U.S. patent application number 14/556416 was filed with the patent office on 2015-03-26 for method for operating an exhaust gas system, method for operating a motor vehicle and motor vehicle.
The applicant listed for this patent is EMITEC GESELLSCHAFT FUER EMISSIONSTECHNOLOGIE MBH. Invention is credited to RICHARD DORENKAMP, THORSTEN DUESTERDIEK, GERHARD KAHMANN, CARSTEN KRUSE, THOMAS NAGEL.
Application Number | 20150086455 14/556416 |
Document ID | / |
Family ID | 48536817 |
Filed Date | 2015-03-26 |
United States Patent
Application |
20150086455 |
Kind Code |
A1 |
KRUSE; CARSTEN ; et
al. |
March 26, 2015 |
METHOD FOR OPERATING AN EXHAUST GAS SYSTEM, METHOD FOR OPERATING A
MOTOR VEHICLE AND MOTOR VEHICLE
Abstract
A method for operating an exhaust gas system of an internal
combustion engine having at least one heater and a catalytic
converter for converting hydrocarbons, includes operating the
heater in such a way that it is adapted to the aging state of the
catalytic converter. A method for operating a motor vehicle and a
motor vehicle are also provided.
Inventors: |
KRUSE; CARSTEN; (TROISDORF,
DE) ; NAGEL; THOMAS; (ENGELSKIRCHEN, DE) ;
DORENKAMP; RICHARD; (BERLIN, DE) ; KAHMANN;
GERHARD; (WOLFENBUETTEL, DE) ; DUESTERDIEK;
THORSTEN; (HANNOVER, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EMITEC GESELLSCHAFT FUER EMISSIONSTECHNOLOGIE MBH |
LOHMAR |
|
DE |
|
|
Family ID: |
48536817 |
Appl. No.: |
14/556416 |
Filed: |
December 1, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2013/060305 |
May 17, 2013 |
|
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14556416 |
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Current U.S.
Class: |
423/212 ;
422/173 |
Current CPC
Class: |
Y02A 50/20 20180101;
F01N 3/2006 20130101; F01N 3/2013 20130101; F01N 9/00 20130101;
Y02T 10/12 20130101; F01N 11/002 20130101; F01N 2550/02 20130101;
F01N 2900/1626 20130101; F01N 2240/16 20130101; Y02T 10/26
20130101; Y02T 10/47 20130101; F01N 2900/1602 20130101; Y02T 10/40
20130101; F01N 3/2026 20130101; Y02A 50/2322 20180101 |
Class at
Publication: |
423/212 ;
422/173 |
International
Class: |
F01N 3/20 20060101
F01N003/20; F01N 9/00 20060101 F01N009/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2012 |
DE |
102012104669.7 |
Claims
1. A method for operating an exhaust system of an internal
combustion engine, the method comprising the following steps:
providing at least one heater; providing a catalytic converter for
the conversion of hydrocarbons; and adapting operation of the at
least one heater as a function of an aging state of the catalytic
converter.
2. The method according to claim 1, which further comprises:
operating the at least one heater at least as a function of a
predefined threshold temperature of the catalytic converter; and
varying the predefined threshold temperature as a function of a
present age of the catalytic converter.
3. The method according to claim 2, which further comprises:
determining a hydrocarbon conversion temperature of the catalytic
converter; comparing the hydrocarbon conversion temperature with a
predefined threshold temperature; and operating the at least one
heater if the hydrocarbon conversion temperature is lower than the
predefined threshold temperature.
4. The method according to claim 1, which further comprises
providing the at least one heater with heating segments, and
adapting a heating power of the at least one heater by operating a
different number of the heating segments.
5. The method according to claim 1, which further comprises
adapting a heating power of the at least one heater by implementing
a different activation duration of the at least one heater.
