Laser welding apparatus and laser welding method

Abstract

To provide a technique that can appropriately maintain a temperature of an object to be welded high by preheating, in laser welding.SOLUTION: A laser welding device, which welds an object to be welded having two or more conductive bodies contacting each other, comprises a welding laser irradiating part that irradiates the object to be welded with a laser beam while opposing to a first surface of the object to be welded so as to weld the object to be welded, and a preheating device that preheats the object to be welded. The preheating device has a first electrode having a first contact part that contacts the first surface and a second electrode having a second contact part that contacts a second surface of the object to be welded, which is at the opposite side of the first surface. The preheating device heats at least a portion of the object to be welded, by heat generated by electric currents flowing into the object to be welded through the first electrode and the second electrode.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a laser welding apparatus and a laser welding method.

Background Art

[0002] In laser welding, a technique for suppressing cracking of a welding object by preheating the welding object is known. For example, Patent Document 1 discloses preheating a welding object by irradiating the welding object with a light beam.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the preheating method of heating the welding object from the outside as in Patent Document 1, the temperature of the welding object may not be appropriately maintained high due to heat radiation from the surface of the welding object.

Means for Solving the Problems

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to a first embodiment of the present disclosure, a laser welding apparatus is provided for welding a workpiece having two or more conductors in contact with each other. The laser welding apparatus comprises a welding laser irradiation unit that faces a first surface of the workpiece and irradiates the workpiece with laser light to weld the workpiece, and a preheating device for preheating the workpiece. The preheating device comprises a first electrode having a first contact portion that contacts the first surface, and a second electrode having a second contact portion that contacts a second surface of the workpiece, which is the second surface opposite to the first surface. The preheating device heats at least a portion of the workpiece by heat generated by the flow of electric current through the workpiece via the first electrode and the second electrode. In this configuration, during preheating, an electric current is passed through the workpiece to be welded via a first contact portion that contacts the first surface of the workpiece and a second contact portion that contacts the second surface, thereby heating the workpiece from the inside. This increases the likelihood of maintaining an appropriately high temperature of the workpiece during preheating. (2) In the above embodiment, the object to be welded has a first plate-shaped member and a second plate-shaped member as the conductor, and the first plate-shaped member and the second plate-shaped member may be stacked on top of each other. (3) In the above embodiment, the object to be welded has a first plate-shaped member and a second plate-shaped member as the conductor, the first plate-shaped member and the second plate-shaped member are arranged side by side in the planar direction, and the welding laser irradiation unit may weld between the first plate-shaped member and the second plate-shaped member. (4) In the above configuration, the welding laser irradiation unit is configured to weld the object to be weld while moving the irradiation position of the laser beam on the object to be welded along a predetermined movement path, and the portion of the object to be welded has a starting end that is welded at the starting point of the movement path and a terminal end that is welded at the end point of the movement path, and the first electrode and the second electrode may be arranged so that the terminal end is heated by the heat. With this configuration, the terminal end can be preheated using the first electrode and the second electrode. Therefore, cracking of the object to be welded can be effectively suppressed. (5) In the above embodiment, the first electrode and the second electrode may be arranged such that a line segment connecting the first contact portion and the second contact portion by the shortest distance through the workpiece to be weld overlaps with at least a portion of the end portion when viewed in the direction from the first surface to the second surface. With this embodiment, compared to the case in which the first electrode and the second electrode are arranged such that the line segment does not overlap with the end portion when viewed in the direction from the first surface to the second surface, a larger current is more likely to flow near the end portion through the first electrode and the second electrode. Therefore, the end portion can be heated efficiently using the first electrode and the second electrode, and cracking of the workpiece to be weld can be suppressed more effectively. (6) In the above configuration, the first contact portion may be positioned in front of the tip of the end portion in the direction of movement of the irradiation position, and the second contact portion may be positioned behind the tip of the end portion. With this configuration, the possibility of arranging the first electrode and the second electrode such that the line segment connecting the first electrode and the second electrode at the shortest distance follows the shape of the end portion increases. Therefore, the possibility of heating the end portion more efficiently using the first electrode and the second electrode increases. (7) In the above embodiment, at least one of the first contact portion and the second contact portion may be made of a material having a higher melting point than the workpiece to be welded. With this embodiment, by making the first contact portion out of a material having a higher melting point than the workpiece to be welded, the first contact portion can be placed closer to the welding area compared to the case where the melting point of the material constituting the first contact portion is less than or equal to the melting point of the workpiece to be welded. Similarly, by making the second contact portion out of a material having a higher melting point than the workpiece to be welded, the second contact portion can be placed closer to the welding area. As a result, the degree of freedom in the placement of the first electrode and the second electrode can be increased.

[0007] This disclosure can be implemented in various forms other than the laser welding apparatus described above, such as a laser welding method or a control method for a laser welding apparatus. [Brief explanation of the drawing]

[0008] [Figure 1]This figure shows the schematic configuration of the laser welding apparatus in the first embodiment. [Figure 2] This is a diagram illustrating the welding target area in the first embodiment. [Figure 3] This is a flowchart of the welding process. [Figure 4] This is a diagram illustrating the welding target area in the second embodiment. [Figure 5] This figure shows the object to be welded in the third embodiment. [Figure 6] This is a diagram illustrating the welding target area in the third embodiment. [Figure 7] This figure shows the schematic configuration of the laser welding apparatus in the fourth embodiment. [Figure 8] This figure illustrates the arrangement of electrode pairs in the fifth embodiment. [Figure 9] This is a diagram illustrating the welding target area in the fifth embodiment. [Figure 10] This is the first figure illustrating the welding target area in the sixth embodiment. [Figure 11] This is a second figure illustrating the welding target area in the sixth embodiment. [Figure 12] This figure illustrates an example of a welding target area in another embodiment. [Modes for carrying out the invention]

[0009] A. First Embodiment: Figure 1 shows a schematic configuration of the laser welding apparatus 10. Figure 1 shows arrows aligned in the mutually orthogonal X, Y, and Z directions. The X, Y, and Z directions are aligned with the three mutually orthogonal spatial axes, the X, Y, and Z axes, and include both the direction along one side of the X, Y, and Z axes, and the opposite direction. The X and Y axes are axes aligned with the horizontal plane, while the Z axis is an axis aligned with the vertical line. Hereafter, the +Z direction will also be referred to as "up," and the -Z direction as "down."

