U.S. patent application number 12/670970 was filed with the patent office on 2010-07-29 for exhaust gas purification apparatus for an internal combustion engine.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Akinori Morishima, Kenichi Tsujimoto.
Application Number | 20100186379 12/670970 |
Document ID | / |
Family ID | 40304375 |
Filed Date | 2010-07-29 |
United States Patent
Application |
20100186379 |
Kind Code |
A1 |
Tsujimoto; Kenichi ; et
al. |
July 29, 2010 |
EXHAUST GAS PURIFICATION APPARATUS FOR AN INTERNAL COMBUSTION
ENGINE
Abstract
An object of the present invention is to improve preferable
promotion of the modification of reducing agent in a precatalyst in
the case where the reducing agent is added through a reducing agent
addition valve in order to supply the reducing agent to an exhaust
gas purification catalyst. According to the present invention, one
end of an exhaust passage in which an exhaust gas purification
catalyst is provided is connected to an exhaust manifold, and a
precatalyst and a reducing agent addition valve are provided in the
exhaust manifold. The precatalyst is configured in such a way that
the exhaust gas flows through the gap between the outer
circumferential surface thereof and the inner wall surface of the
exhaust manifold. The precatalyst and the reducing agent addition
valve are arranged in such a way that the most part of the reducing
agent added through the reducing agent addition valve flows into
the precatalyst.
Inventors: |
Tsujimoto; Kenichi;
(Susono-shi, JP) ; Morishima; Akinori;
(Susono-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi
JP
|
Family ID: |
40304375 |
Appl. No.: |
12/670970 |
Filed: |
July 30, 2008 |
PCT Filed: |
July 30, 2008 |
PCT NO: |
PCT/JP2008/063640 |
371 Date: |
January 27, 2010 |
Current U.S.
Class: |
60/280 ; 415/148;
60/299; 60/303; 60/323 |
Current CPC
Class: |
B01D 53/9477 20130101;
F01N 2340/04 20130101; F01N 3/0842 20130101; Y02T 10/12 20130101;
F01N 13/009 20140601; B01D 2255/91 20130101; F01N 3/0814 20130101;
B01D 53/9431 20130101; F01N 2610/03 20130101; F01N 3/0253 20130101;
F01N 3/2033 20130101; Y02T 10/26 20130101; F01N 2610/14 20130101;
F01N 3/106 20130101; B01D 2258/012 20130101 |
Class at
Publication: |
60/280 ; 60/323;
60/299; 60/303; 415/148 |
International
Class: |
F01N 5/04 20060101
F01N005/04; F01N 1/00 20060101 F01N001/00; F01N 3/10 20060101
F01N003/10; F04D 29/56 20060101 F04D029/56 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 1, 2007 |
JP |
2007-201076 |
Claims
1. An exhaust gas purification apparatus for an internal combustion
engine comprising: an exhaust manifold connected to the internal
combustion engine; an exhaust gas purification catalyst provided in
an exhaust passage, one end of which is connected to said exhaust
manifold; a precatalyst having an oxidizing ability provided in
said exhaust manifold; and a reducing agent addition valve provided
in said exhaust manifold to add a reducing agent to exhaust gas,
wherein said precatalyst is configured in such a way that the
exhaust gas flows through a gap between a circumferential surface
thereof and an inner wall surface of said exhaust manifold, and
said precatalyst and said reducing agent addition valve are
arranged in such a way that said precatalyst is located at a
position toward which a spray jet of the reducing agent formed by
the addition of the reducing agent through said reducing agent
addition valve is directed.
2. An exhaust gas purification apparatus for an internal combustion
engine according to claim 1, wherein the internal combustion engine
is an internal combustion engine equipped with a turbocharger, and
a turbine housing of said turbocharger is provided upstream of said
exhaust gas purification catalyst in said exhaust passage.
3. An exhaust gas purification apparatus for an internal combustion
engine according to claim 2, wherein said turbocharger is a
variable geometry turbocharger having nozzle vanes, and when the
reducing agent is added through the reducing agent addition valve,
the degree of opening of said nozzle vanes is controlled so that
the rotational speed of said turbocharger does not change with an
increase in the quantity of heat generated in said precatalyst.
