Conical roller bearing and speed reducer

Abstract

To improve a radial load resistance of a conical roller bearing while holding sufficient thrust load resistance.SOLUTION: A contact angle of a conical roller bearing is equal to or larger than 3° and equal to or less than 10°.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a tapered roller bearing and a reducer. [Background technology]

[0002] Tapered roller bearings are in widespread use. Tapered roller bearings have the ability to withstand not only radial loads but also thrust loads.

[0003] For example, as disclosed in Patent Document 1, tapered roller bearings can be applied to reducers. In the reducer disclosed in Patent Document 1, a cylindrical roller bearing is arranged on a shaft member. The cylindrical roller bearing supports an external gear so as to be rotatable relative to the shaft member. The cylindrical roller bearing receives a radial load from the external gear. The cylindrical roller bearing receiving the radial load generates a skew force in the axial direction. Tapered roller bearings are arranged on both sides of the cylindrical roller bearing in the axial direction. The tapered roller bearings support the skew force in the axial direction from the cylindrical roller bearing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special issue No. 2022-152790 Summary of the Invention [Problem to be solved by the invention]

[0005] The load required for mechanical devices including tapered roller bearings, such as the load required for reducers, has been increasing in recent years. Along with this trend, there is a demand for an increase in the capacity of tapered roller bearings. The present inventors conducted extensive research into this issue and discovered that it is possible to improve the radial load resistance of tapered roller bearings while maintaining sufficient thrust load resistance. The present invention is based on this finding, and has an object to improve the radial load resistance of tapered roller bearings while maintaining sufficient thrust load resistance. [Means for solving the problem]

[0006] The present invention provides the following <1> ~ <15> Regarding.

[0007] <1> A tapered roller bearing with a contact angle between 3° and 10°.

[0008] <2> With the inner circle, Tapered rollers and a contact angle of 3° or more and 10° or less, and an outer ring that holds the tapered rollers between the inner ring and the outer ring.

[0009] <3> an inner ring including an outer peripheral surface; Tapered rollers and A tapered roller bearing comprising: an inner circumferential surface having a contact angle of 3° or more and 10° or less; and an outer ring that holds the tapered rollers between the outer circumferential surface and the inner circumferential surface.

[0010] <4> The contact angle is 5° or more. <1> ~ <3> 13. The tapered roller bearing according to claim 12.

[0011] <5> The contact angle is 8° or less. <1> ~ <4> 13. The tapered roller bearing according to claim 12.

[0012] <6> The product of the radial thickness (mm) and the length (mm) of the tapered roller is 50 or more and 1400 or less. <1> ~ <5> 13. The tapered roller bearing according to claim 12.

[0013] <7> The product of the diameter (mm) of the tapered roller at the small end surface and the length (mm) of the tapered roller is 20 or more and 550 or less. <1> ~ <6> 13. The tapered roller bearing according to claim 12.

[0014] <8> An external gear; a shaft member for eccentrically rocking the external gear; a carrier that rotatably supports the shaft member; a cylindrical roller bearing provided between the external gear and the shaft member; a tapered roller bearing provided between the carrier and the shaft member and having a contact angle of 3° or more and 10° or less.

[0015] <9> a case including internal teeth that mesh with the external gear and at least partially houses the carrier; <8> The reducer according to claim 1.

[0016] <10> The contact angle is 5° or more. <8> or <9> The reducer according to claim 1.

[0017] <11> The contact angle is 8° or less. <8> ~ <10> The reducer according to any one of claims 1 to 5.

[0018] <12> The product of the thickness (mm) of the tapered roller bearing and the length (mm) of the tapered roller is 50 or more and 1400 or less. <8> ~ <11> The reducer according to any one of claims 1 to 5.

[0019] <13> The product of the diameter (mm) of the tapered roller at the small end surface and the length (mm) of the tapered roller is 20 or more and 550 or less. <8> ~ <12> The reducer according to any one of claims 1 to 5.

[0020] <14> the tapered roller bearing includes a first tapered roller bearing and a second tapered roller bearing arranged in sequence in an axial direction parallel to a rotation axis of the shaft member, the cylindrical roller bearing includes a first cylindrical roller bearing and a second cylindrical roller bearing disposed between a first tapered roller bearing and a second tapered roller bearing in the axial direction, the external gear includes a first external gear supported by the first cylindrical roller bearing and a second external gear supported by the second cylindrical roller bearing, the first tapered roller bearing includes tapered rollers having a center axis inclined away from the rotation axis on a side closer to the second tapered roller bearing in the axial direction, The second tapered roller bearing includes tapered rollers having a center axis inclined away from the rotation axis on a side closer to the first tapered roller bearing in the axial direction. <8> ~ <13> The reducer according to any one of claims 1 to 5.

[0021] <15> a distance along the axial direction between a point of application of the first tapered roller bearing and a point of application of the second tapered roller bearing is equal to or greater than twice the arrangement pitch of the first external gear and the second external gear in the axial direction; <14> The reducer according to claim 1. Effect of the Invention

[0022] According to the present invention, it is possible to improve the radial load resistance of a tapered roller bearing while maintaining sufficient thrust load resistance. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram for explaining an embodiment of the present invention, and is a vertical sectional view showing a reducer. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 3 is a partially enlarged view of FIG. [Figure 4] FIG. 4 is a vertical sectional view showing the tapered roller bearing shown in FIG. [Diagram 5] FIG. 5 is a plan view showing a tapered roller of the tapered roller bearing shown in FIG. [Figure 6] FIG. 6 is a graph showing the relationship between the contact angle and the basic dynamic radial load rating. [Figure 7] FIG. 7 is a graph showing the relationship between the contact angle and the appropriate preload value (appropriate preload load (N)) and the skew force (N). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] An embodiment of the present invention will be described below with reference to the drawings. Figures 1 to 7 are diagrams for explaining an embodiment of the present invention. Configurations shown in some figures may be omitted in other figures. Scales and aspect ratios may differ between the drawings.

[0025] In the illustrated example, the tapered roller bearing according to this embodiment is applied to an eccentric oscillating type reducer. In the following, this embodiment will be described based on a reducer to which a tapered roller bearing is applied. However, the tapered roller bearing according to this embodiment is not limited to eccentric oscillating type reducers and can be applied to various reducers. The tapered roller bearing according to this embodiment is not limited to reducers and can be applied to various devices.

[0026] In this embodiment, the reducer 10 includes an external gear 40, a shaft member 50 that eccentrically oscillates the external gear 40, a carrier 30 that rotatably supports the shaft member 50, a cylindrical roller bearing 70 provided between the external gear 40 and the shaft member 50, and a tapered roller bearing 60 provided between the carrier 30 and the shaft member 50. The tapered roller bearing 60 is designed to improve radial load resistance while maintaining the required thrust load resistance. Specifically, the contact angle α of the tapered roller bearing 60 is 3° or more and 10° or less. As described later, by setting the contact angle α of the tapered roller bearing 60 to 3° or more and 10° or less, the radial load resistance of the tapered roller bearing 60 can be improved while maintaining the required thrust load resistance.

[0027] In this specification, the thrust load used for the tapered roller bearing 60 is a load in a direction parallel to the rotation axis RA of the tapered roller bearing 60. The thrust load is also called an axial load.

[0028] The overall configuration of the reducer 10 will be described with reference to Fig. 1 to Fig. 3. The illustrated reducer 10 further includes a case 20. The case 20 at least partially accommodates a carrier 30. A main bearing 12 is provided between the case 20 and the carrier 30. The case 20 and the carrier 30 are relatively rotatable about a main rotation axis MRA.

