JP2019066037A - Taper roller bearing - Google Patents

Abstract

To provide a taper roller bearing excellent in seizure resistance and having a long life and high durability.SOLUTION: A difference between the maximum value and the minimum value of the arithmetic mean roughness Ra of the circumferential surface region in contact with the large-diameter surface 18 is 0.02 μmRa or less. Assuming that the set radius of curvature of the large end face of the tapered roller 12 is R, and the distance from the point of the conical angle of the tapered roller to the large ridge surface of the inner ring 13 is R, the ratio R/Rof the setting radius of curvature R and the distance Ris set to 0.75 or more and 0.87 or less. Assuming that the actual radius of curvature after grinding of the large end face of the tapered roller is R, a ratio R/R of the actual curvature radius Rand the set curvature radius R is 0.5 or more. The sum of the dropping amount of the crowning formed on the rolling surface 12A of the tapered roller is expressed by the following equation (1).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tapered roller bearing.

  DESCRIPTION OF RELATED ART Conventionally, the conical roller bearing is known as a kind of bearing. The tapered roller bearing is applied to, for example, a mechanical device such as an automobile. In use, the tapered roller bearing can receive a constant axial load because the large end face of the tapered roller and the large flange surface of the inner ring are in contact with each other. However, the contact between the large end face of the tapered roller described above and the large ridge surface of the inner ring is not rolling contact but sliding contact. For this reason, if the lubricating environment at the contact portion between the large end face of the tapered roller and the large ridge surface of the inner ring is insufficient, heat may be generated at the contact portion and the bearing may be rapidly heated.

  In order to solve the above problems, it is necessary to reduce torque loss and heat generation due to friction at the contact portion between the large end face of the tapered roller and the large ridge surface of the inner ring and to improve the oil film formability at the contact portion. .

For example, in Japanese Patent Application Laid-Open No. 2000-170774 (hereinafter referred to as Patent Document 1), the radius of curvature of the large end face of the tapered roller is R, and the large ridge surface of the inner ring (conical roller and It is proposed that the ratio R / R _{BASE be} in the range of 0.75 to 0.87, where R _BASE is the distance to the contact portion of As a result, the oil film formability at the contact portion between the large end surface of the tapered roller and the large ridge surface of the inner ring is improved.

JP 2000-170774 A

However, in patent document 1, the tolerance | permissible_range is not prescribed | regulated about the real curvature radius after processing of the large end surface of a tapered roller. Therefore, even if the value of R / R _BASE is set in the range of 0.75 to 0.87, if the above-mentioned actual radius of curvature becomes smaller, there is a possibility that skew larger than expected may be induced.

  Further, from the viewpoint of improving the reliability and performance of a mechanical device to which the above-described tapered roller bearing is applied, there is also a demand for further prolonging the life and improving the durability of the tapered roller bearing.

  The present invention has been made to solve the problems as described above, and an object of the present invention is to provide a tapered roller bearing which is excellent in seizure resistance and has a long life and high durability. .

The tapered roller bearing according to the present disclosure comprises an outer ring, an inner ring and a plurality of tapered rollers. The outer ring has an outer ring raceway surface on the inner circumferential surface. The inner ring has an inner ring raceway surface on the outer peripheral surface and a large weir surface arranged on the larger diameter side than the inner ring raceway surface, and is arranged inside the outer ring. The plurality of tapered rollers have 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 ridge surface. The plurality of tapered rollers are arranged between the outer ring raceway surface and the inner ring raceway surface. When setting the radius of curvature of the large end face of the tapered roller R, the distance from the apex of the cone angle of the tapered rollers to the large rib surface of the inner ring and the R _BASE, the ratio R / R _BASE setting the radius of curvature R and the distance R _BASE The value is set to 0.75 or more and 0.87 or less. Assuming that the actual radius of curvature after grinding of the large end face of the tapered roller is R _process , the ratio R _process / R between the actual radius of curvature R _process and the set radius of curvature R is 0.5 or more. At the large end face of the tapered roller, the difference between the maximum value and the minimum value of the arithmetic average roughness Ra of the circumferential surface area in contact with the large ridge surface is 0.02 μmRa or less. Crownings are formed on the rolling surfaces of the tapered rollers. The sum of the drop amount of crowning sets K ₁ , K ₂ and z _m as design parameters and Q in the yz coordinate system where the generating line of the rolling surface of the tapered roller is y-axis and the generating line orthogonal direction is z-axis Load, L from the origin along the generatrix direction length of the effective contact portion of the rolling surface of the tapered roller, E 'as equivalent elastic modulus, a from the origin of the rolling surface of the tapered roller to the end of the effective contact portion It is represented by the below-mentioned formula (1) when it is referred to as length of A, 2K ₁ Q / πLE ′.

  According to the above, it is possible to obtain a tapered roller bearing which is excellent in seizure resistance and has a long life and high durability.

It is a cross section showing a tapered roller bearing concerning an embodiment. It is an expanded sectional view of the principal part of FIG. It is a cross section showing the design specifications of the tapered roller bearing concerning an embodiment. It is a cross-sectional schematic diagram for demonstrating the reference | standard curvature radius of a roller in the conical roller bearing which concerns on embodiment. FIG. 5 is a partial cross-sectional schematic view showing a region V shown in FIG. 4; It is a cross-sectional schematic diagram for demonstrating the actual curvature radius of a roller in the conical roller bearing which concerns on embodiment. It is a figure for demonstrating the shape of the nitrogen enrichment layer in the crowning part and center part of the roller of the tapered roller bearing which concerns on embodiment. It is a figure for demonstrating the shape of logarithmic crowning of the roller of the tapered roller bearing which concerns on embodiment. It is a figure which shows the 1st example of the crowning shape of the tapered roller contained in the tapered roller bearing of this Embodiment. It is a figure which shows the 2nd example of the crowning shape of the tapered roller contained in the tapered roller bearing of this embodiment. It is a figure showing the relationship of the generatrix direction coordinate of the tapered roller contained in the tapered roller bearing of this Embodiment, and a drop amount. It is a fragmentary sectional view showing a detailed shape of an inner ring of a tapered roller bearing concerning an embodiment. It is the expansion schematic diagram of the area | region XIII of FIG. It is a schematic diagram which shows the shape of the generatrix direction of the inner ring | wheel track surface shown in FIG. It is a figure showing a former austenite grain boundary of a bearing part concerning an embodiment. It is a figure which shows the former austenite grain boundary of the conventional bearing component. The conical roller bearing which concerns on embodiment WHEREIN: It is a cross-sectional schematic diagram which shows an example of the change method of the contact | abutting position of an inner ring | wheel raceway surface and a rolling surface. The tapered roller bearing which concerns on embodiment WHEREIN: It is a cross-sectional schematic diagram which shows another example of the change method of the contact | abutting position of a rolling surface and a rolling surface. It is a graph which shows the relation between the curvature radius of the large end face of the roller of a tapered roller bearing concerning an embodiment, and oil film thickness. It is a graph which shows the relationship between the curvature radius of the large end face of the roller of the tapered roller bearing concerning embodiment, and the largest Hertzian stress. It is the figure which overlapped and showed the contact surface pressure in the rolling surface of the roller which provided the crowning in which the contour was represented with a logarithmic function and provided the crowning. It is the figure which accumulated and showed the contact surface pressure in the rolling line of a roller, and the outline of the roller which made between the crowning of a partial arc, and a straight part the auxiliary arc. It is a flowchart of the manufacturing method of the tapered roller bearing which concerns on embodiment. It is a figure for demonstrating the heat processing method in embodiment. It is a figure for demonstrating the modification of the heat processing method in embodiment. It is a longitudinal section showing a differential provided with a tapered roller bearing concerning an embodiment.

  Hereinafter, embodiments of the present invention will be described based on the drawings. In the following drawings, the same or corresponding parts have the same reference characters allotted and description thereof will not be repeated.

  <Configuration of conical roller bearing>

  FIG. 1 is a cross-sectional schematic view of a tapered roller bearing according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing, in an enlarged manner, a region where the small end surface 17 and the small ridge surface 19 are disposed and a region around the same among the tapered rollers shown in FIG. FIG. 3 is a schematic cross-sectional view showing the design specifications of the tapered roller bearing shown in FIG. The tapered roller bearing according to the present embodiment will be described using FIGS. 1 to 3.

  The tapered roller bearing 10 shown in FIG. 1 mainly includes an outer ring 11, an inner ring 13, a plurality of conical rollers (also simply referred to as rollers below) 12, and a cage. The outer ring 11 has an annular shape, and has an outer ring raceway surface 11A on its inner circumferential surface. The inner race 13 has an annular shape, and has an inner raceway surface 13A on the outer peripheral surface thereof. The inner ring 13 is disposed on the inner peripheral side of the outer ring 11 such that the inner ring raceway surface 13A faces the outer ring raceway surface 11A. In the following description, the direction along the central axis of the tapered roller bearing 10 is “axial direction”, the direction orthogonal to the central axis is “radial direction”, and the direction along an arc centered on the central axis is “peripheral It is called "direction".

  The roller 12 is disposed on the inner circumferential surface of the outer ring 11. The roller 12 has a roller rolling surface 12A as a rolling surface, and contacts the inner ring raceway surface 13A and the outer ring raceway surface 11A at the roller rolling surface 12A. That is, the plurality of rollers 12 are arranged between the outer ring raceway surface 11A and the inner ring raceway surface 13A. The plurality of rollers 12 are arranged at a predetermined pitch in the circumferential direction by a cage 14 made of metal. Thus, the roller 12 is rotatably held on the annular raceway of the outer ring 11 and the inner ring 13. In the tapered roller bearing 10, each cone of the cone including the outer ring raceway surface 11A, the cone including the inner ring raceway surface 13A, and the cone of the rotation axis when the roller 12 rolls is on the center line of the bearing. It is configured to intersect at one point (point O in FIG. 3). With such a configuration, the outer ring 11 and the inner ring 13 of the tapered roller bearing 10 can rotate relative to each other. The cage 14 is not limited to metal but may be synthetic resin.

  The material constituting the outer ring 11, the inner ring 13 and the roller 12 is, for example, a high carbon chromium bearing steel defined in JIS standard, more specifically JIS standard SUJ2.

