Patent Application
20230311243
The present disclosure relates to a laser welding method and a laser welding device.
A technology for performing laser welding of a plurality of metallic members, such as rectangular wires, is known (for example, Japanese Patent No. 6674588).
As far as laser welding of metallic members, which are not limited to rectangular wires, is concerned; in case voids get formed inside the welded part, then the required joint strength cannot be achieved. Moreover, even if an appearance inspection is done, it is difficult to check the presence or absence of voids.
In that regard, it is desirable to provide a new and improved laser welding method and a new and improved laser welding device that, for example, enable holding down the formation of voids.
In some embodiments, a laser welding method includes: forming a molten weld pool by emitting laser light including a main power region and a sub-power region onto a workpiece, the main power region including at least one main beam, the sub-power region including at least one sub-beam having a lower power density than power density of the main beam; and solidifying the molten weld pool. The sub-beam is emitted onto the workpiece such that a void formed inside the molten weld pool escapes to outside of the molten weld pool before the molten weld pool becomes solidified.
In some embodiments, a laser welding device includes: a laser oscillator; and an optical head configured to emit laser light radiated from the laser oscillator, onto a workpiece. The laser light includes at least one main beam and includes at least one sub-beam having lower power density than power density of the main beam, and the laser light is emitted such that molten weld pool is formed on the workpiece, and the sub-beam is emitted onto the workpiece such that a void formed inside the molten weld pool escapes to outside of the molten weld pool before the molten weld pool becomes solidified.
The above and other objects, features, advantages and technical and industrial significance of this disclosure will be better understood by reading the following detailed description of presently preferred embodiments of the disclosure, when considered in connection with the accompanying drawings.
Exemplary embodiments of the disclosure are described below. The configurations explained in the embodiments described below as well as the actions and the results (effects) attributed to the configurations are only exemplary. The disclosure can be implemented also using some different configuration than the configurations disclosed in the embodiments described below. Meanwhile, according to the disclosure, it becomes possible to achieve at least one of various effects (including secondary effects) that are attributed to the configurations.
The embodiments described below include identical constituent elements. In the following explanation, the identical constituent elements are referred to by the same reference numerals, and their explanation is not given in a repeated manner.
Moreover, in the drawings, the X direction is indicated by an arrow X, the Y direction indicated by an arrow Y, and the Z direction is indicated by an arrow Z. The X direction, the Y direction, and the Z direction intersect with each other and are orthogonal to each other. The Z direction is the direction of extension of a plurality of members constituting a workpiece W. Herein, although the Z direction is oriented substantially vertically upward, it can alternatively be inclined with respect to the vertically upward direction.
In the present written description, ordinal numbers are assigned only for convenience and with the aim of differentiating among the components, among the parts, and among the directions. Thus, the ordinal numbers do not indicate the priority or the sequencing.
The laser welding device 100 emits laser lights L onto the outer surface of the workpiece W that is to be laser-welded. Due to the energy of the laser lights L, the workpiece W undergoes partial melting and then becomes cool and solidified. As a result, the workpiece W gets welded. The workpiece W includes a plurality of members. Thus, when the workpiece W is subjected to laser welding, the members get jointed together.
Each of the members constituting the workpiece W can be manufactured using, for example, the following: a copper based metallic material such as copper or a copper alloy; an aluminum based metallic material such as aluminum or an aluminum alloy; a nickel based metallic material such as nickel or a nickel alloy; an iron based metallic material such as iron or an iron alloy; or titanium based metallic material such as titanium or a titanium alloy. Herein, the members can be made of the same metallic material, or can be made of mutually different materials. Meanwhile, the members constituting the workpiece W may or may not be conducting bodies.
The laser device 110 includes a laser oscillator and, as an example, is configured to output a single-mode laser light having the power of few kW. Alternatively, for example, the laser device 110 can include a plurality of internal semiconductor laser devices and can be configured in such a way that the semiconductor laser devices collectively output a single-mode laser light having the power of few kW. Moreover, the laser device 110 can include various types of laser light sources such as fiber lasers, YAG lasers, and disk lasers. Furthermore, for example, the laser device 110 outputs the laser light having the wavelength equal to or greater than 400 [nm] and equal to or smaller than 1200 [nm].