[0010] The laser welding apparatus 10 welds the welding object OW by irradiating the welding object OW with the laser beam LB. The laser welding apparatus 10 includes a laser oscillator 11, an optical path 15, a welding laser irradiation unit 20, a stage 30, a preheating device 50, and a control unit 90.

[0011] The control unit 90 is configured as a computer including a CPU 91, a storage unit 92, and an input / output interface. By executing the program stored in the storage unit 92, the CPU 91 causes the control unit 90 to realize various functions including a function of preheating the welding object OW and a function of welding the welding object OW. In other embodiments, the control unit 90 may be configured by, for example, a PLC (Programmable Logic Controller). Also, the functions of the control unit 90 may be realized by a circuit.

[0012] The stage 30 supports the welding object OW. The welding object OW includes two or more conductors that contact each other and has a first surface Sd1 and a second surface Sd2. The second surface Sd2 is the surface on the opposite side of the first surface Sd1. In the present embodiment, the welding object OW has a plate shape as a whole. The first surface Sd1 is constituted by the upper surface of the welding object OW. The second surface Sd2 is constituted by the lower surface of the welding object OW. The welding object OW may constitute, for example, the whole of a certain member or product, or may be constituted as a part of a certain member or product.

[0013] In this embodiment, the welding object OW has a first plate-shaped member MP1 and a second plate-shaped member MP2 as conductors constituting the welding object OW. The first plate-shaped member MP1 and the second plate-shaped member MP2 are each a rectangular plate-shaped aluminum plate. The first plate-shaped member MP1 and the second plate-shaped member MP2 are laminated on each other in the plate thickness direction of the welding object OW. The plate thickness direction in this embodiment is the Z direction. The second plate-shaped member MP2 is placed directly above the stage 30. The first plate-shaped member MP1 is placed directly above the second plate-shaped member MP2. The gap between the lower surface of the first plate-shaped member MP1 and the upper surface of the second plate-shaped member MP2 is preferably small enough to suppress welding defects caused by this gap. For example, in order to improve the adhesion between the first plate-shaped member MP1 and the second plate-shaped member MP2, a jig (not shown) for pressing the first plate-shaped member MP1 against the second plate-shaped member MP2 may be appropriately installed on the stage 30.

[0014] Note that the meaning of "the first plate-shaped member MP1 and the second plate-shaped member MP2 are laminated" not only means that the first plate-shaped member MP1 and the second plate-shaped member MP2 are laminated in the plate thickness direction so as to completely overlap each other, but also includes that the first plate-shaped member MP1 and the second plate-shaped member MP2 are laminated in the plate thickness direction so that a part of the first plate-shaped member MP1 overlaps with a part of the second plate-shaped member MP2. When the first plate-shaped member MP1 and the second plate-shaped member MP2 are laminated as in this embodiment, the overlapping portions of both are welded.

[0015] The laser oscillator 11 oscillates a laser beam LB. The type of the oscillated laser beam LB may be arbitrary, such as a CO2 laser, a YAG laser, a fiber laser, a disk laser, an excimer laser, etc. The laser beam LB oscillated by the laser oscillator 11 is transmitted to the welding laser irradiation unit 20 via the optical path 15. The optical path 15 has, for example, an optical fiber cable or a mirror for transmitting the laser beam LB.

[0016] The welding laser irradiation unit 20 is positioned facing the first surface Sd1 of the workpiece OW to be welded. The welding laser irradiation unit 20 focuses the laser beam LB transmitted from the laser oscillator 11 and irradiates it toward the first surface Sd1. The welding laser irradiation unit 20 also welds the workpiece OW by irradiating the workpiece OW to be welded area WP with the laser beam LB. In this embodiment, the direction of irradiation of the workpiece OW with the laser beam LB is in the -Z direction. That is, the optical axis AX of the laser beam LB irradiated from the welding laser irradiation unit 20 is along the Z direction and perpendicular to the plane direction of the workpiece OW to be welded. In other embodiments, the optical axis AX does not have to be perpendicular to the plane direction of the workpiece OW to be welded, that is, it may be inclined with respect to the Z direction.

[0017] In this embodiment, the welding laser irradiation unit 20 is configured as a head having a galvanometer scanner. The welding laser irradiation unit 20 is configured to arbitrarily control the focal position and irradiation position of the laser beam LB irradiated onto the welding target OW by changing the angle of the galvanometer mirror mounted on the galvanometer scanner under the control of the control unit 90. In this embodiment, the focal position is the position in the Z direction, and the irradiation position is the position in the X and Y directions. The welding laser irradiation unit 20 is also configured to be movable relative to the stage 30. More specifically, the welding laser irradiation unit 20 is fixed to a robot arm (not shown) and is moved by the movement of the robot arm under the control of the control unit 90. This robot can be configured as, for example, a 3-axis robot or a 6-axis robot. When the robot is configured as a 6-axis robot, the angle of the welding laser irradiation unit 20 relative to the stage 30 can also be controlled. In other embodiments, the movement of the welding laser irradiation unit 20 may be achieved by, for example, a horizontal movement mechanism or a lifting mechanism configured as an electric actuator.

