Conical roller bearing

Abstract

To provide a conical roller bearing capable of suppressing seizure between a flange part formed on an inner diameter surface of an outer ring and an end surface of a conical roller contacting the flange part.SOLUTION: A conical roller bearing comprises an outer ring and a conical roller. The outer ring has: a first end surface and a second end surface that are end surfaces in an axial direction along a first central axis, which is a central axis of the outer ring; and an inner diameter surface and an outer diameter surface extending along a circumferential direction along a circumference centered on the first central axis. The inner diameter surface faces the first central axis side. The outer diameter surface is the opposite surface of the inner diameter surface in a radial direction perpendicular to the axial direction and passing through the first central axis. The inner diameter surface includes a raceway surface extending along the circumferential direction and inclined so that a distance from the outer diameter surface decreases from the first end surface toward the second end surface. A portion of the inner diameter surface between the raceway surface and the second end surface is provided with a flange part projecting inward in the radial direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tapered roller bearing. More specifically, the present invention relates to a tapered roller bearing having an outer ring with a flange portion formed on the inner diameter surface of the outer ring.

Background Art

[0002] For example, Japanese Patent No. 6778310 (Patent Document 1) describes a tapered roller bearing. The tapered roller bearing described in Patent Document 1 has an outer ring and a plurality of tapered rollers. The direction along the first central axis, which is the central axis of the outer ring, is defined as the axial direction. The direction orthogonal to the axial direction and passing through the first central axis is defined as the radial direction. The direction along the circumference centered on the first central axis is defined as the circumferential direction.

[0003] The outer ring has a first end face and a second end face, which are end faces in the axial direction, and an inner diameter surface and an outer diameter surface that extend along the circumferential direction. The inner diameter surface and the outer diameter surface face the first central axis side and the side opposite to the first central axis, respectively. The inner diameter surface has a raceway surface that contacts the tapered rollers. The raceway surface is inclined such that the distance from the outer diameter surface decreases as it goes from the first end face side to the second end face side. A flange portion that protrudes inward in the radial direction is formed on a portion of the inner diameter surface between the raceway surface and the second end face.

[0004] The tapered rollers have a third end face, a fourth end face, and an outer peripheral surface. The third end face and the fourth end face are end faces in the direction along the second central axis, which is the central axis of the tapered roller. The fourth end face contacts the flange portion. The outer peripheral surface is continuous with the third end face and the fourth end face and contacts the raceway surface.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] As described above, in the tapered roller bearing described in Patent Document 1, a flange is formed on the inner diameter surface of the outer ring. As a result, the speed at which the fourth end face of the tapered roller slides against the flange is greater than when the flange is formed on the outer diameter surface of the inner ring. Consequently, in the tapered roller bearing described in Patent Document 1, the fourth end face may seize up against the flange.

[0007] This invention has been made in view of the problems of the prior art described above. More specifically, this invention provides a tapered roller bearing that can suppress seizure between a flange formed on the inner diameter surface of the outer ring and the end face of a tapered roller that contacts the flange. [Means for solving the problem]

[0008] The tapered roller bearing according to the present invention comprises an outer ring and tapered rollers. The outer ring has a first end face and a second end face, which are end faces in the axial direction along a first central axis, which is the central axis of the outer ring, and an inner diameter surface and an outer diameter surface that extend along the circumferential direction along the circumference of a circle centered on the first central axis. The inner diameter surface faces toward the first central axis. The outer diameter surface is perpendicular to the axial direction and is the opposite surface of the inner diameter surface in the radial direction passing through the first central axis. The inner diameter surface extends along the circumferential direction and includes a raceway surface that is inclined such that the distance to the outer diameter surface decreases as it moves from the first end face toward the second end face. A flange is formed in the portion of the inner diameter surface between the raceway surface and the second end face, projecting radially inward. The tapered roller has a third end face and a fourth end face, which is the opposite surface of the third end face and contacts the flange, in the direction along the second central axis, which is the central axis of the tapered roller. The value obtained by dividing the radius of curvature of the fourth end face by the distance between the vertex of the cone angle of the cone roller and the fourth end face is between 0.75 and 0.95.

[0009] In the above-described tapered roller bearing, the value obtained by dividing the radius of curvature of the fourth end face by the distance between the apex of the cone angle of the tapered roller and the fourth end face may be 0.80 or more and 0.90 or less.

