JP6965005B2 - Conical roller bearing - Google Patents

Description

The present invention relates to conical roller bearings, and more particularly to conical roller bearings for automobiles.

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

Japanese Patent Application Laid-Open No. 2009-197904 states that even for rolling machine elements with weak lubrication, surface damage to the contact surface can be easily and effectively performed without using special materials or performing special heat treatment or surface treatment. The rolling machine elements that can be prevented are disclosed.

Japanese Patent Application Laid-Open No. 2010-255730 describes that the surface pressure and the stress of the contact portion are reduced to prolong the life of the bearing, and the processing defect of the raceway surface is eliminated before the drop amount of both ends of the roller is reduced. A conical roller bearing that can improve the processing efficiency is disclosed.

For conical roller bearings incorporated in automobile transmissions and differentials, the space provided for multi-stage transmissions and expansion of driving space tends to be reduced. Along with this, the load per unit area applied to the bearing is increasing.

Further, in automobile transmissions and differentials, housings containing aluminum as a constituent material tend to be adopted. In this case, the rigidity of the case decreases and the inclination of the spindle increases. Therefore, the conical roller bearing that rotatably supports the spindle with respect to the housing is placed in an environment in which bearing mounting errors (misalignment) are likely to occur, that is, in a so-called high misalignment environment. Therefore, such conical roller bearings are required to have high durability even in a highly misaligned environment.

Japanese Unexamined Patent Publication No. 2003-226918 JP-A-2009-197904 JP-A-2010-255730

A main object of the present invention is a conical roller having high durability even in a high misalignment environment, long life against rolling fatigue, and seizure resistance against skew generated by a high misalignment environment. To provide bearings.

The conical roller bearing according to the present invention has an outer ring having an outer ring raceway surface on the inner peripheral surface, and a large flange surface arranged on the outer peripheral surface on the inner ring raceway surface and a larger diameter side than the inner ring raceway surface. The inner ring is arranged inside, and is arranged between the outer ring raceway surface and the inner ring raceway surface, and has a rolling surface that contacts the outer ring raceway surface and the inner ring raceway surface and a large end surface that contacts the large flange surface, and has an outer ring. It is provided with a plurality of conical rollers arranged between the raceway surface and the inner ring raceway surface.

At least one of the outer ring, the inner ring and the plurality of conical rollers includes a nitrogen-enriched layer formed on the surface layer of the outer ring raceway surface, the inner ring raceway surface or the rolling surface. The distance from the outermost surface of the surface layer to the bottom of the nitrogen-enriched layer is 0.2 mm or more. At least a portion of the large end face of the conical roller is the ground face. When a reference 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 value of R / R _BASE least 0.75 0.87 Is. 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 reference radius of curvature R is 0.8 or more.

Crowning is formed on the rolling surface of the conical roller. The sum of the drop amount of the crowning is a generatrix of the rolling surface of the tapered rollers and y-axis, the generatrix orthogonal direction in y-z coordinate system with the z-axis, K _{1, K 2,} z _m design parameters, the Q Load, L is the length of the effective contact part of the rolling surface of the conical roller in the generatrix direction, E'is the equivalent elastic coefficient, and a is from the origin on the generatrix of the rolling surface of the conical roller to the end of the effective contact part. When the length of A = 2K ₁ Q / πLE', it is expressed by the equation (1).

According to the present invention, a conical roller bearing has high durability even in a high misalignment environment, has a long life against rolling fatigue, and has seizure resistance against skew generated in a high misalignment environment. Can be provided.

It is a vertical sectional view which shows the conical roller bearing which concerns on Embodiment 1. FIG. FIG. 5 is a partial cross-sectional view for explaining a nitrogen-enriched layer in the conical roller bearing according to the first 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 1. FIG. It is a figure for demonstrating the shape of the logarithmic crowning of the roller of the conical roller bearing which concerns on Embodiment 1. FIG. It is a yz coordinate diagram which shows an example of a crowning shape. It is sectional drawing which shows the design specification of the conical roller bearing which concerns on Embodiment 1. FIG. It is sectional drawing for demonstrating the reference radius of curvature of a roller in the conical roller bearing which concerns on Embodiment 1. FIG. FIG. 7 is a partial cross-sectional view showing a region surrounded by a dotted line in FIG. 7. It is sectional drawing for demonstrating the actual radius of curvature of a roller in the conical roller bearing which concerns on Embodiment 1. FIG. It is a figure which shows the time when the crowning which the contour line is represented by a logarithmic function is provided. It is the figure which superposed the contour line of the roller which provided the crowning and the straight part of a partial arc, and the contact surface pressure on the rolling surface of a roller. FIG. 5 is a graph showing the relationship between the radius of curvature of the large end surface of the roller of the conical roller bearing according to the first 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 1 and the maximum Hertz stress. It is a flowchart of the manufacturing method of the conical roller bearing which concerns on Embodiment 1. FIG. It is a figure for demonstrating the heat treatment method in Embodiment 1. FIG. It is a figure for demonstrating the modification of the heat treatment method in Embodiment 1. FIG. It is a figure which shows the austenite grain boundary of the bearing component which concerns on Embodiment 1. FIG. It is a figure which shows the 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 a raceway surface and a rolling surface in the conical roller bearing which concerns on Embodiment 1. FIG. FIG. 5 is a cross-sectional view showing another example of a method of changing the contact position between the raceway surface and the rolling surface in the conical roller bearing according to the first embodiment. It is a partial cross-sectional view of the conical roller bearing which concerns on Embodiment 2. FIG. It is a figure which shows the crowning shape of the roller of the conical roller bearing shown in FIG. It is a figure which shows the relationship between the generatrix direction coordinate of the roller of the conical roller bearing shown in FIG. 21 and the drop amount. It is a figure which shows the relationship between the maximum value of the equivalent stress of Mises, and the logarithmic crowning parameter. It is a figure which shows the modification of the conical roller bearing which concerns on Embodiment 2. It is a figure which shows the other modification of the conical roller bearing which concerns on Embodiment 2. FIG. It is a vertical sectional view which shows the differential which includes the conical roller bearing which concerns on Embodiment 1. FIG. It is a vertical sectional view which shows the transmission which comprises the conical roller bearing which concerns on Embodiment 1. FIG.

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

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

The conical roller bearing 10 shown in FIG. 1 mainly includes an outer ring 11, an inner ring 13, a plurality of rollers 12, and a cage 14. The outer ring 11 has a ring shape and has an outer ring raceway surface 11A on the inner peripheral surface. The inner ring 13 has a ring shape and has an inner ring raceway surface 13A on the outer peripheral surface. 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.

The rollers 12 are arranged on the inner peripheral surface of the outer ring 11. The 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 rollers 12 are arranged at a predetermined pitch in the circumferential direction by a cage 14 made of synthetic resin. As a result, the roller 12 is rotatably held on the annular orbit 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 roller 12 rolls are on the center line of the bearing. It is configured to intersect at one point. With such a configuration, the outer ring 11 and the inner ring 13 of the conical roller bearing 10 can rotate relative to each other.

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

In the above configuration, if carbon exceeds 1.2% by mass, the material hardness is high even if spheroidizing annealing is performed, so that cold workability is hindered, and a sufficient amount of cold work is required for cold work. , Processing accuracy cannot be obtained. In addition, the carburized nitriding treatment tends to cause an over-carburized structure, and there is a risk that the crack strength is lowered. On the other hand, when the carbon content is less than 0.6% by mass, it takes a long time to secure the required surface hardness and the amount of retained austenite, or the internal hardness required for quenching after reheating is obtained. It becomes difficult to get rid of.

The reason why the Si content is 0.15 to 1.1% by mass is that Si can increase tempering resistance and softening resistance to ensure heat resistance and improve rolling fatigue life characteristics under lubrication mixed with foreign matter. Is. If the Si content is less than 0.15% by mass, the rolling fatigue life characteristics under lubrication mixed with foreign matter are not improved, while if the Si content exceeds 1.1% by mass, the hardness after normalizing becomes too high. Inhibits cold workability.