6. A method for operating a motor vehicle, the method comprising
the following steps: providing the motor vehicle with an internal
combustion engine and an exhaust system having at least one heater
and a catalytic converter for the conversion of hydrocarbons;
adapting operation of the at least one heater as a function of an
aging state of the catalytic converter by determining a hydrocarbon
conversion temperature of the catalytic converter, comparing the
hydrocarbon conversion temperature with a predefined threshold
temperature and operating the at least one heater if the
hydrocarbon conversion temperature is lower than the predefined
threshold temperature; and adapting the operation of the at least
one heater not in a first operating phase of the motor vehicle but
only when the predefined threshold temperature reaches a particular
value.
7. A method for operating a motor vehicle, the method comprising
the following steps: providing the motor vehicle with an internal
combustion engine and an exhaust system having at least one heater
with heating segments and a catalytic converter for the conversion
of hydrocarbons; adapting operation of the at least one heater as a
function of an aging state of the catalytic converter by adapting a
heating power of the at least one heater by operating a different
number of the heating segments; and adapting the operation of the
at least one heater not in a first operating phase of a motor
vehicle but only when a predefined threshold temperature reaches a
particular value.
8. A method for operating a motor vehicle, the method comprising
the following steps: providing the motor vehicle with an internal
combustion engine and an exhaust system having at least one heater
and a catalytic converter for the conversion of hydrocarbons;
adapting operation of the at least one heater as a function of an
aging state of the catalytic converter by adapting a heating power
of the at least one heater by implementing a different activation
duration of the at least one heater; and adapting the operation of
the at least one heater not in a first operating phase of a motor
vehicle but only when a predefined threshold temperature reaches a
particular value.
9. A motor vehicle, comprising: an internal combustion engine; an
exhaust system connected to said internal combustion engine, said
exhaust system having at least one heater and a catalytic converter
disposed downstream of said at least one heater for converting
hydrocarbons; and a controller configured to adapt operation of
said at least one heater as a function of an aging state of said
catalytic converter.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation, under 35 U.S.C. .sctn.120, of
copending International Application No. PCT/EP2013/060305, filed
May 17, 2013, which designated the United States; this application
also claims the priority, under 35 U.S.C. .sctn.119, of German
Patent Application DE 10 2012 104 669.7, filed May 30, 2012; the
prior applications are herewith incorporated by reference in their
entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The invention relates to a method for operating an exhaust
system of an internal combustion engine, with the intention of
reducing the pollutant emissions of the internal combustion engine,
in particular, after a cold start. The invention also relates to a
method for operating a motor vehicle and a motor vehicle.
[0003] Exhaust-gas regulations for internal combustion engines have
become ever more stringent in recent years. That also applies, in
particular, to the cold-start behavior of internal combustion
engines, that is to say the time period immediately after
restarting of the internal combustion engine of a motor vehicle. In
that combustion process in particular, increased quantities of
hydrocarbons are discharged, unburned, through the exhaust line
into the environment. In the case of catalytic converters being
used in the exhaust line, the conversion of the unburned
hydrocarbons in the catalytic converter only takes place above a
particular temperature. The so-called light-off temperature is,
however, only reached when the catalytic converter has been
correspondingly heated by exhaust gas or by using other heating
devices.
[0004] Furthermore, systems and configurations are known with which
the cold-start behavior of catalytic converters is improved by
virtue of electrically heatable structures being placed in contact
with the catalytic converter and/or the exhaust gas in order to
accelerate the heating-up process up to the light-off temperature
and thus rapidly initiate effective catalytic conversion. Operation
with adaptation for that heating process is desirable, specifically
in relation to energy consumption, reactivity of the exhaust-gas
pollutants and/or ambient conditions.
SUMMARY OF THE INVENTION
[0005] It is accordingly an object of the invention to provide a
method for operating an exhaust gas system, a method for operating
a motor vehicle and a motor vehicle, which overcome the
hereinafore-mentioned disadvantages and at least partially solve
the highlighted problems of the heretofore-known methods and
vehicles of this general type. In particular, it is sought to
specify a method for operating an exhaust system, which ensures
that the lowest possible quantity of unburned hydrocarbons flows
through the exhaust line into the environment. Furthermore, it
should be possible for a system of this type to be set in a
particularly effective manner and operated efficiently, with regard
to pollutant values, for the entire service life or operating
duration in a motor vehicle.
