JP6871135B2 - Flat wire laser welding method - Google Patents

Description

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

Conventionally, there is a method described in Patent Document 1 as a method for laser welding a flat wire. In this laser welding method, a coating peeling surface is formed in which the insulating coating is peeled off only on one surface of the end portion of the two flat wires. Then, after the coating peeling surfaces are arranged to face each other on the two flat lines, the two coating peeling surfaces are welded by spot-irradiating the two coating peeling surfaces with a laser beam from above.

Japanese Unexamined Patent Publication No. 2013-109948

Energy is likely to be concentrated on the corners of the film peeling surfaces facing each other in each of the two flat lines, and the temperature is likely to rise. Then, a part of the corner portion is melted and gasified to be spattered and easily scattered, and the generated spatter may deteriorate the welding quality.

Therefore, an object of the present invention is to provide a flat wire laser welding method in which sputtering is less likely to occur and welding quality is less likely to deteriorate.

In order to solve the above problems, the method of laser welding a flat wire of the present invention is a flat angle in which the ends of the first flat wire and the second flat wire having a rectangular cross section, which do not have an insulating coating, are welded by laser light. In the method of laser welding a wire, the side surface of the end portion of the first flat wire and the side surface of the end portion of the second flat wire are in contact with each other, and the laser beam is emitted at the end portion of the first flat wire. The first flat line and the second flat line so that the first irradiation surface to which the laser beam is irradiated and the second irradiation surface to which the laser beam is irradiated are located on substantially the same plane at the end of the second flat line. After the flat line arrangement step for arranging the flat lines and the flat line arrangement step, the laser beam is emitted so as to straddle the first and second irradiation surfaces and draw a loop on the first and second irradiation surfaces. In the laser light emitting step, including the laser light emitting step, the energy density of the laser light irradiating the boundary region between the first and second irradiation surfaces of the laser light irradiating other parts. Less than the energy density. The energy density is the energy given to a unit area in a unit time. The energy density decreases as the scanning speed of the laser beam is increased or the output is reduced.

According to the method of laser welding a flat wire according to the present invention, the end side surface of the first flat wire and the end side surface of the second flat wire are brought into contact with each other, and the first irradiation surface at the end of the first flat wire is brought into contact with the surface. The first flat line and the second flat line are arranged so that the second irradiation surface at the end of the second flat line is located on substantially the same plane. Then, the laser beam is emitted so as to straddle the first and second irradiation surfaces and draw a loop on the first and second irradiation surfaces, and irradiate the boundary regions between the first and second irradiation surfaces where energy is likely to be concentrated. The energy density of the laser beam to be applied is made smaller than the energy density of the laser beam irradiating other parts. Therefore, since the temperature rise of the corner portion located near the boundary region on the flat line can be suppressed, the occurrence of spatter can be suppressed, and the deterioration of welding quality due to spatter can be suppressed.

It is a partial perspective view of the stator of a rotary electric machine which can be manufactured by the laser welding method of this invention. It is a schematic diagram which shows the intermediate state of the 1st and 2nd flat wire at the time of positioning the 1st and 2nd flat wire for laser welding. It is a schematic diagram which shows the 1st and 2nd flat wire positioned. It is a plane schematic diagram which shows the 1st and 2nd flat wire which is irradiated with a laser beam in a positioned state. FIG. 4 is a cross-sectional view taken along the line CC of FIG.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. When a plurality of embodiments and modifications are included in the following, it is assumed from the beginning that a new embodiment is constructed by appropriately combining the characteristic portions thereof. Further, in the following drawings and explanations of practical examples, the R direction indicates the radial direction of the stator 1, the θ direction indicates the circumferential direction of the stator 1, and the Z direction is the height direction (axial direction) of the stator 1. Is shown. The R, θ, and Z directions are orthogonal to each other.