[0029] The reducer 10 receives rotation from a driving means such as a motor. The reducer 10 reduces the speed of the input rotation and outputs it. The reducer 10 reduces the speed of the input rotation and outputs it as relative rotation between the case 20 and the carrier 30. The direction parallel to the main rotation axis MRA is called the axial direction D1. The carrier 30 holds the shaft member 50 rotatably. The rotation axis RA of the tapered roller bearing 60 coincides with the rotation axis of the shaft member 50. The rotation axes RA of the tapered roller bearing 60 and the shaft member 50 are parallel to the axial direction D1.

[0030] The driving means inputs rotation to the shaft member 50. The shaft member 50 includes an eccentric body 55. The eccentric body 55 is eccentric from the center of rotation of the shaft member 50. The external gear 40 penetrates the shaft member 50. The external gear 40 is located on the eccentric body 55. As the shaft member 50 rotates, the external gear 40 eccentrically oscillates. The external gear 40 has external teeth 45 that mesh with internal teeth 25 provided on the inner surface of the case 20. The internal teeth 25 and the external teeth 45 have different numbers of teeth. When rotation is input to the shaft member 50, the external gear 40 eccentrically oscillates so that the internal teeth 25 and the external teeth 45 mesh with each other. Due to the difference in the number of teeth between the internal teeth 25 and the external teeth 45, the carrier 30 supporting the external gear 40 and the shaft member 50 rotates relative to the case 20.

[0031] The specific configurations of the case 20, the carrier 30, the external gear 40, and the shaft member 50 shown in the drawings will be described in detail below in order.

[0032] The case 20 has internal teeth 25. The internal teeth 25 are arranged in a circumferential direction DC centered on the main rotation axis MRA. In the illustrated example, the speed reducer 10 has two external gears 40A, 40B arranged in an axial direction D1. Each of the internal teeth 25 extends in the axial direction D1 and meshes with the external teeth 45 of the two external gears 40A, 40B.

[0033] The illustrated case 20 includes a substantially cylindrical case body 21 and an internal tooth pin 24 held on the inner surface of the case body 21. The case body 21 is formed with a plurality of pin grooves arranged in the circumferential direction DC. The pin grooves extend in the axial direction D1 and house and hold cylindrical internal tooth pins 24. Each internal tooth pin 24 constitutes one internal tooth 25.

[0034] The carrier 30 is held in the case 20 via a pair of main bearings 12. The carrier 30 is rotatable relative to the case 20 around the main rotation axis MRA. The illustrated carrier 30 has a carrier base 31 and a carrier plate 32 fixed to each other. The carrier base 31 and the carrier plate 32 can be fixed to each other using a fastener such as a bolt. The carrier base 31 includes a disk-shaped base plate portion 31a and a plurality of pillar portions 31b protruding from the base plate portion 31a in the axial direction D1. The base plate portion 31a and the plurality of pillar portions 31b may be integrally formed. The plurality of pillar portions 31b may be provided at equal intervals in the circumferential direction DC centered on the main rotation axis MRA. In the illustrated specific example, three pillar portions 31b are provided.

[0035] The illustrated carrier 30 is provided with a central hole 34 and a through hole 35. The central hole 34 and the through hole 35 penetrate the carrier base 31 and the carrier plate 32, respectively. The central hole 34 is located on the main rotation axis MRA. The carrier 30 is provided with a plurality of through holes 35. The plurality of through holes 35 are located at equal intervals in the circumferential direction DC centered on the main rotation axis MRA.

[0036] The shaft member 50 is rotatably held by the carrier 30. The illustrated shaft member 50 is inserted into the through hole 35 of the carrier 30. A pair of tapered roller bearings 60 are provided between the carrier 30 and the shaft member 50. The shaft member 50 is rotatable about a rotation axis RA with respect to the carrier 30 via the tapered roller bearings 60. The rotation axis RA is parallel to the axial direction D1. The illustrated speed reducer 10 includes a plurality of shaft members 50 inserted into the plurality of through holes 35, respectively. The plurality of shaft members 50 are positioned at equal intervals in the circumferential direction DC centered on the rotation axis MRA. In the illustrated specific example, three through holes 35 are provided. In the illustrated example, three shaft members 50 are provided.

[0037] The illustrated shaft member 50 includes a shaft main body 51 and a pair of eccentric bodies 55 located on the shaft main body 51. The eccentric bodies 55 are cylindrical. The eccentric bodies 55 are expanded in diameter from the shaft main body 51. The eccentric bodies 55 are eccentric from the rotation axis RA, which is the rotation center of the shaft member 50. The pair of eccentric bodies 55 includes a first eccentric body 55A and a second eccentric body 55B. The first eccentric body 55A and the second eccentric body 55B are eccentric by the same amount of eccentricity on opposite sides from the rotation axis RA. In other words, in a cross section perpendicular to the axial direction D1, the center of the first eccentric body 55A and the center of the second eccentric body 55B are located at positions that are point-symmetric with respect to one point on the rotation axis RA.

[0038] The shaft body 51 has a first bearing support 52a which is an insertion part into the carrier base 31, and a second bearing support 52b which is an insertion part into the carrier plate 32. The bearing supports 52a and 52b support a first tapered roller bearing 60A and a second tapered roller bearing 60B, respectively. The pair of eccentric bodies 55A and 55B are located between the pair of bearing supports 52a and 52b in the axial direction D1. The illustrated shaft member 50 further includes an input gear 59 fixed to the shaft body 51. In the illustrated example, the input gear 59, the first bearing support 52a, the first eccentric body 55A, the second eccentric body 55B, and the second bearing support 52b are located in this order in the axial direction D1.

[0039] The illustrated reducer 10 has a first external gear 40A and a second external gear 40B as the external gear 40. The first external gear 40A is located on a first eccentric body 55A of the multiple shaft members 50. The second external gear 40B is located on a second eccentric body 55B of the multiple shaft members 50. The first external gear 40A and the second external gear 40B are located between the base plate portion 31a of the carrier base 31 and the carrier plate 32 in the axial direction D1.

[0040] The illustrated external gear 40 includes a disk-shaped central plate portion 41 and external teeth 45 arranged on the periphery of the central plate portion 41. The central plate portion 41 is provided with a central hole 42a and a column passing hole 42b. The central hole 42a is located on the main rotation axis MRA. The central hole 42a faces the central hole 34 in the axial direction D1. In the illustrated example, a plurality of column passing holes 42b are located at equal intervals in the circumferential direction DC centered on the central hole 42a. The column portion 31b of the carrier 30 passes through the column passing hole 42b. In the illustrated specific example, three column passing holes 43 are provided.

[0041] The central plate portion 41 is further provided with holes 43. In the illustrated example, the three holes 43 are positioned at equal intervals in the circumferential direction DC centered on the central hole 42a. An eccentric body 55 is disposed in the hole 43. A cylindrical roller bearing 70 is provided between the eccentric body 55 and the external gear 40. The first external gear 40A is supported on the first eccentric body 55A of the shaft member 50 via the first cylindrical roller bearing 70A. The second external gear 40B is supported on the second eccentric body 55B of the shaft member 50 via the second cylindrical roller bearing 70B.

[0042] Each external gear 40 is supported by three eccentric bodies 55. The eccentric bodies 55 included in the three shaft members 50 are aligned in phase. Therefore, the rotation of the three shaft members 50 causes the external gear 40 to eccentrically oscillate. In other words, the rotation of the three shaft members 50 causes the external gear 40 to translate along a circumferential path centered on the main rotation axis MRA. The first external gear 40A and the second external gear 40B operate with a half phase shift.