[0010] In the above-described tapered roller bearing, the flange portion may have a flange surface that contacts the fourth end face. The flange surface may be parallel to the axial direction and, in a cross-sectional view passing through the first central axis, parallel to the tangent to the fourth end face at the point of contact between the fourth end face and the flange surface.

[0011] In the above-described tapered roller bearing, the angle formed by the extension of the raceway surface and the straight line passing through the vertex of the cone angle of the tapered roller and the contact point between the fourth end face and the flange face may be 1 / 6 or less of the cone angle of the tapered roller. In the above-described tapered roller bearing, the angle formed by the extension of the raceway surface and the straight line passing through the vertex of the cone angle of the tapered roller and the contact point between the fourth end face and the flange face may be 1 / 8 or less of the cone angle of the tapered roller. [Effects of the Invention]

[0012] According to the tapered roller bearing of the present invention, it is possible to suppress seizure between the flange formed on the inner diameter surface of the outer ring and the end face of the tapered roller that contacts the flange. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view of the tapered roller bearing 100. [Figure 2] This is an enlarged cross-sectional view of the tapered roller bearing 100 near the flange surface 10ea and the fourth end surface 30b. [Figure 3] This graph shows the relationship between the radius of curvature R divided by the distance DIS and the oil film thickness. [Figure 4] This graph shows the relationship between the radius of curvature R divided by the distance DIS and the PV value of the flange portion 10e. [Figure 5A] This is a schematic diagram showing the range of the contact ellipse when the flange surface 10ea is a straight flange. [Figure 5B] This schematic diagram also shows the range of the contact ellipse when the flange surface 10ea is a spherical flange. [Modes for carrying out the invention]

[0014] Details of embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions will not be repeated. The tapered roller bearing according to the embodiment is designated as tapered roller bearing 100.

[0015] (Configuration of tapered roller bearing 100) The configuration of the tapered roller bearing 100 will be described below.

[0016] FIG. 1 is a cross-sectional view of the tapered roller bearing 100. FIG. 1 shows a cross-section parallel to the axial direction and passing through the first central axis. As shown in FIG. 1, the tapered roller bearing 100 has an outer ring 10, an inner ring 20, and a plurality of tapered rollers 30. The tapered roller bearing 100 is used, for example, in a speed reducer of a robot or a construction machine.

[0017] The central axis of the outer ring 10 is defined as the first central axis. The direction along the first central axis is defined as the axial direction. The direction perpendicular to the axial direction and passing through the first central axis is defined as the radial direction. The direction along the circumference centered on the first central axis is defined as the circumferential direction.

[0018] The outer ring 10 has a first end face 10a, a second end face 10b, an inner diameter surface 10c, and an outer diameter surface 10d. The first end face 10a and the second end face 10b are end faces of the outer ring 10 in the axial direction. The second end face 10b is the opposite face of the first end face 10a in the axial direction.

[0019] The inner diameter surface 10c extends along the circumferential direction. The inner diameter surface 10c faces the first central axis side. The inner diameter surface 10c has a raceway surface 10ca. The raceway surface 10ca is a portion of the inner diameter surface 10c that contacts the tapered roller 30. The raceway surface 10ca extends along the circumferential direction. In a cross-sectional view parallel to the axial direction and passing through the first central axis, the raceway surface 10ca is inclined such that the distance between the raceway surface 10ca in the radial direction and the outer diameter surface 10d decreases from the first end face 10a side toward the second end face 10b side.

[0020] The outer diameter surface 10d extends along the circumferential direction. The outer diameter surface 10d faces the side opposite to the first central axis. In other words, from another perspective, the outer diameter surface 10d is the opposite surface of the inner diameter surface 10c in the radial direction. The outer ring 10 is fitted into a housing (not shown) at the outer diameter surface 10d.

[0021] A flange portion 10e is formed at a portion of the inner diameter surface 10c between the raceway surface 10ca and the second end face 10b. The flange portion 10e protrudes toward the inner side in the radial direction. The surface of the flange portion 10e that contacts the tapered roller 30 is defined as the flange surface 10ea. Note that the flange surface 10ea is continuous with the raceway surface 10ca via the interference fit portion 10f. Also, the inner diameter side end (the end opposite to the interference fit portion 10f) of the flange surface 10ea may be a chamfered portion 10g.

[0022] The inner ring 20 has an end face 20a, an end face 20b, an inner diameter surface 20c, and an outer diameter surface 20d. The end face 20a and the end face 20b are end faces of the inner ring 20 in the axial direction. The end face 20b is the opposite face of the end face 20a in the axial direction. The inner diameter surface 20c extends along the circumferential direction. The inner diameter surface 20c faces the first central axis side. The inner ring 20 is fitted onto a shaft (not shown) at the inner diameter surface 20c.

