Method for calibrating laser welding equipment

Abstract

To provide a laser welding apparatus capable of suppressing fluctuations in a measured value of penetration depth of a welded portion so as to improve measurement accuracy of the penetration depth.SOLUTION: A laser welding apparatus 10 comprises: a laser oscillator 11; and an optical interferometer 20. The optical interferometer 20 comprises: at least a light source 21; an optical branching part 22; an optical coupling part 23; a reference mirror 24; and a reference optical path length adjusting mechanism 50. The light source 21 emits measurement light ML. The optical branching unit 22 branches the measurement light ML into object light ML1 and reference light ML2. The optical coupling part 23 combines the object light ML1 reflected by a welding part 15a and reference light ML2 reflected by a reference mirror 24 so as to generate interference light for measuring penetration depth of the welding part 15a. A reference optical path length adjusting mechanism 50 moves the reference mirror 24 along a traveling direction of the reference light ML2 so as to change optical path length of the reference light ML2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a laser welding apparatus, and more particularly to a laser welding apparatus capable of identifying the penetration depth of a weld. Place Regarding the calibration method. [Background technology]

[0002] Patent Document 1 discloses a laser welding device that welds a welded portion with a laser beam. This laser welding device includes a laser output means that irradiates a workpiece with a laser beam, an optical interferometer that irradiates the welded portion of the workpiece with an object beam, which is light having a different wavelength from the laser beam, and measures the penetration depth of the welded portion from the object beam reflected by the welded portion, and an optical member that irradiates the welded portion with the laser beam from the laser output means and the object beam from the optical interferometer coaxially.

[0003] In the optical interferometer, measurement light emitted from a light source is split into object light and reference light by a first photocoupler. The object light is emitted from the optical interferometer and irradiated onto the welded portion. A portion of the object light irradiated onto the welded portion is reflected by the welded portion and then enters the optical interferometer. The object light that enters the optical interferometer enters a second fiber coupler. Meanwhile, the reference light is irradiated onto a reference mirror. The reference light irradiated onto the reference mirror is reflected by the reference mirror and then enters the second fiber coupler. Then, in the optical interferometer, the penetration depth of the welded portion is measured based on the difference between the optical path length of the object light and the optical path length of the reference light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-236196 A Summary of the Invention [Problem to be solved by the invention]

[0005] In actual laser welding, the laser beam is often irradiated onto the workpiece through a laser head having an optical system inside so as to focus on the workpiece and obtain a predetermined beam diameter. When the object beam is irradiated onto the workpiece, an optical interferometer and a laser head are connected by an optical fiber, and the object beam is irradiated onto the workpiece through the optical fiber and the laser head. In such a case, in order to ensure the safety of the welding operation, the workpiece, the laser head, and the optical fiber connected to the laser head are often arranged in a processing room, which is a space different from the space in which the optical interferometer is installed. Meanwhile, a plurality of optical fibers are arranged inside the optical interferometer to transmit the object beam and the reference beam.

[0006] However, there is often a temperature difference between the processing chamber and the space in which the optical interferometer is installed. This temperature difference causes a refractive index difference between the optical fiber connecting the laser head and the optical interferometer and the optical fiber inside the optical interferometer, which can cause fluctuations in the measured value of the penetration depth.

[0007] The present disclosure has been made in consideration of the above points, and has an object to provide a laser welding apparatus capable of suppressing fluctuations in the measured value of the penetration depth of a weld and improving the measurement accuracy of the penetration depth. How to calibrate The purpose of this invention is to provide [Means for solving the problem]

[0009] A method for calibrating a laser welding apparatus according to the present disclosure includes: Laser welding equipment that uses laser light to weld parts Place The calibration method of the present invention, in which the laser welding device includes a laser oscillator that emits the laser light, a light source, a light branching unit, a light coupling unit, a reference mirror, an object light path, a reference light path, and an optical interferometer having a reference light path length adjustment mechanism, and a control unit. The light source emits measurement light having a wavelength different from the wavelength of the laser light, and the light branching unit branches the measurement light emitted from the light source into object light and reference light. The object light path is configured to guide the object light obtained by the light branching unit to the welding portion, and to guide the object light reflected by the welding portion to the light coupling unit. The reference light path is configured to guide the reference light obtained by the light branching unit to the reference mirror, and to guide the reference light reflected by the reference mirror to the light coupling unit. The light coupling unit generates interference light used for measuring the penetration depth of the welding portion by combining the object light guided by the object light path and the reference light guided by the reference light path. The reference optical path length adjustment mechanism is configured to change the optical path length of the reference light, and the control unit controls the operation of the reference optical path length adjustment mechanism. The method includes at least a first step of measuring a predetermined reference height using the optical interferometer and storing the obtained measurement value as a reference value; a second step of measuring the reference height again and calculating the difference between the obtained measurement value and the reference value if a predetermined condition is satisfied; and a third step of changing the optical path length of the reference light so that the difference falls within the tolerance range if the difference calculated in the second step exceeds a predetermined tolerance range. Effect of the Invention

[0010] Books According to the disclosed method for calibrating a laser welding device, the optical path length of the reference light is changed so that the difference between a predetermined reference value and the measured reference height falls within a predetermined tolerance range, thereby suppressing fluctuations in the measured value of the penetration depth of the weld when the laser welding device is continuously operated, thereby improving the measurement accuracy of the penetration depth. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram illustrating the configuration of a laser welding device according to a first embodiment. [Diagram 2] 4 is a flowchart showing a calibration procedure of the laser welding device. [Diagram 3] FIG. 13 is a diagram showing an example of a reference height measuring jig. [Figure 4] FIG. 13 is a diagram showing the relationship between the output signal intensity of an optical interferometer and the measured value of a reference height. [Diagram 5] FIG. 13 is a diagram showing the temperature dependence of fluctuations in a measurement waveform measured by an optical interferometer. [Figure 6] FIG. 11 is a schematic diagram showing the configuration of a laser welding device according to a second embodiment. [Figure 7] FIG. 13 is a schematic diagram showing the configuration of a laser welding device according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the present embodiment will be described in detail with reference to the drawings. The following description of the preferred embodiment is merely illustrative in nature and is not intended to limit the present disclosure, its application, or its uses.

[0013] (Embodiment 1) [Laser welding equipment configuration] 1 shows a schematic configuration diagram of a laser welding apparatus according to this embodiment, in which a laser welding apparatus 10 welds a welded portion 15a of a workpiece 15 with a laser beam LB. The laser welding apparatus 10 includes a laser oscillator 11, a laser head 12, an optical interferometer 20, and a control unit 13.