  The large ridge surface 18 of the inner ring 13 is disposed on the larger diameter side than the inner ring raceway surface 13A, that is, on the right side of FIG. The large-diameter surface 18 is finished to be a ground surface extending along the large end surface 16 of the tapered roller 12. In the inner ring 13, a relief is formed at the corner where the inner ring raceway surface 13A and the large ridge surface 18 intersect. The large end face 16 is the end face on the largest diameter side of the roller 12 and is in contact with the large weir surface 18. The small ridge surface 19 of the inner ring 13 is disposed on the smaller diameter side than the inner ring raceway surface 13A, that is, on the left side of FIG. The small ridge surface 19 is finished to be a ground surface extending along the small end surface 17 of the tapered roller 12. A relief 25B is formed at a corner where the inner ring raceway surface 13A and the small bowl surface 19 intersect. The relief portion 25B may not be formed. The small end face 17 is the end face on the most small diameter side of the roller 12 and is in contact with the small weir face 19.

  With reference to the enlarged view of FIG. 2, the small ridge surface 19 of the inner ring 13 is finished to be a ground surface parallel to the small end surface 17 of the roller 12, and in the initial assembly state shown by a dashed dotted line in FIG. It is in surface contact with the small end face 17. The small end face 17 has a gap with the small diameter face 19 of the roller 12. The small ridges 19 and 12 of the inner ring 13 are formed in a state where the rollers 12 shown by the solid line are settled in a regular position, that is, the large end face 16 of the rollers 12 is in contact with the large ridges 18 of the inner ring 13 The gap δ with the small end face 17 is within the dimensional control range of δ ≦ 0.4 mm. As a result, the number of rotations required for the roller 12 to reach the normal position in the accustomed operation can be reduced, and the accustomed operation time can be shortened.

  The contact surface between the rolling surface of the roller 12 and the inner ring raceway surface 13A preferably has a straight portion that is linear.

The ratio R / R _{BASE of the} radius of curvature R of the large end face 16 of the tapered roller 12 to the distance R _BASE from the point O to the large ridge surface 18 of the inner ring 13:

As shown in FIG. 3, the conical angular apexes of the tapered rollers 12 and the raceway surfaces 11A and 13A of the outer ring 11 and the inner ring 13 coincide at a point O on the center line of the tapered roller bearing 10. The ratio R / R _BASE of the radius of curvature (also called the set radius of curvature) R of the large end face 16 of the tapered roller 12 to the distance R _BASE from the point O to the large ridge surface 18 of the inner ring 13 is 0.75 or more .87 or less.

  Shape of large end face 16 of tapered roller 12:

When the actual radius of curvature after grinding of the large end face 16 of the tapered roller 12 is R _process , the ratio R _process / R between the actual radius of curvature R _process and the set radius of curvature R is 0.5 or more. However, the ratio may be 0.8 or more. The details will be described below.

  FIGS. 4 and 5 are schematic cross sections along the rolling axis of the tapered roller 12 obtained when grinding is ideally performed. When grinding is ideally performed, the large end face 16 of the resulting tapered roller 12 is part of a spherical surface centered at the point O (see FIG. 3) which is the apex of the conical angle of the tapered roller 12. As shown in FIGS. 4 and 5, when the grinding process is ideally performed so as to leave a part of the convex portion 16A, the large end face 16 of the roller 12 having the end face of the convex portion 16A is a roller It is part of one sphere centered on the apex of 12 cone angles. In this case, the inner peripheral end of the convex portion 16A in the radial direction centering on the rolling shaft (rotational axis) of the roller 12 is connected to the concave portion 16B via the points C2 and C3. The outer peripheral end of the convex portion 16A is connected to the chamfered portion 16C via the points C1 and C4. In the ideal large end face, the points C1 to C4 are disposed on one spherical surface as described above.

  In general, a tapered roller is manufactured by sequentially performing a grinding process including a forming process and a crowning process on a cylindrical roller material. In the central portion of the surface to be the large end face of the molded body obtained by the forging process, a concave portion resulting from the shape of the punch of the forging device is formed. The planar shape of the said recessed part is circular shape, for example.

Here, the radius of curvature (set radius of curvature) R of the large end face 16 of the roller 12 is the R dimension when the large end face 16 of the roller 12 shown in FIG. 4 is an ideal spherical surface. Specifically, as shown in FIG. 5, points C1, C2, C3, C4 at the end of the large end face 16 of the roller 12, an intermediate point P5 of the points C1, C2 and an intermediate point P6 of the points C3, C4 are considered. . When the large end face 16 is the ideal spherical surface, in the cross section shown in FIG. 5, the large end face 16 has a curvature radius R152 passing through the points C1, P5 and C2, and a curvature radius passing through the points C3 P6 and C4. The condition of R152 = R364 = R1564 for the radius of curvature R1564 passing through R364 and points C1, P5, P6, C4 is an ideal single arc curve. The points C1 and C4 are connection points between the convex portion 16A and the chamfered portion 16C, and the points C2 and C3 are connection points between the convex portion 16A and the concave portion 16B. Here, the radius of curvature of an ideal single arc curve which satisfies R = R152 = R364 = R1564 is referred to as a set radius of curvature. The set radius of curvature R is different from the actual radius of curvature R _process measured as the radius of curvature of the large end face 16 of the tapered roller 12 obtained by actual grinding processing as described later. The positions of the points C2 and C3 are not limited to the positions shown in FIG. For example, the point C2 may be slightly shifted toward the point C1, and the point C3 may be slightly shifted toward the point C4.

  FIG. 6 is a schematic cross-sectional view along the rolling axis of the tapered roller obtained by actual grinding processing. In FIG. 6, the ideal large end face shown in FIG. 5 is shown by a dotted line. As shown in FIG. 6, the large end face 16 of the tapered roller 12 which is actually obtained by grinding the formed body having the above-described concave and convex portions is the apex of the conical angle of the tapered roller 12. Not part of a single sphere centered on. Points C1 to C4 of the convex portion of the tapered roller 12 which are actually obtained have a shape in which each of the points C1 to C4 is dropped compared to the convex portion 16A shown in FIG. That is, points C1 and C4 shown in FIG. 6 are arranged on the outer peripheral side in the radial direction with respect to the center of the rolling shaft as compared with points C1 and C4 shown in FIG. They are disposed inward in the direction (the R 152 on one side is not identical to the R 1564 of the entire large end face 16 and can be made smaller).

  The points C2 and C3 shown in FIG. 6 are arranged on the inner peripheral side in the radial direction with respect to the center of the rolling shaft as compared with the points C2 and C3 shown in FIG. 5, and the extending direction of the rolling shaft At one end (the R364 on one side is not identical to the R1564 of the entire large end face 16 and can be made smaller). The middle points P5 and P6 shown in FIG. 6 are formed, for example, at substantially the same positions as the middle points P5 and P6 shown in FIG.

As shown in FIG. 6, in the large end face actually formed by grinding, the vertex C1 and the vertex C2 are disposed on one spherical surface, and the vertex C3 and the vertex C4 are disposed on another spherical surface. It is arranged. In a general grinding process, the radius of curvature of one arc formed by a part of the large end face formed on one protrusion is the arc of the part formed by a part of the large end surface formed on the other protrusion. It becomes equivalent to the radius of curvature. That is, R152 on one side after processing of the large end face 16 of the roller 12 shown in FIG. 6 is substantially equal to R364 on the other side. Here, R152, R364 on one side after processing of the large end face 16 of the roller 12 is called an actual radius of curvature R _process . The actual radius of curvature R _process is equal to or less than the set radius of curvature R.

As described above, in the tapered roller 12 of the tapered roller bearing according to the present embodiment, the ratio R _process / R of the above-mentioned actual radius of curvature R _process to the set radius of curvature R is 0.5 or more.

As shown in FIG. 6, the curvature radius R _{virtual of the} virtual arc passing through the vertex C1, the middle point P5, the middle point P6, and the vertex C4 on the large end face actually formed by grinding processing (hereinafter, virtual curvature The radius is less than or equal to the set radius of curvature R. That is, the tapered rollers 12 of the tapered roller bearing according to the present embodiment, the ratio R _process / R _virtual above actual curvature radius R _process for the virtual radius of curvature R _virtual is 0.5 or more.

  Arithmetic mean roughness (surface roughness) of large end face 16 of tapered roller 12:

Arithmetic mean roughness Ra of the large end face 16 may be 0.10 μm Ra or less. As shown in FIG. 4, the large end face 16 includes a convex portion 16A, a concave portion 16B, and a chamfered portion 16C. At the large end face 16, the chamfered portion 16C is disposed at the outermost periphery. An annular convex portion 16A is disposed on the inner peripheral side of the chamfered portion 16C. The concave portion 16B is disposed on the inner peripheral side of the convex portion 16A. The convex portion 16A is a surface protruding from the concave portion 16B. The chamfered portion 16 </ b> C is formed to connect the convex portion 16 </ b> A and the rolling surface which is the side surface of the tapered roller 12. The arithmetic mean roughness Ra of the large end face 16 described above substantially means the arithmetic mean roughness of the convex portion 16A. Further, at the large end face 16 of the tapered roller 12, the difference between the maximum value and the minimum value of the arithmetic average roughness Ra of the convex portion 16A which is a circumferential surface region in contact with the large ridge surface 18 is 0.02 μmRa or less is there. Thereby, the dispersion | variation in arithmetic mean roughness Ra of the circumferential surface area | region of the large end surface 16 can be made small enough. Further, due to the synergetic effect of the numerical range of the ratio R / R _{BASE and} the numerical range of the ratio R _process / R, as a result, sufficient in the contact portion between the large end face 16 of the tapered roller 12 and the large ridge surface 18 of the inner ring 13 The oil film thickness can be secured.

  The large-diameter surface 18 is ground to an arithmetic average roughness of, for example, 0.12 μm Ra or less. Preferably, the arithmetic mean roughness Ra of the major surface 18 is 0.063 μm Ra or less.

  Shape of rolling surface of tapered roller 12:

  As shown in FIG. 7, the rolling surface 12A (see FIG. 1) of the roller 12 is located at both ends, and a crowning portion 22, 24 on which crowning is formed and a center connecting the crowning portions 22, 24. And 23 are included. No crowning is formed in the central portion 23, and the shape of the central portion 23 in the cross section in the direction along the center line 26 which is the rotation axis of the roller 12 is linear. A chamfered portion 21 is formed between the small end face 17 of the roller 12 and the crowning portion 22. A chamfered portion 16C is also formed between the large end face 16 of the roller 12 and the crowning portion 24.

