Speed reducer

Abstract

The invention provides a speed reducer. The speed reducer includes a housing, a carrier, a crankshaft, a swing gear, and a transmission gear set. The teeth (30a, 40a) of at least one of the at least one pair of gear elements that mesh with each other in the transmission gear set have a convexity-machined section (50) along the tooth trace direction. The tooth-trace-direction equivalent radius R of the convex-surface-processed section (50) satisfies formula (1) and formula (2). The maximum Hertz surface pressure of meshing portions of the gear elements that mesh with each other is 1500 MPa or less. R < = 952.88 * e (0.0174 * crankPCR)... formula (1) 1 / R = 1 / R1 + 1 / R2... formula (2) where CrankPCR is the pitch circle radius of the central axis position of the crankshaft centered on the central axis of the carrier, R1 is the radius in the tooth trace direction of the meshing portion of one gear element, and R2 is the radius in the tooth trace direction of the meshing portion of the other gear element.

Description

Technical Field

[0001] This invention relates to speed reducers. Background Technology

[0002] In industrial robots, machine tools, etc., speed reducers are used to reduce the rotation of drive sources such as motors (for example, see Patent Document 1).

[0003] The reducer described in Patent Document 1 has internal teeth on the inner circumference of a cylindrical housing. A reduction mechanism is housed inside the housing, which meshes with the internal teeth to reduce the input rotation. The reduction mechanism includes: a gear carrier rotatably held in the housing; a crankshaft rotatably supported on the gear carrier; and a oscillating gear that oscillates and rotates due to a rotational force received from the eccentric portion of the crankshaft.

[0004] The oscillating gear has external teeth that mesh with the internal teeth of the housing, having fewer teeth than the internal teeth of the housing. A transmission gear (spur gear) is mounted on the crankshaft of the reduction mechanism section in a manner that allows it to rotate integrally with the crankshaft. The transmission gear meshes with the input gear on the drive source side. The input gear and transmission gear on the drive source side constitute the transmission gear set on the input side of the reducer.

[0005] In this reducer, when rotational power is transmitted from the input-side transmission gear set to the crankshaft, the crankshaft rotates eccentrically, thereby activating the reduction mechanism. As a result, the power from the drive source side is reduced in speed by the reduction mechanism at a predetermined reduction ratio and output to the gear carrier or housing.

[0006] Furthermore, in the reducer described in Patent Document 1, an external spline is formed at the end of the crankshaft, and an internal spline is formed on the transmission gear mounted on the crankshaft.

[0007] The external spline of the crankshaft has a plurality of spline teeth formed at intervals in the circumferential direction of the crankshaft. The plurality of spline teeth are formed to extend from the end of the crankshaft along the axial direction of the crankshaft toward the reduction gear section. Furthermore, the external spline has a groove located between adjacent spline teeth in the circumferential direction. An inclined portion is provided at the end of the groove located on the reduction gear section side. The inclined portion is inclined in the groove in such a way that it extends radially outward toward the reduction gear section side of the crankshaft.

[0008] Therefore, when the internal spline of the transmission gear engages with the external spline of the crankshaft, the teeth of the internal spline of the transmission gear bite into the inclined portion on the side of the external spline. This suppresses the wobble of the transmission gear.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2014-92249 Summary of the Invention

[0012] The problem the invention aims to solve

[0013] In recent years, industrial robots and other equipment have been used more frequently in collaborative spaces where they work with operators. Therefore, in equipment equipped with speed reducers like those described above, it has become important to suppress the noise generated by the speed reducers to a level that is inconsequential to the operator.

[0014] In the reducer described in Patent Document 1, the wobble of the transmission gear relative to the crankshaft is suppressed by the teeth on the internal spline side biting into the inclined portion on the external spline side. However, it is known that the noise generated in the reducer is caused not only by the wobble of the transmission gear but also by the angular contact between the gear elements in the transmission gear set on the input side. In this respect, in the aforementioned reducer, it is difficult to suppress the noise generated by the angular contact between the gear elements in the transmission gear set on the input side.

[0015] The purpose of this invention is to provide a speed reducer capable of suppressing noise generation in the transmission gear set on the input side.