[0014] The laser oscillator 11 emits a laser beam LB. The laser beam LB emitted from the laser oscillator 11 is guided to the laser head 12 via an optical path (for example, an optical fiber) that connects the laser oscillator 11 and the laser head 12.

[0015] The laser head 12 emits the laser light LB guided from the laser oscillator 11 toward the welded portion 15a of the workpiece 15. In this manner, the laser light LB is emitted from the tip of the laser head 12 toward the welded portion 15a. The laser head 12 also irradiates the object light ML1 emitted from the optical interferometer 20 toward the welded portion 15a of the workpiece 15, and emits the object light ML1 reflected by the welded portion 15a to the optical interferometer 20. The object light ML1 will be described in detail later.

[0016] The laser head 12 includes a beam splitter 120 , a first focusing optical system 121 , a second focusing optical system 122 , and a focus lens 123 .

[0017] The beam splitter 120 is provided to combine the laser light LB from the laser oscillator 11 and the object light ML1 from the optical interferometer 20 into a coaxial light beam. In this way, the laser light LB and the object light ML1 are combined into a coaxial light beam by the beam splitter 120, and the light beam is irradiated onto the welded portion 15a of the workpiece 15, so that the penetration depth of the welded portion 15a can be measured simultaneously with the laser welding. In addition, the object light ML1 can be accurately irradiated toward the bottom portion 15c of the keyhole 15b of the welded portion 15a. For example, the beam splitter 120 is composed of a dichroic mirror.

[0018] The first focusing optical system 121 focuses the laser light LB emitted from the laser oscillator 11. The laser light LB focused in the first focusing optical system 121 passes through the beam splitter 120 and the focus lens 123 and is focused on the welded portion 15a. This welds the welded portion 15a of the workpiece 15. The second focusing optical system 122 focuses the object light ML1 emitted from the optical interferometer 20. The object light ML1 focused in the second focusing optical system 122 is reflected by the beam splitter 120, passes through the focus lens 123, and is focused on the welded portion 15a. The object light ML1 reflected by the welded portion 15a passes through the focus lens 123, is reflected by the beam splitter 120, passes through the second focusing optical system 122, and is incident on the optical interferometer 20. The focus lens 123 is provided to adjust the focal length of the laser light LB.

[0019] In the example shown in this embodiment, the focal length of the laser light LB is changeable. For example, the laser head 12 may be replaceable. The focal length of the laser light LB is changed by replacing the laser head 12 with another laser head 12 (another laser head 12 having a different focal length of the laser light LB). Also, the focus lens 123 in the laser head 12 may be replaceable. The focal length of the laser light LB is changed by replacing the focus lens 123 with another focus lens 123 (another focus lens 123 having a different focal length of the laser light LB). Also, the laser head 12 may be provided with an autofocus mechanism that changes the focal length of the laser light LB by adjusting the position of the focus lens 123.

[0020] The workpiece 15 may be placed and fixed on a moving stage (not shown). The moving stage moves in response to control by the control unit 13. By moving the moving stage while the workpiece 15 is being irradiated with the laser light LB, the irradiation position of the laser light LB on the workpiece 15 can be changed.

[0021] The laser head 12 may also be attached to the tip of a multi-joint robot (not shown). The multi-joint robot moves the laser head 12 in response to control by the control unit 13. For example, a motor controlled by the control unit 13 is provided on the joint axis of the multi-joint robot.

[0022] The laser head 12 and the workpiece 15 are installed in a processing room 100, which is a space separate from the control room 110 in which the optical interferometer 20 and the control unit 13 are installed. Furthermore, when an articulated robot (not shown) and a moving stage (not shown) are provided, they are also installed in the processing room 100. The control room 110 is usually temperature-controlled within a range of ± several degrees so as not to deteriorate the performance of the control unit 13 and the like. On the other hand, such strict temperature control is not performed in the processing room 100. This is because a large amount of heat is generated during laser welding, and temperature control is costly. A temperature sensor 101 (not shown) is installed in the processing room 100. The measured value of the temperature sensor 101 is input to the control unit 13. The laser oscillator 11 may be installed in the control room 110 or in a space separate from the control room 110.

[0023] [Configuration of optical interferometer] 1 is provided to measure the penetration depth of a weld 15a of a workpiece 15 using swept source optical coherence tomography (SS-OCT) technology. The optical interferometer 20 has a light source 21, an optical branching unit 22, an optical coupling unit 23, a reference mirror 24, an object optical path 31, a reference optical path 32, a signal processing unit 40, and a reference optical path length adjustment mechanism 50. The signal processing unit 40 has a differential detector 41 and an AD converter 42.

[0024] The light source 21 emits the measurement light ML. The measurement light ML has a wavelength different from the wavelength of the laser light LB. The measurement light ML emitted from the light source 21 enters the optical branching unit 22 via an optical path (in this example, an optical fiber) connecting the light source 21 and the optical branching unit 22.

[0025] The light source 21 continuously emits measurement light ML having a wavelength different from that of the laser light LB and a narrow wavelength width, and periodically changes the central wavelength of the emitted measurement light ML. Such an operation of periodically changing the central wavelength of the measurement light ML is called "wavelength scanning." The light source 21 also supplies a trigger output to the AD converter 42 synchronized with the repetition period of the wavelength scanning. The operation of the AD converter 42 will be described in detail later.

[0026] The optical branching unit 22 branches the measurement light ML emitted from the light source 21 into an object light ML1 and a reference light ML2. The object light ML1 is a part of the measurement light ML that is irradiated onto the welded part 15a that is the measurement target. The reference light ML2 is a part of the measurement light ML that is irradiated onto a reference mirror 24 that is a reference surface. The object light ML1 branched by the optical branching unit 22 is incident on an object optical path 31. The reference light ML2 branched by the optical branching unit 22 is incident on a reference optical path 32.

[0027] The optical branching unit 22 branches 50% of the measurement light ML incident on the optical branching unit 22 from the light source 21 into an object light ML1, and the remaining 50% of the measurement light ML into a reference light ML2. For example, the optical branching unit 22 is formed of a fiber coupler.

[0028] The object light path 31 is configured to guide the object light ML1 obtained by the light branching unit 22 to the welded portion 15a, and to guide the object light ML1 reflected by the welded portion 15a to the light coupling unit .