[0043] Rotation is input from a driving means such as a motor to the reducer 10 having the above configuration. For example, an output gear of the driving means is disposed on the main rotation axis MRA and meshes with the input gear 59 of the three shaft members 50. When the output gear rotates, the shaft members 50 rotate together with the input gear 59, and the external gear 40 eccentrically oscillates. At this time, the external teeth 45 of the external gear 40 mesh with the internal teeth 25 of the case 20. Due to the difference in the number of teeth between the external teeth 45 and the internal teeth 25, the carrier 30 supporting the external gear 40 via the shaft member 50 and the case 20 rotate relatively around the main rotation axis MRA. When the case 20 is fixed, the rotation of the carrier 30 is output. When the carrier 30 is fixed, the rotation of the case 20 is output.

[0044] Next, a description will be given of the tapered roller bearing 60. As shown in Figures 4 and 5, the tapered roller bearing 60 includes an inner ring 61, an outer ring 63, and tapered rollers 65 located between the inner ring 61 and the outer ring 63. The tapered roller bearing 60 may further include a cage 67 that holds the tapered rollers 65.

[0045] The inner ring 61 is annular. The inner ring 61 extends in a circumferential direction DC along a circumference centered on the rotation axis RA. The inner ring 61 includes an inner peripheral surface 62a and an outer peripheral surface 62b. The inner peripheral surface 62a and the outer peripheral surface 62b face a radial direction DR perpendicular to the rotation axis RA. The inner peripheral surface 62a faces inward in the radial direction DR. The outer peripheral surface 62b faces outward in the radial direction. The inner side in the radial direction DR means the side closer to the rotation axis RA in the radial direction DR. The outer side in the radial direction DR means the side farther from the rotation axis RA in the radial direction DR.

[0046] The inner circumferential surface 62a may be perpendicular to the radial direction DR. The inner circumferential surface 62a may be parallel to the axial direction D1. The inner circumferential surface 62a may be in contact with the shaft member 50. In the example shown in FIG. 3, the inner circumferential surface 62a is in contact with the first bearing support portion 52a of the shaft main body portion 51. The inner ring 61 is located on the first bearing support portion 52a of the shaft main body portion 51. The inner ring 61 may be in contact with the shaft member 50, and the first cylindrical roller bearing 70 may be held on the shaft member 50.

[0047] The outer peripheral surface 62b contacts the tapered rollers 65. The outer peripheral surface 62b becomes the raceway surface of the tapered rollers 65. The outer peripheral surface 62b is inclined with respect to the rotation axis RA. In the example shown in FIG. 3, the outer peripheral surface 62b of the inner ring 61 of the first tapered roller bearing 60A moves away from the rotation axis RA in the radial direction DR as it approaches the first cylindrical roller bearing 70A and the first eccentric body 55A along the axial direction D1. The outer peripheral surface 62b of the inner ring 61 of the second tapered roller bearing 60B moves away from the rotation axis RA in the radial direction DR as it approaches the second cylindrical roller bearing 70B and the second eccentric body 55B along the axial direction D1.

[0048] The outer ring 63 is annular. The outer ring 63 extends in the circumferential direction DC. The outer ring 63 includes an inner peripheral surface 64a and an outer peripheral surface 64b. The inner peripheral surface 64a and the outer peripheral surface 64b face each other in the radial direction DR. The inner peripheral surface 64a faces inward in the radial direction DR. The outer peripheral surface 64b faces outward in the radial direction.

[0049] The outer peripheral surface 64b may be perpendicular to the radial direction DR. The outer peripheral surface 64b may be parallel to the axial direction D1. The outer peripheral surface 64b may be in contact with the shaft member 50. In the example shown in Fig. 3, the outer peripheral surface 64b is in contact with the inner surface of the through hole 35 of the carrier 30. The outer ring 63 is positioned in the through hole 35 of the carrier 30. The outer ring 63 may be fitted into the through hole 35 of the carrier 30, thereby holding the tapered roller bearing 60 in the carrier 30.

[0050] The inner peripheral surface 64a contacts the tapered rollers 65. The inner peripheral surface 64a becomes the raceway surface of the tapered rollers 65. The inner peripheral surface 64a is inclined with respect to the rotation axis RA. In the example shown in FIG. 3, the inner peripheral surface 64a of the outer ring 63 of the first tapered roller bearing 60A moves away from the rotation axis RA in the radial direction DR as it approaches the first cylindrical roller bearing 70A and the first eccentric body 55A along the axial direction D1. The inner peripheral surface 64a of the outer ring 63 of the second tapered roller bearing 60B moves away from the rotation axis RA in the radial direction DR as it approaches the second cylindrical roller bearing 70B and the second eccentric body 55B along the axial direction D1.

[0051] A plurality of tapered rollers 65 are disposed between the inner ring 61 and the outer ring 63. The tapered rollers 65 are disposed at intervals in the circumferential direction DC. The relative positions of the tapered rollers 65 are determined by a cage 67. The cage 67 may be, for example, an annular member having a plurality of holes that accommodate the respective tapered rollers 65.

[0052] The tapered roller 65 has a truncated cone shape or a shape obtained by chamfering a truncated cone. The apex of the truncated cone constituting the tapered roller 65 is located on the rotation axis RA. The apexes of the truncated cones constituting the multiple tapered rollers 65 included in the tapered roller bearing 60 are located at the same position on the rotation axis RA. A truncated cone is obtained by cutting a cone with a plane parallel to the base of the cone. In this specification, the apex of the truncated cone means the apex of the cone before it is cut.

[0053] As shown in Fig. 5, the tapered roller 65 includes a small end face 66a, a large end face 66b, and a side face 66c. The side face 66c is located between the small end face 66a and the large end face 66b. The large end face 66b is the larger of the two base faces of the truncated cone that constitutes the tapered roller 65. The small end face 66a is the smaller of the two base faces of the truncated cone that constitutes the tapered roller 65. In the illustrated example, the large end face 66b is a circle. In the illustrated example, the small end face 66a is a circle.

[0054] The large end face 66b of the tapered roller 65 included in the first tapered roller bearing 60A shown in Fig. 3 faces the side approaching the first cylindrical roller bearing 70A and the first eccentric body 55A in the axial direction D1. The large end face 66b of the tapered roller 65 included in the second tapered roller bearing 60B shown in Fig. 3 faces the side approaching the second cylindrical roller bearing 70B and the second eccentric body 55B in the axial direction D1.

[0055] The tapered roller 65 has a central axis CA. The tapered roller 65 rotates around the central axis CA between the inner ring 61 and the outer ring 63. In the illustrated example, the central axis CA passes through the center of the small end face 66a. In the illustrated example, the central axis CA passes through the center of the large end face 66b. The central axis CA of the tapered roller 65 included in the first tapered roller bearing 60A shown in FIG. 3 moves away from the rotation axis RA in the radial direction DR as it approaches the first cylindrical roller bearing 70A and the first eccentric body 55A along the axial direction D1. The central axis CA of the tapered roller 65 included in the second tapered roller bearing 60B shown in FIG. 3 moves away from the rotation axis RA in the radial direction DR as it approaches the second cylindrical roller bearing 70B and the second eccentric body 55B along the axial direction D1.

[0056] The tapered roller bearing 60 can support a load from one side in the axial direction. The tapered roller bearing 60 can support a load applied to the inner ring 61 from the large end face 66b side in the axial direction D1. The tapered roller bearing 60 can support a load applied to the outer ring 63 from the small end face 66a side in the axial direction D1.

[0057] As shown in FIG. 1 and FIG. 3, in the reducer 10, two tapered roller bearings 60A, 60B are arranged in opposite directions so that the central axis CA coincides. The two tapered roller bearings 60A, 60B have large end faces 66b of the tapered rollers 65 facing each other. A cylindrical roller bearing 70 is located between the two tapered roller bearings 60A, 60B. The cylindrical roller bearing 70 is located on the eccentric body 55. The external gear 40 is located on the cylindrical roller bearing 70. In the illustrated example, two cylindrical roller bearings 70A, 70B are located between the two tapered roller bearings 60A, 60B. The first tapered roller bearing 60A, the first cylindrical roller bearing 70A, the second cylindrical roller bearing 70B, and the second tapered roller bearing 60B are arranged in this order in the axial direction D1.

