right corner of the roller 40 is illustrated as having a profile 45, but at least the upper right corner of the end face 41b will have the same profile mirrored about the axis 47. Likewise, the end face 41a can include the same profile 45 mirrored about the axial center point of the roller 40. Each profile segment 51, 52, 53, 54 and 55 is defined by a mathematically defined curvature. The profile segment 51 is a portion of a straight line with a radius of curvature of infinity. The profile segments 52 to 55 are respectively a portion of a straight line with a radius of curvature of R A2 , R B2 , R C2 and R D2 The centers of these curvatures are located at O A2 , O B2 , O C2 and O D2. Profile segments 51 and 52 merge at tangent point A. Profile segments 52 and 53 merge at tangent point B. Profile segments 53 and 54 merge at tangent point C. Profile segments 54 and 55 merge at tangent point D. Profile segment 55 merges with the outer diameter surface 46 of roller 40 at point E. Unlike the other fusion points (A to D), point E may or may not be a tangent point. Profile segment 55 is optional. Without using profile segment 55, profile segment 54 can merge directly with the outer diameter surface 46 at a non-tangent point.

[0028] The positions of the profile sections 51, 52, 53, 54 and 55 of the roller 40 are designed so that when the roller 40 is assembled in the bearing 10 under thrust load and arranged in operation, the contact between the roller end 41a or 41b and the mating flange surface 23 and / or 33 is at point 61 (see Figures 4 to 6 ) starts at . Figure 4 As the contact load increases, a contact patch or footprint 62 is formed. min When the load threshold is relatively low before, the contact footprint 62 remains elliptical or circular. The ellipse or circle corresponds to a curvature radius R B2 As the load continues to increase, the contact footprint 62 begins to deviate from its original elliptical or circular shape. Specifically, the contact footprint 62 is truncated at the upper side by the segment 52 (AB) and at the lower side by the segment 54 (CD), and takes on a non-elliptical or non-oval shape, as represented in the area between 65 and 62. As the load increases further, the aspect ratio (length to width ratio) of the contact footprint 62 increases and at a predetermined design load Q max Under load Q, the contact properties such as flange torque and / or wear rate are achieved to a predetermined or desired value. max Below, the contact footprint is represented by 65 and the shape is non-elliptical.

[0029] In order to achieve the above-mentioned non-elliptical shape during contact, the center of curvature O of the contour segment 53 is B2 The roller axis 47 may be offset or positioned a distance from the roller axis 47 that is within (less than) the distance DS1 (see Figure 3 Similarly, the center of curvature of other profile segments may be offset from or positioned at a distance from roller axis 47 that is outside or exceeds (greater than) DS2 (see Figure 3 ). DS1 <0.5R, and DS2 >0.5R, where R is the radius of the roller body.

[0030] It should be noted that in order to achieve the non-elliptical contact footprint mentioned above, the contour segments 52 and 54 adjacent to the main contour segment 53 do not have to be parts of a circle. They can be, for example, parts of an exponential curve and / or a logarithmic curve. In some other embodiments (such as the following with respect to Figures 7 to 13 As discussed), the main contour segment 53 can be part of an exponential curve and / or a logarithmic curve.

[0031] The above-mentioned multi-radius profile or multi-segment profile on the roller end face can also or alternatively be produced on the flange faces 23 and / or 33 . Figure 5 and Figure 6 Although the flange surface 33 is shown in the figure, the flange surface 23 may also be shown.

[0032] Figure 5 A portion of a roller bearing having a roller 40' with a spherical roller end 41' is depicted. The profile of the roller end 41' consists of a single radius curve (R B2 ), which has a center of curvature at the axis of rotation 47 of the roller. During operation, the roller 40' contacts the inner ring 30' of the bearing. The contact occurs at a mating flange surface 33' having at least three profile segments 34, 35 and 36. Each profile segment 34, 35 and 36 can be mathematically described by a radius of curvature. The radius of curvature (R B1 ) can be infinite, that is, the second profile segment is a straight line. The first profile segment 34 is designed to be tangent to the second profile segment 35. The second profile segment 35 is in turn tangent to the third profile segment 36. The first profile segment 34 merges into the outer diameter 37 of the flange 31' at a non-tangent point. The third profile segment 36 merges into the undercut 38 of the flange at another non-tangent point. When the roller 40' contacts the mating flange 31' at the contact point 61', an elliptical or circular contact footprint is initially formed. This elliptical or circular contact footprint corresponds to the radius of curvature R of the roller end 41'. B2 As the load increases, the ellipse is truncated at the upper side by the profile section 34 ″ and at the lower side by the profile section 36 ″. As the contact load increases, the aspect ratio of the truncated ellipse increases.

