Robot joint structure

Abstract

This disclosure relates to a robot joint structure in which a first member and a second member are connected via a joint and the first member and the second member rotate relative to each other about an axis, comprising: a drive motor for driving the second member relative to the first member; an input shaft to which the rotational force of the drive motor is input; a gear for transmitting the rotational force of the input shaft; a gear support member for supporting the gear; and a reduction gear having a reduction gear case to which the rotational force of the gear is transmitted. The gear support member is fixed to the second member, the reduction gear case is fixed to the first member, the reduction gear further has a cover member that covers the opposite side of the reduction gear in the axial direction with respect to the input shaft, the reduction gear has a lubricant-sealed structure in which a lubricant is sealed inside the reduction gear, the cover member constitutes a part of the lubricant-sealed structure, and in the state in which the lubricant-sealed structure is configured, the cover member is fastened together with the second member and the gear support member, or fastened together with the first member and the reduction gear case by a fastening member.

Description

Technical Field

[0001] The present invention relates to an articulation structure of a robot provided with a drive motor and a speed reducer.

Background Art

[0002] A robot includes a plurality of members connected via joints. A drive motor for driving one member with respect to the other member is disposed at the joint. When the drive motor is driven, the orientation of one member relative to the other member changes. Further, a speed reducer for increasing the output torque of the drive motor is disposed at the joint.

[0003] For example, an articulated robot has a plurality of joints. The articulated robot includes a first arm member (also referred to as a "swivel base", "swivel body", etc.) that rotates around a rotation axis extending in the vertical direction, a second arm member that rotates with respect to the first arm member, and a joint disposed between the first arm member and the second arm member. When the drive motor is driven, the orientation of the second arm member relative to the first arm member changes relatively (see, for example, Patent Document 1).

[0004] The joint can adopt a cantilever structure that supports from one side of the arm member. The drive motor can be fixed to, for example, the first arm member. The speed reducer can have an input shaft, a speed reducer case, gears disposed inside the speed reducer case, and a gear support member that supports the gears. The rotational force is transmitted from the input shaft that receives the rotational force of the drive motor to the gears. When the gears rotate, the gear support member can be rotated relative to the speed reducer case.

[0005] In the case of such a speed reducer, the speed reducer case can be fixed to the first arm member. The gear support member can be fixed to the second arm member. The speed reducer can rotate the second arm member fixed to the gear support member while reducing the output of the drive motor with the gears. <00​ [Patent Documents]

[0006] [Patent Document 1] International Publication No. WO2022 / 181499 [Overview of the project] [Problems that the invention aims to solve]

[0007] Incidentally, the internal space of a speed reducer needs to be filled with a lubricant such as grease for smooth operation of the speed reducer. At the joint, the speed reducer is housed in the housing space of the arm member. Conventionally, the internal space of the speed reducer has not been sealed, and the housing space of the arm member and the internal space of the speed reducer are in communication. In many cases, the lubricant has been used to fill the internal space of the speed reducer in a way that allows communication between the internal space of the speed reducer and the space outside the speed reducer that is inside the housing space of the arm member. In such a configuration, when replacing parts of the speed reducer, there is a problem in that it is necessary to drain and (re)supply (i.e., replace) the filler and release residual pressure.

[0008] On the other hand, there are also known speed reducers with a lubricant-sealed structure in which a lubricant is sealed inside the speed reducer. Speed ​​reducers with a lubricant-sealed structure may solve the aforementioned problems. However, in speed reducers with a lubricant-sealed structure, the radial size (plane direction perpendicular to the axial direction) of the speed reducer tends to be large in order to configure a structure that seals the side opposite the input shaft in the speed reducer. Therefore, it is desirable to make the radial size of the speed reducer compact in speed reducers with a lubricant-sealed structure. [Means for solving the problem]

[0009] One aspect of the present disclosure is a robot joint structure in which a first member and a second member are connected via a joint and the first member and the second member rotate relative to each other about an axis, comprising: a drive motor for driving the second member relative to the first member; an input shaft to which the rotational force of the drive motor is input; a gear for transmitting the rotational force of the input shaft; a gear support member for supporting the gear; and a reduction gear having a reduction gear case to which the rotational force of the gear is transmitted, wherein the gear support member is fixed to the second member and the reduction gear case The robot joint structure is fixed to the first member, the reduction gear further has a cover member that covers the opposite side of the axial direction to the input shaft in the reduction gear, the reduction gear has a lubricant-sealed structure in which a lubricant is sealed inside the reduction gear, the cover member constitutes a part of the lubricant-sealed structure, and in the state in which the lubricant-sealed structure is configured, the cover member is fastened together with the second member and the gear support member by a fastening member, or fastened together with the first member and the reduction gear case. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic perspective view of a robot according to one embodiment of the present disclosure. [Figure 2] This is an enlarged schematic cross-sectional view of the joint portion in the first embodiment. [Figure 3A] This is an enlarged schematic cross-sectional view of the gearbox in the first embodiment (corresponding to Figure 2). [Figure 3B] This is a view of the reduction gear in the first embodiment, seen from the side of the cover member. [Figure 4A] Figure 3A shows the state with the lid removed. [Figure 4B] Figure 3B shows the state with the lid removed. [Figure 5] This is an enlarged schematic cross-sectional view of the joint portion in the second embodiment. [Figure 6A] This is an enlarged schematic cross-sectional view of the gearbox in the second embodiment (corresponding to Figure 5). [Figure 6B] This is a view of the reduction gear in the second embodiment, seen from the side of the cover member. [Figure 7A] Figure 6A shows the state with the lid removed. [Figure 7B] Figure 6B shows the state with the lid removed. [Modes for carrying out the invention]