[0016] Solution for solving the problem

[0017] A speed reducer according to one embodiment of the present invention comprises: a housing having internal teeth on its inner circumference; a gear carrier rotatably held in the housing; a crankshaft rotatably supported on the gear carrier, the eccentric portion of the crankshaft being rotated by an external rotational force; an oscillating gear having external teeth that mesh with the internal teeth in a number fewer than the number of teeth of the internal teeth, oscillating and rotating by the rotational force of the eccentric portion of the crankshaft, outputting rotational power to the gear carrier or the housing; and a transmission gear set on the input side, which is composed of a plurality of gear elements that mesh with each other to transmit rotational power to the crankshaft. At least one of the at least one pair of meshing gear elements in the transmission gear set has a tooth with a convex surface machined portion along the tooth line direction. The equivalent radius R of the tooth line direction of the convex surface machined portion satisfies the following equations (1) and (2). The maximum Hertzian surface pressure of the meshing portion of the meshing gear elements is 1500 MPa or less.

[0018] R≤952.88*e （0.0174*crankPCR） …Formula (1)

[0019] 1 / R = 1 / R1 + 1 / R2… Equation (2)

[0020] Wherein, CrankPCR is the pitch circle radius located at the center axis of the crankshaft, centered on the central axis of the gear carrier.

[0021] R1 is the tooth line radius of the meshing portion of a pair of meshing gear elements.

[0022] R2 is the tooth line radius of the meshing portion of another meshing gear element.

[0023] Based on the above structure, by performing appropriate convex surface machining on the teeth of the gear elements of the transmission gear set, the generation of noise caused by angular contact between gear elements can be suppressed. In addition, since the maximum Hertzian surface pressure of the meshing part of the gear element is set to 1500 MPa or less, the durability of the gear element can be sufficiently ensured even if the equivalent radius R in the tooth line direction of the convex surface machined part is set to be small.

[0024] Alternatively, the convex surface processing portion may be provided on the teeth of both meshing gear elements.

[0025] In this case, the teeth of both meshing gear elements are provided with convex machining portions, and the equivalent radius R of the tooth line direction of the convex machining portions of both teeth is set to satisfy the above equations (1) and (2). Therefore, it is possible to further suppress the generation of noise caused by angular contact between gear elements of the transmission gear set.

[0026] Alternatively, the aforementioned reducer may include: a transmission gear mounted on the crankshaft in a manner capable of rotating integrally with the crankshaft; and an input gear that meshes with the transmission gear to transmit rotational power to the crankshaft. Alternatively, the transmission gear and the input gear may constitute mutually meshing gear elements of the transmission gear set.

[0027] In this case, performing appropriate convex surface machining on the teeth of at least one of the input gear and the transmission gear can suppress the generation of noise caused by the angular contact between the input gear and the transmission gear.

[0028] The effects of the invention

[0029] The speed reducer according to the present invention can suppress the generation of noise in the transmission gear set on the input side. Attached Figure Description

[0030] Figure 1 This is a side view of an industrial robot equipped with a speed reducer.

[0031] Figure 2 This is a schematic front view of the speed reducer according to the implementation method.

[0032] Figure 3 The reducer in the implementation method is along Figure 2 A cross-sectional view along line III-III.

[0033] Figure 4 This is a perspective view showing a portion of the gear element in the embodiment.

[0034] Figure 5 This is a schematic cross-sectional view of the teeth of the gear element in the embodiment.

[0035] Explanation of reference numerals in the attached figures

[0036] 10. Reducer; 11. Housing; 13A. First gear carrier module (gear carrier); 13B. Second gear carrier module (gear carrier); 14. Crankshaft; 14b. Eccentric part; 15A. First oscillating gear (oscillating gear); 15B. Second oscillating gear (oscillating gear); 15Aa, 15Ba. External gear; 20. Internal gear pin (internal gear); 30. Input gear (gear element of the transmission gear set); 30a. Tooth; 40 (40A, 40B, 40C), transmission gear (gear element of the transmission gear set); 40a. Tooth; 50. Convex machined part; 60. Transmission gear set. Detailed Implementation

[0037] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

[0038] Figure 1 This is a side view of an industrial robot 100 that employs the reducer 10 of the embodiment.

[0039] like Figure 1 As shown, the industrial robot 100 is used, for example, for tasks such as component supply and assembly in the manufacture of precision equipment. The industrial robot 100 of this embodiment includes a base 110, a first arm 120, a second arm 130, a working head 140, and an end effector 150.

