Robot joint structure

Abstract

To provide a technique capable of suppressing adverse effect on meshing of an internal tooth gear with an external tooth gear in pressure-welding of a part of a speed reducer with a first robot member in a radial direction.SOLUTION: A joint structure for a robot comprises a first robot member 14, a second robot member, and a speed reducer assembled into a joint part that connects the first robot member 14 with the second robot member. The speed reducer includes an external tooth gear, an internal tooth gear 32 meshed with the external tooth gear, and a fixing member 34 provided so as to be relatively non-rotatable to the internal tooth gear 32 and fixed to the first robot member 14. The fixing member 34 is fixed to the first robot member 14 by pressure-welding of an inner peripheral surface of the first robot member 14 with an outer peripheral surface of the fixing member 34 through fastening of a first fastening member B1. At least a part of an axial range A1 of the first fastening member B1 does not overlap with an internal tooth 32b of the internal tooth gear 32 when viewed from a radial direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a joint structure for a robot. [Background technology]

[0002] Patent Document 1 discloses a joint structure including a first robot member, a second robot member, and a reduction gear incorporated in a joint that connects the first robot member and the second robot member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-181623 Summary of the Invention [Problem to be solved by the invention]

[0004] Customers have various requests regarding the manner in which the reduction gear transmission is fixed to the first robot member. One example of such a fastening method is to radially press a portion of the reduction gear transmission against the first robot member. However, when this method is adopted, a radial load acts on the reduction gear transmission, which can adversely affect the meshing between the internal gear and the external gear. No technology has yet been proposed that addresses this issue.

[0005] An object of the present disclosure is to provide a technique that can suppress adverse effects on the meshing between the internal gear and the external gear when a part of a reduction gear transmission and a first robot member are brought into radial pressure contact. [Means for solving the problem]

[0006] The robot joint structure disclosed herein is a robot joint structure comprising a first robot member, a second robot member, and a reduction gear incorporated in a joint section connecting the first robot member and the second robot member, wherein the reduction gear comprises an external gear, an internal gear that meshes with the external gear, and a fixed member that is fixed to the first robot member and is unable to rotate relative to the internal gear, and wherein the fixed member is fixed to the first robot member by fastening a first fastening member to press the inner circumferential surface of the first robot member against the outer circumferential surface of the fixed member, and at least a portion of the axial range of the first fastening member does not overlap with the internal teeth of the internal gear when viewed radially. [Effects of the Invention]

[0007] According to the present disclosure, adverse effects on the meshing between the internal gear and the external gear can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a side cross-sectional view showing a joint structure of a first embodiment. [Figure 2] FIG. 2 is a side cross-sectional view showing a part of the joint structure of the first embodiment. [Figure 3] FIG. 4 is another side cross-sectional view showing a part of the joint structure of the first embodiment. [Figure 4] FIG. 10 is a side cross-sectional view showing the joint structure of the second embodiment. [Figure 5] FIG. 10 is a perspective view showing a joint structure of a second embodiment. [Figure 6] FIG. 5 is a schematic cross-sectional view showing a part of the cross section taken along line XX in FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes the embodiments. Identical components are designated by the same reference numerals, and redundant explanations will be omitted. In each drawing, components are omitted, enlarged, or reduced as appropriate for the sake of convenience. The drawings should be viewed in accordance with the orientation of the reference numerals.

[0010] (First embodiment) See Fig. 1. A robot 12 in which the joint structure 10 of this embodiment is used is a multi-joint robot, and is used as an industrial robot, a service robot (for example, a cooking robot, a household robot, a medical robot, etc.), etc. Although not shown, the robot 12 includes a base and a plurality of arms supported by the base and connected in series.

[0011] The robot joint structure 10 includes a first robot member 14, a second robot member 16, and an actuator 22 including a reduction gear 20 incorporated in a joint 18 connecting these members. The first robot member 14 and the second robot member 16 serve as either an arm or a base of the robot 12. Here, an example is shown in which both the first robot member 14 and the second robot member 16 serve as arms, but one of them may serve as a base. In this embodiment, the first robot member 14 serves as a support member that supports the actuator 22, and the second robot member 16 serves as a driven member that is driven by the actuator 22.

[0012] The first robot member 14 of this embodiment includes a cylindrical first casing 14a that houses the reduction gear 20 and a second casing 14b that houses the drive unit 26. The first casing 14a and the second casing 14b of this embodiment are separate members and are fixed together using bolts or the like. The second robot member 16 includes a cylindrical third casing 16a that is provided on an extension of the first casing 14a in the axial direction X.

[0013] In addition to the reduction gear 20, the actuator 22 includes a drive device 26 that inputs rotational power to the reduction gear 20. In this embodiment, the drive device 26 is a motor, but the specific example is not particularly limited and may be a gear motor, an engine, or the like. The actuator 22 is formed with a hollow portion 22a that penetrates the actuator 22 in the axial direction X (described later). Wiring members such as cables used in the robot 12 are inserted into the hollow portion 22a.

[0014] The reduction gear 20 includes an input shaft 28 to which rotational power is input from the drive device 26, an external gear 30 driven by the input shaft 28, and a plurality of internal gears 32, 33 that mesh with the external gear 30. In addition, the reduction gear 20 includes a fixed member 34 fixed to the first robot member 14 so as not to rotate relative to the internal gear 32, a main bearing 36 that connects (supports) the first robot member 14 and the second robot member 16 so as to be rotatable relative to each other, a bearing housing 38 that accommodates the main bearing 36, and a synchronizing member 40 fixed to the second robot member 16 and that can synchronize with the rotation component of the external gear 30. The fixed member 34, main bearing 36, bearing housing 38, and synchronizing member 40 will be described later; first, the surrounding structure will be described.

