Tapered roller bearing

Abstract

To provide a tapered roller bearing capable of suppressing vibration at rotation.SOLUTION: A tapered roller bearing 11 includes an outer ring 12 having an outer ring raceway surface 12a, and a tapered roller 14 having a rolling surface 14a coming into contact with the outer ring raceway surface 12a. An angle of the outer ring raceway surface 12a formed relative to a center axis of the outer ring 12 is 35° or greater. A flange 12b protruding radially inward further than a large diameter side end 12al of the outer ring raceway surface 12a is formed on the outer ring 12. The flange 12b has a flange surface 12d which is brought into contact with a large end surface 14B of the tapered roller 14, and a flange back surface 12e which is positioned closer to a radial outer side than a small diameter side end 12ds of the flange surface 12d. Surface roughness Ra of the flange surface 12d is 0.32 μm or less. Surface roughness of the flange back surface 12e is 3.20 μm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0001] The present invention relates to a tapered roller bearing.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2016-196944 (Patent Document 1) discloses a tapered roller bearing provided with a flange portion that protrudes in the inner diameter direction only at the large-diameter side end portion of the outer ring raceway surface. The flange portion has a flange surface disposed radially inward with respect to the large-diameter side end portion of the outer ring raceway surface, and a flange back surface disposed radially outward with respect to the small-diameter side end portion of the flange surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, as a result of investigations, the inventors of the present invention have confirmed that there is room for improvement in the tapered roller bearing described in Patent Document 1 from the viewpoint of suppressing vibration during bearing rotation.

[0005] The main object of the present invention is to provide a tapered roller bearing in which vibration during rotation is suppressed.

Means for Solving the Problems

[0006] [[ID=...]] A tapered roller bearing according to one embodiment of the present invention comprises an outer ring having an outer ring raceway surface and tapered rollers having rolling surfaces in contact with the outer ring raceway surface. The angle between the outer ring raceway surface and the central axis of the outer ring is 35° or more. The outer ring has a flange portion that protrudes radially inward from the large-diameter end of the outer ring raceway surface. The flange portion has a flange surface that contacts the large-end surface of the tapered roller and a flange back surface that is located radially outward from the small-diameter end of the flange surface. The surface roughness Ra of the flange surface is 0.32 μm or less. The surface roughness Ra of the flange back surface is 3.20 μm or less.

[0007] In the above-described tapered roller bearing, it is preferable that the surface roughness Ra of the flange surface is greater than 0.15 μm, and the ratio obtained by dividing the surface roughness Ra of the flange surface by the surface roughness Ra of the back surface of the flange is 0.20 or more and 2.13 or less.

[0008] In the above-described tapered roller bearing, it is preferable that the surface roughness Ra of the flange surface is 0.15 μm or less, and the ratio obtained by dividing the surface roughness Ra of the flange surface by the surface roughness Ra of the back surface of the flange is 0.09 or more and 1.00 or less.

[0009] Another embodiment of the present invention provides a tapered roller bearing comprising an outer ring having an outer ring raceway surface and tapered rollers having rolling surfaces in contact with the outer ring raceway surface. The angle between the outer ring raceway surface and the central axis of the outer ring is 35° or more. The outer ring has a flange portion that protrudes radially inward from the large-diameter end of the outer ring raceway surface. The flange portion has a flange surface in contact with the large-end surface of the tapered roller and a flange back surface located radially outward from the small-diameter end of the flange surface. The surface roughness Ra of the flange surface is 0.50 μm or less. The surface roughness Ra of the flange back surface is 2.50 μm or less.

[0010] In the above-described tapered roller bearing, the ratio obtained by dividing the surface roughness Ra of the flange surface by the surface roughness Ra of the flange back surface is between 0.31 and 3.33. [Effects of the Invention]

[0011] According to the present invention, a tapered roller bearing in which vibration during rotation is suppressed can be provided. [Brief explanation of the drawing]

[0012] [Figure 1] This is a partial cross-sectional view showing a tapered roller bearing according to this embodiment. [Figure 2] This is a partial cross-sectional view illustrating the first state achieved during the process of assembling a cage and a plurality of tapered rollers as an integrated unit onto the outer ring in the manufacturing method of a tapered roller bearing according to this embodiment. [Figure 3] This is a partial cross-sectional view illustrating a second state, which is realized after the first state shown in Figure 2, during the process of assembling the cage and a plurality of tapered rollers as a single unit onto the outer ring in the manufacturing method of a tapered roller bearing according to this embodiment. [Figure 4] This is a partial cross-sectional view illustrating a third state realized after the second state shown in Figure 3 during the process of assembling the cage and a plurality of tapered rollers as a single unit onto the outer ring in the manufacturing method of a tapered roller bearing according to this embodiment. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings. Hereinafter, the direction along the central axis of the outer ring of the tapered roller bearing according to this embodiment will be simply referred to as the axial direction, the radial direction with respect to the central axis will be simply referred to as the radial direction, and the circumferential direction with respect to the central axis will be simply referred to as the circumferential direction.

