JP2023007745A - Differential type planetary speed reducer and robot - Google Patents

Abstract

A differential planetary reduction gear capable of supporting a carrier in a stable posture is provided. A differential planetary reduction gear (1) includes an input member (10), a speed reduction mechanism (20), a housing (30), and an output member (40). The reduction mechanism has a sun gear 21 , a planetary gear 22 , a fixed internal gear 23 , a rotating internal gear 24 and a carrier 25 . The carrier supports the planetary gear so that it can revolve while rotating. The output member has an axially extending protrusion 43 . A first inner bearing 53 is interposed between the input member and the carrier. A second bearing 54 is interposed between the projection of the output member and the carrier. In this way, the carrier is supported by the projections provided on the output member. Thereby, the attitude of the carrier can be stabilized. [Selection drawing] Fig. 1

Description

The present invention relates to a differential planetary reduction gear and a robot.

2. Description of the Related Art Conventionally, reduction gears are known that reduce the rotational motion of an electric motor and output the same. A conventional speed reducer is disclosed, for example, in Japanese Utility Model Laid-Open No. 47-33473. The speed reducer disclosed in Japanese Utility Model Laid-Open No. 47-33473 has three planetary gears (8) around a sun gear (13). Three planetary gears (8) are supported on the planetary gear frame (6). Each planetary gear (8) has two gear parts (9, 10) with different diameters. A small diameter gear portion (9) meshes with the stationary internal gear (2). A large diameter gear portion (10) meshes with a movable internal gear (4). When the sun gear (13) rotates, the planetary gear (8) rotates while revolving together with the planetary gear frame (6).
Japanese Utility Model Laid-Open No. 47-33473

A so-called differential planetary speed reducer, such as the speed reducer described in Japanese Utility Model Laid-Open No. 47-33473, can obtain a high speed reduction ratio. However, the differential planetary speed reducer has complicated gear meshing. Further, in the differential planetary reduction gear, a carrier (planetary gear frame) that supports a plurality of planetary gears is not supported by either the input member or the output member. Therefore, it was difficult to maintain the carrier in a stable posture. In addition, it was difficult to assemble each part including the carrier when manufacturing the differential planetary speed reducer.

SUMMARY OF THE INVENTION An object of the present invention is to provide a structure capable of supporting a carrier in a stable posture in a differential planetary reduction gear.

A first invention of the present application is a differential planetary reduction gear, comprising: an input member that rotates about a central axis at a first rotation speed; a speed reduction mechanism that converts to rotational motion of two revolutions; a housing that houses the speed reduction mechanism; and an output member that rotates at the second speed about the central axis; a sun gear that rotates at the first rotation speed around the central axis together with the input member; a first gear that rotates around a planetary shaft parallel to the central axis while meshing with the sun gear; A planetary gear having a second gear that rotates about the planetary shaft together with the gear; an annular fixed internal gear that is fixed to the housing and meshes with the first gear; and is fixed to the output member, an annular rotating internal gear that meshes with the second gear; and a carrier that supports the planetary gear so that it can rotate about the planetary shaft and revolve about the central axis. the housing includes a housing base located on one side in the axial direction of the speed reduction mechanism; a cylindrical housing wall extending from the outer peripheral portion of the housing base to the other side in the axial direction; The output member includes an output base located on the other side in the axial direction of the speed reduction mechanism, a cylindrical output wall extending from the outer peripheral portion of the output base to the one side in the axial direction, and the output an input-side bearing interposed between an inner peripheral surface of the housing base portion and the input member; the housing wall portion and the housing wall portion; an outer bearing interposed between the output wall portion, a first inner bearing interposed between the input member and the carrier, and a second inner bearing interposed between the convex portion and the carrier; Prepare more.

A second invention of the present application is a differential planetary reduction gear comprising: an input member having a sun gear rotatable about a central axis; a rotatable planetary gear; a carrier that supports the planetary gear so as to be rotatable about the planetary shaft; and an output member, at least a part of which is arranged on the other side of the carrier in the axial direction, is connected to the planetary gear and is rotatable relative to the housing, wherein the output member is an output base portion disposed on the other side in the axial direction of the carrier and extending in a direction substantially perpendicular to the central axis; and a convex portion protruding from the output base portion in the one axial direction, supports the carrier via inner bearings.

According to the first and second inventions of the present application, the carrier is supported by the projection provided on the output member. Thereby, the attitude of the carrier can be stabilized.

FIG. 1 is a longitudinal sectional view of a differential planetary reduction gear. FIG. 2 is a cross-sectional view of the speed reduction mechanism. FIG. 3 is a diagram showing a state of manufacturing the differential planetary reduction gear. FIG. 4 is a longitudinal sectional view of a differential planetary reduction gear according to a first modified example. FIG. 5 is a longitudinal sectional view of a differential planetary reduction gear according to a second modification. FIG. 6 is a schematic diagram of the robot.

Exemplary embodiments of the invention are described below with reference to the drawings. In the present application, the direction parallel to the central axis of the differential planetary reduction gear is defined as "axial direction," the direction perpendicular to the central axis is defined as "radial direction," and the direction along the arc centered on the central axis is defined as "circumferential direction." , respectively. However, the above-mentioned "parallel direction" also includes substantially parallel directions. Moreover, the above-mentioned "perpendicular direction" also includes substantially perpendicular directions.

Further, in the present application, "rotational speed" represents the number of rotations per unit time, that is, the speed of rotation.

