JP7063693B2 - Flat wire laser welding method - Google Patents

Description

The present invention relates to a method for laser welding flat wires.

The stator (stator) for the motor includes a stator core and a plurality of segment coils mounted in slots of the stator core. Usually, each segment coil is an insulatingly coated flat wire. The ends of the segment coils are joined by welding or the like.

Patent Document 1 discloses, for example, a method for laser welding a flat wire used for a segment coil. In the method described in Patent Document 1, the side surfaces of the ends of the first and second flat lines are butted against each other, a loop-shaped laser beam is irradiated into the end faces of the first flat lines, and the scanning locus of the laser beam is gradually changed. The size is increased so that it reaches the butt surface of the first and second flat wire and is joined. In the above method, by joining the first and second flat wire in this way, the gap between the butt planes can be filled by the molten pool, so that the flat wire is insulated by the laser beam penetrating the gap between the butt planes. Damage to the coating can be suppressed.

Japanese Unexamined Patent Publication No. 2018-02340

The inventor has found the following problems with respect to the laser welding method for a flat wire described in Patent Document 1.
FIG. 6 is a plan view showing a laser welding method for a flat wire described in Patent Document 1, and FIG. 7 is a graph showing the relationship between the turning radius and the number of spatters generated when scanning in a loop shape. be. Here, the turning radius corresponds to the length of the long axis when the loop is an ellipse, and corresponds to the diameter when the loop is a circle.

In the method described in Patent Document 1, first, as shown in FIG. 6, at the joint portion 25, the butt surface (end side surface) 23a of the flat wire 20a from which the insulating coating 21a has been peeled off and the insulating coating 21b are peeled off. The abutment surface (end side surface) 23b of the flat wire 20b is abutted against the abutment surface (end side surface) 23b. Then, the laser beam is irradiated vertically downward (z-axis minus direction) to the end face 24a of the flat wire 20a. Next, as shown in FIG. 6, the diameter of the scanning locus of the laser beam, that is, the diameter of the ellipse is increased in the end surface 24a of the flat wire 20a, so that the molten pool 60 reaches the end side surfaces 23a and 23b. As a result, the gap between the end side surfaces 23a and 23b, which are the butt surfaces, is filled by the molten pool 60.

As described above, in the method described in Patent Document 1, since it is necessary to start scanning in a state where the rotation diameter at the time of scanning in a loop shape is smaller than the final size, the rotation diameter at the start is made small. You may have to do it.

When the rotation diameter is small, the energy density in the irradiation range of the laser beam becomes high and keyhole welding is performed, so that the metal easily evaporates, and the laser beam hits the generated metal vapor to generate spatter. There is a risk of In fact, as shown in FIG. 7 the relationship between the rotation diameter and the number of spatters generated, the number of spatters increases as the rotation diameter decreases. Therefore, the method described in Patent Document 1 may increase the number of spatters.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for laser welding a flat wire capable of suppressing the occurrence of spatter.

The method for laser welding a flat wire according to one aspect of the present invention is
By abutting the joining target surfaces of the first and second flat lines against each other and irradiating the other surfaces of the first and second flat lines that are connected to the joining target surfaces with a laser beam, the first It is a laser welding method of a flat wire that welds a flat wire and the second flat wire.
The first step of scanning the laser beam so that the scanning locus of the laser beam draws a loop having a predetermined turning radius in the other plane of the first flat line.
After the first step, the second step of scanning the laser beam so that the scanning locus of the laser beam draws a loop having the predetermined turning radius across the boundary surface where the joining target surfaces are butted against each other.
It has.

In the method of laser welding a flat wire according to one aspect of the present invention, the laser beam is first scanned so as to draw a loop having a predetermined rotation radius in the other plane of the first flat wire, and then the surfaces to be joined are joined to each other. The laser beam is scanned so as to draw a loop having the above-mentioned predetermined turning radius across the abutting interface. In the flat wire laser welding method according to one aspect of the present invention, the energy density in the irradiation range of the laser beam can be suppressed to a low level due to such a configuration, so that the generation of spatter can be suppressed.

According to the present invention, it is possible to provide a laser welding method for a flat wire capable of suppressing the occurrence of spatter.