[0015] In this specification, the direction along the center C32 of the internal gear 32 is referred to as the axial direction X, and the radial and circumferential directions about the center C32 are also simply referred to as the radial and circumferential directions. For ease of explanation, one side of the axial direction X (the right side in FIG. 1) is referred to as the input side, and the other side of the axial direction X is referred to as the non-input side.

[0016] The external gear 30 and the internal gears 32, 33 constitute a gear mechanism that outputs output rotation that is reduced in speed relative to the rotation of the input shaft 28. The gear mechanism can rotate one of the external gear 30 and the internal gears 32, 33 by driving the external gear 30 via the input shaft 28. The reduction gear transmission 20 of this embodiment is a flexible mesh reduction gear in which the external gear 30 is a flexible gear. The reduction gear transmission 20 of this embodiment is also a cylindrical flexible mesh reduction gear having a first internal gear 32 and a second internal gear 33 as the internal gears 32, 33. The first internal gear 32 is connected to the first robot member 14 via a fixed member 34 so as not to rotate relative to the first robot member 14. The second internal gear 33 is connected to the second robot member 16 via a synchronizer 40 so as not to rotate relative to the second robot member 16. In this embodiment, the first internal gear 32 is a stationary internal gear that is fixed so as not to rotate relative to the support member (first robot member 14). The second internal gear 33 serves as a driving-side internal gear that drives the driven member (second robot member 16) by outputting output rotation.

[0017] The input shaft 28 is provided so as to be able to transmit rotational power from the output shaft 26a of the drive unit 26. To achieve this, the input shaft 28 of this embodiment is connected to the output shaft 26a using a connecting member 42 so as to be able to rotate integrally with the input shaft 28. The input shaft 28 is provided with a gear drive unit 28a that drives the external gear 30 by rotating about its own rotation center line C28. The gear drive unit 28a of the input shaft 28 used in the flexible mesh reduction gear transmission 20 is a vibrator that drives the external gear 30 by causing flexible deformation. The gear drive unit 28a that serves as the vibrator has an elliptical shape in a cross section perpendicular to the axial direction X. Here, the term "ellipse" is not limited to a geometrically strict ellipse, but also includes an approximate ellipse.

[0018] The external gear 30, which serves as a flexible gear, is a flexible cylindrical member that can be flexibly deformed by rotation of the gear drive portion 28a of the input shaft 28. The external gear 30 is supported for relative rotation on the input shaft 28 via a gear bearing 44 that is arranged between the external gear 30 and the gear drive portion 28a of the input shaft 28. The gear bearing 44 in this embodiment is a double-row bearing, but the type is not particularly limited, and may be, for example, a single-row bearing such as a roller bearing, a needle bearing, or a ball bearing.

[0019] Unlike the external gear 30, which is a flexible gear, the internal gears 32, 33 of this embodiment have sufficient rigidity not to deform in response to the rotation of the input shaft 28. The first internal gear 32 is provided on the inner periphery of the first internal gear member 46 as part of the first internal gear member 46. The first internal gear member 46 is integrally formed with the first internal gear 32 from the same material. The first internal gear 32 is configured by providing multiple first internal teeth 32b on the inner periphery of a first annular portion 32a provided in the first internal gear member 46. The second internal gear 33 is provided on the inner periphery of the second internal gear member 47 as part of the second internal gear member 47. The second internal gear member 47 is integrally formed with the second internal gear 33 from the same material. The second internal gear 33 is configured by providing multiple second internal teeth 33b on the inner periphery of a second annular portion 33a provided in the second internal gear member 47.

[0020] The operation of the reduction gear 20 will now be described. In the case of the flexible mesh reduction gear 20, when the gear drive portion 28a of the input shaft 28, which serves as the vibration exciter, rotates, the external gear 30 (flexible gear) flexibly deforms to form an elliptical shape that matches the shape of the gear drive portion 28a. When the external gear 30 flexibly deforms in this manner, the meshing position between the external gear 30 and the internal gears 32, 33 changes in the direction of rotation of the input shaft 28. In this example, the number of teeth of the first internal gear 32 (e.g., 102) is 2×n more (n is a positive integer) than the number of teeth of the external gear 30 (e.g., 100), and the number of teeth of the second internal gear 33 is the same as the number of teeth of the external gear 30. Therefore, every time the input shaft 28 rotates once, the external gear 30 rotates by an amount corresponding to the difference in the number of teeth between the first internal gear 32 and the external gear 30, and this rotation component is output from the second internal gear 33, which serves as the driving internal gear, to the second robot member 16, which serves as the driven member. At this time, an output rotation is output that is reduced in speed relative to the input rotation of the input shaft 28 at a reduction ratio according to the number of teeth of the external gear 30 and the internal gears 32, 33.

[0021] Please refer to Figure 2. We will now move on to explaining the fixed member 34 and other components. The fixed member 34 is arranged on the input side of the first internal gear 32 (first internal gear member 46). The fixed member 34 in this embodiment is a separate member from the first internal gear 32 (first internal gear member 46). The fixed member 34 has a continuous disk shape around the center C32 of the first internal gear 32, and the input shaft 28 passes through the inside of the fixed member 34.

[0022] The fixing member 34 is fixed to the first robot member 14 so as not to rotate relative to it by fastening the first fastening member B1, which causes the inner peripheral surface of the first robot member 14 and the outer peripheral surface of the fixing member 34 to be pressed together in the radial direction. Here, "fastening a fastening member" refers to fastening multiple fastened members by applying a fastening force along the shaft of the first fastening member B1 to the multiple fastened members. The first fastening member B1 in this embodiment radially fastens the first robot member 14 and the fixing member 34 as the multiple fastened members. Here, "radially fastening" refers to fastening multiple fastened members by applying a fastening force along the radial direction.