<1. Configuration of Differential Planetary Reducer>
FIG. 1 is a longitudinal sectional view of a differential planetary reduction gear 1 according to one embodiment of the present invention. The differential planetary reduction gear 1 is a device that reduces rotational motion at a first rotational speed input to an input member 10 to rotational motion at a second rotational speed lower than the first rotational speed and outputs the rotational motion. The differential planetary reduction gear 1 is used, for example, by being incorporated in a joint of a robot together with an electric motor. However, the differential planetary reduction gear 1 may be used in other devices such as an assist suit and an automatic guided vehicle.

As shown in FIG. 1, the differential planetary reduction gear 1 of this embodiment includes an input member 10, a speed reduction mechanism 20, a housing 30, an output member 40, a pair of input side bearings 51, a first outer bearing 521, a It has two outer bearings 522 , a first inner bearing 53 and a second inner bearing 54 .

The input member 10 is a member that rotates about a central axis 91 at a first rotational speed before deceleration. The input member 10 of this embodiment is a columnar input shaft extending in the axial direction. The input member 10 is connected to the output shaft of the electric motor via a power transmission mechanism such as gears, belts and couplings. When the electric motor is driven, the driving force supplied from the electric motor causes the input member 10 to rotate about the central axis 91 at the first rotation speed.

The reduction mechanism 20 is a mechanism that converts the rotational motion of the input member 10 into rotational motion at a second rotational speed lower than the first rotational speed and transmits the rotational motion to the output member 40 . FIG. 2 is a cross-sectional view of the speed reduction mechanism 20 seen from the AA position in FIG. In FIG. 2, in order to avoid complication of the drawing, hatching indicating a cross section and illustration of teeth of each gear are omitted.

As shown in FIGS. 1 and 2 , the speed reduction mechanism 20 has a sun gear 21 , a plurality of planetary gears 22 , a fixed internal gear 23 , a rotating internal gear 24 and a carrier 25 .

The sun gear 21 is a gear that rotates around the central axis 91 together with the input member 10 at a first rotation speed. The sun gear 21 has a plurality of sun external teeth 211 on its outer peripheral surface. The plurality of sun outer teeth 211 are provided at a constant angular pitch around the central axis 91 . Each sun outer tooth 211 protrudes radially outward from the outer peripheral surface of the sun gear 21 .

In this embodiment, the input member 10 and the sun gear 21 are formed by a single member. In other words, the input member 10 has the sun gear 21 . However, the input member 10 and the sun gear 21 may be separate members. In that case, the sun gear 21 may be fixed to the input member 10 so as not to be relatively rotatable.

The planetary gear 22 is a gear arranged radially outside the sun gear 21 . As shown in FIG. 2, in this embodiment, three planetary gears 22 are arranged around the sun gear 21 at regular intervals in the circumferential direction. However, the number of planetary gears 22 included in the speed reduction mechanism 20 may be one or two, or may be four or more.

Each planetary gear 22 has a through hole 220 in the center. The through hole 220 axially penetrates the planetary gear 22 . A carrier pin 254 , which will be described later, is inserted into the through hole 220 . A pair of planetary bearings 225 are interposed between the inner peripheral surface of the planetary gear 22 and the carrier pin 254 . As a result, the planetary gear 22 is rotatably supported around a planetary shaft 92 parallel to the central shaft 91 .

As shown in FIG. 1 , the planetary gear 22 has a first gear 221 and a second gear 222 having a smaller diameter than the first gear 221 . The first gear 221 is located on one side in the axial direction of the second gear 222 . In this embodiment, the first gear 221 and the second gear 222 are formed from a single member. However, the first gear 221 and the second gear 222 may be separate members. In that case, the first gear 221 and the second gear 222 should be fixed so as not to rotate relative to each other.

The first gear 221 has a plurality of first external teeth 223 on its outer peripheral surface. The plurality of first external teeth 223 are provided at a constant angular pitch around the planetary shaft 92 . Each first external tooth 223 protrudes away from the planetary shaft 92 on the outer peripheral surface of the first gear 221 . The sun external teeth 211 of the sun gear 21 and the first external teeth 223 of the first gear 221 mesh with each other. The first gear 221 rotates about the planetary shaft 92 while meshing with the sun gear 21 .

The second gear 222 rotates about the planetary shaft 92 together with the first gear 221 . The diameter of the second gear 222 about the planetary shaft 92 is smaller than the diameter of the first gear 221 about the planetary shaft 92 . The second gear 222 has a plurality of second external teeth 224 on its outer peripheral surface. The plurality of second external teeth 224 are provided at a constant angular pitch around the planetary shaft 92 . Each second external tooth 224 protrudes away from the planetary shaft 92 on the outer peripheral surface of the second gear 222 . The number of first external teeth 223 that the first gear 221 has is different from the number of second external teeth 224 that the second gear 222 has.

The fixed internal gear 23 is an annular gear centered on the central axis 91 . The fixed internal gear 23 is positioned radially outside the first gears 221 of the plurality of planetary gears 22 . The fixed internal gear 23 and the housing 30 are fixed to each other by the first bolts 61 . Therefore, the fixed internal gear 23 is always kept stationary with respect to the housing 30 . Note that the fixed internal gear 23 and the housing 30 may be formed of a single member.

The fixed internal gear 23 has a plurality of first internal teeth 231 . The plurality of first internal teeth 231 are provided at a constant angular pitch around the central axis 91 . Each first internal tooth 231 protrudes radially inward from the inner peripheral surface of the fixed internal gear 23 . The first external teeth 223 of the first gear 221 described above mesh with the first internal teeth 231 of the fixed internal gear 23 .

The rotating internal gear 24 is an annular gear centered on the central axis 91 . The rotating internal gear 24 is located on the other side in the axial direction of the fixed internal gear 23 . The inner diameter about the central axis 91 of the rotating internal gear 24 is smaller than the inner diameter about the central axis 91 of the fixed internal gear 23 . The rotating internal gear 24 is positioned radially outside the second gears 222 of the plurality of planetary gears 22 . The rotating internal gear 24 and the output member 40 are fixed to each other by a second bolt 62 . Note that the rotating internal gear 24 and the output member 40 may be formed of a single member.

