JP2018165551A - Tapered-roller bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tapered-roller bearing having high durability even in a high misalignment environment and compatibly improving its rolling fatigue life and seizure resistance.SOLUTION: The tapered-roller bearing includes an outer ring 11 having an outer ring raceway surface on the inner peripheral face, an inner ring 13 having an inner ring raceway surface and a large collar face which is arranged on the large-diameter side further than the inner ring raceway surface, on the outer peripheral face, and arranged inside the outer ring, a plurality of tapered rollers 12 each having a rolling surface and a large end face arrayed between the outer ring raceway surface and the inner ring raceway surface for contacting the outer ring raceway surface and the inner ring raceway surface and for contacting the large collar face, respectively, and arrayed between the outer ring raceway surface and the inner ring raceway surface, and a cage 14 including a plurality of pockets arranged at predetermined spaces in the peripheral direction, and holding the plurality of tapered rollers stored in the plurality of pockets, respectively.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tapered roller bearing, and more particularly to a tapered roller bearing for an automobile.

JP-A-2003-226918 discloses, after carbonitriding a steel of the bearing components in the carbonitriding temperature exceeding the A ₁ transformation point, after cooling to a temperature below the A ₁ transformation point, carburizing at A ₁ transformation point or more A heat treatment method for bearing parts is disclosed in which reheating is performed to a quenching temperature lower than the nitriding temperature. The bearing component obtained by such a heat treatment method has a long life against rolling fatigue, has a high cracking strength, and suppresses an increase in the dimensional change rate over time.

  Japanese Patent Application Laid-Open No. 2009-197904 discloses that, even in rolling machine elements with poor lubrication, surface damage on the contact surface can be easily and effectively performed without using special materials or processing such as special heat treatment or surface treatment. A rolling machine element is disclosed which can be prevented automatically.

  Japanese Patent Application Laid-Open No. 2010-255730 reduces the contact pressure and stress at the contact portion to extend the life of the bearing, and reduces the drop amount at both ends of the roller while eliminating the processing failure of the raceway surface. Therefore, a tapered roller bearing that can improve the machining efficiency is disclosed.

  As for tapered roller bearings incorporated in automobile transmissions and differentials, there is a tendency that the space provided for the multistage transmission and the expansion of the operation space is reduced. As a result, the load applied to the bearing per unit area is increased.

  Further, in automobile transmissions and differentials, a housing containing aluminum as a constituent material tends to be employed. In this case, the rigidity of the case decreases and the inclination of the main shaft increases. Therefore, the tapered roller bearing that rotatably supports the main shaft with respect to the housing is placed in an environment in which a bearing mounting error (misalignment) is likely to occur, that is, a so-called high misalignment environment. Therefore, such a tapered roller bearing is required to have high durability even in a high misalignment environment.

JP 2003-226918 A JP 2009-197904 A JP 2010-255730 A

  A main object of the present invention is to provide a tapered roller bearing which has high durability even in a high misalignment environment and is compatible with improvement in rolling fatigue life and improvement in seizure resistance.

  A tapered roller bearing according to the present invention includes an outer ring having an outer ring raceway surface on an inner peripheral surface, an inner ring raceway surface and a large flange surface disposed on a larger diameter side than the inner ring raceway surface on the outer peripheral surface, An inner ring disposed on the inner side, an outer ring raceway surface arranged between the outer ring raceway surface and the inner ring raceway surface, a rolling surface in contact with the outer ring raceway surface and the inner ring raceway surface, and a large end surface in contact with the large collar surface; It includes a plurality of tapered rollers arranged between the raceway surface and the inner ring raceway surface and a plurality of pockets arranged at predetermined intervals in the circumferential direction, and each of the plurality of tapered rollers is accommodated in each of the plurality of pockets. Holding cage.

The roller coefficient γ exceeds 0.90.
The cage includes a small annular portion that is continuous on the small diameter end surface side of the tapered roller, a large annular portion that is continuous on the large diameter end surface side of the tapered roller, and a plurality of column portions that connect these annular portions.

  The pocket is formed in a trapezoidal shape in which the portion that stores the small diameter side of the tapered roller is the narrow side, and the portion that stores the large diameter side is the wide side.

  From the inner diameter side of the cage to the inner ring side by providing a notch in the column portion on the narrow side of the pocket of the cage with a width extending from the boundary between the small annular portion and the column portion toward the large annular portion The inflowing lubricating oil escapes quickly from the notch to the outer ring side on the outer diameter side, and the pocket-side edge of the small annular portion is shaped so that the bottom side portion of the pocket on the narrow side extends to the column portion.

  At least one of the outer ring, the inner ring, and the plurality of tapered rollers includes a nitrogen-enriched layer formed on a surface layer of the outer ring raceway surface, the inner ring raceway surface, or the rolling surface. The distance from the outermost surface of the surface layer to the bottom of the nitrogen-enriched layer is 0.2 mm or more.

  Crowning is formed on the rolling surface of the tapered roller, and the sum of the crowning drop amounts is a y-z coordinate system in which the generatrix of the rolling surface of the tapered roller is the y-axis and the direction orthogonal to the generatrix is the z-axis. K1, K2, and zm are design parameters, Q is the load, L is the length of the effective contact portion of the rolling contact surface of the tapered roller in the direction of the generating line, E 'is the equivalent elastic modulus, and a is the generating surface of the tapered roller rolling surface. When the length from the taken origin to the end of the effective contact portion, A = 2K1Q / πLE ′, is expressed by Equation (1).

  According to the present invention, it is possible to provide a tapered roller bearing that has high durability even in a high misalignment environment and has a long life against rolling fatigue.

1 is a longitudinal sectional view showing a tapered roller bearing according to Embodiment 1. FIG. 4 is a partial cross-sectional view for explaining a nitrogen-enriched layer in the tapered roller bearing according to Embodiment 1. FIG. It is a figure for demonstrating the shape of the nitrogen enriched layer in the crowning part and center part of the roller of the tapered roller bearing which concerns on Embodiment 1. FIG. It is a figure for demonstrating the shape of the logarithmic crowning of the roller of the tapered roller bearing which concerns on Embodiment 1. FIG. It is a yz coordinate diagram which shows an example of a crowning shape. 1 is a transverse sectional view showing a tapered roller bearing according to Embodiment 1. FIG. FIG. 3 is a developed plan view of a retainer of the tapered roller bearing according to the first embodiment. It is a figure which shows the roller which provided the crowning by which a contour line is represented by a logarithmic function. It is the figure which showed the contour line of the roller which provided the crowning of the partial arc, and the straight part, and the contact surface pressure in the rolling surface of a roller. 3 is a flowchart of a method for manufacturing the tapered roller bearing according to the first embodiment. 6 is a diagram for illustrating a heat treatment method according to Embodiment 1. FIG. FIG. 10 is a diagram for describing a modification of the heat treatment method in the first embodiment. FIG. 3 is a diagram showing an austenite grain boundary of the bearing component according to the first embodiment. It is a figure which shows the austenite grain boundary of the conventional bearing component. 5 is a cross-sectional view showing design specifications of a tapered roller bearing according to Embodiment 2. FIG. 6 is a cross-sectional view for explaining a reference radius of curvature of a roller in a tapered roller bearing according to Embodiment 2. FIG. It is a fragmentary sectional view which shows the area | region enclosed with the dotted line in FIG. 6 is a cross-sectional view for explaining an actual curvature radius of a roller in a tapered roller bearing according to Embodiment 2. FIG. FIG. 9 is a cross-sectional view showing an example of a method for changing a contact position between a raceway surface and a rolling surface in a tapered roller bearing according to a second embodiment. In the tapered roller bearing which concerns on Embodiment 2, it is sectional drawing which shows another example of the change method of the contact position of a raceway surface and a rolling surface. 6 is a graph showing the relationship between the radius of curvature of the large end face of the tapered roller bearing according to Embodiment 2 and the oil film thickness. 6 is a graph showing the relationship between the radius of curvature of the large end face of the tapered roller bearing according to Embodiment 2 and the maximum Hertz stress. 5 is a partial cross-sectional view of a tapered roller bearing according to Embodiment 3. FIG. It is a figure which shows the crowning shape of the roller of the tapered roller bearing shown by FIG. It is a figure showing the relationship between the bus-line direction coordinate of a roller of the tapered roller bearing shown by FIG. 23, and the amount of drops. It is a figure showing the relationship between the maximum value of the equivalent stress of Mises, and a logarithmic crowning parameter. FIG. 10 is a view showing a modification of the tapered roller bearing according to the third embodiment. FIG. 10 is a view showing another modification of the tapered roller bearing according to the third embodiment. FIG. 10 is a development plan view of a retainer of a tapered roller bearing according to a fourth embodiment. FIG. 10 is a development plan view of a modified example of the cage of the tapered roller bearing according to the fourth embodiment. It is sectional drawing which shows the flow of the lubricating oil to the bearing inside of the tapered roller bearing in FIG. It is a graph which shows the result of a torque measurement test. It is a longitudinal cross-sectional view which shows a differential provided with the tapered roller bearing which concerns on Embodiment 4. It is a longitudinal cross-sectional view which shows the transmission provided with the tapered roller bearing which concerns on Embodiment 1. FIG.

  Hereinafter, 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 description thereof will not be repeated.

(Embodiment 1)
<Configuration of tapered roller bearing>
FIG. 1 is a schematic cross-sectional view of a tapered roller bearing according to an embodiment of the present invention. FIG. 2 is a schematic partial sectional view of the tapered roller bearing shown in FIG. FIG. 3 is a partial cross-sectional schematic view of the tapered roller of the tapered roller bearing shown in FIG. FIG. 4 is an enlarged partial cross-sectional schematic diagram of the tapered roller shown in FIG. The tapered roller bearing according to the present embodiment will be described with reference to FIGS.

  A tapered roller bearing 10 shown in FIG. 1 mainly includes an outer ring 11, an inner ring 13, a plurality of rollers 12, and a cage 14. The outer ring 11 has an annular shape and has an outer ring raceway surface 11A on the inner peripheral surface. The inner ring 13 has an annular shape and has an inner ring raceway surface 13A on the outer peripheral surface. The inner ring 13 is disposed on the inner peripheral side of the outer ring 11 so that the inner ring raceway surface 13A faces the outer ring raceway surface 11A.

  The roller 12 is disposed on the inner peripheral surface of the outer ring 11. The roller 12 has a roller rolling surface 12A, and contacts the inner ring raceway surface 13A and the outer ring raceway surface 11A on the roller rolling surface 12A. The plurality of rollers 12 are arranged at a predetermined pitch in the circumferential direction by a cage 14 made of synthetic resin. As a result, the roller 12 is rotatably held on the annular raceway of the outer ring 11 and the inner ring 13. Further, the tapered roller bearing 10 includes a cone including an outer ring raceway surface 11A, a cone including an inner ring raceway surface 13A, and a cone including a locus of a rotation axis when the roller 12 rolls on the center line of the bearing. It is configured to intersect at one point. With such a configuration, the outer ring 11 and the inner ring 13 of the tapered roller bearing 10 are rotatable relative to each other.

  The material constituting the outer ring 11, the inner ring 13, and the roller 12 may be steel. The steel is a portion other than the nitrogen-enriched layers 11B, 12B, and 13B, and at least carbon is 0.6 mass% to 1.2 mass%, silicon is 0.15 mass% to 1.1 mass%, manganese 0.3 mass% or more and 1.5 mass% or less. The steel may further contain 2.0% by mass or less of chromium.

  In the above configuration, if the carbon content exceeds 1.2% by mass, the material hardness is high even if spheroidizing annealing is performed, so that cold workability is hindered and sufficient cold work amount is obtained when performing cold work. The processing accuracy cannot be obtained. In addition, the carbonitriding process tends to become an excessively carburized structure, and there is a risk that the cracking strength is reduced. On the other hand, when the carbon content is less than 0.6% by mass, it takes a long time to secure the required surface hardness and the amount of retained austenite, or the necessary internal hardness is obtained by quenching after reheating. It becomes difficult to be.

  The reason why the Si content is 0.15 to 1.1% by mass is that Si increases resistance to tempering softening to ensure heat resistance, and can improve rolling fatigue life characteristics under lubrication mixed with foreign matter. It is. When the Si content is less than 0.15% by mass, the rolling fatigue life characteristics under lubrication with foreign matters are not improved. On the other hand, when the Si content exceeds 1.1% by mass, the hardness after normalization is too high. Impairs cold workability.

