JP2012206153A - Laser welding method and laser welding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser welding technology allowing certain detection of possibility/impossibility of welding and quality of the welding during a welding process.SOLUTION: This laser welding method by laser light irradiation includes the following processes: (a) a process of overlapping electroconductive objects to be welded or making them abut on each other, and setting them; (b) a process of measuring electric resistance between the objects to be welded set in the above process, obtaining a difference by subtracting a predetermined first setting value from the electric resistance, and resetting the objects to be welded when the difference is a positive value; (c) a process of irradiating laser light to perform laser welding when the difference is not more than zero in the above process; and (d) a process of measuring the electric resistance between the object to be welded during the above process, obtaining a difference between the electric resistance and a second setting value, and irradiating the laser light until the difference becomes not more than zero.

Description

  The present invention relates to a laser welding technique in which the plate-like members are welded to each other by irradiating the plate-like members stacked on each other or the butted plate-like members with a laser beam.

  In general, laser welding in which two or more plate-shaped members are welded together by irradiating a laser beam along a predetermined welding site in a state where two or more plate-shaped members are overlapped or butted together. Processing is widely performed in various manufacturing processes.

  In this type of laser welding process, in order to maintain good welding quality, it is desired to check the welding state, and the following techniques are known (for example, Patent Documents 1 and 2). .

  The technique disclosed in Patent Document 1 is to photograph a welded portion with a CCD camera 5, and based on the photographed image, the image processing means 6 obtains the molten pool length L of the work W and the control means 7. Is sent to the laser oscillator 2 and the processing table 4 to adjust the laser output and the welding speed, so that the ratio L / t of the molten pool length L to the plate thickness t of the workpiece W is in the range of 1 to 3. The welding quality is maintained by controlling to be.

  On the other hand, in the technology disclosed in Patent Document 2, the laser irradiation of the laser welding portion 14 is performed in the vicinity of a portion where the two connection terminal portions 10 and 11 to be electrically connected are welded by the YAG laser device 12. On the side, an ultraviolet sensor 17 for detecting the amount of plasma generated in the ultraviolet region and an infrared sensor 18 for detecting the temperature of the laser welded portion 14 are provided, and the success or failure is indirectly evaluated simultaneously with welding.

JP 2000-210781 A JP 2001-191186 A

  However, as described above, the technique disclosed in Patent Document 1 detects only the welded (melted) state of the surface of the plate-like member irradiated with the laser beam, and the technique disclosed in Patent Document 2 It detects the plasma generation amount and temperature at the welding site. For this reason, since the time and amount of laser beam irradiation are not controlled while directly confirming the welding state, it is impossible to determine whether the laser beam actually penetrates to the lower plate-like member. There is a problem that the welding quality, for example, the welding strength cannot be guaranteed.

  In addition, the welding state is greatly affected by the quality of the welded portion of the overlapped plate member or the butted plate-like member. Therefore, from this point as well, there is a problem that the welding quality of the welded portion, for example, the welding strength cannot be guaranteed.

  Further, the means for confirming the welding state becomes relatively large, and there is a problem that the laser welding apparatus becomes expensive.

    The present invention has been made in view of such a problem, and can directly detect a welding state, and can easily and highly perform laser welding processing of plate members stacked on top of each other or plate members pressed together. A first object is to provide a laser welding method that can be performed with high quality, and a second object is to provide a low-cost laser welding apparatus that is used directly in such a welding method.

  The inventor of the present application pays attention to the correlation between the electrical resistance value when an electric current is passed between the superposed or butted conductive plate members to be welded, the adhesion between the plate members and the welding strength. Thus, the present invention has been made.

