Robot

Abstract

This robot comprises at least one movable mechanism provided with: a first member; a second member that is moved relative to the first member; and an output-side encoder that detects the amount of movement of the second member relative to the first member. The output-side encoder is provided with a scale that is fixed to one of the first member or the second member and extends in the direction of movement, and a detection head that is fixed to the other one of the first member or the second member and reads the scale. The robot further comprises: a cover that is fixed to one of the first member or the second member and surrounds the peripheries of the scale and the detention head; and a seal member that seals a gap between the cover and the other one of the first member or the second member while allowing for the movement of the second member relative to the first member.

Description

Robot

[0001] The present disclosure relates to a robot.

[0002] The operating angles of each axis of a robot are generally calculated based on the rotation angle of a motor shaft detected by an input-side encoder built into the drive motor of each axis. Further, in order to cope with deflection deformation or the like due to insufficient rigidity of the internal mechanism of a speed reducer, a robot is known that includes an output-side encoder that detects the rotation angle of the output shaft of the speed reducer separately from the input-side encoder (see, for example, Patent Document 1). The output-side encoder includes a scale and a detection head that are attached to the outer surfaces of two relatively rotating members of the robot.

[0003] Japanese Unexamined Patent Application Publication No. 2020-121356

[0004] However, in applications such as laser welding, laser cutting, and machining, when using a robot with high precision and high rigidity, it is conceivable that fumes or cutting fluid generated during use may fall on the output-side encoder. If such a situation continues for a long time, it may cause a reading failure of the output-side encoder and reduce the accuracy and rigidity of the robot. Therefore, it is desired that even a robot placed in an environment where fumes or cutting fluid are generated can operate durably with high precision and high rigidity.

[0005] One aspect of the present disclosure includes at least one movable mechanism including a first member, a second member that is moved relative to the first member, and an output-side encoder that detects the amount of movement of the second member relative to the first member, the output-side encoder including a scale fixed to either the first member or the second member and extending along the direction of the movement, a detection head fixed to the other of the first member or the second member that reads the scale, a cover fixed to either the first member or the second member that surrounds the scale and the detection head, and a seal member that seals a gap between the cover and the other of the first member or the second member while allowing the movement of the second member relative to the first member.

[0006] This is a perspective view showing a robot according to one embodiment of the present disclosure. This is a longitudinal cross-sectional view showing an example of the movable mechanism of the robot in Figure 1. This is a partially enlarged longitudinal cross-sectional view illustrating the output encoder and cover in the movable mechanism of Figure 2. This is a plan view illustrating the output encoder and cover in the movable mechanism of Figure 2. This is a partial longitudinal cross-sectional view illustrating the output encoder and cover in another movable mechanism of the robot in Figure 1.

[0007] A robot 1 according to one embodiment of this disclosure will be described below with reference to the drawings. In the example shown in Figure 1, the robot 1 according to this embodiment is a vertical 6-axis articulated robot. The type of robot is not limited to this, and any type can be adopted, such as a horizontal articulated robot or a linear robot.

[0008] The robot 1 shown in Figure 1 comprises a base 2 fixed to a surface to be installed, such as a floor, and a slewing body 3 rotatably supported relative to the base 2 around a vertical first axis (a predetermined axis) A. The robot 1 also comprises a first arm 4 rotatably supported relative to the slewing body 3 around a horizontal second axis (a predetermined axis) B, and a second arm 5 rotatably supported relative to the first arm 4 around a third axis (a predetermined axis) C parallel to the second axis B. Furthermore, the robot 1 includes a three-axis wrist unit 6 attached to the tip of the second arm 5.

[0009] The wrist unit 6 includes a first wrist member 7 that is rotatably supported on the second arm 5 around a fourth axis (a predetermined axis) D, and a second wrist member 8 that is rotatably supported on the first wrist member 7 around a fifth axis (a predetermined axis) E. The wrist unit 6 also includes a third wrist member 9 that is rotatably supported on the second wrist member 8 around a sixth axis (a predetermined axis) F.

