Tapered roller bearings

Abstract

In order to prevent sudden temperature rise and allow the bearing to rotate smoothly even when the tapered roller bearing is used under severe lubrication conditions, the tapered roller bearing is designed as follows: when the intersection of an imaginary line formed by extending the generatrix of the raceway surface (11) of the inner ring (10) toward the ground runout groove (13) and an imaginary line formed by extending the generatrix of the large flange surface (12a) toward the ground runout groove (13) is set as a reference point (O2), the cut-in width of the ground runout groove (13) from the reference point (O2) to the large flange surface (12a) is set as A, and the width of the chamfer (32) of the tapered roller (30) in the direction along the generatrix of the large flange surface (12a) is set as RC, the width RC is less than 0.7 mm, and A<RC.

Description

Technical Field

[0001] The present invention relates to tapered roller bearings. Background Art

[0002] For rolling bearings that support rotating parts, rolling bearings that are suitable for the direction, size, and bearing installation space of the loads borne by the rolling bearings must be used. In the case of supporting the rotating parts of the transmission (MT, AT, DCT, CVT, hybrid, etc.) or differential of the automobile, the use conditions are to bear radial loads, axial loads, and moment loads, and miniaturization is also required. Therefore, tapered roller bearings that can bear radial loads and axial loads and have excellent load-bearing capacity are used.

[0003] In a tapered roller bearing, a thrust force is generated to push the tapered roller toward the larger diameter side during operation. Therefore, a large flange is formed on the inner ring for supporting and guiding the large end face of the tapered roller in the direction of revolution (circumferential direction) of the tapered roller. The large flange has a large flange surface for the large end face of the tapered roller to slide in contact with. The inner ring has a ground overrun groove that connects the large flange surface and the raceway surface over the entire circumference.

[0004] The large end face of the tapered roller and the large flange face of the inner ring are generally designed to be in geometric contact at only one point. During operation, the large end face of the tapered roller is in sliding contact with the large flange face of the inner ring in the direction of revolution, but due to the above-mentioned loads and thrusts, the sliding contact portion is generally generated in an elongated elliptical area with a radial minor axis centered on the designed contact point. If the sliding contact portion is not lubricated sufficiently, heat will be generated and a sudden temperature rise will occur.

[0005] When the tapered roller bearing is running at high speed and the lubricating oil reaches a high temperature, such as in the transmission of an automobile, a good lubrication mode cannot be maintained at the sliding contact portion between the large end face of the tapered roller and the large flange surface of the inner ring, and there is a possibility of boundary lubrication and insufficient lubrication. In order to improve the seizure resistance during such high-temperature operation, the shape and surface properties of the large end face of the tapered roller and the large flange surface of the inner ring have been studied (Patent Documents 1 to 3).

[0006] In Patent Document 1, the curvature radius of the large end surface of the tapered roller is denoted by R, and the distance from the vertex of the tapered angle of the tapered roller to the contact portion of the large flange surface is denoted by R. BASE By using R / R BASE Designing the ratio to be in the range of 0.75 to 0.87 can effectively exert the wedge effect when the lubricating oil is pulled between the large end surface of the tapered roller and the large flange surface of the inner ring, thereby increasing the oil film thickness at the sliding contact portion (reducing heat generation).

[0007] In patent document 2, by forming an avoidance surface with a shape that is away from the large end face of the tapered roller from the outer diameter side edge of the large flange surface toward the chamfered inner diameter side edge of the large flange, the introduction of lubricating oil into the contact portion between the large end face of the tapered roller and the large flange surface of the inner ring can be improved, thereby improving the oil film forming ability.

[0008] In Patent Document 3, when the above R / R BASE The design range is 0.75 to 0.87, and the actual curvature radius of the large end surface of the tapered roller is set to R ACTUAL By ACTUAL By designing R / R to be 0.5 or more, the heat generation of the large end surface of the tapered roller and the large flange surface of the inner ring can be suppressed even in a severe lubrication environment, thereby improving the seizure resistance. In particular, by introducing the flange lubrication coefficient as an indicator of the severity of the lubrication state, R / R can be expanded. ACTUAL The practical range of the ratio of / R is determined by selecting the appropriate bearing specifications according to the usage conditions.

[0009] Patent Document 1: Japanese Patent Application Publication No. 2000-170774

[0010] Patent Document 2: Japanese Patent Application Publication No. 2000-170775

[0011] Patent Document 3: Japanese Patent Application Publication No. 2018-136027

[0012] However, in automotive transmissions and differentials, there is a trend to reduce the viscosity of lubricating oil and the amount of lubricating oil in the unit in order to improve fuel economy, and this trend is expected to continue in the future. Therefore, the lubrication conditions for rolling bearings have become more stringent. In particular, in tapered roller bearings, it is more important to ensure the thickness of the oil film at the sliding contact between the large end face of the tapered roller and the large flange surface of the inner ring, and to pay attention to the suppression of temperature rise caused by the lubricating oil. Summary of the invention

[0013] In view of the above background, an object of the present invention is to prevent a sudden temperature rise and to allow the bearing to rotate smoothly even when the tapered roller bearing is used under severe lubrication conditions.

[0014] In order to achieve the above-mentioned problems, the present invention adopts the following structure, that is, a tapered roller bearing, comprising: an inner ring; an outer ring; a plurality of tapered rollers arranged between the inner ring and the outer ring; and a retainer for accommodating the tapered rollers, wherein the tapered rollers have: a rolling surface formed in a conical shape; a chamfer continuous with the large diameter side of the rolling surface; and a large end surface continuous with the chamfer; the inner ring has: a raceway surface formed in a conical shape; a large flange surface receiving the large end surface of the tapered roller; and a retainer formed to receive the tapered rollers. The above-mentioned large flange surface and the above-mentioned raceway surface are connected to the groove-shaped ground overrun groove, wherein, when the intersection of an imaginary line formed by extending the generatrix of the above-mentioned raceway surface toward the above-mentioned ground overrun groove and an imaginary line formed by extending the generatrix of the above-mentioned large flange surface toward the above-mentioned ground overrun groove is set as a reference point, the cutting width from the reference point to the large flange surface is set as A, and the width of the chamfer of the tapered roller in the direction along the generatrix of the above-mentioned large flange surface is set as RC, the width RC is less than 0.7 mm, and A<RC.

[0015] According to the above structure, the width RC of the chamfer of the tapered roller is formed to be 0.7 mm or less and the cutting width A of the grinding overrun groove is formed to be smaller than the width RC, thereby making it possible to widen the width of the large flange surface and form it to a width sufficient to bear the large end surface of the tapered roller. Therefore, the contact relationship between the large flange surface and the large end surface of the tapered roller can be optimized, and the wedge effect acting between the large flange surface and the large end surface of the tapered roller can be well exerted, thereby improving the oil film forming ability.

[0016] Specifically, when the taper angle of the rolling surface is β and the acute angle formed by the imaginary line connecting the contact point between the large flange surface and the large end surface of the tapered roller to the vertex of the taper angle β with respect to the generatrix of the raceway surface is ρ, β / 7 ≥ ρ. By designing the angle ρ representing the radial height of the contact point between the large flange surface and the large end surface of the tapered roller relative to the reference point to be less than β / 7, ​​it is possible to prevent the increase in the sliding speed at the sliding contact portion, suppress the heat generation of the large flange surface, and prevent sudden temperature rise.

[0017] When the entry angle of the grinding overrun groove relative to the large flange surface of the inner ring is set to a, and the entry angle of the grinding overrun groove relative to the track surface is set to b, a>b, and when the cut-in width from the reference point to the large flange surface is set to A, and the cut-in width from the reference point to the track surface is set to B, A<B. In manufacturing, in order to meet the cut-in width A of less than 0.5 mm, when the grinding amount of the large flange surface fluctuates during processing, it is necessary to consider that the width of the large flange surface depends on the entry angle a of the grinding overrun groove. The larger the entry angle a relative to the large flange surface, the smaller the change in the width of the large flange surface when the grinding amount of the large flange surface fluctuates, so the larger the entry angle a, the better. In addition, if the ease of chip discharge during turning of the grinding overrun groove is considered, it is preferred to satisfy the relationship of a>b and A<B.

