JP2007283398A - Laser welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser welding method which can accurately control a gap between workpieces during welding. <P>SOLUTION: In the invented laser welding method, the following steps are taken before welding: Elastic waves are propagated to workpieces 41 and 42 of which the regions R to be welded are abutted and the vibrational intensity of the elastic waves is detected; Then, the number of times when the intensity of output signals corresponding to the detected vibrational intensity exceeds the threshold value in a prescribed period of time is counted. It is determined whether or not the size of the gap S between the workpieces 41 and 42 is proper, depending on whether or not the counted number of times exceeds a preset prescribed number of times. These steps enable to determine whether the size of the gap S is proper to be even in the case where the abutted portions of the workpieces 41 and 42 are not exposed to the outside, unlike when the size of the gap S is determined by image processing. The gap S can, therefore, be controlled accurately during welding with regard to various welding modes such as butt welding and lap welding. This restrains the production yield after welding from dropping due to the abnormal size of the gap S. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser welding method for welding a second workpiece to a first workpiece by irradiating a laser beam.

    As a pre-process at the time of performing laser welding, there is a process of bringing a planned welding area between the first workpiece and the second workpiece into contact with each other. In this step, it is important to manage the gap between the first workpiece and the second workpiece. When the gap management is insufficient, for example, in the butt welding of the plate material, the welded portion may be thinned, or the laser beam may penetrate to cut the plate material. Further, in the lap welding of plate materials, there is a case where the amount of penetration is insufficient and the welding strength cannot be ensured, or the distortion of the welded portion becomes large.

Therefore, for example, in the laser welding apparatus described in Patent Document 1, a gap amount of a butt portion of a blank material that is a workpiece is detected by a CCD camera. And the increase of the gap amount by the thermal influence from a surface plate is suppressed by feeding back the detection result of the amount of clearances to the temperature control of the surface plate which has mounted the blank material.
JP 2005-66604 A

  However, as in the conventional laser welding apparatus described above, the method using image processing cannot detect the amount of the gap that cannot be visually recognized from the outside. Therefore, for example, in the case where the contact portion between the first workpiece and the second workpiece is inside, as in the case of lap welding, the gap management should be performed with high accuracy. It was difficult.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a laser welding method capable of accurately performing gap management during welding.

  In order to solve the above-described problems, a laser welding method according to the present invention includes a pre-welding process in which a planned welding area of a first workpiece and a second workpiece are brought into contact with each other, and a laser along the welding schedule area. A laser welding method comprising a mid-welding process for irradiating a beam and a post-welding process for inspecting the weld quality of a weld formed in a planned welding area, wherein the pre-welding process contacts the planned welding area with each other In this state, the vibration generated from the vibration generating means is propagated to the first work piece and the second work piece, and the first work piece and the second work piece are propagated. A step of detecting vibration by the vibration detection means, and a step of determining whether or not the gap amount between the first workpiece and the second workpiece is acceptable based on an output signal from the vibration detection means. It is characterized by that.

  In this laser welding method, in the pre-welding process, the first workpiece is based on the vibration of the predetermined frequency propagated to the first workpiece and the second workpiece that are in contact with each other in the planned welding region. It is determined whether or not a gap amount between the workpiece and the second workpiece is acceptable. According to such a method, unlike the case where the gap amount is determined using image processing, the contact portion between the first workpiece and the second workpiece is not exposed to the outside. Even if there is, it is possible to determine the gap amount. Therefore, with respect to various welding forms such as butt welding and lap welding, gap management at the time of welding can be accurately performed, and a decrease in welding yield due to an abnormality in the gap amount can be suppressed.

  Further, the number of times that the output signal exceeds the threshold value within a predetermined time is integrated, and when the integration number does not reach a predetermined number of times set in advance, the first workpiece and the second workpiece are It is preferable to determine that the gap amount between them is abnormal. In this determination method, by setting a threshold value for the output signal, erroneous determination of the gap amount can be suppressed even when noise or the like is mixed in the output signal.

  The output signal is preferably a waveform pattern. By forming the output signal into a waveform pattern, it is possible to visually grasp the state of the gap amount.

  Moreover, it is preferable that the vibration generating means is an oscillator capable of generating a vibration having a predetermined frequency. In this case, since it is possible to generate a vibration of a predetermined frequency by the oscillator, it is possible to stabilize the output signal from the vibration detecting means and accurately determine whether or not the gap amount is acceptable.

  Moreover, it is preferable that a vibration generation means is a jig | tool provided with the press part which consists of a material which can generate | occur | produce a vibration when it contact | abuts to a 1st workpiece or a 2nd workpiece. In this case, for example, a fixing jig used for fixing the first workpiece and the second workpiece can be used as it is as the vibration generating means, so that the configuration for detecting the gap amount can be simplified. it can.

  According to the laser welding method of the present invention, gap management during welding can be performed with high accuracy. Thereby, the fall of the yield of the product after welding by abnormality of gap | interval amount can be suppressed.

