U.S. patent application number 10/172926 was filed with the patent office on 2002-11-07 for egr cooler.
This patent application is currently assigned to HINO MOTORS, LTD.. Invention is credited to Nakagome, Keiichi, Takakura, Takashi.
Application Number | 20020162651 10/172926 |
Document ID | / |
Family ID | 26347299 |
Filed Date | 2002-11-07 |
United States Patent
Application |
20020162651 |
Kind Code |
A1 |
Nakagome, Keiichi ; et
al. |
November 7, 2002 |
EGR cooler
Abstract
The invention relates to an EGR cooler in which cooling water is
supplied into and discharged from a shell, exhaust gas being passed
through tubes from one of hoods to the other hood for thermal
exchange of the exhaust gas with the cooling water. Employed is a
structure in which the cooling water is prevented from leaking to
flow channels of the exhaust gas, so that engine trouble can be
prevented from occurring
Inventors: |
Nakagome, Keiichi;
(Hino-shi, JP) ; Takakura, Takashi; (Hino-shi,
JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
HINO MOTORS, LTD.
Hino-shi
JP
|
Family ID: |
26347299 |
Appl. No.: |
10/172926 |
Filed: |
June 18, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10172926 |
Jun 18, 2002 |
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09889152 |
Jul 12, 2001 |
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09889152 |
Jul 12, 2001 |
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PCT/JP00/00217 |
Jan 19, 2000 |
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Current U.S.
Class: |
165/158 ;
165/178 |
Current CPC
Class: |
F02M 26/32 20160201;
F28D 21/0003 20130101; F02M 26/11 20160201; F28F 9/0229 20130101;
F28F 9/182 20130101 |
Class at
Publication: |
165/158 ;
165/178 |
International
Class: |
F28F 009/02; F28F
009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 20, 1999 |
JP |
11-11777 |
Claims
1. An EGR cooler comprising a cylindrical shell, plates fixed to
axial opposite ends of said shell so as to close the ends of the
shell, hoods fixed to sides of the plates away from said shell so
as to enclose end faces of the plates, tubes extending axially
within the shell and having opposite ends penetratingly fixed to
the respective plates, cooling water being supplied into and
discharged from said shell, exhaust gas being passed through said
tubes from one of the hoods to the other hood for thermal exchange
of said exhaust gas with said cooling water, characterized in that
an end of the tube penetrating the plate is formed as a tapered
portion with diameter gradually increased toward the side away from
the shell, the tapered portion being wholly welded to the plate by
laser radiation from the side away from the shell.
2. An EGR cooler comprising a cylindrical shell, plates fixed to
axial opposite ends of said shell so as to close the ends of the
shell, hoods fixed to sides of the plates away from said shell so
as to enclose end faces of the plates, tubes extending axially
within the shell and having opposite ends penetratingly fixed to
the respective plates, cooling water being supplied into and
discharged from said shell, exhaust gas being passed through said
tubes from one of the hoods to the other hood for thermal exchange
of said exhaust gas with said cooling water, characterized in that
an end of the tube penetrates into a through-hole of the plate
which is formed with a notch on the side toward the shell, and is
welded to the plate by laser radiation from the side away from the
shell such that a laser weld reaches the notch.
3. An EGR cooler comprising a cylindrical shell, plates fixed to
axial opposite ends of said shell so as to close the ends of the
shell, hoods fixed to sides of the plates away from said shell so
as to enclose end faces of the plates, tubes extending axially
within the shell and having opposite ends penetratingly fixed to
the respective plates, cooling water being supplied into and
discharged from said shell, exhaust gas being passed through said
tubes from one of the hoods to the other hood for thermal exchange
of said exhaust gas with said cooling water, characterized in that
the tubes penetrate into and are fixed to the plate via brazed
portions such that an end of the tube extends out from the plate by
a predetermined length and the extending end of the tube penetrates
into and is fixed to a sub plate by laser weld, whereby said sub
plate covers said brazed portions.