First, the structure of the stator 1 of a rotary electric machine that can be manufactured by the laser welding method of the present invention will be described with reference to FIG. FIG. 1 is a partial perspective view of the stator 1. In FIG. 1, the resin portion is not shown so that the structure of the coil and the output line can be easily understood. As shown in FIG. 1, the stator 1 includes a stator core 11 and a stator coil 15 including a flat wire. The stator core 11 is an annular magnetic component. For example, a plurality of silicon steel sheets (electromagnetic steel sheets) are laminated, but even if the stator core 11 is formed by pressure molding a resin binder and a magnetic material powder. Good. The stator core 11 has a yoke 12 which is annularly arranged on the outer peripheral side, and a plurality of teeth 16. The plurality of teeth 16 are arranged at intervals in the θ direction, and each tooth 16 projects inward from the yoke 12 in the R direction. The stator coil 15 includes U, V, and W three-phase coils 20, 21, and 22 that extend spirally. Each of the U, V, and W three-phase coils 20, 21, and 22 is inserted into a slot 17 which is a space between adjacent teeth 16 and wound around the teeth 16.

Each of the three-phase coils 20, 21 and 22 of U, V and W is configured by connecting a plurality of segment coils 20a, 21a and 22a in series, and each of the segment coils 20a, 21a and 22a is abbreviated as a plurality. It is constructed by welding U-shaped segment conductors. When welding, the tip ends of the two legs of each segment conductor are bent so that a plurality of segment conductors overlapping in the R direction form a spiral, and the tips of the legs of different segment conductors are laser-welded. It is joined by welding. The region indicated by R in FIG. 1 is one of a plurality of joints formed by laser welding. Laser welding will be described in detail later. By laser welding between the tip portions, each of the segment coils 20a, 21a, 22a is wound around a plurality of teeth 16 so as to straddle the plurality of teeth 16, and the stator coil 15 is distributedly wound around the plurality of teeth 16.

The protrusions arranged at one end of the coils 20, 21 and 22 of each phase are bent into a crank shape, for example, to become an output line, and the output line of each phase is electrically connected to a power line (not shown) on the power supply side. Be connected. In FIG. 1, the U-phase coil 20 is indicated by a diagonal line along the θ direction, the V-phase coil 21 is indicated by a diagonal line along the R direction, and the W-phase coil 22 is indicated by a narrow (fine) diagonal line. There is. FIG. 1 shows an output line 20U of the U-phase coil 20 and an output line 22W of the W-phase coil 22. On the other hand, the protruding portion 20b arranged at the other end of the U-phase coil 20, the protruding portion 21b arranged at the other end of the V-phase coil 21, and the protruding portion 22b arranged at the other end of the W-phase coil 22 are medium. It is electrically connected by the sex wire 30, and the three-phase coils 20, 21, and 22 are Y-connected by the electrical connection using the neutral wire 30. The neutral wire 30 is arranged on the outer side of the stator core 11 on one side in the Z direction. The stator 1 has a plurality of mounting portions 45 arranged at intervals in the θ direction, and each mounting portion 45 bulges outward in the R direction. The stator 1 is attached to the case by passing a bolt (not shown) through the fastening hole 46 of the attachment portion 45 and then fixing the bolt to the end face in the axial direction of the case (not shown).

Rotors (not shown) are arranged on the inner peripheral side of the stator 1 at intervals from the stator 1. The centers of the stator 1 and the rotor are substantially aligned. The rotor is an annular magnetic component fixed around a rotating shaft, and is composed of, for example, a plurality of annular silicon steel plates (electromagnetic steel plates) laminated. For example, a plurality of permanent magnets are embedded in a rotor at intervals in the θ direction.

