U.S. patent application number 12/811827 was filed with the patent office on 2010-11-04 for exhaust emission control device for internal combustion engine.
This patent application is currently assigned to HONDA MOTOR CO., LTD.. Invention is credited to Jun Iwamoto, Nobuhiro Komatsu, Go Motohashi, Tomoko Tsuyama, Katsuji Wada.
Application Number | 20100275582 12/811827 |
Document ID | / |
Family ID | 40852944 |
Filed Date | 2010-11-04 |
United States Patent
Application |
20100275582 |
Kind Code |
A1 |
Wada; Katsuji ; et
al. |
November 4, 2010 |
EXHAUST EMISSION CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE
Abstract
Provided is an exhaust emission control device for an internal
combustion engine capable of high-efficiency DPF regeneration
processing. The exhaust emission control device comprises a DPF for
collecting PMs in exhaust emissions, which is provided in an
exhaust pipe of an engine, a fuel reformer for reforming fuel to
manufacture a reducing gas containing hydrogen and carbon monoxide
and supplying the reducing gas from an introduction port provided
on the upstream side of the DPF of the exhaust pipe into the
exhaust pipe, which is provided separately from the exhaust pipe, a
catalyst converter for continuously oxidizing the reducing gas,
which is provided between the introduction port and the DPF of the
exhaust pipe, and a regeneration means for performing regeneration
processing for burning the PMs collected by the DPF while the
reducing gas is supplied into the exhaust pipe by the fuel
reformer.
Inventors: |
Wada; Katsuji; (Saitama,
JP) ; Motohashi; Go; (Saitama, JP) ; Iwamoto;
Jun; (Saitama, JP) ; Komatsu; Nobuhiro;
(Saitama, JP) ; Tsuyama; Tomoko; (Saitama,
JP) |
Correspondence
Address: |
ARENT FOX LLP
1050 CONNECTICUT AVENUE, N.W., SUITE 400
WASHINGTON
DC
20036
US
|
Assignee: |
HONDA MOTOR CO., LTD.
MInato-ku, Tokyo
JP
|
Family ID: |
40852944 |
Appl. No.: |
12/811827 |
Filed: |
November 18, 2008 |
PCT Filed: |
November 18, 2008 |
PCT NO: |
PCT/JP2008/070927 |
371 Date: |
July 6, 2010 |
Current U.S.
Class: |
60/276 ; 60/285;
60/295 |
Current CPC
Class: |
C01B 2203/06 20130101;
Y02A 50/20 20180101; F02D 2200/1004 20130101; B01J 35/0006
20130101; Y02A 50/2341 20180101; B01J 37/0246 20130101; F02D
41/1448 20130101; F01N 3/035 20130101; B01D 2255/106 20130101; F01N
9/002 20130101; B01J 29/7615 20130101; F01N 2240/30 20130101; F01N
13/009 20140601; B01D 53/944 20130101; Y02T 10/47 20130101; B01D
2255/1025 20130101; F02D 41/029 20130101; B01J 23/63 20130101; B01J
37/0244 20130101; Y02T 10/40 20130101; F02D 2200/0812 20130101;
F01N 3/023 20130101; B01D 2255/1021 20130101; F01N 3/029 20130101;
F02D 41/123 20130101; F02D 2200/0804 20130101; B01D 2255/1023
20130101; C01B 2203/0261 20130101; F02D 41/1446 20130101; B01J
23/002 20130101; Y02P 20/52 20151101; B01D 2255/104 20130101; F01N
2560/025 20130101; B01J 2523/00 20130101; C01B 3/386 20130101; F01N
2610/03 20130101; B01J 2523/00 20130101; B01J 2523/31 20130101;
B01J 2523/3706 20130101; B01J 2523/3712 20130101; B01J 2523/3718
20130101; B01J 2523/48 20130101; B01J 2523/828 20130101; B01J
2523/00 20130101; B01J 2523/31 20130101; B01J 2523/3712 20130101;
B01J 2523/822 20130101; B01J 2523/824 20130101; B01J 2523/828
20130101 |
Class at
Publication: |
60/276 ; 60/295;
60/285 |
International
Class: |
F01N 9/00 20060101
F01N009/00; F01N 3/025 20060101 F01N003/025; F01N 11/00 20060101
F01N011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 8, 2008 |
JP |
2008001698 |
Jan 8, 2008 |
JP |
2008001699 |
Jan 8, 2008 |
JP |
2008001701 |
Claims
1. An exhaust emission control device for an internal combustion
engine including a particulate filter that is provided in an
exhaust channel of the internal combustion engine, and collects
particulates in exhaust, the device comprising: a fuel reformer
that is provided separately from the exhaust channel, produces a
reducing gas containing hydrogen and carbon monoxide by reforming
fuel, and supplies the reducing gas from an inlet provided in the
exhaust channel upstream of the particulate filter into the exhaust
channel; a catalytic converter that is provided in the exhaust
channel between the inlet and the particulate filter, and
continuously oxidizes the reducing gas; and a regeneration means
for executing a regeneration process to cause particulates
collected in the particulate filter to be combusted while supplying
reducing gas from the fuel reformer into the exhaust channel.
2. An exhaust emission control device for an internal combustion
engine including a particulate filter that is provided in an
exhaust channel of the internal combustion engine, and collects
particulates in exhaust, the device comprising: a fuel reformer
that is provided separately from the exhaust channel, produces a
reducing gas containing hydrogen and carbon monoxide by reforming
fuel, and supplies the reducing gas from an inlet provided in the
exhaust channel upstream of the particulate filter into the exhaust
channel; and a regeneration means for executing a regeneration
process to cause particulates collected in the particulate filter
to be combusted while supplying reducing gas from the fuel reformer
into the exhaust channel, wherein a catalyst having an oxidative
function of continuously oxidizing reducing gas is supported on the
particulate filter.
3. An exhaust emission control device for an internal combustion
engine according to claim 1, wherein the catalytic converter
contains at least one selected from the group consisting of
platinum, palladium, and rhodium.
4. An exhaust emission control device for an internal combustion
engine according to claim 2, wherein the catalyst having the
oxidative function contains at least one selected from the group
consisting of palladium, rhodium, platinum, silver, and gold.
5. An exhaust emission control device for an internal combustion
engine according to claim 3, further comprising an oxygen
concentration detection means for detecting or estimating an oxygen
concentration of exhaust in the exhaust channel flowing into the
particulate filter.
6. An exhaust emission control device for an internal combustion
engine according to claim 5, wherein the reducing gas produced by
the fuel reformer contains more carbon monoxide than hydrogen.
7. An exhaust emission control device for an internal combustion
engine according to claim 6, wherein a temperature of the reducing
gas supplied by the fuel reformer is higher than a temperature of
exhaust flowing through the exhaust channel at the inlet.
8. An exhaust emission control device for an internal combustion
engine according to claim 1, further comprising: a target
concentration setting means for setting an oxygen concentration
target value of exhaust flowing into the particulate filter while
executing the regeneration process by way of the regeneration
means; and an oxygen concentration control means for controlling
the oxygen concentration of exhaust so as to match the oxygen
concentration target value thus set by the oxygen concentration
setting means, by adjusting at least one amount an intake air
amount of the internal combustion engine, an exhaust recirculation
ratio of the internal combustion engine, a fuel injection amount of
the internal combustion engine, and a supply amount of reducing gas
from the fuel reformer.
9. An exhaust emission control device for an internal combustion
engine according to claim 8, wherein the target concentration
setting means sets the oxygen concentration target value based on
at least one among a flow rate of exhaust flowing through the
exhaust channel, a temperature of the exhaust, and a deposition
amount of particulates deposited on the particulate filter.
10. An exhaust emission control device for an internal combustion
engine according to claim 9, wherein the target concentration
setting means, in a case of the internal combustion engine being in
an idle operating state, sets the oxygen concentration target value
to be low compared to a case of not being in an idle operating
state.
11. An exhaust emission control device for an internal combustion
engine according to claim 10, wherein the target concentration
setting means, in a case of the internal combustion engine being in
a deceleration operating state, sets the oxygen concentration
target value to be low compared to a case of not being in a
deceleration operating state.
12. An exhaust emission control device for an internal combustion
engine according to claim 11, wherein the fuel reformer produces
reducing gas with carbon monoxide as a main component by way of a
partial oxidation reaction of hydrocarbon fuel and air.
13. An exhaust emission control device for an internal combustion
engine including a particulate filter that is provided in an
exhaust channel of the internal combustion engine, and collects
particulates in exhaust, the device comprising: a regeneration
means for executing a regeneration process to cause particulates
collected in the particulate filter to be combusted; and a fuel
reformer that is provided separately from the exhaust channel,
produces a reducing gas containing hydrogen and carbon monoxide by
reforming fuel, and supplies the reducing gas from an inlet
provided in the exhaust channel upstream of the particulate filter
into the exhaust channel, wherein the regeneration means includes a
normal regeneration means that executes a regeneration process
without employing reducing gas produced by the fuel reformer, and a
heated regeneration means that allows a regeneration process
employing reducing gas produced by the fuel reformer to be
executed, and switches between executing the regeneration process
by way of the normal regeneration means and executing the
regeneration process by way of the heated regeneration means
according to a predetermined condition.
14. An exhaust emission control device for an internal combustion
engine according to claim 13, wherein the reducing gas produced by
the fuel reformer contains more carbon monoxide than hydrogen.
15. An exhaust emission control device for an internal combustion
engine according to claim 13, wherein the catalytic converter that
continuously oxidizes reducing gas is provided in the exhaust
channel between the inlet and the particulate filter.
16. An exhaust emission control device for an internal combustion
engine according to claim 13, further comprising a combustion
judgment means for judging whether particulates deposited on the
particulate filter are in a combusted state, wherein the
regeneration means executes the regeneration process by way of the
normal regeneration means in a case of having been judged that the
particulate are in a combusted state, and executes the regeneration
process by way of the heated regeneration means in a case of having
been judged that the particulates are not in a combusted state.
17. An exhaust emission control device for an internal combustion
engine according to claim 16, further comprising an oxygen
concentration detection means for detecting or estimating an oxygen
concentration of exhaust in the exhaust channel on a downstream
side of the particulate filter, wherein the combustion judgment
means judges whether the particulates are in a combusted state
based on the oxygen concentration thus detected or estimated by the
oxygen concentration detection means.
18. An exhaust emission control device for an internal combustion
engine according to claim 16, further comprising a downstream
exhaust temperature detection means for detecting or estimating an
exhaust temperature in the exhaust channel on a downstream side of
the particulate filter, wherein the combustion judgment means
judges whether the particulates are in a combusted state based on
the exhaust temperature thus detected or estimated by the
downstream exhaust temperature detection means.
19. An exhaust emission control device for an internal combustion
engine according to claim 16, wherein the heated regeneration means
reduces the intake air amount of the internal combustion engine,
increases the exhaust recirculation ratio of the internal
combustion engine, or sets the charge efficiency of the internal
combustion engine to be small, compared to a case of performing the
regeneration process by way of the normal regeneration means.
20. An exhaust emission control device for an internal combustion
engine according to claim 19, wherein the heated regeneration means
includes a first heated regeneration means for executing a
regeneration process while supplying reducing gas from the fuel
reformer into the exhaust channel, and a second heated regeneration
means for executing a regeneration process without supplying
reducing gas from the fuel reformer into the exhaust channel, and
switches between executing the regeneration process by way of the
first heated regeneration means and executing the regeneration
process by way of the second heated regeneration means according to
a predetermined condition.
21. An exhaust emission control device for an internal combustion
engine according to claim 20, further comprising an upstream
exhaust temperature detection means for detecting or estimating a
temperature of exhaust in the exhaust channel on an upstream side
of the particulate filter, wherein the heated regeneration means
executes the regeneration process by way of the first heated
regeneration means in a case of the temperature thus detected by
the upstream exhaust temperature detection means being lower than a
predetermined judgment value.
22. An exhaust emission control device for an internal combustion
engine according to claim 20, further comprising a filter
temperature estimation means for estimating or detecting a
temperature of the particulate filter, wherein the heated
regeneration means executes the regeneration process by way of the
first heated regeneration means in a case of the temperature thus
estimated or detected by the filter temperature estimation means
being lower than a predetermined judgment value.
23. An exhaust emission control device for an internal combustion
engine according to claim 20, further comprising a torque
estimation means for estimating a generated torque of the internal
combustion engine, wherein the heated regeneration means executes
the regeneration process by way of the first regeneration means in
a case of the generated torque thus estimated or detected by the
torque estimation means being less than a predetermined judgment
value.
24. An exhaust emission control device for an internal combustion
engine according to claim 23, wherein the torque estimation means
estimates the generated torque of the internal combustion engine
based on at least one among a revolution speed of the internal
combustion engine, a fuel injection amount, and a fuel injection
timing.
25. An exhaust emission control device for an internal combustion
engine according to claim 20 further comprising a timing means for
measuring an elapsed time since starting up the internal combustion
engine, wherein the heated regeneration means executes the
regeneration process by way of the first heated regeneration means
in a case of the elapsed time thus measured by the timing means
being less than a predetermined judgment value.
26. An exhaust emission control device for an internal combustion
engine, including a NOx purification catalyst that is provided in
an exhaust channel of the internal combustion engine and that, with
an air/fuel ratio of exhaust flowing through the exhaust channel as
an exhaust air/fuel ratio, adsorbs or occludes NOx in exhaust when
the exhaust air/fuel ratio is made lean, and reduces the NOx
adsorbed or occluded when the exhaust air fuel ratio is made rich,
and a particulate filter that is provided in the exhaust channel
further upstream than the NOx purification catalyst, and that
collects particulates in exhaust, the device comprising: a fuel
reformer that is provided separately from the exhaust channel,
produces a reducing gas containing hydrogen and carbon monoxide by
reforming fuel, and supplies the reducing gas from an inlet
provided in the exhaust channel between the particulate filter and
the NOx purification catalyst into the exhaust channel.
27. An exhaust emission control device for an internal combustion
engine according to claim 26, wherein the reducing gas produced by
the fuel reformer is at a pressure higher than atmospheric
pressure, and contains more carbon monoxide than hydrogen by volume
ratio.
28. An exhaust emission control device for an internal combustion
engine according to claim 26, wherein a temperature of the reducing
gas supplied by the fuel reformer is higher than a temperature of
exhaust flowing through the exhaust channel at the inlet.
29. An exhaust emission control device for an internal combustion
engine according to claim 26, wherein oxygen is contained in the
exhaust flowing through the exhaust channel when reducing gas from
the fuel reformer is introduced into the exhaust channel.
30. An exhaust emission control device for an internal combustion
engine according to claim 26 further comprising: a regeneration
means for selectively executing a normal regeneration operation
that raises the particulate filter in temperature to cause
particulates collected in the particulate filter to combust, and a
simultaneous regeneration operation that supplies reducing gas from
the fuel reformer into the exhaust channel while executing the
normal regeneration operation to purify SOx adsorbed to the NOx
purification catalyst according to a predetermined condition.
31. An exhaust emission control device for an internal combustion
engine according to claim 30, further comprising an exhaust
temperature control means for controlling a temperature of exhaust
when executing the normal regeneration operation by adjusting at
least one among an intake air amount and boost pressure.
32. An exhaust emission control device for an internal combustion
engine according to claim 30, wherein a catalytic converter having
an oxidative function is provided in the exhaust channel on an
upstream side of the particulate filter, and wherein the
regeneration means executes post injection when executing the
normal regeneration operation.
33. An exhaust emission control device for an internal combustion
engine according to claim 30, wherein a catalyst having an
oxidative function is supported on the particulate filter, and
wherein the regeneration means executes post injection when
executing the normal regeneration operation.