[0014] (Embodiment 1) (Construction of a tapered roller bearing) As shown in Figure 1, the tapered roller bearing 11 according to this embodiment 1 comprises an outer ring 12, an inner ring 13, a plurality of tapered rollers 14, and a cage 15.

[0015] The outer ring 12 has an outer ring raceway surface 12a on its inner circumferential surface. The inner ring 13 has an inner ring raceway surface 13a on its outer circumferential surface.

[0016] Each of the plurality of tapered rollers 14 is arranged side by side in the circumferential direction. Each of the plurality of tapered rollers 14 has a rolling surface 14a and a large end face 14b. The rolling surface 14a of each of the plurality of tapered rollers 14 contacts each of the outer ring raceway surface 12a and the inner ring raceway surface 13a. The large end face 14b of each of the plurality of tapered rollers 14 contacts the flange surface 12d of the outer ring 12 described later. Each of the plurality of tapered rollers 14 is held by a cage 15 so that the interval between two adjacent tapered rollers 14 in the circumferential direction falls within a certain range.

[0017] The cage 15 is formed with a plurality of pockets for accommodating and holding each of the plurality of tapered rollers 14. Each pocket of the cage 15 is formed with a claw 15d (see FIG. 2) protruding from the inner circumferential surface of each pocket toward the inside of the pocket. A notch 15e is formed on the large-diameter side of the cage 15 to avoid interference with the flange portion 12b of the outer ring 12.

[0018] The detailed configuration of the outer ring 12 will be described below.

[0019] The outer ring raceway surface 12a is inclined with respect to the central axis of the outer ring 12. The angle α (contact angle) formed by the outer ring raceway surface 12a with respect to the central axis of the outer ring 12 is 35° or more. In FIG. 1, the broken line C1 indicates a virtual straight line extending parallel to the central axis of the outer ring 12.

[0020] The outer ring 12 is formed with a flange portion 12b protruding radially inward from the large-diameter side end portion 12al of the outer ring raceway surface 12a. In the tapered roller bearing 11, the flange portion 12b is formed only on the large-diameter side of the outer ring 12, and the inner ring 13 is not formed with a flange portion. The flange portion 12b has a top portion 12c located most inward in the radial direction, a flange surface 12d arranged on the outer ring raceway surface 12a side with respect to the top portion 12c in the axial direction, and a flange back surface 12e arranged on the side opposite to the flange surface 12d with respect to the top portion 12c in the axial direction.

[0021] The flange surface 12d contacts the large end surface 14b of the tapered roller 14. The flange surface 12d is inclined with respect to the central axis of the outer ring 12. The flange surface 12d has a small-diameter side end portion 12ds and a large-diameter side end portion 12dl. The large-diameter side end portion 12dl is axially continuous with the large-diameter side end portion 12al of the outer ring raceway surface 12a, for example, via a grinding relief portion. The small-diameter side end portion 12ds of the flange surface 12d is arranged on the opposite side of the large-diameter side end portion 12al of the outer ring raceway surface 12a with respect to the large-diameter side end portion 12dl of the flange surface 12d in the axial direction.

[0022] The back surface 12e of the flange does not contact the large end surface 14b of the tapered roller 14. The back surface 12e of the flange is arranged on the opposite side of the outer ring raceway surface 12a with respect to the flange surface 12d in the axial direction. The back surface 12e of the flange is inclined with respect to the central axis of the outer ring 12. The back surface 12e of the flange has a small-diameter side end portion 12es and a large-diameter side end portion 12el. The small-diameter side end portion 12es is axially continuous with the small-diameter side end portion 12ds of the flange surface 12e, for example, via a chamfer portion. The large-diameter side end portion 12el of the back surface 12e of the flange is arranged on the opposite side of the outer ring raceway surface 12a with respect to the small-diameter side end portion 12es of the back surface 12e of the flange in the axial direction. The angle β formed by the back surface 12e of the flange with respect to the central axis of the outer ring 12 is, for example, 35° or more and 60° or less. In FIG. 1, the broken line C2 indicates a virtual straight line extending parallel to the central axis of the outer ring 12.