[0040] The base 110 includes a motor 160 and a reducer 10. The motor 160 is a drive source such as a servo motor. The first arm 120 is connected to the output of the reducer 10.

[0041] The first arm 120 rotates about axis O1. The power of the motor 160 is reduced by the reducer 10 at a predetermined reduction ratio and transmitted to the first arm 120. The second arm 130 is rotatably connected to the front end of the first arm 120.

[0042] The second arm 130 rotates about an axis parallel to axis O1. The second arm 130 rotates using the power of a motor (not shown). A working head 140 is held at the front end of the second arm 130.

[0043] An end effector 150, such as a robotic arm, is mounted on the work head 140. The end effector 150 operates using power from a motor (not shown).

[0044] Figure 2 This is the front view of the reducer 10 when viewed from the input side (the side connected to the motor 160).

[0045] like Figure 2As shown, the reducer 10 includes three transmission gears 40 (40A, 40B, 40C) composed of spur gears and an input gear 30 composed of spur gears. The input gear 30 is connected to the motor 160 (see reference). Figure 1 The output shaft is connected. Both the transmission gear 40 and the input gear 30 are involute gears.

[0046] In this embodiment, the input gear 30 and the transmission gear 40 constitute the transmission gear set 60 on the input side. The input gear 30 and the transmission gear 40 constitute the gear elements of the transmission gear set 60.

[0047] exist Figure 2 The diagram shows the central axis O1 of the input gear 30 and the central axes C1, C2, and C3 of the three transmission gears 40A, 40B, and 40C. The central axis O1 of the input gear 30 coincides with the central axis O1 of the gear carriers (first gear carrier module 13A and second gear carrier module 13B), which will be described later. Furthermore, the central axis O1 of the input gear 30 also coincides with the central axis O1 of the first arm 120 (see reference). Figure 1 The axis O1 of the rotation center of ) is consistent.

[0048] Three transmission gears 40A, 40B, and 40C are arranged at approximately equal intervals on an imaginary circle centered on the central axis O1 of the input gear 30. The central axes C1, C2, and C3 of each transmission gear 40A, 40B, and 40C coincide with the central axes C1, C2, and C3 of the three crankshafts 14, which will be described later. Each tooth 40a (external tooth) of the three transmission gears 40A, 40B, and 40C meshes with the tooth 30a (external tooth) of the input gear 30.

[0049] The rotation input from motor 160 to input gear 30 is transmitted equally to the three transmission gears 40A, 40B, and 40C as a rotation in the opposite direction to the rotation of input gear 30.

[0050] Figure 3 It is along Figure 2 A cross-sectional view along line III-III.

[0051] like Figure 3 As shown, the reducer 10 includes a cylindrical housing 11, a first gear carrier module 13A, a second gear carrier module 13B, three crankshafts 14, a first oscillating gear 15A, and a second oscillating gear 15B.

[0052] The first gear carrier module 13A and the second gear carrier module 13B are rotatably held on the inner circumference of the housing 11. Three crankshafts 14 are rotatably supported on the first gear carrier module 13A and the second gear carrier module 13B. The first oscillating gear 15A and the second oscillating gear 15B rotate together with the two eccentric portions 14b of each crankshaft 14.

[0053] In this embodiment, the housing 11 is fixed to the base 110 of the industrial robot 100. The first gear carrier module 13A and the second gear carrier module 13B constitute a gear carrier that functions as an output rotating body. The first oscillating gear 15A and the second oscillating gear 15B constitute oscillating gears that oscillate and rotate due to rotational force received from the eccentric portion 14b of the crankshaft 14.

[0054] The first gear carrier module 13A has a perforated circular plate-shaped base plate portion 13Aa and a plurality of support portions 13Ab extending from the end face of the base plate portion 13Aa toward the second gear carrier module 13B.

[0055] The second gear carrier module 13B is formed as an open circular plate. The first gear carrier module 13A is assembled with the second gear carrier module 13B with the end face of the support portion 13Ab in contact with the end face of the second gear carrier module 13B. Each support portion 13Ab is fastened to the second gear carrier module 13B using bolts 16.

