JP3174286B2 - Laser welding structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser welding structure most suitable for a bus bar housed in an electric junction box, and more particularly, to a structure capable of stably improving a joining strength.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
A laser beam LB is applied to a crimping portion 3a of a crimping terminal 3 for crimping and connecting the conductor 2, and the crimping portion 3a and the conductor 2 are fused and welded (Japanese Patent Laid-Open No. 1038/1990).
No. 76).

Further, as shown in FIG. 9 (B), a separate metal projection 5 for replenishing the molten volume is provided on the flat metal conductor 4 for welding, and a plurality of metal projections 5 are provided below the projection 5. The conductor 2 composed of the element wire 2a is arranged, and the laser beam LB is
Irradiation is performed to fuse and weld the protruding portion 5 together with the conductor 2 (Japanese Patent Laid-Open No. 6-302).
No. 341).

By the way, in an electric junction box used for branch connection of an automobile wire harness or the like to various electric components, the branch connection points are concentrated at one place, and the wiring is rationally and economically connected. With the increase in the density of wire harnesses, various types have been developed according to vehicle types or applications.

[0005] As shown in FIG. 8, the electric connection box as described above uses a press die to move the bus bar 7 A from the hoop material 6.
To 7C, and each of the bus bars 7A to 7C
The tab terminals 7a and 7b are cut and raised from the pattern portion in the vertical direction, and insulating plates 8A to 8C are interposed between the bus bars 7A to 7C, respectively. And a lower case 9B.

As shown in detail in FIG. 7, of the bus bars 7A to 7C, a tab terminal 7a cut upward from a middle bus bar 7B is connected to an upper insulating plate 8A.
The tab terminals 7a cut upward from the upper bus bar 7A are set so as to have the same height as the tab terminals 7a cut upward from the upper bus bar 7A. The board 8B and the upper insulating plate 8A are penetrated so that the tab terminals 7a cut and raised upward from the upper bus bar 7A are set to have the same height.

Similarly, the tab terminal 7b cut and raised from the middle bus bar 7B is penetrated through the lower insulating plate 8C, and the height of the tab terminal 7b cut and raised from the lower bus bar 7C is reduced. The tab terminals 7 which are set so as to be aligned and cut and raised downward from the upper bus bar 7A.
“b” is set so as to penetrate the middle insulating plate 8B and the lower insulating plate 8C, and to have the same height as the tab terminals 7b cut and raised downward from the lower bus bar 7C.

[0010] As shown in FIG. 8, external components such as a fuse 11 and a relay 12 are inserted and connected to the tab terminals 7 a and 7 b via a relay terminal 10 and the like. The connector on the side is directly inserted and connected.

When the circuit volume in the electric junction box 9 increases, the bus bars 7A (7
B, 7C), the pattern parts of the bus bars 7A to 7C of different levels, and the pattern parts of the bus bars 7A to 7C, and other wiring members (FPC, PC).
B or a conductor such as an electric wire) with a connector.

On the other hand, in recent years, a plurality of electric connection boxes dispersedly mounted in an automobile are integrated into one and arranged in a center cluster or the like, and a wire harness for connecting between the electric connection boxes is provided. Attempts have been made to simplify (line saving).

If the number of circuits in the electric junction box is about 40, a three-layer bus bar laminated structure as described above may be used. However, the number of circuits in the electric junction box is reduced by 80 to 100 due to integration.
When it is increased to the extent, a bus bar laminated structure of 8 to 10 layers is obtained.

With the bus bar laminated structure of eight to ten layers as described above, when the tab terminals are vertically cut from the bus bar pattern portion of each layer, the tab terminals cut and raised upward from the uppermost bus bar are formed. In order to set the height to be the same as the height of the tab terminal cut and raised from the lowermost bus bar, the maximum number of tab terminals is 8 to 1
It is necessary to set the length to penetrate as many as 0 layers of the insulating plate.

However, in order to cut and elongate a long tab terminal from the bus bar pattern portion, a space for cutting and erecting the tab terminal is required in the pattern portion. This space becomes a dead space, and the bus bar is reduced in size and size. Since the density cannot be increased, there is a problem that the number of stacked bus bars cannot be reduced.

To solve this problem, the applicant has
We have proposed a laser welding structure that makes it possible to reduce the size and density of busbars housed in electrical junction boxes by utilizing laser welding technology.