  Here, when the process (carbonitriding process) for forming the nitrogen-rich layer 12B is performed in the method of manufacturing the roller 12, crowning is not formed on the roller 12, and the outer shape of the roller 12 is a dotted line in FIG. It has become the front surface 12E shown by. After the nitrogen-rich layer is formed in this state, the side surface of the roller 12 is processed as shown by the arrow in FIG. 8 as a finishing process, and as shown in FIG. 7 and FIG. , 24 are obtained.

  Crowning shape:

ころ１２の母線をｙ軸とし、ころ１２の母線上であって内輪１３又は外輪１１ところ１２の有効接触部の中央部に原点Ｏをとると共に、母線直交方向（半径方向）にｚ軸をとったｙ−ｚ座標系に、上記式（１）で表されるクラウニングの一例を考える。縦軸はｚ軸、横軸はｙ軸である。有効接触部は、ころ１２にクラウニングを形成していない場合の内輪１３又は外輪１１ところ１２との接触部位である。また、円錐ころ軸受１０を構成する複数のころ１２の各クラウニングは、通常、有効接触部の中央部を通るｚ軸に関して線対称に形成されるので、一方のクラウニング２２Ａ(図８参照）のみを示している。 The shape of the crowning formed in the contact portion crowning portion 27 (which is a portion continuous with the central portion 23 and in contact with the inner ring raceway surface 13A) included in the crowning portions 22 and 24 of the roller 12 is defined as follows. That is, in the yz coordinate system in which the generating line of the rolling surface 12A of the roller 12 is the y-axis and the generating line orthogonal direction is the z-axis, the sum of the crowning drop amounts is K ₁ , K ₂ , z _m as design parameters , Q load, L the length in the generatrix direction of the effective contact portion of the rolling surface 12A at the roller 12, E 'the equivalent elastic modulus, and an origin from the origin taken on the generatrix of the rolling surface of the roller 12 When it is assumed that the length to the end of A, 2K ₁ Q / πLE ′, it is represented by the following formula (1).

The origin of roller 12 is the y-axis, and the origin O is at the center of the effective contact portion of inner ring 13 or outer ring 11 and 12 on the generatrix of roller 12 and the z-axis in the generatrix orthogonal direction (radial direction). In the y-z coordinate system, an example of the crowning represented by the above equation (1) will be considered. 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 where the crown 12 is not formed on the roller 12. Also, since each crowning of the plurality of rollers 12 constituting the tapered roller bearing 10 is normally formed in line symmetry with respect to the z axis passing through the central portion of the effective contact portion, only one crowning 22A (see FIG. 8) It shows.

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

In the above equation (1), z (y) indicates the drop amount of the crowning 22A at the generatrix position y of the roller 12, and the coordinates of the start point O1 of the crowning 22A are (a−K ₂ a, 0) From the above, the range of y in the formula (1) is y> (a−K ₂ a). In addition, since the origin O is at the central portion of the effective contact portion, a = L / 2. Furthermore, since the region from the origin O to the start point O1 of the crowning 22A is the central portion (straight portion) where the crowning is not formed, z (y) = when 0 ≦ y ≦ (a−K ₂ a) It will be 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)} . Design parameters z _m is meant the maximum drop amount of drop amount, i.e. crowning 22A at the end of the effective contact portion. P1 corresponds to the boundary between the contact portion crowning portion 27 and the non-contact portion crowning portion 28 described later.

Here, as crowning of the roller 12, it is possible to consider full crowning with a design parameter K ₂ = 1 and no straight portion. In this case, a sufficient drop amount without edge loading is secured. However, if the drop amount is too large, the machining allowance generated from the material-removed material becomes large at the time of processing, leading to an increase in cost. Therefore, as described below, at least one of the design parameters K ₁ , K ₂ and z _m in equation (1) is optimized with any one of the contact surface pressure, stress and life as an objective function. In the present embodiment, equation (1) is optimized with the contact surface pressure (surface pressure) as an objective function 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 the Rosenbrock method can be adopted. Here, since the damage of the surface starting point on the rolling surface of the roller depends on the contact pressure, obtain the crowning that prevents the oil film breakage of the contact surface under the lean lubrication by setting the objective function of the optimization as the contact pressure. Can.

In addition, when applying logarithmic crowning to the roller 12, in order to ensure the processing accuracy of the roller, it is preferable to provide a straight portion (central portion 23) having a length of 1/2 or more of the entire length in the central portion of the rolling surface 12A. preferable. In this case, K ₂ may be a constant value and optimization may be performed for K ₁ and z _m .

  Here, the shape of the crowning portions 22 and 24 of the tapered roller 12 is a logarithmic curve crowning obtained by the above equation. However, the present invention is not limited to the above equation, and another logarithmic crowning equation may be used to obtain a logarithmic curve.

In the crowning portions 22 and 24 of the tapered roller 12 shown in FIG. 7, crowning having a shape approximating the logarithmic crowning curve obtained by the above equation may be formed. The details of the crowning portion 24 formed on the large end face 16 side of the tapered roller 12 will be described. In the following, in order to make it easy to understand the drop amount of the crowning portion 24, the drop amount is considered to be exaggerated more than the tapered roller 12 shown in FIG. The crowning portion 24 is formed in a complex arc shape by smoothly connecting three arcs having large curvature radii R1, R2, and R3 to the straight portion 23. Then, the drop amount Dr1 of the first gate, the drop amount Dr2 of the second gate in the middle, and the drop amount Dr3 of the third maximum gate are defined as the drop amount of the crowning unit 24, thereby approximating a logarithmic curve. It becomes crowned shape. The drop amount Dr3 corresponds to z _m in Equation 1 described above. Thereby, edge surface pressure can be avoided and surface pressure distribution in the axial direction can be made uniform. The drop amount Dr varies depending on the size and model number, but is about 50 μm at maximum. The shape of the crowning portion 22 formed on the small end face 17 side is the same as that of the crowning portion 24, and therefore the description thereof will not be repeated. The linear shape of the central portion 23 of the rolling surface of the tapered roller 12 in this specification is used in the sense that it includes not only a linear shape but also a substantially linear shape having a crowning with a drop amount of about several μm. .

  P1 here also corresponds to the boundary between the contact portion crowning portion 27 and the non-contact portion crowning portion 28 which will be described later, similarly to P1 described above. Referring to FIG. 7 again, in the tapered roller bearing of the present embodiment, the crowning portion 22 is formed on the rolling surface 12A (see FIG. 1 and FIG. 4) on the outer periphery of the roller 12. It can be thought of as a crowning formation formed. Specifically, the crowning formation portion in the rolling surface 12A is formed as a contact portion crowning portion 27 and a noncontact portion crowning portion 28. Among these, the contact portion crowning portion 27 is in the axial range of the inner ring raceway 13A and is in contact with the inner ring raceway 13A. The noncontact portion crowning portion 28 is out of contact with the inner ring raceway surface 13A out of the axial range of the inner ring raceway surface 13A.

  More specifically, rolling surface 12A of roller 12 has, for example, the shape shown in FIGS. FIG. 9 is a view showing a first example of the crowning shape of the tapered roller included in the tapered roller bearing of the present embodiment. FIG. 10 is a view showing a second example of the crowning shape of the tapered roller included in the tapered roller bearing of the present embodiment. Referring to FIG. 9, the contact portion crowning portion 27 and the non-contact portion crowning portion 28 are lines in which generatrix extending in the roller axial direction are represented by functions different from each other and are smoothly continuous at the connection point P1. In the vicinity of the connection point P1, the curvature R8 of the bus bar of the noncontact portion crowning portion 28 is set smaller than the curvature R7 of the bus bar of the contact portion crowning portion 27. The above-mentioned "smoothly continuous" means continuous without any corners, and ideally, the generatrix of the contact portion crowning portion 27 and the generatrices of the noncontact portion crowning portion 28 are mutually continuous points. , And so as to have a common tangent, that is, the generatrix is a continuously differentiable function at the continuity point.

  According to this configuration, since the crowning portion is formed on the rolling surface 12A on the outer periphery of the roller 12, the grindstone can be made to act on the rolling surface 12A more sufficiently than in the case where the crowning portion is formed only on the raceway surface 13A. Therefore, processing defects on the rolling surface 12A can be prevented in advance. By the crowning portions 22 and 24 formed on the rolling surface 12A, the surface pressure and the stress of the contact portion can be reduced, and the life of the tapered roller bearing 10 can be prolonged. Furthermore, 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 generatrix of the noncontact portion crowning 28 is smaller than the curvature R7 of the generatrix of the contact portion crowning 27 Therefore, it is possible to reduce the drop amount at both ends of the roller 12. Therefore, for example, the amount of grinding can be suppressed more than that of the conventional single arc crowning, the processing efficiency of the roller 12 can be improved, and the manufacturing cost can be reduced.

この対数クラウニングで表される接触部クラウニング部分２７により、面圧や接触部の応力を低減し円錐ころ軸受１０の長寿命化を図ることができる。 The generatrix of the contact crowning portion 27 is formed by a logarithmic curve of logarithmic crowning expressed by the following equation.

By the contact crowning portion 27 represented by the logarithmic crowning, the surface pressure and the stress of the contact can be reduced, and the lifetime of the tapered roller bearing 10 can be prolonged.

  As shown in FIG. 9, one or both of the large diameter side portion and the small diameter side portion of the generatrix of the noncontact portion crowning portion 28 may be straight (in the example of FIG. 9, the large diameter side) Only straight part). In this case, the drop amount Dp (see FIG. 9) can be further reduced as compared to the case where the generatrix of the noncontact portion crowning portion 28 is a circular arc.

  However, the generatrix of the noncontact portion crowning portion 28 may be a circular arc in either or both of the large diameter side portion and the small diameter side portion. 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.

  A part or all of the generatrix of the contact portion crowning portion 27 may be represented by the logarithmic crowning represented by the above equation (1). By the contact crowning portion 27 represented by the logarithmic crowning, the surface pressure and the stress of the contact can be reduced, and the lifetime of the tapered roller bearing can be prolonged.

  That is, for example, as shown in FIG. 10, the generatrix of the contact crowning portion 27 is a straight portion 27A (synonymous with the central portion 23 in FIG. 7) formed flat along the roller axis direction, and a logarithmic curve of logarithmic crowning And the portion 27B formed by In this case, only a part of the generatrix of the contact crowning portion 27 is represented by a logarithmic curve of the logarithmic crowning represented by the above equation (1). On the other hand, the entire contact crowning portion 27 may be represented by a portion 27B formed by a logarithmic curve of logarithmic crowning.

