JP2022011659A - Welding method - Google Patents

Abstract

To provide a welding method by which, when a laser beam including a first laser beam and a second laser beam having an annular beam shape surrounding the first laser beam is caused to scan along an edge of one side of the matched surfaces of conductor segments, the adverse effect of generated heat on the periphery of the edge is suppressed.SOLUTION: An output of a second laser beam L2 in a 4-2 path and a 5-1 path for causing a laser beam to scan along an edge of one side of matched surfaces is made lower than an output of the second laser beam L2 in a first path to 4-1 path for causing a laser beam to scan along a middle portion of the one side. Heat generated when a laser beam is caused to scan along the edge is transmitted through a conductor wire to an insulating film near the edge and exerts an adverse effect on the insulating film. Therefore, by lowering the output of the second laser beam L2, heat generated when the laser beam is caused to scan along the edge is reduced to suppress the adverse effect of the heat on the insulating film.SELECTED DRAWING: Figure 9

Description

The present disclosure relates to a welding method for welding the mating surfaces of two conductor segments constituting a flat wire coil.

As a welding method for welding the mating surfaces of two conductor segments constituting a flat wire coil, for example, in Patent Document 1, a laser beam is scanned twice in a direction orthogonal to the mating surfaces to weld the mating surfaces. Welding methods are disclosed. Further, as a general laser welding method, in Patent Document 2, a laser beam including a first laser beam and a second laser beam having an annular beam shape surrounding the first laser beam is combined with a welding target. A welding method for welding the mating surface by scanning along one side of the surface is disclosed.

Japanese Unexamined Patent Publication No. 2016-208829 Japanese Unexamined Patent Publication No. 2020-44543

Here, the laser beam including the first laser beam and the second laser beam described in Patent Document 2 is scanned along one side of the mating surface of the conductor segment described in Patent Document 1 to scan the mating surface. Welding method is conceivable. In such a case, in order to increase the welding region of the mating surface and increase the bonding strength of the mating surface, the laser beam including the first laser beam and the second laser beam is applied along the central portion and the end portion of one side of the mating surface. It is desirable to scan with a laser. However, when the laser beam is scanned along the edge, the heat generated during scanning, that is, during welding, may adversely affect the insulating coating of the conductor segment, for example, which is present around the edge.

The present disclosure occurs when a laser beam including a first laser beam and a second laser beam having an annular beam shape surrounding the first laser beam is scanned along one end of a mating surface of a conductor segment. It is an object of the present invention to provide a welding method in which the adverse effect of heat generated on the material existing around the end portion is suppressed.

The welding method according to the present disclosure is a welding method in which a laser beam is scanned along one side of a mating surface of two conductor segments constituting a flat wire coil to weld the mating surface, and the laser beam is the first. A central scanning step comprising one laser beam and a second laser beam having an annular beam shape surrounding the first laser beam and scanning the laser beam along the central portion of the one side of the mating surface. The second laser beam output in the central scanning step is output from the second laser beam in the central scanning step. It should be lower than the output of the laser beam.

According to the welding method according to the present disclosure, the output of the second laser beam when the laser beam is scanned along the end of one side of the mating surface is scanned along the center of the one side of the laser beam. Since the temperature is lower than that of the case where the laser beam is scanned, the heat generated when the laser beam is scanned along the end portion can be reduced, and the adverse effect of the heat on what exists around the end portion can be suppressed.

