U.S. patent application number 15/194253 was filed with the patent office on 2017-01-05 for method and system for monitoring the operation of a catalytic converter.
The applicant listed for this patent is Ford Global Technologies, LLC. Invention is credited to Mario Balenovic, Frederik De Smet, Daniel Roettger.
Application Number | 20170002714 15/194253 |
Document ID | / |
Family ID | 57582848 |
Filed Date | 2017-01-05 |
United States Patent
Application |
20170002714 |
Kind Code |
A1 |
De Smet; Frederik ; et
al. |
January 5, 2017 |
METHOD AND SYSTEM FOR MONITORING THE OPERATION OF A CATALYTIC
CONVERTER
Abstract
The present disclosure concerns a method for monitoring the
operation of a catalytic converter that is disposed in an exhaust
system of an internal combustion engine, in particular of a motor
vehicle, wherein an exhaust gas temperature upstream of the
catalytic converter and an exhaust gas temperature downstream of
the catalytic converter are determined. In order to improve the
monitoring of such a catalytic converter regardless of the
respective type of catalytic converter used, it is proposed with
the present disclosure that an exhaust gas mass flow through the
catalytic converter is determined, wherein it is determined whether
a thermal inertia of the catalytic converter is present or absent
according to the presence of a triggering event taking into account
the exhaust gas temperatures and the exhaust gas mass flow.
Inventors: |
De Smet; Frederik; (Genk,
BE) ; Balenovic; Mario; (Waalre, NL) ;
Roettger; Daniel; (Eynatten, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Family ID: |
57582848 |
Appl. No.: |
15/194253 |
Filed: |
June 27, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N 3/10 20130101; F01N
2560/06 20130101; F01N 2900/14 20130101; Y02A 50/2322 20180101;
F01N 2550/24 20130101; Y02A 50/20 20180101; F01N 11/002 20130101;
Y02T 10/40 20130101; F01N 2900/0404 20130101; Y02T 10/47
20130101 |
International
Class: |
F01N 11/00 20060101
F01N011/00; F01N 9/00 20060101 F01N009/00; F01N 3/10 20060101
F01N003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 2, 2015 |
DE |
102015212372.3 |
Claims
1. A method for monitoring an operation of a catalytic converter
disposed in an exhaust system of an internal combustion engine of a
motor vehicle, wherein an exhaust gas temperature upstream of the
catalytic converter and an exhaust gas temperature downstream of
the catalytic converter are determined, wherein an exhaust gas mass
flow through the catalytic converter is determined, wherein it is
determined whether a thermal inertia of the catalytic converter is
present or absent according to a presence of a triggering event
taking into account the exhaust gas temperatures and the exhaust
gas mass flow.
2. The method of claim 1, wherein a temperature signal
corresponding to the exhaust gas temperature upstream of the
catalytic converter is determined and is then low-pass filtered,
wherein a degree of change of the low-pass filtered temperature
signal is detected, wherein a magnitude of the degree of change of
the low-pass filtered temperature signal is detected, low-pass
filtered and then compared with a predetermined limit value, and
wherein the presence of the triggering event is concluded if the
low-pass filtered magnitude exceeds the predetermined limit
value.
3. The method of claim 1, wherein a mass flow signal corresponding
to the exhaust gas mass flow is produced and low-pass filtered,
wherein the low-pass filtered mass flow signal is compared with a
predetermined mass flow limit value, and wherein the presence of
the triggering event is concluded if the low-pass filtered mass
flow signal is less than the predetermined mass flow limit
value.
4. The method of claim 1, wherein a first temperature signal
corresponding to the exhaust gas temperature upstream of the
catalytic converter is produced and low-pass filtered, wherein a
magnitude of a degree of change of the low-pass filtered first
temperature signal is detected, wherein a second temperature signal
corresponding to the exhaust gas temperature downstream of the
catalytic converter is produced and low-pass filtered, wherein a
change of the low-pass filtered second temperature signal is
detected, wherein a mass flow signal corresponding to the exhaust
gas mass flow is produced and low-pass filtered, wherein the change
of the low-pass filtered second temperature signal is subtracted
from the change of the low-pass filtered first temperature signal
and a corresponding temperature difference signal is produced,
wherein a magnitude of the temperature difference signal is
detected, wherein the magnitude of the temperature difference
signal is multiplied by the low-pass filtered mass flow signal and
a corresponding product signal is produced, wherein the product
signal is low-pass filtered, wherein a magnitude of the change of
the low-pass filtered first temperature signal is detected and is
low-pass filtered, wherein the low-pass filtered product signal is
divided either by the low-pass filtered magnitude of the change of
the low-pass filtered first temperature signal or, if the same is
less than a predefined minimum value, by the minimum value and a
corresponding assessment signal is produced, based on which it is
determined whether the thermal inertia of the catalytic converter
is present or absent.
5. A system for monitoring an operation of a catalytic converter
disposed in an exhaust system of an internal combustion engine of a
motor vehicle, comprising at least one temperature sensor that is
disposed upstream of the catalytic converter for detecting a first
exhaust gas temperature and at least one temperature sensor that is
disposed downstream of the catalytic converter for detecting a
second exhaust gas temperature, characterized by at least one
device for detecting an exhaust gas mass flow through the catalytic
converter and at least one electronic unit that has a signaling
connection to the temperature sensors and the device and that is
designed to detect whether a triggering event exists or not, and to
determine whether a thermal inertia of the catalytic converter is
present or absent following the detection of the existence of the
triggering event while taking into account the exhaust gas
temperatures and the exhaust gas mass flow.
6. The system of claim 5, wherein the electronic unit is designed
to produce a temperature signal corresponding to the first exhaust
gas temperature and then to subject the signal to low-pass
filtering, to detect a degree of change of the low-pass filtered
temperature signal, to detect a magnitude of the degree of change
of the low-pass filtered temperature signal, to subject the
magnitude to low-pass filtering and then to compare the low-pass
filtered magnitude with a predetermined limit value, and to
conclude the triggering event being present if the low-pass
filtered magnitude exceeds the predetermined limit value.
7. The system of claim 5, wherein the electronic unit produces a
mass flow signal corresponding to the exhaust gas mass flow and
subjects the signal to low-pass filtering, to compare the low-pass
filtered mass flow signal with a predetermined mass flow limit
value, and to determine the triggering event being present if the
low-pass filtered mass flow signal is less than the predetermined
mass flow limit value.