[0023] The outer diameter surface 20d extends in the circumferential direction. The outer diameter surface 20d faces the side opposite to the first central axis. In other words, from another perspective, the outer diameter surface 20d is the opposite surface of the inner diameter surface 20c in the radial direction. The inner ring 20 is disposed inside the outer ring 10 in the radial direction such that the outer diameter surface 20d faces the inner diameter surface 10c with a gap therebetween.

[0024] The outer diameter surface 20d has a raceway surface 20da. The raceway surface 20da is a portion of the outer diameter surface 20d that contacts the tapered roller 30. The raceway surface 20da extends along the circumferential direction. In a cross-sectional view parallel to the axial direction and passing through the first central axis, the raceway surface 20da is inclined such that the distance between the raceway surface 20da and the inner diameter surface 20c in the radial direction increases from the end face 20a side toward the end face 20b side. Note that no flange portion is formed on the inner ring 20.

[0025] Multiple conical rollers 30 are arranged circumferentially between the raceway surface 10ca and the raceway surface 20da. The central axis of the conical roller 30 is defined as the second central axis. The conical roller 30 has a third end face 30a (small end face), a fourth end face 30b (large end face), and an outer circumferential surface 30c.

[0026] The third end face 30a and the fourth end face 30b are the end faces of the tapered roller 30 in the direction along the second central axis. The fourth end face 30b is the opposite face of the third end face 30a in the direction along the second central axis and is in contact with the flange face 10ea. The diameter of the fourth end face 30b is larger than the diameter of the third end face 30a. The outer circumferential surface 30c is connected to the third end face 30a and the fourth end face 30b. The outer circumferential surface 30c is composed of a conical surface. The outer circumferential surface 30c is in contact with the raceway surface 10ca and the raceway surface 20da.

[0027] The tapered roller bearing 100 further includes a cage (not shown). The cage holds a plurality of tapered rollers 30 such that the spacing between two adjacent tapered rollers 30 in the circumferential direction is within a certain range.

[0028] <Detailed configuration of the outer ring 10 and tapered roller 30> Let the cone angle of the cone roller 30 be θ. Let the vertex of the cone angle θ be vertex P. In a cross-sectional view parallel to the axial direction and passing through the first central axis, the extension of the portion of the outer surface 30c that is in contact with the raceway surface 10ca (the extension of the raceway surface 10ca) is defined as line L1. In a cross-sectional view parallel to the axial direction and passing through the first central axis, the extension of the portion of the outer surface 30c that is in contact with the raceway surface 20da (the extension of the raceway surface 20da) is defined as line L2. The angle between line L1 and line L2 is the cone angle θ, and the point where lines L1 and L2 intersect is vertex P. The first central axis passes through vertex P.

[0029] The fourth end face 30b is parallel to the axial direction and, in a cross-sectional view passing through the first central axis, is partially circular. Let the radius of curvature of the fourth end face 30b be R. Let the distance between vertex P and the fourth end face 30b be distance DIS. Distance DIS is greater than the radius of curvature R. The value obtained by dividing the radius of curvature R by distance DIS is between 0.75 and 0.95. Preferably, the value obtained by dividing the radius of curvature R by distance DIS is between 0.80 and 0.90.

[0030] Figure 2 is an enlarged cross-sectional view of the tapered roller bearing 100 near the flange surface 10ea and the fourth end surface 30b. As shown in Figure 2, the flange surface 10ea and the fourth end surface 30b are in contact with each other at the contact point CP. In a cross-sectional view parallel to the axial direction and passing through the first central axis, the tangent to the fourth end surface 30b at the contact point CP is defined as line L3. In a cross-sectional view parallel to the axial direction and passing through the first central axis, the flange surface 10ea is preferably parallel to line L3. The line passing through the contact point CP and the vertex P is defined as line L4. The angle between line L1 and line L4 is defined as the tangency angle ρ. The tangency angle ρ is preferably 1 / 6 or less of the cone angle θ (i.e., the value obtained by dividing the tangency angle ρ by the cone angle θ is preferably 1 / 6 or less). It is even more preferable that the value obtained by dividing the tangency angle ρ by the cone angle θ is 1 / 8 or less.

