JP2011020213A - Wrist driving structure of industrial robot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wrist driving structure of an industrial robot having a streamlined arm for supporting a wrist member. <P>SOLUTION: A wrist member 15 is oscillatingly and rotatingly arranged on a second arm 14 of a robot. An oscillating mechanism of the wrist member 15 includes: a first gear 21 which is pivotably supported by a first driven rotary shaft 22 connected to the wrist member 15 and rotatingly arranged on the second arm 14; a first motor 61; a reduction gear 40; a first belt 64 for transmitting the rotation of the first motor 61 to the reduction gear 40; and a second gear 41 pivotably supported by an output side rotary shaft of the reduction gear 40 and engaged with the first gear 21. A rotating mechanism of the wrist member 15 includes a second motor 66, a second driven rotary shaft 31 which is coaxially arranged with the first driven rotary shaft 22, bevel gears 35, 36 for converting the rotation of the second driven rotary shaft 31 to the rotation of the shaft orthogonal thereto, and a second belt 69 for transmitting the rotation of the second motor 66 to the second driven rotary shaft 31. The first belt 64 and the second belt 69 are turned in the same plane. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wrist drive structure for an industrial robot such as an arc welding robot, and more particularly to a wrist drive structure for an industrial robot that has improved workability in a narrow part of a structure by slimming an arm.

  As an arc welding robot which is a kind of industrial robot, one having a 6-axis joint structure is widely used. The wrist member that holds the welding torch can be moved by a fifth shaft that is a swing shaft and a sixth shaft that is a rotation shaft. The wrist member is supported on the distal end side of the arm, and a fifth axis is provided perpendicular to the longitudinal direction of the arm, and a sixth axis is provided so as to be orthogonal to the fifth axis. The first to fourth axes of the arc welding robot are provided between the base end side of the arm and the base of the arc welding robot.

  A so-called cantilever support structure is known as a wrist member support structure. FIG. 10 is a transparent perspective view showing an arrangement example of the drive mechanisms of the fifth shaft and the sixth shaft in the conventional cantilever support structure.

(Fifth axis drive mechanism)
The arm 550 is provided with a motor 511. When the motor 511 is driven, the first pulley 512 attached to the rotation shaft of the motor 511 rotates, and the rotation of the first pulley 512 causes the speed reducer 514 to rotate. It is transmitted by a belt 513 to a second pulley (not shown) attached to an input side rotation shaft (not shown). In the speed reducer 514, the rotational speed is reduced by a predetermined speed reduction mechanism, and the first gear 515 attached to the output side rotation shaft (not shown) rotates. The first gear 515 meshes with a second gear 516 that is rotatably arranged around the fifth axis. The second gear 516 is pivotally supported by a cylindrical first driven rotary shaft member (not shown), and the first driven rotary shaft member is disposed on the arm 550 so as to be rotatable about the fifth axis. At the same time, it is fixed to the first wrist member 531 constituting the wrist member 560. Therefore, when the motor 511 is driven, the rotation is transmitted to the second gear 516, and the first driven rotation shaft member is rotated to swing the entire wrist member 560 about the fifth axis.

(Sixth axis drive mechanism)
The arm 550 is provided with a motor 521, and when the motor 521 is driven, the third pulley 522 attached to the rotation shaft of the motor 521 rotates, and the rotation of the third pulley 522 is fourth by the belt 523. It is transmitted to the pulley 524. The fourth pulley 524 is a second driven rotary shaft member (not shown) disposed coaxially with the first driven rotary shaft member of the fifth shaft and penetrating through the inside of the first driven rotary shaft member. ). A rotation axis conversion mechanism (not shown) is provided at the end of the second driven rotation shaft member on the wrist member 560 side, and rotation around the fifth axis is converted into rotation around the sixth axis. In the rotation around the axis, only the second wrist member 532 constituting the wrist member 560 is rotatable. Therefore, when the motor 521 is driven, the rotation is transmitted to the fourth pulley 524 to rotate the second driven rotation shaft member, and the rotation around the fifth axis is converted into the rotation around the sixth axis. The second wrist member 532 of 560 is rotated around the sixth axis.

  For such a cantilever support structure, a so-called both-end support structure is also used (see, for example, Patent Document 1). In the both-end support structure, a fifth-axis drive mechanism is disposed on one support portion, and a sixth-axis drive mechanism is disposed on the other support portion. As the drive mechanisms for the fifth axis and the sixth axis, those equivalent to the drive mechanisms for the fifth axis and the sixth axis used in the cantilever support structure shown in FIG. 10 can be used.

Japanese Patent Laid-Open No. 2003-200376

  However, in the cantilever support structure shown in FIG. 10, in the arm 550, the rotation of the motor 511 is transmitted to the first driven rotation shaft member, and the rotation of the motor 521 is transmitted to the second driven rotation shaft member. The occupied volume for arranging the mechanism is large, and thus the arm 550 is enlarged. As described above, in an arc welding robot having a wrist structure having a large arm 550, workability in a narrow portion of the structure is deteriorated. In addition, the same problem occurs in the double-sided support structure of the wrist member.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a wrist drive structure for an industrial robot in which an arm supporting a wrist member is slimmed.