The rotary internal gear 24 has a plurality of second internal teeth 241 . The plurality of second internal teeth 241 are provided at a constant angular pitch around the central axis 91 . Each second internal tooth 241 protrudes radially inward from the inner peripheral surface of the rotary internal gear 24 . The second external teeth 224 of the second gear 222 described above mesh with the second internal teeth 241 of the rotary internal gear 24 . The number of first internal teeth 231 possessed by the fixed internal gear 23 is different from the number of second internal teeth 241 possessed by the rotating internal gear 24 .

The carrier 25 is a unit that supports the plurality of planetary gears 22 so that they can revolve around the central axis 91 while rotating around the planetary shaft 92 . As shown in FIGS. 1 and 2, carrier 25 has a cage-shaped carrier member 250 and a plurality of carrier pins 254 .

The carrier member 250 has a first disc portion 251 , a second disc portion 252 and a plurality of connecting portions 253 . The first disc portion 251 is positioned on one side in the axial direction of the plurality of planetary gears 22 . The second disc portion 252 is positioned on the other side in the axial direction of the plurality of planetary gears 22 . The first disk portion 251 and the second disk portion 252 each extend in a direction perpendicular to the central axis 91 . The plurality of connecting portions 253 connect the first disc portion 251 and the second disc portion 252 in the axial direction. The planetary gear 22 is arranged axially between the first disk portion 251 and the second disk portion 252 and between adjacent connection portions 253 in the circumferential direction.

Carrier pin 254 is a cylindrical member that extends axially along planetary shaft 92 . One axial end of the carrier pin 254 is fixed to the first disc portion 251 . The other end of the carrier pin 254 in the axial direction is fixed to the second disc portion 252 . The plurality of carrier pins 254 are arranged at equal intervals in the circumferential direction around the central axis 91 . A pair of planetary bearings 225 are interposed between the inner peripheral surface of the planetary gear 22 and the carrier pin 254 . As a result, the planetary gear 22 is rotatably supported around the planetary shaft 92 .

Further, the carrier 25 is rotatably supported about the central axis 91 by a first inner bearing 53 and a second inner bearing 54 which will be described later. The planetary gear 22 can revolve around the central axis 91 together with the carrier 25 while rotating around the planetary shaft 92 .

The housing 30 is a substantially cup-shaped member that accommodates the speed reduction mechanism 20 therein. The housing 30 is fixed to the frame of the device in which the differential planetary reduction gear 1 is mounted. The housing 30 has a substantially flat housing base portion 31 and a cylindrical housing wall portion 32 . At least part of the housing base portion 31 is located on one side in the axial direction of the speed reduction mechanism 20 . The housing base portion 31 extends in a direction perpendicular to the central axis 91 . However, the above "perpendicular direction" also includes "substantially perpendicular direction". The housing wall portion 32 is located radially outside the speed reduction mechanism 20 . The housing wall portion 32 extends from the outer peripheral portion (diametrical outer edge) of the housing base portion 31 toward the other side in the axial direction.

Note that the housing 30 does not necessarily have to house the entire speed reduction mechanism 20 inside. For example, a portion of planetary gear 22 may be located inside housing 30 and another portion of planetary gear 22 may be located outside housing 30 .

A pair of input-side bearings 51 are interposed in a radial gap between the housing base portion 31 and the input member 10 . A ball bearing, for example, is used for the input-side bearing 51 . The inner ring of the input side bearing 51 is fixed to the outer peripheral surface of the input member 10 . The outer ring of the input side bearing 51 is fixed to the inner peripheral surface of the housing base portion 31 . Thereby, the input member 10 is rotatably supported with respect to the housing 30 . Note that the input-side bearing 51 may be a bearing other than a ball bearing.

The output member 40 is a member that rotates about the central axis 91 at the second rotational speed after deceleration. The output member 40 is fixed to a component to be driven of a device in which the differential planetary reduction gear 1 is mounted. The output member 40 has a substantially flat plate-like output base portion 41 and a cylindrical output wall portion 42 . At least part of the output base portion 41 is located on the other side in the axial direction of the speed reduction mechanism 20 . The output base portion 41 extends in a direction perpendicular to the central axis 91 . However, the above "perpendicular direction" also includes "substantially perpendicular direction". The output wall portion 42 is located radially outside the speed reduction mechanism 20 . The output wall portion 42 extends from the outer peripheral portion (diametrical outer edge) of the output base portion 41 toward one side in the axial direction.

The output wall portion 42 is inserted radially inside the housing wall portion 32 . That is, the output wall portion 42 is positioned radially inside the housing wall portion 32 . By arranging the housing wall portion 32 and the output wall portion 42 so as to overlap in the radial direction in this manner, the housing 30 and the output member 40 as a whole can be made compact in the axial direction. Therefore, the differential planetary reduction gear 1 can be thinned in the axial direction.

A first outer bearing 521 and a second outer bearing 522 are interposed in a radial gap between the inner peripheral surface of the housing wall portion 32 and the outer peripheral surface of the output wall portion 42 . The second outer bearing 522 is located on the other axial side of the first outer bearing 521 . Ball bearings, for example, are used for the first outer bearing 521 and the second outer bearing 522 . The outer ring of the first outer bearing 521 and the outer ring of the second outer bearing 522 are fixed to the inner peripheral surface of the housing wall portion 32 . The inner ring of the first outer bearing 521 and the inner ring of the second outer bearing 522 are fixed to the outer peripheral surface of the output wall portion 42 . The housing wall portion 32 rotatably supports the output wall portion 42 via the first outer bearing 521 and the second outer bearing 522 . Thereby, the output member 40 is rotatably supported with respect to the housing 30 . Note that the first outer bearing 521 and the second outer bearing 522 may be bearings other than ball bearings.

