speed reducer

Abstract

To provide a reduction gear that can suppress the generation of noise in the transmission gear group on the input side. [Solution] The gearbox comprises a case, a carrier, a crankshaft, an oscillating gear, and a group of transmission gears. Of the at least one pair of meshing gear elements in the group of transmission gears, at least one of the gear elements has teeth 30a, 40a with crowned portions 50 along the tooth trace direction. The radius R of the crowned portion 50 in the tooth trace direction satisfies equations (1) and (2). The maximum Hertz surface pressure of the meshing portions of the meshing gear elements is set to 1500 MPa or less. R ≤ 952.88 * e (0.0174*crankPCR) …(1) 1 / R = 1 / R1 + 1 / R2 ... (2) crankPCR: Pitch circle radius of the crankshaft's central axis position relative to the carrier's central axis. R1: Radius in the direction of the tooth trace of the meshing portion of one gear element. R2: Radius in the direction of the tooth trace of the meshing portion of the other gear element.

Description

Technical Field

[0001] The present invention relates to a speed reducer.

Background Art

[0002] In industrial robots, machine tools, etc., a speed reducer is used to reduce the rotation of a drive source such as a motor (see, for example, Patent Document 1).

[0003] The speed reducer described in Patent Document 1 has internal teeth provided on the inner circumference of a cylindrical case, and a speed reduction mechanism portion that meshes with the internal teeth to reduce the input rotation is accommodated inside the case. The speed reduction mechanism portion includes a carrier rotatably held by the case, a crankshaft rotatably supported by the carrier, and a swing gear that receives a turning force from the eccentric portion of the crankshaft and swings and rotates. The swing gear has external teeth that mesh with the internal teeth of the case and have fewer teeth than the internal teeth of the case. A transmission gear (spur gear) is integrally rotatably attached to the crankshaft of the speed reduction mechanism portion. The transmission gear meshes with an input gear on the drive source side. The input gear on the drive source side and the transmission gear constitute a transmission gear group on the input side in the speed reducer.

[0004] In this speed reducer, when rotational power is transmitted from the transmission gear group on the input side to the crankshaft, the crankshaft rotates eccentrically, causing the speed reduction mechanism portion to operate. As a result, the power on the drive source side is reduced to a predetermined reduction ratio by the speed reduction mechanism portion and output to the carrier or the case.

[0005] Also, in the speed reducer described in Patent Document 1, a male spline is formed at the end of the crankshaft, and a female spline is formed on the transmission gear attached to the crankshaft. The male spline of the crankshaft has an inclined portion provided at the end on the back side of the groove between the spline teeth so that the outer diameter gradually increases toward the back side. Therefore, when the female spline of the transmission gear is fitted onto the male spline of the crankshaft, the teeth of the female spline of the transmission gear bite into the inclined portion on the male spline side, thereby suppressing backlash of the transmission gear. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2014-92249 [Overview of the project] [Problems that the invention aims to solve]

[0007] In recent years, industrial robots and other equipment are increasingly being used in collaborative spaces with workers. Therefore, in equipment incorporating such speed reducers, it is crucial that the noise generated by the speed reducer is suppressed to a level that does not bother workers.

[0008] In the gear reducer described in Patent Document 1, the teeth of the female spline bite into the inclined portion of the male spline, thereby suppressing play in the transmission gear relative to the crankshaft. However, the noise generated in the gear reducer is not only due to play in the transmission gear, but also to angular contact between the gear elements of the input transmission gear group. In the above-described gear reducer, it is difficult to suppress the noise caused by angular contact between the gear elements of the input transmission gear group.

