tapered roller bearings

Abstract

To provide a low-cost tapered roller bearing which can form a sufficient oil film between a cone back face rib of a bearing cone and a large end face of a tapered roller even when a low-viscosity lubricant is used.SOLUTION: A cone back face rib 8 has: a chamfer part 17; a cone back face rib surface 15 having a linear cross section; an undercut R part 20 having a convex arc-shaped cross section curved away from a large end face 9 of a tapered roller 3; and an undercut straight part 21 connected smoothly to a radial outside of the undercut R part 20 to form a tangent to the undercut R part 20.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tapered roller bearing. [Background technology]

[0002] Tapered roller bearings, which are bearings that can support radial and axial loads simultaneously, are often used in automobile transmissions (manual transmissions (MT), automatic transmissions (AT), dual clutch transmissions (DCT), continuously variable transmissions (CVT), and transmissions for hybrid electric vehicles (HEVs)), reducers for electric vehicles (EVs), and automobile differential mechanisms (see, for example, Patent Document 1).

[0003] A tapered roller bearing has an outer ring, an inner ring arranged coaxially radially inside the outer ring, and multiple tapered rollers spaced circumferentially between the outer and inner rings. The outer circumference of the inner ring is provided with a conical inner ring raceway with rolling contact for the multiple tapered rollers, and a large rib formed to protrude radially outward from the large-diameter end of the inner ring raceway. When the bearing rotates, the large rib of the inner ring comes into sliding contact with the large end faces of the tapered rollers while bearing part of the axial load. Therefore, in tapered roller bearings, it is important to ensure lubrication between the large end faces of the tapered rollers and the large rib of the inner ring.

[0004] The applicant of the present application has already proposed a tapered roller bearing capable of improving lubrication between the large end faces of the tapered rollers and the large rib of the inner ring, as disclosed in Patent Document 2. In the tapered roller bearing of Patent Document 2, the large rib of the inner ring has a large rib surface with a linear cross section that contacts the large end faces of the tapered rollers, and a relief R portion that smoothly connects to the radially outward side of the large rib surface and has a convex arc-shaped cross section that curves away from the large end faces of the tapered rollers. The radial outer end of the relief R portion intersects with a chamfer that slopes radially inward from the outer diameter surface of the large rib toward the tapered rollers.

[0005] In the tapered roller bearing of Patent Document 2, a wedge-shaped gap is formed between the large end face of the tapered roller and the relief R portion of the large rib of the inner ring, which makes it easy for lubricating oil to be drawn into the wedge-shaped gap, resulting in excellent lubrication between the large end face of the tapered roller and the large rib of the inner ring. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-024168 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-170775 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, there has been a trend toward smaller automobile drive units in order to increase the interior space of automobiles. There is also a trend toward higher output from automobile drive units, and furthermore, there is a trend toward using lubricating oils with lower viscosities than before in order to improve automobile fuel economy. Therefore, the bearings used in automobiles are required to be smaller, but at the same time, the loads imposed on the bearings are increasing, and furthermore, it tends to become more difficult to form an oil film inside the bearings.

[0008] In particular, in tapered roller bearings, the large end faces of the tapered rollers and the large rib of the inner ring are in sliding contact with each other, so it is important to ensure lubrication between the large end faces of the tapered rollers and the large rib of the inner ring.However, if a low-viscosity lubricating oil is used, it becomes difficult to form a sufficient oil film between the large end faces of the tapered rollers and the large rib of the inner ring.

[0009] Therefore, in order to make the tapered roller bearing compatible with low-viscosity lubricating oil, the inventors of the present application investigated whether it would be possible to further improve the lubrication between the large end faces of the tapered rollers and the large rib of the inner ring by further improving the tapered roller bearing of Patent Document 2.

[0010] On the other hand, since bearings are required to be low cost, it is preferable that the components of the bearing have a shape that can be machined in a short time.

