JP2019066038A - Taper roller bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conical roller bearing having excellent seizure resistance, long life and high durability. A conical roller bearing 10 includes an outer ring 11, an inner ring 13, a plurality of conical rollers 12, and a cage 14. When the set radius of curvature of the large end surface 16 of the conical roller 12 is R and the distance from the point O which is the apex of the conical angle of the conical roller 12 to the large flange surface 18 of the inner ring 13 is RBASE, the set radius of curvature R and the distance RBASE The value of the ratio R / RBASE of is 0.75 or more and 0.87 or less. In the cage 14, a notch is provided in the pillar portion on the narrow side of the pocket. The notch is provided with a width from the boundary between the small annular portion and the pillar portion toward the large annular portion. The edge of the small annular portion on the pocket side has a shape in which the bottom portion on the narrow side of the pocket extends to the pillar portion. [Selection diagram] FIG. 4

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 bearings are applied to mechanical devices such as automobiles and industrial machines, for example. 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. Therefore, 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 temperature may be rapidly raised.

  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.

  In addition, it is known that the tapered roller bearing has a large torque loss due to the increase of the lubricating oil flowing from between the inner diameter side of the cage and the inner ring. For this reason, it is necessary to promote reduction of a torque loss by setting it as composition which runs away lubricating oil which flows in to the outer wheel side.

  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 excellent in seizure resistance while reducing torque loss during use. is there.

  The tapered roller bearing according to the present disclosure comprises an outer ring, an inner ring, a plurality of tapered rollers and a cage. 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. The cage includes a plurality of pockets arranged at predetermined intervals in the circumferential direction, and each of the plurality of tapered rollers is accommodated and held in each of the plurality of pockets.

The cage includes a plurality of small annular portions continuing on the small diameter end face side of the plurality of conical rollers, a large annular portion continuing on the large diameter end face side of the plurality of conical rollers, and a plurality of column portions linking the small annular portion and the large annular portion And. Each of the plurality of pockets is formed in a trapezoidal shape in which the portion storing the small diameter side of the plurality of tapered rollers is the narrow side, and the portion housing the large diameter side is the wide side. The notch is provided on the narrow side pillar of the pocket of the cage with a width from the boundary between the small annular part and the pillar toward the large annular part, thereby flowing from the inner diameter side of the cage to the inner ring side Lubricating oil quickly escapes from the notch to the outer ring side on the outer diameter side. The pocket side edge of the small annular portion is shaped such that the bottom side portion of the narrow side of the pocket extends to the column portion. 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.

  According to the above, it is possible to obtain a tapered roller bearing having excellent seizure resistance while reducing torque loss during use.

It is a cross section showing a tapered roller bearing concerning an embodiment. FIG. 1 is an exploded plan view of a cage of a tapered roller bearing according to a first embodiment. In the tapered roller bearing which concerns on embodiment, it is a partial cross section schematic diagram for demonstrating a nitrogen-rich layer. 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. 6 is a partial cross-sectional schematic view showing a region VI shown in FIG. 5; 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 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. In the tapered roller bearing which concerns on embodiment, it is sectional drawing which shows another example of the change method of the contact | abutting position of a rolling surface and a rolling surface. 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 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 area | region XV of FIG. It is a schematic diagram which shows the shape of the generatrix direction of the inner ring raceway surface shown in FIG. 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. It is an expanded top view of the modification of the cage of the tapered roller bearing concerning an embodiment. It is a cross-sectional schematic diagram which shows the other modification of the cage | basket of the tapered roller bearing which concerns on 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 developed plan view of a cage of the tapered roller bearing shown in FIG. FIG. 3 is a schematic partial sectional view of the tapered roller bearing shown in FIG. FIG. 4 is a cross-sectional schematic view showing design specifications of the tapered roller bearing shown in FIGS. 1 and 3. FIG. 5 is a cross-sectional schematic view for explaining a reference curvature radius of a roller in the tapered roller bearing according to the embodiment of the present invention. FIG. 6 is a partial cross-sectional schematic view showing region VI shown in FIG. FIG. 7 is a schematic sectional view for explaining the actual radius of curvature of the roller in the tapered roller bearing according to the embodiment of the present invention. The tapered roller bearing according to the present embodiment will be described using FIGS. 1 to 7.