[0018] In Figure 1, the weld target area WP of the workpiece OW is marked with a dotted hatching pattern. The weld target area WP is the part of the workpiece OW that will be welded. More specifically, the weld target area WP is the part of the workpiece OW that is heated above its melting point when irradiated with laser light LB during welding, and is the part where a weld mark is formed by welding. The weld target area WP includes the part that is directly irradiated with laser light LB and the surrounding part that melts due to the heat from the laser light LB. Each conductive material constituting the workpiece OW is joined to each other by welding the weld target area WP. In this embodiment, the weld target area WP does not penetrate the workpiece OW in the direction of irradiation of the laser light LB. This type of welding, which does not penetrate the workpiece OW, is sometimes called non-penetrating welding. A welding method in which the laser light LB penetrates the workpiece OW in the direction of irradiation of the laser light LB is sometimes called penetrating welding. Hereafter, the part of the workpiece OW that is not welded, that is, the part where no weld mark is formed, will also be called the non-welded area.

[0019] The shape of the weld point (WP) can be predicted before welding of the weld object (OW) actually begins, provided that the welding conditions and the weld object (OW) are predetermined. The shape of the weld point (WP) may be predicted, for example, based on the results of welding a similar object to the weld object (OW) under similar conditions beforehand, or based on the results of a welding simulation of the weld object (OW).

[0020] Figure 2 illustrates the welding target area WP in this embodiment. In this embodiment, the welding laser irradiation unit 20 is configured to weld the workpiece OW while moving the irradiation position IP of the laser beam LB on the workpiece OW. Such movement of the irradiation position IP is achieved, for example, by changing the angle of the galvanometer mirror or by moving or changing the angle of the welding laser irradiation unit 20 using a robot arm.

[0021] When the workpiece OW is welded while the irradiation position IP is moved, the welding area WP has a starting point SE and an ending point EE. The starting point SE is the rear end of the welding area WP in the direction of movement of the irradiation position IP, and corresponds to the starting point SP of the movement path RT of the irradiation position IP. The starting point SE is welded at the starting point SP of the movement path RT, that is, at the beginning of welding the welding area WP. The ending point EE is the front end of the welding area WP in the direction of movement of the irradiation position IP, and corresponds to the ending point EP of the movement path RT. The ending point EE is welded at the ending point EP of the movement path RT, that is, at the end of welding the welding area WP. Note that in Figure 2, for illustrative purposes, the movement path RT is omitted midway, but in reality it extends from the starting point SP to the ending point EP.

[0022] In this embodiment, the control unit 90 moves the welding laser irradiation unit 20 during welding so that the irradiation position IP moves linearly in the +X direction from the starting point SP to the ending point EP. Therefore, as shown in Figure 2, the movement path RT and the welding target area WP in this embodiment extend linearly along the X direction when viewed along the Z direction. The end portion EE is located at a position in the +X direction of the starting point SE. More specifically, the welding target area WP in this embodiment extends from the -X direction end of the welding target object OW to a position before the +X direction end. Therefore, the starting point SE is located at the -X direction end of the welding target object OW, and the end portion EE is located in the X direction between the starting point SE and the +X direction end of the welding target object OW.

[0023] The preheating device 50 preheats the workpiece OW to be welded. Details of "preheating" will be described later. As shown in Figures 1 and 2, the preheating device 50 has a first electrode 51, a second electrode 56, and a power supply device 60. The first electrode 51 contacts the first surface Sd1 of the workpiece OW to be welded. The second electrode 56 contacts the second surface Sd2 of the workpiece OW to be welded. In other words, the first electrode 51 and the second electrode 56 are arranged in the Z direction so that the workpiece OW is sandwiched between them. Hereafter, the part of the first electrode 51 that contacts the first surface Sd1 will also be called the first contact part 52, and the part of the second electrode 56 that contacts the second surface Sd2 will also be called the second contact part 57. In Figure 2, the areas where the first contact part 52 is located and the areas where the second contact part 57 is located are hatched upwards to the right. Furthermore, in the following, the combination of the first electrode 51 and the second electrode 56 will also be referred to as an electrode pair.

[0024] In this embodiment, the second electrode 56 is positioned within an opening 31 provided in the stage 30. The opening 31 opens upward toward the stage 30. In other embodiments, the second electrode 56 may be embedded in the stage 30, for example, so that the second contact portion 57 is exposed upward, or it may be positioned above the stage 30. Furthermore, the first electrode 51 and the second electrode 56 may be configured to be movable relative to the stage 30 under the control of the control unit 90, for example, by an electric actuator or a robot.

[0025] In this embodiment, the first contact portion 52 and the second contact portion 57 are each made of a material having a higher melting point than the workpiece OW to be welded. More specifically, in this embodiment, the first electrode 51 and the second electrode 56 are entirely made of steel, and the first contact portion 52 and the second contact portion 57 are made of steel.

[0026] The power supply unit 60 is electrically connected to the first electrode 51 and the second electrode 56 via the wiring section 61. Under the control of the control unit 90, the power supply unit 60 applies voltage to the first electrode 51 and the second electrode 56, thereby causing current to flow through the first contact section 52 and the second contact section 57 to the workpiece OW to be welded. In other words, when current flows through the workpiece OW to be welded in this way, at least a portion of the workpiece OW to function as a current-carrying path connecting the first electrode 51 and the second electrode 56. The flow of current through the workpiece OW generates heat (Joule heat) in the workpiece OW to be welded. Hereinafter, the heat generated in the workpiece OW due to the flow of current through the first contact section 52 and the second contact section 57 as described above will also be referred to as "heat due to current flow". The preheating device 50 heats the workpiece OW to be welded by this heat due to current flow. More specifically, in this embodiment, the preheating device 50 heats at least a portion of the terminal section EE by the heat due to current flow. It can also be said that the first electrode 51 and the second electrode 56 are arranged such that at least a portion of the terminal portion EE is heated by the heat generated by the current.