[0011] The problem to be solved by this invention is to provide a low-cost tapered roller bearing that is capable of forming a sufficient oil film between the large end faces of the tapered rollers and the large ribs of the inner ring even when low-viscosity lubricating oil is used. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention provides a tapered roller bearing having the following configuration. The outer ring and an inner ring arranged coaxially radially inside the outer ring; a plurality of tapered rollers assembled at intervals in the circumferential direction between the outer ring and the inner ring, A tapered roller bearing in which the outer periphery of the inner ring is provided with a conical inner ring raceway surface with which the plurality of tapered rollers come into rolling contact, and a large rib formed to protrude radially outward from a large diameter side end of the inner ring raceway surface, a large rib surface in cross section that contacts the large end face of the tapered roller; a relief R portion that continues smoothly to the radially outward side of the large rib surface and has a convex arc-shaped cross section that curves in a direction away from the large end face of the tapered roller; and a relief straight portion that continues smoothly to the radially outward side of the relief R portion so as to form a tangent to the relief R portion and has a straight cross section that intersects the chamfered portion.

[0013] In this way, the straight relief portion, which has a linear cross section, has a larger contact angle hysteresis of the lubricant than the rounded relief portion, which has a convex arc cross section, and is therefore better able to retain the lubricant due to surface tension. Therefore, the lubrication between the large end face of the tapered roller and the large rib of the inner ring is superior to that of a case in which the entire area from the large rib surface to the chamfer is rounded without a straight relief portion. Furthermore, the grinding time for the large rib can be shortened, resulting in lower costs, compared to a case in which the entire area from the large rib surface to the chamfer is rounded without a straight relief portion.

[0014] The ratio of the width of the relief R portion to the width of the relief straight portion when measured in a direction parallel to the large flange surface can be set within a range of 9:1 to 3.5:6.5.

[0015] The straight relief portion is preferably formed to form an angle of 2° to 15° with respect to the large flange surface.

[0016] By making the angle that the relief straight portion makes with respect to the large rib surface 2° or more, even if the tapered roller is skewed, it is possible to avoid the large end face of the tapered roller coming into contact with the boundary between the relief straight portion and the chamfered portion, and to prevent oil film shortage between the large end face of the tapered roller and the relief straight portion. Also, by making the angle that the relief straight portion makes with respect to the large rib surface 15° or less, it is possible to effectively reduce the grinding depth when forming the relief straight portion and relief R portion by grinding, and it is possible to effectively shorten the grinding time for the large rib.

[0017] When the tapered roller has a recessed portion formed by circularly recessing the center of the large end face of the tapered roller, it is preferable that the recessed portion be formed so that the boundary between the large end face of the tapered roller and the recessed portion is located radially inward of the radial outer end of the large rib surface.

[0018] In this way, stable behavior of the tapered roller can be ensured even if the lubrication conditions of the bearing deteriorate and the large end face of the tapered roller wears due to contact with the large rib surface. In other words, if the recessed portion is formed so that the boundary between the large end face of the tapered roller and the recessed portion is located radially outward rather than radially inward of the radial outer end of the large rib surface, an area will remain on the large end face of the tapered roller that is not in contact with the large rib surface and will not wear, so when the large end face of the tapered roller wears due to contact with the large rib surface, and particularly if skew or the like occurs, the contact state between the large end face of the tapered roller and the large rib will become unstable and the behavior of the tapered roller will become unstable. However, if the recessed portion is formed so that the boundary between the large end face of the tapered roller and the recessed portion is located radially inward of the radial outer end of the large rib surface, the entire surface of the large end face of the tapered roller will come into contact with the large rib surface and the large end face of the tapered roller will wear away, so even when the large end face of the tapered roller wears away due to contact with the large rib surface, the contact state between the large end face of the tapered roller and the large rib will be surface contact and stable, ensuring stable behavior of the tapered roller.

[0019] The distance from the intersection of the straight relief portion and the chamfered portion to the large flange surface is preferably set in the range of 10 μm to 150 μm.

[0020] By setting the distance from the intersection of the relief straight portion and the chamfered portion to the large rib surface to 10 μm or more, it is possible to avoid the large end face of the tapered roller hitting the intersection of the relief straight portion and the chamfered portion even when the tapered roller is skewed, and to prevent localized strong contact with the large end face of the tapered roller. Also, by setting the distance from the intersection of the relief straight portion and the chamfered portion to the large rib surface to 150 μm or less, it is possible to effectively reduce the grinding depth when forming the relief straight portion, relief R portion, and large rib surface by grinding, and it is possible to effectively shorten the grinding time for the large rib.

[0021] The width of the large flange surface is preferably 1.5 mm or more.

[0022] In this way, since the width dimension of the large flange surface is large, it is possible to use a large-sized superfinishing grindstone when superfinishing the large flange surface, and the accuracy of the inclination angle of the large flange surface can be improved.

