JP6856845B2 - Laser welding equipment and laser welding quality judgment equipment - Google Patents

Description

The present invention is a laser welding device that irradiates a metal with laser light to perform welding and determines the quality of the welding, and a laser welding quality determination device that determines the quality of laser welding performed by the laser welding device. It is about.

Laser welding is used in various fields because the energy density of the laser beam of the heat source is high and low distortion, high speed, and high precision welding are possible. However, laser welding has many factors that cause poor quality, and the quality is not constant due to changes in the shape of the object to be welded, the construction conditions at the time of welding, the surrounding environment, and the like. In order to quickly feed back information on such quality variations to the production process and reduce the occurrence of defective products, there is a need for a method for accurately and quickly determining the quality of laser welding in the production process.

In laser welding, it is known that the penetration depth, which indicates the depth at which the metal is melted by irradiating the metal with laser light and heating it, greatly affects the quality of laser welding. Therefore, estimating the penetration depth is useful for determining the quality of laser welding. It is also known that there is a correlation between the width and length of the molten pool, which is the region where the metal is melted by laser irradiation, and the penetration depth. Further, a place where the molten pool is photographed with a camera, the region where the brightness value is equal to or higher than a predetermined threshold value is estimated as the region of the molten pool from the brightness value map of the captured image, and the width and length of the molten pool are maximized. There is known a method of specifying the penetration depth by measuring the length of the above (for example, Patent Document 1).

JP 2015-188938

However, in the method described in Patent Document 1, the brightness depends on the conditions such as the spectral sensitivity of the camera, the optical system, the type of metal material, and the laser intensity. Therefore, if any of these conditions changes, a threshold value is set. Unless it is fixed, the accuracy of identifying the molten pool is lowered, and as a result, there is a problem that the quality of laser welding cannot be accurately determined.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a laser welding apparatus capable of determining the quality of laser welding with high accuracy regardless of measurement conditions.

In order to achieve this object, the laser welding apparatus according to claim 1 irradiates a metal with a laser beam to weld the metal, oscillates the laser beam, and positions the metal relative to the metal. A laser beam irradiating means for irradiating a metal with a laser beam while changing the above, and a measurement for measuring a distribution of a predetermined physical amount that varies depending on the state of the metal in a predetermined region of the metal irradiated with the laser beam by the laser beam irradiating means. Based on the means, the inclination determining means for determining the inclination which is the amount of change of the predetermined physical quantity at each position based on the distribution of the predetermined physical quantity in the predetermined region measured by the measuring means, and the inclination determining means. Based on the determined inclination, the state identification means for discriminating between the solid region which is a metal region only in the solid state and the region containing the metal in the liquid state in the predetermined region, and the state identification means identified by the state identification means. A means for identifying a molten pool that specifies a region containing a metal in a liquid state as a molten pool, a means for determining the quality of laser welding by evaluating the molten pool specified by the means for identifying the molten metal, and a means for determining the quality of laser welding. To be equipped.

The laser welding apparatus according to claim 2 is the laser welding apparatus according to claim 1, wherein the predetermined physical quantity is temperature.

The laser welding apparatus according to claim 3 is the laser welding apparatus according to claim 1 or 2, wherein the state identification means identifies a position in the predetermined region where the inclination of the distribution of the predetermined physical quantity changes. A solid-liquid region, which is a region containing a metal in a liquid state and a metal in a solid state, is distinguished from the solid region.

The laser welding apparatus according to claim 4 is the laser welding apparatus according to any one of claims 1 to 3, wherein the determination means is a direction orthogonal to the direction in which the laser beam moves relative to the metal. The molten pool is evaluated by evaluating the length of the region containing the metal in the liquid state and / or the length of the region containing the metal in the liquid state in the direction in which the laser beam moves relative to the metal. ..

The laser welding apparatus according to claim 5 is the laser welding apparatus according to any one of claims 1 to 4, wherein the determination means is associated with the movement of the laser beam relative to the metal over time. The molten pool is evaluated by evaluating the change over time in the length of the region containing the metal in the liquid state in the direction in which the laser beam moves relative to the metal.

The laser welding apparatus according to claim 6 is the laser welding apparatus according to any one of claims 1 to 5, wherein the determination means emits laser light at at least two positions in a region containing the metal in a liquid state. The molten pool is evaluated by evaluating the difference in length of the region containing the metal in the liquid state in the direction orthogonal to the direction of relative movement with respect to the metal.

The laser welding apparatus according to claim 7 is the laser welding apparatus according to any one of claims 1 to 6, wherein the determination means is at a predetermined distance from the laser beam irradiation position, and the laser beam irradiation position can be moved. The length of the region containing the metal in the liquid state in the direction orthogonal to the direction in which the laser beam moves relative to the metal at a predetermined position in the region containing the metal in the liquid state that moves on the metal with the laser beam. The molten pool is evaluated by evaluating the change over time.

The laser welding apparatus according to claim 8 is the laser welding apparatus according to any one of claims 1 to 7, wherein the determination means is a specific distance from a laser beam irradiation position in a region containing a metal in a liquid state. The molten pool is evaluated by evaluating the presence or absence of the one position in which the difference between the one position and the position around the one position is equal to or more than the predetermined amount in the region separated by the above. To do.

The laser welding quality determination device according to claim 9 irradiates a metal with a laser beam while changing its position relative to the metal, and the quality of the laser welding performed by the laser welding device that welds the metal is good or bad. The distribution of a predetermined physical quantity that fluctuates depending on the state of the metal is measured by the measuring means for measuring the distribution of a predetermined physical quantity in a predetermined region of the metal irradiated with the laser beam by the laser welding apparatus, and the measuring means thereof. Based on the distribution of the predetermined physical quantity in the predetermined region, the inclination determining means for determining the inclination which is the amount of change of the predetermined physical quantity at each position, and the inclination determined by the inclination determining means, the predetermined A state identifying means for discriminating between a solid region which is a region of a metal only in a solid state and a region containing a metal in a liquid state in the region, and a region containing the metal in the liquid state identified by the state identifying means are welded. It is provided with a molten pool specifying means specified as, and a determining means for determining the quality of laser welding by evaluating the molten pool specified by the molten pool specifying means.

According to the laser welding apparatus according to claim 1, the metal is irradiated with the laser beam to weld the metal. The laser light irradiating means irradiates the metal with the laser light while changing the position relative to the metal. The distribution of a predetermined physical quantity that varies depending on the state of the metal irradiated with the laser beam by the laser light oscillating means is measured by the measuring means in a predetermined region of the metal. Based on the distribution of a predetermined physical quantity in a predetermined region measured by the measuring means, the inclination, which is the amount of change in the predetermined physical quantity at each position, is determined by the inclination determining means. Based on the inclination determined by the inclination determining means, the solid region, which is a metal region only in the solid state in the predetermined region, and the region containing the metal in the liquid state are identified by the state identifying means. The region containing the metal in the liquid state identified by the state identifying means is identified as a molten pool by the molten pool identifying means. The molten pool identified by the molten pool identifying means is evaluated by the determining means, and the quality of the laser welding is determined. In this way, the molten pool is specified based on the inclination of a predetermined physical quantity in a predetermined region of the metal irradiated with the laser beam. Here, since the predetermined physical quantity varies depending on the state of the metal, the predetermined physical quantity differs between the solid region and the region containing the metal in the liquid state. Therefore, the slope of a predetermined physical quantity changes at the boundary between the solid region and the region containing the metal in the liquid state. This does not change even if the measurement conditions for identifying the molten pool change. Therefore, regardless of the measurement conditions performed to identify the molten pool, the molten pool can be identified with high accuracy, so that there is an effect that the quality of laser welding can be determined with high accuracy.