[0023] The surface roughness Ra of the flange surface 12d is 〈0.32 μm. The "surface roughness Ra" is the arithmetic mean roughness Ra defined in JIS B0601 (2001 edition). The surface roughness Ra of the flange surface 12d is, for example, 〈0.15 μm or more. Note that the surface roughness Ra of the flange surface 12d may be smaller than 0.15 μm.

[0024] The surface roughness Ra of the back surface 12e of the flange is 〈3.20 μm. Preferably, the surface roughness Ra of the back surface 12e of the flange is 〈2.50 μm. More preferably, the surface roughness Ra of the back surface 12e of the flange is 〈1.60 μm. The surface roughness Ra of the back surface 12e of the flange is, for example, 〈0.15 μm or more. Note that the surface roughness Ra of the back surface 12e of the flange may be smaller than 0.15 μm.

[0025] When the surface roughness Ra of the flange surface 12d is greater than 0.15 μm and 0.32 μm or less, the ratio obtained by dividing the surface roughness Ra of the flange surface 12d by the surface roughness Ra of the flange back surface 12e is preferably 0.20 or more. More preferably, the above ratio is 2.13 or less.

[0026] When the surface roughness Ra of the flange surface 12d is 0.15 μm or less, the ratio obtained by dividing the surface roughness Ra of the flange surface 12d by the surface roughness Ra of the flange back surface 12e is preferably 0.09 or more. More preferably, the above ratio is 1.00 or less.

[0027] The surface roughness Ra of the outer ring raceway surface 12a, the rolling surface 14a, and the large end surface 14b is, for example, less than or equal to the surface roughness Ra of the flange surface 12d. The surface roughness Ra of the outer ring raceway surface 12a is, for example, 0.32 μm or less. The surface roughness Ra of the rolling surface 14a is, for example, 0.32 μm or less. The surface roughness Ra of the large end surface 14b is, for example, 0.32 μm or less.

[0028] In the tapered roller bearing 11, the structure of the inner ring 13, the plurality of tapered rollers 14, and the cage 15 is not limited to the structure shown in Figures 1 to 4.

[0029] (Manufacturing method for tapered roller bearings) The manufacturing method for the tapered roller bearing 11 comprises a step of preparing the workpiece (hereinafter referred to as the preparation step), a step of heat-treating the workpiece prepared in the preparation step (hereinafter referred to as the heat treatment step), a step of performing a finishing process on the workpiece that has been heat-treated in the heat treatment step (hereinafter referred to as the finishing step), and a step of assembling the outer ring 12, inner ring 13, and a plurality of tapered rollers 14 formed in the finishing step (hereinafter referred to as the assembly step).

[0030] In the preparation process, the workpiece to be processed is prepared, which will become the outer ring 12, the inner ring 13, or a plurality of tapered rollers 14 through the heat treatment and finishing processes. The material constituting the workpiece to be processed is steel.

[0031] The heat treatment process includes a heating step, a cooling step, and a tempering step. In the heating step, the workpiece is held at a temperature above the A1 transformation point for a predetermined time. After the heating step, a cooling step is performed. In the cooling step, the workpiece is cooled to a temperature below the Ms transformation point. The tempering step is performed after the cooling step. In the tempering step, the workpiece is held at a temperature below the A1 transformation point for a predetermined time.

[0032] In the finishing process, grinding, polishing, and cleaning are performed on the workpiece as finishing processes. This forms the outer ring 12, the inner ring 13, and the multiple tapered rollers 14. In the finishing process to finish the workpiece into the outer ring 12, the area on the workpiece where the flange surface 12d of the outer ring 12 is to be formed and the area where the flange back surface 12e is to be formed are polished. The polishing conditions are set according to the design values ​​of the surface roughness Ra of the flange surface 12d and the flange back surface 12e, respectively.

[0033] In the assembly process, the outer ring 12, the inner ring 13, and the multiple tapered rollers 14 are assembled together with the cage 15.

[0034] Specifically, firstly, each of the multiple conical rollers 14 is housed in a pocket of the retainer 15, and the multiple conical rollers 14 and the retainer 15 are assembled into a single unit (hereinafter referred to as a roller-retainer assembly).

