JP7029371B2 - Conical roller bearing - Google Patents

Description

The present invention relates to conical roller bearings.

Conventionally, a conical roller bearing is known as a kind of bearing. Conical roller bearings are applied to mechanical devices such as automobiles. When a conical roller bearing is used, the large end surface of the tapered roller and the large flange surface of the inner ring come into contact with each other and can receive a constant axial load. However, the contact between the large end surface of the conical roller and the large flange surface of the inner ring described above is not a rolling contact but a sliding contact. Therefore, if the lubrication environment at the contact portion between the large end surface of the conical roller and the large flange surface of the inner ring is insufficient, there is a concern that heat will be generated at the contact portion and the temperature will rise rapidly.

In order to solve the above problems, it is necessary to reduce the torque crossing and heat generation due to friction at the contact portion between the large end surface of the conical roller and the large flange surface of the inner ring, and to improve the oil film forming property at the contact portion. ..

For example, in Japanese Patent Application Laid-Open No. 2000-170774 (hereinafter, also referred to as Patent Document 1), the radius of curvature of the large end surface of the conical roller is R, and the large flange surface of the inner ring (conical roller) from the apex of the conical angle of the conical roller. It has been proposed that the ratio R / R _BASE be in the range of 0.75 to 0.87 when the distance to the contact portion) is R _BASE . This improves the oil film forming property at the contact portion between the large end surface of the conical roller and the large flange surface of the inner ring.

Japanese Unexamined Patent Publication No. 2000-170774

However, Patent Document 1 does not specify an allowable range for the actual radius of curvature of the large end face of the conical roller after processing. 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 small, a larger skew than expected may be induced.

Further, in the transmission or differential of an automobile, which is one of the uses of conical roller bearings, low-viscosity oil tends to be used in order to reduce the fuel consumption of the automobile. In an environment where low-viscosity oil is used, short-life surface origin peeling due to poor lubrication may occur on the inner ring raceway surface where the surface pressure is high, and it is desired to extend the life of the conical roller bearing.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a conical roller bearing having excellent seizure resistance and a long life.

A conical roller bearing according to the present disclosure includes an outer ring, an inner ring, a plurality of conical rollers, and a cage. The outer ring has an outer ring raceway surface on the inner peripheral surface. The inner ring has an inner ring raceway surface on the outer peripheral surface and a large flange surface arranged on the larger diameter side of the inner ring raceway surface, and is arranged inside the outer ring. The plurality of conical 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 flange surface. The plurality of conical rollers are arranged between the outer ring raceway plane and the inner ring raceway plane. The cage includes a plurality of pockets arranged at predetermined intervals in the circumferential direction, and each of the plurality of conical rollers is housed and held in each of the plurality of pockets. The roller coefficient γ exceeds 0.90.

When the set radius of curvature of the large end face of the conical roller is R and the distance from the apex of the conical angle of the conical roller to the large flange surface of the inner ring is R _{BASE, the ratio of the set radius of curvature R and the distance R BASE R} / R _BASE The value is 0.75 or more and 0.87 or less. When the actual radius of curvature of the large end face of the conical roller after grinding is R _process , the ratio R _process / R of the actual radius of curvature R _process and the set radius of curvature R is 0.5 or more. In addition, since the roller coefficient (roll filling rate) exceeds 0.90, the maximum surface pressure of the raceway surface can be reduced, which prevents surface origin peeling in a short life in a harsh lubrication environment. Can be

According to the above, a conical roller bearing having excellent seizure resistance and a long life can be obtained.

It is sectional drawing which shows the conical roller bearing which concerns on embodiment. It is a development plan view of the cage of the conical roller bearing which concerns on Embodiment 1. FIG. It is a partial cross-sectional schematic diagram for demonstrating the nitrogen-enriched layer in the conical roller bearing which concerns on embodiment. It is sectional drawing which shows the design specification of the conical roller bearing which concerns on embodiment. It is sectional drawing for explaining the reference radius of curvature of a roller in the conical roller bearing which concerns on embodiment. It is a partial cross-sectional schematic diagram which shows the region VI shown in FIG. It is sectional drawing for explaining the actual radius of curvature of a roller in the conical roller bearing which concerns on embodiment. It is a figure which shows the old austenite grain boundary of the bearing component which concerns on embodiment. It is a figure which shows the old austenite grain boundary of the conventional bearing component. It is sectional drawing which shows an example of the method of changing the contact position between the inner ring raceway surface and the rolling surface in the conical roller bearing which concerns on embodiment. It is sectional drawing which shows another example of the method of changing the contact position between a rolling surface and a rolling surface in the conical roller bearing which concerns on embodiment. It is a figure for demonstrating the shape of the nitrogen-enriched layer in the crowning part and the central part of the roller of the conical roller bearing which concerns on embodiment. It is a figure for demonstrating the shape of the logarithmic crowning of the roller of the conical roller bearing which concerns on embodiment. It is a partial cross-sectional schematic diagram which shows the detailed shape of the inner ring of the conical roller bearing which concerns on embodiment. It is an enlarged schematic diagram of the region XV of FIG. It is a schematic diagram which shows the shape of the inner ring raceway surface in the generatrix direction shown in FIG. It is a graph which shows the relationship between the radius of curvature of the large end face of the roller of the conical roller bearing which concerns on embodiment, and the oil film thickness. It is a graph which shows the relationship between the radius of curvature of the large end face of the roller of the conical roller bearing which concerns on embodiment, and the maximum hertz stress. It is the figure which superposed the contour line of the roller which provided the crowning which the contour line is represented by a logarithmic function, and the contact surface pressure on the rolling surface of a roller. It is the figure which superposed the contour line of the roller which made the auxiliary arc between the crowning of a partial arc and the straight part, and the contact surface pressure on the rolling surface of a roller. It is a flowchart of the manufacturing method of the conical roller bearing which concerns on embodiment. It is a figure for demonstrating the heat treatment method in an embodiment. It is a figure for demonstrating the modification of the heat treatment method in Embodiment. It is a vertical sectional view which shows the differential which comprises the conical roller bearing which concerns on embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts will be given the same reference number and the explanation will not be repeated.

<Conical roller bearing configuration>
FIG. 1 is a schematic cross-sectional view of a conical roller bearing according to an embodiment of the present invention. FIG. 2 is a developed plan view of the cage of the conical roller bearing shown in FIG. FIG. 3 is a schematic partial cross-sectional view of the conical roller bearing shown in FIG. FIG. 4 is a schematic cross-sectional view showing the design specifications of the conical roller bearings shown in FIGS. 1 and 3. FIG. 5 is a schematic cross-sectional view for explaining a reference radius of curvature of a roller in a conical roller bearing according to an embodiment of the present invention. FIG. 6 is a schematic partial cross-sectional view showing the region VI shown in FIG. FIG. 7 is a schematic cross-sectional view for explaining the actual radius of curvature of the roller in the conical roller bearing according to the embodiment of the present invention. The conical roller bearing according to the present embodiment will be described with reference to FIGS. 1 to 7.

The conical roller bearing 10 shown in FIG. 1 mainly includes an outer ring 11, an inner ring 13, a plurality of conical rollers 12, and a cage 14. The outer ring 11 has a ring shape, and has an outer ring raceway surface 11A on its inner peripheral surface. The inner ring 13 has a ring shape, and has an inner ring raceway surface 13A on the outer peripheral surface thereof. The inner ring 13 is arranged on the inner peripheral side of the outer ring 11 so that the inner ring raceway surface 13A faces the outer ring raceway surface 11A. In the following description, the direction along the central axis of the conical roller bearing 10 is the "axial direction", the direction orthogonal to the central axis is the "diameter direction", and the direction along the arc centered on the central axis is the "circumferential direction". Called "direction".
The conical roller 12 has a roller rolling surface 12A, and is in contact with the inner ring raceway surface 13A and the outer ring raceway surface 11A on the roller rolling surface 12A. The plurality of conical rollers 12 are arranged at a predetermined pitch in the circumferential direction by the metal cage 14. As a result, the conical roller 12 is rotatably held on the annular orbits of the outer ring 11 and the inner ring 13. Further, in the conical roller bearing 10, the vertices of the cone including the outer ring raceway surface 11A, the cone including the inner ring raceway surface 13A, and the cone including the locus of the rotation axis when the conical roller 12 rolls are on the center line of the bearing. It is configured to intersect at one point (point O in FIG. 4). With such a configuration, the outer ring 11 and the inner ring 13 of the conical roller bearing 10 are relatively rotatable with respect to each other. The inner ring 13 has a large collar portion 41 on the large diameter side of the inner ring raceway surface 13A and a small brim portion 42 on the small diameter side. The cage 14 is not limited to metal, but may be made of resin.

