Welding robot

Abstract

This invention provides a welding robot that can swing its end-effector along multiple axes without using a first axis for movement along a rail. [Solution] The welding robot 10 travels on rails 50 arranged along the outer circumference of the steel pipe column 40 and welds the welding line 41 of the steel pipe column 40. The welding robot 10 is equipped with first to sixth axes J1 to J6, from the first axis on the rail 50 side to the sixth axis J6 on the torch 16 side. The first axis J1 is the rail travel axis, the second and third axes J2 and J3 are linear joints, and the fourth to sixth axes J4 to J6 are rotary joints. The sixth axis J6 causes the torch 16 to swing around the sixth axis O6, which is a straight line parallel to one of the welding line direction X and plate thickness direction Y of the steel pipe column 40. The fifth axis O5 is a straight line parallel to the other of the plate thickness direction Y and welding line direction X, and is in a twisted position with respect to the sixth axis J6, which is parallel to the sixth axis O6.

Description

Technical Field

[0001] The present invention relates to a portable welding robot capable of welding steel pipes at a construction site during construction implementation.

Background Art

[0002] In the construction of high-rise buildings and the like, steel workers are welding steel pipes to assemble steel pipe columns. The number of workers in the construction industry is on the decline, and in order to eliminate the labor shortage, the development of construction robot technology to realize support for workers, automation, remote control, etc. is in progress. For example, Patent Document 1 discloses a portable welding robot that automates the groove welding while orbiting on a guide rail attached to a steel pipe at a construction site.

[0003] When a steel worker welds, he may perform weaving by swinging his hand so that the weld metal reaches every corner of the groove while optimizing the heat input. As the weaving, as disclosed in Patent Document 1, it is common to swing in a zigzag in a direction intersecting the welding line direction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the case of a portable welding robot such as the one disclosed in Patent Document 1, while the end-effector axis can be swung to intersect the welding line direction while maintaining the torch position, the wrist axis cannot be swung along the welding line direction. If weaving motions that involve forward and backward movement in the welding line direction are attempted, it is necessary to move the entire welding robot back and forth in small increments using a rack-and-pinion linear movement mechanism of a Y-type trolley that travels on guide rails. Due to the large moment of inertia, there is a risk of excessive load being placed on the servo motor or unwanted vibrations occurring in the end-effector.

[0006] Therefore, the present invention aims to provide a welding robot that can swing its end-effector on multiple axes without using a rail-running axis for running on rails. [Means for solving the problem]

[0007] A welding robot according to one aspect of the present invention is a welding robot that travels on rails arranged along the outer circumference of a steel pipe column and welds the weld line of the steel pipe column extending along the rails, comprising first to sixth axes from the first axis on the rail side to the sixth axis on the torch side, the first axis being a rail travel axis, the second and third axes being linear joints, and the fourth to sixth axes being rotary joints, the sixth axis causing the torch to swing around a sixth axis which is a straight line parallel to either the weld line direction or the plate thickness direction of the steel pipe column, and the fifth axis causing the torch to swing around a fifth axis which is a straight line parallel to the other of the plate thickness direction or the weld line direction, and is in a skew position with respect to the sixth axis which is parallel to a straight line perpendicular to the sixth axis.

[0008] Adding an external device or drive axis specifically for weaving increases the weight of the welding robot and thus the moment of inertia. In this embodiment, since the sixth axis, which is the terminal axis closest to the end-effector, or the fifth axis immediately adjacent to it, is used for oscillation in the direction of the welding line, the moment of inertia is smaller and the load on each axis is smaller compared to when the first to third axes on the rail side are used for reciprocating motion. The effect of the weight increase due to the addition of a drive axis can be minimized. Even when performing a weaving motion that oscillates in the direction of the welding line, the vibration of the end-effector can be kept to a minimum. Furthermore, because the load is reduced, it is possible to reduce the output of the actuators used, leading to power saving and miniaturization. Even in the case of a portable welding robot that can be used on construction sites with rails installed, the end-effector can be oscillated without using the first axis that moves along the rail. Since both the fifth and sixth axes are oscillation axes, by moving them in conjunction, it is possible to reproduce the movements of a rebar worker and move the torch in a complex trajectory that moves back and forth in the direction of the welding line, optimizing the heat input and ensuring that the weld metal reaches every corner of the groove. You can move your fingertips so that the trajectory of the torch tip traces a spherical shape. Alternatively, you can move your fingertips in conjunction with the third axis so that the trajectory of the torch tip traces a flat surface.

[0009] In the above embodiment, the fourth axis may rotate the link between the fourth axis and the fifth axis around the fourth axis, which is a straight line parallel to the axial direction of the steel pipe column.