  Mn is effective for securing the quench hardening ability of the carbonitrided layer and the core. When the Mn content is less than 0.3% by mass, sufficient quenching and hardening ability cannot be obtained, and sufficient strength cannot be ensured in the core. On the other hand, if the Mn content exceeds 1.5% by mass, the curing ability becomes excessively high, the hardness after normalization becomes high, and the cold workability is hindered. In addition, the austenite is excessively stabilized and the amount of retained austenite in the core is excessively increased to promote a change in size over time. Further, when steel contains 2.0 mass% or less of chromium, chromium carbide and nitride are precipitated in the surface layer portion, and the hardness of the surface layer portion is easily improved. The Cr content is set to 2.0% by mass or less when the content exceeds 2.0% by mass, the cold workability is remarkably lowered, or even if the content exceeds 2.0% by mass, the hardness of the surface layer portion described above. This is because the improvement effect is small.

  Needless to say, the steel of the present disclosure may contain Fe as a main component and may contain inevitable impurities in addition to the above elements. Inevitable impurities include phosphorus (P), sulfur (S), nitrogen (N), oxygen (O), aluminum (Al), and the like. The amounts of these inevitable impurity elements are each 0.1% by mass or less.

  From a different point of view, the outer ring 11 and the inner ring 13 are preferably made of a steel material that is an example of a bearing material, for example, JIS standard SUJ2. The roller 12 may be made of a steel material that is an example of a bearing material, for example, JIS standard SUJ2. Moreover, the roller 12 may be comprised with other materials, for example, a sialon sintered compact.

  As shown in FIG. 2, nitrogen-enriched layers 11 </ b> B and 13 </ b> B are formed on the raceway surface 11 </ b> A of the outer ring 11 and the raceway surface 13 </ b> A of the inner ring 13. In the inner ring 13, the nitrogen-enriched layer 13 </ b> B extends from the raceway surface 13 </ b> A to the small surface and the large surface. The nitrogen-enriched layers 11B and 13B are regions where the nitrogen concentration is higher than the non-nitrided portion 11C of the outer ring 11 or the non-nitrided portion 13C of the inner ring 13, respectively. A nitrogen-enriched layer 12B is formed on the surface of the roller 12 including the rolling surface 12A. The nitrogen-enriched layer 12B of the roller 12 is a region where the nitrogen concentration is higher than that of the non-nitrided portion 12C of the roller 12. The nitrogen-enriched layers 11B, 12B, and 13B can be formed by any conventionally known method such as carbonitriding or nitriding.

  Note that the nitrogen-enriched layer 12B may be formed only on the roller 12, the nitrogen-enriched layer 11B may be formed only on the outer ring 11, or the nitrogen-enriched layer 13B may be formed only on the inner ring 13. Good. Alternatively, a nitrogen enriched layer may be formed on two of the outer ring 11, the inner ring 13, and the roller 12.

  As shown in FIG. 3, the rolling surface 12 </ b> A (see FIG. 2) of the roller 12 is positioned at both ends, and the crowning portions 22 and 24 where the crowning is formed, and the center connecting the crowning portions 22 and 24. Part 23. No crowning is formed in the central portion 23, and the shape of the central portion 23 in a cross section in the direction along the central line 26 that is the rotation axis of the roller 12 is linear. A chamfered portion 21 is formed between the end surface 17 of the roller 12 and the crowning portion 22. A chamfered portion 25 is also formed between the end surface 16 and the crowning portion 24.

  Here, in the manufacturing method of the roller 12, when performing the process (carbonitriding process) for forming the nitrogen-enriched layer 12B, no crowning is formed on the roller 12, and the outer shape of the roller 12 is a dotted line in FIG. It becomes the surface 12E before processing shown by these. After the nitrogen-enriched layer is formed in this state, the side surface of the roller 12 is processed as a finish process as shown by the arrow in FIG. 4 to obtain the crowning portions 22 and 24 in which the crowning is formed.

Nitrogen enriched layer thickness:
The depth of the nitrogen-enriched layer 12B in the roller 12, that is, the distance from the outermost surface of the nitrogen-enriched layer 12B to the bottom of the nitrogen-enriched layer 12B is 0.2 mm or more. Specifically, a first measurement point 31 that is a boundary point between the chamfered portion 21 and the crowning portion 22, a second measurement point 32 that is a distance W of 1.5 mm from the end surface 17, and the center of the rolling surface of the roller. In the measurement point 33, the depths T1, T2, and T3 of the nitrogen-enriched layer 12B at each position are 0.2 mm or more. Here, the depth of the nitrogen-enriched layer 12B means the thickness of the nitrogen-enriched layer 12B in the radial direction perpendicular to the center line 26 of the roller 12 and toward the outer peripheral side. The values of the depths T1, T2, and T3 of the nitrogen-enriched layer 12B depend on the process conditions such as the shape and size of the chamfered portions 21 and 25, the process of forming the nitrogen-enriched layer 12B, and the finishing process described above. It can be changed as appropriate. For example, in the configuration example shown in FIG. 4, the depth T2 of the nitrogen-enriched layer 12B is set to another depth due to the formation of the crowning 22A after the nitrogen-enriched layer 12B is formed as described above. Although it is smaller than the lengths T1 and T3, the magnitude relationship between the values of the depths T1, T2, and T3 of the nitrogen-enriched layer 12B can be appropriately changed by changing the process conditions described above.

  Further, regarding the nitrogen-enriched layers 11B and 13B in the outer ring 11 and the inner ring 13, the thickness of the nitrogen-enriched layers 11B and 13B, which is the distance from the outermost surface to the bottom of the nitrogen-enriched layers 11B and 13B, is 0.2 mm. That's it. Here, the thickness of the nitrogen-enriched layers 11B and 13B means the distance to the nitrogen-enriched layers 11B and 13B in the direction perpendicular to the outermost surface of the nitrogen-enriched layers 11B and 13B.

Crowning shape:
The shape of the crowning formed on the crowning portions 22, 24 of the roller 12 is defined as follows. That is, the sum of the amount of drop of crowning is K ₁ , K ₂ , z _m in the yz coordinate system in which the generatrix of the rolling surface 12A of the roller 12 is the y-axis and the direction orthogonal to the generatrix is the z-axis. , Q is the load, L is the length in the generatrix direction of the effective contact portion of the rolling contact surface 12A of the roller 12, E 'is the equivalent elastic modulus, and a is the effective contact portion from the origin on the generatrix of the rolling contact surface of the roller 12. When the length to the end of A is A = 2K ₁ Q / πLE ′, it is expressed by the following formula (1).

  FIG. 5 is a yz coordinate diagram showing an example of the crowning shape. In FIG. 5, the bus 12 has a y-axis, and the origin O is located at the center of the effective contact portion of the inner ring 13 or the outer ring 11 on the bus 12 and in the direction perpendicular to the bus (radial direction). An example of the crowning represented by the above formula (1) is shown in the yz coordinate system taking the z axis. In FIG. 5, the vertical axis is the z-axis and the horizontal axis is the y-axis. The effective contact portion is a contact portion with the inner ring 13 or the outer ring 11 when the crown 12 is not formed on the roller 12. Further, each crowning of the plurality of rollers 12 constituting the tapered roller bearing 10 is normally formed line-symmetrically with respect to the z axis passing through the central portion of the effective contact portion, and therefore only one crowning 22A is shown in FIG. ing.

  The load Q, the length L in the generatrix direction of the effective contact portion, and the equivalent elastic modulus E ′ are given as design conditions, and the length a from the origin to the end of the effective contact portion is a value determined by the position of the origin. It is.

In the above formula (1), z (y) indicates the drop amount of the crowning 22A at the position y in the generatrix direction of the roller 12, and the coordinates of the starting point O1 of the crowning 22A are (a−K ₂ a, 0). Therefore, the range of y in the formula (1) is y> (a−K ₂ a). In FIG. 5, since the origin O is located at the center of the effective contact portion, a = L / 2. Further, since the region from the origin O to the starting point O1 of the crowning 22A is the central portion (straight portion) where the crowning is not formed, when 0 ≦ y ≦ (a−K ₂ a), z (y) = 0.

Magnification design parameters K ₁ is a load Q, the geometric means the degree of curvature of the crowning 22A. Design parameters K _2, which means the ratio of the generatrix direction length ym of the crowning 22A against generatrix direction length a from the origin O to the end of the effective contact portions _{(K 2 = ym / a)} . The design parameter z _m means the drop amount at the end of the effective contact portion, that is, the maximum drop amount of the crowning 22A.

Here, the crowning of the roller shown in FIG. 8 to be described later is a full crowning with the design parameter K ₂ = 1 and no straight portion, and a sufficient drop amount that does not cause an edge load is secured. However, if the drop amount is excessive, the machining allowance generated from the material that has been removed during processing increases, leading to an increase in cost. Therefore, the design parameters K ₁ , K ₂ , and z _m are optimized as follows.

Various optimization methods for the design parameters K ₁ , K ₂ , and z _m can be adopted. For example, a direct search method such as Rosenblock method can be adopted. Here, since the damage at the rolling origin of the roller depends on the surface pressure, the crowning that prevents oil film breakage on the contact surface under dilute lubrication can be obtained by using the surface pressure as the optimization objective function. Can do.

In addition, when logarithmic crowning is applied to the roller, it is preferable to provide a straight portion (central portion 23) having a length of ½ or more of the total length in the central portion of the rolling surface in order to ensure the processing accuracy of the roller. In this case, K ₂ may be a constant value, and K ₁ and z _m may be optimized.

Roller coefficient:
As shown in FIGS. 1 and 6, the inner ring 13 has a conical raceway surface 13A, and has a large brim portion 41 on the large diameter side of the raceway surface 13A and a small brim portion 42 on the small diameter side. Here, the tapered roller bearing 10 has a roller coefficient γ> 0.90. Here, the roller coefficient γ is defined by the relational expression γ = (Z · DA) / (π · PCD) as the number of rollers Z, the roller average diameter DA, and the roller pitch circle diameter PCD.

Cage shape:
As shown in FIG. 7, the cage 14 includes a small annular portion 106 that is continuous on the small diameter end surface side of the tapered roller 12, a large annular portion 107 that is continuous on the large diameter end surface side of the tapered roller 12, and these small annular portions 106. And a plurality of column portions 108 connecting the large annular portion 107, and a trapezoidal pocket 109 in which the portion storing the small diameter side of the tapered roller 12 is the narrow side and the portion storing the large diameter side is the wide side. Is formed. On the narrow side and wide side of the pocket 109, two notches 110a and 110b are respectively provided in the pillars 108 on both sides, and each of the notches 110a and 110b has a depth of 1.0 mm. The width is 4.6 mm.

Crystal structure of the nitrogen-enriched layer:
FIG. 13 is a schematic view illustrating the microstructure of the bearing component constituting the tapered roller bearing according to the present embodiment, particularly the prior austenite grain boundary. FIG. 13 shows the microstructure in the nitrogen-enriched layer 12B. The prior austenite crystal grain size in the nitrogen-enriched layer 12B in the present embodiment has a JIS standard grain size number of 10 or more, and is sufficiently refined as compared with a conventional general quenched product.

<Measuring method of various characteristics>
Measuring method of nitrogen concentration:
About bearing parts, such as the outer ring | wheel 11, the roller 12, and the inner ring | wheel 13, about the cross section perpendicular | vertical to the surface of the area | region in which the nitrogen enriched layers 11B, 12B, and 13B were formed, respectively, it was lined by EPMA (Electron Probe Micro Analysis) in the depth direction. Perform analysis. In the measurement, each bearing part is cut from the measurement position in a direction perpendicular to the surface to expose the cut surface, and the measurement is performed on the cut surface. For example, with regard to the roller 12, the cut surface is exposed by cutting the roller 12 in a direction perpendicular to the center line 26 from the positions of the first measurement point 31 to the third measurement point 33 shown in FIG. On the cut surface, the nitrogen concentration is analyzed by the EPMA at a plurality of measurement positions that are 0.05 mm from the surface of the roller 12 toward the inside. For example, five measurement positions are determined, and the average value of the measurement data at the five positions is used as the nitrogen concentration of the roller 12.

  Further, for the outer ring 11 and the inner ring 13, after exposing the cross section along the radial direction perpendicular to the central axis and the central axis in the raceway surfaces 11A and 13A with the central portion in the central axis direction of the bearing as the measurement position, The nitrogen concentration is measured for the cross section by the same method as described above.

Method for measuring the distance from the outermost surface to the bottom of the nitrogen-enriched layer:
About the outer ring | wheel 11 and the inner ring | wheel 13, hardness distribution is measured in the depth direction from the surface about the cross section made into the measuring object in the measuring method of the said nitrogen concentration. A Vickers hardness measuring machine can be used as the measuring device. In the tapered roller bearing 10 after tempering at 500 ° C. × 1 h, hardness measurement is performed at a plurality of measurement points arranged in the depth direction, for example, measurement points arranged at intervals of 0.02 mm. And let the area | region whose Vickers hardness is HV475 or more be a nitrogen-rich layer.

