U.S. patent application number 09/907721 was filed with the patent office on 2002-01-31 for method and configuration for cleaning an exhaust-gas flow flowing in an exhaust system of a gasoline engine.
Invention is credited to Bruck, Rolf, Maus, Wolfgang.
Application Number | 20020011069 09/907721 |
Document ID | / |
Family ID | 7894605 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020011069 |
Kind Code |
A1 |
Maus, Wolfgang ; et
al. |
January 31, 2002 |
Method and configuration for cleaning an exhaust-gas flow flowing
in an exhaust system of a gasoline engine
Abstract
A method and a configuration are provided for cleaning exhaust
gas in an exhaust gas system flowing from a gasoline engine. An
air/fuel mixture is preferably supplied to the gasoline engine by
direct injection. In order to provide improved cleaning, the
exhaust gas flows successively in the exhaust gas system through at
least one honeycomb body with a catalytically active coating,
preferably a three-way coating, and a particle filter with a
coating storing at least one pollutant component, in particular
hydrocarbon, carbon monoxide and/or nitrogen oxide, at least from
time to time. In addition to collecting soot particles, in
particular the particle filter advantageously carries out
supplementary oxidation of residual hydrocarbons as well as carbon
monoxide during a cold start phase, and supplementary reduction of
residual nitrogen oxides when the gasoline engine is operated under
load.
Inventors: |
Maus, Wolfgang; (Bergisch
Gladbach, DE) ; Bruck, Rolf; (Bergisch Gladbach,
DE) |
Correspondence
Address: |
LERNER AND GREENBERG, P.A.
PATENT ATTORNEYS AND ATTORNEYS AT LAW
Post Office Box 2480
Hollywood
FL
33022-2480
US
|
Family ID: |
7894605 |
Appl. No.: |
09/907721 |
Filed: |
July 18, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09907721 |
Jul 18, 2001 |
|
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PCT/EP00/00047 |
Jan 5, 2000 |
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Current U.S.
Class: |
60/285 ; 60/274;
60/286; 60/295; 60/311 |
Current CPC
Class: |
B01D 53/9431 20130101;
B01D 53/9495 20130101; F01N 3/0857 20130101; F01N 2610/02 20130101;
F01N 3/0842 20130101; F01N 3/0821 20130101; F01N 3/2066 20130101;
Y02T 10/12 20130101; F01N 3/0814 20130101; B01D 53/9454 20130101;
F02B 2075/125 20130101; F01N 3/0835 20130101 |
Class at
Publication: |
60/285 ; 60/274;
60/286; 60/295; 60/311 |
International
Class: |
F01N 003/00; F01N
003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 18, 1999 |
DE |
199 01 760.3 |
Claims
We claim:
1. A method for cleaning an exhaust-gas flow, which comprises:
supplying an air/fuel mixture to a gasoline engine; conducting an
exhaust-gas flow generated by the gasoline engine through an
exhaust system; and successively conducting the exhaust-gas flow in
the exhaust system through at least one honeycomb body having a
catalytically active coating, and a particle filter having a
coating storing at least one pollutant component at least from time
to time.
2. The method according to claim 1, which further comprises
supplying the air/fuel mixture to the gasoline engine by direct
injection.
3. The method according to claim 1, which further comprises
providing the catalytically active coating as a three-way
coating.
4. The method according to claim 1, which further comprises
carrying out the step of storing the at least one pollutant
component as at least one substance from the group consisting of
hydrocarbon, carbon monoxide and nitrogen oxide.
5. The method according to claim 1, which further comprises feeding
a rich air/fuel mixture to the gasoline engine, and storing
residual HC and CO not converted in the honeycomb body, with the
coating of the particle filter.
6. The method according to claim 1, which further comprises feeding
a lean air/fuel mixture to the gasoline engine, and storing
residual NO.sub.x not converted in the honeycomb body, with the
coating of the particle filter.