According to the laser welding apparatus according to claim 2, in addition to the effects of the laser welding apparatus according to claim 1, the following effects are exhibited. That is, based on the inclination of the temperature distribution in the predetermined region measured by the measuring means, the region containing the metal in the liquid state and the region of the metal in the solid state are identified by the state identifying means, so that during laser welding, the region is identified. It is possible to suppress the mixing of noise due to the generated fume. Therefore, there is an effect that the molten pool can be identified with high accuracy.

According to the laser welding apparatus according to claim 3, in addition to the effects of the laser welding apparatus according to claim 1 or 2, the following effects are exhibited. That is, the state identification means specifies a position in the predetermined region where the slope of the distribution of the predetermined physical quantity changes. In the solid-liquid region, which is a region containing a liquid metal and a solid metal, the predetermined physical quantity is substantially constant, while the predetermined physical quantity changes at the position where the solid-liquid region changes to the solid region. The solid-liquid region and the solid region are distinguished by the position where the slope of the distribution of the physical quantity of the physical quantity changes. Therefore, it is possible to distinguish between the solid-liquid region and the solid region based on the slope of the distribution of physical quantities, and there is an effect that the molten pool can be specified.

According to the laser welding apparatus according to claim 4, in addition to the effect of the laser welding apparatus according to any one of claims 1 to 3, the following effects are exhibited. That is, the length of the region containing the metal in the liquid state in the direction orthogonal to the direction in which the laser light moves relative to the metal and / or the liquid state in the direction in which the laser light moves relative to the metal. The length of the region containing the metal is evaluated by the determination means, and the molten pool is evaluated. The length of the region containing the liquid metal in the direction perpendicular to the direction of movement relative to the metal, and the length of the region containing the liquid metal in the direction in which the laser beam moves relative to the metal. Corresponds to the quality of laser welding. On the other hand, since the molten pool is specified based on the inclination of a predetermined physical quantity, the direction perpendicular to the direction of relative movement with respect to the metal is irrespective of the measurement conditions performed to identify the molten pool. The length of the region containing the metal in the liquid state and the length of the region containing the metal in the liquid state in the direction in which the laser beam moves relative to the metal can be accurately specified. This has the effect of being able to determine the quality of laser welding with high accuracy.

According to the laser welding apparatus according to claim 5, in addition to the effect of the laser welding apparatus according to any one of claims 1 to 4, the following effects are exhibited. That is, as the laser light moves relative to the metal over time, the length of the region containing the metal in the liquid state in the direction in which the laser light moves relative to the metal changes with time. However, it is evaluated by the determination means. The welding depth is not constant due to the gap between the metals to be welded. Therefore, the length of the region containing the metal in the liquid state in the direction in which the laser beam moves relative to the metal changes with time depending on the presence or absence of a gap between the metals to be welded. Therefore, by evaluating the length of the region containing the metal in the liquid state in the direction in which the laser beam moves relative to the metal over time, whether or not the quality of the laser welding is constant at each position where the laser welding is performed. Can be determined. Therefore, there is an effect that the accuracy of laser welding quality determination can be improved.

According to the laser welding apparatus according to claim 6, in addition to the effect of the laser welding apparatus according to any one of claims 1 to 5, the following effects are exhibited. That is, at at least two positions in the region containing the liquid metal, the difference in length of the region containing the liquid metal in the direction orthogonal to the direction in which the laser beam moves relative to the metal is evaluated. As a result, the molten pool is evaluated by the determination means. Therefore, it is possible to determine whether or not the quality of laser welding is constant between these positions. Therefore, there is an effect that the accuracy of laser welding quality determination can be improved.

According to the laser welding apparatus according to claim 7, in addition to the effect of the laser welding apparatus according to any one of claims 1 to 6, the following effects are exhibited. That is, the laser beam is relative to the metal at a predetermined position in a region containing a liquid metal that moves on the metal as the laser beam irradiation position moves at a predetermined distance from the laser beam irradiation position. The change over time in the length of the region containing the metal in the liquid state in the direction orthogonal to the direction of movement is evaluated by the determination means. The welding depth is not constant due to the gap between the metals to be welded. Therefore, the length of the region containing the metal in the liquid state in the direction orthogonal to the direction in which the laser beam at the predetermined position moves relative to the metal changes with time. Therefore, laser welding is performed at each laser-welded position by evaluating the length of the region containing the liquid metal in the direction orthogonal to the direction in which the laser beam moves relative to the metal at a predetermined position over time. It is possible to judge whether or not the quality of the laser is constant. Therefore, there is an effect that the accuracy of laser welding quality determination can be improved.

According to the laser welding apparatus according to claim 8, in addition to the effect of the laser welding apparatus according to any one of claims 1 to 7, the following effects are exhibited. That is, by the determination means, in the region containing the metal in the liquid state, in the region separated from the irradiation position of the laser beam by a specific distance or more, the predetermined physical quantity at one position and the position around the one position. The molten pool is evaluated by evaluating the presence or absence of the one position where the difference is equal to or greater than a predetermined amount. If there is a region containing a metal in a liquid state that is separated from the laser beam irradiation position by a specific distance or more and the physical quantity is different from the surrounding physical quantity, the quality of laser welding may not be constant. .. Therefore, by evaluating the presence or absence of the one position where the difference between the one position and the position around the one position is equal to or more than the predetermined amount, it is possible to determine whether or not the quality of laser welding is constant. It can be determined. Therefore, there is an effect that the accuracy of laser welding quality determination can be improved.

According to the laser welding quality determination device according to claim 9, by using this for the quality determination of the laser welding performed by the laser welding device, the action and effect equivalent to those of the laser welding apparatus according to claim 1 are achieved. Can be played.

It is the schematic which showed the whole image of the laser welding apparatus which is 1st Embodiment of this invention. It is a block diagram which showed the electrical structure of the arithmetic processing unit. (A) is a diagram showing an example of judgment data when the welding speed is 1.8 m / min, and (b) is a diagram showing an example of judgment data when the welding speed is 0.9 m / min. is there. (A) is a schematic diagram showing the state of the metal in a predetermined region, and (b) is a diagram showing the temperature distribution on the x-axis. It is a flowchart which shows the determination process performed by the arithmetic processing unit. (A) is a schematic diagram showing a predetermined region measured by the laser welding apparatus in the second embodiment, and (b) is a diagram showing the temperature distribution in the y-axis direction thereof. It is a flowchart which shows the determination process performed by the arithmetic processing unit. It is a schematic diagram which shows the predetermined area measured by the laser welding apparatus in 3rd Embodiment. It is a flowchart which shows the determination process performed by the arithmetic processing unit. (A) is a schematic diagram showing a predetermined region measured by the laser welding apparatus according to the fourth embodiment, and (b) is a diagram showing a change over time in the width of the molten pool. It is a flowchart which shows the determination process performed by the arithmetic processing unit. It is a schematic diagram which shows the predetermined area measured by the laser welding apparatus in 5th Embodiment. It is a flowchart which shows the determination process performed by the arithmetic processing unit. It is a schematic diagram which shows the state of the metal of the predetermined region measured by the laser welding apparatus in 6th Embodiment, and (b) is the figure which shows the luminance distribution on the x-axis.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. First, with reference to FIG. 1, the outline of the laser welding apparatus S according to the first embodiment of the present invention will be described. FIG. 1 is a schematic view showing an overall image of the laser welding apparatus S.

The laser welding device S welds, for example, two metal objects to be welded (hereinafter, simply referred to as “work”) A by using a laser beam L. A metal such as iron or copper is used for the work A. The laser welding apparatus S has a laser oscillator 10 for oscillating a laser, and the laser beam L oscillated by the laser oscillator 10 passes through an optical fiber 11 which is a light transmission path and reaches one end of the optical fiber 11. It is transmitted to the connected fiber adapter 12. Then, the laser beam L is irradiated from the fiber adapter 12 and enters the laser processing head 16. The laser processing head 16 includes a collimating lens 13, a dichroic lens 14, and a condensing lens 15, and is a device for irradiating the work A with the laser beam L.

