Spot-weld device

Abstract

To provide a technique which can weld two plain faces respectively extending in different directions.SOLUTION: A spot-weld device comprises: a robot arm with a revolving shaft; a welding gun which is arranged at a tip part of the robot arm; a motor which moves an electrode of the welding gun into a direction where the welding gun presses a member to be welded or into an opposite direction thereof; a kinetic part which rotates the welding gun around a kinetic shaft extending in a direction crossing the direction where the welding gun press the member to be welded; and a controller which controls the motor according to a rotation angle of the revolving shaft and a rotation angle of the kinetic shaft.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a spot welding apparatus. [Background technology]

[0002] For example, as described in Patent Document 1, a spot welding device is known in which two or more electrodes are attached to one of a pair of gun arms, each of which faces in a different direction. This makes it possible to take different welding positions by rotating the arm without preparing multiple gun arms. Therefore, for example, two flat surfaces extending in different directions, such as the bottom surface and vertical wall of the workpiece, can be welded. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-341266 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, since it is necessary to prevent the other electrode attached facing in a different direction from interfering with the workpiece during welding, the range in which welding can be performed is narrowed. Therefore, there has been a demand for another technology that allows one spot welding device to weld two planes extending in different directions. [Means for solving the problem]

[0005] The present disclosure has been made to solve the above-mentioned problems, and can be realized in the following forms.

[0006] According to one aspect of the present disclosure, there is provided a spot welding device including a robot arm having a rotation axis, a welding gun provided at a tip of the robot arm, a motor for moving an electrode of the welding gun in a direction in which the welding gun applies pressure to the workpieces and in a direction opposite thereto, a kinetic unit for rotating the welding gun about a kinetic axis extending in a direction intersecting the direction in which the welding gun applies pressure to the workpieces, and a control unit for controlling the motor in accordance with a rotation angle of the rotation axis and the rotation angle of the kinetic axis. According to this type of spot welding device, since it has a kinetic axis, it is possible to weld two planes extending in different directions with one spot welding device. Also, since the motor is controlled according to the rotation angle of the rotation axis and the rotation angle of the kinetic axis, desired control can be performed regardless of the rotation direction of the kinetic axis.

[0007] The present disclosure can be realized in various forms, for example, in the form of a control device or a control method for a welding gun. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing an overview of a spot welding device. [Diagram 2] 4 is a flowchart showing an example of a spot welding process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A. Embodiment: 1 is a schematic diagram showing the configuration of a spot welding apparatus 100 in this embodiment. The spot welding apparatus 100 joins workpieces, which are two or more overlapping metal plates, by spot welding. The spot welding apparatus 100 includes a welding gun 10, a robot arm 20, a kinetic unit 30, and a control unit 40.

[0010] Welding gun 10 is attached to the tip of robot arm 20. Welding gun 10 is moved to a target welding point on the workpieces by robot arm 20 and kinetic unit 30. Welding gun 10 has a movement mechanism 11, a first motor 12, and a pair of opposing electrodes 13. Hereinafter, the direction in which welding gun 10 applies pressure to the workpieces is also referred to as pressure axis ax.

[0011] The movement mechanism 11 raises and lowers the electrode 13 along the axial direction of the pressure axis ax. More specifically, the movement mechanism 11 converts the rotational force of the first motor 12 into a linear movement force in the raising and lowering direction and transmits the converted linear movement force to the electrode 13, thereby moving the electrode 13 in the direction in which the welding gun 10 presses the workpieces and in the opposite direction.

[0012] When welding members to be welded, the spot welding device 100 supplies a welding current to the members to be joined via the electrodes 13 while the members to be joined are sandwiched and pressed by the electrodes 13. In this manner, the members to be joined are melted by Joule heat caused by the passage of current. The members to be joined are then cooled and solidified, thereby being joined.

[0013] The robot arm 20 is, for example, a multi-joint robot. The robot arm 20 is operated by the second motor 22 to move the welding gun 10 in the horizontal and vertical directions and to rotate the welding gun 10 around an arbitrary rotation axis 21, thereby changing the position and angle of the welding gun 10.

[0014] In this embodiment, the kinetic unit 30 is provided on the welding gun 10. The kinetic unit 30 operates to rotate the welding gun 10 about a kinetic axis 31, thereby changing the position and angle of the welding gun 10. The kinetic axis 31 is an axis that extends in a direction intersecting the direction in which the welding gun 10 applies pressure to the workpieces to be welded. In this embodiment, the kinetic axis 31 is perpendicular to the lifting and lowering direction of the welding gun 10. The kinetic unit 30 rotates the welding gun 10 in the direction indicated by the arrow A1 by a third motor 32.

[0015] The range of movement of the welding gun 10 by the kinetic unit 30 is narrower than the range of movement of the welding gun 10 by the robot arm 20. The kinetic unit 30 can move the welding gun 10 more finely than the robot arm 20.

[0016] The control unit 40 is composed of a microcomputer or the like constituted by a central processing unit (CPU) and storage devices such as RAM and ROM. The control unit 40 controls the operation of the spot welding device 100 by the microcomputer executing a program installed in advance. More specifically, the control unit 40 comprehensively controls the current value, the current application time, the electrode pressure, the current application timing, the pressure application timing, and the like. For example, the control unit 40 transmits a current command value to the first motor 12, the second motor 22, and the third motor 32 in order to move the welding gun 10 to the welding target position. The control unit 40 is also called a control device. However, a part or all of these controls may be realized by a hardware circuit.

[0017] 2 is a flowchart showing an example of a spot welding process. In step S100, the control unit 40 performs brake control of the third motor 32 so as to prevent the kinetic unit 30 from moving. More specifically, the control unit 40 stops the third motor 32.