[0056] In addition, the second gear carrier module 13B is provided with a positioning pin 17, which is used to position the second gear carrier module 13B relative to each support portion 13Ab before fastening with bolts 16.

[0057] An axial gap (separation space) is ensured between the base plate portion 13Aa of the first gear carrier module 13A and the second gear carrier module 13B. The first oscillating gear 15A and the second oscillating gear 15B are arranged in this gap (separation space).

[0058] Furthermore, clearance holes 19 are formed in the first oscillating gear 15A and the second oscillating gear 15B respectively, for each support portion 13Ab of the first gear carrier module 13A to pass through. The clearance holes 19 are formed to be sufficiently large compared to the outer shape of the support portion 13Ab, so as to avoid the support portion 13Ab from obstructing the rotational movement of the first oscillating gear 15A and the second oscillating gear 15B.

[0059] The shell 11 has a cylindrical shell body 11a and a flange 11b that protrudes radially outward from the outer periphery of the shell body 11a. The shell body 11a and the flange 11b are integrally formed, for example, by casting.

[0060] The housing body 11a is arranged across the outer peripheral surface of the base plate portion 13Aa of the first gear carrier module 13A and the outer peripheral surface of the second gear carrier module 13B. The base plate portion 13Aa of the first gear carrier module 13A and the second gear carrier module 13B are rotatably supported on both axial sides of the housing body 11a by means of bearings 12.

[0061] In the housing body 11a, a plurality of pin grooves 18 are formed on the inner peripheral surface of a central region located axially in the center (the region opposite to the outer peripheral surfaces of the first oscillating gear 15A and the second oscillating gear 15B), extending parallel to the rotation center (central axis O1) of the first and second gear carrier modules 13A and 13B. Each pin groove 18 rotatably accommodates a cylindrical internal toothed pin 20. The plurality of internal toothed pins 20 mounted on the inner peripheral surface (pin groove 18) of the housing body 11a are opposite to the outer peripheral surfaces of the first oscillating gear 15A and the second oscillating gear 15B.

[0062] In this embodiment, the internal toothed pin 20 installed in the pin groove 18 constitutes the internal teeth of the housing 11.

[0063] The first oscillating gear 15A and the second oscillating gear 15B are formed with an outer diameter slightly smaller than the inner diameter of the housing body 11a. External teeth 15Aa and 15Ba are formed on the outer peripheral surfaces of the first oscillating gear 15A and the second oscillating gear 15B, respectively, and engage with a plurality of internal toothed pins 20 disposed on the inner peripheral surface of the housing body 11a. The number of teeth 15Aa and 15Ba of the first oscillating gear 15A and the second oscillating gear 15B is set to be slightly less than the number of internal toothed pins 20 (pin grooves 18) (for example, one less).

[0064] Three crankshafts 14 are arranged on the same circumference centered on the rotation center (central axis O1) of the first gear carrier module 13A and the second gear carrier module 13B. Each crankshaft 14 is rotatably supported on the first gear carrier module 13A and the second gear carrier module 13B by means of bearings 21.

[0065] Each crankshaft 14 has a pair of shaft support portions 14a arranged axially apart and two eccentric portions 14b disposed between the pair of shaft support portions 14a. At one end of the crankshaft 14 in the axial direction, a gear mounting portion 14c is formed adjacent to the shaft support portion 14a. Each shaft support portion 14a passes through a shaft support hole 13Aa-1 formed in the first gear carrier module 13A (base plate portion 13Aa) and a shaft support hole 13Ba-1 formed in the second gear carrier module 13B. Each shaft support portion 14a is rotatably supported in the shaft support holes 13Aa-1 and 13Ba-1 by means of a bearing 21.

[0066] Each crankshaft 14 has a gear mounting portion 14c that passes through the shaft support hole 13Ba-1 of the second gear carrier module 13B and protrudes axially outward from the second gear carrier module 13B. Transmission gears 40 (40A, 40B, 40C) are mounted on the gear mounting portion 14c. The transmission gears 40 (40A, 40B, 40C) are connected to the gear mounting portion 14c of the crankshaft 14 by means of spline engagement or the like, in a manner that allows them to rotate integrally with the gear mounting portion 14c.

[0067] The central axes of the two eccentric portions 14b of the crankshaft 14 are eccentric relative to the central axis of the shaft support portion 14a. In addition, the two eccentric portions 14b are eccentric in such a way that their phases are offset by 180° around the central axis of the shaft support portion 14a.