[0027] Figures 1 and 2 show a line segment Ls. The line segment Ls represents a virtual line segment that passes through the workpiece OW to weld and connects the first contact portion 52 and the second contact portion 57 by the shortest distance. The area near the line segment Ls corresponds to an area of ​​the workpiece OW to which a larger current is more likely to flow through the first electrode 51 and the second electrode 56 compared to other areas. Therefore, the area near the line segment Ls is more likely to be heated to a higher temperature by the heat generated by the current. In this embodiment, the first electrode 51 and the second electrode 56 are arranged such that, when viewed from the first surface Sd1 to the second surface Sd2, the line segment Ls overlaps with at least a portion of the end portion EE. In other words, in this embodiment, when viewed along the Z direction, the line segment Ls overlaps with at least a portion of the end portion EE.

[0028] In this embodiment, the first contact portion 52 is positioned forward of the tip tp of the end portion EE in the direction of movement of the irradiation position IP. The second contact portion 57 is positioned backward of the tip tp of the end portion EE in the direction of movement of the irradiation position IP. "Forward or backward of the end portion EE in the direction of movement of the irradiation position IP" means, more specifically, forward or backward in the terminal direction d1 of the movement path RT. The terminal direction d1 refers to the direction of movement of the irradiation position IP when it approaches the end point EP in the movement path RT. In other words, the terminal direction d1 coincides with the direction of the velocity vector of the irradiation position IP moving at a position very close to the end point EP on the movement path RT. Therefore, for example, if the movement path RT is linear, the terminal direction d1 is the linear direction from the starting point SP to the end point EP. Also, for example, if the movement path RT is curved, the terminal direction d1 is the direction along the tangent to the movement path RT at the end portion EE, moving away from the position immediately before the end portion EE.

[0029] Figure 3 is a flowchart of the welding process. This welding process flowchart represents the laser welding method in this embodiment. The welding process is performed, for example, when the object to be welded OW is placed on the stage 30 and the first contact portion 52 and the second contact portion 57 are in contact with the first surface Sd1 and the second surface Sd2, respectively, and a predetermined start operation is performed by the user to the control unit 90.

[0030] In step S110, the control unit 90 performs a preheating step to preheat the workpiece OW to be welded. In the preheating step, at least a portion of the workpiece OW is heated by passing an electric current through the first electrode 51 and the second electrode 56 into the workpiece OW. More specifically, in step S110, the control unit 90 controls the power supply unit 60 to pass an electric current through the first electrode 51 and the second electrode 56 into the workpiece OW to be welded. In step S110 in this embodiment, due to the arrangement of the first electrode 51 and the second electrode 56 described above, at least a portion of the end portion EE and a portion of the workpiece WP to be welded that is different from the end portion EE are heated together with the surrounding non-welded areas.

[0031] In step S120, the control unit 90 executes the welding process. The welding process refers to the process of welding the workpiece OW by irradiating it with laser light LB from the welding laser irradiation unit 20. In step S120, the control unit 90 controls the welding laser irradiation unit 20 to irradiate the workpiece WP with laser light LB and move the welding laser irradiation unit 20 along the movement path RT.

[0032] As shown in Figure 3, in this embodiment, the welding process is performed after the preheating process, but this is not limited to other embodiments. More specifically, in preheating, it is sufficient that heating of a portion of the welding target area WP is started before the laser beam LB is irradiated onto that portion. For example, if welding of the end portion EE has not yet begun, preheating of the end portion EE may be started after welding of the other portion of the welding target area WP (e.g., the starting end SE) has begun. In other words, for example, the welding process may be started before the preheating process, or the welding process and the preheating process may be started simultaneously. Also, for example, heating of a portion by the preheating device 50 may continue while the laser beam LB is being irradiated onto that portion.

[0033] The heating temperature of the workpiece OW to be welded by the preheating device 50 can be adjusted, for example, by adjusting the magnitude of the current flowing through each electrode and the duration of current supply to each electrode. During preheating, the workpiece OW to be welded is heated to a temperature lower than its melting point. Furthermore, it is preferable that the heating temperature during preheating be set high enough to suppress the occurrence of hot cracks at the welded area WP during welding. For example, in this embodiment, it is preferable that the heating temperature of the end portion EE during preheating is high enough to suppress the occurrence of hot cracks at the end portion EE. In this case, the heating temperature may be set taking into account the preheating completion timing and the laser beam LB irradiation timing. For example, if the time between the completion of preheating of a certain area and the irradiation of that area with laser beam LB is shorter, welding is more likely to start with the temperature of the preheated area maintained at a higher level compared to when this time is longer. Therefore, in this case, the heating temperature may be set lower. In this way, for example, the time required to raise the temperature of the workpiece OW to be welded and the power consumption can be reduced.

[0034] In the laser welding apparatus 10 of this embodiment described above, the preheating device 50 includes a first electrode 51 that contacts the first surface Sd1 of the workpiece OW to be welded, and a second electrode 56 that contacts the second surface Sd2 of the workpiece OW to be welded. The preheating device 50 heats the workpiece OW to be welded by the heat generated by the current. For example, in other configurations that differ from this embodiment, where heat is supplied from the outside of the workpiece OW to heat it, it can be difficult to maintain a sufficiently high temperature of the workpiece OW, especially if the thermal conductivity of the workpiece OW is relatively high, due to heat dissipation from the surface of the workpiece OW. In such configurations, for example, if the amount or duration of heat supplied to the workpiece OW is increased in order to maintain a high temperature, the temperature near the surface of the workpiece OW may become locally too high. In contrast, in this embodiment, during preheating, an electric current is passed through the workpiece OW to be welded via the first electrode 51 and the second electrode 56, thereby heating at least a portion of the workpiece OW from the inside. Therefore, preheating increases the likelihood of maintaining an appropriately high temperature for the working ocean (OW) of the workpiece.

