Patent Description:
The present invention relates to bearings, and more particularly to roller bearings.

Radial cylindrical bearings are used primarily to bear a substantial amount of radial load. Modern applications however require such bearings to also bear a certain amount of axial load. In these cases, the roller end and the mating faces on the inner and outer flanges of the bearing rings have to be properly designed to produce adequate contact footprints to manage contact stress and friction. Prior art designs, such as those disclosed in <CIT> and <CIT>, propose profiled roller ends that result in elliptical shaped contact portions or footprints between roller ends and flange faces. The shapes of the contact ellipses are determined by the principal radii at the center of the contact, and are independent of contact load. The size of the contact ellipse increases as the contact load increases. To prevent the contact footprint from having undesired interaction (e.g., truncation) with the edges of the flange face created by the undercut and outer diameter or inner diameter surface geometry, which leads to severe edge stresses, the contact ellipses are designed with their semi-major axis lying in the circumferential direction. At light loads, however, when the periphery of the contact ellipse is far away from the edges of the flange face, the shape of the contact footprint ellipse may not be the most desirable for managing the contact stress. <CIT> discloses a track element and a roller bearing comprising the track element, according to the preamble of claim <NUM>.

The present invention is described in the attached claims.

The invention provides a roller bearing including an inner race ring, an outer race ring, and a roller arranged between and in contact with the inner and outer rings. The bearing has a flange on the inner race ring at one axial end, and a flange on the outer race ring at an opposite axial end. At least one of the flanges is profiled to include at least one principal segment intermediate two additional segments. The principle segment is tangentially blended with the two additional segments, and the principle segment has a first curvature that is different from the respective curvatures of the two additional segments.

<FIG> illustrate embodiments of the invention as claimed in the attached claims, the remaining Figures illustrate roller bearings not according to the attached claims.

The invention is capable of other embodiments and of being practiced or of being carried out in various ways within the scope of the attached claims.

Referring to <FIG>, a roller bearing or rolling element bearing <NUM> of the current invention includes an outer ring <NUM>, an inner ring <NUM>, and a set of rollers <NUM> arranged between and in rolling contact with the outer and inner rings <NUM> and <NUM>. While the illustrated embodiment shows a cylindrical roller bearing (with cylindrical rollers), the invention can also be applied to tapered roller bearings, spherical roller bearings, and possibly, needle roller bearings. The outer ring <NUM> includes at least one radially inwardly-extending flange <NUM> at one end of the raceway <NUM> defined on the outer ring <NUM>. In the illustrated embodiment, the outer ring <NUM> includes two radially inwardly-extending flanges <NUM>. Each flange <NUM> includes a flange face <NUM> facing axially inwardly toward the raceway <NUM>.

The inner ring <NUM> includes at least one radially outwardly-extending flange <NUM> at one axial end of the raceway <NUM> defined on the inner ring <NUM>. The flange <NUM> includes a flange face <NUM> facing axially inwardly toward the raceway <NUM>.

Each roller <NUM> has two end faces 41a and 41b, and an outer diameter surface <NUM> that engages and rolls on the raceways <NUM>, <NUM>. The end faces 41a, 41b may be made substantially symmetrical to a center radial plane (a plane perpendicular to roller axis) of the roller <NUM>, however this need not be the case.

With reference to <FIG> and <FIG>, showing a roller bearing out of the scope of the claims, each end face 41a, 41b contains a curved profile <NUM> defined in an axial plane through a rotational axis <NUM> (see <FIG>) of the roller <NUM>. The curved profile <NUM> is formed by multiple segments <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> as, for example, shown in <FIG> and <FIG>. It is to be understood that in <FIG>, only the lower right corner of the roller <NUM> is illustrated with the profile <NUM> for simplicity and clarity, but that at least the upper right corner of the end face 41b would have the same profile mirrored about the axis <NUM>. Likewise, the end face 41a could include the same profile <NUM> mirrored about the axial centerpoint of the roller <NUM>. Each profile segment <NUM>, <NUM>, <NUM>, <NUM> and <NUM> is defined by a mathematically defined curvature. The profile segment <NUM> is a portion of a straight line whose curvature radius is infinity. Profile segments <NUM> to <NUM> are portions of circles with curvature radii of RA2, RB2, RC2, and RD2, respectively. The centers of these curvatures are at OA2, OB2, OC2, and OD2, respectively. Profile segments <NUM> and <NUM> are blended at a tangent point A. Profile segments <NUM> and <NUM> are blended at a tangent point B. Profile segments <NUM> and <NUM> are blended at a tangent point C. Profile segments <NUM> and <NUM> are blended at a tangent point D. Profile segment <NUM> is blended with the outer diameter surface <NUM> of the roller <NUM> at point E. Unlike the other blending points (A-D), point E may or may not be a tangent point. The profile segment <NUM> is optional. In cases where the profile segment <NUM> is not used, profile segment <NUM> can be blended directly with outer diameter surface <NUM> at a non-tangent point.