  For the roller 12, in the cross section at the first measurement point 31 shown in FIG. 3, the hardness distribution in the depth direction is measured as described above to determine the region of the nitrogen-enriched layer.

Measuring method of particle number:
As a method for measuring the prior austenite crystal grain size, a method defined in JIS standard G0551: 2013 is used. The cross section to be measured is the cross section measured by the method for measuring the distance to the bottom of the nitrogen-enriched layer.

Crowning shape measurement method:
The crowning shape of the roller 12 can be measured by any method. For example, the crowning shape may be measured by measuring the shape of the roller 12 with a three-dimensional shape measuring instrument.

<Operational effect of tapered roller bearing>
Although there are some overlapping portions below, the characteristic configurations of the tapered roller bearing described above are listed.

A tapered roller bearing 10 according to the present disclosure includes an outer ring 11, an inner ring 13, and a plurality of tapered rollers 12. The outer ring 11 has an outer ring raceway surface 11A on the inner peripheral surface. The inner ring 13 has an inner ring raceway surface 13 </ b> A on the outer peripheral surface, and is disposed inside the outer ring 11. The plurality of rollers 12 are arranged between the outer ring raceway surface 11A and the inner ring raceway surface 13A, and have a rolling surface 12A that contacts the outer ring raceway surface 11A and the inner ring raceway surface 13A. At least one of the outer ring 11, the inner ring 13 and the plurality of rollers 12 is formed of nitrogen-enriched layers 11B, 13B, and 12B formed on the outer ring raceway surface 11A, the inner ring raceway surface 13A, or the rolling contact surface 12A. including. As for the prior austenite crystal grain size in the nitrogen-enriched layers 11B, 12B, and 13B, the JIS standard grain size number is 10 or more. The distance T1 from the outermost surface of the surface layer to the bottom of the nitrogen-enriched layers 11B, 12B, 13B is 0.2 mm or more. On the rolling surface 12B of the roller 12, a crowning 22A is formed. The sum of the drop amounts of the crowning 22A is a design parameter with K ₁ , K ₂ , and z _m in the yz coordinate system in which the generatrix of the rolling surface 12B of the roller 12 is the y axis and the generatrix orthogonal direction is the z axis. Q is the load, L is the length in the generatrix of the effective contact portion of the rolling contact surface 12A of the roller 12, E 'is the equivalent elastic modulus, and a is the origin of the effective contact portion from the origin on the generatrix of the rolling contact surface of the roller 12. When the length to the end, A = 2K ₁ Q / πLE ′, is expressed by the following formula (1).

  The load Q, the length L in the generatrix direction of the effective contact portion, and the equivalent elastic modulus E ′ are given as design conditions, and the length a from the origin to the end of the effective contact portion is determined according to the position of the origin. Value.

  In this way, the nitrogen-enriched layers 11B, 12B, and 13B in which the prior austenite crystal grain size is sufficiently refined are formed in at least one of the outer ring 11, the inner ring 13, and the roller 12 as a tapered roller. Therefore, while having a high rolling fatigue life, it is possible to improve the Charpy impact value, the fracture toughness value, the crushing strength, and the like.

  Further, since the rolling surface 12A of the roller 12 is provided with a crowning (so-called logarithmic crowning) in which the contour line is represented by a logarithmic function such that the sum of the drop amounts is represented by the above formula (1), As compared with the case where the crowning represented by the partial arc is formed, the local increase in the surface pressure can be suppressed, and the occurrence of wear on the rolling surface of the roller can be suppressed.

  Here, the effect of the logarithmic crowning described above will be described in more detail. FIG. 8 is a diagram in which the contour line of a roller provided with a crowning whose contour line is represented by a logarithmic function and the contact surface pressure on the rolling surface of the roller are overlapped. FIG. 9 is a diagram in which the contour line of the roller provided with the crowning of the partial arc and the straight portion and the contact surface pressure on the rolling surface of the roller are overlapped. The vertical axis on the left side of FIGS. 8 and 9 indicates the amount of crowning drop (unit: mm). The horizontal axis in FIGS. 8 and 9 indicates the position (unit: mm) in the axial direction of the roller. The vertical axis on the right side of FIGS. 8 and 9 represents the contact surface pressure (unit: GPa).

  When the contour line of the rolling surface of the tapered roller is formed in a shape having a partial arc crowning and a straight portion, the contact surface pressure increases at the boundary between the crowning portion and the straight portion, as shown in FIG. For this reason, if a lubricating film having a sufficient thickness is not formed, wear due to metal contact tends to occur. When wear occurs partially on the contact surface, metal contact is more likely to occur in the vicinity of the contact surface, so that wear on the contact surface is promoted and the tapered roller is damaged.

  Therefore, when a crowning whose contour line is represented by a logarithmic function is provided on the rolling surface of the tapered roller as the contact surface, for example, as shown in FIG. 8, the crowning represented by the partial arc of FIG. 9 is provided. Compared to the case, the local surface pressure becomes lower, and the contact surface can be made less likely to be worn. Therefore, even when the lubricant film thickness is reduced by reducing the amount of lubricant present on the rolling surface of the tapered roller or by reducing the viscosity, wear of the contact surface is prevented and damage to the tapered roller is prevented. Can do. 8 and 9 show an orthogonal coordinate system in which the generatrix direction of the roller is the horizontal axis and the generatrix orthogonal direction is the vertical axis, the origin O of the horizontal axis at the center of the effective contact portion of the inner ring or the outer ring. Is set to indicate the contour line of the roller, and the contact pressure is shown with the contact pressure as the vertical axis. Thus, the tapered roller bearing 10 which shows a long lifetime and high durability is realizable by employ | adopting the above structures.

  In the tapered roller bearing 10, the nitrogen concentration in the nitrogen-enriched layers 11B, 12B, and 13B at a depth of 0.05 mm from the outermost surface is 0.1% by mass or more. In this case, since the nitrogen concentration on the outermost surface of the nitrogen-enriched layers 11B, 12B, and 13B can be a sufficient value, the hardness of the outermost surface of the nitrogen-enriched layers 11B, 12B, and 13B can be made sufficiently high. Moreover, it is preferable that the above conditions such as the grain size of the prior austenite grain size, the distance to the bottom of the nitrogen-enriched layer, and the nitrogen concentration are satisfied at least at the first measurement point 31 in FIG.

  In the tapered roller bearing 10, at least one of the outer ring 11, the inner ring 13, and the roller 12 on which the nitrogen-enriched layers 11B, 12B, and 13B are formed is made of steel. In the steel, in portions other than the nitrogen-enriched layers 11B, 12B, and 13B, that is, in the non-nitrided portions 11C, 12C, and 13C, at least carbon (C) is 0.6 mass% or more and 1.2 mass% or less, silicon (Si ) 0.15 mass% to 1.1 mass%, and manganese (Mn) 0.3 mass% to 1.5 mass%. In the tapered roller bearing, the steel may further contain 2.0 mass% or less of chromium. In this case, the nitrogen-enriched layers 11B, 12B, and 13B having the structure defined in the present embodiment can be easily formed by using a heat treatment described later.

In the tapered roller bearing 10, at least one of the design parameters K ₁ , K ₂ , and z _m in the above formula (1) is optimized using the contact surface pressure between the tapered roller and the outer ring or the inner ring as an objective function. .

The design parameters K ₁ , K ₂ , and z _m are determined by optimizing any one of the contact surface pressure, stress, and life as an objective function, and the damage at the surface starting point depends on the contact surface pressure. Here, according to the above-described embodiment, the contact surface pressure is optimized as an objective function and the design parameters K ₁ , K ₂ , and z _m are set, so that the contact surface is prevented from being worn even under conditions where the lubricant is lean. A possible crowning is obtained.

  In the tapered roller bearing 10, at least one of the outer ring 11 and the inner ring 13 includes nitrogen-enriched layers 11B and 13B. In this case, the outer ring 11 or the inner ring 13 having a long life and high durability is obtained by forming the nitrogen-enriched layers 11B and 13B having a refined crystal structure in at least one of the outer ring 11 and the inner ring 13. be able to.

  In the tapered roller bearing 10, the roller 12 includes a nitrogen-enriched layer 12B. In this case, the roller 12 having the long life and high durability can be obtained by forming the nitrogen-enriched layer 12B having a refined crystal structure in the roller 12.

<Method of manufacturing tapered roller bearing>
FIG. 10 is a flowchart for explaining a method of manufacturing the tapered roller bearing shown in FIG. FIG. 11 is a schematic diagram showing a heat treatment pattern in the heat treatment step of FIG. FIG. 12 is a schematic diagram showing a modification of the heat treatment pattern shown in FIG. FIG. 14 is a schematic view illustrating a microstructure of a bearing component as a comparative example, particularly an old austenite grain boundary. Hereinafter, the manufacturing method of a tapered roller bearing is demonstrated.

  As shown in FIG. 10, a component preparation step (S100) is first performed. In this step (S100), members to be bearing parts such as the outer ring 11, the inner ring 13, the roller 12, and the cage 14 are prepared. In addition, the crowning is not yet formed on the member to be the roller 12, and the surface of the member is a pre-processed surface 12E indicated by a dotted line in FIG.

Next, a heat treatment step (S200) is performed. In this step (S200), a predetermined heat treatment is performed to control the characteristics of the bearing component. For example, in order to form the nitrogen-enriched layers 11B, 12B, and 13B according to the present embodiment in at least one of the outer ring 11, the roller 12, and the inner ring 13, a carbonitriding process or a nitriding process, a quenching process, and a tempering process are performed. Perform processing. An example of the heat treatment pattern in this step (S200) is shown in FIG. FIG. 11 shows a heat treatment pattern showing a method of performing primary quenching and secondary quenching. Figure 12 is a material in the course quenching cooled to below the A ₁ transformation point temperature, then, it shows a heat treatment pattern reheated shows the final quenching Ru method. In these figures, in the treatment T ₁ , carbon and nitrogen are diffused in the steel base and the carbon is sufficiently dissolved, and then cooled to below the A ₁ transformation point. Next, in the process T ₂ of the in the figure, than the processing T ₁ is reheated to a low temperature, subjected to oil quenching from there. Thereafter, for example, a tempering process at a heating temperature of 180 ° C. is performed.

  According to the above heat treatment, it is possible to improve the cracking strength and reduce the aging rate of dimensional change while carbonitriding the surface layer portion of the bearing component, rather than normal quenching, that is, carbonitriding once after the carbonitriding treatment. Can do. According to the heat treatment step (S200), in the nitrogen-enriched layers 11B, 12B, and 13B having a quenched structure, the grain size of the prior austenite crystal grains is compared with the microstructure in the conventional quenched structure shown in FIG. As a result, a microstructure as shown in FIG. The bearing component subjected to the above heat treatment has a long life against rolling fatigue, can improve the cracking strength, and can also reduce the rate of dimensional change over time.

  Next, a processing step (S300) is performed. In this step (S300), finishing is performed so that the final shape of each bearing component is obtained. For the roller 12, the crowning 22A and the chamfered portion 21 are formed by machining such as cutting as shown in FIG.

Next, an assembly process (S400) is performed. In this step (S400), the tapered roller bearing 10 shown in FIG. 1 is obtained by assembling the bearing components prepared as described above. In this way, the tapered roller bearing 10 shown in FIG. 1 can be manufactured.
(Experimental example 1)
<Sample>
As a sample, Sample No. Four types of tapered rollers 1 to 4 were prepared as samples. The model number of the tapered roller was 30206. As the material of the tapered roller, JIS standard SUJ2 material (1.0 mass% C-0.25 mass% Si-0.4 mass% Mn-1.5 mass% Cr) was used.

  Sample No. For No. 1, after carbonitriding and quenching, logarithmic crowning according to the present embodiment shown in FIG. 5 was formed at both ends. The carbonitriding temperature was 845 ° C. and the holding time was 150 minutes. The atmosphere of the carbonitriding process was RX gas + ammonia gas. Sample No. For sample 2, sample no. After performing carbonitriding and quenching in the same manner as in No. 1, the partial arc crowning shown in FIG. 9 was formed.

  Sample No. For No. 3, after carrying out the heat treatment pattern shown in FIG. 11, logarithmic crowning according to the present embodiment shown in FIG. 5 was formed at both ends. The carbonitriding temperature was 845 ° C. and the holding time was 150 minutes. The atmosphere of the carbonitriding process was RX gas + ammonia gas. The final quenching temperature was 800 ° C.