  The wrist drive structure for an industrial robot according to the present invention is a wrist drive structure in which a wrist member is swingably and rotatably disposed on a predetermined arm in an industrial robot, and the wrist drive structure includes: A swing mechanism for the wrist member; and a rotation mechanism for the wrist member. The swing mechanism includes a driven rotation mechanism and a rotation drive mechanism for driving the driven rotation mechanism, and the driven rotation mechanism. Comprises a first driven rotary shaft coupled to the wrist member and rotatably arranged on the arm, and a first gear pivotally supported on the first driven rotary shaft, and the rotational drive The mechanism includes a first motor disposed at a predetermined position of the arm, a reduction gear disposed on the arm by pivotally supporting a second gear meshed with the first gear on an output-side rotation shaft, The rotation of the first motor is transmitted to the input side rotation shaft of the speed reducer. A first annular member, and the rotation mechanism includes a second motor disposed at a predetermined position of the arm, a second driven rotation shaft disposed coaxially with the first driven rotation shaft, A rotation converter that converts rotation of the second driven rotation shaft into rotation of an axis orthogonal to the axial direction of the second driven rotation shaft; and a second that transmits rotation of the second motor to the second driven rotation shaft. An annular member, wherein the first annular member is disposed on the inner peripheral side of the second annular member.

  According to such a configuration, since the first annular member is arranged on the inner peripheral side of the second annular member, the swinging mechanism and the rotating mechanism can be saved in space without interfering with each other. Therefore, a wrist driving structure with a slim arm is realized.

  In the wrist drive structure for an industrial robot according to the present invention, it is preferable that the speed reducer is a wave gear device, the rotation conversion unit is a bevel gear, and has a function of a speed reducer.

  According to such a configuration, the tip portion of the arm can be further slimmed by using the wave gear device, and conversion and reduction of the rotation axis can be easily performed by using the bevel gear for the rotation conversion unit. Can be done simultaneously with the structure.

  The wrist drive structure for an industrial robot according to the present invention is suitable for an arc welding robot. That is, the industrial robot is an arc welding robot having a six-axis joint structure, wherein the wrist member holds a welding torch, and the first axis and the second axis move the base end of the arm to a predetermined position. An axis mechanism of an axis and a third axis, and an axis mechanism of a fourth axis for rotating the arm around a central axis parallel to the length direction thereof, the first driven rotation axis being the fifth axis, It is preferable that the axis orthogonal to the axial direction of the second driven rotation axis is a sixth axis.

  In the arc welding robot having such a structure, the arm closest to the welding torch is slimmed, so that the welding workability in the narrow part of the structure is improved.

  According to the present invention, in the wrist drive structure of the industrial robot, the wrist drive structure in which the arm of the industrial robot is slimmed down because the swing mechanism and the rotation mechanism are compactly configured and arranged without interference. Is realized. At this time, the wrist drive structure can be further slimmed by using a wave gear device as a speed reducer for the swing mechanism and a bevel gear for the rotation mechanism. By slimming the wrist drive structure, the workability in the narrow portion is improved, and the work in a narrower space can be performed.

It is a side view which shows schematic structure of the arc welding robot in this invention. FIG. 5 is a transparent perspective view showing a schematic structure of a drive mechanism (swing mechanism) for a wrist swing shaft J5 and a drive mechanism (rotation mechanism) for a wrist rotation shaft J6 in the present invention. It is an AA perspective sectional view of FIG. FIG. 3 is a schematic side view of the swing mechanism of the wrist swing shaft J5 and the rotation mechanism of the wrist rotation shaft J6 according to the present invention when viewed from the direction of the arrow B shown in FIG. It is a schematic perspective view of the 2nd arm and wrist member in this invention. It is a schematic diagram which shows the example of arrangement | positioning of the screw hole formed in the casing of the reduction gear in this invention. In the present invention, (a) is a schematic diagram showing an example of arrangement of bolt insertion holes formed in a frame, and (b) is a communication between the screw holes shown in FIG. 6 and the bolt insertion holes shown in (a). It is a schematic diagram which shows an example of the made state. In this invention, it is the 1st schematic diagram which shows the form of the change of the position of the 2nd gear with respect to the 1st gear at the time of changing the position of the screw hole connected with respect to each bolt insertion hole. In this invention, it is a 2nd schematic diagram which shows the form of a change of the position of the 2nd gear with respect to the 1st gear at the time of changing the position of the screw hole connected with respect to each bolt insertion hole. It is a permeation | transmission perspective view which shows the example of arrangement | positioning of each drive mechanism of the 5th axis | shaft in a conventional cantilever support structure, and a 6th axis | shaft.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, the wrist drive structure of the arc welding robot will be described as an example as the wrist drive structure of the industrial robot according to the present invention.