It is a perspective view of the core and the conductor segment for demonstrating the state of one step of the production method of the stator which uses the welding method which concerns on embodiment of this disclosure. It is a figure which shows the appearance that the leg part of the conductor segment was inserted into the slot of the core in the manufacturing method of the stator which uses the welding method which concerns on embodiment of this disclosure. It is a perspective view which shows the state in which the side surfaces of the tip end portions of two conductor segments are butted against each other, and is the figure which shows the state of scanning the laser beam along one side of the mating surface. It is an elevation view which shows the state in which the side surfaces of the tip portions of two conductor segments are butted against each other, and is the figure which shows the state of scanning the laser beam along one side of the mating surface. It is a figure which shows the beam shape of the 1st laser beam and the 2nd laser beam of a laser beam. It is an elevation view which shows the state of the mating surface at the time of welding by the laser beam of FIG. It is a block diagram which shows the structure of the laser welding apparatus which emits a laser beam of FIG. It is a flowchart of the welding process executed by the laser welding apparatus of FIG. The upper row is a plan view of the side surfaces of the tips of the two conductor segments abutting each other from above, and the lower row is a scanning locus when scanning the laser beam (1st pass to 5-2nd pass). It is a figure which shows. It is a figure which shows the time change of each output of the 1st laser beam and the 2nd laser beam when scanning a laser beam. It is a figure which shows the state when the laser beam which consists only of the 1st laser beam is scanned as a comparative example on one side of the mating surface where a foreign substance exists. It is a figure which shows the state when the laser beam of FIG. 5 is scanned on one side of the mating surface where a foreign substance exists.

Hereinafter, the welding method according to the embodiment of the present disclosure will be described with reference to the drawings. The welding method is used when producing a stator of a rotary electric machine for a vehicle in which a flat wire coil is wound around a core. Hereinafter, the method for producing the stator will be briefly described, and then the welding method according to the present embodiment will be described. The vertical direction in the following description means the central axis direction of the core 11 in FIG.

In the method of producing the stator, as shown in FIG. 1, the conductor segment 14 is inserted from below into the slot 13 between the teeth 12 of the cylindrical core 11. The conductor segment 14 is a component constituting a rectangular wire coil having a rectangular cross section wound around the core 11. The conductor segment 14 has a rectangular cross section and a U-shape, and a pair of parallel legs 14A thereof are inserted into different slots 13. Although two conductor segments 14 are illustrated in FIG. 1, a large number of conductor segments 14 are actually inserted.

As shown in FIG. 2, when the leg portion 14A of the conductor segment 14 is inserted into the slot 13, a part of the leg portion 14A protrudes upward from the core 11. A part of the leg portion 14A protruding from the core 11 is bent, and the tip portion 14B thereof is welded to the tip portion 14B of another conductor segment 14 by the welding method according to the present embodiment. As shown in the broken line circle of FIG. 2, the conductor segment 14 includes a conductor wire 14M and an insulating coating 14N covering the conductor wire 14M. The end portion of the conductor wire 14M is exposed from the insulating coating 14N, and the tip portion 14B welded above refers to the exposed end portion. By sequentially welding the tip portions 14B of the plurality of conductor segments 14 to each other, the conductor segments 14 are electrically connected in series, and a flat wire coil wound around the core 11 is formed.

Next, the welding method according to the present embodiment will be described with reference to FIGS. 3 to 12. In the following description (particularly, the description with reference to FIGS. 3, 4 and 9), the two conductor segments 14 to be welded will be described as conductor segments 15 and 16.

In the welding method according to the present embodiment, as shown in FIGS. 3 and 4, the mating surfaces S (FIG. 4) in which the side surfaces 15C and 16C of the tip portions 15B and 16B of the two conductor segments 15 and 16 are butted against each other. The laser beam L is linearly moved along one side H when viewed from above and scanned. The mating surface S is a mating surface on which the side surface 15C and the side surface 16C overlap. One side H is an upper end edge facing upward of the mating surface S in FIG. 4, and is an upper side from a virtual point A to a virtual point D on the contour of the mating surface S. By scanning the laser beam L, the mating surface S is welded, and the tip portion 15B and the tip portion 16B are electrically connected.

