U.S. patent application number 10/522140 was filed with the patent office on 2005-11-17 for method for cleaning a particulate filter.
Invention is credited to Arlt, Tino, Rosel, Gerd, Schwarz, Roland.
Application Number | 20050252199 10/522140 |
Document ID | / |
Family ID | 30469107 |
Filed Date | 2005-11-17 |
United States Patent
Application |
20050252199 |
Kind Code |
A1 |
Arlt, Tino ; et al. |
November 17, 2005 |
Method for cleaning a particulate filter
Abstract
The invention relates to a method for regenerating a particulate
filter, which is mounted inside the exhaust gas channel of an
internal combustion engine, filters particles out of the exhaust
gas flowing inside of the exhaust gas channel, and which is
intermittently regenerated during operation. According to the
method, the actual air mass flow (Lexp) supplied to the internal
combustion engine is measured, and the air requirement (Lcalc) of
the internal combustion engine is determined. A regeneration of the
particulate filter is initiated based on a difference (.DELTA.L)
between the air mass flow and the air requirement.
Inventors: |
Arlt, Tino; (Regensburg,
DE) ; Rosel, Gerd; (Regensburg, DE) ; Schwarz,
Roland; (Wenzenbach, DE) |
Correspondence
Address: |
MORRISON & FOERSTER LLP
1650 TYSONS BOULEVARD
SUITE 300
MCLEAN
VA
22102
US
|
Family ID: |
30469107 |
Appl. No.: |
10/522140 |
Filed: |
January 24, 2005 |
PCT Filed: |
July 10, 2003 |
PCT NO: |
PCT/DE03/02331 |
Current U.S.
Class: |
60/285 ; 60/277;
60/311 |
Current CPC
Class: |
F01N 2430/00 20130101;
Y02T 10/47 20130101; F01N 3/023 20130101; F01N 9/002 20130101; F02D
41/18 20130101; Y02T 10/40 20130101; F02D 35/0007 20130101; F02D
41/029 20130101; F02D 2200/0402 20130101 |
Class at
Publication: |
060/285 ;
060/311; 060/277 |
International
Class: |
F01N 003/02; F01N
007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 25, 2002 |
DE |
102 33 945.7 |
Claims
1. A method for regenerating a particulate filter, which is mounted
in an exhaust gas channel of an internal combustion engine, filters
particles out of exhaust gas flowing inside of the exhaust gas
channel and is intermittently regenerated during operation,
comprising: measuring actual air mass flow supplied to the internal
combustion engine; determining an air requirement of the internal
combustion engine to be expected at a current operating point; and
a regeneration of the particulate filter is initiated based on a
difference between the air mass flow and the air requirement.
2. The method according to claim 1, characterized in that wherein
the regeneration is triggered if a difference of the actual air
mass flow from the calculated air requirement exceeds a
predetermined threshold value.
3. The method according to one claim 1, wherein the air requirement
is determined taking an empty or cleaned particulate filter as
starting point.
4. The method for regenerating a particulate filter, which is
mounted in an exhaust gas channel of an internal combustion engine,
filters particles out of the exhaust gas flowing inside of the
exhaust gas channel and is intermittently regenerated during
operation, comprising: measuring actual air mass flow supplied to
the internal combustion engine; adapting a model for determining
the an air requirement to be expected at a current operating point
to the actual air mass flow; and regeneration of the particulate
filter is initiated if the model lies outside a predetermined
parameter ranges after the adaptation.
5. The method according to claim 4, wherein the model is adapted to
the actual air mass flow, whereby at least one adjustment value is
suitably set and a regeneration is triggered if the adjustment
value is outside the predetermined ranges.
6. The method according to claim 4, wherein in the determination of
the air requirement, other variables influencing the air
requirement than accumulation of particles in the particulate
filter are taken into consideration.
7. The method according to claim 4, wherein the determination of
the air requirement and a decision as to whether a regeneration is
triggered occur at discrete operating points of the internal
combustion engine.
8. The method according to claim 4, wherein the air requirement is
calculated for control of the internal combustion engine, whereby a
partly loaded filter is taken as a starting point.
9. The method according to claim 4, wherein the actual air mass
flow supplied to the internal combustion engine is determined by an
air mass measuring device mounted in an intake tract of the
internal combustion engine, or by a pressure sensor mounted in the
intake tract of the internal combustion engine.