4. An EGR cooler comprising a shell in the form of a cylindrical
container, tubes extending axially within the shell and having
opposite ends penetratingly fixed to axial opposite ends of said
shell, cooling water being supplied into and discharged from said
shell, exhaust gas being passed through said tubes for thermal
exchange of said exhaust gas with said cooling water, characterized
in that the tubes have increased diameter and thickness so as to
increase cross sectional areas and strength of flow channels, a gas
flange being fitted over tips of the respective tubes extruded out
of the shell.
Description
TECHNICAL FIELD
[0001] This invention relates to an EGR cooler attached to an EGR
apparatus, which recirculates exhaust gas from an engine to
suppress generation of nitrogen oxides, so as to cool the exhaust
gas for recirculation.
BACKGROUND ART
[0002] Known is an EGR apparatus which recirculates part of exhaust
gas from an engine in a vehicle or the like to the engine to
suppress generation of nitrogen oxides. In such an EGR apparatus,
cooling the exhaust gas to be recirculated to the engine will drop
the temperature of and reduce the volume of the exhaust gas to
lower the combustion temperature in the engine without substantial
decrease of output thereof, thereby effectively suppressing
generation of nitrogen oxides. To this end, some EGR apparatuses
are equipped with, midway of exhaust gas recirculation lines to the
engines, EGR coolers for cooling the exhaust gas.
[0003] FIG. 1 is a sectional view showing an example of the
above-described EGR cooler wherein reference numeral 1 denotes a
cylindrical shell with axial opposite ends to which plates 2 are
respectively fixed to close the ends of the shell 1. Penetratingly
fixed to the respective plates 2 are opposite ends of a number of
tubes 3 which extend axially within the shell 1.
[0004] A cooling water inlet 4 is attached from outside to the
shell 1 near one end thereof and a cooling water outlet 5 is
attached from outside to the shell 1 near the other end thereof so
that cooling water 9 is supplied via the cooling water inlet 4 into
the shell 1, flows outside of the tubes 3 and is discharged via the
cooling water outlet 5 out of the shell 1.
[0005] The respective plates 2 have, on their sides away from the
shell 1, bowl-shaped hoods 6 fixed to the plates 2 so as to enclose
end faces of the plates 2. The one and the other hoods 6 provide
central exhaust gas inlet and outlet 7 and 8, respectively, so that
the exhaust gas 10 from the engine enters via the exhaust gas inlet
7 into the one hood 6, is cooled, during passage through the tubes
3, by heat exchange with the cooling water 9 flowing outside of the
tubes 3 and is discharged to the other hood 6 to be recirculated to
the engine via the exhaust gas outlet 8.
[0006] In such conventional EGR cooler, however, the end of the
tube 3 penetrates into and is fixed to the plate 2 via a brazed
portion 11 as shown in FIG. 2 in an enlarged scale. Especially on
an outlet side of the exhaust gas 10 as shown, cooling the exhaust
gas 10 in the tube 3 will generate condensate containing a
vitriolic component which may flow out via the outlet of the tube 3
and corrode the brazing metal (generally nickel brazing metal)
constituting the brazed portion 11. If the cooling water 9 should
leak therethrough, it may be guided to the engine, causing a
trouble.
[0007] Contemplated nowadays is welding the end of the tube 3 to
the plate 2 by laser radiation L as shown in FIG. 3. Use of this
kind of laser radiation will advantageously bring about laser weld
12 highly resistive against corrosion by the condensate; on the
other hand, the weld penetration by the laser radiation L does not
reach deep and sufficient weld depth D is hard to obtain, resulting
in the laser weld 12 with low bonding strength. If the tube 3
should have undergone excessive thermal expansion, the laser weld
12 may be damaged to cause leakage of the cooling water 9.
[0008] More specifically, upon laser-welding the end of the tube 3
to the plate 2, generally effected is laser radiation L on the side
of the plate 2 away from the shell 1 and in parallel with the axis
of the tube 3, and welded is a boundary between the plate 2 and the
end face of the tube 3 with weld depth D of the order of a wall
thickness of the tube 3. As a result, only obtainable is the laser
weld 12 having strength lower than that of the tube 3 itself.