[0058] During operation of the reducer 10, the cylindrical roller bearing 70 receives a radial load between the eccentric body 55 and the external gear 40 in a radial direction perpendicular to the rotation axis of the cylindrical roller bearing 70. When the cylindrical roller bearing 70 receives the radial load, it generates a skew force in a direction along its rotation axis. In a typical reducer 10, the radial load applied to the cylindrical roller bearing 70 is 3000N or more and 50000N or less. It has been confirmed that the skew force is about 5% of the radial load. Therefore, the skew force generated in the cylindrical roller bearing 70 during operation of the reducer 10 is usually 150N or more and 2500N or less.

[0059] The skew force is applied as a thrust load to the tapered roller bearing 60 by the inner ring or the outer ring of the cylindrical roller bearing 70. In another example, the skew force is applied as a thrust load to the tapered roller bearing 60 by the eccentric body 55 fixed to the inner ring of the cylindrical roller bearing 70 or the external gear 40 fixed to the outer ring. In the illustrated example, the two tapered roller bearings 60A and 60B are configured so that the large end faces 66b of the tapered rollers 65 face the cylindrical roller bearing 70 side in the axial direction D1. Furthermore, the two tapered roller bearings 60A and 60B are configured so that the inner ring 61 protrudes toward the cylindrical roller bearing 70 side in the axial direction D1 more than the outer ring 63. The two tapered roller bearings 60A and 60B are applied with a thrust load due to the skew force to their respective inner rings 61, and support this thrust load without substantially moving in the axial direction D1.

[0060] As shown in Fig. 4 etc., the inner ring 61 may include at least one of a small rib 63a and a large rib 63b. The small rib 63a is provided on an inner peripheral surface 62a of the inner ring 61. The small rib 63a contacts a small end face 66a of the tapered roller 65 to suppress relative movement of the tapered roller 65 with respect to the inner ring 61 in the axial direction D1. The large rib 63b contacts a large end face 66b of the tapered roller 65 to suppress relative movement of the tapered roller 65 with respect to the inner ring 61 in the axial direction D1.

[0061] Incidentally, the load required for mechanical devices including tapered roller bearing 60, such as the load required for reducers, has been increasing in recent years. Along with this trend, there is a demand for an increase in the capacity of tapered roller bearings. As a means for solving this problem, in this embodiment, the contact angle α of tapered roller bearing 60 is set to be equal to or greater than 3° and equal to or less than 10°. As shown in FIG. 4, contact angle α is the angle between inner circumferential surface 64a of outer ring 63 and central axis CA. Contact angle α is an angle equal to or greater than 0° and equal to or less than 90°.

[0062] Conventionally, the contact angle α of tapered roller bearings has been set to an angle greater than 10°, for example, 15° or more or 20° or more. The reason for setting the contact angle α so large is that, since tapered roller bearings are used instead of cylindrical roller bearings, it was considered necessary for the tapered roller bearings to have sufficient thrust load resistance. The contact angle specified in "5 Dimension Series a)" of JIS B1512-3:2011, which specifies tapered roller bearings, is in the range of more than 10° and less than 30°. Thus, even in the JIS standard, contact angles of less than 10° are not anticipated.

[0063] However, after extensive research by the present inventors, it was confirmed that a tapered roller bearing 60 with a contact angle α of 10° or less has sufficient thrust load resistance performance depending on the application of the tapered roller bearing 60. For example, the contact angle α may be 10° or less for a tapered roller bearing 60 to which a large thrust load is not applied. The contact angle α may be 10° or less for a tapered roller bearing 60 used alongside a cylindrical roller bearing. The contact angle α may be 10° or less for a tapered roller bearing 60 that receives a skew force from a cylindrical roller bearing. The contact angle α may be 10° or less for a tapered roller bearing 60 that supports the same support member as the cylindrical roller bearing. The contact angle α may be 10° or less for a tapered roller bearing 60 that supports the crankshaft (shaft member 50) of an eccentric oscillating reducer. It was confirmed that a tapered roller bearing 60 with a contact angle α of 10° or less has sufficient thrust load resistance performance when supporting the eccentric shaft of a reducer.

[0064] By setting the contact angle α to 10° or less, which is smaller than the conventional angle, the tapered rollers 65 can be made thicker without increasing the thickness T60 of the tapered roller bearing 60. By setting the contact angle α to 10° or less, which is smaller than the conventional angle, the thickness of the inner ring 61 in the radial direction DR can be made thicker without increasing the thickness T60 of the tapered roller bearing 60. By setting the contact angle α to 10° or less, which is smaller than the conventional angle, the thickness of the outer ring 63 in the radial direction DR can be made thicker without increasing the thickness T60 of the tapered roller bearing 60. According to any of these, the radial load resistance performance of the tapered roller bearing 60 can be efficiently improved without increasing the thickness T60 of the tapered roller bearing 60.

[0065] A thickness T60 of the tapered roller bearing 60 is the distance between an inner peripheral surface 62a of the inner ring 61 and an outer peripheral surface 64b of the outer ring 63 along a radial direction DR, as shown in FIG.

[0066] By reducing the contact angle α, it is possible to significantly improve the radial load resistance performance, as shown in Table 1 and Fig. 5. By reducing the contact angle α, it is possible to significantly reduce the drive torque, as shown in Table 1. By reducing the contact angle α, it is possible to significantly extend the life of the tapered roller bearing 60 and the reducer 10 including the tapered roller bearing 60, as shown in Table 1.

[0067] [Table 1]

[0068] The "basic dynamic load rating" in Table 1 refers to the basic dynamic radial load rating calculated from a theoretical formula based on JIS B1518: 2013. Table 1 and Figure 6 show the relationship between the contact angle α and the basic dynamic load rating ratio.

[0069] The "basic dynamic load rating" is the radial load that a bearing can withstand for a basic rated life of 1 million revolutions. Therefore, the "basic dynamic load rating" is an index showing the radial load resistance performance of a tapered roller bearing. In Table 1 and Fig. 6, the thickness T60 of tapered roller bearing 60 and the dimensions of tapered rollers 65 are kept constant, while the contact angle α, the thickness of inner ring 61, and the thickness of outer ring 63 are changed, and the basic dynamic load rating is relatively evaluated.

[0070] As shown in Table 1 and Fig. 6, the basic dynamic load rating increases as the contact angle α decreases. In other words, by setting the contact angle α to 10° or less, which is smaller than the conventional angle, the radial load resistance of tapered roller bearing 60 can be improved.

[0071] "Bearing span ratio" in Table 1 is the relative ratio of bearing span L60. "Bearing span ratio" in Table 1 shows the change in bearing span L60 according to contact angle α. Bearing span L60 is the distance in a direction parallel to central axis CA between load point P60 of first tapered roller bearing 60A and load point P60 of second tapered roller bearing 60B when applied to reducer 10 shown in Figures 1 to 3.

[0072] As shown in FIG. 4, the point of application P60 of the tapered roller bearing 60 is located on the rotation axis RA of the tapered roller bearing 60. The point of application P60 is located at the intersection of a straight line SL65 perpendicular to the central axis CA of the tapered roller 65 and the rotation axis RA of the tapered roller bearing 60. The straight line SL65 passes through the center 65C of the tapered roller 65. The center 65C of the tapered roller 65 is located on the central axis CA of the tapered roller 65. The distance from the center 65C to the small end face 66a along the central axis CA is equal to the distance from the center 65C to the large end face 66b along the central axis CA. In calculating the bearing span ratio shown in Table 1, the dimensions of the reducer 10 are typical dimensions for a reducer with an output of 1000 Nm or more and 2000 Nm or less.

