JP2018202478A - Laser-sealing port device - Google Patents

Abstract

To provide a laser-sealing port device that achieves high speed welding without welding defects in response to enlargement of on-vehicle lithium batteries, increases joining strength by enabling deep melting-in almost double that with a conventional counterpart of heat conduction type and without causing entry of spatter into the vessel interior in principle, and also allows flexible beam arrangement.SOLUTION: A laser-sealing port device comprises means for dividing one laser beam into two and means for moving the two focus light beams in parallel at a high speed relative to a joining interface in a keyhole state along a butting interface of a sealing part. In doing so, the occurrence of spatter on the joining interface is eliminated by symmmetrically arranging the two focus light beams at positions equal from the joining interface so that the focus light beams do not enter the joining interface.SELECTED DRAWING: Figure 1

Description

  The present invention mainly relates to laser sealing of metal containers such as batteries.

  In recent years, the performance of in-vehicle lithium batteries, EVs, and HEV motors has been enhanced, and the electrification of automobiles has been rapidly progressing as a trump card for environmental measures such as M2.5 and fossil resource depletion. Lithium batteries using square aluminum containers are often used for in-vehicle applications, but in particular, high energy is stored in in-vehicle lithium batteries. There is a risk of causing an accident and burning the car. Therefore, it is necessary to perform laser sealing without spatter mixing in principle on an in-vehicle lithium battery.

  There are two types of laser welding: keyhole type welding and heat conduction type welding. Keyhole welding is a welding method in which the energy density is increased by using a high-concentration laser beam to cause the keyhole to exceed the boiling point of the processed part, but when the metal exceeds the boiling point and becomes metal vapor, the volume rapidly expands and melts. Heat conduction type welding is performed because there is a concern that the metal that has been pushed out may generate so-called spatter and be mixed into the battery and cause an internal short circuit.

JP 2012-79476 A JP2013-132655A JP 2012-110905 A

“Fiber Lasers: Multiple laser beam materials processing” LASER FOCUS WORLD 02/17/2016 volume-52 issue-02 2009 Laser Processing Society Spring Seminar Materials (2009, 5)

  Patent Document 1 can be presumed to be a method in which spatter is not generated in principle by heat conduction welding from the penetration shape shown in FIG. In addition, since the maximum intensity of the laser laser beam is shifted from the joint, the amount of laser light that leaks into the gap from the joint is reduced, so that the organic separator that is sensitive to heat inside the battery is not damaged. Can be.

  The joining principle of heat conduction type welding that does not generate spatter is that the laser beam size at the processing point is increased to lower the energy density, the molten metal temperature is maintained so that the processing point does not exceed the boiling point, and the molten metal by laser irradiation is This is realized by filling the bonding interface with surface tension and bonding. This heat conduction type welding suppresses the metal melting temperature that does not exceed the boiling point of the molten metal, so the phenomenon that the molten metal boils and the steam blows away the molten metal, that is, no bumping occurs, so that spatter is generated in principle. There is no.

  Therefore, this heat conduction type welding is used for sealing an in-vehicle battery container in which spatter contamination is strictly required. Lithium batteries are light weight, have a low melting point, high boiling point, and high thermal conductivity, so aluminum containers are often used. Therefore, they are suitable for heat conduction welding and have been put to practical use as standard laser sealing methods for lithium batteries. Yes.

  Although heat conduction type welding is a welding method that does not generate spatter in principle, there are some drawbacks. Since aluminum and the like have high thermal conductivity, heat is dissipated to the periphery of the surface, so that deep penetration cannot be achieved and welding strength cannot be increased. In addition, since it takes time for the heat to be transferred to the surroundings and melted, the welding speed cannot be increased. When the welding speed is low, high heat conductors such as aluminum and copper have a large loss of input energy because heat escapes to the surroundings.

  In fact, with heat conduction welding, the sealing speed is limited to 100 mm / s even when a laser power of several KW is applied to seal an aluminum lid exceeding 1 mm thickness and an aluminum container exceeding 0.5 mm thickness of a vehicle-mounted battery. It is. Further, the limit is about 0.5 mm which is equivalent to the minimum thickness required for securing the strength of the aluminum container.

  The reason is that even if the laser power is increased, the heat conduction type welding has a limit in the penetration depth because heat diffuses to the surface. Further, when the laser power is further increased, the surface temperature becomes high and becomes brittle even when oxidized, or small bubbles exceeding the boiling point of aluminum are generated on the surface and spattering begins to occur. Moreover, since a big heat energy is given, a deformation | transformation and a crack may generate | occur | produce in a container.

