Sealing structure

Abstract

This sealing structure comprises: a first member and a second member which are provided in a joint portion of a robotic arm, rotate relative to each other about an axis by the driving of a motor, and have opposing surfaces that face each other; a lubricated unit which is located to one side of the opposing surfaces in a direction along the axis and to which a lubricant is applied; an optical sensor that is disposed to the other side of the opposing surfaces in the direction along the axis; and a seal member that is interposed between the opposing surfaces. The seal member comprises pile-like fibers that seal a void between the opposing surfaces.

Description

Seal Structure

[0001] The present invention relates to a sealing structure in a drive mechanism provided in a joint of a robot arm or the like.

[0002] A robot arm having a joint has a structure in which a drive mechanism such as a motor and a reducer that serve as a power source for the robot arm is housed in a housing provided at the joint.

[0003] The drive mechanism incorporates optical sensors such as an encoder for detecting the amount of displacement in the arm's rotation and a torque sensor for detecting the rotational torque applied to the arm by the motor. Optical sensors are delicate, and detection errors can occur if they become dirty. Optical sensors are often placed near the motor or reducer. Since lubricants such as grease are applied to the sliding parts of the reducer, there is a high risk of the lubricant adhering to the optical sensor if it is placed near the reducer.

[0004] In view of these issues, for example, Patent Document 1 proposes a structure in which the main components of an encoder are housed in a container with a sealed space. However, it is practically difficult to apply such a structure to the joint, which has limited space. Alternatively, it is possible to provide a general oil seal such as a packing to prevent the movement of lubricant. However, in this case, friction torque is generated, which leads to a decrease in motor output and a decrease in the transmission efficiency of the reducer, and as a result, the smooth operation of the robot arm may be hindered.

[0005] Therefore, there is a need for a simple sealing structure that can prevent the adhesion of lubricant to the optical sensor without interfering with the smooth operation of the robot arm.

[0006] Japanese Patent Application Laid-Open No. 2020-169918

[0007] An object of the present invention is to provide a seal structure that can suppress adhesion of a lubricant to an optical sensor with a simple structure without interfering with the smooth operation of a robot arm.

[0008] A sealing structure according to one aspect of the present invention is provided at a joint portion of a robot arm, and comprises a first member and a second member that rotate relatively about an axis by being driven by a motor and each have opposing surfaces that face each other; a lubricant application section that is located on one side of the opposing surfaces in a direction along the axis and to which a lubricant is applied; an optical sensor that is disposed on the other side of the opposing surfaces in a direction along the axis; and a sealing member that is interposed between the opposing surfaces, and that comprises pile-like fibers that seal between the opposing surfaces.

[0009] Fig. 1 is a perspective view of an articulated robot according to an embodiment of the present invention. Fig. 2 is a cross-sectional view of a first rotary joint. Fig. 3 is a perspective cross-sectional view of a portion of the first drive mechanism excluding the electric motor. Fig. 4 is a cross-sectional view of an exploded view of the portion of the first drive mechanism excluding the electric motor. Fig. 5 is a cross-sectional view of a main portion of the first drive mechanism showing the seal structure. Fig. 6 is a plan view of a seal member. Fig. 7 is a plan view of a seal member according to a modified example.

[0010] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0011] [Overall Configuration of Robot] Fig. 1 is a perspective view of an articulated robot 1 according to an embodiment. The articulated robot 1 is an example of an industrial robot to which a sealing structure according to the present invention is applied. Here, a vertical articulated seven-axis robot is illustrated as the articulated robot 1. The articulated robot 1 includes a robot arm 10 having seven rotation axes: a first axis 2A, a second axis 2B, a third axis 2C, a fourth axis 2D, a fifth axis 2E, a sixth axis 2F, and a seventh axis 2G. Each of the axes 2A to 2G is a virtual axis line.

[0012] The robot arm 10 includes a base portion 11 , a body portion 12 , a first arm 13 , a second arm 14 , a third arm 15 , and a head portion 16 .

