Gear system

Abstract

To provide a gear system that can reduce noise during operation without increasing the number of gear components. [Solution] The gear device 1 comprises one first gear 11 and a plurality of second gears 12 arranged in the circumferential direction of the first gear 11, centered on the rotation axis A1 of the first gear 11, and each meshing with the first gear 11. The plurality of second gears 12 rotate in conjunction with each other. Each of the plurality of second gears 12 has an external tooth portion 122 in the circumferential direction of the second gear 12 in which a plurality of external teeth 121 that mesh with the first gear 11 are arranged, and a missing portion 123 in the circumferential direction of the second gear 12 in which no external teeth 121 are arranged. The external tooth portion 122 and the missing portion 123 are arranged in the circumferential direction of the second gear 12. There is always at least one second gear 12 that meshes with the first gear 11.

Description

Technical Field

[0001] This invention relates to a gear device.

Background Art

[0002] Patent Document 1 discloses a gear device having a first gear and a plurality of second gears arranged around the first gear and meshing with the first gear. In the gear device of Patent Document 1, each second gear is composed of an outer peripheral portion (gear portion) meshing with the first gear, an inner peripheral portion (substrate portion) arranged inside the outer peripheral portion, and an elastic body structure connecting the outer peripheral portion and the inner peripheral portion. Therefore, the outer peripheral portion of the second gear can swing elastically with respect to the inner peripheral portion. With the second gear having such a configuration, the meshing noise between the first gear and the second gear based on the non-uniform meshing with the first gear in the circumferential direction of the second gear is suppressed, and the noise during the driving of the gear device is reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] [[ID=三十五]]By the way, some of the meshing noise between the first gear and the second gear is caused by the meshing of a plurality of second gears with the first gear. Therefore, there is room for improvement in reducing the noise during the driving of the gear device. In addition, the second gear composed of a plurality of parts like the gear device of Patent Document 1 is heavy compared to the second gear composed of one part, which is not preferable.

[0005] The present invention provides a gear device capable of reducing noise during driving without increasing the number of component parts of the gear.

Means for Solving the Problems

[0006] A gear device according to one aspect of the present invention comprises a first gear and a plurality of second gears arranged in the circumferential direction of the first gear with respect to its rotation axis, each of which meshes with the first gear, wherein the plurality of second gears rotate in conjunction with each other, and each of the plurality of second gears has an external tooth portion in the circumferential direction of the second gear in which a plurality of external teeth that mesh with the first gear are arranged, and a missing portion in the circumferential direction of the second gear in which the external teeth are not arranged, wherein the external tooth portion and the missing portion are arranged in the circumferential direction of the second gear, and there is at least one second gear that always meshes with the first gear.

[0007] Each second gear has both an external tooth portion and a missing portion, which reduces the number of second gears that mesh with the first gear, depending on the rotational position of each of the multiple second gears. Reducing the number of second gears that mesh with the first gear reduces the number of points where noise is generated due to the meshing of the first gear and the multiple second gears. This reduces the meshing noise between the first gear and the second gears. Furthermore, by reducing the number of second gears that mesh with the first gear simultaneously, the force required to force multiple second gears to mesh with the first gear is reduced compared to the case where all second gears always mesh with the first gear. This also reduces the noise produced when the first and second gears mesh together. Furthermore, each second gear, which has both an external tooth portion and a missing portion, can be constructed from a single component. As a result, noise caused by the meshing of the first gear and the second gear can be reduced when the reduction gear is in operation, without increasing the number of components of the second gear (i.e., without increasing the weight of the second gear).

[0008] In the above configuration, the number of second gears may be N, and the number of second gears that mesh with the first gear simultaneously may be (N-1) or less.

[0009] In the above configuration, the number of second gears may be three or more, and the number of second gears that mesh with the first gear at the same time may be two or more.

[0010] In the above configuration, the number of second gears is 3, the shape of the 3 second gears is the same, the number of external teeth and missing teeth in the second gear is equal to each other, the angular range of one external tooth and one missing tooth in the circumferential direction of the second gear is equal to each other, and the number of missing teeth in the second gear may be a multiple of 3.

[0011] In the above configuration, the missing portion may be formed by a recess that is recessed from the outer edge of the second gear when viewed from the axial direction of the second gear. [Effects of the Invention]

[0012] The gear system described above can reduce noise during operation without increasing the number of gear components. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view showing a reduction gear according to one embodiment. [Figure 2] Figure 1 is a plan view of the reduction gear as seen from direction II. [Figure 3] Figure 2 is a plan view showing the spur gear in the reduction gear. [Modes for carrying out the invention]

[0014] Next, embodiments of the present invention will be described with reference to the drawings.