Mn is effective in ensuring the quench hardening ability of the carburized nitride layer and the core portion. If the Mn content is less than 0.3% by mass, sufficient quenching and curing ability cannot be obtained, and sufficient strength cannot be secured in the core portion. On the other hand, when the Mn content exceeds 1.5% by mass, the curing ability becomes excessive, the hardness after normalizing becomes high, and the cold workability is impaired. In addition, it stabilizes austenite too much and excessively increases the amount of retained austenite in the core portion, which promotes dimensional change over time. Further, when the steel contains 2.0% by mass or less of chromium, carbides and nitrides of chromium are precipitated in the surface layer portion, and the hardness of the surface layer portion can be easily improved. The reason why the Cr content is 2.0% by mass or less is that the cold workability is remarkably lowered when it exceeds 2.0% by mass, and the hardness of the surface layer portion is determined even if it is contained in excess of 2.0% by mass. This is because the effect of improvement is small.

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

From a different point of view, the outer ring 11 and the inner ring 13 are preferably made of a steel material which is an example of a bearing material, for example, JIS standard SUJ2. The roller 12 may be made of a steel material which is an example of a bearing material, for example, JIS standard SUJ2. Further, the roller 12 may be made of another material, for example, a Sialon sintered body.

As shown in FIG. 2, 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 collar surface and the large collar surface. 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. Further, a nitrogen-enriched layer 12B is formed on the surface of the roller 12 including the rolling surface 12A. The nitrogen-enriched layer 12B of the roller 12 is a region where the nitrogen concentration is higher than that of the unnitrided 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 rollers 12, the nitrogen-enriched layer 11B may be formed only on the outer ring 11, or the nitrogen-enriched layer 13B may be formed only on the inner ring 13. good. Alternatively, a nitrogen-enriched layer may be formed on two of the outer ring 11, the inner ring 13, and the roller 12.

As shown in FIG. 3, the rolling surfaces 12A (see FIG. 2) of the rollers 12 are located at both ends and are centrally connected between the crowning portions 22 and 24 on which the crowning is formed and the crowning portions 22 and 24. Including part 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 roller 12, is linear. A chamfered portion 21 is formed between the end surface 17 of the roller 12 and the crowning portion 22. A chamfered portion 25 is also formed between the end surface 16 and the crowning portion 24.

Here, in the method for producing the roller 12, when the treatment for forming the nitrogen-enriched layer 12B (carburizing nitriding treatment) is performed, the roller 12 is not crowned, and the outer shape of the roller 12 is the dotted line in FIG. The surface is 12E before processing, which is indicated by. After the nitrogen-enriched layer is formed in this state, the side surface of the roller 12 is processed as shown by the arrow in FIG. 4 as a finishing process, and the crowning portion 22 is formed with crowning as shown in FIGS. 24 is obtained.

Thickness of nitrogen-enriched layer:
The depth of the nitrogen-enriched layer 12B in the roller 12, that is, the distance from the outermost surface of the nitrogen-enriched layer 12B to the bottom of the nitrogen-enriched layer 12B is 0.2 mm or more. Specifically, the first measurement point 31 which is the boundary point between the chamfered portion 21 and the crowning portion 22, the second measuring point 32 where the distance W is 1.5 mm from the end surface 12D, and the center of the rolling surface of the roller. At the measurement point 33, the depths T1, T2, and T3 of the nitrogen-enriched layer 12B at each position are 0.2 mm or more. Here, the depth of the nitrogen-enriched layer 12B means the thickness of the nitrogen-enriched layer 12B in the radial direction orthogonal to the center line 26 of the rollers 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 25, 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. 4, the depth T2 of the nitrogen-enriched layer 12B is another depth due to the formation of the crowning 22A after the nitrogen-enriched layer 12B is formed as described above. Although it is smaller than T1 and T3, the magnitude relationship between the values of the depths T1, T2 and T3 of the nitrogen-enriched layer 12B can be appropriately changed by changing the process conditions described above.

Further, regarding the nitrogen-enriched layers 11B and 13B in the outer ring 11 and the inner ring 13, the thickness of the nitrogen-enriched layers 11B and 13B, which is the distance from the outermost surface to the bottom of the nitrogen-enriched layers 11B and 13B, is 0.2 mm. That is all. Here, the thicknesses of the nitrogen-enriched layers 11B and 13B mean the distances to the nitrogen-enriched layers 11B and 13B in the direction perpendicular to the outermost surfaces of the nitrogen-enriched layers 11B and 13B.

Crowning shape:
The shape of the crowning formed on the crowning portions 22 and 24 of the roller 12 is defined as follows. _{That is, the sum of the crowning drop amounts 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 12A of the roller 12 is the y-axis and the direction orthogonal to the generatrix is the z-axis. , Q is the load, L is the length of the effective contact portion of the rolling surface 12A on the 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 roller 12. When the length to the end of is A = 2K ₁ Q / πLE', it is expressed by the following equation (1).

FIG. 5 is an yz coordinate diagram showing an example of the crowning shape. In FIG. 5, the generatrix of the roller 12 is set as the y-axis, the origin O is set at the center of the effective contact portion of the inner ring 13 or the outer ring 11 and 12 on the generatrix of the roller 12, and the origin O is set in the direction orthogonal to the generatrix (radial direction). An example of crowning represented by the above equation (1) is shown in the yz coordinate system taking the z-axis. In FIG. 5, the vertical axis is the z-axis and the horizontal axis is the y-axis. The effective contact portion is a contact portion with the inner ring 13 or the outer ring 11 and 12 when no crowning is formed on the rollers 12. Further, since each crowning of the plurality of rollers 12 constituting the conical roller bearing 10 is usually formed line-symmetrically with respect to the z-axis passing through the central portion of the effective contact portion, only one crowning 22A is shown in FIG. ing.

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

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

The design parameter K ₁ means the magnification of the load Q, and geometrically, the degree of curvature of the crowning 22A. The design parameter K ₂ means the ratio of the generatrix length ym of the crowning 22A to the generatrix length a from the origin O to the end of the effective contact portion (K ₂ = ym / a). Design parameters z _m is meant the maximum drop amount of drop amount, i.e. crowning 22A at the end of the effective contact portion.

Here, the crowning at the time shown in FIG. 10 described later is a full climbing with a design parameter K ₂ = 1 and no straight portion, and a sufficient drop amount is secured so that edge load does not occur. However, if the drop amount is excessive, the removal allowance generated from the material from which the material has been removed during processing becomes large, which leads to an increase in cost. Therefore, the design parameters K ₁ , K ₂ , and z _m are optimized as follows.

Various methods can be adopted as the optimization method for the design parameters K ₁ , K ₂ , z _m , and for example, a direct search method such as the Rosenblock method can be adopted. Here, since the damage of the surface starting point on the rolling surface of the roller depends on the surface pressure, by setting the objective function of the optimization as the surface pressure, it is possible to obtain crowning that prevents the oil film on the contact surface from running out under dilute lubrication. Can be done.

When the actual radius of curvature after processing the large end face of the conical roller is Rprocess, the ratio Rprocess / R of the actual radius of curvature Rprocess (see FIG. 9) and the reference radius of curvature R (see FIG. 8) is 0.8 or more. Is.

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. From a different point of view, a convex portion due to the punch of the pressing device is formed on the outer peripheral portion of the surface to be the large end surface of the molded body obtained by the pressing process. The planar shape of the convex portion is, for example, an annular shape. At least a part of the convex portion of the molded product is removed by a subsequent grinding process.

7 and 8 are schematic cross-sectional views along the rolling axis of the conical roller obtained when grinding is ideally performed. When the grinding process is ideally performed, the large end face of the obtained conical roller becomes a part of a spherical surface centered on the apex O (see FIG. 6) of the conical angle of the conical roller 12. As shown in FIGS. 7 and 8, when the grinding process is ideally performed so as to leave a part of the convex portion 16A, the large end surface of the conical roller consisting of the end face of the convex portion 16A is a conical roller. It becomes a part of one sphere centered on the apex of the cone angle of. In this case, the inner peripheral end of the convex portion 16A in the radial direction about the rolling axis of the conical roller is connected to the concave portion 16B via points C2 and C3. The outer peripheral end of the convex portion is connected to the chamfered portion via points C1 and C4. In an ideal large end 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. From a different point of view, a convex portion due to the punch of the pressing device is formed on the outer peripheral portion of the surface to be the large end surface of the molded body obtained by the pressing process. The planar shape of the convex portion is, for example, an annular shape. At least a part of the convex portion of the molded product is removed by a subsequent grinding process.