The laser welding method by laser beam irradiation according to the present invention includes the following steps.
a) Step of setting the workpieces to be overlapped or butting together b) Measuring the electrical resistance between the workpieces set in the above step and determining the difference from the first set value determined in advance. C) Step of resetting again when the value is c) Step of performing laser welding by irradiating laser light when the difference is zero or a negative value in the step d) Electric resistance between the workpieces during the step , Measuring a difference from a predetermined second set value, and irradiating the laser beam until the difference becomes 0 or a negative value

Moreover, the laser welding apparatus provided with the laser beam irradiation means according to the present invention includes the following configuration.
a) Setting means for setting the work pieces to be overlapped or butted together b) Electric resistance measuring means for measuring the electric resistance between the work pieces set by the setting means c) Laser light irradiation from the laser light irradiation means Before starting, the set means is driven so that the difference between the resistance value from the electrical resistance measuring means and the first set value set in advance becomes 0 or a negative value, and the laser light irradiation means Control means for driving the laser irradiation means until the difference between the resistance value from the electric resistance measurement means and a predetermined second set value becomes 0 or a negative value after the start of laser light irradiation.

  According to the laser welding method of the present invention, the adhesion of an object to be welded is ensured so that welding is normally performed before the start of laser welding, and the progress of welding can be confirmed during laser welding. Quality control is possible even in the work process. Therefore, a highly reliable laser welding method can be provided.

  Further, according to the laser welding apparatus of the present invention, the adhesion of the welding object is ensured so that the welding is normally executed before the start of laser welding, and the progress of welding can be confirmed during laser welding. Quality control is also possible in the laser welding process. Therefore, a highly reliable laser welding apparatus can be provided.

It is a principal part block diagram of the laser welding apparatus which becomes this invention. It is an enlarged view of a laser beam irradiation part. It is a schematic flowchart figure of the laser welding method which becomes this invention.

Next, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a main part configuration diagram of a laser welding apparatus according to the present invention, FIG. 2 is an enlarged view of a laser beam irradiation portion in the main part configuration diagram, and FIG. 3 is a schematic flowchart of a laser welding method according to the present invention. It is.

  Note that the present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are as means for solving the present invention. It is not always essential.

  In FIG. 1, a laser welding apparatus 100 conveys a conductive first plate-like member 61 and a second plate-like member 63 that are objects to be welded, and positions and places them on a predetermined position of a processing table 71. The processing table is pressed by the pressing member 21 around the portion where the first plate-like member 61 and the second plate-like member 63 placed at predetermined positions on the part 1 and the processing table 71 are welded by irradiating the laser beam 33. 71, the pressure control unit 2 that presses against the laser beam 71, the laser oscillation unit 3 that irradiates the laser beam 33 that welds the first plate member 61 and the second plate member 63, the first plate member 61 and the second plate member 63. The constant voltage power supply unit 4 for applying a low voltage constant voltage for measuring the electrical resistance between the power supply unit 4, the transport unit 1, the pressing control unit 2, the laser oscillation unit 3, and the constant voltage power supply unit 4 from related parts. While controlling these control units individually based on information And a control unit 5 for controlling the entire chromatography. The welding device 100.

  The conveyance control unit 1 holds the first plate-like member 61 and the second plate-like member 63 from the stacking unit (not shown) one by one with the holding members 11, 13 and takes them out to a predetermined position on the processing table 71. A carrying mechanism (not shown) to be placed is controlled based on control from the control unit 5. As this transport mechanism, a known transport mechanism can be used. This transport mechanism is equipped with a camera capable of photographing the processing table 71 for alignment, and the first and second plate members 61 and 63 are aligned using images obtained from the camera. Alternatively, the first and second plate members 61 and 63 may be transported to predetermined positions on the processing table 71 with a teaching function. In FIG. 1, the conveyance control unit 1 is separated into two, “1/2” and “2/2”, but it is actually separated only by making it easy to understand in relation to the controlled object. No (hereinafter the same in the notation of “1/2” and “2/2”).

  The pressing control unit 2 controls a pressing mechanism (not shown) provided with the pressing member 21 under the control of the control unit 5, and is positioned and placed at a predetermined position on the processing table 71 by the pressing member 21. A predetermined pressure is applied to the first and second plate-like members 61 and 63, and the overlapping portions of the first and second plate-like members 61 and 63 including the laser welding portion 81 are brought into close contact with each other. At this time, the predetermined pressure is detected by a load detection unit (not shown) including a load cell or the like provided in the pressing mechanism and fed back to the control unit 5 via the pressing control unit 2. In addition, this press mechanism can utilize a well-known press mechanism.