[0023] The surface roughness of the large flange surface is preferably 0.08 μmRa or less.

[0024] In this way, the surface roughness of the large rib surface is small, so that the skew of the tapered roller can be kept small. [Effects of the Invention]

[0025] This tapered roller bearing has a straight relief portion that smoothly connects to the radially outer side of the relief radius portion. A straight relief portion with a linear cross section has a larger contact angle hysteresis of the lubricant and a higher ability to retain lubricant due to surface tension than a relief radius portion with a convex arc cross section. This provides better lubrication between the large end face of the tapered roller and the large rib of the inner ring than a tapered roller bearing with no straight relief portion and a relief radius extending from the large rib surface to the chamfer. Furthermore, this type of tapered roller bearing can reduce the grinding time of the large rib and is less expensive than a tapered roller bearing with no straight relief portion and a relief radius extending from the large rib surface to the chamfer. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a cross-sectional view of a tapered roller bearing according to an embodiment of the present invention; [Figure 2] Enlarged view of the area around the contact point between the tapered roller and the large rib in Figure 1 [Figure 3] Enlarged view of the area around the large flange surface in Figure 2 [Figure 4] Enlarged view of the relief R and relief straight sections in Figure 3 [Figure 5] An explanatory diagram showing the relationship between the tapered roller, inner ring, and cone center in Figure 1 [Figure 6] FIG. 4 is a diagram showing the grinding allowance when forming the large flange surface, relief R portion, and relief straight portion of the large flange shown in FIG. 3 by grinding. [Figure 7]FIG. 9 is a diagram showing the grinding allowance when the large flange surface and the relief R portion of the large flange shown in FIG. 8 are formed by grinding. [Figure 8] FIG. 4 shows a comparative example of a large flange in which the entire area from the large flange surface to the chamfered portion is an R-shaped relief portion, without the straight relief portion shown in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0027] Figure 1 shows a tapered roller bearing according to an embodiment of the present invention. This tapered roller bearing has an outer ring 1, an inner ring 2 arranged coaxially radially inside the outer ring 1, a plurality of tapered rollers 3 assembled between the outer ring 1 and the inner ring 2 at intervals in the circumferential direction, and a cage 4 that maintains the circumferential spacing of the plurality of tapered rollers 3.

[0028] A conical outer ring raceway surface 5 with which the tapered rollers 3 roll is formed on the inner circumference of the outer ring 1. A conical inner ring raceway surface 6 with which the tapered rollers 3 roll is formed on the outer circumference of the inner ring 2, a small rib 7 that protrudes radially outward from the small diameter end of the inner ring raceway surface 6, and a large rib 8 that protrudes radially outward from the large diameter end of the inner ring raceway surface 6.

[0029] The inner ring raceway surface 6 and the outer ring raceway surface 5 face each other radially, sandwiching the tapered roller 3 between them. The outer ring raceway surface 5 and the inner ring raceway surface 6 are conical surfaces that intersect at a common point (cone center O shown in Figure 5) located on the center line of the inner ring 2. When the bearing rotates, each tapered roller 3 rotates while revolving around the center line of the inner ring 2 between the outer ring raceway surface 5 and the inner ring raceway surface 6. When the bearing rotates, the large rib 8 comes into sliding contact with the large end face 9 of the tapered roller 3, and supports part of the axial load.

[0030] The tapered roller 3 has a small end face 10 facing the small rib 7 of the inner ring 2, a large end face 9 facing the large rib 8 of the inner ring 2, a tapered roller rolling surface 11 that comes into rolling contact with the outer ring raceway surface 5 and the inner ring raceway surface 6, a small diameter side roller chamfered portion 12 that connects the roller rolling surface 11 and the small end face 10, a large diameter side roller chamfered portion 13 that connects the roller rolling surface 11 and the large end face 9, and a recessed portion 14 (see Figure 2) that is a circular recess in the centre of the large end face 9 of the tapered roller 3.

[0031] As shown in Figure 2, the large rib 8 has a large rib surface 15 with a linear cross section that contacts the large end face 9 of the tapered roller 3, a cylindrical outer diameter surface 16, and a chamfered portion 17 that slopes radially inward from the outer diameter surface 16 toward the tapered roller 3. At the intersection of the large rib surface 15 and the inner ring raceway surface 6, a relief groove 18 with a concave arc cross section is formed.