[0023] The fixing member 34 is made of a material with a larger Young's modulus [N / mm2] than the first internal gear 46, i.e., the first internal gear 32. To achieve this, for example, the first internal gear 46 may be made of a resin-based material, and the fixing member 34 may be made of a metal-based material. The resin-based material refers to a material primarily made of resin. The resin-based material may be, for example, a material made solely of resin, such as general-purpose engineering plastic or special engineering plastic, or a composite material made of resin, such as carbon fiber reinforced resin or glass fiber reinforced resin. The metal-based material refers to a material primarily made of metal. The metal-based material may be, for example, a material made solely of metal, such as an iron-based material, an aluminum-based material, or an alloy, or a composite material made of metal, such as a fiber-reinforced metal. Note that the material of each component is not particularly limited. In this embodiment, not only the first internal gear 46 but also the second internal gear 47 and the synchronizing member 40 are made of a resin-based material to reduce weight. On the other hand, the bearing housing 38 is made of a material having a larger Young's modulus than the first internal gear 32, such as a metallic material.

[0024] The first fastening member B1 in this embodiment is a bolt, but the specific example is not particularly limited and may be a rivet (e.g., a blind rivet), for example. The first robot member 14 has a first counterbore hole 14c provided on the outer peripheral surface of the first robot member 14 to accommodate the head of the first fastening member B1. The first counterbore hole 14c is formed as a recess recessed radially inward in the first casing 14a of the first robot member 14. The fixing member 34 has a first female screw hole 34a into which the first fastening member B1 is screwed in the radial direction.

[0025] Consider an axial range A1 of the first fastening member B1. At least a portion of the axial range A1 does not overlap with the first internal teeth 32b of the first internal gear 32 when viewed from the radial direction. In this embodiment, the entire axial range A1 does not overlap with the first internal teeth 32b when viewed from the radial direction. To satisfy this condition, the first fastening member B1 of this embodiment is positioned closer to the input side than the first internal teeth 32b.

[0026] The first robot member 14 has a first inner step portion 14d that contacts the fixed member 34 from the input side, thereby positioning the fixed member 34 in the axial direction X. The fixed member 34 is fixed to the first robot member 14 by screwing a first fastening member B1 radially into the fixed member 34 while the fixed member 34 is in contact with the first inner step portion 14d of the first robot member 14.

[0027] Referring to FIG. 1 , the fixing member 34 of this embodiment is provided by the second fastening member B2 so as to be non-rotatable relative to the first internal gear 32 (first internal gear member 46). The second fastening member B2 of this embodiment is a bolt, but the specific example is not particularly limited, and it may be a rivet (e.g., a blind rivet, etc.). The second fastening member B2 fastens the first internal gear 32 and the fixing member 34 in the axial direction X, thereby preventing the first internal gear 32 and the fixing member 34 from rotating relative to each other. The first internal gear member 46 has a second female threaded hole 46a into which the second fastening member B2 is screwed in the axial direction. The first internal gear member 46 has a first protruding portion 46b that protrudes toward the input side beyond the first internal teeth 32b of the first internal gear 32. The second female threaded hole 46a is formed in an axial range including the first protruding portion 46b. The fixing member 34 has a second countersunk hole 34b that receives the head of the second fastening member B2. The second countersunk hole 34b is provided at a position that radially overlaps the axial position of the pressure-welded portion 60 of the fixed member 34 relative to the first robot member 14. The second countersunk hole 34b is formed as a recess that recesses from the input side surface of the fixed member 34 toward the non-input side.

[0028] The fixing member 34 has a second protruding portion 34c that is positioned radially inward of the first protruding portion 46b and protrudes toward the non-input side. The second protruding portion 34c contacts the external gear 30 from the input side and restricts axial movement of the external gear 30. To achieve this, the fixing member 34 in this embodiment directly contacts the external gear 30, but may also contact it via a spacer.

[0029] Refer to Figure 3. The main bearing 36 is disposed between a bearing housing 38 and a synchronizing member 40. The bearing housing 38 is provided so as to be non-rotatable relative to the first robot member 14, and the synchronizing member 40 is provided so as to be non-rotatable relative to the second robot member 16. The main bearing 36 of this embodiment connects (supports) the bearing housing 38 and the synchronizing member 40 so as to be rotatable relative to each other, thereby connecting (supporting) the first robot member 14 and the second robot member 16 so as to be rotatable relative to each other.

[0030] The main bearing 36 of this embodiment is a cross roller bearing, and includes a dedicated outer ring 36b and inner ring 36c in addition to the rolling elements 36a. Specific examples of the main bearing 36 are not particularly limited, and it may be composed of a single bearing such as a ball bearing, or multiple bearings (angular contact ball bearings, tapered bearings) spaced apart in the axial direction. The main bearing 36 may not include a dedicated outer ring 36b, and the inner peripheral surface of the bearing housing 38 may serve as this. Furthermore, the main bearing 36 may not include a dedicated inner ring 36c, and the outer peripheral surface of the synchronizing member 40 may serve as this.