When the rotary electric machine including the stator 1 functions as a motor and a generator, it operates as shown below, but the rotary electric machine including the stator 1 may function as either a motor or a generator. First, when a rotary electric machine is used as a motor, for example, after the DC current from the battery is converted into a three-phase AC current via an inverter, the three-phase AC current connects the output lines 20U and 22W of each phase. It is supplied to the three-phase coils 20, 21, and 22 of U, V, and W via. By supplying a three-phase AC current to the U, V, and W three-phase coils 20, 21, and 22, the teeth 16 are magnetized to become magnetic poles, and the position of the magnetic poles moves along the θ direction of the stator 1. Occurs. Then, the rotor rotates based on the rotating magnetic field, and rotational power is generated.

On the other hand, when a rotating electric machine is used as a generator to regenerate electric power, when the rotor is rotated by external power, the permanent magnet embedded in the rotor rotates around the rotor central axis. Then, an induced electromotive force based on the law of electromagnetic induction is induced in the three-phase coils 20, 21, 22 of U, V, and W, and the induced current of alternating current is the three-phase coils 20, 21, 22 of U, V, W. It flows through 22. The AC power from the U, V, and W three-phase coils 20, 21, and 22 based on the induced current is converted into DC power by the inverter and then supplied to the battery.

Next, laser welding between the ends of the two segment conductors in the region R of FIG. 1 will be described with reference to FIGS. 2 to 5. In FIGS. 2 to 5, one of the two segment conductors is represented by the first flat wire 50, and the other segment conductor is represented by the second flat wire 60.

FIG. 2 is a schematic view showing an intermediate state of the first and second flat lines 50, 60 when positioning the first and second flat lines 50, 60 for laser welding, and FIG. 3 is a schematic view showing the intermediate state of the first and second flat lines 50, 60. It is a schematic perspective view which shows the 1st and 2nd flat wire 50, 60 which were welded. Laser welding is performed, for example, as follows. First, the tip ends of the two legs of the first flat wire 50 and the tip ends of the two legs of the second flat wire 60 are bent, and the first and second flat lines 50 and 60 are shown in FIG. Make it in a state. At the end 51 of the first flat wire 50, the insulating coating 52 is peeled off to expose the conductor wire to the outside, and at the end 61 of the second flat wire 60, the insulating coating 62 is peeled off and the conductor wire is exposed to the outside. Is exposed to. In bending, a bending device or jig (not shown) has the ends 51, 61 of the first and second flat wire 50, 60 at substantially the same position (approximately the same height) in the axial direction of the stator core 11 when the positioning step is completed. Bend the two legs of each of the flat lines 50 and 60 so as to be. As shown in FIG. 2, in the state where the bending process is completed, the end portion 51 of the first flat wire 50 and the end portion 61 of the second flat wire 60 are not aligned in the θ direction and are half when viewed from the R direction. It is in a state where it overlaps only to the extent.

Next, the first and second flat wires 50 and 60 are arranged so that the one side side surface 59 of the end portion 51 of the first flat wire 50 and the other side side surface 69 of the end portion 61 of the second flat wire 60 come into contact with each other. To do. Further, the first irradiation surface 58 to which the laser beam is irradiated at the end 51 of the first flat wire 50 and the second irradiation surface 68 to which the laser light is irradiated at the end 61 of the second flat wire 60 are substantially on the same plane. The first flat wire 50 and the second flat wire 60 are arranged so as to be located at.

Specifically, for example, a force in the θ direction indicated by an arrow A is applied to the first and second flat lines 50 and 60 by a circumferential position adjusting unit of a holding device (not shown). Specifically, in the circumferential position adjusting portion, the tip surface of the end portion 51 of the first flat wire 50 is pushed to one side in the θ direction, and the tip surface of the end portion 61 of the second flat wire 60 is pushed to the other side in the θ direction. The position in the θ direction of the end 51 of the first flat line 50 and the position in the θ direction of the end 61 of the second flat line 60 are substantially matched. In this state, the holding portion of the holding device applies a force in the R direction indicated by the arrow B to the two ends 51, 61, and as shown in FIG. 3, the two ends 51, 61 are sandwiched from both sides in the R direction. And hold the two ends 51, 61 in place. In the state shown in FIG. 3, the end portion 51 of the first flat wire 50 and the end portion 61 of the second flat wire 60 are at substantially the same position (substantially the same height) in the axial direction of the stator core 11. Further, in the state shown in FIG. 3, when viewed from the R direction, substantially all of the end portions 51 of the first flat wire 50 overlap with substantially all of the end portions 61 of the second flat wire 60. Further, in the state shown in FIG. 3, substantially all of the one-sided side surface 59 at the end of the first flat wire 50 comes into contact with substantially all of the other side surface 69 at the end 61 of the second flat wire 60.