  That is, the heat conduction type welding has some of these problems, and also requires an expensive high-power laser, and the production cost performance is not good.

  In the future, the electrification of cars is expected to increase by several tens of times, and as competition for battery development intensifies, in addition to ensuring higher strength and welding quality, the cost performance that enables high-speed welding A high welding method is required.

  On the other hand, since keyhole type welding achieves high penetration and high-speed welding at the same time, in principle, it solves some problems of the above-mentioned heat conduction type welding and can exceed the welding limit.

  The principle will be described below. Keyhole welding greatly improves the absorption efficiency because more than half of the laser beam is contained in the keyhole. For example, in the case of an aluminum container, the absorptance with respect to a fiber laser having a wavelength of 1070 nm is only a few percent for a solid, but increases to a few tens of percent for a liquid.

  Further, when a keyhole is generated, the laser absorptance is improved to nearly 80% due to the laser multiple reflection confinement effect in the keyhole. Therefore, in the case of aluminum welding, the keyhole type welding may obtain an absorption efficiency more than double that of the heat conduction type welding.

  Therefore, if it is possible to realize a high-speed and deep penetration method that suppresses the amount of spatter generated and does not mix with the spatter inside the container, even though it is keyhole type welding, all the problems of heat conduction type welding in the current production of in-vehicle lithium batteries described above can be achieved. It can be solved at once.

  Patent Document 2 is a method of using a wedge substrate for a soldering application, and dividing a distance between two beams into mm to cm order.

  A method of splitting the beam with the wedge substrate is known, but in order to be able to adjust to an arbitrary intensity ratio, a system that can move the wedge is sought in FIG.

  However, if the wedge is partly divided into large parts on the order of mm, the mode will be lost and the light condensing performance will be reduced, making it impossible to perform highly condensing keyhole welding. In soldering applications, a peak as high as welding is not necessary, and rather defocusing and using a larger beam often causes no problem even if the beam quality is poor.

  However, in laser welding applications, large spatter is generated when the beam quality is reduced to a large condensing size, so that the condensing property essential for keyhole welding is not reduced by preventing the condensing size from increasing. I have to do it.

  Further, in the configuration of FIG. 2 of Patent Document 2, since the purpose is to move the wedge substrate, the wedge substrate is not directly cooled, and heat is stored in the wedge substrate in a sealed lens barrel. It has become.

  In this configuration, it can withstand heat for solder, but it is effective for laser solder that is usually used at several tens of watts in welding applications, but welding is a laser beam split that can withstand laser power of several kW and 100 times or more. An optical system is required.

  In addition, a keyhole type is not required for soldering. Furthermore, the keyhole type + heat conduction type is almost ineffective in soldering applications.

  In Patent Document 3, when a prismatic battery is covered with a beam divided into two beams using a diffraction grating, the diffraction grating is oscillated so that the two beams are always at the target position at the junction interface. By rotating, the short side and the long side can be welded in the same positional relationship.

  However, in order to swing and rotate according to the welding speed and the curvature of the corner that change at the corners and straight portions, a complicated optical system and very complicated control are required. In addition, the dividing means using a diffraction grating first requires a great deal of money to manufacture the diffraction grating, is difficult to design and manufacture to ensure the performance as designed, and the beam characteristics are fixed, so it cannot be used flexibly. .

  Moreover, the diffraction grating has no flexibility, and the diffraction efficiency is only 70 to 90%. Therefore, not only an expensive high-power laser is required, but in the KW class, the dispersed beam may adversely affect the periphery.

  Non-Patent Document 1 is an example of welding using a welding rod 111 in butt welding as shown in FIG. After preheating with the two beams 123 across the bonding interface 112, welding is performed while melting the welding rod 111 with the third laser beam 114, thereby achieving good welding.

  However, since these three beams are generated from three fibers 121 as shown in FIG. 12, the positional relationship of the three beams is fixed and cannot be welded flexibly. There is also a problem that three special fibers 121 are required.

  The present invention solves all of the above-mentioned problems and realizes high-speed welding free of welding defects that are practically problematic. Therefore, the keyhole type welding that usually generates spatter is devised, spatter is pulverized to the smoke level to suppress generation, and in principle, spatter is not mixed inside the container, nearly twice as deep as the conventional heat conduction type Achieves penetration and increases bonding strength. It is another object of the present invention to provide a laser sealing device capable of withstanding a high power of several KW class and capable of a flexible beam configuration.

  In order to achieve the above object, the first means of the present invention includes means for splitting one laser beam into two, and joining the two focused beams in a keyhole state along the butt interface of the sealing portion. A means for parallel translation at high speed is provided for the interface.