In the laser welding structure, basically, the tab terminals are not cut and raised in the vertical direction from the bus bar pattern portion, but the tab terminals are formed separately, and the separate tab terminals are connected to the bus bar pattern portion. By irradiating a laser beam, and melting and welding the tab terminal and the pattern portion, a dead space for cutting and raising the tab terminal in the bus bar pattern portion becomes unnecessary. By adding a pattern part to
The bus bar can be made smaller and denser.

[0016]

However, since the tab terminals are made of a copper material, the laser absorption is low at less than 10%, so that the heat effect when irradiating the laser beam is unstable, There is a problem that connection characteristics such as strength are not stable.

The present invention relates to an improvement in the laser welding structure proposed by the present applicant. In particular, the present invention relates to a laser welding structure which is optimal for welding a bus bar housed in an electric junction box and can stably improve the joining strength. To provide.

[0018]

In order to solve the above-mentioned problems, in the first aspect of the present invention, an object to be welded is applied to the object to be welded, and the object to be welded is welded with a laser beam. The workpiece to be irradiated with the laser beam is a composite material whose main material is a material having a low laser absorption and whose outer shell is a material having a high laser absorption. The present invention provides a laser welding structure characterized by cutting a portion obliquely and irradiating the cut end with a laser beam to perform welding.

According to the first aspect, when the cut end is irradiated with a laser beam, the heat received by the outer shell having a large laser absorptivity is more smoothly transmitted to the center member, and the outer shell and the center member are further separated. Melted efficiently.

[0020]

[0021]

According to a second aspect of the present invention, the laser beam is
In the case of a structure where welding is performed by irradiating the joint interface between the center material and the outer shell at the cut end, the heat received by the outer shell having a large laser absorptivity is directly transmitted to the center material, And the center material is melted very efficiently.

Specifically, the welded body is a bus bar housed in an electric connection box, the welded body is a tab terminal, and the bent portion of the tab terminal is provided on the pattern portion of the bus bar. And can be used to weld the pattern portion of the bus bar and the bent leg portion of the tab terminal with a laser beam.

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the same components and operations as those of the prior art are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 1, as a first embodiment,
The welded body 17a 'is applied to the welded body 17'. The welded body 17 'is, for example, a nickel plate having a high laser absorption rate (laser absorption rate: 28%). Note that a tin (laser absorption rate 46%) plate may be used.

In FIG. 1A, for example, a copper wire (less than 10% laser absorptivity) 17d having a diameter of 2 mm as the center member is formed by welding a 17 d 'welded body 17a' with an inner diameter of 2.2 mm and a thickness of 1 mm.
mm nickel shell 17e as an outer shell,
It is a linear composite material drawn with a 1.8 mm die. The outer shell 17e may be a tin pipe. Also, the center material 17
d may be plated with an outer shell (nickel or tin) 17e.

In FIG. 1B, for example, a plate thickness of 2 mm
This is a plate-shaped composite material in which nickel plating 17e, 17e as an outer shell is applied to a copper plate 17d as a center material, so that the upper and lower thicknesses are each 0.5 mm.

Then, as shown in FIG. 1 (C), when the laser beam LB is applied to the to-be-welded body 17a 'of each composite material from directly above, the material of the outer shell 17e is nickel having a large laser absorptivity. Therefore, the outer shell 17e is immediately affected by heat, and this heat is smoothly transmitted to the center member 17e, so that the outer shell 17e and the center member 17d are efficiently melted and welded to the welded body 17 '. Become.

Therefore, the shape of the heat-affected zone (the crystal grain size of the metal structure is coarsened) is stable, whereby the connection characteristics such as bonding strength are stably improved.

As a second embodiment, as shown in FIG. 2A, the end of the welded body 17a 'which is a linear composite material shown in FIG. Cut diagonally.

As shown in FIG. 2B, FIG.
The end of the welded body 17a ', which is a plate-shaped composite material shown in (B), is cut obliquely at an angle of, for example, 45 degrees.

Then, as shown in FIG. 2C, the laser beam L is applied to the cut end 17f of each of the workpieces 17a 'from directly above.
When B is irradiated, the outer shell 17e and the center member 17d are exposed in a slope shape to the cut end portion 17f when viewed from above, so that the heat received by the outer shell 17e is more smoothly transmitted to the center member 17d. As a result, the outer shell 17e and the center member 17d are more efficiently melted and welded to the welded body 17 ', so that connection characteristics such as joining strength are more stably improved.