[0068] Each eccentric portion 14b of the crankshaft 14 passes through the first oscillating gear 15A and the second oscillating gear 15B respectively. Each eccentric portion 14b is rotatably engaged with the support holes 22 formed in the first oscillating gear 15A and the second oscillating gear 15B respectively by means of the eccentric bearing 23 (cylindrical roller bearing).

[0069] In the reducer 10 of this embodiment, when the plurality of crankshafts 14 are subjected to an external force and rotate in one direction, each eccentric portion 14b of the crankshaft 14 rotates in the same direction with a predetermined radius. As a result, the first oscillating gear 15A and the second oscillating gear 15B rotate (oscillate) in the same direction with the same radius as each eccentric portion 14b rotates. At this time, each external tooth 15Aa and 15Ba of the first oscillating gear 15A and the second oscillating gear 15B contacts in meshing manner with a plurality of internal toothed pins 20 held on the inner circumference of the housing body 11a.

[0070] In the reducer 10 of this embodiment, the number of teeth 15Aa and 15Ba of the external teeth of the first oscillating gear 15A and the second oscillating gear 15B is set to be slightly less than the number of internal tooth pins 20 on the housing body 11a side (for example, one less). Therefore, during the period when the first oscillating gear 15A and the second oscillating gear 15B rotate one revolution according to the rotation of the crankshaft 14, the first oscillating gear 15A and the second oscillating gear 15B are rotated by the reaction force in the direction of rotation from the internal tooth pins 20 on the housing body 11a side, and then revolve in the opposite direction of rotation by a predetermined tooth pitch. As a result, the first and second gear carrier modules 13A and 13B, which engage with the first oscillating gear 15A and the second oscillating gear 15B by means of the crankshaft 14, rotate together with the first and second oscillating gears 15A and 15B in the same direction with the same tooth pitch.

[0071] As a result, the rotation of crankshaft 14 is reduced at a predetermined reduction ratio and output as the rotation of the first and second gear carrier modules 13A and 13B. In this embodiment, the first gear carrier module 13A and Figure 1 The first arm 120 is connected as shown. Therefore, the rotation after being reduced by the reducer 10 is output as the rotation of the first arm 120.

[0072] Furthermore, in this embodiment, since the two eccentric portions 14b of the crankshaft 14 are eccentrically offset by 180° around the central axes C1, C2, and C3, the rotation phases of the first oscillating gear 15A and the second oscillating gear 15B are offset by 180°.

[0073] Figure 4This is a partial perspective view of the gear elements (input gear 30, transmission gear 40) of the input-side transmission gear set 60. Figure 5 It is a schematic cross-sectional view of a pair of meshing gear elements (input gear 30 and transmission gear 40) with their teeth 30a and 40a cut along the tooth line direction.

[0074] At least one of the meshing gear elements in the transmission gear set 60 has a tooth with a convex surface machining portion 50 along the tooth line direction. In this embodiment, the teeth 30a, 40a of all meshing pairs of gear elements (input gear 30 and transmission gear 40) have convex surface machining portions 50.

[0075] The convex surface machining part 50 is a part formed by machining (e.g., grinding) in an arc shape in the tooth line direction, such as by making the middle region of the gear element bulge out in the tooth line direction (see reference). Figure 4 (The part shown is a dot).

[0076] The teeth 30a and 40a of each gear element (input gear 30 and transmission gear 40) are made in a manner that satisfies the following (condition a) and (condition b).

[0077] (Condition a) The equivalent radius R in the tooth line direction of the convex surface machining part 50 satisfies the following equations (1) and (2).

[0078] (Condition b) The maximum Hertzian surface pressure of the meshing part of the meshing gear elements is less than 1500 MPa.

[0079] R≤952.88*e （0.0174*crankPCR） …Formula (1)

[0080] 1 / R = 1 / R1 + 1 / R2… Equation (2)

[0081] Here, crankPCR is the pitch circle radius centered on the central axis O1 of the gear carrier and located at the central axis of crankshaft 14.

[0082] R1 is the tooth line radius of the meshing portion of a pair of meshing gear elements.

[0083] R2 is the tooth line radius of the meshing portion of another meshing gear element.