The optical fiber 130 is optically connected to the laser device 110 and the optical head 120. In other words, the optical fiber 130 guides the laser light, which is output from the laser device 110, to the optical head 120. When the laser device 110 outputs a single-mode laser light, the optical fiber 130 is configured to propagate the single-mode laser light. In that case, the M2 beam quality of the single-mode laser light is set to be equal to or smaller than 1.3. The M2 beam quality can also be called the M2 factor.
The optical head 120 is an optical device meant for emitting the laser light, which is input from the laser device 110, toward the workpiece W. The optical head 120 includes a collimator lens 121, a collecting lens 122, a mirror 123, a diffractive optical element (DOE) 125, and a galvanic scanner 126. The collimator lens 121, the collecting lens 122, the mirror 123, the DOE 125, and the galvanic scanner 126 are also called optical components.
The collimator lens 121 collimates each laser light input via the optical fiber 130. The laser lights subjected to collimation represent collimated lights.
The mirror 123 reflects the laser lights representing the collimated lights obtained at the collimator lens 121, and directs the reflected lights toward the galvanic scanner 126. Meanwhile, in between the mirror 123 and the galvanic scanner 126, the DOE 125 is installed. Regarding the DOE 125, the explanation is given later.
The galvanic scanner 126 includes a plurality of mirrors 126a and 126b, and controls the angles of the mirrors 126a and 126b so as to change the direction of radiation of the laser lights L from the optical head 120. That enables changing the position of irradiation of the laser lights L onto the outer surface of the workpiece W. The angles of the mirrors 126a and 126b can be changed by, for example, a motor (not illustrated) that is controlled by the controller 200. While radiating the laser lights L, when the direction of radiation of the laser lights L is changed, it becomes possible to sweep the laser lights L at the outer surface of the workpiece W.
The collecting lens 122 collects the laser lights coming from the galvanic scanner 126 in the form of the collimated lights, and emits the collected laser lights as the laser lights L (the output light) toward the workpiece W.
Meanwhile, the optical components included in the optical head 120 are not limited to the optical components explained above, and can also include other optical components.
The driving mechanism 140 changes the relative position of the optical head 120 with respect to the workpiece W. For example, the driving mechanism 140 includes: a rotation mechanism such as a motor; a deceleration mechanism for decelerating the rotation output of the rotation mechanism; and a motion conversion mechanism for converting the post-deceleration rotation, which has been decelerated by the deceleration mechanism, into the linear motion. The controller 200 can control the driving mechanism 140 in such a way that the relative position of the optical head 120 changes with respect to the workpiece W in the X direction, the Y direction, and the Z direction. The driving mechanism 140 can change (switch) the workpiece W to be subjected to laser welding, from among a plurality of workpieces W supported by a support mechanism (not illustrated). Moreover, the driving mechanism 140 can change the position of irradiation of the laser lights L onto the workpiece W. Furthermore, the driving mechanism 140 can be used in changing the point of irradiation accompanying a change in the direction of irradiation of the laser lights with respect to the workpiece W. Moreover, while the laser lights L are being emitted onto the outer surface of the workpiece W, the driving mechanism 140 can change the position of irradiation. That is, the driving mechanism 140 is capable of sweeping the laser lights L at the outer surface of the workpiece W.
The sensor 150 detects the temperature of a molten weld pool that gets formed on the workpiece W due to the irradiation of the laser lights L. Examples of the sensor 150 include a radiation thermometer or an infrared thermography camera.
The controller 200 controls the operations of the laser device 110, the driving mechanism 140, and the galvanic scanner 126 based on the detection result obtained by the sensor 150. The laser device 110, the driving mechanism 140, and the galvanic scanner 126 are capable of changing the irradiation state of the laser lights L that are emitted from the optical head 120 onto the workpiece W. That is, the laser device 110, the driving mechanism 140, and the galvanic scanner 126 represent an example of a variation causing mechanism and can be referred to as the control targets for the controller 200.