[0011] The joint structure of the robot in the first embodiment will be described with reference to Figures 1 to 4B. Figure 1 is a schematic perspective view of a robot according to one embodiment of the present disclosure. Figure 2 is an enlarged schematic cross-sectional view of the joint in the first embodiment. Figure 3A is an enlarged schematic cross-sectional view of the reducer in the first embodiment (corresponding to Figure 2). Figure 3B is a view of the reducer in the first embodiment from the side of the cover member. Figure 4A is a view of Figure 3A with the cover member removed. Figure 4B is a view of Figure 3B with the cover member removed.

[0012] As shown in Figure 1, the robot device 100 comprises a hand (not shown) as an end effector for gripping a workpiece, and a robot 101 that moves the hand. In one embodiment, the robot 101 is an articulated robot including a plurality of joints 110, 120, 130. The robot 101 includes a plurality of components. Each component of the robot 101 is configured to rotate around predetermined axes J1, J2, J3, etc.

[0013] Robot 101 includes, as members of the robot 101, a first arm member 11 (which may also be called a "swivel base" or "swivel body", etc.) supported by a base portion 104, a second arm member 21, a third arm member 31, and a wrist 105 connected to an end of the third arm member 31. The base portion 104 is fixed to an installation surface. The first arm member 11 rotates with respect to the base portion 104. The first arm member 11 rotates around an axis J1 extending in a direction perpendicular to the installation surface. The second arm member 21 is supported by the first arm member 11 via a first joint portion 110. The third arm member 31 is supported by the second arm member 21 via a second joint portion 120. The wrist 105 is supported by the third arm member 31 via a third joint portion 130. The hand is fixed to the wrist 105.

[0014] The robot 101 of one embodiment includes a robot drive device that drives each member. The robot drive device of one embodiment includes drive motors 12, 22, and 32 that drive the first arm member 11, the second arm member 21, and the third arm member 31. In one embodiment, a drive motor is arranged for each member. At the joint portions, as the orientation of each member of the robot 101 changes, the position and posture of the robot 101 change.

[0015] In the first embodiment, the first joint portion 110 arranged between the first arm member 11 and the second arm member 21 among the plurality of joint portions 110, 120, and 130 will be described.

[0016] The first joint portion 110 has a cantilever structure in which the second arm member 21 is supported from one side of the first arm member 11. In the first embodiment, the first arm member 11 corresponds to the first member constituting the robot 101. Also, the second arm member 21 corresponds to the second member constituting the robot 101. The second arm member 21 rotates with respect to the first arm member 11.

[0017] As shown in FIGS. 2 to 4B, the first joint portion 110 includes a second drive motor 22 that drives the second arm member 21 with respect to the first arm member 11, and a speed reducer 20 that increases the output torque of the second drive motor 22. The second drive motor 22 is fixed to the first arm member 11. The second drive motor 22 includes a motor main body portion 221 and an output shaft 222 that protrudes from the motor main body portion 221 toward the speed reducer 20 and outputs a rotational force.

[0018] The speed reducer 20 includes an input shaft 23 to which the rotational force of the second drive motor 22 is input, a plurality of gears 24 that transmit the rotational force of the input shaft 23, a gear support member 25 (which may be referred to as a "shaft of the speed reducer") that supports the gears 24, a speed reducer case 26 to which the rotational force of the gears 24 is transmitted, a lid member 27, and an input side cover member 28. The speed reducer case 26 rotates relative to the gear support member 25.

[0019] The gear support member 25 is fixed to the second arm member 21. The fixing means is not limited and may be, for example, screwing with bolts, welding, or adhesion.

[0020] The speed reducer case 26 is configured in a cylindrical shape so as to surround the gear support member 25. The first arm member 11 is fixed to the speed reducer case 26. The fixing means is not limited and may be, for example, screwing with bolts, welding, or adhesion.

[0021] In the first embodiment, the second axial direction D2 is a direction along the second axis J2, and more precisely, a direction parallel to (the same as) the second axis J2. In the speed reducer 20 among the second axial direction D2, the side where the rotational force is input is also referred to as the "side D21 of the input shaft", and the opposite side is also referred to as the "opposite side D22". In the first embodiment, the direction (side) from the first arm member 11 toward the second arm member 21 is referred to as the "side D21 of the input shaft", and the direction (side) from the second arm member 21 toward the first arm member 11 is referred to as the "opposite side D22". The axial directions of the members in the first joint portion 110 are parallel to the second axial direction D2 or the second axis J2.

[0022] The input shaft 23 of the reduction gear 20 is connected to the output shaft 222 of the second drive motor 22 by inserting and engaging it into the insertion hole 231 of the input shaft 23. The rotation axis of the input shaft 23 is arranged to be coaxial with the rotation axis of the output shaft 222. The output shaft 222 and the input shaft 23 rotate around the second axis J2.

