JP2016078082A - Laser welding method and laser welding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a laser welding method and a laser welding device capable of preventing reduction in strength of the joint between a main body and a lid.SOLUTION: A laser welding device 1 for joining a main body and a lid forming a metal container B, together by the laser welding includes: a laser beam irradiation portion 2 for irradiating an irradiation place with a laser beam L1 while moving the irradiation place along a boundary portion G between the main body and the lid; a reflective mirror 3 for reflecting, toward the boundary portion G, reflection L2 of the laser beam L1 emitted by the laser beam irradiation portion 2, and reflected at the irradiation place; a rotation portion 4 for rotating the reflective mirror 3; a vertical movement portion 5 for vertically moving the reflective mirror 3; and a controller 6 for controlling the rotation portion 4 and the vertical movement portion 5. The controller 6 controls the rotation portion 4 and the vertical movement portion 5 so that re-reflection L3 is focused on a predetermined place ahead of the irradiation place, on a movement route at the boundary portion G.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laser welding method and a laser welding apparatus.

  In a battery such as a lithium ion secondary battery, an electrode assembly, an electrolytic solution, and the like are accommodated in a sealed metal container (battery can). This container includes a bottomed cylindrical main body and a lid, and the main body and the lid are joined by laser welding. As a sealing can technique for joining the main body and the lid by laser welding, for example, Patent Document 1 irradiates laser light with an inclination to the workpiece, and reflects the reflected light reflected by the workpiece with a spherical reflector. It is disclosed that the workpiece is irradiated again. The reflected laser light removes oil stains on the surface of the workpiece prior to melting of the workpiece and suppresses the occurrence of spatter.

Japanese Utility Model Publication No. 4-28709

  When laser welding the main body and the lid, the main body and the lid may be slightly separated on the opposite side of the welded portion. This is because the heat of laser welding is transmitted to other than the welded portion, and the lid is partially thermally deformed (thermal expansion). In particular, this problem becomes more conspicuous when the shape of the lid extends long in one direction, such as when the lid has an elongated rectangular shape. If welding is performed in a state where the main body and the lid are separated, the bonding strength between the main body and the lid is reduced. In order to prevent this, it is also conceivable to temporarily weld a plurality of predetermined locations before the main welding. However, if the temporary welding work is performed before the main welding, the time required for the entire welding process (sealing process) becomes longer. In Patent Document 1, although the reflected light is effectively used to suppress spattering, the portion irradiated with the reflected light is a close position slightly preceding the welded portion, so the amount of heat applied to a part of the lid increases. The thermal deformation of the lid becomes more remarkable.

  Then, this invention makes it a subject to propose the laser welding method and laser welding apparatus which can suppress the fall of the joint strength of a main body and a lid | cover, without said inconvenience.

  A laser welding method according to one aspect of the present invention is a laser welding method in which a main body and a lid constituting a metal container are joined by laser welding, and laser light is irradiated along a boundary portion between the main body and the lid. A laser beam irradiation process for irradiating while moving the part, and a reflection process for reflecting the reflected light reflected by the laser beam irradiated in the laser beam irradiation process toward the boundary with a movable reflection mirror In the reflection step, the reflecting mirror is moved to focus the reflected light reflected at a predetermined position on the moving path ahead of the irradiation position at the boundary.

  In this laser welding method, the reflected light reflected at the irradiated location is reflected by a movable reflecting mirror so as to be focused at a predetermined location on the moving path ahead of the irradiated location. Thereby, the location ahead of the location of this welding is temporarily welded using reflected light, and the fall of the joint strength of a main body and a lid | cover can be suppressed.

  In the laser welding method according to one embodiment, the reflection step causes the reflected light reflected at a predetermined location to be focused for a predetermined time. Thereby, temporary welding can be reliably performed using reflected light.

  In the laser welding method according to one embodiment, the container has a substantially rectangular parallelepiped shape, the boundary portion has a substantially rectangular shape having a long side portion and a short side portion, and the predetermined location is one end of the long side portion. It is a location on the other end side of the long side portion when positioned on the side. The long side portion has a long welded portion, and the main body and the lid are easily separated on the front side from the irradiation location, so that a predetermined location on the other end side of the long side portion is temporarily welded.