  Hereinafter, preferred embodiments of a laser welding method according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a configuration diagram showing a laser welding system that realizes the laser welding method according to the first embodiment of the present invention. As shown in FIG. 1, the laser welding system 1 is configured as a system for lap welding an outer panel and a bone member (hereinafter referred to as “workpiece”) used in, for example, a railway vehicle structure, The apparatus includes a conveying device 10 for bringing the planned welding region of the workpiece into contact with each other, an irradiation device 20 for irradiating a laser beam toward the planned welding region, and an inspection device 30 for inspecting the weld quality of the formed welded portion. Each of the transport device 10, the irradiation device 20, and the inspection device 30 is connected to a host control device 40 that performs overall control, and in accordance with operation instruction information output from the control device 40, a pre-welding process, a welding process, And each process of a post-welding process is automatically performed.

  The transfer device 10 includes, as functional components, a workpiece transfer control unit 101, a jig control unit 102, an oscillator control unit 103, a vibration intensity detection sensor (vibration detection unit) 104, and a gap amount determination unit 105. And a determination result output unit 106.

  The workpiece transfer control unit 101 is a part that controls the operation of a transfer arm (not shown) that transfers a workpiece. When the workpiece conveyance control unit 101 receives the start instruction information for instructing the conveyance start of the workpiece from the control device 40, the workpiece conveyance control unit 101 starts control of the conveyance arm. Then, as shown in FIG. 2, the other work (first workpiece) is placed on the upper surface of one work (second workpiece) 41 placed on the feeding device 52 (see FIG. 4) of the irradiation device 20. The workpieces 42 are overlapped to bring the planned welding regions R into contact with each other. When the conveyance of the workpieces 41 and 42 is completed, the workpiece conveyance control unit 101 outputs start instruction information that instructs the jig control unit 102 to start the operation of the pressing jig 43.

  The jig control unit 102 is a part that controls the operation of the pressure jig 43 for fixing the workpieces 41 and 42. When the jig control unit 102 receives the start instruction information from the work conveyance control unit 101, the jig control unit 102 lowers the long pressurizing jig 43 from above the work 42 as shown in FIG. Pressurize each part. Thereby, the adhesiveness of the workpiece | work 41 and 42 of the welding scheduled area | region R vicinity improves. After lowering the pressurizing jig 43, the jig control unit 102 outputs start instruction information that instructs the oscillator control unit 103 and the gap amount determination unit 105 to start operation.

  The oscillator control unit 103 is a part that controls an oscillator (vibration generating means) 44 used for detecting the gap amount S between the workpieces 41 and 42. As shown in FIG. 2, the oscillator 44 is disposed, for example, at one end of the upper surface of the work 42. When the oscillator control unit 103 receives the start instruction information from the jig control unit 102, the oscillator control unit 103 causes the oscillator 44 to oscillate an elastic wave having a frequency component in the ultrasonic region (several tens kHz to several kHz).

  The vibration intensity detection sensor 104 is a part that detects the vibration intensity of the elastic wave oscillated from the oscillator 44. As shown in FIG. 2, the vibration intensity detection sensor 104 is disposed, for example, on the upper surface of the work 41 at the end opposite to the oscillator 44, and outputs an output signal corresponding to the vibration intensity of the elastic wave propagated from the work 42 to the work 41. It outputs to the quantity judgment part 105.

  The clearance amount determination unit 105 is a portion that determines whether or not the clearance amount S between the workpieces 41 and 42 is acceptable. Upon receiving the start instruction information from the jig control unit 102, the gap amount determination unit 105 starts acquiring an output signal from the vibration intensity detection sensor 104, and generates a waveform pattern with respect to the time axis of the output signal. Here, FIG. 3 shows an example of a waveform pattern generated by the gap amount determination unit 105. In the example shown in FIG. 3, the horizontal axis is time, the vertical axis is a value obtained by normalizing the intensity of the output signal based on the standard deviation, and the waveform pattern 61 is opposite to the gap amount S between the workpieces 41 and 42. It is proportional.

  The gap amount determination unit 105 accumulates the number of times that the waveform pattern 61 exceeds the normalized value + 2σ during the predetermined time t. When the cumulative number exceeds a predetermined number (for example, ten times) set in advance, it is determined that the gap amount S between the workpieces 41 and 42 is normal, and the predetermined number is less than the predetermined number. Is determined that the gap amount S between the workpieces 41 and 42 is abnormal. Then, the gap amount determination unit 105 generates determination result information indicating the determination result regarding the gap amount S and outputs the determination result information to the determination result output unit 106. The determination result output unit 106 transmits the received determination result information to the control device 40.

  Next, the irradiation apparatus 20 will be described. As shown in FIG. 1, the irradiation apparatus 20 includes, as functional components, a laser oscillation control unit 201, a work feed control unit 202, an assist gas supply control unit 203, an output state detection sensor group 204, and an operation. An environment detection sensor group 205, a supply power detection sensor 206, a gas pressure detection sensor 207, an abnormality determination unit 208, and a determination result output unit 209 are included.