[0035] Furthermore, in this embodiment, the first electrode 51 and the second electrode 56 are arranged so that at least a portion of the terminal portion EE is heated by the heat generated by the current. It is generally known that hot cracking is more likely to occur in the terminal portion EE compared to other parts of the welding target area WP. In this embodiment, the vicinity of the terminal portion EE can be preheated using the first electrode 51 and the second electrode 56, so that cracking of the welding target OW can be effectively suppressed.

[0036] Furthermore, in this embodiment, the first electrode 51 and the second electrode 56 are arranged such that the line segment Ls connecting the first contact portion 52 and the second contact portion 57 by the shortest distance through the workpiece OW overlaps with at least a portion of the end portion EE when viewed in the Z direction. With this configuration, compared to the case where the first electrode 51 and the second electrode 56 are arranged so that the line segment Ls does not overlap with the end portion EE when viewed in the Z direction, it is easier to pass a larger current near the end portion EE through the first electrode 51 and the second electrode 56. Therefore, the area near the end portion EE can be heated efficiently by the heat generated by the current, and cracking of the workpiece OW can be suppressed more effectively.

[0037] Furthermore, in this embodiment, the first contact portion 52 is positioned in front of the tip tp of the end portion EE in the terminal direction d1, and the second contact portion 57 is positioned behind the end portion EE in the terminal direction d1. In this configuration, the line segment Ls is inclined with respect to the plate thickness direction such that, in the terminal direction d1, the end of the line segment Ls on the first surface Sd1 side is positioned in front of the end on the second surface Sd2 side. Generally, when welding is performed while moving the irradiation position IP along the movement path RT, the shape of the cross section of the end portion EE along the terminal direction d1 and the plate thickness direction is, as a whole, a shape in which the distance from the first surface Sd1 decreases as it approaches the tip tp of the end portion EE. Therefore, by arranging the first contact portion 52 and the second contact portion 57 as described above, the possibility of inclining the line segment Ls to conform to the shape of the end portion EE increases. Consequently, the possibility of more efficient heating of the vicinity of the end portion EE using the first electrode 51 and the second electrode 56 increases. Furthermore, in the above configuration, the first electrode 51 can be positioned so as not to overlap with the movement path RT, that is, in a position where the laser beam LB will not irradiate it regardless of the position of the irradiation position IP on the movement path RT. Therefore, for example, the vicinity of the terminal EE can be easily and efficiently heated until just before the laser beam LB irradiates the endpoint EP. Also, for example, the terminal EE can be heated in the same way even while the laser beam LB is irradiating the endpoint EP.

[0038] Furthermore, in this embodiment, the first contact portion 52 of the first electrode 51 is made of a material having a higher melting point than the workpiece OW to be welded. With this configuration, the first contact portion 52 can be positioned closer to the welding target area WP compared to the case where the melting point of the material constituting the first contact portion 52 is less than or equal to the melting point of the workpiece OW to be welded. Therefore, the degree of freedom in positioning the first electrode 51 can be increased. For example, in this embodiment, it becomes easier to position the first electrode 51 in a position more suitable for heating near the end portion EE. Similarly, in this embodiment, the second contact portion 57 is made of a material having a higher melting point than the workpiece OW to be welded. Therefore, the degree of freedom in positioning the second electrode 56 can be increased.

[0039] B. Second Embodiment: Figure 4 illustrates the welding target area WPb in the second embodiment. Unlike the first embodiment, the welding target area WPb is circular rather than linear when viewed along the Z direction. In Figure 4, as in Figure 2, the areas where the first contact portion 52 is located and the areas where the second contact portion 57 is located are hatched upwards to the right. The configuration of the laser welding apparatus 10 in the second embodiment is the same as in the first embodiment unless otherwise described.

[0040] In this embodiment, the control unit 90 moves the welding laser irradiation unit 20 so that the irradiation position IP moves circumferentially during welding. In other words, the movement path RT in this embodiment is circumferential. More specifically, the movement path RT in this embodiment is a clockwise path with the starting point SP at approximately 6 o'clock and the ending point EP at approximately 6 o'clock when viewed in the -Z direction. Therefore, the terminal direction d1 in this embodiment is the -X direction. In this embodiment, as the irradiation position IP moves circumferentially during welding, when viewed along the Z direction, a welding mark is formed clockwise along the circumferential direction of the welding target part WPb. After welding is completed, when viewed along the Z direction, a circular welding mark remains on the welding target object OW. Note that the movement path RT may be, for example, a path that moves the irradiation position IP circumferentially for a distance longer than one full rotation of the circumference.

[0041] As shown in Figure 4, in this embodiment as well, the line segment Ls overlaps with at least a portion of the terminal portion EE when viewed in the Z direction. Furthermore, the first contact portion 52 is positioned forward of the tip tp of the terminal portion EE in the terminal direction d1. The second contact portion 57 is positioned behind the tip tp of the terminal portion EE in the terminal direction d1. Note that in Figure 4, the starting end portion SE is omitted for illustrative purposes.

[0042] As shown in Figure 4, if the object to be welded OW has multiple weld target areas WPb, for example, multiple electrode pairs may be arranged corresponding to each weld target area WPb. Alternatively, for example, electric actuators may be provided to move the first electrode 51 and the second electrode 56 in the X and Y directions, and the control unit 90 may control these electric actuators to move the first electrode 51 and the second electrode 56 to a position where the weld target area WPb to be preheated can be heated. In Figure 4, three weld target areas WPb are shown, but the number of weld target areas WPb may be two, four or more, or, as in the first embodiment, only one.