[0015] <Deceleration device> As shown in Figures 1 and 2, the reduction gear 1, a type of gear system, reduces the rotation of a drive source (rotational drive source), such as an electric motor (not shown), and outputs the reduced rotation. The reduction gear 1 is a so-called eccentric oscillating reduction gear. The reduction gear 1 comprises a cylindrical case 2, a carrier 3 rotatably mounted radially inside the case 2, and a reduction mechanism 4 connected to the carrier 3. The central axis of the case 2 and the rotation axis of the carrier 3 coincide. In the following description, the common name for these central axis and rotation axis is referred to as the first rotation axis A1. The direction parallel to the first rotation axis A1 is referred to as the axial direction. The rotation direction of the carrier 3 is referred to as the circumferential direction. The radial direction of the case 2 orthogonal to the axial direction and the circumferential direction is simply referred to as the radial direction.

[0016] <Case> On the outer peripheral surface of the case 2, an outer flange portion 2a protruding radially outward is integrally formed. A plurality of bolt holes 2b are formed in the outer flange portion 2a. The bolt holes 2b are arranged at intervals in the circumferential direction. Bolts (not shown) are inserted into the bolt holes 2b, and the reduction gear 1 is fixed, for example, by tightening the bolts to an arm of an industrial robot or the like.

[0017] As shown in FIG. 1, on the inner peripheral surface 2d of the case 2, a plurality of pin grooves 2c extending along the axial direction are formed. The plurality of pin grooves 2c are arranged at equal intervals in the circumferential direction. Inner tooth pins 5 are respectively fitted into the pin grooves 2c. The inner tooth pins 5 function as inner teeth that mesh with the oscillating external teeth gears 15 and 16 of the reduction mechanism 4 described later.

[0018] <Carrier> The carrier 3 is generally formed in a circular shape when viewed from the axial direction, and has a substrate portion 7 and an end plate portion 8 arranged opposite to each other in the axial direction.

[0019] The substrate portion 7 is formed in a disc shape. The substrate portion 7 is supported by the case 2 via the first main bearing 41. Thereby, the substrate portion 7 is relatively rotatable about the first rotation axis A1 with respect to the case 2. A seal portion 24 is provided in a portion between the outer peripheral surface of the substrate portion 7 and the inner peripheral surface 2d of the case 2, on the side opposite to the end plate portion 8 with respect to the first main bearing 41. The seal portion 24 ensures the sealing performance between the substrate portion 7 and the case 2.

[0020] At the radial center of the substrate portion 7, a substrate through-hole 7d penetrating the substrate portion 7 in the axial direction is formed. Around the substrate through-hole 7d in the substrate portion 7, a plurality (for example, three in this embodiment) of crank insertion recesses 7e are formed. Each crank insertion recess 7e is formed in the end face 7f of the substrate portion 7 facing the end plate portion 8. The plurality of crank insertion recesses 7e are arranged at equal intervals in the circumferential direction. Each crank insertion recess 7e is provided with a crank bearing 18. The crank bearing 18 is, for example, a tapered roller bearing 19.

[0021] On the end face 7f of the substrate portion 7, a column portion 9 is formed to project toward the end plate portion 8. Although not shown, a plurality (for example, three in this embodiment) of column portions 9 are arranged at intervals in the circumferential direction. Each column portion 9 is arranged between adjacent crank insertion recesses 7e in the circumferential direction. The plurality of column portions 9 are arranged at equal intervals in the circumferential direction.

[0022] On the tip end face 9a of each column portion 9, a female screw portion 26 is formed. The female screw portions 26 formed on the same column portion 9 may be arranged in a plurality (for example, two) in the circumferential direction, for example. The female screw portion 26 is used to integrate the substrate portion 7 and the end plate portion 8 (details will be described later).

[0023] <End plate portion> The end plate portion 8 is formed in a disk shape. The end plate portion 8 is supported by the case 2 via the second main bearing 42. Thereby, the end plate portion 8 is enabled to rotate relative to the case 2 about the first rotation axis A1.

