Torque sensor support structure and robot

Abstract

Provided is a torque sensor support structure. A torque sensor is disposed between a decelerator and a first member for attaching the decelerator, and detects torque acting between the decelerator and the first member. An adaptor is provided to fix the torque sensor to the first member. The adaptor controls deformation of the first member due to at least one of moment and force which act on the torque sensor.

Description

Torque sensor support structure and robot

[0001] The present disclosure relates to a support structure for a torque sensor and a robot.

[0002] A conventional torque sensor includes at least two sensor units provided between a first structure and a second structure connected by a third structure, and the rigidity of one of the first structure and the second structure, which is closer to the sensor units, is set higher than that of the other structure (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-12660

[0004] When a torque sensor is attached between a reducer and a member that secures the reducer, the rigidity of the member that secures the reducer may itself be low. In this case, even if the rigidity of the torque sensor is improved, the torque sensor may be distorted due to deformation of the member that secures the reducer. Therefore, there is a need for a torque sensor support structure and a robot that can accurately detect torque even if the rigidity of the member that secures the reducer is low.

[0005] One aspect of the present disclosure is a support structure for a torque sensor that includes an adapter that fixes a torque sensor, which is disposed between a reducer and a first member to which the reducer is attached and detects torque around the axis of the reducer, to the first member, and the adapter suppresses deformation of the first member due to at least one of a force and a moment acting on the torque sensor.

[0006] 1 is a partial longitudinal sectional view showing a robot according to an embodiment of the present disclosure. FIG. 2 is a partial enlarged longitudinal sectional view illustrating a support structure for a torque sensor in the robot of FIG. 1. FIG. 3 is an exploded longitudinal sectional view of a reducer, a torque sensor, and an O-ring in the robot of FIG. 1. FIG. 4 is a longitudinal sectional view illustrating an assembled state of the reducer, the torque sensor, and the O-ring of FIG. 3. FIG. 5 is an exploded longitudinal sectional view illustrating an adapter, an O-ring, and a base to be assembled to the assembly of FIG. 4. FIG. 6 is a partial enlarged longitudinal sectional view illustrating the assembly of a torque sensor and an adapter in the support structure for a torque sensor of FIG. 2. FIG. 7 is a partial enlarged longitudinal sectional view illustrating a state in which the torque sensor starts to be fitted to the spigot portion of the adapter of FIG. 6. FIG. 8 is a partial enlarged longitudinal sectional view illustrating a state in which the fitting of the torque sensor to the spigot portion of the adapter of FIG. 6 has been completed. FIG. 9 is a longitudinal sectional view illustrating a state in which the adapter, the O-ring, and the base have been assembled to the assembly of FIG. 4.

[0007] A torque sensor support structure and a robot 1 according to an embodiment of the present disclosure will be described below with reference to the drawings. The robot 1 according to this embodiment is, for example, a vertical articulated robot. As shown in FIG. 1 , the robot 1 includes a base (first member) 2 that is fixed to an installation surface such as a floor. The robot 1 also includes a rotating body (second member) 3 that is supported on the base 2 so as to be rotatable about a first axis A.

[0008] The base 2 and the rotating body 3 are made of a lightweight metal material such as an aluminum alloy. The base 2 has a cylindrical shape with openings 2a and 2b on both sides in the direction of the first axis A. The base 2 also has another opening 2c in a part of the side wall for introducing a wire such as a cable. The base 2 also has a partition wall 2d that divides the internal space in the direction along the first axis A.

[0009] A reducer 4 is disposed between the base 2 and the rotating body 3, which rotates the rotating body 3 about a first axis (axis) A relative to the base 2. A torque sensor 5 and an adapter 6 are fixed between the reducer 4 and the partition wall 2d of the base 2. The torque sensor 5 is disposed between the reducer 4 and the base 2, and detects torque about the first axis A acting between the reducer 4 and the base 2.

[0010] In the support structure for the torque sensor 5 according to this embodiment, the torque sensor 5 is fixed to the base 2 via an adapter 6. The reducer 4 is formed in a cylindrical shape and is indirectly fixed to the base 2 via the adapter 6 and the torque sensor 5. The reducer 4 also includes an output unit 7 that is directly fixed to the rotating body 3, and a case 8 that is indirectly fixed to the base 2.