[0006] With the foregoing and other objects in view there is
provided, in accordance with the invention, a method for operating
an exhaust system of an internal combustion engine in which the
exhaust system has at least one heating device and a catalytic
converter for the conversion of hydrocarbons. The method comprises
operating the heating device with adaptation as a function of the
aging state of the catalytic converter. In particular, this method
is suitable for the operation of an exhaust system of a diesel
combustion engine. In exhaust systems of diesel engines, use is
made of diesel oxidation catalytic converters (DOC) which, by
oxidation, convert particles, hydrocarbons and carbon monoxide
contained in the exhaust gas. In this case, in the new state of the
catalytic converter, the light-off temperatures are approximately
130 to 180.degree. C. These, however, shift toward higher
temperatures as the catalytic converter ages.
[0007] A catalytic converter for the conversion of hydrocarbons
refers, in particular, to a so-called oxidation catalytic converter
or diesel oxidation catalytic converter (DOC), that is to say a
substrate body (for example in the form of a ceramic and/or
metallic honeycomb body) with a coating with oxidizing action. The
coating with oxidizing action may include a carrier substance (for
example a so-called washcoat) that is doped with high-grade metals
and/or rare earth elements. In this case, platinum, palladium and
the like are used in particular.
[0008] The at least one heating device or heater includes, in
particular, an electrical, regulable heating element. In this case,
the heating device is preferably constructed in such a way that the
exhaust gas can flow through it (for example by being formed with a
multiplicity of throughflow openings or ducts) and it is suitable
for increasing the temperature of the exhaust gas as it flows
through. It is very particularly preferable for the heating device
to include a honeycomb body, in particular a honeycomb body
constructed with metallic sheets and/or foils.
[0009] The heating device is preferably disposed upstream of the
catalytic converter, in such a way that the exhaust gas flows
firstly through the heating device and then through the catalytic
converter. In particular, the heating device is at least partially
integrated in the catalytic converter and/or disposed directly
adjacent thereto. In this case, it is particularly preferable for
the heating device and the catalytic converter to form a structural
unit in which a corresponding catalytic coating for the conversion
of hydrocarbons is applied directly to the heatable heating device,
in such a way that as a result of the activation of the heating
device, the catalytic coating is directly heated to correspondingly
desired temperatures.
[0010] For the operation of the at least one heating device, the
latter is generally connected to a corresponding current
supply/voltage supply and to a controller. In this way, it is
possible for an activation or deactivation of the at least one
heating device to be triggered by using the controller at
predefined times and/or in the presence of predefined parameters.
The way in which this regulation or this operation is performed is
the subject matter of the present invention.
[0011] Accordingly, it is the intention for the heating device to
be operated with adaptation as a function of the aging state of the
catalytic converter. In other words, this also means that the
heating power that is provided is approximated, adjusted and/or set
up for the present aging state of the catalytic converter. This
means in particular that, during the operation of the heating
device, the present conversion capability of the catalytic
converter is determined and taken into consideration. This
encompasses, in particular, operating processes which give rise to
operation that varies over the service life of the exhaust system
(exclusively) as a function of the aging state of the catalytic
converter. In this case, the aging state of the catalytic converter
may be characterized, in particular, by the following factors:
[0012] Thermal Aging: [0013] In this case, the thermal loading of
the catalytic converter causes a reduction in size of the
catalytically active surface over the service life, in particular
as a result of sintering processes at temperatures above
800.degree. C. and/or melting. [0014] Chemical Contamination:
[0015] Chemical reactions with foreign substances (fuel, oil
additives, etc.) can likewise destroy the catalytically active
coating. [0016] Mechanical Contamination: [0017] Over the service
life of the catalytic converter, the catalytically active coating
may also become covered to an increasing extent, for example by
lead, sulfur, phosphorus, manganese, etc., or by fuel and/or
oil.
