Tapered roller bearing and speed reducer

Abstract

The invention provides a tapered roller bearing and a speed reducer. A tapered roller bearing includes: an inner ring including an outer peripheral surface; a tapered roller; and an outer ring including an inner circumferential surface. The tapered rollers are held between the outer peripheral surface of the inner ring and the inner peripheral surface of the outer ring. The contact angle of the outer ring is 3 DEG or more and 10 DEG or less.

Description

Technical Field

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

[0002] Tapered roller bearings are becoming more and more popular. Tapered roller bearings are not only able to withstand radial loads, but also have thrust load resistance.

[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 the external gear so that it can rotate relative to the shaft member. The cylindrical roller bearing receives a radial load from the external gear. The cylindrical roller bearing subjected to the radial load generates an axial deflection force. Tapered roller bearings are arranged on both sides of the cylindrical roller bearing in the axial direction. The tapered roller bearing supports the axial deflection force from the cylindrical roller bearing.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2022-152790 Summary of the invention

[0005] The loads required by mechanical devices including tapered roller bearings, such as loads required by reducers, have been increasing in recent years. With this trend, the load capacity of tapered roller bearings is required to increase. The inventor of this case conducted in-depth research on this issue and obtained the following insights: it is possible to maintain sufficient thrust load resistance while improving the radial load resistance of tapered roller bearings. Based on this insight, the present invention aims to maintain sufficient thrust load resistance while improving the radial load resistance of tapered roller bearings.

[0006] The present invention relates to the following <1> to <15>.

[0007] <1> A tapered roller bearing having a contact angle of 3° or more and 10° or less.

[0008] <2> A tapered roller bearing comprising:

[0009] Inner circle;

[0010] Tapered rollers; and

[0011] The outer ring has a contact angle of 3° or more and 10° or less, and holds the tapered roller between the outer ring and the inner ring.

[0012] <3> A tapered roller bearing comprising:

[0013] an inner ring including an outer peripheral surface;

[0014] Tapered rollers; and

[0015] The outer ring includes an inner peripheral surface having a contact angle of 3° or more and 10° or less, and the tapered roller is held between the outer peripheral surface and the inner peripheral surface.

[0016] <4> The tapered roller bearing according to any one of <1> to <3>, wherein

[0017] The contact angle is 5° or more.

[0018] <5> The tapered roller bearing according to any one of <1> to <4>, wherein

[0019] The contact angle is 8° or less.

[0020] <6> The tapered roller bearing according to any one of <1> to <5>, wherein

[0021] The product of the thickness of the tapered roller bearing in the radial direction and the length of the tapered roller is greater than or equal to 50 and less than or equal to 1400, wherein the units of the thickness and the length are mm.

[0022] <7> The tapered roller bearing according to any one of <1> to <6>, wherein

[0023] The product of the diameter at the small end surface of the tapered roller and the length of the tapered roller is greater than or equal to 20 and less than or equal to 550, wherein the units of the diameter and the length are mm.

[0024] <8> A speed reducer comprising:

[0025] External gear;

[0026] a shaft member that causes the external gear to eccentrically swing;

[0027] a gear carrier that rotatably supports the shaft member;

[0028] a cylindrical roller bearing disposed between the external gear and the shaft member; and

[0029] A tapered roller bearing is provided between the gear carrier and the shaft member and has a contact angle of 3° or more and 10° or less.

[0030] <9> The speed reducer according to <8>, wherein:

[0031] The speed reducer includes a housing having internal teeth meshing with the external gear and at least partially accommodating the carrier.

[0032] <10> The speed reducer according to <8> or <9>, wherein:

[0033] The contact angle is 5° or more.

[0034] <11> The speed reducer according to any one of <8> to <10>, wherein:

[0035] The contact angle is 8° or less.

[0036] <12> The speed reducer according to any one of <8> to <11>, wherein:

[0037] The product of the thickness of the tapered roller bearing and the length of the tapered roller is greater than or equal to 50 and less than or equal to 1400, wherein the units of the thickness and the length are mm.

[0038] <13> The speed reducer according to any one of <8> to <12>, wherein:

[0039] The product of the diameter at the small end surface of the tapered roller and the length of the tapered roller is greater than or equal to 20 and less than or equal to 550, wherein the units of the diameter and the length are mm.

[0040] <14> The speed reducer according to any one of <8> to <13>, wherein:

[0041] The tapered roller bearing includes a first tapered roller bearing and a second tapered roller bearing which are sequentially arranged in an axial direction parallel to the rotation axis of the shaft member.

[0042] The cylindrical roller bearing includes a first cylindrical roller bearing and a second cylindrical roller bearing which are arranged between the first tapered roller bearing and the second tapered roller bearing in the axial direction.

[0043] 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.

[0044] The first tapered roller bearing includes a tapered roller having a central axis inclined in such a manner that a side close to the second tapered roller bearing in the axial direction is away from the rotation axis.

[0045] The second tapered roller bearing includes a tapered roller having a center axis that is inclined in such a manner that a side closer to the first tapered roller bearing in the axial direction is away from the rotation axis.

[0046] <15> The speed reducer according to <14>, wherein:

[0047] A distance between a point of action of the first tapered roller bearing and a point of action of the second tapered roller bearing along the axial direction is at least twice a spacing between the first external gear and the second external gear in the axial direction.

[0048] According to the present invention, it is possible to improve the radial load resistance performance of the tapered roller bearing while maintaining sufficient thrust load resistance performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a diagram for explaining one embodiment and is a longitudinal sectional view showing a speed reducer.

[0050] Figure 2 It is along Figure 1 Cross-sectional view along line II-II.

[0051] Figure 3 yes Figure 1 A partial enlarged view of .

[0052] Figure 4 Yes means Figure 3 A longitudinal section of a tapered roller bearing is shown.

[0053] Figure 5 Yes means Figure 4 A top view of the tapered rollers of a tapered roller bearing is shown.

[0054] Figure 6 This is a graph showing the relationship between the contact angle and the radial basic dynamic load rating.

[0055] Figure 7 This is a graph showing the relationship between the contact angle, the appropriate preload value (appropriate preload load (N)), and the deflection force (N).

[0056] Description of Reference Numerals

[0057] 10. Reducer; 30. Gear rack; 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. DETAILED DESCRIPTION

[0058] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Figure 1 to Figure 7 The figures are used to explain one embodiment of the present invention. The structure shown in some figures may be omitted in other figures. The scale and aspect ratio may also be different between the drawings.

[0059] In the example shown in the figure, the tapered roller bearing of this embodiment is applicable to an eccentric swing type reducer. Hereinafter, this embodiment is described based on a reducer to which the tapered roller bearing is applied. However, the tapered roller bearing of this embodiment is not limited to being applicable to an eccentric swing type reducer, but can be applicable to various reducers. The tapered roller bearing of this embodiment is not limited to being applicable to a reducer, but can be applicable to various devices.