A collimating lens 13 for adjusting the direction of the laser beam L in a parallel state is arranged on the output side of the fiber adapter 12 in the laser processing head 16, and the laser beam L emitted from the fiber adapter 12 is collimated. The lens 13 produces parallel light. The laser beam L, which is made parallel light by the collimated lens 13, passes through the dichroic lens 14. The dichroic lens 14 allows the laser light L to pass through, but at least reflects infrared light. Then, the laser light L that has passed through the dichroic lens 14 is focused by the condenser lens 15 for condensing the laser light L, and is irradiated to the work A.

The work A is fixed, and the relative position between the irradiation position of the laser beam L and the work A changes as the laser processing head 16 moves in the welding direction in the drawing. The laser processing head 16 may be fixed and the work A may be moved in the direction opposite to the welding direction in the drawing to change the relative position between the irradiation position of the laser beam L and the work A.

When the work A is heated by the irradiation of the laser beam L, the work A melts and a molten pool is formed. The molten pool refers to a region (a region containing a metal in a liquid state) in which the work A is melted by irradiating the work A with laser light L and heating the work A. At this time, the work A emits different amounts of infrared rays I depending on the temperature. The infrared ray I emitted from the work A passes through the condenser lens 15 and is reflected by the dichroic lens 14 in a direction different from that of the collimating lens 13 (direction of the prism 17).

Then, the infrared ray I reflected by the dichroic lens 14 is reflected on the camera condensing lens 18 side by the prism 17 for reflecting the light. Then, the infrared ray I is condensed by the camera condensing lens 18 for condensing the infrared ray I, and is incident on the infrared camera 19. The infrared camera 19 is a device for visualizing the amount of infrared rays I emitted. Since the work A emits different amounts of infrared rays I depending on the temperature, the infrared camera 19 visualizes the infrared distribution in a predetermined area on the work A, which is the shooting range of the infrared camera 19, to visualize the temperature distribution. can do. Then, the visualized temperature distribution data is transmitted to the arithmetic processing unit 20 as the temperature distribution data 32a. In this embodiment, the temperature distribution is visualized based on the infrared distribution. At the position where the laser beam L is irradiated, dusty fume is generated, but the infrared ray I emitted by the fume is small. Therefore, by visualizing the temperature distribution based on the infrared distribution, the influence of noise due to fume can be suppressed. Therefore, the temperature distribution can be measured with high accuracy. An optical filter such as a visible light cut filter that blocks only visible light or a bandpass filter that transmits only a specific wavelength region (infrared ray) may be provided between the prism 17 and the condenser lens 18 for a camera. As a result, light unnecessary for measurement other than infrared rays can be reduced, so that measurement accuracy can be improved.

The arithmetic processing unit 20 performs arithmetic processing such as determination processing described later based on the temperature distribution data 32a. The arithmetic processing unit 20 determines the quality of laser welding by executing the determination process. Then, the result of the determination is displayed on the display device 21 that displays the quality of the laser welding.

Next, the electrical configuration of the arithmetic processing unit 20 will be described with reference to FIG. FIG. 2 is a block diagram showing the electrical configuration thereof.

The arithmetic processing unit 20 has a CPU (Central Processing Unit) 30, a ROM (Read Only Memory) 31, and a RAM (Random Access Memory) 32, which are connected via a bus line 33. .. Further, the infrared camera 19 and the display device 21 described above are connected to the bus line 33.

The CPU 30 is an arithmetic unit that executes various operations such as a determination process described later according to the program data 31a stored in the ROM 31. The ROM 31 is a non-rewritable non-volatile memory for storing program data 31a, fixed value data, and the like executed by the CPU 30. A rewritable non-volatile memory (for example, a flash memory) may be used instead of the non-rewritable ROM 31.

The program that executes the determination process described later is stored in the ROM 31 as a part of the program data 31a, and the determination data 31b is stored in the ROM 31 as a part of the fixed value data. Further, the determination data 31b is data showing actually measured values obtained by previously measuring the correspondence relationship between the length of the molten pool described later and the penetration depth, which is the depth at which the work A is melted, for each welding speed and the material of the work A. This is used when determining the quality of laser welding in the determination process described later.

Here, the determination data 31b will be described with reference to FIG. FIG. 3A is a diagram showing an example of determination data 31b when an iron plate upper plate 1.0 mm / iron plate lower plate 6 mm is used as the work A and the welding speed is 1.8 m / min. b) is a diagram showing an example of determination data 31b when an iron plate upper plate 1.0 mm / iron plate lower plate 6 mm is used as the work A and the welding speed is 0.9 m / min. For example, when laser welding is performed on an iron plate upper plate 1.0 mm / iron plate lower plate 6 mm at a welding speed of 1.8 m / min, the length and penetration depth of the molten pool depend on the difference in laser output and welding speed. Changes as shown in FIG. 3 (a). That is, when the length of the molten pool is 4000 μm, the penetration depth is 3.60 mm, when the length of the molten pool is 4323 μm, the penetration depth is 3.64 mm, and the length of the molten pool is 3.64 mm. The penetration depth when the length is 4617 μm is 3.96 mm, and the penetration depth when the length of the molten pool is 4970 μm is 4.56 mm. And there is a correlation between the length of these molten pools and the depth of penetration. Therefore, by interpolating these data, the penetration depth can be estimated based on the length of the molten pool. If the estimated penetration depth is within an appropriate range (for example, 3.8 mm to 5.0 mm) where the quality of laser welding is good, it is judged that the quality of laser welding is good, and the quality of laser welding is high. If it is not within the appropriate range, the quality is judged to be poor. The range of the penetration depth when judging the quality of the laser welding is determined by the user so that the quality of the laser welding is good according to the thickness of the upper plate and the lower plate used for the work A. Good.

In the present embodiment, the penetration depth is estimated based on the length of the molten pool by interpolating the data of the length of the molten pool and the penetration depth stored in the determination data 31b. It is not limited to this. For example, even if an approximate straight line equation showing the relationship between the length of the molten pool and the penetration depth is obtained in advance and the length of the molten pool is substituted into the approximate straight line equation, the penetration depth can be estimated. Good.

The explanation will be continued by returning to FIG. The RAM 32 is a rewritable volatile memory, and temporarily stores various data when the program is executed by the CPU 30. As shown in FIG. 2, the RAM 32 stores at least the temperature distribution data 32a and the shape data 32b.

The temperature distribution data 32a is the temperature distribution data of the work A visualized by the infrared camera 19. In the determination process described later, the molten pool is specified from the slope of the temperature distribution of the temperature distribution data 32a.

The shape data 32b is data relating to the shape of the molten pool, such as the width and length of the molten pool, which will be described later, specified in the determination process. In the determination process, the quality of laser welding is determined by estimating the penetration depth based on the shape data 32b and the determination data 31b.

Next, with reference to FIG. 4, the relationship between the temperature distribution of the work A irradiated with the laser and the state of the metal will be described. FIG. 4A is a schematic view of the state of the metal in a predetermined region, which is the region where the temperature was measured by the work A, when viewed from the direction in which the laser beam L is irradiated, and FIG. 4B is a schematic diagram at that time. It is a figure which shows the detailed temperature distribution on the x-axis. In these figures, the state when the laser beam L moves from the side of A1 to the side of A2 is shown. The A1-A2 direction is defined as the x-axis, and the direction orthogonal to the A1-A2 direction is defined as the y-axis.