4. An exhaust gas purification apparatus for an internal combustion
engine according to claim 1, wherein said precatalyst is an NOx
storage reduction catalyst.
5. An exhaust gas purification apparatus for an internal combustion
engine according to claim 1, further comprising estimation unit for
estimating a modification ratio of the reducing agent in the
precatalyst, wherein the quantity of reducing agent added through
the reducing agent addition valve is corrected based on the
modification ratio estimated by said estimation unit.
Description
TECHNICAL FIELD
[0001] The present invention relates to an exhaust gas purification
apparatus for an internal combustion engine.
BACKGROUND ART
[0002] Some exhaust gas purification apparatuses are provided with
a reducing agent addition valve, a precatalyst having an oxidizing
ability, and an exhaust gas purification catalyst arranged in
series in order from upstream in an exhaust passage of the internal
combustion engine. In such apparatuses, when the reducing agent is
added to the exhaust gas through the reducing agent addition valve,
the reducing agent flows firstly into the precatalyst. Then, the
reducing agent having been modified in the precatalyst is supplied
to the exhaust gas purification catalyst.
[0003] The supply of the modified reducing agent to the exhaust gas
purification catalyst tends to facilitate chemical reactions, such
as the oxidation of the reducing agent, in the exhaust gas
purification catalyst.
[0004] Patent Document 1 describes a technology in which a front
oxidation catalyst, an oxidation catalyst, and a particulate filter
are arranged in order from upstream in an exhaust passage of an
internal combustion engine. According to this cited document 1, a
bypass passage that bypasses the front oxidation catalyst and a
flow path switching apparatus for switching the flow of the exhaust
gas between the front oxidation catalyst and the bypass passage are
provided.
[0005] Patent Document 2 discloses a technology in which an
oxidation catalyst is provided in each of branch passages of the
exhaust manifold that are connected to the respective cylinders,
and a particulate filter is provided downstream of the collecting
pipe of the exhaust manifold.
[0006] [Patent Document 1] Japanese Patent Application Laid-Open
No. 2004-176571
[0007] [Patent Document 2] Japanese Patent Application Laid-Open
No. 10 (1998)-89054
[0008] [Patent Document 3] Japanese Patent No. 3796919
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0009] In order to have reducing agent added through a reducing
agent addition valve modified in a precatalyst and to supply the
modified reducing agent to an exhaust gas purification catalyst, it
is necessary to raise the temperature of the precatalyst to an
active temperature or keep the temperature of the precatalyst at an
active temperature. However, the quantity of heat of the exhaust
gas discharged from the internal combustion engine decreases due to
heat radiation as the exhaust gas flows in the exhaust passage to
the precatalyst. For this reason, it is sometimes difficult to heat
the precatalyst to a sufficiently high temperature by the exhaust
gas.
[0010] The present invention has been made in view of the
above-described problem and has an object to provide a technology
that enables an improvement in preferable promotion of the
modification of reducing agent in a precatalyst in the case where
the reducing agent is added through a reducing agent addition valve
in order to supply the reducing agent to an exhaust gas
purification catalyst.
Means for Solving the Problem
[0011] According to the present invention, one end of an exhaust
passage in which an exhaust gas purification catalyst is provided
is connected to the exhaust manifold, and a precatalyst and a
reducing agent addition valve are provided in the exhaust manifold.
In addition, the precatalyst is designed in such a way that the
exhaust gas flows through the gap between the outer circumference
thereof and the inner wall surface of the exhaust manifold.
Furthermore, the precatalyst and the reducing agent addition valve
are arranged in such a way that the most part of the reducing agent
added through the fuel addition valve flows into the
precatalyst.