  The generatrix of the noncontact crowning portion 28 is formed such that the connection with the portion 27B of the contact crowning portion 27 formed by the logarithmic crowning curve of the contact crowning portion 27 is matched with the slope of the logarithmic curve Is preferred. In this way, the generatrix of the contact crowning portion 27 and the generatrices of the noncontact crowning portion 28 can be more smoothly continued at the connection point.

In order to ensure the processing accuracy of the crowning, it is desirable that a straight portion 27A that is 1/2 or more of the total roller length L1 be present on the outer periphery of the roller 12. Therefore, if it is assumed that half of the full length L1 of the roller is the straight portion 27A and the crowning is symmetrical between the small diameter side and the large diameter side with reference to the roller axial center, design in the logarithmic crowning formula Among the parameters, K ₂ is fixed, and K ₁ and z _m are targets of design.

By the way, when crowning is optimized by using a mathematical optimization method with respect to K ₁ and z _m of the above-mentioned formula (1), crowning like “log” in FIG. 11 is obtained under this condition. At this time, the maximum drop amount of the crowning of the roller 12 is 69 μm. FIG. 11 is a diagram showing the relationship between the generatrix directional coordinates of the tapered rollers and the drop amount included in the tapered roller bearing of the present embodiment. However, the region G in FIG. 11 is the crowning portion 24 that faces the large diameter side relief portion 25A and the small diameter side relief portion 25B of the inner ring 13 in FIG. 11 and does not contact the inner ring 13. For this reason, the above G region of the roller 12 does not have to be logarithmic crowning, and may be a straight line or a circular arc or another function. Even if the region G of the roller 12 is a straight line, a circular arc, or any other function, the entire surface of the roller 12 has the same surface pressure distribution as in the case of logarithmic crowning, and there is no inferiority in function.

  We will explain mathematical optimization method of logarithmic crowning.

By appropriately selecting K ₁ and z _m in a functional expression representing logarithmic crowning, optimal logarithmic crowning can be designed.

Crowning is generally designed to reduce the maximum contact pressure or stress at the contact. Here, it is considered that 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. Although various algorithms have been proposed for mathematical optimization methods, one of them, the direct search method, is capable of performing optimization without using the derivative of the function. Useful when functions and variables can not be represented directly by mathematical expressions. Here, the optimal value of K ₁ and z _m is determined using the Rosenbrock method, which is one of direct search methods.

  As long as the contact between the roller 12 and the inner ring 13 is considered, the crowning in the region G in FIG. 11 may have any shape, but considering the contact with the outer ring 11 and the formability of the grinding wheel at the time of processing, It is not desirable that the gradient be smaller than the gradient of the logarithmic crowning at the connection point P1 with the logarithmic crowning. Providing a slope greater than that of the logarithmic crowning for the crowning of the G region is also undesirable as it results in a large drop volume. That is, it is desirable that the crowning and the logarithmic crowning in the region of G be designed so that the slopes coincide and be smoothly connected at the connection point P1. In FIG. 11, the crowning of the region G of the roller 12 is exemplified by a dotted line in the case of a straight line, and by a thick solid line in a case of an arc. When crowning in the region G is straight, the crowning drop amount Dp (see FIGS. 9 and 10) of the roller 12 is, for example, 36 μm. When the crowning of the region G is a circular arc, the drop amount Dp of the crowning of the roller 12 is, for example, 40 μm.

  Shape of inner ring raceway surface and outer ring raceway surface:

  Next, the shape of the inner ring raceway surface 13 </ b> A in the generatrix direction will be described based on FIGS. 12 to 14. FIG. 12 is a partial cross-sectional schematic view showing the detailed shape of the inner ring 13. FIG. 13 is an enlarged schematic view of a region XIII of FIG. FIG. 14 is a schematic view showing the shape of the inner ring raceway surface 13A shown in FIG. 12 in the generatrix direction. In FIG. 12 and FIG. 13, a partial contour of the large end surface 16 side of the tapered roller 12 is indicated by a two-dot chain line.

  As shown in FIGS. 12 to 14, the inner ring raceway surface 13A is formed in a gentle crowned full crowning shape, and is connected to the relief portions 25A and 25B. The radius of curvature Rc of the full crowning of a gentle single arc is an extremely large value that causes a drop amount of, for example, about 5 μm at both ends of the inner ring raceway surface 13A. As shown in FIG. 12, since the relief portions 25A and 25B are provided on the inner ring raceway surface 13A, the effective raceway surface width of the inner ring raceway surface 13A is LG.

  As shown in FIG. 13, a flank surface 18 </ b> A smoothly connected to the major surface 18 is formed on the radially outer side of the major surface 18. The wedge-shaped gap formed between the flank 18A and the large end face 16 of the tapered roller 12 can enhance the function of drawing in the lubricating oil and form a sufficient oil film. The shape of the inner ring raceway surface 13A in the generatrix direction exemplifies a gentle crowned full crowning shape, but the present invention is not limited to this and may have a straight shape.

  Although the shape of the inner ring raceway surface 13A of the inner ring 13 in the generatrix direction has been described above, the shape of the outer ring raceway surface 11A in the generatrix direction is the same as that described above. In other words, in the cross section passing through the central axis of the inner ring 13, the inner ring raceway surface 13A and the outer ring raceway surface 11A are linear or arc-shaped.

  Here, the rolling surface 12A of the tapered roller 12 has a logarithmic crowning shape (the central portion 23 has a straight shape), and the inner ring raceway surface 13A and the outer ring raceway surface 11A have a straight shape or a full crowning shape of a gentle arc. The verification result that has reached the embodiment will be described next.

検証結果を表２に示す。

ミスアライメント無しで高速条件では、荷重条件が比較的軽いため、表２に示すように、試料１、試料２のいずれもエッジ面圧（Ｐ_EDGE）の発生はない。一方、試料２では、外輪のフルクラウニングのドロップ量が大きく、接触楕円（長軸半径）が短くなるので、接触領域が長い場合に比べて、当り位置の中心Ｃのばらつきが大きくなり、円錐ころのスキューを誘発しやすくなり、実用不可（ＮＧ）とした。 Outer ring raceway in the low speed condition (1st speed) with misalignment and the high speed condition (4th speed) without misalignment in the transmission tapered roller bearings (inner diameter φ 35 mm, outer diameter φ 62 mm, width 18 mm) of automobiles The ratio of the contact surface pressure of the surface 11A and the contact ellipse to the effective rolling surface width L (see FIG. 7) of the rolling surface 12A of the tapered roller 12 was verified. The samples used for verification are shown in Table 1.

The verification results are shown in Table 2.

Under high speed conditions without misalignment, the load conditions are relatively light, and therefore, as shown in Table 2, neither sample 1 nor sample 2 generates any edge surface pressure (P _EDGE ). On the other hand, in sample 2, since the drop amount of full crowning of the outer ring is large and the contact ellipse (long axis radius) becomes short, the variation in the center C of the hit position becomes large compared to the case where the contact area is long. It is easy to induce the skew of the

  On the other hand, in the low speed condition with misalignment, since the load is high, in the sample 2, the ratio of the contact ellipse to the roller effective rolling surface width L is 100%, and an edge surface pressure is generated in the outer ring. Furthermore, since the contact is driven on the small end face side of the tapered roller by being in contact with the edge, a large skew is induced, which is not practical (NG).

  From the above, it was verified that it is not preferable to subject the outer ring to full crowning with a large drop amount in order to suppress the skew, and the significance of Sample 1 was confirmed.

  The contact position between the rolling surface of the tapered roller 12 and the inner ring raceway: (Figs. 17 and 22)

  As shown in FIG. 17, the width of the rolling surface 12A in the extending direction of the rolling shaft of the tapered roller 12 is L, and the center C of the contact position of the inner ring raceway surface 13A and the rolling surface 12A in the extending direction Assuming that the shift amount from the middle point N to the large end face 16 side of the rolling surface 12A is α, in the tapered roller bearing 10, the ratio α / L between the width L and the shift amount α is 0% or more and less than 20%. May be

  The present inventors set the center C of the contact position where the ratio α / L is 0% or more and less than 20% and the ratio α / L is more than 0% in the extending direction of the rolling shaft. When the ratio α / L is more than 0%, the center C of the contact position in the extending direction of the rolling shaft is in the center N of the rolling surface at the side or the large end face 16 side than the center N It was confirmed that the skew angle can be reduced and the increase in the rotational torque can be suppressed, as compared with the case where the small end face 17 side is closer to the center N of the rolling surface than the center N.

表３に示すように、スキュー角φは、ずれ量αに関する比率α／Ｌが０％のときよりも大径側当りとした方が小さいことが分かる。また、回転トルクＭは、ずれ量αが大きくなる程増大するが、大径側当りよりも小径側当りの方がその影響が大きい。ずれ量αに関する上記比率α／Ｌが−５％でスキュー角は１．５倍と大きくなることから、発熱への影響が無視できなくなり、実用不可（ＮＧ）と判定した。また、上記比率α／Ｌが２０％以上になると、ころ１２の転動面１２Ａにおけるすべりが大きくなることで回転トルクＭが増大し、別のピーリング等の不具合を引き起こすため、実用不可（ＮＧ）と判定した。 In Table 3, when the shift amount α is 0, that is, the center C of the contact position between the inner ring raceway surface 13A and the outer ring raceway surface 11A and the rolling surface 12A of the tapered roller 12 is a roll in the extending direction of the rolling axis. The calculation results of the respective ratios of the skew angle φ and the rotational torque M when the shift amount α is changed with respect to the skew angle φ0 when located at the center N of the dynamic surface 12A and the rotational torque M0 are shown. In Table 3, the shift amount α is shown as a ratio (α / L) of the shift amount α to the width L of the rolling surface 12A of the roller 12. In addition, the amount of deviation when the contact position is deviated closer to the small end face 17 than the center N is indicated by a negative value. The skew angle φ0 and the torque M0 are values when the deviation amount α is zero.

As shown in Table 3, it can be seen that the skew angle φ is smaller when the large diameter side contact is made than when the ratio α / L relating to the shift amount α is 0%. In addition, the rotational torque M increases as the deviation amount α increases, but the effect of the smaller diameter side contact is larger than the larger diameter side contact. When the ratio α / L relating to the shift amount α is −5% and the skew angle is increased to 1.5 times, the influence on heat generation can not be ignored, and it was judged as not practical (NG). In addition, when the ratio α / L is 20% or more, the slippage of the rolling surface 12A of the roller 12 becomes large to increase the rotational torque M, which causes another failure such as peeling, etc. (NG) It was determined that.