Both members 20 extend in the Z direction and have an end portion 20a (21a and 22a). The end portions 20a expand while intersecting with the Z direction. That is, the end portions 20a extend in the X direction and the Y direction. Herein, the Z direction represents an example of a first direction.
Both members 20 are placed adjacent to each other in the X direction that intersects with the Z direction, and are arranged along the X direction. In between the side faces 21b and 22b (20b) that face each other in the X direction, a gap g is formed. The size of the gap g is equal to or greater than zero. That is, the members 20 can be at least in partial contact with each other. Herein, the X direction represents an example of a second direction.
In the first embodiment, it is assumed that there a misalignment δ equal to or greater than zero between the end portion 21a of the member 21 and the end portion 22a of the member 22 in the Z direction. Herein, of the two members 20 placed in such a relative positional relationship, the end portion 21a that is either at the same position as the position of the end portion 22a in the Z direction or at a misalignment with respect to the end portion 22a in the Z direction represents an example a first end portion; and the end portion 22a that is at a misalignment with respect to the end portion 21a in the opposite direction of the Z direction represents an example of a second end portion. The member 21 that includes the end portion 21a represents an example of a first member, and the member 22 that includes the end portion 22a represents an example of a second member. The member 21 (the first member) can also referred to as a relatively-projecting member in the Z direction, and the member 22 (the second member) can also referred to as a relatively-recessed member.
At the time of welding the workpiece W, that is, welding the two members 20, the optical head 120 emits the laser lights L toward the end portions 20a. The direction of irradiation of the laser lights L is either in the opposite direction of the Z direction or in a direction that is inclined with respect to the opposite direction of the Z direction.
Meanwhile, as explained earlier, the optical head 120 includes the DOE 125 that performs shaping of the shapes of the beams (hereinafter, called the beam shape) of the laser lights.
The DOE 125 divides a collimated laser light into a plurality of beams.
The DOE 125 divides the laser light into a plurality of beams. The divided beams include at least one beam B1 and at least one beam B2. The beam B2 has a lower power density than the power density of the beam B1. Herein, the beam B1 represents an example of a main beam, and the beam B2 represents an example of a sub-beam. Moreover, the beam B1 constitutes a main power region, and the beam B2 constitutes a sub-power region.
In the example illustrated in
In the example illustrated in
In the example illustrated in
In the example illustrated in
Firstly, as illustrated in
In that case, there are times when voids V are formed inside the molten weld pool 23W. The voids V lead to a decline in the welding strength attributed to the welded part 23. Hence, it is desirable that the voids V are no more present in the solidified state.
The laser lights L can be swept in the emitted state.
In this way, it is a known fact that, when the laser lights L1 and L2 are linearly swept, the voids V in the molten weld pool 23 become smaller. That is believed to be possible because of being able to hold down the disturbance in the flow of the fluid metallic material inside the fluid molten weld pool 23W. Moreover, as a result of performing to-and-fro linear sweeping, the heat energy can be applied as needed to a wider area of the molten weld pool 23W, thereby making it possible to hold down the occurrence of regional cooling and solidification of the molten weld pool 23W.
As illustrated in
In the conventional technology, as indicated by the dashed line, a temperature Tr of the molten weld pool 23W drops to a melting temperature Tm at a timing ter. In contrast, in the first embodiment, as indicated by the solid line, the temperature T1 of the molten weld pool 23W drops to the melting temperature Tm at a timing tel that arrives later than the timing ter. At a temperature higher than the melting temperature Tm, the molten weld pool 23W is in the molten state. Herein, the temperature T1 represents the temperature during the formation process for forming the molten weld pool 23W and, as an example, is equal to the maximum temperature during the formation process.