  Sample No. For No. 4, after performing the heat treatment pattern shown in FIG. 11, logarithmic crowning according to the present embodiment shown in FIG. 5 was formed at both ends. The final quenching temperature was 800 ° C. In order to set the nitrogen concentration in the nitride-enriched layer at a depth of 0.05 mm from the outermost surface of the sample to 0.1% by mass or more, the carbonitriding temperature was 845 ° C. and the holding time was 150 minutes. The atmosphere of the carbonitriding process was RX gas + ammonia gas. Furthermore, the furnace atmosphere was strictly controlled. Specifically, the furnace temperature unevenness and the ammonia gas atmosphere unevenness were suppressed. Sample No. mentioned above. 3 and sample no. 4 corresponds to the embodiment of the present invention. Sample No. 1 and sample no. 2 corresponds to the comparative example.

<Experiment details>
Experiment 1: Life test A life test apparatus was used. As test conditions, test load: Fr = 18 kN, Fa = 2 kN, lubricating oil: turbine oil 56, lubrication method: oil bath lubrication were used. In the life test apparatus, two tapered roller bearings as test objects are arranged so as to support both ends of a support shaft. A cylindrical roller bearing for applying a radial load to the tapered roller bearing via the support shaft is disposed at the center in the extending direction of the support shaft, that is, the center of the two tapered roller bearings. A radial load is applied to the tapered roller bearing as a test object by applying a radial load to the cylindrical roller bearing for load application. The axial load is transmitted from one tapered roller bearing to the support shaft through the housing of the life test apparatus, and the other tapered roller bearing is loaded with the axial load. Thereby, the life test of the tapered roller bearing is performed.

Experiment 2: Life test under uneven load The same test equipment as the life test of Experiment 1 was used. The test conditions were basically the same as those in Experiment 1 described above, but the test was performed with an axial load of 2/1000 rad applied to the center axis of the roller and an unbalanced load applied.

Experiment 3: Rotational torque test Sample No. About 1-4, the torque measurement test using the vertical torque tester was done. As test conditions, test load: Fa = 7000N, lubricating oil: turbine oil 56, lubrication method: oil bath lubrication, rotation speed: 5000 rpm were used.

<Result>
Experiment 1: Life test Sample No. 4 showed the best results and was considered to have a long life. Sample No. 2 and Sample No. 3 is sample No. Although it did not reach the result of 4, it showed a good result and was judged to be sufficiently practical. On the other hand, sample No. For 1, the result showed the shortest life.

Experiment 2: Life test under unbalanced load 4 and sample no. 3 showed the best results and was considered to have a long life. Next, sample No. 1 is Sample No. 4 and sample no. Although it was less than 3, comparatively good results were shown. On the other hand, sample No. No. 2 shows a result worse than the result in Experiment 1 above, and it is considered that the life was shortened by the uneven load condition.

Experiment 3: Rotational torque test Sample No. 1, sample no. 3, Sample No. No. 4 showed a sufficiently small rotational torque, which was a good result. On the other hand, sample No. No. 2 had a rotational torque greater than that of the other samples.

From the above results, the sample No. No. 4 showed a good result in any test, and it was the best overall result. Sample No. 3 also sample No. 1 and sample no. The result was better than 2.
(Experimental example 2)
<Sample>
Sample No. in Experimental Example 1 above. 4 was used.

<Experiment details>
Nitrogen concentration measurement at a depth of 0.05 mm from the surface:
Sample No. For No. 4, the measurement of the nitrogen concentration and the depth measurement of the nitrogen-enriched layer were carried out. As a measurement method, the following method was used. That is, at the first to third measurement points shown in FIG. 3, the cut surface is exposed by cutting the tapered roller as a sample in a direction perpendicular to the center line. On the cut surface, the nitrogen concentration is analyzed by the EPMA at a plurality of measurement positions that are 0.05 mm from the surface of the sample toward the inside. In each of the cross sections at the first to third measurement points, five measurement positions were determined, and the average value of the measurement data at the five points was defined as the nitrogen concentration at each measurement point.

Measuring the distance to the bottom of the nitrogen-enriched layer:
In the section at the first to third measurement points of the tapered roller after tempering at 500 ° C. × 1 h, hardness measurement was performed at a plurality of measurement points arranged at intervals of 0.5 mm in the depth direction. And the area | region where Vickers hardness was HV450 or more was made into the nitrogen enriched layer, and the depth of the position where the said hardness became HV450 was made into the bottom part of the nitrogen enriched layer.

<Result>
Nitrogen concentration measurement at a depth of 0.05 mm from the surface:
For the first measurement point, the nitrogen concentration was 0.2% by mass, for the second measurement point, the nitrogen concentration was 0.25% by mass, and for the third measurement point, the nitrogen concentration was 0.3% by mass. . At any measurement point, the measurement result falls within the scope of the present invention.

Measuring the distance to the bottom of the nitrogen-enriched layer:
For the first measurement point, the distance to the bottom of the nitrogen-enriched layer is 0.3 mm, for the second measurement point, the distance is 0.35 mm, and for the third measurement point, the distance is 0.3 mm. It was. At any measurement point, the measurement result falls within the scope of the present invention.

(Experimental example 3)
<Example Sample>
The radius of curvature R of the large end surface of the tapered roller shown in FIG. 15 is in the range of R / R _BASE = 0.75 to 0.87, and the surface roughness Ra of the large collar surface of the inner ring is 0.12 μm. A tapered roller bearing (sample Nos. 5 to 5 in Table 1) having a small flange surface formed by a ground surface parallel to the small end surface of the tapered roller and having a first gap within a size regulation range of 0.4 mm or less. 8) was prepared. The bearings have an inner diameter of 40 mm and an outer diameter of 68 mm.

<Comparative sample>
The value of R / R _BASE is out of the scope of the present application, the small collar surface of the inner ring is inclined outward with respect to the small end surface of the tapered roller, and the first gap exceeds 0.4 mm (see Table 1). Sample Nos. 9 to 11) were prepared. The dimensions of each bearing are the same as in the example.

  An anti-seizure test using a rotation tester was performed on the tapered roller bearings of the above-described examples and comparative examples. Sample No. 6 and sample no. A habituation test was also performed on ten tapered roller bearings. The number of samples of the running-in test is the sample number. 66 for sample 6, sample no. For ten, the number was ten. The test conditions for the seizure resistance test are as follows. Load load: 19.61 kN Number of revolutions: 1000 to 3500 rpm Lubricating oil: Turbine VG56 (oil supply amount 40 ml / min, oil supply temperature 40 ° C. ± 3 ° C.).

  The test results are shown in Table 1. Seizure in the seizure resistance test occurs between the large collar surface of the inner ring and the large end surface of the tapered roller.

  In the tapered roller bearings of the examples, the limit rotational speed for occurrence of seizure in the seizure resistance test is 2700 rpm or more, and it can be seen that the friction resistance between the inner ring large collar surface and the tapered roller large end surface is small. On the other hand, the tapered roller bearing of the comparative example has a limit rotational speed of seizure occurrence of 2500 rpm or less, which may cause a problem under normal use conditions such as a differential. A sample 11 having a large surface roughness Ra of the large ridge surface is a sample No. 1 having the same curvature radius R. The seizure generation limit rotational speed lower than 10 is shown.

  In addition, in the comparative example, the average value of the number of rotations until the tapered roller settles in the normal position is 6 times in the comparative example, whereas the result is about 2.96 times that is about half in the example. Yes. In the embodiment, the standard deviation of the variation in the number of rotations is also small, and it can be seen that the habituation operation time can be stably reduced.

As described above, in the tapered roller bearing of the present invention, the radius of curvature R of the large end surface of the tapered roller is set to a value in the range of R / R _BASE = 0.75 or more and 0.87 or less, and the small collar surface of the inner ring. Is formed with a surface parallel to the small end face of the tapered roller, so that it is possible to prevent the occurrence of seizure by reducing the torque loss and heat generation caused by the friction between the inner ring large collar face and the large end face of the tapered roller. The bearing mounting work can be made efficient by shortening. Further, the durability of the vehicle gear shaft support device can be improved.

  Furthermore, in the tapered roller bearing 10 according to the first embodiment, the cage 14 includes a small annular portion 106 that is continuous on the small diameter end surface side of the tapered roller 12, a large annular portion 107 that is continuous on the large diameter end surface side of the tapered roller 12, and And a plurality of column portions 108 connecting these annular portions. The pocket 109 is formed in a trapezoidal shape in which the portion for storing the small diameter side of the tapered roller 12 is the narrow side and the portion for storing the large diameter side is the wide side. By providing a notch in the narrow pillar portion of the pocket 109 of the cage 14 with a width extending from the boundary between the small annular portion 106 and the pillar portion toward the large annular portion 107, the inner diameter side of the cage 14 is provided. The lubricating oil flowing from the notch to the inner ring side quickly escapes from the notch to the outer ring side on the outer diameter side, the edge of the small annular part 106 on the pocket 109 side, and the bottom part of the narrow side of the pocket 109 to the column part It has an extended shape.

  In tapered roller bearings used in areas where lubricating oil flows from the outside, a notch is provided in the pocket of the cage, and the lubricating oil that flows separately into the outer diameter side and the inner diameter side of the cage is notched. In order to improve the circulation of the lubricating oil inside the bearing. However, in tapered roller bearings in which lubricating oil is divided into the outer diameter side and inner diameter side of the cage and flows into the bearing, torque loss will increase if the proportion of lubricating oil flowing from the inner diameter side of the cage to the inner ring side increases. It turns out that it grows. The reason is considered as follows.

  That is, the lubricating oil flowing from the outer diameter side of the cage to the outer ring side smoothly passes to the larger diameter side of the tapered roller along the raceway surface because there is no obstacle on the inner diameter surface of the outer ring. The lubricating oil that flows out from the inner diameter side of the cage to the inner ring side has a large flaw on the outer diameter surface of the inner ring, so when it passes along the raceway surface to the larger diameter side of the tapered roller It will be dammed up with a large spear and will easily stay inside the bearing. For this reason, when the ratio of the lubricating oil flowing from the inner diameter side to the inner ring side of the cage increases, the amount of the lubricating oil staying inside the bearing increases, and this staying lubricating oil becomes a flow resistance against the bearing rotation and generates torque. Loss is considered to increase.

  Therefore, in the tapered roller bearing 10 according to the first embodiment, the lubricating oil flowing from the inner diameter side of the cage to the inner ring side is provided by providing a notch in the narrow-side column part of the trapezoidal pocket of the cage. On the narrow side of the pocket that houses the small diameter side of the tapered roller, it quickly escapes from the notch to the outer ring side, and the amount of lubricating oil that reaches the main shaft along the raceway surface of the inner ring is reduced and stays inside the bearing. The amount of lubricating oil was reduced to reduce torque loss due to the flow resistance of the lubricating oil.

(Embodiment 2)
15 to 18, the tapered roller bearing according to the second embodiment basically has the same configuration as the tapered roller bearing 10 according to the first embodiment, but the large end surface 16 of the tapered roller 12 has the same configuration. The ratio R / R _BASE between the radius of curvature R and the distance R _BASE from the point O to the large collar surface 18 of the inner ring 13 is 0.75 or more and 0.87 or less, and the small collar surface of the inner ring 13 is: The ground surface is finished in parallel with the small end surface 17 of the tapered roller 12 arranged on the raceway surface 13A.

As shown in FIG. 15, the conical angle vertices of the tapered rollers 12 and the raceway surfaces 11 </ b> A and 13 </ b> A of the outer ring 11 and the inner ring 13 coincide at one point O on the center line of the tapered roller bearing 10. The ratio R / R _BASE between the curvature radius R of the end face 16 and the distance R _BASE from the point O to the large collar surface 18 of the inner ring 13 is manufactured to be in the range of 0.75 to 0.87. . The large collar surface 18 is ground to a surface roughness Ra of, for example, 0.12 μm or less.

The ratio R / R _BASE between the radius of curvature R of the large end face of the tapered roller and the distance R _BASE from the apex of the cone angle of the tapered roller to the inner ring large collar surface is set in the range of 0.75 to 0.87. For the following reasons.

FIG. 21 shows the result of calculating the oil film thickness t formed between the inner ring large collar surface and the tapered roller large end surface using Karna's formula. The vertical axis represents the ratio t / t0 to the oil film thickness t0 when R / _RBASE = 0.76. The oil film thickness t becomes maximum when R / R _BASE = 0.76, and rapidly decreases when R / R _BASE exceeds 0.9.