As shown in FIG. 5, the laser beam L has an annular beam shape that surrounds the first laser beam L1 and has the same optical axis as the first laser beam L1 and the first laser beam L1 that have a circular beam shape. A second laser beam L2 having a As shown in FIG. 6, a molten pool 41 is formed on the irradiation locus of the laser beam L. Further, in the present embodiment, the energy density of the second laser beam L2 is lower than the energy density of the first laser beam L1. Since the keyhole becomes deeper as the energy density of the laser beam increases, the portion of the keyhole 42 formed by the irradiation of the laser beam L that is formed by the second laser beam L2 is formed by the first laser beam L1. It is formed shallower than the part to be formed. For this reason, the keyhole 42 formed by irradiation with the laser beam L is formed in a substantially conical shape whose opening is widened by the second laser beam L2 and is convex downward. Note that FIG. 6 is drawn with the vertical direction crushed. The depth of the keyhole 42 relative to the diameter of the actual laser beam L is deeper than that in FIG. 6 (the same applies to FIGS. 11 and 12 described later).

The laser beam L is emitted from, for example, the laser welding apparatus 50 shown in FIG. 7. The laser welding device 50 is, for example, a fiber laser welding device. The laser welding device 50 includes a first oscillating unit 51 that oscillates the first laser beam L1 and a second oscillating unit 52 that oscillates the second laser beam L2. Further, the laser welding apparatus 50 includes a scanning mechanism 53 that scans the laser beam L by moving the irradiation region of the laser beam L. The scanning mechanism 53 scans the laser beam L by moving the beam emitting end connected to the optical fiber that transmits the first laser beam L1 and the second laser beam L2, respectively. The scanning mechanism 53 may be a galvano scanner mechanism. The laser welding device 50 also includes a first oscillating unit 51, a second oscillating unit 52, and a controller 54 that controls the scanning mechanism 53. The controller 54 is composed of a computer or the like, controls for scanning the laser beam L, and individually controls the output of the first laser beam L1 and the output of the second laser beam L2.

The welding method according to the present embodiment is performed by the laser welding apparatus 50 executing the welding process shown in FIG. 8 by the controller 54.

In the welding process shown in FIG. 8, the laser welding apparatus 50 first executes a central portion scanning step of scanning the laser beam L along the central portion H1 of one side H of the mating surface S (step S11). As shown in FIGS. 4 and 9, the central portion H1 is a portion from the virtual point B to the virtual point C on one side H from the virtual point A to the virtual point D, and is separated from the insulating coatings 15N and 16N. .. In the central portion scanning step, the laser beam L is scanned for a plurality of passes in order to form a molten pool 41 (FIG. 6) having a sufficient depth in the central portion H1. Specifically, as shown in FIG. 9, the laser welding apparatus 50 transmits the laser beam L from the virtual point C to the virtual point B (first pass), from the virtual point B to the virtual point C (second pass), and the virtual point. The central portion H1 is repeatedly scanned for a plurality of passes, such as from C to the virtual point B (third pass) and from the virtual point B to the virtual point C (4-1st pass). Since the central portion H1 is separated from the insulating coatings 15N and 16N, the heat generated when the laser beam L is scanned along the central portion H1 (that is, the heat during welding) is the insulating coatings 15N and 16N. Does not adversely affect.

Returning to FIG. 8, the laser welding apparatus 50 executes an end scanning step of scanning the laser beam L along the end H2 of one side H of the mating surface S after the central scanning step (step S11) (step S11). Step S12). The end portion H2 is a portion from the virtual point C to the virtual point D on one side H shown in FIGS. 4 and 9, and is a portion closer to the insulating coating 16N on one side H than the central portion H1. In the end scanning step, the laser welding apparatus 50 scans the laser beam L from the virtual point C to the virtual point D (the 4-2nd pass), and then virtualizes from the virtual point D, as shown in FIG. Scan to point C (5-1st pass). By this scanning, the molten pool 41 (FIG. 6) formed in the central portion H1 is expanded to the end portion H2, the welded portion is set as the central portion H1 and the end portion H2, and the welding region of the mating surface S is enlarged, and the welding region of the mating surface S is increased. Increase joint strength. Note that, unlike the central portion H1, the end portion H2 is close to the insulating coating 16N, and when the laser beam L is scanned along the end portion H2, if it is scanned with the same output as the central portion H1, it will be scanned. Heat may adversely affect the insulating coating 16N. Due to this adverse effect, for example, the insulating coating 16N may be melted or peeled off. Therefore, in order to suppress this adverse effect, the details will be described later, but in the end scanning step in which the laser beam L is scanned along the end H2, the central scanning step in which the laser beam L is scanned along the central H1 Also, the output of the second laser beam L2 is lowered (see the 4-2nd pass and the 5-1st pass in FIG. 10). The 4-1st pass and the 4-2nd pass are collectively scanned as the 4th pass.

