TECHNICAL FIELD
[0001] The present invention relates to a heat exchanger with a radiator and an oil cooler
integrated that is produced by using aluminum alloy brazing sheets.
BACKGROUND ART
[0002] A heat exchanger having a radiator and an oil cooler in combination is manufactured
by assembling a radiator core part (10) and an oil cooler part (11) (oil passages
(7) formed by joining brazing sheets (8) are illustrated in a simplified manner in
the drawings) and then mechanically associating them with tanks (6), for example,
as shown perspectively in Fig. 4.
[0003] Herein, as is apparent from Fig.5 showing a perspective view, the radiator is made
up of the radiator core part (10), comprising flat tubes (3), thin fins (1), side
supports (12), and headers (4), and the tanks (6). Each of the corrugated thin fins
(1) is formed between the flat tubes (3), with the corrugated thin fin integrated
with the flat tubes, and the ends of the flat tubes (3) are open to space (2) formed
by the headers (4) and the tanks (6), so that a high-temperature refrigerant is passed
from the space in one tank through the flat tubes (3) to another space (2) of the
other tank (6), to recirculate the refrigerant, whose temperature has been lowered
due to the heat exchange at the tubes (3) and the fins (1).
[0004] The radiator part is assembled as follows: as the tube material and the header material,
brazing sheets are used, wherein the core material is, for example, JIS 3003 alloy;
the inner side on the core material, that is, the side to which the refrigerant constantly
contacts is coated with JIS 7072 alloy as a lining material; and the outer side on
the core material is clad with a usual filler material, such as JIS 4045; and the
tubes and the headers are integrated with corrugated fins and other members by brazing.
[0005] In the oil cooler part (11), the oil passages (7) formed by joining the brazing sheets
(8) extend through the space in the tank (2), and an oil having a high temperature
passing through the passages (7) is cooled with the refrigerant passing through the
space (2). For forming the oil passages, brazing sheets are used, wherein, as the
core material, for example, JIS 3003 alloy is used; the outer side on the core material,
that is, the side to which the refrigerant constantly contacts is clad, for example,
with JIS 7072 alloy, and the inner side on the core material is clad, usually, with
a filler material, such as JIS 4045. Generally the brazing sheets are brazed by heating
them to a temperature of about 600 °C.
[0006] Thus, the radiator part and the oil cooler part are assembled by brazing at a temperature
of about 600 °C. The brazing is carried out, for example, by the flux brazing method
or the non-corrosive flux brazing method, wherein a non-corrosive flux is used.
[0007] However, conventionally the tank (6) is generally made of a resin material, and the
tank (6) has to be attached in a step separated from the step of assembling the radiator
part and the oil cooler part by brazing, so that there is a difficulty that additional
step is required. Further, in such a heat exchanger, the part between the resin tank
(6) and the header (4) that is fastened, is required to be caulked through a resin
packing (5) or the like, which leads to a defect that crevice corrosion is apt to
take place at the boundary between the resin packing (5) and the header (4).
[0008] Further, in recent years, recycling of material has attracted attention in view of
effective use of resources on the earth. Heat exchangers, for automobiles are removed
when the automobiles are disassembled, and they are melted as aluminum alloys for
recycling. However, as shown in Fig. 4, when the heat exchanger has, as the tank (6),
a tank made of resin, the resin tank has to be removed purposely when the automobile
is disassembled, and that becomes a bottleneck in the recycling process.
[0009] Therefore, it is desirable that the tank also be made of an aluminum alloy and be
assembled simultaneously by the brazing technique. However, after that brazing, the
oil cooler part is brazed with it covered with the tank. Therefore, if the brazing
of the oil cooler is incomplete, it cannot be repaired anymore. Thus, it is required
that the brazing be effected completely, but it is conventionally difficult due to
the following reason. Since the oil cooler part is covered with the tank, the temperature
of the brazing is not elevated satisfactorily; and defective brazing is apt to occur.
Further, if the heating is carried out to elevate the temperature satisfactorily so
as not to cause defective brazing, the brazing temperature is elevated excessively
for the radiator part, and thus inconveniently the filler material diffuses into the
radiator tubes and the fins. Further, in the oil cooler, since the brazed part is
in contact with a refrigerant, local corrosion is apt to occur due to the potential
difference between the brazed part and the core material part. This problem cannot
be solved by brazing by the conventional brazing technique.
