JP2019056443A - transmission - Google Patents

Abstract

To provide an eccentric oscillation type transmission for improving its back drivability performance.SOLUTION: The eccentric oscillation type transmission includes a plurality of eccentric bodies adapted to be rotated around a central axis together with a first rotation part, having different distances from the central axis to the outer peripheral face depending on peripheral positions, and arranged at mutually different positions in the axial direction. On the outer peripheral faces of the plurality of eccentric bodies, a plurality of external gears are provided via bearings, respectively. The plurality of external gears engage with an internal gear different in tooth number. In each of through-holes provided in positions where the plurality of external gears overlap one another in the axial direction, a carrier pin is inserted. The internal gear engages with the plurality of external gears at their external teeth most distant from the central axis. Positions of engagement of the internal gear with the plurality of external gears are uneven in the peripheral direction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a transmission.

Japanese Unexamined Patent Application Publication No. 2014-16019 describes an eccentric rocking speed reduction mechanism. The speed reduction mechanism of the publication is provided in a motor torque transmission device that transmits the motor torque of an electric motor to a pair of rear wheels in a four-wheel drive vehicle. The speed reduction mechanism includes an internal gear and an external gear disposed inside the internal gear. The external gear swings along the inner surface of the internal gear while meshing with the internal gear. Such an eccentric oscillating speed reduction mechanism is small and can provide a high reduction ratio.
JP 2014-16019 A

  By the way, in recent years, there is an increasing demand for small robots that work in cooperation with people. Then, it has been proposed to use an actuator in which the above-described eccentric oscillating speed reducer and a motor are combined for a joint of a small robot. However, this type of small robot requires smooth operation. Further, this type of small robot has a performance (back drivability) that facilitates transmission to the input side when an external force is applied to the output side. By improving the back drivability, when an impact is applied to the output side, it is easy to suppress damage to the actuator or an application in which the actuator is mounted. Therefore, improvement in back drivability performance is required.

  Therefore, the present inventor has found a configuration that can improve the back drivability by using a plurality of external gears in the transmission.

  In order to solve the above problems, the invention of the present application is an eccentric oscillating type transmission, wherein a first rotating portion that rotates about a central axis, and rotates together with the first rotating portion, and the outer periphery from the central axis. A plurality of eccentric bodies arranged at different positions in the axial direction, a plurality of bearings provided on the outer peripheral surface of each of the plurality of eccentric bodies, A plurality of external gears provided on the outer peripheral surface of each of the bearings, a cylindrical shape surrounding the central axis in the circumferential direction, and an internal gear disposed on the radially outer side of the plurality of external gears; A carrier pin extending in the axial direction, inserted into a through hole provided at a position overlapping each other in the axial direction of each of the plurality of external gears, and a second rotating part to which the carrier pin is fixed and rotating around the central axis The plurality of The number of teeth of the external gear is different from the number of teeth of the internal gear, and the internal gear includes external teeth having the longest distance from the central axis of each of the plurality of external gears. However, the meshing positions of the internal gear and the plurality of external gears are not uniform in the circumferential direction.

  According to the present application, the peak of the back drive torque of the transmission can be lowered.

FIG. 1 is a longitudinal sectional view of a transmission according to an embodiment. FIG. 2 is an exploded perspective view of the transmission. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a diagram for explaining the positional relationship between the central axis of the first eccentric body and the central axis of the second eccentric body. FIG. 5 is a diagram illustrating a simulation result obtained by measuring the backdrive torque.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In the present application, the direction parallel to the central axis of the transmission is referred to as “axial direction”, the direction orthogonal to the central axis is referred to as “radial direction”, and the direction along the arc centered on the central axis is referred to as “circumferential direction”. Called. Further, in the present application, the shape and positional relationship of each part will be described with the axial direction as the vertical direction and the first carrier member side of the second rotating part as the first rotating part. However, this definition of the vertical direction is not intended to limit the direction when the transmission according to the present application is used. The “parallel direction” includes a substantially parallel direction. In addition, the above-mentioned “orthogonal direction” includes a substantially orthogonal direction.

<1. Overall configuration of transmission>
FIG. 1 is a longitudinal sectional view of a transmission according to the present embodiment. FIG. 2 is an exploded perspective view of the transmission 1. 3 is a cross-sectional view taken along line III-III in FIG. In FIG. 3, hatching is omitted to avoid complication of the drawing.