[0018] The aging state of the catalytic converter may be
determined, in particular, on the basis of the distance traveled
with the catalytic converter or by the motor vehicle. Furthermore,
the aging state may be determined on the basis of the time period
since the catalytic converter was manufactured and/or since it was
installed in an exhaust system. Further parameters that may play a
role in the determination of the aging state are: type of catalytic
loading, coating type, coating thickness, number of regeneration
cycles during operation, maximum temperatures reached, averaged
temperature (or temperature histogram), amount of exhaust gas that
has flowed through, exhaust-gas type, fuel type, possible
combination of different fuel types (additives of bioethanol etc.),
oil consumption, etc. A (differently weighted) combination of the
parameters for the determination and/or weighting of the aging
state is also possible. Furthermore, it is also possible for the
conversion performance of the catalytic converter to be detected by
a sensor device, for example using the lambda sensors, which are
disposed in and/or downstream of the catalytic converter and which
determine the storage capacity of the catalytic converter for
oxygen. It is also possible to determine the conversion performance
of the catalytic converter from the measurement values.
[0019] In accordance with another advantageous mode of the method
of the invention, the heating device is operated at least as a
function of a predefined threshold temperature of the catalytic
converter, wherein the predefined threshold temperature varies as a
function of a present age of the catalytic converter.
[0020] The light-off temperature is lower in the case of a new
catalytic converter than in the case of an already aged catalytic
converter. This may have the effect that the light-off temperature
of a new catalytic converter lies in a temperature range so low
that the catalytic converter is already ready for use when only an
insignificant quantity of unburned hydrocarbons has passed through
the catalytic converter. In this case, for example, in the case of
this configuration, heating of the exhaust system is not
imperatively necessary. Due to the progressive aging of the
catalytic converter, however, the light-off temperature and/or the
conversion effectiveness of the catalytic converter is shifted
toward higher temperature values, in such a way that over the
course of the numerous operating hours of the system and thus over
the service life of the system, an inadmissible quantity of
unburned hydrocarbons passes through the catalytic converter before
the catalytic converter disposed downstream even reaches the
light-off temperature. It is then the intention, in accordance with
this present situation, for a supply of heating power to be
implemented.
[0021] For this reason, the operation of the heating device with
adaptation to a predefined threshold temperature of the catalytic
converter is proposed herein. The threshold temperature in this
case is not constant over the service life or operating duration of
the exhaust system, but is variable. The threshold temperature is
affected by the present age or aging state of the catalytic
converter. For the (preferred) situation in which the threshold
temperature (approximately) represents the light-off temperature of
the catalytic converter, the predefined threshold temperature of
the catalytic converter consequently generally increases in this
time period. This may take place continuously and/or in stepped
fashion. If appropriate, the threshold temperature may be lowered
again after a cleaning or decontamination of the catalytic
converter.
[0022] In this regard, it is also advantageous for the
age-dependent threshold temperature at which the catalytic
converter reaches the light-off temperature to be known at all
times during the operation of the internal combustion engine. The
threshold temperature correspondingly varies as a function of the
present age or aging state of the catalytic converter.
Consequently, with progressive aging of the catalytic converter,
the heating device is activated correspondingly earlier, or for
longer, in order for the catalytic converter to be brought,
preferably (precisely) then, to a temperature above or equal to the
threshold temperature. In this case, it must be taken into
consideration, in particular, that not the entire surface area of
the catalytic converter disposed downstream has to be heated to the
threshold temperature by the electric heating device; rather, it is
in particular sufficient for only a small sub-region to be heated
in such a way that the threshold temperature is reached locally. As
a result of the then locally occurring catalytic conversion of the
unburned hydrocarbons, sufficient energy is released from the
exothermic reaction of the combustion of the hydrocarbons in such a
way that very rapid heating of the entire catalytic converter
occurs, and correspondingly, a large quantity of (possibly also
temporarily stored) hydrocarbons can be converted.
[0023] In accordance with a further preferred mode of the
invention, the method has at least the following steps: [0024]
determining a conversion temperature of the catalytic converter,
[0025] comparing the conversion temperature with a predefined
threshold temperature, and [0026] operating the heating device if
the conversion temperature is lower than the predefined threshold
temperature.