[0009] In an actual operation, laser radiation L is effected from
directly above, with the tube 3 being stood upright. Therefore, to
merely increase the laser intensity for the purpose of increasing
the weld depth will disadvantageously result in an increased
possibility that the molten portion may flow into the tube 3 to
narrow the flow channel. Thus, to increase the laser intensity is
inherently limitative.
[0010] Furthermore, as described above, with the laser weld 12
having the shallow weld depth D, the tube 3 is welded to a
through-hole 13 of the plate 2 over only a small area on the side
away from the shell 1. Therefore, minute crevice may be formed over
a major part of the boundary between the through-hole 13 and the
tube 3. In this crevice, cavitation may occur due to variation of
hydraulic pressure derived from minute vibrations of the tube 3,
resulting in generation of crevice corrosion in a deepest portion
of the crevice (a portion abutting on the laser weld 12). As a
result, the end of the tube 3 may be damaged to cause leakage of
the cooling water 9.
[0011] The present invention was made in view of the above facts
and has its object to prevent the cooling water from leaking out to
the flow channels of the exhaust gas, thereby preventing engine
trouble from occurring.
SUMMARY OF THE INVENTION
[0012] An EGR cooler according to claim 1 of the invention
comprises a cylindrical shell, plates fixed to axial opposite ends
of said shell so as to close the ends of the shell, hoods fixed to
sides of the plates away from said shell so as to enclose end faces
of the plates, tubes extending axially within the shell and having
opposite ends penetratingly fixed to the respective plates, cooling
water being supplied into and discharged from said shell, exhaust
gas being passed through said tubes from one of the hoods to the
other hood for thermal exchange of said exhaust gas with said
cooling water, and is characterized in that an end of the tube
penetrating the plate is formed as a tapered portion with diameter
gradually increased toward the side away from the shell, the
tapered portion being wholly welded to the plate by laser radiation
from the side away from the shell.
[0013] In this manner, when the end of the tube is formed as the
tapered portion with diameter gradually increased toward the side
away from the shell, the inner periphery of the tapered portion has
a shape divergent to the side away from the shell to have a bevel
in the form of mortar, so that laser radiation from the side away
from the shell can be readily carried out throughout the inner
periphery of the tapered portion.
[0014] Then, a resulting laser weld has a high bonding strength,
the weld depth being increased to an extent corresponding to the
thickness of the plate. Moreover, formation of minute crevice
between the tube and the through-hole of the plate is avoided so
that no crevice corrosion occurs.
[0015] An EGR cooler according to claim 2 of the invention
comprises a cylindrical shell, plates fixed to axial opposite ends
of said shell so as to close the ends of the shell, hoods fixed to
sides of the plates away from said shell so as to enclose end faces
of the plates, tubes extending axially within the shell and having
opposite ends penetratingly fixed to the respective plates, cooling
water being supplied into and discharged from said shell, exhaust
gas being passed through said tubes from one of the hoods to the
other hood for thermal exchange of said exhaust gas with said
cooling water, and is characterized in that an end of the tube
penetrates into a through-hole of the plate which is formed with a
notch on the side toward the shell, and is welded to the plate by
laser radiation from the side away from the shell such that a laser
weld reaches the notch.
[0016] In this manner, with the through-hole of the plate being
formed with the notch on the side toward the shell, an unwelded
portion is left as the notch widely opened to the shell when the
end of the tube is welded to the plate by means of laser radiation
from the side away from the shell such that the laser weld reaches
the notch. As a result, no minute crevice is formed between the
tube and the through-hole of the plate and no crevice corrosion
occurs. It is therefore possible to have a structure which, under
the condition that no crevice corrosion occurs, has the laser
intensity increased to such a degree that no portion melted by the
laser radiation will flow into the tube to narrow the channel, and
the weld depth increased as much as possible to increase the
bonding strength of the laser weld as high as possible.