  From the above results, in order to reduce the skew angle φ and the rotational torque M, it is desirable that the ratio α / L relating to the deviation amount α be 0% or more and less than 20%. Also preferably, the ratio α / L is greater than 0%. Furthermore, the ratio α / L may be more than 0% and less than 15%.

  The configuration in which the ratio α / L exceeds 0% is shown, for example, in FIG. 17 and FIG. FIGS. 17 and 18 are schematic sectional views showing an example of the method of changing the contact position between the inner ring raceway surface 13A and the rolling surface 12A in the tapered roller bearing.

  As shown in FIG. 17, by relatively shifting the positions of the crownings formed on the rolling surface 12A of the roller 12 and the crownings formed on the inner ring raceway surface 13A and the outer ring raceway surface 11A, It can be realized.

  Further, as shown in FIG. 18, in the configuration in which the ratio α / L exceeds 0%, the angle formed by the inner ring raceway surface 13A with the axial direction of the inner ring and the outer ring raceway surface 11A in the axial direction of the outer ring 11 It can be realized by relatively changing the angle with respect to each other. Specifically, the angle formed by the inner ring raceway surface 13A with respect to the axial direction of the inner ring 13 is increased, as compared with the case where the shift amount α of the contact position shown by the dotted line in FIG. A 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 raceway surface 11A with the axial direction of the outer ring 11.

  <Method of measuring various characteristics>

  How to measure the radius of curvature of the large end face of the roller:

The actual radius of curvature R _process and the virtual radius of curvature R _virtual at the large end face 16 of the roller 12 shown in FIG. 6 can be measured by any method for tapered rollers actually formed by grinding, but for example It can be measured using a profilometer (eg, Mitutoyo surface roughness tester Surftest SV-3100). When a surface roughness measuring machine is used, first, a measurement axis is set along a radial direction centered on the rolling axis, and the surface shape (shape in the generatrix direction) of the large end face is measured. The vertices C1 to C4 and the midpoints P5 and P6 are plotted in the obtained large end face profile. The actual radius of curvature R _process is calculated as the radius of curvature of an arc passing through the plotted vertex C1, the midpoint P5 and the vertex C2. The virtual radius of curvature R _virtual is calculated as the radius of curvature of an arc passing through the plotted vertex C1, the midpoints P5 and P6 and the vertex C4. Alternatively, the virtual radius of curvature R _virtual of the entire large end face 16 may be determined by calculating the approximate arc curve radius with a value obtained by taking four points using the command “input multiple times”. The shape of the large end face 16 in the generatrix direction was measured once in the diametrical direction.

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

  Measurement method of arithmetic mean roughness (surface roughness):

  Arithmetic mean roughness Ra of large end face 16 of roller 12 can be measured by any method, but it can be measured, for example, using a surface roughness measuring machine (for example, Mitutoyo surface roughness measuring machine Surf test SV-3100). Arithmetic mean roughness Ra of the large end face can be measured, for example, by a method of bringing the stylus of the measuring machine into contact with the large end face 16 of the roller 12. In the large end face 16, the difference between the maximum value and the minimum value of the arithmetic average roughness Ra of the convex portion 16A, which is a circumferential surface region in contact with the large ridge surface, is any 4 of the convex portion 16A. Arithmetic mean roughness Ra can be measured using a surface roughness measuring machine, and the difference between the maximum value and the minimum value of the four arithmetic mean roughness values can be calculated.

  <Operation effect of conical roller bearing>

The inventor focused on the following matters regarding the tapered roller bearing, and considered the configuration of the above-described tapered roller bearing.
(1) The ratio of the setting radius of curvature of the large end face of the tapered roller to the actual radius of curvature after processing (2) The shape of the raceway surface of the inner and outer rings to suppress the skew of the conical roller (3) To the rolling surface of the tapered roller Apply logarithmic crowning

  By combining the above configurations (1) to (3), a synergetic effect can be expected on the improvement of the seizure resistance. For example, if logarithmic crowning is applied to the rolling surface of the tapered roller as in configuration (3), the local pressure increase is prevented. As a result, the behavior of the tapered roller can be stably suppressed and the skew can be suppressed, and the oil film thickness at the contact portion between the large end face of the tapered roller and the large ridge surface of the inner ring is stably maintained, thus improving the seizure resistance. Do. Here, by combining the configuration (1) and the configuration (2) contributing to the improvement of the seizure resistance with respect to the configuration (3), the seizure resistance can be further improved in the tapered roller bearing.

  The characteristic configurations of the above-described tapered roller bearings will be listed, although there are some overlapping parts below.

  The tapered roller bearing 10 according to the present disclosure comprises 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 circumferential surface. The inner ring 13 has an inner ring raceway surface 13A on the outer peripheral surface and a large weir surface 18 arranged on the larger diameter side than the inner ring raceway surface 13A, and is arranged inside the outer ring 11. The plurality of tapered rollers 12 have a rolling surface 12A in contact with the outer ring raceway surface 11A and the inner ring raceway surface 13A, and a large end surface 16 in contact with the large bowl surface 18. The plurality of tapered rollers 12 are arranged between the outer ring raceway surface 11A and the inner ring raceway surface 13A.

Setting the radius of curvature of the large end face 16 of the tapered roller 12 as R, and the distance from the point O (see Fig. 3) at the apex of the conical angle of the tapered roller 12 to the large ridge surface 18 of the inner ring 13 as R _BASE the value of the ratio R / R _BASE radius of curvature R and the distance R _BASE 0.75 or 0.87 or less. As shown in FIG. 6, assuming that the actual radius of curvature after grinding of the large end face 16 of the tapered roller 12 is R _process , the ratio R _process / R of the actual radius of curvature R _process to the set radius of curvature R is 0.5 or more It is.

According to the tapered roller bearing 10 described above, by setting the value of the ratio R / R _BASE of the setting radius of curvature R and the distance R _BASE to 0.5 or more, the large end face 16 of the tapered roller 12 and the large diameter of the inner ring 13 A sufficient oil film thickness can be secured at the contact portion with the surface 18 to suppress the contact between the tapered roller 12 and the large-diameter surface 18 and the occurrence of wear, and heat generation at the contact portion can be suppressed.

The value of ratio R / R _BASE was determined with reference to the following findings. FIG. 19 shows the result of calculation of the oil film thickness t formed between the large ridge surface 18 of the inner ring 13 and the large end surface 16 of the tapered roller 12 using the Karna's equation. The vertical axis represents the ratio t / t ₀ of the oil film thickness t to the oil film thickness t ₀ when R / R _BASE = 0.76. The oil film thickness t becomes maximum when R / R _BASE = 0.76, and decreases rapidly when R / R _BASE exceeds 0.87.

FIG. 20 shows the result of calculating the maximum Hertzian stress P between the large ridge surface 18 of the inner ring 13 and the large end surface 16 of the tapered roller 12. The ordinate represents the ratio P / P ₀ to the maximum Hertzian stress P ₀ when R / R _BASE = 0.76, as in FIG. The maximum Hertz stress P monotonously decreases with the increase of R / R _BASE . In order to reduce torque loss and heat generation due to rolling friction between the large ridge surface 18 of the inner ring 13 and the large end surface 16 of the tapered roller 12, it is desirable to increase the oil film thickness t and reduce the maximum Hertz stress P.

Here, as shown in FIG. 19, the relationship between the ratio R / R _BASE and the oil film thickness is specified using Karna's equation, but the factors affecting the relationship are the rotational speed and load of the bearing. The conditions of use of the bearing, such as the viscosity of the lubricating oil, are conceivable. As a result of the inventor's investigation, if the value of the ratio R / R _BASE is approximately 0.8, the oil film thickness can be most sufficiently maintained on average in consideration of such other factors as a whole. Therefore, as described above, the value of the ratio R / R _BASE is determined with the range of 0.8 as the median value.

Further, by setting the value of the ratio R _process / R between the actual radius of curvature R _process and the set radius of curvature R as described above, the contact surface between the large end surface 16 of the tapered roller 12 and the large ridge surface 18 of the inner ring 13 The pressure can be reduced. Furthermore, the skew of the tapered roller 12 can be suppressed, and the oil film thickness at the contact portion between the large end face 16 and the large ridge surface 18 can be stably secured.

Furthermore, the difference between the maximum value and the minimum value of the arithmetic mean roughness Ra of the circumferential surface area (convex portion 16A) in contact with the large-diameter surface 18 at the large end face 16 of the tapered roller 12 is 0.02 μmRa or less Thus, the variation of the arithmetic average roughness Ra of the circumferential surface area of the large end face 16 can be sufficiently reduced, and the above-mentioned ratio R / R _BASE has a synergistic effect with the numerical range of the ratio R _process / R. As a result, a sufficient oil film thickness at the contact portion can be secured. For this reason, it is possible to stably suppress the heat generation at the contact portion, and to obtain the tapered roller bearing 10 having an improved seizure resistance.

この場合、ころ１２の転動面１２Ａに上記式（１）によりドロップ量の和が表されるような、輪郭線が対数関数で表されるクラウニング（いわゆる対数クラウニング）を設けているので、従来の部分円弧で表されるクラウニングを形成した場合より局所的な面圧の上昇を抑制でき、ころ１２の転動面１２Ａにおける摩耗の発生を抑制できる。 In the tapered roller bearing 10, the inner ring raceway surface 13A and the outer ring raceway surface 11A may be linear or arc-shaped in a cross section passing through the central axis of the inner ring 13. Crowning may be formed on the rolling surface 12 </ b> A of the tapered roller 12. The sum of the drop amount of crowning is the design parameter of Q ₁ , K ₂ , z _m in the yz coordinate system in which the generating line of the rolling surface of the tapered roller 12 is y axis and the direction orthogonal to the generating line is z axis Is the load, L is the generatrix length of the effective contact portion of the rolling surface 12A of the tapered roller 12, E 'is the equivalent elastic modulus, and the effective contact is from the origin taken on the generating line of the rolling surface 12A of the tapered roller 12 When the length to the end of the part is A = 2K ₁ Q / πLE ′, it may be represented by the formula (1).

In this case, since crowning (so-called logarithmic crowning) is provided on the rolling surface 12A of the roller 12 such that the outline is represented by a logarithmic function such that the sum of the drop amounts is represented by the above equation (1). In the case where the crowning represented by the partial arc of (4) is formed, the local pressure increase can be suppressed, and the occurrence of wear on the rolling surface 12A of the roller 12 can be suppressed.

