speed reducer

Abstract

The present invention provides a gearbox that can shorten the length of the input shaft while suppressing the generation of vibration and noise during operation. [Solution] The speed reducer comprises a speed reduction mechanism and a transmission gear 40. The transmission gear 40 is spline-engaged with the end of the input shaft and is fixed in position in the axial direction by a pull-out prevention member. The transmission gear 40 meshes with an input gear 30 driven by a drive source and transmits driving force from the input gear 30 to the input shaft. A recess 45 is provided on the axial outer end face of the transmission gear 40 to accommodate the engagement portion between the end of the input shaft and the pull-out prevention member. The recess 45 is formed such that the meshing width w2 of the splines of the input shaft and the transmission gear 40 is 60% or more of the tooth width w1 of the transmission gear 40, and the orthogonal plane S1 passing through the axial center ac of the tooth width w1 of the transmission gear 40 is located within the range of the meshing width w2 of the splines of the input shaft and the transmission gear 40.

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 that is rotatably held by the case, a crankshaft (input shaft) that is rotatably supported by the carrier, and a swing gear that receives a turning force from an 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.

[0004] In this speed reducer, when rotational power is transmitted to the crankshaft through the input gear and the transmission gear, the eccentric portion of the crankshaft eccentrically rotates, 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 is provided with an inclined portion 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 the backlash of the transmission gear.

Prior Art Documents

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

[0007] In the reduction gear described in Patent Document 1, the end of the crankshaft protrudes outward from the axial end face of the carrier, and a transmission gear is attached to the protruding end of the crankshaft. The transmission gear is spline-engaged to the end of the crankshaft and is fixed in the axial position on the crankshaft by a retaining ring or other disengagement prevention member. At this time, the axial end of the crankshaft needs to protrude outward to a certain extent beyond the end face of the transmission gear in order to engage the disengagement prevention member with its outer circumference. As a result, the axial length of the crankshaft is increased by the amount it protrudes from the end face of the transmission gear, which hinders the miniaturization of the entire reduction gear.

[0008] As a countermeasure, we are considering providing a recess on the axially outer end face of the transmission gear and positioning the engagement portion of the crankshaft end and the disengagement-restricting member inside that recess.

[0009] In this case, the displacement restriction is positioned within a recess in the transmission gear, which allows for a reduction in the crankshaft's axial length. However, in this case, the spline meshing portion of the transmission gear with the crankshaft is offset axially inward by the amount of the recess. As a result, the axial center of the transmission gear's tooth width and the axial center of the meshing portion (spline meshing portion) between the transmission gear and the crankshaft are misaligned in the axial direction. This phenomenon can cause the transmission gear to oscillate during power transmission, and this oscillating behavior is likely to cause vibration and noise during the operation of the reduction gear.

[0010] The present invention provides a speed reducer that can shorten the axial length of the input shaft of the reduction mechanism while suppressing the generation of vibration noise during operation. [Means for solving the problem]

[0011] A reduction gear according to one aspect of the present invention comprises a reduction mechanism having an input shaft that reduces and outputs the rotation input to the input shaft, and a transmission gear that is spline-engaged to the end of the input shaft, is fixed in position in the axial direction by a disengagement restricting member, and meshes with an input gear driven by a drive source to transmit driving force from the input gear to the input shaft, wherein the outer end face of the transmission gear in the axial direction is provided with a recess that accommodates the engagement portion between the end of the input shaft and the disengagement restricting member, and the recess is formed such that the meshing width of the splines of the input shaft and the transmission gear is 60% or more of the tooth width of the transmission gear, and the orthogonal plane passing through the axial center of the tooth width of the transmission gear is located within the range of the meshing width of the splines of the input shaft and the transmission gear.

[0012] In this configuration, a recess is provided on the axial outer end face of the transmission gear, and the engagement portion of the input shaft end and the pull-out restricting member is housed in this recess. As a result, the axial outer end of the input shaft does not protrude significantly outward in the axial direction of the transmission gear. Consequently, the axial length of the input shaft is shortened. Furthermore, in this configuration, recesses are formed on the end faces of the transmission gears so as to satisfy the following conditions (1) and (2). (1) The meshing width of the splines of the input shaft and the transmission gear is 60% or more of the tooth width of the transmission gear. (2) The orthogonal plane passing through the axial center of the tooth width of the transmission gear is located within the range of the meshing width between the input shaft and the spline of the transmission gear. Therefore, when the input gear and the transmission gear mesh to transmit power, the transmission gear is less likely to exhibit oscillating behavior. Consequently, in this configuration of a speed reducer, the generation of vibration noise caused by the oscillating behavior of the transmission gear is suppressed.