[0043] In the laser welding apparatus 10 of the second embodiment described above, during preheating, current is passed through the workpiece OW to be welded via the first electrode 51 and the second electrode 56, thereby heating the workpiece OW from the inside by the heat generated by the current. Therefore, the possibility of maintaining an appropriately high temperature of the workpiece OW through preheating is increased.

[0044] C. Third Embodiment: Figure 5 shows the weldable object OWb in the third embodiment. Unlike the first embodiment, the first plate-shaped member MP1b in this embodiment is arranged alongside the second plate-shaped member MP2b in the plane direction of the weldable object OWb. In Figure 5, as in Figure 1, a dotted hatching pattern is applied to the weldable area WPc. The configuration of the laser welding apparatus 10 in the fourth embodiment is the same as in the first embodiment unless otherwise described.

[0045] As shown in Figure 5, the first plate-shaped member MP1b is positioned in the -X direction relative to the second plate-shaped member MP2b. Preferably, the gap between the side surface of the first plate-shaped member MP1b in the +X direction and the side surface of the second plate-shaped member MP2b in the -X direction is small enough to suppress welding defects caused by this gap. In this embodiment as well, a jig for pressing the first plate-shaped member MP1b against the second plate-shaped member MP2b may be provided, similar to that described in the first embodiment.

[0046] Figure 6 is a diagram illustrating the welding target area WPc in the third embodiment. In Figure 6, as in Figure 2, the area where the first contact portion 52 is located and the area where the second contact portion 57 is located are hatched upwards to the right. In this embodiment, the welding target area WPc extends along the Y direction between the first plate-shaped member MP1b and the second plate-shaped member MP2b. In other words, in this embodiment, the welding laser irradiation unit 20 welds between the first plate-shaped member MP1b and the second plate-shaped member MP2b. More specifically, in this embodiment, during welding, the control unit 90 moves the irradiation position IP along the Y direction. In this embodiment, the terminal direction d1 is the -Y direction. As shown in Figure 6, in this embodiment as well, the line segment Ls overlaps with at least a part of the terminal portion EE when viewed in the Z direction. Also, the first contact portion 52 is located in front of the tip tp of the terminal portion EE in the terminal direction d1. The second contact portion 57 is located behind the tip tp of the terminal portion EE in the terminal direction d1.

[0047] In the laser welding apparatus 10 of the third embodiment described above, during preheating, current is passed through the workpiece OWb via the first electrode 51 and the second electrode 56, thereby heating the workpiece OWb from the inside by the heat generated by the current. Therefore, the possibility of maintaining an appropriately high temperature of the workpiece OWb during preheating is increased.

[0048] In addition, in the laser welding apparatus 10 of the third embodiment, for example, the welding object OWb may be welded while moving the irradiation position IP in a circular motion, similar to the method described in the second embodiment.

[0049] D. Fourth Embodiment: Figure 7 shows a schematic configuration of the laser welding apparatus 10b in the fourth embodiment. In the fourth embodiment, unlike the first embodiment, the first electrode 51b has a first electrode member 53 and a second electrode member 54. Also, the second electrode 56b has a third electrode member 58 and a fourth electrode member 59. In Figure 7, as in Figure 1, a dot pattern hatching is applied to the welding target area WP. The configuration of the laser welding apparatus 10b in the fourth embodiment is the same as in the first embodiment unless otherwise described.

[0050] The first electrode member 53 is a component of the first electrode 51b that constitutes the first contact portion 52. The second electrode member 54 is a component of the first electrode 51b that is different from the first contact portion 52. Similarly, the third electrode member 58 is a component of the second electrode 56b that constitutes the second contact portion 57. The fourth electrode member 59 is a component different from the third electrode member 58.

[0051] The first electrode member 53 and the third electrode member 58 are each made of a material having a higher melting point than the workpiece OW to be welded. The second electrode member 54 is made of a different material than the first electrode member 53. Similarly, the fourth electrode member 59 is made of a different material than the third electrode member 58. In this way, for example, the materials constituting the second electrode member 54 and the fourth electrode member 59 can be selected to reduce the electrical resistance of the first electrode 51 and the second electrode 56 while ensuring the heat resistance of each contact part so that each contact part can be placed close to the workpiece WP to be welded. In this case, for example, the first electrode member 53 and the third electrode member 58 may be made of steel, and the second electrode member 54 and the fourth electrode member 59 may be made of copper, chromium copper, zirconium copper, copper tungsten, etc., which have a lower electrical resistivity than steel.

[0052] In the laser welding apparatus 10b of the fourth embodiment described above, during preheating, current is passed through the workpiece OW to be welded via the first electrode 51b and the second electrode 56b, thereby heating the workpiece OW from the inside by the heat generated by the current. Therefore, the possibility of maintaining an appropriately high temperature of the workpiece OW through preheating is increased.

[0053] In other embodiments, for example, either the first electrode 51b or the second electrode 56b may be composed of multiple components, while the other is composed of a single component. Furthermore, the configurations of the first electrode 51b and the second electrode 56b described in the fourth embodiment may be applied to the second and third embodiments.

[0054] E. Fifth Embodiment: Figure 8 is a diagram illustrating the arrangement of electrode pairs in the fifth embodiment. Figure 9 is a diagram illustrating the welding target area WPd in ​​the fifth embodiment. In Figure 8, the power supply unit 60 and wiring unit 61 are omitted. In the fifth embodiment, the preheating device 50b has a first pair Pr1 and a second pair Pr2 as electrode pairs. In the fifth embodiment, the welding target object OW is welded while the irradiation position IP is fixed. Note that in Figure 8, as in Figure 1, the welding target area WPd is hatched with a dot pattern. The configuration of the laser welding apparatus 10 in the fifth embodiment is the same as in the first embodiment unless otherwise described.