In FIG. 4A, the state of the metal in the region t1 closest to the laser center position, which is the position where the laser beam L is irradiated, is the region in the liquid state containing no metal in the solid state (hereinafter, “non-solid region””. The temperature is the highest. The temperature of the region t2 surrounding the surrounding region is the next highest, and is a region in which a metal in a liquid state and a metal in a solid state exist (hereinafter, referred to as a “solid-liquid region”). The region t3 surrounding the region t2 has the lowest temperature, and is a region in which only the metal in the solid state exists (hereinafter, referred to as a “solid region”). On the A2 side, the region t2 is greatly bulged and rounded, whereas on the A1 side, the tip of the region t2 is not bulged. This is because the laser beam L is moving from the A1 side to the A2 side. That is, on the A2 side, the temperature rises sharply after the laser beam L is irradiated, and the temperature rises in a wide range around the area, whereas on the A1 side, the time after the laser beam L is irradiated. This is due to the fact that the course is long and the temperature range that becomes the solid-liquid region continues. Further, on the A1-A2 axis, on the A2 side, the region t3 to the region t1 do not pass through the region t2, but this is close to the laser center position and the temperature rises immediately after the work A is heated. This is due to the rise.

Here, the change of state of the metal in the work A will be described. Work A is a metal that is solid at room temperature. When the laser beam L is irradiated, the temperature of the work A rises, and the work A changes its state from a solid state to a liquid state. When the irradiation position of the laser beam L moves, the temperature of the work A at the position where the laser beam L has been irradiated starts to decrease. When the temperature of the work A reaches the freezing point, the work A begins to change state from a liquid state to a solid state. At this time, the temperature remains at the freezing point and hardly changes until the work A changes to a completely solid state. Then, when the work A completely changes to a solid state, the temperature begins to decrease. That is, it can be said that if the temperature is lower than the freezing point, the work A is in a state of only a solid, at the freezing point, a state in which a solid and a liquid are mixed, and in a state in which the temperature is higher than the freezing point, there is no solid. In addition, the temperature is almost constant at the freezing point, and the temperature changes before and after that. The relationship between the state change of the metal and the temperature change does not change depending on the material of the work A.

A detailed temperature distribution on the x-axis (A1-A2) will be described with reference to FIG. 4 (b). In the region t3 at the end on the A2 side, the temperature is constant below the freezing point. On the A1 side, the temperature rises in the vicinity of the region t1 due to the influence of the laser beam L. Then, in the region t1 where the temperature is higher than the freezing point, the temperature rises sharply toward the laser center position, and after passing the laser center position, the temperature drops sharply. Further toward the A1 side, when the freezing point is reached, the region t2 is reached, and the temperature becomes almost constant. Then, when the temperature drops below the freezing point, the region t3 is reached. In region t3, the temperature becomes constant after it drops. The temperature at the end on the A2 side is not constant at the melting point, but this is because the distance from the laser center position is short and the temperature rises immediately after the work A is heated.

Looking at the boundary between the region t2 and the region t3, it can be seen that the slope of the temperature distribution is changing. That is, the inclination of the temperature distribution is extremely small on the region t2 side, whereas the inclination of the temperature distribution is inclined on the region t3 side. This is because the region t2 is at the freezing point and the temperature is almost constant, whereas the region t3 is lower than the freezing point and the temperature starts to change. Further, the slope of the temperature distribution also changes at the boundary between the region t2 and the region t1. That is, while the temperature on the region t2 side is almost constant at the freezing point, the temperature on the region t1 side is higher than the freezing point and the temperature changes.

As described above, since the temperature in the region t2 hardly changes, it can be seen that the temperature in the region t2 is near the freezing point and the region t2 is a solid-liquid region. On the other hand, it can be seen that the region t1 inclined in the direction higher in temperature than the region t2 is a non-solid region, and the region t3 inclined in the direction lower in temperature than the region t2 is a solid region. Therefore, the solid-liquid region, the non-solid region, and the solid region can be distinguished by the slope of the temperature distribution. Further, as described above, the relationship between the change of state of the metal and the change of temperature does not change depending on the material of the work A. Therefore, even if the material of the work A changes, the solid-liquid region and the solid-liquid region are affected by the slope of the temperature distribution. The non-solid region and the solid region can be distinguished.

As described above, since the molten pool is a region where the work A is melted (a region containing a metal in a liquid state), the molten pool is a region in which a non-solid region (region t1) and a solid-liquid region (region t2) are combined. Point to. In the present embodiment, of the lengths of the molten pools in the A1-A2 direction passing through the laser center position, the distance from the end of the molten pool on the A1 side to the laser center position is defined as the "length of the molten pool". The length of the molten pool in the direction orthogonal to the A1-A2 direction at the position of is defined as the "width of the molten pool".

Next, the determination process executed by the CPU 30 of the arithmetic processing unit 20 will be described with reference to FIG. FIG. 5 is a flowchart showing the determination process. The determination process is a process executed when the arithmetic processing device 20 captures the temperature distribution data 32a for one screen from the infrared camera 19, identifies the molten pool from the temperature distribution data 32a, and is based on the shape of the molten pool. This is a process for determining the quality of laser welding.

In the determination process, first, the temperature distribution data 32a on the A1-A2 axis is read from the RAM 32 (S1). Then, the slope of the temperature distribution on the A1-A2 axis is generated from the temperature distribution data 32a (S2). That is, the temperature difference between neighboring positions on the A1-A2 axis is obtained, and the inclination is obtained from the difference. It is preferable to perform a process of smoothing the temperature distribution data 32a on the A1-A2 axis before generating the slope. As a result, it is possible to prevent the error of the data of each pixel from being reflected in the inclination. Next, the solid-liquid region and the solid region are distinguished from each other based on the slope of the temperature distribution obtained in the treatment of S2 (S3). That is, the solid-liquid region and the solid region are distinguished by determining the boundary where the temperature change changes from the solid-liquid region in which the inclination of the temperature change is extremely small to the solid region in which the temperature changes in the low direction. This makes it possible to recognize the boundary between the solid-liquid region and the solid-liquid region.

Next, the position where the temperature distribution is maximized is specified from the slope of the temperature distribution on the A1-A2 axis generated in the process of S2, and that position is specified as the laser center position (S4). This is because the laser center position is the hottest place in the work A. Then, the length of the molten pool is specified by specifying the distance from the end on the A1 side of the solid-liquid region obtained in the treatment of S3 to the laser center position obtained in the treatment of S4 (S5). Next, based on the length of the molten pool obtained in the process of S5, the determination data 31b is interpolated to estimate the penetration depth (S6). Then, by determining whether or not the penetration depth is within an appropriate range (for example, 3.8 mm to 5.0 mm in the example of FIG. 3) in which the quality of laser welding is good, the laser welding is performed. The quality is judged (S7). If the quality of the laser welding is judged to be good, the laser welding will continue to be performed. On the other hand, if it is determined that the quality of the laser welding is poor, a display device 21 indicates that fact and the laser welding is interrupted. As a result, information that the quality of laser welding is defective can be quickly fed back to the production process, and the occurrence of defective products can be reduced.

As described above, according to the laser welding apparatus S in the first embodiment, the molten pool can be specified based on the inclination of the temperature distribution of the temperature distribution data 32a, and the quality of the laser welding can be judged from the shape of the molten pool. it can. Therefore, it is not necessary to set a threshold value to specify the molten pool. Therefore, even if the measurement conditions change, it is not necessary to reset the threshold value. Therefore, regardless of the measurement conditions performed to identify the molten pool, the molten pool can be identified with high accuracy, so that there is an effect that the quality of laser welding can be determined with high accuracy.

Further, since the temperature distribution varies depending on the state of the metal of the work A, the temperature differs between the solid region and the region containing the metal in the liquid state. Therefore, the slope of the temperature changes at the boundary between the solid region and the region containing the metal in the liquid state. This does not change even if the measurement conditions for identifying the molten pool change. Therefore, regardless of the measurement conditions performed to identify the molten pool, the molten pool can be identified with high accuracy, so that there is an effect that the quality of laser welding can be determined with high accuracy.

Next, the laser welding apparatus S according to the second embodiment will be described with reference to FIGS. 6 and 7. The laser welding apparatus S in the first embodiment estimates the penetration depth from the length of the molten pool, thereby determining the quality of the laser welding. On the other hand, in the second embodiment, the penetration depth is estimated from the width of the molten pool, and the quality of the laser welding is judged accordingly. Since each process of the configuration and the determination process of the other laser welding apparatus S is the same as that of the first embodiment, the same reference numerals are given below to the same configurations as those of the first embodiment, and the description thereof will be described. Omit.