The locations of the profile segments <NUM>, <NUM>, <NUM>, <NUM> and <NUM> of the rollers <NUM> are designed such that when the roller <NUM> is assembled and set in operation in a bearing <NUM> under thrust load, the contact between the roller end 41a or 41b and the mating flange face <NUM> and/or <NUM> starts at point <NUM> (see <FIG>). Referring to <FIG>, a contact patch or footprint <NUM> is developed as contact load increases. The contact footprint <NUM> remains elliptical or circular in shape when the contact load is relatively low before reaching a load threshold of Qmin. This ellipse or circle corresponds to profile segment <NUM> (BC) with the curvature radius RB2. As the load continues to increase, the contact footprint <NUM> starts to deviate from its original elliptical or circular shape. Specifically, the contact footprint <NUM> is truncated by segment <NUM> (AB) at the upper side and by segment <NUM> (CD) at the lower side, and assumes a non-ellipse or non-elliptical shape as represented in the area between <NUM> and <NUM>. As the load further increases, the aspect ratio (length over width) of the contact footprint <NUM> increases, and reaches a predetermined or desirable value for optimal contact attributes, such as flange torque and/or wear rate, under a predetermined design load Qmax. At load Qmax, the contact footprint is represented by <NUM>, and is non-elliptical in shape.

To achieve the above mentioned non-elliptical shape during contact, the curvature center OB2 of the profile segment <NUM> may be offset from or located at a distance from the roller axis <NUM> that is within (smaller than) a distance DS<NUM> (see <FIG>). Likewise, the centers of curvatures for other profile segments may be offset from or located at distances from the roller axis <NUM> that is outside or above (greater than) DS<NUM> (see <FIG>). DS<NUM> <<NUM>. 5R, and DS<NUM> ><NUM>. 5R, where R is the radius of roller body.

It should be noted that to achieve the above-mentioned non-elliptical contact footprint, profile segments <NUM> and <NUM> adjacent to the principal profile segment <NUM> need not be portions of circles. They can be, for example, a portion of exponential curves and/or logarithm curves. In yet other embodiments (such as discussed below with respect to <FIG>), the principle profile segment <NUM> could be a portion of exponential curves and/or logarithm curves.

The above-mentioned multi-radius profile or multi-segment profile on roller end faces can also, or alternatively, be made on flange faces <NUM> and/or <NUM>. <FIG> illustrate the flange faces <NUM>, but can also represent the flange faces <NUM>, according to the invention and described in the appended claims.

<FIG> depicts a portion of a roller bearing having rollers <NUM>' with spherical roller ends <NUM>'. The profile of the roller end <NUM>' is described by a single radius curve (RB2) with the center of curvature at the rotation axis <NUM> of the roller. The roller <NUM>' is brought into contact with inner ring <NUM>' of the bearing during operation. The contact occurs at the mating flange face <NUM>' having at least three profile segments <NUM>, <NUM>, and <NUM>. Each profile segment <NUM>, <NUM>, and <NUM> may be mathematically described by a radius of curvature. The radius of curvature (RB1) for the second profile segment <NUM> can be infinity, that is to say the second profile segment is a straight line. The first profile segment <NUM> is designed to be tangent to the second profile segment <NUM>. The second profile segment <NUM>, in turn, is tangent to the third profile segment <NUM>. The first profile segment <NUM> is blended to the outer diameter <NUM> of the flange <NUM>' at a non-tangent point. The third profile segment <NUM> is blended to the undercut <NUM> of the flange at another non-tangent point. When the roller <NUM>' is brought into contact with the mating flange <NUM>' at the contact point <NUM>', an elliptically-shaped or circular contact footprint initially develops. The elliptically-shaped or circular contact footprint corresponds to the curvature radius RB2 of the roller end <NUM>'. As the load is increased, the ellipse is truncated by profile segment <NUM>" at the upper side and by profile segment <NUM>" at the lower side. The aspect ratio of the truncated ellipse increases as the contact load increases.