FIG. 22 shows the result of calculating the maximum Hertz stress p between the inner ring large collar surface and the tapered roller large end surface. Similarly to FIG. 21, the vertical axis represents the ratio p / p0 to the maximum Hertz stress p0 when R / _RBASE = 0.76. The maximum Hertz stress p decreases monotonically as R / R _BASE increases.

In order to reduce torque loss and heat generation due to rolling friction between the inner ring large collar surface and the tapered roller large end surface, it is desirable to increase the oil film thickness t and decrease the maximum Hertz stress p. The inventors determined the appropriate range of R / R _BASE to be 0.75 or more and 0.87 or less based on the seizure resistance test results shown in Table 1 later with reference to the calculation results of FIGS. 21 and 22. did. In the conventional tapered roller bearing, the value of R / R _BASE is designed in the range of 0.90 to 0.97.

  Furthermore, the tapered roller bearing according to the second embodiment has an actual curvature radius Rprocess (see FIG. 16) and a reference curvature radius R (see FIG. 17), where Rprocess is the actual curvature radius after machining of the large end surface of the tapered roller. It is different in that the ratio Rprocess / R is specified to be 0.8 or more.

  16 and 17 are schematic cross-sectional views along the rolling axis of the tapered roller obtained when the grinding process is ideally performed. When grinding is ideally performed, the large end surface of the tapered roller obtained is a part of a spherical surface centered on the apex O (see FIG. 8) of the cone angle of the tapered roller 12. As shown in FIG. 16 and FIG. 17, when grinding is performed ideally so as to leave a part of the convex portion 16A, the large end surface 16 of the roller 12 having the end surface of the convex portion 16A is It becomes a part of one spherical surface centered on the apex of 12 cone angles. In this case, the inner peripheral end of the convex portion in the radial direction centering on the rolling shaft (spinning shaft) of the roller 12 is connected to the concave portion via points C2 and C3. The outer peripheral end of the convex portion is connected to the chamfered portion via points C1 and C4. In an ideal large end surface, the points C1 to C4 are arranged on one spherical surface as described above.

  Generally, a tapered roller is manufactured by subjecting a cylindrical roller base material to grinding processing including forging and crowning in order. A concave portion resulting from the shape of the punch of the forging device is formed at the center of the surface to be the large end surface of the molded body obtained by the forging process. The planar shape of the concave portion is, for example, a circular shape. If it says from a different viewpoint, the convex part resulting from the punch of a forging apparatus is formed in the outer peripheral part of the surface which should become the big end surface of the molded object obtained by forging. The planar shape of the convex portion is, for example, an annular shape. At least a part of the convex portions of the molded body is removed by a grinding process performed thereafter.

  Here, the radius of curvature R of the large end surface 16 of the roller 12 is an R dimension when the large end surface 16 of the roller 12 shown in FIG. 16 is an ideal spherical surface. Specifically, as shown in FIG. 17, when the intermediate points P5, C3, C4 of the points C1, C2, C3, C4, points C1, C2 at the end of the large end surface 16 of the roller 12 are used. , Radius of curvature R152 passing through points C1, P5, and C2, radius of curvature R364 passing through points C3, P6, and C4 and radius of curvature C1564 passing through points C1, P5, P6, and C4 satisfy R152 = R364 = R1564 It is a single arc curve. Points C1 and C4 are connection points between the convex portion 16A and the chamfered portion 16C, and points C2 and C3 are connection points between the convex portion 16A and the concave portion 16B. Here, an ideal single circular arc curve in which R = R152 = R364 = R1564 is called a reference radius of curvature. The reference radius of curvature R is different from the actual radius of curvature Rprocess measured as the radius of curvature of the large end surface of the tapered roller obtained by actual grinding as described later. FIG. 18 is a schematic cross-sectional view along the rolling axis of a tapered roller obtained by actual grinding. In FIG. 18, the ideal large end face shown in FIG. 17 is indicated by a dotted line. As shown in FIG. 18, the large end surface of the tapered roller that is actually obtained by grinding the molded body on which the concave portion and the convex portion are formed as described above is centered on the apex of the conical angle of the tapered roller. Does not become part of one spherical surface. The points C1 to C4 of the convex part of the tapered roller actually obtained have a shape in which the points C1 to C4 are slanted compared to the convex part shown in FIG. That is, the points C1 and C4 shown in FIG. 18 are arranged on the outer peripheral side in the radial direction with respect to the center of the rolling shaft as compared to the points C1 and C4 shown in FIG. (R152 on one side with respect to R1564 of the entire large end surface 16 is not the same and can be made smaller). The points C2 and C3 shown in FIG. 18 are arranged on the inner peripheral side in the radial direction with respect to the center of the rolling shaft as compared to the points C2 and C3 shown in FIG. 17 and the extending direction of the rolling shaft. (R364 on one side with respect to R1564 of the entire large end surface 16 is not the same and can be made smaller). The intermediate points P5 and P6 shown in FIG. 18 are formed at positions substantially equal to the intermediate points P5 and P6 shown in FIG. 17, for example. As shown in FIG. 18, in the large end surface actually formed by grinding, the vertex C1 and the vertex C2 are arranged on one spherical surface, and the vertex C3 and the vertex C4 are on the other spherical surface. Is arranged. Depending on the general grinding process, the radius of curvature of one arc formed by a part of the large end surface formed on one convex part is the radius of curvature of the arc formed by a part of the large end surface formed on the other convex part. It is about the same as the radius of curvature. That is, R152 on one side after processing of the large end surface 16 of the roller 12 shown in FIG. 18 is substantially equal to R364 on the other side. Here, R152 and R364 on one side after processing of the large end surface 16 of the roller 12 are referred to as an actual curvature radius Rprocess. The actual curvature radius Rprocess is equal to or less than the reference curvature radius R.

  In the tapered roller of the tapered roller bearing according to the present embodiment, the ratio Rprocess / R of the actual curvature radius Rprocess to the reference curvature radius R is 0.8 or more.

  As shown in FIG. 18, on the large end surface actually formed by grinding, the radius of curvature Rvirtual (hereinafter referred to as the virtual radius of curvature) of the virtual arc passing through the vertex C1, the intermediate point P5, the intermediate point P6, and the vertex C4. Is equal to or less than the reference curvature radius R. That is, in the tapered roller of the tapered roller bearing according to the present embodiment, the ratio Rprocess / Rvirtual of the actual curvature radius Rprocess to the virtual curvature radius Rvirtual is 0.8 or more.

  The actual curvature radius Rprocess and the virtual curvature radius Rvirtual can be measured by any method with respect to the tapered roller actually formed by grinding, for example, a surface roughness measuring device (for example, a Mitutoyo surface roughness measuring device). It can be measured using the surf test SV-100). When a surface roughness measuring instrument is used, first, a measurement axis is set along the radial direction centered on the rolling axis, and the surface shape of the large end face is measured. The vertices C1 to C4 and intermediate points P5 and P6 are plotted on the obtained large end face profile. The actual curvature radius Rprocess is calculated as the curvature radius of the arc passing through the plotted vertex C1, intermediate point P5, and vertex C2. The virtual curvature radius Rvirtual is calculated as the curvature radius of the arc passing through the plotted vertex C1, intermediate points P5 and P6, and vertex C4.

  On the other hand, the reference radius of curvature R is estimated based on industrial standards such as JIS standards, for example, from the dimensions of tapered rollers obtained by actual grinding.

  Preferably, the surface roughness Ra of the large end face is 0.10 μm or less. Preferably, the surface roughness Ra of the large ridge surface is 0.063 μm or less.

  Preferably, as shown in FIGS. 19 and 20, the contact positions of the raceway surfaces 11A and 13A of the inner ring and the outer ring 11 and the rolling surface with respect to the width L of the rolling surface of the roller in the extending direction of the rolling shaft. The ratio α / L of the shift amount α from the middle point of the rolling surface in the extending direction is 0% or more and less than 20%. Further, the contact position when the ratio α / L exceeds 0% is at the center position of the rolling surface in the extending direction of the rolling shaft or on the larger end surface side than the center position.

  As shown in FIG. 19, the configuration in which the ratio α / L exceeds 0% includes the crowning formed on the rolling surface of the roller and the crowning formed on the raceway surfaces 11A and 13A of the inner ring and the outer ring 11. This can be realized by relatively shifting the position of each vertex.

  Further, as shown in FIG. 20, the configuration in which the ratio α / L exceeds 0% is that the angle formed by the inner ring raceway surface 13 </ b> A with respect to the axial direction of the inner ring and the raceway surface 11 </ b> A of the outer ring 11 are This can be realized by relatively changing the angle formed with respect to the axial direction. Specifically, the angle formed by the raceway surface 13A of the inner ring with respect to the axial direction of the inner ring is increased compared to the case where the shift amount α of the contact position indicated by the dotted line in FIG. 20 is zero, and the outer ring The configuration in which the ratio α / L exceeds 0% can be realized by at least one of the methods of reducing the angle formed by the 11 raceway surfaces 11A with respect to the axial direction of the outer ring 11.

<Effect>
Since the tapered roller bearing according to the second embodiment has basically the same configuration as the tapered roller bearing 10 according to the first embodiment, the same effect as the tapered roller bearing 10 according to the first embodiment is obtained. Can play.

  Further, in the tapered roller bearing according to the second embodiment, the ratio Rprocess / R of the actual curvature radius Rprocess to the reference curvature radius R is 0.8 or more. The present inventors have confirmed that the tapered roller bearing with the ratio Rprocess / R of 0.8 or more can improve the seizure resistance as compared with the tapered roller bearing with Rprocess / R of less than 0.8.

  In a tapered roller bearing, a certain axial load can be received by sliding contact between the large end surface of the roller and the large collar surface of the inner ring. If the lubrication environment between the large end surface and the large ridge surface becomes insufficient due to the sliding contact, the contact surface pressure between the large end surface and the large ridge surface increases to cause metal contact. As a result, seizure occurs due to heat generation, and eventually the bearing lock is reached.

  Further, when the crowning is formed on the rolling surface of the tapered roller as in the tapered roller bearing, an increase in contact surface pressure between the rolling surface of the roller and the raceway surfaces 11A and 13A of the inner and outer rings is suppressed. However, there is a problem that skew occurs. When the skew occurs, the tangential force applied between the large end surface and the large collar surface increases, and the friction torque increases. Further, when the skew angle is increased, the large end surface and the large collar surface are in contact with each other, so that metal contact occurs between both surfaces, and seizure occurs due to heat generation.

  Therefore, in order to further improve the seizure resistance of the tapered roller bearing, it is necessary to suppress an increase in rotational torque due to friction at the contact point between the large end surface of the roller and the large collar surface of the inner ring and to reduce heat generation. .

  In order to reduce the heat generation by suppressing the metal contact between the large end surface of the roller and the large collar surface of the inner ring, it is necessary to ensure a sufficient oil film thickness between both surfaces.

As described above, the ratio R / R _BASE of the reference curvature radius R of the large end face of the tapered roller to the distance R _BASE from the top of the cone angle of the tapered roller to the large collar surface of the inner ring is not less than 0.75. Since it is 87 or less, the oil film thickness t can be increased based on FIGS. 21 and 22, the maximum Hertz stress p can be reduced, and the torque loss and heat generation due to the sliding friction between the large end surface and the large collar surface can be reduced. can do.

  Furthermore, since the ratio Rprocess / R is 0.8 or more, the tapered roller bearing according to the second embodiment has a large end surface and a large collar surface compared to a tapered roller bearing having a ratio Rprocess / R of less than 0.8. Can be reduced, and an increase in skew angle can be suppressed. As a result, an increase in contact surface pressure between the large end surface and the large collar surface can be suppressed, and a sufficient oil film thickness can be secured between both surfaces. This is confirmed from the following calculation results.

  Table 2 shows the contact surface when the ratio Rprocess / R is changed with respect to the contact surface pressure p0, the skew angle θ0, and the oil film parameter Λ0 between the large end surface and the large collar surface when the ratio Rprocess / R is 1. The calculation result of each ratio of the pressure p, the skew angle θ, and the oil film parameter Λ is shown.

  As shown in Table 2, when the ratio Rprocess / R is 0.7 or less, the contact surface pressure ratio p / p0 between the large end surface and the large collar surface is 1.6 or more, and the skew angle ratio θ / θ0 is The oil film parameter ratio Λ / Λ0 is 0.5 or less. When such a tapered roller bearing is used in an environment where the lubrication state is not good such that the oil film parameter Λ is less than 2, for example, the oil film parameter Λ is less than 1, and the contact state between the large end surface and the large collar surface is This is a boundary lubrication region where metal contact occurs. On the other hand, when the ratio Rprocess / R is 0.8 or more, the contact pressure ratio p / p0 is 1.4 or less, the skew angle ratio θ / θ0 is 1.5 or less, and the ratio Λ / Λ0 of the oil film parameter is 0.8 or more. Therefore, the tapered roller bearing with the ratio Rprocess / R of 0.8 or more ensures the oil film thickness between the large end surface and the large collar surface compared to the tapered roller bearing with the ratio Rprocess / R of less than 0.8. It was confirmed by the above calculation results that it could be done.