[0032] The width dimension a of the large flange surface 15 is set to 1.5 mm or more (preferably 1.6 mm or more, more preferably 1.7 mm or more) and 3.0 mm or less. The large flange surface 15 is a superfinished surface that has been subjected to superfinishing, and its surface roughness is set to 0.005 μmRa or more and 0.080 μmRa or less (preferably 0.050 μmRa or less). The chamfered portion 17 has a convex arc-shaped cross section. The width dimension of the chamfered portion 17 measured in a direction parallel to the large flange surface 15 is set to 0.2 mm or more (preferably 0.4 mm or more) and 1.2 mm or less. Setting the width dimension of the chamfered portion 17 to 0.2 mm or more (preferably 0.4 mm or more) can prevent dents and the like, while setting the width dimension of the chamfered portion 17 to 1.2 mm or less can shorten the turning processing time required to form the chamfered portion 17.

[0033] As shown in Figure 3, the large rib 8 has a relief R portion 20 that smoothly connects to the radially outer side of the large rib surface 15 and has a convex arc-shaped cross section that curves in a direction away from the large end face 9 (see Figure 2) of the tapered roller 3, and a relief straight portion 21 that has a straight cross section that smoothly connects to the radially outer side of the relief R portion 20 so as to form a tangent to the relief R portion 20. The radius of curvature R of the cross section of the relief R portion 20 is larger than the radius of curvature of the cross section of the chamfered portion 17. As shown in Figure 4, the straight line of the cross section of the relief straight portion 21 does not smoothly connect to the chamfered portion 17 so as to form a tangent to the chamfered portion 17, but rather intersects with the chamfered portion 17 to form an intersection.

[0034] As shown in FIG. 2, the diameter e of the recessed portion 14 formed by circularly recessing the center of the large end face 9 of the tapered roller 3 is set so that the boundary between the large end face 9 and the recessed portion 14 (the lower end position of diameter e in the figure) is located radially inward (lower side in the figure) than the radial outer end of the large rib surface 15 (the boundary between the large rib surface 15 and the relief R portion 20; in the figure, the upper end position of the width dimension a of the large rib surface 15).

[0035] As shown in Fig. 3, the distance d from the intersection of the relief straight portion 21 and the chamfered portion 17 to the large flange surface 15 (hereinafter referred to as the "relief drop amount d") is set to a range of 10 µm or more (preferably 15 µm or more, and more preferably 20 µm or more) and 150 µm or less. The ratio of the width dimension b of the relief R portion 20 to the width dimension c of the relief straight portion 21, measured in a direction parallel to the large flange surface 15, is set to a range of 9:1 to 3.5:6.5. The width dimension b + c of the combined region of the relief R portion 20 and the relief straight portion 21, measured in a direction parallel to the large flange surface 15 (hereinafter referred to as the "relief width b + c"), is set to a range of 15 to 60% of the width dimension a of the large flange surface 15.

[0036] As shown in FIG. 4, the angle θ formed between the straight relief portion 21 and the large flange surface 15 is set in the range of 2° to 15°.

[0037] As shown in Figure 5, the inclination angle α of the large rib surface 15 (the angle that the large rib surface 15 forms with the axis-perpendicular direction) is set so that it is perpendicular to the line connecting the contact point between the large rib surface 15 and the large end face 9 of the tapered roller 3 and the cone center O. The angle ρ that this line forms with the inner ring raceway surface 6 is set so that it is β / 8 or more and β / 5 or less, relative to the central angle β of the tapered roller 3. When the angle ρ is β / 8 or more, the large end face 9 of the tapered roller 3 can be brought into stable contact with the large rib surface 15, and when the angle ρ is β / 5 or less, it is possible to suppress a rise in temperature due to contact between the large end face 9 of the tapered roller 3 and the large rib surface 15.

[0038] The inner ring 2 of the tapered roller bearing described above can be manufactured, for example, as follows. First, a preform having a large rib 8 is formed by forging. Next, the large rib 8 of this preform is turned to form the outer diameter surface 16 and chamfered portion 17 shown in Figure 6. Thereafter, as shown in Figure 6, a grinding wheel G1 having a shape corresponding to the straight relief portion 21, the round relief portion 20, and the large rib surface 15 is pressed against the large rib 8 to form the straight relief portion 21, the round relief portion 20, and the large rib surface 15. Then, a superfinishing grinding wheel is pressed against the large rib surface 15 to increase the surface roughness of the large rib surface 15.