[0073] 1 to 3, a radial load is applied to the shaft member 50 and the cylindrical roller bearing 70 from the external gears 40A, 40B. The central position in the axial direction D1 of the radial load from the external gears 40A, 40B corresponds to central positions P40A, P40B in the axial direction D1 of each of the external gears 40A, 40B. In addition, a radial load is applied to each of the tapered roller bearings 60A, 60B from the shaft member 50. The central position in the axial direction D1 of the radial load that each of the tapered roller bearings 60A, 60B receives from the shaft member 50 corresponds to a point of application P60 of the tapered roller bearings 60A, 60B.

[0074] The "bearing load ratio" in Table 1 is the ratio of the radial load applied to the tapered roller bearing 60 at each contact angle α. The radial load at each contact angle α is a value obtained by calculation. In calculating the radial load, only the contact angle α and the bearing span L60 were changed, and the other conditions (the configuration of the shaft member 50, the configuration of the cylindrical roller bearing 70, the configuration of the external gears 40A, 40B, the radial load from the external gears 40A, 40B, etc.) were kept constant regardless of the contact angle α and the bearing span L60.

[0075] As shown in Table 1, as the contact angle α decreases, the bearing span L60 can be increased. According to the contact angle α, the bearing span L60 can be increased while maintaining the length of the shaft member 50 in the axial direction D1 constant.

[0076] As shown in Table 1, the bearing load ratio can be reduced by lengthening the bearing span L60. In other words, the bearing load ratio can be reduced by reducing the contact angle α. In other words, by setting the contact angle α to 10° or less, which is smaller than the conventional angle, the radial load resistance can be improved.

[0077] The "life ratio" in Table 1 indicates the ratio of the rated life of the tapered roller bearings 60 used in the reducer 10 shown in Figures 1 to 3. The rated life is calculated by a formula specified in JIS. The rated life is proportional to the ratio of the basic dynamic load rating of the tapered roller bearing 60 to the radial load applied to each tapered roller bearing 60 at the point of application P60, raised to the power of 10 / 3.

[0078] As described above, by reducing the contact angle α, the basic dynamic load rating of the tapered roller bearing 60 can be increased. Furthermore, by reducing the contact angle α, the radial load (bearing load ratio in Table 1) applied to the tapered roller bearing 60 incorporated in the reducer 10 shown in Figs. 1 to 3 can be reduced. Furthermore, the rated life is proportional to the 10 / 3 power of the ratio of the applied radial load to the basic dynamic load rating. For these reasons, by reducing the contact angle α, the rated life can be significantly extended. In other words, by setting the contact angle α to 10° or less, which is smaller than the conventional value, the radial load resistance performance can be significantly improved.

[0079] The "driving torque ratio" in Table 1 is the ratio of the driving torque required when starting the tapered roller bearing. The driving torque is also called starting torque. The sliding friction between the large end face 66b of the tapered roller 65 and the large rib 63b of the inner ring 61, the rolling friction between the tapered roller 65 and the outer peripheral surface 62b of the inner ring 61 and the inner peripheral surface 64a of the outer ring 63, and the sliding friction between the tapered roller 65 and the cage 67 can affect the driving torque required when starting the tapered roller bearing. Of these, the sliding friction between the large end face 66b of the tapered roller 65 and the large rib 63b of the inner ring 61 has a decisive effect on the torque required when starting the tapered roller bearing. The "driving torque ratio" in Table 1 is the ratio of the driving torque at each contact angle α calculated from the sliding friction between the large end face 66b of the tapered roller 65 and the large rib 63b of the inner ring 61.

[0080] The driving torque is affected by friction at each part due to the preload, which will be described later. As will be described later, there is an optimum value for preload, and the optimum preload value can be reduced by reducing the contact angle. As a result, as shown in Table 1, by reducing the contact angle α, the driving torque can be effectively reduced. By reducing the driving torque, the life of the tapered roller bearing 60 and the reducer 10 in which the tapered roller bearing 60 is incorporated can be extended. In other words, by setting the contact angle α to 10° or less, which is smaller than conventional, the radial load resistance can be improved.

[0081] The illustrated reducer 10 may be assembled as follows. First, a shaft member 50 is prepared in which an inner ring 61, tapered rollers 65, and a cage 67 are mounted on the bearing supports 52a and 52b. A tapered roller bearing 60 may also be mounted on this shaft member 50. Next, the shaft member 50 is inserted into the hole 43 of the external gear 40. At this time, the maximum circumscribing circle of the tapered rollers 65 located on the shaft member 50 must be smaller than the inner diameter of the hole 43. After that, the shaft member 50 that has passed through the hole 43 is inserted into the outer ring 63 mounted in the through hole 35 of the carrier 30. The tapered rollers 65 come into contact with the outer ring 63 to assemble the tapered roller bearing 60. The shaft member 50 is rotatably held by the carrier 30 via this tapered roller bearing 60.

[0082] By setting the contact angle α to 10° or less, which is smaller than the conventional angle, it is possible to increase the diameter on the circumference on which the tapered rollers 65 are arranged (hereinafter referred to as the "pitch circle diameter") without increasing the maximum circumscribing circle of the tapered rollers 65 or thinning the tapered rollers 65. The pitch circle diameter PCD (Pitch Circle Diameter) corresponds to twice the length (arrangement circle radius) along the radial direction DR from the center 65C of each tapered roller 65 arranged along the circumference centered on the rotation axis RA to the rotation axis RA.

[0083] By increasing the arrangement circle diameter PCD of the tapered rollers 65, the diameter of the rolling surface (inner circumferential surface 62a) of the inner ring 61 can be increased without increasing the outer diameter D60b (see FIG. 4) of the tapered roller bearing 60. The bearing transfer surface can be increased in accordance with the increase in the diameter of the rolling surface of the inner ring 61. In other words, by setting the contact angle α to 10° or less, which is smaller than conventionally, the radial load resistance of the tapered roller bearing can be improved through the increase in the arrangement circle diameter PCD of the tapered rollers 65.

[0084] Tapered roller bearings were actually manufactured and incorporated into the reducers configured as shown in Figures 1 to 3, and their life and drive torque were measured. Tapered roller bearings with each contact angle α were evaluated by comparison with a standard bearing with a contact angle α of 20°.

[0085] The "Life" column in Table 1 shows the results of evaluating tapered roller bearings with each contact angle α according to the following criteria. AA: A life span of 1.4 times or more that of the standard bearing was achieved. A: A life span of 1.2 times or more that of the standard bearing was achieved. B: A life span of less than 1.2 times that of the standard bearing was obtained.

[0086] The "Driving torque" column in Table 1 shows the results of evaluating tapered roller bearings with each contact angle α according to the following criteria. AA: The driving torque was 0.70 times or less that of a conventional tapered roller bearing. A: The drive torque was 0.85 times or less that of conventional tapered roller bearings. B: The driving torque was 0.85 times greater than that of a conventional tapered roller bearing.

[0087] The results in Table 1 show that by setting the contact angle α to 10° or less, which is smaller than conventionally, it is possible to improve the radial load resistance of tapered roller bearing 60. From the viewpoint of significantly improving the radial load resistance performance compared to conventional tapered roller bearings, it is preferable to set the contact angle α to 8° or less, and it is more preferable to set the contact angle α to 7° or less.

[0088] In the tapered roller bearings evaluated in Table 1 and Fig. 6, the thickness T60 of tapered roller bearing 60, the configuration of tapered rollers 65, and the arrangement circle diameter PCD were constant regardless of changes in contact angle α. On the other hand, the thicknesses of inner ring 61 and outer ring 63 were changed in accordance with changes in contact angle α.

