U.S. patent application number 12/301578 was filed with the patent office on 2009-10-01 for method for the operation of an emission control system located in an exhaust gas zone of an internal combustion engine.
This patent application is currently assigned to ROBERT BOSCH GMBH. Invention is credited to Horst Harndorf.
Application Number | 20090241519 12/301578 |
Document ID | / |
Family ID | 38330778 |
Filed Date | 2009-10-01 |
United States Patent
Application |
20090241519 |
Kind Code |
A1 |
Harndorf; Horst |
October 1, 2009 |
METHOD FOR THE OPERATION OF AN EMISSION CONTROL SYSTEM LOCATED IN
AN EXHAUST GAS ZONE OF AN INTERNAL COMBUSTION ENGINE
Abstract
Disclosed is a method for operating an emission control system
that is located in an exhaust gas zone of an internal combustion
engine and comprises a catalytic layer causing an oxidation
reaction as well as a particle filter in which at least one exhaust
gas component is deposited when the internal combustion engine is
operated and which is regenerated from said exhaust gas component
in predefined operating phases. According to the inventive method,
the air throughput through at least one combustion chamber of the
internal combustion engine is reduced in the predefined operating
phases in which the particle filter is regenerated.
Inventors: |
Harndorf; Horst;
(Schauenburg, DE) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Assignee: |
ROBERT BOSCH GMBH
Stuttgart
DE
|
Family ID: |
38330778 |
Appl. No.: |
12/301578 |
Filed: |
June 4, 2007 |
PCT Filed: |
June 4, 2007 |
PCT NO: |
PCT/EP2007/055440 |
371 Date: |
November 19, 2008 |
Current U.S.
Class: |
60/287 ; 60/295;
60/297; 60/299 |
Current CPC
Class: |
Y02T 10/12 20130101;
F02D 41/0002 20130101; Y02T 10/40 20130101; F01N 3/023 20130101;
F02D 41/405 20130101; F02D 41/04 20130101; F02D 2041/001 20130101;
Y02T 10/42 20130101; F02D 2041/0022 20130101; F02D 41/029 20130101;
Y02T 10/142 20130101 |
Class at
Publication: |
60/287 ; 60/295;
60/297; 60/299 |
International
Class: |
F01N 9/00 20060101
F01N009/00; F01N 3/023 20060101 F01N003/023; F01N 3/035 20060101
F01N003/035; F01N 3/10 20060101 F01N003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2006 |
DE |
10 2006 028 436.4 |
Claims
1-10. (canceled)
11. A method of operating an emission control system located in an
exhaust gas zone of an internal combustion engine, the emission
control system comprising a catalytic layer causing an oxidation
reaction and a particle filter, the method comprising: depositing
at least one exhaust gas component in the particle filter when the
internal combustion engine is operated; and regenerating the
particle filter from said exhaust gas component in a predefined
operating phase, wherein an air throughput is reduced through at
least one combustion chamber of the internal combustion chamber in
the predefined operating phase.
12. A method according to claim 11, further comprising continuously
reducing the air throughput in the predefined operating phase.
13. A method according to claim 12, wherein the predefined
operating phase is a partial load region of the internal combustion
engine.
14. A method according to claim 11, further comprising reducing the
air throughput through the at least the one combustion chamber via
an advanced closing of at least one intake valve of the at least
one combustion chamber.
15. A method according to claims 14, further comprising reducing
the air throughput through the at least the one combustion chamber
via an advanced closing of at least one intake valve using residual
gas compression.
16. A method according to claim 11, further comprising reducing the
air throughput through the at least one combustion chamber via
actuation of a throttle valve located in an engine air intake.
17. A method according to claim 11, further comprising; positioning
an oxidation catalytic converter that functions as the catalytic
layer after the at least one combustion chamber; and subsequently
attaching a diesel particle filter that functions as the particle
filter to said oxidation catalytic converter.