[0029] Specifically, object light ML1 emitted from light branching unit 22 passes through object light path 31, is emitted from object light path 31, passes through laser head 12, and is irradiated onto welded portion 15a. A portion of object light ML1 irradiated onto welded portion 15a is reflected by welded portion 15a. Object light ML1 reflected by welded portion 15a passes through laser head 12 and is incident on object light path 31. Object light incident on object light path 31 from laser head 12 passes through object light path 31 and is incident on optical coupling unit 23.

[0030] In the following description, the length of the optical path traveled by the object light ML1 from the optical branching unit 22 until it enters the optical coupling unit 23 may be referred to as the "optical path length of the object light ML1."

[0031] The object light path 31 of this embodiment is composed of a first optical fiber system. The first optical fiber system is composed of a plurality of optical fibers. For example, the first optical fiber system includes an optical fiber (first object optical fiber) provided for guiding the object light ML1 from the optical branching unit 22 to the laser head 12, and an optical fiber (second object optical fiber) provided for guiding the object light ML1 from the laser head 12 to the optical coupling unit 23. In addition, a part of the first optical fiber system extends from the optical interferometer 20 to the outside and is connected to the laser head 12. As is clear from FIG. 1, this part, which is a part of the first optical fiber system connected to the laser head 12, is arranged in the processing chamber 100.

[0032] The reference mirror 24 reflects the reference light ML2 branched from the optical branching unit 22 and emitted from the reference optical path 32, and makes the reference light ML2 incident on the reference optical path 32 that guides the reference light ML2 toward the optical coupling unit 23. The reference mirror 24 is also connected to a reference optical path length adjustment mechanism 50, which will be described later. By driving the reference optical path length adjustment mechanism 50, the reference mirror 24 can be moved within a predetermined range along the traveling direction of the reference light ML2 emitted from the reference optical path 32 to the reference mirror 24.

[0033] The reference optical path 32 is configured to guide the reference light ML2 obtained by the optical branching unit 22 to the reference mirror 24, and further guide the reference light ML2 reflected by the reference mirror 24 to the optical coupling unit 23.

[0034] Specifically, the reference light ML2 emitted from the optical branching unit 22 passes through the reference optical path 32, is emitted from the intermediate end 32a of the reference optical path 32, and is irradiated onto the reference mirror 24. The reference light ML2 reflected by the reference mirror 24 enters the intermediate end 32a of the reference optical path 32, passes through the reference optical path 32, and enters the optical coupling unit 23. In the following description, the length of the optical path traveled by the reference light ML2 from being emitted from the optical branching unit 22 to being entered into the optical coupling unit 23 may be referred to as the "optical path length of the reference light ML2."

[0035] The reference optical path 32 of this embodiment is composed of a second optical fiber system. The second optical fiber system is composed of a plurality of optical fibers. For example, the second optical fiber system includes an optical fiber (first reference optical fiber) that transmits the reference light ML2 from the optical branching unit 22 to the reference mirror 24, and an optical fiber (second reference optical fiber) that transmits the reference light ML2 from the reference mirror 24 to the optical coupling unit 23. The intermediate end portion 32a of the reference optical path 32 described above corresponds to a connection portion between the first reference optical fiber and the second reference optical fiber, and is configured to irradiate the reference light ML2 obtained by the optical branching unit 22 onto the reference mirror 24. In addition, the intermediate end portion 32a is configured to receive the reference light ML2 reflected by the reference mirror 24 and guide it to the optical coupling unit 23.

[0036] The reference optical path length adjustment mechanism 50 has a support mechanism 51 and a drive mechanism 52. The support mechanism 51 is connected to the reference mirror 24 and movably supports the reference mirror 24. For example, the support mechanism 51 is composed of a ball screw (not shown) as a linear motion mechanism extending in the traveling direction of the reference light ML2 and a connection part (not shown) that connects the reference mirror 24 and the ball screw.

[0037] The driving mechanism 52 is driven and controlled by the control unit 13, and moves the reference mirror 24 along the traveling direction of the reference light ML2 via the support mechanism 51. For example, the driving mechanism 52 is a stepping motor (not shown) connected to a ball screw (not shown). By rotating the stepping motor forward, the reference mirror 24 moves along the traveling direction of the reference light ML2 emitted from the intermediate end 32a of the reference light path 32 toward the reference mirror 24 so as to move away from the intermediate end 32a of the reference light path 32. By rotating the stepping motor backward, the reference mirror 24 moves along the traveling direction of the reference light ML2 so as to move closer to the intermediate end 32a of the reference light path 32. In this way, the reference light path length adjustment mechanism 50 can adjust the position of the reference mirror 24 and, ultimately, the optical path length of the reference light ML2.

[0038] The optical coupling unit 23 generates interference light by coupling an object light ML1 reflected by the welded portion 15a and guided by an object optical path 31 with a reference light ML2 reflected by the reference mirror 24 and guided by a reference optical path 32. The interference light is used to measure the penetration depth of the welded portion 15a.

[0039] The optical coupling unit 23 is connected to the first input section 41a and the second input section 41b of the differential detector 41 by an optical path such as an optical fiber. The optical coupling unit 23 outputs 50% of the object light ML1 guided by the object optical path 31 to the first input section 41a of the differential detector 41, and outputs the remaining 50% of the object light ML1 to the second input section 41b of the differential detector 41. The optical coupling unit 23 also outputs 50% of the reference light ML2 guided by the reference optical path 32 to the first input section 41a of the differential detector 41, and outputs the remaining 50% of the reference light ML2 to the second input section 41b of the differential detector 41. In this way, in each of the first input section 41a and the second input section 41b of the differential detector 41, the object light ML1 and the reference light ML2 are combined into one light beam to generate interference light. For example, the optical coupling unit 23 is configured by a fiber coupler.

[0040] The signal processing unit 40 performs predetermined signal processing on the interference light generated by the optical coupling unit 23. In this example, the signal processing unit 40 performs processing for reducing noise contained in the interference light and processing for collecting and recording an electrical signal of the interference light.

[0041] Specifically, the differential detector 41 reduces noise contained in the interference light by calculating the difference between the interference light input to the first input section 41a and the interference light input to the second input section 41b. The differential detector 41 then converts the interference light with reduced noise into an electrical signal according to its intensity. The electrical signal of the interference light obtained by the differential detector 41 is output to the AD converter 42.