[0060] In the present embodiment, the reducer 10 includes: an external gear 40; a shaft member 50 that causes the external gear 40 to eccentrically swing; a gear frame 30 that supports the shaft member 50 so as to be rotatable; a cylindrical roller bearing 70 that is disposed between the external gear 40 and the shaft member 50; and a tapered roller bearing 60 that is disposed between the gear frame 30 and the shaft member 50. The tapered roller bearing 60 is studied for maintaining the required thrust load resistance performance while improving the radial load resistance performance. Specifically, the contact angle α of the tapered roller bearing 60 is greater than 3° and less than 10°. As discussed later, by setting the contact angle α of the tapered roller bearing 60 to greater than 3° and less than 10°, the required thrust load resistance performance can be maintained while improving the radial load resistance performance of the tapered roller bearing 60.

[0061] 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 referred to as an axial load.

[0062] Reference Figure 1 to Figure 3 , the overall structure of the speed reducer 10 is described. The speed reducer 10 shown in the figure also includes a housing 20. The housing 20 at least partially accommodates the gear carrier 30. A main bearing 12 is provided between the housing 20 and the gear carrier 30. The housing 20 and the gear carrier 30 can rotate relative to each other around the main rotation axis MRA.

[0063] The reducer 10 receives rotation from a driving component 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 a relative rotation between the housing 20 and the gear frame 30. The direction parallel to the main rotation axis MRA is called the axial direction D1. The gear frame 30 holds the shaft member 50 rotatably. The rotation axis RA of the tapered roller bearing 60 is consistent with the rotation axis of the shaft member 50. The rotation axis RA of the tapered roller bearing 60 and the shaft member 50 is parallel to the axial direction D1.

[0064] The driving component inputs rotation to the shaft member 50. The shaft member 50 includes an eccentric body 55. The eccentric body 55 is eccentric with respect to the rotation center of the shaft member 50. The shaft member 50 passes through the external gear 40. The external gear 40 is located on the eccentric body 55. As the shaft member 50 rotates, the external gear 40 swings eccentrically. The external gear 40 has external teeth 45 that mesh with internal teeth 25 provided on the inner surface of the housing 20. The number of teeth of the internal teeth 25 is different from the number of teeth of the external teeth 45. If the rotation is input to the shaft member 50, the internal teeth 25 mesh with the external teeth 45, and the external gear 40 swings eccentrically. Due to the difference in the number of teeth between the internal teeth 25 and the external teeth 45, the gear frame 30 supporting the external gear 40 and the shaft member 50 rotates relative to the housing 20.

[0065] Hereinafter, the specific structures of the housing 20 , the carrier 30 , the external gear 40 , and the shaft member 50 shown in the drawings will be described in detail in sequence.

[0066] The housing 20 has internal teeth 25. The internal teeth 25 are arranged in the circumferential direction DC centered on the main rotation axis MRA. In the example shown in the figure, the speed reducer 10 has two external gears 40A and 40B arranged in the axial direction D1. Each internal tooth 25 extends in the axial direction D1 and meshes with the external teeth 45 of the two external gears 40A and 40B.

[0067] The housing 20 shown in the figure includes a substantially cylindrical housing body 21 and an internal tooth pin 24 held on the inner surface of the housing body 21. The housing body 21 is provided with a plurality of pin grooves arranged in the circumferential direction DC, the pin grooves extending in the axial direction D1, and accommodating and holding the cylindrical internal tooth pin 24. Each internal tooth pin 24 forms an internal tooth 25.

[0068] The gear frame 30 is held in the housing 20 by a pair of main bearings 12. The gear frame 30 can rotate relative to the housing 20 around the main rotation axis MRA. The illustrated gear frame 30 includes a gear frame base 31 and a gear frame plate 32 fixed to each other. The gear frame base 31 and the gear frame plate 32 can be fixed to each other using fasteners such as bolts. The gear frame base 31 includes a circular plate-shaped base plate portion 31a and a plurality of column portions 31b protruding relative to the base plate portion 31a in the axial direction D1. The base plate portion 31a and the plurality of column portions 31b may also be formed integrally. The plurality of column portions 31b may also be arranged at equal intervals in the circumferential direction DC centered on the main rotation axis MRA. In the illustrated specific example, three column portions 31b are provided.

[0069] The gear frame 30 shown in the figure is provided with a central hole 34 and a through hole 35. The central hole 34 and the through hole 35 penetrate the gear frame base 31 and the gear frame plate 32 respectively. The central hole 34 is located on the main rotation axis MRA. A plurality of through holes 35 are provided in the gear frame 30. The plurality of through holes 35 are positioned at equal intervals in the circumferential direction DC centered on the main rotation axis MRA.

[0070] The shaft member 50 is rotatably held on the gear frame 30. The shaft member 50 shown in the figure is inserted into the through hole 35 of the gear frame 30. A pair of tapered roller bearings 60 are arranged between the gear frame 30 and the shaft member 50. The shaft member 50 can rotate relative to the gear frame 30 with the aid of the tapered roller bearings 60 around the rotation axis RA. The rotation axis RA is parallel to the axial direction D1. The reducer 10 shown in the figure includes a plurality of shaft members 50 respectively inserted into a plurality of through holes 35. The plurality of shaft members 50 are positioned at equal intervals in the circumferential direction DC centered on the rotation axis MRA. In the specific example shown in the figure, three through holes 35 are provided. In the example shown in the figure, three shaft members 50 are provided.

[0071] The illustrated shaft member 50 includes a shaft body portion 51 and a pair of eccentric bodies 55 located on the shaft body portion 51. The eccentric body 55 is a cylindrical portion. The eccentric body 55 is enlarged in diameter relative to the shaft body portion 51. The eccentric body 55 is eccentric relative to 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 to opposite sides with respect to the rotation axis RA by the same amount of eccentricity. In other words, in a cross section orthogonal 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-symmetrical with respect to a point on the rotation axis RA as the center.

[0072] The shaft body portion 51 has a first bearing support portion 52a which serves as an insertion portion inserted into the gear frame base 31, and a second bearing support portion 52b which serves as an insertion portion inserted into the gear frame plate 32. The bearing support portions 52a and 52b support the first tapered roller bearing 60A and the second tapered roller bearing 60B, respectively. A pair of eccentric bodies 55A and 55B are located between the pair of bearing support portions 52a and 52b in the axial direction D1. The illustrated shaft member 50 also includes an input gear 59 fixed to the shaft body portion 51. In the illustrated example, the input gear 59, the first bearing support portion 52a, the first eccentric body 55A, the second eccentric body 55B, and the second bearing support portion 52b are positioned in sequence in the axial direction D1.

[0073] The illustrated reducer 10 has a first external gear 40A and a second external gear 40B as external gears 40. The first external gear 40A is located on a first eccentric body 55A of a plurality of shaft members 50. The second external gear 40B is located on a second eccentric body 55B of a plurality of shaft members 50. The first external gear 40A and the second external gear 40B are located between a base plate portion 31a of a gear carrier base 31 and a gear carrier plate 32 in the axial direction D1.