FIG. 6A is a schematic view of a predetermined region measured by the laser welding apparatus S in the second embodiment, and FIG. 6B is a temperature distribution in the y-axis direction (B1-B2 direction) at that time. It is a figure which shows. As shown in FIG. 6A, in the present embodiment, the width of the molten pool in the B1-B2 direction is specified at a position at a predetermined distance D in the x-axis direction from the laser center position. The temperature distribution in the B1-B2 directions at this time is as shown in FIG. 6 (b). That is, on the B1 side, the temperature is low below the freezing point and is almost constant, but when the laser center position approaches the x-axis that has passed, the temperature rises toward the B2 side, and the temperature becomes the freezing point and becomes almost constant. After that, the temperature drops and then becomes almost constant. That is, the temperature near the x-axis through which the laser center position has passed is high, and the temperature at a position away from the x-axis is low. At this time, both ends on the B1 side and the B2 side are solid regions. The portion sandwiched between the solid regions is a region containing the metal in the liquid state, and the length of the region containing the metal in the liquid state in FIG. 6B is the width of the molten pool.

The width of the molten pool has a correlation with the penetration depth as well as the length of the molten pool. Therefore, by preparing the determination data 31b showing the relationship between the width of the molten pool and the penetration depth in advance, the penetration depth can be estimated from the width of the molten pool in the determination process. Then, the quality of the laser welding can be determined based on the estimated penetration depth.

Next, the determination process will be described with reference to FIG. 7. FIG. 7 is a flowchart showing a determination process executed by the CPU 30 of the arithmetic processing device 20 of the laser welding device S in the second embodiment. In the determination process, after the processes of S1, S2, and S4 similar to those of the first embodiment are performed, a predetermined position on the x-axis at a predetermined distance D from the laser center position specified in the process of S4 is specified ( S11). This predetermined position may be in the molten pool (in the solid-liquid region or non-solid region), and more preferably in the solid-liquid region. This is because the temperature is stable at the freezing point within the solid-liquid region, so that the temperature distribution can be measured with high accuracy.

After that, in the process of S12, the temperature distribution data 32a on the B1-B2 axis at the predetermined position specified in the process of S11 is read out. Then, the slope of the temperature distribution on the B1-B2 axis is generated from the temperature distribution data 32a (S13). Next, the region containing the metal in the liquid state and the solid region are identified based on the inclination of the temperature distribution, and the region containing the metal in the liquid state on the B1 side and the metal in the liquid state on the B2 side from the boundary between the solid region are included. The width of the molten pool is specified by specifying the distance to the boundary between the region and the solid region (S14). After that, the penetration depth is estimated from the width of the molten pool specified by the process of S14 using the determination data 31b (S15). Then, as in the first embodiment, the quality of the laser welding is determined by the treatment of S7. Thereby, the penetration depth can be estimated based on the width of the molten pool, and the quality of the laser welding can be judged from the penetration depth.

As described above, according to the laser welding apparatus S in the second embodiment, the molten pool is specified based on the inclination of the temperature distribution of the temperature distribution data 32a, and the width of the molten pool is specified from the shape of the molten pool for laser welding. It is possible to judge the quality. Therefore, it is not necessary to set a threshold value to specify the molten pool. Therefore, even if the measurement conditions change, it is not necessary to reset the threshold value. As a result, the molten pool can be accurately identified regardless of the measurement conditions performed to identify the molten pool, so that there is an effect that the quality of laser welding can be determined with high accuracy.

Further, since the temperature distribution varies depending on the state of the metal of the work A, the temperature differs between the solid region and the region containing the metal in the liquid state. Therefore, the slope of the temperature changes at the boundary between the solid region and the region containing the metal in the liquid state. This does not change even if the measurement conditions for identifying the molten pool change. Therefore, regardless of the measurement conditions performed to identify the molten pool, the molten pool can be identified with high accuracy, so that there is an effect that the quality of laser welding can be determined with high accuracy.

In the first embodiment, the penetration depth is estimated from the length of the molten pool, and in the second embodiment, the penetration depth is measured from the width of the molten pool. The penetration depth may be estimated based on both. For example, the arithmetic mean of the penetration depth estimated from the length of the molten pool and the penetration depth estimated from the width of the molten pool may be estimated as the penetration depth.

In addition, when both the penetration depth estimated from the length of the molten pool and the penetration depth estimated from the width of the molten pool are within an appropriate range in which the quality of laser welding is good, laser welding is performed. You may judge that the quality is good. Furthermore, laser welding is performed when either the penetration depth estimated from the length of the molten pool or the penetration depth estimated from the width of the molten pool is within an appropriate range in which the quality of laser welding is good. You may judge that the quality of the laser is good.

In addition, the laser welding apparatus S in the second embodiment has the same effect as the first embodiment with the same configuration.

Next, the laser welding apparatus S according to the third embodiment will be described with reference to FIGS. 8 and 9. The laser welding apparatus S in the first embodiment estimates the penetration depth from the length of the molten pool, thereby determining the quality of the laser welding. On the other hand, in the third embodiment, the widths of the molten pools are obtained at a plurality of positions in the region containing the metal in a liquid state, and the difference in the widths of the molten pools is evaluated to determine the quality of laser welding. judge. Since each process of the configuration and the determination process of the other laser welding apparatus S is the same as that of the first embodiment, the same reference numerals are given below to the same configurations as those of the first embodiment, and the description thereof will be described. Omit.

FIG. 8 is a schematic view of a predetermined region measured by the laser welding apparatus S in the third embodiment. As shown in FIG. 8, in the present embodiment, at a predetermined distance (D1, D2, D3) from the laser center position, and at three positions (P1, P2, P3) in the molten pool, the width of the molten pool (W1, P3,) By identifying W2 and W3) and evaluating the difference in the widths of these molten pools, the quality of laser welding is determined.

Next, the determination process will be described with reference to FIG. FIG. 9 is a flowchart showing a determination process executed by the CPU 30 of the arithmetic processing device 20 of the laser welding device S according to the third embodiment. In the determination process, the same processes of S1, S2, and S4 as in the case of the first embodiment are performed. After the processing of S1, S2, S4 is performed, three predetermined positions (P1, P2, P3) on the x-axis at a predetermined distance (D1, D2, D3) from the laser center position specified by the processing of S4. Is specified (S21). These predetermined positions may be in the molten pool (in the solid-liquid region or the non-solid region), and more preferably in the solid-liquid region. This is because the temperature is stable at the freezing point within the solid-liquid region, so that the temperature distribution can be measured with high accuracy.

Next, the temperature distribution data 32a in the y-axis direction at each predetermined position (P1, P2, P3) specified in the process of S11 is read out (S22). Then, the slope of the temperature distribution in the y-axis direction at the predetermined position (P1, P2, P3) is calculated from the temperature distribution data 32a (S23). Next, the region containing the metal in the liquid state and the solid region are distinguished based on the inclination of the temperature distribution, and the region in the y-axis direction from the boundary between the region containing the metal in the liquid state and the solid region on one side in the y-axis direction. The width of the molten pool (W1, W2, W3) is specified by specifying the distance to the boundary between the region containing the liquid metal on the other side and the solid region (S24).

Next, the difference in width between these molten pools is evaluated. Then, if the difference in the widths of these molten pools is within an appropriate range (for example, 35 μm or less) where the quality of laser welding is good, it is judged that the quality of laser welding is good, and the width of these molten pools If the difference is not within an appropriate range in which the quality of laser welding is good, the quality of laser welding is judged to be poor (S25). This is because if the difference in the widths of the molten pools is not within an appropriate range, the quality of laser welding may not be constant due to reasons such as the temperature of the work A irradiated with the laser beam L being not constant. This makes it possible to determine whether or not the quality of laser welding is constant at predetermined positions (P1, P2, P3). Therefore, the user can confirm the constant quality of laser welding.