Roll coefficient:
The conical roller bearing 10 has a roller coefficient γ> 0.90. Here, the roller coefficient γ is defined by the relational expression γ = (Z · DA) / (π · PCD) as the number of rollers Z, the average roller diameter DA, and the roller pitch circle diameter PCD.

Cage shape:
As shown in FIG. 2, the cage 14 includes a small annular portion 14a connected on the small-diameter end face side of the conical roller 12, a large annular portion 14b connected on the large-diameter end face side of the conical roller 12, and these small annular portions 14a. And a plurality of pillar portions 14c connecting the macrocyclic portion 14b. The cage 14 is formed with a plurality of pockets 14d arranged at predetermined intervals in the circumferential direction. The plurality of pockets 14d hold the plurality of conical rollers 12. The cage 14 is arranged at a position closer to the outer ring 11 than the inner ring 13 in the radial direction.

As shown in FIG. 3, the window angle θ of the pocket 14d, that is, the angle formed by each pillar surface facing the pocket 14d of the two pillars 14c adjacent to each other across the pocket 14d is 46 ° or more and 80 ° or less. Is. The reason why the lower limit value of the window angle θ is set to 46 ° or more is to secure a good contact state with the rollers, and the contact state with a place where the window angle is less than 46 ° is deteriorated. That is, when the window angle is 46 ° or more, γ> 0.90 can be ensured while ensuring the cage strength, and a good contact state can be ensured. Further, the reason why the upper limit of the window angle θ is set to 80 ° or less is that when the window angle exceeds 80 °, the pressing force in the radial direction becomes large, and smooth rotation can be obtained even with a self-lubricating resin material. This is because there is a risk that it will not be possible.

The present inventors conducted a life test and confirmed that the roller coefficient is related to the life. Table 1 shows the results of this life test.

In Table 1, sample 3 is a typical conventional conical roller bearing in which the cage and the outer ring are separated and the roller coefficient is 0.90 or less, and sample 1 has a roller coefficient γ with respect to sample 3 as a conventional product. It is a conical roller bearing in which only is over 0.90, and sample 2 is a conical roller bearing of the present invention in which the roller coefficient γ is over 0.90 and the window angle is in the range of 46 degrees or more and 65 degrees or less. The test was conducted under severe lubrication and overload conditions. As is clear from Table 1, Sample 1 had a lifespan more than twice that of Sample 3. In particular, in recent years, in power transmission devices of automobiles such as transmissions or differentials, the viscosity of the lubricating oil used is lowered, so that the conical roller bearings tend to be placed in a harsher lubricating environment than in the past. Therefore, by setting the roller coefficient γ to a range exceeding 0.90, the life of the conical roller bearing 10 can be extended even if it is incorporated in a device in which a low-viscosity lubricating oil as described above is used. can. Further, the bearing of the sample 2 has a roller coefficient of 0.96, which is the same as that of the sample 1, but the life time is about 5 times or more that of the sample 1. The dimensions of sample 3, sample 1 and sample 2 are φ45 × φ81 × 16 (unit: mm), the number of rollers is 24 (sample 3), 27 (sample 1, sample 2), and the oil film parameter Λ = 0.2. Is.

The material constituting the outer ring 11, the inner ring 13, and the conical roller 12 is made of, for example, high carbon chromium bearing steel specified in JIS standard, and more specifically, JIS standard 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-enriched layer 13B extends from the raceway surface 13A to the small flange surface 19 and the large flange surface 18. The nitrogen-enriched 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 flange surface 19 of the inner ring 13 is finished to be a ground surface parallel to the small end surface 17 of the conical rollers 12 arranged on the raceway surface 13A. The large flange surface 18 of the inner ring 13 is finished as a ground surface extending along the large end surface 16 of the conical roller 12. A relief portion 25A is formed at a corner where the inner ring raceway surface 13A and the large flange surface 18 intersect.

Further, a nitrogen-enriched layer 12B is formed on the surface including the rolling surface 12A of the conical roller 12, the large end surface 16 and the small end surface 17. The nitrogen-enriched layer 12B is a region where the nitrogen concentration is higher than that of the unnitriding portion 12C of the roller 12. The nitrogen-enriched layers 11B, 12B, and 13B can be formed by any conventionally known method such as carburizing nitriding treatment and nitriding treatment.

The nitrogen-enriched layer 12B may be formed only on the conical roller 12, the nitrogen-enriched layer 11B may be formed only on the outer ring 11, or the nitrogen-enriched layer 13B may be formed only on the inner ring 13. May be good. Alternatively, a nitrogen-enriched layer may be formed on two of the outer ring 11, the inner ring 13, and the conical roller 12.

Nitrogen-enriched layer thickness and nitrogen concentration:
The thickness of the nitrogen-enriched 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-enriched 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 conical roller 12 to the bottom of the nitrogen-enriched layer 12B may be 0.2 mm or more. The distance from the large end surface 16 or the small end surface 17 as a part of the outermost surface of the surface layer of the conical roller 12 to the bottom of the nitrogen-enriched 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-enriched layer 13B is 0.2 mm or more. The distance from the large flange surface 18 as a part of the outermost surface of the inner ring 13 to the bottom of the nitrogen-enriched layer 13B is 0.2 mm or more.

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

Ratio of radius of curvature R of the large end surface 16 of the conical roller 12 to the distance R _BASE from the point O to the large flange surface 18 of the inner ring 13 R / R _BASE :
As shown in FIG. 4, the conical roller 12 and the cone angle vertices of the raceway surfaces 11A and 13A of the outer ring 11 and the inner ring 13 coincide with each other at a point O on the center line of the conical 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 surface 16 of the conical roller 12 to the distance R _BASE from the point O to the large flange surface 18 of the inner ring 13 is 0.75 or more. It shall be 87 or less.

Shape of large end face 16 of conical roller 12:
When the actual radius of curvature of the large end surface 16 of the conical roller 12 after grinding is R _process , the ratio R _process / R of the actual radius of curvature R _process and the set radius of curvature R is 0.5 or more. Hereinafter, a specific description will be given.

5 and 6 are schematic cross-sectional views taken along the rolling axis of the conical roller 12 obtained when grinding is ideally performed. When ideally ground, the large end face 16 of the resulting conical roller 12 becomes part of a spherical surface centered on point O (see FIG. 4), which is the apex of the conical angle of the conical roller 12. As shown in FIGS. 5 and 6, when the grinding process is ideally performed so as to leave a part of the convex portion 16A, the large end surface 16 of the conical roller 12 having the end surface of the convex portion 16A is formed. It becomes a part of one spherical surface centered on the apex of the cone angle of the cone roller 12. In this case, the inner peripheral end of the convex portion 16A in the radial direction about the rolling axis (rotating axis) of the conical roller 12 is connected to the concave portion 16B via points C2 and C3. The outer peripheral end of the convex portion 16A is connected to the chamfered portion 16C via points C1 and C4. In an ideal large end face, points C1 to C4 are arranged on one spherical surface as described above.

Generally, a conical roller is manufactured by sequentially performing a grinding process including a heading process and a crowning process on a columnar roller shape material. A recess due to the shape of the punch of the squeezing device is formed in the central portion of the surface to be the large end surface of the molded body obtained by the squeezing process. The planar shape of the recess is, for example, a circular shape.

Here, the radius of curvature (set radius of curvature) R of the large end surface 16 of the conical roller 12 is the R dimension when the large end surface 16 of the conical roller 12 shown in FIG. 5 is an ideal spherical surface. Specifically, as shown in FIG. 6, consider an intermediate point P5, C3, and an intermediate point P6 of the points C1, C2, C3, C4, points C1, and C2 at the end of the large end surface 16 of the conical roller 12. .. When the large end surface 16 is the ideal spherical surface, in the cross section shown in FIG. 6, the large end surface 16 has a radius of curvature R152 passing through points C1, P5, and C2, and a radius of curvature passing through points C3, P6, and C4. It is an ideal single arc curve that satisfies the condition of R152 = R364 = R1564 for the radius of curvature R1564 passing through R364 and points C1, P5, P6, and C4. 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 for which R = R152 = R364 = R1564 holds is called 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 surface 16 of the conical roller 12 obtained by actual grinding as described later. The positions of points C2 and C3 are not limited to the positions shown in FIG. For example, the point C2 may be slightly offset to the point C1 side, and the point C3 may be slightly offset to the point C4 side.