Here, the radius of curvature R of the large end surface 16 of the roller 12 is the R dimension when the large end surface 16 of the roller 12 shown in FIG. 7 is an ideal spherical surface. Specifically, as shown in FIG. 8, when the intermediate points P5, C3, and C4 of the points C1, C2, C3, C4, C1, and C2 at the end of the large end surface 16 of the roller 12 are set. Ideally, the radius of curvature R152 passing through points C1, P5, C2, the radius of curvature R364 passing through points C3, P6, C4 and the radius of curvature C1564 passing through points C1, P5, P6, C4 are R152 = R364 = R1564. It is a single arc curve. Points C1 and C4 are connection points between the convex portion 16A and the chamfered portion 16C, and points C2 and C3 are connection points between the convex portion 16A and the concave portion 16B. Here, the ideal single arc curve where R = R152 = R364 = R1564 holds is called a reference radius of curvature. The reference radius of curvature R is different from the actual radius of curvature R process measured as the radius of curvature of the large end face of the conical roller obtained by actual grinding as described later.

FIG. 9 is a schematic cross-sectional view taken along the rolling axis of the conical roller obtained by actual grinding. In FIG. 9, the ideal large end face shown in FIG. 8 is shown by a dotted line. As shown in FIG. 9, the large end surface of the conical roller actually obtained by grinding the molded body in which the concave portion and the convex portion as described above are formed is centered on the apex of the conical angle of the conical roller. It does not become part of one spherical surface. The points C1 to C4 of the convex portion of the actually obtained conical roller have a shape in which the points C1 to C4 are slanted as compared with the convex portion shown in FIG. That is, the points C1 and C4 shown in FIG. 9 are arranged on the outer peripheral side in the radial direction with respect to the center of the rolling axis as compared with the points C1 and C4 shown in FIG. It is arranged inward in the direction (R152 on one side with respect to R1564 of the entire large end surface 16 is not the same and can be made smaller). The points C2 and C3 shown in FIG. 9 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 with respect to R1564 of the entire large end surface 16 is not the same and can be made smaller). The intermediate points P5 and P6 shown in FIG. 9 are formed at positions substantially equal to, for example, the intermediate points P5 and P6 shown in FIG.

As shown in FIG. 9, 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 roller 12 after processing shown in FIG. 9 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 Rprocess. The actual radius of curvature R process is equal to or less than the reference radius of curvature R.

The conical roller 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 reference radius of curvature R of 0.8 or more.

As shown in FIG. 20, the radius of curvature Rvirtual 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 face actually formed by the grinding process (hereinafter, the virtual radius of curvature). ) Is equal to or less than the reference radius of curvature R. That is, in the conical roller of the conical roller bearing according to the present embodiment, the ratio Rprocess / Rvirtual of the actual radius of curvature Rprocess to the virtual radius of curvature Rvirtual is 0.8 or more.

The actual radius of curvature R process and the virtual radius of curvature R virtual can be measured by any method with respect to the conical rollers actually formed by grinding, and for example, a surface roughness measuring instrument (for example, a surface roughness measuring instrument manufactured by Mitutoyo) can be measured. It can be measured using the surf test SV-100). When a surface roughness measuring instrument is used, first, the measuring axis is set along the radial direction centered on the rolling axis, and the surface shape of the large end surface is measured. The vertices C1 to C4 and midpoints 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 Rvirtual is calculated as the radius of curvature of the arc passing through the plotted vertices C1, intermediate points P5 and P6, and vertices C4.

On the other hand, the reference 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.

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

Preferably, as shown in FIGS. 19 and 20, the rolling surface 11A of the outer ring 11 and the rolling surface 13A of the inner ring 13 roll with respect to the width L of the rolling surface of the roller in the extending direction of the rolling shaft. The ratio α / L of the amount of deviation α from the midpoint of the rolling surface in the extending direction of the contact position with the surface 12A is 0% or more and less than 20%. Further, the contact position when the ratio α / L exceeds 0% is at the center position of the rolling surface in the extending direction of the rolling axis or on the large end surface side of the center position.

As shown in FIG. 19, the configuration in which the ratio α / L exceeds 0% is that of the crowning formed on the rolling surface of the roller and the crowning formed on the raceway surfaces 11A and 13A of the inner ring and the outer ring 11. This can be achieved by shifting the positions of the vertices relatively.

Further, as shown in FIG. 20, the configuration in which the ratio α / L exceeds 0% is such that the angle formed by the raceway surface 13A of the inner ring with respect to the axial direction of the inner ring and the raceway surface 11A of the outer ring 11 are the outer ring 11. This can be achieved by changing the angle formed relative to the axial direction. Specifically, as compared with the case where the deviation amount α of the above-mentioned contact position shown by the dotted line in FIG. 20 is zero, the angle formed by the raceway surface 13A of the inner ring with respect to the axial direction of the inner ring is increased, 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 of 11 with respect to the axial direction of the outer ring 11.

Ratio of the reference 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 :
The small collar surface of the inner ring 13 is finished as a ground surface parallel to the small end surface 17 of the conical rollers 12 arranged on the raceway surface 13A.

As shown in FIG. 6, 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 one point O on the center line of the conical roller bearing 10, and the conical roller 12 is large. The ratio R / R _{BASE of the radius of curvature R of the end face 16 to the distance R BASE} from the point O to the large cone surface 18 of the inner ring 13 is manufactured so as to be in the range of 0.75 or more and 0.87 or less. .. Further, the large flange surface 18 is ground to have a surface roughness Ra of, for example, 0.12 μm or less.

Crystalline structure of nitrogen-enriched layer:
FIG. 17 is a schematic view illustrating the microstructure of the bearing component constituting the conical roller bearing according to the present embodiment, particularly the grain boundaries of the former austenite. FIG. 17 shows the microstructure in the nitrogen-enriched layer 12B. The particle size of the old austenite crystal in the nitrogen-enriched layer 12B in the present embodiment has a particle size number of JIS standard of 10 or more, which is sufficiently finer than that of a conventional general hardened product.

<Measurement method of various characteristics>
Nitrogen concentration measurement method:
For bearing parts such as the outer ring 11, roller 12, and 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 lined in the depth direction by EPMA (Electron Probe Micro Analysis), respectively. Perform 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, with respect to the roller 12, the cut surface is exposed by cutting the 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. The nitrogen concentration is analyzed by the EPMA at a plurality of measurement positions located 0.05 mm inward from the surface of the roller 12 on the cut surface. For example, the measurement positions are determined at five locations, and the average value of the measurement data at the five locations is defined as the nitrogen concentration of the roller 12.

Further, with respect to the outer ring 11 and the inner ring 13, after exposing the central axis and the cross section along the radial direction orthogonal to the central axis with the central portion in the central axis direction of the bearing as the measurement position on the raceway surfaces 11A and 13A, The nitrogen concentration of the cross section is measured by the same method as described 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 of the cross section to be measured in the above nitrogen concentration measuring method is measured in the depth direction from the surface. A Vickers hardness measuring machine can be used as the measuring device. In the conical roller bearing 10 after tempering treatment at 500 ° C. × 1 h, hardness measurement is performed at a plurality of measurement points arranged in the depth direction, for example, measurement points arranged at intervals of 0.5 mm. Then, a region having a Vickers hardness of HV450 or higher is designated as a nitrogen-enriched layer.

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

Particle size number measurement method:
As the method for measuring the crystal grain size of the former austenite, the method specified in JIS standard G0551: 2013 is used. The cross section to be measured shall be the cross section measured by the method for measuring the distance to the bottom of the nitrogen-enriched layer.

How to measure crowning shape:
The crowning shape of the roller 12 can be measured by any method. For example, the crowning shape may be measured by measuring the shape of the roller 12 with a three-dimensional shape measuring device.

<Effects of conical roller bearings>
Although there are some overlaps below, the characteristic configurations of the above-mentioned conical roller bearings are listed.

The conical roller bearing 10 according to the present disclosure includes an outer ring 11, an inner ring 13, and a plurality of conical rollers 12. The outer ring 11 has an outer ring raceway surface 11A on the inner peripheral surface. The inner ring 13 has an inner ring raceway surface 13A on the outer peripheral surface, and is arranged inside the outer ring 11. The plurality of rollers 12 are arranged between the outer ring raceway surface 11A and the inner ring raceway surface 13A, and have a rolling surface 12A that comes into contact with the outer ring raceway surface 11A and the inner ring raceway surface 13A. At least one of the outer ring 11, the inner ring 13, and the plurality of rollers 12 is a nitrogen-enriched layer 11B, 13B, 12B formed on the surface layer of the outer ring raceway surface 11A, the inner ring raceway surface 13A, or the rolling surface 12A. including. The distance T1 from the outermost surface of the surface layer to the bottom of the nitrogen-enriched layers 11B, 12B, 13B is 0.2 mm or more. A crowning 22A is formed on the rolling surface 12B of the roller 12. _{The sum of the drop amounts of the crowning 22A 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 12B of the roller 12 is the y-axis and the direction orthogonal to the generatrix is the z-axis. Q is the load, L is the length of the effective contact portion of the rolling surface 12A on the 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 roller 12. When the length to the end is A = 2K ₁ Q / πLE', it is expressed by the following equation (1).