<Schematic structure of arc welding robot>
FIG. 1 is a side view showing a schematic configuration of the arc welding robot. This arc welding robot includes a base 11 fixed on a floor surface and an arm 10 provided on the base 11. The arm 10 includes a base 12, a first arm 13, a second arm 14, and a wrist member 15. The base 12 is pivotably provided on the base 11 so as to function as the pivot axis J1. A first arm 13 is vertically provided on the upper surface of the base 12, and the first arm 13 is swingable so as to function as the front / rear swing shaft J <b> 2.

  The first arm 13 pivotally supports the second arm 14 so that the first arm 13 can function as a vertical swing axis J3, on the tip side thereof (opposite the end where the base 12 is located). The second arm 14 is rotatable so as to function as an arm rotation axis J4, and a wrist member 15 is provided on the distal end side (the side opposite to the end connected to the first arm 13). . The wrist member 15 is swingable and rotatable so as to function as a wrist swing axis J5 and a wrist rotation axis J6.

  A welding torch 17 is disposed on the wrist member 15 via a torch bracket 18. The torch bracket 18 supports a welding torch 17 by a wrist member 15 driven by a wrist rotation axis J6. The welding torch 17 communicates from the front end surface to the rear end surface, and has a consumable electrode type structure in which the welding wire 16 supplied to the rear end surface is inserted into the welding torch 17 and sent out from the front end surface. . The axial direction of the welding torch 17 and the length direction of the welding wire 16 are substantially parallel. The delivery direction of the welding wire 16 is set along the axis of the wrist rotation axis J6 (or so as to intersect the axis at a constant angle).

  In the arc welding robot configured as described above, a plurality of degrees of freedom are provided by the axes J1 to J6, whereby the tip of the welding wire 16 is placed at an arbitrary position in the three-dimensional spatial coordinates (X, Y, Z). Can be moved.

<Structure around wrist swing axis J5 and wrist rotation axis J6>
FIG. 2 is a transparent perspective view showing a schematic structure of the drive mechanism (swing mechanism) of the wrist swing shaft J5 and the drive mechanism (rotation mechanism) of the wrist rotation shaft J6, and FIG. A perspective sectional view is shown, and FIG. 4 is a schematic side view of the swing mechanism of the wrist swing shaft J5 and the rotation mechanism of the wrist rotation shaft J6 when viewed from the direction of the arrow B shown in FIG. In addition, the arrow D shown in FIG. 2 shows the arrow direction of FIGS. 6-9 demonstrated later.

[Oscillation mechanism of wrist oscillation axis J5]
The swing mechanism of the wrist swing shaft J5 generally includes a first driven rotation mechanism 20 and a rotation drive mechanism that drives the first driven rotation mechanism 20. The rotation drive mechanism includes a first motor 61. And a speed reducer 40 and a transmission mechanism (pulley, belt, etc.) for transmitting the rotation of the first motor 61 to the speed reducer 40.

  As shown in FIGS. 2 and 3, the second arm 14 is configured on the base end side of the second arm 14 of the arc welding robot (referring to the first arm 13 side (see FIG. 1) of the second arm 14). A first motor 61 is disposed in the frame 50. A cavity 51 extending in the longitudinal direction of the second arm 14 is formed inside the frame 50, and a first drive pulley 63 fixed to the rotation drive shaft 62 of the first motor 61 is formed in the cavity 51. Has been placed. The rotational drive shaft 62 is parallel to the wrist swing axis J5.

  A first driven rotation mechanism 20 is disposed on the distal end side of the second arm 14. The first driven rotation mechanism 20 includes a first driven rotation shaft 22 that is rotatably attached to the frame 50, and a first gear 21 that is pivotally supported by the first driven rotation shaft 22. The rotation axis of the first driven rotation mechanism 20 is a wrist swing axis J5.

  The first driven rotating shaft 22 has a structure in which a ring-shaped member 102 is fixed to the outer periphery of the cylindrical member 101, and the first gear 21 is fixed to the ring-shaped member 102. The first driven rotary shaft 22 and the first gear 21 are accommodated in a hole 52 provided in the frame 50 so as to be rotatable around the wrist swing axis J5. The shape of the hole 52 is designed so that the ring-shaped member 102 slides on the wall surface (frame 50) of the hole 52, but the first gear 21 does not contact the frame 50.

  As the first gear 21, a spur gear is preferably used as shown in FIG. 2 and 3, detailed drawing of the teeth of the first gear 21 (the outer peripheral irregularities functioning as gears) is omitted (the same applies to the second gear 41 described later).

  The ring-shaped member 102 is connected to a first wrist member 15 a that constitutes the wrist member 15. The wrist member 15 is composed of a first wrist member 15a and a second wrist member 15b, and details thereof will be described later.