  A laser welding apparatus according to one aspect of the present invention is a laser welding apparatus for joining a main body and a lid constituting a metal container by laser welding, and irradiates laser light along a boundary portion between the main body and the lid. A laser beam irradiating unit that irradiates while moving the part, a reflecting mirror that reflects the reflected light reflected by the laser beam irradiated at the irradiated part toward the boundary part, and a rotating unit that rotates the reflecting mirror And a control unit that controls the rotation unit and the vertical movement unit, and the control unit reflects the light to a predetermined position on the moving path ahead of the irradiation point in the boundary part. The rotating unit and the vertical moving unit are controlled so that the reflected light is focused.

  In this laser welding apparatus, the incident angle of the reflected light at the reflecting mirror is adjusted by rotating the reflecting mirror at the rotating part, and the height from the boundary part of the reflecting mirror is adjusted by moving the reflecting mirror up and down at the vertically moving part. Adjust the position. By reflecting the reflected light so that the reflected light is focused at a predetermined location on the front of the moving path with respect to the irradiation location by the adjusted reflection mirror, the predetermined location can be temporarily welded.

  In the laser welding apparatus of one embodiment, the reflection mirror is a mirror having a curvature. By using a reflecting mirror having a curvature, the reflected light can be collected and the focal point can be focused.

  According to the present invention, it is possible to perform temporary welding using reflected light and suppress a decrease in bonding strength between the main body and the lid.

It is a figure which shows typically the laser welding apparatus which concerns on one Embodiment. It is a figure which shows the flow of operation | movement with the laser welding apparatus of FIG. 1, FIG. 2 (a) and FIG.2 (b) are under temporary welding, and FIG.2 (c) is after completion | finish of temporary welding. It is a figure which shows a lithium ion secondary battery typically, FIG. 3 (a) is sectional drawing, FIG.3 (b) is a top view.

  Hereinafter, a laser welding method and a laser welding apparatus according to an embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected about the element which is the same or it corresponds in each figure, and the overlapping description is abbreviate | omitted.

  In the present embodiment, the present invention is applied to a laser welding apparatus for sealing and welding a battery case can (metal container) in the manufacturing process of a rectangular battery. The battery is, for example, a power storage device such as a secondary battery or an electric double layer capacitor. The secondary battery is, for example, a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. Further, the manufactured battery may be a primary battery. In this embodiment, a lithium ion secondary battery is used. In addition to the prismatic battery, the present invention may be applied to a battery having another shape such as a cylindrical battery.

  Before describing the laser welding apparatus 1, a lithium ion secondary battery will be described with reference to FIG. FIG. 3 is a diagram schematically illustrating a lithium ion secondary battery, in which FIG. 3A is a cross-sectional view and FIG. 3B is a plan view. The lithium ion secondary battery A includes a battery case B and an electrode assembly C accommodated in the battery case B, and an electrolytic solution D is injected into the battery case B.

  The battery case B has a substantially rectangular parallelepiped shape. The battery case B is made of metal, for example, aluminum or aluminum alloy. The battery case B includes a bottomed rectangular tube-shaped main body Ba and a lid Bb that covers the opening of the main body Ba. The main body Ba is composed of a substantially rectangular flat plate-shaped bottom plate and four substantially rectangular flat plate-shaped side plates extending vertically upward from the four sides of the bottom plate. A stepped portion Bc is provided inside the upper end of the main body Ba. The lid Bb has a substantially rectangular flat plate shape. The lid Bb has the same shape as the opening at the upper end of the main body Ba, and is slightly smaller than the size of the opening. The lid Bb is placed on the stepped portion Bc of the main body Ba. The battery case B has a substantially rectangular parallelepiped sealed space formed by the body Ba and the lid Bb. A positive terminal E and a negative terminal F are attached to the lid Bb. Insulation rings Ea and Fa are provided at the respective attachment locations.