[0013] The base 11 is a housing that is fixedly installed on a floor, a pedestal, or the like. The trunk 12 is connected to the upper surface of the base 11 via a first rotary joint 21. The first rotary joint 21 allows the trunk 12 to rotate in both forward and reverse directions around a first axis 2A extending vertically. The first arm 13 has a predetermined length, and its base end is connected to the trunk 12 via a first swing joint 22. The first arm 13 is swingable around a second axis 2B extending horizontally via the first swing joint 22. The first arm 13 includes a second rotary joint 23 at its intermediate position. The tip piece of the first arm 13 is rotatable around a third axis 2C extending in the arm axial direction via the second rotary joint 23.

[0014] The second arm 14 is an arm connected to the downstream side of the first arm 13, and its base end is connected to the tip end of the first arm 13 via a second pivot joint 24. The second arm 14 is capable of pivoting around a fourth axis 2D extending horizontally via the second pivot joint 24. The second arm 14 is provided with a third rotary joint 25 at its intermediate position. The tip piece of the second arm 14 is capable of rotating around a fifth axis 2E extending in the arm axial direction via the third rotary joint 25.

[0015] The third arm 15 is an arm connected downstream of the second arm 14, and its base end is connected to the tip of the second arm 14 via a third swing joint 26. The third arm 15 can swing around a sixth shaft 2F extending horizontally by the third swing joint 26. The head unit 16 is attached to the tip of the third arm 15 so as to be rotatable around a seventh shaft 2G extending vertically.

[0016] Each of the joints 21 to 26 houses a drive mechanism that drives the robot arm 10. Specifically, the first rotary joint 21 houses a first drive mechanism 3A that rotates the torso 12 relative to the base 11 about a first axis 2A, the first swing joint 22 houses a second drive mechanism 3B that swings the first arm 13 about a second axis 2B relative to the torso 12, and the second rotary joint 23 houses a third drive mechanism 3C that rotates the tip piece of the first arm 13 about a third axis 2C.

[0017] The second pivot joint 24 houses a fourth drive mechanism 3D that pivots the second arm 14 about a fourth axis 2D relative to the first arm 13, the third rotary joint 25 houses a fifth drive mechanism 3E that rotates the tip piece of the second arm 14 about a fifth axis 2E, and the third pivot joint 26 houses a sixth drive mechanism 3F that pivots the third arm 15 about a sixth axis 2F relative to the second arm 14. The third arm 15 also houses a seventh drive mechanism 3G that rotates the head unit 16 about a seventh axis 2G.

[0018] [Detailed Structure of Joints] The detailed structures of the first rotary joint 21, the second rotary joint 23, and the third rotary joint 25 will be described using the first rotary joint 21 as an example. The second rotary joint 23 and the third rotary joint 25 also have substantially the same structure as the first rotary joint 21.

[0019] Figure 2 is a cross-sectional view of the first rotary joint 21 shown in Figure 1. As described above, the first rotary joint 21 (hereinafter simply referred to as the joint 21) is a joint that connects the base 11 and the trunk 12 to be rotatable in both forward and reverse directions around the first shaft 2A (axis).

[0020] The joint unit 21 is provided with a storage unit 4 for storing the drive mechanism of the robot arm 10. The joint unit 21 is configured such that the upper end of the housing of the base unit 11 and the lower end of the body unit 12 are aligned vertically, and has a generally cylindrical shape. The storage unit 4 is a generally cylindrical storage space provided inside the generally cylindrical joint unit 21.

[0021] The first drive mechanism 3A (hereinafter simply referred to as the drive mechanism 3A) is housed in the housing 4. As described above, the drive mechanism 3A is a drive mechanism that rotates the body 12 relative to the base 11 about the first axis 2A (axis line).

[0022] The drive mechanism 3A includes an electric motor 30, a reducer 40, and a sensor unit 50. The electric motor 30, the reducer 40, and the sensor unit 50 are arranged in this order from top to bottom. The drive mechanism 3A is configured as a modular component having a generally cylindrical shape in which the electric motor 30, the reducer 40, and the sensor unit 50 are assembled together with a gear holder 45 and a bearing 47, which will be described later.

[0023] The electric motor 30 is a drive source that rotates the body 12 about the first axis 2A. The electric motor 30 includes a cylindrical motor housing 31, a stator 32 fixed to the inner wall surface of the motor housing 31, and a rotor 33 disposed inside the stator 32. The rotor 33 has a cylindrical shape that also serves as the motor shaft, and is rotatably supported by the motor housing 31 via a bearing 31a.

