U.S. patent application number 13/350482 was filed with the patent office on 2012-07-19 for method for diagnosing an exhaust gas post-treatment.
This patent application is currently assigned to FEV GmbH. Invention is credited to Markus Schonen, Christopher Severin.
Application Number | 20120180455 13/350482 |
Document ID | / |
Family ID | 46489687 |
Filed Date | 2012-07-19 |
United States Patent
Application |
20120180455 |
Kind Code |
A1 |
Severin; Christopher ; et
al. |
July 19, 2012 |
METHOD FOR DIAGNOSING AN EXHAUST GAS POST-TREATMENT
Abstract
Method for the on-board diagnosis of an exhaust gas
post-treatment device for a combustion engine, wherein the exhaust
gas post-treatment device has means for converting an exhaust gas
component and wherein sensor means are provided downstream of the
exhaust gas post-treatment device, wherein the exhaust gas
component is acquired by the sensor means and that by means of the
quantity of the acquired exhaust gas component the quality of the
means for converting the exhaust gas component is derived, wherein
a signal of the sensor means is transmitted to a system for the
on-board diagnosis.
Inventors: |
Severin; Christopher;
(Aachen, DE) ; Schonen; Markus; (Duren,
DE) |
Assignee: |
FEV GmbH
Aachen
DE
|
Family ID: |
46489687 |
Appl. No.: |
13/350482 |
Filed: |
January 13, 2012 |
Current U.S.
Class: |
60/274 ;
60/276 |
Current CPC
Class: |
F02D 41/0235 20130101;
F02D 41/029 20130101; F01N 2550/02 20130101; F02D 2041/228
20130101; F02D 41/146 20130101; F01N 3/035 20130101; F02D 41/1439
20130101; Y02T 10/47 20130101; F01N 11/002 20130101; Y02T 10/40
20130101; F01N 2550/04 20130101; F02D 41/1452 20130101; F02D
41/1454 20130101; F02D 41/025 20130101; F02D 41/401 20130101 |
Class at
Publication: |
60/274 ;
60/276 |
International
Class: |
F01N 11/00 20060101
F01N011/00; F01N 3/035 20060101 F01N003/035 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 14, 2011 |
DE |
102011000153.0 |
Claims
1. A method for the on-board diagnosis of an exhaust gas
post-treatment device for a combustion engine, comprising:
providing an exhaust gas post-treatment device, a means of
converting an exhaust gas component and a sensor means arranged
downstream of the exhaust gas post-treatment device, wherein the
exhaust gas post-treatment device has at least one carbon particle
filter with a catalytic coating for converting the exhaust gas
component; acquiring the exhaust gas component by the sensor means
and determining the quantity of the acquired exhaust gas component;
determining the quality of the means for converting the exhaust gas
component; transmitting a signal of the sensor means to a system
for on-board diagnosis; and regenerating the carbon particle
filter, during which the exhaust gas component is produced.
2. The method according to claim 1, wherein the exhaust gas
component is acquired during a time interval, which extends from a
first point in time during the starting phase of the regeneration
at least up to a second point in time during the regeneration.
3. The method according to claim 2, wherein the first point in time
coincides with the start of the regeneration or a time after the
start of the regeneration.
4. The method according to claim 1, wherein the exhaust gas
component is carbon monoxide, which content is determined by a
carbon monoxide sensor.
5. The method according to claim 1, wherein, when exceeding a
threshold value of the quantity of the exhaust gas component, a
signal of the sensor means is transmitted to the system for the
on-board diagnosis.
6. A device for on-board diagnosis of an exhaust gas post-treatment
device for a combustion engine comprising an exhaust gas
post-treatment device for converting an exhaust gas component and a
sensor, wherein the exhaust gas post-treatment device has at least
one carbon particle filter with a catalytic coating for converting
the exhaust gas component, the sensor means is arranged downstream
of the exhaust gas post-treatment device, to detect an incomplete
conversion of the exhaust gas component during a regeneration of
the carbon particle filter by detecting the same, and the sensor is
connected to a system for the on-board diagnosis.
7. The device according to claim 6, wherein the sensor means has a
carbon monoxide sensor.
8. The device according to claim 6, wherein the sensor for
measuring the carbon monoxide is adapted from a lambda-sensor, a
NOx-sensor or an electro-chemically operating sensor.
9. The device according to claim 6, wherein the sensor has a
catalytic coating and a temperature sensor.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority of German Patent
Application No. 102011000153.0 filed on Jan. 14, 2011, which is
incorporated herein in its entirety by reference.
FIELD OF THE INVENTION
[0002] The invention relates to a method for the on-board diagnosis
of an exhaust gas post-treatment device for a combustion engine,
wherein the exhaust gas post-treatment device has means for
converting an exhaust gas component and wherein sensor means are
provided downstream of the exhaust gas post-treatment device.