  The transmission 1 is a gear reducer that converts rotational motion at a first rotational speed (input rotational speed) into rotational motion at a second rotational speed (output rotational speed) that is lower than the first rotational speed. The transmission 1 is used, for example, in a joint of a small robot such as a service robot that performs work in cooperation with a person. However, you may use the transmission which has an equivalent structure for other uses, such as a large sized industrial robot, a machine tool, an XY table, a material cutting device, a conveyor line, a turntable, a rolling roller.

  The transmission 1 includes a first rotating unit 10, a first eccentric body 21 and a second eccentric body 22, a first external gear 31 and a second external gear 32, a frame 40, and a plurality of carrier pins 50. , A second rotation unit 60.

  The first rotating unit 10 is a columnar member that extends vertically along the central axis 9. As conceptually shown in FIG. 1, the first rotating unit 10 is connected to a motor, which is a drive source, directly or via another power transmission mechanism. When the motor is driven, the first rotating unit 10 rotates at the first rotation speed about the central axis 9 by the power supplied from the motor. That is, in the present embodiment, the first rotating unit 10 is an input unit.

  The first eccentric body 21 is a member that is fixed to the outer peripheral surface of the first rotating unit 10 and rotates together with the first rotating unit 10. The first rotating unit 10 and the first eccentric body 21 may be a single member or different members. As shown in FIG. 3, the first eccentric body 21 has a true circular outer peripheral surface when viewed from the axial direction. The central axis 91 of the first eccentric body 21 is located away from the central axis 9. Therefore, the distance from the central axis 9 to the outer peripheral surface of the first eccentric body 21 varies depending on the position in the circumferential direction.

  The second eccentric body 22 is fixed to the outer peripheral surface of the first rotating unit 10. The second eccentric body 22 is fixed at a position different from the first eccentric body 21 in the axial direction. The second eccentric body 22 is a member that rotates together with the first rotating unit 10. The first rotating unit 10 and the second eccentric body 22 may be a single member or different members. Similar to the first eccentric body 21, the second eccentric body 22 has a true circular outer peripheral surface when viewed from the axial direction. The central axis 92 of the second eccentric body 22 is located away from the central axis 9. Therefore, the distance from the central axis 9 to the outer peripheral surface of the second eccentric body 22 varies depending on the position in the circumferential direction.

  FIG. 4 is a diagram for explaining the positional relationship between the central axis 91 of the first eccentric body 21 and the central axis 92 of the second eccentric body 22. The central axis 91 and the central axis 92 are on the same circle centered on the central axis 9 and are located at different positions when viewed from the axial direction. That is, the distance between the central axis 9 and the central axis 91 and the distance between the central axis 9 and the central axis 92 are the same. Further, the central axis 91 and the central axis 92 are unevenly positioned in the circumferential direction. Here, “non-uniform” means that the angular interval around the central axis 9 is not constant. When the number of eccentric bodies is two as in the present embodiment, the angle R1 from the central axis 91 to the central axis 92 centering on the central axis 9 and the central axis 92 to the central axis 91 in the clockwise direction. This means that the angle R2 is different. In the present embodiment, the central axis 92 is located 144 ° away from the central axis 91 clockwise with the central axis 9 as the center. That is, the angle R1 in FIG. 4 is 144 °.

  When the first rotating unit 10 rotates about the central axis 9, the first eccentric body 21 and the second eccentric body 22 rotate about the central axis 9. At this time, the central axis 91 of the first eccentric body 21 and the central axis 92 of the second eccentric body 22 also rotate about the central axis 9.

  The first external gear 31 is disposed on the radially outer side of the first eccentric body 21. A first bearing 71 is interposed between the first eccentric body 21 and the first external gear 31. For the first bearing 71, for example, a ball bearing is used. The first external gear 31 is supported by the first bearing 71 so as to be rotatable about the central axis 91. As shown in FIG. 3, a plurality of external teeth 311 are provided on the outer peripheral portion of the first external gear 31. Each external tooth 311 protrudes outward in the radial direction. The first external gear 31 has a plurality (10 in the example of FIG. 3) of through holes 312. Each through hole 312 penetrates the first external gear 31 in the axial direction. The plurality of through holes 312 are arranged at equiangular intervals along the circumferential direction around the central axis 91.