  At this time, the two converging beams are arranged symmetrically at the same position from the bonding interface so that the condensing beam does not enter the bonding interface, so that the laser beam does not hit the bonding interface, so that sputtering is performed at the bonding interface. It has been eliminated.

  Also, as a beam splitting means that can withstand a strong laser beam of several kilowatts, it condenses a 1 to 3 mm thick quartz circular cover glass with sufficient heat dissipation by sandwiching the circumference between an aluminum screw ring and a lens barrel housing. Inserted in front of the lens.

  One side of this circular cover glass is half-moon shaped with an angle of only 1 degree or less and tapered to a flat surface and coated on both sides with AR coating, so there is almost no branch loss and no heat generation. Are separated into two beams. In addition, in order to secure the light condensing property that is indispensable for generating a keyhole, the beam divided into two utilizes the property that it becomes a circular condensing shape of the same size as the original beam at the condensing point. .

  Further, since the distance between the two sub-mm beams is extremely short, it is suitable for the metal melted using the generated keyhole as a heat source to fill the joining interface so as to penetrate into the brazing material by surface tension. Further, the spot at the condensing point of the beam divided into two is as small as 50 μm or less, and the laser beam leakage into the gap can be completely prevented.

  Therefore, it also serves to shield the generated spatter. Furthermore, the sputter generated from a 50 μm spot is usually 50 μm or less, and the size can be reduced to 20 μm or less, which is considered to be no problem even if most of the spatter is mixed.

  Moreover, such spatters as small as smoke or fume can be blown away by nitrogen gas blown for preventing oxidation. In addition, since the direction blown away is a direction away from the laser irradiation part to joining of a container, it does not enter into an unsealed part.

  In order to achieve the above object, the second means of the present invention changes the directions of the two laser beams at the time of welding the short side of the opening to the rectangular container having the opening of the long side and the short side. Instead, the conventional heat conduction type welding can be performed by simply bringing the laser column close to the container about several millimeters, defocusing and seam welding.

  Naturally, the penetration depth on the short side is about half that of keyhole welding, but the short side is usually a fraction of the length of the long side, so in the container pressure test, even the penetration depth of less than half breaks from the short side. There is nothing to do. In the container pressure test, since it deforms into a spherical shape, the place where the maximum stress is generated is the center of the long side, and it is sufficient to deepen the penetration on the long side.

  As described above, in the present invention, a diameter of 0.6 mm, which is a spot size necessary for normal heat conduction welding, can be easily formed by simply defocusing the laser barrel without rotating the beam at the short side. . The formation principle will be described in detail in Examples.

  In order to achieve the above object, the third means of the present invention is to provide a third laser beam having an intensity distribution that causes heat conduction type welding so as to wrap two laser beams that cause keyhole welding at a joint. Superimpose. When this third laser beam is superposed, the temperature is increased by heating the vicinity where the keyhole welding is performed with the two laser beams, so that the metal melting point necessary for melting the peripheral metal using the keyhole as a heat source. Since it extends to a wide range, the penetration depth can be further increased while maintaining the keyhole welding state.

  In addition, due to the preheating effect, sudden bumping due to metal boiling can be suppressed suddenly and the occurrence of spatter can be reduced. Furthermore, since the time during which the molten metal is liquid is increased due to the residual heat effect, it is possible to secure time for the bubbles generated in the keyhole to escape to the atmosphere before the molten metal is cured, thereby eliminating the blowhole and realizing high-quality welding.

  As described above, according to the present invention, not only prevents spatter mixing that occurs in keyhole welding, but also eliminates defects such as voids and cracks that can occur in keyhole welding, and does not cause liquid leakage. It becomes possible to realize welding.

  Furthermore, compared to conventional heat conduction type welding, it can be produced at a high speed of more than double speed with the same laser power, which can contribute to the reduction of air pollution due to the diffusion effect by reducing the manufacturing cost of the battery. Moreover, since the strength of the on-vehicle battery container is increased by simultaneously realizing a high-speed penetration depth, there is also an advantage of suppressing a car ignition accident.

  In recent years, attempts have been made to increase the size of in-vehicle square batteries in order to increase the travel distance and reduce costs. As described above, the heat conduction type welding has a limit of a penetration depth of 0.5 mm, and if the welding speed is lowered to increase the penetration depth, the welding state becomes unstable.

  The reason for this will be described in detail in Examples. Further, when the battery is enlarged, the stress at the center of the long side increases in proportion to the size. Therefore, it is considered difficult to increase the size of the battery due to the limit of the penetration depth of 0.5 mm.