Returning to FIG. 8, the laser welding apparatus 50 performs a central portion rescanning step of scanning the laser beam L again along the central portion H1 of one side H of the mating surface S after the end scanning step (step S12). This is executed (step S13), and the welding process is completed. In the central rescanning step, the laser welding apparatus 50 scans the laser beam L from the virtual point C to the virtual point B (pass 5-2), as shown in FIG. The 5-1st pass and the 5-2nd pass are collectively scanned as the 5th pass. As a modification, the laser welding apparatus 50 scans the laser beam L along the end portion H3 from the virtual point A to the virtual point B to the virtual point A or the middle thereof in order to further expand the molten pool 41 (FIG. 6). You may.

When the laser welding apparatus 50 executes the welding process, the laser welding apparatus 50 individually controls the outputs of the first laser beam L1 and the second laser beam L2 of the laser beam L. The time change of each output will be described with reference to FIG. Each output is set so that the energy density of the first laser beam L1 is lower than the energy density of the second laser beam L2, but the area of the former beam shape is smaller than the area of the latter beam shape. Therefore, the output itself shown in FIG. 10 is generally smaller in the former. Further, each output is set by the strength at which a molten pool is formed in the central portion H1 of one side H of the mating surface S in the scanning of the first pass.

As shown in FIG. 10, the laser welding apparatus 50 is the second in the end scanning step (4-2th pass to 5-1th pass of t3 to t4) for scanning the laser beam L along the end H2. The output of the laser beam L2 is P2, which is the output of the second laser beam L2 in the central portion scanning step (1st pass to 4-1st pass of t0 to t3) in which the laser beam L is scanned along the central portion H1. It is set to P1 by making it lower than P3. On the other hand, the laser welding apparatus 50 maintains the output of the first laser beam L1. As described above, the heat generated when the laser beam L is scanned along the central portion H1 does not adversely affect the insulating coatings 15N and 16N, but the laser beam L is scanned along the edge portion H2. Occasionally, the heat generated is transmitted to the insulating coating 16N near the end H2 via the conductor wire 16M, and adversely affects the insulating coating 16N. In particular, when the laser beam L reaches the virtual point D closest to the insulating coating 16N, the heat generated by the outer second laser beam L2 in the laser beam L adversely affects the insulating coating 16N. Due to such an adverse effect, the insulating coating 16N is melted or peeled off. Therefore, by reducing the output of the second laser beam L2 as described above, the heat generated when the laser beam L is scanned along the end portion H2 is reduced, and the adverse effect of heat on the insulating coating 16N is suppressed. By not changing the output of the first laser beam L1, the formation of the molten pool 41 by the first laser beam L1 is ensured. The laser welding apparatus 50 immediately after the 5-1st pass of scanning the laser beam L along the end portion H2, that is, at the start of the 5-2nd pass of scanning the laser beam L along the central portion H1 (time). At t4), the output of the second laser beam L2 is returned to P2, which is the output before the reduction.

The laser welding apparatus 50 increases the output (outputs of t0 to t1) of the second laser beam L2 of the first pass to P3 so that the molten pool 41 (FIG. 6) is surely formed from the first pass. .. Further, the laser welding apparatus 50 reduces the output of the second laser beam L2 from P3 to P2 at the beginning of the second pass (t1 to t2) after the molten pool 41 is formed once, and 4-1 passes. Maintain P2 until the end of the eye (t2-t3). As a result, the second laser beam is formed in the second to 4-1 passes (passes for deepening the depth of the molten pool 41 formed in the first pass) after the molten pool 41 is formed once. The energy density of L2 is reduced, the region formed by the second laser beam L2 in the keyhole 42 is reduced, and the amount of spatter generated is reduced accordingly.