[0011] The torque sensor 5 is formed in a disk shape with an outer diameter smaller than that of the reducer 4. The torque sensor 5 includes a ring-shaped first portion 9 disposed radially inward and a ring-shaped second portion 10 disposed radially outward. The torque sensor 5 also includes a third portion 11 connecting the first portion 9 and the second portion 10.

[0012] A sensor such as a strain gauge (not shown) for detecting torque based on strain is disposed in the third portion 11. The sensor may be disposed near either the first portion 9 or the second portion 10, or may be disposed equidistant therefrom.

[0013] A plurality of through holes 9a penetrating in the thickness direction are provided at intervals in the circumferential direction in the first portion 9 of the torque sensor 5. The torque sensor 5 also has a circular recess 5c centered on the first axis A on one end surface 5d of the first portion 9.

[0014] On the other hand, the case 8 of the reducer 4 has a protrusion 8b that fits into the recess 5c of the torque sensor 5, and an end face 8c that closely contacts the end face 5d of the torque sensor 5. The protrusion 8b of the case 8 and the recess 5c of the torque sensor 5 fit together with an extremely short fitting length, for example, 1 to 2 mm.

[0015] With the protrusion 8b fitted into the recess 5c and the end face 8c in close contact with the end face 5d, the bolt 12 is passed through the through hole 9a and fastened to the screw hole 8a, thereby fixing the torque sensor 5 to the reducer 4. The second portion 10 of the torque sensor 5 is also provided with a plurality of screw holes 10a that penetrate in the plate thickness direction and are spaced apart in the circumferential direction.

[0016] The adapter 6 is made of a material, such as iron, that is more rigid than the material that constitutes the base 2, and is formed in a large disk shape that is radially outward of the torque sensor 5. The adapter 6 also has a plurality of through holes 6a that penetrate in the plate thickness direction and are spaced apart in the circumferential direction around the first axis A. The adapter 6 is fixed to the torque sensor 5 by fastening bolts 13 that pass through the through holes 6a into screw holes 10a in the second part 10.

[0017] The adapter 6 has an outer diameter that is sufficiently larger than the outer diameter of the torque sensor 5. That is, the adapter 6 extends radially outward beyond the outer peripheral surface 5 a of the torque sensor 5. In the example shown in FIG. 1 , the outer diameter of the adapter 6 is equal to the outer diameter of the reducer 4.

[0018] Furthermore, the adapter 6 is large enough to cover the entire radial area of ​​the torque sensor 5. That is, the adapter 6 is large enough to extend radially inward of the second portion 10 of the torque sensor 5, which is necessary for fixing. The adapter 6 also has a thickness dimension that is sufficiently larger than the thickness of the torque sensor 5. This ensures that the adapter 6 has sufficient rigidity to suppress deformation of the base 2.

[0019] The adapter 6 has a first fitting portion 15 consisting of a circular protrusion that fits into a circular recess 14 provided in the base 2 about the first axis A. The adapter 6 also has a second fitting portion 16 consisting of a circular recess that fits into the outer peripheral surface 5 a of the torque sensor 5. The outer diameter of the protrusion that constitutes the first fitting portion 15 and the inner diameter of the recess that constitutes the second fitting portion 16 are set to be approximately equal.

[0020] 2, the second fitting portion 16 has an inner circumferential surface 16a that is disposed with a gap radially outward from the outer circumferential surface 5a of the torque sensor 5. The second fitting portion 16 also has a bottom surface 16b that abuts against the end surface 5b of the second portion 10 of the torque sensor 5 in the thickness direction.

[0021] The second fitting portion 16 includes a spigot portion 16c into which only one end of the outer circumferential surface 5a fits when the end face 5b of the torque sensor 5 abuts against the bottom surface 16b. The fitting length of the spigot portion 16c is set slightly larger than the appropriate crushing allowance (amount of compression) of the O-ring (sealing member) 17, which will be described later, but is preferably as short as possible. For example, if the appropriate crushing allowance of the O-ring 17 is 0.7 mm, the fitting length of the spigot portion 16c is preferably greater than 0.7 mm and equal to or less than 2 mm.