FIG. 7 is a schematic cross-sectional view taken along the rolling axis of the conical roller obtained by actual grinding. 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 surface 16 of the conical roller 12 actually obtained by grinding the molded body in which the concave portion and the convex portion as described above are formed is the apex of the conical angle of the conical roller 12. It does not become a part of one spherical surface centered on. The points C1 to C4 of the convex portion of the actually obtained conical roller 12 have a shape in which the points C1 to C4 are sagging as compared with the convex portion 16A shown in FIG. That is, the 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 the points C1 and C4 shown in FIG. It is arranged inward in the direction (R152 on one side is not the same as R1564 of the entire large end surface 16 and can be made smaller).

The 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 the points C2 and C3 shown in FIG. (R364 on one side is not the same as R1564 of the entire large end surface 16 and can be made smaller). The intermediate points P5 and P6 shown in FIG. 7 are formed at positions substantially equal to, for example, the intermediate points P5 and P6 shown in FIG.

As shown in FIG. 7, in the large end face actually formed by grinding, the vertices C1 and C2 are arranged on one spherical surface, and the vertices C3 and C4 are on the other spherical surface. Have been placed. Depending on the general grinding process, the radius of curvature of one arc formed by a part of the large end face formed on one convex part is the arc formed by a part of the large end face formed on the other convex part. It is about the same as the radius of curvature. That is, R152 on one side of the large end surface 16 of the conical roller 12 shown in FIG. 7 after processing is substantially equal to R364 on the other side. Here, R152 and R364 on one side of the large end surface 16 of the roller 12 after processing are referred to as 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, the conical roller 12 of the conical roller bearing according to the present embodiment has a ratio R _process / R of the actual radius of curvature R _process to the set radius of curvature R of 0.5 or more.

As shown in FIG. 7, the radius of curvature R _virtual of the virtual arc passing through the apex C1, the intermediate point P5, the intermediate point P6, and the apex C4 on the large end surface actually formed by the grinding process (hereinafter, virtual curvature). The radius) is equal to or less than the set radius of curvature R. That is, in the conical roller 12 of the conical roller bearing according to the present embodiment, the ratio R _process / R _virtual of the actual radius of curvature R _process to the virtual radius of curvature R _virtual is 0.8 or more.

Surface roughness of the large end surface 16 of the conical roller 12:
The arithmetic average roughness Ra of the large end surface 16 may be 0.10 μmRa or less. Hereinafter, description will be made with reference to FIG. The large end surface 16 includes a chamfered portion 16C, a convex portion 16A, and a concave portion 16B. On the large end surface 16, the chamfered portion 16C is arranged on the outermost circumference. An annular convex portion 16A is arranged on the inner peripheral side of the chamfered portion 16C. The concave portion 16B is arranged 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 16C is formed so as to connect the convex portion 16A and the rolling surface which is the side surface of the conical roller 12. The arithmetic average roughness Ra of the large end surface 16 described above substantially means the surface roughness of the convex portion 16A. Further, on the large end surface 16 of the conical roller 12, the difference between the maximum value and the minimum value of the arithmetic average roughness arithmetic average roughness Ra of the convex portion 16A, which is a circumferential surface region in contact with the large flange surface 18, is 0. It may be 0.02 μm or less. As a result, the variation in the surface roughness Ra of the circumferential surface region of the large end surface 16 can be sufficiently reduced, and the result is due to the synergistic effect with the numerical range of the ratio R / R _BASE and the numerical range of the ratio R _process / R. Therefore, it is possible to secure a sufficient oil film thickness at the contact portion.

The large flange surface 18 is ground to a surface roughness of, for example, 0.12 μmRa or less. Preferably, the arithmetic mean roughness Ra of the large collar surface is 0.063 μmRa or less.

Crystal structure of nitrogen-enriched layer:
The particle size of the old austenite in the nitrogen-enriched layers 11B, 12B, and 13B has a particle size number of JIS standard of 10 or more. Here, FIG. 8 is a schematic diagram illustrating the microstructure of the bearing component constituting the conical roller bearing according to the present embodiment, particularly the former austenite grain boundaries. FIG. 9 is a schematic diagram illustrating the old austenite grain boundaries of conventional hardened bearing parts. FIG. 8 shows the microstructure in the nitrogen-enriched layer 12B. The old austenite crystal grain size in the nitrogen-enriched layer 12B in the present embodiment has a JIS standard particle size number of 10 or more, and is the same as the old austenite crystal grain size of the conventional general hardened product shown in FIG. Even if compared, it is sufficiently miniaturized.

Contact position between the rolling surface of the conical roller 12 and the inner ring raceway surface:
As shown in FIG. 10, the width of the rolling surface 12A in the extending direction of the rolling axis of the conical roller 12 is L, and the center C of the contact position between the inner ring raceway surface 13A and the rolling surface 12A is in the extending direction. When the amount of deviation from the midpoint N of the rolling surface 12A to the side of the large end surface 16 is α, in the conical roller bearing 10, the ratio α / L of the width L and the amount of deviation α is 0% or more and less than 20%. May be.

The present inventors have found that the center C of the contact position when the ratio α / L is 0% or more and less than 20% and the ratio α / L is more than 0% is the extending direction of the rolling axis. By being on the midpoint N of the rolling surface or on the large end surface 16 side of the midpoint N, the center C of the contact position when the ratio α / L exceeds 0% extends the rolling axis. It was confirmed that the skew angle can be reduced and the increase in rotational torque can be suppressed as compared with the case where the rolling surface is on the small end surface 17 side of the midpoint N of the rolling surface in the direction.

In Table 2, when the deviation 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 conical roller 12 rolls in the extending direction of the rolling shaft. The calculation results of the ratios of the skew angle φ0 when the moving surface 12A is located at the midpoint N and the skew angle φ and the rotation torque M when the deviation amount α is changed with respect to the rotation torque M0 are shown. In Table 2, the deviation amount α is shown as the ratio (α / L) of the deviation amount α to the width L of the rolling surface 12A of the conical roller 12. Further, the amount of deviation when the contact position is displaced toward the small end surface 17 side from 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 0.

As shown in Table 2, it can be seen that the skew angle φ is smaller when the ratio α / L with respect to the deviation amount α is set to the large diameter side than when the ratio α / L is 0%. Further, the rotational torque M increases as the deviation amount α increases, but the effect is greater on the small diameter side than on the large diameter side. Since the ratio α / L with respect to the deviation amount α was −5% and the skew angle was as large as 1.5 times, the influence on heat generation could not be ignored, and it was judged to be impractical (NG). Further, when the ratio α / L is 20% or more, the slip on the rolling surface 12A of the conical roller 12 becomes large and the rotational torque M increases, causing another problem such as peeling, which is not practical (NG). ).

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 with respect to the deviation amount α is 0% or more and less than 20%. Further, preferably, the ratio α / L exceeds 0%. Further, 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 in FIGS. 10 and 11, for example. 10 and 11 are schematic cross-sectional views showing an example of a method of changing the contact position between the inner ring raceway surface 13A and the rolling surface 12A in a conical roller bearing.

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

Further, in the configuration in which the ratio α / L exceeds 0%, as shown in FIG. 11, 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 changing the angle with respect to the relative angle. 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 deviation amount α of the above-mentioned contact position shown by the dotted line in FIG. 11 is zero, and the outer ring is formed. A configuration in which the ratio α / L exceeds 0% can be realized by at least one method of reducing the angle formed by the raceway surface 11A with respect to the axial direction of the outer ring 11.

Shape of rolling surface of conical roller 12:
As shown in FIG. 12, the rolling surfaces 12A (see FIG. 3) of the conical roller 12 are located at both ends and connect between the crowning portions 22 and 24 on which the crowning is formed and the crowning portions 22 and 24. Including the central portion 23. 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 conical roller 12 is linear. A chamfered portion 21 is formed between the small end surface 17 of the conical roller 12 and the crowning portion 22. A chamfered portion 16C is also formed between the large end surface 16 of the conical roller 12 and the crowning portion 24.