8. The system of claim 5, wherein the electronic unit produces a
first temperature signal corresponding to the first exhaust gas
temperature and then to subject the signal to low-pass filtering,
to detect a change of the low-pass filtered first temperature
signal, to produce a second temperature signal corresponding to the
second exhaust gas temperature and then to subject the signal to
low-pass filtering, to detect a change of the low-pass filtered
second temperature signal, to produce a mass flow signal
corresponding to the exhaust gas mass flow and then to subject the
signal to low-pass filtering, to subtract the change of the
low-pass filtered second temperature signal from the change of the
low-pass filtered first temperature signal and to produce a
corresponding temperature difference signal, to detect a magnitude
of the temperature difference signal, to multiply the magnitude of
the temperature difference signal by the low-pass filtered mass
flow signal and to produce a corresponding product signal, to
subject the product signal to low-pass filtering, to detect a
magnitude of the detected change of the low-pass filtered first
temperature signal and to subject the signal to low-pass filtering,
to divide the low-pass filtered product signal either by the
low-pass filtered magnitude of the change of the low-pass filtered
first temperature signal or, if the low-pass filtered magnitude is
less than a predefined minimum value, by the minimum value and to
produce a corresponding assessment signal, and to determine whether
the thermal inertia of the catalytic converter is present or absent
based on said assessment signal.
9. A method comprising: determining upstream and downstream
emissions control device temperature changes by differentiating
low-pass filtered upstream and downstream temperature measurements
against time; calculating a product by multiplying a difference
between the upstream and downstream temperature change signals by a
low-pass filtered exhaust mass flow; and estimating an assessment
of the device by low-pass filtering the product and dividing the
low-pass filtered product by each of a threshold value or a
low-pass filter of a magnitude of a difference between the upstream
temperature change signal and an upstream temperature measurement
depending on the magnitude.
10. The method of claim 9, further comprising indicating the device
as catalytically active when the assessment signal is greater than
a threshold assessment signal.
11. The method of claim 10, further comprising indicating the
device as catalytically inactive when the assessment signal is less
than a threshold assessment signal and adjusting engine operating
parameters in response to the catalyst being inactive.
12. The method of claim 9, wherein the upstream and downstream
temperature measurements are measured via temperature sensors
upstream and downstream of the device, respectively.
13. The method of claim 9, wherein the low-pass filtered exhaust
mass flow is calculated from a measured exhaust mass flow.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to German Patent
Application No 102015212372.3, filed Jul. 2, 2015, the entire
contents of which are hereby incorporated by reference for all
purposes.
FIELD
[0002] The present disclosure relates generally to methods and
system for a catalytic converter.
BACKGROUND/SUMMARY
[0003] Exhaust gases of an internal combustion engine, in
particular of a gasoline engine or a diesel engine, can be treated
with an exhaust aftertreatment system downstream of the internal
combustion engine.
[0004] The exhaust aftertreatment system can comprise a catalytic
converter, which is one example of an emission control device, that
may be designed for selective catalytic reduction (SCR), with which
oxides of nitrogen (NO.sub.X) can be reduced to nitrogen and water.
Furthermore, an exhaust aftertreatment system can comprise a
NO.sub.X storage catalytic converter, in which oxides of nitrogen
can be temporarily stored in defined operating situations. An
exhaust aftertreatment system can also comprise a diesel oxidation
catalytic converter (DOC), with which carbon monoxide (CO) and
hydrocarbons can be removed from the exhaust gas of a diesel engine
by oxidation with the residual oxygen of the exhaust gas.
Furthermore, an exhaust aftertreatment system can comprise a diesel
particulate filter, with which carbon particles can be removed from
the exhaust gas. An exhaust aftertreatment system can also comprise
a combination of at least two of the aforementioned emission
control devices.
[0005] It is desired to monitor the operation of the catalytic
converter. In doing so, a predetermined minimum number of
monitoring processes may be observed during the operation of the
internal combustion engine. In some cases, a degradation of a
catalytic converter, e.g., a device removal or a malfunction of the
catalytic converter, may be detectable. In any case it is desirable
to use an inexpensive sensor device for monitoring the operation of
a catalytic converter.
[0006] It is known to detect a degradation of a catalytic converter
by means of temperature signals upstream and downstream of the
catalytic converter. This is advantageous because temperature
sensors are relatively inexpensive. Temperature sensors are also
often already existing parts of a catalytic converter control
system.
[0007] There are systems in which the presence of a diesel
oxidation catalytic converter can be monitored by the analysis of
heat produced by exothermal reactions in the diesel oxidation
catalytic converter during the regeneration of a diesel particulate
filter. Such a regeneration is used for cleaning the diesel
particulate filter and is usually carried out after driving 500 km
to 800 km. Such long monitoring pauses between individual
detections of the operating state can be sufficient for monitoring
the operation of a diesel particulate filter or of a diesel
oxidation catalytic converter. The operating state of a NO.sub.X
storage catalytic converter and of an SCR catalytic converter may,
however, be detected and thereby monitored at significantly shorter
time intervals. The detection of the operating state of a NO.sub.X
storage catalytic converter or of an SCR catalytic converter may
meet legal requirements, the so-called "In-Use Performance
Requirements" (IUPR), which define a lower limit for monitoring
processes during real driving operations. The value for monitoring
processes to be carried out on a NO.sub.X storage catalytic
converter or a SCR catalytic converter is currently IUPR=0.336 for
EU6.
[0008] EP 2,098,695 discloses a method and a system for monitoring
the operation of a catalytic converter that is disposed in an
exhaust system of an internal combustion engine. The system
comprises a temperature sensor that is disposed upstream of the
catalytic converter for detecting a first exhaust gas temperature
and a temperature sensor that is disposed downstream of the
catalytic converter for detecting a second exhaust gas temperature.
A catalyst bed temperature and a degree of emission control can be
determined from the detected exhaust gas temperatures. The degree
of degradation of the catalytic converter is determined
therefrom.