7. The method according to claim 1, which further comprises feeding
a reducing agent to the particle filter as a function of a residual
NO.sub.x concentration in the exhaust gas downstream of the
honeycomb body.
8. The method according to claim 7, which further comprises
selecting the reducing agent as ammonia.
9. The method according to claim 7, which further comprises
carrying out the step of feeding the reducing agent
continuously.
10. The method according to claim 7, which further comprises
carrying out the step of feeding the reducing agent in
intervals.
11. The method according to claim 10, which further comprises
carrying out the step of feeding the reducing agent in intervals as
a function of quantities of residual NO.sub.x stored in the
particle filter.
12. The method according to claim 1, which further comprises
feeding an oxidizing agent to the particle filter as a function of
a residual HC--CO concentration in the exhaust gas downstream of
the honeycomb body.
13. The method according to claim 12, which further comprises
feeding oxygen to the particle filter as the oxidizing agent.
14. The method according to claim 1, which further comprises
storing oxygen with the coating of the particle filter, at least
from time to time.
15. The method according to claim 1, which further comprises
measuring at least one residual pollutant component not converted
in the honeycomb body, with at least one measuring probe disposed
between the honeycomb body and the particle filter.
16. The method according to claim 15, which further comprises
carrying out the measuring step with at least one measuring probe
respectively measuring each of hydrocarbon, carbon monoxide and
nitrogen oxide as a residual pollutant component.
17. The method according to claim 1, which further comprises
regenerating the particle filter by burning particles.
18. The method according to claim 17, which further comprises
triggering the particle burning step by at least one of engine heat
and exothermic reactions in the honeycomb body.
19. The method according to claim 17, which further comprises
triggering the particle burning step at predeterminable
intervals.
20. A configuration for cleaning an exhaust-gas flow, comprising: a
gasoline engine receiving an air/fuel mixture and generating the
exhaust-gas flow; an exhaust system conducting the exhaust-gas flow
from said gasoline engine in a flow direction; at least one
honeycomb body disposed in said exhaust system, said at least one
honeycomb body having a catalytically active coating; and a
particle filter disposed in said exhaust system downstream of said
at least one honeycomb body in said flow direction, said particle
filter having a coating storing at least one pollutant component at
least from time to time.
21. The configuration according to claim 20, wherein said gasoline
engine receives the air/fuel mixture by direct injection.
22. The configuration according to claim 20, wherein said at least
one honeycomb body is a three-way catalytic converter.
23. The configuration according to claim 20, wherein the at least
one pollutant component stored by said coating is selected from the
group consisting of hydrocarbon, carbon monoxide and nitrogen
oxide.
24. The configuration according to claim 20, wherein said gasoline
engine receives a rich air/fuel mixture, and said coating of said
particle filter stores hydrocarbon and carbon monoxide not
converted in said at least one honeycomb body.
25. The configuration according to claim 20, wherein said gasoline
engine is fed a lean air/fuel mixture, and said coating of said
particle filter stores nitrogen oxides not converted in said at
least one honeycomb body.
26. The configuration according to claim 20, including a
reducing-agent reservoir, and at least one reducing-agent line
feeding a reducing agent from said reducing-agent reservoir to said
particle filter, as a function of a residual NO.sub.x concentration
in the exhaust gas downstream of said at least one honeycomb
body.
27. The configuration according to claim 26, wherein the reducing
agent is ammonia.
28. The configuration according to claim 26, wherein said
reducing-agent line ends at said particle filter.
29. The configuration according to claim 28, wherein said particle
filter has an integrated distribution device connected to said
reducing-agent line.
30. The configuration according to claim 20, wherein said particle
filter receives an oxidizing agent as a function of a residual
HC--CO concentration in the exhaust gas downstream of said at least
one honeycomb body.
31. The configuration according to claim 30, wherein the oxidizing
agent is oxygen.
32. The configuration according to claim 20, wherein said coating
of said particle filter stores oxygen, at least from time to
time.