[0010] Therefore, an object of the present invention is to provide a heat exchanger that
is made of an aluminum alloy by using an aluminum material instead of a resin tank,
can be easily recycled, is excellent in corrosion resistance, and can be produced
without requiring a step of caulking a tank.
[0011] Other advantages of the invention will appear more fully from the following description,
taken in connection with the accompanying drawings.
State of Art:
[0012] EP 637 481 A1 discloses an aluminum alloy brazing material for heat exchanges. This
document is the basis for the preamble of claim 1.
DISCLOSURE OF INVENTION
[0013] The above object has been attained by providing a heat exchanger made of an aluminum
alloy having the following constitution.
[0014] According to the present invention there is provided:
a heat exchanger made of an aluminum alloy having a radiator part and an oil cooler
part in combination and assembled integrally by a brazing method, and a refrigerant
tank for covering and sealing said oil cooler part, comprising the features of claim
1.
BRIEF DESCRIPTION OF DRAWINGS
[0015]
Fig. 1 is a perspective view, partly in cross section, of an embodiment of the heat
exchanger of the present invention with a radiator and an oil cooler integrated.
Fig. 2 is an illustrative view of an oil cooler part of another embodiment of the
heat exchanger of the present invention made of an aluminum alloy.
Fig. 3 is an illustrative view of an oil cooler part of still another embodiment of
the heat exchanger of the present invention made of an aluminum alloy.
Fig. 4 is a perspective view of a conventional heat exchanger having a radiator and
an oil cooler in combination.
Fig. 5 is a perspective view of the conventional radiator.
BEST MODE FOR CARRYING OUT THE INVENTION
[0016] Now, the present invention is described in detail referring to the drawing.
[0017] Fig. 1 is an embodiment of a heat exchanger of the present invention made of an aluminum
alloy with a radiator and an oil cooler integrated by brazing (a double pipe-type,
brazing-type heat exchanger), wherein instead of a resin tank (6) shown in Fig. 4,
a tank (13) in which brazing sheets of an aluminum alloy are used is employed, and
a header (4) of a radiator core part and the tank (13) are assembled by one step by
brazing-heating. Accordingly a packing (5) as used in the prior art is not required.
In the present invention, since the tank is made of an aluminum alloy and its joining
is made by the brazing method, crevice corrosion between the tank and the header does
not occur, and when the exchanger is recovered as waste refuse, the tank can also
be recycled as an aluminum material without dismounting it. Further, since the header
and the tank are integrated by one step of brazing, a step of caulking the tank is
not required. In passing, in Fig. 1, the same reference numerals are used to indicate
the corresponding parts of Fig. 4.
[0018] The present invention is directed to the thus integral heat exchanger and as the
brazing alloy of the brazing sheets (e.g., the above brazing sheets (8) in Fig. 1)
used for the oil cooler, an aluminum alloy containing Si in an amount from more than
7.0 wt% to 12.0 wt%, Fe in an amount from more than 0.05 wt% to 0.5 wt%, Cu in an
amount from more than 0.4 wt% to 8.0 wt%, Zn in an amount from more than 0.5 wt% to
10.0 wt%, and the balance of aluminum and inevitable impurities, is used. This aluminum
alloy is an alloy suggested as a low-temperature brazing alloy, for example, in JP-A
("JP-A" means unexamined published Japanese patent application) No. 90442/1995. The
reason why brazing sheets clad with the brazing alloy having the above specified composition
are used in the present production method is described below.
[0019] In the above brazing alloy, Si lowers the melting point of the alloy. If its amount
is 7.0 wt% or less, the melting point is not lowered satisfactorily whereas if its
amount is over 12.0 wt%, the melting point is elevated contrarily and therefore the
brazing properties are deteriorated. In particular, taking the brazing flow property
into account, the amount of Si to be added is desirably 8.0 to 11.0 wt%.
[0020] Fe functions to make the crystals fine to make high the strength of the fillet of
the brazed joint when the brazing alloy is melted and is then allowed to solidify
and if its amount is 0.05 wt% or less, the effect is not satisfactorily exhibited.
When the brazing alloy is solidified, Fe forms intermetallic compounds, which act
as starting points of corrosion. Accordingly, in view of the balance between the effect
of making the crystals fine and the corrosiveness, the upper limit of the amount of
Fe is 0.5 wt% and the amount of Fe is preferably 0.2 wt% or less in view of the corrosiveness.