[0042] The AD converter 42 collects the electrical signal of the interference light output from the differential detector 41 based on a trigger output (a trigger output synchronized with the repetition frequency of the wavelength scanning) supplied from the light source 21. In this way, the electrical signal of the interference light is collected in synchronization with the repetition period of the wavelength scanning in the light source 21. The electrical signal of the interference light collected by the AD converter 42 is output to the control unit 13.

[0043] The control unit 13 controls each part of the laser welding apparatus 10 based on the outputs of various sensors (not shown) provided in each part of the laser welding apparatus 10 and instructions from the outside. Specifically, the control unit 13 controls the operations of the laser oscillator 11, the laser head 12, the optical interferometer 20, the moving stage (not shown), the articulated robot (not shown), the drive mechanism 52 of the reference optical path length adjustment mechanism 50, and the like. For example, the control unit 13 is composed of a processor and a memory that stores programs and information for operating the processor.

[0044] Furthermore, control unit 13 measures the penetration depth of welded portion 15a based on the interference light obtained by optical interferometer 20. Interference occurs in the interference light according to the difference between the optical path length of object light ML1 and the optical path length of reference light ML2. Control unit 13 measures the penetration depth of welded portion 15a based on the interference occurring in the interference light. Specifically, control unit 13 performs a fast Fourier transform on the electrical signal of the interference light obtained by optical interferometer 20, and measures the penetration depth of welded portion 15a based on the result of the fast Fourier transform.

[0045] For example, the interference light includes a frequency peak of object light ML1 (hereinafter referred to as "object light peak") corresponding to the optical path length of object light ML1 passing through object light path 31, and a frequency peak of reference light ML2 (hereinafter referred to as "reference light peak") corresponding to the optical path length of reference light ML2 passing through reference light path 32. Controller 13 measures the penetration depth of welded portion 15a based on the distance between the reference light peak and the object light peak.

[0046] Furthermore, control unit 13 evaluates the quality of welded portion 15a based on the penetration depth of welded portion 15a measured as described above. For example, control unit 13 determines that welded portion 15a is "good" when the penetration depth of welded portion 15a is within a predetermined allowable range, and determines that welded portion 15a is "poor" when the penetration depth of welded portion 15a is outside the allowable range. Control unit 13 then causes a display unit (not shown) to display the result of the quality evaluation of welded portion 15a.

[0047] Furthermore, the control unit 13 executes various judgments and calculations in the calibration of the laser welding apparatus 10, which will be described later, and operates the reference optical path adjustment mechanism 50 based on the judgment results, calculation results, and the like.

[0048] [Calibration procedure for laser welding equipment] FIG. 2 shows the calibration procedure for a laser welding device, specifically, the calibration procedure for measuring the penetration depth of the weld 15a, FIG. 3 shows an example of a jig for measuring the reference height, and FIG. 4 shows the relationship between the output signal intensity of an optical interferometer and the measured value of the reference height.

[0049] As described above, a part of the first optical fiber system that is connected to the laser head 12 and that constitutes the object optical path 31 is disposed in the processing chamber 100. On the other hand, as shown in FIG. 1, the remaining part of the first optical fiber system that constitutes the object optical path 31 and the second optical fiber system that constitutes the reference optical path 32 are accommodated inside the optical interferometer 20 and disposed in the control chamber 110. When the processing amount of the workpiece 15 increases, the temperature of the processing chamber 100 increases due to heat generated by laser welding. As a result, the temperature difference between the processing chamber 100 and the control chamber 110 increases, and a refractive index difference occurs between a part of the first optical fiber system disposed in the processing chamber 100 and the optical fiber disposed in the control chamber 110, which may cause the measured value of the penetration depth to fluctuate. In order to eliminate such a problem, in this embodiment, the laser welding device 10 is calibrated in the following procedure.

[0050] First, a reference height measuring jig 70 (hereinafter simply referred to as jig 70) shown in Fig. 3(a) is set at a position where the workpiece 15 will be placed (step S1). The jig 70 is a stepped part in cross section, and is made of a material that has small dimensional fluctuation due to temperature changes, such as ceramic. Note that the surface may be covered with a conductive material such as metal to prevent charging up.

[0051] A reference surface 71 that serves as a reference for calibration is provided on the jig 70 . For example, the bottom surface of the step of the jig 70 serves as the reference surface 71 .

[0052] For example, the bottom surface of the step of jig 70 is set as a reference surface 71, and the height of the laser head is determined as the measurement position where the measurement light is irradiated with respect to reference surface 71. A laser is then irradiated onto reference surface 71 of jig 70 as the object light, and the measurement value, which is the difference between the optical path length of object light ML1 and the optical path length of reference light ML2 at this time, is set as the reference height H.

[0053] In this embodiment, the reference height H is set to, for example, 2 mm. However, this is not particularly limited, and may be changed as appropriate depending on the design value of the penetration depth of the welded portion 15, etc.

[0054] Alternatively, the height of the laser head may be moved while measuring the object light emitted from a laser onto a reference surface 71 at a predetermined height on the jig 70, and the position at which the measurement value for the reference height H (the difference between the optical path length of the object light and the optical path length of the reference light) is, for example, 2 mm, may be determined as the measurement height of the laser head relative to the reference surface 71.

[0055] The shape of the jig 70 is not limited to the shape shown in FIG. 3(a). It is sufficient if the shape allows the reference surface 71 to be provided. For example, as shown in FIG. 3(b), the jig 70 may have a recess in cross section. For example, the bottom surface of this recess becomes the reference surface 71. Although the shape of the jig 70 can be calibrated even if it is a flat shape, it is more preferable to use a step-shaped jig with multiple possible reference heights as shown in FIG. 3, since it is possible to easily check whether the signal changes depending on the height (depth) at an early stage of calibration. This allows for stable and accurate calibration.

[0056] Next, each component of the optical interferometer 20 is operated to measure the initial reference height H of the jig 70 (step S2). As shown in Fig. 4, a measurement value of the initial reference height H is obtained based on the peak position of the signal strength output from the signal processing unit 40. Furthermore, this measurement value is stored as a reference value Ia in the control unit 13 or a storage unit (not shown). As shown in Fig. 4, in this embodiment, the reference value Ia is 2.0 mm.