[0035] Secondly, the roller-cage assembly is assembled onto the outer ring 12. At this time, as shown in Figure 2, the rolling surfaces 14a of each conical roller 14 of the roller-cage assembly are in contact with the flange back surface 12e of the outer ring 12. From this state, the roller-cage assembly is further pressed against the outer ring 12 along the axial direction, causing the rolling surfaces 14a to slide on the flange back surface 12e, resulting in the state shown in Figure 3. In the state shown in Figure 3, the rolling surfaces of each conical roller 14 are pressed against the claws 15d of the cage 15. From the state shown in Figure 3, the roller-cage assembly is further pressed against the outer ring 12 along the axial direction, so that the roller-cage assembly is inserted into the outer ring 12 as shown in Figure 4. In this way, the outer ring 12, the multiple conical rollers 14, and the cage 15 are assembled into a single unit (hereinafter referred to as the outer ring-roller-cage assembly).

[0036] Thirdly, the inner ring 13 is assembled into the outer ring-roller-cage assembly. This completes the manufacture of the tapered roller bearing 11 shown in Figure 1.

[0037] (Effects of tapered roller bearings) The inventors have confirmed that even in tapered roller bearings where the surface roughness Ra of the outer ring raceway surface and rolling surface formed by the above finishing process is 0.32 μm or less, vibration may occur when the inner ring is rotated at a rotational speed of 2000 rpm with the outer ring fixed, and that the above vibration also depends on the surface roughness Ra of the flange surface and the back surface of the outer ring.

[0038] Specifically, the inventors have compared a tapered roller bearing 11 in which the surface roughness Ra of the flange surface 12d is 0.32 μm or less and the surface roughness Ra of the flange back surface 12e is 3.20 μm or less with a tapered roller bearing in which the surface roughness Ra of the flange surface 12d is greater than 0.32 μm and the surface roughness Ra of the flange back surface 12e is greater than 3.20 μm, and have confirmed that the former can suppress the above vibrations compared with the latter. Details will be described later.

[0039] More specifically, in the evaluation tests described later, it was confirmed that the smaller the surface roughness Ra of the flange surface 12d, the smaller the vibration described above tended to be. In the tapered roller bearing 11, the flange surface 12d of the outer ring 12 is in contact with the large end surface 14b of each tapered roller 14, so it is thought that the magnitude of the surface roughness Ra of the flange surface 12d directly affects the vibration described above.

[0040] On the other hand, in evaluation tests described later, it was confirmed that even if the surface roughness Ra of the flange surface 12d is small, the above vibration is relatively large if the surface roughness Ra of the flange back surface 12e is large, and the above vibration cannot be sufficiently suppressed unless the surface roughness Ra of the flange back surface 12e is also small. Furthermore, the inventors confirmed that scratches (irregularities) are formed on the rolling surface of the tapered roller bearing in which the above vibration is relatively large. In this regard, it is thought that when the roller-cage assembly is assembled into the outer ring during the assembly process of the manufacturing method of the tapered roller bearing, the rolling surface slides against the flange back surface, and if the surface roughness of the flange back surface is large, scratches are formed on the surface of the rolling surface due to the above sliding, and this causes the above vibration to be relatively large.

[0041] Furthermore, the inventors confirmed that tapered roller bearings 11 with a flange surface roughness Ra of 0.32 μm or less have higher seizure resistance compared to tapered roller bearings with a flange surface roughness Ra greater than 0.32 μm. Details will be described later.

[0042] In the tapered roller bearing 11, if the surface roughness Ra of the flange surface 12d is greater than 0.15 μm and 0.32 μm or less, it is preferable that the ratio obtained by dividing the surface roughness Ra of the flange surface 12d by the surface roughness Ra of the flange back surface 12e is 0.20 or more. In the evaluation tests described later, it was confirmed that in tapered roller bearings where the above ratio is less than 0.20, snagging occurs when assembling the roller-cage assembly into the outer ring during the assembly process, resulting in poor workability during assembly (hereinafter referred to as "assembly efficiency"). On the other hand, in tapered roller bearings 11 where the above ratio is 0.20 or more, it was confirmed that snagging does not occur when assembling the roller-cage assembly into the outer ring during the assembly process of the manufacturing method of the tapered roller bearing, resulting in high assembly efficiency. In other words, in tapered roller bearings 11 where the above ratio is 0.20 or more, the above vibration is suppressed and the above assembly efficiency is improved.