  The tapered roller bearing 10 shown in FIG. 1 mainly includes an outer ring 11, an inner ring 13, a plurality of tapered rollers 12, and a cage 14. 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 tapered roller 12 has a roller rolling surface 12A, and contacts the inner ring raceway surface 13A and the outer ring raceway surface 11A at the roller rolling surface 12A. The plurality of tapered rollers 12 are arranged at a predetermined pitch in the circumferential direction by a metal cage 14. Thus, the tapered rollers 12 are rotatably held on the annular races of the outer ring 11 and the inner ring 13. In the tapered roller bearing 10, each of the apexes 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 tapered roller 12 rolls is the center line of the bearing. It is comprised so that it may cross at one point (point O of FIG. 4). 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 inner ring 13 has a large flange portion 41 on the large diameter side of the inner ring raceway surface 13A and a small flange portion 42 on the small diameter side.

Shape of cage:
As shown in FIG. 2, the cage 14 has a small annular portion 106 continuous with the small diameter end face of the tapered roller 12, a large annular portion 107 continuous with the large diameter end face of the tapered roller 12, and these small annular portions 106. And a plurality of pillars 108 connecting the large annular portion 107. The holder 14 is formed with a plurality of pockets 109 arranged at predetermined intervals in the circumferential direction. The plurality of pockets 109 hold the plurality of tapered rollers 12. The plurality of pockets 109 have a trapezoidal shape in which the portion for storing the small diameter side of the tapered roller 12 is the narrow side, and the portion for storing the large diameter side is the wide side. On the narrow side and the wide side of the pocket 109, two notches 110a and 110b are provided in each of the pillars 108 on both sides. The dimensions of the notches 110a and 110b are respectively 1.0 mm in depth and 4.6 mm in width. The notch 110 a is provided with a width from the boundary between the small annular portion 106 and the column portion 108 toward the large annular portion 107. As a result, the lubricating oil flowing from the inner diameter side of the cage 14 to the inner ring 13 side quickly escapes from the notch 110 a to the outer ring 11 side on the outer diameter side. The edge of the small annular portion 106 on the pocket 109 side is shaped such that the bottom portion on the narrow side of the pocket 109 extends to the column 108. In other words, the base portion on the narrow side of the pocket 109, and the edge located on the narrow side of the notch 110a and also provided so as to be continuous with the base flat portion are one axially perpendicular to the axial direction. It is a plane.

  The material which comprises the outer ring 11, the inner ring 13, and the tapered roller 12 is comprised, for example by high carbon chromium bearing steel prescribed | regulated to JIS specification, and more specifically JIS specification SUJ2.

  As shown in FIG. 3, nitrogen enriched layers 11B and 13B are formed on the raceway surface 11A of the outer ring 11 and the raceway surface 13A of the inner ring 13. In the inner ring 13, the nitrogen-rich layer 13 B extends from the raceway surface 13 A to the small ridge surface 19 and the large ridge surface 18. The nitrogen-rich layers 11B and 13B are regions in which the nitrogen concentration is higher than that of the unnitrided portion 11C of the outer ring 11 or the unnitrided portion 13C of the inner ring 13, respectively. 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 tapered roller 12 arranged on the raceway surface 13A. The large-diameter surface 18 of the inner ring 13 is finished to be a ground surface extending along the large end surface 16 of the tapered roller 12. A relief 25A is formed at a corner where the inner ring raceway surface 13A and the large rib surface 18 intersect.

  Further, a nitrogen-rich layer 12B is formed on the surface including the rolling surface 12A of the tapered roller 12, the large end face 16 and the small end face 17. The nitrogen-rich layer 12B of the tapered roller 12 is a region where the nitrogen concentration is higher than the non-nitrided portion 12C of the tapered roller 12. The nitrogen-rich layers 11B, 12B and 13B can be formed by any conventionally known method such as carbonitriding and nitriding.

  The nitrogen-rich layer 12B may be formed only on the tapered rollers 12, or the nitrogen-rich layer 11B may be formed only on the outer ring 11, or the nitrogen-rich layer 13B is formed only on the inner ring 13. It is also good. Alternatively, a nitrogen-rich layer may be formed on two of the outer ring 11, the inner ring 13, and the tapered rollers 12.

