Method for welding metal honeycomb carrier

This invention relates to a method for welding a metal honeycomb carrier in which the metal honeycomb carrier for a catalyst convertor is welded. The method for welding the metal honeycomb carrier according to this invention radiates laser beam to one end surface of a core section formed of metal corrugated and flat plates to mutually weld said corrugated and flat plates, where said laser beam is moved in the direction perpendicular to the welding direction while oscillating at a certain amplitude and masking is applied to the amplitude end of said laser beam and its neighboring area on the end surface of said core section.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method for welding a metal honeycomb carrier in 
which the metal honeycomb carrier for a catalyst convertor is welded. 
2. Description of the Prior Art 
Generally, to clean automobile exhaust, the automobile exhaust system is 
provided with a metal honeycomb carrier as disclosed in the Japanese 
Patent Application Laid-open No. 54-13462. 
FIG. 7 shows the details of such a metal honeycomb carrier. This metal 
honeycomb carrier is formed by alternatively piling metal corrugated plate 
11 and flat plate 13 and rolling the piled plates into a multiple form 
with a core material at the center, thereby providing a core section 17. 
In this core section 17, when the corrugated plate 11 and the flat plate 13 
are kept as rolled, flow of exhaust into the core section 17 causes the 
corrugated plate 11 and the flat plate 13 arranged at the center of the 
core section 17 to protrude in the axial direction of the core section 17, 
causing so-called film out phenomenon. To remedy this, the corrugated 
plate 11 and the flat plate 13 are mutually welded after the core section 
17 is formed. 
FIG. 8 shows one example of existing methods for welding a metal honeycomb 
carrier. In this method, with one end surface 19 of the core section 17 
upside, laser beam 23 is radiated to the end surface 19 from a welding 
head 21 which is disposed above the end surface 19. The welding head 21 is 
moved in the radial direction of the core section 17 to weld the 
corrugated plate 11 and the flat plate 19 at the end surface 19 which is 
exposed to the laser beam 23. 
But, in this conventional method of welding the honeycomb carrier, to weld 
with the laser beam 23 focused on the end surface 19 of the core section 
17, the laser beam 23 spotted on the end surface 19 has a small diameter 
of about 0.2 mm for example. Therefore, to weld the plates with 2-mm width 
of 2 mm, the welding head 21 must go and return 5 times, entailing a 
disadvantage of consuming a great time for welding. 
To remedy this disadvantage, the end surface 19 of the core section 17 is 
approached to the welding head 21 from the focal point of the laser beam 
23 so as to be welded with the laser beam 23 having relatively greater 
diameter. But, the power density differs between the center and peripheral 
portions of the laser beam 23, resulting in causing a drawback that it is 
difficult to uniformly weld the end surface 19. 
SUMMARY OF THE INVENTION 
The present invention aims to remedy the above disadvantages and to provide 
a method for welding a metal honeycomb carrier in which corrugated and 
flat plates can be mutually welded quickly and securely.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
The present invention will be described by examples in detail with 
reference to the drawings. 
FIG. 1 shows a welding device for metal honeycomb carrier to enforce one 
embodiment of the method according to this invention, wherein reference 
numeral 31 shows a core section which is formed by piling a stainless 
steel corrugated plate 33 and flat plate 35 and coiling them in multiple. 
The stainless steel here used consists of Cr of 19.0-21.0 wt %, Al of 
4.5-5.5 wt %, REF (Ce, La, etc.) of 0.001-0.1 wt %, C of 0.01 wt % or 
below, and the balance of F. And it has thickness of 50 um. And the 
corrugated plate 33 has a distance of 2.56 mm between its ridges (or 
grooves) and height of 1.24 mm from the groove to the ridge; and the 
radius at the top of ridge and groove is 0.5. 
This core section 31 is disposed with its end surface 37 upside, and a 
total reflection mirror (oscillating mirror) 39 above the end surface 37. 
This total reflection mirror 39 receives laser beam 43 from a CO.sub.2 gas 
laser generator 41 through a condensing lens 45. 
The total reflection mirror 39 and the condensing lens 45 are accommodated 
in a welding head 47, which has an oscillating device 49 disposed to 
oscillate the total reflection mirror 39 in the arrow direction A shown in 
FIG. 1. 