As is clear from
Moreover, in the first embodiment, the speed of the temperature drop after the timing t1 is slower (lower) as compared to the conventional technology. That too is attributed to the fact that the laser light L includes the beams B1 and B2 as illustrated in
In the molten state of the molten weld pool 23W, that is, in the fluid state of the molten weld pool 23W, the voids V representing air bubbles in the molten weld pool 23W rise upward inside the molten weld pool 23W and escape to the outside of the molten weld pool 23W. Hence, longer the period of time for which the molten weld pool 23W is in the molten state, a greater number of voids V are discharged out of the molten weld pool 23W. Consequently, there is a decrease in the number of voids V remaining in the solidified welded part 23. In that regard, as explained earlier, according to the first embodiment, since the laser light L includes the beams B1 and B2, the temperature drop period Δt1 becomes longer as compared to the case of using a single beam. Accordingly, the molten weld pool 23W can be maintained in the molten state for a longer period of time. Hence, according to the first embodiment, the welded part 23 can be formed in which the number of voids V is smaller.
According to the study undertaken by the inventors, it was confirmed that, when the beams B1 and B2 were placed as illustrated in
According to the first embodiment, the placement and the power density of the beams B1 and B2 is set in such a way that the required temperature T1 of the molten weld pool 23W can be secured that enables at least one of the voids V to escape to the outside of the molten weld pool 23W, and the temperature drop period Δt1 (=te1-t1) can be secured that is required for the temperature T1 to drop to the melting temperature Tm. Meanwhile, the temperature T1 and the temperature drop period Δt1 differ according to the material, the environmental heat dissipation, and the ambient temperature.
The rectangular wire 10 can constitute a coil installed in a rotating electrical machine such as a motor or a motor generator. The laser welding method implemented in the laser welding device 100 according to the first embodiment can be used in welding the end portions of mutually adjacent coils that are set in a stator core.
However, the members 20 to be treated as the workpiece W are not limited to the cores of the rectangular wires 10. Alternatively, as illustrated in
In this way, the laser light L, particularly the beam B2 is appropriately set in such a way that the number of voids V present in the lower half Rl is equal to or smaller than the number of voids V present in the upper half Ru.
As a result, it becomes possible to have the required joint strength and the required electrical conductivity, and to form the welded part 23 having a smaller number of voids V. Meanwhile, in the example illustrated in
As explained above, in the laser welding method and the laser welding device 100 according to the first embodiment, the beam B2 (sub-beam) is emitted onto the workpiece W in such a way that at least one of the voids V, which are formed in the molten weld pool 23 before the solidification of the molten weld pool 23W, escapes to the outside of the molten weld pool 23. Moreover, the beam B1 (main beam) and the beam B2 (sub-beam) are set in such a way that the molten weld pool 23W is formed on the workpiece W and that the temperature of the molten weld pool 23W undergoes temporal change to ensure escape of at least one of the voids V formed in the molten weld pool 23W.
Thus, according to the first embodiment, it becomes possible to reduce a greater number of voids V from the welded part 23. As a result, it becomes possible to hold down any decline in the strength of the welded part 23 as caused by the voids V.
Each of the laser devices 111 and 112 (110) includes a laser oscillator. In the second embodiment, the laser devices 111 and 112 output laser lights having different wavelengths.
The laser device 111 outputs first-type laser lights having the wavelength equal to or greater than 800 [nm] and equal to or smaller than 1200 [nm]. The laser device 111 can also be called a first laser device, and the laser oscillator of the laser device 111 can also be called a first laser oscillator.
The laser device 112 outputs second-type laser lights having the wavelength equal to or smaller than 550 [nm]. The laser device 112 can also be called a second laser device, and the laser oscillator of the laser device 112 can also be called a second laser oscillator. Moreover, as an example, the laser device 112 includes a semiconductor laser (element) as a laser light source. Meanwhile, the laser device 112 can output laser light having the wavelength equal to or greater than 400 [nm] and equal to or smaller than 500 [nm].
Along with the installation of the laser device 112, a filter 124 is disposed in the optical head 120A. The first-type laser lights reflect from the mirror 123 and travel toward the filter 124 in the opposite direction of the X direction. Meanwhile, in a configuration in which the first-type laser lights are so input that they travel in the opposite direction of the X direction in the optical head 120A, the mirror 123 is not required.