[0009] This invention provides a gearbox that can suppress the generation of noise in the transmission gear group on the input side. [Means for solving the problem]

[0010] A gearbox according to one aspect of the present invention comprises a case having internal teeth on its inner circumference, a carrier rotatably held in the case, a crankshaft rotatably supported by the carrier and whose eccentric portion rotates upon receiving rotational force from the outside, an oscillating gear having external teeth that mesh with the internal teeth with fewer teeth than the internal teeth, which oscillates upon receiving rotational force from the eccentric portion of the crankshaft and outputs output rotation to the carrier or the case, and an input-side transmission gear group consisting of a plurality of gear elements whose teeth mesh with each other to transmit rotational power to the crankshaft, wherein the teeth of at least one of the at least pair of meshing gear elements of the transmission gear group have crowned portions along the tooth trace direction, the radius R equivalent to the tooth trace direction of the crowned portion satisfies the following equations (1) and (2), and the maximum Hertz surface pressure of the meshing portions of the meshing gear elements is 1500 MPa or less. R ≤ 952.88 * e (0.0174*crankPCR) …(1) 1 / R = 1 / R1 + 1 / R2 ... (2) crankPCR: Pitch circle radius of the crankshaft's central axis position relative to the carrier's central axis. R1: Radius in the direction of the tooth trace of the meshing portion of one of the gear elements that mesh with the other. R2: Radius in the direction of the tooth trace of the meshing portion of the other gear element that meshes with it.

[0011] With the above configuration, the teeth of the gear elements in the transmission gear group are subjected to appropriate crowning, thereby suppressing the generation of noise due to angular contact between gear elements. Furthermore, in this embodiment, since the maximum Hertz surface pressure of the meshing portion of the gear elements is set to 1500 MPa or less, sufficient durability of the gear elements can be ensured even if the radius R equivalent to the tooth trace direction of the crowned portion is set small.

[0012] Preferably, the crowned portion is provided on both teeth of the gear elements that mesh with each other.

[0013] In this case, crowning portions are provided on the teeth of both of the meshing gear elements, and the pitch circle radius R in the tooth trace direction of the crowning portions of both teeth is set so as to satisfy the above formulas (1) and (2). For this reason, it becomes possible to further suppress the generation of noise due to corner contact between the gear elements of the transmission gear group.

[0014] The speed reducer described above includes a transmission gear that is rotatably attached to the crankshaft integrally, and an input gear that meshes with the transmission gear and transmits rotational power to the crankshaft. The transmission gear and the input gear constitute the meshing gear elements of the transmission gear group.

[0015] In this case, appropriate crowning is performed on at least one of the teeth of the input gear and the transmission gear, and the generation of noise due to corner contact between the input gear and the transmission gear is suppressed.

Advantages of the Invention

[0016] The speed reducer described above can suppress the generation of noise in the transmission gear group on the input side.

Brief Description of the Drawings

[0017] [Figure 1] Side view of an industrial robot equipped with the speed reducer of the embodiment. [Figure 2] Schematic front view of the speed reducer of the embodiment. [Figure 3] Cross-sectional view of the speed reducer of the embodiment taken along line III-III of FIG. 2. [Figure 4] Perspective view showing a part of the gear element of the embodiment. [Figure 5] Schematic cross-sectional view of the tooth of the gear element of the embodiment.

Modes for Carrying Out the Invention

[0018] ​​​​​FIG. 1 is a side view of an industrial robot 100 employing a speed reducer 10 according to an embodiment. The industrial robot 100 is used, for example, in operations such as component supply and assembly when manufacturing precision equipment. As shown in FIG. 1, the industrial robot 100 according to the present embodiment includes a base 110, a first arm 120, a second arm 130, a work head 140, and an end effector 150.

[0020] The base 110 includes a motor 160 which is a drive source such as a servo motor, and a speed reducer 10. The first arm 120 is connected to the output portion of the speed reducer 10. The first arm 120 rotates around an axis O1. The power of the motor 160 is reduced by the speed reducer 10 to a predetermined reduction ratio and transmitted to the first arm 120. A second arm 130 is rotatably connected to the tip of the first arm 120. The second arm 130 rotates around an axis parallel to the axis O1. The second arm 130 rotates by the power of a motor (not shown). A work head 140 is held at the tip of the second arm 130. An end effector 150 such as a robot hand is attached to the work head 140. The end effector 150 operates by the power of a motor (not shown).