Moreover, the output member 40 has a convex portion 43 . The convex portion 43 protrudes from the center (center in the radial direction) of the output base portion 41 toward one side in the axial direction. The input member 10 and the convex portion 43 are arranged coaxially along the central axis 91 . The output wall portion 42 is located radially outside the convex portion 43 .

One axial end of the projection 43 is positioned radially inside the second gear 222 of the planetary gear 22 . The second gear 222 of the planetary gear 22 has a smaller diameter than the first gear 221 . Therefore, a space exists radially inside the second gear 222 . An end portion on one side in the axial direction of the convex portion 43 is arranged in the space. In this way, the planetary gear 22 and the output member 40 can be brought closer together in the axial direction. Therefore, the axial dimension of the differential planetary reduction gear 1 can be further reduced.

As shown in FIG. 1, the convex portion 43 has a support surface 431 and a conical portion 432 . The support surface 431 is a cylindrical surface extending in the axial direction. A second inner bearing 54 to be described later is supported by the support surface 431 . The conical portion 432 is located on one side of the support surface 431 in the axial direction. The conical portion 432 gradually decreases in diameter toward one side in the axial direction.

A first inner bearing 53 is interposed in the radial gap between the input member 10 and the carrier member 250 . The first inner bearing 53 is located on one side in the axial direction of the planetary gear 22 . The first inner bearing 53 is interposed between the outer peripheral surface of the input member 10 and the inner peripheral surface of the first disk portion 251 of the carrier member 250 .

A ball bearing, for example, is used for the first inner bearing 53 . The inner ring of the first inner bearing 53 is fixed to the outer peripheral surface of the input member 10 . The outer ring of the first inner bearing 53 is fixed to the inner peripheral surface of the first disc portion 251 of the carrier member 250 . The input member 10 supports the first disc portion 251 of the carrier member 250 via the first inner bearing 53 . This allows the input member 10 and the carrier 25 to rotate about the central axis 91 at different rotational speeds. Note that the first inner bearing 53 may be a bearing other than a ball bearing.

As shown in FIG. 1 , the input member 10 has an input side flange 11 . The input-side collar portion 11 protrudes radially outward from the outer peripheral surface of the input member 10 . The input-side collar portion 11 axially contacts an end face on one side in the axial direction of the inner ring of the first inner bearing 53 . As a result, the first inner bearing 53 is prevented from shifting to one side in the axial direction with respect to the input member 10 .

Also, the outer ring of the first inner bearing 53 has a first collar portion 531 . The first collar portion 531 protrudes radially outward from the outer peripheral surface of the outer ring of the first inner bearing 53 . The first flange portion 531 axially contacts the surface of the first disk portion 251 of the carrier member 250 on one side in the axial direction. As a result, the first inner bearing 53 is prevented from shifting to the other side in the axial direction with respect to the carrier 25 . Moreover, the carrier 25 is prevented from slipping to one side in the axial direction with respect to the first inner bearing 53 .

Also, the first disc portion 251 and the first inner bearing 53 are positioned on a first plane orthogonal to the central axis 91 . In this manner, if the first disk portion 251 and the first inner bearing 53 are arranged so as to overlap in the radial direction, the axial dimension of the first disk portion 251 and the first inner bearing 53 as a whole can be reduced to can be reduced. Therefore, the differential planetary reduction gear 1 can be made thinner in the axial direction.

A second inner bearing 54 is interposed in the radial gap between the projection 43 of the output member 40 and the carrier member 250 . The second inner bearing 54 is located on the other axial side of the planetary gear 22 . The second inner bearing 54 is interposed between the support surface 431 of the convex portion 43 and the inner peripheral surface of the second disc portion 252 of the carrier member 250 .

A ball bearing, for example, is used for the second inner bearing 54 . The inner ring of the second inner bearing 54 is fixed to the support surface 431 of the protrusion 43 . The outer ring of the second inner bearing 54 is fixed to the inner peripheral surface of the second disc portion 252 of the carrier member 250 . The convex portion 43 supports the second disc portion 252 of the carrier member 250 via the second inner bearing 54 . This allows the output member 40 and the carrier 25 to rotate about the central axis 91 at different rotational speeds. Note that the second inner bearing 54 may be a bearing other than a ball bearing.

As shown in FIG. 1 , the output member 40 has an output-side collar portion 44 . The output-side collar portion 44 protrudes radially outward from the support surface 431 of the convex portion 43 . The output-side collar portion 44 axially contacts the end surface of the inner ring of the second inner bearing 54 on the other side in the axial direction. As a result, the second inner bearing 54 is prevented from shifting to the other side in the axial direction with respect to the output member 40 .

Also, the outer ring of the second inner bearing 54 has a second flange portion 541 . The second collar portion 541 protrudes radially outward from the outer peripheral surface of the outer ring of the second inner bearing 54 . The second collar portion 541 axially contacts the surface of the second disk portion 252 of the carrier member 250 on the other side in the axial direction. As a result, the second inner bearing 54 is prevented from slipping to one side in the axial direction with respect to the carrier 25 . In addition, the carrier 25 is prevented from shifting to the other side in the axial direction with respect to the second inner bearing 54 .