[0009] U.S. Pat. No. 5,706,652 concerns a system for monitoring the
operation of a catalytic converter that is disposed in an exhaust
system of an internal combustion engine of a motor vehicle. The
system comprises a temperature sensor that is disposed upstream of
the catalytic converter for detecting a first exhaust gas
temperature and a temperature sensor that is disposed downstream of
the catalytic converter for detecting a second exhaust gas
temperature. The extent of the exothermal reactions in the
catalytic converter is detected by means of the detected exhaust
gas temperatures. The extent of the exothermal reactions is
compared with predetermined criteria in order to be able to draw
conclusions regarding the state of the catalytic converter.
[0010] The present disclosure concerns a method for monitoring the
operation of a catalytic converter that is disposed in an exhaust
system of an internal combustion engine, in particular of a motor
vehicle, wherein an exhaust gas temperature upstream of the
catalytic converter and an exhaust gas temperature downstream of
the catalytic converter are determined.
[0011] Furthermore, the present disclosure concerns a system for
monitoring the operation of a catalytic converter that is disposed
in an exhaust system of an internal combustion engine, in
particular of a motor vehicle, comprising at least one temperature
sensor that is disposed upstream of the catalytic converter for
detecting a first exhaust gas temperature and at least one
temperature sensor that is disposed downstream of the catalytic
converter for detecting a second exhaust gas temperature.
[0012] It is an object of the present disclosure to monitor a
catalytic converter that is disposed in an exhaust system of an
internal combustion engine regardless of the respective type of
catalytic converter used.
[0013] In one example, the issues described above may be addressed
by a method for monitoring the operation of a catalytic converter
that is disposed in an exhaust system of an internal combustion
engine, in particular of a motor vehicle, an exhaust gas
temperature upstream of the catalytic converter, an exhaust gas
temperature downstream of the catalytic converter and an exhaust
gas mass flow through the catalytic converter are determined,
wherein it is determined whether a thermal inertia of the catalytic
converter is present or not according to the existence of a
triggering event and while taking into account the exhaust gas
temperatures and the exhaust gas mass flow.
[0014] As an example, the exhaust gas mass flow through the
catalytic converter can be estimated from a measured air mass flow
delivered to the internal combustion engine and an injected amount
of fuel. In the case of low pressure exhaust gas recirculation, an
exhaust gas recirculation mass flow still has to be added if the
catalytic converter sits in the exhaust gas recirculation loop.
This enables the detection of the activity (e.g., presence) or the
inactivity (e.g., absence) of a catalytic converter in an arbitrary
operating cycle of the internal combustion engine, once the
triggering event exists. In particular, by suitable selection of
the triggering event such a detection can take place after a third
operating cycle of the internal combustion engine. In this case the
triggering event can comprise the fulfillment of one or more
triggering criteria. The detection of the presence or the absence
of the catalytic converter is triggered by the occurrence of the
triggering event at suitable short time intervals, which enables
accurate monitoring of the operation of the catalytic converter. In
particular, specified requirements relating to the monitoring of
the catalytic converter can be reliably met in this way. If the
catalytic converter is present, its mass and hence its thermal
inertia are present. If the catalytic converter is not present, its
thermal inertia is also not present. Hence it can be concluded
whether the catalytic converter is present or not from the presence
or absence of the thermal inertia of the catalytic converter.
[0015] It should be understood that the summary above is provided
to introduce in simplified form a selection of concepts that are
further described in the detailed description. It is not meant to
identify key or essential features of the claimed subject matter,
the scope of which is defined uniquely by the claims that follow
the detailed description. Furthermore, the claimed subject matter
is not limited to implementations that solve any disadvantages
noted above or in any part of this disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows a schematic representation of an exemplary
embodiment of a system according to the present disclosure in
combination with an exemplary embodiment of a diesel internal
combustion engine.
[0017] FIG. 2 shows a schematic representation of a further
exemplary embodiment of a system according to the present
disclosure in combination with a further exemplary embodiment of a
diesel internal combustion engine.
[0018] FIG. 3 shows a schematic representation of an exemplary
embodiment of an algorithm for the detection of a triggering
event.
[0019] FIG. 4 shows a schematic representation of a further
exemplary embodiment of an algorithm for the detection of a
triggering event.
[0020] FIG. 5 shows a schematic representation of a part of an
exemplary embodiment of an algorithm designed for performing the
method according to the present disclosure.
[0021] FIG. 6 shows a schematic representation of a further part of
an exemplary embodiment of an algorithm designed for performing the
method according to the present disclosure.
[0022] FIG. 7 shows a graphical representation of an assessment
result obtained with the method according to the present
disclosure.
DETAILED DESCRIPTION
[0023] The following description relates to systems and methods for
measuring exhaust gas temperatures proximal to a catalytic
converter to determine a temperature of the catalytic converter. A
location of the temperature sensors relative to the catalytic
converter is shown in FIGS. 1 and 2. An algorithm for applying one
or more filters to temperature measurements for estimating a
temperature of the catalytic converter is shown in FIGS. 3, 4, 5,
and 6. A graph depicting final values of the algorithm is shown in
FIG. 7.
[0024] The method may be used regardless of the respective type of
catalytic converter used, because in particular NO.sub.X storage
catalytic converters and SCR catalytic converters can also be
monitored because of the short time intervals between detections of
the presence or the absence of such catalytic converters with the
method according to the present disclosure. With the method,
however, the operation of a diesel particulate filter, of a diesel
oxidation catalytic converter and similar can also be monitored,
where longer time intervals between individual detections of the
presence or the absence are considered to be sufficient. The
catalytic converter can be disposed at any point in the exhaust
system of the internal combustion engine.
[0025] The exhaust gas temperatures can be detected by means of a
temperature sensor that is disposed upstream of the catalytic
converter and a temperature sensor that is disposed downstream of
the catalytic converter. The temperature sensor that is disposed
upstream of the catalytic converter can be a specific temperature
sensor for performing the method according to the present
disclosure or a temperature sensor that is already present upstream
on a further device of the internal combustion engine, by means of
which the exhaust gas temperature upstream of the catalytic
converter can be measured or estimated.
[0026] The present disclosure is based inter alia on the knowledge
that a graph resulting from a time recording of the exhaust gas
temperature upstream of the catalytic converter coincides with a
graph resulting from a time recording of the exhaust gas
temperature downstream of the catalytic converter without the
presence of the catalytic converter. The graphs resulting from the
time derivatives of said temperature profiles also coincide. By
contrast, in the presence of the catalytic converter there is a
time offset between the graphs of the exhaust gas temperatures and
the graphs of the time derivatives of the exhaust gas temperature
profiles. This is the case because the temperature signal of the
exhaust gas temperature downstream of the catalytic converter is
delayed and filtered by the mass present in the catalytic converter
between the temperature sensors compared to the temperature signal
of the exhaust gas temperature upstream of the catalytic
converter.