[0012] More specifically, an exhaust gas purification apparatus for
an internal combustion engine according to the present invention
comprises:
[0013] an exhaust manifold connected to the internal combustion
engine;
[0014] an exhaust gas purification catalyst provided in an exhaust
passage one end of which is connected to said exhaust manifold;
[0015] a precatalyst having an oxidizing ability provided in said
exhaust manifold; and
[0016] a reducing agent addition valve provided in said exhaust
manifold to add a reducing agent to exhaust gas, wherein
[0017] said precatalyst is configured in such a way that the
exhaust gas flows through a gap between a circumferential surface
thereof and an inner wall surface of said exhaust manifold, and
[0018] said precatalyst and said reducing agent addition valve are
arranged in such a way that said precatalyst is located at a
position toward which a spray jet of the reducing agent formed by
the addition of the reducing agent through said reducing agent
addition valve is directed.
[0019] In the apparatus according to the present invention, the
quantity of heat carried away from the exhaust gas due to heat
radiation during the period until the exhaust gas discharged from
the internal combustion engine reaches the precatalyst is smaller
than that in the case where the precatalyst is provided in the
exhaust passage. Therefore, the temperature of the precatalyst can
be raised by the exhaust gas more quickly, and the precatalyst can
be maintained at a higher temperature by the exhaust gas.
[0020] Furthermore, in the apparatus according to the present
invention, the exhaust gas flows through the gap between the outer
circumferential surface of the precatalyst and the inner wall
surface of the exhaust manifold. Consequently, an increase in the
back pressure caused by the provision of the precatalyst in the
exhaust manifold can be reduced.
[0021] In the apparatus according to the present invention,
although the exhaust gas flows through the gap between the outer
circumferential surface of the precatalyst and the inner wall
surface of the exhaust manifold, the most part of the reducing
agent added through the reducing agent addition valve flows into
the precatalyst. Therefore, a larger amount of reducing agent can
be modified in the precatalyst.
[0022] Therefore, according to the present invention, when the
reducing agent is added through the reducing agent addition valve
in order to supply the reducing agent to the exhaust gas
purification catalyst, the modification of the reducing agent in
the precatalyst can promoted in a more preferable manner.
[0023] In the apparatus according to the present invention, the
temperature of the precatalyst and the temperature of the ambient
atmosphere around the precatalyst are higher than those in the case
where the precatalyst is provided in the exhaust passage.
Therefore, the adhesion of particulate matter (which will be
hereinafter referred to as PM) contained in the exhaust gas to the
upstream end surface of the precatalyst can be reduced.
Consequently, clogging can be prevented from occurring on the
upstream end surface of the precatalyst. Furthermore, according to
the present invention, since the reducing agent is modified in the
exhaust manifold, the adhesion of the reducing agent in the exhaust
passage can be reduced.
[0024] The present invention may be applied to an internal
combustion engine equipped with a turbocharger. In this case, a
turbine housing of the turbocharger is provided upstream of the
exhaust gas purification catalyst in the exhaust passage.
[0025] Providing the precatalyst upstream of the turbine housing
may lead to a deterioration in response characteristics in changing
the supercharging pressure. However, according to the present
invention, since the exhaust gas flows through the gap between the
outer circumferential surface of the precatalyst and the inner wall
surface of the exhaust manifold, the precatalyst can be prevented
from hindering the flow of the exhaust gas into the turbine
housing. Therefore, the aforementioned deterioration in response
characteristics of the supercharging pressure can be prevented.
[0026] In the above-described case, the turbocharger is prevented
from becoming immobile due to the adhesion of the reducing agent.
In addition, since the reducing agent flows into the turbine
housing together with the exhaust gas, the diffusion of the
reducing agent can be more facilitated in the exhaust gas flowing
into the exhaust gas purification catalyst.
[0027] In the above-described case, the turbocharger may be a
variable geometry turbocharger having nozzle vanes. In this case,
when the reducing agent is added through the reducing agent
addition valve, the degree of opening of the nozzle vanes may be
controlled so that the rotational speed of the turbocharger does
not change with an increase in the quantity of heat generated in
the precatalyst.
[0028] With this feature, a change in the supercharging pressure
can be prevented from occurring at the time when the reducing agent
is added through the reducing agent addition valve.
[0029] In the present invention, the precatalyst may be an NOx
storage reduction catalyst. In this case, NOx in the exhaust gas
can be removed in the exhaust manifold.