[0021] FIG. 2 is a front view of the speed reducer 10 as viewed from the input side (the side to which the motor 160 is connected). As shown in FIG. 2, the speed reducer 10 includes three transmission gears 40 (40A, 40B, 40C) formed of spur gears, and an input gear 30 also formed of a spur gear. The input gear 30 is connected to the output shaft of the motor 160 (see FIG. 1). Both the transmission gear 40 and the input gear 30 are formed as involute gears. In the present embodiment, the input gear 30 and the transmission gears 40 constitute a transmission gear group 60 on the input side. The input gear 30 and the transmission gears 40 constitute the gear elements of the transmission gear group 60.

[0022] Figure 2 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 carriers (first carrier block 13A and second carrier block 13B), which will be described later. Furthermore, the central axis O1 of the input gear 30 also coincides with the axis O1 which is the rotation center of the first arm 120 (see Figure 1).

[0023] The three transmission gears 40A, 40B, and 40C are arranged at approximately equal intervals on a virtual 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 teeth 30a (external teeth) of the input gear 30. The rotation input from the motor 160 to the input gear 30 is transmitted equally to the three transmission gears 40A, 40B, and 40C as rotation in the opposite direction to the rotation of the input gear 30.

[0024] Figure 3 is a cross-sectional view taken along the line III-III in Figure 2. The reduction gear 10 comprises a case 11 having a generally cylindrical shape, a first carrier block 13A and a second carrier block 13B rotatably held on the inner circumference of the case 11, three crankshafts 14 rotatably supported by the first carrier block 13A and the second carrier block 13B, and a first oscillating gear 15A and a second oscillating gear 15B that rotate orbitally together with two eccentric portions 14b of each crankshaft 14. In this embodiment, the case 11 is fixed to the base 110 of the industrial robot 100, and the first carrier block 13A and the second carrier block 13B constitute a carrier which is an output rotating body. In addition, in this embodiment, the first oscillating gear 15A and the second oscillating gear 15B constitute an oscillating gear which oscillates by receiving a rotational force from the eccentric portion 14b of the crankshaft 14.

[0025] The first carrier block 13A has a perforated disc-shaped base portion 13Aa and a plurality of support columns 13Ab extending from the end face of the base portion 13Aa toward the second carrier block 13B. The second carrier block 13B is formed in the shape of a perforated disc. The end faces of the support columns 13Ab of the first carrier block 13A abut against the end face of the second carrier block 13B, and each support column 13Ab is fastened and fixed to the second carrier block 13B by bolts 16. Reference numeral 17 in the figure indicates a positioning pin for positioning the second carrier block 13B toward each support column 13Ab before fastening with bolts 16.

[0026] An axial gap (separated space) is provided between the substrate portion 13Aa of the first carrier block 13A and the second carrier block 13B. The first oscillating gear 15A and the second oscillating gear 15B are arranged in this gap (separated space). Furthermore, the first oscillating gear 15A and the second oscillating gear 15B have relief holes 19 through which each support column 13Ab of the first carrier block 13A passes. The relief holes 19 are formed to be sufficiently larger than the outer surface shape of each support column 13Ab so that the support columns 13Ab do not obstruct the rotational movement of the first oscillating gear 15A and the second oscillating gear 15B.

[0027] The case 11 comprises a cylindrical case body 11a and a flange 11b that protrudes radially outward from the outer circumferential surface of the case body 11a. The case body 11a and the flange 11b are integrally formed by casting or the like.

[0028] The case body 11a is positioned across the outer circumferential surface of the base portion 13Aa of the first carrier block 13A and the outer circumferential surface of the second carrier block 13B. The base portion 13Aa of the first carrier block 13A and the second carrier block 13B are rotatably supported on both axial sides of the case body 11a via bearings 12. In addition, a plurality of pin grooves 18 are formed on the inner circumferential surface of the central axial region of the case body 11a (the region facing the outer circumferential surfaces of the first oscillating gear 15A and the second oscillating gear 15B), extending parallel to the rotation centers (central axis O1) of the first and second carrier blocks 13A and 13B. A substantially cylindrical internal tooth pin 20 is rotatably housed in each pin groove 18. The plurality of internal tooth pins 20 attached to the inner circumferential surface (pin grooves 18) of the case body 11a face the respective outer circumferential surfaces of the first oscillating gear 15A and the second oscillating gear 15B. In this embodiment, the internal tooth pin 20 attached to the pin groove 18 constitutes the internal teeth of the case 11.