[0027] The present disclosure is further based on the knowledge
that the time constant of a heat exchange between the exhaust gas
mass flow through the catalytic converter and the catalytic
converter is proportional to the quotient of the mass of the
catalytic converter and the exhaust gas mass flow. Consequently,
the mass of the catalytic converter is proportional to the product
of the exhaust gas mass flow and the time constant for the heat
exchange. The exhaust gas mass flow through the catalytic converter
can be detected or estimated according to the method according to
the present disclosure, and determined thereby. According to the
present disclosure, an expression can be derived from the detected
exhaust gas mass flow and the detected exhaust gas temperatures,
based on which expression an assessment can be carried out of
whether the catalytic converter to be monitored is present or
absent.
[0028] According to an advantageous embodiment, a temperature
signal corresponding to the exhaust gas temperature upstream of the
catalytic converter is produced and then low-pass filtered, wherein
a degree of change of the low-pass filtered temperature signal is
detected, wherein a magnitude of the degree of change of the
low-pass filtered temperature signal is detected, low-pass filtered
and then compared with a predetermined limit value, and wherein the
presence of the triggering event is concluded if the low-pass
filtered magnitude exceeds the predetermined limit value. The
low-pass filtering of the temperature signal can be carried out
using a low-pass filter of the second or a higher order. The degree
of change of the low-pass filtered temperature signal is determined
by means of the second time derivative of the temperature profile
of the temperature signal. The low-pass filtering of the magnitude
of the degree of change of the low-pass filtered temperature signal
can be carried out using a low-pass filter of the first or a higher
order. The comparison of the low-pass filtered magnitude of the
degree of change of the low-pass filtered temperature signal with
the predetermined limit value can be carried out using a comparison
operator. If the low-pass filtered magnitude of the degree of
change of the low-pass filtered temperature signal is greater than
the predetermined limit value, it is detected whether the catalytic
converter is active, e.g., present, or inactive, e.g., not present.
The probability that the low-pass filtered magnitude of the degree
of change of the low-pass filtered temperature signal exceeds the
predetermined limit value is such that the detection of the
presence or absence of the catalytic converter is carried out at
relatively short time intervals during operating cycles of the
internal combustion engine. Owing to the large filter constants of
the low-pass filter, a separation between temperature signals into
exhaust gas temperatures detected upstream of the catalytic
converter and temperature signals for exhaust gas temperatures
detected downstream of the catalytic converter is possible after a
certain time. The temperature signals may have very minimal
dynamics. In a static state the dynamics of the two temperature
signals are equal, so that separation of the two temperature
signals is unlikely.
[0029] According to a further advantageous embodiment, a mass flow
signal corresponding to the mass flow of the exhaust gas is
produced and then low-pass filtered, wherein the low-pass filtered
mass flow signal is compared with a predetermined mass flow limit
value, and wherein the presence of the triggering event is
concluded if the low-pass filtered mass flow signal is less than
the predetermined mass flow limit value. The low-pass filtering of
the mass flow signal can be carried out using a low-pass filter of
the first or a higher order. The comparison of the low-pass
filtered mass flow signal with a predetermined mass flow limit
value can be carried out using a comparison operator. If the
low-pass filtered mass flow signal is less than the predetermined
mass flow limit value, it is detected whether the catalytic
converter is active, e.g., present, or inactive, e.g., not present.
The probability that the low-pass filtered mass flow signal is less
than the predetermined mass flow limit value is such that the
detection of the presence or absence of the catalytic converter is
carried out at relatively short time intervals during operating
cycles of the internal combustion engine. The higher the exhaust
gas mass flow through the catalytic converter corresponds to a
shorter time delay between the temperature signals upstream and
downstream of the catalytic converter.
[0030] A further advantageous embodiment provides that a first
temperature signal corresponding to the exhaust gas temperature
upstream of the catalytic converter is produced and then low-pass
filtered, wherein a change of the low-pass filtered first
temperature signal is detected, wherein a second temperature signal
corresponding to the exhaust gas temperature downstream of the
catalytic converter is produced and then low-pass filtered, wherein
a change of the low-pass filtered second temperature signal is
detected, wherein a mass flow signal corresponding to the exhaust
gas mass flow is produced and is then low-pass filtered, wherein
the change of the low-pass filtered second temperature signal is
subtracted from the change of the low-pass filtered first
temperature signal and a corresponding temperature difference
signal is produced, wherein a magnitude of the temperature
difference signal is detected, wherein the magnitude of the
temperature difference signal is multiplied by the low-pass
filtered mass flow signal and a corresponding product signal is
produced, wherein the product signal is low-pass filtered, wherein
a magnitude of the change of the low-pass filtered first
temperature signal is detected and is low-pass filtered, wherein
the low-pass filtered product signal is divided either by the
low-pass filtered magnitude of the change of the low-pass filtered
first temperature signal or, if the same is less than a predefined
minimum value, by the minimum value and a corresponding assessment
signal is produced, based on which it is determined whether the
thermal inertia of the catalytic converter is present or absent.
The low-pass filtering of the first temperature signal can be
carried out using a low pass of the second or a higher order. The
change of the low-pass filtered first temperature signal can be
detected by means of the first time derivative of the profile of
the first temperature signal. The low-pass filtering of the second
temperature signal can be carried out using a low pass of the
second or a higher order. The change of the low-pass filtered
second temperature signal can be detected by means of the first
time derivative of the profile of the second temperature signal.