[0074] The illustrated external gear 40 includes a disk-shaped central plate portion 41 and external teeth 45 arranged on the peripheral portion of the central plate portion 41. A central hole 42a and a column through hole 42b are provided in the central plate portion 41. 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 through holes 42b are spaced at equal intervals and are located in the circumferential direction DC centered on the central hole 42a. The column 31b of the gear frame 30 passes through the column through hole 42b. In the illustrated specific example, three column through holes 43 are provided.

[0075] A hole 43 is also provided in the central plate portion 41. In the example shown in the figure, three holes 43 are spaced at equal intervals and are located in the circumferential direction DC centered on the central hole 42a. An eccentric body 55 is arranged 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 by means of the first cylindrical roller bearing 70A. The second external gear 40B is supported on the second eccentric body 55B of the shaft member 50 by means of the second cylindrical roller bearing 70B.

[0076] 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, due to the rotation of the three shaft members 50, the external gear 40 eccentrically swings. In other words, due to the rotation of the three shaft members 50, the external gear 40 moves in parallel on a circumferential path centered on the main rotation axis MRA. The first external gear 40A and the second external gear 40B move with a half phase difference.

[0077] Rotation is input from a driving component such as a motor to the reducer 10 having the above structure. For example, the output gear of the driving component is arranged on the main rotation axis MRA and meshes with the input gear 59 of the three shaft members 50. If the output gear rotates, the shaft member 50 rotates together with the input gear 59, and the external gear 40 swings eccentrically. At this time, the external teeth 45 of the external gear 40 mesh with the internal teeth 25 of the housing 20. Due to the difference in the number of teeth between the external teeth 45 and the internal teeth 25, the gear frame 30 and the housing 20 that support the external gear 40 by means of the shaft member 50 rotate relative to each other around the main rotation axis MRA. When the housing 20 is fixed, the rotation of the output gear frame 30. When the gear frame 30 is fixed, the rotation of the output housing 20.

[0078] Next, the tapered roller bearing 60 will be described. Figure 4 and Figure 5 As shown, 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. Alternatively, the tapered roller bearing 60 further includes a retainer 67 for retaining the tapered rollers 65.

[0079] The inner ring 61 is annular. The inner ring 61 extends in the circumferential direction DC along the circumference of a circle 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 are opposite to each other in the radial direction DR orthogonal to the rotation axis RA. The inner peripheral surface 62a faces the inner side of the radial direction DR. The outer peripheral surface 62b faces the outer side of the radial direction. The inner side of the radial direction DR refers to the side close to the rotation axis RA on the radial direction DR. The outer side of the radial direction DR refers to the side away from the rotation axis RA on the radial direction DR.

[0080] The inner circumferential surface 62a may be orthogonal 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. Figure 3 In the example shown, the inner peripheral surface 62a contacts the first bearing support portion 52a of the shaft body 51. The inner ring 61 is located on the first bearing support portion 52a of the shaft body 51. Alternatively, the inner ring 61 contacts the shaft member 50, and the first cylindrical roller bearing 70 is held on the shaft member 50.

[0081] The outer peripheral surface 62b contacts the tapered roller 65. The outer peripheral surface 62b serves as a raceway surface for the tapered roller 65. The outer peripheral surface 62b is inclined relative to the rotation axis RA. Figure 3 In the example shown, 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.

[0082] 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 are opposite to each other in the radial direction DR. The inner peripheral surface 64a faces the inner side of the radial direction DR. The outer peripheral surface 64b faces the outer side of the radial direction.

[0083] The outer peripheral surface 64b may be orthogonal to the radial direction DR. The outer peripheral surface 64b may be parallel to the axial direction D1. Figure 3 In the example shown, the outer peripheral surface 64b contacts the inner surface of the through hole 35 of the carrier 30. The outer ring 63 is located in the through hole 35 of the carrier 30. The tapered roller bearing 60 may be held on the carrier 30 by fitting the outer ring 63 into the through hole 35 of the carrier 30.

[0084] The inner circumferential surface 64a contacts the tapered roller 65. The inner circumferential surface 64a serves as a raceway surface for the tapered roller 65. The inner circumferential surface 64a is inclined relative to the rotation axis RA. Figure 3In the example shown, the inner circumferential surface 64a of the outer ring 63 of the first tapered roller bearing 60A is separated 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 circumferential surface 64a of the outer ring 63 of the second tapered roller bearing 60B is separated 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.

[0085] The plurality of tapered rollers 65 are arranged between the inner ring 61 and the outer ring 63. The plurality of tapered rollers 65 are arranged at intervals in the circumferential direction DC. The plurality of tapered rollers 65 are positioned relative to each other by a retainer 67. The retainer 67 may be, for example, an annular member having a plurality of holes for accommodating the tapered rollers 65.

[0086] The tapered roller 65 has a truncated cone shape or a shape obtained by chamfering a truncated cone. The position of the vertex of the truncated cone constituting the tapered roller 65 is located on the rotation axis RA. The positions of the vertices of the truncated cones constituting the plurality of tapered rollers 65 included in the tapered roller bearing 60 are located at the same position on the rotation axis RA. The truncated cone is obtained by cutting the cone using a surface parallel to the bottom surface of the cone. In this specification, the vertex of the truncated cone means the vertex of the cone before cutting.

[0087] like Figure 5 As shown, 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 bottom face of the two bottom faces of the truncated cone of the tapered roller 65. The small end face 66a is the smaller bottom face of the two bottom faces of the truncated cone of the tapered roller 65. In the example shown in the figure, the large end face 66b is a circle. In the example shown in the figure, the small end face 66a is a circle.

[0088] Figure 3 The large end surface 66 b of the tapered roller 65 included in the first tapered roller bearing 60A shown faces the side close to the first cylindrical roller bearing 70A and the first eccentric body 55A in the axial direction D1 . Figure 3 The large end surface 66 b of the tapered roller 65 included in the second tapered roller bearing 60B shown faces the side close to the second cylindrical roller bearing 70B and the second eccentric body 55B in the axial direction D1 .

[0089] The tapered roller 65 has a central axis CA. The tapered roller 65 rotates between the inner ring 61 and the outer ring 63 about the central axis CA. In the example shown in the figure, the central axis CA passes through the center of the small end face 66a. In the example shown in the figure, the central axis CA passes through the center of the large end face 66b. Figure 3The center axis CA of the tapered rollers 65 included in the first tapered roller bearing 60A shown in the figure 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 in the axial direction D1. Figure 3 The center axis CA of the tapered rollers 65 included in the second tapered roller bearing 60B shown in the figure 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.

[0090] 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 surface 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 surface 66a side in the axial direction D1.

[0091] like Figure 1 and Figure 3 As shown, in the reducer 10, the two tapered roller bearings 60A and 60B are arranged in opposite directions so that the central axis CA is consistent. The large end faces 66b of the tapered rollers 65 of the two tapered roller bearings 60A and 60B are opposite to each other. The cylindrical roller bearing 70 is located between the two tapered roller bearings 60A and 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 example shown in the figure, the two cylindrical roller bearings 70A and 70B are located between the two tapered roller bearings 60A and 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 sequence in the axial direction D1.

