U.S. patent application number 13/203532 was filed with the patent office on 2011-12-22 for egr cooler.
This patent application is currently assigned to KOMATSU LTD.. Invention is credited to Kazuo Furuhashi, Keiichi Inaba, Taisei Okubo, Hiroshi Tsuda.
Application Number | 20110308778 13/203532 |
Document ID | / |
Family ID | 42665528 |
Filed Date | 2011-12-22 |
United States Patent
Application |
20110308778 |
Kind Code |
A1 |
Tsuda; Hiroshi ; et
al. |
December 22, 2011 |
EGR COOLER
Abstract
An EGR cooler includes: a casing in which cooling water flows; a
plurality of tubes in which exhaust gas flows, the plurality of
tubes being housed in the casing; a header plate to which ends of
the plurality of tubes are bonded, the header plate being bonded to
an end of the casing; an inlet tank into which the exhaust gas is
introduced, the inlet tank being bonded to the end of the casing;
and a shielding member being provided in the inlet tank to shield a
circumferential wall of the inlet tank from the introduced exhaust
gas.
Inventors: |
Tsuda; Hiroshi; (Ibaraki,
JP) ; Okubo; Taisei; (Tochigi, JP) ;
Furuhashi; Kazuo; (Tochigi, JP) ; Inaba; Keiichi;
(Ibaraki, JP) |
Assignee: |
KOMATSU LTD.
Tokyo
JP
|
Family ID: |
42665528 |
Appl. No.: |
13/203532 |
Filed: |
February 23, 2010 |
PCT Filed: |
February 23, 2010 |
PCT NO: |
PCT/JP2010/052766 |
371 Date: |
August 26, 2011 |
Current U.S.
Class: |
165/157 |
Current CPC
Class: |
F02M 26/32 20160201 |
Class at
Publication: |
165/157 |
International
Class: |
F28D 7/10 20060101
F28D007/10 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 27, 2009 |
JP |
2009-045584 |
Claims
1. An EGR cooler comprising: a casing in which cooling water flows;
a plurality of tubes in which exhaust gas flows, the plurality of
tubes being housed in the casing; a header plate to which ends of
the plurality of tubes are bonded, the header plate being bonded to
an end of the casing; an inlet tank into which the exhaust gas is
introduced, the inlet tank being bonded to the end of the casing;
and a shielding member being provided in the inlet tank to shield a
circumferential wall of the inlet tank from the introduced exhaust
gas, the shielding member being fixed to the inlet tank with a
clearance being formed between the shielding member and the header
plate.
2. (canceled)
3. (canceled)
4. The EGR cooler according to claim 1, wherein an opening of an
exhaust gas outlet of the shielding member covers entrances of all
the tubes.
5. The EGR cooler according to claim 1, wherein the shielding
member is gradually widened toward an exhaust gas outlet.
6. The EGR cooler according to claim 4, wherein, the opening of the
exhaust gas outlet is provided with a cylindrical outlet end having
a diameter substantially constant along a flow direction of the
exhaust gas.
Description
TECHNICAL FIELD
[0001] The present invention relates to an EGR (Exhaust Gas
Recirculation) cooler.
BACKGROUND ART
[0002] Some typical EGR systems usable in a diesel engine are
provided with an EGR cooler for cooling exhaust gas to be returned
to an air-intake side. The EGR cooler includes a plurality of tubes
through which exhaust gas passes and a casing (sometimes called as
a "shell") in which these tubes are housed. The casing has a first
end that defines an inlet through which cooling water is introduced
and a second end that defines an outlet through which the cooling
water is discharged.
[0003] The casing is formed in a cylindrical shape. An opening of
the first end of the casing is provided with an inlet tank into
which exhaust gas is introduced and from which the exhaust gas is
discharged into the tubes. An end of the second end of the casing
is provided with an outlet tank from which the exhaust gas from the
tubes is discharged. Both ends of each tube in the casing are fixed
to header plates by brazing or the like. The header plates are
fixed to the inner circumferential surface of the casing by welding
to close the openings of the casing. In other words, in the casing,
both ends of which are closed by the header plates, cooling water
flows outside the plurality of tubes while the exhaust gas flows
inside the tubes.