In the present embodiment, the width of the molten pool is specified for three predetermined positions in the solid-liquid region, but the predetermined positions in the solid-liquid region and the predetermined positions in the non-solid region may coexist. For example, the width of the molten pool may be determined at one position in the non-solid region and one position in the solid-liquid region. In this case, if the difference between the width of the molten pool at the non-solid region and the width of the molten pool at the solid-liquid region is out of the appropriate range for good laser welding quality, the laser welding quality. May be determined to be defective. Moreover, the predetermined position is not limited to three positions. It suffices if the difference in the width of the molten pool between the predetermined positions can be evaluated, and at least two positions may be set as the predetermined positions.

In addition, the laser welding apparatus S in the third embodiment has the same effect as the first embodiment with the same configuration.

Next, the laser welding apparatus S according to the fourth embodiment will be described with reference to FIGS. 10 and 11. The laser welding apparatus S in the first embodiment estimates the penetration depth from the length of the molten pool, thereby determining the quality of the laser welding. On the other hand, in the fourth embodiment, the width of the molten pool is specified over time at a predetermined position in the region containing the metal in a liquid state at a predetermined distance from the center position of the laser, and the width of the molten pool with time. The quality of laser welding is judged by evaluating the magnitude of the change. Since each process of the configuration and the determination process of the other laser welding apparatus S is the same as that of the first embodiment, the same reference numerals are given below to the same configurations as those of the first embodiment, and the description thereof will be described. Omit.

FIG. 10A is a schematic view of a predetermined region measured by the laser welding apparatus S in the fourth embodiment, and FIG. 10B is a diagram showing a change over time in the width of the molten pool. As shown in FIG. 10A, in the present embodiment, the width W of the molten pool is specified at a predetermined position in a region containing a metal in a liquid state at a predetermined distance D from the laser center position. Here, the position where the laser beam L is applied to the work A moves from the side of A1 toward the side of A2. Along with this, a predetermined position for specifying the width of the molten pool also moves. That is, when the position where the laser beam L is irradiated changes with time, the predetermined position also changes. In the present embodiment, the width of the molten pool at the predetermined position when the predetermined position changes with time is specified. Then, the quality of the laser welding is judged by evaluating the change in the width of the molten pool with time.

As shown in FIG. 10B, the width of the molten pool fluctuates with time. Therefore, the magnitude of the change over time in the width of the molten pool is determined by using the difference between the maximum value and the minimum value of the width of the molten pool within a predetermined period as the amount of fluctuation.

Next, the determination process will be described with reference to FIG. FIG. 11 is a flowchart showing a determination process executed by the CPU 30 of the arithmetic processing device 20 of the laser welding device S according to the fourth embodiment. In the determination process, the same processes of S1, S2, and S4 as in the case of the first embodiment are performed. After the processing of S1, S2, and S4 is performed, a predetermined position at a predetermined distance D from the laser center position specified by the processing of S4 is specified (S31). This predetermined position may be in the molten pool (in the solid-liquid region or non-solid region), and more preferably in the solid-liquid region. This is because the temperature is stable at the freezing point within the solid-liquid region, so that the temperature distribution can be measured with high accuracy.

After that, in the process of S32, the temperature distribution data 32a in the y-axis direction at the predetermined position specified in the process of S31 is read out. Then, the inclination of the temperature distribution in the y-axis direction at the predetermined position is generated from the temperature distribution data 32a (S33). Next, in the treatment of S34, the region containing the metal in the liquid state and the solid region are distinguished based on the inclination of the temperature distribution, and the region containing the metal in the liquid state and the solid region on one side in the y-axis direction are defined. The width of the molten pool is specified by specifying the distance from the boundary to the boundary between the solid metal region and the liquid metal region on the other side in the y-axis direction. After that, the width of the molten pool specified in the process of S34 is stored as shape data 32b in the RAM 32 (S35). Next, among the data of the width of the molten pool stored in the shape data 32b, the amount of fluctuation is obtained from the difference between the maximum value and the minimum value of the data stored within the latest predetermined period, so that the fluctuation amount is within the predetermined period. The magnitude of the change in the width of the molten pool over time is evaluated (S36).

Next, in the process of S37, if the amount of fluctuation is within an appropriate range (for example, 35 μm or less) at which the quality of laser welding is good, it is determined that the quality of laser welding is good. On the other hand, if the amount of fluctuation is not within an appropriate range in which the quality of laser welding is good, the quality of laser welding is judged to be poor. For example, in work A, which is a double-layered metal plate, if there is a gap between the metal plates that causes poor quality of laser welding, the temperature change becomes large, and as a result, the amount of fluctuation is within a certain range. This is because it will not fit. Thereby, when the irradiation position of the laser beam L moves, it is possible to determine whether or not the quality of the laser welding at each position of the laser welding is constant. Therefore, the user can confirm the constant quality of laser welding.

After the treatment of S37, it is determined whether or not the welding is completed (S38). When it is determined that the welding is not completed in the process of S38 (S38: No), the process returns to the process of S1. Then, the process from S1 to the process of S38 is repeatedly executed at 1-second intervals until the welding is completed. On the other hand, when it is determined that the welding is completed (S38: Yes), the determination process ends.

In the present embodiment, the quality of laser welding is determined by evaluating the magnitude of the change in the width of the molten pool with time, but the quality is not limited to this. For example, the quality of laser welding may be determined by evaluating the magnitude of the change over time in the length of the molten pool, which is the length from the center position of the laser to the end on the A1 side of the molten pool.

In the present embodiment, among the data of the width of the molten pool stored in the shape data 32b, the fluctuation amount is obtained from the difference between the maximum value and the minimum value of the data stored within the latest predetermined period, so that the latest predetermined value is obtained. The magnitude of the change in the width of the molten pool over time during the period is evaluated, but it is not limited to this. For example, the amount of fluctuation may be obtained from the difference between the maximum value and the minimum value from the start of laser welding to the present.

In addition, the laser welding apparatus S in the fourth embodiment has the same effect as the first embodiment with the same configuration.

Next, the laser welding apparatus S according to the fifth embodiment will be described with reference to FIGS. 12 and 13. The laser welding apparatus S in the first embodiment estimates the penetration depth from the length of the molten pool, thereby determining the quality of the laser welding. On the other hand, in the fifth embodiment, among the regions containing the metal in the liquid state, the temperature gradient in the solid-liquid region separated from the irradiation position of the laser beam L by a specific distance or more is evaluated to perform laser welding. Judge the quality. Since each process of the configuration and the determination process of the other laser welding apparatus S is the same as that of the first embodiment, the same reference numerals are given below to the same configurations as those of the first embodiment, and the description thereof will be described. Omit.

FIG. 12 is a schematic view of a predetermined region measured by the laser welding apparatus S in the fifth embodiment. As shown in FIG. 12, when there is an abnormally high temperature portion E in the solid-liquid region in the observation region O provided at a specific distance D away from the irradiation position of the laser beam L, the quality of laser welding is performed at that location E. There is a possibility that a blow hole with a large amount of metal evaporation has occurred, which causes the defect. At this time, since the temperature is higher than the surroundings at the location E where the temperature is abnormally high, the temperature gradient changes in the direction of high. Therefore, if the temperature gradient changes, it is judged that the quality of laser welding is poor.

Next, the determination process will be described with reference to FIG. FIG. 13 is a flowchart showing a determination process executed by the CPU 30 of the arithmetic processing device 20 of the laser welding device S according to the fifth embodiment. In the determination process, the same processes of S1, S2, and S4 as in the case of the first embodiment are performed. After the processing of S1, S2, and S4 is performed, the observation region O is specified in the solid-liquid region separated from the laser center position specified by the processing of S4 by a specific distance D (S41). This observation area O is an area for observing the slope of the temperature distribution. It is desirable that the observation region O is in the solid-liquid region. This is because if it is in the solid-liquid region, the temperature is not high unlike the non-solid region because it is far from the laser center position, and it is easy to find an abnormally high temperature portion. Therefore, it is desirable to set a specific distance so as not to include the non-solid region.