Here, in the method for manufacturing the conical roller 12, when the treatment for forming the nitrogen-enriched layer 12B (carburizing nitriding treatment) is performed, crowning is not formed on the conical roller 12, and the outer shape of the conical roller 12 is shown in the figure. It is the unprocessed surface 12E shown by the dotted line of 14. After the nitrogen-enriched layer is formed in this state, the side surface of the conical roller 12 is processed as a finishing process as shown by the arrow in FIG. 14, and the crowning portion is formed as shown in FIGS. 12 and 14. 22 and 24 are obtained.

Specific examples of the thickness of the nitrogen-enriched layer:
The depth of the nitrogen-enriched layer 12B in the conical roller 12, that is, the distance from the outermost surface of the nitrogen-enriched layer 12B to the bottom of the nitrogen-enriched layer 12B is 0.2 mm or more as described above. Specifically, the rolling of the first measuring point 31, which is the boundary point between the chamfered portion 21 and the crowning portion 22, the second measuring point 32, which is the position where the distance W is 1.5 mm from the small end surface 17, and the conical 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-enriched layer 12B at each position are 0.2 mm or more. Here, the depth of the nitrogen-enriched layer 12B means the thickness of the nitrogen-enriched layer 12B in the radial direction orthogonal to the center line 26 of the conical roller 12 and toward the outer peripheral side. The values of the depths T1, T2, and T3 of the nitrogen-enriched layer 12B are set according to the process conditions such as the shape and size of the chamfered portions 21 and 16C, the process for forming the nitrogen-enriched layer 12B, and the finishing conditions. It can be changed as appropriate. For example, in the configuration example shown in FIG. 14, since the crowning 22A is formed after the nitrogen-enriched layer 12B is formed as described above, the depth T2 of the nitrogen-enriched layer 12B is the other depths T1 and T3. Although it is smaller, the magnitude relationship between the values of the depths T1, T2, and T3 of the nitrogen-enriched layer 12B can be appropriately changed by changing the above-mentioned process conditions.

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

Crowning shape:
The shape of the crowning formed in the contact portion crowning portion 27 included in the crowning portions 22 and 24 of the conical roller 12 (the portion connected to the central portion 23 and in contact with the inner ring raceway surface 13A) is defined as follows. .. That is, the sum of the drop amounts of crowning has K1, K2, zm as design parameters and Q in the yz coordinate system in which the generatrix of the rolling surface 12A of the conical roller 12 is the y-axis and the generatrix orthogonal direction is the z-axis. Is the load, L is the length of the effective contact portion of the rolling surface 12A on the conical roller 12 in the generatrix direction, E'is the equivalent elastic coefficient, and a is the effective contact portion from the origin taken on the generatrix of the rolling surface of the conical roller 12. When the length to the end of is A = 2K1Q / πLE', it is expressed by the following equation (1).

Here, the shapes of the crowning portions 22 and 24 of the conical roller 12 are logarithmic curve crowning obtained by the above mathematical formula. However, the present invention is not limited to the above formula, and a logarithmic curve may be obtained by using another logarithmic crowning formula.

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 with reference to FIGS. 14 to 16. FIG. 14 is a schematic partial cross-sectional view showing the detailed shape of the inner ring 13. FIG. 15 is an enlarged schematic view of the 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 FIGS. 14 and 15, a partial contour of the conical roller 12 on the large end surface 16 side is shown by a two-dot chain line.

As shown in FIGS. 14 to 16, the inner ring raceway surface 13A is formed in a full crowning shape with a gentle arc, and is connected to the relief portions 25A and 25B. The radius of curvature Rc of the full crowning of a gentle arc is extremely large, for example, a drop amount of about 5 μm is generated at both ends of the inner ring raceway surface 13A. As shown in FIG. 14, since the inner ring raceway surface 13A is provided with relief portions 25A and 25B, the effective raceway surface width of the inner ring raceway surface 13A is LG.

As shown in FIG. 15, a flank surface 18A that smoothly connects to the large flange surface 18 is formed on the outer side of the large flange surface 18 in the radial direction. The wedge-shaped gap formed between the flank 18A and the large end surface 16 of the conical roller 12 enhances the drawing action of the lubricating oil and can form a sufficient oil film. The shape of the inner ring raceway surface 13A in the generatrix direction exemplifies a full crowning shape with a gentle arc, but the shape is not limited to this and may be a straight shape.

In the above, the shape of the inner ring raceway surface 13A of the inner ring 13 in the generatrix direction has been described, but since the shape of the outer ring raceway surface 11A in the generatrix direction is also the same, the description will not be repeated.

Here, the rolling surface 12A of the conical 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 with a gentle arc. The verification results leading to the embodiment will be described below.

Outer ring track for conical roller bearings for automobile transmissions (inner diameter φ35 mm, outer diameter φ62 mm, width 18 mm) under low-speed conditions (1st speed) with misalignment and high-speed conditions (4th speed) without misalignment. The ratio of the contact ellipse to the contact surface pressure of the surface 11A and the effective rolling surface width L (see FIG. 12) of the rolling surface 12A of the conical roller 12 was verified. The samples used for verification are shown in Table 3.

The verification results are shown in Table 4.

Under high-speed conditions without misalignment, the load conditions are relatively light, so as shown in Table 4, neither sample 4 nor sample 5 generates edge surface pressure (P _EDGE ). On the other hand, in the sample 5, since the drop amount of the full crowning of the outer ring is large and the contact ellipse (semi-major axis) is short, the variation of the center C of the contact position is large as compared with the case where the contact region is long, and the conical roller It became easy to induce the skew of, and it was judged to be impractical (NG).

On the other hand, in the sample 5, the ratio of the contact ellipse to the effective roller rolling surface width L is 100% and the edge surface pressure is generated in the outer ring because the load is high under the low-speed condition with misalignment. Further, when it hits the edge, it is contact-driven on the small end surface side of the conical roller, which induces a large skew, which makes it impractical (NG).

From the above, it was verified that it is not preferable to apply a large drop amount of full crowning to the outer ring in order to suppress skew, and the significance of sample 4 was confirmed.

<Measurement method of various characteristics>
Nitrogen concentration measurement method:
For bearing parts such as the outer ring 11, the conical 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 is measured in the depth direction by EPMA (Electron Probe Micro Analysis). Perform line analysis. In the measurement, each bearing component is cut from the measurement position in the direction perpendicular to the surface to expose the cut surface, and the measurement is performed on the cut surface. For example, for the conical roller 12, the cut surface is exposed by cutting the conical roller 12 in the direction perpendicular to the center line 26 from each position of the first measurement point 31 to the third measurement point 33 shown in FIG. Let me. The nitrogen concentration is analyzed by the above EPMA at a plurality of measurement positions located 0.05 mm inward from the surface of the conical roller 12 on the cut surface. For example, the measurement positions are determined at five points, and the average value of the measurement data at the five points is taken as the nitrogen concentration of the conical roller 12.

For the outer ring 11 and the inner ring 13, for example, on the raceway surfaces 11A and 13A, the central portion in the central axis direction of the bearing is set as the measurement position, and the central axis and the cross section along the radial direction orthogonal to the central axis are exposed. , The nitrogen concentration of the cross section is measured by the same method as above.

How to measure the distance from the outermost surface to the bottom of the nitrogen-enriched layer:
For the outer ring 11 and the inner ring 13, the hardness distribution is measured in the depth direction from the surface of the cross section to be measured in the above nitrogen concentration measuring method. A Vickers hardness measuring machine can be used as the measuring device. In the conical roller bearing 10 after tempering with a heating temperature of 500 ° C. and 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 intervals of 0.5 mm. A region having a Vickers hardness of HV450 or higher is used as a nitrogen-enriched layer.

Further, for the conical 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-enriched layer is determined.

How to measure the radius of curvature of the large end face of a roller:
The actual radius of curvature R _process and the virtual radius of curvature R _virtual on the large end surface 16 of the conical roller 12 shown in FIG. 7 can be measured by any method with respect to the conical roller actually formed by grinding, for example, the surface. It can be measured using a roughness measuring machine (for example, Mitutoyo surface roughness measuring machine Surftest SV-3100). When a surface roughness measuring machine is used, first, the measuring axis is set along the radial direction centered on the rolling axis, and the surface shape (shape in the generatrix direction) of the large end surface is measured. The above vertices C1 to C4 and intermediate points P5 and P6 are plotted on the obtained large end face profile. The actual radius of curvature R _process is calculated as the radius of curvature of the arc passing through the plotted vertices C1, midpoint P5 and vertices C2. The virtual radius of curvature R _virtual is calculated as the radius of curvature of an arc passing through the plotted vertices C1, midpoints P5, P6 and vertices C4. Alternatively, the virtual radius of curvature R _virtual of the entire large end surface 16 may be determined by calculating the approximate arc curve radius with the value obtained by taking four points using the command "input multiple times". The shape of the large end surface 16 in the generatrix direction was measured once in the diameter direction.