[0092] During the operation of the reducer 10, the cylindrical roller bearing 70 is subjected to a radial load in a radial direction orthogonal to the rotation axis of the cylindrical roller bearing 70 between the eccentric body 55 and the external gear 40. The cylindrical roller bearing 70 subjected to the radial load generates a deflection force in the direction along the rotation axis. In a general reducer 10, the radial load applied to the cylindrical roller bearing 70 becomes greater than 3000N and less than 50000N. It is confirmed that the deflection force becomes about 5% of the radial load. Therefore, the deflection force generated in the cylindrical roller bearing 70 during the operation of the reducer 10 is usually greater than 150N and less than 2500N.

[0093] The deflection force is applied to the tapered roller bearing 60 as a thrust load by the inner ring or outer ring of the cylindrical roller bearing 70. In another example, the deflection force is applied to the tapered roller bearing 60 as a thrust load 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 example shown in the figure, the two tapered roller bearings 60A and 60B are configured so that the large end surface 66b of the tapered roller 65 faces the cylindrical roller bearing 70 side in the axial direction D1. In addition, the two tapered roller bearings 60A and 60B are configured so that the inner ring 61 protrudes to the cylindrical roller bearing 70 side in the axial direction D1 relative to the outer ring 63. The thrust load caused by the deflection force is applied to each inner ring 61 of the two tapered roller bearings 60A and 60B, and the two tapered roller bearings 60A and 60B support the thrust load without substantially moving in the axial direction D1.

[0094] like Figure 4 As shown in FIG. 1 , the inner ring 61 may include at least one of a small flange 63a and a large flange 63b. The small flange 63a is provided on the outer peripheral surface 62b of the inner ring 61. The small flange 63a contacts the small end surface 66a of the tapered roller 65 to suppress the relative movement of the tapered roller 65 in the axial direction D1 relative to the inner ring 61. The large flange 63b contacts the large end surface 66b of the tapered roller 65 to suppress the relative movement of the tapered roller 65 in the axial direction D1 relative to the inner ring 61.

[0095] However, the loads required by mechanical devices including the tapered roller bearing 60, such as the loads required by the reducer, have been increasing in recent years. With this trend, the load capacity of the tapered roller bearing is required to be increased. As a solution to this problem, in this embodiment, the contact angle α of the tapered roller bearing 60 is set to be greater than 3° and less than 10°. Figure 4 As shown in FIG. 1 , the contact angle α is an angle between the inner peripheral surface 64a of the outer ring 63 and the rotation axis RA. The contact angle α is an angle of 0° or more and 90° or less.

[0096] In the past, the contact angle α of the tapered roller bearing was set to an angle greater than 10°, for example, greater than 15° or greater than 20°. The background for setting the contact angle α to be larger is that it is believed that the tapered roller bearing is used to replace the cylindrical roller bearing, so the thrust load resistance performance of the tapered roller bearing needs to be sufficient. In the "5-dimensional series a" of JIS B1512-3: 2011 that specifies tapered roller bearings, the specified contact angle is within the range of more than 10° and less than 30°. In this way, the JIS standard does not envision a contact angle of less than 10°.

[0097] However, the inventors of this case conducted in-depth research and confirmed that: depending on the purpose of the tapered roller bearing 60, the tapered roller bearing 60 with a contact angle α of 10° or less has sufficient thrust load resistance performance. For example, for a tapered roller bearing 60 that is not subjected to a large thrust load, the contact angle α can also be set to 10° or less. For a tapered roller bearing 60 used in parallel with a cylindrical roller bearing, the contact angle α can also be set to 10° or less. For a tapered roller bearing 60 that receives a deflection force from a cylindrical roller bearing, the contact angle α can also be set to 10° or less. For a tapered roller bearing 60 that supports the same supporting member as a cylindrical roller bearing, the contact angle α can also be set to 10° or less. For a tapered roller bearing 60 that supports the crankshaft (shaft member 50) of an eccentric swing type reducer, the contact angle α can also be set to 10° or less. It is confirmed that the 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 the reducer.

[0098] By setting the contact angle α to be 10° or less, which is smaller than before, the tapered roller 65 can be thickened without increasing the thickness T60 of the tapered roller bearing 60. By setting the contact angle α to be 10° or less, which is smaller than before, the thickness of the inner ring 61 in the radial direction DR can be thickened without increasing the thickness T60 of the tapered roller bearing 60. By setting the contact angle α to be 10° or less, which is smaller than before, the thickness of the outer ring 63 in the radial direction DR can be thickened 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.

[0099] like Figure 4 As shown, the thickness T60 of the tapered roller bearing 60 is the distance between the inner peripheral surface 62 a of the inner ring 61 and the outer peripheral surface 64 b of the outer ring 63 along the radial direction DR.

[0100] By reducing the contact angle α, as shown in Table 1 and Figure 6 As shown in Table 1, the radial load resistance can be significantly improved. By reducing the contact angle α, as shown in Table 1, the driving torque can be significantly reduced. By reducing the contact angle α, as shown in Table 1, the life of the tapered roller bearing 60 and the reducer 10 including the tapered roller bearing 60 can be significantly extended.

[0101]

Table 1

[0102] Table 1 Evaluation results of load resistance performance

[0103]

[0104] The "basic dynamic load rating" in Table 1 refers to the radial basic dynamic load rating calculated from the theoretical formula based on JIS B1518:2013. Figure 6 Indicates the relationship between the contact angle α and the basic dynamic load rating ratio.

[0105] The "basic dynamic load rating" is the radial load that the bearing can withstand for a basic rated life of 1 million revolutions. Therefore, the "basic dynamic load rating" becomes an indicator of the radial load resistance of tapered roller bearings. Figure 6 In the above, the thickness T60 of the tapered roller bearing 60 and the size of the tapered roller 65 are kept constant, and the contact angle α, the thickness of the inner ring 61, and the thickness of the outer ring 63 are changed to relatively evaluate the basic dynamic load rating.

[0106] As shown in Table 1 and Figure 6 As shown in FIG. 1 , as the contact angle α decreases, the basic dynamic load rating increases. That is, by setting the contact angle α to be 10° or less, which is smaller than the conventional contact angle, the radial load resistance performance of the tapered roller bearing 60 can be improved.

[0107] The "bearing span ratio" in Table 1 is the relative ratio of the bearing span L60. The "bearing span ratio" in Table 1 indicates the change in the bearing span L60 corresponding to the contact angle α. The bearing span L60 is applicable to Figures 1 to 3 The distance in the direction parallel to the central axis CA between the action point P60 of the first tapered roller bearing 60A and the action point P60 of the second tapered roller bearing 60B of the speed reducer 10 shown.