  In the laser welding apparatus 1, the entire circumference of the boundary portion G between the main body Ba and the lid Bb is laser-welded to join the main body Ba and the lid Bb. As shown in FIG. 3B, the boundary portion G has a substantially rectangular shape having a long side portion G1 and a short side portion G2. When welding is started on one end side of the long side portion G1, the main body Ba and the lid Bb may be slightly separated from the welding portion of the long side portion G1 on the front side. The battery case B is made of metal. In particular, when the lid Bb is made of aluminum or aluminum alloy excellent in heat conduction, the heat applied by laser welding is transmitted to the periphery of the welded portion. For this reason, when welding is continuously performed on one end side of the long side portion G1, the lid Bb extends to the other end side of the long side portion G1 due to thermal expansion. The longer the long side portion G1, the larger the amount of elongation due to thermal expansion, and the easier it is for the main body Ba and the lid Bb to separate. When welding is performed in a state where the main body Ba and the lid Bb are separated from each other, the joint strength of the portion is lowered. Therefore, in the laser welding apparatus 1, when one end side of the long side portion G1 is main-welded, an arbitrary portion on the other end side of the long side portion G1 is temporarily welded. The number of places to be temporarily welded is at least one, and may be two or more. Since the short side portion G2 is short, even if one end side of the short side portion G2 is welded, the main body Ba and the lid Bb are not separated so as to affect the welding (particularly the bonding strength). Therefore, the laser welding apparatus 1 does not perform temporary welding on the short side portion G2.

  The electrode assembly C includes a positive electrode, a negative electrode, and a separator that insulates the positive electrode from the negative electrode, and the positive electrode, the negative electrode, and the separator are laminated. The positive electrode includes a metal foil and a positive electrode active material layer formed on at least one surface of the metal foil. The positive electrode has a tab Ca in which the positive electrode active material layer is not formed at the end of the metal foil. The tab Ca is provided at the upper end portion of the positive electrode, and is electrically connected to the positive electrode terminal E through the conductive member Cb. The negative electrode includes a metal foil and a negative electrode active material layer formed on at least one surface of the metal foil. The negative electrode has a tab Cc in which the negative electrode active material layer is not formed at the end of the metal foil. The tab Cc is provided at the upper end portion of the negative electrode, and is electrically connected to the negative electrode terminal F through the conductive member Cd. The separator separates the positive electrode and the negative electrode and allows lithium ions to pass while preventing a short circuit of current due to contact between the two electrodes.

  The positive electrode and the negative electrode have a thin sheet shape and have a rectangular active material layer and tabs Ca and Cc at the upper end thereof. The separator has a thin sheet shape or a bag shape, and has a rectangular shape. The electrode assembly C is a laminated structure having a substantially rectangular parallelepiped shape in which a large number of positive electrodes and negative electrodes having this shape are stacked with a separator interposed therebetween, and tabs Ca and Cc of the respective electrodes are provided at the upper end portion.

  Now, the laser welding apparatus 1 will be described with reference to FIG. FIG. 1 is a diagram schematically showing a laser welding apparatus. The laser welding apparatus 1 welds a boundary portion G between the main body Ba and the lid Bb of the battery case B using a laser beam as a heat source, and joins the main body Ba and the lid Bb. In particular, the laser welding apparatus 1 uses the reflected light of the laser beam of main welding to temporarily weld a portion ahead of the main welding portion of the long side portion G1 of the boundary portion G. The laser welding apparatus 1 includes a laser light irradiation unit 2, a reflection mirror 3, a rotation unit 4, a vertical movement unit 5, and a control unit 6.

  The laser beam irradiation unit 2 irradiates the laser beam L1 while moving along the boundary G between the main body Ba and the lid Bb. The laser beam irradiation unit 2 is configured by using a conventional well-known laser device, for example, preferably by using a fiber laser. When the battery case B is made of aluminum, a semiconductor laser, a YAG laser, or the like May be used. In the case of a fiber laser, the wavelength of the laser beam is 1.07 μm. The Nd: YAG laser has a laser beam wavelength of about 1.06 μm, which is a preferable wavelength for welding.