Also, the second disk portion 252 and the second inner bearing 54 are positioned on a second plane orthogonal to the central axis 91 . If the second disk portion 252 and the second inner bearing 54 are arranged so as to overlap in the radial direction in this way, the axial dimension of the second disk portion 252 and the second inner bearing 54 as a whole can be reduced to can be reduced. Therefore, the differential planetary reduction gear 1 can be made thinner in the axial direction.

In such a differential planetary reduction gear 1 , when the input member 10 and the sun gear 21 rotate at the first rotation speed, the planetary gear 22 rotates around the planetary shaft 92 due to meshing with the sun gear 21 . In addition, since the planetary gear 22 meshes with the sun gear 21 and the fixed internal gear 23, the planetary gear 22 rotates about the planetary shaft 92 and circumferentially rotates around the sun gear 21 along the fixed internal gear 23. revolve. That is, the plurality of planetary gears 22 revolve around the central axis 91 while rotating around the planetary shaft 92 . At this time, the number of revolutions of the planetary gear 22 around the central axis 91 becomes an intermediate number of revolutions lower than the first number of revolutions.

Also, the ratio of the number of first external teeth 223 of the first gear 221 to the number of first internal teeth 231 of the fixed internal gear 23 and the number of second internal teeth 241 of the rotary internal gear 24 The ratio of the number of the second external teeth 224 that the two gears 222 have is different. Therefore, as the planetary gear 22 revolves, the rotating internal gear 24 rotates with respect to the fixed internal gear 23 at a rotational speed corresponding to the difference in the number of teeth. The rotation speed of this rotary internal gear 24 becomes a second rotation speed which is lower than the intermediate rotation speed. As a result, the rotating internal gear 24 and the output member 40 rotate about the central axis 91 at the second rotation speed. Therefore, the rotational motion at the second rotational speed after deceleration can be extracted from the output member 40 .

As described above, in this differential planetary reduction gear 1 , the input member 10 supports the carrier 25 via the first inner bearing 53 . Also, the convex portion 43 of the output member 40 supports the carrier 25 via the second inner bearing 54 . That is, the carrier 25 is supported by two members, the input member 10 and the output member 40 . Thereby, the carrier 25 can be supported in a stable posture. If the posture of the carrier 25 is stabilized, the posture of the planetary gear 22 in rotation and revolution can also be stabilized.

In particular, in the differential planetary reduction gear 1 of the present embodiment, the diameter of the sun gear 21 about the central axis 91 is smaller than the diameter of the second gear 222 about the planetary axis 92 . By reducing the diameter of the sun gear 21 in this way, the reduction ratio of the differential planetary reduction gear 1 can be increased. However, if the diameter of the sun gear 21 is reduced, it becomes difficult to stably support the carrier 25 with respect to the sun gear 21, and it becomes difficult to reduce the thickness in the axial direction. However, in the structure of this embodiment, the carrier 25 is supported by two members, the input member 10 and the output member 40 . Thereby, the carrier 25 can be supported more stably.

Further, in the present embodiment, the first outer bearing 521 and the second outer bearing 522 are arranged with an interval in the axial direction. Thereby, the output member 40 can be supported in a stable posture with respect to the housing 30 . As a result, the posture of the carrier 25 supported by the output member 40 can be further stabilized.

<2. Manufacturing Method of Differential Planetary Reducer>
3A and 3B are diagrams showing the manufacturing state of the differential planetary reduction gear 1. FIG.

As shown in FIG. 3 , when manufacturing the differential planetary reduction gear 1 , first, the input member 10 and portions of the reduction mechanism 20 other than the rotary internal gear 24 are assembled to the housing 30 . As a result, the input member 10 , the sun gear 21 , the plurality of planetary gears 22 , the fixed internal gear 23 , the carrier 25 , the housing 30 , the input side bearing 51 , the first inner bearing 53 , and the second inner bearing 54 . 1 unit U1 is ready.

Also, the rotary internal gear 24 is fixed to the output member 40, and the first outer bearing 521 and the second outer bearing 522 are assembled. Thereby, the second unit U2 including the rotating internal gear 24, the output member 40, the first outer bearing 521 and the second outer bearing 522 is ready.

3, the second unit U2 is brought closer to the one axial side from the other axial side of the first unit U1. Then, the second unit U2 is inserted inside the housing wall portion 32 . Thereby, the second unit U2 is assembled to the first unit U1. After that, a retaining ring 34 is attached to the groove 33 provided in the inner peripheral surface of the housing wall portion 32 . This prevents the second unit U2 from coming off from the first unit U1.

When assembling the second unit U2 to the first unit U1, the projection 43 of the output member 40 is inserted radially inward of the second inner bearing . At this time, since the end portion on one side in the axial direction of the convex portion 43 is the conical portion 432 , the convex portion 43 can be easily inserted radially inward of the second inner bearing 54 . Further, by inserting the conical portion 432 into the inner ring of the second inner bearing 54 while bringing the outer peripheral surface of the conical portion 432 into contact therewith, the center of the convex portion 43 is aligned with the central axis 91 so that the first unit U1 is placed in the second position. Unit U2 can be positioned incrementally. Specifically, even if the straight line connecting the rotation axis of the first inner bearing 53 and the rotation axis of the second inner bearing 54 is inclined with respect to the central axis 91, it is corrected coaxially by the guide of the conical surface 432. It becomes possible to The conical portion 432 after insertion is located radially inside the second gear 222 as shown in FIG.

In addition, in the example of FIG. 3, the rotary internal gear 24 belongs to the second unit U2. However, the rotating internal gear 24 may belong to the first unit U1. In that case, after the second unit U2 is assembled to the first unit U1, the rotary internal gear 24 may be fixed to the output member 40 with the second bolt 62. In this case, the outer peripheral surface of the rotating internal gear 24 is inserted into the inner peripheral surface of the output wall portion 42 . The output wall portion 42 can be easily inserted into the rotating internal gear 24 by providing the tapered surface 421 on one side of the inner peripheral surface of the output wall portion 42 in the axial direction, the diameter of which decreases toward the other side in the axial direction.