[0039] As shown in Figure 3, this tapered roller bearing has a straight relief portion 21 that smoothly connects to the radially outer side of the relief radius portion 20, and the straight relief portion 21, which has a straight cross section, has a larger contact angle hysteresis of the lubricating oil than the relief radius portion 20, which has a convex arc cross section, and is therefore more capable of retaining lubricating oil due to surface tension. Therefore, as shown in Figure 8, this tapered roller bearing has better lubrication between the large end face 9 of the tapered roller 3 and the large rib 8 of the inner ring 2 than a bearing that does not have the straight relief portion 21 and has the entire area from the large rib surface 15 to the chamfered portion 17 as a relief radius portion 20, and is able to form a sufficient oil film between the large end face 9 of the tapered roller 3 and the large rib 8 of the inner ring 2 even when a low-viscosity lubricating oil is used. The low-viscosity lubricating oil referred to here has a viscosity of 3 to 6 mm at an oil temperature condition of 100°C. 2 / sec (The viscosity of conventional lubricating oil is 6 to 12 mm at an oil temperature of 100°C. 2 / second).

[0040] Furthermore, as shown in Figure 3, this tapered roller bearing has a straight relief portion 21 that smoothly continues radially outward from the R relief portion 20, and therefore it is possible to reduce the grinding time for the large rib 8 compared to a bearing in which the entire area from the large rib surface 15 to the chamfered portion 17 is made into the R relief portion 20 without providing the straight relief portion 21, as shown in Figure 8.

[0041] A description will be given with reference to FIGS. 6 and 7. FIG. 6 is a diagram for explaining the grinding of the large collar 8 having a relief straight portion 21 that smoothly continues to the radially outer side of the relief R portion 20 as shown in FIG. 3. In FIG. 6, the grinding wheel G1 has a shape corresponding to the relief straight portion 21, the relief R portion 20, and the large collar surface 15 shown in FIG. 3. By pressing this grinding wheel G1 against the large collar 8, grinding starts from the portion corresponding to the relief straight portion 21 (see FIG. 3), and finally the shaded portion in the figure is cut off by the grinding wheel G1, thereby forming the relief straight portion 21, the relief R portion 20, and the large collar surface 15 shown in FIG. 3. The dimension s in FIG. 6 is the distance from the grinding wheel G1 to the machining start point of the large collar 8, and the dimension t1 in FIG. 6 is the distance from the portion corresponding to the large collar surface 15 of the grinding wheel G1 to the large collar 8.

[0042] On the other hand, FIG. 7 is a diagram for explaining the grinding of the large collar 8 in which, as shown in FIG. 8, no relief straight portion 21 is provided and all of the chamfered portion 17 to the large collar surface 15 is the relief R portion 20. In FIG. 7, the grinding wheel G2 has a shape corresponding to the relief R portion 20 and the large collar surface 15. By pressing this grinding wheel G2 against the large collar 8, grinding starts from the relief R portion 20, and finally the shaded portion in the figure is cut off by the grinding wheel G2, thereby forming the relief R portion 20 and the large collar surface 15. The dimension s in FIG. 7 is the distance from the grinding wheel G2 to the machining start point of the large collar 8, and the dimension t2 in FIG. 7 is the distance from the portion corresponding to the large collar surface 15 of the grinding wheel G2 to the large collar 8. The dimension s in FIG. 6 and the dimension s in FIG. 7 are of the same size.

[0043] Comparing FIGS. 6 and 7, the relationship s < t1 < t2 holds for the dimension s in FIGS. 6 and 7, the dimension t1 in FIG. 6, and the dimension t2 in FIG. 7. That is, the grinding distance (grinding depth) in FIG. 6 is smaller than the grinding distance (grinding depth) in FIG. 7. Therefore, as shown in FIG. 3, the grinding time of the large collar 8 when the relief straight portion 21 that smoothly continues to the radially outer side of the relief R portion 20 is provided can be shortened compared to the grinding time of the large collar 8 when, as shown in FIG. 8, no relief straight portion 21 is provided and all of the chamfered portion 17 to the large collar surface 15 is the relief R portion 20.

