U.S. patent application number 10/032351 was filed with the patent office on 2002-06-27 for heat exchanger made of aluminum alloy.
Invention is credited to Hirao, Koji, Makihara, Masamichi, Nagasawa, Toshiya, Torigoe, Eiichi.
Application Number | 20020078566 10/032351 |
Document ID | / |
Family ID | 26479176 |
Filed Date | 2002-06-27 |
United States Patent
Application |
20020078566 |
Kind Code |
A1 |
Torigoe, Eiichi ; et
al. |
June 27, 2002 |
Heat exchanger made of aluminum alloy
Abstract
A manufacturing method for an evaporator made of aluminum alloy.
First, a three-layer aluminum alloy plate having a core made of
Al--Mn alloy, a sacrifice anode layer made of aluminum alloy which
is electro-chemically base with respect to the core and clad on one
side of the core, and a brazing layer made of Al--Si alloy and clad
on the other side of the core is uniformly rolled to be
work-hardened. Next, the thin work-hardened aluminum alloy plate is
bent to form a tube so that the sacrifice anode layer is disposed
outside the tube to face air and the brazing layer is disposed
inside the tube to face refrigerant. Then, plural tubes and outer
fins are alternately laminated and are integrally brazed to tanks
to form the evaporator. As a result, a thickness of the tube is
reduced without deteriorating corrosion resistance of the tube,
thereby decreasing a weight and a size of the evaporator.
Inventors: |
Torigoe, Eiichi; (Anjo-city,
JP) ; Hirao, Koji; (Tokai-city, JP) ;
Makihara, Masamichi; (Gamagori-city, JP) ; Nagasawa,
Toshiya; (Obu-city, JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
26479176 |
Appl. No.: |
10/032351 |
Filed: |
December 21, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10032351 |
Dec 21, 2001 |
|
|
|
09579167 |
May 25, 2000 |
|
|
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Current U.S.
Class: |
29/890.03 |
Current CPC
Class: |
B23K 2101/14 20180801;
F28D 1/0391 20130101; F28F 19/004 20130101; B23K 1/0012 20130101;
F28F 21/084 20130101; F28F 3/025 20130101; Y10T 29/4935 20150115;
F28F 21/089 20130101; F28F 19/06 20130101 |
Class at
Publication: |
29/890.03 |
International
Class: |
B21D 053/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 28, 1999 |
JP |
11-149242 |
Jan 13, 2000 |
JP |
2000-9956 |
Claims
What is claimed is:
1. A method of manufacturing a heat exchanger integrally brazed,
the method comprising steps of: uniformly work-hardening a
plurality of three-layer aluminum alloy plates to form a plurality
of work-hardened plates, each of the three-layer aluminum alloy
plates having a core made of a first aluminum alloy including
manganese, a sacrifice anode layer clad on one side of the core and
made of a second aluminum alloy which is electro-chemically base
with respect to the first aluminum alloy, and a brazing layer clad
on the other side of the core and made of a brazing third aluminum
alloy; forming a fluid passage and a tank portion on each of the
plurality of work-hardened plates by drawing so that the sacrifice
anode layer is disposed to face a corrosive fluid and the brazing
layer is disposed to face a non-corrosive fluid; and laminating the
plurality of work-hardened plates.
2. A method of manufacturing a heat exchanger integrally brazed,
the method comprising steps of: uniformly work-hardening a
three-layer aluminum alloy plate to form a work-hardened plate, the
three-layer aluminum alloy plate having a core made of a first
aluminum alloy including manganese, a sacrifice anode layer clad on
one side of the core and made of a second aluminum alloy which is
electro-chemically base with respect to the first aluminum alloy,
and a brazing layer clad on the other side of the core and made of
a brazing third aluminum alloy; and forming a tube from the
work-hardened plate so that the sacrifice anode layer is disposed
to face a corrosive fluid and the brazing layer is disposed to face
a non-corrosive fluid.
3. The method according to claim 2, wherein the tube is formed by
bending.
4. A heat exchanger comprising: a core having a plurality of tubes
and a plurality of outer fins made of a first aluminum alloy, the
tubes and the outer fins being alternately laminated; and a tank
separately formed from the tubes, the tank into which one end of
each of the tubes is inserted, wherein: each of the tubes is
produced by the following method: uniformly work-hardening a
three-layer aluminum alloy plate to form a work-hardened plate, the
three-layer aluminum alloy plate having a core made of a second
aluminum alloy including manganese, a sacrifice anode layer clad on
one side of the core and made of a third aluminum alloy which is
electro-chemically base with respect to the second aluminum alloy,
and a brazing layer clad on the other side of the core and made of
a brazing fourth aluminum alloy; and forming each of the tubes by
bending the work-hardened plate so that the sacrifice anode layer
is disposed to face a corrosive fluid and the brazing layer is
disposed to face a non-corrosive fluid.