[0033] Figure 6 A roller bearing having a roller 40" having a tapered roller end 41". The profile of the mating surface 33" of the flange 31" is mathematically described by a multi-radius curve. The profile has at least three segments 34", 35", and 36". Any two adjacent segments are tangent to each other. When the roller 40" contacts the mating flange 31" at the contact point 61", an elliptical or circular contact footprint is initially formed. The elliptical or circular contact footprint corresponds to the radius of curvature R of the profile segment 35".B1 As the load increases, the ellipse is truncated at the upper side by the profile segment 34" and at the lower side by the profile segment 36". As the contact load increases, the aspect ratio of the truncated ellipse increases. At a predetermined design load for the bearing, the contact footprint is non-elliptical.

[0034] A non-elliptical contact footprint can be achieved by a composite profile at the contact location between the roller end and the mating flange face. That is, a multi-radius profile or multi-segment profile can be placed on the roller end, on the flange face, or on both the roller end and the flange face. The radius of curvature of a profile segment (or segments) at the center of the contact footprint is substantially greater than the radius of curvature of the segments adjacent to the center segment. At a predetermined design load for the bearing, the contact footprint is non-elliptical.

[0035] Figures 7 to 11 Another embodiment of a roller or rolling element bearing 100 of the present invention is shown. Figure 7 , the bearing 100 includes: an outer ring 120; an inner ring 130; and a set of rollers 140, which are arranged between and in rolling contact with the outer ring 120 and the inner ring 130. Although the illustrated embodiment shows a cylindrical roller bearing (with cylindrical rollers), the present invention can also be applied to tapered roller bearings, spherical roller bearings, and possibly needle roller bearings. The outer ring 120 includes at least one radially inwardly extending flange 121 at one end of a raceway 122 defined on the outer ring 120. In the illustrated embodiment, the outer ring 120 includes two radially inwardly extending flanges 121. Each flange 121 includes a flange surface 123 facing axially inwardly toward the raceway 122.

[0036] The inner ring 130 includes at least one radially outwardly extending flange 131 at one axial end of a raceway 132 defined on the inner ring 130. The flange 131 includes a flange surface 133 facing the raceway 132 axially inwardly.

[0037] Each roller 140 has two end faces 141a and 141b and an outer diameter surface 146 that engages and rolls on raceways 122, 132. The end faces 141a, 141b can be made substantially symmetrical about a central radial plane of the roller 140 (a plane perpendicular to the roller axis), but this need not be the case.

[0038] refer to Figure 8 and Fig. 9 Each end face 141a, 141b includes a curved profile 145 defined by a rotation axis 147 passing through the roller 140 (see Fig. 9). The curved profile 145 is formed by a plurality of segments 151, 152, 153 and 154, such as in Figure 8 and Fig. 9 It will be understood that Fig. 9 In the figure, for simplicity and clarity, only the lower left corner of the roller 140 is illustrated as having a profile 145, but at least the upper left corner of the end face 141a will have the same profile 145 mirrored about the axis 147. Each profile segment 151, 152, 153 and 154 is defined by a mathematically described or defined curvature. Each segment 151, 152, 153 and 154 can be a straight line, a portion of a circle or a complex curve described, for example, by a logarithmic or exponential equation.

[0039] The contour segment 151 is a portion of a straight line having a curvature radius of infinity. The contour segments 152 and 154 are respectively a portion of a straight line having a curvature radius of R B2 and R D2 The centers of these curvatures are located at O B2 and O D2 . Profile segments 151 and 152 merge at tangent point A. Profile segments 152 and 153 merge at tangent point B. Profile segments 153 and 154 merge at tangent point D. Profile segment 153 extends from point B to point D and includes point C. In this way, profile segment 153 can be divided into segment portions 153B and 153D. Profile segment 154 merges with the body 146 or outer diameter of roller 140 or with the green corner of the roller at point E. Unlike the fusion points (A to D), point E may or may not be a tangent point.

[0040] Profile segment 153 is a logarithmic curve or curves described by the following equation in a local xy coordinate system having its origin at the central contact point indicated by reference point C or 161 where the x-axis is tangent to the roller end profile at contact point C. Angle b represents the contact angle, which is also the local xy coordinate system and the global X G -Y G The rotation angle between the coordinate systems.

[0041]

[0042]

[0043] in A b and A d is a constant related to the deflection of the contact surface in the y-direction under a nominal design load (eg, in some embodiments, may vary from 1 to 100 microns, or more preferably from 10 to 25 microns);l b , l d , y b and y d Yes Fig.10 More specifically, l b is the distance between point C and point B along the local x direction, l d is the distance between points C and D along the local x direction, y b is the distance between point C and point B along the local y direction, and y d is the distance between points C and D along the local y direction.