On the other hand, the set radius of curvature R is estimated from each dimension of the conical roller obtained by the actual grinding process, for example, based on an industrial standard such as a JIS standard.

Surface roughness measurement method:
The arithmetic average roughness Ra of the large end surface 16 of the conical roller 12 can be measured by any method, and can be measured using, for example, a surface roughness measuring machine (for example, Mitutoyo surface roughness measuring machine Surftest SV-3100). Arithmetic mean roughness of the large end surface The arithmetic average roughness Ra can be measured, for example, by a method in which the stylus of the measuring machine is brought into contact with the large end surface 16 of the conical roller 12. Further, on the large end surface 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 flange surface, is any 4 of the convex portion 16A. It can be obtained by measuring the arithmetic average roughness Ra using a surface roughness measuring machine and calculating the difference between the maximum value and the minimum value of the surface roughness of the four locations.

<Effects of conical roller bearings>
The present inventor paid attention to the following matters concerning the conical roller bearing, and came up with the above-mentioned configuration of the conical roller bearing.
(1) Ratio of the set radius of curvature of the large end face of the conical roller to the actual radius of curvature after processing (2) Roller coefficient γ
(3) Shape of the raceway surface of the inner and outer rings that suppresses skew of the conical roller (4) Application of logarithmic crowning to the rolling surface of the conical roller (5) Application of the nitrogen-enriched layer to the conical roller, inner ring and outer ring The following Although there are some overlaps, the characteristic configurations of the above-mentioned conical roller bearings are listed.

By setting the ratio R / R _BASE value of the set radius of curvature R and the distance R _BASE as described above, a sufficient oil film thickness is provided at the contact portion between the large end surface 16 of the conical roller 12 and the large flange surface 18 of the inner ring 13. It is possible to suppress the contact between the conical roller 12 and the large flange surface 18 and the occurrence of wear by ensuring the radius, and to suppress the heat generation at the contact portion.

The value of the ratio R / R _BASE was determined with reference to the following findings. FIG. 17 shows the result of calculating the oil film thickness t formed between the large flange surface 18 of the inner ring 13 and the large end surface 16 of the conical roller 12 using Karna's formula. The vertical axis is 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 sharply when R / R _BASE exceeds 0.87.

FIG. 18 shows the result of calculating the maximum Hertz stress P between the large flange surface 18 of the inner ring 13 and the large end surface 16 of the conical roller 12. The vertical axis is the ratio P / P0 to the maximum Hertz stress P0 when R / R _BASE = 0.76, as in FIG. The maximum Hertz stress P decreases monotonically with the increase of R / R _BASE . In order to reduce the torque crossing and heat generation due to the sway friction between the large flange surface 18 of the inner ring 13 and the large end surface 16 of the conical roller 12, it is desirable to increase the oil film thickness t and reduce the maximum Hertz stress P. The present inventors determined the conditions of the above ratio R / R _BASE with reference to the calculation results of FIGS. 17 and 18 and taking into consideration the seizure resistance test results and the crossing range at the time of manufacture.

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

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 that affect the relationship are the rotational speed and load of the bearing. , Bearing usage conditions such as the viscosity of lubricating oil can be considered. As a result of examination by the inventor, when the value of the ratio R / R _BASE is about 0.8 when such other factors are comprehensively considered, the oil film thickness can be sufficiently maintained on average. Therefore, as described above, the range of the ratio R / R _BASE value is determined with 0.8 as the median value.

Further, by setting the value of the ratio R _process / R of 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 conical roller 12 and the large flange surface 18 of the inner ring 13. The pressure can be reduced. Further, it is possible to suppress the skew of the conical roller 12 and stably secure the oil film thickness at the contact portion between the large end surface 16 and the large flange surface 18.

Further, the conical roller bearing 10 has a roller coefficient exceeding 0.90. By setting the roller coefficient γ of the tapered roller bearing to γ> 0.90, not only the load capacity can be improved, but also the maximum surface pressure of the raceway surface can be reduced, so that the life is extremely short under severe lubrication conditions. It is possible to prevent the surface starting point peeling at.

In the conical roller bearing 10, the nitrogen-enriched layers 11B, 12B, and 13B may be formed in at least one of the outer ring 11, the inner ring 13, and the roller 12 as a conical roller. Such a conical roller bearing 10 has an improved rolling fatigue life, a long life, and high durability. Further, since the tempering and softening resistance is improved by forming the nitrogen-enriched layers 11B, 12B, and 13B, the temperature of the contact portion between the large end surface 16 and the large flange surface 18 is raised by sliding contact. However, it can show high seizure resistance. The nitrogen-enriched layers 12B and 13B may be formed on both the large end surface 16 and the large flange surface 18. The nitrogen-enriched layer 12B may be formed in the circumferential surface region (convex portion 16A) on the large end surface 16.

In the conical roller bearing 10, the particle size of the old austenite crystals in the nitrogen-enriched layers 11B, 12B, and 13B may have a JIS standard particle size number of 10 or more. In this case, since the nitrogen-enriched layers 11B, 12B, and 13B having the old austenite crystal grain size sufficiently finely formed are formed, they have a high rolling fatigue life and also have a Charpy impact value, fracture toughness value, and crushing. It is possible to obtain a conical roller bearing 10 having improved strength and the like.

In the conical roller bearing 10, the width of the rolling surface of the conical roller 12 in the extending direction is L, and the rolling surface at the contact position between the inner ring raceway surface 13A and the rolling surface 12A in the extending direction. When the amount of deviation from the midpoint N of 12A to the side of the large end surface 16 is α, the ratio α / L of the width L and the amount of deviation α may be 0% or more and less than 20%. From a different point of view, it is preferable that the contact position is at the center position of the rolling surface 12A in the extending direction of the rolling axis or on the large end surface 16 side of the center position. In this case, the tangential force generation position (large end surface 16 and inner ring) that causes skew in the rollers is compared to the case where the contact position is on the small end surface side of the center position of the rolling surface in the extending direction of the rolling axis. Since the distance from the contact position with the large flange surface 18 of 13) to the contact position can be reduced, the skew angle of the rollers can be reduced and the increase in rotational torque can be suppressed.

In the conical roller bearing 10, a relief portion 25A may be formed in the inner ring 13 at a corner where the inner ring raceway surface 13A and the large flange surface 18 intersect. In this case, by locating the end portion of the rolling surface 12A of the conical roller 12 on the large end surface 16 side at the relief portion 25A, it is possible to prevent the end portion from coming into contact with the inner ring 13.

In the conical roller bearing 10, the inner ring raceway surface 13A and the outer ring raceway surface 11A may be linear or arcuate in a cross section passing through the central axis of the inner ring 13. Crowning may be formed on the rolling surface 12A of the conical roller 12. The sum of the dropping amounts of crowning is calculated by setting K1, K2, and _zm as design parameters in the yz coordinate system with the generatrix of the rolling surface of the conical roller 12 as the y _- axis and the generatrix orthogonal to the generatrix as the z _- axis. Is the load, L is the length of the effective contact portion of the rolling surface 12A of the conical roller 12 in the generatrix direction, E'is the equivalent elastic coefficient, and a is the effective contact from the origin taken on the generatrix of the rolling surface 12A of the conical roller 12. It may be expressed by the equation (1) when the length to the end of the portion is A = 2K ₁ Q / πLE'.

In this case, since the rolling surface 12A of the roller 12 is provided with crowning (so-called logarithmic crowning) in which the contour line is represented by a logarithmic function, the sum of the drop amounts is represented by the above equation (1). It is possible to suppress a local increase in surface pressure and suppress the occurrence of wear on the rolling surface 12A of the conical roller 12 as compared with the case where the crowning represented by the partial arc of is formed.