[0017] An EGR cooler according to claim 3 of the invention
comprises a cylindrical shell, plates fixed to axial opposite ends
of said shell so as to close the ends of the shell, hoods fixed to
sides of the plates away from said shell so as to enclose end faces
of the plates, tubes extending axially within the shell and having
opposite ends penetratingly fixed to the respective plates, cooling
water being supplied into and discharged from said shell, exhaust
gas being passed through said tubes from one of the hoods to the
other hood for thermal exchange of said exhaust gas with said
cooling water, and is characterized in that the tubes penetrate
into and are fixed to the plate via brazed portions such that an
end of the tube extends out from the plate by a predetermined
length and the extending end of the tube penetrates into and is
fixed to a sub plate by laser weld, whereby said sub plate covers
said brazed portions.
[0018] Thus, such covering of the plate with the sub plate will
cause any condensate containing a vitriolic component, which may be
generated by cooling the exhaust gas in the tube and may flow out
via the outlet of the tube, to be isolated by the sub plate to
which the tubes penetratingly fixed via the laser welds having high
resistance against corrosion such that no condensate contacts the
brazed portions of the plate. As a result, corrosion of the brazing
filler metal constituting the brazed portions due to the condensate
is positively avoided while the bonding strength of the tubes to
the plate is kept high by the brazed portions. Even if water should
leak due to any crack created in the brazed portions, the cooling
water is dammed by the sub plate to stay between the sub plate and
the plate.
[0019] An EGR cooler according to claim 4 of the invention
comprises a shell in the form of a cylindrical container, tubes
extending axially within the shell and having opposite ends
penetratingly fixed to axial opposite ends of said shell, cooling
water being supplied into and discharged from said shell, exhaust
gas being passed through said tubes for thermal exchange of said
exhaust gas with said cooling water, and is characterized in that
the tubes have increased diameter and thickness so as to increase
cross sectional areas and strength of flow channels, a gas flange
being fitted over tips of the respective tubes extruded out of the
shell.
[0020] This allows the number of tubes to be reduced to a required
minimum and line for recirculation of exhaust gas may be properly
branched and directly connected to the gas flange at the tips of
the respective tubes extruded out of the shell. Therefore, even if
condensate containing a vitriolic component is generated due to
cooling of the exhaust gas in the tubes, avoided is its adverse
effect such as corrosion on the penetrating fixed portions of the
tubes to the shell. If a crack should be generated on the
penetrating fixed portions of the tubes to the shell to cause water
leakage, the leaked, cooling water leaks out only outside of the
shell and is prevented from intruding into the flow channels of the
exhaust gas.
BRIEF DESCRIPTION OF DRAWINGS
[0021] FIG. 1 is a sectional view showing a conventional EGR
cooler;
[0022] FIG. 2 is an enlarged sectional view showing details of a
penetrating, fixed portion between a tube and a plate in FIG.
1;
[0023] FIG. 3 is an enlarged sectional view showing another example
of the penetrating, fixed portion between the tube and the
plate;
[0024] FIG. 4 is an enlarged sectional view showing an embodiment
of the invention as set forth in claim 1;
[0025] FIG. 5 is an enlarged sectional view showing the tube
laser-welded to the plate in FIG. 4;
[0026] FIG. 6 is an enlarged sectional view showing an embodiment
of the invention as set forth in claim 2;
[0027] FIG. 7 is an enlarged sectional view showing the tube
laser-welded to the plate in FIG. 6;
[0028] FIG. 8 is an enlarged sectional view showing an embodiment
of the invention as set forth in claim 3; and
[0029] FIG. 9 is an enlarged sectional view showing an embodiment
of the invention as set forth in claim 4.
BEST MODE FOR CARRYING OUT THE INVENTION
[0030] Now, embodiments of the invention will be described with
reference to the drawings.
[0031] FIGS. 4 and 5 show an embodiment of the invention as set
forth in claim 1 in which the same parts as those in FIGS. 1 to 3
are denoted by the same reference numerals.
[0032] In this embodiment, with regard to an EGR cooler constructed
substantially in the same manner as that described above with
reference to FIG. 1, an end of a tube 3 penetrating a plate 2 is
formed as a tapered portion 14 with diameter gradually increased
toward the side away from a shell 1; the tapered portion 14 is
wholly welded to the plate 2 by laser radiation L from the side
away from the shell 1.