<3. Variation>
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. Various modifications will be described below, focusing on differences from the above-described embodiment. It should be noted that redundant description of parts equivalent to those of the above-described embodiment will be omitted.

<3-1. First modification>
FIG. 4 is a longitudinal sectional view of a differential planetary reduction gear 1 according to a first modified example. The differential planetary reduction gear 1 of FIG. 4 is used, for example, by being incorporated in wheels of an automatic guided vehicle. In the example of FIG. 4, an electric motor 70 is directly connected to one axial side of the differential planetary reduction gear 1 . An output shaft of the electric motor 70 serves as an input member 10 of the differential planetary reduction gear 1 . In this way, the number of parts can be reduced compared to the case where the output shaft of the electric motor 70 and the input member 10 of the differential planetary reduction gear 1 are separate parts. In addition, the electric motor 70 and the differential planetary reduction gear 1 can be made compact in the axial direction as a whole.

Further, in the example of FIG. 4 , the housing wall portion 32 is inserted radially inward of the output wall portion 42 . That is, the housing wall portion 32 is located radially inside the output wall portion 42 . The first outer bearing 521 and the second outer bearing 522 are interposed between the outer peripheral surface of the housing wall portion 32 and the inner peripheral surface of the output wall portion 42 . Even with such an arrangement, by arranging the housing wall portion 32 and the output wall portion 42 so as to overlap in the radial direction, the housing 30 and the output member 40 as a whole can be miniaturized in the axial direction. Therefore, the differential planetary reduction gear 1 can be thinned in the axial direction.

Further, the differential planetary reduction gear 1 of FIG. 4 further includes an annular tire 80 . A tire 80 is fixed to the outer peripheral surface of the output wall portion 42 . The tire 80 is made of rubber, for example. With this configuration, the speed reduction mechanism 20 is arranged radially inward of the tire 80 . Thereby, the mechanism for rotating the tire 80 can be thinned in the axial direction. Note that the differential planetary reduction gear 1 may further include a wheel between the output wall portion 42 and the tire 80 .

<3-2. Second modification>
FIG. 5 is a longitudinal sectional view of a differential planetary reduction gear 1 according to a second modification. In the differential planetary reduction gear 1 of FIG. 5, the input member 10 is a shaft coupling. The output shaft of the electric motor can be directly connected to the coupling as input member 10 . In this way, compared to the case where other parts are interposed between the output shaft of the electric motor and the input member 10 of the differential planetary speed reducer 1, the electric motor and the differential planetary speed reducer 1 can be The overall size can be reduced in the axial direction.

In the embodiment described above, the differential planetary reduction gear 1 includes the first outer bearing 521 and the second outer bearing 522 . In contrast, the differential planetary reduction gear 1 of FIG. 5 has one outer bearing 52 . The outer bearing 52 is interposed in a radial gap between the inner peripheral surface of the housing wall portion 32 and the outer peripheral surface of the output wall portion 42 .

The outer bearing 52 in FIG. 5 is a cross roller bearing. A cross roller bearing has a plurality of rollers between an outer ring and an inner ring. The plurality of rollers are arranged while alternately changing their directions between the V-shaped groove provided on the inner peripheral surface of the outer ring and the V-shaped groove provided on the outer peripheral surface of the inner ring. Such cross roller bearings do not have to be used in pairs like ball bearings, but a single cross roller bearing can provide the required rigidity. Therefore, it is possible to stably support the output member 40 with respect to the housing 30 while reducing the number of the outer bearings 52 .

The carrier 25 in FIG. 5 is a unit that supports the plurality of planetary gears 22 so that they can revolve around the central axis 91 while rotating around the planetary shaft 92 . Carrier 25 has a carrier member 250 and a plurality of carrier pins 254 .

Carrier member 250 has a first disc portion 251 and a second disc portion 252 . The carrier member 250 of this embodiment does not have a connecting portion 253 . The first disk portion 251 and the second disk portion 252 are separate members. The first disc portion 251 is positioned on one side in the axial direction of the plurality of planetary gears 22 . The second disc portion 252 is positioned on the other side in the axial direction of the plurality of planetary gears 22 . The first disk portion 251 and the second disk portion 252 each extend in a direction perpendicular to the central axis 91 . The planetary gear 22 is arranged axially between the first disc portion 251 and the second disc portion 252 .

Carrier pin 254 is a cylindrical member that extends axially along planetary shaft 92 . One axial end of the carrier pin 254 is fixed to the first disc portion 251 . The outer peripheral portion on the other axial side of each of the plurality of carrier pins 254 contacts the outer peripheral portion of the second disk portion 252 . The plurality of carrier pins 254 are arranged at equal intervals in the circumferential direction around the central axis 91 . A pair of planetary bearings 225 are interposed between the inner peripheral surface of the planetary gear 22 and the carrier pin 254 . As a result, the planetary gear 22 is rotatably supported around the planetary shaft 92 .

In the example of FIG. 5 , the planetary gear 22 is supported by the carrier pin 254 and the first disc portion 251 , and the carrier 25 is supported by the input member 10 by the first inner bearing 53 . However, since it is difficult to hold the planetary shaft 92 parallel to the central shaft 91 only with the first inner bearing 53 , the radial displacement of the carrier pin 254 is prevented by the outer peripheral surface of the second disk portion 252 . , the planetary shaft 92 can rotate stably.