The laser welding apparatus 50 outputs each output of the first laser beam L1 and the second laser beam L2 to the latter half of the 5-2nd pass (central rescanning step), that is, just before the end of scanning of the laser beam L (t5 to ...). In t6), the downslope is controlled to gradually lower the slope. As a result, it is possible to prevent an air pool from being generated when the molten pool 41 cools and hardens. When the laser beam L is scanned up to the end portion H3 as in the above-described modification, the output of the second laser beam L2 is output at the end portion H3 in the 4-2nd pass and the 5-1th pass. It is preferable to reduce the amount to the same level as that of the eyes to suppress the adverse effect on the insulating film 15N.

In FIG. 10, the output of the first laser beam L1 is constant during the period (t0 to t5) from the start of scanning to the downslope control, that is, from the first pass to the middle of the 5-2nd pass. However, the output of the first laser beam L1 may change as appropriate during the period.

As described above, in the present embodiment, the output of the second laser beam L2 when the laser beam L is scanned along the end portion H2 (end scanning step), and the laser beam L is along the central portion H1. Since it is lower than when scanning (central scanning step), the heat generated when the laser beam L is scanned along the end H2 is reduced, and the insulating coating existing around the end H2 due to the heat is reduced. The adverse effect on 15N can be suppressed.

In the present embodiment, the laser beam L is scanned along the central portion H1 far from the insulating coatings 15N and 16N (central scanning step, 1st pass to 4-1st pass), and then the laser beam L is coated with the insulating coating. Scan along the end H2 close to 16N (end scanning step, 4-2nd pass to 5-1st pass). As a result, first, the molten pool 41 was formed in the central portion H1 in a state where there was no adverse effect of heat on the insulating coatings 15N and 16N, and then the adverse effect of heat on the insulating coating 16N was suppressed by reducing the output of the second laser beam L2. In this state, the molten pool 41 can be expanded to the end H2. As a result, the welding region on the mating surface S can be widened while suppressing the adverse effect on the insulating coatings 15N and 16N due to the heat generated when the laser beam L is scanned, and sufficient bonding strength can be obtained. Further, by moving the laser beam L linearly along one side H of the mating surface S, the time for welding is short, the molten cross section becomes smooth, and sufficient bonding strength can be obtained.

In the present embodiment, the foreign matter P (FIGS. 11 and 12) may be sandwiched between the mating surfaces S. Examples of the foreign matter P include a residual piece of an insulating film or a residual piece of slot paper. The foreign matter P evaporates when it is irradiated with the laser beam L, but if the laser beam L is only the first laser beam L1, the molten pool may explode during this evaporation. In the present embodiment, the laser beam L includes the first laser beam L1 and the second laser beam L2, so that this explosion can be avoided. More specifically, as shown in FIG. 11, when the laser beam L is composed of only the first laser beam L1, the keyhole 72 formed by the laser beam L during scanning is thin due to the absence of the second laser beam L2. It is formed. In this case, when the foreign matter P is heated by the first laser beam L1 and evaporates, the molten pool 71 exists above the foreign matter P as shown in FIG. 11, and the molten pool 71 is generated by the steam when the foreign matter P evaporates. Will explode. On the other hand, when the laser beam L includes the first laser beam L1 and the second laser beam L2 as in this embodiment, the keyhole 42 has a conical shape with a wide opening as shown in FIGS. 6 and 12. It is formed. Therefore, in the present embodiment, as shown in FIG. 12, a space is secured by the keyhole 42 above the foreign matter P to evaporate, and this space serves as an escape route for steam when the foreign matter P evaporates, and the above-mentioned explosion occurs. Is avoided. This improves the robustness against foreign matter P.

