U.S. patent application number 15/737527 was filed with the patent office on 2018-07-05 for method for operating an exhaust gas aftertreatment system, exhaust gas aftertreatment system, and internal combustion engine with an exhaust gas aftertreatment system.
The applicant listed for this patent is MTU FRIEDRICHSHAFEN GMBH. Invention is credited to Daniel CHATTERJEE, Klaus RUSCH, Guido SCHAFFNER, Klaus WEHLER.
Application Number | 20180187588 15/737527 |
Document ID | / |
Family ID | 56561330 |
Filed Date | 2018-07-05 |
United States Patent
Application |
20180187588 |
Kind Code |
A1 |
CHATTERJEE; Daniel ; et
al. |
July 5, 2018 |
METHOD FOR OPERATING AN EXHAUST GAS AFTERTREATMENT SYSTEM, EXHAUST
GAS AFTERTREATMENT SYSTEM, AND INTERNAL COMBUSTION ENGINE WITH AN
EXHAUST GAS AFTERTREATMENT SYSTEM
Abstract
A method for operating an exhaust gas aftertreatment system,
having the following steps: determining a permissible energy input
into at least one exhaust gas aftertreatment element of the exhaust
gas aftertreatment system; ascertaining a current energy input into
the at least one exhaust gas aftertreatment element by ascertaining
at least one energy input variable which characterizes the current
energy input; and actuating an adjusting device which varies a
distribution of an exhaust gas mass flow to the at least one
exhaust gas aftertreatment element and a bypass path that runs
about the at least one exhaust gas aftertreatment element depending
on the permissible energy input and the current energy input.
Inventors: |
CHATTERJEE; Daniel; (Lindau,
DE) ; RUSCH; Klaus; (Achberg, DE) ; SCHAFFNER;
Guido; (Horgenzell, DE) ; WEHLER; Klaus;
(Friedrichshafen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MTU FRIEDRICHSHAFEN GMBH |
Friedrichshafen |
|
DE |
|
|
Family ID: |
56561330 |
Appl. No.: |
15/737527 |
Filed: |
June 6, 2016 |
PCT Filed: |
June 6, 2016 |
PCT NO: |
PCT/EP2016/000934 |
371 Date: |
December 18, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N 2560/07 20130101;
F01N 2900/0418 20130101; F01N 2560/08 20130101; F01N 9/00 20130101;
F01N 2560/06 20130101; F01N 2410/02 20130101; Y02T 10/12 20130101;
F01N 3/18 20130101; F01N 3/2066 20130101; F01N 2550/06 20130101;
Y02T 10/40 20130101; F01N 3/2053 20130101; F01N 3/031 20130101;
Y02T 10/24 20130101; Y02T 10/47 20130101; F01N 11/00 20130101; F01N
2900/1404 20130101 |
International
Class: |
F01N 9/00 20060101
F01N009/00; F01N 3/18 20060101 F01N003/18; F01N 3/031 20060101
F01N003/031 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 17, 2015 |
DE |
10 2015 211 169.5 |
Claims
1-9. (canceled)
10. A method for operating an exhaust gas aftertreatment system,
comprising the steps of: determining a permissible energy input
into at least one exhaust gas aftertreatment element of the exhaust
gas aftertreatment system; ascertaining an instantaneous energy
input into the at least one exhaust gas aftertreatment element by
ascertaining at least one energy input variable which characterizes
the instantaneous energy input; and actuating an actuation device
which varies, a distribution of an exhaust gas mass flow to the at
least one exhaust gas aftertreatment element and varies a bypass
path that leads around the at least one exhaust gas aftertreatment
element, as a function of the permissible energy input and the
instantaneous energy input.
11. The method according to claim 10, including determining the
permissible energy input as a function of at least one operating
parameter of the at least one exhaust gas aftertreatment
element.
12. The method according to claim 11, including determining the
permissible energy input as a function of a soot charge of a
particle filter, a reducing agent charge of an SCR catalytic
converter and/or a hydrocarbon charge of a catalytic converter.
13. The method according to claim 10, wherein an exhaust gas mass
flow through the at least one exhaust gas aftertreatment element
and/or an exhaust gas temperature are/is ascertained as the energy
input variable.
14. The method according to claim 13, including measuring the
exhaust gas temperature upstream of the at least one exhaust gas
aftertreatment element, downstream of the at least one exhaust gas
aftertreatment element, and/or in the at least one exhaust gas
aftertreatment element.
15. The method according to claim 10, including ascertaining the
exhaust gas mass flow as a function of an instantaneous operating
state of an internal combustion engine in combination with which
the exhaust gas aftertreatment system is operated, as a function of
a pressure loss variable across the at least one exhaust gas
aftertreatment element, and/or as a function of a pressure loss
variable across at least one actuation element of the actuation
device.
16. An exhaust gas aftertreatment system, comprising: at least one
exhaust gas aftertreatment element; a bypass path around the at
least one exhaust gas aftertreatment element; an actuation device,
configured to selectively distribute an exhaust gas mass flow to
the at least one exhaust gas aftertreatment element and the bypass
path; and a control device having determining means for determining
a permissible energy input into the at least one exhaust gas
aftertreatment element, ascertaining means for ascertaining an
instantaneous energy input into the at least one exhaust gas
aftertreatment element, and actuation means for actuating the
actuation device, wherein the control device is configured to
actuate the actuation device as a function of the permissible
energy input and the instantaneous energy input.