Nitrogen-rich layer thickness and nitrogen concentration:
The thickness of the nitrogen-rich layers 11B, 12B and 13B is 0.2 mm or more. Specifically, the distance from the outer ring raceway surface 11A as the outermost surface of the surface layer of the outer ring 11 to the bottom of the nitrogen-rich layer 11B is 0.2 mm or more. The distance from the rolling surface 12A as a part of the outermost surface of the surface layer of the tapered roller 12 to the bottom of the nitrogen-rich layer 12B is 0.2 mm or more. The distance from the large end face 16 or the small end face 17 as a part of the outermost surface of the surface layer of the tapered roller 12 to the bottom of the nitrogen-rich layer 12B is 0.2 mm or more. The distance from the inner ring raceway surface 13A as a part of the outermost surface of the surface layer of the inner ring 13 to the bottom of the nitrogen-rich layer 13B is 0.2 mm or more. The distance from the major surface 18 as a part of the outermost surface of the surface of the inner ring 13 to the bottom of the nitrogen-rich layer 13B is 0.2 mm or more.

  In the tapered roller bearing 10, the nitrogen concentration in the nitrogen-rich layers 11B, 12B and 13B at a depth position of 0.05 mm from the outermost surface may be 0.1 mass% or more.

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. The details will be described below.

  5 and 6 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. 4) which is the apex of the conical angle of the tapered roller 12. As shown in FIGS. 5 and 6, when the grinding process is ideally performed to leave a part of the convex portion 16A, the large end face 16 of the tapered roller 12 having the end face of the convex portion 16A is It becomes part of one spherical surface centered on the apex of the cone angle of the tapered roller 12. 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 tapered 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 tapered roller 12 is an R dimension when the large end face 16 of the tapered roller 12 shown in FIG. 5 is an ideal spherical surface. Specifically, as shown in FIG. 6, consider the points C1, C2, C3, C4 at the end of the large end face 16 of the tapered roller 12, and the intermediate point P6 of the intermediate points P5, C3, C4 between the points C1, C2. . When the large end face 16 is the ideal spherical surface, in the cross section shown in FIG. 6, the large end face 16 has a radius of curvature R152 passing through the points C1, P5 and C2, and a radius of curvature passing through the points C3 and 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 Rprocess 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 to the point C1, and the point C3 may be slightly shifted to the point C4.

  FIG. 7 is a schematic cross-sectional view along a rolling axis of a tapered roller obtained by actual grinding processing. In FIG. 7, the ideal large end face shown in FIG. 6 is shown by a dotted line. As shown in FIG. 7, the large end face 16 of the tapered roller 12 which is actually obtained by grinding a 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. The points C1 to C4 of the convex portion of the tapered roller 12 which are actually obtained have a shape in which the respective points C1 to C4 are dropped compared with the convex portion 16A shown in FIG. That is, points C1 and C4 shown in FIG. 7 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).

  Points C2 and C3 shown in FIG. 7 are arranged on the inner peripheral side in the radial direction with respect to the center of the rolling shaft as compared with points C2 and C3 shown in FIG. 6, 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). Incidentally, the middle points P5 and P6 shown in FIG. 7 are formed, for example, at substantially the same positions as the middle points P5 and P6 shown in FIG.

As shown in FIG. 7, 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 machining of the large end face 16 of the tapered roller 12 shown in FIG. 7 is substantially equal to R364 on the other side. Here, R152 and R364 on one side after processing of the large end face 16 of the tapered roller 12 will be referred to as a real 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. 7, the curvature radius R _{virtual of the} virtual arc passing through the vertex C 1, the middle point P 5, the middle point P 6, and the vertex C 4 on the large end face actually formed by grinding 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.

Surface roughness of large end face 16 of tapered roller 12:
The arithmetic surface roughness Ra of the large end face 16 may be 0.10 μm Ra or less. Hereinafter, as shown in FIG. 5 which will be described with reference to FIG. 5, the large end face 16 includes a chamfered portion 16C, a convex portion 16A, and a concave portion 16B. 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 surface roughness Ra of the large end face 16 described above substantially means the surface 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 surface roughness Ra of the convex portion 16A which is a circumferential surface region in contact with the large ridge surface 18 is 0.02 μm or less It may be. As a result, the variation of the surface roughness Ra of the circumferential surface region 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. Thus, a sufficient oil film thickness at the contact portion can be secured.

  The large ridge surface 18 is ground to an arithmetic surface roughness of, for example, 0.12 μm Ra or less. Preferably, the arithmetic surface roughness Ra of the large scale surface is 0.063 μm Ra or less.