In the device for welding the metal honeycomb carrier configured as 
described above, the laser beam 43 generated from the laser generator 41 
is condensed with the condensing lens 45, lead to the total reflection 
mirror 39, reflected thereon, and radiated to the end surface 37 of the 
core section 31. The welding head 47 is moved at a certain speed in the 
arrow direction B when the laser beam 43 is oscillated. 
And in the present device, since the total reflection mirror 39 is 
oscillated with the oscillating device 49, the trace of the laser beam 43 
radiated on the end surface 37 of the core section 31 forms a zigzag curve 
51 as shown in FIG. 2. 
Where the trace of the laser beam 43 forms the zigzag curve 51, an energy 
supply amount per unit time at an amplitude end 53 becomes extremely great 
as compared with that at the center section C, resulting in causing 
so-called burn through on the corrugated plate 33 or flat plate 35 
positioned at the amplitude end 53. 
Thus, the occurrence of burn through on the corrugated plate 33 or flat 
plate 35 clogs the metal honeycomb carrier, increasing the exhaust 
resistant of the metal honeycomb carrier against the exhaust. 
In the method of the present invention, therefore, the amplitude end 53 and 
its neighbor of the laser beam 43 on the end surface 37 of the core 
section 31 are masked with masking material 55 which reflects the laser 
beam 43. 
This masking is effected by attaching the masking material 55 in a pair at 
a certain interval on the end surface 37 of the core section 31. 
To practice the method of this invention, for example in FIG. 2, when the 
output of the CO.sub.2 gas laser generator 41 is about 1,000 W and the 
amplitude D of the laser beam 43 is 2 mm to 30 mm, the oscillating 
frequency by means of the oscillating device 49 is desirably 120-150 Hz. 
And the masking is preferably effected to cover a distance E of at least 
0.3 mm inside from the amplitude end 53. 
In the method of the present invention, the laser beam 43 is designed to 
move in the vertical direction with respect to the welding direction at 
the certain amplitude D, so that if the diameter of the laser beam 43 on 
the end surface 37 of the core section 31 is as small as about 0.2 mm for 
example, welding can be done with a width substantially corresponding to 
the amplitude D of the laser beam 43, thereby surely being able to weld 
the corrugated plate 33 and the flat plate 35. 
In the method of this invention, the amplitude end 53 and its neighbor of 
the laser beam 43 on the end surface 37 of the core section 31, or the 
section which receives extremely great energy supply per unit time is 
masked with the masking material 55, thereby surely being able to prevent 
the burn through on the corrugated plate 33 or flat plate 35 exposed at 
the position of the amplitude end 53. 
In the above embodiment, the masking material 55 is directly applied to the 
end surface 37 of the core section 31. But this invention is not limited 
to the above embodiment. For example, an appropriate masking material may 
be well disposed on the way of the laser beam 43 from the welding head 47. 
In the above embodiment, the condensing lens 45 is disposed between the 
laser generator 41 and the total reflection mirror 39. But, the method of 
this invention is not limited to that embodiment. It is naturally possible 
to arrange the condensing lens 45 between the total reflection mirror 39 
and the core section 31. 
In the above embodiment, the condensing lens 45 and the total reflection 
mirror 45 are independently arranged within the welding head 47. But the 
method of this invention is not limited to that arrangement. For example, 
using so-called R lens which integrally consists of a condensing mirror 
and a total reflection mirror is effective to oscillate this R lens. 
Generally, welding depends on an energy charging amount per unit area and 
unit time. Therefore, the welding condition may be adjusted to meet the 
amplitude end to which the laser beam energy is concentrated without 
masking the amplitude end and its neighbor of the laser beam, determining 
the amplitude to 2-3 mm and oscillating the laser beam perpendicular to 
the welding direction at a certain amplitude, thereby effecting the 
welding. In this case, welding is effected at both amplitude ends only. 
FIG. 3 shows a device for welding the metal honeycomb carrier to conduct 
another embodiment of the method according to this invention, where the 
structure is same with that of the device in the embodiment shown in FIG. 
1 except that a condensing member 60 is different. Therefore, the same 
reference numerals as in the above embodiment are used for the same 
elements. 