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

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

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

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

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

In order to suppress metal contact between the large end surface of the roller and the large flange surface of the inner ring and reduce heat generation, it is necessary to secure a sufficient oil film thickness between both sides.

As described above, the ratio of the reference radius of curvature R of the large end face of the conical roller _{to the distance R BASE} from the apex of the conical angle of the conical roller to the large brim surface of the inner ring _{The value of R / R BASE} is 0.75 or more. Since it is 87 or less, the oil film thickness t can be increased and the maximum hertz stress p can be reduced based on FIGS. 12 and 13, and the torque cross and heat generation due to the sliding friction between the large end surface and the large flange surface can be reduced. can do.

Further, since the conical roller bearing according to the first embodiment has a ratio Rprocess / R of 0.8 or more, it has a large end face and a large flange surface as compared with a conical roller bearing having a ratio Rprocess / R of less than 0.8. The contact surface pressure with and can be reduced, and an increase in the skew angle can be suppressed. As a result, it is possible to suppress an increase in the contact surface pressure between the large end surface and the large flange surface, and it is possible to secure a sufficient oil film thickness between both surfaces. This has been confirmed from the calculation results of Experimental Example 4 described later.

Preferably, in the conical roller bearing according to the first embodiment, the surface roughness Ra of the large end surface is 0.10 μm or less, and the surface roughness Ra of the large collar surface is 0.063 μm or less. By doing so, it is possible to secure a sufficient oil film thickness between the large end surface of the roller and the large flange surface of the inner ring. Specifically, when the surface roughness Ra of the large end surface and the surface roughness Ra of the large collar surface Ra are within the above numerical range, and when each surface roughness is outside the above numerical range. The oil film parameter Λ (= h / σ) defined by "the ratio of the oil film thickness h obtained by the elastic fluid lubrication theory to the combined roughness σ of the root mean square roughness of the large end surface and the large flange surface". Can be enhanced. Therefore, a sufficient oil film thickness can be secured between the large end surface and the large flange surface.

Preferably, in the conical roller bearing according to the first embodiment, the contact positions of the raceway surfaces 11A and 13A of the inner ring and the outer ring 11 with respect to the width L of the rolling surface of the roller in the extending direction of the rolling shaft are located. The ratio α / L of the amount of deviation α from the midpoint of the rolling surface in the extending direction is 0% or more and less than 20%, and the contact position is the rolling surface in the extending direction of the rolling shaft. It is located at the center position of the bearing or on the large end face side of the center position. The present inventors, when the ratio α / L is 0% or more and less than 20% and the ratio α / L is more than 0%, the contact position is rolling in the extending direction of the rolling shaft. By being at the center position of the surface or on the large end surface side of the center position, the contact position when the ratio α / L exceeds 0% is the center position of the rolling surface in the extending direction of the rolling 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 position is closer to the small end surface than the central position (see Experimental Example 4 described later).

Further, 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 so that the sum of the drop amounts is represented by the above equation (1), it is conventional. It is possible to suppress a local increase in surface pressure and suppress the occurrence of wear on the rolling surface of the roller as compared with the case where the crowning represented by the partial arc is formed.

Here, the effect of the logarithmic crowning described above will be described in more detail. FIG. 10 is a diagram showing the contour line of the roller provided with crowning whose contour line is represented by a logarithmic function and the contact surface pressure on the rolling surface of the roller in an overlapping manner. FIG. 11 is a diagram showing the contour line of the roller provided with the crowning and the straight portion of the partial arc and the contact surface pressure on the rolling surface of the roller superimposed. The vertical axis on the left side of FIGS. 10 and 8 indicates the amount of crowning drop (unit: mm). The horizontal axes of FIGS. 10 and 8 indicate the axial positions (unit: mm) of the rollers. The vertical axis on the right side of FIGS. 10 and 8 indicates 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, the contact surface pressure increases at the boundary between the crowning portion and the straight portion, as shown in FIG. Therefore, 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 contact surface is worn more and the conical roller is 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. 10, the crowning represented by the partial arc of FIG. 11 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, wear of the contact surface is prevented and damage to the conical roller is prevented. Can be done. In addition, in FIGS. 10 and 11, 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 generatrix of the roller is the horizontal axis and the direction perpendicular to the generatrix 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-described configuration, the conical roller bearing 10 exhibiting a long life and high durability can be realized.

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

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

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

The design parameters K ₁ , K ₂ , z _m are determined by optimizing any one of the contact surface pressure, stress, and life as an objective function, and the damage at the surface origin depends on the contact surface pressure. Here, according to the above embodiment, since the design parameters K ₁ , K ₂ , and z _m are set by optimizing the contact surface pressure as an objective function, wear of the contact surface is prevented even under conditions where the lubricant is lean. You can get the crowning you can.

In the conical roller bearing 10, at least one of the outer ring 11 and the inner ring 13 includes nitrogen-enriched layers 11B and 13B. In this case, the nitrogen-enriched layers 11B and 13B having a fine crystal structure are formed in at least one of the outer ring 11 and the inner ring 13 to obtain the outer ring 11 or the inner ring 13 having a long life and high durability. be able to.

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

The particle size of the former austenite in the nitrogen-enriched layers 11B, 12B, and 13B has a particle size number of JIS standard of 10 or more.

In this way, nitrogen-enriched layers 11B, 12B, and 13B having a sufficiently fine-grained old austenite crystal grain size are formed in at least one of the outer ring 11, the inner ring 13, and the roller 12 as a conical roller. Therefore, the Charpy impact value, fracture toughness value, crush strength and the like can be improved while having a high rolling fatigue life.

The small collar surface of the inner ring was formed as a surface parallel to the small end surface of the conical roller for the following reasons. By making the small flange surface 19 of the inner ring 13 parallel to the small end surface 17 of the conical rollers 12 arranged on the raceway surface 13A, the large end surface 16 of the conical rollers 12 and the large inner ring 13 in the above-mentioned initial assembly state are large. The chamfer size and shape of the small end surface 17 of the conical roller 12 with respect to the first gap of the collar surface 18 (equal to the gap between the small end surface 17 when the conical roller 12 settles in the normal position and the small flange surface 19 of the inner ring 13). The effect of variation can be eliminated. That is, even if the chamfering dimensions and shapes of the small end surface 17 are different, in the initial assembly state, the small end surface 17 and the small flange surface 19 parallel to each other are in surface contact with each other. The first gap is always constant, and it is possible to eliminate the variation in the time required for each conical roller 12 to settle in the normal position, and to shorten the acclimatization operation time.

The ratio R / R _{BASE of the radius of curvature R of the large end face of the conical roller to the distance R BASE} from the apex of the cone angle of the conical roller to the inner ring large flange surface was set in the range of 0.75 or more and 0.87 or less. For the following reasons.

FIG. 12 shows the result of calculating the oil film thickness t formed between the inner ring large collar surface and the conical roller large end surface using Karna's equation. The vertical axis is the ratio t / t0 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 0.9.}

FIG. 13 shows the result of calculating the maximum Hertz stress p between the inner ring large collar surface and the conical roller large end surface. 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 as the _{R / R BASE increases.}

In order to reduce the torque crossing and heat generation due to the rubbing friction between the inner ring large collar surface and the conical roller large end surface, it is desirable to increase the oil film thickness t and reduce the maximum Hertz stress p. _{The present inventors have determined the appropriate range of R / R BASE} to be 0.75 or more and 0.87 or less based on the seizure resistance test results shown in Table 1 below with reference to the calculation results of FIGS. 12 and 13. bottom. In the conventional conical roller bearing, the R / R _BASE value is designed in the range of 0.90 or more and 0.97 or less.

<Manufacturing method of conical roller bearings>
FIG. 14 is a flowchart for explaining a method for manufacturing the conical roller bearing shown in FIG. FIG. 15 is a schematic view showing a heat treatment pattern in the heat treatment step of FIG. FIG. 16 is a schematic view showing a modified example of the heat treatment pattern shown in FIG. FIG. 18 is a schematic view illustrating the microstructure of the bearing component as a comparative example, particularly the former austenite grain boundaries. Hereinafter, a method for manufacturing a conical roller bearing will be described.