A reduction gear 40 is disposed on the frame 50 so as to be aligned with the first driven rotation mechanism 20 along the longitudinal direction of the second arm 14. The speed reducer 40 includes a second gear 41 that meshes with the first gear 21, an output-side rotation shaft (not shown) that pivotally supports the second gear 41, a casing 42 that rotatably holds the output-side rotation shaft, It has. The speed reducer 40 includes a first driven pulley 44 and an input side rotating shaft 45 that pivotally supports the first driven pulley 44 as input side components for operating the speed reducer 40. The rotation of the side rotation shaft 45 is converted into the rotation of the output side rotation shaft (not shown) by a speed conversion unit (not shown) provided in the casing 42. An input rotary shaft 45 and the output rotary shaft is disposed coaxially with the central axis Q ₂ about the central axis Q ₂ is parallel to the wrist swing shaft J5.

  When a spur gear is used as the first gear 21, a spur gear is used as the second gear 41 as shown in FIG. The first driven pulley 44 is disposed in the cavity 51. Further, a first belt (between the first drive pulley 63 fixed to the rotation drive shaft 62 of the first motor 61 and the first driven pulley 44 fixed to the input side rotation shaft 45 of the speed reducer 40 is provided. The first annular member 64 is suspended in a state where a certain tension is applied. The first drive pulley 63 and the first driven pulley 44 are arranged so that the first belt 64 rotates in one plane, that is, when viewed from the direction of the arrow C shown in FIG. The arrangement position is adjusted.

  With such a configuration, in the swing mechanism of the wrist swing shaft J5, when the first motor 61 is driven, the rotation drive shaft 62 rotates via the first drive pulley 63 and the first belt 64. The first driven pulley 44 is transmitted, and the input side rotating shaft 45 that pivotally supports the first driven pulley 44 rotates. Then, the rotation speed of the input side rotation shaft 45 is decelerated by the speed conversion unit, and appears as rotation of the output side rotation shaft, thereby rotating the second gear 41. As the second gear 41 rotates, the first gear 21 meshing with the second gear 41 and the first driven rotating shaft 22 that pivotally supports the first gear 21 rotate. Thus, the wrist member 15 can be swung.

  As the speed reducer 40, a wave gear device is preferably used. Since the wave gear device has a large reduction ratio, is small and light, has a large torque capacity, and has a small number of components, the second arm 14 can be made lighter or thinner. . In addition, since the wave gear device has a large number of simultaneously meshing teeth, the influence of the tooth pitch error and the cumulative pitch error on the rotation accuracy is averaged, so that excellent position accuracy and rotation accuracy can be obtained. Has characteristics.

  A casing 42 of the speed reducer 40 is attached to a bottomed hole 53 formed in the frame 50. A method of attaching the casing 42 to the hole 53 will be described later in detail with reference to FIGS. 6 to 9, and an outline thereof will be described here. FIG. 5 is a schematic perspective view of the second arm and the wrist member. As shown in FIG. 5, a plurality of bolt insertion holes 80 (collectively referred to as bolt insertion holes 80 a to 80 h described later) are formed at a constant interval on the same circumference in the portion corresponding to the bottom wall surface of the hole 53 in the frame 50. Is provided. On the other hand, as shown in FIG. 3, the same number of screw holes 70 as the bolt insertion holes 80 (screw holes 70 a to 70 h to be described later) are provided in the casing 42 at positions where they can communicate with the bolt insertion holes 80. It has been. The casing 42 is attached to the hole 53 by screwing the bolt 75 into the screw hole 70 through the bolt insertion hole 80.

[Rotation mechanism of wrist rotation axis J6]
As shown in FIGS. 2 and 3, the second motor 66 is disposed on the base end side in the frame 50, and the rotational drive shaft 67 of the second motor 66 is rotationally driven by the first motor 61. It is parallel to the shaft 62. In the cavity 51 formed in the frame 50, a second drive pulley 68 fixed to the tip of the rotary drive shaft 67 is disposed.

  A second driven rotation mechanism 30 driven by a second motor 66 is disposed near the tip of the second arm 14. The second driven rotation mechanism 30 includes a second driven rotation shaft 31, a second driven pulley 32 that is pivotally supported on one end (the cavity portion 51 side) of the second driven rotation shaft 31 and disposed in the cavity portion 51, And a bevel gear 35 fixed to the other end (the wrist member 15 side) of the second driven rotary shaft 31.

  As shown in FIG. 3, the second driven rotary shaft 31 rotates inside the cylindrical member 101 constituting the first driven rotary shaft 22 via a bearing 103 so as to be coaxial with the first driven rotary shaft 22. Arranged freely. Thus, the first driven rotary shaft 22 and the second driven rotary shaft 31 can rotate independently of each other. Since the rotation shaft of the first driven rotation shaft 22 is the wrist swing shaft J5, the rotation shaft of the second driven rotation shaft 31 is also the wrist swing shaft J5.