It is a perspective view which shows the schematic structure of a stator. It is a top view which shows the laser welding method of the flat wire which concerns on embodiment of this invention. It is a graph which shows an example of the relationship between the turning radius of a loop, and the amount of melting. It is a figure which shows an example of the molten shape of the part welded by the laser welding method of FIG. It is a graph which shows an example of the relationship between the output value of a laser beam, and the number of circumferences at the time of welding by the laser welding method of FIG. It is a top view which shows the laser welding method of the flat wire described in Patent Document 1. FIG. It is a graph which shows the relationship between the turning radius and the number of spatters generated.

Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. Further, in order to clarify the explanation, the following description and drawings are appropriately simplified.

First, an example of the configuration of a stator including a segment coil welded by using the flat wire laser welding method according to the present embodiment will be described with reference to FIG. 1. FIG. 1 is a perspective view showing a schematic configuration of a stator.

As shown in FIG. 1, the stator 1 which is a stator of a motor has a stator core 10 and a plurality of segment coils 20.
The stator core 10 is formed by laminating annular electromagnetic steel sheets in the axial direction of the stator 1 (z-axis direction in FIG. 1), and has a substantially cylindrical shape as a whole. The inner peripheral surface of the stator core 10 is provided with a teeth 11 projecting to the inner peripheral side and extending in the axial direction of the stator 1 and a slot 12 which is a groove formed between adjacent teeth 11. There is. A segment coil 20 is mounted in each slot 12.

The segment coil 20 is an electric wire having a rectangular cross section, that is, a flat wire. Normally, the segment coil 20 is made of pure copper, but may be made of a metal material having high conductivity such as aluminum, an alloy containing copper or aluminum as a main component.

Each segment coil 20 is formed into a substantially U shape. As shown in FIG. 1, each end portion (coil end) of the segment coil 20 protrudes from the upper end surface of the stator core 10. The joint portion 25 is a portion where the ends of the segment coils 20 adjacent in the radial direction are welded to each other. A plurality of joints 25 are arranged in an annular shape in the circumferential direction of the stator core 10. In the example of FIG. 1, 48 joints 25 are arranged in an annular shape. Further, the joint portions 25 arranged in an annular shape are arranged in four rows in the radial direction.

Next, a laser welding method for a flat wire according to the present embodiment will be described with reference to FIGS. 2 to 5. FIG. 2 is a plan view showing a laser welding method for a flat wire according to the present embodiment. As a matter of course, the right-handed xyz coordinates shown in FIG. 2 are for convenience to explain the positional relationship of the components. The z-axis direction of FIG. 1 and the z-axis direction of FIG. 2 coincide with each other. Usually, the z-axis plus direction is vertically upward, and the xy plane is a horizontal plane.

The joint portion 25 of the segment coil 20 shown in FIG. 1 can be laser welded by using the flat wire laser welding method (hereinafter referred to as the present laser welding method) according to the present embodiment. Since this laser welding method joins the flat wire coils used for the stator to each other, it can also be referred to as a stator coil joining method. Although the description is omitted, as the laser welding apparatus used in this laser welding method, for example, the laser welding apparatus described in Patent Document 1 can be used. For example, the present laser welding method can be executed by programming the laser welding apparatus to irradiate the laser beam according to the following procedure.

In this laser welding method, first, as shown in FIG. 2, at the joint portion 25, the end side surface 23a of the flat wire (segment coil) 20a from which the insulating coating 21a has been peeled off and the flat wire from which the insulating coating 21b has been peeled off. The end side surface 23b of the (segment coil) 20b and the end side surface 23b are butted against each other.

Then, in this laser welding method, the flat wire 20a and the flat wire 20b are finally welded by irradiating the end faces 24a and 24b of the flat wire 20a and 20b with a laser beam. As described above, in this laser welding method, the end side surfaces 23a and 23b, which are the butt surfaces, are used as the joining target surfaces, and the end faces 24a and 24b are irradiated with the laser beam.

This laser welding method has the main features of this laser beam scanning method. This main feature will be described below. This laser welding method has the following first step and second step, which are executed in a state where the end side surfaces 23a and 23b are butted against each other.

In the first step, the laser beam is drawn so that the scanning locus of the laser beam draws a loop having a predetermined rotation radius within the end face 24b of one flat line (the flat line 20b in the example of FIG. 2 and the same applies hereinafter). Scan. That is, in the first step, the laser beam is irradiated vertically downward (z-axis minus direction) to the end surface 24b of the flat wire 20b, and the laser beam is scanned in a loop with the predetermined rotation radius.