[0024] An annular flange 121 is formed on the inner wall of the housing lower end of the body 12. The motor housing 31 is fixed to this flange 121, thereby fixing the electric motor 30 to the body 12. In other words, the stator 32 side of the electric motor 30 is fixed to the body 12.

[0025] The reducer 40 reduces the rotation of the electric motor 30 at a predetermined reduction ratio and transmits the rotation. The reducer 40 is made of a well-known strain wave gear device called Harmonic Drive (registered trademark).

[0026] FIG. 3 is a perspective cross-sectional view of the drive mechanism 3A excluding the electric motor 30, and FIG. 4 is an exploded cross-sectional view of the drive mechanism 3A excluding the electric motor 30.

[0027] The reducer 40 has a generally cylindrical shape and, as shown in FIGS. 2 to 4 , includes a wave generator 41, a circular spline 42, and a flexspline 43. The wave generator 41 has a configuration in which a thin-walled elastic metal body is fitted onto the outer periphery of a cam that is elliptical in plan view, via a bearing. FIG. 3 does not show a detailed cross section of the wave generator 41. The flexspline 43 is disposed on the outer periphery of the wave generator 41 so that the outer periphery of the flexspline 43 is in sliding contact with the wave generator 41, and includes a thin-walled elastic metal body having a toothed surface (gear) on the outer periphery. More specifically, the flexspline 43 has a cup-like shape with a cylindrical circumferential surface portion 431 and a bottom surface portion 432, and has a toothed surface on the outer periphery of the upper end portion of the circumferential surface portion 431. The circular spline 42 is a rigid metal ring whose inner periphery meshes with the gear of the flexspline 43 and has a toothed surface (gear) with fewer teeth than the gear.

[0028] The rotor 33 of the electric motor 30 is fixed to the wave generator 41 of the reducer 40. Therefore, the rotation of the electric motor 30 is input to the wave generator 41.

[0029] The reducer 40 is disposed in a cup-shaped gear holder 45. The gear holder 45 is an intermediate member for transmitting the output from the reducer 40 to the body portion 12.

[0030] The gear holder 45 includes a peripheral wall portion 451 located on the outer periphery of the reducer 40, and a bottom wall portion 452 facing the underside of the reducer 40, more specifically, the bottom surface portion 432 of the flexspline 43. As shown in Figures 2 and 3 , the peripheral wall portion 451 is fixed to the circular spline 42 and is also fixed to the lower end of the motor housing 31 of the electric motor 30.

[0031] A bearing 47 is disposed on the outer periphery of the gear holder 45. The bearing 47 is, for example, a cross roller bearing. The bearing 47 includes an outer ring 471 and an inner ring 472 that are rotatable relative to each other around the first shaft 2A. The lower end of the gear holder 45 is inserted into the inner ring 472 of the bearing 47, and the peripheral wall portion 451 is fixed to the inner ring 472. In other words, the gear holder 45 is fixed to the circular spline 42 of the reducer 40, the motor housing 31 of the electric motor 30, and the inner ring 472 of the bearing 47.

[0032] A sensor unit 50 is disposed below the bearing 47. The sensor unit 50 detects the amount of rotational displacement of the body 12 and also detects the rotational torque that the electric motor 30 applies to the body 12.

[0033] The sensor unit 50 includes a strain body 53 and an optical sensor 54. The strain body 53 is a structure made of a metal or resin material and is primarily used to detect rotational torque. The strain body 53 has a spoke-wheel shape in a plan view and includes an outer cylindrical portion 531, an inner cylindrical portion 532, and a plurality of connecting portions 533 that connect the outer cylindrical portion 531 and the inner cylindrical portion 532 at a plurality of positions in the circumferential direction.

[0034] 2, an annular flange portion 111 is formed on the inner wall of the housing of the base portion 11. The outer cylinder portion 531 of the strain element 53 is fixed to the flange portion 121 while being supported by the flange portion 121. In this way, the strain element 53 is fixed to the base portion 11.

[0035] 3 and 4, the optical sensor 54 includes a sensor substrate 55, an upper reflector 56, and a lower reflector 57. The sensor substrate 55, the upper reflector 56, and the lower reflector 57 all have an annular shape in a plan view.