[0108] like Figure 4 As shown in FIG. 1 , the point of action P60 of the tapered roller bearing 60 is located on the rotation axis RA of the tapered roller bearing 60. The point of action P60 is located at the intersection of a straight line SL65 orthogonal to the center 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 a position on the center axis CA of the tapered roller 65. The distance from the center 65 to the small end face 66a along the center axis CA is equal to the distance from the center 65C to the large end face 66b along the center axis CA. When calculating the bearing span ratio shown in Table 1, the dimensions of the reducer 10 are set to general dimensions in a reducer whose output is 1000 Nm or more and 2000 Nm or less.

[0109] exist Figure 1 to Figure 3In the example shown, radial loads are applied from the external gears 40A and 40B to the shaft member 50 and the cylindrical roller bearing 70. The center position of the radial load from the external gears 40A and 40B in the axial direction D1 becomes the center position P40A and P40B in the axial direction D1 of each external gear 40A and 40B. In addition, radial loads are applied from the shaft member 50 to each tapered roller bearing 60A and 60B. The center position of the radial load received by each tapered roller bearing 60A and 60B from the shaft member 50 in the axial direction D1 becomes the point of action P60 of the tapered roller bearing 60A and 60B.

[0110] 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. For the calculation of the radial load, only the contact angle α and the bearing span L60 are changed, and other conditions (the structure of the shaft member 50, the structure of the cylindrical roller bearing 70, the structure of the external gears 40A and 40B, the radial load from the external gears 40A and 40B, etc.) are set constant regardless of the contact angle α and the bearing span L60.

[0111] As shown in Table 1, as the contact angle α decreases, the bearing span L60 can be ensured to be longer. According to the contact angle α, the bearing span L60 can be extended while maintaining the length of the shaft member 50 in the axial direction D1 constant.

[0112] As shown in Table 1, the bearing load ratio can be reduced by extending the bearing span L60. In other words, the bearing load ratio can be reduced by reducing the contact angle α. That is, by setting the contact angle α to 10° or less than the conventional one, the radial load resistance performance can be improved.

[0113] The “lifetime ratio” in Table 1 indicates Figure 1 to Figure 3 The ratio of the rated life of the tapered roller bearings 60 used in the speed reducer 10 shown. The rated life is calculated using the calculation formula specified in JIS. The rated life is proportional to the value obtained by raising the ratio of the basic rated dynamic load of the tapered roller bearings 60 to the radial load applied to each tapered roller bearing 60 at the action point P60 to the power of 10 / 3.

[0114] As described above, by reducing the contact angle α, the basic dynamic load rating of the tapered roller bearing 60 can be increased. In addition, by reducing the contact angle α, the contact angle of the tapered roller bearing 60 can be reduced. Figure 1 to Figure 3 The radial load applied by the tapered roller bearing 60 of the reducer 10 shown in FIG. 1 (bearing load ratio in Table 1). In addition, the rated life is proportional to the ratio of the applied radial load to the basic rated dynamic load raised to the power of 10 / 3. Thus, by reducing the contact angle α, the rated life can be significantly extended. That is, by setting the contact angle α to less than 10° smaller than before, the radial load resistance performance can be significantly improved.

[0115] 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 the starting torque. The sliding friction between the large end face 66b of the tapered roller 65 and the large flange 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 retainer 67 can affect the driving torque required when starting the tapered roller bearing. Among them, the sliding friction between the large end face 66b of the tapered roller 65 and the large flange 63b of the inner ring 61 has a decisive influence 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 based on the sliding friction between the large end face 66b of the tapered roller 65 and the large flange 63b of the inner ring 61.

[0116] The driving torque is affected by the friction of each part caused by the preload discussed later. As discussed later, there is an appropriate value for preload, and the appropriate value for preload can be reduced by reducing the contact angle. As a result, as shown in Table 1, the driving torque can be effectively reduced by reducing the contact angle α. 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 installed can be extended. That is, by setting the contact angle α to less than 10° smaller than before, the radial load resistance performance can be improved.

[0117] In addition, the assembly of the illustrated reducer 10 may be implemented as follows. First, prepare a shaft member 50 having an inner ring 61, a tapered roller 65, and a retainer 67 mounted on bearing support portions 52a, 52b. Alternatively, a tapered roller bearing 60 may also be mounted on the shaft member 50. Next, the shaft member 50 is inserted into the hole 43 of the external gear 40. At this time, the maximum circumscribed circle of the tapered roller 65 located on the shaft member 50 needs to be smaller than the inner diameter of the hole 43. Thereafter, the shaft member 50 that has passed through the hole 43 is inserted into the outer ring 63 that has been mounted on the through hole 35 of the gear frame 30. The tapered roller 65 contacts the outer ring 63 and the tapered roller bearing 60 is assembled. The shaft member 50 is rotatably held on the gear frame 30 by means of the tapered roller bearing 60.

[0118] Furthermore, by setting the contact angle α to be less than 10° smaller than before, the diameter on the circumference of the tapered rollers 65 (hereinafter referred to as the "arrangement circle diameter") can be increased without increasing the maximum circumscribed circle of the tapered rollers 65 or making the tapered rollers 65 thinner. The arrangement circle diameter PCD (Pitch Circle Diameter) is equivalent to twice the length along the radial direction DR (arrangement circle radius) from the center 65C of each tapered roller 65 arranged along a circle centered on the rotation axis RA to the rotation axis RA.

[0119] By increasing the arrangement circle diameter PCD of the tapered roller 65, it is possible to achieve a smooth and stable operation without increasing the outer diameter D60b (see Figure 4 ) is increased in diameter of the rolling surface (outer peripheral surface 62b) of the inner ring 61. As the rolling surface of the inner ring 61 is enlarged in diameter, the bearing transmission surface can be enlarged. That is, by setting the contact angle α to be less than 10° smaller than before, the radial load resistance performance of the tapered roller bearing can be improved by increasing the diameter of the configuration circle diameter PCD of the tapered roller 65.

[0120] In fact, tapered roller bearings are made and installed in Figures 1 to 3 The life and driving torque of the speed reducer with the structure shown were measured. The tapered roller bearings with various contact angles α were evaluated by comparing with a reference bearing with a contact angle α of 20°.

[0121] The column "Life" in Table 1 shows the results of evaluating the tapered roller bearings having various contact angles α according to the following criteria.

[0122] AA: A life of 1.4 times or more of the standard bearing was achieved.

[0123] A: A life of 1.2 times or more of the standard bearing was achieved.

[0124] B: A life shorter than 1.2 times that of the reference bearing was obtained.

[0125] The column "Driving Torque" in Table 1 shows the results of evaluating the tapered roller bearings having various contact angles α according to the following criteria.

[0126] AA: The driving torque becomes 0.70 times or less of the driving torque of the conventional tapered roller bearing.

[0127] A: The driving torque becomes 0.85 times or less of the driving torque of the conventional tapered roller bearing.

[0128] B: The driving torque is 0.85 times greater than the driving torque of the conventional tapered roller bearing.