[0004] In the inlet tank, since one surface of the header plate,
i.e., the surface opposed to the inlet tank, is directly exposed to
the exhaust gas having a high temperature, a brazed portion between
the header plate and each tube is heated to a high temperature by
the exhaust gas, which lowers the bonding strength therebetween and
thus causes a crack in the brazed portion.
[0005] In view of the above, in order to prevent the header plate
from being directly exposed to the exhaust gas, there has been
suggested an arrangement of an EGR cooler in which a shielding
plate in substantially the same shape as that of the header plate
is provided at the upstream side of the header plate and the tube
end is extended to the shielding plate (e.g., Patent Literature
1).
[0006] According to this arrangement, since a double-layered
structure is provided between the inlet tank and the inner side of
the casing, the header plate is not exposed to the exhaust gas
having a high temperature introduced into the inlet tank and thus
the temperature of the brazed portion to each tube is restrained
from becoming high. Thus, the brazed portion is unlikely to have
any crack and leakage of the cooling water from the casing can be
prevented.
CITATION LIST
[0007] Patent Literature
[0008] Patent Literature 1: JP-A-2000-45882
SUMMARY OF THE INVENTION
[0009] Problems to be Solved by the Invention
[0010] In the EGR cooler as disclosed in the above patent
literature, although the brazed portion can be prevented from being
directly exposed to the exhaust gas, a circumferential wall
(bonnet) in the inlet tank is still directly exposed to the exhaust
gas. Thus, the inlet tank suffers from a large outward thermal
expansion of the circumferential wall, which results in a
difference in thermal expansion between the inlet tank and the
casing and the header plate to which the inlet tank is fixed. In
other words, while the temperatures of the casing and the header
plate are not so increased with a resulting small degree of thermal
expansion because the majority thereof is exposed to the cooling
water, the circumferential wall of the inlet tank suffers from a
considerable thermal expansion because the circumferential wall is
exposed only to the exhaust gas without being exposed to the
cooling water.
[0011] Thus, at the bonding portion between the inlet tank and the
casing and the header plate, the considerable thermal expansion of
the inlet tank causes the outward deformation of the casing and the
header plate. As a result of this deformation, a high stress is
generated to cause a crack in the bonding portion between the
header plate and each tube.
[0012] An object of the invention is to provide an EGR cooler
capable of restraining thermal deformation resulting from a large
difference in thermal expansion as compared with an inlet tank to
prevent occurrence of a crack.
[0013] Means for Solving the Problems
[0014] According to an aspect of the invention, an EGR cooler
includes: a casing in which cooling water flows; a plurality of
tubes in which exhaust gas flows, the plurality of tubes being
housed in the casing; a header plate to which ends of the plurality
of tubes are bonded, the header plate being bonded to an end of the
casing; an inlet tank into which the exhaust gas is introduced, the
inlet tank being bonded to the end of the casing; and a shielding
member being provided in the inlet tank to shield a circumferential
wall of the inlet tank from the introduced exhaust gas.
[0015] In the EGR cooler, it is preferable that the shielding
member is provided in the inlet tank.
[0016] In the EGR cooler, it is preferable that a clearance is
formed between the shielding member and the header plate.
[0017] In the EGR cooler, it is preferable that an opening of an
exhaust gas outlet of the shielding member covers entrances of all
the tubes.
[0018] In the EGR cooler, it is preferable that the shielding
member is gradually widened toward an exhaust gas outlet.
[0019] In the EGR cooler, it is preferable that the opening of the
exhaust gas outlet is provided with a cylindrical outlet end having
a diameter substantially constant along a flow direction of the
exhaust gas.
[0020] According to the aspect of the invention, the shielding
member is provided in the inlet tank. Since the exhaust gas having
a high temperature introduced into the inlet tank is unlikely to
contact with the circumferential wall of the inlet tank, the
outward thermal expansion of the circumferential wall is
restrained. Thus, the casing and the header plate bonded to the
inlet tank are not affected by the thermal expansion of the inlet
tank, so that a large deformation in the casing and header plate is
unlikely to occur. As a result, generation of a large stress is
prevented at the bonding portion between the header plate and each
tube and thus no crack occurs.