[0089] As described above, by setting the contact angle α to 10° or less, which is smaller than the conventional angle, the radial load resistance can be improved. On the other hand, when the contact angle α is made smaller, the thrust load resistance decreases. In this embodiment, the lower limit of the contact angle α is set to 3°. By setting the contact angle α to 3° or more, the thrust load resistance can be sufficiently ensured.

[0090] In actual use, radial loads and thrust loads are not applied individually to the tapered roller bearing 60, but are likely to be applied in combination with radial loads and thrust loads. For evaluating the life of the tapered roller bearing 60 in such use, the dynamic equivalent load specified in JIS B1518:2013 is used.

[0091] The dynamic equivalent load is a hypothetical load that has the same life as the life of the tapered roller bearing 60 when a combined load is applied. A dynamic equivalent radial load is known as a dynamic equivalent load. The dynamic equivalent radial load is a hypothetical radial load that has the same life as the life of the tapered roller bearing 60 when a combined load is applied.

[0092] As specified in JIS B1518:2013, the dynamic equivalent radial load is known to be calculated by the following formula X. P r =X×F r +Y×F s ...Formula X "F" in formula X r " is the radial load acting on the tapered roller bearing 60. "F s " is the thrust load acting on the tapered roller bearing 60. "X" is the radial load coefficient, and "Y" is the thrust load coefficient. The radial load coefficient X and the thrust load coefficient Y arer Thrust load F against s Ratio of (F s / F r ) is determined depending on the ratio (F s / F r It is known that when x = 1 and y = 0, then x = 1 and y = 0.

[0093] That is, "(F s / F r When the radial load F )≦e, the life of the tapered roller bearing 60 is r Only the thrust load F s can be ignored. The value e for the tapered roller bearing is "1.5 × tan α" using the contact angle α. The radial load F acting on the tapered roller bearing 60 during use r and thrust load F s By selecting an appropriate contact angle α according to the thrust load F s In other words, by appropriately selecting the contact angle α depending on the application of the tapered roller bearing 60, the thrust load resistance performance of the tapered roller bearing 60 can be made sufficient.

[0094] In application to the reducer 10 shown in FIGS. 1 to 3, the tapered roller bearing 60 is subjected to a radial load F from the shaft member 50. r is applied, and the skew force generated by the cylindrical roller bearing 70 is a thrust load F s According to the study by the present inventors, the radial load F r Thrust load F against s Percentage of (F s / F r ) was confirmed to be 0.06 or 0.07.

[0095] When the contact angle α is 3°, the value e expressed by "1.5 × tan α" is 0.079. When the contact angle α is 2°, the value e expressed by "1.5 × tan α" is 0.052. Therefore, according to the tapered roller bearing 60 whose contact angle α is 3° or more, the thrust load F scan be neglected. In other words, the tapered roller bearing 60 having a contact angle α of 3° or more maintains the necessary thrust load resistance performance.

[0096] From this point of view, the contact angle α may be set to 3° or more and 10° or less, or 3° or more and 8° or less, or 3° or more and 7° or less.

[0097] A preload may be applied to the tapered roller bearing 60 when in use. Specifically, the tapered roller bearing 60 may be assembled in a device to which the tapered roller bearing 60 is applied, that is, in the illustrated example, the reducer 10, with the inner ring 61 and the outer ring 63 being pressurized toward each other in the direction D1 along the rotation axis RA. By using the tapered roller bearing 60 in a state in which the inner ring 61 and the outer ring 63 are pressurized toward each other, it is possible to suppress abnormalities such as rattle and vibration during use of the tapered roller bearing 60. By suppressing such abnormalities, it is possible to effectively extend the life of the tapered roller bearing 60 and the life of the device in which the tapered roller bearing 60 is assembled, for example, the reducer 10.

[0098] Incidentally, there is an appropriate value for the preload applied to tapered roller bearing 60. In tapered roller bearing 60 to which the appropriate preload value has been applied, no gaps are generated between tapered rollers 65 and the inner ring 61 and between tapered roller bearing 60 and the outer ring 63. It is preferable that all tapered rollers 65 included in tapered roller bearing 60 are in contact with both the inner ring 61 and the outer ring 63.

[0099] When a constant radial load acts on tapered roller bearing 60 from a constant direction, the maximum radial load generated on tapered roller bearing 60 when the preload is smaller than the optimum preload value is greater than the maximum radial load generated on tapered roller bearing 60 when the preload is at the optimum preload value. When a constant radial load acts on tapered roller bearing 60 from a constant direction, the maximum radial load generated on tapered roller bearing 60 when the preload is greater than the optimum preload value is greater than the maximum radial load generated on tapered roller bearing 60 when the preload is at the optimum preload value. In other words, when the preload is at the optimum preload value, the maximum radial load generated on tapered roller bearing 60 can be minimized.

[0100] FIG. 7 shows the results of a survey of the optimum preload value for three specific examples A to C of the tapered roller bearing 60. The specific examples A to C of the tapered roller bearing 60 shown in FIG. 7 are tapered roller bearings 60 assumed to be applied to three reducers that are actually manufactured. The specific example A assumed to be applied to a larger, high-output reducer 10 is a tapered roller bearing with a relatively large capacity. As shown in FIG. 7, the optimum preload value is large for the specific example A assumed to be applied to a larger, high-output reducer 10. The specific example C assumed to be applied to a smaller, low-output reducer 10 is a tapered roller bearing with a relatively small capacity. As shown in FIG. 7, the optimum preload value is small for the specific example C assumed to be applied to a smaller, low-output reducer 10.

[0101] Fig. 7 shows the change in optimum preload value according to contact angle α for three specific examples A to C of tapered roller bearing 60. In the tapered roller bearings evaluated in Fig. 7, the thickness T60 of tapered roller bearing 60, the configuration of tapered rollers 65, and the arrangement circle diameter PCD were constant regardless of changes in contact angle α. Meanwhile, the thicknesses of inner ring 61 and outer ring 63 were changed according to changes in contact angle α.

[0102] In the tapered roller bearing 60 of each specific example intended for application to the illustrated reducer, the following has been confirmed regarding the contact angle α and the appropriate preload value: As the contact angle α increases, the appropriate preload value increases. As the contact angle α decreases, the appropriate preload value decreases. The theoretical value of the appropriate preload value (N) is directly proportional to the contact angle α (°). As the capacity of the tapered roller bearing 60 increases, the slope of the appropriate preload value relative to the contact angle α increases.

[0103] As in the reducer 10 shown in Figs. 1 to 3, two tapered roller bearings 60A, 60B may be arranged in opposite directions to support the same shaft member. In this example, a preload is applied to the two tapered roller bearings 60A, 60B so as to pressurize them toward each other. The preload applied to the two tapered roller bearings 60A, 60B is preferably greater than the thrust load applied to the two tapered roller bearings 60A, 60B. More preferably, the appropriate preload value applied to the two tapered roller bearings 60A, 60B is greater than the thrust load applied to the two tapered roller bearings 60A, 60B. In this case, when a thrust load is generated, the inner ring 61 and the outer ring 63 are maintained in a state in which they are pressed toward each other in both bearings 60A, 60B. Therefore, abnormalities such as rattle and vibration during use of the tapered roller bearing 60 can be suppressed, and the life of the tapered roller bearing 60 and the life of the reducer 10 in which the tapered roller bearing 60 is incorporated can be stably extended.

[0104] In the reducer 10 shown in Figs. 1 to 3, the skew force generated in the cylindrical roller bearings 70A, 70B is applied as a thrust load to the tapered roller bearings 60A, 60B. The skew force generated in the cylindrical roller bearings 70A, 70B is about 5% of the radial load applied to the cylindrical roller bearings 70A, 70B. The radial load applied to the cylindrical roller bearings 70A, 70B in the reducer 10 is about 3000N or more and 50000N or less. Therefore, the skew force generated in the cylindrical roller bearing 70 during operation of the reducer 10 is about 150N or more and 2500N or less, as shown in Fig. 7.