[0031] The main bearing 36 is positioned offset in the axial direction X from the first internally geared member 46 and the second internally geared member 47. This means that the main bearing 36 is positioned offset in the axial direction X from a certain axial range of the first internally geared member 46 and the second internally geared member 47. The inner diameter R36-1 of the main bearing 36 is smaller than the outer diameters R46 and R47 of the internally geared members 46 and 47. Here, the outer diameters R46 and R47 refer to the largest outer diameters of the first internally geared member 46 and the second internally geared member 47, respectively. Furthermore, in this specification, "inner diameter" and "outer diameter" both refer to radii. When multiple internally geared members 46 and 47 are present, as in this embodiment, it is sufficient that this condition is satisfied between the main bearing 36 and any of the internally geared members 46 and 47. In this embodiment, the inner diameter R36-1 is smaller than both the outer diameters R46 and R47. The outer diameter R36-2 of the main bearing 36 is smaller than the outer diameters R46 and R47 of the internally geared members 46 and 47. When there are multiple internally toothed members 46, 47 as in the present embodiment, it is sufficient that this condition is satisfied between any of the internally toothed members 46, 47. The outer diameter R36-2 in this embodiment is smaller than both the outer diameters R46, R47. Note that in this embodiment, the inner diameter R36-1 is smaller than the inner diameters of the tip circles of the first internally toothed member 46 and the second internally toothed member 47. Furthermore, the outer diameter R36-2 is larger than the inner diameters of the tip circles of the first internally toothed member 46 and the second internally toothed member 47.

[0032] The bearing housing 38 is disposed radially outward of the main bearing 36. The bearing housing 38 in this embodiment is configured as a separate member from the first robot member 14. The first robot member 14 in this embodiment has a second inner step portion 14e that can position the bearing housing 38 in the axial direction by coming into contact with the bearing housing 38 from the input side.

[0033] The bearing housing 38 of this embodiment is formed by combining multiple housing members 38a and 38b. The multiple housing members 38a and 38b include a first housing member 38a disposed radially outward from the main bearing 36 and a second housing member 38b disposed radially inward from the first housing member 38a. The first housing member 38a is provided with a first movement restricting portion 38c that contacts the main bearing 36 from the input side to restrict axial movement of the main bearing 36 toward the input side. In this embodiment, the first movement restricting portion 38c is formed by an inner step provided on the first housing member 38a, but may also be formed by a snap ring or the like provided on the first housing member 38a. The second housing member 38b is provided with a second movement restricting portion 38d that contacts the main bearing 36 from the non-input side to restrict axial movement of the main bearing 36 toward the non-input side. In this embodiment, the second movement restricting portion 38d is configured by an inner step provided on the second housing member 38b, but may also be configured by a snap ring or the like provided on the second housing member 38b. The main bearing 36 is positioned axially with respect to the bearing housing 38 by coming into contact with the first movement restricting portion 38c and the second movement restricting portion 38d of the bearing housing 38.

[0034] The bearing housing 38 is radially fastened to the first robot member 14 by the third fastening member B3. The bearing housing 38 is fixed to the first robot member 14 by pressing the inner circumferential surface of the first robot member 14 against the outer circumferential surface of the bearing housing 38 by fastening the third fastening member B3. In this embodiment, the third fastening member B3 is a bolt, but the specific example is not particularly limited and may be a rivet (e.g., a blind rivet). The first robot member 14 has a third counterbore hole 14f provided on the outer circumferential surface of the first robot member 14 to accommodate the head of the third fastening member B3. The third counterbore hole 14f is formed as a recess recessed radially inward in the first casing 14a of the first robot member 14. The bearing housing 38 has a third female threaded hole 38e into which the third fastening member B3 is radially screwed. The third female threaded hole 38e is formed in the second housing member 38b of the bearing housing 38. The first housing member 38a of the bearing housing 38 is formed with an insertion hole 38f without threads for radially passing the shaft portion of the third fastening member B3 therethrough.

[0035] Consider the axial range A3 of the third fastening member B3. At least a portion of the axial range A3 does not overlap with the first internal teeth 32b of the first internal gear 32 or the second internal teeth 33b of the second internal gear 33 when viewed from the radial direction. In this embodiment, the entire axial range A3 satisfies this condition. To satisfy this condition, the third fastening member B3 in this embodiment is positioned on the anti-input side of the second internal teeth 33b of the second internal gear 33. This means that neither the entire axial range A1 of the first fastening member B1 nor the entire axial range A3 of the third fastening member B3 overlaps with the first internal teeth 32b of the first internal gear 32 or the second internal teeth 33b of the second internal gear 33 when viewed from the radial direction.

[0036] The synchronizing member 40 is disposed on one axial side (here, the non-input side) of the external gear 30. The synchronizing member 40 of this embodiment includes a first synchronizing component 40a disposed on the external gear 30 side in the axial direction X, and a second synchronizing component 40b disposed on the axially opposite side of the external gear 30 with respect to the first synchronizing component 40a.

[0037] The synchronizing member 40 is radially fastened to the second robot member 16 by fourth fastening members B4 such as bolts. A fourth female screw hole 40c is provided in a flange portion 40i (described later) of the second synchronizing part 40b of the synchronizing member 40, into which the fourth fastening member B4 is radially screwed. A fourth counterbore hole 16b is provided in the third casing 16a of the second robot member 16 to accommodate the head of the fourth fastening member B4. The fourth counterbore hole 16b is formed as a recess that recesses radially inward of the third casing 16a of the second robot member 16.

[0038] The first synchronizing component 40a includes a first outer diameter portion 40d fastened to the second internal gear member 47 in the axial direction X by a fifth fastening member B5 such as a bolt, and a second outer diameter portion 40e having an outer diameter smaller than that of the first outer diameter portion 40d. The main bearing 36 is disposed on the second outer diameter portion 40e. The second outer diameter portion 40e is provided with a stepped shoulder portion 40f that contacts the main bearing 36 from the axial input side to restrict axial movement of the main bearing 36. The second internal gear member 47 includes a fifth female threaded hole 47a into which the fifth fastening member B5 is threaded in the axial direction. The second internal gear member 47 includes a third protruding portion 47b that protrudes toward the non-input side beyond the second internal teeth 33b of the second internal gear member 47. The fifth female threaded hole 47a is formed in an axial range that includes the third protruding portion 47b.