[0018] In step S110, the control unit 40 measures the amount of wear of the electrode 13. More specifically, the control unit 40 measures the amount of wear using the amount of displacement of the electrode 13 on the pressure axis ax when the welding gun 10 applies pressure to a target member for measuring the amount of wear (not shown). The control unit 40 obtains the position of the electrode 13 by detecting the rotation angle position of the output shaft of the first motor 12, for example, by an encoder (not shown).

[0019] In step S120, the control unit 40 drives the third motor 32. More specifically, the control unit 40 releases the brake control of the third motor 32 performed in step S100, and makes the kinetic unit 30 movable.

[0020] In step S130, control unit 40 moves welding gun 10 to the position to be welded. More specifically, control unit 40 uses the amount of wear measured in step S110 to determine the amount of movement of welding gun 10 by movement mechanism 11, robot arm 20, and kinetic unit 30 so that electrode 13 is positioned at the welding point on the workpieces, and moves welding gun 10 to the position to be welded.

[0021] In step S140, the control unit 40 determines the pressing force in spot welding according to the coordinate values ​​of the coordinate system based on the rotation axis 21 of the robot arm 20 and the coordinate values ​​of the coordinate system based on the kinetic axis 31 of the kinetic unit 30. More specifically, the control unit 40 estimates the rotation angle of the pressing axis ax using the rotation angles of each rotation axis 21 and the rotation angle of the kinetic axis 31, and determines the pressing force in spot welding using the estimated rotation angle of the pressing axis ax. The control unit 40 estimates the rotation angle of the rotating axis 21 from the rotation speed and rotation angle of the second motor 22, for example. Also, it estimates the rotation angle of the kinetic axis 31 from the rotation speed and rotation angle of the third motor 32. The control unit 40 determines the pressing force based on a map or function that defines the relationship between each coordinate value and the pressing force that is experimentally determined in advance.

[0022] In step S150, the control unit 40 performs welding while applying pressure to the workpieces with the pressure force determined in step S140. More specifically, the control unit 40 controls the first motor 12 so that the workpieces can be pressed with the pressure force determined in step S140, and performs welding.

[0023] According to the spot welding apparatus 100 of the present embodiment described above, since it has the kinetic axis 31, it is possible to weld two planes extending in different directions with one spot welding apparatus 100. Furthermore, since the motor is controlled according to the rotation angle of the rotation axis 21 and the rotation angle of the kinetic axis 31, it is possible to execute desired control regardless of the rotation direction of the kinetic axis 31.

[0024] In addition, the range of movement of the welding gun 10 by the kinetic unit 30 is narrower than the range of movement of the welding gun 10 by the robot arm 20. Therefore, the virtual safety fence (VSF), which is the range in which the welding gun 10 interferes with other robots or welded parts, is smaller than when the welding gun 10 is moved by the robot arm 20 alone.

[0025] In addition, the control unit 40 is a control device that controls the robot arm 20 and the kinetic unit 30. Therefore, it is possible to save space compared to a case where a control device that controls the robot arm 20 and a control device that controls the control unit 40 are provided separately.

[0026] Furthermore, the control unit 40 measures the amount of wear of the electrode 13 while the kinetic unit 30 is not moving by controlling the brake of the third motor 32. Therefore, the amount of wear of the electrode 13 can be accurately measured because the kinetic unit 30 is prevented from moving due to the reaction force generated when the workpieces are pressed.

[0027] Furthermore, the control unit 40 estimates the coordinate system of the kinetic unit 30 based on the rotation angle of the third motor 32. This allows for space saving compared to the case where the coordinate system of the kinetic unit 30 is acquired using a sensor.

[0028] B. Other embodiments: In the embodiment described above, the control unit 40 determines the welding target position using the wear amount of the electrode 13 measured in step S110. However, the present invention is not limited to this, and the control unit 40 may notify the replacement of the electrode 13 via a notification device (not shown) when the wear amount of the electrode 13 is equal to or greater than a predetermined threshold value.

[0029] C.Reference example: In the above-described embodiment, the spot welding apparatus 100 includes a robot arm 20 having a rotation axis and a kinetic unit 30. Alternatively, the spot welding apparatus 100 may include only a robot arm 20 that moves only in a linear direction. Even in this case, the control unit 40 measures the coordinate system of the robot arm using motor angle information. When measuring the coordinate system of the robot arm using a sensor, if there are multiple types of objects to be welded that have different sizes, it is difficult to install a sensor in a different position for each type of object to be welded. This can reduce space compared to when a coordinate system of the kinetic section 30 is obtained using a stator.

[0030] The present disclosure is not limited to the above-mentioned embodiment, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features in the embodiments corresponding to the technical features in each form described in the Summary of the Invention column can be appropriately replaced or combined in order to solve the above-mentioned problems or to achieve some or all of the above-mentioned effects. Furthermore, if the technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0031] Reference Signs List 10: welding gun, 11: moving mechanism, 12: first motor, 13: electrode, 20: robot arm, 21: rotating shaft, 22: second motor, 30: kinetic section, 31: kinetic shaft, 32: third motor, 40: control section, 100: spot welding device

Claims

[Claim 1] A spot welding device comprising: A robot arm having a rotation axis; a welding gun provided at the tip of the robot arm; a motor that moves an electrode of the welding gun in a direction in which the welding gun presses the workpiece and in a direction opposite thereto; a kinetic unit that rotates the welding gun about a kinetic axis that extends in a direction intersecting a direction in which the welding gun presses the workpiece; a control unit that controls the motor in accordance with a rotation angle of the rotation shaft and a rotation angle of the kinetic shaft.

Images