[0055] In Figure 8, as in Figure 1, the welding target area WPd is shown with a dotted hatching pattern. In Figure 9, the region where the first pair Pr1 and the second pair Pr2 are located when viewed in the Z direction is shown with upward-sloping hatching. As shown in Figure 8, in each electrode pair, the first electrode 51 is located directly above the second electrode 56. Therefore, the line segments Ls for each electrode pair are aligned in the Z direction. As shown in Figures 8 and 9, the first pair Pr1 is located in the -X direction relative to the second pair Pr2.

[0056] As shown in Figure 9, the welding target area WPd in ​​this embodiment is approximately circular in shape when viewed in the Z direction, with the irradiation position IP as the center. Furthermore, the welding target area WPd penetrates the object to be welded OW in the Z direction. In other words, the welding method in this embodiment is through welding. As shown in Figures 8 and 9, the welding target area WPd is located between the first pair Pr1 and the second pair Pr2 in the X direction. More specifically, the welding target area WPd is located between two line segments Ls in the X direction.

[0057] In the fifth embodiment described above, the laser welding apparatus 10 can also heat the workpiece OW from the inside by the heat generated by the current during preheating. Therefore, the possibility of maintaining an appropriately high temperature of the workpiece OW during preheating is increased.

[0058] For example, in the configuration described in the third embodiment, where the first plate-shaped member MP1b and the second plate-shaped member MP2b are arranged side by side in the planar direction, the object to be welded OW may be welded while the irradiation position IP remains fixed, similar to the fifth embodiment. Furthermore, the configurations of the first electrode 51b and the second electrode 56b described in the fourth embodiment may be applied to the configuration of the fifth embodiment.

[0059] F. Sixth Embodiment: Figure 10 is the first diagram illustrating the welding target area WPe in the sixth embodiment. Figure 11 is the second diagram illustrating the welding target area WPe in the sixth embodiment. In Figure 10, as in Figure 1, the welding target area WPe is hatched with a dot pattern. In this embodiment, unlike the first embodiment, the welding target area WPe does not extend to the -X side end of the workpiece OW. Therefore, the starting end SE is located in the +X direction rather than the -X end of the workpiece OW. The configuration of the laser welding apparatus 10 in the sixth embodiment is the same as in the first embodiment unless otherwise described. Even with this configuration, the workpiece OW can be heated from the inside by the heat generated by the current during preheating. Therefore, the possibility of maintaining an appropriately high temperature of the workpiece OW through preheating is increased. For example, even when the first plate-shaped member MP1 and the second plate-shaped member MP2 are arranged side by side in the planar direction, as in the third embodiment, the starting end SE does not have to be located at the end of the workpiece OW.

[0060] G. Other embodiments: (G1) In the above embodiment, the weldable object OW is composed of two conductors, but it may be composed of three or more conductors. Also, the weldable object OW does not have to be plate-shaped overall, as long as it has a first surface Sd1 and a second surface Sd2, and may be rod-shaped or columnar, for example. Also, each component constituting the weldable object OW does not have to be plate-shaped, and may be rod-shaped or columnar, for example. Also, the weldable object OW does not have to be made of aluminum, and may be formed of any other metal such as iron, magnesium or various alloys, or it may be formed of conductive ceramics. Also, for example, the materials of the conductors constituting the weldable object OW may be different.

[0061] (G2) In the above embodiment, the first contact portion 52 is positioned forward of the tip tp of the end portion EE in the terminal direction d1. In contrast, the first contact portion 52 may be positioned at the same position as the tip tp in the terminal direction d1, or it may be positioned behind the tip tp. The second contact portion 57 may be positioned at the same position as the tip tp in the terminal direction d1, or it may be positioned forward of the tip tp. The first contact portion 52 may be positioned at the same position as the second contact portion 57 in the terminal direction d1, or it may be positioned behind the second contact portion 57. Both the first contact portion 52 and the second contact portion 57 may be positioned forward of the tip tp, behind the tip tp, or at the same position in the terminal direction d1.

[0062] (G3) In the above embodiment, the first electrode 51 and the second electrode 56 are arranged such that when viewed in the direction from the first surface Sd1 to the second surface Sd2, that is, when viewed along the Z direction, the line segment Ls overlaps with at least a part of the terminal portion EE. In contrast, the first electrode 51 and the second electrode 56 may be arranged such that when viewed in the Z direction, the line segment Ls does not overlap with the terminal portion EE.

[0063] (G4) In the above embodiment, the first electrode 51 and the second electrode 56 are arranged so that the terminal portion EE is heated by the heat generated by the current. In contrast, the terminal portion EE does not necessarily have to be heated by the heat generated by the current. For example, the first electrode 51 and the second electrode 56 may be arranged so that only the portion of the welding target area WP other than the terminal portion EE is heated.

[0064] (G5) In the above embodiment, the movement of the irradiation position IP may be achieved, for example, by moving the workpiece OW to be welded relative to the welding laser irradiation unit 20. In this case, for example, an electric actuator for moving the stage 30 may be provided, and the control unit 90 may control this electric actuator to move the workpiece OW to be welded relative to the welding laser irradiation unit 20. In this case, the first electrode 51 and the second electrode 56 may be configured to move together with the stage 30 relative to the welding laser irradiation unit 20.

[0065] (G6) In the above embodiment, the movement path RT of the irradiation position IP is linear or circular. However, the movement path RT does not have to be linear or circular; for example, it may be a path with a shape that combines multiple straight lines or curves, or a path with a shape that combines a straight line and a curve.

