U.S. patent application number 11/474866 was filed with the patent office on 2006-12-28 for heat exchange apparatus for exhaust gas.
This patent application is currently assigned to DENSO Corporation. Invention is credited to Takayuki Hayashi.
Application Number | 20060288694 11/474866 |
Document ID | / |
Family ID | 37563203 |
Filed Date | 2006-12-28 |
United States Patent
Application |
20060288694 |
Kind Code |
A1 |
Hayashi; Takayuki |
December 28, 2006 |
Heat exchange apparatus for exhaust gas
Abstract
In an EGR module including a tank, an EGR gas cooler arranged on
the downstream side of the flow of the exhaust gas inside the tank,
a bypass arranged in parallel with the EGR gas cooler and an
exhaust gas flow rate ratio regulating valve arranged on the
downstream side of the flow of the exhaust gas of the EGR gas
cooler and the bypass, wherein the inlet port is arranged at a
position of the tank at which at least an area of a portion of the
inlet port opposing the bypass is greater than an area of a portion
of the inlet port opposing the EGR gas cooler.
Inventors: |
Hayashi; Takayuki;
(Nagoya-city, JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
DENSO Corporation
Kariya-city
JP
|
Family ID: |
37563203 |
Appl. No.: |
11/474866 |
Filed: |
June 26, 2006 |
Current U.S.
Class: |
60/298 ;
60/320 |
Current CPC
Class: |
F02M 26/28 20160201;
F02M 26/73 20160201; F28D 21/0003 20130101; F02M 26/26 20160201;
F28F 9/0275 20130101; F02M 26/51 20160201 |
Class at
Publication: |
060/298 ;
060/320 |
International
Class: |
F01N 3/00 20060101
F01N003/00; F01N 5/02 20060101 F01N005/02; F01N 3/02 20060101
F01N003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2005 |
JP |
2005-188339 |
Claims
1. A heat exchange apparatus for an exhaust gas including: a tank
which has an inlet port through which an exhaust gas generated by
combustion passes and into which said exhaust gas flows from said
inlet port; a heat exchanger for an exhaust gas connected to said
tank on the downstream side of the flow of said exhaust gas inside
said tank, for executing heat exchange between said exhaust gas
flowing from inside said tank and a cooling fluid; a bypass
connected to said tank on the downstream side of the flow of said
exhaust gas inside said tank, for said exhaust gas inside said tank
bypass said exhaust gas heat exchanger; and an exhaust gas flow
rate ratio regulating valve arranged on the downstream side of the
flow of said exhaust gas of said exhaust gas heat exchanger and
said bypass, for regulating a ratio of the flow rate of said
exhaust gas flowing inside said exhaust gas heat exchanger and the
flow rate of said exhaust gas flowing inside said bypass; wherein
said inlet port is arranged at a position of said tank at which at
least an area of a portion of said inlet port opposing said bypass
is greater than an area of a portion of said inlet port opposing
said exhaust gas heat exchanger.
2. A heat exchange apparatus for an exhaust gas according to claim
1, wherein said inlet port is formed in said tank at a position
opposing only said bypass of said exhaust gas heat exchanger and
said bypass.
3. A heat exchange apparatus for an exhaust gas according to claim
2, wherein said inlet port is formed in said tank at a position at
which an open end of said inlet port positioned on the side of said
exhaust gas heat exchanger and an open end of said bypass
positioned on the side of aid exhaust gas heat exchanger oppose
each other.
4. A heat exchange apparatus for an exhaust gas according to claim
1, wherein said tank includes a first outlet port to which said
heat exchanger is connected, for guiding said exhaust gas inside
said tank to said exhaust gas heat exchanger, and a second outlet
port to which said bypass is connected, for guiding said exhaust
gas inside said tank into said bypass.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a heat exchange apparatus, for an
exhaust gas, that performs heat exchange between an exhaust gas,
resulting from the combustion in an internal combustion engine, and
a cooling fluid and is applied to an exhaust gas recirculation
apparatus generally called an EGR apparatus.
[0003] 2. Description of the Related Art
[0004] An apparatus having an EGR gas cooler and bypass is known as
a heat exchange apparatus for an exhaust gas, as will be later
described (refer to the pamphlet of International Publication No.
02/10575, for example), and one construction is the one shown in
FIG. 6 (refer to FIG. 1 of Japanese Unexamined Patent Publication
(Kokai) No. 2005-98278, for an example). Incidentally, the heat
exchange apparatus for the exhaust gas will be hereinafter called
an "EGR module 7". In FIG. 6, reference numerals the same as in
FIG. 2 are used to identify similar constituent members in the EGR
module 7 according to the later-appearing first embodiment shown in
FIG. 1.
[0005] The EGR module 7 shown in FIG. 6 includes a tank 13, an EGR
gas cooler 14 arranged inside the tank 13 on the downstream side of
the flow of an exhaust gas, that is, on the right side in the
drawing, bypass 15 arranged in parallel with the EGR gas cooler 14
and an exhaust gas flow rate ratio regulating valve 18 arranged on
the downstream side of the flow of the exhaust gas of the EGR gas
cooler 14 and the bypass 15, that is, on the right side in the
drawing.
[0006] Here, the EGR gas cooler 14 is a heat exchanger for an
exhaust gas that conducts heat exchange between an exhaust gas,
generated by combustion, and a cooling fluid in order to reduce the
generation of nitrogen oxides (NOx) by lowering the EGR gas
temperature inside an internal combustion engine.
[0007] The EGR gas cooler 14 is mainly constituted by a casing 21,
a plurality of exhaust tubes 22 which is accommodated inside the
casing 21 and through which the exhaust gas flows, and an inlet
side core plate 34 that holds one of the ends of each exhaust tube
22 and separates the inside of the tank 13 from the inside of the
casing 21. The periphery of the plurality of exhaust tubes 22
inside the casing 21 is a cooling medium passage 23 through which a
cooling fluid such as cooling water flows.
[0008] The bypass 15 is pipe that makes the exhaust gas flowing
into the EGR module 7 to bypass the EGR gas cooler 14 and allows
the exhaust gas to flow out from the EGR module 7. To reduce the
number of components, this bypass 15 is inserted into a fitting
port for the bypass 15 formed in an inlet side core plate 34
extended to the side of the bypass 15 and is bonded to the inlet
side core plate 34.
[0009] The exhaust gas exhausted from the internal combustion
engine flows into the tank 13 and this tank 13 distributes the
flowing exhaust gas into the EGR gas cooler 14 and the bypass 15.
The tank 13 has one inlet port 13a so disposed as to permit the
inflow of the exhaust gas and one outlet port 13j positioned on the
opposite side to the inlet port 13a and so arranged as to exhaust
the exhaust gas inside the tank 13. The inlet side core plate 34 is
bonded to this outlet port 13j.
[0010] The inlet port 13a of the tank 13 is so arranged as to
oppose both the EGR gas cooler 14 and the bypass 15 and is
positioned closer to the EGR gas cooler 14 than to the bypass 15.
In other words, the area of the portion 13h of the opening area of
the inlet port 13a opposing the bypass 15 is smaller than the area
of the portion 13i opposing the EGR gas cooler 14.
[0011] This is because the EGR module 7 is mainly directed to cool
the exhaust gas and to suppress the pressure loss when the exhaust
gas passes through the inside of the EGR gas cooler 14.
[0012] In the EGR gas module 7 having such a construction, control
by the exhaust gas flow rate ratio regulating valve 18 makes it
possible to introduce the exhaust gas into the EGR gas cooler 14
when the combustion temperature is high inside the engine, for
example, and to supply the cooled exhaust gas into the engine, and
to introduce the exhaust gas into the bypass 15 and to supply the
warm exhaust gas into the engine when the combustion temperature
inside the engine is low.