  As shown in FIGS. 3 and 5, a second belt (second annular member) 69 is stretched between the second drive pulley 68 and the second driven pulley 32 in a state where a certain tension is applied. The rotation of the rotary drive shaft 67 (see FIG. 2) of the second motor 66 is transmitted to the second driven pulley 32 via the second drive pulley 68 and the second belt 69, and thus the second driven rotary shaft 31. Rotates. The rotation trajectory of the second belt 69 is adjusted by a fixed pulley 65 disposed on the frame 50 so that the first belt 64 and the second belt 69 do not interfere (contact). The second belt 69, the second belt 69, and the second driving pulley 68 are arranged so as to rotate in one plane (that is, when seen from the direction of the arrow C shown in FIGS. 2 and 3). 2 The arrangement positions of the driven pulley 32 and the fixed pulley 65 are adjusted.

  The bevel gear 35 is disposed inside the wrist member 15. A ring-shaped bevel gear 36 is fixed to the second wrist member 15 b constituting the wrist member 15 so as to mesh with the bevel gear 35. The bevel gears 35 and 36 function as a rotation conversion unit that converts the rotation of the second driven rotation shaft 31 into the rotation of the wrist rotation shaft J6 that is an axis orthogonal to the axial direction of the second driven rotation shaft 31. That is, the rotating shaft of the bevel gear 36 is the wrist rotating shaft J6, and the rotating shaft of the bevel gear 35 is the wrist swinging shaft J5 that is the rotating shaft of the second driven rotating shaft 31. 36, the rotation of the second driven rotation shaft 31 around the wrist swing axis J5 is converted into the rotation of the second wrist member 15b around the wrist rotation axis J6.

  In addition, since the number of teeth of the bevel gear 35 is set to be smaller than the number of teeth of the bevel gear 36, the bevel gears 35 and 36 also function as a speed reducer. By using the bevel gears 35 and 36, rotation conversion and rotation speed reduction can be performed with a small number of parts.

[Positional relationship between the first belt 64 and the second belt 69]
As described above, in the swing mechanism of the wrist swing shaft J5, the first belt 64 rotates in one plane, and in the rotation mechanism of the wrist rotation shaft J6, the second belt 69 rotates in one plane. 2 and 3, the first belt 64 is arranged on the inner peripheral side of the second belt 69 so that the first belt 64 and the second belt 69 rotate in the same plane. ing. “The first belt 64 and the second belt 69 rotate in the same plane” means in the direction of the arrow C shown in FIG. 2 (in the longitudinal direction of the second arm 14 and the axial direction of the swing rotation axis J5). It means that the first belt 64 and the second belt 69 are in a positional relationship when viewed from a direction orthogonal to both. By adopting such a configuration, the width of the cavity 51 in the axial direction of the rotary drive shafts 62 and 67 can be set narrow, and the second arm 14 has a cantilever structure and a special feature as shown in FIG. Compared with a double-sided structure as disclosed in Japanese Patent Application Laid-Open No. 2003-200376, it can be slimmed.

[Structure of wrist member 15]
The wrist member 15 includes a first wrist member 15a and a second wrist member 15b. As described above, the first wrist member 15 a is connected to the ring-shaped member 102 that constitutes the first driven rotating shaft 22. On the other hand, the second wrist member 15b is connected to the first wrist member 15a so as to be rotatable around the wrist rotation axis J6 with respect to the first wrist member 15a. As described above, the second wrist member 15b is connected to the second wrist member 15a. A bevel gear 36 is fixed to the member 15b.

  When the first gear 21 of the first driven rotation mechanism 20 is rotated by driving the first motor 61, the first driven rotation shaft 22 rotates about the wrist swing axis J5, and the wrist is rotated according to the rotation angle. The member 15 swings together with the first wrist member 15a and the second wrist member 15b. On the other hand, when the second driven pulley 32 is rotated by driving the second motor 66, the second driven rotating shaft 31 rotates around the wrist swing axis J5, and this rotation is caused by the bevel gears 35 and 36 to rotate the second wrist. The rotation of the member 15b around the wrist rotation axis J6 is converted, and only the second wrist member 15b rotates without moving the first wrist member 15a.

[Adjustment of Backlash of First Gear and Second Gear-Positioning and Fixing Method of Reducer 40]
As for the method of adjusting the backlash between the first gear 21 and the second gear 41 when the swing mechanism of the wrist member 15 is disposed on the second arm 14 slimmed as described above, FIGS. This will be described below with reference. Since the speed reducer 40 is a single device, adjusting the backlash of the second gear 41 with respect to the first gear 21 is nothing but positioning and fixing the speed reducer 40, The positioning and fixing is to fix and fix the position where the casing 42 of the speed reducer 40 is attached to the hole 53.

  FIG. 6 is a schematic view showing the arrangement of screw holes formed in the casing, and is a view seen from the direction of the arrow D shown in FIGS. FIG. 7A is a schematic diagram showing the arrangement of bolt insertion holes formed in the portion corresponding to the bottom wall surface of the hole in the frame of the second arm, and the direction of the arrow D shown in FIGS. It is the figure seen from. FIG. 7B is a schematic diagram illustrating an example of a state in which the screw hole illustrated in FIG. 6 and the bolt insertion hole illustrated in FIG. Further, FIG. 8 is a first schematic diagram showing a form of change in the position of the second gear relative to the first gear when the position of the screw hole communicating with each bolt insertion hole is changed. It is a 2nd schematic diagram.