[0018] When the depth of the grinding overrun groove relative to the track surface of the inner ring is set to c, and the depth of the grinding overrun groove relative to the large flange surface is set to d, c>d. In this way, the stress of the large flange caused by the load applied from the large end surface of the tapered roller to the large flange surface of the inner ring can be reduced, thereby improving the strength of the large flange of the inner ring.

[0019] When the depth of the grinding groove relative to the large flange surface of the inner ring is denoted as d, the depth d may be 0.3 mm or less. In this way, the strength of the large flange of the inner ring can be reliably improved.

[0020] When the entry angle of the grinding overrun groove relative to the large flange surface of the inner ring is set to a, 20°≤a≤50° is sufficient. In this way, it is easy to control the cutting width A when grinding the large flange surface.

[0021] When the acute angle formed by the generatrix of the above-mentioned raceway surface with respect to the central axis of the above-mentioned inner ring is set to θ, the large end diameter of the rolling surface of the above-mentioned tapered roller is set to Dw, the roller length of the above-mentioned tapered roller is set to L, and the width of the above-mentioned large flange surface is set to W, the width W can be a value that satisfies the following formula 1.

[0022] W≥{Dw×(1 / 2)×Tanθ / (L / Dw)}···Equation 1

[0023] This allows the large flange surface to fully face the large end surface of the tapered roller, and good contact is maintained even when the sliding contact portion between the large end surface of the tapered roller and the large flange surface of the inner ring rises toward the large flange outer diameter side.

[0024] The grain size number of the prior austenite grains of the large flange surface of the inner ring may be 6 or more. Such a large flange surface is suitable for delaying surface damage caused by metal contact with the large end surface of the tapered roller.

[0025] The large flange surface of the inner ring may be formed of a nitrided layer having a nitrogen content of 0.05 wt % or more. Such a large flange surface is suitable for delaying surface damage caused by metal contact with the large end surface of the tapered roller.

[0026] The surface roughness of the large flange surface of the inner ring may be 0.1 μm Ra or less, and the surface roughness of the large end surface of the tapered roller may be 0.12 μm Ra or less. In this way, a good oil film can be formed between the large flange surface and the large end surface of the tapered roller.

[0027] The configuration may be such that the set curvature radius of the large end surface of the tapered roller is set to R, and the basic curvature radius from the vertex of the cone angle of the rolling surface to the large flange surface of the inner ring is set to R BASE When R / R BASE is greater than or equal to 0.70 and less than or equal to 0.95, and the actual curvature radius of the large end surface of the tapered roller is set to R ACTUAL When at least one of the plurality of tapered rollers has an R ACTUAL In the present invention, the oil film forming ability can be improved on the large flange surface side, so that the R / R ratio can be relaxed compared to the tapered roller bearing of Patent Document 3. BASE , R ACTUAL / R. Accordingly, the yield rate of the tapered rollers is improved, and thus the tapered roller bearings can be provided at a relatively low cost.

[0028] The tapered roller bearing according to the present invention has excellent seizure resistance under severe lubrication conditions and is therefore suitable for use in supporting a rotating portion provided in a transmission or differential of an automobile.

[0029] As described above, by adopting the above-mentioned structure, the present invention can optimize the contact relationship between the large flange surface of the inner ring and the large end surface of the tapered roller, thereby improving the oil film forming ability, thereby preventing sudden temperature rise and allowing the bearing to rotate smoothly even when the tapered roller bearing is used under severe lubrication conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a diagram showing a generatrix shape near a large flange surface of a tapered roller bearing according to an embodiment of the present invention.

[0031] Figure 2 It is a cross-sectional view of the tapered roller bearing according to the present embodiment.

[0032] Figure 3 Yes means Figure 2 A diagram of the generatrix shape near the large flange surface when the large end surface of the tapered roller is in ideal contact with the large flange surface.

[0033] Figure 4 Yes means Figure 2 Semi-longitudinal section of the design specifications of a tapered roller bearing.

[0034] Figure 5 Yes means Figure 2 Schematic diagram of the detailed shape of the large end face of the tapered roller.

[0035] Figure 6 Yes means Figure 5 Schematic diagram of the processed shape of the large end surface of the tapered roller.

[0036] Figure 7 Yes means Figure 2 A graph showing the relationship between the radius of curvature of the large end surface of a tapered roller and the oil film thickness.

[0037] Figure 8 Yes means Figure 1 FIG. 1 is a diagram showing an example of a change in the shape of the generatrix near the large flange surface.

[0038] Fig. 9 Yes means that there is Figure 2 A cross-sectional view of an example of a tapered roller bearing for an automotive differential.

[0039] Fig.10 Yes means that there is Figure 2 A cross-sectional view of an example of a tapered roller bearing for an automotive transmission. DETAILED DESCRIPTION

[0040] A tapered roller bearing according to an embodiment as an example of the present invention will be described with reference to the drawings.

[0041] Figure 2 The tapered roller bearing shown in the figure includes: an inner ring 10; an outer ring 20; a plurality of tapered rollers 30 arranged between the inner ring 10 and the outer ring 20; and a retainer 40 for accommodating the tapered rollers 30. The tapered roller bearing is a bearing that is mainly used in a transmission or differential for an automobile and is also assumed to be applied to a transmission or differential for a passenger car, and the outer diameter of the bearing is 150 mm or less.

[0042] like Figure 2 , Figure 3 As shown, the inner ring 10 is composed of a raceway ring, which has on the outer peripheral side: a raceway surface 11 formed in a conical shape; a large flange 12 formed with a larger diameter than the large diameter side edge of the raceway surface 11; a grinding overrun groove 13 formed from the base of the large flange 12 to the raceway surface 11; a small flange 14 formed with a larger diameter than the small diameter side edge of the raceway surface 11; and a small diameter side grinding overrun groove 15 formed from the base of the small flange 14 to the raceway surface 11.

[0043] like Figure 2 As shown in FIG. 1 , the outer ring 20 is composed of a raceway ring having a raceway surface 21 formed in a conical shape on the inner circumference. Lubricating oil is supplied from the outside to the internal space of the bearing between the inner ring 10 and the outer ring 20.

[0044] The tapered roller 30 is composed of a rolling element having: a rolling surface 31 formed in a conical shape; a chamfer 32 continuous with the large diameter side of the rolling surface 31; a large end surface 33 continuous with the chamfer 32; and a small end surface 34 formed on the side opposite to the large end surface 33. The large end surface 33 and the small end surface 34 of the tapered roller 30 include both side ends that define the roller length L of the tapered roller 30.

[0045] The plurality of tapered rollers 30 are arranged in a single row between the inner and outer raceways 11 and 21. The retainer 40 is composed of an annular bearing member that retains the plurality of tapered rollers 30 at equal intervals in the circumferential direction. The tapered rollers 30 are accommodated in pockets formed in the retainer 40 at equal intervals in the circumferential direction.

[0046] The cage 40 shown in the figure is a cage punched cage, but the material and manufacturing method of the cage 40 are arbitrary.

[0047] Here, the direction along the center axis CL, which is the center of rotation of the inner ring 10, is called the "axial direction", the direction orthogonal to the center axis CL is called the "radial direction", and the circumferential direction around the center axis CL is called the "circumferential direction". The center axis CL of the inner ring 10 is equivalent to the rotation center of the tapered roller bearing in design.

[0048] The inner and outer raceway surfaces 11 and 21 are surface portions with which the rolling contact surfaces 31 of the tapered rollers 30 can roll and which receive radial loads from the rolling contact surfaces 31 .

[0049] like Figure 4 As shown, the center axes of the inner ring 10, the outer ring 20, and the tapered roller 30 are included in the same imaginary axial plane, and the center axis of the tapered roller 30 (not shown) is aligned with a point O on the center axis CL of the inner ring 10. 1 When the inner and outer raceways 11 and 21 and the rolling surface 31 of the tapered roller 30 are in a straight-opposing relationship, the apex of each cone is aligned with the point O. 1 In terms of design, the large end face 33 of the tapered roller 30 is based on Figure 4 The center is placed at the connection point O 1 The radius of curvature R is defined as a spherical shape on a straight line with the center axis of the tapered roller 30 .