[0013] Incidentally, the reason why the warm exhaust gas is
circulated and supplied into the engine when the combustion
temperature inside the engine is low is because HC (hydrocarbons)
are likely to occur when the combustion temperature inside the
engine is low, such as at the start of the engine, and the
generation of HC is suppressed by keeping the combustion
temperature at a suitable temperature.
[0014] To immediately set the combustion temperature to the
suitable temperature, the exhaust gas to be circulated and supplied
into the engine preferably has a temperature that is as high as
possible. Therefore, when the exhaust gas is not heated by heating
means, the heat loss of the exhaust gas flowing through the bypass
15 is preferably small in the EGR module 7 having the construction
described above.
[0015] Nonetheless, the heat loss of the exhaust gas flowing
through the bypass 15 is great in the EGR module 7 having the
construction described above for the following reasons.
[0016] One of the reasons is as follows. When the exhaust gas is
allowed to flow through only the bypass 15, the exhaust gas flowing
into the tank 13 strikes the inlet side core plate 34 of the EGR
gas cooler 14 as indicated by arrow of dash line in FIG. 6 and then
flows inside the bypass 5.
[0017] In other words, of the inlet side core plate 34, the portion
that constitutes the EGR gas cooler 14 keeps contact with the
cooling medium inside the casing 21 and its temperature is low.
Therefore, when the exhaust gas strikes the portion of the inlet
side core plate 34 constituting the EGR gas cooler 14, the exhaust
gas is deprived of its heat by the inlet side core plate 34.
[0018] Another reason is as follows. In the EGR module 7 having the
construction described above, the bypass 15 is fixed to the inlet
side core plate 34 of the EGR gas cooler 14. Therefore, when the
exhaust gas passes through the inlet side core plate 34, the heat
of the exhaust gas moves to the portion of the inlet side core
plate 34 connected to the bypass 15 and further moves to the
portion constituting the EGR gas cooler 14 as indicated by a solid
line arrow in FIG. 6.
SUMMARY OF THE INVENTION
[0019] In view of the problems described above, the present
invention aims at providing a heat exchange apparatus for an
exhaust gas that can reduce the heat loss from an exhaust gas
flowing through a bypass in comparison with a heat exchange
apparatus for an exhaust gas according to the prior art.
[0020] To accomplish the object described above, the present
invention has a feature in that at least the area of the portion of
the inlet port (13a) in the tank (13) opposing the bypass (15) is
greater than the area of the portion of the inlet port (13a)
opposing the exhaust gas heat exchanger (14).
[0021] Consequently, when the exhaust gas is caused to flow through
the bypass, the exhaust gas flowing from the inlet port of the tank
is allowed to more easily flow into the bypass and the amount of
the exhaust gas striking the low temperature portion of the core
plate, etc, can be decreased to reduce the heat loss from the
exhaust gas in comparison with the heat exchange apparatus for the
exhaust gas according to the prior art shown in FIG. 6.
[0022] Incidentally, the term "position at which at least the area
of the portion of the inlet port (13a) in the tank (13) opposing
the bypass (15) is greater than the area of the portion of the
inlet port (13a) opposing the exhaust gas heat exchanger (14)"
includes also the position at which the inlet port (13a) does not
oppose the exhaust gas heat exchanger (14) but opposes only the
bypass (15) of the exhaust gas heat exchanger (14) and the bypass
(15).
[0023] The position of the inlet port of the tank described above
can be the position at which the inlet port opposes only the bypass
(15) of the exhaust gas heat exchanger (14) and the bypass (15),
for example, as in the present invention.
[0024] When the inlet port of the tank is arranged at the position
at which it opposes only the bypass in this way, the main stream of
the exhaust gas does not strike the low temperature portions such
as the core plate constituting the exhaust gas heat exchanger when
the exhaust gas is allowed to flow through the bypass, and the
exhaust gas can be guided from the inlet port of the tank to the
bypass.
[0025] In consequence, the heat loss of the exhaust gas can be
reduced in comparison with the heat exchange apparatus for the
exhaust gas according to the prior art in which the inlet port is
arranged at the position at which it opposes either wholly or
partially the exhaust gas heat exchanger.
[0026] In such a case, the heat loss of the exhaust gas when the
exhaust gas is caused to flow through the bypass can be reduced
much more when the distance between the inlet port of the tank and
the exhaust gas heat exchanger becomes greater in a planar
direction when the inlet port of the tank, the bypass and the
exhaust gas heat exchanger are projected on the same plane in the
longitudinal direction, but the pressure loss of the gas occurring
when the exhaust gas is allowed to flow through the exhaust gas
heat exchanger becomes greater.
[0027] Therefore, the position of the inlet port of the tank can be
set to the position at which the open end (13e) of the inlet port
(13a) positioned on the side of the exhaust gas heat exchanger (14)
and the open end (15b) of the bypass (15) positioned on the side of
the exhaust gas heat exchanger (14) oppose each other.
[0028] Consequently, when the inlet port of the tank is arranged at
the position at which it opposes only the bypass, the pressure loss
of the gas that occurs when the exhaust gas is caused to flow
through the exhaust gas heat exchanger can be reduced to
minimum.
[0029] Incidentally, the term "open end (13e) of the inlet port
(13) and the open end (15b) of the bypass (15) oppose each other"
means that when the inlet port of the tank and the bypass are
projected on the same plane, the open end (13e) of the inlet port
(13a) and the open end (15b) of the bypass (15) overlap with each
other.
[0030] Another feature of the present invention resides in that the
tank (13) has a first outlet port (13b) and a second outlet port
(13c). Here, the first outlet port (13b) is an outlet port to which
the exhaust gas heat exchanger (14) is connected and which guides
the exhaust gas inside the tank (13) to the exhaust gas heat
exchanger (14). On the other hand, the second outlet port (13c) is
an outlet port which is arranged in the spaced-apart relation from
the first outlet port (13b), to which the bypass (15) is connected
and which guides the exhaust gas inside the tank (13) to the bypass
(15).
[0031] As described above, the first outlet port (13b) connected to
the exhaust gas heat exchanger (14) and the second outlet port
(13c) connected to the bypass (15) are separately provided to the
tank in this invention. Therefore, the bypass can be fixed to the
tank without relying on the core plate constituting the exhaust gas
heat exchanger.
[0032] As a result, the present invention can suppress heat
migration from the bypass to the core plate and can reduce the heat
loss of the exhaust gas flowing through the bypass in comparison
with the exhaust gas heat exchange apparatus according to the prior
art in which the bypass is fixed to the core plate.
[0033] Incidentally, the reference numerals in parentheses, to
denote the above means, are intended to show the relationship of
the specific means which will be described later in an embodiment
of the invention.
[0034] The present invention may be more fully understood from the
description of preferred embodiments of the invention, as set forth
below, together with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 is a schematic view showing an overall construction
of an exhaust gas recirculation apparatus for a diesel engine;
[0036] FIG. 2 is a partial sectional view of an EGR module 7 in
FIG. 1 in the first embodiment of the present invention;
[0037] FIG. 3 is a side view showing a part of an EGR module 7 in
FIG. 1 in the second embodiment of the present invention;
[0038] FIG. 4 is a side view showing a part of an EGR module 7 in
FIG. 1 in one example of another embodiment of the present
invention;
[0039] FIG. 5 is a partial sectional view showing a part of an EGR
module 7 in FIG. 1 in a second example of another embodiment of the
present invention;
[0040] FIG. 6 is a partial sectional view showing an EGR module 7
in FIG. 1 according to the prior art.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] To begin with, the first embodiment of the invention will be
explained. In this embodiment, an example where the invention is
applied to an EGR module 7, as an exhaust gas heat exchange
apparatus used in an exhaust gas recirculation apparatus for an
internal combustion engine, will be explained.