Description
CLAIM FOR PRIORITY
[0001] This application is a national stage of PCT/DE2003/02331,
filed in the German language on Jul. 10, 2003, which claims the
benefit of priority to German Application No. 102 33 945.7, which
was filed on Jul. 25, 2002.
TECHNICAL FIELD OF THE INVENTION
[0002] The invention relates to a method for regenerating a
particulate filter, and in particular, a particulate filter which
is mounted inside the exhaust gas channel of an internal combustion
engine, filters particles out of the exhaust gas flowing inside of
the exhaust gas channel and is intermittently regenerated during
operation.
BACKGROUND OF THE INVENTION
[0003] Modern internal combustion engines, in particular, gasoline
and diesel internal combustion engines, are usually equipped with
an exhaust emission control system, in order to reduce exhaust gas
emissions. With the permitted emission limits being tightened more
and more in all the main industrial countries, particulate filters
are being used increasingly in exhaust emission control systems.
Particulate filters are important especially for diesel internal
combustion engines, as with these there can be comparatively large
emissions of soot particulates.
[0004] A particulate filter filters out particles contained in the
exhaust gas, mainly soot particulates, and stores these particles.
Typically, it contains a filter element, which the exhaust gas to
be filtered flows through. The choice of the porosity of the filter
chosen depends on the size of the particles to be filtered out.
Above a certain size, the particles are retained in the filter
element of the particulate filter. Thus the particulate filter is
increasingly loaded with particles. The particulate filter must be
cleaned or replaced at regular intervals to avoid the particulate
filter becoming blocked ("clogging-up"). This is necessary so that
the particulate filter can always fulfill its function of cleaning
the exhaust gas with sufficient efficiency.
[0005] A new particulate filter can replace the particulate filter,
or the particulate filter used can be cleaned. Possible cleaning
methods to be considered are cleaning the filter externally outside
the internal combustion engine or cleaning while the engine is in
operation, which is called regeneration of the particulate filter
in this invention.
[0006] The regeneration of the particulate filter can, for example,
be achieved by combustion of the stored particles. To that end, the
particulate filter is brought temporarily to a temperature above
the ignition temperature of the particles. As soon as the ignition
temperature is reached, and as long as there is sufficient oxygen
concentration in the exhaust the stored particles are burned away
spontaneously. As the ignition temperature is well above the usual
operating temperature of the particulate filter, typically the
particle filter must be actively heated up to attain this. For
example, burning away soot particulates without the addition of
additives requires an ignition temperature of at least 550.degree.
C. The addition of additives can reduce the ignition temperature,
but this then makes it necessary to have a device for adding the
additives and a control procedure for operating it.
[0007] To achieve the optimal efficiency from the particulate
filter and to keep the operating costs arising from the
regeneration of the particulate filter as low as possible, in the
prior art, typically, the particulate filter is continuously
monitored. The aim of the monitoring is to determine the optimal
time for a regeneration procedure. If the time intervals between
regenerations are too long, the efficiency of the particulate
filter drops steeply, especially towards the end of each time
interval. The increasing "clogging" of the particulate filter
results in the exhaust gas flow being impeded, which causes an
increase in the exhaust gas counter pressure and thus fuel
consumption. On the other hand, if the time intervals between
regenerations are too short, the operating costs involved are
higher than necessary.
[0008] Pressure sensors can be used to monitor the particulate
filter, which sensors measure the exhaust gas pressure in the
exhaust gas channel upstream and downstream of the particulate
filter. Monitoring methods are also possible whereby only one
single pressure sensor is used, which sensor measures the pressure
difference of the exhaust gas directly before and after the
particulate filter. In both cases, pressure-measuring signals are
fed into a control unit, which uses these to determine the pressure
difference between the exhaust gas pressure upstream and downstream
of the particulate filter. If the pressure difference exceeds a
preset threshold value, then measures are initiated for the
regeneration of the particulate filter.
[0009] The disadvantage of this procedure is, however, additional
costs of material and manufacture involved with the required sensor
technology. Thus the pressure sensors must either be mounted
directly on the exhaust gas pipe or be connected to the exhaust gas
system by means of pipes. Thereby, mounting directly onto the
exhaust gas pipe is problematic, as, in this case, the pressure
sensor or sensors must be designed, in particular, for high exhaust
gas temperatures, for vibration load, for splash water from outside
and also for stones striking from outside.
