JPH10328862A - Laser welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve workability by preheating a laser beam irradiation part of an object to be welded, then welding through a laser beam irradiation, and thereby unnecessitating separate working such as providing projecting parts. SOLUTION: A welding body 17' is abutted on with a body 17a' to be welded. These 17', 17a' are for example copper plates with a low laser absorptivity (less than 10%). The laser beam irradiation part 17e of the body 17a' to be welded is preheated by an arc P to a temperature (e.g. 500 deg.) that is slightly lower than the melting temperature (e.g. 540 deg.) by the irradiation of a laser beam LB. Thus, the irradiation part 17e is sufficiently preheated first, and then the body 17a' is welded to the welding body 17'. The preheating is also desirably done by electrical resistance, continuous oscillation laser or a preheating furnace other than by the arc.; it is also advisable that a material with a high laser absorptivity is attached to the laser beam irradiation part. As a result, it greatly reduces scattering of copper materials due to spattering for example.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 11A, a crimping portion 3a of a crimp terminal 3 for crimping and connecting a conductor 2 of an electric wire 1 is irradiated with a laser beam LB to melt the crimping portion 3a and the conductor 2. (Japanese Patent Application No. 2-103) has been proposed.
No. 8786).

As shown in FIG. 11 (B), a separate metal projection 5 for replenishing the molten volume is provided on the flat metal welding conductor 4, and a plurality of metal projections 5 are provided below the projection 5. Strand 2a
The conductor 2 made of
There is also proposed a method in which the projection 5 is melted and welded together with the conductor 2 by irradiating B (Japanese Patent Laid-Open No. 6-30).
No. 2341).

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 an electric junction box as described above, FIG.
As shown in FIG.
A to 7C are punched out, and the bus bars 7A to 7
The tab terminals 7a and 7b are cut and raised in the vertical direction from the pattern portion of C, and are laminated by interposing insulating plates 8A to 8C between the bus bars 7A to 7C, respectively. 9A and a lower case 9B.

As shown in detail in FIG. 9 of each of the bus bars 7A to 7C, a tab terminal 7a cut and raised 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 extends downward through the lower insulating plate 8C, and the height of the tab terminal 7b cut and raised from the lower bus bar 7C is lowered. 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.

As shown in FIG. 10, external components such as a fuse 11 and a relay 12 are inserted and connected to the tab terminals 7a and 7b 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 pattern portion of the bus bar becomes unnecessary. By adding a pattern part to
The bus bar can be made smaller and more dense.

[0016]

However, since the tab terminals are made of copper, which is a highly reflective material, when laser welding is performed, heat diffusion occurs due to the high thermal conductivity of the material itself, so that high energy is required. Since it is necessary to irradiate a laser beam and the copper material is scattered more by sputtering or the like, another processing such as providing a protruding portion must be performed as in the conventional technique shown in FIG. Therefore, there is a problem that workability is poor.

The present invention relates to an improvement in the laser welding structure proposed by the present applicant, and in particular, provides a laser welding method which is optimal for welding a bus bar housed in an electric junction box and which can improve workability. Things.

[0018]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention applies a workpiece to a welded body and welds the welded body and the workpiece with a laser beam. Accordingly, the present invention provides a laser welding method characterized in that a laser beam irradiating portion of the above-mentioned workpiece is preheated, and thereafter, the laser beam is irradiated to perform welding.

According to the present invention, the laser beam irradiating portion of the workpiece is preheated at a temperature slightly lower than the melting temperature by the laser beam irradiation (for example, when the melting temperature is 540 degrees). , Preheating temperature is about 500 degrees),
After that, it is sufficient to irradiate the laser beam in a short time with low energy, so that scattering of the copper material due to sputtering or the like is remarkably reduced.

As means for preheating the laser beam irradiating portion of the object to be welded, an arc, an electric resistance, a continuous wave laser or a preheating furnace can be used.

When a material having a high laser absorptivity is attached to the laser beam irradiating section, a laser beam having lower energy can be irradiated.

