JP7803640B2 - Automatic welding method and automatic welding device - Google Patents

Description

This disclosure relates to an automatic welding method and automatic welding device for performing fillet welding while operating a welding torch.

When attempting to achieve consistent quality in arc welding, automatic welding is used. Automatic welding uses welding robots or carts, and employs a method of welding by moving a welding torch along the weld line, and is equipped with a detection device for detecting the weld line.

Methods have been proposed for detecting weld lines to allow the welding torch to follow the weld line, depending on the shape of the joint. For fillet welding, methods such as those shown in Patent Documents 1 and 2 are available. Patent Document 1 discloses a device using a welding robot, which scans the vicinity of the weld line with a laser beam and detects the weld line by processing the trajectory of the reflected laser beam captured by a camera. Patent Document 2 discloses a welding method using a cart, which uses multiple laser rangefinders to measure whether or not there is any tilt between the cart and the weld line, and if tilt does occur, controls the wheel movement of the traveling cart to rotate the cart and correct the tilt to a parallel position.

Japanese Patent Application Laid-Open No. 2001-62566 Japanese Patent Application Publication No. 11-216566

In the case of the device described in Patent Document 1, in order to process the image of the laser beam trajectory obtained by the camera, it is necessary to identify the shape of the part to be welded and detect the weld line based on that shape. Therefore, in addition to a laser beam scanning device, a complex device is required to perform precise shape identification and weld line detection.

Furthermore, the device in Patent Document 2 requires measuring multiple distances, and is equipped with multiple distance measurement devices and a complex travel function for controlling multiple wheels to keep the carriage parallel to the weld line. Therefore, it is necessary to control the multiple distance measurement devices and the wheel rotation operation in accordance with the measurement results with high precision and stability, which also complicates the control aspect.

When adopting automatic welding methods and equipment, the increased complexity of the equipment and controls not only increases costs, but can also lead to increased processing time and weight.

The present invention aims to provide a method for automatic welding that detects the position of a welding line using simpler equipment and control without requiring complex processing, as well as an automatic welding device that can achieve this.

The present invention therefore provides an automatic welding method using a welding machine that performs fillet welding while moving a welding torch in line with the weld line, as follows:

The welding machine advances in a direction inclined to the weld line, measuring the torch measurement distance, which is the distance from the welding torch to the workpiece, and when the torch measurement distance changes, the welding torch moves in a first orthogonal direction that is approximately perpendicular to the direction of advancement of the welding machine and in a second orthogonal direction that is approximately perpendicular to the measurement direction of the torch measurement distance and different from the first orthogonal direction.

This allows for good welding along the desired weld line by simply operating (moving) the welding torch as described above to a position where the measured torch distance reaches a predetermined distance based on changes in the torch distance. In other words, stable, consistent quality welding can be achieved with simple means and control.

The present invention also provides an automatic welding device equipped with an extension guide and a carriage that travels along the extension guide and has a welding torch that welds the workpieces, and which has the following configuration.

The extension guide extends in a direction inclined relative to the weld line of the workpieces to be welded, and the carriage has a distance measurement unit that measures the torch-measured distance between the welding torch and the workpieces to be welded, a distance determination unit that determines whether the measured distance matches a predetermined distance based on the measurement data of the distance measurement unit, and a torch movement unit that can move the welding torch based on the distance determination unit, and is controlled so that the torch-measured distance can be maintained at the predetermined distance as the carriage moves.

With this configuration, the torch movement unit moves the welding torch unit until the predetermined distance is met, based on the determination by the distance determination unit, thereby achieving good welding.

According to the present invention, welding of consistent quality can be performed by measuring the distance from the welding torch to the workpiece in one direction and controlling the position of the welding torch so that the measured distance (torch measurement distance) matches a predetermined value, thereby providing an automatic welding method and automatic welding device with a control method and device configuration that are simpler than conventional methods.