  Further, in a cross section passing through the central axis of the inner ring 13, the inner ring raceway surface 13A and the outer ring raceway surface 11A are linear or arc-shaped, and the rolling surface 12A of the tapered roller 12 has, for example, a straight surface at its central portion. Since so-called logarithmic crowning is provided continuously to the straight surface, the dimensions of the contact area between the rolling surface 12A of the tapered roller 12 and the inner ring raceway surface 13A and the outer ring raceway surface 11A (for example, the major axis size of the contact ellipse) Can be lengthened, and as a result, skew can be suppressed. Furthermore, the variation in the contact position between the inner ring raceway surface 13A or the outer ring raceway surface 11A and the rolling surface 12A can be reduced.

  In addition, if the dimension (for example, the major axis dimension of the contact ellipse) of the contact area between the rolling surface 12A and the inner ring raceway surface 13A and the outer ring raceway surface 11A is elongated as described above, In the case of forming full crowning as in the prior art, there is a risk that edge surface pressure may occur at the end in the generatrix direction. However, in the above-described tapered roller bearing 10, logarithmic crowning is applied to the tapered rollers 12, so that the generation of such edge surface pressure can be suppressed while securing the necessary contact area size.

  Here, the effect of the above-mentioned logarithmic crowning will be described in more detail. FIG. 21 is a diagram showing the contour of a roller provided with crowning whose contour is represented by a logarithmic function and the contact surface pressure on the rolling surface of the roller. FIG. 22 is a diagram showing an outline of a roller in which a portion between the crowning of the partial arc and the straight portion is an auxiliary arc and a contact surface pressure on the rolling surface of the roller. The left vertical axis in FIGS. 21 and 22 indicates the crowning drop amount (unit: mm). The horizontal axes in FIG. 21 and FIG. 22 indicate the position (unit: mm) in the axial direction of the roller. The vertical axes on the right side of FIGS. 21 and 22 indicate the contact surface pressure (unit: GPa).

  When the contour of the rolling surface of the tapered roller is formed to have a partial arc crowning and a straight portion, as shown in FIG. 22, the gradient at the boundary between the straight portion, the auxiliary arc and the crowning is continuous. Even if the curvature is discontinuous, the contact surface pressure increases locally. Therefore, there is a possibility that oil film breakage and surface damage may be caused. If a lubricating film having a sufficient thickness is not formed, abrasion due to metal contact is likely to occur. If the contact surface is partially worn away, metal contact is likely to occur in the vicinity of the contact surface, which accelerates the wear of the contact surface, resulting in a disadvantage that the tapered roller may be damaged.

  Therefore, when the rolling surface of the tapered roller as the contact surface is provided with a crowning whose contour is represented by a logarithmic function, for example, as shown in FIG. 21, the crowning represented by the partial arc of FIG. As compared with the case, the local contact pressure is lower, and the contact surface can be made less susceptible to wear. Therefore, even when the film thickness of the lubricating film becomes thin due to the reduction of the amount of the lubricant present on the rolling surface of the tapered roller and the viscosity reduction, the wear of the contact surface is prevented and the damage of the tapered roller is prevented. Can. In FIGS. 21 and 22, in an orthogonal coordinate system in which the generatrix direction of the roller is taken as the horizontal axis and the generatrix orthogonal direction is taken as the vertical axis, the origin O of the horizontal axis at the center of the effective contact portion of the inner or outer ring Is set to indicate the contour of the roller, and the contact pressure is superimposed on the surface pressure as the vertical axis. Thus, the tapered roller bearing 10 exhibiting long life and high durability can be realized by adopting the configuration as described above.

  In the tapered roller bearing 10, the width of the rolling surface in the extending direction of the rolling shaft of the tapered roller 12 is L, and the rolling surface in the extending direction at the contact position of the inner ring raceway surface 13A and the rolling surface 12A. The ratio α / L between the width L and the shift amount α may be 0% or more and less than 20% when the shift amount from the middle point N to the large end face 16 side of 12A is α. From a different point of view, it is preferable that the contact position be on the central position of the rolling surface 12A in the extension direction of the rolling shaft or on the large end face 16 side of the central position. In this case, as compared with the case where the contact position is on the small end face side with respect to the central position of the rolling surface in the extending direction of the rolling shaft, the generation position of the tangential force causing the roller to skew Since the distance from the contact position with the large-diameter surface 18 of 13 to the contact position can be reduced, the skew angle of the roller can be reduced, and an increase in rotational torque can be suppressed.

  In the tapered roller bearing 10, a relief 25A may be formed at a corner where the inner ring raceway surface 13A and the large-diameter surface 18 intersect in the inner ring 13. In this case, when the end on the large end face 16 side of the rolling surface 12A of the tapered roller 12 is positioned at the relief 25A, the end can be prevented from contacting the inner ring 13.

In the tapered roller bearing 10, the ratio R _process / R between the actual radius of curvature R _process and the set radius of curvature R may be 0.8 or more. When the tapered roller bearing 10 is used in an extremely severe lubrication environment, the ratio R _process / R is set to 0.8 or more to make contact between the large end surface 16 of the tapered roller 12 and the large ridge surface 18 of the inner ring 13 The oil film thickness in the part can be made sufficiently thick.

  In the tapered roller bearing 10, the arithmetic mean roughness Ra of the large end face 16 of the tapered roller 12 may be 0.10 μm Ra or less. In this case, the oil film thickness at the contact portion between the large end surface 16 of the tapered roller 12 and the large-diameter surface 18 of the inner ring 13 can be sufficiently secured.

表４に示すように、ころのＲ／Ｒ_BASE比が小さくなる程、スキュー角は大きくなる。一方、すでに説明した図４のころ１２の大端面１６の曲率半径Ｒは大端面１６が理想的な球面でできていた時の曲率半径であり、大端面１６は図５に示すようにＲ１５２＝Ｒ３６４＝Ｒ１５６４という条件が成り立つ、理想的な単一円弧曲線となる。しかし、実際には図６に示すように円錐ころ１２の大端面１６は、円錐ころ１２の円錐角の頂点を中心とする１つの球面の一部とならない。図６に示すように、大端面１６全体のＲ１５６４に対して片側のＲ１５２は同一ではなく、Ｒ１５６４より小さくなる。 Here, the relationship between the skew angle of the tapered roller 12 and the ratio R / R _BASE will be examined. The ratio R / R _BASE is provided on the condition that the large end face 16 of the tapered roller 12 is in contact with the set ideal spherical surface (does not include machining errors). The relationship between the ratio R / R _BASE and the skew angle of the tapered roller 12 is shown in Table 4.

As shown in Table 4, the smaller the roller R / R _BASE ratio, the larger the skew angle. On the other hand, the radius of curvature R of the large end face 16 of the roller 12 of FIG. 4 already described is the radius of curvature when the large end face 16 is an ideal spherical surface, and the large end face 16 is R152 = as shown in FIG. It becomes an ideal single arc curve in which the condition of R364 = R1564 is satisfied. However, in fact, as shown in FIG. 6, the large end face 16 of the tapered roller 12 does not become part of one spherical surface centered on the apex of the conical angle of the tapered roller 12. As shown in FIG. 6, R152 on one side is not identical to R1564 of the entire large end face 16 and is smaller than R1564.

As shown in FIG. 6, when both end surfaces of the large end surface 16 of the roller 12 sag, the large end surface 16 and the large ridge surface 18 of the inner ring 13 contact only on one side (convex portion 16A) of the large end surface 16. For this reason, the calculated R dimension of the large end face 16 is R152 (actual curvature radius R _{process in} FIG. 6), which is smaller than the ideal R dimension (set curvature radius R) (ratio R _process / R is small Become). As a result, the contact surface pressure between the large weir surface 18 and the large end face 16 increases and at the same time the skew angle also increases. If the skew angle is increased, the contact ellipse generated at the contact portion between the roller 12 and the large-diameter surface 18 may cause the oil film to break off the large-diameter surface 18, resulting in occurrence of galling or seizure.

  Here, in an environment where the lubrication state is not sufficient, the skew angle of the roller 12 increases, and the contact surface pressure at the contact portion between the large-diameter surface 18 and the large end surface 16 also increases. The oil film parameter Λ falls between. When the oil film parameter Λ falls below 1, it becomes boundary lubrication where metal contact starts. As a result, wear starts to occur at the contact portion between the large end face 16 of the roller 12 and the large-diameter surface 18 of the inner ring, and when this state continues, wear is further promoted and concern about occurrence of seizure increases.

Here, the oil film parameter Λ is defined by “the ratio of the large end face at the oil film thickness h determined by the elastic fluid lubrication theory to the combined roughness σ of the large-diameter surface of the inner ring and the mean surface roughness”. That is, the oil film parameter Λ = h / σ. The arithmetic mean roughness Ra and the root mean square roughness Rq generally have a relationship of Rq = 1.25 Ra, and the root mean square roughness of the large end face of the roller is Rq ₁ and the root mean square roughness of the major surface is Rq Assuming that it is ₂ , the synthetic roughness σ can be expressed as σ = √ ((Rq ₁ ² + Rq ₂ ² ) / 2) using this Rq.

  The oil film parameter Λ depends on the synthetic roughness σ, and the smaller the value of σ, the thicker the oil film thickness can be. For this reason, the arithmetic mean roughness of the large end face 16 of the roller 12 and the large ridge surface 18 of the inner ring 13 is a roughness equivalent to superfinishing, and it is desirable that the value of σ be 0.09 μm Rq or less.

The ratio of the actual radius of curvature R _process to the set radius of curvature R from the examination result of the influence of the difference between the set radius of curvature R and the radius of curvature of the large end face of the tapered roller (actual radius of curvature R _process ) The relationship between the contact pressure between the large end face and the large ridge surface, the oil film thickness, the skew angle, and the oil film parameters was verified. Furthermore, to verify the practicable range of the ratio between the actual radius of curvature R _process and the set radius of curvature R, the peak temperature of the lubricant used between the large ridge surface of the inner ring and the large end face of the tapered roller in sliding contact It has been found that the level of severity of the lubrication condition at times affects.