17. The exhaust gas aftertreatment system according to claim 16,
comprising a plurality of exhaust gas aftertreatment elements,
including at least one first exhaust gas aftertreatment element and
at least one second exhaust gas aftertreatment element are each
assigned a separate bypass path and a separate actuation
device.
18. The exhaust gas aftertreatment system according to claim 16,
wherein the actuation device has precisely one actuation element
for distributing the exhaust gas mass flow.
19. The exhaust gas aftertreatment system according to claim 16,
wherein the actuation device has an actuation element in the bypass
path and an actuation element upstream of the exhaust gas
aftertreatment element, wherein the actuation elements are coupled
to one another in opposite directions.
20. An internal combustion engine, comprising an exhaust gas
aftertreatment system according to claim 16.
Description
[0001] The invention relates to a method for operating an exhaust
gas aftertreatment system, to an exhaust gas aftertreatment system
and to an internal combustion engine with an exhaust gas
aftertreatment system.
[0002] Under certain operating conditions there is a risk of damage
or destruction of exhaust gas aftertreatment systems, or an
undesired release of substances stored in an exhaust gas
aftertreatment system can occur. In order to avoid such
circumstances and, in particular, overheating of exhaust gas
aftertreatment elements of an exhaust gas aftertreatment system, it
is basically known to provide bypass paths around exhaust gas
aftertreatment elements, wherein typically in such bypass paths an
actuation element, in particular a bypass flap, is provided for
setting an exhaust gas mass flow which flows through the bypass
path. The setting of the actuation element can be adjusted here,
for example, to a temperature which is measured upstream of the
exhaust gas aftertreatment system. A disadvantage of this is that
slow heating of an exhaust gas aftertreatment element is virtually
impossible to sense. In particular, the temperature measured
upstream of an exhaust gas aftertreatment element says nothing
about the time profile of a rise in temperature in the exhaust gas
aftertreatment element. Alternatively, it is possible to adjust the
setting of the actuation element to a temperature measured
downstream of an exhaust gas aftertreatment system. It is
disadvantageous here that such adjustment is too slow acting, and
in particular destructive or damaging events which occur quickly
cannot be avoided. Finally, it is also possible to prevent damage
or destruction of an exhaust gas aftertreatment system by means of
a thermal management system for the engine. This is not possible
under all operating conditions of an engine, in particular not in
the case of a rapid acceleration of the engine.
[0003] The invention is based on the object of providing a method
for operating an exhaust gas aftertreatment system, an exhaust gas
aftertreatment system and an internal combustion engine whereby the
abovementioned disadvantages do not occur.
[0004] The object is achieved by providing the subject matters of
the independent claims. Advantageous refinements can be found in
the dependent claims and the description.
[0005] The object is achieved, in particular, by providing a method
for operating an exhaust gas aftertreatment system which has the
following steps: a permissible energy input into at least one
exhaust gas aftertreatment element of the exhaust gas
aftertreatment system is determined. An instantaneous energy input
into the at least one exhaust gas aftertreatment element is
ascertained by ascertaining at least one energy input variable
which characterizes the instantaneous energy input, and an
actuation device by means of which a distribution of an exhaust gas
mass flow to the at least one exhaust gas aftertreatment element,
on the one hand, and a bypass path around the at least one exhaust
gas aftertreatment element, on the other can be varied, is actuated
as a function of the permissible energy input and as a function of
the instantaneous energy input. By determining the permissible
energy input it is possible to define what quantity of energy, in
particular what quantity of energy per unit of time, can be input
into an exhaust gas aftertreatment element without said element
being damaged or destroyed. Since the instantaneous energy input is
ascertained, there is always sufficient information available in
order to detect whether there is a risk of damage or destruction of
the at least one exhaust gas aftertreatment element. Since the
actuation device is actuated as a function of the permissible
energy input, on the one hand, and the instantaneous energy input,
on the other, it is possible to prevent in a very efficient way
damage or destruction of the at least one exhaust gas
aftertreatment element at any operating point of the exhaust gas
aftertreatment system. In contrast to pure temperature measurement
upstream or downstream of the at least one exhaust gas
aftertreatment element, with the instantaneous energy input a
variable is made available which is actually directly informative
and relevant for the loading of the exhaust gas aftertreatment
element. It also becomes apparent here that the energy which is
input into the exhaust gas aftertreatment element constitutes a
comparatively slow acting variable which is very suitable for
actuating the actuation device as a function thereof. In contrast,
pure temperature measurement is significantly more volatile and
less suitable for carrying out stable open-loop or closed-loop
control.
[0006] The term "energy input" is understood to mean a quantity of
energy which is input into the at least one exhaust gas
aftertreatment element. In this context, according to one
refinement of the method this is a quantity of energy which is
input per unit of time so that the energy input has the dimension
of a power value. According to a different embodiment of the method
it is possible that energy which is input in absolute terms into
the at least one exhaust gas aftertreatment element during a
predetermined time period is used as the energy input. For example,
in this case it is possible that a quantity of energy which is
input per unit of time into the at least one exhaust gas
aftertreatment element is ascertained and integrated over a
predetermined time period, in order to obtain the quantity of
energy which is input in absolute terms. Both energy which is input
per unit of time and energy which is input in absolute terms over a
predetermined time period are suitable variables for permitting
reliable prediction of possible damage or destruction of the
exhaust gas aftertreatment element.