[0010] In this configuration, the fourth axis, which is the third of the four to sixth axes and is located closest to the rail, becomes the vertical axis of rotation that is least affected by gravity. Therefore, compared to a configuration in which the fourth axis is the horizontal axis of rotation, the output of the actuator used can be reduced, resulting in power savings and miniaturization.

[0011] In the above embodiment, the sixth axis may be parallel to the welding line direction and distal to the fifth axis when viewed from the rail.

[0012] When weaving in sync with the 5th and 6th axes, the amplitude in the width direction of the groove may be greater than the amplitude in the extension direction of the groove. In this embodiment, the oscillating axis with the larger amplitude becomes the 6th axis, which is the terminal axis, so the moment of inertia can be reduced.

[0013] In the above embodiment, either the second or third axis may be a linear joint in the thickness direction of the steel pipe column, or the other may be a linear joint in the axial direction of the steel pipe column.

[0014] According to this embodiment, either the second or second shaft, which is a linear joint, can be used to move the torch in a straight line in the plate thickness direction and axial direction, approaching and moving away from the rail, and to position the tip of the torch so that it approaches the groove, making it easier to control the swinging motion of the torch. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a welding robot that can swing its end-effector on multiple axes without using a rail-running axis for traveling on rails. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 shows a schematic configuration of a welding robot system according to one embodiment of the present invention. [Figure 2] Figure 2 is a perspective view showing an example of the welding robot shown in Figure 1. [Figure 3] Figure 3 is a side view showing the positional relationship of the three terminal axes of the welding robot shown in Figure 2. [Figure 4] Figure 4 is a front view showing the positional relationship of the three terminal axes of the welding robot shown in Figure 2. [Modes for carrying out the invention]

[0017] A preferred embodiment of the present invention will be described with reference to the attached drawings. In each drawing, components with the same reference numerals have the same or similar configuration. The present invention will be described in detail below with reference to the drawings. Each drawing is conveniently accompanied by a Cartesian coordinate system consisting of the X, Y, and Z axes to clarify the relationships between the drawings and to help understand the positional relationships of each component.

[0018] The direction parallel to the X-axis is called the X-axis direction, the direction parallel to the Y-axis is called the Y-axis direction, and the direction parallel to the Z-axis is called the Z-axis direction. The X-axis direction is, for example, the direction of the welding line and is parallel to the extending direction of the rail 50 which is installed so as to be parallel to the welding line. The X-axis direction may also be called the welding line direction X. The Y-axis direction is, for example, the thickness direction of the steel pipe column 40, approaching or moving away from the steel pipe column 40, and is perpendicular to the extending direction of the rail 50. The Y-axis direction may also be called the thickness direction Y, or if the steel pipe column 40 is a circular steel pipe column, it may be called the radial direction Y. The Z-axis direction is, for example, the height direction of the welding robot 10 parallel to the axial direction of the steel pipe column 40. The Z-axis direction may also be called the height direction Z. The X-axis direction and the Y-axis direction are each approximately horizontal, and the Y-axis direction is approximately vertical. In the following explanation, the Z-axis arrow, which indicates the direction from the upper steel pipe column 40A to the lower steel pipe column 40B, will be described as pointing downwards, and the opposite direction to the Z-axis arrow, which indicates the direction from the lower steel pipe column 40B to the upper steel pipe column, will be described as pointing upwards.

[0019] Figure 1 shows a schematic configuration of a welding robot system 1 according to one embodiment of the present invention. The welding robot system 1 includes, for example, a welding robot 10, a robot control device 20, a welding wire feeding device 30, etc., and is connected to a welding power source (not shown).

[0020] The welding robot system 1 forms a steel pipe column 40 such as a column for a large building such as a high-rise building or a four-sided box column by welding and connecting steel pipes 40A and 40B. The steel pipes 40A and 40B are temporarily fixed by an erection piece 60 or the like, and are connected by welding a groove 41 which is a connecting portion of the steel pipes 40A and 40B. The groove 41 extends in a substantially horizontal direction. The steel pipe 40B may be referred to as a lower steel pipe column 40B, and the steel pipe 40A located vertically above the steel pipe 40B may be referred to as an upper steel pipe column 40A.

[0021] A rail 50 is arranged along the outer periphery of the steel pipe 40A so as to go around the steel pipe 40A. The welding robot 10 can travel along the rail 50 so as to go around the steel pipe 40A. The welding robot 10 is connected to the robot control device 20 by wire or wirelessly, and performs welding while traveling based on an operation command from the robot control device 20.