A loop means an annular loop (closed loop) or a spiral loop (open loop). FIG. 2 gives an example in which the scanning locus of the laser beam is an elliptical loop. In FIG. 2, the first loop, which is a loop including the scanning start position (START indicated by the arrow), is drawn with a thick line, but it is only drawn visually in an easy-to-understand manner, and is the same beam as the other loops. Scanning by diameter shall be made.

Further, since the conductor portions 22a and 22b of the flat wire 20a and 20b are made of a metal material having high conductivity, they are also excellent in thermal conductivity. Therefore, the melted portion is rapidly solidified by irradiating the laser beam. However, by forming the scanning locus of the laser beam in a loop shape, the formed molten pool can be grown. That is, in the first step, a molten pool can be formed and grown in the end surface 24b of the flat wire 20b (a region that does not correspond to the boundary line between the end side surfaces 23a and 23b). The predetermined turning radius will be described later.

The second step is a step executed after the first step, in which the laser beam is scanned so as to draw a loop in which the scanning locus of the laser beam crosses the boundary surface where the end side surfaces 23a and 23b are butted against each other. The boundary surface can be a flat surface located between the end side surface 23a and the end side surface 23b in a state where the end side surface 23a and the end side surface 23b are butted against each other. This plane (the boundary surface) includes the boundary line between the end side surfaces 23a and 23b in FIG. The loop in the second step is also a loop having the same turning radius (that is, the predetermined turning radius) as the loop in the first step.

That is, in the second step, after the first step, the loop is moved while maintaining the predetermined turning radius so that the scanning locus of the laser beam becomes a loop that crosses the boundary surface. Since the loop after movement crosses the boundary surface, it becomes a loop straddling the inside of the end face 24a of the flat wire 20a and the inside of the end face 24b of the flat wire 20b. In the second step, the laser beam is irradiated vertically downward (z-axis minus direction) with respect to the end face 24b of the flat wire 20b and the end face 24a of the flat wire 20a so as to draw such a loop.

As described above, in this laser welding method, after always melting the flat wire 20b on one side at a constant turning radius, the loop is moved to the butt surface side to draw a loop straddling the flat wire 20a, 20b on both sides. The laser beam is irradiated so as to.

In this laser welding method, the energy density in the irradiation range of the laser beam can be suppressed to a low level by such a procedure, so that the generation of spatter can be suppressed. In this laser welding method, by suppressing the generation of spatter in this way, it is possible to suppress quality deterioration due to welding defects. In addition, as a countermeasure against frequent occurrence of spatter in the region where the turning radius is small, it is conceivable to reduce the output of the laser beam, but this will increase the processing time and damage the insulating film such as enamel due to the increase in processing time. It will be connected. However, according to this laser welding method, the spatter amount can be reduced without increasing the processing time.

Further, in the first step executed before the second step, as shown in FIG. 2 as an example of the scanning locus, from the first loop to the loop crossing the boundary surface according to the second step. The scan can be performed so as to move the loop step by step.

Further, in the second step, as shown in FIG. 2 as an example of the scanning locus, the laser beam is used to translate the loop along the boundary surface between the end side surfaces 23a and 23b (in the plus direction of the x-axis). Can include a third step of scanning. Thereby, as shown in FIG. 2, it is possible to cope with the case where the boundary surface is long (the butt surface is long) with respect to the predetermined rotation radius.

The scanning start position and the scanning end position (END indicated by an arrow in FIG. 2) are not limited to the positions shown in FIG. The scan may be started from one point of the loop on the end face 24b of one flat wire 20b, and the scan may be ended at one point of the loop on the end faces 24a, 24b of both flat lines 20a, 20b.

Next, the predetermined rotation diameter, which is a common loop diameter in the first and second steps, will be described. In this laser welding method, since the rotation diameter of the loop is constant (the predetermined rotation diameter), it is preferable to select a size such that spatter generation can be suppressed and a molten pool can be formed as the predetermined rotation diameter. In particular, for the predetermined turning radius, it is preferable to select an optimum size that maximizes melting.

