Encoder unit and robot

Abstract

The encoder unit comprises: a case member that defines a space that can be opened and closed by a cover member and that can be fixed to a second member; a shaft member that is supported on the case member so that it can rotate around a predetermined axis; and an encoder that is arranged in the space; the shaft member passes through a through hole provided in the case member and one end of the shaft member in the axial direction is exposed to the outside of the case member; the encoder comprises an annular scale that is fixed to the shaft member with its central axis aligned with the axis, and a sensor that is fixed to the case member opposite the scale and reads the scale; the case member can be attached to the second member with the axis of the shaft member aligned with the rotation axis, and one end of the shaft member can be fixed to the first member.

Description

[Technical Field]

[0001] The present disclosure relates to an encoder unit and a robot. [Background technology]

[0002] Because the internal mechanism of the reducer lacks rigidity and can bend or rattle, robots are known that are equipped with an output encoder that detects the rotation angle of the output shaft of the reducer in addition to an input encoder that detects the rotation angle of the motor's rotating shaft (see, for example, Patent Document 1).

[0003] In this robot, at a joint that rotates a first arm about a second axis relative to a rotating body, a scale formed in an annular shape about the second axis is fixed to the first arm, and a sensor is fixed to a fixed member extending from the rotating body. In this robot, the scale and sensor of the output-side encoder are exposed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-121356 Summary of the Invention [Problem to be solved by the invention]

[0005] However, since robots may operate in environments where they are subject to droplets or dust scattered from the outside, if the sensors or scales are exposed, they may malfunction due to dust or the like. Therefore, it is desirable to effectively protect the output encoder from dust and the like, particularly when the output encoder cannot be incorporated inside the robot mechanism or when it is attached externally to the robot mechanism. [Means for solving the problem]

[0006] One aspect of the present disclosure is an encoder unit that detects the relative rotation angle between a first member and a second member that are supported so that they can rotate relative to each other around a first rotation axis of a robot, the encoder unit comprising: a first case member that defines a first space that can be opened and closed by a first cover member and that can be fixed to the second member; a shaft member that is supported on the first case member so that it can rotate about a predetermined first axis; and a first encoder that is arranged in the first space, wherein the shaft member passes through a first through hole provided in the first case member and has one end in the axial direction exposed to the outside of the first case member, the first encoder comprising: a first annular scale that is fixed to the shaft member with its central axis aligned with the first axis, and a first sensor that is fixed to the first case member opposite the first scale and reads the first scale, wherein the first case member can be attached to the second member with the first axis of the shaft member aligned with the first rotation axis, and the one end of the shaft member can be fixed to the first member.

[0007] Another aspect of the present disclosure is a robot including the encoder unit. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a partial plan view showing a wrist unit portion of a robot according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a longitudinal cross-sectional view of an encoder unit according to an embodiment of the present disclosure. [Figure 3] FIG. 10 is a vertical cross-sectional view of the encoder unit for two axes of the wrist unit. DETAILED DESCRIPTION OF THE INVENTION

[0009] An encoder unit 10 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 1, and includes a base (not shown) that is placed on an installation surface such as a floor, and a rotating body (not shown) that is supported rotatably relative to the base about a vertical first axis. The robot also includes a first arm (not shown) that is supported rotatably relative to the rotating body about a horizontal second axis, and a second arm 2 that is supported rotatably relative to the first arm about a third axis that is parallel to the second axis.

[0010] The robot 1 also includes a three-axis wrist unit 3 attached to the tip of the second arm 2. The wrist unit 3 includes a first wrist element 4 supported rotatably about a fourth axis J4 relative to the second arm 2, and a second wrist element 5 supported rotatably about a fifth axis J5 perpendicular to the fourth axis J4 relative to the first wrist element 4. The wrist unit 3 also includes a third wrist element 6 supported rotatably about a sixth axis J6 perpendicular to the fifth axis J5 relative to the second wrist element 5.

[0011] 1, the encoder unit 10 according to this embodiment is mounted between a first wrist element (first member) 4 and a second wrist element (second member) 5, which are mechanical parts of the robot 1. The encoder unit 10 detects the rotation angle of the second wrist element 5 relative to the first wrist element 4 about a fifth axis (first rotation axis) J5.

[0012] Specifically, as shown in FIG. 2, the encoder unit 10 includes a case member (first case member) 11, a cover member (first cover member) 12, a shaft member 13, and an encoder (first encoder) 14. Case member 11 is formed in a box shape with an opening (first opening) 11a. Cover member 12 is detachably attached to opening 11a with a sealing member 15 such as an O-ring sandwiched therebetween. As a result, a space (first space) 16 is defined by case member 11 and cover member 12.