After that, in the process of S42, the temperature distribution data 32a of the observation region O specified in the process of S41 is read out. Then, the inclination of the temperature distribution in the y-axis direction at each position on the x-axis in the observation region is generated from the temperature distribution data 32a (S43). Next, in the treatment of S44, the region containing the metal in the liquid state and the solid region are identified based on the slope of the temperature distribution, and the range of the molten pool is specified. Then, in the molten pool in the observation region O, the inclination of the temperature is evaluated (S45). Next, in the treatment of S46, if there is a place where the slope of the temperature becomes a slope equal to or higher than an appropriate slope in which the quality of the laser welding is good in the treatment of S45, it is determined that the quality of the laser welding is poor. On the other hand, if there is no place where the slope of the temperature is greater than the appropriate slope for which the quality of laser welding is good, it is judged that the quality of laser welding is good. This makes it possible to determine whether or not the quality of laser welding in the molten pool in the observation region is constant. Therefore, the user can confirm the constant quality of laser welding.

In the present embodiment, it is determined whether or not there is an abnormally high temperature portion in the solid-liquid region by evaluating the temperature gradient in the molten pool in the observation region O, but the present invention is limited to this. It's not something. For example, in the molten pool in the observation region O, it may be determined whether or not there is an abnormally high temperature portion in the solid-liquid region depending on the presence or absence of a portion having a temperature higher than a preset temperature. At this time, if the area of the part where the temperature is abnormally high is equal to or larger than the predetermined area, it is judged that the quality of laser welding is poor, and if the area of the part where the temperature is abnormally high is not more than the predetermined area, it is determined. You may judge that the quality of laser welding is good.

In addition, the laser welding apparatus S in the fifth embodiment has the same effect as the first embodiment with the same configuration.

Next, the laser welding apparatus S according to the sixth embodiment will be described with reference to FIG. The laser welding apparatus S in the first embodiment discriminates between a solid region, a solid-liquid region, and a non-solid region from the slope of the temperature distribution, and identifies the molten pool based on this. On the other hand, in the sixth embodiment, the solid region, the solid-liquid region, and the liquid region are identified from the slope of the luminance distribution, and the molten pool is specified based on this. Since each process of the configuration and the determination process of the other laser welding apparatus S is the same as that of the first embodiment, the same reference numerals are given below to the same configurations as those of the first embodiment, and the description thereof will be described. Omit.

In the laser welding apparatus S of the first embodiment, as the dichroic lens 14, a lens that allows the laser beam L to pass through but at least reflects infrared light is used. On the other hand, in the present embodiment, the laser beam L is passed from the collimating lens 13 side to the work A side, but at least visible light is reflected from the work A side to the prism 17 side. Then, instead of the infrared camera 19, an image is taken by a camera that takes visible light. An optical filter such as an infrared cut filter that blocks only infrared rays or a bandpass filter that transmits only a specific wavelength region (visible light) may be provided between the prism 17 and the condenser lens 18 for a camera. As a result, light unnecessary for measurement other than visible light can be reduced, so that measurement accuracy can be improved.

FIG. 14A is a schematic view of the state of the metal in a predetermined region measured by the laser welding apparatus S in the present embodiment, and FIG. 14B shows a detailed luminance distribution on the x-axis thereof. It is a figure. In the state of the metal in the predetermined region in FIG. 14A, the region closest to the laser center position, which is the position where the laser beam L is irradiated, is the non-solid region, and the brightness is the highest. The brightness of the solid-liquid region surrounding the solid-liquid region is the next highest, and the brightness of the solid-liquid region surrounding the solid-liquid region is the lowest.

A detailed luminance distribution on the A1-A2 axis (x-axis) will be described with reference to FIG. 14 (b). This change in the slope of the luminance distribution is very similar to the change in the slope of the temperature distribution in FIG. 3 (b). That is, the brightness is constant at a low brightness in the solid region on the A2 side, and the brightness increases as it approaches the non-solid region. Then, in the non-solid region, the brightness increases and becomes maximum near the center position of the laser. After that, the brightness decreases, and the brightness becomes almost constant in the solid-liquid region. Then, in the solid region, the brightness decreases and then becomes almost constant. This is because the brightness of the metal changes depending on the state of the metal. As described above, since the change in the slope of the luminance distribution is very similar to the change in the slope of the temperature distribution, the solid-liquid region, the non-solid region, and the solid region can be distinguished by the slope of the luminance distribution. That is, there is almost no inclination of the brightness distribution in the solid-liquid region. On the other hand, the region inclined in the direction of higher brightness than the solid-liquid region is the non-solid region, and the region inclined in the direction of lower brightness than the solid-liquid region is the solid region. Therefore, the solid-liquid region, the non-solid region, and the solid region can be distinguished by the slope of the brightness distribution. As a result, it is not necessary to use the infrared camera 19, and the molten pool can be easily identified. The brightness is highest near the center position of the laser, which is due to the brightness of the laser light L itself.

As described above, according to the laser welding apparatus S in the sixth embodiment, the molten pool can be specified based on the inclination of the brightness distribution, and the quality of the laser welding can be judged from the shape of the molten pool. Therefore, it is not necessary to set a threshold value to specify the molten pool. Therefore, even if the measurement conditions change, it is not necessary to reset the threshold value. Therefore, regardless of the measurement conditions performed to identify the molten pool, the molten pool can be identified with high accuracy, so that there is an effect that the quality of laser welding can be determined with high accuracy.

Further, since the brightness distribution varies depending on the state of the metal of the work A, the brightness differs between the solid region and the region containing the metal in the liquid state. Therefore, the slope of the brightness changes at the boundary between the solid region and the region containing the metal in the liquid state. This does not change even if the measurement conditions for identifying the molten pool change. Therefore, regardless of the measurement conditions performed to identify the molten pool, the molten pool can be identified with high accuracy, so that there is an effect that the quality of laser welding can be determined with high accuracy.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments, and it is easy to make various improvements and modifications within a range that does not deviate from the gist of the present invention. It can be inferred. For example, each embodiment is provided by adding a part or a plurality of parts of the configuration of another embodiment to the embodiment or exchanging a part or a plurality of parts of the structure of the embodiment with each other. The embodiment may be modified to form the configuration. Further, the numerical values given in each of the above embodiments are examples, and it is naturally possible to adopt other numerical values.

For example, at least two of the first to fifth embodiments may be combined and implemented. For example, in addition to estimating the penetration depth from the length and / or width of the molten pool to determine the quality of laser welding, multiple regions within the region containing the metal in the liquid state. The quality of the laser welding may be judged by determining the width of the molten pool at the position and evaluating the difference in the widths of the molten pools. Further, among the data of the length and / or the width of the molten pool stored in the shape data 32b, the fluctuation amount is obtained from the difference between the maximum value and the minimum value of the data stored within the latest predetermined period. Therefore, the quality of laser welding may be judged from the magnitude of the change over time in the length of the molten pool and / or the width of the molten pool within the latest predetermined period. In addition to these, the quality of the laser welding may be judged by evaluating the inclination of the temperature in the solid-liquid region separated from the irradiation position of the laser beam L by a specific distance or more. In this case, if the quality of the laser welding is not judged to be good in all the judgments, it may be regarded as a defect. Further, it may be acceptable as long as the quality of the laser welding is judged to be good by at least one of all the judgments. In addition, at least two of the first to fifth embodiments may be combined so as to be another combination.