The selection of the optimum size will be described with reference to FIG. FIG. 3 is a graph showing an example of the relationship between the turning radius of the loop (here, the length of the long axis in the elliptical loop) and the melting amount (melting cross-section). For example, when the loop is circular, the turning radius refers to the diameter.

As shown in FIG. 3, when the rotation diameter is small, a large amount of spatter occurs and the amount of melting is small. On the other hand, when the laser beam is irradiated, the melted portion is rapidly solidified, so that the rotation diameter is large. If it is too much, the amount of melting will decrease and it will not be possible to form a molten pool. In fact, as shown by the broken line circle in FIG. 3, the melting amount becomes maximum at a certain turning radius. As shown in FIG. 3, it can be said that the molten cross-sectional area can be represented by an approximately convex quadratic function with the turning radius as a variable.

Therefore, in the case of the example of FIG. 3, the turning radius in the vicinity indicated by the broken line circle (more preferably, the turning radius showing the maximum melting amount indicated by the apex of the quadratic function) is selected as the predetermined turning radius. Therefore, it is possible to form a wide molten pool while suppressing the generation of spatter as much as possible. Actually, according to the performance of the laser welding device used, the conditions of the laser beam actually output from the laser welding device (output value, beam diameter, etc.), and the shape of the work on which the flat wires 20a and 20b are set, etc. The rotation diameter with the largest amount of melting can be selected.

Further, when there is a gap in the butt surface as in the example of FIG. 2, the laser beam may penetrate downward, and if it penetrates, the insulating coatings 21a, 21b of the flat wire 20a, 20b existing below may penetrate. Will damage the laser. This measure will be described below.

Irradiating the butt surface with a laser beam from the beginning increases the occurrence of spatter. However, as described above, in this laser welding method, the end surface 24b of the flat wire 20b on one side is melted in the first step so that the butt surfaces of the end side surfaces 23a and 23b are not irradiated first, and the end surface 24b is used. Form a molten pool above.

Then, as described above, in the first step executed before the second step, scanning is performed so as to move the loop step by step from the first loop to the loop that crosses the boundary surface. A molten pool is formed so as to reach a part of the boundary surface.

Specifically, after irradiating the laser beam from the scanning start position (START indicated by the arrow in FIG. 2) once or multiple times in the same loop, the laser beam is slid in the plus direction of the y-axis, and the same as the base point. Irradiate once or multiple times in a loop and repeat this. As a result, the molten pool reaches the end side surfaces 23a and 23b, which are the abutting surfaces, at the stage where the laser beam is scanned in the end surface 24b of the flat wire 20b. At this time, as described above, if the turning radius is too small, spattering occurs frequently, and if it is too large, the melting amount decreases, so the optimum size is used to maximize the melting amount.

By such scanning, before the execution of the second step, the molten pool formed on the end face 24b of the flat wire 20b enters the gap, and the gap is filled by the molten pool. As a result, it is possible to suppress the laser beam from entering the gap between the end side surfaces 23a and 23b, and it is possible to prevent the laser beam from penetrating downward and damaging the insulating coatings 21a and 21b. In particular, in the example of FIG. 2, since the long axis of the elliptical scanning locus is parallel to the end side surfaces 23a and 23b, the molten pool is formed in a wide range of the gap between the end side surfaces 23a and 23b in a short time. Can be reached.

After that, as described above, in this laser welding method, the loop is moved to the butt surface side, and in the second step, a loop straddling the flat lines 20a and 20b on both sides is drawn (that is, the butt surface is welded). As such), irradiate the laser beam. By the above processing, according to the present embodiment, it is possible to suppress the occurrence of spatter and the adverse effect of the laser beam penetrating into the gap between the butt surfaces.

Next, a preferable example of the above-mentioned third step will be described.
In this laser welding method, it is preferable to adjust the output so that the melting is uniform even if welding is performed from the end in the x-axis direction. Therefore, in this laser welding method, it is preferable to adjust (change) the output of the laser beam so as to be maximum near the center of the portion to be welded.

An example of such adjustment will be described with reference to FIGS. 4 and 5. FIG. 4 is a diagram showing an example of the molten shape of the portion welded by this laser welding method, and FIG. 5 is a diagram showing the output value and the number of circumferences of the laser beam (1 in the same loop) when welding by this laser welding method. It is a graph showing an example of the relationship with the number) which indicates the number of loops. In the example of FIG. 4, unlike the example shown in FIG. 2, in order to reduce the amount of the flat wire 20a and 20b used and to reduce the size of the stator 1, the flat wire 40a having a substantially triangular butt surface. 40b is used.