[0042] FIG. 1 shows an overall construction of an exhaust gas
recirculation apparatus for an internal combustion engine that uses
the EGR module 7 according to the first embodiment. The exhaust gas
recirculation apparatus for an internal combustion engine shown in
FIG. 1 is used for a diesel engine, as an internal combustion
engine, for example.
[0043] The exhaust gas recirculation apparatus for an internal
combustion engine includes an exhaust tube 2 through which an
exhaust gas of the engine 1 flows and an exhaust gas recirculation
circuit 4 connected to an intake tube 3 through which intake air
filtered by an air cleaner flows.
[0044] The exhaust gas recirculation circuit 4 is for recirculating
a part of the exhaust gas flowing through the exhaust tube 2 into
the intake tube 3. The exhaust gas so recirculated is the EGR gas.
The exhaust gas recirculation circuit 4 includes an exhaust side
exhaust gas recirculation tube 5 branching from the exhaust tube 2,
an intake side exhaust gas recirculation tube 6 that is confluent
with the intake tube 3, and an EGR module 7 directly connected
between the exhaust side exhaust gas recirculation tube 5 and the
intake side exhaust gas recirculation tube 6.
[0045] An engine cooling water circuit for circulating and
supplying engine cooling water to the EGR module 7 is provided to
the engine 1. The engine cooling water circuit includes a cooling
water pipe 8 for circulating and supplying cooling water from a
water jacket, not shown, of the engine 1 to a cooling water inlet
pipe 11 of the later-appearing EGR module 7, a cooling water pipe 9
for circulating and supplying engine cooling water from a cooling
water outlet pipe 12 of the EGR module 7 to the water jacket of the
engine 1 through a radiator not shown, and a water pump for
generating a circulating flow of cooling water inside the engine
cooling water circuit.
[0046] As will be described later, the EGR module 7 includes an EGR
gas cooler 14, a bypass 15, an exhaust gas flow rate ratio
regulating valve 18 and an exhaust gas flow rate controlling valve
19.
[0047] Next, the construction of the EGR module 7 will be
concretely explained. FIG. 2 shows a partial sectional view of the
EGR module 7 according to this embodiment. Incidentally, an up-down
direction of FIG. 2 corresponds to a vertical direction and the EGR
module 7 is mounted to a car in the state shown in FIG. 2.
[0048] The EGR module 7 of this embodiment is different from the
EGR module 7 of the prior art shown in FIG. 6 mainly with regard to
the shape of a tank 13 and a fixing method of a bypass 15, but
other structural portions are the same as those of the EGR module 7
of the prior art shown in FIG. 6. Incidentally, the EGR module 7
shown in FIG. 6 is described in Patent Document 2. Therefore, the
explanation will be given mainly on the different portions from the
EGR module 7 shown in FIG. 6 and explanations of the portions
similar to those of the EGR module 7 in FIG. 6 will be partly
omitted.
[0049] In the same way as does the EGR module 7 of the prior art
shown in FIG. 6, the EGR module 7 of this embodiment includes a
tank 13, an EGR gas cooler 14 as an exhaust gas heat exchanger
arranged on the downstream side of the flow of the exhaust gas of
the tank 13, a bypass 15 arranged in parallel with the EGR gas
cooler 14, a connection joining portion 16 arranged on the
downstream side of the flow of the exhaust gas of the EGR gas
cooler 14 and the bypass 15, a valve housing 17 connected to the
EGR gas cooler 14 and to the bypass 15 through the connection
joining portion 16, and an exhaust gas flow rate ratio regulating
valve 18 and an exhaust gas flow rate controlling valve 19
accommodated inside the valve housing 17.
[0050] The EGR gas cooler 14 conducts heat exchange between the
high temperature EGR gas introduced from the exhaust gas
recirculation circuit 4 with low temperature engine cooling water
flowing from the cooling water passage formed inside the cooling
water pipe 8 and cools the EGR gas to a desired exhaust gas
temperature.
[0051] The EGR gas cooler 14 includes a casing 21, a plurality of
exhaust tubes 22, an inlet side core plate 34 and an outlet side
core plate 35. The casing 21 constitutes a cooling water passage 23
through which engine cooling water circulates around a plurality of
exhaust tubes 22.
[0052] A tank 13 is integrally connected to one of the ends of the
casing 21 in the longitudinal direction and the valve housing 17 is
integrally connected through the connection joining portion 16 to
the other end of the casing 21 in the longitudinal direction.
Consequently, the EGR gas flowing into the tank 13 flows from the
side of the tank 13 to the valve housing 17 inside a plurality of
exhaust tubes 22.
[0053] A cooling water inlet pipe 11 for allowing engine cooling
water to flow from a water jacket of the engine 1 into a cooling
water passage 23 and a cooling water outlet tube 24 for guiding
engine cooling water from the cooling water passage 23 into the
valve housing 17 through the connection joining portion 16 are
provided in the casing 21.
[0054] In this embodiment, the cooling water inlet pipe 11 is
arranged on the tank 13 side and engine cooling water is allowed to
flow inside the casing 21 as the cooling water passage 23 in the
same direction as the EGR gas flowing inside a plurality of exhaust
tubes 22.
[0055] The casing 21 is formed of a metal material having high heat
resistance and high corrosion resistance such as stainless steel
and has a prismatic shape, for example. Incidentally, a plurality
of reinforcing ribs 25 are equidistantly formed in such a fashion
as to describe a protrusive shape towards the outside for improving
the pressure resistance.
[0056] The plural exhaust tubes 22 are formed of a metal material
having high heat resistance and high corrosion resistance such as
stainless steel in the same way as the casing 21. The exhaust tubes
22 are shaped into a flat tubular shape, for example, and a first
exhaust gas passage 31 through which the EGR gas flows is formed
inside each exhaust tube. A plurality of exhaust tubes 22 is
stacked in the direction of a minor diameter with predetermined
gaps among them and the direction of the major diameter is so
extended as to cover the full length of the cylindrical direction
of the casing 21.
[0057] To increase the heat transfer area with the EGR gas and to
improve heat exchange efficiency between the EGR gas and engine
cooling water, inner fins (not shown) of a rectangular wave shape,
for example, are arranged inside a plurality of exhaust tubes
22.
[0058] The plurality of exhaust tubes 22 is integrally bonded to
the inlet side core plate 34 by brazing or welding, on the tank 13
side in the state where one of the end of each exhaust tube 22 is
fitted into each of insertion holes formed in the inlet side core
plate 34. One of the ends of the tank 13 side of the casing 21 is
integrally bonded to this inlet side core plate 34.
[0059] On the side of the tank 13 of the casing 21 and the
plurality of exhaust tubes 22, the casing 21, the inlet side core
plate 34, and the tank 13 are integrally bonded in the state where
the inlet side core plate 34 is interposed between one of the ends
of the tank 13 of the casing 21 and the tank 13. Incidentally, the
inlet side core plate 34 of this embodiment is not connected to the
bypass 15.
[0060] The plurality of exhaust tubes 22 is integrally bonded to
the outlet side core plate 35 by brazing or welding, on the valve
housing 17 side, in the state where one of the end of each exhaust
tube 22 on the valve housing side 17 is fitted into each of
insertion holes formed in the outlet side core plate 35.
