JP2014004619A - Laser joining method and joining component - Google Patents

Abstract

To provide a laser bonding method having sufficient strength while minimizing thermal influence.
An optical axis of a laser beam emitted from a laser irradiation unit moves on an overlapping portion of an irradiation-side bonding material V1 serving as two bonding materials and a bonding material V2 to avoid thermal influence. In this way, a continuous joint (intermittent weld bead) 10A is formed instead of continuous. If the irradiation of the laser beam 103 is stopped when the temperature on the opposite side of the irradiation surface of the bonding material V2 is predetermined, the accumulated heat is dissipated and the temperature is lowered. When a certain time (distance) is left and irradiation is started again and repeated at a point where the temperature on the opposite side of the irradiation surface of the bonding material V2 becomes predetermined, intermittent weld beads 10B and 10C are formed. After forming the outer peripheral shape weld bead in this way, the inner peripheral intermittent weld beads 20A, 20B, and 20C are formed. The distance P between the outer periphery and the inner periphery at this time is Each time the operation is repeated, the length is shortened.
[Selection] Figure 1

Description

  The present invention relates to a laser joining method and a joining component in which two materials are firmly joined with a laser beam, and in particular, to a product obtained by joining, such as a storage battery, which needs to suppress the thermal influence during joining. It relates to joining technology.

  As a conventional joining method that suppresses the influence of heat, the laser beam output is adjusted so as not to penetrate the joining material while adjusting the thickness and material of the joining material. As an example, the melting point of the joining material There is a laser bonding using the difference (for example, see Patent Document 1). 8 to 9 show a conventional joining method described in Patent Document 1 described above.

  A conventional joining method will be described with reference to FIGS.

  First, the optical axis of the laser beam is irradiated to the high melting point material side of the bonding material composed of two kinds of materials having different melting points, and the low melting point material is melted by the heat of the melt of this material. The different materials are joined by melting and joining the joining materials.

  In FIG. 8, a welding head 101 is attached to an arm tip of an articulated robot (not shown) or a tip of a three-dimensional orthogonal moving body (not shown) that moves orthogonally. Then, the welding head 101 has an overlapping portion of a bonding material W1 having a high melting point and a bonding material W2 having a low melting point, which are two bonding materials, with the optical axis of the laser beam 103 emitted from the laser irradiation unit 102 at the tip ( Irradiation is performed so that W1 moves along the upper welding line 105, and a joint (weld bead) 104 is formed.

  Then, the optical axis of the laser beam 103 is applied to a bonding position O1 appropriately separated from the end position O of the bonding material W1 having a high melting point toward the center as shown in FIG. 9 when FIG. 8 is viewed from the back side. As a result, the joint shape of the joint 104A is obtained.

  The laser beam output value is such that the melt on the material side with a high melting point breaks the intermetallic compound and oxide film and melts into the wedge material with an appropriate depth to the inside of the material with the low melting point, so that the atoms of both metals are fused. It is said that it will be in a semi-kneaded state that mixes together. In addition, since stress is concentrated on the weld bead when a force is applied to the joint, the reliability of the joint decreases, but a certain gap is provided between the joint materials to adjust the depth of the weld bead. A method has also been proposed (see, for example, Patent Document 2). FIG. 7 shows a conventional joining method described in Patent Document 2.

  In FIG. 7, the optical axis of the laser beam 103 emitted from the welding head 101 is irradiated onto the bonding material W1, and a welding bead (not shown) is formed as in Patent Document 1, but the upper bonding material. A gap 106 was provided between W1 and the lower bonding material W2, and a weld bead was generated also in the gap to adjust the depth of the welding bead of the lower bonding material W2.

  As described above, as a result of using laser light for bonding between different kinds of metal materials, thin plates are efficiently bonded to each other, where heat exists locally and hardly affects the heat other than necessary portions.

Japanese Unexamined Patent Publication No. 2007-136489 (FIGS. 1 and 4) Japanese Patent Laid-Open No. 2004-040253 (FIG. 1)

  However, the above-described conventional configuration has the following problems because copper, aluminum, and the like having high thermal conductivity are often used, although electrical resistance is low particularly in joining at electrodes such as storage batteries. It was.

  (1) By using a material having high thermal conductivity, heat is transferred to a place where thermal influence is not desired at the time of joining.

  (2) In the case where the irradiation side plate is thick and the heat capacity is increased, the thermal effect should be kept locally.