[0027] The conversion temperature refers, in particular, to the
temperature of the catalytic converter at the time at which a
certain (still admissible) quantity of unburned hydrocarbons has
already flowed through the catalytic converter without being
converted by the (active) catalytic converter. In particular, the
determination of the conversion temperature of the catalytic
converter is performed only when it is to be assumed, due to the
aging state of the catalytic converter, that the threshold
temperature is already higher than the conversion temperature.
Cyclic and/or continuous interrogation of the conversion
temperature of the catalytic converter is also possible. For
reliable conversion of the unburned hydrocarbons, the conversion
temperature preferably corresponds to the temperature that the
catalytic converter must be at at the time when a number of
unburned hydrocarbons reaching the catalytic converter would exceed
the admissible quantity of unburned hydrocarbons that may be
discharged to the environment. The admissible quantity is, in
particular, predefined by emissions regulations. In particular, the
conversion temperature does not need to be measured at the
catalytic converter itself and/or correspond to temperatures
measured at other locations in the exhaust line. Rather, the
conversion temperature may also be determined mathematically on the
basis of the exhaust-gas temperature. Accordingly, the heating
device for heating the catalytic converter is, in particular,
operated only when the conversion temperature falls below the
present threshold temperature, that is to say for example when the
light-off temperature of the catalytic converter has not yet been
reached.
[0028] In accordance with an added mode of the method of the
invention, an adaptation of a heating power of the heating device
is realized by operating a different number of heating segments or
by implementing a different activation duration of the heating
device. The measures may self-evidently be implemented in
combination with one another. By operating individual heating
segments and/or by heating sub-regions of the catalytic converter
(separately), it is possible to realize rapid local heating of the
catalytic converter, with little electrical power being used. As a
result of the light-off temperature being reached locally, the
conversion of the unburned hydrocarbons takes place there first. As
a result of the exothermic reaction, however, adjacent regions of
the catalytic converter heat up so rapidly that further electrical
heating can be dispensed with.
[0029] With the objects of the invention in view, there is also
provided a method for operating a motor vehicle, which comprises
implementing the method not in a first operating phase of the motor
vehicle but only when the predefined threshold temperature reaches
a particular value. This means in particular that, until a
particular threshold temperature is reached, or until a certain
aging state of the catalytic converter is reached, it can be
assumed that heating of the catalytic converter is not required,
because the catalytic converter generally reaches the light-off
temperature before an inadmissible quantity of unburned
hydrocarbons has passed through the catalytic converter.
Accordingly, an unnecessary determination of the conversion
temperature of the catalytic converter is eliminated, and thus the
controller of the motor vehicle is not burdened by such unnecessary
interrogations. In this case, the first operating phase may, in
particular, be characterized by at least one of the following
parameters: [0030] kilometerage or mileage of the motor vehicle, in
particular 20,000 km; [0031] operating duration of the motor
vehicle, in particular 100 hours.
[0032] With the objects of the invention in view, there is
concomitantly provided a motor vehicle, comprising an internal
combustion engine, an exhaust system and a controller, wherein the
exhaust system has at least one heating device and a catalytic
converter disposed downstream of the heating device. In this case,
the controller is constructed or programmed for carrying out the
method according to the invention.
[0033] Other features which are considered as characteristic for
the invention are set forth in the appended claims, noting that the
features specified individually in the claims may be combined with
one another in any desired technologically expedient manner and
form further embodiments of the invention.
[0034] Although the invention is illustrated and described herein
as embodied in a method for operating an exhaust gas system, a
method for operating a motor vehicle and a motor vehicle, 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.
[0035] 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.
The description, in particular in conjunction with the figures,
explains the invention further and specifies supplementary
exemplary embodiments of the invention.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0036] FIG. 1 is a block diagram of a motor vehicle having an
exhaust system;
[0037] FIG. 2 is a diagrammatic, cross-sectional view of a heating
device;
[0038] FIG. 3 is a diagram showing a possible variation of a
threshold temperature of a catalytic converter as a function of its
age; and
[0039] FIG. 4 is a diagram showing an operating state of an
internal combustion engine.