Also, in the example of FIG. 5 , the first disc portion 251 of the carrier member 250 has a third collar portion 255 . The third collar portion 255 protrudes radially inward from the inner peripheral surface of the first disc portion 251 . The third flange portion 255 axially contacts the end surface of the outer ring of the first inner bearing 53 on the other side in the axial direction. As a result, the first inner bearing 53 is prevented from shifting to the other side in the axial direction with respect to the carrier 25 . Moreover, the carrier 25 is prevented from slipping to one side in the axial direction with respect to the first inner bearing 53 .

5, the second disc portion 252 of the carrier member 250 has a fourth collar portion 256. As shown in FIG. The fourth collar portion 256 protrudes radially inward from the inner peripheral surface of the second disc portion 252 . The fourth collar portion 256 axially contacts an end face on one axial side of the outer ring of the second inner bearing 54 . As a result, the second inner bearing 54 is prevented from slipping to one side in the axial direction with respect to the carrier 25 . In addition, the carrier 25 is prevented from shifting to the other side in the axial direction with respect to the second inner bearing 54 .

In the example of FIG. 5, a snap ring or a collar is inserted between the other axial end surface of the inner ring of the planetary bearing 225 located on the other axial side and the one axial end surface of the second disk portion 252 . there is Thus, the carrier 25 is formed by preventing the first disc portion 251 and the second disc portion 252 from approaching each other. Therefore, the second inner bearing 54 is prevented from slipping to one side in the axial direction with respect to the first inner bearing 53 . Moreover, the first inner bearing 53 is prevented from shifting to the other side in the axial direction with respect to the second inner bearing 54 .

<3-3. Others>
In the above embodiment, the input member 10 supports the carrier 25 via the first inner bearing 53, and the projection 43 of the output member 40 supports the carrier 25 via the second inner bearing 54. Was. That is, in the above embodiment, the carrier 25 is supported by two members, the input member 10 and the output member 40 . However, the carrier 25 may be supported only by the output member 40 of the input member 10 and the output member 40 . Even in this case, the posture of the carrier 25 can be stabilized by supporting the carrier 25 with the projections 43 provided on the output member 40 .

The shape of the details of the differential planetary speed reducer may differ from the shapes shown in the drawings of this application. Moreover, each element appearing in the above embodiments or modifications may be appropriately selected within a range that does not cause contradiction.

<4. Robot>
FIG. 6 is a schematic diagram of a robot 100 equipped with a differential planetary reduction gear 1. As shown in FIG. The robot 100 is, for example, a so-called industrial robot that carries out operations such as transportation, processing, and assembly of parts in a manufacturing line for industrial products. As shown in FIG. 6 , the robot 100 has a base frame 101 , an arm 102 , a differential planetary reduction gear 1 and an electric motor 70 . The differential planetary reduction gear 1 and the electric motor 70 are incorporated in the joint between the base frame 101 and the arm 102 . Thereby, the robot 100 having the differential planetary reduction gear 20 capable of supporting the carrier 25 in a stable posture can be realized.

The base frame 101 is fixed to either the housing 30 of the differential planetary reduction gear 1 or the casing of the electric motor 70 . An output shaft of the electric motor 70 is fixed to the input member 10 of the differential planetary reduction gear 1 . Arm 102 is fixed to output member 40 of differential planetary reduction gear 1 . When the electric motor 70 is driven, the input member 10 rotates together with the output shaft of the electric motor 70 at the first rotation speed. Then, the arm 102 rotates together with the output member 40 at the second rotation speed.

INDUSTRIAL APPLICABILITY The present invention can be used for differential planetary reduction gears and robots.

Reference Signs List 1 differential planetary reduction gear 10 input member 11 input-side flange 20 speed reduction mechanism 21 sun gear 22 planetary gear 23 fixed internal gear 24 rotating internal gear 25 carrier 30 housing 31 housing base 32 housing wall 40 Output member 41 Output base portion 42 Output wall portion 43 Protruding portion 44 Output side collar portion 51 Input side bearing 52 Outer bearing 53 First inner bearing 54 Second inner bearing 91 Center shaft 92 Planetary shaft 100 Robot 221 First gear 222 Second Gear 250 Carrier member 251 First disc portion 252 Second disc portion 253 Connection portion 254 Carrier pin 255 Third flange portion 256 Fourth flange portion 431 Support surface 432 Conical portion 521 First outer bearing 522 Second outer bearing 531 Second 1 collar portion 541 2nd collar portion U1 1st unit U2 2nd unit

Claims (22)

