JP2014161864A - Laser welding method for copper alloy terminal, and copper alloy terminal formed using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser welding method of copper alloy for a terminal which is excellent in energy efficiency.SOLUTION: A laser welding method is intended for a tubular caulked portion 30 that is formed by punching a copper alloy plate material, followed by bending. The method includes welding, over portion to be weld in the longitudinal direction of the tubular caulked portion 30, by irradiating a laser beam of a wavelength of not less than 300 nm nor more than 600 nm in which a laser beam absorption rate of a copper alloy plate rapidly starts to decrease with increasing the wavelength.

Description

  The present invention relates to a laser welding method for a copper alloy sheet and a copper alloy terminal welded using the welding method. In more detail, it is related with the copper alloy terminal which connects an electric wire.

  2. Description of the Related Art Conventionally, in a wire connecting portion in an assembled wire for automobiles, a form in which a wire conductor is crimped with a terminal is common. Usually, copper wires are used as the assembled wires, but aluminum wires (hereinafter also referred to as aluminum wires) may be used for the purpose of weight reduction. In general, the crimp portion has a structure in which the electric wire conductor is exposed. Therefore, when an aluminum electric wire is used, there is a possibility that the aluminum of the conductor is corroded and electrical conduction cannot be secured.

  In order to prevent this, it is conceivable to shield the aluminum conductor from the environment. For example, it is desirable to cover the aluminum surface so as not to touch air. From the standpoint of preventing corrosion, a method of molding the entire crimped part with resin (for example, see Patent Document 1) is reliable, but the molded part becomes enlarged and the size of the connector housing needs to be increased. As a result, the entire assembled electric wire could not be formed into a high-density compact size. In addition, since the molding process is performed on each crimped part after crimping, there are problems such as greatly increasing the number of steps for manufacturing the assembled wire and complicated operations.

  On the other hand, a technique for blocking the aluminum conductor from the outside by a method of crimping after covering the electric wire conductor with the metal can was proposed (for example, see Patent Document 2), but the can is attached to each conductor before the crimping. There are problems such as a complicated process and a case where the can is broken by a wire barrel and a water immersion path is formed at the time of pressure bonding.

  The above-mentioned problem is that the wire conductor is cut off from the outside without enlarging the crimping part by adopting a structure in which the connecting part with the electric wire is crimped by inserting the wire into a tubular (bag-like) terminal. Can be solved. There are several methods for forming the tube, but in addition to being able to reduce the width of the welded portion, it is preferable to use a laser welding method (for example, see Patent Document 3) from the viewpoint of processing speed and cost. is there.

  However, since the laser reflectivity of copper and copper alloys is high (that is, the laser absorptivity is low), laser welding of copper and copper alloys requires high-power laser irradiation, and explosion occurs at the laser irradiation part. Prone to occur. In response to this problem, when a brass material having a nickel-phosphorus (Ni-P) coating on the surface is irradiated with laser, the laser reflectivity of the nickel-phosphorus coating and brass is substantially the same, and the melting point of the nickel-phosphorus coating is The heat of the laser is consumed to melt the nickel-phosphorous film in synergy with the higher melting point of the brass material, and it works to stop the rapid melting of the brass material. Has been suggested to be prevented (see, for example, Patent Document 4).

JP 2011-222243 A JP 2004-207172 A Japanese Patent Laid-Open No. 2003-191085 Japanese Patent No. 31777982

  However, since the nickel-phosphorus film suggested in Patent Document 4 is formed by electroless plating, the process is complicated, which causes an increase in cost. Further, the copper alloy terminal is generally subjected to Sn plating or Ag plating in order to ensure various characteristics as a terminal, but a nickel-phosphorus film is not particularly required.

  Then, this invention is made | formed in view of the said problem, Comprising: It aims at providing the laser welding method of the copper alloy for terminals excellent in energy efficiency.

  The feature of the laser welding method of the copper alloy terminal of the present invention is a laser welding method of a tubular crimping portion of a terminal formed by punching and bending a copper alloy plate material, and is provided in the longitudinal direction of the tubular crimping portion. The gist is that welding is performed by irradiating a laser beam having a wavelength of 300 nm or more and 600 nm or less over a portion to be welded.

  The laser absorptance of the copper alloy plate is drastically decreased at a wavelength of about 600 nm as the wavelength of the laser beam is increased, so that the laser weldability can be improved by welding using a laser having a wavelength of 600 nm or less. .