The low-pass filtering of the mass flow signal can be carried out
using a low-pass filter of the first or a higher order. The
low-pass filtering of the exhaust gas mass flow signal is used for
the synchronization of the exhaust gas mass flow signal with the
temperature signals of the temperature sensors, which are delayed
in time relative to the exhaust gas mass flow signal because of the
slow reaction of the temperature sensors. The subtraction of the
change of the low-pass filtered second temperature signal from the
change of the low-pass filtered first temperature signal and the
production of a corresponding temperature difference signal can be
carried out by means of a subtractor. The multiplication of the
magnitude of the temperature difference signal by the low-pass
filtered mass flow signal and the production of the corresponding
product signal can be carried out by means of a multiplier. The
low-pass filtering of the product signal can be carried out using a
low-pass filter of the first or a higher order. The low-pass
filtering of the magnitude of the change of the low-pass filtered
first temperature signal can be carried out using a low-pass filter
of the first or a higher order. The comparison of the magnitude of
the low-pass filtered change of the low-pass filtered first
temperature signal with the predetermined minimum value can be
carried out using a minmax element. The division of the low-pass
filtered product signal either by the low-pass filtered magnitude
of the change of the low-pass filtered first temperature signal or
by the minimum value, and the production of the corresponding
assessment signal can be carried out using a divider. It has been
found that the mass of the catalytic converter can be identified
from the product of the exhaust gas mass flow and the expression
(T.sub.upstream-T.sub.downstream)/T.sub.upstream, wherein
T.sub.upstream is the exhaust gas temperature upstream of the
catalytic converter and T.sub.downstream is the exhaust gas
temperature downstream of the catalytic converter. The assessment
signal is a modification of said product, in order to be able to
reliably assess whether the catalytic converter is active, e.g.,
present, or inactive, e.g., not present, using the respective
product value.
[0031] A system according to the present disclosure for monitoring
the operation of a catalytic converter that is disposed in an
exhaust system of an internal combustion engine, in particular of a
motor vehicle, comprises at least one temperature sensor that is
disposed upstream of the catalytic converter for detecting a first
exhaust gas temperature, at least one temperature sensor that is
disposed downstream of the catalytic converter for detecting a
second exhaust gas temperature, at least one device for detecting
an exhaust gas mass flow through the catalytic converter and at
least one electronic unit that has a signaling connection to the
temperature sensors and the device and that is designed to detect
whether a triggering event exists or not by taking into account the
exhaust gas temperatures and the exhaust gas mass flow, and
following the detection of the existence of the triggering event to
determine whether thermal inertia of the catalytic converter exists
or not.
[0032] The method is correspondingly associated with the system. In
particular, the system may perform the method according to one of
the aforementioned embodiments or any combination thereof. The
device can be in the form of a sensor device for directly detecting
the exhaust gas mass flow through the catalytic converter or for
indirectly estimating the exhaust gas mass flow through the
catalytic converter.
[0033] According to one embodiment, the electronic unit is designed
to produce a temperature signal corresponding to the first exhaust
gas temperature and then to subject it to low-pass filtering, to
detect a degree of change of the low-pass filtered temperature
signal, to detect a magnitude of the change of the low-pass
filtered temperature signal, to subject it to low-pass filtering
and then to compare the same with a predetermined limit value, and
to conclude the presence of the triggering event if the low-pass
filtered magnitude exceeds the predetermined limit value.
[0034] According to another embodiment, the electronic unit is
designed to produce a mass flow-signal corresponding to the exhaust
gas mass flow and then to subject said signal to low-pass
filtering, to compare the low-pass filtered mass flow signal with a
predetermined mass flow limit value, and to conclude the presence
of the triggering event if the low-pass filtered mass flow signal
is less than the predetermined mass flow limit value.
[0035] Another embodiment provides that the electronic unit is
designed to produce a first temperature signal corresponding to the
first exhaust gas temperature and then to subject the signal to
low-pass filtering, to detect a magnitude of the change of the
low-pass filtered first temperature signal, to produce a second
temperature signal corresponding to the second exhaust gas
temperature and then to subject said signal to low-pass filtering,
to detect a magnitude of the change of the low-pass filtered second
temperature signal, to produce a mass flow signal corresponding to
the exhaust gas mass flow and then to subject said signal to
low-pass filtering, to subtract the change of the low-pass filtered
second temperature signal from the change of the low-pass filtered
first temperature signal and to produce a corresponding temperature
difference signal, to detect a magnitude of the temperature
difference signal, to multiply the magnitude of the temperature
difference signal by the low-pass filtered mass flow signal and to
produce a corresponding product signal, to subject said product
signal to low-pass filtering, to detect a magnitude of the detected
change of the low-pass filtered first temperature signal and to
subject said signal to low-pass filtering, to divide said low-pass
filtered product signal either by the magnitude of the low-pass
filtered change of the low-pass filtered first temperature signal,
or if the same is less than a predefined minimum value, by the
minimum value, and to produce a corresponding assessment signal,
and based on said assessment signal to determine whether the
thermal inertia of the catalytic converter exists or not.
[0036] FIG. 1 shows a schematic representation of an exemplary
embodiment of a system according to the system 1 for monitoring the
operation of an SCR catalytic converter 4 that is disposed in an
exhaust system 2 of a diesel internal combustion engine 3 of a
motor vehicle. A NO.sub.X storage catalytic converter 5 and a
diesel particulate filter 6 downstream thereof are also disposed in
the exhaust system 2. The SCR catalytic converter 4 is located in
an underfloor arrangement. There are a temperature sensor 7
upstream of the NO.sub.X storage catalytic converter 5, a
temperature sensor 8 downstream of the NO.sub.X storage catalytic
converter 5 and upstream of the diesel particulate filter 6 as well
as a temperature sensor 9 downstream of the diesel particulate
filter 6.
[0037] The system 1 comprises a temperature sensor 10 that is
disposed in the exhaust system 2 upstream of the SCR catalytic
converter 4 for detecting a first exhaust gas temperature and a
temperature sensor 11 that is disposed in the exhaust system 2
downstream of the SCR catalytic converter 4 for detecting a second
exhaust gas temperature. Furthermore, the system 1 comprises a
device 47 for detecting an exhaust gas mass flow through the SCR
catalytic converter 4 and an electronic unit 12 that has a
signaling connection to the temperature sensors 10 and 11 and the
device 47 and that is designed to detect whether a triggering event
exists or not, and following detection of the existence of the
triggering event, while taking into account the exhaust gas
temperatures and the exhaust gas mass flow, to determine whether
thermal inertia of the SCR catalytic converter 4 exists or not. The
exhaust gas mass flow in the catalytic converter can be estimated
from the measured air mass flow in the diesel internal combustion
engine (AMF, air mass flow) and the injected fuel.