As shown in FIG. 14, 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 roller 12, and a cage 14 are prepared. Crowning has not yet been formed on the member to be the 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 roller 12, and the inner ring 13, carburizing nitriding treatment or nitriding treatment, quenching treatment, and tempering treatment are performed. Perform processing etc. An example of the heat treatment pattern in this step (S200) is shown in FIG. FIG. 15 shows a heat treatment pattern showing a method of performing primary quenching and secondary quenching. FIG. 16 _{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 after the carbon is sufficiently dissolved, the steel base is 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 treatment at 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 bearing component and then quenching once. Can be done. According to the heat treatment step (S200), in the nitrogen-enriched layers 11B, 12B, and 13B having a hardened structure, 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. 17, which is less than half. The bearing component that has undergone the above heat treatment has a long life against rolling fatigue, can improve crack strength, and can reduce the rate of dimensional change over time.

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 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.
(Experimental Example 1)
<Sample>
As a sample, sample No. Four types of cones 1 to 4 were prepared as samples. The model number of the conical roller was 30206. As the material of the conical roller, JIS standard SUJ2 material (1.0 mass% C-0.25 mass% Si-0.4 mass% Mn-1.5 mass% Cr) was used.

Sample No. For No. 1, after carburizing, nitriding and quenching, logarithmic crowning according to the present embodiment shown in FIG. 5 was formed at both ends. The carburizing and nitriding treatment temperature was 845 ° C., and the holding time was 150 minutes. The atmosphere of the carburizing nitriding treatment was RX gas + ammonia gas. Sample No. Regarding 2, the sample No. After carburizing, nitriding and quenching in the same manner as in No. 1, the partial arc crowning shown in FIG. 11 was formed.

Sample No. For No. 3, after the heat treatment pattern shown in FIG. 15 was carried out, logarithmic crowning according to the present embodiment shown in FIG. 5 was formed at both ends. The carburizing and nitriding treatment temperature was 845 ° C., and the holding time was 150 minutes. The atmosphere of the carburizing nitriding treatment was RX gas + ammonia gas. The final quenching temperature was 800 ° C.

Sample No. For No. 4, after the heat treatment pattern shown in FIG. 15 was carried out, logarithmic crowning according to the present embodiment shown in FIG. 5 was formed at both ends. In order to make the nitrogen concentration in the nitrogen-enriched layer at a depth of 0.05 mm from the outermost surface of the sample 0.1% by mass or more, the carburizing nitriding treatment temperature was set to 845 ° C. and the holding time was set to 150 minutes. The atmosphere of the carburizing nitriding treatment was RX gas + ammonia gas. Furthermore, the atmosphere inside the furnace was strictly controlled. Specifically, unevenness in the temperature inside the furnace and unevenness in the atmosphere of ammonia gas were suppressed. The final quenching temperature was 800 ° C. The above-mentioned sample No. 3 and sample No. 4 corresponds to the embodiment of the present invention. Sample No. 1 and sample No. 2 corresponds to a comparative example.

<Experimental content>
Experiment 1: Life test A life test device was used. As the test conditions, the conditions of test load: Fr = 18 kN, Fa = 2 kN, lubricating oil: turbine oil 56, and lubrication method: oil bath lubrication were used. In the life test apparatus, the two conical roller bearings as the test piece are arranged so as to support both ends of the support shaft. A cylindrical roller bearing for applying a radial load to the conical roller bearing via the support shaft is arranged at the central portion of the support shaft in the extending direction, that is, the central portion of the two conical roller bearings. Then, by applying a radial load to the cylindrical roller bearing for load loading, the radial load is applied to the conical roller bearing as the test piece. Further, the axial load is transmitted from one conical roller bearing to the support shaft through the housing of the life test device, and the axial load is applied to the other conical roller bearing. As a result, the life test of the conical roller bearing is performed.

Experiment 2: Life test under eccentric load The same test equipment as the life test in Experiment 1 above was used. The test conditions are basically the same as those in Experiment 1 above, but the test was carried out with the central axis of the roller loaded with an axial inclination of 2/1000 rad and with an eccentric load applied.

Experiment 3: Rotational torque test Sample No. Torque measurement tests were performed on 1 to 4 using a vertical torque tester. As the test conditions, the conditions of test load: Fa = 7000N, lubricating oil: turbine oil 56, lubrication method: oil bath lubrication, and rotation speed: 5000 rpm were used.

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

Experiment 2: Life test under eccentric load Sample No. 4 and sample No. 3 showed the best results and was considered to have a long life. Next, sample No. 1 is sample No. 4 and sample No. Although it was less than 3, it showed relatively good results. On the other hand, sample No. No. 2 shows a worse result than the result at the time of the above experiment 1, and it is considered that the life is shortened due to the eccentric load condition.

Experiment 3: Rotational torque test Sample No. 1. Sample No. 3. Sample No. 4 showed a sufficiently small rotational torque, and good results were obtained. On the other hand, sample No. In No. 2, the rotational torque was larger than that of the other samples.

Based on the above results, the sample No. 4 showed good results in all the tests, and was the best overall result. In addition, sample No. Sample No. 3 is also No. 3. 1 and sample No. It showed better results than 2.
(Experimental Example 2)
<Sample>
Sample No. 1 in Experimental Example 1 above. 4 was used.

<Experimental content>
Nitrogen concentration measurement at a depth of 0.05 mm from the surface:
Sample No. For No. 4, the nitrogen concentration was measured and the depth of the nitrogen-enriched layer was measured. The following method was used as the measurement method. That is, at the first to third measurement points shown in FIG. 3, the cut surface is exposed by cutting the conical roller as a sample in the direction perpendicular to the center line. 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 sample on the cut surface. Five measurement positions were determined for each of the cross sections at the first to third measurement points, and the average value of the measurement data at the five points was taken as the nitrogen concentration at each measurement point.

Measurement of distance to the bottom of the nitrogen-enriched layer:
In the cross section of the conical roller after the tempering treatment at 500 ° C. × 1 h at the first to third measurement points, the hardness was measured at a plurality of measurement points arranged at intervals of 0.5 mm in the depth direction. The region where the Vickers hardness was HV450 or higher was defined as the nitrogen-enriched layer, and the depth at the position where the hardness was HV450 was defined as the bottom of the nitrogen-enriched layer.

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

Measurement of distance to the bottom of the nitrogen-enriched layer:
For the first measurement point, the distance to the bottom of the nitrogen-enriched layer is 0.3 mm, for the second measurement point, the distance is 0.35 mm, and for the third measurement point, the distance is 0.3 mm. rice field. At any of the measurement points, the measurement results were within the scope of the present invention.

(Experimental Example 3)
<Example sample>
The radius of curvature R of the large end surface of the conical roller shown in FIG. 6 falls _{within the range of R / R BASE} = 0.75 or more and 0.87 or less, and the surface roughness Ra of the large flange surface of the inner ring is 0.12 μm. , Conical roller bearings in which the small flange surface is formed by a ground surface parallel to the small end surface of the conical roller and the first gap is within the dimensional regulation range of 0.4 mm or less (Sample Nos. 5 to 5 in Table 1). 8) was prepared. The bearings have an inner diameter of 40 mm and an outer diameter of 68 mm.

<Comparative example sample>
A conical roller bearing in which the value of R / R _BASE is out of the range of the present application, the small collar surface of the inner ring is inclined outward with respect to the small end surface of the conical roller, and the first gap exceeds 0.4 mm (in Table 1). Samples No. 9 to 11) were prepared. The dimensions of each bearing are the same as in the embodiment.

The seizure resistance test using a rotation tester was carried out on the conical roller bearings of the above example and the comparative example. In addition, sample No. 6 and sample No. A break-in operation test was also performed on 10 conical roller bearings. The number of samples in the break-in test is the sample No. For 6, 66 samples, sample No. The number was 10 as opposed to 10. The test conditions for the seizure resistance test are as follows. Load load: 19.61 kN rpm: 1000 to 3500 rpm Lubricating oil: Turbine VG56 (lubrication amount 40 ml / min, lubrication temperature 40 ° C ± 3 ° C).

The results of each test are shown in Table 1. The seizure in the seizure resistance test occurs between the large brim surface of the inner ring and the large end surface of the conical roller.