<FIG> depicts a roller bearing having rollers <NUM>" that have conical roller ends <NUM>". The profile of the mating face <NUM>" of the flange <NUM>" is mathematically described by multi-radius curves. The profile has at least three segments <NUM>", <NUM>", and <NUM>". Any two adjacent segments are tangent to each other. When the roller <NUM>" is brought into contact with the mating flange <NUM>" at the contact point <NUM>", an elliptically-shaped or circular contact footprint initially develops. The elliptically-shaped or circular contact footprint corresponds to the curvature radius RB1 of the profile segment <NUM>". As the load is increased, the ellipse is truncated by profile segment <NUM>" at the upper side and by profile segment <NUM>" at the lower side. The aspect ratio of the truncated ellipse increases as the contact load increases. At a predetermined design load for the bearing, the contract footprint is non-elliptical.

A non-elliptical contact footprint can be obtained by composite profiles at the contact location between the roller end and the mating flange face. This is to say that multi-radius profiles or multi-segment profiles can be placed either on the flange face, or on both the roller end and the flange faces, according to the invention within the scope of the claims. The profile segment (or segments) at the center of the contact footprint has a radius of curvature that is substantially greater than that of the segments adjacent to that center segment. At a predetermined design load for the bearing, the contract footprint is non-elliptical.

<FIG> illustrate another roller or rolling element bearing <NUM> out of the scope of the claims. Referring to <FIG>, the bearing <NUM> includes an outer ring <NUM>, an inner ring <NUM>, a set of rollers <NUM> arranged between and in rolling contact with the outer and inner rings <NUM>, and <NUM>. While the illustrated embodiment shows a cylindrical roller bearing (with cylindrical rollers), the invention can also be applied to tapered roller bearings, spherical roller bearings, and, possibly, needle roller bearings. The outer ring <NUM> includes at least one radially inwardly-extending flange <NUM> at one end of the raceway <NUM> defined on the outer ring <NUM>. In the illustrated embodiment, the outer ring <NUM> includes two radially inwardly-extending flanges <NUM>. Each flange <NUM> includes a flange face <NUM> facing axially inwardly toward the raceway <NUM>.

Each roller <NUM> has two end faces 141a and 141b, and an outer diameter surface <NUM> that engages and rolls on the raceways <NUM>, <NUM>. The end faces 141a, 141b may be made substantially symmetrical to a center radial plane (a plane perpendicular to roller axis) of the roller <NUM>, however this need not be the case.

With reference to <FIG> and <FIG>, each end face 141a, 141b contains a curved profile <NUM> defined in an axial plane that passes through the rotational axis <NUM> (See <FIG>) of the roller <NUM>. The curved profile <NUM> is formed by multiple segments <NUM>, <NUM>, <NUM>, and <NUM> as for example shown in <FIG> and <FIG>. It is to be understood that in <FIG>, only the lower left corner of the roller <NUM> is illustrated with the profile <NUM> for simplicity and clarity, but that at least the upper left corner of the end face 141a would have the same profile <NUM> mirrored about the axis <NUM>. Each profile segment <NUM>, <NUM>, <NUM>, and <NUM> is defined by a mathematically described or defined curvature. Each segment <NUM>, <NUM>, <NUM>, and <NUM> can be a straight line, a portion of a circle, or a complex curve described for example by logarithmic or exponential equations.

The profile segment <NUM> is a portion of a straight line whose curvature radius is infinity. Profile segments <NUM> and <NUM> are portions of circles with curvature radii of RB2 and RD2, respectively. The centers of these curvatures are at OB2 and OD2 respectively. Profile segments <NUM> and <NUM> are blended at tangent point A. Profile segments <NUM> and <NUM> are blended at a tangent point B. Profile segments <NUM> and <NUM> are blended at a tangent point D. Profile segment <NUM> extends from point B to point D and includes point C. As such, profile segment <NUM> can be broken into segment portions 153B and 153D. Profile segment <NUM> is blended with the body <NUM> or outer diameter of the roller <NUM> or a green comer of the roller at point E. Unlike blending points (A-D), point E may or may not be a tangent point.

Profile segment <NUM> is a logarithmic curve or logarithmic curves described by the following equations in local x-y coordinate system whose origin is at the central contact point indicated by the reference point C or <NUM>, with the x-axis being tangent to the roller end profile at the contact point C. The angle b represents the contact angle, which is also the rotation angle between the local x-y and global XG-YG coordinate systems. <MAT> <MAT> where Ab and Ad are constants related to deflection of the contact surfaces in y-direction under nominal design load (e.g., in some embodiments may vary from <NUM>-<NUM> microns, or more preferably from <NUM>-<NUM> microns); lb, ld, yb and yd are the distances as defined in <FIG>. More specifically, lb is a distance in the local x-direction between point C and point B, ld is a distance in the local x-direction between point C and point D, yb is a distance in the local y-direction between point C and point B, and yd is a distance in the local y-direction between point C and point D.