34. An exhaust emission control device for an internal combustion
engine according to claim 30, further comprising a particulate
deposition amount estimation means for estimating or detecting a
particulate deposition amount of the particulate filter, wherein
the regeneration means executes the normal regeneration operation
or the simultaneous regeneration operation in response to the
particulate deposition amount thus estimated or detected by the
particulate deposition amount estimation means having become at
least a predetermined first estimation judgment value.
35. An exhaust emission control device for an internal combustion
engine according to claim 30, further comprising: a catalyst
temperature estimation means for estimating or detecting a
temperature of the NOx purification catalyst; and a SOx poisoning
amount estimation means for estimating or detecting a SOx poisoning
amount of the NOx purification catalyst, wherein the regeneration
means executes the simultaneous regeneration operation in response
to the temperature thus estimated or detected by the catalyst
temperature estimation means being at least a predetermined
temperature judgment value, and the SOx poisoning amount thus
estimated or detected by the SOx poisoning amount estimation means
having become at least a predetermined first poisoning judgment
value.
36. An exhaust emission control device for an internal combustion
engine according to claim 35, wherein the regeneration means ends
execution of the simultaneous regeneration operation and executes
the normal regeneration operation, in response to the SOx poisoning
amount estimated or detected by the SOx poisoning amount estimation
means having become smaller than a predetermined second poisoning
judgment value.
37. An exhaust emission control device for an internal combustion
engine according to claim 26, further comprising: an oxygen
concentration detection means for detecting an oxygen concentration
of exhaust in the exhaust channel in a vicinity of the NOx
purification catalyst; and a supply amount control means for
controlling a supply amount of reducing gas supplied from the fuel
reformer into the exhaust channel, according to the oxygen
concentration thus detected by the oxygen concentration detection
means.
38. An exhaust emission control device for an internal combustion
engine according to claim 26, wherein the fuel reformer produces
reducing gas by way of a partial oxidation reaction of hydrocarbon
fuel and air.
39. An exhaust emission control device for an internal combustion
engine according to claim 26, wherein the internal combustion
engine uses light oil as fuel, and combusts the fuel by way of
compression ignition.
Description
TECHNICAL FIELD
[0001] The present invention relates to an exhaust emission control
device for an internal combustion engine. Specifically, it relates
to an exhaust emission control device for an internal combustion
engine having a DPF (diesel particulate filter) that collects PM
(particulate matter) in the exhaust.
[0002] In addition, in the present invention, the terminology
"rich" indicates a ratio of air/fuel (hereinafter referred to as
"air/fuel ratio") of fuel that is smaller than a stoichiometric
air/fuel ratio, and the terminology "lean" indicates an air/fuel
ratio of fuel that is larger than the above stoichiometric air/fuel
ratio. Moreover, in the following explanation, a mass ratio of air
and fuel in a mixed gas flowing into the engine is called an engine
air/fuel ratio, and a mass ratio of air and combustible gas inside
exhaust plumbing is called an exhaust air/fuel ratio.
[0003] In addition, as a method for controlling the exhaust
air/fuel ratio, there is a method in which the exhaust air/fuel
ratio is made low (hereinafter referred to as "enriching") by
reducing the intake air amount of the engine and adjusting the fuel
injection (hereinafter referred to as "main injection") amount
contributing to torque, and a method in which the exhaust air/fuel
ratio is enriched by performing fuel injection that does not
contribute to torque (hereinafter referred to as "post injection")
to flow unburned fuel into the exhaust path. Moreover,
alternatively, a method has also been known in which fuel is
directly injected into the exhaust path (hereinafter referred to as
"exhaust injection").
BACKGROUND ART
[0004] Diesel engines, lean-burn engines, and the like have
air/fuel ratios inside the cylinders that become heterogeneous, and
thus PM with carbon as a main component is emitted due to
combusting in a state in which oxygen is insufficient at a portion
that has become locally rich. Consequently, in order to reduce the
emission amount of such PM, a technique has been widely used that
reduces the emission amount of PM by providing a DPF that collects
PM in the exhaust to the exhaust system. Since there is a
limitation to the PM amount that can be collected by this DPF, a
DPF regeneration process in which the PM deposited on the DPF is
caused to combust is executed as appropriate. In recent years,
various proposals have been made related to techniques for this DPF
regeneration process.
[0005] For example, in Patent Document 1, an exhaust emission
control device is exemplified that arranges a catalytic converter
coated with a catalyst having high oxidation performance in an
exhaust channel on an upstream side of the DPF, and that performs
exhaust injection of unburned fuel into the exhaust channel,
thereby causing this fuel to combust in the catalytic converter to
raise the temperature of the exhaust, and combusts PM deposited on
the DPF by causing the exhaust thereby made high temperature to
flow into the DPF.
[0006] In addition, in Patent Document 2, for example, an exhaust
emission control device is exemplified that, by performing post
injection instead of exhaust injection as described above, causes
fuel to be combusted in the catalytic converter to raise the
temperature of exhaust, similarly to the exhaust emission control
device of Patent Document 1, and combusts PM deposited on the
DPF.
[0007] Incidentally, in addition to this exhaust injection and post
injection, a method has been known as a method to make the exhaust
air/fuel ratio rich in which a fuel reformer that produces reducing
gas containing carbon monoxide and hydrogen by way of a reforming
reaction is provided to the exhaust channel. Herein, as the
reforming reaction of a reforming catalyst of the fuel reformer,
for example, a reaction has been known that produces a gas
containing hydrogen and carbon monoxide by the partial oxidation
reaction of hydrocarbons, such as that shown in formula (1)
below.
C.sub.nH.sub.m+1/2nO.sub.2.fwdarw.nCO+1/2mH.sub.2 (1)
[0008] This partial oxidation reaction is an exothermal reaction
employing fuel and oxygen, and the reaction progresses
spontaneously. As a result, upon the reaction being started, it is
possible to continuously produce hydrogen without the supply of
heat from outside. In addition, in this kind of partial oxidation
reaction, in a case in which fuel and oxygen coexist in a high
temperature state, the combustion reaction as shown in formula (2)
below also progresses on the reforming catalyst.
C.sub.nH.sub.m+(n+1/4m)O.sub.2.fwdarw.nCO.sub.2+1/2mH.sub.2O
(2)
[0009] As the reforming reaction, in addition to the partial
oxidation reaction, the steam reforming reaction as shown in
formula (3) below has also been known.
C.sub.nH.sub.m+nH.sub.2O.fwdarw.nCO+(n+1/2m)H.sub.2 (3)
[0010] This steam reforming reaction is an endothermic reaction
employing fuel and steam, and is not a reaction that progresses
spontaneously. As a result, the steam reforming reaction is easily
controlled relative to the partial oxidation reaction described
above. On the other hand, it is necessary to input energy such as
of a heat supply from outside.
[0011] Patent Document 1: Japanese Patent No. 3835241
[0012] Patent Document 2: Japanese Unexamined Patent Application
Publication No. H8-42326
[0013] Incidentally, if the oxygen amount flowing into the DPF
suddenly increases while PM is being combusted by causing exhaust
of a high temperature to flow into the DPF, an oxidation reaction
in the DPF may suddenly progress and the DPF may melt. Herein, as
main causes for a sudden increase in the oxygen amount in the
exhaust, for example, a case in which fuel injection has been
interrupted (hereinafter referred to as "deceleration fuel-cut")
accompanying deceleration of the vehicle, a case in which the
engine transitions to idle operation, or the like can be
exemplified.
[0014] In order to avoid such a situation, for example, it has been
considered to consume a surge in oxygen in the catalytic converter
provided upstream of the DPF by way of performing exhaust injection
or post injection, as with the exhaust emission control devices
exemplified in the aforementioned Patent Documents 1 and 2, thereby
lowering the oxygen amount flowing into the DPF.
[0015] However, in a case of performing exhaust injection as in the
exhaust emission control device of Patent Document 1, unburned fuel
makes direct contact with the catalytic converter, the temperature
of the catalyst surface becomes high locally, and thus the catalyst
may deteriorate due to sintering or the like. In addition, when
fuel contacts the catalyst in a droplet state, the temperature of
the catalyst surface at the contacting portion thereof will
decrease locally due to the latent heat of vaporization, and thus
coking may occur. Moreover, if exhaust injection is performed in a
case in which the exhaust temperature is low, the exhaust
temperature will decrease further due to the latent heat of
vaporization of the fuel supplied by exhaust injection, whereby
liquid fuel collects in the exhaust channel, the catalyst
deteriorates, and exhaust system components may corrode.
[0016] In addition, in a case of performing post injection as in
the exhaust emission control device of Patent Document 2, a portion
of the fuel injected adheres to the surface of the wall of the
cylinders, and thus this fuel may mix into the engine oil. In such
a case, not only the fuel injected not contributing to combustion
of PM, but also so-called oil dilution in which engine oil is
diluted by this fuel may occur.
[0017] Moreover, a majority of the reducing agent consumed by the
oxidation reaction in the catalytic converter, as in the exhaust
emission control device of Patent Documents 1 and 2, is
hydrocarbons. Therefore, it is necessary to maintain the catalytic
converter at a certain temperature at which the oxidation reaction
of the hydrocarbons flowing thereinto is possible. However, in a
case in which low-load operation continues or the like, the
temperature of the catalytic converter will decrease to a
temperature at which it is difficult for the oxidation reaction to
occur, and the DPF regeneration process may not be able to be
executed.
[0018] On the other hand, in a case of providing a fuel reformer in
an exhaust channel, there are the following issues.
[0019] Specifically, in a case of providing the fuel reformer in an
exhaust channel having an exhaust amount that regularly fluctuates
as described above, it is necessary to increase the reaction time
for which the reforming catalyst of the fuel reformer and the
exhaust come into contact, in order to effectively produce hydrogen
in this fuel reformer. However, in order to increase the reaction
time as such, it is necessary to increase the size of the reforming
catalyst, which may raise cost.
[0020] In addition, in order to operate the fuel reformer in a
stable state, it is necessary to maintain the reaction temperature
of the reforming catalyst of this fuel reformer to be constant.
However, when providing a fuel reformer in an exhaust channel for
which the oxygen amount, steam amount, and temperature are always
fluctuating as described above, it becomes difficult to operate the
fuel reformer in a stable state.
[0021] Incidentally, in addition to the aforementioned DPF, a
technique has been known from the prior art in which NOx (nitrogen
oxides) in exhaust is absorbed by providing a NOx purification
catalyst in the exhaust system of the internal combustion engine,
thereby reducing the emitted amount of NOx. On the other hand,
sulfur components in the fuel and engine oil are contained in
exhaust emitted from the internal combustion engine. When such
sulfur components accumulate on the NOx purification catalyst, the
NOx purification performance declines. Therefore, the following
technique has been proposed that aims to prevent the purification
performance from declining due to such poisoning of the NOx
purification catalyst.
[0022] For example, an exhaust emission control device that
provides a fuel reformer, which produces a reducing gas containing
hydrogen, carbon monoxide, etc. by way of a reforming reaction,
upstream of a NOx purification catalyst is proposed in Patent
Document 3. According to this exhaust emission control device,
removal of sulfur components is promoted by adding hydrogen thus
produced by the fuel reformer to the exhaust when executing the SOx
regeneration process of the NOx purification catalyst.
[0023] Such a SOx regeneration process of a NOx purification
catalyst and a DPF regeneration process of the aforementioned DPF
are basically executed separately according to the states of the
NOx purification catalyst and the DPF. However, even in a case of
performing either of the regeneration processes, it is necessary to
cause the temperature of the exhaust system to rise. Therefore, in
order to prevent the fuel economy from deteriorating, it is more
preferable to execute the SOx regeneration process and the DPF
regeneration process simultaneously than to execute
individually.
[0024] Consequently, in Patent Document 4, for example, an exhaust
emission control device has been proposed in which the NOx
purification catalyst is provided downstream of the DPF, and the
DPF regeneration process of the DPF and the SOx regeneration
process of the NOx purification catalyst are executed
simultaneously by controlling the oxygen concentration flowing into
the DPF.
[0025] Patent Document 3: Japanese Patent No. 3896923
[0026] Patent Document 4: Japanese Unexamined Patent Application
Publication No. 2005-133721
[0027] Incidentally, in a case of executing the SOx regeneration
process of the NOx purification catalyst, it is necessary to make
the exhaust air/fuel ratio flowing into this NOx purification
catalyst to be less than a stoichiometric ratio. On the other hand,
in a case of executing the DPF regeneration process of the DPF, it
is necessary to make the exhaust air/fuel ratio flowing into the
DPF to be larger than the stoichiometric ratio, thereby making an
oxygen-excess atmosphere.
[0028] The exhaust emission control device illustrated in the
aforementioned Patent Document 4 aims to adjust the oxygen
concentration of the exhaust flowing into the NOx purification
catalyst by controlling the oxygen concentration of exhaust flowing
into the DPF, and to execute the DPF regeneration process and SOx
regeneration process simultaneously. However, with the exhaust
emission control device of Patent Document 4, when the oxygen
concentration of exhaust flowing into the DPF becomes high, the
exhaust air/fuel ratio flowing into the NOx purification catalyst
will become large, and thus it is difficult to simultaneously
execute the DPF regeneration process and the SOx regeneration
process with high efficiency. As a result, the time consumed in
this simultaneous process will become long, whereby fuel economy
may deteriorate and the catalyst may degrade.
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0029] As described above, with the exhaust emission control
devices illustrated in Patent Documents 1 and 2 and the exhaust
emission control devices provided with a fuel reformer in the
exhaust channel, the efficiency of the DPF regeneration process may
decline depending on the operating state of the internal combustion
engine.
[0030] In addition, with the exhaust emission control device
illustrated in Patent Document 4, in a case of performing the DPF
regeneration process and the SOx regeneration process
simultaneously, the efficiency of the processes may decline.
[0031] An object of the present invention is to provide an exhaust
emission control device for an internal combustion engine that can
perform a DPF regeneration process with high efficiency
irrespective of the operating state of the internal combustion
engine. In addition, concomitant with this, providing an exhaust
emission control device for an internal combustion engine that can
simultaneously execute a DPF regeneration process and SOx
regeneration process with high efficiency is also made an object of
the present invention.
Means for Solving the Problems
[0032] In order to achieve the above objects, the present invention
provides an exhaust emission control device for an internal
combustion engine (1) including a particulate filter (32) that is
provided in an exhaust channel (4, 5) of the internal combustion
engine, and collects particulates in exhaust. The exhaust emission
control device includes a fuel reformer (50) that is provided
separately from the exhaust channel, produces a reducing gas
containing hydrogen and carbon monoxide by reforming fuel, and
supplies the reducing gas from an inlet (14) provided in the
exhaust channel upstream of the particulate filter into the exhaust
channel; a catalytic converter (31) that is provided in the exhaust
channel between the inlet and the particulate filter, and
continuously oxidizes the reducing gas; and a regeneration means
(40) for executing a regeneration process to cause particulates
collected in the particulate filter to be combusted while supplying
reducing gas from the fuel reformer into the exhaust channel.
[0033] According to this configuration, the catalytic converter
that continuously oxidizes reducing gas is provided in the exhaust
channel between the particulate filter and the inlet at which
reducing gas produced by the fuel reformer is supplied, and
furthermore, the regeneration means that executes the regeneration
process causing particulates to combust while supplying reducing
gas into the exhaust channel is provided therein.
[0034] This enables the oxygen concentration of exhaust flowing
into the particulate filter to be controlled irrespective of the
operating state of the internal combustion engine, by supplying
reducing gas into the exhaust channel when executing the
regeneration process. As a result, even in a case in which the
particulate filter may melt such as during an idle operating state
or fuel-cut state described above, this can be avoided by lowering
the oxygen concentration. This enables the regeneration process to
be stably executed irrespective of the operating state of the
internal combustion engine.