[0050] In addition, the cone shapes of the inner and outer raceways 11, 21 and the rolling surface 31 of the tapered roller 30 are not limited to the shape in which the generatrix is ​​set as a straight line, but include the concept of a shape having a raised surface. Here, the generatrix refers to a line segment that generates a certain curved surface as a trajectory generated by movement around an axis. For example, the generatrix of the raceway 11 is a line segment that forms the raceway 11 on an imaginary axial plane including the center axis CL of the inner ring 10, and the generatrix of the rolling surface 31 is a line segment that forms the rolling surface 31 on an arbitrary imaginary plane including the center axis of the tapered roller 30. As the above-mentioned raised surface shape, the applicant can adopt the full raised surface shape or the cut raised surface shape disclosed in Patent Document 3, and as the cut raised surface shape of the rolling surface 31, a logarithmic raised shape, such as a shape specified by the formula of Japanese Patent Gazette No. 5037094 cited in Patent Document 3, can be adopted.

[0051] like Figure 2 , Figure 3 As shown, the large flange 12 of the inner ring 10 has: a large flange surface 12a that receives the large end surface 33 of the tapered roller 30; an outer diameter surface 12b that defines the outer diameter of the large flange 12; and a flange side chamfer 12c that connects the outer diameter side edge of the large flange surface 12a and the outer diameter surface 12b throughout the circumference. The end surface of the large flange 12 on the side opposite to the large flange surface 12a forms a part of the side surface of the inner ring 10.

[0052] The large flange surface 12a is a surface portion for the large end surface 33 of the tapered roller 30 to slide in contact in the circumferential direction. The generatrix of the large flange surface 12a is a straight line inclined relative to the radial direction. Therefore, the large flange surface 12a is a conical shape coaxial with the track surface 11. The large flange surface 12a can be any shape that can geometrically contact the large end surface 33 of the tapered roller 30 at only one point, and the generatrix shape can be changed to a concave shape (in this case, it is abutment with a contact surface, but for convenience, it is expressed as a point abutment at the abutment position between the concave bottom and the large end surface of the roller), a convex shape, etc.

[0053] The grinding overrun groove 13 of the inner ring 10 is formed into a groove shape connecting the large flange surface 12a and the raceway surface 11. The grinding overrun groove 13 is a full-circumferential groove for grinding and superfinishing the raceway surface 11 and the large flange surface 12a, and has a depth relative to the raceway surface 11 and the large flange surface 12a.

[0054] like Figure 2 As shown, the small flange 14 of the inner ring 10 prevents the plurality of tapered rollers 30 from falling off from the raceway surface 11 to the small diameter side, and is a portion used to constitute an assembly composed of the tapered rollers 30, the retainer 40, and the inner ring 10. The small flange 14 and the small diameter side ground overrun groove 15 used in conjunction with its formation are not necessarily portions as components of the inner ring.

[0055] The inner ring 10 , the outer ring 20 , and the tapered rollers 30 are formed by processing necessary portions in the order of forging, turning, and grinding.

[0056] The raceway surface 11 and the large flange surface 12a of the inner ring 10 are formed by turning and grinding a forged body, and are polished by super finishing.

[0057] like Figure 1 , Figure 3 As shown, the grinding run-over groove 13 of the inner ring 10 is turned based on a predetermined generatrix shape. The generatrix in the turning of the grinding run-over groove 13 is defined by a large-diameter straight portion inclined from the large flange surface 12a, a small-diameter straight portion inclined from the raceway surface 11, and an arc-shaped line portion connecting the large-diameter straight portion and the small-diameter straight portion. The grinding run-over groove 13 is not actively ground or super-finished, but when the raceway surface 11 and the large flange surface 12a are ground, the grinding wheel slightly rounds the large-diameter side end of the raceway surface grinding portion and the inner-diameter side end of the large flange surface grinding portion. Therefore, the substantially entire surface of the grinding run-over groove 13 is composed of a turned surface, but the connection portion of the grinding run-over groove 13 with the raceway surface 11 and the connection portion with the large flange surface 12a are slightly rounded ground surfaces or super-finished surfaces.

[0058] Here, if Figure 1 As shown in FIG. 1 , the intersection of an imaginary line formed by extending the generatrix of the raceway surface 11 of the inner ring 10 toward the grinding run-over groove 13 and an imaginary line formed by extending the generatrix of the large flange surface 12a toward the grinding run-over groove 13 is set as a reference point O. 2 . The entry angle of the grinding overrun groove 13 relative to the large flange surface 12a is set to a. In addition, the entry angle of the grinding overrun groove 13 relative to the track surface 11 is set to b. In addition, the depth of the grinding overrun groove 13 relative to the track surface 11 is set to c. In addition, the depth of the grinding overrun groove 13 relative to the large flange surface 12a is set to d. In addition, the reference point O is set to 2 The cutting width to the large flange surface 12a is set to A. 2 The cutting width to the track surface 11 is set as B. In addition, Figure 3 As shown in FIG. 1 , the width of the chamfer 32 of the tapered roller 30 in the direction along the generatrix of the large flange surface 12 a is denoted by RC.

[0059] Figure 1 The entry angles a, b, cut-in widths A, B, and depths c, d shown are physical quantities for defining the shape of the grinding run-over groove 13. However, since the rounding condition is unstable, the connection between the grinding run-over groove 13 and the track surface 11 and the large flange surface 12a is difficult to use in defining the entry angles a, b. Therefore, as the entry angles a, b, the inclination angle of the machined surface of the grinding run-over groove 13 relative to the track surface 11 and the large flange surface 12a is used.

[0060] Specifically, the entry angle a of the grinding run-over groove 13 is the acute angle formed by the large diameter side straight portion of the generatrix of the grinding run-over groove 13 relative to the inner diameter side edge of the large flange surface 12a. The entry angle b of the grinding run-over groove 13 is the acute angle formed by the small diameter side straight portion of the generatrix of the grinding run-over groove 13 relative to the large diameter side edge of the track surface 11.

[0061] The cutting width A of the grinding overrun groove 13 is the width from the inner diameter side edge of the large flange surface 12a to the direction along the generatrix of the large flange surface 12a to the reference point O. 2 The cutting width B of the grinding overrun groove 13 is the width from the large diameter side edge of the track surface 11 to the direction along the generatrix of the track surface 11 to the reference point O. 2 Length.

[0062] The entry angle a of the grinding run-over groove 13 is greater than the entry angle b. When the grinding amount of the large flange surface 12a (the cutting allowance in the direction perpendicular to the generatrix of the large flange surface 12a) fluctuates from the target value during the grinding process, Figure 3 The width W of the large flange surface 12a shown varies depending on the entry angle a of the grinding overrun groove 13. Here, the width W of the large flange surface 12a is the distance between the two ends of the generatrix of the large flange surface 12a. In the example shown in the figure, the generatrix of the large flange surface 12a is a straight line, so the length of the generatrix is ​​equivalent to the width W. Figure 1 The larger the entry angle a shown, the smaller the variation of the width W of the large flange surface 12a can be. That is, the larger the entry angle a is, the less sensitive the influence of the cutting width A is when the grinding amount of the large flange surface 12a fluctuates.

[0063] The entry angle a of the grinding run-over groove 13 may be 20° or more and 50° or less. Within this range, even if the grinding amount of the large flange surface 12a fluctuates, the effect on the size of the cut-in width A is stable, and it is easy to control the cut-in width A. More preferably, the entry angle a may be 30° or more and 40° or less.

[0064] The depth c of the grinding run-over groove 13 is the depth of the grinding run-over groove 13 considered in a direction perpendicular to an imaginary line formed by extending the generatrix of the raceway surface 11, with the large diameter side edge of the raceway surface 11 as the reference. The depth d of the grinding run-over groove 13 is the depth of the grinding run-over groove 13 considered in a direction perpendicular to an imaginary line formed by extending the generatrix of the large flange surface 12a, with the inner diameter side edge of the large flange surface 12a as the reference.

[0065] The depth c of the grinding run-over groove 13 is greater than the depth d. This is to prevent the wall thickness between the grinding run-over groove 13 and the side surface of the inner ring 10 from becoming thinner. In order to sufficiently increase the wall thickness, the depth d is preferably 0.3 mm or less.