[0024] At the radial center of the end plate portion 8, an end plate through-hole 8d penetrating the end plate portion 8 in the axial direction is formed. The end plate through-hole 8d is arranged coaxially with the substrate through-hole 7d. Around the end plate through hole 8d in the end plate portion 8, a plurality of crank insertion holes 8e (for example, three in this embodiment) are formed, each penetrating the end plate portion 8 in the axial direction. Each crank insertion hole 8e is arranged at equal intervals in the circumferential direction. Each crank insertion hole 8e is arranged coaxially with the crank insertion recess 7e of the base plate portion 7. That is, the central axis A2 of the axially opposing crank insertion holes 8e and crank insertion recess 7e is parallel to the first rotation axis A1. Each crank insertion hole 8e is provided with a crank bearing 18, similar to the crank insertion recess 7e.

[0025] On the end face 8f of the end plate portion 8 facing the substrate portion 7, multiple end plate protrusions 62 (for example, three in this embodiment) are formed at locations facing the column portion 9 in the axial direction. The tip surface 9a of the column portion 9 abuts against the end plate protrusions 62.

[0026] Multiple bolt insertion holes 63 are formed in each of the end plate portion 8 corresponding to each end plate protrusion 62. Multiple bolt insertion holes 63 (for example, two) may be arranged in the circumferential direction in the portion of the end plate portion 8 corresponding to the same end plate protrusion 62. A bolt 91 is inserted into the bolt insertion hole 63 from the side opposite to the base plate portion 7, and the bolt 91 is tightened into the female thread portion 26 of the column portion 9. This fixes the end plate portion 8 to the base plate portion 7. In this state, a space with a width equal to the height of the column portion 9 is formed between the base plate portion 7 and the end plate portion 8. With the end plate portion 8 fixed to the base plate portion 7, the carrier 3, which integrates the base plate portion 7 and the end plate portion 8, becomes rotatable relative to the case 2 around the first rotation axis A1.

[0027] <Deceleration mechanism> The reduction mechanism 4 reduces the rotation of a rotational drive source (not shown) by a constant ratio to rotate the carrier 3. As shown in Figures 1 and 2, the reduction mechanism 4 comprises one input gear 11 (first gear) connected to the rotational shaft of the rotational drive source, a plurality of spur gears 12 (second gears) that mesh with the input gear 11, a crankshaft 13 attached to the spur gears 12, and two oscillating external gears 15 and 16 (first oscillating external gear 15, second oscillating external gear 16) provided between the base plate portion 7 and the end plate portion 8.

[0028] The input gear 11 is formed in a circular shape when viewed from the axial direction and has a plurality of external teeth 111 around its entire outer circumference. In this embodiment, the rotation axis of the input gear 11 coincides with the first rotation axis A1, but is not limited to this.

[0029] As shown in Figures 2 and 3, each spur gear 12 is formed in a generally circular shape when viewed from the axial direction and has a plurality of external teeth 121 on its outer circumference for meshing with the external teeth 111 of the input gear 11. The plurality of external teeth 121 of the spur gear 12 are arranged in the circumferential direction of the spur gear 12 around the rotation axis A2 of the spur gear 12 (the second rotation axis A2 described later). Furthermore, each spur gear 12 has an external tooth portion 122 in which multiple external teeth 121 are arranged in the circumferential direction of the spur gear 12, and a missing portion 123 in which no external teeth 121 are arranged in the circumferential direction of the spur gear 12. In this embodiment, the missing portion 123 is composed of a recess 125 that is recessed from the outer edge of the spur gear 12, which is circular when viewed from the axial direction.

[0030] In each spur gear 12, the external teeth 122 and missing teeth 123 are arranged alternately in the circumferential direction of the spur gear 12. The number of external teeth 122 and missing teeth 123 in each spur gear 12 is equal to the number of missing teeth 123. Also, the number of external teeth 122 and missing teeth 123 in each spur gear 12 is a multiple of 3. In Figures 2 and 3, the number of external teeth 122 and missing teeth 123 is 3 each, but it could be 6, 9, or other numbers, for example.

[0031] As shown in Figure 3, the angular range θ1 of one external tooth portion 122 and the angular range θ2 of one missing portion 123 in the circumferential direction of the spur gear 12 are equal to each other. In this embodiment, the angular range θ1 of one external tooth portion 122 and the angular range θ2 of one missing portion 123 are both 60 degrees. The angular ranges θ1 and θ2 of the external tooth portion 122 and the missing portion 123, respectively, are angles centered on the rotation axis A2 of the spur gear 12. Furthermore, the sum of the angles of the multiple external tooth portions 122 and the sum of the angles of the multiple missing portions 123 in the circumferential direction of the spur gear 12 are both 180 degrees. As shown in Figure 2, the shape of the spur gear 12 described above is the same among multiple spur gears 12.