Crystalline structure of the nitrogen-rich layer:
The grain size number of the JIS standard of the former austenite crystal grain diameter in the nitrogen-rich layers 11B, 12B, and 13B is 10 or more. Here, FIG. 8 is a schematic view illustrating the microstructure of the bearing component constituting the tapered roller bearing according to the present embodiment, in particular, the prior austenite grain boundary. FIG. 9 is a schematic view illustrating prior austenite grain boundaries of a conventional hardened bearing component. FIG. 8 shows the microstructure in the nitrogen-rich layer 12B. The former austenite crystal grain diameter in the nitrogen-rich layer 12B in the present embodiment is 10 or more of the grain size number of JIS standard, and the former austenite crystal grain size of the conventional general quenched product shown in FIG. It is sufficiently miniaturized even in comparison.

The contact position between the rolling surface of the tapered roller 12 and the inner ring raceway: (Fig. 10)
As shown in FIG. 10, 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 of the rolling shaft extends when the ratio α / L exceeds 0% by being on the large end face 16 side of the middle point N of the rolling surface or the middle point N It was confirmed that the skew angle can be reduced and an increase in rotational torque can be suppressed as compared with the case where the small end face 17 side is more than the middle point N of the rolling surface in the direction.

  In Table 1, 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 and the rotational torque M0 when located at the middle point N of the dynamic surface 12A are shown. In Table 1, 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 tapered roller 12. Further, the amount of deviation when the contact position is deviated closer to the small end face 17 than the midpoint 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 1, 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 tapered roller 12 on the rolling surface 12A becomes large, so that the rotational torque M increases and causes problems such as another peeling. 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. 10 and FIG. FIGS. 10 and 11 are schematic sectional views showing an example of the method of changing the contact position of the inner ring raceway surface 13A and the rolling surface 12A in the tapered roller bearing.

  As shown in FIG. 10, by relatively shifting the positions of the crowning formed on the rolling surface 12A of the tapered roller 12 and the crowning formed on the inner ring raceway surface 13A and the outer ring raceway surface 11A, It can be realized.

  Further, as shown in FIG. 11, in the configuration in which the ratio α / L exceeds 0%, the angle formed by the inner ring raceway surface 13A with respect to 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.

Shape of rolling surface of tapered roller 12:
As shown in FIG. 12, the rolling surface 12A (see FIG. 3) of the tapered roller 12 is located at both ends, and connects between the crowning portions 22 and 24 on which crownings are formed and the crowning portions 22 and 24. And a central portion 23. No crowning is formed in the central portion 23, and the shape of the central portion 23 in a cross section in the direction along the center line 26 which is the rotation axis of the tapered roller 12 is linear. A chamfered portion 21 is formed between the small end face 17 of the tapered roller 12 and the crowning portion 22. A chamfered portion 16C is also formed between the large end face 16 of the tapered roller 12 and the crowning portion 24.

  Here, in the method of manufacturing the tapered roller 12, when the process (carbonitriding treatment) for forming the nitrogen-rich layer 12B is performed, crowning is not formed on the tapered roller 12, and the external shape of the tapered roller 12 is shown in FIG. The front surface 12E is indicated by a dotted line 13 in FIG. After the nitrogen-enriched layer is formed in this state, the side surface of the tapered roller 12 is processed as shown by the arrow in FIG. 13 as a finishing process, and as shown in FIG. 12 and FIG. 22, 24 are obtained.

Specific examples of nitrogen-rich layer thickness:
The depth of the nitrogen-rich layer 12B in the tapered roller 12, that is, the distance from the outermost surface of the nitrogen-rich layer 12B to the bottom of the nitrogen-rich layer 12B is 0.2 mm or more as described above. Specifically, rolling of the first measurement point 31, which is a boundary point between the chamfered portion 21 and the crowning portion 22, the second measurement point 32, which is a position where the distance W is 1.5 mm from the small end face 17, and the tapered roller 12 At the third measurement point 33 which is the center of the surface 12A, the depths T1, T2, and T3 of the nitrogen-rich layer 12B at each position are 0.2 mm or more. Here, the depth of the nitrogen-rich layer 12B means the thickness of the nitrogen-rich layer 12B in the radial direction perpendicular to the center line 26 of the tapered roller 12 and toward the outer peripheral side. The values of the depths T1, T2, and T3 of the nitrogen-rich layer 12B depend on the shape and size of the chamfers 21 and 16C, and the process conditions such as the processing for forming the nitrogen-rich layer 12B and the above-described finishing conditions. Depending, it is possible to change appropriately. For example, in the configuration example shown in FIG. 13, since the crowning 22A is formed after the nitrogen-rich layer 12B is formed as described above, the depth T2 of the nitrogen-rich layer 12B is another depth T1, T3. Although the size is smaller, the magnitude relationship between the values of the depths T1, T2, and T3 of the nitrogen-rich layer 12B can be appropriately changed by changing the above-described process conditions.