[0036] The sensor substrate 55 is disposed above the connecting portion 533 of the strain generating body 53 and in the space between the outer cylinder portion 531 and the inner cylinder portion 532. The sensor substrate 55 is fixed to the outer cylinder portion 531 via a sensor holder 58. Therefore, the sensor substrate 55 is capable of displacement around the first axis 2A relative to the inner cylinder portion 532.

[0037] The lower reflecting plate 57 and the upper reflecting plate 56 are arranged symmetrically above and below the sensor substrate 55. Specifically, the lower reflecting plate 57 is arranged on the outer periphery of the inner cylindrical portion 532 of the strain generating body 53 and in a position facing the lower surface of the sensor substrate 55. The lower reflecting plate 57 is fixed to the inner cylindrical portion 532.

[0038] On the other hand, the upper reflecting plate 56 is fixed to the lower surface of the bottom wall portion 452 of the gear holder 45 at a position facing the upper surface of the sensor board 55. More specifically, as shown in FIGS. 2 to 4, the bottom wall portion 452 of the gear holder 45 is disposed inside the inner ring 472 of the bearing 47 together with the bottom surface portion 432 of the flexspline 43 of the reducer 40. A circular opening 453 (see FIG. 4) is formed in the bottom wall portion 452 of the gear holder 45, and the upper reflecting plate 56 is fixed along the edge of this opening 453.

[0039] The inner cylindrical portion 532 of the flexure body 53 is inserted into the opening 453 of the gear holder 45. The inner cylindrical portion 532 is fixed to the bottom surface portion 432 of the flexspline 43. Therefore, the gear holder 45 is rotatable around the first axis 2A relative to the inner cylindrical portion 532 of the flexure body 53.

[0040] The sensor substrate 55 includes a rotation detection sensor on its upper surface for detecting rotational displacement and a torque detection sensor on its lower surface for detecting rotational torque. Both the rotation detection sensor and the torque detection sensor are photosensors equipped with a light-emitting element and a light-receiving element. Reflecting surfaces that reflect light emitted from the light-emitting element are provided at regular intervals in the circumferential direction on the lower surface of the upper reflecting plate 56 and the upper surface of the lower reflecting plate 57. With this configuration, when the upper reflecting plate 56 together with the gear holder 45 displaces around the first axis 2A relative to the sensor substrate 55, the rotation detection sensor outputs an electrical signal corresponding to the amount of rotational displacement. Furthermore, when the lower reflecting plate 57 together with the inner cylindrical portion 532 of the strain element 53 displaces around the first axis 2A relative to the sensor substrate 55—in other words, when the inner cylindrical portion 532 distorts (twists) relative to the outer cylindrical portion 531—the torque detection sensor outputs an electrical signal corresponding to the amount of distortion.

[0041] That is, the sensor board 55 (rotation detection sensor) and the upper reflecting plate 56 of the sensor unit 50 function as a rotary encoder 52 that detects the amount of rotational displacement of the trunk 12. Furthermore, the strain element 53, the sensor board 55 (torque detection sensor), and the lower reflecting plate 57 of the sensor unit 50 function as a torque sensor 51 that detects the rotational torque that the electric motor 30 applies to the trunk 12.

[0042] The relationship between the operation of the drive mechanism 3A and the sensing by the sensor unit 50 is as follows.

[0043] When the electric motor 30 is operated and the rotor 33 rotates relative to the stator 32, this rotation is input to the wave generator 41 of the reducer 40. When the wave generator 41 rotates, the flexspline 43 elastically deforms in accordance with the rotation and meshes with the circular spline 42 at the major axis portion of the wave generator 41. As a result, the rotation of the electric motor 30 is reduced at a predetermined reduction ratio according to the number of teeth of the flexspline 43 and the circular spline 42.

[0044] As described above, the flexspline 43 is fixed to the strain element 53 (inner cylindrical portion 532) of the sensor unit 50. Therefore, the flexspline 43 does not rotate, and the meshing position between the flexspline 43 and the circular spline 42 moves in the circumferential direction, causing the circular spline 42 to rotate. The circular spline 42 is fixed to the motor housing 31 and the bearing 47 (inner ring 472) via the gear holder 45. Therefore, when the electric motor 30 is operated, the stator 32 and motor housing 31 rotate relative to the rotor 33, and as a result, the body portion 12 rotates relative to the base portion 11.