[0066] The cutting width A of the grinding run-over groove 13 is smaller than the cutting width B. If the cutting width A is smaller than the cutting width B, it is beneficial to make the entry angle a larger than the entry angle b. The machining of the grinding run-over groove 13 is performed by turning. For the chips at this time, it is easier to discharge them to the side of the track surface 11 where a relatively wide space is obtained than to discharge them to the side of the large flange surface 12a relative to the grinding run-over groove 13. Therefore, the discharge of chips to the side of the track surface 11 enables efficient turning. By satisfying the entry angle a>b and the cutting width A<B of the grinding run-over groove 13, the discharge pressure of the chips is relatively small on the side of the entry angle b and the cutting width B during turning, and the chips are easily discharged to the side of the track surface 11. Therefore, the turning processability can be improved and the processing cost can be suppressed.

[0067] like Figure 3 As shown, the width RC of the chamfer 32 of the tapered roller 30 is the length from the outer diameter side edge of the large end surface 33 to the large end side edge of the rolling surface 31 in the direction along the generatrix of the large flange surface 12a. In the example shown in the figure, the width RC of the chamfer 32 is the same as the length from the outer diameter side edge of the large end surface 33 to the reference point O 2 The width RC of the chamfer 32 of the tapered roller 30 is 0.7 mm or less.

[0068] On the other hand, the cutting width A of the grinding run-out groove 13 is smaller than the width RC of the chamfer 32 of the tapered roller 30. The small cutting width A is adopted in order to reduce the inner diameter of the large flange surface 12a so as to reduce the inner diameter of the large flange surface 12a. Figure 3 As shown, the width W of the large flange surface 12a facing the large end surface 33 of the tapered roller 30 is sufficiently widened so that the sliding contact between the large end surface 33 of the tapered roller 30 and the large flange surface 12a does not reach the inner diameter side edge of the large flange surface 12a. Widening the width W of the large flange surface 12a is advantageous in maintaining the large end surface 33 of the tapered roller 30 and the large flange surface 12a in a good contact state even if the position of the sliding contact portion between the large end surface 33 of the tapered roller 30 and the large flange surface 12a moves. The cut-in width A can be designed to be, for example, 0.5 mm or less.

[0069] In addition, if Figure 2 , Figure 4 As shown in FIG. 1 , the acute angle formed by the generatrix of the raceway surface 11 with respect to the central axis CL of the inner ring 10 is denoted as θ. In addition, the large end diameter of the rolling surface 31 of the tapered roller 30 is denoted as Dw. Figure 2 In the geometric relationship of the roller length L shown, Figure 3 The width W of the large flange surface 12 a shown is a value satisfying the following formula 1.

[0070] W≥{Dw×(1 / 2)×Tanθ / (L / Dw)}···Equation 1

[0071] The above formula 1 is used to determine the lower limit value of the width W of the appropriate large flange surface 12a so as to Figure 2 , Figure 3 The formula shown in the figure maintains the large end face 33 of the tapered roller 30 and the large flange face 12a of the inner ring 10 in a good contact state. That is, when a radial load (dynamic equivalent load in combination with the axial load) is applied to the tapered roller bearing, the load applied to the track face 11 and the load applied to the large flange face 12a are distributed according to the inclination angle θ of the track face 11. The distribution ratio is represented by Tanθ, which is multiplied by the large end diameter Dw of the rolling surface 31, which is closely related to the bearing capacity. Generally, the load applied to the tapered roller bearing during operation is approximately less than half of the bearing capacity, so in order to take this into account, the large end diameter Dw of the rolling surface 31 is multiplied by (1 / 2). Furthermore, if the roller length L is longer, the bearing rate on the track face 11 in the above distribution ratio becomes larger, and the relationship between the roller length L and the large end diameter Dw of the rolling surface 31 is also expressed as (L / Dw) -1 The lower limit of the width W of the large flange surface 12a corresponding to the load is set by using Formula 1. Thus, even when the sliding contact portion between the large end surface 33 and the large flange surface 12a rises toward the large flange outer diameter side due to the deflection of the tapered roller 30 or the tilting of the large flange 12 of the inner ring 10 caused by a large moment load, good contact can be maintained.

[0072] In addition, the upper limit of the width W of the large flange surface 12a may be several mm depending on the purpose of supporting and guiding the large end surface 33 of the tapered roller 30, but it is preferably 3 times or less of the lower limit value obtained by Formula 1. If the width W of the large flange surface 12a is too large (that is, the outer diameter of the large flange surface 12a is too large), it is difficult for the lubricating oil to reach the sliding contact portion between the large end surface 33 of the tapered roller 30 and the large flange surface 12a, and a good lubrication state cannot be ensured.

[0073] Here, if Figure 3 As shown in FIG. 1 , the acute angle formed by the large flange surface 12a with respect to the radial direction is defined as the flange surface angle α. In addition, the contact point between the large flange surface 12a and the large end surface 33 of the tapered roller 30 and the reference point O 2 The radial height difference between the two is set as the contact point height H. The contact point height H is the basic curvature radius R of the large end surface 33 of the tapered roller 30. BASE The combination of and flange face angle α is uniquely determined. Figure 2 , Figure 4 As shown in FIG. 1 , the cone angle of the rolling surface 31 of the tapered roller 30 is β. The cone angle β of the rolling surface 31 is the angle between the cone of the rolling surface 31 and its apex O 1In addition, the contact point between the large flange surface 12a of the inner ring 10 and the large end surface 33 of the tapered roller 30 is connected to the vertex O of the cone angle β. 1 The acute angle formed by the imaginary line of the track surface 11 with respect to the generatrix of the track surface 11 is set as ρ. Figure 3 As shown, the angle ρ corresponds to the contact point height H. Here, when the large flange surface has a curvature toward the convex side of the large end surface of the tapered roller or the concave side away from the large end surface, the angle connecting the deepest or highest part of the large flange surface and the contact point of the large end surface is set to ρ.

[0074] The sliding speed in the circumferential direction of the contact point between the large flange surface 12a and the large end surface 33 of the tapered roller 30 depends on the contact point height H. Assume that at the virtual intersection point O of the raceway surface 11 of the inner ring 10 and the large flange surface 12a 2 If the above contact point exists (contact point height H = 0), the sliding speed is zero, and the distance from the reference point O 2 The higher the contact point height H is, the higher the sliding speed at the contact point is. As described above, with the adoption of a small cut-in width A, the contact point height H can be reduced by widening the large flange surface 12a toward the grinding overrun groove 13 side. Therefore, the contact point between the large flange surface 12a and the large end surface 33 of the tapered roller 30 is determined at a low position satisfying β / 7≥ρ. Setting the contact point at a low position in this way slows down the sliding speed at the sliding contact portion between the large flange surface 12a and the large end surface 33 of the tapered roller 30 to suppress the heat generation at the large flange surface 12a, which is effective in preventing the sudden temperature rise of the large flange surface 12a.

[0075] about Figure 4 The set curvature radius R of the large end surface 33 of the tapered roller 30 shown in the figure and the vertex O of the cone angle β from the rolling surface 31 1 The basic curvature radius R of the large flange surface 12a to the inner ring 10 is BASE R / R BASE , the actual curvature radius R of the large end surface 33 ACTUAL Ratio R to the set curvature radius R ACTUAL / R, the applicant can adopt the numerical range disclosed in Patent Document 3. These R / R BASE , R ACTUAL The details and technical significance of R / R are the same as those disclosed in Patent Document 3, so in the description of this embodiment, only R / R BASE , R ACTUAL / R is explained below.

[0076] Right now, Figure 4 The set curvature radius R of the large end surface 33 of the tapered roller 30 shown in FIG. 1 is the R dimension when an ideal spherical surface is formed by the large end surface 33 in design. Figure 5 As shown, if point P at the end of the large end surface 33 is considered1 , P 2 , P 3 , P 4 , click P 1 , P 2 The midpoint P 5 , click P 3 , P 4 The midpoint P 6 , through point P 1 , P 5 , P 2 The radius of curvature R 152 , through point P 3 , P 6 , P 4 The radius of curvature R 364 And through point P 1 , P 5 , P 6 , P 4 The radius of curvature R 1564 , then ideally R=R 152 =R 364 =R 1564 . Click P 1 , P 4 It is the connection point between the large end surface 33 and the chamfer 32. Point P 2 , P 3 It is the connection point between the large end surface 33 and the avoidance portion 35. In fact, Figure 6 As shown in the figure, the two ends of the large end surface 33 collapse during the grinding process, so the R 1564 One-sided R 152 , R 364 The R of one side after processing the large end surface 33 cannot be the same and is formed to be smaller. 152 , R 364 It is called the actual radius of curvature R ACTUAL .