  Further, as for the nitrogen-rich layers 11B and 13B in the outer ring 11 and the inner ring 13, the thickness of the nitrogen-rich layers 11B and 13B, which is the distance from the outermost surface to the bottom of the nitrogen-rich layers 11B and 13B, is as described above Is 0.2 mm or more. Here, the thickness of the nitrogen-rich layers 11B and 13B means the distance to the nitrogen-rich layers 11B and 13B in the direction perpendicular to the outermost surface of the nitrogen-rich layers 11B and 13B.

Crowning shape:
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 tapered 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 tapered roller 12 is the y axis and the generating line orthogonal direction is the z axis, the sum of the drop amount of crowning is K1, K2, zm as design parameters, Q 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 origin is a starting point taken on the generatrix of the rolling surface of the tapered roller 12 When it is assumed that the length to the end portion of A = 2K1Q / πLE ′, it is represented by the following formula (1).

  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.

Shape of inner ring raceway surface and outer ring raceway surface:
Next, the shape of the inner ring raceway surface 13A in the generatrix direction will be described based on FIGS. FIG. 14 is a partial cross-sectional schematic view showing the detailed shape of the inner ring 13. FIG. 15 is an enlarged schematic view of a region XV of FIG. FIG. 16 is a schematic view showing the shape of the inner ring raceway surface 13A shown in FIG. 14 in the generatrix direction. In FIG. 14 and FIG. 15, 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. 14 to 16, the inner ring raceway surface 13A is formed in a gentle circular arc full crowning shape and is connected to the relief portions 25A and 25B. The radius of curvature Rc of the full crowning of the gradual arc is a very large one where a drop amount of, for example, about 5 μm is generated at both ends of the inner ring raceway surface 13A. As shown in FIG. 14, 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. 15, a flank 18 </ b> A that is 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 full crowning shape of a gentle arc, but is not limited to this and may be 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.

  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.

  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 ellipse of the contact surface pressure of the surface 11A to the effective rolling surface width L (see FIG. 12) of the rolling surface 12A of the tapered roller 12 was verified. The samples used for verification are shown in Table 2.

  The verification results are shown in Table 3.

Under high speed conditions without misalignment, the load conditions are relatively light, and therefore, as shown in Table 3, 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.

<Method of measuring various characteristics>
How to measure nitrogen concentration:
With respect to bearing parts such as the outer ring 11, the tapered roller 12 and the inner ring 13, the cross section perpendicular to the surface of the region where the nitrogen enriched layers 11B, 12B and 13B are formed respectively in the depth direction by EPMA (Electron Probe Micro Analysis) Perform line analysis. A measurement exposes a cut surface by cutting each bearing component from the measurement position in a direction perpendicular to the surface, and performs measurement on the cut surface. For example, with respect to the tapered roller 12, the cut surface is exposed by cutting the tapered roller 12 in the direction perpendicular to the center line 26 from the respective positions of the first measurement point 31 to the third measurement point 33 shown in FIG. Let In the said cut surface, it analyzes about the nitrogen concentration by said EPMA in the several measurement position which becomes a position 0.05 mm toward the inside from the surface of the tapered roller 12. FIG. For example, the measurement position is determined at five locations, and the average value of the measurement data at the five locations is taken as the nitrogen concentration of the tapered roller 12.

  With respect to outer race 11 and inner race 13, for example, after a cross section along the radial direction orthogonal to the central axis and the central axis is exposed, with the central portion in the central axial direction of the bearing in track surface 11A, 13A as the measurement position The nitrogen concentration of the cross section is measured by the same method as described above.

To measure the distance from the top surface to the bottom of the nitrogen-rich layer:
With regard to the outer ring 11 and the inner ring 13, the hardness distribution is measured in the depth direction from the surface for the cross section to be measured in the method of measuring the nitrogen concentration. As a measuring device, a Vickers hardness measuring machine can be used. In the tapered roller bearing 10 after tempering at a heating temperature of 500 ° C. for a heating time of 1 h, hardness measurement is performed at a plurality of measurement points arranged in the depth direction, for example, measurement points arranged at 0.5 mm intervals. Then, a region having a Vickers hardness of HV 450 or more is used as a nitrogen-rich layer.