[0023] The gear reducer 20 in the first embodiment has a lubricant-filled structure. A lubricant such as grease or oil is sealed and arranged inside the internal space of the gear reducer 20. The internal space is surrounded by a gear support member 25, a gear reducer case 26, a cover member 27, an input-side cover member 28, an input shaft 23, a sealing member, etc. The sealing member can be made of an elastic material such as rubber. For example, the sealing member is an oil seal 29. As will be described later, the opposite side D22 of the gear support member 25 is sealed mainly by the cover member 27. The input shaft side D21 of the gear support member 25 is sealed mainly by the input-side cover member 28, the input shaft 23, and the oil seal 29.

[0024] As shown in Figures 2 to 4B, the reduction gear 20 in the first embodiment is an eccentric oscillating type planetary gear reduction gear. The rotational force of the output shaft 222 of the second drive motor 22 is transmitted to the input shaft 23 of the reduction gear 20. External teeth 232 are formed on the circumferential surface of the input shaft 23. The input shaft 23 is rotatably supported by a gear support member 25.

[0025] Multiple gears 24 (also called "spur gears") capable of eccentric rotation are engaged with the input shaft 23. The gears 24 have external teeth formed on them. The gears 24 engage with the external teeth 232 formed on the input shaft 23. The multiple gears 24 rotate on different axes of rotation 242.

[0026] When the second drive motor 22 is driven, the input shaft 23 of the reduction gear 20 rotates via the output shaft 222. The rotational force of the input shaft 23 is transmitted to the gears 24. The gears 24 revolve around the second axis J2 while rotating on their respective axis 242. The rotational force of the gears 24 is transmitted to the reduction gear case 26 via a reduction mechanism (not shown). As the reduction gear case 26 rotates, the second arm member 21 rotates. The rotational speed of the input shaft 23 is reduced according to the reduction mechanism of the reduction mechanism. In this way, the reduction gear 20 in the first embodiment can increase the rotational torque by reducing the rotational speed output from the output shaft 222 of the second drive motor 22.

[0027] The reduction gear is not limited to this form, and any reduction gear having a reduction gear case and a gear support member (shaft) that rotates relative to the reduction gear case can be used. For example, a reduction gear equipped with a planetary gear mechanism in which planetary gears rotate on their own axis while revolving around a sun gear, or an eccentric differential type reduction gear can be used.

[0028] In the first embodiment, the reduction gear 20 includes a lid member 27 and an input-side cover member 28 to realize a lubricant-sealed structure. The gear support member 25 protrudes in the second axial direction D2 from the input shaft side D21 and the opposite side D22 of the second axial direction D2 relative to the input shaft 23 in the reduction gear case 26. In the second axial direction D2, which is along the second axis J2, the gear 24 is housed in the gear support member 25.

[0029] The cover member 27 is a member that covers the opposite side D22 of the second axial direction D2 with respect to the input shaft 23 in the gear support member 25 of the reduction gear 20. The input side cover member 28 is a member that covers the side D21 of the input shaft in the gear support member 25 of the reduction gear 20.

[0030] The lid member 27 and the input-side cover member 28 are flat. The surface 277 of the lid member 27 on the side D21 facing the input shaft is flat. The surface 272 of the lid member 27 on the side D22 opposite to the second axial direction D2 with respect to the input shaft 23 is flat.

[0031] As shown in Figures 3A, 3B, 4A, and 4B, the cover member 27 has a plurality of first through holes 273 and a plurality of second through holes 275 spaced apart in the circumferential direction DC on its peripheral edge 271. A fastening bolt B1 for fastening the cover member 27 and the gear support member 25 together to the second arm member 21 is inserted through the first through hole 273. A first fixing bolt B2 for fixing the cover member 27 to the gear support member 25 is inserted through the second through hole 275. In Figures 3A and 3B, the fastening bolt B1 is not actually connected to the gear support member 25 when the second arm member 21 is detached, but for convenience, it is shown connected to the gear support member 25.

[0032] In detail, the first fastening member, the shared fastening bolt B1, has a first head B11 and a first male threaded portion B12. The second fastening member, the first fixing bolt B2, has a second head B21 and a second male threaded portion (not shown). The cover member 27 has a first through hole 273 through which the first male threaded portion B12 passes, and a second through hole 275 through which the second male threaded portion (not shown) passes.

[0033] As shown in Figure 4B, the gear support member 25 has a first female threaded portion 253 and a second female threaded portion 255 on the surface that abuts against the peripheral edge 271 of the cover member 27 (the opposite side D22). The first female threaded portion 253 faces the first through hole 273. The second female threaded portion 255 faces the second through hole 275.

[0034] The cover member 27 and the gear support member 25 are fixed (fastened together) to the second arm member 21 by a fastening bolt B1 which is inserted through the first through hole 273 and screwed into the first female threaded portion 253. The "fastening bolt B1" corresponds to the "fastening member" or "first fastening member" in the present invention. In Figure 2, a counterbore hole is provided in the second arm member 21, and the first head B11 of the fastening bolt B1 fits into the counterbore hole. However, a configuration without a counterbore hole is also possible.

[0035] The cover member 27 is fixed to the gear support member 25 by a first fixing bolt B2, which is inserted through a second through hole 275 and screwed into a second female threaded portion 255. The "first fixing bolt B2" corresponds to the "second fastening member" in this invention. In the state in which the lubricant-sealed structure is configured, the first fixing bolt B2, which is the second fastening member, fastens the cover member 27 to the gear support member 25 without functioning as a co-fastening member.