18. A method according to claim 11, further comprising positioning
a layered particle filter, particularly a catalytic soot filter,
that functions as the catalytic layer after the at least one
combustion chamber.
19. A computer program to implement, if the computer program is
executed on an arithmetic unit, a method of operating an emission
control system located in an exhaust gas zone of an internal
combustion engine, the emission control system comprising a
catalytic layer causing an oxidation reaction and a particle
filter, the method comprising: depositing at least one exhaust gas
component in the particle filter when the internal combustion
engine is operated; and regenerating the particle filter from said
exhaust gas component in a predefined operating phase, wherein an
air throughput is reduced through at least one combustion chamber
of the internal combustion chamber in the predefined operating
phase.
20. A computer program product with a program code stored on a
machine-readable carrier to implement, if executed on a computer or
in a control unit, a method of operating an emission control system
located in an exhaust gas zone of an internal combustion engine,
the emission control system comprising a catalytic layer causing an
oxidation reaction and a particle filter, the method comprising:
depositing at least one exhaust gas component in the particle
filter when the internal combustion engine is operated; and
regenerating the particle filter from said exhaust gas component in
a predefined operating phase, wherein an air throughput is reduced
through at least one combustion chamber of the internal combustion
chamber in the predefined operating phase.
Description
TECHNICAL FIELD
[0001] The invention relates to a method for operating an emission
control system, which is located in the exhaust gas zone of an
internal combustion engine and comprises a catalytic layer causing
an oxidation reaction and a particle filter, according to the class
of the independent claim 1.
[0002] The subject matter of the invention at hand is also a
computer program according to claim 9 as well as a computer program
product according to claim 10.
BACKGROUND
[0003] A method for the regeneration of a particle filter located
in an exhaust gas zone of an internal combustion engine became
known from the German patent DE 199 06 287 A1. Said method changes
between different operating states as a function of the last
prevailing operating state and as a function of the condition of
the particle filter. According to the innovative method, the
particle filter is regenerated from the deposited particles in one
operating state. This regeneration takes place at an increased
temperature, whereat the particles, mainly sooty particles and ash
particles, are burned by means of an oxidation reaction.
[0004] The German patent DE 103 23 561 A1 describes a method for
operating a structural member, especially a particle filter, which
is located in an exhaust gas zone of an internal combustion engine,
and an apparatus for the implementation of this method, wherein the
regeneration phase is started as a function of the operating state
of the internal combustion engine and/or as a function of the
operating state of the structural member, particularly of the
degree of depletion of the particle filter. The regeneration phase
is thereby arbitrarily started by means of an extreme start signal.
The regenerated state of the structural member can in this way be
produced by a service technician, for example, when the vehicle,
wherein the internal combustion engine is disposed, is being
serviced in a garage. In so doing, a diagnosis of the internal
combustion engine and its components can be performed.
[0005] The regeneration of the diesel particle filter thereby takes
place intermittently, for example, as a function of the exhaust gas
backpressure. The exhaust gas and filter temperature necessary for
an oxidation process for regeneration of the filter presume a
sufficient rate of oxidation as a rule above approximately
600.degree. C. Because said temperature can only be expected in the
upper average pressure/rotational speed characteristic diagram of
the internal combustion engine, an exhaust gas temperature boost,
which is required for the regeneration of the filter, is induced by
means of an afterinjection of diesel fuel into the combustion
chamber or into the exhaust gas tract, while utilizing the reaction
heat released in the process. These interventions are coupled with
a disadvantageous increase in fuel consumption.
[0006] Besides by means of an afterinjection, the regeneration of
diesel particle filters can also take place by means of auxiliary
burners in the complete exhaust gas stream or a secondary exhaust
gas stream, engine management interventions which increase
temperature, supplementary electrical energy or fuel additives.
Regeneration by means of fuel additives is problematic with respect
to the long term stability of the diesel particle filter. This
results in this case from an input of metal ash, which can lead to
a reduction in the service life of the diesel particle filter.