  Moreover, since the energy will become low when the wavelength of a laser beam is too short as less than 300 nm, penetration welding will become impossible.

  As the wavelength of the laser beam, it is preferable to select a wavelength at which the laser absorption rate of the copper alloy plate starts to rapidly decrease as the wavelength increases.

  The wavelength of the laser beam can be synthesized by generating a sum frequency using a wavelength conversion element.

  Moreover, the summary of the copper alloy terminal of the present invention is that a tubular caulking portion is provided by performing the laser welding described above.

  ADVANTAGE OF THE INVENTION According to this invention, the laser welding method of the copper alloy for terminals excellent in energy efficiency can be provided.

It is a perspective view which shows the terminal which concerns on embodiment of this invention. It is a perspective view which shows the connection structure of the terminal which concerns on embodiment of this invention, and the terminal of an electric wire. It is a perspective view which shows typically an example of the welding method of the terminal which concerns on embodiment of this invention. It is a figure which shows the wavelength dependence of the laser absorptivity of the copper alloy for terminals shown in Table 1.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a terminal 1 according to an embodiment of the present invention. The terminal 1 has a female terminal box portion 20 and a tubular caulking portion 30, and has a transition portion 40 as a bridge between them. Further, the terminal 1 has a welded portion 50 (portion indicated by hatching in the drawing) in the tubular caulking portion 30. The terminal 1 is manufactured with a copper alloy base material in order to ensure conductivity and strength. Further, the shape of the welded portion is not particularly limited. Although it is good to form in the strip | belt shape in the longitudinal direction of the tubular crimping part 30 like the welding part 50 shown in figure, you may form in a wavy line shape or a helical shape.

(Box part)
The box part 20 of the female terminal is a box part that allows insertion of an insertion tab such as a male terminal. The detailed shape of the box portion is not particularly limited. That is, it is not necessary to have a box part, for example, it may be an insertion tab of a male terminal. Moreover, the edge part of another terminal may be sufficient. In the present embodiment, an example of a female terminal is shown for the sake of convenience in order to describe the terminal of the present invention, and any terminal having a connecting end portion is tubular through the transition portion 40. It has a caulking portion 30 and the tubular caulking portion 30 is formed by welding.

(Tubular caulking part)
The tubular caulking part 30 is a part that crimps and joins the terminal 1 and an aluminum or aluminum alloy electric wire (not shown). One end thereof has an electric wire insertion port 31 into which an aluminum electric wire can be inserted, and the other end is connected to the transition portion 40. It is preferable that the transition part 40 side of the tubular caulking part 30 is closed. If moisture adheres to the contact between the brass of terminal 1 and the aluminum or aluminum alloy wire, either metal (alloy) will corrode due to the difference in electromotive force between the two metals, so that no moisture or the like enters the caulking portion from the outside. It is like this. If the crimping portion of the terminal is tubular, a certain effect against corrosion can be obtained. Therefore, the crimping portion is not necessarily cylindrical with respect to the longitudinal direction, and may be an elliptical or rectangular tube depending on circumstances. Moreover, the diameter does not need to be constant, and the radius may change in the longitudinal direction.

  In the tubular caulking portion 30, the copper alloy and the aluminum or aluminum alloy electric wire constituting the tubular caulking portion are mechanically pressure-bonded to each other, thereby ensuring electrical connection at the same time. The copper alloy base material and the electric wire (core wire) are plastically deformed and joined by caulking. Accordingly, the tubular caulking portion 30 needs to be designed to have a thickness so that it can be caulked and joined, but since it can be joined freely by manual machining or machining, it is particularly limited. is not.

  Although not shown in the present application, grooves and protrusions (serrations) for connecting electric wires may be provided in the tubular caulking portion 30.

(Wire end connection structure)
Next, FIG. 2 shows an end connection structure 10 for electric wires according to the present invention. The terminal connection structure 10 has a structure in which the terminal 1 of the present invention is connected to an aluminum or aluminum alloy electric wire (electric wire 60). In the terminal connection structure 10, the terminal 1 and the electric wire 60 are crimped and joined by the tubular caulking portion 30. Although the manner of crimping is not particularly limited, in FIG. 2, it is composed of a first crimping reduced diameter portion 35 and a second crimping reduced diameter portion 36. Normally, when crimped and joined, the tubular caulking portion 30 undergoes plastic deformation and is crimped to the electric wire 60 by being reduced in diameter from the original diameter. In the example shown in FIG. 2, the first crimped reduced diameter portion 35 is a portion where the diameter reduction rate is the highest. In this way, the crimp bonding may be performed with two stages of diameter reduction.