[0036] Figure 3B shows a state in which only a portion of the multiple fastening bolts B1 are screwed into the first female threaded portion 253, and only a portion of the multiple first fixing bolts B2 are screwed into the second female threaded portion 255. Furthermore, although the fastening bolts B1 are actually screwed into the first female threaded portion 253 with the second arm member 21 and the cover member 27 in between, in Figures 3A and 3B, the fastening bolts B1 are shown virtually as being screwed into the first female threaded portion 253 with the cover member 27 in between, as if the second arm member 21 were absent.

[0037] The cover member 27 is fixed to the gear support member 25, thereby sealing the opposite side D22 of the gear support member 25. In other words, the cover member 27 constitutes a sealing structure for the opposite side D22 of the reduction gear 20 and forms part of the lubricant-sealed structure.

[0038] Instead of using fixing bolts B2, the parts can also be fixed by welding, adhesive, or other means. Note that bolts and the holes through which they are inserted are omitted from the illustration as appropriate.

[0039] In the first embodiment, with the lubricant-filled structure configured, the lid member 27 is fastened together with the second arm member 21 and the gear support member 25, which are second members, by a first fastening member, which is a shared fastening bolt B1.

[0040] In the first embodiment, the alignment of the gear support member 25 with respect to the second arm member 21 is defined by the fact that the second arm member 21 and the gear support member 25 abut in the radial direction DR with respect to the second axis J2. On the other hand, the outer circumference of the cover member 27 does not function (contribute) to the alignment. For example, the outer circumference of the cover member 27 is not in contact with or in close contact with the second arm member 21.

[0041] In the state in which the lubricant-sealed structure described above is configured, the first male threaded portions B12 of the multiple fastening bolts B1 are arranged circumferentially around the second axis J2. The second male threaded portions (not shown) of the multiple fixing bolts B2 are also arranged circumferentially around the second axis J2. The first virtual ring VC1, which virtually connects the first male threaded portions B12 of the multiple fastening bolts B1, is located inside the second virtual ring VC2, which virtually connects the second male threaded portions (not shown) of the multiple fixing bolts B2. The shape of the "virtual ring" may be not only a perfect circle, but also an annular shape approximating a circle. "Located inside" includes not only the case where the second virtual ring VC2 is located completely inside the first virtual ring VC1, but also the case where the second virtual ring VC2 coincides with the first virtual ring VC1. In the first embodiment, the second virtual ring VC2 is located completely inside the first virtual ring VC1.

[0042] The input-side cover member 28, together with the input shaft 23 and the oil seal 29 which is an external sealing member fitted onto the input shaft 23, constitutes a sealing structure for side D21 of the input shaft in the reduction gear 20. More specifically, the input-side cover member 28 seals the side D21 of the input shaft on the gear support member 25 which protrudes from the reduction gear case 26 to side D21 of the input shaft. The input-side cover member 28 is fixed to the side D21 of the input shaft on the gear support member 25 by a second fixing bolt B3. Note that the sealing structure for side D21 of the input shaft in the reduction gear 20 may include members other than the input-side cover member 28, the input shaft 23, and the oil seal 29.

[0043] Next, the effects of the first embodiment will be described. In the first embodiment, the reduction gear 20 further has a cover member 27 that covers the axial opposite side D22 with respect to the input shaft 23 in the reduction gear 20. The reduction gear 20 has a lubricant-sealed structure in which a lubricant is sealed inside the reduction gear 20. The cover member 27 constitutes a part of the lubricant-sealed structure. When the lubricant-sealed structure is configured, the cover member 27 is fastened together with the second arm member 21 and the gear support member 25, which are second members, by fastening bolts B1, which are fastening members. Therefore, according to the first embodiment, since the cover member 27, the second arm member 21, and the gear support member 25 are fastened together, the space required for fixing is reduced when configuring a structure to seal the axial opposite side with respect to the input shaft in the reduction gear in order to configure a reduction gear with a lubricant-sealed structure. Consequently, the radial size of the reduction gear can be made more compact.

[0044] Furthermore, when the lid member 27 is fastened together with the second arm member 21, which is a second member, and the gear support member 25, by a fastening bolt B1, the centering of the gear support member 25 relative to the second arm member 21 is determined by the fact that the second arm member 21 and the gear support member 25 abut in the radial direction DR with respect to the axis J2. Therefore, it is not necessary for the outer circumference of the lid member 27 to function (contribute) to the centering. Consequently, it is not necessary to increase the strength of the lid member 27, and it is easy to thin the lid member 27 or form it into a desired shape.

[0045] The fastening member, the shared fastening bolt B1, has a male threaded portion B12, and the cover member 27 has a through hole 273 through which the male threaded portion B12 passes. Therefore, by providing a female threaded portion (in the first embodiment, a female threaded portion 253) into which the male threaded portion B12 is screwed in at an appropriate location on the gear support member 25, the second arm member 21 which is a second member (in the first embodiment, the gear support member 25), etc., a shared fastening structure can be realized with a simple configuration.

[0046] The reduction gear 20 has a first fastening member, a shared fastening bolt B1, as well as a second fastening member, a first fixing bolt B2. In the state where a lubricant-sealed structure is configured, the first fixing bolt B2 fastens the cover member 27 to the gear support member 25 without functioning as a shared fastening member. Therefore, even when the shared fastening bolt B1 is not used, the cover member 27 is fastened to another part of the reduction gear 20 (the gear support member 25 in the first embodiment) by the first fixing bolt B2, making it easy to handle the reduction gear as a standalone unit.