DETAILED DESCRIPTION OF THE INVENTION
[0040] Referring now in detail to the figures of the drawing for
explaining the invention and the technical field in more detail by
showing particularly preferred structural variants to which the
invention is not restricted and in which the same reference
numerals are used to denote identical objects, and first,
particularly, to FIG. 1 thereof, there are seen components that are
preferably provided for the method according to the invention. In
this case, a motor vehicle 6 has an internal combustion engine 5
with an exhaust system 1, in which a heating device or heater 4 and
a catalytic converter 3 are provided in the exhaust system 1. The
catalytic converter 3 is assigned sensors 13 which are suitable,
for example, for determining the respectively prevailing
temperature of the catalytic converter 3. The sensors 13 are
connected by control lines 14 to a controller 7, so that it is
possible firstly for the determined sensor values to be transmitted
and also secondly for electric heating of the heating device 4 to
be realized over the control lines 14. Furthermore, the controller
7 is connected to the internal combustion engine 5 through control
lines 14, in such a way that the controller 7 can receive
information regarding operating states of the internal combustion
engine 5. The controller may additionally be formed with at least
one memory element or have access to such a memory element in
which, for example, characteristic maps, empirical values,
parameter threshold values and the like can be accessed and/or
adapted.
[0041] FIG. 2 shows, in a cross section, a structural variant of a
heating device 4 in the form of a honeycomb body wherein, in this
case, various heating segments 10 are additionally disposed
annularly around one another. The heating device 4 has smooth
metallic foils 17 and structured metallic foils 16 which are
stacked and/or wound and/or coiled on one another to form the
heating device 4. For this purpose, the structured foils 16 and/or
smooth foils 17 are connected to one or more non-illustrated
electrodes, in such a way that the heating device 4 can be
operated, for example, as a resistance heater.
[0042] FIG. 3 shows a potential profile or course of a threshold
temperature 8 over the operating duration or service life of the
catalytic converter in the exhaust system as a function of the age
11 of the catalytic converter. The temperature 9 is plotted on the
vertical axis, and the age 11 of the catalytic converter is plotted
on the horizontal axis. FIG. 3 shows that, with progressive aging
11 of the catalytic converter, the threshold temperature 8 is also
shifted toward higher temperature values. Accordingly, at a
particular time 12, an aging state of the catalytic converter is
reached at which a particular threshold temperature 8 can be
determined.
[0043] FIG. 4 shows an operating state of the internal combustion
engine 5, wherein the time 15 is plotted on the horizontal axis and
the temperature 9 is plotted on the vertical axis. In this case,
the temperature 9 is, in particular, the respectively present
temperature detected by using a temperature sensor 13. At a
particular time 12, the determined temperature 9 of the catalytic
converter corresponds to the conversion temperature 2 at which the
catalytic conversion of hydrocarbons by the catalytic converter
must take place because a quantity of unburned hydrocarbons that is
still just admissible has already passed through the catalytic
converter. At this time 12, corresponding to FIG. 4, a threshold
temperature 8 prevails which lies above the presently determined
temperature 9 or the conversion temperature 2. This means that
heating by using the heating device is necessary in order to heat
the catalytic converter to a corresponding threshold temperature 8
in such a way that the unburned hydrocarbons can be converted in
the catalytic converter.
[0044] The present invention, with all of its variants, solves the
problems highlighted with regard to the prior art. In particular, a
method for operating an exhaust system is specified, which ensures
that the lowest possible quantity of unburned hydrocarbons flows
through the exhaust line into the environment. Furthermore, the
proposed system can be set in a particularly effective manner and
operated efficiently, with regard to pollutant values, for the
entire service life or operating duration in a motor vehicle. In
particular, this yields cost advantages, and permits practically
complete conversion of the hydrocarbons over the entire operating
duration of the exhaust system, with little expenditure of
energy.
* * * * *