[0022] In the illustrated example, a welding wire is fed from a welding torch 16 provided at the tip of a multi-joint arm of the welding robot 10, and an arc is generated between the steel pipes 40A and 40B while moving the tip of the torch 16 along the welding line of the groove 41, thereby performing arc welding. The welding line is a hypothetical line when representing a bead or a welded portion as one line (JIS Z 3001-1:2018). The above-described X-axis direction (welding line direction) is the extending direction of the welding line. The rail 50 is arranged along the welding line.

[0023] The torch 16 is electrically connected to a welding power source and receives supply of a welding voltage and a welding current to the welding wire. In arc welding, when the welding wire is instantaneously brought into contact with a metal material such as the groove 41 of the steel pipes 40A and 40B and energized, an arc discharge occurs between the welding wire and the groove 41, and welding is performed by melting the welding wire and the groove 41 by the heat of the arc.

[0024] The robot control device 20 is a device that controls the welding robot 10. The robot control device 20 controls the welding robot 10, the welding wire feeder 30, the welding power supply, etc., based on a work program, for example. The work program includes teaching data that has been generated in advance, instructing the welding robot 10 to weld the groove 41 while traveling along the rail 50.

[0025] The teaching data may include, for example, operational information of the welding robot 10, such as its position, posture, and movement speed; information regarding the feeding of the welding wire; and information regarding welding conditions, such as welding voltage, welding current, welding speed, and welding time. Furthermore, this information included in the work program may be set by the operator using an operating device such as a teach pendant, or it may be set while actually operating the welding robot 10.

[0026] The welding wire feeder 30 is controlled by the robot control device 20 and can, for example, feed the welding wire at a predetermined speed in the forward direction from the tip of the torch 16 toward the groove 41, or feed it in the reverse direction. The welding power supply is connected to the welding robot 10 and the welding wire feeder 30 via a cable and supplies the welding voltage and welding current to the torch 16 based on commands from the robot control device 20.

[0027] Figure 2 is a perspective view showing an example of the welding robot 10 shown in Figure 1. As shown in Figure 2, the welding robot 10 is equipped with a multi-joint arm. The multi-joint arm is composed of multiple links connected in series from the rail 50 to the torch 16. The drive shafts (joints) that connect adjacent links cause each link to move in a straight line or rotate. Connecting one drive shaft to another means that the drive shafts are connected indirectly via links, or that the drive shafts are connected directly without links.

[0028] In the illustrated example, the welding robot 10 is equipped with first to sixth axes J1 to J6, from the first axis J1 on the rail 50 side to the sixth axis J6 on the torch 16 side. The first axis J1 is a rail-running axis that travels on the rail 50, the second and third axes J2 and J3 are linear joints that move the link in a straight line, and the fourth to sixth axes J4 to J6 are rotary joints that rotate the link.

[0029] The first axis J1 connects the rail 50 and the link 11, causing the link 11 to move in a straight line along the first axis O1, which is a straight line on the rail 50 parallel to the X-axis direction. Since the first axis J1 moves the link 11 approximately horizontally in the X-axis direction relative to the rail 50, the first axis J1 may also be called the horizontal axis. The link 11 may also be called the base 11. In addition to the second axis J2, the first axis J1 is also an example of another linear joint as seen from the third axis J3.

[0030] The second axis J2 connects link 11 and link 12, and causes link 12 to move in a straight line along the second axis O2, which is a straight line parallel to the Y-axis direction and is at a skew position to the first axis O1, which is perpendicular to the first axis O1. Since the second axis J2 moves link 12 approximately horizontally in the Y-axis direction relative to link 11, the second axis J2 may also be called a horizontal axis.

[0031] The third axis J3 connects link 12 and link 13 and slides along the third axis line O3, which is a straight line in the Z-axis direction, causing link 13 to move straight (up and down). The third axis J3 may also be called the lifting axis. The third axis J3 may also be called the vertical axis because it moves link 13 approximately vertically relative to link 12 in the Z-axis direction. The second axis J2 and link 12 may be omitted, and the third axis J3 may be configured to connect link 11 and link 13.

[0032] In other words, the base axes J1 to J3 include at least one horizontal axis J1, J2 which includes the rail-running axis J1 that travels on the rail 50, and the third axis J3 which is a vertical axis connected to the second axis J2 (or first axis J1), which is a horizontal axis. The fourth axis J4, which is a rotary joint, is connected to the third axis J3. The third axis J3 raises and lowers multiple rotary joints J4 to J6 in the height direction Z of the welding robot 10, which is parallel to the axial direction of the steel pipe column 40.

[0033] The fourth axis J4 connects links 13 and 14, and rotates link 14 around the fourth axis O4, which is a straight line in the Z-axis direction. Link 14 is formed in a cylindrical shape that extends in the Z-axis direction. The fifth axis J5 connects links 14 and 15, and rotates link 15 around the fifth axis O5, which extends in the Y-axis direction. The fifth rotation axis J5 is located closer to the rail 50 in the plate thickness direction Y than the fourth rotation axis J4.

