Header tank structure for heat exchanger

The invention relates to a header tank structure for a heat exchanger formed by rounding a clad material (a header tank material) into a circular tube form, and the header tank structure eliminates occurrence of swollen portions around the connecting portion of the ends of the header tank, and displacement of the connecting surfaces from each other is reduced, thereby to provide the header tank structure having an improved quality of brazing the connecting surfaces of the ends. The invention is, in a header tank structure for a heat exchanger formed by rounding a header tank material to bring the ends thereof into butting with each other and connecting them together by brazing, the header tank material having either one of the surfaces which becomes the outer surface of the header tank or both surfaces which become outer and inner surfaces of the header tank are being coated with a brazing material, and the ends of the header tank material are formed with inclined surfaces which are respectively inclined with respect to a direction of wall thickness, each with a portion of end edge surface being left there.

PRIOR ART 
Conventional heat exchanger, for example, a parallel flow type heat 
exchanger, comprises a plurality of tubes and fins which are alternately 
stacked one upon another, and the ends of each of the stacked tubes are 
inserted into insertion holes provided in the header tank and connected 
therewith. 
Conventionally, the header tank of circular tube formed by rounding a clad 
material by roll forming and connect the ends thereof is known (for 
example, as disclosed in Japanese Utility Model Laid-Open Publication No. 
2(1990)-48268 and Japanese Patent Laid-Open Publication No. 
4(1992)-220129). 
As shown in FIGS. 10 and 11, this type of header tank 21 uses, as a header 
tank material, a double-faced clad material 23 having both surfaces coated 
with a brazing material 22, and is formed by rounding the double-faced 
clad material 23 into a circular form by roll forming, and butting 
surfaces 24, 24 of the ends are connected together by brazing. 
Further, the butting surfaces 24, 24 of the double-faced clad material 23 
for forming the header tank 21 are inclined with respect to the direction 
of wall thickness. In other words, the butting surfaces 24, 24 of the ends 
of the double-faced clad material are so formed that the surface of one 
end is gradually thinned from the outer surface towards the inner surface 
with respect to the direction of wall thickness and the surface of other 
end is gradually thinned from the inner surface towards the outer surface. 
Then, such inclined butting surfaces 24, 24 are formed to have the brazing 
material 22 remained thereon. Thereafter, the double-faced clad material 
23 is rounded into the circular tube by roll forming, and the inclined 
butting surfaces 24, 24 of the ends are connected by brazing to form the 
header tank 21. In these FIGURES, numeral 26 designates a flat tube, and 
27 designates a tube insertion hole. 
However, the above-described conventional header tank of heat exchanger has 
such disadvantages that when forming the inclined butting surfaces by 
press forming, the material of the wall at the end portion, which was 
crushed during pressing, tends to escape into other portions, and It 
causes swollen portions 28 around the wall of the inclined butting 
surfaces, as shown in FIG. 12, or waves are formed in the inclined butting 
surfaces. Further, during assembly of the header tank, the butting 
surfaces are displaced from each other even when the inclined butting 
surfaces are held down in a radial direction of the header tank to have 
them butting properly. 
When the wall around the butting surfaces is swollen or the butting 
surfaces are displaced from each other, it is inconvenient to attach an 
additional member, for example, a bracket, to the header tank, because it 
needs to chop off such swollen portions or protruding portions caused by 
displacement. Thus, it requires such an additional and separate processing 
step of chopping off, which causes an increase of manufacturing cost. 
A further problem is that when the inclined butting surfaces are waving, 
there will be gaps between connecting surfaces which results in lowering 
the quality of brazing the connecting surfaces. 
The present invention provides an improved header tank structure for heat 
exchanger which does not cause swollen portions around the butting 
surfaces and minimizes occurrence of displacement of the butting surfaces 
from each other during assembly, and consequently, the quality of brazing 
the connecting surfaces is improved. 
DISCLOSURE OF THE INVENTION 
In order to achieve the above-described objects, a first aspect of this 
invention is that in a header tank structure for heat exchanger formed by 
rounding a header tank material to bring the ends thereof into butting 
with each other and connecting them together by brazing, the header tank 
material having one of surfaces to become the outer surface of the header 
tank being coated with a brazing material, the surface of each of the ends 
of the header tank material is inclined with respect to a direction of 
wall thickness, with a portion of end edge surface being left there. 