[0010] If a differential pressure sensor is used, then the sensor
must be connected by pipe to the appropriate points of the exhaust
gas system.
[0011] In addition, it has been found that piping and pressure
sensors are prone to blocking. Such blocking can be caused by, for
example, the particles contained in the exhaust gas or by other
contaminants, such as oil combustion residue. Condensation water
with the inherent problem of ice formation at low outside
temperatures can also result in clogging up.
SUMMARY OF THE INVENTION
[0012] The invention relates to development of a method of the type
presented at the beginning in such a way that the regeneration
times of the particulate filters can be determined without recourse
to additional sensor technology.
[0013] In one embodiment of the invention, the air mass flow
supplied to the internal combustion is measured, which is
determined at the expected air requirement of the internal
combustion engine with the current operating parameters and by
introducing a regeneration of the particulate filter based on a
difference between air mass flow and the air requirement.
[0014] Thus, the invention does not determine the regeneration
times by means of the fall in pressure over the particulate filter
in the exhaust gas channel, but by exploiting another effect that
goes along with the particulate filter becoming increasingly
loaded. The solution according to one embodiment of the invention
builds on the observation that when the particulate filter becomes
increasingly loaded, the exhaust gas counterpressure rises, which
leads to a reduction of the fresh air mass sucked in by the
internal combustion engine each working stroke. This reduction in
the fresh air mass causes the air mass flow to sink in the
operation of the internal combustion engine, and at the same time
the maximum power sinks. Without the particulate filter's effect of
raising the exhaust gas counterpressure, a higher air requirement
would be expected from the internal combustion engine. Thus from
the difference between the air mass flow, which is supplied to the
internal combustion engine, and the air requirement expected at the
current operating point, the condition of the particulate filter
can be judged. Thus, advantageously, an assessment is made of the
immediate effect of the clogging.
[0015] In the embodiment described above, the air requirement is
calculated on the basis of operating parameters of the internal
combustion engine, e.g. using a model, and the regeneration times
of the particulate filter are determined on the basis of the
difference of the present volume of the measured air mass flow from
the calculated air requirement. In fact if the exhaust gas
counterpressure increases because of an increasing accumulation in
the particulate filter, then the air mass throughput through the
internal combustion engine falls increasingly in comparison with
the condition with an empty or freshly regenerated particulate
filter. This effect occurs in naturally aspirated internal
combustion engines and is also to be observed even more pronounced
in supercharged internal combustion engines because of the
turbo-superchargers' sensitivity to counterpressure.
[0016] Here, in the invention, the determination of the volume of
the air mass flow includes, in particular, a direct measurement of
the air mass flow as well as a measurement of a volume connected to
the air mass flow, from which volume the air mass flow can then be
determined.
[0017] Advantageously, the method according to the invention
provides that the volume of the air mass flows supplied to the
internal combustion engine is determined by an air mass measuring
device mounted in a suction tract of the internal combustion engine
or by a pressure sensor mounted in the intake tract of the internal
combustion engine.
[0018] As a rule, a model for load detection is integrated into
modern controls for internal combustion engines, which model uses
different operating parameters of the internal combustion engine to
determine the air requirement of such engine. Thus in the
invention, there is no additional requirement needed to determine
the cleaning times, if the determination of the air requirement
already being done for the load detection can also be used in
addition to monitor the condition of the particulate filter.
[0019] In one aspect of the invention, the particulate filter is
judged to be clogged and a regeneration procedure initiated, if the
difference in the present volume of the air mass flow measured from
the air requirement calculated from the operating parameters
exceeds a certain predetermined threshold value. Such an assessment
allows the control system to be designed especially simply.
[0020] The predetermined threshold value can, for example, be
determined experimentally. Advantageously, its value then takes
into account the fact that the air requirement calculated according
to a load detection model and air mass flow measured in practice do
not correspond completely. Thereby, it is understood that
influencing variables other than the accumulation of particles in
the particulate filter are also taken into consideration and
included in the calculation of the air requirements of the internal
combustion engine. These influencing variables, for example the
ambient pressure or component tolerances, can throw the load
detection system, and hence lead to the measured air mass flow
being different from the calculated air requirement, when cleaning
the particulate filters might be neither necessary or useful.