[0057] Next, it is determined whether the laser welding device 10, or its installation environment, or the processing status of the workpiece 15 satisfies a predetermined condition (for example, "Has the number of welding operations reached a predetermined number during processing of the workpiece 15?") (step S3). Step S3 is executed by the control unit 13 or a welding operator (not shown). If the result of the determination in step S3 is negative, the process returns to step S3 again. On the other hand, if the result of the determination in step S3 is positive, the jig 70 is set or the laser head 12 is moved to the jig 70 that is set for a calibration operation, and the reference height H after the predetermined condition is satisfied is measured again (step S4). The predetermined condition in step S3 can be various, and corresponds to, for example, the number of welding operations of the workpiece 15 reaching a predetermined number. The predetermined condition will be described in detail later.

[0058] The control unit 13 calculates the difference between the measurement value H1, which is the remeasured reference height H in step S4, and the above-mentioned reference value Ia (step S5). Furthermore, the control unit 13 judges whether or not this difference is within the calibration possible range in absolute value (step S6). If the absolute value is greater than the calibration possible range and the judgment result in step S6 is negative, it is an error region that requires "stopping the laser welding device 10, then inspecting and repairing it", and there is a possibility that some kind of malfunction has occurred in the laser welding device 10, for example, an internal failure of the optical interferometer 20 or a misalignment of optical components inside the laser welding device 10. Therefore, the welding operator or manager stops the laser welding device 10, inspects each part, and replaces or repairs parts as necessary (step S9). Furthermore, after the end of step S9, the process returns to step S1 and executes the subsequent series of processes again.

[0059] On the other hand, if the determination result in step S6 is positive, the control unit 13 further determines whether or not the difference calculated in step S5 is within a predetermined allowable range (reference value Ia±a) (step S7). If the determination result in step S7 is positive, the predetermined conditions are reset (not shown), and the process returns to step S3 (broken arrow) for determining whether or not the laser welding device 10, its installation environment, or the processing status of the workpiece 15 satisfy the predetermined conditions (for example, "Has the number of welding times reached a predetermined number during processing of the workpiece 15?"), and regular calibration is performed during processing of the workpiece 15.

[0060] The period during which the calibration is performed can be changed as appropriate depending on the environment in which the laser welding apparatus 10 is used, the number of workpieces 15 to be processed, and the like.

[0061] In this embodiment, the calibration possible range in step S6 is reference value Ia (=2.0 mm)±c (=1.0 mm) as shown in Fig. 4. The allowable range in step S7 is reference value Ia (=2.0 mm)±a (=0.2 mm). However, the values ​​a and c are not particularly limited to these values ​​and can be changed as appropriate depending on the reference value Ia, the allowable range of the penetration depth of welded portion 15a, and the like.

[0062] On the other hand, if the result of the determination in step S7, which determines whether the difference is within a predetermined allowable range with respect to the reference value Ia (reference value Ia±a), is negative, it is considered that calibration is possible even though an error occurs in the measurement value by the optical interferometer 20 due to some reason, for example, the refractive index difference between the optical fibers described above. In other words, as shown in Fig. 4, calibration is possible when the absolute value of the difference between the measurement value and the reference value is within the range b (0.2≦b≦1.0), in other words, when the absolute value is within the calibration possible range of the range b.

[0063] Therefore, the control unit 13 operates the reference optical path length adjustment mechanism 50 to move the reference mirror 24 along the traveling direction of the reference light ML2 emitted from the intermediate end 32a of the reference optical path 32 toward the reference mirror 24 so as to cancel the above-mentioned difference (step S8). In other words, the optical path length of the reference light ML2 is changed so that the difference falls within the allowable range. For example, the direction in which the reference mirror 24 is brought closer to the intermediate end 32a of the reference optical path 32 is defined as the + (plus) direction, and the direction in which it is moved away from the intermediate end 32a of the reference optical path 32 is defined as the - (minus) direction. If the measured value in step S5 is 2.5 mm, that is, the difference is +0.5 mm, the reference optical path length adjustment mechanism 50 is operated to move the reference mirror 24 0.5 mm in the - direction so as to achieve the reference value Ia=2.

[0064] After step S8 is executed, the process returns to step S4, and the series of processes are repeatedly executed until the determination result in step S7 becomes positive.

[0065] [Effects, etc.] As described above, the laser welding apparatus 10 according to this embodiment welds the welded portion 15a of the workpiece 15 with a laser beam LB, and includes at least a laser oscillator 11 that emits the laser beam LB, an optical interferometer 20, and a control unit 13.

[0066] The optical interferometer 20 includes at least a light source 21 , an optical branching unit 22 , an optical coupling unit 23 , a reference mirror 24 , an object optical path 31 , a reference optical path 32 , and a reference optical path length adjustment mechanism 50 .

[0067] The light source 21 emits measuring light ML having a wavelength different from the wavelength of the laser light LB, and the light branching section 22 branches the measuring light ML emitted from the light source 21 into an object light ML1 and a reference light ML2.

[0068] The object optical path 31 is configured to guide the object light ML1 obtained by the optical branching unit 22 to the welded portion 15a, and guide the object light ML1 reflected by the welded portion 15a to the optical coupling unit 23. The reference optical path 32 is configured to guide the reference light ML2 obtained by the optical branching unit 22 to the reference mirror 24, and guide the reference light ML2 reflected by the reference mirror 24 to the optical coupling unit 23.

[0069] The optical combiner 23 combines the object light ML1 guided by the object optical path 31 and the reference light ML2 guided by the reference optical path 32 to generate interference light used for measuring the penetration depth of the welded portion 15a.

[0070] The reference optical path length adjustment mechanism 50 is configured to change the optical path length of the reference light ML2 by moving the reference mirror 24 within a predetermined range along the traveling direction of the reference light ML2 emitted from the intermediate end portion 32a of the reference optical path 32 toward the reference mirror 24. The control unit 13 controls at least the operation of the reference optical path length adjustment mechanism 50.

[0071] By configuring the laser welding apparatus 50 in this manner, it is possible to easily change the optical path length of the reference light ML2 required for measuring the penetration depth of the welded portion 15a. This makes it possible to suppress fluctuations in the measured value of the penetration depth of the welded portion 15a and to improve the measurement accuracy of the penetration depth.

[0072] The object optical path 31 is configured by a first optical fiber system, the reference optical path 32 is configured by a second optical fiber system, and a part of the first optical fiber system connected to the laser head 12 is disposed in a processing chamber 100 where welding of the welded portion 15a is performed with the laser light LB. The remaining part of the first optical fiber system and the second optical fiber system are disposed in a space separate from the processing chamber, in this case, a control room 110.