  In this case, for example, in the case of a battery, the heat effect is that the insulating resin component deteriorates due to heat at the time of bonding or melts in the worst case, or the electrolytic solution is chemically decomposed by the heat at the time of bonding. It can change and deteriorate, or it can vaporize in the worst case. Furthermore, with the advent of electric cars and hybrid passenger cars in recent years, a large load capacity is required for large-capacity storage batteries, but copper and aluminum are used as the material around the electrodes because of their electrical characteristics. In many cases, it is difficult to improve the strength per bonding area, and because the bonding strength is improved by having a large bonding area on a narrow electrode on the battery, the thermal conditions during bonding become more severe. ing.

  The present invention solves the above-described conventional problems, and a laser joining method and a joining component that suppresses the thermal effect even in joining in which a material having high thermal conductivity or a plate on the irradiation side is thick and the heat capacity is increased. The purpose is to provide.

  In order to achieve the above object, in the laser joining of the present invention, the weld bead is intermittently formed in a plurality of circular shapes, specifically, the weld bead may have a constant intermittent bead length, In order to make the weld bead length longer in a limited area, the pitch between the adjacent weld beads may be the same while taking a circular shape of three or more turns, but as a whole it becomes wider gradually. It has a shape that suppresses thermal effects.

  With this configuration, the weld bead that is to be locally heated gradually takes a distance in time and space, and the temperature rise of the object to be joined is not adjusted by the output adjustment of the laser beam. Therefore, it is possible to perform bonding while suppressing the thermal influence on the opposite side of the irradiated surface of the stacked thin plates.

  As described above, according to the laser joining method and the joining parts of the present invention, in the joining using copper, aluminum, or the like, which has been difficult in the past but has a low electrical resistance, it is opposite to the irradiation surface of the stacked thin plates. Bonding with sufficient bonding strength can be obtained while suppressing the thermal influence on the side.

The model perspective view which shows the mode of the laser joining in Embodiment 1 of this invention Schematic diagram of concentric weld beads in Embodiment 1 of the present invention The schematic diagram of the weld bead of the shape which should be avoided in Embodiment 1 of this invention Simplified sectional view in Embodiment 1 of the present invention The model perspective view which shows the mode of the laser joining in Embodiment 2 of this invention Schematic diagram of a spiral weld bead in Embodiment 2 of the present invention Schematic diagram showing the state of conventional laser bonding described in Patent Document 2 Schematic perspective view showing a state of conventional laser bonding described in Patent Document 1 Sectional drawing which shows the conventional laser joining part described in patent document 1

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

(Embodiment 1)
FIG. 1 is a schematic perspective view showing a state of a laser joining method in the case of joining a metal plate to an electrode of a round lithium ion storage battery according to Embodiment 1 of the present invention. FIG. 4 is a simplified cross-sectional view when the electrode plate is joined to the positive electrode terminal of the round lithium ion storage battery.

  Furthermore, the storage battery described in this embodiment is a can-shaped battery in which a power storage unit immersed in an electrolytic solution is contained in a metal container. 1 and 6, the same components as those in FIGS. 8 to 9 are denoted by the same reference numerals and description thereof is omitted.

  In recent years, round lithium ion storage batteries have been steadily increasing in production capacity due to their large charge capacity and frequent charge / discharge cycles. In many cases, a plurality of storage batteries are used together as a battery pack. At this time, the electrode plates are joined to the positive and negative electrodes of the round lithium ion storage battery to be electrically integrated. Therefore, the laser bonding method of the present invention is effective.

  In FIG. 4, a power storage unit 200 in a lithium ion storage battery is immersed in an electrolytic solution 202 with a structure in which a positive and negative electrode plate and a separator are wound, and when charged, lithium ions are stored in the power storage unit 200 in the lithium ion storage battery. During the discharge, electricity is generated by generating electricity using the stored lithium ions. Electricity at the time of charging / discharging flows through the positive electrode lead 201 to the bonding material (positive electrode side terminal) U2 through the electric contact 203. In Embodiment 1 of the present invention, a case where a plate-shaped irradiation-side bonding material U1 is bonded to this bonding material (positive electrode side terminal) U2 will be described with reference to FIG.