  The laser oscillation control unit 201 is a part that controls the operation of the welding laser device 51 that irradiates the planned welding region R of the workpieces 41 and 42. As shown in FIG. 4, the laser device 51 is disposed above the workpieces 41 and 42. For example, a YAG laser having a wavelength of 1.06 μm and an output of about 4.0 kW is used. When the laser oscillation control unit 201 receives start instruction information for instructing the start of laser beam irradiation from the control device 40, the laser oscillation control unit 201 irradiates the laser beam 51 toward the planned welding region R for a predetermined time.

  The workpiece feeding control unit 202 is a part that controls the operation of the feeding device 52 for scanning the irradiation position of the laser beam on the workpieces 41 and 42. When the workpiece feed control unit 202 receives the start instruction information for instructing the start of scanning from the control device 40, the workpiece feed control unit 202 scans the feed device 52 in the arrow F direction at a constant speed. Thereby, the irradiation position of the laser beam moves along the planned welding region R of the workpieces 41 and 42, and the welded portion W is sequentially formed in the planned welding region R.

  The assist gas supply control unit 203 is a part that controls the amount of assist gas supplied from a gas supply device (not shown). When the assist gas supply control unit 203 receives the start instruction information for instructing the supply start from the control device 40, the assist gas supply control unit 203 supplies the assist gas to the irradiation position of the laser beam with a predetermined supply amount. As the assist gas, helium gas or argon gas or the like is used for the purpose of preventing the workpieces 41 and 42 from being oxidized and preventing sputtering. As shown in FIG. 4, the assist gas is supplied from the tip of the supply nozzle 53 of the gas supply device inclined at about 45 degrees with respect to the workpieces 41 and 42 toward the irradiation position of the laser beam. Each of the laser oscillation control unit 201, the workpiece feed control unit 202, and the assist gas supply control unit 203 outputs start instruction information for instructing the start of the operation to the abnormality determination unit 208.

  The output state detection sensor group 204 is a part that detects a change in the physical quantity of the output state of the laser beam. More specifically, as shown in FIG. 4, the output state sensor group 204 includes a laser output intensity detection sensor 204a, a plasma / plume light intensity detection sensor 204b, a reflected light intensity detection sensor 204c, and a processing temperature detection sensor. 204d.

  The laser output intensity detection sensor 204a is a photosensor that detects the light intensity of the laser beam applied to the workpieces 41 and 42. The laser output intensity detection sensor 204a is disposed in the vicinity of the irradiation position of the laser beam, and outputs an output signal corresponding to the intensity of light having the same wavelength as the laser beam to the abnormality determination unit 208. The plasma / plume light intensity detection sensor 204b is a photosensor that detects the light intensity of plasma and plume generated on the surfaces of the workpieces 41 and 42 by irradiation of a laser beam. Similar to the laser output intensity detection sensor 204a, the plasma / plume light intensity detection sensor 204b is disposed in the vicinity of the irradiation position of the laser beam and corresponds to the intensity of light having a wavelength of about 300 nm to about 800 nm excluding the wavelength of the laser beam. The output signal to be detected is detected. Then, the plasma / plume light intensity detection sensor 204b outputs an output signal corresponding to the plasma light intensity and an output signal corresponding to the plume light intensity to the abnormality determination unit 208, respectively. The output signal corresponding to the light intensity of the plasma and the output signal corresponding to the light intensity of the plume may be output together to the abnormality determination unit 208, or may be separated by a bandpass filter or the like to determine the abnormality determination unit. You may output to 208.

  The reflected light intensity detection sensor 204 c is a photosensor that detects the light intensity of the laser beam reflected by the surfaces of the workpieces 41 and 42. The reflected light intensity detection sensor 204 c is disposed in the vicinity of the laser beam emission end of the laser device 51, and outputs an output signal corresponding to the intensity of light having the same wavelength as the laser beam to the abnormality determination unit 208. The processing temperature detection sensor 204d is a photosensor for detecting the temperature at the laser irradiation position. The processing temperature detection sensor 204d is disposed in the vicinity of the laser beam irradiation position in the same manner as the laser output intensity detection sensor 204a, and outputs an output signal corresponding to the light intensity of light in the infrared region excluding the wavelength of the laser beam to the abnormality determination unit 208. Output to.

  The welding environment detection sensor group 205 is a part that detects a change in a physical quantity of the environmental state during welding. More specifically, the welding environment detection sensor group 205 includes a processing sound detection sensor 205a and a vibration detection sensor 205b as shown in FIG.

  The processing sound detection sensor 205a is a directional microphone that detects sound generated on the surfaces of the workpieces 41 and 42 at the irradiation position of the laser beam. The processed sound detection sensor 205a has a built-in bandpass filter (not shown) having a frequency band of about 20 Hz to about 20 kHz, and outputs an output signal corresponding to the loudness of the frequency band to the abnormality determination unit 208. To do. The vibration detection sensor 205 b is an acceleration sensor that detects the magnitude of vibration in the pressurizing jig 43 that fixes the workpieces 41 and 42. The vibration detection sensor 205b is attached to, for example, the shaft portion of the pressurizing jig 43, and outputs an output signal corresponding to each acceleration in the XYZ directions of each pressurizing jig 43 to the abnormality determining unit 208.

