Tapered roller bearings

Abstract

To provide a tapered roller bearing for reducing a change in the posture of tapered rollers to actualize stable torque at starting.SOLUTION: A tapered roller bearing 1 includes an inner ring 2 having a tapered raceway surface 2a and a large collar surface 7 provided on the large diameter side of the raceway surface 2a, an outer ring 3 having a tapered raceway surface 3a, and tapered rollers 4 provided between the raceway surfaces 2a, 3a of the inner and outer rings 2, 3. An outer ring angle α as the taper angle of the raceway surface 3a of the outer ring 3 is 45°-68°. The large collar surface 7a of the inner ring 2 is a ground surface, and the arithmetic mean roughness of the large collar surface 7a is 0.1-0.4 μmRa and a maximum height Rz of the large collar surface 7a is 1-3 μm. Furthermore, the arithmetic mean roughness of a large end face 4a of each of the tapered rollers 4 is 0.04-0.2 μmRa.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tapered roller bearing used for, for example, a hydraulic pump, a hydraulic motor, etc. of a construction machine.

Background Art

[0002] In a tapered roller bearing, by setting the ten-point average roughness of the large end face of the tapered roller to 0.3 to 1.2 μm [Rz], the combined roughness of the roughness of the large end face of this tapered roller and the roughness of the flange portion of the inner ring is set to 0.34 to 1.44 μm [Rz] (Patent Document 1). Thereby, when assembling the tapered roller bearing to the object to be used, it is possible to avoid the phenomenon that the preload when obtaining the required rotational torque becomes excessive or insufficient for each product.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the roughness of the large flange surface of the inner ring is good, that is, when the roughness of the large flange surface of the inner ring is small, the oil retention property of the large flange surface of the inner ring is small, and it becomes difficult for oil to remain on the large flange surface of the inner ring and the large end surface of the tapered roller. In this state, when the rotation and sudden stop of the tapered roller bearing are repeated, the large flange surface of the inner ring and the large end surface of the tapered roller do not form a sufficient oil film, come into metal contact, and the friction coefficient increases.

[0005] At this time, due to the sudden stop, the large end surface of the tapered roller stops while being dragged on the large flange surface of the inner ring, so that the tapered roller cannot maintain a normal posture and undesirably tilts (skews). This phenomenon is particularly likely to occur in a tapered roller bearing with a large outer ring angle, that is, a steep slope, which is the inclination angle of the raceway surface of the outer ring. When the tapered roller bearing is restarted while the tapered roller is in a tilted position, a force is required to return the tilted tapered roller to its normal position, increasing the starting torque of the tapered roller bearing. Therefore, there is a need for a product in which the starting torque of the tapered roller bearing is less affected by the rolling position.

[0006] An object of the present invention is to provide a tapered roller bearing capable of reducing changes in the position of the tapered roller and stabilizing the torque during startup.

Means for Solving the Problems

[0007] The tapered roller bearing of the present invention is a tapered roller bearing including an inner ring having a tapered raceway surface with a large flange surface provided on the large-diameter side of the raceway surface, an outer ring having a tapered raceway surface, and tapered rollers provided between the raceway surfaces of the inner and outer rings, wherein an outer ring angle, which is a taper angle of the raceway surface of the outer ring, is 45° to 68°, the large flange surface of the inner ring is a ground surface, an arithmetic mean roughness Ra of the large flange surface is 0.1 to 0.4 μm, a maximum height Rz of the large flange surface is 1 to 3 μm, and an arithmetic mean roughness Ra of a large end surface of the tapered roller is 0.04 to 0.2 μm.

[0008] The tapered roller bearing of the present invention may hereinafter be simply referred to as a "bearing". According to this configuration, for a tapered roller bearing with an outer ring angle of 45° to 68° (45° or more and 68° or less), since the large flange surface of the inner ring is a ground surface and 0.1 μm < arithmetic mean roughness Ra of the large flange surface < 0.4 μm and 1 μm < maximum height Rz of the large flange surface < 3 μm, it is possible to reduce changes in the position of the tapered roller and stabilize the torque during bearing startup. When the arithmetic mean roughness Ra of the large flange surface is 0.1 μm or less, the position of the tapered roller changes when the bearing suddenly stops, increasing the restart torque after the bearing stops. When the arithmetic mean roughness Ra of the large flange surface is 0.4 μm or more, the torque during bearing operation increases, increasing friction and wear of the bearing and raising concerns about excessive temperature rise. Since the large flange surface of the inner ring is a ground surface, it contributes to the lubrication of the lubricant in the bearing.