  The second external gear 32 is disposed on the radially outer side of the second eccentric body 22. A second bearing 72 is interposed between the second eccentric body 22 and the second external gear 32. The second external gear 32 is supported by the second bearing 72 so as to be rotatable about the central shaft 92. As the second bearing 72, for example, a ball bearing is used. Similar to the first external gear 31, the second external gear 32 is provided with a plurality of external teeth 321 on the outer peripheral portion. The second external gear 32 is provided with a plurality of through holes 322 penetrating in the axial direction. The plurality of through holes 322 are arranged at equiangular intervals along the circumferential direction around the central axis 92. The through hole 322 has the same diameter as the through hole 312. A part of each through hole 322 overlaps each through hole 312 of the first external gear 31 in the axial direction.

  The frame 40 is a cylindrical member that surrounds the central shaft 9 in the circumferential direction and extends in the axial direction. The frame 40 is disposed so as to surround the radially outer sides of the first external gear 31 and the second external gear 32. As shown in FIG. 3, a plurality of internal teeth 41 are provided on the inner peripheral surface of the frame 40. Each of the plurality of inner teeth 41 protrudes radially inward from the inner peripheral surface of the frame 40. In the present embodiment, the internal gear including the internal teeth 41 is a part of the frame 40. However, the internal gear may be a separate member from the frame 40. When the internal teeth 41 are the same member as the frame 40 as in the present embodiment, it is not necessary to provide an internal gear having the internal teeth 41 separately from the frame 40, and thus the transmission 1 can be easily downsized. It becomes.

  A part of each of the plurality of external teeth 311 of the first external gear 31 and a part of each of the plurality of external teeth 321 of the second external gear 32 mesh with a part of the plurality of internal teeth 41 of the frame 40. Specifically, the external teeth 311 of the first external gear 31 and the internal teeth 41 mesh with each other at the position farthest from the center axis 9. In addition, the external teeth 321 of the second external gear 32 and the internal teeth 41 mesh with each other at a position farthest from the center shaft 9. Hereinafter, the meshing position between the external teeth 311 of the first external gear 31 and the internal teeth 41 is referred to as a meshing position A1 (see FIG. 3). A meshing position between the external teeth 321 of the second external gear 32 and the internal teeth 41 is referred to as a meshing position A2 (see FIG. 3).

  The positional relationship between the meshing position A1 and the meshing position A2 is unequal in the circumferential direction, as is the positional relationship between the central shaft 91 and the central shaft 92. As described above, the central axis 92 of the second eccentric body 22 is located 144 degrees away from the central axis 91 of the first eccentric body 21 clockwise about the central axis 9. Therefore, the meshing position A1 and the meshing position A2 are located 144 ° apart from each other in the circumferential direction around the central axis 9.

  As described above, the first external gear 31 and the second external gear 32 have the same configuration except for the meshing position with the internal teeth 41. Therefore, in the following description, only the first external gear 31 will be described.

  When the first rotating unit 10 rotates about the central axis 9, the first external gear 31 revolves around the central axis 9 together with the central axis 91. The first external gear 31 rotates as the external teeth 311 of the first external gear 31 mesh with the internal teeth 41 of the frame 40. Here, the number of internal teeth 41 included in the frame 40 is larger than the number of external teeth 311 included in the first external gear 31. For this reason, for each revolution of the first external gear 31, the position of the external teeth 311 that mesh with the internal teeth 41 at the same position of the frame 40 is shifted. Thereby, the 1st external gear 31 rotates in the direction opposite to the rotation direction of the 1st rotation part 10 with the 2nd number of rotations lower than the 1st number of rotations. Therefore, the position of the through hole 312 of the first external gear 31 also rotates at the second rotational speed. During the operation of the transmission 1, the first external gear 31 performs a rotational motion combining such revolution and rotation.

  When the number of external teeth 311 included in the first external gear 31 is N and the number of internal teeth 41 included in the frame 40 is M, the reduction ratio P of the transmission 1 is P = (first rotational speed) / ( 2nd rotation speed) = N / (MN). In the example of FIG. 3, since N = 29 and M = 30, the reduction ratio in this example is P = 29. That is, the second rotation speed is 1/29 of the first rotation speed. However, the number N of the outer teeth 311 and the number M of the inner teeth 41 may be other values.