  The laser oscillation unit 3 oscillates the laser by supplying a drive current to a laser (not shown) under the control of the control unit 5 and aligns it at a predetermined position on the processing table 71 via the condensing optical system 31. The laser beam 33 is irradiated to the welded portion 81 of the first and second plate-like members 61 and 63 placed in this manner. A known technique can be used for the laser oscillation unit 3 and the condensing optical system 31, and the condensing optical system 31 is preferably configured integrally with the pressing mechanism.

  The constant voltage power supply unit 4 applies a constant voltage of a low voltage (several tens to several hundreds mV) under the control of the control unit 5 through the welding terminals 81 of the first and second plate members 61 and 63 via the supply terminals 41 and 43. It is supplied between the first and second plate-like members 61 and 63 with being sandwiched. The constant voltage power source 4 has a function of measuring the current to be supplied. The current is always measured while the power is supplied, and the current and voltage are sent to the control unit 5. . The supply terminals 41 and 43 are provided in a known lifting mechanism (not shown), and the lifting terminals can press the supply terminals 41 and 43 against the first and second plate members 61 and 63 with an appropriate pressing force. It is good to keep it.

  The control unit 5 controls the transport control unit 1, the press control unit 2, the laser oscillation unit 3, and the constant voltage power supply unit 4 as described above. At this time, the electrical resistance value is calculated from the information on the voltage and current supplied between the first and second plate-like members 61 and 63 from the constant voltage power supply unit 4, and based on this result, the first value before the start of laser welding is calculated. Whether or not the second plate-like members 61 and 63 are capable of laser welding is judged during laser welding.

  That is, before the start of laser welding, when this electrical resistance value is larger than a preset first set value, it is determined that the adhesion of the welded portion 81 is low and laser welding is not possible, and the pressure control unit 2 Increase the pressing force to improve adhesion. On the other hand, if the adhesiveness is still low, the pressure control unit 2 is once controlled to drive the pressing mechanism, the pressing member 21 is moved away from the welding part 81, and the conveyance control unit 1 is controlled to drive the conveyance mechanism. Then, the positioning of the first and second plate-like members 61 and 63 is performed again, and then the pressing control unit 2 is controlled again to drive the pressing mechanism to press the welding part 81 with the pressing member 21.

  On the other hand, after starting laser welding by controlling the laser oscillation unit 3 to drive the laser and irradiate the welding part 81 with the laser beam 33, the electric resistance value is set to a second set value that is set in advance. If larger, the formation of the weld nugget at the weld site 81 is not sufficient, and it is determined that an appropriate welding strength has not been obtained, and the laser drive is continued to continue irradiation with the laser beam 33. On the other hand, when the electric resistance value becomes smaller than the second set value, it is determined that a sufficient weld nugget is formed in the welded portion 81 and appropriate welding strength is obtained, and the laser driving is stopped. Then, the irradiation of the laser beam 33 is stopped.

  From the constant voltage power supply unit 4 and the convex portion 71a having an appropriate height and width so as to eliminate the step generated when the first plate-like member 61 and the second plate-like member 63 are superposed on the processing table 71. A hole 71b of an appropriate size is formed so that the supply terminals 41 and 43 for supplying the constant voltage can be pressed against the first and second plate-like members 61 and 63.

  Next, a welding operation using such a laser welding apparatus 100 will be described with reference to FIG. Prior to the welding operation, the first and second set values, the laser drive current, and the like are set.

  First, the conductive first and second plate-like members 61 and 63 are transported from their respective stacking units (not shown) under the control of the transport control unit 1 and aligned with predetermined positions on the processing table 71. (S301 in FIG. 3). At this time, the plate-like member placed on the upper side is arranged so as to be provided with the convex portion 71a. This is to improve the adhesion of the overlapping portion of the first and second plate-like members 61 and 63 that also become the welded portion 81.