[0010] In other words, robot 1 is equipped with six movable mechanisms, each of which is a rotational mechanism capable of rotating around the first to sixth axes A, B, C, D, E, and F. Each movable mechanism is equipped with a motor 10 that is rotationally driven in response to a control command signal from a control device (not shown), and a reduction gear 12 that reduces the rotation of the motor shaft 11 of the motor 10.

[0011] The motor 10 is equipped with an input-side encoder 13 for detecting the rotational speed of the motor shaft 11. In addition, each movable mechanism is equipped with an output-side encoder 14, as shown in Figure 2.

[0012] Here, the output encoder 14 will be described using the movable mechanism shown in Figure 2, which includes a base 2 and a swivel drum 3, as an example. This movable mechanism consists of a rotation mechanism that rotates the swivel drum 3, which is the second member, around a first axis A relative to the base 2, which is the first member.

[0013] For example, a motor 10 is fixed to the slewing drum 3, and a gear train consisting of a reduction gear 12 is provided between the motor 10 and the base 2. The rotation of the motor shaft 11 is reduced by the reduction gear 12 and transmitted to the base 2, so that the slewing drum 3 rotates around the first axis A at a reduced rotational speed relative to the base 2 which is fixed to the floor.

[0014] In the example shown in Figure 2, the gear 15, which is the input gear of the reduction gear 12 fixed to the base 2, is formed in an annular shape with a central hole 16, and a cylindrical member 17 is positioned to pass through the central hole 16 in the vertical direction. The lower end of the cylindrical member 17 is fixed to the base 2, and the upper end of the cylindrical member 17 extends upward through a through hole 18 provided in the slewing drum 3.

[0015] This allows the wires 19, such as cables or pipes, that are routed within the base 2 to be pulled out above the slewing drum 3 via the internal space of the cylindrical member 17. As described above, since the cylindrical member 17 is fixed to the base 2, the cylindrical member 17 also constitutes part of the first member, just like the base 2.

[0016] As shown in Figures 3 and 4, the output encoder 14 is fixed to the outer surface of the tip of a cylindrical member 17 and comprises an annular scale 20 extending in the circumferential direction, and a detection head 21 positioned opposite the outer surface of the scale 20 with a small radial gap between them. The scale 20 is, for example, a magnetic scale, and the detection head 21 is a magnetic detection type sensor that reads the magnetism applied to the scale 20. The scale 20 is fixed to the vicinity of the tip of the cylindrical member 17 by bolts. The detection head 21 is fixed to an annular plate 22 fixed to the slewing drum 3 by bolts. Since the plate 22 is fixed to the slewing drum 3, the plate 22 also constitutes part of the second member, just like the slewing drum 3.

[0017] In other words, when the second component, the slewing drum 3, is rotated around the first axis A relative to the first component, the base 2, the detection head 21, which is fixed to the slewing drum 3, is moved circumferentially relative to the scale 20, which is fixed to the base 2. As a result, the output encoder 14 can directly detect the amount of rotational movement of the slewing drum 3 relative to the base 2.

[0018] As shown in Figure 3, the robot 1 according to this embodiment includes a cover 24 fixed to a plate 22 by bolts 23. The cover 24 includes a cylindrical peripheral wall portion 25 and a ring-shaped partition wall portion 27 extending radially inward from one end of the peripheral wall portion 25 and having a central hole 26. The peripheral wall portion 25 and the partition wall portion 27 are integrally constructed.

[0019] The peripheral wall portion 25 surrounds the scale 20 and the detection head 21 radially outward, extending around their entire circumference. The partition wall portion 27 is positioned on the opposite side of the plate 22 in the axial direction from the scale 20 and the detection head 21. A cylindrical member 17 is inserted through the central hole 26 of the partition wall portion 27, and a gap is formed between the outer peripheral surface 17a of the cylindrical member 17 and the central hole 26.