In Figure 6-9, it shows the location of the wrist swing shaft J5 is the center axis of the first driven rotor 22 as viewed from the direction of arrow D shown in FIG. 2 at the center of rotation j _5, the reduction gear 40 The position of the center axis Q ₂ of the output side rotation shaft (same as the center axis of the input side rotation shaft 45) is indicated by the rotation center q ₂ . In addition, since the rotation center j ₅ is the rotation center of the first gear 21 and the rotation center q ₂ is the rotation center of the second gear 41, in the following description, “rotation center j ₅ of the first gear 21 is appropriately selected. ”,“ Rotation center q ₂ of the second gear 41 ”, and instead of the first driven rotation shaft 22 and the output-side rotation shaft, the first gear 21 and the second gear 41 are schematically shown in FIGS. It shall be illustrated. Here, with respect to the first gear 21 and the second gear 41, detailed drawing of the teeth (outer surface irregularities (see FIG. 4) functioning as gears) is omitted, and the first gear 21 is between the arcs M ₁ and M _2. In the second gear 41, the region between the arcs N ₁ and N ₂ is a tooth (unevenness) region.

As shown in FIG. 6, in the casing 42, a radius r centered on a point P ₁ (hereinafter referred to as “center point P ₁ ”) that is separated from the rotation center q ₂ of the second gear 41 by a distance S in the radial direction. at equal intervals in eight positions on the circumference _{C 1} of the screw holes 70a, 70b, 70c, 70d, 70e, 70f, 70g, 70h ( in view indicating the position, and to draw by black dots) are formed . Here, as the rotation center q ₂ of the second gear 41 is located at the screw hole 70e side on a line connecting the screw holes 70a and the screw holes 70e, it defines the position of the center point P _1.

  The value of the distance S is an adjustable length of the backlash between the first gear 21 and the second gear 41. As will be described later, the backlash can be adjusted with a predetermined value within the range of twice the distance S. In FIGS. 6 to 9, in order to clearly show the change of the meshing region of the first gear 21 and the second gear 41 depending on the mounting position of the casing 42, the value of the distance S is set large. 6-9, the area | region of each tooth | gear (unevenness | corrugation) of the 1st gearwheel 21 and the 2nd gearwheel 41 is taken widely. Further, in FIGS. 6 to 9, the deformation is schematically illustrated so that the positional relationship can be clearly understood.

As shown in FIG. 7 (a), the bottom wall surface portion corresponding to the hole 53 in the frame 50 (not shown in FIG. 7 (a)), a certain distance from the rotational center j ₅ of the first gear 21 at equal intervals R only 8 points on the circumference _{C 2} of the distant point _{P 2} (hereinafter referred to as "center point _{P 2")} radius centered on r, bolt insertion holes 80a, 80b, 80c, 80d, 80e, 80f, 80g, and 80h are formed. The distance R is unchanged and is determined in consideration of the diameters and tooth depths of the first gear 21 and the second gear 41.

Rotation center _{j 5} and the direction connecting the center point _{P 2} of the circumference _{C 2} to the X direction, the X direction and the wrist swing shaft J5 (wrist swing shaft J5 of the first gear 21, the rotational center _{j 5} The direction perpendicular to the paper plane is defined as the Y direction. Furthermore, as shown in FIG. 7 (a), determining the X-Y coordinate system with origin at the center point _{P 2} of the circumference _{C 2} (same in FIG. 7 (b), 8,9).

Since the same number of screw holes 70 and bolt insertion holes 80 are formed on the circumferences C ₁ and C _{2 of} radius r at the same interval, as shown in FIG. 7B, [bolt insertion holes 80 -The casing 42 is inserted into the hole 53 so that the combination of the screw holes 70 is, for example, [80a-70a], [80b-70b], ..., [80g-70g], [80h-70h]. It can be attached using a bolt 75 (see FIGS. 2 and 3).

As mentioned above, the distance between the center point P ₂ of the rotational center j5 and the hole 53 which is set to the circumference C ₂ of the first gear 21 for a constant R, was shown in FIG. 7 (b) in the state, the rotation center _{q 2} of the coordinates of the second gear 41 (X, Y) becomes (S, 0). That is, the rotation center _{j 5} of the first gear 21 distance between the rotation center _{q 2} of the second gear 41 becomes "R + S".

The wrist swing shaft J5 about the drive mechanism, upon attachment to the hole 53 of the reducer 40, by changing the combination of the bolt insertion hole 80-threaded hole 70, the rotation center q ₂ of the second gear 41 Coordinates change. The backlash between the first gear 21 and the second gear 41 is adjusted using the change in the distance between the rotation center j ₅ of the first gear 21 and the rotation center q _{2 of} the second gear 41. This will be described in more detail with reference to FIGS.