  Next, a predetermined pressing force is applied to the peripheral portion around the welded portion 81 of the first and second plate-like members 61 and 63 by the control from the pressing control unit 2 to press the processing table 71 (see FIG. 3 S302). At this time, the load applied to the first and second plate-like members is fed back to the pressing control unit 2 and controlled so as to be the preset pressing force.

  Next, the supply terminals 41 and 43 are pressed against the first and second plate-like members 61 and 63, respectively, and a constant low voltage (several tens to several hundred mV) is applied to the supply terminals 41 and 43 from the constant voltage power supply unit 4. (S303 in FIG. 3). In this way, a current is passed through the first and second plate-like members 61 and 63 via the welded portion 81, and this current is measured (S304 in FIG. 3).

  Next, the control unit 5 receives the current and voltage and calculates an electric resistance value (S305 in FIG. 3). The control unit 5 compares the electric resistance value with a preset first set value. When the electrical resistance is not equal to or less than the first set value (No in S306 in FIG. 3), the pressing force from the pressing control unit 2 is increased. Further, if the increase in the pressing force does not fall below the first set value, the pressing force is once released, and the conveyance control unit 1 is controlled to control the first and second plate members 61 and 63 on the processing table 71. Then, the pressing control unit 2 is controlled again to perform pressing (S307 in FIG. 3). Then, the above-described current measurement, calculation of the electric resistance value, and comparison between the electric resistance value and the first set value are repeated until the electric resistance value becomes equal to or lower than the first set value (S304 to S307 in FIG. 3). It should be noted that an upper limit is set in advance for the number of repetitions, and if the electrical resistance value does not become the first set value or less even when the number of repetitions reaches the upper limit, it is determined that “welding is impossible” and the welding process is terminated. It is good to leave.

  On the other hand, when the electrical resistance value is less than or equal to the first set value (Yes in S306 in FIG. 3), the laser oscillation unit 3 is controlled to pass a drive current to the laser, and the laser is passed through the condensing optical system 31. The light 33 is irradiated to the welding part 81 (S308 in FIG. 3).

  While laser welding is being performed by irradiating the laser beam 33, a constant low voltage from the supply terminals 41 and 43 is supplied from the supply terminals 41 and 43 through the welding portion 81 as described above. Supplied in between. During this time, the current flowing through the supply terminals 41 and 43 is measured (S309 in FIG. 3).

  Next, as described above, the control unit 5 receives the current and voltage and calculates the electrical resistance (S310 in FIG. 3). The control unit 5 compares the electrical resistance value with a preset second set value, and when the electrical resistance is not less than or equal to the second set value (No in S311 in FIG. 3), the control of the laser oscillation unit The laser is continuously driven to oscillate the laser, and the welding part 81 is continuously irradiated via the condensing optical system 31.

  On the other hand, when the electrical resistance value is less than or equal to the second set value (Yes in S311 in FIG. 3), a predetermined nugget is formed and appropriate welding strength is obtained. Control is made to stop the drive current from flowing to the laser, and the irradiation of the laser beam 33 to the welding site 81 is stopped (S312 in FIG. 3). Thus, the first and second plate-like members 61 and 63 are welded at the welding portion 81. An upper limit of the irradiation time of the laser beam 33 is set in advance, and if the electric resistance value does not become the second set value or less even when the laser beam 33 is irradiated until this upper limit time, it is determined as “welding abnormality”. It is preferable to end the welding process.

Next, the supply of the constant voltage from the constant voltage power supply unit 4 is stopped (S313 in FIG. 3). And the press to the 1st, 2nd plate-shaped members 61 and 63 is cancelled | released by control from the press control part 2 (S314 of FIG. 3). Thereafter, the welded first and second plate-like members 61 and 63 are carried out of the processing table 71 under the control of the conveyance control unit 1 (S315 in FIG. 3).
In this way, laser welding of the first and second plate members is completed.