SUMMARY
[0007] The method according to the invention with the
characteristics of the independent claim 1 in contrast allows for a
regeneration of the filter without a significant increased
consumption by the internal combustion engine. By means of reducing
the air throughput through at least one combustion chamber of the
internal combustion engine, a significant increase in the heating
value of the mixture and thereby an increase in the exhaust gas
temperature, which is required for the regeneration of the filter,
is in fact achieved at practically the same fuel consumption.
[0008] The reduction of the air throughput through at least one
combustion chamber of the internal combustion engine preferably
takes place continuously during the entire predefined operating
phase. A continuous regeneration of the filter is possible to a
certain extent within certain limits by means of this continuous
reduction of the air throughput. Even if no complete regeneration
of the filter can take place in the process, the intervals for an
intermittent regeneration of the filter are lengthened, for
example, through additional measures in the form of afterinjections
of diesel fuel into the combustion chamber or into the exhaust gas
tract or, for example, by means of fuel additives.
[0009] The predefined operating phase, wherein the regeneration of
the filter takes place, is preferably a partial load range of the
internal combustion engine.
[0010] The reduction of the air throughput through at least the one
combustion chamber can fundamentally be implemented in different
ways. Provision is made in an advantageous embodiment for the
reduction of the air throughput through at least the one combustion
chamber of the internal combustion engine to be implemented by
advancing the closing of at least one intake valve of at least one
combustion chamber analogous to the Miller cycle. What is
understood in the invention at hand by the closing of at least one
intake valve in internal combustion engines with in each case one
intake valve per combustion chamber is the advanced closing of this
intake valve. Said advanced closing can take place in one or a
plurality of combustion chambers, depending on the number of
cylinders and the power stroke of these cylinders of the internal
combustion engine. In internal combustion engines with, for
example, two intake valves per combustion chamber, the advanced
closing of both intake valves in one or a plurality of combustion
chambers analogous to the Miller cycle is understood.
[0011] Provision can also alternatively or additionally be made to
the advanced closing of the one or several intake valves for an
advanced closing of the one or several exhaust valves, whereby the
residual gas content is increased and the air throughput decreases
through the combustion chamber of the internal combustion engine as
well. Also in this instance in an internal combustion engine, which
has one exhaust valve per combustion chamber, the closing of this
exhaust valve is in turn advanced. In internal combustion engines,
which have more than one exhaust valve per combustion chamber,
particularly two exhaust valves per combustion chamber, the closing
of both of these exhaust valves is advanced in at least one
combustion chamber.
[0012] These embodiments assume a variable valve drive. It is the
basic idea behind these configurations that the so-called Miller
cycle, which up until now is only employed in large diesel engines,
for example ship engines, is employed in a diesel internal
combustion engine with direct fuel injection of a motor vehicle in
order then to bring about a significant increase in the heating
value of the mixture and thereby in the exhaust gas temperature in
partial load areas with as a matter of principle high excess air.
The advantage of this method is first of all that only small
increases in consumption arise due to advancing the closing of the
one or several intake valves and/or the one or several exhaust
valves. Furthermore, as a result of this method, an impairment of
the untreated exhaust gas emissions is no longer a factor.
[0013] Provision is made according to another configuration of the
method for a reduction in the air throughput to be brought about by
at least one throttle valve located in the engine air intake.
[0014] In so doing, the emission control system can be configured
in different ways. Provision is made in one configuration for the
catalytic layer causing the oxidation reaction to be configured as
an oxidation catalytic converter, to which a diesel particle filter
is subsequently attached.
[0015] In another embodiment, provision is made for a diesel
particle filter with an integrated catalytic layering, a so-called
catalytic soot filter.