[0077] Set the curvature radius R and the actual curvature radius R ACTUAL It is determined as follows. Figure 6 The radius of curvature R 1564 is through Figure 5 Point P shown 1 , P 5 , P 6 , P 4 These four points approximate the circle. 152 =R 364 =R 1564The measurement of the surface roughness is carried out using the "surftest surface roughness measuring machine manufactured by Mitutoyo Co., Ltd." model name: SV-3100. The measurement method is to determine the shape of the large end surface 33 of the tapered roller 30 along the generatrix using the above measuring machine, and then plot the point P. 1 , P 2 , P 3 , P 4 Then, plot the midpoint P 5 and the midpoint P 6 Calculate the radius of curvature R 152 As the passing point P 1 , P 5 , P 2 The radius of the arc curve (radius of curvature R 364 For the radius of curvature R 1564 For example, the approximate arc radius is calculated using the values ​​obtained at four points using the "multiple input" command. The shape of the large end surface 33 along the generatrix is ​​measured once in the radial direction.

[0078] Figure 3 The large flange surface 12a of the inner ring 10 shown is only Figure 6 The curvature radius R of one side of the large end face 33 of the tapered roller 30 shown is 152 , radius of curvature R 364 The actual sliding contact between the large end surface 33 and the large flange surface 12a is smaller than the set curvature radius R (R 1564 )'s actual radius of curvature R ACTUAL (R 152 , R 364 ). Accordingly, the actual contact surface pressure between the large end face 33 and the large flange surface 12a and the deflection angle of the tapered roller 30 are greater than the ideal values ​​in their respective designs. If the deflection angle and the contact surface pressure increase in an environment where the oil film is insufficient, the sliding contact between the large end face 33 and the large flange surface 12a becomes unstable and the oil film parameters decrease. If the oil film parameter exceeds 1, the large end face 33 and the large flange surface 12a become boundary lubrication at the beginning of metal contact, and the concern about sintering increases. Here, the oil film parameter is defined as Λ (=h / σ) based on the ratio of the oil film thickness h obtained by the elastic fluid lubrication theory to the composite roughness σ of the root mean square roughness of the large end face 33 and the large flange surface 12a. The actual radius of curvature R ACTUAL Verification of the practical range of the ratio to the set curvature radius R is affected by the severity of the lubrication state at the peak of the lubricating oil use temperature between the large end surface 33 and the large flange surface 12 a .

[0079] When the generatrix shape of the large flange surface 12a is straight and constant, the lubrication state between the large end surface 33 and the large flange surface 12a is determined by the actual curvature radius R ACTUALDetermined by the use temperature of the lubricant, the lubricant used in the transmission and differential is basically determined, so the viscosity of the lubricant is also determined. As the maximum condition at the peak of the use temperature of the lubricant, an extremely severe temperature condition of 120°C for 3 minutes (180 seconds) is assumed, and the actual curvature radius R is used to set the lubrication state that does not produce a sudden temperature rise while taking into account the viscosity characteristics of the lubricant in the assumed peak temperature condition. ACTUAL Ratio R to the set curvature radius R ACTUAL The threshold value of / R is used as the flange lubrication coefficient. The flange lubrication coefficient is: Flange lubrication coefficient = 120℃ viscosity × (oil film thickness h) 2 / 180 seconds. The oil film thickness h is calculated using the Karna formula. Considering the contact surface pressure between the large end surface 33 and the large flange surface 12a, the oil film thickness h, the deflection angle, and the oil film parameters, if R ACTUAL / R is set to a value that exceeds 8×10 -9 (threshold), it can be practical.

[0080] In the case of the ISO viscosity grade VG32, a lubricating oil commonly used in transmissions, the viscosity at 120°C is 7.7 cSt (=7.7 mm 2 / s). VG32 has a low viscosity at 120°C, and the lubrication state that takes the viscosity of the lubricating oil into account in the assumed peak temperature condition becomes an extremely severe condition. Therefore, it is preferred that the above R ACTUAL / R is 0.8 or more. In the case of SAE 75W-90, which is a gear lubricant commonly used in differentials, R ACTUAL / R is 0.5 or more.

[0081] like Figure 7 As shown, Figure 4 The set curvature radius R of the large end surface 33 of the tapered roller 30 shown in the figure is the same as the vertex O of the cone angle β of the rolling surface 31. 1 The basic curvature radius R of the large flange surface 12a to the inner ring 10 is BASE R / R BASE It is related to the oil film forming ability of the sliding contact portion between the large end surface 33 and the large flange surface 12a. R / R BASE The larger the value, the smaller the maximum Hertz stress p of the sliding contact portion between the large flange surface 12a and the large end surface 33. BASE The smaller it is, the larger the deflection angle.

[0082] If it will be formed in Figure 4 The oil film thickness of the sliding contact portion between the large end surface 33 and the large flange surface 12a is set to t, then Figure 7 The vertical axis is relative to R / R BASE When the oil film thickness is 0.76, t0 The ratio of t / t 0 Indicates. Figure 7 , in R / R BASE When R / R BASE When the ratio exceeds 0.9, the oil film thickness t decreases sharply. In terms of the optimal value of the oil film thickness, R / R is particularly preferred. BASE It is greater than 0.75 and less than 0.87.

[0083] In this tapered roller bearing, as described above, the cut-in width A of the grinding run-out groove 13 is reduced to make the width W of the large flange surface 12a wider toward the grinding run-out groove 13, thereby optimizing the large flange surface 12a so as to maintain a good contact state with the large end surface 33 of the tapered roller 30, thereby also being able to adjust the R / R BASE , R ACTUAL Each of / R expands the permissible range.

[0084] Specifically, R / R BASE It may be 0.70 to 0.95, preferably 0.70 to 0.90, and most preferably 0.75 to 0.87.

[0085] In addition, R ACTUAL / R may be 0.3 or more, preferably 0.5 or more, and most preferably 0.8 or more. ACTUAL The tapered roller 30 manufactured with / R in the range of not less than 0.3 and not more than 0.5 can maintain good contact with the large end face 33 of the tapered roller 30 by optimizing the large flange surface 12a as described above, even if there is a slight disturbance in the movement of the sliding contact portion such as the deviation of the tapered roller 30 or the tilting of the large flange 12 due to a large moment load.

[0086] Therefore, it is allowed that the plurality of tapered rollers 30 include R / R BASE 0.70 or more and 0.95 or less, R ACTUAL The tapered roller 30 manufactured with / R being 0.3 or more and less than 0.5 can improve the yield rate of the tapered roller 30 .

[0087] The above-mentioned oil film parameters depend on the combined roughness of the large end face 33 of the tapered roller 30 and the large flange face 12a of the inner ring 10. By mirror finishing the large end face 33 and the large flange face 12a, the oil film formation can be improved to maintain a good oil film thickness. Specifically, the surface roughness of the large flange face 12a is 0.1 μmRa or less, preferably 0.08 μmRa or less. In addition, the surface roughness of the large end face 33 is 0.12 μmRa or less, preferably 0.1 μmRa or less. Here, the surface roughness refers to the arithmetic mean roughness Ra specified in JIS standard B0601:2013 "Product Geometric Characteristics Specification (GPS)-Surface Texture: Profile Curve Method-Terms, Definitions and Surface Texture Parameters".

[0088] In addition, in order to prevent the large end face 33 of the tapered roller 30 from sliding in contact (edge ​​contact) with the outer diameter side edge of the large flange surface 12a of the inner ring 10, it is also possible to Figure 1 The large flange surface 12a and the flange side chamfer 12c shown form an avoidance surface. Figure 8 . As shown in the figure, an escape surface 12d is formed between the large flange surface 12a and the flange side chamfer 12c. The escape surface 12d is bent toward the outer diameter surface 12b from the outer diameter side edge of the large flange surface 12a toward the flange side chamfer 12c. The generatrix of the escape surface 12d is a circular arc with a curvature radius of Rd.