[0029] 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 case body 11a. External teeth 15Aa and 15Ba are formed on the outer circumferential surfaces of the first oscillating gear 15A and the second oscillating gear 15B, respectively, which mesh with and contact a plurality of internal tooth pins 20 arranged on the inner circumferential surface of the case body 11a. The number of teeth on the external teeth 15Aa and 15Ba formed on the outer circumferential surfaces 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 (pin grooves 18) (for example, one less).

[0030] The three crankshafts 14 are arranged on the same circumference centered on the rotation center (central axis O1) of the first carrier block 13A and the second carrier block 13B. Each crankshaft 14 is rotatably supported by the first carrier block 13A and the second carrier block 13B via bearings 21. Each crankshaft 14 has a pair of shaft support portions 14a arranged axially spaced apart, and two eccentric portions 14b arranged between the pair of shaft support portions 14a. A gear mounting portion 14c is formed adjacent to the shaft support portion 14a at one axial end of the crankshaft 14. Each shaft support portion 14a is inserted through a shaft support hole 13Aa-1 formed in the first carrier block 13A (base portion 13Aa) and a shaft support hole 13Ba-1 formed in the second carrier block 13B, and is rotatably supported by these shaft support holes 13Aa-1 and 13Ba-1 via bearings 21. The gear mounting portion 14c of each crankshaft 14 passes through the shaft support hole 13Ba-1 of the second carrier block 13B and protrudes axially outward from the second carrier block 13B. Transmission gears 40 (40A, 40B, 40C) are attached to the gear mounting portion 14c that protrudes from the second carrier block 13B. The transmission gears 40 (40A, 40B, 40C) are connected to the gear mounting portion 14c of the crankshaft 14 so as to be able to rotate as a single unit by spline fitting or the like.

[0031] The two eccentric portions 14b of the crankshaft 14 have their respective central axes eccentric with respect to the central axis of the shaft support portion 14a. Furthermore, the two eccentric portions 14b are eccentric such that their phases are shifted by 180° around the central axis of the shaft support portion 14a.

[0032] Furthermore, 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 support holes 22 formed in the first oscillating gear 15A and the second oscillating gear 15B, respectively, via eccentric portion bearings 23 (cylindrical roller bearings).

[0033] In this embodiment, when the multiple crankshafts 14 of the reduction gear 10 are subjected to an external force and rotate in one direction, each eccentric portion 14b of the crankshafts 14 pivots in the same direction with a predetermined radius, and consequently, the first oscillating gear 15A and the second oscillating gear 15B pivot (oscillate) in the same direction with the same radius. At this time, the external teeth 15Aa and 15Ba of the first oscillating gear 15A and the second oscillating gear 15B contact a plurality of internal tooth pins 20 held on the inner circumference of the case body 11a so as to mesh with them.

[0034] In the reduction gear 10 of this embodiment, the number of teeth on the external teeth 15Aa and 15Ba of the first oscillating gear 15A and the second oscillating gear 15B is set to be slightly less than (for example, one less than) the number of internal tooth pins 20 on the case body 11a side. Therefore, while the first oscillating gear 15A and the second oscillating gear 15B rotate once in response to the rotation of the crankshaft 14, the first oscillating gear 15A and the second oscillating gear 15B rotate on their own axis due to a reaction force in the rotational direction from the internal tooth pins 20 on the case body 11a side, and consequently revolve by a predetermined pitch in the opposite direction to the rotational direction. As a result, the first and second carrier blocks 13A and 13B, which are engaged with the first and second oscillating gears 15A and 15B via the crankshaft 14, rotate together with the first and second oscillating gears 15A and 15B in the same direction and at the same pitch. As a result, the rotation of the crankshaft 14 is reduced to a predetermined reduction ratio and output as the rotation of the first and second carrier blocks 13A and 13B. In this embodiment, the first carrier block 13A is connected to the first arm 120 shown in Figure 1. Therefore, the rotation reduced by the reduction gear 10 as described above is output as the rotation of the first arm 120. 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 rotational phases of the first oscillating gear 15A and the second oscillating gear 15B will be offset by 180°.