[0039] The first synchronizing component 40a has a fourth protruding portion 40g that is positioned radially inward of the third protruding portion 47b and protrudes toward the input side. The second internal gear member 47 and the first synchronizing component 40a are fastened in the axial direction X by a fifth fastening member B5 with the third protruding portion 47b and the fourth protruding portion 40g in a spigot-fit state, thereby preventing relative rotation. The fourth protruding portion 40g contacts the external gear 30 from the non-input side and restricts axial movement of the external gear 30. To achieve this, the fourth protruding portion 40g in this embodiment directly contacts the external gear 30, but may also contact the external gear 30 via a spacer.

[0040] The second synchronizing component 40b is fastened to the first synchronizing component 40a in the axial direction X by screwing a sixth fastening member B6, such as a bolt, in the axial direction. The second synchronizing component 40b includes a movement restricting portion 40h provided on the input side of the second synchronizing component 40b and protruding toward the input side. The movement restricting portion 40h of the second synchronizing component 40b is spigot-fitted with the non-input side end of the first synchronizing component 40a. The movement restricting portion 40h of the second synchronizing component 40b contacts the main bearing 36 from the non-input side in the axial direction X, thereby restricting axial movement of the main bearing 36. The second synchronizing component 40b includes a flange portion 40i provided on the non-input side of the second synchronizing component 40b and protruding radially outward. The flange portion 40i of the second synchronizing component 40b is disposed inside the third casing 16a of the second robot member 16. The third casing 16a has an inner surface provided with a fitting portion 16c into which a flange portion 40i of the second synchronizing component 40b is fitted.

[0041] The gear unit 62, which is a combination of the input shaft 28, the internal gears 32 and 33, the external gear 30, and the gear bearing 44 used in the joint structure 10 of this embodiment, can be handled as a component independent of the other elements used in the joint structure 10. A user of this gear unit 62 can obtain the joint structure 10 by combining the gear unit 62 provided by a provider (e.g., a manufacturer or a seller) with other elements prepared by the user separately from the gear unit 62.

[0042] The effects of the above-described joint structure 10 will now be described.

[0043] When a part of the reduction gear 20 (here, the fixed member 34) and the first robot member 14 are brought into radial pressure contact, a radial load F1 resulting from fastening the first fastening member B1 acts on the reduction gear 20. In this embodiment, a tensile force acting radially outward acts on the fixed member 34, which is the fastened member, as the radial load F1 due to fastening the first fastening member B1 (see FIG. 2). If the fixed member 34 is deformed together with the first internal gear 32 having the first internal teeth 32b due to this radial load F1, this may have an adverse effect on the meshing between the first internal gear 32 and the external gear 30.

[0044] (A) Here, at least a portion of the axial range A1 of the first fastening member B1 does not overlap with the first internal teeth 32b of the first internal gear 32 when viewed from the radial direction. Therefore, compared to a case where the entire axial range A1 of the first fastening member B1 overlaps with the first internal teeth 32b, it is possible to make it less likely that the radial load F1 caused by fastening the first fastening member B1 will act on the first internal gear 32. Consequently, the first internal gear 32 is less likely to be deformed by the radial load F1 caused by the first fastening member B1, and it is possible to suppress the adverse effects of the radial load F1 on the meshing between the first internal gear 32 and the external gear 30.

[0045] (B) In particular, in this embodiment, the entire axial range A1 of the first fastening member B1 does not overlap, when viewed radially, with the first internal teeth 32b of the first internal gear 32. This makes it even more difficult for the radial load F1 caused by the first fastening member B1 to act on the first internal gear 32.

[0046] Consider a case in which the first robot member 14 and the fixed member 34 are fastened together in the axial direction X by the first fastening member B1. In this case, the seating surface (the bottom surface of the first countersunk hole 14c) on which the first fastening member B1 sits extends radially, which tends to increase the outer diameter of the first robot member 14. In this regard, the first fastening member B1 of this embodiment fastens the first robot member 14 and the fixed member 34 together in the radial direction, thereby bringing the first robot member 14 and the fixed member 34 into pressure contact. Therefore, the seating surface for the first fastening member B1 on the first robot member 14 does not need to extend radially, which makes it easy to reduce the outer diameter of the first robot member 14 around the first fastening member B1. This is particularly effective in that the outer diameter of the first robot member 14 can be reduced while maintaining the inner diameter of the hollow portion 22a of the actuator 22.

[0047] (C) The fixing member 34 is a separate member from the first internal gear 32. Therefore, compared to when the first internal gear 32 and the fixing member 34 are configured from the same member, the radial load F1 caused by the first fastening member B1 is less likely to act on the first internal gear 32.

[0048] (D) The fixing member 34 is made of a material with a larger Young's modulus than the first internal gear 32. Therefore, compared to when the fixing member 34 is matched to the Young's modulus of the first internal gear 32, the fixing member 34 is less likely to be deformed by the radial load F1, and the radial load F1 is even less likely to act on the first internal gear 32.

[0049] The bearing housing 38 is fastened to the first robot member 14 in the radial direction by the third fastening member B3. Therefore, compared to when the bearing housing 38 and the first robot member 14 are fastened in the axial direction X, it is not necessary to extend the seat surface (the bottom surface of the third countersunk hole 14f) for the third fastening member B3 in the first robot member 14 in the radial direction. Consequently, the outer diameter of the first robot member 14 around the third fastening member B3 can be easily reduced.