ADVANTAGEOUS EFFECT OF THE INVENTION
[0030] According to the present invention, when the reducing agent
is supplied through the reducing agent addition valve in order to
supply the reducing agent to the exhaust gas purification catalyst,
the modification of the reducing agent in the precatalyst can be
promoted more preferably.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a diagram showing the general configuration of an
internal combustion engine and its air-intake and exhaust system
according to embodiment 1.
[0032] FIG. 2 is a diagram showing a first modification of the
internal combustion engine and its air-intake and exhaust system
according to embodiment 1.
[0033] FIG. 3 is a diagram showing a second modification of the
internal combustion engine and its air-intake and exhaust system
according to embodiment 1.
[0034] FIG. 4 is a diagram showing the general configuration of a
turbocharger according to embodiment 2.
[0035] FIG. 5 is a flow chart showing a routine of a fuel addition
control according to embodiment 2.
DESCRIPTION OF THE REFERENCE SIGNS
[0036] 1: internal combustion engine, [0037] 2: cylinder, [0038] 3:
fuel injection valve, [0039] 4: intake passage, [0040] 5: intake
manifold, [0041] 6: exhaust passage, [0042] 7: exhaust manifold,
[0043] 8: turbocharger, [0044] 8a: compressor housing, [0045] 8b:
turbine housing, [0046] 9: NOx storage reduction catalyst, [0047]
10: ECU, [0048] 11: air flow meter, [0049] 12: fuel addition valve,
[0050] 13: oxidation catalyst, [0051] 14: air-fuel ratio sensor,
[0052] 15: temperature sensor, [0053] 17: nozzle vane, and [0054]
18: actuator.
THE BEST MODE FOR CARRYING OUT THE INVENTION
[0055] In the following, a specific embodiment of the exhaust gas
purification apparatus for an internal combustion engine according
to the present invention will be described with reference to the
drawings.
Embodiment 1
<General Configuration of Internal Combustion Engine and
Air-Intake and Exhaust System Thereof>
[0056] FIG. 1 is a diagram showing the general configuration of an
internal combustion engine according to this embodiment and an
air-intake and exhaust system thereof. The internal combustion
engine 1 is a diesel engine having four cylinders 2 for driving a
vehicle. Each cylinder 2 is equipped with a fuel injection valve 3
that injects fuel directly into the cylinder 2.
[0057] The internal combustion engine 1 is connected with an intake
manifold 5 and an exhaust manifold 7. One end of an intake passage
4 is connected to the intake manifold 5. One end of an exhaust
passage 6 is connected to the exhaust manifold 7.
[0058] An air flow meter 11 and a compressor housing 8a of a
turbocharger (supercharger) 8 are provided in the intake passage 4.
A turbine housing 8b of the turbocharger 8 is provided in the
exhaust passage 6.
[0059] An NOx storage reduction catalyst (which will be simply
referred to as the NOx catalyst hereinafter) 9 is provided in the
exhaust passage 6 downstream of the turbine housing 8b. In this
embodiment, the NOx catalyst 9 corresponds to the exhaust gas
purification catalyst according to the present invention.
Alternatively, a three-way catalyst, an oxidation catalyst, or a
particulate filter on which an oxidation catalyst or an NOx
catalyst, etc. is supported may be provided in place of the NOx
catalyst 9. In this case, the three-way catalyst, the oxidation
catalyst, and the particulate filter on which an oxidation catalyst
or an NOx catalyst is supported each correspond to the exhaust gas
purification catalyst according to the present invention.
[0060] An air-fuel ratio sensor 14 that senses the air-fuel ratio
of the exhaust gas is provided in the exhaust passage 6 downstream
of the turbine housing 8b and upstream of the NOx catalyst 9. In
addition, a temperature sensor 15 that senses the temperature of
the exhaust gas is provided in the exhaust passage 6 downstream of
the NOx catalyst 9.
[0061] In the exhaust manifold 7 are provided a fuel addition valve
12 that adds fuel as a reducing agent to the exhaust gas and an
oxidation catalyst 13. The oxidation catalyst 13 is provided in the
exhaust manifold 7 in the vicinity of the portion joining to the
exhaust passage 6. In other words, the oxidation catalyst 13 is
provided in the collecting pipe portion of the exhaust manifold 7.