  Further, for the tapered roller 12, in the cross section at the first measurement point 31 shown in FIG. 12, the hardness distribution in the depth direction is measured as described above, and the region of the nitrogen-rich layer is determined.

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 tapered roller 12 shown in FIG. 7 can be measured by any method for the tapered roller actually formed by grinding, but for example It can be measured using a roughness measuring machine (e.g. Mitutoyo surface roughness measuring machine Surf Test 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.

Measuring method of surface roughness:
Arithmetic surface roughness Ra of the large end face 16 of the tapered roller 12 can be measured by any method, but can be measured using, for example, a surface roughness measuring machine (for example, Mitutoyo surface roughness measuring machine Surftest SV-3100). The arithmetic surface roughness Ra of the large end face 16 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 tapered roller 12. Further, in the large end face 16, the difference between the maximum value and the minimum value of the arithmetic surface roughness Ra of the convex portion 16A which is a circumferential surface region in contact with the large ridge surface is an arbitrary four of the convex portion 16A. Arithmetic surface roughness Ra can be measured using a surface roughness measuring machine, and the difference can be obtained by calculating the difference between the maximum value and the minimum value of the four arithmetic surface roughness values.

<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 pocket of the cage and the shape of the notch provided in the pocket (3) The skew of the tapered roller is suppressed Shape of raceway surface of inner and outer ring (4) Application of logarithmic crowning to rolling surface of tapered roller (5) Application of nitrogen-rich layer to conical roller, inner ring and outer ring The characteristic configurations of the tapered roller bearings are listed.

By setting the values of ratio R / R _BASE of the setting radius of curvature R and the distance R _BASE as described above, sufficient oil film thickness at the contact portion between the large end surface 16 of the tapered roller 12 and the large ridge surface 18 of the inner ring 13 Thus, the contact between the tapered roller 12 and the large-diameter surface 18 and the occurrence of wear can be suppressed, 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. 17 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 / t0 of the oil film thickness t to the oil film thickness t0 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. 18 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 / P0 to the maximum Hertz stress P0 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. The present inventors determined the condition of the ratio R / R _BASE in consideration of the anti-seizure test results, the cross range at the time of manufacture, and the like with reference to the calculation results of FIGS. 17 and 18.

Here, as shown in FIG. 17, the relationship between the set radius of curvature R and the distance R _BASE is uniquely determined by the Karna's equation to the oil film thickness t. However, as described later, as R _BASE increases, the skew angle of the roller tends to increase. Therefore, in consideration of the influence of the skew angle, the numerical range of ratio R / R _BASE was set.

Here, as shown in FIG. 17, 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.

  In the tapered roller bearing 10, the nitrogen-rich layers 11B, 12B, and 13B may be formed in at least one of the outer ring 11, the inner ring 13, and the tapered roller 12 as a tapered roller. Such a tapered roller bearing 10 has an improved rolling fatigue life and has a long life and high durability. Further, since the resistance to temper softening is improved by the formation of the nitrogen-rich layers 11B, 12B, and 13B, the temperature of the contact portion between the large end face 16 and the large ridge surface 18 is increased by sliding contact. However, high seizure resistance can be exhibited. The nitrogen-rich layers 12 B and 13 B may be formed on both the major end face 16 and the major surface 18. The nitrogen-rich layer 12 B may be formed on the circumferential surface region (convex portion 16 A) of the large end face 16.

  In the tapered roller bearing 10, the grain size number of the JIS standard may be 10 or more for the prior austenite crystal grain size in the nitrogen-rich layers 11B, 12B, 13B. In this case, since the nitrogen-rich layers 11B, 12B, and 13B in which the former austenite grain size is sufficiently reduced are formed, the Charpy impact value, the fracture toughness value, and the crush are obtained after having a high rolling fatigue life. The tapered roller bearing 10 can be obtained with improved strength and the like.

  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 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, crowning (so-called logarithmic crowning) is provided on the rolling surface 12A of the tapered roller 12 such that the contour line 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 conventional partial arc is formed, the local pressure increase can be suppressed, and the occurrence of wear on the rolling surface 12A of the tapered 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 a 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. 19 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 in an overlapping manner. FIG. 20 is a diagram showing an outline of a roller with an auxiliary arc between the crowning of the partial arc and the straight portion, and a contact surface pressure on the rolling surface of the roller. The left vertical axis in FIGS. 19 and 20 indicates the crowning drop amount (unit: mm). The horizontal axes in FIGS. 19 and 20 indicate the axial position (unit: mm) of the roller. The vertical axes on the right side of FIGS. 19 and 20 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. 20, the slope 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. 19, the crowning represented by a partial arc in 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. 19 and 20, 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 ring or the 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 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.