5. The heat exchanger according to claim 4, wherein: each of the
outer fins is corrugated to have a plurality of parallel folds,
each of the folds having a flat top through which each of the outer
fins is joined to the tubes; and a brazing material is applied in a
substantially straight line to a joint surface between the flat top
and the tubes.
6. The heat exchanger according to claim 4, wherein: each of the
outer fins is corrugated to have a plurality of parallel folds,
each of the folds having a flat top through which each of the outer
fins is joined to the tubes; and a brazing material is applied in
stripes to a joint portion between the flat top and each of the
tubes.
7. The heat exchanger according to claim 4, wherein an inner fin is
disposed inside each of the tubes.
8. A method of manufacturing a heat exchanger integrally brazed,
the method comprising steps of: uniformly work-hardening a
plurality of two-layer aluminum alloy plates to form a plurality of
work-hardened plates, each of the two-layer aluminum alloy plates
having a core made of a first aluminum alloy including manganese
and a sacrifice anode layer clad on one side of the core and made
of a second aluminum alloy which is electro-chemically base with
respect to the first aluminum alloy; forming a fluid passage and a
tank portion on each of the plurality of work-hardened plates by
drawing so that the sacrifice anode layer is disposed to face a
corrosive fluid and the core is disposed to face a non-corrosive
fluid; and laminating the plurality of the work-hardened
plates.
9. The method according to claim 8, further comprising a step of:
applying a brazing material to the core of each of the
work-hardened plates.
10. A method of manufacturing a heat exchanger integrally brazed,
the method comprising steps of: uniformly work-hardening a
two-layer aluminum alloy plate to form a work-hardened plate, the
two-layer aluminum alloy plate having a core made of a first
aluminum alloy including manganese and a sacrifice anode layer clad
on one side of the core and made of a second aluminum alloy which
is electro-chemically base with respect to the first aluminum
alloy; and forming a tube by bending the work-hardened plate so
that the sacrifice anode layer is disposed to face a corrosive
fluid and the core is disposed to face a non-corrosive fluid.
11. The method according to claim 10, further comprising a step of:
applying a brazing material to the core of the work-hardened
plate.
12. A heat exchanger comprising: a core having a plurality of tubes
and a plurality of outer fins made of a first aluminum alloy, the
tubes and the outer fins being alternately laminated; and a tank
separately formed from the tubes, the tank into which one end of
each of the tubes is inserted, wherein: each of the tubes is
produced by the following method: uniformly work-hardening a
two-layer aluminum alloy plate to form a work-hardened plate, the
two-layer aluminum alloy plate having a core made of a second
aluminum alloy including manganese and a sacrifice anode layer clad
on one side of the core and made of a third aluminum alloy which is
electro-chemically base with respect to the second aluminum alloy;
and forming a tube by bending the work-hardened plate so that the
sacrifice anode layer is disposed to face a corrosive fluid and the
core is disposed to face a non-corrosive fluid.
13. The heat exchanger according to claim 12, wherein: each of the
outer fins is corrugated to have a plurality of parallel folds,
each of the folds having a flat top through which each of the outer
fins is joined to the tubes; and a brazing material is applied in a
substantially straight line to a joint surface between the flat top
and the tubes.
14. The heat exchanger according to claim 12, wherein: each of the
outer fins is corrugated to have a plurality of parallel folds,
each of the folds having a flat top through which each of the outer
fins is joined to the tubes; and a brazing material is applied in
stripes to a joint portion between the flat top and each of the
tubes.
15. The heat exchanger according to claim 12, wherein an inner fin
is disposed inside each of the tubes.
16. The heat exchanger according to claim 4, wherein: the
non-corrosive fluid is a refrigerant; and the core evaporates the
refrigerant.
17. The heat exchanger according to claim 12, wherein: the
non-corrosive fluid is a refrigerant; and the core evaporates the
refrigerant.
18. The heat exchanger according to claim 16, wherein a thickness
of each of the tubes is set to be in a range of 0.10-0.35 mm.
19. The method according to claim 2, wherein the forming step is
performed while the work-hardened plate has distortion.
20. The method according to claim 2, wherein the forming step is
performed while the work-hardened plate has a distortion rate of
approximately 10-20%.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application relates to and claims priority from
Japanese Patent Application Nos. 11-149242 filed on May 28, 1999
and 2000-9956 filed on Jan. 13, 2000, the contents of which are
hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to heat exchangers,
and particularly to a heat exchanger made of aluminum alloy and
integrally formed by brazing. The present invention is suitably
applied to an evaporator, a condenser and a supercooler for an air
conditioner and an oil cooler for an engine cooler.