[0032] In this embodiment, the diameter of each spur gear 12 as viewed from the axial direction is larger than the diameter of the input gear 11. Therefore, when the input gear 11 is rotated with the input gear 11 meshed with the spur gear 12, the rotational speed of the spur gear 12 becomes slower than the rotational speed of the input gear 11. In other words, the reduction gear 1, including the input gear 11 and the spur gear 12, outputs a rotational speed lower than the input rotational speed.

[0033] As shown in Figure 1, each spur gear 12 is mounted on the axial end of the crankshaft 13. In the illustrated example, the spur gear 12 is mounted on the end of the crankshaft 13 (shaft body 13c, described later) located on the end plate portion 8 side in the axial direction. The spur gear 12 and the input gear 11 that meshes with it are located adjacent to the carrier 3 on the end plate portion 8 side.

[0034] As shown in Figure 2, the multiple spur gears 12 are arranged around the input gear 11 in the circumferential direction of the input gear 11, with the first rotation axis A1 as the center. Specifically, the multiple spur gears 12 are arranged at equal intervals in the circumferential direction of the input gear 11. In this embodiment, there are three spur gears 12. The relationship between the single input gear 11 and the multiple spur gears 12 will be described later.

[0035] As shown in Figure 1, the crankshaft 13 is inserted into the crank insertion recess 7e of the base plate portion 7 and the crank insertion hole 8e of the end plate portion 8. The crankshaft 13 is rotatably supported on the carrier 3 (base plate portion 7 and end plate portion 8) via each crank bearing 18. The crankshaft 13 has a shaft body 13c that rotates about a central axis A2, and a first eccentric portion 13a and a second eccentric portion 13b formed in the axial center of the shaft body 13c. Both axial portions of the shaft body 13c are rotatably supported on the carrier 3 (base plate portion 7 and end plate portion 8) via the crank bearings 18.

[0036] The crankshaft 13 (shaft body 13c) and the spur gear 12 are arranged coaxially and integrated. As a result, the crankshaft 13 and the spur gear 12 rotate together around the central axis A2. Hereinafter, the central axis A2 will be referred to as the second rotation axis A2 of the crankshaft 13.

[0037] The first eccentric portion 13a and the second eccentric portion 13b of the crankshaft 13 are eccentric from the second rotation axis A2. Therefore, as the crankshaft 13 rotates, the first eccentric portion 13a and the second eccentric portion 13b oscillate. The first eccentric portion 13a and the second eccentric portion 13b are positioned adjacent to each other in the axial direction between the two crank bearings 18. In other words, the first eccentric portion 13a and the second eccentric portion 13b are positioned adjacent to each other in the axial direction between the base plate portion 7 and the end plate portion 8. The first eccentric portion 13a and the second eccentric portion 13b are positioned with a phase angle difference of 180°. The inner circumferential surfaces of roller bearings 19 are fitted to each of the eccentric portions 13a and 13b. The roller bearings 19 are, for example, cylindrical roller bearings. The first oscillating external gear 15 and the second oscillating external gear 16 are rotatably supported on the crankshaft 13 via the roller bearings 19.

[0038] The first oscillating external gear 15 and the second oscillating external gear 16 are positioned in the space between the base plate portion 7 and the end plate portion 8. The first oscillating external gear 15 and the second oscillating external gear 16 overlap in the axial direction. The first oscillating external gear 15 and the second oscillating external gear 16 have crank insertion holes 15a and 16a that penetrate them in the axial direction. The outer circumferential surface of a roller bearing 19 is fitted into each of the crank insertion holes 15a and 16a. As a result, when the first eccentric portion 13a and the second eccentric portion 13b oscillate due to the rotation of the crankshaft 13, the first oscillating external gear 15 and the second oscillating external gear 16 oscillate via the roller bearing 19.

[0039] The first oscillating external gear 15 and the second oscillating external gear 16 each have openings 15b and 16b, respectively, to avoid interference with the column portion 9. Through holes 15c and 16c are formed at the radial center of the first oscillating external gear 15 and the second oscillating external gear 16, penetrating them axially. External teeth 15d and 16d are formed on the outer circumference of the first oscillating external gear 15 and the outer circumference of the second oscillating external gear 16, respectively. The number of teeth on each external tooth 15d and 16d is, for example, one less than the number of internal tooth pins 5 in case 2.