Next, the irradiation of the laser beam will be described with reference to FIGS. 4 and 5. FIG. 4 is a schematic plan view showing the first and second flat lines 50 and 60 that are irradiated with the laser beam in the positioned state. Further, FIG. 5 is a cross-sectional view taken along the line CC of FIG.

As shown in FIG. 5, when the laser beam is emitted, the first irradiation surface 58 of the first flat line 50 is flush with the second irradiation surface 68 of the second flat line 60 and is substantially on the same surface. The one side surface 59 of the first flat wire 50 is in contact with the other side surface 69 of the second flat wire 60 without a gap. In the example shown in FIG. 3, the same surface is a curved surface, but the same surface may be a flat surface.

As shown in FIG. 4, the laser light extends from the laser irradiation port of the laser light scanning device to the first and second irradiation surfaces 58,68 and draws a loop on the first and second irradiation surfaces 58,68. It is emitted. By scanning the laser beam in a loop with a laser beam scanning device, a molten pool made of molten metal is formed. The loop shape means that it is annular (closed loop) or spiral (open loop).

In the example shown in FIG. 4, the scanning locus of the laser beam has a shape similar to an ellipse. More specifically, in the plan view shown in FIG. 4, the first irradiation surface 58 of the first flat line 50 and the second irradiation surface 68 of the second flat line 60 are abutted by the linear abutting portion 90. In the plan view shown in FIG. 4, the scanning locus of the laser beam is a pair of arcuate portions 70,71 facing each other with the abutting portion 90 in the orthogonal direction orthogonal to the linear abutting portion 90, and a pair of linear portions. It is composed of 80,81. One arc-shaped portion 70 has a convex shape on the side opposite to the other arc-shaped portion 71 side, and the other arc-shaped portion 71 has a convex shape on the side opposite to the one arc-shaped portion 70 side. Have. Further, one linear portion 80 exists between one end of one arc-shaped portion 70 and one end of the other arc-shaped portion 71, and the other linear portion 81 is the other of the one arc-shaped portion 70. It exists between one end and the other end of the other arcuate portion 71. Each of the pair of linear portions 80,81 exists so as to straddle the first and second irradiation surfaces 58,68.

Although not described in detail, a laser light scanning device (not shown) includes, for example, a light source, a power supply, a power control unit, a first optical system formed of a concave lens, a second optical system formed of a convex lens, and reflection. Equipped with a mirror. The power control unit controls the amount of power supplied from the power source to the light source. Further, the first and second optical systems are arranged so that their respective optical axes are orthogonal to each other. The reflection mirror is composed of a tilt mirror, a galvano mirror, or the like, and is arranged around the intersection position of the optical axis of the first optical system and the optical axis of the second optical system.

The laser beam emitted from the light source passes through the first optical system, is reflected by the reflection mirror toward the second optical system, and is emitted from the second optical system. The laser beam scanning apparatus expands the laser beam incident on the first optical system, expands the beam diameter without changing the angle or the optical axis, and emits the laser light from the second optical system.