[0050] When the bearing housing 38 and the first robot member 14 are radially fastened by the third fastening member B3, a radial load F3 acts on the bearing housing 38 due to the fastening of the third fastening member B3. In this embodiment, a tensile force acting radially outward acts on the bearing housing 38 as the radial load F3 due to the fastening of the third fastening member B3 (see FIG. 3). Here, the axial range A3 of the third fastening member B3 does not overlap with the second internal teeth 33b of the second internal gear 33 when viewed from the radial direction. Therefore, compared to when the axial range A3 of the third fastening member B3 overlaps with the second internal teeth 33b, the radial load F3 acting due to the fastening of the third fastening member B3 is less likely to act on the second internal gear 33. As a result, the second internal gear 33 is less likely to deform due to the radial load F3 caused by the third fastening member B3, and the adverse effect of the radial load F3 on the meshing between the second internal gear 33 and the external gear 30 can be suppressed.

[0051] In order to suppress such adverse effects on the meshing between the second internal gear 33 and the external gear 30, it is more preferable to adopt the configuration described below. The axial range A3 of the third fastening member B3 does not overlap with the second internal gear member 47 when viewed from the radial direction. The third fastening member B3 of this embodiment is positioned on the anti-input side of the second internal gear member 47. At least a portion of the axial range A3 does not overlap with the main bearing 36 when viewed from the radial direction, and is positioned on the anti-input side of the main bearing 36. The entire axial range A3 of this embodiment is positioned on the anti-input side of the main bearing 36.

[0052] The synchronizer 40 is fastened to the second robot member 16 in the radial direction by the fourth fastening member B4. Therefore, it is not necessary to extend the bearing surface (the bottom surface of the fourth countersunk hole 14b) for the fourth fastening member B4 in the second robot member 16 in the radial direction. Consequently, the outer diameter of the second robot member 16 around the fourth fastening member B4 can be easily reduced.

[0053] (E) The inner diameter R36-1 of the main bearing 36 is smaller than the outer diameters R46, R47 of the internal gear members 46, 47. Therefore, compared to when the inner diameter R36-1 of the main bearing 36 is set to be equal to or larger than the outer diameters R46, R47 of the internal gear members 46, 47, the outer diameter of the first robot member 14 can be easily reduced in size.

[0054] Second Embodiment: See Figures 4, 5, and 6. The joint structure 10 of the second embodiment differs from the joint structure 10 of the first embodiment mainly in the first robot member 14, the second robot member 16, the bearing housing 38, and the synchronizing member 40.

[0055] The bearing housing 38 of this embodiment also serves as part of the first robot member 14 (here, the first casing 14a), and is integrally formed from the same material as that part of the first robot member 14. The bearing housing 38 of this embodiment also includes a first movement restricting portion 38c and a second movement restricting portion 38d similar to those of the first embodiment, and positions the main bearing 36 in the axial direction X.

[0056] The synchronizing member 40 of this embodiment includes only the first synchronizing component 40a out of the first synchronizing component 40a and the second synchronizing component 40b, but does not include the second synchronizing component 40b. The second robot member 16 is fastened to the synchronizing member 40 by a sixth fastening member B6 and includes a movement restricting portion 40h similar to the second synchronizing component 40b.

[0057] The first robot member 14 has a plurality of divided sections 80 (two in this embodiment) formed by dividing a part of the first robot member 14 (here, the first casing 14a) in the circumferential direction. The plurality of divided sections 80 as a whole have a cylindrical cross section in a cross section perpendicular to the axial direction X. Adjacent divided sections 80 have butt ends 80a provided at the circumferential ends of the individual divided sections 80 and butting against each other. The plurality of divided sections 80 are fastened in the circumferential direction (tangential direction) by a first fastening member B1 arranged on the input side and a third fastening member B3 arranged on the anti-input side.

[0058] In this embodiment, the first fastening member B1 fastens the multiple segments 80 as multiple fastened members in the circumferential direction, thereby pressing a portion of the first robot member 14 (here, the first casing 14a) comprising the multiple segments 80 against the fixed member 34. Here, "fastening in the circumferential direction" refers to fastening the multiple segments 80 by applying a fastening force in the tangential direction on the outer circumferential surface of the first robot member 14. The fixed member 34 is fixed to the first robot member 14 by friction applied to the pressure contact points 60 with the first robot member 14 by the fastening force of the first fastening member B1. The first fastening member B1 is used individually for each butt end 80a on both circumferential sides of the segment 80, and fastens the butt end 80a of adjacent segments 80.

[0059] At least a part of the axial range A1 of the first fastening member B1 is disposed in a position that does not overlap with the fixed member 34 when viewed from the radial direction. To satisfy this condition, at least a part of the first fastening member B1 is disposed on the opposite side (input side) of the first internal gear 32 in the axial direction X with respect to the fixed member 34. At least a part of the axial range A1 of the first fastening member B1 in this embodiment is disposed on the input side of the first internal step portion 14d of the first robot member 14.

[0060] The third fastening member B3 of this embodiment fastens the multiple segments 80 together in the circumferential direction, thereby also serving as the bearing housing 38 and pressing a part of the first robot member 14 (here, the first casing 14a) that constitutes the multiple segments 80 against the main bearing 36. Like the first fastening member B1, the third fastening member B3 is used individually for each of the butt end portions 80a on both circumferential sides of the segments 80, and fastens the butt end portions 80a of adjacent segments 80 together.

[0061] Consider the axial range A3 of the third fastening member B3. The axial range A3 of the third fastening member B3 has similar characteristics to the axial range A3 of the third fastening member B3 of the first embodiment. For example, at least a portion of the axial range A3 of the third fastening member B3 does not overlap with either the first internal teeth 32b of the first internal gear 32 or the second internal teeth 33b of the second internal gear 33 when viewed from the radial direction.