The outer diameter of the oxidation catalyst 13 is smaller than the
inner diameter of the portion of the exhaust manifold 7 in which
the oxidation catalyst 13 is disposed. From this follows that the
cross sectional area of the oxidation catalyst 13 in a plane
perpendicular to the direction of flow of the exhaust gas is
smaller than the cross sectional area of the portion of the exhaust
manifold 7 in which the oxidation catalyst 13 is provided in a
plane perpendicular to the direction of flow of the exhaust gas.
Consequently, a portion of the exhaust gas passes through the
oxidation catalyst 13, and the other portion of the exhaust gas
flows through the gap between the outer circumferential surface of
the oxidation catalyst 13 and the inner wall surface of the exhaust
manifold 7.
[0062] The fuel addition valve 12 is provided in the exhaust
manifold 7 in such a way that fuel is added toward the upstream end
surface of the oxidation catalyst 13. That is, the fuel addition
valve 12 is disposed in such a way that the oxidation catalyst 13
is located at a position to which the spray jet of fuel, which is
formed as fuel is added through the fuel addition valve 12, is
directed (the spray jet of fuel that is formed as fuel is added
through the fuel addition valve 12 being represented by the hatched
portion in FIG. 1). Thus, the most part of the fuel added through
the fuel addition valve 12 flows into the oxidation catalyst
13.
[0063] In this embodiment, the oxidation catalyst 13 corresponds to
the precatalyst according to the present invention. The oxidation
catalyst 13 is not limited to be an oxidation catalyst, but it may
be any catalyst having an oxidizing ability. In this embodiment,
the fuel addition valve 12 corresponds to the reducing agent
addition valve according to the present invention.
[0064] An electronic control unit (ECU) 10 that controls the
operation state of the internal combustion engine 1 is annexed to
the internal combustion engine 1. The ECU 10 is electrically
connected with the air flow meter 11, the air-fuel ratio sensor 14,
and the temperature sensor 15. Output signals of them are input to
the ECU 10. The ECU 10 estimates the temperature of the NOx
catalyst 9 based on a measurement value of the temperature sensor
15.
[0065] The ECU 10 is electrically connected with the fuel injection
valves 3 and the fuel addition valve 12. They are controlled by the
ECU 10.
<Addition of Fuel>
[0066] In this embodiment, fuel is added through the fuel addition
valve 12, when the temperature of the NOx catalyst 9 is to be
raised, and when NOx or SOx stored in the NOx catalyst 9 is to be
reduced. The fuel added through the fuel addition valve 12 flows
into the oxidation catalyst 13. At least a portion of the fuel
flowing into the oxidation catalyst 13 is modified in the oxidation
catalyst 13. The fuel modified in the oxidation catalyst 13 is
supplied to the NOx catalyst 9.
[0067] As the fuel modified as above is supplied to the NOx
catalyst 9, the oxidation reaction of the fuel and the reduction
reaction of NOx or SOx with the fuel functioning as the reducing
agent that occur in the NOx catalyst 9 tend to be promoted.
Therefore, when fuel is added through the fuel addition valve 12 in
order to raise the temperature of the NOx catalyst 9, the
temperature of the NOx catalyst 9 can be raised more efficiently by
the heat of oxidation generated in the oxidation of fuel.
Furthermore, when fuel is added through the fuel addition valve 12
in order to reduce NOx or SOx stored in the NOx catalyst 9, they
can be reduced more efficiently.
[0068] In this embodiment, the oxidation catalyst 13 is disposed in
the exhaust manifold 7. In this case, the quantity of heat that is
carried away from the exhaust gas due to heat radiation until the
exhaust gas discharged from the internal combustion engine 1
reaches the oxidation catalyst 13 is smaller than in the case where
the oxidation catalyst 13 is disposed in the exhaust passage 6. In
consequence, the temperature of the oxidation catalyst 13 can be
raised more quickly by the exhaust gas, and the temperature of the
oxidation catalyst 13 can be kept higher by the exhaust gas.