[0035] In addition, by employing such a reducing gas, the
temperature of the exhaust can be raised without supplying unburned
fuel such as in exhaust injection and post injection. This enables
problems such as the occurrence of coking, degradation and
corrosion of the catalyst and components of the exhaust channel,
deterioration in fuel economy, and occurrence of oil dilution as
described above to be avoided.
[0036] In addition, the molecular diameters of carbon monoxide and
hydrogen contained in the reducing gas are small compared to the
molecular diameters of the hydrocarbons supplied by exhaust
injection and post injection. As a result, even in a case of a
great amount of particulates depositing on the particulate filter,
it is possible to supply reducing gas along with oxygen to deep
parts thereof. This can effectively promote the combustion of
particulates.
[0037] In addition, by providing the fuel reformer that supplies
reducing gas to be separate from the exhaust channel, the
regeneration time period of the particulate filter can be decided
independently of the state of the internal combustion engine.
Therefore, the regeneration process of the particulate filter can
be suitable executed as needed while always controlling the
internal combustion engine to an optimal state. Moreover, by
providing the fuel reformer to be separate from the exhaust
channel, reducing gas can always be produced at optimum efficiency
and this reducing gas can be supplied into the exhaust channel,
irrespective of the operating state of the internal combustion
engine, oxygen concentration and steam concentration of exhaust,
etc.
[0038] On the other hand, in a case of providing the fuel reformer
inside the exhaust channel, it is necessary to enlarge the fuel
reformer so as to be able to operate without influencing the
components, temperature, and flow rate of the exhaust; however,
according to this configuration, it is possible to perform
operation stably without enlarging the device by providing the fuel
reformer to be separate from the exhaust channel. In addition, by
providing the fuel reformer to be separate from the exhaust
channel, it becomes possible to activate the catalyst provided to
the fuel reformer at an early stage, by performing control of an
independent system from the control of the internal combustion
engine.
[0039] In order to achieve the above-mentioned object, the present
invention provides an exhaust emission control device for an
internal combustion engine (1) including a particulate filter that
is provided in an exhaust channel (4, 5) of the internal combustion
engine, and collects particulates in exhaust. The exhaust emission
control device includes a fuel reformer (50) that is provided
separately from the exhaust channel, produces a reducing gas
containing hydrogen and carbon monoxide by reforming fuel, and
supplies the reducing gas from an inlet (14) provided in the
exhaust channel upstream of the particulate filter into the exhaust
channel; and a regeneration means (40) for executing a regeneration
process to cause particulates collected in the particulate filter
to be combusted while supplying reducing gas from the fuel reformer
into the exhaust channel. A catalyst having an oxidative function
of continuously oxidizing reducing gas is supported on the
particulate filter.
[0040] According to this configuration, in addition to effects
similar to the above-mentioned exhaust emission control device, by
supporting a catalyst having an oxidative function on the
particulate filter, the exhaust emission control device can be made
compact, and the combustion reaction of particulates can be further
promoted. Therefore, the time from supplying reducing gas until
combustion of particulates begins can be further shortened.
[0041] Preferably, the catalytic converter contains at least one
selected from the group consisting of platinum, palladium, and
rhodium.
[0042] According to this configuration, the catalytic converter
contains at least one selected from the group consisting of
platinum, palladium, and rhodium. By containing these active
species, the catalytic combustion reaction such as of hydrogen,
carbon monoxide, and light hydrocarbons contained in the reducing
gas can be promoted.
[0043] Preferably, the catalyst having the oxidative function
contains at least one selected from the group consisting of
palladium, rhodium, platinum, silver, and gold.
[0044] According to this configuration, the catalyst supported on
the particulate filter contains at least one selected from the
group consisting of palladium, rhodium, platinum, silver, and gold.
This enables effects similar to the above-mentioned exhaust
emission control device to be exerted.
[0045] Preferably, the exhaust emission control device further
includes an oxygen concentration detection means (23) for detecting
or estimating an oxygen concentration (AF) of exhaust in the
exhaust channel flowing into the particulate filter.
[0046] According to this configuration, an oxygen concentration
detection means is provided for detecting the oxygen concentration
of exhaust flowing into the particulate filter. This enables the
oxygen concentration of exhaust flowing into the particulate filter
to be controlled to a predetermined target value with good
accuracy. Moreover, by controlling the oxygen concentration of
exhaust flowing into the particulate filter, an excessive rise in
temperature of the particulate filter during execution of the
regeneration process can be prevented.
[0047] Preferably, the reducing gas produced by the fuel reformer
contains more carbon monoxide than hydrogen.
[0048] According to this configuration, more carbon monoxide than
hydrogen is contained in the reducing gas. Carbon monoxide combusts
at a lower temperature than hydrogen. Particulates deposited on the
particulate filter can be effectively combusted by supplying such a
reducing gas containing carbon monoxide.
[0049] Preferably, a temperature of the reducing gas supplied by
the fuel reformer is higher than a temperature of exhaust flowing
through the exhaust channel at the inlet.
[0050] According to this configuration, reducing gas is supplied at
a temperature higher than the temperature of exhaust flowing
through the exhaust channel at the inlet. This enables the
combustion of particulates to be promoted by causing the
temperature of the exhaust flowing into the catalytic converter to
rise.
[0051] Preferably, the exhaust emission control device further
includes a target concentration setting means (40) for setting an
oxygen concentration target value (AFTV) of exhaust flowing into
the particulate filter while executing the regeneration process by
way of the regeneration means; and an oxygen concentration control
means (40) for controlling the oxygen concentration (AF) of exhaust
so as to match the oxygen concentration target value (AFTV) thus
set by the oxygen concentration setting means, by adjusting at
least one amount an intake air amount of the internal combustion
engine, an exhaust recirculation ratio of the internal combustion
engine, a fuel injection amount of the internal combustion engine,
and a supply amount of reducing gas from the fuel reformer.
[0052] According to this configuration, while executing the
regeneration process, the oxygen concentration of exhaust flowing
into the particulate filter is controlled so as to match the target
oxygen concentration by adjusting at least one among the intake air
amount, exhaust recirculation ratio, fuel injection amount, and
supply amount of reducing gas. This enables the oxygen
concentration of exhaust to be made to match the target oxygen
concentration with good accuracy.
[0053] Preferably, the target concentration setting means sets the
oxygen concentration target value (AFTV) based on at least one
among a flow rate (GE) of exhaust flowing through the exhaust
channel, a temperature (TE) of the exhaust, and a deposition amount
(QPM) of particulates deposited on the particulate filter.
[0054] According to this configuration, the oxygen concentration
target value is set based on at least one among the flow rate of
exhaust flowing through the exhaust channel, the temperature of
exhaust, and the deposition amount of particulates deposited on the
particulate filter. This enables the target oxygen concentration to
be set so that particulates are made to combust at an adequate
temperature.
[0055] Preferably, the target concentration setting means, in a
case of the internal combustion engine being in an idle operating
state, sets the oxygen concentration target value to be low
compared to a case of not being in an idle operating state.
[0056] According to this configuration, in a case of the internal
combustion engine being in an idle operating state, the oxygen
concentration target value is set to be low compared to a case of
not being in an idle operating state. With this, even in a case in
which the oxygen concentration in exhaust increases with the
internal combustion engine having transitioned to an idle operating
state, the oxidation reaction in the particulate filter is
suppressed by setting the oxygen concentration target value to be
low, and thus an excessive rise in temperature of this particulate
filter can be prevented.
[0057] Preferably, the target concentration setting means, in a
case of the internal combustion engine being in a deceleration
operating state, sets the oxygen concentration target value to be
low compared to a case of not being in a deceleration operating
state.
[0058] According to this configuration, in a case of the internal
combustion engine being in a deceleration operating state, the
oxygen concentration target value is set to be low compared to a
case of not being in a deceleration operating state. With this,
even in a case in which the oxygen concentration in exhaust
increases with the internal combustion engine transitioning to a
deceleration operating state and deceleration fuel-cut having been
performed, the oxidation reaction in the particulate filter is
suppressed by setting the oxygen concentration target value to be
low, and thus an excessive rise in temperature of this particulate
filter can be prevented.
[0059] Preferably, the fuel reformer produces reducing gas with
carbon monoxide as a main component by way of a partial oxidation
reaction of hydrocarbon fuel and air.
[0060] According to this configuration, this fuel reformer can be
made a smaller size by producing the reducing gas by way of the
partial oxidation reaction. In order words, this is because a
device to continually supply extra energy from outside does not
need to be provided since the partial oxidation reaction as
described above is an exothermic reaction, and once the reaction
starts, the reaction progresses spontaneously. In addition, there
is also no need to also provide a converter and system for
concentrating hydrogen of a shift reaction, etc. Moreover, the
light-off time of the fuel reformer can be shortened by making the
fuel reformer to be small in this way. Therefore, reducing gas can
be quickly supplied into the exhaust channel as needed.
[0061] Furthermore, by introducing light hydrocarbons generated
secondarily in this partial oxidation reaction to the catalytic
converter along with carbon monoxide and hydrogen, it can also be
used in raising the temperature of exhaust.
[0062] In order to achieve the above objects, the present invention
provides an exhaust emission control device for an internal
combustion engine (1) including a particulate filter (32) that is
provided in an exhaust channel (4) of the internal combustion
engine, and collects particulates in exhaust. The exhaust emission
control device includes a regeneration means (40A) for executing a
regeneration process to cause particulates collected in the
particulate filter to be combusted; and a fuel reformer (50) that
is provided separately from the exhaust channel, produces a
reducing gas containing hydrogen and carbon monoxide by reforming
fuel, and supplies the reducing gas from an inlet (14) provided in
the exhaust channel upstream of the particulate filter into the
exhaust channel. The regeneration means includes a normal
regeneration means (40A) that executes a regeneration process
without employing reducing gas produced by the fuel reformer, and a
heated regeneration means (40A) that allows a regeneration process
employing reducing gas produced by the fuel reformer to be
executed, and switches between executing the regeneration process
by way of the normal regeneration means and executing the
regeneration process by way of the heated regeneration means
according to a predetermined condition.
[0063] According to this configuration, when executing the
regeneration process in which particulates collected in the
particulate filter are caused to combust, the normal regeneration
means that executes the regeneration process without employing
reducing gas and the heated regeneration means that allows
execution of the regeneration process employing reducing gas are
switched according to predetermined conditions. Herein, molecules
that easily combust such as hydrogen and carbon monoxide are
contained in the reducing gas produced by the fuel reformer. Even
in a state in which the exhaust temperature is low and it is
difficult to cause particulates to combust, the temperature of
exhaust can be quickly raised by supplying such a reducing gas to
the particulate filter, for example. In addition, by switching
between the normal regeneration means and heated regeneration means
according to predetermined conditions, for example, a regeneration
process can be executed even if it enters a state in which a
regeneration process on the particulate filter would be difficult
to execute by a conventional method as described above, such as in
a case of immediately after engine startup or having transitioned
to low-load operation. In other words, it is possible to reduce the
frequency at which the operating state of the internal combustion
engine enters a situation in which it is difficult to continue the
regeneration process on the particulate filter, thereby forcing
interruption of the regeneration process. Therefore, the time
required in the regeneration process can be shortened.
[0064] In addition, by employing such a reducing gas, the
temperature of exhaust can be made to rise without supplying
unburned fuel as in exhaust injection and post injection. This
enables problems such as the occurrence of coking, degradation and
corrosion of the catalyst and components of the exhaust channel,
deterioration in fuel economy, and occurrence of oil dilution as
described above to be avoided.
[0065] In addition, the molecular diameters of carbon monoxide and
hydrogen contained in the reducing gas are small compared to the
molecular diameters of the hydrocarbons supplied by exhaust
injection and post injection. As a result, even in a case of a
great amount of particulates depositing on the particulate filter,
it is possible to supply reducing gas along with oxygen to deep
parts thereof. This can effectively promote the combustion of
particulates.
[0066] In addition, by providing the fuel reformer that supplies
reducing gas to be separate from the exhaust channel, the
regeneration time period of particulates can be decided
independently of the state of the internal combustion engine.
Therefore, the regeneration process on the particulate filter can
be suitable executed as needed while always controlling the
internal combustion engine to an optimal state. In addition, by
providing the fuel reformer to be separate from the exhaust
channel, reducing gas can always be produced at optimum efficiency
and this reducing gas can be supplied into the exhaust channel,
irrespective of the operating state of the internal combustion
engine, oxygen concentration and steam concentration of exhaust,
etc.
[0067] On the other hand, in a case of providing the fuel reformer
inside the exhaust channel, it is necessary to enlarge the fuel
reformer so as to be able to operate without influencing the
components, temperature, and flow rate of the exhaust; however,
according to this configuration, it is possible to perform
operation stably without enlarging the device by providing the fuel
reformer to be separate from the exhaust channel. In addition, by
providing the fuel reformer to be separate from the exhaust
channel, it becomes possible to activate the catalyst provided to
the fuel reformer at an early stage, by performing control of an
independent system from the control of the internal combustion
engine.
[0068] Preferably, the reducing gas produced by the fuel reformer
contains more carbon monoxide than hydrogen.
[0069] According to this configuration, more carbon monoxide than
hydrogen is contained in the reducing gas. Carbon monoxide combusts
at a lower temperature than hydrogen. Particulates deposited on the
particulate filter can be efficiently combusted by supplying such a
reducing gas containing carbon monoxide.
[0070] Preferably, the catalytic converter (31) that continuously
oxidizes reducing gas is provided in the exhaust channel between
the inlet and the particulate filter.
[0071] According to this configuration, the reducing gas produced
by the fuel reformer flows into the catalytic converter and
combusts by way of this catalytic converter. By combusting reducing
gas by way of the catalytic converter in this way, the temperature
of exhaust is raised, and particulates deposited on the particulate
filter can be efficiently combusted.
[0072] Preferably, the exhaust emission control device further
includes a combustion judgment means (40A, 29D) for judging whether
particulates deposited on the particulate filter are in a combusted
state. The regeneration means executes the regeneration process by
way of the normal regeneration means in a case of having been
judged that the particulate are in a combusted state, and executes
the regeneration process by way of the heated regeneration means in
a case of having been judged that the particulates are not in a
combusted state.
[0073] According to this configuration, in a case of having
determined that the particulates deposited on the particulate
filter are in a combusted state, a regeneration process not
employing reducing gas is executed by way of the normal
regeneration means, and in a case of having determined that the
particulates are not in a combusted state, a regeneration process
is executing employing reducing gas by way of the heated
regeneration means. This enables the regeneration process to be
efficiently executed while preventing the reducing gas from being
consumed for no purpose.
[0074] Preferably, the exhaust emission control device further
includes an oxygen concentration detection means for detecting or
estimating an oxygen concentration of exhaust in the exhaust
channel on a downstream side of the particulate filter. The
combustion judgment means judges whether the particulates are in a
combusted state based on the oxygen concentration thus detected or
estimated by the oxygen concentration detection means.
[0075] According to this configuration, it is determined whether
the particulates are in a combusted state based on the oxygen
concentration on a downstream side of the particulate filter. This
enables the combusted state of particulates to be determined with
good accuracy.
[0076] Preferably, the exhaust emission control device further
includes a downstream exhaust temperature detection means (29D) for
detecting or estimating an exhaust temperature (TD) in the exhaust
channel on a downstream side of the particulate filter. The
combustion judgment means judges whether the particulates are in a
combusted state based on the exhaust temperature (TD) thus detected
or estimated by the downstream exhaust temperature detection
means.