[0061] On the side of the valve housing 17 of the casing 21 and the
plurality of exhaust tubes 22, one of the ends of each of the
outlet side core plate 35 and one of the ends of the casing 21 on
the valve housing side 17 are integrally bonded to the connection
joining portion 16.
[0062] The bypass 15 is arranged between the tank 13 and the
connection joining portion 16 and is substantially the same size as
the size of the casing 21 of the EGR gas cooler 14 in the
cylindrical direction, in parallel with the EGR gas cooler 14 and
in the proximity of the EGR gas cooler 14. The bypass 15 is
arranged, for example, below the EGR gas cooler 14 in the vertical
direction.
[0063] The bypass 15 is formed of a metal material excellent in
heat resistance and corrosion resistance such as the stainless
steel in the same way as the casing 21. The bypass 15 is shaped
into a round cylindrical tube, for example, and a second exhaust
gas passage 32 through which the EGR gas flows is formed inside the
bypass 15.
[0064] The end portion of the bypass 15 on the tank 13 side in the
longitudinal direction is directly connected to the tank 13 and its
end portion on the valve housing side 17 in the longitudinal
direction is directly connected to the connection joining portion
16. A bellows portion 36 capable of extending and contracting in
the cylindrical direction of the bypass 15 is integrally formed
with the bypass 15.
[0065] The inside of the tank 13 is a space for guiding the EGR gas
introduced from the exhaust side exhaust gas recirculation tube 5
to either one, or both, of the EGR cooler 14 and the bypass 15.
[0066] The tank 13 is constituted by a tank plate 33. The tank 13
has therein one inlet port 13a formed in the tank plate 33 so as to
guide the EGR gas from the exhaust side exhaust gas recirculation
tube 5 and two outlet ports 13b and 13c formed in the tank plate 33
so as to guide the EGR gas inside the tank 13 into the EGR gas
cooler 14 or into the bypass 15. The EGR gas passes through these
inlet hole 13a and outlet holes 13b and 13c.
[0067] Here, the tank plate 33 is formed of a metal material
excellent in heat resistance and corrosion resistance, such as the
stainless steel, in the same way as is the casing 21.
[0068] The two outlet ports 13b and 13c are positioned on the
opposite side to the inlet port 13a in the tank 13. The two outlet
ports 13b and 13c are arranged at upper and lower positions in the
spaced-apart relation in the vertical direction. Incidentally, of
the two outlet ports, the outlet port 13b arranged at the upper
position will be called "upper outlet port" and the outlet port at
the lower position, "lower outlet port". The upper outlet port 13b
and the lower outlet port 13c correspond to a first outlet port and
a second outlet port, as described in the Scope of Claim for
Patent, respectively.
[0069] The opening shape of the upper outlet port 13b corresponds
to the opening shape at the end of the casing 21 on the tank 13
side in the EGR gas cooler 14. The end portion of the casing 21 on
the tank 13 side is connected by brazing or welding to the upper
outlet port 13b of the tank 13 through the core plate 34.
[0070] On the other hand, the opening shape of the lower outlet
port 13c corresponds to the opening shape at the end of the bypass
15 on the tank 13 side. The end portion of the pipe 15 on the tank
13 side is directly connected by brazing or welding to the lower
outlet port 13c of the tank 13. Incidentally, the bypass 15 can be
connected indirectly to the lower outlet port 13c of the tank 13
through the connection portion, though this construction is not
shown in the drawing.
[0071] The inlet port 13a is arranged at a position deviated
towards the down side in FIG. 2, that is, towards the bypass 15, in
comparison with the inlet port 13a of the tank 13 shown in FIG. 6.
More concretely, the inlet port 13a is arranged at the position
opposing only the lower outlet port 13c of the upper and lower
outlet ports 13b and 13c with respect to the tank 13 as shown in
FIG. 2. In other words, the inlet port 13a is arranged at the
position opposing only the bypass 15, among the EGR cooler 14 and
the bypass 15, in the tank 13.
[0072] In this embodiment, in particular, the opening shape of the
inlet port 13a of the tank 13 and the opening shape of the bypass
15 on the tank 13 side are equivalent to each other. In other
words, the opening diameter 13d of the inlet port 13a of the tank
13 is equal to the opening diameter 15a of the bypass 15 on the
tank 13 side.
[0073] The position of the open upper end 13e of the inlet port 13a
of the tank 13 is coincident with the position of the open upper
end 15b of the bypass 15 in the vertical direction, and the
position of the open lower end 13f of the inlet port 13a of the
tank 13 is coincident with the position of the open lower end 15c
of the bypass 15.
[0074] In this way, the inlet 13a of the tank 13 completely opposes
the second exhaust gas passage 32 constituted inside the bypass 15.
Incidentally, a flange 13g that is to be connected and fixed to the
exhaust side exhaust gas recirculation tube 5 is disposed on the
inlet side of the tank 13 and the inlet port 13a is disposed on the
center side.
[0075] The connection joining portion 16 directly couples, in
series, the downstream side of the EGR gas cooler 14 and the bypass
15 to the valve housing 17. The connection joining portion 16 is
formed of a metal material excellent in heat resistance and
corrosion resistance, such as stainless steel, in the same way as
the casing 21.
[0076] The connection joining portion 16 has on its outer
peripheral side a fitting flange portion 37 for direct coupling
with the valve housing 17. The connection joining portion 16 has on
its inner peripheral side a side wall portion 38 on the EGR gas
cooler 14 side, a side wall portion 39 on the bypass 15 side and a
connection portion 40 positioned between the side wall portion 38
on the EGR gas cooler 14 side and the side wall portion 39 on the
bypass side 15, for connecting these side wall portions.
Incidentally, the thickness of the connection portion 40 in the
longitudinal direction of the EGR gas cooler 14, that is, the
thickness in the horizontal direction, is smaller than that of the
flange portion 37.
[0077] An outlet side core plate 35 of the EGR gas cooler 14 is
integrally connected to the side wall portion 38 on the EGR gas
cooler 14 side and one of the ends of the casing 21 of the EGR gas
cooler 14 is integrally connected to the flange portion 37.
[0078] A space is defined between the side wall portion 38 on the
EGR gas cooler 14 side and the flange portion 37 above the side
wall portion 38 on the EGR gas cooler 14 side inside the connection
joining portion 16. This space is positioned at the upper end of
the portion of the outlet side core plate 35 into which a plurality
of exhaust tubes 22 is inserted, and the extension portion 35a of
the outlet side core plate 35 extending in the longitudinal
direction of the EGR gas cooler 14 divides this space into the
cooling water passage 26 through which cooling water flows and the
first exhaust gas passage 31b through which the EGR gas flows.
[0079] The cooling water passage 26 inside the connection joining
portion 16 directly communicates the cooling water outlet portion
24 of the cooling passage 23 of the casing 21 with the cooling
water passage 27 inside the valve housing 17 to be later described.
The first exhaust gas passage 31b inside the connection joining
portion 16 communicates with a plurality of exhaust tubes 22.
[0080] The bypass 15 is integrally bonded by brazing or welding to
the side wall portion 39 and the flange portion 37 on the side of
the bypass 15. These side wall portion 39 and flange portion 37 on
the side of the bypass 15 constitute therein the second exhaust gas
passage 32b through which the EGR gas from the bypass 15 flows.
[0081] The exhaust gas flow rate ratio regulating valve 18 and the
exhaust gas recirculation rate controlling valve 19 are integrally
fitted to the valve housing 17.