Further, even when the molten pool is specified by the brightness, it may be carried out in combination with any of the first to fifth embodiments. Further, it may be carried out in combination with at least two of the first to fifth embodiments. For example, the penetration depth may be estimated from the length and / or the width of the molten pool, thereby determining the quality of the laser welding. In addition, the quality of laser welding may be determined by determining the widths of the molten pools at a plurality of positions in the region containing the metal in a liquid state and evaluating the difference in the widths of the molten pools. Further, among the data of the length and / or the width of the molten pool stored in the shape data 32b, the fluctuation amount is obtained from the difference between the maximum value and the minimum value of the data stored within the latest predetermined period. Then, the quality of the laser welding may be judged from the magnitude of the change over time in the length of the molten pool and / or the width of the molten pool. In addition to these, the quality of the laser welding may be judged by evaluating the inclination of the temperature in the solid-liquid region separated from the irradiation position of the laser beam L by a specific distance or more. In this case, if the quality of the laser welding is not judged to be good in all the judgments, it may be regarded as a defect. Further, it may be acceptable as long as the quality of the laser welding is judged to be good by at least one of all the judgments. In addition, at least two of the first to fifth embodiments may be combined so as to be another combination.

In the first embodiment, the distance from the laser center position to the end of the molten pool on the A1 side is determined as the length of the molten pool, but the length is not limited to this. For example, the distance from the end on the A1 side of the molten pool to the end on the A2 side (the length of the solid-liquid region) may be the length of the molten pool. This is because the length of the solid-liquid region also correlates with the penetration depth.

In the first embodiment, the penetration depth is estimated from the length of the molten pool, and the quality of the laser welding is determined from the penetration depth, but the quality is not limited to this. For example, data indicating the relationship between the length of the molten pool and the quality of laser welding is stored in the determination data 31b, and the measured length of the molten pool is within an appropriate range in which the quality of laser welding is good. If so, the quality of laser welding may be judged to be good. Since there is a correlation between the length of the molten pool and the depth of penetration, and there is a correlation between the depth of penetration and the quality of laser welding, there is also a correlation between the length of the molten pool and the quality of laser welding. Because it can be said that there is. Similarly, regarding the width of the molten pool, data indicating the relationship between the width of the molten pool and the quality of laser welding is stored in the determination data 31b, and the measured width of the molten pool is the quality of laser welding. The quality of laser welding may be judged to be good if it is within an appropriate range that is good.

In the above embodiment, the laser welding apparatus S determines the quality of laser welding, but the quality is not limited thereto. For example, in the laser welding quality determination device used together with the laser welding device S, the quality of the laser welding may be determined. Specifically, the laser welding quality apparatus includes at least an infrared camera 19 and an arithmetic processing apparatus 20, and the arithmetic processing apparatus 20 identifies a molten pool from the inclination of the temperature distribution of the temperature distribution data 32a captured by the infrared camera 19. Then, the penetration depth may be estimated from the length and / or width of the molten pool, and the quality of laser welding may be judged from the penetration depth. In addition, the quality of laser welding may be determined by determining the widths of the molten pools at a plurality of positions in the region containing the metal in a liquid state and evaluating the difference in the widths of the molten pools. Further, among the data of the length and / or the width of the molten pool stored in the shape data 32b, the fluctuation amount is obtained from the difference between the maximum value and the minimum value of the data stored within the latest predetermined period. Then, the quality of the laser welding may be judged from the magnitude of the change over time in the length of the molten pool and / or the width of the molten pool. In addition to these, the quality of the laser welding may be judged by evaluating the inclination of the temperature in the solid-liquid region separated from the irradiation position of the laser beam L by a specific distance or more. In this case, if the quality of the laser welding is not judged to be good in all the judgments, it may be regarded as a defect. Further, it may be acceptable as long as the quality of the laser welding is judged to be good by at least one of all the judgments.

S Laser Welding Device 10 Laser Oscillator (Part of Laser Irradiation Means)
11 Optical fiber (part of laser irradiation means)
12 Fiber adapter (part of laser irradiation means)
16 Laser processing head (part of laser irradiation means)
19 Infrared camera (measuring means)
S Laser welding device S2 (Inclination determination means)
S3 (state identification means)
S5 (Melting pond identification means)
S7 (judgment means)

Claims (9)

A laser welding device that irradiates a metal with a laser beam to weld the metal.
A laser beam irradiating means that oscillates a laser beam and irradiates the metal with the laser beam while changing the position relative to the metal.
A measuring means for measuring a distribution of a predetermined physical quantity that varies depending on the state of the metal in a predetermined region of the metal irradiated with the laser beam by the laser beam irradiating means.
An inclination determining means for determining an inclination, which is an amount of change in the predetermined physical quantity at each position, based on the distribution of the predetermined physical quantity in the predetermined region measured by the measuring means.
A state identification means for discriminating between a solid region, which is a region of metal only in the solid state, and a region containing metal in the liquid state, based on the inclination determined by the inclination determining means.
A molten pool identifying means for identifying a region containing the metal in the liquid state identified by the state identifying means as a molten pool,
A laser welding apparatus comprising: a determination means for determining the quality of laser welding by evaluating the molten pool specified by the molten pool specifying means. The laser welding apparatus according to claim 1, wherein the predetermined physical quantity is a temperature. The state identifying means specifies a position in the predetermined region where the inclination of the distribution of the predetermined physical quantity changes, thereby forming a solid-liquid region which is a region containing a metal in a liquid state and a metal in a solid state, and the solid. The laser welding apparatus according to claim 1 or 2, wherein the laser welding apparatus is characterized by distinguishing from a region. The determination means is the length of the region containing the metal in the liquid state in the direction orthogonal to the direction in which the laser beam moves relative to the metal and / or the direction in which the laser beam moves relative to the metal. The laser welding apparatus according to any one of claims 1 to 3, wherein the molten pool is evaluated by evaluating the length of the region containing the metal in the liquid state. The determination means determines the length of the region containing the metal in the liquid state in the direction in which the laser light moves relative to the metal as the laser light moves relative to the metal over time. The laser welding apparatus according to any one of claims 1 to 4, wherein the molten pool is evaluated by evaluating a change over time. The determination means is the length of the region containing the metal in the liquid state in the direction orthogonal to the direction in which the laser beam moves relative to the metal at at least two positions in the region containing the metal in the liquid state. The laser welding apparatus according to any one of claims 1 to 5, wherein the molten pool is evaluated by evaluating the difference between the two. The determination means is at a predetermined distance from the irradiation position of the laser beam, and the laser beam is directed to the metal at a predetermined position in the region containing the metal in the liquid state, which moves on the metal as the irradiation position moves. Claims 1 to 6, wherein the molten pool is evaluated by evaluating a change over time in the length of the region containing the metal in the liquid state in a direction orthogonal to the direction of relative movement. The laser welding apparatus according to any one. The determination means has a predetermined physical quantity at one position and a position around the one position in a region containing a metal in a liquid state, which is separated from a laser beam irradiation position by a specific distance or more. The laser welding apparatus according to any one of claims 1 to 7, wherein the molten pool is evaluated by evaluating the presence or absence of the one position where the difference is equal to or more than a predetermined amount. A laser welding quality determination device that irradiates a metal with laser light while changing its relative position with the metal and determines the quality of laser welding performed by the laser welding device that welds the metal.
A measuring means for measuring the distribution of a predetermined physical quantity that varies depending on the state of the metal in a predetermined region of the metal irradiated with the laser beam by the laser welding apparatus.
An inclination determining means for determining an inclination, which is an amount of change in the predetermined physical quantity at each position, based on the distribution of the predetermined physical quantity in the predetermined region measured by the measuring means.
A state identification means for discriminating between a solid region, which is a region of metal only in the solid state, and a region containing metal in the liquid state, based on the inclination determined by the inclination determining means.
A molten pool identifying means for identifying a region containing the metal in the liquid state identified by the state identifying means as a molten pool, and a molten pool identifying means.
A laser welding quality determining apparatus comprising: a determining means for determining the quality of laser welding by evaluating the molten pool specified by the molten pool specifying means.

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