[0020] An annular sealing member 28 is positioned in the gap between the outer circumferential surface 17a of the cylindrical member 17 and the central hole 26 of the partition wall 27. The sealing member 28 seals (seals) the gap between the cylindrical member 17 and the partition wall 27 while allowing them to rotate around the first axis A. In particular, the sealing member 28 seals the space enclosed by the cover 24 to prevent foreign matter from entering from the outside.

[0021] Furthermore, a metal gasket 29 is sandwiched between the peripheral wall portion 25 and the plate 22. This seals the space enclosed by the cover 24, preventing foreign matter from entering through the gap between the cover 24 and the plate 22. Additionally, an O-ring 29a is sandwiched between the plate 22 and the slewing drum 3. This seals the space enclosed by the cover 24, preventing foreign matter from entering through the gap between the plate 22 and the slewing drum 3.

[0022] Furthermore, a bearing 30 is positioned between the cylindrical member 17 and the slewing drum 3 to support them so that they do not move relative to each other in the radial direction. Reference numeral 31 in the figure indicates a sealing member that prevents lubricant from leaking out of the space on the bearing 30 side.

[0023] The cable connected to the detection head 21 is routed out of the cover 24 via a rubber bushing (not shown), such as a known cable gland, which is placed in a through-hole (not shown) that penetrates a part of the peripheral wall 25 or partition wall 27 of the cover 24. The bushing, such as a cable gland, blocks the space inside and outside the cover 24 even in the through-hole through which the cable passes, protecting the cover 24 from foreign objects entering from the outside.

[0024] According to this embodiment, the space housing the output encoder 14, which directly detects the amount of rotational movement of the slewing cylinder 3 relative to the base 2, is sealed by the cover 24, the sealing member 28, and the gasket 29. This allows the space housing the output encoder 14 to be sealed without hindering the rotational movement of the slewing cylinder 3 relative to the base 2. Therefore, welding fumes or cutting fluids from the outside are prevented from falling onto the output encoder 14 during the operation of the robot 1, and reading errors of the output encoder 14 can be prevented over the long term.

[0025] Furthermore, according to this embodiment, the scale 20 and the detection head 21 are not directly fixed to the base 2 and the slewing drum 3 which is rotatably supported by a large bearing on the base 2. Instead, the scale 20 and the detection head 21 are fixed to a cylindrical member 17 fixed to the base 2 and a plate 22 fixed to the slewing drum 3, respectively, and a bearing 30 is provided between the cylindrical member 17 and the slewing drum 3.

[0026] As a result, when the slewing drum 3 is rotated relative to the base 2, the cylindrical member 17, which has relatively low rigidity, is supported by the bearing 30 so as not to vibrate or fluctuate radially relative to the slewing drum 3. In other words, during the rotational movement of the slewing drum 3 relative to the base 2, the gap between the outer surface 17a of the cylindrical member 17 and the central hole 26 of the cover 24 is supported so as not to fluctuate radially, and the sealing performance of the sealing member 28 is maintained without fluctuation. This makes it possible to more reliably prevent foreign matter from entering the inside of the cover 24 from the outside, and also prevents uneven wear of the sealing member 28, thereby maintaining durable sealing performance.

[0027] Figure 5 shows another example of the output encoder 14, cover 24, and sealing member 28. This example shows the output encoder 14 in a movable mechanism comprising a first member, a slewing drum 3, and a second member, a first arm 4, which is rotated relative to the slewing drum 3 around a second axis B.

[0028] In Figure 3, the scale 20 is fixed to the fixed first member and the detection head 21 is placed on the moving second member. However, in the example shown in Figure 5, the opposite is true: the detection head 21 is fixed to the first member and the scale 20 is fixed to the second member. Specifically, a cylindrical outer surface (circumferential surface) 4a extending around the second axis B is formed on the outer surface of the first arm 4 that constitutes the second member, and an annular scale 20 extending in the circumferential direction is fixed so as to wrap around the cylindrical outer surface 4a.