[0082] Inside the valve housing 17 are formed a first exhaust gas
introduction passage 41, a second exhaust gas introduction passage
42, an exhaust gas recirculation circuit 43, a communication
passage 45 communicating with this exhaust gas recirculation
circuit 43 and an exhaust gas recirculation circuit 46 for
introducing the EGR gas from this communication passage 45 into the
exhaust gas recirculation circuit 4 formed inside the intake side
exhaust gas recirculation tube 6.
[0083] Here, the first exhaust gas introduction passage 41 is
constituted in such a fashion that the EGR gas can be introduced
from the first exhaust gas passage 31 of the EGR gas cooler 14
through the first exhaust gas passage 31b. The second exhaust gas
introduction passage 42 is constituted in such a fashion that the
EGR gas can be introduced from the second exhaust gas passage 31 of
the bypass 15 through the second exhaust gas passage 32b.
[0084] The exhaust gas recirculation circuit 43 is constituted in
such a fashion that the EGR gas can be introduced from the first
exhaust gas introduction passage 41 through the first introduction
port 51 and from the second exhaust gas introduction passage 42
through the second introduction port 52.
[0085] The communication passage 45 constitutes a valve port of the
exhaust gas recirculation rate controlling valve 19 that
communicates with the first exhaust gas passage 31 of the EGR gas
cooler 14 through the first exhaust gas introduction passage 41 and
the first introduction port 51 and communicates with the exhaust
gas passage 32 through the second exhaust introduction passage 42
and the second introduction port 52.
[0086] These first exhaust gas introduction passage 41, second
exhaust gas introduction passage 42, exhaust gas recirculation
circuit 43, communication passage 45 and exhaust gas recirculation
circuit 46 constitute the exhaust gas recirculation circuit 4.
[0087] Inside the valve housing 17 is formed the cooling water
passage 27 into which engine cooling water is introduced from the
cooling water outlet portion of the cooling water passage 23 of the
EGR gas cooler 14 through the cooling water passage 26. This
cooling water passage 27 is for cooling the valve housing 17.
Incidentally, the cooling water inlet portion 27a disposed at the
extreme left of the cooling water passage 27 in the drawing is
directly coupled in series with the cooling water passage 26 of the
connection joining portion 16. A cooling water outlet pipe 12
connected to the cooling water pipe 9 is disposed at the extreme
left of the cooling water passage 27 in the drawing.
[0088] The valve housing 17 is integrally molded, into a
predetermined shape, as an aluminum casting or an aluminum die
casting and is fixed to the downstream portion of the connection
joining portion 16 by using a screw or a fastening bolt not shown
in the drawing. Known measures are employed for the connection
portion between the valve housing 17 and the connection joining
portion 16 lest engine cooling water and the EGR gas leak.
[0089] When a metal material capable of being integrally brazed to
the connection joining portion 16 is used as the material of the
valve housing 17, the valve housing 17 can be brazed, too, when the
EGR module 7 is integrally molded. The valve housing 17 and the
connection joining portion 16 can be bonded by welding, too.
[0090] The exhaust gas flow rate regulating valve 18 continuously
regulates the ratio of the flow rate of the EGR gas flowing inside
each first exhaust gas passage 31 of the EGR gas cooler 14 to the
flow rate of the EGR gas flowing inside the second exhaust gas
passage 32 of the bypass 14.
[0091] The exhaust gas flow rate ratio regulating valve 18 includes
a metallic double poppet valve 53 for regulating the opening areas
of first and second introduction ports 51 and 52 disposed inside
the valve housing 17, a metallic valve shaft 54 reciprocating
integrally with the double poppet valve 53 in the axial direction,
a negative pressure operation type actuator as valve body driving
means for driving the double poppet valve 53 and the valve shaft 54
upward in the drawing and valve body urging means for urging
downward the double poppet valve 53 and the valve shaft 54 in the
drawing.
[0092] Here, the double poppet valve 53 includes a first valve body
61 for regulating an opening area of the first introduction port
51, a second valve body 62 for regulating an opening area of the
second introduction port 52 and a cylindrical connection portion 63
for connecting the first and second valve bodies 61 and 62. The
double poppet valve 53 is formed of a metal material excellent in
heat resistance and corrosion resistance, such as stainless steel,
and is shaped into a substantially disk-like shape, for
example.
[0093] The valve shaft 54 is disposed in a bearing 57 that is
accommodated and held, inside a bearing support portion of the
valve housing 17 on the left side in the drawing, in such a fashion
as to be capable of sliding, and is formed of a metal material
excellent in heat resistance and corrosion resistance, such as
stainless steel, in the same way as the double poppet valve 53. The
double poppet valve 53 is held and fixed to a valve holding portion
of the valve shaft 54 by fixing means such as welding.
[0094] The negative pressure operation actuator allows the double
poppet valve 53 as well as the valve shaft 54 to undergo
reciprocation and displacement in the axial direction by
controlling a pressure difference between a negative pressure
chamber 65a defined between a casing 60 and a thin membrane-like
diagram 64 and an atmospheric pressure chamber 65b, by an
electromagnetic or electric negative pressure valve, to cause
displacement of the diaphragm 64.
[0095] The exhaust gas recirculation controlling valve 19
continuously regulates the total flow rate of the EGR gas passing
through the valve housing 17.
[0096] The exhaust gas recirculation flow rate controlling valve 19
includes a metallic valve 71 for regulating an opening area of a
communication passage 45 formed inside the valve housing 17, a
metallic valve shaft 72 operating integrally with this valve 71 in
a rotating direction, valve driving means, not shown, for driving
the valve 71 and the valve shaft 72 in the valve opening direction
and urging means, not shown, for urging the valve 71 and the valve
shaft 72 in a valve closing direction.
[0097] The valve 71 is formed of a metal material excellent in heat
resistance and corrosion resistance, such as stainless steel, and
is shaped into a substantially disk-like shape, for example. The
valve shaft 72 is formed of a metal material excellent in heat
resistance and corrosion resistance, such as stainless steel, in
the same way as the valve 71. The valve 71 is held and fixed to a
holding portion of the valve shaft 72 by fixing means such as
welding.
[0098] The valve body driving means of the exhaust gas
recirculation rate controlling valve 19 drives the valve 71 in the
valve opening direction by rotating and driving the valve shaft 72
by an electric actuator constituted by a power unit.
[0099] The power unit includes a driving motor, not shown in the
drawing, for driving the valve 71 and the valve shaft 72 of the
exhaust gas recirculation rate controlling valve 19 in the rotating
direction and a power transmission mechanism, not shown, for
transmitting the turning power of the driving motor to the valve
shaft 72 of the exhaust gas recirculation rate controlling valve
19.
[0100] Next, the operation of the EGR module 7 of this embodiment
will be explained.
[0101] The EGR gas flows into the intake tube 3 from the exhaust
tube 2 through the exhaust gas recirculation circuit 4, the EGR
module 7 and the intake side exhaust gas recirculation tube 6 as
indicated by an arrow in FIG. 1.
[0102] At this time, the valve 71 of the exhaust gas recirculation
rate controlling valve 19 is driven by the valve body driving means
through the valve shaft 72 and the opening area of the
communication passage 45 is adjusted. Consequently, the total flow
rate of the EGR gas passing through the exhaust gas recirculation
circuit 43 of the valve housing 17, the communication passage 45
and the exhaust gas recirculation circuit 46, that is, the total
flow rate of the EGR gas to be circulated and supplied to the
intake tube 3, is regulated.
[0103] As the double poppet valve 52 of the exhaust gas flow rate
regulating valve 18 is driven by the valve body driving means, the
opening areas of the first and second introduction holes 51 and 52
are adjusted.
[0104] In other words, when the valve shaft 54 is driven upward in
the drawing by the valve body driving means, the first valve body
61 on the side of the EGR gas cooler 14 moves in the valve closing
direction and at the same time, the second valve body 62 on the
side of the bypass 15 moves in the valve opening direction.