  However, according to the present invention, since the penetration is more than double, a large battery having a size twice as large as that of the current situation and a volume larger than 8 times is also possible.

  Furthermore, even with highly reflective materials such as aluminum and copper, when keyhole welding is performed, the absorption rate increases from about 10% to about 80% in the case of aluminum, and from 1% to 2% to several tens of percent in the case of copper. Therefore, not only the efficiency is improved, but also the effect of reducing voids and other defects by preheating + slow cooling effect by superimposing with heat conduction type welding by semiconductor laser, and reducing spatter by reducing the size significantly. A high quality weld bead with a mirror surface can be produced.

Configuration diagram of a laser head having the function of processing with three laser beams Diagram showing the structure of an optical system that separates two laser beams and the principle that a half-moon shaped beam becomes a perfect circle The figure which shows the state welded with two laser beams Configuration diagram of another optical system that separates into two laser beams Diagram showing the principle that return light does not return to the fiber Diagram showing the principle that return light does not return to the fiber type semiconductor laser fiber due to oblique incidence The figure which showed three laser beam states in a processing point at the time of welding the long side and short side of a square container Enlarged view of machining points Illustration of keyhole welding phenomenon Effect of welding speed and power Laser welding application examples other than aluminum containers according to the present invention Optical system in the case of FIG. Basic condensing state diagram of condenser lens

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of one embodiment of the apparatus of the present invention. The fiber laser beam 2 with NA <0.1 from the fiber laser 1 is collimated by the collimating lens 3, passes through the wedge plate 4 that is obliquely cut and polished, and is reflected by the folding mirrors 5 and 6, for example, at a wavelength of 1070 nm of the fiber laser 1. After passing through a mirror 8 that reflects, for example, a wavelength of 915 nm of the LD laser 7 and condensing by the condenser lens 9, two circular spots 11 of 40 μm, for example, GAP = 0.3 mm are obtained at the condensing point 10. It is done.

  On the other hand, the laser beam 13 with NA> 0.1 from the LD laser 7 is emitted from the optical fiber 12, collimated by the collimating lens 14, and then folded by the mirror 8 which can be angle-adjusted, and the mirror 8. After superimposing the light 2, the light is condensed at a condensing point 10 to a spot size of, for example, 400 μm so as to wrap around the two circular spots 11, and a spot 16 in which three laser beams are superimposed is obtained.

  Here, the alignment of the three spots is performed by, for example, changing the angle of the folding mirror 15 using the CCD camera 17.

  FIG. 2 is a diagram showing a process in which two perfect circles SPOT 11 are obtained at the condensing point after passing through the half-moon shaped wedge plate 20. Here, the wedge plate 20 has a shape and a mounting direction different from the wedge plate 4 shown in FIG. 1, and is attached in the opposite direction, but both show flexibility that can be separated into two perfect circles.

  The laser beam 21 at the position A-A that has just passed through the wedge plate 20 has substantially the same round shape as before the passage, but the laser beam 22 at the position BB incident on the condenser lens 9 has only two half moons. Are separated. Thereafter, as the light is condensed, the corner is rounded at the laser beam 23 at the position CC, and further, at the condensed position DD, the round shape 24 appears and becomes gradually stronger.

  And two perfect circle spots 11 are obtained in condensing position EE. The two spots 11 are respectively keyholed by the lid 25 of the lithium battery container 70 and the spot 11 of the case 26 to melt the periphery, and are seam welded while proceeding in the traveling direction 27 as shown in FIG.

  Next, the principle of obtaining the same true spot size as that without the wedge plate at the condensing point even when the circular beam is separated into the half-moon shaped laser beam 22 by the wedge plate 20 will be described with mathematical expressions.

  In general, as shown in FIG. 13, when the beam size is C, the half angle of the condensing angle is θ, and the focal length is f, it is already known mathematically that the spot size ω0 at the condensing point satisfies the following equation. .

  This equation means that the spot size ω 0 increases in proportion to the beam size C.

  Therefore, even if the circular beam is made into a half-moon beam by dividing into two, the long side = diameter is the same as the original circular beam, so it is the same as the spot size ω0.

  Also, the beam size of the short side = radius is halved, but if the beam size is halved, the spot size will be doubled, so the spot size is the same as ω0 by half x 2 times = 1, so the focal point is half a month Instead, it means that a perfect circular shape having the same spot size ω 0 as that of the original circular beam is maintained.

  Further, the spot size ω0 does not change according to the same principle even if it is divided into two at an arbitrary position instead of half a month. This means that the beam mode is preserved when the wedge plate is divided into two small spots.