[0073] As described above, a temperature difference is likely to occur between the inside of the processing chamber 100 and the inside of the control chamber 110, and this temperature difference causes the measured value of the penetration depth of the welded portion 15a to vary. This will be further explained.

[0074] Fig. 5 shows the temperature dependency of the fluctuation of the measurement waveform measured by the optical interferometer. When the temperature inside the processing chamber 100 or the control chamber 110 changes and the temperature difference between them increases, the measurement waveform of the penetration depth itself shifts and the value of the penetration depth also changes. This causes the measurement waveform to go out of the range that can be measured by the optical interferometer 20, making it impossible to accurately evaluate the penetration depth. In the case shown in Fig. 5, the temperature dependency of the measured value fluctuation of the penetration depth is about 0.2 mm to 0.3 mm / °C.

[0075] On the other hand, according to the laser welding apparatus 10 of the present embodiment, by changing the optical path length of the reference light ML2 by moving the reference mirror 24, it is possible to suppress the shift in the measurement waveform of the penetration depth and the fluctuation in the measured value of the penetration depth as shown in Fig. 5. In addition, the measurement accuracy of the penetration depth can be improved.

[0076] The calibration method for laser welding apparatus 10 according to this embodiment is a calibration method related to measurement of the penetration depth of welded portion 15a.

[0077] The method includes at least a first step (step S2) of measuring a predetermined reference height H using an optical interferometer 20 and storing the obtained measurement value as a reference value Ia; a second step (step S5) of measuring the reference height H again if a predetermined condition (e.g., "Has the number of weldings reached a predetermined number during processing of the workpiece 15?") is satisfied, and calculating the difference between the measurement value obtained as the remeasured reference height H and the reference value Ia; and a third step (step S8) of moving the reference mirror 24 to change the optical path length of the reference light ML2 so that the difference falls within the allowable range if the difference calculated in the second step exceeds a predetermined allowable range (reference value Ia±a) for the reference value Ia.

[0078] According to this embodiment, the optical path length of the reference light ML2 is changed so that the difference between the predetermined reference value Ia and the measured value of the reference height H falls within a predetermined allowable range. This makes it possible to suppress fluctuations in the measured value of the penetration depth of the welded portion 15a when the laser welding apparatus 10 is continuously operated, thereby improving the measurement accuracy of the penetration depth.

[0079] It is preferable to further include a step (sixth step) of measuring the reference height H again after the third step and checking whether the difference between the measurement value obtained as the re-measured reference height H and the reference value Ia is within the allowable range.

[0080] By doing this, fluctuations in the measured value of the penetration depth of the welded portion 15a when the laser welding apparatus 10 is operated continuously (due to changes over time (temperature changes), etc.) can be reliably suppressed, thereby improving the measurement accuracy of the penetration depth.

[0081] As the predetermined condition in step S3 in FIG. 2, other than the number of times the workpiece 15 is welded as described above, for example, the following condition may be considered.

[0082] (1) When a predetermined time interval has elapsed since the previous measurement of the reference height H, for example, every few hours or every other day, each step from step S4 onward shown in FIG. 2 is executed. Note that, during times when the temperature inside the processing chamber 100 changes significantly, such as in the morning and evening or when the laser welding device 10 is started up, it is expected that the refractive index difference of the optical fiber inside and outside the processing chamber 100 will increase in a short period of time. In this case, that is, during the aforementioned time period, it is preferable to set the time interval shorter than during other time periods. In this way, the fluctuation in the measured value of the penetration depth of the welded portion 15a when the laser welding device 10 is continuously operated can be suppressed, and the measurement accuracy of the penetration depth can be improved.

[0083] (2) When the temperature of the processing chamber 100 has fluctuated by a predetermined value or more since the previous calibration, for example, when the temperature of the processing chamber 100 exceeds ±10° C. from the set value, each step from step S4 onward shown in FIG. 2 is executed. In this case, it is considered that the difference in refractive index of the optical fiber inside and outside the processing chamber 100 has increased. Therefore, the reference height H is measured again, and recalibration is performed to adjust the optical path length of the reference light ML2 by moving the reference mirror 24 as necessary. In this way, it is possible to suppress fluctuations in the measured value of the penetration depth of the welded portion 15a when the laser welding device 10 is continuously operated, and to improve the measurement accuracy of the penetration depth.

[0084] The control unit 13 determines whether or not recalibration is necessary based on the temperature of the processing chamber 100 measured by the temperature sensor 101. If recalibration is necessary, the control unit 13 preferably notifies the welding operator or the manager of the necessity through a display unit or a sound notification unit (not shown).

[0085] (3) Measure the penetration depth of the welded portion 15a each time the number of times the workpiece 15 has been welded reaches a predetermined number of times. If the measured value obtained at this time gradually increases or gradually decreases as the number of times the workpiece 15 has been welded increases, execute each step from step S4 onwards shown in FIG. 2.

[0086] Such gradual fluctuations in the measured values ​​may occur because the characteristics of the components of the optical interferometer 20 change over time or because the arrangement of the optical components inside the laser welding apparatus 10 changes little by little over time.

[0087] 2 and changing the optical path length of reference light ML2, it is possible to suppress fluctuations in the measured value of the penetration depth of welded portion 15a when laser welding apparatus 10 is continuously operated, thereby improving the measurement accuracy of the penetration depth. Note that, if the calibration of laser welding apparatus 10 is performed and the result of the determination in step S6 of whether the difference with respect to reference value Ia is within the calibration possible range is negative, it goes without saying that laser welding apparatus 10 is stopped and each part is inspected.

[0088] (Embodiment 2) Fig. 6 is a schematic diagram of a laser welding device according to this embodiment. In Fig. 6 and Fig. 7 shown later, the same parts as those in the first embodiment are given the same reference numerals and detailed description thereof will be omitted.

[0089] The laser welding apparatus 10 of this embodiment shown in FIG. 6 differs from the configuration of the first embodiment shown in FIG.

[0090] The second adjustment mechanism 62 has the same structure as the reference optical path length adjustment mechanism 50 shown in Fig. 1. That is, although not shown, the second adjustment mechanism 62 has a support mechanism 51 and a drive mechanism 52. Also, the operation of the second adjustment mechanism 62 is controlled by a control signal from the control unit 13. Also, the second adjustment mechanism 62 has the same function as the reference optical path length adjustment mechanism 50.

[0091] On the other hand, the first adjustment mechanism 61 is a manual slide mechanism indirectly connected to the reference mirror 24 via the second adjustment mechanism 62. In addition, the second adjustment mechanism 62 is held by the first adjustment mechanism 61 and connected to the reference mirror 24.