[0013] Case member 11 includes mounting wall portion 11b and intermediate wall portion 11c, which are arranged with a gap 17 in the depth direction. Gap 17 is formed in the shape of a slit and continues to the space outside case member 11. Mounting wall portion 11b is provided with a mounting hole (not shown) for mounting case member 11 to second wrist element 5.

[0014] The intermediate wall portion 11c is provided with a through-hole (first through-hole) 18 that penetrates the case member 11 in the depth direction. The through-hole 18 connects the internal space 16 of the case member 11 with the external space. The intermediate wall portion 11c is also provided with a seat surface 11d on which a sensor (first sensor) 20 (described later) is attached.

[0015] The shaft member 13 has a columnar portion 13a with a cylindrical outer circumferential surface. The columnar portion 13a of the shaft member 13 is disposed so as to penetrate through a through-hole 18 provided in the case member 11, with one end portion 13b exposed within the space 16 of the case member 11 and an end face 13d on the opposite axial side exposed to the gap 17.

[0016] A bearing (not shown) is disposed between the case member 11 and the cylindrical portion 13a of the shaft member 13. As a result, the shaft member 13 is supported by the case member 11 so as to be rotatable about the axis (first axis) A of the cylindrical portion 13a. A connecting member 22, which will be described later, is fixed to an end surface 13d of the shaft member 13. In addition, a seal member (first seal member) 23 such as an oil seal is disposed between the case member 11 and the cylindrical portion 13a of the shaft member 13. This seals the gap between the through hole 18 of the case member 11 and the shaft member 13.

[0017] The encoder 14 includes a scale (first scale) 24 fixed to the cylindrical portion 13a of the shaft member 13, and a sensor 20 fixed to the seating surface 11d of the case member 11. The scale 24 is formed in an annular shape with a central hole 24a, and has a pattern provided on a cylindrical outer peripheral surface 24b. The scale 24 is fixed to the shaft member 13 by fitting the central hole 24a into the outer peripheral surface of the cylindrical portion 13a of the shaft member 13.

[0018] The sensor 20 is disposed radially outward from the outer peripheral surface 24b of the scale 24, facing the outer peripheral surface 24b with a small gap therebetween. The sensor 20 includes a light-emitting unit and a light-receiving unit (not shown). The light-emitting unit emits light that is reflected by the outer peripheral surface 24b of the scale 24 and returns, and the light-receiving unit receives the light. The sensor 20 can read the pattern based on changes in the intensity of the received light. Any known type of sensor, such as a mechanical, optical, or magnetic type, can be used as the sensor 20.

[0019] The operation of the encoder unit 10 according to this embodiment configured as above will be described below. As shown in FIG. 2, the encoder unit 10 is attached to the robot 1 in an external state by fixing the case member 11 to the second wrist element 5 of the robot 1.

[0020] At this time, the shaft member 13, which is rotatably supported by the case member 11, is attached so that its axis A coincides with the fifth axis J5. One end of the plate-shaped connecting member 22 is then inserted into the slit-shaped gap 17 in the case member 11, and the end face 13d of the shaft member 13 and the connecting member 22 are fixed with a bolt or the like (not shown). The other end of the connecting member 22 is fixed to a seat provided on the first wrist element 4 with a bolt or the like (not shown). As a result, the shaft member 13 is fixed to the first wrist element 4.

[0021] When the second wrist element 5 rotates about the fifth axis J5 relative to the first wrist element 4, the case member 11 rotates about the fifth axis J5 together with the second wrist element 5. In contrast, the shaft member 13 is fixed to the first wrist element 4 by the connecting member 22, and is therefore maintained stationary together with the first wrist element 4.

[0022] That is, the scale 24 fixed to the shaft member 13 is maintained stationary. On the other hand, the sensor 20 fixed to the case member 11 is rotated around the scale 24 about the fifth axis J5 with respect to the scale 24, while maintaining a small gap between the sensor 20 and the outer peripheral surface of the scale 24. As a result, while the sensor 20 moves relative to the scale 24 in the circumferential direction, the pattern on the scale 24 is read, and the rotation angle of the second wrist element 5 about the fifth axis J5 with respect to the first wrist element 4 is detected.

[0023] According to the encoder unit 10 of this embodiment configured as described above, the encoder 14 is disposed in the space 16 surrounded by the case member 11 and the cover member 12. The space 16 is sealed by the seal member 23 and the seal member 15, so that the encoder 14 can be protected from droplets, dust, and the like that may fly from the outside.