[0077] According to this configuration, it is determined whether
the particulates are in a combusted state based on the exhaust
temperature on a downstream side of the particulate filter. This
enables the combusted state of particulates to be determined with
good accuracy.
[0078] Preferably, the heated regeneration means reduces the intake
air amount (GE) of the internal combustion engine, increases the
exhaust recirculation ratio of the internal combustion engine, or
sets the charge efficiency of the internal combustion engine to be
small, compared to a case of performing the regeneration process by
way of the normal regeneration means.
[0079] According to this configuration, in a case of executing the
regeneration process by way of the heated regeneration means, the
intake air amount of the internal combustion engine is reduced, the
exhaust recirculation ratio of the internal combustion engine is
increased, or the charge efficiency of the internal combustion
engine is set to be small, compared to a case of executing the
regeneration process by way of the normal regeneration means. By
executing the regeneration process by way of such a heated
regeneration means, the temperature of the particulate filter can
be quickly raised.
[0080] Preferably, the heated regeneration means includes a first
heated regeneration means (40A) for executing a regeneration
process while supplying reducing gas from the fuel reformer into
the exhaust channel, and a second heated regeneration means (40A)
for executing a regeneration process without supplying reducing gas
from the fuel reformer into the exhaust channel, and switches
between executing the regeneration process by way of the first
heated regeneration means and executing the regeneration process by
way of the second heated regeneration means according to a
predetermined condition.
[0081] According to this configuration, a first heated regeneration
means for executing a regeneration process while supplying reducing
gas and a second heated regeneration means for executing a
regeneration process without supplying reducing gas are provided to
the heated regeneration means, and the first heated regeneration
means and the second regeneration means are switched according to
predetermined conditions. This enables the regeneration process to
be appropriately executed according to the conditions.
[0082] Preferably, the exhaust emission control device further
includes an upstream exhaust temperature detection means (29U) for
detecting or estimating a temperature (TU) of exhaust in the
exhaust channel on an upstream side of the particulate filter. The
heated regeneration means executes the regeneration process by way
of the first heated regeneration means in a case of the temperature
(TU) thus detected by the upstream exhaust temperature detection
means being lower than a predetermined judgment value (TCTH).
[0083] According to this configuration, in a case in which the
exhaust temperature on an upstream side of the particulate filter
is less than the predetermined judgment value, the regeneration
process is executed by way of the first heated regeneration means
while supplying reducing gas. With this, even in a state in which
the exhaust temperature is low and it is difficult to cause the
particulates to combust, the exhaust temperature is quickly raised,
and thus combustion of the particulates can be promoted.
[0084] Preferably, the exhaust emission control device further
includes a filter temperature estimation means for estimating or
detecting a temperature (TDPF) of the particulate filter. The
heated regeneration means executes the regeneration process by way
of the first heated regeneration means in a case of the temperature
(TDPF) thus estimated or detected by the filter temperature
estimation means being lower than a predetermined judgment value
(TDTH).
[0085] According to this configuration, in a case of the
temperature of the particulate filter being lower than the
predetermined judgment value, the regeneration process is executed
by way of the first heated regeneration means while supplying
reducing gas. With this, even in a state in which the temperature
of the particulate filter is low and it is difficult to cause
particulates to combust, the exhaust temperature is quickly raised,
and thus the combustion of the particulates can be promoted.
[0086] Preferably, the exhaust emission control device further
includes a torque estimation means (40A) for estimating a generated
torque (TRQ) of the internal combustion engine. The heated
regeneration means executes the regeneration process by way of the
first regeneration means in a case of the generated torque (TRQ)
thus estimated or detected by the torque estimation means being
less than a predetermined judgment value (TRQTH).
[0087] According to this configuration, in a case of the generated
torque being lower than the predetermined judgment value, the
regeneration process is executed by way of the first heated
regeneration means while supplying reducing gas. With this, even in
a state in which the internal combustion engine is in a low-load
operating state and it is difficult to cause particulates to
combust, the exhaust temperature is quickly raised, and thus the
combustion of the particulates can be promoted.
[0088] Preferably, the torque estimation means estimates the
generated torque of the internal combustion engine based on at
least one among a revolution speed of the internal combustion
engine, a fuel injection amount, and a fuel injection timing.
[0089] Preferably, the exhaust emission control device further
includes a timing means (40A) for measuring an elapsed time (TIM)
since starting up the internal combustion engine. The heated
regeneration means executes the regeneration process by way of the
first heated regeneration means in a case of the elapsed time (TIM)
thus measured by the timing means being less than a predetermined
judgment value (TIMTH).
[0090] According to this configuration, in a case of the elapsed
time from starting up the internal combustion engine is less than
the predetermined judgment value, the regeneration process is
executed while supplying reducing gas. With this, even in a case of
not being long after startup of the internal combustion engine and
it being difficult to cause particulates to combust, the exhaust
temperature is quickly raised, and thus the combustion of
particulates can be promoted.
[0091] In order to achieve the above objects, the present invention
provides an exhaust emission control device for an internal
combustion engine (1), including a NOx purification catalyst (33)
that is provided in an exhaust channel (4,5) of the internal
combustion engine and that, with an air/fuel ratio of exhaust
flowing through the exhaust channel as an exhaust air/fuel ratio,
adsorbs or occludes NOx in exhaust when the exhaust air/fuel ratio
is made lean, and reduces the NOx adsorbed or occluded when the
exhaust air fuel ratio is made rich, and a particulate filter (32)
that is provided in the exhaust channel further upstream than the
NOx purification catalyst, and that collects particulates in
exhaust. The exhaust emission control device includes a fuel
reformer (50B) that is provided separately from the exhaust
channel, produces a reducing gas containing hydrogen and carbon
monoxide by reforming fuel, and supplies the reducing gas from an
inlet (14B) provided in the exhaust channel between the particulate
filter and the NOx purification catalyst into the exhaust
channel.
[0092] According to this configuration, the particulate filter is
provided in the exhaust channel on an upstream side of the NOx
purification catalyst, and the fuel reformer is provided that
supplies reducing gas containing hydrogen and carbon monoxide from
the inlet provided between this NOx purification catalyst and this
particulate filter. With this, the exhaust air/fuel ratio of
exhaust flowing into the NOx purification catalyst is kept low and
the SOx regeneration process of the NOx purification catalyst can
be executed with high efficiency by supplying reducing gas from
downstream of the particulate filter, while the oxygen
concentration of exhaust flowing into the particulate is kept high,
and the regeneration process on the particulate filter is executed
with high efficiency. In this way, according to this configuration,
it is possible to execute the regeneration process on the
particulate filter and the SOx regeneration process simultaneously
with high efficiency. Therefore, the time required in these
processes is shortened, which can improve fuel economy, whereby
degradation to the particulate filter and the NOx purification
catalyst can also be reduced.
[0093] In addition, by providing the fuel reformer to be separate
from the exhaust channel, reducing gas can be supplied without
increasing the heat capacity upstream of the NOx purification
catalyst. This enables the SOx regeneration process to be executed
without reducing the NOx purification performance when at low
temperature such as immediately after engine startup.
[0094] Moreover, by providing the fuel reformer that produces
reducing gas to be separate from the exhaust channel, the execution
time period of the SOx regeneration process can be decided
independently of the state of the internal combustion engine.
Therefore, the SOx regeneration process can be suitable executed as
needed while always controlling the internal combustion engine to
an optimal state. In addition, by providing the fuel reformer to be
separate from the exhaust channel, reducing gas can always be
produced at optimum efficiency and this reducing gas can be
supplied into the exhaust channel, irrespective of the operating
state of the internal combustion engine, the oxygen concentration
or steam concentration of the exhaust, etc.
[0095] On the other hand, in a case of providing the fuel reformer
inside the exhaust channel, it is necessary to enlarge the fuel
reformer so as to be able to operate without influencing the
components, temperature, and flow rate of the exhaust; however,
according to this configuration, it is possible to perform
operation stably without enlarging the device by providing the fuel
reformer to be separate from the exhaust channel. In addition, by
providing the fuel reformer to be separate from the exhaust
channel, it becomes possible to activate the catalyst provided to
the fuel reformer at an early stage by performing control of an
independent system from the control of the internal combustion
engine.
[0096] Preferably, the reducing gas produced by the fuel reformer
is at a pressure higher than atmospheric pressure, and contains
more carbon monoxide than hydrogen by volume ratio.
[0097] According to this configuration, more carbon monoxide than
hydrogen is contained in the reducing gas by volume ratio.
Moreover, the temperature at which carbon monoxide begins to
combust on the catalyst is a temperature lower than the temperature
at which hydrogen begins to combust. The NOx purification catalyst
is quickly raised in temperature by supplying such a reducing gas
containing carbon monoxide, and thus the purification of SOx can be
promoted in the SOx regeneration process. In addition, reducing gas
thus produced can be supplied into the exhaust channel without
adding an extra device by producing reducing gas of a pressure
higher than atmospheric.
[0098] Preferably, a temperature of the reducing gas supplied by
the fuel reformer is higher than a temperature of exhaust flowing
through the exhaust channel at the inlet.
[0099] According to this configuration, reducing gas of a
temperature higher than the temperature of exhaust flowing through
the exhaust channel at the inlet is supplied. This enables the NOx
purification catalyst to be quickly raised in temperature, and thus
the purification of SOx to be promoted in the SOx regeneration
process.
[0100] Preferably, oxygen is contained in the exhaust flowing
through the exhaust channel when reducing gas from the fuel
reformer is introduced into the exhaust channel.
[0101] Preferably, the exhaust emission control device further
includes: a regeneration means (40B) for selectively executing a
normal regeneration operation that raises the particulate filter in
temperature to cause particulates collected in the particulate
filter to combust, and a simultaneous regeneration operation that
supplies reducing gas from the fuel reformer into the exhaust
channel while executing the normal regeneration operation to purify
SOx adsorbed to the NOx purification catalyst according to a
predetermined condition.
[0102] According to this configuration, the normal regeneration
operation that performs the regeneration process on the particulate
filter and the simultaneous regeneration operation that supplies
reducing gas and performs the SOx regeneration process while
executing this normal regeneration operation are selectively
executed according to predetermined conditions. This enables these
regeneration processes to be efficiently executed while minimizing
consumption of reducing gas, by executing the normal regeneration
operation in a case of only performing the regeneration process on
the particulate filter being necessary, and executing the
simultaneous operation process in a case in which performing the
regeneration process on the particulate filter and the SOx
regeneration process simultaneously is preferable.
[0103] Preferably, the exhaust emission control device further
includes an exhaust temperature control means (40B) for controlling
a temperature of exhaust when executing the normal regeneration
operation by adjusting at least one among an intake air amount and
boost pressure.
[0104] According to this configuration, the temperature of the
exhaust is controlled by adjusting at least one among the intake
air amount and the boost pressure when executing the normal
regeneration operation. This enables the temperature of the exhaust
to be controlled to a required temperature in order for the
particulates to be made to combust, and the regeneration process on
the particulate filter to be performed efficiently.
[0105] Preferably, a catalytic converter (31) having an oxidative
function is provided in the exhaust channel on an upstream side of
the particulate filter. The regeneration means executes post
injection when executing the normal regeneration operation.
[0106] According to this configuration, when providing the
catalytic converter having an oxidative function on an upstream
side of the particulate filter, post injection is executed while
executing the normal regeneration operation. With this, the
temperature of the exhaust flowing into the particulate filter can
be raised and thus the regeneration process on the particulate
filter can be performed with high efficiency, by causing fuel
supplied by way of post injection to combust by way of the
catalytic converter.
[0107] Preferably, a catalyst having an oxidative function is
supported on the particulate filter. The regeneration means
executes post injection when executing the normal regeneration
operation.
[0108] According to this configuration, when the catalyst having an
oxidative function is made to be supported on the particulate
filter, post injection is executed while executing the normal
regeneration operation. Therefore, by causing fuel supplied by post
injection to combust by way of the catalytic converter when
executing the normal regeneration operation, the temperature of the
exhaust flowing into the particulate filter is raised, and thus the
regeneration process on the particulate filter can be executed with
high efficiency. In addition, the exhaust emission control device
can be made compact, and the combustion reaction of particulates
can be further promoted, compared to a case of providing the
catalytic converter and the particulate filter separately. This
enables the efficiency of the regeneration process on the
particulate filter to be further improved.
[0109] Preferably, the exhaust emission control device further
includes a particulate deposition amount estimation means (40B, 27)
for estimating or detecting a particulate deposition amount (QPM)
of the particulate filter. The regeneration means executes the
normal regeneration operation or the simultaneous regeneration
operation in response to the particulate deposition amount (QPM)
thus estimated or detected by the particulate deposition amount
estimation means having become at least a predetermined first
estimation judgment value (QPMATH).
[0110] According to this configuration, in a case of the
particulate deposition amount having become at least the first
deposition judgment value, the normal regeneration operation or the
simultaneous regeneration operation is executed. This enables the
regeneration process on the particulate filter to be executed at a
suitable opportunity prior to the deposition amount of particulates
reaching the limit.
[0111] Preferably, the exhaust emission control device further
includes a catalyst temperature estimation means (40B, 26B) for
estimating or detecting a temperature (TLNC) of the NOx
purification catalyst; and a SOx poisoning amount estimation means
(40B, 28) for estimating or detecting a SOx poisoning amount (QSO)
of the NOx purification catalyst. The regeneration means executes
the simultaneous regeneration operation in response to the
temperature (TLNC) thus estimated or detected by the catalyst
temperature estimation means being at least a predetermined
temperature judgment value (TLNCTH), and the SOx poisoning amount
(QSO) thus estimated or detected by the SOx poisoning amount
estimation means having become at least a predetermined first
poisoning judgment value (QSOATH).
[0112] According to this configuration, the simultaneous
regeneration operation is executed in response to the temperature
of the NOx purification catalyst being at least the predetermined
temperature judgment value and the SOx poisoning amount of the NOx
purification catalyst having become at least the first poisoning
judgment value. This enables the SOx regeneration process to be
performed at an opportunity before the NOx purification performance
of the NOx purification catalyst declines drastically. Furthermore,
SOx desorbed from the NOx purification catalyst can be purified
with good efficiency by executing the simultaneous regeneration
operation in a case in which the temperature of the NOx
purification catalyst is at least the predetermined temperature
judgment value.
[0113] Preferably, the regeneration means ends execution of the
simultaneous regeneration operation and executes the normal
regeneration operation, in response to the SOx poisoning amount
(QSO) estimated or detected by the SOx poisoning amount estimation
means having become smaller than a predetermined second poisoning
judgment value (QSOBTH).
[0114] According to this configuration, execution of the
simultaneous regeneration operation ends in response to the SOx
poisoning amount having become less than the predetermined second
poisoning judgment value, and the normal regeneration operation is
executed. This enables execution of the simultaneous regeneration
operation to end according to recovery of the NOx purification
performance of the NOx purification catalyst, and the regeneration
process on the particulate filter to continue.
[0115] Preferably, the exhaust emission control device further
includes an oxygen concentration detection means (23B) for
detecting an oxygen concentration of exhaust in the exhaust channel
in a vicinity of the NOx purification catalyst; and a supply amount
control means (40B) for controlling a supply amount of reducing gas
supplied from the fuel reformer into the exhaust channel, according
to the oxygen concentration thus detected by the oxygen
concentration detection means.
[0116] According to this configuration, the supply amount of
reducing gas is controlled according to the oxygen concentration in
a vicinity of the NOx purification catalyst. This enables the
exhaust air/fuel ratio of exhaust flowing into the NOx purification
catalyst to be adjusted appropriately, and thus the efficiency of
the SOx regeneration process to be further improved.