[0047] In the configuration of the lubricant-filled structure, multiple fastening members, the first male threaded portion B12 of the shared fastening bolt B1, are arranged circumferentially around the second axis J2, and multiple second fastening members, the second male threaded portion (not shown) of the first fixing bolt B2, are also arranged circumferentially around the second axis J2. The first virtual ring VC1, which virtually connects the multiple shared fastening bolts B1 (first male threaded portion B12), is located inside the second virtual ring VC2, which virtually connects the multiple first fixing bolts B2 (second male threaded portion (not shown)). Therefore, even if shared fastening is achieved using the shared fastening bolt B1, the expansion of the radial DR of the reduction gear 20 is suppressed.

[0048] The reduction gear 20 further includes an input-side cover member 28, which, together with the input shaft 23 and an oil seal 29 which is an externally fitted sealing member on the input shaft 23, constitutes a sealed structure on the input shaft side D21 of the reduction gear 20. Therefore, a sealed structure on the input shaft side D21 of the reduction gear 20 can be realized with a simple configuration.

[0049] The surface 277 on the side D21 of the input shaft in the cover member 27 is flat. Therefore, the size (dimension) of the second axial direction D2 in the reduction gear 20 can be made compact.

[0050] Next, the second embodiment will be described. While the first embodiment is an embodiment relating to the second reduction gear 20, the second embodiment is an embodiment relating to the third reduction gear 30. Corresponding components in both embodiments are basically indicated by the same reference numeral, or by a reference numeral in which the tens or hundreds digit is changed from "2" to "3". Relevant explanations may be omitted.

[0051] The joint structure of the robot in the second embodiment will be described with reference to Figures 5 to 7B. Figure 5 is an enlarged schematic cross-sectional view of the joint in the second embodiment. Figure 6A is an enlarged schematic cross-sectional view of the reducer in the second embodiment (corresponding to Figure 5). Figure 6B is a view of the reducer in the second embodiment from the side of the cover member. Figure 7A is a view of Figure 6A with the cover member removed. Figure 7B is a view of Figure 6B with the cover member removed.

[0052] In the second embodiment, the second joint portion 120, which is located between the second arm member 21 and the third arm member 31, will be described among the multiple joint portions 110, 120, and 130.

[0053] The second joint 120 has a cantilever structure in which the third arm member 31 is supported from one side of the second arm member 21. In the second embodiment, the second arm member 21 corresponds to the first member constituting the robot 101. The third arm member 31 corresponds to the second member constituting the robot 101. The third arm member 31 rotates relative to the second arm member 21.

[0054] As shown in Figures 5 to 7B, the second joint 120 includes a third drive motor 32 that drives the third arm member 31 relative to the second arm member 21, and a reduction gear 30 that increases the output torque of the third drive motor 32. The third drive motor 32 is fixed to the third arm member 31. The third drive motor 32 includes a motor body 321 and an output shaft 322 that protrudes from the motor body 321 toward the reduction gear 30 and outputs rotational force.

[0055] The reduction gear 30 includes an input shaft 33 to which the rotational force of the third drive motor 32 is input, a plurality of gears 34 that transmit the rotational force of the input shaft 33, a gear support member 35 that supports the gears 34, and a reduction gear case 36 to which the rotational force of the gears 34 is transmitted. The reduction gear case 36 rotates relative to the gear support member 35.

[0056] The gear support member 35 is fixed to the third arm member 31. The means of fixing it are not limited and may include, for example, bolting, welding, or adhesive bonding.

[0057] The gearbox case 36 is cylindrical in shape so as to surround the gear support member 35. The second arm member 21 is fixed to the gearbox case 36. The means of fixing it are not limited and may be, for example, bolted, welded, or bonded.

[0058] In this embodiment, the third axial direction D3 is along the third axis J3, or more precisely, it is parallel to (same as) the third axis J3. Of the third axial direction D3, the side to which rotational force is input in the reduction gear 30 is also called the "input shaft side D31," and the opposite side is also called the "opposite side D32." In this embodiment, the direction (side) from the second arm member 21 toward the third arm member 31 is called the "input shaft side D31," and the direction (side) from the third arm member 31 toward the second arm member 21 is called the "opposite side D32." The direction of the axis of each member in the second joint 120 is parallel to the third axial direction D3 or the third axis J3.

[0059] The input shaft 33 of the reduction gear 30 is connected to the output shaft 322 of the third drive motor 32 by inserting and engaging it into the insertion hole 331 of the input shaft 33. The rotation axis of the input shaft 33 is arranged to be coaxial with the rotation axis of the output shaft 322. The output shaft 322 and the input shaft 33 rotate around the third axis J3.

[0060] The gearbox 30 in this embodiment has a lubricant-filled structure. A lubricant is sealed and arranged inside the internal space of the gearbox 30. The internal space is surrounded by the gear support member 35, the gearbox case 36, the cover member 37, the input shaft 33, the sealing member, etc. For example, the sealing member is an oil seal 39. As will be described later, the opposite side D32 of the gearbox case 36 is mainly sealed by the cover member 37.

[0061] The rotational force of the output shaft 322 of the third drive motor 32 is transmitted to the input shaft 33 of the reduction gear 30. External teeth 332 are formed on the circumferential surface of the input shaft 33. The input shaft 33 is rotatably supported by a gear support member 35.