[0105] 7 shows with dotted lines the skew forces SA to SC that occur in a specific example of reducer 10. Skew force SA is the skew force in reducer 10 incorporating the tapered roller bearing of specific example A described above. Skew force SB is the skew force in reducer 10 incorporating the tapered roller bearing of specific example B described above. Skew force SC is the skew force in reducer 10 incorporating the tapered roller bearing of specific example C described above.

[0106] As shown in FIG. 7, when the contact angle α is 5° or more, the optimum preload value of the tapered roller bearing 60 incorporated in the reducer 10 is greater than the skew force generated in the cylindrical roller bearing 70 incorporated in the reducer 10. Therefore, by setting the contact angle α to 5° or more, it is possible to impart more appropriate thrust load resistance performance to the tapered roller bearing 60. According to this example, it is possible to effectively prevent the preload from being released from the tapered roller bearing 60 due to the generation of a thrust load. Therefore, it is possible to prevent the occurrence of abnormalities such as rattle and vibration in the tapered roller bearing 60 during the operation of the reducer 10. By preventing the occurrence of such abnormalities, it is possible to stably extend the life of the tapered roller bearing 60 and the life of the reducer 10 in which the tapered roller bearing 60 is incorporated.

[0107] From this point of view, the contact angle α may be set to 5° or more and 10° or less, 5° or more and 8° or less, or 5° or more and 7° or less.

[0108] The dimensions of tapered roller bearing 60 applied to reducer 10 shown in Figures 1 to 3 may be determined as follows. When tapered roller bearing 60 having the dimensions described below is applied to reducer 10, the effect of setting the contact angle α to be equal to or greater than 3° and equal to or less than 10° described above is more effectively and more stably achieved. In other words, the radial load resistance of the tapered roller bearing can be improved more effectively and more stably while the necessary thrust load resistance performance is stably maintained.

[0109] The inner diameter D60a of the tapered roller bearing 60 may be 9.4 mm or more and 60 mm or less, 20 mm or more and 50 mm or less, or 25 mm or more and 45 mm or less. The inner diameter D60a of the tapered roller bearing 60 is the inner diameter of the tapered roller bearing 60, as shown in Figure 4. In the illustrated example, the inner diameter D60a of the tapered roller bearing 60 is the inner diameter of the tapered roller bearing 60 defined by the inner circumferential surface 62a of the inner ring 61.

[0110] The outer diameter D60b of the tapered roller bearing 60 may be 24 mm or more and 130 mm or less, 40 mm or more and 115 mm or less, or 55 mm or more and 100 mm or less. The outer diameter D60b of the tapered roller bearing 60 is the outer diameter of the tapered roller bearing 60 as shown in Figure 4. In the illustrated example, the outer diameter D60b of the tapered roller bearing 60 is the outer diameter of the tapered roller bearing 60 defined by the outer peripheral surface 64b of the outer ring 63.

[0111] The thickness T60 of the tapered roller bearing 60 may be 7.3 mm or more and 35 mm or less, 10 mm or more and 32.5 mm or less, or 15 mm or more and 27.5 mm or less. As described above, the thickness T60 is the length in the radial direction DR. In the illustrated example, the thickness T60 is the distance along the radial direction DR between the inner peripheral surface 62a of the inner ring 61 and the outer peripheral surface 64b of the outer ring 63.

[0112] The diameter D65a (see FIG. 5) of the small end face 66a of the tapered roller 65 may be 3.0 mm or more and 13.7 mm or less, 4.5 mm or more and 12 mm or less, or 6.0 mm or more and 10.5 mm or less.

[0113] The diameter D65b (see FIG. 5) of the large end face 66b of the tapered roller 65 may be 3.5 mm or more and 14.4 mm or less, 5.0 mm or more and 13 mm or less, or 6.5 mm or more and 11.5 mm or less.

[0114] The length L65 of the tapered roller 65 may be 6.8 mm or more and 33.7 mm or less, 10 mm or more and 30 mm or less, or 13 mm or more and 27 mm or less. The length L65 of the tapered roller 65 is the length along the central axis CA of the tapered roller 65 as shown in FIG.

[0115] By setting lower limits to the thickness T60 of the tapered roller bearing 60, the diameters D65a, D65b of the tapered rollers 65, and the length L65 of the tapered rollers 65, it is possible to improve the radial load resistance performance of the tapered roller bearing 60. By setting upper limits to the thickness T60 of the tapered roller bearing 60, the diameters D65a, D65b of the tapered rollers 65, and the length L65 of the tapered rollers 65, it is possible to reduce the size of the tapered roller bearing 60.

[0116] Therefore, a lower limit may be set for the product (T60×L65) of the thickness T60 (mm) of the tapered roller bearing 60 and the length L65 (mm) of the tapered roller 65. By setting a lower limit for the product (T60×L65) of the thickness T60 and the length L65, the radial load resistance performance of the tapered roller bearing 60 can be improved more stably. By setting an upper limit for the product (T60×L65) of the thickness T60 and the length L65, the tapered roller bearing 60 can be more effectively downsized. The product of the thickness T60 (mm) of the tapered roller bearing 60 and the length L65 (mm) of the tapered roller 65 may be 50 or more and 1400 or less, 58 or more and 1200 or less, 100 or more and 980 or less, or 200 or more and 740 or less.

[0117] Similarly, a lower limit may be set for the product (D65a×L65) of the diameter D65a (mm) of the small end face 66a of the tapered roller 65 and the length L65 (mm) of the tapered roller 65. By setting a lower limit for the product (D65a×L65) of the diameter D65a and the length L65, the radial load resistance performance of the tapered roller bearing 60 can be improved more stably. By setting an upper limit for the product (D65a×L65) of the diameter D65a and the length L65, the tapered roller bearing 60 can be more effectively downsized. The product (D65a×L65) of the diameter D65a (mm) of the small end face 66a of the tapered roller 65 and the length L65 (mm) of the tapered roller 65 may be 20 or more and 550 or less, 24 or more and 460 or less, 45 or more and 360 or less, or 78 or more and 280 or less.

[0118] The illustrated reducer 10 is configured as follows. As the tapered roller bearing 60, a first tapered roller bearing 60A and a second tapered roller bearing 60B are provided, which are arranged in order in an axial direction D1 parallel to the rotation axis RA of the shaft member 50. As the cylindrical roller bearing 70, a first cylindrical roller bearing 70A and a second cylindrical roller bearing 70B are provided, which are arranged between the two tapered roller bearings 60A, 60B in the axial direction D1. As the external gear 40, a first external gear 40A supported by the first cylindrical roller bearing 70A and a second external gear 40B supported by the second cylindrical roller bearing 70B are provided. The first tapered roller bearing 60A includes tapered rollers 65 inclined away from the rotation axis RA on the side closer to the second tapered roller bearing 60B in the axial direction D1. The second tapered roller bearing 60B includes tapered rollers 65 inclined away from the rotation axis RA on the side closer to the first tapered roller bearing 60A in the axial direction D1.

[0119] In the reducer 10 having this configuration, the shaft member 50 is rotatably supported by two tapered roller bearings 60A, 60B. A radial load is applied to the shaft member 50 from the first external gear 40A via the first cylindrical roller bearing 70A. A radial load is applied to the shaft member 50 from the second external gear 40B via the second cylindrical roller bearing 70B.

[0120] The direction of the radial load applied to the shaft member 50 from the first external gear 40A changes with the rotation of the shaft member 50. The direction of the radial load applied to the shaft member 50 from the second external gear 40B changes with the rotation of the shaft member 50. The radial load applied to the shaft member 50 from the first external gear 40A is directed in a different direction from the radial load applied to the shaft member 50 from the second external gear 40B. In the illustrated example, the radial load applied to the shaft member 50 from the first external gear 40A is directed in the opposite direction to the radial load applied to the shaft member 50 from the second external gear 40B.