When the laser beam LB is applied to the joint interface E between the outer shell 17e above the cut end 17f and the center member 17d thereunder, the heat received by the upper outer shell 17e is directly applied. Is propagated to the center material 17d and the outer shell 17
Since e and the center member 17d are melted very efficiently, connection characteristics such as bonding strength are extremely stably improved. Incidentally, the laser beam LB 'may be applied to the joint interface E' between the lower outer shell 17e and the center member 17d thereon.

(Experimental Example 1) As a first embodiment, FIG.
A welded body 17a 'having an outer shell 17e shown in FIG.
Then, a laser beam LB was irradiated to a body to be welded having no outer shell as a conventional example, and the joining strength of the welded portion was measured. Table 1 shows the results.

[0035]

[Table 1]

As is clear from Table 1, the welded body 17a 'of the first embodiment is different from the conventional welded body.
It can be seen that the bonding strength is about three times higher and the variation (standard deviation) of the bonding strength is as small as about ４.

(Experimental Example 2) As a second embodiment, FIG.
A welded body 17a 'having an outer shell 17e shown in FIG.
Then, a laser beam LB was irradiated to a body to be welded having no outer shell as a conventional example, and the joining strength of the welded portion was measured. Table 2 shows the results.

[0038]

[Table 2]

As is clear from Table 2, the welded body 17a 'of the first embodiment, in which the center material (copper Cu) 17d or the outer shell 17e (nickel Ni) is irradiated with the laser beam LB, is different from the conventional one. It can be seen that the joining strength is about 3 to 4 times higher and the variation (standard deviation) of the joining strength is as small as about 1/4 as compared with the welded body of the example.

The welded body 17a 'in which the outer shell 17e (nickel... Ni) is irradiated with the laser beam LB is more joined than the welded body 17a' in which the center member (copper .Cu) 17d is irradiated with the laser beam LB. It can be seen that the strength is as high as about 20%.

In the case where the welded body 17a 'is welded to the welded body 17', as will be described later, assuming that the welded body 17 'is the bus bar 17 and the welded body 17a' is the tab terminal 17a, as will be described later. In the case of resistance welding, a large jig is required for each busbar in order to sandwich the busbar between the electrodes, so that the number of processing steps and facilities are expensive, which is not suitable for mass productivity. In the case of conventional arc welding, since the gap between the busbar and other circuits is narrow, it is necessary to insulate or widen the gap, so that the density cannot be increased, and it is necessary to ground each circuit to be welded. Therefore, processing man-hours and the like become expensive, which is not suitable for mass production. Furthermore, in ultrasonic welding, it is not possible to perform welding on portions having plating on the busbars, so partial plating is required. Also, the busbar shapes are different one by one, and jigs are required for the number of circuits. However, they are expensive and unsuitable for mass production.

On the other hand, in the case of the laser welding according to the present invention, the laser beam LB is not in contact with the above-described laser welding, arc welding, ultrasonic welding, etc. The bus bar 17 can be welded to
Since the welding seconds per location are short, mass productivity is good, and since the laser beam LB has a small beam diameter, the pitch between the bus bar 17 and the tab terminal 17a can be narrowed to improve the degree of freedom in design wiring. There is an advantage of doing so.

Among various laser weldings, YAG laser welding is non-contact, has a small heat affected layer,
It has low power consumption, is small in size, can be easily used for three-dimensional welding due to the use of optical fibers, and can divide a beam into multiple parts for simultaneous multipoint welding.
It is optimal because the automation is easy and the production cost is significantly reduced.

FIGS. 3 and 4 show a laser welding structure of the bus bar 17 as a specific example of the first embodiment. As shown in FIG. 4, the tab terminals 17 a are not cut and raised in the vertical direction from the pattern portion of the bus bar 17 as in the related art. Instead, the tab terminals 17 a are separated from each other, and the bent legs 17 b are formed at the lower ends of the tab terminals 17 a. Integrally formed. Using the bent legs 17b as a center material (17d), nickel is plated on the upper and lower surfaces as an outer shell 17e.

Then, as shown in FIG.
The bent leg 17b of the bus bar 17 on the insulating plate 18
And the laser beam LB is applied to the center position of the outer shell 17e above the leg 17b.

By this irradiation, the bent leg portion 17b of the tab terminal 17a and the pattern portion of the bus bar 17 are melted and welded.

All the tab terminals 17a of the bus bar 17
Are not welded as separate bodies, but if necessary, the tab terminals 17a
Can be used in combination with each other.