[0024] Then, the case member 11 is fixed to the second wrist element 5, and the end face 13d of the shaft member 13 exposed to the outside from the case member 11 is fixed to the first wrist element 4 by the connecting member 22. With just this, the encoder unit 10 can be easily attached externally to the wrist unit 3 of the robot 1. In other words, even if the robot 1 does not have an encoder 14 built into its mechanical section, the encoder unit 10 can be easily attached externally. This makes it possible to easily equip the reducer with an encoder 14 that detects the rotation angle of the output shaft of the reducer in addition to an encoder that detects the rotation angle of the motor's rotating shaft, even if the internal mechanism of the reducer lacks rigidity and causes bending deformation or rattle.

[0025] That is, it is possible to use both the encoder attached to the motor and the encoder 14 that directly detects the rotation angle of the second wrist element 5 relative to the first wrist element 4. This improves the accuracy of the rotation angle, and also improves the positioning accuracy and trajectory accuracy of the wrist tip.

[0026] According to this embodiment, the first wrist element 4, the second wrist element 5, the mounting wall portion 11b, the connecting member 22 fixed to the first wrist element 4, and the case member 11 fixed to the second wrist element 5 are arranged alternately along the fifth axis J5, from the fourth axis J4 side. This allows the connecting member 22 extending from the first wrist element 4 to be arranged close to the fourth axis J4, and the amount of radial protrusion around the fourth axis J4 can be kept small, reducing interference of the connecting member 22 with external objects.

[0027] Furthermore, the connecting member 22 extends long from the first wrist element 4 and is configured as a thin plate that can be inserted into the gap 17 in the case member 11, so the rigidity of the connecting member 22 itself is low. According to this embodiment, the shaft member 13 fixed to the connecting member 22 is rotatably supported by bearings on the case member 11 that is fixed to the second wrist element 5. This makes it possible to support the connecting member 22 not in a cantilevered manner but in a doubly supported manner. In other words, there is the advantage that the scale 24 can be maintained in a stable stationary state even when the second wrist element 5 is rotated about the fifth axis J5 relative to the first wrist element 4, and the rotation angle can be detected with high accuracy.

[0028] Furthermore, according to this embodiment, the space 16 inside the case member 11 can be opened by removing the cover member 12 from the case member 11. This makes it possible to expose the encoder 14 housed in the space 16, and makes it possible to easily replace the scale 24 and / or the sensor 20 without removing the case member 11 from the second wrist element 5.

[0029] In this embodiment, a second encoder unit 30 that detects the rotation angle of the third wrist element 6 relative to the second wrist element 5 may be provided, as shown in FIG. The second encoder unit 30 includes a case member (second case member) 31, a cover member (second cover member) 32, and an encoder (second encoder) 33.

[0030] The case member 31 is formed in a box shape having an opening (second opening) 31a. A lid member 32 is detachably attached to the opening 31a with a sealing member 34 such as an O-ring sandwiched therebetween. This allows the case member 31 and the lid member 32 to define a space (second space) 35.

[0031] The case member 31 is provided with a mounting hole (not shown) for mounting to the second wrist element 5. The case member 31 is fixed to the second wrist element 5 via a seal member 36 such as an O-ring.

[0032] The case member 31 is provided with a through-hole 37 that allows the third wrist element 6 to pass through and exposes the mounting flange surface 6a. The gap between the through-hole 37 of the case member 31 and the cylindrical outer peripheral surface around the sixth axis J6 of the third wrist element 6 is sealed by a seal member (second seal member) 38 such as an oil seal. In addition, the bottom surface of the case member 31 is provided with a seat surface 31b on which a sensor (second sensor) 39 is attached.

[0033] Furthermore, case member 11 is provided with a through-hole 40 that connects case member 11 and case member 31 to each other at a position that corresponds to when case member 11 is fixed to second wrist element 5. A seal member 43 such as an O-ring is disposed between the two case members 11, 31 to seal the internal space.

[0034] The encoder 33 includes a scale (second scale) 44 fixed to the outer circumferential surface of the third wrist element 6, and a sensor 39 fixed to the seating surface 31b of the case member 31. The scale 44 is formed in an annular shape having a central hole 44a, and a pattern is provided on the cylindrical outer circumferential surface 44b. The scale 44 is fixed to the third wrist element 6 by fitting the central hole 44a into the outer circumferential surface of the third wrist element 6. The sensor 39 is disposed radially outwardly of the outer peripheral surface 44b of the scale 44, facing the outer peripheral surface 44b with a small gap therebetween. The sensor 39 is similar to the sensor 20 described above.