For this reason, an index indicating the level of severity of the lubricating state at the peak of the lubricating oil use temperature between the large ridge face of the inner ring and the large end face of the tapered roller was examined as follows.
(1) The state of lubrication between the large ridge surface of the inner ring and the large end surface of the tapered roller is focused on the fact that it is determined by the radius of curvature (real radius of curvature R _process ) of the large end surface of the tapered roller and the operating temperature of the lubricating oil.
(2) In addition, we focused on the viscosity of the lubricating oil used in transmission and differential applications and considered for practical use.
(3) And, as the maximum condition at the peak of lubricating oil use temperature, an extremely severe temperature condition lasting for 3 minutes (180 seconds) at 120 ° C. was assumed. This temperature condition is the maximum condition at the time of peak, and means that it will return to the steady state after approximately 3 minutes pass, and this temperature condition is referred to as "estimated peak temperature condition" in the present specification. It is found that the threshold value for setting the ratio between the actual curvature radius R _process and the set curvature radius R which does not cause rapid temperature rise in the lubrication state in which the viscosity characteristics of the lubricating oil are added to this "assumed peak temperature condition" The

ここで、今回設定した「つば部潤滑係数」は、円錐ころ軸受のつば部潤滑限度を判明できる絶対評価指標値であると言える。自動車用途での上記とは別の条件での使用、または自動車以外の他の用途で使用される場合においては、潤滑油の最高温度、粘度または想定ピーク温度条件を適宜変更して「つば部潤滑係数」を算出し、後述する閾値と比較し潤滑状態の厳しさを判別できる。さらには、内輪の大鍔面が本発明のような概略直線でなく曲面（中凹側）であったとしても、その曲面である内輪の大鍔面ところの大端面とで構成される幾何形状組合せにより算出される油膜厚さで「つば部潤滑係数」を導けば後述の閾値と比較し判別できる。すなわち、本明細書において、「つば部潤滑係数」は、油膜厚さ使用条件に基づいた絶対評価として表される円錐ころ軸受の潤滑状態の厳しさを評価した指標値である。本発明者は、円錐ころ軸受の耐焼き付き性を向上するために、円錐ころの大端面の最適な曲率半径と加工後の実曲率半径との比率を規定するとの新たな着想に至り、当該比率の最適化にあたっては、前述の通り実使用で絶対評価を可能とした「つば部潤滑係数」を導入して評価を行なった。この評価によって、用途を限らない円錐ころ軸受の耐焼付け性向上に寄与する上記比率の規定を一般化し導き出すことができた。
次に、本発明の実施の形態の変形例に係る円錐ころ軸受を説明する。本実施の形態の変形例に係る円錐ころ軸受は、一般的な円錐ころ軸受に比べて、「想定ピーク温度条件」に潤滑油の粘度特性を加味した潤滑状態の厳しさのレベルが、若干緩和されたレベルで使用されることと、円錐ころの大端面の実曲率半径Ｒ_processと設定曲率半径Ｒとの比の実用可能な範囲が拡大された点が異なる。その他の構成及び技術内容については、上述した実施の形態に係る円錐ころ軸受と同じであるので、上述した実施の形態に係る円錐ころ軸受に関する説明のすべての内容を準用し、相違する点のみ説明する。 Based on the above findings, it was devised that an index representing the level of severity of the lubricating state can be determined by the following equation, based on the lubricating state in which the viscosity of the lubricating oil is added to the "assumed peak temperature conditions". This index is referred to herein as the "spinal section lubrication coefficient".
"Flange portion lubricating Factor" = 120 ° C. Viscosity × (oil film thickness ^h) 2/180 seconds, where the oil film thickness h, for example, be determined from the following equation Karna.

Here, it can be said that the "spindle part lubrication coefficient" set this time is an absolute evaluation index value which can identify the collar portion lubrication limit of the tapered roller bearing. In the case of use under conditions other than the above for automotive applications, or in other applications other than automobiles, change the maximum temperature, viscosity or assumed peak temperature conditions of the lubricating oil as appropriate, and then The "coefficient" can be calculated and compared with a threshold described later to determine the severity of the lubrication state. Furthermore, even if the large ridge surface of the inner ring is not a straight line as in the present invention but a curved surface (inside concave side), a geometric shape formed by the large edge surface of the large ridge surface of the inner ring which is the curved surface If the "collar portion lubrication coefficient" is derived from the oil film thickness calculated by the combination, it can be determined by comparing with a threshold described later. That is, in the present specification, the “collar portion lubrication coefficient” is an index value obtained by evaluating the severity of the lubricating state of the tapered roller bearing expressed as an absolute evaluation based on the oil film thickness use condition. The inventor of the present invention has reached a new idea of defining the ratio of the optimum radius of curvature of the large end face of the tapered roller to the actual radius of curvature after processing in order to improve the seizure resistance of the tapered roller bearing, In the optimization of the above, the evaluation was conducted by introducing the "spinal part lubrication coefficient" which enables absolute evaluation in actual use as described above. By this evaluation, it has been possible to generalize and derive the definition of the above-mentioned ratio which contributes to the improvement of the anti-seizure property of the conical roller bearing which has no application.
Next, a tapered roller bearing according to a modification of the embodiment of the present invention will be described. In the tapered roller bearing according to the modification of the present embodiment, the level of severity of the lubrication state in which the viscosity characteristics of the lubricating oil are added to the "supposed peak temperature condition" is slightly relaxed compared to the general tapered roller bearing. It differs in that the practical range of the ratio of the actual curvature radius R _process of the large end face of the tapered roller to the setting curvature radius R is expanded. The other configurations and technical contents are the same as the conical roller bearing according to the above-described embodiment, and therefore all the contents of the description regarding the conical roller bearing according to the above-described embodiment are applied mutatis mutandis and only different points are described Do.

７５Ｗ−９０の１２０℃粘度は、ＶＧ３２に比べて若干高く、「想定ピーク温度条件」に潤滑油の粘度特性を加味した潤滑状態は、上述した実施の形態の場合に比べて若干緩和された条件となる。この潤滑状態を本明細書において「厳しい潤滑状態」という。 In the tapered roller bearing according to the modified example of the present embodiment, “the flange portion lubrication coefficient” was calculated using SAE 75W-90, which is gear oil often used for differentials, as a sample. The 120 ° C. viscosity of 75 W-90 is 10.3 cSt (= 10.3 mm ² / s), and the oil film thickness h determined from the equation (2) is the ratio of the actual radius of curvature R _process to the set radius of curvature R The values are as shown in Table 5.

The viscosity at 120 ° C of 75 W-90 is slightly higher than that of VG32, and the lubrication condition in which the viscosity characteristics of the lubricating oil are added to the "assumed peak temperature condition" is a condition slightly relaxed as compared with the above embodiment. It becomes. This lubrication state is referred to herein as "severe lubrication state".

About the tapered roller bearing which concerns on the modification of embodiment of this invention, the anti-seizure test using the rotation tester was implemented. The test conditions of the seizure resistance test are as follows.
<Test conditions>
・ Loading load: Radial load 4000N, Axial load 7000N
・ Number of revolutions: 7000 min ^-1
· Lubricating oil: SAE 75W-90
・ Test bearing: Conical roller bearing (inner diameter φ 35 mm, outer diameter φ 74 mm, width 18 mm)

表６中の試験結果（１）〜（６）、総合判定（１）〜（６）の詳細を表７に示す。

表６および表７の結果より、デファレンシャル等のギヤオイルである７５Ｗ−９０が使用される「厳しい潤滑状態」では、実曲率半径Ｒ_processと設定曲率半径Ｒとの比Ｒ_process／Ｒは、０．５以上であることが望ましいという結論に至った。したがって、本実施の形態は、実曲率半径Ｒ_processと設定曲率半径Ｒとの比Ｒ_process／Ｒを０．５以上としている。このように、潤滑状態の厳しさのレベルを表す指標として「つば部潤滑係数」を導入することにより、実曲率半径Ｒ_processと設定曲率半径Ｒとの比の実用可能な範囲を拡大することができる。これにより、使用条件に応じて、適正な軸受仕様を選定することができる。 For each value of the ratio between the actual radius of curvature R _process and the set radius of curvature R, the contact surface pressure between the large end face and the large ridge surface, the oil film thickness, the skew angle, the oil film parameter, and the result of “brim part lubrication coefficient” Is shown in Table 6. Table 6 shows the contact surface pressure, oil film thickness, skew angle, and oil film parameters as a ratio, but when the denominator serving as the reference can be processed to have the same actual radius of curvature R _process as the set radius of curvature R And 0 is added to each code.

Details of test results (1) to (6) in Table 6 and comprehensive judgments (1) to (6) are shown in Table 7.

From the results in Table 6 and Table 7, in the “severe lubrication state” where 75 W-90 which is a gear oil such as differential is used, the ratio R _process / R of the actual radius of curvature R _process to the set radius of curvature R is 0. It came to the conclusion that it is desirable that it is 5 or more. Therefore, in the present embodiment, the ratio R _process / R between the actual radius of curvature R _process and the set radius of curvature R is 0.5 or more. As described above, the practical range of the ratio of the actual radius of curvature R _process to the set radius of curvature R can be expanded by introducing the "slip portion lubrication coefficient" as an index indicating the level of severity of the lubrication state. it can. Thereby, appropriate bearing specifications can be selected according to the use conditions.

When setting the ratio between the practicable actual radius of curvature R _process and the set radius of curvature R, only the vicinity of the threshold may be tested and confirmed. This can reduce the number of design steps. Incidentally, in the “severe lubrication condition” of Table 6, a sufficient “brim portion lubrication coefficient” was obtained even when the ratio R _process / R between the actual radius of curvature R _process and the set radius of curvature R is 0.4. In a "severe lubrication state" where a lubricating oil having a viscosity slightly lower than that of Table 6 is used, the threshold 8 × is obtained when the ratio R _process / R between the actual radius of curvature R _process and the set radius of curvature R is 0.4. Since the possibility of not satisfying 10 ⁻⁹ or more is considered, and the skew angle also increases, a ratio R _process / R between the actual radius of curvature R _process and the set radius of curvature R is appropriately 0.5 or more. is there.

ＶＧ３２の１２０℃粘度は低く、「想定ピーク温度条件」に潤滑油の粘度を加味した潤滑状態は極めて厳しい条件となる。この潤滑状態を本明細書において「極めて厳しい潤滑状態」という。 In addition, with respect to the tapered roller bearings according to another modification of the embodiment of the present invention, “brim part lubrication coefficient” was calculated using the turbine oil ISO viscosity grade VG32, which is a lubricating oil often used for transmission, as a sample. The 120 ° C. viscosity of VG32 was 7.7 cSt (= 7.7 mm ² / s), and the oil film thickness h was determined from Formula (2). For each value of the ratio of the actual radius of curvature R _process to the set radius of curvature R, the oil film thickness h is as shown in Table 8.