  The laser beam irradiation unit 2 includes, for example, a laser beam oscillator, an optical system, a moving unit, and the like. The laser beam oscillator oscillates a laser beam L1 having a predetermined wavelength. The optical system tilts the laser beam L1 oscillated by the laser beam oscillator with respect to the surface Ga of the boundary G, and makes the laser beam L1 incident at a predetermined angle with respect to the surface Ga. Further, the optical system condenses the laser light L1 and focuses the laser light L1 on the surface Ga. Since the spot diameter of the laser beam on this surface Ga is very small, high-density energy can be obtained. When the laser beam irradiation unit 2 is configured by a fiber laser, a condensing lens that collects the laser beam L1 is not necessary, and the laser beam L1 can be easily inclined with respect to the surface Ga. A moving part moves the laser beam L1 to be irradiated along the boundary part G. In the moving unit, for example, the irradiation position of the laser beam L1 is moved by moving a part or all of the optical system. The moving unit is configured by an actuator that converts electrical energy or the like into translational motion, for example. The laser beam irradiation unit 2 is controlled by the control unit 6. Note that the moving unit may move the main body Ba and the lid Bb instead of moving the irradiated laser beam. In FIG. 1, the moving direction of the irradiated portion of the laser beam L1 is indicated by an arrow M. In the long side part G1 of the boundary part G, a predetermined part ahead of the irradiation part of the laser beam L1 in the moving direction M is a temporary welding part. Therefore, this temporary welding location is a predetermined location on the moving path ahead of the irradiation location at the boundary G.

  When the laser beam L1 is irradiated to the surface Ga of the boundary G by the laser beam irradiation unit 2, the main body Ba and the lid Bb are welded (main welding) using the high-density energy of the laser beam L1 as a heat source. However, many of the irradiated laser beams L1 are reflected by the surface Ga and scattered. For example, when the battery case B is made of aluminum and the laser light irradiation unit 2 is formed of a fiber laser, the laser light is reflected by approximately 90%. Hereinafter, the reflected laser light is referred to as reflected light L2.

  The reflection mirror 3 reflects the reflected light L2 toward the boundary portion G. The reflecting mirror 3 is a curved mirror having a predetermined curvature in order to collect the scattered reflected light L2. The predetermined curvature is appropriately set in consideration of the degree of scattering of the reflected light L2. The reflection mirror 3 is, for example, a mirror in which a flat mirror is bent into a curved surface with a predetermined curvature. The reflection mirror 3 is arranged on the optical path of the reflected light when the laser light L1 incident on the surface Ga of the boundary portion G at a predetermined angle is regularly reflected. The reflection mirror 3 is held so as to be rotatable around an axis parallel to the surface Ga. The reflection mirror 3 is held in a state of being moved up and down in a direction perpendicular to the surface Ga. Hereinafter, the laser light reflected by the reflecting mirror 3 is referred to as re-reflected light L3. The reflection mirror 3 may be a spherical mirror.

  In the laser welding apparatus 1, the front side of the irradiation part of the laser beam L1 of the long side part G1 of the boundary part G is temporarily welded by the re-reflected light L3. However, the energy of the re-reflected light L3 is reduced compared to the laser light L1. Therefore, in order to perform temporary welding with the re-reflected light L3, it is necessary to irradiate the same part continuously for a predetermined time. Since the irradiation spot (main welding spot) of the laser beam L1 is moving, when the incident angle of the reflected light L2 on the reflecting mirror 3 is fixed, the reflecting mirror 3 reflects the re-reflected light L3 to the same spot. I can't let you. Therefore, in the laser welding apparatus 1, by adjusting the incident angle of the reflected light L2 on the reflection mirror 3 and the height position of the boundary portion G of the reflection mirror 3 from the surface Ga, the reflection mirror 3 continuously repeats for a predetermined time. The reflected light L3 is reflected at the same location.

  The rotating unit 4 rotates the reflecting mirror 3 around an axis parallel to the surface Ga of the boundary G. By rotating the reflection mirror 3 in this way, the incident angle (= reflection angle) of the reflected light L2 on the reflection mirror 3 can be changed. The rotating unit 4 is composed of, for example, an actuator that converts electrical energy or the like into rotational motion. The rotating unit 4 is controlled by the control unit 6.