The logarithmic curves of segment portion 153B (CB) and 153D (CD) are described by equations (1a) and (1b), respectively, and have continuously variable curvature radii. For example, at the starting point C, the curvature radii for CB and CD are, respectively, <MAT> <MAT>.

At the end ending points (B or D) of the logarithmic curves (CB and CD), the curvature radii are, respectively, <MAT> <MAT>.

In general, the following inequalities hold true, <MAT> <MAT>.

At the center of the contact point C, the curvature radii of the logarithmic curves are the largest. Therefore, the curvature radius at a given point decreases as the point moves along the curve away from the center of the contact point C.

It may be desirable to select design parameters such that the following equations hold true, <MAT> <MAT> <MAT> where RB2 and RD2 are curvature radii of circular segments AB and DE, respectively.

<FIG> shows a graphical example of a multi-segment roller end profile according to the above equations. In this example, the relationships set forth in equations (5a) - (5c) were incorporated.

With reference to <FIG>, the locations of the profile segments <NUM>, <NUM>, <NUM>, and <NUM> of the rollers <NUM> are designed such that when the roller <NUM> is assembled and set in operation in a bearing <NUM> under thrust load, the contact between roller end 141a or 141b and the mating flange face <NUM> and/or <NUM> starts at point <NUM>. A footprint <NUM> is developed as contact load increases. The size and shape of the footprint <NUM> change as contact load increases. At a predetermined design load for the bearing <NUM>, the contract footprint is non-elliptical.

Profile segments <NUM> and <NUM> adjacent to the principal profile segment <NUM> need not be portions of circles. They can be, for example, be portions of exponential curves or portions of logarithmic curves. In yet other alternatives, the profile segments <NUM>, <NUM> might be extensions of the logarithmic curves used for the principle profile segment <NUM>. In yet other embodiments, there need not be additional, adjacent profile segments <NUM> and <NUM>. Instead, the principle segment <NUM> can be the sole segment of the curved profile <NUM>.

The above-mentioned multi-segment roller end profiles can also, or alternatively, be made on flange faces <NUM> and/or <NUM>. In an alternative arrangement not covered by the attached claims, <FIG> illustrates the flange face <NUM>, but can also represent the flange faces <NUM>.

<FIG> depicts a roller bearing with rollers <NUM>' having conical roller ends <NUM>'. The profile of the mating face <NUM>' of the flange <NUM>' is mathematically described by multi-segment curves. The profile has at least three segments <NUM>, <NUM> and <NUM>. Any two adjacent segments are tangent to each other. When the roller <NUM>' is brought into contact with the mating flange <NUM>' at the contact point <NUM>, a non-elliptical contact footprint develops at a predetermined design load. In an alternative arrangement not covered by the attached claims, the non-elliptical contact footprint corresponds to the logarithmic curves of the profile segment <NUM>, which can have same curvature as the profile segment <NUM> described above. The aspect ratio of the contact footprint increases as the contact load further increases.

Once again, a non-elliptical contact footprint can be obtained by composite profiles at the contact location between the roller end and the mating flange face. This is to say that multi-segment profiles can be placed either on the flange face, or on both the roller end and the flange faces. As illustrated on <FIG>, out of the scope of the claims, the profile segment or segments at the center of the contact footprint is a portion of a logarithmic curve that has continuously changing curvature radii. The curvature radii of the logarithmic segment are no less than that of the segments adjacent to the logarithmic segment.

Claim 1:
A roller bearing (<NUM>) comprising:
an inner race ring (<NUM>'; <NUM>");
an outer race ring (<NUM>); and
a roller (<NUM>'; <NUM>") arranged between and in contact with the inner and outer rings (<NUM>'; <NUM>", <NUM>); wherein the bearing has a flange (<NUM>'; <NUM>") on the inner race ring (<NUM>'; <NUM>") at one axial end, and a flange (<NUM>) on the outer race ring (<NUM>) at an opposite axial end;
wherein at least one of the flanges (<NUM>, <NUM>'; <NUM>") is profiled to include at least one principal segment (<NUM>; <NUM>") intermediate two additional segments (<NUM>, <NUM>; <NUM>", <NUM>"), the principle segment (<NUM>; <NUM>") being tangentially blended with the two additional segments (<NUM>, <NUM>; <NUM>", <NUM>");
wherein the principle segment (<NUM>; <NUM>") has a first curvature that is different from the respective curvatures of the two additional segments; and
wherein the curvatures of each of the principle segment (<NUM>; <NUM>") and the two additional segments (<NUM>, <NUM>; <NUM>", <NUM>") are portions of a circle, and characterized in that the first curvature has a greater radius (RB1) of curvature than the respective radii of curvatures (RA1, RC1) of the two additional segments (<NUM>, <NUM>; <NUM>", <NUM>").