In order to avoid the above-mentioned explosion, the energy density of the second laser beam L2, particularly t0 to t3 in the first to 4-1 passes forming the molten pool 41 (FIG. 10), t4 in the 5-2nd pass. The energy density during the period from t5 (FIG. 10) is preferably in the range of 15% to 30% of the energy density of the first laser beam L1 at the same timing. If the former is less than 15% of the latter, the keyhole 42 becomes thin and it becomes difficult to avoid the above-mentioned explosion.

The above embodiment can be changed as appropriate. The welding method according to this embodiment can be applied to various weldings of conductor segments constituting a flat wire coil. For example, the welding method according to the present embodiment can also be applied to the formation of a flat wire coil of a stator of a rotary electric machine used for applications other than vehicles.

The shape of the conductor segment 14 and the like are arbitrary. The beam shapes of the first laser beam L1 and the second laser beam L2 of the laser beam L are also arbitrary. For example, the beam shape of the first laser beam L1 may be a polygonal shape, and the beam shape of the second laser beam L2 may be a polygonal ring road. The energy densities of the first laser beam L1 and the second laser beam L2 may be equal. The positions of virtual points A to D are arbitrary. The scanning of the laser beam L may be performed by moving the conductor segment to be welded instead of moving the irradiation region of the laser beam L.

When scanning the laser beam L along the end H2 or H3, the laser beam L may not be scanned to the virtual point D or the virtual point A, but may be scanned to the middle of the end H2 or H3. The insulating coatings 15N and 16N may not be present near the ends H2 or H3. Even in such a case, when the laser beam L is scanned along the end H2 or H3, the output of the second laser beam L2 is reduced to generate heat for those existing around the end H2 or H3. The adverse effect can be suppressed.

When reducing the output of the second laser beam L2 at the end H2 or H3, the output of the first laser beam L1 may be appropriately reduced. In this case, the output of the first laser beam L1 is an output at which a molten pool can be formed at the end H2 or H3. When the output of the second laser beam L2 is reduced, the output may be reduced to 0. The laser beam L is scanned along the edge H2 or H3 and then along the central portion H1 to increase the output of the second laser beam L2 when the laser beam L is scanned along the central portion H1. You may. The central scan step may be performed after the end scan step.

In the above embodiment, the laser beam L is scanned a plurality of times along one side H of the mating surface S. For example, when a sufficient energy density is obtained as the energy density of the laser beam L, the scanning of the laser beam L is performed. It may be a scan for one pass. For example, the laser beam L is scanned for one pass along the central portion H1 and the end portion H2 from the virtual point B to the virtual point D, and the output of the second laser beam L2 is performed at the end portion D2 from the virtual point C to the virtual point D. To reduce. Alternatively, the laser beam L is scanned from the virtual point A to the virtual point D, and the output of the second laser beam L2 is output from the virtual point A to the virtual point B (end H3) and from the virtual point C to the virtual point D (end H2). Is lower than the virtual point B to the virtual point C (central portion H1).

11 cores, 12 teeth, 13 slots, 14-16 conductor segments, 14A legs, 14B-16B tips, 14M-16M conductor wires, 14N-16N insulation coatings, 15C, 16C sides, 16B tips, 41,71 melts. Pond, 42, 72 keyhole, 50 laser welder, 51 1st oscillator, 52 2nd oscillator, 53 scanning mechanism, 54 controller, AD virtual point, H side, H1 center, H2, H3 end , L laser beam, L1 first laser beam, L2 second laser beam, P foreign matter, S mating surface.

Claims (1)

A welding method in which a laser beam is scanned along one side of a mating surface of two conductor segments constituting a flat wire coil to weld the mating surface.
The laser beam includes a first laser beam and a second laser beam having an annular beam shape surrounding the first laser beam.
A central scanning step that scans the laser beam along the central portion of the one side of the mating surface.
It comprises an end scanning step that scans the laser beam along the edge of one side.
The output of the second laser beam in the edge scanning step is lower than the output of the second laser beam in the central scanning step.
Welding method.

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