  The vertical movement unit 5 moves the reflection mirror 3 up and down in a direction perpendicular to the surface Ga of the boundary G. Thus, the height position from the surface Ga of the reflective mirror 3 can be changed by moving the reflective mirror 3 up and down. The vertical movement part 5 is comprised by the actuator which converts an electrical energy etc. into a translational motion, for example. The vertical movement unit 5 is controlled by the control unit 6.

  In addition, the laser beam L1 irradiated by the laser beam irradiation unit 2 moves along the boundary portion G between the main body Ba and the lid Bb. In order to arrange the reflecting mirror 3 on the optical path of the reflected light L2 of the moving laser light L1, the reflecting mirror 3 is also moved along the boundary portion G in synchronization with the movement of the laser light L1. Depending on the configuration of the rotation unit 4 and the vertical movement unit 5, the rotation unit 4 and the vertical movement unit 5 are also moved along the boundary G. For example, the reflecting mirror 3, the rotating unit 4, and the up / down moving unit 5 are also assembled to the moving unit of the laser light irradiation unit 2 and moved together by the moving unit.

  The control unit 6 is an electronic control unit that controls the laser welding apparatus 1 and includes a memory such as a CPU [Central Processing Unit], a ROM [Read Only Memory], and a RAM [Random Access Memory], an input / output circuit, and the like. The control unit 6 may be incorporated as a function of the control device for the battery production line, or may be configured as a dedicated control unit for the laser welding apparatus 1. The control unit 6 controls the laser beam irradiation unit 2 to perform the main welding and also controls the rotating unit 4 and the vertical movement unit 5 to perform the temporary welding.

  Control of the laser beam irradiation unit 2 will be described. When the sealing process starts, the control unit 6 transmits a start command to the laser beam oscillator of the laser beam irradiation unit 2. Further, the control unit 6 transmits a movement command to the moving unit of the laser beam irradiation unit 2 in order to move the irradiation spot of the laser beam L1 along the boundary G at a predetermined speed. The predetermined speed is appropriately set in consideration of the energy level of the laser beam L1, the thickness of the lid Bb, and the like. When the entire circumference of the boundary portion G is irradiated with laser light (when main welding is completed), the control unit 6 transmits a stop command to the laser beam oscillator and transmits a stop command to the moving unit.

  The rotating unit 4 and the vertical movement unit 5 will be described. When the main welding on one end side of the long side G1 of the boundary G is started with the laser light L1, the control unit 6 responds to the irradiation position (main welding) of the long side G1 of the laser light L1 for a predetermined time. The incident angle of the reflected light L2 at the reflecting mirror 3 and the height position from the surface Ga of the boundary G of the reflecting mirror 3 necessary for focusing the re-reflected light L3 at the temporary welding point in the long side G1. calculate. The predetermined time is appropriately set in consideration of the energy level of the re-reflected light L3, the thickness of the lid Bb, and the like. As the temporary welding location, the location on the other end side of the long side portion G1 is appropriately set. When a predetermined time has elapsed, the control unit 6 causes the incident angle of the reflected light L2 at the reflecting mirror 3 and the surface Ga of the reflecting mirror 3 from the surface Ga to be necessary for the re-reflected light L3 to be directed to the main body Ba and the lid Bb. Calculate the height position. However, when two or more temporary welding locations are set, the control unit 6 performs the same process as described above for the next temporary welding location. Further, when the main welding is performed at the short side G2 of the boundary portion G with the laser light L1, the control unit 6 has a reflection mirror necessary for directing the re-reflected light L3 in a direction in which the main body Ba and the lid Bb are not irradiated. The incident angle of the reflected light L2 at 3 and the height position from the surface Ga of the reflecting mirror 3 are calculated. In addition, instead of calculating the reflection angle and the height position for each irradiation spot of the laser beam L1, the reflection angle and the height position are calculated in advance for each irradiation spot of the laser beam L1, and the irradiation spot Each reflection angle and height position may be stored in the memory of the control unit 6.