The filter 124 is, for example, a high-pass filter that transmits the first-type laser lights but that reflects the second-type laser lights without transmitting them. The first-type laser light passes through the filter 124 and travels toward the galvanic scanner 126. The filter 124 reflects the second-type laser lights in the form of the collimated lights obtained at the collimator lens 121-2. After getting reflected from the filter 124, the second-type laser lights also travel toward the galvanic scanner 126.
The filter 127 is disposed in between the mirror 123 and the filter 124. The filter 127 transfers the first-type laser lights, which are coming from the mirror 123, toward the filter 124, and reflects the light that has come from the outer surface Wa of the workpiece W (see
Meanwhile, in the second embodiment too, the DOE 125 is installed. The DOE 125 is placed in between the collimator lens 121-2 and the filter 124, and performs shaping of the beams of the second-type laser lights. Alternatively, the optical head 120A can include a DOE that performs shaping of the beams of the first-type laser lights.
Meanwhile, in the laser welding device 100A, the sensor 150 can replaced by the sensor 150 according to the first embodiment. Alternatively, the laser welding device 100 can include the sensor 150 attached to the body of the optical head 120 as explained in the second embodiment.
Given below is the explanation of the absorption rates of metallic materials.
Although different materials exhibit different properties, as far as the metals illustrated in
When the laser light is emitted onto the workpiece W having a relatively lower absorption rate with respect to the used wavelength, the major part of the optical energy gets reflected and does not affect the workpiece W in the form of heat. For that reason, in order to obtain a sufficiently deep welded part, a relatively greater amount of power needs to be applied. In that case, since the energy is rapidly input into the central portion of the beam, it results in sublimation and a keyhole gets formed.
On the other hand, when the laser light is emitted onto the workpiece W having a relatively higher absorption rate with respect to the used wavelength, the major part of the input energy gets absorbed in the workpiece W and is converted into heat energy. In that process, if laser light having a low power density is emitted, it results in melting of the heat conduction type.
Using the optical head 120A according to the second embodiment, the workpiece W can be emitted with the laser lights L that have the beams B1 attributed to the first-type laser lights coming from the laser device 111 and have the beams B2 attributed to the second-type laser lights coming from the laser device 112.
From the explanation given above, by ensuring that the first-type laser lights having the wavelength equal to or greater than 800 [nm] and equal to or smaller than 1200 [nm] are output and that the second-type laser lights having the wavelength equal to or smaller than 500 [nm] are output, and by emitting the second-type laser lights after the workpiece W has melted due to the first-type laser lights; the heat energy can be efficiently applied to the molten weld pool 23W. Hence, it becomes possible to efficiently hold down the occurrence of regional cooling and solidification of the molten weld pool 23W. Meanwhile, in order to emit the second-type laser lights after the workpiece W has melted due to the first-type laser lights, as explained later, the time slots for emitting the first-type laser lights and the time slots for the second-type laser lights can be individually controlled. Alternatively, with respect to the first-type laser lights, at the back of the sweeping direction of the laser light L, at least some past of the second-type laser lights can be emitted. At that time, it can be ensured that there is at least partial overlapping between the region of irradiation of the first-type laser lights and the region of irradiation of the second-type laser lights.
The controller 200 can control the operations of the laser device 111 as well as the operations of the laser device 112. That is, the controller 200 can independently control the time slots for radiation of the first-type laser lights, that is, the beams B1 from the laser device 111, and independently control the time slots for radiation of the second-type laser lights, that is, the beams B2 from the laser device 112.
As illustrated in
In between the timing t0 and the timing t2, the laser lights L include the beams B1 and B2. As a result of irradiation of the laser lights L onto the workpiece W during that period of time, the molten weld pool 23W is formed. That is, in the laser welding method according to the second embodiment, the formation process of the molten weld pool 23W is carried out between the timing t0 and the timing t2.