Further, 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 arcuate, and the rolling surface 12A of the conical roller 12 has, for example, a straight surface at the center. Since the so-called logarithmic crowning is provided in connection with the straight surface, the dimension of the contact region between the rolling surface 12A of the conical roller 12, the inner ring raceway surface 13A and the outer ring raceway surface 11A (for example, the major axis dimension of the contact ellipse). Can be lengthened, and as a result, skew can be suppressed. Further, 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.

Further, if the dimension of the contact region between the rolling surface 12A, the inner ring raceway surface 13A and the outer ring raceway surface 11A (for example, the major axis dimension of the contact ellipse) is lengthened as described above, the roller is used under conditions in which a moment load acts. When the conventional full crowning is formed, edge surface pressure may be generated at the end portion in the generatrix direction. However, in the conical roller bearing 10, since logarithmic crowning is applied to the conical roller 12, it is possible to suppress the generation of such edge surface pressure while ensuring the required dimensions of the contact region.

Here, the effect of the logarithmic crowning described above will be described in more detail. FIG. 19 is a diagram showing the contour line of a roller whose contour line is represented by a logarithmic function and the contact surface pressure on the rolling surface of the roller superimposed. FIG. 20 is a diagram showing the contour line of a roller having an auxiliary arc between the crowning of the partial arc and the straight portion and the contact surface pressure on the rolling surface of the roller superimposed. The vertical axis on the left side of FIGS. 19 and 20 shows the drop amount (unit: mm) of crowning. The horizontal axis of FIGS. 19 and 20 indicates the position (unit: mm) in the axial direction of the roller. The vertical axis on the right side of FIGS. 19 and 20 shows the contact surface pressure (unit: GPa).

When the contour line of the rolling surface of the conical roller is formed into a shape having a crowning of a partial arc and a straight portion, as shown in FIG. 20, the gradient at the boundary between the straight portion, the auxiliary arc, and the crowning is continuous. However, if the curvature is discontinuous, the contact surface pressure will increase locally. Therefore, there is a risk of oil film shortage and surface damage. If a lubricating film having a sufficient film thickness is not formed, wear due to metal contact is likely to occur. When the contact surface is partially worn, metal contact is more likely to occur in the vicinity thereof, so that the wear of the contact surface is promoted and the conical roller is inconvenienced to be damaged.

Therefore, when the rolling surface of the conical roller as the contact surface is provided with crowning whose contour line is represented by a logarithmic function, for example, as shown in FIG. 19, crowning represented by a partial arc of FIG. 20 is provided. The local surface pressure is lower than in the case, and the contact surface can be less likely to be worn. Therefore, even when the thickness of the lubricating film becomes thin due to the reduction of the amount of lubricant existing on the rolling surface of the conical roller or the decrease in viscosity, the contact surface is prevented from being worn and the conical roller is prevented from being damaged. Can be done. In FIGS. 19 and 20, the origin O of the horizontal axis is located at the center of the effective contact portion of the inner ring or the outer ring in the Cartesian coordinate system in which the direction of the bus of the roller is the horizontal axis and the direction perpendicular to the bus is the vertical axis. Is set to show the outline of the roller, and the contact surface pressure is also shown with the surface pressure as the vertical axis. As described above, by adopting the above-mentioned configuration, it is possible to realize a conical roller bearing 10 having a long life and high durability.

In the conical roller bearing 10, the ratio R _process / R of the actual radius of curvature R _process and the set radius of curvature R may be 0.8 or more.

In this case, the conical roller bearing 10 applied to the transmission of an automobile does not have a better lubrication environment than the case where it is applied to other mechanical devices (for example, a differential device), so the above ratio R _process / R is 0.8 or more. Therefore, the oil film thickness at the contact portion between the large end surface 16 of the conical roller 12 and the large bearing surface 18 of the inner ring 13 can be sufficiently increased.

In the conical roller bearing 10, the arithmetic average roughness of the large end surface 16 of the conical roller 12 may be 0.10 μmRa or less. In this case, it is possible to sufficiently secure the oil film thickness at the contact portion between the large end surface 16 of the conical roller 12 and the large flange surface 18 of the inner ring 13.

Here, the relationship between the skew angle of the conical roller 12 and the ratio R / R _BASE will be examined. The ratio R / R _BASE is conditioned on the condition that the large end surface 16 of the tapered rollers 12 is in a contact state on the set ideal spherical surface (excluding machining error). Table 5 shows the relationship between the ratio R / R _BASE and the skew angle of the conical roller 12.

As shown in Table 5, the smaller the R / R _BASE ratio of the rollers, the larger the skew angle. On the other hand, the radius of curvature R of the large end surface 16 of the conical roller 12 already described in FIG. 5 is the radius of curvature when the large end surface 16 is made of an ideal spherical surface, and the large end surface 16 is as shown in FIG. It is an ideal single arc curve that satisfies the condition of R152 = R364 = R1564. However, in reality, as shown in FIG. 7, the large end surface 16 of the conical roller 12 does not become a part of one spherical surface centered on the apex of the conical angle of the conical roller 12. As shown in FIG. 7, R152 on one side is not the same as R1564 of the entire large end surface 16, and is smaller than R1564.

As shown in FIG. 7, when both end faces of the large end surface 16 of the conical roller 12 are sagging, the large end surface 16 and the large flange surface 18 of the inner ring 13 come into contact with each other only on one side (convex portion 16A) of the large end surface 16. Therefore, the calculated R dimension of the large end surface 16 is R152 (actual radius of curvature R _process in FIG. 7), which is smaller than the ideal R dimension (set radius of curvature R) (ratio R _process / R is smaller). Become). As a result, the contact surface pressure between the large flange surface 18 and the large end surface 16 increases, and at the same time, the skew angle also increases. When the skew angle is increased, the contact ellipse generated at the contact portion between the conical roller 12 and the large flange surface 18 protrudes from the large flange surface 18, and the oil film is cut off, resulting in galling and seizure.

Here, in an environment where the lubrication state is not sufficient, the skew angle of the conical roller 12 increases, and further, when the contact surface pressure at the contact portion between the large flange surface 18 and the large end surface 16 also increases, the conical roller 12 and the large flange The oil film parameter Λ between the surfaces 18 decreases. When the oil film parameter Λ is less than 1, metal contact begins and the boundary lubrication is achieved. As a result, wear begins to occur at the contact portion between the large end surface 16 of the conical roller 12 and the large flange surface 18 of the inner ring, and if this state continues, the wear is further promoted and the concern about seizure increases.

Here, the oil film parameter Λ is defined by "the ratio of the root mean square roughness of the large end surface and the large flange surface of the inner ring where the oil film thickness h is obtained by the elastic fluid lubrication theory to the combined roughness σ". That is, the oil film parameter Λ = h / σ. Further, the arithmetic mean roughness Ra and the root mean square Rq generally have a relationship of Rq = 1.25Ra, and the root mean square roughness of the large end surface of the roller is Rq ₁ and the root mean square roughness of the large flange surface is Rq. If 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. Therefore, the surface roughness of the large end surface 16 of the conical roller 12 and the large flange surface 18 of the inner ring 13 is a roughness equivalent to that of super-finishing, and it is desirable that the value of σ is 0.09 μmRq or less.

The ratio of the actual radius of curvature R _process and the set radius of curvature R based on the results of the examination of the effect of the difference between the set radius of curvature R and the radius of curvature of the large end face of the conical roller (actual radius of curvature R _process ) due to the above-mentioned grinding process. We examined the relationship between the contact surface pressure between the large end surface and the large radius surface, the oil film thickness, the skew angle, and the oil film parameters. Furthermore, in order to verify the practical range of the ratio between the actual radius of curvature R _process and the set radius of curvature R, the peak of the lubricating oil operating temperature between the large flange surface of the inner ring and the large end surface of the conical roller, which is the sliding contact, is used. It has been found that the level of severity of lubrication at times has an effect.

Therefore, the index showing the level of severity of the lubrication state at the peak of the lubricating oil operating temperature between the large flange surface of the inner ring and the large end surface of the conical roller was examined as follows. (1) Note that the lubrication state between the large flange surface of the inner ring and the large end surface of the conical roller is determined by the radius of curvature (actual radius of curvature R _process ) of the large end surface of the large flange cone roller and the operating temperature of the lubricating oil. did. (2) In addition, we focused on the viscosity of the lubricating oil used in transmissions and differential applications, and examined it in consideration of practical use. (3) Then, as the maximum condition at the peak of the lubricating oil operating temperature, an extremely severe temperature condition that continues for 3 minutes (180 seconds) at 120 ° C. was assumed. This temperature condition is the maximum condition at the peak time, and has the meaning of returning to the steady state after about 3 minutes, and this temperature condition is referred to as "assumed peak temperature condition" in the present specification. It was found that a threshold value for setting the ratio between the actual radius of curvature R _process and the set radius of curvature R that does not cause a rapid temperature rise in the lubricated state in which the viscosity characteristic of the lubricating oil is added to this "assumed peak temperature condition" is obtained. rice field.