[0004] 2. Related Art
[0005] Conventionally, an evaporator for a refrigeration cycle of a
vehicle air conditioner has plural core plates made of aluminum
alloy. Each of the core plates has a fluid passage and a tank
portion and is integrally formed by drawing a three-layer aluminum
alloy plate. As shown in FIG. 15, the three-layer aluminum alloy
plate has a core 101 made of aluminum-manganese (Al--Mn) alloy and
brazing layers 102, 103 made of aluminum-silicon (Al--Si) alloy and
uniformly clad on one side and the other side of the core 101,
respectively. A whole thickness of the three-layer aluminum alloy
plate is 0.6 mm while each thickness of the brazing layers 102, 103
is 90 .mu.m. The plural core plates and plural corrugated outer
fins are alternately laminated and integrally brazed to form the
evaporator.
[0006] Recently, improvement of fuel efficiency of a vehicle is
demanded due to environmental concerns. Fuel efficiency of the
vehicle is improved by reducing a size and a weight of parts of the
vehicle such as the evaporator. The size and the weight of the
evaporator are effectively reduced by decreasing a thickness of
each of the core plates of the evaporator. However, when a
thickness of the core plate is excessively reduced, the core plate
may crack during the drawing process. Therefore, it is difficult to
reduce the size and the weight of the evaporator by reducing a
thickness of the core plate.
[0007] Further, an outer surface of the core plate facing air
passing through the evaporator does not have sufficient pitting
corrosion resistance. Therefore, the outer fins made of aluminum
alloy which is electro-chemically base with respect to the core
plate are disposed on the outer surface of the core plate so that
the outer fins become sacrifice anodes and protect the outer
surface of the core plate from corrosion. However, the outer
surface of the core plate has a relatively low conductivity and
allows condensed water to adhere thereto. Therefore, the outer fins
may protect only a limited area of the core plate around the outer
fins, and a whole area of an outer surface of the evaporator may
not be sufficiently protected from corrosion.
[0008] Further, after the evaporator is integrally brazed, residual
brazing material remains on the outer surface of the evaporator.
Since the residual brazing material has a relatively non-uniform
composition of Si and Al, a relatively large potential difference
is produced between Si and Al. As a result, only an Al portion of
the core plate may corrode in an early stage so that corrosion of
the core plate proceeds from the corroding Al portion in a
direction of a thickness of the core plate. Therefore, the
thickness of the core plate can not be sufficiently reduced.
[0009] Moreover, when the core plate, which is an Al--Mn alloy
plate, is drawn, the brazing layers 102, 103 erode significantly at
a low-distortion portion of the core plate which has a low
distortion rate such as 10% or less. As a result, the core 101 is
eroded and a thickness of the core 101 is reduced at the
low-distortion portion, thereby decreasing a life of corrosion
resistance of the core plate. When the core plate is work-hardened,
erosion of the core 101 is effectively restricted. However, when
the core plate is work-hardened, the core plate may not have a
sufficient ductility for the drawing process in which the fluid
passage and the tank portion are formed.
[0010] The core plate may have a sufficient corrosion resistance by
an appropriate surface treatment. However, in this case,
manufacturing cost of the evaporator may be increased.
SUMMARY OF THE INVENTION
[0011] In view of the foregoing problems, it is an object of the
present invention to provide a heat exchanger made of aluminum
alloy and reduced in weight while having an excellent corrosion
resistance and a low manufacturing cost.
[0012] According to the present invention, a heat exchanger
integrally brazed is manufactured as follows. First, a plurality of
three-layer aluminum alloy plates are uniformly work-hardened to
form a plurality of work-hardened plates. Each of the three-layer
aluminum alloy plates has a core made of a first aluminum alloy
including manganese, a sacrifice anode layer clad on one side of
the core and made of a second aluminum alloy which is
electro-chemically base with respect to the first aluminum alloy,
and a brazing layer clad on the other side of the core and made of
a brazing third aluminum alloy. Next, a fluid passage and a tank
portion are formed on each of the plurality of work-hardened plates
by drawing so that the sacrifice anode layer is disposed to face a
corrosive fluid and the brazing layer is disposed to face a
non-corrosive fluid. Then, the plurality of work-hardened plates
are laminated to form the heat exchanger.
[0013] Since the three-layer aluminum alloy plate is uniformly
work-hardened, the brazing layer is restricted from eroding,
thereby restricting the core from eroding. Further, a surface of
the work-hardened plate facing the corrosive fluid is protected
from corrosion by the sacrifice anode layer. Also, since the
brazing layer is disposed to face the non-corrosive fluid,
corrosion resistance of an outer surface of the heat exchanger is
improved. As a result, each of the plates forming the heat
exchanger can be reduced in thickness while having a sufficient
corrosion resistance, thereby reducing a weight and a size of the
heat exchanger without increasing a manufacturing cost.