[0007] The term "energy input variable" is to be understood as
meaning a variable which is characteristic of the instantaneous
energy input, or on which the instantaneous energy input depends.
In particular, this comprises at least one variable or a
multiplicity of variables from which the instantaneous energy input
can be derived, in particular calculated. It is possible that the
instantaneous energy input is ascertained directly, for example on
the basis of a model calculation or simulation. In this case, the
at least one energy input variable is directly the instantaneous
energy input.
[0008] The fact that the actuation device is actuated includes an
open-loop or closed-loop control operation being carried out for
the actuation device. A control operation can be carried out, for
example, if the instantaneous energy input is not ascertained by
measuring variables which are suitable for this at the exhaust gas
aftertreatment element but instead by means of a model calculation
or simulation, with the result that no precise knowledge is
available and, in particular, no feedback of the actual
instantaneous energy input occurs. Adjustment can be carried out,
in particular, by virtue of the fact that the instantaneous energy
input is ascertained on the basis of variables which are actually
measured in the region of the or at the exhaust gas aftertreatment
element, with the result that a feedback takes place. The fact that
the actuation takes place as a function of the permissible energy
input and the instantaneous energy input means, in particular, that
the instantaneous energy input is compared with the permissible
energy input, wherein the actuation device is actuated as a
function of the comparison result. For example, it is possible for
a difference between the instantaneous energy input and the
permissible energy input to be formed, wherein the actuation device
is actuated as a function of the difference. For example, it is
possible to actuate the actuation device in such a way that a main
part of the exhaust gas mass flow flows via the bypass path if the
instantaneous energy input exceeds the permissible energy input.
Conversely, the actuation device can be actuated in such a way that
a main part of the exhaust gas mass flow is directed via the at
least one exhaust gas aftertreatment element if the instantaneous
energy input is less than the permissible energy input.
[0009] A bypass path is understood here to be, in particular, a
bypass, specifically a line section, which branches off from a main
exhaust gas path of the exhaust gas aftertreatment system upstream
of the at least one exhaust gas aftertreatment element, and which
has the at least one exhaust gas aftertreatment element, and opens
again into the main exhaust gas path downstream of the at least one
exhaust gas aftertreatment element.
[0010] The actuation device preferably has an actuation element or
a multiplicity of actuation elements, in particular an actuation
flap or a multiplicity of actuation flaps by which the exhaust gas
mass flow can be distributed by the exhaust gas aftertreatment
system to the at least one exhaust gas aftertreatment element, on
the one hand, and to the bypass path, on the other. In this
context, continuous distribution to the various paths of
respectively 0% to 100% is preferably possible.
[0011] An embodiment of the method is preferred which is
distinguished by the fact that the permissible energy input is
determined as a function of at least one operating parameter of the
at least one exhaust gas aftertreatment system. The permissible
energy input varies, in particular, as a function of the specific
operating conditions for the at least one exhaust gas
aftertreatment element.
[0012] In particular, the permissible energy input is preferably
determined as a function of a soot load of an exhaust gas
aftertreatment element which is embodied as a particle filter. In
this context, the permissible energy input typically varies as a
function of whether a soot load threshold of the particle filter
which triggers a regeneration event is exceeded or not. If such a
predetermined soot load threshold is exceeded, the soot is to be
ignited, for which purpose a relatively high permissible energy
input is preferably set than before the soot load threshold is
exceeded. On the other hand, the intension is to prevent the soot
burn-off reaction from carrying on, wherein the particle filter
would be loaded too highly in thermal terms. Instead, the soot
burn-off is to take place continuously and with a predetermined,
maximum burn-off rate, and preferably in a controlled fashion, in
order to avoid excessively high thermal loading of the particle
filter. For this purpose, the permissible energy input is
preferably also limited upward in the case of a soot burn-off.
[0013] It is also possible for the permissible energy input to be
determined as a function of a reducing agent load of an exhaust gas
aftertreatment element which is designed as a catalytic converter
for selective catalytic reduction of nitrogen oxides. Such a
catalytic converter, which is also referred to as an SCR catalytic
converter, typically acts as an accumulator for a reducing agent,
in particular for ammonia, which is not to be expelled or
discharged from the catalytic converter. In this context,
discharging or expulsion of the reducing agent from the catalytic
converter is dependent on the energy input into the catalytic
converter. The more energy that is input into the catalytic
converter, the greater the degree to which the reducing agent is
expelled therefrom. Furthermore, the discharge is higher at a given
energy input the larger the amount of reducing agent which is
stored in the catalytic converter. Therefore, the permissible
energy input is dependent, in terms of preventing the discharging
of reducing agent, on the loading of the catalytic converter with
reducing agent.