  Preferably, in the tapered roller bearing according to the second embodiment, the surface roughness Ra of the large end surface is 0.10 μm or less, and the surface roughness Ra of the large collar surface is 0.063 μm or less. In this way, a sufficient oil film thickness can be ensured between the large end surface of the roller and the large collar surface of the inner ring. Specifically, when the surface roughness Ra of the large end surface and the surface roughness Ra of the large ridge surface are within the above numerical range, and each surface roughness is outside the above numerical range Oil film parameter Λ (= h / σ) defined by “ratio of oil film thickness h determined by elastohydrodynamic lubrication theory to the combined roughness σ of the mean square roughness of the large end surface and large corrugated surface” Can be increased. Therefore, a sufficient oil film thickness can be ensured between the large end surface and the large collar surface.

  Preferably, in the tapered roller bearing according to the second embodiment, the contact position between the raceway surfaces 11A and 13A of the inner ring and the outer ring 11 and the rolling surface with respect to the width L of the rolling surface of the roller in the extending direction of the rolling shaft. The ratio α / L of the deviation amount α from the middle point of the rolling surface in the extending direction is 0% or more and less than 20%, and the contact position is the rolling surface in the extending direction of the rolling shaft. Or the larger end face side than the center position. The present inventors have found that when the ratio α / L is 0% or more and less than 20% and the ratio α / L is more than 0%, the contact position is rolling in the extending direction of the rolling shaft. When the ratio α / L exceeds 0%, the contact position when the ratio α / L exceeds 0% is the center position of the rolling surface in the extending direction of the rolling shaft or It was confirmed that the skew angle can be reduced and the increase in rotational torque can be suppressed compared to the case where the center position is on the small end face side.

  Table 3 shows that when the shift amount α is 0, that is, the contact position between the raceway surfaces 11A and 13A of the inner ring and the outer ring 11 and the rolling surface is located at the middle point of the rolling surface in the extending direction of the rolling shaft. The calculation results of the respective ratios of the skew angle θ and the rotational torque M when the deviation amount α is changed with respect to the skew angle θ0 and the rotational torque M0 during the rotation are shown. In Table 3, the shift amount when the hit position is shifted to the small end face side from the midpoint is indicated by a negative value. When the rotational torque ratio M / M0 is 1.1 or less, it is evaluated as good (◯ in Table 3), and when the rotational torque ratio M / M0 exceeds 1.1, it is evaluated as defective (× in Table 3). did.

  As shown in Table 3, when the hit position is relatively largely shifted from the midpoint toward the small end face, that is, when the shift amount α is less than −5%, the skew angle ratio θ / θ0 is 2 As described above, a slight increase in the amount of deviation causes a significant increase in rotational torque.

  On the other hand, when the hit position is shifted relatively small toward the small end face side from the midpoint, that is, when the shift amount α is −5% or more and less than 0%, the shift amount α is less than −5%. Compared to a certain case, the skew angle ratio θ / θ0 is small, and the rate of increase of the rotational torque with respect to the increase of the shift amount is small.

  Further, if the deviation amount α is 0% or more and 20% or less, the skew angle ratio θ / θ0 is 1 or less, and a slight increase in the deviation amount does not cause a significant increase in rotational torque.

  In addition, if it is not described in Table 3 or if the deviation amount α exceeds 20%, the rotational torque becomes high enough to cause other problems such as peeling, which is not preferable. Therefore, when the ratio α / L is 0% or more and less than 20% and the ratio α / L is more than 0%, the hit position is the center position of the rolling surface in the extending direction of the rolling shaft. It was confirmed from the above calculation results that the skew angle can be reduced by being on the large end face side of the center position.

(Embodiment 3)
The tapered roller bearing according to the third embodiment basically has the same configuration as the tapered roller bearing 10 according to the first embodiment, but is not in contact with the inner ring raceway surface 13A in the crowning formation portion of the roller rolling surface. The difference is that the curvature R8 of the bus of the non-contact portion crowning portion 28 is set smaller than the curvature R7 of the bus of the contact portion crowning portion 27 that contacts the inner ring raceway surface 13A.

  As shown in FIG. 1, the tapered roller bearing according to Embodiment 3 includes an inner ring 13, an outer ring 11, and a plurality of rollers 12 interposed between the inner and outer rings. An inner ring raceway surface 13A is formed on the outer periphery of the inner ring 13, and has a large collar portion 41 and a small collar portion 42 on the large diameter side and the small diameter side of the inner ring raceway surface 13A, respectively. A grinding relief portion 43 is formed at a corner where the inner ring raceway surface 13A and the large collar portion 41 intersect, and a grinding relief portion 44 is formed at a corner portion between the inner ring raceway surface 13A and the small collar portion. . In the inner ring raceway surface 13A, the generatrix extending in the inner ring axial direction is a straight line. An outer ring raceway surface 11A facing the inner ring raceway surface 13A is formed on the inner periphery of the outer ring 11, and there is no wrinkle. The outer ring raceway surface 11A has a straight line extending in the outer ring axial direction.

  As shown in FIGS. 1, 2, and 24, crowning is formed on the roller rolling surface on the outer periphery of the roller 12, and chamfered portions 21 and 25 are provided on both ends of the roller 12. The crowning forming portion of the roller rolling surface is formed into a contact portion crowning portion 27 and a non-contact portion crowning portion 28. Of these, the contact portion crowning portion 27 is in the axial range of the inner ring raceway surface 13A and contacts the inner ring raceway surface 13A. The non-contact portion crowning portion 28 is out of the axial range of the inner ring raceway surface 13A and is not in contact with the inner ring raceway surface 13A.

  The contact portion crowning portion 27 and the non-contact portion crowning portion 28 are lines in which buses extending in the roller axis direction are expressed by different functions and smoothly continue at the connection point P1. In the vicinity of the connection point P1, the curvature R8 of the bus of the non-contact portion crowning portion 28 is set smaller than the curvature R7 of the bus of the contact portion crowning portion 27.

  By the way, in the tapered roller bearing, the contact pressure on the inner ring 13 side and the contact part on the outer ring 11 side have higher surface pressure because the equivalent radius in the circumferential direction is smaller on the inner ring 13 side. Therefore, in the design of the crowning, the contact on the inner ring 13 side may be considered.

  Consider a case where a radial load of 35% of the basic dynamic load rating acts on the tapered roller bearing, nominal number 30316, and the misalignment is 1/600. At this time, it is assumed that misalignment is inclined in the direction in which the surface pressure increases on the large diameter side rather than the small diameter side of the roller 12. The basic dynamic load rating means that the direction and size are such that when the same group of bearings are individually operated under the condition that the inner ring 13 is rotated and the outer ring 11 is stationary, the low rated life is 1 million revolutions. A load that does not fluctuate. The misalignment is a misalignment between a housing (not shown) fitted with the outer ring 11 and a shaft fitted with the inner ring 13, and is expressed as a fraction as described above as an inclination amount.

  The bus bar of the contact portion crowning portion 27 is formed by a logarithmic curve of logarithmic crowning represented by the above formula (1).

In order to ensure the processing accuracy of the crowning, it is desirable that a straight portion having a length equal to or greater than ½ of the roller total length L1 exists on the outer periphery of the roller 12. Therefore, assuming that 1/2 of the roller total length L1 is a straight portion and the small diameter side portion and the large diameter side portion are symmetrical with respect to the center in the roller axial direction, the logarithmic crowning equation (1) among the design parameters, K2 is fixed, K ₁ and z _m is the target design.

  By the way, when the crowning is optimized by using a mathematical optimization method to be described later, under this condition, a crowning like “logarithm” in FIG. 25 is obtained. At this time, the maximum drop amount of the crowning of the roller 12 is 69 μm. However, a region G in FIG. 25 is a region E facing the grinding relief portions 43 and 44 of the inner ring 13 in FIG. 23 and does not contact the inner ring 13. For this reason, the G region of the roller 12 does not need to be logarithmic crowning, and may be a straight line, a circular arc, or other functions. Even if the G region of the roller 12 is a straight line, a circular arc, or other functions, the entire roller has the same surface pressure distribution as in the case of logarithmic crowning, and there is no functional difference.

A mathematical optimization method for logarithmic crowning is described.
By appropriate selection of K _1, z _m of the function formula (1) representing a logarithmic crowning it can be designed optimal logarithmic crowning.

Crowning is generally designed to reduce the maximum surface pressure or stress at the contact. Here, it is assumed that the rolling fatigue life occurs according to the yield condition of Mises, and K ₁ and z _m are selected so as to minimize the maximum value of the equivalent stress of Mises.

K ₁ and z _m can be selected using an appropriate mathematical optimization method. Various algorithms for mathematical optimization methods have been proposed. One of the direct search methods is that optimization can be performed without using the derivative of the function. Useful when functions and variables cannot be directly represented by mathematical expressions. Here, the optimal values of K ₁ and z _m are obtained using the Rosenbrock method, which is one of the direct search methods.

When a radial load of 35% of the basic dynamic load rating acts on the tapered roller bearing, nominal number 30316, and the misalignment is 1/600, the maximum value sMises_max of the Mises equivalent stress and the logarithmic crowning parameter K ₁ , z _m Are in a relationship as shown in FIG. Giving an appropriate initial value K _1, z _m, As you modify the K _1, z _m according to the rules of Rosenbrok method to reach the optimum combination of values in FIG. 26, SMises_max is minimized.

  As long as the contact between the roller 12 and the inner ring 13 is considered, the crowning in the region G in FIG. 25 may have any shape, but considering the contact with the outer ring 11 and the formability of the grindstone during processing, In the connection point P1 with the logarithmic crowning part, it is not desirable that the slope is smaller than that of the logarithmic crowning part. Giving a gradient larger than the gradient of the logarithmic crowning portion for the crowning in the region G is not desirable because the drop amount increases. That is, it is desirable that the crowning and logarithmic crowning in the region G are designed so that the gradients coincide at the connection point P1 and are smoothly connected. In FIG. 25, the crowning of the G region of the roller 12 is exemplified by a dotted line, and the case of an arc is exemplified by a thick solid line. When the crowning of the region G is a straight line, the drop amount Dp of the crowning of the roller 12 is, for example, 36 μm. When the crowning in the region G is an arc, the crowning drop amount Dp of the roller 12 is, for example, 40 μm.

  According to the tapered roller bearing described above, since the crowning is formed on the roller rolling surface on the outer periphery of the roller 12, a grindstone is applied to the roller rolling surface more and more than necessary when the crowning is formed only on the inner ring raceway surface 13A. obtain. Therefore, the processing defect with respect to a rolling surface can be prevented beforehand. The crowning formed on the roller rolling surface can reduce the surface pressure and the stress at the contact portion, thereby extending the life of the tapered roller bearing. Further, in the vicinity of the connection point P1 between the contact portion crowning portion 27 and the non-contact portion crowning portion 28, the curvature R8 of the bus bar of the non-contact portion crowning portion 28 is smaller than the curvature R7 of the bus line of the contact portion crowning portion 27. Therefore, the drop amount Dp at both ends of the roller 12 can be reduced. Therefore, for example, the amount of grinding can be suppressed from that of the conventional single arc crowning, the processing efficiency of the roller 12 can be improved, and the manufacturing cost can be reduced.

  As for the bus line of the non-contact part crowning part 28, either one or both of the part on the large diameter side and the part on the small diameter side may be an arc. In this case, the drop amount Dp can be reduced more than that in which the generatrix of the entire roller rolling surface is represented by a logarithmic curve, for example. Therefore, the amount of grinding can be reduced. As shown in FIG. 27, the generatrix of the non-contact portion crowning portion 28 may have either one or both of a large-diameter side portion and a small-diameter side portion being straight (in the example of FIG. Only the straight line). In this case, the drop amount Dp can be further reduced as compared with the case where the bus of the non-contact portion crowning portion 28 is an arc.

  A part or all of the bus of the contact portion crowning portion 27 may be represented by logarithmic crowning. The contact portion crowning portion 27 represented by the logarithmic crowning can reduce the surface pressure and the stress at the contact portion, thereby extending the life of the tapered roller bearing. As shown in FIG. 28, the generatrix of the contact portion crowning portion 27 may be represented by a straight portion 27A formed flat along the roller axis direction and a portion 27B formed by a logarithmic curve of logarithmic crowning. .