  The supply power detection sensor 206 is a wattmeter that detects the amount of power supplied to the laser device 51, the feeding device 52, and the gas supply device. The supplied power detection sensor 206 outputs an output signal corresponding to the detected power amount to the abnormality determination unit 208. The gas pressure detection sensor 207 is a pressure sensor that detects the pressure of the assist gas supplied from the gas supply device to the planned welding region R. The gas pressure detection sensor 207 outputs an output signal corresponding to the gas pressure to the abnormality determination unit 208.

  The abnormality determination unit 208 is a part that determines whether there is an abnormality in the output state of the laser beam, the environmental state during welding, the supply power, and the assist gas pressure. When the abnormality determination unit 208 receives start instruction information from each of the laser oscillation control unit 201, the workpiece feed control unit 202, and the assist gas supply control unit 203, the abnormality determination unit 208, the welding environment detection sensor group 205, the supply Acquisition of each output signal from the power detection sensor 206 and the gas pressure detection sensor 207 is started, and a waveform pattern with respect to the time axis of each output signal is generated.

  Here, FIG. 5 shows the relationship between the physical quantity detected by the output state detection sensor group 204, the welding environment detection sensor group 205, the supply power detection sensor 206, and the gas pressure detection sensor 207, and the abnormality detectable by this physical quantity. An example is shown. As shown in FIG. 5, when the laser output intensity is abnormal, the abnormality of the laser device 51 can be detected. When the light intensity and reflected light intensity between the plasma and the plume are abnormal, it is possible to detect abnormality of each item of the weld bead, the penetration amount, the assist gas, the blowhole generation, and the work state. When the processing temperature is abnormal, it is possible to detect abnormality of each item of the weld bead, the penetration amount, and the assist gas.

  Further, when there is an abnormality in the processing sound, an abnormality in each item of the weld bead, the penetration amount, the blow hole, the feeding device 52, and the pressurizing jig 43 can be detected. When there is an abnormality in vibration, an abnormality in the feeding device 52 and the pressing jig 43 can be detected. When there is an abnormality in the supplied power, an abnormality in the feeding device 52 and the laser device 51 can be detected. When there is an abnormality in the gas pressure, an abnormality in the gas supply device can be detected.

  6 to 9 show examples of waveform patterns generated by the abnormality determination unit 208. FIG. In each figure, the horizontal axis represents time, and the vertical axis represents output signal intensity. FIG. 6 is a diagram illustrating an example of a waveform pattern of an output signal from the laser output intensity detection sensor 204a. In the example shown in FIG. 6, the abnormality determination unit 208 monitors the waveform pattern 62 of the laser output intensity, and determines that the laser device 51 is abnormal when the laser output intensity decreases to 90% or less of the initial value. .

  FIG. 7 is a diagram illustrating an example of a waveform pattern of output signals from the plasma / plume light intensity detection sensor 204b and the processing temperature detection sensor 204d. In the example shown in FIG. 7, the waveform pattern 63 of the light intensity of plasma and plume and the waveform pattern 64 of the processing temperature are each subjected to smoothing processing, for example, by taking a moving average value for every 100 data points. The abnormality determination unit 208 monitors the waveform patterns 63 and 64, and determines that the assist gas component is abnormal when both the light intensity and the processing temperature of the plasma and plume exceed twice normal values.

  FIG. 8 is a diagram illustrating an example of a waveform pattern of an output signal from the reflected light intensity detection sensor 204c. In the example shown in FIG. 8, the waveform pattern 65 of the reflected light intensity is subjected to smoothing processing, for example, by taking a moving average value for every 50 data points. In order to determine the threshold value of the waveform pattern 65, the waveform pattern 65a of the upper limit measurement value and the waveform pattern 65b of the lower limit measurement value of the reflected light intensity are measured in advance, and the minimum value of the waveform pattern 65a and the maximum value of the waveform pattern 65b are measured. Are set as the upper and lower thresholds of the waveform pattern 65 of the reflected light intensity, respectively. When the waveform pattern 65 exceeds the upper limit threshold, the laser beam loss at the irradiation position is large and the amount of penetration may be insufficient. When the waveform pattern 65 is below the lower limit threshold, the laser beam loss is small. It is considered that the amount of melt is excessive. The abnormality determination unit 208 monitors the waveform pattern 65, and determines that the amount of penetration is abnormal when the reflected light intensity falls below a preset lower threshold or exceeds an upper threshold.

  FIG. 9 is a diagram illustrating an example of a waveform pattern of an output signal from the supply power detection sensor 206 of the feeding device 52. In the example shown in FIG. 9, the waveform pattern 66 of the supplied power amount is subjected to smoothing processing, for example, by taking a moving average value for every 100 data points. The abnormality determination unit 208 sends the data when, for example, the slope of the rising portion 66a of the waveform pattern 66 is equal to or smaller than a predetermined threshold value or when a data point exceeding the predetermined threshold value is detected in the steady portion 66b of the waveform pattern 66. It is determined that the device 52 is abnormal. Then, when there is an abnormality in the output state of the laser beam, the environmental state at the time of welding, the supply power, and the assist gas pressure, the abnormality determination unit 208 generates determination result information indicating the abnormality and the item. The result is output to the determination result output unit 209. The determination result output unit 209 transmits the received determination result information to the control device 40.