[0016] The combination of a catalytic layer, which causes an
oxidation reaction, and a particle filter is absolutely necessary
for the method described above. This is the case because an
oxidation of the nitrogen oxide into nitrogen dioxide, which is
required for the continuous regeneration of the particle filter,
particularly the diesel particle filter, first takes place by means
of the catalytic layer. Such a continuous regeneration can only
take place if the ratio of nitrogen dioxide NO2 to carbon C is
proportionally larger than or equal to 8.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Examples of embodiment of the invention are depicted in the
drawings and are described in detail in the description below.
[0018] FIG. 1 is a technical environment wherein a method according
to the invention is operating; and
[0019] FIG. 2 schematically shows the process of the method
according to the invention using a flow diagram.
DETAILED DESCRIPTION
[0020] FIG. 1 schematically and exemplary shows a combustion
chamber 100 of an internal combustion engine, wherein a piston 105
travels upwards and downwards in an inherently known manner. The
combustion chamber 100 has an inlet port 110 as well as an outlet
port 120. The outlet port 120 opens out into an exhaust gas tract
122, wherein an emission control system comprising an oxidation
catalytic converter 130 as well as a particle filter 140 is
disposed. Provision can also be made for an inherently known,
so-called CSF (catalytic soot filter) instead of the arrangement of
an oxidation catalytic converter 130, which causes an oxidation
reaction, and a particle filter 140. Said CSF is therefore a
layered particle filter, whose catalytic layer brings about an
oxidation reaction, particularly an oxidation of nitrogen oxide NO
to nitrogen dioxide NO2.
[0021] The inlet port 110 can be connected to the combustion
chamber 100 by an intake valve 112. The outlet port 120 can be
connected to the combustion chamber by an exhaust valve 122. The
intake valve 112 as well as the exhaust valve 122 can be actuated
by a variable valve drive in order to change the intake and exhaust
control times within predefined limits. The intake valve 112 and
the exhaust valve 122 can, for example, be actuated by an
electrohydraulic valve control or something similar. The actuation
can thereby take place via an engine control unit 150.
[0022] The depletion of the particle filter 140 is acquired in an
inherently known manner, for example, by a differential pressure
sensor 145, which acquires the differential pressure of the exhaust
gas in the exhaust gas direction of flow before and behind the
filter 140. The output signal of the differential pressure sensor
145 is likewise provided to the control unit 150. Different
operating states of the internal combustion engine are acquired by
suitable sensors, for example by a sensor for acquiring the engine
rotational speed, a sensor for acquiring the combustion temperature
and the like. A sensor 160, which is representative of this
plurality of sensors, is shown in FIG. 1, whose output signal is
provided to the control unit 150.
[0023] A throttle valve 170, whose position is determined in the
control unit 150 and which can be electrically activated, can
furthermore be disposed in the inlet port 110.
[0024] The method for the regeneration of the particle filter 140
is described below in connection with FIG. 2.
[0025] It is the basic idea of the invention to reduce the air
throughput through the combustion chamber 100 of the internal
combustion engine in predefined operating phases, in fact
especially in the partial load range of the internal combustion
engine. The consideration underlying the basic idea with respect to
said partial load range is that a significant increase in the
heating value of the mixture and thereby the exhaust gas
temperature can be brought about by a reduction in the air
throughput through the combustion chamber 100 in partial load
ranges. The exhaust gas temperature can thereby be increased in
such a manner that a passive, continuous regeneration of the
particle filter 140 is possible. For this purpose, a test is
initially made in step 210 to determine whether the operating phase
for the regeneration, i.e. the partial load range, is present. If
this is the case, a test is made in step 220 to determine whether
the boundary conditions for a regeneration prevail, which are
subsequently described in more detail, particularly a desired ratio
of nitrogen dioxide NO2 to carbon C. If this is the case, the air
throughput through the combustion chamber is reduced in step 230.
This can, for example, thereby result, in that the closing of the
intake valve 112 is advanced, i.e. a displacement of the closing
time of the intake valve 112 toward an advanced engine crankshaft
angle.