BACKGROUND OF THE INVENTION
[0003] The State of the Art is, that a carbon particle filter
stores soot in the so-called adsorption operation. Carbon particle
filters are also called Diesel particulate filters (DPF). When the
particle filter cannot absorb any further soot, it has to be
cleaned by a regeneration. For this, different measures are
available, whereof one is, for example, to additionally heat the
exhaust gas by corresponding measures, so that the soot burns-off
in the filter with oxygen contained in the lean exhaust gas. This
soot burning is mostly incomplete, i.e. products of an incomplete
burning, for example carbon monoxide, are produced. Furthermore, it
belongs to the State of the Art, that the particle filter is
catalytically coated, whereby the carbon monoxide is oxidised to a
very large extent to carbon dioxide, so that the carbon monoxide
behind the filter emission is very low during a regeneration phase
of the particle filter. Problems arise from the fact, that this
catalytic layer ages within the particle filter, so that it becomes
inactive and a conversion of the carbon monoxide, produced by the
regeneration, is not ensured anymore. This ageing process of the
catalytic coating and the, thus, increased carbon monoxide emission
during the regeneration of the particle filter is in practice a not
directly recognisable problem.
[0004] DE 10 2007 009 873 A1 discloses a method for detecting the
occurrence of cross sensitivities of an exhaust gas sensor. The
method is used in Diesel engines, which have in their
exhaust-system branch an oxidising catalyst, a particulate filter
and a particle sensor. It is provided, to conclude a defect of the
catalyst concerning its ability in converting a second exhaust gas
component by means of operational or specifically carried-out
variations of the concentration of this second exhaust gas
component upstream of the catalyst. It should enable, to recognise
the presence of non-converted exhaust gas components in the area of
the exhaust gas sensor and if necessary to carry out a
corresponding correction of the sensor signal.
SUMMARY OF THE INVENTION
[0005] It is object of the present invention to diagnose the
effectiveness of the catalytic coating of particle filters.
[0006] The object is solved by a method for the on-board diagnosis
of an exhaust gas post-treatment device for a combustion engine,
wherein the exhaust gas post-treatment device comprises means for
converting an exhaust gas component and wherein sensor means,
arranged downstream of the exhaust gas post-treatment device, are
provided, wherein the exhaust gas component is acquired by the
sensor means and that by means of the quantity of the detected
exhaust gas component, the quality of the means for converting the
exhaust gas component is determined, wherein a signal of the sensor
means is transmitted to a system for the on-board diagnosis. Thus,
a method is provided in an advantageous manner, in which the
presence or the missing of the relevant exhaust gas component can
be detected. In an exhaust gas post-treatment device, working
efficiently, and with correspondingly effective means for
converting the relevant exhaust gas component, which, if at all, is
only present in very low concentrations, it can be determined, that
the means for converting this exhaust gas component operate
efficiently. If on the other hand a distinctly increased
concentration of the relevant exhaust gas component is measured by
the sensor means, this is an indication, that the means for
converting the exhaust gas component are faultily operating or are
defective. Especially, in this case, a comparison with a reference
value, for example, of a correctly working exhaust gas
post-treatment device can be provided, which is taken as reference.
If the value is larger than the reference value, it can be
determined that the means for converting the exhaust gas component
are faulty.
[0007] According to the invention it is provided, that the exhaust
gas post-treatment device comprises at least one carbon particle
filter with a catalytic coating for converting the exhaust gas
component, wherein a regeneration of the exhaust gas post-treatment
device is carried out, during which the exhaust gas component is
produced. Of advantage is, that the function of filtering and the
function of converting is combined into one component, which is
available on the market in different configurations. It is also
advantageous, that the carbon particle filter, which contains also
the catalytic coating for converting the exhaust gas component,
converts the exhaust gas components, produced during the
regeneration phase.
[0008] As individual method steps it can be provided, that the
exhaust gas component is acquired over a time interval, which
extends from a first point in time during the starting phase of the
regeneration at least up to a second point in time during the
regeneration, preferably, at the end of the regeneration. In this
case, it can be provided, that the first point in time coincides
with the starting of the regeneration or can be after the start of
the regeneration. If the first point in time coincides with the
start of the regeneration, this has the advantage of a simple
starting condition. Generally, the start of the regeneration is
carried out by measures inside the engine like throttling, later
injection timing, additional and/or later injection. Intentionally,
non-combusted fuel amounts reach the oxidation catalyst. Because of
the thus forced reactions in the oxidation catalyst, the exhaust
gas temperature increases up to approximately 620.degree. C. to
630.degree. C. inside the same, however, only with some time delay
to the start of the measures inside the engine. During this time
interval, a breakthrough or a slippage of the exhaust gas
component, not converted by the oxidation catalyst, can take place.
