Aluminum-made heat exchanger with brazed joint portion

Details Aluminum-made heat exchanger with brazed joint portion Aluminum-made heat exchanger with brazed joint portion

2000-09-25

2001-10-09

Flanigan, Allen (Department: 3743)

Heat exchange

With coated, roughened or polished surface

C165S134100, C165S167000

Reexamination Certificate

active

06298910

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of Japanese Patent Application No. 11-278823 filed on Sep. 30, 1999, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a brazing structure of an aluminum-made heat exchanger formed by integrally brazing alternately laminating first and second metallic plates that are mainly made of aluminum, and particularly to a brazing structure of a water cooling type oil cooler capable of preventing corrosion of a passage wall on which cooling water flows as medium for cooling oil.
2. Description of the Related Art
Conventionally, there is an aluminum-made heat exchanger such as a water cooling type oil cooler for cooling engine oil (hereinafter, referred to as oil) by exchanging heat with engine cooling water. As shown in
FIG. 7
, such a water cooling type oil cooler is formed by integrally brazing laminated several pairs of first and second plates
101
and
102
that are formed from aluminum alloy by plastic working (pressing). For instance, one first plate
101
forms a cooling water passage
103
with a second plate
102
adjacent thereto at a lower side thereof, and forms an oil passage
104
with another second plate
102
adjacent thereto at an upper side thereof.
In this water cooling type oil cooler, cooling water deteriorates to have high corrosiveness and to easily cause pitting corrosion on the first and second plates defining the cooling water passage as passage walls, and accordingly, a lifetime of a product is shortened. To prevent the pitting corrosion of the passage walls, as shown in
FIG. 7
, the passage walls are clad with sacrifice corrosion layers
111
,
121
. Incidentally, reference numerals
105
,
106
respectively indicate oil passages formed in the first and second plates by pressing. However, in the conventional water cooling type oil cooler, as shown in
FIG. 7
, because no brazing filler metal exists at the joint portion between the first and second plates
101
,
102
, the first and second plates
101
,
102
cannot be bonded together by brazing.
As a countermeasure against the above problem, as shown in
FIG. 8A
, it is conceivable to adopt a plate composed of a base member (core member)
110
made of aluminum alloy, one surface of which is clad with sacrifice corrosion material
113
and further both surfaces of which are clad with brazing filler metal layers
114
,
115
. This plate is, however, accompanied by high material cost since it is composed of four layers.
As shown in
FIG. 8B
, it can also be conceivable to adopt a three-layered plate including the core member (core member)
110
made of aluminum alloy, both surfaces of which are clad with brazing filler metal layers
116
,
117
containing Zn that can serve as a sacrifice corrosion material simultaneously. However, when this plate is integrally brazed within a heating furnace such as a vacuum furnace, Zn component is liable to evaporate and flows into a joint part of the plate. Because of this, it is difficult to control the amount of the sacrifice corrosion material covering the passage walls of the cooling water passage. This may result in insufficient corrosion resistance.
As a result, pitting corrosion may be produced on the passage walls of the cooling water passage, or the brazing filler metal layers may be corroded first to cause insufficient sealing that allows communication between the oil passage and the cooling water passage. In consequence, oil can be mixed with cooling water.
It can also be conceivable to adopt first and second plates each having a three-layered structure and joined together as shown in FIG.
9
. The first and second plates are respectively composed of first and second plates
101
,
102
, one surface of which is clad with sacrifice corrosion material
111
,
112
, and the other surface of which is clad with brazing filler metal
120
,
122
. The three-layered first and second plates are formed by pressing (burring) processing to form, for instance, burring portions
119
,
129
defining oil communication passages
105
,
106
through which two oil passages
104
communicate each other.
In this oil cooler, the outer wall surface of the burring portion
129
of the second plate is brazed to the inner wall surface of the burring portion
119
of the first plate. However, it is difficult to raise accuracy of a clearance between the inner wall surface of the burring portion
119
and the outer wall surface of the burring portion
129
. For instance, when the burring portion
129
is inserted into the burring portion
119
for assembling, the burring portion
119
may expand outward or bent inward to produce brazing failures at many points. The brazing failures lessen the sealing property at the joining portion between the first and second plates, and the joining strength of the oil cooler.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems. An object of the present invention is, in an aluminum-made heat exchanger, to improve a brazing property at a joint portion between first and second plates so as to improve the sealing property and the bonding strength of the joint portion and so as to lengthen the product lifetime of the heat exchanger.
According to the present invention, a heat exchanger has a first plate and a second plate laminated with and brazed to each other in a plate thickness direction thereof to form a passage therebetween. The first plate has a first brazing filler metal layer member on a first surface thereof and a first sacrifice layer on a second surface thereof. The second plate has a second brazing filler metal layer on a first surface thereof and a second sacrifice layer on a second surface thereof. The first sacrifice layer and the second sacrifice layer face each other and define the passage as passage walls. The second plate is plastically deformed such that the first brazing filler metal layer is stacked with the second sacrifice layer at the joint portion in the plate thickness direction of the first and second plates forming the passage.
Accordingly, the first brazing filler metal layer can be interposed between the first and second plates having a three-layered structure, at the joint portion. Therefore, the first and second plates can be brazed securely, and the sealing property and the bonding strength of the joint portion are improved. In consequence, the heat exchanger can have a lengthened lifetime as a product.


REFERENCES:
patent: 5099912 (1992-03-01), Tajima et al.
patent: 5292595 (1994-03-01), Yamauchi et al.
patent: 5720340 (1998-02-01), Ohara et al.
patent: 5744255 (1998-04-01), Doko et al.
patent: 5979542 (1999-11-01), Inoue et al.
patent: 0 712 681 A2 (1996-05-01), None
patent: 0 843 146 A2 (1998-05-01), None
patent: A-6-170519 (1994-06-01), None
patent: A-10-185462 (1998-07-01), None

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