[0084] Furthermore, the gear element used in this embodiment has a tooth surface hardness of HRC50 to 64 and a tooth surface roughness of Ra1.6 or less.

[0085] Tables 1, 2, and 3 below show the results obtained by determining the threshold value of the equivalent radius R in the tooth direction of the convex surface machining part 50 of the gear element for three different CrankPCR reducers, investigating the noise generation when the equivalent radius R in the tooth direction of the convex surface machining part 50 of the gear element is greater than the threshold value and when the equivalent radius R in the tooth direction of the convex surface machining part 50 of the gear element is less than the threshold value.

[0086] [Table 1]

[0087]

[0088] Table 1 shows the results obtained when the reducer was operated under the conditions of a CrankPCR of 33.75 mm (the threshold of the equivalent radius R in the tooth direction is 530), a tooth surface hardness of HRC50-64, and a tooth surface roughness of Ra1.6 or less.

[0089] The upper part of Table 1 shows the presence or absence of angular contact and noise level of the reducer A(1) using a gear element with a tooth line equivalent radius R of 1000 mm using a convex surface machining section 50 (the gear element of the comparative example). The lower part of Table 1 shows the presence or absence of angular contact and noise level of the reducer A(2) using a gear element with a tooth line equivalent radius R of 480 mm using a convex surface machining section 50 (the gear element of the embodiment).

[0090] [Table 2]

[0091]

[0092] Table 2 shows the results obtained when the reducer was operated under the conditions of a CrankPCR of 45 mm (the threshold of the equivalent radius R in the tooth direction is 436), a tooth surface hardness of HRC50-64, and a tooth surface roughness of Ra1.6 or less.

[0093] The upper part of Table 2 lists the presence or absence of angular contact and noise level of the reducer B(1) using a gear element with a tooth line equivalent radius R of 480 mm (the gear element of the comparative example) that uses a convex surface machining section 50. The lower part of Table 2 lists the presence or absence of angular contact and noise level of the reducer B(2) using a gear element with a tooth line equivalent radius R of 160 mm (the gear element of the embodiment).

[0094] [Table 3]

[0095]

[0096] Table 3 shows the results obtained when the reducer was operated under the conditions of a CrankPCR of 66 mm (the threshold of the equivalent radius R in the tooth direction is 303), a tooth surface hardness of HRC50-64, and a tooth surface roughness of Ra1.6 or less.

[0097] The upper part of Table 3 lists the presence or absence of angular contact and noise level of the reducer C(1) using a gear element with a tooth line equivalent radius R of 343 mm (the gear element of the comparative example) that uses the convex surface machining part 50. The lower part of Table 3 lists the presence or absence of angular contact and noise level of the reducer C(2) using a gear element with a tooth line equivalent radius R of 210 mm (the gear element of the embodiment).

[0098] As shown in Tables 1, 2, and 3, in reducers A(2), B(2), and C(2) that use gear elements (gear elements of the embodiments) with a tooth line equivalent radius R satisfying the above-mentioned equations (1) and (2), no angular contact occurs between the gear elements, and the noise level is also low. In contrast, in reducers A(1), B(1), and C(1) that use gear elements (gear elements of the comparative examples) that do not satisfy the above-mentioned equations (1) and (2), angular contact occurs between the gear elements, and the noise level is high.

[0099] In addition, Tables 4, 5, and 6 below show the results of investigating the presence or absence of wear-induced gear component failure in three different CrankPCR reducers, with the maximum Hertzian surface pressure of the meshing part of the gear components set to be greater than 1500 MPa and set to be less than 1500 MPa.

[0100] [Table 4]

[0101]

[0102] Table 4 shows the results obtained after the reducer was operated for a specified time under the conditions of a CrankPCR of 33.75 mm, a tooth surface hardness of HRC50-64, and a tooth surface roughness of Ra1.6 or less.

[0103] The upper part of Table 4 records whether the gear element of reducer A(1), in which the maximum Hertzian surface pressure of the meshing part of the gear element is set to 1600 MPa, is damaged. The lower part of Table 4 records whether the gear element of reducer A(2), in which the maximum Hertzian surface pressure of the meshing part of the gear element is set to 1300 MPa, is damaged. Reducer A(1) uses the gear element of the comparative example, and reducer A(2) uses the gear element of the embodiment.