[0029] Meanwhile, the rotating drum 3, which constitutes the first member, has a cylindrical member 32 fixed to its cylindrical outer surface 4a by a connecting member 33, which is arranged coaxially with the second axis B. The first arm 4 and the cylindrical member 32 are supported by a bearing 34 so as to be rotatable around the second axis B. The detection head 21 is supported on the cylindrical member 32 by an arm-shaped member 36 fixed to the cylindrical member 32, at a position with a small gap radially outward from the scale 20.

[0030] The cover 24 has a peripheral wall portion 25 fixed to the first arm 4, and an annular gap is formed between the central hole 26 of the partition wall portion 27 extending radially inward from the peripheral wall portion 25 and the outer circumferential surface 32a of the cylindrical member 32. This gap between the cover 24 and the outer circumferential surface 32a of the cylindrical member 32 is sealed by a sealing member 28. The space between the peripheral wall portion 25 and the first arm 4 is sealed by an O-ring 35.

[0031] As a result, the space in which the scale 20 and detection head 21 are located is surrounded by the cover 24 and sealed from the outside by the sealing member 28. Consequently, welding fumes or cutting fluids from the outside are prevented from falling onto the output encoder 14 during the operation of the robot 1, and reading errors of the output encoder 14 can be prevented in the long term.

[0032] In this embodiment as well, a bearing 34 is provided between the cylindrical member 32, which has relatively low rigidity and is fixed to the slewing drum 3, and the first arm 4. As a result, when the first arm 4 is rotated relative to the slewing drum 3, the cylindrical member 32 that fixes the detection head 21 is supported by the bearing 34 so as not to vibrate or fluctuate radially relative to the first arm 4. This maintains a constant sealing performance of the seal member 28 and more reliably prevents foreign matter from entering the inside of the cover 24 from the outside.

[0033] In this embodiment, examples of movable mechanisms include a mechanism in which the slewing drum 3 rotates around a first axis A relative to the base 2, and a mechanism in which the first arm 4 rotates around a second axis B relative to the slewing drum 3. Alternatively, the output encoder 14 may be arranged in a similar structure to the above in a mechanism in which the second arm 5 rotates around a third axis C relative to the first arm 4.

[0034] Furthermore, the output encoder 14 may be arranged in a similar manner in a movable mechanism in which the first wrist member 7 rotates around the fourth axis D relative to the second arm 5. Also, the output encoder 14 may be arranged in a similar manner in a movable mechanism in which the second wrist member 8 rotates around the fifth axis E relative to the first wrist member 7. Moreover, the output encoder 14 may be arranged in a similar manner in a movable mechanism in which the third wrist member 9 rotates around the sixth axis F relative to the second wrist member 8.

[0035] Furthermore, while this embodiment exemplifies a magnetic detection type output encoder 14, it is not limited to this, and any sensor with an optical detection method or dielectric detection method may be used. In addition, the control device may control the robot 1 by selecting either the rotation amount of the motor shaft 11 detected by the input encoder 13 or the rotation amount of the second member relative to the first member detected by the output encoder 14.

[0036] Furthermore, although a rotary mechanism is given as an example of a movable mechanism in this embodiment, the invention is not limited to this and may also be applied to a movable mechanism consisting of a linear motion mechanism.

[0037] While embodiments and modifications of the present disclosure have been described above, the robot 1 of the present disclosure is not limited to the embodiments and modifications described above, and various modifications are possible without departing from the gist of the present disclosure.

[0038] With respect to the above embodiments and modifications, the following further notes are disclosed. (Note 1) A robot comprising at least one movable mechanism comprising a first member, a second member that is moved relative to the first member, and an output encoder for detecting the amount of movement of the second member relative to the first member, wherein the output encoder comprises a scale fixed to either the first member or the second member and extending along the direction of the movement, and a detection head fixed to the other of the first member or the second member and reading the scale, and a cover fixed to either the first member or the second member and surrounding the scale and the detection head, and a sealing member that seals the gap between the cover and the other of the first member or the second member while allowing the movement of the second member relative to the first member.