[0043] Furthermore, if the surface roughness Ra of the flange surface 12d is greater than 0.15 μm and less than or equal to 0.32 μm, the larger the above ratio, the smaller the surface roughness Ra of the flange back surface 12e. If the above ratio is greater than 2.13, it is presumed that the above vibration and assembly performance will mainly depend on the surface roughness Ra of the flange surface 12d rather than the surface roughness Ra of the flange back surface 12e, and will not be easily improved by simply reducing the surface roughness Ra of the flange back surface 12e. In other words, from the viewpoint of improving the above vibration and assembly performance, it is presumed that the cost-effectiveness will decrease if the above ratio is greater than 2.13.

[0044] In contrast, if the above ratio is 2.13 or less when the surface roughness Ra of the flange surface 12d is greater than 0.15 μm and 0.32 μm or less, it is presumed that the cost-effectiveness will be higher in terms of improving the above vibration and ease of assembly.

[0045] (Embodiment 2) (Construction of a tapered roller bearing) The tapered roller bearing according to Embodiment 2 has basically the same configuration as the tapered roller bearing 11 according to Embodiment 1 and provides similar effects, but differs from the tapered roller bearing 11 in that the surface roughness Ra of the flange surface 12d is 0.50 μm or less, and the surface roughness Ra of the flange back surface 12e is 2.50 μm or less. Below, the differences between the tapered roller bearing according to Embodiment 2 and the tapered roller bearing 11 according to Embodiment 1 will be mainly explained.

[0046] In the tapered roller bearing according to Embodiment 2, the surface roughness Ra of the flange surface 12d is 0.32 μm or more and 0.50 μm or less.

[0047] The surface roughness Ra of the back surface 12e of the guard is 2.50 μm or less. Preferably, the surface roughness Ra of the back surface 12e of the guard is 1.60 μm or less. The second surface roughness Ra2 is, for example, 0.15 μm or more.

[0048] The ratio of the surface roughness Ra of the flange surface 12d to the surface roughness Ra of the flange back surface 12e is preferably 0.31 or greater. More preferably, the above ratio is 3.33 or less.

[0049] (Manufacturing method for tapered roller bearings) The tapered roller bearing according to Embodiment 2 can be manufactured by the same manufacturing method as the tapered roller bearing 11 according to Embodiment 1.

[0050] (Effects of tapered roller bearings) The inventors have found that when comparing a tapered roller bearing in which the surface roughness Ra of the flange surface 12d is 0.35 μm or more and 0.50 μm or less and the surface roughness Ra of the flange back surface 12e is 2.50 μm or less with a tapered roller bearing in which the surface roughness Ra of the flange surface 12d is 0.35 μm or more and 0.50 μm or less and the surface roughness Ra of the flange back surface 12e is greater than 2.50 μm, the former can suppress the above vibrations compared to the latter.

[0051] Furthermore, the inventors have confirmed that even in a tapered roller bearing where the surface roughness Ra of the flange surface 12d is 0.35 μm or more and 0.50 μm or less, if the surface roughness Ra of the flange back surface 12e is 2.50 μm or less, the above vibration can be suppressed to the same extent as in the tapered roller bearing 11. Details will be described later.

[0052] In the tapered roller bearing according to Embodiment 2, it is preferable that the ratio obtained by dividing the surface roughness Ra of the flange surface 12d by the surface roughness Ra of the flange back surface 12e is 0.31 or higher. In the evaluation test described later, it was confirmed that in tapered roller bearings where the surface roughness Ra of the flange surface 12d is 0.35 μm or more and 0.50 μm or less and the above ratio is less than 0.31, snagging occurs when assembling the roller-cage assembly into the outer ring during the assembly process, resulting in poor workability during assembly (hereinafter referred to as "assembly efficiency"). On the other hand, in tapered roller bearings where the surface roughness Ra of the flange surface 12d is 0.35 μm or more and 0.50 μm or less and the above ratio is 0.31 or higher, snagging does not occur when assembling the roller-cage assembly into the outer ring during the assembly process of the manufacturing method of the tapered roller bearing, resulting in high assembly efficiency. In other words, in the tapered roller bearing according to Embodiment 2, the above vibration is suppressed and the above assembly efficiency is improved.

[0053] Furthermore, the inventors confirmed that tapered roller bearings 11 with a flange surface roughness Ra of 0.50 μm or less have higher seizure resistance compared to tapered roller bearings with a flange surface roughness Ra greater than 0.50 μm. Details will be described later.