[0031] A flange that is parallel to the axial direction and whose flange surface 10ea is parallel to the straight line L3 in a cross-sectional view passing through the first central axis is sometimes called a straight flange. A flange that is parallel to the axial direction and whose flange surface 10ea is arc-shaped along the fourth end face 30b in a cross-sectional view passing through the first central axis is sometimes called a spherical flange.

[0032] (Effects of tapered roller bearing 100) The effects of the tapered roller bearing 100 are explained below.

[0033] In the tapered roller bearing 100, a flange portion (flange portion 10e) is formed on the outer ring 10 that contacts the tapered roller 30. Therefore, in the tapered roller bearing 100, the sliding speed of the fourth end face 30b relative to the flange portion 10e is greater than in the case where the inner ring 20 has a flange portion that contacts the tapered roller 30. As a result, heat generation in the vicinity of the flange portion 10e and the fourth end face 30b increases. This heat generation in the vicinity of the flange portion 10e and the fourth end face 30b can cause seizure of the flange portion 10e against the fourth end face 30b.

[0034] Figure 3 is a graph showing the relationship between the radius of curvature R divided by the distance DIS and the oil film thickness. In Figure 3, the horizontal axis represents the value obtained by dividing the radius of curvature R by the distance DIS, and the vertical axis represents the relative value of the oil film thickness between the flange surface 10ea and the fourth end surface 30b. In Figure 3, the vertical axis is displayed relatively, with the oil film thickness between the flange surface 10ea and the fourth end surface 30b set to 1 when the value obtained by dividing the radius of curvature R by the distance DIS is 0.75.

[0035] As shown in Figure 3, the oil film thickness between the flange surface 10ea and the fourth end surface 30b reaches its maximum value when the value obtained by dividing the radius of curvature R by the distance DIS is 0.75, and decreases as the value obtained by dividing the radius of curvature R by the distance DIS becomes greater than 0.75. When the value obtained by dividing the radius of curvature R by the distance DIS becomes greater than 0.95, the oil film thickness between the flange surface 10ea and the fourth end surface 30b decreases rapidly.

[0036] In the tapered roller bearing 100, the value obtained by dividing the radius of curvature R by the distance DIS is between 0.75 and 0.95, so that the lubricating oil film thickness between the flange surface 10ea and the fourth end surface 30b is ensured. The better the lubrication between the flange surface 10ea and the fourth end surface 30b, the more heat generation in the vicinity of the flange portion 10e and the fourth end surface 30b is suppressed.

[0037] Figure 4 is a graph showing the relationship between the value obtained by dividing the radius of curvature R by the distance DIS and the PV value of the flange portion 10e. In Figure 4, the horizontal axis represents the relative value of the value obtained by dividing the radius of curvature R by the distance DIS, and the vertical axis represents the PV value of the flange portion 10e. In Figure 4, the vertical axis is displayed relatively, with the PV value when the value obtained by dividing the radius of curvature R by the distance DIS is 0.80 set to 1. Here, the PV value of the flange portion 10e is the product of the P value and the V value. The P value is the maximum contact pressure at the flange surface 10ea, and the V value is the sliding speed of the flange portion 10e and the fourth end surface 30b relative to the flange portion 10e. The larger the PV value of the flange portion 10e, the greater the heat generation in the vicinity of the flange portion 10e and the fourth end surface 30b.

[0038] As shown in Figure 4, the PV value of the flange portion 10e decreases as the value obtained by dividing the radius of curvature R by the distance DIS exceeds 0.75. In the tapered roller bearing 100, the value obtained by dividing the radius of curvature R by the distance DIS is 0.75 or greater, so the increase in the PV value and, consequently, the heat generation near the flange portion 10e and the fourth end face 30b is suppressed.

[0039] As described above, in the tapered roller bearing 100, the value obtained by dividing the radius of curvature R by the distance DIS is set to be between 0.75 and 0.95. Therefore, by ensuring sufficient oil film thickness between the flange surface 10ea and the fourth end surface 30b and suppressing the rise in the PV value at the flange portion 10e, heat generation in the vicinity of the flange portion 10e and the fourth end surface 30b, and consequently seizure between the flange portion 10e and the fourth end surface 30b, is suppressed.

[0040] To confirm the effect of having the radius of curvature R divided by the distance DIS be between 0.75 and 0.95, samples 1 through 7 of tapered roller bearings were prepared. In samples 1 through 7, the value of the radius of curvature R divided by the distance DIS varied within the range of 0.70 to 1.00.