[0033] In this manner, when the end of the tube 3 is formed as the
tapered portion 14 with diameter gradually increased toward the
side away from the shell 1, the inner periphery of the tapered
portion 14 has a shape divergent to the side away from the shell 1
to have a bevel in the form of mortar, so that laser radiation L
from the side away from the shell 1 can be readily carried out
throughout the inner periphery of the tapered portion.
[0034] Then, a resulting laser weld 12 has a high bonding strength,
the weld depth D being increased to an extent corresponding to the
thickness of the plate 2. Moreover, formation of minute crevice
between the tube 3 and a through-hole 13 of the plate 2 is avoided
so that no crevice corrosion occurs.
[0035] Therefore, according to the above embodiment, the laser weld
12 highly resistant against corrosion allows the tube 3 to be
penetratingly fixed to the plate 2 with a high bonding strength,
the weld depth D being increased in comparison with the
conventional cases. Moreover, formation of minute crevice between
the tube 3 and the through-hole 13 of the plate 2 is avoided to
prevent crevice corrosion from occurring. As a result, the cooling
water 9 can be positively prevented from leaking out to the flow
channel of the exhaust gas 10, which eliminates any possibility of
the cooling water 9 being guided to the engine, thereby preventing
engine trouble from occurring.
[0036] FIGS. 6 and 7 show an embodiment of the invention as set
forth in claim 2. In this embodiment, an end of a tube 3 penetrates
into a through-hole 13 of a plate 2 which is formed with a notch 15
on the side toward the shell 1, and is welded to the plate 2 by
laser radiation L from the side away from the shell 1 such that a
laser weld 12 reaches the notch 15.
[0037] In this manner, with the through-hole 13 of the plate 2
being formed with the notch 15 on the side toward the shell 1, an
unwelded portion is left as the notch 15 widely opened to the shell
1 when the end of the tube 3 is welded to the plate 2 by laser
radiation L from the side away from the shell 1 such that the laser
weld 12 reaches the notch 15. As a result, no minute crevice is
formed between the tube 3 and the through-hole 13 of the plate 2
and no crevice corrosion occurs. It is therefore possible to have a
structure which, under the condition that no crevice corrosion
occurs, has the laser intensity increased to such a degree that no
portion melted by the laser radiation L will flow into the tube 3
to narrow the channel, and the weld depth D increased as much as
possible to increase the bonding strength of the laser weld 12 as
high as possible.
[0038] Accordingly, also in this embodiment, formation of minute
crevice between the tube 3 and the through-hole 13 of the plate 2
can be avoided to prevent crevice corrosion from occurring. As a
result, the cooling water 9 can be positively prevented from
leaking out to the flow channel of the exhaust gas 10, which
eliminates the possibility of the cooling water 9 being guided to
the engine, thereby preventing engine trouble from occurring.
[0039] FIG. 8 shows an embodiment of the invention as set forth in
claim 3. In this embodiment, tubes 3 penetrate into and are fixed
to a plate 2 via brazed portions 11 such that an end of the tube 3
extends out from the plate 2 by a predetermined length and the
extending end of the tube 3 penetrates into and is fixed to a sub
plate 16 by laser weld 12. Thus, the sub plate 16 covers the brazed
portions 11.
[0040] Especially in this embodiment, an outer periphery of the
plate 2 is bent toward the axial direction of the tube 3 with a
stepped portion being intervened, and the shell 1 and the bonnet 6
are butt-welded with the outer periphery of the plate 2 being
therebetween.
[0041] Thus, such covering of the plate 2 with the sub plate 16
will cause any condensate containing a vitriolic component, which
may be generated by cooling the exhaust gas 10 in the tube 3 and
may flow out via the outlet of the tube 3, to be isolated by the
sub plate 16 to which the tubes 3 penetratingly fixed via the laser
welds 12 having high resistance against corrosion such that no
condensate contacts the brazed portions 11 of the plate 2. As a
result, corrosion of the brazing filler metal constituting the
brazed portions 11 due to the condensate is positively avoided
while the bonding strength of the tubes 3 to the plate 2 is kept
high by the brazed portions 11. Even if water should leak due to
any crack created in the brazed portions 11, the cooling water 9 is
dammed by the sub plate 16 to stay between the sub plate 16 and the
plate 2.