[0129] According to the results of Table 1, by setting the contact angle α to 10° or less, which is smaller than before, the radial load resistance of the tapered roller bearing 60 can be improved. From the viewpoint of significantly improving the radial load resistance compared with the conventional tapered roller bearing, the contact angle α is preferably set to 8° or less, and more preferably to 7° or less.

[0130] In addition, for Table 1 and Figure 6In the tapered roller bearing to be evaluated, the thickness T60 of the tapered roller bearing 60, the structure of the tapered roller 65, and the configuration circle diameter PCD are set constant regardless of the change in the contact angle α. On the other hand, the thickness of the inner ring 61 and the thickness of the outer ring 63 are changed according to the change in the contact angle α.

[0131] As described above, by setting the contact angle α to 10° or less, which is smaller than before, the radial load resistance performance can be improved. On the other hand, if the contact angle α is reduced, the thrust load resistance performance is reduced. 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 performance can be fully ensured.

[0132] In actual use, radial load and thrust load are not applied independently to the tapered roller bearing 60, but radial load and thrust load are likely to act in combination on the tapered roller bearing 60. The life evaluation of the tapered roller bearing 60 in use is performed using the equivalent dynamic load also specified in JIS B1518:2013.

[0133] The equivalent dynamic load is a hypothetical load that will have a lifespan equivalent to that of the tapered roller bearing 60 in a state where a combined load is applied. As an equivalent dynamic load, a radial equivalent dynamic load is known. The radial equivalent dynamic load is a hypothetical radial load that will have a lifespan equivalent to that of the tapered roller bearing 60 in a state where a combined load is applied.

[0134] As also specified in JIS B1518:2013, it is known that the radial equivalent dynamic load is calculated by the following formula X.

[0135] P r =X×F r +Y×F s ...Formula X

[0136] The "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 factor and "Y" is the thrust load factor. The radial load factor X and the thrust load factor Y depend on the thrust load F. s With radial load F r The ratio (F s / F r ) is determined. It is known that there is a ratio (F s / F r ) is less than a value e determined by the type of bearing, X=1 and Y=0.

[0137] That is, in becoming "(F s / F r)≤e”, only radial load F r The life of the tapered roller bearing 60 can be neglected due to the thrust load F s For the tapered roller bearing, the value e is "1.5×tanα" using the contact angle α. By selecting the radial load F acting on the tapered roller bearing 60 in use, r and thrust load F s The corresponding appropriate contact angle α can ignore the thrust load F s In other words, by appropriately selecting the contact angle α according to the application of the tapered roller bearing 60 , the thrust load resistance performance of the tapered roller bearing 60 can be made sufficient.

[0138] In applicable Figure 1 to Figure 3 In the case of the speed reducer 10 shown in FIG. 1 , a radial load F is applied to the tapered roller bearing 60 from the shaft member 50. r , the deflection force generated by the cylindrical roller bearing 70 is used as the thrust load F s According to the research conducted by the inventors of this case, it was confirmed that the thrust load F s Relative to radial load F r The ratio (F s / F r ) becomes 0.06 or 0.07.

[0139] When the contact angle α is 3°, the value e represented by "1.5×tanα" is 0.079. When the contact angle α is 2°, the value e represented by "1.5×tanα" is 0.052. Therefore, according to the tapered roller bearing 60 with a contact angle α of 3° or more, the thrust load F can be ignored in the life evaluation. s In other words, the tapered roller bearing 60 maintains the required thrust load resistance performance when the contact angle α is 3° or more.

[0140] In this regard, the contact angle α may be set to 3° or more and 10° or less, 3° or more and 8° or less, or 3° or more and 7° or less.

[0141] The tapered roller bearing 60 may also be preloaded when in use. Specifically, the tapered roller bearing 60 may be installed in a device as an applicable object, such as the reducer 10 in the illustrated example, in a state where the inner ring 61 and the outer ring 63 are pressurized toward each other in the direction D1 along the rotation axis RA. By using the inner ring 61 and the outer ring 63 in a state where they are pressurized toward each other, abnormalities such as shaking and vibration during use of the tapered roller bearing 60 can be suppressed. By suppressing such abnormalities, the life of the tapered roller bearing 60 and the life of the device in which the tapered roller bearing 60 is installed, such as the reducer 10, can be effectively extended.

[0142] However, there is an appropriate value for the preload applied to the tapered roller bearing 60. The tapered roller bearing 60 to which the appropriate value for the preload is applied does not produce a gap between the tapered roller 65 and the inner ring 61 and between the tapered roller 65 and the outer ring 63. All the tapered rollers 65 included in the tapered roller bearing 60 are preferably in contact with both the inner ring 61 and the outer ring 63.

[0143] If a constant radial load acts on the tapered roller bearing 60 from a constant direction, the maximum radial load generated in the tapered roller bearing 60 when the preload is smaller than the appropriate preload value is larger than the maximum radial load generated in the tapered roller bearing 60 when the preload is the appropriate preload value. If a constant radial load acts on the tapered roller bearing 60 from a constant direction, the maximum radial load generated in the tapered roller bearing 60 when the preload is larger than the appropriate preload value is larger than the maximum radial load generated in the tapered roller bearing 60 when the preload is the appropriate preload value. That is, when the preload is the appropriate preload value, the maximum radial load generated in the tapered roller bearing 60 can be minimized.

[0144] Figure 7 The results of investigating appropriate preload values ​​for three specific examples A to C of the tapered roller bearing 60 are shown. Figure 7 The specific examples A to C of the tapered roller bearing 60 shown are tapered roller bearings 60 that are assumed to be applicable to three speed reducers actually manufactured. The specific example A, which is assumed to be applicable to a larger and higher-output speed reducer 10, is a tapered roller bearing with a relatively large load capacity. Figure 7 As shown, for the specific example A which is assumed to be applicable to a larger and higher-output reducer 10, the appropriate value of the preload becomes larger. The specific example C which is assumed to be applicable to a smaller and lower-output reducer 10 becomes a tapered roller bearing with a relatively small load capacity. Figure 7 As shown, in the specific example C which is assumed to be applicable to a smaller and lower-output speed reducer 10 , the appropriate preload value becomes smaller.

[0145] Figure 7 The changes in the appropriate value of the preload according to the contact angle α are shown for three specific examples A to C of the tapered roller bearing 60. Figure 7 In the tapered roller bearing to be evaluated, the thickness T60 of the tapered roller bearing 60, the structure of the tapered roller 65, and the configuration circle diameter PCD are set constant regardless of the change in the contact angle α. On the other hand, the thickness of the inner ring 61 and the thickness of the outer ring 63 are changed according to the change in the contact angle α.

[0146] In the tapered roller bearing 60 of each specific example intended to be applied to the illustrated reducer, the following contents were confirmed regarding the contact angle α and the appropriate preload value. If the contact angle α becomes larger, the appropriate preload value becomes larger. If the contact angle α becomes smaller, the appropriate preload value becomes smaller. The theoretical value of the appropriate preload value (N) is proportional to the contact angle α (°). If the load capacity of the tapered roller bearing 60 becomes larger, the inclination of the appropriate preload value relative to the contact angle α becomes larger.