[0117] Preferably, the fuel reformer produces reducing gas by way
of a partial oxidation reaction of hydrocarbon fuel and air.
[0118] According to this configuration, this fuel reformer can be
made a smaller size by producing reducing gas by way of a partial
oxidation reaction. In order words, this is because a device to
supply extra energy from outside does not need to be provided since
the partial oxidation reaction as described above is an exothermic
reaction, and once the reaction starts, the reaction progresses
spontaneously. In addition, there is also no need to also provide a
converter and system for concentrating hydrogen of a shift
reaction, etc. Moreover, the light-off time of the fuel reformer
can be shortened by making the fuel reformer to be small in this
way. Therefore, reducing gas can be quickly supplied into the
exhaust channel as needed.
[0119] Furthermore, by introducing light hydrocarbons generated
secondarily in this partial oxidation reaction to the NOx
purification catalyst along with carbon monoxide and hydrogen, it
can also be used in the purification of SOx.
[0120] Preferably, the internal combustion engine uses light oil as
fuel, and combusts the fuel by way of compression ignition.
BRIEF DESCRIPTION OF THE DRAWINGS
[0121] FIG. 1 is a view showing a configuration of an internal
combustion engine and an exhaust emission control device thereof
according to a first embodiment of the present invention;
[0122] FIG. 2 is a flowchart showing a sequence of a DPF
regeneration process by an ECU according to the embodiment;
[0123] FIG. 3A is a graph showing an example of control of the DPF
regeneration processing according to the embodiment;
[0124] FIG. 3B is a graph showing an example of control of the DPF
regeneration process according to the embodiment;
[0125] FIG. 4 is a view showing a configuration of an internal
combustion engine and an exhaust emission control device thereof
according to a second embodiment of the present invention;
[0126] FIG. 5 is a flowchart showing a sequence of a DPF
regeneration process by an ECU according to the embodiment;
[0127] FIG. 6 is a view showing a configuration of an internal
combustion engine and an exhaust emission control device thereof
according to a third embodiment of the present invention;
[0128] FIG. 7 is a flowchart showing a sequence of a regeneration
process by an ECU according to the embodiment;
[0129] FIG. 8 is a graph showing a relationship between a PM
deposition amount on the DPF and two threshold values used in the
updating of flags; and
[0130] FIG. 9 is a graph showing a relationship between a SOx
poisoning amount of the NOx purification catalyst and two threshold
values used in the updating of flags.
EXPLANATION OF REFERENCE NUMERALS
[0131] 1 Engine (internal combustion engine) [0132] 4 Exhaust
plumbing (exhaust channel) [0133] 5 Exhaust manifold (exhaust
channel) [0134] 14 Inlet [0135] 14B Inlet [0136] 23 UEGO sensor
(oxygen concentration detection means) [0137] 23B UEGO sensor
(oxygen concentration detection means) [0138] 26B exhaust
temperature sensor (catalyst temperature estimation means) [0139]
27 Pressure differential sensor (deposition amount estimation
means) [0140] 28 NOx sensor (SOx poisoning amount estimation means)
[0141] 29U Upstream temperature sensor (upstream exhaust
temperature detection means) [0142] 29D Downstream temperature
sensor (downstream exhaust temperature detection means) [0143] 31
Catalytic converter [0144] 32 DPF [0145] 33 NOx purification
catalyst [0146] 40 Electronic control unit (regeneration means,
target concentration setting means, oxygen concentration control
means) [0147] 40A Electronic control unit (regeneration means,
normal regeneration means, heated regeneration means, first heated
regeneration means, second heated regeneration means, combustion
determination means, filter temperature estimation means, torque
estimation means, and timing means) [0148] 40B Electronic control
unit (regeneration means, exhaust temperature control means,
deposition amount estimation means, SOx poisoning amount estimation
means, catalyst temperature estimation means, supply amount control
means) [0149] 50 Fuel reformer [0150] 50B Fuel reformer
PREFERRED MODE FOR CARRYING OUT THE INVENTION
First Embodiment
[0151] FIG. 1 is a view showing a configuration of an internal
combustion engine and the exhaust emission control device thereof
according to an embodiment of the present invention. An internal
combustion engine (hereinafter referred to as "engine") 1 is a
diesel engine that directly injects fuel into the combustion
chamber of each cylinder 7 and combusts the fuel by way of
compression ignition, and uses diesel oil as the fuel. In addition,
a fuel injector, which is not illustrated, is provided to each
cylinder 7. These fuel injectors are electrically connected to an
electronic control unit (hereinafter referred to as "ECU") 40, and
the valve-open duration and the valve-close duration of the fuel
injectors, i.e. the fuel injection amount and fuel injection
timing, are controlled by the ECU 40.
[0152] The engine 1 is provided with intake plumbing 2 in which
intake air flows, exhaust plumbing 4 in which exhaust gas flows, an
exhaust-gas recirculation path 6 that recirculates a portion of the
exhaust in the exhaust plumbing 4 to the intake plumbing 2, and a
turbocharger 8 that compresses and feeds intake air to the intake
plumbing 2.
[0153] The intake plumbing 2 is connected to the intake port of
each cylinder 7 of the engine 1 via a plurality of branches of an
intake manifold 3. The exhaust plumbing 4 is connected to the
exhaust port of each cylinder 7 of the engine 1 via a plurality of
branches of an exhaust manifold 5. The exhaust-gas recirculation
path 6 branches from the exhaust manifold 5 and leads to the intake
manifold 3.
[0154] The turbocharger 8 includes a turbine, which is not
illustrated, provided to the exhaust plumbing 4, and a compressor,
which is not illustrated, provided to the intake plumbing 2. The
turbine is driven by the kinetic energy of exhaust gas flowing in
the exhaust plumbing 4. The compressor is rotationally driven by
the turbine, and compresses and feeds intake air into the intake
plumbing 2. In addition, the turbine is provided with a plurality
of variable vanes, which are not illustrated, and is configured so
that the turbine revolution number (revolution speed) can vary by
way of causing the aperture of the variable vanes to change. The
vane aperture of the turbine is electromagnetically controlled by
the ECU 40.
[0155] A throttle valve 9 that controls the intake air amount GA of
the engine 1 is provided inside the exhaust plumbing 2 at an
upstream side of the turbocharger 8. This throttle valve 9 is
connected to the ECU 40 via an actuator, and the aperture thereof
is electromagnetically controlled by the ECU 40. In addition, an
intercooler 11 for cooling the intake air compressed by the
turbocharger 8 is provided in the intake plumbing 2 at a downstream
side of the turbocharger 8.
[0156] The exhaust-gas recirculation path 6 connects the exhaust
manifold 5 and the intake manifold 3, and recirculates a portion of
the exhaust emitted from the engine 1. An EGR cooler 12, which
cools exhaust gas that is recirculated, and an EGR valve 13 that
controls the flow rate of exhaust gas being recirculated are
provided in the exhaust-gas recirculation path 6. The EGR valve 13
is connected to the ECU 40 via an actuator, which is not
illustrated, and the valve aperture thereof is electromagnetically
controlled by the ECU 40.
[0157] A catalytic converter 31 and DPF 32 are provided from an
upstream side in this order downstream of the turbocharger 8 in the
exhaust plumbing 4.
[0158] The catalytic converter 31 includes a three-way catalyst
that continuously oxidizes reductive gas supplied from the fuel
reformer 50 described later. This catalytic converter 31 contains
at least one selected from the group consisting of platinum (Pt),
palladium (Pd) and rhodium (Rh) as a noble metal active species in
a catalytic combustion reaction such as of carbon monoxide,
hydrogen and light hydrocarbons contained in the reductive gas
described below, and ceria (CeO.sub.2), which has oxygen storage
ability. By supplying reductive gas to such a catalytic converter
31, the temperature can be quickly raised even in a state in which
the exhaust temperature is low. In addition, by containing ceria,
stable catalyst action can be demonstrated, even under a sudden
oxygen concentration fluctuation or the like.
[0159] In the present embodiment, a substance, which is prepared by
producing a slurry by way of agitating and mixing 2.4 (g/L) of
platinum, 1.2 (g/L) of rhodium, 6.0 (g/L) of palladium, 50 (g/L) of
ceria, 150 (g/L) of alumina (Al.sub.2O.sub.3), and 10 of binder
along with an aqueous medium in a ball mill, then after coating
this slurry on a support made of Fe--Cr--Al alloy, drying and
calcining this at 600.degree. C. over 2 hours, is used for the
catalytic converter 31.
[0160] The DPF 32 collects, when exhaust flows through the fine
pores in the filter walls, PM with elemental carbon as a main
component in exhaust, by way of causing deposition thereof on the
surface of the filter walls and in the pores inside the filter
walls. For example, a ceramic such as silicon carbide (SiC) and a
metallic madreporic body is used as a constituent material of the
filter wall.
[0161] When PM is collected until the limit of the collection
ability of the DPF 32, i.e. until the collection limit, since the
pressure drop becomes large, it is necessary to appropriately
perform the DPF regeneration process to cause the PM thus collected
to combust. This DPF regeneration process is performed by raising
the temperature of the exhaust flowing into the DPF 32 up to the
combustion temperature of the PM collected in the DPF 32. A
sequence of this DPF regeneration process is explained in detail
with reference to FIG. 2 below.
[0162] In addition, a fuel reformer 50, which reforms fuel gas to
produce a reformed gas containing hydrogen (H.sub.2), and carbon
monoxide (CO) is connected upstream of the catalytic converter 31
and DPF 32 inside the exhaust plumbing 4. This fuel reformer 50
supplies the reformed gas thus produced into the exhaust plumbing 4
from an inlet 14 formed upstream of the catalytic converter 31 and
DPF 32 inside the exhaust plumbing 4 as reductive gas.
[0163] The fuel reformer 50 is configured to include a gas path 51
that connects one end side to the exhaust plumbing 4, a fuel gas
supply device 52 that supplies fuel gas from another end side of
this gas path 51, and a reforming catalyst 53 as a reforming
catalyst provided in the gas path 51.
[0164] The fuel gas supply device 52 produces fuel gas by mixing
fuel stored in a fuel tank and air supplied by the compressor at a
predetermined ratio, and supplies this fuel gas to the gas path 51.
This fuel gas supply device 52 is connected to the ECU 40, and a
supply amount of fuel gas and a mixture ratio thereof are
controlled by the ECU 40. In addition, it is made possible to
control the supply amount GRG (amount of reducing gas supplied into
the exhaust plumbing 4 per unit time) of reductive gas supplied to
the exhaust plumbing 4 by controlling the supply amount of this
fuel gas.
[0165] The reforming catalyst 53 contains rhodium and ceria. This
reforming catalyst 53 is a catalyst that reforms the fuel gas
supplied from the fuel gas supply device 52, and produces a
reformed gas containing hydrogen, carbon monoxide, and
hydrocarbons. More specifically, this reforming catalyst 53
produces reformed gas that is higher pressure than atmospheric
pressure and contains more carbon monoxide than hydrogen by volume
ratio by way of the partial oxidation reaction of hydrocarbon fuel
constituting the fuel gas and air. In other words, the reformed gas
contains more carbon monoxide than hydrogen. In addition, as
described above, the partial oxidation reaction is an exothermal
reaction. As a result, the fuel reformer 50 is able to supply into
the exhaust plumbing 4 reducing gas of a temperature that is higher
than the exhaust in the vicinity of the inlet 14 in the exhaust
plumbing 4.
[0166] In addition, a heater (not illustrated) configured to
include a glow plug, spark plug, or the like is connected to the
reforming catalyst 53, whereby it is possible to heat the reforming
catalyst 53 with startup of the fuel reformer 50. Moreover, the
fuel reformer 50 is provided separately from the exhaust plumbing
4. In other words, the fuel gas supply device 52 and reforming
catalyst 53 of the fuel reformer 50 are not provided in the exhaust
plumbing 4.
[0167] An air-flow meter 21 that detects an intake air amount GA
(air amount newly aspirated into the engine 1 per unit time) of the
engine 1, an exhaust temperature sensor 22 that detects a
temperature TE of exhaust in the exhaust plumbing 4 flowing into
the catalytic converter 31 and DPF 32, a UEGO sensor 23 that
detects an oxygen concentration AF of the exhaust in the exhaust
plumbing 4 flowing into the catalytic converter 31 and the DPF 32,
and a pressure sensor 26 that detects a pressure PE of exhaust on a
downstream side of the DPF 32 in the exhaust plumbing 4 are
connected to the ECU 40, and detection signals of these sensors are
supplied to the ECU 40.
[0168] The ECU 40 includes an input circuit that has functions such
as of shaping input signal wave forms from every kind of sensor,
correcting the voltage levels to predetermined levels, and
converting analog signal values to digital signal values, and a
central processing unit (hereinafter referred to as "CPU"). In
addition to this, the ECU 40 includes a storage circuit that stores
every kind of calculation program executed by the CPU and
calculation results, and an output circuit that outputs control
signals to the fuel reformer 50, throttle valve 9, EGR valve 13,
turbocharger 8, fuel injectors of the engine 1, and the like.
[0169] FIG. 2 is a flowchart showing a sequence of the DPF
regeneration process by the ECU. As shown in FIG. 2, the DPF
regeneration process makes it possible to cause PM collected in the
DPF to be combusted while supplying reductive gas produced by the
fuel reformer into the exhaust plumbing 4.
[0170] In Step S1, it is determined whether a DPF regeneration
request flag FDPFRR is "1". In a case of this determination being
YES, Step S2 is advanced to, and in a case of being NO, this
process ends immediately. Herein, when the consumed amount of fuel
has reached a predetermined value, or when a traveled distance of
the vehicle has reached a predetermined value, this DPF
regeneration request flag FDPFRR is set to "1". In addition, upon
being set to "1", this DPF regeneration request flag FDPFRR is
returned to "0" by way of a process not illustrated, after a
predetermined regeneration time has elapsed.
[0171] In Step S2, it is determined whether the engine is in an
idle operating state. In a case of this determination being YES,
Step S5 is advanced to, and in a case of being NO, Step S3 is
advanced to.
[0172] In Step S3, it is determined whether the engine is in a
deceleration operating state. In a case of this determination being
YES, Step S5 is advanced to, and in a case of being NO, Step S4 is
advanced to.
[0173] In Step S4, an oxygen concentration target value AFTV of
exhaust flowing into the DPF during DPF regeneration process
execution is set based on a first control map, which is not
illustrated, and then Step S6 is advanced to.
[0174] In Step S5, the oxygen concentration target value AFTV of
exhaust flowing into the DPF during DPF regeneration process
execution is set based on a second control map, which is not
illustrated, and then Step S6 is advanced to.
[0175] The first control map and the second control map
respectively set the target value AFTV of the oxygen concentration
AF of exhaust flowing into the DPF, with at least one among a flow
rate GE of exhaust flowing into the DPF, the exhaust temperature TE
detected by the exhaust temperature sensor, and a PM deposition
amount QPM deposited on the DPF as a parameter.
[0176] For example, in a case of including the exhaust flow rate GE
as a parameter, the oxygen concentration target value AFTV is set
so as to become lower as the exhaust flow rate GE decreases. In a
case of including the exhaust temperature TE as a parameter, the
oxygen concentration target value AFTV is set so as to become lower
as the exhaust temperature TE rises. In addition, in a case of
including the PM deposition amount QPM as a parameter, it is set so
as to become lower as the PM deposition amount QPM increases.
[0177] Herein, if comparing the first control map and the second
control map, the first control map sets the oxygen concentration
target value AFTV to a concentration that is higher than the second
control map. Specifically, in a case of using a parameter of the
same value, the oxygen concentration target value set according to
the first control map will be larger than the oxygen concentration
target value set according to the second control map. In other
words, in a case of being in an idle operating state or
deceleration operating state, the oxygen concentration target value
is set to a lower concentration.