[0105] On the contrary, when the valve shaft 54 is not driven by
the valve body driving means, the valve shaft 54 moves downward in
the drawing owing to the valve body urging means 55, so that the
first valve body 61 on the side of the EGR gas cooler 14 moves in
the valve opening direction and at the same time, the second valve
body 62 on the side of the bypass 15 moves in the valve closing
direction.
[0106] In this way, the double poppet valve 53 regulates the
opening areas of the first and second introduction ports 51 and 52.
Consequently, the ratio of the flow rate of the EGR gas flowing
inside each first exhaust gas passage 31 of the EGR gas cooler 14
to the flow rate of the EGR gas flowing inside the second exhaust
gas passage 32 of the bypass 15 is regulated.
[0107] When the combustion temperature inside the engine is high,
for example, the first valve body 61 on the side of the EGR gas
cooler 14 is opened while the second valve body 62 on the side of
the bypass 15 is closed. Consequently, regarding the EGR gas cooler
14 and the bypass 15, the EGR gas is allowed to flow only through
each first exhaust gas passage 31 of the EGR gas cooler 14 and the
EGR gas cooled by engine cooling water can be circulated and
supplied to the intake tube 3 of the engine 1.
[0108] When the combustion temperature inside the engine is low, on
the other hand, the first valve body 61 on the side of the EGR gas
cooler 14 is closed while the second valve body 62 on the side of
the bypass 15 is opened. Consequently, regarding the EGR gas cooler
14 and the bypass 15, the EGR gas is allowed to flow only through
the second exhaust gas passage 32 of the bypass 15 and the EGR gas
having a high temperature can be circulated and supplied as such to
the intake tube 3 of the engine 1.
[0109] Incidentally, the temperature of the EGR gas can be adjusted
by opening both of the first and second valve bodies 61 and 62 and
adjusting both of the opening degrees.
[0110] Engine cooling water for cooling the EGR gas inside the EGR
gas cooler 14 flows inside the cooling water pipe 8 from the water
jacket of the engine 1, not shown, flows into the cooling water
passage 23 of the EGR gas cooler 14 through the cooling water inlet
pipe 11, takes away the heat of the EGR gas flowing inside the
first exhaust gas passage 31 of the EGR gas cooler 14 and cools the
EGR gas.
[0111] Subsequently, engine cooling water flows from the cooling
water outlet portion of the cooling water passage 23 of the EGR gas
cooler 14 into the cooling water passage 26 of the connection
joining portion 16. Engine cooling water flowing into the cooling
water passage 26 flows into the cooling water passage 27 of the
housing 17 and cools the valve housing 17 heated to a high
temperature by the heat of the EGR gas. Engine cooling water is
thereafter circulated and supplied to the water jacket of the
engine 1 from the cooling water outlet pipe 12 of the EGR module 7
through the radiator.
[0112] Next, the main effects of the EGR module 7 according to this
embodiment will be explained.
(1) The inlet port 13a disposed in the tank 13 in this embodiment
is arranged at a position opposing only the bypass 15 among the EGR
gas cooler 14 and the bypass 15 in the tank 13.
[0113] When the EGR gas is caused to flow only through the second
exhaust gas passage 32 of the bypass 15 of the EGR gas cooler 14
and the bypass 15 in the EGR module 7, the EGR gas flows into the
tank 13 from the exhaust tube 2 through the exhaust side exhaust
gas recirculation tube 5 and flows through the second exhaust gas
passage 32 of the bypass 14 from the lower outlet port 13c of the
tank 13.
[0114] According to the EGR module 7 of this embodiment, at this
time, the main stream of the exhaust gas flowing into the tank 13
from the inlet port 13a as indicated by arrow of broken line in
FIG. 2 can be guided to the bypass 15 without striking the inlet
side core plate 34 constituting the EGR gas cooler 14.
[0115] As shown in FIG. 6, therefore, the heat loss resulting from
the impingement of the EGR gas against the inlet side core plate 34
constituting the EGR gas cooler 14 can be reduced in comparison
with a heat exchanger for an exhaust gas in which a part of the
inlet port 13a is arranged at a position opposing the EGR gas
cooler 14 and a heat exchanger for an exhaust gas according to the
prior art in which the inlet port 13a is fully arranged at a
position opposing the EGR gas cooler 14.
[0116] In this embodiment, in particular, the inlet port 13a of the
tank 13 completely opposes the second exhaust gas passage 32 formed
inside the bypass 15. In other words, the opening shape of the
inlet port 13a of the tank 13 and the shape of the second exhaust
gas passage 32 formed inside the bypass 15 are similar and their
positions in the vertical direction are coincident.
[0117] Therefore, the portion ranging from the inlet port 13a of
the tank 13 to the second exhaust gas passage 32 of the bypass 15
can be regarded as one tube having a uniform inner diameter. In
comparison with the case where the inlet port 13a does not
completely oppose the second exhaust gas passage 32 of the bypass
15, the pressure loss in the EGR gas when the EGR gas flows from
the inlet port 13a of the tank 13 to the second exhaust gas passage
32 of the bypass 15 can be reduced.
[0118] Incidentally, when the EGR gas is caused to flow only
through each first exhaust gas passage 31 of the EGR gas cooler 14,
the second introduction port 52 is closed by the double poppet
valve 53 of the exhaust gas flow rate ratio regulating valve 18.
Consequently, even when the inlet port 13a is arranged at the
position opposing only the bypass 15, the EGR gas flowing into the
tank 13 can be caused to flow into each first exhaust gas passage
31 of the EGR gas cooler 14 from the upper outlet port 13b of the
tank 13.
(2) In this embodiment, the position of the open upper end 13e of
the inlet port 13a of the tank 13 is coincident with the position
of the open upper end 15b of the bypass 15 in the vertical
direction.
[0119] From the aspect of reducing the heat loss of the EGR gas
when the EGR gas is caused to flow through only the second exhaust
gas passage 32 of the bypass 15, it is preferred to arrange the
open upper end 13e of the inlet port 13a of the tank 13 as close as
possible to the down position of the tank 13 in the vertical
direction because, when the open upper end 13e of the inlet port
13a of the tank 13 is arranged at the position as lower as possible
than the inlet side core plate 34 of the EGR gas cooler 14, it
becomes more difficult for the EGR gas to impinge against the inlet
side core plate 34.
[0120] However, when the open upper end 13e of the inlet port 13a
of the tank 13 is arranged below the inlet side core plate 34, the
pressure loss of the EGR gas when the EGR gas is caused to flow
through the EGR gas cooler becomes greater when the position of the
open upper end 13e is deviated downward.
[0121] Therefore, the position of the open upper end of the inlet
port 13a of the tank 13 is preferably coincident with the position
of the open upper end 15b of the bypass 15 in the vertical
direction as in this embodiment.
[0122] Consequently, when the EGR gas is caused to flow only
through the bypass 15, the main stream of the EGR gas can be
allowed to flow through the bypass 15. On the other hand, when the
EGR gas is caused to flow only through the EGR gas cooler 14, the
pressure loss of the EGR gas when the EGR gas flows from the inside
of the tank 13 through the inside of the EGR gas cooler 14 can be
made smaller than when the open upper end 13e of the inlet port 13a
of the tank 13 is positioned below the open upper end 15b of the
bypass 15.
[0123] As a result, it becomes possible to simultaneously reduce
the heat loss of the EGR gas when it is caused to flow only through
the second exhaust gas passage 32 of the bypass 15 and to suppress
the pressure loss of the EGR gas when the EGR gas is caused to flow
through the EGR gas cooler 14.