Only after the oxidation catalyst has been heated up to an exhaust
gas temperature of approximately 620.degree. C. to 630.degree. C.,
this exhaust gas component is converted. This can be designated as
the end of the starting phase. The heated exhaust gas starts then
the burning-off procedure of the carbon-particulates in the
particle filter. To not determine this portion of the non-converted
exhaust gas component, the first point in time of the measurement
can be later than the starting of the regeneration by means of the
sensor means arranged downstream of the particle filter. As a
release condition for the temporal determination of this point in
time relative to the starting of the regeneration, the temperature
of the exhaust gas behind the oxidation catalyst can be used.
[0009] As the first point in time is set before the start of the
regeneration, it is ensured, that the relevant exhaust gas
component, if it is already emitted by the combustion engine, but
has not been converted by an oxidation catalyst arranged upstream,
can already be detected concerning its concentration. This can be
used at a later point in time as a correction factor.
[0010] In detail it is provided, that the exhaust gas component is
carbon monoxide, which content is determined by the carbon monoxide
sensor. As already explained above, this is a product of the
generally incomplete burning of the carbon-particulates during the
regeneration phase. In a functionally effective catalytic coating
of the particle filter, carbon monoxide oxidises to carbon dioxide.
By the carbon monoxide sensor it can directly be determined, how
high the concentration of the exhaust gas component, carbon
monoxide, is during a regeneration phase of the particle filter,
i.e. how much carbon monoxide is not effectively converted to
carbon dioxide.
[0011] Preferably, it is provided, that, when exceeding a threshold
of the quantity of the exhaust gas component, a signal of the
sensor means is transmitted to a system of an on-board diagnosis
(OBD). Preferably, the signal of the sensor means, which are,
preferably, formed as a carbon monoxide sensor, represents the
quantity, the concentration or the amount of the non-converted
exhaust gas component in the total exhaust gas flow behind the
filter. Thus, it is ensured in an advantageous manner, that during
the operation control lights--malfunction indicator light MIL--can
then be activated and the causing malfunction can be recorded.
[0012] Furthermore, the object is solved by a device for the
on-board diagnosis of an exhaust gas post-treatment device for a
combustion engine, wherein the exhaust gas post-treatment device
comprises means for converting an exhaust gas component and wherein
sensor means are provided, and the sensor means are arranged
downstream of the exhaust gas post-treatment device to determine an
incomplete conversion of the exhaust gas component by means of
detecting the same, and wherein the sensor means are connected to a
system for the on-board diagnosis.
[0013] According to the invention it is provided, that the exhaust
gas post-treatment device has at least one carbon particle filter
with a catalytic coating for converting the exhaust gas component.
In this case, it is advantageous, that the function of filtering
and the function of converting are combined in one component.
[0014] In a preferred embodiment it is provided, that the sensor
means comprise a carbon monoxide sensor. By means of the carbon
monoxide sensor, it can be directly determined, how high the
concentration of the exhaust gas component carbon monoxide is
during a regeneration phase of the particle filter, i.e. how much
carbon monoxide was not effectively converted into carbon
dioxide.
[0015] Alternatively, it can be provided, that the sensor means for
measuring carbon monoxide are adapted from a lambda-sensor, a
NOx-sensor or an electro-chemically operating sensor. Thus, the
advantage is achieved, that these sensors are available on the
market in many types, as they have already been used in the
surroundings of an exhaust-system branch.
[0016] As a further alternative, it can be provided, that the
sensor means comprise a catalytic coating and a temperature sensor.
In this embodiment the detection of the exhaust gas component
carbon monoxide, as far as this is not converted because of a
defective catalytic coating within the particle filter, such, that
the carbon monoxide, which leaves the particle filter in a
non-converted condition, is followingly converted in the catalytic
coating of the sensor means, arranged behind, and, in this case,
causes an increase in temperature, which is detected by the
temperature sensor.
[0017] For each of the embodiments it can be provided, that the
sensor means are connected to a system for the on-board diagnosis
(OBD). Thus, it is ensured in an advantageous manner, that during
the operation, control lights--malfunction indicator light MIL--can
then be activated and the causing malfunction can be recorded.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In the following, the method according to the invention and
the device for diagnosing the ability of converting of a carbon
particles filter by means of carbon monoxide measurement is
described by using the figures. It shows:
[0019] FIG. 1 is a principal representation of an exhaust-system
branch;
[0020] FIG. 2a is a temperature gradient of a carbon particle
filter with a phase of regeneration;
[0021] FIG. 2b is the carbon monoxide emissions of a carbon
particle filter with catalytic coating; and
[0022] FIG. 2c is the carbon monoxide emissions of a carbon
particle filter without catalytic coating.