1 is a diagram showing the appearance of a garbage compactor according to an embodiment of the present invention; 2A is a cross-sectional view of the body of a refuse compactor according to an embodiment of the present invention, taken along the line A-A in FIG. 2, and FIG. 2B is an enlarged view of part B. 1 is a front view showing the overall configuration of an automatic welding apparatus according to an embodiment of the present invention; FIG. 2 is a top view showing the relationship between the rail, the workpieces to be welded, the weld line, and the carriage. FIG. 10 is a diagram showing a state in which a welding torch and a laser rangefinder are set at appropriate positions. This is an enlarged view of the weld line and the edge area. (a) shows the state where the laser beam from the laser rangefinder is irradiating the upper steel member, and (b) shows the state where the torch part has moved to the right and is irradiating the lower steel member.

An example of an embodiment of the present invention will be described below.
1 shows a garbage truck 1 equipped with a cargo box 11 to be welded by the automatic welding device according to the present invention. The cargo box 11 is a steel box mounted on a chassis frame whose longitudinal direction is the fore-and-aft direction of the vehicle, and has an elongated shape whose longitudinal direction is the fore-and-aft direction of the vehicle.

2(a) is a cross-sectional view of the cargo box 11 taken along the line A-A in FIG. 1. As shown, the cargo box 11 is composed of multiple metal plates (steel members) assembled together. In this embodiment, the welding of part B, where these steel members are joined together, will be mainly described. As shown in FIG. 2(b), which is an enlarged view of part B, a steel member 14 is placed on top of a steel member 13 that forms the floor of the cargo box. In this embodiment, the top surface of steel member 13 is welded to the end surface of steel member 14. The intersection of the top surface of steel member 13 and the end surface of steel member 14, with the longitudinal direction of the vehicle as the longitudinal direction, forms weld line 12. In this embodiment, welding is performed along weld line 12. Therefore, multiple steel members are spot-welded together (locally welded at several locations along the longitudinal direction of the vehicle) to create a temporary assembly state. An automatic welding device is then inserted into the space S, which is surrounded by multiple steel members on all sides as shown, and continuous welding (full welding) is performed along the longitudinal direction of the vehicle.

The configuration of an automatic welding device 2 according to this embodiment for continuous welding will be described with reference to Fig. 3. Fig. 3 is a front view of the automatic welding device 2.
The automatic welding device 2 includes a rail 3 installed on a steel member 13 and a carriage 4 that runs on the rail 3. The carriage 4 is provided with a control unit 41 provided on the top, an arm 42 that extends to the side (the negative X-axis direction), and a torch unit 43 attached to the arm 42 and facing downward.

The rail 3 functions to guide the travel of the bogie 4 and is a long member extending in the longitudinal direction of the vehicle at an angle on a horizontal plane relative to the weld line. The rail 3 has a base portion 301 and a guide portion 302. The base portion 301 is provided with a fixing magnet 303 at its bottom, and is fixed to the upper surface of the steel member 13 via the magnetic force of the magnet 303. The guide portion 302 is fixed on top of the base portion 301 and has a substantially inverted T-shaped cross section. Both the base portion 301 and the guide portion 302 are long members extending in the above-mentioned inclined direction.

In addition to the control unit 41, arm 42, and torch unit 43, the carriage 4 also includes rollers 50 and a roller drive unit 51. There are two sets of rollers 50, one at the front and one at the rear of the carriage 4; one set is shown in the figure. The carriage 4 has four rollers that roll on the approximately inverted T-shaped upright portion of the guide unit 302. Two of the four rollers roll on the side of the upright portion of the guide unit 302 (the right side in the figure), one roller rolls on the opposite side of the upright portion (the left side in the figure), and the remaining roller rolls on the top surface of the upright portion. The front set of rollers overlaps with the rear set and is therefore not shown. These rollers enable the carriage 4 to move stably along the extension direction of the guide unit 302. The roller drive unit 51 has a drive source (not shown) that drives the rollers 50, and controls the on/off of the drive source at the appropriate time to start automatic welding.