In all of the conical roller bearings of the examples, the limit rotation speed at which seizure occurs in the seizure resistance test is 2700 rpm or more, and it can be seen that the frictional resistance between the inner ring large flange surface and the conical roller large end surface is small. On the other hand, the conical roller bearing of the comparative example has a limit rotation speed at which seizure occurs at 2500 rpm or less, which may cause a problem under normal use conditions such as a differential. The sample 11 having a rough surface roughness Ra on the large collar surface had the same radius of curvature R as the sample No. It shows a seizure occurrence limit rotation speed lower than 10.

In addition, the result of the break-in operation test is that the average value of the number of rotations until the conical roller settles in the normal position is 6 times in the comparative example, but it is about half, 2.96 times in the example. There is. In the embodiment, the standard deviation of the variation in the number of rotations is also small, and it can be seen that the break-in operation time can be stably shortened.

As described above, in the conical roller bearing of the present invention, the radius of curvature R of the large end surface of the conical roller is _{set to a value in the range of R / R BASE} = 0.75 or more and 0.87 or less, and the small collar surface of the inner ring. Is formed on a surface parallel to the small end surface of the conical roller, so that it is possible to prevent seizure by reducing torque crossing and heat generation due to swaying friction between the inner ring large bearing surface and the large end surface of the conical roller, and to reduce the running-in time. It can be shortened to improve the efficiency of bearing mounting work. In addition, the durability of the gear shaft support device for vehicles can be improved.

(Experimental Example 4)
About the above ratio Rprocess / R:
Table 2 shows the contact surface when the ratio Rprocess / R is changed with respect to the contact surface pressure p0 between the large end surface and the large collar surface when the ratio Rprocess / R is 1, the skew angle θ0, and the oil film parameter Λ0. The calculation results of each ratio of the pressure p, the skew angle θ, and the oil film parameter Λ are shown.

As shown in Table 2, when the ratio Rprocess / R is 0.7 or less, the contact surface pressure ratio p / p0 between the large end surface and the large flange surface is 1.6 or more, and the skew angle ratio θ / θ0 is It becomes 3 or more, and the ratio Λ / Λ0 of the oil film parameter becomes 0.5 or less. When such a conical roller bearing is used in an environment where the lubrication state is not good, for example, the oil film parameter Λ is less than 2, the oil film parameter Λ is less than 1, and the contact state between the large end surface and the large flange surface is It is a boundary lubrication area where metal contact occurs. On the other hand, when the ratio Rprocess / R is 0.8 or more, the contact surface pressure ratio p / p0 is 1.4 or less, the skew angle ratio θ / θ0 is 1.5 or less, and the oil film parameter ratio Λ / Λ0 is It will be 0.8 or more. Therefore, a conical roller bearing having a ratio Rprocess / R of 0.8 or more secures an oil film thickness between the large end surface and a large flange surface as compared with a conical roller bearing having a ratio Rprocess / R of less than 0.8. It was confirmed by the above calculation result that it can be done.

About the above ratio α / L:
In Table 3, when the deviation amount α is 0, that is, the contact position between the raceway surfaces 11A and 13A of the inner ring and the outer ring 11 and the rolling surface is located at the midpoint of the rolling surface in the extending direction of the rolling axis. The calculation results of the respective ratios θ / θ0 and M / M0 of the skew angle θ and the rotational torque M when the deviation amount α is changed with respect to the skew angle θ0 and the rotational torque M0 are shown. In Table 3, the amount of deviation when the contact position is shifted toward the small end surface side from the midpoint is shown by a negative value. Those with a rotational torque ratio M / M0 of 1.1 or less are evaluated as good (○ in Table 3), and those with a rotational torque ratio M / M0 exceeding 1.1 are evaluated as defective (x in Table 3). bottom.

As shown in Table 3, the skew angle ratio θ / θ0 is 2 when the contact position is displaced relatively significantly toward the small end surface side from the midpoint, that is, when the deviation amount α is less than -5%. As mentioned above, a slight increase in the amount of displacement causes a large increase in rotational torque.

On the other hand, when the contact position is displaced relatively small toward the small end surface side from the midpoint, that is, when the deviation amount α is -5% or more and less than 0%, the deviation amount α is less than -5%. Compared with a certain case, the skew angle ratio θ / θ0 is small, and the rate of increase in rotational torque with respect to an increase in the amount of deviation is small.

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

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

(Embodiment 2)
The conical roller bearing according to the second embodiment basically has the same configuration as the conical roller bearing 10 according to the first embodiment, but is not in contact with the inner ring raceway surface 13A at the crowning forming portion of the roller rolling surface. The difference is that the curvature R8 of the bus of the non-contact portion crowning portion 28 is set smaller than the curvature R7 of the bus of the contact portion crowning portion 27 in contact with the inner ring raceway surface 13A.

As shown in FIG. 1, the conical roller bearing according to the second embodiment includes an inner ring 13, an outer ring 11, and a plurality of rollers 12 interposed between the inner and outer rings. An inner ring raceway surface 13A is formed on the outer circumference of the inner ring 13, and a large brim portion 41 and a small brim portion 42 are provided on the large diameter side and the small diameter side of the inner ring raceway surface 13A, respectively. A grinding relief portion 43 is formed at the corner where the inner ring raceway surface 13A and the large brim portion 41 intersect, and a grinding relief portion 44 is formed at the corner portion between the inner ring raceway surface 13A and the small brim portion 42. .. The inner ring raceway surface 13A has a straight bus line extending in the inner ring axial direction. On the inner circumference of the outer ring 11, an outer ring raceway surface 11A facing the inner ring raceway surface 13A is formed so as to have no collar, and the outer ring raceway surface 11A has a generatrix extending in the outer ring axial direction as a straight line.

As shown in FIGS. 1, 2 and 22, crowning is formed on the roller rolling surface on the outer circumference of the roller 12, and chamfered portions 21 and 25 are provided on both ends of the roller 12. The crowning forming portion of the roller rolling surface is formed in the contact portion crowning portion 27 and the non-contact portion crowning portion 28. Of these, the contact portion crowning portion 27 is in the axial range of the inner ring raceway surface 13A and is in contact with the inner ring raceway surface 13A. The non-contact portion crowning portion 28 deviates from the axial range of the inner ring raceway surface 13A and becomes non-contact with the inner ring raceway surface 13A.

The contact portion crowning portion 27 and the non-contact portion crowning portion 28 are lines in which the bus lines extending in the roller axis direction are represented by different functions and are smoothly continuous with each other at the connection point P1. In the vicinity of the connection point P1, the curvature R8 of the generatrix of the non-contact portion crowning portion 28 is set to be smaller than the curvature R7 of the generatrix of the contact portion crowning portion 27.

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

A case where a radial load of 35% of the basic dynamic load rating acts on the conical roller bearing, nominal number 30316, and the misalignment is 1/600 will be examined. At this time, the misalignment is assumed to be tilted in the direction in which the surface pressure increases not on the small diameter side of the roller 12 but on the large diameter side. The basic dynamic load rating is the direction and size such that when the same group of bearings is individually operated under the condition that the inner ring 13 is rotated and the outer ring 11 is stationary, the low rating life becomes 1 million rotations. A load that does not fluctuate. The misalignment is a misalignment between a housing (not shown) in which the outer ring 11 is fitted and a shaft in which the inner ring 13 is fitted, and is expressed as a fraction as described above as the amount of inclination.

The generatrix of the contact portion crowning portion 27 is formed by the logarithmic curve of the logarithmic crowning represented by the above equation (1).

In order to ensure the processing accuracy of crowning, it is desirable that a straight portion having a length of 1/2 or more of the total roller length L1 exists on the outer circumference of the roller 12. Therefore, if 1/2 of the total roller length L1 is a straight portion and the crowning is symmetrical between the small diameter side portion and the large diameter side portion with reference to the center in the roller axial direction, the logarithmic crowning equation (1) is used. Of the design parameters of, K 2 is fixed, and K ₁ and z _m are the objects of design.

By the way, when the crowning is optimized by using the mathematical optimization method described later, the crowning becomes as shown in the “logarithm” of FIG. 23 under this condition. At this time, the maximum drop amount of crowning of the roller 12 is 69 μm. However, the region G in FIG. 23 is the region of E facing the grinding relief portions 43 and 44 of the inner ring 13 of FIG. 21 and does not come into contact with the inner ring 13. Therefore, the region of G of the roller 12 does not have to be logarithmic crowning, and may be a straight line, an arc, or other function. Even if the region of G of the roller 12 is a straight line, an arc, or another function, the entire roller has the same surface pressure distribution as in the case of logarithmic crowning, and is functionally comparable.