[0178] It should be noted that, in Steps S4 and S5, the flow rate
GE of exhaust flowing into the DPF is estimated based on the intake
air amount GA, and the PM deposition amount QPM is estimated based
on the pressure PE detected by the pressure sensor.
[0179] In Step S6, supply of reductive gas is started, and the
supply amount GRG of reductive gas and the intake air amount GA are
adjusted so that the oxygen concentration AF of exhaust flowing
into the DPF matches the oxygen concentration target value AFTV
thus set, and then this process ends.
[0180] In addition, the supply amount GRG of reductive gas and the
intake air amount GA are adjusted so that the exhaust air/fuel
ratio of exhaust flowing into the DPF does not fall below the
stoichiometric ratio.
[0181] FIGS. 3A and 3B are graphs showing examples of control of
the above DPF regeneration process.
[0182] FIG. 3A shows time variation of the PM deposition amount
QPM. In this figure, a time t.sub.0 is set as a DPF regeneration
process start time, and the PM deposition amount QPM gradually
reduces from this time t.sub.0.
[0183] FIG. 3B is a graph showing time variation of the oxygen
concentration target value AFTV. In this figure, the solid line 91
indicates the time variation of the oxygen concentration target
value in a case of having been set based on the first control map,
and the solid line 92 indicates the time variation of the oxygen
concentration target value in a case of having been set based on
the second control map. In addition, the time t.sub.1 indicates a
time at which an idle operating state was transition to from a
normal operating state. As shown in FIG. 3B, the oxygen
concentration target value is determined based on the first control
map from when the DPF regeneration process is started at time
t.sub.0 until when the idle operating state is transitioned to at
time t.sub.1 (refer to Step S4 of FIG. 2), and the oxygen
concentration target value is determined to be a lower
concentration based on the second control map (refer to Step S5 of
FIG. 2).
[0184] As explained in detail above, according to the present
embodiment, the catalytic converter 31 that continuously oxidizes
reductive gas is provided in the exhaust plumbing 4 between the DPF
32 and the inlet 14 at which reductive gas produced by the fuel
reformer 50 is supplied, and a regeneration process to cause PM to
be combusted is executed while supplying reductive gas into the
exhaust plumbing 4.
[0185] This enables the oxygen concentration of exhaust flowing
into the DPF 32 to be controlled irrespective of the operating
state of the engine 1, by supplying reductive gas into the exhaust
plumbing 4. As a result, even in a case in which the DPF 32 may
melt such as during an idle operating state or fuel-cut state
described above, this can be avoided by lowering the oxygen
concentration. This enables the regeneration process to be stably
executed irrespective of the operating state of the engine 1.
[0186] In addition, by employing such a reductive gas, the
temperature of the exhaust can be raised without supplying unburned
fuel such as in exhaust injection and post injection. This enables
problems such as the occurrence of coking, degradation and
corrosion of the catalyst and components of the exhaust channel,
deterioration in fuel economy, and occurrence of oil dilution as
described above to be avoided.
[0187] In addition, the molecular diameters of carbon monoxide and
hydrogen contained in the reductive gas are small compared to the
particle diameters of the hydrocarbons supplied by exhaust
injection and post injection. As a result, even in a case of a
great amount of PM depositing on the DPF 32, it is possible to
supply reductive gas along with oxygen to deep parts thereof. This
can effectively promote the combustion of PM.
[0188] In addition, by providing the fuel reformer 50 that supplies
reductive gas to be separate from the exhaust plumbing 4, the DPF
regeneration time period can be decided independently of the state
of the engine 1. Therefore, the DPF regeneration process can be
suitable executed as needed while always controlling the engine 1
to an optimal state. In addition, by providing the fuel reformer 50
to be separate from the exhaust plumbing 4, reductive gas can
always be produced at optimum efficiency and this reductive gas can
be supplied into the exhaust plumbing 4, irrespective of the
operating state of the engine 1, oxygen concentration and steam
concentration of exhaust, etc.
[0189] On the other hand, in a case of providing the fuel reformer
50 inside the exhaust plumbing 4, it is necessary to enlarge the
fuel reformer so as to be able to operate without influencing the
components, temperature, and flow rate of the exhaust; however,
according to the present embodiment, it is possible to perform
operation stably without enlarging the device by providing the fuel
reformer 50 to be separate from the exhaust plumbing 4. In
addition, by providing the fuel reformer 50 to be separate from the
exhaust plumbing 4, it becomes possible to activate the reforming
catalyst 53 provided to the fuel reformer 50 at an early stage, by
performing control of an independent system from the control of the
engine 1.
[0190] Furthermore, according to the present embodiment, the
catalytic converter 31 contains at least one selected from the
group consisting of platinum, palladium, and rhodium. By containing
these active species, the catalytic combustion reaction such as of
hydrogen, carbon monoxide, and light hydrocarbons contained in the
reductive gas can be promoted.
[0191] In addition, according to the present embodiment, an oxygen
concentration detection means is provided for detecting the oxygen
concentration of exhaust flowing into the DPF 32. This enables the
oxygen concentration of exhaust flowing into the DPF 32 to be
controlled to a predetermined target value with good accuracy.
Moreover, by controlling the oxygen concentration of exhaust
flowing into the DPF 32, an excessive rise in temperature of the
DPF 32 during execution of the regeneration process can be
prevented.
[0192] Furthermore, according to the present embodiment, more
carbon monoxide than hydrogen is contained in the reductive gas.
Carbon monoxide combusts at a lower temperature than hydrogen.
Particulates deposited on the particulate filter can be effectively
combusted by supplying such a reducing gas containing carbon
monoxide.
[0193] In addition, according to the present embodiment, reductive
gas is supplied at a temperature higher than the temperature of
exhaust flowing through the exhaust plumbing 4 at the inlet 14.
This enables the combustion of PM to be promoted by causing the
temperature of the exhaust flowing into the catalytic converter 31
to rise.
[0194] Moreover, according to the present embodiment, while
executing the regeneration process, the oxygen concentration of
exhaust flowing into the DPF 32 is controlled so as to match a
target oxygen concentration by adjusting at least one among the
intake air amount, exhaust recirculation ratio, fuel injection
amount, and supply amount of reductive gas. This enables the oxygen
concentration of exhaust to be made to match the target oxygen
concentration with good accuracy.
[0195] In addition, according to the present embodiment, the oxygen
concentration target value is set based on at least one among the
flow rate of exhaust flowing through the exhaust plumbing 4, the
temperature of exhaust, and the deposition amount of PM deposited
on the DPF 32. This enables the target oxygen concentration to be
set so that PM is made to combust at an adequate temperature.
[0196] Moreover, according to the present embodiment, in a case of
the engine 1 being in an idle operating state, the oxygen
concentration target value is set to be low compared to a case of
not being in an idle operating state. With this, even in a case in
which the oxygen concentration in exhaust increases with the engine
1 having transitioned to an idle operating state, the oxidation
reaction in the DPF 32 is suppressed by setting the oxygen
concentration target value to be low, and thus an excessive rise in
temperature of this DPF 32 can be prevented.
[0197] In addition, according to the present embodiment, in a case
of the engine 1 being in a deceleration operating state, the oxygen
concentration target value is set to be low compared to a case of
not being in a deceleration operating state. With this, even in a
case in which the oxygen concentration in exhaust increases with
the engine 1 transitioning to a deceleration operating state and
deceleration fuel-cut having been performed, the oxidation reaction
in the DPF 32 is suppressed by setting the oxygen concentration
target value to be low, and thus an excessive rise in temperature
of this DPF 32 can be prevented.
[0198] Furthermore, according to the present embodiment, this fuel
reformer 50 can be made a smaller size by producing the reductive
gas by way of the partial oxidation reaction. In order words, this
is because a device to continually supply extra energy from outside
does not need to be provided since the partial oxidation reaction
as described above is an exothermic reaction, and once the reaction
starts, the reaction progresses spontaneously. In addition, there
is also no need to also provide a converter and system for
concentrating hydrogen of a shift reaction, etc. Moreover, the
light-off time of the fuel reformer 50 can be shortened by making
the fuel reformer 50 to be small in this way. Therefore, reductive
gas can be quickly supplied into the exhaust plumbing 4 as
needed.
[0199] Furthermore, by introducing light hydrocarbons generated
secondarily in this partial oxidation reaction to the catalytic
converter 31 along with carbon monoxide and hydrogen, it can also
be used in raising the temperature of exhaust.
[0200] According to the present embodiment, the ECU 40 configures
the regeneration means, target concentration setting means, and
oxygen concentration control means. More specifically, the means
related to Steps S1 to S6 of FIG. 2 correspond to the regeneration
means, the means related to Steps S4 and S5 correspond to the
target concentration setting means, and the means related to Step
S6 corresponds to the oxygen concentration control means.
[0201] It should be noted that various modifications are possible
to the aforementioned embodiment.
[0202] For example, although the catalytic converter 31 having an
oxidative function of continuously oxidizing reductive gas was
provided in the exhaust plumbing 4 on an upstream side of the DPF
32 in the above-mentioned embodiment, it is not limited thereto.
For example, a similar catalyst having an oxidative function may be
supported on the DPF, without providing the catalytic converter to
be separate from the DPF. In addition, in this case, it is
preferable for the catalyst supported on the DPF to contain at
least one selected from the group consisting of palladium, rhodium,
platinum, silver, and gold.
[0203] This enables the following effects to be exerted in addition
to the effects of the above-mentioned embodiment. In other words,
by supporting a catalyst having an oxidative function on the DPF,
the exhaust emission control device can be made compact, and the
combustion reaction of PM can be further promoted. Therefore, the
time from supplying reductive gas until combustion of PM begins can
be further shortened.
[0204] Moreover, in the above-mentioned embodiment, although the
supply amount GRG of reductive gas and the intake air amount GA are
adjusted so that the oxygen concentration AF of exhaust flowing
into the DPF matches the oxygen concentration target value AFTV
that has been set in Step S6, it is not limited thereto. The
exhaust recirculation ratio, fuel injection amount of the engine,
and the like may be adjusted in addition to the supply amount GRG
of reductive gas and the intake air amount GA.
Second Embodiment
[0205] A second embodiment of the present invention is explained
below while referring to the drawings. In the explanation of the
second embodiment below, constitutional requirements identical to
the first embodiment are assigned the same reference symbol, and
explanations thereof are omitted or simplified.
[0206] FIG. 4 is a view showing a configuration of an engine 1 and
an exhaust emission control device thereof according to the second
embodiment of the present invention. The second embodiment is
mainly different from the first embodiment in the configuration of
an ECU 40A.
[0207] An upstream temperature sensor 29U that detects an exhaust
temperature TU in the exhaust plumbing 4 on an upstream side of the
DPF 32 and the catalytic converter 31, and a downstream temperature
sensor 29D that detects an exhaust temperature TD in the exhaust
plumbing 4 on a downstream side of the DPF 32 are connected to the
ECU 40A, and detection signals of these sensors are supplied to the
ECU 40A.
[0208] FIG. 5 is a flowchart showing a sequence of a DPF
regeneration process by the ECU. As shown in FIG. 5, in the DPF
regeneration process, a normal regeneration process that executes
the regeneration process without employing reductive gas supplied
by the fuel reformer, and a heated regeneration process that allows
execution of the regeneration process employing reductive gas
become switchable according to predetermined conditions. In
addition, this DPF regeneration process is performed every
predetermined time period, for example.
[0209] In Step S11, it is determined whether the DPF regeneration
request flag FDPFRR is "1". In a case of this determination being
YES, Step S12 is advanced to, an in a case of being NO, this
process ends immediately. Herein, when the consumed amount of fuel
has reached a predetermined value, or when a traveled distance of
the vehicle has reached a predetermined value, this DPF
regeneration request flag FDPFRR is set to "1".
[0210] In Step S12, it is determined whether the exhaust
temperature TD on a downstream side of the DPF detected by the
downstream temperature sensor is lower than a predetermined
judgment temperature TATH, and in a case of this determination
being YES, it is determined that the PM deposited on the DPF is not
in a combusted state, and Step S14 is advanced to, whereas in a
case of being NO, it is determined that PM is in a combusted state,
and Step S13 is advanced to.
[0211] In Step S13, the normal regeneration process is executed,
and then Step S19 is advanced to. In this normal regeneration
process, for example, the temperature of exhaust is made to rise up
to the combustion temperature of PM by executing post
injection.
[0212] In Step S14, the temperature TTWC of the catalytic converter
is estimated based on the exhaust temperature TU upstream of the
catalytic converter detected by the upstream temperature sensor, it
is determined whether this catalytic converter temperature TTWC is
lower than a predetermined judgment temperature TBTH, and in a case
of this determination being YES, Step S17 is advanced to, whereas
in a case of being NO, Step S15 is advanced to.
[0213] In Step S15, it is determined whether the engine is in a
low-load operating state, and in a case of this determination being
YES, Step S17 is advanced to, whereas in a case of being NO, Step
S16 is advanced to. More specifically, a generated torque TRQ of
the engine is estimated, and it is determined whether the engine is
in a low-load operating state by determining whether this generated
torque TRQ is less than a predetermined torque judgment value
TRQTH. In addition, in the present embodiment, the generated torque
TRQ of the engine is estimated based on at least one among the
revolution speed of the engine, fuel injection amount, and fuel
injection timing.
[0214] In Step S16, it is determined whether it is immediately
after startup, and in a case of this determination being YES, Step
S17 is advanced to, whereas in a case of being NO, Step S18 is
advanced to. Herein, this determination as to whether being
immediately after startup is performed based on whether the elapsed
time TIM since startup of the engine that is measured by a timer,
which is not illustrated, is less than a predetermined judgment
time TIMTH.
[0215] In Step S17, execution of a first heated regeneration
process is started, and then Step S19 is advanced to. In this first
heated regeneration process, reductive gas produced by the fuel
reformer is supplied into the exhaust plumbing along with the
intake air amount GA being reduced to a predetermined amount by
closing the throttle valve.
[0216] In addition, in Step S18, execution of a second heated
regeneration process is started, and then Step S19 is advanced to.
In this second heated regeneration step, the intake air amount GA
is reduced to a predetermined amount by closing the throttle valve.
Moreover, in this second heated regeneration process, supply of
reductive gas is not performed.
[0217] In Step S19, it is determined whether a predetermined
regeneration time has elapsed. In a case of this determination
being YES, Step S20 is advanced to and this process ends after the
DPF regeneration request flag is returned to "0", whereas in a case
of being NO, this process ends immediately.
[0218] As described above in detail, according to the present
embodiment, when executing the DPF regeneration process in which PM
collected in the DPF 32 is caused to combust, the normal
regeneration process that executes the regeneration process without
employing reductive gas and the first and second heated
regeneration processes that allow execution of the regeneration
processing employing reductive gas are switched according to
predetermined conditions. Herein, molecules that easily combust
such as hydrogen and carbon monoxide are contained in the reductive
gas produced by the fuel reformer 50. Even in a state in which the
exhaust temperature is low and it is difficult to cause PM to
combust, the temperature of exhaust can be quickly raised by
supplying such a reductive gas to the DPF 32, for example.
[0219] In addition, by switching between the normal regeneration
process and first and second heated regeneration processes
according to predetermined conditions, for example, a regeneration
process can be executed even if it enters a state in which a DPF
regeneration process would be difficult to execute by a
conventional method as described above, such as in a case of
immediately after engine startup or having transitioned to low-load
operation. In other words, it is possible to reduce the frequency
at which the operating state of the engine enters a situation in
which it is difficult to continue the DPF regeneration process,
thereby forcing interruption of the regeneration process.