[0034] The sixth axis J6 connects the link 15 and the torch 16, causing the torch 16 to rotate around the sixth axis O6, which is a straight line parallel to the X-axis direction. The sixth axis J6 is the terminal axis, and the fifth axis J5 is the axis adjacent to the terminal axis. In the following description, the fourth to sixth axes J4-J6, which are the terminal three axes, and the adjacent links 14 and 15 connected by them are referred to as the wrist axis structure. The fourth to sixth axes J4-J6, which are rotational joints, may also be referred to as the first to third rotation axes J4-J6. Their central axes may also be referred to as the first to third rotation axes O4-O6. The arrangement of the fourth axis J4 is not limited to the illustrated example. For example, the link 13 may be extended downward to the position of the fifth axis J5, and the fourth axis J4 may be placed close to the fifth axis J5.

[0035] Figure 3 is a side view showing the positional relationship of the three terminal axes J4 to J6 of the welding robot 10 shown in Figure 2. Actuators such as motors that drive each axis may be built into the axis, or they may be located outside each axis and the driving force may be transmitted from a distance by belts or gears. Figure 4 is a front view showing the positional relationship of the three terminal axes J4 to J6. As shown in Figures 3 and 4, the sixth axis J6 causes the torch 16 to oscillate around the sixth axis O6, a straight line extending parallel to the X-axis direction, which is the welding line direction.

[0036] In contrast, the fifth axis J5 causes the torch 16 to swing around the fifth axis O5, which is a straight line in the Y-axis direction, which is the thickness direction of the plate. Conversely to the illustrated example, the sixth axis O6 may be configured to be a straight line in the Y-axis direction, and the fifth axis O5 may be configured to be a straight line parallel to the X-axis direction. The sixth axis O6 is located below the fifth axis O5. As shown in Figures 1, 3, and 4, in the Z-axis direction, the fifth axis J5 is positioned at a certain distance from the sixth axis J6. In the illustrated example, in the Z-axis direction, the distance H2 between the sixth axis O6 and the fifth axis O5 is greater than one-tenth of the distance H1 between the groove 41 of the steel pipe column 40 and the rail 50.

[0037] With the welding robot 10 of this embodiment configured as described above, the end-effector can be swung using multiple axes such as the fifth and sixth axes J5 and J6, without using the first axis J1, which is a rail-traveling axis for traveling on the rail 50.

[0038] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The elements, arrangement, materials, conditions, shapes, and sizes of the embodiments are not limited to those exemplified and can be modified as appropriate. Furthermore, it is possible to partially substitute or combine the configurations shown in different embodiments. [Explanation of Symbols]

[0039] 1...Welding robot system, 10...Welding robot, 11,12,13,14,15...Multiple links, 16...Torch, 20...Robot control device, 30...Welding wire feeder, 40...Steel pipe column, 40A,40B...Steel pipe, 41...Bevel, 50...Rail, 60...Erection piece, J1...First axis, J2...Second axis, J3...Third axis, J4...Fourth axis, J5...Fifth axis, J6...Sixth axis, O4...Fourth axis, O5...Fifth axis, O6...Sixth axis, X...Welding line direction, Y...Steel pipe column plate thickness direction, Z...Height direction.

Claims

1. A welding robot that travels along rails arranged along the outer circumference of a steel pipe column and welds the weld lines of the steel pipe column extending along the rails, The system comprises six axes, from the first axis on the rail side to the sixth axis on the torch side, the first axis being a rail running axis, the second and third axes being linear joints, and the fourth to sixth axes being rotary joints. The sixth axis is a straight line parallel to either the welding line direction or the plate thickness direction of the steel pipe column, and the torch is oscillated around this sixth axis. The fifth axis is a straight line parallel to either the plate thickness direction or the welding line direction, and the torch is oscillated around the fifth axis, which is a straight line parallel to the sixth axis and perpendicular to the sixth axis, and is at a twisted position to the sixth axis. Welding robot.

2. The fourth axis rotates the link between the fourth axis and the fifth axis around the fourth axis, which is a straight line parallel to the axial direction of the steel pipe column. The welding robot according to claim 1.

3. The sixth axis is parallel to the direction of the weld line and is distal to the fifth axis when viewed from the rail. The welding robot according to claim 1.

4. The second and third axes are such that one of them is a linear joint in the plate thickness direction of the steel pipe column, and the other is a linear joint in the axial direction of the steel pipe column. The welding robot according to claim 1.

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