[0121] Therefore, the load acting on the first tapered roller bearing 60A and the second tapered roller bearing 60B from the shaft member 50 changes periodically. When the range of change in the magnitude of the periodically changing load, that is, the amplitude of the load, becomes large, the tapered roller bearing 60 becomes susceptible to fatigue failure even if the absolute value of the load is small.

[0122] Therefore, it is effective to increase the bearing span L60 with respect to the arrangement pitch AP40 in the axial direction D1 of the first external gear 40A and the second external gear 40B. By increasing the bearing span L60, the amplitude of the load applied to the tapered roller bearings 60A, 60B can be reduced. The bearing span L60 is the distance along the axial direction D1 between the application point P60 of the first tapered roller bearing 60A and the application point P60 of the second tapered roller bearing 60B. However, from the viewpoint of miniaturizing the reducer 10, it is preferable not to make the bearing span L60 too large with respect to the arrangement pitch AP40. The bearing span L60 may be 2 to 5 times, 2.5 to 4.5 times, or 3 to 4 times the arrangement pitch AP40.

[0123] As described above, tapered roller bearing 60 according to this embodiment has a contact angle α of 3° or more and 10° or less. Tapered roller bearing 60 according to this embodiment includes inner ring 61, tapered rollers 65, and outer ring 63 which holds tapered rollers 65 between inner ring 61 and has a contact angle of 3° or more and 10° or less. Tapered roller bearing 60 according to this embodiment includes inner ring 61 including outer peripheral surface 62b, tapered rollers 65, and outer ring 63 which includes inner peripheral surface 64a which has a contact angle of 3° or more and 10° or less and holds tapered rollers 65 between outer peripheral surface 62b and inner peripheral surface 64a.

[0124] The reducer 10 of this embodiment includes an external gear 40, a shaft member 50 that eccentrically oscillates the external gear 40, a carrier 30 that rotatably supports the shaft member 50, a cylindrical roller bearing 70 provided between the external gear 40 and the shaft member 50, and a tapered roller bearing 60 provided between the carrier 30 and the shaft member 50 and having a contact angle α of 3° or more and 10° or less.

[0125] In the tapered roller bearing 60 and the reducer 10 according to the present embodiment, the contact angle α of the tapered roller bearing 60 is 3° or more and 10° or less. By setting the contact angle α to 10° or less, which is smaller than the conventional angle, it is possible to increase the thickness of the inner ring 61, increase the thickness of the outer ring 63, increase the diameters D65a and D65b of the tapered rollers 65, and increase the circumferential diameter PCD on which the tapered rollers 65 are arranged, without increasing the installation space of the tapered roller bearing 60. In other words, by reducing the contact angle α, it is possible to improve the radial load resistance performance while maintaining the installation space of the tapered roller bearing 60. By setting the lower limit of the contact angle α to 3°, it is possible to suppress the influence of the thrust load on the life of the tapered roller bearing 60. In other words, it is possible to improve the radial load resistance performance of the tapered roller bearing 60 while imparting the necessary thrust load resistance performance to the tapered roller bearing 60. As a result, it is possible to extend the life of the tapered roller bearing 60 and the reducer 10.

[0126] In one specific example of the present embodiment described above, the contact angle α may be 5° or more. When the lower limit of the contact angle α is set to 5°, the appropriate preload value to be applied to the tapered roller bearing 60 can be made larger than the skew force that can be applied to the tapered roller bearing 60 from the cylindrical roller bearing 70. This makes it possible to prevent the preload from being completely released from the tapered roller bearing 60, causing abnormalities such as vibration in the tapered roller bearing 60. This makes it possible to prevent an unintended large load from being applied to the tapered roller bearing 60 during use. It is possible to prevent unexpected damage to the tapered roller bearing 60 and the reducer 10.

[0127] Although one embodiment has been described with reference to one specific example, the above example is not intended to limit the embodiment. The above-described one embodiment can be implemented with various other specific examples, and various omissions, substitutions, changes, and additions can be made without departing from the spirit of the embodiment.

[0128] For example, although an example has been shown in which the tapered roller bearing 60 is applied to a reducer having a plurality of shaft members 50, the application is not limited to this example. The tapered roller bearing 60 may also be applied to a reducer having only one shaft member 50 located on the rotation axis MRA.

[0129] Among the embodiments disclosed in this specification, those that are composed of multiple objects may be integrated, and conversely, those that are composed of one object may be divided into multiple objects. Regardless of whether they are integrated or not, it is sufficient that they are configured to achieve the object of the invention. [Explanation of symbols]

[0130] 10: reducer, 30: carrier, 40, 40A, 40B: external gear, 50: shaft member, 60, 60A, 60B: tapered roller bearing, 61: inner ring, 63: outer ring, 65: tapered roller, 66a: small end face, 70, 70A, 70B: cylindrical roller bearing, α: contact angle

Claims

1. an inner ring including an outer peripheral surface; Tapered rollers and A tapered roller bearing comprising: an inner circumferential surface having a contact angle of 3° or more and 10° or less; and an outer ring that holds the tapered rollers between the outer circumferential surface and the inner circumferential surface.

2. 2. The tapered roller bearing according to claim 1, wherein the contact angle is 5° or greater.

3. 2. The tapered roller bearing according to claim 1, wherein the contact angle is equal to or less than 8 degrees.

4. 2. The tapered roller bearing according to claim 1, wherein the product of the radial thickness (mm) and the length (mm) of the tapered roller is 50 or greater and 1,400 or less.

5. 2. The tapered roller bearing according to claim 1, wherein the product of a diameter (mm) of the tapered roller at the small end face and a length (mm) of the tapered roller is 20 or greater and 550 or less.

6. An external gear; a shaft member for eccentrically rocking the external gear; a carrier that rotatably supports the shaft member; a cylindrical roller bearing provided between the external gear and the shaft member; a tapered roller bearing provided between the carrier and the shaft member and having a contact angle of 3° or more and 10° or less.

7. The reducer according to claim 6 , wherein the contact angle is 5° or more.

8. The reducer according to claim 6 , wherein the contact angle is equal to or smaller than 8°.

9. 7. The reducer according to claim 6, wherein a product of a thickness (mm) of the tapered roller bearing and a length (mm) of the tapered roller is equal to or greater than 50 and equal to or less than 1,400.

10. 7. The reducer according to claim 6, wherein a product of a diameter (mm) of the tapered roller at the small end face and a length (mm) of the tapered roller is equal to or greater than 20 and equal to or less than 550.

11. the tapered roller bearing includes a first tapered roller bearing and a second tapered roller bearing arranged in sequence in an axial direction parallel to a rotation axis of the shaft member, the cylindrical roller bearing includes a first cylindrical roller bearing and a second cylindrical roller bearing disposed between a first tapered roller bearing and a second tapered roller bearing in the axial direction, the external gear includes a first external gear supported by the first cylindrical roller bearing and a second external gear supported by the second cylindrical roller bearing, the first tapered roller bearing includes tapered rollers having a center axis inclined away from the rotation axis on a side closer to the second tapered roller bearing in the axial direction, The reducer according to claim 6 , wherein the second tapered roller bearing includes tapered rollers having a center axis that is inclined away from the rotation axis on a side closer to the first tapered roller bearing in the axial direction.

12. 12. The reducer according to claim 11, wherein a distance along the axial direction between a point of load of the first tapered roller bearing and a point of load of the second tapered roller bearing is equal to or greater than twice an arrangement pitch of the first external gear and the second external gear in the axial direction.

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