[0021] Cu lowers the melting point of the alloy to improve the brazing alloy flow property.
Further Cu serves to increase the outer corrosion resistance of the filler material.
Since the brazed parts of the oil cooler come in direct contact with a refrigerant,
the outer corrosion resistance is required. Here, in view of the corrosion resistance,
if the amount of Cu is 0.4 wt% or less, its effect is not satisfactory. To secure
stable brazing properties, the amount of Cu to be added is over 1.0 wt%. If the amount
of Cu is over 8.0 wt%, since the electric potential of the brazing alloy becomes noble
to make members constituting refrigerant passages preferentially corroded, that is,
to make the corrosion resistance lowered and the workability in rolling of the alloy
is lowered, the brazing alloy will not be suitable as a filler material used for brazing
sheets for the heat exchanger. Therefore, when the amount of Cu is over 1.0 wt% but
8.0 wt%, preferably 4.0 wt% or less to take the workability in rolling into account,
and particularly from 1.0 to 3.5 wt%, stable properties are exhibited.
[0022] The addition of Zn lowers the melting point of the alloy to stabilize the brazing
properties. Further, a conventional brazing alloy wherein Cu is added as in the present
invention had the problem that the electric potential of the brazing alloy becomes
nobler than that of the core and the outer corrosion occurs in a pitted pattern and
at a high speed. The addition of Zn in this invention lowers the electric potential
of the brazing alloy to bring the electric potential of the brazing alloy near to
the electric potential of the core alloy to improve the corrosion resistance. However,
if its amount is 0.5 wt% or less, its effect is not satisfactory whereas if its amount
is over 10.0 wt%, since the corrosion resistance of the brazing alloy itself is lowered
and the workability in rolling of the alloy is lowered, the brazing alloy is not suitable
as a filler material to be used for brazing sheets for the heat exchanger. Although
the above range is within the present invention, taking the brazing alloy flow properties
into account, in the present alloy, the amount of Zn to be added is desirably over
2.0 wt%, and taking the workability in rolling into account, the amount of Zn to be
added is desirably 6.0 wt% or less, preferably 5.0 wt% or less.
[0023] As inevitable impurities, other elements may be contained if the amounts are 0.30
wt% or less respectively, and the amounts are desirably 0.05 wt% or less respectively.
Herein typical inevitable impurities include Ni, Cr, Zr, Ti, Mg, etc. which are often
added into brazing sheets.
[0024] Herein, the brazing conditions employed in the present invention may be usual conditions
under which the radiator can be brazed without any problems. That is, there is no
particular restriction and, for example, the flux brazing method and the non-corrosive
flux brazing wherein a non-corrosive flux is used can be used. For example, assembling,
cleaning, and, if required, applying a flux before the brazing may be carried out
in a usual manner.
[0025] In the present invention, so long as the radiator and the oil cooler are integrated,
there is no particular restriction on the type of the heat exchanger made of an aluminum
alloy and various types can be formed. Examples of the heat exchanger are illustrated
in Figs. 2 and 3. The oil cooler part shown in Fig. 2 is of a double pipe type having
an inner pipe and an outer pipe. In Fig. 2, the radiator core part is omitted since
it may be basically the same as that in Fig. 1. In Fig. 2, (14) indicates a tubular
oil cooler, which comprises an inner pipe (15) and an outer pipe (16). (19) indicates
an aluminum alloy tank. The same reference numerals as those in Fig. 1 are used to
indicate the corresponding same parts. (17) indicates a pipe and (18) indicates a
connector. As shown in Fig. 2, the aluminum alloy tank (19) is made of brazing sheets
and is brazed integrally to a header plate (4). Herein, the inside of the outer pipe
(16) is made of the filler material having the specified composition according to
the present invention. Fig. 3 shows another embodiment of the oil cooler part that
is of a multi-plate type. In Fig. 3, (20) indicates an oil cooler, (21) indicates
inner fins, (22) indicates a tube plate, and (23) indicates an aluminum alloy tank
made of brazing sheets, the same reference numerals as those in Fig. 2 being used
to indicate the corresponding same parts. In Fig. 3, the inside of the tube plate
(22) is made of a brazing sheet clad with the specified filler material according
to the present invention. In Fig. 3, the tank (23) is brazed integrally to the header
plate (4).