[0069] Therefore, it is possible to promote the modification of
fuel in the oxidation catalyst 13 in a wider operation range
without performing the addition of fuel through the fuel addition
valve 12, sub fuel injection through the fuel injection valve(s) 3,
or heating by an electric heater etc. to raise the temperature of
the oxidation catalyst 13.
[0070] In this embodiment, the exhaust gas can flow through the gap
between the outer circumferential surface of the oxidation catalyst
13 and the inner wall surface of the exhaust manifold 7.
Consequently, an increase in the back pressure caused by the
provision of the oxidation catalyst 13 in the exhaust manifold 7
can be reduced. In consequence, influences on the operation state
of the internal combustion engine 1 caused by the provision of the
oxidation catalyst 13 in the exhaust manifold 7 can be made
smaller. In addition, since the oxidation catalyst 13 is prevented
from hindering the flow of the exhaust gas into the turbine housing
8b, a deterioration in the response characteristics in changing the
supercharging pressure can be prevented.
[0071] Furthermore, although this embodiment is configured in such
a way that the exhaust gas can flow through the gap between the
outer circumferential surface of the oxidation catalyst 13 and the
inner wall surface of the exhaust manifold 7, the most part of the
fuel added through the fuel addition valve 12 flows into the
oxidation catalyst 13. Therefore, a major quantity of fuel can be
modified in the oxidation catalyst 13. Consequently, a major
quantity of modified fuel can be supplied to the NOx catalyst
9.
[0072] As described above, according to this embodiment, when fuel
is added through the fuel addition valve 12 in order to supply fuel
to the NOx catalyst 9, the modification of fuel in the oxidation
catalyst 13 can be promoted in a more preferably manner. Therefore,
the temperature of the NOx catalyst 9 can be raised more
preferably, and NOx or Sox stored in the NOx catalyst 9 can be
reduced more preferably.
[0073] Furthermore, in this embodiment, the temperature of the
oxidation catalyst 13 and the temperature of the ambient atmosphere
around the oxidation catalyst 13 are higher than those in the case
in which the oxidation catalyst 13 is provided in the exhaust
passage 6. In consequence, PM contained in the exhaust gas is
unlikely to adhere to the upstream end surface of the oxidation
catalyst 13. Therefore, clogging can be prevented from occurring on
the upstream end surface of the oxidation catalyst 13.
[0074] Still further, in this embodiment, fuel is modified in the
exhaust manifold 7. In consequence, the adhesion of fuel in the
exhaust passage 6 can be reduced. In addition, the adhesion of fuel
to a turbine wheel or other components in the turbine housing 8b
can also be reduced. Therefore, the turbocharger 8 can be prevented
from becoming immobile.
[0075] Still further, in this embodiment, the fuel added through
the fuel addition valve 12 flows into the turbine housing 8b
together with the exhaust gas. Therefore, the diffusion of the fuel
can be more facilitated in the exhaust gas flowing into the NOx
catalyst 9. This facilitates the oxidation reaction of the fuel and
the reduction reaction of NOx or SOx using the fuel as a reducing
agent, in the NOx catalyst 9.
[0076] The modification ratio of fuel in the oxidation catalyst 13
upon the addition of fuel through the fuel addition valve 12 (i.e.
(the quantity of fuel modified in the oxidation catalyst 13)/(the
quantity of fuel added through the fuel addition valve
12).times.100) varies depending on the temperature of the oxidation
catalyst 13 and the flow rate of the exhaust gas. In the case where
fuel is added through the fuel addition valve 12 in order to reduce
NOx stored in the NOx catalyst 9, the higher the modification ratio
of fuel in the oxidation catalyst 13 is, the more the reduction of
NOx in the NOx catalyst 9 is promoted. Therefore, the higher the
modification ratio of fuel in the oxidation catalyst is, the
smaller the quantity of added fuel with which NOx stored in the NOx
catalyst 9 can be adequately reduced is.