[0013] A reduction gear according to another 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 fewer teeth than the internal teeth but with external teeth that mesh with the internal teeth, which oscillates upon receiving rotational force from the eccentric portion of the crankshaft and outputs output rotation to the carrier, and a gear that is spline-engaged to the end of the crankshaft, fixed in the axial position by a disengagement-retaining member, and driven by a drive source. The device comprises a transmission gear that meshes with a driven input gear and transmits driving force from the input gear to the crankshaft, wherein the axial outer end face of the transmission gear is provided with a recess for accommodating the engagement portion between the end of the crankshaft and the disengagement restricting member, and the recess is formed such that the meshing width of the splines of the crankshaft and the transmission gear is 60% or more of the tooth width of the transmission gear, and the orthogonal plane passing through the axial center of the tooth width of the transmission gear is located within the range of the meshing width of the splines of the crankshaft and the transmission gear.

[0014] In this configuration, a recess is provided on the axial outer end face of the transmission gear, and the engagement portion of the crankshaft end and the disengagement retaining member is housed in this recess. As a result, the axial outer end of the crankshaft does not protrude significantly outward from the transmission gear in the axial direction. Consequently, the axial length of the crankshaft is shortened. Furthermore, in this configuration, recesses are formed on the end faces of the transmission gears so as to satisfy the following conditions (1A) and (2A). (1A) The meshing width of the splines of the crankshaft and the transmission gear is 60% or more of the tooth width of the transmission gear. (2A) The orthogonal plane passing through the axial center of the tooth width of the transmission gear is located within the meshing width of the crankshaft and the splines of the transmission gear. Therefore, when the input gear and the transmission gear mesh to transmit power, the transmission gear is less likely to exhibit oscillating behavior. Consequently, in this configuration of a speed reducer, the generation of vibration noise caused by the oscillating behavior of the transmission gear is suppressed. Moreover, particularly in the speed reducer of this aspect, the carrier rotates as an output rotating body during the operation of the speed reducer. Therefore, in the case of a structure where the crankshaft is supported at a position offset from the rotation center of the carrier, the transmission gear rotates while revolving around the rotation center of the carrier and meshes with the input gear to rotate. In this case, due to changes in the output of the drive source or the like, a force is likely to act on the transmission gear so as to cause a nodding behavior. However, in this configuration, since a recess is formed on the end face of the transmission gear so as to satisfy the above conditions (1A) and (2A), it is possible to effectively suppress the generation of vibration noise caused by the nodding behavior of the transmission gear.

Advantages of the Invention

[0015] The above-described speed reducer can suppress the generation of vibration noise during operation while shortening the axial length of the input shaft of the speed reduction mechanism portion.

Brief Description of the Drawings

[0016] [Figure 1] Side view of an industrial robot provided 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] Enlarged view of part IV of the speed reducer of the embodiment in FIG. 3. [Figure 5] Cross-sectional view of the transmission gear of the embodiment and the transmission gear of the comparative example.

Modes for Carrying Out the Invention

[0017] Next, embodiments of the present invention will be described based on the drawings.

[0018] FIG. 1 is a side view of an industrial robot 100 employing the speed reducer 10 of the 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 of the present embodiment includes a base 110, a first arm 120, a second arm 130, a work head 140, and an end effector 150.

[0019] 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 part of the speed reducer 10. The first arm 120 rotates around an axis O1. The power of the motor 160 is decelerated 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 is rotated 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.

[0020] FIG. 2 is a front view of the speed reducer 10 as seen 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) each composed of spur gears, and an input gear 30 also composed of a spur gear. The input gear 30 is connected to the output shaft of the motor 160 (see FIG. 1). Both the transmission gears 40 and the input gear 30 are formed as involute gears.

[0021] In FIG. 2, the central axis O1 of the input gear 30 and the central axes C1, C2, C3 of the three transmission gears 40A, 40B, 40C are shown. The central axis O1 of the input gear 30 coincides with the central axis O1 of a carrier (the first carrier block 13A and the second carrier block 13B) described later. Also, the central axis O1 of the input gear 30 coincides with the axis O1 which is the rotation center of the first arm 120 (see FIG. 1).

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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).

[0029] 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 integrally.

[0030] 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.

[0031] 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).

[0032] 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.

[0033] 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°.

[0034] In this embodiment, the case 11, the first and second carrier blocks 13A and 13B, the first and second oscillating gears 15A and 15B, the crankshaft 14, etc., constitute the reduction mechanism 35 of the reduction gear 10. The crankshaft 14 also constitutes the input shaft of the reduction mechanism 35.