As shown in FIG. 4, the required melting shape is required most in the central portion of the weld bead. In addition, a gap may exist in a portion other than the central portion, that is, a portion shown as a gap in FIG.

In order to obtain such a molten shape, the output value is set to be the highest in the central portion as shown in the laser output value (W) illustrated in FIG. Since 20b or the flat wires 40a and 40b are easily melted, adjust the output low so that they do not melt too much.

(Alternative example)
Next, an alternative example in this embodiment will be described.
Although this laser welding method has been described, the shape of the flat wire, the shape of the loop, etc. are not limited to the examples. For example, the shape of the loop is not limited to an elliptical shape and a circular shape, and may be a rectangular loop. However, when the shape of the loop is elliptical or circular, the laser beam can always be scanned smoothly as compared with the case where the loop has a rectangular shape with corners, so that the generation of spatter can be suppressed. can. Further, the movement locus of the loop is not limited to the example as long as the conditions of the first step and the second step are satisfied. Of course, the configuration of the stator is not limited to the one shown in the figure.

Further, in the present laser welding method, the first and second flat wire are insulated and coated, and the side surfaces of the ends from which the insulating coating is peeled off are butted against each other in the first and second flat wires, and the first And the explanation was made on the premise that the end face of the second flat wire is irradiated with the laser beam. However, the surface to be joined (that is, the butt surface) is not limited to the end side surface. In that case, the end surface corresponds to another surface connected to the bonding target surface (for example, a surface substantially perpendicular to the bonding target surface).

Furthermore, this laser welding method is based on the premise that it is executed when joining the flat wire used for the stator (coils of the flat wire), but the flat wire to be joined is used for other than the stator. There may be.

Although the present embodiment has been described above, the above-described embodiment has the following features.
That is, in the method of laser welding a flat wire according to the above embodiment, the first and second flat wire 20a, 20b are butted against each other to be joined, and the first and second flat wire are abutted against each other. The first flat wire 20a and the second flat wire 20b are welded by irradiating the other surfaces (end faces 24a and 24b) connected to the joining target surface in 20a and 20b with a laser beam. This method has a first step and a second step. In the first step, the laser beam is scanned so that the scanning locus of the laser beam draws a loop having a predetermined rotation radius in the other surface (end surface 24b) of one flat line 20b. In the second step, after the first step, the laser is drawn so that the scanning locus of the laser beam crosses the boundary surface where the joining target surfaces (end side surfaces 23a, 23b) are butted against each other and draws a loop having the predetermined rotation radius. Scan the beam.

In the above laser welding method, the laser beam is first scanned so as to draw a loop having a predetermined rotation radius in the other plane of one flat wire, and then the predetermined plane crosses the boundary surface where the surfaces to be joined are butted against each other. The laser beam is scanned so as to draw a loop of the turning radius of. Therefore, in the above laser welding method, the energy density in the irradiation range of the laser beam can be suppressed to a low level, so that the generation of spatter can be suppressed and the quality deterioration due to welding defects can be suppressed.

The present invention is not limited to the above embodiment, and can be appropriately modified without departing from the spirit.

1 Stator 10 Stator core 11 Teeth 12 Slot 20 Segment coil 20a, 20b, 40a, 40b Flat wire 21a, 21b Insulation coating 22a, 22b Conductor part 23a, 23b End side surface 24a, 24b End face 25 Joint part 60 Molten pond

Claims (1)

By abutting the joining target surfaces of the first and second flat lines against each other and irradiating the other surfaces of the first and second flat lines that are connected to the joining target surfaces with a laser beam, the first It is a laser welding method of a flat wire that welds a flat wire and the second flat wire.
The first step of scanning the laser beam so that the scanning locus of the laser beam draws a loop having a predetermined turning radius in the other plane of the first flat line.
After the first step, the second step of scanning the laser beam so that the scanning locus of the laser beam draws a loop having the predetermined turning radius across the boundary surface where the joining target surfaces are butted against each other.
Have ,
The predetermined turning radius in the first step and the second step is a constant turning radius and is a size that maximizes the amount of melting.
Flat wire laser welding method.

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