The laser light scanning device further includes a fluctuation mechanism that fluctuates the reflection angle of the reflection mirror, and a reflection angle control unit. The fluctuation mechanism supports the reflection mirror, and the fluctuation mechanism changes the reflection direction of the reflection mirror by its movement. The reflection angle control unit outputs a control signal to the fluctuation mechanism and controls the operation of the fluctuation mechanism. The laser light scanning device controls the emission direction of the emitted laser light by controlling the operation of the fluctuation mechanism with a control signal from the reflection angle control unit to control the reflection direction of the reflection mirror. In the laser light scanning device, the power control unit controls the amount of power supplied from the power source to the light source, and the reflection angle control unit controls the operating speed of the fluctuation mechanism to control the scanning speed (moving speed) of the laser light. This controls the energy density of the emitted laser light. Here, the energy density is the energy given to a unit area in a unit time. The energy density decreases as the scanning speed of the laser beam is increased or the output is reduced.

The laser light is based on software stored in the storage unit of the laser light scanning device under pre-programmed conditions, that is, with a predetermined timing, a predetermined direction, and a predetermined energy density. , Is irradiated from the laser irradiation port of the laser light scanning device. More specifically, with reference to FIG. 4, the scanning locus of the laser beam moves from one end side to the other end side of the abutting portion 90 while drawing a loop. In the example shown in FIG. 4, the scanning locus moves from one end side to the other end side of the abutting portion 90 while drawing an annular loop (closed loop). The scanning locus of the laser light can be realized, for example, by changing the emission direction of the laser light by the above-mentioned mechanism and moving the abutting portion 90 relative to the laser light scanning device in the extending direction thereof. In this relative movement, for example, the laser light scanning device is moved in the extending direction of the abutting portion 90 with respect to the stator core 11 by using an electric cylinder or the like, or the fixed base on which the stator core 11 is fixed is moved by the laser light scanning device. It can be executed by moving the butt portion 90 in the extending direction.

The laser beam becomes large when the heat input draws a pair of arcuate portions 70,71, while the heat input increases the pair of arcuate portions 70,71 when drawing a pair of linear portions 80,81. It is irradiated from the laser irradiation port so that it is smaller than when drawing. Each of the pair of linear portions 80,81 exists across the first and second irradiation surfaces 58,68. Therefore, since the corners of the first and second flat lines 50 and 60 are located around the abutment portions of the first and second irradiation surfaces 58 and 68, the heat input to the corners is the arcuate portion 70, It is smaller than the heat input to 71.

For example, when drawing the arcuate portions 70 and 71, the moving speed of the laser beam is slowed down and the output of the laser beam is increased. On the other hand, when drawing the pair of linear portions 80,81, the moving speed of the laser beam is made faster than when drawing the arcuate portions 70,71, and the output of the laser light is increased to the arcuate portion 70. Make it smaller than when drawing, 71. In this way, the above-mentioned heat input can be easily and efficiently realized.

In one example, when drawing a pair of arcuate portions ^{70,71, a laser beam having an energy density of 2.25 × 10 7} W / cm ^{2 to} 2.75 × 10 ⁷ W / cm ² is emitted, preferably. A laser beam having an energy density of 2.50 × 10 ⁷ W / cm ^{2 may be emitted.} When drawing a pair of linear portions ^{80,81, a laser beam having an energy density of 1.00 × 10 7} W / cm ^{2 to} 1.50 × 10 ⁷ W / cm ² is emitted, preferably energy. A laser beam having a density of 1.25 × 10 ⁷ W / cm ^{2 may be emitted.} The energy density of the emitted laser light is not limited to these values. In the present invention, if the energy density of the laser light irradiating the boundary region between the first and second irradiation surfaces is smaller than the energy density of the laser light irradiating other parts, the laser light emitted from the laser irradiation port. The energy density of can be any value.