[0040] In the reduction mechanism 4 configured as described above, the multiple spur gears 12 rotate in conjunction with each other via their respective crankshafts 13 and two oscillating external gears 15 and 16. Therefore, the spur gears 12 that are not meshed with the input gear 11 rotate in conjunction with the spur gears 12 that are meshed with the input gear 11.

[0041] <Relationship between one input gear and multiple spur gears> As shown in Figure 2, in the reduction mechanism 4, each of the three spur gears 12 has an external tooth portion 122 and a missing tooth portion 123, so that the spur gear 12 that meshes with the input gear 11 is switched as the input gear 11 rotates. When the input gear 11 and the spur gears 12 are rotating, the number of spur gears 12 that mesh with the input gear 11 at the same time is two or less. The fact that the number of spur gears 12 that mesh with the input gear 11 at the same time is two or less may also include the case where the number of spur gears 12 that mesh with the input gear 11 is one at a time.

[0042] To ensure that only two or fewer spur gears mesh with the input gear 11 simultaneously, even though there are three spur gears 12, this can be achieved by forming the three spur gears 12 in the aforementioned shape (for example, the shape shown in Figure 3), and then adjusting the phase angles of the multiple spur gears 12 based on the straight line connecting the first rotation axis A1 and each second rotation axis A2. Specifically, the phase angles of the three spur gears 12 centered on each second rotation axis A2 are shifted by 40 degrees. This ensures that the number of spur gears 12 meshing with the input gear 11 simultaneously is reliably two or fewer (one or two). Furthermore, only one spur gear 12 needs to be constantly meshed with the input gear 11. This allows the rotation of the input gear 11 to be constantly transmitted to multiple spur gears 12, thereby rotating multiple spur gears 12. In other words, it prevents interruptions in the transmission of rotation between the input gear 11 and the multiple spur gears 12.

[0043] <Operation of the speed reducer> Next, the operation of the reduction gear 1 will be explained. In the reduction gear 1, the rotation of the rotational drive source is transmitted from the input gear 11 to the spur gears 12 that mesh with the input gear 11, causing each spur gear 12 to rotate around the second rotation axis A2. Here, since the diameter of the spur gears 12 is larger than the diameter of the input gear 11, the rotation of the spur gears 12 is reduced relative to the rotation of the input gear 11 (rotational drive source). The spur gears 12 that are not meshed with the input gear 11 rotate via the spur gears 12 that mesh with the input gear 11, the crankshaft 13, and the two oscillating external gears 15 and 16. In other words, the multiple spur gears 12 rotate in conjunction with each other. Furthermore, when the rotation of the spur gear 12 is transmitted to the crankshaft 13, the crankshaft 13 rotates around the second rotation axis A2.

[0044] As a result, each oscillating external gear 15, 16 oscillates and rotates. Here, the number of teeth on the external teeth 15d, 16d of the oscillating external gears 15, 16 is, for example, one less than the number of internal tooth pins 5 on the case 2 side. Therefore, each oscillating external gear 15, 16 rotates such that the meshing points of each external tooth 15d, 16d with respect to the internal tooth pins 5 (case 2) are sequentially shifted in the circumferential direction. This rotation is decelerated relative to the rotation of the crankshaft 13.

[0045] As each oscillating external gear 15, 16 rotates, each crankshaft 13 also rotates on its own axis around the second rotation axis A2 while revolving around the first rotation axis A1. Each crankshaft 13 is rotatably supported on the carrier 3 (base portion 7, end plate portion 8). Therefore, as each crankshaft 13 revolves, the carrier 3 rotates around the first rotation axis A1. As a result, the reduction gear 1 reduces the rotation of, for example, the rotation drive source and outputs it. If the carrier 3 is fixed to the arm of an industrial robot, for example, the reduction gear 1 can reduce the rotation of, for example, the rotation drive source and output it from the case 2. Also, if the case 2 is fixed to the arm of an industrial robot, for example, the reduction gear 1 can reduce the rotation of, for example, the rotation drive source and output it from the carrier 3.