[0092] Both the first adjustment mechanism 61 and the second adjustment mechanism 62 are configured to move the reference mirror 24 along the traveling direction of the reference light ML2. However, the movement range of the reference mirror 24 by the second adjustment mechanism 62 (hereinafter referred to as the second range) is set to be narrower than the movement range of the reference mirror 24 by the first adjustment mechanism 61 (hereinafter referred to as the first range).

[0093] That is, the reference optical path length adjustment mechanism 60 is configured to be able to change the optical path length of the reference light ML2 by the first adjustment mechanism 61 when the focal length of the laser light LB changes significantly in accordance with a change in the focal length of the laser light LB.

[0094] By configuring the reference optical path length adjustment mechanism 60 of the laser welding apparatus 10 in this multi-stage configuration, even if the focal length of the laser beam LB is changed significantly, the first adjustment mechanism 61, which has a large range of movement, moves the reference mirror 24 accordingly to change the optical path length of the reference beam ML2, thereby suppressing fluctuations in the measured value of the penetration depth of the welded portion 15a and improving the measurement accuracy of the penetration depth. This will be further explained.

[0095] As described above, the laser welding device 10 is configured so that the focal length of the laser light LB, in other words, the distance between the laser head 12 and the welded portion 15a of the workpiece 15, can be changed.

[0096] For example, the focal length of the laser beam LB may be changed to avoid the laser head 12 from irradiating the welded portion 15a of the workpiece 15 with the laser beam LB due to the shape of the workpiece 15 or the shape of the jig around the workpiece. In blaze welding, the focal position of the laser beam LB is shifted from the welded portion 15a of the workpiece 15 by several mm to several cm, thereby lowering the power density of the laser beam LB irradiated to the welded portion 15a compared to the case of keyhole welding. Note that blaze welding is a so-called "brazing" and is a welding method that does not melt the workpiece 15 as much as possible. For example, a brazing material is melted and added to a joint having a groove, and welding is performed without melting the base material as much as possible. In addition, keyhole welding is a laser welding in which a keyhole 15b is formed by heat input with high power density as shown in FIG. 1, and by using this high power density laser beam LB, a deep penetration depth can be obtained in the welded portion 15a.

[0097] In response to such a request to change the focal length of the laser light LB, the focal length of the laser light LB can be changed in the laser welding apparatus 10 by replacing the laser head 12, replacing the focus lens 123, or adjusting the position of the focus lens 123 using an autofocus mechanism (not shown).

[0098] However, when the focal length of the laser beam LB changes, it is also necessary to change the optical path length of the reference beam ML2 required to measure the penetration depth of the welded portion 15a of the workpiece 15. In particular, when the focal length of the laser beam LB is changed significantly, the amount of change in the optical path length of the reference beam ML2 also increases accordingly.

[0099] In the configuration shown in the first embodiment, the driving amount of the driving mechanism 52 is increased to increase the movement amount of the reference mirror 24, but in this case, it is necessary to increase the sizes of the support mechanism 51 and the driving mechanism 52. In addition, there is a risk that the load on the driving mechanism 52 will become excessive.

[0100] On the other hand, according to this embodiment, when the optical path length of the reference light ML2 is to be changed significantly, the reference mirror 24 is first moved using the first adjustment mechanism 61, thereby ensuring the approximate amount of movement of the reference mirror 24 and reducing the load on the driving mechanism 52.

[0101] For example, first adjustment mechanism 61 is manually operated so that the peak position of the measured waveform of the penetration depth as shown in Fig. 5 is approximately in the center of the measurable range of optical interferometer 20. Thereafter, second adjustment mechanism 62 is automatically operated with high resolution and high accuracy in response to a control signal from control unit 13 to adjust the position of reference mirror 24, thereby making it possible to match the optical path length of reference light ML2 to a desired value with high accuracy. This makes it possible to suppress fluctuations in the measured value of the penetration depth of welded portion 15a and improve the measurement accuracy of the penetration depth.

[0102] <Modification> FIG. 7 shows a schematic configuration diagram of a laser welding device according to this modified example, which differs from the configuration of embodiment 2 shown in FIG. 6 in that a reference optical path length adjustment mechanism 60 has a first adjustment mechanism 61 and a third adjustment mechanism 63.

[0103] The first adjustment mechanism 61 is similar to that shown in FIG. 6, and is a manual slide mechanism connected to the reference mirror 24.

[0104] The third adjustment mechanism 63 has a structure similar to that of the reference optical path length adjustment mechanism 50 shown in Fig. 1. That is, although not shown, the third adjustment mechanism 63 has a support mechanism 51 and a drive mechanism 52. Also, the operation thereof is automatically controlled by a control signal from the control unit 13. Meanwhile, the third adjustment mechanism 63 is connected to the intermediate end portion 32a of the second optical fiber system of the reference optical path 32, and is configured to move the intermediate end portion 32a, which emits the reference light ML2 toward the reference mirror 24, with high accuracy along the traveling direction of the reference light ML2 toward the reference mirror 24.

[0105] Moreover, the movement range of the reference mirror 24 by the third adjustment mechanism 63 (hereinafter referred to as the third range) is set to be narrower than the first range, which is the movement range of the reference mirror 24 by the first adjustment mechanism 61.

[0106] That is, similarly to the configuration shown in FIG. 6, the reference optical path length adjustment mechanism 60 is configured to be able to change the optical path length of the reference light ML2 in response to a change in the focal length of the laser light LB.

[0107] This modification can achieve the same effects as those achieved by the configuration shown in embodiment 2. That is, even if the focal length of laser light LB is changed significantly, by changing the optical path length of reference light ML2 accordingly, it is possible to suppress fluctuations in the measured value of the penetration depth of welded portion 15a and improve the measurement accuracy of the penetration depth.

[0108] (Other embodiments) New embodiments can be created by appropriately combining the components shown in the first and second embodiments and the modified examples. For example, the third adjustment mechanism 63 shown in the modified example may be applied to the configuration shown in the first embodiment. That is, the reference optical path length change mechanism 50 may be connected to the intermediate end portion 32a of the second optical fiber system of the reference optical path 32, and the intermediate end portion 32a may be moved along the traveling direction of the reference light ML2 to change the optical path length of the reference light ML2.