[0062] The first fastening member B1 and the third fastening member B3 of this embodiment include a bolt 82 and a nut 84. The bolt 82 is inserted into an insertion hole 80b provided in the butt ends 80a of adjacent divided sections 80. The outer peripheral surface of the first robot member 14 includes a first counterbore hole 14c that accommodates the head of the bolt 82 and the nut 84, respectively.

[0063] The effects of the above-described joint structure 10 will now be described.

[0064] In this embodiment, due to the fastening of the first fastening member B1, a load directed radially inward from the divided portion 80, which is the fastened member, acts on the fixed member 34 as a radial load F1 (see FIG. 6). As described above, at least a portion of the axial range A1 of the first fastening member B1 does not overlap with the first internal teeth 32b of the first internal gear 32 when viewed from the radial direction. Therefore, as described above, it is possible to make it difficult for the radial load F1 caused by the first fastening member B1 to act on the first internal gear 32. Consequently, even when multiple divided portions 80 are fastened in the circumferential direction, it is possible to suppress the adverse effects of the radial load on the meshing between the first internal gear 32 and the external gear 30, as in (A) above.

[0065] Furthermore, a load directed radially inward from the divided portion 80 acts as a radial load (not shown) on the main bearing 36 due to fastening of the third fastening member B3. Here, the axial range A3 of the third fastening member B3 does not overlap with the second internal teeth 33b of the second internal gear 33 when viewed from the radial direction. Therefore, compared to when the axial range A3 of the third fastening member B3 overlaps with the second internal teeth 33b, it is possible to make it more difficult for the radial load acting due to fastening of the third fastening member B3 to act on the second internal gear 33.

[0066] In addition, the joint structure 10 of this embodiment includes the components (not shown) described above in (B) to (E), and provides the effects corresponding to those descriptions.

[0067] Next, variations of the components described above will be described.

[0068] Although the reduction gear 20 has been described as a flexible mesh reduction gear, the type is not limited to this. For example, the reduction gear 20 may be an eccentric oscillating reduction gear that uses a crankshaft as the input shaft. In this case, the reduction gear 20 may be a center crank type in which the crankshaft is located at the center of the internal gear, or a distributed type in which multiple crankshafts are located at positions offset from the center of the internal gear. In this case, the number of internal gears may be one. Furthermore, in the case of a flexible mesh reduction gear, a cylindrical type having two internal gears 32, 33 has been described as a specific example, but the type is not limited to this. For example, a cup type or top hat type having one internal gear may also be used. Furthermore, the reduction gear 20 may be a simple planetary gear device.

[0069] In the embodiment, an example has been described in which the first robot member 14 serves as a supporting member and the second robot member 16 serves as a driven member. Alternatively, the first robot member 14 may serve as a driven member and the second robot member 16 may serve as a supporting member. In this case, when a cylindrical flexible mesh reduction gear transmission is used, the first internal gear 32 may serve as a driving-side internal gear that drives the first robot member 14, which serves as a driven member, and the second internal gear 33 may serve as a stationary-side internal gear that is fixed to the second robot member 16, which serves as a supporting member.

[0070] In the case of an eccentric oscillating reduction gear device, the gear drive portion 28a of the input shaft 28 may be an eccentric body that drives by oscillating the external gear 30. In this case, the synchronizing member 40 may be disposed on one axial side of the external gear 30 and serve as a carrier that can be synchronized with the rotation component of the external gear 30 by a pin that penetrates the external gear 30.

[0071] The fixing member 34 may be fixed to the first robot member 14 by fastening the first fastening member B1 to press the first robot member 14 and the fixing member 34 together in the radial direction, and the specific structure for this is not limited to that described in the embodiment. The fixing member 34 may be formed integrally with the internal gear 32 using the same material. The Young's modulus of the fixing member 34 may be equal to or less than the Young's modulus of the internal gear 32.

[0072] At least a portion of the axial range A1 of the first fastening member B1 does not need to overlap with the internal teeth 32b of the internal gear 32 when viewed from the radial direction, and a portion of the first fastening member B1 may overlap with the internal teeth 32b of the internal gear 32.

[0073] The means for preventing relative rotation between the internal gear 32 and the fixed member 34 is not limited to the second fastening member B2. For example, a spline, a key or other fitting may be used to achieve this.

[0074] The means for preventing relative rotation between the bearing housing 38 and the first robot member 14 is not limited to the third fastening member B3. For example, a spline, key, or other fitting may be used to achieve this. The bearing housing 38 may also be fastened to the first robot member 14 in the axial direction X by the third fastening member B3.

[0075] Although the bearing housing 38 has been described as being formed by combining multiple housing members 38a and 38b, it may also be formed from a single member. In this case, the bearing housing 38 may also be provided with multiple movement restricting portions 40h.

[0076] The third fastening member B3 may overlap either the first internal teeth 32b of the first internal gear 32 or the second internal teeth 33b of the second internal gear 33 when viewed in the radial direction.

[0077] There are no particular limitations on the specific means for disposing the synchronizing member 40 so that it cannot rotate relative to the second robot member 16. To achieve this, for example, a spline, key or other fitting may be used.

[0078] The main bearing 36 may be disposed at a position where it is not misaligned with the internal gear members 46, 47 in the axial direction X, that is, where it overlaps with them when viewed from the radial direction. In this case, the inner diameter R36-1 of the main bearing 36 may be equal to or larger than the outer diameters R46, R47 of the internal gear members 46, 47.