[0035] Figure 4 is an enlarged view of section IV of the reduction gear 10 in Figure 3. As shown in Figure 4, a male spline 52 is formed on the outer circumferential surface of the gear mounting portion 14c of the crankshaft 14 (the axial end portion that protrudes outward from the second carrier block 13B). An engagement hole 51 is formed in the axial center of the transmission gear 40, penetrating the transmission gear 40 in the axial direction. A female spline 53 is formed on the inner circumferential surface of the engagement hole 51. The female spline 53 of the transmission gear 40 engages with the male spline 52 of the crankshaft 14. With the female spline 53 engaged (fitted) with the male spline 52 on the crankshaft 14 side, the transmission gear 40 is fixed in the axial position on the crankshaft 14 by a pair of retaining rings 48, which are retaining members. The pair of retaining rings 48 are attached to the outer circumferential surface of the crankshaft 14 on the axial inner side (the side facing the second carrier block 13B) and the outer side (the side separated from the second carrier block 13B) of the transmission gear 40. In Figure 4, reference numeral 54 denotes an annular locking groove formed on the outer circumferential surface of the crankshaft 14. Each retaining ring 48 is locked into the corresponding locking groove 54.

[0036] Furthermore, a recess 45 is formed on the axial outer end face of the transmission gear 40 to accommodate the engagement portion of the retaining ring 48 and the end of the crankshaft 14 (the portion protruding from the engagement hole 51). In this embodiment, the recess 45 is formed in a circular shape when viewed from the front. The inner diameter of the recess 45 is such that the retaining ring 48 can be attached to and detached from the end of the crankshaft 14.

[0037] Furthermore, the recess 45 of the transmission gear 40 is formed to satisfy the following conditions (1A) and (2A). (1A) The meshing width w2 of the splines of the crankshaft 14 and the transmission gear 40 is 60% or more of the tooth width w1 of the transmission gear 40. (2A) The orthogonal plane S1 passing through the axial center ac of the tooth width w1 of the transmission gear 40 is located within the range of the meshing width w2 of the splines of the crankshaft 14 and the transmission gear 40. Furthermore, "axis-orthogonal plane S1" refers to a plane that passes through the axial center ac of the meshing portion and is perpendicular to the central axis C1 (C2, C3) of the transmission gear 40.

[0038] In this embodiment, the speed reducer 10 employs an eccentric oscillating type speed reducer mechanism 35. However, the structure of the rotary input section described above can also be applied to speed reducers that employ speed reducers other than the eccentric oscillating type. In this case, the transmission gear 40 can be attached to the input shaft of the speed reducer mechanism in the same manner as described above. In this case, the recess 45 of the transmission gear will be formed to satisfy the following conditions (1) and (2). (1) The meshing width w2 of the splines of the input shaft and the transmission gear 40 is 60% or more of the tooth width w1 of the transmission gear 40. (2) The orthogonal plane S1 passing through the axial center ac of the tooth width w1 of the transmission gear 40 is located within the range of the meshing width w2 of the spline of the input shaft and the transmission gear 40.

[0039] <Effects of the speed reducer in this embodiment> As described above, in this embodiment, the reduction gear 10 has a recess 45 formed on the axial outer end face of the transmission gear 40, and the engagement portion of the end of the input shaft (crankshaft 14) of the reduction mechanism 35 and the retaining ring 48 (dislodgement prevention member) is housed in the recess 45. Therefore, the axial outer end of the input shaft (crankshaft 14) does not protrude significantly outward in the axial direction of the transmission gear 40. Furthermore, in the reduction gear 10 of this embodiment, a recess 45 is formed on the end face of the transmission gear 40 so as to satisfy the conditions (1) and (2) above. Therefore, when the input gear 30 and the transmission gear 40 mesh and transmit power, the meshing load acting between the input gear 30 and the transmission gear 40 is stably received by the spline engagement portion of the crankshaft 14 and the transmission gear 40. Consequently, when the reduction gear 10 is in operation, the transmission gear 40 is less likely to exhibit oscillating behavior. Therefore, by adopting the reduction gear 10 of this embodiment, it becomes possible to shorten the axial length of the input shaft of the reduction mechanism 35 while suppressing the generation of vibration noise during operation.

[0040] Figure 5 is a diagram showing a cross-sectional view (a) of a transmission gear 40 that satisfies the above conditions (1) and (2), and a cross-sectional view (b) of a transmission gear 40' that does not satisfy the above conditions (1) and (2). The transmission gear 40 shown in Figure 5(a) has a recess 45 formed such that the meshing width w2 of the splines of the transmission gear 40 and the input shaft (crankshaft 14) is 60% of the tooth width w1 of the transmission gear 40. The axis-orthogonal plane S1 passing through the center ac of the tooth width w1 of the transmission gear 40 is located within the range of the meshing width w2. In the transmission gear 40' shown in Figure 5(b), a recess 45 is formed such that the meshing width w2' of the splines of the transmission gear 40' and the input shaft (crankshaft 14) is 50% of the tooth width w1 of the transmission gear 40'. The orthogonal plane S1 passing through the axial center ac of the tooth width w1 of the transmission gear 40' falls outside the range of the meshing width w2'.