  This is very important in fiber welding, meaning that a single mode fiber laser preserves the single mode. Preserving the single mode has a further excellent effect when placed in a lithium battery seal made of an aluminum container.

  That is, in aluminum welding, the generated spatter and void have a large correlation with the keyhole hole size. That is, when the keyhole is small, these spatters and voids are small. Therefore, the preservation of the mode in the single mode means that a minute spot can be held, and good welding is achieved.

  Further, when the key plate is divided into two by the wedge plate to make two keyholes, the power of each keyhole can be halved, so that the spatter and void that increase with the power increase can be suppressed to half or less before the two divisions.

  Further, even if the division into two is performed, if the GAP between the two separated spots is small, the energy absorbed by the aluminum is the same, and therefore the substantially same molten volume as before the two divisions can be obtained.

  FIG. 4 shows another form of FIG. Since the wedge plate 20 simply changes the direction of the laser beam, even if the wedge plate 20 is arranged behind the condenser lens 9 as shown in FIG. 4A, the front of the collimating lens 3 as shown in FIG. 4B. Even if it arrange | positions to, it is obvious that it isolate | separates into two beams.

  The object of the present invention is not only to divide into two beams but also to realize keyhole welding without breaking the beam mode, and devised a configuration and principle for realizing it.

  FIG. 5 shows a configuration in which, for example, a half-moon wedge plate 50 having a diameter of 50 mm is added so that the straight portions face each other.

  This configuration is very effective in production, especially when welding high reflectors such as copper and aluminum.

  When sealing a lithium battery or welding a copper electrode, the fiber end face 51 may be burned by the return light, or the return light may return to the inside of the laser and be damaged to the inside of the laser.

  However, by passing the two wedge plates as shown in FIG. 5 and making the optical axis oblique, the return light does not return to the fiber end face 51 but becomes an optical path as shown by a solid line 52. It can be prevented that the laser main body is damaged or the return beam propagates inside.

  FIG. 6 shows the optical axis from the fiber 12 of the semiconductor laser 7 in FIG. 1 to the condensing point 10 as a processing point. Reference numeral 60 denotes a laser optical axis from the fiber 12, and reference numeral 61 denotes an optical axis of return light from the condensing point 10. In order to prevent the return light 61 from returning to the fiber end face 62, it can be easily realized by providing an angle adjusting mechanism on the folding mirror and shifting it slightly from 45 degrees.

  In addition, it becomes diagonally incident on the condensing point 10 and deviates by d from the optical axis 63 at the time of vertical incidence.

  Here, when the fiber laser beam 2 is superimposed in the configuration of FIG. 1, the laser spot 11 of the fiber laser separated into two is condensed at a position shifted by d while observing the condensing point 10 with the CCD camera 17. What is necessary is just to superimpose by a point. Then, both the fiber laser 1 and the semiconductor laser 7 can be adjusted so that there is no return light to the respective optical fibers 12 and 17.

  FIG. 7 shows an experimental example in which the lid 25 and the box 26 of the aluminum container 70 are sealed and welded using the hybrid torch 18 on which the fiber laser 1 + semiconductor laser 7 shown in FIG. 1 is superimposed.

  Two spots 11 each having a diameter of 36 μm branched from the fiber laser 1 are irradiated with the lid 25 and the box 26 separated by GAP = 0.3 mm.

  As the size of the aluminum container, the wall thickness is 0.6 mm long, the short side is 0.5 mm, the lid thickness is 2 mm, and the laser spot is 36 μm × 2 points of the fiber laser (GAP = 0.3 mm between two points), A 915 nm semiconductor laser of 360 μm is superimposed, and the welding speed is 200 mm / s.

Table 1 summarizes the experimental results that gave favorable results. In Table 1, the minimum required reference numerical value is indicated by>, and the non-defective product evaluation was performed according to the following judgment.
◎: Far beyond required specifications, ○: Specification pass, △: Insufficient strength at specification level

  As shown in Table 1, good welding conditions far exceeding the required specifications could be found with the configuration of the present invention. That is, high quality and beautiful aluminum welding with deep penetration, which has never been observed before, could be realized.

  Next, Table 2 shows a comparison of long side welding in the present invention with the conventional heat conduction type.

  As shown in Table 2, in the method of the present invention, not only the performance of twice the speed and the laser power ½ times = 4 times, that is, 4 times that of the heat conduction type was obtained, but the depth was 0.9 / 0.0. A penetration depth of 6 = 1.5 times was obtained.