[0044] The logarithmic curves of segments 153B (CB) and 153D (CD) are described by equations (1a) and (1b), respectively, and have continuously variable radii of curvature. For example, at the starting point C, the radii of curvature of CB and CD are, respectively,

[0045]

[0046] .

[0047] At the end point (B or D) of the logarithmic curve (CB and CD), the radius of curvature is,

[0048]

[0049] .

[0050] In general, the following inequality holds,

[0051]

[0052] .

[0053] The radius of curvature of the logarithmic curve is greatest at the center of contact point C. Thus, the radius of curvature at a given point decreases as the point moves away from the center of contact point C along the curve.

[0054] It is desirable to choose the design parameters so that the following equation holds,

[0055]

[0056]

[0057]

[0058] Where R B2 and R D2 are the radii of curvature of the circular segments AB and DE respectively.

[0059] Fig.11 A graphical example of a multi-segment roller end profile according to the invention is shown. In this example, the relationships set out in equations (5a) to (5c) are incorporated.

[0060] refer to Fig.12 , the positions of the profile segments 151, 152, 153 and 154 of the roller 140 are designed so that when the roller 140 is assembled and set in operation in the bearing 100 under thrust load, the contact between the roller end 141a or 141b and the mating flange surface 123 and / or 133 begins at point 161. As the contact load increases, a footprint 162 is formed. As the contact load increases, the size and shape of the footprint 162 changes. At a predetermined design load for the bearing 100, the contact footprint is non-elliptical.

[0061] The profile segments 152 and 154 adjacent to the main profile segment 153 do not have to be parts of a circle. For example, they can be parts of an exponential curve or parts of a logarithmic curve. In some alternatives, the profile segments 152, 154 can be extensions of the logarithmic curve for the main profile segment 153. In some embodiments, additional adjacent profile segments 152 and 154 are not required. Alternatively, the main segment 153 can be the only segment of the curved profile 145.

[0062] The above-mentioned multi-segment roller end profile can also or alternatively be produced on the flange surfaces 123 and / or 133 . Fig.13 Although the flange surface 133 is shown in the figure, the flange surface 123 may also be shown.

[0063] Fig.13 A roller bearing having a roller 140' is depicted, the roller 140' having a tapered roller end 141'. The profile of the mating surface 133' of the flange 131' is mathematically described by a multi-segment curve. The profile has at least three segments 134, 135 and 136. Any two adjacent segments are tangent to each other. When the roller 140' contacts the mating flange 131' at the contact point 161, a non-elliptical contact footprint is formed under a predetermined design load. The non-elliptical contact footprint corresponds to a logarithmic curve of the profile segment 135, which can have the same curvature as the profile segment 153 described above. As the contact load increases further, the aspect ratio of the contact footprint increases.

[0064] Once again, a non-elliptical contact footprint can be achieved by a composite profile at the contact location between the roller end and the mating flange face. That is, a multi-segment profile can be placed on the roller end, on the flange face, or on both the roller end and the flange face. The profile segment or segments at the center of the contact footprint are part of a logarithmic curve with a continuously varying radius of curvature. The radius of curvature of a logarithmic segment is not less than the radius of curvature of a segment adjacent to the logarithmic segment.

[0065] Various features and advantages of the invention are set forth in the following claims.

Claims

1. A roller bearing, comprising: inner rolling ring; Outer roller; as well as A roller, the roller being arranged between the inner roller ring and the outer roller ring and contacting the inner roller ring and the outer roller ring; wherein the bearing has a flange on the inner race at one axial end and a flange on the outer race at the opposite axial end; wherein at least one of the flanges is formed to include at least one main section intermediate two additional sections, the main section tangentially merging with the two additional sections; and wherein the main section has a first curvature that is different from the corresponding curvatures of the two additional sections; wherein the curved portion of each of the main section and the two additional sections is a portion of a circle, and wherein the radius of curvature of the first curved portion is greater than the corresponding radii of curvature of the two additional sections, wherein the corresponding radii of curvature of the two additional sections are different.

2. The roller bearing according to claim 1, wherein: The roller includes a roller end engaging a formed flange, the roller end being spherical.

3. The roller bearing according to claim 1, wherein: The roller includes a roller end that engages a formed flange, the roller end being conical.

4. The roller bearing according to claim 1, wherein: When the bearing is operating under a predetermined design load, the shape of the contact footprint defined between the contoured flange and the end of the roller is non-elliptical.

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