[0147] like Figures 1 to 3 In the reducer 10 shown, the two tapered roller bearings 60A and 60B are sometimes arranged in reverse to support the same shaft member. In this example, a preload is applied to pressurize the two tapered roller bearings 60A and 60B toward each other. The preload applied to the two tapered roller bearings 60A and 60B is preferably greater than the thrust load applied to the two tapered roller bearings 60A and 60B. More preferably, the appropriate preload value applied to the two tapered roller bearings 60A and 60B is greater than the thrust load applied to the two tapered roller bearings 60A and 60B. In this case, when the thrust load is generated, in any bearing 60A and 60B, the inner ring 61 and the outer ring 63 are maintained in a state of being pressurized toward each other. Therefore, it is possible to suppress abnormalities such as shaking and vibration during the use of the tapered roller bearing 60 and 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 installed.

[0148] exist Figures 1 to 3 In the speed reducer 10 shown in the figure, the deflection force generated by the cylindrical roller bearings 70A and 70B is applied to the tapered roller bearings 60A and 60B as a thrust load. The deflection force generated by the cylindrical roller bearings 70A and 70B is about 5% of the radial load applied to the cylindrical roller bearings 70A and 70B. In the speed reducer 10, the radial load applied to the cylindrical roller bearings 70A and 70B becomes more than 3000N and less than 50000N. Therefore, if Figure 7 As shown, the deflection force generated in the cylindrical roller bearing 70 during the operation of the speed reducer 10 is about 150N or more and 2500N or less.

[0149] Figure 7 The dotted lines indicate the deflection forces SA to SC generated in the specific example of the reducer 10. The deflection force SA is the deflection force in the reducer 10 equipped with the tapered roller bearing of the above-mentioned specific example A. The deflection force SB is the deflection force in the reducer 10 equipped with the tapered roller bearing of the above-mentioned specific example B. The deflection force SC is the deflection force in the reducer 10 equipped with the tapered roller bearing of the above-mentioned specific example C.

[0150] like Figure 7As shown, when the contact angle α becomes 5° or more, the appropriate value of the preload of the tapered roller bearing 60 installed in the reducer 10 is greater than the deflection force generated in the cylindrical roller bearing 70 installed in the reducer 10. Therefore, by setting the contact angle α to be 5° or more, it is possible to give the tapered roller bearing 60 a more appropriate thrust load resistance performance. According to this example, it is possible to effectively suppress the release of the preload from the tapered roller bearing 60 due to the generation of the thrust load. Therefore, it is possible to suppress the generation of abnormalities such as shaking and vibration in the tapered roller bearing 60 during the operation of the reducer 10. By suppressing the generation of such abnormalities, the life of the tapered roller bearing 60 and the life of the reducer 10 in which the tapered roller bearing 60 is installed can be stably extended.

[0151] In this regard, the contact angle α may be 5° or more and 10° or less, 5° or more and 8° or less, or 5° or more and 7° or less.

[0152] You can also determine the applicable Figure 1 to Figure 3 The dimensions of the tapered roller bearing 60 of the speed reducer 10 shown in the figure. The tapered roller bearing 60 having the dimensions described below can more effectively and stably achieve the effect of setting the contact angle α to be greater than 3° and less than 10° when applied to the speed reducer 10. That is, the required thrust load resistance performance can be stably maintained, and the radial load resistance performance of the tapered roller bearing can be more effectively and stably improved.

[0153] The inner diameter D60a of the tapered roller bearing 60 may be greater than 9.4 mm and less than 60 mm, greater than 20 mm and less than 50 mm, or greater than 25 mm and less than 45 mm. Figure 4 As shown, the inner diameter D60a of the tapered roller bearing 60 is the inner diameter of the tapered roller bearing 60. In the example shown in the figure, the inner diameter D60a of the tapered roller bearing 60 is the inner diameter of the tapered roller bearing 60 defined by the inner peripheral surface 62a of the inner ring 61.

[0154] The outer diameter D60b of the tapered roller bearing 60 may be greater than 24 mm and less than 130 mm, greater than 40 mm and less than 115 mm, or greater than 55 mm and less than 100 mm. Figure 4 As shown, the outer diameter D60b of the tapered roller bearing 60 is the outer diameter of the tapered roller bearing 60. In the example shown in the figure, 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.

[0155] 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 example shown in the figure, the thickness T60 is the distance between the inner peripheral surface 62a of the inner ring 61 and the outer peripheral surface 64b of the outer ring 63 along the radial direction DR.

[0156] The diameter D65a of the small end surface 66a of the tapered roller 65 (see Figure 5 ) can also be greater than 3.0 mm and less than 13.7 mm, can also be greater than 4.5 mm and less than 12 mm, or can also be greater than 6.0 mm and less than 10.5 mm.

[0157] The diameter D65b of the large end surface 66b of the tapered roller 65 (see Figure 5 ) can also be greater than 3.5 mm and less than 14.4 mm, can also be greater than 5.0 mm and less than 13 mm, or can also be greater than 6.5 mm and less than 11.5 mm.

[0158] The length L65 of the tapered roller 65 may be greater than 6.8 mm and less than 33.7 mm, greater than 10 mm and less than 30 mm, or greater than 13 mm and less than 27 mm. Figure 5 As shown, the length L65 of the tapered roller 65 is the length of the tapered roller 65 along the center axis CA.

[0159] By setting lower limits for the thickness T60 of the tapered roller bearing 60, the diameters D65a and D65b of the tapered roller 65, and the length L65 of the tapered roller 65, the radial load resistance performance of the tapered roller bearing 60 can be improved. By setting upper limits for the thickness T60 of the tapered roller bearing 60, the diameters D65a and D65b of the tapered roller 65, and the length L65 of the tapered roller 65, the tapered roller bearing 60 can be miniaturized.

[0160] 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 of the tapered roller bearing 60 can be more stably improved. 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 miniaturized. 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 greater than 50 and less than 1400, greater than 58 and less than 1200, greater than 100 and less than 980, or greater than 200 and less than 740.

[0161] 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 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 miniaturized. 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 greater than 20 and less than 550, greater than 24 and less than 460, greater than 45 and less than 360, or greater than 78 and less than 280.

[0162] The illustrated reducer 10 is constructed 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 sequence in the 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 and 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 a tapered roller 65 which is inclined in a manner away from the rotation axis RA on the side close to the second tapered roller bearing 60B in the axial direction D1. The second tapered roller bearing 60B includes tapered rollers 65 that are inclined so as to be separated from the rotation axis RA on the side close to the first tapered roller bearing 60A in the axial direction D1.

[0163] In the speed reducer 10 having such a structure, the shaft member 50 is rotatably supported by two tapered roller bearings 60A and 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.