  Next, the inspection apparatus 30 will be described. As shown in FIG. 1, the inspection apparatus 30 includes a laser displacement meter control unit 301, a laser displacement meter (first strain amount detection unit, second strain amount detection unit) 302, a welding quality determination unit 303, And a determination result storage unit 304.

  The laser displacement meter control unit 301 is a part that controls the operation of the laser displacement meter 302 for detecting the strain amount of the workpieces 41 and 42. When the laser displacement meter control unit 301 receives start instruction information for instructing the start of inspection of welding quality from the control device 40, the laser displacement meter control unit 301 outputs the start instruction information to the welding quality determination unit 303. Next, the laser displacement meter control unit 301 emits a distance measuring laser beam from the laser displacement meter 302 and crosses the welded portion W on the surface of the work 42 where the welded portion W is exposed as shown in FIG. Then, the laser displacement meter 302 is scanned. Furthermore, the laser displacement meter control unit 301 is configured such that, for example, the welded portion W is not exposed as shown in FIG. 11 after the workpieces 41 and 42 are turned upside down by a transfer arm (not shown) of the transfer device 10. On the surface of the workpiece 41, the laser displacement meter 302 is scanned so as to cross the facing portion V of the welded portion W. Laser displacement meter 302 outputs an output signal corresponding to the detected strain amount to welding quality determination unit 303.

  The welding quality judgment unit 303 is a part that judges the welding quality of the welding part W in the workpieces 41 and 42 based on the output signal from the laser displacement meter 302. As the inspection items of the welding quality, the undercut amount / underfill amount of the welded portion W and the unevenness amount / folding amount of the facing portion V are set. When welding quality determination unit 303 receives start instruction information from laser displacement meter control unit 301, welding quality determination unit 303 starts obtaining an output signal from laser displacement meter 302 and generates a waveform pattern for the scanning position of the output signal.

  Here, FIGS. 12 to 15 show examples of waveform patterns of output signals from the laser displacement meter 302. FIG. In each figure, the horizontal axis represents the scanning position, and the vertical axis represents the amount of distortion obtained from the intensity of the output signal. Each waveform pattern is smoothed by taking, for example, a moving average value for every 100 data points. Processing has been applied. FIG. 12A is a diagram illustrating an example of a waveform pattern corresponding to the amount of distortion in the vicinity of the weld W in the work 42. In this case, the welding quality judgment unit 303 recognizes that an undercut has occurred in the welded portion W by detecting, for example, three inflection points 67a, 67b, and 67c where the slope of the waveform pattern 67 changes. . The undercut refers to a defect in which a concave portion is formed around the welded portion W as shown in FIG. And the welding quality judgment part 303 calculates the difference of the distortion amount in the inflection point 67a (or inflection point 67c) and the inflection point 67b, for example as an undercut amount, and when this difference exceeds the preset threshold value It is determined that the welding quality of the welded portion W is abnormal.

  FIG. 13A is a diagram illustrating another example of the waveform pattern corresponding to the distortion amount in the vicinity of the welded portion W in the workpiece 42. In this case, the welding quality judgment unit 303 detects the three inflection points 68a, 68b, 68c of the waveform pattern 68 as in the case of FIG. 12, but the scanning position interval from the inflection point 68a to the inflection point 68c is different. When the width is equal to or greater than the predetermined width, it is recognized that an underfill has occurred in the welded portion W. The underfill is a defect in which the top of the weld W is formed in a concave shape as shown in FIG. And the welding quality judgment part 303 calculates the difference of the distortion amount in the inflection point 68a (or inflection point 68c) and the inflection point 68b, for example as an underfill amount, and when this difference exceeds the preset threshold value It is determined that the welding quality of the welded portion W is abnormal.

  FIG. 14A is a diagram illustrating an example of a waveform pattern corresponding to the distortion amount of the facing portion V of the welded portion W in the work 41. The welding quality judgment unit 303 detects the three inflection points 69a, 69b, and 69c of the waveform pattern 69, thereby recognizing the irregularities of the workpieces 41 and 42 that occur in the facing portion V as shown in FIG. . And the welding quality judgment part 303 calculates the difference of the distortion amount in the inflection point 69a (or inflection point 69c) and the inflection point 69b, for example as an unevenness | corrugation amount, and when this difference exceeds the preset threshold value, It is determined that the welding quality of the welded portion W is abnormal.