  We could eliminate sinks that would cause cracks, and we were able to obtain welding strength nearly doubled. Here we will explain why not only the 4x productivity performance but also the penetration has increased 1.5x.

  In heat transfer type welding of aluminum, the absorption rate is only a few percent at a fiber laser wavelength of 1070 nm, but in the keyhole type, not only does it melt deeply with high brightness, but also the absorption rate is several because the laser is confined in the keyhole. Ten times. Therefore, the absorption efficiency is increased, and the performance can be greatly improved.

  Next, based on the above-mentioned preferable experimental results, before conducting theoretical considerations, the contents of “2009 Laser Processing Society Spring Seminar Materials (2009.5)” of FIG. 9 and FIG. Will be described.

  At low speed, the energy absorbed by the laser per unit time increases, so the temperature around the keyhole 99 increases, the amount of molten metal increases, and the amount of evaporated metal increases, so the keyhole increases. When the keyhole 99 becomes large, bubbles blown off at the tip of the keyhole 99 are solidified in a state of being caught in a large convection, and a large blowhole 100 is generated.

  At high speeds and high powers, by moving fast and with high brightness, it becomes a stable small-diameter keyhole 93, and sputters metal vapor 97 called plume stably and at high speed. 95 and porosity 96 can be suppressed. However, there was a drawback that the penetration depth was shallow.

  In one embodiment of the present invention, the state shown in FIG. 9 in FIG. 9 is applied, and the third beam 16 in FIG. While maintaining the welded state of No. 4, the keyhole could be enlarged in a similar shape.

  Therefore, it was confirmed by experiments that it was possible to deepen the penetration while suppressing the generation of spatter 95 and to realize ideal welding with high speed, high quality, and high strength without defects and suppressing PROSITY 96.

  Furthermore, even if spatter occurs in an abnormal state such as when there is a foreign substance on the surface, the sputter 96 does not occur because there is no keyhole 93 at the bonding interface, and the sputter 96 enters the container from the bonding interface. This can be eliminated in principle.

  Further, as shown in FIG. 7, in mass production, a gap S and a step difference are inevitably generated between the container 26 and the lid 25, but the positions where the two high-intensity laser beams 11 are outside the gap at the bonding interface. Since the melted metals are interlaced like soldering using the keyhole 93 as a heat source, sealing is possible even if the gap S is large.

  Moreover, since the time for the molten metal to solidify due to the residual heat effect of the third beam 16 can be lengthened, it has been verified by the above experiment that the generation of the blow hole 96 is suppressed because the bubbles 101 escape during that time. .

  Next, problems and solutions for mass production in one embodiment of the present invention will be theoretically shown.

  In the conventional method in which keyhole type welding is performed at the joint interface C in FIG. 8, it is impossible to prevent the sputter 95 generated by keyhole welding from passing through the gap and entering the aluminum container 70.

  However, in one embodiment of the present invention, a keyhole 93 that does not penetrate is generated not at the joint 27 of the lid 25 and the container 26 but at a position away from the joint interface C, so that the sputter 95 generated from the keyhole 93 is generated. Flies away from the container 26.

  Therefore, as long as there is no laser welding abnormality such as the laser irradiation locus being shifted and the laser beam 11 being irradiated to the bonding interface C, the container 26 will not be entered in principle.

  If the spatter is larger than several hundred μm, it does not physically enter the aluminum container 70 controlled to have a maximum gap of 50 μm, but it is heavy and has a large volume. There is a possibility that the position of the laser irradiation position shifts due to the container 70 attached to a jig for regulating the position.

  However, in the present invention, since it becomes a smoke-like rapidly solidified fume having a sputter size of 40 to 50 μm or less in principle, it does not melt and adhere. In addition, since foreign matter inside the lithium battery is safe if it is 50 μm or less, even if it enters through a gap of 50 μm at the maximum, it is still safe.

  In addition, the size of the spatter generated by keyhole welding and the size of the blow hole tended to become smaller as the spot size became smaller, and it was confirmed by experiments that the laser size could be made smaller than the spot size.

  Therefore, by increasing the power of the third heat-conducting beam 16 relative to the beam that generates the keyhole, the power of the two laser beams 11 that generate the keyhole can be relatively lowered. By optimizing the power ratio, a beautiful and stable weld bead with a mirror surface could be obtained by high-speed, deep penetration welding at 200 mm / s.

  Next, the reason why the sputter and blowhole size of 40 μm or less can be realized in one embodiment of the present invention will be considered.