The core section 31 is disposed with the end surface 37 upside, and the 
condensing member 60 is disposed above the end surface 37. 
The laser beam 43 is lead to the condensing member 60 from the laser 
generator 41 through the condensing lens 45. 
The condensing member 60 and the condensing lens 45 are accommodated in the 
welding head 47, which is freely movable in the arrow direction C. 
The condensing member 60 in this embodiment is formed of a cylindrical 
concave mirror as shown in FIG. 4, and works to reflect cylindrical laser 
beam 61 from the condensing lens 45 at an angle of 90.degree. and also 
convert this laser beam 61 into a linear beam 63. 
The condensing member 60 is disposed in the welding head 47 so that an axis 
65 of the cross section of the linear beam 63 is perpendicular to the 
moving direction F of the welding head 47. 
With the device for welding the metal honeycomb carrier configured as 
described above, the laser beam 43 generated from the laser generator 41 
is condensed through the condensing lens 45, lead to the condensing member 
60, reflected on the condensing member 60, and at the same time converted 
into the linear beam 63, and radiated onto the end surface 37 of the core 
section 31. And the welding head 47 is moved at a certain speed in the 
arrow direction F as shown in FIG. 3 when the laser beam 61 is generated. 
According to the method of the present invention, the laser beam 61 is 
converted into the linear beam 63 with the condensing member 60 and 
radiated onto the end surface 37 of the core section 31. The welding width 
can be made extensively broader than before by setting the axis 51 of the 
linear beam 63 to be perpendicular to the moving direction C of the 
welding head 47. Thus the corrugated plate 33 and the flat plate 35 can be 
mutually welded quickly and securely. 
The linear beam 63 produced by the condensing member 60 is capable of 
welding uniformly because the power densities at the center and the 
peripheral area have a very small difference. 
More specifically, in the method of the present invention, even if the 
diameter of the laser beam 61 condensed by the condensing lens 45 is for 
example as small as about 0.2 mm, welding can be substantially done on the 
corrugated plate 33 and the flat plate 35 quickly and securely with width 
corresponding to the length of the axis 65 of the linear beam 63. 
The above embodiment describes an example of applying the method of this 
invention to the cylindrical core section 31. To apply the method of this 
invention to an ellipse core section 67 as shown in FIG. 5, moving the 
welding head 47 in parallel with the linear side of the flat plate 69 as 
shown by an arrow G allows more uniform welding. 
Specifically, as indicated by the arrow H, to weld from the position 
perpendicular to the flat plate 69, the linear beam 63 may have a state to 
spot on the corrugated plate 71 or flat plate 69 only. Therefore, the burn 
through of the flat plate 69 becomes relatively greater than the 
corrugated plate 71 but, welding in parallel to the longitudinal direction 
the flat plate 69 results in producing uniform burn through because the 
linear beam 63 is always in a state to straddle the corrugated plate 71 
and the flat plate 69. 
FIG. 6 shows another condensing member used in this method of the 
invention. This condensing member 60 consists of a cylindrical convex lens 
and can convert the cylindrical laser beam 61 into the linear beam 63 by 
passing the laser beam 61 through it. 
In the above embodiment, the condensing lens 45 is arranged between the 
laser generator 41 and the condensing member 39. But the method of this 
invention is not limited to that embodiment. It is naturally true that the 
condensing lens 45 may be disposed between the condensing member 60 and 
the core section 31. 
And also in the above embodiment, the axis 65 of the linear beam 63 is set 
in the direction perpendicular to the moving direction of the welding head 
47. But the method of this invention is not limited to that embodiment. It 
is naturally true that the axis 65 of the linear beam 63 is tilted toward 
the moving direction of the welding head 47. 
Further in the above each embodiment, a method for welding a metal 
honeycomb carrier where the flat plate and the corrugated plate are 
rolled. This method can be also applied to welding of a metal honeycomb 
carrier which is of a type forming the core section by laminating the flat 
plate and the corrugated plate. 
The present invention is not limited to the specific embodiments excepting 
for these restriction in the attached claims because much broader 
embodiments can be configured without departing from the spirit and scope 
of this invention.