  FIG. 15A is a diagram illustrating another example of the waveform pattern corresponding to the distortion amount of the facing portion V of the welded portion W in the work 41. Similarly to the case of FIG. 14, three inflection points 70a, 70b, 70c of the waveform pattern 70 are detected. When the interval between the scanning positions from the inflection point 70a to the inflection point 70c is equal to or larger than a predetermined width, FIG. As shown in (b), it is recognized that the workpieces 41 and 42 are bent. The welding quality determination unit 303 calculates, for example, a difference in strain amount between the inflection point 70a (or inflection point 70c) and the inflection point 70b as a fold amount, and when this difference exceeds a preset threshold, It is determined that the welding quality of W is abnormal. Then, the welding quality determination unit 303 outputs determination result information indicating the determination results of the undercut amount, underfill amount, unevenness amount, and bending amount to the determination result storage unit 304.

  The determination result storage unit 304 is a part that stores the determination result information output from the welding quality determination unit 303 in association with the product numbers of the workpieces 41 and 42. An example of information stored in the determination result storage unit 304 is shown in FIG. In the example shown in FIG. 16, the undercut amount “0.3 mm”, the underfill amount “undetected”, and the unevenness amount “0.0” are associated with the product numbers “001-A” and “001-B” of the workpieces 41 and 42. 2 mm "and the folding amount" undetected "are stored. Further, the undercut amount “undetected”, the underfill amount “0.1 mm”, the unevenness amount “0.2 mm”, and the folds are associated with the product numbers “002-A” and “002-B” of the workpieces 41 and 42. The quantity “0.1 mm” is stored.

  Finally, the control device 40 will be described. The control device 40 is physically a computer system including a CPU, a memory, a communication interface, a storage unit such as a hard disk, a display unit such as a display, and the like. The control device 40 receives the predetermined operation by the user of the laser welding system 1 and transmits start instruction information for instructing the conveyance device 10 to start conveying the workpiece. When receiving the determination result information indicating that the gap amount S is normal from the conveying device 10 in the pre-welding process, the control device 40 transmits start instruction information for instructing the start of laser beam irradiation to the irradiation device 20. When the determination result information indicating that the gap amount S is abnormal is received, the irradiation prohibition information for prohibiting the start of laser beam irradiation is transmitted to the irradiation device 20.

  In addition, the control device 40 receives from the irradiation device 20 the laser beam output state, the welding environment state, the supply power, the assist gas pressure, and the determination result information indicating the item during the welding process. If not, start instruction information for instructing start of welding quality inspection is transmitted to the inspection apparatus 30. If determination result information is received, operation stop information for instructing stop of operation is sent to the irradiation apparatus 20. The inspection prohibition information for prohibiting the start of the inspection of the welding state is transmitted to the inspection apparatus.

  Next, the operation of the laser welding system 1 having the above-described configuration will be described with reference to the flowcharts shown in FIGS.

  First, when a predetermined operation is performed by the user, start instruction information is transmitted from the control device 40 to the conveying device 10 (step S01), and a pre-welding process is executed by the conveying device 10 (step S02). In the pre-welding process, as shown in FIG. 18, first, the workpieces 41 and 42 are overlapped by a transfer arm (not shown), and the planned welding regions R of the workpieces 41 and 42 are brought into contact with each other (step S21). Next, the periphery of the welding planned region R is pressed by the pressing jig 43, and the workpieces 41 and 42 are fixed (step S22).

  When the workpieces 41 and 42 are fixed, an elastic wave having a predetermined frequency is oscillated from the oscillator 44. The elastic wave propagating through the workpieces 41 and 42 in which the planned welding area R is in contact with each other is detected by the vibration intensity detection sensor 104, and the vibration intensity detection sensor 104 outputs an output signal corresponding to the detected signal intensity of the elastic wave. Output (step S23). Based on the waveform pattern of the output signal, it is determined whether or not the gap amount S between the workpieces 41 and 42 is acceptable (step S24), the determination result information is transmitted to the control device 40, and the pre-welding process is completed (step S24). S25).

  When the pre-welding process is completed, as shown in FIG. 17, the control device 40 determines the content of the determination result information received from the transport device 10 (step S03). When the gap amount S is normal, start instruction information is transmitted from the control device 40 to the irradiation device 20 (step S04), and the welding process is executed by the irradiation device 20 (step S05). On the other hand, when the gap amount S is abnormal, the irradiation prohibition information is transmitted from the control device 40 to the irradiation device 20 (step S09), and the process ends without performing the welding process.

  In the process during welding, as shown in FIG. 19, first, laser irradiation, workpiece feeding, and supply of assist gas are started, and welds W are sequentially formed on the workpieces 41 and 42 along the planned welding region R ( Step S31). During the welding, each physical quantity is detected by the output state detection sensor group 204, the welding environment detection sensor group 205, the supply power detection sensor 206, and the gas pressure detection sensor 207 (step S32). Based on the waveform pattern of the corresponding output signal, it is determined whether there is an abnormality in the output state of the laser beam, the environmental state during welding, the supply power, and the assist gas pressure (step S33).