In keyhole welding, the following magnitude relationship is physically established.
Laser spot size ≥ keyhole port size ≥ spatter size ≥ blowhole size

  The reason for this will be described again with reference to FIG. 9 in FIG. 9 shows the behavior during high-speed keyhole welding. During high-speed keyhole welding, when the laser beam 91 is irradiated onto the metal 92 such as aluminum with high brightness, a part of the area that has vaporized beyond the boiling point of the metal 92 becomes the keyhole 93. Therefore, the laser spot size 94 ≧ keyhole opening size.

  The sputter 95 is a metal 98 melted inside the keyhole 93 and ejected by volume expansion when transforming from liquid to gas, and naturally the keyhole port size 94 ≧ sputter size 95 is satisfied.

  The blow hole 96 is also called PORPSITY, but is formed by cooling and solidifying the metal vapor 97 called plume generated at the keyhole tip 95 before being discharged from the keyhole 93. The keyhole tip 101 is much smaller than the size of the keyhole port 97. Therefore, the size of the generated blow hole 96 is smaller than the sputter 95.

  As described above, when the spot size is 40 μm as in the embodiment of the present invention, both the sputter 95 and the blow hole 96 can be reduced to 40 μm or less according to the equation (1).

  In the lithium battery sealing, both the sputter 95 and the blow hole 96 are 50 μm or less. Therefore, spatter mixing can be prevented. Even if the gap exceeds 50 μm due to some trouble and enters the inside of the container, there is no problem in quality if it is 50 μm or less as described above.

  In addition, when the sputter | spatter 95 which generate | occur | produces slightly is analyzed, it was a fine powder of 40-50 micrometers or less which can be removed with nitrogen assist gas.

  Such a fine powder spatter 95 can be managed so that it is attached to a jig for fixing the aluminum container 70 by periodic cleaning and causes a welding position shift. Also. If the blowhole 96 is 50 μm or less, it is too small to cause a problem in welding strength, so it is considered that high-quality high-speed welding can be realized.

  In mass production, various positional variations occur. For example, as shown in FIG. 8, the gap S between the lid 25 and the box 26 varies from 0 to a maximum of about 50 μm.

  Also, the aluminum container 70 itself varies up to ± 0.025 mm, and the laser irradiation trajectory also varies up to ± 0.025 mm. Therefore, it was branched into two at the wedge plate 4

  The shortest distance likelihood Δ (μm) between the spot 11 and the gap S when the center C of the gap S is indicated at the center of GAP = 300 to 350 μm of the spot 11 of 36 μm ± 10 is shown below.

  Δ = (GAP300−spot 50−gap 50−container 50−track 50) / 2 = 50 μm, and sufficient likelihood can be ensured as compared with the spot 11 of 36 μm ± 10.

  Therefore, high-intensity laser light that causes a keyhole does not enter the aluminum can through the gap even during the maximum variation during mass production, and does not cause thermal damage to the resin such as the separator inside.

  Further, when the semiconductor laser light 16 having a light density that does not cause a keyhole is superimposed, a beautiful specular bead that has never been seen can be obtained by preheating and slow cooling effects under suitable conditions.

  In addition, the occurrence of spatter could be dramatically suppressed. In the experimental results, the long side 28 of the aluminum container 70 is a superposition of the two spots 11 that cause the keyhole and the spot 16 of one heat conduction beam, but the short side 29 is defocused in the same direction. I was able to get a bead with a mirror surface.

  In addition, since the stress concentration of the short side 29 is far smaller than that of the long side 28, it is possible to withstand the expansion test even if the penetration depth is shallow, so it is not necessary to increase the power extremely when welding the short side 29.

  Further, since the two spots 11 are displaced by a maximum of 50 μm from the bonding interface C, the spatter 95 does not enter the inside in principle even if variations are taken into account.

  Compared with the conventional heat conduction type welding [Patent Document 1] that welds relatively slowly with 4 to 6 KW 60 to 100 mm / s [Patent Document 1], the speed is twice and the power is half, so the performance is four times.

  Further, as described above, when the spot 16 of the third laser beam having the intensity distribution causing the heat conduction type welding is superimposed so as to wrap the two spots 11 causing the keyhole welding at the joint, as described above. , Sputtering due to sudden bumping can be suppressed by the heating effect.

  In addition, since the temperature is increased by heating the vicinity where the keyhole welding is performed by the two spots 11, the metal melting point necessary for melting the peripheral metal using the keyhole 93 as a heat source extends to a wide range. The penetration depth can be further increased while maintaining the keyhole welding state.