  As another embodiment of the present invention, in the tapered roller bearing, the crowning may be provided not only on the roller 12 but also on the inner ring 13. In this case, the sum of the drop amount of the roller 12 and the drop amount of the inner ring 13 is made equal to the optimized drop amount. By these crowning, it is possible to reduce the surface pressure and the stress at the contact portion and to extend the life of the tapered roller bearing. Furthermore, the amount of grinding can be suppressed from that of the conventional single arc crowning, the processing efficiency of the roller 12 can be improved, and the manufacturing cost can be reduced.

(Function and effect)
The tapered roller bearing according to the present invention is a tapered roller bearing including inner and outer rings and rollers, wherein at least a roller rolling surface on the outer periphery of the roller is formed with a crowning, and a crowning formation portion of the roller rolling surface is formed on the inner ring raceway surface. A contact portion crowning portion that is in the axial range and is in contact with the inner ring raceway surface, and a non-contact portion crowning portion that is out of the axial range of the inner ring raceway surface and is not in contact with the inner ring raceway surface. The non-contact part crowning part is a line in which the buses extending in the roller axis direction are expressed by different functions and are continuously connected to each other at the connection point. In the vicinity of the connection point, the bus line of the non-contact part crowning part A curvature is smaller than the curvature of the bus-line of a contact part crowning part, It is characterized by the above-mentioned.

  The above “smoothly continuous” means continuous without generating a corner, and ideally, the bus of the contact portion crowning portion and the bus bar of the non-contact portion crowning portion are at a continuous point of each other, By continuing so as to have a common tangent, that is, the bus is a function that can be continuously differentiated at the continuous point.

  According to this configuration, since the crowning is formed on the roller rolling surface on the outer periphery of the roller, the grindstone can be applied to the roller rolling surface more and more than necessary when the crowning is formed only on the inner ring raceway surface. Therefore, the processing defect with respect to a rolling surface can be prevented beforehand. The crowning formed on the roller rolling surface can reduce the surface pressure and the stress at the contact portion, thereby extending the life of the tapered roller bearing. Further, in the vicinity of the connection point between the contact portion crowning portion and the non-contact portion crowning portion, the curvature of the busbar of the non-contact portion crowning portion is smaller than the curvature of the busbar of the contact portion crowning portion. The drop amount can be reduced. Therefore, for example, the amount of grinding can be suppressed from that of the conventional single arc crowning, the processing efficiency of the rollers can be improved, and the manufacturing cost can be reduced.

  The generatrix of the non-contact portion crowning portion may have one or both of a large-diameter portion and a small-diameter portion being an arc. In this case, the amount of drop can be reduced compared to the case where the generatrix of the entire roller rolling surface is represented by a logarithmic curve, for example. Therefore, the amount of grinding can be reduced.

  The generatrix of the non-contact portion crowning portion may be such that either one or both of the large diameter side portion and the small diameter side portion are straight. In this case, the drop amount can be further reduced as compared with the case where the bus of the non-contact portion crowning portion is an arc.

  A part or all of the bus of the contact portion crowning portion may be represented by logarithmic crowning. The contact portion crowning portion represented by the logarithmic crowning can reduce the surface pressure and the stress at the contact portion, thereby extending the life of the tapered roller bearing.

  The generatrix of the contact portion crowning portion may be represented by a straight portion formed flat along the roller axis direction and a portion formed by a logarithmic curve of logarithmic crowning.

  Of the buses of the non-contact portion crowning portion, a connection portion with a portion formed by a logarithmic curve of logarithmic crowning may be matched with the slope of the logarithmic curve. In this case, the bus bar of the contact portion crowning portion and the bus bar of the non-contact portion crowning portion can be continued more smoothly at the connection point.

  The bus line of the contact portion crowning portion may be formed by a logarithmic curve of logarithmic crowning represented by the above formula (1).

Of the above equation (1), at least K ₁ and z _m may be optimally designed using a mathematical optimization method.

  The inner ring raceway surface may be crowned, and the sum of the crowning drop amount on the inner ring raceway surface and the crowning drop amount on the outer periphery of the roller may be a predetermined value.

  The method for designing a tapered roller bearing according to the present invention is a method for designing a tapered roller bearing including inner and outer rings and rollers, and forms a crowning on at least the roller rolling surface of the outer periphery of the roller, and a crowning forming portion of the roller rolling surface Are formed into a contact portion crowning portion that is in the axial range of the inner ring raceway surface and is in contact with the inner ring raceway surface, and a non-contact portion crowning portion that is out of the axial range of the inner ring raceway surface and is not in contact with the inner ring raceway surface. The contact portion crowning portion and the non-contact portion crowning portion are such that the bus bars extending in the roller axis direction are represented by different functions and smoothly connected to each other at the connection points, and the bus bars of the contact portion crowning portion are It is formed by a logarithmic curve of logarithmic crowning expressed by the formula (1), and the curvature of the bus bar of the non-contacting part crowning part is determined in the vicinity of the connection point as Characterized by designing smaller than generatrix curvature of the crowning portion.

According to the design method of the present invention, it is possible to easily design a tapered roller bearing capable of reducing the surface pressure and the stress at the contact portion and extending the life. Further, it is possible to design a tapered roller bearing that can reduce the drop amount of the roller and reduce the manufacturing cost.
(Embodiment 4)
The tapered roller bearing according to the fourth embodiment has basically the same configuration as the tapered roller bearing 10 according to the first embodiment, but the notch configuration of the cage 14 is different.

  As shown in FIG. 29, the small annular portion 106 on the narrow side of the pocket 109 is also provided with a notch 110c, and the total area of the three notches 10a and 10c on the narrow side is equal to the two notches on the wide side. It is wider than the total area of the notches 10b. The notch 110c has a depth of 1.0 mm and a width of 5.7 mm.

  In the modified example shown in FIG. 30, the depth of each notch 10a of the narrow-side column portion 108 is 1.5 mm, which is deeper than each notch 10b of the wide-side column portion 108. The total area of each notch 10a is wider than the total area of each notch 10b on the wide side.

  As shown in FIG. 31, a radially inward flange 50 facing the outer diameter surface of the small collar portion 42 of the inner ring 13 is provided on the outer side in the axial direction of the small annular portion 106 of the cage 14. The second gap δ between the inner diameter surface of the flange 50 of the small annular portion 106 and the outer diameter surface of the small collar portion 42 of the inner ring 13 is set narrowly to 2.0% or less of the outer diameter dimension of the small collar portion 42. ing.

  FIG. 33 shows a differential of an automobile using the tapered roller bearing 10 described above. This differential is connected to a propeller shaft (not shown), and a drive pinion 122 inserted through the differential case 121 is engaged with a ring gear 124 attached to the differential gear case 123 and attached to the inside of the differential gear case 123. The pinion gear 125 is engaged with a side gear 126 connected to a drive shaft (not shown) inserted through the differential gear case 123 from the left and right, and the driving force of the engine is transmitted from the propeller shaft to the left and right drive shafts. It is like that. In this differential, a drive pinion 122 and a differential gear case 123, which are power transmission shafts, are supported by a pair of tapered roller bearings 10a and 10b, respectively.

  When each tapered roller bearing 10a, 10b rotates at high speed and its lower part is immersed in an oil bath, as shown by an arrow in FIG. The lubricating oil flowing into the bearing divided into the inner diameter side and the inner diameter side and flowing into the outer ring 11 from the outer diameter side of the cage 14 passes along the raceway surface 11A of the outer ring 11 to the larger diameter side of the tapered roller 12. Out of the bearing. On the other hand, the lubricating oil flowing from the inner diameter side of the cage 14 to the inner ring 13 side has a narrow second gap δ between the flange 50 of the small annular portion 106 of the cage 14 and the small collar portion 42 of the inner ring 13. Therefore, it is much less than the lubricating oil flowing in from the outer diameter side of the cage 14, and most of the lubricating oil flowing in from the second gap δ is cut off in the narrower column portion 108 of the pocket 109. It passes through the notch 10 a and moves to the outer diameter side of the cage 14. Therefore, the amount of the lubricating oil that reaches the large collar portion 41 along the raceway surface 13A of the inner ring 13 is extremely reduced, and the amount of the lubricating oil staying in the bearing can be reduced.

  In the tapered roller bearing according to the fourth embodiment, the small annular portion on the narrow side of the trapezoidal pocket is provided with a notch so that the lubricating oil flowing from the inner diameter side of the cage to the inner ring side can be supplied to the small annular portion. The amount of lubricating oil that escapes from the notch to the outer ring side and reaches the main ring along the raceway surface of the inner ring can be further reduced, and torque loss due to the flow resistance of the lubricating oil can be further reduced.

  By providing a notch in at least the column part on the wide side of the trapezoidal pocket, the tapered roller can be brought into sliding contact with the column part with a good balance.

  By making the total area of the notches provided on the narrow side of the trapezoidal pocket larger than the total area of the notches provided on the wide side of the trapezoidal pocket, it can reach the surface along the raceway of the inner ring. The amount of lubricating oil to be reduced can be further reduced, and torque loss due to the flow resistance of the lubricating oil can be further reduced.

  A radially inward flange opposite to the outer ring surface of the inner ring is provided on the axially outer side of the small ring part of the cage. By making the clearance with the outer diameter surface of the inner ring 2.0% or less of the outer diameter of the inner ring, the amount of lubricating oil flowing from the inner diameter side of the cage to the inner ring side is reduced, Torque loss due to flow resistance can be further reduced.

(Experimental example 4)
As examples, a tapered roller bearing (Example 1) using the cage shown in FIG. 7 and a tapered roller bearing (Example 2) using the cage shown in FIG. 29 were prepared. Moreover, as a comparative example, a tapered roller bearing using a cage having no notch in the pocket (Comparative Example 1) and a tapered roller bearing having a notch provided in the center of the column portion between the pockets of the cage (Comparison) Example 2) and a tapered roller bearing (Comparative Example 3) in which notches were provided in the small and large annular portions at both axial ends of the pocket of the cage were prepared. Each tapered roller bearing has an outer diameter of 100 mm, an inner diameter of 45 mm, and a width of 27.25 mm, and the portions other than the pocket notch are the same.

About the tapered roller bearing of the said Example and the comparative example, the torque measurement test using the vertical torque tester was done. The test conditions are as follows.
・ Axial load: 300kgf
・ Rotation speed: 300-2000 rpm (100 rpm pitch)
・ Lubrication conditions: Oil bath lubrication (lubricating oil: 75W-90)
FIG. 32 shows the results of the torque measurement test. The vertical axis of the graph of FIG. 32 represents the torque reduction rate with respect to the torque of Comparative Example 1 using a cage that has no notch in the pocket. The comparative example 2 in which a notch is provided in the central part of the pocket column part and the comparative example 3 in which a notch is provided in the small annular part and the large annular part of the pocket also show a torque reducing effect, but the narrow side of the pocket In Example 1, in which a notch is provided in the column portion, a torque reduction effect superior to those of the comparative examples is recognized, a notch is provided in the narrow annular portion, and the notch on the narrow side is provided. In Example 2 in which the total area is wider than that on the wide side, a further excellent torque reduction effect is recognized.

  In addition, the torque reduction rate at 2000 rpm, which is the maximum rotation speed of the test, was 9.5% in Example 1 and 11.5% in Example 2, which was excellent even under high-speed rotation conditions in a differential or transmission. A torque reduction effect can be obtained. In addition, the torque reduction rate in the rotational speed 2000rpm of the comparative example 2 and the comparative example 3 is 8.0% and 6.5%, respectively.

(Embodiment 5)
The tapered roller bearing according to the fifth embodiment has basically the same configuration as the tapered roller bearing 10 according to the first embodiment, but the window angle θ of the column surface 14d shown in FIG. 6 is 46 degrees or more and 65 degrees. It differs in that it is specified that: The column surface 14d is a surface facing the pocket 109 in the column portion 108 where the notch is not formed.

  The reason why the lower limit window angle θmin is set to 46 ° or more is to ensure a good contact state with the roller, and when the window angle is less than 46 °, the contact state with the roller is deteriorated. That is, when the window angle is 46 degrees or more, the strength of the cage is secured, γ> 0.90, and a good contact state can be secured. Further, the upper limit window angle θmax is set to 65 degrees or less. If the upper limit window angle θmax is larger than this, the pressing force in the radial direction increases, and there is a risk that smooth rotation cannot be obtained even with a self-lubricating resin material. Because. Note that the window angle is as large as about 50 degrees in a typical tapered roller bearing with a cage in which the cage is separated from the outer ring.