[0066] (G7) In the above embodiment, the first contact portion 52 is made of a material having a melting point higher than that of the workpiece OW. In contrast, the first contact portion 52 may be made of a material having a melting point lower than or equal to that of the workpiece OW. In this case, for example, by positioning the first contact portion 52 relatively far from the welding area WP, the thermal effects of the laser beam LB on the first electrode 51 can be suppressed, and deformation of the first electrode 51 due to heat can be suppressed. Similarly, the second contact portion 57 may be made of a material having a melting point lower than or equal to that of the workpiece OW.

[0067] (G8) In the above embodiment, when welding the object to be welded OW while moving the irradiation position IP along the movement path RT, the welding method may be through welding. For example, Figure 12 is a diagram illustrating an example of a welding target area WPf in another embodiment. In Figure 12, as in Figure 1, the welding target area WPf is hatched with a dot pattern. In the example of Figure 12, the welding target area WPf penetrates the object to be welded OW in the Z direction. In other words, the welding method in the example of Figure 12 is through welding. Even in this configuration, the vicinity of the welding target area WPf can be heated from the inside of the object to be welded OW by the heat from the current. Note that when welding the object to be welded OW through welding as in Figure 12, the starting end SE of the welding target area WPf does not have to be located at the end of the object to be welded OW, as in the sixth embodiment.

[0068] (G9) In the above embodiment, the arrangement of the first electrode 51 and the second electrode 56 may be determined, for example, based on the temperature distribution within the weld OW when current is passed through the first electrode 51 and the second electrode 56 into the weld OW. For example, the temperature distribution within the weld OW may be simulated using the finite element method, and based on the simulation results, the first electrode 51 and the second electrode 56 may be arranged so that a desired portion of the weld area WP is heated to a higher temperature. More specifically, for example, the first electrode 51 and the second electrode 56 may be arranged so that the portion heated to a higher temperature in the simulation overlaps with the terminal portion EE.

[0069] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of symbols]

[0070] 10, 10b…Laser welding apparatus, 11…Laser oscillator, 15…Optical path, 20…Welding laser irradiation unit, 30…Stage, 31…Aperture, 50, 50b…Preheating device, 51, 51b…First electrode, 52…First contact part, 53…First electrode member, 54…Second electrode member, 56, 56b…Second electrode, 57…Second contact part, 58…Third electrode member, 59…Fourth electrode member, 60…Power supply unit, 61…Wiring unit, 90…Control unit, 91…CPU, 92…Storage unit

Claims

1. A laser welding apparatus for welding a workpiece having two or more conductive materials in contact with each other, A welding laser irradiation unit that faces the first surface of the object to be welded and irradiates the object to be welded with laser light to weld the object, The system includes a preheating device for preheating the object to be welded, The preheating device is A first electrode having a first contact portion that contacts the first surface, The second electrode has a second contact portion that contacts the second surface of the object to be welded, which is the second surface opposite to the first surface, The preheating device heats at least a portion of the workpiece to be welded by the heat generated when an electric current flows through the workpiece to be welded via the first electrode and the second electrode. The welding laser irradiation unit is configured to weld the object to be weld while moving the irradiation position of the laser beam on the object to be welded along a predetermined movement path. The portion of the object to be welded has a starting end that is welded at the starting point of the movement path and a terminal end that is welded at the end point of the movement path. The first electrode and the second electrode are arranged such that their terminal portions are heated by the heat. A laser welding apparatus in which the first electrode and the second electrode are arranged such that a line segment connecting the first contact portion and the second contact portion by the shortest distance through the workpiece to be welded overlaps with at least a portion of the end portion when viewed along the direction from the first surface to the second surface.

2. A laser welding apparatus according to claim 1, The object to be welded comprises a first plate-shaped member and a second plate-shaped member as the conductor. A laser welding apparatus in which the first plate-shaped member and the second plate-shaped member are stacked on top of each other.

3. A laser welding apparatus according to claim 1, The object to be welded comprises a first plate-shaped member and a second plate-shaped member as the conductor. The first plate-shaped member and the second plate-shaped member are arranged side by side in the planar direction. The welding laser irradiation unit is a laser welding apparatus that welds the first plate-shaped member and the second plate-shaped member.

4. A laser welding apparatus according to claim 1, The first contact portion is positioned in front of the tip of the terminal portion in the direction of movement of the irradiation position. The laser welding apparatus wherein the second contact portion is positioned behind the tip of the terminal portion.

5. A laser welding apparatus according to any one of claims 1 to 4, A laser welding apparatus in which at least one of the first contact portion and the second contact portion is made of a material having a higher melting point than the object to be welded.

6. A laser welding method for welding objects having two or more conductive materials in contact with each other, A preheating step for preheating the object to be welded, The welding process includes welding the object to be welded by irradiating the welding area of ​​the object to be welded with laser light from a welding laser irradiation unit positioned opposite the first surface of the object to be welded, In the preheating step, at least a portion of the workpiece to be weld is heated by the heat generated by passing an electric current through a first electrode having a first contact portion that contacts the first surface and a second electrode having a second contact portion that contacts the second surface of the workpiece to be weld, which is the second surface opposite to the first surface. The welding laser irradiation unit is configured to weld the object to be weld while moving the irradiation position of the laser beam on the object to be welded along a predetermined movement path. The portion of the object to be welded has a starting end that is welded at the starting point of the movement path and a terminal end that is welded at the end point of the movement path. The first electrode and the second electrode are arranged such that their terminal portions are heated by the heat. A laser welding method in which the first electrode and the second electrode are arranged such that a line segment connecting the first contact portion and the second contact portion at the shortest distance through the workpiece to be welded overlaps with at least a portion of the end portion when viewed along the direction from the first surface to the second surface.

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