33. The configuration according to claim 20, including at least one
measuring probe disposed between said at least one honeycomb body
and said particle filter, for measuring at least one residual
pollutant component not converted in said at least one honeycomb
body.
34. The configuration according to claim 33, wherein said at least
one measuring probe includes at least one measuring probe
respectively measuring each of hydrocarbon, carbon monoxide and
nitrogen oxide as residual pollutant components.
35. The configuration according to claim 20, wherein said particle
filter is to be regenerated by a process triggered by at least one
of engine heat and exothermic reactions in said at least one
honeycomb body.
36. The configuration according to claim 35, wherein said particle
filter is to be regenerated at predeterminable intervals.
37. The configuration according to claim 20, wherein said at least
one honeycomb body at least has partial regions forming said
particle filter.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of copending
International Application No. PCT/EP00/00047, filed Jan. 5, 2000,
which designated the United States.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method and a
configuration for cleaning an exhaust-gas flow, which is flowing in
an exhaust system, from a gasoline engine that is fed with an
air/fuel mixture, preferably by direct injection.
[0004] During the combustion of hydrocarbons which are found, for
example, in gasoline, when using air in a gasoline engine,
byproducts, in particular pollutants, substantially including
hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxide
(NO.sub.x), and possibly soot particles as well, are formed in
addition to the principal combustion products carbon dioxide and
steam. The level of pollutants and soot particles in the exhaust
gas is predominantly dependent on the air/fuel ratio being
supplied. Where the air/fuel ratios are low, the mixture
composition is said to be "rich" (air deficit). If the air/fuel
ratios are high, the mixture composition is described as "lean"
(excess air).
[0005] Soot is formed predominantly when burning with an extreme
deficit of air. Although that condition is not normally reached in
a gasoline engine, it may occur locally as a result of
inhomogeneity, in particular during a cold-start phase. The
formation of soot is generally initiated by thermal cracking of the
fuel molecules when there is a lack of oxygen and leads to the
polymerization of carbon-rich macromolecules, with hydrogen being
cleaved off. Those macromolecules then agglomerate to form the soot
particles which are ultimately produced. The considerable increase
in soot when the stoichiometric air ratio is approached results
from an increasing expansion of rich mixture zones due to an
injection quantity being increased. Soot which is formed in rich
mixture zones in general scarcely burns without further
measures.
[0006] In order to ensure that unburned soot particles do not
pollute the environment, it is known, for example, from German
Published, Non-Prosecuted Patent Application DE 41 17 676 A1,
corresponding to U.S. Pat. No. 5,207,990, to provide at least one
filter with a structure which promotes the deposition of soot
particles in particular in the exhaust system of diesel engines. A
particle filter of that type is regenerated, i.e. deposited soot
particles are burnt, for example by supplying fuel and air from
time to time in order to heat up the particle filter, so that even
soot particles formed with a deficit of air burn again. It is also
known, for example from German Published, Non-Prosecuted Patent
Application DE 40 12 719 A1, to provide the filter with a catalytic
converter which converts at least one pollutant component, in
particular hydrocarbon (HC), carbon monoxide (CO) and/or nitrogen
oxide (NO.sub.x).
[0007] Moreover, when burning with an extreme deficit of air, the
exhaust gas contains relatively large quantities of CO and HC,
while with excess air CO and HC can be almost completely oxidized,
up to a certain point. The NO.sub.x content reaches a maximum in
the range of slightly lean mixture compositions. However, the
specific fuel consumption for the gasoline engine is optimized in
that very range. Therefore, if gasoline engines are set to an
optimally low consumption, there are high NO.sub.x concentrations
as well as moderate CO and HC concentrations in the exhaust gas.
Heretofore, the fact that gasoline engines also generate particles
which, however, are generally smaller and occupy a lower overall
volume than in the case of diesel engines, had received scarcely
any consideration. Nevertheless, particles of that type may pollute
the environment.