With the above-described header tank structure for heat exchanger according 
to the first aspect of the invention, a first preferred embodiment is that 
the inclined surfaces of the ends are so formed that the surface of one 
end is gradually thinned from the outer surface towards the inner surface 
with respect to the wall thickness with the portion of end edge surface 
being left there, and the surface of the other end is gradually thinned 
from the inner surface towards the outer surface with respect to the 
direction of wall thickness with the portion of end edge surface being 
left there. When the two inclined surfaces are brought into pressure 
contact with each other, a recess is formed respectively in both outer 
surface and inner surface of the header tank by the portion of the end 
edge surface being left there and the inclined surface. 
A second preferred embodiment of the header tank structure for heat 
exchanger of the first aspect of the invention is that the inclined 
surfaces formed at the ends of the header tank material are both gradually 
thinned from the outer surface towards the inner surface with respect to 
the wall thickness, each surface with the portion of end edge surface 
being left there. When the portions of the end edge surface left are 
brought into pressure contact with each other, a recess is formed in the 
outer surface of the header tank by the two inclined surfaces. 
A second aspect of the invention is that in a header tank structure for 
heat exchanger formed by rounding a header tank material to bring the ends 
thereof into butting with each other and connecting them together by 
brazing, the header tank material having both surfaces which become the 
outer surface and the inner surface of the header tank being coated with a 
brazing material, and each end has an inclined surface with respect to the 
direction of wall thickness with a portion of the end edge surface being 
left there. 
A first preferred embodiment of the header tank structure for heat 
exchanger according to the second aspect of the invention is that the 
inclined surfaces at the ends of the header tank material are so formed 
that the surface of one end is gradually thinned from the outer surface 
towards the inner surface with respect to the direction of wall thickness 
and the surface of the other end is thinned from the outer surface towards 
the inner surface with respect to the direction of wall thickness, each 
with a portion of end edge surface being left there. When the inclined 
surfaces are brought into pressure contact with each other, a recess is 
formed in both outer surface and inner surface of the header tank by the 
portion of end edge surface being left there and the inclined surface. 
A second preferred embodiment of the header tank structure for heat 
exchanger of the second aspect of the invention is that the inclined 
surfaces at the ends of the header tank material are so formed that the 
surface of one end is gradually thinned from the outer surface towards the 
inner surface with respect to the direction of wall thickness with the 
center portion of end edge surface being left, and the surface of the 
other end is thinned in a reverse direction with the center portion of end 
edge surface being left, so that the center portions of the end edge 
surfaces being left interpose between the two surfaces. When the center 
portions of the end edge surfaces of both ends are brought into pressure 
contact with each other, a recess is formed in the outer surface and the 
inner surface of the header tank by the inclined surfaces. 
According to the header tank structure of the present invention, the clad 
material, that is, the header tank material, is rounded by roll forming or 
press forming, and the ends of header tank material are butted to each 
other and connected together by brazing. 
With the header tank structure of the present invention, each end of the 
header tank material is formed with an inclined surface with respect to 
the direction of wall thickness with a portion of end edge surface being 
left there. Thus, only a portion of the end, not the entire end, is 
subjected to press forming. This minimizes the portion of material tending 
to escape to other portions as a result of being crushed during press 
forming, thereby a possible deformation of the ends caused by press 
forming is kept to as little as possible. In this respect, in the prior 
art header tank, the entire portions of the ends are pressed during press 
forming, and the surfaces of the ends are thinned either from the outer 
surface towards the inner surface with respect to the direction of wall 
thickness or from the inner surface towards the outer surface with respect 
to the direction of wall thickness. In other words, with the prior art 
header tank, the inclined surface is formed uniformly over the entire 
surface of each end of the header tank material. Consequently, during the 
oblique pressing process, the ends of the material are always displaced 
laterally, and, as a result, dimensions of the portions to be in pressure 
contact cannot be uniform. The present invention is improved in this 
respect. 