[0045] Furthermore, as the gear holder 45 rotates together with the circular spline 42, the upper reflecting plate 56 fixed to the gear holder 45 moves in the circumferential direction relative to the sensor substrate 55. As a result, the rotary encoder 52 of the sensor unit 50 detects the amount of rotational displacement of the trunk portion 12.

[0046] On the other hand, when a load torque acts on the body 12, the load torque acts on the inner cylindrical portion 532 of the flexure body 53 via the wave generator 41, the circular spline 42, and the flexspline 43. As a result, the inner cylindrical portion 532 of the flexure body 53 rotates relative to the outer cylindrical portion 531. That is, the flexure body 53 is distorted. This distortion of the flexure body 53 causes the lower reflecting plate 57 fixed to the outer cylindrical portion 531 to move in the circumferential direction relative to the sensor board 55. As a result, the torque sensor 51 of the sensor unit 50 detects the load torque, i.e., the rotational torque that the electric motor 30 applies to the body 12.

[0047] 2, reference numeral 35 denotes a harness pipe. The harness pipe 35 is a pipe member for wiring that is arranged vertically in the center of the first drive mechanism 3A. The harness pipe 35 has its lower end fixed to the inner cylindrical portion 532 of the strain element 53 and is arranged to pass through the centers of the reducer 40 and the electric motor 30. With this configuration, a wire harness can be routed from the base portion 11 to the trunk portion 12 through the inside of the first drive mechanism 3A.

[0048] 2 to 4, grease is applied to the drive mechanism 3A to ensure continuous smooth operation of the reducer 40. Grease is a semi-solid or solid lubricant made by adding a thickener and additives to a base oil such as mineral oil or synthetic oil.

[0049] 3, the grease application area Ga (lubricant application portion) is indicated by a dashed line frame. The area where the wave generator 41, the circular spline 42, and the flexspline 43 overlap is the grease application area Ga. In other words, the grease application area Ga is the sliding portion between the wave generator 41 and the flexspline 43 and the meshing portion between the flexspline 43 and the circular spline 42.

[0050] Applying grease is essential for smooth operation of the reducer 40. However, the optical sensor 54 is disposed below the reducer 40, and the optical sensor 54 is sensitive, and detection errors occur if it becomes dirty. In the structure of the drive mechanism 3A described above, the gear holder 45 rotates relative to the flexspline 43. Therefore, gaps exist between the outer circumferential surface of the peripheral surface portion 431 of the flexspline 43 and the inner circumferential surface of the peripheral wall portion 451 of the gear holder 45, and between the lower surface of the bottom surface portion 432 of the flexspline 43 and the upper surface of the bottom wall portion 452 of the gear holder 45. Similarly, a gap exists between the inner circumferential surface 453a of the opening 453 formed in the bottom wall portion 452 of the gear holder 45 and the outer circumferential surface 532a of the inner cylindrical portion 532 of the strain body 53. If grease moves from the application area Ga to the optical sensor 54 along a path Gr consisting of these gaps, the grease may adhere to the optical sensor 54.

[0051] For this reason, the drive mechanism 3A is provided with a seal structure to prevent the grease applied to the reducer 40 from adhering to the optical sensor 54.

[0052] 3 to 5, a seal member 60 is provided between an inner peripheral surface 453a of the opening 453 of the gear holder 45 (second member) and an outer peripheral surface 532a of the inner cylindrical portion 532 (first member) of the strain body 53.

[0053] The inner circumferential surface 453a of the opening 453 of the gear holder 45 and the outer circumferential surface 532a of the inner cylindrical portion 532 of the flexure body 53 are opposing surfaces that face each other in the radial direction about the first axis 2A. In the direction of the first axis 2A, the application area Ga is located above the opposing surfaces, and the optical sensor 54 is located below the opposing surfaces. The seal member 60 seals between the inner circumferential surface 453a of the opening 453 of the gear holder 45 and the outer circumferential surface 532a of the inner cylindrical portion 532 of the flexure body 53, thereby suppressing the movement of grease along the path Gr from the application area Ga to the optical sensor 54.