[0046] In the reduction gear 1 (gear device) configured as described above, each of the multiple spur gears 12 has an external tooth portion 122 and a missing tooth portion 123. Therefore, the number of spur gears 12 that mesh with the input gear 11 can be reduced according to the rotational position of each of the multiple spur gears 12. By reducing the number of spur gears 12 that mesh with the input gear 11, the number of points where noise is generated due to the meshing of the input gear 11 and the multiple spur gears 12 is reduced. As a result, the meshing noise between the input gear 11 and the spur gears 12 can be reduced. Furthermore, by reducing the number of spur gears 12 that mesh with the input gear 11 simultaneously, the force that forces multiple spur gears 12 to mesh with the input gear 11 is reduced compared to the case where all spur gears 12 are always meshing with the input gear 11. This also reduces the meshing noise between the input gear 11 and the spur gears 12. Furthermore, each spur gear 12 having an external tooth portion 122 and a missing portion 123 can be constructed from a single component. As a result, noise based on the meshing of the input gear 11 and the spur gear 12 can be reduced when the reduction gear 1 is driven, without increasing the number of components of the spur gear 12 (i.e., without increasing the weight of the spur gear 12).

[0047] Furthermore, in the reduction gear 1 described above, there are three spur gears 12, and the maximum number of spur gears 12 that mesh with the input gear 11 simultaneously is two. Therefore, compared to the case where there is always only one spur gear 12 meshing with the input gear 11, the load on the spur gears 12 can be reduced when the input gear 11 and the spur gears 12 meshing with it rotate. In other words, the reduction gear 1 can be protected. Furthermore, since there are two spur gears 12 that mesh with the input gear 11 at the same time, it is possible to easily assemble multiple spur gears 12 to the input gear 11 when assembling the reduction gear 1.

[0048] Furthermore, in the reduction gear 1 described above, there are three spur gears 12, and the number of spur gears 12 that mesh with the input gear 11 simultaneously is two or less (one or two). In other words, the number of spur gears 12 that mesh with the input gear 11 simultaneously is less than the total number of spur gears 12. Therefore, the number of points where noise is generated due to the meshing of the input gear 11 and multiple spur gears 12 can always be reduced. This further reduces the meshing noise between the input gear 11 and the spur gears 12.

[0049] Furthermore, in the reduction gear 1 described above, there are three spur gears 12 of the same shape, the angular ranges θ1 and θ2 of one external tooth portion 122 and one missing portion 123 in each spur gear 12 are equal, and the number of missing portions 123 in each spur gear 12 is a multiple of 3. This ensures that the number of spur gears 12 that mesh with the input gear 11 at the same time is 2 or less (1 or 2). In other words, the number of spur gears 12 that mesh with the input gear 11 at the same time can be less than the total number of spur gears 12 (3).

[0050] Furthermore, in the reduction gear 1 described above, the missing portion 123 of each spur gear 12 is composed of a recess 125 that is recessed from the outer edge of the spur gear 12 when viewed from the axial direction. Therefore, compared to the case where only the external teeth 121 are missing in the missing portion 123, the weight of each spur gear 12 can be reduced. This makes it possible to reduce the weight of the reduction gear 1.

[0051] [Other variations] The present invention is not limited to the embodiments described above, but includes various modifications to the embodiments described above, without departing from the spirit of the invention.

[0052] In the above-described embodiment, the missing portion 123 of the spur gear 12 may be, for example, a spur gear 12 that is circular when viewed from the axial direction, with only the external teeth 121 missing.

[0053] In the above-described embodiment, it is sufficient that at least a plurality of spur gears 12 each have an external tooth portion 122 and a missing portion 123, and for example, all spur gears 12 may momentarily mesh with the input gear 11 simultaneously. Even with such a configuration, there are moments when each spur gear 12 does not mesh with the input gear 11, so the meshing noise between the input gear 11 and the spur gears 12 can be reduced.

[0054] In the above-described embodiment, the angular range θ1 of one external tooth portion 122 and the angular range θ2 of one missing portion 123 in each spur gear 12 may be arbitrary. Furthermore, in each spur gear 12, the angular range θ1 of one external tooth portion 122 and the angular range θ2 of one missing portion 123 may be equal to each other as in the above-described embodiment, but they may also be different.

[0055] Furthermore, for example, the sum of the angles of the external teeth 122 on each spur gear 12 may be greater than the sum of the angles of the missing teeth 123. In such a configuration, although there are moments when all the spur gears 12 mesh with the input gear 11 simultaneously, there are also moments when fewer spur gears 12 mesh with the input gear 11 because each spur gear 12 has a missing tooth 123. This reduces the meshing noise between the input gear 11 and the spur gears 12, thereby reducing overall noise.