[0109] Furthermore, the first adjustment mechanism 61 shown in the second embodiment and the modified example may be structured so that its operation is automatically controlled by the control unit 13. If the first adjustment mechanism 61 is of a manual type, the structure can be simplified and costs can be reduced. [Industrial Applicability]

[0110] The laser welding device disclosed herein is useful because it can suppress fluctuations in the measured values ​​of the penetration depth and improve the measurement accuracy of the penetration depth. [Explanation of symbols]

[0111] 10 Laser welding equipment 11 Laser Oscillator 12 Laser head 13 Control section 15 Work 15a Welding 15b Keyhole 20 Optical Interferometer 21 Light source 22 Optical branching section 23 Optical coupling part 24 Reference Mirror 31 Object optical path 32 Reference optical path 32a Middle end 40 Signal Processing Section 41 Differential Detector 42 AD converter 50,60 Reference optical path length adjustment mechanism 51 Support mechanism 52 Drive mechanism 61 1st adjustment mechanism 62 Second adjustment mechanism 63 Third adjustment mechanism 70 Reference height measuring tool 100 processing room 101 Temperature Sensor 110 Control Room LB laser light ML measurement light ML1 object light ML2 reference light

Claims

1. 1. A method for calibrating a laser welding apparatus that welds a welded portion by using a laser beam, comprising the steps of: The laser welding apparatus includes: a laser oscillator that emits the laser light; an optical interferometer including a light source, an optical branching unit, an optical coupling unit, a reference mirror, an object optical path, a reference optical path, and a reference optical path length adjustment mechanism; A control unit, the light source emits measurement light having a wavelength different from the wavelength of the laser light, The optical branching unit branches the measurement light emitted from the light source into an object light and a reference light, the object light path is configured to guide the object light obtained by the optical branching unit to the welding portion and to guide the object light reflected at the welding portion to the optical coupling unit; the reference light path is configured to guide the reference light obtained by the optical branching unit to the reference mirror and guide the reference light reflected by the reference mirror to the optical coupling unit; the optical coupling unit couples the object light guided by the object optical path and the reference light guided by the reference optical path to generate interference light used for measuring a penetration depth of the weld; the reference light path length adjustment mechanism is configured to change the light path length of the reference light; The control unit controls an operation of the reference optical path length adjustment mechanism, a first step of measuring a predetermined reference height using the optical interferometer and storing the obtained measurement value as a reference value; a second step of measuring the reference height again when a predetermined condition is satisfied, and calculating a difference between the obtained measurement value and the reference value; and a third step of changing the optical path length of the reference light so that the difference falls within a predetermined tolerance range if the difference calculated in the second step exceeds a predetermined tolerance range.

2. 2. The method for calibrating a laser welding apparatus according to claim 1, A calibration method for a laser welding apparatus, characterized in that the reference optical path length adjustment mechanism is configured to change the optical path length of the reference light by moving the reference mirror within a predetermined range along the traveling direction of the reference light.

3. 3. The method for calibrating a laser welding apparatus according to claim 1, further comprising: the reference optical path is constituted by an optical fiber system, the optical fiber system has an intermediate end portion configured to irradiate the reference light obtained by the optical branching unit onto the reference mirror, receive the reference light reflected by the reference mirror, and guide the reference light to the optical coupling unit; A calibration method for a laser welding apparatus, characterized in that the reference optical path length adjustment mechanism is configured to change the optical path length of the reference light by moving the intermediate end portion along the traveling direction of the reference light.

4. 3. The method for calibrating a laser welding apparatus according to claim 2, the reference optical path length adjustment mechanism includes at least a first adjustment mechanism and a second adjustment mechanism, the first adjustment mechanism is configured to move the reference mirror within a first range along a traveling direction of the reference light, the second adjustment mechanism is configured to move the reference mirror within a second range narrower than the first range along a traveling direction of the reference light, A method for calibrating a laser welding apparatus, wherein the control unit controls the operation of at least the second adjustment mechanism.

5. 4. The method for calibrating a laser welding apparatus according to claim 3, the reference optical path length adjustment mechanism includes at least a first adjustment mechanism and a third adjustment mechanism, the first adjustment mechanism is configured to move the reference mirror within a first range along a traveling direction of the reference light, the third adjustment mechanism is configured to move the intermediate end portion along a traveling direction of the reference beam within a third range narrower than the first range, A method for calibrating a laser welding apparatus, wherein the control unit controls the operation of at least the third adjustment mechanism.

6. 6. The method for calibrating a laser welding apparatus according to claim 4, further comprising the steps of: The focal length of the laser light is variable; A method for calibrating a laser welding apparatus, characterized in that the reference optical path length adjustment mechanism is configured to be able to change the optical path length of the reference light in response to a change in the focal length of the laser light.

7. 7. The method for calibrating a laser welding apparatus according to claim 4, further comprising: The first adjustment mechanism is manually operated, A method for calibrating a laser welding apparatus, comprising the steps of: automatically operating the second adjustment mechanism or the third adjustment mechanism in response to a control signal from the control unit.

8. 8. The method for calibrating a laser welding apparatus according to claim 1, the object optical path is constituted by a first optical fiber system; the reference optical path is constituted by a second optical fiber system; a portion of the first optical fiber system is disposed in a processing chamber in which welding of the weld portion is performed by the laser light; 2. A method for calibrating a laser welding apparatus, comprising: disposing a remaining portion of the first optical fiber system and the second optical fiber system in a space different from the processing chamber.

9. A method for calibrating a laser welding apparatus according to any one of claims 1 to 8, a fourth step of measuring the reference height again after the third step and confirming whether the difference between the obtained measurement value and the reference value falls within the allowable range.

10. 10. The method for calibrating a laser welding apparatus according to claim 1, The predetermined condition is either that the number of times the workpiece has been welded reaches a predetermined number or that the number of times is every predetermined time interval.

11. A method for calibrating a laser welding apparatus, comprising: setting the predetermined time interval to be shorter in a specific time period than in other time periods.

11. 10. The method for calibrating a laser welding apparatus according to claim 1, A method for calibrating a laser welding apparatus, characterized in that the specified condition is that the temperature of a processing chamber in which welding of the weld portion is performed by the laser light has changed by more than a specified value since the previous calibration.

12. 10. The method for calibrating a laser welding apparatus according to claim 1, A method for calibrating a laser welding apparatus, characterized in that the specified condition is a case in which the penetration depth of the weld is measured each time a specified number of times the workpiece is welded, and the obtained measured value gradually increases or gradually decreases as the number of times the workpiece is welded increases.

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