[Other Embodiments]
In the above-described embodiment, the conductive plate-like members 61 and 63 that are the workpieces are overlapped and laser welding is performed at the overlapped portion. Laser welding can also be performed.

The laser welding at the butt portion is not substantially different depending on whether laser welding is performed at the overlapping portion or laser welding at the butt portion.
In other words, since there is only a difference that replaces the overlapping portion in the above description with the matching portion, the details are omitted. If there is any concern about the strength of welding at the part that is just abutted, a plate-shaped member with an appropriate width is used as a backing plate across the butted part, and this plate-shaped member is also welded. Strength can be increased.

The laser welding method and laser welding apparatus described above are merely examples, and various modifications can be made without changing the gist of the invention. For example, instead of performing laser beam irradiation stop when the electrical resistance value is equal to or lower than a preset second set value, sufficient welding strength is obtained according to the welding object obtained in advance by experiments or the like. The laser beam irradiation duration time for obtaining the laser beam can be determined, and the laser beam irradiation may be stopped after the elapse of this time. Light irradiation may be stopped.
Moreover, in the laser welding apparatus, all are controlled by one control unit, but the transport system, the pressing system, the laser oscillation system, and the constant voltage power supply system are separately formed as one device, and these are formed. A control system that is controlled as a whole may be formed as one apparatus to form a laser welding system.

DESCRIPTION OF SYMBOLS 1 Conveyance control part 2 Press control part 3 Laser oscillation part 4 Constant voltage power supply part 5 Control part 11 Holding member 21 Pressing member 31 Condensing optical system 33 Laser beam 41, 43 Supply terminal 61 1st plate-shaped member 63 2nd plate shape Member 71 Machining table

Claims (8)

A laser welding method in which a conductive workpiece is overlapped or butted and welded by irradiating the overlapped portion or the butted portion with laser light, and includes the following steps.
a) A step of setting the conductive workpieces to be overlapped or butting together b) Measuring an electrical resistance value between the workpieces set in the step, and obtaining a difference from a predetermined first set value A step of resetting when the difference is a positive value c) a step of performing laser welding by irradiating a laser beam when the difference is 0 or a negative value in the step d) during the step, the workpiece to be welded Measuring the electrical resistance between them, obtaining a difference from a predetermined second set value, and irradiating the laser beam until the difference becomes zero or a negative value The laser welding method according to claim 1, further comprising the following step.
The step of determining the upper limit number of times of the resetting step in step b) in advance, and determining that welding is impossible when the upper limit number is reached. The laser welding method according to claim 1, further comprising the following step.
A step of determining an upper limit time of the laser beam irradiation continuation time in the step d) in advance, and determining that a welding abnormality occurs if the difference in the step d) does not become 0 or a negative value even when the upper limit time is reached.   4. The laser welding method according to claim 1, wherein the conductive workpiece is a plate member. A laser welding apparatus for welding by superimposing or butting conductive workpieces to be welded by irradiating a laser beam onto the overlapped or butted portion. The laser welding apparatus includes the following means.
a) Setting means for setting the conductive workpieces to be overlapped or butted against each other b) Electrical resistance measuring means for measuring the electrical resistance between the workpieces set by the setting means c) From the laser beam irradiation means Before the start of laser beam irradiation, the set unit is driven so that the difference between the resistance value from the electrical resistance measuring unit and the predetermined first set value becomes zero or a negative value, and the laser beam irradiation unit Control means for driving the laser irradiation means until the difference between the resistance value from the electric resistance measurement means and the predetermined second set value becomes 0 or a negative value after starting the laser light irradiation from 6. The laser welding apparatus according to claim 5, further comprising the following determination means.
Determination means for determining that welding is impossible when the difference between the resistance value and the first set value is not 0 or a negative value by the control means. 6. The laser welding apparatus according to claim 5, further comprising the following determination means.
Determination means for determining a welding abnormality when the difference between the resistance value and the second set value is not 0 or a negative value in the control means.   The laser welding apparatus according to claim 5, wherein the conductive workpiece is a plate-like member.

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