[0022] Furthermore, the through holes 6a are provided at positions that coincide with the screw holes 10a when the outer peripheral surface 5a of the torque sensor 5 is fitted into the second fitting portion 16. Furthermore, the base 2 has a plurality of through holes 2e at positions that coincide with the through holes 6a when the first fitting portion 15 of the adapter 6 is fitted into the recess 14.

[0023] The bolt 13 that passes through the through hole 2e of the base 2 and the through hole 6a of the adapter 6 is fastened to the screw hole 10a of the torque sensor 5. In this way, the torque sensor 5 and the adapter 6 can be fixed to the base 2 by being fastened together with the bolt 13.

[0024] An outer portion of the adapter 6 radially outward from the torque sensor 5 has parallel end faces (flat surfaces) 6b, 6c on both sides in the thickness direction, which are perpendicular to the thickness direction. The base 2 has an end face (flat surface) 2f that faces the end face 6b of the outer portion of the adapter 6 with a gap in the direction of the first axis A. In addition, an end face (flat surface) 8c of the case 8 faces the end face 6c of the outer portion of the adapter 6 with a gap in the direction of the first axis A.

[0025] An O-ring 18 formed in a ring shape surrounding the first fitting portion 15 is disposed between the end face 2f of the base 2 and the end face 6b of the adapter 6. In addition, an O-ring 17 is disposed between the end face 8c of the case 8 of the reducer 4 and the end face 6c of the adapter 6.

[0026] The gap between the flat surface 2 f of the base 2 and the flat surface 6 b of the adapter 6 has a dimension that allows the O-ring 18 to be crushed with an appropriate crushing margin. Also, the gap between the end surface 8 c of the case 8 and the end surface 6 c of the adapter 6 has a dimension that allows the O-ring 17 to be crushed with an appropriate crushing margin.

[0027] The crushing allowance is the difference in wire diameter of the O-rings 17, 18 in the direction of the first axis A when they are not crushed and when they are crushed. When the O-rings 17, 18 are crushed with an appropriate crushing allowance, they seal the gap so as not to allow liquids and gases to pass through.

[0028] The O-ring 17 is formed in an annular shape surrounding the torque sensor 5, and, for example, as shown in Fig. 4, when it is not crushed, has an inner diameter that is equal to or larger than the outer diameter of the outer peripheral surface 5a of the torque sensor 5. When it is crushed, as shown in Fig. 2, the O-ring 17 has an inner diameter that does not contact or lightly contacts the outer peripheral surface 5a of the torque sensor 5.

[0029] As a result, the O-ring 17 seals the gap between the end faces 6 c and 8 c that contact the O-ring 17 from both sides in the direction of the first axis A. The O-ring 18 seals the gap between the end faces 2 f and 6 b that contact the O-ring 18 from both sides in the direction of the first axis A.

[0030] The base 2, adapter 6, torque sensor 5, and reducer 4 have a hollow hole 19 that communicates with the space including the first axis A from the base 2 to the inside of the rotating body 3. A wire (not shown) introduced from the opening 2c of the base 2 can be wired to the rotating body 3 side via the hollow hole 19.

[0031] The following describes the support structure for the torque sensor 5 according to this embodiment configured as above, and the operation of the robot 1. The robot 1 according to this embodiment is assembled as follows.

[0032] First, as shown in Figure 3, the reducer 4 is placed with the case 8 facing up and the first axis A aligned vertically. Then, the torque sensor 5 is brought close to the reducer 4 from above. The protrusion 8b of the case 8 is fitted into the recess 5c of the torque sensor 5, and the end face 5d of the torque sensor 5 is brought into close contact with the end face 8c of the case 8.

[0033] In this state, the phase of the through hole 9a of the first portion 9 of the torque sensor 5 is aligned with the phase of the screw hole 8a of the case 8. Then, as shown in Fig. 4, the bolt 12 passed through the through hole 9a of the first portion 9 of the torque sensor 5 is fastened to the screw hole 8a of the case 8. As a result, the torque sensor 5 is fixed to the case 8 of the reducer 4 in a mutually positioned state in the direction of the first axis A and in a direction perpendicular to the first axis A.

