JP7035406B2 - transmission - Google Patents

Description

The present invention relates to a transmission.

Japanese Unexamined Patent Publication No. 2014-16019 describes an eccentric swing / deceleration mechanism. The deceleration mechanism of the publication is provided in a motor rotational force transmission device that transmits the motor rotational force of an electric motor to a pair of rear wheels in a four-wheel drive vehicle. The reduction mechanism has an internal gear and an external gear arranged 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 swing type reduction mechanism is compact and can obtain a high reduction ratio.
Japanese Unexamined Patent Publication No. 2014-16019 Japanese Unexamined Patent Publication No. 2012-0077

By the way, in recent years, there is an increasing demand for small robots that work in cooperation with humans. Then, it has been proposed to use an actuator that combines the above-mentioned eccentric swing type speed reducer and a motor for a joint of a small robot. However, this kind of small robot is required to operate smoothly. For this reason, it is desired to reduce the gap between the external teeth and the internal teeth, the gap between the bearing and the external teeth, the gap between the shaft and the bearing, and the like (backlash). When the backlash is made small, it is possible to suppress wear between gears caused by dimensional deviation, impact, etc. during reverse rotation, so that the machine life can be extended. In Japanese Unexamined Patent Publication No. 2012-0077, the tooth width of the external tooth is adjusted in order to reduce the backlash. However, adjusting the width of the external or internal teeth is difficult to process and may reduce productivity.

Therefore, the present inventor has found that the backlash can be reduced by adjusting the tooth length of the external teeth of the external gear in the transmission.

In order to solve the above problems, the present invention is an eccentric swing type transmission, which rotates together with a first rotating portion that rotates about a central axis and the first rotating portion, and rotates from the central axis to an outer circumference. It has a first eccentric body whose distance to the surface differs depending on the position in the circumferential direction, a first bearing provided on the outer peripheral surface of the first eccentric body, and a first through hole penetrating in the axial direction. A first external gear provided on the outer peripheral surface of the bearing, an internal gear having a cylindrical shape surrounding the central axis in the circumferential direction and arranged radially outside the first external gear, and the first external gear. 1 The first external gear is provided with a cylindrical carrier pin inserted into a through hole and extending in the axial direction, and a second rotating portion to which the plurality of carrier pins are fixed and rotate about the central axis. The number of teeth is different from the number of teeth of the internal gear, and the external tooth at the position farthest from the central axis of the first external gear meshes with the internal gear, and the first external tooth meshes with the internal gear. The tip of each of the external teeth of the gear has a curved surface that is convexly curved from both ends toward the center in the axial direction, and the curved surface has a radius of curvature equal to the outer diameter dimension of the first external gear. On the other hand, it is 6 times .

According to the present application, the backlash can be reduced.

FIG. 1 is a vertical sectional view of a transmission according to an embodiment. FIG. 2 is an exploded perspective view of the transmission. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. FIG. 4 is an enlarged perspective view of a part of the first external tooth gear. FIG. 5 is a cross-sectional view of the external teeth of the first external gear including the central axis. FIG. 6 is a diagram showing a simulation result of measuring backlash.

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 "axial direction", the direction orthogonal to the central axis is "diametrical direction", and the direction along the arc centered on the central axis is "circumferential direction", respectively. Refer to. Further, in the present application, the shape and positional relationship of each portion will be described with the axial direction as the vertical direction and the first carrier member side of the second rotating portion facing up with respect to the first rotating portion. However, this definition of the vertical direction does not intend to limit the orientation of the transmission according to the present application when it is used. Further, the above-mentioned "parallel direction" includes a direction substantially parallel. Further, the above-mentioned "orthogonal direction" includes a direction substantially orthogonal to each other.

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

The transmission 1 is a gear speed reducer that converts the rotational movement of the first rotation speed (input rotation speed) into the rotational movement of the second rotation speed (output rotation speed) lower than the first rotation speed. The transmission 1 is used, for example, for the joints of a small robot such as a service robot that works in cooperation with a person. However, a transmission having an equivalent structure may be used for other applications such as large industrial robots, machine tools, XY tables, material cutting devices, conveyor lines, turntables, rolling rollers and the like.