[0054] FIG. 6 is a plan view showing the seal member 60. The seal member 60 includes a base portion 61 that is ring-shaped in plan view and a fibrous seal portion 62 fixed to the inner circumferential surface of the base portion 61. The base portion 61 is formed from a metal leaf spring. More precisely, the base portion 61 is C-shaped, with a gap 61a between both ends. The base portion 61 is elastically deformable in the radial direction within the range of this gap 61a. In other words, the base portion 61 can be deformed between a state in which both ends abut each other and a state in which they are separated. The seal portion 62 is made of pile-like fibers fixed to the inner circumferential surface of the base portion 61. The pile-like fibers are a fibrous material with a high density of pile-like nap.

[0055] The seal member 60 is disposed inside the opening 453 of the gear holder 45 with the base portion 61 deformed in the radial direction, and is held inside the opening 453 by the elastic force of the base portion 61. As a result, the seal member 60 is disposed between the inner circumferential surface 453a of the opening 453 of the gear holder 45 and the outer circumferential surface 532a of the inner cylindrical portion 532 of the strain body 53 with the base portion 61 in close contact with the inner circumferential surface 453a of the opening 453 of the gear holder 45 and the seal portion 62 compressed.

[0056] In this way, the seal member 60 is provided to prevent the grease from moving from the application area Ga to the optical sensor 54 .

[0057] Step portions 454 (restricting portions) are formed on the inner peripheral surface 453a of the opening 453 of the gear holder 45 on both the top and bottom sides of the seal member 60. The step portions 454 can be engaged with the base portion 61 of the seal member 60, thereby restricting displacement (misalignment) of the seal member 60 in the up and down direction.

[0058] A downwardly recessed recess 452a is formed on the upper surface of the bottom wall portion 452 of the gear holder 45. The recess 452a is continuous in the circumferential direction along the opening 453 and is formed in a circular ring shape in a plan view. The recess 452a has a depth sufficient to store grease when the grease moves from the application area Ga to the optical sensor 54 along the path Gr. For example, the recess 452a is formed to be approximately equal to or deeper than the width (vertical width) of the inner circumferential surface 453a of the opening 453 along the first axis 2A. By storing grease in the recess 452a, the movement of grease to the optical sensor 54 is restricted.

[0059] [Effect] According to the above-described sealing structure of the drive mechanism 3A, the seal member 60 provided between the application area Ga of the reducer 40 and the optical sensor 54 effectively prevents grease from migrating from the application area Ga toward the optical sensor 54. In this case, the seal member 60 seals the gap between the inner circumferential surface 453a of the gear holder 45 (second member) and the inner circumferential surface 453a of the inner cylindrical portion 532 (first member) of the strain body 53 with a seal portion 62 including pile fibers. Pile fibers are flexible and have lower frictional resistance than typical oil seals such as rubber packings, while retaining grease in the pile portion and preventing its migration. This allows for a simple structure to prevent grease from adhering to the optical sensor 54 without impeding the smooth operation of the drive mechanism 3A and, ultimately, the robot arm 10.

[0060] In particular, the seal member 60 has pile fibers interposed in a compressed state between the inner circumferential surface 453 a of the gear holder 45 and the inner circumferential surface 453 a of the inner cylindrical portion 532 of the strain generating body 53. This allows the pile fibers to densely fill the gap between the inner circumferential surface 453 a of the gear holder 45 and the inner circumferential surface 453 a of the inner cylindrical portion 532, thereby more reliably preventing the movement of grease.

[0061] The sealing member 60 includes an elastically deformable base portion 61 and a sealing portion 62 made of pile fibers attached to the base portion 61, and is held between the inner circumferential surface 453 a of the gear holder 45 and the inner circumferential surface 453 a of the inner cylinder portion 532 by the elastic force of the base portion 61. Therefore, the sealing member 60 can be stably interposed between the inner circumferential surface 453 a of the gear holder 45 and the inner circumferential surface 453 a of the inner cylinder portion 532 with a simple configuration that utilizes the elastic force of the base portion 61.