[0038] FIG. 2 shows a schematic representation of an exemplary
embodiment of the system 1. As such, components previously
described are similarly numbered in subsequent figures. The system
1 may monitor the operation of a catalytic converter 13 that is
disposed in an exhaust system 2 of a diesel internal combustion
engine 3 of a motor vehicle. The catalytic converter 13 is a
combination of an SCR catalytic converter and a diesel particulate
filter. A NO.sub.X storage catalytic converter 5 is also connected
immediately upstream of the catalytic converter 13. There are a
temperature sensor 7 upstream of the NO.sub.X storage catalytic
converter 5, a temperature sensor 8 downstream of the NO.sub.X
storage catalytic converter 5 and upstream of the catalytic
converter 13 as well as a temperature sensor 9 downstream of the
catalytic converter 13.
[0039] The system 1 comprises a temperature sensor 10 that is
disposed in the exhaust system 2 upstream of the catalytic
converter 13 for detecting a first exhaust gas temperature and a
temperature sensor 11 that is disposed in the exhaust system 2
downstream of the catalytic converter 13 for detecting a second
exhaust gas temperature. Furthermore, the system comprises 1 a
device 47 for detecting an exhaust gas mass flow through the
catalytic converter 13 and an electronic unit 12 that has a
signaling connection to the temperature sensors 10 and 11 and the
device 47 and that is designed to detect whether a triggering event
exists or not, and following detection of the existence of the
triggering event, while taking into account the exhaust gas
temperatures and the exhaust gas mass flow, to determine whether a
thermal inertia of the catalytic converter 13 exists or not. The
exhaust gas mass flow in the catalytic converter can be estimated
from the measured air mass flow in the diesel internal combustion
engine (AMF, air mass flow) and the injected fuel. FIGS. 3, 4, 5,
and 6 describe a method for measuring a first temperature of
exhaust gas with a first temperature sensor and a second
temperature of exhaust gas with a second temperature sensor. The
first temperature sensor is upstream of a catalyst and the second
temperature sensor is downstream of the catalyst. Thus, the first
temperature of exhaust gas is substantially equal to a temperature
of exhaust gas entering the catalyst and the second temperature of
exhaust gas is substantially equal to the temperature of exhaust
gas exiting the catalyst. Additionally an exhaust gas mass flow is
measured with an exhaust mass flow sensor integrated into the
catalyst.
[0040] The method further comprises low-pass filtering the first
and second temperatures with a low-pass filter of a second or
higher order. The low-pass filtered first and second temperature
signals are differentiated against time to determine first and
second temperature change signals, respectively. The exhaust gas
mass flow is low-pass filtered with a low-pass filter of a first or
higher order.
[0041] The method further includes calculating a difference between
the first and second temperature change signals and multiplying the
difference by the low-pass filtered exhaust gas mass flow to
generate a product signal. The product signal is then low-pass
filtered via a low-pass filter of a first or higher order.
[0042] A change between the differentiated first temperature change
signal and the low-pass filtered first temperature signal is
calculated. The change is then compared to a threshold value. If
the change is larger than the threshold value, then the low-pass
filtered product signal is divided by the change. If the change is
smaller than the threshold value, then the low-pass filtered
product signal is divided by the threshold value. This creates an
assessment signal. The catalyst is active when the assessment
signal is greater than a threshold assessment signal (e.g., 10).
The catalyst is inactive when the assessment signal is less than
the threshold assessment signal. As such, engine adjustments may
occur in response to the catalyst being inactive as an attempt to
reduce emissions. Adjustments may include decreasing torque output,
increasing exhaust gas temperature, decreasing vehicle speed,
and/or other adjustments conducive toward activating the catalyst
and/or reducing emissions. Adjustments for increasing the exhaust
gas temperature may include retarding spark, delaying a primary
injection, and/or increasing a secondary injection volume.
[0043] FIG. 3 shows a schematic representation of an exemplary
embodiment of an algorithm for the detection of a triggering event.
The algorithm can, for example, be implemented with an electronic
unit (e.g., electronic unit 12) according to FIGS. 1 and 2. A first
exhaust gas temperature upstream of a catalytic converter m be
monitored is initially detected in step 48. This can be carried out
by means of a separate temperature sensor or a temperature sensor
that is already provided on an upstream device of the exhaust
system. In step 48 a temperature signal corresponding to the first
exhaust gas temperature is produced. In step 14 the temperature
signal corresponding to the first exhaust gas temperature is
subjected to low-pass filtering by means of a low-pass filter of
the second or a higher order. The low-pass filtered temperature
signal is then differentiated against time twice in step 15,
whereby a degree of change of the low-pass filtered temperature
signal is detected. In step 16 the magnitude of the degree of
change of the low-pass filtered temperature signal is detected. In
step 17 the magnitude of the degree of change of the low-pass
filtered temperature signal is subjected to low-pass filtering by
means of a low-pass filter of the first or a higher order. In step
18 the low-pass filtered magnitude of the degree of change of the
low-pass filtered temperature signal is compared with a
predetermined limit value 19 in order to conclude the presence of
the triggering event if the low-pass filtered magnitude exceeds the
predetermined limit value 19, whereupon a triggering signal 20 is
produced.
[0044] FIG. 4 shows a schematic representation of an exemplary
embodiment of an algorithm for the detection of a triggering event.
The algorithm can, for example, be implemented with an electronic
unit (e.g., electronic unit 12 shown in FIGS. 1 and 2). In step 21
an exhaust gas mass flow is detected and a mass flow signal
corresponding to the exhaust gas mass flow is produced. In step 22
the mass flow signal is subjected to low-pass filtering by means of
a low-pass filter of the first or a higher order. In step 23 the
low-pass filtered mass flow signal is compared with a predetermined
mass flow limit value 24 to conclude the presence of the triggering
event if the low-pass filtered mass flow signal is less than the
predetermined mass flow limit value 24, whereupon a triggering
signal 25 is produced.