  When it is determined that the output state of the laser beam, the environmental state at the time of welding, the supply power, and the assist gas pressure are normal, it is determined whether or not welding has been completed (step S34). If welding has been completed, the process is terminated as it is. If welding has not been completed, the processes of steps S32 to S33 described above are repeated. In addition, when it is determined that the laser beam output state, welding environment state, power supply, and assist gas pressure are abnormal, the control device 40 immediately stops laser irradiation, workpiece feed, and assist gas supply ( Step S35). Then, determination result information is transmitted from the irradiation device 20 to the control device 40 (step S36).

  When the welding process is finished, as shown in FIG. 17, the control device 40 determines whether or not the determination result information is received from the irradiation device 20 (step S06). When the determination result information is not received, start instruction information is transmitted from the control device 40 to the inspection device 30 (step S07), and a post-welding process is executed by the inspection device 30 (step S08). On the other hand, when the determination result information is received, the inspection prohibition information is transmitted from the control device 40 to the inspection device 30 (step S10), and the process ends without performing the post-welding process.

  In the post-welding process, as shown in FIG. 20, the amount of strain in the vicinity of the welded portion W exposed to the workpiece 42 is detected by scanning with a laser displacement meter 302 (step S41). Next, after the workpieces 41 and 42 are turned upside down, the amount of distortion of the facing portion V of the welded portion W in the workpiece 41 is detected (step S42). Based on the waveform pattern of the output signal corresponding to each distortion amount, whether or not each item of the welding quality of the workpieces 41, 42, that is, the undercut amount, the underfill amount, the unevenness amount, and the bending amount is determined. This is done (step S43). The determination result is stored in the determination result storage unit 304 in association with the product numbers of the workpieces 41 and 42 (step S44), and the post-welding process ends.

  As described above, in this laser welding method, in the pre-welding process, the gap amount between the workpieces 41 and 42 is based on the vibration intensity of the elastic wave propagated through the workpieces 41 and 42 with which the planned welding region R is in contact. Judge whether S is acceptable. According to such a method, unlike the case where the gap amount S is determined using image processing, the gap amount S can be determined even when the contact portions of the workpieces 41 and 42 are not exposed to the outside. It becomes possible. Therefore, with respect to various welding forms such as butt welding and lap welding, gap management during welding can be performed with high accuracy, and a decrease in welding yield due to an abnormality in the gap amount S can be suppressed.

  When determining the gap amount S, the number of times that the intensity of the output signal exceeds the threshold value within a predetermined time is integrated, and when this integration number does not reach the predetermined number of times set in advance, the gap amount between the workpieces 41 and 42. It is determined that S is abnormal. Thus, by setting the threshold value of the intensity of the output signal, erroneous determination of the gap amount S can be suppressed even when noise or the like is somewhat mixed in the output signal. Further, since the output signal is formed into a waveform pattern, it is possible to visually grasp the state of the gap amount S.

(Second Embodiment)
Next, a laser welding method according to the second embodiment of the present invention will be described. FIG. 21 is a diagram illustrating a configuration of a transfer device in a laser welding system for realizing the laser welding method according to the second embodiment of the present invention.

  The laser welding method according to the second embodiment is a first embodiment in which the oscillator 44 is used as the vibration generating means in that the pressure jig 43 itself is used as the vibration generating means in detecting the gap amount S between the workpieces 41 and 42. Is different. That is, in the laser welding method according to the second embodiment, as shown in FIG. 21, the oscillator 44 is not arranged at one end of the upper surface of the work 42 in the transfer device 10, and instead, the tip of the pressurizing jig 43. For example, a metal long pressing plate (pressing portion) 43a is provided. Then, when the pressing jig 43 is lowered by the jig control unit 102, the vibration intensity detection sensor 104 indicates the intensity of vibration generated when the pressing plate 43a comes into contact with both edges of the work 42 along the planned welding region R. Based on the waveform pattern of the output signal from the vibration intensity output sensor 104, it is determined whether or not the gap amount S between the workpieces 41 and 42 is acceptable.

  In such a laser welding method as well as in the first embodiment, in the pre-welding process, based on the intensity of vibration propagated through the workpieces 41 and 42 with which the planned welding region R is brought into contact, the gap between the workpieces 41 and 42 is determined. Therefore, it is possible to determine the gap amount S even when the contact portions of the workpieces 41 and 42 are not exposed to the outside. Therefore, with respect to various welding forms such as butt welding and lap welding, gap management during welding can be performed with high accuracy, and a decrease in welding yield due to an abnormality in the gap amount S can be suppressed.

  Moreover, in this laser welding method, the vibration which a metal elongate press board 43a contact | abuts to both the edge parts along the scheduled welding area | region R in the workpiece | work 42 is utilized. Therefore, it is not necessary to arrange the oscillator 44 with respect to the workpieces 41 and 42, and the configuration can be simplified. In addition, since there is a vibration source along both edges, the influence of vibration attenuation can be reduced. As a result, the S / N ratio of the output signal from the vibration intensity detection sensor 104 can be sufficiently ensured, and whether or not the gap amount can be determined can be accurately performed. This is particularly effective when the length of the workpieces 41 and 42 in the longitudinal direction exceeds several meters and it is difficult to sufficiently propagate the elastic waves to the workpieces 41 and 42 when the oscillator 44 is used.