[0035] Figure 4 is a perspective view showing a portion of the element gears (input gear 30, transmission gear 40) of the input-side transmission gear group 60. Figure 5 is a schematic cross-sectional view of the teeth 30a and 40a of a pair of meshing gear elements (input gear 30 and transmission gear 40), cross-sectionally along the tooth trace direction. In the transmission gear group 60, at least one of the pairs of meshing gear elements has crowned teeth 50 along the tooth trace direction. In this embodiment, both teeth 30a, 40a of all pairs of meshing gear elements (input gear 30 and transmission gear 40) have crowned teeth 50. The crowned portion 50 is a part that has been machined in an arc shape in the direction of the tooth trace (for example, grinding) so that the central region in the direction of the tooth trace of the gear element bulges out (see the dotted area in Figure 4).

[0036] The teeth 30a and 40a of each gear element (input gear 30 and transmission gear 40) are manufactured to satisfy the following conditions (a) and (b). (a) The radius R equivalent to the tooth trace direction of the crowned section 50 satisfies the following equations (1) and (2). (b) The maximum Hertz surface pressure at the meshing portion of the gear elements that mesh with each other is 1500 MPa or less. R ≤ 952.88 * e (0.0174*crankPCR) …(1) 1 / R = 1 / R1 + 1 / R2 ... (2) crankPCR: Pitch circle radius of the crankshaft 14 at the central axis position centered on the carrier's central axis O1. R1: Radius in the direction of the tooth trace of the meshing portion of one of the gear elements that mesh with the other. R2: Radius in the direction of the tooth trace of the meshing portion of the other gear element that meshes with it. In this embodiment, the gear elements have a tooth surface hardness of HRC50-64 and a tooth surface roughness of Ra1.6 or less.

[0037] Tables 1, 2, and 3 below show the results of determining the threshold value of the tooth trace direction equivalent radius R of the crowned portion 50 of the gear element for three types of speed reducers with different crankPCR values, and investigating the noise generated when the tooth trace direction equivalent radius R of the crowned portion 50 of the gear element is greater than the threshold value and when it is less than or equal to the threshold value.

[0038] [Table 1]

[0039] Table 1 shows the results of operating the gearbox under the following conditions: crankPCR of 33.75 mm (threshold for the tooth trace direction radius R is 530), tooth surface hardness of HRC 50-64, and tooth surface roughness of Ra 1.6 or less. The upper section of Table 1 shows the presence or absence of corner contact and noise level for a gear reducer A(1) using a gear element (comparative example gear element) with a crowned section 50 equivalent radius R in the tooth trace direction of 1000 mm. The lower section of Table 1 shows the presence or absence of corner contact and noise level for a gear reducer A(2) using a gear element (embodiment gear element) with a crowned section 50 equivalent radius R in the tooth trace direction of 480 mm.

[0040] [Table 2] Table 2 shows the results of operating the gearbox under the following conditions: crankPCR of 45 mm (threshold for the equivalent radius R in the tooth trace direction is 436), tooth surface hardness of HRC 50-64, and tooth surface roughness of Ra 1.6 or less. The upper section of Table 2 shows the presence or absence of corner contact and noise level for a gear reducer B(1) using a gear element (comparative example gear element) with a crowned section 50 equivalent radius R in the tooth trace direction of 480 mm. The lower section of Table 2 shows the presence or absence of corner contact and noise level for a gear reducer B(2) using a gear element (embodiment gear element) with a crowned section 50 equivalent radius R in the tooth trace direction of 160 mm.