[0014] It is also possible that the permissible energy input is
determined as a function of a hydrogen load of a catalytic
converter, in particular of an oxidation catalytic converter or of
an SCR catalytic converter. It becomes apparent here that
hydrocarbons which are stored in the catalytic converter are to be
expelled, in particular baked out, but this is to occur without
said hydrocarbons being ignited, which could otherwise lead to
thermal damage of the catalytic converter. However, this is
particularly critical since the interval between a minimum
temperature at which the hydrocarbons are actually expelled and a
maximum temperature at which the expelled hydrocarbons ignite is
comparatively small and is, in particular, between 10 K and 20 K.
Therefore, in particular in this case it is important to select the
permissible energy input suitably as a function of the hydrocarbon
load of the catalytic converter.
[0015] An embodiment of the method is preferred which is
distinguished by the fact that an exhaust gas mass flow through the
at least one exhaust gas aftertreatment element and/or an exhaust
gas temperature are/is ascertained as an energy input variable. It
is possible for just one of these variables to be measured, wherein
the other variable is preferably determined by simulation, model
calculation or on the basis of a characteristic curve or a
characteristic diagram. However, both the exhaust gas mass flow
through the at least one exhaust gas aftertreatment element and an
exhaust gas temperature are particularly preferably ascertained by
measurement in the region of the exhaust gas aftertreatment
element. The energy input can be ascertained with a high level of
accuracy if both the exhaust gas mass flow and the exhaust gas
temperature are ascertained, in particular, measured, at the at
least one exhaust gas aftertreatment element. It becomes apparent
here, in fact, that the thermal capacity c.sub.p of the exhaust gas
at a constant pressure is very well known and moreover is also
constant in a good approximation over all the operating points of
the exhaust gas aftertreatment system. If this thermal capacity
c.sub.p is known, and the exhaust gas mass flow through the at
least one exhaust gas aftertreatment system as well as the exhaust
gas temperature are also known, the energy which is input into the
at least one exhaust gas aftertreatment element per unit of time
can readily be ascertained, in particular calculated, therefrom
with a high level of accuracy. The instantaneous energy input is
preferably calculated from the exhaust gas mass flow through the at
least one exhaust gas aftertreatment element and the exhaust gas
temperature.
[0016] Alternatively or additionally, it is also possible to
ascertain the instantaneous energy input into the at least one
exhaust gas aftertreatment element directly from a model
calculation or simulation, a characteristic curve or a
characteristic diagram.
[0017] In one embodiment of the method there is provision that the
exhaust gas temperature is measured upstream of the at least one
exhaust gas aftertreatment element. In a different embodiment of
the method there is provision that the exhaust gas temperature is
measured downstream of the at least one exhaust gas aftertreatment
element. Alternatively or additionally there is preferably
provision that the exhaust gas temperature is measured in the at
least one exhaust gas aftertreatment element. For this purpose,
preferably, in particular, temperature sensors are provided,
wherein a temperature sensor is arranged upstream, downstream
and/or in the at least one exhaust gas aftertreatment element. It
is possible for an average exhaust gas temperature in the exhaust
gas aftertreatment element to be determined by forming mean values
of a temperature which is measured upstream of the exhaust gas
aftertreatment element and a temperature which is measured
downstream of the exhaust gas aftertreatment element. Additionally
or alternatively, it is possible that the energy which is taken up
by the exhaust gas aftertreatment element is determined by
measuring differences between the exhaust gas temperature upstream
of the exhaust gas aftertreatment element and downstream of the
exhaust gas aftertreatment element. Alternatively or additionally,
it is possible that the energy which is taken up by the exhaust gas
aftertreatment element is determined, on the basis of the exhaust
gas temperature, from a model or a simulation of the exhaust gas
aftertreatment element.
[0018] It is also possible that an exhaust gas temperature is not
measured but instead is determined from a model or a simulation or
a characteristic diagram or a characteristic curve, in particular
from a model or a simulation of an internal combustion engine in
combination with which the exhaust gas aftertreatment system is
operated. It is possible here for the exhaust gas temperature to be
determined very precisely as a function of the operating point, by
means of a model, a simulation, a characteristic diagram or a
characteristic curve.
[0019] An embodiment of the method is also preferred which is
distinguished by the fact that the exhaust gas mass flow is
determined as a function of an instantaneous operating state of an
internal combustion engine, in combination with which the exhaust
gas aftertreatment system is operated. In this context it is, in
particular, possible to determine the exhaust gas mass flow on the
basis of a model calculation, a simulation, a characteristic
diagram or a characteristic curve as a function of the operating
point. Alternatively or additionally, it is possible for the
exhaust gas mass flow to be determined as a function of a pressure
loss variable across the at least one exhaust gas aftertreatment
element. Alternatively or additionally, it is possible for the
exhaust gas mass flow to be ascertained as a function of a pressure
loss variable across at least one actuation element of the
actuation device--in particular additionally as a function of an
instantaneous actuation position, in particular an actuation angle,
of the actuation element. The pressure loss variable is preferably
determined by measuring a pressure upstream of the exhaust gas
aftertreatment element and/or of the actuation element, as well as
a pressure downstream of the exhaust gas aftertreatment element
and/or of the actuation element. From these pressure values it is
possible to determine a differential pressure value which can be
used as a pressure loss variable. If at the same time the exhaust
gas temperature in the region of the at least one exhaust gas
aftertreatment element and/or of the actuation element and, if
appropriate, the actuation position of the actuation element is/are
known, it is readily possible to determine the exhaust gas mass
flow with a high level of accuracy from the pressure loss variable
and the exhaust gas temperature. It is also possible for the
pressure loss variable to be determined by means of a differential
pressure sensor.