[0034] Next, the O-ring 17 is wrapped around the outer periphery of the torque sensor 5 fixed on the reducer 4, and the torque sensor 5 is placed on the end face 8c of the case 8 radially outward of the outer periphery 5a. In this state, as shown in Fig. 5, the adapter 6 is lowered from above the torque sensor 5, and the torque sensor 5 is inserted into the second fitting portion 16 of the adapter 6 as shown in Figs. 6 and 7. Then, as shown in Fig. 8, the outer periphery 5a of the torque sensor 5 is fitted into the spigot portion 16c near the bottom surface 16b of the second fitting portion 16.

[0035] In this case, according to this embodiment, the fitting length of the torque sensor 5 into the spigot portion 16c is set to be slightly larger than the appropriate crushing allowance of the O-ring 17. Therefore, as shown in FIG. 7 , fitting of the torque sensor 5 into the spigot portion 16c starts before the adapter 6 comes into contact with the O-ring 17.

[0036] If mating begins after the adapter 6 comes into contact with the O-ring 17, the worker cannot sense the start of mating by touch, which reduces the workability of the assembly work. In contrast, by bringing the adapter 6 into contact with the O-ring 17 after mating has begun, the worker can more reliably sense the start of mating. Therefore, the workability of the assembly work is improved.

[0037] 8, the outer peripheral surface 5a of the torque sensor 5 is fitted into the spigot portion 16c. The bottom surface 16b of the second fitting portion 16 of the adapter 6 is brought into close contact with the end surface 5b of the torque sensor 5, thereby crushing the O-ring 17 with an appropriate crushing allowance. In this state, the through hole 6a of the adapter 6 and the screw hole 10a of the torque sensor 5 are aligned in phase.

[0038] In this state, an O-ring 18 is placed on the radially outer flat surface 6b of the first fitting portion 15 of the adapter 6. Then, as shown in Figure 5, the base 2 is turned upside down and brought close from above the adapter 6, and the first fitting portion 15 of the adapter 6 is fitted into the recess 14 of the base 2.

[0039] When the bottom surface of the recess 14 of the base 2 comes into close contact with the end surface of the adapter 6, the through hole 2e of the base 2 is aligned with the through hole 6a of the adapter 6. Then, as shown in Figure 9, the bolt 13 passed through the through holes 2e and 6a of the base 2 and adapter 6 is fastened into the screw hole 10a of the torque sensor 5.

[0040] By fastening the bolts 13, the torque sensor 5 and the adapter 6 are fastened together and fixed to the base 2. The torque sensor 5, the adapter 6, and the base 2 are then fixed in a mutually positioned state in the direction of the first axis A and in a direction perpendicular to the first axis A.

[0041] By fastening the bolts 13 together, the torque sensor 5 and the adapter 6, and the adapter 6 and the base 2 can be fixed at the same radial distance. Compared to when the fixing distances are different in the radial direction, the torque sensor 5 can be less susceptible to the influence of moments generated around an axis perpendicular to the first axis A.

[0042] Furthermore, by fastening them together, there is no need to countersink the adapter 6, which would be necessary if the adapter 6 were fixed separately to the torque sensor 5 and the base 2. This makes it possible to prevent a decrease in the rigidity of the adapter 6 and to prevent the adapter 6 from becoming larger than necessary.

[0043] When the co-tightening is complete, the gaps between the case 8 and the adapter 6 and between the base 2 and the adapter 6 become equal to the dimensions when the O-rings 17, 18 are crushed with appropriate crushing allowances. As a result, the gap between the case 8 of the reducer 4 and the adapter 6 is sealed over the entire circumference by the O-ring 17, radially outward of the torque sensor 5. In addition, the gap between the base 2 and the adapter 6 is also sealed over the entire circumference by the O-ring 18, radially outward of the first fitting portion 15 of the adapter 6.

[0044] As described above, according to this embodiment, the torque sensor 5 is fixed to the base 2 via the adapter 6. The adapter 6 is made of a material that is more rigid than the base 2. Furthermore, the adapter 6 is thick and has a shape that extends widely not only over the second portion 10 of the torque sensor 5 to which it is fixed, but also radially inward and outward.

[0045] This allows the adapter 6 to have sufficiently high rigidity and can sufficiently suppress deformation of the base 2 at the bottom surface of the recess 14 to which the adapter 6 is fixed. In other words, deformation of the base 2 due to the force or torque applied to the torque sensor 5 from the reducer 4 side can be suppressed, and the detection accuracy of the torque sensor 5 can be improved.