Furthermore, since the heat exchanger is formed by laminating only
the work-hardened plates without any outer fins, the fluid passage
and the tank portion can be formed by shallow-drawing on each of
the work-hardened plates. Therefore, each of the work-hardened
plates is restricted from having a crack.
[0014] Instead of forming the fluid passage and the tank portion on
each of the work-hardened plates by drawing, each of the
work-hardened plate may be formed into a tube by bending so that
the sacrifice anode layer is disposed to face the corrosive fluid
and the brazing layer is disposed to face the non-corrosive
fluid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] This and other objects and features of the present invention
will become more readily apparent from a better understanding of
the preferred embodiments described below with reference to the
accompanying drawings, in which:
[0016] FIG. 1 is a schematic perspective view showing an evaporator
according to a first preferred embodiment of the present
invention;
[0017] FIG. 2 is a schematic partial perspective view showing the
evaporator according to the first embodiment;
[0018] FIG. 3A is a partial sectional view showing a work-hardened
aluminum alloy plate according to the first embodiment;
[0019] FIG. 3B is a partial perspective view showing a tube of the
evaporator according to the first embodiment;
[0020] FIG. 4 is a perspective view showing a joint portion between
the tube and an outer fin of the evaporator according to the first
embodiment;
[0021] FIG. 5 is a graph showing a relationship between time and a
maximum corrosion depth of a work-hardened aluminum alloy plate of
sample evaporators "a", "b" and "c";
[0022] FIG. 6 is a perspective view showing a joint portion between
a tube and an outer fin of an evaporator according to a second
preferred embodiment of the present invention;
[0023] FIG. 7 is a perspective view showing a joint portion of a
tube, an outer fin and an inner fin of an evaporator according to a
third preferred embodiment of the present invention;
[0024] FIG. 8 is a perspective view showing a joint portion of a
tube, an outer fin and an inner fin of an evaporator according to a
fourth preferred embodiment of the present invention;
[0025] FIG. 9A is a partial sectional view showing a work-hardened
aluminum alloy plate according to a fifth preferred embodiment of
the present invention;
[0026] FIG. 9B is a partial perspective view showing a tube of an
evaporator according to the fifth embodiment;
[0027] FIG. 10 is a perspective view showing a joint portion
between the tube and an outer fin of the evaporator according to
the fifth embodiment;
[0028] FIG. 11 is a perspective view showing a joint portion
between a tube and an outer fin of an evaporator according to a
sixth preferred embodiment of the present invention;
[0029] FIG. 12 is a perspective view showing a joint portion of a
tube, an outer fin and an inner fin of an evaporator according to a
seventh preferred embodiment of the present invention;
[0030] FIG. 13 is a perspective view showing a joint portion of a
tube, an outer fin and an inner fin of an evaporator according to
an eighth preferred embodiment of the present invention;
[0031] FIG. 14 is an exploded perspective view showing an
evaporator according to a ninth preferred embodiment of the present
invention; and
[0032] FIG. 15 is a partial sectional view showing a conventional
three-layer aluminum alloy plate used for forming an
evaporator.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] Preferred embodiments of the present invention are described
hereinafter with reference to the accompanying drawings.
[0034] (First Embodiment)
[0035] A first preferred embodiment of the present invention will
be described with reference to FIGS. 1-5. As shown in FIG. 1, an
evaporator 1 for a refrigeration cycle of a vehicle air conditioner
has plural tubes 2 each having a refrigerant passage 3 therein. The
evaporator 1 performs heat exchange between refrigerant (i.e.,
non-corrosive fluid) flowing through each of the refrigerant
passages 3 and air (i.e., corrosive fluid) passing through the
evaporator 1.
[0036] The evaporator 1 has a first core portion, a second core
portion disposed at an upstream or downstream air side of the first
core portion with respect to a direction of air flow, an inlet tank
5, an outlet tank 6, an intermediate tank 7 and a pair of side
plates 8 for holding the first and second core portions. The inlet
tank 5 is connected to one end (i.e., upper end in FIG. 1) of the
first core portion, and an outlet tank 6 is connected to one end
(i.e., upper end in FIG. 1) of the second core portion. The
intermediate tank 7 is connected to the other ends (i.e., lower
ends in FIG. 1) of the first and second core portions.
[0037] As shown in FIG. 2, each of the inlet and outlet tanks 5, 6
is made of a flat base plate 11 and a tank portion 13 having a
U-shaped cross section. One end of each of the tubes 2 is inserted
into the base plate 11. The base plate 11 and the tank plate 13 are
connected to form a tank space 12 therebetween. The intermediate
tank 7 is also made of a flat base plate (not shown) into which the
other end of each of the tubes 2 is inserted, and a tank portion
(not shown) having a U-shaped cross section. Thus, the inlet tank
5, the outlet tank 6 and the intermediate tank 7 are formed
separately from the tubes 2. Referring back to FIG. 1, one of the
side plates 8 has an inlet pipe 14 through which refrigerant from
an expansion valve (not shown) is introduced to the first core
portion, and an outlet pipe 15 through which refrigerant in the
second core portion is discharged to a compressor (not shown).