[0020] The object is also achieved in that an exhaust gas
aftertreatment system is provided which has at least one exhaust
gas aftertreatment element, a bypass path around the exhaust gas
aftertreatment element, an actuation device which is configured to
distribute an exhaust gas mass flow to the at least one exhaust gas
aftertreatment element, on the one hand, and the bypass path, on
the other, and a control device. In this context, the control
device has a determining means for determining a permissible energy
input into the at least one exhaust gas aftertreatment element, an
ascertaining means for ascertaining an instantaneous energy input
into the at least one exhaust gas aftertreatment element, and an
actuation means for actuating the actuation device. The control
device is configured to actuate the actuation device as a function
of the permissible energy input and as a function of the
instantaneous energy input. In particular, the control device is
preferably configured to carry out a method as claimed in one of
the embodiments described above. In this context, the advantages
which have already been explained in relation to the method are
obtained in relation to the exhaust gas aftertreatment system.
[0021] It is possible for the control device to be configured to
determine the permissible energy input and/or the instantaneous
energy input on the basis of model calculations and/or simulations.
The control device is, however, preferably operatively connected to
at least one sensor in order to determine the permissible energy
input and/or the instantaneous energy input. This sensor is
preferably at least one pressure sensor and/or at least one
temperature sensor, which are arranged, in particular, in the
region of the at least one exhaust gas aftertreatment element. With
suitable pressure sensors, for example a soot load of a particle
filter can readily be determined, preferably on the basis of a
pressure loss variable across the particle filter, wherein such a
procedure is known per se, and more details will therefore not be
given on it here. In a similar way, a pressure-sensor arrangement,
as already explained above, can be used to determine an exhaust gas
mass flow via the at least one exhaust gas aftertreatment element
in order to ascertain the instantaneous energy input.
[0022] At least one temperature sensor is preferably arranged
upstream of, downstream of and/or in the at least one exhaust gas
aftertreatment element and operatively connected to the control
device.
[0023] It is possible for further suitable sensors to be provided
in order to detect, for example, a reducing agent load of an SCR
catalytic converter and/or a hydrocarbon load of an oxidation
catalytic converter or of an SCR catalytic converter.
[0024] The exhaust gas aftertreatment system preferably has a
multiplicity of exhaust gas aftertreatment elements. In particular,
it is possible for the exhaust gas aftertreatment system to have a
multiplicity of different exhaust gas aftertreatment elements, for
example a particle filter, an oxidation catalytic converter and/or
an SCR catalytic converter.
[0025] At least one first exhaust gas aftertreatment element and at
least one second exhaust gas aftertreatment element are each
assigned a separate bypass path and a separate actuation device. In
this context it is possible for various groups of exhaust gas
aftertreatment elements to be assigned separate bypass paths and
separate actuation devices. Alternatively or additionally, it is
possible for separate bypass paths and separate actuation devices
to be individually assigned to specific exhaust gas aftertreatment
elements. In the case of an assignment of a bypass path and of an
actuation device to a group of exhaust gas aftertreatment elements,
this group can be appropriately selected in this context, wherein
exhaust gas aftertreatment elements which are assigned to the group
preferably have similar conditions for a permissible energy input.
In particular, it is possible to combine various exhaust gas
aftertreatment elements of the same type, for example a
multiplicity of particle filters, to which particle filters a
bypass path and an actuation device are then jointly assigned. If
specific individual bypass paths and actuation devices are assigned
to specific individual exhaust gas aftertreatment elements, it is
possible for each of these specific exhaust gas aftertreatment
elements to define an individual permissible energy input and to
actuate the actuation device in a correspondingly individual
fashion, wherein each exhaust gas aftertreatment element is
relieved of loading in an optimum way and protected against damage
or destruction.
[0026] Alternatively or additionally, it is also possible for a
global bypass path to be provided with a global actuation device,
wherein the bypass path is provided around all the exhaust gas
aftertreatment elements of the exhaust gas aftertreatment system.
This constitutes a simultaneously effective and economical
solution, because all the exhaust gas aftertreatment elements can
be protected against damage and destruction with minimum
expenditure in terms of cost and parts.
[0027] An exemplary embodiment of the exhaust gas aftertreatment
system is preferred which is distinguished by the fact that the
actuation device has precisely one actuation element for
distributing the exhaust gas mass flow. This actuation element can
be, for example, an exhaust gas switch by means of which the
exhaust gas flow can be distributed to the main exhaust gas path
via the at least one exhaust gas aftertreatment element, and the
bypass path, or it can be an actuation flap in the bypass path, in
particular a bypass flap, by which the bypass path can be closed
and opened, preferably continuously.