With the present invention as described above and where the inclined 
surfaces serve as the connecting surfaces, swollen portions are not formed 
on the inclined surfaces, and a V-shaped recess is formed at the 
connecting portion when the two connecting surfaces are butted with each 
other, thereby the brazing material is pulled into the V-shaped recess 
during brazing process. This assures the quality of brazing the connecting 
surfaces and provides a good brazing effect. 
Further, with the present invention which forms the surfaces of the ends of 
the header tank material being inclined with respect to the direction of 
wall thickness, each with a portion of end edge surface being left there, 
the portions of end edge surfaces left are brought into pressure contact 
with each other, since the end edge surfaces are transversely to the 
direction of wall thickness, thereby to assure the pressure contact of the 
end edge surfaces. In this case, too, the V-shaped recess is formed, so 
that the brazing material is pulled into the V-shaped recess during the 
brazing process as same as the above-described aspect of the invention, 
thereby to assure the quality of brazing the connecting surfaces and to 
provide a good brazing effect.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Now a first embodiment of the present invention will be described by 
referring to the accompanying drawings. With this embodiment, the heat 
exchanger incorporating the header tank of this invention is a parallel 
flow type heat exchanger. 
Referring to FIG. 1, a heat exchanger 1 of this embodiment comprises a 
plurality of flat tubes 2 and corrugated fins 3 which are alternately 
stacked one upon another, and the ends of the stacked flat tubes 2, 2 are 
respectively inserted into insertion holes 5, 5 of a header tank 4 to be 
connected therewith. 
Numeral 6 designates a side plate having a U-shaped cross-section and 
arranged at the upper end and the lower end of the stacked flat tube 2, 
and numeral 7 designates a blank cap provided at the upper opening and the 
lower opening of the header tank 4. 
A partition plate 8 is arranged at the required place in each header tank 
4, and a heat exchanger medium flows in a zigzag form by making a 
plurality of turns between an inlet joint 9 and an outlet Joint 10 of the 
header tank 4. 
As shown in FIG. 2, the header tank 4 is formed by rounding a sheet of 
header tank material and connecting the ends thereof to make It in a 
circular tube form. 
With this embodiment, the material of the header tank 4 is a clad material 
11 having one of the surfaces coated with a brazing material 14, as shown 
in FIG. 3. Numeral 11a designates the surface of end edge of the clad 
material 11. 
The ends of the clad material 11 are, before the material is being rounded, 
formed with inclined surfaces 12, 12 each with a portion of end edge 
surface 13 being left there as shown in FIG. 4. The inclined surface 12 of 
one end is gradually thinned from the outer surface towards the inner 
surface with respect to the direction of wall thickness (this inclined 
surface 12 is being coated with the brazing material 14), and the inclined 
surface 12 of the other end is gradually thinned from the inner surface 
towards the outer surface with respect to the direction of wall thickness 
(this inclined surface 12 is not coated with the brazing material 14). 
The inclined surface 12 is formed by press forming and the like, and the 
portion of end edge surface 13 is left there as described above. In the 
prior art where the inclined surface is formed without having the portion 
of end edge surface 13 being left, the portion of the material which has 
been crushed during pressing process tends to escape into other portions 
of the material so that the swollen portions 28 as shown in FIG. 12 are 
formed, or the inclined butting surfaces have a phenomenon of waves 
appeared thereon. However, with the portion of end edge surface 13 being 
left there, the material which has been crushed during press forming and 
tending to escape into other portions is reduced, thereby, deformation of 
the ends which might be caused during press forming is reduced to as 
little as possible. Needless to say, with this embodiment, if such 
deformation is caused during press forming, the deformation appears at the 
end edge surface 13, and if the deformation is great, the deformed portion 
can be simply chopped off. On the other hand, with the prior art 
invention, chopping of the swollen portions is not so simple as expected 
and it involves troublesome work. 
A preferred dimension of the portion of the end edge surface 13 to be left 
is within 1/2 of wall thickness of the clad material 11 from the 
standpoint of positioning the two inclined surfaces 12, 12 for butting 
with each other. 
The inclined surfaces 12, 12 are brought into pressure contact with each 
other as shown in FIG. 5 when the clad material 11 of FIG. 4 is rounded 
and the ends thereof are connected together. Since the portion of end edge 
surface 13 is being left at each end as described above, a V-shaped recess 
15 is formed respectively at the outer surface and the inner surface of 
the header tank, by the portion of the end edge surface 13 being left at 
the side and the inclined surface 12. With the presence of this V-shaped 
recess 15, the brazing material is pulled into the recess thereby to 
assure the quality of brazing the connecting surfaces of the ends and 
provide a good brazing effect. 