[0041] [Table 3] Table 3 shows the results of operating the gearbox under the following conditions: crankPCR of 66 mm (threshold for the equivalent radius R in the tooth trace direction is 303), tooth surface hardness of HRC 50-64, and tooth surface roughness of Ra 1.6 or less. The upper section of Table 3 shows the presence or absence of corner contact and noise level for a gear reducer C(1) using a gear element (comparative example gear element) with a crowned section 50 equivalent radius R in the tooth trace direction of 343 mm. The lower section of Table 3 shows the presence or absence of corner contact and noise level for a gear reducer C(2) using a gear element (embodiment gear element) with a crowned section 50 equivalent radius R in the tooth trace direction of 210 mm.

[0042] As is clear from the results shown in Tables 1, 2, and 3, the reducers A(2), B(2), and C(2) using gear elements (gear elements of the embodiment) whose tooth trace direction equivalent radius R satisfies the above equations (1) and (2) do not experience angular contact between gear elements, and the level of generated noise is low. In contrast, the reducers A(1), B(1), and C(1) using gear elements that do not satisfy the above equations (1) and (2) (gear elements of the comparative example) experience angular contact between gear elements, and the level of generated noise is high.

[0043] Furthermore, Tables 4, 5, and 6 below show the results of an investigation into whether or not gear element damage occurred due to wear when the maximum Hertz surface pressure at the meshing portion of the gear elements was set to more than 1500 MPa and when it was set to 1500 MPa or less, for three types of speed reducers with different crankPCRs.

[0044] [Table 4]

[0045] Table 4 shows the results of operating the gearbox for a specified time under conditions where the crankPCR was 33.75 mm, the tooth surface hardness was HRC50-64, and the tooth surface roughness was Ra1.6 or less. The upper section of Table 4 shows whether or not the gear elements of reducer A(1) were damaged, with the maximum Hertz surface pressure at the meshing portion of the gear elements set to 1600 MPa. The lower section of Table 4 shows whether or not the gear elements of reducer A(2) were damaged, with the maximum Hertz surface pressure at the meshing portion of the gear elements set to 1300 MPa. Reducer A(1) uses the gear elements of the comparative example, while reducer A(2) uses the gear elements of the embodiment.

[0046] [Table 5]

[0047] Table 5 shows the results of operating the gearbox for a specified time under conditions where the crankPCR was 45 mm, the tooth surface hardness was HRC 50-64, and the tooth surface roughness was Ra 1.6 or less. The upper section of Table 5 shows whether or not the gear elements of reducer B(1) were damaged, with the maximum Hertz surface pressure at the meshing portion of the gear elements set to 1550 MPa. The lower section of Table 5 shows whether or not the gear elements of reducer B(2) were damaged, with the maximum Hertz surface pressure at the meshing portion of the gear elements set to 1400 MPa. Reducer B(1) uses the gear elements of the comparative example, while reducer B(2) uses the gear elements of the embodiment.

[0048] [Table 6]

[0049] Table 6 shows the results of operating the gearbox for a specified time under conditions where the crankPCR was 66 mm, the tooth surface hardness was HRC 50-64, and the tooth surface roughness was Ra 1.6 or less. The upper section of Table 6 shows whether or not the gear elements of reducer C(1), where the maximum Hertz surface pressure of the gear element meshing portion is set to 1600 MPa, were damaged. The lower section of Table 6 shows whether or not the gear elements of reducer C(2), where the maximum Hertz surface pressure of the gear element meshing portion is set to 1400 MPa, were damaged. Reducer C(1) uses the gear elements of the comparative example, while reducer C(2) uses the gear elements of the embodiment.

[0050] As is clear from the results shown in Tables 4, 5, and 6, when the maximum Hertz surface pressure of the meshing portion of the gear elements is set to 1500 MPa or less, no damage due to wear occurs on the tooth surface of the gear elements. However, when the maximum Hertz surface pressure of the meshing portion of the gear elements is set to more than 1500 MPa, wear occurs on the tooth surface of the gear elements.

[0051] As described above, in the reduction gear 10 of this embodiment, at least one of the gear elements (input gear 30 and transmission gear 40) of the input-side transmission gear group 60 has crowned teeth 30a and 40a. The radius R equivalent to the tooth trace direction of the crowned teeth 50 satisfies equations (1) and (2) above, and the maximum Hertz surface pressure of the meshing portion of the gear elements is set to 1500 MPa or less. Therefore, as shown in the test results above, it is possible to suppress the generation of noise due to angular contact between gear elements while ensuring sufficient durability of the gear elements.