[0021] According to the arrangement in which the shielding member
is provided in the inlet tank, since a core, i.e., the header plate
and the tubes, is not provided with the shielding member, the front
and rear configurations of the core are identical. Thus, the core
is not inadvertently installed back to front in a casing whose
front and rear sides are not invertible, which facilitates an
assembling process.
[0022] With the clearance formed between the shielding member and
the header plate, even when the shielding member is exposed to the
exhaust gas and thus thermally expanded, the shielding member is
prevented from contacting with the header plate. Thus, the header
plate is prevented from being pressed to generate stress.
[0023] According to the arrangement in which the opening of the
outlet of the shielding member is sufficiently large to cover the
ends of all the tubes, the exhaust gas from the shielding member
can be equally fed into the tubes, thereby cooling the exhaust gas
with an improved efficiency.
[0024] With the shielding member gradually widened toward the
outlet, even when the inlet casing has a small opening area at the
inlet thereof while having a large opening area at the outlet
thereof, the exhaust gas can be reliably guided into the tubes,
thereby providing a favorable cooling efficiency.
[0025] According to the arrangement in which the outlet end for
restraining diffusion is provided to the outlet of the shielding
member, the exhaust gas can be fed into the tubes without
diffusion. Thus, a flow of the exhaust gas becomes smooth, so that
cooling efficiency can be further improved.
BRIEF DESCRIPTION OF DRAWINGS
[0026] FIG. 1 is a sectional view of an EGR cooler according to an
exemplary embodiment of the invention along a flow direction of
exhaust gas.
[0027] FIG. 2 is a sectional view taken along the line II-II in
FIG. 1.
[0028] FIG. 3 is an enlarged view showing a primary part of the EGR
cooler.
[0029] FIG. 4 is a view showing components used in the EGR
cooler.
[0030] FIG. 5 is a sectional perspective view showing the
components.
[0031] FIG. 6 is a sectional view showing a modification of the
invention.
DESCRIPTION OF THE EXEMPLARY EMBODIMENT
[0032] An exemplary embodiment of the invention will be described
below with reference to the attached drawings.
[0033] FIG. 1 is a sectional view of an EGR cooler 10 according to
this exemplary embodiment along a flow direction of exhaust gas
(see a hatched arrow). FIG. 2 is a sectional view taken along the
line II-II in FIG. 1. FIG. 3 is an enlarged view showing a primary
part of the EGR cooler 10. FIG. 4 is a view showing components used
in the EGR cooler 10 and FIG. 5 is a sectional perspective view
thereof In the following description, "front" means the upstream
side of a flow of exhaust gas and "rear" means the downstream side.
Further, "right and left" means right and left when viewed from the
front.
[0034] Referring to FIG. 1, the EGR cooler 10 includes: a
cylindrical casing 11; a plurality of flattened tubes 12 for
exhaust gas circulation housed in the casing 11; opposed header
plates 13 to which the ends of the tubes are bonded; and an inlet
tank 14 and an outlet tank 15 bonded to the casing 11 via the
header plates 13, respectively. The inlet tank 14 is provided with
an attachment flange 16 having an inflow opening 16A. The outlet
tank 15 is provided with an attachment flange 17 having an outflow
opening 17A.
[0035] Cylindrical projections 18 are formed at first and second
ends of the casing 11, the projections 18 each having a diameter
slightly larger than the diameter of a center body of the casing
11. Provided on the lower side of front one of the projections 18
is an inflow opening 21 through which cooling water (see an
outlined arrow) is introduced into the casing 11. Provided on the
upper side of rear one of the projections 18 is an outflow opening
22 through which cooling water is discharged from the casing 11.
Provided on the top of the projection 18 having the inflow opening
21 for cooling water are a pair of degassing holes 23
circumferentially arranged at a distance corresponding to a
predetermined angle (only one of them being shown in FIG. 1).
[0036] Referring to FIG. 2, gaps between opposed surfaces of the
tubes 12 arranged side by side serve as cooling water passages 24
through which cooling water passes. All the cooling water passages
24 are preferably designed to have the same width. According to
this exemplary embodiment in which the tubes 12 are arranged side
by side in a right-and-left direction, the inflow opening 21 for
cooling water (FIG. 1) is located on the lower side of the
projection 18 so that cooling water from the inflow opening 21
immediately enters the cooling water passages 24. In view of the
above, the inflow opening 21 is preferably located at the lower
central portion of the projection 18 as in this exemplary
embodiment. In other words, according to this exemplary embodiment,
immediately after cooling water is introduced through the inflow
opening 21, a flow direction of the cooling water coincides with
the vertical direction of the tubes 12, so that a flow of the
cooling water is not hampered.