[0062] Furthermore, in the above-described seal structure, a step portion 454 is provided on the inner circumferential surface 453a of the gear holder 45 to engage with the base portion 61 and restrict vertical displacement of the seal member 60 (the direction along the first axis 2A). This prevents the seal member 60 from shifting from its fixed position, and the seal member 60 can continuously and stably prevent the movement of grease from the application area Ga toward the optical sensor 54.

[0063] Furthermore, in the above-described seal structure, a recess 452a that prevents the movement of grease is provided midway along the path Gr from the application area Ga to the seal member 60. This recess 452a has a shape that allows the grease to be stored. Therefore, with the above-described seal structure, the movement of grease to the optical sensor 54 can be more effectively prevented, and as a result, the adhesion of grease to the optical sensor 54 can be more reliably suppressed.

[0064] [Modifications] The industrial robot 1 to which the sealing structure according to the present invention is applied has been described above. However, the articulated robot 1 is merely an example of an industrial robot equipped with a robot arm to which the sealing structure according to the present invention is applied, and the specific configuration of the articulated robot and the specific sealing structure can be modified as appropriate without departing from the spirit of the present invention. For example, the following configurations can also be applied.

[0065] (1) In the seal structure of the embodiment, the seal member 60 is disposed with the base portion 61 in close contact with the inner circumferential surface 453a of the opening 453 of the gear holder 45. However, the seal member 60 may also be disposed with the base portion 61 in close contact with the outer circumferential surface 532a of the inner cylindrical portion 532 of the strain body 53. In this case, for example, as shown in FIG. 7 , the seal member 60 having the seal portion 62 on the outer circumferential surface of the base portion 61 can be fitted onto the inner cylindrical portion 532 of the strain body 53 by its elastic force. In this case, similar to the stepped portion 454, a restricting portion that engages with the base portion 61 to restrict displacement of the seal member 60 can be provided on the inner cylindrical portion 532.

[0066] (2) In the embodiment, the seal member 60 is provided between the inner circumferential surface 453 a of the opening 453 of the gear holder 45 and the outer circumferential surface 532 a of the inner cylindrical portion 532 of the strain body 53. However, the seal member 60 may be provided to seal between the upper surface of the bottom wall portion 452 of the gear holder 45 and the lower surface of the bottom portion 432 of the reducer 40, for example.

[0067] (3) In the embodiment, a recess 452a is provided as an obstacle that prevents the movement of grease along the path Gr from the application area Ga to the seal member 60. However, the obstacle is not limited to the recess 452a and can be changed as appropriate. For example, the obstacle may be a convex portion (annular convex portion) formed on the upper surface of the bottom wall portion 452 of the gear holder 45. Alternatively, the obstacle may be a configuration in which a plurality of concentric recesses (or convex portions) are provided on the upper surface of the bottom wall portion 452 of the gear holder 45, the convex portion being continuous in the circumferential direction.

[0068] (4) In the embodiment, the detailed structures of the first rotary joint 21, the second rotary joint 23, and the third rotary joint 25 have been described using the first rotary joint 21 as an example. However, the structure of the first rotary joint 21, i.e., the structure of the first drive mechanism 3A including the sealing structure, can also be applied to the first swing joint 22, the second swing joint 24, and the third swing joint 26. In this case, since the second shaft 2B, the fourth shaft 2D, and the sixth shaft 2F extend horizontally, if the structure of the first drive mechanism 3A of the embodiment is applied directly to the first swing joint 22, the second swing joint 24, and the third swing joint 26, the recess 452a of the gear holder 45 will be configured to be recessed sideways. This makes it difficult for grease to accumulate in the recess 452a. However, since the recess 452a hinders the movement of grease, the recess 452a functions as an obstacle in the present invention.

[0069] [Invention Included in the Above Embodiments] A sealing structure according to one aspect of the present invention is provided at a joint portion of a robot arm, and comprises a first member and a second member that are driven by a motor to rotate relatively about an axis and each have opposing surfaces that face each other, a lubricant application section that is located on one side of the opposing surfaces in a direction along the axis and to which a lubricant is applied, an optical sensor that is disposed on the other side of the opposing surfaces in the direction along the axis, and a sealing member that is interposed between the opposing surfaces, and the sealing member comprises pile-like fibers that seal between the opposing surfaces.