According to a fourth aspect of the present invention, the laser beam irradiating portion is provided at a bonding interface between an upper surface of the welded body and an end face of the workpiece or a bonding interface between the welded body and each end face of the workpiece. In this case, heat tends to be trapped in that part.

More specifically, the welded body is a bus bar housed in an electric junction box, the welded body is a tab terminal, and the bent leg portion of the tab terminal is provided on a 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, a welded body 17a 'is applied to a welded body 17'. The welded body 17 'and the welded body 17a' are, for example, copper plates having a low laser absorption rate (laser absorption rate is less than 10%).

The laser beam irradiating section 17e of the workpiece 17a 'is irradiated with an
Is preheated at a temperature (for example, 500 degrees) slightly lower than the melting temperature (for example, 540 degrees) by the irradiation.

As the preheating means, in addition to the arc shown in FIG. 1, non-contact or contact means such as electric resistance Q shown in FIG. 2 is suitable. When the shape of the workpiece 17a 'is restricted, a non-contact laser such as a continuous wave laser R as shown in FIG. 3 or a preheating (heating) furnace (not shown) is suitable.

Further, as shown in FIG.
a ′ is made of a material having a high laser absorptivity, for example, black paint 2
1 (see black) is preferably applied.

As described above, the laser beam irradiating portion 17e of the workpiece 17a 'is preheated at a temperature lower than the melting temperature by the irradiation of the laser beam LB. Laser beam L in time
Even when the irradiation with B is performed, the irradiated portion 17e is sufficiently melted and the welded body 17a 'is welded to the welded body 17'.

Therefore, the object 1 to be welded 1
Since the scattering of 7a 'is reduced, it is not necessary to perform another processing such as providing a protruding portion as in the prior art, and the workability is improved.

When a black paint 21 having a high laser absorptivity is applied to the laser beam irradiating portion 17e of the workpiece 17a ', a laser beam LB having lower energy can be irradiated. Body 17
The scattering of a 'is further reduced.

Further, as shown in FIG. 5, the laser beam irradiation section 17e of the above-mentioned welded body 17a 'is
Interface E1 between the upper surface of the workpiece and the end face of the workpiece 17a '
When the black paint 21 is applied to each laser beam irradiating section 17e as a joining interface E2 between the welding body 17 'and each end face of the workpiece 17a', the joining interfaces E1, E2
And the heat is easily stored, so that the effect of preheating is greater.

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, partial plating is necessary because welding cannot be performed on a portion of the bus bar that has plating, and the bus bar shape is different one by one, so jigs are required for the number of circuits, so processing man-hours and equipment are required. However, they are expensive and unsuitable for mass production.

On the other hand, in the case of the laser welding of the present invention, the laser beam LB is not in contact with the laser beam LB, so that the laser beam LB is not in contact with the above-described resistance welding, arc welding, ultrasonic welding and the like. 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.

FIG. 6 shows a laser welding structure of the bus bar 17 as a specific example of the first embodiment. Instead of cutting the tab terminals 17a from the pattern portion of the bus bar 17 in the vertical direction as in the related art, the tab terminals 17a are separately formed, and bent legs 17b are integrally formed at the lower ends of the tab terminals 17a.

Then, the bent leg 1 of the tab terminal 17a
7b is applied to the pattern portion of the bus bar 17 from above, and the laser beam LB is applied to the center position of the bent leg portion 17b from directly above.

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.

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

FIG. 7 shows a laser welding structure of the bus bar 17 as a specific example of the second embodiment.

As in FIG. 6, the tab terminal 17a is separately provided, and a bent leg 17b is integrally formed at the lower end of the tab terminal 17a.

The front end face 17 of the bent leg 17b
A laser beam LB is applied to the joint interface E1 between the upper surface 17j of the bus bar 17 and the upper surface 17j of the bus bar 17 obliquely from above. When the laser beam LB is irradiated from right beside, the bent leg 17 of the tab terminal 17a is bent.
b and the pattern portion of the bus bar 17 are joined at the joint interface E
At 1, E2, it is melted and welded.