an input member that rotates about a central axis at a first rotation speed;
a speed reduction mechanism that converts rotational motion of the input member into rotational motion at a second rotational speed lower than the first rotational speed;
a housing that houses the speed reduction mechanism;
an output member that rotates at the second rotation speed about the central axis;
with
The speed reduction mechanism is
a sun gear that rotates at the first rotation speed about the central axis together with the input member;
a planetary gear having a first gear that rotates about a planetary axis parallel to the central axis while meshing with the sun gear, and a second gear that rotates about the planetary axis together with the first gear;
an annular fixed internal gear fixed to the housing and meshing with the first gear;
an annular rotating internal gear fixed to the output member and meshing with the second gear;
a carrier that supports the planetary gear so that it can rotate about the planetary shaft and revolve about the central axis;
has
The housing is
a housing base located on one side in the axial direction of the speed reduction mechanism;
a cylindrical housing wall portion extending from the outer peripheral portion of the housing base portion to the other side in the axial direction;
has
The output member is
an output base located on the other side in the axial direction of the speed reduction mechanism;
a cylindrical output wall portion extending from the outer peripheral portion of the output base portion to one side in the axial direction;
a convex portion extending from the center of the output base portion to one side in the axial direction;
has
an input-side bearing interposed between the inner peripheral surface of the housing base portion and the input member;
an outer bearing interposed between the housing wall and the output wall;
a first inner bearing interposed between the input member and the carrier;
a second inner bearing interposed between the projection and the carrier;
A differential planetary reducer, further comprising: The differential planetary reduction gear according to claim 1,
The diameter of the second gear centered on the planetary shaft is smaller than the diameter of the first gear centered on the planetary shaft,
A differential planetary reduction gear, wherein the diameter of the sun gear centered on the central axis is smaller than the diameter of the second gear centered on the planetary shaft. The differential planetary reduction gear according to claim 1 or claim 2,
The carrier is
a first disk portion positioned on one side in the axial direction of the planetary gear;
a second disk portion positioned on the other side in the axial direction of the planetary gear;
has
The first inner bearing is interposed between the input member and the first disk portion,
The second inner bearing is a differential planetary reduction gear interposed between the convex portion and the second disk portion. A differential planetary reduction gear according to claim 3,
the first disk portion and the first inner bearing are positioned on a first plane perpendicular to the central axis;
A differential planetary reduction gear, wherein the second disk portion and the second inner bearing are positioned on a second plane orthogonal to the central axis. The differential planetary reduction gear according to claim 3 or claim 4,
The first disk portion and the second disk portion are separate members,
The carrier is
further comprising a carrier pin extending axially along the planetary axis;
one end of the carrier pin in the axial direction is fixed to the first disc portion;
A differential planetary reduction gear, wherein an outer peripheral portion of the carrier pin on the other side in the axial direction is in contact with an outer peripheral portion of the second disk portion. The differential planetary reduction gear according to any one of claims 1 to 5,
The outer bearing is
a first outer bearing;
a second outer bearing located on the other side in the axial direction of the first outer bearing;
A differential planetary reducer, including The differential planetary reduction gear according to any one of claims 1 to 5,
A differential planetary reduction gear, wherein the outer bearing is a cross roller bearing. The differential planetary reduction gear according to any one of claims 1 to 7,
The output wall portion is inserted radially inward of the housing wall portion,
The outer bearing is a differential planetary reduction gear interposed between an inner peripheral surface of the housing wall portion and an outer peripheral surface of the output wall portion. The differential planetary reduction gear according to any one of claims 1 to 7,
The housing wall is inserted radially inward of the output wall,
The outer bearing is a differential planetary reduction gear interposed between an outer peripheral surface of the housing wall portion and an inner peripheral surface of the output wall portion. A differential planetary reduction gear according to claim 9,
A differential planetary reduction gear further comprising a tire fixed to an outer peripheral surface of the output wall. The differential planetary reduction gear according to any one of claims 1 to 10,
The convex portion is
a cylindrical support surface supporting the second inner bearing;
a conical portion located on one side in the axial direction of the support surface and decreasing in diameter toward the one side in the axial direction;
A differential planetary reducer having a The differential planetary reduction gear according to any one of claims 1 to 11,
A differential planetary reduction gear, wherein one axial end of the convex portion is positioned radially inward of the second gear. The differential planetary reduction gear according to any one of claims 1 to 12,
The input member is
having an input-side flange that axially contacts the inner ring of the first inner bearing;
The output member is
A differential planetary reduction gear having an output-side flange that axially contacts the inner ring of the second inner bearing. The differential planetary reduction gear according to any one of claims 1 to 13,
The outer ring of the first inner bearing is
Having a first collar portion that is in axial contact with the carrier,
The outer ring of the second inner bearing,
A differential planetary reduction gear having a second collar portion axially contacting the carrier. The differential planetary reduction gear according to any one of claims 1 to 13,
The carrier is
a third flange axially contacting the outer ring of the first inner bearing;
a fourth flange axially contacting the outer ring of the second inner bearing;
A differential planetary reducer having a A differential planetary reduction gear according to any one of claims 1 to 15,
A differential planetary reduction gear, wherein the input member is an output shaft of an electric motor. A differential planetary reduction gear according to any one of claims 1 to 15,
A differential planetary reduction gear, wherein the input member is a shaft coupling connectable to an output shaft of an electric motor. A differential planetary reduction gear according to any one of claims 1 to 15,
A differential planetary reduction gear, wherein the input member is an input shaft. A differential planetary reduction gear according to any one of claims 1 to 18,
The differential planetary reduction gear, wherein the inner peripheral surface of the output wall portion has a tapered surface whose diameter decreases from the one axial side toward the other axial side. an input member having a sun gear rotatable about a central axis;
a planetary gear meshing with the sun gear and rotatable about a planetary axis parallel to the central axis;
a carrier that supports the planetary gear rotatably around the planetary shaft;
a housing, at least a part of which is arranged on one side in the axial direction of the planetary gear and which houses at least a part of the planetary gear;
an output member at least partially arranged on the other side in the axial direction of the carrier, connected to the planetary gear and rotatable relative to the housing;
has
The output member is
an output base portion arranged on the other side of the carrier in the axial direction and extending in a direction substantially orthogonal to the central axis;
a convex portion protruding from the output base portion to one side in the axial direction;
has
A differential planetary reduction gear, wherein the projection supports the carrier via an inner bearing. 21. A differential planetary reduction gear according to claim 20,
the output member has an output wall portion disposed radially outwardly of the convex portion and protruding from the output base portion to one side in the axial direction;
The housing is
a housing base portion disposed on one axial side of the planetary gear and extending in a direction substantially orthogonal to the central axis;
a housing wall portion projecting from the radial outer edge of the housing base portion toward the other side in the axial direction;
has
The differential planetary reduction gear, wherein the housing wall rotatably supports the output wall via an outer bearing. A robot comprising a differential planetary reducer according to any one of claims 1 to 21.

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