[0054] <Evaluation test of tapered roller bearings> The following describes the results of the evaluation test for tapered roller bearings. In this evaluation test, multiple types (28 types) of test specimens (tapered roller bearings) were prepared, differing only in the combination of surface roughness Ra of the flange surface and the flange back surface of the outer ring. For each test specimen, the above-mentioned ease of assembly, appearance of the tapered rollers, vibration resistance, and seizure resistance of the flange were evaluated.

[0055] (Test sample) The surface roughness Ra of the flange surface of the outer ring of each test specimen was set to one of the following: 0.15 μm, 0.32 μm, 0.50 μm, or 0.80 μm. The surface roughness Ra of the back surface of the flange of the outer ring of each test specimen was set to one of the following: 0.15 μm, 0.32 μm, 0.80 μm, 1.60 μm, 2.50 μm, 3.20 μm, or 6.30 μm.

[0056] (Evaluation test of embedding compatibility) To evaluate the assembly characteristics of each test product, sensory evaluation was conducted to determine the presence and degree of snagging during the assembly of the roller-retainer assembly onto the outer ring. The assembly process was carried out according to the procedure shown in Figures 2 to 4. The evaluation results are shown in Table 1.

[0057] [Table 1]

[0058] In Table 1, "A" in the "Ease of Integration" column means that no resistance was felt, "B" means that integration was possible but resistance was felt, and "C" means that integration was not possible with the above procedure.

[0059] As shown in Table 1, the smaller the surface roughness Ra on the back of the guard, the better the evaluation results. The evaluation results for the fitability described above were more strongly correlated with the surface roughness Ra on the back of the guard than with the surface roughness Ra on the front of the guard.

[0060] Regardless of the surface roughness Ra of the flank face, all test samples with a surface roughness Ra of 6.30 μm on the flank back side received a rating of "C". Regardless of the surface roughness Ra of the flank face, all test samples with surface roughness Ra of 2.50 μm and 3.20 μm on the flank back side received a rating of "B". Regardless of the surface roughness Ra of the flank face, all test samples with surface roughness Ra of 0.15 μm, 0.32 μm, 0.80 μm, and 1.60 μm on the flank back side received a rating of "A".

[0061] (Evaluation test of the appearance of conical rollers) The rolling surfaces of the conical rollers of each test specimen were observed at a magnification of 200x using a confocal differential interference microscope to evaluate the presence and degree of scratches (irregularities). The evaluation results are shown in Table 1 above.

[0062] In Table 1, "A" in the "Appearance" column means that no damage was found, "B" means that minor damage was found, and "C" means that relatively large damage was found. More specifically, "B" means that the maximum width of the damage was 0.1 mm or less, and "C" means that the maximum width of the damage was greater than 0.1 mm.

[0063] As shown in Table 1, it was confirmed that the higher the evaluation result for integrateability in the previous evaluation test, the better the evaluation result for appearance in this evaluation test. The smaller the surface roughness Ra on the back of the flange, the better the evaluation result for the appearance of the rolling surface of the tapered roller. The evaluation result for the appearance of the rolling surface of the tapered roller was more strongly correlated with the surface roughness Ra on the back of the flange than with the surface roughness Ra on the front of the flange.

[0064] Regardless of the surface roughness Ra of the flank face, all test samples with a surface roughness Ra of 6.30 μm on the flank back side received a rating of "C". Regardless of the surface roughness Ra of the flank face, all test samples with surface roughness Ra of 2.50 μm and 3.20 μm on the flank back side received a rating of "B". Regardless of the surface roughness Ra of the flank face, all test samples with surface roughness Ra of 0.15 μm, 0.32 μm, 0.80 μm, and 1.60 μm on the flank back side received a rating of "A".

[0065] (Vibration evaluation test) In this evaluation test, vibration was assessed using each test specimen whose fitability and appearance had been evaluated in the above evaluation test. Specifically, the presence and degree of vibration were evaluated by tactile testing when the inner ring of each test specimen was rotated at a rotational speed of 2000 rpm while the outer ring was fixed to a rotational testing machine. In the tactile testing, multiple inspectors (2 people) each touched the outer surface of the shaft fitted into the inner ring to evaluate the vibration. The evaluation results are shown in Table 1 above.

[0066] In Table 1, "A" in the "Vibration" column means that no vibration was detected by the inspector, "B" means that a small vibration was detected by the inspector, and "C" means that a large vibration was detected by the inspector. The distinction between "B" and "C" is that each inspector judged that the vibration was acceptable in light of the specifications required for tapered roller bearings used in industrial machinery at medium to low speeds, and "C" means that each inspector judged that the vibration was not acceptable in light of those specifications.