  In the present embodiment, a plurality of internal teeth 41 are provided as a part of the frame 40 that is a single member. For this reason, it is not necessary to provide an internal gear having a plurality of internal teeth 41 separately from the frame 40. Thereby, size reduction of the transmission 1 becomes easy.

  Each of the plurality of carrier pins 50 is a cylindrical member extending in the axial direction. The plurality of carrier pins 50 are arranged in an annular shape at equal angular intervals along the circumferential direction around the central axis 9. In this example, as shown in FIG. 3, the transmission 1 has ten carrier pins 50. Accordingly, each of the plurality of carrier pins 50 is disposed at equiangular intervals of 36 ° (360 ° / 10) along the circumferential direction around the central axis 9. The angle 144 ° of the meshing positions A1 and A2 described above is a multiple of the equal angle of 36 ° where the plurality of carrier pins 50 are arranged. Further, the meshing positions A1 and A2 are at a position deviated by an equal angle of 36 ° from the state where the meshing positions A1 and A2 are made uniform in the circumferential direction.

  Each of the plurality of carrier pins 50 is inserted into the through hole 312 of the first external gear 31 and the through hole 322 of the second external gear 32 that are overlapped in the axial direction. As a result, the plurality of carrier pins 50 are pushed by the first external gear 31 and the second external gear 32, and are centered at the same second rotational speed as the first external gear 31 and the second external gear 32. It rotates around the axis 9.

  The second rotating unit 60 includes an annular first carrier member 61 and an annular second carrier member 62. The first carrier member 61 is disposed above the first external gear 31 in the axial direction. A bearing 73 is interposed between the first rotating part 10 and the first carrier member 61. A bearing 74 is interposed between the first carrier member 61 and the frame 40.

  The second carrier member 62 is disposed on the lower side in the axial direction than the second external gear 32. A bearing 75 is interposed between the first rotating part 10 and the second carrier member 62. A bearing 76 is interposed between the second carrier member 62 and the frame 40. As the bearing 73 and the bearing 75, for example, ball bearings are used. For the bearing 74 and the bearing 76, for example, a sliding bearing made of a resin such as polyacetal is used.

  The upper end of each carrier pin 50 in the axial direction is fixed to the first carrier member 61. A lower end portion of each carrier pin 50 in the axial direction is fixed to the second carrier member 62. For example, press-fitting is used as a method of fixing the carrier pin 50 to the first carrier member 61 and the second carrier member 62. For this reason, when the plurality of carrier pins 50 rotate at the second rotational speed around the central axis 9, the first carrier member 61 and the second carrier member 62 also rotate at the second rotational speed around the central axis 9. .

  The second rotating unit 60 is connected to a member to be driven directly or via another power transmission mechanism. That is, in the present embodiment, the second rotating unit 60 is an output unit.

  <2. Simulation example>

  In the transmission 1 configured as described above, the meshing position A1 and the meshing position A2 are non-uniformly positioned in the circumferential direction about the central axis 9. With this configuration, the back drivability of the transmission 1 is improved.

  The following shows the result of a simulation for measuring the back drive torque, which was performed by creating a model equivalent to the transmission 1 in the simulation software. FIG. 5 is a diagram illustrating a simulation result obtained by measuring the backdrive torque.

  The back drive torque is the magnitude of resistance when the second rotating unit 60 that is the output unit is rotated by an external force. When the back drive torque is small, the rotation resistance of the second rotation unit 60 is small and the rotation loss is reduced. That is, back drivability is improved.

  A waveform (A) in FIG. 5 is a simulation result in the case where the meshing position A1 and the meshing position A2 are arranged at an equal interval of 180 ° along the circumferential direction with the central axis 9 as the center. A waveform (B) in FIG. 5 is a simulation result of the transmission 1 having the above-described configuration in which the meshing position A1 and the meshing position A2 are uneven in the circumferential direction. Conditions other than the positional relationship between the meshing positions A1 and A2 are the same in the waveform (A) and the waveform (B).

  As can be seen from the comparison between the waveform (A) and the waveform (B), the peak of the back drive torque of the transmission 1 is greater when the meshing positions A1 and A2 are non-uniform with the central axis 9 as the center. small.