FIG. 8A shows a state in which the casing 42 is attached to the hole 53 by rotating the casing 42 45 ° counterclockwise (counterclockwise) from the state shown in FIG. 7B. The combination of [bolt insertion hole 80-screw hole 70] is as shown in FIG. The coordinates (X, Y) of the rotation center q ₂ of the second gear 41 are (S / 2 ^1/2 , S / 2 ^1/2 ), and the rotation center j ₅ of the first gear 21 and the rotation of the second gear 41 The distance in the X direction from the center q ₂ is “R + S / 2 ^1/2 ”. That is, the state shown in FIG. 8A is compared with the state shown in FIG. 7B by moving the second gear 41 to the first gear 21 by the distance “S−S / 2 ^1/2 ” in the X direction. This shows a state in which the backlash between the first gear 21 and the second gear 41 is adjusted.

In the state shown in FIG. 8A, the second gear 41 is displaced by “S / 2 ^1/2 ” in the Y direction. Even in such a state, in the meshing state of the first gear 21 and the second gear 41, the distance between the gears is important and is not affected by the angle, and therefore no adverse effect is caused.

8B, the casing 42 is rotated 90 ° counterclockwise from the state shown in FIG. 7B (the casing 42 is rotated 45 ° counterclockwise from the state shown in FIG. 8A). The state which attached the casing 42 to the hole 53 is shown. The combination of [bolt insertion hole 80-screw hole 70] is as shown in FIG. The coordinate (X, Y) of the rotation center q ₂ of the second gear 41 is (0, S), and the X-direction distance between the rotation center j ₅ of the first gear 21 and the rotation center q ₂ of the second gear 41 is “ R ". That is, the state shown in FIG. 8B is compared with the state shown in FIG. 7B by bringing the second gear 41 closer to the first gear 21 by the distance “S” in the X direction. The state in which the backlash between the gear 21 and the second gear 41 is adjusted is shown.

9A, the casing 42 is rotated 135 ° counterclockwise from the state shown in FIG. 7B (the casing 42 is rotated 45 ° counterclockwise from the state shown in FIG. 8B). The state which attached the casing 42 to the hole 53 is shown. The combination of [bolt insertion hole 80-screw hole 70] is as shown in FIG. The coordinates (X, Y) of the rotation center q ₂ of the second gear 41 are (−S / 2 ^1/2 , S / 2 ^1/2 ), and the rotation center j ₅ of the first gear 21 and the second gear 41 are The distance in the X direction from the rotation center q ₂ is “R−S / 2 ^1/2 ”. That is, the state shown in FIG. 9A is compared with the state shown in FIG. 7B by moving the second gear 41 to the first gear 21 by a distance “S + (S / 2 ^1/2 )”. A state in which the backlash between the first gear 21 and the second gear 41 is adjusted by approaching in the direction is shown.

9B, the casing 42 is rotated 180 ° counterclockwise from the state shown in FIG. 7B (the casing 42 is rotated 45 ° counterclockwise from the state shown in FIG. 9A). The state which attached the casing 42 to the hole 53 is shown. The combination of [bolt insertion hole 80-screw hole 70] is as shown in FIG. 9B. The coordinate (X, Y) of the rotation center q ₂ of the second gear 41 is (−S, 0), and the distance in the X direction between the rotation center j ₅ of the first gear 21 and the rotation center q ₂ of the second gear 41 is “RS”. That is, the state shown in FIG. 9B is compared with the state shown in FIG. 7B by bringing the second gear 41 closer to the first gear 21 by the distance “2S” in the X direction. The state in which the backlash between the gear 21 and the second gear 41 is adjusted is shown.

  From the viewpoint of adjusting the backlash between the first gear 21 and the second gear 41, the state in which the casing 42 is rotated 45 ° counterclockwise from the state shown in FIG. The state shown in FIG. 9B is equivalent to the state shown in FIG. 9B, and the state where the casing 42 is rotated 90 ° counterclockwise from the state shown in FIG. 9B is equivalent to the state shown in FIG. The state in which the casing 42 is rotated counterclockwise by 135 ° from the state shown in FIG. 9B is equivalent to the state shown in FIG.

  Thus, the value that can be taken by the adjustment amount of the backlash when the casing 42 is attached to the hole 53 is not a continuous value but a stepwise value. Therefore, which state of the states shown in FIGS. 7B, 8, and 9 is determined as the attachment position with respect to the hole portion 53 of the casing 42 and is actually attached is determined by the first gear 21 and the second gear. Is performed based on a predetermined adjustment amount.

  Specifically, each state (attachment position) shown in FIGS. 7B, 8, and 9 is realized by temporarily fixing the casing 42 in the hole 53, and the first gear 21 in each state The backlash of the second gear 41 is measured. Then, it is determined whether the measured value of the backlash is at a predetermined adjustment amount or a value close to the adjustment amount when the casing 42 is located, the attachment position is determined, and the screw hole 70 is passed through the bolt insertion hole 80. A predetermined bolt 75 is screwed onto the casing 42 and the casing 42 is attached to the hole 53. In addition, when the measured value of the backlash before and after rotating the casing 42 by 45 ° is substantially the same at the two attachment positions, the driving performance of the second arm 14 can be improved regardless of which position is selected. There is no effect. The tension of the first belt 64 may be adjusted after the speed reducer 40 has been positioned.