  In FIG. 1, the laser beam 103 emitted from the laser irradiation unit 102 is reflected by the galvanometer mirror 40 and focused by the objective lens 41, and heat influence is exerted on the plate-shaped irradiation side bonding material U <b> 1 and the back side. Irradiated so as to move on the overlapping portion (U1 is on the upper side) of the joining material U2 that is desired to be avoided, not continuous but intermittent joint portions (intermittent weld beads) 10A, 10B, 10C, 20A, 20B, 20C are formed. The

  The weld beads are formed in the order of 10A, 10B, 10C, 20A, 20B, and 20C in time series, but the arrangement may not be the same as the order of time series. Further, the intermittent weld beads 10A to 10C and the intermittent weld beads 20A to 20C are continuous for the purpose of keeping the temperature of a portion (in the case of the present embodiment, the back surface of the bonding material U2) that is desired to avoid a thermal effect at a predetermined level or lower. Instead, intermittent weld beads are formed, and the length of each weld bead may not be constant.

  In addition, although the case where it comprised on the circumference is mentioned as an example as a shape to circulate, this may be a polygon. In the case of a round battery, the joining material U2 side often has a round shape, so it is reasonable to make the outer shape a circumferential shape. However, the electrode shape is constant due to other constraints. It does not take shape. Therefore, when the aspect ratio of the area where the joining material U1 and the joining material U2 on the plate-like irradiation side are not 1: 1, the outermost shape of the weld bead is an ellipse.

  In particular, in this embodiment, a plurality of storage batteries are configured as a battery pack, and the shape of the bonding material U1 on the irradiation side is different between the positive electrode and the negative electrode due to the difference in function between the positive electrode side and the negative electrode side. The weld bead is formed with a circumferential shape on one side and an elliptical shape on the other side.

  In many cases, a metal plate is joined to the electrode of a can-shaped battery. For example, the electrode plate is joined to a finished product of a single battery to form a unit. During such joining, the inside of the can is filled with an electrolyte. Has been. Here, when the temperature inside the can rises during joining, first, there is a possibility that the plastic part for sealing the electrolytic solution is deteriorated or melted. If the temperature rises further, the electrolyte solution may undergo chemical changes other than charging and discharging, and in the worst case, it may vaporize in the battery can. In particular, a temperature rise near the joint is often a problem.

  In the case of joining, the temperature rises to the melting point of the material at the joint, but this temperature rise is locally suppressed, and unless the joining method does not exceed the predetermined temperature due to the temperature rise due to heat transfer, this It cannot be used in a process such as joining a plate to a finished product of such a single battery unit.

  By irradiating the bonding material U1 on the plate-shaped irradiation side with the laser beam 103, when the temperature rises locally and exceeds the melting point of the material, the inside of the material of the bonding material U2 is melted into a wedge shape with an appropriate depth and both metals 9 is fused and mixed, and the joined shape of the joined portion 104A in FIG. 9 is obtained. In the present embodiment, since the irradiation-side bonding material U1 uses an alloy mainly made of aluminum, the melting point of the material is 650 ° C. When the irradiation time becomes longer in such a process, specifically, when the joint portion (weld bead 10) formed intermittently becomes longer, both the irradiation-side bonding material U1 and the bonding material U2 increase in temperature due to heat storage. As a result, the wedge-shaped depth of the bonding portion 104A increases, and the temperature on the opposite side of the irradiation surface of the bonding material U2 increases.

  Here, when the temperature on the opposite side of the irradiation surface of the bonding material U2 becomes predetermined, if the irradiation of the laser beam 103 is stopped, the accumulated heat is dissipated and the temperature of both the bonding material U1 and the bonding material U2 on the irradiation side is lowered. To do. In this embodiment, since the welding head 101 moves at a constant speed after a certain period of time, the laser beam 103 is irradiated again and the temperature on the opposite side of the irradiation surface of the bonding material U2 is set to a predetermined temperature. If it stops repeatedly when it becomes, the junction parts (intermittent welding bead) 10A, 10B, 10C which are not continuous but discontinuous will be formed. In the present embodiment, the temperature on the opposite side of the irradiation surface of the bonding material U2 is set to be within 100 ° C. in order not to affect the plastic parts in the storage battery.

  Further, in the same manner, the intermittently joined portions (intermittent weld beads) 20A, 20B, and 20C are formed on the inner periphery, and the distance between the intermittent weld beads 10A, 10B, and 10C and 20A, 20B, and 20C is formed. If P is increased, the influence of the heat stored when the intermittent weld beads 10A, 10B, 10C are formed can be reduced, and the intermittent weld beads 20A, 20B, 20C can be formed.

  However, the outer diameters of the outer peripheral intermittent weld beads 10A, 10B, and 10C cannot be increased beyond a certain level due to the size limitations of the irradiation-side joining material U1 and the joining material U2. Further, FIG. 1 shows only the first two rounds of the cyclic shape of the intermittent weld bead for explaining the operation, but in order to achieve a joining distance to satisfy the required strength in practice. Since the distance is three or more, the distance P is not necessarily large.