In the period of time from the timing t2 to the timing tk, the beam B1 is not included in the laser lights L and only the beam B2 is included. Hence, the output of the laser lights L is lower than the output during the period of time from the timing t0 to the timing t2 in which the beams B1 and B2 are included. During that period, the laser lights L are set in such a way that the irradiation of the laser lights L onto the molten weld pool 23W enables maintaining the molten state of the molten weld pool 23W. That is, in the laser welding method according to the second embodiment, during the period of time from the timing t2 to the timing tk, a process (hereinafter, called a maintenance process) is carried out in which, the specifications are set in regard to the irradiation of the laser lights L and the beams B1 and B2, such as the shape of the beams B1 and B2, the placement, the power density, the irradiation position, the sweeping route, and the sweeping speed. With that, the molten state of the molten weld pool 23W is temporarily maintained while holding down further formation and expansion of the molten weld pool 23W and while also holding down solidification of the molten weld pool 23W. The maintenance process can also be referred to as an extension process.
As is clear from
Moreover, when the laser light L is emitted onto the molten weld pool 23W, on the outer surface of the molten weld pool 23W, an indent is formed in the region emitted with the laser light L (an indent in the opposite direction to the Z direction, hereinafter simply called the indent). According to the study undertaken by the inventors, it was found that, if the indent formed due to the irradiation of the laser light L during the maintenance process is shallower than the indent formed due to the irradiation of the laser light L during the process of forming the molten weld pool 23W, then it becomes possible to perform welding having a better quality and having less sputtering and less voids V. The indent becomes deeper according to the power density. Hence, it is implied that the power density of the laser light L on the outer surface of the molten weld pool 23W during the maintenance process is preferably lower than the power density of the laser light L on the outer surface of the molten weld pool 23W during the process of forming the molten weld pool 23W.
With reference to
According to the experimental study conducted by the inventors, it was found that there is an optimum range for the power density [W/cm2] of the laser light L, which is emitted during the maintenance process, on the outer surface of the molten weld pool 23W.
In Table 1 is illustrated the determination result that was obtained as a result of carrying out an experiment regarding a plurality of samplers having different power densities of the laser light and that indicates the welding quality based on the number of voids V present in the molten weld pool 23W according to the range of the power density. In the measurement of the number of voids V, such voids V are counted which have the diameter equal to or greater than 100 [µm] within a single cross-sectional surface viewed from a side face of a post-welding sample. In the determination, “excellent” indicates that the number of voids is equal to or smaller than 10; “good” indicates that the number of voids V is greater than 10 but equal to or smaller than 20; “manageable” indicates that the number of voids V is greater than 20 but equal to or smaller than 30; and “poor” indicates the number of voids V is greater than 30.
As illustrated in Table 1, it was found that a power density Pd is preferably equal to or lower than 107 [W/cm2] and is more preferably equal to or lower than 106 [W/cm2]. That is because, if the power density Pd is too high, it can be estimated that a keyhole gets formed in the molten weld pool 23W and there is an increase in sputtering and in turn an increase in the number of voids V.
Moreover, it was found that the power density Pd is preferably equal to or higher than 103 [W/cm2] and is more preferably higher than 104 [W/cm2]. That is because, if the power density Pd is too low, it can be estimated that the molten state of the molten weld pool 23W cannot be sufficiently maintained, and that the molten weld pool 23W gets solidified more quickly.
As explained above, in the laser welding method and the laser welding device 100A according to the second embodiment, after the process of forming the molten weld pool 23W (i.e., the formation process), it is possible to perform the process of temporarily maintaining the molten weld pool 23W in the molten state by emitting the laser lights L1 and L2 (L) onto the molten weld pool 23W (i.e., the maintenance process).
Thus, according to the second embodiment, it becomes possible to further reduce the voids V in the welded part 23, and further hold down a decline in the strength of the welded part 23 as caused by the voids V.
Moreover, according to the second embodiment too, as the effect of the maintenance process, it becomes possible to achieve the state in which the number of voids V present in the lower half R1 in the molten part 23 becomes equal to or smaller than the number of voids V present in the upper half Ru.