SUMMARY OF THE INVENTION
[0008] It is accordingly an object of the invention to provide a
method and a configuration for cleaning an exhaust-gas flow flowing
in an exhaust system of a gasoline engine, which overcome the
hereinafore-mentioned disadvantages of the heretofore-known methods
and devices of this general type and which provide measures and
devices for improved cleaning of the exhaust-gas flow.
[0009] With the foregoing and other objects in view there is
provided, in accordance with the invention, a method for cleaning
an exhaust-gas flow, which comprises supplying an air/fuel mixture
to a gasoline engine, preferably by direct injection. An
exhaust-gas flow generated by the gasoline engine flows through an
exhaust system. The exhaust-gas flow in the exhaust system
successively flows through at least one honeycomb body having a
catalytically active coating, preferably a three-way coating, and a
particle filter having a coating storing at least one pollutant
component, in particular hydrocarbon, carbon monoxide and/or
nitrogen oxide, at least from time to time, so that it is
advantageously possible to achieve improved cleaning of the exhaust
gas.
[0010] With the objects of the invention in view, there is also
provided a configuration for cleaning an exhaust-gas flow,
comprising a gasoline engine receiving an air/fuel mixture,
preferably by direct injection, and generating the exhaust-gas
flow. An exhaust system conducts the exhaust-gas flow from the
gasoline engine in a flow direction. At least one honeycomb body
disposed in the exhaust system has a catalytically active coating,
preferably in a three-way catalytic converter. A particle filter
disposed in the exhaust system downstream of the at least one
honeycomb body in the flow direction has a coating storing at least
one pollutant component, in particular hydrocarbon, carbon monoxide
and/or nitrogen oxide, at least from time to time.
[0011] The structure and mode of operation of the invention have
been provided in this way because it has been found that, with a
configuration of a particle filter with a coating which, at least
from time to time, stores at least one of the pollutant components
downstream of at least one honeycomb body with a catalytically
active coating, it is surprisingly possible to achieve improved
cleaning of the exhaust gas flowing in the exhaust system. This
occurs both with regard to the pollutant components and with regard
to any soot particles which may occur.
[0012] Therefore, in accordance with another feature of the
invention, if a rich air/fuel mixture is being supplied to the
gasoline engine, for example during the cold-start phase, in order
to improve the exhaust-gas cleaning, the coating of the particle
filter stores residual HC and/or CO which has not been converted in
the honeycomb body.
[0013] In accordance with a further feature of the invention, if a
lean air/fuel mixture is being supplied to the gasoline engine, in
order to improve the exhaust-gas cleaning, the coating of the
particle filter stores residual NO.sub.x which has not been
converted in the honeycomb body.
[0014] As a result, it is advantageously possible to eliminate the
elevated concentrations of pollutants in the exhaust gas in each
case in a controlled and almost complete manner.
[0015] In accordance with an added feature of the invention, in
order to further minimize the nitrogen oxide (NO.sub.x) levels, a
reducing agent, preferably from a reducing-agent reservoir through
at least one reducing-agent line, is fed, for example continuously,
to the particle filter as a function of a residual NO.sub.x
concentration in the exhaust gas downstream of the honeycomb
body.
[0016] Alternatively, in accordance with an additional feature of
the invention, the reducing agent is fed to the particle filter at
intervals, in particular as a function of quantities of residual
NO.sub.x stored in the particle filter.
[0017] Supplying a reducing agent, for example ammonia, as a
function of a residual NO.sub.x concentration in the exhaust gas
downstream of the honeycomb body, almost completely prevents excess
metering of the reducing agent. As a result, approximately a
stoichiometric ratio between residual NO.sub.x and reducing agent
is achieved and the cleaning of NO.sub.x-containing exhaust gas
from the gasoline engine is advantageously improved. A further
advantage is that significantly smaller quantities of reducing
agents are required than if, for example, reducing agent is fed
into an exhaust gas before it flows through a honeycomb body with a
catalytically active coating.