[0028] Alternatively it is possible for the actuation device to
have in each case an actuation element in the bypass path and
upstream of the exhaust gas aftertreatment element, preferably
downstream of a branch of the bypass path, ahead of the exhaust gas
aftertreatment element when viewed in the direction of flow. In
this case, two actuation elements are therefore provided,
specifically a first in the main exhaust gas path downstream of the
branch of the bypass path and a second in the bypass path, as a
result of which a very sensitive and precise distribution of the
exhaust gas mass flow is possible. In this context there is
particularly preferably provision for the two actuation devices to
be coupled to one another in opposite directions, in particular in
such a way that the one actuation device opens by the same amount
as the other actuation device closes. This can ensure that the
positions of the actuation elements always correspond to suitable
portions of the exhaust gas mass flow, which add up to form
100%.
[0029] The at least one actuation element which has the actuation
device is preferably embodied as a flap. Alternatively, it is
possible for the at least one actuation element to be embodied as a
valve or in some other suitable way.
[0030] Finally, the object is achieved by providing an internal
combustion engine which has an exhaust gas aftertreatment system as
claimed in one of the exemplary embodiments described above. In
this context, the advantages which have already been explained in
relation to the exhaust gas aftertreatment system and the method
are obtained in relation to the internal combustion engine.
[0031] At least one control unit of the internal combustion engine,
in particular the central control unit of the internal combustion
engine (engine control unit-ECU) is used as the control device of
the exhaust gas aftertreatment system. However, it is also possible
for the functionality of the control device of the exhaust gas
aftertreatment system to be performed by a multiplicity of control
units which interact with one another. These may be control units
of the exhaust gas aftertreatment system or of the internal
combustion engine in the stricter sense. It is also possible for
the control device to be assigned completely to the exhaust gas
aftertreatment system.
[0032] It is possible for the method to be permanently implemented
in an electronic structure, in particular a hardware structure, of
the control device. Alternatively or additionally, it is possible
that a computer program product which has instructions on the basis
of which the method can be carried out when the computer program
product runs on the control device is loaded into the control
device.
[0033] The invention also includes a computer program product which
has machine-readable instructions, on the basis of which an
embodiment of the method can be carried out when the computer
program product runs on a computing device, in particular on a
control device.
[0034] The invention also includes a data carrier which has such a
computer program product.
[0035] The internal combustion engine is preferably embodied as
reciprocating piston engine. It is possible for the internal
combustion engine to be configured to drive a passenger car, a
truck or a utility vehicle. In one preferred exemplary embodiment,
the internal combustion engine serves to drive, in particular,
relatively heavy land vehicles or watercraft, for example mining
vehicles or trains, wherein the internal combustion engine is used
in a locomotive or a power car, or ships. Use of the internal
combustion engine to drive a vehicle which is used in defence, for
example a tank, is also possible. An exemplary embodiment of the
internal combustion engine is preferably also used in a stationary
fashion, for example for providing a stationary power supply in an
emergency operating mode, continuous load mode or peak load mode,
wherein in this case the internal combustion engine preferably
drives a generator. A stationary application of the internal
combustion engine for driving auxiliary assemblies, for example
fire extinguisher pumps on drills is also possible. Furthermore, an
application of the internal combustion engine in the field of
mining fossil raw materials and, in particular, fossil fuels, for
example oil and/or gas. It is also possible to use the internal
combustion engine in the industrial field or in the field of
construction, for example in a construction or building machine,
for example in a crane or an excavator. The internal combustion
engine is preferably embodied as a diesel engine, as a gasoline
engine, as a gas engine for operation with natural gas, biogas,
special gas or some other suitable gas. In particular, if the
internal combustion engine is embodied as a gas engine, it is
suitable for use in a block heating plant for the stationary
generation of energy.
[0036] The description of the method, on the one hand, and of the
exhaust gas aftertreatment system as well as of the internal
combustion engine, on the other hand, are to be understood as
complementary to one another. Features of the exhaust gas
aftertreatment system and/or of the internal combustion engine
which have been explicitly or implicitly explained in relation to
the method are preferably features, individually or when combined
with one another, of a preferred exemplary embodiment of the
exhaust gas aftertreatment system and/or of the internal combustion
engine. Method steps which were described explicitly or implicitly
in relation to the exhaust gas aftertreatment system and/or the
internal combustion engine are preferably individually, or when
combined with one another, steps of a preferred embodiment of the
latter. This preferably distinguished by means of at least one
method step which is conditional on at least one feature of an
inventive or preferred exemplary embodiment of the exhaust gas
aftertreatment system and/or of the internal combustion engine. The
internal combustion engine and/or the exhaust gas aftertreatment
system are/is preferably distinguished by at least one feature
which is conditional on at least one step of an inventive or
preferred embodiment of the method.
[0037] The invention will be explained in more detail below with
reference to the drawing, in which:
[0038] FIG. 1 shows a schematic illustration of a first exemplary
embodiment of an internal combustion engine having a first
exemplary embodiment of an exhaust gas aftertreatment system;
[0039] FIG. 2 shows a schematic illustration of a second exemplary
embodiment of the exhaust gas aftertreatment system, and
[0040] FIG. 3 shows a schematic illustration of a third exemplary
embodiment of the exhaust gas aftertreatment system.