Also, as shown in FIG.
When the relay terminal 17c is integrally formed with the 7a, a separate relay terminal is not required.

FIG. 5 shows a laser welding structure of the bus bar 17 as a specific example of the second embodiment.

As in FIGS. 3 and 4, the tab terminal 17a is separately provided, and a bent leg 17 is attached to the lower end of the tab terminal 17a.
b is integrally formed, and this bent leg 17b is used as a central material (1).
In step 7d), nickel as the outer shell 17e is plated on the upper and lower surfaces, and the end of the bent leg 17b is cut obliquely at an angle of, for example, 45 degrees.

When the cut end 17f of the bent leg 17b is irradiated with a laser beam LB from directly above, the bent leg 17b of the tab terminal 17a and the pattern portion of the bus bar 17 are melted and welded. Become. In this case, it is preferable to irradiate the laser beam LB to the bonding interface E between the outer shell 17e above the cut end portion 17f and the central member 17d thereunder. Incidentally, the laser beam LB 'may be applied to the joint interface E' between the lower outer shell 17e and the center member 17d thereon.

[0052]

As is apparent from the above description, in the laser welding structure according to the first aspect of the present invention, when the cut end is irradiated with the laser beam, the heat received by the outer shell is more smoothly applied to the central member. Since the heat is propagated and the outer shell and the center material are more efficiently melted, the shape of the heat-affected zone is further stabilized, whereby the connection characteristics such as bonding strength are more stably improved.

When the laser beam is applied to the joint interface between the center member at the cut end and the outer shell and welded, the heat received by the outer shell is directly transmitted to the center member. And the outer shell and the center material are melted very efficiently, so that connection characteristics such as bonding strength can be extremely stably improved.

Further, specifically, as in claim 3,
The present invention can be suitably used for welding a bus bar (weld) and a tab terminal (weld) housed in an electric junction box with a laser beam.

[Brief description of the drawings]

FIG. 1 is a laser welding structure according to a first embodiment of the present invention, in which (A) is a perspective view in which a linear welded body is laser-welded to a welded body, and (B) is a plate-shaped welded body being welded. FIG. 3C is a perspective view of the laser-welded body, and FIG.

FIG. 2 is a laser welding structure according to a second embodiment,
(A) is a perspective view in which a cut end of a linear welded body is laser-welded to a welded body, (B) is a perspective view in which a cut end of a plate-shaped welded body is laser-welded to a welded body, and (C) is a perspective view. () Is a sectional view of a welded portion.

FIG. 3A is a perspective view corresponding to the first embodiment in which a tab terminal is laser-welded to a bus bar, and FIG. 3B is a side sectional view.

FIG. 4 is an exploded perspective view before a tab terminal is laser-welded to a bus bar.

FIG. 5A is a perspective view corresponding to the second embodiment in which a tab terminal is laser-welded to a bus bar, and FIG. 5B is a side cross-sectional view.

FIG. 6 is a perspective view of a tab terminal formed integrally with a relay terminal.

FIG. 7 is a perspective view of a conventional bus bar.

FIG. 8 is an exploded perspective view of a conventional bus bar processing and assembling procedure.

FIGS. 9A and 9B are perspective views of a conventional laser welding structure such as a crimp terminal.

[Explanation of symbols]

 9 Electrical junction box 17 'Welded body 17a' Workpiece 17 Bus bar 17a Tab terminal 17b Bend leg 17d Center material 17e Outer shell 17f Cut end LB Laser beam a Welding

────────────────────────────────────────────────── (5) References JP-A-8-218137 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 26/00 310 B23K 26/18 H01R 4 / 02 H01R 43/02

Claims (3)

(57) [Claims] 1. A method according to claim 1, wherein the object to be welded is applied to the object to be welded, and the object to be welded is welded to the object with a laser beam. This is a composite material with a small material as the center material and a material with a large laser absorptivity as its outer shell. The end of this composite material is cut diagonally, and the cut end is irradiated with a laser beam and welded Laser welding structure characterized by performing. 2. The laser beam according to claim 1, wherein the laser beam is applied to a joint interface between a central member at a cut end and an outer shell to perform welding.
2. The laser welding structure according to item 1. 3. The bus bar according to claim 1, wherein the welded body is a bus bar housed in an electrical junction box, the welded body is a tab terminal, and the bent leg of the tab terminal is applied to a pattern portion of the bus bar. The laser welding structure according to claim 1 , wherein the portion and the bent leg portion of the tab terminal are welded by a laser beam.