[0018] In accordance with yet another feature of the invention,
there is provided a reducing-agent line preferably ending at the
particle filter. The particle filter preferably has an integrated
distribution device, to which the reducing-agent line is
connected.
[0019] In accordance with yet a further feature of the invention,
in order to further minimize the hydrocarbon (HC) and carbon
monoxide (CO) levels, an oxidizing agent, preferably oxygen
(O.sub.2), is fed to the particle filter as a function of a
residual HC--CO concentration in the exhaust gas downstream of the
honeycomb body.
[0020] Alternatively and/or in addition, in accordance with yet an
added feature of the invention, the coating of the particle filter
preferably, at least from time to time, stores oxygen
(O.sub.2).
[0021] Supplying an oxidizing agent as a function of residual
hydrocarbons (HC) and residual carbon monoxide (CO) almost
completely prevents excess metering. As a result, approximately a
stoichiometric ratio between residual HC and/or CO, on one hand,
and the oxidizing agent, on the other hand, is achieved and the
cleaning of HC-containing and/or CO-containing exhaust gas from the
gasoline engine is advantageously improved.
[0022] Modern gasoline engines usually have an electronic engine
control unit or similar control measures. In accordance with yet an
additional feature of the invention, in order to provide improved
control of the exhaust-gas cleaning, for example through the use of
an engine control unit, at least one measuring probe, which
measures at least one pollutant component that has not been
converted in the honeycomb body, is disposed between the honeycomb
body and the particle filter. In this case it is preferable for at
least one measuring probe to be provided in each case to measure
the residual pollutant components hydrocarbon (HC), carbon monoxide
(CO) and nitrogen oxide (NO.sub.x). In this way, it is
advantageously possible to detect residual pollutants which have
not been converted in the honeycomb body and to convert them in the
downstream particle filter, which has a coating with a
corresponding storage capacity, with the assistance of the reducing
or oxidizing agent supplied to the filter. The metering of that
agent is controlled, for example, through the use of the electronic
engine control unit.
[0023] In accordance with again another feature of the invention,
the particle filter is regenerated by burning the particles. This
process is triggered in particular by engine heat and/or by
exothermic reactions in the honeycomb body, preferably at intervals
which can be predetermined, for example through the use of the
engine control unit.
[0024] In accordance with a concomitant feature of the invention,
as an alternative to the separate configuration which has been
described heretofore, the honeycomb body may, at least in partial
regions, at the same time form the particle filter. It is therefore
advantageously possible to achieve a space-saving structure.
[0025] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0026] Although the invention is illustrated and described herein
as embodied in a method and a configuration for cleaning an
exhaust-gas flow flowing in an exhaust system of a gasoline engine,
it is nevertheless not intended to be limited to the details shown,
since various modifications and structural changes may be made
therein without departing from the spirit of the invention and
within the scope and range of equivalents of the claims.
[0027] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The FIGURE of the drawing is a diagrammatic and schematic
illustration of an exemplary embodiment of the invention, on the
basis of which further features, advantages and configurations
thereof the will be explained.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] Referring now in detail to the single FIGURE of the drawing,
there is seen a configuration for cleaning an exhaust-gas flow
which flows in an exhaust system or tract 2 of a gasoline or
spark-ignition engine 1 that is fed with an air/fuel mixture,
preferably through the use of direct injection. At least one
honeycomb body 3 with a catalytically active coating, preferably a
three-way catalytic converter, and a particle filter 4, are
disposed in succession in the exhaust system, as seen in a flow
direction S. The particle filter 4 has a coating which, at least
from time to time or temporarily, stores or accumulates at least
one pollutant component, in particular hydrocarbon (HC), carbon
monoxide (CO) and/or nitrogen oxide (NO.sub.x).