[0021] With the increasingly used supercharged internal combustion
engines, the ambient pressure is generally measured using a
suitable sensor, so that it can be taken into consideration in the
load detection model without further ado. However, in the prior
art, methods are also known for adapting the load detection model
to the ambient pressure in suitable operating states without using
an ambient pressure sensor. Adaptations to other values affecting
the load detection model, such as, for example, the component
tolerances mentioned, can be achieved, for example, by adapting the
load research model in ranges with a well-defined particulate
filter condition, for example, an empty or freshly regenerated
filter.
[0022] It is understood that there is an interaction between the
threshold value, which, when exceeded, will trigger a regeneration
procedure of the particulate filter, and the exactitude with which
further influencing variables are taken into consideration in the
load detection model. If the load detection model only compensates
for only a few influencing variables or if it only provides a
comparatively rough compensation, then a bigger threshold value is
selected than with an exact compensation of numerous influencing
variables.
[0023] In another embodiment of the invention, there is a method of
the same generic type which provides that air mass flow supplied to
the internal combustion engine is measured, a model for determining
the air requirement to be expected at the present operating point
is adapted to the air mass flow and a regeneration of the
particulate filter is initiated if, after adaptation, the model
lies outside the predetermined parameter areas.
[0024] According to another embodiment of the invention, a
calculation system for the air requirement of the internal
combustion engine is adapted to the determined, actual air mass
flow. With this embodiment, the particulate filter is judged to be
clogged and a regeneration procedure is initiated if the
calculation system leaves the parameter ranges predetermined by the
adaptation. This is especially the case if the above named load
detection model enters ranges of an implausible behavior of the
model. The conclusion can then be drawn that the deviation of the
model from the plausible behavior can be put down to a clogging of
the particulate filter.
[0025] For this embodiment, the above arguments for interacting
between the threshold value and the model exactitude apply
analogously. The more influencing variables with higher exactitude
are taken into consideration in the load detection model, the
tighter the limits of the parameter ranges of the model can be
drawn, the leaving of which ranges triggers a cleaning process of
the particulate filter.
[0026] If the system in which the invention is used is equipped
with a lambda probe, which regulates the fuel-air mixture by
measuring the residual oxygen content of the exhaust gas to the
value for stoichiometric combustion, lambda=1, thus the signal of
the lambda probe and values derived from that, such as from the
lambda control, a lambda adaptation, or adaptation information
relating to the injection valves, can be used in addition, in order
to improve the air requirement calculation and thereby the
assessment of the condition of the particulate filter.
Misinterpretations with respect to the condition of the particulate
filter, as can occur otherwise, for example when there is a leaky
intake manifold, are thus effectively avoided.
[0027] The air requirement of the internal combustion engine is
calculated advantageously in a model that (unadapted) takes an
empty or cleaned particulate filter as its starting point in order
to obtain a well-defined and reproducible fixed point for the
calculation. Further, the calculation of the air requirement and
the decision as to whether a regeneration procedure should be
initiated can occur at all the operating points or only at one or
some predetermined operating points of the internal combustion
engine. Then, the calculation of the air requirement in the
remaining operating ranges can be better adapted to the actual
current condition of the particulate filter, which on average
presents a partly loaded particulate filter.
[0028] In a preferred embodiment of the invention, the air
requirement of the internal combustion engine is calculated using a
model in order to determine the regeneration times, which model
takes an empty or cleaned particulate filter as its starting point,
and for the control of the internal combustion engine, an air
requirement is calculated using a model that takes a partly loaded
particulate filter as its starting point. Thereby, in standard
operation, it is possible to calculate more exactly the air
requirement for the control on average, and the decision as to
whether a regeneration procedure is necessary can be based on a
more exact current load condition of the particulate filter.
[0029] If the two last embodiments described above are combined,
then the air requirement for determining the regeneration times is
calculated on one or some predetermined operating points taking an
empty or cleaned particulate filter as starting point, and the air
requirement for the control system of the internal combustion
engine is calculated from the other operating points taking a
partly loaded particulate filter as starting point. The chosen
operating points then permit an assessment of the condition of the
particulate filter, the remaining operating ranges a realistic
calculation of the air requirement of the engine, for example, for
the control based on a load detection model.
[0030] In another preferred embodiment of the invention, the
calculation system for the air requirement of the internal
combustion engine after the implementation of a regeneration
procedure of the particulate filter is adapted again.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The invention is explained in more detail below by referring
to the drawings and exemplary embodiments. In the drawings:
[0032] FIG. 1 shows a diagrammatic view of an internal combustion
engine according to the invention.