[0037] Further, according to this exemplary embodiment, the
surfaces of the tubes 12 are partly brazed to one another at
dot-like projections while the header plates 13 are brazed to the
ends of the tubes 12 (the detailed illustration thereof is
omitted). A combination including the tubes 12 and the header
plates 13 serves as a core 25.
[0038] For assembling the EGR cooler 10, the core 25 is produced in
advance by brazing the tubes 12 to one another and then brazing the
header plates 13 to the tubes 12. The core 25 is housed in the
casing 11 provided by upper-and-lower or right-and-left halved
structures, namely casing halves 11A and 11B. The casing halves 11A
and 11B are bonded to each other by welding or the like. The tanks
14 and 15 are attached to the ends of the casing 11 (header plates
13) by welding or the like, respectively.
[0039] For the attachment, as shown in FIG. 3 in an enlarged
manner, cylindrical portions 131 formed on the outer circumferences
of the header plates 13 are fitted in opening ends 111 of the
casing 11, respectively, while opening ends 141 and 151 of the
tanks 14 and 15 are fitted in the cylindrical portions 131,
respectively, and all of them are bonded together by welding.
Incidentally, according to this exemplary embodiment, the contour
of each of the opening ends 111, 141 and 151 and the cylindrical
portions 131 is not a circle but a slightly square-like deformed
shape, which is exemplified by the contour of the opening end 141
of the inlet tank 14 in FIG. 4.
[0040] A detailed description will be made below on the inlet tank
14 used in this exemplary embodiment with reference to FIGS. 1, 4
and 5. The inlet tank 14 includes: a cylindrical inlet end 142
fitted in the inflow opening 16A of the attachment flange 16; the
opening end 141 that defines the outlet; and a circumferential wall
143 that connects the ends 141 and 142 to each other. The
circumferential wall 143 is gradually widened from the inlet end
142 toward the opening end 141.
[0041] A shielding member 19 is provided in the inlet tank 14 so
that an inner surface of the circumferential wall 143 is unlikely
to be exposed to the introduced exhaust gas. The shielding member
19 includes: a cylindrical inlet end 192 fitted in the inlet end
142 of the inlet tank 14 and welded thereto; an outlet end 191 with
a square contour opened toward the rear side; and a circumferential
wall 193 that connects the ends 191 and 192 to each other.
[0042] The contour of the outlet end 191 may be not a square but a
circle or the like or may be appropriately determined in accordance
with the sectional shape of the tubes 12, the shape of the end of
the core 25, the shape of the opening end 141 of the inlet tank 14,
or the like.
[0043] The opening area of the outlet end 191 is sufficiently large
to entirely cover the entrances of all the tubes 12 arranged side
by side, so that the introduced exhaust gas is equally fed into the
tubes 12. The outlet end 191 is formed in the shape of a straight
cylinder having a constant diameter along the flow direction of the
exhaust gas (from front to rear) to allow a favorable feeding of
the exhaust gas from the shielding member 19 into the tubes 12
without diffusion.
[0044] A slight clearance S is formed between the outlet end 191
and the header plate 13 (in FIG. 1, the clearance S is exaggerated
to be easily visible). The clearance S is desirably narrowed not
only for preventing the exhaust gas from flowing toward the
circumferential wall 143 of the inlet tank 14 but also for smoothly
directing the exhaust gas into the tubes 12. In view of the above,
according to this exemplary embodiment, as long as the shielding
member 19 does not contact with the header plate 13 even when the
shielding member 19 is thermally expanded due to exposure to the
exhaust gas having a high temperature, the clearance S is narrowed
as much as possible.
[0045] The circumferential wall 193 is gradually widened from the
inlet end 192 toward the outlet end 191. In other words, the
opening area of the outlet end 191 is larger than the opening area
of the inlet end 192. Incidentally, the shape of the
circumferential wall 193 may be determined in accordance with the
size of the inflow opening 16A. For instance, when the inflow
opening 16A has a larger opening area and is widened with a
dimension substantially equal to the vertical dimension of the
tubes 12 in the figure, the circumferential wall 193 is formed in
the shape of a straight cylinder identical to those of the inlet
end 192 and the outlet end 191.