[0041] FIG. 1 shows a schematic illustration of a first exemplary
embodiment of an internal combustion engine 1 with a first
exemplary embodiment of an exhaust gas aftertreatment system 3. In
this context, an engine block 5 of the internal combustion engine 1
is connected to the exhaust gas aftertreatment system 3 in such a
way that exhaust gas can be fed from the engine block 5 via the
exhaust gas aftertreatment system 3 to an outlet, in particular an
exhaust, which is illustrated here schematically by an arrow P. The
exhaust gas aftertreatment system 3 has at least one exhaust gas
aftertreatment element 7 which can be embodied, for example, as a
particle filter, as an SCR catalytic converter or as an oxidation
catalytic converter. It is possible for the exhaust gas
aftertreatment system 3 to have more than one exhaust gas
aftertreatment element 7.
[0042] The exhaust gas aftertreatment system 3 also has a bypass
path 9 around the at least one exhaust gas aftertreatment element
7, which bypass path 9 is embodied, in particular, as a bypass. In
this context it is possible that the bypass path 9 is provided to
bypass precisely one exhaust gas aftertreatment element 7, or that
it is provided to bypass a group of exhaust gas aftertreatment
elements 7 or else also all the exhaust gas aftertreatment elements
7 of the exhaust gas aftertreatment system 3.
[0043] The exhaust gas aftertreatment system 3 also has an
actuation device 11 which is configured to distribute an exhaust
gas mass flow to the at least one exhaust gas aftertreatment
element 7, on the one hand, and the bypass path 9, on the other. In
the exemplary embodiment illustrated here, the actuation device 11
has precisely one actuation element 13, which is provided here as
an exhaust gas switch in a branch 15, at which a main exhaust gas
path 17, comprising the exhaust gas aftertreatment element 7, and
the bypass path 9 separate off. Here, the actuation element 13 is
preferably embodied as a flap which can pivot along a schematically
indicated double arrow, by which flap the exhaust gas mass flow can
be divided between the main exhaust gas path 17, on the one hand,
and the bypass path 9, on the other.
[0044] The exhaust gas aftertreatment system 3 also has a control
device 19. For its part, said control device 19 has a determining
means 21 for determining a permissible energy input into the at
least one exhaust gas aftertreatment element 7, an ascertaining
means 23 for ascertaining an instantaneous energy input into the at
least one exhaust gas aftertreatment element 7, and an actuation
means 25 for actuating the actuation device 11. In this context,
the control device 19 is configured to actuate the actuation device
11 as a function of the permissible energy input and of the
instantaneous energy input into the at least one exhaust gas
aftertreatment element 7, in particular in order to perform
open-loop or closed-loop control of the actuation device 11 and
preferably of an actuation position of the actuation element
13.
[0045] In this context it is possible for the permissible energy
input to be used as a setpoint value within the scope of an
adjustment process, wherein the instantaneous energy input is used
as an actual value.
[0046] It is possible for the control device 19 to be embodied as
an engine control unit or as a central control unit of the internal
combustion engine 1. In particular, the control device 19 is
preferably operatively connected to the engine block 5 in order to
ascertain an instantaneous operating state of the internal
combustion engine 1.
[0047] The ascertaining means 23 is preferably configured to
ascertain the instantaneous energy input by ascertaining at least
one energy input variable which characterizes the instantaneous
energy input. In this context, preferably an exhaust gas mass flow
through the at least one exhaust gas aftertreatment element 7
and/or an exhaust gas temperature in the region of the exhaust gas
aftertreatment element 7, preferably the exhaust gas mass flow and
the exhaust gas temperature, is used as energy input variable. A
thermal capacity c.sub.p at a constant pressure of the exhaust gas
is preferably stored as a constant in the control device 19, in
particular in the ascertaining means 23.
[0048] The determining means is preferably configured to determine
the permissible energy input as a function of at least one
operating parameter of the at least one exhaust gas aftertreatment
element 7.
[0049] In order to ascertain an operating parameter of the at least
one exhaust gas aftertreatment element and/or to determine an
energy input variable, the exhaust gas aftertreatment system 3
preferably has a multiplicity of sensors, in particular a first
pressure sensor 27 upstream of the exhaust gas aftertreatment
element 7 and a second pressure sensor 29 downstream of the exhaust
gas aftertreatment element 7. In particular, a pressure loss
variable can be ascertained across the exhaust gas aftertreatment
element 7 by means of the pressure sensors 27, 29. Instead of two
separate pressure sensors 27, 29 it is also possible to use one
differential pressure sensor.
[0050] A soot load of a particle filter can be ascertained from the
pressure loss variable, for example as an operating parameter of
the exhaust gas aftertreatment element 7. Additionally or
alternatively, an exhaust gas mass flow can be ascertained across
the exhaust gas aftertreatment element 7 from the pressure loss
variable, preferably using the exhaust gas temperature in the
region of the exhaust gas aftertreatment element 7.