The control unit 41 is connected to the roller drive source 51, allowing it to output drive control commands, and is also connected to the arm drive unit 422, distance measurement unit 432, and distance determination unit (not shown), which will be described later, allowing it to input and output data.

The arm 42 is composed of a joint 421 with the carriage 4, an arm drive unit 422 extending horizontally from the joint 421, and an arm movement unit 423 attached to the arm drive unit 422 and movable horizontally. The arm movement unit 423 can be moved horizontally relative to the carriage 4 by the arm drive unit 422, and the arm drive unit 422 has a known configuration such as a unit consisting of an electric motor and ball screw, or a unit consisting of an electric motor and belt. In addition, the torch unit 43 is attached to the arm movement unit 423.

The torch unit 43 includes a welding torch 431 for arc welding, a distance measurement unit 432 for measuring the distance between the welding torch 431 and the steel members 13 and 15 (torch measurement distance), and a light shielding plate 433 (shown by a dashed line in Figure 3) arranged so as not to interfere with the measurement function of the distance measurement unit 432.

As shown, the welding torch 431 is positioned to point toward the weld line formed by the steel members 13 and 15, enabling fillet welding of the steel members 13 and 15. The distance measurement unit 432 includes a laser rangefinder 432a capable of measuring the distance from a predetermined location on the torch unit 43 to the top surface of the upper of the two steel members, the steel member 14. The distance measurement unit 432 is positioned adjacent to the welding torch 431 in front of the carriage 4 in the direction of travel. It irradiates the steel member 14 with a laser beam and measures the distance using the reflected light. Information on the measured distance (torch-measured distance) is sent to a distance determination unit in the control unit 41. The distance determination unit determines whether the data measured and output by the distance measurement unit 432 matches a predetermined size. The control unit 41 outputs a drive control command to the arm drive unit 422 based on the determination result of the distance determination unit. A light shielding plate 433 is provided between the laser rangefinder 432a and the welding torch 431 to prevent the welding arc light from affecting the measurements of the laser rangefinder 432a. The torch unit 43 is also provided with a tracing mechanism 434 that maintains a constant distance from the steel member 14. The tracing mechanism 434 has a rod-shaped extension member that extends toward the steel member 14 and a wheel attached to the tip of the extension member, and can move vertically together with the torch unit 43. Gravity or other factors press the wheel against the member to be welded, helping to maintain a constant distance between the torch unit 43 and the steel member 14.

Next, an automatic welding method for fillet welding the steel members 13 and 15 using the automatic welding device 4 will be described.
As shown in Figure 4, which is a top view of the steel members 13, 15 and the bogie 4, the bogie 4 is mounted on rails 3 that are inclined in the X-axis direction with respect to a weld line 12, the longitudinal direction of which is the fore-and-aft direction of the vehicle (the Y-axis direction) on the steel members 13, and is moved in the direction of arrow A. As the bogie 4 moves forward, the distance between the weld line 12 and the rail 3 increases, but the difference in the distance between the end (starting point) and the end (ending point) of the steel members 13 and the weld line 12 is set to a value sufficiently small relative to the movable range of the arm moving unit 423. Note that, for ease of explanation, the weld line 12, which is hidden by the end of the steel member 14 located above, is shown by a dashed line in Figure 4.

However, before the carriage 4 begins to move, the positions of the welding torch 431 and laser rangefinder 432a are adjusted using their respective position adjustment mechanisms 435a and 435b. In this embodiment, as shown in FIG. 5, the laser beam emitted from the laser rangefinder 432a is directed in a direction approximately vertical to the top surface of the steel member 14 (the right end in the figure). At this time, the irradiation position 103 of the laser beam is adjusted so that it is near the end of the steel member 14, as shown in FIG. 6(a). The distance measured by the laser rangefinder 432a at this time is set as the predetermined distance.