  Further, due to the preheating effect, sudden bumping due to metal boiling can be suppressed suddenly, and the generation of spatter 95 can be reduced. Furthermore, due to the residual heat effect, the time during which the molten metal is in liquid is increased, so that the bubble 101 generated in the keyhole 93 can have time to escape to the atmosphere before the molten metal is cured, eliminating the blowhole 96 and realizing high-quality welding. it can.

  The present invention can bond not only a seal for a lithium battery but also a current collector of a lithium battery with high quality.

  According to one embodiment of the present invention, the two keyholes result in a wide and deep penetration shape.

  Since the melting range is wide in the vicinity of the two keyholes, the third heat-conducting beam was also superimposed on the copper electrode perpendicular to the copper foil current collector of the lithium battery, which was impossible in the past, and was melted. The copper foil end face can be contact-bonded to the electrode metal by surface tension.

  Since the laser does not directly hit the bonding interface, foil fusing can be prevented, and foil damage and spatter generation due to laser irradiation can be suppressed and high quality welding can be performed.

  In addition, the present invention is not only for lithium batteries, but also in the non-patent document 1 shown in FIG. 11 described above, a special fiber in which three fibers 121 are bundled by brazing welding using the welding rod 11 in butt welding is produced. Even if not, it can be realized simply by shifting the irradiation position of the second spot 16.

  In addition, the optical fiber 12 for sending the third laser spot 16 can be flexibly adapted to obtain a square spot by changing it to a square cross section, and can easily cope with more shapes and sizes.

4 ... Wedge plate 11 cut obliquely polished ... Two circular spots 15 ... Folding mirror 16 with adjustable angle ... Spot 18 with three laser beams superimposed ... Fiber laser 1 + semiconductor laser 7 A hybrid torch 20 with a superposition of a half-moon shaped wedge plate 25 ... a lid 26 ... a box 70 ... an aluminum container

Claims (9)

  A welding apparatus for covering an opening of a container and sealing with a laser beam, wherein the laser beam is divided into a half-moon shape or an arc portion and a straight portion by a branching optical system, and a second laser beam. The first laser beam is irradiated near the butt joint surface of the opening of the container, the second laser beam is irradiated near the joint surface of the lid, and the two laser beam irradiators Either or both of them has a circular focal point at the joining surface, and a means for translating in a keyhole state along the joining interface is provided, and the joining surface is made of molten metal obtained by melting the keyhole as a heat source. A laser sealing device characterized in that, by filling the joint surface, seam welding can be performed robustly against gap variations in the joint surface.   As the laser beam dividing means, a heat radiating part to the lens barrel by heat conduction is provided in the peripheral part where the laser beam is not transmitted with respect to the circular glass plate or the meniscal glass plate, and half of one side of the circular glass plate is made into a half-moon shape A meniscus plate having a taper-polished shape or a taper-polished whole surface on one side is inserted in the middle of the optical path of the laser beam, and divided into two meniscus laser beams having different optical axis directions, and the taper polishing angle is several degrees. When the half-moon shaped laser beam separated below is condensed, a keyhole is generated at the condensing point by utilizing the optical characteristic that becomes a circular spot having the same size as the spot shape when there is no insert at the condensing point. The laser sealing device according to claim 1, wherein the two circular condensing spots with sufficient condensing performance are generated.   3. A long focus lens is added in one of the two laser beam paths of the divided laser beams, keyhole welding is performed on one side, and heat conduction welding is performed on one side. Laser sealing device.   The container has a square shape having an opening of a long side and a short side, and a short side welding portion of the opening defocuses the two laser beams, thereby the container of the two laser beams. 4. The laser sealing device according to claim 1, wherein the heat conduction type welding effect is increased from the keyhole type welding at the joint portion.   A third laser beam that causes heat conduction type welding is superimposed so as to wrap the first laser beam and second laser beam that cause keyhole welding at the joint. The laser sealing device according to claim 1.   The laser beam source divided into two laser beams uses a fiber laser having a process fiber with a core diameter of 105 μ or less as a light source, and the third laser beam has a core diameter of 100 μ or more and generates a keyhole by single irradiation. 6. The laser sealing device according to claim 5, wherein a laser having a brightness that does not squeeze is used as a light source.   By providing a folding mirror having a function of adjusting the angle of the third laser beam with respect to the optical axes of the first and second laser beams with respect to the optical axis other than 45 degrees, the return light is made of a semiconductor or the like. The laser sealing device according to claim 6, wherein the laser sealing device does not return to the laser light source.   The laser sealing device according to any one of claims 1 to 6, wherein the third laser beam is superimposed on the back of the first laser beam and the second laser beam.   9. The laser sealing device according to claim 1, wherein at least one of the spot sizes at a condensing point of the laser beam is 50 μm or less.

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