[0077] In view of the above, in the case where fuel is added
through the fuel addition valve 12 in order to reduce NOx stored in
the NOx catalyst 9, the modification ratio of fuel in the oxidation
catalyst 13 may be estimated based on the temperature of the
oxidation catalyst 13 and the flow rate of the exhaust gas, and the
quantity of fuel added through the fuel addition valve 12 may be
corrected based on the modification ratio. Thereby, the fuel
economy can be prevented from being made worse by the addition of
fuel through the fuel addition valve 12. In addition, the quantity
of fuel flowing out of the NOx catalyst 9 without being used in the
reduction of NOx can be reduced. In connection with the above, the
temperature of the oxidation catalyst 13 can be estimated based on,
for example, the operation state of the internal combustion engine
1.
[0078] The arrangement of the oxidation catalyst 13 and the fuel
addition valve 12 in the exhaust manifold 7 is not limited to the
arrangement shown in FIG. 1. FIGS. 2 and 3 show other arrangements
of the oxidation catalyst and the fuel addition valve 12 in the
exhaust manifold 7. (In FIGS. 2 and 3 also, the spray jet of fuel
that is formed as fuel is added through the fuel addition valve 12
is represented by the hatched portion.)
[0079] In the case of the arrangement shown in FIG. 2, the fuel
added through the fuel addition valve 12 strikes on the inner wall
surface of the exhaust manifold 7, and the most part thereof is
involved in the stream of the exhaust gas to flow into the
oxidation catalyst 13. In this way, the fuel addition valve 12 and
the oxidation catalyst 13 may be arranged in such a way that the
oxidation catalyst 13 is located at a position toward which the
sprayed fuel added through the fuel addition valve 12 is
directed.
[0080] In the case of the arrangement shown in FIG. 3, the
oxidation catalyst 13 is disposed at a position in the exhaust
manifold 7 distant from the neighborhood of the portion at which
the exhaust manifold 7 is joined to the exhaust passage 6. In this
case, the exhaust gas discharged only from the cylinder disposed
upstream of the oxidation catalyst 13 with respect to the stream of
the exhaust gas in the exhaust manifold 7 passes thorough the
oxidation catalyst 13. On the other hand, the exhaust gas
discharged from the cylinders disposed downstream of the oxidation
catalyst 13 with respect to the stream of the exhaust gas in the
exhaust manifold 7 flows into the exhaust passage 6 without passing
through the oxidation catalyst 13. Consequently, an increase in the
back pressure caused by the provision of the oxidation catalyst 13
in the exhaust manifold 7 can be further reduced. In this case
also, the cross sectional area of the oxidation catalyst 13 in a
plane perpendicular to the direction of flow of the exhaust gas is
smaller than the cross sectional area of the portion of the exhaust
manifold 7 in which the oxidation catalyst 13 is provided in a
plane perpendicular to the direction of flow of the exhaust gas.
Consequently, an increase in the back pressure in the region
upstream of the oxidation catalyst 13 can be made small. In this
case also, the fuel addition valve 12 is disposed in the exhaust
manifold 7 in such a way as to add fuel toward the upstream end
surface of the oxidation catalyst 13. In consequence, the most part
of the fuel added through the fuel addition valve 12 flows into the
oxidation catalyst 13. Therefore, a larger quantity of fuel can be
modified in the oxidation catalyst 13.
Embodiment 2
<General Configuration of Turbocharger>
[0081] FIG. 4 is a diagram showing the general configuration of the
turbocharger 8 according to this embodiment. The turbine housing 8b
of the turbocharger according to this embodiment has a plurality of
blade-like nozzle vanes 17 attached along the circumferential
direction of the turbine wheel. The nozzle vanes 17 are driven by
an actuator 18.
[0082] As the degree of opening of the nozzle vanes 17 is changed
by the actuator 18, the gaps between the adjacent nozzle vanes 17
change. This causes a change in the flow speed of the exhaust gas
blown onto the turbine wheel, which in turn causes a change in the
rotational speed of the turbocharger 8. In consequence, the
supercharging pressure in the internal combustion engine 1
changes.
[0083] The actuator 18 is electrically connected with the ECU 10
and controlled by the ECU 10. The construction of the internal
combustion engine and its air-intake and exhaust system other than
the turbocharger 8 are the same as that in embodiment 1. Therefore,
the like components will be denoted by like reference numerals, and
descriptions thereof will be omitted.