  In this way, when the second arm 14 is slimmed down, if a conventional backlash adjusting mechanism (see, for example, Japanese Patent Laid-Open No. Hei 6-297377) is used, it is difficult to adjust the backlash. On the other hand, by using the speed reducer 40 capable of positioning and fixing as described above (a configuration in which the screw hole 70 of the casing 43 is formed so as to be eccentric from the concentric circle of the rotating shaft 42 provided in the casing 43). The adjustment work of the backlash between the first gear 21 and the second gear 41 is facilitated, and the load on the adjustment work can be reduced. Moreover, since the attachment position of the speed reducer 40 does not vary depending on the operator, variation in the swing performance of the wrist member 15 for each arc welding robot can be suppressed.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the wrist drive structure of an industrial robot according to the present invention is not limited to the wrist drive structure of an arc welding robot, and other various industrial robots (spot welding robots, assembly robots, transfer robots, etc.) ) Wrist drive structure. In addition, the wrist drive structure of the industrial robot according to the present invention can be applied not only to the operation of the wrist member but also to the connection structure of two arms.

  In the embodiment according to the present invention, the first belt 64 is used as the first annular member that transmits the rotation of the first motor 61 to the input side rotation shaft 45 of the speed reducer 40, and the rotation of the second motor 66 is the second driven. Although the second belt 69 has been described as the second annular member transmitted to the rotating shaft 31, the first and second annular members are not limited to belts, and may be, for example, a chain. Moreover, although the spur gear was illustrated as the 1st gearwheel 21 and the 2nd gearwheel 41, the 1st gearwheel 21 and the 2nd gearwheel 41 can adjust backlash according to the positioning fixing method of the reduction gear 40 as mentioned above. As long as it is possible, for example, a tapered gear may be used. Furthermore, although the input side rotating shaft 45 and the output side rotating shaft are shown as coaxial as the speed reducer 40, the positional relationship that the first belt 64 is arranged on the inner peripheral side of the second belt 69 is not changed. As long as the speed reducer 40 is used, an input side rotating shaft 45 and an output side rotating shaft that are parallel axes may be used.

14 Second arm 20 First driven rotation mechanism 21 First gear 22 First driven rotation shaft 30 Second driven rotation mechanism 31 Second driven rotation shaft 32 Second driven pulley 40 Reducer 41 Second gear 42 Casing 44 First driven Pulley 50 Frame 61 First motor 63 First drive pulley 64 First belt (first annular member)
65 Fixed pulley 66 Second motor 68 Second drive pulley 69 Second belt (second annular member)
70, 70a to 70h Screw hole 75 Bolt 80, 80a to 80h Bolt insertion hole

Claims (3)

A wrist drive structure in which a wrist member is swingably and rotatably disposed on a predetermined arm in an industrial robot,
The wrist drive structure includes a swing mechanism of the wrist member and a rotation mechanism of the wrist member,
The swing mechanism includes a driven rotation mechanism, and a rotation drive mechanism that drives the driven rotation mechanism,
The driven rotation mechanism includes a first driven rotation shaft coupled to the wrist member and rotatably disposed on the arm, and a first gear pivotally supported on the first driven rotation shaft. ,
The rotation drive mechanism includes a first motor disposed at a predetermined position of the arm and a second gear engaged with the first gear supported by an output-side rotation shaft, and a reduction gear disposed on the arm. And a first annular member that transmits the rotation of the first motor to the input-side rotation shaft of the speed reducer,
The rotation mechanism includes a second motor disposed at a predetermined position of the arm, a second driven rotation shaft disposed coaxially with the first driven rotation shaft, and rotation of the second driven rotation shaft. A rotation converter that converts the rotation of an axis perpendicular to the axial direction of the two driven rotation shafts, and a second annular member that transmits the rotation of the second motor to the second driven rotation shaft,
The wrist drive structure for an industrial robot, wherein the first annular member is disposed on an inner peripheral side of the second annular member. The speed reducer is a wave gear device;
The industrial robot wrist drive structure according to claim 1, wherein the rotation conversion unit is a bevel gear and has a function of a speed reducer. The industrial robot is an arc welding robot having a six-axis joint structure, and the wrist member holds a welding torch;
A first shaft, a second shaft, and a third shaft mechanism that move the base end of the arm to a predetermined position; and a fourth shaft mechanism that rotates the arm about a central axis parallel to the length direction thereof. With
The first driven rotation shaft is a fifth shaft;
The wrist drive structure for an industrial robot according to claim 1 or 2, wherein an axis orthogonal to the axial direction of the second driven rotation axis is a sixth axis.

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