[0033] FIG. 2 shows a flow chart for the implementation of a method
according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0034] In FIG. 1, an internal combustion engine 10 is shown in
diagrammatic view. The internal combustion engine 10 is supplied
with fuel 14 by an injection device 12. Combustion air 16 is fed
through an intake tract 18. After the combustion of a fuel-air
mixture in the internal combustion engine 10, which will not be
gone into in more detail, exhaust gases 20 are discharged through
an exhaust gas tract 22.
[0035] A particulate filter 24 is mounted in the exhaust gas tract
22, which filter filters out particles included in the exhaust gas
20, in particular soot particles, by storing them. The particulate
filter 24 is intermittently cleared of accumulated particles in
so-called regeneration procedures. To this end, at a control signal
36 emitted by a control appliance 30, the temperature of the
particulate filter 24 is raised above the ignition temperature of
the soot particles by means of a heating device. Alternatively, it
is possible to adjust the operating point on the internal
combustion engine to increase the exhaust gas temperature (broken
line). When there is sufficient oxygen concentration in the exhaust
gas 20, the soot particles stored in the particulate filter 24
spontaneously burn away.
[0036] The control appliance 30 includes an arithmetic unit 32,
which calculates the air requirement Lcalc of the internal
combustion engine 10 based on different operating parameters
jointly referenced by 40 in FIG. 1. A load detection model is used
to make the calculation. Such models, which evaluate operating
parameters of the internal combustion engine, e.g. speed, pressure
in the intake tract, fuel mass supplied, throttle position,
operating temperature, etc., and output the air requirement that is
to be expected at the operating point, are known to the person
skilled in the art. The operating parameters 40 include, for
example, the ambient pressure and the operating temperature of the
internal combustion engine or such like.
[0037] The control appliance 30 is connected to an air mass flow
sensor 26 mounted in the intake tract 18, which air mass sensor
measures an actual air mass flow flowing through the intake tract
and delivers a corresponding signal 38 to the control appliance 30.
A measurement Lexp for the actual air mass flow is, on the one
hand, transmitted to the arithmetic unit 32 in order, if necessary,
to adapt the load detection model to the current conditions. On the
other hand, the measurement is supplied together with the
calculated air requirement Lcalc to an evaluation unit 34, which
unit, as described in more detail below, decides on the basis of
the two values whether a regeneration procedure for the particulate
filter 24 should be initiated.
[0038] In order to determine the optimal regeneration times for the
particulate filter 24, first the load detection system is adapted
for an empty or a freshly cleaned particulate filter 24 by means of
the arithmetic unit 32 and a threshold value Lthres determined,
whose significance will become clear with the description below. In
the operation of the internal combustion engine 10, the procedure
represented as a flow chart in FIG. 2 is then started in a step
S10.
[0039] In a step S12, with the help of the load detection model,
the arithmetic unit 32 first calculates the current air requirement
Lcalc of the internal combustion engine 10 for the present
operating parameters 40. In a step S14, the actual value Lexp of
the air mass flow in the intake tract 18 is determined from the
signal 38 of the air mass flow sensor 26 and transmitted to the
control appliance 30.
[0040] The evaluation unit 34 receives the calculated air mass
requirement Lcalc and the measured air mass flow Lexp in the
control appliance 30 as input values and, in a step S16, determines
the amount of difference between the two values,
.DELTA.L=.vertline.Lcalc-Lexp.vertline.
[0041] In a step S18, the difference .DELTA.L is compared with a
predetermined threshold value Lthres. If the difference is smaller
than the threshold value, then no action is taken. The method then
goes back to step S12, in which it again calculates the air
requirement for the current operating parameters.
[0042] If the difference .DELTA.L is greater than the threshold
value Lthres the particulate filter 24 is considered blocked and in
a step S20, a regeneration of the particulate filter 24 is
initiated. The procedure then ends in the step S22. The
implementation of the regeneration itself is known in the prior art
and, therefore, will not be explained in detail.
[0043] After the regeneration of the particulate filter 24 has been
successfully completed, then the load detection model is adapted to
the new condition of the particulate filter 24. If this adaptation
of the load detection model or of its components delivers an
implausible result, then an error message is output. Otherwise the
procedure represented in FIG. 2 is begun anew.
* * * * *