A mathematical optimization method for logarithmic crowning will be described.
Optimal logarithmic crowning can be designed by appropriately selecting _{K 1} and z _m in the function equation (1) representing logarithmic crowning.

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

K ₁ and z _m can be selected using an appropriate mathematical optimization method. Various algorithms have been proposed for mathematical optimization methods, and one of them, the direct search method, is capable of performing optimization without using the fine coefficients of the function, and has the purpose. This is useful when functions and variables cannot be directly represented by mathematical formulas. Here, the optimum values of _{K 1} and z _m are obtained using the Rosenbrock method, which is one of the direct search methods.

When a radial load of 35% of the basic dynamic load rating acts on the conical roller bearing, nominal number 30316, and the misalignment is 1/600, the maximum value of the Mises equivalent stress sMises_max and the logarithmic crowning parameter K ₁ , z _m Has the relationship shown in FIG. If K ₁ and z _{m are given appropriate initial values and K 1} and z _m are modified according to the rules of the Rosenbrok method, the optimum combination of values in Fig. 24 is reached and sMises_max becomes the minimum.

As long as the contact between the roller 12 and the inner ring 13 is considered, the crowning in the region G in FIG. 23 may have any shape, but if the contact with the outer ring 11 and the formability of the grindstone at the time of processing are taken into consideration, the crowning may have any shape. At the connection point P1 with the logarithmic crowning portion, it is not desirable that the gradient is smaller than the gradient of the logarithmic crowning portion. For the crowning of the region of G, it is not desirable to give a gradient larger than the gradient of the logarithmic crowning portion because the amount of drop increases. That is, it is desirable that the crowning in the region of G and the logarithmic crowning are designed so that the gradients match and are smoothly connected at the connection point P1. In FIG. 23, the case where the crowning of the region G of the roller 12 is a straight line is illustrated by a dotted line, and the case where it is an arc is illustrated by a thick solid line. When the crowning in the region of G is a straight line, the drop amount Dp of the crowning of the roller 12 is, for example, 36 μm. When the crowning in the region of G is an arc, the drop amount Dp of the crowning of the roller 12 is, for example, 40 μm.

According to the conical roller bearing described above, since crowning is formed on the roller rolling surface on the outer circumference of the roller 12, the grindstone is allowed to act on the roller rolling surface more than necessary and sufficient as compared with the case where crowning is formed only on the inner ring raceway surface 13A. obtain. Therefore, it is possible to prevent processing defects on the rolling surface. The crowning formed on the roller rolling surface reduces the surface pressure and the stress of the contact portion, and can extend the life of the conical roller bearing. Further, in the vicinity of the connection point P1 between the contact portion crowning portion 27 and the non-contact portion crowning portion 28, the curvature R8 of the generatrix of the non-contact portion crowning portion 28 is smaller than the curvature R7 of the generatrix of the contact portion crowning portion 27. Therefore, it is possible to reduce the drop amount Dp at both ends of the roller 12. Therefore, for example, the grinding amount can be suppressed as compared with the conventional single arc crowning, the processing efficiency of the roller 12 can be improved, and the manufacturing cost can be reduced.

The generatrix of the non-contact portion crowning portion 28 may be an arc in either or both of the large diameter side portion and the small diameter side portion. In this case, the drop amount Dp can be reduced as compared with the generatrix of the entire roller rolling surface represented by, for example, a logarithmic curve. Therefore, the amount of grinding can be reduced. As shown in FIG. 25, the generatrix of the non-contact portion crowning portion 28 may be a straight line in either or both of the large diameter side portion and the small diameter side portion (in the example of FIG. 25, the large diameter side). Only the part of is a straight line). In this case, the drop amount Dp can be further reduced as compared with the case where the generatrix of the non-contact portion crowning portion 28 is an arc.

Part or all of the generatrix of the contact portion crowning portion 27 may be represented by logarithmic crowning. The contact portion crowning portion 27 represented by the logarithmic crowning can reduce the surface pressure and the stress of the contact portion and extend the life of the conical roller bearing. As shown in FIG. 26, the generatrix of the contact portion crowning portion 27 may be represented by a straight portion 27A formed flat along the roller axis direction and a portion 27B formed by a logarithmic curve of logarithmic crowning. ..

As another embodiment of the present invention, in the conical roller bearing, crowning may be provided on the roller 12 as well as on the inner ring 13. In this case, the sum of the drop amount of the roller 12 and the drop amount of the inner ring 13 is made equal to the optimized drop amount described above. By these crownings, it is possible to reduce the surface pressure and the stress of the contact portion and extend the life of the conical roller bearing. Further, the grinding amount can be suppressed as compared with the conventional single arc crowning, the processing efficiency of the roller 12 can be improved, and the manufacturing cost can be reduced.

The conical roller bearing of the present invention is a conical roller bearing including inner and outer rings and rollers, in which crowning is formed on at least the roller rolling surface on the outer periphery of the roller, and the crowning forming portion of the roller rolling surface is formed on the inner ring raceway surface. A contact portion crowning portion that is in the axial range and is in contact with the inner ring raceway surface, and a non-contact portion crowning portion that deviates from the axial range of the inner ring raceway surface and is not in contact with the inner ring raceway surface. The non-contact portion crowning portion is a line in which the bus lines extending in the roller axis direction are represented by different functions and are smoothly continuous at the connection points, and in the vicinity of the connection points, the bus lines of the non-contact portion crowning portion The curvature is smaller than the curvature of the bus of the contact portion crowning portion.

The above-mentioned "smoothly continuous" means that the bus is continuous without forming a corner, and ideally, the generatrix of the contact portion crowning portion and the generatrix of the non-contact portion crowning portion are at continuous points with each other. By continuing to have a common tangent, that is, the generatrix is a continuously differentiable function at the continuum.

According to this configuration, since the crowning is formed on the roller rolling surface on the outer circumference of the roller, the grindstone can act on the rolling surface of the roller more than necessary and sufficient as compared with the case where the crowning is formed only on the inner ring raceway surface. Therefore, it is possible to prevent processing defects on the rolling surface. The crowning formed on the roller rolling surface reduces the surface pressure and the stress of the contact portion, and can extend the life of the conical roller bearing. Further, in the vicinity of the connection point between the contact portion crowning portion and the non-contact portion crowning portion, the curvature of the generatrix of the non-contact portion crowning portion is smaller than the curvature of the generatrix of the contact portion crowning portion. The amount of drops can be reduced. Therefore, for example, the grinding amount can be suppressed as compared with the conventional single arc crowning, the machining efficiency of the rollers can be improved, and the manufacturing cost can be reduced.

The generatrix of the non-contact portion crowning portion may be an arc in either or both of the large diameter side portion and the small diameter side portion. In this case, the drop amount can be reduced as compared with the generatrix of the entire roller rolling surface represented by, for example, a logarithmic curve. Therefore, the amount of grinding can be reduced.

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

A part or all of the generatrix of the contact portion crowning portion may be represented by logarithmic crowning. The contact portion crowning portion represented by the logarithmic crowning can reduce the surface pressure and the stress of the contact portion and extend the life of the conical roller bearing.

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

Of the generatrix of the non-contact portion crowning portion, the connecting portion with the portion formed by the logarithmic curve of the logarithmic crowning may be made to match the gradient of the logarithmic curve. In this case, the generatrix of the contact portion crowning portion and the generatrix of the non-contact portion crowning portion can be made continuous more smoothly at the connection point.

The generatrix of the contact portion crowning portion may be formed by the logarithmic curve of the logarithmic crowning represented by the above equation (1).

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

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

The method for designing a conical roller bearing of the present invention is a method for designing a conical roller bearing including inner and outer rings and rollers. Is formed into a contact portion crowning portion that is in the axial range of the inner ring raceway surface and is in contact with the inner ring raceway surface, and a non-contact portion crowning portion that is out of the axial range of the inner ring raceway surface and is not in contact with the inner ring raceway surface. In the contact portion crowning portion and the non-contact portion crowning portion, the bus lines extending in the roller axis direction are represented by different functions and are smoothly continuous at the connection points, and the bus line of the contact portion crowning portion is defined as the above. It is formed by the logarithmic curve of the logarithmic crowning represented by the equation (1), and the curvature of the bus line of the non-contact portion crowning portion is designed to be smaller than the curvature of the bus line of the contact portion crowning portion in the vicinity of the connection point. It is a feature.

According to the design method of the present invention, it is possible to easily design a conical roller bearing capable of reducing the surface pressure and the stress of the contact portion and extending the life. In addition, it is possible to design a conical roller bearing that can reduce the amount of roller drop and reduce the manufacturing cost.