[0089] Here, the imaginary intersection of an imaginary line formed by extending the generatrix of the large flange surface 12a and an imaginary line formed by extending the generatrix of the flange side chamfer 12c is considered, and the distance from the imaginary intersection in the direction along the generatrix of the large flange surface 12a to the position having the same diameter as the outer diameter surface 12b is set as the width L of the flange side chamfer 12b. 1 The distance from the outer diameter side edge of the large flange surface 12a to the imaginary intersection in the direction along the generatrix of the large flange surface 12a is defined as the width L of the avoidance surface 12d. 2 In order to prevent the width L of the avoidance surface 12d 2 The curvature radius Rd of the avoidance surface 12d is preferably 2 mm or less. 2 , preferably the width L of the flange side chamfer 12c 1 Less than 1mm.

[0090] In addition, preferably by Figure 1 , Figure 3 , Figure 8The combination of the optimization of the large flange surface 12a of the inner ring 10 and the heat treatment characteristics of the inner ring 10 as shown in the figure achieves further functional improvement. That is, when the lubrication conditions of the sliding contact between the large end surface 33 of the tapered roller 30 and the large flange surface 12a are severe, there is a concern about surface damage due to metal contact, so the large flange surface 12a side can be provided with a characteristic of delaying surface damage.

[0091] Specifically, the grain size number of the original austenite grains of the large flange surface 12a of the inner ring 10 can be 6 or above. Here, the grain size number of the original austenite grains refers to the grain size number specified in the JIS standard G0551:2013 "Steel-Microscope test method for grain size". The original austenite grains refer to the grains of austenite after quenching. The boundary (grain boundary) of the original austenite grains is called the original austenite grain boundary, and the original austenite grains are surrounded by the original austenite grain boundary. The finer the grain size of the original austenite grains (the larger the grain size number), the more the development of damage can be delayed by the grain boundaries. Therefore, for the metal base material structure in sliding contact such as the large flange surface 12a, the grain size number is preferably 6 or above, more preferably 10 or above, and further preferably 11 or above.

[0092] In addition, the large flange surface 12a of the inner ring 10 can be formed by a nitrided layer with a nitrogen content of 0.05wt% or more, or a nitrogen penetration depth of 0.1mm or more. The nitrided layer with a nitrogen content of 0.05wt% or more has temper softening resistance due to its nitrogen-rich effect. Therefore, the resistance to local heat generation caused by sliding contact of the large flange surface 12a is improved. The nitrided layer is a layer with an increased nitrogen content formed on the surface of the large flange surface 12a, for example, by carbonitriding, nitriding, nitriding and other treatments. The nitrogen content of the nitrided layer is preferably 0.1wt% or more and 0.7wt% or less. If the nitrogen content is 0.1wt% or more, it can be expected that the rolling life under the condition of foreign matter mixing can be improved. If the nitrogen content exceeds 0.7wt%, holes called voids appear, or excessive retained austenite causes hardness to disappear, and the concern of short life increases. The nitrogen content is a value of 10 μm in the surface layer of the large flange surface 12 a after grinding, and can be measured by, for example, EPMA (wavelength dispersive X-ray microanalyzer).

[0093] Figure 2The inner ring 10, outer ring 20 and tapered roller 30 shown are made of high carbon chromium bearing steel (for example, SUJ2 material). In order to form a nitride layer, the inner ring 10, outer ring 20 and tapered roller 30 are subjected to heat treatment. The heat treatment method may be the method disclosed in Patent Document 3 or another method. The materials of the inner ring 10, outer ring 20 and tapered roller 30 are not limited to high carbon chromium bearing steel. For example, the inner ring 10 and outer ring 20 may also be carburized steel such as chrome steel or chrome-molybdenum steel, and the carburizing quenching and tempering that has always existed may be used as the heat treatment.

[0094] Tests were conducted to verify the effectiveness of the tapered roller bearing. The verification conditions and basic specifications of the test product in the first test are as follows (hereinafter, refer to Figure 1 to Figure 3 ).

[0095] <Verification conditions>

[0096] Test bearing: Model 32007X (JIS mm series standard tapered roller bearing)

[0097] Bearing size: φ35×φ62×18

[0098] Lubricating oil: turbine oil ISO VG32 (viscosity 32mm 2 / s@40℃,5.5mm 2 / s@100℃)

[0099] Load conditions: Radial load = 0.3Cr (Cr is the basic rated dynamic load)

[0100] Rotation speed: 4000r / min

[0101] Lubricating oil quantity: dripping oil supply 8mL / min

[0102] <Quality of test products>

[0103] ·R ACTUAL / R=0.35

[0104] ·Width W of large flange surface 12a = 1.65

[0105] ·Surface roughness of large flange surface 12a = 0.029 μmRa

[0106] ·Surface roughness of large end surface 33 = 0.046 μmRa

[0107] ·R / R BASE =0.79

[0108] In addition to the above basic specifications, various specifications such as the width RC of the chamfer 32 of the tapered roller 30 and the cutting width A of the ground runout groove 13 were evaluated as follows. Table 1 shows the evaluation results.

[0109] [Table 1]

[0110]

[0111] As shown in Table 1 above, in test pieces 1 to 3 where the width RC of the chamfer 32 is ≤ 0.69 mm and the cut-in width A is less than the width RC, the temperature rise can be suppressed and sufficient bearing life can be obtained even under severe lubrication conditions. In test piece 4, the width RC is 0.65 mm, which is smaller than that of test piece 3, but the cut-in width A is 0.73 mm, which is larger than the width RC, so that even if the temperature rises easily, it does not become a temperature that has a negative impact on the bearing life. In test pieces 5 and 6 where the width RC is further reduced and the cut-in width A is further increased, the temperature rise cannot be suppressed and the bearing life cannot be expected. That is, it can be considered that the width RC is less than 0.7 mm and the cut-in width A is less than the width RC, which is effective in suppressing the temperature rise even under severe lubrication conditions.

[0112] The verification conditions and basic specifications of the test products in the second test are as follows.

[0113] <Verification conditions>

[0114] Test bearing: Model 32007X (JIS mm series standard tapered roller bearing)

[0115] Bearing size: φ35×φ62×18

[0116] Lubricating oil: turbine oil ISO VG32 (viscosity 32mm 2 / s@40℃,5.5mm 2 / s@100℃)

[0117] Load conditions: Radial load = 0.3Cr (Cr is the basic rated dynamic load)

[0118] Rotation speed: 4000r / min

[0119] Lubricating oil quantity: dripping oil supply 8mL / min

[0120] <Quality of test products>

[0121] ·R ACTUAL / R=0.54

[0122] ·Width W of large flange surface 12a = 1.69

[0123] ·Surface roughness of large flange surface 12a = 0.039 μmRa

[0124] ·Surface roughness of large end surface 33 = 0.032 μmRa

[0125] ·R / R BASE =0.75

[0126] In the second test, in addition to the above basic specifications, various specifications were evaluated as follows, in which the ratio of the taper angle β to the angle ρ was constant, the width RC of the chamfer 32 of the tapered roller 30 and the cutting width A of the ground runout groove 13 were different. Table 2 shows the evaluation results.

[0127] [Table 21

[0128]

[0129] As shown in Table 2 above, when β / ρ is 8.0, in test pieces 7 to 9 where the width RC of the chamfer 32 is ≤0.69 mm and the cut-in width A is less than the width RC, the temperature rise can be suppressed and sufficient bearing life can be obtained even under severe lubrication conditions. In test piece 10, the width RC is 0.65 mm, which is smaller than that of test piece 3, but the cut-in width A is 0.77 mm, which is larger than the width RC, so that even if the temperature rises easily, it does not become a temperature that has a negative impact on the bearing life. In test pieces 11 and 12 where the width RC is further reduced and the cut-in width A is further increased, the temperature rise cannot be suppressed and the bearing life cannot be expected. That is, when β / ρ=8.0 (β / 8=ρ), it can be considered that the width RC is less than 0.7 mm and the cut-in width A is less than the width RC, which is effective in suppressing the temperature rise even under severe lubrication conditions.