[0164] The direction of the radial load from the first external gear 40A applied to the shaft member 50 changes as the shaft member 50 rotates. The direction of the radial load from the second external gear 40B applied to the shaft member 50 changes as the shaft member 50 rotates. The direction of the radial load from the first external gear 40A applied to the shaft member 50 is different from the direction of the radial load from the second external gear 40B applied to the shaft member 50. In the example shown in the figure, the radial load from the first external gear 40A applied to the shaft member 50 is opposite to the radial load from the second external gear 40B applied to the shaft member 50.

[0165] 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. If the magnitude of the periodically changing load, i.e., the amplitude of the load, increases, the tapered roller bearing 60 is prone to fatigue failure even if the absolute value of the load is small.

[0166] Therefore, it is effective to increase the bearing span L60 relative to the configuration spacing AP40 on 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 and 60B can be reduced. The bearing span L60 is the distance along the axial direction D1 between the action point P60 of the first tapered roller bearing 60A and the action point P60 of the second tapered roller bearing 60B. However, from the perspective of miniaturizing the reducer 10, it is preferred not to make the bearing span L60 too large relative to the configuration spacing AP40. The bearing span L60 may be more than twice and less than 5 times the configuration spacing AP40, or more than 2.5 times and less than 4.5 times, or more than 3 times and less than 4 times.

[0167] As described above, the tapered roller bearing 60 of the present embodiment has a contact angle α of 3° or more and 10° or less. The tapered roller bearing 60 of the present embodiment includes: an inner ring 61; tapered rollers 65; and an outer ring 63, which sets the contact angle to 3° or more and 10° or less, and holds the tapered rollers 65 between the inner ring 61 and the outer ring 63. The tapered roller bearing 60 of the present embodiment includes: an inner ring 61, which includes an outer peripheral surface 62b; tapered rollers 65; and an outer ring 63, which includes an inner peripheral surface 64a with a contact angle of 3° or more and 10° or less, and holds the tapered rollers 65 between the outer peripheral surface 62b and the inner peripheral surface 64a.

[0168] The reducer 10 of this embodiment includes: an external gear 40; a shaft member 50, which causes the external gear 40 to eccentrically swing; a gear frame 30, which supports the shaft member 50 so that it can rotate; a cylindrical roller bearing 70, which is arranged between the external gear 40 and the shaft member 50; and a tapered roller bearing 60, which is arranged between the gear frame 30 and the shaft member 50 and has a contact angle α of greater than 3° and less than 10°.

[0169] In the tapered roller bearing 60 and the reducer 10 of 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 one, the thickness of the inner ring 61 can be thickened, the thickness of the outer ring 63 can be thickened, the diameters D65a and D65b of the tapered roller 65 can be increased, and the diameter PCD of the circumference on which the tapered roller 65 is arranged can be increased without expanding the installation space of the tapered roller bearing 60. That is, by reducing the contact angle α, the radial load resistance performance can be improved while maintaining the installation space of the tapered roller bearing 60. By setting the lower limit of the contact angle α to 3°, the influence of the thrust load on the life of the tapered roller bearing 60 can be suppressed. That is, the required thrust load resistance performance can be given to the tapered roller bearing 60, and the radial load resistance performance of the tapered roller bearing 60 can be improved. As a result, the life of the tapered roller bearing 60 and the reducer 10 can be extended.

[0170] In a specific example of the present embodiment described above, the contact angle α may be set to be greater than 5°. When the lower limit of the contact angle α is set to 5°, the appropriate value of the preload to be applied to the tapered roller bearing 60 may be greater than the deflection force that can be applied to the tapered roller bearing 60 from the cylindrical roller bearing 70. Therefore, it is possible to suppress the preload from being completely released from the tapered roller bearing 60 and causing abnormalities such as vibration in the tapered roller bearing 60. Thus, it is possible to suppress an unexpectedly large load from being applied to the tapered roller bearing 60 during use. It is possible to suppress unexpected damage to the tapered roller bearing 60 and the reducer 10.

[0171] Although one embodiment has been described with reference to one specific example, the above example is not intended to limit one embodiment. The above embodiment can be implemented with various other specific examples, and various omissions, substitutions, changes, and additions can be made without departing from the gist of the invention.

[0172] For example, the tapered roller bearing 60 is applied to a speed reducer having a plurality of shaft members 50, but the invention is not limited to this example. The tapered roller bearing 60 may be applied to a speed reducer having only one shaft member 50 located on the rotation axis MRA.

[0173] In the embodiments disclosed in this specification, a component composed of multiple objects may be integrated into one, or a component composed of one object may be divided into multiple objects. Regardless of whether the components are integrated or not, they may be configured in a manner that can achieve the purpose of the invention.

Claims

1. A tapered roller bearing, wherein: The tapered roller bearing has: an inner ring including an outer peripheral surface; Tapered rollers; and The outer ring includes an inner peripheral surface having a contact angle of 3° or more and 10° or less, and the tapered roller is held between the outer peripheral surface and the inner peripheral surface.

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

3. The tapered roller bearing according to claim 1, wherein: The contact angle is 8° or less.

4. The tapered roller bearing according to claim 1, wherein: The product of the thickness of the tapered roller bearing in the radial direction and the length of the tapered roller is greater than or equal to 50 and less than or equal to 1400, wherein the units of the thickness and the length are mm.

5. The tapered roller bearing according to claim 1, wherein: The product of the diameter at the small end surface of the tapered roller and the length of the tapered roller is greater than or equal to 20 and less than or equal to 550, wherein the units of the diameter and the length are mm.

6. A reducer, wherein: The reducer has: External gear; a shaft member that causes the external gear to eccentrically swing; a gear carrier that rotatably supports the shaft member; a cylindrical roller bearing disposed between the external gear and the shaft member; and A tapered roller bearing is provided between the gear carrier and the shaft member and has 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 8° or less.

9. The reducer according to claim 6, wherein: The product of the thickness of the tapered roller bearing and the length of the tapered roller is greater than or equal to 50 and less than or equal to 1400, wherein the units of the thickness and the length are mm.

10. The reducer according to claim 6, wherein: The product of the diameter at the small end surface of the tapered roller and the length of the tapered roller is greater than or equal to 20 and less than or equal to 550, wherein the units of the diameter and the length are mm.

11. The reducer according to claim 6, wherein: The tapered roller bearing includes a first tapered roller bearing and a second tapered roller bearing which are sequentially arranged in an axial direction parallel to the rotation axis of the shaft member. The cylindrical roller bearing includes a first cylindrical roller bearing and a second cylindrical roller bearing which are arranged between the first tapered roller bearing and the 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 a tapered roller having a central axis inclined in such a manner that a side close to the second tapered roller bearing in the axial direction is away from the rotation axis. The second tapered roller bearing includes a tapered roller having a center axis that is inclined in such a manner that a side closer to the first tapered roller bearing in the axial direction is away from the rotation axis.

12. The reducer according to claim 11, wherein: A distance between a point of action of the first tapered roller bearing and a point of action of the second tapered roller bearing along the axial direction is at least twice a spacing between the first external gear and the second external gear in the axial direction.

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