[0046] Furthermore, according to this embodiment, the fitting between the outer peripheral surface 5 a of the torque sensor 5 and the adapter 6 is achieved by the spigot portion 16 c with a sufficiently small fitting length. By fitting the outer peripheral surface 5 a of the torque sensor 5 into the spigot portion 16 c, the centers of the torque sensor 5 and the adapter 6 can be aligned with high precision.

[0047] Furthermore, by reducing the fitting length of the spigot portion 16c, it is possible to prevent a force or moment from acting on the outer peripheral surface 5a of the torque sensor 5 from the adapter 6 side. That is, it is possible to prevent a force or moment acting on the outer peripheral surface 5a of the torque sensor 5 from being detected as torque by the torque sensor 5. This makes it possible to prevent a decrease in the accuracy of torque detection by the torque sensor 5.

[0048] Furthermore, the gap between the case 8 of the reducer 4 and the adapter 6 is sealed by an O-ring 17, radially outward of the torque sensor 5. This prevents liquid that has entered from the outside through the gap between the base 2 and the rotating body 3 from entering the torque sensor 5 side.

[0049] The gap between the adapter 6 and the base 2 is also sealed with an O-ring 18. This prevents liquid that has entered from the outside through the gap between the base 2 and the rotating body 3 from entering radially inward of the adapter 6.

[0050] Another method for preventing liquid from entering through the gap between the base 2 and the rotating body 3 is to seal the cylindrical gap between the reducer 4 and the base 2. In this case, only one O-ring is required.

[0051] However, in this case, sliding resistance from the crushed O-ring acts between the reducer 4 and the base 2 during the operation of fitting the adapter 6 to the base 2. For this reason, the worker may not be able to sense the start of fitting by touch. Furthermore, tightening the bolt 13 without proper fitting can cause problems such as damage to the fitting surfaces or assembly at an angle.

[0052] According to this embodiment, the O-ring 17 is crushed between the planes 6c and 8c perpendicular to the first axis A. As a result, the O-ring 17 does not produce sliding resistance during the operation of fitting the first fitting portion 15 of the adapter 6 into the recess 14 of the base 2. Therefore, the worker can easily recognize the start of fitting by touch, allowing for proper assembly.

[0053] In this embodiment, the O-ring 17 is crushed by being compressed in the direction of the axis A between the case 8 and the adapter 6, radially outward of the torque sensor 5. The crushed O-ring 17 does not come into contact with the outer peripheral surface 5 a of the torque sensor 5, or only comes into light contact with it.

[0054] Therefore, the force or moment passing through the O-ring 17 does not act on the torque sensor 5. This prevents the torque sensor 5 from detecting the force or moment that acts on the torque sensor 5 via the O-ring 17 as torque.

[0055] Furthermore, in this embodiment, the O-ring 17 is arranged using the outer peripheral surface 5a of the torque sensor 5 as a guide. This allows the surfaces of the case 8 of the reducer 4 and the adapter 6, which crush the O-ring 17, to be simple flat surfaces 8c, 6c. This makes it easier to process the case 8 and the adapter 6.

[0056] Similarly, the O-ring 18 is positioned using the first fitting portion 15, which is a convex portion of the adapter 6, as a guide. This allows the surfaces of the base 2 and adapter 6 that crush the O-ring 18 to be simple flat surfaces 2f and 6b. This makes it easier to process the base 2 and adapter 6.

[0057] In this embodiment, a vertical articulated robot is exemplified as the robot 1. However, the present invention may be applied to any other form of robot 1. Furthermore, in this embodiment, the support structure for the torque sensor 5 provided between the base 2 and the rotating body 3 is exemplified. Alternatively, a similar structure may be adopted as the support structure for a torque sensor disposed between the reducer of another joint shaft and the first member.

[0058] In addition, in this embodiment, the case where the torque sensor 5 is fixed between the case 8 of the reducer 4 and the base 2 has been described. Instead of this, the present invention may be applied to a case where the torque sensor 5 is fixed between the output portion 7 of the reducer 4 and the rotating body 3.

[0059] In addition, in this embodiment, the base 2, the adapter 6, and the torque sensor 5 are fastened together and fixed at the same distance around the first axis A. Alternatively, the base 2 and the adapter 6 may be fixed by a first bolt, and the adapter 6 and the torque sensor 5 may be fixed by a second bolt. In this case, the first bolt and the second bolt may be arranged at intervals in the circumferential direction at the same distance around the first axis A.