[0042] Therefore, according to the above embodiment, the brazed
portion 11 can be protected by the sub plate 16 against the
condensate of the exhaust gas 10 while kept high is the bonding
strength of the tubes 3 to the plate 2 by the brazed portions 11.
As a result, corrosion of the brazed portions 11 can be prevented
from occurring. Even if a crack may occur in the brazed portion 11
due to a factor other than the condensate of the exhaust gas 10,
resulting in water leakage, the cooling water 9 can be dammed by
the sub plate 16 to be accumulated between the sub plate 16 and the
plate 2. As a result, the cooling water 9 may not be guided to the
engine, and engine trouble can be prevented from occurring.
[0043] FIG. 9 shows an embodiment of the invention as set forth in
claim 4. Used in this embodiment is a structure with a shell 1 in
the form of a cylindrical container; opposite ends of tubes 3
axially extend in a shell 1 and are penetratingly fixed to opposite
axial ends of the shell 1, respectively; the tubes 3 are increased
in diameter and thickness in comparison with the conventional cases
to increase flow sectional areas and strengths of flow channels,
which allows the number of tubes 3 to be reduced to a required
minimum (for example, three or so). A gas flange 17 is fitted over
tips of the respective tubes 3 extruded out of the shell 1.
[0044] More specifically, in the conventional EGR coolers, the
tubes 3 are decreased in diameter and thickness for effective
cooling of the recirculated exhaust gas 10, which causes a cross
sectional area per tube 3 to be decreased, resulting in necessity
of using a great number of tubes 3 and of using a structure in
which the tubes are supported by the plates 2 for passing of all
the tubes 3 into the hoods 6. By contrast, according to this
embodiment, the tubes 3 are increased in diameter and thickness in
comparison with the conventional cases to increase the cross
sectional areas and the strengths of the flow channels, which
allows the number of tubes 3 to be reduced to a required
minimum.
[0045] However, of course, the shell 1 and tube 3 must be properly
increased in length so as to maintain the cooling efficiency as
before.
[0046] As described above, when the number of tubes 3 is reduced to
a required minimum and the ends of the respective tubes 3 are
penetratingly fixed to the axial opposite ends of the shell 1, line
for recirculation of exhaust gas 10 may be properly branched and
directly connected to the gas flange 17 at the tips of the
respective tubes 3 extruded out of the shell 1. Therefore, even if
condensate containing a vitriolic component is generated due to
cooling of the exhaust gas 10 in the tubes 3, avoided is its
adverse effect such as corrosion on the penetrating fixed portions
of the tubes 3 to the shell 1. If a crack should be generated on
the penetrating fixed portions of the tubes 3 to the shell 1 to
cause water leakage, the leaked, cooling water 9 leaks out only
outside of the shell 1 and is prevented from intruding into the
flow channels of the exhaust gas 10.
[0047] Therefore, according to the above embodiment, it can be
positively avoided that the condensate of the exhaust gas 10 has an
adverse effect such as corrosion on the penetrating, fixed portions
of the tubes 3 to the shell 1. Moreover, even if a crack should
occur in the penetrating, fixed portions due to a factor other than
the condensate of the exhaust gas 10 to cause water leakage, the
leaked cooling water 9 can be positively prevented from intruding
into the flow channels of the exhaust gas 10. As a result, the
cooling water 9 may not be guided to the engine and engine trouble
is prevented from occurring.
[0048] It is to be understood that the EGR cooler of the invention
is not limited to the above embodiments and that various changes
and modifications may be made without departing from the scope of
the invention. For example, the outlet side of the exhaust gas is
shown in the drawings; however, similar construction may be
applicable on the inlet side of the exhaust gas.
INDUSTRIAL APPLICABILITY
[0049] As described above, the EGR cooler according to the
invention is suitable for use in an EGR apparatus for recirculating
exhaust gas from the engine to suppress generation of nitrogen
oxides. claims
* * * * *