[0062] Multiple gears 34 capable of eccentric rotation are engaged with the input shaft 33. The gears 34 have external teeth formed on them. The gears 34 engage with the external teeth 332 formed on the input shaft 33. The multiple gears 34 rotate on different axes of rotation 342.

[0063] When the third drive motor 32 is driven, the input shaft 33 of the reduction gear 30 rotates via the output shaft 322. The rotational force of the input shaft 33 is transmitted to the gears 34. The gears 34 revolve around the third axis J3 while rotating on their respective axis 342. The rotational force of the gears 34 is transmitted to the reduction gear case 36 via a reduction mechanism (not shown). As the reduction gear case 36 rotates, the third arm member 31 rotates. The rotational speed of the input shaft 33 is reduced according to the reduction mechanism of the reduction mechanism. In this way, the reduction gear 30 in one embodiment can increase the rotational torque by reducing the rotational speed output from the output shaft 322 of the third drive motor 32.

[0064] In the second embodiment, the reduction gear 30 includes a cover member 37 to realize a lubricant-filled structure. The cover member 37 is a member that covers the opposite side D32 of the third axial direction D3 with respect to the input shaft 33 in the reduction gear case 36.

[0065] The cover member 37 has a shape that can accommodate gears 34 that are not housed in the reduction gear case 36 in the third axis direction D3, which is along the third axis J3. The cover member 37 has an internal space 374 that bulges out toward the opposite side D32. Overall, the cover member 37 has a hat shape. Gears 34 that are not housed in the reduction gear case 36 can be housed in this internal space 374.

[0066] As shown in Figures 6A, 6B, 7A, and 7B, the lid member 37 has a plurality of first through holes 373 and a plurality of second through holes 375 spaced apart in the circumferential direction DC on its peripheral edge 371. A bolt B1 for fastening the lid member 37 and the reduction gear case 36 together to the second arm member 21 is inserted through the first through hole 373. A first fixing bolt B2 for fixing the lid member 37 to the reduction gear case 36 is inserted through the second through hole 375. In Figures 6A and 6B, the bolt B1 is not actually connected to the reduction gear case 36 when the second arm member 21 is detached, but for convenience, the bolt B1 is shown connected to the reduction gear case 36.

[0067] In detail, the first fastening member, the shared fastening bolt B1, has a first head B11 and a first male threaded portion B12. The second fastening member, the first fixing bolt B2, has a second head B21 and a second male threaded portion (not shown). The cover member 37 has a first through hole 373 through which the first male threaded portion B12 passes, and a second through hole 375 through which the second male threaded portion (not shown) passes.

[0068] As shown in Figure 7B, the gearbox case 36 has a through hole 363 and a second female threaded portion 365 on the surface (opposite side D22) that abuts against the peripheral edge 371 of the cover member 37. The second arm member 21 has a female threaded portion 213. The female threaded portion 213 faces the first through hole 373. The through hole 363 faces the first through hole 373. The second female threaded portion 365 faces the second through hole 375.

[0069] The lid member 37 and the gearbox case 36 are fixed (fastened together) to the second arm member 21 by a fastening bolt B1 that passes through the first through holes 373 and 363 and is screwed into the female threaded portion 213. The lid member 37 is fixed to the gearbox case 36 by a first fixing bolt B2 that passes through the second through hole 375 and is screwed into the second female threaded portion 365. In the state in which the lubricant-sealed structure is configured, the first fixing bolt B2, which is the second fastening member, fastens the lid member 37 to the gearbox case 36 without functioning as a fastening member.

[0070] Figure 6B shows a state in which only a portion of the multiple fastening bolts B1 are screwed into the female threaded portion 213, and only a portion of the multiple first fixing bolts B2 are screwed into the second female threaded portion 365. Furthermore, although the fastening bolts B1 are actually screwed into the female threaded portion 213 with the second arm member 21 and the cover member 37 in between, Figures 6A and 6B show a hypothetical state in which the fastening bolts B1 are screwed into the female threaded portion 213 with the cover member 37 in between, as if the second arm member 21 were absent.

[0071] The cover member 37 is fixed to the gearbox case 36, thereby sealing the opposite side D32 of the gearbox case 36. In other words, the cover member 37 constitutes a sealing structure for the opposite side D32 of the gearbox 30 and forms part of the lubricant-filled structure.

[0072] In the second embodiment, with the lubricant-filled structure configured, the lid member 37 is fastened together with the first member, the second arm member 21, and the reduction gear case 36 by a first fastening member, the shared fastening bolt B1. The reduction gear case may be configured to have a female threaded portion, with the head of the shared fastening bolt positioned on the side of the first member.

[0073] In the second embodiment, the alignment of the gearbox case 36 with respect to the second arm member 21 is defined by the fact that the second arm member 21 and the gearbox case 36 abut radially DR with respect to the third axis J3. On the other hand, the outer periphery of the cover member 37 does not function (contribute) to the alignment. For example, the outer periphery of the cover member 37 is not in contact with or in close contact with the second arm member 21.