  Further, if the distance P is increased, the outer diameter of the circumferential shape of the intermittent weld beads 20A, 20B, and 20C is reduced, and consequently the length of the weld bead itself is shortened. Will be reduced.

  2 to 3 are diagrams for explaining the shape of an actual intermittent weld bead when operated in this manner.

  In FIG. 2, the distance P2 between the weld bead 20 and the inner peripheral weld bead 30 is larger than the distance P1 between the outermost weld bead 10 formed first and the weld bead 20 formed next. Is getting bigger. That is, the pitch between the second weld beads is configured to be larger than the pitch between the weld beads at the start of irradiation. Thereby, when continuously forming an intermittent weld bead, the weld bead becomes deeper later due to the influence of the stored heat, and the temperature of the back surface of the bonding material U2 increases.

  At this time, it is possible to prevent the depth of the weld bead from exceeding a certain level due to the effect of lowering the planar thermal influence due to the pitch between the circumferential shapes of the weld beads spreading, and the temperature of the back surface of the joining material U2 is reduced. It will be prevented from exceeding a certain level.

  In FIG. 2, the weld bead is only three rounds, but this is the same even if there are four or more rounds. Compared to the pitch between the weld beads at the start of irradiation, the distance between the second and third weld beads is the same. The pitch is equal or shorter. Also, the irradiation conditions are adjusted so that each weld bead is thin at the start of irradiation and gradually thickens. This is because sufficient heat is stored in the material in a short time, and later, the bonding strength, the bonding length, and the bonding area are increased.

  Further, as shown in FIG. 3, when the intermittent part 31 of the weld bead is solidified in one direction of the circular shape, the part becomes weak and the joint strength is broken because the intermittent part is broken due to the stress concentration. Will eventually become weaker. In order to avoid this, it is important to adjust the length of the weld bead in the circular shape so that the intermittent portion does not harden in one direction of the circular shape.

  According to such a configuration, by repeating the above-described operation, the laser bonding has a sufficient bonding strength while minimizing the thermal influence, specifically, a welding bead having a sufficient length to obtain a predetermined strength. Is possible. Further, in the conventional laser bonding method, it is necessary to reduce the input heat amount in order to avoid the thermal effect, and the heat capacity of the irradiation-side bonding material U1 is smaller than the bonding material U2, specifically the material thickness. In the present embodiment, it is important that the material thickness of the bonding material U1 on the irradiation side is larger than that of the bonding material U2. Bonding with minimal temperature rise has been realized.

  In this embodiment, after the outermost weld bead 10 is formed first, the inner bead 20 and 30 are formed inward in order, but the innermost periphery is formed first. The weld beads may be formed in order toward the outside. In this case, the same effect can be obtained by making the distance P2 between the weld bead 20 and the inner weld bead 30 smaller than the distance P1 between the outermost weld bead 10 and the weld bead 20. Can be obtained.

  Further, in this embodiment, the turns of adjacent weld beads are formed in order. For example, the turns of the weld beads are formed every other and every two turns later, and then the turns that are skipped thereafter. Even if it forms, it has the same effect regarding a thermal influence. In this case, the pitch between the weld beads does not gradually change from the outer circumference to the inner circumference or from the inner circumference to the outer circumference, but the pitch between the weld beads changes in the final weld bead shape. Yes.

  In the first embodiment, since the shape of the weld bead is close to a free shape, the irradiation method using a galvano mirror that is advantageous for such laser irradiation is described, but the galvano mirror is not used. Irradiation may be performed by mechanically operating the irradiation head or the workpiece to be irradiated.

(Embodiment 2)
FIG. 5 is a schematic diagram of laser joining when a metal plate is joined to the electrode of the round lithium ion storage battery according to the second embodiment of the present invention, when a higher speed operation is required than in the first embodiment. is there. FIG. 6 is a schematic diagram showing a one-stroke writing pattern of the weld bead in the second embodiment of the present invention. 5 and 6, the same components as those in FIGS. 1 and 8 are denoted by the same reference numerals, and description thereof is omitted.

  In FIG. 5, the laser beam 103 emitted from the laser irradiation unit 102 is reflected by the galvanometer mirror 40 and focused by the objective lens 41, so that the thermal effect is exerted on the plate-shaped irradiation side bonding material U <b> 1 and the back side. Irradiation is performed so as to move on the overlapping portion (U1 is on the upper side) of the joining material U2 to be avoided, and a discontinuous but discontinuous joining portion (intermittent weld bead) 10 is formed.