  The electric wire 60 includes an insulating coating 61 and a core wire of aluminum or aluminum alloy (not shown). Although the electric wire 60 may be a bare wire, from the viewpoint of corrosion prevention, an electric wire with an insulation coating is usually used.

  In the present embodiment, the electric wire 60 obtained by removing the insulating coating 61 at the tip portion by a predetermined length using the electric wire 60 coated with the insulating coating is used. It is inserted into the tubular caulking portion 30 so as to overlap the tubular caulking portion 30 by the length, and the caulking process is carried out with a dedicated jig or a press machine.

(Terminal manufacturing method)
First, a strip made of a copper alloy base material is punched into a terminal shape developed in a plane, and a box portion and a caulking portion are provided by bending. At this time, since the caulking portion has a C-shaped cross section when bent from a flat surface, the open caulking portion is joined by welding to form a tubular caulking portion. In the present embodiment, the tubular caulking portion 30 is manufactured by performing fiber laser welding.

  Copper and copper alloys have low laser absorptivity and high thermal conductivity, so the welding width may not be reduced or the width of the heat affected zone may not be reduced. Improved. The laser beam by the fiber laser has the characteristics that the condensing diameter is small, the energy density is high, the condensing distance is long, and the output can be increased by connecting modules in parallel. Furthermore, by using a lens or a mirror, there is an advantage that even if the distance between the fiber laser main body device and the object to be processed (the part to be welded) is long, it can be transmitted directly to the object to be processed by the fiber.

  FIG. 3 is a diagram schematically illustrating an example of a welding method for the terminal 1 according to the present embodiment. FL in the figure represents a fiber laser welding apparatus. The laser beam L emitted from the fiber laser welding apparatus FL is irradiated so as to weld the welded portion 37 (butting portion) of the tubular caulking portion 30. Although FIG. 3 shows an example in which a laser beam is irradiated from one fiber laser welding apparatus, a plurality of fiber laser welding apparatuses may be connected in parallel to irradiate a plurality of laser beams. In this case, each beam may have the same output or a combination of different outputs.

  In addition, although the to-be-welded part 37 of this application makes it the butt | matching of the edge parts of a base material, a to-be-welded part is not restricted to this. For example, the aspect which overlap | superposed the edge parts of the base material may be sufficient. A mode in which the butt and the overlap are combined may be used.

  Table 1 shows the chemical composition of a copper alloy that can be used for the terminal 1 in this embodiment.

  When the terminal 1 is manufactured by fiber laser welding the tubular caulking portion 30 using the copper alloy for terminals shown in Table 1 as a base material, the laser absorptance of the base material in the wavelength range of 1030 to 1100 nm of the fiber laser is in a solid state. Is as low as about 10%. Since the wavelength of the YAG laser is 1064 nm, the same applies when the YAG laser is used. For this reason, it is necessary to irradiate a high-energy laser beam for through-welding. However, if the laser beam energy is too high, melting of the base material starts abruptly, resulting in a blowhole in the weld. It becomes easy to do. As shown in FIG. 4, the laser absorptance of the copper alloys shown in Table 1 depends on the wavelength of the laser beam. Starts to decrease to about 10% at wavelengths exceeding 600 nm. Therefore, from the viewpoint of laser absorptance, it is only necessary to irradiate a laser beam with a wavelength of 600 nm or less, which is as high as possible, but if the wavelength is too short, less than 300 nm, the laser beam energy will be low, It becomes impossible to weld through. In order to enable penetration welding, it is preferable to irradiate a laser beam having a wavelength indicated by A in the figure.

  A laser beam having a wavelength of 600 nm or less may be a light source that can output the wavelength as it is, but a special device must be used and the wavelength is limited. Therefore, it is preferable to synthesize using a wavelength conversion element.

  In the fiber laser, a laser beam having a wavelength in the range of 1030 to 1100 nm is oscillated by an element (for example, Yb, Er, etc.) doped in the core of the optical fiber. A fiber laser beam having such a wavelength is wavelength-converted by generating a sum frequency using an SHG (second harmonic generation) element or a higher harmonic generation element as a wavelength conversion element. The YAG laser oscillates a laser beam having a wavelength of 1064 nm, which can also be wavelength-converted by the above method.