[0038] As shown in FIGS. 1 and 2, each of the first and second core
portions is formed by alternately laminating the plural tubes 2 and
plural outer fins 4. The outer fins 4 are used for improving
efficiency of heat transfer between refrigerant and air. Each of
the outer fins 4 is corrugated and has plural parallel folds. As
shown in FIG. 4, each fold of each of the outer fins 4 is formed to
have a flat top so that a joint area between each of the outer fins
4 and each of the tubes 2 is increased. Preferably, each of the
outer fins 4 is made of an aluminum alloy which is
electro-chemically base with respect to a core 21 and a sacrifice
anode layer 22 of each of the tubes 2 and is different from a
material of the core 21. For example, each of the outer fins 4 is
made of aluminum alloy corresponding to "3003 (Japanese Industrial
Standard No.)+Zn". "3003" corresponds to an aluminum alloy
consisting of 1.2% Mn, 0.15% copper (Cu) by weight and impurity.
"3003+Zn" consists of "3003" added with 2.5% zinc (Zn) by
weight.
[0039] Referring to FIG. 3A, a work-hardened aluminum alloy plate
20 is formed by uniformly rolling a three-layer aluminum alloy
plate. The three-layer aluminum alloy plate is made of the core 21,
the sacrifice anode layer 22 clad on one side surface of the core
21 and a brazing layer 23 clad on the other side surface of the
core 21. As shown in FIG. 3B, each of the tubes 2 is formed by
bending the work-hardened aluminum alloy plate 20. Preferably, the
core 21 is made of Al--Mn alloy corresponding to "3103" or "3003".
"3103" corresponds to an aluminum alloy consisting of 1.3% Mn, 0.5%
Si, 0.5% Cu by weight and impurity. "3003" corresponds to an
aluminum alloy consisting of 1.0% Mn, 0.6% Si, 0.7% iron (Fe), 0.1%
Cu, 0.1% Zn by weight and impurity. The sacrifice anode layer 22 is
made of Al--Zn alloy which is electro-chemically base with respect
to the core 21 and corresponds to "7072". "17072", corresponds to
an aluminum alloy consisting of 1.5% Zn by weight and impurity. The
brazing layer 23 is made of Al--Si alloy corresponding to "4045".
"4045" corresponds to an aluminum alloy consisting of 10% Si by
weight and impurity.
[0040] Next, a manufacturing method of the evaporator 1 will be
described with reference to FIGS. 1-4.
[0041] First, the work-hardened aluminum alloy plate 20 is formed
by uniformly rolling the three-layer aluminum alloy plate having
the core 21, the sacrifice anode layer 22 and the brazing layer 23.
Conventionally, a work-hardened aluminum alloy plate is refined by
annealing to have a distortion rate of 0%, that is, to have no
distortion. In the first embodiment, the work-hardened aluminum
alloy plate 20 needs to be refined to have a distortion rate of 10%
or more, theoretically. However, the work-hardened aluminum alloy
plate 20 needs to be softened by slight heat treatment to assure a
sufficient processability. Therefore, in the first embodiment, the
three-layer aluminum alloy plate is cold rolled at a rolling rate
of approximately 70% during a work-hardening process, and then the
work-hardened aluminum alloy plate 20 is refined to have a
distortion rate of 10-20% by a heat treatment.
[0042] In the first embodiment, as shown in FIG. 3A, a thickness of
the work-hardened aluminum alloy plate 20 is 0.25 mm while a
thickness of the three-layer aluminum alloy plate is 0.8 mm. A
thickness of the sacrifice anode layer 22 is 40 .mu.m and a
thickness of the brazing layer 23 is 30 .mu.m. As a result, the
whole thickness of the work-hardened aluminum alloy plate 20 is
largely reduced in comparison with a conventional not-work-hardened
one, thereby reducing a thickness of each of the tubes 2.
[0043] Next, the work-hardened aluminum alloy plate 20 is set in a
pressing device and is cut into a predetermined shape. Then, as
shown in FIG. 3B, the work-hardened aluminum alloy plate 20 is
formed into each of the tubes 2 by bending so that the sacrifice
anode layer 22 is disposed on an outer surface of each of the tubes
2 to face air and the brazing layer 23 is disposed on an inner
surface of each of the tubes 2 to face refrigerant. Further, as
shown in FIG. 4, a brazing member 24 made of the same material as
the brazing layer 23 is applied to the outer surface of each of the
tubes 2 in a straight line so that each fold of each of the outer
fins 4 is brazed to the outer surface of each of the tubes 2
through the brazing member 24.