Welding begins and the carriage 4 also begins to move forward. Even if the relative positions of the carriage 4 and the weld line 12 change slightly due to undulations in the steel members 13, the vertical distance between the welding torch 431 and the weld line 12 is kept constant by the tracing mechanism 434. However, because the extension direction of the rail 3 is tilted relative to the weld line 12, the carriage 4 gradually moves away from the weld line 12 (steel members 13) as it moves forward.

In particular, because the laser beam from the laser rangefinder 432a is directed toward the right end of the steel member 14, if the position of the welding torch 431 shifts slightly to the right as the carriage 4 advances, the target of the laser beam irradiation will be the upper surface of the steel member 13, as shown in Figure 6(b). At this time, the measured distance (torch measured distance) of the laser rangefinder 432a increases approximately by the thickness of the steel member 14 stacked on top. Data regarding the torch measured distance is output to the distance determination unit, which determines that it does not match the predetermined distance. Based on this determination result, the control unit 41 outputs a drive command to the arm drive unit 422. When the arm drive unit 422 is driven, the arm movement unit 423 moves toward the tip of the arm 42; specifically, it moves toward the weld line 12 in a direction that is approximately perpendicular to the extension direction of the rail and approaches the weld line 12 (see Figure 4), along an XY plane (see Figure 4) that is approximately perpendicular to the laser irradiation direction (distance measurement direction) of the laser rangefinder 432a.

The laser rangefinder 432a continues to measure the torch measurement distance while the carriage 4 is moving, and the arm drive unit 422 continues to drive and move the arm movement unit 423 until the torch measurement distance value returns to the predetermined distance value. When torch measurement distance data that matches the predetermined distance value is input to the distance determination unit and the distance determination unit determines that the distance matches the predetermined distance, the control unit 41 stops issuing a drive command to the arm drive unit 422. This stops the movement of the arm movement unit 423, eliminates any misalignment of the welding torch 431 with respect to the weld line 12, and allows the welding torch 431 to continue welding appropriately on the weld line 12.

In this embodiment, the torch unit 43 actively moves the carriage 4 away from the weld line as it advances, and is controlled based on the torch measurement distance and the judgment by the distance judgment unit. This eliminates the need to measure the distance of the welding torch 431 to the weld line 12 or to provide means or control to identify the position and shape of the weld line, enabling automatic welding with sufficient accuracy with a simpler device configuration and control than conventional methods. Furthermore, because the position of the weld line 12 is detected by changes in the measurement value of the laser distance meter 432a, which measures in the approximately vertical direction, the position can be detected without complex processing.

If the welding torch 431 can be positioned appropriately, the rail 3 can be installed on the steel member 14 and tilted in a direction that approaches the weld line 12 as the carriage 4 moves forward, allowing for similar control.

Similar control is also possible when the laser rangefinder 432a is set to target the steel member 13 below, with the extension direction of the rail 3 tilted toward the weld line 12 as the bogie 4 moves forward. However, because several small welds have been made in advance on the weld line 12 by tack welding, if the tack weld locations overlap with the irradiation position of the laser beam, the torch measurement distance will be shortened due to the influence of the raised portions caused by the tack welding. The shortened distance depends on the size of the tack welding, so the tack welding must be performed so that the change in the torch measurement distance is sufficiently smaller than the thickness of the steel member 14. However, this does not apply when the influence of the tack welding can be ignored or when tack welding is not performed.

In this embodiment, fillet welding of steel members 13, 15 with their main surfaces overlapping each other is shown, but the shape of the welded joint to which this can be applied is not limited to this. As long as the position of the weld line can be detected based on changes in distance, it can also be applied to fillet welding of plates butted together in a T-shape, for example.

Furthermore, while the rail 3 is fixed to the workpiece 12 using a magnet 31, the fixing means is not limited to the magnet 31.

Furthermore, while the rails 3 are fixed to the workpieces 12 and the carriage 4 moves over the workpieces 12, this is not a limitation. For example, if the workpieces 12 that are covered (surrounded) on all sides of the weld line 12 are not to be welded, the rails 3 may be provided in a position different from the workpieces to be welded, and the carriage 4 may move over the rails 3.