[0041] In samples 1 through 7, the inner diameter, outer diameter, and width of the tapered roller bearings were 30.162 mm, 64.292 mm, and 21.433 mm, respectively. In samples 1 through 7, the inner ring 20 was rotated relative to the outer ring 10 at a rotational speed of 7000 rpm. An axial load of 650 kgf (approximately 6.37 kN) was applied to samples 1 through 7. The seizure resistance of samples 1 through 7 was evaluated by measuring the initial peak temperature on the outer diameter surface of the outer ring.

[0042] Furthermore, an evaluation of A was given if the initial peak temperature on the outer diameter surface of the outer ring was 160°C or higher but less than 170°C, an evaluation of B was given if the initial peak temperature on the outer diameter surface of the outer ring was 170°C or higher but less than 180°C, and an evaluation of C was given if the initial peak temperature on the outer diameter surface of the outer ring was 180°C or higher.

[0043] [Table 1]

[0044] As shown in Table 1, samples 2 through 6, where the value obtained by dividing the radius of curvature R by the distance DIS was between 0.75 and 0.95, received a seizure resistance rating of B or higher. Sample 1, where the value obtained by dividing the radius of curvature R by the distance DIS was less than 0.75, and sample 7, where the value obtained by dividing the radius of curvature R by the distance DIS was greater than 0.95, received a seizure resistance rating of C. From this comparison, it was experimentally revealed that seizure between the flange portion 10e and the fourth end face 30b is suppressed by setting the value obtained by dividing the radius of curvature R by the distance DIS to between 0.75 and 0.95.

[0045] For samples 3 through 5, where the value obtained by dividing the radius of curvature R by the distance DIS was between 0.80 and 0.90, the seizure resistance was evaluated as A. From this comparison, it was experimentally revealed that seizure between the flange portion 10e and the fourth end face 30b is further suppressed by setting the value obtained by dividing the radius of curvature R by the distance DIS to between 0.80 and 0.90.

[0046] Figure 5A is a schematic diagram showing the range of the contact ellipse when the flange surface 10ea is a straight flange. Figure 5B is a schematic diagram showing the range of the contact ellipse when the flange surface 10ea is a spherical flange. In Figures 5A and 5B, the range of the contact ellipse is indicated by cross-hatching. As shown in Figures 5A and 5B, the area of ​​the contact ellipse when the flange surface 10ea is a spherical flange is larger than that when the flange surface 10ea is a straight flange. The larger the area of ​​the contact ellipse, the greater the heat generated near the flange portion 10e and the fourth end face 30b. Therefore, when the flange surface 10ea is a straight flange, seizing between the flange portion 10e and the fourth end face 30b is further suppressed. In this case, interference between the concave portion 10f and the chamfered portion 10g with the contact ellipse and the occurrence of skew can be suppressed.

[0047] As the value of the contact angle ρ decreases, the sliding velocity of the fourth end face 30b at the contact point CP decreases. On the other hand, as the value of the contact angle ρ increases, the sliding velocity of the fourth end face 30b at the contact point CP increases. When the sliding velocity of the fourth end face 30b at the contact point CP increases, heat generation in the vicinity of the flange portion 10e and the fourth end face 30b increases. Therefore, when the contact angle ρ is 1 / 6 or less of the cone angle θ, the sliding velocity of the fourth end face 30b at the contact point CP decreases, and seizure between the flange portion 10e and the fourth end face 30b is further suppressed.

[0048] To confirm the effect of reducing the value obtained by dividing the contact angle ρ by the cone angle θ to 1 / 6 or less, samples 8 through 14 were prepared as tapered roller bearing samples. In samples 8 through 14, the value obtained by dividing the contact angle ρ by the cone angle θ varied within the range of 1 / 10 to 1 / 4.

[0049] For samples 8 through 14, the inner diameter, outer diameter, and width of the tapered roller bearings were 30 mm, 62 mm, and 17.25 mm, respectively. For samples 8 through 14, the inner ring 20 was rotated relative to the outer ring 10 at a rotational speed of 3000 revolutions per minute. An axial load of 650 kgf (approximately 6.37 kN) was applied to samples 8 through 14. The seizure resistance of samples 8 through 14 was evaluated by measuring the temperature on the outer diameter surface of the outer ring after rotation at the above rotational speed for one hour.