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

The first rotating portion 10 is a columnar member extending 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, either directly or via another power transmission mechanism. When the motor is driven, the power supplied from the motor causes the first rotation unit 10 to rotate at the first rotation speed around the central shaft 9. That is, in the present embodiment, the first rotation unit 10 is an input unit.

The first eccentric body 21 is a member fixed to the outer peripheral surface of the first rotating portion 10 and rotating together with the first rotating portion 10. The first rotating portion 10 and the first eccentric body 21 may be a single member or may be another member. As shown in FIG. 3, the first eccentric body 21 has a perfect 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 differs depending on the position in the circumferential direction.

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

Further, the central axis 92 of the second eccentric body 22 is located 180 ° away from the central axis 91 of the first eccentric body 21 with respect to the central axis 9. That is, the first eccentric body 21 and the second eccentric body 22 have a point-symmetrical relationship with the central axis 9 as the center.

When the first rotating portion 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. Further, as described above, the central axis 91 of the first eccentric body 21 and the central axis 92 of the second eccentric body 22 are located 180 ° away from each other with respect to the central axis 9. Therefore, the position of the center of gravity of the first eccentric body 21 and the second eccentric body 22 as a whole is always located on the central axis 9. Therefore, the fluctuation of the center of gravity due to the rotation of the first eccentric body 21 and the second eccentric body 22 can be suppressed.

The first external tooth gear 31 is arranged on the radial 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 rotatably supported by the first bearing 71 about the central shaft 91. As shown in FIG. 3, a plurality of external teeth 311 are provided on the outer peripheral portion of the first external tooth gear 31. Each external tooth 311 projects radially outward.

FIG. 4 is an enlarged perspective view of a part of the first external tooth gear 31. FIG. 5 is a cross-sectional view of the external tooth 311 of the first external tooth gear 31 including the central shaft 91.

The tip of each of the external teeth 311 of the first external gear 31 has a curved surface 311A. The curved surface 311A is a surface that intersects in the radial direction. The curved surface 311A is formed by processing both ends in the axial direction into a curved surface while ensuring the length of the tooth length at the center in the axial direction of the external teeth 311 at the time of manufacturing. By forming in this way, the curved surface 311A becomes a surface curved in a convex shape from both ends toward the center in the axial direction. In the present embodiment, the cross section including the central axis 91 of the curved surface 311A is arcuate. The radius of curvature of the curved surface 311A is preferably 4.8 times or more and 8.9 times or less with respect to the outer diameter dimension d of the external gear.

The first external gear 31 has a plurality of (10 in the example of FIG. 3) through holes 312. Each through hole 312 penetrates the first external tooth gear 31 in the axial direction. The plurality of through holes 312 are arranged at equal intervals in the circumferential direction with the central axis 91 as the center.

The second external tooth gear 32 is arranged on the radial 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 rotatably supported by the second bearing 72 about the central shaft 92. For the second bearing 72, for example, a ball bearing is used. The second external tooth gear 32 is provided with a plurality of external teeth 321 on the outer peripheral portion thereof, similarly to the first external tooth gear 31. The tooth tip of the external tooth 321 is a curved surface like the external tooth 311 of the first external tooth gear 31. Further, 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 equal angular intervals along the circumferential direction with the central axis 92 as the center. Further, a part of each through hole 322 overlaps with 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 axis 9 in the circumferential direction and extends in the axial direction. The frame 40 is arranged so as to surround the radial outer side 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 internal teeth 41 projects 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. As in the present embodiment, when the same member as the frame 40 is used as the same member as the internal tooth 41, it is not necessary to provide an internal tooth gear having the internal tooth 41 separately from the frame 40. Therefore, the transmission 1 has a transmission 1. It becomes easy to miniaturize.

A part of each of the plurality of external teeth 311 of the first external gear 31 and 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 tooth 311 of the first external tooth gear 31 at the position farthest from the central axis 9 and the second external tooth gear 32 at the position farthest from the central axis 9. The outer teeth 321 of the above mesh with the inner teeth 41. That is, the meshing position between the external tooth 311 of the first external gear 31 and the internal tooth 41 of the frame 40 and the meshing position between the external tooth 321 of the second external gear 32 and the internal tooth 41 of the frame 40 are centered. It is point-symmetrical about the axis 9.

As described above, the first external gear 31 and the second external gear 32 have the same configuration and are point-symmetrical with respect to the central axis 9. Therefore, in the following description, only the first external tooth gear 31 will be described.