[0044] Thereafter, the tubes 2 and the outer fins 4 are alternately
laminated to form the first and second core portions. As shown in
FIG. 1, one end of each of the tubes 2 of the first core portion is
inserted into the inlet tank 5, and one end of each of the tubes 2
of the second core portion is inserted into the outlet tank 6.
Other end of each of the tubes 2 of the first and second core
portions is inserted into the intermediate tank 7. Then, the first
and second core portions are integrally held by the side plates 8
to form an assembled body of the evaporator 1. Flux powder is
applied to an outer surface of the assembled body so that the
brazing layer 23 is uniformly wet, and then the assembled body is
integrally brazed in a furnace. As a result, the evaporator 1 is
formed.
[0045] Conventionally, when a distortion rate of the Al--Mn alloy
plate is low as 10% or less, a brazing layer of the Al--Mn alloy
plate erodes significantly, thereby decreasing a thickness of a
core of the Al--Mn alloy plate. According to the first embodiment,
the work-hardened aluminum alloy plate 20 having a distortion rate
of 10-20% is used to form the tubes 2 of the evaporator 1. As a
result, the brazing layer 23 is restricted from eroding, thereby
restricting erosion of the core 21. Therefore, a thickness of the
core 21 is restricted from decreasing, and a life of corrosion
resistance of each of the tubes 2 is increased. Further, the inlet
tank 5, the outlet tank 6 and the intermediate tank 7 are formed
separately from the tubes 2. Therefore, each of the tubes 2 is
formed only by bending the work-hardened aluminum alloy plate 20
without any drawing process. As a result, the work-hardened
aluminum alloy plate 20 is restricted from cracking.
[0046] Moreover, each of the tubes 2 is formed so that the
sacrifice anode layer 22 is exposed outside each of the tubes 2 to
face air. As a result, the outer surface of each of the tubes 2 is
sufficiently protected from corrosion by the sacrifice anode layer
22, and a whole area of the evaporator 1 is effectively protected
from corrosion. Further, since the brazing layer 23 is disposed
inside each of the tubes 2 to face refrigerant and is not exposed
outside the each of the tubes 2 to face air, each of the tubes 2 is
effectively restricted from corrosion.
[0047] Thus, in the first embodiment, while securing a sufficient
corrosion resistance of the evaporator 1, a thickness of each of
the tubes 2 is reduced, thereby reducing an amount of a material
required to form the evaporator 1. As a result, the evaporator 1 is
reduced in a size and a weight without deteriorating a cooling
performance thereof nor increasing a manufacturing cost thereof.
Therefore, fuel efficiency of the vehicle is improved.
[0048] Next, results of a corrosion test for sample evaporators
"a", "b" and "c" will be described with reference to FIG. 5. The
sample evaporator "a" has plural tubes made of an aluminum alloy
plate with a thickness of 0.5 mm. The sample evaporator "b" has
plural tubes made of the work-hardened aluminum alloy plate 20 with
a thickness of 0.10 mm, which includes the sacrifice anode layer 22
having a thickness of 40 .mu.m. The sample evaporator "c"
corresponds to the evaporator 1 according to the first embodiment
and has plural tubes made of the work-hardened aluminum alloy plate
20 with a thickness of 0.25 mm, which includes the sacrifice anode
layer 22 having a thickness of 40 .mu.m.
[0049] In the corrosion test, each of the sample evaporators
"a"-"c" is sprayed with simulated condensed water (i.e., highly
corrosive aqueous solution) for a predetermined time and is dried
for a predetermined time. The spraying process and the drying
process were continued to be performed alternately. A maximum depth
of corrosion of the tubes of each of the sample evaporators "a"-"c"
was measured as time elapsed. The results are shown in FIG. 5.
[0050] As shown in FIG. 5, one of the tubes of the sample
evaporator "a" was penetrated when elapsed time exceeded 800 hours.
One of the tubes of the sample evaporator "b" was penetrated when
elapsed time exceeded 1,000 hours. However, none of the tubes of
the sample evaporator "c" was penetrated even when elapsed time
exceeded 1,000 hours and further exceeded 1,800 hours, with a
maximum depth of corrosion of the tubes remaining about 0.06 mm.
Thus, according to the first embodiment, the tubes 2 are
effectively protected from corrosion.
[0051] (Second Embodiment)
[0052] A second preferred embodiment of the present invention will
be described with reference to FIG. 6. In this and following
embodiments, components which are substantially the same as those
in previous embodiments are assigned the same reference
numerals.