The viscosity of VG 32 at 120 ° C. is low, and the lubrication state in which the viscosity of the lubricating oil is added to the “supposed peak temperature condition” is an extremely severe condition. This lubrication state is referred to herein as "extremely severe lubrication state".

In addition, a seizure resistance test was performed using a rotation tester. The test conditions of the seizure resistance test are as follows.
<Test conditions>
・ Loading load: Radial load 4000N, Axial load 7000N
・ Speed of rotation: 7000 min ^-1
· Lubricating oil: Turbine oil ISO VG32
・ Test bearing: Conical roller bearing (inner diameter φ 35 mm, outer diameter φ 74 mm, width 18 mm)

表９中の試験結果（１）〜（６）、総合判定（１）〜（６）の詳細を表１０に示す。

表９、表１０の結果より、トランスミッションオイルである低粘度のＶＧ３２が使用される「極めて厳しい潤滑状態」では、実曲率半径Ｒ_processと設定曲率半径Ｒとの比Ｒ_process／Ｒは、０．８以上であることが望ましいという結論に至った。したがって、本実施の形態の他の変形例に係る円錐ころ軸受では、実曲率半径Ｒ_processと設定曲率半径Ｒとの比Ｒ_process／Ｒを０．８以上としている。 For each value of the ratio between the actual radius of curvature R _process and the set radius of curvature R, the contact surface pressure between the large end face and the large ridge surface, the oil film thickness, the skew angle, the oil film parameter, and the result of “brim part lubrication coefficient” Is shown in Table 9. Table 9 shows each of the contact surface pressure, oil film thickness, skew angle, and oil film parameters as a ratio, but the denominator serving as the reference can be processed to the same dimension as the set curvature radius R for the actual radius of curvature R _process. And 0 is added to each code.

Details of test results (1) to (6) in Table 9 and comprehensive judgments (1) to (6) are shown in Table 10.

From the results in Table 9 and Table 10, in the "very severe lubrication state" in which the low viscosity VG 32 which is a transmission oil is used, the ratio R _process / R of the actual curvature radius R _process to the set curvature radius R is 0. It came to the conclusion that it is desirable that it is 8 or more. Therefore, in the tapered roller bearing according to another modification of the present embodiment, the ratio R _process / R between the actual radius of curvature R _process and the set radius of curvature R is 0.8 or more.

The results shown in Table 9 and Table 10 revealed the following. When comparing the calculated “collar portion lubrication coefficient” with the result of the anti-seizure test, the ratio R _process / R of the actual radius of curvature R _process to the set radius of curvature R so that the “collar portion lubrication coefficient” exceeds 8 × 10 ^−9. It was confirmed that setting R was practical. As a result, as a threshold value for setting the ratio R _process / R between the practicable actual radius of curvature R _process and the set radius of curvature R, it is possible to use "collar portion lubrication coefficient" = 8 ^10-9 .

  <Method of manufacturing conical roller bearing>

  FIG. 23 is a flow chart for explaining a method of manufacturing the tapered roller bearing shown in FIG. FIG. 24 is a schematic view showing a heat treatment pattern in the heat treatment step of FIG. FIG. 25 is a schematic view showing a modified example of the heat treatment pattern shown in FIG. Hereinafter, a method of manufacturing the tapered roller bearing 10 will be described.

  As shown in FIG. 23, first, the component preparation step (S100) is performed. In this step (S100), members to be bearing parts such as the outer ring 11, the inner ring 13, the rollers 12, and the cage 14 are prepared. Note that crowning is not yet formed on the member to be the roller 12, and the surface of the member is the front surface 12E shown by the dotted line in FIG.

Next, the 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-rich 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, carbonitriding treatment or nitriding treatment, quenching treatment, tempering Perform processing etc. An example of the heat treatment pattern in this step (S200) is shown in FIG. FIG. 24 shows a heat treatment pattern showing a method of performing primary hardening and secondary hardening. FIG. 25 shows a heat treatment pattern showing a method of cooling the material to below the A ₁ transformation temperature during quenching, and then reheating and finally quenching. In these figures, it was sufficiently the penetration of addition of carbon to diffuse carbon and nitrogen in the matrix of the treated T ₁ steel is cooled 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 treatment at a heating temperature of 180 ° C. is performed.

  According to the above heat treatment, the crack strength is improved and the dimensional change rate over time is reduced while carbonizing and nitriding the surface layer portion of the bearing component, as compared with ordinary hardening, that is, once hardening directly after carbonitriding treatment. Can. According to the heat treatment step (S200), the grain size of the prior austenite crystal grains in the nitrogen-enriched layers 11B, 12B, and 13B having the quenched structure is compared with the microstructure in the conventional quenched structure shown in FIG. Thus, it is possible to obtain a microstructure as shown in FIG. 15, which is less than half. The bearing component subjected to the above heat treatment has a long life against rolling fatigue, can improve the cracking strength, and can reduce the dimensional change rate over time.

  Next, the processing step (S300) is performed. In this step (S300), finish processing is performed to obtain the final shape of each bearing component. As for the roller 12, as shown in FIG. 8, the crowning 22A and the chamfered portion 21 are formed by machining such as cutting.

  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 parts prepared as described above. Thus, the tapered roller bearing 10 shown in FIG. 1 can be manufactured.

  <Example of application of conical roller bearing>

  Next, an example of application of the tapered roller bearing according to the present embodiment will be described. The tapered roller bearing according to the present embodiment is preferably incorporated in a power transmission device of a vehicle such as a differential or a transmission. That is, the tapered roller bearing according to the present embodiment is preferably used as a tapered roller bearing for an automobile. FIG. 26 shows a differential of a car using the tapered roller bearing 10 described above. The differential is connected to a propeller shaft (not shown), and the drive pinion 122 inserted into the differential case 121 is engaged with the ring gear 124 attached to the differential gear case 123 and mounted inside the differential gear case 123 The pinion gear 125 is engaged with a side gear 126 connected to a drive shaft (not shown) which is inserted into the differential gear case 123 from the left and right, so that the driving force of the engine is transmitted from the propeller shaft to the left and right drive shafts It is supposed to be. 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. The tapered roller bearings 10a and 10b may be used not only for differentials of automobiles but also for transmissions.

  By the way, in transmissions or differentials, etc., which are power transmission devices for automobiles, the viscosity of lubricating oil (oil) tends to be reduced or the amount of oil is reduced to save fuel consumption, and tapered roller bearings are sufficient Oil film may be difficult to form. Therefore, the above-mentioned demand can be satisfied by incorporating the above-mentioned tapered roller bearing 10 with improved life into a transmission or a differential.

  Although the embodiments of the present invention have been described above, various modifications of the above-described embodiments are possible. Further, the scope of the present invention is not limited to the above-described embodiment. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  10, 10a, 10b conical roller bearing, 11 outer ring, 11A outer ring raceway surface, 11B, 12B, 13B nitrogen enriched layer, 12 rollers, 12A roller rolling surface, 13 inner ring, 13A inner ring raceway surface, 14 cage, 16 large End face, 16A convex part, 16B concave part, 16C, 21 chamfered part, 17 small end face, 18 large surface, 18A flank surface, 19 small surface, 22, 24 crowning part, 22A crowning, 23 straight part (central part), 25A, 25B relief part, 26 center line, 27 contact part crowning part, 27A straight part, part formed by 27B logarithmic curve, 28 non contact part crowning part, 31 first measurement point, 32 second measurement point, 33 third 3 measurement points, 121 differential case, 122 drive pinion, 123 differential gear case, 124 Ring gear, pinion gear 125, 126 side gears.

Claims (4)

An outer ring having an outer ring raceway surface on an inner circumferential surface;
An inner ring having an inner ring raceway surface on the outer peripheral surface and a large weir surface arranged on the larger diameter side than the inner ring raceway surface, and arranged on the inner side of the outer ring;
A plurality of tapered rollers having rolling surfaces in contact with the outer ring raceway surface and the inner ring raceway surface and a large end surface in contact with the large ridge surface, and arranged between the outer ring raceway surface and the inner ring raceway surface Equipped with
Assuming that the set radius of curvature of the large end face of the tapered roller is R, and the distance from the apex of the conical angle of the tapered roller to the large ridge surface of the inner ring is R _BASE
The value of the ratio R / R _BASE of the said set the radius of curvature R distance R _BASE and 0.75 or more 0.87 or less,
When an actual radius of curvature after grinding of the large end face of the tapered roller is R _process , a ratio R _process / R between the actual radius of curvature R _process and the set radius of curvature R is 0.5 or more.
At the large end face of the tapered roller, the difference between the maximum value and the minimum value of the arithmetic average roughness Ra of the circumferential surface area in contact with the large weir surface is 0.02 μmRa or less,
Crownings are formed on the rolling surface of the tapered rollers,
In the yz coordinate system in which the generating line of the rolling surface of the tapered roller is the y-axis and the generating line orthogonal to the generating line is the z-axis, the sum of the dropping amount of the crowning is K ₁ , K ₂ , z _m as design parameters , Q as load, L as meridional length of the effective contact portion of the rolling surface in the tapered roller, E ′ as equivalent elastic modulus, and from the origin taken a on the generating surface of the rolling surface of the tapered roller the effective contact portion of the up edge length, when the _{a = 2K 1 Q / πLE '} , represented by the formula (1), tapered roller bearings.

The tapered roller bearing according to claim 1, wherein at least one of K ₁ , K ₂ , and z _{m in} the equation (1) is optimized using a surface pressure as an objective function. The crowning formation portion in which the crowning is formed in the rolling surface of the tapered roller is in the axial direction range of the inner ring raceway surface and in contact with the inner ring raceway surface, and the axial direction of the inner ring raceway surface And a non-contacting crowning portion which is out of range and is not in contact with the inner ring raceway surface,
The contact crowning portion and the non-contact crowning portion are lines in which the generatrix extending in the roller axial direction are represented by functions different from each other and are smoothly continuous at connection points.
The tapered roller bearing according to claim 1, wherein a curvature of the bus bar of the noncontact portion crowning portion is smaller than a curvature of the bus bar of the contact portion crowning portion in the vicinity of the connection point.   The tapered roller bearing according to any one of claims 1 to 3, wherein an arithmetic mean roughness Ra of the large end face of the tapered roller is 0.10 m Ra or less.

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