Based on the above findings, it was devised that an index indicating the level of severity of the lubrication state can be obtained by the following equation according to the lubrication state in which the viscosity of the lubricating oil is added to the "assumed peak temperature condition". This index is referred to as "brimmed lubrication coefficient" in the present specification.
"Brim lubrication coefficient" = 120 ° C. viscosity x (oil film thickness h) ^2/180 seconds Here, the oil film thickness h can be obtained from, for example, the following formula of Karna.

Here, it can be said that the "brimmed lubrication coefficient" set this time is an absolute evaluation index value that can determine the brim lubrication limit of the conical roller bearing. When used under conditions other than the above in automobile applications, or when used in other applications other than automobile applications, the maximum temperature, viscosity, or assumed peak temperature conditions of the lubricating oil may be changed as appropriate to create a "brimmed part". The "lubrication coefficient" can be calculated and compared with the threshold value described later to determine the severity of the lubrication state. Further, even if the large flange surface of the inner ring is a curved surface (middle concave side) instead of a substantially straight line as in the present invention, the geometric shape combination composed of the large end surface of the large flange surface which is the curved surface is used. If the "brimmed lubrication coefficient" is derived from the calculated oil film thickness, it can be discriminated by comparing it with the threshold value described later. That is, in the present specification, the "brimmed lubrication coefficient" is an index value for evaluating the severity of the lubrication state of the conical roller bearing, which is expressed as an absolute evaluation based on the oil film thickness usage condition. The present inventor has come up with a new idea of defining the ratio between the optimum radius of curvature of the large end face of tapered rollers and the actual radius of curvature after processing in order to improve the seizure resistance of tapered roller bearings. In optimizing the bearing, the "brear lubrication coefficient", which enables absolute evaluation in actual use, was introduced and evaluated as described above. Through this evaluation, it was possible to generalize and derive the above-mentioned ratio specifications that contribute to the improvement of seizure resistance of tapered roller bearings that are not limited in use.

Next, a conical roller bearing according to a modified example of the embodiment of the present invention will be described. Compared to general conical roller bearings, the conical roller bearing according to the modified example of this embodiment has a slightly less severe level of lubrication in which the viscosity characteristics of the lubricating oil are added to the "assumed peak temperature conditions". The difference is that it is used at the specified level and the practical range of the ratio of the actual radius of curvature R _process of the large end face of the conical roller to the set radius of curvature R is expanded. Since other configurations and technical contents are the same as those of the conical roller bearing according to the above-described embodiment, all the contents of the description of the conical roller bearing according to the above-described embodiment are applied mutatis mutandis, and only the differences are explained. do.

In the conical roller bearing according to the modified example of the present embodiment, the "brimmed lubrication coefficient" was calculated using SAE 75W-90, which is a gear oil often used for differentials, as a sample. The viscosity of 75W-90 at 120 ° C. is 10.3 cSt (= 10.3 mm ² / s), and the oil film thickness h obtained from the equation (2) is the ratio of the actual radius of curvature R _process and the set radius of curvature R, respectively. Table 6 shows the values.

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

A seizure resistance test was carried out using a rotation tester for the conical roller bearing according to the modified example of the embodiment of the present invention. The test conditions for the seizure resistance test are as follows.
<Test conditions>
-Load load: Radial load 4000N, Axial load 7000N
・ Rotation speed: 7000min ^-1
-Lubricant: SAE 75W-90
-Test bearing: Conical roller bearing (inner diameter φ35 mm, outer diameter φ74 mm, width 18 mm)
For each value of the ratio of the actual radius of curvature R _process and the set radius of curvature R, the contact surface pressure between the large end surface and the large flange surface, the oil film thickness, the skew angle, the oil film parameters, and the results of the "brimmed lubrication coefficient". Is shown in Table 7. Table 7 shows the contact surface pressure, oil film thickness, skew angle, and oil film parameter as ratios, but the reference denominator is when the actual radius of curvature R _process can be processed to the same dimensions as the set radius of curvature R. The value is set to 0, and 0 is added to each code.

Table 8 shows the details of the test results (1) to (6) and the comprehensive judgments (1) to (6) in Table 7.

From the results in Tables 7 and 8, in the "severe lubrication state" where 75W-90, which is a gear oil such as a differential, is used, the ratio R _process / R of the actual radius of curvature R _process and the set radius of curvature R is 0. We came to the conclusion that 5 or more is desirable. Therefore, in this embodiment, the ratio R _process / R of the actual radius of curvature R _process and the set radius of curvature R is set to 0.5 or more. In this way, by introducing the "brimmed lubrication coefficient" as an index showing the level of strictness of the lubrication state, it is possible to expand the practical range of the ratio between the actual radius of curvature R _process and the set radius of curvature R. can. This makes it possible to select appropriate bearing specifications according to the usage conditions.

When setting the ratio between the practical 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 design man-hours. In the "severe lubrication state" in Table 7, a sufficient "brimmed lubrication coefficient" was obtained even when the ratio R _process / R of the actual radius of curvature R _process and the set radius of curvature R was 0.4. When the ratio R _process / R of the actual radius of curvature R _process and the set radius of curvature R is 0.4 in a "severe lubrication state" in which a lubricating oil having a slightly lower viscosity than that in Table 7 is used, the threshold value is 8 ×. Since it is possible that ^10-9 or more may not be satisfied and the skew angle becomes large, 0.5 or more is appropriate as the ratio R _process / R of the actual radius of curvature R _process and the set radius of curvature R. be.

Further, for the conical roller bearing according to another modification of the embodiment of the present invention, the "brimmed 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 viscosity of VG32 at 120 ° C. was 7.7 cSt (= 7.7 mm ² / s), and the oil film thickness h was obtained from the formula (2). Table 9 shows the oil film thickness h for each value of the ratio of the actual radius of curvature R _process and the set radius of curvature R.

The viscosity of VG32 at 120 ° C. is low, and the lubrication state in which the viscosity of the lubricating oil is added to the "assumed peak temperature condition" is an extremely severe condition. This lubrication state is referred to as "extremely severe lubrication state" in the present specification.

At the same time, a seizure resistance test was conducted using a rotation tester. The test conditions for the seizure resistance test are as follows.
<Test conditions>
-Load load: Radial load 4000N, Axial load 7000N
・ Rotation speed: 7000min ^-1
-Lubricating oil: Turbine oil ISO VG32
-Test bearing: Conical roller bearing (inner diameter φ35 mm, outer diameter φ74 mm, width 18 mm)
For each value of the ratio of the actual radius of curvature R _process and the set radius of curvature R, the contact surface pressure between the large end surface and the large flange surface, the oil film thickness, the skew angle, the oil film parameters, and the results of the "brimmed lubrication coefficient". Is shown in Table 10. Table 10 shows the contact surface pressure, oil film thickness, skew angle, and oil film parameter as ratios, but the reference denominator is when the actual radius of curvature R _process can be processed to the same dimensions as the set radius of curvature R. The value is set to 0, and 0 is added to each code.

The details of the test results (1) to (6) and the comprehensive judgment (1) to (6) in Table 10 are shown in Table 11.

From the results of Tables 10 and 11, in the "extremely severe lubrication state" in which the low viscosity VG32 which is the transmission oil is used, the ratio R _process / R of the actual radius of curvature R _process and the set radius of curvature R is 0. We came to the conclusion that 8 or more is desirable. Therefore, in the conical roller bearing according to another modification of the present embodiment, the ratio R _process / R of the actual radius of curvature R _process and the set radius of curvature R is set to 0.8 or more.

From the results in Tables 10 and 11, the following was found. Comparing the calculated "brimmed lubrication coefficient" with the result of the seizure resistance test, the ratio R _process of the actual radius of curvature R _process and the set radius of curvature R so that the "brimmed lubrication coefficient" exceeds 8 × ^10-9 . It was confirmed that it was practical to set R. Thereby, "brimmed lubrication coefficient" = 8 × 10 ^-9 can be used as a threshold for setting the ratio R _process / R of the practical actual radius of curvature R _process and the set radius of curvature R.