[0045] FIG. 5 shows a schematic representation of a part of an
exemplary embodiment of an algorithm designed for performing the
method according to the present disclosure. The algorithm can for
example be implemented with an electronic unit (e.g., electronic
unit 12 shown in FIGS. 1 and 2). In step 26 a first exhaust gas
temperature upstream of a catalytic converter to be monitored is
initially detected. This can be carried out by means of a separate
temperature sensor or by a temperature sensor that is already
present on an upstream device of the exhaust system. In step 26 a
temperature signal 27 corresponding to the first exhaust gas
temperature is produced. In parallel therewith, in step 26 a second
exhaust gas temperature downstream of the catalytic converter to be
monitored is detected. In step 26 a temperature signal 28
corresponding to the second exhaust gas temperature is produced. In
parallel therewith, in step 26 an exhaust gas mass flow is
determined and a mass flow signal 29 corresponding to the exhaust
gas mass flow is produced. In step 30 the temperature signals 27
and 28 are each low-pass filtered by means of a low-pass filter 31
or 32 of the second or a higher order. In parallel therewith, the
mass flow signal 29 is low-pass filtered by means of a low-pass
filter 33 of the first or a higher order and a low-pass filtered
mass flow signal 34 is produced thereby. In step 35 the low-pass
filtered temperature signals are each differentiated once against
time in order to detect a change of the low-pass filtered
temperature signals and to produce a respective temperature change
signal 36 or 37. The low-pass filtered mass flow signal 34 and the
temperature change signals 36 and 37 are processed further
according to FIG. 6.
[0046] FIG. 6 shows a schematic representation of a further part of
an exemplary embodiment of an algorithm designed for performing the
method according to the present disclosure. The algorithm can for
example be implemented with an electronic unit (e.g., electronic
unit 12 shown in FIGS. 1 and 2). In step 38 the change of the
low-pass filtered second temperature signal or the temperature
change signal 37 is subtracted from the change of the low-pass
filtered first temperature signal or the temperature change signal
36 and a corresponding temperature difference signal is produced,
the magnitude of which is detected in step 39. The magnitude of the
temperature difference signal is multiplied in step 40 by the
low-pass filtered mass flow signal 34 and a corresponding product
signal is produced, which is subjected to low-pass filtering in
step 41 by means of a low-pass filter of the first or a higher
order. In step 42 the magnitude of the detected change of the
low-pass filtered first temperature signal or of the temperature
change signal 36 is detected. In step 43 the magnitude of the
temperature change signal 36 is subjected to low-pass filtering by
means of a low-pass filter of the first or a higher order. In step
44 the low-pass filtered product signal is divided either by the
low-pass filtered magnitude of the change of the low-pass filtered
first temperature signal or, if this is less than a predefined
minimum value 45, by the minimum value 45 and a corresponding
assessment signal 46 is produced, based on which it is determined
whether thermal inertia of the catalytic converter is present or
absent. A minmax element 49 is provided for this purpose. The
values of the assessment signal 46 are significantly higher in the
presence of a catalytic converter than when no catalytic converter
is present. This is shown graphically in FIG. 7.
[0047] In one example, additionally or alternatively, engine
operating parameters may be adjusted if the catalytic converter is
not present (e.g., not lit off). As an example, a torque output may
be decreased to reduce emissions expelled from the engine when the
catalytic converter is unable to treat the emissions. It will be
appreciated that other engine operating parameters may be adjusted
to decrease engine emissions when the catalytic converter is not
present.
[0048] FIG. 7 shows a graphical representation of an assessment
result obtained with the method according to the present
disclosure. The assessment signal D is plotted against the time t.
The values of the assessment signal D that are greater than or
equal to 10 are associated with a catalytic converter being
present, whereas values of the assessment signal D that are less
than 10 are associated with a catalytic converter not being
present. A clear separation between the assessment signals
associated with the catalytic converter being present and the
assessment signals associated with the catalytic converter not
being present is thus possible.
[0049] In this way, a catalytic converter temperature may be
determined by temperature sensors located upstream and downstream
of the catalytic converter. The technical effect of determining a
temperature of the catalytic converter by measuring exhaust gas
temperature is to calculate if the catalytic converter is present.
Engine operating parameters may be adjusted based on whether the
catalytic converter is present or not present.
[0050] A first method for monitoring an operation of a catalytic
converter disposed in an exhaust system of an internal combustion
engine of a motor vehicle, wherein an exhaust gas temperature
upstream of the catalytic converter and an exhaust gas temperature
downstream of the catalytic converter are determined, wherein an
exhaust gas mass flow through the catalytic converter is
determined, wherein it is determined whether a thermal inertia of
the catalytic converter is present or absent according to a
presence of a triggering event taking into account the exhaust gas
temperatures and the exhaust gas mass flow. A first example of the
method further includes where a temperature signal corresponding to
the exhaust gas temperature upstream of the catalytic converter is
determined and is then low-pass filtered, wherein a degree of
change of the low-pass filtered temperature signal is detected,
wherein a magnitude of the degree of change of the low-pass
filtered temperature signal is detected, low-pass filtered and then
compared with a predetermined limit value, and wherein the presence
of the triggering event is concluded if the low-pass filtered
magnitude exceeds the predetermined limit value. A second example
of the method optionally including the first example further
includes where a mass flow signal corresponding to the exhaust gas
mass flow is produced and low-pass filtered, wherein the low-pass
filtered mass flow signal is compared with a predetermined mass
flow limit value, and wherein the presence of the triggering event
is concluded if the low-pass filtered mass flow signal is less than
the predetermined mass flow limit value. A third example of the
method optionally including one or more of the first and second
examples further includes where a first temperature signal
corresponding to the exhaust gas temperature upstream of the
catalytic converter is produced and low-pass filtered, wherein a
magnitude of a degree of change of the low-pass filtered first
temperature signal is detected, wherein a second temperature signal
corresponding to the exhaust gas temperature downstream of the
catalytic converter is produced and low-pass filtered, wherein a
change of the low-pass filtered second temperature signal is
detected, wherein a mass flow signal corresponding to the exhaust
gas mass flow is produced and low-pass filtered, wherein the change
of the low-pass filtered second temperature signal is subtracted
from the change of the low-pass filtered first temperature signal
and a corresponding temperature difference signal is produced,
wherein a magnitude of the temperature difference signal is
detected, wherein the magnitude of the temperature difference
signal is multiplied by the low-pass filtered mass flow signal and
a corresponding product signal is produced, wherein the product
signal is low-pass filtered, wherein a magnitude of the change of
the low-pass filtered first temperature signal is detected and is
low-pass filtered, wherein the low-pass filtered product signal is
divided either by the low-pass filtered magnitude of the change of
the low-pass filtered first temperature signal or, if the same is
less than a predefined minimum value, by the minimum value and a
corresponding assessment signal is produced, based on which it is
determined whether the thermal inertia of the catalytic converter
is present or absent.