EXAMPLE
[0026] The present invention is specifically described with reference to the following examples,
but the present invention is not restricted to the following examples.
Example 1
[0027] First, the following shows an example for the first and second filler material.
[0028] A heat exchanger wherein a radiator and an oil cooler were integrally formed as shown
in Fig. 1 and the tank material was aluminum alloy brazing sheets was produced under
heating conditions of 600 °C x 5 min. Any packings were not used. The materials of
the radiator are shown in Table 1. The tubes of the radiator were tubes electroseamed
by using the tube material shown in Table 1. As the material for the oil cooler, brazing
sheets having the following constitution were used. In their constitution, the brazing
sheets were made by press molding O-material plates having a thickness of 0.6 mm,
wherein the core material was an Al-0.5wt%Si-0.3wt%Fe-0.5wt%Cu-1.1wt%Mn alloy, the
sacrificial material outside the core material of an Al-2wt%Zn alloy was clad thereon,
and the brazing alloy inside the core material shown in Table 2, was clad thereon
in amounts of 10% for the total thickness respectively.
[0029] The oil cooler part was cut from the obtained heat exchanger and the leakage test
and the corrosion test were performed.
Table 2
|
No. |
Si |
Fe |
Cu |
Zn |
In |
Sn |
Al |
Example of the present invention |
A1 |
10.2 |
0.08 |
2.5 |
3.9 |
- |
- |
balance |
B1 |
9.2 |
0.12 |
0.7 |
1.1 |
- |
- |
balance |
C1 |
9.9 |
0.09 |
1.6 |
2.2 |
- |
- |
balance |
D1 |
10.1 |
0.10 |
3.8 |
4.3 |
- |
- |
balance |
E1 |
8.5 |
0.09 |
2.6 |
2.5 |
0.02 |
- |
balance |
F1 |
10.5 |
0.28 |
2.4 |
4.6 |
- |
0.02 |
balance |
Comparative Example |
G1 |
10.0 |
0.07 |
- |
3.0 |
- |
- |
balance |
H1 |
5.6 |
0.15 |
1.5 |
3.4 |
- |
- |
balance |
I1 |
9.9 |
0.08 |
2.6 |
0.2 |
- |
- |
balance |
Conventional Example |
J1 |
8.5 |
0.41 |
- |
- |
- |
- |
balance |
K1 |
10.1 |
0.42 |
- |
- |
- |
- |
balance |
(wt%) |
[0030] The corrosion test was performed in such a way that from the oil cooler a part that
had no leakage defect was cut out, the end of the part was masked, the part was immersed
for 5 months in a tap water to which Cu
2+ ions had been added to give a concentration 10 ppm, and cycles of 80 °C x 8 hours
and room temperature x 16 hours were repeated. The state of formation of corrosion
around the brazed section was examined in cross section.
[0031] The results are shown in Table 3.
[0032] Since the oil cooler part was covered with the heater tank in Examples A1 to F1,
the temperature reached at brazing was lower than 600 °C, that was 570 to 585 °C,
the brazing of the oil cooler was good and no leakage defect occurred because of the
use of the filler material for low-temperature at this part. Further, the potential
difference between the brazing alloy and the core material alloy in any of these Examples
was within 100 mV. As a result, through-hole corrosion did not occur in the corrosion
test.
[0033] In contrast, in Comparative Example H1, wherein the amount of Si was smaller than
that of the present invention, and in the prior art Examples J1 and K1, wherein Cu
and Zn were not contained, the oil coolers were brazed incompletely, and leakaging
parts were recognized in the leakage test.
[0034] Further, in Comparative Examples G1 and I1 and the prior art Examples J1 and K1,
wherein Cu and Zn were outside the present invention, the potential difference between
the brazing alloy and the core material was over 100 mV. As a result, through-hole
corrosions occurred in the corrosion test.
INDUSTRIAL APPLICABILITY
[0035] Since the heat exchanger produced in accordance with the present invention does not
use a resin tank, the heat exchanger is characterized in that it is readily recycled,
the corrosion resistance is excellent, and a step of caulking the tank is not required
to produce the heat exchanger.