The controller 200 is a computer that includes a processor (circuit) such as a central processing unit (CPU); and main memory units such as a random access memory (RAM) and a read only memory (ROM). The controller 200 is, for example, a micro controller unit (MCU). The memory unit 210 includes a nonvolatile memory device such as a solid state drive (SSD) or a hard disk drive (HDD). The controller 200 is an example of a controller. The memory unit 210 can also be referred to as an auxiliary memory device.
The processor reads computer programs stored in the ROM or the memory unit 210, and executes operations so as to operate as an irradiation control unit 201, a detection control unit 202, a determining unit 203, an output control unit 204, and a parameter changing unit 205. The computer programs can be recorded as installable files or executable files in a computer-readable recording medium. The recording medium can also be called a computer program product. The computer programs, the values used in the arithmetic operations performed by the processor, and information such as tables and maps either can be stored in advance in a ROM or the memory unit 210, or can be stored in a memory unit of a computer connected to a communication network and can be downloaded into the memory unit 210 via the communication network. The memory unit 210 is used to store the data written by the processor. Meanwhile, the arithmetic operations performed by the controller 200 can be at least partially implemented using hardware. In that case, the controller 200 can include, for example, a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC).
The output portion 220 is a device capable of outputting information indicating determination results in the form of sounds or images. Examples of the output portion 220 include a monitor (display), a speaker, a buzzer, and a printer. Alternatively, the output portion 220 can be a communication unit that outputs the determination results to devices on the outside of the controller 200.
Subsequently, the controller 200 functions as the detection control unit 202 and detects the temperature of the molten weld pool 23W (S12). At S12, for example, the detection control unit 202 either can detect the maximum temperature of the molten weld pool 23W or can detect the temperature of the molten weld pool 23W corresponding to at least one timing since the elapse of a predetermined period of time from the irradiation start timing (i.e., the timing t0) .
Then, the controller 200 functions as the determining unit 203 and determines the quality of the welded part 23 based on the temperature detection result (S13). At S13, the determining unit 203 determines the quality according to a predetermined determination criterion. For example, if the detected temperature at a predetermined point of time is equal to or higher than a threshold value corresponding to that predetermined point of time, then the determining unit 203 determines that the quality of the welded part 23 is good. However, if the detected temperature is lower than the threshold value, then the determining unit 203 determines that the quality of the welded part 23 is poor. The threshold temperature corresponding to the correctness of the determination result, and the examination timing are set in advance from the experimental result.
Subsequently, the controller 200 functions as the output control unit 204 and controls the output portion 220 in such a way that the determination result is output in a predetermined output format (S14).
Then, the controller 200 functions as the parameter changing unit 205 and, according to the determination result, changes the variable control parameters related to the irradiation of the laser lights L (S15). At S15, examples of the variable control parameters include the output of the laser device 110, the output period of the laser device 110, the output period of the beam B1, and the output period of the beam B2. The parameter changing unit 205 stores the changed values of the parameters in the memory unit 210. At the time of performing identical laser welding from the next time onward, the controller 200 reads the control parameters stored in the memory unit 210, and controls the control targets including the laser device 110, the galvanic scanner 126, and the driving mechanism 140 in such a way that laser welding is performed according to the stored control parameters, that is, according to the changed control parameters.
Meanwhile, at S21, the controller 200 can perform feedback control of the control targets (the variation causing mechanism) including the laser device 110, the galvanic scanner 126, and the driving mechanism 140 so as to ensure that the temperature of the molten weld pool 23W is maintained at a predetermined temperature or undergoes transition according to a predetermined temporal change.
Then, the controller 200 functions as the determining unit 203 and determines whether or not a predetermined condition (a first condition) regarding the formation process of the molten weld pool 23W is satisfied (S22). At S22, for example, based on the temporal change in the temperature of the molten weld pool 23W, if the period of time having the temperature equal to or higher than a first threshold temperature continues for a first threshold time period or beyond, then the determining unit 203 determines that the first condition is satisfied. As a result, the molten weld pool 23W and the members 20 can be brought to such a state in which it becomes possible to secure the temperature drop periods Δt1 and Δt2 at a sufficient level for enabling the escape of the voids V.