[0051] A first system for monitoring an operation of a catalytic
converter disposed in an exhaust system of an internal combustion
engine of a motor vehicle, comprising at least one temperature
sensor that is disposed upstream of the catalytic converter for
detecting a first exhaust gas temperature and at least one
temperature sensor that is disposed downstream of the catalytic
converter for detecting a second exhaust gas temperature,
characterized by at least one device for detecting an exhaust gas
mass flow through the catalytic converter and at least one
electronic unit that has a signaling connection to the temperature
sensors and the device and that is designed to detect whether a
triggering event exists or not, and to determine whether a thermal
inertia of the catalytic converter is present or absent following
the detection of the existence of the triggering event while taking
into account the exhaust gas temperatures and the exhaust gas mass
flow. A first example of the system further includes where the
electronic unit is designed to produce a temperature signal
corresponding to the first exhaust gas temperature and then to
subject the signal to low-pass filtering, to detect a degree of
change of the low-pass filtered temperature signal, to detect a
magnitude of the degree of change of the low-pass filtered
temperature signal, to subject the magnitude to low-pass filtering
and then to compare the low-pass filtered magnitude with a
predetermined limit value, and to conclude the triggering event
being present if the low-pass filtered magnitude exceeds the
predetermined limit value. A second example of the system
optionally including the first example further includes where the
electronic unit produces a mass flow signal corresponding to the
exhaust gas mass flow and subjects the signal to low-pass
filtering, to compare the low-pass filtered mass flow signal with a
predetermined mass flow limit value, and to determine the
triggering event being present if the low-pass filtered mass flow
signal is less than the predetermined mass flow limit value. A
third example of the system optionally including one or more of the
first and second examples further includes where the electronic
unit produces a first temperature signal corresponding to the first
exhaust gas temperature and then to subject the signal to low-pass
filtering, to detect a change of the low-pass filtered first
temperature signal, to produce a second temperature signal
corresponding to the second exhaust gas temperature and then to
subject the signal to low-pass filtering, to detect a change of the
low-pass filtered second temperature signal, to produce a mass flow
signal corresponding to the exhaust gas mass flow and then to
subject the signal to low-pass filtering, to subtract the change of
the low-pass filtered second temperature signal from the change of
the low-pass filtered first temperature signal and to produce a
corresponding temperature difference signal, to detect a magnitude
of the temperature difference signal, to multiply the magnitude of
the temperature difference signal by the low-pass filtered mass
flow signal and to produce a corresponding product signal, to
subject the product signal to low-pass filtering, to detect a
magnitude of the detected change of the low-pass filtered first
temperature signal and to subject the signal to low-pass filtering,
to divide the low-pass filtered product signal either by the
low-pass filtered magnitude of the change of the low-pass filtered
first temperature signal or, if the low-pass filtered magnitude is
less than a predefined minimum value, by the minimum value and to
produce a corresponding assessment signal, and to determine whether
the thermal inertia of the catalytic converter is present or absent
based on said assessment signal.
[0052] A second method comprising determining upstream and
downstream emissions control device temperature changes by
differentiating low-pass filtered upstream and downstream
temperature measurements against time, calculating a product by
multiplying a difference between the upstream and downstream
temperature change signals by a low-pass filtered exhaust mass
flow, and estimating an assessment of the device by low-pass
filtering the product and dividing the low-pass filtered product by
each of a threshold value or a low-pass filter of a magnitude of a
difference between the upstream temperature change signal and an
upstream temperature measurement depending on the magnitude. A
first example of method further includes indicating the device as
catalytically active when the assessment signal is greater than a
threshold assessment signal. A second example of the method
optionally including the first example further includes indicating
the device as catalytically inactive when the assessment signal is
less than a threshold assessment signal and adjusting engine
operating parameters in response to the catalyst being inactive. A
third example of the method optionally including one or more of the
first and second examples further includes where the upstream and
downstream temperature measurements are measured via temperature
sensors upstream and downstream of the device, respectively. A
fourth example of the method optionally including one or more of
the first through third examples further includes where the
low-pass filtered exhaust mass flow is calculated from a measured
exhaust mass flow.
[0053] Note that the example control and estimation routines
included herein can be used with various engine and/or vehicle
system configurations. The control methods and routines disclosed
herein may be stored as executable instructions in non-transitory
memory and may be carried out by the control system including the
controller in combination with the various sensors, actuators, and
other engine hardware. The specific routines described herein may
represent one or more of any number of processing strategies such
as event-driven, interrupt-driven, multi-tasking, multi-threading,
and the like. As such, various actions, operations, and/or
functions illustrated may be performed in the sequence illustrated,
in parallel, or in some cases omitted. Likewise, the order of
processing is not necessarily required to achieve the features and
advantages of the example embodiments described herein, but is
provided for ease of illustration and description. One or more of
the illustrated actions, operations and/or functions may be
repeatedly performed depending on the particular strategy being
used. Further, the described actions, operations and/or functions
may graphically represent code to be programmed into non-transitory
memory of the computer readable storage medium in the engine
control system, where the described actions are carried out by
executing the instructions in a system including the various engine
hardware components in combination with the electronic
controller.
[0054] It will be appreciated that the configurations and routines
disclosed herein are exemplary in nature, and that these specific
embodiments are not to be considered in a limiting sense, because
numerous variations are possible. For example, the above technology
can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine
types. The subject matter of the present disclosure includes all
novel and non-obvious combinations and sub-combinations of the
various systems and configurations, and other features, functions,
and/or properties disclosed herein.
[0055] The following claims particularly point out certain
combinations and sub-combinations regarded as novel and
non-obvious. These claims may refer to "an" element or "a first"
element or the equivalent thereof. Such claims should be understood
to include incorporation of one or more such elements, neither
requiring nor excluding two or more such elements. Other
combinations and sub-combinations of the disclosed features,
functions, elements, and/or properties may be claimed through
amendment of the present claims or through presentation of new
claims in this or a related application. Such claims, whether
broader, narrower, equal, or different in scope to the original
claims, also are regarded as included within the subject matter of
the present disclosure.
* * * * *