[0074] In the state in which the lubricant-sealed structure described above is configured, the multiple fastening bolts B1 (the first male threaded portion B12) are arranged circumferentially around the third axis J3. The multiple fixing bolts B2 (the second male threaded portion (not shown)) are arranged circumferentially around the third axis J3. The first virtual ring VC1 that virtually connects the multiple fastening bolts B1 (the first male threaded portion B12) is located inside the second virtual ring VC2 that virtually connects the multiple fixing bolts B2 (the second male threaded portion (not shown)). "Located inside" includes not only the case where the second virtual ring VC2 is located completely inside the first virtual ring VC1, but also the case where the second virtual ring VC2 coincides with the first virtual ring VC1. In the second embodiment, the second virtual ring VC2 coincides with the first virtual ring VC1.

[0075] The second housing space 212 is the space in the second arm member 21 that houses the reduction gear 30. The second housing space 212 communicates with the first housing space 211, which is located at a position offset in the direction in which the second arm member 21 extends. The first housing space 211 is formed to thin the second arm member 21, even if the reduction gear has an unsealed structure, and is located at a position offset from the reduction gear case 36.

[0076] Next, the effects of the second embodiment will be described. The effects similar to those of the first embodiment will not be explained.

[0077] In the second embodiment, the cover member 37 has a shape that can accommodate gears 34 that are not housed in the reducer case 36 in the direction along the third axis J3 (third axis direction D3). Therefore, the peripheral edge 371 of the cover member 37 (which is indirectly fixed to the second arm member 21) can be positioned closer to the input shaft side D31, so that when the reducer 30 is attached to the second arm member 21 the axial dimension (third axis direction D3) can be shortened, and the second arm member 21 can be made more compact.

[0078] Although embodiments of this disclosure have been described in detail above, this disclosure is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of the invention or from the spirit and intent of the invention derived from the claims and their equivalents. For example, the order of operations and processes in the embodiments described above are shown as examples only and are not limited thereto.

[0079] In the above embodiment, the first joint 110 between the first arm member 11 and the second arm member 21, or the second joint 120 between the second arm member 21 and the third arm member 31, were used as examples for the description, but the embodiment is not limited to these forms. The structure of the above embodiment can be applied to joints that connect any member of a robot. For example, the structure of the joint in the above embodiment can be applied to a joint 130 between the third arm member 31 and the wrist 105, etc.

[0080] Furthermore, in the above embodiment, the second arm member 21, as a second member, rotates relative to the first arm member 11, as a first member, or the third arm member 31, as a second member, rotates relative to the second arm member 21, as a first member, but the embodiment is not limited to this configuration. The structure of the above embodiment can be adopted for the joint of a robot in which the first member and the second member rotate relative to each other.

[0081] The robot in one embodiment is a multi-joint robot, but is not limited to this form. Any robot in which at least one member is supported via a joint can be employed. For example, the joint structure of one embodiment can be applied to a robot having a single joint.

[0082] The embodiments described above can be combined as appropriate. The embodiments described above are illustrative and do not limit the present invention.

[0083] The following additional information is disclosed regarding the above embodiments and modifications. (Note 1) A joint structure for a robot (101) in which a first member (11, 21) and a second member (21, 31) are connected via joints (110, 120), and the first member (11, 21) and the second member (21, 31) rotate relative to each other around an axis (J2, J3), comprising a drive motor (22, 32) for driving the second member (21, 31) relative to the first member (11, 21), and the drive motor The reduction gear (20, 30) comprises an input shaft (23, 33) to which the rotational force of a gear (22, 32) is input, gears (24, 34) that transmit the rotational force of the input shaft (23, 33), gear support members (25, 35) that support the gears (24, 34), and a reduction gear case (26, 36) to which the rotational force of the gears (24, 34) is transmitted, wherein the gear support members (25, 35) are the second member (21 A robot joint structure, wherein the reduction gear case (26, 36) is fixed to the first member (11, 21), the reduction gear (20, 30) further has cover members (27, 37) that cover the axial opposite side (D22, D32) of the reduction gear (20, 30) with respect to the input shaft (23, 33), the reduction gear (20, 30) has a lubricant-sealed structure in which lubricant is sealed inside the reduction gear (20, 30), the cover members (27, 37) constitute a part of the lubricant-sealed structure, and in the state in which the lubricant-sealed structure is configured, the cover members (27, 37) are fastened together with the second member (21) and the gear support member (25) by a fastening member (B1), or fastened together with the first member (21) and the reduction gear case (36).

[0084] (Note 2) In the state in which the lubricant-filled structure described above is configured, when the lid member (27) is fastened together with the second member (21) and the gear support member (25) by the fastening member (B1), the alignment of the gear support member (25) with respect to the second member (21) is defined by the second member (21) and the gear support member (25) contacting each other in the radial direction (DR) with respect to the axis (J2), as described in Appendix 1, for the joint structure of a robot.

[0085] (Note 3) In the state in which the lubricant-filled structure described above is configured, the lid member (37) is fastened together with the first member (21) and the reduction gear case (36) by the fastening member (B1), and the alignment of the reduction gear case (36) with respect to the first member (21) is defined by the first member (21) and the reduction gear case (36) contacting each other in the radial direction (DR) with respect to the axis (J3), as described in Appendix 1, for the joint structure of the robot.

[0086] (Note 4) The joint structure of a robot according to any one of the appendices 1 to 3, wherein the fastening member (B1) has a male screw portion (B12), and the cover members (27, 37) have through holes (273, 373) through which the male screw portion (B12) passes.