[0035] When the third wrist element 6 is rotated about the sixth axis J6 relative to the second wrist element 5, the scale 44 fixed to the third wrist element 6 also rotates about the sixth axis J6. Because the sensor 39 is fixed to the second wrist element 5, it can be moved relatively in the circumferential direction with respect to the scale 44 with a small constant gap left radially outward from the scale 44, and can read the scale 44.

[0036] According to this embodiment, the two encoders 14, 33 that detect the rotation angles around the two axes, the fifth axis J5 and the sixth axis J6, are housed in a single space that communicates with the spaces 16, 35. Therefore, the cables 45 connected to the sensors 20, 39 can be combined into a single cable and routed from the second arm 2 side. The routed cable 45 branches within the space 16 and is connected to the two sensors 20, 39. This simplifies the wiring work, reduces the number of cables 45, and reduces costs, and reduces interference between the cables 45 and external objects.

[0037] Furthermore, in this embodiment, the encoder unit 10 placed in the wrist unit 3 is exemplified, but the present invention is not limited to this and may be applied to cases where the encoder unit 10 is attached externally to another joint.

[0038] Furthermore, the robot 1 according to this embodiment may be provided with a joint structure (for example, composed of a first wrist element 4 and a second wrist element 5) having a reducer, and the encoder unit 10 may be disposed in the joint structure on the opposite side of the reducer with respect to the fourth axis J4, which is the joint axis of the joint structure. With this configuration, the center of gravity of the joint structure composed of the first wrist element 4 and the second wrist element 5 can be positioned closer to the fourth axis J than when the encoder unit 10 is disposed on the reducer side. This reduces inertia, making it easier to rotate the joint. Furthermore, the interference radius around the fourth axis J4 can also be reduced.

[0039] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible to these embodiments without departing from the gist of the invention or the idea and intent 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 and the order of each process are shown as examples and are not limited to these.

[0040] The following additional notes are provided regarding the above-described embodiment and modifications. (Appendix 1) An encoder unit that detects a relative rotation angle between a first member and a second member that are supported so as to be relatively rotatable around a first rotation axis of a robot, a first case member that defines a first space that can be opened and closed by a first cover member and that can be fixed to the second member; a shaft member supported by the first case member so as to be rotatable about a predetermined first axis; a first encoder disposed in the first space; the shaft member passes through a first through-hole provided in the first case member, and one end of the shaft member in the axial direction is exposed to the outside of the first case member; the first encoder comprises: a first annular scale fixed to the shaft member with its central axis aligned with the first axis; and a first sensor fixed to the first case member in a state facing the first scale and configured to read the first scale; the first case member can be attached to the second member with the first axis of the shaft member aligned with the first rotation axis, The one end of the shaft member is fixable to the first member.

[0041] (Appendix 2) The encoder unit described in Appendix 1, further comprising a first seal member that seals a gap between the shaft member and the first case member. (Appendix 3) The encoder unit according to claim 1 or 2, further comprising a connecting member that connects the one end of the shaft member and the first member.

[0042] (Appendix 4) a second encoder unit that detects a relative rotation angle between the second member and a third member that are supported so as to be relatively rotatable about a second rotation axis of the robot; The second encoder unit a second case member that defines a second space that can be opened and closed by a second cover member and that can be fixed to the second member; a second encoder disposed in the second space, the second case member has a through hole that exposes to the outside one axial end of the third member or a member fixed to the third member, the second encoder comprises: an annular second scale fixed to the third member or to a cylindrical outer peripheral surface of the member fixed to the third member around the second rotation axis with its central axis coinciding with the second rotation axis; and a second sensor fixed to the second case member in a state facing the second scale and configured to read the second scale, The encoder unit according to any one of Supplementary Note 1 to Supplementary Note 3, wherein the first space and the second space are in communication with each other, and wiring to the first sensor and the second sensor can be laid inside the first space and the second space.

[0043] (Appendix 5) The encoder unit described in Appendix 4, further comprising a second seal member that seals between the outer peripheral surface of the third member or the member fixed to the third member and the second case member.

[0044] (Appendix 6) A robot comprising the encoder unit according to any one of Supplementary Note 1 to Supplementary Note 5.