[0053] In the first embodiment, although the brazing member 24 is
necessary to braze each of the outer fins 4 to each of the tubes 2,
the brazing member 24 may deteriorate corrosion resistance of the
tubes 2. In the second embodiment, as shown in FIG. 6, a brazing
member 25 is applied in stripes to a joint portion between the
sacrifice anode layer 22 and each of the folds of each of the outer
fins 4. The brazing member 25 is made of Al--Si alloy corresponding
to "4045" or "14104". As a result, corrosion resistance of the
tubes 2 is less affected by the brazing member 25.
[0054] (Third Embodiment)
[0055] A third preferred embodiment of the present invention will
be described with reference to FIG. 7. In the third embodiment, a
brazing member 26 made of aluminum alloy corresponding to "4047" is
applied in a straight line to a joint portion between the sacrifice
anode layer 22 and each of the folds of each of the outer fins 4.
"14047", corresponds to an aluminum alloy consisting of 12% Si by
weight and impurity, and is used for preplaced brazing or the
like.
[0056] Further, an inner fin 9 is inserted into each of the
refrigerant passages 3 formed in each of the tubes 2 for improving
efficiency of heat transfer between refrigerant and air. Therefore,
the inner fin 9 is disposed on the brazing layer 23. The inner fin
9 is made of aluminum alloy which may be the same as the material
of the core 21 or different from the material of the core 21. The
inner fin 9 is brazed to the tubes 2 by brazing material of the
brazing layer 23. According to the third embodiment, the same
effect as in the second embodiment is obtained.
[0057] (Fourth Embodiment)
[0058] A fourth preferred embodiment of the present invention will
be described with reference to FIG. 8. In the fourth embodiment, a
brazing member 27 made of aluminum alloy corresponding to "4047" is
applied in stripes to a joint portion between the sacrifice anode
layer 22 and each of the folds of each of the outer fins 4.
Further, the inner fin 9 is inserted into each of the refrigerant
passages 3 formed in each of the tubes 2, similarly to the third
embodiment. According to the fourth embodiment, the same effect as
in the second embodiment is obtained.
[0059] (Fifth Embodiment)
[0060] A fifth preferred embodiment of the present invention will
be described with reference to FIGS. 9A-10. In the fifth
embodiment, a work-hardened aluminum alloy plate 30 is formed by
uniformly rolling a two-layer aluminum alloy plate in a roller
mill. As shown in FIG. 9A, the two-layer aluminum alloy plate has a
core 31 and a sacrifice anode layer 32 clad on one side surface of
the core 31. Materials of the core 31 and the sacrifice anode layer
32 may be respectively same as those of the core 21 and the
sacrifice anode layer 23 in the first embodiment.
[0061] Similarly to the first embodiment, after the two-layer
aluminum alloy plate has been cold rolled at a rolling rate of
approximately 70%, the work-hardened aluminum alloy plate 30 is
applied with heat treatment to have a distortion rate of about
10-20%. Next, the work-hardened aluminum alloy plate 30 is set in a
pressing device and is cut to have a predetermined size. Then, as
shown in FIG. 9B, the work-hardened aluminum alloy plate 30 is
formed into each of tubes 200 having a refrigerant passage 300
therein. The sacrifice anode layer 32 is disposed outside the tubes
200 to face air, and the core 31 is disposed inside the tubes 200
to face refrigerant.
[0062] In the fifth embodiment, each end of the work-hardened
aluminum alloy plate 30 is applied with brazing material (not
shown) corresponding to "4047". Each end of the work-hardened
aluminum alloy plate 30 is brazed together by the brazing material
to form each of the tubes 200. Further, as shown in FIG. 10, a
brazing member 34 is applied in a straight line to a joint portion
between the sacrifice anode layer 32 and each of folds of each of
the outer fins 4. The brazing member 34 is made of Al--Si alloy
corresponding to "14045", or "4104".
[0063] (Sixth Embodiment)
[0064] A sixth preferred embodiment of the present invention will
be described with reference to FIG. 11. In the sixth embodiment, a
brazing member 35 is applied in stripes to a joint portion between
the sacrifice anode layer 32 and each of the folds of each of the
outer fins 4. The brazing member 35 is made of Al--Si alloy
corresponding to "4045" or "4104" . As a result, the same effect as
in the second embodiment is obtained.
[0065] (Seventh Embodiment)
[0066] A seventh preferred embodiment of the present invention will
be described with reference to FIG. 12. In the seventh embodiment,
the brazing member 34 is applied in a straight line to a joint
portion between the sacrifice anode layer 32 and each of the folds
of each of the outer fins 4. Further, the inner fin 9 is inserted
into each of the refrigerant passages 300 formed in each of the
tubes 200 for improving efficiency of heat transfer between
refrigerant and air. That is, the inner fin 9 is disposed on the
core 31.