[0124] (3) In this embodiment, the tank 13 has two outlet ports 13b
and 13c that are arranged at upper and lower positions in the
vertical direction in the spaced-apart relation. Of these two
outlet ports 13b and 13c, the casing 21 of the EGR gas cooler 14 is
connected to the upper outlet port 13b through the inlet side core
plate 34 and the bypass 15 is connected to the lower outlet port
13c without passing through the inlet side core plate 34.
[0125] As the upper outlet port 13b connected to the EGR gas cooler
14 and the lower outlet port 13c connected to the bypass 15 are
separately provided to the tank 13 as described above, the bypass
15 can be connected to the tank 13 without passing through the
inlet side core plate 34.
[0126] As the upper outlet port 13b and the lower outlet port 13c
are spaced apart from each other, heat migration from the bypass 15
to the inlet side core plate 34 of the EGR gas cooler 14 can be
routed to the tank 13. In other words, the movement of heat of the
bypass 15 to the inlet side core plate 34 of the EGR gas cooler 14
becomes more difficult than in the EGR module 7 shown in FIG.
6.
[0127] Accordingly, in comparison with the exhaust gas heat
exchange apparatus of the prior art in which the bypass 15 is fixed
to the inlet side core plate 34, the heat movement from the bypass
15 to the inlet side core plate 34 can be suppressed and the heat
loss of the EGR gas flowing inside the bypass 15 can be
reduced.
[0128] (4) As to the connection of the EGR gas cooler 14 and the
bypass 15 with the connection joining portion 16 in this
embodiment, the outlet side core plate 35 of the EGR gas cooler 14
is integrally connected to the side wall portion 38 on the side of
the EGR gas cooler 14 positioned on the inner peripheral side of
the connection joining portion 16, and the bypass 15 is integrally
connected to the side wall portion 39 on the side of the bypass
15.
[0129] The side wall portion 38 of the connection joining portion
16 on the side of the EGR gas cooler 14 and the side wall portion
39 on the side of the bypass 15 have a continuous shape through the
connection portion 40.
[0130] Consequently, when the heat moves from the bypass 15 to the
outlet side core plate 35 of the EGR gas cooler 14 through the
connection joining portion 16, the heat of the bypass 15 transfers
to the side wall portion 39 on the side of the bypass 15, bypasses
the connection portion 40, transfers to the side wall portion 38 on
the side of the EGR gas cooler 14 and then moves to the outlet side
core plate 35 of the EGR gas cooler 14.
[0131] In comparison with the EGR module 7 of the prior art shown
in FIG. 6, therefore, this embodiment can make the heat movement
from the bypass 15 to the outlet side core plate 35 of the EGR gas
cooler 14 more difficult. As a result, the heat loss of the EGR gas
flowing through the bypass 15 can be reduced.
[0132] Next, the second embodiment will be explained. FIG. 3 shows
a part of the EGR module 7 in the second embodiment. FIG. 3 is a
view corresponding to the portion near the tank 13 in FIG. 2.
Incidentally, like reference numerals are used in FIG. 3 to
identify like constituent members in the EGR module 7 shown in FIG.
2.
[0133] The first embodiment was explained with respect to the EGR
module 7 having the construction in which the bypass 15 is arranged
outside the casing 21 of the EGR gas cooler 14 by way of example
but the bypass 15 can be arranged inside the casing 81 of the EGR
gas cooler 14 as in this embodiment.
[0134] As shown in FIG. 3, the EGR module 7 according to this
embodiment includes an integral casing 81 of the EGR gas cooler 14
and the bypass 15 and a separator 82 in place of the casing 21 of
the EGR gas cooler 14 shown in FIG. 2. Incidentally, the
constructions of the tank 13 and other members are the same as
those of the EGR module 7 shown in FIG. 2.
[0135] The integral casing 81 has a rectangular cylindrical shape,
for example. The separator 82 is arranged inside the casing 81 and
divides the inside of the casing 81 into two areas.
[0136] Of these two areas, one of the areas, on the upper side of
the drawing above the separator 82, is the area for the EGR gas
cooler 14. A plurality of exhaust tubes 22 is arranged in this
area, though not shown in the drawing, in the same way as the EGR
module 7 shown in FIG. 2. In this way, the casing 81 and the
separator 82 constitute the outer wall of the EGR gas cooler 14 in
this embodiment.
[0137] The casing 81 and the separator 82 constituting the outer
wall of the EGR gas cooler 14 are integrally connected to the upper
outlet hole 13b of the tank 13 through the inlet side core plate 34
so that the upper area above the separator 82 inside the casing 81
communicates with the inside of the tank 13. The casing 81 and the
separator 82 are formed of a metal material excellent in heat
resistance and corrosion resistance such as stainless steel.
[0138] On the other hand, the bypass 15 is arranged in the other
area, that is, the lower area, below the separator 82 and inside
the casing 81. The bypass 15 is similar to the bypass 15 shown in
FIG. 2 and is integrally connected to the lower outlet hole 13c of
the tank through the inlet portion 15d. Incidentally, this inlet
portion 15d is integral with the casing 81 and the bypass 15.
[0139] In this embodiment, too, the inlet hole 13a disposed in the
tank 13 is arranged at the position opposing only the bypass 15
among the EGR gas cooler 14 and the bypass 14 in the tank 13 in the
same way as in the first embodiment. The position of the open upper
end of the inlet hole 13a of the tank 13 is coincident with the
position of the open upper end 15b of the bypass 15 in the vertical
direction.
[0140] Therefore, this embodiment has the effects (1) and (2)
explained in the first embodiment.
[0141] Incidentally, this embodiment has been explained in the case
where the bypass 15 is arranged inside the casing 81 of the EGR gas
cooler 14 by way of example but the EGR gas cooler 14 and the
bypass 15 can be constituted inside the casing 81 by merely
partitioning the inside of the EGR gas cooler 14 by a
separator.
[0142] Finally, other embodiments will be explained.
[0143] (1) Each of the foregoing embodiments has been explained in
the case, by way of example, where the inlet port 13a of the tank
13 opposes only the bypass 15 and the open upper end 13e of the
inlet port 13a of the tank 13 is coincident with the open upper end
15b of the bypass 15 in the vertical direction. However, the open
upper end 13e of the inlet port 13a of the tank 13 may be
positioned below the open upper end 1b of the bypass tank 15 in the
vertical direction.
[0144] In consequence, as the position of the inlet port 13a of the
tank 13 is spaced apart from the EGR gas cooler 14 in the vertical
direction, it is more hard for the EGR gas to impinge against the
inlet side core plate 34 than in the first and second embodiments
when the EGR gas is caused to flow through the bypass 15.
[0145] (2) Each of the foregoing embodiments has been explained
about the case, by way of example, where the inlet port 13a of the
tank 13 opposes only the bypass 15 and the open lower end 13f of
the lower outlet port 13c of the tank 13 is coincident with the
open lower end 15c of the bypass 15 in the vertical direction.
However, the position of the open lower end 13f of the lower outlet
port 13c of the tank 13 may be different from the position of the
open lower end 15c of the bypass tank 15 in the vertical
direction.
(3) FIG. 4 shows a part of the EGR module 7 in another embodiment.
FIG. 4 corresponds to the portion near the tank 13 in FIG. 2. In
FIG. 4, like reference numerals are used to identify like
constituent members as in FIG. 2.
[0146] Each of the foregoing embodiments has been explained, by way
of example, in the case where the position of the inlet port 13a of
the tank 13 is moved towards the bypass 15 in the EGR module 7
shown in FIG. 6 and the position of the inlet port 13a of the tank
13 is arranged at the position opposing only the bypass 15.