  Each time the controller 6 calculates the incident angle of the reflected light L2 on the reflecting mirror 3, the controller 6 calculates an angle and a rotating direction for rotating the reflecting mirror 3 necessary to obtain the incident angle, and the angle and the rotating direction. Is transmitted to the rotating unit 4. Further, every time the height of the reflecting mirror 3 from the surface Ga is calculated, the control unit 6 calculates a distance and a moving direction for moving the reflecting mirror 3 up and down necessary to reach this height position. A vertical movement command indicating the distance and the moving direction is transmitted to the vertical movement unit 5.

  With reference to FIG. 2 in addition to FIG. 1 and FIG. 3, the flow of operation when the laser welding apparatus 1 performs main welding and temporary welding at the long side portion G1 of the boundary portion G will be described. FIG. 2 is a diagram showing a flow of operation in the laser welding apparatus 1, FIG. 2 (a) is being temporarily welded at the long side portion, and FIG. 2 (b) is being temporarily welded at the long side portion. (When the main welding location has moved forward relative to FIG. 2A), FIG. 2C is after the end of temporary welding. In addition, as shown in FIG. 2, only one place shown by the code | symbol P0 in the long side part G1 is used as a temporary welding location.

  In the laser beam irradiating unit 2, the laser beam oscillator and the moving unit are operated in accordance with an instruction from the control unit 6, and the laser beam L1 is irradiated while moving along the boundary G between the main body Ba and the lid Bb (laser beam). Irradiation step). The portion irradiated with the laser beam L1 is welded (main welding), and the main body Ba and the lid Bb are joined. The irradiation spot moves in the movement direction M at a predetermined speed. A part of the irradiated laser light L1 is reflected and becomes reflected light L2.

  As shown in FIG. 2A, the laser beam irradiation unit 2 irradiates the irradiation point P1 on one end side of the long side portion G1 with the laser beam L1. At this time, in the control unit 6, the incident angle θ1 and the height position H1 necessary for focusing the re-reflected light L3 at the temporary welding point P0 on the other end side of the long side part G1 according to the irradiation point P1. Is calculated.

  The control unit 6 transmits a rotation command indicating a rotation angle and a rotation direction necessary for setting the incident angle θ1 to the rotation unit 4. When receiving the rotation command, the rotation unit 4 rotates the reflection mirror 3 in accordance with the rotation command. In addition, the control unit 6 transmits an up / down movement command indicating the up / down movement distance and the movement direction necessary for the height position H <b> 1 to the up / down movement unit 5. When receiving the vertical movement command, the vertical movement unit 5 moves the reflection mirror 3 up and down according to the vertical movement command. Thereby, in the reflection mirror 3, the reflected light L2 is incident at an incident angle θ1 and reflected (reflection process). The re-reflected light L3 reflected by the reflecting mirror 3 is focused at the temporary welding point P0.

  As shown in FIG. 2B, the laser beam irradiation unit 2 irradiates the irradiation point P2 on one end side of the long side portion G1 with the laser beam L1. This irradiation location P2 is a location ahead of the irradiation location P1 in the moving direction M, and is closer to the temporary welding location P0 than the irradiation location P1. The controller 6 calculates the incident angle θ2 and the height position H2 necessary for the re-reflected light L3 to focus at the temporary welding point P0 according to the irradiation point P2. The incident angle θ2 is smaller than the incident angle θ1. The height position H2 is higher than the height position H1.

  The control unit 6 transmits a rotation command indicating a rotation angle and a rotation direction necessary for setting the incident angle θ2 to the rotation unit 4. When receiving the rotation command, the rotation unit 4 rotates the reflection mirror 3 in accordance with the rotation command. The reflecting mirror 3 after the rotation is counterclockwise (however, when the reflecting mirror 3 is viewed from the lid Bb side) as compared with the angle of the reflecting mirror 3 shown in FIG. It is rotated by a predetermined angle. In addition, the control unit 6 transmits an up / down movement command indicating the up / down movement distance and the movement direction necessary for the height position H <b> 2 to the up / down movement unit 5. When receiving the vertical movement command, the vertical movement unit 5 moves the reflection mirror 3 up and down according to the vertical movement command. Thereby, in the reflective mirror 3, the reflected light L2 is incident at an incident angle θ2 and reflected (reflecting step). The re-reflected light L3 reflected by the reflecting mirror 3 is focused at the temporary welding point P0.