[0009] Not only the large flange surface of the inner ring, but also the large end face roughness of the tapered roller affects the torque, friction, wear, and excessive temperature rise during bearing stop and start-up. Therefore, the arithmetic mean roughness (roller large end face roughness) of the large end face of the tapered roller is set to 0.04 to 0.2 μm Ra. If the roller large end face roughness is 0.04 μm or less, it promotes the attitude change after sudden bearing stop and increases the starting torque. If the roller large end face roughness is 0.2 μm or more, there is a concern that the torque during bearing operation increases, the friction and wear of the bearing increase, and excessive temperature rise occurs.

[0010] The skewness Rsk of the large flange surface of the inner ring may be -2 μm to 0 (-2 μm or more and 0 or less). The skewness Rsk is the skewness Rsk of the roughness curve defined in 4.2.3 of Japanese Industrial Standard (JIS) B0601:2013. In this case, an oil film is sufficiently formed between the large flange surface of the inner ring and the roller large end face, and it is possible to reduce the torque during bearing operation. When the skewness Rsk of the large flange surface is less than -2 μm, the oil retention property of the large flange surface of the inner ring is small, and it becomes difficult for oil to remain on the large flange surface of the inner ring and the roller large end face. When the skewness Rsk of the large flange surface is greater than 0, the torque during bearing operation increases.

[0011] The raceway surface of the outer ring has a single arc crowning shape or a composite crowning shape, and the outer ring crowning parameter CD / LS obtained by dividing the crowning amount CD by the raceway length LS on the raceway surface of the outer ring may be 0.02 to 0.3 (0.02 or more and 0.3 or less). In this case, the attitude of the tapered roller during sudden bearing stop is less likely to change, the starting torque can be reduced, and the torque loss during bearing operation can also be reduced. Each time the crowning amount of the raceway surface of the outer ring is increased, the starting torque gradually increases. If the crowning amount is increased too much, skew occurs, and the attitude of the tapered roller during sudden stop is likely to change, and the starting torque increases. Therefore, the outer ring crowning parameter CD / LS is set to 0.3 or less. The value of the outer ring crowning parameter CD / LS is set to 0.02 or more at the minimum to have a crowning state in order to reduce the torque loss during bearing operation.

[0012] The raceway surface of the inner ring and the rolling surface of the tapered roller have crowning, and this crowning may be of a single arc crowning shape or a composite crowning shape. In this case, torque loss during bearing operation and the like can be further reduced.

[0013] It may be a tapered roller bearing used in hydraulic equipment. In this case, since the torque at the time of bearing startup can be stabilized, the versatility of the hydraulic equipment can be enhanced.

Advantages of the Invention

[0014] The tapered roller bearing of the present invention has an outer ring angle of 45° to 68°, the large flange surface of the inner ring is a ground surface, the arithmetic mean roughness of this large flange surface is 0.1 to 0.4 μm Ra and the maximum height Rz of the large flange surface is 1 to 3 μm, and the arithmetic mean roughness of the large end face of the tapered roller is 0.04 to 0.2 μm Ra. For this reason, changes in the attitude of the tapered roller can be reduced and the torque at startup can be stabilized.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0016] [First Embodiment] The tapered roller bearing according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. As shown in Fig. 1, this tapered roller bearing 1 includes an inner ring 2 having a tapered raceway surface 2a, an outer ring 3 having a tapered raceway surface 3a, a plurality of tapered rollers 4 provided between the raceway surfaces 2a and 3a of the inner and outer rings 2 and 3, and a cage 5 for holding these tapered rollers 4. The inner ring 2 has a small-diameter flange portion 6 formed at the small-diameter end and a large-diameter flange portion 7 formed at the large-diameter end. The large-diameter flange portion 7 has a large flange surface 7a on the surface facing the large end surface 4a of the tapered roller 4. The tapered roller 4 has a tapered rolling surface 4b in the shape of a tapered surface whose outer diameter surface follows the raceway surface 3a of the outer ring 3 and the raceway surface 2a of the inner ring 2.

[0017] The outer ring angle α, which is the taper angle of the raceway surface 3a of the outer ring 3, is 45° to 68° (45° or more and 68° or less). The larger the outer ring angle α of the tapered roller bearing 1, the higher the ability to bear the axial load. In other words, the outer ring angle α of the tapered roller bearing 1 is appropriately set according to the usage conditions of the equipment using this tapered roller bearing 1. Here, as shown in Fig. 3, when the raceway surface 3a of the outer ring 3 is a single-arc crowning shape or a composite crowning shape, the outer ring angle α is defined as follows. In the longitudinal section of the outer ring 3, the angle formed by a straight line L1 connecting one side edge portion P1 and the other side edge portion P2 on one raceway surface 3a with a 180-degree different phase and a straight line L2 connecting one side edge portion P3 and the other side edge portion P4 on the other raceway surface 3a is defined as the outer ring angle α.