Therefore, the time required in the regeneration process can be
shortened.
[0220] In addition, by employing such a reductive gas, the
temperature of exhaust can be made to rise without supplying
unburned fuel as in the exhaust injection and post injection. This
enables problems such as the occurrence of coking, degradation and
corrosion of the catalyst and components of the exhaust channel,
deterioration in fuel economy, and occurrence of oil dilution as
described above to be avoided.
[0221] In addition, the molecular diameters of carbon monoxide and
hydrogen contained in the reductive gas are small compared to the
molecular diameters of the hydrocarbons supplied by exhaust
injection and post injection. As a result, even in a case of a
great amount of PM depositing on the DPF 32, it is possible to
supply reductive gas along with oxygen to deep parts thereof. This
can efficiently promote the combustion of PM.
[0222] In addition, by providing the fuel reformer 50 that supplies
reductive gas to be separate from the exhaust plumbing 4, the
regeneration time period of PM can be decided independently of the
state of the engine 1. Therefore, the DPF regeneration process can
be suitable executed as needed while always controlling the engine
1 to an optimal state. In addition, by providing the fuel reformer
50 to be separate from the exhaust plumbing 4, reductive gas can
always be produced at optimum efficiency and this reductive gas can
be supplied into the exhaust plumbing 4, irrespective of the
operating state of the engine 1, oxygen concentration and steam
concentration of exhaust, etc.
[0223] On the other hand, in a case of providing the fuel reformer
50 inside the exhaust plumbing 4, it is necessary to enlarge the
fuel reformer 50 so as to be able to operate without influencing
the components, temperature, and flow rate of the exhaust; however,
according to the present embodiment, it is possible to perform
operation stably without enlarging the device by providing the fuel
reformer 50 to be separate from the exhaust plumbing 4. In
addition, by providing the fuel reformer 50 to be separate from the
exhaust plumbing 4, it becomes possible to activate the reforming
catalyst 53 of the fuel reformer 50 at an early stage, by
performing control of an independent system from the control of the
engine 1.
[0224] Furthermore, according to the present embodiment, more
carbon monoxide than hydrogen is contained in the reductive gas.
Carbon monoxide combusts at a lower temperature than hydrogen. PM
deposited on the DPF 32 can be efficiently combusted by supplying
such a reductive gas containing carbon monoxide.
[0225] In addition, according to the present embodiment, the
reductive gas produced by the fuel reformer 50 flows into the
catalytic converter 31 and combusts by way of this catalytic
converter 31. By combusting reductive gas by way of the catalytic
converter 31 in this way, the temperature of exhaust is raised, and
PM deposited on the DPF 32 can be efficiently combusted.
[0226] Moreover, according to the present embodiment, in a case of
having determined that the PM deposited on the DPF 32 is in a
combusted state, the normal regeneration process is executed, and
in a case of having determined that the PM is not in a combusted
state, the first heated regeneration process or the first heated
regeneration process is executed. This enables the regeneration
process to be efficiently executed while preventing the reductive
gas from being consumed for no purpose. In addition, this enables
the time required for the regeneration process to be shortened
according to the operating state of the engine or the like.
[0227] Moreover, according to the present embodiment, it is
determined whether the PM is in a combusted state based on the
exhaust temperature on a downstream side of the DPF 32. This
enables the combusted state of PM to be determined with good
accuracy.
[0228] Furthermore, according to the present embodiment, in a case
of executing the first or second heated regeneration process, the
intake air amount of the engine 1 is reduced compared to a case of
executing the normal regeneration process. As such, the temperature
of the DPF 32 can be quickly raised by executing the first or
second heated regeneration process.
[0229] In addition, according to the present embodiment, in a case
of the temperature TTWC of the catalytic converter 31 being lower
than the predetermined judgment temperature TBTH, the first heated
regeneration process is executed. With this, even in a state in
which the exhaust temperature is low and it is difficult to cause
PM to combust, the exhaust temperature is quickly raised, and thus
combustion of PM can be promoted.
[0230] In addition, according to the present embodiment, in a case
of the generated torque TRQ being lower than the predetermined
judgment value TRQTH, the first heated regeneration process is
executed. With this, even in a state in which the engine 1 is in a
low-load operating state and it is difficult to cause PM to
combust, the exhaust temperature is quickly raised, and thus the
combustion of PM can be promoted.
[0231] Moreover, according to the present embodiment, in a case of
the elapsed time TIM from starting up the engine 1 is less than the
predetermined judgment time TIMTH, the first heated regeneration
process is executed. With this, even in a case of not being long
after startup of the engine 1 and it being difficult to cause PM to
combust, the exhaust temperature is quickly raised, and thus the
combustion of PM can be promoted.
[0232] In the present embodiment, the ECU 40A configures a
regeneration means, normal regeneration means, heated regeneration
means, first heated regeneration means, second heated regeneration
means, combustion judgment means, a portion of a filter temperature
estimation means, a portion of a torque estimation means, and a
timing means. More specifically, the means related to Steps S11 to
S20 of FIG. 5 correspond to the regeneration means, the means
related to Step S13 correspond to the normal regeneration means,
the means related to Steps S17 and S18 correspond to the heated
regeneration means, the means related to Step S17 correspond to the
first heated regeneration means, the means related to Step S18
correspond to the second heated regeneration means, the means
related to Step S12 and the downstream temperature sensor 29D
correspond to the combustion judgment means, the means related to
Step S15 correspond to the torque estimation means, and the means
related to Step S16 correspond to the timing means.
[0233] It should be noted that various modifications are possible
to the aforementioned embodiment.
[0234] For example, although the catalytic converter 31 having an
oxidative function of continuously oxidizing reductive gas was
provided in the exhaust plumbing 4 on an upstream side of the DPF
32 in the above-mentioned embodiment, it is not limited thereto.
For example, a similar catalyst having an oxidative function may be
supported on the DPF, without providing the catalytic converter to
be separate from the DPF. With this, compared to a case in which
the catalytic converter and the DPF are provided separately, the
exhaust emission control device can be made compact, and the
combustion reaction of PM can be further promoted. Therefore, the
time from supplying reductive gas until combustion of PM beings can
be further shortened.
[0235] Moreover, in the above-mentioned embodiment, although it was
determined whether the PM deposited on the DPF is in a combusted
state based on the exhaust temperature TD on a downstream side of
the DPF detected by the downstream temperature sensor 29D in Step
S12, it is not limited thereto. For example, an oxygen
concentration detection means for detecting or estimating the
oxygen concentration of exhaust on a downstream side of the DPF may
be provided, and it may be determined whether the PM is in a
combusted state based on the oxygen concentration detected or
estimated by this oxygen concentration detection means. Effects
similar to the above-mentioned embodiment can be exerted also if
configured in this way.
[0236] For example, in the above-mentioned embodiment, although
determination of whether to execute the first heated regeneration
process or to execute the second heated regeneration process was
performed based on the temperature of the catalytic converter, the
operating state of the engine, and the elapsed time from beginning
startup of the engine in Steps S14 to S16, it is not limited
thereto. For example, in a case of the exhaust temperature TU
detected by the upstream temperature sensor being lower than a
predetermined judgment temperature TCTH, it may be configured so as
to execute the first heated regeneration process. In addition, a
filter temperature estimation means for estimating a temperature
TDPF of the DPF may be provided, for example, and it may be
configured so as to execute the first heated regeneration process
in a case in which the DPF temperature TDPF estimated by this
filter temperature estimation means is lower than a predetermined
judgment temperature TDTH. Effects similar to the above-mentioned
embodiment can be exerted also if configured in this way.
[0237] In addition, in the above-mentioned embodiment, although the
intake air amount GA is reduced to a predetermined amount by
closing the throttle valve in Step S17 and Step S18, when executing
the first heated regeneration process and the second regeneration
process, it is not limited thereto. These processes are not limited
to reduction of the intake air amount, and it may be configuration
to increase the exhaust recirculation flow rate by opening the EGR
valve or to lower the charging efficiency of the engine. Effects
similar to the above-mentioned embodiment can be exerted also if
configured in this way.
Third Embodiment
[0238] A third embodiment of the present invention is explained
below while referring to the drawings. In the explanation of the
third embodiment below, constitutional requirements identical to
the first embodiment are assigned the same reference symbol, and
explanations thereof are omitted or simplified.
[0239] FIG. 6 is a view showing a configuration of an engine 1 and
an exhaust emission control device thereof according to the third
embodiment of the present invention. In addition to the
configuration of the fuel reformer 50B and the configuration of the
ECU 40B, the third embodiment is mainly different from the first
embodiment in the aspect of providing a NOx purification catalyst
33.
[0240] The catalytic converter 31, DPF 32, and NOx purification
catalyst 33 are provided in this sequence from an upstream side in
the exhaust plumbing 4.
[0241] The NOx purification catalyst 33 includes platinum (Pt) that
acts as a catalyst and is supported on a carrier of alumina
(Al.sub.2O.sub.3), ceria (CeO.sub.2), and a complex oxide of cerium
and a rare earth (hereinafter referred to as "ceria-based complex
oxide"), a ceria or a ceria-based complex oxide having NOx
adsorption capacity, and a zeolite having a function of retaining
ammonia (NH.sub.3) generated on the catalyst as ammonium ion
(NH.sub.4.sup.+).
[0242] In the present embodiment, a material formed by loading a
NOx reduction catalyst composed of two layers onto a catalyst
support is used as the NOx purification catalyst 33.
[0243] The lower layer of the NOx reduction catalyst is formed by
producing a slurry by placing a material constituted with 4.5 (g/L)
of platinum, 60 (g/L) of ceria, 30 (g/L) of alumina, 60 (g/L) of
Ce--Pr--La--Ox, and 20 (g/L) of Zr--Ox into a ball mill with an
aqueous medium, then agitating and mixing, followed by coating this
slurry on the catalyst support.
[0244] In addition, the upper layer of the NOx reduction catalyst
is formed by producing a slurry by placing a material constituted
with 75 (g/L) of a beta zeolite ion-exchanged with iron (Fe) and
cerium (Ce), 7 (g/L) of alumina, and 8 (g/L) of a binder into a
ball mill with an aqueous medium, then agitating and mixing,
followed by coating this slurry on the lower layer described
above.
[0245] When the amount of adsorbed ammonia of the NOx purification
catalyst 33 is small, since the NOx purification ability decreases,
supply of a reducing agent (hereinafter referred to as "reduction")
to the NOx purification catalyst 33 is performed in order to reduce
the NOx appropriately. With this reduction, the reducing agent is
supplied to the NOx purification catalyst 33 by making the air/fuel
ratio (engine air/fuel ratio) of the mixture inside the combustion
chamber of the engine 1 to be richer than the stoichiometric ratio.
In other words, by enriching the exhaust air/fuel ratio emitted
from the engine 1, the concentration of reducing agent in the
exhaust flowing into the NOx purification catalyst 33 becomes
higher than the concentration of oxygen, thereby carrying out
reduction.
[0246] Purification of NOx in this NOx purification catalyst 33
will be explained.
[0247] First, the engine air/fuel ratio is set to be leaner than
stoichiometric, and when so-called lean burn operation is
performed, the concentration of reducing agent in the exhaust
flowing into the NOx purification catalyst 33 becomes lower than
the concentration of oxygen. As a result thereof, nitrogen monoxide
(NO) and oxygen (O.sub.2) in the exhaust react by action of the
catalyst, and is adsorbed to ceria or a ceria-based complex oxide
as NO.sub.2. In addition, carbon monoxide (CO) that has not reacted
with oxygen is also adsorbed to ceria or the ceria-based complex
oxide.
[0248] Next, so-called rich operation is performed in which the
engine air/fuel ratio is set to be richer than stoichiometric, and
the exhaust air/fuel ratio is enriched. In other words, when
reduction to make the concentration of the reducing agent in the
exhaust higher than the concentration of oxygen is carried out,
carbon dioxide (CO.sub.2) and hydrogen (H.sub.2) are generated by
carbon monoxide in the exhaust reacting with water (H.sub.2O), and
carbon monoxide (O) and carbon dioxide (CO.sub.2) as well as
hydrogen are generated by hydrocarbons (HO) in the exhaust reacting
with water. Furthermore, NOx contained in the exhaust and NOx (NO,
NO.sub.2) adsorbed to ceria or the ceria-based complex oxide (and
platinum) react with the hydrogen thus generated by action of the
catalyst, thereby generating ammonia (NH.sub.3) and water. In
addition, the ammonia thus generated here is adsorbed to zeolite in
the form of ammonium ions (NH.sub.4.sup.+).
[0249] Next, lean burn operation is performed in which the engine
air/fuel ratio is set to be leaner than stoichiometric, and when
the concentration of the reducing agent in the exhaust flowing into
the NOx purification catalyst 33 is set to be lower than the
concentration of oxygen, NOx is adsorbed to ceria or the
ceria-based complex oxide. Furthermore, in a state where ammonium
ions are adsorbed to the zeolite, NOx and oxygen in the exhaust
react with ammonia, thereby generating nitrogen (N.sub.2) and
water.
[0250] In this way, according to the NOx purification catalyst 33,
ammonia generated during reducing agent supply is adsorbed to the
zeolite, and the ammonia adsorbed during lean burn operation reacts
with NOx; therefore, it is possible to perform purification of NOx
efficiently.
[0251] When SOx in exhaust is absorbed to the NOx purification
catalyst 33, the NOx purification performance of the NOx
purification catalyst 33 declines. As a result, it is necessary to
perform a SOx regeneration process to purify the SOx absorbed to
the NOx purification catalyst 33. More specifically, by way of the
regeneration process, which is explained in detail referring to
FIG. 7, the exhaust flowing into the NOx purification catalyst 33
is made a reducing atmosphere and this NOx purification catalyst 33
is raised in temperature thereby.
[0252] In the present embodiment, the fuel reformer 50B is
connected in the exhaust plumbing 4 between the DPF 32 and the NOx
purification catalyst 33. In other words, the reductive gas
produced by the fuel reformer 50B is supplied from an inlet 14B
formed in the exhaust plumbing 4 between the DPF 32 and the NOx
purification catalyst 33 into the exhaust plumbing 4.
[0253] A UEGO sensor 23B that is set in a vicinity of the NOx
purification catalyst 33 and detect an oxygen concentration of the
exhaust in the exhaust plumbing 4 between the inlet 14 and the NOx
purification catalyst 33, i.e. exhaust air/fuel ratio AFB, an
exhaust temperature sensor 26B that detects a temperature TEB of
exhaust in the exhaust plumbing 4 between the inlet 14B and the NOx
purification catalyst 33, a differential pressure sensor 27 that
detects a pressure differential .DELTA.P between an upstream side
and a downstream side of the DPF 32, and a NOx sensor 28 that
detects a NOx concentration DND of exhaust in the exhaust plumbing
4 on a downstream side of the NOx purification catalyst 33 are
connected to the ECU 40B, and detection signals of these sensors
are supplied to the ECU 40B.
[0254] The engine 1 is normally operated by setting the engine
air/fuel ratio to be leaner than the stoichiometric ratio, and in a
case in which PM deposited on the DPF 32 is caused to combust or in
a case in which SOx adsorbed to the NOx purification catalyst is
purified, the regeneration process is performed.
[0255] The regeneration process of the present embodiment will be
explained with reference to FIGS. 7 to 9.