In this case, in the tapered roller bearing 10 applied to the transmission of a car, the above-mentioned ratio R _process / R is 0.8 or more because the lubrication environment is not better than when applied to other mechanical devices (for example, differential devices). By doing this, 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 made sufficiently thick.

  In the tapered roller bearing 10, the arithmetic surface roughness Ra of the large end face 16 of the tapered roller 12 may be 0.10 μmRa 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.

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 conical conical 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 tapered roller 12 shown in FIG. 5 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 as shown in FIG. It becomes an ideal single arc curve in which the condition of R152 = R364 = R1564 is satisfied. However, in reality, as shown in FIG. 7, 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. 7, 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. 7, when both end surfaces of the large end surface 16 of the tapered roller 12 droop, 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. Therefore, the calculated R dimension of the large end face 16 is R152 (actual curvature radius R _{process in} FIG. 7), 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 tapered 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, when the skew angle of the tapered roller 12 increases and the contact surface pressure at the contact portion between the large weir surface 18 and the large end face 16 also increases, The oil film parameter Λ between the faces 18 is reduced. 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 tapered roller 12 and the large-diameter surface 18 of the inner ring, and when this condition 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 surface roughness of the large end face 16 of the tapered 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) Note that the lubrication condition between the large ridge surface of the inner ring and the large end surface of the tapered roller is determined by the radius of curvature (actual radius of curvature R _process ) of the large end surface of the large conical roller and the operating temperature of the lubricating oil did. (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

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. When used under conditions other than the above for automotive applications, or in other applications other than automotive applications, change the maximum temperature, viscosity or assumed peak temperature conditions of the lubricating oil as appropriate, and then The lubrication 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 rough straight line as in the present invention but a curved surface (inside concave side), the geometric shape combination configured with the large end surface of the large ridge surface which is the curved surface If the "oil section lubrication coefficient" is derived from the calculated oil film thickness, it can be determined by comparing with the 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 was possible to generalize and derive the definition of the above-mentioned ratio that contributes to the improvement of the seizure resistance of the tapered roller bearing having no limitation in 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.

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)
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.

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)
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. 21 is a flow chart for explaining a method of manufacturing the tapered roller bearing shown in FIG. FIG. 22 is a schematic view showing a heat treatment pattern in the heat treatment step of FIG. FIG. 23 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. 21, 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 tapered rollers 12, and the cage 14 are prepared. In addition, crowning is not yet formed in the member which should become the tapered roller 12, and the surface of the said member is the processing front surface 12E shown by the dotted line of 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 tapered rollers 12, and the inner ring 13, carbonitriding or nitriding, quenching, and quenching Perform return processing etc. An example of the heat treatment pattern in this step (S200) is shown in FIG. FIG. 22 shows a heat treatment pattern showing a method of performing primary hardening and secondary hardening. FIG. 23 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), in the nitrogen-rich layers 11B, 12B, and 13B having a quenched structure, the grain size of the prior austenite crystal grains is compared with the microstructure in the conventional quenched structure shown in FIG. Thus, it is possible to obtain a microstructure as shown in FIG. 8 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 tapered rollers 12, crownings 22A and chamfers 21 are formed by machining such as cutting as shown in FIG.

  Next, an assembly process (S400) is performed. In this step (S400), the tapered roller bearing 10 shown in FIG. 1 is obtained by assembling the bearing 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. 24 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 bearing 10 is not limited to a differential of an automobile, and may be used for a transmission.

  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.

<Modification>
As shown in FIG. 25, a notch 110 c may be provided also in the small annular portion 106 on the narrow side of the pocket 109. In this case, the total area of the three notches 110a and 110c on the narrow side is larger than the total area of the two notches 110b on the wide side. The notch 110c is, for example, 1.0 mm deep and 5.7 mm wide.

  As described above, by providing the notch 110 c also in the small annular portion 106 on the narrow side of the pocket 109, the lubricating oil flowing from the inner diameter side of the cage 14 to the inner ring side is also obtained from the notch 10 c of the small annular portion 106. It is possible to further reduce the torque loss due to the flow resistance of the lubricating oil by escaping to the outer ring side and further reducing the amount of the lubricating oil reaching the vat along the raceway surface of the inner ring 13.