[0030] The coating of the particle filter 4 is preferably provided
in such a way that, at least partially, when a rich air/fuel
mixture is fed to the gasoline engine 1, residual HC and CO which
has not been converted in the honeycomb body 3 is stored. When a
lean air/fuel mixture is fed to the gasoline engine 1, residual
NO.sub.x which has not been converted in the honeycomb body 3 is
stored.
[0031] In each case at least one measuring probe 5, 6, 7 is
provided in order to measure the residual pollutant components
hydrocarbon (HC), carbon monoxide (CO) and nitrogen oxide
(NO.sub.x). These probes are disposed between the honeycomb body 3
and the particle filter 4 and are in communication, for example,
with a non-illustrated electronic engine control unit which
advantageously also includes programs for controlling exhaust-gas
cleaning. In particular, the electronic engine control unit can be
used to determine metered quantities of reducing and/or oxidizing
agents which may need to be added.
[0032] Therefore, an oxidizing agent is fed to the particle filter
4 or a reducing agent is fed to the particle filter 4 from a
reducing-agent reservoir 8 through a reducing-agent line 9 by a
pump 11, as a function of a measured residual HC--CO concentration
or a measured residual NO.sub.x concentration in the exhaust gas
downstream of the honeycomb body 3. Preferably, the particle filter
4 has an integrated distribution device 10 which is connected to
the reducing-agent line 9, in particular for supplying the reducing
agent.
[0033] The reducing agent which is preferably used is fluid ammonia
that is carried in the reducing-agent reservoir 8 and can be
supplied when required. Alternatively, the reducing agent may also
be carried as a stored precursor, for example urea, in the
reducing-agent reservoir 8 and can be produced on demand, in
particular by pyrolysis. The reducing agent is then fed as a fluid
to the particle filter 4, in particular through the distribution
device 10.
[0034] The structure of the particle filter 4 which promotes
deposition of soot particles is preferably a porous structure or a
channel structure. In the case of a channel structure, channels are
preferably at least partially disposed offset and/or transversely.
In order to regenerate the particle filter 4, i.e. to burn the soot
particles which have been deposited therein, the particle filter 4
is at least disposed sufficiently close enough behind the honeycomb
body 3 for the particles to burn, in particular as a result of
exothermic reactions in the honeycomb body 3, preferably at
predeterminable intervals.
[0035] Preferably, according to the invention, the honeycomb body 3
may also at the same time form the particle filter 4, at least in
partial regions.
[0036] It should also be pointed out that further components, as
well as the configuration of the honeycomb body 3 and the particle
filter 4 according to the invention, may be provided in the exhaust
system or line 2 of a gasoline engine 1. In particular, it is
possible for at least one water trap to be disposed upstream of the
honeycomb body 3. This water trap keeps the honeycomb body 3 and
its catalytic coating as dry as possible, in order to be able to
effect the desired oxidation or reduction processes in the
honeycomb body 3 even at exhaust-gas temperatures of only a few
hundred degrees centigrade. Water traps therefore contain materials
which are able to collect and store large quantities of water below
a defined temperature.
[0037] In addition, it is possible for an electrically heatable
catalytic converter to be disposed in the exhaust system 2 upstream
of the honeycomb body 3, in order to provide an exhaust-gas
temperature which is elevated at least from time to time. In that
way, the pollutants are catalytically converted even immediately
after the engine has been started. Finally, the honeycomb body 3
itself may be electrically heatable.
[0038] The present invention is particularly suitable for exhausts
of gasoline engines. In this case, the particle filter 4, in
addition to its task of trapping any soot particles, is also
advantageously responsible, during the cold-start phase, in
particular, for providing the supplementary oxidation of residual
hydrocarbons (HC) and carbon monoxide (CO). When the gasoline
engine 1 is running with load, the particle filter 4 is
responsible, in particular, for providing the supplementary
reduction of residual nitrogen oxides (NO.sub.x).
* * * * *