[0256] FIG. 7 is a flowchart showing a sequence of the regeneration
process by the ECU. As shown in FIG. 7, in the regeneration process
of the present embodiment, the normal regeneration operation that
performs a DPF regeneration process in which the DPF is raised in
temperature by executing a reduction in the intake air amount and
post injection, whereby PM collected on the DPF is caused to
combust (Steps S32 to S39), and the simultaneous regeneration
operation that performs a SOx regeneration process in which SOx
adsorbed to the NOx purification catalyst is purified by supplying
reductive gas while executing this normal regeneration operation
(Steps S35 to S37) become selectively executable according to
predetermined conditions.
[0257] In addition, in the regeneration process shown in FIG. 7, a
normal regeneration execution request flag FDPFRP, a normal
regeneration end request flag FDPFRE, a simultaneous regeneration
execution request flag FSIMRP, and a simultaneous regeneration end
request flag FSIMRE, which request the execution or end of this
normal regeneration operation and simultaneous regeneration
operation, are employed.
[0258] FIG. 8 is a graph showing a relationship of a deposition
amount QPM of PM on the DPF with a first threshold value QPMATH and
a second threshold value QPMBTH, which are used in updating the
normal regeneration execution request flag FDPFRP and the normal
regeneration end request flag FDPFRE. Herein, these two threshold
values are set so that QPMATH>QPMBTH.
[0259] If the engine operates continuously, the PM deposition
amount QPM will increase. Consequently, the normal regeneration
execution request flag FDPFRP that requests execution of the normal
regeneration operation is set to "1" in response to the PM
deposition amount QPM having become at least the first threshold
value QPMATH.
[0260] Next, if the normal regeneration operation is executed, the
PM deposition amount QPM will decrease. Consequently, the normal
regeneration end request flag FDPRRE that requests to end the
normal regeneration operation is set to "1" in response to the PM
deposition amount QPM having dropped below the second threshold
value QPMBTH.
[0261] It should be noted that, in the present embodiment, the PM
deposition amount QPM is estimated based on the differential
pressure .DELTA.P between an upstream side and a downstream side of
the DPF detected by the differential pressure sensor.
[0262] FIG. 9 is a graph showing a relationship of a SOx poisoning
amount QSO of the NOx purification catalyst with a first threshold
value QSOATH and a second threshold value QSOBTH, which are used in
updating the simultaneous regeneration execution request flag
FSIMRP and the simultaneous regeneration end request flag FSIMRE.
Herein, these two threshold values are set so that
QSOATH>QSOBTH.
[0263] If the engine operates continuously, the SOx poisoning
amount QPM will increase. Consequently, the simultaneous
regeneration execution request flag FSIMRP that requests execution
of the simultaneous regeneration operation is set to "1" in
response to the SOx poisoning amount QSO having become at least the
first threshold value QSOATH.
[0264] Next, if the simultaneous regeneration operation is
executed, the SOx poisoning amount QSO will decrease. Consequently,
the simultaneous regeneration end request flag FSIMRE that requests
to end the simultaneous regeneration operation is set to "1" in
response to the SOx poisoning amount QSO having dropped below the
second threshold value QSOBTH.
[0265] It should be noted that, in the present embodiment, the SOx
poisoning amount of the NOx purification catalyst is estimated
based on the NOx concentration DND of exhaust on a downstream side
of the NOx purification catalyst detected by the NOx sensor.
[0266] In addition, the normal regeneration execution request flag
FDPFRP, normal regeneration end request flag FDPFRE, simultaneous
regeneration execution request flag FSIMRP, and simultaneous
regeneration end request flag FSIMRE are constantly updated with
the PM deposition amount QPM and the SOx poisoning amount QSO by
the ECU.
[0267] Referring again to FIG. 7, in Step S31, it is determined
whether either of the normal regeneration execution request flag
FDPFRP or the simultaneous regeneration execution request flag
FSIMRP is "1". In a case of this determination being YES, Step S32
is advanced to, and in a case of being NO, this process ends
immediately.
[0268] In Step S32, intake air amount reduction control and post
injection control are executed, and Step S33 is advanced to. With
this intake air amount reduction control, the temperature of the
exhaust is controlled by adjusting the intake air amount. More
specifically, the throttle valve is controlled and the intake air
amount GA is reduced to a predetermined set amount, whereby the
exhaust temperature is made to rise. In addition, with the post
injection control, post injection is executed, with the post
injection amount being adjusted to a predetermined set amount.
[0269] In Step S33, it is determined whether the simultaneous
regeneration execution request flag FSIMRP is "1". In a case of
this determination being YES, Step S34 is advanced to, and in a
case of being NO, Step S36 is advanced to.
[0270] In Step S34, a temperature TLNC of the NOx purification
catalyst is estimated based on the exhaust temperature TEE detected
by the exhaust temperature sensor, and it is determined whether
this catalyst temperature TLNC is at least a predetermined
temperature judgment value TLNCTH. In a case of this determination
being YES, Step S35 is advanced to, and in a case of being NO, Step
S36 is advanced to.
[0271] In Step S35, reductive gas supply control is executed, i.e.
the simultaneous regeneration operation is executed, and then Step
S36 is advanced to. More specifically, the supply of reductive gas
produced by the fuel reformer into the exhaust plumbing is started,
with the supply amount of reductive gas being controlled based on
an exhaust air/fuel ratio AFB detected by the UEGO sensor.
[0272] Herein, it is also preferable for oxygen to be contained in
the exhaust flowing through this exhaust plumbing when supplying
reductive gas into the exhaust plumbing.
[0273] In Step S36, it is determined whether the simultaneous
regeneration end request flag FSIMRE is "1". In a case of this
determination being YES, Step S37 is advanced to, and in a case of
being NO, Step S38 is advanced to.
[0274] In Step S37, reductive gas supply control ends, i.e. the
simultaneous regeneration operation ends, the simultaneous
regeneration execution request flag FSIMRP and the simultaneous
regeneration end request flag FSIMRE return to "0", and Step S38 is
advanced to.
[0275] In Step S38, it is determined whether the normal
regeneration end request flag FDPFRE is "1". In a case of this
determination being YES, Step S39 is advanced to, and in a case of
being NO, this process ends.
[0276] In Step S39, the intake air amount reduction control and
post injection control end, and the normal regeneration execution
request flag FDPFRP and the normal regeneration end request flag
FDPFRE return to "0".
[0277] As described in detail above, according to the present
embodiment, the DPF 32 was provided in the exhaust plumbing 4 on an
upstream side of the NOx purification catalyst 33, and the fuel
reformer 50B was provided that supplies reductive gas containing
hydrogen and carbon monoxide from the inlet 14B provided between
this NOx purification catalyst 33 and this DPF 32. With this, the
exhaust air/fuel ratio of exhaust flowing into the NOx purification
catalyst 33 is kept low and the SOx regeneration process of the NOx
purification catalyst 33 can be executed with high efficiency by
supplying reductive gas from downstream of the DPF 32, while the
oxygen concentration of exhaust flowing into the DPF 32 is kept
high, and the DPF regeneration process is executed with high
efficiency. In this way, according to the present embodiment, it is
possible to execute the DPF regeneration process and the SOx
regeneration process simultaneously with high efficiency.
Therefore, the time required in these processes is shortened, which
can improve fuel economy, whereby degradation to the DPF 32 and the
NOx purification catalyst 33 can also be reduced.
[0278] In addition, by providing the fuel reformer 50B to be
separate from the exhaust plumbing 4, reductive gas can be supplied
without increasing the heat capacity upstream of the NOx
purification catalyst 33. This enables the SOx regeneration process
to be executed without reducing the NOx purification performance
when at low temperature such as immediately after startup of the
engine 1.
[0279] Moreover, by providing the fuel reformer that produces
reductive gas to be separate from the exhaust channel, the
execution time period of the SOx regeneration process can be
decided independently of the state of the internal combustion
engine. Therefore, the SOx regeneration process can be suitable
executed as needed while always controlling the engine 1 to an
optimal state. In addition, by providing the fuel reformer 50B to
be separate from the exhaust plumbing 4, reductive gas can always
be produced at optimum efficiency and this reductive gas can be
supplied into the exhaust plumbing 4, irrespective of the operating
state of the engine 1, the oxygen concentration or steam
concentration of the exhaust, etc.
[0280] On the other hand, in a case of providing the fuel reformer
50B inside the exhaust plumbing 4, it is necessary to enlarge the
fuel reformer 50B so as to be able to operate without influencing
the components, temperature, and flow rate of the exhaust; however,
according to the present embodiment, it is possible to perform
operation stably without enlarging the device by providing the fuel
reformer 50B to be separate from the exhaust plumbing 4. In
addition, by providing the fuel reformer 50B to be separate from
the exhaust plumbing 4, it becomes possible to activate the
reforming catalyst 53 at an early stage by performing control of an
independent system from the control of the engine 1.
[0281] In addition, according to the present embodiment, more
carbon monoxide than hydrogen is contained in the reductive gas by
volume ratio. Moreover, the temperature at which carbon monoxide
begins to combust on the catalyst is a temperature lower than the
temperature at which hydrogen begins to combust. The NOx
purification catalyst 33 is quickly raised in temperature by
supplying such a reductive gas containing carbon monoxide, and thus
the purification of SOx can be promoted in the SOx regeneration
process. In addition, reductive gas thus produced can be supplied
into the exhaust plumbing 4 without adding an extra device by
producing reductive gas of a pressure higher than atmospheric.
[0282] Moreover, according to the present embodiment, reductive gas
of a temperature higher than the temperature of exhaust flowing
through the exhaust plumbing 4 at the inlet 14B is supplied. This
enables the NOx purification catalyst 33 to be quickly raised in
temperature, and thus the purification of SOx to be promoted in the
SOx regeneration process.
[0283] In addition, according to the present embodiment, the normal
regeneration operation that performs the DPF regeneration process
and the simultaneous regeneration operation that supplies reductive
gas and performs the SOx regeneration process while executing this
normal regeneration operation are selectively executed according to
predetermined conditions. This enables these regeneration processes
to be efficiently executed while minimizing consumption of
reductive gas, by executing the normal regeneration operation in a
case of only performing the DPF regeneration process being
necessary, and executing the simultaneous regeneration operation in
a case in which performing the DPF regeneration process and the SOx
regeneration process simultaneously is preferable.
[0284] Moreover, according to the present embodiment, the
temperature of the exhaust is controlled by adjusting the intake
air amount when executing the normal regeneration operation. This
enables the temperature of the exhaust to be controlled to a
required temperature in order for the PM to be made to combust, and
the DPF regeneration process to be performed efficiently.
[0285] Furthermore, according to the present embodiment, when
providing the catalytic converter 31 having an oxidative function
on an upstream side of the DPF 32, post injection is executed when
executing the normal regeneration operation. With this, the
temperature of the exhaust flowing into the DPF 32 can be raised
and thus the DPF regeneration process can be performed with high
efficiency, by causing fuel supplied by way of post injection to
combust by way of the catalytic converter 31 when executing the
normal regeneration operation.
[0286] In addition, according to the present embodiment, in a case
of the PM deposition amount QPM having become at least the first
threshold value QPMATH, the normal regeneration execution request
flag FDPFRP is set to 1, and the normal regeneration operation or
simultaneous regeneration operation is executed. This enables the
DPF regeneration process to be executed at a suitable opportunity
prior to the PM deposition amount reaching the limit.
[0287] Moreover, according to the present embodiment, the
simultaneous regeneration execution request flag FSIMRP is set to
1, and the simultaneous regeneration operation is executed in
response to the temperature TLNC of the NOx purification catalyst
33 being at least the predetermined temperature judgment value
TLNCTH and the SOx poisoning amount QSO of the NOx purification
catalyst 33 having become at least the first threshold value
QSOATH. This enables the SOx regeneration process to be performed
at an opportunity before the NOx purification performance of the
NOx purification catalyst 33 declines drastically. Furthermore, SOx
desorbed from the NOx purification catalyst 33 can be purified with
good efficiency by executing the simultaneous regeneration
operation in a case in which the temperature TLNC of the NOx
purification catalyst is at least the predetermined temperature
judgment value TLNCTH.
[0288] In addition, according to the present embodiment, the
simultaneous regeneration end request flag FSIMRE is set to 1 in
response to the SOx poisoning amount QSO having become less than
the predetermined second threshold value SQOBTH, then execution of
the simultaneous regeneration operation ends, and the normal
regeneration operation is executed. This enables execution of the
simultaneous regeneration operation to end according to recovery of
the NOx purification performance of the NOx purification catalyst,
and the DPF regeneration process to continue.
[0289] Moreover, according to the present embodiment, the supply
amount of reductive gas is controlled according to the exhaust
air/fuel ratio AFB in a vicinity of the NOx purification catalyst
33. This enables the exhaust air/fuel ratio of exhaust flowing into
the NOx purification catalyst 33 to be adjusted appropriately, and
thus the efficiency of the SOx regeneration process to be further
improved.
[0290] Furthermore, according to the present embodiment, the fuel
reformer 50B can be made a smaller size by producing reductive gas
by way of a partial oxidation reaction. In order words, this is
because a device to supply extra energy from outside does not need
to be provided since the partial oxidation reaction as described
above is an exothermic reaction, and once the reaction starts, the
reaction progresses spontaneously. In addition, there is also no
need to also provide a converter and system for concentrating
hydrogen of a shift reaction, etc. Moreover, the light-off time of
the fuel reformer 50B can be shortened by making the fuel reformer
50B to be small in this way. Therefore, reductive gas can be
quickly supplied into the exhaust plumbing 4 as needed.
[0291] Furthermore, by introducing light hydrocarbons generated
secondarily in this partial oxidation reaction to the NOx
purification catalyst 33 along with carbon monoxide and hydrogen,
it can also be used in the purification of SOx.
[0292] In the present embodiment, the ECU 40B configures the
regeneration means, exhaust temperature control means, deposition
amount estimation means, a portion of the SOx poisoning amount
estimation means, a portion of the catalyst temperature estimation
means, and the supply amount control means. More specifically, the
means related to Steps S31 to S39 of FIG. 7 correspond to the
regeneration means, the means related to Step S32 correspond to the
exhaust temperature control means, the ECU 40B and the differential
pressure sensor 27 correspond to the deposition amount estimation
means, the ECU 40B and the NOx sensor 28 correspond to the SOx
poisoning amount estimation means, the ECU 40B and the exhaust
temperature sensor 26B correspond to the catalyst temperature
estimation means, and the means related to Step S35 of FIG. 7
correspond to the supply amount control means.
[0293] It should be noted that, in the aforementioned embodiment,
various modifications thereto are possible.
[0294] For example, in the above-mentioned embodiment, although the
catalytic converter 31 having an oxidative function of continuously
oxidizing reductive gas was provided in the exhaust plumbing 4 on
an upstream side of the DPF 32, it is not limited thereto. For
example, a catalyst having a similar oxidative function may be
supported on the DPF, without providing a catalytic converter
separately from the DPF. In addition to effects similar to the
above-mentioned embodiment, this enables the exhaust emission
control device to be made compact, and can promote the combustion
reaction of PM. Therefore, the efficiency of the DPF regeneration
process can be further improved.
[0295] In addition, in the above-mentioned embodiment, although the
intake air amount was adjusted in Step S32 of FIG. 7, it is not
limited thereto, and the boost pressure may be adjusted, for
example. This enables effects similar to the above-mentioned
embodiment to be exerted.
[0296] It should be noted that the present invention is not to be
limited to the aforementioned first to third embodiments, and
various modifications thereto are possible.
[0297] For example, in the above-mentioned first to third
embodiments, although an example is shown in which the present
invention is applied to a diesel internal combustion engine, the
present invention can also be applied to a gasoline internal
combustion engine. In addition, the present invention can be
applied to an exhaust emission control device of an engine for
nautical propulsion such as an outboard engine in which the crank
shaft is arranged vertically, or the like.
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