[0026] The displacement of the closing time to an advanced position
results analogous to the Miller cycle. However, in contrast to the
Miller cycle, the reduced air throughput resulting from the
advanced closing of the intake valve is not compensated for in this
case by a higher pressure in the inlet port 110, which is produced
by means of an exhaust gas turbocharger, a compressor or the like.
According to the invention, less ballast air is supposed to be
allowed into the combustion chamber precisely as a result of the
advanced closing of the intake valve 112 in the partial load range
of concern here, wherein already a high air excess exists. This
action is done in order to bring about such a significant increase
in the heating value of the mixture and thereby in the exhaust gas
temperature required for the regeneration.
[0027] The reduction in the air throughput through the combustion
chamber 100 can strictly as a matter of principle also be achieved
by an advanced closing of the exhaust valve 122 analogous to the
Miller cycle using residual gas compression.
[0028] A reduction of the air throughput through the combustion
chamber 100 can also furthermore alternatively or additionally take
place by means of a corresponding activation of the throttle valve
170.
[0029] The advantage of the method previously described lies as a
result of the thermodynamic boundary conditions therein, in that
only slight increases in consumption arise when the mass of fresh
mixture is curbed, and said slight increases in consumption are
accompanied by a continuous, passive regeneration of the particle
filter 140 resulting from the increase in exhaust gas temperature.
Moreover, the quality of the untreated exhaust gas emissions in the
exhaust gas tract 120 improves. For this reason, the possibility
exists to achieve a complete regeneration of the particle filter
140 in the low temperature range.
[0030] This regeneration advantageously takes place thereby
continuously during the entire operating phase, i.e. in the entire
partial load range. In so doing, the continuous regeneration takes
place in the manner described below. The nitrogen monoxide NO,
which is present in the exhaust gas, is oxidized to nitrogen
dioxide NO2 in the oxidation catalytic converter because the
oxidation of unburned carbon (soot), i.e. carbon C to carbon
monoxide CO or to carbon dioxide CO2, now takes place with nitrogen
dioxide NO2 at significantly lower temperatures, which can be
implemented in the previously described manner, than with molecular
oxygen O2. It is therefore necessary for the oxidation catalytic
converter 130 to constantly produce so much nitrogen dioxide NO2,
that the unburned carbon, which simultaneously accumulates, is
oxidized and that preferably an undesirable accumulation of
unburned carbon, which leads to pressure losses in the particle
filter 140, does not occur. The oxidation of unburned carbon is
thereby significantly determined by the ratio of carbon (soot) to
nitrogen dioxide NO2. A complete regeneration is only possible at a
ratio of nitrogen dioxide NO2 to carbon C, which is greater than
8.
[0031] The method previously described for the continuous
regeneration of the particle filter 140 located in the exhaust gas
zone requires only a slight increase in consumption during the
regeneration phase because high pressure losses at the particle
filter 140 cannot arise, respectively the time intervals up to a
forced regeneration, which, for example, is performed with
afterinjections, significantly lengthen and the increase in fuel
consumption is thereby significantly reduced. It is also very
advantageous, in that an improved homogenization of the mixture can
be realized as a result of the advanced closing of the intake
valve, while at the same time the charge temperature is reduced
prior to the initiation of combustion. In this way, the sooty
emissions in the untreated exhaust gas are significantly
reduced.
[0032] Furthermore, an improvement in the cold start emissions,
particularly in the emission of hydrocarbons and carbon monoxide,
is feasible. These are significantly reduced by the increase in the
heating value of the mixture and thereby the average gas
temperature.
[0033] It must be mentioned that the method previously described
can be used parallel to the methods for the regeneration of the
particle filter, which are known from the technical field. In said
methods, a forced regeneration takes place in certain operating
phases. In the case of this parallel application, the additional
time-lag considerably increases between the two regeneration
intervals, in which a forced regeneration, for example, by means of
afterinjections is performed.
* * * * *