[0067] As shown in Table 1, a tendency was observed where the degree of vibration was smaller as the surface roughness Ra of the back surface of the guard decreased.

[0068] In each test specimen with a surface roughness Ra of 0.80 μm on the guard surface, significant vibration was observed in the specimen with a surface roughness Ra of 3.20 μm or more on the back surface of the guard, and minute vibration was observed in the specimen with a surface roughness Ra of 2.50 μm on the back surface of the guard. However, no vibration was detected in any of the test specimens with a surface roughness Ra of 1.60 μm or less on the back surface of the guard.

[0069] In each test specimen with a surface roughness Ra of 0.50 μm on the flange surface, significant vibration was observed in the specimens with a surface roughness Ra of 3.20 μm or more on the flange back surface. However, no vibration was detected in the specimens with a surface roughness Ra of 2.50 μm or less on the flange back surface.

[0070] In each test specimen with a surface roughness Ra of 0.32 μm on the flange surface, significant vibration was observed in the specimen with a surface roughness Ra of 6.30 μm on the flange back surface, but no vibration was detected in any of the test specimens with a surface roughness Ra of 3.20 μm or less on the flange back surface.

[0071] Regarding the above results, it is considered that the vibration during rotation is influenced not only by the surface roughness Ra of the flange surface of the outer ring that contacts the large end face during rotation, but also by the irregularities on the rolling surface that contacts the outer ring raceway surface during rotation. Furthermore, it is thought that the irregularities on the rolling surface of the tapered roller are formed when the roller-cage assembly is assembled onto the outer ring during the assembly process of the tapered roller bearing manufacturing method, as the rolling surface slides against the back surface of the flange. As a result, it is thought that the larger the surface roughness Ra of the back surface of the flange, the larger the aforementioned irregularities are formed, and the greater the vibration. In fact, the results of this evaluation test correlated with both the surface roughness Ra of the flange surface and the results of the visual evaluation test of the rolling surface of the tapered roller described above.

[0072] In each tapered roller bearing according to Embodiment 1 and Embodiment 2, vibration can be suppressed because, based on the results of the above evaluation test, the combination of surface roughness of the flange surface and the flange back surface is set within the respective numerical ranges.

[0073] (Evaluation test for seizure resistance) In this evaluation test, the seizure resistance of the flange surface was evaluated using each test specimen whose vibration performance had been evaluated in the above evaluation test. The above-mentioned rotary testing machine was used for the test. The test conditions were: rotation speed: 2000 rpm (MAX), load: 29.4 kN, lubricating oil: VG320, oil supply temperature: room temperature, lubrication conditions: oil bath. The presence and degree of seizure between the flange surface and the big end surface of the outer ring of each test specimen was evaluated. The evaluation results are shown in Table 1 above.

[0074] In Table 1, "A" in the "Seizure Resistance" column means that no seizure was observed, "B" means that seizure was observed in a small area, and "C" means that seizure was observed in a large area.

[0075] As shown in Table 1, the seizure resistance of the flange surface was found to be strongly correlated with the surface roughness Ra of the flange surface.

[0076] The overall judgment results, based on a comprehensive assessment of the results of each evaluation test described above, are shown in Table 1. As shown in Table 1, the overall judgment result for test samples whose evaluation result for vibration during rotation was "C" was set to "C". Furthermore, the overall judgment result for test samples whose evaluation result for seizure resistance was "C" was set to "C". The overall judgment result for test samples whose evaluation result for vibration during rotation was "A" and whose evaluation results for seizure resistance, ease of assembly, and appearance were all "B" was set to "B".

[0077] A test sample that received an "A" rating for each of the following evaluations—vibration during rotation, ease of assembly, and appearance—and a "B" rating for seizure resistance, was given an overall rating of "A".

[0078] The above evaluation results for vibration during rotation were "A" and seizure resistance was "A," but the overall evaluation result for the test sample was "AA" because its ease of assembly and appearance were "B."

[0079] A test sample that received an overall rating of "AAA" for all evaluation results—vibration during rotation, seizure resistance of the flange surface, ease of assembly, and appearance—was given an "A" rating.

[0080] From the results of the above evaluation tests, it was confirmed that the tapered roller bearing 11 according to Embodiment 1 has the same configuration as each test sample that received an overall rating of "AA" or "AAA", and is therefore less prone to vibration during rotation and less prone to seizure of the flange surface.