According to the above embodiment, the one side surface 59 of the end portion 51 of the first flat wire 50 and the other side surface 69 of the end portion 61 of the second flat wire 60 are brought into contact with each other, and the end portion of the first flat wire 50 is brought into contact with each other. The first flat line 50 and the second flat line 60 are arranged so that the first irradiation surface 58 of 51 and the second irradiation surface 68 of the end portion 61 of the second flat line 60 are located on substantially the same plane. Then, the laser beam is emitted from the laser irradiation port so as to form a loop on the first and second irradiation surfaces 58, 68 while straddling the first and second irradiation surfaces 58, 68, and the first and second irradiation surfaces 58, In 68, the energy density of the laser light irradiating the boundary regions where energy is likely to be concentrated is made smaller than the energy density of the laser light irradiating the other parts. Therefore, since the temperature rise of the corners of the first and second flat lines 50 and 60 located near the boundary region can be suppressed, the occurrence of spatter can be suppressed, and the deterioration of welding quality due to spatter can be suppressed.

Further, when the laser beam is reciprocally scanned, heat is concentrated on the folded portion, and sputtering is likely to occur. On the other hand, according to the present embodiment, since the laser beam scanning locus is loop-shaped, the laser beam can be scanned smoothly. Therefore, it is difficult for heat to concentrate and the generation of spatter can be suppressed.

Further, the laser beam scanning locus has a shape similar to an ellipse, and the axis corresponding to the long axis extends so as to substantially coincide with the abutting portion 90. As a result, a molten pool can be generated in a short time at the butt portion 90 that requires welding, and welding can be performed in a short time.

The present invention is not limited to the above-described embodiment and its modifications, and various improvements and modifications can be made within the scope of the claims of the present application and the equivalent scope thereof.

For example, in the above embodiment, when drawing the arcuate portions 70,71, the moving speed (scanning speed) of the laser light is slowed down and the output of the laser light is increased, while the pair of linear portions 80,81 are drawn. In this case, the moving speed of the laser beam is increased in comparison with the case of drawing the arcuate portions 70,71, and the output of the laser beam is reduced in comparison with the case of drawing the arcuate portions 70,71. Was explained. However, while the moving speed of the laser beam is always kept constant, the output of the laser beam is increased when drawing an arcuate portion, and the output of the laser beam is changed to an arcuate shape when drawing a pair of linear portions. It may be smaller than when drawing a part. Alternatively, while the output of the laser light is always kept constant, the moving speed of the laser light is slowed down when drawing an arcuate part, and the moving speed of the laser light is changed to a circle when drawing a pair of linear parts. It may be faster than when drawing an arc. Further, a case where the scanning locus of the laser beam includes a closed loop composed of a pair of arcuate portions 70,71 and a pair of linear portions 80,81 has been described. However, the scanning locus of the laser beam may include any closed loop, for example an ellipse or a circle. Alternatively, the scanning locus of the laser beam may include any open loop and may have a spiral shape.

50 1st flat wire, 51 1st flat wire end, 52 1st flat wire insulating coating, 58 1st irradiation surface, 59 1st flat wire one side surface, 60 2nd flat wire, 61 2nd flat wire The end of the wire, 62 the insulating coating of the second flat wire, 68 the second irradiation surface, 69 the other side surface of the second flat wire.

Claims (1)

A method of laser welding a flat wire, in which the ends of the first flat wire and the second flat wire having a rectangular cross section, which do not have an insulating coating, are welded to each other by a laser beam.
The side surface of the end of the first flat line abuts the side surface of the end of the second flat line, and the end of the first flat line is irradiated with the laser beam. A flat line arrangement step in which the first flat line and the second flat line are arranged so that the second irradiation surface to which the laser beam is irradiated is located on substantially the same plane at the end of the second flat line. When,
After the flat line arrangement step, the laser light emitting step of straddling the first and second irradiation surfaces and emitting the laser light so as to draw a loop on the first and second irradiation surfaces is included.
In the laser light emitting step, the energy density of the laser light irradiating the boundary region between the first and second irradiation surfaces is smaller than the energy density of the laser light irradiating other parts of the flat line. Laser welding method.

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