[0018] As shown in Fig. 2, the large flange surface 7a of the inner ring 2 is, for example, a ground surface composed of iris-shaped grinding marks. Specifically, the skewness Rsk of the large flange surface 7a of the inner ring 2 is -2 μm to 0 (-2 μm or more and 0 or less). The skewness Rsk is the skewness Rsk of the roughness curve defined in 4.2.3 of Japanese Industrial Standard (JIS) B0601:2013. Since the large flange surface 7a of the inner ring 2 is a ground surface, it contributes to the lubrication of the lubricant inside the bearing. Also, since the ground surface is in the shape of an iris, the lubricant can be evenly distributed in the circumferential direction and the radial direction.

[0019] Since the skew Rsk of the large flange surface 7a of the inner ring 2 is -2 μm or more and 0 or less, an oil film is sufficiently formed between the large flange surface 7a of the inner ring 2 and the large end face 4a, and it is possible to reduce the torque during bearing operation. When the skew Rsk of the large flange surface 7a is less than -2 μm, the oil retention property of the large flange surface 7a of the inner ring 2 is small, and it becomes difficult for oil to remain on the large flange surface 7a and the large end face 4a of the inner ring 2. When the skew Rsk of the large flange surface 7a is greater than 0, the torque during bearing operation increases.

[0020] Also, the arithmetic mean roughness of the large flange surface 7a of the inner ring 2 is 0.1 to 0.4 μm Ra and the maximum height Rz of the large flange surface 7a is 1 to 3 μm. For a tapered roller bearing with an outer ring angle α of 45° or more and 68° or less, since the large flange surface 7a of the inner ring 2 is a ground surface and 0.1 μm < arithmetic mean roughness Ra of the large flange surface 7a < 0.4 μm and 1 μm < maximum height Rz of the large flange surface 7a < 3 μm, it is possible to reduce the change in the posture of the tapered roller 4 and stabilize the torque during bearing startup. When the arithmetic mean roughness Ra of the large flange surface 7a is 0.1 μm or less, the posture of the tapered roller 4 changes during a sudden stop of the bearing, so the restart torque after bearing stop increases. When the arithmetic mean roughness Ra of the large flange surface 7a is 0.4 μm or more, the torque during bearing operation increases, there is a concern that the friction and wear of the bearing increase, and excessive temperature rise occurs.

[0021] Not only the large flange surface 7a of the inner ring 2 but also the large end face roughness of the tapered roller 4 affects the torque, friction and wear, and excessive temperature rise during bearing stop and startup. Therefore, the arithmetic mean roughness (roller large end face roughness) of the large end face 4a of the tapered roller 4 is set to 0.04 to 0.2 μm Ra (a value greater than 0.04 μm Ra and less than 0.2 μm Ra). When the roller large end face roughness is 0.04 μm or less, it promotes the posture change after a sudden stop of the bearing, and the startup torque increases. When the roller large end face roughness is 0.2 μm or more, the torque during bearing operation increases, there is a concern that the friction and wear of the bearing increase, and excessive temperature rise occurs.

[0022] Regarding the tapered roller bearings and the like of the examples according to the embodiments of the present invention, a torque test simulating sudden stop and restart by repeating start and stop was carried out using a testing machine, and the presence or absence of torque change was determined. The test conditions are as follows. Axial load: 2950 N Lubrication method: Oil bath ISO VG10 Inner ring rotation speed: 30 min ―1 Test bearing: Tapered roller bearing (inner diameter φ60 mm, outer diameter φ125 mm, width 37 mm, outer ring angle 57°18′

[0023] After repeating sudden stop and restart a predetermined number of times, the starting torque at the time of restart was measured by a torque measuring device (not shown). Taking the torque value of Example 1 as the reference value, the torque values of Examples 2 to 5 and the comparative example were taken as relative values, that is, multiples, with respect to the reference value of Example 1. In Table 1, when the torque value was substantially equivalent to the reference value of Example 1, it was determined that there was no torque change (〇), and when the torque value was 1.7 times or more the reference value, it was determined that there was a torque change (×).

[0024]

Table 1

[0025] According to the test results, in Examples 1 to 5 where 0.1 μm < arithmetic mean roughness Ra of the large rib surface < 0.4 μm and the roller large end face roughness satisfies 0.04 to 0.2 μm Ra, restart was repeated a predetermined number of times from the stopped state, but there was no significant torque fluctuation regarding the starting torque at the time of restart and there was no problem. In the comparative example where the inner ring large rib surface roughness was as low as 0.01 μm, when restart was repeated a predetermined number of times from the stopped state, a large torque was required regarding the starting torque at the time of restart, and the starting torque at the time of restart was not stable and changed to a value of approximately 1.7 to 3.0 times, so there was a problem. As described above, a correlation was obtained between the inner ring large rib surface roughness, the roller large end face roughness, and the starting torque.