<Application example of conical roller bearing>
An example of applications of the conical roller bearings 1A and 1B according to the above embodiments 1 to 5 will be described. As described above, the conical roller bearings according to the first to fifth embodiments are suitable for differentials and transmissions. The above-mentioned conical roller bearing 10 is used for an automobile differential or transmission. That is, the conical roller bearing 10 is a conical roller bearing for automobiles.

FIG. 27 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 a drive pinion 122 inserted through the differential case 121 is meshed with a ring gear 124 attached to the differential gear case 123 and attached to the inside of the differential gear case 123. The pinion gear 125 is 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 and the differential gear case 123, which are power transmission shafts, are supported by a pair of conical roller bearings 10a and 10b, respectively.

FIG. 28 shows a manual transmission of an automobile using the above-mentioned conical roller bearing 10. The manual transmission 100 is a constantly meshing type manual transmission, and includes an input shaft 111, an output shaft 112, a counter shaft 113, gears 114a to 114k, and a housing 115.

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

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

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

Further, each of the gear 114f and the gear 114g is formed on the outer periphery of the same member. The member on which the gear 114f and the gear 114g are formed is attached to the output shaft 112 so as to rotate integrally with the output shaft 112 and to slide in the axial direction of the output shaft 112. When the member forming the gear 114f and the gear 114g slides to the left side in the drawing, the gear 114f can mesh with the gear 114b, and when the member slides to the right side in the drawing, the gear 114g and the gear 114d It can be meshed.

Gears 114h to 114k are formed on the counter shaft 113. Two thrust needle roller bearings 130 are arranged between the counter shaft 113 and the housing 115, whereby an axial load (thrust load) of the counter shaft 113 is supported. The gear 114h is always in mesh with the gear 114a, and the gear 114i is in constant mesh with the gear 114c. Further, the gear 114j can mesh with the gear 114e when the gear 114e slides to the left side in the drawing. Further, the gear 114k can mesh with the gear 114e when the gear 114e slides to the right side in the drawing.

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

When the rotation of the input shaft 111 is transmitted to the output shaft 112, by changing the gear that meshes between the input shaft 111 and the counter shaft 113 and the gear that meshes between the counter shaft 113 and the output shaft 112. , The rotation speed of the output shaft 112 can be changed stepwise with respect to the rotation speed of the input shaft 111. Further, the rotation of the input shaft 111 can be directly transmitted to the output shaft 112 by directly engaging the gear 114b of the input shaft 111 and the gear 114f of the output shaft 112 without going through the counter shaft 113.

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

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

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

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

By the way, in transmissions or differentials, which are power transmission devices for automobiles, in addition to using low-viscosity lubricating oil, there is a tendency to reduce the amount of oil in order to save fuel consumption, which is sufficient for conical roller bearings. It may be difficult to form an oil film. In addition, when the transmission or differential is used in a low temperature environment (for example, -40 ° C to -30 ° C), the viscosity of the lubricating oil increases, so that the lubricating oil is not sufficiently supplied to the cone roller bearings, especially at the time of starting. There is. For this reason, conical roller bearings for automobiles are required to have seizure resistance and improved life. Therefore, the above requirements can be satisfied by incorporating the above-mentioned conical roller bearing 10 having improved seizure resistance and life into a transmission or a differential.

It should be considered that the embodiments and examples disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is not shown in the above embodiments and examples, but is indicated by the scope of claims, and is intended to include all modifications and modifications within the meaning and scope equivalent to the scope of claims. ..

10,10a bearing, 11 outer ring, 11A, 13A raceway surface, 12A rolling surface, 11B, 12B, 13B nitrogen enriched layer, 11C, 12C, 13C unnitrided part, 12D end face, 12E unprocessed surface, 13 inner ring, 14 Cage, 14d Pillar surface, 16 large end surface, 17 small end surface, 18 large collar surface, 19 small collar surface, 21 chamfered part, 22, 24 crowning part, 23 center part, 26 center line, 31 first measurement point, 32 2nd measurement point, 33 3rd measurement point, 41 large brim, 42 small brim, 43,44 grinding relief.

Claims (12)

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 surface 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 an outer ring raceway surface, a rolling surface in contact with 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. With and
At least one of the outer ring, the inner ring and the plurality of conical rollers includes a nitrogen-enriched layer formed on the surface layer of the outer ring raceway surface, the inner ring raceway surface or the rolling surface.
The nitrogen-enriched layer is a region in which the Vickers hardness is HV450 or higher when the hardness distribution is measured in the depth direction with respect to the cross section perpendicular to the outermost surface of the surface layer using a Vickers hardness measuring machine.
The distance from the outermost surface of the surface layer to the bottom of the nitrogen-enriched layer is 0.2 mm or more.
At least a portion of the large end surface of the conical roller is a ground surface.
Crowning is formed on the rolling surface of the conical roller.
A chamfered portion is formed between the large end surface of the conical roller and the crowning.
A recess is formed in the central portion of the large end surface.
A convex portion having an inner peripheral end connected to the concave portion and an outer peripheral end connected to the chamfered portion is formed on the outer peripheral portion of the large end surface.
In a cross section along the rolling axis of the conical roller, the large end surface of the conical roller has points C1 and C4 connecting the outer peripheral end of the convex portion and the chamfered portion, and the inside of the convex portion. Points C2 and C3 connecting the peripheral end and the recess, an intermediate point P5 between the point C1 and the point C2 on the large end surface, and an intermediate point between the point C3 and the point C4 on the large end surface. Including point P6
In the cross section, 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 set as the reference radius of curvature R, and the large diameter of the inner ring from the apex of the conical angle of the conical roller. when the distance to the flange surface and the R _BASE, the value of R / R _BASE is 0.75 or more 0.87 or less,
In the cross section, the point C1, the midpoint P5, the radius of curvature of the arc passing through the point C2 actual radius of curvature R _process, and the time, the ratio R _process and the actual curvature radius R _process and the reference radius of curvature R / R is 0.8 or more,
_{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. A conical roller bearing represented by the equation (1) when the length to the end of the effective contact portion is A = 2K _{1 Q / πLE'.}

The conical roller bearing according to claim 1, wherein the former austenite crystal particle size in the nitrogen-enriched layer has a JIS standard particle size number of 10 or more. The conical roller bearing according to claim 1 or 2, wherein the nitrogen concentration in the nitrogen-enriched layer at a depth of 0.05 mm from the outermost surface is 0.1% by mass or more. The conical roller bearing according to any one of claims 1 to 3, wherein at least one _{of K 1} , K ₂ , and z _m of the above formula (1) is optimized with the surface pressure as an objective function. The crowning-forming portion in which the crowning is formed on the rolling surface of the conical roller is a contact portion crowning portion in the axial range of the inner ring raceway surface and in contact with the inner ring raceway surface, and the axial direction of the inner ring raceway surface. Including a non-contact portion crowning portion that is out of range and is non-contact with the inner ring raceway surface.
In the contact portion crowning portion and the non-contact portion crowning portion, the generatrix extending in the roller axis direction is a line represented by a function different from each other and smoothly continuous at the connection point.
The conical roller bearing according to any one of claims 1 to 4, wherein the curvature of the generatrix of the non-contact portion crowning portion is smaller than the curvature of the generatrix of the contact portion crowning portion in the vicinity of the connection point. The conical roller bearing according to claim 5, wherein the generatrix of the non-contact portion crowning portion is an arc in either or both of the large diameter side portion and the small diameter side portion. The conical roller bearing according to claim 5, wherein the generatrix of the non-contact portion crowning portion is a straight line in either or both of the large diameter side portion and the small diameter side portion. The conical roller bearing according to any one of claims 5 to 7, wherein a part or all of the generatrix of the contact portion crowning portion is represented by logarithmic crowning. The conical roller bearing according to claim 8, wherein the generatrix of the contact portion crowning portion is represented by a straight portion formed flat along the roller axis direction and a portion formed by a logarithmic curve of logarithmic crowning. The conical roller bearing according to any one of claims 1 to 9, wherein the surface roughness Ra of the large end surface is 0.10 μm or less, and the surface roughness Ra of the large collar surface is 0.063 μm or less. The conical roller bearing according to any one of claims 1 to 10, wherein at least one of the outer ring and the inner ring includes the nitrogen-enriched layer. The conical roller bearing according to any one of claims 1 to 11, wherein the conical roller includes the nitrogen-enriched layer.

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