Now another preferred embodiments of the present invention will be 
described below successively. 
Referring to FIG. 6, an embodiment shown uses, for the header tank material 
of the header tank 4, the clad material 11 having both surfaces coated 
with the brazing material 14 for the header tank material of the header 
tank 4. Similar to the above-described embodiment, the inclined surfaces 
12, 12 are formed to be inclined with respect to the direction of wall 
thickness, each with the portion of end edge surface 13 being left there. 
The inclined surfaces 12, 12 are so formed that the inclined surface 12 
coated with the brazing material 14 of one end is gradually thinned from 
the outer surface towards the inner surface with respect to the direction 
of wall thickness with the portion of end edge surface being left, and the 
inclined surface 12 coated with the brazing material 14 of the other end 
is gradually thinned from the inner surface towards the outer surface with 
respect to the direction of wall thickness with the portion of end edge 
surface being left. When the clad material 11 is rounded and the ends are 
butted to each other, the inclined surfaces 12, 12, both of which are 
coated with the brazing material 14, are brought into pressure contact 
with each other. 
Consequently, with the embodiment of FIG. 6, the recess 15 is formed in the 
outer surface and the inner surface of the header tank, respectively, by 
the portion of the side end edge surface 13 left there and the inclined 
surface 12. 
Thus, in this embodiment,too, with the presence of the V-shaped recess 15, 
the brazing material is pulled into the recess during brazing, thereby to 
assure the quality of brazing of both connecting surfaces and provide a 
good brazing effect. 
Referring to FIG. 7, an embodiment shown uses, for the header tank material 
of the header tank 4, the clad material 11 with one of the surfaces being 
coated with the brazing material 14 for the header tank material of the 
header tank 4. Similar to the above-described embodiments, inclined 
surfaces 12, 12 are formed to be inclined with respect to the direction of 
wall thickness with the portion of end edge surface 13 being left there, 
respectively. 
In this embodiment, both inclined surfaces 12, 12 are gradually thinned 
from the outer surface towards the inner surface with respect to the 
direction of wall thickness with the portion of end edge surface being 
left, respectively, thereby to form the inclined surface 12 coated with 
the brazing material 14. When the clad material 11 is rounded and the ends 
are brought into butting with each other, the portions of end edge 
surfaces 13, 13 being left are brought into pressure contact with each 
other, and a recess 15 is formed at the outer surface of the header tank 
by the inclined surfaces 12, 12. 
Since the recess 15 of this embodiment is formed by both inclined surfaces 
12, 12, it has a greater volume than that of formed by one of the inclined 
surfaces 12 (for example, the recess 15 shown in FIGS. 5 and 6), view of 
the fact that the recess having the same or similar volume with that of 
the above-described embodiments can be obtained by forming the inclined 
surfaces 12 in relatively short length, this embodiment is best suited for 
using the header tank material having a thin wall thickness. 
Thus, with the embodiment of FIG. 7, the recess 15 is also formed in the 
outer surface of the header tank by the inclined surfaces 12, 12, and due 
the presence of the V-shaped recess 15, the brazing material is pulled 
into the recess during brazing, thereby to assure the quality of brazing 
of the connecting surfaces and provide a good brazing effect. 
Moreover, with this embodiment, the portions of end edge surfaces 13, are 
brought into pressure contact with each other, namely, the end edge 
surfaces 13, 13 which are formed transversely to the direction of wall 
thickness are brought into pressure contact, thereby to assure the 
pressure contact of the end edge surfaces 13, 
As described earlier, with the prior art shown in FIG. 11 the butting 
surfaces 24, 24 at the ends of the clad material 23 are so formed that the 
surface of one end is gradually thinned from the outer surface towards the 
inner surface with respect to the direction of wall thickness, and the 
surface of the other end is gradually thinned from the inner surface 
towards the outer surface. Since the forward end of each of butting 
surfaces 24, 24 is protruding, the clad material 23 should be rounded with 
the butting surface 24 at the left side in FIG. 11 be at the lower side 
and the butting surface 24 at the right side in FIG. 11 should be at the 
upper side, otherwise the forward ends of both butting surfaces are 
caught. In other words, the left side butting surface 24 should be bent 
first followed by bending the right side butting surface 24, otherwise the 
forward ends of both surfaces are caught. Thus, with the prior art of FIG. 