[0044] As shown in Figure 4, in this tapered roller bearing, the angle θ that the relief straight portion 21 makes with respect to the large rib surface 15 is set to be 2° or more, so even if the tapered rollers 3 are skewed, the large end faces 9 of the tapered rollers 3 are prevented from coming into contact with the boundary between the relief straight portion 21 and the chamfered portion 17, and it is possible to prevent oil film shortage between the large end faces 9 of the tapered rollers 3 and the relief straight portion 21. Furthermore, because the angle θ that the relief straight portion 21 makes with respect to the large rib surface 15 is set to be 15° or less, it is possible to effectively reduce the grinding depth when forming the relief straight portion 21, relief R portion 20 and large rib surface 15 by grinding, and it is possible to effectively shorten the grinding time for the large rib 8.

[0045] Furthermore, as shown in Figure 2, in this tapered roller bearing, the recessed portion 14 is formed so that the boundary between the large end face 9 of the tapered roller 3 and the recessed portion 14 is located radially inward of the radial outer end of the large rib surface 15. Therefore, even if the lubrication conditions of the bearing deteriorate and the large end face 9 of the tapered roller 3 wears due to contact with the large rib surface 15, stable behavior of the tapered roller 3 can be ensured.

[0046] In other words, if the recessed portion 14 is formed so that the boundary between the large end face 9 of the tapered roller 3 and the recessed portion 14 is located radially outward rather than radially inward from the radially outer end of the large rib surface 15, an area will remain on the large end face 9 of the tapered roller 3 that is not in contact with the large rib surface 15 and will not wear out, and therefore when the large end face 9 of the tapered roller 3 wears due to contact with the large rib surface 15, and particularly if skew or the like occurs, the contact state between the large end face 9 of the tapered roller 3 and the large rib 8 will become unstable, and the behavior of the tapered roller 3 will become unstable. However, if the recessed portion 14 is formed so that the boundary between the large end face 9 of the tapered roller 3 and the recessed portion 14 is located radially inward of the radial outer end of the large rib surface 15, the entire surface of the large end face 9 of the tapered roller 3 will come into contact with the large rib surface 15 and the large end face 9 of the tapered roller 3 will be worn all over. Therefore, even when the large end face 9 of the tapered roller 3 is worn due to contact with the large rib surface 15, the contact state between the large end face 9 of the tapered roller 3 and the large rib 8 will be a surface contact and will be stable, and stable behavior of the tapered roller 3 can be ensured.

[0047] Furthermore, as shown in Figure 3, this tapered roller bearing has a relief drop amount d of 10 µm or more, so even if the tapered rollers 3 are skewed, the large end faces 9 of the tapered rollers 3 are prevented from hitting the intersections of the relief straight portions 21 and the chamfered portions 17, preventing localized strong contact on the large end faces 9 of the tapered rollers 3. Furthermore, because the relief drop amount d is 150 µm or less, the grinding depth when the relief straight portions 21, relief R portions 20 and large rib surface 15 are formed by grinding can be effectively reduced, and the grinding time for the large rib 8 can be effectively shortened.

[0048] Furthermore, in this tapered roller bearing, the width dimension a of the large rib surface 15 shown in Figure 3 is 1.5 mm or more (preferably 1.6 mm or more, and more preferably 1.7 mm or more), and because the width dimension a of the large rib surface 15 is large, it is possible to use a large-sized superfinishing stone when superfinishing the large rib surface 15, making it possible to improve the accuracy of the inclination angle α (see Figure 5) of the large rib surface 15. Specifically, it is possible to superfinish the large rib surface 15 so that the inclination angle α of the large rib surface 15 falls within a range of ±15' (preferably ±10', more preferably ±7') of the design value set so that the angle ρ, which is the angle formed by the line connecting the contact position of the large end face 9 of the tapered roller 3, which is perpendicular to the large rib surface 15, and the cone center O, with the inner ring raceway surface 6, is β / 8 or more and β / 5 or less with respect to the central angle β of the tapered roller 3. This stabilizes the contact state between the large end face 9 of the tapered roller 3 and the large rib surface 15, making it possible to stably suppress the amount of skew of the tapered roller 3 even when a low-viscosity lubricant is used. Table 1 shows the relationship between the width dimension a of the large rib surface 15 and the inclination angle α of the large rib surface 15.

[0049] [Table 1]

[0050] Furthermore, this tapered roller bearing has a surface roughness of 0.08 μmRa or less on the large rib surface 15, and because the surface roughness of the large rib surface 15 is small, it is possible to keep the skew of the tapered rollers 3 small. Table 2 shows the relationship between the surface roughness of the large rib surface 15 and the amount of skew of the tapered rollers 3.