(Examples 1-5)
In Examples 1 to 5, a rectangular copper alloy plate having a thickness of 0.25 mm having the composition shown in Table 2 was used as a base material, and the laser absorption rate of the copper alloy base material rapidly increased over 1 cm. The test piece was subjected to penetration welding with a fiber laser having a wavelength of 532 nm or 542 nm, which started to decrease, and the weldability was evaluated.

  In Example 1, the wavelength of a YAG laser having a wavelength of 1064 nm was converted to a wavelength of 532 nm. In Examples 2 to 5, the wavelength of a fiber laser having a wavelength of 1084 nm was converted to a wavelength of 542 nm.

<Fiber laser welding conditions>
Laser welding equipment: ASF1J23 (trade name, manufactured by Furukawa Electric Co., Ltd.), 500 W, CW fiber laser Laser beam output: 400 W
Wavelength: 1084 nm (single mode oscillation laser beam) converted to 542 nm Sweep speed: 135 mm / sec.
Sweep distance: 9mm (butting part about 7mm)
All condition just focus

<YAG laser welding conditions>
Laser welding equipment: SL-125 (manufactured by NEC)
Wavelength: 1064 nm (pulse oscillation, pulse width: 2.0 ms) converted to 532 nm Sweep speed: 1 mm / sec.
Sweep location: 9mm (approx. 7mm butt)
Defocus amount for all conditions: 0 to ± 1mm

<Weldability evaluation>
Weldability was evaluated according to the following criteria by taking a photograph with transmission X-rays with a blow hole as a welding defect, counting the number of blow holes.
◎: 10 or less ○: More than 10 and 20 or less ×: More than 20 to welding not possible

<Penetration evaluation>
The welded portion was visually observed to evaluate the possibility of penetration.
○: Penetrating possible ×: Non-penetrating

(Comparative Examples 1 and 2)
A rectangular copper alloy plate having a thickness of 0.25 mm having the composition shown in Table 2 was used as a base material. A fiber laser having a wavelength of 271 nm was used in Comparative Example 1, and a YAG laser having a wavelength of 1064 nm without wavelength conversion was used in Comparative Example 2. Except having used, it is the same as that of Examples 1-5.

  Table 2 shows the evaluation results. As can be seen from Table 2, in Examples 1 to 5 using a fiber laser having a wavelength of 532 nm or 542 nm, both weldability and penetrability were good, whereas in Comparative Example 1 using a fiber laser having a wavelength of 271 nm, Welding was not possible and therefore penetrability was not good. In Comparative Example 2 using a 1064 nm YAG laser, the laser beam intensity was too high and penetrability was possible, but the weldability was poor. From the above, a terminal having a tubular caulking portion with a low energy laser and few welding defects by irradiating and welding a laser beam having a wavelength of 600 nm or less at which the laser absorptance of the copper alloy substrate starts to rapidly decrease. It was confirmed that can be manufactured.

  As mentioned above, although this invention was demonstrated using embodiment, it cannot be overemphasized that the technical scope of this invention is not limited to the range as described in the said embodiment. In particular, although the present invention has been described with respect to female terminals, it is naturally applicable to male terminals. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiments. Further, it is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Terminal 10 Termination connection structure 20 Female terminal box part 30 Tubular caulking part 31 Electric wire insertion slot 35 1st crimping | compression-reducing diameter part 36 2nd crimping | compression-reducing diameter part 37 Welded part 40 Transition part 50 Welding part 60 Electric wire 61 Insulation coating FL Fiber laser welding equipment L Laser beam

Claims (4)

A laser welding method of a tubular caulking portion formed by punching a copper alloy sheet and bending it,
A method for laser welding copper alloy terminals, comprising welding a laser beam having a wavelength of 300 nm or more and 600 nm or less over a welded portion provided in a longitudinal direction of the tubular caulking portion.   2. The method for laser welding copper alloy terminals according to claim 1, wherein the wavelength of the laser beam is a wavelength at which the laser absorptance of the copper alloy plate starts to rapidly decrease as the wavelength increases.   3. The laser welding method for copper alloy terminals according to claim 1, wherein the wavelength of the laser beam is synthesized by generating a sum frequency using a wavelength conversion element. The copper alloy terminal in which the tubular crimping part was provided by performing laser welding using the laser welding method in any one of Claim 1 to 3.

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