11, the ends of the clad material cannot be rounded simultaneously in roll 
forming of the clad material, but It requires to have time lag for bending 
the ends. 
However, with this embodiment, bending of the ends can be made 
simultaneously, since the end edge surfaces 13, 13 are formed transversely 
to the direction of wall thickness. The capability of bending the ends of 
clad material simultaneously facilitates rounding of the clad material by 
roll forming. 
Referring to FIG. 8, an embodiment shown uses, for the header tank material 
of the header tank 4, the clad material 11 having both surfaces being 
coated with the brazing material 14. In this embodiment, the inclined 
surfaces 12, 12 are so formed that one of them is gradually thinned from 
the outer surface towards the inner surface with respect to the direction 
of wall thickness with the center portion of end edge surface 16 being 
left, and the other surface is gradually thinned in a reverse direction 
with the center portion of end edge surface 16 being left, so that the 
center portions of edge surfaces left there interpose between the inclined 
surfaces 12, 12. Thus, when the clad material 11 is rounded and the ends 
are butted to each other, the center portions of end edge surfaces 16, 16 
being left are brought into pressure contact with each other, and recesses 
15, 15 are formed in the outer surface and the inner surface of the header 
tank respectively by the inclined surfaces 12, 12. 
Consequently, with the embodiment of FIG. 8, the recess 15 is formed at 
both the outer surface and the inner surface of the header tank by the 
inclined surfaces 12, 12, and due to the presence of the V-shaped recess 
15, the brazing material is pulled into the recess during brazing, thereby 
to assure the quality of brazing of the connecting surfaces and provide a 
good brazing effect. 
Further, with this embodiment, the center portions of end edge surfaces 16, 
16 left are brought into pressure contact, namely, the end edge surfaces 
16, 16 left at the center are formed transversely to the direction of wall 
thickness, thereby their pressure contact with each other is made sure. 
Moreover, the capability of simultaneous bending of the ends facilitates 
rounding of clad material by roll forming. 
Referring to FIG. 9, an embodiment shown uses, for the header tank material 
of the header tank 4, the clad material 11 having one of the surfaces 
being coated with the brazing material 14. In this embodiment, the 
inclined surfaces 12, 12 are so formed that one of them is gradually 
thinned from the outer surface towards the inner surface with respect to 
the direction of wall thickness with the center portion of end edge 
surface 16 being left, and the other surface is gradually thinned in a 
reverse direction with the center portion of end edge surface 16 being 
left, so that the center portions of edge surfaces left there interpose 
between the inclined surfaces 12, 12. Then, when the clad material 11 is 
rounded and the ends are butted to each other, the center portions of end 
edge surfaces 16, 16 being left are brought into pressure contact with 
each other, and recesses 15, 15 are formed in the outer surface and the 
inner surface of the header tank respectively by the inclined surfaces 12, 
12. 
Accordingly, with the embodiment of FIG. 9, the recess 15 is forked by the 
inclined surfaces 12, 12 at least in the outer surface of the header tank, 
so that, like the embodiment of FIG. 7, due to the presence of the 
V-shaped recess 15, the brazing material 14 is pulled into the recess 
during brazing, thereby to assure the quality of brazing of the connecting 
surfaces and provide a good brazing effect. 
Further, like the embodiment of FIG. 8, the center portions of end edge 
surfaces 16, 16 left are brought into pressure contact also in this 
embodiment, thereby the pressure contact of end edge surfaces 16, 16 with 
each other is made sure. 
Moreover, bending of the ends can be made simultaneously, like the 
embodiments of FIGS. 7 and 8, which facilitates rounding of clad material 
by roll forming. 
The above-described preferred embodiments of the present invention have 
been explained as applied for the parallel type heat exchanger as an 
example, but It is readily appreciated that the present invention can be 
also applied for other types of heat exchanger.