[0051] [Table 2]

[0052] A sample of the tapered roller bearing according to the above embodiment was manufactured and subjected to an evaluation test. The tapered roller bearing used had the following configuration. Bearing size: inner ring diameter 70mm, outer ring diameter 150mm, bearing width 40mm Width of large flange surface 15: 3.5 mm Surface roughness of large flange surface 15: 0.078 μmRa Relief drop amount d: 60mm Width of chamfer: 0.8mm Relief width b+c: 0.69mm

[0053] The test conditions are as follows: Test axial load: P / C=0.11 Test speed: 3000 r / min Lubrication conditions: The tapered roller bearing was immersed in lubricating oil (differential oil), removed, and left for 30 minutes, after which the tapered roller bearing was operated without lubrication.

[0054] As a result of the above test, seizure occurred between the large end face 9 of the tapered roller 3 and the large rib 8 400 seconds after the tapered roller bearing began operation. Meanwhile, when a similar evaluation test was conducted on a tapered roller bearing that did not have the relief R portion 20 and straight relief portion 21, seizure occurred 75 seconds after the tapered roller bearing began operation. From these results, it can be seen that a tapered roller bearing that has the relief R portion 20 and straight relief portion 21 on the large rib 8 has a lifespan that is approximately five times longer than a tapered roller bearing that does not have the relief R portion 20 and straight relief portion 21 on the large rib 8.

[0055] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0056] 1 outer ring 2. Inner circle 3 Tapered rollers 6 Inner ring raceway 8. Large brim 9 Big end face 14 Nusumi Club 15 Large-brimmed face 16 Outer diameter surface 17 Chamfered part 20 Escape R section 21 Escape straight section a Width of the large flange d Relief drop amount θ Angle that the straight relief section makes with the large rib surface

Claims

1. The outer ring (1) and an inner ring (2) arranged coaxially on the radially inner side of the outer ring (1); a plurality of tapered rollers (3) assembled at intervals in the circumferential direction between the outer ring (1) and the inner ring (2), In this tapered roller bearing, a conical inner ring raceway surface (6) with which the plurality of tapered rollers (3) roll and contact is provided on the outer periphery of the inner ring (2), and a large rib (8) formed to protrude radially outward from a large diameter side end of the inner ring raceway surface (6), The large rib (8) has a chamfered portion (17) that slopes radially inward from the outer diameter surface (16) of the large rib (8) toward the tapered roller (3), a large rib surface (15) in cross section that contacts the large end face (9) of the tapered roller (3), a relief R portion (20) that smoothly connects to the radially outer side of the large rib surface (15) and has a convex arc-shaped cross section that curves in a direction away from the large end face (9) of the tapered roller (3), and a relief straight portion (21) that smoothly connects to the radially outer side of the relief R portion (20) so as to form a tangent to the relief R portion (20) and has a straight cross section that intersects the chamfered portion (17), The tapered roller (3) has a recessed portion (14) formed by circularly recessing the center of the large end face (9) of the tapered roller (3), A tapered roller bearing characterized in that the boundary between the large end face (9) of the tapered roller (3) and the recessed portion (14) is located radially inward of the radial outer end of the large rib surface (15).

2. 2. The tapered roller bearing according to claim 1, wherein a ratio of a width dimension (b) of the relief R portion (20) to a width dimension (c) of the relief straight portion (21) when measured in a direction parallel to the large rib surface (15) is set in the range of 9:1 to 3.5:6.

5.

3. 3. The tapered roller bearing according to claim 1, wherein the straight relief portion (21) is formed to form an angle (θ) of 2° to 15° with respect to the large rib surface (15).

4. 4. A tapered roller bearing according to claim 1, wherein a distance (d) from an intersection of the straight relief portion (21) and the chamfered portion (17) to the large rib surface (15) along a direction perpendicular to the large rib surface (15), i.e., a relief drop amount, is set in the range of 10 μm to 150 μm.

5. 5. A tapered roller bearing according to claim 1, wherein the width dimension (a) of the large rib surface (15) is 1.5 mm or more.

6. 6. A tapered roller bearing according to claim 1, wherein the surface roughness of the large rib surface (15) is 0.08 μm Ra or less.

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