  Here, the weld bead 10 formed intermittently has a spiral shape that cuts inwardly from the outer periphery, unlike the outer peripheral shape of the first embodiment and the shape formed by multiple turns of the similar shape. The laser irradiation itself is intermittent, but the trajectory including the irradiation pause portion is a single stroke.

  Then, the joint (intermittent weld bead) 10 that is cut off from the outermost periphery and is formed on the inner periphery thereof is formed, but if the distance P between the outermost periphery of the intermittent weld bead and the trajectory after the cut is taken large. As in the first embodiment, it is possible to reduce the influence of the previously stored heat and to form a continuation of the intermittent weld bead.

  FIG. 6 is a diagram for explaining the shape of an actual intermittent weld bead when operated in this way.

  In FIG. 6, the distance P2 between the outermost weld bead formed first and the weld bead formed after cutting is larger than the distance P2 between the inner weld bead and the weld bead formed there after. It has become. That is, the pitch between the second weld beads is configured to be larger than the pitch between the weld beads at the start of irradiation.

  As a result, when intermittent weld beads are continuously formed, the weld bead becomes deeper and the temperature of the back surface of the joining material U2 rises later due to the effect of accumulated heat. Preventing the weld bead depth from exceeding a certain level and preventing the temperature of the back surface of the joining material U2 from exceeding a certain level due to the effect of lowering the planar thermal effect due to the spread of the pitch between them. It becomes. In FIG. 6, the weld bead has only three rounds, but this is the same even when there are four or more rounds. Compared to the pitch between the weld beads at the start of irradiation, the pitch between the second and third weld beads is the same. Are equivalent or short.

  According to such a configuration, by repeating the above-described operation, the laser bonding has a sufficient bonding strength while minimizing the thermal influence, specifically, a welding bead having a sufficient length to obtain a predetermined strength. Is possible.

  In the present embodiment, laser irradiation is started from the outermost periphery, but a spiral weld bead may be formed from the innermost periphery toward the outermost periphery.

  The laser joining method and joining parts of the present invention connect a positive or negative electrode terminal of a storage battery and a metal plate or a plurality of storage batteries, which often use copper or aluminum having a low electrical resistance but high thermal conductivity. It can also be used for joining between storage batteries when used, and for joining thin metal exterior covers that could not be joined so far because the appearance deteriorates due to thermal effects.

DESCRIPTION OF SYMBOLS 10 Welding bead 10A-10C Intermittent welding bead 20A-20C Intermittent welding bead 30 Welding bead 31 Intermittent part of welding bead 40 Galvano mirror 41 Objective lens 101 Welding head 102 Laser irradiation part 103 Laser beam 20 Welding bead 105 Welding line 200 Lithium ion storage battery Power storage unit 201 Positive electrode lead 202 Electrolyte 203 Electrical contact U1, U2, V1, V2, W1, W2 Bonding material

Claims (7)

Laser joining for joining the first material and the second material by superimposing the first and second materials and irradiating the surface of the first material with laser light from the first material side In the method
When forming a weld bead on the surface of the first material by irradiating the laser beam intermittently while moving the laser beam to the overlapping portion with the first and second materials, the circumference of the circular shape Forming with varying pitch,
A laser bonding method. The laser welding method according to claim 1, wherein a plurality of the weld beads are arranged in a spiral shape or a concentric shape, and are composed of three or more rounds from the center to the outer circumference. The laser joining method according to claim 1 or 2, wherein the outermost periphery of the circular shape is formed of a circle, an ellipse, or a hexagon or more polygon. The laser welding method according to any one of claims 1 to 3, wherein the weld bead is formed in an intermittent shape, and has a spiral shape or a concentric shape and does not solidify the intermittent cut in one direction. The laser joining method according to any one of claims 1 to 4, wherein the wedge shapes of adjacent weld bead joint portions are arranged at a pitch that does not overlap. The pitch of the adjacent weld beads may be the circumference of the weld beads irradiated at the same pitch, but when irradiation starts from the inner circumference, it is larger at the outer periphery, and when irradiation starts from the outer periphery, The laser joining method according to any one of claims 1 to 5, wherein the laser joining method increases on the inner periphery. In the joined part formed by joining the first material and the second material,
In the region where the first material and the second material overlap, a plurality of weld beads are intermittently formed on the surface of the first material, and the circumferential pitch of the circular shape is changed. about,
Joined parts characterized by

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