[0060] By separately fixing the base 2 to the adapter 6 and fixing the adapter 6 to the torque sensor 5, the adapter 6 can be fixed to the torque sensor 5 in advance. This allows the torque sensor 5 and the adapter 6 to be managed as a unit.

[0061] Furthermore, the base 2 and the adapter 6 may be fixed to each other radially outward from the torque sensor 5. In this case, the size of the bolts 13 can be increased, and the number of bolts 13 can be reduced.

[0062] Furthermore, although O-rings 17 and 18 are used as sealing members, any other sealing member, such as a ring-shaped gasket, may be used instead. In this embodiment, the radial positions of O-rings 17 and 18 are roughly guided by the inner outer peripheral surface 5a or the first fitting portion 15. Alternatively, O-ring grooves may be formed in the adapter 6, the case 8, or the base 2 to define the radial positions of O-rings 17 and 18.

[0063] In addition, in this embodiment, openings 2c are provided in the side walls of the base 2, but since the openings 2c in the side walls have a significant effect on the deformation of the base 2, it is desirable that the openings 2c be smaller in size and the fewer the number of openings 2c.

[0064] The present disclosure has the advantage that even if the base 2, which is the first member that fixes the reducer 4, has low rigidity, the torque acting from the reducer 4 to the base 2 can be detected with high precision. Furthermore, the robot 1 according to the present disclosure can perform force control with high precision thanks to the support structure of the torque sensor 5 that can detect torque with high precision.

[0065] Although the embodiments of the present disclosure have been described in detail, the present disclosure is not limited to the individual embodiments described above. These embodiments can be variously added, replaced, modified, partially deleted, etc., without departing from the gist of the invention or the concept and spirit of the present invention derived from the content of the claims and their equivalents. For example, in the above-described embodiments, the order of each operation, the order of each process, the omission or addition of some operations depending on conditions, and the omission or addition of some processes depending on conditions can be changed without being bound by the above examples. The same applies when numerical values ​​or mathematical expressions are used in the description of the above embodiments.

[0066] DESCRIPTION OF SYMBOLS 1 Robot 2 Base (first member) 3 Rotating body (second member) 4 Reducer 5 Torque sensor 6 Adapter 12 Bolt 13 Bolt 17 O-ring (sealing member) 16c Spigot portion A First axis (axis)

Claims

1. A torque sensor, which detects torque around the axis of the reduction gear, is positioned between the reduction gear and the first member to which the reduction gear is attached, and an adapter is provided to fix the torque sensor to the first member. A torque sensor support structure in which the adapter suppresses deformation of the first member due to at least one of the force and moment acting on the torque sensor.

2. The torque sensor support structure according to claim 1, wherein the adapter is made of a material with higher rigidity than the first member.

3. A torque sensor support structure according to claim 1 or claim 2, wherein the torque sensor is fixed to the reduction gear, and the adapter and the first member are fastened to the torque sensor by bolt fastening together.

4. A torque sensor support structure according to claim 1 or claim 2, wherein the torque sensor is fastened to the reduction gear by bolts, the first member is fastened to the adapter by first bolts, and the adapter is fastened to the torque sensor by second bolts.

5. The torque sensor is formed in the shape of a disc, The torque sensor support structure according to claim 1 or claim 2, wherein the adapter is formed in a plate shape that is radially larger outward than the torque sensor.

6. The torque sensor is provided with an annular sealing member surrounding it, The torque sensor support structure according to claim 5, wherein the sealing member is compressed in the axial direction between the reduction gear and the adapter.

7. The torque sensor and the adapter are fitted together by the spigot portion. The torque sensor support structure according to claim 6, wherein the fitting length of the spigot portion is slightly greater than the appropriate compression amount of the sealing member.

8. First member and The second member and A reduction gear that supports the second member so that it can rotate around a predetermined axis relative to the first member, A torque sensor is disposed between the reduction gear and the first member and detects the torque acting between the reduction gear and the first member. The torque sensor and the first member are provided with an adapter fixed between them. A robot in which the adapter suppresses deformation of the first member due to at least one of the force and moment acting on the torque sensor.