  In addition, the distance from the reflecting mirror 3 of the re-reflected light L3 to the temporary welding location P0 as shown in FIG. 2A and the temporary welding location P0 from the reflecting mirror 3 of the re-reflected light L3 as shown in FIG. Is the same distance (corresponding to the focal length). Since the reflection mirror 3 is a curved mirror, the reflected light L2 that is scattered can be collected and focused. The focal length is determined according to the curvature of the reflection mirror 3.

  The re-reflected light L3 is continuously irradiated for a predetermined time to the temporary welding spot P0. Thereby, temporary welding location P0 is welded (temporary welding), and main body Ba and lid | cover Bb are joined. Therefore, it is possible to prevent the main body Ba and the lid Bb from separating on the front side of the main welding portion in the moving direction M when the one end side of the long side portion G1 is main-welded with the laser beam L1. Therefore, when the remaining portion of the long side portion G1 is welded with the laser beam L1, welding can be performed in a state where the main body Ba and the lid Bb are in close contact with each other.

  As shown in FIG. 2C, the laser beam irradiation unit 2 irradiates the irradiation point P3 of the long side portion G1 with the laser beam L1. At this time, a predetermined time or more has elapsed since the start of temporary welding. The control unit 6 calculates the incident angle θ3 and the height position H3 that are necessary for turning the re-reflected light L3 in the direction in which the main body Ba and the lid Bb are not irradiated.

  The control unit 6 transmits a rotation command indicating a rotation angle and a rotation direction necessary for setting the incident angle θ3 to the rotation unit 4. When receiving the rotation command, the rotation unit 4 rotates the reflection mirror 3 in accordance with the rotation command. In addition, the control unit 6 transmits an up / down movement command indicating the up / down movement distance and the movement direction necessary for the height position H3 to the up / down movement unit 5. When receiving the vertical movement command, the vertical movement unit 5 moves the reflection mirror 3 up and down according to the vertical movement command. Thereby, in the reflective mirror 3, the reflected light L2 enters at an incident angle θ3 and is reflected. The re-reflected light L3 reflected by the reflecting mirror 3 is detached from the main body Ba and the lid Bb.

  According to the laser welding apparatus 1, the reflected light L2 is utilized by reflecting the reflected light L2 with the movable reflecting mirror 3 so that the reflected light L2 is focused on the temporary welding location ahead of the main welding irradiation location. A part ahead of the main welding part can be temporarily welded. In particular, when one end side of the longer long side portion G1 of the boundary portion G is subjected to main welding, the other end side of the long side portion G1 is temporarily welded, so that the main welding portion in the long side portion G1 is Can prevent the front main body Ba and the lid Bb from separating. As a result, even the long long side portion G1 can be subjected to main welding in a state where the main body Ba and the lid Bb are in close contact with each other, and a decrease in the bonding strength between the main body Ba and the lid Bb can be prevented.

  Further, according to the laser welding apparatus 1, by performing temporary welding immediately after the start of the main welding, the lid Bb is thermally expanded by the heat transmitted from the welding location of the main welding to the surroundings, and before the main body Ba and the lid Bb are separated. Moreover, temporary welding can be performed. Moreover, according to the laser welding apparatus 1, since temporary welding is also performed during the main welding, the time required for the entire welding process (sealing process) does not increase.

  Further, according to the laser welding apparatus 1, the reflection mirror 3 is rotated to adjust the incident angle of the reflected light L <b> 2 at the reflection mirror 3, and the reflection mirror 3 is moved up and down so that the surface Ga of the boundary portion G of the reflection mirror 3. By adjusting the height position, the re-reflected light L3 can be focused on the same location (temporary welding location) even though the laser beam L1 and the reflected beam L2 are moving. Moreover, according to the laser welding apparatus 1, temporary welding can be reliably carried out using the reflected light L2 whose energy is reduced by irradiating the same portion with the re-reflected light L3 for a predetermined time. Moreover, according to the laser welding apparatus 1, by using the reflection mirror 3 having a predetermined curvature, the scattered reflected light L2 can be condensed without using a condensing lens.