In addition, while the rail 3 is shown as a single piece in this embodiment, it may be divided into multiple pieces and connected to match the length of the weld line. Regarding the extension direction of the rail 3, while it is shown as a linear one-way in this embodiment, it may also be curved or have multiple bends. Similarly, the weld line 12 is not limited to being linear.

Furthermore, the distance measurement means is not limited to the laser distance meter 432a. Any other method can be selected as appropriate as long as it can properly detect changes in distance. Furthermore, the direction of distance measurement is not limited to a direction approximately perpendicular to the workpieces to be welded; other angles can also be used as long as they do not impede the simplicity of the welding method or the welding equipment.

Furthermore, while this embodiment focuses on a cargo box 11 mounted on a refuse compactor 1, it may also be mounted on other types of vehicles or may be a welded component in a field other than the automotive field.

1 Garbage truck 11 Packing box 12 Welding line 13 Steel member (bottom)
14 Steel members (top)
2 Automatic welding device 3 Rail 301 Guide section 302 Base section 303 Magnet 4 Cart 41 Control section 42 Arm 421 Joint section 422 Arm drive section 423 Arm movement section 43 Torch section 431 Welding torch 432 Distance measurement section 432a Laser distance meter 433 Light shielding plate 434 Copying mechanism 435a Position adjustment mechanism 435b Position adjustment mechanism 50 Roller 51 Roller drive section 103 Laser irradiation position

Claims (7)

In an automatic welding method using a welding machine that performs fillet welding while moving a welding torch along the weld line,
The welding machine advances in a direction oblique to the weld line,
Measure a torch measurement distance, which is the distance from the welding torch to the workpiece;
an automatic welding method, characterized in that, when the torch measurement distance changes, the welding torch is moved in a first orthogonal direction that is approximately orthogonal to a direction of travel of the welding machine and in a second orthogonal direction that is approximately orthogonal to a measurement direction of the torch measurement distance and different from the first orthogonal direction. 2. The automatic welding method according to claim 1, wherein the welding torch is moved in the first orthogonal direction and the second orthogonal direction so as to maintain the magnitude of the torch measurement distance when the welding machine advances in the forward direction. The workpieces are two stacked steel plates,
3. The automatic welding method according to claim 2, wherein the welding torch is extended when the torch measurement distance changes from the distance from the welding torch to the top surface of the upper one of the two steel plates to the distance from the welding torch to the top surface of the lower one of the two steel plates. An automatic welding device comprising an extension guide and a carriage having a welding torch that travels along the extension guide and welds members to be welded,
the extension guide extends in a direction inclined with respect to the weld line of the workpieces to be welded,
The carriage includes a distance measurement unit that measures a torch-measured distance between the welding torch and the workpiece, a distance determination unit that determines whether the measured distance matches a predetermined distance based on the measurement data of the distance measurement unit, and a torch movement unit that can move the welding torch based on the distance determination unit,
a movement direction of the welding torch of the torch movement unit is set to a first orthogonal direction that is substantially orthogonal to the extension direction of the extension guide and a second orthogonal direction that is substantially orthogonal to the measurement direction of the distance measurement unit and different from the first orthogonal direction,
An automatic welding device characterized in that when the cart moves, the torch moving unit moves the welding torch based on the judgment of the distance judgment unit, thereby controlling the torch measurement distance so that the specified distance can be maintained. The automatic welding device according to claim 4, wherein the distance measurement unit is provided on the front side of the welding torch in the direction of travel of the carriage.
6. The automatic welding apparatus according to claim 4, wherein the carriage includes a position adjustment mechanism that can adjust the positions of the welding torch and the distance measurement unit. 7. The automatic welding device according to claim 4 , wherein the extension guide is detachable by a magnet, and a plurality of the extension guides can be connected in accordance with the length of the welding line.