[0079] The above-described embodiments and variations are merely examples. The abstract technical concepts should not be interpreted as being limited to the contents of the embodiments and variations. Many design modifications are possible in the contents of the embodiments and variations, such as changing, adding, or deleting components. In the above-described embodiments, the term "embodiment" is used to emphasize the contents in which such design modifications are possible. However, design modifications are also permitted even in contents without such notation. Hatching on cross sections in the drawings does not limit the material of the hatched objects. The structures referred to in the embodiments and variations naturally include those that can be considered identical when manufacturing errors are taken into account.

[0080] In the embodiments, a component that is made up of a single member may be made up of multiple members. Similarly, in the embodiments, a component that is made up of multiple members may be made up of a single member. [Explanation of symbols]

[0081] B1...first fastening member, B2...second fastening member, B3...third fastening member, B4...fourth fastening member, 10...joint structure, 12...robot, 14...first robot member, 16...second robot member, 18...joint portion, 20...reduction gear, 30...external gear, 32...first internal gear, 32b...first internal gear, 33...second internal gear, 33b...second internal gear, 34...fixed member, 36...main bearing, 38...bearing housing, 40...synchronizing member, 46...internal gear member.

Claims

1. A joint structure of a robot comprising: a first robot member; a second robot member; a reduction gear device incorporated into a joint portion connecting the first robot member and the second robot member; and a drive device disposed on an input side of the reduction gear device in an axial direction and inputting rotational power to the reduction gear device, the reduction gear transmission includes an external gear, an internal gear that meshes with the external gear, and a fixed member that is provided so as not to rotate relatively to the internal gear and is fixed to the first robot member, the fixing member is fixed to the first robot member by fastening a first fastening member to bring an inner circumferential surface of the first robot member and an outer circumferential surface of the fixing member into pressure contact, the first fastening member is disposed on the input side in the axial direction relative to the internal teeth of the internal gear, A robot joint structure in which at least a portion of the axial range of the first fastening member does not overlap with the internal teeth when viewed from the radial direction.

2. The robot joint structure according to claim 1 , wherein the first fastening member fastens the first robot member and the fixed member in a radial direction, thereby bringing the first robot member and the fixed member into pressure contact with each other.

3. A robot joint structure comprising a first robot member, a second robot member, and a reduction gear incorporated in a joint portion connecting the first robot member and the second robot member, the reduction gear transmission includes an external gear, an internal gear that meshes with the external gear, and a fixed member that is provided so as not to rotate relatively to the internal gear and is fixed to the first robot member, the fixing member is fixed to the first robot member by fastening a first fastening member to bring an inner circumferential surface of the first robot member and an outer circumferential surface of the fixing member into pressure contact, At least a portion of the axial range of the first fastening member does not overlap with the internal teeth of the internal gear when viewed from the radial direction, the first robot member includes a plurality of divided portions formed by dividing a part of the first robot member in a circumferential direction, The first fastening member fastens the plurality of divided portions in the circumferential direction, thereby pressing the first robot member and the fixed member together.

4. 4. The robot joint structure according to claim 1, wherein the entire axial range of the first fastening member does not overlap with the internal teeth when viewed from the radial direction.

5. 5. The robot joint structure according to claim 1, wherein the fixed member is a separate member from the internal gear.

6. 6. The robot joint structure according to claim 5, wherein the fixed member is made of a material having a larger Young's modulus than the internal gear.

7. 7. The robot joint structure according to claim 5, wherein the fixed member is fastened to the internal gear in the axial direction by a second fastening member.

8. A robot joint structure comprising a first robot member, a second robot member, and a reduction gear incorporated in a joint portion connecting the first robot member and the second robot member, the reduction gear transmission includes an external gear, an internal gear that meshes with the external gear, and a fixed member that is provided so as not to rotate relatively to the internal gear and is fixed to the first robot member, the fixing member is fixed to the first robot member by fastening a first fastening member to bring an inner circumferential surface of the first robot member and an outer circumferential surface of the fixing member into pressure contact, At least a portion of the axial range of the first fastening member does not overlap with the internal teeth of the internal gear when viewed from the radial direction, The joint structure includes: a main bearing that connects the first robot member and the second robot member so as to be capable of relative rotation; a bearing housing disposed radially outside the main bearing and accommodating the main bearing, The bearing housing is radially fastened to the first robot member by a third fastening member.

9. The reduction gear device is a flexible mesh type reduction gear device having a first internal gear and a second internal gear as internal gears, the first internal gear is connected to the first robot member so as not to rotate relative to the first robot member; the second internal gear is connected to the second robot member so as not to rotate relative to the second robot member; The robot joint structure according to claim 8 , wherein the third fastening member does not overlap with the internal teeth of the second internal gear when viewed in a radial direction.

10. A robot joint structure comprising a first robot member, a second robot member, and a reduction gear incorporated in a joint portion connecting the first robot member and the second robot member, the reduction gear transmission includes an external gear, an internal gear that meshes with the external gear, and a fixed member that is provided so as not to rotate relatively to the internal gear and is fixed to the first robot member, the fixing member is fixed to the first robot member by fastening a first fastening member to bring an inner circumferential surface of the first robot member and an outer circumferential surface of the fixing member into pressure contact, At least a portion of the axial range of the first fastening member does not overlap with the internal teeth of the internal gear when viewed from the radial direction, the joint structure includes a synchronizing member that is provided so as not to rotate relative to the second robot member and that synchronizes with a rotation component of the external gear, The synchronizing member is fastened to the second robot member in the radial direction by a fourth fastening member.

11. a main bearing that connects the first robot member and the second robot member so that they can rotate relative to each other; the main bearing is disposed axially offset from an internal gear member that is integrally formed with the internal gear from the same material, 11. The robot joint structure according to claim 1, wherein the inner diameter of the main bearing is smaller than the outer diameter of the internal gear member.

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