[0041] Noise tests were conducted under the same conditions for a speed reducer equipped with the transmission gear 40 shown in Figure 5(a) and a speed reducer equipped with the transmission gear 40' shown in Figure 5(b). The noise generated when using the transmission gear 40 shown in Figure 5(a) was 73.5 dBA, and the noise generated when using the transmission gear 40' shown in Figure 5(b) was 75 dBA. When the transmission gear 40 of this embodiment (Figure 5(a)) is used, the rigidity of the meshing portion with the input gear 30 is improved by about 10-15% and the noise level is improved by about 1.0-2.0 bBA compared to when the transmission gear 40' of the comparative example (Figure 5(b)) is used.

[0042] As is clear from the above test results, when the recess 45 of the transmission gear 40 is formed to satisfy the above conditions (1) and (2), the generated noise can be suppressed to a level that does not bother the worker. Conversely, when the recess 45 is formed in a specification that does not satisfy the above conditions (1) and (2), the generated noise cannot be suppressed to a level that does not bother the worker.

[0043] Furthermore, in this embodiment, the reduction gear 10 employs an eccentric oscillation type reduction mechanism 35, and the crankshaft 14 is supported at a position offset from the rotation center (axis O1) of the carrier (first carrier block 13A and second carrier block 13B). In this configuration of the reduction gear 10, the transmission gear 40 rotates while meshing with the input gear 30, while orbiting around the rotation center of the carrier. Therefore, when transmitting rotational power, complex torques act on the transmission gear 40 from various directions due to changes in the output of the drive source, etc., making it easy for the transmission gear 40 to exhibit oscillation behavior. However, in this embodiment, the reduction gear 10 has a recess 45 formed on the end face of the transmission gear 40 so as to satisfy the above conditions (A) and (B). Therefore, it is possible to shorten the axial length of the crankshaft 14 while effectively suppressing the generation of vibration noise caused by the oscillating behavior of the transmission gear 40.

[0044] 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.

[0045] Furthermore, in the above embodiment, a retaining ring 48 is used as a retaining member to prevent the transmission gear 40 from coming loose in the axial direction at the end of the input shaft (crankshaft 14), but the retaining member is not limited to a retaining ring. The retaining member may be any member that can fix the transmission gear 40 in the axial direction on the input shaft (crankshaft 14), such as a pin or other type of member.

[0046] 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.

[0047] 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.

[0048] Furthermore, in 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 is only necessary to achieve its objective. [Explanation of Symbols]

[0049] 10...Reducer, 11...Case, 13A...First carrier block (carrier), 13B...Second carrier block (carrier), 14...Crankshaft (input shaft), 15A...First oscillating gear (oscillating gear), 15B...Second oscillating gear (oscillating gear), 30...Input gear, 35...Reduction mechanism, 40...Transmission gear, 45...Recess, 48...Retaining ring (retaining member), ac...Axial center, S1...Plane perpendicular to the axis, w1...Tooth width, w2...Spline meshing width.

Claims

1. A reduction mechanism having an input shaft and reducing the rotation input to the input shaft to output the reduced rotation, The input shaft end is spline-engaged, and the transmission gear is fixed in the axial position by a disengagement-retaining member, and meshes with an input gear driven by a drive source, transmitting driving force from the input gear to the input shaft. The outer end face in the axial direction of the transmission gear is provided with a recess that accommodates the engagement portion between the end of the input shaft and the disengagement restricting member. A gear reducer in which the recess is formed such that the meshing width between the input shaft and the spline of the transmission gear is 60% or more of the tooth width of the transmission gear, and the orthogonal plane passing through the axial center of the tooth width of the transmission gear is located within the range of the meshing width between the input shaft and the spline of the transmission gear.

2. 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 fewer teeth than the internal teeth but with external teeth that mesh with the internal teeth, receiving a rotational force from the eccentric portion of the crankshaft to oscillate and output rotation to the carrier, The crankshaft end is spline-engaged, and the transmission gear is fixed in the axial position by a disengagement-retaining member, and meshes with an input gear driven by a drive source, thereby transmitting driving force from the input gear to the crankshaft. The outer end face in the axial direction of the transmission gear is provided with a recess that accommodates the engagement portion between the end of the crankshaft and the disengagement restricting member. A gearbox in which the recess is formed such that the meshing width between the crankshaft and the spline of the transmission gear is 60% or more of the tooth width of the transmission gear, and the orthogonal plane passing through the axial center of the tooth width of the transmission gear is located within the range of the meshing width between the crankshaft and the spline of the transmission gear.

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