[0070] According to the above-described sealing structure, a sealing member interposed between the lubricant application portion and the optical sensor prevents the lubricant from migrating from the lubricant application portion to the optical sensor. In this case, the sealing member seals the space between the opposing surfaces of the first and second members with pile fibers. The pile fibers are flexible and have lower frictional resistance than typical oil seals such as rubber packings, while retaining the lubricant in the pile portion and preventing its migration. This makes it possible to suppress the adhesion of lubricant to the optical sensor with a simple structure without interfering with the smooth operation of the motor-driven robot arm.

[0071] In the above seal structure, the seal member may be interposed between the opposing surfaces with the pile fibers compressed.

[0072] According to this structure, the pile fibers are densely filled between the opposing surfaces, so that the movement of the lubricant can be more reliably prevented.

[0073] In the above-described sealing structure, the sealing member may include a base portion capable of elastic deformation and a sealing portion made of the pile-like fibers attached to the base portion, and may be configured to be held between the opposing surfaces by the elastic force of the base portion.

[0074] According to this structure, the seal member can be stably interposed between the opposing surfaces with a simple configuration that utilizes the elastic force of the base portion.

[0075] In this case, for example, if the opposing surfaces are the outer peripheral surface of the first member and the inner peripheral surface of the second member, which face each other in a radial direction perpendicular to the axis, the base portion can have a C-shaped ring shape that can elastically deform in the radial direction, and the sealing portion can be configured to be provided on the inner peripheral surface or outer peripheral surface of the base member.

[0076] According to this structure, the C-shaped ring-shaped base portion can be deformed in the radial direction, and the resulting elastic force can be used to hold the seal member between the outer peripheral surface of the first member and the inner peripheral surface of the second member.

[0077] In the above seal structure, a restricting portion may be provided on the opposing surface, which engages with the base portion and restricts displacement of the seal member in a direction along the opposing surface.

[0078] This structure prevents the seal member from shifting from its fixed position, allowing the seal member to more continuously and stably prevent the lubricant from moving from the lubricant application portion to the optical sensor side at the fixed position.

[0079] In the above seal structure, an obstacle for preventing the movement of the lubricant may be provided midway along the path from the lubricant application portion to the seal member.

[0080] According to this structure, the obstruction prevents the movement of the lubricant from the lubricant application portion to the sealing member side, which makes it possible to more effectively prevent the lubricant from adhering to the optical sensor.

[0081] In this case, the obstruction portion may be a recess capable of storing the lubricant.

[0082] According to this structure, the lubricant is collected in the recess, and thus migration toward the seal member can be prevented.

Claims

1. A sealing structure comprising: a first member and a second member provided at a joint portion of a robot arm, which rotate relatively about an axis driven by a motor and each have opposing surfaces facing each other; a lubricant application unit located on one side of the opposing surfaces in a direction along the axis and to which a lubricant is applied; an optical sensor disposed on the other side of the opposing surfaces in a direction along the axis; and a sealing member interposed between the opposing surfaces, wherein the sealing member has pile-like fibers that seal between the opposing surfaces.

2. A seal structure according to claim 1, wherein the seal member has the pile fibers interposed between the opposing surfaces in a compressed state.

3. A seal structure according to claim 1 or 2, wherein the seal member comprises an elastically deformable base portion and a seal portion made of the pile-like fibers attached to the base portion, and is held between the opposing surfaces by the elastic force of the base portion.

4. A seal structure as claimed in claim 3, wherein the opposing surfaces are the outer peripheral surface of the first member and the inner peripheral surface of the second member, which face each other in a radial direction perpendicular to the axis, the base portion has a C-shaped ring shape that is elastically deformable in the radial direction, and the seal portion is provided on the inner peripheral surface or the outer peripheral surface of the base member.

5. A seal structure according to claim 3 or 4, wherein the opposing surface is provided with a restricting portion that engages with the base portion and restricts displacement of the seal member in a direction along the opposing surface.

6. A seal structure according to any one of claims 1 to 5, wherein an obstacle for preventing the movement of the lubricant is provided midway along the path from the lubricant application portion to the seal member.

7. A seal structure according to claim 6, wherein the obstruction portion is a recess capable of storing the lubricant.

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