[0026] <Regarding other embodiments> In the following description, parts corresponding to matters described in advance in each embodiment are given the same reference numerals, and redundant descriptions are omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those in the embodiments described in advance unless otherwise specified. The same configuration exhibits the same operational effects. Not only combinations of parts specifically described in each embodiment, but also partial combinations of embodiments are possible as long as there is no problem with the combination.

[0027] [Second Embodiment] As shown in FIG. 3, the raceway surface 3a of the outer ring 3 may have a single-arc crowning shape or a composite crowning shape, and the outer ring crowning parameter CD / LS obtained by dividing the crowning amount CD on the raceway surface 3a of the outer ring 3 by the raceway length LS may be 0.02 to 0.3 (0.02 or more and 0.3 or less). The raceway length LS does not include the chamfered portion. The other configurations are the same as those in the above-described embodiments.

[0028] According to this configuration, the posture of the tapered roller at the time of sudden stop of the bearing is less likely to change, the starting torque can be reduced, and torque loss during bearing operation can also be reduced. As the crowning amount CD of the raceway surface 3a of the outer ring 3 increases, the starting torque gradually increases. If the crowning amount CD is too large, skew occurs, that is, the posture of the tapered roller at the time of sudden stop is likely to change, and the starting torque increases. Therefore, the outer ring crowning parameter CD / LS is set to 0.3 or less. The value of the outer ring crowning parameter CD / LS is set to 0.02 or more at the minimum to have a crowning state in order to reduce torque loss and the like during bearing operation.

[0029] [Third Embodiment] As shown in FIG. 4, the raceway surface 2a of the inner ring 2 and the rolling surface 4b of the tapered roller 4 may have crowning, and this crowning may have a single-arc crowning shape or a composite crowning shape. In this case, torque loss and the like during bearing operation can be further reduced.

[0030] The tapered roller bearing 1 according to any one of the embodiments may be applied to hydraulic equipment. As the hydraulic equipment, for example, an axial piston pump used in construction machinery or the like is applicable, but is not limited to this example. In this hydraulic equipment, the tapered roller bearing 1 according to the embodiment is applied to a bearing on which an axial load is dominantly applied.

[0031] When the tapered roller bearing 1 according to any one of the embodiments is applied to hydraulic equipment, the versatility of the hydraulic equipment can be enhanced in order to stabilize the torque at the time of bearing startup. It is also possible to apply the tapered roller bearing according to the embodiment to industrial machines, robots, wind power generation devices, hydraulic power generation devices, machine tools, and the like.

[0032] The embodiments of the present invention have been described above. However, the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0033] 1... tapered roller bearing, 2... inner ring, 2a... raceway surface, 3... outer ring, 3a... raceway surface, 7a... large flange surface, 4... tapered roller, 4a... large end face, α... outer ring angle

Claims

1. A tapered roller bearing comprising an inner ring having a tapered raceway surface with a large rib surface provided on the large diameter side of the raceway surface, an outer ring having a tapered raceway surface, and tapered rollers provided between the raceway surfaces of the inner and outer rings, A tapered roller bearing in which an outer ring angle, which is the taper angle of the raceway surface of the outer ring, is 45° to 68°, and the large rib surface of the inner ring is an iris-shaped ground surface that spreads lubricant in circumferential and radial directions, the arithmetic mean roughness of this large rib surface is 0.1 to 0.4 μmRa and the maximum height Rz of the large rib surface is 1 to 3 μm, the arithmetic mean roughness of the large end faces of the tapered rollers is 0.04 to 0.2 μmRa, and the skewness Rsk of the large rib surface of the inner ring is -2 μm to 0.

2. 2. The tapered roller bearing according to claim 1, wherein the raceway surface of the outer ring has a single arc crowning shape or a compound crowning shape, and an outer ring crowning parameter CD / LS, obtained by dividing the crowning amount CD by the raceway length LS, on the raceway surface of the outer ring, is 0.02 to 0.

3.

3. 3. A tapered roller bearing according to claim 1, wherein the raceway surface of said inner ring and the rolling surfaces of said tapered rollers are provided with crownings, said crownings being in the form of a single arc or a compound crowning shape.

4. 4. The tapered roller bearing according to claim 1, which is used in hydraulic equipment.

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