  In addition, when the length of the workpieces 41 and 42 in the longitudinal direction is longer than the length of the pressing plate 43a, a plurality of pressing jigs 43 are provided along both edges along the planned welding region R of the workpiece 42. You may arrange. In this case, a plurality of pressing plates 43a may be brought into contact with both edges of the workpiece 42 at a time. For example, the pressing plates 43a closer to the vibration intensity detection sensor 104 are sequentially applied to both edges of the workpiece 42. You may contact | abut. Further, the pressing plate 43a is not limited to a metal as long as it is a material that can generate vibration when it comes into contact with the workpiece 42. For example, the pressing plate 43a may be made of cured plastic or cured glass.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, whether or not the gap amount S is acceptable is determined based on whether or not the number of times the waveform pattern exceeds the normalized value + 2σ within a predetermined time exceeds the predetermined number. In consideration of the interference (swell) of the generated elastic wave, whether the gap amount S is acceptable or not is determined based on whether or not the number of appearances of the waveform pattern having a normalized value ± 0 is a predetermined number or more. Good.

  In addition to determining whether or not the gap amount S is acceptable, the distance from the head of the laser device 51 to the workpieces 41 and 42 is measured by a non-contact type or contact type distance measuring means (not shown), and the focus at the time of laser irradiation. You may make it manage the presence or absence of abnormality of a position and the feeder 52. FIG.

It is a figure which shows the structure of the laser welding system for implement | achieving the laser welding method which concerns on 1st Embodiment of this invention. It is a figure which shows the structure of a conveying apparatus. It is a figure which shows an example of the waveform pattern produced | generated by the clearance gap judgment part. It is a figure which shows the structure of an irradiation apparatus. It is the figure which showed an example of the relationship between the physical quantity detected with an output state detection sensor group, a welding environment detection sensor group, a supply electric power detection sensor, and a gas pressure detection sensor, and the abnormality which can be detected by this physical quantity. It is a figure which shows an example of the waveform pattern of the output signal from a laser output intensity detection sensor. It is a figure which shows an example of the waveform pattern of the output signal from a plasma / plume light intensity detection sensor and a process temperature detection sensor. It is a figure which shows an example of the waveform pattern of the output signal from a reflected light intensity detection sensor. It is a figure which shows an example of the waveform pattern of the output signal from a supply electric power detection sensor. It is a figure which shows operation | movement of the test | inspection apparatus at the time of detecting the distortion amount near a welding part. It is a figure which shows operation | movement of the test | inspection apparatus at the time of detecting the distortion amount of an opposing site | part. It is a figure which shows an example of the waveform pattern corresponding to the distortion amount of the welding part vicinity. It is a figure which shows another example of the waveform pattern corresponding to the distortion amount of a welding part vicinity. It is a figure which shows an example of the waveform pattern corresponding to the distortion amount of an opposing site | part. It is a figure which shows another example of the waveform pattern corresponding to the distortion amount of an opposing site | part. It is a figure which shows an example of the information stored in a welding result storage part. It is a flowchart which shows operation | movement of the laser welding system shown in FIG. It is a flowchart of the process before welding. It is a flowchart of a process during welding. It is a flowchart of a post-welding process. It is a figure which shows the structure of the conveying apparatus in the laser welding system for implement | achieving the laser welding method which concerns on 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser welding system, 41 ... Workpiece (2nd workpiece), 42 ... Workpiece (1st workpiece), 43 ... Pressure jig (vibration generating means), 43a ... Pressing plate (pressing part) 44 ... Oscillator (vibration generating means) 104 ... Vibration intensity detecting sensor (vibration detecting means) 61 ... Wave pattern, R ... Welding area, S ... Gap amount, W ... Welded part.

Claims (5)

A pre-welding process in which the welding target areas of the first workpiece and the second workpiece are brought into contact with each other, a welding process in which the laser beam is irradiated along the welding planned area, and the welding scheduled area A laser welding method comprising a post-welding process for inspecting the weld quality of the formed weld,
The pre-welding process includes
Propagating vibration generated from vibration generating means to the first workpiece and the second workpiece in a state where the planned welding regions are in contact with each other;
Detecting the vibration propagated through the first workpiece and the second workpiece by a vibration detecting means;
Laser welding, comprising: determining whether or not a gap amount between the first workpiece and the second workpiece is possible based on an output signal from the vibration detecting means. Method.   The number of times that the output signal exceeds a threshold value within a predetermined time is integrated, and when the number of integration does not reach a predetermined number of times set in advance, the first workpiece and the second workpiece The laser welding method according to claim 1, wherein the gap amount is determined to be abnormal.   3. The laser welding method according to claim 1, wherein the output signal is a waveform pattern.   The laser welding method according to any one of claims 1 to 3, wherein the vibration generating means is an oscillator capable of generating vibration at a predetermined frequency. The vibration generating means is a jig including a pressing portion made of a material capable of generating vibration when abutting against the first workpiece or the second workpiece. Item 4. The laser welding method according to any one of Items 1 to 3.

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