  As mentioned above, although embodiment of this invention was described, it is implemented in various forms, without being limited to the said embodiment.

  For example, in the above embodiment, a curved (or spherical) reflecting mirror having a predetermined curvature is used, but a flat reflecting mirror may be used. In the case of using a flat reflection mirror, a condensing lens is preferably interposed between the reflection mirror and the battery case can in order to condense the laser light.

  Moreover, in the said embodiment, although applied to the sealing can welding of the substantially rectangular parallelepiped battery case, only the long side part of the substantially rectangular boundary part was temporarily welded, but even if it performs temporary welding also to a short side part Good. Since the main body and the lid may be slightly separated if the short side portion is longer than a certain length, it is possible to prevent the main body and the lid from being separated by temporary welding even in the short side portion. Moreover, when applying to sealing welding of a substantially cylindrical battery case, a plurality of places may be temporarily welded at predetermined intervals in a substantially circular boundary. It can prevent that a main body and a lid | cover leave | separate by this temporary welding of several places.

  In the above embodiment, the reflected light L2 is reflected so as to be focused on the temporary welding position ahead in the movement direction M from the irradiation position of the main welding, but it is not particularly limited thereto. You may make it reflect so that it may focus on the unwelded part which hits ahead on a movement path | route rather than an irradiation location, and you may make it carry out temporary welding. For example, as shown in FIG. 3 (b), when the current irradiation position of the main welding is a position P4 in one long side portion G1, the other long side deviating from the moving direction M at the time of the irradiation position P4. The part P5 in the part G1 is set as a temporary welding part. In this case, the number of axes for rotating the reflection mirror can be increased and the reflection mirror can be rotated in a plurality of rotation directions.

  Further, in the above embodiment, the case where the laser beam is irradiated from the upper side of the battery case can to the boundary part of the upper surface of the battery case can has a boundary part between the main body and the lid on the side surface of the battery case. It can also be applied when laser light is irradiated from the side of the can. Even when laser light is irradiated from the side, temporary welding can be performed using reflected light.

  DESCRIPTION OF SYMBOLS 1 ... Laser welding apparatus, 2 ... Laser beam irradiation part, 3 ... Reflection mirror, 4 ... Rotation part, 5 ... Vertical movement part, 6 ... Control part.

Claims (5)

A laser welding method for joining a main body and a lid constituting a metal container by laser welding,
A laser beam irradiation step of irradiating the laser beam while moving the irradiation spot along the boundary between the main body and the lid;
A reflection step of reflecting the reflected light reflected by the laser light irradiation step at the irradiation point toward the boundary portion with a movable reflection mirror;
Including
The reflection step is a laser welding method in which the reflecting mirror is moved to focus the reflected light reflected at a predetermined position ahead of the irradiation position in the boundary portion on the moving path.   2. The laser welding method according to claim 1, wherein in the reflecting step, a focus of the reflected light reflected on the predetermined portion is set for a predetermined time. The container has a substantially rectangular parallelepiped shape,
The boundary part is a substantially rectangular shape having a long side part and a short side part,
The laser welding according to claim 1 or 2, wherein the predetermined location is a location on the other end side of the long side portion when the irradiation location is located on one end side of the long side portion. Method. A laser welding apparatus for joining a main body and a lid constituting a metal container by laser welding,
A laser beam irradiation unit configured to irradiate a laser beam while moving an irradiation point along a boundary between the main body and the lid;
A reflection mirror that reflects the reflected light reflected by the laser beam irradiated from the laser beam irradiation unit toward the boundary part; and
A rotating unit for rotating the reflecting mirror;
An up-and-down moving unit for moving the reflection mirror up and down;
A control unit for controlling the rotating unit and the vertical movement unit;
With
The control unit controls the rotating unit and the up-and-down moving unit so that the reflected light reflected is focused on a predetermined location on the moving path ahead of the irradiation location at the boundary portion. .   The laser welding apparatus according to claim 4, wherein the reflection mirror is a mirror having a curvature.

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