  Table 4 shows the results of bearing life tests. In Table 4, “Sample No. 14” in the “Bearing” column is a typical conventional tapered roller bearing in which the cage and the outer ring are separated, and “Sample No. 12” is a conventional product among the tapered roller bearings of the present invention. In contrast, the tapered roller bearing in which only the roller coefficient γ exceeds 0.90, “Sample No. 13” has the roller coefficient γ exceeding 0.90, and the window angle is in the range of 46 degrees to 65 degrees. It is a tapered roller bearing of the present invention. The test was conducted under severe lubrication and overload conditions. As is apparent from Table 4, “Sample No. 12” has a longer life than “Sample No. 14” twice or more. Further, the bearing of “Sample No. 13” has a roller coefficient of 0.96 which is the same as that of “Sample No. 12”, but the life time is about five times or more that of “Sample No. 12”. The dimensions of “Sample No. 14”, “Sample No. 12”, and “Sample No. 13” are φ45 × φ81 × 16 (unit mm), the number of rollers is 24 (“Sample No. 14”), 27 This (“Sample No. 12”, “Sample No. 13”) and the oil film parameter Λ = 0.2.

<Application example of tapered roller bearing>
An example of the use of the tapered roller bearings 1A and 1B according to the first to fifth embodiments will be described. As described above, the tapered roller bearing according to the first to fifth embodiments is suitable for a differential and a transmission. That is, it is preferable to use the tapered roller bearing according to Embodiments 1 to 5 as an automotive tapered roller bearing. Here, other application examples of the tapered roller bearing according to Embodiments 1 to 5 other than the application example to the differential shown in FIG. 33 will be described.

  Referring to FIG. 34, manual transmission 100 is a constant-mesh manual transmission, and includes input shaft 111, output shaft 112, counter shaft 113, gears (gears) 114a to 114k, and housing 115. It has.

  The input shaft 111 is rotatably supported with respect to the housing 115 by tapered roller bearings 1A and 1B. A gear 114a is formed on the outer periphery of the input shaft 111, and a gear 114b is formed on the inner periphery.

  On the other hand, the output shaft 112 is rotatably supported on the housing 115 by the tapered roller bearings 1A and 1B on one side (right side in the figure), and on the input shaft 111 by the rolling bearing 120A on the other side (left side in the figure). It is rotatably supported. Gears 114c to 114g are attached to the output shaft 112.

  The gear 114c and the gear 114d are respectively formed on the outer periphery and the inner periphery of the same member. The member in which the gear 114c and the gear 114d are formed is rotatably supported with respect to the output shaft 112 by the rolling bearing 120B. The gear 114e is attached to the output shaft 112 so as to rotate integrally with the output shaft 112 and to be slidable in the axial direction of the output shaft 112.

  Each of the gear 114f and the gear 114g is formed on the outer periphery of the same member. The member in which the gear 114f and the gear 114g are formed is attached to the output shaft 112 so as to rotate integrally with the output shaft 112 and to be slidable in the axial direction of the output shaft 112. When the member on which the gear 114f and the gear 114g are formed slides to the left in the figure, the gear 114f can mesh with the gear 114b. When the member slides to the right in the figure, the gear 114g and the gear 114d Engageable.

  Gears 114 h to 114 k are formed on the countershaft 113. Two thrust needle roller bearings 130 are disposed between the countershaft 113 and the housing 115, thereby supporting an axial load (thrust load) of the countershaft 113. The gear 114h always meshes with the gear 114a, and the gear 114i always meshes with the gear 114c. The gear 114j can mesh with the gear 114e when the gear 114e slides to the left side in the drawing. Furthermore, the gear 114k can mesh with the gear 114e when the gear 114e slides to the right in the drawing.

  Next, the shifting operation of the manual transmission 100 will be described. In the manual transmission 100, the rotation of the input shaft 111 is transmitted to the countershaft 113 by meshing between the gear 114 a formed on the input shaft 111 and the gear 114 h formed on the countershaft 113. The rotation of the countershaft 113 is transmitted to the output shaft 112 by meshing the gears 114 i to 114 k formed on the countershaft 113 with the gears 114 c and 114 e attached to the output shaft 112. Thereby, the rotation of the input shaft 111 is transmitted to the output shaft 112.

  When the rotation of the input shaft 111 is transmitted to the output shaft 112, the gear meshing between the input shaft 111 and the counter shaft 113 and the gear meshing between the counter shaft 113 and the output shaft 112 are changed. The rotational speed of the output shaft 112 can be changed stepwise with respect to the rotational speed of the input shaft 111. Further, the rotation of the input shaft 111 can be directly transmitted to the output shaft 112 by directly meshing the gear 114 b of the input shaft 111 and the gear 114 f of the output shaft 112 without using the counter shaft 113.

  Hereinafter, the shifting operation of the manual transmission 100 will be described more specifically. When the gear 114f does not mesh with the gear 114b, the gear 114g does not mesh with the gear 114d, and the gear 114e meshes with the gear 114j, the driving force of the input shaft 111 is the gear 114a, the gear 114h, the gear 114j, and It is transmitted to the output shaft 112 via the gear 114e. This is the first speed, for example.

  When the gear 114g meshes with the gear 114d and the gear 114e does not mesh with the gear 114j, the driving force of the input shaft 111 is transmitted via the gear 114a, the gear 114h, the gear 114i, the gear 114c, the gear 114d, and the gear 114g. It is transmitted to the output shaft 112. This is the second speed, for example.

  When the gear 114f meshes with the gear 114b and the gear 114e does not mesh with the gear 114j, the input shaft 111 is directly coupled to the output shaft 112 by meshing with the gear 114b and the gear 114f, and the driving force of the input shaft 111 is Directly transmitted to the output shaft 112. This is the third speed, for example.

  As described above, the manual transmission 100 supports the tapered roller bearings 1A and 1B in order to rotatably support the input shaft 111 and the output shaft 112 as rotating members with respect to the housing 115 disposed adjacent thereto. I have. As described above, the tapered roller bearings 1A and 1B according to the first and second embodiments can be used in the manual transmission 100. The tapered roller bearings 1A and 1B with reduced torque loss and improved seizure resistance and life are suitable for use in the manual transmission 100 in which high surface pressure is applied between the rolling elements and the raceway member. It is.

  By the way, in transmissions or differentials that are power transmission devices for automobiles, there is a tendency to use low-viscosity lubricating oil or to reduce the amount of oil in order to save fuel consumption. May be difficult to form. In addition, when the transmission or differential is used in a low temperature environment (for example, −40 ° C. to −30 ° C.), the viscosity of the lubricating oil increases. Lubricating oil may not be sufficiently supplied to the tapered roller bearing. For this reason, tapered roller bearings for automobiles are required to be improved in seizure resistance and life. Therefore, the above requirements can be satisfied by incorporating the tapered roller bearing 10 having improved seizure resistance and life into a transmission or a differential.

  It should be considered that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above embodiments and examples but by the scope of claims, and is intended to include all modifications and variations within the meaning and scope equivalent to the scope of claims. .

  10, 10a bearing, 11 outer ring, 11A, 13A raceway surface, 12A rolling surface, 11B, 12B, 13B nitrogen-enriched layer, 11C, 12C, 13C non-nitrided portion, 12E surface before processing, 13 inner ring, 14 cage, 14d Column surface, 16 large end surface, 17 small end surface, 18 large ridge surface, 19 small ridge surface, 21 chamfered portion, 22, 24 crowning portion, 23 central portion, 26 center line, 31 first measurement point, 32 second measurement Point, 33 Third measurement point, 41 Large brim, 42 Small brim, 50 mm, 106 Small ring, 107 Large ring, 108 Column, 109 Pocket, 121 Differential case, 122 Drive pinion, 123 Differential gear Case, 124 ring gear, 125 pinion gear, 126 side gear.

Claims (10)

An outer ring having an outer ring raceway surface on the inner circumferential surface;
An outer ring having an inner ring raceway surface and a large collar surface disposed on a larger diameter side than the inner ring raceway surface, and an inner ring disposed on the inner side of the outer ring,
A plurality of tapered rollers having a rolling surface in contact with the outer ring raceway surface and the inner ring raceway surface and a large end surface in contact with the large collar surface and arranged between the outer ring raceway surface and the inner ring raceway surface. When,
Including a plurality of pockets arranged at predetermined intervals in the circumferential direction, and a cage for holding and holding each of the plurality of tapered rollers in each of the plurality of pockets,
The small ring surface of the inner ring is formed by a surface parallel to the small end surface of the tapered roller, the radius of curvature of the large end surface of the tapered roller is R, and the large ring of the inner ring from the apex of the cone angle of the tapered roller when the distance to the surface was R _BASE, the value of R / R _BASE is 0.75 or more 0.87 or less,
The roller coefficient γ exceeds 0.90,
The cage includes a small annular portion that is continuous on the small diameter end surface side of the tapered roller, a large annular portion that is continuous on the large diameter end surface side of the tapered roller, and a plurality of column portions that connect these annular portions,
The pocket is formed in a trapezoidal shape in which the portion that stores the small diameter side of the tapered roller is the narrow side, and the portion that stores the large diameter side is the wide side,
The retainer is provided with a notch in the column portion on the narrow side of the pocket of the retainer with a width extending from the boundary between the small annular portion and the column portion toward the large annular portion. The lubricating oil flowing from the inner diameter side to the inner ring side quickly escapes from the notch to the outer ring side on the outer diameter side, and the pocket side edge of the small annular portion is arranged on the narrow side of the pocket. The base part has a shape extending to the column part,
At least any one of the outer ring, the inner ring, and the plurality of tapered rollers includes a nitrogen-enriched layer formed on a surface layer of the outer ring raceway surface, the inner ring raceway surface, or the rolling surface,
The distance from the outermost surface of the surface layer to the bottom of the nitrogen-enriched layer is 0.2 mm or more,
Crowning is formed on the rolling surface of the tapered roller,
The sum of the amount of drop of the crowning is K ₁ , K ₂ , z _m in the yz coordinate system in which the generatrix of the rolling surface of the tapered roller is the y axis and the z axis is the generatrix orthogonal direction. , Q is a load, L is a length in a generatrix direction of an effective contact portion of the rolling surface of the tapered roller, E ′ is an equivalent elastic modulus, and a is an origin on a generatrix of the rolling surface of the tapered roller A tapered roller bearing represented by the formula (1) when the length to the end of the effective contact portion is A = 2K ₁ Q / πLE ′.

  2. The tapered roller bearing according to claim 1, wherein the prior austenite crystal grain size in the nitrogen-enriched layer has a JIS standard grain size number of 10 or more.   The tapered roller bearing according to claim 1 or 2, wherein a nitrogen concentration in the nitrogen-enriched layer at a depth of 0.05 mm from the outermost surface is 0.1 mass% or more. At least one, but is optimized surface pressure as an objective function, the tapered roller bearing according to any one of claims 1 to 3 K _1, K _2, zm of the formula (1). The crowning forming portion in which the crowning is formed on the rolling surface of the tapered roller is a contact portion crowning portion that is in an axial range of the inner ring raceway surface and is in contact with the inner ring raceway surface, and an axial direction of the inner ring raceway surface. A non-contact portion crowning portion that is out of range and is non-contact with the inner ring raceway surface,
In the contact portion crowning portion and the non-contact portion crowning portion, the generatrix extending in the roller axis direction is a line that is represented by a function different from each other and smoothly connected to each other at a connection point,
The tapered roller bearing according to any one of claims 1 to 4, wherein a curvature of a bus of the non-contact portion crowning portion is smaller than a curvature of a bus of the contact portion crowning portion in the vicinity of the connection point.   6. The tapered roller bearing according to claim 5, wherein one or both of the large-diameter side portion and the small-diameter side portion of the bus of the non-contact portion crowning portion is an arc.   The tapered roller bearing according to claim 5 or 6, wherein one or both of the large-diameter side portion and the small-diameter side portion of the bus of the non-contact portion crowning portion is a straight line.   The tapered roller bearing according to any one of claims 1 to 7, wherein the small annular portion on the narrow side of the pocket is also provided with a notch. The ratio R _process / R between the actual curvature radius R _process and the reference curvature radius R is 0.8 or more, where R _process is the actual curvature radius after grinding of the large end surface of the tapered roller. The tapered roller bearing according to any one of Items 1 to 8.   The tapered roller bearing according to claim 9, wherein the surface roughness Ra of the large end surface is 0.10 μm or less, and the surface roughness Ra of the large collar surface is 0.063 μm or less.

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