[0147] In contrast, it is possible to employ the construction of
the EGR module 7 in which the inlet port 13a of the tank 13 opposes
both the EGR gas cooler 14 and bypass 15 and the position of the
inlet port 13a of the tank 13 is more deviated towards the bypass
15 than the EGR gas cooler 14.
[0148] In this case, of the opening area of the inlet port 13a of
the tank 13, the area of the portion 13h opposing the bypass 15 is
greater than the area of the portion 13i opposing the EGR gas
cooler 14. Here, the term "portion opposing the bypass 15" in the
opening area of the inlet port 13a, represents the portion with
which a projection image overlaps when the inside of the bypass 15
is projected on the inlet port 13a in the longitudinal direction of
the bypass 15.
[0149] Consequently, with this construction of the EGR module 7, it
becomes more difficult for the EGR gas flowing from the inlet port
13a of the tank 13 to impinge against the inlet side core plate 34
of the EGR gas cooler 14 but it becomes easier for it to flow into
the bypass 15 than in the EGR module 7 of the prior art shown in
FIG. 6 when the EGR gas is caused to flow through the bypass 15. In
other words, in comparison with the EGR module 7 of the prior art
shown in FIG. 6, the amount of the EGR gas flowing from the inlet
port 13a of the tank 13 and impinging against the inlet side core
plate 34 of the EGR gas cooler 14 can be reduced, so that the heat
loss of the EGR gas can be reduced, too.
[0150] It can be said from the first and second embodiments as well
as this embodiment that the inlet port 13a of the tank 13 may well
be arranged at the position at which at least the area 13h of the
portion of the opening area of the inlet port 13a of the tank 13
opposing the bypass 15 is greater than the area 13i opposing the
EGR gas cooler 14 in order to reduce the heat loss of the EGR gas
in comparison with the EGR module 7 of the prior art shown in FIG.
6.
[0151] Incidentally, "the position at which at least the area of
the portion of the opening area of the inlet port 13a of the tank
13 opposing the bypass 15 is greater than the area opposing the EGR
gas cooler 14" includes the position that does not oppose the EGR
gas cooler 1 but opposes only the bypass 15.
[0152] It can be said that the area of the portion of the opening
area of the inlet port 13a of the tank 13 opposing the EGR gas
cooler 14 in the first and second embodiments is zero and, quite
naturally, the area of the portion opposing the bypass 15 is
greater than the area opposing the EGR gas cooler 14.
(4) In each of the embodiments described above, the explanation has
been given for an example where the inlet port 13a of the tank 13
is moved closer to the bypass 15 than the position of the inlet
port 13a of the tank 13 shown in FIG. 6.
[0153] In contrast, it is possible to decrease the diameter of the
casing 21 and to increase the diameter of the bypass 15 while the
inlet hole 13a is kept arranged near the center of the tank 13 in
the vertical direction in the EGR module 7 shown in FIG. 6.
[0154] It becomes possible in this way to make the area 13h of the
opening area of the inlet hole 13a of the tank 13 opposing the
bypass 15 greater than the area 13i opposing the EGR gas cooler
14.
[0155] (5) Each of the foregoing embodiments has been explained for
an example where the downstream portions of the EGR gas cooler 14
and the bypass 15 are connected to the valve housing 17 through the
connection joining portion 16 but they may be directly connected to
the valve housing 17 without passing through the connection joining
portion 16.
[0156] In this case, the casing 21 of the EGR gas cooler 14 and the
bypass 15 can be integrally brazed or welded to the valve housing
17.
[0157] (6) Each of the foregoing embodiments has been explained in
the example where the EGR gas cooler 14 is arranged on the upstream
side and the bypass 15 on the downstream side, in the vertical
direction, but the positional relationship between the EGR gas
cooler 14 and the bypass 15 may be changed.
[0158] For example, it is possible to arrange the EGR gas cooler 14
on the lower side and the bypass 15 on the upper side, in the
vertical direction, though this construction is not shown in the
drawing. The EGR gas cooler 14 and the bypass 15 may be juxtaposed
in the horizontal direction.
[0159] In these cases, the open end of the inlet port 13a of the
tank 13 on the side of the EGR gas cooler 14 and the open end of
the bypass 15 on the side of the EGR gas cooler 14 correspond to
the open upper end 13e of the inlet port 13a of the tank 13 and the
open upper end 15b of the bypass 15, respectively.
[0160] (7) Each of the foregoing embodiments has been explained
about the example where the exhaust gas flow rate ratio regulating
valve 18 and the exhaust gas recirculation rate controlling valve
19 are integrally fitted to the valve housing 17 and the exhaust
gas recirculation rate controlling valve 19 is provided to the EGR
module 7. However, the exhaust gas recirculation rate controlling
valve 19 may be separated from the EGR module 7.
[0161] (8) Each of the foregoing embodiments has been explained in
the example where the structure having the double poppet valve 53
is employed as the exhaust gas flow rate ratio regulating valve 18
but this structure is not particularly restrictive and other
structures may also be used. For example, it is possible to use a
so-called "butterfly" structure.
[0162] (9) The shape of the tank 13 explained in each of the
foregoing embodiments can be changed to other shapes. For example,
the shape of the tank 13 may be changed to the shape such that an
elbow-shaped pipe can be connected to the inlet port 13a of the
tank 13 shown in FIG. 2, though the construction is not shown in
the drawing. In this case, the inlet port of the tank described in
the Scope of Claim for Patent means the port 13a at which the EGR
gas starts flowing into the tank 13 in the same way as the inlet
port 13a of the tank 13 shown in FIG. 2 but not the inlet of the
elbow-shaped pipe.
(10) FIG. 5 shows a partial sectional view of the EGR module 7 in
the second example of another embodiment. Incidentally, like
reference numerals are used in FIG. 5 to identify like constituent
members as in FIG. 2.
[0163] As for the construction of the connection joining portion
16, each of the foregoing embodiments has been explained about the
example where the side wall portion 38 on the side of the EGR gas
cooler 14, the side wall portion 39 on the side of the bypass 15
and the thickness of the connection portion 40 are decreased and
the thickness of the flange portion 37 is greater than the
thickness of the connection portion 40, etc. Incidentally, the term
"thickness" hereby used means the thickness in the direction
vertical to the flowing direction of the EGR gas flowing inside the
bypass 15, that is, the thickness in the vertical direction in the
drawing.
[0164] In contrast, the thickness of the flange portion 37 can be
set to be substantially equal to the side wall portion 38 on the
side of the EGR gas cooler 14, the side wall portion 39 on the side
of the bypass 15 and the connection portion 40 as shown in FIG. 5.
Incidentally, the thickness of each of the flange portion 37, the
side wall portion 38 on the side of the gas cooler 14, the side
wall portion 39 on the side of the bypass 15 and the connection
portion 40 is equal to the thickness of the bypass 15 in FIG.
5.
[0165] When the thickness of each of the flange portion 37, the
side wall portion 38 on the side of the gas cooler 14, the side
wall portion 39 on the side of the bypass 15 and the connection
portion 40 is reduced in this way, the passage sectional area when
the heat moves from the bypass 15 to the outlet side core plate 35
of the EGR gas cooler 14 through the connection joining portion 16
can be reduced. Consequently, heat radiation of the exhaust gas
after passing through the bypass 15 can be suppressed.
[0166] While the invention has been described by reference to
specific embodiments chosen for purposes of illustration, it should
be apparent that numerous modifications could be made thereto, by
those skilled in the art, without departing from the basic concept
and scope of the invention.
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