<Control of Nozzle Vane Opening Degree>
[0084] As the fuel added through the fuel addition valve 12 flows
into the oxidation catalyst 13, a portion of the fuel is oxidized
in the oxidation catalyst 13. For this reason, performing the
addition of fuel through the fuel addition valve 12 may sometimes
cause a rise in the temperature of the exhaust gas flowing into the
turbine housing 8b. This may consequently lead to an increase in
the rotational speed of the turbocharger 8.
[0085] In view of this, in this embodiment when fuel is added
through the fuel addition valve 12, the degree of opening of the
nozzle vanes 17 is controlled so that the rotational speed of the
turbocharger 8 does not change.
[0086] In the following, a routine of the fuel addition control
according to this embodiment will be described with reference to
the flow chart shown in FIG. 5. This routine is stored in the ECU
10 in advance and executed repeatedly at predetermined intervals
during the operation of the internal combustion engine 1.
[0087] In this routine, first in step S101, the ECU 10 determines
whether or not a condition for performing the addition of fuel
through the fuel addition valve 12 is met. Here, the condition for
performing the addition of fuel is the condition for performing
heating-up of the NOx catalyst 9 or the condition for performing
the reduction of NOx or SOx stored in the NOx catalyst 9. If the
determination in step S101 is affirmative, the ECU 10 proceeds to
step S102, and if the determination is negative, the ECU 10 once
terminates execution of this routine.
[0088] In step S102, the ECU 10 estimates the temperature Tc of the
oxidation catalyst 13 based on the operation state of the internal
combustion engine 1.
[0089] Then, the ECU 10 proceeds to step S103, where it estimates
the quantity of heat Qh generated by the oxidation of fuel in the
oxidation catalyst 13 as the addition of fuel through the fuel
addition valve 12 is performed. The quantity of generated heat Qh
can be estimated based on the temperature Tc of the oxidation
catalyst 13, the quantity of fuel added through the fuel addition
valve 12, and the operation state of the internal combustion engine
1.
[0090] Then, the ECU 10 proceeds to step S104, where it calculates
the opening degree increase Dn of the nozzle vanes 17 based on the
quantity of generated heat Qh. The opening degree increase Dn is
calculated so that even when the heat (the quantity of which is the
quantity of generated heat Qh) is generated by oxidation in the
oxidation catalyst 13 by the addition of fuel through the fuel
addition valve 12 whereby a rise in the temperature of the exhaust
gas flowing into the turbine housing 8b is caused, the rotational
speed of the turbocharger 8 can be maintained substantially equal
to that before the addition of fuel by increasing the degree of
opening of the nozzle vanes 17 by an amount equal to the opening
degree increase Dn. The relationship between the quantity of
generated heat Qh and the opening degree increase Dn is calculated
beforehand based on, for example, experiments, and stored in the
ECU 10 as a map.
[0091] Then, the ECU 10 proceeds to step S105, where it increases
the degree of opening of the nozzle vanes 17 by an amount equal to
the opening degree increase Dn.
[0092] Then, the ECU 10 proceeds to step S106, where it executes
the addition of fuel through the fuel addition valve 12.
Thereafter, the ECU 10 once terminates execution of this
routine.
[0093] According to the above-described routine, when fuel is added
through the fuel addition valve 12, the rotational speed of the
turbocharger 8 is prevented from increasing with an increase in the
quantity of heat generated in the oxidation catalyst 13.
Consequently, the supercharging pressure in the internal combustion
engine 1 can be prevented from changing through the addition of
fuel through the fuel addition valve 12.
[0094] In embodiments 1 and 2, the oxidation catalyst 13 may be an
NOx catalyst. If this is the case, NOx in the exhaust gas can be
removed in the exhaust manifold 7. Furthermore, NOx stored in the
NOx catalyst can be reduced as fuel is added through the fuel
addition valve 12 in order to raise the temperature of the NOx
catalyst 9 or reduce NOx stored in the NOx catalyst 9.
* * * * *