[0104] [Table 5]

[0105]

[0106] Table 5 shows the results obtained by running the reducer for a specified time under the conditions of a CrankPCR of 45 mm, a tooth surface hardness of HRC50-64, and a tooth surface roughness of Ra1.6 or less.

[0107] The upper part of Table 5 records whether the gear element of the reducer B(1), in which the maximum Hertzian surface pressure of the meshing part of the gear element is set to 1550 MPa, is damaged. The lower part of Table 5 records whether the gear element of the reducer B(2), in which the maximum Hertzian surface pressure of the meshing part of the gear element is set to 1400 MPa, is damaged. The reducer B(1) uses the gear element of the comparative example, and the reducer B(2) uses the gear element of the embodiment.

[0108] [Table 6]

[0109]

[0110] Table 6 shows the results obtained by running the reducer for a specified time under the conditions of a CrankPCR of 66 mm, a tooth surface hardness of HRC50-64, and a tooth surface roughness of Ra1.6 or less.

[0111] The upper part of Table 6 records whether the gear element of the reducer C(1), in which the maximum Hertzian surface pressure of the meshing part of the gear element is set to 1600 MPa, is damaged. The lower part of Table 6 records whether the gear element of the reducer C(2), in which the maximum Hertzian surface pressure of the meshing part of the gear element is set to 1400 MPa, is damaged. The reducer C(1) uses the gear element of the comparative example, and the reducer C(2) uses the gear element of the embodiment.

[0112] The results shown in Tables 4, 5, and 6 indicate that when the maximum Hertzian surface pressure of the meshing portion of the gear element is set to below 1500 MPa, no wear-induced breakage occurs on the tooth surface of the gear element. Conversely, when the maximum Hertzian surface pressure of the meshing portion of the gear element is set to above 1500 MPa, wear occurs on the tooth surface of the gear element.

[0113] As described above, in the reducer 10 of this embodiment, at least one of the meshing gear elements (input gear 30 and transmission gear 40) of the transmission gear set 60 on the input side has a convex surface machining portion 50 on its teeth 30a, 40a. Furthermore, the equivalent radius R in the tooth line direction of the convex surface machining portion 50 satisfies equations (1) and (2), and the maximum Hertzian surface pressure of the meshing portion of the meshing gear elements is set to 1500 MPa or less.

[0114] Therefore, as the test results above show, the durability of gear components can be fully ensured and the generation of noise caused by angular contact between gear components can be suppressed.

[0115] In a reducer 10 that is assembled with multiple rotating components such as housing 11, gear carrier (13A, 13B), crankshaft 14, oscillating gears (15A, 15B), and transmission gear set 60, the gear elements (input gear 30 and transmission gear 40) of the transmission gear set 60 on the input side are prone to swaying behavior due to the accumulation of tolerances caused by the assembly of multiple components.

[0116] In this regard, if the gear elements of the transmission gear set 60 are properly convexly machined as in the reducer 10 of this embodiment, the generation of noise in the transmission gear set 60 on the input side during the operation of the reducer 10 can be effectively suppressed.

[0117] On the other hand, when a convex surface is machined in the tooth line direction of the gear element, although the generation of contact noise (noise caused by angular contact) on the end side in the tooth line direction can be suppressed, the durability of the tooth surface is easily reduced due to the reduction of the contact area between the tooth surfaces.

[0118] In this regard, in the reducer 10 of this embodiment, since the maximum Hertz surface pressure of the meshing portion of the gear element of the transmission gear set 60 on the input side is appropriately set (set to 1500 MPa or less), the durability of the tooth surface can be sufficiently ensured.

[0119] Based on the above description, when the reducer of this embodiment is used, sufficient durability of the gear components can be ensured and noise generation in the transmission gear set 60 on the input side can be suppressed.

[0120] Furthermore, in the reducer 10 of this embodiment, the teeth 30a and 40a of the meshing gear elements (input gear 30 and transmission gear 40) of the transmission gear set 60 on the input side are provided with convex surface processed portions 50. Moreover, the tooth line equivalent radius R of the convex surface processed portions 50 of both teeth 30a and 40a is set to satisfy equations (1) and (2).

[0121] Therefore, when the reducer 10 of this embodiment is used, the generation of noise caused by angular contact between gear elements of the transmission gear set 60 can be further suppressed.