When the first rotating portion 10 rotates about the central shaft 9, the first external gear 31 revolves around the central shaft 9 together with the central shaft 91. Further, the first external gear 31 rotates on its axis when a part of the plurality of external teeth 311 of the first external gear 31 meshes with the internal teeth 41 of the frame 40. Here, the number of internal teeth 41 possessed by the frame 40 is larger than the number of external teeth 311 possessed by the first external gear 31. Therefore, for each revolution of the first external tooth gear 31, the position of the external tooth 311 that meshes with the internal tooth 41 at the same position of the frame 40 shifts. As a result, the first external gear 31 rotates in the direction opposite to the rotation direction of the first rotating portion 10 at a second rotation speed lower than the first rotation speed. Therefore, the position of the through hole 312 of the first external gear 31 also rotates at the second rotation speed. When the transmission 1 is operated, the first external gear 31 performs a rotational motion that combines such revolution and rotation.

Assuming that the number of external teeth 311 possessed by the first external gear 31 is N and the number of internal teeth 41 possessed by the frame 40 is M, the reduction ratio P of the transmission 1 is P = (first rotation speed) / (. Second 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 external teeth 311 and the number M of the internal teeth 41 may have other values.

In this embodiment, the plurality of internal teeth 41 are provided as a part of the frame 40 which is a single member. Therefore, it is not necessary to provide an internal gear having a plurality of internal teeth 41 separately from the frame 40. This facilitates miniaturization of the transmission 1.

The carrier pin 50 is a columnar 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 with the central axis 9 as the center. Then, the carrier pin 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 overlap in the axial direction. As described above, the through hole 312 and the through hole 322 rotate at the second rotation speed after deceleration. The carrier pin 50 inserted into the through hole 312 and the through hole 322 rotates at the second rotation speed around the central axis 9 together with the through hole 312 and the through hole 322.

The second rotating portion 60 has an annular first carrier member 61 and an annular second carrier member 62. The first carrier member 61 is arranged on the upper side in the axial direction with respect to the first external tooth gear 31. A bearing 73 is interposed between the first rotating portion 10 and the first carrier member 61. Further, a bearing 74 is interposed between the first carrier member 61 and the frame 40.

The second carrier member 62 is arranged on the lower side in the axial direction with respect to the second external tooth gear 32. A bearing 75 is interposed between the first rotating portion 10 and the second carrier member 62. Further, a bearing 76 is interposed between the second carrier member 62 and the frame 40. For the bearing 73 and the bearing 75, for example, ball bearings are used. For the bearing 74 and the bearing 76, for example, a slide bearing made of a resin such as polyacetal is used.

The upper end in the axial direction of each carrier pin 50 is fixed to the first carrier member 61. The lower end in the axial direction of each carrier pin 50 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. Therefore, when the plurality of carrier pins 50 rotate at the second rotation speed around the central shaft 9, the first carrier member 61 and the second carrier member 62 also rotate at the second rotation speed around the central shaft 9. ..

The second rotating unit 60 is connected to a member to be driven, either 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 backlash of the transmission 1 is formed by making the tooth tips of the external teeth 311 of the first external gear 31 and the external teeth 321 of the second external gear 32 curved. Becomes smaller.

Below, in the simulation software, a model equivalent to the above-mentioned transmission 1 is created, and the simulation result of measuring the backlash is shown. FIG. 6 is a diagram showing a simulation result of measuring backlash. The vertical axis of FIG. 6 indicates the back drive torque, and the horizontal axis indicates the backlash. In FIG. 6, the movable angle range in the rotation direction of the second rotating portion 60 when the first rotating portion 10 is fixed is measured as a “backlash”.

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

In the simulation, the tooth tips of the external teeth 311 of the first external gear 31 and the external teeth 321 of the second external gear 32 are curved surfaces, and the radius of curvature is changed. The white circle mark in FIG. 6 is a simulation result using an external gear that does not have a curved surface at the tip of the external tooth. The cross mark is a simulation result using an external gear having a curved surface whose radius of curvature is 3.6 times the outer diameter dimension d of the external gear. The square mark is a simulation result using an external gear having a curved surface in which the tip of the external tooth has a radius of curvature 6 times the outer diameter dimension d of the external gear. The triangular mark is a simulation result using an external gear having a curved surface whose radius of curvature is 12 times the outer diameter dimension d of the external gear. The conditions other than the tooth tip shape of the external teeth 311 and 321 are the same.