<Manufacturing method of conical roller bearings>
FIG. 21 is a flowchart for explaining a method for manufacturing the conical roller bearing shown in FIG. FIG. 22 is a schematic diagram showing a heat treatment pattern in the heat treatment step of FIG. 21. FIG. 23 is a schematic diagram showing a modified example of the heat treatment pattern shown in FIG. 22. Hereinafter, a method for manufacturing the conical roller bearing 10 will be described.

As shown in FIG. 21, first, the parts preparation step (S100) is carried out. In this step (S100), members to be bearing parts such as an outer ring 11, an inner ring 13, a conical roller 12, and a cage 14 are prepared. Crowning has not yet been formed on the member to be the conical roller 12, and the surface of the member is the unprocessed surface 12E shown by the dotted line in FIG.

Next, the heat treatment step (S200) is carried out. In this step (S200), a predetermined heat treatment is performed in order to control the characteristics of the bearing component. For example, in order to form the nitrogen-enriched layers 11B, 12B, 13B according to the present embodiment in at least one of the outer ring 11, the conical roller 12, and the inner ring 13, a carburizing nitriding treatment or a nitriding treatment, a quenching treatment, and a quenching treatment are performed. Performs return processing, etc. FIG. 22 shows an example of the heat treatment pattern in this step (S200). FIG. 22 shows a heat treatment pattern showing a method of performing primary quenching and secondary quenching. FIG. 23 shows a heat treatment pattern showing a method of cooling the material below the A ₁ transformation point temperature during quenching and then reheating to finally quench. In these figures, in the treatment T ₁ , carbon and nitrogen are diffused in the steel substrate and the carbon is sufficiently dissolved, and then cooled to less than the A ₁ transformation point. Next, in the treatment T ₂ in the figure, the heat is reheated to a lower temperature than the treatment T ₁ and oil quenching is performed from there. Then, for example, a tempering process having a heating temperature of 180 ° C. is carried out.

According to the above heat treatment, the crack strength is improved and the aging dimensional change rate is reduced while carburizing and nitriding the surface layer portion of the bearing component, rather than normal quenching, that is, carburizing and nitriding the surface layer portion of the bearing component once as it is. Can be done. According to the heat treatment step (S200), in the nitrogen-enriched layers 11B, 12B, 13B which are the hardened structures, the particle size of the former austenite crystal grains is compared with the microstructure in the conventional hardened structure shown in FIG. Therefore, 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 crack strength, and can reduce the aging rate of change.

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

Next, the assembly step (S400) is carried out. In this step (S400), the conical roller bearing 10 shown in FIG. 1 is obtained by assembling the bearing parts prepared as described above. In this way, the conical roller bearing 10 shown in FIG. 1 can be manufactured.

<Examples of applications for conical roller bearings>
Next, an example of the use of the conical roller bearing according to the present embodiment will be described. The conical roller bearing according to the present embodiment is preferably incorporated in a power transmission device of an automobile such as a differential or a transmission. That is, the conical roller bearing according to the present embodiment is suitable for use as a conical roller bearing for automobiles. FIG. 24 shows a differential of an automobile using the above-mentioned conical roller bearing 10. This differential is connected to a propeller shaft (not shown), and the drive pinion 122 inserted into the differential case 121 is meshed 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 meshed with the side gear 126 connected to the drive shaft (not shown) inserted from the left and right into the differential gear case 123, and the driving force of the engine is transmitted from the propeller shaft to the left and right drive shafts. It has become like. In this differential, the drive pinion 122, which is a power transmission shaft, and the differential gear case 123 are supported by a pair of conical roller bearings 10a and 10b, respectively. The conical roller bearing 10 is not limited to the differential of an automobile, and may be used for a transmission.

By the way, in transmissions or differentials, which are power transmission devices for automobiles, there is a tendency to reduce the viscosity of lubricating oil (oil) or reduce the amount of oil in order to reduce fuel consumption, which is sufficient for conical roller bearings. It may be difficult to form an oil film. Therefore, the above-mentioned requirements can be satisfied by incorporating the above-mentioned conical roller bearing 10 having an improved life into the transmission or the differential.

Although the embodiment of the present invention has been described above, it is possible to modify the above-described embodiment in various ways. Further, the scope of the present invention is not limited to the above-described embodiment. The scope of the present invention is indicated by the scope of claims and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

10,10a, 120A, 120B bearing, 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 unprocessed surface, 13 Inner ring, 13A Inner ring raceway surface, 14 Cage, 16 Large end surface, 16A convex part, 16B concave part, 16C, 21 chamfering part, 17 small end surface, 18 large flange surface, 18A escape surface, 19 small collar surface, 22, 24 Crowning part, 22A crowning, 23 straight part (center part), 25A, 25B relief part, 26 center line, 27 contact part crowning part, 31 1st measurement point, 32 2nd measurement point, 33 3rd measurement point, 41 large Collar, 42 small brim, 100 manual transmission, 106 small ring, 107 large ring, 108 pillars, 109 pockets, 121 differential case.

Claims (5)

An outer ring having an outer ring raceway surface on the inner peripheral surface,
An inner ring having an inner ring raceway surface and a large collar plane arranged on a larger diameter side than the inner ring raceway surface on the outer peripheral surface, and an inner ring arranged inside the outer ring.
A plurality of conical rollers having a rolling surface in contact with the outer ring raceway surface and the inner ring raceway surface and a large end surface in contact with the large collar surface, and arranged between the outer ring raceway surface and the inner ring raceway surface. When,
It comprises a plurality of pockets arranged at predetermined intervals in the circumferential direction, and includes a cage for accommodating and holding each of the plurality of conical rollers in each of the plurality of pockets.
The roller coefficient γ exceeds 0.90,
The large end surface includes a chamfered portion arranged on the outermost periphery of the large end surface, a convex portion arranged in an annular shape on the inner peripheral side of the chamfered portion, and a concave portion arranged on the inner peripheral side of the convex portion. Including,
The large end surface has points C1 and C4 connecting the outer peripheral end of the convex portion and the chamfered portion in a cross section along the rolling axis of the conical roller, and the inner peripheral end and the concave portion of the convex portion. Further includes points C2 and C3 connecting the above points C2 and C3, an intermediate point P5 between the points C1 and the point C2 on the large end face, and an intermediate point P6 between the points C3 and the point C4 on the large end surface.
In the cross section, the radius of curvature of the large end face of the conical roller, which is the radius of curvature of a single arc passing through the point C1, the intermediate point P5, the intermediate point P6, and the point C4, is R, of the conical roller. When the distance from the apex of the conical angle to the large flange surface of the inner ring is R _BASE ,
The value of the ratio R / R _BASE of the set radius of curvature R and the distance R _BASE is set to 0.75 or more and 0.87 or less.
When the actual radius of curvature of the conical roller after grinding of the large end surface is R _process , the actual radius of curvature R _process is shorter than the set radius of curvature R, and the actual radius of curvature R _process and the set radius of curvature R A conical roller bearing having a ratio R _process / R of 0.5 or more. The first aspect of claim 1, wherein the 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 flange surface on the large end surface of the conical roller is 0.02 μm or less. Conical roller bearing. The conical roller bearing according to claim 1 or 2, wherein the window angle of the pocket is 46 ° or more and 80 ° or less. In the cross section passing through the central axis of the inner ring, the inner ring raceway surface and the outer ring raceway surface are linear or arcuate.
Crowning is formed on the rolling surface of the conical roller.
The sum of the drop amounts of the crowning has K ₁ , K ₂ , and z _m as design parameters in the y-z coordinate system in which the generatrix of the rolling surface of the conical roller is the y-axis and the generatrix orthogonal direction is the z-axis. , Q is the load, L is the length of the effective contact portion of the rolling surface of the conical roller in the generatrix direction, E'is the equivalent elastic coefficient, and a is from the origin taken on the generatrix of the rolling surface of the conical roller. The conical roller bearing according to any one of claims 1 to 3, represented by the formula (1), when the length to the end of the effective contact portion is A = 2K ₁ Q / πLE'. ..

The conical roller bearing according to any one of claims 1 to 4, wherein the arithmetic average roughness Ra of the large end surface of the conical roller is 0.10 μmRa or less.

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