[0122] Furthermore, in the reducer 10 of this embodiment, at least one of the teeth 40a of the transmission gear 40 mounted on the crankshaft 14 and the teeth 30a of the input gear 30 that meshes with the transmission gear 40 to transmit rotational power to the crankshaft 14 is provided with a convex surface machining portion 50. Moreover, the equivalent radius R in the tooth line direction of the convex surface machining portion 50 is set to satisfy equations (1) and (2).

[0123] Therefore, by performing appropriate convex surface machining on the teeth 30a, 40a of at least one of the input gear 30 and the transmission gear 40, the generation of noise caused by the angular contact between the input gear 30 and the transmission gear 40 can be suppressed.

[0124] Furthermore, the present invention is not limited to the embodiments described above, and various design changes can be made without departing from its spirit. For example, the reducer 10 of the above embodiment has two oscillating gears (first oscillating gear 15A and second oscillating gear 15B), but the number of oscillating gears may be one, or even three or more.

[0125] Furthermore, in the above embodiment, the housing 11 side of the reducer 10 is fixed to the base, and the gear carrier (first gear carrier module 13A and second gear carrier module 13B) rotates as an output rotating body. However, it is also possible to fix the gear carrier side to the base and use the housing 11 side as the output rotating body.

[0126] Furthermore, in the reducer 10 of the above-described embodiment, the input-side transmission gear set 60 is composed of the input gear 30 connected to the output shaft of the motor 160 and the transmission gear 40 mounted on the crankshaft 14. However, the structure of the input-side transmission gear set 60 is not limited to this. For example, the transmission gear set may also have an intermediate gear sandwiched between the input gear and the transmission gear. In this case, the aforementioned convex surface machining portion can be provided on the teeth of at least one meshing gear pair among the input gear, intermediate gear, and transmission gear constituting the transmission gear set. However, the aforementioned convex surface machining portion may also be provided on all gear elements of the transmission gear set.

[0127] Furthermore, in the above embodiment, the reducer 10 is applied to the drive unit of the industrial robot 100, but the application of the reducer 10 is not limited to the drive unit of the industrial robot 100. The reducer 10 can also be applied to the drive units of various other equipment such as machine tools, other than the industrial robot 100.

[0128] In the embodiments disclosed in this specification above, for a component composed of multiple objects, the multiple objects can also be integrated into one, or conversely, a component composed of one object can be divided into multiple objects. Whether or not they are integrated, as long as the configuration achieves the purpose of the invention.

Claims

1. A speed reducer, wherein, This reducer has the following features: The shell has internal teeth on its inner circumference; A gear carrier, which is rotatably held in the housing; A crankshaft, which is rotatably supported on the gear carrier, has an eccentric portion that rotates due to external rotational force. An oscillating gear, having external teeth that mesh with the internal teeth in a number fewer than the number of teeth of the internal teeth, oscillates and rotates due to a rotational force from the eccentric portion of the crankshaft, outputting rotational output to the gear carrier or the housing; and The input-side transmission gear set consists of multiple gear elements that mesh with each other to transmit rotational power to the crankshaft. At least one of the at least two meshing gear elements in the transmission gear set has a tooth with a convex surface machined along the tooth line direction. The equivalent radius R in the tooth direction of the convex surface machining part satisfies the following equations (1) and (2). The maximum Hertzian surface pressure at the meshing portion of the meshing gear elements is below 1500 MPa. R≤952.88*e （0.0174*crankPCR） …Formula (1) 1 / R = 1 / R1 + 1 / R2… Equation (2) CrankPCR is the pitch circle radius located at the center axis of the crankshaft, centered on the central axis of the gear carrier. R1 is the tooth line radius of the meshing portion of a pair of meshing gear elements. R2 is the tooth line radius of the meshing portion of another meshing gear element.

2. The reducer according to claim 1, wherein, The convex surface machining portion is provided on the teeth of both meshing gear elements.

3. The reducer according to claim 1 or 2, wherein, This reducer has the following features: A transmission gear, which is mounted on the crankshaft in a manner capable of rotating integrally with the crankshaft; and An input gear meshes with the transmission gear to transmit rotational power to the crankshaft. The transmission gear and the input gear constitute the meshing gear elements of the transmission gear set.

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