[0067] (Eighth Embodiment)
[0068] An eighth preferred embodiment of the present invention will
be described with reference to FIG. 13. In the eighth embodiment,
the brazing member 35 is applied in stripes to a joint portion
between the sacrifice anode layer 32 and each of the folds of each
of the outer fins 4. Further, the inner fin 9 is inserted into each
of the refrigerant passages 300 similarly to the seventh
embodiment.
[0069] (Ninth Embodiment)
[0070] A ninth preferred embodiment of the present invention will
be described with reference to FIG. 14.
[0071] As shown in FIG. 14, an evaporator 100 has a laminated body
50 formed by laminating plural refrigerant passage members and side
plates 51, 52. Each of the side plates 51, 52 is respectively
connected to end surfaces of the laminated body 50. Each of the
passage members is made by connecting a pair of thin core plates 40
made of aluminum alloy. Each of the core plates 40 has a recessed
refrigerant passage 41 and a recessed refrigerant passage 42. The
pair of the core plates 40 are connected so that the recessed
passages 41, 42 are disposed inside each of the passage members.
Refrigerant is introduced into the recessed passage 41 from an
inlet pipe 53 formed on the side plate 51. Refrigerant flowing
through the recessed passage 42 is discharged from an outlet pipe
54 formed on the side plate 51. A size of the recessed passage 42
is larger than that of the recessed passage 41 in a direction in
which air passes through the evaporator 100. Heat exchange between
refrigerant flowing through the recessed passages 41, 42 and air
passing through the evaporator 100 is performed so that refrigerant
is evaporated and air is cooled.
[0072] Each of the core plates 40 has tank portions 43, 44
respectively formed at upper and lower ends of the recessed passage
41, and tank portions 45, 46 respectively formed at upper and lower
ends of the recessed passage 42. Each of the tank portions 43-46 is
an opening and communicates with a corresponding tank portion of
adjacent passage members. Further, ribs 47, 48 are respectively
formed in the recessed passages 41, 42. That is, the ribs 47, 48
are disposed at a refrigerant side of each of the core plates 40.
The ribs 47, 48 function as reinforcing members for improving
pressure resistance of each of the core plates 40 and as inner fins
for improving efficiency of heat transfer between air and
refrigerant at the refrigerant side of each of the core plates 40,
that is, inside the evaporator 100. Further, the ribs 47, 48
function as outer fins for improving efficiency of heat transfer
between air and refrigerant at an air side of each of the core
plates 40, that is, outside the evaporator 100.
[0073] Next, a manufacturing method of the evaporator 100 will be
described. First, each of the core plates 40 having the recessed
passages 41, 42, the tank portions 43-46 and the ribs 47, 48 is
integrally formed by shallow-drawing the work-hardened aluminum
alloy plate 20 or 30 respectively according to the first or fifth
embodiments. Each of the core plates 40 is formed so that the
sacrifice anode layer 22 or 32 is disposed at the air side thereof,
and the brazing layer 23 or the core 31 is disposed at the
refrigerant side thereof.
[0074] Then, the plural core plates 40 are laminated to form the
laminated body 50. The side plates 51, 52 are connected to the
respective end of the laminated body 50 to form an assembled body.
Thereafter, the assembled body is applied with flux powder so that
the brazing layer 23 is uniformly wet, and is integrally brazed in
a furnace. As a result, the evaporator 100 is formed.
[0075] Conventionally, a corrugated outer fin having a height of
8-10 mm is disposed between adjacent passage members. Therefore, a
tank portion of a core plate needs to be formed by deep-drawing to
have a height of 4-5 mm. However, according to the ninth
embodiment, the laminated body 50 is formed by laminating only the
core plates 40, and no outer fin is required to be disposed between
adjacent passage members. Therefore, the tank portions 43-46 may be
formed by shallow-drawing to have a height of 1 mm or the like. As
a result, the evaporator 100 is formed only by shallow-drawing of
the core plates 40. Therefore, a thickness of each of the core
plates 40 can be decreased without causing crack, thereby reducing
a size and a weight of the evaporator 100.
[0076] The present invention is not limited to an evaporator, and
may be applied to any other heat exchangers made of aluminum alloy
such as a condenser or a supercooler for a vehicle air conditioner,
or an oil cooler for an engine cooler. When the present invention
is applied to a heat exchanger for a refrigeration cycle such as a
condenser or a supercooler, refrigerant is used as non-corrosive
fluid and air is used as corrosive fluid, similarly to the
evaporator 1. When the present invention is applied to an oil
cooler, oil such as lubricant oil or operation oil is used as
non-corrosive fluid and coolant or air is used as corrosive
fluid.
[0077] Although the present invention has been fully described in
connection with preferred embodiments thereof with reference to the
accompanying drawings, it is to be noted that various changes and
modifications will become apparent to those skilled in the art.
Such changes and modifications are to be understood as being within
the scope of the present invention as defined by the appended
claims.
* * * * *