  On the axially outer side of the small annular portion 106 of the cage 14, as shown in FIG. 1, a radially inward facing ridge 50 is provided facing the outer diameter surface of the small flange portion 42 of the inner ring 13. . As shown in FIG. 26, the gap δ between the inner diameter surface of the ridge 50 and the outer diameter surface of the small collar portion 42 of the inner ring 13 has an outer diameter dimension of 2 of the small collar portion 42. It may be set narrowly to .0% or less.

  A radially inward ridge 50 facing the outer diameter surface of the small collar portion 42 of the inner ring 13 is provided on the axially outer side of the small annular portion 106 of the cage 14, and the ridge 50 of the small annular portion 106 opposed The clearance σ between the inner diameter surface of the inner ring 13 and the outer diameter surface of the small collar portion 42 of the inner ring 13 is 2.0% or less of the outer diameter dimension of the small collar portion 42 of the inner ring 13. The amount of lubricating oil flowing into the inner ring 13 can be reduced, and torque loss due to the flow resistance of the lubricating oil can be further reduced.

  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, 120A, 120B bearings, 11 outer ring, 11A outer ring raceway surface, 11B, 12B, 13B nitrogen enriched layer, 11C, 12C, 13C unnitrided part, 12 conical rollers 12A rolling surface, 12E front surface processed, 13 Inner ring, 13A inner ring raceway surface, 14 cage, 16 large end face, 16A convex portion, 16B concave portion, 16C, 21 chamfered portion, 17 small end face, 18 large ridge surface, 18A flank surface, 19 small ridge surface, 22 and 24 crowning Part, 22A crowning, 23 straight part (central part), 25A, 25B relief part, 26 center line, 27 contact part crowning part, 31 first measurement point, 32 second measurement point, 33 third measurement point, 41 large diameter Section, 42 small collar, 100 manual transmission, 106 small ring, 107 large ring, 108 column, 109 Pocket.

Claims (6)

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 When,
And a plurality of circumferentially spaced pockets, each of the plurality of tapered rollers being accommodated in each of the plurality of pockets.
The cage connects a small annular portion continuing on the small diameter end face side of the plurality of tapered rollers, a large annular portion continuing on the large diameter end face side of the plurality of tapered rollers, the small annular portion and the large annular portion Containing multiple columns
Each of the plurality of pockets is formed in a trapezoidal shape in which a portion storing the small diameter side of the plurality of tapered rollers is narrow and a portion housing the large diameter side is wide.
The retainer is formed by providing a notch in the column portion on the narrow side of the pocket of the cage with a width toward the large annular portion from the boundary between the small annular portion and the column portion. The lubricating oil flowing from the inner diameter side to the inner ring side quickly escapes from the notch to the outer ring side on the outer diameter side, and the pocket side edge of the small annular portion is the narrow side of the pocket The bottom portion has a shape extending to the column portion,
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,
A cone having a ratio R _process / R between the actual radius of curvature R _process and the set radius of curvature R of 0.5 or more, where an actual radius of curvature after grinding of the large end face of the tapered roller is R _process Roller bearing.   The difference between the maximum value and the minimum value of the arithmetic surface roughness Ra of the circumferential surface area in contact with the large weir surface at the large end face of the tapered roller is 0.02 μm or less. Conical roller bearings.   The tapered roller bearing according to claim 1, wherein the small annular portion on the narrow side of the pocket is also provided with a notch.   A radially inward ridge facing the outer diameter surface of the small ridge of the inner ring is provided on the axially outer side of the small annular portion of the cage, and the inner diameter surface of the ridge of the small annular portion opposed and the inner ring The tapered roller bearing according to any one of claims 1 to 3, wherein a gap between the outer ring and the outer diameter surface of the small ring is 2.0% or less of the outer diameter of the small ring of the inner ring. In a cross section passing through a central axis of the inner ring, the inner ring raceway surface and the outer ring raceway surface are linear or arc-shaped,
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 portions end to a length of, when the _{a = 2K 1 Q / πLE '} , represented by the formula (1), tapered roller bearing according to any one of claims 1 to 4 .
  The tapered roller bearing according to any one of claims 1 to 5, wherein an arithmetic surface roughness Ra of the large end face of the tapered roller is 0.10 μmRa or less.