[0056] In the above-described embodiment, the number (total number) of spur gears 12 arranged circumferentially around one input gear 11 is not limited to three, but may be two, four or more. If the total number of spur gears 12 having external teeth 122 and missing teeth 123 is two or more, the number of spur gears 12 meshing with the input gear 11 can be less than the total number of spur gears 12. This makes it possible to reduce noise based on the meshing sound between the input gear 11 and the spur gears 12.

[0057] Furthermore, if the total number of spur gears 12 is two, it is preferable to ensure that at least one spur gear 12 is always meshing with the input gear 11, for example, by setting the total angle of the external teeth 122 of each spur gear 12 to 180 degrees or more and the total angle of the missing teeth 123 to 180 degrees or less.

[0058] When the total number of spur gears 12 is three or more, it is preferable that the number of spur gears 12 that mesh with the input gear 11 simultaneously (maximum number) is two or more. In such a configuration, as in the embodiment described above, the load on a single spur gear 12 can be reduced to protect the reduction unit 1. Furthermore, having two or more spur gears 12 that mesh with the input gear 11 simultaneously makes it easier to assemble multiple spur gears 12 to the input gear 11 when assembling the reduction unit 1.

[0059] Furthermore, if the total number of spur gears 12 is three or more, it is preferable to set the total number of spur gears 12 to N and the number of spur gears 12 that mesh with the input gear 11 simultaneously (maximum number) to (N-1) or less. Even with such a configuration, similar to the embodiment described above, the number of spur gears 12 that mesh with the input gear 11 simultaneously is kept less than the total number of spur gears 12, thereby always reducing the number of points where noise is generated due to the meshing of the input gear 11 and multiple spur gears 12. This further reduces the meshing noise between the input gear 11 and the spur gears 12.

[0060] The shapes of the multiple spur gears 12 may differ from one another, for example. For instance, the angular range θ1 of the external tooth portion 122 and the angular range θ2 of the missing portion 123 may differ from one another among the multiple spur gears 12.

[0061] In the embodiment described above, the multiple spur gears 12 are not limited to the crankshaft 13 and the oscillating external gears 15 and 16, but may rotate in conjunction with each other via any rotational transmission mechanism (e.g., a gear mechanism).

[0062] The present invention is not limited to reduction gear 1, but is applicable to any gear apparatus comprising one first gear and a plurality of second gears arranged in the circumferential direction of the first gear with respect to its rotation axis, each meshing with the first gear, wherein the plurality of second gears rotate in conjunction with each other.

[0063] 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]

[0064] 1…Gear reducer (gear system) 111... External teeth of input gear 11 121...External teeth of spur gear 12 122...External tooth part 123... Missing part 125…recess A1…First axis of rotation (axis of rotation) A2…Second rotation axis, center axis (rotation axis) θ1...Angular range of the external tooth portion 122 θ2...Angular range of missing portion 123

Claims

1. One first gear, The system comprises a plurality of second gears arranged in the circumferential direction of the first gear, centered on the rotation axis of the first gear, and each meshing with the first gear, Multiple second gears rotate in conjunction with each other. Each of the multiple second gears has an external tooth portion in which multiple external teeth that mesh with the first gear are arranged in the circumferential direction of the second gear, and a missing portion in which the external teeth are not arranged in the circumferential direction of the second gear. The external tooth portion and the missing portion are aligned in the circumferential direction of the second gear. A gear apparatus in which at least one second gear is always meshed with the first gear.

2. The gear apparatus according to claim 1, wherein the number of second gears is N, and the number of second gears that mesh with the first gear simultaneously is (N-1) or less.

3. The number of the aforementioned second gears is three or more, The gear apparatus according to claim 2, wherein the number of second gears that mesh with the first gear at the same time is two or more.

4. The number of the aforementioned second gears is three, The three aforementioned second gears have the same shape, The number of external teeth and missing teeth in the second gear are equal to each other. The angular ranges of one of the external tooth portions and one of the missing portions in the circumferential direction of the second gear are equal to each other. The gear apparatus according to claim 3, wherein the number of missing portions in the second gear is a multiple of 3.

5. The gear apparatus according to any one of claims 1 to 4, wherein the missing portion is formed by a recess that is recessed from the outer edge of the second gear when viewed from the axial direction of the second gear.

Images