If the first condition is not satisfied (No at S22), then the formation process at S21 is continued for forming the molten weld pool 23W. When the first condition is satisfied (Yes at S22), the flow of operations is ended with respect to the laser welding device 100 according to the first embodiment. As far as the laser welding device 100A according to the second embodiment is concerned, the system control proceeds to S23.
At S23, the controller 200 functions as the irradiation control unit 201 and controls the control targets including the laser device 110, the galvanic scanner 126, and the driving mechanism 140 in such a way that the laser lights L, for example, only the beams B2 are emitted onto the workpiece W according to a predetermined sequence and the molten state of the molten weld pool 23W is maintained (S23). The operation at S23 represents the maintenance process regarding the molten weld pool 23W. At S23, the controller 200 functions as the detection control unit 202 and detects the temperature of the molten weld pool 23W at predetermined timings, for example, at regular time internals.
Meanwhile, at S23, the controller 200 can perform feedback control of the control targets (the variation causing mechanism) including the laser device 110, the galvanic scanner 126, and the driving mechanism 140 so as to ensure that the temperature of the molten weld pool 23W is maintained at a predetermined temperature or undergoes transition according to a predetermined temporal change.
Subsequently, the controller 200 functions as the determining unit 203 and determines whether or not a predetermined condition (a second condition) regarding the maintenance process of the molten weld pool 23W is satisfied (S24). At S24, for example, based on the temporal change in the temperature of the molten weld pool 23W, if the period of time having the temperature equal to or higher than a second threshold temperature continues for a second threshold time period or beyond, then the determining unit 203 determines that the second condition is satisfied. As a result, it becomes possible to secure the maintenance time period Δtk and in turn to secure the temperature drop period Δt2 sufficient for enabling the escape of the voids V.
If the second condition is not satisfied (No at S24), then the maintenance process at S23 is continued for maintaining the molten weld pool 23W. When the second condition is satisfied (Yes at S24), the flow of operations is ended.
As explained above, according to the second embodiment, the laser welding devices 100 and 100A can include the sensor 150 that detects the temperature of the molten weld pool 23W, and can include the output portion 220 that outputs information indicating the welding quality based on the detection result obtained by the sensor 150.
With such a configuration and such control, the presence or absence of the voids V in the welded part 23 can be examined relatively easily in a non-destructive manner; and the control parameters of the laser welding devices 100 and 100A can be changed based on the determination result about the welding quality. That enables achieving enhancement in the welding quality during laser welding from the next time onward.
Moreover, as explained in the second embodiment, the controller 200 can control the operations of the control targets (the variation causing mechanism) including the laser device 110, the galvanic scanner 126, and the driving mechanism 140 based on the detection result obtained by the sensor 150 that detects the temperature of the molten weld pool 23W.
With such a configuration and such control, the formation of the molten weld pool 23W and the maintenance thereof in the molten state can be performed with a higher degree of accuracy. That offers advantages such as enabling holding down the formation of the voids V in a more reliable manner and reducing unnecessary energy consumption while holding down the formation of the voids V.
While certain embodiments and modification examples have been described, these embodiments and modification examples have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. Moreover, regarding the constituent elements, the specifications about the configurations and the shapes (structure, type, direction, shape, size, length, width, thickness, height, number, arrangement, position, material, etc.) can be suitably modified.
For example, the laser welding device can include a plurality of laser devices (laser light sources) for outputting the laser lights having the same wavelength.
Moreover, for example, at the time of irradiation of the laser light, a known type of wobbling, weaving, and output modulation can be performed, and the surface area of the molten weld pool can be adjusted.
According to the disclosure, for example, it becomes possible to provide a new and improved laser welding method and a new and improved laser welding device that, for example, enable holding down the formation of voids.
Although the disclosure has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-176331 | Oct 2020 | JP | national |
This application is a continuation of International Application No. PCT/JP2021/038448, filed on Oct. 18, 2021 which claims the benefit of priority of the prior Japanese Patent Application No. 2020-176331, filed on Oct. 20, 2020, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2021/038448 | Oct 2021 | WO |
| Child | 18301459 | US |