[0045] (Appendix 7) a joint structure having a reducer, 7. The robot according to claim 6, wherein the encoder unit is disposed on the side of the joint structure opposite to the side on which the reducer is disposed with respect to the joint axis of the joint structure. [Explanation of symbols]

[0046] 1. Robot 4. First wrist element (first member) 5 Second wrist element (second member) 6 Third wrist element (third member) 10 Encoder Unit 11 Case member (first case member) 12 Cover member (first cover member) 13 Shaft member 14 Encoder (1st encoder) 16 Space (1st space) 18 Through hole (first through hole) 20 Sensor (1st Sensor) 22 Connecting member 23 sealing member (first sealing member) 24 scale (1st scale) 30 Second encoder unit 31 Case member (second case member) 32 Cover member (second cover member) 33 Encoder (second encoder) 35 Space (Second Space) 37 Through hole 38 Second seal member 39 Sensor (Second Sensor) 44 scale (2nd scale) A axis (1st axis) J5 5th axis (1st rotation axis) J6 6th axis (2nd rotation axis)

Claims

1. A first member; the second member supported so as to be rotatable relative to the first member about a first rotation axis; An encoder unit for detecting a relative rotation angle between the first member and the second member, a first case member that defines a first space that can be opened and closed by a first cover member and that can be fixed to the second member; a shaft member supported by the first case member so as to be rotatable about a predetermined first axis; a first encoder disposed within the first space; the shaft member passes through a first through-hole formed in the first case member, exposing the one end in the axial direction to the outside of the first case member; the first encoder is an encoder unit including: an annular first scale fixed to the shaft member with its central axis aligned with the first axis; and a first sensor fixed to the first case member in a state facing the first scale and configured to read the first scale; a connecting member that connects one end of the shaft member and the first member, the first case member can be attached to the second member with the first axis of the shaft member aligned with the first rotation axis, A robot in which the first member, the second member, a portion of the first case member fixed to the second member, the connecting member fixed to the first member, and another portion of the first case member fixed to the second member are arranged in this order along the first axis.

2. The robot according to claim 1 , further comprising a first seal member that seals a gap between the shaft member and the first case member.

3. The robot according to claim 1 , wherein the connecting member is configured as a thin plate that extends longitudinally from the first member and can be inserted between the one portion and the other portion of the first case member.

4. a third member supported to be rotatable relative to the second member about a second rotation axis; a second encoder unit that detects a relative rotation angle between the second member and the third member, The second encoder unit a second case member that defines a second space that can be opened and closed by a second cover member and that can be fixed to the second member; a second encoder disposed in the second space, the second case member has a through hole that exposes to the outside one axial end of the third member or a member fixed to the third member, the second encoder comprises: an annular second scale fixed to the third member or to a cylindrical outer peripheral surface of the member fixed to the third member around the second rotation axis, with its central axis coinciding with the second rotation axis; and a second sensor fixed to the second case member in a state facing the second scale and configured to read the second scale, The robot according to claim 1 , wherein the first space and the second space are in communication with each other, and wiring to the first sensor and the second sensor can be laid inside the first space and the second space.

5. The robot according to claim 4 , further comprising a second seal member that seals between the second case member and the outer circumferential surface of the third member or the member fixed to the third member.

6. a joint structure having a reducer, The robot according to claim 1 , wherein the encoder unit is disposed on a side of the joint structure opposite to a side on which the reducer is disposed with respect to a joint axis of the joint structure.

7. an encoder unit that detects a relative rotation angle between a first member and a second member that are supported so as to be relatively rotatable about a first rotation axis of a robot, a first case member that defines a first space that can be opened and closed by a first cover member and that can be fixed to the second member; a shaft member supported by the first case member so as to be rotatable about a predetermined first axis; a first encoder disposed in the first space; the shaft member passes through a first through-hole provided in the first case member, and one end of the shaft member in the axial direction is exposed to the outside of the first case member; the first encoder comprises: a first annular scale fixed to the shaft member with its central axis aligned with the first axis; and a first sensor fixed to the first case member in a state facing the first scale and configured to read the first scale; the first case member can be attached to the second member with the first axis of the shaft member aligned with the first rotation axis, the one end of the shaft member is fixable to the first member; a second encoder unit configured to detect a relative rotation angle between the second member and a third member supported so as to be relatively rotatable about a second rotation axis of the robot; The second encoder unit a second case member that defines a second space that can be opened and closed by a second cover member and that can be fixed to the second member; a second encoder disposed in the second space, the second case member has a through hole that exposes to the outside one axial end of the third member or a member fixed to the third member, the second encoder comprises: an annular second scale fixed to the third member or to a cylindrical outer peripheral surface of the member fixed to the third member around the second rotation axis, with its central axis coinciding with the second rotation axis; and a second sensor fixed to the second case member in a state facing the second scale and configured to read the second scale, The encoder unit has the first space and the second space communicating with each other, and wiring to the first sensor and the second sensor can be laid inside the encoder unit.

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