[0051] A first temperature sensor 31 is preferably provided
upstream of the exhaust gas aftertreatment element 7, wherein a
second temperature sensor 32 is provided downstream of the exhaust
gas aftertreatment element 7. For example, a mean value for the
exhaust gas temperature in the exhaust gas aftertreatment element 7
can be ascertained on the basis of the measured values of the
temperature sensors 31, 32. Alternatively or additionally, it is
also possible to use a temperature sensor which is integrated into
the exhaust gas aftertreatment element 7, or a temperature sensor
which is arranged on the exhaust gas aftertreatment element 7 in
such a way that it measures an exhaust gas temperature in the
exhaust gas aftertreatment element 7. On the basis of a temperature
difference between a measuring point upstream of the exhaust gas
aftertreatment element 7 and a measuring point downstream of the
exhaust gas aftertreatment element 7, in particular therefore on
the basis of a temperature difference which is sensed with the
temperature sensors 31, 32, it is possible to ascertain energy
which is actually taken up by the exhaust gas aftertreatment
element 7, by means of the heat loss in the exhaust gas.
[0052] It is also possible to ascertain the instantaneous energy
input into the exhaust gas aftertreatment element 7 from the
exhaust gas mass flow through the exhaust gas aftertreatment
element 7, the known thermal capacity c.sub.p of the exhaust gas at
a constant pressure and the exhaust gas temperature. In particular,
it is therefore readily possible to ascertain energy which is input
per unit of time into the exhaust gas aftertreatment element 7. By
integration over a predetermined time period it is therefore also
possible to ascertain energy which is in absolute terms input into
the exhaust gas aftertreatment element 7 in the predetermined time
period.
[0053] The control device 19 is preferably operatively connected to
the actuation device 11, in particular to the actuation element 13,
in order to actuate it. The control device 19 is also preferably
operatively connected to the pressure sensors 27, 29 and the
temperature sensors 31, 33.
[0054] If one of the energy input variables which is preferably
used to ascertain the instantaneous energy input, that is to say in
particular the exhaust gas mass flow and/or the exhaust gas
temperature, is not determined by measurement, it is possible to
acquire them on the basis of a model calculation or a simulation,
in particular for the engine block 5, or to read them out from a
characteristic diagram or a characteristic curve of the internal
combustion engine 1.
[0055] It is important that within the scope of the method proposed
here, not only pure control of the exhaust gas temperature of the
actuation device is used but instead the energy input into the
exhaust gas aftertreatment element 7 is ascertained, said energy
input being actually informative about possible damage or
destruction of the exhaust gas aftertreatment element 7.
[0056] FIG. 2 shows a schematic illustration of a second exemplary
embodiment of the exhaust gas aftertreatment system 3. Identical
and functionally identical elements are provided with the same
reference symbols, with the result that in this respect reference
is made to the preceding description. Here, the actuation device 11
has precisely one actuation element 13 which is preferably embodied
as an actuation flap and is arranged in the bypass path 9. The
actuation element 13 is embodied, in particular, as a bypass
flap.
[0057] FIG. 3 shows a schematic illustration of a third exemplary
embodiment of the exhaust gas aftertreatment system 3. Identical
and functionally identical elements are provided with the same
reference symbols, with the result that in this respect reference
is made to the preceding description. In this exemplary embodiment,
the actuation device 11 has in each case one actuation element 13,
13' in the bypass path 9, on the one hand, and in the main exhaust
gas path 17, on the other, upstream of the exhaust gas
aftertreatment element 7 and downstream of the branch 15. In this
context, the two actuation elements 13, 13' are preferably coupled
to one another in opposite directions, with the result that on the
basis of their actuation positions or actuation angles the exhaust
gas mass flow can also be divided clearly into portions which add
up overall to 100%. In this context it is also possible to
determine the exhaust gas mass flow through the exhaust gas
aftertreatment element 7 by determining the exhaust gas mass flow,
preferably by means of a pressure loss variable, by means of the
actuation element 13' in the bypass path 9. If, in fact, this
exhaust gas mass flow is known and at the same time the actuation
position of the actuation element 13' is known, it is in turn
possible to use this to infer the actuation position of the
actuation element 13 in the main exhaust gas path 17, from which it
is in turn possible to infer the exhaust gas mass flow through the
exhaust gas aftertreatment element 7. For reasons of construction
space, it may be appropriate to provide a sensor system for
acquiring an exhaust gas mass flow only in the region of the
actuation element 13' which is assigned to the bypass path 9.
[0058] Overall it becomes apparent that by means of the method, the
exhaust gas aftertreatment system 3 and the internal combustion
engine 1 it is possible to acquire in a very precise fashion an
energy input into the exhaust gas aftertreatment element 7, with
the result that it is possible, under operating conditions which
are hazardous for the exhaust gas aftertreatment system 3, to
conduct exhaust gas via the bypass path 9 and in doing so actuate
the actuation device 11, with the result that the exhaust gas
aftertreatment element 7 is enabled in a controlled fashion after a
critical situation, or can be disabled in a controlled fashion when
a critical situation occurs. In this context it is also to be noted
that, in particular in the marine field, bypasses are in any case
required around an exhaust gas aftertreatment system, with the
result that no additional components are necessary to carry out the
method. All that is necessary is to configure a means of actuating
the actuation device 11 in such a way that said actuation device 11
is actuated, in particular adjusted, on the basis of the
instantaneous energy input and the permissible energy input.
Overall, it is therefore possible to prevent excessive ageing,
damage or destruction of exhaust gas aftertreatment elements.
Furthermore, an undesired emission of stored substances from an
exhaust gas aftertreatment element can be prevented.
* * * * *