Heat exchange – Structural installation – Engine
Reexamination Certificate
2003-02-03
2004-02-03
Ford, John K. (Department: 3743)
Heat exchange
Structural installation
Engine
C165S158000, C165S174000, C165S179000, C165S184000, C123S568120, C060S278000, C060S320000
Reexamination Certificate
active
06684938
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority to Japanese Application No. 11-11776, filed Jan. 20, 1999, Japanese Application No. 11-158053, filed Jun. 4, 1999, and Japanese Application No. 11-251546, filed Sep. 6, 1999. The present application also claims priority to the U.S. application Ser. No. 09/889,389, filed Jul. 17, 2001, now abandoned. The contents of those applications are incorporated herein by reference in their entirety.
TECHNICAL FIELD
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
FIG. 1
is a sectional view showing a conventional EGR cooler in which reference numeral
1
denotes a cylindrical shell with axial opposite ends to which plates
2
are respectively fixed so as 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 in parallel with axial extension x of the shell
1
. The tubes
3
extend axially within the shell
1
.
The shell
1
is provided with cooling water inlet
4
in the vicinity of one end of the shell
1
and with cooling water outlet
5
in the vicinity of the other end of the shell
1
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
.
The respective plates
2
have, on their sides away from the shell
1
, hoods
6
A and
6
B fixed to the plates
2
so as to enclose end faces of the plates
2
. The one and the other hoods
6
A and
6
B 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
A, is cooled, during passage through the tubes
3
, by means of heat exchange with the cooling water
9
flowing outside of the tubes
3
and is discharged to the other hood
6
B to be recirculated via the exhaust gas outlet
8
to the engine.
However, such conventional EGR cooler has a drawback of poor heat exchange efficiency since the exhaust gas
10
flows straight in the tubes
3
and is insufficiently contacted with inner peripheries of the tubes
3
.
Moreover, as shown in
FIG. 2
in an enlarged scale, the one hood
6
A is composed of a tapered portion
6
x
divergent in a linear contour from the exhaust gas inlet
7
toward the shell
1
and a cylindrical portion
6
y
with substantially the same same diameter as that of the shell
1
. With such construction, the flow of the exhaust gas
10
introduced via the exhaust gas inlet
7
tends to come off from the inner periphery of the tapered portion
6
x
to generate turbulence inside from the tapered portion
6
x
to the cylindrical portion
6
y,
leading to difficulty in introduction of the exhaust gas
10
into the tubes
3
arranged on the circumferential side of the plate
2
. Such non-uniform distribution of the exhaust gas
10
to the respective tubes
3
also adversely affects on heat exchange efficiency and causes a fear that the tubes
3
on the central side may have higher temperature than that of the tubes
3
on the circumferential side, leading to local thermal deformation.
On the other hand, as shown in
FIG. 3
in an enlarged scale, the other hood
6
B is formed in the same manner as the one hood
6
A described above, so that the exhaust gas
10
discharged out of the tubes
3
on the circumferential side collides against the tapered portion
6
x
of the hood
6
A and is abruptly changed in direction of flow, which causes pressure increase of outlet portions of the tubes
3
on the circumferential side, which in turn provides ventilation resistance to the exhaust gas
10
in the tubes
3
on the circumferential side, resulting in much more difficulty in introducing the exhaust gas
10
to the tubes
3
on the circumferential side. This cause also results in non-uniform distribution of the exhaust gas
10
to the respective tubes
3
to thereby deteriorate the heat exchange efficiency and results in a fear that the temperature of the tubes
3
on the central side may be increased more than that of the tubes
3
on the circumferential side, leading to local thermal deformation.
Moreover, as shown in
FIG. 4
, the conventional arrangement of the tubes
3
is such that tubes
3
are arranged in staggered layout based on triangle as shown by two-dot chain line in the figure, which provides a relatively large clearance between the cylindrical shell
1
and the tubes
3
on the circumferential side. As a result, the cooling water
9
introduced via the cooling water inlet
4
tends to flow preferentially on the circumferential side where the flow resistance is low whereas the cooling water
9
flows insufficiently on the central side where the tubes
3
are arranged closely. Also due to this cause, the heat exchange efficiency in the tubes
3
on the central side is deteriorated than that in the tubes
3
on the circumferential side, causing a fear that the temperature of the tubes
3
on the central side may be increased more than that of the tubes
3
on the circumferential side to thereby cause local thermal deformation.
Furthermore, in the conventional EGR cooler described above, there is also a disadvantage that the cooling water
9
supplied via the cooling water inlet
4
to the shell
1
flows toward the cooling water outlet
5
non-uniformly with respect to cross section of the shell
1
. As shown by a route
12
in
FIG. 1
, prevailing is the flow which, after flowing into the shell
1
via the cooling water inlet
4
, crooks catercorner toward the cooling water outlet
5
to thereby result in stagnation of the cooling water
9
in the vicinity of corners in the shell
1
opposed to the cooling water inlet and outlet
4
and
5
, respectively, thus providing cooling water stagnant areas
13
; as a result, arises a problem that the heat exchange efficiency in these areas decreases. In particular, at a position diametrically opposed to the cooling water inlet
4
where the hot exhaust gas
10
is introduced, there is a fear that the tubes
3
may locally have high temperature in the vicinity of the cooling water stagnant area
13
, causing thermal deformation.
FIGS. 5 and 6
show a further conventional EGR cooler. With the EGR cooler shown here, a shell
1
is formed in a box shape flattened longitudinally (perpendicular to the axial extension x of the shell
1
) due to issues raised in mounting it on a vehicle. The respective hoods
6
A and
6
B are diverged outwardly of the longer sides of the end faces of the shell
1
(vertically in the example shown in the figure) from the exhaust gas inlet and outlet
7
and
8
, respectively, to the shell
1
so as to wholly enclose the end faces of the respective plates
2
.
In the EGR cooler formed in such flattened box shape, the exhaust gas
10
introduced via the exhaust gas inlet
7
into the hood
6
A tends to flow straight in the flow direction at the time of being introduced and is hardly diffused outwardly of the longer sides of the end face of the shell
1
; also arises a disadvantage that the gas flow tends to come off in the hood
6
A in the vicinity of the exhaust gas inlet
7
to readily cause turbulence. As a result, there is a fear that the exhaust gas
10
may flow one-sidedly into the tubes
3
centrally of the longer side of the end face of the shell
1
so that the temperature of the tubes
3
in question may increase mainly on the inlet side of the exhaust gas
10
, thereby causing local thermal deformation, whereas the amount of the exhaust gas
10
distributed to the tubes
3
outwardly of the longer sides of the end face of the shell
1
is insufficient, causing a problem that the heat exchange efficiency in this area decreases.
FIG. 7
shows a still further conventional EGR cooler. With this EGR cooler shown here, the hoods are omitted due to issues raised in mounting
Inoue Katsuji
Nakagome Keiichi
Tsujita Makoto
Yamashita Yoji
Ford John K.
Hino Motors Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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