[0081] Furthermore, in the tapered roller bearing 11 according to Embodiment 1, if the surface roughness Ra of the flange surface 12d is greater than 0.15 μm and 0.32 μm or less, the ratio obtained by dividing the surface roughness Ra of the flange surface 12d by the surface roughness Ra of the flange back surface 12e is 0.20 or more, which means that it has the same configuration as each test product that received an overall evaluation result of "AAA". Also, in the tapered roller bearing 11, if the surface roughness Ra of the flange surface 12d is 0.15 μm or less, the ratio obtained by dividing the surface roughness Ra of the flange surface 12d by the surface roughness Ra of the flange back surface 12e is 0.09 or more, which means that it has the same configuration as each test product that received an overall evaluation result of "AAA". In other words, the above evaluation tests confirmed that these tapered roller bearings 11 not only are less prone to vibration during rotation and seizure of the flange surface, but also have high ease of assembly and a good appearance.

[0082] Furthermore, it was confirmed that the tapered roller bearing according to Embodiment 2 has the same configuration as each test sample that received an overall evaluation result of "B" or "A," and therefore is less prone to vibration during rotation.

[0083] Furthermore, in the tapered roller bearing according to Embodiment 2, the ratio obtained by dividing the surface roughness Ra of the flange surface 12d by the surface roughness Ra of the flange back surface 12e is between 0.31 and 3.33, resulting in a configuration similar to that of each test sample that received an overall rating of "A". As a result, it was confirmed that such a tapered roller bearing not only generates less vibration during rotation, but also has high ease of assembly and a good appearance.

[0084] Although embodiments of the present invention have been described above, it is possible to modify these embodiments in various ways. Furthermore, the scope of the present invention is not limited to the embodiments described above. The scope of the present invention is indicated by the claims and is intended to include all modifications within the meaning and scope equivalent to the claims. [Explanation of Symbols]

[0085] 11 Tapered roller bearing, 12 Outer ring, 12a Outer ring raceway surface, 12al Large diameter side end, 12b Flange, 12c Top, 12d Flange surface, 12dl Large diameter side end, 12ds Small diameter side end, 12e Flange back surface, 12el Large diameter side end, 12es Small diameter side end, 13 Inner ring, 13a Inner ring raceway surface, 14a Rolling surface, 14b Large end surface, 15 Cage.

Claims

1. An outer ring having an outer ring raceway surface, It comprises a tapered roller having a rolling surface that contacts the outer ring raceway surface, The angle that the outer ring raceway surface makes with respect to the central axis of the outer ring is 35° or more. The outer ring has a flange portion formed therein that protrudes radially inward from the larger diameter end of the outer ring raceway surface. The flange portion has a flange surface that contacts the large end face of the conical roller, and a flange surface that is positioned radially outward from the small diameter end of the flange surface. The surface roughness Ra of the flange surface is 0.32 μm or less. A tapered roller bearing in which the surface roughness Ra of the back surface of the flange is 3.20 μm or less.

2. The surface roughness Ra of the flange surface is greater than 0.15 μm. The tapered roller bearing according to claim 1, wherein the ratio obtained by dividing the surface roughness Ra of the flange surface by the surface roughness Ra of the flange back surface is 0.20 or more and 2.13 or less.

3. The surface roughness Ra of the flange surface is 0.15 μm or less. The tapered roller bearing according to claim 1, wherein the ratio obtained by dividing the surface roughness Ra of the flange surface by the surface roughness Ra of the flange back surface is 0.09 or more and 1.00 or less.

4. An outer ring having an outer ring raceway surface, It comprises a tapered roller having a rolling surface that contacts the outer ring raceway surface, The angle that the outer ring raceway surface makes with respect to the central axis of the outer ring is 35° or more. The outer ring has a flange portion formed therein that protrudes radially inward from the larger diameter end of the outer ring raceway surface. The flange portion has a flange surface that contacts the large end face of the conical roller, and a flange surface that is positioned radially outward from the small diameter end of the flange surface. The surface roughness Ra of the flange surface is 0.50 μm or less. A tapered roller bearing in which the surface roughness Ra of the back surface of the flange is 2.50 μm or less.

5. The tapered roller bearing according to claim 4, wherein the ratio obtained by dividing the surface roughness Ra of the flange surface by the surface roughness Ra of the flange back surface is 0.31 or more and 3.33 or less.

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