[0087] (Note 5) The reduction gear (20, 30) has a second fastening member (B2) in addition to the first fastening member (B1) as a fastening member, In the state in which the lubricant-filled structure is configured, the second fastening member (B2) fastens the cover members (27, 37) to the gear support member (25) or the reduction gear case (36) without functioning as a joint fastener, as described in any of Appendix 1 to 4 of the robot joint structure.

[0088] (Note 6) In the state in which the lubricant-filled structure is configured, the plurality of first fastening members (B1) are arranged circumferentially around the axis (J2, J3), and the plurality of second fastening members (B2) are arranged circumferentially around the axis (J2, J3). The robot joint structure described in Appendix 5, wherein a first virtual ring (VC1) that virtually connects a plurality of the first fastening members (B1) is located inside a second virtual ring (VC2) that virtually connects a plurality of the second fastening members (B2).

[0089] (Note 7) The reduction gear (20) further includes an input-side cover member (28), The input-side cover member (28), together with the input shaft (23) and a sealing member (29) externally fitted to the input shaft (23), constitutes a sealed structure on the input shaft side (D21) of the reduction gear (20), as described in any of the appendices 1 to 6.

[0090] (Note 8) The joint structure of a robot according to any one of the appendices 1 to 7, wherein the surface (277) of the cover member (27) on the side (D31) of the input shaft is flat.

[0091] (Note 9) The joint structure of a robot according to any one of the appendices 1 to 7, wherein the cover member (37) has a shape capable of accommodating the gear (34) that is not housed in the reduction gear case (36) in the direction (D3) along the axis (J3). [Explanation of Symbols]

[0092] 101 Robots 110 First joint (joint) 120 Second joint (joint) 11. First arm member (first member) 20 Reducer 21. Second arm member (first member, second member) 22. Second drive motor (drive motor) 23 Input axes 24 gears 25 Gear support member 26 Gear reducer case 27 Lid component 273 Through hole 277 sides 28 Input side cover member 29. Oil seal (sealing component) 30 Reducer 31 Third arm member (second member) 32 Third drive motor (drive motor) 33 Input axes 34 gears 35 Gear support member 36 Gear reducer case 37 Lid member 373 Through hole B1 Bolt for fastening (first fastening member, fastening member) B12 1st male thread part B2 Fixing bolt D2 2nd axis direction (axial direction) D21 Input shaft side D22 Opposite side in the axial direction D3 Third axis direction (axis direction) D31 Input shaft side D32 Opposite side in the axial direction DC circumferential direction DR radial direction J2 2nd axis (axis) J3 3rd axis (axis) VC1 First Virtual Ring VC2 Second Virtual Ring

Claims

1. A robot joint structure in which a first member and a second member are connected via a joint, and the first member and the second member rotate relative to each other about an axis, A drive motor for driving the second member relative to the first member, The device comprises an input shaft to which the rotational force of the drive motor is input, a gear that transmits the rotational force of the input shaft, a gear support member that supports the gear, and a reduction gear having a reduction gear case to which the rotational force of the gear is transmitted. The gear support member is fixed to the second member, and the reduction gear case is fixed to the first member. The reduction gear further includes a cover member that covers the opposite side in the axial direction from the input shaft in the reduction gear, The reduction gear has a lubricant-sealed structure in which a lubricant is sealed inside the reduction gear. The lid member constitutes a part of the lubricant-filled structure, In the state in which the lubricant-filled structure described above is configured, the lid member is fastened together with the second member and the gear support member by a fastening member, or fastened together with the first member and the reduction gear case, in a robot joint structure.

2. In the state in which the lubricant-filled structure is configured, when the lid member is fastened together with the second member and the gear support member by the fastening member, the alignment of the gear support member with respect to the second member is defined by the second member and the gear support member contacting each other radially with respect to the axis, the robot joint structure according to claim 1.

3. In the state in which the lubricant-filled structure is configured, when the lid member is fastened together with the first member and the reduction gear case by the fastening member, the alignment of the reduction gear case with respect to the first member is defined by the first member and the reduction gear case contacting each other radially with respect to the axis, the joint structure of a robot according to claim 1.

4. The joint structure for a robot according to any one of claims 1 to 3, wherein the fastening member has a male screw portion, and the cover member has a through hole through which the male screw portion passes.

5. The reduction gear has a second fastening member in addition to the first fastening member, which is a fastening member. In the state in which the lubricant-filled structure is configured, the second fastening member fastens the lid member to the gear support member or the reduction gear case without functioning as a joint fastener, as described in any one of claims 1 to 3.

6. In the state in which the lubricant-filled structure is configured, the plurality of first fastening members are arranged circumferentially around the axis, and the plurality of second fastening members are arranged circumferentially around the axis. The first virtual ring that virtually connects the plurality of first fastening members is located inside the second virtual ring that virtually connects the plurality of second fastening members. The robot joint structure according to claim 5.

7. The aforementioned reduction gear further includes an input-side cover member, The joint structure of a robot according to any one of claims 1 to 3, wherein the input-side cover member, together with the input shaft and a sealing member fitted externally to the input shaft, constitutes a sealing structure on the input shaft side of the reduction gear.

8. The joint structure of a robot according to any one of claims 1 to 3, wherein the surface of the cover member on the side of the input shaft is flat.

9. The joint structure for a robot according to any one of claims 1 to 3, wherein the cover member has a shape capable of accommodating the gears that are not housed in the reduction gear case in a direction along the axis.

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