As described above, the radius of curvature of the curved surface 311A is preferably 4.8 times or more and 8.9 times or less with respect to the outer diameter dimension d of the first external gear. As can be seen from FIG. 6, when the radius of curvature is 6 times the outer diameter dimension d of the external gear in the above range, the backlash is smaller than the others.

As described above, the backlash can be reduced by making the tooth tips of the external teeth 311 of the first external gear 31 and the external teeth 321 of the second external gear 32 curved.

The transmission 1 is not limited to the above configuration. For example, in the above embodiment, the tooth tips of the external teeth 311 of the first external tooth gear 31 and the external teeth 321 of the second external tooth gear 32 are curved surfaces, but only one tooth tip is a curved surface. You may. Further, the transmission 1 includes a first external gear 31 and a second external gear 32, but may be configured to include only one of them. Further, the configuration may include three or more external gears. 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 as long as there is no contradiction.

The present application can be used for transmissions.

1: Transmission 9: Central shaft 10: 1st rotating part 21: 1st eccentric body 22: 2nd eccentric body 31: 1st external gear 32: 2nd external gear 40: Frame 41: Internal tooth 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: central shaft 92: central shaft 311 : External tooth 311A: Curved surface 312: Through hole 321: External tooth 322: Through hole

Claims (8)

It is an eccentric swing type transmission,
The first rotating part that rotates around the central axis and
A first eccentric body that rotates together with the first rotating portion and whose distance from the central axis to the outer peripheral surface differs depending on the position in the circumferential direction.
The first bearing provided on the outer peripheral surface of the first eccentric body and
A first external gear having a first through hole penetrating in the axial direction and provided on the outer peripheral surface of the first bearing, and a first external gear.
A cylindrical internal gear that surrounds the central axis in the circumferential direction and is arranged radially outside the first external gear.
A cylindrical carrier pin inserted in the first through hole and extending in the axial direction,
A second rotating portion to which the plurality of carrier pins are fixed and rotates about the central axis is provided.
The number of teeth of the first external gear and the number of teeth of the internal gear are different.
The internal tooth gear is engaged with the external tooth at a position farthest from the central axis of the first external tooth gear.
The tip of each of the external teeth of the first external gear has a curved surface that is convexly curved from both ends toward the center in the axial direction, and the curved surface has a radius of curvature of the first external gear. 6 times the outer diameter of the
transmission. The transmission according to claim 1.
The cross section of the curved surface including the central axis is arcuate.
transmission. The transmission according to claim 1 or 2.
The first eccentric body 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 any one of claims 1 to 3 .
A second eccentric body that rotates together with the first rotating portion, the distance from the central axis to the outer peripheral surface differs depending on the position in the circumferential direction, and is arranged at a position different from the first eccentric body in the axial direction.
A second bearing provided on the outer peripheral surface of the second eccentric body, and
A second external gear having a second through hole penetrating in the axial direction and an external tooth having the same number of teeth as the first external gear, and provided on the outer peripheral surface of the second bearing.
Further prepare
The first through hole and the second through hole overlap each other in the axial direction.
The carrier pin is inserted into the first through hole and the second through hole, and the carrier pin is inserted into the first through hole and the second through hole.
The internal gear extends in the axial direction and faces the first external gear and the second external gear in the radial direction.
The internal tooth gear is engaged with the external tooth at a position farthest from the central axis of the second external tooth gear.
transmission. The transmission according to claim 4 .
The tip of each of the external teeth of the second external gear has a curved surface that is convexly curved from both ends toward the center in the axial direction.
transmission. The transmission according to claim 4 or 5 .
The second eccentric body 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 any one of claims 4 to 6 .
The meshing position between the internal gear and the first external gear and the meshing position between the internal gear and the second external gear are point-symmetrical with respect to the central axis.
transmission. The transmission according to any one of claims 1 to 7 .
The first rotation unit is an input unit that rotates at the first rotation speed by the power obtained from the motor.
The second rotation unit is an output unit that rotates at a second rotation speed lower than the first rotation speed.
transmission.

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