DETAILED DESCRIPTION OF THE INVENTION
[0023] FIG. 1 shows a principal representation of a common
exhaust-system branch 6 with a combustion engine 1, which operates,
for example, according to the Diesel principle, and is, when seen
in flow direction A, arranged downstream of an oxidation catalyst
2, a carbon particle filter 3 and a carbon monoxide sensor 4, which
is connected to a control device 5 for monitoring the sensor
signals. The combustion engine can also be a lean operated
Otto-engine (petrol engine). In the manner, which is not described
in more detail, but generally known, the control device is at least
part of a system for the on-board-diagnosis (OBD). The carbon
particle filter 3 is provided with a catalytic coating on its
inside, which is not shown in detail in FIG. 1 because of the
principal representation.
[0024] Furthermore, a possibility for the temperature measurement
can be provided downstream of the oxidation catalyst 2. Thus, a
diagnosis of the oxidation catalyst 2 is achieved by evaluating a
temperature gradient behind the catalyst, after emissions in the
form of not-burnt-off hydrocarbon or carbon monoxide are fed
upstream of the catalyst.
[0025] In FIG. 2 over the time, different temperature gradients of
a carbon particle filter and of the emissions of carbon monoxide
behind the filter are shown. In detail, FIG. 2a shows a temperature
gradient of a carbon particle filter across a specific time
interval, within which by means of common measures a regeneration
is started. A possible measure can be, to additionally heat the
exhaust gas by corresponding internal engine operating conditions,
so that the carbon-particulates burn-off in the filter with the
oxygen contained in the lean exhaust gas. This phase of the
regeneration R is visible in the temperature gradient of FIG. 2 by
means of the temperature increase.
[0026] FIG. 2b shows the carbon monoxide emissions of a carbon
particle filter provided with a catalytic coating. Directly after
the beginning of the regeneration, the concentration K of carbon
monoxide temporarily increases, until the catalytic coating is
heated-up and the carbon monoxide is oxidised to carbon dioxide.
Further in FIG. 2b, the integral I of the carbon monoxide emissions
is shown.
[0027] For comparison, in FIG. 2c the carbon monoxide emissions of
a non-catalytic coated carbon particle filter are shown. In such a
filter, during the regeneration R, a distinct increase of the
concentration K of carbon monoxide is observed. By means of the
integral I, it is shown, that a distinct larger total amount of
carbon monoxide was emitted compared to a catalytic coated carbon
particle filter (FIG. 2b).
[0028] The basic idea of the method and of the device according to
the invention is based on the fact, that by means of a carbon
monoxide sensor downstream of the filter, the concentration of
carbon monoxide can be measured in the exhaust gas flow and that a
catalytic coated carbon particle filter, which coating, however, is
functionally ineffective because of ageing or other damaging
influencing factors, will at least generally have the concentration
gradient of carbon monoxide as shown in FIG. 2c, during the
regeneration R. In this case, the carbon monoxide sensor measures
during the regeneration an increased concentration of carbon
monoxide. When it can be excluded, that because of other
malfunctions in the exhaust-system branch 6 upstream of the carbon
particle filter 3, an increased concentration of carbon monoxide is
produced, it can be diagnosed, that the catalytic coating of the
carbon particle filter is damaged, so that it cannot convert carbon
monoxide produced during the regeneration R to carbon dioxide, and
the carbon monoxide is emitted in a non-converted manner.
[0029] A possible procedure during the carrying out of the method
according to the invention consists of the steps: [0030] starting
the regeneration by common measures, [0031] measuring the emission
of carbon monoxide, [0032] integrating the emission of carbon
monoxide, preferably, up to the end of the regeneration, [0033]
comparing the integral of the emissions of carbon monoxide with a
reference value of a reference filter, which, preferably, is a
filter, fully functioning concerning the conversion, for example
with a conversion rate of 99%, [0034] starting the measures in
dependency of the value comparison, wherein a faulty coating can be
determined, when the measured value is larger than the reference
value.
[0035] As a starting measure, initially a control light
(malfunction indicator light MIL) lights up for information
purposes. As a further measure, the emergency operation of the
combustion engine can be taken into account.
[0036] By means of the described method, it is possible to detect
an ageing of the catalytic coating of a carbon particle filter.
When the catalytic coating is aged, allows this again conclusions,
that also the conversion of carbon monoxide (CO) and of unburnt
hydrocarbon (HC) at cold temperatures, like after the cold start of
the engine, can be reduced. Because of this, it is also indirectly
possible by means of the method according to the invention, to
diagnose also the ability to convert CO and HC during the normal
operation, to which also a cold start belongs.
[0037] It is to be understood that various modifications are
readily made to the embodiments disclosed herein without departing
from the scope and spirit thereof. Accordingly, it is to be
understood that the invention is not to be limited by the specific
illustrated embodiment, but by the scope of the appended
claims.
* * * * *