[0130] The verification conditions and basic specifications of the test products in the third test are as follows.

[0131] <Verification conditions>

[0132] Test bearing: Model 32007X (JIS mm series standard tapered roller bearing)

[0133] Bearing size: φ35×φ62×18

[0134] Lubricating oil: turbine oil ISO VG32 (viscosity 32mm 2 / s@40℃,5.5mm 2 / s@100℃)

[0135] Load conditions: Radial load = 0.3Cr (Cr is the basic rated dynamic load)

[0136] Rotation speed: 4000r / min

[0137] Lubricating oil quantity: dripping oil supply 8mL / min

[0138] <Quality of test products>

[0139] ·R ACTUAL / R=0.61

[0140] ·Width W of large flange surface 12a = 1.71

[0141] ·Surface roughness of large flange surface 12a = 0.023 μmRa

[0142] ·Surface roughness of large end surface 33 = 0.025 μmRa

[0143] ·R / R BASE =0.76

[0144] In the third test, in addition to the above basic specifications, various specifications were evaluated as follows, in which the cut width A was constant and the width RC of the chamfer 32 of the tapered roller 30 and the ratio of the taper angle β to the angle ρ were different. Table 3 shows the evaluation results.

[0145] [Table 3]

[0146] [Table 3]

[0147]

[0148] As shown in Table 3, when the cutting width A is 0.7 mm, in the test pieces 13 to 15 where the width RC of the chamfer 32 is ≤ 0.65 mm and β / ρ is 7.1 or more, the temperature rise can be suppressed even under severe lubrication conditions and sufficient bearing life can be obtained. In the test piece 16, the width RC is 0.55 mm, which is smaller than the test pieces 13 to 15, but β / ρ is 6.7, which is smaller than the test pieces 13 to 15, so that even if the temperature rises easily, it does not become a temperature that has a negative impact on the bearing life. In the test pieces 17 and 18 where the width RC is further reduced and β / ρ is further reduced, the temperature rise cannot be suppressed and the bearing life cannot be expected. That is, when the cutting width A is 0.7 mm, it can be considered that the width RC is less than 0.7 mm and β / ρ≥7 (β / 7≥ρ) is effective in suppressing the temperature rise even under severe lubrication conditions.

[0149] Considering the results of the second test and the third test together, it can be considered that the width RC is 0.7 mm or less, the cut width A<width RC, and β / 7≥ρ are particularly effective in suppressing the temperature rise even under severe lubrication conditions.

[0150] As described above, the tapered roller bearing is formed to a particularly small size such that the width RC of the chamfer 32 of the tapered roller 30 is 0.7 mm or less and the cut-in width A of the grinding overrun groove 13 is less than the width RC, thereby making it possible to widen the width W of the large flange surface 12a to be formed to a width sufficient to bear the large end surface 33 of the tapered roller 30. Therefore, the contact relationship between the large flange surface 12a and the large end surface 33 can be optimized, the wedge effect acting between the large flange surface 12a and the large end surface 33 can be well exerted, and the oil film forming ability of the sliding contact portion between the large flange surface 12a and the large end surface 33 can be improved. Therefore, even when the tapered roller bearing is used under severe lubrication conditions, it is possible to prevent sudden temperature rise and allow the bearing to rotate smoothly.

[0151] For example, when the lubrication conditions are particularly severe and the lubrication of the sliding contact portion between the large flange surface 12a and the large end surface 33 is at the level of a boundary film, it is also considered that the large flange surface 12a side is worn. If the wear of the large flange surface 12a reaches the grinding overrun groove 13, the large end surface 33 and the inner diameter side edge of the large flange surface 12a will be in angular contact, resulting in a large stress concentration, which will cause instability in the sliding action of the tapered roller 30 and cause a concern of sudden temperature rise. In contrast, in the tapered roller bearing, even if the large flange surface 12a is worn, the width W of the large flange surface 12a is relatively wide and fully opposed to the large end surface 33, and the grinding overrun groove 13 (cut-in width A) is relatively small, so the wear of the large flange surface 12a does not reach the boundary with the grinding overrun groove 13 (the inner diameter side edge of the large flange surface 12a), thereby ensuring the end area on the inner diameter side of the large flange surface 12a. Therefore, even under such particularly harsh lubrication conditions, the large flange surface 12a and the large end surface 33 can be kept in a state of proper contact.

[0152] In addition, the cone angle β / 7 of the tapered roller 30 of the tapered roller bearing is ≥ angle ρ, so the large flange surface 12a of the inner ring 10 and the large end surface 33 relative to the reference point O 2 The radial contact height H is low, which prevents an increase in the sliding speed at the sliding contact portion between the large flange surface 12a and the large end surface 33, and suppresses the heat generation of the large flange surface 12a to prevent a sudden temperature increase.

[0153] In this way, the tapered roller bearing can optimize the contact relationship between the large flange surface 12a of the inner ring 10 and the large end surface 33 of the tapered roller 30, thereby improving the oil film forming ability in the sliding contact portion and preventing an increase in the sliding speed in the sliding contact portion. Therefore, even when the tapered roller bearing is used under severe lubrication conditions, it is possible to prevent sudden temperature rise and allow the bearing to rotate smoothly.

[0154] In addition, the entry angle a>b and the cut-in width A<B of the grinding run-out groove 13 of the inner ring 10 of the tapered roller bearing are excellent in turning processability of the grinding run-out groove 13, and when the grinding amount of the large flange surface 12a fluctuates, it is difficult to affect the change amount of the width W of the large flange surface 12a (the size of the cut-in width A), and the grinding process of the large flange surface 12a does not become difficult. Therefore, for this tapered roller bearing, there is no need to worry about the processing cost, and the cost is not particularly high.

[0155] In addition, the depth c of the ground overrun groove 13 of the inner ring 10 of the tapered roller bearing is greater than d, so that the stress of the large flange 12 caused by the load applied from the large end surface 33 of the tapered roller 30 to the large flange surface 12a of the inner ring 10 can be reduced, thereby improving the strength of the large flange 12. This is helpful in suppressing the tilting of the large flange 12 due to interference and the like, and appropriately maintaining the contact state between the large flange surface 12a and the large end surface 33.

[0156] Furthermore, since the depth d of the ground overrun groove 13 of the inner ring 10 of the tapered roller bearing is 0.3 mm or less, the strength of the large flange 12 can be reliably improved.

[0157] In addition, the entry angle a of the grinding overrun groove 13 of the inner ring 10 of the tapered roller bearing is in the range of 20°≤a≤50°. Therefore, even if the grinding amount of the large flange surface 12a fluctuates, the influence on the size of the change in the width W of the large flange surface 12a (cut-in width A) is stable, and the width W (cut-in width A) of the large flange surface 12a can be easily controlled.

[0158] In addition, the width W of the large flange surface 12a of the inner ring 10 of the tapered roller bearing is a value that satisfies the above-mentioned formula 1, so that the large flange surface 12a and the large end surface 33 of the tapered roller 30 can be fully opposed to each other, and good contact can be maintained even when the sliding contact portion between the large end surface 33 and the large flange surface 12a rises toward the outer diameter side of the large flange due to interference.

[0159] In addition, the grain size number of the prior austenite grains of the large flange surface 12 a of the inner ring 10 of the tapered roller bearing is 6 or more, so that surface damage caused by metal contact with the large end surface 33 of the tapered roller 30 can be delayed.

[0160] Furthermore, since the large flange surface 12 a of the inner ring 10 of the tapered roller bearing is formed of a nitride layer having a nitrogen content of 0.05 wt % or more, surface damage caused by metal contact with the large end surface 33 of the tapered roller 30 can be delayed.

[0161] In addition, the surface roughness of the large flange surface 12a of the inner ring 10 of the tapered roller bearing is less than 0.1μmRa, and the surface roughness of the large end surface 33 of the tapered roller 30 is less than 0.12μmRa, so that the oil film parameters between the large flange surface 12a and the large end surface 33 can be improved, so that the oil film is formed well.

[0162] In addition, for this tapered roller bearing, R / R BASE is 0.70 or more and 0.95 or less, even if the R ACTUAL / R is 0.3 or more and less than 0.5, and can be used even under severe lubrication conditions. In addition, compared with the tapered roller bearing disclosed in Patent Document 3, the yield of the tapered roller 30 can be improved, and it can be provided at a relatively low cost.