[0052] In a speed reducer 10, which is assembled with numerous rotating parts such as case 11, carriers (13A, 13B), crankshaft 14, oscillating gears (15A, 15B), and transmission gear group 60, the accumulation of tolerances due to the assembly of multiple parts makes it easy for the gear elements of the input-side transmission gear group 60 (input gear 30 and transmission gear 40) to exhibit oscillating behavior. Therefore, if the gear elements of the transmission gear group 60 are subjected to appropriate crowning, as in the speed reducer 10 of this embodiment, the generation of noise in the input-side transmission gear group 60 during the operation of the speed reducer 10 can be effectively suppressed. On the other hand, when crowning is applied to the gear elements in the direction of the tooth trace, the generation of contact noise (noise due to corner contact) at the end side in the direction of the tooth trace is suppressed, but at the same time, the durability of the tooth surface tends to decrease due to the reduction in the contact area between the tooth surfaces. In contrast, in the reducer 10 of this embodiment, by appropriately setting the maximum Hertz surface pressure of the meshing portion of the gear elements of the transmission gear group 60 on the input side (1500 MPa or less), it is possible to ensure sufficient durability of the tooth surface. Therefore, when the reduction gear of this embodiment is adopted, it becomes possible to suppress noise generation in the input-side transmission gear group 60 while ensuring sufficient durability of the gear elements.

[0053] Furthermore, in the reduction gear 10 of this embodiment, crowned portions 50 are provided on both teeth 30a and 40a of the gear elements (input gear 30 and transmission gear 40) that mesh with each other in the input-side transmission gear group 60, and the radius R equivalent to the tooth trace direction of the crowned portions 50 of both teeth 30a and 40a is set to satisfy the above equations (1) and (2). Therefore, when the reduction gear 10 of this embodiment is adopted, it becomes possible to further suppress the generation of noise caused by angular contact between the gear elements of the transmission gear group 60.

[0054] Furthermore, in this embodiment, the reduction gear 10 is provided with a crowned portion 50 on at least one of the teeth 40a of the transmission gear 40 attached to the crankshaft 14 and the teeth 30a of the input gear 30 that meshes with the transmission gear 40 and transmits rotational power to the crankshaft 14. The radius R equivalent to the tooth trace direction of the crowned portion 50 is set to satisfy the above equations (1) and (2). As a result, appropriate crowning is applied to at least one of the teeth 30a, 40a of the input gear 30 and the transmission gear 40, making it possible to suppress the generation of noise due to angular contact between the input gear 30 and the transmission gear 40.

[0055] It should be noted that the present invention is not limited to the embodiments described above, and various design modifications are possible without departing from the spirit of the invention. For example, the reduction gear 10 in the above embodiment is equipped with two oscillating gears (first oscillating gear 15A and second oscillating gear 15B), but the number of oscillating gears may be one or three or more.

[0056] Furthermore, in the above embodiment, the case 11 side of the reduction gear 10 is fixed to the base, and the carriers (first carrier block 13A and second carrier block 13B) rotate as output rotating bodies. However, conversely, the carrier side may be fixed to the base, and the case 11 side may be used as the output rotating body.

[0057] Furthermore, in the reduction gear 10 of the above embodiment, the input-side transmission gear group 60 is composed of an input gear 30 connected to the output shaft of the motor 160 and a transmission gear 40 attached to the crankshaft 14. However, the configuration of the input-side transmission gear group 60 is not limited to this. The transmission gear group may, for example, have an intermediate gear interposed between the input gear and the transmission gear. In this case, with respect to at least one pair of gears that mesh with each other among the input gear, intermediate gear, and transmission gear that constitute the gear elements of the transmission gear group, the crowning portion described above should be provided on the teeth of at least one of the gears. However, the crowning portion described above may be provided on all gear elements of the transmission gear group.