[0050] Furthermore, a rating of A was given if the temperature rise on the outer diameter surface of the outer ring after rotation at the above rotation speed for one hour was less than 40°C, a rating of B was given if the temperature rise on the outer diameter surface of the outer ring after rotation at the above rotation speed for one hour was 40°C or more but less than 60°C, a rating of C was given if the temperature rise on the outer diameter surface of the outer ring after rotation at the above rotation speed for one hour was 60°C or more but less than 80°C, and a rating of D was given if the temperature rise on the outer diameter surface of the outer ring after rotation at the above rotation speed for one hour was 80°C or more.

[0051] [Table 2]

[0052] As shown in Table 2, in samples 8 to 12, where the value obtained by dividing the contact angle ρ by the cone angle θ was 1 / 6 or less, the seizure resistance evaluation was B or higher. In samples 13 and 14, where the value obtained by dividing the contact angle ρ by the cone angle θ was greater than 1 / 6, the seizure resistance evaluation was C or lower. From this comparison, it was experimentally revealed that by setting the value obtained by dividing the contact angle ρ by the cone angle θ to 1 / 6 or less, seizure between the flange portion 10e and the fourth end face 30b is further suppressed. Furthermore, in samples 8 to 10, where the value obtained by dividing the contact angle ρ by the cone angle θ was 1 / 8 or less, the seizure resistance evaluation was A. From this comparison, it was experimentally revealed that by setting the value obtained by dividing the contact angle ρ by the cone angle θ to 1 / 8 or less, seizure between the flange portion 10e and the fourth end face 30b is particularly suppressed.

[0053] While embodiments of the present invention have been described above, various modifications of these embodiments are possible. Furthermore, the scope of the present invention is not limited to the embodiments described above. The scope of the present invention is indicated by the claims and is intended to include all modifications within the meaning and scope equivalent to the claims. [Industrial applicability]

[0054] The above embodiment is particularly advantageous to a tapered roller bearing used, for example, in a speed reducer, in which a flange is formed on the outer ring. [Explanation of Symbols]

[0055] 10 Outer ring, 10a End face, 10b End face, 10c Inner diameter face, 10ca Raceway face, 10d Outer diameter face, 10e Flange, 10ea Flange face, 10f Bracing, 10g Chamfered part, 20 Inner ring, 20a First end face, 20b Second end face, 20c Inner diameter face, 20d Outer diameter face, 20da Raceway face, 30 Tapered roller, 30a Third end face, 30b Fourth end face, 30c Outer circumference face, 100 Tapered roller bearing, CP Contact point, DIS Distance, L1, L2, L3, L4 Straight line, P Vertex, R Radius of curvature.

Claims

1. The outer ring and tapered rollers; the outer ring has a first end face and a second end face which are end faces in an axial direction along a first center axis which is a center axis of the outer ring, and an inner diameter surface and an outer diameter surface which extend in a circumferential direction along a circumference centered on the first center axis, the inner diameter surface faces the first center axis, the outer diameter surface is an opposite surface to the inner diameter surface in a radial direction perpendicular to the axial direction and passing through the first center axis, the inner diameter surface includes a raceway surface that extends along the circumferential direction and is inclined such that the distance from the outer diameter surface decreases as the raceway surface moves from the first end face toward the second end face, a flange portion protruding inward in the radial direction is formed on a portion of the inner diameter surface between the raceway surface and the second end face, the tapered roller has, in a direction along a second central axis that is a central axis of the tapered roller, a third end face and a fourth end face that is the surface opposite to the third end face and that comes into contact with the rib portion, a value obtained by dividing the radius of curvature of the fourth end face by the distance between the apex of the cone angle of the tapered roller and the fourth end face is equal to or greater than 0.75 and equal to or less than 0.

95.

2. 2. The tapered roller bearing according to claim 1, wherein a value obtained by dividing the radius of curvature by the distance between the apex and the fourth end face is equal to or greater than 0.80 and equal to or less than 0.

90.

3. the flange portion has a flange surface that contacts the fourth end surface, 3. The tapered roller bearing according to claim 1, wherein the rib surface is parallel to the axial direction and, in a cross-sectional view passing through the first center axis, parallel to a tangent to the fourth end surface at a contact point between the fourth end surface and the rib surface.

4. 4. The tapered roller bearing according to claim 3, wherein an angle formed by an extension of said raceway surface and a straight line passing through said apex and said contact point is 1 / 6 or less of said cone angle.

5. 4. The tapered roller bearing according to claim 3, wherein an angle formed by an extension of said raceway surface and a straight line passing through said apex and said contact point is 1 / 8 or less of said cone angle.

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