[0039] (Note 2) The robot according to Note 1, wherein the movable mechanism includes a motor that generates the driving force for the movement of the second member relative to the first member, and an input encoder that detects the amount of rotation of the motor shaft of the motor around the axis.

[0040] (Note 3) The robot according to Note 1 or Note 2, wherein the movable mechanism is a rotation mechanism that rotates the second member relative to the first member about a predetermined axis.

[0041] (Note 4) The robot according to Note 3, wherein the scale is formed in an annular shape and wrapped around the outer surface of the first member in the circumferential direction, and the detection head is fixed to the second member with a minute radial gap on the outer surface of the scale.

[0042] (Note 5) The robot according to Note 3, wherein the scale is formed in an annular shape and is wrapped around the outer surface of the second member in the circumferential direction, and the detection head is fixed to the first member with a minute radial gap on the outer surface of the scale.

[0043] (Appendix 6) The cover is formed in an annular shape that is disposed over the entire circumference outside the outer peripheral surface of the first member, and the sealing member seals an annular gap between the outer peripheral surface of the first member and the cover. The robot according to Appendix 3.

[0044] (Appendix 7) A bearing that supports the rotation of both is provided between the first member and the second member. The robot according to any one of Appendices 3 to 6.

[0045] 1. Robot 2. Base (first member) 3. Swivel body (first member, second member) 4. First arm (first member, second member) 4a. Cylindrical outer surface (outer peripheral surface) 5. Second arm (first member, second member) 7. First wrist member (first member, second member) 8. Second wrist member (first member, second member) 9. Third wrist member (second member) 10. Motor 11. Motor shaft 13. Input-side encoder 14. Output-side encoder 17a. Outer peripheral surface 20. Scale 21. Detection head 24. Cover 28. Sealing member 30, 34. Bearings A. First axis (predetermined axis) B. Second axis (predetermined axis) C. Third axis (predetermined axis) D. Fourth axis (predetermined axis) E. Fifth axis (predetermined axis) F. Sixth axis (predetermined axis)

Claims

1. A robot comprising at least one movable mechanism comprising a first member, a second member that is moved relative to the first member, and an output encoder for detecting the amount of movement of the second member relative to the first member, wherein the output encoder comprises a scale fixed to either the first member or the second member and extending along the direction of movement, and a detection head fixed to the other of the first member or the second member for reading the scale, and a cover fixed to either the first member or the second member and surrounding the scale and the detection head, and a sealing member that seals the gap between the cover and the other of the first member or the second member while allowing the movement of the second member relative to the first member.

2. The robot according to claim 1, wherein the movable mechanism includes a motor that generates the driving force for the movement of the second member relative to the first member, and an input encoder that detects the amount of rotation of the motor shaft of the motor around the axis.

3. The robot according to claim 1 or 2, wherein the movable mechanism is a rotation mechanism that rotates the second member relative to the first member about a predetermined axis.

4. The robot according to claim 3, wherein the scale is formed in an annular shape and is wrapped around the outer surface of the first member in the circumferential direction, and the detection head is fixed to the second member with a minute radial gap between it and the outer surface of the scale.

5. The robot according to claim 3, wherein the scale is formed in an annular shape and is wrapped around the outer surface of the second member in the circumferential direction, and the detection head is fixed to the first member with a minute radial gap on the outer surface of the scale.

6. The robot according to claim 3, wherein the cover is formed in an annular shape and is arranged around the entire circumference of the outer peripheral surface of the first member, and the sealing member seals the annular gap between the outer peripheral surface of the first member and the cover.

7. The robot according to any one of claims 3 to 6, further comprising a bearing between the first member and the second member for supporting the rotation of both.

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