[0046] In the EGR cooler 10 according to this exemplary embodiment
as described above, the exhaust gas having a high temperature
introduced into the inlet tank 14 through the inflow opening 16A is
guided by the shielding member 19 to be fed into the tubes 12 while
hardly contacting with the circumferential wall 143. The exhaust
gas passing through the tubes 12 is cooled by the cooling water
flowing outside the tubes 12 in the casing 11 and is discharged
into the outlet tank 15. The exhaust gas is returned to an
air-intake side of the engine.
[0047] In the above manner, the exhaust gas is unlikely to contact
with the circumferential wall 143 in the inlet tank 14, so that the
thermal expansion of the circumferential wall 143 shown by a
two-dot chain line in FIG. 3 can be significantly reduced to
prevent deformation in the casing 11 and the header plate 13. In
particular, prevention of deformation in the header plate 13
results in restraint of generation of stress at the bonding portion
between the header plate 13 and each of the tubes 12 and thus
prevention of a crack in an outer bonding portion.
[0048] It should be appreciated that the scope of the invention is
not limited to the above exemplary embodiment but modifications and
improvements that are compatible with an object of the invention
are included within the scope of the invention.
[0049] For instance, although the inlet tank 14, the attachment
flange 16 and the shielding member 19 are provided as separate
bodies and are bonded together by welding or the like according to
the above exemplary embodiment, these components may be molded into
one piece component as shown in FIG. 6.
[0050] Although the shielding member 19 is provided in the inlet
tank 14 according to the above exemplary embodiment, the shielding
member 19 may be provided to the header plate 13.
[0051] The shielding member 19 may have a configuration in which
the straight cylindrical outlet end 191 according to the above
exemplary embodiment is omitted and the circumferential wall 143 is
directly opened at the rear without departing the scope of the
invention. However, the outlet end 191 is preferably provided
because the outlet end 191 serves to efficiently guide a flow of
the exhaust gas into the tubes 12.
[0052] Although the outlet end 191 has an opening area sufficiently
large to cover the ends of all the tubes 12 according to the above
exemplary embodiment, the outlet end 191 may have an opening area
insufficiently large to cover the ends of all the tubes 12 without
departing the scope of the invention. However, the opening area is
preferably sufficiently large to cover the ends of all the tubes 12
because such an opening area serves to equally feed the exhaust gas
into the tubes 12 as described above and thus cooling efficiency
can be improved.
[0053] Further, since the shape of the circumferential wall 193 is
optional, instead of the linearly widened shape according to the
above exemplary embodiment, a round shape may be selected such that
the circumferential wall 193 is curved as a whole. In other words,
the shape of the circumferential wall 193 is appropriately
selectable in implementation of the invention.
[0054] Although the above exemplary embodiment uses the flattened
tubes 12 as the tubes according to the invention, tubes with a
circular cross section may alternatively be used. In other words,
tubes of any shape may be usable. When tubes with a circular cross
section are used, it is preferable that the outlet end 191 of the
shielding member 19 likewise has a circular shape.
[0055] Further, since the configuration of the header plate 13 is
also optional, the cylindrical portion 131 as in the above
exemplary embodiment may be omitted. In other words, the header
plate 13 may be formed in a plate-like shape and bonded to the
inner circumferential surface of the casing 11 at the outer
circumference thereof Even in such a configuration, the thermal
expansion of the circumferential wall 143 of the inlet tank 14 can
cause deformation in the header plate 13 along with deformation in
the casing 11 and thus a large stress is likely to be generated at
the bonding section between the header plate 13 and each of the
tubes 12. Accordingly, the invention is effectively applicable to
prevent generation of stress.
INDUSTRIAL APPLICABILITY
[0056] The invention is suitably applicable to construction
machines, transport vehicles and various industrial machines in
which an engine having an EGR system is mounted.
EXPLANATION OF CODES
[0057] 10...EGR cooler, 11...casing, 12... tube, 13...header plate,
14... inlet tank, 19...shielding member, 191...outlet end, S...
clearance
* * * * *