[0043]

As is apparent from the above description, the welding method of the present invention preheats the laser beam irradiating portion of the workpiece to a temperature slightly lower than the melting temperature of the laser beam irradiation. Therefore, after preheating, the energy is low and it is sufficient to irradiate the laser beam in a short time.
Scattering of a copper material or the like due to sputtering or the like is remarkably reduced, so that it is not necessary to perform a separate process such as providing a protruding portion as in the related art, thereby improving workability.

As means for preheating, an arc, a continuous wave laser, or the like can be appropriately used as necessary.

Further, when a material having a high laser absorptivity is attached to the laser beam irradiating section, a laser beam having lower energy can be irradiated. Further, when the laser beam irradiating section to which a material having a high laser absorptivity is attached is used as a bonding interface between the welded body and the welded body, heat is easily trapped in that part, so that the effect of preheating is reduced. Advantageously, it is larger.

More specifically, the present invention is suitably used for welding a bus bar (weld) and a tab terminal (weld) housed in an electric junction box with a laser beam. be able to.

[Brief description of the drawings]

FIG. 1 is a perspective view of a laser welding method for preheating by an arc according to the present invention.

FIG. 2 is a perspective view of a laser welding method of preheating by electric resistance.

FIG. 3 is a perspective view of a laser welding method for preheating with a continuous oscillation laser.

FIG. 4 is a perspective view of a laser welding method in which a black paint is applied to a laser beam irradiation unit.

FIG. 5 is a perspective view of a laser welding method for preheating a bonding interface with a continuous wave laser.

FIG. 6A is a perspective view in which a tab terminal is bent to a bus bar by laser welding at a leg, and FIG. 6B is a side sectional view.

7A is a perspective view in which a tab terminal is laser-welded to a bus bar at a bonding interface, and FIGS. 7B and 7C are cross-sectional views of the bonding interface.

FIG. 8 is a perspective view of a tab terminal formed integrally with a relay terminal.

FIG. 9 is a perspective view of a conventional bus bar.

FIG. 10 is an exploded perspective view of a conventional bus bar processing and assembling procedure.

FIGS. 11A and 11B are perspective views of a conventional laser welding structure such as a crimp terminal.

[Explanation of symbols]

 9 Electric junction box 17 'Welded body 17a' Workpiece 17 Bus bar 17a Tab terminal 17b Bend leg 17e Laser beam irradiation part LB laser beam P arc Q Electric resistance R Continuous wave laser E1, E2 Joining interface a Welding

Continued on the front page (72) Inventor Atsuhiko Fujii 1-7-10 Kikuzumi, Minami-ku, Nagoya City, Aichi Prefecture Inside Harness Research Institute, Inc. (72) Inventor Takahiro Onizuka 1-7-10 Kikuzumi, Minami-ku, Nagoya City, Aichi Prefecture No. Harness Research Institute, Inc. (72) Inventor Atsuhiro Togawa 1-7-10 Kikusumi, Minami-ku, Nagoya-shi, Aichi Harness Research Institute, Inc.

Claims (5)

[Claims] An object to be welded is applied to the object to be welded, and the object to be welded and the object to be welded are welded with a laser beam. A laser welding method characterized by irradiating with a laser beam thereafter. 2. The laser welding method according to claim 1, wherein the means for preheating the laser beam irradiation part of the workpiece is an arc, electric resistance, a continuous wave laser, or a preheating furnace. 3. The laser welding method according to claim 1, wherein a material having a high laser absorptivity is attached to the laser beam irradiation section. 4. The laser beam irradiation section is a bonding interface between an upper surface of a welded body and an end face of a welded body or a bonded interface between a welded body and each end face of a welded body. 2. The laser welding method according to 1., 5. The bus bar according to claim 1, wherein the welded body is a bus bar housed in an electric junction box, the welded body is a tab terminal, and a bent leg of the tab terminal is applied to a pattern portion of the bus bar. The laser welding method according to claim 1, wherein the portion and the bent leg of the tab terminal are welded by a laser beam.