1. Wärmetauscher, der aus einer Aluminiumlegierung hergestellt wird, mit einem Radiatorteil
und einem Ölkühlerteil in Kombination, die integral durch ein Hartlötverfahren hergestellt
werden, und einem Kühlmitteltank zur Umhüllung und Abdichtung des Ölkühlerteils, dadurch gekennzeichnet, daß der Kühlmitteltank zur Umhüllung und Abdichtung des Ölkühlerteils aus einer Aluminiumlegierung
hergestellt wird, und daß eine Aluminium-Hartlotlegierung, die Si in einer Menge von
mehr als 7,0 Gew.% bis 12,0 Gew.%, Fe in einer Menge von mehr als 0,05 Gew.% bis 0,5
Gew.%, Cu in einer Menge von mehr als 0,4 Gew.% bis 8,0 Gew.%, Zn in einer Menge von
mehr als 0,5 Gew.% bis 10,0 Gew.% enthält, wobei der Rest aus Aluminium und unvermeidliche
Verunreinigungen besteht, als ein Füllmaterial für die Hartlotbleche verwendet wird,
die für das Ölkühlerteil verwendet werden und in dem Tank hartgelötet werden, und
daß der Kühlmitteltank integral mit der Kopfplatte des Radiatorteils und dem Ölkühlerteil
durch Hartlöten mit dem Hartlotmaterial in einem Schritt hartgelötet und zusammengebaut
wird und daß der Kühlmitteltank mit der Kopfplatte hartgelötet und zusammengebaut
wird, ohne eine Dichtung zu verwenden.
2. Wärmetauscher, der aus einer Aluminiumlegierung hergestellt wird, nach Anspruch 1,
dadurch gekennzeichnet, daß die Aluminiumlegierung, die als die Hartlotlegierung der Hartlotbleche verwendet
wird, zusätzlich In in einer Menge von mehr als 0,002 Gew.% bis 0,3 Gew.% und/oder
Sn in einer Menge von mehr als 0,002 Gew.% bis 0,3 Gew.% enthält.
3. Wärmetauscher, der aus einer Aluminiumlegierung hergestellt wird, nach Anspruch 1
oder 2, wobei der Wärmetauscher ein Doppelrohr-Hartlot-Wärmetauscher, ein Innen-/Außen-Doppelrohrwärmetauscher
oder ein Mehrplatten-Wärmetauscher ist.
1. Un échangeur thermique réalisé en alliage d'aluminium, ayant une partie radiateur
et une partie refroidisseur d'huile en combinaison et réalisées en une seule pièce
par une méthode de brasage et un réservoir de réfrigérant pour couvrir et étanchéifier
ladite partie refroidisseur d'huile, caractérisé en ce que ledit réservoir de réfrigérant pour couvrir et étanchéifier ladite partie refroidisseur
d'huile est réalisé en alliage d'aluminium, et qu'un alliage de brasage de l'aluminium
contenant du Si à une teneur allant de plus de 7,0 % en poids à 12,0 % en poids, du
Fe à une teneur allant de plus de 0,05 % en poids à 0,5 % en poids, du Cu à une teneur
allant de plus de 0,4 % en poids à 8,0 % en poids, du Zn à une teneur allant de plus
de 0,5 % en poids à 10,0 % en poids, le solde étant constitué d'aluminium et des inévitables
impuretés, est utilisé comme matériau de remplissage pour les tôles de brasage utilisées
pour ladite partie refroidisseur d'huile et sont brasées dans ledit réservoir, et
en ce que ledit réservoir de réfrigérant est brasé et assemblé de façon intégrale avec la plaque
collectrice de la partie radiateur et ladite partie refroidisseur d'huile par brasure
avec ledit matériau de brasage en une étape et en ce que le réservoir de réfrigérant est brasé et assemblé avec la plaque collectrice sans
utiliser de garniture.
2. L'échangeur thermique réalisé en alliage d'aluminium selon la revendication 1, caractérisé en ce que ledit alliage d'aluminium utilisé comme ledit alliage de brasage desdites tôles de
brasage contient en sus l'un ou chacun des deux éléments que sont l'In à une teneur
allant de plus de 0,002 % en poids à 0,3% en poids et le Sn à une teneur allant de
plus de 0,002 % en poids à 0,3 % en poids.
3. L'échangeur thermique réalisé en alliage d'aluminium selon la revendication 1 ou 2,
dans lequel l'échangeur thermique est un échangeur thermique du type à double tube
et à brasure, un échangeur thermique du type à double tube intérieur-extérieur, ou
un échangeur thermique du type multi-plaque.