[0058] Furthermore, although the reduction gear 10 is applied to the drive unit of the industrial robot 100 in the above embodiment, the application of the reduction gear 10 is not limited to the drive unit of the industrial robot 100. The reduction gear 10 can also be applied to the drive units of various other devices such as machine tools other than the industrial robot 100.

[0059] Among the embodiments disclosed herein, those composed of multiple objects may be integrated, and conversely, those composed of a single object may be divided into multiple objects. Whether or not they are integrated, the invention can be constructed in a way that achieves its objective. [Explanation of Symbols]

[0060] 10... Reducer, 11... Case, 13A... First carrier block (carrier), 13B... Second carrier block (carrier), 14... Crankshaft, 14b... Eccentric part, 15A... First oscillating gear (oscillating gear), 15B... Second oscillating gear (oscillating gear), 15Aa, 15Ba... External teeth, 20... Internal tooth pin (internal teeth), 30... Input gear (gear element of transmission gear group), 30a... Teeth, 40 (40A, 40B, 40C)... Transmission gear (gear element of transmission gear group), 40a... Teeth, 50... Crowned part, 60... Transmission gear group.

Claims

1. Cases with internal teeth on the inner circumference, A carrier rotatably held in the aforementioned case, A crankshaft rotatably supported on the carrier, in which an eccentric portion rotates upon receiving rotational force from the outside, A rocking gear having external teeth that mesh with the internal teeth with fewer teeth than the internal teeth, receiving a rotational force from the eccentric portion of the crankshaft to oscillate and output rotation to the carrier or the case, It comprises an input-side transmission gear group consisting of multiple gear elements whose teeth mesh with each other to transmit rotational power to the crankshaft, Of the at least pair of meshing gear elements of the transmission gear group, the teeth of at least one of the gear elements have a crowned portion along the tooth trace direction. The radius R corresponding to the tooth trace direction of the crowned portion is 480 mm. The pitch circle radius (crankPCR) of the crankshaft's central axis position, centered on the carrier's central axis, is 33.75 mm. reducer.

2. A case having internal teeth on its inner circumference, A carrier rotatably held in the aforementioned case, A crankshaft rotatably supported on the carrier, in which an eccentric portion rotates upon receiving rotational force from the outside, A rocking gear having external teeth that mesh with the internal teeth with fewer teeth than the internal teeth, receiving a rotational force from the eccentric portion of the crankshaft to oscillate and output rotation to the carrier or the case, It comprises an input-side transmission gear group consisting of multiple gear elements whose teeth mesh with each other to transmit rotational power to the crankshaft, Of the at least pair of meshing gear elements of the transmission gear group, the teeth of at least one of the gear elements have a crowned portion along the tooth trace direction. The radius R corresponding to the tooth trace direction of the crowned portion is 160 mm. The pitch circle radius (crankPCR) of the crankshaft's central axis position, centered on the carrier's central axis, is 45 mm. reducer.

3. A case having internal teeth on its inner circumference, A carrier rotatably held in the aforementioned case, A crankshaft rotatably supported on the carrier, in which an eccentric portion rotates upon receiving rotational force from the outside, A rocking gear having external teeth that mesh with the internal teeth with fewer teeth than the internal teeth, receiving a rotational force from the eccentric portion of the crankshaft to oscillate and output rotation to the carrier or the case, It comprises an input-side transmission gear group consisting of multiple gear elements whose teeth mesh with each other to transmit rotational power to the crankshaft, Of the at least pair of meshing gear elements of the transmission gear group, the teeth of at least one of the gear elements have a crowned portion along the tooth trace direction. The radius R corresponding to the tooth trace direction of the crowned portion is 210 mm. The pitch circle radius (crankPCR) of the crankshaft's central axis position, centered on the carrier's central axis, is 66 mm. reducer.

4. The crowning portion is provided on both teeth of the gear elements that mesh with each other. A gearbox according to any one of claims 1 to 3.

5. A transmission gear is mounted integrally and rotatably on the crankshaft, The system comprises an input gear that meshes with the transmission gear and transmits rotational power to the crankshaft, The transmission gear and the input gear constitute the gear elements of the transmission gear group that mesh with each other. A gearbox according to any one of claims 1 to 3.

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