[0163] The tapered roller bearing is suitable for use in supporting a rotating shaft of a transmission or differential for an automobile, where lubricating oil is supplied from the outside to the inside of the bearing by splash lubrication or oil bath lubrication. Fig. 9 An example of its use will be described. Fig. 9 An example of a differential for an automobile is shown.

[0164] Fig. 9 The differential shown in the figure includes: a driving pinion 104 supported by two tapered roller bearings 102 and 103 so as to be rotatable relative to a housing 101; a ring gear 105 meshing with the driving pinion 104; and a differential gear mechanism (not shown), which are accommodated in a housing 101 in which gear lubricating oil is sealed. The gear lubricating oil also becomes lubricating oil for lubricating each tapered roller bearing 102 and 103, and is supplied to the bearing side surface by splashing or oil bath lubrication.

[0165] based on Fig.10 Another use example of the tapered roller bearing will be described. Fig.10 An example of a transmission for an automobile is shown.

[0166] Fig.10 The transmission shown is a multi-stage transmission that changes the speed ratio in stages, and has tapered roller bearings 202 to 205 that support its rotating shaft (for example, the input shaft 201 that inputs the rotation of the engine) so that it can rotate, and are provided with tapered roller bearings involved in any of the above-mentioned embodiments. The transmission shown in the figure changes the speed ratio of the rotation transmitted from the input shaft 201 to the output shaft side by selectively engaging a clutch (not shown). In addition, in the transmission, the lubricating oil (transmission lubricating oil) splashes with the rotation of the gears, and the lubricating oil adheres to the side surfaces of each tapered roller bearing 202 to 205.

[0167] Fig. 9 , Fig.10 The tapered roller bearings 102, 103, 202 to 205 shown in the example are Figure 1 The structure is equivalent to the tapered roller bearing shown in the figure, so even if a thin lubrication environment is used for low oil consumption, it is possible to prevent sudden temperature rise caused by sliding contact between the large flange surface of the inner ring and the large end surface of the tapered roller during the initial lubrication at the beginning of operation. In addition, even if the operating temperature rises and the viscosity of the lubricating oil decreases, stable sliding contact can be maintained and a good oil film can be formed, thereby preventing damage to their two surfaces.

[0168] However, the tapered roller bearing is not limited to transmission applications, but can be applied to other applications under extremely severe lubrication conditions. The embodiments disclosed herein should be understood to be illustrative rather than restrictive in all respects. Therefore, the scope of the present invention is indicated by the claims rather than the above description, and is intended to include all changes within the meaning and scope equivalent to the claims.

[0169] Description of reference numerals:

[0170] 10…inner ring; 11…raceway surface; 12…large flange; 12a…large flange surface; 13…ground overrun groove; 20…outer ring; 30…tapered roller; 31…rolling surface; 32…chamfer; 33…large end surface; 102, 103, 202~205…tapered roller bearing; 104…driving pinion (rotating part); 201…input shaft (rotating part).

Claims

1. A tapered roller bearing comprising: an inner ring; an outer ring; a plurality of tapered rollers disposed between the inner ring and the outer ring; and a retainer for accommodating the tapered rollers. The tapered roller has: a rolling surface formed in a conical shape; a chamfer continuous with the large diameter side of the rolling surface; and a large end surface continuous with the chamfer. The inner ring has: a raceway surface formed in a conical shape; a large flange surface receiving the large end surface of the tapered roller; and a groove-shaped ground overrun groove connecting the large flange surface and the raceway surface. The tapered roller bearing is characterized in that: When the intersection of an imaginary line formed by extending the generatrix of the raceway surface toward the grinding run-over groove and an imaginary line formed by extending the generatrix of the large flange surface toward the grinding run-over groove is set as a reference point, the cut-in width from the reference point to the large flange surface is set as A, and the width of the chamfer of the tapered roller in the direction along the generatrix of the large flange surface is set as RC, the width RC is less than 0.7 mm, and A<RC, When the depth of the ground clearance groove relative to the raceway surface of the inner ring is c, and the depth of the ground clearance groove relative to the large flange surface is d, c>d.

2. The tapered roller bearing according to claim 1, characterized in that: When the taper angle of the rolling surface is β and the acute angle formed by the imaginary line connecting the contact point between the large flange surface and the large end surface of the tapered roller to the vertex of the taper angle β with respect to the generatrix of the raceway surface is ρ, β / 7≥ρ.

3. The tapered roller bearing according to claim 1 or 2, characterized in that: When the entry angle of the grinding run-over groove relative to the large flange surface of the inner ring is set to a, and the entry angle of the grinding run-over groove relative to the raceway surface is set to b, a>b, When A is a cut width from the reference point to the large flange surface, and B is a cut width from the reference point to the raceway surface, A<B.

4. The tapered roller bearing according to claim 1 or 2, characterized in that: When the depth of the ground overrun groove relative to the large flange surface of the inner ring is denoted as d, the depth d is 0.3 mm or less.

5. The tapered roller bearing according to claim 1 or 2, characterized in that: When an entry angle of the grinding overrun groove relative to the large flange surface of the inner ring is set to a, 20°≤a≤50°.

6. The tapered roller bearing according to claim 1 or 2, characterized in that: When the acute angle formed by the generatrix of the raceway surface with respect to the central axis of the inner ring is θ, the large end diameter of the rolling surface of the tapered roller is Dw, the roller length of the tapered roller is L, and the width of the large flange surface is W, the width W is a value satisfying the following formula 1, W≥{Dw×(1 / 2)×Tanθ / (L / Dw)}···Equation 1.

7. A tapered roller bearing comprising: an inner ring; an outer ring; a plurality of tapered rollers disposed between the inner ring and the outer ring; and a retainer for accommodating the tapered rollers. The tapered roller has: a rolling surface formed in a conical shape; a chamfer continuous with the large diameter side of the rolling surface; and a large end surface continuous with the chamfer. The inner ring has: a raceway surface formed in a conical shape; a large flange surface receiving the large end surface of the tapered roller; and a groove-shaped ground overrun groove connecting the large flange surface and the raceway surface. The tapered roller bearing is characterized in that: When the intersection of an imaginary line formed by extending the generatrix of the raceway surface toward the grinding run-over groove and an imaginary line formed by extending the generatrix of the large flange surface toward the grinding run-over groove is set as a reference point, the cut-in width from the reference point to the large flange surface is set as A, and the width of the chamfer of the tapered roller in the direction along the generatrix of the large flange surface is set as RC, the width RC is less than 0.7 mm, and A<RC, When the acute angle formed by the generatrix of the raceway surface with respect to the central axis of the inner ring is θ, the large end diameter of the rolling surface of the tapered roller is Dw, the roller length of the tapered roller is L, and the width of the large flange surface is W, the width W is a value satisfying the following formula 1, W≥{Dw×(1 / 2)×Tanθ / (L / Dw)}···Equation 1.

8. The tapered roller bearing according to claim 1 or 7, characterized in that: The grain size number of the original austenite grains on the large flange surface of the inner ring is 6 or above.

9. The tapered roller bearing according to claim 1 or 7, characterized in that: The large flange surface of the inner ring is formed of a nitrided layer having a nitrogen content of 0.05 wt % or more.

10. The tapered roller bearing according to claim 1 or 7, characterized in that: The surface roughness of the large flange surface of the inner ring is 0.1 μmRa or less, and the surface roughness of the large end surface of the tapered roller is 0.12 μmRa or less.

11. The tapered roller bearing according to claim 1 or 7, characterized in that: The set curvature radius of the large end surface of the tapered roller is set as R, and the basic curvature radius from the vertex of the cone angle of the rolling surface to the large flange surface of the inner ring is set as R BASE When R / R BASE 0.70 or more and 0.95 or less, When the actual curvature radius of the large end surface of the tapered roller is set to R ACTUAL When R of at least one of the plurality of tapered rollers is ACTUAL / R is 0.3 or more.

12. The tapered roller bearing according to claim 1 or 7, characterized in that: The tapered roller bearing supports a rotating part of a transmission or a differential of an automobile.

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