  The transmission 1 includes the first external gear 31 and the second external gear 32, but may be configured to include three or more external gears. The waveform (C) in FIG. 5 is a transmission 1 in which three external gears are provided and the meshing positions of the three external gears and the internal teeth are unevenly distributed in the circumferential direction around the central axis 9. This is a simulation result. As can be seen from the comparison between the waveform (B) and the waveform (C), when the number of external gears is three, the back drive torque of the transmission 1 is larger than when the number of external gears is two. The peak is even smaller.

  As described above, the back drivability of the transmission 1 is improved by positioning the meshing positions of the external teeth and the internal teeth of the plurality of external gears unevenly in the circumferential direction around the central axis 9. be able to.

  The transmission 1 is not limited to the configuration described above. For example, the meshing position A1 and the meshing position A2 are located at 144 ° apart from the central axis 9, but the angle is not limited to this. Further, the number of external teeth of the external gear and the number of internal teeth of the internal gear can be appropriately changed.

  Although the embodiments of the present invention have been described above, the elements appearing in the above-described embodiments and modifications may be appropriately combined within a range where no contradiction occurs.

  The present application can be used for a transmission.

1: Transmission 9: Center shaft 10: 1st rotation part 21: 1st eccentric body 22: 2nd eccentric body 31: 1st external gear 32: 2nd external gear 40: Frame 41: Internal gear 50: Carrier Pin 60: 2nd rotating part 61: 1st carrier member 62: 2nd carrier member 71: 1st bearing 72: 2nd bearing 73: Bearing 74: Bearing 75: Bearing 76: Bearing 91: Center shaft 92: Center shaft 311 : External tooth 312: Through hole 321: External tooth 322: Through hole A1: Engagement position A2: Engagement position R1: Angle R2: Angle

Claims (7)

An eccentric rocking type transmission,
A first rotating part that rotates about a central axis;
A plurality of eccentric bodies that rotate together with the first rotating portion, the distance from the central axis to the outer peripheral surface varies depending on the position in the circumferential direction, and are arranged at different positions in the axial direction;
A plurality of bearings provided on the outer peripheral surface of each of the plurality of eccentric bodies;
A plurality of external gears provided on the outer peripheral surface of each of the plurality of bearings;
A cylindrical shape surrounding the central axis in the circumferential direction, and an internal gear disposed radially outside the plurality of external gears;
A carrier pin extending in the axial direction, inserted into a through-hole provided at a position overlapping in the axial direction of each of the plurality of external gears;
A second rotating part that is fixed with the carrier pin and rotates about the central axis;
With
The number of teeth of the plurality of external gears is different from the number of teeth of the internal gears,
In the internal gear, the external teeth having the longest distance from the central axis mesh with each of the number of teeth of the plurality of external gears,
The meshing positions of the internal gear and each of the plurality of external gears are uneven in the circumferential direction.
transmission. The transmission according to claim 1,
Each of the plurality of eccentric bodies is
It is a perfect circle when viewed from the axial direction, and the center of the perfect circle is located off the central axis.
transmission. The transmission according to claim 1 or 2, wherein
A plurality of carrier pins;
Each of the plurality of external gears is provided with a plurality of the through holes along the circumferential direction,
Each of the plurality of carrier pins is inserted into each of the plurality of through holes.
transmission. The transmission according to claim 3, wherein
The plurality of carrier pins are arranged at equiangular intervals along the circumferential direction around the central axis,
An angular difference around the central axis of the meshing position between the internal gear and each of the plurality of external gears is a multiple of the equal angle.
transmission. The transmission according to claim 4, wherein
The meshing position is
The meshing position of each of the internal gear and each of the plurality of external gears is a position that is deviated by the same angle from a state that is uniform in the circumferential direction.
transmission. A transmission according to any one of claims 1 to 5, wherein
The plurality of external gears include a first external gear and a second external gear,
The meshing position of the internal gear and the first external gear and the meshing position of the internal gear and the second external gear are located at a distance of 144 ° in the circumferential direction around the central axis. To
transmission. The transmission according to any one of claims 1 to 6,
The first rotating part is an input part that rotates at a first rotational speed by power obtained from a motor;
The second rotation unit is an output unit that rotates at a second rotation number lower than the first rotation number.
transmission.

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